Neighbour down the road milks cows. This past two mornings, an hour into milking, the cows started jumping to the roof like they were getting a large shock. It would happen every 10seconds etc in pulses like a cattle fencer/energiser. Would last for a minute or so but the farmer would open the gates and get the cows out and Isolate the electric at the same time. Got sparky out but could find nothing wrong and it never did it again after he let the cows out. RCD’s never tripped and the sparky tested them. Yesterday morning before a cow was milking, it did it again and the cows were booted out. The farmer has one of those fluke non contact pens and the pen would flash when the cows jumped. It appears the steel work is getting a pulse spike from somewhere. After a minute or two, it never happened again. The sparky was out and again it’s head scratching. No RCD tripped. Apparantly it happened last night. Anyone experienced this before?