Indian Standard Code-Abstract (IS:1554/IS:15652/IS:1678/IS:1255/IS:694


 

Abstract of IS 1554

Insulation Color (up to 11 KV) For reduced neutral conductors, the insulation color shall be black
Arrangement of Marking (up to 11 KV)

 

For cables having more than 5 cores, the core identification may be done by numbers. In that case, the insulation of cores shall be of the same color and numbered sequentially, starting with number 1 for the inner layer. The numbers shall be printed in Hindu-Arabic numerals on the outer surface of the cores. All the numbers shall be of the same color which shall contrast with the color of the insulation. The numerals shall be legible.
When the number is a single numeral, a dash shall be placed underneath it. If the number consists of two numerals, these shall be disposed one below the other and a dash placed below the lower numeral. The spacing between consecutive numbers shall not exceed 50 mm.
Type of Armor (up to 11 KV)

 

Where the calculated diameter below armoring does not exceed 13 mm, the armor shall consist of galvanized round steel wires. Where the calculateddiameter below armoring is greater than 13 mm, the armor shall consist of either galvanized round steel wires or galvanized steel strips.
Cable Identification/ Marking (up to 11 KV)

 

Type of Cable Legend: (i) Improved fire performance or Category C1 FR ( Cables in constrained areas, Does not propagate fire even when installed in groups in vertical ducts),(ii) Improved fire performance for Category C2 FR—LSH (Cables in constrained areas with limited human activity and/or presence of  sophisticated systems)
Aluminum conductor= A,

PVC insulation=Y,

Steel round wire armor= W,

Steel strip armor= F,

Steel double round wire armor= WW,

Steel double strip armor =FF,

PVC outer sheath= Y

Insulating Rubber Mat Four classes of mats, covered under this standard nd differing in electrical characteristics for different use voltages are designated
Insulating Rubber Mat Class = AC (Rms)KV=DC(V)=Thickness(mm)

A=3.3=240= 2.0

B=11= 240=2.5                                                          C=33=240=3.0

D =66= 240=3.5

Insulating Rubber Mat Most of all classes hall be resistant to acid and oil and low temperagre and shall be identified by the respective class symbol. However a category with special property of resistance to extreme ‘low’ ternperature will be identified by a subscript’s ‘to, the ‘respective “c” Class symbol
Insulating Rubber Mat Roll of Mat shall be in multiple Length of of 5000mm and ion width of 1000mm.Standard Shape in length of 1000, 2000, 3000mm.
Insulating Rubber Mat Leakage current for all Class of Mat shall not be more than 10 Micro Amp.

 

Abstract of IS: 15652 for Insulating Mat

Insulating Rubber Mat

 

Class AC Voltage DC Voltage Thicknes
Class A AC (Rms)KV=3.3 DC(V)  =240 2.0mm
Class B AC (Rms)KV=11 DC(V)  =240 2.5mm
Class C AC (Rms)KV=33 DC(V)  =240 3.0mm
Class D AC (Rms)KV=66 DC(V)  =240 3.5mm
Class A AC (Rms)KV=3.3 DC(V)  =240 2.0mm
Resistance Most of all classes hall be resistant to acid and oil and low temperature and shall be identified by the respective class symbol. However a category with special property of resistance to extreme ‘low’ ternperature will be identified by a subscript’S ‘to, the ‘respective “C” Class symbol.
Length Roll of Mat shall be in multiple Length of 5000mm and ion width of 1000mm.Standard Shape in length of 1000, 2000, 3000mm.
In Case of Mat in Roll It shall be min 1m X 1m.
Leakage current Leakage current for all Class of Mat shall not be more than 10 Micro Amp.

 

Abstract of IS: 1678 for Pole

PCC Pole Class of Pole Length of Pole Min Ultimate Transverse Load
Class 1 17 Meter 3000 Kg
Class 2 17 Meter 2300 Kg
Class 3 17 Meter 1800 Kg
Class 4 17 Meter 1400 Kg
Class 5 16 Meter 1100 Kg
Class 6 12.5 Meter 1000 Kg
Class 7 12 Meter 800 Kg
Class 8 12 Meter 700 Kg
Class 9 11Meter 450 Kg
Class 10 9 Meter 300 Kg
Class 11 7.5Meter 200 Kg
PCC Pole Tolerance Tolerance: The tolerance of overall length of the poles shall be + 15 mm.
The tolerance on cross-sectional dimensions shall be + 3 mm.
The tolerance on cross-sectional dimensions shall be + 3 mm.
The tolerance on uprightness of the pole shall be 0.5 per cent
PCC Pole depth in Ground:

