大型电动机差动保护误动分析

Maloperation analysis of differential protection for large electromotor

WCZ - 1型微机电动机差动保护用于大型 (2 0 0 0kV·A)电动机内部短路保护 ,与WDZ - 1.1型微机电动机综合保护共同构成大型电动机的全套就地保护。铜陵电厂新建 30 0MW机组引风机采用该保护装置 ,在高压辅机试运转期间 ,引风机开启时 ,差动保护频繁动作跳闸。通过理论分析计算和实际试验 ,确认选配的TA容量严重不足 ,通过增大TA容量和减小回路阻抗及合理配置比率制动系数 ,使引风机差动保护误动得以彻底解决。

Type WCZ?1 microcomputer based differential protection is used for interior short circuit protection of large electromotor.Together with type WDZ?1.1 microcomputer based integrated protection,it constitutes a full local protection.It is applied for the induced draft fan of Tongling 300 MW unit.But it trips frequently when the induced draft fan starts in commissioning period of HV auxiliary electromotor.Its cause is found by theoretic analysis and practical test,it is because the TA capacity chosen by design institute is not sufficient.By increasing the TA capacity,reducing the circuit impedance and properly setting the coefficient the maloperation of the differential protection is removed completely.