This paper reports on the investigation of incipient fault mechanisms of a widely used family of Cable Sealing Ends (CSEs) which use an earthed metallic clip on top of the stress cone to fasten the cable termination stress grading. Finite element simulations indicate that the clip is causing localised electric field enhancement which could also cause impurities in the oil to move towards the clip under the influence of the dielectrophoretic force. Accelerated ageing tests of stress cones in the laboratory have corroborated the simulation results, with the high electric field causing degradation of the semi-conducting tape underneath the clip as well as initiation of tracking on the surface of the stress cone originating from the edges of the clip. Partial discharge (PD) testing using a bespoke test rig in the high voltage laboratory has shown that incipient faults originating from the ageing of the solid CSE materials can only be detected after surface tracking has progressed substantially. Even then, the intermittent nature of PD activity can pose a risk to the accurate condition assessment of CSEs if continuous monitoring is not employed and if the ultra-high frequency method is used on its own.

中文翻译：

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66 kV 充油电缆密封端早期故障调查

本文报告了对广泛使用的电缆密封端 (CSE) 系列的初期故障机制的调查，该系列在应力锥顶部使用接地金属夹来固定电缆端接应力等级。有限元模拟表明，夹子导致局部电场增强，这也可能导致油中的杂质在介电泳力的影响下向夹子移动。实验室中应力锥的加速老化测试证实了模拟结果，高电场导致夹子下方的半导体胶带退化，并在应力锥表面上开始跟踪，起源于夹子的边缘夹子。在高压实验室中使用定制测试台进行的局部放电 (PD) 测试表明，源自固体 CSE 材料老化的初始故障只能在表面跟踪已取得实质性进展后才能检测到。即使那样，如果不采用连续监测并且单独使用超高频方法，PD 活动的间歇性也会对 CSE 的准确状态评估构成风险。