1. A monitoring and control system comprising: a control apparatus configured to control equipment-to-be-monitored; and a monitoring apparatus configured to perform monitoring based on data transmitted from the control apparatus, wherein the control apparatus comprises: a data input section to which sensor data indicating a state of the equipment-to-be-monitored is inputted; a time stamp adding section configured to add a time stamp to each sensor data inputted to the data input section; a data processing section configured to extract, from the sensor data added with the time stamp by the time stamp adding section, sensor data satisfying a given condition, and set the extracted sender data as transmission data; and a transmitting section configured to transmit the sensor data having been set as the transmission data by the data processing section, to a predetermined network, and wherein the monitoring apparatus comprises: a receiving section configured to receive the sensor data transmitted from the control apparatus to the network; and a display processing section configured to create a graph whose time axis is appropriately taken based on the time stamp added to the sensor data received by the receiving section. 2 The monitoring and control system according to claim 1, wherein the given condition determined by the data processing section is a case where the value of the sensor data has a variation exceeding a given threshold value. 25

3. The monitoring and control system according to claim 2, wherein, if a state where the value of the sensor data has no variation exceeding the given threshold value continues and if a predetermined time has elapsed since the transmitting section performed the last transmission, the data processing section will set inputted sensor data as the transmission data.

4. The monitoring and control system according to claim 1, wherein the display processing section creates a graph in which time period while the receiving section receives no sensor data is plotted by continuing the value of the last received sensor data.

5. The monitoring and control system according to claim 1, wherein the transmitting section transmits the set transmission data at a predetermined period.

6. A monitoring and control method applied to a system including a control apparatus configured to control equipment-to-be-monitored, and a monitoring apparatus configured to perform monitoring based on data transmitted from the control apparatus, the method comprising: a time stamp adding step of adding a time stamp to each sensor data supplied from the equipment-to-be-monitored; a transmitting step of extracting, from the sensor data supplied from the equipment-to-be-monitored, sensor data satisfying a given condition, and transmitting the extracted sender data from the control apparatus; a receiving step of receiving, by using the monitoring 26 apparatus, the sensor data transmitted in the transmitting step; and a display graph creating step of creating a graph whose time axis is appropriately taken based on the time stamp added to the sensor data received in the receiving step.

MONITORING AND CONTROL SYSTEM AND MONITORING AND CONTROL METHOD
CROSS REFERENCES TO RELATED APPLICATIONS
The present invention contains subject matter related to Japanese Patent Application JP 2014-121460 filed in the Japanese Patent Office on June 12, 2014, the entire contents of which being incorporated herein by reference.
BACKGROUND OF THE INVENTION Field of the Invention:
The present invention relates to a monitoring and control system, as well as a monitoring and control method, for monitoring equipment such as a power-generating plant. Description of the Related Art:
A monitoring and control system for monitoring a power-generating station is adapted to monitor and control a power-generating plant with a monitoring apparatus installed at a central control room. The monitoring apparatus is constituted by a computer and connected via a network to a plurality of control apparatuses for controlling respective equipment, such as a turbine, a boiler and/or the like, in the power-generating plant.
The monitoring apparatus transmits operation instructions to the control apparatuses to activate respective equipment in the power-generating plant, so that the power-generating plant operates in a desired state. Further, the control apparatuses collect data associated with the operation state of the turbine, the boiler, and the like in the power-generating plant, and transmit the collected data to the monitoring apparatus. Based on the received
2

data, the monitoring apparatus displays the operation state of the turbine, the boiler, and the like on monitors, and thereby operators can monitor the operation state of the power-generating plant.
One of monitoring functions carried out by the monitoring apparatus is a trend graph function for displaying a graph indicating the operation trend of the plant. In such a function, arithmetic processes for plant control, plant control instructions and the like are registered and grouped in advance, and thereby signals associated with each other can be monitored on one screen. By monitoring the trend graph, operators can recognize the operation state of the plan, and find sign of abnormality of both the power-generating plant and the control apparatuses.
In order to enable the monitoring apparatus to display such a trend graph, it is necessary for the control apparatuses in the power-generating plant to transmit data obtained by the sensors of the respective equipment of the plant to the monitoring apparatus via the network.
Japanese Unexamined Patent Application Publication No. 2008-204166 (referred to as "Patent Literature 1" hereinafter) discloses a monitoring and control system for monitoring a plant, in which data collected from the plant are added with time stamps and transmitted to a monitoring apparatus; based on the time stamps, the monitoring apparatus displays a trend graph in which data are arranged in correct time series.
However, in the case of monitoring a power-generating plant by using a trend graph, items whose operation state needs to be minutely monitored at a short period and items whose operation state is allowed to be monitored at a relatively long period are mixed with each other, depending on the property of the items to be

