Connecting Generators in a Single Bay

[CKent]

Our existing generation is connected to a main 115 kV swithcyard (1 1/2 breaker scheme). The same 115 kV switchyard is connected to 2-ITT upstream to 380 KV switchyard (1 1/2 breaker) where 2 inter-tie line connects our system to a much bigger system.

We are planning to put up an expansion through 500MW new generating plants to be connected to the 380 KV switchyard by installation of a single additional bay. The new plant shall be compose of 2x250 MW units and was initially intended to be connected to the two points from the additional bay.

I know that preferably it should be connected on different section of the 1 1/2 breaker and thus requires 2 additional bays. However, to limit the cost, it was proposed that way. Is there a siginificant effect on the reliability of the resulting set-up?

 

[ScottyUK]

You could do this by using providing a GSU transformer with dual LV windings and individual generator circuit breakers, each rated for to suit your generators. It's fairly common practice, although in a world run by accountants that doesn't mean to say it is good practice. Any problem on the GSU transformer or HV switchgear means a double-unit outage, perhaps a long one, and most operators would rather have the flexibility to keep at least one unit in service while the other is in outage. Consider if your GSU develops a serious fault there's a leadtime of over a year to get a new one. That's a long time to lose 500MW of generation.


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If we learn from our mistakes I'm getting a great education!

 

[CKent]

Thanks Scotty..
But that set-up was already ruled out.
Most of our existing GTGs rated 60MW are having that kind of set-up and is connected to the 115 kV bus.
However, since these units are relatively bigger, it is to be connected individually to the 380 kV bus. But economics have it that only 1 additional bay is to be constructed to connect the 2-units. My questions is, will there be significant impact in terms of reliability say compared if we built 2 bays and connect each unit to the opposite sides (upper & lower or left & right) of the breaker and a half system?

 

[ScottyUK]

Post a couple of sketches of your alternative single-lines and we'll throw stones at 'em. At least we'll all know what configurations are under consideration.


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If we learn from our mistakes I'm getting a great education!

 

[davidbeach]

Construct one new bay, move one existing connection. Next?