The onsite refinery electricians at our facility were given a "NCCER Skills Validation" test recently. One of the questions had everyone stumped, including myself. The question was focused on a formula used to calucate the acceptable Megger reading (per the NEC) on a cable. We normally refer to the manufacturer's recommendations for new cable. But this was not one of the muliple choice answers.
I realize specific information is needed to calculate this properly (i.e. AWG/kcmil, resistance & length).
Can anyone give me direction of where to find this Megger formula?