wye primary

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electrofelon said:
when, if ever, would you connect the neutral of a wye system to the primary along with the ungrounded conductors?
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Your question is extremely vague. There must be a reason for your question.
Is this a test question or is it simply curiosity? I can think of one very common application that could be answered in one simple reply but there are also other less common applications also.
 
electrofelon said:
Just a general question. I just cant think of when it would be necessary or what it would accomplish, and there have been multiple threads on here recently when the consensus was to leave it off.....So wye land it :) ?
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There are times that you do but the OP has neglected to provide any information about the application and as such there are times that you don't.
To provide a answered as you have done may be a correct answer but it is based upon an assumption.
 
templdl said:
There are times that you do but the OP has neglected to provide any information about the application and as such there are times that you don't.
To provide a answered as you have done may be a correct answer but it is based upon an assumption.
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I dont quite understand your response. Perhaps you didnt notice I was the original poster and responding to you not the OP?
 
electrofelon said:
I dont quite understand your response. Perhaps you didnt notice I was the original poster and responding to you not the OP?
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I restate my original reply:
"Your question is extremely vague. There must be a reason for your question.
Is this a test question or is it simply curiosity? I can think of one very common application that could be answered in one simple reply but there are also other less common applications also."
OK, well start with the question and answer routine as it is difficult to provide a diffinitive answer while being provided very limited information.
Is your question in regards to a POCO substation or other power distribution transformer where a wye primarary is commonly used or may I venture to guess that you are referring to a 480d-208y/120 transformer being used to step up from 208v 3ph- 480v 3ph.
Often people ask questions in a way to get an answer that they want wa
 
templdl said:
I restate my original reply:
"Your question is extremely vague. There must be a reason for your question.
Is this a test question or is it simply curiosity? I can think of one very common application that could be answered in one simple reply but there are also other less common applications also."
OK, well start with the question and answer routine as it is difficult to provide a diffinitive answer while being provided very limited information.
Is your question in regards to a POCO substation or other power distribution transformer where a wye primarary is commonly used or may I venture to guess that you are referring to a 480d-208y/120 transformer being used to step up from 208v 3ph- 480v 3ph.
Often people ask questions in a way to get an answer that they want wa
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My previous reply was cut off at the bottom and as such this is a resend:
"Your question is extremely vague.
Is this a test question or is it simply curiosity? I can think of one very common application that could be answered in one simple repother less common applications also."
OK, well start with the old question and answer routine as it is difficult to provide a diffinitive answer while being provided very limited information.
Is your question in regards to a POCO substation or other power distribution transformer where a wye primarary is commonly used or may I venture to guess that you are referring to a 480d-208y/120 transformer being used to step up from 208v 3ph- 480v 3ph.
Often people ask questions in a way to get an answer that they want to hear. Without being provided with more information about what you are trying to do there are may answers to what appears to be a simple but the answer can include numerous senerios unless you can be more specific.
Just tell me about the transformer and what you're trying to do.
 
This is commonly done by utilites on underground distribution systems to prevent ferroesonance when the supply switches can be operated one pole at a time. See IEEE Std 142-2007 starting on about page 30 if you have access.
 
SG-1 said:
This is commonly done by utilites on underground distribution systems to prevent ferroesonance when the supply switches can be operated one pole at a time. See IEEE Std 142-2007 starting on about page 30 if you have access.
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Most awesome, Thanks. What you have described so well is an application that most are not familiar with.
I would be enclined to "assume" that he may be referring to using a common 480v delta to 208y/120 step down transformer as a step up transformer but I'm reluctant to answer based upon my assumption.
Unless the OP can define his application it would be irresponsible for us to submit a reply based upon guessing what he means. It's similar to pulling teeth.
 
templdl said:
Most awesome, Thanks. What you have described so well is an application that most are not familiar with.
I would be enclined to "assume" that he may be referring to using a common 480v delta to 208y/120 step down transformer as a step up transformer but I'm reluctant to answer based upon my assumption.
Unless the OP can define his application it would be irresponsible for us to submit a reply based upon guessing what he means. It's similar to pulling teeth.
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This is a purely academic question - not working on something or trying to do something. Just dont understand what have the primary neutral in the mix would accomplish. For the sake of the discussion lets assume NEC systems, both primary and secondary 600 volts or less. Does that help?
 
According to Transformers for The Electrician page 90, the common point of the wye primary should be connected to a system neutral for a wye to delta transformer or there may be voltage fluctuations with unbalanced loads on the secondary delta side.
 
electrofelon said:
when, if ever, would you connect the neutral of a wye system to the primary along with the ungrounded conductors?
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I am trying to understand exactly what you are asking.

If you connect all those points together you have a pretty good fault current, or else I am not understanding what you are talking about. You could do so beyond an open switch as extra safety should the switch get closed for some reason when doing work on the lines.
 
kwired said:
I am trying to understand exactly what you are asking.

If you connect all those points together you have a pretty good fault current, or else I am not understanding what you are talking about. You could do so beyond an open switch as extra safety should the switch get closed for some reason when doing work on the lines.
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I think he is just asking when should you use the primary neutral on a Wye-wye or Wye-delta transformer & what is the problem if you should connect the neutral & do not.
 
