Transmission line protection using local information in the presence of inverter-interfaced renewable energy sources

Although inverter-interfaced renewable energy sources (IIRESs) have great economic and environmental benefits, their fault current characteristics differ from those of synchronous generators. IIRESs also comply with modern grid code (GC) requirements for injecting reactive current to compensate for voltage drop during fault conditions. Moreover, the limits of renewable energy-side fault current contribution and the phase angle difference between the local and infeed fault current from conventional sources lead to incorrect reactance estimation by the traditional distance relay at the IIRES substation and negatively affect relay dependability. As a result, the IIRES-side distance protection is prone to incorrect operation. Furthermore, an improved relaying scheme is proposed to alleviate the adverse effects of IIRES on the reactance calculation. This research aims to improve the performance of the ground distance protection scheme in the case of a single-phase to ground fault in zone one. The proposed method, with more than 99% accuracy, is solely dependent on the local information and, therefore, no communication link is required to implement the algorithm. Moreover, the algorithm is compatible with the existing pilot protection methods used in the industry. The simulation studies are modeled in the Digsilent Power Factory environment.