Grounding for employee protection

Under 1926.962(a) this grounding standard applies to grounding of transmission and distribution lines and equipment for the protection of employees. See 1926.962(a).

• The paragraph also notes that grounding under this section is required when this Subpart specifically requires protective grounding and whenever an employer chooses to ground lines or equipment to protect employees.

Under 1926.962(b) an employer must ensure that lines or equipment are deenergized under 1926.961 and are properly grounded as specified in 1926.962(c)–(h) before employees work them as deenergized. See 1926.962(b) and 1926.961.

• In short: deenergize per 1926.961, then apply the protective grounding rules in 1926.962.

Under 1926.962(b) an employer may treat lines or equipment as deenergized without installing a protective ground only if the employer demonstrates that installing a ground is impracticable or would create greater hazards and that all three conditions in 1926.962(b)(1)–(3) apply. See 1926.962(b).

• The three required conditions are: (1) the lines/equipment are deenergized per 1926.962(b)(1); (2) there is no possibility of contact with another energized source per 1926.962(b)(2); and (3) no induced voltage hazard exists per 1926.962(b)(3).

• The employer bears the burden of demonstrating these conditions.

Under 1926.962(c) an equipotential zone is a temporary area created by protective grounds arranged so employees are not exposed to hazardous differences in electric potential, and temporary protective grounds must be placed and arranged to achieve that equipotential protection. See 1926.962(c).

• Appendix C to the subpart contains guidelines for establishing the equipotential zone, and OSHA will deem grounding practices that meet those guidelines to comply with 1926.962(c).

Under 1926.962(d)(1) protective grounding equipment must be capable of conducting the maximum fault current at the point of grounding for the time needed to clear the fault, and must have ampacity greater than or equal to that of No. 2 AWG copper. See 1926.962(d)(1) and 1926.962(d)(1)(ii).

• In practice this means selecting grounding conductors and clamps sized at least as large as No. 2 AWG copper unless you can demonstrate the equipment meets the fault current conduction requirement.

Under 1926.962(d)(2) protective grounds must have sufficiently low impedance so they do not delay operation of overcurrent or other protective devices if the line or equipment is accidentally energized. See 1926.962(d)(2).

• Employers can follow ASTM F855-09 and IEEE Std 1048-2003 for guidance on selecting grounding equipment and on acceptable impedance and installation practices (these standards are noted in the 1926.962(d) note).

Under 1926.962(e) employees must test lines and equipment and verify the absence of nominal voltage before installing any ground unless a previously installed ground is already present. See 1926.962(e).

• Testing must be done by the employer to ensure the line is deenergized prior to employees installing grounds, unless an existing ground that provides protection is already in place.

Under 1926.962(f)(1) the employee must attach the ground-end connection first to the grounding device, then attach the other (line) end by means of a live-line tool. See 1926.962(f)(1).

• For lines or equipment operating at 600 volts or less, an employer may allow insulating equipment other than a live-line tool provided the line is not energized at the time of connection or the employer demonstrates equivalent protection for employees.

Under 1926.962(f)(2) the employee must remove the grounding device from the line or equipment using a live-line tool before removing the ground-end connection. See 1926.962(f)(2).

• This order minimizes the window when the employee could be exposed to potential voltage on the line.

Under 1926.962(g) an employer must ensure that when an employee works on a cable remote from the cable terminal, the cable is not grounded at the terminal if there is any possibility of hazardous transfer of potential should a fault occur. See 1926.962(g).

• In other words, avoid grounding at locations that could create a dangerous potential shift at the worker's location if a fault happens.

Under 1926.962(h) employees may temporarily remove grounds during tests, but the employer must ensure each employee uses insulating equipment, isolates employees from hazards involved in the test, and implements any additional measures needed to protect employees if the previously grounded lines become energized. See 1926.962(h).

• Employers must plan test procedures to protect workers from accidental energization while grounds are removed.

