A new method to check the polarity of neutral reactor for 500 kV shunt-reactor

The polarity of the zero-sequence current differential protection of 500 kV shunt-reactor is not easy to be checked by using the neutral reactor CT winding because there is no current during the normal operation. It may easily lead to misoperation when outside faults happen. This paper presents a method to check the polarity of neutral reactor CT winding. The basic idea is to simulate a single-phase ground by the reactor single-phase operation. There will be a current in the neutral reactor CT winding. The polarity of the zero-sequence protection can be checked by observing the protection's action. Using this method should avoid the impact on the other equipments. Some measures should be taken. The dangerous points in the testing are analyzed and the testing process as well as realative countermeasures is presented. At last, the effectiveness of this method is proved by the on-site testing.