并联电容器不平衡电流保护的改进方法研究

并联电容器不平衡电流保护是通过检测电容器组三相不平衡电流来判断电容器组内部是否发生故障,从而给出报警信号或者跳闸信号使电容器组退出运行。不平衡电流保护不能够识别故障相、不能够对三相平衡故障保护以及在多相同时发生故障时会发生误操作。为了克服这些缺陷,对电容器不平衡电流保护进行了改进方法的研究。分析了中性点接地电容器组内部故障时的内部过电压和相电流变化,并给出了相应计算公式。同时,提出了在检测、判断不平衡电流的同时增加对三相电流变化进行判断的改进方法,该改进方法能够克服不平衡电流保护的缺陷。

Study of mended unbalanced current protection scheme for shunt capacitor bank

Shunt capacitor unbalanced current protection can judge whether the outage of internal capacitor elements exists in banks by detecting three-phase unbalanced current to send a warning signal or a trip signal for the bank's breaker to remove the bank from the system.Shunt capacitor unbalanced current protection fails to identify the faulted phase and three-phase balanced failures and causes misoperation when failures exist in two or three phases simultaneously.In order to overcome its disadvantages,a study of mended unbalanced current protection scheme for shunt capacitor is made.This paper analyses the internal overvoltage and the phase current of grounded wye shunt capacitor bank when there are failures in it,and gives corresponding equations.A mended unbalanced current protection scheme is also provided,which requires to judge the phase current variation while detecting and judging the unbalanced current.This mended scheme can overcome those disadvantages of unbalanced current protection.