Loading power transformer

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.
 
Take extra precautions powering up devices that have been out of service, especially power transformers. Not all insulation ages well, and you have to gradually condition it even as a safety check under reduced voltages and load, to be safe.
 
Thanks Dave.
Let's say a 15MVA, 33KV/11KV unit has been out of service for 2 days due to a fault on the 33KV feeder. After the fault on the feeder has been repaired and the transformer successfully re-energized, how long should the transformer be on soak before being loaded ?
 
Thanks Phil !
But the chart only gives a procedure, it doesn't not specify any time duration for the transformer to be energised but unloaded.
 
Deji...
Please note, it starts with several relatively simple tests to detect if the Xfmr was unintentionally damaged during the time it was de-energized to the day it's to be re-energized !
If those tests lead to "NO !" Then energize and load it !
BTW, can you provide some info as to Voltage, kVA, Air/Oil cooling, and if equipped with cooling fans !
Phil
 
Deji...
Please note, it starts with several relatively simple tests to detect if the Xfmr was unintentionally damaged during the time it was de-energized to the day it's to be re-energized !
If those tests lead to "NO !" Then energize and load it !
BTW, can you provide some info as to Voltage, kVA, Air/Oil cooling, and if equipped with cooling fans !
Phil
33KV/11KV, 15MVA, ONAN cooling.
Transformer was de-energized and relocated to another substation.

At the new substation, many of the tests in the chart you supplied were conducted and no problem was indicated.

Transformer was then energised without incident but my supervisor said to not load it until it sits for another 8 hours.
 
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