There are many reasons for the vibration of the generator rotor. There are mechanical factors such as rotor mass imbalance rotor misalignment and resonance, and wire, short-circuit cooling system blockage line, expansion resistance of the collector ring and shaft friction caused by rotor thermal imbalance. And oil film whirl or oil film oscillation can also cause vibration. The former is caused by stable vibration, while the latter often causes the generator to produce sudden or unstable vibration during operation, which is more harmful. This paper will focus on the vibration characteristics and diagnostic methods of the cause mechanism of the sudden vibration of the generator rotor, and give examples of vibration analysis and processing of three sites to illustrate.

1.1 Oil film whirl and oil film oscillation instability Oil film whirl is the main reason for the occurrence of subsynchronous unstable vibration of ordinary lubricating bearings. Oil film lubrication is the vibration excited by the oil film force. At this time, the change of normal operating conditions, such as the inclination angle and the eccentricity rate, causes the oil wedge to move in the bearing, so that there is sufficient damping in the direction of rotation, then the shaft returns to its In the normal position, it becomes stable; otherwise, the rotor will continue to move and a large unstable vibration will appear. The unstable eddy of the oil film is caused by excessive bearing wear or clearance, improper bearing design, changes in lubricating oil parameters and other factors. According to the vibration spectrum, it is easy to identify the eddy instability of the oil film. The vibration frequency when it appears is 4048 of the synchronous vibration frequency, which is close to the half of the rotational frequency. It is also often called the oil film half-speed whirl.

The oil film oscillates when the oil turbulence of the machine is unstable and the oil film whirl frequency is equal to the natural frequency of the system. Oil film oscillations can only occur if the machine is running at a speed greater than 2 times the rotor critical speed. When the rotational speed is increased to 2 times the critical speed, the vortex frequency is very close to the critical speed of the rotor to generate resonance and cause a large vibration to cause the oil film to lose support. Usually, when the oil film oscillates, the vortex frequency will always remain at the rotor-order critical speed frequency regardless of the speed.

Because the step critical speed of the generator rotor is higher than that of the turbine rotor oil film or the oil film oscillates. The early domestic 200 PCT and 3001 twin units were designed with a small bearing stability margin, which caused the generator rotors of some units to have oil film oscillation failure under over-speed and load-bearing operating conditions, and then adopted measures such as replacing bearings. Solved the oil film oscillation of this type of unit. However, in recent years, there have been some sudden occurrences of oil film eddy instability in the generator rotor of some units, especially those of medium and small capacity units 100, Jia. Under operating conditions, it is susceptible to changes in the temperature of the oil supply due to the alignment of the shaft.

1.2 Rotor Thermal Unbalance Rotor thermal imbalance refers to the phenomenon of shaft bending that occurs after the rotor is heated. Usually the vibration generated by thermal imbalance is the fundamental frequency component. When the vibration is related to the field current, and there is a time lag between the change in vibration and the change in current, it can be confirmed that there is thermal imbalance in the rotor of the generator. In addition to the anisotropic unevenness of the rotor forging material, other common causes of thermal imbalance of the generator rotor are the rotor rotor cooling system, the asymmetric rotor, the uneven rotor wire, the internal friction force generated by the uneven thermal expansion and the dynamic and static rubbing.

1.2.1 Asymmetric asymmetric cooling of the rotor cooling system refers to the clogging of the cooling system resulting in uneven cooling. At this time, the rotor has a temperature asymmetry in the radial direction, and the radial temperature difference causes the rotor to bend. The ventilation caused by the misalignment of the faulty strip in the hydrogen internal cooling generator is not smooth. The cause of this failure in a water-cooled generator is that a foreign matter enters the cooling water conduit causing a partial water blockage or a gas entering the cooling water system causing a cooling water channel plug.

The thermal unbalance vibration caused by the uneven cooling of the rotor is often related to the temperature and temperature of the cooled hydrogen. The higher the temperature, the smaller the vibration. The vibration also has the following characteristics: rapid load reduction, disengagement, and braking. The vibration value at the critical speed of the generator rotor is greatly enlarged compared with the corresponding value at the start, and the large shaft sway value measured immediately after the shutdown is also higher than that before the start. Increase a lot.

