Comprehensive current amplitude ratio based pilot protection for line with converter-interfaced sources

Fault behaviours of converter-interfaced renewable energy sources (CIRESs) are greatly diverse from those of synchronous generators (SGs), so the traditional proportional restraint differential protection may fail to be activated. In order to deal with this issue, a comprehensive current amplitude ratio-based pilot relay is proposed. Since the fault current from CIRESs is much smaller than that of SGs, so phase current amplitude ratio on both end is lower than 1. In order to improve protection sensitivity for high resistance faults and grounding faults, sequence current ratio is also introduced to constitute a comprehensive protection criterion. The proposed method only uses the amplitude feature, so it has a lower time synchronization requirement for the currents on both terminals. Meanwhile, it can be applied for different fault ride through (FRT) strategies because the current limiting is always satisfied. Furthermore, the proposed method is easy to be deployed in protection devices after a small revision is done for the original protection algorithm. PSCAD simulation demonstrates that the proposed method is effective for different fault scenarios.