末端制动的新型数字式高压并联电抗器纵差保护

高压并联电抗器内部线圈接地故障或引出线的接地及相间短路故障是电抗器常见的故障形式,电抗器纵差保护是这些故障形式的主保护,但是在空投电抗器以及区外扰动的暂态过程中,由于直流分量大而且衰减慢可能引起CT直流饱和而导致纵差保护误动。针对上述问题,提出了一种取电抗器末端电流作为制动电流、采用三段式比率制动特性的数字式纵差保护的方法。本保护具有电抗器空投检测功能、间隙性电流互感器断线检测判据以及电流互感器直流饱和检测判据。经动模试验及现场运行结果证明该保护灵敏反应内部故障,并在空投和区外扰动情况下可靠闭锁保护。

Numerical differential protection restrained by end terminal current for HV shunt reactor

For HV shunt reactor, severe faults include mainly ground fault in its interior coil, inter-phase fault and ground fault in leading-out wire. Saturation of TA, which caused by the high level DC current and slow current attenuation when switch-on reactor or exterior faults, may lead to the misoperation of the differential protection. This paper presents a new numerical longitudinal differential protection whose restraint current is from end terminal of reactor. The ratio differential protection is of triple-folded characteristic. The protection is very complete since it can also detect switching-on reactor, intermissive line-broken of TA as well as direct current (DC) saturation of TA. The results show that the differential protection never mal-operates and can detect internal faults correctly.