Selection of Various Types of Inverter-(Part-1)

Introduction:

• In this modern society, electricity has vital role on the most daily activities for domestic and industrial utilization of electric power for operations.
• An inverter is used to provide uninterrupted 220V AC supply to the load connected to its output socket. It provides constant AC supply at its output socket, even when the AC mains supply is not available.
• There are many factors, which are affecting on selecting of the best inverter for our application

Block Diagram of Inverter:

• Power inverter is a device that converts electrical power from DC form to AC form using electronic circuits. It is typical application is to convert battery voltage into conventional household AC voltage to use Equipments, when an AC power is not available.
• There are two methods, in which the low voltage DC power is inserted into AC Power.
• In First Method first is the conversion of the low voltage DC power to a high voltage DC source, an then It is the conversion of the high DC source to an AC waveform using pulse width modulation.
• In Second method the outcome would be to first convert the low voltage DC power to AC, and then use a transformer to boost the voltage to 220 volts.
• The widely used method in the current residential inverter is the second.
• An Inverter not only converts the DC Voltage of battery to 220V V AC Signals but also charge the Battery when the AC mains are present.
• The block diagram shown above is a simple depiction of the way an Inverter Works.

When the AC mains power supply is available.

• When the Utility Company AC mains supply is available.
• C Main Sensor: the AC sensor senses it and the 230V A.C supply feeds to the Relay and battery charger.
• Relay or Change over Switch: AC main sensor activates a relay and this relay will directly pass the 230V AC mains supply to the Load.
• Battery Charger: Battery Charger converts line A.C Voltage to DC Voltage and Charges the Battery even when A.C Power is available.
• Battery: Battery is charged and it is stopped when it is full charged.

 When the AC mains power supply is not available.

• When the AC mains power supply is not available.
• Relay or Change over Switch: AC main sensor activates a relay and this relay will connected to battery in absent of the AC mains supply.
• Battery: Battery is providing DC Power to Oscillator circuit through Relay.
• Oscillator Circuit: An oscillator circuit inside the inverter use pulse width modulator to generate the 50Hz frequency required to generate AC supply by the inverter.
• The battery DC supply is connected to the Oscillator. The flip-flop converts the incoming signal into signals with changing polarity such that in a two-signal with changing polarity.
• The first is positive while the second is negative and vice versa. This process is repeated 50times per second to give an alternating signal with 50Hz frequency. This alternating signal is known as “MOS Drive Signal “.
• Driver Circuit: The MOS drive signals are given to the base of driver transistor which separated into two different channels.
• Amplifier Circuit: The transistors amplify the 50Hz MOS drive signal at their base to a sufficient level and output them from the emitter.
• Inverter Transformer: The transformer used for this is a center-tapping which divides the primary into two equal sections.
• This center-tapping is connected to the positive terminal of the battery. Two ends of the primary are connected to the negative terminal of the battery through switches S1 and S2.
• MOSFETs or Transistors are used for the switching operation. These MOSFETs or Transistors are connected to the primary winding of the inverter transformer.
• When these switching devices receive the MOS drive signal from the driver circuit, they start switching between ON & OFF states at a rate of 50 Hz. This switching action of the MOSFETs or Transistors creates a 50Hz current to the primary of the inverter transformer. This results in a 220V AC or 2300V AC (depending on the winding ratio of the inverter transformer) at the secondary or the inverter transformer. This secondary voltage is made available at the output socket of the inverter by a changeover relay.

 Type of Inverter

• The inverters are classified by depending on their output
• Sine wave
• Modified sine wave
• Square wave.

(1) Sine Wave Inverter:

• In utility Company Sine wave generated by rotating AC machinery and sine waves is a natural product of rotating AC machinery.
• Pure sine wave inverters provide an output same as a sine wave which is similar to the utility supplied grid power, hence Pure Sine Wave inverter produces a better and cleaner current

• All commercial instruments are designed to run on pure sine wave. Characteristics of such devices are greatly depending upon the input wave shape. A change in wave shape will affect the performance and efficiency of the appliances.
• Sine Wave guarantees by Sine way Inverter is pure so the equipment will work to its full specifications as per its design. Appliances like Motors, refrigerators, Ovens etc will generate full power on pure sine wave input only.
• A few appliances, such as Toaster, light dimmers, and some battery chargers require a sine wave to work propellerly. Operation of these appliances in Square or stepped waves will considerably affect the life of such equipment due to the generation of heat.
• Distortion in the sine wave creates humming noise in transformers, and audio devices
• Some time we noticed that audio amplifiers, Televisions, Fluorescent lamps etc make noise on inverter power. This indicates that inverter output is not pure sine wave.
• It is always advisable and recommended to go for a pure sine wave inverter for the safety and effective performance of your appliances.

Advantages:

• Output voltage wave form is pure sine wave with very low harmonic distortion and clean power like utility-supplied electricity.
• Inductive loads like microwave ovens and motors run faster, quieter and cooler.
• Reduces audible and electrical noise in fans, fluorescent lights, audio amplifiers, TV, Game consoles, Fax, and answering machines.
• This type of inverters will save your current bill compared to square wave inverters.
• Prevents crashes in computers, weird print out, and glitches and noise in monitors.
• Back up time will be better than square wave inverters.

Disadvantages:

• Sine wave inverters are 2 to 3 times expensive compared to square wave and modified sine wave inverters.

Application:

• More sensitive electrical or electronic items
• Desktop computers, laptops, Laser printers, photocopiers,
• Camera battery chargers, cell phone chargers,
• Mixer,
• Fluorescent lights with electronic ballasts ,
• Digital clocks ,
• Sewing machines with speed/microprocessor control ,
• Medical equipment,
• Small house hold water pumping motors, Drives etc.

(2) Modified Sine Wave:

• A modified sine wave inverter has a waveform like a square wave, but with an extra step.
• Modified sine wave is a simulation of the pure sine wave output when the inverter sharply drops or increases voltage to switch polarity. As a result, the output form closely matches pure sine wave but still has much greater distortions.
• A modified sine wave inverter will work fine with most equipment, although the efficiency or power will be reduced with some.

• The devices are usually about 70% efficient, so we can expect some significant power losses if we are using a modified sine wave inverter in your system.
• Motors, such as refrigerator motor, pumps, fans etc will use more power from the inverter due to lower efficiency. Most motors will use about 20% more power.
• Some fluorescent lights will not operate quite as bright, and some may buzz or make annoying humming noises.
• Because the modified sine wave is noisier and rougher than a pure sine wave, clocks and timers may run faster or not work at all. They also have some parts of the wave that are not 50 Hz, which can make clocks run fast. Items such as bread makers and light dimmers may not work at all in many cases appliances that use electronic temperature controls will not control. The most common is on such things as variable speed drills will only have two speeds on and off.
• The difference between Sine wave and modified Sine wave inverter is the cost. Sine wave is considerably more expensive. We can find it practical way from it .We can install a small Pure Sine Wave inverter for any “special need” and also a larger Modified Sine Wave inverter for the rest of our applications.

Advantages:

• Cheaper than pure sine wave inverters
• Output correction waveform; relatively stable; suitable for ordinary personal users with TV, fan, lamp, computer, hot pot etc.
• Output wave form have a very low harmonic distortion compare to Square wave inverter

Disadvantages:

• Lower efficiency than pure sine wave inverters.
• Power Loss is more compared to sine wave inverter.
• Modified Sine Wave output is not suitable for continuous long time operation of certain appliances with capacitive and electromagnetic devices such as a fridge, microwave oven and most kinds of motors, printers as well as capacitive fluorescent lights etc
• Some fans with synchronous motors may slightly increase in speed (RPM) when powered by a modified sine wave inverter. This is not harmful to the fan or to the inverter.
• Certain rechargers for small nickel-cadmium batteries can be damaged if plugged into a modified sine wave inverter

Application:

• Some household appliances and power tools.
• Inductive loads like micro ovens and motors.
• Fans and fluorescent lights,
• Audio amplifiers, TVs, game consoles, fax and answering machines.

 (3) Square Wave Inverter:

• The Output wave form of the Inverter is like square.
• This is old-fashioned and the cheapest inverters, but the hardest to use.
• A square wave inverter will run simple things like tools with universal motors without a problem, but not much else.

