I found a small scuffed portion of 12awg wire right where it enters a box at the fitting. I think its just the nylon sheath got damaged when pulling. I didnt see exposed copper so I covered it in heatshrink tubing as a repair. My only concern is that the portion of copper is weakened or actually nicked or that I fatigued it when I repaired it. However, copper wire seems pretty tough when it comes to fatigue, im thinking the insulation would split, exposing copper, before severing in half. It may take some serious, abnormal flexing inside an electrical box to cause failure in this way. Have you ever seen a broken wire where only the nylon portion of the insulation was compromised? Does a nick or weak portion of wire heat and burn/melt insulation?

run 150 ft. 200 amp to my shop in conduit 3'sec.40