Protection technique based on Δ-zero sequence voltages for generator stator ground fault

A mathematical model on a coil basis is used to study the characteristics of the zero sequence voltage of a generator. The proposed technique for the stator ground fault detection simultaneously takes into account the fault contributed zero sequence fundamental voltage and the fault contributed third-harmonic voltage (Δ-zero sequence voltage). The effect of the start-up component based on the wavelet transform is also highlighted. As information both on the fault contributed zero sequence fundamental voltage and the third-harmonic voltage is used simultaneously, the scheme can obtain higher sensitivity. Results from the experiment and in the field show that the proposed technique can detect the ground fault with high sensitivity and reliability during all operating conditions.