变压器绕组短路接地故障的保护

Protection on transformer winding grounding fault

用安匝平衡关系分析了星形绕组单相短路接地故障 ,导出了普通纵差保护和零差保护的差动电流。由此证明当接地点靠近中性点附近时零差保护的灵敏度很高 ,但是在国内的故障统计资料中没有发生此类故障的记录。对这种故障普通纵差保护相对于零差保护只是灵敏性较低 ,且并非完全不起作用 ,因此增加零差保护的必要性值得商榷。

The single phase grounding fault of transformer's star winding is analyzed with the ampere turns balance.The differential currents for the longitudinal differential protection and the restricted earth protection are derived in term of ampere turns.It shows that the restricted earth protection is very sensitive when the fault is near the neutral point of the star winding.The longitudinal differential protection can also protect such faults though it is less sensitive than restricted earth protection.There is no this kind of fault records in the fault statistics of China.The necessity of adding the restricted earth protection should be discussed.