250.6 allows disconnecting or switching of the grounds or neutrals where OBJECTIONABLE current flows through the grounding conductor. IMHO the current through the ground wire in the cord between a portable generator and the transfer switch is not objectionable. How is this situation a hazard?
During the emergency, the generator runs and supplies power to the selected loads. The neutral is connected to the frame. The generator sits outside. Why is it a shock hazard to touch this generator? What potential is there between the frame and the earth? If one is worried about paralling the neutral and grounding conductors in the cord, then use a three conductor cord. You don't need to run a grounding conductor to a portable generator. (250.34)