• The current we get from grid is neither square wave nor pure sine wave, it’s nearly sine wave. So, our electronic devices like fan and tube light will emit some buzz noise while operating in square wave current. In some rare cases, these square wave inverters have spoiled the speed control dimmers of ceiling fans.
• In the form of square wave, The load voltage must be switched majorly from high voltage  to low Voltage, without  using  for an intermediate step of 0Volt.
• The main reason for this fault is high voltage output. Normally, voltage output from square wave inverters is 230 volt to 290 volt, hence it is not recommended to sensitive electronic devices like computers.
• They just flip the voltage from plus to minus creating a square waveform. They are not very efficient because the square wave has a lot of power in higher harmonics that cannot be used by many appliances. Synchronous motors, for example, use the 50Hz component and turn the rest of the frequencies into heat
• Square wave inverters are seldom seen any more.

Advantages:

• It is very cheap

Disadvantages:

• Life of Application is less.
• Speed control of some equipment is not possible
• Voltage Variation is high.
• Large 3rd and 5th harmonic components which burn power and severely cut down on the efficiency of devices

Application:

• Low cost AC motor drives
• Some electronic ballast for fluorescent lamps

Electrical Thumb Rules-(Part-15)

 

Selection of MCB
MCB curve	Type of Load	Residential	Commercial
B curve	Resistive Loads	Incandescent lights	Incandescent lights
		Geyser	Boilers
		Heater	Heaters
		Fan blower heaters	Oil radiator heaters
	Slight Inductive Loads	Florescent Lights	Florescent lights
		Small motors (FHP)	High pressure mercury vapor lamps
C curve	Slight Inductive Loads	Fans & small pumps	Sodium vapor lamps
		Window / Split ACs
		Lights with ballasts
		Microwave
		Refrigerators
		General household equipment
D curve	Inductive Loads	Water lifting pumps	Florescent lights
		UPS	ID & FD fans
			Small control transformers
			Medium size motors
			Refrigerators for commercial use

 

Type of MCB
MCB Curve	Type of Load	Response	Tripping	Application	Uses
B curve	Resistive loads	MCBs react quickly to overloads	3 To 5 times F.L current (0.04 To 13 Sec)	Domestic & Commercial applications	Suitable for incandescent lighting, socket-outlet, bulbs, heaters etc. Protection of DG sets (since DG sets have low short-circuit capacity)
C curve	Slightly inductive loads	MCBs react more slowly,	5 To 10 times F.L current  (0.04 To 5 Sec)	Commercial and Industrial applications	Highly Inductive loads such as motors, air conditioners, fluorescent lighting lights, fans & household electrical appliances.
D curve	Inductive loads	MCBs are slower	10 To 20 times F.L current  (0.04 To 3 Sec)	Commercial and Industrial applications	Very high inrush Inductive currents, Small transformers, welding machines. UPS, small motor & pumps, x-ray machines etc. Note, however, that MCBs with Type K characteristics may provide better protection in some applications of this type.
K curve	Inductive loads	MCBs are slower	8 To 10 times F.L current  (0.04 To 3 Sec)		Placing them between the traditional Type C and Type D breakers. In most cases, they allow improved cable protection to be provided in circuits that include motors, capacitors and transformers, where it would previously have been necessary to use Type D devices. This enhanced protection is achieved without increasing the risk of nuisance tripping.

 

Selection of RCCB
Type of RCCB	Sensitive	Application
Type AC	Sensitive to AC Currents Only	Suitable for most domestic and commercial applications.
Type A	Sensitive to AC Currents + Pulsating DC Currents (Produced by Rectifier, Thyristors)	Used where there are a lot of “electronic” loads, such as computer equipment or lighting systems with electronic ballasts.
Type B	Sensitive to AC Currents + Pulsating DC Currents+ Pure DC Currents	Use in photovoltaic (PV) solar energy installations because the PV panels produce a DC Output and some types of fault can result in the leakage of DC Currents to Earth.
Type B+	Similar to Type B, but respond to ac leakage currents over a wider frequency range	Type B and Type B+ devices can be used wherever a Type AC or Type A device is specified, as they provide the same functionality as these types and more.

 

TYPE of RCCB
TYPE	AC Current 50Hz	AC Current 50Hz To 1KHZ	Pulsating Current with DC Component	Multi Frequency Current Generated By 1Phase Inverter	Multi Frequency Current Generated By 3Phase Inverter
AC	√	–	–	–	–
A	√	–	√	–	–
F	√	–	√	√	–
B	√	√	√	√	√
AS	√	–	√	–	–
BS	√	√	√	√	√

 

Sensitivity of RCCB
RCCBs	Application
30 mA	personal protection domestic installation / direct contact
100 mA	limited personal protection / indirect contact
300 mA	building / fire protection

 

MCB Enclosure Size
MCB Rating (A)	Min. Enclosure Size
	Height	Width	Depth
100A	370mm	216mm	72mm
125A	310mm	180mm	83mm
225A	370mm	217mm	72mm
250A	380mm	195mm	83.5mm
300A to 400A	506mm	381mm	153mm
600A to 800A	520mm	420mm	200mm
1000A to 1200A	704mm	554mm	173mm
1600A to 3000A	1016mm	608mm	615mm

 

Switch Gear Protection
Switch Gear	Protection		Isolation	Control
	Over Load	Short Circuit
Fuse	YES	YES	NO	NO
Switch	NO	NO	YES	YES
Circuit Breaker	YES	YES	YES	YES
Contactor	NO	NO	NO	YES
Disconnector	NO	NO	YES	NO

 

Type of Faults
Types of Fault	Reason	Consequences	Protective Device to be used
Overload	When Equipment tries to run beyond its rated capacity, or there is a fault in the equipment E.g. When you keep a heater on without any water in it.	It can lead to reduction in life of equipment, Failure of insulation and hence damaging the equipment.	MCB / RCBO
Short Circuit	Insulation Failure, Shorting of the Phase to Phase or Phase and Neutral Wires.	High Inrush Current, causing permanent damage to equipment and may lead to a Fire.	MCB
Earth Fault	Short circuit between Phase and Earth Conductor.	Can result in Fire due to sparking.	RCBO / RCCB
Earth Leakage	Human Body Touching Live Wires. Insulation failure		RCBO / RCCB
Over Voltage	Opening of Neutral Connection increase in Phase To Phase Voltage of 440V, Surge through Lighting or transients, Over voltage from Utility.	Damage to sensitive Electronic Equipment.	OV protection Device
Under Voltage	Drop in supply voltage, starting of heavy loads	Damage of Equipment, Flickering of Lights.	UV relays

 

MCB Type (BS EN 60898-2)
Trip Type	instantaneous Trip (< 0.1 s)	Load Type	Typical Load
B	3 to 5 In (AC)	Resistive	Heaters, showers, cookers, socket outlets.
	4 to 7 In (DC)
C	5 to 10 In (AC)	Inductive	Motors, general lighting circuits, power supplies.
	7 to 15 In (DC)
D	10 to 20 In	High Inductive	Transformers, motors, discharge lighting circuits, computers

 

Relays for Transformer
Capacity of Transformer	Relays on HV Side	Relays on LV Side	Common Relays
Generator Transformer	3 Nos Non-Directional O/L Relay	– –	Differential Relay or
	1 no Non-Directional E/L Relay		Overall differential Relay
	and/or standby E/F + REF Relay		Over flux Relay
			Buchholz Relay
			OLTC Buchholz Relay
			PRV Relay
			OT Trip Relay
			WT Trip Relay
220 /6.6KV Station Transformer	3 Nos Non-Directional O/L Relay	3 Nos Non-Directional O/L Relay	Differential Relay
	1 no Non-Directional E/L Relay		Over flux Relay
	and/or standby E/F + REF Relay		Buchholz Relay
			OLTC Buchholz Relay
			PRV Relay
			OT Trip Relay
			WT Trip Relay
132/33/11KV up to 8 MVA	3 Nos O/L Relay	2 Nos O/L Relays	Buchholz Relay
	1 no E/L Relay	1 no E/L Relay	OLTC Buchholz Relay
			PRV Relay
			OT Trip Relay
			WT Trip Relay
132/33/11KV up to 8 MVA to 31.5 MVA	3 Nos O/L Relay	3 Nos O/L Relay	Differential Relay
	1 no Directional E/L Relay	1 no E/L Relay	Buchholz Relay
			OLTC Buchholz Relay
			PRV Relay
			OT Trip Relay
			WT Trip Relay
132/33KV, 31.5 MVA & above	3 Nos O/L Relay	3 Nos O/L Relay	Differential Relay
	1 no Directional E/L Relay	1 no E/L Relay	Over flux Relay
			Buchholz Relay
			OLTC Buchholz Relay
			PRV Relay
			OT Trip Relay
			WT Trip Relay
220/33 KV, 31.5MVA & 50MVA , 220/132KV, 100 MVA	3 No O/L Relay	3 Nos O/L Relay	Differential Relay
	1 no Directional E/L Relay	1 no Directional E/L Relay	Over flux Relay
			Buchholz Relay
			OLTC Buchholz Relay
			PRV Relay
			OT Trip Relay
			WT Trip Relay
400/220KV 315MVA	3 Nos Directional O/L Relay	3 Nos Directional O/L Relay	Differential Relay
	1 no Directional E/L relay.	1 no Directional E/L relay.	Over flux Relay
	Restricted E/F relay	Restricted E/F relay	Buchholz Relay
	3 Nos Directional O/L Relay for action		OLTC Buchholz Relay
			PRV Relay
			OT Trip Relay
			WT Trip Relay
			Over Load (Alarm) Relay

