Has anyone ever had large aluminum AC BUS fabricated in a shop ? 1

[bdn2004]

A client is proposing to move a large transformer...20 MVA, 15kV-480V from one location to another to replace a similar transformer. The problem is the secondary bus on the proposed new location will have to be reworked and re-fabricated to fit it in right.
That works out to like 24,000 Amps per phase at 480V.

There are Utility type manufacturers that have stuff like this...and those have been investigated. The problem with that...everything right now is very long lead times.

On this site there are large aluminum DC Busses and AC busses that are available to be used that are in the scrap yard. There are also local companies that can cut and form aluminum.

But building that bus to spec so there are no hot spots, what kind of welds, bolts spacing etc, that's the question. Where do you find that info?

 

[waross]

A friend of mine was factory trained and certified to weld aluminum bus.
He said that any spots showing up on the x-ray had to be cut out and re-welded.
The x-rays had to be perfect.

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

 

[Overvoltage]

24,000A per phase? Ok, I've got to ask. What kind of process/manufacturer is this serving? Electroplating or something? That's a LOT of current at 480V.

 

[cuky2000]

Here are a couple of questions:
1) How many buses per phase are expected to meet 24,000 A?
2) What kind of protective device will be used to protect 24,000 A continuous?

 

[bdn2004]

This is an aluminum plant. Aluminum does not occur naturally on earth. It's an electrolytic process to make it that requires lots of DC Current. These are going to feed into a huge DC rectifier, 1 of 7 on that line.

We'd like to have 2 busses per phase, as there are two connections per phase on the rectifier input. That's what I'd like to find - the specs on how to do that.

One article we've found in the "Bus Conductor Handbook" say this:
"For large alternating current, particularly where space is critical, the interleaved arrangement of the bars (See Fig 29) is excellent. Skin effect and proximity effect are reduced to a minimum in this case, and the current carrying capacity, even on 60-cycles ac, is approximately the same as on dc." What they are showing is about 4 busses stacked like books with spacers in between them in Fig 29. That's an option.

There are lots of diodes in the rectifiers that I guess provide overcurrent protection on that side. The transformers have many sensors as well as overcurrent relays protecting them. These things are like 50 years old...so no one is complaining about that.

Another company did something similar a while back - and tried to do this with big high ampacity cables, many per phase. That proved not to be effective as the current did not distribute equally among the cables and they got very hot.

 

[FacEngrPE]

Aluminum Electrical Conductor Handbook

https://www.aluminum.org/resources/electrical-faqs-and-handbooks/electrical

has a section on buss conductors.

Chapter 13 Bus Conductor Design and Applications has some information about bolted and welded busbar connections.

The above is offered as a possible additional source of information. it is not my field, so I would not attempt a design myself.

Fred