Plant operation aid device

The present invention automatically diagnoses a plant state to aid the plant operation, automatically diagnoses integrity of each of measuring devices containing sensors and also diagnoses a system having a chaotic behavior. Namely, an input processing section receives signals as an input from plant equipments and outputs observation signals. A characteristic memory section memorizes equipment models quantitatively simulating static characteristics of plant constitutional equipments. A state estimation section estimates a process state of the plant based on the observation signals using equipment models. The estimated process state is compared with the observation signals to judge the extent of normality of the observation signals using a fuzzy theory. The observation signals and the result of the judgement are displayed. An operator can recognize the reliability of the observation values, that is, integrity of gauges by numerical information, thereby enabling to judge the essential qualities of an abnormal event. (I.S.)