Four-year-old Ron managed to avoid the box as it landed in his field, and escaped an 11,000 volt shock from the tumbling cables.
But it left homes in three nearby villages in South Lanarkshire without electricity.
Owner Hazel Laughton told BBC Scotland she was amazed that Ron had survived.
It is thought that Ron, a limousin bull, brought the transformer down sometime between 22:00 and 23:00 on Thursday at East Shawtonhill Farm in Chapelton.
Mrs Laughton, who owns the farm with her husband Greg, said power was not restored to the local area until about 04:00 on Friday morning.
The agricultural consultant said: "We got up around 06:00 and we saw a big generator sitting at the bottom of our road, all linked up to the poles. We thought that was a bit strange.
"We went up to feed our cows and it was my husband that noticed the transformer box had been knocked off the pole.
"We put two and two together and realised our bull had been scratching against the telegraph pole and he had knocked the box off the pole. All the wires were down in the field as well."
As the couple surveyed the damage, they were joined by Ron.
Ms Laughton added: "We were standing looking at it and the bull just sheepishly walked up to the fence. He just looked a bit stunned. I don't think he really knew what had happened during the night."
Engineers from SP Energy Networks informed the couple that Ron had cut off power to 800 homes in Chapelton, Strathaven and Glassford.
Mrs Laughton sought to lighten the mood by posting an apology from Ron on the local Facebook group page.
She wrote: "He had an itchy bum so scratched it on the electricity pole and knocked the transformer off".
She described the response to her post, in which she also suggested renaming the bull Sparky, as "unbelievable".
And she explained that it is not unusual for the bulls to seek a good scratch as they still have their winter coats on.
Mrs Laughton added: "They are always itchy when they go out. Ron weighs over a ton so he has been rubbing and pushing against this pole and just knocked it off.
"We have seen them shake the wires before when they do it but for the box to come off is completely new."
The engineers who arrived to fit a new box were also surprised by the damage Ron had caused.
Mrs Laughton added: "They said they have seen bulls scratch poles and maybe crack them but they have never had a bull knock the box off the pole like he has.
"He is going to lose his scratch pole as we need to fence it off now so he can't get to it."
Meanwhile, Ron has spent the day relaxing in the field, oblivious to his brush with death and new-found celebrity.
Ms Laughton said: "This has given everyone a good laugh - people have been walking up the road looking for him."
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