At what voltage can an arc flash occur?

At what voltage can an arc flash occur?

There are many variables that can influence the scale of an Arc Flash, including voltage. But the idea that such an extreme and intense explosion can only arise in high voltage environments is a myth.

Though it’s broadly true that the greater the voltage the more significant the safety risk associated with an Arc Flash, there are many other variables which can influence the severity of an incident – even in low voltage environments.

Arc Flash incidents happen when there’s a fault between a phase conductor and, either, another conductor or the ground, causing an electrical current to pass through the air between the two points.

Within a fraction of a second, the Arc Flash temperature can reach over 19,0000 C, which is more than 3.5 times hotter than the surface of the sun. At this temperature, copper expands at a factor of 67,000 times within a few milliseconds and there’s a blast from the sudden expansion in the temperature of the surrounding air.

The extent of the heat radiation, acoustical energy and the pressure wave which form part of an Arc Flash blast are influenced by many factors, such as whether the incident occurred within a contained space such as a distribution box (focusing all the released energy out of the box in one direction) or in an open space where the energy disperses equally over 360o.

It’s also influenced by the type of equipment, the gap between conductors, the arc distance, the current and the fault clearing time.

Even low voltage installations such as power supply equipment in offices and factories can cause an Arc Flash incident if there’s a fault.

One common misconception is that transformers and other system impedances in low voltage environments dramatically reduce the risks, but small distribution transformers can still produce short circuit fault currents posing significant safety risks for workers.

And it isn’t just electrical workers who are at risk. Construction workers and engineers using ground-breaking equipment and plant machinery such as pneumatic drills and diggers are also at risk through cable strike incidents.

The following video shows the very real danger of breaking ground and striking an underground cable.

Unfortunately, misconceptions that the likelihood or scale of an Arc Flash incident is determined by the Voltage can lead to a lack of risk awareness and even complacency on site.

It’s important that risk assessments take account of the risk of an Arc Flash incident and that company method statements and PPE requirements identify the appropriate safety precautions.

Here at ProGARM, we provide a last line of defence against an Arc Flash in the form specialist safety garments for men and women including underwear, base layers and outer garments, headwear, footwear, belts, gloves and more.

For more information about our industry leading Arc Flash protective clothing, please contact us on +44 (0) 1482 679 600 to speak to one of our sector specialists.

This is one post in a series ‘All about Arc Flash’. Continue reading the next in the series or return to the start if you like.