What Are Typical Impedance Values for Power Plant Transformers?

[Idea04]

When it comes to power plant transformers, What is the typical inductance and impedance on the primary winding?

 

[jedishrfu]

http://www.scribd.com/doc/27073343/Transformer-Engineering

 

[jim hardy]

that's an excellent reference, j-rfu.

Impedance is indeed given in Per Unit, % of nominal nameplate ratings.
Transformers for our internal distribution were a few percent, 2 to 5 -ish.

Our main transformer (the one connecting generator to grid) was 17% .
The impedance will be mostly inductive so as to not waste kilowatts as heat.
Electrical system designers spend a lot of time optimizing voltage drops so everything stays within ~10% over operating range of plant.

The main transformer connecting generator to grid was 894MVA so you can see what 0.1% loss would be in kw - almost a megawatt . It's worth making the big ones highly efficient.

Sorry i just don't remember the exact numbers but the guidelines in that reference should give you a feel.

old jim