When Glen Payne first contacted me, his questions told me his application for fiber optics was an unusual one, so I asked for some background information. I learned that an arc flash incident has plenty of light to sense. Light intensities can be thousands of times higher than the normal lighting. ABB had developed an arc flash relay system using fiber optics as a sensor over 30 years ago. Since sensing arc flash and tripping relays needs to be done extremely quickly to mitigate the severity of the incident, fiber optics had the speed necessary to detect incidents. But fiber had another big advantage: it is immune to electromagnetic interference, so the electrical noise created by an incident does not affect the transmission of the information to the remote control unit.
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