Calculation sheet - Elect

short - circuit current calculation

1- Isc at secondary terminas of a HV/LV distribution transformer

I sc = In / Usc

where

Isc : short circuit Fault current In Amps . Usc In %

Usc : Short-Circuit Impedance Voltage Of Transformer In % KVA 50 - 630

In : Nominal current In Amps . 800-2500

In : Nominal current In Amps .

In = P ( KVA )*1000 / U20

U20 : Secondary Volts At Open Circuit.

transfomer rated power (KVA) 50 100

transfomer current Ir (A) 69 137

oil - immersed transformer Isc (KA) Psc = 250 MVA 1.71 3.40

Psc = 500 MVA 1.71 3.42

cast - resin transformer Isc (KA) Psc = 250 MVA 1.14 2.28

Psc = 500 MVA 1.14 2.28

tables H1-33 : Isc at the LV terminals of 3-phase HV/LV transformers supplied from a HV system with a 3-phase faults level of 500 MVA,or 250 MVA at 420 V no load voltage

* Note

the case of several transformers in parallel feeding a busbar

the value of Isc can be estimated as the sum of the Isc from each transformer calculated separately

Data Must Be Known

Power Usc Rated Voltage

In KVA In % in volt

1000 6 420

RESULTS

Rated Current In Amps Short Circuit Fault Current In Amps

In 1375 Isc = 22.91

3 - phase short - circuit (Isc) at any point within a LV installation

in a 3-phase installation Isc at any point is given by

Isc = U20/ √ ZT

U20 = phase -to-phase voltage of the open circuited secondary , windings of the power supply transformers ZT = total impedance per phase of the installation upstream of the fault loctin (in ohms) ______________________________________________________________________________________

method of caculating ZT

Each component of an installation (HV network,transformer, cable,circuit breaker,busbar, and so on …. )

ZT = √ RT2 +XT2______________________________________________________________________________________

determination of the impedance of the HV network

Zs = impedance of the HV voltage network,expressed in milli-ohms

Ra is generally found to be negligible compared with Xa

Zs = U0²/Psc Uo = phase-to-phase no load LV voltage, expressed in volts.

for accurate calculation Ra = 0.15 Xa

Psc Uo (V)

250 MVA 420

500 MVA 420

tables H1-36 : the impedance of the HV network referred to the LV side of the HV/LV transformer

circuit brakerswhile the resistance is neglected , Rc.b= 0 , Xc.b = 0.15 m Ω per circuit breaker

busbarswhile the resistance is neglected , Rb.b= 0 , Xb.b = 0.15 m Ω per meter length

circuit conductors Rc = ρ x L / S where

Note Xc =0.08 m Ω / m for 50 HZ system Xc =0.096 m Ω / m for 60 HZ system

for prefabricated bus-trunking and similar pre-wired ducting systems, the manfacturer should be consulted .

R

HV networkPsc = 500 MVA 0.053 0.353

transformer20 KV/420V , Pn = 1000 KVA 2.35 10.34

single-core cables Rc = (22.5/4) x (5/240) Xc = 0.08 x 5 5m copper = 0.12 = 0.40

maincircuit breaker RD = 0 XD = 0.15

busbar RB = 0 XB = 1.510 meter

three-core cable Rc = 22.5 x (100/95) Xc = 100x 0.08 100 m = 23.68 = 8

ρ = 22.5 m Ω .mm ρ = 36 m Ω .mm

for c.s.a of less than 50 mm² reactance may be ignored

R (mΩ) X (mΩ)

Usc = 6 % , Pcu = 13.3 x 10³ watts

4 x 240 mm² / phase

three-core cable 20 m Rc = 22.5 x (20/10) Xc = 20x 0.08

=45 = 1.6final circuits

three-core cable Rc = 22.5 x (20/10) xc = 20x 0.08 20 m = 45 = 1.6

final circuits

table H1-39 : example of short-circuit current calculations for a LV installation supplied at 400 V (nominal) from a 1000 KVA HV/LV transformer

95 mm² copper

10 mm² copper

10 mm² copper

short - circuit current calculation

1- Isc at secondary terminas of a HV/LV distribution transformer

I sc = In / Usc

Usc In %

oil Cast-Resin

4 6

6 6

160 250 315 400 500 630 800 1000 1250 1600

220 344 433 550 687 866 1100 1375 1718 2199

5.41 8.38 10.5 13.2 16.4 20.4 17.4 21.5 26.4 33.1

5.45 8.49 10.7 13.5 16.8 21.0 17.9 22.2 27.5 34.8

3.63 5.63 7.07 8.93 11.1 13.9 17.4 21.5 26.4 33.1

3.65 5.68 7.14 9.04 11.3 14.1 17.9 22.2 27.5 34.8


the value of Isc can be estimated as the sum of the Isc from each transformer calculated separately

