Utilizing Transformers at Other than Rated Voltages

[coloradog1]

All,

I am looking for information on the affects of utilizing transformers at system voltage levels which differ from the rating of a transformer. For example: utilizing a 161kV/20.9kV transformer on a 161kV/22.8kV power system. What will be the consequences?

Any references, papers, etc. would be appreciated.

Thank a bunch for your help.

 

[davidbeach]

Well, if you use the nominal taps your voltage will be low. How about a bunch more information about why you are asking the question and maybe you can get meaningful answers.

 

[coloradog1]

I have heard that if you have a spare transformer but the voltage(s) does not quite match your system, sometimes it can still be used. I was curious if there were any "rule of thumbs" or calculations you could perform to determine if a transformer is acceptable to use in this way and how it would affect the performance of the transformer.

 

[cranky108]

Most transformwers have no-load taps that can be used to correct for off nominol applications.

 

[davidbeach]

So does your hypothetical 161kV/20.9kV transformer have a tap that would put it closer to being a 161kV/22.8kV transformer? Better detail make for better answers.

 

[prc]

If your 20.9 Kv system and 22.8 Kv system are not interconnected,nothing will happen and you can use as such.If you are connecting together ie parallely operating, a circulating current among trfs will flow so as to reach a common voltage.Details of calculation-see IEC 60076-8 Application Guide for trfs.

 

[waross]

You will get 20.9 volts instead of 22.8 volts.
The difference is about 8%. You may get close with adjustable taps.
In my little system the nominal voltage is 13,200 V. The most readily available distribution transformers are 13,800 V. (The closest large utility uses 13,800 V and that is what is usually in local stock.)
When a 13,800 V transformer ends up on our system, we get about 115V instead of 120 V. We sometimes leave it, and sometimes bump down the taps. It depends!
We avoid using different transformer voltages in three phase banks.

Bill
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"Why not the best?"
Jimmy Carter