The primary electrical safety concern of 29 CFR 1910.269(p)(4) and 1926.550 is work in proximity to live and unguarded electrical overhead lines by uninsulated equipment. Unless these lines are visibly grounded at the point of work and the owner of the lines indicates that they are deenergized, barriers or insulating protective material shall be installed to prevent worker contact with them. The following clearances shall be maintained between equipment and electrical overhead lines:

1. Lines 50 kV or below: 10 ft between the lines and any part of the equipment or load

2. Lines over 50 kV: 10 ft plus 0.4 in. for every 1 kV above 50 kV.

In locations and situations where it is possible that the operator may have difficulty observing that these clearances are being maintained, someone shall be designated to monitor the clearances and provide the operator with timely warning before contact can be made. The use of cage-type boom guards, insulating links, or a proximity sensor shall not alter the electrical safety requirements of 29 CFR 1910.269(p)(4) and 1926.550, even if these devices are required. (See Figure 6-2.)

Figure 6-2. A minimum clearance of 10 ft between overhead power lines and equipment is required for 50 kV and below while a clearance of 10 ft plus 4 in. for every kV above 50 kV is required.