 

Relays for Transmission & Distribution Lines Protection
Lines to be protected	Relays to be used
400 KV Transmission Line	Main-I: Non switched or Numerical Distance Scheme
	Main-II: Non switched or Numerical Distance Scheme
220 KV Transmission Line	Main-I : Non switched distance scheme (Fed from Bus PTs)
	Main-II: Switched distance scheme (Fed from line CVTs)
	With a changeover facility from bus PT to line CVT and vice-versa.
132 KV Transmission Line	Main Protection : Switched distance scheme (fed from bus PT).
	Backup Protection: 3 Nos. directional IDMT O/L Relays and
	1 No. Directional IDMT E/L relay.
33 KV lines Transmission Line	Non-directional IDMT 3 O/L and 1 E/L relays.
11 KV lines Transmission Line	Non-directional IDMT 2 O/L and 1 E/L relays.

 

Selection Chart for 3Ph Induction Motor
Motor Rating,415V,3Ph		Full Load Current (A)	CONTACTOR (A)		OVER LOAD RELAY (A)		BACK UP FUSE (A)	Cable Size
								DOL Starter		STAR-DELTA Starter
HP	KW		DOL	STAR-DELTA	DOL	STAR-DELTA		Alu.	Cu.	Alu.	Cu.
0.75	0.52	1.6	16		1.0 To 1.6		4	1.5	1.5
1	0.75	2	16		1.6 To 2.5		6	1.5	1.5
2	1.5	3.5	16		3.0 To 4.5		10	1.5	1.5
3	2.2	5	16		4.5 To 7.0		10	1.5	1.5
5	3.7	7.5	16		6.5 To 10		16	1.5	1.5
7.5	5.5	11	16	16	10 To 15	4.5 To 7.0	16	2.5	1.5	2.5	1.5
10	7.5	14	16	16	13 To 20	6.5 To 10	20	2.5	2.5	2.5	2.5
12.5	9.3	18	25	16	13 To 20	10 To 15	25	4	2.5	4	2.5
15	11	21	25	16	15 To 22	13 To 20	25	6	4	6	4
20	15	28	32	18	24 To 30	13 To 20	32	10	6	10	6
25	18.5	35	40	25	25 To 30	15 To 22	50	16	10	16	10
30	22.5	40	50	25	32 To 50	24 To 30	50	16	16	16	16
35	26	47	70	32	32 To 50	25 To 30	63	25	16	25	16
50	37	66	70	40	57 To 70	32 To 50	80	35	25	35	25
60	45	80	95	50	70 To 105	32 To 50	100	50	35	50	35
75	55	100	125	70	100 To 150	40 To 57	100	70	50	70	50
90	67.5	120	140	70	100 To 150	57 To 70	160	95	70	95	70
100	75	135	140	95	100 To 150	70 To 105	160	95	70	95	70
125	90	165		125		70 To 105	160			150	95
150	110	200		125		100 To 150	200			185	150

 

MCB Selection Chart For Motor Protection
Kw	HP	1Phase 230V DOL Starting		3Phase 400V DOL Starting		3 Phase 400V Star Delta
		Full Load Current	MCB Selection	Full Load Current	MCB Selection	Full Load Current	MCB Selection	MCB Selection
0.18	0.24	2.8	10	0.9	2	—	—	—
0.25	0.34	3.2	10	1.2	2	—	—	—
0.37	0.5	3.5	10	1.2	2	—	—	—
0.55	0.74	4.8	16	1.8	3	—	—	—
0.75	1.01	6.2	20	2	3	—	—	—
1.1	1.47	8.7	25	2.6	6	—	—	—
1.5	2.01	11.8	32	3.5	10	—	—	—
2.2	2.95	17.5	50	4.4	10	—	—	—
3	4.02	20	63	6.3	16	6.3	16	10
3.75	5.03	24	80	8.2	20	8.2	20	10
5.5	7.37	26	80	11.2	25	11.2	32	16
7.5	10.05	47	125	14.4	40	14.4	40	25
10	13.4	—	—	21	50	21	50	32
15	20.11	—	—	27	100	27	63	40
18.5	24.8	—	—	32	125	32	—	50
22	29.49	—	—	38	125	38	—	63
30	40.21	—	—	51	125	51	—	63

 

