Arc flash protection advances improve electrical design for safety

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In this blog series, we’ll be looking at the industry trends and technologies that are helping improve safety in electrical environments. We’ll look first at arc flash protection.

Electrical safety remains a top-of-mind concern for facilities of all kinds. And though the National Fire Protection Association (NFPA) reports that there has been a slight downward trend in the annual number of electrical fatalities in recent years, the number of injuries has remained fairly flat. When it comes to electrical distribution systems, safety and reliability go hand in hand, as improving safety will also help companies stay competitive by avoiding risks to productivity.

Leading electrical manufacturers, like Schneider Electric are responding to this demand with new safety-related technologies. Our electrical safety innovations have helped set customer expectations higher, and established our focus on ‘Safety by Design.’ This means implementing designs that are outcome-oriented, taking into account end-user safety requirements today while ensuring facilities are future-ready. Let’s look at the specific example of arc flash protection.

Arc Flash Protection

Traditional Arc Flash Protection

Wide ranges of arc flash mitigation controls are in use today. These include PPE and working protocols. For example, the use of an absence of voltage tester during lock-out/tag-out procedures will reduce risk to workers by ensuring equipment is de-energized while doors and covers are still in place.

Mitigation also includes engineering controls to reduce or isolate the hazard. At a passive level, this can include the use of automatic shutters that cover exposed stabs at the back of circuit breaker cells once a breaker has been racked out. However, arc faults can occur when a breaker is being racked out or back in. To reduce exposure an affordable solution is a remote racking system that enables the worker to perform the procedure from a distance using a push button control on a cable.

Another example of an active mitigation control is the energy reducing maintenance switch (ERMS) or arc reducing maintenance switch on circuit breakers. Before working on equipment, the technician will set the breaker into ‘maintenance mode’, enabling the breaker to operate faster to enhance worker safety. Some advanced circuit breakers enable ERMS mode to be activated using a mobile device, to keep the technician safely outside of the arc flash zone. Once work is completed, the breaker is set back to ‘normal’ mode to optimize breaker coordination for the plant.

Recent Arc Flash Protection Innovations

Beyond the methods above, there have been many newer innovations in arc flash protection. NFPA 70E, the Standard for Electrical Safety in the Workplace, is the primary industry consensus standard in the US that addresses arc flash safety. Annex ‘O’ in the 2018 update included new arc flash design requirements, and it is expected that the 2021 edition will include more.

One of the newest innovations is in optimizing breaker performance. Ideally, a breaker or relay will maintain its coordination settings while also enabling fast fault clearing to mitigate an arc flash. This is now possible using systems that include optical sensors. When the protective device detects both an arc current and arc flash, it will operate faster to clear the fault. This fast and reliable arc protection improves safety and may save human lives in case of an arc fault arising in switchgear during work in or near the installation. It can also help reduce equipment damage and avoid a power outage.

Advances in connectivity and embedded intelligence are enabling the newest arc flash protection innovations. First, intelligent protective relays, circuit breakers, and power meters enable facility and service teams to remotely track and diagnose abnormal conditions throughout the electrical network, while also predicting maintenance needs and potential equipment failures.

IoT-enabled wireless thermal sensors can be used for continuous thermal monitoring on all critical connection points to detect loose connections or other defects that can create dangerous ‘hot spots.’ This a more comprehensive and safe approach compared to infrared thermography. This is because thermal monitoring is continuous, unlike IR thermography, which is only done at scheduled time intervals. Combined with predictive analytics, thermal monitoring will alert a facility manager to an issue in their equipment early enough to remedy it before it becomes a dangerous and costly arc-flash event.

Finally, as facility teams at manufacturing sites are more regularly working near motor control centers (MCCs) than any other LV distribution equipment, MCCs are the second highest source of arc flash incidents. Internal arc resistant protection will contain an arc, but will not reduce the arc flash incident energy (AFIE), so will not protect assets from destruction.

Following our ‘Safety by Design’ concept, Schneider Electric has introduced ArcBlok™ technology, as part of our Model 6 low voltage MCC. ArcBlok isolates the line side electrical conductors to reduce the potential for arc faults. If an arc occurs, it reduces the arc duration and self-extinguishes it in less than one cycle. This contains the event to reduce potential damage to the equipment and protects the person working on the equipment from a potentially fatal event. ArcBlok has been tested and validated to comply with ANSI/IEEE Std. C37.20.7-2017. To learn more, read the blog post.

In our next post, we’ll discuss how to use digital tools to ensure you are designing for electrical safety. To learn more about Schneider Electric arc flash protection solutions, visit our Electrical Safety page.

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