There are many causes of generator rotor vibration, such as rotor imbalance, rotor misalignment and other mechanical factors, another line, short-circuit cooling system plugging line, and expansion-impeded collector ring and shaft friction caused by rotor thermal imbalance And oil whirl or film oscillation can also cause vibration. The former is caused by stable vibration, while the latter often causes the generator to generate sudden or unstable vibration during operation, which is more harmful. This article will focus on the causes of the sudden vibration of the generator rotor vibration characteristics and diagnostic methods described, and gives three on-site vibration analysis and processing examples to illustrate.
1.1 Oil film whirl and oil film oscillation instability Oil film whirl is the main reason for sub-synchronous unstable vibration of ordinary lubricating bearings. The oil film motion is the vibration of the film force. At this time, the normal operating conditions such as the inclination and eccentricity cause the oil wedge to move in the bearing, so that there is enough damping in the rotation direction, then the shaft will return to its In the normal position, it becomes stable; otherwise, the rotor will continue to move, causing large unstable vibrations. The instability of the oil film is caused by excessive bearing wear or clearance, improper bearing design, and changes in lubricant parameters. According to the vibration spectrum, it is easy to identify the unstable whirl of the oil film. The frequency of its occurrence is 4048 of the synchronous vibration frequency, which is close to half of the rotational speed and frequency. It is also often referred to as the oil film half speed whirl.
When the oil film whirl is unstable and the film vortex frequency is equal to the natural frequency of the system, oil film oscillation occurs. Oil film oscillations may only occur if the machine operating speed is greater than 2 times the critical rotor speed. When the rotational speed rises to 2 times the critical rotational speed, the vortex frequency is very close to the critical rotational speed of the rotor to generate resonance and cause great vibration so that the oil film loses its supporting effect. Normally, once the oil film oscillates, the whirl frequency will always remain at the critical rotor speed, regardless of how much the speed continues to increase.
Because the order of critical rotation speed of the generator rotor vortex or oil film oscillation than the turbine rotor oil film. In the early domestic 200 jijia and 3001 twin sets, the bearing stability margins of the designed bearings were too small, causing the generator rotors of these units to have oil film oscillation failures in the overspeed and load operating conditions. Solved the oil film oscillation of this type of unit. However, in recent years, there are still some generator rotors that have sudden and unstable phenomenon of oil film whirl, especially some small and medium-sized units 100 and Jia. Under operating conditions, it is susceptible to changes in shaft alignment and changes in oil temperature.
1.2 Rotor Thermal Unbalance The thermal imbalance of the rotor refers to the phenomenon of shaft bending occurring after the rotor is heated. Vibration generated by thermal imbalance is the fundamental frequency component. When the vibration is related to the excitation current, and there is a time lag between the change in the vibration and the change in the current, it can be confirmed that there is a thermal imbalance in the rotor of the generator. In addition to the anomalous anisotropy of the rotor forging materials, other common causes of thermal imbalance in the rotor of the generator include uneven heating of the asymmetrical rotor of the rotor cooling system, internal friction caused by uneven thermal expansion, and static and dynamic impact grinding.
1.2.1 Asymmetric Cooling of the Rotor Cooling System Asymmetric cooling refers to uneven cooling due to blockages in the cooling system. At this point, the temperature in the radial direction of the rotor is asymmetric, and the radial temperature difference causes the rotor to bend. In the hydrogen-internal-cooled generator, the ventilation caused by the failure of the faulty strip is not smooth. The cause of this failure in the water-internal cooling generator is that foreign matter entering the cooling water conduit causes a blockage of the local water line or gas entering the cooling water system causing a cooling water plug.
The unbalanced vibration caused by the uneven cooling of the rotor is often related to the temperature and temperature of the cooling hydrogen. The higher the temperature, the smaller the vibration. The vibration also has the following characteristics: Quickly de-energizing and de-energizing. The vibration value at the critical speed of the rotor of the generator is much larger than the corresponding value at the start of the fast-load de-energizing and de-energizing. The measured value of the large shaft's swiftness after the shutdown is also higher than that before the start of the shutdown. Increase a lot.
1.2.2 Inhomogeneous rotor heating Non-uniform heating of the rotor generally refers to rotor windings, short circuit between windings, and short-circuit current resulting in local overheating due to winding insulation damage. As a result, a radial temperature difference of the rotor cross section causes the rotor to bend. Rotor inter-turn short circuits are classified into static and dynamic inter-turn short circuits. However, the latter occurs only when the operating conditions are hot, so sometimes the detection is not easy to detect.
