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  1. SMA7875

    Reversal of Transformer Phasing from Dyn11 to Dyn1

    dpc, Thanks. I found the FAQ a few hours ago and went through it. It really helped me understanding the pahsor references, vector group conversion and roation. All, The above FAQ has a reference to Basler Electric Company paper (http://www.basler.com/downloads/3phXfmrs.pdf). I was trying to...
  2. SMA7875

    Reversal of Transformer Phasing from Dyn11 to Dyn1

    Thanks for your answer Marmite, Sincere apologies for a mistake in original post. When we rotate the transformer physically, only U and W bushings are swapped whereas V remains in the middle. This would mean a swap of only two phases or a transformation to Dy1 instead of Dy11. And I dont think...
  3. SMA7875

    Reversal of Transformer Phasing from Dyn11 to Dyn1

    Hi, Come across a situation where an old 33/11 Dyn11 transformer has to be replaced. The old transformer was connected R-Y-B to U-V-W bushings on 33kV side and R-Y-B to u-v-w on the 11kV side. The new transformer orientation is such that it is very difficult to connect R-Y-B to U-V-W bushings...
  4. SMA7875

    Two LV bus bars with Transformer Different Phasing / Phase Rotation

    Many thanks for your responses. The problem was all 132kV connections for GT5 are done, would be a disaster to chnage, we couldn't switch off or change VT earth for GT3 and the 132kV tie breaker due to load demands however we have done some more voltage measurments between GT3 132 and 11 and GT5...
  5. SMA7875

    Two LV bus bars with Transformer Different Phasing / Phase Rotation

    Thanks Marmite, I am also thinking on the same lines as the results suggest it. My biggest worry is if we need to alter the HV side of GT5 which would be a disaster as it is all built and bus bar connected in a tight old yard. I am not very good with vector diagrams and phase rotation. Is there...
  6. SMA7875

    Two LV bus bars with Transformer Different Phasing / Phase Rotation

    I understand that for a Red / Blue HV cross for GT3 would be matched by an Red / Blue LV cross on GT5 as both are Y0y0. However when we ran simple voltmeter tests on VT secondaries (yellow phase earthed, I am in UK), it didn't phase out and the vector diagram from the readings showed something...
  7. SMA7875

    Two LV bus bars with Transformer Different Phasing / Phase Rotation

    Stevenal, Thanks for your response. During the normal operation when the bus bars are running separately with the interconnector breaker open, its OK, however when one of the transformer is out of service, and we have to close the interconnector breaker, the previosuly Red phase on, say, GT5...
  8. SMA7875

    Two LV bus bars with Transformer Different Phasing / Phase Rotation

    Hi, We have come across an issue where we need to connect two 132/11kV power transformer LV (11kV) bus bars in parallel through an interconnector. The vector group of both is YN0yn0 however the HV bushing of one of the transformers is connected as Red phase to C Bushing, Yellow Phase to B...

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