 

Length of Pole Min depth in ground
6 Meter To 7.5 Meter 1.2 Meter
8 Meter To 9 Meter 1.5 Meter
9.5 Meter To 11 Meter 1.8 Meter
11.5 Meter To 13 Meter 2.0 Meter
13.5 Meter To 14.5 Meter 2.2 Meter
15 Meter To 16.5 Meter 2.3 Meter
17 Meter 2.4 Meter

 

Abstract of IS :1255 for Installation of Cable

Cable Route Indicator (Up to 33KV) Power cable route indicators should be provided at an interval not exceeding 200 M and also at turning points of the power cable route wherever practicable
Cable Corrosion

(Up to 33KV)

Electrolytic corrosion: Where the possibility of electrolytic corrosion exists, for example, adjacent to dc traction system, the potential gradient along the pipe-line and the cable sheath should be specified.
Neutral (Up to 33KV) The neutral point is earthed in such a manner that during a line-to-earth fault the highest rms voltage to earth of a sound phase(s) expressed as a percentage of the highest line-to-line voltage, does not exceed 80 percent, irrespective of the fault location,
Earthing

(Up to 33KV)

The neutral point is not earthed but a device is installed which automatically and instantly cuts out any part of the system which becomes accidentally earthed,
Earthing

(Up to 33KV)

In case of ac systems only, the neutral point is earthed through an arc suppression coil with arrangement for isolation within one hour for the non-radial field cables and within 8 hours for radial field cables, of occurrence of the fault provided that the total of such periods in a year does not exceed 125 hours.
Cable Tensile Strength (Up to 33KV) PVC and XLPE insulated armored power cables P = 9 D2 ,P=Pulling Strength(N),D=Outer Dia of Cable(mm)
Cable Tensile Strength (Up to 33KV) PVC and XLPE insulated unarmored power cables P = 5 D2
Cable Tensile Strength (Up to 33KV) Paper insulated armoured power cables P = 5 D3
Cable Pulling

(Up to 33KV)

For Cables Pulled by Pulling Eye : If the cables are pulled by gripping the conductor directly with pulling eye, the maximum permissible tensile stress depends on the material of the conductor and on their cross-section as given below: For aluminum conductors 30 N/mm2 and
For copper conductors 50 N/mm2
Cable Pulling

(Up to 33KV)

Expected Pulling Force When Pulling Cables by Winch :

The following values of pulling force are expected = (approximately percentage of cable weight): In trenches without large bends 15-20 %
In trenches with 1 or 2 bends of 90° each 20-40 %
In trenches with 3 bends of 90° each (assuming the use of easy-running support and corner rollers) 50-60 %
In ducts with bends totalling 360° Up to 100 %

Cable Laying Direct in Ground

(Up to 33KV)

This method involves digging a trench in the ground and laying cable(s) on a bedding of minimum 75 mm riddled soil or sand at the bottom of the trench, and covering it with additional riddled soil or sand of minimum 75 mm and protecting it by means of tiles, bricks
Cable Laying Direct in Ground

(Up to 33KV)

