Protection from the elements

Published:  08 July, 2011

Electrical Arc Flash Mitigation is becoming an increasingly important element of safety management within any industrial setting and forms a central part of ensuring site security and minimising lost time. PWE reports.

There is still a need for greater awareness across industry of the dangers of arc flash and the effects it can have on the safety of personnel and the productivity of facilities, explains specialists TAS Engineering Consultants.

An Arc Flash Hazard is a dangerous condition associated with the release of energy in the form of a passage of electric current between two electrodes. An electrical arc can result in an explosive release of energy, which can cause injury to nearby personnel, and in extreme cases fatalities, damage to equipment and interruption to operations.
Generating temperatures in the region of 19,500oC, it is often assumed that an arc flash incident will only occur on large-scale electrical systems. 
“That is not the case as a hazard can exist at any voltage level”, advises John Maplesden, deputy chairman of TAS.  He continues: “In particular, analysis of a comprehensive collection of study results has revealed that around 5% of switchgear installations operating at 415v present a dangerous arc flash hazard.
“Awareness of the arc flash hazard has been growing over the past 15 years. However, despite these developments, the application of effective Arc Flash Studies and mitigation processes is not uniform, which results in serious lost time incidents, unnecessary injuries or even deaths.”
According to research by Chicago-based Capelli Schellpfeffer, Inc., there are between five and 10 arc flash injuries every day in the United States.
In addition, the American Institute of Electrical and Electronic Engineers (IEEE) reports more than 2000 US workers have been admitted to burn centres as a result of electrical incidents. 
“There have been no specific UK studies of the number of arc flash incidents”, reveals Maplesden.
“However, based on TAS Engineering Consultants’ experience, there may be more than 300 incidents in Britain every year and over 5000 across Europe.
“The fact that these figures are not definitive demonstrates that the UK and Europe is playing catch up with the US with regard to acknowledging and recognising the magnitude of the issue.”
Depending on the size and operational requirements of a switchboard, an Arc Flash incident can cause major interruption to site security and productivity.
Maplesden highlights: “In our experience, we have seen facilities lose up to £200,000 a day in lost productivity due to an electrical arc incident, based on shut down and replacement of systems.”
An Arc Flash explosion can cause several days of lost time depending on the severity of the incident and the operations of a facility.  While some organisations may lose a few days, specialist facilities such as petrochemical plants or offshore platforms will be far longer.
Maplesden adds: “We have seen some facilities have their productivity severely compromised for anything up to eight weeks depending on the specialist switchboards that will need replacing.
“A subsequent Health and Safety Executive investigation will also affect operations. In fact, it won’t just be the source of the incident that would be subject to scrutiny. The HSE could also place a shut down order on any similar equipment in a plant until they are satisfied with their safe operation.
“The same is also true if there is a death and an HSE restriction order could be placed on all electrical equipment that is at risk of causing an Arc Flash incident.”
To help prevent incidents and the potential enforced isolation of major electrical systems, appropriate risk assessment should be conducted to demonstrate that adequate measures are in place to mitigate any risks arising from electric arcs.
A risk assessment in the form of an Arc Flash Study has two elements.  The first is to perform calculations to quantify the energy released by an electric arc and the potential impact of incident energy on personnel.
The second element of the study involves an Electrical Safety Review covering risk assessment and the mitigation of the risks posed by electric arcs.
The Electrical Safety Review is a qualitative assessment of the probability of an arcing incident, based on multiple factors including the site operation and maintenance regime, together with the physical features of individual items of switchgear.
Maplesden warns: “Each Arc Flash Study is specific to each individual facility and there are no ‘rules of thumb’ or generic guidelines.
“This is because the energy generated by an electric arc is directly proportional to the arc current and the arc duration.”
He adds that the increasing acceptance of the role Arc Flash Studies play in site safety and lost time mitigation within wider site protocols ensures that greater knowledge is being gathered about arc flash: “Ongoing tests and research will provide a greater understanding of the electric arc: “It will bring significant safety benefits to industrial facilities as well as working towards eradicating site interruptions and productivity loss as a result of electrical arc incidents.”


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