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240 Grounded B phase distribution #71907 11/10/06 12:09 AM
Joined: Sep 2006
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Almost Fried Offline OP
Member
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.

Work Gear for Electricians and the Trades
Re: 240 Grounded B phase distribution #71908 11/10/06 03:07 AM
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gfretwell Offline
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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.


Greg Fretwell
Re: 240 Grounded B phase distribution #71909 11/10/06 02:36 PM
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pauluk Offline
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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.

Re: 240 Grounded B phase distribution #71910 11/10/06 02:45 PM
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SteveFehr Offline
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We have a term for corner-grounded delta around here... "ground fault!"

Re: 240 Grounded B phase distribution #71911 11/10/06 04:00 PM
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gfretwell Offline
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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.


Greg Fretwell
Re: 240 Grounded B phase distribution #71912 11/11/06 11:18 PM
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WFO Offline
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We use corner grounded 3 wire 3 phase xfmrs. all the time on pump jacks in the oil field.

Re: 240 Grounded B phase distribution #71913 11/12/06 01:41 AM
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Almost Fried Offline OP
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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).]

Re: 240 Grounded B phase distribution #71914 11/12/06 09:09 AM
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SteveFehr Offline
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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!"

Re: 240 Grounded B phase distribution #71915 11/12/06 09:18 AM
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iwire Offline
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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?


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: 240 Grounded B phase distribution #71916 11/12/06 11:18 AM
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SteveFehr Offline
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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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