Never had anything near power lines specifically but I did have a really strange episode on Dartmoor about three years back where I lost roughly 45 minutes I genuinely cannot account for. No pylons nearby but there was a mobile phone mast visible on the ridge. Makes me wonder if its the electromagnetic component thats the common factor rather than power lines as such.
What were the circumstances when it happened to you? Were you on foot or in a vehicle? I ask because I've read a few accounts where people driving under high voltage lines report the car clock jumping, which seems like a slightly different mechanism to what happens to people on foot.
Also did you feel anything physical beforehand, like a pressure in your ears or a kind of heaviness? That seems to come up a lot in the accounts I've been going through.