Short Circuit Fault Current In Amps

22.91 KA

windings of the power supply transformers ZT = total impedance per phase of the installation upstream of the fault loctin (in ohms) ______________________________________________________________________________________

Each component of an installation (HV network,transformer, cable,circuit breaker,busbar, and so on …. )

______________________________________________________________________________________

Zs = impedance of the HV voltage network,expressed in milli-ohms

Ra is generally found to be negligible compared with Xa

= phase-to-phase no load LV voltage, expressed in volts.

Ra (m-ohm) Xa ( m-ohm)

0.106 0.71

0.053 0.353


while the resistance is neglected , Rc.b= 0 , Xc.b = 0.15 m Ω per circuit breaker

while the resistance is neglected , Rb.b= 0 , Xb.b = 0.15 m Ω per meter length

Xc =0.08 m Ω / m for 50 HZ system Xc =0.096 m Ω / m for 60 HZ system

for prefabricated bus-trunking and similar pre-wired ducting systems, the manfacturer should be consulted .

COMMENT

0.353 Ra = 0.15 Xa

10.34

Xc = 0.08 x 5 2.523 11.1 Isc1 = 21.3 KA

Rc = ρ L / S

RD = 0XD = 0.15 XD = 0.15 Per Circuit Breaker

XB = 1.5 2.523 12.75 Isc2 = 18.6 KA RB = 0

Xc = 100x 0.08 26.2 20.75 Isc3 = 7.24 KA

Rc = ρ L / S

ρ = 22.5 m Ω .mm ² / m for copper ρ = 36 m Ω .mm ² / m for aluminium

X (mΩ) RT (mΩ) XT (mΩ) Isc = 420 / √3 * √ ( RT² + XT² )

Zs = Uo² / Psc ,

Rtr = Pcu x 10³ / 3 In² Xa = √ Ztr ² - Rtr ² avec Ztr = ( U² 2o/Pn ) * ( Usc / 100 )

Xc = 0.08 mΩ / meter

XB = 0.15 mΩ / meter


26.2 20.75 Isc3 = 7.24 KA

Xc = 20x 0.08 71.2 22.35 Isc4 = 3.24 KA

Rc = ρ L / S

xc = 20x 0.08 71.2 22.35 Isc4 = 3.24 KA

Rc = often negligible for S ≥ 200 mm² in the formula below

table H1-39 : example of short-circuit current calculations for a LV installation supplied at 400 V (nominal) from a 1000 KVA HV/LV transformer


R = ρ L / S Xc = 0.08 mΩ / meter

2000 2500

2749 3437

40.4 49.1

43.0 52.9

40.4 49.1

43.0 52.9



COMMENT

Zs = HV impedance in milli - ohmUo = phase-to-phase no- load LV in volts

Psc = HV 3-phase short-circuit fault level in KVA .Rtr = is often negligible compared to Xtr for trn ≥ 100 KVA

or Isc = In x100/Usc Rc = ρ L / S

RD = 0 XD = 0.15 Per Circuit Breaker

RB = 0

Rc = ρ L / S TRN1TRN2

Rtr = Pcu x 10³ / 3 In²

avec Ztr = ( U² 2o/Pn ) * ( Usc / 100 )

0.08 mΩ / meter where ρ = 22.5 milli-ohms x mm² for copper .where ρ = 36 milli-ohms x mm² for aluminium .

0.15 mΩ / meter

0.08 mΩ / meter where ρ = 22.5 milli-ohms x mm² for copper .

Rc = ρ L / S

Rc = often negligible for S ≥ 200 mm² in the formula below

CABLE1CABLE2CABLE3

CB1CB2CB3CB4

B.B1

B.B2

DATA

Uo (V)230

where ρ = 36 milli-ohms x mm² for aluminium .

0.08 mΩ / meter where ρ = 22.5 milli-ohms x mm² for copper .where ρ = 36 milli-ohms x mm² for aluminium .