monitored. For example, data associated with the steam pressure and flow rate of the boiler and the turbine are required to be monitored at a relatively short period of millisecond order; while data associated with the temperature of the boiler and the like are allowed to be monitored at a relatively long period of second order.
Accordingly, since a large amount of data are transferred at different periods over one network on which the monitoring and control system is constructed, and further, since the shortest period is approximately several milliseconds, it will cause a problem that data transmission load will be very high. High load of the network means that the load of the arithmetic processing of the computer constituting the monitoring apparatus will also become high.
In the state where load of the network is high, there is a possibility that the data received by the monitoring apparatus may not be correctly processed. That is, there is a possibility that the data transmitted from each control apparatus may arrive at the monitoring apparatus in incorrect time-order, depending on the load on the network, and further, in the worst case, there is a possibility that a part of data may be missing, so that the data may lose consistency. As described in Patent Literature 1, by adding a time stamp to each data and transferring the data, it at least becomes possible to correctly determine the order of the data. However, the load of both the network and the monitoring apparatus cannot be reduced simply by adding the time stamp.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a monitoring

and control apparatus and a monitoring and control method, which reduce the load of a monitoring apparatus and a network, and allow good monitoring.
A monitoring and control system according to an aspect of the invention is a monitoring and control system including a control apparatus configured to control equipment-to-be-monitored, and a monitoring apparatus configured to perform monitoring based on data transmitted from the control apparatus.
The control apparatus includes a data input section, a time stamp adding section, a data processing section, and a transmitting section.
The data input section is supplied with sensor data indicating a state of the equipment-to-be-monitored.
The time stamp adding section adds a time stamp to each sensor data inputted to the data input section.
The data processing section extracts, from the sensor data added with the time stamp by the time stamp adding section, sensor data satisfying a given condition, and sets the extracted sensor data as transmission data.
The transmitting section transmits the sensor data having been set as the transmission data by the data processing section, to a predetermined network.
The monitoring apparatus includes a receiving section and a graph creating section.
The receiving section receives the sensor data transmitted from the control apparatus to the network.
The graph creating section creates a graph whose time axis is appropriately taken based on the time stamp added to the sensor data received by the receiving section, and thereby enables

determination of a trend of the sensor data as well as a trend of the result of a logical arithmetic process based on the created graph.
A monitoring and control method according to an aspect of the invention is a monitoring and control method that is applied to a system including a control apparatus configured to control equipment-to-be-monitored, and a monitoring apparatus configured to perform monitoring based on data transmitted from the control apparatus, and the method includes:
9 A time stamp adding step of adding a time stamp to each sensor datasupplied from the equipment-to-be-monitored;
9 A transmitting step of extracting, from the sensor data supplied from the equipment-to-be-monitored, sensor data satisfying a given condition, and transmitting the extracted sensor data from the control apparatus;
9 A receiving step of receiving, by using the monitoring apparatus, the sensor data transmitted in the transmitting step; and 9 A display graph creating step of creating a graph whose time axis is appropriately taken based on the time stamp added to the sensor data received in the receiving step, and thereby enabling determination of a trend of the sensor data as well as a trend of the result of a logical arithmetic process based on the created graph. •
According to the present invention, among the sensor data obtained from the equipment-to-be-monitored, only the sensor data satisfying a given condition is transmitted to the monitoring apparatus with a time stamp added thereto, and thereby it is possible to thin the transmission data when, for example, the variation of the sensor data is small. Thus, the load on the network on which

