Process Hypercube Comparison for Signal Validation

The optimal control and safe operation of a nuclear power plant requires reliable information concerning the state of the process. Signal validation is the detection, isolation, and characterization of faulty signals. Properly validated process signals are beneficial from the standpoint of increased plant availability and reliability of operator actions. A signal validation technique utilizing a process hypercube comparison (PHC) was originated during this research. The hypercube is merely a multidimensional joint histogram of the process conditions. The hypercube is created off-line during a learning phase using operational plant data. In the event that a newly observed plant state does not match with those in the learned hypercube, the PHC algorithm performs signal validation by progressively hypothesizing that one or more signals is in error. This assumption is then either substantiated or denied. In the case where many signals are found to be in error, a conclusion that the process conditions are abnormal is reached. The global data base contained within the hypercube provides a best estimate of the process conditions in the event a signal is deemed failed. The hypercube signal validation methodology was tested using operational data from a commercial pressurized water reactor (PWR) and the Experimental Breeder Reactor II (EBR-II). This research was part of a larger project aimed at the development of a comprehensive signal validation software system for application to nuclear power plants.