Single-phase earth fault relay protection method based on before-fault voltage actual-measurement line

Abstract

The invention discloses a single-phase earth fault relay protection method based on a before-fault voltage actual-measurement line. The method comprises the steps of firstly measuring fault phase voltage break variable, fault phase current break variable and zero sequence current at a protection mounting part of a power transmission line and two other normal phase voltages; calculating fault phase voltage before a line single-phase earth fault in real time by using the two normal phase voltage after the line single-phase earth fault; then judging whether the amplitude of the fault phase voltage during the normal operation of the power transmission line is greater than the amplitude of fault phase voltage at a protection setting range of the power transmission line or not, so as to determine whether to send an action trip signal or not. According to the method, memorizing the voltage before the line fault is not needed, and a voltage keeping loop before the line fault does not need to be arranged for relay protection hardware; an action characteristic circle corresponding to the method passes a third quadrant, and an origin of coordinates is in the action characteristic circle, so no protection dead zone for action characteristics exists when an exit single-phase earth fault is protected, and misoperation is avoided when a reverse-direction exit single-phase earth fault is protected.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a single-phase ground fault relay protection method based on the actual voltage measurement before the fault. Background technique [0002] Traditional transmission line single-phase ground distance protection assumes that the single-phase ground fault is a metallic short-circuit fault, calculates the measured impedance through the ratio of the fault phase voltage to the fault phase current, and reflects the distance of the fault point according to the measured impedance to determine whether to issue an action trip Signal. In fact, in the power system, in addition to the artificially constructed metallic ground short-circuit fault, the transition resistance of the single-phase ground fault point of the actual transmission line is not zero, and the additional impedance generated by the transition resistance will seriously affect the action performanc...

AI Technical Summary

Problems solved by technology

Since the origin of the coordinates is located on the boundary of the action characteristic circle, there is a possibility of misoperation for a single-phase ground short-circuit fault at the outlet in the opposite direction of protection, and the larger the transition resistance is, the easier it is to malfunction when the single-phase ground short-circuit fault at the outlet in the opposite direction is protected, which seriously threatens Safe and Stable Operation of the Power Grid

Images