the system is constructed as well as the load on the monitoring apparatus connected to the network can be reduced, which allows good monitoring with reduced load.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a configuration diagram illustrating an example of an entire monitoring and control system according to an embodiment of the present invention.
Fig. 2 is a block diagram illustrating an example of a control apparatus according to the embodiment of the present invention.
Fig. 3 is a block diagram illustrating an example of a monitoring apparatus according to the embodiment of the present invention.
Fig. 4 is a flowchart illustrating an example of processing performed by the control apparatus, according to the embodiment of the present invention.
Figs. 5A and 5B are views illustrating examples of data transmission states according to the embodiment of the present invention.
Fig. 6 is a flowchart illustrating an example of processing performed by the monitoring apparatus according to the embodiment of the present invention.
Fig. 7 is a diagram illustrating a display example of a trend graph according to the embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, an embodiment according to the present invention
(hereinafter, referred to as "present embodiment") will be

described with reference to the accompanying drawings. [Configuration of entire Monitoring and Control System]
Fig. 1 is a diagram illustrating the configuration of an
entire monitoring and control system of the present embodiment.
The monitoring and control system of the present embodiment
is a system for monitoring and controlling a power-generating plant
10 . The power-generating plant 10 includes a turbine 11 and a boiler
12. The turbine 11 is controlled by a control apparatus 20, and
the boiler 12 is controlled by a control apparatus 30. The turbine
11 and the boiler 12 are each provided with a sensor (not
illustrated) for detecting the operation state thereof. Data
detected by the sensor of the turbine 11 and data detected by the
sensor of the boiler 12 are supplied to the control apparatuses
20 and 30, respectively. For example, data on rotation number,
rotation speed, and the like of the turbine 11 is supplied to the
control apparatus 20; while data on pressure, temperature, and the
like of the boiler 12 is supplied to the control apparatus 30.
Further, the operation state of the turbine 11 and the operation
state of the boiler 12 are controlled by the control apparatus 20
and the control apparatus 30, respectively.
The control apparatuses 20 and 30 are connected to a monitoring apparatus 40 via a network 90. Various kinds of wired or wireless networks, such as a WAN (Wide Area Network) , a LAN (Local Area Network) or the like, can be used as the network 90.
The monitoring apparatus 40 is installed, for example, in a central control room of the power-generating plant 10. The monitoring apparatus 40 creates monitoring screens for monitoring the operation state of the power-generating plant 10. The created monitoring screens are displayed on a display inside the monitoring

apparatus 40. Further, operation instructions created by the monitoring apparatus 40 are transmitted to the control apparatuses
20 and 30 via the network 90. The control apparatuses 20 and 30
control the turbine 11 and the boiler 12, respectively, based on
the received control instructions.
[Configuration of Control Apparatus]
Fig. 2 is a diagram illustrating a configuration example of the control apparatus 20. Fig. 2 illustrates a configuration of the control apparatus 20 for controlling the turbine 11, and the control apparatus 30 for controlling the boiler 12 also has a similar configuration.
The control apparatus 20 includes a data input section 21. Sensor data detected by the sensor provided to the turbine 11 is supplied to the data input section 21. For example, sensor data indicating the rotation number and the rotation speed of the turbine 11 is supplied to the data input section 21. The sensor data supplied, to the data input section 21 is digital data obtained by sampling, at a predetermined period, signals output from the sensor. For example, in the case of data indicating the rotation speed of the turbine 11, the sensor data is supplied to the data input section
21 at a predetermined period of, for example, several milliseconds.
The sensor data supplied to the data input section 21 is supplied to a time stamp adding section 22 where a time stamp is added to each sensor data supplied at a predetermined period. The time stamp is data having a predetermined number of digits; the value of the time stamp increases per unit data, and thereby the time stamp indicates a time series of data. In addition, the time stamp may also be data indicating an absolute clock time such as hour, minute, and second.

