Health & Safety
The complex hazard of electric arc
Mike Frain and Elaina Harvey outline how to assess and manage this risk of electric arc flash.
U
nfortunately, electrical flashover or arc flash is one of the most deadly and least understood hazards of electricity and is prevalent in most industries, particularly the utility sector.
Each year around 1,000 electrical accidents at work are reported and as many as 251
people die
from their injuries. It is widely recognised the higher the voltage of an electrical power system, the greater the risk for people working on or near energised conductors and equipment. However, arc flash can actually be worse and more common at lower voltages and can cause devastating, severe burn injury and even death.
The law Te introduction of the Corporate Manslaughter Law in April 2008 in the UK meant that, for the first time, companies and organisations can be found guilty of corporate manslaughter through serious management failures resulting in a gross breach of a duty of care. Te Act clarifies the criminal liabilities of companies including large organisations where serious failures in the management of health and safety result in a fatality. Ultimately this law has been implemented to persuade businesses and those responsible to conduct best practice at all times to ensure the safety of their employees and reduce accidents and deaths at work.
What is an electric arc flash? An arc flash is usually caused by inadvertent contact between an energised conductor such as a bus bar or wire with another conductor or an earthed surface. When this occurs, the resulting short circuit current will melt the conductors, ionise the air and create a conducting plasma fireball with temperatures in the core of the arc that can reach upwards of 20,000˚C. Severe injury and even death can not only occur to persons working on the electrical equipment but also to people located nearby. Arc flash injury can include external burns to the skin, internal burns from inhaling hot gasses and vaporised metal, hearing damage, eye damage such as blindness from the ultraviolet light of the flash as well as many other devastating injuries.
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Depending on the severity of the arc flash, an explosive force known as an arc blast may also occur which can result in pressures of over 100 kiloPascal (kPa), launching debris as shrapnel at speeds up to 300 metres per second (m/s).
Fig. 1. Arc flash is usually caused by inadvertent contact between an energised conductor such as a bus bar or wire with another conductor or an earthed surface.
Survivors of such injuries may require extensive treatment and rehabilitation and the cost of these injuries can be extreme, physically, emotionally and
Picture: DuPont
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