Study on wide-area protection algorithm based on composite impedance directional principle

•A novel wide-area protection (WAP) algorithm is proposed.•The scheme is not affected by the high grounding resistance and the load current.•The high dependence on the synchronization of wide-area information is overcome. Wide-area differential protection uses the wide-area multiple-information to quickly identify faults. It is not affected by factors such as grounding resistance and distributed capacitance. As the wide-area measurement requires the high synchronization of wide-area information, its protection sensitivity is reduced by the accumulative errors. A novel wide-area protection (WAP) algorithm is proposed in this paper to solve these problems. Firstly, the information of the single-terminal voltage phasor and the differential current phasors of the transmission line are used to construct the protection criteria based on the composite impedance. Then, the criteria of the fault identification and fault branch are established based on the information of the wide-area branch direction and regional direction. The advantages of the wide-area differential protection are retained in the proposed algorithm. The high dependence on the synchronization of wide-area information is overcome and it is not affected by the high grounding resistance and the load current. The validity of the proposed algorithm is verified by simulation tests of the IEEE 10-generator 39-bus system.