SCADA Systems or Supervisory Control and Data Acquisition systems is a software application used in the control industry. This system is used to monitor and control field devices at remote sites. In layman’s language, SCADA is a software package designed to display information, log data, and show alarms.
This software application is mainly used in process control that composes of a central control system with controller network interfaces. It also has input/output and communication equipment. The application’s control may be automatic or it can be initiated by the operator’s command. The data acquisition by the software is accomplished by the RTU’s also known as Remote Terminal Units.
The SCADA systems usually implement the distributed databases also known as tag databases. These tag databases contain data elements called points or tags. A point is a single output or input value that is used to control and monitor the system. Points can be either soft or hard.
What does SCADA Hardware comprise?
The Hardware of SCADA comprises the components of the Distributed Control System. It helps in the easy execution of logic processes without involving the master computer. It is because of smart PLCs or RTUs. IEC 61131-3 requires very little training, unlike other procedural languages like FORTRAN and C programming language.
The SCADA system engineers are able to perform the implementation and design of programs. These programs are then executed on PLC or RTU. The compact controller, a Programmable automation controller, combines the features of a PC-based control system that has a typical PLC.
By using station computers or information processors the Distributed RTUs in the various electrical substations are used for communicating with PACs, protective relays, and other I/O devices.
What is RTU (Remote Terminal Unit)
Physical equipment is connected to The RTU. The RTU converts the electrical signals into digital values like the status: open or closed, which are coming from the equipment. When the electrical signals are converted, those signals are sent to the equipment. RTU may be controlling the equipment, like closing or opening a valve or a switch, or setting the speed of the pump.
What are the Communication methods and Infrastructure of SCADA?
SCADA systems are used for modem connections. They are also used for combinations of direct and radio serial to meet communication requirements. The SCADA protocols are designed to be compact. They send information to the master station only when the master station polls the RTU.SCADA protocols have been designed to be extremely compact and to send information to the master station only when the RTU is polled by the master station.
For improved communication between different software and hardware, PLE for Process Control is a commonly used solution that helps in communication between the devices that were not originally part of the industrial network.
The four main functions of SCADA systems :
Helps in acquiring Data
SCADA collects data frequently and it involves some kind of analog to digital conversion. Like, the temperature is converted into degrees celsius. It helps in converting transmit signal strength to dBm. Errored seconds are used to measure Channel quality.
Systematic Data communication
The data collected is transmitted through response to a request for data to some kind of upstream consolidator or master. The communication channel used can be either analog or digital. SCADA network topology typically also includes some kind of transport validation independent of any content validation.
Data Presentation through SCADA
The collected data is used to process, organize and present to the system operators. The system operators in turn make appropriate response and control decisions. The presentation varies from either a tabular presentation of logged events or graphical representation against mapping or image backgrounds.
Control decisions are warranted
If control decisions are justified and your system supports output then appropriate commands can be dispatched. These commands will affect specific operational or configuration changes. Most of the control actions are run by RTUs and PLCs.
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