Which Class of Wire need to be used for House Wiring

Different Class of Conductor

• As per IEC 60228, Electrical wires/cables are classified into different classes according to the conductor’s flexibility, conductor hardness & thermal effects.
• There are four classes of flexibility for electrical cables
• Class 1 = Solid conductor= ideal conductors for permanent installations.
• Class 2 =Stranded conductor= conductors designed for fixed installation.
• Class 5 =Flexible conductor= preferred to used where flexibility is required, for movable equipment , where there is vibration in equipment.
• Class 6 =Very Flexible conductor= highly flexible conductors used in robotics, flexible codes.
• Classes 3 and 4 are not described in IEC 60228.
• The most basic type of conductor is a single, solid wire (Class 1). It provides a smaller diameter, the largest Cross-Sectional Area (CSA), and the clearest signal, it is mechanically fragile and susceptible to breakage after repeated bending cycles.
• To improve flexibility, wires are stranded together (Class-2, Class-5, Class-6). Class 2 is a multi-wired conductor, while classes 5 and 6 are fine or ultra-fine wired conductors. The IEC standard specifies values such as the maximum diameter and maximum resistance for the individual wires.
• The more wires that are stranded together to make a given size, the more flexible the conductor will be. This indicates that a higher class corresponds to a greater number of strands within the conductor. Additionally, stranded wires are significantly easier to manipulate and bend during installation compared to a single wire of equivalent cross-section.
• Classes 1 and 2 are intended for use in cables for fixed installations. On the other hand, Classes 5 and 6 are designed for use in flexible cables and cords but may also be used for fixed installations.

(A) Class 1: Solid Conductors

• Construction: Single Conductor, solid copper wire.
• Flexibility: Rigid and non-flexible. the cable should not be bent more than about four times its diameter
• Characteristics: High electrical conductivity and resistance to corrosion, but less suitable for environments requiring flexibility.
• Advantages: Less expensive than cables with multiple wires
• Disadvantages: Less suitable for applications involving movement.
• Heat and Losses: Class 1 wires are more efficient for fixed wiring due to lower resistance and heat generation. 
• Applications: Typically used in permanent, stationary installations, House wiring where the conductor will not be subject to frequent movement or low flexibility is not a problem such as in building wiring and power distribution.
• They are often used when cables with larger cross-sections are required for fixed installations. They are not suitable for very flexible cables, which are used, for example, in continuously moving objects such as robotic arms in industrial production

(B) Class 2: Stranded Conductors

• Construction: Composed of multiple smaller copper wires twisted or braided together to form a single conductor.
• Flexibility: More flexible than Class 1, allowing for some movement without breaking or damaging the wire.
• Characteristics: Offers a balance of flexibility and durability but may not be as conductive as a solid conductor of the same gauge.
• Advantages:Lower electrical resistance and less heat buildup under load.
• Disadvantages:Less suitable for applications involving movement.
• Heat and Losses:Class 2 wires are more efficient for fixed wiring due to lower resistance and heat generation. 
• Applications: Primarily used for fixed installations like permanent building and house wiring and for industrial applications with increased cable flexibility requirements.

(C) Class 5: Flexible Conductors

• Construction: Consists of many fine copper wires (often tinned for corrosion resistance) twisted together, making the conductor highly flexible.
• Flexibility: Extremely flexible, designed for applications where the conductor needs to withstand frequent movement, bending, or vibration without damage.
• Characteristics: High flexibility, durable against wear and tear, but may have slightly lower conductivity compared to solid conductors due to the finer strands.
• Advantages:Superior flexibility.
• Disadvantages:Higher electrical resistance, which can result in greater heat loss and voltage drops.
• Heat and Losses:Class 5 wires are not efficient for fixed wiring due to higher resistance and heat generation compared to Class-2. 
• Applications: Used in situations where more flexibility is required, such as in circuits that may need to be bent, coiled, or moved occasionally. Ideal for portable appliances and equipment that move constantly like portable cords, flexible cables, and power tools that require a durable, yet highly flexible conductor.

(D) Class 6: Extra Flexible Conductors

• Construction: Made up of very fine copper wires, typically tinned, twisted into a very flexible configuration.
• Compared to class 5, the number of strands and wires arranged around each other is even larger, which can further increase the flexibility of the wire
• Flexibility: The highest level of flexibility among copper conductors, suitable for applications requiring frequent movement or twisting.
• Characteristics: Very high flexibility, ideal for dynamic applications, but may have lower conductivity due to the fine strands.
• Applications: Used in highly flexible cable assemblies, robotics, automobile, machine and tool construction and flexible power cables where the conductor will experience constant movement and mechanical stress.

Which Class of Conductor Used for House hold Wiring:

• To reduce power consumption, eliminate heating of wires, The Selection of House wire is most important.
• The selection of Wires broadly depends on conductor Resistance, Current, Quality of conductor material, Cross section area and power consumption.
• Resistance: A conductor with higher resistance will consume more power (P = I²R, where P is power, I is current, and R is resistance).
• Current: If both conductors are used in the same application with the same current, the one with the higher resistance will consume more power.
• Conductor Quality: Many people believe that wire quality simply by measuring its diameter and doing a mathematical calculation to estimate resistance. Conductor resistance is not just about the size of copper but it also depends on copper purity. For example, impure or recycled copper may have a bigger cross-sectional area but still higher resistance, which means more heat, more energy loss and shorter wire life.
• Conductor Size: The material (copper, aluminum, etc.) and the cross-sectional area of the conductor also significantly affect resistance and power consumption.
• Power Consumption: The power consumption of a conductor is primarily determined by its resistance and the current flowing through it, rather than its classification (Class 2 or Class 5). However, the classification itself does provide some context regarding the conductor’s characteristics:
• There are mainly two types of Conductors solid (Class-1) and stranded (Class-2 & Class-5).

(A) Selection between Class-1 or Class-2 (Solid or Standard):

• Solid conductor (Class-1) has less flexibility hence not easily passing in conceal conduits of house wires and making hot spots at conductor bends. Due to less flexibility easily break conductor at its termination location.
• The cables used in Building wiring switched to Class 2 copper conductors as it offered better flexibility over the Class 1 solid copper conductors. It is also technically superior and avoid hot spots at bends without compromising the current carrying capacity on account of its resistance being the same as specified for Class 1 copper conductors.
• Multi-stranded conductor (Class-2) shall be replaced to single solid conductors (Class-1) for all the House wiring.

(B) Selection between Class-2 & Class-5 (Standard or fine Standard):

• Stranded conductor can be divided broadly in two types one is multi-strand conductor (known as class-2 conductor) other is Flexible stranded conductor (known as class-5 conductor).
• The difference between Class-2 & Class-5 Wires are as under
• Resistance: The conductor resistance of class 5 is high compared to class 2 conductor, the heat generated for the same current loading will be different on both class of conductors

Copper Conductor Resistance based on class (IS:694)
Wire Size	Copper Conductor Resistance (Ω/Km)		Insulation Thickness (mm)		Tensile Strength (N/mm2)
	CLASS-2	CLASS-5	CLASS-2	CLASS-5	CLASS-2	CLASS-5
0.75 Sq.mm	24.5	26	0.7	0.6	12.5	10
1 Sq.mm	18.1	19.5	0.7	0.6	12.5	10
1.5 Sq.mm	12.1	13.3	0.7	0.6	12.5	10
2.5 Sq.mm	7.41	7.98	0.8	0.7	12.5	10
4 Sq.mm	4.61	4.95	0.8	0.8	12.5	10

• Insulation: The insulation thickness for the class 5 conductor cable is lesser than specified for class 2, not better for higher load conditions
• Mechanical Strength: The mechanical strength of insulation for class 5 is lesser in comparison to class 2, this can lead to issues during conduit pull.
• Flexibility: The difference lies mainly in flexibility.
• Class 2 wires have fewer strands (Conductor) of more diameter. Example :14/0.31mm(max.) 14 strands each of 0.31 mm (max.). typically, 7 strands are used which makes them less flexible and more suitable for fixed installations.
• Class 5 wires have more strands (Conductor) of less diameter. Example: 32/0.21mm(max.) 32 strands each of 0.21 mm (max.). Typically, 30 to 50 strands are used, which makes them more flexible and easier to bend.
• Application: For fixed wiring application conductors with Class 2 copper shall be used. Worldwide the usage of class 2 conductors is specified for building wires as it offers lower resistance, mechanical strength is higher.
• Class 5 wires are commonly used in applications where flexibility is important, such as in portable appliances and equipment where the lengths are preferably 1.5 to 2-meter, power tools, panel wiring (As bending and routing of such cables in constricted paths do not stress on the cable and handling and installation of such conductors in confined areas is easier).
• Amount of Copper content: Actually, in class 5 conductors, copper content is less than that of class 2 conductor which make them more flexible wires. The reason is copper wires with class 5 conductor are cheaper.
• Lesser copper content in wire leads to increased cable resistance and which may in turn increase power consumption and loss. on the other side these coper wires with class 5 conductor can bring disaster in a building as it increases the disconnection time of protective device due to its increased resistance. The power loss of class 5 conductor is higher and is against the concepts of energy conservation or sustainability.

Comparison of Class 2 and Class 5 copper conductors
Property	Characteristic	CLASS-2	CLASS-5
Installation	Passing through Conduit	Easy to Pass through Conduits due to less flexible compared to Class-5	Conductor is more Flexible hence change of Cable getting Stuck in Conduit
	Termination	No of Strands are less hence easy to crip Lugs	No of Strands are higher hence difficult to hold all strand under Lugs while crimping
	Maintenance	In case of replacement easy to pull out Wire from Conduit	difficult to pullout from conduit after installation.
Mechanical	Tensile Strength	Higher mechanical Strength to withstand Stress	Mechanically weak compared to Class-2
	Loose Connection	Cable stay firm near its termination in case of vibration	Might get loose in case of vibration
	Conductor Roundness	Conductor bunch is circular due to less number of strands	Due to more no of Strands and it’s arrangement. Not circular as compared to class-2
	Conductor Structure	Fewer Strands (Conductor) of large Size	More Strands (Conductor) of Small Size
Electrical	Resistance	Less conductor Resistance	Higher Conductor Resistance
	Current Capacity	Higher Current carrying capacity	Less Current carrying capacity
	Derating Factor	Better conductor roundness makes symmetrical arrangement in conduit, reduce derating Factor	Higher derating Factor
	Amount of Copper	Use of Copper is higher than Class-5 for the Same Size of Conductor	Use of Copper is less than Class-2 for the Same Size of Conductor
	Power Loss	Less Power Loss due to less resistance	6 to 8% Higher Power Loss compared to Class-2
	Insulation	Insulation thickness is higher than Class-5	Insulation thickness is less than Class-2
	Heat Built up	Minimal (Due to less Resistance)	Heat Faster under Load
Cost	Cheaper	5 to 8% Costly (due to more Copper) than Class-5	Cheaper than Class-2
Application	Fixed /Movable	Typically used fixed / Permeant Wires installation in wall and ceiling where wires are permeant and used regularly	Used for Flexible application like Power cord, extension Wires Board, for Movable parts

• Multi-stranded conductor (Class-2) shall be used for house wiring due to its Less Resistance, Less heat loss, Low Power consumption, better insulation, higher mechanical Strength.

Conclusion:

• Actually, Wires with Class-5 copper are used for appliance wiring and panel wiring (Not Fixed Wiring) only and they are also manufactured accordingly. Wiring with Class-5 copper conductors do not conform to the code of practice of wiring and hence it’s illegal to use them in fixed wiring and In IS 694 specifies panel wire and building wire as a similar group of functioning. This created a confusion and an create opportunity to misuse of Class 5 conductors as building wires because Class-5 Wires are 8 % cheaper than wires with Class-2 copper conductor.
• However, we must avoid to use Class-5 Wires for Wiring Application due to its less copper content (due to its more flexibility) in wire will lead to increase cable resistance and which may in turn increase the power consumption, higher watt loss, higher voltage drops, higher fault loop impedance.
• Higher impedance of the circuit may lead to accidents due to higher disconnection time of protective device. Less mechanical strength, less insulation hence heats up in load and not safe in continuous load.
• For fixed wiring application, House Wiring conductors with Class 2 copper shall be used.

