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.
I am aware that sympathetic tripping occurs in resistance grounded systems where a feeder trips due to an earth fault occurring on another feeder.
Does the phenomenon apply to solidly grounded MV feeders also?
I have read an old post: "earth fault protection settings for an 11kV feeder,"...
In the power distribution company where I work, the earth fault relays are usually set to 20% of the nominal feeder current. I have also seen online sources that specify between 10% and 20% for earth fault settings.
I am aware that even in an unbalanced load situation, there is a very...