1910.269(l)(12) Opening and Closing Circuits Under Load

The employer shall ensure that devices used by employees to open circuits under load conditions are designed to interrupt the current involved.

The employer shall ensure that devices used by employees to close circuits under load conditions are designed to safely carry the current involved.

Table R-3 — AC Live-Line Work Minimum Approach Distance
[The minimum approach distance (MAD; in meters) shall conform to the following equations.]

For phase-to-phase system voltages of 50 V to 300 V: 1
MAD = avoid contact
For phase-to-phase system voltages of 301 V to 5 kV: 1
MAD = M + D, where
D = 0.02 m	the electrical component of the minimum approach distance.
M = 0.31 m for voltages up to 750 V and 0.61 m otherwise	the inadvertent movement factor.
For phase-to-phase system voltages of 5.1 kV to 72.5 kV:1 4
MAD = M + AD, where
M = 0.61 m	the inadvertent movement factor.
A = the applicable value from Table R-5	the altitude correction factor.
D = the value from Table R-4 corresponding to the voltage and exposure or the value of the electrical component of the minimum approach distance calculated using the method provided in appendix B to this section	the electrical component of the minimum approach distance.
For phase-to-phase system voltages of more than 72.5 kV, nominal:2 4
MAD = 0.3048(C a)VL-G TA + M
C = 0.01 for phase-to-ground exposures that the employer can demonstrate consist only of air across the approach distance (gap),
0.01 for phase-to-phase exposures if the employer can demonstrate that no insulated tool spans the gap and that no large conductive object is in the gap, or
0.011 otherwise
VL-G = phase-to-ground rms voltage, in kV
T = maximum anticipated per-unit transient overvoltage; for phase-to-ground exposures, T equals TL-G, the maximum per-unit transient overvoltage, phase-to-ground, determined by the employer under paragraph (l)(3)(ii) of this section; for phase-to-phase exposures, T equals 1.35TL-G 0.45
A = altitude correction factor from Table R-5
M = 0.31 m, the inadvertent movement factor
a = saturation factor, as follows:

Phase-to-Ground Exposures
VPeak = TL-GVL-G√2	635 kV or less	635.1 to 915 kV	915.1 to 1,050 kV	More than 1,050 kV
a	0	(VPeak -635)/140,000	(VPeak - 645)/135,000	(VPeak - 675)/125,000
Phase-to-Phase Exposures 3
VPeak = (1.35TL-G 0.45)VL-G√2	630 kV or less	630.1 to 848 kV	848.1 to 1,131 kV	1,131.1 to 1,485 kV	More than 1,485 kV
a	0	(VPeak - 630)/155,000	(VPeak - 633.6)/152,207	(VPeak - 628)/153,846	(VPeak - 350.5)/203,666

¹ Employers may use the minimum approach distances in Table R-6. If the worksite is at an elevation of more than 900 meters (3,000 feet), see footnote 1 to Table R-6.

² Employers may use the minimum approach distances in Table R-7, except that the employer may not use the minimum approach distances in Table R-7 for phase-to-phase exposures if an insulated tool spans the gap or if any large conductive object is in the gap. If the worksite is at an elevation of more than 900 meters (3,000 feet), see footnote 1 to Table R-7. Employers may use the minimum approach distances in Table 14 through Table 21 in appendix B to this section, which calculated MAD for various values of T, provided the employer follows the notes to those tables.

³ Use the equations for phase-to-ground exposures (with V_Peak for phase-to-phase exposures) unless the employer can demonstrate that no insulated tool spans the gap and that no large conductive object is in the gap.

⁴ Until March 31, 2015, employers may use the minimum approach distances in Table 6 through Table 13 in Appendix B to this section.

Table R-4 — Electrical Component of the Minimum Approach Distance at 5.1 to 72.5 kV

[D; In meters]
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 R-5 — 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 R-6 — Alternative Minimum Approach Distances for Voltages of 72.5 kV and Less ¹

Nominal voltage (kV) phase-to-phase	Distance
	Phase-to-ground exposure		Phase-to-phase exposure
	m	ft	m	ft
0.050 to 0.300 2	Avoid Contact		Avoid Contact
0.301 to 0.750 2	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 R-5 corresponding to the altitude of the work.

² For single-phase systems, use voltage-to-ground.

Table R-7 — Alternative Minimum Approach Distances for Voltages of More Than 72.5 kV ¹²³

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 R-5 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 R-8 — DC Live-Line Minimum Approach Distance with Overvoltage Factor ¹
[In meters]

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 R-5 corresponding to the altitude of the work.

Table R-9 — 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