Application Research of Fault Current Limiter on the EHV Grid

Abstract

This paper introduces recent researches about fault current limiter(FCL).Due to weakness of instability of many kinds of FCLs,they are not applied on the EHV.The series reactor is mostly used on the EHV for its stability,however,it adds power loss to the system,and specially,it decreases the system transient stability.Short circuit current limiter(SCCL) based on series resonance can avoid the disadvantages of the series reactor.This paper also analyzes how SCCL increases the transient stability by the equivalent square rule.It can decrease the acceleration square and increase system speed-down area.Resonance parameters design is the key point in the engineering design.If the restrain coefficient is too high,the power strength of SCCL would be challenged.To protect the capacitor to be safely switched is the key technology of SCCL for the voltage of the capacitor would be quickly increased when a fault occurs.Multi-bypass breaker,which consists of MOV,thyristor,spark-gap and high speed breaker,can resist the disaster of the capacitor broken down by the overvolatage.MOV acts as the first line.SCR acts the second line.If SCR fails to act or delays much time,spark-gap would be triggered quickly,then high speed breaker closes up to endure bulk fault current.Thus the transmission line would not be interrupted by the capacitor breaking down.Based on the main circuit of SCCL,lots of simulation experiments are observed to find the effects of the resonance parameters.Through optimizing the parameters,SCCL gets good response to the fault current and the capacitor is protected in the reasonable range.