A novel Single-phase-to-ground fault identification and isolation strategy in wind farm collector line

- A single-phase-to-ground fault detection method in wind farm is proposed.
- The mechanism of wind turbine terminal overvoltage is revealed.
- The resonance model of wind turbine with distributed parameter line is constructed.
- Two isolation strategies for single-phase-to-ground fault in wind farm are proposed.

The collector system of wind farm is a non-effectively grounding (small current grounding) system, where the single-phase-to-ground fault can easily develop into a three-phase fault, and without timely identification and isolation, it may cause incalculable hazard to wind farms. In fact, the present fault identification methods based on single fault characteristic quantity or majority voting rule all have certain limitations when dealing with some certain faults theoretically. Furthermore, the wind turbine could be possibly exposed to overvoltage several times of the rated voltage after the fault isolation by direct switching off the grid-side breaker in collector line. To solve these problems, this paper first analyzes the mechanism of overvoltage by constructing the resonance model of wind farm with distributed parameter. A novel single-phase-to-ground fault identification method based on D-S evidence theory is proposed. Then two flexible fault isolation methods are further proposed. Simulation results verify the validity and superiority of the proposed strategy.