Fire Door / Fire Wall / Fire Sealant / Fire Rated Equipment’s Guideline

Fire Door / Fire Wall / Fire Sealant / Fire Rated Equipment’s
Code	Clause No	Area	Descriptions
NBC-2016	2.24	Fire Tower Wall / Fire Tower Door	Fire Tower An enclosed shaft having protected area of 120 min Fire resistance rating comprising protected lobby, staircase and Fireman lift, connected directly to exit discharge or through exit passageway with 120 min Fire resistant wall at the level of exit discharge to exit discharge. The Fire fighting shaft shall be equipped with 120 min Fire doors.
NBC-2016	5.1.1(g)	Fire Fighting Shaft (Fire Hose Cabinet) Door	Hydrants for firefighting and hose reels shall be located in the lobby in firefighting shaft. Those hydrants planned to be provided near fire exit staircase on the floor shall be within 5 m from exit door in exit access. Such hydrant cabinet may finish with doors to meet interior finishes with requirement of glass panel to provide visibility to the installations inside and inscribed with the word: FIRE HOSE CABINET of letter size 75 mm in height and 12 mm in width. Such door of the fire hose cabinet need not be fire resistant rated. The location of such cabinets shall be shown on floor plan and duly displayed in the landing of the respective fire exit staircase.
NBC-2016	3.4.5.4	Electrical Shaft Door	The inspection door for electrical shafts/ducts shall be not less than 120 min Fire resistance.
Model Building-Bye-laws-2016	7.14.d	Electrical Shaft Door	The inspection panel doors and any other opening in the shaft shall be provided with airtight Fire doors having Fire resistance of not less then 1 hour.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.2	Electrical Shafts Door	Electrical Shafts shall have not less than 2 hours Fire resistance
Model Building-Bye-laws-2016	7.13.a	Service Shafts Door	Service duct shall be enclosed by walls and door, if any, of 2 hours Fire rating. If ducts are larger than 10 sq m. the floor should seal them, but provide suitable opening for the pipes to pass through, with the gaps sealed.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.2	Service Shafts Door	Services Shafts other than Electrical Shaft, the Fire resistance shall be not less than 1 hour.
NBC-2016	3.4.5.4	Plumbing Shaft Door (Inside the Building)	For plumbing shafts in the core of the building, with shaft door opening inside the building, the shafts shall have inspection doors having Fire resistance rating not less than 30 min
NBC-2016	3.4.5.4	Plumbing Shaft Door (Outside the Building)	For plumbing shafts doors which open in wet areas or in naturally ventilated areas or on external wall of the building, the shafts may not require doors having any specified Fire rating.
NBC-2016	3.4.5.4	Service Shafts Sealing	Service ducts and shafts Openings in walls or floors which are necessary to be provided to allow passages of all building services like cables, electrical wirings, telephone cables, plumbing pipes, etc, shall be protected by enclosure in the form of ducts/shafts having a Fire resistance not less than 120 min.
Central Electricity Authority	38.2	Service Shafts Sealing	No other service pipes shall be taken along the ducts provided for laying power cables. All ducts provided for power cables and other services shall be provided with Fire-barrier at each floor crossing
NBC-2016	3.4.5.4	Electrical Cable Sealing	The space between the electrical cables/conduits and the walls/slabs shall be filled in by a Fire stop material having Fire resistance rating of not less than 120 min. This shall exclude requirement of Fire stop sealing for low voltage services shaft.
NBC-2016	3.4.6.1	Electrical Shaft Sealing	The electric distribution cables/wiring shall be laid in a separate shaft. The shaft shall be sealed at every floor with Fire stop materials having the same Fire resistance as that of the floor.
IS	IS 3034	Electrical Cable Entry Sealing	All cable entries in the switch gear room shall be effectively sealed by use of Fire stops.
Model Building-Bye-laws-2016	7.14.a	Electrical Shaft Sealing	The electric distribution cables/wiring shall be laid in a separate duct shall be sealed at every floor with non-combustible material having the same Fire resistance as that of the duct.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.11	Electrical Services Shaft Sealing	The electric distribution cable/wiring shall be laid in a separate duct. The duct shall be sealed at every floor with non-combustible materials having the same Fire resistance as that of the duct.
NBC-2016	3.4.6.3	Meter Room Door	Meter rooms on upper floors shall not open into staircase enclosures and should be ventilated directly to open air outside or in electrical room of 120 min Fire resistant walls.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.11	Electrical Services Room Door	The doors provided for the Service Room shall have Fire resistance of not less than 2 hours
Model Building-Bye-laws-2016	7.14.f	Electrical Service Room Door	An independent and well-ventilated service room shall be provided on the ground floor with direct access from outside or from the corridor for the purpose of termination of electrical supply from the licenses service and alternative supply cables. The doors provided for the service room shall have Fire resistance of not less than 1 hour
NBC-2016	3.4.6.3	Substation / Transformers Room Door	An independent, ventilated or air conditioned MV panel room shall be provided on the ground level or first basement. This room shall be provided with access from outside (or through exit passageway accessible from outside). The MV panel room shall be provided with Fire resistant walls and doors of Fire resistance of not less than 120 min.
NBC-2016	3.4.6.3.2	Dry type Substation Door	Transformers located inside a building shall be of dry type and all substation/switch room walls, ceiling, floor, opening including doors shall have a Fire resistance rating of 120 min. Access to the substation shall be provided from the nearest Fire exit/exit staircase for the purpose of electrical isolation.
Model Building-Bye-laws-2016	7.19.37	Sub Station Door	Exits from basement electric substation shall have self-closing Fire smoke check doors of 2-hours Fire rating near entry to ramp
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.23	Outside Sub-Stations Door	The outside walls, ceiling and floor including doors and windows to the sub-station area shall be of 2 hours Fire rating.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.23	Inside Sub-Stations door	Oil Filled Equipment at Basement: A sub-station or a switch-station with oil- filled equipment must not be located in the building. When housed inside the building, The transformer shall be of premises by walls/doors/cut outs having Fire Resistance rating of 4 hours.
IEC	IEC 61936-1	Electrical Room / Sub Switching Room Door	Doors shall have a Fire resistance of at least 60 minutes. The doors of switchgear cubicles or bays should close in the direction of escape. Doors which open to the outside are adequate if they are of Fire-retardant material and construction. Ventilation openings necessary for the operation of the transformers are permitted. When designing the openings, the possible escape of hot gases shall be considered.
NEC	110.31	Electrical Room Door	Each doorway leading into a vault from the building interior shall be provided with a tight-fitting door that has a minimum Fire rating of 3 hours. Doors shall be equipped with locks, and doors shall be kept locked, with access allowed only to qualified persons. Personnel doors shall swing out and be equipped with panic bars, pressure plates, or other devices that are normally latched but that open under simple pressure.
NEC	110.31	Electrical Room Wall & Roof	The walls and roof shall be constructed of a minimum Fire rating of 3 hours. For the purpose of this section, studs and wallboard construction shall not be permitted.
NBC-2016	3.4.6.3.1	Oil filled substation Fire Barrier Wall	Substation equipment (exceeding oil capacity of 2000 litre) in utility building shall have Fire rated baffle walls of 240 min rating constructed between such equipment, raised to at least 600 mm above the height of the equipment (including height of oil conservators) and exceeding 300 mm on each side of the equipment.
NBC-2016	3.4.6.3	Electrical Panel Fire Protection	Electrical MV main distribution panel and lift panels shall be provided with CO2 /inert gas flooding system for all panel compartments with a cylinder located beside the panel
NFPA	NFPA 850	Outdoor Sub Station Fire Barrier Wall	OUTDOOR: Oil-insulated outdoor type transformer containing 1890 liters or more of oil. It is strongly recommended that any  is separated from nearby structures by a 2-hour–rated Firewall
NFPA	NFPA 850	Indoor Sub Station Fire Barrier Wall	INDOOR : oil-insulated transformer. In case however, an oil-insulated transformer is installed indoors, then if its oil content exceeds 379 Liters, then it should be separated from nearby areas by a Fire barrier of 3-hour Fire resistance rating.
NFPA	NFPA 850	Indoor Sub Station Fire Barrier Wall	INDOOR: oil-insulated transformer. In case an automatic Fire extinguishment system is installed, then it is allowed that the Fire resistance rating of the Fire barrier is reduced to 1 hour.
Central Electricity Authority	46.2.10.b	Transformer Room Wall	the direct access to the transformer room be provided from outside and the surrounding walls of 4-hours fire withstand rating be provided as per relevant standards
Central Electricity Authority	46.2.10.c	Transformer Room Door	the entrances to the transformer room be provided with fire resistant doors of 2- hour fire rating and the door shall always be kept closed and a notice of this effect be affixed on outer side of the door.
NBC-2016	3.4.6.3.1	Transformer Fire Protection (Water Spray )	All transformers where capacity exceeds 10 MVA shall be protected by high velocity water spray systems or nitrogen injection system
NBC-2016	3.4.6.4	Disel Generator Room Door	Standby supply Diesel generator set(s)shall not be installed at any floor other than ground/first basement. If the same are installed indoors, proper ventilation and exhaust shall be planned. The DG set room shall be separated by 120 min Fire resistance rated walls and doors.
NBC-2016	3.4.12	Fire Command Centre (FCC) Door	Fire command center shall be constructed with 120 min rating walls with a Fire door.
NBC-2016	5.1.2.2.(c)	Fire Fighting Pump house Door	Pump house shall be separated by Fire walls all around and doors shall be protected by Fire doors of 120 min rating.
NBC-2016	5.1.2.2.(b)	Fire Fighting Pump house	Pump house shall be installed not lower than the second basement. When installed in the basement, staircase with direct accessibility (or through enclosed passageway with 120 min Fire rating) from the ground, shall be provided. Access to the pump room shall not require to negotiate through other occupancies within the basement.
NBC-2016	3.4.9.2.1.(a)	Boiler Room Wall	The boilers shall be installed in a Fire resisting room of 180 min Fire resistance rating.
NBC-2016	3.4.9.2.1.(b)	Boiler Room Door	Entry to this room shall be provided with a composite door of 120 min Fire resistance rating.
NBC-2016	3.4.9.2.1.(c)	Mechanical ventilation system for Boiler rooms	The boiler room shall be provided with its dedicated natural or mechanical ventilation system. Mechanical ventilation system for the boiler room would be accepted with 120 min Fire resistance rating ductwork, if it has interface with other mechanical areas. Ventilation system should not be allowed to be routed through electrical room area or through exit corridor/exits
NBC-2016	3.4.8.1	Air conditioning and mechanical ventilation Room Wall	Wherever batteries are provided, the same shall be segregated by 120 min Fire rated construction. Ventilation to the room shall be provided as per manufacturer instructions.
NBC-2016	3.4.8.2.2	Air conditioning Shafts or ducts Sealing	Shafts or ducts, if penetrating multiple floors, shall be of masonry construction with Fire damper in connecting ductwork or shall have Fire rated ductwork with Fire dampers at floor crossing. Alternatively, the duct and equipment may be installed in room having walls, doors and Fire damper in duct exiting/entering the room of 120 min Fire resistance rating. Such shafts and ducts shall have all passive Fire control meeting 120 min Fire resistance rating requirement to meet the objective of isolation of the floor from spread of Fire to upper and lower floors through shaft/duct work.
NBC-2016	3.4.8.3.3	Air conditioning ducts Crossing on Wall Sealing	Wherever the ducts pass through Fire walls or floors, the opening around the ducts shall be sealed with materials having Fire resistance rating of the compartment. Such duct shall also be provided with Fire dampers at all Fire walls and floors unless such ducts are required to perform for Fire safety operation; and in such case Fire damper may be avoided at Fire wall and floor while integrity of the duct shall be maintained with 120 min Fire resistance rating to allow the emergency operations for Fire safety requirements
NBC-2016	3.4.8.3.4	Air conditioning ducts work within Fire Compartment	The ducting within compartment would require minimum Fire resistance rating of 30 min. Such ducting material in substantial gauge shall be in accordance with good practice. If such duct crosses adjacent compartment/floor and not having Fire dampers in such compartment/floor, it would require Fire resistance duct work rating of 120 min. The requirements of support of the duct shall meet its functional time requirement as above.
Model Building-Bye-laws-2016	7.16.1.c	Air Conditioning Duct Sealing	Wherever the ducts pass through Fire walls or floor, the opening around the ducts should be sealed with Fire resisting material of same rating as of walls / floors.
NBC-2016	3.4.8.4.1	Fire or Fire/smoke dampers	The dampers shall be evaluated to be located in supply air ducts, fresh air and return air ducts/ passages at the following points: (a) At the Fire separation wall, (b) Where ducts/passages enter the vertical shaft, (c) Where the ducts pass through floors, and d) At the inlet of supply air duct and the return air duct of each compartment on every floor.
NBC-2016	4.6.1	Smoke Exhaust Fan	The smoke exhaust fans in the mechanical ventilation system shall be Fire rated, that is, 250°C for 120 min
NBC-2016	4.6.2	Supply Air & Exhaust Air	All supply air and exhaust air fans on respective levels shall be installed in Fire resisting room of 120 min.
NBC-2016	4.6.2	Smoke Exhaust Fan	The smoke exhaust fans in the mechanical ventilation system shall be Fire rated, that is, 250°C for 120 min.
NBC-2016	4.6.2	Jet Fans	The smoke ventilation of the basement car parking areas. Jet Fans shall be Fire rated, that is, 250°C for 120 min.
NBC-2016	3.4.10.2	Glass facade	All gaps between floor-slabs and facade assembly shall be sealed at all levels by approved Fire resistant sealant material of equal Fire rating as that of floor slab to prevent Fire and smoke propagation from one floor to another
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.33	Glass facades	Glass facade for high rise building shall be of 1 hour Fire resistance.
NBC-2016	3.4.5.6	Floor’s Vertical opening Sealing	Every vertical opening between the floors of a building shall be suitably enclosed or protected, as necessary, to provide the following: Reasonable safety to the occupants while using the means of egress by preventing spread of Fire, smoke, or fumes through vertical openings from floor to floor to allow occupants to complete their use of the means of egress.
NBC-2016	4.8	Hazardous Areas (Gaseous, Oil Storage Yard ) Wall	Machinery, transformers or other service equipment subject to possible explosion shall not be located directly under or adjacent to exits. All such rooms shall be effectively cut-off from other parts of the building and shall be provided with adequate vents to the outside air. All rooms or areas of high hazard in additions to those hereinbefore mentioned, shall be segregated or shall be protected with Fire resistant walls having Fire rating of 120 min as Fire, explosion or smoke therefrom is likely to interfere with safe egress from the building.
NBC-2016	3.4.5.5	Refuse chutes Wall	If any provided in a building, shall have opening at least 1 meter above roof level for venting purpose and they shall have an enclosure wall of non-combustible material with Fire resistance of not less than 120 min.
NBC-2016	3.4.5.5	Refuse chutes Door	Refuse chutes inspection panel and doors shall be tight fitting with 60 min Fire resistance. Sprinkler protection system shall be provided for the refuse chutes. Refuse chutes shall be at least 6 meter away from exits.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.2	Refuse Cute Door	Refuse chutes shall have opening at least 1 m above roof level for venting purpose and they shall have an enclosure wall of non-combustible material with Fire resistance of not less than 2 hours. Inspection panel and doors shall be tight fitting with 1 hour Fire resistance.
NBC-2016	6.1.1.3 Subdivision A-4	Residential Buildings (Group A) Staircase Door	In case of high rise apartments, of the minimum exits as specified, the naturally ventilated exit staircases may not require the provision of Fire door. However, Fire door shall be provided for all other staircases and pressurized staircases. Panic bars shall be provided in the Fire exits. Panic  bars  shall  be  located  at  a  height between 865 mm and 1220 mm from the floor level.
NBC-2016	6.1.2.(d)	Residential Buildings (Group A) Storage Door	Stores, engineering workshops, areas of high hazard, etc used for storage of substantial amount of flammable liquids shall be of 120 min Fire resistance rating wall. Such areas shall be provided with Fire doors, to be kept closed and shall be posted with a sign on each side of the door in 25 mm high block letters stating FIRE DOOR  KEEP CLOSED.
NBC-2016	6.3	Institutional Buildings (Group C)	All compartments shall be divided with self closing (door closers) Fire doors with electromagnetic hold open. A coordinator shall be provided to sequence the closing of double leaf in case of emergency.
NBC-2016	6.3.g.6	Hospitals All Rooms Door	Operation  theatres,  delivery  rooms, Intensive care units, recovery rooms, etc, that  containing  patients  lacking  self-preservation in case of emergencies shall be  Fire/smoke  separated  (120  min minimum rating) from all the adjoining areas.
NBC-2016	6.3.g.12	Hospitals Corridor Exit Door	Exit access corridors from a compartment to another compartment shall be divided at the compartment intersection by a Fire door of 120 min Fire rating in the Fire compartment wall.
NBC-2016	6.3.g.13	Hospitals Laboratory Door	Rooms designated for laboratory and the like shall not exceed 100 m2 in area and if  additional  space  is  required,  Fire separation of 120 min shall be provided
NBC-2016	4.6.1	Corridors Exist Door in Hospital	Exit access corridors of guest rooms and indoor patient department/areas having patients lacking self-preservation and for sleeping accommodations such as apartments, custodial, penal and mental institutions, etc, shall be provided with 60 min Fire resistant wall and 20 min self-closing Fire doors along with all Fire stop sealing of penetrations.
NBC-2016	7.1.1.(c)	Lift Wall	Buildings of Height 15 m and Above: Walls of the lift bank well enclosure for a lift or group of lifts shall have a Fire rating of 120 min.
Model Building-Bye-laws-2016	7.10.1.a	Lift Wall	Walls of lift enclosures shall have a Fire rating of 120 min.
NBC-2016	7.1.1.(d)	Lift Landing doors	Buildings of Height 15 m and Above: Lift landing doors shall be imperforate. Collapsible doors shall not be permitted. Lift landing doors provided in the lift enclosure shall have a minimum Fire resistance rating of 60 min.
Model Building-Bye-laws-2016	7.10.1.c	Lift Landing doors	Landing door in lift enclosures shall have a Fire resistance of not less than 1 hour.
Model Building-Bye-laws-2016	7.10.1.e	Lift Car Door	Lift car door shall have a Fire resistance rating of 1 hour.
NBC-2016	6.1.1	Lift Well Enclosure Wall	Totally enclosed Lift Well shall be 120 min Fire-resistant.
Model Building-Bye-laws-2016	7.10.1.h	Lift Lobby Exit / Lift Enclosure Door	Exit from the lift lobby, if located in the core of the building, shall be through a self-closing Fire smoke check door of 1 hour Fire resistance.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.5	Lift Lobby / Staircase Exit Door	Fire doors with 2-hour Fire resistance shall be provided at appropriate places along the escape route and particularly at the entrance to lift lobby and stairwell where a funnel or flue effect may be created, inducing an upward spread of Fire and smoke.
NBC-2016	4.2.7	Non Ventilated Area’s Exit Door	For non-naturally ventilated areas, Fire doors with120 min Fire resistance rating shall be provided and particularly at the entrance to lift lobby and stair well where a ‘funnel or flue effect’ may be created, inducing an upward spread of Fire, to prevent spread of Fire and smoke.
NBC-2016	4.2.19	Direct  Basement Exit Door	Where basement is used for car parking and also there is direct approach from any occupancy above to the basement, door openings leading to the basement shall need to be protected with Fire doors with 120 min Fire rating, except for exit discharge doors from the basements.
NBC-2016	4.4.2.4.3.2	Internal staircases Door	Internal stairs shall be constructed of non-combustible materials throughout, and shall have Fire resistant rating of minimum 120 min.
NBC-2016	4.4.2.4.3.4	External staircases Door	The external stairs shall be constructed of non-combustible materials, and any doorway leading to it shall have minimum 120 min Fire resistance.
NBC-2016	4.4.2.5 (g)	Pressurized Staircase Wall	Wherever pressurized staircase is to be connected to unpressurized area, the two areas shall be segregated by 120 min Fire resistant wall.
NBC-2016	4.6.1	Exist Passage way Door	All exit passage way (from exit to exit discharge) shall be pressurized or naturally ventilated. The mechanical pressurization system shall be automatic in action with manual controls in addition. All such exit passageway shall be maintained with integrity for safe means of egress and evacuation. Doors provided in such exit passageway shall be Fire rated doors of 120 min rating.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.8	Internal /Additional Staircases Door	Around Lift Shaft: A staircase shall not be provided around a lift shaft unless provided with Fire stop door of 1 hour rating at every floor level and no other openings in the inside walls
Gujarat Fire Prevention and Life Safety Regulations, 2023	17 /18/19	Staircase Door	Buildings of Height more than 15 meters up to 70 meters: If the lifts and staircase from higher floors go directly to the basement then this area shall be protected by 1 hour Fire resistance construction including Fire doors subject to opinion and requirement of local Fire authority in specially designed building have to be considered and observed.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.5.3	External Stairs Door	The external stairs shall be constructed of non- combustible materials and any doorway leading to it shall have the required Fire resistance.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.5.4	Horizontal Exit Door	A horizontal exit shall be equipped with at least one Fire/smoke door of minimum 2-hour Fire resistance of self-closing type. Further, it should have direct connectivity to the Fire escape staircase for evacuation. horizontal exits shall be open able at all times from both side
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.28	Enclosed type Basement Staircase Door	The staircase of basements shall be of enclosed type having Fire resistance of not less than 2 hours and shall be situated at the periphery of the basement to be entered at ground level only from the open air and in such position that smoke from any Fire in the basement shall not obstruct any exit serving the ground and upper storey of the building.
Gujarat Fire Prevention and Life Safety Regulations, 2023	15.28	Enclosed type Basement Lift Lobby Door	Enclosed type Basement Lift lobby provided with Fire resisting self-closing doors of one hour resistance. If the travel distance exceeds the desired level, additional staircases shall be provided at proper places. The basement shall not open in to the staircase or lift well directly. If so then it has to be protected by 2 hours Fire resistant self-closing doors.
NBC-2016	4.4.2.4.1 (f)	Fire Certificate for Fire Door	All Fire rated doors and assembly shall be provided with certificate and labels prominently indicating the manufacturer identification, door details covering door type, serial/batch number, month and year of manufacture, Fire resistance rating, etc. The doors and assembly shall be certified with all prescribed hardware such as hinges, locks, panic bars, door closer, and door viewers.

