A data acquisition and transmitting unit samples the signal indicating the apparatus state quantity from a sensor provided on an apparatus, converts the signal into absolute-time-tagged monitoring data S(t), stores the data S(t), and transmits the data S(t) to a network. A digital protection and control unit takes in the quantity data E about the system of the apparatus and the operating state data P about the apparatus, converts these data into absolute-time-tagged data E(t) and operating state data P(t), stores these converted data, and transmits these data E(t) and P(t) to the network. A data display unit receives the data S(t), E(t), and P(t) from the data acquisition and transmitting unit and digital protective and control unit via the network and displays the state of the apparatus on the basis of the data S(t), E(t), and P(t).