Arc-Flash Relay is a high-speed, arc-detection device for electrical power-distribution systems. The protection relay has outputs for trip coils in several zones, and has inputs for up to several optical sensors for optimal arc detection. The inputs support both point sensors and fiber-optic line sensors,
which cover a larger area.
Using optical sensors rather than relying strictly on current measurement allows a much faster detection time than overcurrent relays or a circuit breaker alone can typically provide, as the light from the arc is unique for the fault, whereas current pulses above the nominal level are part of normal operation for many systems.
On the occurrence of an arc fault, the protection relay detects the fault and pulses the trip contact in less than one millisecond, which trips the circuit breaker(s) supplying the fault. The total arcing time is effectively reduced to the mechanical opening time of the circuit breaker, typically between 30 and 75 milliseconds. This reduces the energy of the arc fault significantly, increasing worker safety, reducing fault damage, and improving uptime. Switchgear can often be simply cleaned, inspected, and put back in service after an arc fault instead of having to be replaced.