Calculate Diesel Generator Protection Setting

Recommended Generator Protection are

Recommended Generator Protection
ANSI Code	Protection Function
27	Under Voltage
32	Reverse Power
37	Under Power
40	Loss of Excitation
46	Negative Phase Sequence /Un Balance Load
49T	Thermal Overload
50	Instantaneous Over Current
51	Time grade Over Current
51G	Earth Fault Time Overcurrent
50/51V	Voltage Restrained Overcurrent
59	Over voltage
60G	Fuse Failure Monitor
64S	Stator Earth Fault Protection
81	Under / Over Frequency
87	Three Phase Current Differential
87N	Neutral Current Differential
87G	Generator Differential Protection
24G	Over excitation (Volt/Hertz) Protection
21G	Impedance Protection
59N or 64G1	Stator EF protection (0-95%)
27TN or 64G2	Stator EF protection (100%)
50BF	Breaker Failure Protection
24G	Over excitation (Volt/Hertz) Protection
78G	Pole slip protection

Protection Setting Calculation:

(1) Under Voltage Relay (27):

• The Under Voltage Relay measure either phase-to-phase (Ph-Ph) or phase-to-neutral (Ph-N) fundamental RMS voltage depending on the input voltage setting. If the value of measured voltages deviates from the setting values, then these relays will give a trip indication.
• Reason:
• An under-voltage condition in a diesel generator can occur due to several reasons, overloading the generator beyond its capacity, faulty Automatic Voltage Regulator (AVR), issues with the stator windings, problems with the voltage sampling line, loose connections, low engine speed, fuel problems, and issues with the excitation system
• Setting:
• The Typical under-voltage setting is usually 80 % of the normal rated voltage. If the voltage falls below this level for the set amount of time, then the tripping command is issued by the relay and hence the system is isolated. The time setting is used to avoid tripping due to any transient disturbances. the exact setting can vary depending on the specific generator and system requirements.
• Usually, motors stall at below 80% of their rated voltage. An under-voltage element can be set to trip motor circuits once fall below 80% so that on the restoration of supply an overload is not caused by the simultaneous starting of all the motors.
• Normally Generators are designed to operate continuously at minimum voltage of 95% of its rated voltage.
• Two levels of tripping are provided depending on the severity of the condition, these under voltage elements are blocked from tripping when the generator breaker is open to allow for startup conditions.
• Calculation:
• For 415V Diesel Generator
• Level 1 (Slow)= 80% of Rated Voltage
• Level 1 (Slow)= 80% x 415V =332 V
• Time Delay = 5 sec.
• Level 2 (Fast): 70% of Rated Voltage
• Level 2 (Fast)= 70% x 415V =290 V
• Time Delay = 0 sec.

(2) Over Voltage Protection [59]:

• The Over Voltage Relay measure either phase-to-phase (Ph-Ph) or phase-to-neutral (Ph-N) fundamental RMS voltage depending on the input voltage setting. If the value of measured voltages deviates from the setting values, then these relays will give a trip indication.
• Reason:
• System over voltages can damage the insulation of components. Over voltages occur due to sudden loss of load, improper working of tap changer, Generator AVR malfunction, Reactive component malfunctions, etc.
• Setting:
• The Overvoltage setting is usually 110 to 130 % of the normal operating voltage depending on the system requirement.
• If the voltage rises above this level for the set amount of time then the tripping command issued by the relay and hence the system is isolated. The time setting is used to avoid tripping due to any transient disturbances.
• Calculation:
• For 415V Diesel Generator
• Level 1 (Slow)= 110% of Rated Voltage
• Level 1 (Slow)= 110% x 415V =456 V
• Time Delay = 5 sec.
• Level 2 (Fast): 130% of Rated Voltage
• Level 2 (Fast)= 130% x 415V =539 V
• Time Delay = 0 sec.

(3) Reverse Power Protection [32R]:

• Reverse power relay is an electronic, microprocessors-based protection device which is used for monitoring and stopping the power supply flowing grid side to the DG side or generator running in parallel with another generator. If accidentally leakage current is received by generator, then it can start to running as motor. This situation may be very dangerous for generator set.
• The function of the reverse power relay is to prevent a reverse power condition in which power flows from the bus bar into the generator.
• This condition can occur when there is a failure in the prime mover such as an engine or a turbine which drives the generator.
• Relay detects the reverse flow of power from the load back to the generator, which can occur during system faults or abnormal operating conditions. By sensing this reverse power flow, the relay triggers a protective action, typically disconnecting the generator to prevent further issues.
• The generator are classified by their Prime Mover which determine the amount of Reverse power they can motor.

Sr. No	Prime Mover	Motorizing Power in % of Unit Rating
1	Gas Turbine (single shaft)	100%
2	Gas Turbine (Double Shaft)	10-15%
3	4 Cycle Diesel	15%
4	2 Cycle Diesel	25%
5	Hydraulic Turbine	2-100
6	Steam Turbine (Conventional)	1-4%
7	Steam Turbine (Cond Cooled)	0.5 to 1.0%

• Reason:
• When Two or more unit running in parallel
• In LT panel if the DG supply is running then grid supply should be switched off and if the grid supply is running then DG supply should be switched off. When one source is on then second source accidentals starts to leakage current resultant a large fault may be occurred and system can be failed. So, for prevention of other source leakage the RPR relay is used.
• Failure of Speed controller or another breakdown. When the prime mover of a generator running in a synchronized condition fails. There is a condition known as motoring, where the generator draws power from the bus bar, runs as a motor and drives the prime mover. This happens as in a synchronized condition all the generators will have the same frequency. Any drop in frequency in one generator will cause the other power sources to pump power into the generator. The flow of power in the reverse direction is known as the reverse power relay.
• If the frequency of the machine to be synchronized is slightly lesser than the bus bar frequency and the breaker is closed, power will flow from the bus bar to the machine. Hence, during synchronization(forward), frequency of the incoming machine is kept slight higher than that of the bus bar i.e. the synchroscope is made to rotate in the “Too fast” direction. This ensures that the machine takes on load as soon as the breaker is closed.
• Loss of excitation:
• Failure of AVR
• Setting:
• A generator reverse power relay setting is typically set between 2% to 8% of the generator’s rated power, depending on the type of prime mover (like a diesel engine or steam turbine), with diesel engines generally requiring a higher setting (around 8%) compared to turbines (around 2 to 5%) to prevent unnecessary tripping during transient conditions; this setting essentially determines the threshold at which the relay will activate to protect the generator from reverse power flow, which can damage the machine if it becomes too significant. 
• Calculation:
• Generator capacity :500KVA ,415V,0.9 Power factor
• Full Load Current =500×1000/(1.732*415)
• Full Load Current =695A
• Setting at 5%
• Reverse Power = -5%*500*0.9 = -22.5KW
• Relay Setting= Reverse Power / Real Power =-22.5 / 500 =-4.50%
• Relay Setting =-4.50%
• Time delay proposed=5 sec

(4) Negative Phase Sequence (Unbalance Phase) Relay (46):

• The Negative Sequence Overcurrent function provides protection against possible rotor overheating and damage due to unbalanced faults or other system conditions which can cause unbalanced three phase currents in the generator.
• Negative Phase Sequence detects imbalances in the network that does not cause energy loss out of the system.
• Reason:
• Generator or Motor are design to operate in balance three phase loading.
• Generator negative phase sequence currents can result from any unbalance condition on the system including un transposed lines, single phase loads, unbalanced type line faults and open conductors. the unbalance condition leads negative sequence currents having opposite rotation that of power system in generator leads. This reversed rotating current produce double frequency current in rotor structure. This resulting over heating of rotor.
• Setting:
• A generator Negative Phase Sequence (NPS) relay setting is typically set between 2 to 10% of the full load current depending on the specific generator design and manufacturer’s recommendations, aiming to detect significant unbalances in the power system while avoiding unnecessary tripping due to normal load variations; this setting should be based on the generator’s maximum allowable negative sequence I² (current squared) value to prevent excessive rotor heating. 
• Generator withstand limit against negative sequence overcurrent (K) = 10 (As per IEC-60034-1)
• Normally Generator continuous withstand limit: 8 %
• Calculation:
• Generator capacity :500KVA ,415V , CT is 800/1
• Full Load Current =500×1000/(1.732*415)
• Full Load Current =695A
• Setting at 10% .
• Desired pickup current = 10% of rated current
• Relay setting = (0.1 x Rated Current) / CT ratio 
• Relay setting =(0.1×695) / 800
• Relay setting =0.0868A

(5) Thermal Overload Relay (49T):

• In general, generators can operate successfully at rated kVA, frequency, and power factor for a voltage variation of 5% above or below rated voltage. Under emergency condition, it is possible to exceed the continuous output capability for a short time.
• The stator overload function provides protection against possible damage during overload conditions.
• Reason:
• A generator becomes overloaded when too many appliances or devices are plugged in and drawing power simultaneously, exceeding the generator’s rated capacity, often happening when attempting to power heavy appliances like air conditioners, heaters, or electric stoves at the same time; essentially, drawing more power than the generator can supply. 
• Peak usage times: Running multiple high-power appliances simultaneously. 
• Damaged components: Faulty electrical components within the generator can contribute to overload issues. 
• Improper load management: Not prioritizing which appliances to run on the generator. 
• Adding new equipment: Plugging in additional appliances without considering the generator’s capacity. 
• Setting:
• A generator thermal overload relay setting is typically based on a percentage of the motor’s full load current.
• Common settings are:
• For motors with Service Factor (SF) ≥ 1.15, Set to 125% of FLA.
• For motors with Service Factor (SF) < 1.15, Set to 115% of FLA
• As per IEEE Generator short time thermal capability for balanced three-phase loading diagram (Short time capability curve) the wining will withstand 117% rated current for 120 second.
• Calculation:
• Generator capacity :500KVA ,415V , CT is 800/1
• Full Load Current =500×1000/(1.732*415)
• Full Load Current =695A
• Setting at 117% .
• Desired pickup current = 117% of rated current
• Relay setting = (1.17 x Rated Current) / CT ratio 
• Relay setting =(1.17×695) / 800
• Relay setting =1.016A

(6) Generator Under Frequency Protection (81 G):

• Prevents the steam turbine and generator from exceeding the permissible operating time at reduced frequencies.
• Ensures that the generating unit is separated from the network at a preset value of frequency.
• Prevent over fluxing (v/f) of the generator (large over fluxing for short times).
• The stator under frequency relay measures the frequency of the stator terminal voltage.
• Setting Recommendations:
• within 0.2 to 0.5Hz below the nominal frequency
• For Alarm: 48.0 Hz, 2.0 Sec. time delay. 
• For Trip: 47.5 Hz, 1.0 Sec. or as recommended by Generator Manufacturers.

(7) Instantaneous Over Current Relay (50):

• Instantaneous overcurrent protection is where a protective relay initiates a breaker trip based on current exceeding a pre-programmed “pickup” value for any length of time. 
• Setting:
• A generator phase instantaneous overcurrent relay setting is typically set between 2 to 1.5 times the full load current (FLA) of the generator, ensuring quick tripping in case of a severe fault while avoiding unnecessary trips due to momentary current surges during starting or load fluctuations; this setting is usually referred to as the “pickup current” of the relay. 
• This is back up protection for Generator. To avoid unnecessary trip of the generator we recommend making OFF this function in generator protection.
• Calculation:
• Generator full Load Current = 130A & CT is 300/5 =60
• Setting =1.5 times of Full Load Current
• Setting= 1.5×130 =195A
• 51 Current Setting = Setting / CT Ratio = 195/60 =3.25A.
• Time setting =5 Second.
• The proposed above setting is coordinated with other O/C protection setting.

(8) Time grade Over Current Relay (51):

• Time overcurrent protection is where a protective relay initiates a breaker trip based on the combination of overcurrent magnitude and overcurrent duration, the relay tripping sooner with greater current magnitude. This is a more sophisticated form of overcurrent protection than instantaneous.
• Setting:
• This is back-up protection of the generator, for better time gradings the overcurrent setting should be co-ordinate with load connected feeder overcurrent setting.
• A generator Phase Overcurrent (51) setting is typically set between 125% and 150% of the generator’s full load current, however, the exact setting depends on the specific application and should be coordinated with other system protections.
• Calculation:
• Generator full Load Current = 130A & CT is 300/5 =60
• Setting =150% of Full Load Current
• Setting= 1.5×130 =195A
• 51 Current Setting = Setting / CT Ratio = 195/60 =3.25A.
• Time setting =5 Second.
• The proposed above setting is coordinated with other O/C protection setting.

(9) Earth Fault Time Overcurrent (51G)

• This is back-up protection in Earth Fault of generator, for better time gradings the overcurrent setting should be co-ordinate with load connected feeder setting.
• Setting:
• Earth Fault Relay setting shall be 10 to 20 % Full Load Current
• Calculation:
• Generator full Load Current = 130A & CT is 300/5 =60
• Setting =20% of Full Load Current
• Setting= 0.2×130 =26A
• 51G Current Setting = Setting / CT Ratio = 26/60 =0.43A.
• Time setting =5 Second.
• The proposed above setting is coordinated with other O/C protection setting.

(9) Ground Differential (87 N)

• The ground differential element (87N) that operates based on the difference between the measured neutral current and the sum of the three-phase current inputs.
• The 87N element provides sensitive ground fault detection on resistance-grounded particularly where multiple generators are connected directly to a load bus.
• The relay provides two definite-time delayed ground current differential elements designed to detect ground faults on resistance grounded generator.
• The relay uses the neutral CT connected to the relay input to measure the generator neutral current. It then calculates the residual current, which is the sum of the three phase current inputs (from CTs located at generator terminals).
• The relay adjusts the residual current by the ratio of the CTR and CTRN settings to scale the residual current in terms of the secondary neutral current. It then calculates the difference. Normally, under balanced load or external ground fault conditions, the difference current should be zero. In the event of an internal ground fault, the difference current is nonzero. If the difference current magnitude is greater than the element pickup setting, the element picks up and begins to operate the definite time-delay.
• Setting:
• Earth Fault Relay setting shall be 10 to 20 % Maximum Ground Fault Current
• Calculation:
• Generator grounded through 39.8 Ohms Resistance.
• Generator rated Voltage=13800V, Current 130A
• Maximum Earth Fault Current =(138000 / 1.732) / 39.8
• Maximum Earth Fault Current =7967.4 / 39.8
• Maximum Earth Fault Current = 200 A
• 87N pickup current setting = 10% x 200 / CT Ratio
• 87N pickup current setting = 20 / 60
• 87N pickup current setting = 0.3
• 87N Time delay =0.2s

Calculate Earthing Strip Size for Electrical Equipment’s in Power Distribution Network

EXAMPLE:

Calculate Earthing Strip / Cable Size for Electrical Equipment’s / Panels in Power Distribution Networks.

• At RMU
• At Transformer
• At D.G Set
• At Main Distribution Panel
• At Sub Panel-1
• At Sub Panel-2

CALCULATION:

(1) Earthing Strip Size at RMU:

• Shot circuit capacity at RMU is 18.37 KA for 1 Second.
• Corrosion in Strip is 1% per year
• Earthing Strip shall be replaced after 25 Years.
• Safety Factor for Strip is 1.5
• Earthing Strip Material is GI

Calculation

• As per IS: 3043, clause 17.2.2.1:
• Cross section area of Earthing Strip (A) =(Isc x√t)/k
• Where Isc= Shot circuit current capacity in Ampere.
• t= Time for Shot circuit current in Second.
• K= Material Constant

Bare Conductor Material with No Risk of Fire or Danger to any Other Touching or Surrounding Material
TABLE 11A (IS:3043)
Material	K value (1 second)	K value (2 second)
Steel	80	46
Aluminum	126	73
Copper	205	118

• Cross section area of Earthing Strip (A) = (Isc x√t)/k
• Cross section area of Earthing Strip (A) = (18.37×1000 x√1)/80
• Cross section area of Earthing Strip (A) = 229.69 Sq.mm
• Allowable corrosion =1% per Year
• No of Year for replacement = 25 Year
• Allowable corrosion in 25 Years = 229.69x1x25% =57.40 Sq.mm
• Allowable Safety Factor = 229.69×1.5%=3.44 Sq.mm
• Required Earthing Strip size = Cross sectional area + Total Corrosion allowance + Safety factor
• Required Earthing Strip size=229.69+57.40+3.44 Sq.mm
• Required Earthing Strip size=290.47 Sq.mm
• Proposed GI Earthing Strip shall be 50×6 mm = 300 Sq.mm.
• Here Proposed Earthing Strip Size > Required Earthing Strip Size
• Proposed Earthing Strip is OK

(2) Earthing Strip Size at Transformer:

• Shot circuit capacity at Transformer is 25.32 KA for 1 Second.
• Corrosion in Strip is 1% per year
• Earthing Strip shall be replaced after 25 Years.
• Safety Factor for Strip is 1.5
• Earthing Strip Material for Transformer Neutral is Copper
• Earthing Strip Material for Transformer Body is GI

Calculation

• For Neutral
• As per IS: 3043, clause 17.2.2.1:
• Cross section area of Earthing Strip (A) =(Isc x√t)/k
• Where Isc= Shot circuit current capacity in Ampere.
• t= Time for Shot circuit current in Second.
• K= Material Constant

Bare Conductor Material with No Risk of Fire or Danger to any Other Touching or Surrounding Material
TABLE 11A (IS:3043)
Material	K value (1 second)	K value (2 second)
Steel	80	46
Aluminum	126	73
Copper	205	118

• Cross section area of Earthing Strip (A) = (Isc x√t)/k
• Cross section area of Earthing Strip (A) = (25.32×1000 x√1)/205
• Cross section area of Earthing Strip (A) = 125.51 Sq.mm
• Allowable corrosion =1% per Year
• No of Year for replacement = 25 Year
• Allowable corrosion in 25 Years = 125.51 x1x25% =30.87 Sq.mm
• Allowable Safety Factor = 125.51 x1.5%=1.85 Sq.mm
• Required Earthing Strip size = Cross sectional area + Total Corrosion allowance + Safety factor
• Required Earthing Strip size=125.51+30.87+1.85 Sq.mm
• Required Earthing Strip size=156.24 Sq.mm
• Proposed Cu Earthing Strip shall be 32×6 mm = 192 Sq.mm.
• Here Proposed Earthing Strip Size > Required Earthing Strip Size
• Proposed Earthing Strip is OK
• For Body
• As per IS: 3043, clause 17.2.2.1:
• Cross section area of Earthing Strip (A) =(Isc x√t)/k
• Where Isc= Shot circuit current capacity in Ampere.
• t= Time for Shot circuit current in Second.
• K= Material Constant

Bare Conductor Material with No Risk of Fire or Danger to any Other Touching or Surrounding Material
TABLE 11A (IS:3043)
Material	K value (1 second)	K value (2 second)
Steel	80	46
Aluminum	126	73
Copper	205	118

