2.1. A Basic SCADA Diagram

2.2. Components and its functions

SCADA system comprises of the following components

2.2.1. Sensors

Field instruments are an array of transmitters, monitors, and sensors. Sensors are the transducers which detect changes in physical quantity. These sensors can be analog or digital, but ultimately their purpose is the same. Sensors help its users to measure and collect data from various locations. The more complex a system, the more sensors we may need in place.

2.2.2. Conversion units

Sensors are responsible for collecting data, but we also need something to be able to receive and interpret the data. This is where the conversion unit comes in. Conversion units are the computerized units deployed at a specific location in the field. These are connected to sensors. They convert the information they receive into digital format, which is then sent to the centralized system to display.

The two most common types of conversion units used in a SCADA system are PLCs and RTUs. How do we determine which unit we need? that depends on what our specification is.

Programmable logic controllers (PLCs)

Programmable logic controllers are good for situations where we want more localized control. The programmable logic controller is an industrial digital computer designed for output arrangements and multiple inputs. PLC is used sometimes in place of other conversion units due to their versatility, flexibility, affordability, and configuration. However, one may need good programming skills to make the most out of it.

Remote terminal units (RTU)

Remote terminal units are microprocessor-controlled electronic devices. Their objective is to interface a SCADA system with a sensor or whatever object the RTU is connected to.

Normally, they transmit information through wireless communication. Therefore, they are considered good for functions covering a broad area geographically.

The above conversion units assist as local collection points for gathering information from sensors and delivering commands to control and protection relays.

2.2.3. Communication network

SCADA system cannot exist without a properly designed communication network system. All the SCADA system aspects rely solely on the communication network. It provides a channel for the flow of data between the supervisory control, the data acquisition units, and any controller that is connected to the system.

The main function of a communication network within a SCADA system is to connect the Conversion units with the SCADA master station. The data can be transmitted through various communication platforms such as ethernet, telephone line, power line carrier communication, optical fiber line, cellular, radio, satellite, Wi-Fi, microwave, or other wireless protocol.