The Impact Of Double-Circuit Transmission Line With Series Capacitor Compensation On Line Relay

With the development of Chinese UHV transmission line, series capacitor compensation has been widely applied on UHV transmission line. The capacitors wich are in series with transmission line can compensate impedance of lines, reduce electrical distance of AC transmission, improve dynamic and transient stability remarkably, reduce the loss when electricity transmission.The voltage and current comprises low frequence component when fault occurs, series capacitors destroy the uniformity of transmission line impedance as a concentrate capacitive reactance, make the phase of the voltage and current reverse and measured-impedance at relay become capacitive reactance. The dissertation also discusses the installation of PT.According to the working characteristic of series capacitors,the influence of it on relay is analyzing furthermore. As for directional relay and distance relay, because series capacitors change the impedance characteristic of transmission line,protection may mal operation. As for zero sequence protection, it may affected by zero sequence current which is produced by the bypass of series capacitors.Furthermore, as for current comparison relay, series capacitors only bring little influence on such relay.According to the influence of series capacitors on relay, the paper improve directional relay, distance relay and distance relay using power fault frequence fault component to apply on the line with series capacitors. The compensated voltage is introduced to make directional relay without the influence of capacitors. As for distance relay, the influence of series capacitors can be eliminated by the calculation of reactance of capacitors.Because autoreclosure can’t apply to double-circuit UHV transmission line with series capacitors compensation, the paper proposed a new scheme of self-adaptive autoreclosure.This is scheme can increase the percent of reclosure success on the premise of serious impact to system brought by reclosure through the criteria of the identification of fault characteristic and reclosure according to phase sequence.Last the simulation model of1000kV transmission line is established to test the theoretical analysis above.