Electric Power Generation, Transmission, and Distribution eTool
The "269" standard identifies required Minimum Approach Distances (MAD) in Table R-6 (1910.269(l)(2)) that must be maintained, based on the voltage involved, by unprotected 269-qualified employees [See 1910.269(x)] when exposed to energized parts. In order to work within a MAD, 269-qualified employees must use proper work techniques, equipment, and PPE. Section 43 of the National Electrical Safety Code (NESC) (ANSI-C2, 2002) also provides MADs.
Section 43 of the current NESC (ANSI-C2) has more recent and slightly greater values for Minimum Approach Distances than the "269" standard; employers and workers are advised to review the NESC MAD values and incorporate them into work procedures. Additional tables in the "269" standard provide guidance for adjusting MADs for:
Avoiding over-voltage exposures. Tables R-7, R-8, and R-9 provide guidance for adjusting the Minimum Approach Distances to avoid possible over-voltage exposures due to switching surges, operation of overcurrent devices, etc. on ransmission systems.
Altitude adjustments. Table R-10 provides guidance for making altitude adjustments. At very high altitudes, the air is thinner and does not provide as uch insulation as altitudes near sea level.
The use of MAD tables other than R-6 must be based on engineering analysis using system parameters.
OSHA has proposed changing the MAD tables. See the proposed rule for additional information.