RELAY CODE (ANSI)
Code	Type of Relay
1	Master Element
2	Time-delay Starting or Closing Relay
3	Checking or Interlocking Relay
4	Master Contactor
5	Stopping Device
6	Starting Circuit Breaker
7	Rate of Change Relay
8	Control Power Disconnecting Device
9	Reversing Device
10	Unit Sequence Switch
11	Multifunction Device
12	Over speed protection
13	Synchronous-Speed Device
14	Under speed Device
15	Speed or Frequency Matching Device
16	Data Communications Device
17	Shunting or Discharge Switch
18	Accelerating or Decelerating Device
19	Starting-to-Running Transition Contactor
20	Electrically-Operated Valve
21	Distance protection Relay
21G	Ground Distance
21P	Phase Distance
22	Equalizer circuit breaker
23	Temperature control device
24	Volts per hertz relay
25	Synchronizing or synchronism-check device
26	Apparatus thermal device
27	Under voltage relay
27P	Phase Under voltage
27S	DC under voltage relay
27TN	Third Harmonic Neutral Under voltage
27TN/59N	100% Stator Earth Fault
27X	Auxiliary Under voltage
27 AUX	Under voltage Auxiliary Input
27/27X	Bus/Line Under voltage
27/50	Accidental Generator Energization
28	Flame Detector
29	Isolating Contactor
30	Annunciator Relay
31	Separate Excitation Device
32	Directional Power Relay
32L	Low Forward Power
32N	Watt metric Zero-Sequence Directional
32P	Directional Power
32R	Reverse Power
33	Position Switch
34	Master Sequence Device
35	Brush-Operating or Slip-ring Short Circuiting Device
36	Polarity or Polarizing Voltage Device
37	Undercurrent or Under power Relay
37P	Under power
38	Bearing Protective Device / Bearing Rtd
39	Mechanical Condition Monitor
40	Field Relay / Loss of Excitation
41	Field Circuit Breaker
42	Running Circuit Breaker
43	Manual Transfer or Selector Device
44	Unit Sequence Starting Relay
45	Atmospheric Condition Monitor
46	Reverse-Phase or Phase Balance Current Relay or Stator Current Unbalance
47	Phase-Sequence or Phase Balance Voltage Relay
48	Incomplete Sequence Relay / Blocked Rotor
49	Machine or Transformer Thermal Relay / Thermal Overload
49RTD	RTD Biased Thermal Overload
50	Instantaneous Overcurrent Relay
50BF	Breaker Failure
50DD	Current Disturbance Detector
50EF	End Fault Protection
50G	Ground Instantaneous Overcurrent
50IG	Isolated Ground Instantaneous Overcurrent
50LR	Acceleration Time
50N	Neutral Instantaneous Overcurrent
50NBF	Neutral Instantaneous Breaker Failure
50P	Phase Instantaneous Overcurrent
50SG	Sensitive Ground Instantaneous Overcurrent
50SP	Split Phase Instantaneous Current
50Q	Negative Sequence Instantaneous Overcurrent
50/27	Accidental Energization
50/51	Instantaneous / Time-delay Overcurrent relay
50Ns/51Ns	Sensitive earth-fault protection
50/74	Ct Trouble
50/87	Instantaneous Differential
51	Phase Inverse Time Overcurrent IDMT (Time delay phase overcurrent )
51G	Ground Inverse Time Overcurrent
51LR	AC inverse time overcurrent (locked rotor) protection relay
51N	Neutral Inverse Time Overcurrent
51P	Phase Time Overcurrent
51R	Locked / Stalled Rotor
51V	Voltage Restrained Time Overcurrent
51Q	Negative Sequence Time Overcurrent
52	AC circuit breaker
52a	AC circuit breaker position (contact open when circuit breaker open)
52b	AC circuit breaker position (contact closed when circuit breaker open)
53	Exciter or Dc Generator Relay
54	Turning Gear Engaging Device
55	Power Factor Relay
56	Field Application Relay
57	Short-Circuiting or Grounding Device
58	Rectification Failure Relay
59	Overvoltage Relay
59B	Bank Phase Overvoltage
59P	Phase Overvoltage
59N	Neutral Overvoltage
59NU	Neutral Voltage Unbalance
59P	Phase Overvoltage
59X	Auxiliary Overvoltage
59Q	Negative Sequence Overvoltage
60	Voltage or current balance relay
60	Voltage or Current Balance Relay
60N	Neutral Current Unbalance
60P	Phase Current Unbalance
61	Density Switch or Sensor
62	Time-Delay Stopping or Opening Relay
63	Pressure Switch Detector
64	Ground Protective Relay
64F	Field Ground Protection
64R	Rotor earth fault
64REF	Restricted earth fault differential
64S	Stator earth fault
64S	Sub-harmonic Stator Ground Protection
64TN	100% Stator Ground
65	Governor
66	Notching or Jogging Device/Maximum Starting Rate/Starts Per Hour/Time Between Starts
67	AC Directional Overcurrent Relay
67G	Ground Directional Overcurrent
67N	Neutral Directional Overcurrent
67Ns	Earth fault directional
67P	Phase Directional Overcurrent
67SG	Sensitive Ground Directional Overcurrent
67Q	Negative Sequence Directional Overcurrent
68	Blocking Relay / Power Swing Blocking
69	Permissive Control Device
70	Rheostat
71	Liquid Switch
72	DC Circuit Breaker
73	Load-Resistor Contactor
74	Alarm Relay
75	Position Changing Mechanism
76	DC Overcurrent Relay
77	Telemetering Device
78	Phase Angle Measuring or Out-of-Step Protective Relay
78V	Loss of Mains
79	AC Reclosing Relay / Auto Reclose
80	Liquid or Gas Flow Relay
81	Frequency Relay
81O	Over Frequency
81R	Rate-of-Change Frequency
81U	Under Frequency
82	DC Reclosing Relay
83	Automatic Selective Control or Transfer Relay
84	Operating Mechanism
85	Pilot Communications, Carrier or Pilot-Wire Relay
86	Lock-Out Relay, Master Trip Relay
87	Differential Protective Relay
87B	Bus Differential
87G	Generator Differential
87GT	Generator/Transformer Differential
87L	Segregated Line Current Differential
87LG	Ground Line Current Differential
87M	Motor Differential
87O	Overall Differential
87PC	Phase Comparison
87RGF	Restricted Ground Fault
87S	Stator Differential
87S	Percent Differential
87T	Transformer Differential
87V	Voltage Differential
88	Auxiliary Motor or Motor Generator
89	Line Switch
90	Regulating Device
91	Voltage Directional Relay
92	Voltage And Power Directional Relay
93	Field-Changing Contactor
94	Tripping or Trip-Free Relay
Abbreviation Code
AFD	Arc Flash Detector
CLK	Clock or Timing Source
CLP	Cold Load Pickup
DDR	Dynamic Disturbance Recorder
DFR	Digital Fault Recorder
DME	Disturbance Monitor Equipment
ENV	Environmental data
HIZ	High Impedance Fault Detector
HMI	Human Machine Interface
HST	Historian
LGC	Scheme Logic
MET	Substation Metering
PDC	Phasor Data Concentrator
PMU	Phasor Measurement Unit
PQM	Power Quality Monitor
RIO	Remote Input/output Device
RTD	Resistance Temperature Detector
RTU	Remote Terminal Unit/Data Concentrator
SER	Sequence of Events Recorder
TCM	Trip Circuit Monitor
LRSS	Local/Remote selector switch
VTFF	Vt Fuse Fail
Suffixes Description
_1	Positive-Sequence
_2	Negative-Sequence
A	Alarm, Auxiliary Power
AC	Alternating Current
AN	Anode
B	Bus, Battery, or Blower
BF	Breaker Failure
BK	Brake
BL	Block (Valve)
BP	Bypass
BT	Bus Tie
BU	Backup
C	Capacitor, Condenser, Compensator, Carrier Current, Case or Compressor
CA	Cathode
CH	Check (Valve)
D	Discharge (Valve)
DC	Direct Current
DCB	Directional Comparison Blocking
DCUB	Directional Comparison Unblocking
DD	Disturbance Detector
DUTT	Direct Under reaching Transfer Trip
E	Exciter
F	Feeder, Field, Filament, Filter, or Fan
G	Ground or Generator
GC	Ground Check
H	Heater or Housing
L	Line or Logic
M	Motor or Metering
MOC	Mechanism Operated Contact
N	Neutral or Network
O	Over
P	Phase or Pump
PC	Phase Comparison
POTT	Pott: Permissive Overreaching Transfer Trip
PUTT	Putt: Permissive Under reaching Transfer Trip
R	Reactor, Rectifier, or Room
S	Synchronizing, Secondary, Strainer, Sump, or Suction (Valve)
SOTF	Switch On To Fault
T	Transformer or Thyratron
TD	Time Delay
TDC	Time-Delay Closing Contact
TDDO	Time Delayed Relay Coil Drop-Out
TDO	Time-Delay Opening Contact
TDPU	Time Delayed Relay Coil Pickup
THD	Total Harmonic Distortion
TH	Transformer (High-Voltage Side)
TL	Transformer (Low-Voltage Side)
TM	Telemeter
TT	Transformer (Tertiary-Voltage Side)
U	Under or Unit
X	Auxiliary
Z	Impedance

 

Harmonic Effects
Harmonic	R Phase	Y Phase	B Phase	Phase Rotation Sequence	Harmonic Effect
	Rotation	Rotation	Rotation
Fundamental	0°	120°	240°	R-Y-B
3th	3×0°=0°	3×120°=360°=0°	3×240°=720°=0°	No Rotation          (In Phase)	Adds Voltages or Currents in Neutral Wire causing Heating
9th	9×0°=0°	9×120°=1080°=0°	9×240°=2160°=0°
15th	15×0°=0°	15×120°=1800°=0°	15×240°=3600°=0°
21th	21×0°=0°	21×120°=2520°=0°	21×240°=5040°=0°
5th	5×0°=0°	5×120°=600°=(600-720)=(-120°)	5×240°=1200°=(1200-2400)=(-240°)	Rotate Against Fundamental (-) (B-Y-R)	Motor Torque Problems
11th	11×0°=0°	11×120°=1320°=(1320-1400)=(-120°)	11×240°=2640°=(2880-2640)=(-240°)
17th	17×0°=0°	17×120°=2040°=(2040-2160)=(-120°)	17×240°=4080°=(4320-4080)=(-240°)
23th	23×0°=0°	23×120°=2760°=(2760-2880)=(-120°)	23×240°=5520°=(5760-5520)=(-240°)
7th	7×0°=0°	7×120°=840°=(840-720)=(+120°)	7×240°=1680°=(1680-1440)=(+240°)	Rotate with Fundamental (+) (R-Y-B)	Excessive Heating Effect
13th	13×0°=0°	13×120°=1560°=(1560-1440)=(+120°)	13×240°=3120°=(3120-2880)=(+240°)
19th	19×0°=0°	19×120°=2280°=(2280-2160)=(+120°)	19×240°=4560°=(4560-4320)=(+240°)
25th	25×0°=0°	25×120°=3000°=(3000-2880)=(+120°)	25×240°=6000°=(6000-5760)=(+240°)

Difference Between High Bay-Low Bay and Flood Light Fixture

Introduction:

• In the lighting industry, the term “bay” means to illuminate any large area.
• High Bay fixtures and Low Bay fixtures are used to for illumination in Buildings with higher ceilings like warehouse lighting, industrial lighting, Commercial lighting, retail lighting, and gym lighting.
• High Bay Lighting and Low Bay Lighting are mounted at high level via a pendant, chain, or directly to a ceiling or ceiling girder.

