Distance protection of lines connected to doubly fed induction generator based wind farms

Penetration of wind farms in High Voltage transmission lines is increasing day by day. Hence the necessity for protection of lines connected to the wind farms is also increasing. This paper proposes protection scheme for the transmission lines connected to Doubly Fed Induction Generator based wind farm. Generally, distance protection scheme is applied to the transmission line protection. The Doubly Fed Induction Generator is represented as Norton equivalent model. Owing to the variations in the frequency of voltages and currents on occurrence of fault on the transmission line, the impedance as seen by the relay is incorrect. Issues related to such mal operation of the Doubly Fed Induction Generator during various fault conditions are analyzed and a solution is proposed. The proposed scheme gives modifications in conventional pilot protection scheme and it is validated using PSCAD/EMTDC simulation. Encouraging results have been obtained with the new proposed scheme.