High Current Passes Through Neutral

Treat it as any professional would.

Call in a competent electrical engineer to trouble shoot and fix your problem.

What were the readings from the insulation test that was carried out before its being bought into use?

is the generator wye connected? Voltage? Actual phase current readings? When you say current was high, it does not give any information. Do you have loads connected phase to neutral?

Did the rewinder make a mistake when rewinding the generator? (Perhaps).

What does the power station's Chief Engineer have to say on the matter?

He is the station's Chief Engineer

Some dimensioned numbers would be a good starting point.

Well, Thanx all for ur concern.

firstly when we start troubleshooting this problem we do megger test to check generator, then we test it on dummy load bank (resistive load without neutral ).

when the generator tripped when put it in parallel with other generators we raise the setting of ground fault to complete testing.

we confirm that there isn't neutral current on other generators before loading the rewound generator.

neutral current before loaded generator are (19,7,25)

We confirm that no big single phase load causing neutral current.

So now we load generator found high current in generator ((180A))

and high current through other generators neutral (45,95,50)A

So please kindly advise us to know what root cause of the problem and how could it be serius problem and how we can solve it

Please also check this link

http://www.mirusinternational.com/downloads/EGSA-PL-SO11-Mirus-Article-b.pdf

Any advise will be appreciatted

Thanx

Adel

This may be an issue with the terminations within the newly wound motor.

What values did you get when you megger'd each winding? At what point were the measurements taken, at the output terminal or at each winding termination in the case?

But...

I would compare the LCR stator winding measurements. This will give you an idea of the pitch relationship of the windings. Turn the motor over one complete revolution and measure the LCR values at equal points over the 360 degrees. Do this for each phase relationship. Plot your results through a simple Excel run chart and look for inconsistencies in the phase to phase relationships.

Research locked-rotor impedance.

dooola2020,

very good article, which you have linked, it also suggestes the probable cause of the problem and the solution to get rid of the Problem..

Thank you for sharing this Article..

Secondly we do not connect the neutrals of the Generators in Parallet Operation, rather we connect the Neutral of Biggest (Capacity) generator to Earth and the neutrals of all others will be kepy floating..

Regards..

Well, that's a unique way of doing it. Kinda makes synchronization difficult, though, eh?

Once more than one source is connected to the load, only one of their neutrals needs to be connected, otherwise high neutral currents will ensue.

If in doubt, consult a qualified Electrical Engineer locally.