JP4779574B2 - Polymer material degradation diagnosis method - Google Patents

Description

  The present invention relates to a method for diagnosing the degree of degradation of a polymer material, and more particularly to a method for diagnosing degradation of a polymer material used as an insulating member in an electrical device such as a transformer device.

In electrical equipment and the like, a polymer material such as an epoxy resin is used as an insulating member. The usage conditions may involve high temperature, high humidity, and temperature changes. When exposed to harmful light such as ultraviolet rays, or when used for a long time under harsh conditions such as radiation, the material of the polymer material changes. The electrical or mechanical properties are degraded. This is called deterioration. If the deterioration of the polymer material progresses, it may cause a malfunction of the device, which may cause a safety problem. Therefore, it is required to investigate and diagnose the deterioration state every predetermined period and appropriately deal with it before a failure occurs.
The degradation mechanism of polymer materials includes molecular weight reduction due to molecular chain scission, release of CC bond by oxidation of terminal atom, generation and decomposition of carbonyl group of terminal functional group, acceleration and breakage of side chain crosslinking There is a disconnection of a bond with a foreign material used as a filler. By these mechanisms, there is a possibility that the insulating performance and other electrical characteristics of the polymer material are deteriorated, or a crack is generated on the surface of the member due to a decrease in mechanical strength, which grows and breaks.

Many methods are applied to the degradation diagnosis of polymer materials. In order to ascertain the degree of deterioration as accurately as possible, take out all or part of the polymeric material used in the equipment that is actually in use, and perform chemical / physical analysis, mechanical tests, and various physical property measurements. This is a destructive inspection. In this respect, it is desirable to apply the nondestructive inspection method so that the equipment can be used continuously when it is judged as healthy as a diagnostic result. Need to get. As a non-destructive inspection method, a chromaticity test for the member surface and an acoustic propagation test for the inside of the material are performed.
The acoustic propagation test method is an effective deterioration diagnosis method that comprehensively captures material changes based on various deterioration mechanisms, since it makes a diagnosis based on changes in the waveform and speed of sound waves that have propagated through polymer materials. is there.

Examples of the inventions that have used the acoustic propagation characteristics for diagnosis of the degree of deterioration include those disclosed in Patent Documents 1 to 4. In any of these inventions, a laterally propagated transverse wave sound wave, that is, an SH wave, is propagated through a polymer material, and the propagation time or sound speed reflects the degree of deterioration well. In addition, there is an invention already disclosed in Patent Document 5. The sound wave used in the present invention is a longitudinal wave of horizontal propagation, which is suitable for a soft material such as a wire covering material, and discloses a method of making a diagnosis using propagation time, that is, the speed of sound.
Japanese Patent Laid-Open No. 11-211699 JP-A-10-104207 JP-A-9-236585 Japanese Patent Laid-Open No. 9-5309 JP-A-11-337532

  In the deterioration diagnosis of polymer materials used in equipment installed in the field, non-destructive diagnosis is made so that the equipment can be used continuously when the diagnosis result is judged to be healthy. Law is required. However, the conventional non-destructive diagnostic methods for polymer materials do not always have sufficient diagnostic accuracy. An object of the present invention is to make it possible to diagnose the degree of deterioration of a polymer material with a sufficiently high accuracy in a nondestructive manner using ultrasonic waves.

In order to solve the above problems, the present invention propagates near the surface of an undegraded polymer material in a method for non-destructively diagnosing the degradation degree of the polymer material by propagating ultrasonic waves to the polymer material. Using the correlation between the ratio of the acoustic spectrum intensity obtained from the waveform of the ultrasonic wave propagated near the surface of the degraded polymer material to the acoustic spectrum intensity obtained from the waveform of the ultrasonic wave and the degree of degradation, the polymer material This is a diagnosis of the degree of deterioration, and three levels of frequencies for obtaining the acoustic spectrum intensity, ie, f1, f2, and f3, are selected, and the horizontal axis propagates through the undegraded polymer material at each frequency. The acoustic spectrum intensity is plotted on the vertical axis by taking the ratio of the acoustic spectrum intensity propagated through the degraded polymer material to the acoustic spectrum intensity propagated through the undegraded polymer material. It shall diagnosing the deterioration degree by using the area of a triangle obtained by connecting the points with a straight line (the invention of claim 1).
As described above, in order to non-destructively diagnose the deterioration level by propagating ultrasonic waves to the polymer material, in the present invention, from the sound wave waveform when the ultrasonic waves are propagated near the surface of the polymer material. Obtain the acoustic spectrum intensity. The relationship between the acoustic spectrum intensity, mechanical strength, and other necessary characteristic values in a polymer material without deterioration is obtained in advance. On the other hand, a sample in which the polymer material is forcibly accelerated and deteriorated to change the degree of deterioration is prepared, and the correlation between the acoustic spectrum intensity, the mechanical intensity, and other necessary characteristic values is obtained. Then, the degree of deterioration is converted from the correlation obtained in advance by measuring the acoustic spectrum intensity of the polymer material of the equipment member in use, and the object is achieved.