Type of Lighting Fixture for Larger Area Illumination:

• There are three type of lighting fixture to illuminate large open Area
• Low Bay Lighting Fixtures
• High Bay Lighting Fixtures
• Flood Lights

 (1) Low Bay Light Fixture.

• As the name says, these bay lights are often used with lower ceilings in open areas.
• Low bay lights are designed to illuminate open areas with ceilings Between 12 foot to 20 foot.
• Anything use over this height treat as high bays, and anything lower is very uncommon in large open area facilities, and would require a different type of light fixture.
• The reflectors or lens for low bays also spread the light far out to maintain a desired lighting level.

Applications:

• Ware House.
• Petrol Station.
• Retail Store.

(2) High Bay Light Fixture.

• As their name implies, high-bay lights are used to illuminate spaces with high ceilings. That usually means ceilings ranging from 20 feet to 45 feet.
• These light is effective at high Ceiling Level to provide well distributed and uniform light for open areas.
• They need specifically reflectors (for HPS / MH bulbs) or lens angles to ensure light reaches the floor evenly and reduces wasted light. Different kinds of reflectors can accomplish different kinds of illumination tasks for high-bay lights. Aluminum reflectors make light from the fixtures flow directly downward to the floor, while prismatic reflectors create a more diffused lighting useful for illuminating shelves and other elevated objects in a space.
• High-ceiling location has more space to fill, hence a high-bay by definition is a powerful light source that can brighten up a large area.
• High-bay lighting is provides clear, uniform lighting of what’s below it with little glare.
• Numerous types of fixtures can be used as a high-bay lights like LED lights, induction lights, metal halide lights, and fluorescent lights.
• For instance, LED lights offer extremely long life and energy efficiency but require a bigger initial investment, while traditional incandescent lights are less expensive to purchase initially but don’t last as long and use more energy.
• There are several types of fixtures available for high-bay lights. Round high-bay lights, linear high-bays, architectural high-bays and grid-mount high-bays.

Applications:

• Whenever a large indoor space needs to be illuminated, high bay lighting is usually appropriate. These area is typically vast and cover a lot of vertical as well as horizontal space. This need powerful lighting to provide the appropriate Lux levels to adequately illuminate.
• High bay lighting fixtures typically hang from the ceiling via hooks, chains or pendants, or they may be fixed to the ceiling directly (similar to troffer lights).  
• Various industries and facilities require high bay lighting. Some of the most common are
• Industrial facilities.
• Manufacturing facilities.
• School and university gymnasiums.
• Municipal facilities like community centers or recreation centers.
• Commercial applications like department stores.
• Airport hangar or any large open area industrial and commercial space with relatively high ceilings

Choosing the Correct High Bay & Low Bay Fixture

• Choosing the right High Bay fixture can make the difference between a successful lighting project or
• A light designed for a warehouse is a totally different than a light designed for a gymnasium or a factory floor. In gymnasium or a factory floor, a light can distribute in the area evenly while in a warehouse, a light can light up the face of the shelves and on the path way between two shelves.

(A) Lumen Output of Lamps:

• We cannot be assumed that 100% of the lamp output will be emitted from the fitting or that the light output will be constant over its operational lifetime.
• The actual total illumination levels that can be provided by an installed commercial light fitting will depend on the Light Output Ratio:
• As an example, an industrial or warehouse high bay light fitting with a LOR of 70%, this indicates that 30% of the lamp’s light output is lost due to the design of the fitting.
• The light output ratio is need to be consider in commercial lighting installation because when a lamp is positioned in a light fitting (such as an industrial 400W metal halide high bay) losses of light occur within the fitting itself.

(B) Beam Angle:

• For maximum light coverage, we need to select a beam configuration that matches the height of the high bay light.

• The common beam angles used for high-bay lighting are 60°, 90° and 120°.
• The narrow beam angle creates a more focused beam enabling a high lux level on the floor or the platform.
• The wider beam angle ensures large open areas with lower roof heights receive an excellent spread of light.

Beam Angle
Beam Angle	Ceiling Height
140°	Up to 4 meter
120°	4 to 6 meter
90°	6 to 8 meter
60°	8 to12 meter

 

Beam Angle & Applications
Beam Angle	Applications
10°	Spot Lights Stadium Lights
25°	Spot Lights Stadium Lights
40°	Residential and Architectural Lighting
60°	Commercial and Industrial Lighting
90°	Commercial and Industrial Lighting
120°	Low Ceiling Gas Stations and Public Spaces
150°	Industrial Lighting Parking Garages

 

Beam Angle & Fitting Type
Beam Angle	Type of Fitting
4° To 9°	Spot Light
20° To 35°	Flood Light
36° To 49°	Wide Flood Light
More than 60°	Very Wide Flood Light

(C) Glare:

• When there is an excessive contrast between the dark areas and bright areas in the direction of viewing, then glare can occur. When there is too much light, it will cause glare.
• Glare can happen during daytime and nighttime. Examples of where glare can occur includes moving from a shaded location into bright sunlight, and the reflection of light from a surface which is shiny.

(D) Fixtures Shape

• Circular fixtures creates circular beams; rectangular fixtures creates rectangular beams.
• Round LED high bays certainly have their universal application, but if we are going to illuminate a long workbenches or a production line, we may get more efficient results from a rectangular linear high bay

(3) Flood Light Fixture.

• A floodlight is called Flood Light because it illuminate evenly a large area with high intensity of Light.
• Flood lights are a general method for illuminating areas where a conventional mounting arrangement of Fixtures may or may not be an available and we can also change direction Light or tilt Angle.

• The flood light have an asymmetric throw of light which can be angled into the space to be illuminate.
• Flood light illuminate uniformly in all directions and its exposure range can be adjusted.
• Flood Lights utilizing light bulbs of high power to illuminate a big outdoor location.
• Flood light is able to equably shine in all directions. Besides, the shine angels could change freely and is able to generate shadow. It is most widely used to illuminate the whole area.
• When we install floodlights, we should need to care about glare because the brightness of the fitting is high and it angled close to horizontal.
• Flood Light is different from spot light. Its light beam is highly diffuse without direction. Therefore, its shadow is gentle and transparency.

 Applications:

• Floodlights are broad beamed, high intensity lights often used to illuminate outdoor playing fields while an outdoor sports event.
• Flood light is a good choice for lighting and decoration of construction sites, squares, parks, arts venues.
• Flood light also use as a object Lighting.
• Factory buildings, stadiums, golf courses, shops, hotels, subway stations, gas stations, buildings.
• Sculptures and other indoor and outdoor applications.

Difference between High Bay and Low Bay Lighting.

• Normally, there is a confusion between high bay light and low bay light because both looks like same and having same applications except installation height and intensity of illumination and lumen output.
• High bay and low bay fixtures both are typically suspension mounted using chains or hooks, but they may also have the option of being surface mounted depending on the fixture.
• Actually both are not same lights. There are some differences between them.
• The wattage
• The wattage or applications of both are different. The wattage and application determines whether to call them high bay or low bay.
• If the wattage used is above 100 Watts then it is called  high bay. Those using below 100 Watts are called low bay fixtures.
• The Mounting Height
• The  low bay light fixtures are used in areas where the bottom of the fixture is up to 20 feet or less above the floor.
• They are usually spread the light evenly. They also contain optical refractors which cover the lamp thereby reducing glare. Their widespread distribution improves the vertical illumination and also permits spacing as much as 2 or more times the mounting height.
• High bay lighting fixtures, they are mostly used in areas where the bottom of the fixture is 20 feet or more above the floor.
• They allowing for a more concentrated beam spreading with a prominent downward component. High wattage is needed so as to illuminate the space properly.

