Barn. Electric fence. Electric fence drifted a little too close to the non-electric fence and it started arc'ing between them with every pulse. Very small arc, across about 1mm.
No big deal - happens once in a while and is easy to fix.
BUT, this time, I happened to walk into the barn with all of the lights off while this was happening and I just happened to see all of my 100W LED flood lights pulse the very slightest of light ... with ... every ... single ... arc.
Why is this happening ? I do think these LED flood lights are on the same circuit breaker as the electric fence energizer, but of course they are also on a lightswitch and that lightswitch was OFF.
So how do my LED floods get a tiny little flash of electricity to produce a tiny little glow every single time the electric fence pulse makes an arc ?
No, this does not happen during normal (non arc-ing) operation.