±500kV换流变压器电容隔直装置保护动作分析

为实现某换流站直流偏磁治理功能,在换流变网侧中性点加装电容隔直装置。针对一起±500 k V同塔双回高压直流输电工程换流变电容隔直装置保护动作事件,介绍了该事件发生经过,分析了电容隔直装置保护动作原理和内部结构,阐述了造成本次动作事件的原因。分析表明,该电容隔直装置保护配置不合理,在直流偏磁电流较大时,用于电容器保护的晶闸管回路持续导通,导致装置失去隔离直流偏磁的效果,对换流变压器造成较大的偏磁危害。最后,针对上述问题,给出了改进后的处理措施。

Analysis on protective action of capacitive DC current blocking device for ±500 kV converter transformer

In order to isolate the DC magnetic bias current , the capacitive DC current blocking device has been installed in the neutral point of converter transformers .Based on the protective action of capacitive DC current blocking device of the ±500 kV HVDC project , the occurring process of the accident , and the protection action principle and the internal struc-ture of the capacitive DC current blocking device are introduced in this paper .The reason of the accident is analyzed .The analysis results show that the protection configuration of the DC blocking device is unreasonable .When the DC bias current is large, the thyristor circuit for capacitor protection is continuously turned on , which causes the device to lose DC current isolation effect .At last , in view of the above problem , the preventive measures are presented .