230.50 Protection of Open Conductors and Cables Against Damage ? Above Ground.
Service-entrance conductors installed above ground shall be protected against physical damage as specified in 230.50(A) or (B).
(A) Service Cables. Service cables, where subject to physical damage, shall be protected by any of the following:
(1) Rigid metal conduit
(2) Intermediate metal conduit
(3) Schedule 80 rigid nonmetallic conduit
(4) Electrical metallic tubing
(5) Other approved means
(B) Other Than Service Cable. Individual open conductors and cables other than service cables shall not be installed within 3.0 m (10 ft) of grade level or where exposed to physical damage.
Exception: Type MI and Type MC cable shall be permitted within 3.0 m (10 ft) of grade level where not exposed to physical damage or where protected in accordance with 300.5(D).