高压线路断路器开断故障电流零点漂移问题分析

Analysis of zero drift in fault current interruption by circuit breakers in high voltage lines

高压交流输电线路需要准确预测电流零点时刻,从而有效确定断路器开断动作时刻,使断路器在接近于过零点时刻开断故障电流。导致开断相故障电流零点相对于预期的稳态短路电流发生漂移有以下两个因素:一是当发生短路故障时,首次开断故障电流相后,后开断相的故障电流的衰减直流分量在瞬态过程中将叠加在交流分量上从而导致其零点漂移;另一个是三相电流具有不同的零点时刻,当断路器中的一相断开电弧熄灭时,整个三相电路的拓扑结构将发生变化,从而导致其他两相的零点漂移。研究结果表明,针对中性点接地系统及非接地系统,在各种短路故障条件下,首开断相断开后,次开断相的电流零点会向前移动,而末开断相的电流过零点会向后移动。

In high-voltage AC transmission lines,accurately predicting the zero crossing of current is crucial for determining the optimal timing for circuit breaker operations to interrupt fault currents near this point.Two factors contribute to the drift of the fault current zero point from the expected steady-state short circuit current.Two main factors contribute to the zero drift of the fault current from the expected steady-state short-circuit current.The first factor is the superimposition of the decaying DC component on the AC component during the transient process in the initially interrupted phase,causing zero drift.The second factor involves different zero crossing times of the three-phase currents;when an arc extinguishes in one phase of the circuit breaker,it alters the topology of the entire three-phase circuit,resulting in zero drift in the other two phases.This study shows that in both grounded and ungrounded systems,under various short circuit fault conditions,the zero point of the next interrupted phase advances after the first phase interruption,while the last phase′s zero point shifts backward.These conclusions provide a theoretical basis for determining the timing of relay protection device actions.