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#53119 - 06/17/05 08:32 PM 7200V Underground Cable 1300' Pull
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
Hey Folks, I'm back with some serious questions regarding a project Musser Electric has taken on.

We're installing a 7200V Primary Single phase cable (10KV, full neutral, #2 AWG Cu) in 3" Conduit between two Transformer pads. Open faced Transformers requiring Load Break Ells and Neither me nor Joe Musser have worked on anything above 600V. PoCo won't touch it, US Forestry land and privately owned by the Gov't. We bid it so high we never thought we'd actually get the job.

So, now we're scrambling...

Where can I find 10KV #2AWG Cu Cable (less than $3 a foot)? My supplier can only get 15KV - overkill by 2x.

We're also a little nervous about landing this cable with our limited knowledge of such potential.

Plus: How many pull boxes should we use? Can it be done in one pull?

Any and all advice is appreciated.

PS: Joe's brother who is the lineman we were hoping to use is canoeing the Colorado River right now and will be unavailable... Drat!

Thanks in advance...

-Virgil

[This message has been edited by sparky66wv (edited 06-17-2005).]
_________________________
-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

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#53120 - 06/17/05 11:45 PM Re: 7200V Underground Cable 1300' Pull
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Hi Virgil,
How long is the run?.
15kV would be under-kill, because of the line current.
7.2kV lines are roughly twice the size of 15kV for the same capacity of line.
Higher Voltage=Lower Current.
Regardless of that, get yourself some good Hot Gloves and Leather Outers.
ASTM Grade 2.
I can only say so much here, but I'll give a hand should it be required.
Sorry Virgil, I never saw the 1300 foot part of your post title.
Run it through HDPE or Rigid PVC,as your Codes allow.
In my own opinion I'd use 1 Core URD, for this run.
Also bear in mind, with this sort of run, ask your PoCo or read any guidelines they may have (you may be able to find them on the web), with regard to the burying of HV Lines.
My understanding of the rules is that you either cover the thing with cement or you bury a very hard and flat "Signal Strip" at half depth of the excavation.

[This message has been edited by Trumpy (edited 06-18-2005).]
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Let's face it, these days if you're not young, you're old - Red Green grin

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#53121 - 06/18/05 01:19 PM Re: 7200V Underground Cable 1300' Pull
Bob Offline
Member

Registered: 02/05/02
Posts: 182
Loc: Mobile, AL, USA
I just made pulling caculations for your installation using the following:
1 90 degree bend 4' radius
1 1300 ft straight run of 3" pvc
1 90 degree bend 4" radius

Caculations show no problems with the pull.

Rome Cable make a URD type cable #2 CU 15kv, .175 mils insulation, condentric neutral and PE jacket overall that will do the trick. If you do not know how to install the elbows, hire someone who does. It won't last if the installation is wrong.

Most Utilities use AL cable.


[This message has been edited by Bob (edited 06-18-2005).]

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#53122 - 06/18/05 01:38 PM Re: 7200V Underground Cable 1300' Pull
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
Welcome back.

I can not add much, the company I work for pulls a lot of highvoltage cable but we always sub out the terminations.

I agree with Bob the pull should be fairly easy.

I do not think we ever use copper high voltage cable.

Is it a specification?

[This message has been edited by iwire (edited 06-18-2005).]
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Construction & Maintenance Electrician
Massachusetts

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#53123 - 06/18/05 02:02 PM Re: 7200V Underground Cable 1300' Pull
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
This job is a "replacement" job, the X-formers and primary voltage are unchangeable at 7200V, do I still need the 15KV stuff or can I use 10KV?

The old stuff was direct buried and after being shut down for some sewer line work (where it crossed) when fired back up, it started shorting about every 10 feet or so each time it was patched. Lotsa crack and fissure in the insulation that was kept dry as long as it was kept warm... Ooops!

That's when we were called in...

MASTEC had been there and we figured they'd get the bid... Oops!

