• • • ARC FLASH • • • Safety must be the primary focus
when working near Arc Flash zones By Fluke, Manufacturer of Industrial Test, Measurement and Diagnostic equipment
E
ngineers working near exposed energised conductors or live circuit components face significant risks, including severe injury or death, due to a phenomenon called arc flash. As a result, it is crucial for companies to prioritise the safety of their workers in these hazardous environments.
What is Arc Flash?
Arc flash is the intense light and heat produced by a violent electrical arc fault explosion, where temperatures can range from 2,800°C to 19,000°C (5,000°F to 35,000°F). To put this in perspective, the surface temperature of the sun is about 5,500°C (9,932°F), meaning an arc flash can be up to four times hotter than the sun. These extreme temperatures can ignite clothing, burn skin, vaporise metals like copper, aluminium and steel, and cause serious damage to lungs and eyes, leading to hospitalisation or death. Arc flash incidents occur globally every day. In the U.S. alone, 1,000 electrical workers suffer from shocks and burns each year, with some fatal. It is critical that no engineer or health and safety team assumes an arc flash won’t occur on their watch. They should also be aware that a plasma arc, once established, can carry virtually unlimited current, and if vaporised metals are present, it can escalate a single-phase arc into a far more dangerous three-phase arc.
What Causes Arc Faults? Understanding how arc flash is created is essential in minimising injury. An arc flash occurs when an electrical current flows through ionised air, causing an explosive release of energy. This energy converts primarily into heat and light, while the associated arc blast creates pressure waves capable of rupturing panels, sending debris flying, and causing acoustic injuries or severe physical trauma to anyone nearby.
Common causes of arc flash include voltage transients or spikes, often triggered by switching reactive loads or lightning strikes. Although the transient may only last microseconds, it can carry thousands of amps of energy, potentially forming a plasma arc during testing. Other unpredictable causes include improper handling of test probes, dropped tools, worn or loose connections, gaps in insulation, poor installation, dust or corrosion.
What is an Arc Flash Boundary? To reduce the risk of electrical injury, three arc flash boundaries are defined: the restricted boundary, which is closest to the exposed equipment; the limited approach boundary, which is further out; and the arc flash boundary, typically the farthest boundary. The closer a worker is to live equipment within these boundaries, the greater the need for personal protective equipment (PPE).
The arc flash boundary represents the minimum ‘safe’ distance from an arc fault, calculated to be 1.2 calories/cm² of incident energy, the distance at which a worker without proper PPE would suffer second-degree burns. Depending on the potential hazard, this boundary may be the farthest or second-farthest from exposed equipment. If it is the furthest boundary, it marks the line no one should cross without the right PPE and training.
De-Energised Equipment When possible, operators should work on de-energised equipment, as this is the only way to eliminate the risk of arc flash. Before performing any tests, engineers should verify the absence of voltage. Until voltage absence is confirmed, circuits should be treated as live. Additionally, regular equipment inspections using condition monitoring tools or infrared (IR) windows can identify potential issues before they become hazardous. Understanding the normal behaviour of equipment through baseline readings will help engineers spot abnormalities and take corrective action. However, the best way to stay safe while inspecting live circuits is to stay outside the arc flash boundary entirely. There’s no need for anyone to enter this zone unless absolutely necessary.
Using the Right Tools
One of the safest ways to remain distanced from danger is by using non-contact thermal imaging, wireless test equipment, and remote displays to take accurate readings on energised components without physical contact. For example, Fluke’s PQ400 Electrical Measurement Window (EMW) provides workers with access to critical power data without opening the panel door. The EMW enhances safety, reduces downtime and lowers maintenance costs. Similarly, the Fluke CV400 ClirVu 4in infrared window allows workers to view panel interiors safely without the need for PPE. Fluke’s TiS75+ thermal camera enables operators to detect hot or cold spots without direct contact, offering one-handed image capture and saving features. The Fluke 376 FC clamp meter allows technicians to remotely read measurements from outside the arc flash zone using the Fluke Connect app. This helps reduce the time spent in hazardous areas, logs data and tracks faults. Similarly, the Fluke 3000FC digital multimeter allows readings to be taken remotely, further reducing time spent in danger zones. While it’s impossible to completely eliminate electrical hazards, effective planning, training, and the use of specialised tools can significantly minimise the risk of arc flash injuries. For more information, visit the Fluke website.
12 ELECTRICAL ENGINEERING • DECEMBER/JANUARY 2025
electricalengineeringmagazine.co.uk
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