Arc-flash hazard on direct current (DC) systems

The most common concern when performing electrical work is arc flash hazards on alternative current (AC) systems. In fact, in the last 15 years, significantly more companies have acknowledged the importance of performing arc flash studies for AC-powered systems, in accordance with the CSA Z462 standard, to properly protect employees.

Although arc flashes hazards on direct current (DC) systems are just as real, they are often minimized or even ignored. Not only is it unrealistic to assume it is enough to take into account the incident energy in AC systems when assessing arc flash hazards, this in itself can be hazardous. For example, for a distribution panel that is fed by a battery room with a nominal capacity of 1000 ah, the level of calculated incident energy for the battery terminals would be 18 cal/cm². This high value requires protection with anti-arc coveralls for a standard work distance of 46 cm (18 inches). That’s why assessing arc flashes for DC systems is just as important to ensure worker safety.

Remember that a risk assessment is intended to provide workers with a safe work environment. To do this, all businesses must properly train their staff and provide appropriate personal protective equipment (PPE) to perform tasks in accordance with Bill C-21 of the Criminal Code of Canada; otherwise, these businesses can receive hefty penalties and be held criminally liable in case of injury or death. There are various ways to assess incident energy that can be caused by an arc flash on DC systems.

In this document, we will introduce a quick and easy calculation to demonstrate how important it is to apply the methods indicated in the CSA Z462-15 standard. This standard is the benchmark in terms of assessing electrical hazards. Likewise, qualified experts must be mandated to adequately apply and obtain accurate and realistic calculations. After all, worker safety depends on it.

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