Arc Flash: What It Is, Why It Happens, Why it's Dangerous and How To Protect Against It
Whether you’re seeking OSHA compliance, or want to learn about the life-threatening dangers of flashover, arc flash protection is essential for operation of a safe and reliable power infrastructure.
What is Arc Flash?
Arc flash (sometimes called a flashover) is an electrical phenomenon that creates a dangerous, high-temperature explosion or discharge that results from fault condition or short circuit (often called an arc fault).
What causes Arc flash?
Arc faults are caused by electrical current leaving its intended path and traveling through the air to another conductor, another voltage phase in the system or to ground.
For example, when a wire makes contact with an earthed system.
There are a variety of reasons why an Arc Flash can occur, but most of them are human error and preventable. Many arc flashes occur when maintenance workers are manipulating live equipment for testing or repair and accidentally cause a fault or short circuit. Improper tools, improper electrical equipment, corrosion of equipment, improper work techniques and lack of electrical safety training are just some of the events factors that can lead to a devastating arc flash or arc blast.
Additional factors that contribute to an Arc flash accident including:
Dropping un-insulated tools or metal parts
Equipment or Material failure
Using incorrectly specified instruments
Live work on damaged equipment such as cables
Loose connections and exposed live parts
Lack of awareness and training
Why Is An Arc Flash Dangerous?
When an arc flash happens, it does so without warning and is lightning quick. When there is a rapid expansion of air and vaporized material from arc flash, an arc-plasma fireball or arc blast may occur with temperatures exceeding 35,000° F (the surface of the sun is 9000° F). These high temperatures cause rapid heating of surrounding air and extreme pressures, resulting in an arc blast.
The heat and explosive force from an arc blast can exceed 2,000 lbs. / sq.ft, creating fire, vaporizing all solid copper conductors and causing the propulsion of molten metal and equipment parts at up to 984 ft/s meters per second.
In power systems with improper arc flash protection, the results of an arc flash are often violent - damaging the electrical infrastructure and when a human is in close proximity, serious injury and even death can occur.
Injuries from arc flash or arc blast can include but are not limited to:
External burns (i.e. severe burns to the skin)
Internal burns from inhaling hot gasses
Shrapnel wounds from debris impact
Eye damage and blindness from the ultraviolet light of the flash
Aside from the danger, an arc flash can also render equipment unusable and force extended downtime with serious financial consequences. PPE helps avoid bodily harm, but it does not prevent equipment damage. This leads to the question of how to prevent an arc flash in the first place.
Proper safety and protection measures must be taken to protect your people and limit the damage from an arc flash, which include conducting an arc flash study, short circuit study, and NFPA 70E electrical safety training.
How To Protect Against It
Other than isolating the power supply, completely eliminating the arc flash hazard is very difficult, control measures can be adopted to reduce both the hazard and likelihood of taking place, therefore reducing the risk.
Because an electrical arc flash can happen at any time during your power equipment’s lifecycle, one of the critical steps for optimizing safety is to use proper PPE. That’s why one goal of HIPP’s arc flash protection studies is to “right size” the amount of personal protective equipment (PPE) and potential arc flash energy to levels that allow tasks to be performed on equipment in an unobtrusive manner.
Electrical PPE includes items such as rubberized clothing that does not conduct electricity. While PPE helps avoid bodily harm, it does not prevent equipment damage. This leads to the question of how to prevent an arc flash in the first place.
One of the best ways to combat the risk of arc flash is to have an arc flash study performed by an electrical safety professional.
HIPP offers a number of arc flash mitigation solutions that make this possible, starting with a power system study. A power system study typically consists of short circuit, coordination, and arc-flash hazard studies. While sometimes these individual areas may be considered separately they are all very much interrelated and it is recommended that these be performed at the same time, by the same entity, to ensure the most accurate results and greatest cost efficiency.
With a HIPP power system study, risks are identified and a mitigation strategy developed which allows both passive and active arc flash protection solutions to be implemented. Our systems work in compliance with the National Fire Protection Association (NFPA) 70E: Standard for Electrical Safety in the Workplace.
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