The system of SCADA (Supervisory Control and Data Acquisition) is applied in Power plants such as Hydro, Gas Plans, Nuclear and Thermal for realizing control interlocks for equipments of electrical in the data acquisition and switch yard functions for switch yard and systems of electrical auxiliary in the power plant. The system of SCADA is both Software and Hardware.
The system of SCADA contains of below components:
1. A MMI (Man-Machine Interface) is the equipment which shows process data to a human operator, and the human operator, controls and monitors the process.
2. A acquiring data and supervisory system on the process and transferring commands to the process.
3. PLCs (Programmable Logic Controller) are more flexible than RTUs and perform RTUs the job and also manage the process when receive the command from the supervisory control.
4. RTUs (Remote Terminal Units) relating to sensors in the process, translating the sensor signals to data digital and sending data digital to the system of supervisory.
5. The infrastructure of communication connecting the system of supervisory to the RTUs.
Actually, the most control actions are executed automatically by programmable logic controllers (PLC) or by RTU. The functions of host control are generally controlled to basic superseding or supervisory level interference. For instance, a PLC might manage the flow of cooling water through a process part industry, but the SCADA might allow users to alter the setpoints for the water flow, and allow alarm states, for instance the loss of high temperature and flow, to be recorded and showed. The control loop feedback passes through the PLC or RTU, while the system of SCADA monitors the general loop performance.
The System of SCADA in Power Plants:
The system of electrical SCADA in power plant is positioned in two control locations; Main Control Room, and Switch yard Control Room. In Switch yard Control Room the system of SCADA is to control and monitor of high voltage transmission lines, 400kV/220kV, from switch yard control room via MMI (Man Machine Interface) of the system of electrical SCADA. The MMI (Man machine Interface) is an Units of Video Display which show diagrams, tabular designs, bar charts, analog trends etc to show parameters for example currents, voltages, etc and annunciations.
The main transformers control in the power plant for instance Generation transformer utilized for step up the voltage of generation from the generator and Station transformer utilized for deriving the power during plant start up and control of circuit breaker in plant is performed via the MMI. Important auxiliaries like system Battery, systems UPS, Generators Diesel are also checked and window annunciations and important alarm annunciations are offered at the Main Control Room.
SCADA system functions:
• Intervallic monitoring and logging of data for example current, voltage, frequency, etc. from auxiliaries of electrical
• The alarms classification in order of providing and priority annunciations at the events time
• Showing isolators status, breakers and single line diagram of a variety of systems in switch yard
• Isolators in switch yard and controlling circuit breakers.