External thermal resistance of buried cables and troughs

The paper describes how an integral-equation method of potential theory may be used to compute the external thermal resistance of an arbitrary configuration of buried cables or of a buried trough. It is assumed, following Goldenberg, that the outer surface of each cable or cable group is isothermal, this being approximately true when the layer of serving is very thin around the metallic sheath of each cable. With this assumption, numerical results have been obtained for a number of examples. Results for pairs of cables and for three cables in trefoil-touching formation confirm Goldenberg´s theoretical estimates for large depths of burial. Results for three touching cables at the same depth and for a rectangular trough appear to be new. The method adopted here is valid for any depth of burial and is also applicable to cables whose shapes are markedly noncircular.