Software Components of SCADA systems


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A SCADA system can be implemented with the hardware and software components that constitute a whole SCADA system.

Using SCADA system the various application programs that can be implemented in power supply systems are fault location, load balancing, load shedding etc.

Now a detailed description of hard ware components, software components and application programs is given.

Software Components of SCADA systems

Data Acquisition and Processing

This serves as a data collector from the devices to our SCADA system is connected and presents it as a processed data to user. Data acquisition can be done in multiple scan rates and uses different protocols.

The data can be fetched as a whole or as a group and also report by exception. Data processing means conversion of fetched data into engineering conversions, zero suppression, reasonability check, and calculation subsystem. So, user can use this processed data for future purposes.

Control

Users are allocated to groups, which have defined read/write access privileges to the process parameters in the system and often also to specific product functionality. The allocated users can have the access to the devices, which are to be controlled.

Control can be either single or group, open or closed loop control. The execution of control can be executed at selective places, can be immediately executed, can be executed at required time etc.

Man machine interface

The products support multiple screens, which can contain combinations of synoptic diagrams and text. They also support the concept of a “generic” graphical object with links to process variables. These objects can be “dragged and dropped” from a library and included into a synoptic diagram.

Most of the SCADA products that were evaluated decompose the process in “atomic” parameters (e.g. a power supply current, its maximum value, its on/off status, etc.) to which a Tag-name is associated.

The Tag-names used to link graphical objects to devices can be edited as required. The products include a library of standard graphical symbols, many of which would however not be applicable to the type of applications encountered in the experimental physics community.

Standard windows editing facilities are provided: zooming, re-sizing, scrolling etc. On-line configuration and customization of the MMI is possible for users with the appropriate privileges. Links can be created between display pages to navigate from one view to another.

Alarm handling

Alarm handling is based on limit and status checking and performed in the data servers. More complicated expressions (using arithmetic or logical expressions) can be developed by creating derived parameters on which status or limit checking is done by the data server.

The alarms are logically handled centrally, i.e., the information only exists in one place and all users see the same status (e.g., the acknowledgement), and multiple alarm priority levels (in general many more than 3 such levels) are supported

Most of the SCADA products that were evaluated decompose the process in “atomic” parameters (e.g. a power supply current, its maximum value, its on/off status, etc.) to which a Tag-name is associated. The Tag-names used to link graphical objects to devices can be edited as required.

The products include a library of standard graphical symbols, many of which would however not be applicable to the type of applications encountered in the experimental physics community.

Logging and Archiving

The terms logging and archiving are often used to describe the same facility. However, logging can be thought of as medium-term storage of data on disk, whereas archiving is long-term storage of data either on disk or on another permanent storage medium.

Logging is typically performed on a cyclic basis, i.e., once a certain file size, time period or number of points is reached the data is overwritten. Logging of data can be performed at a set frequency, or only initiated if the value changes or when a specific predefined event occurs. Logged data can be transferred to an archive once the log is full.

The logged data is time-stamped and can be filtered when viewed by a user. The logging of user actions is in general performed together with either a user ID or station ID. There is often also a VCR facility to play back archived data.