Depth : The desired minimum depth of laying from ground surface to the top of cable is as follows:                                                                                                                                             High voltage cables, 3.3 kV to 11 kV rating =0.9 m
High voltage cables, 22 kV, 33 kV rating= 1.05 m
Low voltage and control cables = 0.75 m
Cables at road crossings = 1.00 m
Cables at railway level crossings (measured from bottom of sleepers to the top of pipe)=1.00m
Cable Clearance           (Up to 33KV) Clearances :The desired minimum clearances are as follows:                                                                                                                                                    Power cable to power cable = Clearance not necessary; however, larger the clearance, better would be current carrying capacity
Power cable to control cables = 0.2 m
Power cable to communication cable = 0.3 m
Power cable to gas/water main = 0.3 m                                                                                                                                                                                        Inductive influence on sensitive control cable on account of nearby power cables should be checked
Cable Clearance           (Up to 33KV) The power cable should not be laid above the telecommunication cable, to avoid danger to life of the person, digging to attend to the fault in the Telecommunication cable.
Crossing (Up to 33KV) Cables Laid Across Roads, Railway Tracks and Water Pipe Lines: Steel, cast iron, plastics, cement or earthenware ducts, or cable ducting blocks should be used where cables cross roads and railway tracks. Spare ducts for future extensions should be provided. Spare duct runs should be sealed off. Buried ducts or ducting blocks should  project into footpath or up to the edge of road, where there is no footpath, to permit smooth entry of cable without undue bending
Diameter of Pipe            (Up to 33KV) The diameter of the cable conduit or pipe or duct should be at least 1.5 times the outer diameter of cable. The ducts/pipes should be mechanically strong to withstand forces due to heavy traffic when they are laid across road/railway tracks.
Bending Radius          (Up to 33KV) The bending radius of steel or plastics ducts should not be less than 1.5 m.
Cable on Over Bridge (Up to 33KV) Cable Over Bridges : On bridges, the cables are generally supported on steel cable hooks or clamped on steel supports at regular intervals. While designing a cable layout on a bridge; expansion of bridge due to changes in atmospheric temperature should be taken into account. On most of the rail-cum-road bridges, the cables are subjected to vibrations. For such conditions, round wire armoured and lead alloy ‘B’ sheathed cables are preferred. Cables can be laid on bridges duly suspended from catenary wire at regular intervals
Cable on Railway Crossing (Up to 33KV) Cables Below Railway Crossing : When the cables are laid under railway tracks the cables should be laid in reinforced spun concrete or cast iron or steel pipes at such depths as may be specified by the railway authorities but not less than 1 m measured from the bottom of sleepers to the top of the pipe.
Cable on Duct

(Up to 33KV)

On long run ducts, it is desirable to apply lubrication to the lead or serving/outer sheath as it enters the duct. Petroleum jelly or graphite powder or a combination of both is effective for this purpose and through lubrication will reduce the pulling tension by about 40 percent.
Laying on Racks in Air (Up to 33KV) Lying on Racks in Air-The vertical distance between the two racks should be minimum 0.3 m and the clearance between the first cable and the wall (if racks are mounted on wall) should be 25 mm. The width of the rack should not exceed 0.75 m in order to facilitate installation of cables.
Laying on Racks in Air (Up to 33KV) Ungalvanized steel work of cable racking/trays should be painted with a coat of primer and thereafter finished with suitable anti-corrosive paint.
Laying on Racks in Air (Up to 33KV) Only single-core cables laid on horizontal racks need be clamped at suitable intervals. Multi-core cables need not be clamped. The distance between the vertical clamps should not be more than 2 m.
Laying Cables on Racks Inside a Tunnel(Up to 33KV) Laying Cables on Racks Inside a Tunnel: Horizontal distance between Two cable is min Diameter of Cable and vertical distance between two cable row is 30cm.In cable tunnel, the head room should not be less than 2 m and width sufficient to leave a free passage of at least 600 to 800 mm either from one side or in the middle.
Laying Cables on Racks Inside a Tunnel(Up to 33KV) With temperatures below 3°C, the cables should be warmed before the laying out, since otherwise the bending would damage the insulation and protective coverings of cables. The cable laying must be carried out swiftly, so that the cable does not cool down too much
Laying Cables on Racks Inside a Tunnel(Up to 33KV) Identification strips/tags of metal or plastics should be attached to the cables, particularly if several are laid in parallel, 8 to 10 m apart. Identification tags should also be attached at every entry point into the buildings and at the cable end termination
Laying Cables on Racks Inside a Tunnel(Up to 33KV) The spacing between three cables laid in one plane should be not less than the cable diameter.
Laying Cables on Racks Inside a Tunnel(Up to 33KV) When the cable run is several kilometres long, the cables should be transposed at one-third and at two-thirds of the total lengths.
Trefoil arrangement in ducts (Up to 33KV) If several single-core cables are laid per phase, these should be arranged as follows to ensure balanced current distribution in Horizontal direction : R-Y-B-Distance-B-Y-R, (Distance=2 X Diameter of  Cable) , vertical distance shall be 6 X Diameter of Cable

 

Abstract IS 694 (Cable)

Cable Sheath (Up to 1.1KV)

 

The color of the sheath shall be black or any other color as agreed to between the purchaser and the supplier. For weatherproof cables, the color of sheath shall be black only.
The difference between maximum and minimum measured values of overall diameter of sheathed circular cables shall not exceed 15 percent of the maximum measured value at the same cross-section.
Cable Construction

