690VAC distribution in USA

[robinbreak]

Hi,
I am part of a Canadian company that is possibly going to be awarded a job in New Mexico, USA.

For this particular plant, as we're in the feasibility study phase, we are considering installing both a 690VAC MCC system and a 480VAC MCC system to build a steel shop plant.

I don't like two different low-voltage systems, so I'm trying to get it simplified.

Ideally, I would like to have only 690VAC through the plant, but I've been told that 690VAC is considered Medium Voltage in US?

What would that imply from the construction point of view? And what about commissioning/operation?

Is there a simple way to get the US codebook so I can give it a look?

Thanks in advance to anyone who will take the time to answer me.

 

[dpc]

Low voltage cables in the US have a standard insulation rating of 600 V. You'll need 1000 V cable for 690 V, which is going to be drastically more difficult to source. Also, transformer lead time will be worse for 690 V secondaries and transformer lead times are already horrendous even for standard voltages.

I've never seen a 690 V (nominal) 60 Hz motor. I'm sure they can be made, but you're just making things much more complicated and expensive than necessary.

I think 600 V would be a reasonable compromise.

 

[waross]

Lots of 1000 Volt rated cable out of Canada.
That may be a good choice for 600 Volt VFD drives.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[jraef]

I know Rockwell and Siemens provide 690VAC rated equipment (MCC, VFD, etc), but my worry is about long delivery spare parts for these components.

Yes they do, but it is all IEC designed equipment, no UL listing, and in New Mexico, you can't install it if it is not listed by an NRTL (such as UL). MCCs must be listed under UL845, which stops at 600V.

I have seen a few customers in the US install 600V for similar reasons, postulating that because Canada uses it, it is "readily" available. But that is a false equivalency. Yes, you can ORDER 600V equipment in the US and it will be UL or CSA listed, but you will WAIT for it. So once your facility goes on line and something breaks (and it WILL), the cost of down time for waiting for replacement parts will far exceed any perceived savings on using the higher voltage.

Don't do it.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[davidbeach]

Unless you're going to be defined as an 800lb gorilla, do what your neighbors do. Unless you're going to do enough of something that you can define the local market, go with what everybody else in the neighborhood is doing. It's like the case where 138kV is a perfectly acceptable transmission voltage but you'd be horribly stupid to use it around here where everybody uses 115kV. But 115kV would be a rather stupid voltage choice in a 138kV neighborhood.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[waross]

I used to look after a 13,200 Volt generation and distribution system next to a much larger 13,800 Volt neighbourhood.
If we had time, we would order a 13,200 Volt distribution transformer.
If we were in a hurry, we would get a 13,800 Volt transformer locally and set the taps high.
Our crew were good workers but not very technically inclined.
We got a 13,200 Volt transformer sent in. The boys set the taps up as if it was a local transformer.
Everyone on that transformer saw their consumption jump about 10%.
The manager checked the billing on the customers on each transformer each month to spot energy theft and noticed the 10% jump on one transformer.
As others have said, do what the neighbours do.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!