Supervisory Control and Data Acquisition (SCADA) System
SCADA systems are used to monitor power distribution networks, pipe lines, urban sewage collection, and similar geographically dispersed systems. They provide network monitoring capabilities as well as the command functions required to control product flow or to correct alarm or fault conditions. They comprise a central Master Station that communicates with the field monitoring and control devices via slaved controllers. A leading supplier of such systems decided to redesign its expensive mini-computer Master Station to take advantage of the reduced costs of microprocessor technology.
The Sombers Group was assigned the task of redesigning the Master Station. First on the priority list was establishing the station as a redundant pair to ensure greater reliability. The pair could be separated geographically to permit monitoring and control from two distinct areas. However, should one partner fail, the other could assume its workload without the loss of any data.
Several hundred slave stations, monitoring thousands of points, were polled to acquire events defining the current state of the network. These events, stored in a mirrored data base, were used to drive sophisticated color graphic displays. The user could specify each display’s content, which usually comprised a hierarchical set of network schematics showing ever greater detail. Alarm conditions were flashed on each screen; with the use of a light pen, the operator quickly could obtain detailed information.
The operator also could respond to alarm information or other control requirements by issuing commands to alter the network. Each such command was acknowledged by actually displaying the resulting network change.
The Sombers Group also developed a sophisticated interpretive math package that allowed the user to specify complex computations and to define pseudo-points representing the results of these computations. Using this facility, for instance, one rural power company instituted controlled brownouts to minimize its peak usage of power purchased from other grids, a key to minimizing its costs.