Transformer charging with Generator

[sakaran51]

Hi,
Can anyone throw some light on the long term impact on the generator,energizing the transformer?
A 5 MVA 33/11kV Transformer needs to be charged with a 10MVA,11kV Steam Turbine Generator.Is there any thumb rule for Generator-Transformer charging?

 

[waross]

The best solution when possible is to connect the transformer to the generator before starting the generator.

Bill
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"Why not the best?"
Jimmy Carter

 

[sakaran51]

Dear Waross,
I do agree with your recommendation.But in practice it is not always possible to charge the transformer with the generator directly connected as a single unit.Hence I am wondering is there a cut off limit by which we can design and operate plant electricals,which will be of some guideline.

 

[waross]

I suggest searching this site for information. There have been some good discussions of methods to mitigate transformer inrush.
You may consider pre-charging,- That is energizing the transformer through current limiting resistors and then shorting out the resistors.
I seem to recall also some discussion of a method to reduce the residual magnetism when a transformer is de-energized to avoid the worst case asymmetrical energization surges.

Bill
--------------------
"Why not the best?"
Jimmy Carter