JP2010071961A - Deterioration diagnosis method of polymer material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To discover deterioration of a polymer material in an early stage before a potential distribution is changed on the polymer material surface. <P>SOLUTION: Deterioration of the polymer material is diagnosed by determining physicochemical variation on the polymer material surface. As determination of the physicochemical variation, determination of hydrophilic chemical species on the polymer material surface by spectroscopic analysis can be used. As the spectroscopic analysis, infrared spectroscopic analysis or Raman spectroscopic analysis can be enumerated. As the hydrophilic chemical species, a hydroxyl group, a hydrogen-reduced phenyl group, a carboxyl group and sulfate ion are illustrated. As the determination of the physicochemical variation, measurement of an average surface potential distribution per unit area on the polymer material surface can be enumerated. As the measurement of the average surface potential distribution, a measuring method of an atomic force microscope image can be enumerated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for diagnosing insulation deterioration of electrical equipment using a polymer material as an insulating material.

  Examples of conventional techniques for diagnosing insulation deterioration of electrical equipment include the diagnostic methods disclosed in Patent Documents 1 to 3.

  The creeping insulation deterioration detection device of Patent Document 1 monitors the surface resistance by attaching a comb-shaped electrode to the insulating frame as a method of directly measuring the deterioration of the insulating material as compared to measuring the degree of contamination on the surface of the insulating material. When the monitored resistance value falls below the threshold value, an alarm signal is output.

  The diagnostic method of Patent Document 2 measures the change in surface electrical resistivity of an undegraded part and a deteriorated part made of a material equivalent to a solid insulating material used for a main circuit part constituting a power distribution facility, The remaining life of the power distribution facility is calculated based on the time-dependent reference curve of resistivity.

  In these diagnostic methods, when an insulation material causes a short-circuit accident, in the measurement of the insulation resistance in the apparatus before and after the accident, as shown in FIG. It is difficult to accurately measure the insulation deterioration state.

  In electrical equipment, a large amount of nitrate has been detected in the vicinity of the insulating material after a short circuit accident. According to Non-Patent Document 1, as shown in FIG. 16, among calcium carbonate, polyester resin, and glass fiber, which are constituents of insulators, deliquescent calcium nitrate is generated by reacting with NOx in the atmosphere. This is the cause of the decrease in surface resistivity. From the standpoint of inspection, it was difficult to disassemble and investigate the insulating material used in the operating equipment, so it was necessary to investigate nitrate ion contaminants on the resin surface, resin components, resin surface gloss, A technique has been proposed in which the insulation degradation state is estimated from indirect information by the MT method, which is a statistical reliability technique, using the Mahalanobis distance as an index by discoloration (Non-patent Document 1).

Further, the degradation diagnosis method for polymer materials disclosed in Patent Document 3 uses a single wavelength utilizing the fact that the gloss and color change slightly when the polymer material including the filler deteriorates due to environmental load such as heat. The reflectance is measured by irradiating light, and the degree of deterioration is diagnosed in comparison with the change in reflectance due to accelerated deterioration.
JP-A-8-220158 JP 2002-372561 A Mitsubishi Electric "Deterioration Diagnosis Technology from the Viewpoint of Insulation Materials for Electric Power Facilities" Research Special Committee, Degradation Diagnosis and Remaining Life Estimation Technology for Delivered Electrical Insulators by MT Method, January 25, 2008 JP 2007-285930 A

  It is true that a large amount of nitrate ion is detected when an accident occurs in which the insulating frame of the polymer material burns out and is short-circuited. However, when the environmental dependency of the insulation deterioration rate of the polymer material is investigated, particularly high concentrations of nitrogen oxides are not detected in the environment where the accident occurred. Before and after the accident, the nitrate ion concentration was high only around the insulation frame that was short-circuited and burned, and no abnormal amount of nitrate ion was detected in another panel installed in the same facility. From the environmental survey results, nitrate ions at the time of insulation frame short-circuiting are generated by the combination of nitrogen and oxygen in the atmosphere due to discharge plasma due to a short-circuit accident. There is no good correlation with the deterioration state of the field sample, and it is difficult to consider it as the main cause of deterioration (Table 1).