• Cross section area of Earthing Strip (A) = (Isc x√t)/k
• Cross section area of Earthing Strip (A) = (25.32 x1000 x√1)/80
• Cross section area of Earthing Strip (A) = 316.5 Sq.mm
• Allowable corrosion =1% per Year
• No of Year for replacement = 25 Year
• Allowable corrosion in 25 Years = 316.5 x1x25% =79.12 Sq.mm
• Allowable Safety Factor = 316.5 x1.5%=4.74 Sq.mm
• Required Earthing Strip size = Cross sectional area + Total Corrosion allowance + Safety factor
• Required Earthing Strip size=316.5+79.12+4.74 Sq.mm
• Required Earthing Strip size=400.37 Sq.mm
• Proposed GI Earthing Strip shall be 75×6 mm = 450 Sq.mm.
• Here Proposed Earthing Strip Size > Required Earthing Strip Size
• Proposed Earthing Strip is OK

(3) Earthing Cable Size at D.G Set:

• Shot circuit capacity at D.G Set is 10KA for 1 Second.
• Corrosion in Strip is 1% per year
• Earthing Strip shall be replaced after 25 Years.
• Safety Factor for Strip is 1.5
• Earthing Wire Material is Copper, XLPE Insulated

Calculation

• As per IS: 3043, clause 17.2.2.1:
• Cross section area of Earthing Strip (A) =(Isc x√t)/k
• Where Isc= Shot circuit current capacity in Ampere.
• t= Time for Shot circuit current in Second.
• K= Material Constant

Insulated Protective Conductors Not Incorporated in Cables or Bare Conductors Touching Other Insulated Cables
TABLE 11B (IS:3043)
Material	K value (1 second)	K value (3 second)
Copper , PVC Insulated	136	79
Copper, Rubber Insulated	150	92
Copper, XLPE Insulated	170	98
Aluminum, PVC Insulated	90	52
Aluminum, Rubber Insulated	106	61
Aluminum, XLPE Insulated	112	65
Steel, PVC Insulated	49	28
Steel, Rubber Insulated	58	33
Steel, XLPE Insulated	62	36

• Cross section area of Earthing Strip (A) = (Isc x√t)/k
• Cross section area of Earthing Strip (A) = (10×1000 x√1)/170
• Cross section area of Earthing Strip (A) = 58.82 Sq.mm
• Allowable corrosion =1% per Year
• No of Year for replacement = 25 Year
• Allowable corrosion in 25 Years = 58.82x1x25% =14.70 Sq.mm
• Allowable Safety Factor = 58.82 x1.5%=0.88 Sq.mm
• Required Earthing Strip size = Cross sectional area + Total Corrosion allowance + Safety factor
• Required Earthing Strip size=58.82+14.7+0.88 Sq.mm
• Required Earthing Strip size=74.41 Sq.mm
• Proposed Earthing Single Core Copper, XLPE Cable=95 Sq.mm
• Here Proposed Earthing Cable Size > Required Earthing Cable Size
• Proposed Earthing Cable is OK

(4) Earthing Strip Size at Main Panel :

• Shot circuit capacity at Main Panel is 21 KA for 1 Second.
• Corrosion in Strip is 1% per year
• Earthing Strip shall be replaced after 25 Years.
• Safety Factor for Strip is 1.5
• Earthing Strip Material is GI

Calculation

• As per IS: 3043, clause 17.2.2.1:
• Cross section area of Earthing Strip (A) =(Isc x√t)/k
• Where Isc= Shot circuit current capacity in Ampere.
• t= Time for Shot circuit current in Second.
• K= Material Constant

Bare Conductor Material with No Risk of Fire or Danger to any Other Touching or Surrounding Material
TABLE 11A (IS:3043)
Material	K value (1 second)	K value (2 second)
Steel	80	46
Aluminum	126	73
Copper	205	118

• Cross section area of Earthing Strip (A) = (Isc x√t)/k
• Cross section area of Earthing Strip (A) = (21 x1000 x√1)/80
• Cross section area of Earthing Strip (A) = 262.5 Sq.mm
• Allowable corrosion =1% per Year
• No of Year for replacement = 25 Year
• Allowable corrosion in 25 Years = 262.5 x1x25% =65.62 Sq.mm
• Allowable Safety Factor = 262.5 x1.5%=3.93 Sq.mm
• Required Earthing Strip size = Cross sectional area + Total Corrosion allowance + Safety factor
• Required Earthing Strip size=262.5+65.62+3.93 Sq.mm
• Required Earthing Strip size=332.06 Sq.mm
• Proposed GI Earthing Strip shall be 75×6 mm = 450 Sq.mm.
• Here Proposed Earthing Strip Size > Required Earthing Strip Size
• Proposed Earthing Strip is OK

(5) Earthing Strip Size at Sub Panel-1 :

• Shot circuit capacity at Sub Panel-1 is 11 KA for 1 Second.
• Corrosion in Strip is 1% per year
• Earthing Strip shall be replaced after 25 Years.
• Safety Factor for Strip is 1.5
• Earthing Strip Material is GI

Calculation

• As per IS: 3043, clause 17.2.2.1:
• Cross section area of Earthing Strip (A) =(Isc x√t)/k
• Where Isc= Shot circuit current capacity in Ampere.
• t= Time for Shot circuit current in Second.
• K= Material Constant

Bare Conductor Material with No Risk of Fire or Danger to any Other Touching or Surrounding Material
TABLE 11A (IS:3043)
Material	K value (1 second)	K value (2 second)
Steel	80	46
Aluminum	126	73
Copper	205	118

• Cross section area of Earthing Strip (A) = (Isc x√t)/k
• Cross section area of Earthing Strip (A) = (11 x1000 x√1)/80
• Cross section area of Earthing Strip (A) = 137.5 Sq.mm
• Allowable corrosion =1% per Year
• No of Year for replacement = 25 Year
• Allowable corrosion in 25 Years = 137.5 x1x25% =34.37 Sq.mm
• Allowable Safety Factor = 137.5 x1.5%=2.06 Sq.mm
• Required Earthing Strip size = Cross sectional area + Total Corrosion allowance + Safety factor
• Required Earthing Strip size=137.5+34.37+2.06 Sq.mm
• Required Earthing Strip size=173.93 Sq.mm
• Proposed GI Earthing Strip shall be 32×6 mm = 192 Sq.mm.
• Here Proposed Earthing Strip Size > Required Earthing Strip Size
• Proposed Earthing Strip is OK

(5) Earthing Strip Size at Sub Panel-2 :

• Shot circuit capacity at Sub Panel-2 is 6 KA for 1 Second.
• Corrosion in Strip is 1% per year
• Earthing Strip shall be replaced after 25 Years.
• Safety Factor for Strip is 1.5
• Earthing Strip Material is GI

Calculation

• As per IS: 3043, clause 17.2.2.1:
• Cross section area of Earthing Strip (A) =(Isc x√t)/k
• Where Isc= Shot circuit current capacity in Ampere.
• t= Time for Shot circuit current in Second.
• K= Material Constant

Bare Conductor Material with No Risk of Fire or Danger to any Other Touching or Surrounding Material
TABLE 11A (IS:3043)
Material	K value (1 second)	K value (2 second)
Steel	80	46
Aluminum	126	73
Copper	205	118

• Cross section area of Earthing Strip (A) = (Isc x√t)/k
• Cross section area of Earthing Strip (A) = (6 x1000 x√1)/80
• Cross section area of Earthing Strip (A) = 75.0 Sq.mm
• Allowable corrosion =1% per Year
• No of Year for replacement = 25 Year
• Allowable corrosion in 25 Years = 75 x1x25% =18.75 Sq.mm
• Allowable Safety Factor = 75 x1.5%=1.12 Sq.mm
• Required Earthing Strip size = Cross sectional area + Total Corrosion allowance + Safety factor
• Required Earthing Strip size=75+18.75+1.12 Sq.mm
• Required Earthing Strip size=94.87 Sq.mm
• Proposed GI Earthing Strip shall be 25×6 mm = 150 Sq.mm.
• Here Proposed Earthing Strip Size > Required Earthing Strip Size
• Proposed Earthing Strip is OK

CONCLUSION:

• At RMU=GI Earthing Strip: 50x6MM
• At Transformer Neutral=CU Earthing Strip: 32x6MM
• At Transformer Body=GI Earthing Strip: 75x6MM
• At D.G Set=CU, XLPE Earthing Cable: 1Cx95 SQ.MM
• At Main Distribution Panel=GI Earthing Strip: 75x6MM
• At Sub Panel=1=GI Earthing Strip: 32x6MM
• At Sub Panel-2=GI Earthing Strip: 25x6MM.

Calculate Short Circuit Current at Sub Panel (End user side)

EXAMPLE:

• Calculate short circuit current at Electrical Equipment Panel / Distribution Board at end user side.
• HT Power is received by 11KV RMU and given to 11/0.415KV,1000KVA Transformer by 1 no of 3Cx185 Sq.mm 11KV HT Cable of 25 Meter Length.
• Resistance and Reactance of HT cable are 0.21 Ώ / KM and 0.1 Ώ / KM
• Transformer impedance is 6.25%.
• LT Side of Transformer is connected to Main LT Panel by 8 no of 3.5Cx300 Sq.mm cable of 70 Meter.
• Resistance and Reactance of 3.5Cx300 Sq.mm, XLPE cable are 0.129 Ώ / KM and 0.071 Ώ / KM.
• Main LT Panel is connected to Sub Panel-1 by 1 no of 3.5Cx300 Sq.mm cable of 80 Meter.
• Resistance and Reactance of 3.5Cx300 Sq.mm, XLPE cable are 0.129 Ώ / KM and 0.071 Ώ / KM.
• Main LT Panel is connected to Sub Panel-2 by 1 no of 3.5Cx95 Sq.mm cable of 80 Meter.
• Resistance and Reactance of 3.5Cx95 Sq.mm, XLPE cable are 0.409 Ώ / KM and 0.072 Ώ / KM.
• Calculate Short circuit Current at Sub Panel-1 & Sub Panel-2.

CALCUALTION

• Short Circuit Current is calculated at various points of Power Distribution Networks, At Power Receiving Point (11KV), At Main Panel Point (0.415V) and At Sub Distribution Point (0.415V)

(1) SHORT CIRCUIT CURRENT AT 11 KV PANEL / RMU:

• Assume that 11KV Side System Fault MVA is 350 MVA.
• Shor Circuit Current at 11KV System = Fault MVA / 1.732 x System Voltage at Fault Point.
• Shor Circuit Current at 11KV System = 350 / 1.732 x 11.
• Shor Circuit Current at 11KV System = 18.37 KA.

 (2) SHORT CIRCUIT CURRENT AT TRANSFORMER:

• To calculate Short Circuit Current at Transformer Side, First We need to sum Impedance of the system up to Transformer (Impedance of HT Source +Impedance of HT Cable + Impedance of Transformer).
• Transformer Capacity is 1000 KVA
• Base MVA = TC Size / 1000
• Base MVA = 1000 / 1000
• Base MVA = 1 MVA or
• Base KVA = 1000 KVA
• % Impedance of Source = Base MVA x100 / System Fault MVA
• % Impedance of Source = 1 x100 / 350
• % Impedance of Source = 0.29 Ώ / KM.
• CALCULATE % RESISTANCE & REACTANCE OF CABLE ( 185 SQ.MM HT CABLE)
• % Resistance of Cable =Base KVA (TC Capacity) x Cable Resistance x No of Run x Length of Cable / (System Voltage in KV)²x10.
• % Resistance of Cable =1000 x 0.21 x 1 x 25 / 11x11x10
• % Resistance of Cable =0.004339 % Ώ
• % Reactance of Cable =Base KVA (TC Capacity) x Cable Reactance x No of Run x Length of Cable / (System Voltage in KV)²x10.
• % Reactance of Cable =1000 x 0.1 x 1 x 25 / 11x11x10
• % Reactance of Cable =0.002066 % Ώ
• % Impedance of Cable =√ R² + X²
• % Impedance of Cable =√ (0.004339) ² + (0.002066) ²
• % Impedance of Cable =0.00481 % Ώ.
• Considering 10% Tolerance in Transformer Impedance
• % Impedance of Transformer = Impedance of Transformer – 10% Variation of Transformer Impedance
• % Impedance of Transformer = 6.25 -(6.25X10%)
• % Impedance of Transformer =5.63 % Ώ.
• Total % Impedance up to Transformer = % Impedance of Source +%Cable Impedance + % Transformer Impedance
• Total % Impedance up to Transformer = 0.29+0.00481+5.63 % Ώ.
• Total % Impedance up to Transformer = 5.92% Ώ.
• Fault KVA on LT Side of Transformer = Base MVA of Transformer x100 / Total % Impedance up to Transformer.
• Fault KVA on LT Side of Transformer = 1 x100 / 5.92.
• Fault KVA on LT Side of Transformer = 16.9 KVA.
• Short Circuit Current at Transformer LT Side= Fault KVA / 1.732 x System Voltage at Fault Point.
• Short Circuit Current at Transformer LT Side= 16.9 / 1.732 x 0.415
• Short Circuit Current at Transformer LT Side= 25.32 KA

 (3) SHORT CIRCUIT CURRENT AT MAIN LT PANEL:

• To calculate Short Circuit Current at Main LT Panel, we need to sum Impedance of the system up to Main LT Panel (Total Impedance up to Transformer LT Side + Impedance of LT Cable).
• Total % Impedance up to Transformer LT Side= 5.92% Ώ.
• CALCULATE % RESISTANCE & REACTANCE OF CABLE (300 SQ.MM)
• % Resistance of Cable =Base KVA (TC Capacity) x Cable Resistance x Length of Cable / (System Voltage in KV)²x10.
• % Resistance of Cable =1000 x 0.129 x 1 x 70 / 0.415 x 0.415 x10
• % Resistance of Cable =0.66 % Ώ
• % Reactance of Cable =Base KVA (TC Capacity) x Cable Reactance x No of Run x Length of Cable / (System Voltage in KV)² x10.
• % Reactance of Cable =1000 x 0.071 x 8 x 70 / 0.415×0.415×10
• % Reactance of Cable =0.36 % Ώ
• % Impedance of Cable =√ R² + X²
• % Impedance of Cable =√ (0.66) ² + (0.36) ²
• % Impedance of Cable =0.747 % Ώ.——————————–(B)
• Total % Impedance up to Main LT Panel = % Impedance up Transformer +%Cable Impedance
• Total % Impedance up to Main LT Panel = = 5.92+0.747 % Ώ.
• Total % Impedance up to Main LT Panel = = 6.662% Ώ. ————————–(B)
• Fault KVA on Main LT Panel= Base MVA x100 / Total % Impedance.
• Fault KVA on LT Side of Transformer = 1 x100 / 6.662.
• Fault KVA on LT Side of Transformer = 15.01 KVA.
• Short Circuit Current at Main LT Panel = Fault KVA / 1.732 x System Voltage at Fault Point.
• Short Circuit Current at Main LT Panel = 15.01 / 1.732 x 0.415
• Short Circuit Current at Main LT Panel = 20.88 KA.
• Short Circuit Current at Main LT Panel = 21 KA

(4) SHORT CIRCUIT CURRENT AT SUB PANEL-1:

• To calculate Short Circuit Current at Sub Panel-1, We need to sum Total Impedance of the system up to Sub Panel-1 (Total Impedance up to Main LT Panel + Impedance of LT Cable-1).
• Total % Impedance up to Main LT Panel= 6.662 % Ώ. (Calculated as per (B))
• CALCULATE % RESISTANCE & REACTANCE OF CABLE-1 (300 SQ.MM)
• % Resistance of Cable =Base KVA (TC Capacity) x Cable Resistance x Length of Cable / (System Voltage in KV)²x10.
• % Resistance of Cable =1000 x 0.129 x 1 x 80 / 0.415 x 0.415 x10
• % Resistance of Cable =5.99 % Ώ
• % Reactance of Cable =Base KVA (TC Capacity) x Cable Reactance x No of Run x Length of Cable / (System Voltage in KV)² x10.
• % Reactance of Cable =1000 x 0.071 x 1 x 80 / 0.415×0.415×10
• % Reactance of Cable =3.27 % Ώ
• % Impedance of Cable =√ R² + X²
• % Impedance of Cable =√ (5.99) ² + (3.27) ²
• % Impedance of Cable =6.82 % Ώ.
• Total % Impedance up to Sub Panel-1 = % Impedance up Main LT Panel  +%Cable Impedance
• Total % Impedance = 5.92+6.82 % Ώ.
• Total % Impedance = 13.49% Ώ.
• Fault KVA on Sub Panel-1= Base MVA x100 / Total % Impedance.
• Fault KVA on Sub Panel-1 = 1 x100 / 13.49.
• Fault KVA on Sub Panel-1 = 7.41 KVA.
• Short Circuit Current at Sub Panel-1 = Fault KVA on Sub Panel-1 / 1.732 x System Voltage at Fault Point.
• Short Circuit Current at Sub Panel-1 = 7.41 / 1.732 x0.415.
• Short Circuit Current at Sub Panel-1 = 10.33 KA.
• Short Circuit Current at Sub Panel-1 = 11 KA

(5) SHORT CIRCUIT CURRENT AT SUB PANEL-2:

• To calculate Short Circuit Current at Sub Panel-2, We need to sum Total Impedance of the system up to Sub Panel-2 (Total Impedance up to Main LT Panel + Impedance of LT Cable-2).
• Total % Impedance up to Main LT Panel= 6.662 % Ώ. (Calculated as per (B))
• CALCULATE % RESISTANCE & REACTANCE OF CABLE-2 (95 SQ.MM)
• % Resistance of Cable =Base KVA (TC Capacity) x Cable Resistance x Length of Cable / (System Voltage in KV)²x10.
• % Resistance of Cable =1000 x 0.409 x 1 x 80 / 0.415 x 0.415×10
• % Resistance of Cable =19 % Ώ
• % Reactance of Cable =Base KVA (TC Capacity) x Cable Reactance x No of Run x Length of Cable / (System Voltage in KV)² x10.
• % Reactance of Cable =1000 x 0.072 x 1 x 80 / 0.415×0.415×10
• % Reactance of Cable =3.36 % Ώ
• % Impedance of Cable =√ R² + X²
• % Impedance of Cable =√ (19) ² + (3.36) ²
• % Impedance of Cable =19.294 % Ώ.
• Total % Impedance up to Sub Panel-2 = % Impedance up Main LT Panel +%Cable Impedance
• Total % Impedance up to Sub Panel-2 = 6.662+19.294 % Ώ.
• Total % Impedance up to Sub Panel-2 = 25.956% Ώ.
• Fault KVA on Sub Panel-2 = Base MVA x100 / Total % Impedance up to Sub Panel-2.
• Fault KVA on Sub Panel-2 = 1 x100 / 25.956.
• Fault KVA on Sub Panel-2 = 3.85 KVA.
• Short Circuit Current at Sub Panel-2 = Fault KVA on Sub Panel-2 / 1.732 x System Voltage at Fault Point.
• Short Circuit Current at Sub Panel = 3.85 / 1.732 x 415.
• Short Circuit Current at Sub Panel = 5.36 KA.
• Short Circuit Current at Sub Panel-2 = 6 KA

 CONCLUSION:

• Shor Circuit Current at 11KV System = 18.37 KA.
• Short Circuit Current at Transformer LT Side= 25.32 KA
• Short Circuit Current at Main LT Panel = 21 KA
• Short Circuit Current at Sub Panel-1 = 11 KA
• Short Circuit Current at Sub Panel-2 = 6 KA

Basic of External Lightning Protection System (LPS)-(Part-4)

Material Combinations and Dimensions

• Required to use galvanically compatible metals in lightning protection system components and surface materials on which the components are mounted. For example, do not connect copper to aluminum.
• Do not use together metals that are not galvanically compatible. Bad matching accelerates their corrosion in the presence of moisture.
• With aluminum conductors, use only connection devices designed for aluminum. Make sure to use the right fastening torque.

