In my introduction to this guide, I explained my view that arc flash is, very simply a hazard which should be approached in the same way as any other. 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. Other electrical hazards such as electric shock obviously need to be assessed but are not the focus of this guide.

A risk assessment must be performed where there could be danger which may include performing an arc flash calculation study to define the severity of the hazard. It is a fact that many workers are put to work on very high incident energy equipment without a thought for the consequences which results in a huge risk to the company and the individual. There is a need to evaluate the arc flash risk and the methods for controlling that risk as part of the process. The amount of energy that could be released in an electrical flashover is the starting point in that evaluation. Once that is known then risk control measures can be explored to determine the test of reasonableness in working live and also suitable precautions that will be required to prevent injury.

In 1989, what would be known as the “European Framework Directive” number 89/391/EEC (Workplace Health and Safety Directive) was passed which introduced measures to encourage improvements to the safety and health of workers. A cornerstone of this directive is risk assessment which means that any employer must evaluate all the risks to the safety and health of workers. For electrical safety, this means that the arc flash hazard cannot be simply ignored even though there are no prescriptive standards in place, such as in the US and Canada and certainly no direct link from the hazard directly to arc flash PPE.

Directive 89/391/EEC creates an obligation on behalf of the employer to assess the level of risk involved in the workplace and the effectiveness of the precautions in place. For electrical work, all hazards should be considered, including the arc flash hazard and not purely shock, as is often the case with many European companies. Arc flash risk assessment for workers who operate in proximity to, or on, energized electrical equipment, cables and overhead lines, is an essential part of electrical safety management. Electrical work must be carried out with conductors de-energized and isolated wherever possible and there is an extremely low tolerance for live working in many European countries.

As a result, many manufacturing plants restrict live working to inspection, diagnostic testing and commissioning purposes. There are, however, many tasks that require working either on, or near to energized equipment. Even then, it should also be acknowledged that the process of de-energization often requires exposure to the hazard through interactions such as switching, racking, and testing of equipment.

The need for risk assessment is embodied in Law through Directive 89/391/EEC and UK Management of Health and Safety at Work Regulations 1999 and the associated guidance which identifies electrical work as a “high risk” activity. As a minimum you must:

1. Identify what could cause injury or illness in your business (hazards).
2. Decide how likely it is that someone could be harmed and how seriously (the risk).
3. Take action to eliminate the hazard, or if this is not possible, then control the risk.

3.1 Hazard and Risk

Before we consider the subject further, it may be worth defining what we mean by the terms hazard and risk in the context of arc flash.

The European definition for the term hazard means anything that has the potential to cause harm. In the case of arc flash the potential to cause harm will vary with the current that can flow in an arc, the amount of time that the arcing fault is sustained, the length of the gaps between the conductive parts, which are bridged by the arc, electrodes, the confinement around the arc, the chemical compositions of the conductors and the materials around the arc, and the distance of the worker from the arc. Arc flash hazard is generally derived by system parameters.

The term risk is the chance (or likelihood), high or low, that someone might be harmed by the hazard as expressed above. Arc flash risk is generally derived from system conditions and the task being performed.

Although the arc flash hazard may be high, control measures can be adopted to reduce both the hazard, and subsequently the associated risk, to as low as possible. (Note: There is, in Great Britain and in international health and safety standards, the term as low “as is reasonably practicable” or ALARP for short. The concept of “reasonably practicable” lies at the heart of the British health and safety system and is a key part of the general duties of the Health and Safety at Work etc. Act 1974). However, many readers may not be governed by standards or laws that are influenced by such an approach and therefore, the advice that I would offer, is to ensure compliance with local and company risk tolerance when making final judgments regarding the residual degree of risk.