Further, the sensor data having the time stamp added thereto in the time stamp adding section 22 is supplied to a data processing section 23. The data processing portion 23 determines a value of the sensor data, and sets the sensor data as transmission data if the value satisfies a given condition.
An example of the given condition to be determined by the data processing section 23 under control of a control section 24 will be described herein. In order for the data processing section 23 to perform the above determination, a threshold value is determined and registered in the data processing section 23 in advance for each type of sensor data. Further, the data processing section 23 calculates the difference between the sensor data having been transmitted lastly and the sensor data having been input thereafter, and determines whether or not the absolute value of the difference exceeds the threshold value. If it is determined that the difference exceeds the threshold value, the data processing section 23 will set the sensor data as transmission data. That is, the data processing section 23 performs the following determination.
Threshold value > | current data - lastly set data |
If the condition represented by the above formula is satisfied, the sensor data will not be set as transmission data; while if the condition represented by the above formula is not satisfied (i.e., if the difference exceeds the threshold value), the sensor data will be set as transmission data. Further, if a predetermined time, such as one second, has elapsed since the last transmission, the sensor data will be set as transmission data without performing the above determination using the threshold value. Incidentally,
10

the first inputted sensor data is also set as transmission data.
The sensor data having been set as transmission data by the data processing section 23 is supplied to a network communication section 25, and is transmitted from the network communication section 25 to the monitoring apparatus 40 via the network 90 (Fig. 1) . That is, the network communication section 25 functions as a transmitting section that transmits data to the monitoring apparatus 40.
The transmission from the network communication section 25 to the monitoring apparatus 40 is performed, for example, at a predetermined period. That is, the network communication section 25 transmits transmission data having been set during the predetermined period to the monitoring apparatus 40 in a batch. For example, the network communication section 25 transmits the sensor data every one second. The value of the predetermined period, such as one second, at which the transmission is performed may be equal to the value of the aforesaid predetermined time in accordance with which an elapse of time since the last transmission is determined.
Incidentally, the above configuration in which the network communication section 25 transmits the sensor data at a predetermined period is just an example, and the network communication section' 25 may perform transmission every time when the transmission data has been set.
Further, the control instruction transmitted from the monitoring apparatus 40 is received by the network communication section 25, and the content of the received control instruction is recognized by the control section 24 connected to the data processing section 23. Based on the recognized, the control
11

section 24 causes an instruction creating section 26 to create an instruction for instructing the turbine 11 to perform a specific operation. The instruction created by the instruction creating section 26 and which instructs the turbine 11 to perform a specific operation is supplied to individual portions of the turbine 11 from a data output section 27, and the specific operation of the turbine 11 is controlled in accordance with the instruction. [Configuration of Monitoring Apparatus]
Fig. 3 is a diagram illustrating a configuration example of the monitoring apparatus 40.
The monitoring apparatus 40 includes a network communication section 41. The network communication section 41 not only functions as a data receiving section for receiving data transmitted from the control apparatuses 20 and 30 (see Fig. 1), but also functions as a data transmitting section for transmitting data to the control apparatuses 20 and 30 from the network communication section 41.
The data received by the network communication section 41 is supplied to a data processing section 42, which processes the received data for each type of the received data under control of a control section 43. For example, when the network communication section 41 has received the sensor data transmitted from the control apparatus 20, the sensor data will be stored in a storage section 44 connected to the data processing section 42. At this time, based on the time stamp added to the sensor data, the data processing section 42 determines the timing at which a value indicated by the sensor data has been detected, and stores the sensor data into the storage section 44 as data with correct arrangement.
Further, under control of the control section 43, the data
12

processing section 42 supplies the data received by the network communication section 41 and the data stored in the storage section 44 to a display processing section 45. The display processing section 45 uses the data supplied from the data processing section 42 to create display data for monitor screens of the power-generating plant 10, and supplies the created display data to a display 46. The display 46 displays the monitor screens based on the display data.
Here, when the display 46 displays a trend graph for individual portions of the power-generating plant 10, as the monitor screens, the sensor data stored in the storage section 44 is read out by the data processing section 42, which performs display graph creating processing. That is, the data processing section 42 functions as a display graph creating processing section. Further, the trend graph data processed by the data processing section 42 is transmitted to a display processing section 45, which creates display data for trend graph. Further, the display data for trend graph created by the display processing section 45 is supplied to the display 46, which displays a trend graph. Further, the created trend graph is stored in the storage section 44. The trend graph stored in the storage section 44 can be displayed any time on the display 46 by the operation performed by a monitoring operator. Further, as for the trend graph stored in the storage section 44, the trend graph data can be transferred an external device from the monitoring apparatus 40 according to necessity. [Operation of Control Apparatus]
Fig. 4 is a flowchart illustrating processing performed by the control apparatus 20 to transmit the sensor data to the monitoring apparatus 40. The processing to transmit the sensor
13

