The Identification Between Transient Fault And Permanent Fault On Transmission Lines

In order that autoreclose circuit breaker reliably recluse in the transient fault and avoid to recluse in the permanent fault, people hope that autoreclose circuit breaker be able to identify transient fault and permanent fault to improve the stability and reliability of system.This paper studies the characteristic of recovery voltage when ground fault occurs in EHV transmission line with shunt reactor, and then, the fault identification criterion is proposed. The recovery voltage contains power frequency component and low-frequency decaying component when transient fault occurs, and it only contains power frequency component when permanent fault occurs. Using the orthogonality between signal vector and noise subspace, the power spectrum estimation algorithm based on matrix eigenvalue decomposition can accurately estimate power frequency components and low-frequency decaying component, and the system noise has no great effect on the accuracy of criterion. In this paper, voltage signal of shunt reactor is measured for detecting power frequency component and low-frequency decaying component using this algorithm. What have two lines (peaks) is the transient fault, and what has one line (peak) is the permanent fault.The simulation models are established in the platform of ATP-EMTP to verify the validity of proposed fault identification criterion. Simulation results show that the criterion can reliably distinguish transient fault and permanent fault both single circuit line or double circuit line, unaffected by fault locations or transition resistance. In the series compensation system, although the increase of series capacitor circuit, the fault identification criterion still can identify transient fault and permanent fault.