Spacing between lights
Height	Spacing
15 feet	12 feet to 15 feet
20 feet	15 feet to 18 feet
30 feet	20 feet to 25 feet

 

Height and lumens
Height	Spacing
10 to 15 feet	10,000 to 15,000 lumens
15 to 20 feet	16,000 to 20,000 lumens
25 to 30 feet	33,000 lumens

 

Low Bay / High Bay Lighting Fixtures
Watt	Installation height	Distance Fixture To Fixture
50 Watt	3 Meter	3 To 6 Meter
90 Watt	4 Meter	6 Meter
120 To 150 Watt	5 Meter	6 To 8 Meter
200 Watt	7 Meter	9 To 10 Meter
300 Watt	8 Meter	More than 10 Meter

Difference between Spot Light and Flood Light.

• A spotlight casts a narrow beam of light, usually no wider than 45°. This beam is more concentrated and easier to point and control.
• A floodlight can have a beam spread of up to 120°. It can illuminate a larger amount of space with the same wattage and lumen output as a spotlight.
• Flood Lights is generally utilized for highlighting the architectural appearance of an outstanding or historically Building.
• By utilizing flood lights, we can boost the in-depth framework of a building.

Determining beam width:

• The width of a light’s beam in degrees is not always helpful. It should be much easier to know the beam width in feet, from a given distance away.
• There is a simple formula to know Beam width
• Beam Width =Angle of Beam x 0.018 x Distance from Light Bulb
• If we have an 80 degree floodlight, and we want to know how wide the beam will be from 10 feet away.
• Beam Width = 80 degrees x 0.018 x 10 feet = 14.4 feet wide

LED Vs Metal Halide
LED Watt	Metal Halide Watt
20W to 50W	75W
30W to 75W	100W
40W to 125W	150W
50W to 175W	225W
60W to 225W	250W
80W to 250W	300W
100W to 350W	350W
120W to 400W	400W
150W to 500W	500W

 

Electrical Thumb Rules-(Part-15).

 

Luminous Efficacy, Lumen Maintenance and Color Rendition (Table-8) NBC
Light Source	Wattage	Efficacy (lm/W )	Average Life	Maintenance	Color Rendition
Incandescent lamps	15 to 200	12 to 20	500 to 1000	Fair to good	Very good
Tungsten halogen	300 to 1500	20 to 27	200 to 2000	Good to very good	Very good
Standard fluorescent lamps	20 to 80	55 to 65	5000	Fair to good	Good
Compact fluorescent lamps (CFL)	5 to 40	60 to 70	7500	Good	Good to very good
Slim line fluorescent	18 to 58	57 to 67	5000	Fair to good	Good
High pressure mercury vapor lamps	60 to 1000	50 to 65	5000	Very low to fair	Federate
Blended – light lamps	160 to 250	20 to 30	5000	Low to fair	Federate
High pressure sodium vapor lamps	50 to 1000	90 to 125	10000 to 15000	Fair to good	Low to good
Metal halide lamps	35 to 2000	80 to 95	4000 to 10000	Very low	Very good
Low pressure sodium	10 to 180	100 to 200	10000 to 20000	Good to very good	Poor
LED	0.5 to 2.0	60 to 100	10000	Very good	Good for white LED

 

Approximate Cable Current Capacity
Cable Size	Current Capacity	MCB Size
1.5 Sq.mm	7.5 To 16 A	8A
2.5 Sq.mm	16 To 22 A	15A
4 Sq.mm	22 To 30 A	20A
6 Sq.mm	39 To 39 A	30A
10 Sq.mm	39 To 54A	40A
16 Sq.mm	54 To 72A	60A
25 Sq.mm	72 To 93A	80A
50 Sq.mm	117 To 147A	125A
70 Sq.mm	147 To 180A	150A
95 Sq.mm	180 To 216A	200A
120 Sq.mm	216 To 250A	225A
150 Sq.mm	250 To 287A	275A
185 Sq.mm	287 To 334A	300A
240 Sq.mm	334 To 400A	350A

 

Requirements  for  Physical  Protection  of Underground Cables  (As per NBC)
Protective  Element	Specifications
Bricks	(a) 100 mm minimum  width
	(b) 25 mm thick
	(c) sand cushioning 100  mm  and  sand  cover 100 mm
Concrete slabs	At least 50 mm thick
Plastic  slabs (polymeric cover  strips) Fiber  reinforced plastic	depending on properties  and has to be matched with the protective cushioning and cover
PVC  conduit  or  PVC  pipe  or stoneware  pipe or Hume pipe	The  pipe  diameter should  be  such  so  that the  cable  is  able  to easily slip down the pipe
Galvanized pipe	The  pipe  diameter should  be  such  so  that the  cable  is  able  to easily slip down the pipe
The Trench : The trench shall be back filled to cover the cable initially by 200 mm of sand fill; and then a plastic marker strip  hall be put over the full length of cable in the trench.
The Marker Signs: The marker signs shall be provided where any cable enters or leaves a building. This will identify that there is a cable located underground near the building.
The trench shall then be completely filled. If the cables rise above ground to enter a building or other structure, a mechanical protection such as a GI pipe or PVC pipe for the cable from the trench depth to a height of 2.0 m above ground shall be provided.

 

AREA REQUIRED FOR GENERATOR IN ELECTRIC SUBSTATION (As per NBC)
Capacity  kVA	Area m2	Clear Height below the Soffit of the Beam m
25	56	3.6
48	56	3.6
100	65	3.6
150	72	3.6
248	100	4.2
350	100	4.2
480	100	4.2
600	110	4.6
800	120	4.6
1010	120	6.5
1250	120	6.5
1600	150	6.5
2000	150	6.5

 

Low Voltage Cabling for Building (As per NBC)
Low Voltage Cable	Cables/wires, such as fiber optic cable, co-axial cable, etc. These shall be laid at least at a distance of 300 mm from any power wire or cable. The distance may be reduced only by using completely closed earthed metal trucking with metal separations for various kind of cable. Special care shall be taken to ensure that the conduit runs and wiring are laid properly for low voltage signal to flow through it.
	The power cable and the signal or data cable may run together under floor and near the equipment. However, separation may be required from the insulation aspect, if the signal cable is running close to an un-insulated conductor carrying power at high voltage. All types of signal cables are required to have insulation level for withstanding 2 kV impulse voltages even if they are meant for service at low voltage.
Conduit Color Scheme	Power conduit=Black Security conduit=Blue Fire alarm conduit=Red Low voltage conduit=Brown UPS conduit Green

 

