Regulating transformer 1

[NewbieButTrying]

66kv/7kv substation bank. Consists of 3-10,000kva single phase transformers, and 1-regulating transformer/LTC.

question: What should the KVA rating be on the regulating transformer?

 

[Skogsgurra]

Normally same as transmitted power times regulation range. So, if regulation is +/- 5 percent, you have a 10 percent regulation range. Or 0.1 of total voltage. That would mean 10000x0.1 = 10 kVA on each transformer. Or something close to that number.

Gunnar Englund

http://www.gke.org

 

[tinfoil]

If you want say +- 10%, you use the same windings both ways (to 'boost' or 'buck' the voltage) in the regulator, with a reversing connection when the unit is in neutral.

Your 3 phase bank has a total kVA rating of 30,000kVA (30 MVA). Therefore, you need 10% * 30MVA or 3MVA (3000kVA) rating on your automatic regulator.

Make sure that you consider the maximum possible ratings, as there may be fans available to increase ratings on either the regulator or the 3 power transformers (or both).

 

[NewbieButTrying]

Thank You Tinfoil

I have 2 other banks, basically identical to the one I asked about. On those two, the LTC's has a kva rating of 3000kva.

The one i was inquiring about, has a nameplate rating of 36500 kva. Obviously an error. I first thought maybe they ment 3"phase" 6500 kva. But now that doesn't make sense either.

I am a lineman that is just starting to learn what goes on "inside" the substation. Every day is a learning experience.

Thanks

 

[tinfoil]

I suppose it's conceivable that it is describing 'throughput' as opposed to 'energy transformed', although I am not familiar with that practice.

Check to see if there are Amp ratings as well as kVA. That should sort it out.

 

[stevenal]

Different IEEE standards apply to voltage regulators than to power transformers with LTCs even though they may be functionally the same. Regulators are sized by the amount of regulation they do. Power transformers (including autotransformers with LTCs) are sized by their thoughput. Outside the USA it may be different. As tinfoil indicated, any current rating should be a throughput value.

 

[NewbieButTrying]

Thanks for the info. Unfortunetly, the LTC in question only has 36500 kva listed. I imagine I'll finally get the bottom of this. Guess I'll just put this on the back burner and keep on learning.
thanks

Newbie

 

[stevenal]

Newbie
What country are you in and who's the manufacturer?

 

[NewbieButTrying]

Stevenal,
I'm in southern California, the U.S. of A.
And the manufacturer is GE, circa 1950.