Electric Power Generation,

Transmission, and Distribution

Electrical Protective

Equipment—

Minimum Approach Distances

MAD

§§1910.269(l)(3), (l)(4)(ii), (l)(5)(ii) & 1926.960(c)(1), (c)(2),

(d)(2)

How to comply

§§1910.269(l)(3), (l)(4)(ii), (l)(5)(ii) & 1926.960(c)(1), (c)(2),

(d)(2)

What is the minimum approach

distance for the worksite?

Voltage

TOV, if applicable

Meters or feet

What is the expected reach of the

employee?

Expected reach may not enter MAD.

What is the distance?

Employer must establish minimum approach

distances based on formulas in the standard.

For voltages up to 72.5 kV, the default distances

are the same as proposed.

For voltages exceeding 72.5 kV, the distances are

based on the equations used to calculate the

proposed distances (D = TOV × (C + a) + M).

§1910.269(l)(3) & Table R-3, & §1926.960(c)(1) & Table V-2

What is the distance?

Employer must establish minimum approach

distances based on formulas in the standard.

For voltages up to 72.5 kV, the default distances

are the same as proposed.

For voltages exceeding 72.5 kV, the distances are

based on the equations used to calculate the

proposed distances (D = TOV × (C + a) + M).

§1910.269(l)(3) & Table R-3, & §1926.960(c)(1) & Table V-2

MAD for ≤72.5 kV (showing difference compared to existing §1910.269)

§1910.269(l)(3) & Table R-3, & §1926.960(c)(1) & Table V-2

Voltage(kV phase-to-

phase) m ft

0.50 to 0.300 Avoid contact

0.301 to 0.750 0.33 (+0.33) 1.09 (+1.09)

0.751 to 5.0 0.63 (-0.01) 2.07 (-0.01)

5.1 to 15.0 0.65 (+0.01) 2.14 (+0.06)

15.1 to 36.0 0.77 (+0.05) 2.53 (+0.20)

36.1 to 46.0 0.84 (+0.07) 2.76 (+0.18)

46.1 to 72.5 1.00 (+0.10) 3.29 (+0.29)

MAD for >72.5 kV

MAD = 0.3048(C + a)VL-GTA + M

C = constant, 0.01 or 0.011, depending on exposure

a = saturation factor (per equations in Table R-3)

VL-G = phase-to-ground rms voltage, in kV

T = maximum anticipated per-unit transient overvoltage

(for phase-to-phase exposures, T = 1.35TL-G + 0.45)

A = altitude correction factor from Table R–5

M = 0.31 m (1.0 ft), the inadvertent movement factor

§1910.269(l)(3) & Table R-3, & §1926.960(c)(1) & Table V-2

Significant risk

OSHA determined significant risk for the standards

as a whole, not for individual provisions.

MAD is based on probability of 1/1000 of sparkover.

OSHA does not require accidents to demonstrate

significant risk.

See National Maritime Safety Ass’n v. OSHA, —

F.3d, 2011 WL 2417109 (D.C. Cir. 2011).

§1910.269(l)(3) & Table R-3, & §1926.960(c)(1) & Table V-2

Changes for Voltages >72.5 kV Maximum transient overvoltage (TOV)

Highest is 3.5 rather than 3.0.

Final rule anticipates that most employers will determine

maximum TOV.

Appendix B includes MAD tables for various values of

maximum TOV.

MAD for phase-to-phase exposures increases

substantially for voltages >350 kV because of error.

§1910.269(l)(3) & Table R-3, & §1926.960(c)(1) & Table V-2

Portable protective gap

Line end Ground end

Don and doff rubber gloves Put on and take off rubber insulating gloves in a

position where the worker cannot reach into MAD.

§§1910.269(l)(4)(ii) & 1926.960(c)(2)(ii)

Unprotected workers

For work near live parts of >600 volts but ≤ 72.5 kV,

work from a position where the worker cannot reach

into MAD, except:

wearing rubber insulating gloves,

protected by insulating equipment,

using live-line tools, and

performing live-line barehand work.

§§1910.269(l)(5)(ii) & 1926.960(d)(2)