Circuits supplying power to ungrounded receptacles for hand-held, cord- and plug-connected equipment shall meet the following requirements:
The circuits shall be electrically isolated from any distribution system supplying areas other than the cell line working zone and shall be ungrounded;
The circuits shall be supplied through isolating transformers with primaries operating at not more than 600 volts between conductors and protected with proper overcurrent protection;
The secondary voltage of the isolating transformers may not exceed 300 volts between conductors; and
All circuits supplied from the secondaries shall be ungrounded and shall have an approved overcurrent device of proper rating in each conductor.
Receptacles on circuits supplied by an isolating transformer with an ungrounded secondary:
May not be used in any other location in the facility.
Receptacles and their mating plugs for ungrounded equipment may not have provision for a grounding conductor and shall be of a configuration that prevents their use for equipment required to be grounded.