Process visualization systems — SCADA

More and more often PC's and their networks are integrated in the systems.

Usually PC task in the automation systems is to ensure automated control of processes, registration and visualization. Internationally such systems are usually called SCADA (Supervisory Control And Data Acquisition). The most common principle of process tasks distribution among PLC and PC is the following: PLC controls and regulates the process, but PC registers and performs functions of extended process operator panel. PLC's of several companies (for example, Allen — Bradley) are created with PC like ideology. In such case function distribution principles could be different.

Software packages for SCADA system are offered almost by all common PLC producers (Siemens — WinCC, General Electric Fanuc — Cimplicity, etc.). Some companies specialize only in SCADA software (for example, Citect, Wonderware). Any SCADA program tries to find an opportunity of ensuring communication with the help of different exchange protocols. Interface between SCADA program, PLC of other producers and hardware of other companies could be ensured with several methods, the most progressive of which is considered to be exploitation of OPC server.

General basic functions ensured by SCADA programs of almost all companies are:

1. Data registration

SCADA should ensure continuous information reading from PLC and other devices that should be analyzed in compliance with programmed formulas and logic interconnections, as well as to ensure its demonstrative presentation in a graphic and tabular form. Data is collected, ie. archived, so that procedure of the process could be observed for any period of time during system operation.

2. Operators' assistant-interface

SCADA collects all information about the process and ensures its demonstrative visualization, so that the operator could follow the process procedure. Therefore, it is important to workout — program process visualization diagram, visual version of which in the consciousness of a man would nicely associate with the real process. For this occasion visual figures of the devices are fashioned, where colors of the devices or other features change depending from the their status (devices could be turned on/off, could be in the manual or automatic mode, at the state of readiness to complete operation, in alarm or warning situation etc.) At the process visualization diagram it is often important to see the upcoming process progress way.

3. Alarm and events monitoring

SCADA system must detect, depicture and save alarms and other important process events. Usually, such systems consider operator registration option, as well as option to record time, when alarm message has appeared, when operator has found it and when averted it. Convenient option to inspect alarms and other messages in the archive allows engineers and programmers to analyze causes of failures, in result of which it is possible to improve system operation safety.

4. Databases

An important component of SCADA is an opportunity to save databases (in SQL and other formats) and export them to other structures of the enterprise. For example, quite often it is necessary to provide information about certain product consumption to the department of financial accounting.


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