  As described in Patent Document 2, the insulation resistance value of the insulating frame is too high because the resistance of the polymer material is too high, and the change in resistance value due to the ambient environment such as temperature and humidity (measured value variation) is too large. An accurate deterioration diagnosis cannot be performed (FIG. 17A). In addition, as shown in FIG. 17B, the surface resistivity measurement range is narrow before an electrical abnormality such as partial discharge occurs, and measurement is difficult by electrical evaluation.

  As described above, the insulation frame deterioration evaluation method has been conventionally performed mainly by measuring the insulation resistance. However, it is difficult to accurately grasp the signs of deterioration due to the influence of the surrounding temperature and humidity.

  Recently, as in Non-Patent Document 1, a method of estimating a deterioration sign from information on nitrate ions adhering to the surface of an insulator and information such as gloss and color tone has been proposed as in Patent Document 3. However, these diagnostic methods are evaluations from the later stage of deterioration in the mechanism leading to dielectric breakdown (see FIG. 1 described later), and it is difficult to evaluate highly correlated with insulation resistance.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for diagnosing deterioration of a polymer material that can detect deterioration of the polymer material at an early stage before a change in potential distribution on the surface of the polymer material occurs. On offer.

  Therefore, a polymer material deterioration diagnosis method for solving the above problem diagnoses the deterioration of the polymer material by quantifying the amount of physicochemical change on the surface of the polymer material.

  As the quantification of the amount of physicochemical change, there is a quantification of the hydrophilic species on the surface of the polymer material by spectroscopic analysis. Examples of the spectroscopic analysis include infrared spectroscopic analysis and Raman spectroscopic analysis. If the hydroxyl group or the hydrogen-reduced phenyl group is quantified as the hydrophilic species, the degree of hydrolysis of the polymer material over time can be diagnosed. When the carboxyl group is quantified as the hydrophilic chemical species, the degree of thermal degradation of the polymer material can be diagnosed. When sulfate ions are quantified as the hydrophilic chemical species, the oxidation state of the polymer material surface by the corrosive gas can be diagnosed.

  Moreover, the measurement of the average surface potential distribution per unit area on the surface of the polymer material can be cited as the quantification of the physicochemical change amount. By this measurement, the degree of deterioration of the surface resistance of the polymer material can be diagnosed. Examples of the measurement of the average surface potential distribution include a measurement method using an atomic force microscope image.

  According to the above invention, deterioration of the polymer material can be found at an early stage before the change in potential distribution on the surface of the polymer material occurs.

1. New degradation mechanism based on investigation of insulation breakdown products According to the investigation of insulation frames of accident products, OH groups (hydroxyl groups) that should not exist in the original polyester resin were detected from the polymer surface remaining without burning. It was not detected from the resin inside the insulating frame.

  Therefore, when the mapping image of the OH group of the resin cross section of the accident product was collected using the imaging IR method, OH groups were found on the surface of the accident product as shown in the OH group distribution of the polymer material cross section shown in FIG. Many were present, and it was confirmed that the number decreased rapidly from several μm to several tens of μm. From this investigation result, it is considered that there is a causal relationship between the amount of change of OH groups from the surface of the polymer material to the depth direction and the deterioration of insulation.

  Further, when an IR analysis was performed on the surface of the polymer material of the insulating frame where no accident occurred during operation, OH groups having different amounts depending on the operation time and installation environment were detected as shown in FIG.

  From the above, the nitrogen oxides in the environment do not cause the calcium carbonate in the polymer material to become hygroscopic calcium nitrate and lower the insulation resistance, but as shown in the explanatory diagram of FIG. It is conceivable that the surface resistance of the insulating frame decreases due to the hydrolysis of the polyester resin and partial discharge occurs, and the deterioration of the insulation is accelerated by nitrate ions caused by this discharge, leading to an accident.

2. Correlation between surface resistance and chemical change in insulation degradation of polymer materials The surface resistance of insulation materials is greatly influenced by the surrounding environment, and it is difficult to detect the difference due to degradation in the local insulation resistance measurement, but the insulation frame is kept in a constant temperature and humidity chamber If you measure the environment with a highly accurate insulation resistance meter, you can accurately detect changes in insulation resistance due to deterioration. If there is a strong correlation between the resistance characteristics and the numerical value quantifying the chemical change of the polymer material per unit area, it can be used as an indicator of insulation degradation using a chemical state change that is easy to detect and easy to quantify. Deterioration diagnosis is possible.

