Research on the Impact Mechanism of Electric Field to the Waterproof Buffer Layer in HV Power Cables

In recent years, the ablation faults of waterproof buffer layer inside the HV power cables are reported frequently by electrical companies at home and abroad. The characteristic of the faults in common is that the ablation spots appear on the surface of the buffer layer, with white powder producing. An axisymmetric model of 110 kV XLPE power cable was established in this paper to analyze the impact mechanism of electric field distribution to the waterproof buffer layer of HV power cables. The results showed that the local electric field strength appeared in the air interval between the aluminum sheath and the buffer layer, varied with the size of it and the conductivity of buffer layer. The smaller the size and the conductivity is, the larger the electric field strength is in the air interval, which may result in partial discharge, thus arise ablation in the buffer layer.

I. Introduction

With the rapid progress of urbanization, the overhead lines have been substituted by the underground power cables gradually, for the charm of the city. High voltage (HV) cross-linked polyethylene (XLPE) insulated power cables, due to their excellent insulation performance, have been massively put to use by local electrical companies [1]. To avoid the insulation deformation and damage for the heat expansion, the waterproof buffer layer has been deployed between the corrugated aluminum sheath and the insulation shield layer. Not only could it prevent the power cables from damp or humidity, but also it provides an electrical connection to the corrugated aluminum sheath and insulation shield layer.