1.2.2 Uneven heating of the rotor The uneven heating of the rotor means that the rotor wire, the turn-to-turn short circuit, and the short-circuit current cause local overheating due to insulation damage of the winding, etc., and the result is that the rotor cross section produces a radial temperature difference causing the rotor to bend. The inter-turn short circuit of the rotor is divided into two types: static and dynamic interturn short circuit. However, the latter happens only in the hot state of the fixed operating conditions, so sometimes the detection is not easy to find.

The sudden vibration caused by uneven heating is related to the magnitude of the excitation current. The larger the current, the greater the amount of thermal bending of the rotor and the greater the amplitude of the vibration reflected. The thermal unbalanced vibration caused by the uneven cooling of the rotor, the thermal bending of the rotor caused by the fault such as short circuit makes the vibration of the generator rotor passing the critical speed during the shutdown process significantly increase compared with the corresponding value at the start, and the sway of the brake is also increased. Significantly increased.

1.2.3 Internal friction generated by uneven thermal expansion of the rotor coil During the rotation, the rotor component is pressed by the centrifugal force. Due to the different material temperatures of the various components, the expansion coefficient is also different, there is a relative expansion tendency, and the contact surface exhibits friction. If the friction is asymmetric, the rotor will withstand an eccentric axial force, creating a bending moment that bends the rotor. Di often produces this frictional effect between the end coil and the inner surface of the grommet between the coil and the slot die. For example, when the coil is heated and the expansion is blocked, an asymmetrical axial force is generated. In addition, the excitation wire, the thermal elongation of the end portion is hindered by the end block, causing a slight displacement in the circumferential direction, and the balance is destroyed. Generally, the vibration generated by the frictional force has a certain suddenness. In addition, the thermal unbalance vibration caused by the internal friction has the following characteristics: 1 and the thermal imbalance caused by other causes, and the vibration also increases as the excitation current increases. The difference is that even if the excitation current is reduced, the vibration will not recover and will often remain at a high level. 2 When the vibration is at a high position, if the speed is reduced by several hundred turns, and then raised to the rated speed, it is possible to return to the original cold level.

1.2.4 Dynamic and static friction oil retaining ring seal ring The static part such as the collector ring touches the rotating shaft. When the highest point of the rotating shaft touches the fixed part, the rotating shaft is locally heated, and a temperature difference is generated on the circumference, so that the rotating shaft has a short bending. The vibration caused by the friction between the generator rotor journal and the collector ring tends to be periodic.

The sudden vibration group caused by the oil film half-speed vortex of the 6-inch unit and the vibration characteristics of the unit are the Nanjing Steam Turbine Works, which was delivered in the month of 1995.

During the commissioning of the unit from December 1996 to January 1997, when the load was heavy, the front bearing of the No. 3 bearing generator showed sudden vibration. When the generator parameter is 5.5 station Jia 3.50, the vibration value of No. 3 bearing is 40! The left and right suddenly increased to about 70, and the other three bearing vibrations of the shafting system also have a sudden increase, but the amplitude is relatively small. From the vibration spectrum analysis, the sudden vibration is mainly based on the half frequency 25, 2, the vertical and horizontal vibration half frequency components of the No. 3 bearing are 25, respectively, and 40 accounts for 42 and 81 of the frequency vibration. In addition, when sudden vibration occurs, in addition to the half-frequency component, there are some harmonic components of 1.5 times 2 times frequency. The sudden vibration lasted about 30, when the active power fell to 2.8, the evaluation, the reactive power fell to 1.5, and disappeared when people.

2.1.2 Vibration Analysis and Processing According to the above vibration phenomenon, it can be judged that the oil film half-speed whirl occurs in the No. 3 bearing under the large load and high reactive state of the generator, so it is decided to check whether the bearing bush is properly installed. Since there was no original installation record, the cover of the 23rd bearing housing had to be opened for on-site measurement. The measurement results show that the top clearance of the bearing No. 3 is 260, the gap between the two sides is about 250 bearing bushes, and the south side is biased by 50. The 721 is cooled and the rotor is measured. The elevation of the bearing No. 3 is found to be 150 lower than that of the No. 2 bearing, and the manufacturer requires cooling installation. The bearing height of No. 2 bearing is, and the elevation of No. 13 bearing is raised upward. Therefore, the reason for the half-speed running of the No. 3 bearing is that the bearing bush is improperly installed, the bearing height of the No. 3 bearing is low, and the bearing height of the hot bearing of the unit changes with the heavy load operation, resulting in the light load of the No. 3 bearing and the stability of the bearing bush.

