Arc Fault Detector

The subject of arc fault detection and circuit interruption has gained a lot of attention in recent years, particularly in the aviation industry. This is primarily due to a spate of in-flight fires which have been linked to faulty electrical systems and wiring on aircraft. Typical causes of faults are wiring chafing, dust build up and moisture [1][2]. Until recently, aircraft circuit breakers, either electromechanical or solid state i.e. Remote Controlled Circuit Breaker, Solid State Power Controller, Solid State Relay etc. were considered the first line of defense. However, research has shown that arc faults, with temperatures as high as 6000°C, can go undetected by these devices. Aerospace circuit breakers are designed to protect wiring from thermal damage that occurs during an over-current situation. They are able to do this by deploying a bi-metallic element that mimics the thermal effect of current on a wire’s insulation. Their electronic counterparts provide the same functions electronically. Electrical arcing is a localized, high-energy event. Current levels during arcing can significantly exceed the current rating of the circuit breaker. However, arc fault events, like many transients, are very short lived and therefore cause little impact on the bi-metallic element or the electronics. Consequently, conventional circuit breakers and electronic wire protection methods do not interrupt the circuit fast enough to prevent damage or perhaps a catastrophic event like fire. Domestic arc fault detection for 60Hz, single phase low current loads is mandatory for domestic use, but has yet to be defined for high power 400Hz, three phase aircraft loads. It is these that require improved levels of protection. Typically an arc fault adds to an existing load current causing a fast three-phase imbalance. Arc Profile: 70 Amperes at 115Vac, 400Hz