In this case, the diagnosis is performed using the ratio of the acoustic spectrum intensity of the deteriorated polymer material to the acoustic spectrum intensity of the undegraded polymer material, that is, a normalized value.
Further, as described above, since the ultrasonic wave is propagated in the vicinity of the surface of the polymer material, it is possible to reduce the influence of the thickness and shape of the polymer material to be subjected to the deterioration diagnosis .

Moreover, since the acoustic spectrum intensity is obtained at three frequencies as described above, the reliability and accuracy of the deterioration diagnosis can be further increased.
Further, in the polymer material deterioration diagnosis method according to claim 1 , the relationship between the three frequencies is f1 <f2 <f3, and f2 is at or near the peak of the acoustic spectrum intensity propagated through the undegraded polymer material. , F3-f2≈f2-f1 is preferably selected so that the three frequencies are satisfied (invention of claim 2 ).
Further, in the polymer material deterioration diagnosis method according to claim 1 or 2 , a correlation between the area of the triangle and characteristics of the polymer material is obtained in advance, and the triangle is calculated using the correlation. It is preferable to determine the degree of deterioration from the area (invention of claim 3 ).
Further, in the polymer material deterioration diagnosis method according to any one of claims 1 to 3, an ultrasonic transmitter and an ultrasonic receiver are arranged at intervals on the surface of the polymer material, and the super An ultrasonic wave is incident on the polymer material from a sound wave transmitter, and the incident ultrasonic wave is propagated near the surface of the polymer material to reach a surface portion in contact with the ultrasonic wave receiver. It is preferable that sound waves are received by the ultrasonic wave receiver and an acoustic spectrum intensity obtained from the received ultrasonic waveform is used (invention of claim 4).
As described above, in order to propagate ultrasonic waves to the polymer material, the ultrasonic transmitter and the ultrasonic receiver are arranged at an appropriate interval on the surface of the polymer material, and the ultrasonic transmitter and the ultrasonic receiver are arranged. Ultrasonic waves are propagated near the surface of the polymer material between the children. At this time, an acoustic wave in which the ultrasonic wave incident on the polymer material from the ultrasonic transmitter propagates in the vicinity of the surface of the polymer material, reaches the surface portion in contact with the ultrasonic receiver, and is received by the ultrasonic receiver. An ultrasonic transmitter and an ultrasonic receiver configured to satisfy the refraction condition are arranged on the surface of the polymer material. For example, a spacer processed at an angle according to Snell's law so as to satisfy the refraction condition Is preferably interposed between the transmitter and receiver and the polymer material surface.
Further, in the polymer material deterioration diagnosis method according to any one of claims 1 to 4 , the temperature during operation is lower than that of the diagnosis target portion and the lowest temperature portion in the device or a high temperature in the vicinity thereof. The molecular material may be used as a substitute for the undegraded polymer material (the invention of claim 5 ).

As described above, the undegraded polymer material can be diagnosed by using the polymer material that was in the lowest temperature region during operation and comparing it with the polymer material that was exposed to the high temperature region. .
Further, in the polymer material deterioration diagnosis method according to any one of claims 1 to 5, an apparatus in which a polymer material to be subjected to deterioration diagnosis is incorporated in a part of a constituent material is a transformer, a transformer. It may be an electric device such as a switch, a switch, a rotating machine, an insulating spacer, and an insulating bushing (invention of claim 6 ).
The polymer material deterioration diagnosis method of the present invention based on the ultrasonic acoustic spectrum can diagnose the deterioration degree of the polymer material in a non-destructive and highly accurate manner. The present invention can also be suitably applied to devices.

According to the present invention, it is possible to nondestructively diagnose the degree of degradation of a polymer material using ultrasonic waves, and in particular, by using a high correlation between the acoustic spectrum intensity of the ultrasonic waves and the degree of degradation. The diagnostic accuracy can be made sufficiently high in practice.
Further, since the ultrasonic wave is propagated in the vicinity of the surface of the polymer material, the influence of the thickness and shape of the polymer material to be subjected to deterioration diagnosis can be reduced.