(1) Temperature and humidity characteristics of insulation deterioration of polymer materials Insulation resistance in a normal environment has a large error during measurement and the difference due to deterioration cannot be observed. Therefore, cut out the insulation frame (polymer material) as a sample, As shown in FIG. 4, it is installed in the resistance cell 2 in the environmental test apparatus 1, and a measurement electrode (not shown) is attached to the cell, and the behavior of the surface resistance is measured using the high resistance meter 3 while controlling the temperature and humidity. did. The measured surface resistance was monitored on a terminal PC.

  FIG. 5 shows the temperature / surface resistance characteristics of a polymer material for an insulating frame made of a new polyester resin at a humidity of 90.degree. FIG. 6 shows the temperature / surface resistance characteristics at a humidity of 90 ° C. of a polymer material for an insulating frame made of a polyester resin aged 32 years.

  As shown in FIG. 5, the surface resistance of the new polymer material for the insulating frame at 90% humidity and the characteristics due to temperature change have some fluctuations at the moment when the temperature is changed, but the surface temperature of the insulating material and the surroundings. It shows the characteristic that it stabilizes when the temperature difference disappears.

On the other hand, in the polymer material for insulating frames of aged 32, as shown in FIG. 6, a decrease in resistance due to leakage current was observed immediately after the temperature was switched, and a short circuit due to partial discharge was reproduced below 10 ⁹ Ω. . However, a phenomenon was observed in which the resistance recovered when the temperature difference between the surface temperature of the material and the ambient temperature disappeared.

  FIG. 7 shows the change over time of the surface resistance characteristics at 35 ° C. and 90% humidity of an insulating frame polymer material made of polyester resin. The surface resistance characteristics of polymer insulating frames with different aging are averaged, and the resistance conductivity is plotted from the average value of stable surface resistance at 35 ° C and humidity of 90%. It was possible to determine a threshold value that leads to conductivity at which partial discharge is likely to occur at room temperature.

(2) Quantification of the chemical change on the surface of the polymer material The quantification of the chemical change on the surface of the polymer material is as follows: the fluctuation range is 1% regardless of where the surface condition of the polymer material is measured. It is possible to determine the amount of chemical change over time by spectroscopic analysis by determining the measurement area to be less than Examples of the spectroscopic analysis method include infrared spectroscopic analysis method and Raman spectroscopic analysis method. As a specific analysis method of the infrared spectroscopy, there is an imaging IR method (FIGS. 8, 9, and 10). As a Raman spectroscopic analysis method, there is a Raman confocal-Raman analysis method (FIGS. 8, 11, 12, and Table 2).

  FIG. 8A is a schematic configuration diagram of the measurement system of the spectroscopic analysis, and FIG. 8B is an explanatory diagram of the measurement principle of the measurement system. In the measurement system based on the infrared spectroscopy or the Raman spectroscopy shown in FIG. 8A, the light irradiated from the light source 11 passes through the interferometer 12 and the sample 17 in the sample chamber 13 (see FIG. 8B). It is used for the measurement surface. Then, the light component (infrared absorption spectrum in the case of infrared spectroscopy, scattered light (see FIG. 8B) in the case of Raman spectroscopy) detected by the substance on the measurement surface of the sample 17 or the substance on the measurement surface is detected. Detected by the instrument 14. The detected light component is input to the terminal 16 via the AD converter 15. On the terminal 16, the difference in the amount of various substances existing on or inside the detected measurement surface is displayed in a visualized state (imaging).

  FIG. 9 shows the distribution of OH groups generated by hydrolysis of the surface of a polymer material for an insulating frame made of a new polyester resin as aged (new, 16 years, 20 years, 30 years) by imaging IR. It is an image. It can be confirmed that the distribution of OH groups expands with time on the surface of the polymer material.

  FIG. 10 shows the change over time in the ratio of the detected amount of hydroxyl groups (OH groups) on the surface of the polymer material for insulating frames made of polyester resin. As is clear from the comparison between the characteristic diagram of FIG. 10 and the characteristic diagram of FIG. That is, it was confirmed that the increase in the amount of OH groups by hydrolysis over time of the polyester polymer material shows a very good correlation with the deterioration of the surface resistance when it exceeds a certain unit area. From this, it is determined that the surface of the hydrophobic polymer is covered with the hydrophilic OH group, thereby causing deterioration of insulation and partial discharge due to change in temperature and humidity and surface moisture absorption in a normal environment. Therefore, the degree of deterioration of the sample can be diagnosed by measuring hydrophilic chemical species such as OH groups on the unknown sample.

