6 December 2006
Including change 1, 7 December 2006
location of energized equipment and its voltage level at each job site. Additionally,
workers must be aware of the possible sources of electrical feedback from other
energized power sources into the work site. These hazards must be determined before
starting work. Pre-job planning must include engineering guidance in understanding the
system's operation and review of up-to-date single line and schematic as-built drawings.
All apparel, tools, and other equipment required for worker safety must be identified and
available before beginning the job.
Electrical Shock Dangers and Effects. Electric shock results from setting
up an electric current path within the human body. The current flows because there is a
potential gradient (voltage difference) between an energized object and the grounded
worker. Figure 1-1 shows potential gradients and the safe area or equipotential zone
which has no potential gradient. Figure 1-2 indicates current flow paths. Table 1-1
indicates the effects of 60-hertz current on humans.
Figure 1-1. Ground Potential Gradient
Ground Potential Gradient
Energized Grounded Object