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Cable Resistance Conversion Calculation

Resistance of cable conductor varies with ambient temperature. This cable resistance conversion calculation tool used to alter cable resistance from one temperature base to another in accordance to IEC 60228.

Cable resistance conversion calculation will convert cable resistance at 20oC to operating temperature prior to perform voltage drop calculation or cable short-circuit rating calculation.


Temperature Correction Factor kt
Cable Resistance Rt at Conductor Temperature (Ω/km)

Formula for cable resistance conversion

Formula for cable resistance correction is as follows:

Cable Resistance Conversion Formula
Rt:Conductor resistance at temperature t oC
R20:Conductor resistance at 20oC
kt:Conversion factor

Conversion factor kt will vary with temperature t and conductor material.

For annealed copper conductors (plain or metal coated):

For aluminium conductors:

Other inputs

Maximum conductor temperatures for different types of insulating material has been specified by IEC 60502.

Maximum insulation material  temperature

The temperatures in above table are based on the physical properties of the insulation materials. It is important to take into account other factors (i.e. cable arrangement derating) when using these values for the calculation of current ratings.