In view of the actual measurement situation of the No. 3 bearing installation, it is proposed to raise the bearing elevation to reduce the gap between the top clearance and the two sides, and re-find the wheel. The final adjustment result is the No. 3 bearing lower pad height 100 south side pad 50, the No. 3 bearing mid-face demolition pad 1004 bearing bottom bottom pad height 1001. Finally measuring the No. 3 bearing lower tile side clearance 250, the top clearance 180, After the top of the upper tile is tightened, the unit can be operated with a large load and successfully completed the 72 test run. During this period, the unit had been subjected to over-rated active power and 4.8-in reactive operation, and no sudden vibration occurred. The vibration of the unit is stable after heavy load operation, and the maximum vibration of No. 3 bearing near rated working condition is about 301. The vibration of all other bearings in all directions is caused by dynamic short-circuit between 2.2 sets of 100-unit West Unit generators. 2.2.1 Unit Overview and Vibration Characteristics The unit is a 100-Jiao steam turbine generator set produced by Beijing Heavy-duty Motor Factory. The unit was put into production in 1978. During the overhaul in September and September 1997, the Beihe Plant implemented a through-flow partial transformation of its turbine high and low pressure rotors, and replaced all cooling water pipes and stator coils of the dual water internal cooling generator rotors.

In the start-up operation after the overhaul, the vibration of the unit exceeded the standard, which was mainly reflected in the No. 56 bearing No. 56 bearing as the generator supporting bearing. When the load was large, the vibration continued to increase, and the unit could only be limited to the operation below 70%. Through the vibration test, the vibration of the unit has the following characteristics: 1 Before the grid connection, except for the horizontal vibration of the No. 6 bearing, the values ​​of the remaining vibration points of the 89 and 36 bearings are all below 301. 2 After the grid is connected, the vibration of bearing No. 46 gradually increases, which is related to the excitation current of the generator and the active load. When the excitation current is greater than 950 people or the active load exceeds 70 stations, the vibration quickly climbs. Bearing No. 46 vibration is dominated by the fundamental frequency component.

In the hot state, the No. 6 bearing has the largest vibration variation. For example, if the active load is 70 angstroms, the excitation current is 1400, the vibration of the artificial condition is compared with the data before the grid connection, and the vertical and horizontal vibrations of the No. 6 bearing are increased by 45, 1 and 70, respectively. After the rotor inlet water temperature is increased by 20, except for the vibration of the No. 5 bearing increases by 10151, the values ​​of the other vibration measuring points are basically unchanged. 5 During the start-up process, the measured value of the critical speed of the generator is 1360 er, and the horizontal vibration of the 46th bearing is 441 and 56 respectively. However, the 70 偌 汉 汉 袄 袄 袄 袄 袄 袄 人工 人工 人工 人工 人工 人工 人工 人工 人工 人工 人工When the critical speed of the generator is disengaged and the brake is stopped, the horizontal vibration of the 46th bearing is as high as 104, called 1921 and 382. 2.2.2 Vibration cause analysis and rotor inspection processing. The vibration is based on the fundamental frequency component and the excitation current. Relevant, and the vibration of the generator at the critical speed of the generator during the shutdown and rapid load reduction is very large, and the rotor of the generator is judged to have thermal bending. Because the temperature change of the cooling water of the generator rotor has little effect on the vibration, the blocking factor of the waterway can be basically eliminated. It is reported that the generator rotor has undergone a negative sequence current to burn out the slot wedges at both ends of the rotor and the inter-turn short circuit fault. After the fault, the large retaining ring is removed and processed. According to the above vibration characteristics, the generator rotor may have a partial short circuit after the completion of the flow reform, but the vibration increases rapidly when the excitation current increases to 950 or above. A partial short circuit fault occurs only when a hot condition is above.

The vibration of the unit is not only increased with the excitation current of the generator, but also increases with the increase of the active load of the generator. In particular, the vibration of the No. 5 bearing is more affected by the active load. This phenomenon indicates that the low-voltage generator rotor coupling also has a fixed imbalance in the hot state.

In summary, the main reason for the vibration of the unit is that the generator rotor is partially short-circuited when operating above a certain hot working condition, and the imbalance of the low-voltage generator coupling may also have a certain influence on the vibration of the unit.

