unit auxiliary transformer supply

[Mlmlzx]

Dear sirs,

Can somebody please share: for unit connected system with generator breaker, does a fault just below the power transformer trips the generator circuit breaker? in that case, unit auxiliary transformer, the supply of which is taken after the generator breaker may not get supply and as a result unit auxiliary transformer may be off and may not feed unit auxiliaries.

Regards,

 

[crshears]

True, which is why a separate unit station service transformer may be connected to the generator terminals, meaning before the generator breaker. Units so arranged will commonly be started using power supplied by the grid or, quite uncommonly, from some black-start source, with some or all unit auxiliaries being switched onto the unit SST once synchronization has been completed.

The 300 MW coal-fired units I was part of operating had a procedure that specified transfer of part of the unit auxiliaries onto the unit SST once a generator output of 20-30 MW had been reached. By this means the auxiliaries were supplied from two separate sources during normal operation, such that the unit was designed to survive loss of one of the two supplies.

Hopefully this helps.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[Mlmlzx]

doesn't power from generator has to go to unit auxiliary transformer even when generator is on no load..

 

[crshears]

Upon further review, I see you have already posed a similar question [ see thread @

https://www.eng-tips.com/viewthread.cfm?qid=489462

] . . .

What question are you asking now that has not already been addressed?

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[RRaghunath]

"doesn't power from generator has to go to unit auxiliary transformer even when generator is on no load" - generator will feed the auxiliaries through its own transformer when unit is islanded from grid due to some disturbance in the grid.
Islanding refers to opening of grid breaker with GCB remaining closed.

 

[crshears]

Hi Rraghunath, OP does not seem to make the presupposition that such an electrical configuration is in play.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]