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Fault current to Generator Neutral or only to Transformer Neutral

Fault current to Generator Neutral or only to Transformer Neutral

Fault current to Generator Neutral or only to Transformer Neutral

(OP)
At LV, a ground fault happens. At Transformer Neutral, fault current will undoubtedly flow. Flow of fault current at the neutral of the generator?

RE: Fault current to Generator Neutral or only to Transformer Neutral

If there's a delta winding on the generator side of the transformer then no ground fault current to the generator neutral.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

RE: Fault current to Generator Neutral or only to Transformer Neutral

Dear Mr. NickParker (Electrical)(OP)11 Jan 23 18:09
"....At LV, a ground fault happens. At Transformer Neutral, fault current will undoubtedly flow. Flow of fault current at the neutral of the generator? "
A transformer is an induction equipment. There is NO solid/physical electrical connection between the primary winding and the secondary.
Therefore, any LV SC current would flow through the secondary start winding Neutral. If the secondary winding is Delta, [no current flow when only one line is shorted the earth]. No current flow to the Generator neutral in any case.
Che Kuan Yau (Singapore)

RE: Fault current to Generator Neutral or only to Transformer Neutral

A single phase short to ground on a wye secondary will cause a fault current to flow in the corresponding delta phase.
That current will cause a voltage drop in the corresponding delta winding.
The other two windings form an open delta with the same phase angle and characteristics as the shorted winding.
When one transformer in a delta bank is removed, the remaining two transformers form an open delta which develops a virtual transformer with the same characteristics as the transformer that was removed.
So the same current value in each of the three windings.
50% of the current is supplied by the inphase winding and 50% of the current is supplied by the open delta windings.
The open delta windings are running at 50% PF, one leading and one lagging, so the arithmetic works out.
No neutral current on the generator.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

RE: Fault current to Generator Neutral or only to Transformer Neutral

That is why I like to see a generator looking into a delta transformer bank.
Single phase loads on the secondary are more evenly distributed on the generator windings.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

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