SCADA control system model

Feature image monitoring system

Monitoring systems allow the data information of production processes or physical installations to be monitored. For example, the information is collected through data collection devices. They will be processed, analyzed, and stored. This information will then be sent to the user. These systems are called SCADA (Supervisory Control and Data Acquisition) control systems.


How SCADA systems work?

Today, industrial automation systems use computers and communication technologies. They are used to automate industrial monitoring and control processes. The mission of these systems is to collect data in complex environments. These data should then be presented in an operator-friendly manner. Complex graphic resources (human-computer interface) and multimedia content will assist in this task.

Schematic description of SCADA control system

Schematic description of SCADA control system

During operation, SCADA system will continuously identify information tags. Those are variables or letters. They are related to applications that can be performed by computer functions or represent control input / output points. In this case, each variable of the actual process will be represented by a corresponding connection. This connection takes place between the controller and the system. The information based on the values of the tags has been collected and presented to the user. Examples are temperature, level, flow, etc.

The hardware components of the monitoring system

A monitoring system consists of 3 main hardware components. These are sensors and actuators; Communication network and central monitoring stations. These stations are also called SCADA computer systems (SCADA computing system).

Sensors and actuators

Actuators and actuators are connected to the controlled devices. SCADA systems will monitor these devices. They will then convert the aforementioned physical parameters into digital signals. Similarly, these figures can be read from stations far from the center. Actuators are devices that perform tasks in the system. Their mission is to close / cut devices.


Communication network

Platform for information to be run from PLCs / RTUs on SCADA systems. There is also a review of system requirements and system distance covered. Communication network is built with the support of Ethernet cables, optical cables, subscriber or dial-up lines for data, radio waves, etc.

Central monitoring station

The main equipment of SCADA systems. These monitoring stations are responsible for aggregating the information generated by the stations. They will function in accordance with the events performed. Central monitoring stations can be centralized into a single computer. Or maybe they are distributed to computer networks. The goal is to enable the collection of information shared within the network.

Monitoring center of SCADA system

Monitoring center of SCADA system

The logical components of the SCADA system

Internally, SCADA systems often divide tasks into blocks or modules. This allows the system to be flexible and capable of performing powerful tasks.

  • The tasks that the system can execute are divided
  • The processing core of the system
  • Communication with the PLC / RTU
  • Manage alerts
  • Past database and system configuration
  • Internal programming logic (scripts) and controls
  • Graphic interface
  • Reports in the system
  • Communicate with other SCADA stations
  • Communication with external / internal systems
  • Other duties

The mode of communication

The main function of any SCADA control system is data / information exchange (communication). Communication modes of SCADA system include:

Communication with school equipment

This mode is implemented through sharing protocols with methods that can be public domain or limited. This mode usually operates when polling or interrupting, according to common indications with the Report by Exception.

Communication by polling method (Master / Slave)

This mode takes place when the central station (Master). It has control over the entire station system, querying remote stations (Slave) in sequence. The remote station only responds to the central station after receiving a request from this station. This makes data collection simple, without any conflicts about data transmission on the network. Especially do not need intelligent remote station. In other words, this mode is capable of communication from the central station to the remote station.

Communication on session interruption basis

In other words, this mode is executed when the PLC or RTU monitors its input values. It is also useful when checking for technical changes or values ​​that exceed pre-set limits. PLC / RTU will then send information / data to the central station. This helps to avoid the transmission of unnecessary data. (Because it will increase network bandwidth occupancy). This also allows quick check of important information, as well as data transmission between remote stations (Slave-to-Slave).

Communication between SCADA stations

This mode is possible with protocols developed by SCADA system manufacturers, or even by known protocols. They are implemented over Ethernet TCP / IP networks, private subscriber lines or dial-up modems.

Communication with other systems

For example, coordination sequences, or data collectors or vendors, can be done with separate modules, through databases or other technologies. Examples are XML and OPC

Hopefully this article has provided you with useful information about the SCADA system. See you in the next posts!

Read more: What is system integration?