Sequence-component-based current differential protection for transmission lines connected with IIGs

Current differential protection is normally designed as the primary protection for the high-voltage transmission lines. However, for the transmission line that is connected with the large-scale inverter-interfaced generators (IIGs), the performance of the conventional current differential protection is significantly affected by the difference between the sequence components of the fault currents on both sides of this line. This may result in the mal-operation of protection relays. This study proposes a sequence-component-based current differential protection from a suitable fault model of IIGs under positive-sequence control strategy. A differential coefficient is introduced to overcome the low sensitivity and poor reliability of the conventional differential protection. The proposed scheme discriminates the internal faults accurately from the external faults and the normal operating conditions. Additionally, the robustness analysis shows that this scheme is immune to different fault resistances, fault locations, and system parameters. Simulation results in power systems computer-aided design/electro-magnetic transient design and control validate the effectiveness of the proposed sequence-component-based protection scheme.