0.08 mΩ / meter

230230230230230230230230230

(1) determination of the impedance of the HV network

DATA RESULTS COMMENT

Psc Uo X(mΩ) R(mΩ) Z(mΩ) Isc Psc 500/250 MVA500 420 0.353 0.053 0.357 679.74 Uo = 420 v , 400 v , for rated load 400v , 380 v 300 400 0.320 0.048 0.324 713.72 X,R,Z in milli ohm (mΩ) and Isc in KA

(2) determination of Isc at secondary terminals of a HV/LV distribution transformer

DATA RESULTS

Pn(KVA) Uo(V) Usc(%) Pcu(W) X(mΩ) R(mΩ) Z(mΩ) In(A) Isc(KA)1000 230 6 15 2.47 1.99 3.17 2510.29 41.841000 420 6 13.3 10.1 3.22 10.58 1374.68 22.91

(2) quick estimation

DATA RESULTS COMMENT

P(KVA) Usc(%) Uo(V) In (A) Isc(KA) Usc = 6 % for 800 to 630 KVA

1000 6 230 2510.29 41.84Usc = 4 % for 50 to 2500 KVA

(3) determination of Isc for low voltage cables

DATA RESULTS

L (m) Uo(V) N (n) ρ R(mΩ) X(mΩ) Z(mΩ) Isc(KA)10 300 230 5 22.5 0.15 0.80 0.81 163.1550 120 230 2 22.5 4.69 4.00 6.16 21.5510 25 230 1 22.5 9.00 0.80 9.04 14.70

(4) determination of Isc for circuit breaker

DATA RESULTS

N (n) Uo(V) R(mΩ) X(mΩ) Z(mΩ) Isc(KA)1 0 0.00 0.15 0.15 0.001 0 0.00 0.15 0.15 0.001 0 0.00 0.15 0.15 0.001 0 0.00 0.15 0.15 0.00

(5) determination of Isc for busbars

DATA RESULTS

L (m) Uo(V) R(mΩ) X(mΩ) Z(mΩ) Isc(KA)10 0 0.00 1.50 1.50 0.00

5 0 0.00 0.75 0.75 0.00

DATA RESULTS

NO Item R(mΩ) X(mΩ) Z(mΩ) 0 0 Rt(mΩ)1 transformer 1.99 2.47 3.17 1.99 2.47 1.99

S (mm²)

2 cable (1) 0.15 0.8 0.81 2.14 3.27 2.143 circuit breaker (1) 0 0.15 0.15 2.14 3.42 2.144 busbar (1) 0 1.5 1.5 2.14 4.92 2.145 circuit breaker (2) 0 0.15 0.15 2.14 5.07 2.146 cable (2) 4.69 4 6.16 6.83 9.07 6.837 circuit breaker (3) 0 0.15 0.15 6.83 9.22 6.838 busbar (2) 0 0.75 0.75 6.83 9.97 6.839 circuit breaker (4) 0.00 0.15 0.15 6.83 10.12 6.83

10 cable (3) 9.00 0.80 9.04 15.83 10.92 15.83

(1) determination of the impedance of the HV network

COMMENT

Psc 500/250 MVAUo = 420 v , 400 v , for rated load 400v , 380 v

X,R,Z in milli ohm (mΩ) and Isc in KA

(2) determination of Isc at secondary terminals of a HV/LV distribution transformer

COMMENT

For roughly estimation Isc = In/Usc In= nominal current in amp. Usc = sc impedance voltage in %

(2) quick estimation

COMMENT

(3) determination of Isc for low voltage cables

COMMENT

L : length of cable in meter S : c.s.a of cable in mm²

N : no. of conductor /phase

(4) determination of Isc for circuit breaker

COMMENT

N : no of poleRd = 0 ( negligible )

Xd = 0.15 mΩ / pole

(5) determination of Isc for busbars

COMMENT

L : length of busbar in meterRb = 0 ( negligible )Xb = 0.15 mΩ / m

RESULTS COMMENT

Xt(mΩ) Zt(mΩ) Isc(KA)2.47 3.17 41.84

ρ :22.5 / 36 mΩxmm²/m for copper / alumimuim

3.27 3.91 33.963.42 4.04 32.904.92 5.37 24.745.07 5.50 24.129.07 11.35 11.709.22 11.47 11.579.97 12.09 10.99

10.12 12.21 10.8810.92 19.23 6.91

CABLE AND BREAKER SIZE TABLE ACCORDING TO SCECO

connected Amp Range Minimum (cu) Maximum (cu)

