Understanding and eliminating arc flash
What is the leading cause of arc flash, and what procedural changes can be adopted to eliminate the threat?
Responding is Michael Riccio, global marketing manager, IRISS, Bradenton, FL.
Answer: The No. 1 cause of an arc flash is simple: human interaction with equipment. Even if an asset has been “deenergized” before any type of inspection or maintenance activity takes place, there’s still a small amount of electrical charge within the system. The still-charged particles aren’t affected only by internal issues, but are also attracted to metallic objects nearby when the panel is removed. These tend to include eyeglasses, belt buckles and keys, to name a few. If conducting any type of open-panel activity, removal of all metallic objects from a worker must accompany the use of properly rated personal protective equipment.
Although proper PPE is a component of the NFPA 70E’s Hierarchy of Risk Control Methods, it’s rated very low. Not only is it expensive from a materials standpoint, but it’s also time consuming as the process for vesting and divesting becomes a “work-hour cost.” Additionally, PPE (regardless of rating) doesn’t remove worker exposure to risk of injury or fatality because the process itself is a flawed approach.
Instead, equipment and procedures should focus on the hierarchy’s top two tiers: elimination and substitution. The safety and reliability technologies that have been developed over the past few decades now make it possible to eliminate most risk-based behaviors. Instead of employing “maintenance” processes that are calendar-driven through a computerized maintenance management system in which panels need to be opened for equipment to be inspected, adopting a no-touch system based on asset condition monitoring allows for closed-panel monitoring and inspections.
With the use of a wireless temperature monitoring system, asset conditions can be continually collected, trended and assessed. Monitors feed data through a gateway to software and apps, allowing the information to be continuously accessed from workstations and mobile devices. When the asset-condition data exceeds the custom parameters, alarms can notify electrical technicians of a possible issue that may require inspection. Keeping human interaction with equipment to only instances in which confirmation inspections of potential faults are deemed necessary minimizes worker risk of arc exposure and eliminates the human-error threat to asset functionality.
Once the wireless monitoring system notifies technicians of a possible issue with a piece of electrical equipment, the use of pre-installed inspection windows on the asset allows a safe, efficient method of inspecting and assessing any possible issue during an energized condition. Visual, infrared and ultrasound inspections can be done simultaneously by a single employee. This design protects inspectors from arc flash/electrocution risk and removes the need for bulky and expensive PPE.
Electrical power assets being monitored remotely cuts down on technicians’ exposure by providing around-the-clock coverage. When an alarm notification is received, correctly designed and installed inspection windows allow an individual technician to safely do visual, infrared, ultrasound and partial discharge assessments of the energized equipment. The panels remain closed, the risk of arc flash/blast is minimized and worker safety (and efficiency) is maximized.
Editor's note: This article represents the independent views of the author and should not be construed as a National Safety Council endorsement.