40.5kV真空断路器开断并联电抗器的现场试验

Field tests of 40.5 kV vacuum circuit breakers switching off shunt reactors

针对国内40.5kV真空断路器开断并联电抗器绝缘事故多发的情况,进行了一系列现场试验,并对该工况下开断操作的暂态过程及过电压的机理进行分析。结果表明:截流不会产生危险的过电压;而首开相的多次复燃和电压级升,以及相间高频耦合造成多次后开两相的等效截流值很高的电流截断(不同于通常所说的工频电流零点前截流)是该真空断路器开断并联电抗器频繁出现高过电压的主要原因。研究还发现,虽然后开相触头间隙的介质多次击穿大大限制了过电压,但负载侧电压特别是相间过电压仍可能明显超过允许值。

Overvoltage failures frequently occur in China with 40.5 kV vacuum circuit breakers switching off shunt reactors. Field tests were made to analyze the transient process caused by the opening operation and the overvoltage principles for this condition. The results indicate that current chopping does not induce critical overvoltages,but that the frequent high overvoltages are caused by the multiple reignitions and voltage escalation of the first clearing pole,as well as the virtual current chopping with large equivalent chopping currents of the last two clearing poles due to high-frequency interphase coupling. Although multiple reignitions of the last clearing poles greatly decrease the overvoltage amplitude,the load overvoltages,especially the interphase overvoltages,probably may significantly exceed the permitted values.