Leo R. Gauthier

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/spl deg/C, which is well below the 1083/spl deg/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.

Radiometric dynamic scene processing for uncooled IRFPAs

The widespread use of cameras based on uncooled infrared focal plane arrays (IRFPAs) is largely because of rapid commercialization, impressive miniaturization, and low per-unit cost. As performance improves, long-wave IR cameras using uncooled IRFPAs have replaced more expensive cooled units in many applications. The uncooled units generally have a much higher noise floor. However, if the signal is robust, the uncooled units can make the measurements at lower cost. New cameras with smaller pixels continue to reduce the pixel response time, enabling higher frame rates and more applications. Uncooled IRFPAs are thermal detectors, not charge-based devices, and the implicit pixel response time can greatly affect radiometric accuracy. In addition to the pixel response time, the fidelity of radiometric measurements is affected by target size, pixel fill factor, spectral response, stray light, self-heating, and other variables. If radiometric accuracy is required, it is necessary to quantify the effects of these variables. Calibration methods and measurement compensation techniques are described with emphasis on dynamic scene processing applications.