ARC FLASH & arc flash hazard analysis
 An Arc Flash is an electrical explosion due to a fault condition or short circuit when either a phase to ground or phase to phase conductor is connected.
An Arc flashs creates an arc-plasma fireball that has extreme pressures and
temperatures, causing electrical equipment to explode. 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.
The amount of energy released by an arc flash is dependent:
1. System Voltage
2. Magnitude of Current
3. Fault Clearing Time (duration of the arc)
Many of the most dangerous arc flash hazards are found at low voltages (<480v)
due to a longer clearing time of the fault protection equipment.
WHY ARC FLASHES HAPPEN
There are a variety of reasons why an Arc Flash can occur, but most of them are
human error and are preventable. An arc flashs can occur when maintenance workers are manipulating live
electrical equipment for testing or repair and accidentally cause a fault.
Improper tools, improper electrical equipment, corrosion of equipment, improper
work techniques and lack of training are just some of the events that can lead
to a devastating arc flash / arc blast.
ARC FLASH COMPLIANCE
There are four main regulations and standards that work together to govern
arc flash as it relates to electrical safety. In the most simple terms,
OSHA is a federal law that states that workers must identify and warn workers of
hazards in their facility and provide them the proper training and protection to
work near those hazards. While OSHA is law and defines "what" to do,
it does not define "how" to do it. The other three standards, NFPA 70E,
NEC and IEEE1584 define "how" to properly identify and warn workers of arc flash
hazards.
1. 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. 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
a federal law.
2. 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 done 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
incident energy, the level of Personal Protection Equipment (PPE) that a worker
must use and the Arc Flash Boundary for each location. Each panel must be marked with an ANSI z535 approved Arc Flash Warning Label.
3. The National Fire Protection Association (NFPA) Standard 70
- 2002 “The National Electrical Code” (NEC) contains requirements for warning
labels that identify the arc flash hazard.
4. The Institute of Electronics and Electrical Engineers (IEEE) 1584
provides the guidelines on how to perform Arc-Flash Hazard Calculations.
THE ARC FLASH ANALYSIS
An Arc Flash Analysis is a calculation performed by Professional Engineer to
determine the incident energy found at each location that determines the various
arc flash boundaries as well as determining what personal protective equipment
(PPE) must be used in approaching each boundary. An Arc Flash Analysis
should only be performed by experienced and qualified engineers.
ARC FLASH LABELING
The NEC®and NFPA 70E 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.
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