Output drop of hydro generator
(1) Cause
Under the condition of constant water head, when the guide vane opening has reached the no-load opening, but the turbine does not reach the rated speed, or when the guide vane opening is greater than the original at the same output, it is considered that the unit output decreases. The main reasons for the decrease of output are as follows: 1. Flow loss of hydraulic turbine; 2. Hydraulic loss of hydraulic turbine; 3. Mechanical loss of hydraulic turbine.
(2) Handle
1. Under the condition of unit operation or shutdown, the submerged depth of draft tube shall not be less than 300mm (except impulse turbine). 2. Pay attention to the water inflow or outflow to keep the water flow balanced and unobstructed. 3. Keep the runner running under normal conditions and shut down for inspection and treatment in case of noise. 4. For axial flow fixed blade turbine, if the unit output drops suddenly and the vibration intensifies, it shall be shut down immediately for inspection.
2,Unit bearing pad temperature rises sharply
(1) Cause
There are two kinds of turbine bearings: guide bearing and thrust bearing. The conditions to ensure the normal operation of the bearing are correct installation, good lubrication and normal supply of cooling water. Lubrication methods usually include water lubrication, thin oil lubrication and dry lubrication. The reasons for the sharp rise of shaft temperature are as follows: first, the bearing installation quality is poor or the bearing is worn; Second, lubricating oil system failure; Third, the lubricating oil label is inconsistent or the oil quality is poor; Fourth, cooling water system failure; Fifth, the unit vibrates due to some reason; Sixth, the oil level of the bearing is too low due to oil leakage.
(2) Handle
1. For water lubricated bearings, the lubricating water shall be strictly filtered to ensure the water quality. The water shall not contain a large amount of sediment and oil substances to reduce the wear of bearings and the aging of rubber.
2. Thin oil lubricated bearings generally adopt self circulation, with oil slinger and thrust disc. They are rotated by the unit and supplied with oil by self circulation. Pay close attention to the working condition of the oil slinger. The oil slinger shall not be stuck. The oil supply to the thrust disc and the oil level of the mail oil tank shall be level.
3. Lubricate the bearing with dry oil. Pay attention to whether the specification of dry oil is consistent with the bearing oil and whether the oil quality is good. Add oil regularly to ensure that the bearing clearance is 1 / 3 ~ 2 / 5.
4. The sealing device of bearing and cooling water pipe shall be intact to prevent pressure water and dust from entering the bearing and damaging the normal lubrication of the bearing.
5. The installation clearance of lubricating bearing is related to the unit pressure, linear speed of rotation, lubrication mode, oil viscosity, component processing, installation accuracy and vibration of the unit.
3、 Unit vibration
(1) Mechanical vibration, vibration caused by mechanical reasons.
reason; First, the hydraulic turbine is biased; Second, the axis center of water turbine and generator is not correct and the connection is not good; Third, the bearing has defects or improper clearance adjustment, especially the clearance is too large; Fourth, there is friction and collision between rotating parts and stationary parts
(2)Hydraulic vibration, the vibration of the unit caused by the imbalance of the water flowing into the runner
Reasons: first, the guide vane is damaged and the bolt is broken, resulting in different opening of the guide vane and uneven water flow around the runner; Second, there are sundries in the volute or the runner is blocked by sundries, so that the water flow around the runner is uneven; Third, the water flow in the draft tube is unstable, resulting in periodic changes in the water pressure of the draft tube, or air enters the spiral case of the hydraulic turbine, causing the vibration of the unit and the roar of water flow.
(3) Electrical vibration refers to the vibration of the unit caused by the loss of balance or sudden change of electrical quantity.
Reasons: first, the three-phase current of the generator is seriously unbalanced. Due to the current imbalance, the three-phase electromagnetic force is unbalanced; Second, the instantaneous change of current caused by electrical accident leads to the instantaneous non synchronization of the speed of generator and turbine; Third, the uneven gap between stator and rotor causes the instability of rotating magnetic field.
(4) Cavitation vibration, unit vibration caused by cavitation.
Reasons: first, the amplitude of vibration caused by hydraulic imbalance increases with the increase of flow; Second, the vibration caused by unbalanced runner, poor unit connection and eccentricity, and the amplitude increases with the increase of rotating speed; The third is the vibration caused by the electrical generator. The amplitude increases with the increase of excitation current. When the excitation is removed, the vibration can disappear; The fourth is the vibration caused by cavitation erosion. Its amplitude is related to the regionality of the load, sometimes interrupted and sometimes violent. At the same time, there is knocking noise in the draft tube, and there can be swing on the vacuum meter.
4,The bearing pad temperature of the unit rises and is too high
(1) Cause
1. Reasons for maintenance and installation: leakage of oil basin, incorrect installation position of pitot tube, unqualified tile gap, abnormal unit vibration caused by installation quality, etc;
2. Operation reasons: operating in the vibration area, failing to observe the abnormal bearing oil quality and oil level, failing to add oil in time, failing to observe the interruption of cooling water and insufficient water volume, resulting in long-term low-speed operation of the machine, etc.
(2) Handle
1. When the bearing temperature rises, first check the lubricating oil, add supplementary oil in time or contact to replace the oil; Adjust the cooling water pressure or switch the water supply mode; Test whether the vibration swing of the unit exceeds the standard. If the vibration cannot be eliminated, it shall be shut down;
2. In case of temperature protection outlet, monitor whether the shutdown is normal and check whether the bearing bush is burned. Once the Bush is burned, replace it with a new bush or grind it again.
5,Speed regulation failure
When the governor opening is fully closed, the runner cannot stop until the guide vane opening cannot be effectively controlled. This situation is called speed regulation failure. Reasons: first, the connection of guide vane is bent, which can not effectively control the opening of guide vane, so that the guide vane can not be closed, and the unit can not stop. It should be noted that some small units do not have braking devices, and the unit cannot stop for a moment under the action of inertia. At this time, do not mistakenly think that it has not been closed. If you continue to close the guide vane, the connecting rod will be bent. Second, the failure of speed regulation is caused by the failure of automatic governor. In case of abnormal operation of the water turbine unit, especially in case of crisis to the safe operation of the unit, try to stop the machine immediately for treatment. Barely running will only expand the fault. If the governor fails and the guide vane opening mechanism cannot stop, the main valve of the turbine shall be used to cut off the water flow into the turbine.
Other treatment methods: 1. Regularly clean the sundries of the water guide mechanism, keep it clean, and regularly refuel the movable part; 2. Trash rack must be set at the inlet and cleaned frequently; 3. For the hydraulic turbine with any vehicle device, pay attention to timely replace the brake pads and add brake oil.
Post time: Oct-18-2021
