Voltage Drop Calculation

This article provides a guideline on 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 Resistance at 90oC (Ω/km)
Single cores in trefoil Reactance at 50Hz (Ω/km)
Three cores in trefoil Resistance at 90oC (Ω/km)
Three cores in trefoil Reactance at 50Hz (Ω/km)
Approximate armouring resistance GSWB at 60oC 3 or 4 cores (Ω/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
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