基于积分比分布的单相接地故障熄弧时刻识别策略

现有自适应重合闸在识别出瞬时性故障后普遍经过固有延时合闸,忽视了故障点电弧熄灭与否,为进一步提高重合闸的自适应能力,有必要对故障熄弧时刻进行识别。通过计算分析超高压线路接地点熄弧前后故障相端电压特性,对比发生瞬时性故障时故障相端电压绝对值函数在二次电弧阶段和恢复电压阶段的差异,发现二次电弧阶段绝对值函数的积分在相邻时间窗内大小始终不变,积分比约为1,而恢复电压阶段初期相邻时间窗内的积分存在显著差异,其积分比出现较为明显的突变。通过设定上下阈值,将故障相端电压绝对值函数积分比作为熄弧时刻识别判据,若积分比连续5次超过所设阈值,则判断故障熄弧。大量EMTP-ATP仿真表明,该判据能可靠识别熄弧时刻,且不受并联补偿度、故障位置以及过渡电阻影响,具有较强的自适应性。

Identification strategy of arc extinguishing time of single-phase grounding fault based on integral ratio distribution

The existing adaptive reclosure usually recloses by inherent delay after transient fault is identified, and ignores whether the arc has extinguished at the fault point. So it is necessary to identify the time of the fault arc extinguishing to further improve adaptive capability of reclosure. The characteristics of fault phase terminal voltage of EHV(Extra High Voltage) transmission lines before and after arc extinguishing are calculated and analyzed. The difference of absolute value function about fault phase terminal voltage at the stage of secondary arc and recovery voltage when transient fault occurs is compared. It is found that the integral of the absolute value function at the stage of secondary arc is always unchanged in adjacent time windows, and the integral ratio is about 1. However, the integral in adjacent time windows at the initial stage of recovery voltage is significantly different, and the integral ratio shows obvious mutation. The integral ratio of absolute value function about fault phase terminal voltage is used as a criterion for identification of extinguishing time by setting up and down threshold values. If the integral ratio exceeds the threshold value five times in a row, the arc distinguishing is judged. A large number of EMTP-ATP simulations show that the proposed criterion can identify the extinguishing time reliably, and is immune to parallel compensation degree, fault location and fault resistance, so it has strong adaptability.