The Analysis Of Large Generator-Transformer Stator Ground-Fault Protection

Stator ground-fault is the most common generator fault, and it is the direct cause of phase-to-phase fault which may immediately damage generator. Protection schemes based on the zero sequence fundamental voltage and the third harmonic voltage and the injection voltage are presented in this paper, and based on which, the factors which affects the protection schemes based on the zero sequence fundamental voltage and the relevant measures is presented. This paper also discusses another new neutral grounding method, a neutralizer with series resistance, which can limit the ground fault current and decrease the transferring over-voltage effectively. It is deduced in detail that the characteristics of the hydro-generator neutral displacement voltage and the relationship between the displacement voltage and the asymmetry of three-phase distributed capacitance. Take the 20Hz injection voltage for example, this paper detailedly analyze and simulate the influence of the source internal resistance and the transformer's parameter under different neutral grounding methods. Hou Youtao(Automation of Electric Power Systems) Directed by Prof. Zhang Ju...