Use of socket outlets in hostile operating environment

Subregulation (2) does not apply if the supply of electricity to the electrical equipment —
(a) does not exceed 50 volts alternating current; or
(b) is direct current; or
(c) is provided through an isolating transformer that provides at least an equivalent level of protection; or
(d) is provided from a non-earthed socket outlet supplied by an isolated winding portable generator that provides at least an equivalent level of protection.