Novel differential protection using model recognition and unsymmetrical vector reconstruction for the transmission line with wind farms connection

The large-scale integration of different kinds of wind farms (WFs) in a transmission grid can bring special adaptability issues to the traditional phasor-based line differential protection in both the transient and steady states. In this paper, a novel composite fault model based differential protection (CFMDP) is proposed. The CFMDP detects the fault status by evaluating the consistency between the sampled fault data and the pre-defined differential model. Since the full-frequency fault information in time-domain is directly used in the consistency calculation, the CFMDP method performs better transient behaviours than the conventional scheme. Besides, the compensated currents are used to build the differential model, which overcomes the 'over angle difference' caused steady-state adaptability issue in the phasor based differential relay. This steady-state protective issue mainly happens with the interphase faults in large-scale Type-IV wind turbine generators (WTGs) integrated power grid. The electro-magnetic transient (EMT) simulation results demonstrate the effectiveness and merits of the proposed CFMDP schemes.