POWER CABLE SIZING CALCULATION
1. Cable sizing for 630KVA Auxiliary Transformer Rating of the equipment Voltage Full Load current
630 KV KVA 415 V 876.49 A
Cable type considered Rated continuous continuous current current when directly laid in ground
a) b) c)
d)
1C x 630 sq.mm. AL, XLPE 565 A
Derating Factors Variation of ground temperature (of cond. Temp 90 deg C for XLPE) Variation of soil thermal resistivity (3 cables in trefoil) Group rating factor for 3 group of cables in trefoil formation and touching each other Rating factor for depth of laying
0.91 ----------> a 1.11 ----------> b 0.88 -----------------> -> c
0.91 ----------> d
Composite derating factor (a*b*c*d)
0.81
Cont Contin inuo uous us curr curren entt ratin atingg afte afterr appl applyi ying ng the derating factor Hence number of run required For the Phase For the Neutral Total run
457 457.02 .02 A
1C x 630 sq.mm. AL, XLPE 2 nos. 1 nos. 7 nos.
2. Cable sizing for 800KVA Auxiliary Transformer Rating of the equipment Voltage Full Load current
800 KV KVA 415 V 1113.00 A
Cable type considered Rated continuous continuous current current when laid in air
1C x 630 sq.mm. AL, XLPE 723 A
Derating Factors a) Variation of ambient temperature to 50 deg C b) Grou Groupp rati rating ng fact factor or for for 2 ckt. ckt. of cabl cables es in trefoil formation to top tire with horizontal formation.
1 ----------> a 0.98 0.98 ----------------> b
Composite derating factor (a*b)
0.98
Cont Contin inuo uous us curr curren entt ratin atingg afte afterr appl applyi ying ng the derating factor Hence number of run required for For the Phase For the Neutral Total run
96729044.xls.ms_office
708 708.54 .54 A
1C x 630 sq.mm. AL, XLPE 2 nos. 1 nos. 7 nos.
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POWER CABLE SIZING CALCULATION
3. Cable sizing for 250kVA Diesel Generator Rating of the equipment Voltage Full Load current
250 KVA 415 V 347.81 A
Cable type considered Rated continuous current when laid in air
1C x 630 sq.mm. AL, XLPE 723 A
Derating Factors a) Variation of ambient temperature to 50 deg C b) Group rating factor for 2 ckt. of cables in trefoil formation to top tire with horizontal formation.
1 ----------> a 0.98 ----------> b
Composite derating factor (a*b)
0.98
Continuous current rating after applying the derating factor Hence number of run required for For the Phase For the Neutral Total run
708.54 A
1C x 630 sq.mm. AL, XLPE 1 nos. 1 nos. 4 nos.
4. Cable sizing for 100kVA Lighting Transformer Rating of the equipment Voltage Full Load current
100 KVA 415 V 139.12 A
Cable type considered Rated continuous current when laid in air
3.5C x 300 sq.mm. AL, XLPE 461 A
Derating Factors a) Variation of ambient temperature to 50 deg C b) Group rating factor for 2 ckt. of cables in trefoil formation to top tire with horizontal formation.
1 ----------> a 0.98 ----------> b
Composite derating factor (a*b)
0.98
Continuous current rating after applying the derating factor Hence number of run required for For the Phase
96729044.xls.ms_office
451.78 A
3.5C x 300 sq.mm. AL, XLPE 1 nos.
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POWER CABLE SIZING CALCULATION
5. Cable sizing for 150kW H.V.W. Motor Rating of the equipment Voltage Full Load current at power factor 0.8
150 KW 415 V 260.86 A
Cable type considered Rated continuous current when laid in air
3.5C x 300 sq.mm. AL, XLPE 461 A
Derating Factors a) Variation of ambient temperature to 50 deg C b) Group rating factor for multi core cables with 6 cables in rack, laid in horizontal formation.
