What is the purpose of remote terminal units (RTUs) in a SCADA system for a biomass power plant?

In a SCADA (Supervisory Control and Data Acquisition) system for a biomass power plant, Remote Terminal Units (RTUs) serve as the interface between the central SCADA system and the plant's field devices and equipment. The primary purpose of RTUs is to collect data from sensors and instruments located throughout the plant, and to transmit this data to the central SCADA system for monitoring and control. RTUs also receive commands from the SCADA system and execute those commands by controlling actuators and other equipment in the field. More specifically, RTUs perform the following functions: 1) Data Acquisition: RTUs connect to various sensors and instruments, such as temperature transmitters, pressure transmitters, flow meters, and level sensors. They convert the analog signals from these devices into digital data and transmit the data to the SCADA system. 2) Control: RTUs receive control commands from the SCADA system, such as start/stop commands for motors, open/close commands for valves, and setpoint adjustments for controllers. They then execute these commands by controlling the appropriate actuators and equipment. 3) Communication: RTUs communicate with the central SCADA system using various communication protocols, such as Modbus, DNP3, or IEC 60870-5-104. They may use wired or wireless communication channels, depending on the plant's configuration. 4) Local Logic and Control: Some RTUs have built-in processing capabilities and can perform local logic and control functions, such as alarm annunciation, sequence control, and PID control. This allows them to operate autonomously in the event of a communication failure with the central SCADA system. 5) Data Storage: RTUs may store historical data locally, allowing for data retrieval and analysis even if the communication link to the SCADA system is temporarily unavailable. RTUs are essential components of a SCADA system, enabling remote monitoring and control of the biomass power plant's operations, improving efficiency, and ensuring reliable performance.