Cable Size Cable Size

GT LE mm2 mm2

1 30 4x25 4x25

30 72 4x35 4x35

72 130 4x35 4x50

130 198 4x70 4x95

198 250 4x95 4x120

250 350 4x150 4x185

350 400 4x240 4x240

400 500 4x240 2x4x240

500 600 2x4x240 2x4x300

600 700 2x4x300 2x4x300

700 800 2x4x300 2x4x300

800 1000 3x4x240 3x4x240

1000 1250 7x1x630 7x1x630

1250 1600 7x1x630 7x1x630

1600 2000 11x1x630 11x1x630

2000 2500 14x1x630 14x1x630

2500 3000 14x1x630 14x1x630

NEW MINISTRY GUIDELINES FOR CUSTOMER LOAD ESTIMATION (T-1)

127/220 V

RESIDENTIAL CUSTOMERS ( T-1 )

COVERED AREA TOTAL UNIT A/C CONTRACTED LOAD KWH Meter SQ METER CONNECTED CONNECTED C.B RATING

(KVA) Size (Amps)LOAD (KVA) LOAD (KVA) (Amps)

25 4 2.530 11.43 3x25 (100)50 8 5

74 11 7.4

75 12 7.5

60 22.86 3x25 (100)100 16 10125 20 12.5150 24 15174 27 17.4

175 28 17.5

100 38.11 3x25 (100)

200 32 20225 36 22.5250 40 25275 43 27.5300 46 30324 49 32.4

325 50 32.5

150 57.16 3x40 (160)

350 53 35375 56 37.5400 60 40425 63 42.5450 66 45475 70 47.5500 73 50524 75 52.4

525 76 52.5

200 76.21 C.T.

550 80 55575 83 57.5600 86 60625 90 62

650 93 65

200 76.21 C.T.

674 95 67.4

NEW MINISTRY GUIDELINES FOR CUSTOMER LOAD ESTIMATION

127/220 V

RESIDENTIAL CUSTOMERS ( T-1 )

675 96 67.5

300 114.32 C.T.

700 100 70725 103 72.5750 106 75775 110 77.5800 113 80825 116 82.5850 120 85875 123 87.5900 126 90925 130 92.5950 133 95

951 134 95.1

400 152.42 C.T.

975 136 97.51000 140 1001025 143 102.51050 146 1051075 150 107.51100 152 110

1101 153 110.1

500 190.53 C.T.

1125 156 112.51150 160 1151175 163 117.51200 166 1201300 180 1301400 193 1401500 206 1501600 220 1601658 228 165.8

1659 229 165.9

800 304.84 C.T.

1700 233 1701800 246 1801900 260 1902000 273 2002100 286 210

2200 300 220

800 304.84 C.T.

2236 305 223.6


127/220 V

COMMERCIAL CUSTOMERS ( T-2 )



25 6 330 11.43 3x25 (100)50 10 6

55 11 6.6

56 12 6.7

60 22.86 3x25 (100)75 16 9

100 22 12125 27 15

126 28 15.1

100 38.11 3x25 (100)

150 32 18175 36 21200 40 24225 43 27230 49 27.6

231 50 27.7

150 57.15 3x40 (160)

250 54 30275 59 33300 64 36325 70 39350 75 42

351 76 42.1

200 76.21 C.T.375 80 45400 86 48425 91 51449 95 53.9

450 96 54

300 114.3 C.T.

475 102 57500 107 60

525 112 63300 114.3 C.T.

550 118 66575 123 69600 128 72624 133 74.9


127/220 V

COMMERCIAL CUSTOMERS ( T-2 )



625 134 75.5

400 152.4 C.T.650 139 78675 144 81700 150 84711 152 85.3

712 153 85.4

500190.5 C.T.

725 155 87750 160 90775 166 93800 171 96825 176 99850 182 102875 187 105900 192 108925 198 111950 203 114975 208 117

1000 214 1201025 219 1231050 224 1261069 228 128

1070 229 128.4

800304.8 C.T.

1075 230 1291100 235 1321125 240 1351150 246 1381175 250 1411200 256 1441300 278 1561400 299 1681429 305 171.5


RESIDENTIAL CUSTOMERS 220/380 V ( T-3 )



25 4 2.5

30 19.74 3x25 (100)50 8 575 12 7.5

100 16 10124 19 12.4

125 20 12.5

60 39.48 3x25 (100)

150 24 15175 28 17.5200 32 20225 36 22.5250 40 25275 43 27.5300 46 30312 47 31.2

313 48 31.3

100 65.8 3x25 (100)

325 50 32.5350 53 35375 56 37.5400 60 40425 63 42.5450 66 45475 70 47.5500 73 50525 76 52.5550 80 55575 83 57.5599 85 59.9

600 86 60

150 98.7 3x40 (160)

625 90 62.5650 93 65675 96 67.5700 100 70

725 103 72.5

150 98.7 3x40 (160)750 106 75775 110 77.5800 113 80825 116 82.5850 120 85875 123 87.5900 126 90930 130 93


RESIDENTIAL CUSTOMERS 220/380 V ( T-3 )



931 131 93.1

200 131.6 C.T.

