What is an arc flash and four strategies to prevent it

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Learning what is an arc flash is key for electrical professionals. According to the NFPA, five to ten arc flash incidents occur every day and nearly 2,000 people are exposed to the harmful effects each year. The direct financial impact of an arc flash event is substantial and so too are the costs related to business operations, insurability, and reputation.

Then, what is an arch flash?

An arc flash is an electrical accident that creates a dangerous, high-temperature explosion.

An arc flash results from an arc fault. Arc faults are caused by electricity discharging between two or more conductors that are improperly connected, such as frayed wires. Dust or moisture can also cause arcing between conductors, which explains why high-voltage power lines will glow in foggy weather.

As electrical professionals, we’re often tasked with mitigating these safety and financial risks for our employees and our customers. Fortunately, our industry has spent the last few years developing solutions to prevent arc flashes and reduce severity when one occurs. In this blog, I will walk you through four ways you can use these solutions to fortify your safety program and better safeguard your workers and equipment from arc flash risks, including helpful controls, procedures, and equipment.

#1: Deenergize equipment before work

The first step in preventing an arc flash from occurring is to create an electrically safe working condition (ESWC). Article 100 of the NFPA 70E defines an ESWC as “A state in which an electrical conductor or circuit part has been disconnected from energized parts, locked/tagged in accordance with established standards, tested to ensure the absence of voltage, and grounded if determined necessary.” This means that work should only be performed on deenergized equipment; it’s the foundation of every workplace safety program. There are exceptions, such as hospitals and other environments where deenergizing could create a greater hazard than working on energized equipment. But it is universally accepted that deenergizing is the most effective way to prevent arc flash events, shock, and electrocution.

#2: Assess the risks

There is always a risk of arc flash when working around electrical equipment, so it is critical to establish arc flash boundaries that keep workers away from hazards and protect them from injury. The radius of an arc flash boundary is determined by calculating the arc flash incident energy (AFIE) using the methods described in IEE 1584 and the NFPA 70E standard. NFPA 70E requires that arc flash labels be applied to equipment showing:

  • The calculated AFIE in cal/cm2
  • The arc flash boundaries
  • The required level of PPE

Table 130.4(C)(a) in NFPA 70E shows the limited access and restricted approach boundaries based on AFIE; PPE categories relative to AFIE can be found in Table 130.5(G). In addition to labels, marking the arc flash boundaries with floor tape and PPE categories clearly shows workers where they can go and what level of protection they must wear in those categories.

#3: Digitalization

Implementing digital technology as a native feature in electrical systems is a powerful strategy for preventing arc flash. With innovative connected equipment that reduces the need to open panels and interact directly with electrical equipment, the risks associated with monitoring and maintenance have been greatly reduced. In addition, real-time data provides new levels of visibility that increase efficiency, reliability, and safety. Continuous thermal monitoring (CTM) is a good example of the way digitalization has transformed the industry.

Infrared thermography has long been a preventative maintenance tool for monitoring temperatures and identifying hotspots where faults could occur. While it is effective, infrared thermography is expensive and only provides a single moment-in-time view of the system. It also must be performed on energized equipment by qualified electrical workers who are required to wear bulky PPE. CTM sensors in equipment like SureSeT medium voltage switchgear provide a continuous stream of data that can be accessed remotely on a smart device or in the cloud. With no direct contact needed, CTM eliminates a primary cause of arc flash while it increases system visibility and enables proactive maintenance to reduce downtime.

#4: Isolate and compartmentalize energized components

Accidental contact with line-side connectors and other energized conductors is one of the primary causes of arc flash incidents. Isolating energized components prevents inadvertent touches from a worker’s hand or from dropped tools or debris. ArcBlok™ from Schneider Electric encloses line-side connectors in an ANSI/IEEE C37.20.7-2017 cable vault to prevent arc flashes from occurring. The passive system is available in the Square D™ Model 6 Arc Resistant MCC and will be available on PowerPact P-frame and R-frame circuit breakers on other MCCs and switchboard products in 2022.

Instead of a fully enclosed cable vault, Power-Zone 4 low voltage switchgear and SureSeT MV switchgear are engineered with physical barriers between bus areas and cable connections. By compartmentalizing energized conductors, fault propagation is controlled so arcing faults cannot occur. Line-side barriers in heavy duty and general duty safety switches provide both isolation and compartmentalization by shielding the connections from accidental contact and separating conductors where an electrical arc could occur.

Safety by design protects workers and equipment

Engineering arc flash risk out of electrical systems requires designing these systems with safety in mind. Taking advantage of the tools and processes noted above can help you protect the health and safety of workers, reduce downtime, and meet your regulatory compliance obligations. Schneider Electric has more than a century-long commitment to safety by design with products and services that reduce the chances of arc flashes and other dangerous electrical events. To learn more about creating an electrically safe working condition, please visit our safety content hub.

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