An arc flash is an electrical breakdown of insulation in an electrical circuit resulting in an electric arc which can occur where there is sufficient voltage and a path to ground or lower voltage. Arc flash, and the blast associated with it, can cause electrical equipment to explode, resulting in an arc‐plasma fireball. The arc flash is accompanied by Ionization of the surrounding air, and vaporizing the conductive metal. Temperatures may exceed 35,000 degrees F in less than 1/1000 of a second, (the surface of the sun is 9000° F), in that amount of time, the flash heat can severely burn human skin and set clothing on fire. These high temperatures cause rapid heating of surrounding air and extreme pressures, resulting in an arc blast. The arc blast will likely vaporize all solid copper conductors which will expand up to 67,000 times its original volume when it is vaporized. The result of this violent event is usually destruction of the equipment involved, fire, and severe injury or death to any nearby people.
What Causes an Arc Flash?
Common causes of Arc‐Flash Incidents are; a reduction of the insulation or isolation distance between energized components and improper equipment operation such as a failure of a protective device to open or close properly. The root cause may be lack of proper maintenance, tools being inserted or dropped into a breaker or service area or conductive items accidentally left behind that compromise the distance between energized components. The most dangerous incidents occur when a worker is unaware of the hazard and fails to insure that the equipment has been properly de‐energized.
Why Should I be Concerned?
Arc Flash incidents typically occur in applications above 120V and can occur when electrical equipment is being serviced or inspected. The average cost of medical service for each of those incidents is over 1.2 million
dollars per occurrence, and does not address any lost wages or other damages or court costs.
An arc flash with 1000 amperes or more can cause substantial damage, fire, injury or death. The massive energy released in the fault rapidly vaporizes the metal conductors involved, blasting molten metal and expanding plasma outward with extreme force. In addition to the explosive blast of such a fault, destruction also arises from the intense radiant heat produced by the arc. The metal plasma arc produces tremendous amounts of light energy from far infrared to ultraviolet. Surfaces of nearby people and objects absorb this energy and are instantly heated to vaporizing temperatures. The effects of this can be seen on adjacent walls and equipment ‐ they are often ablated and eroded from the radiant effects. Usually the damage renders the equipment no longer usable causing a disruption of a facilities operation. The explosion can also bend and distort pieces of the equipment leaving it unsuitable for service. Recent studies indicate that gun powder and copper expand at roughly the same rate, so there is a correlation in blast patterns with arc flash/blast incidents.
What Can I do to Prevent an Arc Flash Incedent?
Arc Flash Hazard Analysis – An Arc‐Flash Study, performed by a knowledgeable Power Systems Engineer, will (1) identify the level of hazard for each electrical component and (2) Make recommendations regarding equipment and protective device settings and (3)provide warning labels to properly inform personnel of the hazard and appropriate Personal Protective Equipment required.
Training and awareness – All personnel that will be exposed to electrical equipment and potentially hazardous situation must be trained and aware of all known hazards.
Proper equipment maintenance ‐ All electrical equipment requires regular maintenance. Equipment malfunctions are a common cause of Arc Flash incidents. Equipment that is regularly serviced and maintained is more likely to function properly and reduce or eliminate an Arc‐Fault Incident.
Protective Device Coordination‐ Proper protective device coordination increases the likelihood that a fault will be isolated at the nearest upstream protective device and therefore minimize the hazard, downtime and equipment damage.
What is Required by Regulation?
OSHA 29CFR 1910.335 (a) (1)(i) requires the use of protective equipment when working where a potential electrical hazard exists and 29CFR 1910.132(d) (1) which requires the employer assess the workplace for hazards and the need for personal protective equipment.
OSHA compliance is required by any plant building or facility. OSHA standard CFR Part 1910 promotes the safety of employees working on or near electrical equipment, and clearly defines employers’ responsibilities such as:
Equipment must be de‐energized before work is performed.
If equipment cannot be de‐energized prior to work, Employees must be properly protected, and the employer must provide the appropriate Personal Protective Equipment (PPE)
Employers are responsible for performing a hazard assessment to identify the potential hazard so that the appropriate PPE can be determined.
NFPA 70E provides guidance on implementing appropriate work practices that are required to safeguard workers from injury while working on or near exposed electrical conductors or circuit parts that could become energized. Part II 2‐1.3.3 regarding Arc Flash Analysis states that a “Flash Hazard Analysis shall be performed before a person approaches any exposed electrical conductor or circuit part that has not been placed in an electrical safe work condition”. This Arc Flash Hazard Analysis must be done to determine the level of Personal Protection Equipment PPE that a worker must use, and the Arc Flash Boundary in inches along with the incident energy found at each location. Each panel must be marked with an ANSI z535 approved Arc Flash Warning Label.
The National Fire Protection Agency (NFPA) 70E Standard for Electrical Safety in the Workplace 2009 Edition Section 110.8(B)(1) requires that an electrical hazard analysis be performed to ensure that workers are properly protected whenever they work on or near equipment that is not in an “electrically safe condition”. This type of hazard analysis is typically performed by a registered engineer, experienced in this type of study. According to the NFPA 70E Section 130.3, the goal of arc flash hazard analysis is to identify:
The arc flash‐protection boundary, as “an approach limit at a distance from exposed live parts within which a person could receive a second degree burn if an electrical arc flash were to occur “based on the incident energy present at the working distance for the task to be performed, the proper PPE shall be selected.
The National Fire Protection Association (NFPA) Standard 70 ‐ 2008 “The National Electrical Code” (NEC) require labeling of equipment to warn of potential arc flash hazards. Each panel must be marked with an ANSI approved Arc Flash Warning Label to warn and instruct workers of the arc flash hazard, voltage, arc flash boundary and required PPE (Personal Protective Equipment). Subject to the requirements of the facility and arc flash analysis, labels are provided and attached for each analyzed point of concern.