(Up to 1.1KV)

 

Copper Cable up to 6mm2 =Solid/Stranded ,
Copper Cable up to 10mm2 =Solid/Stranded
Copper Cable above 6mm2 =Stranded ,
Copper Cable above 10mm2 =Stranded
Cable-Testing (Up to 1.1KV)

 

The core(s) shall be carefully removed from a sample approximately 3 m long from the finished cable. They shall be so immersed in a water-bath at 60±3ºC that their ends protrude at least 200 mm above the water-level. After 24 hours, a voltage of 3 kV (rms) shall be applied between conductors and water. This voltage shall be raised to 6 kV (rms) within 10 seconds and held constant at this value for 5 minutes. If the sample fails in this test, one more sample shall be subjected to this test, which should pass.
The cores which have passed the preliminary test given in 16.2.1 shall be subsequently tested with a dc voltage of 1.2 kV in the same water-bath at the same temperature. The conductors shall be connected to the negative pole and water to the positive pole of dc supply by means of a copper electrode.
The core shall withstand this dc voltage test for 240 hours without breakdown.
The voltage shall be applied continuously, but if there are any unavoidable interruptions during the 4 hours period, that period shall be increased by the time of interruptions. The total of such interruptions shall not exceed 1 hour otherwise the test shall be started again.
The cables and cords shall withstand without breakdown an ac voltage of 3 kV (rms) or a dc voltage of 7.2 kV applied for a period of 5 min for each test connection
Single-core cables shall be immersed in water at ambient temperature one hour before the testing and the test voltage shall be applied between conductor and water for the specified period.

 

Earthing Strip /Wire / Pit Quick Reference-(Part-1)


Transformer-Earthing Wire / Strip Size:

Size of T.C or DG

Body Earthing

Neutral Earthing

<315 KVA 25×3 mm Cu / 40×6 mm GI Strip 25×3 mm Cu Strip
315 KVA to 500 KVA 25×3 mm Cu / 40×6 mm GI Strip 25×3 mm Cu Strip
500 KVA to 750 KVA 25×3 mm Cu / 40×6 mm GI Strip 40×3 mm Cu Strip
750 KVA to 1000 KVA 25×3 mm Cu / 40×6 mm GI Strip 50×3 mm Cu Strip

 Motor- Earthing Wire / Strip Size:

Size of Motor

Body Earthing

< 5.5 KW

85 SWG GI Wire

5.5 KW to 22 KW

25×6 mm GI Strip

22 KW to 55 KW

40×6 mm GI Strip

>55 KW

50×6 mm GI Strip

 Panel- Earthing Wire / Strip Size:

Type of Panel

Body Earthing

Lighting & Local Panel

25×6 mm GI Strip

Control & Relay Panel

25×6 mm GI Strip

D.G & Exciter Panel

50×6 mm GI Strip

D.G & T/C Neutral

50×6 mm Cu Strip

 Electrical Equipment Earthing:

Equipment

Body Earthing

LA (5KA,9KA)

25×3 mm Cu Strip

HT Switchgear

50×6 mm GI Strip

Structure

50×6 mm GI Strip

Cable Tray

50×6 mm GI Strip

Fence / Rail Gate

50×6 mm GI Strip

 Earthing Wire (As per BS 7671)

Cross Section Area of Phase, Neutral Conductor(S) mm2

Minimum Cross Section area of Earthing Conductor (mm2)

S<=16

S (Not less than 2.5 mm2)

16<S<=35

16

S>35

S/2

 Earthing Resistance value:

Earthing Resistance Value

Power Station 0.5 Ω
Sub Station Major 1.0 Ω
Sub Station Minor 2.0 Ω
Distribution Transformer 5.0 Ω
Transmission Line 10 Ω
Single Isolate Earth Pit 5.0 Ω
Earthing Grid 0.5 Ω
As per NEC Earthing Resistance should be <5.0 Ω

 

Electrical Motor Quick Reference


Standard Size of Motor (HP):

Electrical Motor (HP)

1,1.5,2,3,5,7.5,10,15,20,30,40,50,60,75,100,125,150,200,250,300,400,450,500,600,700,

