一起区外短路引起主变高零序差动保护误动分析

Analysis of a High Zero-sequence Differential Protection Mis-operation of the Main Transformer due to External Interphase Short Circuit

介绍了柬埔寨达岱水电站开关站T4降压变压器高零序差动保护故障,对故障原因进行了分析,其原因是两组CT间串联且极性接反。所以,正确设定两侧CT同名端,才能体现差动保护的灵敏性、速动性及有选择性的特点,才不致使故障范围扩大,更有利于电力系统的安全运行。

In the switch station of the Tatay Hydropower Station of Cambodia,a high zero-sequence differential protection mis-operation is observed in the T4 step-down transformer. Analysis shows that the fault is caused by the wrong series connection of two current transformers and also the reverse connection of their polarities. Thus,it is important to correctly set the dotted terminals of the current transformers in both sides. In such way,the sensitivity,speed and selectivity of the differential protection can be ensured. Safe operation of the power system is also ensured.