Beware arc flash!

What is an arc flash?

An arc flash is an instantaneous and uncontrolled release of significant energy when a short circuit fault occurs.

The arc flash plasma temperature can be as high as 20,000°C.

Arc flash hazards

Arc flash hazards include:

•• electric shock from contact with an electric circuit

•• burns from exposure to heat energy

•• blast trauma from exposure to blast pressure waves

•• respiratory trauma from exposure to toxic gases.

Understanding electrical arc flash hazards

Employers have a duty to not expose employees to hazards in the workplace. To understand the electrical arc flash hazard, an arc flash study should be conducted by a competent electrical engineer. This will provide the data necessary to determine effective controls that reduce the risk of harm to workers from the arc flash hazard.

The actions taken from the arc flash study to inform and protect employees are often in the form of labelling on the electrical switchgear. Labelling in itself does nothing unless its intent is understood by users of the equipment.

Several international standards exist relating to assessing arc flash hazards. Although IEEE 1584 Guide to performing arc flash calculations (from the Institute of Electrical and Electronic Engineers, USA) and NFPA 70E Standard for electrical safety in the workplace (from the National Fire Protection Association, USA) are not mandated standards in Australia, they provide guidance on hazard quantification and electrical work practices relating to arc flash.

Arc flash risk management

The risk of an arc flash incident should be minimised by applying the hierarchy of controls.

Eliminating the hazard (level 1) through deenergisation of equipment is the preferred method. This method is reflected in the Department's new code of practice for working on or near energised electrical installations.

The second option, which is becoming more prevalent, is remote switching of electrical switchgear. This removes the switching operator from the line of fire when either de-energising or energising switchgear (isolating or segregating the hazard from people).

If elimination or isolation of the hazard is not possible, engineering controls may be introduced. Typical engineering controls include well-designed electrical protection systems, supported by a preventative maintenance program, to ensure circuit protection equipment operates correctly when required.

The time and effort spent implementing the recommendations of a thorough arc flash assessment will generally have ongoing benefits for the business not only through the safety and health benefits for employees, but also by minimising damage and down time associated with a major electrical fault.

New code of practice for persons working on or near energised electrical installations

In May 2018, the Department released a code of practice for persons working on or near energised electrical installations.

This code of practice requires that all electrical installations to be de-energised before any nearby work commences, except for certain specific situations that are prescribed in regulation 55 of the Electrical (Licensing) Regulations 1991.