What are the six major protection systems of a steam turbine?

[IanLee]

The six major protection systems of a steam turbine are: OPC overspeed protection, electrical overspeed protection, mechanical overspeed protection, emergency trip device, reset test valve assembly, and steam turbine trip system. A steam turbine, also known as a steam turbine engine, is a rotary steam power device. High-temperature and high-pressure steam passes through fixed nozzles to become accelerated airflow, which is then ejected onto the blades, causing the rotor with blade rows to rotate and perform external work. Steam turbines are the main equipment in modern thermal power plants and are also used in metallurgical industries, chemical industries, and marine power plants. Electrical overspeed protection: To ensure high reliability of the steam turbine overspeed protection, an independent two-out-of-three signal system is adopted. The system periodically conducts fixed tests. The overspeed protection system has a fast response speed, high reliability, and safety. Mechanical overspeed: Composed of the emergency trip device, emergency trip mechanism, high-pressure trip assembly, and emergency trip linkage. The action speed is 110%-111% of the rated speed (3300～3330r/min). When the speed reaches the set value of the emergency trip device, the flywheel (or flyweight) of the emergency trip device is ejected, striking the latch of the emergency trip mechanism, causing the latch to release. Through the emergency trip linkage, the emergency trip valve in the high-pressure trip assembly is activated, cutting off the high-pressure safety oil supply and releasing the high-pressure safety oil, quickly closing all steam inlet valves and interrupting the unit's steam intake. Emergency trip device: A protection device used to prevent severe overspeed of the steam turbine, also known as the emergency safety (trip) device or overspeed safety device. The emergency trip device is one of the important overspeed protection devices. Reset test valve assembly: In the tripped state, according to the operator's command, the reset solenoid valve 1YV of the reset test valve assembly is energized and activated, introducing lubricating oil into the piston side chamber of the emergency trip mechanism. The piston moves up to the top dead center, and through the linkage of the emergency trip mechanism, the latch of the emergency trip mechanism is reset. Steam turbine trip system: The steam turbine trip system is a dual-channel system connecting electronic protection, overspeed protection systems, and trip solenoid valves. All steam turbine trip commands, overspeed protection systems, electronic protection systems, generator protection, trip buttons, etc., generate shutdown signals, which are executed by the steam turbine trip system to activate the trip solenoid valves and interrupt the unit's operation.