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Thread: The Wye/Wye

  1. #1
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    Default The Wye/Wye

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    Most are 120/208 or 277/480. There are others out there I know. I have seen a few other types.

    The following is from a GE transformer connections book copy righted in 1970.

    Y-Y connected transformers, excepting three-phase core-type units, are not capable of supplying an appreciable single-phase load from line to neutral without a serious shift in the position of the neutral, owing to the fact that the corresponding primary currents of such loads, flowing through the primaries of the unloaded phases, magnetize them. This statement is primarily true for Y-Y connected single-phase units and shell-type three-phase units. Core-type units, however, may, on account of the interlinking of the magnetic fluxes in the three legs, give tolerably good results under conditions of single-phase loads from line to neutral or unbalanced electrostatic charging currents.
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    I have only worked significantly on about 5 properties. No where have I worked that it was not stated that you "never float the Wye/Wye".

    I believe that it would work on strictly 3 phase as I have hooked several Delta/Wye and floated the secondary Wye. Oil field only. From that I'm sure that the reverse would work. But NEVER where single phase load might be involved.
    Last edited by wtdoor67; 03-11-2011 at 04:52 PM.

  2. #2
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    Default This is from a transmission and distribution book copyrighted in

    1954.

    The wye-wye- is used under the same condition and to supply the same mixed distribution loads as the delta-wye connection. The division of load between transformers is also similar to t hat of the delta-wye. CARE SHOULD BE EXERCISED IN MAKING THE WYE-WYE CONNECTION TO MAKE SURE THAT A WIRE CONNECTS PRIMARY BANK AND PRIMARY CIRCUIT NEUTRALS. iF NOT, TWO PRIMARY WINDINGS WILL BE IN SERIES BETWEEN EACH TWO PHASE WIRES.

    Current into a transformer from its phase wire can return only through the other two phase since there is no neutral return. Thus , the wye-wye without connected primary bank and primary source neutrals can operate satisfactorily only when the load is EXACTLY balanced between each phase and neutral on the secondary with equal phase to neutral voltages. Only then will the vector sum of the phase currents add up to zero at the neutral point so that the return current equal zero.

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    I am sure there are some out there but they are essentially wrong if so connected.

  3. #3
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    http://www.geindustrial.com/publibra...388B%7Cgeneric

    This bank only works if the load is "perfectly balanced", but that rarely if ever happens in the field.

    It was considered obsolete in 1910.

    Two simple questions have never been answered:

    1. Why would a utility build a bank that was not in their spec book and was shown unfeasible 70 years ago?

    2. Why would you (intentionally) build it when it is too easy to make one more connection....there are ZERO REASONS......unless, of course, it wasn't intentional?

  4. #4
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    Default Good article Jimmy. I damn near understand it.

    I love to yak about transformer connections but I'll admit I do most of it by rote as most hands do.

    I have seen quite a variety of hookups but I know there are probably many I haven't seen.

    As far as chief engineers at a Muni. I would doubt if they had a Bona Fide engineer at most of them. By this I mean a person with a double EE and probably a PE qualification. The Muni I worked at just had a supt. who was a person with a lot of experience as a Meter Relay Type and mostly just had a pretty good take on theory but was not a college educated type. The person prior to him was just an ex lineman and in conversing with him (he was retired) you would realize he was just an old hand who only knew about one way to do things. Eventually they did acquire a supt. with a double E and I think their subsequent supts. have been degreed engineers.

    Engineers are another interest of mine. I have seen many, as most have, that really had no take on how this stuff works, even though they had a sheepskin from major universities. Just a very few, in my opinion, that really understood and could explain the theories of electricity where the average hand could grasp it.

    A bunch of so called engineers with some co's are just technicians and most of their instructions for hook ups etc. are usually scrutinized pretty closely by the hands. Or should be anyway.

  5. #5
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    Default Yes Greg.

    I believed you built it alright, I just thought it was a screwup. However I had a short tenure at a Muni. About 40 to 50 thousand pop. when I worked for em. Saw some pretty dumb things while I was there.

    Come to think of it I saw some dumb things with a Utility. Maybe they're all the same. Ha.

  6. #6

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    They are out there, old school. But they soon learned that this connection overheated transformers and dramatically shortened the life of the TX.

  7. #7
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    We have determined this connection exists.

    We have determined they were found to be impractical as early as 1910.

    We have determined some places have used them recently enough for some of us to have seen them (though apparently Swamp is the only one who has ever built one "allegedly")......

    What we have not determined is why they would have been used?

    Why would a utility build one when the same voltage could be achieved using a standard connection and made safer for the equipment and the hands (any imbalance can result in high potential differences between any grounds and the neutral)?

    Barehander said they had a purpose, but what was it? I cannot find any reasons in any of the articles regarding this to even remotely suggest this connection should have been considered.
    Last edited by Boomer gone soft; 03-12-2011 at 01:46 AM.

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    Quote Originally Posted by Swamprat View Post
    Yup. Me too.
    I been tellin ya for years I hooked up a Wye Wye 208 with a floatin Neutral..... But, ya never believed me.
    35 years ago danny, there was ALOT of shit that was done different than today. "We've come a long way baby".

    The day I built it, I'd never seen or heard of one either. We were given the print, and told to build it. I even talked to my foreman about it. He said, "I've seen em, they're rare, but it works fine." Case closed. I built it, closed the doors....and Said...."I'll be god damned".
    Got in the truck, and went to the next job.
    This seems to be a different story than what you have been saying.

    You are now suggesting the secondary neutral was floating.

    What is the story? Was the high side floating as you have always contended or was the low side floating as you are now implying?

    Was it truly floating, or was it grounded but isolated from the system neutral?

    How did you energize the bank? Did you, as this implies, only close the doors and walk away; or were there other steps you are now omitting?

  9. #9

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    Quote Originally Posted by Boomer gone soft View Post
    We have determined this connection exists.

    We have determined they were found to be impractical as early as 1910.

    We have determined some places have used them recently enough for some of us to have seen them (though apparently Swamp is the only one who has ever built one "allegedly")......

    What we have not determined is why they would have been used?

    Why would a utility build one when the same voltage could be achieved using a standard connection and made safer for the equipment and the hands (any imbalance can result in high potential differences between any grounds and the neutral)?

    Barehander said they had a purpose, but what was it? I cannot find any reasons in any of the articles regarding this to even remotely suggest this connection should have been considered.
    You know something, some places in this world are still in 1910........some, 1 BC. It doesn't matter why this connection was used. You, Door, and others have used this to pound Swamp to discredit him. But, other people who read this stuff, need to understand that personal complaints about someone should not distort the facts about Linework. This site is about Linework, and yes, politics and personal grudges happens to be a part of the site.

  10. #10
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    You two want to be taken seriously, but don't answer simple questions?

    Interesting......

    Swamp, was it truly floating, or was it grounded but isolated from the system neutral?

    How did you energize the bank? Did you, as this implies, only close the doors and walk away; or were there other steps you are now omitting?


    BH, I would like to know why/what applications simply because I would like to know. If you don't know, just say so.

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