Remote Terminal Unit (RTU) role in switchgear automation

Edwiin

05/04/2025

Remote Terminal Unit (RTU)

A Remote Terminal Unit (RTU) is a microprocessor - based device that plays a crucial role in a Supervisory Control and Data Acquisition (SCADA) system. It acts as an intermediary, transmitting telemetry data from the field to the master station while also being able to modify the state of connected switchgear. This modification can occur based on control messages received from the master station or commands generated internally by the RTU itself. In essence, the RTU serves as a two - way communication hub, facilitating the transfer of data from the field devices to the master station and enabling the master station to issue control commands to the field equipment.

Typical RTUs are equipped with physical hardware inputs designed to interface directly with various field devices. These inputs allow the RTU to collect real - time data from sensors, meters, and other equipment in the field. Additionally, RTUs feature one or more communication ports, which enable them to establish connections with the master station and other networked devices, ensuring seamless data transfer.

Several key software modules are integral to the operation of an RTU:

Central Real - Time Database (RTDB): This module acts as the core of the RTU's software architecture, providing an interface that connects with all other software components. It stores and manages real - time data, ensuring that information is readily accessible for processing and transmission.
Physical I/O Application: Responsible for acquiring data from the RTU's hardware components that interface with physical input/output devices. This module ensures that data from the field, such as sensor readings and switch statuses, is accurately captured and prepared for further processing.
Data Collection Application (DCA): Focuses on gathering data from devices with data communication capabilities, such as Intelligent Electronic Devices (IEDs), through the RTU's communication ports. It enables the RTU to interface with a wide range of networked devices and collect diverse types of data.
Data Processing Application (DPA): Takes the collected data and processes it to present meaningful information to the master station or Human - Machine Interface (HMI). This module may perform operations such as data aggregation, filtering, and transformation to ensure that the data is in a suitable format for analysis and decision - making.
Data Translation Application (DTA): Some RTUs are equipped with this optional module, which manipulates data before sending it to the master station. The DTA can also support stand - alone functionality at the RTU level, enabling local data processing and control operations.

The figure below illustrates the data flow architecture between an RTU and a SCADA system, highlighting how these various components interact to enable efficient monitoring and control of industrial processes.