Interchanging phases and neutral of a 3 phase transformer LV secondary 3

[edison123]

A 11 KV / 415 V, 1600 KVA, Dyn11 transformer nameplate and secondary terminals.

Nameplate

Original – neutral at bottom and phases at top

Proposed – neutral at top and phases at bottom

Will this interchange of phases and neutral change the transformer characteristics in any way, like phase angle, polarity etc.?

This is a Dyn11 transformer. If I interchange the phase and neutral as above, will the phase angle change, for example to Dyn1?

Thanks in advance for your tips.


Muthu

http://www.edison.co.in

 

[prc]

It will become Dy5 vector group +positive polarity. But if you are working in isolated mode it may not create problem. Check the live clearances from bottom connections to ground.

 

[edison123]

Thanks, prc.

The vector group Dyn11 changed to Dyn5 because the current flow direction changed?

Muthu

http://www.edison.co.in

 

[prc]

Vector group shows the relative position of LV phase voltage with respect to HV phase voltage. The voltage vector changes from 11 o'clock position to 5 o'clock position when you interchange line and neutral.

 

[cuky2000]

Yes, It is possible to swap the connection of the neutral and the phase conductors converting the connection from Dyn11 to Dyn5 as mentioned by prc in the post above.
We should be aware that both connections have 180⁰ apart (+30⁰ & -150⁰). Therefore, make sure if there is the intention of paralleling two systems the phase displacement should be identical. Also if the changes are implemented, the relay and CT polarities should be reviewed.
By visual inspection, it appears that the phase to ground clearances are OK in both cases as indicated in the illustration below. Also, the physical view, connection diagrams, and phase-shifting vector group is shown as a result of swapping the neutral with the phases.

.....

 

[edison123]

Thanks, prc.

Thanks, cuky2000 for the great illustration.

Since this is not operated in isolated mode, I have decided to keep the original connections.

Muthu

http://www.edison.co.in