On February 9 we had the pleasure of welcoming Frédérique St-Arnaud, a project engineer with Stantec. She gave a talk on the dangers of incident energy and how to reduce the risks of an arc flash accident during live-line electrical work.
Incident energy is the energy suddenly projected from an electrical source to another surface during an arc flash incident. During a short circuit, ionized air creates an invisible conductor that allows electricity to travel a short or long distance beyond the main conductor.
It can be caused by accidental contact with a live conductor or conductive parts, defective or poorly maintained equipment, a worn or broken insulator or simply by carelessness. Depending on the system voltage and the distance and duration of the arc flash, incident energy can be extremely dangerous for workers (severe burns, internal organs damaged by blasts or pressure waves, shrapnel wounds, temporary or permanent blindness, loss of hearing, death), and can also cause extensive damage to property and equipment.
The explosive impact of a potential arc flash is directly linked to the different types of equipment in an electrical system, which is why knowledge of your electrical systems is essential.
Good Planning, Good Prevention
Basic precautions obviously include disconnecting the power supply to equipment and verifying that there is no live electric current before undertaking any work. Under some circumstances, however, live-line work is impossible to avoid. In some cases, testing and diagnosis of electrical circuits or shutting off the power supply would have serious consequences, and in some situations a lack of electrical power could jeopardize the safety and lives of others.
Adhere to a few basic safety rules during live-line work:
- Evaluate the risks and plan the work based on arc flash labels identifying potential hazards on energized switch boards, control panels, etc. and follow the workplace electrical safety recommendations of CSA Z462;
- Determine, correctly identify and prepare the work area;
- Clearly communicate all information essential to users;
- Use personal protective equipment (PPE) appropriate for the task to be performed;
- Know and always respect the approach limits or flash protection boundaries for electrical equipment;
- Work calmly and avoid distractions so that you remain concentrated on the work.
Are your teams adequately prepared for regular or emergency live-line work?
Managers must plan beforehand and should call on specialists to catalogue and thus better understand the component parts of their electrical systems, identifying dangerous equipment. They can thus provide adequate protection for employees or, on the contrary, avoid situations of unnecessary overprotection. There are a number of options that will mitigate the risk of arc flash accidents, and these can be identified when conducting audits of electrical equipment or studies specific to a given context.
These professionals will help you to correctly identify and document the different categories of risk, determine PPE requirements and draw up essential safety instructions, in particular approach limits or flash protection boundaries for electrical equipment. They can also provide training to learn and/or upgrade safety preparations and responses.
As always, better understanding leads to better maintenance practices and better management of operations.
A word to the wise!