The T-850 tried to overload the T-X with voltage, however, it only disabled the Terminatrix for seconds. Ironically, the T-850 was affected even longer and was then reprogrammed by the T-X. Terminator 3: Rise of the Machines
Due to being entirely composed of mimetic polyalloy, the T-1000 Terminator is just like a huge mass of metal, thus making it electrically conductive, and, unlike endoskeleton-based Terminators, can withstand a high-voltage charge without being knocked offline.
↑After being knocked out, Cameron reboots after around thirty seconds rather than the 120-second norm. It is possible she wears shoes with rubber soles — so she isn't actually knocked out.