中性点不接地电力系统异地两相短路故障的案例分析

Case analysis on phase-to-phase grounding faults in different spots of electric power systems with neutral-point ungrounded

在中性点不接地电力系统继电保护的整定和接地线校验热稳定分析等工作中,需要对复杂的异地两相接地短路电流进行计算,现有算法求解困难.通过分拆系统零序阻抗,将异地两相接地短路电流计算化简为2个单相接地短路电流计算,对35kV系统的异地两相接地短路事故实际案例进行分析,验证了该算法,并给出供电线路继电保护整定的改进建议.

Calculation of short-circuit current caused by phase-to-phase grounding faults in different spots is necessary for the protection relay setting for electric power systems with neutralpoint ungrounded and the grounding line thermal stability calculation. However, Traditional methods are difficult to calculate the short-circuit current. A new method was introduced in this paper to simplify the current calculation for a phase-to-phase grounding faults into that for two single-phase short circuits through separating the system zero-sequence impedance. The proposed method was verified by a case of phase-to-phase grounding fault in a 35 kV power supply system. In addition, some suggestions are presented on protection relay setting issues for power supply.