Power Cable Sizing
13
document.xls Page 1 of 13 POWER CABLE SIZING CALCULATION 1. Cable sizing for 630KVA Auxiliary Transformer Rating of the equipment 630 KVA Voltage 415 V Full Load current 876.49 A Cable type considered 1C x 630 sq.mm. AL, XLPE Rated continuous current wh 565 A directly laid in ground Derating Factors a) Variation of ground tempera 0.91 ----------> a (of cond. Temp 90 deg C for XLPE) b) Variation of soil thermal r 1.11 ----------> b (3 cables in trefoil) c) Group rating factor for 3 g 0.88 ----------> c cables in trefoil formation and touching each other d) Rating factor for depth of 0.91 ----------> d Composite derating factor ( 0.81 Continuous current rating a 457.02 A the derating factor Hence number of run require 1C x 630 sq.mm. AL, XLPE For the Phase 2 nos. For the Neutral 1 nos. Total run 7 nos. 2. Cable sizing for 800KVA Auxiliary Transformer Rating of the equipment 800 KVA Voltage 415 V Full Load current 1113.00 A Cable type considered 1C x 630 sq.mm. AL, XLPE Rated continuous current wh 723 A laid in air Derating Factors a) Variation of ambient temper 1 ----------> a to 50 deg C b) Group rating factor for 2 c 0.98 ----------> b trefoil formation to top tire with horizontal formation. Composite derating factor ( 0.98 Continuous current rating a 708.54 A the derating factor Hence number of run require 1C x 630 sq.mm. AL, XLPE For the Phase 2 nos. For the Neutral 1 nos. Total run 7 nos.
-
Upload
pagdi-srini -
Category
Documents
-
view
63 -
download
6
Transcript of Power Cable Sizing
document.xls Page 1 of 8
POWER CABLE SIZING CALCULATION
1. Cable sizing for 630KVA Auxiliary Transformer
Rating of the equipment 630 KVAVoltage 415 VFull Load current 876.49 A
Cable type considered 1C x 630 sq.mm. AL, XLPERated continuous current when 565 Adirectly laid in ground
Derating Factorsa) Variation of ground temperature 0.91 ----------> a
(of cond. Temp 90 deg C for XLPE)b) Variation of soil thermal resistivity 1.11 ----------> b
(3 cables in trefoil) c) Group rating factor for 3 group of 0.88 ----------> c
cables in trefoil formation and touchingeach other
d) Rating factor for depth of laying 0.91 ----------> d
Composite derating factor (a*b*c*d) 0.81
Continuous current rating after applying 457.02 Athe derating factor
Hence number of run required 1C x 630 sq.mm. AL, XLPEFor the Phase 2 nos.For the Neutral 1 nos.Total run 7 nos.
2. Cable sizing for 800KVA Auxiliary Transformer
Rating of the equipment 800 KVAVoltage 415 VFull Load current 1113.00 A
Cable type considered 1C x 630 sq.mm. AL, XLPERated continuous current when 723 Alaid in air
Derating Factorsa) Variation of ambient temperature 1 ----------> a
to 50 deg Cb) Group rating factor for 2 ckt. of cables in 0.98 ----------> b
trefoil formation to top tire with horizontal formation.
Composite derating factor (a*b) 0.98
Continuous current rating after applying 708.54 Athe derating factor
Hence number of run required for 1C x 630 sq.mm. AL, XLPEFor the Phase 2 nos.For the Neutral 1 nos.Total run 7 nos.
document.xls Page 2 of 8
POWER CABLE SIZING CALCULATION
3. Cable sizing for 250kVA Diesel Generator
Rating of the equipment 250 KVAVoltage 415 VFull Load current 347.81 A
Cable type considered 1C x 630 sq.mm. AL, XLPERated continuous current when 723 Alaid in air
Derating Factorsa) Variation of ambient temperature 1 ----------> a
to 50 deg Cb) Group rating factor for 2 ckt. of cables in 0.98 ----------> b
trefoil formation to top tire with horizontal formation.
Composite derating factor (a*b) 0.98
Continuous current rating after applying 708.54 Athe derating factor
Hence number of run required for 1C x 630 sq.mm. AL, XLPEFor the Phase 1 nos.For the Neutral 1 nos.Total run 4 nos.
