Transformer Phase Shift 2

[nightfox1925]

I looked and read a lot of threads in this forum regarding transformer vector groups. A FAQ sheet was laso readily available explaining the same.

My curiousity through drove me to raise this question. is there a criteria that governs us which vector group has to be chosen for a specific power system aside from paralleling requirements? Since I can vary the vector groups by making modifications on the winding connections, is it ok to specify different transformers with different delta-wye vector angles or is it required that all vector group angles should be the same? (For material stock purposes). Does phase shifting affect power flow?

GO PLACIDLY, AMIDST THE NOISE AND HASTE-Desiderata

 

[dpc]

For transformers built to ANSI standards, there are standard phase shifts. Different phase shifts can be specified when necessary, but life is much simpler if the standard is used.

For delta wye and wye delta transformers, ANSI standard is the the low voltage winding will lag the high voltage winding by 30 degrees.

There are some situations where a non-standard phase shift is required, as has been discussed.

 

[lansford]

Nightfox,
The second part of your question...Phase shift does not affect power flow.
JIM

 

[cranky108]

Under ANSI the phase shift is fixed, but the phase rotation into the transformer can reverse this shift into the oposit direction

 

[nightfox1925]

Thanks gentlemen. I was wondering if there is a phase shift related effects that pose as a requirement in specifying vector groups aside from transformer paralleling. Does this mean that all the vector group angles: 1, 5, 7, 11 are developed as options for us to choose with no technical requirment as to when to apply each one of them?

In our day-to-day job, we just specify the vector group angle as a matter of client standard requirement or when paralleling to an existing system. I just wanna know if there is a deeper reason of having lots of them in the first place.


GO PLACIDLY, AMIDST THE NOISE AND HASTE-Desiderata

 

[dpc]

If you are stepping down from one common system and ever want to tie the two secondaries together for any reason, the phase shift has to be the same, or else parallel operation is not possible.

As long as the secondary of the transformer is never connected to another power source, the phase shift is not a concern.

 

[nightfox1925]

Thanks for the enlightening responses. That erases my doubts on this subject matter which has been clinging my mind for a long time.

GO PLACIDLY, AMIDST THE NOISE AND HASTE-Desiderata