Ageing equipment poses arc flash risk
Mipac Engineering Manager Jon Burton explains how Mipac electrical engineers help clients with ageing plants minimise exposure to arc flash hazards.
Many of Mipac’s clients have been in the business of operating plants for many years.
Often their electrical distribution systems were designed in an era where the potentially more stringent requirements of today’s standards did not apply.
Electrical safety used to be primarily concerned with avoiding the potential for electric shock.
In more recent times, the focus has turned to preventing serious and sometimes lethal hazards associated with working near energised conductors caused by an arc flash.
An arc flash is the result of a rapid release of energy due to an arcing fault between a phase conductor and another phase conductor, neutral conductor or earth.
An arcing fault is similar to the arc obtained during electric welding and the fault can be initiated by an event such as accidental contact of a test probe between an energized conductor and earth or a failure such as an insulation breakdown.
(Aging electrical equipment is particularly susceptible to arc flash because of deteriorating insulating material.)
Energy discharge from an arc flash can be significant. The release can generate temperatures nearing that of the surface of the sun, as well as explosive pressure waves, shrapnel and toxic gasses, and they can cause severe burns and even death.
New electrical equipment is designed to standards that recognise and address arc flash hazards.
Some recent design approaches include the inclusion of arc flash vent ducts to direct hot gases away from a working area, the use of remote racking breakers to minimise workers’ exposure to arc flashes during high-risk activities and/or consideration of fast fault clearing time solutions.
The challenge for some of Mipac’s clients is what to do about existing electrical equipment.
The redesign or use of new technology is not always an economical or practical solution given the age of some clients’ equipment.
Mipac electrical engineers have the experience and knowledge to conduct arc flash hazard analysis studies to review a client’s present exposure and to determine the best solution to mitigate any risk.
The arc flash analysis requires the completion of a short circuit study and a co-ordination study.
Mipac electrical engineers perform these studies using ETAP® software.
The studies determine fault current levels and fault level clearing times which can then be used to perform the arc fault calculations outlined in IEEE 1584.
An arc fault calculation identifies the incident energy potentially present during an arc fault event.
An approach distance is also determined, as well as the appropriate PPE to be worn.
Mipac electrical engineers have the technical knowledge along with the industry experience to provide a practical and economical solution to this potential hazard.