Mike Frain Writes An Article For The Maintenance And Asset Management Magazine – July 2012

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Arc Flash – What is it and could it really occur in your business?

So you’ve got your personnel in place to ensure that you’re compliant with the legislative requirements around electrical safety in the workplace. Personnel within the business don’t come in to contact with high voltage equipment so arc flash just isn’t a concern for you, right?…Wrong!

Lets look at Arc Flash, what is it? How easily can it occur and how can you safeguard your company and personnel.

What is Electrical Flashover or 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

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 kPa, launching debris as shrapnel at speeds up to 300 m/s.

Bearing this in mind, it’s clear that should arc flash occur whilst personnel are operating or working on equipment, the consequences could not only be catastrophic for them but also for others working in the vicinity.

It goes without saying that the injuries caused by arc flash can be devastating and life threatening, therefore it’s imperative that management personnel within almost any business should be aware of the risk and put steps in place to minimise it.

Does Arc Flash only occur in high-voltage work?

The short and simple answer to this question is NO. All industries have a level of risk, but there are, of course, those that carry a higher risk, such as utilities, energy producers and providers, mining, manufacturing companies (particularly those in the food, pharmaceutical and chemical sectors), hospitals, large commercial organisations, data centres, education establishments and large leisure facilities.

For low voltage work, the following is a list of those activities that have the potential to initiate an arc (and some of which have been shown to be common causes of electrical flashover)

  • Connecting cables into live equipment
  • Testing; especially with substandard instruments and test methods
  • Testing on damaged cables and equipment. There are several known cases of arc flash due to using voltage indicators on faulted cables
  • Inspections or any interactions which involve the exposure of live voltage conductors
  • Work on, or adjacent to, live low voltage conductors that are insulated but where the work may adversely affect the integrity of that insulation. Examples are drilling into panels and drawing cables into cable management systems
  • Custom and practice activities such as installing or repairing equipment which is adjacent to exposed live low voltage conductors
  • Removal and replacement/insertion of components such as circuit breakers into energised panel boards and large power bus bar tap off units
  • Live underground cable jointing
  • Switching and racking out poorly maintained or legacy LV switchgear
  • Replacement of fuses and links especially onto faults

How to minimise the risk of Arc Flash in your workplace

The arc flash hazard needs to be determined by risk assessment, out of which the decision to work live or dead and the required precautions will be derived. The need for risk assessment is embodied in European Law through Directive 89/391 (EU Workplace Health and Safety Directive) and the associated guidance which identifies electrical work as a ‘high risk’ activity. The European Agency for Safety and Health at Work defines risk assessment as the process of evaluating risks to workers’ safety and health from workplace hazards. It is a systematic examination of all aspects of work that considers – 1. What could cause injury or harm, 2. Whether the hazards could be eliminated and, if not, 3. What preventive or protective measures are, or should be.

Working with a company such as Electrical Safety UK to carry out initial risk assessments, develop and initiate safety programs in your work place and train staff team on safe working practices provides piece of mind for you and your employees whilst setting your company up with a robust electrical safety program to safeguard both the company and those working within it well into the future.

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