Isolated, Equally-loaded, and Unequally loaded multiple cable circuits

ELEK Cable HV Software provides calculation settings applicable for multiple buried cable circuit arrangements. These settings are explained with examples as follows.

Isolated ratings

For the Isolated ratings option, the current rating of the circuits is calculated without considering the effect of mutual heating between the circuits. In effect, the current rating of the circuits is calculated independently (isolated) from the other circuits. The external thermal resistance of an isolated circuit is lower than when the mutual heating is considered, and therefore, the current rating is higher than for the other cases.

Equally loaded

The cable temperatures are calculated for the Equally loaded option, assuming the circuits carry equal current. The hottest circuit will generally dictate the rating of the other circuits in the system. The cable electrical losses and temperatures will depend on the arrangement and cable type for multiple circuits. Although the equally loaded will work for multiple circuits of different cable types in different arrangements, the option is normally used for multiple circuits consisting of the same cable types in the same arrangement for single-core cables, with the same bonding, and under the same installation conditions.

Unequally loaded.

For the Unequally loaded option, the current rating of the circuits is calculated considering the mutual heating of the circuits whilst allowing the losses for each circuit to be different. This calculation setting deals with multiple circuits of different cable types and configurations. The external thermal resistance of the circuits can be different.