According to Article 100, an “Electrically Safe Work Condition” is a “state in which an electrical conductor or circuit part has been disconnected from energized parts, locked/tagged in accordance with established standards, tested to verify the absence of voltage, and, if necessary, temporarily grounded for personnel protection”.

Temporary protective grounding equipment must be placed at such locations and arranged in such a manner as to prevent each employee from being exposed to a shock hazard. In addition, when placing temporary protective grounding cables, care should be taken to ensure that excess cable length is secured out of the way and away from the worker. If for some reason the electrical equipment is inadvertently energized while the temporary protective ground cables are in place, cable whip can occur and possibly harm the worker.

Below is a sample of NFPA 70E. For the complete section, see the actual NFPA 70E text at NFPA.ORG. Once there, click on the free access link to NFPA 70E.

120.5

(8) Where the possibility of induced voltages or stored electrical energy exists, ground the phase conductors or circuit parts before touching them. Where it could be reasonably anticipated that the conductors or circuit parts being de-energized could contact other exposed energized conductors or circuit parts, apply temporary protective grounding equipment in accordance with the following:

a. Placement. Temporary protective grounding equipment shall be placed at such locations and arranged in such a manner as to prevent each employee from being exposed to a shock hazard (i.e., hazardous differences in electrical potential). The location, sizing, and application of temporary protective grounding equipment shall be identified as part of the employer’s job planning.

b. Capacity. Temporary protective grounding equipment shall be capable of conducting the maximum fault current that could flow at the point of grounding for the time necessary to clear the fault.

c. Impedance. Temporary protective grounding equipment and connections shall have an impedance low enough to cause immediate operation of protective devices in case of unintentional energizing of the electric conductors or circuit parts.