Encyclopedia of Grounding (CA09040E)

that do not performan engineering determination found in 1910.269 Appendix C, should also be in conductive contact with a metal spike or nail that penetrates thewood at least as far as the climber’s gaffs, bonding it to thepotentiallymoreconductive interior of the pole. Additional protective jumpers are then installed fromthecluster bar to theneutral and then to each conductor, beginning with the closest one and ending with the farthest one. The workermust remainclear of theconductorsduring the installation of this safety equipment and not approach within the minimum approach distance. Acluster bar would typically not be used on a steel transmission tower. The worker’s parallel protec tive jumper would connect from the tower to the conductor, still below the worker’s feet. While the tower is itself a connection to theEarth, depending upon the tower’s age, the amount of corrosion or paint present may or may not represent a suitable current path. A part of the personal protective jumper assembly should consist of clamps with cable of sufficient length to reach from the ele vated worksite to the Earth below and be installed as described above. Procedures may be altered to fit different working conditions (for example, in substations or working froma bucket truck). More information is provided in following sections detailing these situations. Try to minimize the maximum number of jumpers in series that can be in parallel with the worker. There will be three series jumpers in parallel with the worker if hand contact is made to the further most distant phase (see Figure 9-6 of Section 9). Figure9-7reduces themaximumnumberofparallel jumpers to twoby thoughtful placement. Thismay or may not present a problem, depending upon their total resistances. The process of calculating themaximumresistancewiththeworker (inSection 9) should be reviewed. If the center phase can be safely connected first, the maximum number of jumpers in parallel with the worker will be reduced to two. If the resistance is still too high, it may be

Figure 9-7

necessary to use a larger cable size to obtain the necessary reduction in resistance.

Each connection should be situated so as not to interfere with the work being done. Finally, mini mize the cable slack because shorter cables have lower resistance and reduce possible mechanical whippingactionduringa fault that could strikeand injure a worker. This is especially true as fault cur rents approach 40,000 to 50,000 Ampere levels.

CHANCE® LINEMAN GRADE TOOLS™

10-3