What is OPC protection?

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The OPC protection is activated in situations such as a 103% overspeed of the turbine, an angular acceleration exceeding 49 r/min/s, or load shedding (when the actual load is 15% higher than the rated value and the generator is disconnected from the grid). The OPC solenoid valve and the control valve solenoid valve then operate to release oil, quickly shutting off the high and medium pressure control valves in order to prevent the unit from overspeeding. The main function of OPC is to take prompt action (closing valves) when the turbine shows a tendency to overspeed, thereby preventing the turbine speed from rising too high and avoiding severe damage to the turbine equipment as a result of overspeed, thus ensuring the safe and stable operation of the turbine. The OPC action is triggered when the following condition is met: 1. Turbine speed > 3090 r/min (103%). 2. The rotational speed acceleration exceeds 49 r/min/s. 3. Load shedding (actual load > 15% of rated load and generator disconnection). During the OPC operation, the high and medium pressure control valves, the extraction check valves for each stage, and the high-pressure exhaust check valve are closed, while the high-pressure exhaust ventilation valve is opened. When the turbine speed is < 3060 r/min, the OPC returns to normal, and the turbine maintains a stable operation of the unit at 3000 r/min through speed control.