US Patent 9407082 Arc flash system for a power circuit

An arc flash system includes a circuit breaker having separable contacts, an operating mechanism, a trip unit including a sensor sensing current flowing in a power circuit, a trip circuit cooperating with the operating mechanism to trip open the contacts responsive to the sensed current or a first signal, and a communication interface outputting the sensed current, and an interface circuit including a processor having a first output of the first signal, an input of a second signal, and a second output of a third signal, and a communication interface cooperating with the processor to determine and communicate cause of trip information to the trip unit communication interface, input the sensed current, and communicate the sensed current to the processor. A light sensor senses light from an arc flash associated with the power circuit and outputs the second signal. A shorting apparatus shorts the circuit responsive to the third signal.