950 133 95975 136 97

1000 140 1001025 143 102.51050 146 1051075 150 107.51100 152 1101125 156 112.51150 160 1151175 163 117.51188 164 118.8

1189 165 118.9

300 197.4 C.T.

1200 166 1201300 180 1301400 193 1401500 206 1501600 220 1601679 230 167.9

1680 231 168

400 263.2 C.T.1700 233 1701800 246 1801900 260 1901923 263 192.3

1924 264 192.4

500 329 C.T.

2000 273 2002100 286 2102200 300 2202300 313 2302400 326 2402500 340 2502600 353 260

2700 366 270

500 329 C.T.

2800 380 2802900 393 2902916 395 291.6

2917 396 291.7800 526.4 C.T.3000 406 300

3890 526 389


COMMERCIAL CUSTOMERS 220/380 V ( T-4 )



25 6 3

30 19.74 3x25 (100)50 10 675 16 992 19 11

93 20 11.2

60 39.48 3x25 (100)

100 22 12125 27 15150 32 18175 38 21200 43 24224 47 26.9

225 48 27

100 65.8 3x25 (100)

250 54 30275 59 33300 64 36325 70 39350 75 42375 80 45399 85 47.9

400 86 48

150 98.7 3x40 (160)

425 91 51450 96 54475 102 57500 107 60525 112 63550 118 66575 123 69600 128 72611 130 73.3

612 131 73.4

200 131.6 C.T.

625 134 75650 139 78675 144 81700 150 84725 155 87750 160 90772 164 92.6


COMMERCIAL CUSTOMERS 220/380 V ( T-4 )



773 165 92.8

300 197.4 C.T.

775 166 93800 171 96825 176 99850 182 102875 187 105900 192 108925 198 111950 203 114975 208 117

1000 214 1201025 219 1231050 224 1261075 230 129

1076 231 129.1

400 263.2 C.T.

1100 235 1321125 240 1351150 246 1381175 250 1411200 256 1441233 263 148

1234 264 148.1

500 329 C.T.

1300 278 1561400 299 1681500 320 1801600 342 1921700 363 2041800 384 2161852 395 222.2

1853 396 222.4

800 526.4 C.T.

1900 405 2282000 427 2402100 448 2522200 469 2642300 491 2762400 512 2882465 526 295.8

INDIVIDUAL EQUIPMENT DEMAND FACTORS

( TABLE - 5 )

S/N TYPE OF LOAD CONTRACTED LOAD

RESIDENTIAL COMMERCIAL INDUSTRIAL AGR.FARMS

1 CENTRAL A/CS 1 1 1 1

2 WINDOW TYPE A/CS 0.6 0.6 0.7 0.7

3 LIGHTING ( INTERIOR / EXTERIOR ) 1 1 1 1

4 REFRIGERATION / COOLING 0.6 0.6 0.6 0.6

5 FANS/BLOWERS 0.2 0.2 0.2 0.2

6 EQUIPMENT USED IN KITCKENS 0.2 0.2 0.2 ___

7 WATER HEATERS 0.2 0.2 0.2 ___

8 LAUNDARY EQUIPMENT 0.2 0.2 0.2 ___

9 APPLIANCES USED FOR RECREATION 0.2 0.2 ___ ___

10 APPLIANCES USED FOR SEVICES 0.2 0.2 0.2 ___

11 EQUIPMENT USED IN OFFICE/LABS ____ 0.2 0.2 ___

12 WELDING EQUIPMENT ____ 0.15 0.15 ___

13 ELECTRIC MOTORS USED FOR CRAFTS,

WORKSHOPS & SERVICE CENTERS ____ 0.25 0.25 ___

14 ELECTRIC MOTORS USED FOR BATCH WORKS,

FLUCTUATING OR MULTIPLE PRODUCTION ____ ____ 0.4 0.4

15 ELECTRIC MOTORS USED FOR CONTINOUS

PROCESS AND MASS PRODUCTION ____ ____ 0.6 ___

16 PROCESS HEATING USING OVENS ____ ____ 0.35 ___

17 PROCESS HEATING USING FURNACES ____ ____ 0.75 ___

18 MISCELLANEOUS ( NOT COVERED ABOVE ) 0.1 0.1 0.1 0.1

DIVERSITY FACTORS

( TABLE - 6 )

