Ground Clamps

DOE-HDBK-1092-98

OSHA Sects. 29 CFR 1910.269(n) and 1926.954(t)

Figure 4-9. Equipotential personnel protective grounds are used to protect electrical workers while they

service, repair, or are close to circuits that can be accidentally reenergized.

3. The following are factors that contribute to adequate capacity:

a. Terminal strength depends on the ferrules installed on the cable ends

b. Cross-sectional area to carry maximum current without melting

c. Low resistance to keep voltage drop across the areas in which personnel are working at

a safe level during any period to prevent reenergization. The voltage drop should not

exceed 100 volts for 15 cycle or 75 volts for 30 cycle clearing times.

d. Verify that the grounding cable and clamp assembly is tested periodically by using the

millivolt drop, micro-ohm meter, AC resistance, or DC resistance test methods. For

example, if it is desired to maintain a maximum of 100 volts across a worker whose body

resistance is 1000 ohms, during a fault of 1000 amperes, a personnel protective ground

resistance of 10 millohms or less is required.

4. For further information on the construction of personnel protective grounds, refer to ASTM

F855-90, IEEE 524A, IEEE 1048, and Section 7.5.

4.15.3 GROUNDING CLAMPS

Grounding clamps used in personnel protective grounds are manufactured specifically for this use.

The size of grounding clamps shall match the size of conductor or switchgear bus being grounded.

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