A SYSTEM FOR DETERMINING ABNORMAL PLANT OPERATION BASED ON WHITENESS INDEXES

In a method and a system for diagnosing a thermal power plant system including a thermal power plant, provided with an automatic power plant control system performing PID control, and a direct digital control system utilizing a control model representing the combination of the plant and the automatic power plant control system and controlling the plant to conduct an optimum control, the automatic power plant control system and the direct digital control system conducting control complementarily: a plant diagnostic model formed of a mathematical model representing the combination of the plant, the automatic power plant control system, the control model and the direct digital control system, is provided and used to determine predicted values of the plant variables; difference between the predicted value of each of the plant variables and the actual value of the same plant variable is determined, and stored thereby to provide a time series of the differences which have been successively determined; whiteness indexes used for testing the whiteness level of the time series of the differences are determined in accordance with the time series of the differences; judgement is made as to whether or not any of the plant variables is abnormal in accordance with the whiteness indexes; judgement is made as to whether or not any of the manipulated variables is faulty in accordance with the whiteness indexes and the result of judgement as to abnormality; and an alarm is outputted when an abnormality or a fault is detected.