NO OF CUSTOMERS APPLICABLE NO OF CUSTOMERS APPLICABLE

IN THE GROUP ( N) DIVERSITY FACTOR ( DVF) IN THE GROUP ( N) DIVERSITY FACTOR ( DVF)

1 1 9 1.603

2 1.383 10 1.615

3 1.453 11--15 1.656

4 1.497 16--20 1.681

5 1.529 21--30 1.712

6 1.553 31--50 1.745

7 1.572 50--100 1.798

8 1.59 ABOVE 100 1.8

CF = (0.67+(.33/√N )) / 1.25 CF = COVERAGE FACTOR

DVF = 1.25/(0.67+(.33/√N )) DVF = DIVERSITY FACTOR

CABLE AND BREAKER SIZE TABLE ACCORDING TO SCECO

connected Amp Range Minimum (cu) Maximum (cu) Maximum

Cable Size Cable Size C.B. Size

GT LE mm2 mm2 Amp.

1 30 4x25 4x25 30

30 72 4x35 4x35 60

72 130 4x35 4x50 100

130 198 4x50 4x50 150

198 250 4x95 4x120 200

250 350 4x150 4x185 300

350 400 4x240 4x240 400

400 500 4x240 2x4x240 500

500 600 2x4x240 2x4x300 600

600 700 2x4x300 2x4x300 700

700 800 2x4x300 2x4x300 800

800 1000 3x4x240 3x4x240 1000

1000 1250 7x1x630 7x1x630 1250

1250 1600 7x1x630 7x1x630 1600

1600 2000 11x1x630 11x1x630 2000

2000 2500 14x1x630 14x1x630 2500

2500 3000 14x1x630 14x1x630 3000

Derating factors for low voltage cable ( Sauidi cable company )

Table 15

Derating factors for variation in ground temprature

Ground temperature ( C ) 25 30 35 40 45 50

XLPE Insul.cable 1.09 1.04 1.00 0.95 0.90 0.85

PVC ( rated 85 C ) cable 1.10 1.05 1.00 0.95 0.89 0.84

PVC ( rated 70 C ) cable 1.13 1.07 1.00 0.93 0.85 0.76

Table 16

Derating factors for variation in depth of burial ( to centre of the trefoil group of cables )

Depth of 600/1000 volt cable _________________________________________________________

laying ( Meter ) up to 70 mm2 to Above

50 mm2 300 mm2 300 mm2

0.60 0.99 0.98 0.97

0.80 0.97 0.96 0.94

1.00 0.95 0.93 0.92

1.25 0.94 0.92 0.89

1.50 0.93 0.9 0.87

1.75 0.92 0.89 0.86

2.00 0.91 0.88 0.85

Table 17

Derating factors for variation in thermal resistivity of soil

Thermal resistivity of

soil ( k.m/w ) 0.80 0.90 1.00 1.20 1.50 2.00

Rating factor 1.17 1.12 1.07 1.00 0.89 0.84

Table 18

Derating factors for variation in air temprature

Ground temperature ( C ) 25 30 35 40 45 50

XLPE Insul.cable 1.14 1.10 1.05 1.00 0.95 0.89

PVC ( rated 85 C ) cable 1.15 1.11 1.05 1.00 0.94 0.88

PVC ( rated 70 C ) cable 1.22 1.15 1.08 1.00 0.91 0.82

Table 19

Group derating factors for multicore cables in flat formation

Spacing

Spacing _______________________________________________________

No of cables in group Touching 0.15 m 0.30 m

2 0.81 0.87 0.91

3 0.70 0.78 0.84

4 0.63 0.74 0.81

5 0.59 0.70 0.78

6 0.55 0.68 0.77

Table 20

Group derating factors for three single core cables in trefoil formation

Spacing _______________________________________________________

No of cables in group Touching 0.15 m 0.30 m

2 0.78 0.83 0.88

3 0.66 0.73 0.79

4 0.61 0.68 0.73

5 0.56 0.64 0.73

6 0.53 0.61 0.71

Current Carrying Capacity


Table 7


Single core cables with copper conductor XLPE insulated and PVC sheathed

Cross In ground In air

Section _____________________________________________________________________

Direct laid In duct Free In Pipe

______________________________________________________________________________________________

mm2 Amps. Amps. Amps. Amps.

