Thermal considerations in splicing of distribution class cables

In the design of splices for distribution class cables, primary consideration has been given to adequately replacing the electrical insulation material removed during the splicing operation and to provide control of the electric field stress distribution. Failure experienced in cables operating near their ampacity limits has indicated that high temperatures in the splice region have been a major contributor to the failure mechanisms. For highest reliability of splices in distribution class buried cabled, the splice design, splice materials and splicing practice must provide a structure having heat dissipating capabilities at least as good as the original cable. A parametric computer calculation has been made which predicts an optimum outer diameter of splice for maximum heat dissipation. This diameter is a strong function of the thermal resistivity of the insulation material. Results of laboratory tests performed on splices insulated with standard 500 thermal ohm-cm rubber tape and with rubber tapes having resistivities of 410 and 300 thermal ohm-cm are presented.