Sub Station Guideline (As per NBC)
Substation Location	Location of substation in the basement should be avoided, as far as possible.
	If there is only one basement in a building, the substation/switch room shall not be provided in the basement and the floor level of the substation shall not be lowest point of the basement.
	Substation shall not be located immediately above or below plumbing water tanks or sewage treatment plant (STP) water tanks at the same location
Substation Door/Shutter	All door openings from substation, electrical rooms, etc, should open outwards
	Vertical shutters (like rolling shutters) may also be acceptable provided they are combined with a single leaf door opening outwards for exit in case of emergency
	For large substation room/electrical  room  having  multiple equipment,  two  or more  doors  shall  be provided which shall be remotely located from each other
	No services or ventilation shafts shall open into substation or switch room unless specific to substation or switch room
Transformer Location	In case of HV panel and transformers located at different floors or at a distance more than 20 m, HV isolator shall be  provided  at transformer end
	In case transformer and main MV/LV panel room are located at different floors or are at a distance more than 20 m, MV/LV isolator shall be provided at  transformer  end
	In  case  of  two  transformers  (dry  type  or transformers with oil quantity less than 2 000 liter)  located  next  to  each  other without intermittent wall, the distance between the two shall  be minimum  1 500 mm  for  11  kV, minimum 2 000 mm for 22 kV and minimum 2 500 mm for 33 kV. Beyond 33 kV, two transformers shall be separated by baffle wall of 4 h fire rating.
	If dry type transformer is used, it may be located adjacent to medium voltage switch gear in the form of unit type substation. In such a case, no separate room or fire barrier for the transformer is required either between transformers or between transformer and the switch gear, thereby decreasing the room space requirement; however, minimum distances as specified.
Oil Filled Equipment (Transformer / C.B)	Substations with oil-filled equipment/apparatus transformers and high voltage panels shall be either located in open or in a utility building
	They shall not be located in any floor other than the ground floor or the first basement of a utility building  not be located below first basement slab of utility building.
	They shall have direct access from outside the building for operation and maintenance of the equipment.
	It shall be separated from the adjoining buildings including the main building by at least 6 m clear distance to allow passage of fire tender between the substation/utility building and adjoining building/main building.
	Substation equipment having more than 2 000 liter of oil whether located indoors in the utility building or outdoors shall have  baffle walls  of  4  h  fire  rating between apparatus.
	Provision of  suitable oil soak-pit, and where use of more than 9 000 liter of oil in any one oil tank, receptacle or chamber is involved, provision shall be made for the draining away or removal of any oil which may leak or escape from the tank, receptacle or chamber containing the same
Power Supply Voltage	supply  is  at  240  V  single  phase  up  to  5  kVA, 415/240 V 3-phase from 5 kVA to 100 kVA, 11 kV (or 22 kV) for loads up to 5 MVA and 33 kV or 66 kV for consumers of connected load or contract demand more than 5 MVA.
	In case of connected load of 100 kVA and above, the relative advantage of high voltage three-phase supply should be considered.
	In case of single point high voltage metering, energy meters shall  be  installed  in  building  premise,such a place which is readily accessible to the owner/operator of the building and the Authority. The supplier or owner of the installation shall provide at the point of commencement of supply a suitable isolating device fixed in a conspicuous position at not more than 1.7 m above the ground so as to completely isolate the supply to the building in case of emergency
Trench Drain	In case of cable trench in substation/HV switch room/MV switch room, the same shall be adequately drained to ensure no water is stagnated at any time with live cables.
Fence for Substation	Enclose any part of the substation which is open to the air, with a fence (earthed efficiently at both ends) or wall not less than 1800 mm (preferably not less than 2400 mm) in height
HV Distribution in Building	The power supply HV cables voltage shall not be more than 12 kV and a separate dedicated and  fire  compartmented  shaft  should  be provided for carrying such high voltage cables to upper floors in a building. These shall not be mixed with any other shaft and suitable fire detection and suppression measures shall be provided throughout the length of the cable on each floor.
Switch Room / MV switch room	Switch room / MV switch room shall be arrived at considering 1200 mm clearance requirement from top of the equipment to the below of the soffit of the beam .In case cable entry/exit is from above the  equipment  (transformer,  HV switchgear, MV  switchgear),  height  of substation room/HV switch room/MV switch room shall also take into account requirement of space for turning radius of cable above the equipment height.

 

 

What is Correct Method of MCB Connections

Introduction:

• MCB is a mechanical switching device which can carry and break currents under normal circuit conditions and also under specified abnormal conditions, such as overload and short circuit.
• The MCB can provide protection until and unless we have install input power (LINE) connection and Output (LOAD) connections in proper Terminals of MCB.
• Electrical engineers seem to be confused to indentify where is the Line and Load terminal of an MCB (on the top or on the bottom).

Terminal Marking of MCB:

• There are two type of MCB available in market.
• MCB having terminal marking (LINE / LOAD Marking) (Polarized MCB)
• MCB having No terminal marking (No any Marking) (Non Polarized MCB)
• Some manufacture clearly indicates where to apply Input Power and where to connect Load on MCB while some manufacture does not indicate such Terminal Marking.
• The constructions of both MCB are almost same even though we need to understand difference between them.

(1) LINE / LOAD Terminal Marking on MCB (Polarized MCB)

• For AC Circuit:
• If manufactures indicate Input (LINE) making on MCB then we have to give Supply at “LINE” Terminal and Load at “LOAD” Terminal for perfect operation of MCB.
• If we do wrong connection than MCB may or may not give proper protection in fault Condition.
• As Per UL 489 Paragraph 9.1.1.13: It is clearly indicate that “Circuit breakers shall be marked “Line” and “Load” unless the construction and test results are acceptable with the line and load connections reversed. This marking requirement specifies that UL MCB shall be marked with the word “Line” on one end of the circuit breaker and the word “Load” on the other end”, as shown in Figure

• If MCB is not live (ON) from long time (in Cold state) than there is possibility of MCB to not operate in fault conditions.
• In MCB ,The fixed contact is encompassed by the arc chute, and the arc products are de ionized, cooled and ejected uneventfully when the incoming power is on “Line” Terminal (when the fixed contact is ‘live’ or ‘hot’).There is less chance to re strike arc again.
• If the power is applied to moving contact ,”Load” Terminal, the flexible connector, the trip system, everything is live/hot after the arc is quenched. Chances of restrike/flashover are much higher.
• For DC Circuit:
• The polarized DC MCB have a marking of ‘+’ and ‘–‘ symbol
• If Polarized DC MCB are wired incorrectly, they are a possibility of hazard and When we turned off under load, the MCB might not be able to extinguish the arc and the circuit breaker will burn out.
• Polarized DC MCB use a small magnet to direct the arc away from the contacts and up into the arc shoot and arc disrupter cage. If the direction of current flow through the unit is reversed, then the magnet directs the arc away from the arc shoot and into the mechanism of the unit thus destroying it.

(2) No Terminal Marking on MCB (Non Polarized MCB)

• For AC Circuit:
• If manufacture has not indicated any Terminal Marking than we are free to connect line or load at any side as we wish.
• If construction / Operating principle of both MCB are same then what are the different between them.
• Without Terminal Marking MCB has following additional features.
• (1) By Design improvement (Manufacture has provided some more provision for quenching of arc (So it cannot reproduce it again).
• (2) By doing some more extra test as per IEC 60947-2 and UL 489

• The performance of single-break circuit breakers is slightly different when the “LINE” and “LOAD” feed either from the bottom or Top hence IEC 60947-2 specifies that one additional SC test be carried out with connections required when the terminals are not specifically marked ‘Line’ and/or ‘Load’

Table 10- Number of samples for test (IS / IEC 60947-2)
Test Sequences	Terminal Marking (Line / Load)		No of Sample for Testing	Sample For *
	YES	NO
In	√	√	1	1
Ics (Rated service short-circuit breaking capacity)  (Ics=25%Icu)	√		2	1
				2
		√	3	1
				2
				3
	√	√	3	1
				2
				3
	√	√	4	1
				2
				3
				4
Icu  (Rated ultimate short-circuit breaking capacity)	√		2	1
				2
		√	3	1
				2
				3
	√	√	3	1
				2
				3
	√	√	4	1
				2
				3
				4
* Sample For Indications
1	In of a given frame size.
2	This sample is omitted in the following cases:
	A circuit-breaker having a single non-adjustable current setting for a given frame size;
	A circuit-breaker provided only with a shunt release (i.e. without an integral over current release);
	A circuit-breaker with electronic over current protection, of a given frame size, having an adjustable current rating by electronic means only (i.e. without change of current sensors).
3	Connections reversed.
4	Connections reversed, if terminals unmarked.

• As Per UL 489, Paragraph 7.1.1.18: “if a circuit breaker is not marked “Line” and “Load,” one sample of each set tested, or one additional sample, shall be connected with the line and load connections reversed during the overload, endurance and interrupting tests”.
• This UL test requirement specifies that for MCC to be UL Listed for reverse-feed applications, samples shall be tested with the line and load terminals reverse-fed, as shown in Figure, and that the test results shall be the same as those of “normally” fed circuit breakers. Depending on the design configuration and construction, the circuit breaker may or may not be affected by the application of power in a reverse-feed connection during these tests.

• If Line / Load are not marked, we can connect Line or Load either on Top or bottom of MCB. However, it is a good practice to keep the fixed contact side connected to the bus bar.
• For DC Circuit:
• The Non polarized DC MCB have a No marking as ‘+’ and ‘–‘ symbol
• Non polarized DC MCB operate safely as load breaking isolators and for fault current protection regardless of the direction of current flow through them.

Conclusion:

• When a MCB are marked “Line” and “Load,” the power supply conductors must be connected to the marked “Line.” These MCB cannot be reverse-fed.
• If “Line” and “Load” are not marked on MCB, the power supply conductors may be connected to either end. These devices are suitable for reverse-feed applications.

