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#23626 - 03/22/03 10:52 PM Single Phase service at 3500 amps
joeh20 Offline
Member

Registered: 03/21/02
Posts: 95
Loc: Tullahoma, TN, 37388
I stopped out by the local marina today. The guy that trained me 20 years ago was doing a major expansion for them, new floating resturant, 60 new slips, new fuel dock and all.
The local POCO never had anything but single phase down this dead end road that serves the marina area. Three phase is at least three miles away or further.
So to serve the new marina needs they built a 3500 amp single phase service. Set it up on a steel i beam platform 6 feet off the ground I guess in case of flood.
What is some of the larger single phase services anyone has seen or installed. I'll try to get some pictures, as it was quite neat and really professional installation.
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#23627 - 03/23/03 01:11 PM Re: Single Phase service at 3500 amps
C-H Offline

Member

Registered: 09/17/02
Posts: 1508
Loc: Stockholm, Sweden
Wow, that has to be one of the largest single phase services in the world! Is it a single transformer? 3500A at 120V works out to 420kVA! I better ask: Is it two 'hots' of 1750A each or 3500A per pole? In case of the latter I figure it'll be a 840kVA service?

Some pictures would be really cool!

[This message has been edited by C-H (edited 03-23-2003).]

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#23628 - 03/23/03 10:05 PM Re: Single Phase service at 3500 amps
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
That must be one helluva cable!.
I would have thought that a multi-phase supply would be utilised, in a case like this, with all of the single-phase loads, spread over these accordingly?.
We don't tend to use anything larger than 25 mm2, over here in NZ, for single phase houses, but this would be a toss-up, between this and poly-phase.
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#23629 - 03/24/03 12:14 PM Re: Single Phase service at 3500 amps
joeh20 Offline
Member

Registered: 03/21/02
Posts: 95
Loc: Tullahoma, TN, 37388
Lets see if this links to the service pics. The local poco would only give them a 167 kva Xformer. They said using monthly averages that was enough. Come Memorial day, they expect brownouts at the houseboats. http://community.webtv.net/GaryKidd/joeh20spics
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#23630 - 03/24/03 01:32 PM Re: Single Phase service at 3500 amps
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
Offhand, the phrase "extreme load diversity" comes to mind. 167kVA is the largest single-phase transformer I’ve come across, but in my case, always as part of a 208Y or 480Y bank.

Based on typical REA design, I can understand the reluctance to build more poleline. 7200 volts into 167000 voltamperes is less than 24 amperes on the primary. That seems like budgetary belt-tightening taken to a very high degree, but with the state of “deregulation” in the US, it’s not surprising.

One ANSI standard that deals with oil-insulated distribution transformer loading states: “Transformers may be operated above 110°C…for short periods provided they are operated for much longer periods at temperatures below 110°C…” and “Because the cumulative effects of temperature and time in deterioration of transformer insulation are not thoroughly established, it is not possible to predict with any great degree of accuracy the length of life of a transformer even under constant or closely controlled conditions, much less under widely varying service conditions.”

There may be some entertainment value in periodically checking the adjacent watthour-meter demand register, if one exists.

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#23631 - 03/24/03 04:18 PM Re: Single Phase service at 3500 amps
ameterguy Offline
Member

Registered: 05/17/02
Posts: 33
Loc: Mass
The 167 kva transformer is the largest size single phase unit our utility will install. Our construction and operating standards would have required us to extend the three phase primary to the above property & the electrician would have had to install a three phase service. As a huge single phase load has an adverse affect on a distribution systems balancing and voltage stability.

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#23632 - 03/24/03 04:46 PM Re: Single Phase service at 3500 amps
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
Typical utility boilerplate way out west: If the load requires a transformer installation in excess of 100 kva, the service normally will be three-phase.

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#23633 - 03/24/03 09:56 PM Re: Single Phase service at 3500 amps
joeh20 Offline
Member

Registered: 03/21/02
Posts: 95
Loc: Tullahoma, TN, 37388
The POCO offered three phase to the owners, but being a membership cooperative elecrical provider, they estimated the customer charge at $50,000. The nearest three phase is about 3 miles up the hill. Its a rather rural area.
If anyone fishes for Striper/Rockfish- Tims Ford Lake is one of the best, several fish over 60 pounds have been caught over the years, the marina in the photo is Holiday Marina just out of Tullahoma TN.
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#23634 - 03/25/03 01:01 PM Re: Single Phase service at 3500 amps
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
It’s hard to know what the total connected load is, but $3/foot for poleline rebuild is probably a fair price.

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