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#71907 - 11/09/06 08:09 PM 240 Grounded B phase distribution
Almost Fried Offline
Member

Registered: 09/04/06
Posts: 104
Loc: Madison County, Ark. USA
I am curious to know how common this configuration is? I first ran into it in KC, where it is all over the place. They use 2 pole gear, makes for some simpler setups where you have a lot of meters and gear for a single building.

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#71908 - 11/09/06 11:07 PM Re: 240 Grounded B phase distribution
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
I saw it on sewer lift pumps. That was just a motor load in a remote area so it made perfect sense. Simple and cheap.
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#71909 - 11/10/06 10:36 AM Re: 240 Grounded B phase distribution
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
KC = Kansas City?

I find corner-grounded delta an interesting configuration, as it's something we've never (to the best of my knowledge) used over here, at least not unless it was perhaps employed in the very, very early days.

It makes perfect sense for saving extra switch poles, fuses, etc.

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#71910 - 11/10/06 10:45 AM Re: 240 Grounded B phase distribution
SteveFehr Offline
Member

Registered: 03/19/05
Posts: 1192
Loc: Chesapeake, VA
We have a term for corner-grounded delta around here... "ground fault!"

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#71911 - 11/10/06 12:00 PM Re: 240 Grounded B phase distribution
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
I don't know why corner delta seems so strange to people. We ground transformer taps and use them as current carrying legs all the time.
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#71912 - 11/11/06 07:18 PM Re: 240 Grounded B phase distribution
WFO Offline
Member

Registered: 09/03/05
Posts: 206
Loc: Cat Spring, TX
We use corner grounded 3 wire 3 phase xfmrs. all the time on pump jacks in the oil field.

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#71913 - 11/11/06 09:41 PM Re: 240 Grounded B phase distribution
Almost Fried Offline
Member

Registered: 09/04/06
Posts: 104
Loc: Madison County, Ark. USA
Pauluk-Yes, the one and only Kansas City.

Steve F. please explain what you mean?

[This message has been edited by Almost Fried (edited 11-12-2006).]

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#71914 - 11/12/06 05:09 AM Re: 240 Grounded B phase distribution
SteveFehr Offline
Member

Registered: 03/19/05
Posts: 1192
Loc: Chesapeake, VA
I've never seen a corner-grounded delta used, but I have seen a lot of floating deltas on numerous switchboards. Naval ships use floating delta exclusively- even for single-phase circuits, both wires are "hot" legs of a 110/63V Delta. The idea is that if there happens to be a single phase ground fault, it won't interrupt power to the loads, and the worst a single-phase shock could be is 63V, which is especially important when you might be half-submerged in salt water at the time. I see it a lot in buildings, too, even some floating wye (with X0 ungrounded)- the reasoning is always the same; that a ground fault won't cause an unplanned outage.

So, when I hear talk of corner grounding a delta, I immediately think "Ground Fault!"

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#71915 - 11/12/06 05:18 AM Re: 240 Grounded B phase distribution
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
 Quote:
I see it a lot in buildings, too, even some floating wye (with X0 ungrounded)- the reasoning is always the same; that a ground fault won't cause an unplanned outage.


What kinds of buildings?
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Construction & Maintenance Electrician
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#71916 - 11/12/06 07:18 AM Re: 240 Grounded B phase distribution
SteveFehr Offline
Member

Registered: 03/19/05
Posts: 1192
Loc: Chesapeake, VA
IT and communications. Often the switchboards and generators are 480V delta with local power supplies providing 208/120Y to the electronics. This creates some problems, as TVSSs and UPSs don't work properly on floating delta, and can malfunction if the delta drifts too far from center.

[This message has been edited by SteveFehr (edited 11-12-2006).]

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