Distance Relay Monitored Phase Comparison Carrier Schemes for Protecting Circuits with Series Capacitor Installations

In this paper, a scheme is described which employs distance relays with quadrilateral polar characteristics to monitor phase comparison carrier schemes intended for protecting circuits with series capacitor installations. Emphasis is placed on the development of the quadrilateral polar characteristic which is obtained by using the ‘Block spike’ scheme. The characteristic with its inherent out of step blocking feature provides maximum stability against mal-operations due to load encroachments and power swings and hence is ideally suited for protecting long E.H.V. lines. The blocking and the tripping characteristics are so chosen as to ameliorate the disadvantage arising from the uncertain nature of the series capacitor protective gap flashover.