SG-1 said:
I think he is just asking when should you use the primary neutral on a Wye-wye or Wye-delta transformer & what is the problem if you should connect the neutral & do not.
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This is the problem with vague question. If the question was specific then the answer can be provided directly for that question. If it is vague either a reference book or resource can be given so that the OP can take the time read about the "subject" them selves. You may notice that when a question is vague and not specifics it generated a lot AF answers based upon assumptions, guesses, "I think that what he means" which can be misunderstood by the OP otherwise he would have been more specific with his question
From my perspective I would venture to " guess" that he may be referring to a delta/wye step down transformer that is intended to be used as a step up transformer where you are feeding the wye. If the supply is a 208y/120 and you have L1-L2-L3,N,G and the transformer's X1,X2,X3,X0 how do you connect them. I have found that it was not all that unusual for the primary of a transformer to order with a wye primary based upon their supply being a 208y/120. Yes, it happens.
I have to explain that when using a 480d-208y/120 as a step I instruct them to just bring out the 208 L-L-L and EGC conductors only, no need for the neutral. Make sure that the X0 of the transformer is unbounded from the transformer enclosure leaving the X0 floating, simply terminating the lines to the X connection on the transformer and the EGC to the frame/enclosure of the transformer.
But that is simple. What has been avoided if my scenario is true what do you do with a 480v delta secondary? Are they familiar with ungraunded/grounded/ground detection, etc? Feeding a wye primary is simpler to address that the understanding of what to do whith a Delta secondary.
Is this the actual application that the OP may be referring to?
 
SG-1 said:
I think he is just asking when should you use the primary neutral on a Wye-wye or Wye-delta transformer & what is the problem if you should connect the neutral & do not.
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You got it. Sorry Didn't Think I Was Being Vague. Assumed it was obvious when I said "connect the neutral of a wye system to the primary...." that I was talking about a wye primary transformer, but people do propose some wacky things. .... I have to digest templdls reply then I'll respond
 
templdl said:
This is the problem with vague question. If the question was specific then the answer can be provided directly for that question. If it is vague either a reference book or resource can be given so that the OP can take the time read about the "subject" them selves. You may notice that when a question is vague and not specifics it generated a lot AF answers based upon assumptions, guesses, "I think that what he means" which can be misunderstood by the OP otherwise he would have been more specific with his question
From my perspective I would venture to " guess" that he may be referring to a delta/wye step down transformer that is intended to be used as a step up transformer where you are feeding the wye. If the supply is a 208y/120 and you have L1-L2-L3,N,G and the transformer's X1,X2,X3,X0 how do you connect them. I have found that it was not all that unusual for the primary of a transformer to order with a wye primary based upon their supply being a 208y/120. Yes, it happens.
I have to explain that when using a 480d-208y/120 as a step I instruct them to just bring out the 208 L-L-L and EGC conductors only, no need for the neutral. Make sure that the X0 of the transformer is unbounded from the transformer enclosure leaving the X0 floating, simply terminating the lines to the X connection on the transformer and the EGC to the frame/enclosure of the transformer.
But that is simple. What has been avoided if my scenario is true what do you do with a 480v delta secondary? Are they familiar with ungraunded/grounded/ground detection, etc? Feeding a wye primary is simpler to address that the understanding of what to do whith a Delta secondary.
Is this the actual application that the OP may be referring to?
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Yes that is one scenario, although just a little more specific. Perhaps a better rewording of the original question would be "given a transformer with a wye primary and a wye system supply, are there situations when you do or don't connect the primary neutral to the primary xo? If so what?"

Templdl from your scenario, what happens if the neutral is connected? Does the answer change if the secondary is left ungrounded vs corner grounded?
 
electrofelon said:
Yes that is one scenario, although just a little more specific. Perhaps a better rewording of the original question would be "given a transformer with a wye primary and a wye system supply, are there situations when you do or don't connect the primary neutral to the primary xo? If so what?"

Templdl from your scenario, what happens if the neutral is connected? Does the answer change if the secondary is left ungrounded vs corner grounded?
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Thanks for following up.
I can't think of any common applications where using a day as a step up where the X0 would be connect to the supply neutral.
Think about it, if you connect the wye as you are questioning draw out a wye (star) winding draw a line from each line of the supply to X1,X2,X3 of the wye. The connect the neutral of the supple to the X0 where the 3 windings meet to the center. The bring out the EGC to the transform keeping in mind that thevX0 it connected to the frame of the the transformer with a bonding strap are jumper.
Don't consider any load on the transformer, consider it yo be unloaded.
As such you will have current from each line of the supply to the XO back to the source neutral and there isn't any load on the transformer at all. Then consider that the supply neutral and EGC are connected together at transformer an now you have current on the EGC and the transformer still isn't loaded.
There is no reason to not remove the bonding strap/bumper and just leave the X0 to float. All that is required is to connect the 3 phases to X1, X2, and X3.
On a very rare occasion I have supplied a Y-Y but it had to do with maintain a phase relationship between the primary and secondary an how that sendary phase may be related to the secondary phase of another system. There are other design reasons for both Y-D and Y-Y.
Keep in mind that the are occasions where there is a need to parallel supplies amd it extremely important that the paralled sources be in phase. The common D-Y transformer design is DY11 where the Y lags the D by 30deg as I can recall. With a Y-Y the phase relationship is zero phase shift.
The important thing is that you really seem interested in this stuff do some research on transformer vector diagrams as well as transformer connection as may have innocently opened up a can of worms be as kind some probing questions.
 
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