Ground fault currents in unit generator-transformer at various NGR and transformer configurations

Single line to ground faults are the most frequent faults likely to occur in the electric power system. The effect of ground fault is determined by generating station arrangements and transformer connections. In this paper, the performance of the generator within the single line to ground fault at various Neutral Grounding Resistors (NGR) and transformer configurations is studied. Simulations were conducted in MATLAB/Simulink and the results are analyzed. A comparison with the impact of faults at various transformer connections is presented. The impact of faults for generator with NGR is also analyzed. On the unit generator-transformer, fault current in the generator neutral is greatest at Yg-Yg transformer connection followed by Yg-Y and Yg-Δ, In addition, for the transformer winding Y-Y, Y-Yg, Y-Δ, Δ-Y, Δ-Yg and Δ-Δ no current flows through the NGR of generator.