Different Contact Material
Material	Suitable Contact Material
Copper	Nickel /Brass / Tin / Lead / Stainless steel / Monel (nickel–copper alloy)
Aluminum	Magnesium / Zinc / Galvanized steel / Stainless steel / Lead / Wrought iron / Galvalume (an aluminum-coated sheet steel product)

LPS Material

LPS Materials and Conditions of Use
Table-5 (IEC 62305-3)
Material	Use				Corrosion
	In Open Air	In Earth	In Concrete	Resistance		Increased by	May be destroyed by Galvanic Coupling with
Copper	Solid	Solid	Solid	Good in many environments		Sulphur compounds	–
	Stranded	Stranded	Stranded	–		Organic materials	–
	–	As coating	As coating	–		–	–
Hot galvanized steel123	Solid	Solid	Solid	Acceptable in air, in concrete, and in benign soil		High chlorides content	Copper
	Stranded 4	–	Stranded 4	–		–	–
Steel with electro-deposited copper	Solid	Solid	Solid	Good in many environments		Sulphur compounds	–
Stainless steel	Solid	Solid	Solid	Good in many environments		High chlorides content
	Stranded	Stranded	Stranded	–		–	–
Aluminum	Solid	Unsuitable	Unsuitable	Good in atmospheres containing low concentration of Sulphur and chloride		Alkaline solutions	Copper
	Stranded	–	–	–		–	–
Lead 5	Solid	Solid	Unsuitable	Good in atmospheres with high concentration of sulphates		Acid soils	Copper
	As coating	As coating	–	–		–	Stainless steel

Material Dimensions

• Several lightning protection system codes and standards define minimum dimensions for the components of a grounding system. These standards are designed to protect buildings and other inhabited or otherwise critical facilities.
• Practical minimums are based on field experience and indicate what is needed to protect the installed equipment in a cost-effective way during the foreseeable technical lifetime, typically a few decades, taking into account local regulations. To ensure proper operation of the grounding system, periodic inspection and maintenance is needed

Minimum Dimensions of Earth Electrode as per IEC 623053 

• Table 1 and Table 2 are based on standard IEC 62305-3 Ed 2. The tables list minimum dimensions for the lightning protection system equipment.
• The following table lists the different materials and shapes that are used in air terminals, down conductors, and ground electrodes, including the cross-sectional area.

Minimum Dimensions of Earth Electrodes
Table-7, IEC-62305-3
Material	Configuration	Dimensions
		Earth Rod Diameter	Earth Conductor	Earth Plate
Copper, Tin-plated copper	Stranded	–	50 Sq.mm (8 mm)	–
	Solid round	15 mm	50 Sq.mm (8 mm)	–
	Solid tape	–	50 Sq.mm (8 mm)	–
	Pipe	20 mm	–	–
	Solid plate	–	–	500 × 500 mm
	Lattice plate	–	–	600 × 600 mm
Hot-dipped galvanized steel	Solid round	14 mm	78 Sq.mm (9.96 mm)	–
	Pipe	25 mm	–	–
	Solid tape	–	90 Sq.mm (10.7 mm)	–
	Solid plate	–	–	500 × 500 mm
	Lattice plate	–	–	600 × 600 mm
	Profile	*	–	–
Bare steel (Shall be embedded in  concrete  for a minimum depth of 50 mm.)	Stranded	–	70 Sq.mm (9.4 mm)	–
	Solid round	–	78 Sq.mm (9.96 mm)	–
	Solid tape		75 Sq.mm (9.72 mm)
Copper coated steel	Solid round	14 mm	50 Sq.mm (8 mm)
	Solid tape		90 Sq.mm (10.7 mm)
Stainless steel	Solid round	15 mm	78 Sq.mm (9.96 mm)
	Solid tape		100 Sq.mm (11.28 mm)
Mechanical and electrical characteristics as well as corrosion resistance properties shall meet the requirements of the future IEC 62561 series.
In case of a type B arrangement foundation earthing system, the earth electrode shall be correctly connected at least every 5 m with the reinforcement steel.
* Different profiles are permitted with a cross-section of 290 mm2 and a minimum thickness of 3 mm, e.g. cross profile.

Minimum Cross-sectional Area of Air-termination Conductors

Minimum Cross-sectional Area of Air-termination Conductors
Table 6 (IEC 62305-3)
Material	Configuration	Cross-sectional Area	Comments
Copper, tin-plated copper	Solid tape	50 Sq.mm / 8mm *	2 mm min. thickness
	Solid round1	50 Sq.mm / 8mm *	8 mm diameter
	Stranded 1	50 Sq.mm / 8mm *	1.7 mm min. dia of each strand
	Solid round***	176 Sq.mm /15mm	16 mm diameter
Aluminum	Solid tape	70  Sq.mm*	3 mm min. thickness
	Solid round	50 Sq.mm / 8mm *	8 mm diameter
	Stranded	50 Sq.mm / 8mm *	1.7 mm min. dia of each strand
Aluminum alloy	Solid tape	50 Sq.mm / 8mm *	2.5 mm min. thickness
	Solid round	50 Sq.mm / 8mm *	8 mm diameter
	Stranded	50 Sq.mm / 8mm *	1.7 mm min. dia of each strand
	Solid round***	176 Sq.mm /15mm	16 mm diameter
Copper-coated aluminum alloy	Solid round	50 Sq.mm / 8mm *
Hot-dipped galvanized steel **	Solid tape	50 Sq.mm / 8mm *	2.5 mm min. thickness
	Solid round	50 Sq.mm / 8mm *	8 mm diameter
	Stranded	50 Sq.mm / 8mm *	1.7 mm min. dia of each strand
	Solid round***	176 Sq.mm /15mm	16 mm diameter
Copper-coated steel	Solid round	50 Sq.mm / 8mm *
	Solid tape	50 Sq.mm / 8mm *
Stainless steel	Solid tape	50 Sq.mm / 8mm *	2 mm min. thickness
	Solid round***	50 Sq.mm / 8mm *	8 mm diameter
	Stranded	70 Sq.mm / 9.5mm*	1.7 mm min. dia of each strand
	Solid round ***	176 Sq.mm /15mm*	16 mm diameter
* If thermal and mechanical considerations are important, these dimensions can be increased to 60 mm2 for solid tape and to 78 mm2 for solid round.
** The coating should be smooth, continuous and free from flux stains with a minimum thickness coating of 50 μm.
***Applicable for air-termination rods only. For applications where mechanical stress such as wind loading is not critical, a 10 mm diameter, 1 m long maximum air-termination rod with an additional fixing may be used.

Minimum values of the cross-section of the bonding conductors with different bonding bars

Minimum dimensions of conductors connecting internal metal installations to the bonding bar
Table-8 (IEC-62305-3)
Class of LPS	Material	Cross-section (mm2)
I to IV	Copper	16 Sq.mm
	Aluminum	25 Sq.mm
	Steel	50 Sq.mm

 

Minimum dimensions of conductors connecting internal metal installations to the bonding bar
Table-9 (IEC-62305-3)
Class of LPS	Material	Cross-section (mm2)
I to IV	Copper	6 Sq.mm
	Aluminum	10 Sq.mm
	Steel	16 Sq.mm

 

Table 10: Minimum thickness of metal sheets or metal pipes in air termination systems
(IEC/BS EN 62305-3 Table 3)
Class of LPS	Material	Thickness (1) t	Thickness (2) t’
I to IV	Lead	–	2 MM
	Steel (stainless, galvanized)	4 MM	0.5 MM
	Titanium	4 MM	0.5 MM
	Copper 5 mm 0.5 mm	5 MM	0.5 MM
	Aluminum 7 mm 0.65 mm	7 MM	0.65 MM
	Zinc – 0.7 mm	–	0.70 MM
Thickness t prevents puncture, hot spot or ignition
Thickness t’ only for metal sheets if it is not important to prevent puncture, hot spot or ignition problems

Minimum Dimensions

Air Terminal Minimum Dimensions
Material	Dimension
Copper, aluminum	Tube with a 16 mm diameter, minimum wall thickness of 2 mm
	8 mm (0.31 in) solid round
Steel	10 mm

 

Down Conductor Minimum Dimensions
Material	Dimension
Copper	25 mm2 solid or stranded wire or solid tape
Aluminum	35 mm2 in solid or stranded aluminum
Steel	35 mm2  solid steel or stranded wires

 

Minimum Thickness of Tapes
Material	Thickness
Copper	1 mm
Aluminum	2 mm
Galvanized steel	2 mm
Stainless steel	2 mm

 

Minimum Thickness of Strand Diameters in Stranded Cables
Material	Thickness
Copper	1 mm
Aluminum	1.6 mm
Steel	1.6 mm

 

Ground Rod Minimum Dimensions
Material	Thickness
Copper	Solid round 15 mm
	Pipe 20 mm diameter with a minimum wall thickness of 2 mm
Copper clad solid steel	14 mm
Galvanized steel	16 mm
Galvanized steel, pipe	25 mm diameter with a minimum wall thickness of 2 mm

 

Horizontal Ground Electrode Minimum Dimensions
Material	Thickness
Copper	25 mm2 solid/strand/tape with a minimum 2 mm thickness
Galvanized steel, round wire	50 mm2 with a minimum 8 mm diameter
Galvanized steel, stranded	50 mm2 with a minimum strand diameter of 1.7 mm
Galvanized steel, tape	50 mm2 with a minimum thickness of 2 mm

 

Installation Depth of Ground Electrode
Ground Electrode Type	Installation Depth
Ground rod	3 meter
Horizontal ground electrode	0.6 meter

 

Typical Ground Electrode Length and Spacing
Minimum values	Ground rod	Horizontal ground electrode
Length	Typically, 3 Meter	10 Meter to 30 Meter as per soil type dependent
Loop diameter	–	5 Meter to 6 Meter
Spacing	Min. 2 × rod length	–

Guideline for LPS System:

• The following design guidelines need to be adhered to ensure safer installation of the external LPS.
• Air Terminal:
• Air terminal should be selected and provided only based on the protection angle or rolling sphere method
• Proper safety distance between the air terminal and any metallic object needs to be maintained as per the calculation mentioned earlier to avoid dangerous spark-overs.
• Different Material Jointing & Insulations:
• Wherever incompatible materials to be joined (Ex. Copper with Aluminum), suitable bi-metal connectors should be used.
• Suitable expansion joints must be provided on the horizontal conductors on top to take care of thermal effects.
• Special conductor holders of insulating type need to be provided on top of the terrace floor for routing the conductor to ensure electrocution impact does not happen in case of water stagnation.
• Equip potential Bonding:
• Required measures to ensure shielding, bonding / equipotential bonding techniques are handled properly to avoid LEMPs.
• Establishing connection for equipotential bonding with nearby metallic components need to be taken care of.
• Joints should be mechanically and electrically effective, should be protected against corrosion or erosion from the elements or the environment and should present an adequate contact area.
• Reinforcement Structure:
• In the case of using reinforcement in concrete structures as lightning down conductor details should be decided at the design stage, before building construction begins.
• Good contact between reinforcing bars to be ensured only by using connection clamps tested as per the requirement of IEC 62561-1
• Down Conductor:
• A down-conductor should be installed at each exposed corner of the structure where it is possible.
• The Down conductor should run as straight and vertical as possible so that they provide the shortest and most direct path of a low impedance from the air termination to the earth electrode so that the lightning current can be safely conducted to earth.
• The formation of loops in bring the down conductor shall be avoided, but where this is not possible the distance shall be maintained
• There should be a test joint arrangement to have separation between down conductor and earth termination for safety and for measurement of earth resistance.
• At least two down conductors are mandatory for any size of Building.
• The termination of the down conductor to an earth electrode should be done minimum of 1 meter away from the structure and minimum of 0.5m depth inside the ground.
• Earth electrodes for each down conductor shall be provided.
• Connection of down conductors to gutters or down-spouts even if they are covered by insulating materials.
• Usage of multiple connections with different materials should not be permitted.
• Insufficient conductor dimensions (non-complying material as mentioned in IEC 62305-3 Table – 5) should be strictly avoided.
• When the distance from down conductors to combustible materials cannot be assured, the cross section of the down conductor shall not be less than 100 mm²

Basic of External Lightning Protection System (LPS)-(Part-3)

COMPARISION OF VARIOUS PROTECTION METHOD

COMPARISION OF VARIOUS PROTECTION METHOD
Protection Method	Type of Structure
	Simple structure	Complex shaped structure	Plane Structure
Protection Angle	(*) YES	NO	NO
Mesh Method	NO	YES	YES
Rolling sphere Method	YES	YES	YES
(*) This method is not suitable for structure height more than radius of the rolling sphere relevant to the selected protection level of LPS

(2) Down Conductor system:

• In Air-termination systems, down-conductor systems and earth-termination systems should be harmonized to produce the shortest possible path for the lightning current.
• Down-conductors should preferably be connected to junctions of the air-termination system network and routed vertically to the junctions of the earth-termination system network.
• The function of a down conductor system is to conduct the lightning impulse from air-termination system to the earthing system. The down conductor system should be installed in such a way that the following points are ensured.
• (i) Several parallel current paths exist
• (ii) Length of current path is kept to minimum.
• (iii) Equipotential bonding to conducting parts is performed.
• Selection and installation of down conductors plays a major role in protecting electrical and electronic installations in a building. The number of down conductors to a typical building depends upon the class of LPS.
• A down conductor should be installed at each exposed corner of the structure and form a direct continuation of the air-termination conductors. Drown conductors are installed in such a way that they provide the shortest and most direct route to earth. Avoiding the formation of bends and loops is required.
• To reduce damage caused by lightning current, the down conductors are arranged so that the current path around the building’s perimeter is parallel and at equal distances.
• Even if the down conductor encased in insulating material, down conductors must not be installed in service shafts, gutters, or downspouts, as doing so invites severe damage during a lightning strike.
• Electrical insulation between LPS components and other metallic installation in the building are necessary to avoid flashover between different metal parts.
• Integration of down conductor with Building Natural Components:
• External down-conductors should be installed between the air-termination system and the earth-termination system. Wherever natural components (Steel reinforcement, metal framework structure) are available, they can be used as down-conductors.
• Down conductors are also integrated into structural steel reinforcement, metal framework of structure, steel roof, metal façade, handrails etc. is the best and practical solution for new and upcoming high raise buildings. In this integrated approach high safety is offered with no maintenance, long life, no influence on aesthetics. Separation distance need not be considered in this case.
• Down conductors can be embedded in RCC columns. In this case, bonding different metallic installations in the building is simple, thereby eliminating potential differences. This integrated method is not only cost-effective but has no negative effect on the building’s aesthetics. It also reduces the failure of electronic equipment inside the building from radiated lightning effects.
• Test joints are not required, and earth resistance measurements are not necessary in the location where the natural down conductors are terminated to foundation earthing.

• Number & distance between each Down Conductor:
• For each non-isolated LPS, the number of down conductors shall be not less than two and should be distributed around the perimeter of the structure to be protected. An equal spacing of the down conductors is preferred around the perimeter. The typical values of the distance between the conductors are shown below.

DISTANCE BETWEEN DOWN CONDUCTORS
(IEC/BS EN 62305-3 Table 4)
Class of LPS	Distance between conductors
CLASS I- (Very High Risk)	10 Meter
CLASS II- (High Risk)	10 Meter
CLASS III- (Moderate Risk)	15 Meter
CLASS IV- (Low Risk)	20 Meter

• If the distance between down-conductors is too large with the reference to the Table, the number of down-conductors should be increased to meet the required separation distance.
• As stated, a down-conductor should be installed at each exposed corner of the structure, where this is possible. However, an exposed each corner does not need a down conductor if the distance between this exposed corner to the nearest down-conductors complies with the following conditions:
• (i)the distance to both adjacent down-conductors is half the distance according to Tables or smaller.
• (ii) the distance to one adjacent down-conductor is one-quarter of the distance according to Tables or smaller.

