There are several issues that should be noted.

The force of the end of the stator winding of the steam turbine generator and the lead wire are relatively complicated, and the electromagnetic force of the double frequency is mainly used. If the natural frequency of the end winding is equal to or close to the frequency of the electromagnetic force, resonance or large vibration force will occur, resulting in damage of the winding fixed platen, pad, etc. and vibration fatigue of the nose conductor and the water guiding wire. Breaking, while its long-term effects can also damage the coil insulation. Since the electromagnetic force is proportional to the square of the current, the larger the capacity, the greater the exciting force that the generator winding is subjected to.

In recent years, there have been many generator equipment accidents caused by natural frequency resonance, such as No. 6 generator of Shandong Shiheng Power Plant and No. 2 generator of No. C Factory of Guangdong Shajiao. To this end, the State Power Corporation issued 25 major requirements for preventing major accidents in power production in 2000. The National Economic and Trade Commission also issued test standards on November 3, 2000. Testing of the vibration characteristics of the generator stator winding ends has begun. Now introduce the test principle and method, give a test example, and finally introduce some test experience.

2 The basic principle of test analysis Because the stator windings and lead structures of large generators are complex, their natural frequencies are difficult to calculate by calculation methods, and are generally obtained by test and test methods. During the test, the end of the winding and the lead are hammered with a hammer. The piezoelectric sensor mounted on the hammer obtains an impact (excitation) signal, and the accelerometer mounted on the end of the winding and the lead obtains a corresponding response signal. These two signals are estimated by the frequency response function to obtain the natural frequency. The sum of the intrinsic frequencies of each point is the overall vibration mode.

The force signal represents the input signal of a system (ie, the impact signal obtained by the hammer), and the displacement signal (") represents the output (response) signal (ie, the response signal obtained by the accelerometer), then the frequency response of the dynamic signal analyzer The function is usually calculated as (1).

The equation (1) is changed to multiply the two sides of the equation (2) by the conjugate complex F(/) of F(/), and then multiply both sides of the equation (2) by the conjugate complex X of X(/). (/), get (/) and (/) are two expressions of the frequency response function, the ratio of 1 (/) and (/) is called the coherence function, which indicates the degree of coherence between the response signal and the force signal. . When it is close to 1, it indicates that the response signal is excited by the force signal and there is a good linear relationship between them. When it is significantly less than 1, it indicates that the signal is disturbed or the system has nonlinear characteristics.

3 Test method The test model is established. The steam and excitation side windings of the generator are arranged in two sections along the axial position into several measuring points. One section is located at the outer end of the generator near the nose of the bar (such as 1 in the middle) Position), another section is arranged in the slot part of the inner ring winding (2 positions in the middle). Generally, the outer ring data is measured first, and if necessary, the inner ring data is added.

The test uses a hammering method, which can stimulate a multi-point response or a multi-point excitation with a little response. Generally, a one-point excitation multi-point response method is adopted, and a tapping is performed on the end of the stator winding, and the dynamic signal analyzer picks up the radial vibration response of each measuring point on the end winding, and the modal analysis software analyzes and processes the vibration signal to obtain Modal parameters such as modal frequency, mode shape and damping of the stator winding end.

When measuring the natural frequency, hammer the stator end joints, lead wires and transition leads respectively, and measure the vibration response of the corresponding measuring points. The corresponding transient excitation frequency response function is obtained through software analysis, and the transient excitation frequency response is obtained. On the amplitude-frequency characteristic curve of the function, the maximum value of the coherence function value above 0.9 is the natural frequency value of each measurement point.

4Measured example Huaxia Yuyu Power Plant No. 2 steam turbine generator is a domestic FSN-300-2 type generator. The test results of the vibration characteristics of the winding end during the overhaul of the machine in June 2002 are shown in Table 1. Modal vibration modes such as 3 Among them, the 3rd order frequency of the steam side and the 2nd order frequency of the excitation side are in the range of 94-115Hz, but the amplitude of the whole amplitude-frequency characteristic curve is small, and the machine is running normally without obvious wear marks, so it is not correct. It is processed, but it is recommended to enhance operational monitoring.

