Screw-Tightening Devices

DOE-HDBK-1092-98

The ground clamp also shall be rated to handle the full capacity of the available fault currents. Fault

currents can typically range in magnitude up to over 200,000 A.

4.15.4 SCREW-TIGHTENING DEVICES

Approved screw-tightening devices designed for the purpose of pressure metal-to-metal contact are

required for connections to an adequate system ground.

4.15.5 GROUNDING CABLE LENGTH

Grounding cables should be no longer than is necessary, both to minimize voltage drop and to prevent

violent movement under fault conditions. For example, as a general rule, grounding cables should

not exceed 30 ft for a transmission line and 40 ft for substation use.

4.15.6 GROUNDING CABLE CONNECTION

Grounding cables shall be connected between phases to the grounded structure and to the system

neutral to minimize the voltage drop across the work area if the circuit should become inadvertently

reenergized. Workers shall install the ground end clamp of a grounding cable first and remove it last.

4.15.7 CONNECTING GROUNDING CABLES IN SEQUENCE

Grounding cables shall be connected to the ground bus, structure, or conductor first, then to the

individual phase conductors. The first connection of the grounding cables to the circuit phase

conductors shall be to the closest phase of the system and then to each succeeding phase in the order

of closeness.

4.15.8 REMOVING PROTECTIVE GROUNDS

When removing personnel protective grounds, reverse the order they were applied to the phases. The

grounding cable conductors attached to the ground bus, structure, or conductors shall always be

removed last.

4.15.9 PROTECTIVE APPAREL AND EQUIPMENT

Protective apparel shall be worn when applying or removing grounds. An insulating tool (hot stick)

shall be used to install and remove grounding cables. (See 29 CFR 1910.269(n)(6) and (7),

1926.954(e) and NESC Rule 445).

Protective apparel (personnel protective equipment) should include at least the following:

1. Safety glasses and, if necessary, face shield appropriate for fault currents available.

2. Hardhat (Class B) (See 2.12.3)

3. Appropriate electrical gloves and protectors (See 2.12.3).

4. Appropriate clothing (See note in 2.11.3).

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