Faulty line identification by distance relay in series-compensated parallel transmission lines

Distance relay is typically assisted by earth-current balance scheme (ECBS) to classify healthy and faulty lines when used to protect parallel transmission lines. This paper highlights the problem of distance relay maloperation when conventional ECBS is used to classify healthy and faulty lines in series compensated parallel transmission lines (SCPTL). The existence of the problem is shown mathematically for different tower configurations, varying compensation levels and for different remote end in-feed levels. Analysis shows that conventional ECBS is not able to classify healthy and faulty lines which may result in tripping of both lines depending upon the fault location. This paper proposes a similar logic, which relies on angle information instead of magnitude information. Analysis shows that angle information is able to classify healthy and faulty lines, which can be used to assist distance relay protecting SCPTL.