Table 1 Steam side, excitation side winding modal parameter summary order number steam side frequency / Hz damping /% excitation side frequency / Hz damping /% test the natural frequency of the stator winding nose joint and the lead wire and transition lead, found part The natural frequency is in the range of 94-115 Hz. After being re-bonded and reinforced by the technicians of the motor factory, the frequency of the re-test results is all qualified. The natural frequency data before and after treatment is shown in Table 2. The natural frequency before and after the treatment of the part 11 (lead wire rod) of Table 2 is the Hz number. The problem should be paid attention to before the treatment of the side steam side. The problem should be ensured in the test. The accuracy of the test results should be emphasized in the test: when hammering with a hammer, the direction of the tapping must be kept consistent. At the same time, the action should be simple and not combo when tapping, otherwise the reliability of the measured data is poor.

Since the accelerometer cannot be fixed on the winding, it is necessary to have a special person (turn down on page 43) to find the moment of the front wheel pivot point of the transport vehicle. Conclusion: The brake will not tip over when the transport vehicle is up and down; similarly, the transport vehicle It will not tip over when starting uphill.

Since the stability and safety of the 10m tower on the 12m flatbed is much better than that of the 30m tower on the flatbed, it is not necessary to check.

In summary, the transport vehicles selected for tower transport and the placement of the towers on the vehicle meet the requirements for transport safety and stability.

5 safety technical measures 5.1 strictly control the speed of transport vehicles! 5k in h, turn (on page 11) by hand, so you should be careful not to use the force pressure sensor, otherwise it will cause interference to the response signal.

In the test, the coherence function is mainly seen. Under normal circumstances, it should be close to 1, which indicates that the response signal is excited by the force signal, and there is a good linear causal relationship between them. If it is significantly less than 1, it indicates that the signal is interfered or the system linearity is poor, and the data reliability is poor. On the amplitude-frequency characteristic curve of the transient excitation frequency response function, only the maximum value of the coherence function value above 0.9 or even 0.95 is the natural frequency value of each measurement point.

The signal line used for the test is thin, the connector is easily damaged, the measurement signal is lost, the interference is easy, and the reliability of the data is low. If a significant interference waveform appears in the response signal, the signal cable is damaged and must be replaced.

As mentioned before, the test measurement uses a one-point excitation multi-point response or multi-point excitation one-point response method, if one point stimulates the multi-point response process speed! 3k to h. 5.2 tower on the flatbed should have a special bracket to prevent the tower from rolling during transportation; a rubber mat is placed between the tower and the special bracket to improve the contact surface stress and prevent the tower surface The local force is too large to deform.

5.3 The tower tube should be placed on the flatbed in front and rear, left and right direction.

5.4 In case of heavy rain, heavy rain and high winds of level 6 or above, transportation and loading and unloading operations are not carried out.

5.5 Transportation process, please contact the traffic police to ensure traffic safety.

5.6 Power lines with insufficient clearance space along the way take power-off and heightening measures, and the communication lines with insufficient clearance are subject to heightening measures.

5.7 Before the transportation, go to the transportation department to handle the overload transportation permit.

6 Conclusion According to the above-mentioned determination of the transport tower vehicle selection and the location of the tower on the vehicle and the safety and stability check results of the transport vehicle travel process, the safety and stability of the transport vehicle in the transport tower process meets the requirements, therefore This transportation scheme is feasible and has been verified during the actual transportation process. In terms of transportation safety, the author believes that the design length of a single tower should not be too long, because the long length of a single tower will increase many safety risks and transportation costs. The length of a single tower should not exceed 15m. Vehicles and vehicles have advantages in terms of road safety and transportation costs. In addition, this tower transport can also provide reference for future wind turbine tower transport.

The excitation point or the multi-point excitation point response pickup point is just above or near the mode node, and it is possible to miss the mode. Therefore, the position of the excitation point or the pickup point should be changed several times to check if there is a missing mode.

6 Conclusion The vibration characteristic test of the stator winding end of the generator is a non-destructive inspection test. The test result can simulate the vibration state of the end of the generator during actual operation, guide the maintenance and maintenance of the generator, and compare the historical data and the trend of change. Can help identify accidents in future operations. Therefore, when the unit is overhauled, the bar is replaced, the stator winding end is fixed, or if necessary, the stator winding should be tested for vibration characteristics. If the natural frequency is found to be in the range of 94=115H during the test, it should be comprehensively analyzed and processed in conjunction with the historical operation of the generator. If necessary, the end fixed structure should be reinforced or changed to avoid the resonance frequency range.

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