1 ----------> a 0.93 ----------> b
Composite derating factor (a*b)
0.93
Continuous current rating after applying the derating factor Hence number of run required for Check for voltage drop AC Resistance of the cable Equivalent Star reactance Equivalent Impedance Route length Cable Impedance Voltage drop during normal load Percentage Drop
428.73 A
3.5C x 300 sq.mm. AL, XLPE 1 nos. 0.1 ohms/km 0.0877 ohms/km 0.1330 ohms/km 0.07 km 0.0093 ohms Note: Starting is not critical becasuse 4.2066 Volts of Delta / Star start 1.01% < 3% (permissible limit)
6. Cable sizing for 15kW Jockey Pump Motor for Fire Fighting System Rating of the equipment Voltage Full Load current at power factor 0.8
30 KW 415 V 52.17 A
Cable type considered 3.5C x 35 sq.mm. AL, PVC Rated continuous current when 70 A laid in air Derating Factors a) Variation of ambient temperature 1 ----------> a to 50 deg C b) Group rating factor for multi core cables 0.93 ----------> b with 6 cables in rack, laid in horizontal formation. Composite derating factor (a*b) 0.93 Continuous current rating after applying 65.10 A the derating factor Hence number of run required for Check for voltage drop AC Resistance of the cable Equivalent Star reactance Equivalent Impedance Route length
96729044.xls.ms_office
3.5C x 35 sq.mm. AL, PVC 1 nos. 1.1 0.0827 1.1031 0.07 Page 3 of 8
ohms/km ohms/km ohms/km km
(2 nos. of 15kW each)
POWER CABLE SIZING CALCULATION
Cable Impedance Voltage drop during normal load Percentage Drop
0.0772 ohms 6.9775 Volts 1.68% < 3% (permissible limit)
Starting ( with one motor running and othet motor starting) current Voltage drop starting of motor Percentage Drop
182.601074 A 24.4211 Volts 5.88% < 20% (permissible limit)
7. Cable sizing for Chiller Unit for Air Conditioning Rating of the equipment Voltage Full Load current at power factor 0.8
43.08 KW 415 V 74.92 A
Cable type considered 3.5C x 70 sq.mm. AL, PVC Rated continuous current when 105 A laid in air Derating Factors a) Variation of ambient temperature 1 ----------> a to 50 deg C b) Group rating factor for multi core cables 0.93 ----------> b with 6 cables in rack, laid in horizontal formation. Composite derating factor (a*b) 0.93 Continuous current rating after applying 97.65 A the derating factor Hence number of run required for Check for voltage drop AC Resistance of the cable Equivalent Star reactance Equivalent Impedance Route length Cable Impedance Voltage drop during normal load Percentage Drop
3.5C x 70 sq.mm. AL, PVC 1 nos. 0.533 ohms/km 0.0771 ohms/km 0.5385 ohms/km 0.045 km 0.0242 ohms 3.1447 Volts 0.76% < 3% (permissible limit)
8. Cable sizing for Chiller Water Pump for Air Conditioning Rating of the equipment Voltage Full Load current at power factor 0.8
3.7 KW 415 V 6.43 A
Cable type considered 4C x 16 sq.mm. AL PVC Rated continuous current when 42 A laid in air Derating Factors a) Variation of ambient temperature 1 ----------> a to 50 deg C b) Group rating factor for multi core cables 0.93 ----------> b with 6 cables in rack, laid in horizontal formation. Composite derating factor (a*b) 0.93 Continuous current rating after applying 39.06 A the derating factor Hence number of run required for
96729044.xls.ms_office
4C x 16 sq.mm. AL PVC 1 nos. Page 4 of 8
A
POWER CABLE SIZING CALCULATION
Check for voltage drop AC Resistance of the cable Equivalent Star reactance Equivalent Impedance Route length Cable Impedance Voltage drop during normal load Percentage Drop Starting Current Voltage drop at starting of motor Percentage Drop
2.29 ohms/km 0.097 ohms/km 2.2921 ohms/km 0.045 km 0.1031 ohms 1.1495 Volts 0.28% < 3% (permissible limit) 38.6070842 A 6.8969 Volts 1.66% < 20% (permissible limit)
9. Cable sizing for Air Handling Unit (A.H.U.) for Air Conditioning Rating of the equipment Voltage Full Load current at power factor 0.8
3.7 KW 415 V 6.43 A
Cable type considered 4C x 16 sq.mm. AL PVC Rated continuous current when 42 A laid in air Derating Factors a) Variation of ambient temperature 1 ----------> a to 50 deg C b) Group rating factor for multi core cables 0.93 ----------> b with 6 cables in rack, laid in horizontal formation. Composite derating factor (a*b) 0.93 Continuous current rating after applying 39.06 A the derating factor Hence number of run required for Check for voltage drop AC Resistance of the cable Equivalent Star reactance Equivalent Impedance Route length Cable Impedance Voltage drop during normal load Percentage Drop Starting Current Voltage drop at starting of motor Percentage Drop
A
4C x 16 sq.mm. AL PVC 1 nos. 2.29 ohms/km 0.097 ohms/km 2.2921 ohms/km 0.045 km 0.1031 ohms 1.1495 Volts 0.28% < 3% (permissible limit) 38.6070842 A 6.8969 Volts 1.66% < 20% (permissible limit)
10. Cable sizing for Winter Heating Unit for Air Conditioning Rating of the equipment Voltage Full Load current at power factor 0.8 Cable type considered Rated continuous current when laid in air
96729044.xls.ms_office
9 KW 415 V 15.65 A 4C x 6 sq.mm. AL PVC 30 A
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(Non - Motor)
POWER CABLE SIZING CALCULATION
