Plant monitoring device, method and program using a corrected Mahalanobis distance to determine plant abnormality

A plant monitoring method for monitoring an operation state of a plant, the plant monitoring method comprising:

• acquiring a state quantity of each of a plurality of characteristic items of the plant;
• calculating, for the state quantity acquired at a monitoring timing of the plant, an abnormality degree indicating a degree of approach to an abnormality side with a limit value set in advance for each characteristic item as a reference;
• calculating a distance which indicates a degree of separation of the state quantity and the abnormality degree at the monitoring timing from a normal operation state of the plant, using a statistical method;
• and
• determining the operation state of the plant based on the calculated distance,
• wherein in the calculating of the abnormality degree, an approach degree is calculated such that a value of the approach degree increases as the state quantity approaches to the abnormality side which is a side exceeding the limit value, and the abnormality degree is calculated by converting the approach degree into the abnormality degree such that a value of the abnormality degree when the state quantity reaches the limit value matches a predetermined threshold value of the distance,
• wherein in the calculating of the distance, a Mahalanobis distance of the state quantity acquired at the monitoring timing with a unit space formed by the state quantity acquired when the operation state of the plant is normal as a reference is calculated, and a composite distance is calculated as the distance, wherein the composite distance is
• a Euclidean norm of the Mahalanobis distance and a maximum value among a plurality of the abnormality degrees, or
• a Manhattan distance of the Mahalanobis distance and the maximum value among the plurality of the abnormality degrees, and
• wherein in the determining of the operation state, it is determined that the operation state of the plant is abnormal in a case where the composite distance is larger than a predetermined threshold value, and abnormality information is output to a display unit or a terminal device upon determining that the operation state of the plant is abnormal.

A non-transitory computer readable media storing a program thereon that causes a computer of a plant monitoring device for monitoring an operation state of a plant to function, the program causing the computer to execute:

• acquiring a state quantity of each of a plurality of characteristic items of the plant;
• calculating, for the state quantity acquired at a monitoring timing of the plant, an abnormality degree indicating a degree of approach to an abnormality side with a limit value set in advance for each characteristic item as a reference;
• calculating a distance which indicates a degree of separation of the state quantity and the abnormality degree at the monitoring timing from a normal operation state of the plant, using a statistical method;
• and
• determining the operation state of the plant based on the calculated distance,
• wherein in the calculating of the abnormality degree, an approach degree is calculated such that a value of the approach degree increases as the state quantity approaches to the abnormality side which is a side exceeding the limit value, and the abnormality degree is calculated by converting the approach degree into the abnormality degree such that a value of the abnormality degree when the state quantity reaches the limit value matches a predetermined threshold value of the distance,
• wherein in the calculating of the distance, a Mahalanobis distance of the state quantity acquired at the monitoring timing with a unit space formed by the state quantity acquired when the operation state of the plant is normal as a reference is calculated, and a composite distance is calculated as the distance, wherein the composite distance is
• a Euclidean norm of the Mahalanobis distance and a maximum value among a plurality of the abnormality degrees, or
• a Manhattan distance of the Mahalanobis distance and the maximum value among the plurality of the abnormality degrees, and
• wherein in the determining of the operation state, it is determined that the operation state of the plant is abnormal in a case where the composite distance is larger than a predetermined threshold value.