4. Cable sizing for 100kVA Lighting Transformer
Rating of the equipment 100 KVAVoltage 415 VFull Load current 139.12 A
Cable type considered 3.5C x 300 sq.mm. AL, XLPERated continuous current when 461 Alaid in air
Derating Factorsa) Variation of ambient temperature 1 ----------> a
to 50 deg Cb) Group rating factor for 2 ckt. of cables in 0.98 ----------> b
trefoil formation to top tire with horizontal formation.
Composite derating factor (a*b) 0.98
Continuous current rating after applying 451.78 Athe derating factor
Hence number of run required for 3.5C x 300 sq.mm. AL, XLPEFor the Phase 1 nos.
document.xls Page 3 of 8
POWER CABLE SIZING CALCULATION
5. Cable sizing for 150kW H.V.W. Motor
Rating of the equipment 150 KWVoltage 415 VFull Load current at power factor 0.8 260.86 A
Cable type considered 3.5C x 300 sq.mm. AL, XLPERated continuous current when 461 Alaid in air
Derating Factorsa) Variation of ambient temperature 1 ----------> a
to 50 deg Cb) Group rating factor for multi core cables 0.93 ----------> b
with 6 cables in rack, laid inhorizontal formation.
Composite derating factor (a*b) 0.93
Continuous current rating after applying 428.73 Athe derating factor
Hence number of run required for 3.5C x 300 sq.mm. AL, XLPE1 nos.
Check for voltage dropAC Resistance of the cable 0.1 ohms/kmEquivalent Star reactance 0.0877 ohms/kmEquivalent Impedance 0.1330 ohms/kmRoute length 0.07 kmCable Impedance 0.0093 ohms Note: Starting is not critical becasuseVoltage drop during normal load 4.2066 Volts of Delta / Star startPercentage Drop 1.01% < 3% (permissible limit)
6. Cable sizing for 15kW Jockey Pump Motor for Fire Fighting System
Rating of the equipment 30 KW (2 nos. of 15kW each)Voltage 415 VFull Load current at power factor 0.8 52.17 A
Cable type considered 3.5C x 35 sq.mm. AL, PVCRated continuous current when 70 Alaid in airDerating Factors
a) Variation of ambient temperature 1 ----------> ato 50 deg C
b) Group rating factor for multi core cables 0.93 ----------> bwith 6 cables in rack, laid inhorizontal formation.Composite derating factor (a*b) 0.93Continuous current rating after applying 65.10 Athe derating factor
Hence number of run required for 3.5C x 35 sq.mm. AL, PVC
document.xls Page 4 of 8
POWER CABLE SIZING CALCULATION1 nos.
Check for voltage dropAC Resistance of the cable 1.1 ohms/kmEquivalent Star reactance 0.0827 ohms/kmEquivalent Impedance 1.1031 ohms/kmRoute length 0.07 kmCable Impedance 0.0772 ohmsVoltage drop during normal load 6.9775 VoltsPercentage Drop 1.68% < 3% (permissible limit)
Starting ( with one motor running and 182.601074 Aothet motor starting) currentVoltage drop starting of motor 24.4211 VoltsPercentage Drop 5.88% < 20% (permissible limit)
7. Cable sizing for Chiller Unit for Air Conditioning
Rating of the equipment 43.08 KWVoltage 415 VFull Load current at power factor 0.8 74.92 A
Cable type considered 3.5C x 70 sq.mm. AL, PVCRated continuous current when 105 Alaid in airDerating Factors
a) Variation of ambient temperature 1 ----------> ato 50 deg C
b) Group rating factor for multi core cables 0.93 ----------> bwith 6 cables in rack, laid inhorizontal formation.Composite derating factor (a*b) 0.93Continuous current rating after applying 97.65 Athe derating factor
Hence number of run required for 3.5C x 70 sq.mm. AL, PVC1 nos.
