Function, 1 Introduction The generator is gradually aging due to the combined action of electrothermal and mechanical stress during operation. Aging can cause defects such as air gap delamination in epoxy mica insulation. The presence of defects not only reduces the useful life of the insulation. Moreover, the operational reliability of the color ring system may even cause a sudden shutdown. The diagnostic technology of the insulation state has been vigorously developed before. Commonly used non-destructive testing techniques include traditional dielectric parametric analysis such as dielectric loss, volume 8 and polarization index 0; partial discharge history 0 detection, such as electrical and acoustic measurements; and acoustic hammer detection by manual hammering Wait. Although these detection methods can reflect the insulation state of the generator or the entire fixed-line bar from different degrees, the aging and the degree of damage of the insulation and the degree of damage of the insulation cannot give satisfactory conclusions. . The measuring device is subjected to electric heating and mechanical stress to accelerate the old chemical measurement, passing through the domain frequency domain and wavelet transform analysis. The acoustic spectrum of the wire rod aging state and defect information can be objectively reflected. A simple and accurate method for determining epoxy mica insulation. 2 Measurement principle Vibration and sound are closely related. Mechanical vibration often causes the Guangpei gift body to report and stimulate the particle vibration of the old medium. Under the interaction of the mass point, the vibration propagates point by point to form a sound wave sound wave. In the air, it can also be transmitted in the elastic medium such as liquid solids. The National Natural Science Foundation of China funded project 59837260 Electrical insulation state diagnosis and aging mechanism research; Xie Heng 194 male, Jiangxi. Professor, Ph.D., focusing on online monitoring and diagnostic technology for electrical insulation of power equipment, 15; senior member. broadcast. The mass point in the medium causes displacement relative to the equilibrium position due to the passage of the sound wave, and the change of the sound wave can be understood by measuring the vibration displacement of the particle. This is the basic principle of detecting acoustic physics. When sound waves propagate to two different media interfaces, they also have refraction and reflection like light waves, whether they are reflected on the media surface. Also praying in the body. Both will cause the vibration form of the sound wave to change, and this change depends on the acoustic impedance of the medium surface and the density of the media. The generator stator winding is insulated by epoxy mica tape, which is a fine layered medium with longitudinal periodicity. Since the thickness of the single-layer master tape is sufficiently small for the wavelength of the acoustic wave propagating in the medium, the composite medium behavior can be regarded as a uniform anisotropic medium. Under the long-term effect of electrothermal and mechanical stress, the insulating layer of the stator winding may cause defects such as air gap delamination or peeling due to aging. These defects cause changes in insulator density and acoustic impedance. Therefore, the propagation characteristics of the sound in the insulation will change accordingly. In order to facilitate the calculation, we use a circular thin plate model with fixed edge and no tension to describe the frequency of the vibration of the melon-like thin plate at the inner defect of the insulation. The following formula can reach 121, which is the coefficient under different vibration modes. , is the radius of the defect; the denseness of the insulating village material is Poisson's ratio; it is the Young's mode; 4 is the thickness of the insulation above the defect. The base frequency of the vibration that can be obtained by the team = 3.20 is the same as the following. The other vibration mode frequencies are as follows. 3 Experiment 3.1 The test test bar is the standard model bar provided by the Harbin Institute of Electrical Machinery. The wrong conductor size is 1315! In order to prevent the pressing of the test line and the long-term support, the fastening line is fixed in the fixed + slot. During the test, the wire rod is fixed by the movable clamp. 1. When testing, the shock absorber gain is fixed, and the distance between the hammer and the sample surface is adjusted to ensure that the measurement conditions are basically the same. 3 Dip chuck 4 digging rubber gasket 3.2 Acoustic detection system for acoustic detection device is self-developed type 01 insulation defect detection, measurement system 2. During the measurement, the force signal generated by the shock absorber is applied to the test wire rod under the action of the helium, argon, and argon. The acoustic signal generated by the test bar is amplified and converted into an illusion, and then sent to the computer for data processing by the data acquisition card. 1 acoustic signal detector 2 sampling card 3 laptop computer 4 exciter 5 acoustic sensor 6 excitation hammer 2 acoustic detection system 4 measurement results and discussion 4.1 time and frequency domain analysis of acoustic detection results aging model bar typical Time domain and frequency domain waveforms. We can see that the amplitude in the time domain waveform decays rapidly after about a period of oscillation, forming a characteristic waveform consisting essentially of two peaks and small peaks. In the spectrum corresponding to the 1-transform, the dominant frequency component is about 2. The results of acoustic testing after 2000 hours of electrothermal and mechanical stress aging. From the 3rd, we can observe that in the time domain waveform of the electric aging sample, more oscillations are added near the small peak. In the corresponding spectrum of the Ding transformation, it can be observed that there is a large near 21 Frequency component. However, no obvious defects were observed from the observation state of the sample and the artificial tapping. Epoxy mica insulated wire rods, under the action of high electric field, partial discharge will occur in the insulator. High-energy particles generated by partial discharge bombard the polymer surface, causing macromolecular chain scission and insulation surface damage. Therefore, the bulk density of the insulation is lowered, and the adhesion of the epoxy to the mica is deteriorated to cause fine delamination. According to the aforementioned circular thin plate model and the fundamental frequency amount, it will drift in the high frequency direction. Therefore, the change