×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Reversal of Transformer Phasing from Dyn11 to Dyn1

Reversal of Transformer Phasing from Dyn11 to Dyn1

Reversal of Transformer Phasing from Dyn11 to Dyn1

(OP)
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 on 33kV but to W-U-V due to base size and clearances etc. We cannot change the 3kV bus bars due to cost. We can change cables on 11kV side as they are replaced. I am a bit confused whether this connection will work. I have been told that by doing this I will change the vector group to Dyn1 instead of 11 but I don't know how it works. Normally there are links on LV side to convert Dyn11 to Dyn1 but not on this transformer (its an emergency replacement). I thought if we change the 11kV cables according to 33kV side (R-Y-B to w-u-v instead of v-u-w) it will be in phase with existing but there is definitely something I don't know. Phasing has never been my strongest area. Your expert opinion requested. I am in UK.

RE: Reversal of Transformer Phasing from Dyn11 to Dyn1

Connecting WUV as you describe should work as it retains the phase sequence. It's commonly called a "roll" in the UK. Do the same roll on both HV and LV sides. The way a Dy11 transformer changes to a Dy1 or vice versa is when you cross any two phases which changes the phase sequence, not when you roll them.
Regards
Marmite

RE: Reversal of Transformer Phasing from Dyn11 to Dyn1

(OP)
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 we can do anything on the LV side to bring it back to Dy11 as we cant chnage the winding connections. So unfortunately this is not a roll anymore. The only option would be to ratate the transfomer in such a way that U-V-W can be connected to R-Y-B as before. Or am I missing something?

RE: Reversal of Transformer Phasing from Dyn11 to Dyn1

(OP)
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 understand figure 11 for Dy11 transforer on page 13 but got very confused. The H and x representation looks OK but the UVW doesn't look right to me. Looks like V and W vectors need to be swapped unless I am missing something.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources