One numerical method to determine improved cable terminations

Abstract

In HV and MV systems, cable terminations (CT) are one of the weakest links. The majority of cable failures on distribution system are caused by defects in cable terminations and cable joints. There is a number of CT developed in last few years, but cable failures still happen, causing great economic losses, mainly because of a CT breakdown. For that reason any improvement in the cable termination construction is of interest. Two different approaches have been proposed to evaluate a field distribution. Geometrical control of the electric field, applying multilayer dielectric deflectors with different permittivities, as well as application of the grounded embedded electrodes for strong electric field reduction at the cable ends, is presented in this paper.One numerical method, the equivalent electrodes method (EEM), has been applied for electric field calculation at the modelled cable terminations. The accuracy of results of the EEM depends on the number of used equivalent electrodes (EE). The method is very simple and exact and in limit process with the number of EE gives exact results. Improvement proposed in this paper enables accurate calculation using small number of EE. Some results obtained by the application of the EEM have been compared with values obtained using the finite elements method and a very good matches have been identified.