WYE - WYE?

[arrehman1]

Why Wye?

Why Wye?

It is my understanding that

historically, when power transformers were first connected in WYE- they were ungrounded. Which caused a ton of problems. Most issues with wye connected transformers are resolved when they are grounded. I'll try to find this awesome article I read once by GE Transformer Design team back in the day.

 

[arrehman1]

The Why of the Wyes

The Why of the Wyes

here the the GE white paper on the Wye winding... be warn - it' super technical.

"The Why of the Wyes" --> http://files.engineering.com/downlo...fe-ae2985db6804&file=GE_Transformer_Paper.pdf

 

[iceworm]

OK-
Going back to my original post,
When these transformers failed, say because of a phase loss on the HV side or primary arcing externally, what actually would cause them to explode and burn up? I understand over pressurization and flammable gas...
But what happened to the transformer itself?:?

Is this type of failure more common in a wye vs delta primary?

The over current protecton switch is set to NESC instead of NEC. An internal xfm failue does not trip the primary feeder. Couple that with the utilities tend to operate service transformers significantly over loaded (read "hot"). Add lack of maintenance for smaller (1000 kva and smaller) transformers.

My personal opinion (possibly an informed opinion) -- No

ice

 

[JRW 70]

Transformer Fusing

Transformer Fusing

In our system the fusible cutout fuses are coordinated to
protect the distribution line first and foremost so reclosers
or substation breakers don't trip. The transformer is not
the driving factor (in so far as it's protection), but keeping
as much of the system on line at any given time, after all
that's what keeps us paid.
Now on the flipside, where I work in our generation div.
the step up transformers are all protected to near rated
capacity and the c.b.'s and fusible elements are definately
sized for bussing and transformer protection. They are not
"disposable" items like distribution equipment.

As a side note, most of our transformer failures are not
catastrophic like mentioned above. I'm sorry to hear about
this, as most staff (at least where I have been) do care
about the safety of what's installed out there. But unfortunately,
economic forces come into the calculation and things like this
can and will happen

JR