data is carried out under control of the control section 24.
First, the control section 24 determines whether or not the sensor data has been inputted to the data input section 21 (step Sll) . Here, if it is determined that the sensor data has not been inputted, the control section 24 will wait until the sensor data is inputted to the data input section 21.
While if it is determined in step Sll that the sensor data has been inputted to the data input section 21, the time stamp adding section 22 will add a time stamp to the sensor data under control of the control section 24 (step S12).
The sensor data having the time stamp added thereto is send to the data processing section 23, where determination processing for transmission is performed. Here, the data processing section 23 determines whether or not the supplied sensor data is first inputted data or data inputted at timing when one second has elapsed since the last transmission (step S13). Here, in the case where the supplied sensor data is the first inputted data and in the case where the supplied sensor data is the data inputted at timing when one second has elapsed since the last transmission, the data processing section 23 sets the sensor data inputted this time as transmission data (step S15) .
Further, in the case where, in step S13, the supplied sensor data is not the first inputted data, but the data inputted at timing when one second has not elapsed since the last transmission, the data processing section 23 moves the processing to a determination in step S14 . In step S14, the data processing section 23 calculates the difference between the value indicated by the inputted sensor data and the value of the data transmitted lastly, and determines whether or not the value of the difference exceeds a predetermined
14

threshold value. Further, if it is determined, in the determination in step S14, that the value of the difference exceeds the predetermined threshold value, the data processing section 23 will move the processing to the processing in step S15, and sets the sensor data inputted this time as transmission data.
while if it is determined, in the determination in step S14, that the value of the difference is equal to or smaller than the predetermined threshold value, the data processing section 23 will not set the sensor data inputted this time as transmission data, and returns the processing to the determination in step Sll. Further, after having set the sensor data inputted in step S15 as transmission data, the data processing section 23 also returns the processing to the determination in step Sll.
In this manner, the data processing section 23 performs processing of determining whether or not to set the inputted sensor data as transmission data every time when the sensor data is inputted. Further, in the network communication section 25, the sensor data having been set as the transmission data in step S15 is transmitted in a state where the data has a time stamp added thereto. The data set as the transmission data is transmitted from the network communication section 25 in a batch at a predetermined period of, for example, one second. [Example of Data Transmission State]
Figs . 5A and 5B are views illustrating examples of sensor data transmission states in the control apparatus 20. Fig. 5A illustrates an example of a case in which the variations of the sensor data are small; while Fig. 5B illustrates an example of a case in which the variations of the sensor data are large.
In each of the examples shown in Figs. 5A and 5B, the sensor
15

data is supplied to the control apparatus 20 from the turbine 11 at a short period (here, the period is ten milliseconds). For example, as shown in Fig. 5A, sensor data DO is supplied at timing tO; next, after elapse of ten milliseconds, sensor data Dl is supplied at timing tl; and thereafter, the sensor data is supplied every ten milliseconds. At this time, in the control apparatus 20, a series of time stamps with consecutive numbers are added to the
sensor data DO, Dl, 02, , respectively.
Here, transmission states of the sensor data will be described below. The sensor data DO having been inputted first at the timing to is set as transmission data. Further, in the state shown in Fig. 5A, it is determined, in step S14 of the flowchart shown in Fig. 4, that the differences between the sensor data DO and each of the
sensor data Dl, D2, supplied subseguent to the sensor data DO
are all equal to or smaller than the threshold value. In this case, no sensor data is set as transmission data until a predetermined time (one second) elapses.
Further, sensor data DlOO inputted at timing tlOO when one second has elapsed since the transmission of the sensor data DO is set as transmission data.
In such a manner, in the state where the sensor data has no variation exceeding the threshold value, the sensor data is set as transmission data every one second.
The example shown in Fig. 5B is a case where, after the sensor data DO first inputted at timing tO has been set as transmission data, the variation of sensor data Dl inputted at next timing tl exceeds the threshold value. In such a case, subsequent to setting the sensor data DO inputted at the timing tO as transmission data, the sensor data Dl inputted at the timing tl is set as transmission
16

