I've found out the hard way that an HV transformer outputting EV over uninsulated HV cable will instakill player (not sure about with armour though).
The biggest problem I've found with electric defenses is that power will only be transmitted over a cable while something on the other end is drawing it. So, if your sending out of a HV transformer to a MFSU (or similar), the defense will only work so long as the MSFU isn't full.
So, you have to come up with a way to "loop" power around a ring, or have the MSFU turn around as start firing power back down the cable once it's full to a MSFU on the other end.
Also, the wire will only damage when a EU packet is sent through it - so especially with EV (2048EU) - you may have long delays between deadly "ticks" as the HV transformer builds up 2048 EU before firing it out down the cable. So you need to have a way to send a lot of EU/s into HV transformer so it's almost constantly sending out 2048EU packets.