The sudden vibration caused by uneven heating is related to the magnitude of the excitation current. The larger the current is, the greater the amount of thermal bending of the rotor is, and the larger the vibration amplitude is. With the thermal imbalance vibration sample caused by uneven cooling of the rotor, the thermal bending of the rotor due to short-circuit and other failures makes the vibration of the generator rotor passing through the critical rotation speed significantly increase compared with the corresponding value at the start of the shutdown. Significantly increased.
1.2.3 Internal friction caused by uneven thermal expansion of the rotor coil During rotation, the rotor components are squeezed by centrifugal force. Due to the different temperature of the various components, the expansion coefficient is also different, there is a relative expansion trend, the contact surface friction. If the friction is not symmetrical, the rotor will bear an eccentric axial force and generate a bending moment that will cause the rotor to bend. Di often produces this frictional effect between the end coils of the coil and the slot die and the inner face of the guard ring. If the coil is hindered from expansion after being heated, it will generate an asymmetrical axial force. In addition, the excitation line, the end of the thermal elongation is hindered by the end of the block, so that a small displacement in the circumferential direction, the balance will be destroyed. Usually the vibration generated by the friction has a certain suddenness. In addition, the thermal imbalance vibration caused by internal friction has the following characteristics 1 and other causes of thermal imbalance, the vibration is also increased with the increase of the excitation current. The difference is that even if the excitation current is reduced, the vibration is not always recoverable, and it tends to remain high. 2 When the vibration is at a high level, if the rotational speed is reduced by several hundred revolutions, it is possible to return to the original cold level only when the speed is increased to the rated speed.
1.2.4 Dynamic friction friction oil seal ring The static part of the ring, such as the collector ring, touches the fixed part at the highest point of the shaft when it touches the shaft, causing local heating of the shaft, creating a temperature difference on the circumference and causing the shaft to bend for a short time. The vibration caused by the impact grinding of the generator rotor journal and the slip ring often presents a periodicity.
The sudden vibration caused by the turbulence of the oil film at half speed of the unit of the 6th unit. Unit Overview and Characteristics of Vibration The unit was manufactured by Nanjing Steam Turbine Factory in January 1995.
During the commissioning of the unit from December 1996 to January 1997, sudden shocks occurred on the front bearing of the No. 3 bearing generator with a large load. When the generator parameter is 5.5 station Jia 3.50, the No. 3 bearing vibration value is 40! Left and right suddenly increased to about 70, while the shaft of the remaining three bearing vibration also has a sudden increase, but the amplitude is relatively small. From the perspective of vibration spectrum analysis, the sudden vibration is mainly dominated by half-frequency 25,2, and the half-frequency component of vertical and horizontal vibrations of No. 3 bearing reaches 25 calls respectively, and 40 accounts for about 42 and 81 of its pass-frequency vibration. In addition, when a sudden vibration occurs, in addition to half-frequency components, there are some harmonic components such as 1.5 times 2 times frequency. The sudden vibration lasted for about 30 hours, when the active power dropped to 2.8, and the evaluation dropped to 1.5, only disappeared.
2.1.2 Vibration Analysis and Processing Based on the above vibration phenomenon, it can be determined that the No. 3 bearing has half-speed whirl of the oil film under large load and high reactive state of the generator, so it is decided to check whether the bearing bush is installed properly. Since there was no original installation record, the No.23 bearing housing cover was opened for on-site measurement. The measurement results show that the No. 3 bearing has a clearance of 260 at the top, and the side clearances on both sides are about 250 and the rotor is offset to the south by 50. 721 After measuring the lift of the rotor after cooling, it is found that the bearing height of No. 3 bearing is 150 lower than that of No. 2 bearing, and the manufacturer requires a cooling installation. The No. 2 bearing elevation is the elevation of No. 13 bearing elevation. Therefore, the reason why the No. 3 bearing appears to be running at half speed is that the bearing bush is not properly installed, the No. 3 bearing has a low elevation, and the bearing temperature in the hot state of the unit changes during heavy load operation, causing the No. 3 bearing to lightly load and reducing the stability of the bearing bush.