in the time-frequency characteristic of the acoustic signal of the sample after electrical aging is a high-frequency component formed by the decrease in the density of the insulator. Due to the acceleration of thermal stress, the sample has obvious emptying and local delamination. From the time domain waveform, we can clearly see the overlap of the waveform at the beginning of the rise and the broadening of the first peak. In the corresponding spectrum, a frequency component near Zhang's appears, and the frequency band of the dominant frequency component is narrowed and drifts toward the low frequency direction. Similarly, the fundamental frequency of the circular thin plate model is up to 103. This is related to the measured results. Learn the test results. Similar to the detection result of the electric aging sample, there are several times of oscillation near the small peak in the time domain waveform, and a large frequency component near 22 appears in the spectrum. The mechanical stress exerted on the test wire rod, in terms of mechanical fatigue, causes the polymer macromolecule to be broken. On the other hand, by fatigue bending, the degumming between epoxy and mica will cause fine delamination in the insulator, causing the acoustic signal to drift in the high frequency direction. 4.2 Wavelet analysis of wavelet analysis results of acoustic detection results. The small stream transform decomposes the acoustic signal into a set of multi-chanceband bands of the same size in logarithmic coordinates. When the cell element is changed with the change of the scale factor, when the frequency is small, the frequency domain resolution performance is poor, and the time domain resolution performance is better; when increasing, the frequency domain resolution is increased, and the time domain resolution is decreased. Due to its good time-scale localization characteristics, wavelet transform can not reflect the frequency domain characteristics of the signal well, and can better give the feature description in the time domain. It satisfies the city 1 Ning, which is the basic wavelet, and for 612, the continuous wavelet transform milk of the signal is defined as its function corresponding to the decomposition of 612 feet on the function level, and the scale and time. The result of the calculation of the scale. Each of them, a 1-wave transform, describes the characteristics of the sub-primary acoustic signal produced by the test bar under the action of the exciter. And 0 and 1 respectively represent the scale 2 transformation, which reflects the insulation of the wire rod by the vibration of the exciter. In the wavelet transformation of =1, the most human amplitude can be observed. 1 time and 2 times; only the amplitude of the mechanical stress aging sample does not change much with respect to the amplitude of the unaged sample. In the scale, =2, the unaged sample has a oscillating decay peak at 81218 with an amplitude of about 1. In the same scale analysis, the electric aging sample has two peaks, and the amplitude is reduced to 0.040.03. The heat aging sample is called 1 positive èš± and 1 human negative peak. The amplitude also changes to 0.250.4 and 0.4. The attenuation is very fast. There is a small oscillating peak on the reference line. The mechanical stress aging sample has only a vibration amplitude of 0.04. Therefore, the amplitude of the acoustic signal of the aged sample is significantly reduced compared with the amplitude of the unaged sample. The analysis of the above two scales shows that the density of the dense and dense insulating body in the insulator of the sample is reduced after aging, which leads to The change in the acoustic impedance of the insulation will also increase the number of reflections in the acoustic propagation process. The sound waves are attenuated to reduce the amplitude. In the analysis of scale = 3, the spectrum of the unaged sample can be clearly peaked at about 58 and 18, the amplitudes are 2.1 and 5, respectively, and the oscillating attenuation peak of the electrically aged sample is located at about 610 sen. 1020 served in two places with amplitudes of 1 and 0.5. The heat aged samples also had two oscillating peaks. The amplitude is similar to about 3, the amplitude of the unaged sample is similar, and the spectrum of the mechanical stress aging sample has an envelope with a half-sine wave-like oscillation peak in 5151. The amplitude is approximately in the scale, =4 analysis, the amplitude of the unaged bar is about 0.8. After about 671. Stable at around 0.3. The amplitude of the electrothermally aged sample also tends to be similar. The mechanical attenuation of the aged sample is slow and maintained at about 0.8.5. The above two-scale analysis shows that the low-frequency characteristics of the heat-aging bar are basically the same as those of the unaged sample. That is, heat aging does not significantly affect the face impedance of the test bar. However, the difference between the aging samples and the aging samples indicates that the partial discharge in the electric aging is too low. Only the low-density area is formed in the polymer body of the Ting machine, and the corona is also changed along the surface. Try to pay for the cloud, the face state. In the mechanical stress aging test, mainly the fixed fixture pair 5 conclusions are used to detect the insulation of the generator mica winding of the epoxy mica insulation by acoustic method. Insulation defects can be detected quickly and easily, and the positioning is accurate. The acoustic method is applied to the aging study of epoxy mica insulation. The variation of the time-frequency characteristic spectrum of acoustic signals and the wavelet analysis of different scales can be used to judge the nature of defects in the insulation. Therefore, it provides a powerful auxiliary analysis method for studying the aging mechanism of epoxy mica insulation. Through acoustic testing, we can think of electrical aging and mechanical stress aging to reduce the density of organic insulators. This effect is small because of the effects on the micro scale. While heat aging, the stratification of the epoxy cloud plays a key role, that is, it is the main factor that produces macro defects. 3 Ding Qinghai, and so on. Application of chaotic fractal and wavelet theory in feature extraction of passive acoustic signals 1. Acoustics Journal, 199 points 24 on page 4 of this. 43 Zhuo Fang, and so on. Active power filter for phased systems. Journal of Xi'an Jiaotong University, 200034 Zhuo Fangyu, Yang Jun, Hu Junfei, Wang Zhaoan. The structure and control of the main circuit of the phase line active power filter. New technology for electrical energy, 2000, 19216.
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