I am curious how the maximum values allowed for MV breakers and fuses are establisted for protecting MV cables. I know the NEC allows a breakers long time pickup to be up to 6x the MV cable ampacity and fuses are allowed to be applied up to 3x the MC cable ampacity.
Why for MV cables are these overload tolerances much greater than those of LV cables?
Why are breaker long time pickups allowed up to 6x cable ampacity while fuses are only allowed at 3x ampacity?
Are using the 3x and 6x guidelines good practice for protection of MV cables or are there rules of thumbs that typically dictate lower protection of MV cables?
Why for MV cables are these overload tolerances much greater than those of LV cables?
Why are breaker long time pickups allowed up to 6x cable ampacity while fuses are only allowed at 3x ampacity?
Are using the 3x and 6x guidelines good practice for protection of MV cables or are there rules of thumbs that typically dictate lower protection of MV cables?