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Thread: Faults with Transformers

  1. #21
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    Quote Originally Posted by Ingenieur View Post
    starting on 174 http://www.zmuda.ece.ufl.edu/Fall_20...Components.pdf
    good explanation

    page 193 shows yg:d

    a ground fault on the y will cause a current to circulate in the delta, in essence, that is the 'ground fault current'
    Thats 100% rue, but I mentioned delta- wye, meaning power is "going" into the delta primary and out the wye secondary. You are thinking the opposite.
    I'm in over my head...

  2. #22
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    Quote Originally Posted by mbrooke View Post
    Thats 100% rue, but I mentioned delta- wye, meaning power is "going" into the delta primary and out the wye secondary. You are thinking the opposite.
    glad you agree facts are 'true' lol
    you misunderstand the concepts
    why do you think they only show a yg;d? because it identical to a d:yg, only signs change
    pretty sure I know the difference between the prim and sec
    the term is power is 'delivered' to the prim, and 'supplied' to the load by the sec
    doesn't matter though
    the sequence components are the same
    if Y sec, the fault circulates in the delta prim
    has to, the fault dissipates energy/power and it has to come from somewhere, and the only somewhere is the prim
    The difference between genius and stupidity is that genius has its limits.

  3. #23
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    Quote Originally Posted by Ingenieur View Post
    glad you agree facts are 'true' lol
    you misunderstand the concepts
    pretty sure I know the difference between the prim and sec
    the term is power is 'delivered' to the prim, and 'supplied' to the load by the sec
    doesn't matter though
    the sequence components are the same
    if Y sec, the fault circulates in the delta prim
    has to, the fault dissipates energy/power and it has to come from somewhere, and the only somewhere is the prim
    And, as I said, in delta wye zero sequence current will not pass through. Your basically confirming what I'm saying.
    I'm in over my head...

  4. #24
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    Quote Originally Posted by mbrooke View Post
    And, as I said, in delta wye zero sequence current will not pass through. Your basically confirming what I'm saying.
    what you are saying is like saying 'a dog is not a cat'
    zero seq can't exist in a delta
    but fault current can, and it circulates in the delta
    look at the math in the text

    but we digress
    xfmr's are not used for fault reduction
    CLR
    I limiting fuses
    NGR's or NGZ's for gf's
    etc
    The difference between genius and stupidity is that genius has its limits.

  5. #25
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    Quote Originally Posted by Ingenieur View Post
    what you are saying is like saying 'a dog is not a cat'
    zero seq can't exist in a delta
    but fault current can, and it circulates in the delta
    look at the math in the text

    but we digress
    xfmr's are not used for fault reduction
    CLR
    I limiting fuses
    NGR's or NGZ's for gf's
    etc


    I don't think we even disagree- what I said was that a delta wye will not pass zero sequence current- you mistook that for wye grounded delta.


    In regards to fault reduction, why wouldn't a trafo be used? Is cost what you have in mind?
    I'm in over my head...

  6. #26
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    Quote Originally Posted by mbrooke View Post
    I don't think we even disagree- what I said was that a delta wye will not pass zero sequence current- you mistook that for wye grounded delta.


    In regards to fault reduction, why wouldn't a trafo be used? Is cost what you have in mind?
    BOTH will see the fault reflected
    the math is the same for yg:d or d:yg

    there are many better and less costly waysvto do it
    research 'current limiting reactors'
    The difference between genius and stupidity is that genius has its limits.

  7. #27
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    Quote Originally Posted by Ingenieur View Post
    BOTH will see the fault reflected
    the math is the same for yg:d or d:yg

    there are many better and less costly waysvto do it
    research 'current limiting reactors'
    No need to research, I've personally seen current limiting reactors (air type) put on 23kv feeders to limit current. I've also seen power plant single lines where 480:277/480 trafos were used to reduce fault current- but to be fair a lot of those had ungrounded systems and it was to get a neutral for lighting- however fault current was still in the consideration.

    I agree, a trafo is perhaps the most expensive way out of a dozen, but still technically possible.


    But I do get your point- and I think we can agree on this one.
    I'm in over my head...

  8. #28
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    Quote Originally Posted by mbrooke View Post
    ...I've also seen power plant single lines where 480:277/480 trafos were used to reduce fault current- but to be fair a lot of those had ungrounded systems and it was to get a neutral for lighting- however fault current was still in the consideration.

    I agree, a trafo is perhaps the most expensive way out of a dozen, but still technically possible.


    But I do get your point- and I think we can agree on this one.

    the 480 d: 480 y was to derive a neut as you said
    not fault limitation
    if it already were y they would insert a y:y iso xfmr to reduce i fault

    techically possible
    not economically feasible and there are much better ways
    that is why it is never done
    The difference between genius and stupidity is that genius has its limits.

  9. #29
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    Quote Originally Posted by Ingenieur View Post
    if it already were y they would insert a y:y iso xfmr to reduce i fault

    I have yet to see a Y-Y 600 volt and under transformer. Sure you could custom make one (MGM does it https://www.mgmtransformer.com/ ), but an off the shelf delta wye will do. Saves on N wire as well. So even if fault current was purely a concern and the supply was wye, the trafo would still be delta wye.
    I'm in over my head...

  10. #30
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    Quote Originally Posted by mbrooke View Post
    No need to research, I've personally seen current limiting reactors (air type) put on 23kv feeders to limit current. I've also seen power plant single lines where 480:277/480 trafos were used to reduce fault current- but to be fair a lot of those had ungrounded systems and it was to get a neutral for lighting- however fault current was still in the consideration.

    I agree, a trafo is perhaps the most expensive way out of a dozen, but still technically possible.


    But I do get your point- and I think we can agree on this one.
    those reactors are shunt, not series
    different function
    The difference between genius and stupidity is that genius has its limits.

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