For the above analysis, it was decided to take out the generator rotor for comprehensive overhaul. After multiple electrical tests in the electric field, the magnetic pole line corresponding to the short lead of the collector ring is in the side of the excitation end, and the row of the second package is located at the intersection of the large coil and the small coil, and the short circuit point is found. There are 2,81 burn marks between the coils, the insulation is carbonized, and the copper wire at the large coil scale is partially melted. The reason for the analysis is that the insulating plate under the retaining ring fails to be placed according to the paper requirements. When the positioning pin and the hot retaining ring are not hit, the insulating plate moves to cause a serious climbing phenomenon, so that the tightening force of the retaining ring and the stress state of the coil change. . The small coil is in a loose state, while the large coil has a large tightening force, and the generator is heated to cause a dynamic turn-to-turn short circuit.

2.2.3 Shaft system dynamic balance The short circuit point of the generator is processed and the balance weight of the core ring at both ends of the generator rotor is shifted to the center of the main body. The cumulative balance weight of the core ring at both ends exceeds 41 and the unit starts. After the fixed speed is 300, the vertical horizontal vibration of the No. 5 bearing is 63471 and 40, respectively. The vibration may be caused by the deviation of the weight. After the core rings at both ends of the generator are respectively weighted 4858, B, and 7,237,223, the vibration value of the airborne 300, 1 is reduced by one. Except for the vertical vibration value of bearing No. 5, about 301!1, the vibration values ​​of all other measuring points are below 25μl. The unit is smoothly brought to the rated load. After the steam turbine is modified, it is found from the vibration data measured by the load process, although the generator is eliminated. After the rotor wire and dynamic turn-to-turn short-circuit fault, the vibration of No. 46 bearing is basically not affected by the increase of the excitation current of the generator. However, the vibration is still affected by the active load. After the unit is loaded, the vibration of bearing No. 45 still has a certain degree of increase, especially the horizontal vibration of the 45 bearing and the vertical vibration of the No. 5 bearing. The value is about 50 μLm near the rated load condition, and the vibration increases in the hot state. The amount of 1525 Ming low-voltage generator rotor coupling has a fixed imbalance. After 5 months, the unit repair opportunity was used to increase the 703 B 340 in the low-voltage generator rotor coupling. Not only the vibration of the no-load 30001 unit continued to improve significantly, but the vibration increment after the load basically disappeared, and the vibration of each bearing near the rated load condition Values ​​are all within 25,1.

2.3 Sudden vibration caused by the expansion of generator coil of a 3007 unit 2.3.1 Unit introduction and vibration characteristics The unit is a 300 PCT unit supplied by Harbin Power Station Equipment Complete Set, which was put into operation in March 1993. Since June 1998, the unit has experienced sudden vibrations of generator No. 56 bearings under heavy load operation conditions. Through the relevant tests, the unit has the following vibration characteristics: 1 liter speed over the generator rotor critical speed 120, the left and right vibration is very small, the 56th bearing wattage vibration does not exceed 20, the shaft relative vibration does not exceed 40 working speed under the 56th bearing tile vertical The relative vibration of the vibration at 131 and 16,556,6 points respectively is 92460pm26pmff31pm.2 The vibration has little relationship with the oxygen temperature and oxygen pressure of the generator. 3 Vibration is basically independent of active load. In the smaller reactive power and large active load conditions, the amplitude and phase of the bearing vibration and shaft vibration of the No. 56 bearing are basically the same as those under the no-load 300,1. 4 Vibration is related to the magnitude of the reactive load. When the active load is maintained at 250, the reactive load rises to 100. At this time, the excitation current of the generator rotor is about 2,450, and the rated value is 2,580. After about 221, the phase of the vibration of the fundamental vibration of the 5th 566 is mutated by 90180195. And about 135., then the vibration quickly increased. In 151, its amplitude increased from about 100,924,412,241 in stable state to about 20,484,73,1221. Although the reactive load was reduced to about 50 PCT, the vibration increased, and the maximum vibration of the above-mentioned measuring points reached 222 il 134200142, respectively, and the vibration phase remained basically unchanged during the vibration increase. Gradually reduce the active load, the amplitude gradually declines, until about 2, the active load 20, Jia, reactive load 400, the above-mentioned measuring point vibration still maintains a large level, the values ​​are 128, 80, 6 called 90, the fundamental frequency Both the amplitude and phase of the vibration are restored to the level before the sudden vibration. At the same time as the sudden increase of the vibration of the rotating shaft, the bearing vibration also shows a similar phenomenon. The fundamental frequency phase of the vertical wattage of the 56th bearing was firstly mutated by 75 and 175 respectively, and then the vibration amplitude increased rapidly, increasing from 101 and 1 before the sudden vibration to the maximum value of 01 and 90, respectively. 12 List the changes in bearing relative shaft vibration and vibration. The unit is disengaged, the vibration is rapidly reduced after the fixed speed of 300, 1, and the amplitude and phase of the shaft vibration and the bearing vibration are basically restored to the level before the sudden vibration. 5 In the case of sudden vibration, and the amplitude is still increasing, the load is quickly reduced and the brake is stopped in almost 1 minute. The vibration during the critical speed of the rotor through the rotor is colder. The numerical value is obviously increased. The relative axis vibration values ​​of measuring points 5 and 6, respectively, are 255+, and the shaft sway of the No. 56 bearing measured vertically by the bearing of No. 5 and No. 5 is clear, and its value is normal. And the state of the cranking after the unit is stopped immediately uses the percentage to measure the large shaft yaw of the generator shaft, and its value is basically the same as the value before the cold start.