800,900,1000,1250,1250,1500,1750,2000,2250,3000,3500,4000

 Approximate RPM of Motor

HP

RPM

< 10 HP

750 RPM

10 HP to 30 HP

600 RPM

30 HP to 125 HP

500 RPM

125 HP to 300 HP

375 RPM

 Standard Size of Motor (HP):

Electrical Motor (HP)

1,1.5,2,3,5,7.5,10,15,20,30,40,50,60,75,100,125,150,200,250,300,400,450,500,600,700,

800,900,1000,1250,1250,1500,1750,2000,2250,3000,3500,4000

 Motor Line Voltage:

Motor (KW)

Line Voltage

< 250 KW

440 V (LV)

150 KW to 3000KW

2.5 KV to 4.1 KV (HV)

200 KW to 3000KW 3.3 KV to 7.2 KV (HV)
1000 KW to 1500KW 6.6 KV to 13.8 KV (HV)

 Motor Starting Current:

Supply

Size of Motor

Max. Starting Current

1 Phase < 1 HP 6 X Motor Full Load Current
1 Phase 1 HP to 10 HP 3 X Motor Full Load Current
3 Phase 10 HP 2 X Motor Full Load Current
3 Phase 10 HP to 15 HP 2 X Motor Full Load Current
3 Phase > 15 HP 1.5 X Motor Full Load Current

Motor Starter:

Starter

HP or KW

Starting Current

Torque

DOL <13 HP(11KW) 7 X Full Load Current Good
Star-Delta 13 HP to 48 HP 3 X Full Load Current Poor
Auto TC > 48 HP (37 KW) 4 X Full Load Current Good/ Average
VSD   0.5 to 1.5 X Full Load Current Excellent
Motor > 2.2KW Should not connect direct to supply voltage if it is in Delta winding

Max. Lock Rotor Amp for 1 Phase 230 V Motor (NEMA)

HP

Amp

1 HP

45 Amp

1.5 HP

50 Amp

2 HP

65 Amp

3 HP

90 Amp

5 HP

135 Amp

7.5 HP

200 Amp

10 HP

260 Amp

 Three Phase Motor Code (NEMA)

HP

Code

<1 HP

L

1.5 to 2.0 HP

L,M

3 HP

K

5 HP

J

7 to 10 HP

H

>15 HP

G

 Service Factor of Motor:

HP

Synchronous Speed (RPM)

3600 RPM

1800 RPM

1200 RPM

900 RPM

720 RPM

600 RPM

514 RPM

1 HP

1.25

1.15

1.15

1.15

1

1

1

1.5 to 1.25  HP

1.15

1.15

1.15

1.15

1.15

1.15

1.15

150 HP

1.15

1.15

1.15

1.15

1.15

1.15

1

200 HP

1.15

1.15

1.15

1.15

1.15

1

1

> 200 HP

1

1.15

1

1

1

1

1

 Type of Contactor:

Type

Application

AC1

Non Inductive Load or Slightly Inductive Load

AC2

Slip Ring Motor, Starting, Switching OFF

AC3

Squirrel Cage Motor

AC4,AC5,AC5a, AC5b,AC6a

Rapid Start & Rapid Stop

AC 5a

Auxiliary Control circuit

AC 5b

Electrical discharge Lamp

AC 6a

Electrical Incandescent Lamp

AC 6b

Transformer Switching

AC 7a

Switching of Capacitor Bank

AC 7b

Slightly Inductive Load in Household

AC 5a

Motor Load in Household

AC 8a

Hermetic refrigerant compressor motor with Manual Reset O/L  Relay

AC 8b

Hermetic refrigerant compressor motor with Automatic Reset O/L  Relay

AC 12

Control of Resistive Load & Solid State Load

AC 13

Control of Resistive Load & Solid State Load with Transformer Isolation

AC 14

Control of small Electro Magnetic Load (<72 VA)

AC 15

Control of Electro Magnetic Load (>72 VA)

 Contactor Coil:

Coil Voltage

Suffix

24 Volt

T

48 Volt

W

110 to 127 Volt

A

220 to 240 Volt

B

277 Volt

H

380 to 415 Volt

L

Size of Capacitor for P.F Correction:

For Motor

Size of Capacitor = 1/3 Hp of Motor ( 0.12x KW of Motor)

For Transformer

< 315 KVA 5% of KVA Rating
315 KVA to 1000 KVA 6% of KVA Rating
>1000 KVA 8% of KVA Rating

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