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Operation Specification for Starting, Running and Shutting Down of Hydro-generator in Power Station

August 17, 2020

Operation specification for starting, running and shutting down of hydro-generator in power station


1. The generator in standby should be monitored and maintained so that it is always in good condition and can be started immediately at any time. If you need to deal with the defects, regardless of whether it affects the start of the unit, the consent of the grid dispatching should be obtained. When the generator is in standby state for a long time, appropriate measures should be taken to prevent the winding from getting wet and keep the winding temperature above 5°C.


2. For hydropower plants with multiple units, a system of unit rotation operation should be established on site.


3. After the generator is overhauled, the maintenance work ticket should be recovered before starting, and the cleanliness of all parts of the generator and its surroundings should be checked in detail. All related equipment must be restored, complete and easy to use, and the short-circuit and grounding lines must be removed. And conduct various tests before starting. The on-site operation regulations shall specify the inspection and test items before start-up in detail.


4. After the inspection of all related electrical equipment is completed, the insulation resistance of the generator stator and excitation circuit should be measured and recorded before the generator is started. The measurement of the insulation resistance of the generator stator circuit can include various electrical equipment connected to the generator stator circuit that cannot be disconnected by an isolating switch, and is measured by a 2500V megohmmeter. The insulation resistance value is not specified. If the measurement result is significantly lower than the normal value of the past years (considering the change of temperature and air humidity, such as reducing to 1/3 of the normal value of the past years) or the insulation absorption ratio of bitumen dipping and baking cirrus mica is less than 1.3, epoxy powder The mica insulation absorption ratio is less than 1.6, and the cause should be found out and eliminated. Measure the insulation resistance of the generator excitation circuit, including the generator rotor and main (auxiliary) exciter. Whether to measure the insulation resistance of various rectifier excitation devices should be carried out in accordance with the requirements of relevant regulations. The 500V~1000V megohmmeter should be used for measurement, and the insulation resistance value of the excitation circuit should not be less than 0.5MΩ. If it is lower than the above value, measures should be taken to restore it. If it cannot be restored for a while, whether to allow operation or not should be decided by the chief engineer of the power plant. The insulation resistance of the stator and excitation circuit of the generator, which is responsible for peak load regulation and frequent starting, should be measured at least once a month.


5. After the generator is overhauled and the unit is out of operation for a long time, before restarting, the opening and closing test of the generator circuit breaker and automatic de-excitation switch (including the interlock between the two) and the electric and hydraulic turbine protection linkage should be carried out Operation test of generator circuit breaker.


6. After the generator starts to rotate, it should be considered that the generator and all its equipment are live. After the overhaul, the unit for the first start-up test should slowly increase the speed and monitor the sound of each part of the generator, and check the bearing lubrication, cooling system working conditions and vibration conditions of each unit. When the generator speed reaches about half of the rated speed, check whether the brushes on the commutator and slip ring are bounced, jammed or have poor contact. If there are any above phenomena, try to eliminate them. When the speed reaches the rated value, check the bearing oil pressure, oil flow, oil temperature and tile temperature, as well as the air leakage of the cooling system, test the swing of each bearing, and monitor whether the swing exceeds the specification.


7. Before the generator starts normally, no matter what synchronous parallel mode is adopted, the excitation adjusting device should be placed at the no-load rated voltage position.

 

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8. The parallel operation of generators should be based on automatic quasi-synchronous parallel mode. If the automatic quasi-synchronous parallel mode is not good, it should be changed to manual quasi-synchronous parallel mode. Regardless of the synchronization method used, the field regulations should specify various methods of synchronization and the switches, sockets and synchronization devices used.


9. There is no regulation on the increase speed of the generator voltage, and it can be immediately increased to the rated value. If there is a manufacturer's regulations, the regulations shall be implemented.


10. When increasing the voltage of the generator, it should be noted that the three-phase stator currents are equal to or close to zero. When the generator speed has reached the rated value and the position of the excitation adjustment device is at a position equivalent to the no-load rated voltage, pay attention to whether the generator stator voltage has reached the rated value, and check whether the rotor current is normal according to the rotor ammeter. The excitation current at no-load rated voltage matches.


11. After the generator is integrated into the power grid, the speed at which the active load increases is not limited. When adding load, you must pay attention to monitor the temperature rise of the generator cooling medium, the temperature of the iron core, the temperature of the winding, and the working conditions of the brushes and the excitation device.


12. Under normal circumstances, the active power and reactive power must be reduced to no load before the generator is de-loaded, and then the generator circuit breaker should be opened. Only when the above steps are completed, the shutdown operation can be carried out. For hydro-generator units with a capacity of less than 200MW in a 220kV system, the neutral point of the ungrounded transformer must be put into operation before decommissioning. The generator will only open the bus disconnect switch and close the valve in front of the turbine when it is overhauled or for a long period of time.


13. After the generator is shut down, check whether the cooling water supply to the windings and bearings has been stopped, and all the actuators have been reset, ready for the next startup.


14. When the generator is stopped, no matter what kind of locking method is adopted, it should be able to be continuously locked until it stops rotating. When the electric switch is used to stop, the stator current should be monitored during the stop.


15. When the unit is shut down under phase modulation conditions, the air in the runner room should be drained before shutting down.