Transformer Primary Voltage & Tap Changers

[sjohns4]

I'm looking to possibly re-cover and re-use some 25 & 50 kVA single phase distribution transformers. We're a primary power customer on a 13.2kV / 7.6 kV system. The transformers are name plate 13200GRDY / 7600 HV and have 2x2.5% taps over and below nameplate. By my math, with the tap changer at the extremes the transformers would be suitable for 7220 Volt to 7980 Volt, so assuming the system was running pretty close to nominal voltage, could these same transformers be used on a 12470/7200 or 13800/7970 primary system?

If it'll work, how likely is it anyone will care (i.e. utility, inspectors, etc.)?

I usually live on the secondary side of transformers and this, to me, sounds like a 208V vs 240V thing.

I'm asking because I have no idea what part of the country or who's system we'll be connected to next.

Thanks,

Mike

 

[waross]

could these same transformers be used on a 12470/7200 or 13800/7970 primary system?

It depends on the actual voltage of the nominal 12470/7200 or 13800/7970 primary systems.
Some systems start with higher than nominal voltage at the substation. Due to line losses the voltage tends to drop with distance until it is below nominal. Voltage regulators may be used to boost the voltage back above nominal and the voltage again drops with distance.
Voltages, voltage regulators settings and transformer taps are a compromise.
The best answer to your question?
It depends.


--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[edison123]

Since the turns ratio is almost the same in all 3 cases, I don't see why not as long as they are of the same frequency.

Muthu

http://www.edison.co.in

 

[waross]

What edison says.




--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[prc]

You can use the transformer at 12.47/7.2 kV condition without any tap changing. If situation is 13.8/7.98 kV , then also you can use as such but transformer will be over fluxed by 5 % . This is acceptable with extra iron losses and noise. But if you want 7.6 kV with 13.8 kV incoming, put the transformer on maximum tap.

 

[sjohns4]

Thanks all. The concept seemed too simple to actually work.

Mike

 

[bacon4life]

These sound like single bushing 7600 V[sub]line to ground[/sub] transformers with normal 120/240 V low sides. If you adjust taps, the transformers will typically work on either system.

Some areas of the USA require transformers that connect line-to-line rather than Line-to-ground due to operating an ungrounded 15 kV system.