Check for voltage dropAC Resistance of the cable 0.533 ohms/kmEquivalent Star reactance 0.0771 ohms/kmEquivalent Impedance 0.5385 ohms/kmRoute length 0.045 kmCable Impedance 0.0242 ohmsVoltage drop during normal load 3.1447 VoltsPercentage Drop 0.76% < 3% (permissible limit)
8. Cable sizing for Chiller Water Pump for Air Conditioning
Rating of the equipment 3.7 KWVoltage 415 VFull Load current at power factor 0.8 6.43 A
Cable type considered 4C x 16 sq.mm. AL PVCRated continuous current when 42 Alaid in airDerating Factors
a) Variation of ambient temperature 1 ----------> ato 50 deg C
b) Group rating factor for multi core cables 0.93 ----------> b
A
document.xls Page 5 of 8
POWER CABLE SIZING CALCULATIONwith 6 cables in rack, laid inhorizontal formation.Composite derating factor (a*b) 0.93Continuous current rating after applying 39.06 Athe derating factor
Hence number of run required for 4C x 16 sq.mm. AL PVC1 nos.
Check for voltage dropAC Resistance of the cable 2.29 ohms/kmEquivalent Star reactance 0.097 ohms/kmEquivalent Impedance 2.2921 ohms/kmRoute length 0.045 kmCable Impedance 0.1031 ohmsVoltage drop during normal load 1.1495 VoltsPercentage Drop 0.28% < 3% (permissible limit)
Starting Current 38.6070842 A
Voltage drop at starting of motor 6.8969 VoltsPercentage Drop 1.66% < 20% (permissible limit)
9. Cable sizing for Air Handling Unit (A.H.U.) for Air Conditioning
Rating of the equipment 3.7 KWVoltage 415 VFull Load current at power factor 0.8 6.43 A
Cable type considered 4C x 16 sq.mm. AL PVCRated continuous current when 42 Alaid in airDerating Factors
a) Variation of ambient temperature 1 ----------> ato 50 deg C
b) Group rating factor for multi core cables 0.93 ----------> bwith 6 cables in rack, laid inhorizontal formation.Composite derating factor (a*b) 0.93Continuous current rating after applying 39.06 Athe derating factor
Hence number of run required for 4C x 16 sq.mm. AL PVC1 nos.
Check for voltage dropAC Resistance of the cable 2.29 ohms/kmEquivalent Star reactance 0.097 ohms/kmEquivalent Impedance 2.2921 ohms/kmRoute length 0.045 kmCable Impedance 0.1031 ohmsVoltage drop during normal load 1.1495 VoltsPercentage Drop 0.28% < 3% (permissible limit)
Starting Current 38.6070842 A
Voltage drop at starting of motor 6.8969 VoltsPercentage Drop 1.66% < 20% (permissible limit)
A
A
document.xls Page 6 of 8
POWER CABLE SIZING CALCULATION
10. Cable sizing for Winter Heating Unit for Air Conditioning
Rating of the equipment 9 KW (Non - Motor)Voltage 415 VFull Load current at power factor 0.8 15.65 A
Cable type considered 4C x 6 sq.mm. AL PVCRated continuous current when 30 Alaid in airDerating Factors
a) Variation of ambient temperature 1 ----------> ato 50 deg C
b) Group rating factor for multi core cables 0.93 ----------> bwith 6 cables in rack, laid inhorizontal formation.Composite derating factor (a*b) 0.93Continuous current rating after applying 27.90 Athe derating factor
Hence number of run required for 4C x 6 sq.mm. AL PVC1 nos.
Check for voltage dropAC Resistance of the cable 3.69 ohms/kmEquivalent Star reactance 0.0942 ohms/kmEquivalent Impedance 3.6912 ohms/kmRoute length 0.045 kmCable Impedance 0.1661 ohmsVoltage drop during normal load 4.5028 VoltsPercentage Drop 1.09% < 3% (permissible limit)
11. Cable sizing for Ventilation Fan (Axail Flow type) for Exhaust Ventilation
Rating of the equipment 0.74 KW (Two 0.37kW Fan will be paralled)Voltage 415 VFull Load current at power factor 0.8 1.29 A
Cable type considered 3C x 2.5 sq.mm., Cu PVCRated continuous current when 24 Alaid in airDerating Factors
a) Variation of ambient temperature 1 ----------> ato 50 deg C
b) Group rating factor for multi core cables 0.93 ----------> bwith 6 cables in rack, laid inhorizontal formation.Composite derating factor (a*b) 0.93Continuous current rating after applying 22.32 Athe derating factor
Hence number of run required for 3C x 2.5 sq.mm., Cu PVC1 nos.