1.5 30 22 22 19

2.5 39 29 29 24

4 50 38 38 32

6 63 47 49 40

10 83 63 66 54

16 107 82 88 70

25 137 105 116 92

35 165 127 143 112

50 195 151 175 134

70 238 187 222 168

95 286 225 274 205

120 327 258 326 237

150 363 290 367 269

150 363 290 367 269

185 410 330 425 308

240 474 382 505 361

300 532 431 583 411

400 600 489 676 469

500 673 550 779 533

630 752 615 900 603

Table 7


Three and four core cables with copper conductor XLPE insulated and PVC sheathed

Cross In ground

Section _____________________________________________________________________________________________________________

Unarmoured Armoured

_____________________________________________________________________________________________________________ Direct laid In duct Direct laid Free

mm2 Amps. Amps. Amps. Amps.

1.5 27 22 - 22

2.5 35 29 - 29

4 45 37 46 38

In air

Unarmoured

4 45 37 46 38

6 56 46 57 48

10 76 62 76 67

16 98 80 98 88

25 128 104 128 118

35 157 125 158 142

50 187 149 188 175

70 229 183 229 220

95 276 220 274 272

120 313 251 310 316

150 350 283 346 363

185 395 321 387 418

240 458 372 444 496

300 516 420 494 571

400 584 478 549 665

500 655 538 597 760

EXAMPLE ACTUAL ( MADINA PROJECT )

1000 AMP. FOR A/C PANEL , FEEDER 3 X ( 3X300+150 ) MM2 ,UNARMOURED ON CABLE TRAY TEMP 50 C

CHECK THE AMPACITY AFTER DERATING

AMPACITY FROM TABLE 7 FOR THE MENTION CABLE , ( 571 ) AMP.

DERATING FACTOR ACC TO 3 CABLE IN GROUP AND TEMP, 50 C , TABLES 20,18

DERATING FACTORS = ( 0,78 X 0.89 ) = 0.69

DERATING AMPACITY = 571 X ( 0,78 X 0.89 ) X 3 = 1189 AMP.



2500 AMP. FOR MDP PANEL , FEEDER 6 X ( 3X300+150 ) MM2 , DIRECT LAID UNARMOURED CABLE



DERATING FACTOR ACC TO 6 CABLE IN GROUP AND GROUND TEMP, 50 C , TABLES 20,15






2500 AMP. FOR MDP PANEL , FEEDER 14 X ( 1X630 ) MM2 , DIRECT LAID UNARMOURED 1 PH CABLE







AMPACITY FOR MULTICORE CABLES

1- UNBUIRED CABLES

DATA OF CABLES SHOULD BE KNOWN

rated CABLE SIZELOAD KW

AMPACITY INSTALLATION FACTOR TEMP. FACTOR GROUP FACTOR

voltage mm2 (A) K1 K2 K3

380 16 25 88 1 1 0.7

RESULT

RATED CURRENT Ib (A) CIRCUIT BREAKER In (A)

MAX.CIRCUIT CURRENT Iz (A)

COMMENTS

DERATED AMPACITY

47.48 62 62

FOR CIRCUIT BRAKER

Ib ≤ In ≤ Iz

Derating factors for variation in ground temprature

50 55

0.85 0.80

0.84 0.77

0.76 0.65

2.00 2.00

0.84 0.77

50 55

0.89 0.84

0.88 0.82

0.82 0.71

In air _____________________________________________________________________

In Pipe

______________________________________________________________________________________________

Amps.

19

24

32

40

54

70

92

112

134

168

205

237

269

269269

308

361

411

469

533

603

_____________________________________________________________________________________________________________

Armoured

_____________________________________________________________________________________________________________ Free In Pipe Free

Amps. Amps. Amps.

22 18 -

29 24 -

38 31 39

In air

Unarmoured

3838 31 39

48 39 50

67 52 67

88 68 89

118 90 120

142 107 149

175 129 182

220 161 229

272 196 280

316 226 322

363 258 368

418 295 420

496 346 491

571 394 557

665 454 636

760 515 705

1000 AMP. FOR A/C PANEL , FEEDER 3 X ( 3X300+150 ) MM2 ,UNARMOURED ON CABLE TRAY TEMP 50 C


DERATING FACTOR ACC TO 3 CABLE IN GROUP AND TEMP, 50 C , TABLES 20,18







GROUP FACTOR COMMENT

K3

0.7

K1 Type of installation for cable tray = 1

Data from table H1-13 Page 235 schnieder

Data for K2 from above table no 18

Data for K3 from above table no 19

RESULT

COMMENTS

FOR CIRCUIT BRAKER

Ib ≤ In ≤ Iz

Approximate voltage drop at 60 hz for single core stranded plain copper / aluminium conductors