For the actual measurement of the No. 3 bearing installation, it is proposed to raise the elevation of the bearing to reduce the gap between the top clearance and the back of the wheel, and to re-find the wheel. The final adjustment result is the No. 3 bearing bearing pad height 100 south pad 50, No. 3 bearing faceted disassembly bearing No. 1004 bearing seat bottom padding 1001. The last measurement bearing No. 3 bearing lower tile clearance 250 on both sides, top clearance 180, After the adjusting scheme is implemented on the top of the upper tile, the unit can be operated with a large load and 72 test runs can be successfully completed. During this period, the unit had had over-rated active power and 4.8-volt reactive power operation. No sudden vibration occurred. The unit has stable vibration after heavy load operation, and the maximum vibration of No. 3 bearing near the rated working condition is 301 or so. The vibrations of all the other bearings in all directions are 2.2 sets of 100 units of West units. The dynamic short-circuit in the generator caused 2.2.1 General situation of the unit and its vibration characteristics. The unit is a 100, Jiahe turbine generator set produced by Beijing Heavy-Duty Motor Factory. The unit was put into production in 1978. During the overhaul period in September, 1997, the North Heavy Plant carried out the transformation of the through-flow part of its turbine high and low pressure rotors, and replaced all the cooling water pipes and stator coils of the double water internal-cooled generator rotor.
After the overhaul, the vibration of the generator set exceeded the limit during the start-up operation, which was mainly reflected in No. 46 bearing No. 56 bearing, which was supported by the generator. When the load was large, the vibration continued to increase, and the generator set could only be limited to operate under 70 Centigrade. Through the vibration test, the vibration of this unit showed the following characteristics: 1 Before the grid connection, except for the horizontal vibration of the No. 6 bearing, the values ​​of the other vibration measurement points of the No. 89 and No. 36 bearings were all less than 301. 2 After grid-connected, No. 46 bearing vibration gradually increases, which is related to the generator excitation current and also related to the active load. When the excitation current is more than 950 people or the active load exceeds 70 stations, the vibration quickly climbs. No. 46 bearing vibration is dominated by the fundamental frequency component.
8 In the hot state, No. 6 bearing has the largest vibration variation. For example, when the vibration of the active load of 70 肘 J. exciter current 1400 under artificial conditions is compared with the data of no-load 3 000 kWh before and after the grid connection, the vertical and horizontal vibrations of No. 6 bearing are increased by 45, 1 and 70, and 1.4 respectively. After the temperature of the rotor inlet water increases by 20, except that the vibration of No. 5 bearing increases by 10,151, the values ​​of the remaining vibration measurement points do not change substantially. 5 During the start-up process, when the critical speed of the generator is reached, the disease value is 1360 rpm. The horizontal vibration of the No.46 bearing is 441 and 56 respectively. However, the load is quickly reduced by the 70-finger Hanseed and Novo 400 artificial conditions. During the process of splitting and turning off the critical speed of the generator during shutdown, the No. 46 bearing horizontal vibration is as high as 104, which is called 1921 and 382. 2.2.2 Vibration Analysis and Rotor Check Processing The vibration is mainly based on the fundamental frequency and excitation current. Relevant, and the difference between the vibration of the unit when starting the unit and quickly de-loading and de-listing the critical speed of the generator during shutdown is very large, and it is judged that the rotor of the generator has thermal bending. Because the change of the cooling water temperature of the generator rotor has little effect on the vibration, the water blocking factor can be basically eliminated. According to the investigation, the negative-sequence current of the rotor of the generator has been used to burn out the wedges at both ends of the rotor and faults in the inter-turn short circuit. After the fault, the large guard ring was removed for processing. According to the above vibration characteristics, a partial short circuit may occur in the rotor of the generator during start-up after the completion of the through-flow transformation. However, when the excitation current increases to 950 or more, the vibration rapidly increases, and the rotor of the generator may be Partial short-circuit faults occur when above a hot condition.
The vibration of the unit not only increases 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 bearing No. 5 is more significantly affected by the active load. This phenomenon indicates that the low-voltage generator rotor coupling also has a certain imbalance in the hot state.
In summary, the main reason for the vibration of this unit is that a partial short-circuit fault occurs when the rotor of the generator runs above a hot working condition. At the same time, 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 extract the rotor of the generator for a complete overhaul. After several electrical tests, the magnetic pole lines corresponding to the short lead of the collector ring are located in the excitation end. The row of the No. 2 package is located at the intersection of the large coil and the small coil. The short circuit point is found. There are 2,81 burn marks between the coils, the insulation is carbonized, and the copper wire is partially melted at the large coil ruler. The reason for the analysis is that the insulation board under the grommet fails to be placed in accordance with the requirements of the paper, and the insulation plate moves when the positioning pin and the heat sleeve guard ring are not hit, resulting in a more serious climbing of the table, which changes the tightness of the grommet and the force state of the coil. . The small coil is in a loose state, and the large coil has a large tightness, and the generator is heated to cause a dynamic short circuit.