#2 Cu may not be required. I need to find out from Joe M. ... I wonder how much cheaper I can find say #1 Al?

Does anyone have a website I can search? I'm not having much luck weeding through the crap while googling. Heck, I'm even having trouble finding anything at Romecable.com ...

Oh, specs require magnetic warning tape and compaction every 6 inches of cover as well as "not being able to tell you were ever there after a couple of months growng season"(verbal quote).

The pull isn't that straight forward, although 2 90's (up at end) should be all we need. We have to cross two creeks and a swamp and it is US Forestry land at a lake resort (Lake Sherwood, WV)... We "...hit three trees and you're outta there" is what we were told. Plus even the grass seeding is specified to the nth degree. Even at just under $25K, we are going to run tight on this job unless I can get cable cheaper than $3 a foot.

HALP!

Thanks for the welcome back...

[This message has been edited by sparky66wv (edited 06-18-2005).]
_________________________
-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

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#53124 - 06/18/05 02:36 PM Re: 7200V Underground Cable 1300' Pull
Bob Offline
Member

Registered: 02/05/02
Posts: 182
Loc: Mobile, AL, USA
The std cable is 15 kv for 7200 volts.
#2cu is rated 150 amps and #1cu at 171 amps in conduit. #2 al is 119 amps and #1 al is 137 amps. What is the load?

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#53125 - 06/18/05 03:54 PM Re: 7200V Underground Cable 1300' Pull
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
Thanks Bob...

The load is assumed to be unchanged and the same size cable as before is allowed to be used which is #2 Cu, so we are told by a PoCo rep who worked on it the fateful day that it kept popping on them.

Other than that, we know it feeds a bath house and an RV park. Heck, 7200V at 100A, that's 3000A at 240 and it ain't got but a 200A 120/240V Panel on the secondary side of it... I think it will be OK without getting any algebra involved..

Thanks for all the help.
_________________________
-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

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#53126 - 06/18/05 05:30 PM Re: 7200V Underground Cable 1300' Pull
luckyshadow Offline
Member

Registered: 01/04/05
Posts: 305
Loc: Maryland USA
Sparky66-
I am in the Baltimore Md area. We use a small but good high voltage company to do all our HV work. They have been known to travel. How close to Baltimore / Washington DC are you ? I can have their number for you by Monday evening or Monday during the day if I had a number to call.
Email me if you want

[This message has been edited by luckyshadow (edited 06-18-2005).]

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#53127 - 06/20/05 10:19 PM Re: 7200V Underground Cable 1300' Pull
Nick Offline
Member

Registered: 08/13/01
Posts: 603
Loc: Riverside, CA
Virgil,
I have never seen 10KV rated cable. It usually goes 5, 8 then 15KV. 8KV would work but it seems the manufacturers don't offer it in JCN. Rome cable has shut down all their warehousing and distribution. To get cable from them these days they make it when you order it. That means unless some supplier has it on the shelf you'll need to order 10,000ft. Try Southwiwre, Okonite, Kerite, General Cable or Perelli.
Allot of high voltage contractors use 15KV cable and components on 5KV systems because they can be a little sloppier on the terminations and get away with it. Same would hold true with your 7200V system. I don't know how excited someone is going to be about traveling long distances for two terminations so your better off finding someone local. I would have to agree with Bob that if there not done right they won't last very long.
Keep us updated and send some pictures if you can.

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#53128 - 06/20/05 11:29 PM Re: 7200V Underground Cable 1300' Pull
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Virgil,
Just how high did you quote?.
It seems that converting a Buried Direct cable into individual wires in Conduit could be two different things.
11kV here is buried with a single 3 Core cable,
Neutral Screened if required.
Easy enough to bend and run through the conduit, provided there is enough lube.
With respect to protection, covering the conduit with concrete and then having a hard protection strip at half depth, would be enough here.
Where is Bjarney at a time like this?.
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

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