Electric arc flash is a serious hazard which has the potential for personnel injury, equipment damage and loss of business objectives. The UK is regulated by the Health and Safety At Work Act and the electrical industry specifically by the Electricity At Work Regulations. But neither makes specific reference to the dangers and risks of arc flash. The UK electrical industry tends to puts less emphasis on the dangers of arc flash than some other countries and yet the risks exist within any electrical installation.
What is an Arc Flash?
An arc flash is an electrical explosion resulting from a low impedance connection to earth or another voltage phase in an electrical system. High temperatures cause rapid heating of surrounding air and extreme pressures, resulting in an arc blast. The arc blast (that results from the arc flash) will likely vaporize all solid copper conductors, expanding 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. An arc flash happens without warning. This typically results in the complete destruction of equipment involved and severe injury or death to people inside the arc flash boundary at the time of the incident. The energy released by an arc flash is a function of system voltage, available fault current at the location, and duration of the arc.
Where or when can an arc flash occur?
The theory that arc flash hazards are greater at higher voltages is a common misconception.
It is far more common for low voltages, such as 400v/230v, to have higher arc flash hazard levels because of the combination of higher fault currents and long clearing times of the protective devices.
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.
What can be done to minimize the risk of Arc Flash?
There is no way to completely prevent an arc flash from happening in electrical distribution systems.
The best one can do is to mitigate or reduce the risk. This requires procedures to be employed to identify the hazard and put in place measures to minimise the risk.
One of those measures is to conduct an Arc Flash Study to identify the arc flash energy incident levels at various points within an electrical installation. This will determine the working procedures to be adopted and the level of PPE required. Other measures include regular maintenance and training.
What Protection is available against Arc Flash?
In order to select the proper PPE (personal protective equipment), incident energy must be known at every point where workers may be required to perform work on electrically energized equipment.
These calculations are determined in an arc flash study and need to be performed by a qualified person such as an electrical engineer. NFPA 70E offers a guide to proper protection. All parts of the body that may be exposed to the arc flash need to be covered by the appropriate type and quality of PPE. Proper PPE can include Arc Resistant clothing, hardhat, hood, face shield, safety glasses, gloves, shoes, etc. depending upon the magnitude of the incident energy present.
What Training is Available for Arc Flash Hazard Awareness ?
Proactive Technical Training offers a one day course in Arc Flash safety awareness. This one-day course has been designed to introduce students to arc flash hazard safety. It covers legislation, terminology, an explanation of arc flash studies and energy incident levels, hazard and risk analysis and the requirements for PPE.
This course is open to Electrical Engineers, Electricians, Technicians and anyone responsible for, or working on or near electrical installations and switchgear.
