Farmers sometimes place luminous tubes next to electric fencing to check if it works, when there's a power pulse the tube lights up.

Beautiful art sculpture.
Electric fencing technology has moved on a bit. I can operate the energizer from my phone get fault reports sent to my phone if the fence is not energized or if the wire is broken (cattle are out roaming) plus overall health status of the system. This is useful given the energizer can power 25 miles of fence wire.
High Voltage overhead power lines can induce lethal current in cattle fencing that is run parallel to the direction of the power lines. Before the days of checking the insulators on the pylons with an infra red camera from a helicopter, it was quite possible to bury a coil out of sight underneath the power lines and obtain free electricity. Now such attempts are easily spotted.