Arc Flash incident is one of the most dangerous hazards faced by electricians all over the world. According to statistics, 5 to 10 arc flash explosions occur in electric equipment every day in the United States.
An electrical arc is a luminous bridge seen in the air gap between two set of conductors. The air between these conductors ionizes and creates a low resistance path for the current originating from one of those conductors. A low resistance path is created when a certain threshold voltage is developed on the conductor flowing through air and straight into the ground or any conductor nearby.
An arc flash occurs when a short circuit current flows through the air gap during a fault condition. When the magnitude of short circuit current is significantly high, the intensity of arc flash increases. This results in an increased temperature and pressure in the surrounding air between the conducting path causing an explosion known as an 'Arc blast.'The exploding arc blast comprises of heat, pressure waves and flying shrapnel, travelling at more than 700 miles per hour, which results in serious damage to nearby people and surrounding equipment.
OSHA recognizes arc flash as a life hazard which must be analyzed in order to assess the risk category of an equipment.
The Occupational Safety and Health Act of 1970 states, "An Act: To assure safe and healthful working conditions for working men and women…". According to Section 5 Duties, "Each employer shall furnish to each of his employee's employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees".
Additionally, it also states in 1910.132(d)(1) titled Personal Protective Equipment, "The employer shall assess the workplace to determine if hazards are present, or are likely to be present, which necessitate the use of personal protective equipment (PPE)".
NFPA 70E, article 130-5 states that an arc flash risk assessment shall be performed to govern the hazard, arc flash boundary, incident energy at working distance, and the PPE required within the working distance.
In summary, OSHA states what one must do, whereas NFPA states how one must do it. OSHA then measures how well the facility complies with the regulations set by NFPA.
Energy levels associated with an arc flash
In section 110.16 of the 2008 National Electric Code (NEC), it is stated that electrical equipment should be marked with hazards associated with an Arc Flash. These hazards are categorized based on a parameter known as "incident energy", which is a measure of the amount of electrical energy present on the surface of the equipment measured at a specific distance from the arc flash location.NFPA 70E outlines the hazard risk category associated with incident energy levels and suggests the protective clothing required to protect against arc flash.
|Hazard Risk Category||Clothing Description||Layer Requirement||Cal/cm²|
|0||Long Sleeves Shirts & Pants Hearing Protect Safety Glasses & Googles||1 Layer||0|
|1||Arc Rated FR Shirt & FR Pants or FR Coverall||1 Layer of PPE||4|
|2||Arc Rated FR Shirt & FR Pants or FR Coverall||1 or 2 Layer of PPE||8|
|3||Arc Rated FR Shirt & FR Pants or FR Coverall; & Arc Flash Suit that meets Minimum Arc Rating||2 or 3 Layer of PPE||25|
|4||Arc Rated FR Shirt & FR Pants or FR Coverall; & Arc Flash Suit that meets Minimum Arc Rating||3 or 4 Layer of PPE||40|
|Extreme Danger||No PPE Available||-||>40|
AllumiaX, LLC. specializes in conducting arc flash studies and complies with the global standards set up by OSHA and NFPA. Following the acts suggested above, we provide "Arc flash Reports" along with "Arc Flash Labels" indicating an equipment's risk category along with associated PPE clothing required for employees to interact. Moreover, we also provide training on arc flash, educating the employees on how to work with equipment.
We boast a group of talented and skilled engineers who are always ready to serve our clients requirements. Following is a short summary of what we provide in each of these studies:
Perform the analysis under worst-case arc-flash conditions to determine arc-flash incident energy levels and protection boundary distance and provide an analysis of all possible operating scenarios. Consequently, we provide you with relevant arc-flash labels for such equipment to ensure a safer workplace.
Determine SCCR & continuous current rating of Panelboards, Switchgears, Cables, ATS, etc. and provide you with respective reports.
Determine best achievable protective device coordination and provide relay/breaker settings and recommendations to optimize protection and minimal loss of power through selective coordination.
Identify key areas for improvement under normal and emergency conditions of the electrical network for safe operation of the power system.
Improve reliability of the system by minimizing the damaging effects of switching transients through snubber circuit studies.
AllumiaX is a licensed Engineering company headquartered in Seattle, Washington USA. We work with sub-contractors to deliver Power System Engineering Studies for industrial customers, hospitals, multi-residential housing building, heavy concrete facilities, commercial buildings, power plants, and more.
You can inquire for a quote any time and get a response promptly within 12 hours. Our team will coordinate with you regarding any queries and have your required studies completed as soon as possible.
About The Author
Abdur Rehman is a professional electrical engineer with more than eight years of experience working with equipment from 208V to 115kV in both the Utility and Industrial & Commercial space. He has a particular focus on Power Systems Protection & Engineering Studies.