Circuit single-phase earth fault impedance distance protection method based on additional impedance actual measurement correction

Abstract

The invention discloses a circuit single-phase earth fault impedance distance protection method based on additional impedance actual measurement correction. Additional impedance caused by transition resistance is calculated by means of protection for measured fault phase electricity amount, correction for a computed result of fault impedance of traditional earth impedance distance protection is carried out through the measured additional impedance, the fault impedance zrelay which reflects a real fault distance is obtained, a protection device judges whether a movement equation / zrelay-0.5*(zset1+zset2) / < / 0.5*(zset1-zset2) / is right, if the equation is right, the protection device sends out movement trip signals, and the zset1 and the zset 2 are respectively forward setting impedance and reverse setting impedance. According to the method, precise measurement for the additional impedance caused by the transition resistance is achieved, the correction for the computed result of the fault impedance of the traditional earth impedance distance protection is carried out through the measured additional impedance, the fault impedance which reflects the real fault distance is obtained, influences of the additional impedance caused by the transition resistance on impedance distance protection movement performance are eliminated, and the method is suitable for the power transmission circuit single-phase earth fault impedance distance protection.

Description

technical field [0001] The invention relates to the technical field of impedance distance protection for power systems, in particular to a line single-phase ground fault impedance distance protection method based on additional impedance measurement and correction. Background technique [0002] Traditional earth impedance distance protection measures fault impedance z relay The calculation formula is ,because ,therefore , that is, the traditional grounding impedance distance protection measures the fault impedance z relay The calculation result of is composed of two parts, one part is the fault impedance xz that reflects the real fault distance 1 , the other part is the additional impedance caused by the transition resistance . In the above formula, is the ground fault phase voltage; is the voltage at the ground fault point; is the ground fault phase current; is the zero-sequence current; φ is the ground fault phase: A phase, B phase, C phase; z 1 is the ...

AI Technical Summary

Problems solved by technology

[0003] The additional impedance generated by the transition resistance will cause the refusal or malfunction of the impedance distance protection. The refusal of the protection will make the fault unable to be isolated from the grid in time, which is not conducive to the stable operation of the grid; Transfer, and then lead to the occurrence of large-scale power outage accidents

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