High voltage series-compensated transmission line - evaluation of new distance protection

This paper investigates a new distance protection principle for a transmission line compensated with 3-phase capacitor banks installed in the middle of the line. Series Capacitors (SCs) equipped with Metal-Oxide Varistors (MOVs), when set on a transmission line, create certain problems for its protective devices. Direct application of the classic distance protection (designed for traditional lines) to series-compensated lines results in considerable shortening of the first zone reach and also in poor transient behaviour. In order to overcome these difficulties the new distance protection principle for the first zone has been developed. The detailed model of considered transmission lines including the SCs&MOVs banks as well as the measurement channels has been developed. Using this model, the reliable fault data has been generated for evaluation of the new distance protection principle under variety of fault conditions. The study has shown considerable improvement of series-compensated line protection as a result of applying the developed new principle.