Arc flash hazards: How engineering and standards can make for safer electricity use
March 24, 2022
March 24, 2022
Electricity has empowered our lives and industry, but what happens when unintentional circuits are created?
Electric energy plays a massive role in our lives. It powers manufacturing, transportation, water treatment, computing, healthcare, entertainment, and more. It is almost more challenging to think of activities in our daily lives that do not need electricity.
Some of the biggest users and producers of electricity include the industrial, commercial, and utility sectors. These users harness and distribute electric energy with a combination of high- and low-voltage power distribution equipment.
Of course, power distribution equipment can present risks to its users. One of the key risks? The development of arc flash incident energy.
Exposure to arc flash incident energy is potentially lethal. It can be disastrous to equipment. So, it’s vital that organizations introduce safeguards and awareness around arc flash hazards in any electrical safety program for industrial, commercial, and utility power systems.
You can integrate an electrical safety program through engineering analysis and design, the understanding and interpretation of standards, worker education, and engineered arc flash hazard analysis. Let’s further explore some key aspects of arc flash hazards to make sure you’re doing everything you can to stay safe.
What is an electric arc flash? Electrical arcs are the product of substantial electrical current flow through hot and ionized air. And while air is not as good of a conductor, compared to metallic wires, it can still conduct electricity under certain conditions.
Electrical arcs can be intentional—like those formed by sparkplugs—or unintentional. An arc flash event is the unintentional formation of an electrical arc between two terminals. You can attribute the causes of arc flashes to a few hazards: interrupting and closing actions on circuits (e.g., actuating a disconnect switch), short-circuits, and human error (e.g., accidently contacting energized parts with tools).
What happens when an arc is formed? Large and uncontrolled amounts of kinetic, electrical, sound, and thermal energies are released.
An arc flash energy release can create a catastrophic failure of equipment. These failures can cause significant property damage, extended outages, fire, and financial losses. When people are exposed to an arc flash event, serious or fatal injuries can occur.
In the context of arc flash hazards, thermal injuries—caused by the extreme heat released by the electrical arc—are the most concerning injury due to their severity and least curability. Engineering standards help mitigate and reduce the likelihood of thermal injuries. In North America, the CSA Z462 and NFPA 70E provide guidance for signage, work methods, and analysis to manage exposure to arc flash incident energy.
In addition, the IEEE Std. 1584 has been the benchmark in the engineering analysis for calculating the severity of arc flash thermal energy release within a power system.
It is vital to keep up with standards. As of 2021, the NFPA 70E and CSA Z462 have been revised. It is important to note that although these standards are produced by two organizations, their content and purpose are closely matched through active collaboration by both the CSA Group (formerly the Canadian Standards Association) and the National Fire Protection Association (NFPA).
Both standards have a common goal: provide personnel with safe work practices to reduce exposure to major electrical hazards.
The use of IEEE Std. 1584-2018 revision represents one of the key changes in both standards. It offers greatly improved empirical models of arc flash hazard calculation. This has helped pave the way for more accurate arc flash labels and better-informed personal protective equipment (PPE) options.
The CSA has also introduced the new arc flash PPE Category 5, which provides thermal energy protection up to 75 calories/cm2. Traditionally, PPE has been limited to Category 4 at 40 calories/cm2. Although higher levels of PPE are now available, it’s important to still perform arc flash hazard analysis and mitigation. And you should still follow safe work practices.
An arc flash hazard refers to the unintentional formation of an electrical arc between two terminals.
Arc flash hazards will always exist. Their only method of elimination is through de-energization. So, it is necessary to establish work practices and perform engineering to help counteract the effects of arc flash energy release.
As part of a comprehensive electrical safety program, electrical equipment should be labelled with arc flash energy and PPE information to allow informed decisions in the field.
The information on the labels should be updated every five years, and/or when a major upgrade to the power system occurs. The arc flash analysis and labels should be developed by qualified persons and sealed by a professional engineer. Field level risk assessment—as well as knowledge of PPE use, maintenance, and procedures—should be taught to all personnel.
It is equally important to keep diagrams and models of a power system up to date to proactively monitor arc flash levels. You can also deploy limits on arc flash energy and use engineered mitigation strategies. Recently, electrical protective devices have introduced better early detection technologies that can extinguish an arc flash nearly instantaneously. Being proactive, combined with engineering analysis and design, can limit arc flash energy—and drastically reduce the risks.
It’s been rewarding to help several of our clients quantify and mitigate their power system’s arc flash energy through engineering analysis and design. We are committed to providing education to our client’s teams on arc flash hazards to foster a culture of safe electrical work.
Thankfully, when people follow work procedures and teams receive the right engineering support, arc flashes are a rare occurrence. But since the consequences of an arc flash can be substantial, it is better to be safe than sorry.