Optimization of stator ground fault protection for synchronous generators based on negative sequence current supervision

This paper proposes a strategy to optimize the performance of stator ground fault protection function for synchronous generators based on supervision of negative sequence currents, in order to allow the selectivity and speed for unbalanced faults in the generator side and ensure proper coordination for transmission line side faults. Through a hardware-in-the-loop test scheme, the sensitivity of the ANSI 64G function is investigated for different scenarios, including those where the influences of lift transformer coupling capacitances are expected. The proposed logic demonstrates effectiveness by providing a faster response of the ANSI 64G function, which consequently protects the generator against longer overvoltages by preventing short circuit evolution.