Research And Application Of PT Multi-point Grounding On-line Monitor In Substation

In operation of PT secondary circuit two, must and can only be connected to the gridthrough a point. If an electrical communication circuit in substations of different pointssimultaneously grounding, grounding on the potential difference will enter thecommunication loop, causing unnecessary shunting, even the voltage does not exist a systemintroduced in the relay protection testing loop, resulting in impedance element and directionalelement incorrect action.This paper tests the data by selecting30substations, through to the PT multi pointgrounding phenomenon of data analysis on development of CT PT, opening and multi pointground fault criterion, respectively, forming load current of three PT multi point method formonitoring grounding imbalance, signal injection method, resistance method, design a N600grounding current exceeds the set value, the N600grounding current mutation, and amount ofchange exceeds the set value, the imbalance in the current method or the zero line currentmethod as the method of multi-point grounding judgment based on PT, which is applied to amonitoring device, and with the zero line current method, unbalance load current method wascarried out online monitoring application in10operation of substation, the zero line currentmethod and the unbalanced load current method can accurately detect and locate the PTmultipoint earthing fault detection sensitivity, unbalanced load current method is good to thezero line current, and the zero line current method, safety performance is higher than that ofunbalanced load current method. Among them,220kV detected Yuanjiang substationgrounding of3PT, and find the specific ground fault point. Simulation of multi pointgrounding test, device can correct alarm and positioning, to validate the device. PT multipoint detecting ground on-line monitoring method can replace every6months for a N600grounding current, more can be found in time PT grounding, the detecting process also neednot disconnect N600ground, reduce the risk and difficulty, to improve the safe operation ofthe system has important significance.