I just though about this idea!
If a cable is been exposed for a higher voltage than its capable of, and it has insulation it will first drop the and a few seconds later it will get destroyed like before.
Lets say a cobber cable can handle 64 EU packets for 3 seconds then the insulation will drop, then it will get destroyed 2 seconds after that, and if it is exposed for 128 EU packets it will only last 1,5 sec. You get my point 
Maybe a another feature like the cable can set things on fire beside it if exposed for a current higher than it is capable of? Don't know how easy this is to code but it would be a nice feature!
Real wires can transfer as much current as you can imagine, but it's a matter of time.
First the insulation will burn, then it will set things around it on fire (if there is anything to set on fire) and then finaly the material itself will melt.
If my idea will take to much time, you should drop it
Use of idea: If you wan't to create a fuse setup you can put a preasureplate under the wire, and when the insulation drops it will send a redstonesignal to a splitter cable which will stop the current.
Just a though 
