变压器差动保护的隐患

Hidden Defect of Transformer Differential Protection

随着电力系统容量的增大,接地故障导致的零序电流也逐渐增加,而目前的变压器差动保护在消除零序电流时,均未计及电流互感器误差的影响,存在误动的可能。分析了当变压器电源侧发生区外接地故障时,各序电流的分布及大小,以及此时变压器差动保护中的穿越电流及差动电流,指出了目前差动保护的隐患,提出了采用零序制动来消除该隐患。

With the increase of power system capacity, zero-sequence current caused by earth fault increases. However, traditional transformer differential protection does not take the current transformer error into account to eliminate the zero-sequence current and hence the possibility of mal-operation exists. This paper analyzes the distribution and magnitude of fault current as well as the through current and the differential current in the protection when external earth fault occurs at source side of the transformer. The hidden defect of traditional differential protection is picked out. The countermeasure of zero-sequence current restraint is presented to eliminate this hidden defect.