Restricting Fault current - Neutral Grounding Transformer

[mylgcookie]

Can anyone tell me "How Neutral Grounding Transformer / NGR prevents Damage of Generator by restricting fault Current?"

As far as my understanding, NGR/NGT is connected to Neutral of Generator, Which will have resistor to limit the current.

Almost, everyone know that NGT/NGR limits the fault current to some level.

My Question is NGT/NGR is connected at the Neutral terminal of the generator, but how come we are able to restrict de fault current floe inside the generator coils

 

[wirenut1980]

The resistance in the neutral will limit fault current flow for a single line to ground fault. This gives the benefit of an ungrounded system in that a single line to ground fault does not shut anything down, only without the disadvantage of high line to ground voltages that are characteristic of an ungrounded system. If there is a line to line fault, the resistor in the neutral will not do anything to limit fault current as it is not in the fault current path. So normal fault current will flow. A properly sized overcurrent protective device will limit line to line fault current duration to a short duration providing protection to the generator windings.

Welcome to the forum!

 

[ron]

The resistance goes between the neutral of the gen and the ground. During a L-G fault, as current travels back on the equipment ground conductor to reach its source (across the N-G bond), it "sees" resistance in that path due to this added device.

 

[SG-1]

Should the fault be internal to the generator neither the NGR or the transformer would limit the fault current. The added resistance/impedance will not be in the fault circuit path.