基于阻性电流和护层电流的交叉互联电缆绝缘监测及诊断

Insulation monitoring and diagnosis for cross-bonded cablesbased on resistive and sheath current

长距离高压电缆采用三相金属护层交叉互联的接地方式减小金属护层中的感应电压,这种交叉互联方式给电缆绝缘在线监测及诊断带来了困惑。因此,提出一种基于阻性电流和护层电流分析的电缆绝缘在线监测及诊断方法,给出泄漏电流与护层电流分离的公式推导,并得到从泄漏电流中分离出阻性电流的计算公式。运用MATLAB/Simulink平台建立三相电缆的等效模型,对方法进行了仿真验证,同时搭建三相电缆实验模型,分别对交叉互联电缆绝缘劣化、护层回路开路、中间接头护层击穿这3类典型故障进行实验研究。结果表明:实现了对交叉互联后每一段电缆绝缘状况的在线监测及诊断;配合安装在同轴电缆上的电流传感器的测量电流,能够实现对金属护层开路、中间接头击穿故障的诊断;实现了对不同类型电缆故障的诊断及故障位置的确定,同时也验证了方法的正确性和可行性。

In order to reduce the induction voltage in the metal sheath,the cross-linked grounding way is widely adopted in long distance high voltage power cable,which brings confusion to on-line monitoring and diagnosis of cable insulation.An on-line monitoring and diagnosis method of cable insulation based on the analysis of resistive current and sheath current is put forward in this paper.The formula of separation of leakage current and sheath current was derived,and the calculation formula of separation of resistive current from leakage current was obtained.The equivalent model of three-phase cable was established by using Matlab/Simulink platform.The test model of three-phase cable had been established to study on three typical faults,such as the cable insulation deterioration and the open sheath circuit fault and the sheath breakdown of intermediate joint fault.The results show that the method can be realized to monitoring and diagnosis the insulation condition of each cable under metal sheath cross-bonded,and it can diagnose the metal sheath open circuit and intermediate joint breakdown fault by installing the current sensor on the coaxial cable.It can diagnose the different types of cable faults and determine fault location,which verified the validity and feasibility of the method.