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and turbine startup and shutdown procedures. The startup and shutdown sequences are executed in accordance with the logic design, and the DCS human machine interface (HMI) clearly shows the status of the sequence and the facility conditions. It also guides operators in the acknowledgement of messages and alarms and the triggering of interlock sequences. Operator intervention during the automated plant and turbine startup and shutdown processes is minimized, ensuring safe and smooth startup and shutdown. This greatly reduces operator workload and errors, shortens the startup and shutdown times, and mitigates thermal and physical stress on the turbine.Backup system Geothermal power plants have less auxiliary equipment and their control loops are not as complex as those at fossil fuel power plants. In addition, they cost less to operate. It is therefore feasible and desirable to run a geothermal power plant nonstop at full load. When a plant is operated in this way, reliability is a key concern. And even when the plant’s DCS has redundant controllers and is extremely reliable, there is still a risk that it might fail in a corrosive environment. For this reason, Yokogawa has provided a backup system. This backup system includes the following features:•Monitors by using a graphical user interface to ensure safety operation while the backup system is engaged•Handles effective alarms•Performs emergency operation in the event that the DCS failsThe backup system ensures that the plant can run safely without any interruptions.Sequence-of-events (SOE) stationAll events are precisely recorded with millisecond accuracy and displayed in a sequence of events (SOE) window for later analysis. Using this, operators can assess the problem cause and request a fix by maintenance personnel. Test systemWhen application software needs to be modified, the revised software must be tested before it can be downloaded to the controller, requiring a plant shutdown. To maximize plant uptime, Yokogawa provided a test system that uses the test functions of the DCS. This test system accurately replicates the plant control and graphical interfaces, and the software can be easily checked under the same conditions as with the actual plant system. It can be also used to train the operators.Customer SatisfactionThe design and structure of the CENTUM CS 3000 and CENTUM VP systems for these geothermal power plants exceeded PT PLN’s high expectations. The use of the same HMI in these three systems allows for complete consistency in the monitoring and control of the power plants and turbines at these plants. PT PLN greatly appreciates having the ability to automatically execute flawless plant and turbine startups and shutdowns, and PT PLN is looking forward to further such technology collaboration with Yokogawa.Central control roomGraphic of turbine systemSystem DetailsLahendong III project System:CENTUM CS 3000 R3 • Field control stations • Backup system • Operator stations • Supervisor station • SOE station • Test system • Time synchronization with GPS master clockLahendong IV project System: CENTUM VP • Field control stations • Operator stations • Supervisor station • SOE station • Time synchronization with GPS master clockLahendong I DCS replacement System: CENTUM VP • Field control stations • Operator stations • Supervisor station • SOE station • Time synchronization with GPS master clock • Plant Information and Management System • Virtual Training SimulatorSuccess Story Collection10PLN Lahendong Geothermal Power Plants / Indonesia