typical power cable sizing_r1

Symbol Value Unit 1 Inputs 1.1 : 1.2 : 1.3 Motor kW rating : 55 KW (As per mfr. Datasheets) 1.4 No. of poles : 4 1.5 Motor Power factor : 0.85 (As per mfr. Datasheets) 1.6 : 65 kVA 1.7 : 0.415 kV 1.8 L : 0.065 kM 1.9 : Solidly Earthed 1.10 cos ф1 : 0.85 1.11 cos ф2 : 0.25 1.12 Efficiency of the motor η : 0.94 As per mfr. Datasheets 1.13 : As per reputed Manufacturer Datasheets 1.14 Type of feeder : DOL 1.15 I f : 95.56 Amps 95.56 1.16 I S = I f Χ 7.2 : 688.06 Amps 7.2 times in case of DOL 3 times in case of Star-Delta 2.5 times in case of Soft Starter 1.17 Transformer KVA : 2500 2 Sizing Criteria Cable selected should be 2.1 Thermally strong to with stand the full load current 2.2 Mechanically strong to withstand shortcircuit froces 2.3 Electrically stable to limit voltage drop within specified limits 3 Sizing the cable for thermal capacity 3.1 Conditions of laying : Laid on Trays (In Air) 3.2 Deration Factor F = K 1 x K 3 : 0.5984 where, K 1 = Deration factor for Ambient Air Temperature of 50 °C : 0.88 As per reputed Manufacturer Datasheets K3 = Deration factor for Grouping : 0.68 As per reputed Manufacturer Datasheets 3.3 Size of the cable selected : 3C x 95 mm² 3.4 Continuous rating of the cable I C : 194 Amps 3.5 Dearted capacity of the cable I = I C x F : 116.09 Amps 3.6 No. of runs required = I f / I : 0.82 Runs 3.7 No. of Runs selected : 1.00 Runs 1.00 4 Check for Short Circuit withstand level of the cable 4.1 I sc : 35 kA 4.2 Short Circuit MVA = MVA SC = : 25.157 MVA 4.3 X SO = kV 2 / MVA SC : 0.0068 Ohm (Ω) 4.4 R = : 0.0267 Ohm (Ω) As per reputed Manufacturer Datasheets 4.5 X = : 0.0048 Ohm (Ω) As per reputed Manufacturer Datasheets 4.6 = : 8.83 kA 4.7 : 0.12 Sec 0.5 Sec being fault clearing time 4.8 = : 8.93 kA (for 1 Se As per reputed Manufacturer Datasheets 25.78 kA (for 0.5 Sec) 4.9 I W : 25.78 kA (for 0.5 Sec) 4.10 5 Check for Steady state voltage drop in the cable 5.1 5.2 = : 2.41 Volts 5.3 = Voltage drop/(380/√3) : 1.01 % 1.09945539 5.4 The voltage drop allowable as per specifications is 3% and hence within the limits. Hence, the proposed cable (1 Runs 3C x95 Sqmm Al. XLPE) is sufficient. 6 Check for Voltage drop during starting of LT Motor 6.11 : 7.80 Volts 6.12 : % 6.13 : 3.26 % Equation Comments / Reference Typical LT Cable Sizing : XLPE Insulated Armoured Cable from LT MCC to LT Motor System Neutral Earthing Rated PF Starting PF Type of cable Selected Cable from Cable to Motor Capacity Rated Voltage Total route length √3 x V x Source Fault Level Source reactance converted to Net Resistance of cable (from LT (Ohm / kM as per Mfg. Datasheet x 1.1 kV (E), Cu, Cable Short Circuit withstand time Short circuit withstand capacity of 1 Full load current of the feeder Starting Current Source fault level Net Reactance of cable (from LT Starting voltage drop at in cable V ms = 0.85 V 1 and V bs = 0.9 V 1 % Voltage at the motor terminal % Drop at motor terminal Based on results 3.7, 4.1, 5.4, 6.17 above, the cable selected (1 Runs 3C x95Sqmm Al. XLPE) shall safely withstand the effects of short circuit and shall carry the Full Load Current within the permitted temperature limits and voltage drops. (Ohm / kM as per Mfg. Datasheet x % Voltage Drop Fault level at the load end of the V / [√3 x {R + j(X SO + X)}] Short circuit withstand capacity of 1 Hence, the selected cable (1 Runs of 3C x95Al. XLPE) is suitable for withstanding 3ф fault at the load end. For checking steady state and starting voltage drop in the cable, the presence of tap changer in the distribution transformer is considered. Hence, during steady state conditions, the Steady State Voltage Drop I f x [ R cos Φ1 + X sin Φ1 ] Page 1 of 1

