4.4: Preventive Measures for Workers to Consider
- Page ID
- 63471
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Before work begins, be sure that the: (1) Equipment/activity is located within a safe working distance from power lines (2) Utility company has de-energized and visibly grounded the power lines or installed insulated sleeves on power lines (3) Flagged warning lines have been installed to mark horizontal and vertical power line clearance distances (4) Tools and materials used are nonconductive.
Be sure the utility company has confirmed the voltage and therefore the safe working distance from the power lines. Also, if applicable and feasible, use a/an: observer; insulated link; boom cage guard; proximity device. If provided, use installed rider posts under power lines to avoid working too close to the power lines. Use nonconductive ladders and be sure to retract them before moving. Ensure that no materials are stored under power lines. Use caution tape and signs to cordon off area under power lines. Locate and know what the markings from the local underground line locator service has marked before digging. Hand dig within three feet of cable location. Be aware that more than one underground cable may be buried in area of locator markings.
A ground fault circuit interrupter (GFCI) is a fast-acting circuit breaker that senses small imbalances in the circuit caused by current leakage to ground and, in a fraction of a second, shuts off the electricity. The GFCI continually matches the amount of current going to an electrical device against the amount of current returning from the device along the electrical path. Whenever the amount “going” differs from the amount “returning” by approximately 5 milliamps, the GFCI interrupts the electric power within as little as 1/40 of a second. A "GFCI" is a ground fault circuit interrupter that is designed to protect people from severe and sometimes fatal electrical shock. A GFCI detects ground faults and interrupts the flow of electric current, and is designed to protect the worker by limiting the duration of an electrical shock.
Example of the GFCI at work: An old drill that has a loose bare wire inside it touching the outer metal housing is being used. With the drill plugged in, the housing is charged with electricity. If it is used outside in the rain and the worker is standing on the ground, there is a path from the hot wire inside the drill through the worker to ground. If electricity flows from hot to ground through the worker, it could be fatal. The GFCI can sense the current flowing through you because not all of the current is flowing from hot to neutral as it expects -- some of it is flowing through the worker to the ground. As soon as the GFCI senses that, it trips the circuit and cuts off the electricity.
Workers need to inspect extension cords prior to their use for any cuts or abrasion. Extension cords may have damaged insulation. Sometimes the insulation inside an electrical tool or appliance is damaged. When the insulation is damaged, exposed metal parts may become energized if a live wire inside touches them. Electric hand tools that are old, damaged, or misused may have damaged insulation inside. Flexible cords used with temporary and portable lights shall be designed for hard or extra-hard usage. They shall be marked with usage type designation size and number of conductors. The cord could be marked with a 14/3 meaning the conductor size (AWG) is 14 and the number of conductors is 3.