Heat Run Test of Power Transformers

One way to find out would just be to try it.

None. On method draws more current than the other, the other uses higher voltage than the other.

If the circuit protection equipment is set-up and working, the transformer will survive the experience undamaged.

Not necessarily. When used as a type/design test, a heat run may uncover uneven cooling and/or unanticipated hot-spots that can lead to insulation charring, outgassing, and premature dielectric failure.

Ah! "Testing to destruction." Understood.

Primary and secondary of a transformer are application related.

Usually the branch powered during all transformer tests is the one you have test equipment for, as a transformer can be used in different configurations.

As an example, if you have a transformer from 48Vac to 400Vac, tests are very likely to consist on powering the secondary 400Vac side, mostly because 400Vac power equipment is more common than 48Vac equipment.

The voltages involved in a factory heat run are not directly related to the primary or secondary voltage, they are based on forcing the rated full load current through one winding while short-circuiting the other. The input voltage is slowly increased until the current on the shorted side reaches the desired current, the actual voltage is recorded as a check variable.

I supervised multiple heat run tests of generators, in the past. Of course we tested the transformers, as well, because we shorted the transformer output (after disconnecting the transmission lines, of course.) We could control the generator current with the manual voltage regulators.

Control of current and measurement of temperature would be VERY HARD, from the secondary side.

A suitable voltage is applied on the high voltage side to ensure a full load current in shorted secondary.it is much easier to ensure a higher current on lower voltage side.

There is no difference in the heating if you set rated current in the appropriate winding.