How to test three-phase transformer's rated kVA

Question

I work as an electrical quality engineer at the borders. I test electrical transformers, and the government takes tax money according to the capacity rated kVA of the electric transformer.

We discovered that merchants change the nameplate of the transformer with one that shows a lower-capacity kVA, so that less money is paid for the tax, because for higher-capacity kVA the merchant pays more money for the tax. Then after crossing the border, they change the nameplate to the original nameplate of the electric transformer.

So I want a way to test the real capacity rated kVA of the transformer, or test the voltage and current so that I can calculate it from the apparent power law. Is there a device or method for testing the rated kVA?

Answer 1

Idea: It's pointless to cheat on the voltage.
Use DC sources to push primary&secondary rated currents.
If temperature rise isn't anywhere near \$\frac{P_{Cu}}{P_{Cu}\ \ +\ P_{Fe}}\$ the range quoted, something is off.

Answer 2

It's too easy for the importers to cheat, they may declare any small power rating specifying low temperature rise, large oversize for reliability and so on, plenty of good reasons

In my opinion the simple and fair way is to tax transformers by the weight. Their nominal power is strongly correlated.

So it all boils down to changing the rules, it may be anything from plain sailing or just impossible depending on your own country rules.

Otherwise, the same thing from a different point of view more specifically addressing the question.

Prepare a look-up table from reputable manufacturers datasheet for different type of transformers. The need to have the legal power to enforce this table to unwilling importers however remanins.