Failure analysis of three 230kV XLPE cables

This paper presents a case study on the failures of three 230 kV XLPE cables. These cables failed after only 4 years of service. It was found that the copper woven fibre glass (CWFG) tape and the water swellable tape had many burnt stains. The causes of these stains were analysed. It was proved from theoretical analysis and experimental investigations that there was a problem of bad contact between the outer semi-conductive screen and the aluminum sheath. During operation, the charging current from system ac voltage damaged the semi-conductive layer and caused the insulation breakdown. The lessons learnt from these failures are also discussed in the paper.