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Tuesday, June 28, 2011

SCADA : Supervisory Control and Data Acquisition (Part 1) - Wonderware (Intouch10.0)

SCADA stands for Supervisory Control and Data Acquisition. From the meaning itself, SCADA is important for controls of equipment and data gathering of different parameters of gauges and meters. SCADA is a process management tool for data management, user-control interface and visual window. As data management, it is a powerful tool to manage and process data.
Different alarm monitoring can be generated and saved for future references. Reports can be done on hourly basis. For example, the different values that are read on power meters (voltage, current, real power, reactive power, energy, power factor and others) as well as the readings on temperature monitors and pressure gauges can be configures so as to get the data and store it on a specified duration (hourly, daily, every five minutes, etc.). Through SCADA, there is a user-control interface which the operator can control the different operation of the system. User can trip/close a power circuit breaker, on/off a power motor, open/close a gauge just by clicking the desired equipment on the monitor. This visual window on the monitor, is a summary of the common human machine interface (HMI) like the seven segment display, lamp, position indicator, power meters and others.
The SCADA system is a software that is installed to create a screen just intended for a specific operation. A simple diagram of the SCADA operation is illustrated below:

On the diagram, the SCADA software is installed in the computer. That is where the user can control the different equipment and access the data stored. Then, between the computer and the meter is the programmable logic control (PLC). Sometimes, PLC is replaced with remote terminal unit (RTU). Both of these equipment converts sensor data from meters and gauges to digital data going to SCADA computer. Since RTU are very big, expensive and dedicated to special purposes only, most of the SCADA system uses PLC. They are also easier to configure, flexible and versatile compared to RTU. The meter represents the communication infrastracture on which different data are gathered directly from the equipment being controlled and monitored.
In developing SCADA System Design, there are necessary tools that are being used which are inherent to the software. First is the Object-link Embedding (OLE) for process control. This tool is used to link the visual object on the computer monitor so that it can be controlled through the SCADA computer. This tool also allows the visual object to have animation or visual change if the equipment being controlled.

The next tool which of equal importance is the Structured Query Language (SQL). With this tool, it enables the programmer to create database for the users to access. Next are the Visual Basic Commands (VBA). This is similar to the powerpoint presentation on which you can create different animations for your object that appears on the SCADA sreeen. The last tool is the Transmission Control/Internet Protocol (TCP/IP). This tool is necessary in assigning the correct IP address of the different servers connected to the SCADA system as well as in assigning the IP address of the PLC which is being accessed.


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