The lockout/tagout procedure must consider several factors, one of which is grounding. Sometimes, installing temporary protective grounding is necessary.

Temporary protective grounding may include using a grounding cluster equipped with clamps which are connected to each de-energized phase bus and to the equipment grounding terminal bar. One idea behind joining all components together is to ensure that if a mistake was made and the equipment being serviced was unintentionally energized, the bolted fault condition would initiate the overcurrent device ahead of the equipment being serviced to open much faster than if all phases and the equipment ground bar were not joined together (see 120.5(8)(c)).

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.

120.4(B)(7) Grounding. Grounding requirements for the circuit shall be established, including whether the temporary protective grounding equipment shall be installed for the duration of the task or is temporarily established by the procedure. Grounding needs or requirements shall be permitted to be covered in other work rules and might not be part of the lockout/tagout procedure.

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:

1. 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.
2. 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.
3. 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.