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Distribution transformer for phase reference

Distribution transformer for phase reference

Distribution transformer for phase reference

(OP)
Has anyone seen a distribution transformer used like a PT for syncing distributed generation?
What problems did you see?



 

RE: Distribution transformer for phase reference

Voltage is voltage, isn't it?

RE: Distribution transformer for phase reference

It was not uncommon to use distribution transformers as PT's in the utility I used to work for.

old field guy

RE: Distribution transformer for phase reference

(OP)
That's my thoughts. But the typical distribution transformer dosen't have polarty marks. And in there diagrams H1 lines up with X3, which is sort of confusing.

I am suspecting we have a 180 problem, but the needed 240 to 120 aux. might be messing with us also. (I suspect some wiring errors also).

So I'm asking if there might be something that I haven't seen (Like a phase shift).

RE: Distribution transformer for phase reference

Try this link:

thread238-204434: Transformer Polarity

You can also do a low voltage test with a primary and secondary bushing connected to determine polarity if necessary.

Alan

RE: Distribution transformer for phase reference

The Distribution transformer (DT) and the PT are designed for different purposes.
I foresee problems if DT is used for synchronising purpose:
1. The allowable Ratio error for DT is high, as high as 10%
2. The core of DT is allowed to saturate much earlier than PT giving rise to much higher errors if the voltage happens to be above nominal.
Referring to Instrument transformers IEC-60044 and comparing that with IEC 60076 (code for power transformers)could throw more light on the subject.  

RE: Distribution transformer for phase reference

The phase angle error will be negligible. You can close on a much, much  greater phase angle than any error differences in the transformers. If you calculate the voltage difference between two sources that are closed 10 degrees out of sync, you will see that voltage errors are not serious. If you see a voltage error after the first closing, this may be allowed for on subsequent closings.
Used as an unloaded PT, you can expect the voltage shown to be high by about the same percentage as the transformer regulation, hence the turns ratio error. (Not an error really, it is a calculated amount so that the voltage will be correct at full load.)

Bill
--------------------
"Why not the best?"
Jimmy Carter

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