【摘要】 电压互感器二次回路出现两点接地情况(简称"两点接地")下再发生单相故障,若引起零序方向元件误判,零序电压和故障相电压之间相位差较小,而正常情况下故障零序电压与故障相电压之间的相位差一般较大,文中据此提出了电压互感器二次回路两点接地的实时识别方法。根据两点接地再故障时附加电压分量对各相电压影响的特点,提出用健全相相间电压替代零序电压的零序方向算法。将两点接地的实时识别和零序方向新算法结合形成一种不受两点接地影响的零序方向元件,可有效防止纵联零序保护不正确动作。现场事故录波数据的分析验证了该方法的有效性。更多还原

【Abstract】 When two-point-ground fault happened in secondary circuit of the potential transformer,and at the same time a single-phase ground fault happened in the primary system,if the zero sequence current directional protection misjudged,the phase difference between the zero sequence voltage and the fault phase voltage is small. But in normal condition this difference is large. Based on this phenomenon,a real-time identification method is proposed to identify the two-point-ground fault in secondary circuit of the potential transformer ("two-point-ground" for short). Under "two-point-ground" situation,according to the characteristics of additional voltage components influence on each single phase voltage,a new zero sequence direction algorithm with healthy phase voltage instead of zero sequence voltage is put forward. Then the real-time identification method and the new zero sequence direction algorithm of "two-point-ground" is combined together to form a new zero sequence direction element,which is not affected by "two-point-ground". This protective element can effectively avoid malfunction of pilot zero sequence direction protection. And the validity of above method is proved through the analysis of recorded field data.更多还原