Generator Step Up Transformer

[mvsubstations]

Is there any risk to using a step up transformer that has a capacity about 10 times larger than the capacity of the generator? (i.e. a generator that is rated for 10MVA with a step up transformer of 100MVA as an example).

 

[edison123]

The generator will be feeding most likely ten times no-load current and no-load loss for 100 MVA trafo, which can significantly cut down the generator's useful KW output.

Muthu

http://www.edison.co.in

 

[waross]

You will have to connect the transformer and then start the generator.
You will never energize it at rated voltage and frequency.

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

 

[FreddyNurk]

waross, that's probably not strictly true, at 10MVA it may not be a blackstart capable set.
I'll admit I'm struggling to come up with a reason for such a mismatch of generation and step up transformer though.

EDMS Australia

 

[itsmoked]

Ah, they probably just had a 100MVA laying around. Don't you have a couple?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

I guess I should have added DOL.
We have several threads in regards to the difficulty of energizing a transformer DOL to a generator of approximately the same or greater capacity.
It doesn't have to be a black start to have issues energizing the transformer.

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

 

[ravindranathan]

When transformer operates at less than 10% of its capacity --what will be its efficiency ???.
It will be extremely poor.The Generator shall be feeding a highly inefficient transformer and losses will be very high.
Further inrush current shall be very high.You will need to control inrush current as well.
There is small write up on below link..

https://www.quora.com/How-can-we-reduce-an-inrush-current-in-a-transformer.

Check Fahad Hashmi's note...help it helps

 

[FreddyNurk]

waross, you're right, it doesn't have to be black start to be problematic, I was more expecting that it might well be energised on the load side rather than generator, in which case its no longer a starting issue.
I'll also admit blackstart isn't quite correct in that context either, rather that a site that needs grid power to operate can use the grid to energise.

Apologies if this is too much semantics.


EDMS Australia

 

[waross]

Freddy. You and I both know what we mean. Thanks for the good explanation for those who may be following this thread in order to learn.

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