Distance Relay Impedance Measuring Problems in Presence of Wind Farms

Environmental concerns along with the increasing demand on electrical power, have led to power generation of renewable sources like wind. Connecting wind turbines in large scale powers with transmission network makes new challenges like the impact of these renewable sources on power system protection. This paper studies the impact of fault resistance and its location on voltage and current fundamental frequencies of faulted lines connected to DFIG based wind farms and it will be demonstrated that because of the large differences between these frequencies, impedance measuring of distance relays is inefficient. Hence in these power systems using conventional impedance measurements is not suitable anymore and new impedance measuring approaches are required in distance relays.