基于相间故障弧光电压特征的高压线路选相元件

提出了一种基于相间故障弧光电压特征的高压线路选相新原理,应用于振荡闭锁期间的选相元件.对接地故障,利用零、负序电流相位差进行分区,每个分区包括某相单相接地和另外两相短路接地两种故障.然后根据相间故障弧光电压Ucosψ小于某一定值,而健全相相间电压的余弦值Ucosψ一般比较大的特征,来得到选相结果,解决了目前选相元件在电力系统振荡时可能发生的误选相问题.通过对不对称故障开放条件的改进,大大提高了单相接地故障的选相速度.该选相元件具有很强的耐过渡电阻能力,并且完全不受分支系数和系统运行方式的影响.RTDS试验验证了新选相元件的准确性和有效性.

Fault Phase Selector for HV Transmission Line Protective Relaying Based on the Characteristic of the Arc Voltage Between Two Faulted Phases

Based on the characteristic of the arc voltage between two faulted phases, a novel phase selector is proposed which can be applied to HV transmission lines even during power swings. When a grounding fault occurs, three regions can be selected by the phases-angle between the zero sequence and negative sequence components of the current. Each region contains a kind of single-phase-to-ground fault and another two phase-to-phase-with-ground fault. For phase-to-phase fault, the cosine relay of faulted phases at the fault point is lower than a certain threshold; while for sound phases, that is usually very high. Based on that, the fault phase can be selected. The proposed selector does not mal-operate during power swings. After changing the criterion for the asymmetry fault during power swing, the selector can work more quickly for single-phase-to-ground fault. The selector proposed in the paper is of excellent performance under high-resistance grounding fault conditions. The inequality between the positive sequence and negative sequence impedance of the system has no effect on the selector. Furthermore, the selector is not influenced by the difference of system cases. The performance of the method is evaluated by data created using RTDS (real-time digital simulator). It shows that the selector can determine fault phases correctly.