Over the next few installments of “Voice of Experience,” I’ll be reviewing some accidents that have taken place in the electric utility industry. I’ve had many requests for information about incident investigations and would like to share some details in hopes of preventing similar accidents in the future. Distribution cover-up will be the focus for this issue’s column.
Approximately half – or even more – of accidents that result in flashes and electrical contacts are the result of poor cover-up or total lack of rated protective cover. Why would a lineworker not take the time to install protective cover that would assure a safe work area? According to statistics and accident reports, the industry suffers an average of one contact or flash every week. That needs to stop.
Investigations into many accidents, some of which involved fatal contact with system or source voltages, have revealed that failure to cover up all differences of potential in the immediate work area was the common denominator in most flashes and contacts. If you are or your company is following the minimum requirements found in OSHA 29 CFR 1910.269(l), “Working on or near exposed energized parts,” it is simply not enough to ensure an employee is totally protected from differences of potential in the work area.
The human body essentially is a 1,000-ohm resistor in an electrical circuit. When a lineworker fails to cover energized parts as well as differences of potential in the immediate work area, as little as a 50-volt AC electrical source may enter the body. If the current path crosses the heart, as few as 40 to 50 milliamps can induce atrial fibrillation, cause the heart to stop sinus rhythm and electrocute the worker. The industry is quite familiar with medium-voltage contacts but many times lacks respect for low-voltage contacts that can be just as fatal.