真空断路器开断35 kV并联电抗器过电压及防护方案分析

Analysis on Overvoltage and Protection Proposal of Breaking 35 kV Shunt Reactors by Vacuum Circuit Breakers

开断35 kV并联电抗器时频繁出现操作过电压事故,主要原因是真空断路器在开断过程中的截流和多次重燃效应。为有效避免此类事故的发生,分析了截流、重燃和三相同时开断过电压的机理,采用ATP-EMTP建立了开断35 kV并联电抗器的电磁暂态模型。仿真结果表明,避雷器只能对过电压幅值进行限制,不能改变过电压的振荡频率,RC阻容吸收器能够改变高频振荡回路,降低过电压波头陡度和振荡频率,抑制真空断路器截流和多次重燃的发生。目前在35 kV母线和并抗侧安装三相星形避雷器的防护方案无法有效限制相间过电压,三相组合式避雷器能够对相间过电压起到限制作用,RC阻容吸收器的限制效果更好。针对该220 kV变电站,推荐在变电站35 kV母线侧安装三相组合式避雷器,在并联电抗器侧安装三相组合式避雷器或RC阻容吸收器。

The main reason of frequent operating overvoltage in breaking 35 kV shunt capacitor is the chopping current and multiple reignition of the vacuum circuit breaker during the breaking period.For avoiding the occurrence of such fault the mechanism of chopping current,reignition and simultaneously breaking overvoltage of three phases is analyzed,the electromagnetic transient model for breaking 35 kV shunt reactor is set up by the use of ATP-EMTP.It is shown by the simulation result that the lightning arrester only limit overvoltage amplitude,cannot change oscillation frequency of the overvoltage.The RC-absorber not only can change the high frequency oscillation circuit and reduce the steepness of wave front and the oscillation frequency of the overvoltage,but also can suppress the chopping current and multiple reignition of vacuum circuit breakers.At present,the protection scheme of installing 3-phase star-connected arrester on the 35 kV busbar and the shunt reactor side has no way to limit effectively overvoltage between phases,while the threephase combination arrester can do and the RC absorber is much better.For the 220 kV substation,it is recommended to install three-phase combined arrester on 35 kV busbar side of the substation and to install either three-phase combined arrester or RC absorber on the shunt reactor side.