Measuring point relative axis vibration frequency μ, time active load reactive load change reactive load test each bearing bearing vibration frequency pm active reactive time 4 watts 5 watts 6 watts load vertical 2.3.2 vibration fault diagnosis and treatment due to The vibration of the unit is independent of the hydrogen temperature and hydrogen pressure of the generator, and the possibility of uneven cooling of the rotor can be basically eliminated. The vibration is closely related to the reactive load of the generator. When the excitation current increases to a constant value, the vibration suddenly increases, and the excitation current decreases. The vibration decreases slowly and remains at a high level. After the sudden vibration occurs, the vibration mode of the generator rotor changes, and the vibration is mainly controlled by the heat variable. As the excitation current increases, the thermal variables increase rapidly and the direction does not change. Both the shaft and the vibration of the two bearings vibrate in phase. Therefore, the vibration of the unit is caused by the thermal imbalance of the generator rotor.

According to the case of large vibration, the rapid load reduction is disengaged and the brake is stopped. When the speed is over the critical speed of the generator rotor, the vibration of the shaft of the No. 56 bearing and the vibration of the bearing bush are relatively cold. Increased, but the measured shaft sway of the generator after the shutdown is basically the same as the value before the start, indicating that although the generator rotor has a large thermal bending, the thermal bending quickly disappears as the speed decreases. In addition, when the unit is re-set at 3,000, the speed first rises, then quickly drops to 2800, below, and then rises to 3000, the vibration rapidly decreases, and returns to the original level before sudden vibration. Therefore, the vibration characteristics of the generator rotor are substantially similar to those of the thermal unbalance vibration caused by internal friction. Therefore, it can be judged that the cause of the large thermal imbalance of the generator rotor may be that the rotor coil expansion is blocked.

Due to the tight load, the unit operated straight from October 1998 to February 1999, but basically maintained a low reactive load. In the maintenance of March 1999, the rotor of the generator was taken out, and the inspection of the protective ring was found. The end coil and the end of the steam end had extrusion marks, and the insulating tile also had a fixed indentation. The running end line generates a certain axial displacement to both ends, causing the end line to be able to reduce the expansion gap to both ends, causing the generator rotor to be in a hot state, the expansion is blocked, and a large thermal imbalance occurs. . Subsequently, the axial gap is expanded. After the unit was overhauled, it was started on April, 1999. After a large load, the shaft and vibration of the two bearings of the generator were stable, and no sudden vibration occurred.

1 The sudden vibration generated in the operation of the generator rotor is caused by the instability of the bearing oil film in the hot state or the thermal imbalance of the rotor, which is often related to the active load and the magnitude of the excitation current of the active load. 2 The rotor cooling unevenness is affected by the heat unevenness coil expansion and the static and dynamic friction and other faults can cause the generator rotor to be thermally unbalanced. 8 According to the relevant vibration characteristics, the cause of the sudden vibration generated in the operation of the generator rotor can be determined to take corresponding treatment measures.

Zhang Xueyan, Wang Yanbo. Vibration Fault Diagnosis and Treatment of No.1 Generator in Tieling Power Plant I.

Thermal Power Generation, 20065.

Zhang Xueyan, Zhang Weijun. Vibration analysis and treatment of Unit 5 of Heshan Power Plant in Guangxi 1. Winning victory. The thermal unbalance vibration of the turbine generator. Large motor technology, 1998, 5.

寇 Victory, Zhang Xueyan. Vibration diagnosis and treatment of No. 2 steam turbine generator in Han Power Plant.

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