Derating Factors a) Variation of ambient temperature to 50 deg C b) Group rating factor for multi core cables with 6 cables in rack, laid in horizontal formation. Composite derating factor (a*b) Continuous current rating after applying the derating factor Hence number of run required for Check for voltage drop AC Resistance of the cable Equivalent Star reactance Equivalent Impedance Route length Cable Impedance Voltage drop during normal load Percentage Drop
1 ----------> a 0.93 ----------> b
0.93 27.90 A
4C x 6 sq.mm. AL PVC 1 nos. 3.69 ohms/km 0.0942 ohms/km 3.6912 ohms/km 0.045 km 0.1661 ohms 4.5028 Volts 1.09% < 3% (permissible limit)
11. Cable sizing for Ventilation Fan (Axail Flow type) for Exhaust Ventilation Rating of the equipment Voltage Full Load current at power factor 0.8
0.74 KW 415 V 1.29 A
(Two 0.37kW Fan will be paralled)
Cable type considered 3C x 2.5 sq.mm., Cu PVC Rated continuous current when 24 A laid in air Derating Factors a) Variation of ambient temperature 1 ----------> a to 50 deg C b) Group rating factor for multi core cables 0.93 ----------> b with 6 cables in rack, laid in horizontal formation. Composite derating factor (a*b) 0.93 Continuous current rating after applying 22.32 A the derating factor Hence number of run required for Check for voltage drop AC Resistance of the cable Equivalent Star reactance Equivalent Impedance Route length Cable Impedance Voltage drop during normal load Percentage Drop Starting Current Voltage drop at starting of motor Percentage Drop
96729044.xls.ms_office
3C x 2.5 sq.mm., Cu PVC 1 nos. 8.87 ohms/km 0.105 ohms/km 8.8706 ohms/km 0.115 km 1.0201 ohms 2.2738 Volts 0.55% < 3% (permissible limit) 7.72141685 A 13.6426 Volts 3.29% < 20% (permissible limit)
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POWER CABLE SIZING CALCULATION
12. Cable sizing for Ventilation Fan (Propeller) for Exhaust Ventilation Rating of the equipment Voltage Full Load current at power factor 0.8
0.72 KW 415 V 1.25 A
(Four 0.18kW Fan will be paralled)
Cable type considered 3C x 2.5 sq.mm., Cu PVC Rated continuous current when 24 A laid in air Derating Factors a) Variation of ambient temperature 1 ----------> a to 50 deg C b) Group rating factor for multi core cables 0.93 ----------> b with 6 cables in rack, laid in horizontal formation. Composite derating factor (a*b) 0.93 Continuous current rating after applying 22.32 A the derating factor Hence number of run required for Check for voltage drop AC Resistance of the cable Equivalent Star reactance Equivalent Impedance Route length Cable Impedance Voltage drop during normal load Percentage Drop Starting Current Voltage drop at starting of motor Percentage Drop
3C x 2.5 sq.mm., Cu PVC 1 nos. 8.87 ohms/km 0.105 ohms/km 8.8706 ohms/km 0.115 km 1.0201 ohms 2.2123 Volts 0.53% < 3% (permissible limit) 7.5127299 A 13.2739 Volts 3.20% < 20% (permissible limit)
13. Cable sizing of Feeder for Oil Filtration Unit Voltage Rating of the equipment
415 V 100.00 A
Cable type considered 3.5C x 300 sq.mm. AL, XLPE Rated continuous current when 461 A laid in air Derating Factors a) Variation of ambient temperature 1 ----------> a to 50 deg C b) Group rating factor for multi core cables 0.93 ----------> b with 6 cables in rack, laid in horizontal formation. Composite derating factor (a*b) 0.93 Continuous current rating after applying 428.73 A the derating factor Hence number of run required for Check for voltage drop AC Resistance of the cable Equivalent Star reactance Equivalent Impedance
96729044.xls.ms_office
3.5C x 300 sq.mm. AL, XLPE 1 nos. 0.533 ohms/km 0.0771 ohms/km 0.5385 ohms/km Page 7 of 8
POWER CABLE SIZING CALCULATION
Route length Cable Impedance Voltage drop during normal load Percentage Drop
0.045 km 0.0242 ohms 4.1974 Volts 1.01% < 3% (permissible limit)
14. Cable sizing of Switchyard Bay Marshalling Kiosk Typical Runnind Loads on the Bay MK at a given point of time 2 nos. Circuit Breaker Compressor 1 no. Isolator Motor Operating Space Heater (40W each) Total running load Voltage Full Load current at power factor 0.8
6 kW (3 KW each) 0.373 kW 0.8 kW (20 nos. of heater out of 35 nos. running) 7.173 kW 415 V 12.47 A
Cable type considered 3.5C x 35 sq.mm. AL PVC Rated continuous current when 70 A laid in air Derating Factors a) Variation of ambient temperature 1 ----------> a to 50 deg C b) Group rating factor for multi core cables 0.93 ----------> b with 6 cables in rack, laid in horizontal formation. Composite derating factor (a*b) 0.93 Continuous current rating after applying 65.10 A the derating factor Hence number of run required for
3.5C x 35 sq.mm. AL PVC 1 nos.
Check for voltage drop AC Resistance of the cable Equivalent Star reactance Equivalent Impedance Route length Cable Impedance Voltage drop during normal load Percentage Drop
1.1 ohms/km 0.0827 ohms/km 1.1031 ohms/km 0.5 km (Actual Length is 255m max.) 0.5516 ohms 11.9167 Volts 2.87% < 3% (permissible limit)
Starting Current with 1 Comp. Start and other load running. Voltage drop at starting of motor Percentage Drop
96729044.xls.ms_office
17.692 A 16.90 Volts 4.1% < 20% (permissible limit)
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