data. Subsequently, in the case where successive variations each exceed the threshold value, the sensor data will be set as transmission data every ten milliseconds in the order of: sensor data D2 inputted at timing t2, sensor data D3 inputted at timing
t3, However, the transmission data are transmitted in a batch
at a predetermined period. Further, in the case where the difference between the sensor data and the lastly set transmission data is equal to or smaller than the threshold value, the sensor data will be set as transmission data at a period of one second as shown in FIG. 5A.
In such a manner, if variation of the sensor data inputted to the control apparatus 20 exceeds the threshold value, the sensor data will be set as transmission data. [Operation of Monitoring Apparatus]
Fig. 6 is a flowchart illustrating processing performed by the monitoring apparatus 40 to display a trend graph. The processing to display a trend graph is carried out under control of the control section 43.
First, the control section 43 determines whether or not sensor data has been received by the network communication section 41 (step S21) . Here, if it is determined that the sensor data has not been received, the control section 43 will wait until the sensor data has been received.
Further, if it is determined, in step S21, that the sensor data has been received, the control section 43 will cause the data processing section 42 to appropriately adjust a time axis based on the time stamp added to the received sensor data, and plot the value of the received sensor data on a graph (step S22) . Further, the control section 43 causes the display processing section 45
17

to update display data, which is created by the display processing section 45, in accordance with the trend graph on which a value of the received sensor data is plotted in step S22 (step S23).
After the display data has been updated in step S23, the control section 43 returns the processing to the determination in step S21. [Example of Trend Graph]
Fig. 7 is a diagram illustrating an example of a trend graph displayed by the display 46 of the monitoring apparatus 40.
In the trend graph illustrated in Fig. 7, the vertical axis represents the rotation speedof the turbine 11, and the horizontal axis represents the time (in units of seconds (denoted by "s" in Fig. 7)) . In a state where the variations in the rotation speed are relatively small, the trend graph is a graph plotted based on the sensor data transmitted every one second; while, in period x and period y, during which the variations are large, the trend graph is a graph plotted based on the sensor data transmitted at a period shorter than one second. The example shown in Fig. 7 shows a state where the respective values plotted on the graph are interconnected by a line L.
Incidentally, when creating a trend graph such as shown in Fig. 7, each of rotation speed values is plotted at correct position on the time axis (the horizontal axis) based on the time stamps added to the respective sensor data.
Further, in the line L that connects the respective values plotted on the graph, each interval in which the value of data is plotted every one second is a step-shaped line segment that includes a straight portion and a curved portion, wherein the straight portion means a previous value continues until immediately before

a new value is plotted, and the curved portion connects, immediately before a new value is plotted, the previous value to the new value.
Since such a trend graph is displayed, it becomes possible for a monitoring operator who is monitoring the monitoring apparatus 40 to not only determine the trend of the sensor data based on the trend graph, but also determine the trend of results of logical arithmetic processes, such as a calculation process, on the sensor data. That is, when a certain abnormality has occurred in the equipment-to-be-monitored, it becomes possible to understand the details of the abnormality on the basis of a display based on the sensor data transmitted at a short period. Also, it becomes possible to determine the trend of the results of logical arithmetic processes, such as a calculation process, on the sensor data, on the basis of the sensor data transmitted at a short period. Further, in the case where the operation state of the equipment-to-be-monitored is stable, it becomes possible to recognize the stable state on the basis of the display based on the sensor data transmitted at a minimum period. Furthermore, it becomes possible to perform detailed analysis of abnormality and analysis of sign of abnormality of the power-generating plant based on the trend graphs stored in the storage section 44 of the monitoring apparatus 40. Accordingly, with the monitoring and control system according to the present embodiment, it is possible to perform good monitoring.
Further, since the transmission data set at the side of the control apparatuses 20 and 30 are transmitted in a batch at a predetermined period over the network 90 which connects the control apparatuses 20 and 30 to the monitoring apparatus 40, it becomes possible to prevent the sensor data from being transmitted over
19

