An Arc Flash is a type of electrical fault and electrical explosion or discharge that results from a connection through air to ground or another voltage phase in an electrical system.
Light, heat, fire and sound produced from an electric arc flash can cause substantial damage to personnel and equipment. High temperatures cause rapid heating of surrounding air that can vaporize all solid copper conductors, which will expand up to 67,000 times its original
volume when it is vaporized. The arc blast releases fire, intense light, and pressure waves in an
explosion of flying shrapnel.
When significant fault currents are flowing through several conductors that are in close proximity of
each other, the differences in potential, among other factors, will ionize the air, allowing a low
resistance path between the conductors. Improper tools, improper electrical equipment, corrosion of
electrical equipment, improper work techniques, lack of electrical safety training, and a lack of
preventative maintenance are just some of the events that make an arc flash more likely.
The energy released by an arc flash is a function of system voltage, available fault current at the location, and duration of the arc or fault clearing time. The fault clearing time is often the biggest contributor to the hazard level. This means that lower voltage equipment can frequently have higher arc flash hazards than higher voltage equipment.
There is no way to completely prevent an arc flash from happening.
There are a few ways we can limit the arc flash hazards:
2. Remote racking of breakers can be done with robotics and remove the worker from the arc flash boundary to eliminate injury, but it doesn’t prevent an arc flash from occurring.
3. Performing proper electrical maintenance and routine inspections such as infrared inspections and tightening of lugs helps prevent arc flash incidents from happening. Loose connections or missing insulation are common reasons for arc flash incidents that can be prevented with proper maintenance.
4. Training. Many arc flash incidents are preventable and the result of human error. Proper training of the operations of equipment as well as how to prevent an arc flash can help reduce the risk.
Arc Flash PPE protects workers from heat, noise, light and shrapnel.
Arc Flash clothing is designed to limit burns to second-degree burns. Clothing is FR (Fire Resistant) and the material designed to limit the amount of heat that can penetrate the material in order to prevent the skin from burning.
Additional equipment such as face shield, eye protection, leather glove and hearing protection protect the worker from light, noise, shrapnel and heat.
Working in Category 3 or Category 4 PPE can be hot, difficult and result in loss of dexterity and
vision. Some workers argue that while working in Category 4 PPE provides them more protection in
the event of an accident, they are more likely to make a mistake and cause and accident when
wearing Category 4 PPE. If the work does not require this for safety purposes, the worker should not
be exposed to this. Also, sometimes a situation exists where hazard levels are greater than 40
cal/cm2, aka over Category 4.
No. Arc Flash data is collected by Qualified Persons wearing appropriate PPE to collect the electrical data while the system is energized.
The cost of an arc flash risk assessment is based on a lot of variables with the electrical system design with the primary factor being the number of devices to be assessed and require an arc flash label. Other variables may include accessing equipment on overhead bus bars that require an aerial lift or drive time between locations.
Yes, you may conduct your own arc flash study, however, there are many IMPORTANT issues to
consider.
Conducting an arc flash study / analysis is a complex process and requires engineers familiar with
conducting power analysis studies and arc flash analysis in particular. Properly collecting all the data
is the first phase of the project, which is difficult for anyone to do if they are not first familiar with all
the potential outcomes and pitfalls of conducting an arc flash analysis. The engineer that conducts
the study needs to proficient in conducting short circuit studies, protective device coordination
studies and have a strong understanding of NFPA 70E and IEEE 1584.
Beyond technical qualifications, in-house assessments are something that plant managers or
engineers have little time for, often resulting in the project not getting completed or conditions of the
electrical equipment changing before completion, making the results void.
The biggest reason not to do the study internally is the cost of getting it wrong. If someone is injured
or killed due to an arc flash and the analysis was incorrect and done by someone who is not
considered qualified to conduct the study, the liability will rest with the person or group that
performed the study.
For some larger organizations that have multiple and large facilities and are willing to invest in
developing a team to perform the analysis and are comfortable with the liability, conducting the
studies internally can help save money. For all other organizations, conducting an arc flash analysis
internally typically has little or no upside compared to any cost savings.
OSHA mandates that employers identify electrical hazards, warn their workers about them and
provide the proper protective equipment and training related to working around the hazards. OSHA
provides the employer “what” to do, but does not define “how” to do it. The role of NFPA 70E, IEEE
and NEC is to provide guidance on “how” to properly implement the OSHA regulations.
The regulations that govern arc flash are:
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.
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 Study / Analysis states that an ” Arc
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 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 electrical panel must be marked with an ANSI z535 approved Arc Flash Warning
Label.
3. The National Fire Protection Association (NFPA) Standard 70 – “The National Electrical Code”
(NEC) contains requirements for warning labels, including ANSI compliance.
4. The Institute of Electronics and Electrical Engineers (IEEE) 1584 – Provides the Guide to
Performing Arc Flash Hazard Study Calculations.
The time to complete an arc flash risk assessment can vary greatly based on the following:
Compliance with OSHA involves adherence to a six-point plan:
A facility must provide, and be able to demonstrate, a safety program with defined responsibilities.
1. Calculations for the degree of arc flash hazard.
2. Correct personal protective equipment (PPE) for workers
3. Electrical Safety Training for workers on the hazards of arc flash.
4. Appropriate tools for safe working.
5. Warning labels on equipment. Note that labels are provided by the equipment
owners, not the manufacturers.