The Method and Application of Discrimination and Search for Multi-point Grounding of N600 in Secondary Circuit of Voltage Transformer in Substation

The voltage transformer in the substation convert high voltage into low voltage, and its second circuit must be grounded at one point through the zero phase line N600. The long-term existence of N600 multi-point grounding increase the possibility of power grid accident. This situation is usually found through patrol inspection. However, the patrol inspection is conducted every six months, the circle is so long that the problem cannot be identified in time. This paper proposes a method to identify and find the N600 multiple grounding point in real time. It judges the situation of multi-point grounding through the changes of N600 grounding current value, and determines the position of redundant grounding point through working event in the substation when the event happens, to achieve real-time monitoring of multi-point grounding situation of N600. In addition, this paper also implemented an N600 grounding current monitoring device and an N600 multi-point grounding monitoring and decision-making system, and verified the effectiveness and real-time performance of this method and the system in a testing environment.