Need for generator breaker before step-up transformer 16

[njengr1]

Is there a Code or other reason to require a generator breaker between the generator and the step-up transformer. No auxiliaries are supplied at the generator voltage (4160 v). This is for a small (4MW) cogeneraton installation. A breaker is on the high voltage side. The stepup transformer is connected to a utility

 

[busbar]

In the US NEC, facilities considered Not Covered are “Installations… under the exclusive control of electric utilities…” so it would be unusual to apply the NEC to unit-connected generation. There are other national consensus standards that are more fitting to the application.

 

[RRaghunath]

In power plants where the grid available is at 220 or 400kV level, it makes economic sense not to install grid connected station transformers and go for generator circuit breaker. This way, start up power also can be drawn from the UAT through Generator transformer keeping the GCB open.
This will save cost of two nos. switchyard bays, two nos. station transformers and associated civil costs. All this could be substantial especially when one is looking at minimising the project costs.

 

[bobthewiz]

I completely disagree with the cost of a full size GCB. In 2001, a fully rated GCB for a 250 MW plant would cost between $275,000 and $300,000 per unit. There are now at least four major manufactures of GCB's based upon SF6 interrupting technology. Perhaps njengr1 was refering to the old airblast cb's that cost $1.0 million or more.GCB's enhance the overall unit reliability and are almost standard on the design of combined cycle powerplants that are now inuse or in the planning stages. Usually they are only applied on the GT units not the ST's.Since the cost have come down from $1.0 million they also are also a factor in the overall cost of the plant(They eliminate the cost of a start up system).So powerplants are cheaper to build with GCB's and are also more reliable. They also make it a little harder to motor the machine. Not a good idea as explained in a previous post.

 

[buzzp]

Tell me if I am wrong, but this particular installation would not even use a generator breaker as defined by IEEE ANSI C37.013. If it does not, is there a specific standard that would encompass this size of a generator breaker?