Voltage Drop Calculation

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Voltage drop

This article is the first of a series in the selection of electrical cables.

Cable selection is an important part of electrical installation design. Selecting the correct size of cable could lower initial cost, lower operating cost, better voltage regulation notwithstanding the safety factor.

Cable parameters are provided in values per unit length, usually ohms per kilometer(Ω/km) for IEC or miles(Ω/mi) for North American Standards.

The following table illustrate the typical parameters for industrial cables



Table 1. 600/1000 V. Cu/EPR/CSP/GSWB run on open trays or enclosed in air. 1 to 6 x single, 3 or 4 cores
Nominal
conductor
area (mm2)		 Single cores
in trefoil		 3 cores Approximate
armouring
resistance
Resistance
at 90oC
(ohm/km)		 Reactance
at 50Hz		 Resistance
at 90oC
(ohm/km)		 Reactance
at 50Hz		 GSWB at 60oC
3–4 cores
(ohm/km)
1.5 15.6 0.185 15.6 0.118 46.2
2.5 9.64 0.173 9.64 0.111 51.3
4 5.99 0.163 5.99 0.108 60.3
6 3.97 0.153 3.97 0.105 30.5
10 2.35 0.148 2.35 0.0983 36.7
16 1.48 0.134 1.48 0.0933 23.1
25 0.936 0.125 0.936 0.0892 28.1
35 0.674 0.121 0.674 0.0867 10.43
50 0.499 0.118 0.499 0.0858 11.81
70 0.344 0.112 0.344 0.0850 13.61
95 0.271 0.108 0.271 0.0825 10.87
120 0.214 0.106 0.214 0.0808 11.92
150 0.175 0.105 0.175 0.0808 7.38
185 0.140 0.105 0.140 0.0808 8.15
240 0.108 0.103 0.108 0.0800 8.94
300 0.087 0.101 0.087 0.0800 10.10
400 0.069 0.0992 0.069 0.0795 10.00