Arc flash is the exposure of the skin to incident energy from an electrical arc. The severity of the exposure can be quantified in terms of thermal energy per unit area of exposure.
In the USA, the NFPA 70E-12, Electrical Safety in the Workplace, the focus is on a burn injury from arc flash being reduced and to be survivable. The energy threshold used in most standards to determine survivable is the energy which would result in a second-degree burn - 1.2 Cal/cm2.
A second-degree burn is identified as:
· Deep partial thickness
· Extends into deep (reticular) dermis
· Appears yellow or white, less blanching, may be blistering
· Being a fairly dry texture
· Causing pressure or discomfort
· Having a healing time of 3-8 weeks
· Prognosis of scarring and contractures (may require excision and skin grafting
[Refer Wikipedia – Burn]
The risk associated with an electrical arc flash can be managed through a variety of methods of risk assessment and risk control. Ideally, the risk should be as low as reasonably practicable (ALARP). For a person suffering an arc flash at work, there is a cost associated with a second-degree burn, to the person, to the employer and to the facility
The level of possible arc flash exposure can be identified during the design phase of a project and action taken to minimise the incident energy of a potential arc flash. For an existing installation, an audit of the electrical system can expose areas of excessive arc flash incident energy and remedial action can be proposed. Arc flash labels are fitted to electrical equipment to clearly identify the arc-flash boundary, working distance, incident energy and the required protective clothing (PPE).
Is it compulsory to provide arc flash studies and arc flash warning labels? In the USA the arc flash standard was introduced as NFPT 70 and it is mandatory because of occupational health and safety (OHS) regulations. NFPT 70 covers both low voltage and medium voltage installations.
In Australia, there is the standard AS/NZS 4836:2011, safe working on or near low-voltage electrical installations and equipment. The standard covers the principles of safe working practices and the recommended procedures for safe working practices. It includes recommendations to manage many hazards associated with electricity, including
arc flash. This standard is referenced in legislation. It applies to all persons carrying out work on or near low-voltage electrical installations and equipment.
BESST provides arc flash services both for the design phase of a project and for audits of existing installations.
The most cost effective method of reducing arc flash energy can be identified and the measures required for implementation can be advised. BESST provide arc flash labels for each item of electrical equipment. The arc flash study is based on IEEE 1584 2002-2004 and is in compliance with NFPA 70E 2000, 2004, & 2009.