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1910.269(l)(12) Opening and Closing Circuits Under Load
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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.
^{1 }Employers may use the minimum approach distances in Table R6. If the worksite is at an elevation of more than 900 meters (3,000 feet), see footnote 1 to Table R6.
^{2} Employers may use the minimum approach distances in Table R7, except that the employer may not use the minimum approach distances in Table R7 for phasetophase 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 R7. 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 phasetoground exposures (with V_{Peak} for phasetophase 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.
^{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 R5 corresponding to the altitude of the work.
^{2} For singlephase systems, use voltagetoground.
^{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 R5 corresponding to the altitude of the work.
^{2} Employers may use the phasetophase 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 liveline tool distance shall equal or exceed the values for the indicated voltage ranges.
^{1} The distances specified in this table are for air, barehand, and liveline 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 R5 corresponding to the altitude of the work.
For phasetophase system voltages of 50 V to 300 V: ^{1}  
MAD = avoid contact  
For phasetophase 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 phasetophase 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 R5

the altitude correction factor. 
D = the value from Table R4 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 phasetophase system voltages of more than 72.5 kV, nominal:^{2 4}  
MAD = 0.3048(C a)V_{LG} TA + M  
C = 0.01 for phasetoground exposures that the employer can demonstrate consist only of air across the approach distance (gap),


0.01 for phasetophase 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


V_{LG} = phasetoground rms voltage, in kV


T = maximum anticipated perunit transient overvoltage; for phasetoground exposures, T equals T_{LG}, the maximum perunit transient overvoltage, phasetoground, determined by the employer under paragraph (l)(3)(ii) of this section; for phasetophase exposures, T equals 1.35T_{LG} 0.45


A = altitude correction factor from Table R5


M = 0.31 m, the inadvertent movement factor


a = saturation factor, as follows:

PhasetoGround Exposures


V_{Peak} = T_{LG}V_{LG}√2  635 kV or less  635.1 to 915 kV  915.1 to 1,050 kV  More than 1,050 kV  
a  0  (V_{Peak} 635)/140,000  (V_{Peak}  645)/135,000  (V_{Peak}  675)/125,000  
PhasetoPhase Exposures ^{3}


V_{Peak} = (1.35T_{LG} 0.45)V_{LG}√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  (V_{Peak}  630)/155,000  (V_{Peak}  633.6)/152,207  (V_{Peak}  628)/153,846  (V_{Peak}  350.5)/203,666 
^{1 }Employers may use the minimum approach distances in Table R6. If the worksite is at an elevation of more than 900 meters (3,000 feet), see footnote 1 to Table R6.
^{2} Employers may use the minimum approach distances in Table R7, except that the employer may not use the minimum approach distances in Table R7 for phasetophase 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 R7. 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 phasetoground exposures (with V_{Peak} for phasetophase 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.
[D; In meters]  
Nominal voltage (kV)phasetophase  Phasetoground exposure  Phasetophase 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 
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 
Nominal voltage (kV) phasetophase 
Distance  
Phasetoground exposure  Phasetophase 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 R5 corresponding to the altitude of the work.
^{2} For singlephase systems, use voltagetoground.
Voltage range phase to phase (kV)  Phasetoground exposure  Phasetophase 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 R5 corresponding to the altitude of the work.
^{2} Employers may use the phasetophase 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 liveline tool distance shall equal or exceed the values for the indicated voltage ranges.
Maximum anticipated perunit transient overvoltage 
Distance (m) maximum linetoground 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, barehand, and liveline 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 R5 corresponding to the altitude of the work.
Voltage range (kV) 
Type of current (ac or dc) 
Assumed maximum perunit 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 