Wiring Issue - Damage Located

[SkURTnDSM92T]

After checking my factory wiring harness (the main one through the engine bay that goes along the bottom edge of the radiator) I located some serious wire damage. I traced it back through the harness as far as I could go, and obviously I plan on replacing the damaged wire if I can get to it all.

I do not want to fix the wire and have the same thing happen, so I was hoping someone could tell me what the black and brown wire on the main engine bay harness of a 92 1G TSi is? It starts right by the engine bay fuse box and goes all the way around the front of the car, but the damage stops around the lines that go to the alternator..

It looks like it is just a series of ground wires, but I am not sure why they would have become hot enough to eat through the wire insulation. Any help is appreciated... Thanks

 

[DSM90AWD]

Could you have swiched polarity on the battery cables at some time?

 

[silver bullit]

Could have been a short, accident pinched the wires to short or touch, or you could have switched battery terminals.