  FIG. 1 is a conceptual diagram of an ultrasonic propagation characteristic measurement system, and FIG. 1A is an arrangement of a transmitter 1 and a receiver 2 for diagnosing degradation of a polymer material using ultrasonic vertical propagation characteristics. It is a conceptual diagram. FIG. 1A shows the arrangement of sensors in the case where ultrasonic waves are propagated perpendicularly to the material surface. The ultrasonic pulse transmitted from the transmitter 1 is incident on the surface of the sample 10 perpendicularly. Is received by the receiver 2. FIG. 1B is a conceptual diagram of a sound wave waveform. The ultrasonic wave is attenuated by scattering and absorption that occur while propagating through the sample 10. A trapezoidal wave incident from the transmitter 1 is transformed into a vibration waveform and detected by the receiver 2, where it is converted into an electrical signal and output. When the speed of sound is used as the ultrasonic propagation characteristic, the difference between the incident time and the reception time of the ultrasonic pulse, that is, the propagation time 201 of the ultrasonic pulse and the ultrasonic propagation distance 101, that is, the thickness of the sample is accurately known. If so, the speed of sound can be calculated. In addition to installing the transmitter 1 and the receiver 2 on the front and back of the material to be measured, as shown in FIG. It can also be measured. This method is effective when a receiver cannot be installed on the back side, but these vertical propagation methods often fail to accurately measure the thickness of the material when applied to an actual machine, and the shape of the material being measured varies. However, there is a problem that it is difficult to apply due to restrictions such as the thickness changing depending on the location. In addition, in the measurement system having the sensor arrangement shown in FIG. 1A, by performing spectrum analysis on the sound wave waveform detected by the receiver 2, the acoustic spectrum intensity can be obtained as the ultrasonic propagation characteristic.

  FIG. 2 is a conceptual diagram of the arrangement of the transmitter 3 and the receiver 4 for diagnosing deterioration of the polymer material using the horizontal propagation characteristic of ultrasonic waves, and FIG. 2 (a) is a plan view. 2 (b) is a side view. The ultrasonic pulse incident on the surface of the sample 11 to be measured from the transmitter 3 propagates along the surface of the sample 11, reaches the receiver 4 and is detected as an electrical signal. In this case, the ultrasonic pulse incident from the transmitter 3 propagates in the vicinity of the surface of the sample 11, reaches the surface portion in contact with the receiver 4, and satisfies the refraction condition such that it is received by the receiver 4. Spacers (not shown) are provided between the transmitter 3 and the sample 11 and between the receiver 4 and the sample 11, and these spacers have angles according to Snell's law according to the difference in sound speed between these spacers and the sample. Use what was processed in. Compared with the vertical propagation method, this horizontal propagation method makes the ultrasonic wave propagation path close to the sample surface, and therefore can perform measurement without being restricted by the shape and structure in the thickness direction of the sample. When the speed of sound is used as the ultrasonic propagation characteristic, it is actually impossible to accurately grasp the position of transmission and reception of sound waves in the sensor, so the time between transmission and reception can be changed by changing the distance between the transmitter and the receiver. Measure and calculate the speed of sound from the difference. In addition, in the measurement system having the sensor arrangement shown in FIG. 2, by performing spectrum analysis on the sound wave waveform detected by the receiver 4, the acoustic spectrum intensity can be obtained as the ultrasonic propagation characteristic.

In order to diagnose the degree of degradation of the polymer material, the material is forcibly altered in advance, for example, by heating the material at a high temperature for a long time, and the acoustic characteristics are measured by the method shown in FIG. 1 or FIG. Although the relationship between the deterioration of the material and the acoustic characteristics can be obtained, the present invention particularly uses the acoustic spectrum intensity of the ultrasonic waves as the acoustic characteristics, that is, the ultrasonic propagation characteristics. Below, the example which applied the polymeric material degradation diagnostic method of this invention based on an ultrasonic acoustic spectrum to an epoxy resin is demonstrated with FIGS. In addition, the epoxy resin used as the object of the deterioration diagnosis has the same composition in FIGS.
FIG. 3 shows an example of a sound wave waveform transmitted through a rectangular wave ultrasonic wave propagating on the epoxy resin surface. The waveforms of the undegraded material that has not been subjected to degradation treatment and the sample that has been thermally degraded under the heating temperature condition of 180 ° C in air are compared and shown. There is a difference in the sample transmission waveform between the two. FIG. 4 shows the relationship between the frequency and acoustic spectrum intensity obtained by spectral analysis of the first peak and third peak ranges of these waveforms. The acoustic spectrum in FIG. 4 shows a shape close to a normal distribution. The peak of the spectrum intensity is shifted to the low frequency side due to the deterioration. Degradation can be diagnosed using this frequency shift.

