1、 The output of wheel generator decreases
（1） Cause
Under the condition of constant water head, when the guide vane opening has reached the no-load opening, but the turbine has not reached the rated speed, or when the guide vane opening is increased than the original at the same output, it is considered that the unit output has decreased. The main reasons for output decrease are as follows: 1. Flow loss of hydraulic turbine; 2. Hydraulic loss of hydraulic turbine; 3. Mechanical loss of hydraulic turbine.
（2） Processing
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 smooth. 3. Keep the runner running under normal conditions, and stop the machine 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 bearings for hydraulic turbines: 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. There are usually three lubrication methods: 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; 4. Cooling water system failure; 5. The unit vibrates due to some reason; Sixth, the oil level of the bearing is too low due to oil leakage.
（2） Processing
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. Oil slingers and thrust discs are used. The oil is supplied automatically by the rotation of the unit. Pay close attention to the working condition of the oil slinger. The oil slinger is not allowed to be stuck. The oil supply condition of the thrust disc and the oil level of the mail oil tank shall be ensured.
3. Lubricate the bearing with dry oil. Pay attention to whether the specification of the 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 devices of bearings and cooling water pipes are in good condition to prevent pressurized water and dust from entering the bearings and damaging the normal lubrication of the bearings.
5. The installation clearance of lubricating bearing is related to the unit pressure of bearing bush, linear speed of rotation, lubrication mode, oil viscosity, component processing, installation accuracy and vibration of unit.
3、 Unit vibration
（1） Mechanical vibration, vibration caused by mechanical reasons.
reason; First, the hydraulic turbine is biased; Second, the axis center of the turbine and the generator is not aligned and the connection is not good; Third, the bearing is defective or the clearance adjustment is improper, especially the clearance is too large; 4. Friction and collision between rotating parts and stationary parts
（2） Hydraulic vibration, the vibration of the unit caused by the imbalance of the water flow into the runner
Reasons: first, the guide vane was damaged and the bolts were broken, resulting in uneven 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; Thirdly, the water flow in the draft tube is unstable, which causes 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 the water flow.
（3） Electrical vibration refers to unit vibration caused by unbalance 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 makes the speed of generator and turbine unable to synchronize instantly; Thirdly, the gap between stator and rotor is uneven, which causes the instability of rotating magnetic field.
（4） Cavitation vibration, unit vibration caused by cavitation.
Reasons: first, the vibration caused by hydraulic imbalance, whose amplitude increases with the increase of flow; The second is the vibration caused by the unbalance caused by the eccentric weight of the runner, the poor connection of the unit and the eccentricity, and the amplitude increases with the increase of the rotating speed; The third is the vibration caused by the electrical surface. 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 regional load, sometimes interrupted and sometimes violent. At the same time, there is knocking noise in the draft tube, and there may be swinging phenomenon on the vacuum meter.
4、 Unit bearing pad temperature rises and is too high
（1） Cause
1. Maintenance and installation reasons: the oil basin leaks, the pitot tube installation position is incorrect, the tile gap does not meet the requirements, and the unit vibration caused by installation quality is abnormal;
2. Operating reasons: operating in the vibration area, failing to add oil timely due to abnormal bearing oil quality and oil level, failing to observe the interruption of cooling water and insufficient water volume, resulting in long-term low-speed operation of the machine.
（2） Processing
1. When the bearing temperature rises, first check the lubricating oil, and timely add or contact to replace the oil; Adjust the cooling water pressure or switch the water supply mode; Test whether the vibration of the unit exceeds the standard. If the vibration cannot be eliminated, the unit shall be shut down;
2. In case of temperature protection outlet, monitor whether the shutdown is normal, and check whether the bearing bush is burnt. Once the Bush is burnt, replace it with a new one 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, which is called speed regulation failure. Reasons: first, the guide vane connection is bent, which can not effectively control the opening of the guide vane, resulting in that the guide vane cannot be closed and the unit cannot be stopped. It should be noted that some small units do not have braking devices, and the unit cannot stop for a while 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 speed regulation failure is caused by the failure of the 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. Reluctantly running will only enlarge 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 racks must be set at the inlet and regularly sorted out; 3. For the hydraulic turbine with any vehicle device, pay attention to timely replace the brake pads and add brake oil.
Post time: Jun-28-2022
