基于相间电阻变化特征的故障选相元件

针对现有选相元件在系统振荡期间存在误选相问题,提出了一种基于相间电阻变化特征的高压输电线路故障选相新原理。发生不对称接地故障时,首先利用零序和负序电流之间的相位关系分成3个区域,每个区域存在单相接地和两相短路接地2种故障类型,在判断出某个分区后根据相间测量电阻的变化特征得到选相结果。在系统振荡期间,健全相相间测量电阻是连续缓慢变化的;短路相之间的相间测量电阻,在发生故障瞬间是突变的,而故障后则基本没有变化。仿真结果表明,发生相间故障时,相间测量电阻不受负荷电流、过渡电阻、分支系数和系统振荡等的影响,该选相元件有很高的动作可靠性和准确性,适用于系统振荡期间的选相元件。

Faulty phase selector based on inter-phase resistance change

Aiming at the misoperation of phase selector during power oscillation,the faulty phase selector based on inter-phase resistance change is proposed for HV transmission lines. When a unsymmetrical grounding fault occurs,three zones can be set according to the phase-angle between zero and negative sequence currents,each of which may have two fault types:single-phase and inter-phase grounding fault. The faulty phase(s) can be selected according to the inter-phase resistance change in a zone. During power oscillation,the resistance between sound phases changes continuously and laggardly,while the resistance between shorted phases changes abruptly at fault occurrence and keeps almost constant after fault occurrence. Simulation results show that the measured inter - phase resistance is not influenced by load current,transition resistance,branch coefficient and system oscillation when inter-phase fault occurs. The proposed faulty phase selector has excellent performance and veracity and is suitable for system oscillation period.