FIG. 5 shows the result of normalization by dividing the acoustic spectrum intensity of the deteriorated sample by the acoustic spectrum intensity of the undegraded sample together with the acoustic spectrum diagram shown in FIG. Due to the deterioration, the normalized value in the high frequency region, that is, the acoustic spectrum intensity ratio is lowered. In addition, although the peak is seen in the value normalized in the frequency vicinity of 4 MHz, this is due to the influence of the reflection of the sound wave on the back side of the sample and has no relation to the deterioration state.
In FIG. 6, the horizontal axis represents the acoustic spectrum intensity of the undegraded sample, and the vertical axis represents the result of plotting the normalized spectral intensity of the degraded sample that has been heat-degraded under the heating temperature condition of 180 ° C. Each point plots values at three frequencies: 1 MHz, 2 MHz and 3 MHz. The intermediate frequency of 2 MHz is a value close to the peak of the spectral intensity of the undegraded sample. When three points are connected, a triangle is formed. As the deterioration time increased, the triangle area (quadrature value) tended to increase. As a precaution, the frequency range was divided into 10 parts, and the results plotted at 11 points were compared and shown together with a two-dot chain line, but a large difference was not seen from the triangle formed by 3 points. The quadrature value of the undegraded sample is naturally zero. By selecting three levels of frequency, it was possible to overcome the problem that high-precision diagnosis was difficult due to large variations at one point, and it was confirmed that even three points were not significantly different from the result of ten points. By selecting 3 levels, reliable diagnosis is possible.

FIG. 7 shows the results of plotting the relationship between the area of the triangle (the quadrature value) and the tensile strength of a sample that has been deteriorated by heating an epoxy resin. It was confirmed that there was a correlation between the two. Therefore, if the correlation between the tensile strength and the quadrature quadrature value is obtained for each type of polymer material and expressed in mathematical formulas, the waveform of the ultrasonic wave that has propagated through the sample is analyzed, and the acoustic spectrum strength is obtained, The degree of deterioration of the molecular material can be diagnosed. The polymer material can be broadly classified into a thermosetting polymer material and a thermoplastic polymer material, but the present invention can be applied to both from the principle.
The data used in the above description is the result of spectral analysis performed at the peak / peak range of the ultrasonic waveform, but it has been confirmed that the same result can be obtained even if processing is performed in the zero cross / zero cross range. The boundary of the acoustic spectrum analysis range in the polymer material degradation diagnosis method according to the above may be a peak point of the transmitted acoustic waveform or a zero cross point of the transmitted acoustic waveform.

Moreover, although the example which applied the polymeric material degradation diagnostic method by this invention to the epoxy resin was demonstrated with FIGS. 3-7, in the above-mentioned example, the horizontal propagation longitudinal wave is used as an ultrasonic wave for degradation diagnosis.
In addition, as described above, the material to be diagnosed by the polymer material deterioration diagnosis method according to the present invention may be a thermosetting polymer material or a thermoplastic polymer material. In other words, if the correlation between the ultrasonic acoustic spectrum and various characteristics is obtained in advance for each material, whether the diagnosis target material is a thermosetting polymer material or a thermoplastic polymer material, The polymer material degradation diagnosis method of the present invention based on the ultrasonic acoustic spectrum can be effectively applied.
In addition, as a device to be diagnosed by the polymer material deterioration diagnosis method according to the present invention, all devices that use a polymer material are targeted, but particularly important devices that require high reliability are targeted for diagnosis. In this case, the deterioration diagnosis method of the present invention that can perform non-destructive and highly accurate deterioration degree diagnosis is preferable. Specific examples of equipment to be inspected and diagnosed for deterioration include electrical equipment such as various transformers and rotating machines. Representative transformers include resin-insulated transformers, measuring transformers, There are switches. The member of the polymer material used in these devices usually has a size of several tens of centimeters, which is sufficiently larger than several mm to several tens of mm, which is the size of the diagnostic part of the present invention. Applicable enough.

  The main cause of polymer material degradation is long exposure to high temperatures. The temperature of the polymer material varies depending on where the polymer material is used. That is, locations near the heat generating portion, locations above the lower portion, locations with poor convection, and the like tend to be high in temperature and deteriorate easily, so the polymer material at those locations is the object of diagnosis. On the other hand, the polymer material where the temperature hardly rises during operation does not proceed with deterioration, so that it can be handled as a sample that has not been deteriorated. The soundness evaluation of substation equipment and the like is often performed after use for 20 to 30 years, and an unused material of the same type as the polymer material used in the equipment to be diagnosed is often not newly available. In such a case, in the present invention, a polymer material at a low temperature as described above can be used as a comparative sample for deterioration diagnosis.

