Abstract The mutual coupling impedance between two circuits of double-circuit transmission lines degrades the performance of the fault location module and ground fault unit of distance relays. The distance measuring unit may underreach when both circuits are in operation. Meanwhile, the overreach problem may arise when one of the parallel circuits is disconnected and grounded at both sides. The appearance of the zero sequence mutual coupling impedance between two circuits causes that single line to ground faults would not be accurately determined by the fault locator module and distance measuring units. Thus, in this paper a new analytical method is presented based on the measurement of voltage and current signals at both ends of the line in service. The fault distance is calculated by analysis of the equivalent sequence network during single line to ground fault condition while the switched-off circuit is grounded at both sides. The proposed formulation for fault location is independent of the fault resistance, so that the estimation accuracy dose not decrease for high fault resistances. In order to evaluate the proposed method performance, a 230 kV double-circuit transmission line is simulated in PSCAD/EMTDC environment considering different transposition strategies. The obtained results show that the proposed method is able to locate the fault distance precisely with the maximum error of 1%, while for most of the cases the error is even much lower. Moreover, fault location, source impedance, external noise and CT saturation have ignorable impact on the estimation accuracy.

中文翻译：

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双回输电线路故障定位的精确分析方法

摘要 双回输电线路两回路之间的互耦阻抗降低了距离继电器故障定位模块和接地故障单元的性能。当两个电路都在运行时，距离测量单元可能不足。同时，当其中一个并联电路在两侧断开并接地时，可能会出现超程问题。两个电路之间零序互耦阻抗的出现，导致故障定位模块和测距单元无法准确判断单线接地故障。因此，本文提出了一种基于在役线路两端电压和电流信号测量的新分析方法。故障距离是通过对单线接地故障条件下等效序网络的分析来计算的，同时切断电路在两侧接地。所提出的故障定位公式与故障电阻无关，因此对于高故障电阻，估计精度不会降低。为了评估所提出的方法的性能，在考虑不同换位策略的 PSCAD/EMTDC 环境中模拟了 230 kV 双回输电线路。得到的结果表明，所提出的方法能够精确定位故障距离，最大误差为1%，而在大多数情况下，误差甚至更低。此外，故障位置、源阻抗、外部噪声和 CT 饱和度对估计精度的影响可以忽略不计。