the network 90 at a short period. Thus, it is possible to reduce data transmission amount on the network 90, to effectively reduce the loads imposed on the network 90, and to minimally suppress delay and/or missing of transmission data caused by heavy network load. In the system shown in Fig. 1, only the two control apparatuses 20 and 30 are illustrated; however, in actual cases, a large number of control apparatuses are connected to the single network 90, and further, a large number of kinds of sensor data are handled by a single control apparatus. Thus, by reducing data transmission amount of the sensor data, it becomes possible to significantly reduce the total amount of communication over the entire network.
Further, similarly, for the processing to create the trend graph in the monitoring apparatus 40, it is possible to create a trend graph in which the interval of values of the sensor data is small only in the case where the sensor data has variation, and create a trend graph in which the interval of values of the sensor data is large in the case where the sensor data is stable, so that it is also possible to reduce the processing load of the monitoring apparatus 40.
Further, in the present embodiment, it is also possible to reduce the loads on the monitoring apparatus 40 through the method shown in Fig. 7, in which, in each interval in which the value of data is plotted at a long period such as one second, a straight line means a previous value continues until immediately before a new value is plotted a previous value continues until immediately before a new value is plotted. That is, when creating a trend graph, the monitoring apparatus 40 does not need to change a state indicated by the trend graph until receiving respective sensor data. Thus, when creating a trend graph, the monitoring apparatus 40 can create
20

the graph with less processing; in this respect, it also becomes possible to reduce the load on the monitoring'apparatus 40.
Incidentally, for step-like line segments of the line L shown in Fig. 7, the processing in the monitoring apparatus 40 may be performed such that, after elapse of a certain amount of time, each two adjacent plotted points are connected by a straight line so that the line L becomes a smooth line. [Modification Examples]
The embodiment described above is an example applied to a monitoring and control system for a power-generating plant. The present invention, nevertheless, may also be applied to monitoring and control systems for monitoring and controlling equipment-to-be-controlled installed in other kinds of plants, or the like.
Also, using the trend graph described in the aforementioned embodiment to indicate the rotation speed of the turbine is just an example, and other kinds of sensor data may also be indicated using the trend graph. Further, transmitting the sensor data at a predetermined period such as one second is also just an example, and the transmission period may also be appropriately set for each kind of data.
Further, in the aforementioned embodiment, the threshold value used for determining whether or not the sensor data is to be set as transmission data is a predetermined value; however, the threshold value may also be obtained by, for example, multiplying the value of the last transmitted data by a predetermined coefficient. Thus, if the sensor data is a large value, the threshold value will be set to relatively large value, while if the sensor data is a small value, the threshold value will be set
21

to relatively small value, so that it becomes possible to set a threshold value suitable for the condition that time.
Further, in the aforementioned embodiment, the transmission of the sensor data from each of the control apparatuses 20 and 30 to the monitoring apparatus 40 is performed such that the transmitting section transmits the sensor data having been set as the transmission data in a batch at a predetermined period. The period at which the sensor data are transmitted in a batch may either be a constant value, such as one second, or be changeable depending on the state. For example, in a state where the amount of the sensor data set as the transmission data is large, the period may be changed from one second to 0. 5 seconds. Alternatively, in the case where a state where variation of the sensor data is large continues for a predetermined time, the batch transmission of the sensor data may be temporarily halted, and the sensor data set as the transmission data may be sequentially transmitted to the monitoring apparatus 40 piece by piece. Further, the system may also be configured in a manner so that both the period at which the batch transmission is performed by the control apparatuses 20 and 30 and the interval at which the transmission data is set can be changed according to instructions from the monitoring apparatus 40. With such an arrangement, the monitoring apparatus 40 can perform monitoring suitable for the condition of a plant-to-be monitored.
Further, the processing in which only the sensor data satisfying a given condition are transmitted, as is described in the aforementioned embodiment, may be selectively performed in accordance with the condition of the network. For example, when having detected a state where communication over the network is congested, the monitoring apparatus 40 may transmit an instruction
22

