Single-phase-to-ground fault detection in wind farm collector line using transient phase current criterion

The wind farm collector grid is normally a neutral ineffectively grounded network. Because of the increasingly sophisticated control system and relatively short collector lines of modern wind farms, the current amplitude variation during single-phase-to-ground fault in collector line becomes extremely slight, which may lead to the failure of conventional feeder relays and result in consequential damages. It is thus necessary to take the unique features of wind farms into consideration in detecting single-phase-to-ground fault. Based on detailed analysis of the amplitude characteristics of transient current in the faulted network, the paper provides a novel single-phase-to-ground fault detection method vis-à-vis the present requirements. This method firstly calculates the ratio of the fault component of faulted phase current to that of healthy phase current, aiming at determining the state of the line, namely healthy, faulted or “likely faulted”. If considered as likely faulted, the state of the line will be judged further by recalculating the ratio within the dominant transient frequency band, where the healthy phase transient current is most centralized. The algorithm provides a new approach of capturing adaptively the dominant transient frequency band based on amplitude-frequency analysis. Simulation results on PSCAD/EMTDC prove this algorithm effective and reliable in wind farm collector line single-phase-to-ground fault detection considering various fault conditions.