FIG. 11 is an image of a composition distribution obtained by confocal-Raman analysis of a polymer material for an insulating frame made of a new polyester resin. FIG. 12 is an image of a composition distribution obtained by confocal-Raman analysis of a polymer material for an insulating frame made of a polyester resin aged 30 years. 11 and 12, number 1 is the distribution of hydrogen bonded to the phenyl group, number 2 is the distribution of CO ₃ ^2- derived from calcium carbonate, and number 3 is the bond between carbon and hydrogen (− The distribution of CH ₂ —), number 4 represents the distribution of sulfate ions (SO ₄ ²⁻ groups). The image images not numbered in FIGS. 11 and 12 visually show the distribution of each component.

Table 2 is a list of components quantified by the confocal-Raman composition of polymer materials for insulating frames made of new and 30-year-old polyester resins. The occupation area ratio described in the table means the ratio of each chemical species to the measurement area. The Raman spectroscopy in this test example showed that the increase in hydrogen-reduced phenyl groups due to aging and the state of oxidation by SO ₄ groups can be quantified.

  As described above, the amount of physicochemical changes on the surface of the polymer material is quantified by spectroscopic analysis of the hydrophilic chemical species on the surface of the polymer material. Degradation of polymer materials can be diagnosed. Moreover, the determination of the hydrophilic chemical species on the surface of the polymer material has the following effects (a) to (c).

(A) Ease Quantification is easy because the amount of chemical species per unit area is measured with a small amount of sample using spectroscopic analysis. Since the measurement result by the diagnostic method of the present invention is in good agreement with the measurement result of the surface resistance degradation characteristic by the prior art, which is difficult and time consuming to measure, the diagnostic method of the present invention is faster than the prior art to insulate the polymer. Deterioration diagnosis can be performed.

(B) Remaining life prediction and reduction of maintenance costs The method of constantly monitoring the surface resistance is good as an alarm when the surface resistance drops to a certain threshold, but it is not possible to know how long the insulation state of the device can be maintained. Absent. In this method, it is possible to estimate how many years it can be used in the same environment from the years before measurement and the degree of deterioration at the time of measurement, and it is possible to greatly reduce the frequency of equipment maintenance inspection.

(C) Correspondence to various degradation modes In the spectroscopic analysis using a wide range of wavelengths, it is possible to compare the amount of chemical change against degradation due to various environmental loads. It can be applied to various deteriorations such as increase in acid and increase in SO ₄ groups due to corrosive gas.

3. Degradation diagnosis of polymer material by measuring average surface potential distribution per unit area of polymer material surface FIG. 13 is a surface potential by AFM (atomic force microscope) of polymer material for insulating frame made of a new polyester resin. A microscopic image (20 μm square) showing the distribution is shown. FIG. 14A shows an atomic force microscope image (20 μm square) obtained by AFM of a polymer material for an insulating frame made of a polyester resin aged 30 years. FIG. 14B shows a surface potential microscope image (20 μm square) by AFM of a polymer material for an insulating frame made of a polyester resin aged 30 years. FIG. 15 shows a surface potential microscope image (20 μm square) by AFM of a polymer material for an insulating frame made of a polyester resin of 30 years and an average surface potential difference.

  According to the optical observation result in FIG. 13, it can be seen that the surface of the frame is not very uneven. On the other hand, according to the microscopic image observation results shown in FIGS. 14 (a) and 14 (b), irregularities formed on the surface of the insulating frame over 30 years were confirmed. Further, as disclosed in FIG. 15, the average surface potential difference of 20 μm square by the surface potential microscope was 2.804V. Thus, according to the surface potential microscope measurement by the atomic force microscope, the average surface potential difference of the polymer insulating material per unit area is not directly quantified but by quantification by each degradation product. It has been shown that it is possible to diagnose insulation deterioration of polymer insulation materials.

  As described above, the amount of physicochemical change on the surface of the polymer material is also high at an early stage before the change in the potential distribution on the surface of the polymer material occurs by measuring the average surface potential distribution per unit area of the polymer material surface. Degradation of molecular materials can be diagnosed. Moreover, the spectroscopic analysis and the measurement of the average surface potential distribution have the following effects (a) to (c).

