220 kV电缆线路终端故障及仿真分析

为分析某220 k V电缆线路终端应力锥、电缆表面贴合状态与故障发生的深层次原因,本文对某220 k V故障电缆终端开展故障解体、X射线检测以及仿真工作,分析发现接头应力锥过盈量高于安装工艺要求,且搭接面表面不平整。在应力锥、电缆表面贴合良好时,运行电压下应力锥、电缆主绝缘最大电场强度均远小于对应绝缘材料的击穿场强,而应力锥、电缆表面贴合不良交界面存在微小气隙时,运行电压下气隙内部电场强度大于空气击穿场强,表明运行电压下气隙内部存在放电现象。因此,电缆终端应力锥、电缆表面贴合不良、交界面存在微小气隙时,在运行电压下,气隙内部长期放电引起主绝缘破坏是造成电缆故障的原因。

Terminal Fault and Simulation Analysis of 220 kV Cable Line

In order to analyze the deep cause of fault for surface fitting state between stress cone and cable body,this paper carries out cable disintegration,X-ray inspection,material inspection and simulation work for a 220 kV fault cable terminal.It is find that the interference fit on joint stress cone is higher than the installation process requirement,and the lap joint is not flat.When the stress cone and cable body surface are well bonded,the maximum electric field strength of the stress cone and the main insulation of the cable under operating voltage are much smaller than the breakdown field strength of the corresponding insulating material.When there is a small air gap between the stress cone and the cable surface,the internal electric field strength of the air gap is greater than the air breakdown field strength under the operating voltage,indicating that there is a discharge phenomenon inside the air gap under the operating voltage.Therefore,when the cable terminal stress cone,the cable surface is poorly attached,and there is a slight air gap at the interface,the main insulation damage caused by long-term discharge inside the air gap is the cause of the cable failure under the operating voltage.