Transformer loss from %Z and X/R
Transformer loss from %Z and X/R
(OP)
Hi all,
Is it possible to calculate/ make an educated guess about iron and copper losses from the following information:
1) Transformer ratings: 20MVA (34.5kV -> 70kV)
2) %z = 10% impedance at base
3) X/R = 23
I need to make some preliminary assessments and I'm not a power systems engineer so I'm lost. Thanks for the help!!!
Is it possible to calculate/ make an educated guess about iron and copper losses from the following information:
1) Transformer ratings: 20MVA (34.5kV -> 70kV)
2) %z = 10% impedance at base
3) X/R = 23
I need to make some preliminary assessments and I'm not a power systems engineer so I'm lost. Thanks for the help!!!






RE: Transformer loss from %Z and X/R
Z^2 = R^2 + X^2
= R^2 [ 1 + (X/R)^2 ]
So, taking sqrt and rearranging, you get
R = Z / SQRT[ 1 + X/R)^2 ]
Now Z in ohms can be derived from your %Z and the base ohms.
Base ohms = kV^2 / MVA or 34.5 * 34.5 / 20 if you are looking at the 34.5 kV side
Zpu = 0.10
Z(ohms) = Zpu * Base ohms
Plug and chug
You won't be able to estimate the iron or core losses from what you've provided.
RE: Transformer loss from %Z and X/R
RE: Transformer loss from %Z and X/R
From your equation, it seems that the whole result will change based on "if" the primary or secondary voltage is chosen.
What is the actual rule please?
Thanks.
RE: Transformer loss from %Z and X/R
It depends on what you're using the results for. As you said, you'll get a different result if you base it on 34.6 kV than you will if you do it for 70 kV.
RE: Transformer loss from %Z and X/R
RE: Transformer loss from %Z and X/R
RE: Transformer loss from %Z and X/R
RE: Transformer loss from %Z and X/R
RE: Transformer loss from %Z and X/R
As per IEC 60076-8 ch.7.2
"The test permits separation of the series impedance into a resistance, representing the load loss, and a reactance:
Z = R + jX "
As per IEC 60076-1
ch.10.4 Measurement of short-circuit impedance and load loss:
"the a.c. resistance derived from the load loss"