How to size the Collector Bus?

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sccat

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I have 3 1600kW/400V gengerators Synchronized and connected to the Collector Bus.

The arrangement of the switchgears is as follows:
1600kW Generator;
1300kW Load;
1600kW Generator;
1300kW Load;
1600kW Generator;
1300kW Load;

How to size the Collector Bus?
Should the Ampacity of Collector Bus Be 3X1600kW or 3X1300kW or 2X1300kW?

Thanks.
 
sc -
Not really. You're going to have to hire an engineer familiar with the codes and design practices in your area.

Let me guess:
You are not in the US. The system will be 50 hz. The equipment will be covered by the IEC. NEC could possibly apply - but probably not.
The NESC could apply - but probably not.

1.6MW is about 2000FLA. So you are looking at 3000A CBs for the generators. 1300KVA loads are about 1600A. Depending of the load contribution the SCC could be up in the 50kA range.

Maybe 3000A will work - maybe 4000A is more common.

First thing I would do: If the generators have not been purchased, approach the owners about changing to your equivalent of 13.8KV, or 4160V. Either way this will get the SCC down, switchgear amp rating down, conductor sizes down.

If not, and I had to stay with the 400V, then I'd be looking at the SCC withstand of the generators. Sometimes with parallel generation, grounded systems, if one gen develops a fault, the other two can deliver more SCC that the one can stand.

Point is you may be sizing the switchgear bus to other specs besides the load currents.

carl
 
Bus

Bus

You have 3x1600kW at 400V 3-phase, that is about 7000A. You need 8000A or more bus, plus bracing for the worst case fault currents.
 
I think I know where this is coming from: If my memory serves in Europe switchgear up to 6300A is fairly common and easy to come by, but above that it gets harder.

I get the load of 3900KW to be 5636A, and thus could be accomodated by a 6300A busbar system. Just. providing your engineer agrees. Because each genset could deliver 2312A thus all three in theory could deliver 6936A, but you dont have the load to support that overload. Two gensets running flat out with a third offline is a realistic poossibility as long as the load isn't more than two gensets can support.
 
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