2.2.3 The shafting balancing generator short-circuit point is completed and the balance weight of the core ring at both ends of the generator rotor is moved to the center of the body. The cumulative balance weight of both ends of the core ring exceeds 41 and the unit starts. At a constant speed of 300, the vertical horizontal vibration of the No. 56 bearing is 63471 and 40,1501. This vibration may be caused by the weight shift. After the two core rings of the generator increase 4858B131 and 7238223 respectively, the vibration value of the no-load 300, 1 by 1 is greatly reduced. Except for the No.5 bearing vertical vibration value of about 301!1, the vibration values ​​of the remaining measurement points are all below 25μl. The turbine is successfully brought to the rated load and the turbine is 0. From the vibration data measured with the load process, it is found that although the generator is eliminated After rotor line and dynamic inter-turn short-circuit fault, No.46 bearing vibration is basically not affected by the increase of generator excitation current. However, the vibration is still affected by the active load. After the unit is loaded, the vibration of No. 45 bearing still increases to a certain extent, especially the horizontal vibration of No. 45 bearing and the vertical vibration of No. 5 bearing. The value is about 50μLm around the rated load condition, and the vibration increases in the hot state. There is a definite imbalance in the rotor coupling of the low-voltage generator with a quantity of 1525. After 5 months, the rotator coupling 703 B340 was used in the low-voltage generator rotor coupling to make minor repairs. Not only did the vibration of the no-load 30001 unit continue to improve significantly, but the vibration increase after the load disappeared. The vibration of the bearings near the rated load condition Values ​​are within 25,1.
2.3 Sudden vibration caused by the expansion of the generator coil of a 3007 generating unit 2.3.1 Brief introduction of the unit and vibration characteristics The unit was a 300 贾C unit supplied by Harbin Power Station Equipment Co., Ltd. and was put into production in March 1993. The unit has experienced a sudden occurrence of vibration on the No. 56 bearing in heavy load operating conditions since June 1998. Through related tests, it was found that the unit has the following vibration characteristics: 1-speed over-speed generator rotor critical speed 120, left and right vibration is very small, No. 56 bearing vibration no more than 20, relative shaft vibration no more than 40 working speed No. 56 bearing tile vertical The relative axis vibrations at the measurement points of 131 and 16,556,6 were respectively 92460 pm and 26 pmff 31 pm.2 The vibration and generator oxygen temperature and oxygen pressure did not correlate significantly. 3 Vibration and active load are basically irrelevant. In the case of smaller reactive power and larger active load condition, the amplitude and phase of the bearing vibration and shaft vibration of No. 56 bearing are basically the same as those under no-load 300,1. 4 The vibration is related to the size of the reactive load. When the active load is maintained at 250, the reactive load rises to 100. At this time, the generator rotor magnetizing current is about 2 450, and the rated value is 2580. After about 221, the 5th parent 566 measuring point relative to the axial vibration of the shaft vibration momentarily mutates 90180195 respectively. And 135. or so, then the vibration quickly increased, in 151, its amplitude from the stability of the 100 Seoul 9244412241 to about 20,484,73,1221 or so. Although the reactive power load was subsequently reduced to about 50 PCT, the vibration still increased. The maximum vibration of the above-mentioned measuring points was 222 134 134200142 and the vibration phase remained basically unchanged during the vibration increase. And gradually reduce the active load, the amplitude gradually decreased until about 2 after the active load 20, Jia, reactive load 400, the measurement point vibration still maintain a large level, the value was 128,80,6 is 90, the fundamental frequency Both the amplitude and phase of the vibration are restored to the level before the sudden vibration. While the vibration of the shaft has suddenly increased, similar phenomena have appeared in the vibration of the bearing bush. The frequency of the 56th-bearing vertical-wave vibration fundamental frequency first oscillates around 75 and 175, respectively, and then the vibration amplitude rapidly increases, from about 101 and 1 before the sudden vibration to a maximum of 01 and 90, respectively. 12 List the changes in bearing relative axis vibration and wave vibration, respectively. The unit was disentangled and the vibration was rapidly reduced after a constant speed of 300,1. The amplitude and phase of shaft vibration and bearing vibration basically recovered to the level before the sudden vibration. 5 In the event of sudden vibration, and the amplitude is still increasing, the load is rapidly de-rated and de-energized and stopped during almost 1 min. The vibration during the deceleration process passing through the critical speed of the generator rotor starts at a colder state. The value is obviously increased. The measurement points 5 and 6 have relative axis vibration values ​​of 255+ and 18, respectively. The vertical bearing of No. 56 bearing, measured at the 56th bearing axis, is bright and its value is normal. After the unit stopped, the state of the disc brakes immediately measured the large shaft sway of the generator shaft using the percentage, and its value was basically caused by the value before the cold start.