(A) Direct observation of insulation deterioration state In surface potential microscope (SPoM) image observation using an atomic force microscope, even if the chemical deterioration mechanism is unknown, how much the surface resistance of the insulating material deteriorates with a small amount of sample. Can be determined.

(B) Simple on-site inspection and remaining life prediction For materials whose failure mechanism of insulation deterioration is known, a portable type spectroscopic analyzer using a single-spectrum light source for the functional group serving as a surrogate property is used locally. Can also be diagnosed.

(C) Understanding the three-dimensional degradation state Depending on the sample and the functional group that serves as a measurement marker in degradation, the three-dimensional resistance distribution (from the surface resistance and the cross section) can be analyzed by analyzing the surface distribution in the cross section of the polymer material. The spatial distribution of volume resistance) can be predicted.

Explanatory drawing explaining the outline | summary of the deterioration diagnosis of the polymeric material which concerns on invention, and the deterioration diagnosis of the polymeric material which concerns on a prior art. (A) OH group distribution in cross section of polymer material (27-year-old product) by imaging IR, (b) OH group distribution in cross-section of polymer material (14-year product) by imaging IR. Infrared absorption spectrum by IR analysis of polyester resins with different aging. Schematic of a surface resistance / environment measurement system for verifying the temperature and humidity characteristics of insulation deterioration of a polymer material. Temperature / surface resistance characteristics at 90% humidity of a polymer material for an insulating frame made of a new polyester resin. Temperature / surface resistance characteristics at 90% humidity of a polymer material for an insulating frame made of a polyester resin of 32 years. The time-dependent change of the surface resistance characteristic in 35 degreeC humidity 90% of the polymeric material for insulation frames which consists of polyester resins. (A) Schematic configuration diagram of the spectroscopic analysis measurement system, (b) Explanatory diagram of the measurement principle of the spectroscopic analysis system. An image of the distribution of OH groups generated by hydrolysis of the surface of a polymer material for an insulating frame made of polyester resin as aged (new, 16 years, 20 years, 30 years) by imaging IR. Change over time in the ratio of the detected amount of hydroxyl groups (OH groups) on the surface of the polymer material. Image of composition distribution obtained by confocal-Raman analysis of a polymer material for an insulating frame made of a new polyester resin. An image of composition distribution obtained by confocal-Raman analysis of a polymer material for an insulating frame made of polyester resin aged 30 years. The microscope image (20 micrometer square) which showed the surface potential distribution by the AFM (atomic force microscope) of the polymeric material for insulation frames which consists of a new polyester resin. (A) Atomic force microscope image (20 μm square) of polymer material for insulating frame made of polyester resin 30 years old, (b) AFM of polymer material for insulating frame made of polyester resin 30 years old Surface potential microscope image (20 μm square). A surface potential microscope image (20 μm square) by AFM of a polymer material for an insulating frame made of a polyester resin of 30 years and an average surface potential difference. Insulation degradation mechanism that was previously expected. (A) Influence of humidity on insulation resistance, (b) Secular change of surface resistivity.

Claims (8)

  A method for diagnosing deterioration of a polymer material, wherein the deterioration of the polymer material is diagnosed by quantifying the amount of physicochemical change on the surface of the polymer material.   The method for diagnosing deterioration of a polymer material according to claim 1, wherein the hydrophilic chemical species on the surface of the polymer material is quantified by spectroscopic analysis as the physicochemical change amount.   3. The method for diagnosing deterioration of a polymer material according to claim 2, wherein the spectroscopic analysis is infrared spectroscopic analysis or Raman spectroscopic analysis.   The method for diagnosing deterioration of a polymer material according to claim 3, wherein the hydrophilic chemical species is a hydroxyl group or a hydrogen-reduced phenyl group.   5. The method for diagnosing deterioration of a polymer material according to claim 4, wherein the hydrophilic chemical species is a carboxyl group.   6. The method for diagnosing deterioration of a polymer material according to claim 4, wherein the hydrophilic chemical species is sulfate ion.   The method for diagnosing deterioration of a polymer material according to claim 1, wherein an average surface potential distribution per unit area on the surface of the polymer material is measured as the quantification of the amount of physical chemical change.   The method for diagnosing deterioration of a polymer material according to claim 7, wherein the average surface potential distribution is measured by an atomic force microscope image.