JPH059805B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plant diagnostic method for identifying abnormal events in a plant online in real time in order to contribute to improving the operational reliability and availability of large-scale plants.

A conventional device of this type is shown in FIG. In the figure, 1 is a data acquisition device (for example, an analog-to-digital converter) for reading process data, and 2 is a data acquisition device that compares the process data with a reference value. arithmetic processing unit 3 for converting
A storage device 4 stores the results of calculations performed by the arithmetic processing unit 2. A storage device 5 stores the cause-and-effect tree (hereinafter referred to as CCT).A storage device 5 stores the process data stored in the storage device 3. 4 is a diagnostic processing device that identifies the first cause of the abnormality using the stored CCT, and 6 is a cathode ray tube display device for displaying the diagnostic results.

Next, the operation will be explained.

Process data Xi (i=1, 2,...,N)
shall be. Xi is quantized by the data acquisition device 1. Using the quantized data Xi as input, the arithmetic processing unit 2 performs the processing shown in the formula, and the result is
Si (i=1, 2, . . . , N) and the event occurrence time are stored in the storage device 3.

X ^L < _i- Xi< _- X ^U _i −>Si=0 X ^U _i <Xi or Xi<X ^L _i => Si=1 i=1, 2,..., N X ^L _i : Lower limit alarm level, X ^U _i : Upper limit alarm level - Here, Si is called the status of Xi. Further, the time when the status becomes 1 is called the event occurrence time.

An example of a portion of the CCT stored in the storage device 4 is shown in FIG. In FIG. 2, M6 and M7 are diagnostic messages, τ is a time delay, G ₁₁ and G ₁₂ are AND gates, and G ₂₁ and G ₂₂ are OR gates, respectively.
In CCT, the position where Si is defined is called a node. S ₁ , ..., S ₇ in Fig. 2 are storage devices 3
is stored in. CCT describes the abnormality propagation sequence as a logical relationship between statuses, but if the event propagation time between statuses is important, a time delay (τ in Figure 2) is used. CCT
The execution process is performed by the diagnostic processing device 5 based on information from the storage devices 3 and 4. The following process is performed to search for the first cause of disturbance.

First, subs to be searched from a large number of CCT groups.
In order to extract the CCT portion, an entry node whose status has changed (designated in advance as a node to start analysis) stored in the storage device 3 is detected, and a plan is started from that node to the lower nodes. And the first gate?
Find out whether it is an AND gate or an OR gate. Next, it is checked whether the relationship between the state of each input of the gate and the event occurrence time, which is the plant observation data written in the storage device 3, matches the CCT model written in the storage device 4. If the logic is established, the next node to be searched is determined according to the CCT model stored in the storage device 4 in order to expand to lower nodes. The order of search nodes is to start with the entry node, search for all nodes that are children of the entry node, and then search for all nodes that are grandchildren of the entry node.

In this way, in order, for each gate connected below the entry node, it is determined whether the node on the input side of each gate is false (mismatch) or true (match), and the true branches are spliced together. . When the expansion reaches the primary node, the logic of this entry node is established, and it is determined that the cause has been successfully identified. Time delays between events are set in various parts of the CCT, but if an event actually progresses faster than this, nodes below that will not be expanded.

In other words, when it is found that there is no cassette set for the entry node during the expansion, the diagnosis is stopped and all messages attached to nodes that are "true" below the entry node called the second best message are output. do. For example, if one side of the AND logic is "false", the following expansion is not performed and the second best message is output. Therefore, once the diagnosis is aborted or finished, analysis from the next entry node is performed taking priority into account. The above processing will be explained with respect to the CCT shown in FIG. Third
In the figure, M ₁ , M ₄ , M ₁₇ , M ₁₈ are diagnostic messages,
G ₁₃ , G ₁₄ , G ₁₅ , G ₁₆ are AND gates, G ₂₃ , G ₂₄ ,
G ₂₅ , G _26, G ₂₇ , G ₂₈ , G ₂₉ are OR gates, ● are observation nodes, ○ are non-observation nodes, ○†Ilu┘鵐肇蝓

Claims (1)

[Claims] 1 In a plant diagnosis method that processes a cause-and-effect tree that describes the propagation sequence of various abnormal events that occur in a plant using logical formulas, when identifying the cause,
If the cause identification is successful, the contents of the predetermined storage area are changed; if the cause identification is unsuccessful, the contents of the storage area are checked to see if other related entry nodes are successful. If the entry node is successful, proceed to the next step; if it is not successful, the plant diagnosis method is suspended, and after all entry nodes have been completed, a second best message is output for the suspended entry node.