Keeping Electricians Safe

Philip B. Allen, President, Grace Engineered Products, Inc
Creating and insuring an electrically safe work condition is critical for electricians performing maintenance on de-energized systems. The presence of voltage is the only determining factor if an electrical accident or an arc flash can possibly occur -- No voltage, No accident, No arc flash. "Voltage or no voltage" is also the basis of the NFPA 70E''s two primary themes: a) establishing an electrically safe work condition, and b) achieving safety while working on energized systems.
A voltage warning indicator, like the one shown here, is like a "hard-wired voltmeter" with the advantage that it needs no power supply because it is powered from the same "voltage" that it indicates. A voltage indicator is an additional safety measure between maintenance personnel and hazardous voltage.

Electrical accidents have the highest fatality rate of all industrial accidents and the NFPA 70e was the tool OSHA needed to enforce electrical workplace safety. Furthermore, this document demanded new procedures, added personnel protection equipment (PPE), and required rigorous training standards.
Higher electrical safety standards inevitably create a need for new safety products. An externally mounted voltage indicator . . . provides electricians with a flashing indication of voltages within a panel, before they open the panel.
If a typical plant electrician has an electrical accident while working on 600 V or below, there is a 4.1% chance that it will be fatal. This is 20 times the fatality rate when compared to the leading cause of occupational fatalities -- "Contact with Objects and Equipment" (fatality rate of 0.2% -- 873 deaths and 400,033 injuries). The National Safety Council estimates the direct cost for the employer of a fatality is $1,070,000.

External voltage indicators with redundant circuit designs and inherent reliability features combined with a lockout/tagout procedure that requires electricians to see it stop flashing after the isolator is opened will increase safety tenfold.
Hard-wired voltage indicators check voltage all the time without using a voltmeter. They operate on either ac or dc over a wide range of voltage; warn personnel if one, two, or all three phases are live; and accommodate unique power sources.
In most cases, an electrical system is electrically safe when the isolator is open. However, stored energy can be a secondary lethal power source, present for a time, after the system has been electrically isolated. Stored energy, created under an ac power source, is dissipated by the flow of dc currents to ground until the voltage level is zero. Because of this, the voltage-warning indicator needs to operate on dc and ac current and a wide range of voltage. This ensures that personnel have a visual warning until the stored energy has bled down to a safe level of 50 V or less.
Unique safety risks occur when a control panel has multiple power sources. If an electrician is greeted with flashing voltage indicators showing the locations of all live power sources within the panel, he immediately knows how the panel is being fed. Even a de-energized voltage warning indicator provides the physical location of de-energized sources of power.
An arc flash explosion may occur whenever there is a phase-to-phase or phase-to-ground fault. The arc flash risk increases every time a voltmeter checks live voltage between phases and/or ground. An external voltage indicator shows an electrician that no voltage exists, while the panel is closed. The arc flash risk is reduced because the electrician uses his meter to check that the panel is dead, not live. Remember -- no voltage, no arc flash.