to each of the control apparatus 20 and 30, and upon receiving the instruction, the control apparatuses 20 and 30 each perform processing to transmit only the sensor data satisfying a given condition in a batch at a predetermined period. Further, in a state where communication over the network is not congested, the control apparatuses 20 and 30 may each transmit the sensor data at a period shorter than the above period.
Alternatively, in the case where the monitoring apparatus 40 is required to monitor specific monitoring items more strictly than in a normal situation, the monitoring apparatus 40 may transmit an instruction to the control apparatus 20 and the like to cause the control apparatus 20 and the like to so that sensor data associated with the specific monitoring items obtained at all timing are transmitted to the monitoring apparatus 40 even if the difference is equal to or smaller than the threshold value. With such an arrangement, it becomes possible to deal with a state in which, for example, a certain adjustment is performed for a specific turbine, and therefore the operation state after the adjustment is desired to be monitored in detail for a while.
Further, a configuration may be made such that the monitoring and control system according to the present invention is constituted by a program (a software) , and in an existing monitoring and control system, the programs are installed into existing control apparatuses 20 and 30 as well as an existing monitoring apparatus 40 so that the existing control apparatuses 20 and 30 as well as the existing monitoring apparatus 40 can perform the processing having been described in the aforementioned embodiment. In this case, the programs can be installed into the existing control apparatuses 20 and 30 as well as the existing monitoring apparatus
23

40 via recording media which belong to one of various kinds of recording media, such as a semiconductor memory device and an optical disc, and which contain the programs recorded therein.

WE claim:
1. A monitoring and control system comprising:
a control apparatus configured to control equipment-to-be-monitored; and
a monitoring apparatus configured to perform monitoring based on data transmitted from the control apparatus, wherein the control apparatus comprises:
a data input section to which sensor data indicating a state of the equipment-to-be-monitored is inputted;
a time stamp adding section configured to add a time stamp to each sensor data inputted to the data input section;
a data processing section configured to extract, from the sensor data added with the time stamp by the time stamp adding section, sensor data satisfying a given condition, and set the extracted sender data as transmission data; and
a transmitting section configured to transmit the sensor data having been set as the transmission data by the data processing section, to a predetermined network, and wherein the monitoring apparatus comprises:
a receiving section configured to receive the sensor
data transmitted from the control apparatus to the network; and
a display processing section configured to create a
graph whose time axis is appropriately taken based on the time stamp
added to the sensor data received by the receiving section.
2 The monitoring and control system according to claim 1, wherein the given condition determined by the data processing section is a case where the value of the sensor data has a variation exceeding a given threshold value.
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3. The monitoring and control system according to claim 2, wherein, if a state where the value of the sensor data has no variation exceeding the given threshold value continues and if a predetermined time has elapsed since the transmitting section performed the last transmission, the data processing section will set inputted sensor data as the transmission data.
4. The monitoring and control system according to claim 1, wherein the display processing section creates a graph in which time period while the receiving section receives no sensor data is plotted by continuing the value of the last received sensor data.
5. The monitoring and control system according to claim 1, wherein the transmitting section transmits the set transmission data at a predetermined period.
6. A monitoring and control method applied to a system including a control apparatus configured to control equipment-to-be-monitored, and a monitoring apparatus configured to perform monitoring based on data transmitted from the control apparatus, the method comprising:
a time stamp adding step of adding a time stamp to each sensor data supplied from the equipment-to-be-monitored;
a transmitting step of extracting, from the sensor data supplied from the equipment-to-be-monitored, sensor data satisfying a given condition, and transmitting the extracted sender data from the control apparatus;
a receiving step of receiving, by using the monitoring
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apparatus, the sensor data transmitted in the transmitting step; and
a display graph creating step of creating a graph whose time axis is appropriately taken based on the time stamp added to the sensor data received in the receiving step.