Generator GSU paralleling

[Adam1980]

Dear all,

is there any considerable problems of paralleling generators' GSUs with OLTC to the same busbar.

will there be any problem if operating the OLTC action is delayed from the first generator on the busbar to the last one?

This question is concerning thermal power plants with several generators (> 200 MW).

Thank you.

 

[slavag]

Sorry, but your Q is not clear.
With OLTC or without, is not problem.
Do you have some synchrocheck ( 25 )?

 

[ScottyUK]

You will need some form of automatic tapchanger control otherwise you will find that currents circulate among the transformers. Depending on the mis-match the currents could be substantial. There are several schemes available: master / slave and minimal circulating current being two of them. Be sure you understand failure modes and their effects - some are more graceful than others. ;-)

 

[Adam1980]

Hello Thanks for the reply.

Slavag the question is concerning the mismatch of the OLTC during operation.

Scotty mismatch and circulating current were the things I am looking for. Any literature about that, specifically for generator GSU?

Thanks.

 

[ScottyUK]

Reinhausen are about the best in the business of building OLTCs. Their regulator manuals contain some information on scheme operation although you'll have to dig out the bits you want.

http://www.reinhausen.com/desktopde...w-42/categories-42/catname-Voltage Regulators

 

[slavag]

Sorry, issue is transformer paralleling operation .
So, as Scotty said.
But, from other hand: for what you need OLTC in GSU? Do you regulate reactive power with OLTC?

 

[rcw retired EE]

Circulating currents will not be a problem unless there is a paralleling connection on the generator side (low voltage side) of the GSU transformers. Different GSU taps will just change the reactive output (MVAR)'s from the individual generators. Worst case is the voltage on the common HV bus gets too high as each GSU is tapped up and the last generator trips on under excitation due to the MVAr's flowing into the generator.

But usually the voltage steps are small enough that the operator's can make the required generator voltage adjustements to maintain the desired system and generator voltages.