You should not die from peeing on an electric fence unless it is someone who has made their own with lethal current or you have a weak heart/pacemaker. Proper electric fences use a voltage of around 10Kvolt but in very short non-lethal pulses. Of course some idiots just plug a length of conductor into mains and manage to kill people every so often but then you have a good chance to die on contact, no peeing needed.

I can confirm one case of pee on fence survival, a mate of mine did this when we were about 14 to prove how tough he was. He screamed like a girl and ended up on his back with an embarrassing wet patch. Most amusing for the rest of us but the string of profanity from him confirmed his non-dead status.

Cheers,
R.