PLANT EVALUATION DEVICE AND PLANT EVALUATION METHOD

A plant evaluation apparatus includes: a first computation unit configured to compute a first estimated value of a plant state quantity by using a steady-state model; a first determination unit configured to compute a second estimated value of the plant state quantity by assigning an equipment parameter in a normal state to an equipment parameter of a non-steady-state model; a second computation unit configured to compute a third estimated value of the plant state quantity by using the steady-state model in a case where the first determination unit determines that an error between the second estimated value and an actually measured value is equal to or more than a threshold value; and a second determination unit configured to determine whether or not a difference between the equipment parameter in the normal state and the equipment parameter in an abnormal state is equal to or more than a predetermined value.