Power transformer loading

Hi DJ,

I can think of two good reasons:-

1. If it does self-destruct it will not do any more damage - use a suitable mcb and rcd and set up well away from flammables.

2. With no load it will run reasonably hot (max flux in the core) - a good stress test and it will dry out.

Chris

Flux in the core will not change much with load, but without resistive copper losses the thing should run cooler.

(on substation transformers with fans, the fans cut in at high load, not low.)

That said, my money is also on the drying out, and a low heat and slowly is better than super hot, and nothing else being damaged if it fails.  Generally faults become obvious on switch on or switch off, or during a stress event like a thunderstorm...

Mind you on a big one, I'd like the oil condition checked (for water - it is a conductivity meter test)  before even bothering to wire it in.


Rewound  11kV/400V units quite often 400V is applied t to the 11kV side as a first  soak test during factory checks, this warms it up a bit and finds shorted turns and so on in a "limited damage" sort of way.

M,.

Thanks Mr Chris.

Thanks mapj1. So the idea is that the insulation temperature should increase gradually and not abruptly. Supposing the Power transformer(15MVA, 33KV/11KV UNITS) was just out due to a fault on the 33KV bus that persisted for several days, after repairing the fault on the bus and re-energizing the power transformer, how long do you need to soak the transformer before loading ?