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cable sizing calculation

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Symbol Value Unit

1 Inputs1.1 :1.2 :1.3 Motor kW rating : 55 KW (As per mfr. Datasheets)1.4 No. of poles : 41.5 Motor Power factor : 0.85 (As per mfr. Datasheets)1.6 : 65 kVA1.7 : 0.415 kV1.8 L : 0.065 kM1.9 : Solidly Earthed

1.10 cos 1 : 0.851.11 cos 2 : 0.251.12 Efficiency of the motor : 0.94 As per mfr. Datasheets1.13 : As per reputed Manufacturer Datasheets1.14 Type of feeder : DOL1.15 If : 95.56 Amps 95.56 1.16 IS = If 7.2 : 688.06 Amps 7.2 times in case of DOL

3 times in case of Star-Delta2.5 times in case of Soft Starter

1.17 Transformer KVA : 25002 Sizing Criteria

Cable selected should be 2.1 Thermally strong to with stand the full load current2.2 Mechanically strong to withstand shortcircuit froces2.3 Electrically stable to limit voltage drop within specified limits

3 Sizing the cable for thermal capacity3.1 Conditions of laying : Laid on Trays (In Air)3.2 Deration Factor F = K1 x K3 : 0.5984

where, K1 = Deration factor for Ambient Air Temperature of 50 C : 0.88 As per reputed Manufacturer Datasheets K3 = Deration factor for Grouping : 0.68 As per reputed Manufacturer Datasheets

3.3 Size of the cable selected : 3C x 95 mm3.4 Continuous rating of the cable IC : 194 Amps3.5 Dearted capacity of the cable I = IC x F : 116.09 Amps3.6 No. of runs required = If / I : 0.82 Runs3.7 No. of Runs selected : 1.00 Runs 1.00

4 Check for Short Circuit withstand level of the cable4.1 Isc : 35 kA4.2 Short Circuit MVA = MVASC = : 25.157 MVA4.3 XSO = kV2 / MVASC : 0.0068 Ohm ()4.4 R = : 0.0267 Ohm () As per reputed Manufacturer Datasheets4.5 X = : 0.0048 Ohm () As per reputed Manufacturer Datasheets4.6 = : 8.83 kA4.7 : 0.12 Sec 0.5 Sec being fault clearing time4.8 = : 8.93 kA (for 1 Sec)As per reputed Manufacturer Datasheets

25.78 kA (for 0.5 Sec)4.9 IW : 25.78 kA (for 0.5 Sec)

4.10

5 Check for Steady state voltage drop in the cable5.15.2 = : 2.41 Volts5.3 = Voltage drop/(380/3) : 1.01 % 1.099455395.4 The voltage drop allowable as per specifications is 3% and hence within the limits. Hence, the proposed cable (1 Runs 3C x95 Sqmm Al. XLPE) is sufficient.

6 Check for Voltage drop during starting of LT Motor6.11 : 7.80 Volts6.12 : %6.13 : 3.26 %

Equation Comments / Reference

Typical LT Cable Sizing : XLPE Insulated Armoured Cable from LT MCC to LT Motor

System Neutral EarthingRated PF Starting PF

Type of cable Selected

Cable fromCable to

Motor CapacityRated VoltageTotal route length

3 x V x Source Fault LevelSource reactance converted to Net Resistance of cable (from LT (Ohm / kM as per Mfg. Datasheet x

1.1 kV (E), Cu,

Cable Short Circuit withstand timeShort circuit withstand capacity of 1

Full load current of the feederStarting Current

Source fault level

Net Reactance of cable (from LT

Starting voltage drop at in cable Vms = 0.85 V1 and Vbs = 0.9 V1 % Voltage at the motor terminal% Drop at motor terminalBased on results 3.7, 4.1, 5.4, 6.17 above, the cable selected (1 Runs 3C x95Sqmm Al. XLPE) shall safely withstand the effects of short circuit and shall carry the Full Load Current within the permitted temperature limits and voltage drops.

(Ohm / kM as per Mfg. Datasheet x

% Voltage Drop

Fault level at the load end of the V / [3 x {R + j(XSO + X)}]

Short circuit withstand capacity of 1 Hence, the selected cable (1 Runs of 3C x95Al. XLPE) is suitable for withstanding 3 fault at the load end.

For checking steady state and starting voltage drop in the cable, the presence of tap changer in the distribution transformer is considered. Hence, during steady state conditions, the Steady State Voltage Drop If x [ R cos 1 + X sin 1 ]

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