真空断路器开断并联电抗器过电压抑制措施

真空断路器开断并联电抗器过程中,因截流、重燃会出现幅值、频率极高的过电压。为真实地再现分闸过电压,依托重庆云阳站现场实测的断路器电压、电流数据,同时考虑了截流值、介质动态绝缘强度和高频熄弧能力3个因素,在ATP-EMTP中搭建了更加精确的真空断路器电弧重燃模型,并以此为基础讨论合理的抑制措施。仿真中采用了避雷器、阻容吸收器和延长电缆3种过电压抑制措施。仿真结果表明,电缆长度对过电压抑制效果并不显著,避雷器与阻容吸收器的型号、安装数量和位置对抑制效果存在影响。结合仿真与实际,最后提出最佳抑制方案,即在站用变和电抗器处电缆末端均安装伏安特性曲线较低的避雷器,可以将两处最大分闸过电压分别限制在3.44 pu和3.67pu。

Research on Measures Suppressing Overvoltage Caused by Switching-off Shunt Reactor With Vacuum Circuit Breaker

During the process of switching-off shunt reactor with vacuum circuit breaker(VCB), overvoltage with high amplitude and frequency will occur due to current chopping and reignition. In order to reproduce the switching overvoltage faithfully, relying on field test data of Yunyang Substation in Chongqing, a more accurate VCB arc reignition model was built in ATP-EMTP, and three factors were taken into account, including chopping current value, dielectric dynamic insulation strength and high frequency quenching capability. Then the paper discussed reasonable suppression measures. The simulation used three kinds of overvoltage suppression measures: surge arrester, RC snubber and extension of cable length. The simulation results indicated that cable length has little effect on overvoltage suppression.Besides, the type, installation quantity and position of protective device have an impact on suppression performance.Finally, the best suppression scheme is proposed, that is,installing the surge arresters with lower V-I characteristics at the terminals of cables for both shunt reactor and substation transformer. Their maximum overvoltage can be limited to3.44 p.u. and 3.67 p.u. respectively.