用于12kV环网柜的新型空气绝缘电缆接头研究

Research on New Type of Air-insulated Cable Joint for 12 kV Ring Main Unit

T型或肘型电缆终端接头是12 kV环网柜与电缆连接的常用关键部件,但在运的环网柜发生多起电缆头绝缘击穿甚至发生爆炸的事故。经过分析,放电的主要原因是由于固体绝缘界面因安装不当、硅脂失效等原因出现的微小气隙导致。为了从结构创新的角度彻底解决该问题,提出了采用非界面绝缘的思路,设计了一种新型环氧树脂浇注、空气主绝缘的电缆接头结构,对新型电缆接头进行了电场仿真,施加电压75 kV,空气处最大电场小于3.7 kV/mm。制造了新型电缆接头的样机,进行了绝缘、密封等试验,工频耐压大于42 kV,雷电冲击耐压大于75 kV,整体局部放电小于3 p C,满足相关标准的要求,可以作为一种新的结构试点应用。

Either type T or elbow type cable termination joint is commonly used key part for connection between the cable and 12 kV ring main unit.However,there have been multiple accidents of insulation breakdown and even explosion of cable joint in the ring main unit in operation.The main reason for the discharge through analysis is the small air gap due to improper installation of solid insulation interface and failure of silicone grease.In order to thoroughly solve this problem from the perspective of structural innovation,the idea of using non interface insulation was proposed,and a new type of cable joint structure with epoxy resin casting and air main insulation was designed,and the electric field simulation for the new type of joint was performed.The voltage at 75 kV was applied and the maximum electric field in the air was less than 3.7 kV/mm.A prototype of a new type of cable joint was manufactured,and such tests as insulation and sealing performance were performed with power frequency voltage higher than 42 kV,lightning impulse withstand voltage higher than 75 kV and complete partial discharge less than 3 pC,which meet requirement of related standards and can be used as a kind of trial application of new structure.