高压电缆金属护套多点接地情况下的环流模型及参数计算

Sheath Currents Model and Parameter Calculation Method on High Voltage Cable Sheath Multipoint Grounding

为探索电缆金属护套多点接地情况下环流变化规律,利用集中参数电路,提出了基于复矩阵方程形式的环流模型.为求解该复矩阵方程,提出了泄露电流和大地漏电流的等值电路及其求解公式.为验证环流模型的准确度,利用仿真软件ATP对金属护套多点接地的多种情况进行了仿真.对比在不同接地方式、敷设方式、多点接地个数和位置的仿真结果与模型计算结果,环流模型平均相对误差小于3. 79%,能够较为准确地计算护套环流.运用该模型分析了在交叉互联接地方式下,金属护套发生故障接地时环流的变化规律,结果表明,换相点附近的护套发生故障接地时,环流为极大值.文中基于该变化规律,提出了仅根据电缆线路首末端接地线处测量的三相环流值判断故障电缆的相位和大体位置的方法.

In order to explore the variation of sheath current on high voltage( HV) cable metal sheath multipoint grounding,a circulation model based on complex matrix equations is proposed by means of centralized parameter circuit. In order to solve this complex matrix equation,the equivalent circuit of leakage current and earth current in multipoint grounding branch and its solution are proposed. In order to verify the accuracy of the model,simulations are performed by ATP-EMTP. By comparing the simulation results with the calculated values of different grounding modes,laying ways and numbers and locations of multipoint grounding,the average relative error of the model is less than 3. 26%,which can be used to calculate the sheath current accurately. The model is used to analyze the variation of sheath current on sheath multipoint grounding at cross connecting models. The results show that the sheath current peak appears around the phase-change points. On the basis of the change rule,a method according to the sheath current value monitored at the head and the end of the cable line is proposed,to judge fault phase and location.