Appendix 2: Line conductor resistance

The effective resistance of a conductor varies with temperature and with the frequency of the current flowing through it.

• Temperature correction

  Evening r ₂₀ the kilometric resistance at 20 °C and r the resistance at θ °C.

  We have :

  r = r ₂₀ [1 + α (θ _C – θ ₂₀ )]

  This relationship is approximate, but sufficiently accurate for current cable temperatures in service.

  The values of the temperature coefficients α for the main metals and alloys used for cables are given...