A novel directional relay applicable to power system with wind farms

A novel directional relay in time domain is proposed in the paper and can be used in the transmission line for wind power integration. Firstly, the models of grounding fault and non-grounding fault in the forward and reverse side of relay location are established, respectively. As for a forward non-grounding fault, the current and voltage of fault phases satisfies a module with positive resistance and positive inductance. As for a forward grounding fault, the zero module current and voltage measured at the relay location satisfies a model with negative resistance and negative inductance model in the zero module net. Then, the forward fault model conformity is defined on the basis of correlation analysis theory. Using the resistance and inductance calculated based on least square method, the forward fault model conformity is almost equal to 1 for a forward fault and -1 for a reverse fault. Thus, the fault direction can be identified by model recognition. Eventually, the effectiveness of the proposed scheme is verified by simulation in PSCAD.