Measure point relative shaft vibration through frequency μ, time active load reactive load change reactive load test each bearing bush vibration frequency pm active reactive time 4W 5W 6W load vertical 2.3.2 vibration fault diagnosis and processing The vibration of this unit has nothing to do with the hydrogen temperature and hydrogen pressure of the generator, but basically eliminates the possibility of uneven cooling of the rotor. The vibration is closely related to the reactive power load of the generator. The vibration occurs suddenly when the excitation current increases to a fixed value and increases rapidly, and the excitation current is reduced, and the vibration reduction is slower and remains at a high level. After the abrupt vibration occurs, the vibration mode of the generator rotor changes, and the vibration is mainly controlled by the thermal variable. With the increase of the excitation current, the thermal variable increases rapidly and the direction does not change. Both the shaft vibration and the wave vibration of the two bearings exhibit the same phase vibration. Therefore, the vibration of the unit is caused by the thermal imbalance of the generator rotor.
According to the situation of large vibration, rapid load shedding and tripping and shutting down, down speed over the critical speed of the rotor of the rotor, the vibration of the shaft of the No. 56 bearing and the vibration of the bearing bush are larger than the corresponding vibration values ​​during the cold start. Increase, but the generator shaft rotation and the value before the start of the generator measured after shutdown are basically the same, indicating that although the rotor of the generator has large thermal bending, the thermal bending quickly disappears as the rotation speed decreases. In addition, the turbine unit decoupled the re-regulation at 3,000 hours when the speed first rose, and then quickly dropped to 2800, the following, and then rose to 3,000, the vibration rapidly reduced, and returned to the original level before the sudden vibration. Therefore, the vibration characteristics of the generator rotor are basically similar to the characteristics of thermal imbalance vibration caused by internal friction. Therefore, it can be determined that the cause of large thermal imbalance in the rotor of the generator may be that the expansion of the rotor coil is blocked.
Because of the tight load, the unit went straight from October 1998 to February 1999, but it basically maintained a low reactive load. In March 1999, the rotor of the generator was pulled out, and the inspection of the guard ring revealed that the end coils and the insulation ring of the excitation end and the steam end had squeezing marks, and the insulation tile also had a constant indentation. The end of the line of operation, the end of the axial displacement generated, resulting in the end of the line, the gap can be reduced to the two ends of the expansion, resulting in the thermal state of the generator rotor off the expansion blocked, resulting in greater thermal imbalance . After that, the expansion of the axial gap. After the unit was overhauled, it 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 during the operation of the generator rotor is caused by the instability of the bearing oil film or the thermal imbalance of the rotor in the hot state. The occurrence of the sudden vibration is related to the magnitude of the active current and the active load excitation current. 2 Uneven cooling of the rotor The uneven heat expansion coils and the static and dynamic impact grinding can cause thermal imbalance in the generator rotor. 8 Based on the relevant vibration characteristics, the cause of the sudden vibration generated during 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 Disposal of Unit 5 of Heshan Power Plant in Guangxi Thermal unbalanced vibration of turbine generators. Motor Technology, 1998, 5.
He won, Zhang Xueyan. Vibration Diagnosis and Treatment of No. 2 Turbo-generator in Han Power Plant.
The term mainly selects subject words according to the China Power Encyclopedia, and constitutes its main and auxiliary according to the system structure of the lexicon only. Its professional scope includes energy and thermal power plants and nuclear power plants, water power generation and new energy power systems, and power transmission and distribution overhead transmission lines. And power cable lines, substations and converter stations High-voltage technology Over-voltage and insulation coordination Motor transformers and power supplies, Boiler turbine Turbine and gas turbine electrical appliances and series-parallel compensation devices, Power supply and power, Automation technology Communication technology and computers, Measurement And tests, electrical materials, metal supervision and power plant chemistry, environmental science, economics and management.
The term is 16 hardcover, about 1,000 pages, and the postage is 280 yuan per book. Please contact us immediately.
CHANGXING GUANGDA NEW MATERIALS CO.,LTD. , https://www.gdbentonite.com