300.37 Aboveground Wiring Methods.
conductors shall be installed in rigid metal conduit in intermediate
metal conduit, in electrical metallic tubing, in
RTRC and PVC conduit, in cable trays, in auxiliary gutters,
as busways, as cablebus, in other identified raceways, or as
exposed runs of metal-clad cable suitable for the use and
purpose. In locations accessible to qualified persons only,
exposed runs of Type MV cables, bare conductors, and bare
busbars shall also be permitted. Busbars shall be permitted
to be either copper or aluminum.