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From the Forensic Files of NIOSH

Jan 1, 2007 12:00 PM

Even the most experienced electrical industry employee is susceptible to on-the-job hazards. Case in point: A journeyman electrician with 20 years of experience was electrocuted when he made direct contact with a bare section of an energized 240V electrical conductor in the base of a streetlight pole. The victim, who worked for an electrical construction company contracted by a state agency, was the foreman of a two-person day crew charged with replacing existing mercury vapor lamp heads with high-pressure sodium lamp heads on streetlight poles along a busy city roadway in Minnesota. Working at the base of the 50-foot poles, he would remove a fuse on the line-side of the ballast to kill power in the pole to the lamp head, disconnect the ballast, and prepare/splice together wires to bypass the ballast. He would then reinsert the fuse when the other crew member (situated at the top of the pole in an aerial bucket) had disconnected the old head and installed a new one.

Cones and directional traffic signs for barricading workers were in place, and the workers were wearing full reflective suits. The weather was hot and humid after a recent rain, with dew remaining on the grass late into the morning. Although high-voltage and leather work gloves were on hand at the site, they were not in use at the time of the incident.

Electrical power from feeder boxes to the base of poles was not shut down during the replacement process so that new lamp heads could be checked for operation immediately after installation. At the time of the accident, work had proceeded to the point where the fuse had been removed from the base of the pole, and the black wire from the ballast to the fuse had been cut and trimmed in preparation for the splice. The next step would have been to cut the wire from the lamp and splice it to the black wire with the fuse retainer. Evidence suggests that the victim inadvertently contacted the 240V lead conductor from the feeder box, on the energized side of the fuse, as he reached for the wire that went to the lamp, ultimately leading to his electrocution. Later inspection of this conductor showed that approximately 2 inches of insulation had been gnawed away by rodents.

Despite his coworker's efforts at CPR, the victim could not be resuscitated and was pronounced dead at a local hospital. Burns were found on his right thumb, middle, and ring fingers. No exit wounds were observed.

NIOSH recommends following these guidelines to avoid similar tragedies:

Perform electrical work with electrical power off, if possible. Power to the streetlights could have been disconnected during the day when lights for traffic were not necessary. After head replacement on all poles was complete, power could be reconnected to determine which heads, if any, required repair. A work procedure such as this, although it may require more time, may be warranted when conductor condition inside poles is unknown.

Install nonconductive barriers where maintenance may be required. When poles are initially installed, barriers to separate energized and de-energized conductors at fuses likely to require later maintenance could be put in place. If it is necessary to work near the conductors with electrical power on, then the barrier would provide protection for the worker.

Wear protective gloves when working around energized conductors. High-voltage and leather work gloves were at the incident site, but were not being used by the victim. It is sometimes difficult for workers to perform fine, manipulative electrical work with heavy gloves on, but when conductors are exposed to damaging environments and/or cannot readily be seen by workers, gloves should be worn at all times. Supple leather work gloves that provide protection up to 750V are available.

Examine and ensure the integrity of conductor insulation. When it is absolutely necessary to work near energized conductors, examination of conductor insulation is essential to ensure worker safety. If damage to the insulation is observed, proper personal protective equipment (gloves) and/or measures (disconnect power) should be used to prevent injury to workers.

Reprinted with permission from the National Institute for Occupational Safety and Health (NIOSH), Division of Safety Research (DSR). All electrical-related FACE reports can be viewed in their entirety at http://www.cdc.gov/niosh/face/default.html.

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