UFC 3-560-01
6 December 2006
Including change 1, 7 December 2006
CHAPTER 7
DEENERGIZED LINE GROUNDING
7-1
TEMPORARY GROUNDING. Temporary grounding is provided to protect
workers engaged in deenergized electric line maintenance. In addition, lines and
equipment are protected. Unsafe potentials can occur on the line from static charge
buildup, induced voltages through magnetic and capacitive coupling from nearby
energized lines, and accidental energizing of the line. The temporary grounding will
cause an inadvertently energized line to become deenergized through the action of
an impedance low enough to cause immediate operation of protective devices in case
of accidental energizing of the lines or equipment. Further information on temporary
grounding may be found in IEEE Standard 1048, Guide for Protective Grounding of
Power Lines, and IEEE 1245, Guide for Temporary Protective Grounding Systems Used
in Substations.
7-1.1
Testing. Test the line to be sure it is deenergized before installing protective
grounds.
WARNING
Protective grounds should be placed on the
disconnected lines or equipment to be worked on in accordance with 29
CFR 1910.269(n), Grounding for Protection of Employees. All
lines/equipment that are not effectively deenergized will be worked as if
they are operating at their full potential.
7-1.2
Installation Criteria. A good temporary ground provides adequate current-
carrying capacity and a low-resistance path to the reference ground, and is connected
at the proper points with clean tight joints. If the temporary ground is not installed
correctly, a worker might feel secure but not actually be protected. When connecting
grounds to conductors, maintain the proper clearances from energized lines, using hot-
line tools as required. To avoid hazardous touch and step potentials, persons on the
ground within the work area must stay at least 10 ft (3 m) from any protective grounds
or devices, and from vehicles bonded to them. If this is not feasible, workers must wear
insulated footwear or use other protective measures to minimize the hazard.
7-1.3
Temporary Grounding System Components. Use system application
(overhead, underground, substation) sets with ASTM F 855, Temporary Grounding
Systems to be Used on De-Energized Electric Power Lines and Equipment, grounding
jumpers (clamps, ferrules, and clear 600 volt jacketed elastomer flexible cable) to the
maximum possible extent. Store in accordance with the requirements for electrical tools
and rubber protective equipment. Grounding sets and jumpers should be workbench
assembled and tested annually using an instrument specifically designed to test
7-1
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