Influence of Converter-based Power Sources on the Distance Relay under System Asymmetrical Faults

This work mainly focuses on the influences of the power electronic-interfaced renewable energy (PE-RE) on the distance relay in the transmission system. Combined with the theoretical parse of the protective issues, simulation results show that the distance relay installed at the PE-RE side may risk of mal-operating under the existing grid code. This is because that the angle difference between the double-sided currents causes an extra ‘virtual’ imaginary part of the measured impedance. Meanwhile, the limited capacity of the PE-RE plant relative to the capacity of the main grid further enlarges the magnitude of the error. Finally, the conclusive discussion states the protective challenges and future countermeasures.