Under 1926.962(d) employers are not mandated to use a specific outside standard, but the standard notes that ASTM F855-09 and IEEE Std 1048-2003 contain guidelines for protective grounding equipment and will help ensure compliance with paragraph (d). See 1926.962(d).

• Using those standards is a recognized way to meet the ampacity and impedance expectations in 1926.962(d)(1)–(2).

Under 1926.962(b)(2) and 1926.962(b)(3) "no possibility of contact" means there must be no chance the deenergized line or equipment could contact another energized source, and "no induced voltage" means the employer must ensure there is no hazardous induced voltage present (for example from nearby energized circuits) that could energize the supposedly deenergized equipment.

• Employers who claim grounding is impracticable must document and demonstrate both conditions before treating equipment as deenergized without grounds.

Under 1926.962(f) for lines or equipment operating at 600 volts or less, an employer may permit insulating equipment other than a live-line tool if the employer ensures the line or equipment is not energized at the time the ground is connected or if the employer can demonstrate that each employee is protected from hazards that could develop if the line becomes energized. See 1926.962(f)(1).

• The employer must be able to justify the alternate insulating equipment and confirm the line is deenergized or protective measures are equivalent.

Under 1926.962(d)(1)(i) protective grounding equipment must be capable of conducting the maximum fault current that could flow at the point of grounding for the time necessary to clear the fault. See 1926.962(d)(1)(i).

• This requires knowing potential fault current values and selecting grounding conductors and clamps rated to carry that current without failing during the protective device clearing time.

Under 1926.962(e) a previously installed ground does relieve employees from testing the line for nominal voltage before installing another ground; testing is required only when a previously installed ground is not present. See 1926.962(e).

• Employers must be sure the existing ground provides the needed protection before relying on it instead of conducting new tests.

Under 1926.962(b) the employer is responsible for demonstrating that installation of a ground is impracticable or that installing a ground would create greater hazards, and must show that the conditions in 1926.962(b)(1)–(3) are met. See 1926.962(b).

• The employer should document the analysis and conclusions supporting the demonstration.

Under 1926.962(c) and the Subpart's Appendix C, practical steps to create an equipotential zone include placing temporary protective grounds so that all conductors and the work area are bonded together at low impedance, positioning grounds near the work to equalize potential, and using jumper grounds to keep employees within the established equipotential area. See 1926.962(c).

• Appendix C contains non-mandatory guidelines that OSHA will accept as compliant if followed.

Under 1926.962(g) employers must ensure cables are not grounded at the cable terminal when employees work remotely on a cable if grounding at the terminal could cause hazardous transfer of potential to the worker in the event of a fault. See 1926.962(g).

• Employers should evaluate system grounding locations and use alternative grounding arrangements or isolation to prevent dangerous potential shifts to the remote work location.

Under 1926.962(h) when grounds are temporarily removed for testing, the employer must ensure employees use insulating equipment, isolate employees from hazards involved in the test, and implement any additional protective measures necessary if the lines or equipment become energized. See 1926.962(h).

• Employers should prepare and communicate the test procedure, ensure use of appropriate personal protective equipment and live-line tools, and maintain clear isolation zones.

Under 1926.962(f)(1) the standard requires attaching the ground-end connection first to ensure the grounding system becomes continuous only after the employee establishes the safe ground reference point, reducing the chance that the employee will be exposed to hazardous voltage during the connection process. See 1926.962(f)(1).

• Attaching the ground-end first and using a live-line tool to make the line connection keeps the worker physically separated from the potentially hazardous conductor until the protective connection is complete.

Under 1926.962(d) OSHA points to ASTM F855-09 and IEEE Std 1048-2003 as sources of guidance for selecting and installing temporary protective grounds; following those guidelines helps meet the ampacity and impedance requirements in 1926.962(d). See 1926.962(d).

• Employers should consult those documents for conductor sizing, clamp selection, and installation techniques that ensure safe temporary grounding.