Purpose of Personnel Protective Grounds

DOE-HDBK-1092-98

NEC Section 250- 81

OSHA Section 29 CFR 1910.304 (f)

Figure 4-8. If the building steel, metal water pipe, concrete-encased electrode, and ground ring are available,

they must be grounded and bonded to the service equipment to create the grounding electrode system.

4.15.1 PURPOSE OF PERSONNEL PROTECTIVE GROUNDS

Personnel protective grounds are applied to deenergized circuits to provide a low-impedance path

to ground should the circuits become reenergized while personnel are working on or close to the

circuit. In addition, the personnel protective grounds provide a means of draining off static and

induced voltage from other sources while work is being performed on a circuit. (Figure 4-9 illustrates

an example of a personnel protective ground.)

4.15.2 CRITERIA FOR PERSONNEL PROTECTIVE GROUNDS

Before personnel protective grounds are selected, the following criteria shall be met for their use,

size, and application.

1. A grounding cable shall have a minimum conductance equal to #2 AWG copper.

2. Grounding cables shall be sized large enough to carry fault current long enough for the

protective devices to sense and the circuit breaker to clear the fault without damage to cable

insulation. An example would be a 4/0 Neoprene-insulated welding cable that will pass 30,000

A for 0.5 sec without melting its insulation.

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