Stator Earth Fault

The voltage each generator phase of R,S and T found unbalance can read from Neutral Grounding Resistor (NGR) measurement.

Grounding resistor in the neutral will limit the ground fault current in case of an stator ground fault. Typically the resistor is chosen to limit the maximum fault current to approx. 5 - 15% of nominal current. A Uo voltage protection measuring across the resistor will detect stator ground fault and disconnect the generator.


As far as my understanding, NGR/NGT is connected to Neutral of Generator, but how by controlling the current in neutral terminal help us in restricting the fault current which flow inside the generator?

NGR is connected with transformer which primary transformer is grounded and secondary transformer is paralel with resistor and stator earth fault relay.