17.2kV Overhead Distribution Transformer Standard

[saladhawks]

The utility that I work for has finally decided to convert our existing 4.16kV Overhead System to 17.2kV. One of the first steps is the need to create a 17.2kV Overhead Distribution Transformer Standard in order to go out to bid. Since this is a somewhat unique primary voltage, I was wondering if any U.S. utility personnel on this site have an existing standard they could share with me for this voltage level.

Thanks in advance.

 

[jghrist]

Why 17.2 kV? You would end up using 25 kV rated equipment except for transformers, which would have to be made especially for your utility (are there others with this voltage?).

 

[davidbeach]

17.2kV would be a very bad choice. As jghrist hints at, most equipment has a 15kV class and a 25kV class. You will find very few standard voltages between 14.4kV and 20.8kV for a very good reason. Your line-neutral voltage of 9.93kV doesn't correspond to anything standard either. If you are going to force any primary service customers into 25kV gear for 2.2kV they aren't going to be particularly thrilled. 14.4kV would be a far better choice and if the surrounding utilities have a common distribution voltage that would be a great choice. Odd-ball always means higher costs.

 

[2000Kvar]

It is an old voltage though. Take a look at this link. This is a 17.2Kv setup in AZ.

http://www.omegape.com/projects/oaksub/index.html#Overview

 

[tinfoil]

Just because someone somewhere has used a particular voltage doesn't make it common!

Stick with a 'regionally common' voltage for your general area if you want to leverage purchasing power and existing knowledge bases.

You mentioned '4160' and 'U.S.', so I would expect that 15kV or 25kV (perhaps nominally 14400V L-G or 24970V L-L) would be far better choices.

 

[dpc]

REA, now RUS, used to have standard specifications - you might give them a call, or search their website.

Other than that, I'd suggest contacting Cooper or other manufacturers. I know Cooper has "sample" specs that would be a good starting point. You'll have to weed out anything that is overly proprietary, of course.

You'll have to decide if you're using single-bushing or two-bushing configuration, what accessories you want, and most importantly, what efficiency you're willing to pay for.

FWIW, I agree (mostly) with other comments on voltage level. I've never seen it, but if it's common in your area, then maybe you're OK. In the Northwest we see 20.8 kV and some 23 kV - in addition to normal hodgepodge of 12 kV, 12.47 kV, 13.2 kV, and 13.8 kV. If you're going to jump over 15 kV level, you might as well jump up a little higher than 17.9. You'll get more kVA per $$.