Because mining is an energy-intensive process, it is subject to potential arc-flash hazards, which can produce dangerously large amounts of heat, ultraviolet radiation, blast pressure, flying shrapnel, and deafening sound waves. To protect against these risks, mines are increasing their use of arc-flash mitigation solutions as part of their electrical equipment configurations.
One North American mining operation recently experienced an arc-flash event that underscored the value of arc-flash mitigation. A rodent made a nest between two phases of newly installed switchgear, triggering an arc-flash event. However, this potentially devastating event was safely mitigated, providing a timely reminder of the benefits of having arc-flash mitigation technology in place.
This particular mining operation began using SEL-501 Dual Overcurrent Relays in their substations in 1994. They began adding arc-flash mitigation capability in 2000 by installing SEL-751 Feeder Protection Relays and SEL-710 Motor Protection Relays configured with arc-flash detection.
When the arc-flash event actually occurred, it reinforced the importance of arc-flash safety and piqued their interest in how arc-flash mitigation works. “The total [incident] energy was significantly minimized by having the arc-flash technology,” said the engineer. “It was clear [to the 30 electrical contractors] that this technology was good to have—it’s not just academic.”
Diagram depicting a representative arc-flash detection scheme using overcurrent and light sensors (LSs) for fast and secure arc-flash protection.
Heightened Awareness. After using arc-flash mitigation technology for several years and never having an event, the lead engineer and his associates sometimes wondered if their investment in arc-flash detection was truly necessary. However, the mitigation of the potentially deadly arc-flash event proved the technology's worth.
Retrofit Application. The mining operation now plans to add arc-flash mitigation to its remaining switchgear equipment. According to the electrical engineer, “[The] older gear doesn’t have any venting, so it’s even more important to have arc-flash protection.”
The equipment was installed to protect personnel, but [it was clear that] the SEL relays also protected our equipment from potentially devastating damage.