Note to paragraph (c)(1)(ii): See appendix B to this subpart for information on how to calculate the maximum anticipated per-unit transient overvoltage, phase-to-ground, when the employer uses portable protective gaps to reduce maximum transient overvoltages.
Note 1 to paragraph (g)(2): Appendix E to this subpart provides guidance on estimating available heat energy. The Occupational Safety and Health Administration will deem employers following the guidance in appendix E to this subpart to be in compliance with paragraph (g)(2) of this section. An employer may choose a method of calculating incident heat energy not included in appendix E to this subpart if the chosen method reasonably predicts the incident energy to which the employee would be exposed.
Note 2 to paragraph (g)(2): This paragraph does not require the employer to estimate the incident heat energy exposure for every job task performed by each employee. The employer may make broad estimates that cover multiple system areas provided the employer uses reasonable assumptions about the energy-exposure distribution throughout the system and provided the estimates represent the maximum employee exposure for those areas. For example, the employer could estimate the heat energy just outside a substation feeding a radial distribution system and use that estimate for all jobs performed on that radial system.
Note to paragraph (g)(3): This paragraph prohibits clothing made from acetate, nylon, polyester, rayon and polypropylene, either alone or in blends, unless the employer demonstrates that the fabric has been treated to withstand the conditions that may be encountered by the employee or that the employee wears the clothing in such a manner as to eliminate the hazard involved.
Note to paragraph (g)(4)(iii): This paragraph does not apply to conductors that are capable of carrying, without failure, the maximum available fault current for the time the circuit protective devices take to interrupt the fault.
Note to paragraph (g): See appendix E to this subpart for further information on the selection of appropriate protection.
Table V-3-Electrical Component of the Minimum Approach Distance (D; in Meters) at 5.1 to 72.5 kV
Nominal voltage (kV) phase-to-phase | Phase-to-ground exposure | Phase-to-phase exposure |
D (m) | D (m) | |
5.1 to 15.0 | 0.04 | 0.07 |
15.1 to 36.0 | 0.16 | 0.28 |
36.1 to 46.0 | 0.23 | 0.37 |
46.1 to 72.5 | 0.39 | 0.59 |
Table V-4-Altitude Correction Factor
Altitude above sea level (m) | A |
0 to 900 | 1.00 |
901 to 1,200 | 1.02 |
1,201 to 1,500 | 1.05 |
1,501 to 1,800 | 1.08 |
1,801 to 2,100 | 1.11 |
2,101 to 2,400 | 1.14 |
2,401 to 2,700 | 1.17 |
2,701 to 3,000 | 1.20 |
3,001 to 3,600 | 1.25 |
3,601 to 4,200 | 1.30 |
4,201 to 4,800 | 1.35 |
4,801 to 5,400 | 1.39 |
5,401 to 6,000 | 1.44 |
Table V-5-Alternative Minimum Approach Distances for Voltages of 72.5 kV and Less1
Nominal voltage (kV) phase-to-phase | Distance | |||
Phase-to-ground exposure | Phase-to-phase exposure | |||
m | ft | m | ft | |
0.050 0.3002 | Avoid contact | Avoid contact | ||
0.301 to 0.7502 | 0.33 | 1.09 | 0.33 | 1.09 |
0.751 to 5.0 | 0.63 | 2.07 | 0.63 | 2.07 |
5.1 to 15.0 | 0.65 | 2.14 | 0.68 | 2.24 |
15.1 to 36.0 | 0.77 | 2.53 | 0.89 | 2.92 |
36.1 to 46.0 | 0.84 | 2.76 | 0.98 | 3.22 |
46.1 to 72.5 | 1.00 | 3.29 | 1.20 | 3.94 |
1 Employers may use the minimum approach distances in this table provided the worksite is at an elevation of 900 meters (3,000 feet) or less. If employees will be working at elevations greater than 900 meters (3,000 feet) above mean sea level, the employer shall determine minimum approach distances by multiplying the distances in this table by the correction factor in Table V-4 corresponding to the altitude of the work.
2 For single-phase systems, use voltage-to-ground.
Table V-6-Alternative Minimum Approach Distances for Voltages of More Than 72.5 kV1 2 3
Voltage range phase to phase (kV) | Phase-to-ground exposure | Phase-to-phase exposure | ||
m | ft | m | ft | |
72.6 to 121.0 | 1.13 | 3.71 | 1.42 | 4.66 |
121.1 to 145.0 | 1.30 | 4.27 | 1.64 | 5.38 |
145.1 to 169.0 | 1.46 | 4.79 | 1.94 | 6.36 |
169.1 to 242.0 | 2.01 | 6.59 | 3.08 | 10.10 |
242.1 to 362.0 | 3.41 | 11.19 | 5.52 | 18.11 |
362.1 to 420.0 | 4.25 | 13.94 | 6.81 | 22.34 |
420.1 to 550.0 | 5.07 | 16.63 | 8.24 | 27.03 |
550.1 to 800.0 | 6.88 | 22.57 | 11.38 | 37.34 |
1 Employers may use the minimum approach distances in this table provided the worksite is at an elevation of 900 meters (3,000 feet) or less. If employees will be working at elevations greater than 900 meters (3,000 feet) above mean sea level, the employer shall determine minimum approach distances by multiplying the distances in this table by the correction factor in Table V-4 corresponding to the altitude of the work.
2 Employers may use the phase-to-phase minimum approach distances in this table provided that no insulated tool spans the gap and no large conductive object is in the gap.
3 The clear live-line tool distance shall equal or exceed the values for the indicated voltage ranges.
Table V-7-DC Live-Line Minimum Approach Distance (in Meters) With Overvoltage Factor1
Maximum anticipated per-unit transient overvoltage | distance (m) maximum line-to-ground voltage (kV) | ||||
250 | 400 | 500 | 600 | 750 | |
1.5 or less | 1.12 | 1.60 | 2.06 | 2.62 | 3.61 |
1.6 | 1.17 | 1.69 | 2.24 | 2.86 | 3.98 |
1.7 | 1.23 | 1.82 | 2.42 | 3.12 | 4.37 |
1.8 | 1.28 | 1.95 | 2.62 | 3.39 | 4.79 |
1 The distances specified in this table are for air, bare-hand, and live-line tool conditions. If employees will be working at elevations greater than 900 meters (3,000 feet) above mean sea level, the employer shall determine minimum approach distances by multiplying the distances in this table by the correction factor in Table V-4 corresponding to the altitude of the work.
Table V-8-Assumed Maximum Per-Unit Transient Overvoltage
Voltage range (kV) | Type of current (ac or dc) | Assumed maximum per-unit transient overvoltage |
72.6 to 420.0 | ac | 3.5 |
420.1 to 550.0 | ac | 3.0 |
550.1 to 800.0 | ac | 2.5 |
250 to 750 | dc | 1.8 |
29 C.F.R. §1926.960