Load Flow?

[RonShap]

There is a generator paralleling SWGR in which there are (4) 1500kW diesel generators connected and approx 20 distribution circuit breakers tapped at various positions at either end of the SWGR.
I have not performed a load flow study before and I'm trying to determine if that is what is needed to determine, based on the ampacity of the internal SWGR bus, whether the SWGR can be operated with all four generators serving load (approaching 6000kW of load), or due to the internal design of the paralleled bus must it be limited to 4500kW of load and operate N+1.
It is old SWGR and has always been run as N+1 and the client is asking if it could be run as "N". The original design intent is not clear from documents found laying around.
If not load flow, what type of study would help in determining any bottlenecks in the ampacity of the internal SWGR bus.

 

[DanDel]

What is the amperage rating of the switchgear bus?

 

[RonShap]

It is 480V, 5000A horizontal across the entire lineup.

 

[DanDel]

If all the generators were at one end of the bus, and all the loads were at the other, I would say the 5000A bus would be overloaded with 6000kW (7225A).

If the load connections were in between the Gen connections, you could model the individual bus sections (as a small impedance) between the Gen connections and the load C/B connections, and you could probably find out if any particular section is overloaded.

This may be difficult, since the actual connection points may not be obvious. And it may not be very accurate, since you don't know the true impedance of each section between the connections. But if it shows fairly distributed current, you may be able to allow the loading.

 

[RonShap]

The generators on connected to the center of the line-up and the loads are on either end.

 

[DanDel]

That makes it really easy to model, then. As long as each end's load is less than 5000A, you should be OK.

 

[dpc]

You can split the bus up into as many pieces (nodes) as you want and connect the pieces with sections of busway (branches) so you can see the current flow between each node in your power flow model.

 

[waross]

I'll go with DanDel;
As long as the load on each end does not exceed 5000A you should be safe. If the load on either end exceeds 5000A there is no generator arrangement that will help you.

 

[JensenDrive]

The question mentioned something about "paralleled bus." Would a 5000A bus consist of two parallel 2500A buses tied together at strategic locations? Does that affect the discussion? How would the two parallel busses be connected together? Just at the ends? Other locations?