Sometimes, things go wrong. But, as electrical engineers, it’s our job to prevent errors, injuries, or worse – catastrophes. One of the problems that can occur when a piece of equipment is being worked on is arc flash – which is a dangerous release of energy.
Arc flashes are caused by an arc fault between a phase bus bar and another phase bus bar, a neutral, or a ground. When the fault occurs, energy is released, resulting in an explosion of light and heat that can cause damage to the equipment, surrounding area, the person working on the equipment.
The intensity and danger of an arc flash depends on the available fault current at the equipment, the time that passes before the circuit breaker protecting the equipment opens, and the distance from the fault. No matter the intensity, arc flashes are extremely dangerous and steps must be taken in order to protect equipment as well as any personnel that may work on the equipment.
All equipment that is likely to require examination, adjustment servicing, or maintenance while energized is required to have arc flash labeling per the National Fire Protection Agency to warn any personnel working on the equipment of the dangers.
These requirements are listed in the National Electrical Code (NEC) and The Handbook for Electrical Safety in the Workplace (NFPA 70E). Section 110.16 in the NEC simply requires a label on equipment warning of the possibility of an arc flash. Section 130.5(C) in NFPA 70E requires a label on equipment warning of the possibility of an arc flash as well as the hazard/risk category of the equipment, required protective equipment for any personnel working on the equipment, the system voltage, and the arc flash boundary.
Since the label required by NFPA 70E is so complex, electrical engineers must perform arc flash analysis that provides all the required information. To do this, the engineer must collect data about the electrical system and model the system in special arc flash analysis software that determines the conditions that would occur if an arc flash occurred.
Once this analysis is complete, a label can be created and given to the electrical contractor to place on the equipment after installation. The NEC and NFPA 70E do not give specific requirements for the design of the label, but the NEC refers users to the ANSI Z535 Product Safety Signs and Labels standard for guidance.
Arc flashes are a dangerous occurrence that can happen anywhere at any time. These arc flashes and explosions can cause serious injury and death to anyone near or working on equipment. An arc flash analysis is required on each piece of equipment in order to provide required labeling that will inform anyone working on the equipment of the appropriate precautions to take in order to minimize danger. The main goal of arc flash analysis is to protect those working on the equipment and try to minimize the chances of injury if an arc flash does occur.
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