XLPE insulation , PVC sheath 600/1000 volts

Nominal area of Copper conductor Aluminium conductor

conductor mv / amp / m mv / amp / m

1.5 22.9 -

2.5 14.1 -

4 8.8 -

6 5.9 -

10 3.6 -

16 2.3 3.7

25 1.5 2.4

35 1.1 1.8

50 0.84 1.3

70 0.61 0.95

95 0.47 0.71

120 0.39 0.58

150 0.34 0.5

185 0.29 0.42

240 0.25 0.34

300 0.22 0.29

400 0.19 0.25

500 0.17 0.22

630 0.16 0.19

data for single phase cable must be known

length of cable rated current rated voltage Parallel Case

in meter in amp in volt Number of Cable

14 11.4 220 1

% voltage drop

in percentage

0.64

single phase cable

the percentage voltage drop = 0.64

Approximate voltage drop at 60 hz for single core stranded plain copper / aluminium conductors


data for single phase cable must be known

Parallel Case mv/amp/m

Number of Cable from above table

1 8.80

single phase cable

0.64 %

Approximate voltage drop at 60 hz for three and four core stranded plain copper / aluminium conductors


Nominal area of Copper conductor Aluminium conductor

conductor mv / amp / m mv / amp / m

1.5 22.8 -

2.5 14 -

4 8.7 -

6 5.9 -

10 3.5 -

16 2.2 3.7

25 1.5 2.4

35 1.1 1.7

50 0.81 1.3

70 0.58 0.92

95 0.44 0.68

120 0.37 0.56

150 0.31 0.47

185 0.27 0.39

240 0.23 0.32

300 0.20 0.27

400 0.18 0.23

500 0.15 0.20

data for three phase cable must be known

length of cable rated current rated voltage

in meter in amp in volt

100 100 380

% voltage drop

in percentage

2.13

three phase cable

the percentage voltage drop =

Approximate voltage drop at 60 hz for three and four core stranded plain copper / aluminium conductors


Aluminium conductor

mv / amp / m

-

-

-

-

-

3.7

2.4

1.7

1.3

0.92

0.68

0.56

0.47

0.39

0.32

0.27

0.23

0.20

data for three phase cable must be known

rated voltage (Parralel Case) mv/amp/m

in volt Number of cable from above table

380 1 0.81

three phase cable

the percentage voltage drop = 2.13 %

Single Core THHN Wires ( 600 V )

Copper Conductor PVC Insulated NAYLON Jacketed THHN / THWN Wires UL 83,1581

AWG

Equiv. Overall

CommentDiameter

mm² mm

18 2.3

16 2.5

14 2.9

12 3.4

10 4.3

8 8.37 5.6

Single Core

Unarmoured Cable - Copper Conductors XLPE insulation , PVC sheath 600/1000 volts

Nominal Overall

CommentArea Diameter

mm

1x1.5 6

1x2.5 7

1x4 7

1x6 8

1x10 9

1x16 10

1x25 11

1x35 13

1x50 14

1x70 16

1x95 18

1x120 20

1x150 22

1x185 24

1x240 27

1x300 30

1x400 34

1x500 37

1x630 42

Two Core


0.82 ~ 1

1.31 ~ 1.5

2.08 ~ 2

3.31 ~ 4

5.26 ~ 6

mm²


Nominal Overall


mm

2x1.5 13

2x2.5 13

2x4 14

2x6 16

2x10 17

2x16 19

2x25 23

2x35 25

Three Core


Nominal Overall


mm

3x1.5 11

3x2.5 12.5

3x4 13.5

3x6 15.5

3x10 19

3x16 21.5

four Core


Nominal Overall


mm

4x1.5 13

4x2.5 15

4x4 16

4x6 17

4x10 20

4x16 22

4x25 26

mm²

mm²

mm²

4x35 26

4x50 30

4x70 34

4x95 38

4x120 43

4x150 47

4x185 52

4x240 58

4x300 64

4x400 73

4x500 80


PIPES PIPES CABLE CONDUCTOR EARTHING

SIZE INCH SIZE INCH SIZE mm2 DIAMETER mm DIAMETER mm

1.5 38.1 6 15.5 0

RESULT

INSIDE PIPE AREA mm2 CABLE AREA mm2 FILLING FACTOR

823.3 188.6 0.23


No.Of Cables

No.Of Wire

1

RESULT

FILLING FACTOR

0.23

Calculation sheet - Elect

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