Effects of connection conditions between insulation screen and Al sheath on the buffer layer failures of high-voltage XLPE cables

Abstract

Recently, high-voltage XLPE cables often suffer from buffer layer failures. The typical characteristics are white powder and ablation appear on the insulation screens, buffer layers, and corrugated aluminum (Al) sheaths. However, little is known about the causes of failure. In this paper, two test platforms of material samples and a cable sample were set up. Partial discharge tests were carried out with material samples, a cable sample, and buffer layer simulation samples to study the resistance and discharge characteristics under different connection conditions between the insulation screen and corrugated Al sheath (IS-Al). The buffer layer’s ablation was reproduced in the material samples test. The material samples test revealed that partial discharge was easy to occur when IS-Al’s air gaps were tiny, or the IS-Al was “point connection” without air gaps. The buffer layer simulation samples test indicated that the better the IS-Al’s connection conditions are, the smaller the resistance, potential difference, and discharge quantity are, and the more stable the discharge pulse is. Judging from these results, the IS-Al’s connection conditions seem to impact the buffer layer failures of high-voltage XLPE cables.