一起220 kV电缆预制式中间接头击穿故障及其原因分析

通过一起发生在220 kV电缆线路上的电缆预制式中间接头击穿故障和在故障抢修过程中,同批同规格的中间接头备品在正常预扩张中开裂情况,进行了检查、试验和原因分析,根据故障中间接头的三元乙丙橡胶绝缘件开裂的外表现象和解剖后的放电痕迹分析,该中间接头在运行过程中绝缘件突然开裂是引起放电击穿的主要原因;同时提出备用的中间接头在正常扩径后开裂的三元乙丙橡胶绝缘件,其绝缘老化试验前后的断裂伸长率较低,直接降低了中间接头机械强度,引起备品接头整体绝缘件发生开裂。

Analysis of a Breakdown Failure of Prefabricated 220 kV Cable Joint

A breakdown failure of prefabricated cable joint occurred on the 220 kV cable line,and the spare joint with the same batch and specification cracked under normal pre-expansion during the process of urgent repair.The inspection,testing and cause analysis are conducted in this paper.According to the surface examination and discharge tracking analysis of the cracked EPDM rubber insulation on the broken-down joint,the main reason of this failure is the sudden crack of the insulation during operation process of the joint.Moreover,the cracked EPDM rubber insulation of the spare joint after normal expansion was checked by insulation aging test,and the result shows its breaking elongation ratio is low,which directly reduces the mechanical strength of the middle joint and leads to entire crack of the spare joint insulation.