Understand Architecture and Block Diagram of SCADA System

Hey, in this article we are going to see the architecture and block diagram of SCADA System. The full form of SCADA is Supervisory Control and Data Acquisition. The main objectives of a SCADA system are,

• To operate and interact with ground-level devices such as different types of sensors and actuators.
• To operate single or multiple machines from local or remote locations through HMI.
• To control a bunch of operations from a central room.
• To operate and control multiple operations and gather data, scheduling events.

The SCADA system is used by large industrial organizations, private as well as government product manufacturers, mass traffic controlling systems, smart travel agencies, etc.

First of all, let's see the architecture of the SCADA system to understand its actual operating mechanism.

SCADA System Block Diagram

Here, you can see the block diagram of the SCADA System that represents its different parts and components.

As you see in the above block diagram, the SCADA system has the following important components or devices,

• Supervisory Computer
• Remote Terminal Units (RTUs) or Programmable Logic Controllers (PLCs)
• Communication Infrastructure
• Human-Machine Interface (HMI)
• Database and Historian
• Alarming System
• Security Measures

Working Principle

In the above block diagram, you can see there are so many devices and systems. The whole system can be divided into five levels to understand the working principle of each part of the SCADA system.

Level 0 (Sensors/ Actuators)

The ground-level devices that actually interact with the physical environment or work as technicians in a supervision system. Different types of sensors and actuators come under this level. A sensor is a device that can sense the physical changes around it and generate appropriate electrical or electronic signals. For, example we can measure the temperature using a thermostat. Flow sensors, pressure sensors, LDR, and many more sensors are used in a SCADA system.

The actuator is a device that makes physical changes when an electrical or electronic signal is applied to it. For, example if we want to control the flow of a liquid using an electrical method we can use a solenoid. Same as there are so many different types of actuators are used in SCADA Systems.

Level 1 (Programming Devices)

Different types of programming devices such as PLC(Programmable Logic Controller), and RTU(Remote Terminal Unit) are come under this level. These are the devices that directly control the ground-level devices such as sensors and actuators. A SCADA system can be built with only local area networks or a combination of both local and wide area networks. The PLC helps to build the SCADA system with local area network only whereas the RTU system helps to build the SCADA system with the wide-area network. Here, in the above block diagram, we have used both devices for better understanding.

Level 2 (Local Control and HMI)

The supervisory computers are come under this level. All the programming devices that operate the ground-level devices are connected to these computers. Supervisory computers are those from where the SCADA software starts working. From these computers, the actual instructions and commands are given to do the operations. The supervisory computer may be connected to a particular machine or multiple same types of machines or a whole manufacturing plant. These computers are operated by machine operators, plant supervisors, and technicians of a manufacturing plant. The main functions of these computers are to observe and control the production, errors, etc.

Level 3 (Coordination)

Coordinating computers are comes under level. Generally, these computers are connected to multiple plants. So, it can help to gather data from different plants from one place. At this level, the production planning, scheduling, event timing management are done by the plant in charge, managers, etc.

Level 4 (Central Control)

It is top-level of the SCADA System. At this level, a central computer is connected to all the plants and machinery. Generally, this is operated and controlled by the management team. All the data and information are collected and stored here. Using these data and information they can take any decision. From this computer, the management team can see all the actions and operations, etc.

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