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    ikasudar's Avatar
    ikasudar Posts: 1, Reputation: 1
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    #1

    Jul 13, 2011, 02:06 AM
    Effect unbalance load on transformer?
    What is effect unbalance load on transformer? For Distribution Transformer 150/20 kV 60 MVA Ynynd1 with solid earthing.
    There is typical setting recommendation for unbalance load??
    sinnadurai's Avatar
    sinnadurai Posts: 127, Reputation: 2
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    #2

    Jul 16, 2011, 03:53 AM
    What do you mean by Ynynd1,is it a 3winding transformer,if so what is the rating of thirdwinding?
    sathe1963's Avatar
    sathe1963 Posts: 97, Reputation: 4
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    #3

    Jul 17, 2011, 08:15 AM
    Primary winding is star connected. Secondary winding is also start connected. Tertiary winding is delta connected. Third winding is meant for nullifying 3rd harmonic effect. Normally, load is not connected to this winding.
    sathe1963's Avatar
    sathe1963 Posts: 97, Reputation: 4
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    #4

    Jul 17, 2011, 08:23 AM
    The transformer shall not be unbalance loaded more than 15-20%. More the unbalance load... more the unbalance current flown through through neutral earth. Transformer efficiency drastically reduced.
    sinnadurai's Avatar
    sinnadurai Posts: 127, Reputation: 2
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    #5

    Jul 18, 2011, 03:16 AM
    There are unbalance relays for voltage as well as for current. You may install both and set them accordingly (% variation)to suit the performance of the load as recommended by manufacturers of Motors,VSD etc
    sathe1963's Avatar
    sathe1963 Posts: 97, Reputation: 4
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    #6

    Jul 18, 2011, 07:46 AM
    Voltage or current unbalance relays are directly applied / connected on the motor feeder not on the transformer feeder.
    sathe1963's Avatar
    sathe1963 Posts: 97, Reputation: 4
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    #7

    Jul 18, 2011, 07:51 AM
    Capital y indicates star connection on hv winding. Small n against the same indicates neutral is brought out.
    Small letter y indicates lv winding start connection. Small n against the same indicates neutral is brought out. d1 indicates; third winding is delta and vector is at 1 o'clock position i.e. at 13.00 hrs. position; means leading by 30 degree than the primary.
    sinnadurai's Avatar
    sinnadurai Posts: 127, Reputation: 2
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    #8

    Jul 18, 2011, 07:24 PM
    Comment on sathe1963's post
    Yeah.I didn't say fix on transformer feeder. If you say unbalanced load on transformer it means load connected to the secondary
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