Arc-Flash Relays Help Mines Reduce Accidents

Reduce Accidents
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Mine operators understand the critical importance of ground-fault protection for their mining equipment. This requirement is addressed by the CSA Standard M421: Use of Electricity in Mines. This standard mandates ground-fault current limitation, usually achieved through neutral-grounding resistances and electrical protection against ground faults in surface and underground mines where a ground failure could lead to a catastrophe. For over 20 years, the mining industry has been a pioneer in utilizing sensitive ground-fault relays on electrical mining equipment, enhancing safety by detecting and interrupting ground faults.

The mining industry excels in protecting against ground faults and implementing resistance grounding. However, these measures alone cannot safeguard personnel or equipment from the devastating consequences of an arc flash event. Such an event occurs when a live-phase conductor short-circuits with another phase without a ground connection.

Short circuits can happen due to cable or equipment failures, damage, misplacement of voltmeters, incorrect installations, dropped tools, or the accumulation of dust on insulators. These events can take place during routine maintenance on power generation and distribution equipment, as well as in motor control centers and portable substations frequently accessed by personnel. An arc flash generates a substantial amount of electricity, ionizing the air around the conductors. This energy release can lead to catastrophic equipment damage and even result in fatalities and severe burns for nearby personnel.

According to the NIOSH Office of Mine Safety and Health Research in the United States, arc-flash injuries account for 35% of lost workdays caused by electrical injuries between 1990 and 2001, making them the leading non-fatal electrical injury. On average, there were 21 lost workdays. Over the 11-year study period, the total number of lost workdays reached approximately 12,000.

In addition to the immediate risks, a flash arc can produce toxic fumes and smoke from vaporized copper or other materials. While the mine ventilation system should eventually remove these fumes and smoke, an arc flash can temporarily disable it.

These events can occur in surface mining operations, process plants, and underground operations if the equipment is not protected by ground-fault relays (GFRs) and resistance grounding. High-level ground faults may blow fuses or open circuit breakers, but the fault current can still travel through electrical components and conductors not rated for high-energy levels, which can lead to fires. Therefore, mitigating arc-flash incidents is essential for both above-ground and underground equipment.

This post was written by Justin Tidd, Director at Becker/SMC. For nearly a half a century, Becker Mining has been at the forefront of safety, producing the best ground fault relay in the industry. Becker/SMC is the industry’s leader in increasingly more sophisticated electrical control systems. Most of the major innovations, design features and specialized electrical components have been developed by Becker/SMC.

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