  The present invention can be optimally used for various transformers, for example, resin insulated transformers, measuring transformers and switches. In addition to this, it can be used for general electric equipments that are resin-insulated or products having a polymer material as a structural member.

Conceptual diagram of ultrasonic propagation characteristics measurement system Schematic diagram of transmitter and receiver placement for diagnosing degradation of polymer materials using ultrasonic horizontal propagation characteristics The figure which shows the waveform example of the ultrasonic wave which propagated the epoxy resin surface neighborhood The figure which shows the acoustic spectrum analysis result of the ultrasonic waveform of FIG. The figure which shows the normalization result of the acoustic spectrum of a deterioration material together with the acoustic spectrum of FIG. Characteristic diagram showing plot points at three frequencies: acoustic spectrum intensity of undegraded sample (horizontal axis) and normalized spectral intensity of degraded sample (vertical axis) Fig. 6 is a characteristic diagram showing the relationship between the area of the triangle formed in Fig. 6 (triangle quadrature) and the tensile strength.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Vertical transmitter, 2 ... Vertical receiver, 3 ... Horizontal transmitter 4 ... Horizontal receiver, 10 ... Sample to be measured (for vertical), 11 ... Sample to be measured (For horizontal)
101 ... Ultrasonic propagation distance (sample thickness), 102 ... Ultrasonic propagation distance (horizontal)
201 ... Ultrasonic propagation time

Claims (6)

In the method of non-destructively diagnosing the degradation level of the polymer material by propagating ultrasonic waves to the polymer material, the degradation to the acoustic spectrum intensity obtained from the waveform of the ultrasound propagated near the surface of the undegraded polymer material using the correlation between the ratio and the degree of deterioration of the sound spectrum intensity obtained from the ultrasonic wave propagated through the vicinity of the surface of the polymer material, there is for diagnosing the deterioration degree of the polymeric material, the acoustic Three levels of frequencies for obtaining the spectrum intensity, namely f1, f2 and f3, are selected. At each of the frequencies, the horizontal axis represents the acoustic spectrum intensity propagated in the undegraded polymer material, and the vertical axis represents the undegraded high frequency. Plotting the ratio of the acoustic spectrum intensity propagated in the degraded polymer material to the acoustic spectrum intensity propagated in the molecular material, and connecting these points with a straight line Polymeric material degradation diagnostic method, which comprises diagnosing the deterioration degree by using an area shape. 2. The polymer material deterioration diagnosis method according to claim 1 , wherein the relationship between the three frequencies is f1 <f2 <f3, and f2 is the peak of the acoustic spectrum intensity propagated in the undegraded polymer material or near the peak, and f3 A method for diagnosing deterioration of a polymer material, wherein three frequencies are selected so as to satisfy a relationship of -f2≈f2-f1. In the polymeric material deterioration diagnostic method according to claim 1 or 2 , a correlation between the area of the triangle and the characteristics of the polymeric material is obtained in advance, and the correlation is used to calculate the area of the triangle. A method for diagnosing deterioration of a polymer material characterized by determining the degree of deterioration. The polymer material degradation diagnosis method according to any one of claims 1 to 3 , wherein an ultrasonic transmitter and an ultrasonic receiver are arranged on the surface of the polymer material at intervals, and the ultrasonic transmission is performed. An ultrasonic wave is incident on the polymer material from a child, and the incident ultrasonic wave is propagated near the surface of the polymer material to reach a surface portion in contact with the ultrasonic wave receiver. A method for diagnosing deterioration of a polymer material, characterized in that an acoustic spectrum intensity obtained from a waveform of an ultrasonic wave received by the ultrasonic wave receiver is used. In the polymer material degradation diagnostic method according to any one of claims 1 to 4, diagnosed low temperature during operation than the site, and the lowest temperature or near the site in the equipment polymeric material A method for diagnosing deterioration of polymer materials, characterized by using as a substitute for undegraded polymer materials. The polymer material degradation diagnosis method according to any one of claims 1 to 5 , wherein a device in which a polymer material to be subjected to degradation diagnosis is incorporated in a part of a constituent material includes a transformer, a transformer, A method for diagnosing deterioration of a polymer material, which is an electrical device such as a switch, a rotating machine, an insulating spacer, and an insulating bushing.

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