500 kV变压器电容隔直装置存在的问题分析及改进

Analysis and Improvement of Problems Existing in Capacitance DC Isolation Device of 500 kV Transformer

为治理某500 kV变电站变压器直流偏磁,在3台主变中性点分别加装了电容隔直装置。针对一起500 kV变压器中性点电容隔直装置动作不同步异常事件,介绍了电容隔直装置原理结构和动作逻辑,分析了该事件发生经过,阐述了造成该次动作异常的原因。分析结果表明,该电容隔直装置控制逻辑不合理,由于PT存在测量误差,不能实现“同投同退”,因此装置短时失去隔离直流偏磁的功能,对变压器造成较大的危害。最后,针对该问题,给出了改进措施。

In order to control the DC magnetic bias of transformer in a 500 kV substation,capacitor DC blocking devices are installed at the neutral points of 3 main transformers.In view of an abnormal event of unsynchronized action of capacitor DC-blocking device at neutral point of 500 kV transformer,the principle structure and action logic of capacitor DC blocking device are introduced,the occurrence process of the event is analyzed,and the causes of abnormal action are expounded.The analysis shows that the control logic of the capacitor DC isolation device is unreasonable.For measurement errors of PT,"same switching and same returning"cannot be realized,which leads to the device losing the effect of isolating DC magnetic bias for a short time and causing great harm to the transformer.Finally,aiming at the above problems,the improved treatment measures are given.