Design of a sensor to predict arcing faults in nuclear switchgear

The U.S. Navy made a major step forward in the protection of switchgear from arcing faults with the installation of arc fault detection systems beginning in 1990. These systems have a proven history of responding to arcs quickly enough to minimize damage and have reliability high enough to be certified for use in nuclear reactor power systems. However, all damage is not eliminated and loss of power never occurs at a convenient time. The predominant cause of arcing failures in Navy switchboards has been identified. Test data that confirms how these failures develop will be discussed. A low-cost sensor has been designed that will allow the detection of the majority of impending arcing failures by performing continuous thermal monitoring of the switchboard. A single detector can determine if a connection within the switchboard has exceeded 300°C, which is well below the 1083°C needed to melt copper. The operator is notified upon the detection of an impending failure and corrective action can be taken before arcing occurs. Details of the development of the sensor will be discussed.