Selection of Transformer Primary Configuration
Selection of Transformer Primary Configuration
(OP)
We have a 3-P system that is 21600 VLL or 12740 VLG. We typically use delta-wye transformers, but in this case we are considering a wye-wye due to availability. There is a 12470Y-480Y/277 transformer available that the vendor suggested we use. The idea is that the transformer may be connected to the 21600 system since the line to ground voltage will only be 12470.
Is it possible to use a wye 12470 V primary transformer on a 21600 VLL system? The vendor states that 21600 rated windings are only required if we are using delta.
Are there any references or codes that directly address this directly?
Thanks,
JC
Is it possible to use a wye 12470 V primary transformer on a 21600 VLL system? The vendor states that 21600 rated windings are only required if we are using delta.
Are there any references or codes that directly address this directly?
Thanks,
JC






RE: Selection of Transformer Primary Configuration
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Selection of Transformer Primary Configuration
I'm not completely sure I understand what you are saying here. Is it valid to connect a 12470Y transformer to a 21600 volt system?
RE: Selection of Transformer Primary Configuration
RE: Selection of Transformer Primary Configuration
Regards
Marmite
RE: Selection of Transformer Primary Configuration
Wye-wye is different than delta wye in a few ways:
1. No place for harmonics to circulate as well as transients. Basically you just complete a circuit.
2. A blown cutout can cause inductive tank heating. A 3 legged core is the most concern by far.
3. Zero sequence currents pass through. Any neutral current on the secondary shows up on the primary neutral.
A plus for some is a greatly reduced ferroresonacne risk where single phase switching takes place on circuits that are susceptible to causing it.
RE: Selection of Transformer Primary Configuration
RE: Selection of Transformer Primary Configuration
To guard against ferroresonance we have usually used wye-wye. In power transformers you can put a delta in the secondary for harmonics. Another thing that can be done is the site's individual equipment can be isolated with delta transformers to prevent harmonics from entering the overhead system.
JC