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(1) https://electricalnotes.wordpress.com/2016/10/04/how-to-select-mcb-mccb-part1/

(2) https://electricalnotes.wordpress.com/2013/06/02/calculate-size-of-contactor-fuse-c-b-over-load-relay-of-dol-starter/

 

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Calculate Size of Contactor / Fuse / CB / OL Relay of Star-Delta Starter

• Calculate Size of each Part of Star-Delta starter for 10HP, 415 Volt Three Phase Induction Motor having Non Inductive Type Load, Code A, Motor efficiency 80%, Motor RPM 600, Power Factor 0.8. Also Calculate Size of Overload Relay if O/L Relay Put in the wingdings (overload is placed after the Winding Split into main and delta Contactor) or in the line (Putting the overload before the motor same as in DOL).

 

Basic Calculation of Motor Torque & Current:

• Motor Rated Torque (Full Load Torque) =5252xHPxRPM
• Motor Rated Torque (Full Load Torque)=5252x10x600=88 lb-ft.
• Motor Rated Torque (Full Load Torque) =9500xKWxRPM
• Motor Rated Torque (Full Load Torque)=9500x(10×0.746)x600 =119 Nm
• If Motor Capacity is less than 30 KW than Motor Starting Torque is 3xMotor Full Load Current or 2X Motor Full Load Current.
• Motor Starting Torque=3x Motor Rated Torque (Full Load Torque).
• Motor Starting Torque==3×119=356 Nm.
• Motor Lock Rotor Current =1000xHPx figure from below Chart/1.732×415

Locked Rotor Current
Code	Min	Max
A	1	3.14
B	3.15	3.54
C	3.55	3.99
D	4	4.49
E	4.5	4.99
F	5	2.59
G	2.6	6.29
H	6.3	7.09
I	7.1	7.99
K	8	8.99
L	9	9.99
M	10	11.19
N	11.2	12.49
P	12.5	13.99
R	14	15.99
S	16	17.99
T	18	19.99
U	20	22.39
V	22.4

• As per above chart Minimum Locked Rotor Current =1000x10x1/1.732×415=14 Amp
• Maximum Locked Rotor Current =1000x10x3.14/1.732×415=44 Amp.
• Motor Full Load Current (Line) =KWx1000/1.732×415
• Motor Full Load Current (Line) = (10×0.746)x1000/1.732×415=13 Amp.
• Motor Full Load Current (Phase) =Motor Full Load Current (Line)/1.732.
• Motor Full Load Current (Phase) ==13/1.732=7 Amp.
• Motor Starting Current (Star-Delta Starter) =3xFull Load Current.
• Motor Starting Current (Line)=3×13=39 Amp

(1) Size of Fuse:

Fuse  as per NEC 430-52
Type of Motor	Time Delay Fuse	Non-Time Delay Fuse
Single Phase	300%	175%
3 Phase	300%	175%
Synchronous	300%	175%
Wound Rotor	150%	150%
Direct Current	150%	150%

• Maximum Size of Time Delay Fuse =300% x Full Load Line Current.
• Maximum Size of Time Delay Fuse =300%x13= 39 Amp.
• Maximum Size of Non Time Delay Fuse =1.75% x Full Load Line Current.
• Maximum Size of Non Time Delay Fuse=1.75%13=23 Amp.

(2) Size of Circuit Breaker:

Circuit Breaker as per NEC 430-52
Type of Motor	Instantaneous Trip	Inverse Time
Single Phase	800%	250%
3 Phase	800%	250%
Synchronous	800%	250%
Wound Rotor	800%	150%
Direct Current	200%	150%

• Maximum Size of Instantaneous Trip Circuit Breaker =800% x Full Load Line Current.
• Maximum Size of Instantaneous Trip Circuit Breaker =800%x13= 104 Amp.
• Maximum Size of Inverse Trip Circuit Breaker =250% x Full Load Line Current.
• Maximum Size of Inverse Trip Circuit Breaker =250%x13= 32 Amp.

(3) Thermal over Load Relay:

Thermal over Load Relay (Phase):

• Min Thermal Over Load Relay setting =70%xFull Load Current(Phase)
• Min Thermal Over Load Relay setting =70%x7= 5 Amp
• Max Thermal Over Load Relay setting =120%xFull Load Current(Phase)
• Max Thermal Over Load Relay setting =120%x7= 9 Amp

Thermal over Load Relay (Line):

• For a star-delta starter we have the possibility to place the overload protection in two positions, in the line or in the windings.
• If O/L Relay Placed in Line: (Putting the O/L before the motor same as in DOL).Supply>Over Load Relay>Main Contactor
• If Over Load Relay supply the entire motor circuit and are located ahead of where the power splits to the Delta and Star contactors, so O/L Relay size must be based upon the entire motor Full Load Current.
• Thermal over Load Relay setting =100%xFull Load Current (Line).
• Thermal over Load Relay setting =100%x13= 13 Amp
• Disadvantage: O/L Relay will not give Protection while Motor runs in Delta (Relay Setting is too High for Delta Winding)
• If O/L Relay Placed In the windings: (overload is placed after the Winding Split into main and delta Contactor).Supply>Main Contactor-Delta Contactor>O/L Relay
• If overload is placed after the Point where the wiring Split into main and delta Contactor, Size of over load relay at 58% (1/1.732) of the motor Full Load Current because we use 6 leads going to the motor, and only 58% of the current goes through the main set of conductors (connected to the main contactor).
• The overload then always measures the current inside the windings, and is thus always correct. The setting must be x0.58 FLC (line current).
• Thermal over Load Relay setting =58%xFull Load Current (Line).
• Thermal over Load Relay setting =58%x13= 8 Amp.
• Disadvantage: We must use separate short-circuit and overload protections

(4) Size and Type of Contactor:

• Main and Delta Contactor:

• The Main and Delta contactors are smaller compared to single contactor used in a Direct on Line starter because they Main and Delta contactors in star delta starter are controlling winding currents only. The currents through the winding are 1/√3 (58%) of the current in the line. These two contactors (Main contactor and Delta Contactor) are close during run. These rated at 58% of the current rating of the motor.

• Star Contactor:

• The third contactor is the star contactor and that only carries star current while the motor is connected in star in starting. The current in star winding is 1/√3= (58%) of the current in delta, so this contactor can be rated at 1/3 (33%) of the motor rating. Star contactor can be selected smaller than the others, providing the star contactor pulls first before the main contactor. Then no current flows when third contactor pulls.
• In star connection at start, the motor draws and delivers 1/3 of its full rated power.
• When the starter switches over to Delta, the motor draws full power, but since the contactors and the overload relay are usually wired within the Delta, you need to use contcators and relay which are only rated 1/√3 =58% of the full rated power of the motor.

Application	Contactor	Making Cap
Non-Inductive or Slightly Inductive ,Resistive Load	AC1	1.5
Slip Ring Motor	AC2	4
Squirrel Cage Motor	AC3	10
Rapid Start / Stop	AC4	12
Switching of Electrical Discharge Lamp	AC5a	3
Switching of Electrical Incandescent Lamp	AC5b	1.5
Switching of Transformer	AC6a	12
Switching of Capacitor Bank	AC6b	12
Slightly Inductive Load in Household or same type load	AC7a	1.5
Motor Load in Household Application	AC7b	8
Hermetic refrigerant Compressor Motor with Manual O/L Reset	AC8a	6
Hermetic refrigerant Compressor Motor with Auto O/L Reset	AC8b	6
Control of Restive & Solid State Load with opto coupler Isolation	AC12	6
Control of Restive Load and Solid State with T/C Isolation	AC13	10
Control of Small Electro Magnetic Load ( <72VA)	AC14	6
Control of Small Electro Magnetic Load ( >72VA)	AC15	10

• As per above Chart
• Type of Contactor= AC1
• Making/Breaking Capacity of Contactor= Value above Chart x Full Load Current (Line).
• Making/Breaking Capacity of Contactor=1.5×13= 19 Amp.
• Size of Star Contactor (Starting Condition) = 33%X Full Load Current (Line).
• Size of Star Contactor =33%x13 = 4 Amp.
• Size of Main Contactor (Starting-Transition-Running) = 58%X Full Load Current (Line).
• Size of Main Contactor =58%x13 = 8 Amp.
• Size of Delta Contactor (Running Condition) = 58%X Full Load Current (Line).
• Size of Delta Contactor =58%x13 = 8 Amp.

Summary:

•  Type of Contactor= AC1
• Making/Breaking Capacity of Contactor=19 Amp.
• Size of Star Contactor =4 Amp.
• Size of Main Contactor = 8 Amp.
• Size of Delta Contactor =8 Amp.