Check for voltage dropAC Resistance of the cable 8.87 ohms/kmEquivalent Star reactance 0.105 ohms/kmEquivalent Impedance 8.8706 ohms/kmRoute length 0.115 kmCable Impedance 1.0201 ohms
document.xls Page 7 of 8
POWER CABLE SIZING CALCULATIONVoltage drop during normal load 2.2738 VoltsPercentage Drop 0.55% < 3% (permissible limit)
Starting Current 7.72141685 A
Voltage drop at starting of motor 13.6426 VoltsPercentage Drop 3.29% < 20% (permissible limit)
12. Cable sizing for Ventilation Fan (Propeller) for Exhaust Ventilation
Rating of the equipment 0.72 KW (Four 0.18kW Fan will be paralled)Voltage 415 VFull Load current at power factor 0.8 1.25 A
Cable type considered 3C x 2.5 sq.mm., Cu PVCRated continuous current when 24 Alaid in airDerating Factors
a) Variation of ambient temperature 1 ----------> ato 50 deg C
b) Group rating factor for multi core cables 0.93 ----------> bwith 6 cables in rack, laid inhorizontal formation.Composite derating factor (a*b) 0.93Continuous current rating after applying 22.32 Athe derating factor
Hence number of run required for 3C x 2.5 sq.mm., Cu PVC1 nos.
Check for voltage dropAC Resistance of the cable 8.87 ohms/kmEquivalent Star reactance 0.105 ohms/kmEquivalent Impedance 8.8706 ohms/kmRoute length 0.115 kmCable Impedance 1.0201 ohmsVoltage drop during normal load 2.2123 VoltsPercentage Drop 0.53% < 3% (permissible limit)
Starting Current 7.5127299 A
Voltage drop at starting of motor 13.2739 VoltsPercentage Drop 3.20% < 20% (permissible limit)
13. Cable sizing of Feeder for Oil Filtration Unit
Voltage 415 VRating of the equipment 100.00 A
Cable type considered 3.5C x 300 sq.mm. AL, XLPERated continuous current when 461 Alaid in airDerating Factors
a) Variation of ambient temperature 1 ----------> a
document.xls Page 8 of 8
POWER CABLE SIZING CALCULATIONto 50 deg C
b) Group rating factor for multi core cables 0.93 ----------> bwith 6 cables in rack, laid inhorizontal formation.Composite derating factor (a*b) 0.93Continuous current rating after applying 428.73 Athe derating factor
Hence number of run required for 3.5C x 300 sq.mm. AL, XLPE1 nos.
Check for voltage dropAC Resistance of the cable 0.533 ohms/kmEquivalent Star reactance 0.0771 ohms/kmEquivalent Impedance 0.5385 ohms/kmRoute length 0.045 kmCable Impedance 0.0242 ohmsVoltage drop during normal load 4.1974 VoltsPercentage Drop 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 6 kW (3 KW each)1 no. Isolator Motor Operating 0.373 kW Space Heater (40W each) 0.8 kW (20 nos. of heater out of 35 nos. running)Total running load 7.173 kWVoltage 415 VFull Load current at power factor 0.8 12.47 A
Cable type considered 3.5C x 35 sq.mm. AL PVCRated continuous current when 70 Alaid in airDerating Factors
a) Variation of ambient temperature 1 ----------> ato 50 deg C
b) Group rating factor for multi core cables 0.93 ----------> bwith 6 cables in rack, laid inhorizontal formation.Composite derating factor (a*b) 0.93Continuous current rating after applying 65.10 Athe derating factor
Hence number of run required for 3.5C x 35 sq.mm. AL PVC1 nos.
Check for voltage dropAC Resistance of the cable 1.1 ohms/kmEquivalent Star reactance 0.0827 ohms/kmEquivalent Impedance 1.1031 ohms/kmRoute length 0.5 km (Actual Length is 255m max.)Cable Impedance 0.5516 ohmsVoltage drop during normal load 11.9167 VoltsPercentage Drop 2.87% < 3% (permissible limit)
Starting Current with 1 Comp. Start and 17.692 Aother load running.Voltage drop at starting of motor 16.90 VoltsPercentage Drop 4.1% < 20% (permissible limit)