• The number and position of down-conductors is important because if the lightning current is shared in several down-conductors, the risk of side flash and electromagnetic disturbances inside the structure is reduced. It follows that, as far as possible, the down-conductors should be uniformly placed along the perimeter of the structure and with a symmetrical configuration.
• The current sharing is improved not only by increasing the number of down-conductors but also by equipotential interconnecting rings.
• Down-conductors should be placed as far as possible away from internal circuits and metallic parts in order to avoid the need for equipotential bonding with the LPS., In cantilevered structures the separation distance should also be evaluated with reference to the risk of side-flashing to persons.
• If it is not possible to place down-conductors at a side, or part of a side, of the building because of practical or architectural constraints, the down-conductors that ought to be on that side should be placed as extra compensating down-conductors at the other sides. The distances between these down-conductors should not be less than one-third of the distances in Table.
• A variation in spacing of the down-conductors of ±20 % is acceptable as long as the mean spacing conforms to Table.
• In closed courtyards with more than 30-meter perimeter, down-conductors have to be installed.
• Insulation / Separation of LPS parts
• If it is not possible to make a straight connection because of large roof overhangs, etc. the connection of the air-termination system and the down-conductor should be a dedicated one and not through natural components like rain gutters, etc.
• It is permitted, where aesthetic consideration needs to be taken into account, to use a thin coating of protective paint or PVC covering over the external down-conductors.
• Down conductors, even if covered in insulating material, shall not be installed in gutters or waterspouts. The effects of moisture in the gutters lead to intensive corrosion of the down conductor.

Minimum Size of Down conductor
Protection level	Material	Section
I-IV	Steel	50 mm2
I-IV	Aluminum	25 mm2
I-IV	Copper	16 mm2

• For non-isolated LPS, down conductors are mounted directly onto the building (without separation distance) if the wall is made of flame resistant or normally inflammable material, the down conductors may be installed directly on or in the wall.
• Metal framework of a steel structure or the interconnected reinforcing steel of the structure can be used as a down conductor. Reinforcement of existing structure cannot be used as natural down conductor unless the reinforcement is safely interconnected. Separate external down conductors must be installed.
• Conductors on roofs and the connections of air-termination rods may be fixed to the roof using both conductive or non-conductive spacers and fixtures. The conductors may also be positioned on the surface of a wall if the wall is made of non-combustible material.
• Recommended fixing centers for these conductors are shown in the Table.

Suggested fixing centers
Table E.1 IEC- 62305-3
Arrangement	Fixing centers for tape and stranded conductors (mm)	Fixing centers for round solid conductors (mm)
Horizontal conductors on horizontal surfaces	500 mm	1000 mm
Horizontal conductors on vertical surfaces	500 mm	1000 mm
Vertical conductors from the ground to 20 m	1000 mm	1000 mm
Vertical conductors from 20 m and thereafter	500 mm	1000 mm
NOTE: Assessment of environmental conditions (i.e. expected wind load) should be undertaken and fixing centers different from those recommended may be found to be necessary.

(3) Earth Termination:

• The purpose of the earth termination system is to provide a safe low-impedance path to high frequency lightning current into the ground.
• To minimize dangerous over voltage due to lightning, The shape and the dimension of the earth termination system are important.
• The earth termination system should be designed to have a resistance to earth of less than 10 ohms, as per the IEC/BS EN 62305 standards.
• There are two basic types of earth electrode arrangements are recommended in IS/IEC 62305 and NBC-2016 such as vertical /horizontal
• Type A arrangement: Horizontal earth electrodes or vertical earth electrodes installed outside the structure and connected to down conductors.
• Type B arrangement: Ring earth electrodes installed around the perimeter of the structure.
• POINTS NEED TO BE CONSIDER:
• Step Voltage: If earthing termination network is used in public access area, then the selection of suitable types of earth electrodes and safe distances from structure and from the external conductive parts in the soil (cables, metal ducts, etc.) are important. Hence special steps need to be taken for the protection against dangerous step voltages in the vicinity of the earth-termination networks.
• Earth resistance value: The recommended value of the overall earth resistance of 10 Ω is fairly conservative in the case of structures in which direct equipotential bonding is applied. The resistance value should be as low as possible in every case but especially in the case of structures endangered by explosive material. Still the most important measure is equipotential bonding.
• Depth of Electrode: The embedded depth and the type of earth electrodes should be such as to minimize the effects of corrosion, soil drying and freezing and thereby stabilize the equivalent earth resistance.
• It is recommended that the first half meter of a vertical earth electrode should not be regarded as being effective under frost conditions. Deep-driven earth electrodes can be effective in special cases where soil resistivity decreases with depth and where substrata of low resistivity occur at depths greater than those to which rod electrodes are normally driven.
• Mechanical Splitting / Stressing: When the metallic reinforcement of concrete is used as an earth electrode, special care should be exercised at the interconnections to prevent mechanical splitting of the concrete.
• If the metal reinforcement is also used for the protective earth, the most severe measure in respect of thickness of the rods and the connection should be chosen. In this case, larger sizes of reinforcement bars could be considered. The need for short and straight connections for the lightning protection earthing should be always recognized.
• In the case of pre-stressed concrete, consideration should be given to the consequences of the passage of lightning discharge currents, which may produce unacceptable mechanical stresses.

(A) Type-A Earthing (Embedded Earth Electrode)

• This is the conventional type of LPS Earthing System where earthing rodsare used to form the earth electrode and connected each down conductor to an earth rod. The earth electrodes installed outside the structure.
• The type A earth-termination system is suitable for low structures (family houses ,Low rise building).
• This type of arrangement comprises horizontal or vertical earth electrodes connected to each down-conductor.
• Where there is a ring conductor, which interconnects the down-conductors, in contact with the soil, the earth electrode arrangement is still classified as type A, if the ring conductor is in contact with the soil for less than 80 % of its length.
• The total number of earth electrodes in Type A arrangement shall not be less than two.
• Type-A earthing suitable for:
• The type A earth termination arrangement is suitable for low structures (Houses), (below 20 meters in height)
• existing structures or an LPS with rods or stretched wires or for an isolated LPS.
• It is suitable for locations with low fault currents and provides safety and functional grounding.
• commonly used in residential and commercial settings.
• Type A earthing system depends upon the soil resistivity and class of LPS.
• Each down conductor shall have a vertical earth electrode with a minimum length as per the table. In case of horizontal electrode, the length shall be double.
• The earth electrodes shall be installed at a depth of upper end at least 0.5 m in soil if an earth chamber is not used.
• In general, a low earthing resistance (if possible lower than 10 Ω when measured at low frequency) is recommended for type A earthing if the specific length cannot be ensured.
• The minimum length of each earth electrode at the base of each down-conductor is specified in BS EN 62305 and the table below.

Horizontal & Vertical electrode Length for Type A & Type-B earth electrode (based on soil resistivity)
IEC- 62305-3
Class of LPS	<500 Ωm			<1000 Ωm		<2000 Ωm		<3000 Ωm
	Horizontal electrodes (l1)	Vertical electrodes 0.5 x I1	Horizontal electrodes (l1)		Vertical electrodes 0.5 x I1	Horizontal electrodes (l1)	Vertical electrodes 0.5 x I1	Horizontal electrodes (l1)	Vertical electrodes 0.5 x I1
I	5 Meter	2.5 Meter	20 Meter		10 Meter	50 Meter	25 Meter	80 Meter	40 Meter
II	5 Meter	2.5 Meter	10 Meter		5 Meter	30 Meter	15 Meter	45 Meter	22 Meter
III	5 Meter	2.5 Meter	5 Meter		2.5 Meter	5 Meter	2.5 Meter	5 Meter	2.5 Meter
IV	5 Meter	2.5 Meter	5 Meter		2.5 Meter	5 Meter	2.5 Meter	5 Meter	2.5 Meter

• The minimum length of each earth electrode at the base of each down-conductor is l1 for horizontal electrodes, or 0.5 x l1 for vertical (or inclined) electrodes,
• where l1 is the minimum length of horizontal electrodes. For combined (vertical or horizontal) electrodes, the total length shall be considered.
• Reduction of earthing resistance by the extension of earth electrodes is practically convenient up to
• 60 m. In soil with resistivity higher than 3000 Ωm, the use of type B earth electrodes or earthing enhancing compounds is recommended.

• Radial and vertical earth electrodes
• Each down-conductor should be provided with an earth electrode.
• Radial earth electrodes should be connected to the lower ends of the down-conductors by using test joints.
• During installation it is necessary to measure the earthing resistance regularly. Additional electrodes can then be installed in more suitable locations.
• The earth electrode should have sufficient separation from existing cables and metal pipes in the earth. The separation distance depends on the electrical impulse strength and resistivity of the soil and the current in the electrode.
• In the type A arrangement, vertical earth electrodes are more cost-effective and give more stable earthing resistances in most soils than horizontal electrodes.
• In some cases, it may be necessary to install the earth electrodes inside the structure, for example in a basement or cellar.
• Advantages:
• If there is a danger of an increase in resistance near to the surface, it is often necessary to employ deep-driven earth electrodes of greater length. Radial earth electrodes should be installed at a depth of 0,5 m or deeper. A deeper electrode ensures that in countries in which low temperatures occur during the winter, the earth electrode is not situated in frozen soil (which exhibits extremely low conductivity).
• An additional benefit is that deeper earth electrodes give a reduction of the potential differences at the earth surface and thus lower step voltages reducing the danger to living creatures on the earth surface. Vertical electrodes are preferred to achieve a seasonally stable earthing resistance.
• Limitation:
• When the type A earthing arrangement is provided, it is necessary to all electrodes are at equal equalization. This can be achieved by bonding all conductors by bonding bars. Special care also needs to be cared to control step voltage.

(B) Type-B Earthing (Foundation /Ring Earthing)

• Type B Earthing consists of either a Ring conductor external to the structure to be protected (in contact with the soil for at least 80% of its total length) or a Foundation earth electrode forming closed loop.
• Type-B Earthing is also done by combination of both Ring earthing and Foundation earthing.
• Foundation earthing is done using conductors embedded in foundation of the building.
• Foundation earthing also serves as protective and functional earthing. This is the most efficient earthing system to protect electronic equipment. Materials used and construction techniques availed must fulfil various mechanical, electrical and chemical requirements to provide long life for the installation.
• Connection of a Lightning Protection System to the steel in the concrete foundation can be done for all new constructions since this steel is usually good for equipotential bonding. A dedicated Earth Rod can also be installed in the foundation but then these Earth Electrodes would need to be bonded to the steel in the concrete.
• Earth-termination systems should serve the following three purposes.

1. conduction of the lightning current into the earth.
2. equipotential bonding between the down-conductors.
3. potential control in the vicinity of conductive building walls.

• The foundation earth electrodes and the type B ring-type earth electrodes meet all these requirements.
• Type A radial earth electrodes or deep-driven vertical earth electrodes do not meet these requirements with respect to equipotential bonding and potential control.
• The structure foundations of interconnected steel-reinforced concrete should be used as foundation earth electrodes. They exhibit very low earthing resistance and perform an excellent equipotentialization reference. When this is not possible, an earth-termination system, preferably a type B ring earth electrode, should be installed around the structure.
• Type-B Earthing Suitable for:
• Structures built on rocky ground
• Structures housing sensitive electronics/equipment
• Large structures
• It is used in areas with high fault currents, such as critical infrastructure and industrial facilities, to provide enhanced protection against surges and transients, often resulting from lightning or equipment malfunctions.
• The type B earth-termination system is preferred for meshed air-termination systems and for LPS with several down-conductors.
• Type B is recommended for buildings with electrical and electronic installations and buildings in high soil resistivity.
• Type B earth electrodes also perform the function of potential equalization between the down conductors at ground level, since the various down-conductors give different potentials due to the unequal distribution of lightning currents due to variations in the earth resistance and different lengths in the above ground conductor current paths. The different potentials result in a flow of equalizing currents through the ring earth electrode, so that the maximum rise in potential is reduced and the equipotential bonding systems connected to it within the structure are brought to approximately the same potential.
• In some Area it is not possible to install a ring earth electrode that will fully surround the structure Where structures belonging to different owners are built closely to each other or common for both. In this case the efficiency of the earth-termination system is somewhat reduced, since the conductor ring acts partly as a type B electrode, partly as foundation earth and partly as an equipotential bonding conductor.
• Where large numbers of people frequently assemble in an area adjacent to the structure to be protected, further potential control for such areas should be provided. More ring earth electrodes should be installed at distances of approximately 3 m from the first and subsequent ring conductors. Ring electrodes further from the structure should be installed more deeply below the surface i.e. those at 4 m from the structure at a depth of 1 m, those at 7 m from the structure at a depth of 1,5 m and those at 10 m from the structure at a depth of 2 m. These ring earth electrodes should be connected to the first ring conductor by means of radial conductors.
• POINTS NEED TO BE CONSIDER:
• If it is not possible to close the ring, a connection must be made inside the buildingusing conductive metallic equipment such as pipes.
• Ring shall be at least 0.5meter below the surface
• Ring shall be maintained at least 1 meter from the structure / from the external walls.
• It is recommended that 80% of the length of the ring shall be in contact with natural soil. Thus, no more than 20% of the total length may be in the basement of the structure instead of in direct contact with the soil.
• If the radius of the ring electrode is less than the length of vertical or horizontal earth electrodes required for Earthing, then additional horizontal or vertical earth electrodes can be connected to the ring.
• Bonding of different metallic installations in the building avoid dangerous potential differences and flashover
• Ring earth electrode Radius length: For the ring earth electrode (or foundation earth electrode), the mean radius (re) of the area enclosed by the ring earth electrode (or foundation earth electrode) shall be not less than the horizontal electrodes value (l1)
• re ≥ l1
• When the required value of l1 is larger than the convenient value of re, additional horizontal or vertical (or inclined) electrodes shall be added with individual lengths lr (horizontal) and lv (vertical) given by the following equations:
• lr = l1 – re (2) and lv = (l1 – re) / 2
• It is recommended that the number of electrodes should be not less than the number of down-conductors, with a minimum of two.
• The additional electrodes should be connected to the ring earth electrode at points where the down-conductors are connected and, for as many as possible, equidistantly.
• EARTH TERMINATION SYSTEM IN LARGE AREAS:
• An industrial plant typically comprises a number of associated structures, between which a large number of power and signal cables are installed. The earth-termination systems of such structures are very important for the protection of the electrical system. A low impedance earth system reduces the potential difference between the structures and so reduces the interference injected into the electrical links.
• A low earth impedance can be achieved by providing the structure with foundation earth electrodes and additional type B and type A earth arrangements.
• Interconnections between the earth electrodes, the foundation earth electrodes and the down conductors should be installed at the test joints. Some of the test joints should also be connected to the equipotential bars of the internal LPS.
• Internal down-conductors, or internal structural parts used as down–conductors, should be connected to an earth electrode and the reinforcement steel of the floor to avoid step and touch voltages. If internal down-conductors are near expansion joints in the concrete, these joints should be bridged as near to the internal down-conductor as possible.
• The lower part of an exposed down-conductor should be insulated by PVC tubing with a thickness of at least 3 mm or with equivalent insulation.
• When the area adjacent to the structure is covered with a 50 mm thick slab of asphalt of low conductivity, sufficient protection is provided for people making use of the area.

