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Power transformer loading

Former Community Member
Former Community Member

Greetings.



 



I have often come across the notion that newly commissioned power transformers and transformers that have been out of service due to a fault or outage should be kept on no-load for some hours before loading.



 



I like to know the reason for this.



 



Thanks.


Parents
  • 0
    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,.
Reply
  • 0
    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,.
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