Is the Arc Flash risk greater at high or low voltage?

Is the Arc Flash risk greater at high or low voltage?

Electrical engineers working at high voltage are acutely aware of the risks – and implications – of incidents, but is the risk of an arc flash greater at high or low voltage? Is there complacency among those working only on low voltage systems and what are the implications?

Low voltage, low Arc Flash incidence?

It would be easy to assume that low voltage systems pose less of a risk of arc flash incidents, but that is just not the case. Arc Flash hazard levels may actually be higher at low voltages, due to the high fault currents. And because awareness among engineers working on low voltage systems is so much lower, the risks to them as individuals could be perceived as greater due to this false sense of security.

In 2016 an operative’s life was saved by wearing one of our polo shirts when he struck a 120 CNE 3 Phase low voltage cable which led to an Arc Flash.  

Low-voltage distribution panels are essential components of the electrical systems which support critical infrastructure like hospitals, airports and data centres. Yet the demands placed on these panels as the systems expand over time are very often overlooked, leading to an increased risk that an Arc Flash incident will occur.

It’s also a common misconception that transformers and other system safeguards reduce the risk of arc flash incidents. Small distribution transformers can produce short circuit fault currents, leaving the worker exposed to the arc flash risk.

Arc Flash risks on low voltage systems

Should an Arc Flash occur on a low voltage system would the risk to the worker be any lower? The simple answer is no, because an arc flash is a burst of energy, not solely electricity, so the voltage of the electrical system on which it occurs isn’t the major factor in the scale of the blast.

The Energy Institute published its first guidance on Arc Flash incidents in May 2018. It says: “Arc flash poses a significant risk to personnel working on electrical systems, with high consequences including severe burns and death, as well as damage to equipment.”

The severity of an Arc Flash can be impacted by the space in which it occurs – Arc Flashes in confined environments such as a distribution box are significantly more dangerous to workers than if there is more space for the energy to dissipate. It’s also influenced by the type of equipment, the gap between conductors, the arc distance, the current and the fault clearing time.

Arc Flash incidents are measured in “incident energy” – the measure of thermal energy at a working distance from a fault. It’s measured in cal/cm2 which is why you will see all of ProGARM’s specialist Arc Flash PPE has a “cal rating”. An Arc Flash hazard assessment will calculate the cal rating of the PPE your workers will need for each task in order to be protected in the event of an incident.

Can it really happen to me?

In the UK it’s tricky to understand the true scale of the number of Arc Flash incidents because the RIDDOR reporting system simply categorises them as electrical incidents.

In America, where statistics are much more readily available than in the UK, the lower-end estimates suggest that 5-10 people are injured in Arc Flash incidents every day, with one of those being a fatality.

Shockingly, our own research found that an astonishing 57% of UK electrical workers surveyed had first-hand experience of an Arc Flash incident.

ProGARM – protecting your team from Arc Flash, even at low voltage

You want all of your team to come home, every time. To discuss your PPE needs for working on high or low voltage systems, give one of our experts a call on 01482 679600.