EVs and the DC Hazard: Poly/Cotton Workwear in a DC Arc

With the rapid growth of electric vehicles (EVs), and the infrastructure needed to support them, so too grows the importance of understanding the direct current (DC) arc hazard. That’s where Tyndale comes in! This series lays out the differences between the alternating current (AC) arc hazard and its lesser-known DC counterpart and demonstrates – through first-of-its-kind real-world video footage – the power of DC arcs. Follow along to learn more and witness firsthand the life-saving difference the right arc-rated (AR) clothing makes in the face of a DC arc.

Did you know that polyester and cotton (“poly/cotton”) blend is one of the most common fabric choices for making non-protective workwear? In fact, this type of fabric is being worn by many people who work in and around EVs. But what happens to poly/cotton fabric when it’s exposed to a DC arc flash? We put this question to the test in a leading-edge DC arc demonstration. Join host Scott Margolin, Vice President of Technical, to see firsthand:

With an incident energy of just 6.9 calories, the outcome is catastrophic – resulting in a minimum of 45-50% second-degree and third-degree burns to the worker.

The video starts with the DC arc in slow motion – and as you can see, the intensity of this arc changes as the arc evolves but the size does not. The disparity arises from the fact that, unlike its AC counterpart, the current is uninterrupted and continuous.

In real time, we watch as the garment instantly ignites – and not just above the waist but also on the left leg below the waist. At the same time, the overhead view shows just how quickly the wearer would be breathing in fire and sustaining burns to the face as well.

From there, a flammable baselayer worn under the outer non-protective coverall adds fuel to the fire, which rapidly spreads to the back of the garment and down the left leg. The garment then begins to melt and drip.

It takes our crews not one but two blasts with a fire extinguisher to put the fire out.

This video shows why it’s so important to wear arc-rated (AR) clothing and appropriate PPE when there is an arc hazard in your job environment. In fact, in most of the injuries and fatalities we see, the outcomes were preventable – caused by people wearing fuel. This video shows that the DC arc hazard is no exception. Don’t leave home without your last line of defense.

Think 100% cotton workwear is the solution? Think again. In our next episode we conduct a similar test, only this time the manikin is wearing 100% non-AR cotton fabric. Does the DC arc require any more or less energy to ignite cotton fabric? Tune in to find out.


Series: EVs and the DC Hazard

Think you know arc flash? Think again. DC arcs are different. Following along with this series to see how different – and how to stay safe.

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