Arc flash is the result of an electrical fault (such as a voltage source contacting a grounding source), and it presents an extremely hazardous condition.
The light and heat energy produces sufficient electrical energy to cause substantial damage, fire, injury or death. When an uncontrolled arc forms at high voltages, arc flashes can produce deafening noises, searing shrapnel and extremely dangerous temperatures.
Arc flash temperatures can reach or exceed 35,000 degrees F (19,400 C) at the arc terminals. The result is a volatile explosion that can cause destruction of equipment and injury not only to an electrical worker but also to bystanders. During the arc flash, electrical energy vaporizes metal, which changes from solid state to gas vapor, expanding it with explosive force.
Arc flashes are often witnessed from lines or transformers just before a power outage, creating bright sparks and flashes like lightning that can be seen for long distances.
One of the most common causes of arc flash injuries happens when switching on electrical circuits and, especially, tripped circuit-breakers. A tripped circuit-breaker frequently indicates a fault has occurred somewhere down the line from the panel. The fault should be isolated before switching the power on, or an arc flash can easily be generated.
The 43-second video below shows how quickly a situation can change when an arc flash occurs and the seriousness of the event.
The preferred way to remove the hazards of an arc flash is to de-energize electrical equipment before interacting with it. However, de-energizing electrical equipment is in and of itself an arc flash hazard.
One solution is called remote racking. Remote racking devices permit the insertion and removal of electrical devices while the operator is outside the flash protection boundary. Electrically operated devices, such as motor control and switchgear, can be opened and closed from a remote location, removing the operator outside the arc flash protection boundary.
Many companies offer arc flash personal protective equipment (PPE). The materials are tested for their arc rating. PPE provides protection after an arc flash incident has occurred and should be viewed as the last line of protection.
Reducing the frequency and severity of incidents should be the first option. This can be achieved through a complete arc flash hazard assessment and through the application of technology such as high-resistance grounding, which has been proven to reduce the frequency and severity of incidents.
Both the Institute of Electrical and Electronics Engineers (IEEE) and the National Fire Protection Association (NFPA) have joined forces in an initiative to fund and support research and testing to increase the understanding of arc flash. The results of this collaborative project will provide information that will be used to improve electrical safety standards, predict the hazards associated with arcing faults and accompanying arc blasts, and provide practical safeguards for employees in the workplace.
Arc flash hazard software exists that allows businesses to comply with the myriad of government regulations while providing their workforce with an optimally safe environment. Many software companies now offer arc flash hazard solutions.
For more information check out these specific guidelines below:
Standards
- OSHA Standards 29-CFR, Part 1910. Occupational Safety and Health Standards. 1910 sub part S (electrical) Standard number 1910.333 specifically addresses Standards for Work Practices and references NFPA 70E.
- The National Fire Protection Association (NFPA) Standard 70 - 2011 "The National Electrical Code" (NEC) contains requirements for warning labels. See NEC Article 110.16.
- NFPA 70E is the standard for related Personal Protective Equipment (PPE) as well as hazard ratings, equipment approach boundaries and labeling for electrical equipment. Failure to meet the requirements of NFPA 70E potentially puts service personnel at risk as well as provides for significant financial risk and litigation for a company.
- The Institute of Electronics and Electrical Engineers IEEE 1584 – Guide to Performing Arc-Flash Hazard Calculations.
