XLPE电缆绝缘仿真判据探讨

Simulation Criteria of XLPE Cable Insulation

为获得交联聚乙烯绝缘电缆(简称XLPE电缆)绝缘击穿的判据,对10kV XLPE电缆单相和三相接地不平衡电流建立绝缘仿真模型,用Matlab软件对单相、三相的整体、局部绝缘故障进行仿真计算,得出接地不平衡电流i与绝缘层电阻、电容、介质损耗因数之间的关系。仿真结果:绝缘层电容、介质损耗因数的变化对i的影响较明显;三相整体老化时i的变化极小,三相局部绝缘故障时i的变化较明显;单相局部绝缘故障的i值随故障严重程度变化,三相局部绝缘故障时电缆首尾两端接地不平衡电流之比随故障点位置变化。对仿真结果进行分析并得出结论:通过监测接地不平衡电流可以判断电缆绝缘状况和确定故障点位置,绝缘判据与电缆长度、电压、负载和电缆劣化前参数有关。

To obtain the criteria for insulation breakdown of cross-linked polyethylene insulated （XLPE） cable, an insulation simulation model is built for single-phase and three-phase grounding unbalanced current of 10 kV XLPE cable; Matlab software is used in the simulation calculation of overall and local insulation faults of single phase and three phases, thereby deriving the relationship among grounding unbalanced current i and the resistance, capacitance and dissipation factor of insulation layer. Simulation results show that the changes in the capacitance and dissipation factor of insulation layer exert more obvious effects on i; the change in i is tiny during overall three-phase aging and noticeable during three-phase local insulation fault; the i value during single-phase local insulation fault varies with the fault magnitude, and the ratio of grounding unbalanced currents at both ends of cable during three-phase local insulation fault changes with the fault point position. Upon analysis of simulation results, it is concluded that the condition of cable insulation can be judged and the fault point position determined by monitoring grounding unbalanced current, the insulation criterion being related to the cable length, voltage, load and pre-deterioration parameters.