• Foundation Earth Electrodes are simply concrete reinforced foundations – they are considered to be Type B Earthing. For these Foundation Earth Electrodes, there should be at 50mm of concrete covering the electrode to minimize corrosion.
• The type B earthing is recommended as either a ring conductor outside the perimeter of the structure which it’s recommended should be in contact with the soil for at least 80% of its total length.
• The alternative is to use a foundation earth electrode which can be in a mesh form.
• The reinforced concrete floor slab can be used around the structure.
• If the required resistance cannot be achieved by this method the vertical or radial earthing electrodes can be added to the network.
• For ease of testing after installation an inspection pit with an earth bar should be installed where the legs of the ring and conductor routing onto the ring from each test clamps join
• FOUNDATION EARTHING / NATURAL CONDUCTORS AS PART OF THE LPS
• The building’s natural components, metal roof, rebar, steelwork etc. can be considered as part of the LPS
• The reinforcing bars within the concrete structure can be used as a natural component of the LPS provided they are electrically continuous by either welding or clamping the joints.
• The re-bars are considered as electrically continuous provided that a major part of interconnections of vertical and horizontal bars are welded or otherwise securely connected by clamps conforming to BS EN 50164 standards.
• Forming:
• Foundation grounding is one of the most healthy grounding methods. Foundation grounding of buildings must be started at the beginning of construction, i.e. foundation stage. It is performed by installing a galvanized conductor between the reinforcing bars in the foundation. This conductor is connected to reinforcing bars at certain distances. The ends of the grounding conductor are taken out from some specified points and left as the connection bud. Once these ends are connected to the equipotential grounding bus bars, the grounding is completed by connecting all systems to be grounded to these buses.
• Foundation grounding must be performed in the form of a closed ring and placed in the foundation of the external walls of the building, or the foundation platform. In buildings with a large perimeter, foundation grounding rods must be divided into sections of 20x20m. Connection must be established with reinforcing bars every few meters.
• Foundation earthing can be accomplished in various ways, such as by using cable or flat conductor, connected to earth rods or by surrounding the foundation with conductor that enters the foundation through an earth terminal. Grounding standards, such as IEEE 80 Standard, provide guidelines for the design and installation of earthing systems, including those for foundations.
• For the foundation earthing’s connection with a lightning rod, a conductor is placed inside the pillars before the concrete placement, ending on the building’s rooftop.
• Circumferentially on the rooftop, an aluminum or copper conductor is placed on braces, in spots that include chimneys, solar water heaters, etc. Then spikes are placed, and the construction of the lightning rod is complete

• The connecting rebar must overlap and be clamped using rebar clamps or welded to a minimum of 20 times the diameter of the rebar a (Welding to be done on either side of the rebars.)
• The concrete used for the foundations of buildings has a certain conductivity (relative comparison) and, in general, “a large contact area” with the ground. It is highly recommended to use bare metal electrodes completely embedded in concrete (to a minimum depth of 5 cm) for grounding purposes, as they are highly protected against corrosion, usually for the entire life of the building according to IEC 60364
• It is recommended to use a foundation earth electrode embedded in concrete during the construction of the building (itself) to obtain a lower earth resistance value.
• Materials for Earth-Termination Systems
• The foundation earth electrode has to be made of
• Round steel (min. diameter 10 mm) or
• Strip steel (min. dimension 30 mm x 3.5 mm) which has to be galvanized (or black) for laying in concrete, or for laying in soil.
• Advantages:
• Does not require additional excavation work.
• Provides good contact with the ground.
• It extends over virtually the entire surface of the building foundation and results in minimum ground electrode impedance that can best be achieved with this surface.
• It also provides an optimal grounding arrangement for the lightning protection system.
• It is erected at a depth that is normally free from negative influences resulting from seasonal weather conditions.
• Step voltage elimination
• Equipotential connections
• Corrosion resistant

Basic of External Lightning Protection System (LPS)-(Part-2)

(B) ROLLING SPHERE METHOD: (Suitable for complex shape building)

•  The rolling sphere method should be used to protect the areas of a structure when there is design limitation to use the protection angle method.
• The rolling sphere method is recommended as the main method to be used in the design of lightning protection system with location of air terminals for structures with complex shapes.
• This method is more accurate, and complex compared to other lightning protection schemes, because it specifies the exact number of spikes needed for each building and considers the worst-case scenarios, in which a lightning strike hits the side of the building.
• Position of Air Termination Rod:
• In this method, the positioning of the Air-Termination system is adequate so that no point of the structure to be protected comes in to contact with a sphere with radius ‘r’ depending on the class of LPS (see table) rolling around on top of the structure in all possible directions. In this way, the sphere only touches the air termination system (see figure).
• Radius of Sphere:
• The rolling sphere lightning protection method assumes the electrically charged field that produces a lightning strike has a radius “r” and the sphere with that radius rolling over the surface of the building. Any place the sphere touches the building is a location where lightning can strike the building.  By installing air terminals, the sphere cannot touch the building because electrical charges flow through the lightning protection system into the ground.
• The radius of the rolling sphere is correlated with the peak value of the current in the lightning that strikes the structure: r = 10xIx0.65 where I define as kA.
• In the rolling sphere method, the radius of the sphere is selected in such a way that its radius is equal to the striking distance. Since the striking distance is a function of the prospective return stroke current, the radius of the sphere “r” is defined as a function of the probable return stroke current according to the relationship between the lightning striking distance and the peak return stroke current.
• The lightning stroke depends on the degree of risk considered.  So, for a high-risk facility, the sphere radius is at its smallest, e.g. 20meter or a 40meter diameter ball. The smallest size ball means the amount of protection installed will be at its highest. Thus, lowering the risk profile and increasing the protection afforded.
• For a low-risk scenario method, the sphere radius is at its largest distance, 60 meters (120-meter diameter ball), which means a lot less hardware to install.
• The radius r of the rolling sphere depends on the class of LPS as per given Table.

RADIUS OF THE ROLLING SPHERE
Class of LPS	Rolling sphere radius, r (m)
CLASS I- (Very High Risk)	20 Meter
CLASS II- (High Risk)	30 Meter
CLASS III- (Moderate Risk)	45 Meter
CLASS IV- (Low Risk)	60 Meter

• Figure shows the application of the rolling sphere method to different types of structures. The sphere of radius r is rolled around and over all the structure until it meets the ground plane or any permanent structure or object in contact with the ground plane which can act as a conductor of lightning.
• A striking point could occur where the rolling sphere touches the structure and at such points protection by an air-termination conductor is required.
• Any part of the structure that is in contact with the sphere is considered to be vulnerable to a direct lightning strike; the untouched volume defines a lightning protected zone.

• When the rolling sphere method is applied to the structure, the structure should be considered from all directions to ensure that no part protrudes into an unprotected zone a point which might be overlooked if only front, side and plan views on drawings are considered.

PENETRATION DISTANCE:

• The distance between the two air terminals should be chosen in such a way that protection is provided for all the objects placed on the surface to be protected.
• The protection of the objects placed on the surface can be ensured by calculating the penetration distance of the rolling sphere.
• The distance between the level of air terminals and the least point of sphere in the space between the air terminals is called penetration distance.

• Let us consider an object of height ‘h’ placed on the surface to be protected. Let ‘ht’ be the height of the air terminal, ‘p’ be the penetration distance and ‘d’ be the distance between the two terminals.
• In this case, the penetration distance ‘p’ should be less than the physical height of the air-termination rods above the reference plane minus the height of the objects to be protected.
• P<(ht-h)

DISTANCE BETWEEN TWO AIR TERMINALS:

• The penetration distance of the rolling sphere below the level of conductors in the space between the conductors can be calculated by using the below formula (IS 62305-3).
• p=r-√(r^2-(d/2)^2 )
• Were,
• p : penetration distance
• r : radius of rolling sphere
• d: distance between the air terminals
• For attaining a particular penetration distance, we can derive the required distance between the air terminals from the above equation.
• d=2x√(2 x p x r-p^2 )
• If there are no objects protruding from the structure to be protected, then the penetration distance can be increased up to the height of the air terminal to provide maximum protection. At this condition, the distance can be calculated by substituting the value of height of air terminal (ht) in place of penetration distance (p).
• d=2x√(2 x ht x r-ht^2 )
• The distance between the air terminals(d) in rolling sphere method depends on two factors.
• Height of the air terminal and
• Radius of the rolling sphere
• Among these two factors, the radius of rolling sphere is a constant value which depends on the class of LPS as specified by IS/IEC 62305-3. Hence for particular class of LPS, the distance between the air terminals purely depends on the height of air terminal.

Distance between Air Terminals (Meter)
Height of Air Terminal (ht)	Radius of Rolling Sphere(r)
	LPS-I	LPS-II	LPS-III	LPS-IV
	r=20 Meter	r=30 Meter	r=45 Meter	r=60 Meter
0.5 Meter	8.8	10.9	13.37	15.45
1 Meter	12.48	15.36	18.86	21.81
1.5 Meter	15.2	18.7	23	26.66
2 Meter	17.43	21.5	26.53	30.72
3 Meter	21.07	26.15	32.31	34.36
4 Meter	24	29.9	37	43
6 Meter	28.56	36	44	52.3

• Example:
• Conclude the equipment installed on Terrace is whether protected by LPS System or not by LPS system installed on Building (Calculate penetration height) having following details.
• LPS Level is -IV (Low Risk).
• The maximum height of equipment is 1 meter from Terrace Floor.
• The distance between the two Air terminals is 10 meters.
• Height of Air Terminal is 2 Meter.
• Calculation:
• First, we calculate the maximum distance between two Air terminal according to LPS level.
• Here Height of Air terminal (ht)= 2Meter.
• Height of equipment (h)=1 Meter
• According to LPS-IV Radius of rolling sphere (r) = 60 meter
• Distance between two Air terminals (d) =2√(2*ht*r-ht^2 )
• Distance between two Air terminals (d) =2√(2x2x60-2^2 )
• Distance between two Air terminals (d) =30.72 Meter
• Distance between actual installed Air terminals is 10 meter which is less than maximum calculated distance between two Air terminals.
• Now to calculate penetration height.
• penetration height (p)=r-√(r^2-(d/2)^2 )
• penetration height (p)=60-√(60^2-(10/2)^2 )
• penetration height (p)=0.20 Meter.
• Now Height of Air terminal (ht)-Height of equipment(h) = 2-1 =1Meter.
• Check condition of P< (ht-h)
• Here 0.2 <1 meter
• Hence equipment installed on terrace which height is 1 meter is protected from installed LPS System.

SIDE FLASHES IN TALL STRUCTURE

• On all structures higher than the rolling sphere radius “r”, flashes to the side of structure may occur. Each lateral point of the structure touched by the rolling sphere is a possible point of strike. However, the probability for flashes to the sides is generally negligible for structures lower than 60 meters.
• For taller structures, a major part of all flashes will hit the top, horizontal leading edges and corners of the structure. Only a few percentages of all flashes will be to the side of the structure.
• The probability of flashes to the sides decreases rapidly as the height of the point of strike on tall structures when measured from the ground.
• Therefore, consideration should be given to install a lateral air-termination system on the upper part of tall structures (typically the top 20 % of the height of the structure). In this case the rolling sphere method will be applied only to the positioning of the air-termination system of the upper part of the structure.

(1) Buildings Taller Than 120-meter High

• For structures taller than 120 meters, the standard recommends that all parts above 120 meters be protected. It is expected that due to the height and nature of such a structure, it would require a design to LPL I or II (99% or 97% protection level).
• For tall buildings, the actual risk of flashes to the side are estimated by the industry to be less than 2%, and typically these would be the smaller lightning flashes, e.g., from branches of the downward leader. Therefore, this recommendation would only be appropriate for high-risk locations or structures.

(2) Buildings Above 60-meter High

• In the IEC standards, for buildings above 60-meter, protection is required to the sides of the upper 20% of height. The same placement rules used for roofs should apply to the sides of the building.
• While the mesh method is preferable, particularly if using natural components, protection is permitted using horizontal rods and rolling sphere method. However, horizontal rods on most structures are impractical due to window washing access equipment, etc.

(3) Buildings Less Than 60-meter High

• Note that for structures less than 60 meters high the risk of flashes to the sides of the building is low, and therefore protection is not required for the vertical sides directly below protected areas.

(4) Buildings Taller Than 30 meters:

• For buildings taller than 30 m, additional equipotential bonding of internal conductive parts should occur at a height of 20 m and every further 20 m of height. Live circuits should be bonded via SPDs.

(C) THE MESH METHOD (Suitable for all flat surface building)

• The mesh method is the simplest and most flexible method for LPS because it does not depend on the height of the structure. However, it requires flat but non curved surfaces. The Flat surface may be horizontal or vertical surfaces.
• It is mostly used for simple Building like domestic households, mainly for perfectly square or rectangular buildings.
• In the mesh method, a mesh is created by a flat conductor and placed on the structure. The separation distance of the conductors is based upon the class of protection determined during the risk assessment.
• Mesh Size:
• According to IEC 62305, mesh conductor size is based on the selected class of LPS and that is totally dependable on user requirements.
• In the Mesh method, a conducting mesh with a cell size determined by the minimum return stroke current that is allowed to strike the protected structure.
• In order to avoid a direct strike, the mesh has to be located at a critical distance above the flat surface to be protected. This procedure is called “protective mesh method”.
• The maximum mesh size should be in accordance with the table below.

Mesh Size
Class of LPS	Mesh Size (M)
CLASS I-(VERY HIGH RISK)	5 X 5 METER
CLASS II-(HIGH RISK)	10X 10 METER
CLASS III-(MODERATE RISK)	15 X 15 METER
CLASS IV-(LOW RISK)	20 X 20 METER

• The following conditions shall be considered while selecting the Mesh Method.
• (a) Air-termination conductors are positioned, on roof edge lines, on roof overhangs, on roof ridge lines, if the slope of the roof exceeds 1/10.
• (b) The mesh dimensions of the air-termination network are not greater than the values given in Table.
• (c) The network of the air-termination system is constructed in such a way that the lightning current will always encounter at least two distinct metal routes to earth-termination.
• (d) No metal installation protrudes outside the volume protected by air-termination systems.
• (e) The air-termination conductors follow, as far as possible, the shortest and most direct
• Location of Mesh
• The corners and edges of roofs are most susceptible to damage due to lightning. Therefore, designers and installers should place the conductors as close to the edge of the roof as possible.
• IEC 62305 allows for the use of conductors under the roof of a structure. Thus, the natural components of a structure can be used as part of the mesh grid, or even the whole grid. These components may be the rebar structure underneath the roof or dedicated lightning protection conductors, but they must be connected to the air termination rods that are mounted above the roof.
• For structures, with a protruding metallic structure, the Protective Angle Method is generally used as a supplement to the Mesh Method

•  Mesh Method with combination of other Methods:
• For Medium to large scale buildings mesh can be implemented, but due to its limitations, it does not come alone. It must be merged with other types of LPS, either protection angle or rolling sphere, subject to the suitable class number of each type.
• Air termination conductors and down conductors should be inter-connected by means of conductors at the roof level to provide sufficient current distribution over the down conductors.
• Conductors on roof and the connections of air termination rods may be fixed to the roof using both conductive or non-conductive spacers and fixtures. The conductors may also be positioned on the surface of a wall if the wall is made of non-combustible material. The fixing centers shall be minimum 1 meter apart.
• For each non-isolated LPS, the number of down conductors shall be not less than two. A down conductor should be installed at each exposed corner of the structure, where this is possible.

• Limitations:
• The mesh method is suitable for horizontal and inclined roofs with no curvature.
• The mesh method is suitable for flat lateral surfaces to protect against side flashes.
• If the slope of the roof exceeds 1/10, parallel air-termination conductors, instead of a mesh, may be used provided the distance between the conductors is not greater than the required mesh width.

Basic of External Lightning Protection System (LPS)-(Part-1)

Introduction:

• A lightning protection system does not attract or prevent a lightning strike. but the lightning protection system provides a low impedance path to lightning currents to flow from Lightning striking Point to the ground to prevent dangerous flashovers and lightning-caused fires.
• Lightning protection systems are designed to protect structures, equipment or people from the damaging effects of lightning strikes. These systems create pathways for lightning strikes to travel safely from the top of a structure to the ground with a lightning conductor. They protect the internal electrical components of a building by preventing fires or electrocution for that all metallic installations in the building must be made at equal potential.
• The basic goal of LPS is to prevent thermal, mechanical, and electrical effects that can cause damage to the protected structure or to humans via touch or step voltages within the structure.

Lighting Protection Standards:

• There are various lighting protection standards. Widely use are
• IEC 62305
• IS 2309
• NFPA 780
• NBC-2016

 IEC:62305 -Part 1 to 5:

COMPARISON BETWEEN IEC AND IS STANDARD FOR LPS: 

Comparison between IEC and IS standard for External LPS
Description	LPS as per IEC 62305	LPS as per IS 2309	ESE (Early Streamer Emission)
Coverage area	Real, Calculated and approved design as per building type complying to IEC 62305-3.	Real, Calculated and approved design as per building type complying to IEC 62305-3.	Imaginary – no proof available, Not complying and national or international standard.
Approvals / Applicability of latest standard	IEC 62305-3 – International standard, Released in 2010	IS 2309 & IS 3043 – National standard, Released in 1989	Approved only in France which is their local standard
Insurance cover	Yes.	Yes.	No. Not approved by IS & CEA
Height limitation	No height limitation as the LPS is based on horizontal air terminal	No height limitation as the LPS is based on horizontal air terminal	Height restriction is applicable surrounding the airport area as ESE is based on Vertical air terminal.
Air Termination Design	Rolling sphere method	Protective Angle method & Mesh method	Not as per any international method.
LPS for Type of Building	Any type of complex building.	Simple and Flat /Slopped Building
Material for Air terminal & down conductor.	8mm Aluminum round, which is easier to install, bend & needs less conductor holder.	25X3 GI is used which is difficult to install, bend & needs twice the amount of conductor holder.	Not as per any international method.
Material compatibility	Taken care using bi-metal connector	No specific mention in the standard.	Not taken care.
Expansion /contraction of metal in summer/winter	Taken care of using Expansion pieces.	Not taken care	Not applicable as it is based on vertical air terminal.
No of Down Conductor.	More than one down conductor to dissipate the Lightning current to the ground (Multiple Dissipation)	Less number of down conductors when compared to IEC 62305	In most of the sites, only one down conductor is installed.
Current sharing Path	Many Parallel paths. LEMP has minimal effects	Few parallel paths	Maximum 2 Parallel paths. High LEMP can damage electronic equipment.
Design of LPS	based on LPL 1 to 4 backed up by IEC 62305	Based on Experience & old IEC, BS standards.	Not as per any international method.
Experience	Used for many decades without any problem.	Used for many decades without any problem.	Approximately 15 years old. In Some country many buildings with ESE were damaged.
Grounding	Type B as per IEC 62305-1	Ring earthing as per IS 3043	Recommended only for small residences (not even apartments) where electronic equipment is not available.
Installation	time consuming but effective	time consuming but effective	less time consuming but ineffective

Lighting Protection Levels:

• Lighting Protection Level are divided into four categories. For each category, a set of maximum and minimum lightning current parameters is fixed (LPL I to IV).
• The maximum values of lightning current parameters are used to design lightning protection components (e.g. Cross section of conductors, thickness of metal sheets, current capability of SPDs and Separation distance against dangerous sparking).
• The minimum values of lightning current amplitude for the different LPL are used to derive the Rolling Sphere Radius to define the Lightning Protection Zone (LPZ0B) which cannot be reached by direct strike.

RELATION BETWEEN LPL AND CLASS OF LPS
Table-7, IEC- 62305-3
LPL	RISK LEVEL	CLASS OF LPS
CLASS I	Very High Risk	I
CLASS II	High Risk	II
CLASS III	Moderate Risk	III
CLASS IV	Low Risk	IV

 

CLASSIFICATION OF LPS
Table-4, IEC- 62305-1
CLASSIFICATION OF LPL	Maximum Current (KA)	Minimum Current (KA)
CLASS I- (Very High Risk)	200 KA	3 KA
CLASS II-(High Risk)	150 KA	5 KA
CLASS III-(Moderate Risk)	100 KA	10 KA
CLASS IV-(Low Risk)	100 KA	16 KA

Types of Lighting Protection System (LPS):

• There are two types of Lightning Protection System
• External Lighting Protection
• Internal Lighting Protection.
• External lightning protection
• External lightning protection protects buildings in case of a direct lightning strike. It basically intercepts direct lightning flashes to the structure and conduct the lightning current from the point of strike to the ground and creates a protective sheath around the building which prevents it from catching fire and protects the people within.
• The External LPS also disperses this current into the earth without causing damage to the structures or causing unsafe potential rise / sparking.

• Internal Lighting Protection:
• An Internal LPS protects equipment against transient voltages and currents.
• Internal Lighting Protection / Surge protection provides safety within the building. It keeps surges which might enter the house via power supply cables / Power Line and protect electrical /electronic devices of house (which would otherwise be at risk via these routes).

Types of External LPS System

• There are two types of External LPS System
• Non-Conventional System / Early Streamer Emission (Isolated System)
• Conventional System (Non-Isolated System)
• Non-Conventional / Early Streamer Emission (Isolated System):
• Non-Conventional System / Isolated System does not mean that the system is electrically isolated from earth (a common misconception). It just means of physical distance achieved between the lightning current and the item being protected.
• In Non-Conventional / Isolated System, Lightning conductor does not directly attach to the structure or asset being protected. There is little or more separation between Structure and Lightning system.
• This can be achieved with free-standing masts (or poles) which stand someway off the item being covered at highest Point. Or, in some cases, separation can be achieved by using non-sparking conductors.
• Lightning Rods are installed at the highest point of protected building with sufficient separation distance to each other electrically and physically. Separate (Isolated) Lighting Rod provides conductive path to lighting current to the earth.
• Conventional (Non-Isolated System):
• In Conventional / Non-isolated System is typically attached conductor arrangements directly to the structure or asset being protected with little or no separation.

Components of External Lighting Protection System:

• An external Lightning Protection System has following parts

1. Air terminal system= Intercept a lightning flash to a structure
2. The down conductor system =provides the safest path to the lightning current towards the earth.
3. Earthing system =Disperse the lightning current into the earth.

• These individual elements of an LPS should be connected using appropriate lightning protection components. This will ensure that in the event of a lightning current discharge to the structure, any potential damage to the structure protected will be minimized.
• In most cases, the external LPS may be attached to the structure to be protected. An isolated LPS is preferred for areas at risk of explosion and fire.

(1) Air Termination System:

• The role of an air termination system is to capture the lightning discharge current and dissipate harmlessly to earth via down conductor and earth termination system. Therefore, it is very important to use a correctly designed Air-termination system.
• Air Termination System can be composed of any combination of the following elements.
• (i) Rods (including free standing masts)
• (ii) Catenary wires (suspended wires)
• (iii) Meshed conductors that may lie in direct contact with the roof or be suspended above it.

AIR TERMINATION SYSTEM DESIGN

•  As per considering Class of Lighting Protection System, the air-termination system shall be design by following methods.
• All methods should be used, independently or in any combination to ensure that the protection zones by different parts of the air-termination overlap and ensure that the structure is entirely protected.
• Methods for the air-termination for Lighting Protection System is
• (A) Protection Angle Method
• (B) Rolling Sphere Method and
• (C) Mesh Method
• All three methods may be used for the design of an LPS. The choice of the method depends on a practical evaluation of its suitability and the vulnerability of the structure to be protected.
• The major difference in Air Termination methods is as below.
• (i) The protection angle method is suitable for simple structures or for small parts of bigger structures. It also has limitations on the height of the air terminal. This method is not suitable for structures higher than the radius of the rolling sphere relevant to the protection level of the LPS.
• (ii) The rolling sphere method is suitable for complex shaped structures. This method is mostly used in all the cases.
• (iii) The mesh method is for general purposes, and it is particularly suitable for the protection of plane surface.

(A) PROTECTION ANGLE METHOD (Suitable for Simple-Shaped building)

• The Protection Angle method is wider used compared to mesh method, because it can be installed at simple structure, on not smooth/not flat surface, on protruding metallic structure.
• This method is used for structures that do not exceed 15 Meter in height.
• For structures less than 7.5 Meter in height, a Protection angle shall be 60 degrees, or 1:2, angle is permitted.
• For structures over 7.5 Meter but not in excess of 7.5 Meter a Protection angle shall be 45 degrees, or 1:1, angle is used. This is illustrated in Figure
• The Protective Angle Method is generally used as a supplement to the Mesh Method.
• Air-termination rods should be positioned so that all the parts of the structure, including metallic equipment installed on the roof like HVAC units, PV panels to be protected inside the envelope generated by the air-termination rods.
• In this method several air terminals are placed at the highest points on top of buildings/structures at different locations. Each air terminal covers a certain angle of protection.
• The degree of protection can be selected based on the height of terminal from base to tip. For example, if class I is selected, this means that the angle of protection is 70 degrees, considering 2 meters height of the terminal.
• In the case of installing metallic equipment’s, like HVAC Unit, PV panels at roof, sufficient distance among the equipment and air terminals shall be considered to avoid sparking, as well as selecting the appropriate protection angle.
• The real physical dimension of metal Air-termination shall be considered to calculate area protected by Lighting terminal. Typically, if the air rod is 5 meters tall, then the zone of protection offered by this air terminal rod would be based on 5 meters and the relevant class of LPS.
• If the building height is less than 30 meters, 45-degree cone of protection can be used. For building height more than 30 Meters, 30-degree cone of protection shall be considered

Volume protected by a vertical rod air-termination system

• Air-termination conductors, rods, masts and wires should be positioned so that all parts of the structure to be protected are inside the envelope surface generated by projecting points on the air-termination conductors to the reference plane, at an angle α to the vertical in all directions.
• The volume protected by a vertical rod is assumed to have the shape of a right circular cone with the vertex placed on the air-termination axis, semi-apex angle α, depending on the class of LPS, and on the height of the air-termination system as given in Table.

• The protection angle should confirm to the table mentioned below, with h being the height of the air-termination above the surface to be protected.

Height of Air Termination Rod-Protection Angle & Protection Distance
Height of Air termination rod in meter	LPS-CLASS-I		LPS-CLASS-II		LPS-CLASS-III		LPS-CLASS-IV
	Angle	Protection Distance in Meter	Angle	Protection Distance in Meter	Angle	Protection Distance in Meter	Angle	Protection Distance in Meter
1	71	2.9	74	3.49	77	4.33	79	5.14
2	71	5.81	74	6.97	77	8.66	79	10.29
3	66	6.74	71	8.7	74	10.46	76	12.03
4	62	7.52	68	9.9	72	12.31	74	13.95
5	59	8.32	65	10.72	70	13.74	72	15.39
6	56	8.9	60	11.28	68	14.85	71	17.43
7	53	9.29	58	12.12	66	15.72	69	18.24
8	50	9.53	56	12.8	64	16.4	68	19.8
9	48	10	54	13.34	62	16.93	66	20.21
10	45	10	52	13.76	61	18.04	65	21.45
11	43	10.26	50	14.08	59	18.31	64	22.55
12	40	10.07	49	14.3	58	19.2	62	22.57
13	38	10.16	47	14.95	57	20.02	61	23.45
14	36	10.17	45	15.01	55	19.99	60	24.25
15	34	10.17	44	15	54	20.65	59	24.96
16	32	10	42	15.45	53	21.23	58	25.61
17	30	9.81	40	15.31	51	20.99	57	26.18
18	27	9.17	39	15.1	50	21.45	56	26.69
19	25	8.26	37	15.39	49	21.86	55	27.13
20	23	8.49	36	15.07	48	22.21	54	27.53
21			35	15.26	47	22.52	53	27.87
22			36	16.71	46	22.78	52	28.16
23			32	15	47	24.66	53	30.52
24			30	14.43	44	23.18	50	28.6
25			29	14.41	43	23.31	49	28.76
26			27	13.76	41	22.6	49	29.91
27			26	13.66	40	22.66	48	29.99
28			25	13.52	39	22.67	47	30.03
29			23	12.73	38	22.66	46	30.03
30					37	22.61	45	30
31					36	22.52	44	29.94
32					35	22.41	44	30.9
33					35	23.11	43	30.77
34					34	22.93	42	30.61
35					33	22.73	41	30.43
36					32	22.5	40	30.21
37					31	22.23	40	31.5
38					30	21.94	39	30.77
39					29	21.62	38	30.47
40					28	21.27	37	30.14
41					27	20.89	37	30.9
42					26	20.48	36	30.51
43					25	20.05	35	30.11
44					24	19.59	35	30.81
45					23	19.1	34	30.35
46							33	29.87
47							32	29.37
48							32	29.99
49							31	29.44
50							30	28.87
51							30	29.44
52							29	28.82
53							28	28.18
54							27	27.51
55							27	28.02
56							26	27.31
57							25	26.58
58							25	27.05
59							24	26.27
60							23	25.47

• Air termination conductors and down conductors should be inter-connected by means of conductors at the roof level to provide sufficient current distribution over the down conductors.
• Conductors on roof and the connections of air termination rods may be fixed to the roof using both conductive or non-conductive spacers and fixtures. The conductors may also be positioned on the surface of a wall if the wall is made of non-combustible material. The fixing centers shall be minimum 1 meter apart.
• For each non-isolated LPS, the number of down conductors shall be not less than two.
• A down conductor should be installed at each exposed corner of the structure, where this is possible.

Limitation:

• The protection angle method has geometrical limits and cannot be applied if Building height (H) is larger than the rolling sphere radius (r).
• The angle will not change for values of Building height (H) below 2 meters.

Calculate Size of Diesel Generator for various types of Load

Calculate Size of Diesel Generator set for following types of various equipment’s

D.G Set Detail:

• G Set Phase-Phase Voltage=415V, Phase-Neutral Voltage=230V, Future Load expansion=10%, D.G overload capacity =130%.

Connected Load:

1. Fire Fighting Pump: 1No,3 Phase, 90KW, starting P.F is 0.7 & running P.F is 0.8, Soft Starter, Continuous use.
2. HVAC Load: 1No, 3 Phase, 20KW, starting P.F is 0.7 & running P.F is 0.8, Intermediate use.
3. UPS Load: 1No, 3 Phase, 7KW, starting P.F is 0.7 & running P.F is 0.8, Continuous use.
4. Lighting Load: 10No, 1Phase ,400Watt, starting P.F is 0.7 & running P.F is 0.8, Continuous use.

• Linear Load =General Electrical equipment, Heater
• Non-Linear Load = UPS, Inverter, Ballast, Drives

CALCULATION:

LOAD NO:1 (MOTOR LOAD)

• Total Load (KW)= No of Equipment X Size of Equipment
• Total Load (KW)=01×90 =90KW
• Diversify Load (KW)= Total Load X Duty factor (0=Stand by Load,1=continuous Load, 0 to 1 =Intermediate Load)
• Diversify Load (KW) = 90×1= 90KW————————————–(1)
• Running KVA = Diversify Load (KW) / Running P.F
• Running KVA = 90 x 0.8
• Running KVA =113 KVA————————————–(2)
• Running Amp (Amp) = Diversify Load (KW) / 1.732 x Volt x Running P.F
• Running Amp (Amp) =90×1000 / 1.732 x 415 x 0.8
• Running Amp (Amp) =156.7 Amp
• Starting Amp = Running Amp X Multiplying Factor of Starter
• Multiplying Factor of Starter is as under.

Starter Starting current
Method	Starting current
Direct-on-Line (DOL)	5 to 10 times the full load current
Star-Delta Starter	3 to 4 times the full load current
Auto-transformer	2 to 3 times the full load current
Soft starter	1.1 to 2 times full load current
Variable Speed drive	1.1 to 1.5 times full load current

• Considering Multiplying Factor for Soft Starter is 2
• Starting Amp = 156.7 X 2
• Starting Amp =313Amp
• Starting KVA = (Diversify Load (KW) / Starting P.F) X Multiplying Factor of Starter
• Starting KVA = (90/0.7) X 2
• Starting KVA = 257 KVA——————————————–(3)

LOAD NO:2 (HVAC LOAD)

• Total Load (KW)= No of Equipment X Size of Equipment
• Total Load (KW)=01×20 =20KW
• Diversify Load (KW)= Total Load X Duty factor (0=Stand by Load,1=continuous Load, 0 to 1 =Intermediate Load)
• Diversify Load (KW) = 20×0.8= 16KW————————————–(4)
• Running KVA = Diversify Load (KW) / Running P.F
• Running KVA = 16 x 0.8
• Running KVA =20 KVA————————————–(5)
• Running Amp (Amp) = Diversify Load (KW) / 1.732 x Volt x Running P.F
• Running Amp (Amp) =16×1000 / 1.732 x 415 x 0.8
• Running Amp (Amp) =28 Amp
• Starting Amp = Running Amp X Multiplying Factor of HVAC
• Multiplying Factor of Starting Current for various type of Load is as under.

Starting current
Type of Load	Starting current for Load
Linear	1 time the full load current
Non-Linear	1.2 to 1.6 times the full load current
HVAC	1.2 to 1.5 times the full load current

• Considering Multiplying Factor of HVAC is 1.3
• Starting Amp = 28X 1.3
• Starting Amp =36Amp
• Starting KVA = (Diversify Load (KW) / Starting P.F) X Multiplying Factor of HVAC
• Starting KVA = (16/0.7) X1.3
• Starting KVA = 30 KVA——————————————–(6)

LOAD NO:3 (NON-LINEAR LOAD)

• Total Load (KW)= No of Equipment X Size of Equipment
• Total Load (KW)=01×7 =7KW
• Diversify Load (KW)= Total Load X Duty factor (0=Stand by Load,1=continuous Load, 0 to 1 =Intermediate Load)
• Diversify Load (KW) = 7×1= 7KW————————————–(7)
• Running KVA = Diversify Load (KW) / Running P.F
• Running KVA = 7 x 0.8
• Running KVA =9 KVA————————————–(8)
• Running Amp (Amp) = Diversify Load (KW) / 1.732 x Volt x Running P.F
• Running Amp (Amp) =7×1000 / 1.732 x 415 x 0.8
• Running Amp (Amp) =12 Amp
• Starting Amp = Running Amp X Multiplying Factor of Non-Linear Load
• Multiplying Factor of Starting Current for various type of Load is as under.

Starting current
Type of Load	Starting current for Load
Linear	1 time the full load current
Non-Linear	1.2 to 1.6 times the full load current
HVAC	1.2 to 1.5 times the full load current

• Considering Multiplying Factor of Non-Linear Load (UPS) is 1.6
• Starting Amp = 12X 1.6
• Starting Amp =19Amp
• Starting KVA = (Diversify Load (KW) / Starting P.F) X Multiplying Factor of HVAC
• Starting KVA = (7/0.7) X1.6
• Starting KVA = 16 KVA——————————————–(9)

LOAD NO:4 (LINEAR LOAD)

• Total Load (KW)= No of Equipment X Size of Equipment
• Total Load (KW)=10×0.4 =4KW
• Diversify Load (KW)= Total Load X Duty factor (0=Stand by Load,1=continuous Load, 0 to 1 =Intermediate Load)
• Diversify Load (KW) = 4×1= 4KW————————————–(10)
• Running KVA = Diversify Load (KW) / Running P.F
• Running KVA = 4 x 0.8
• Running KVA =5 KVA————————————–(11)
• Running Amp (Amp) = Diversify Load (KW) / 1.732 x Volt x Running P.F
• Running Amp (Amp) =4×1000 / 230 x 0.8
• Running Amp (Amp) =22 Amp
• Starting Amp = Running Amp X Multiplying Factor of Linear Load
• Multiplying Factor of Starting Current for various type of Load is as under.

Starting current
Type of Load	Starting current for Load
Linear	1 time the full load current
Non-Linear	1.6 times the full load current
HVAC	1.2 to 1.5 times the full load current

• Considering Multiplying Factor of Linear Load is 1
• Starting Amp =22×1
• Starting Amp =22Amp
• Starting KVA = (Diversify Load (KW) / Starting P.F)
• Starting KVA = (4/0.7)
• Starting KVA = 6 KVA——————————————–(12)

TOTAL LOAD CALCULATION:

• Total Starting KVA= Starting KVA of (Load 1+ Load 2+ Load 3 +Load 4)
• Total Starting KVA= 257+30+16+6
• Total Starting KVA= 309 KVA————————————(A)
• Total Running KVA =Running KVA of (Load 1+ Load 2+ Load 3 +Load 4)
• Total Running KVA =113+20+9+5
• Total Running KVA = 146 KVA—————————–(B)
• D.G set Size (KVA) = Total Starting KVA x Future Load Expansion.
• D.G set Size (KVA) = 309×1.1 (10% Future expansion)
• D.G set Size (KVA) = 339 KVA—————————————-(C)

CONDITION FOR SELECTING D.G SET:

• CONDITION-1:
• Total Non-Linear Load < 30% of D.G Size
• Here Value no (9) < Value no (C)
• 16 KVA < 102 KVA
• Condition-1 is full fill
• CONDITION-2:
• Overloads withstand Capacity of D.G > Total Required starting KVA
• Overload withstand capacity of D. G= D.G size X D.G over Load Capacity
• Overload withstand capacity of D. G= 339 x 130%
• Overload withstand capacity of D. G= 401 KVA——————–(D)
• Total Required starting KVA = Total Load (KVA) -Largest Motor rating (KVA)+ Largest Motor starting (KVA)
• Total Required starting KVA =146 -113+257
• Total Required starting KVA =291 KVA ————————(E)
• Here Value no (D) > Value no (E)
• 401 KVA > 291 KVA
• Condition-2 is full fill

 CONCLUSION:

• Here Condition-1 & Condition-2 is full fill hence selected D.G Size is OK.
• Hence D.G size is 339 KVA or near its 380 KVA