JP2005061901A - Insulation diagnostic method for electric equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulation diagnostic method for an electric equipment allowing measurement without being affected by an external circumstance in the measurement, and capable of correcting an obtained diagnostic data to that in an optional environment. <P>SOLUTION: A diagnostic item, and a plurality of measuring items having a strong correlation with the diagnostic item are selected, the correlation between the diagnostic item and measured data are displayed by a correlation diagram, based on the diagnostic item collected from an insulation object sample and the measured data of the respective measuring items (S11), a characteristic diagram or characteristic expression indicating a relation between the diagnostic item and an external circumstance factor is prepared (S12), the diagnostic measured data measured the measuring item by the measuring item are expressed by one index, as to the measuring objective insulator for insulation diagnosis, a numerical value of the diagnostic item corresponding thereto is read out from the correlation diagram prepared preliminarily (S13), a relation between the read numerical value and the external circumstance factor is expressed by a characteristic curve using the characteristic diagram or characteristic expression, and a corrected value of the diagnostic item with an influence of the external circumstance factor taken into account is acquired thereby (S14). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for diagnosing performance deterioration due to aging of an insulator used in an electric device.

Insulators used in electrical equipment such as power distribution facilities deteriorate over time due to the surrounding environment, electrical and mechanical stress, etc. As a method of diagnosing performance deterioration of electrical equipment insulation, for example, insulation resistance Many methods such as measurement, partial discharge measurement, leakage current measurement, decomposition gas measurement, and tan δ measurement are known. If you classify by measurement method, measurement that destroys the object and non-destructive measurement, measurement that contacts the measuring instrument directly with insulation and non-contact measurement, measurement in the operating state of electrical equipment and in the stopped state Measurement and the like. The optimum method for the electrical equipment is appropriately selected from such a variety of diagnostic methods, and the deterioration of the insulator is diagnosed. As a specific conventional technique for such insulation diagnosis, for example, the surface electrical resistance of a solid insulating material used for a main circuit part constituting a power distribution facility, or a material equivalent to a solid insulating material provided for the main circuit part The first step of measuring the surface electrical resistance of the sensor unit comprising: the relative humidity of the surface electrical resistivity measurement environment measured in advance for each time corresponding to the actual usage time or the actual usage time of the power receiving and distribution equipment as a parameter The second step of creating a humidity-dependent reference curve based on the measured value of surface electrical resistivity, and the life of the power distribution equipment by comparing the humidity-dependent reference curve with the surface electrical resistivity measured in the first step 3rd step to calculate the remaining life of judgment or distribution / distribution equipment, and the threshold value in life judgment is a constant value such as “surface electrical resistivity is 10 ⁹ Ω at 80% relative humidity” A life diagnosis method for power receiving and distribution equipment is disclosed (for example, see Patent Document 1).

Japanese Patent Laying-Open No. 2003-9316 (Page 2, FIGS. 1 and 2)

  In the conventional electrical equipment insulation diagnosis method as described above, since the surface resistivity of the insulator is measured at the site where the electrical equipment to be diagnosed is installed, the measurement depends on the external environment, such as high or low humidity. The measurement data is likely to be affected by noise and the reliability of the measurement data may be reduced, and the measurement result is corrected by the humidity dependence reference curve. However, since the reliability of the underlying data is low, accurate diagnosis cannot be performed. There was a problem.

  In addition, in order to carry out electrical measurements such as surface resistivity locally, there is a problem that the measurement operation requires proficiency and expertise and cannot be easily performed by anyone.

  In addition, since the threshold value is constant regardless of the type and shape of the insulator and the usage environment (voltage applied, etc.), it may not be the actual condition of the insulator to be diagnosed, and was assumed in the initial stage. When the usage method or environmental conditions change significantly, a malfunction occurs before the number of years specified by the threshold value has passed, or conversely, it can be used without problems even after the specified number of years. Can also happen.

The present invention has been made to solve the above-described problems, and can be easily measured in the field without being affected by the external environment during measurement, and can be diagnosed by comprehensively determining the cause of deterioration. An object of the present invention is to provide an insulation diagnosis method for electrical equipment with improved accuracy.
It is another object of the present invention to provide an insulation diagnosis method for electrical equipment that can logically obtain a threshold value and perform objective and accurate life estimation.

  The electrical equipment insulation diagnosis method according to the present invention selects a diagnostic item for diagnosing deterioration of an insulator used in the electrical equipment, and a plurality of measurement items having a strong correlation with the diagnostic item. Collect measurement data of diagnostic items from the insulator sample of the product used in a certain environment, collect measurement data of each measurement item in a normal environment, and measure each item using the MT (Mahalanobis Taguchi System) method. The first step of expressing the measurement data of one by one index and creating a correlation diagram representing the correlation between the one index and the measurement data of the diagnostic item, and the external environmental factors that affect the diagnostic item and the diagnostic item The second step of preparing a characteristic diagram or characteristic equation showing the relationship between the measurement object and the measurement target insulator to be insulation-diagnosed, one piece of diagnostic measurement data measured for each measurement item using the MT method A characteristic diagram prepared in advance in the third step, which is represented by an index, and which reads the numerical value of the diagnostic item corresponding to this one index from the correlation diagram prepared in advance in the first step. Alternatively, using a characteristic equation, create a characteristic curve that shows the relationship between the numerical value of the diagnostic item obtained in the third step and external environmental factors, and correct the diagnostic item at the time of insulation diagnosis considering the influence of external environmental factors And a fourth step of acquiring a value, and using this correction value, the deterioration state of the insulator is diagnosed.

  According to the present invention, a plurality of measurement items having a strong correlation with a diagnosis item are selected, and a correlation diagram representing the correlation between the measurement value of the plurality of measurement items represented by one index and the measurement value of the diagnosis item; A characteristic diagram or characteristic formula that corrects the influence of diagnostic items due to external environmental factors is prepared in advance, and measurement data obtained by measuring multiple measurement items is represented by one index, and correlation is based on this. The correction value of the diagnostic item is obtained using the figure and the characteristic diagram or the characteristic equation, and the deterioration of the insulator is diagnosed using this correction value, so the influence of noise from the external environment is eliminated. Diagnostic data in a certain environment can be easily obtained, and diagnostic data in an arbitrary external environment can be obtained, thereby improving the accuracy of deterioration diagnosis.

Embodiment 1 FIG.
The present invention determines the diagnosis item in the diagnosis of insulation deterioration of electrical equipment in consideration of the type of insulation to be diagnosed and the external environment (temperature, humidity, external noise, etc.), and has a strong correlation with this diagnosis item. Select multiple measurement items that can be easily measured in a short time without being affected by the external environment, make comprehensive judgments based on those measurement results, and perform accurate deterioration diagnosis. The “lifetime” or “remaining life” is estimated using the threshold value derived in step (1).

FIG. 1 is a flowchart showing a procedure of an electrical equipment insulation diagnosis method according to the first embodiment. The procedure of the invention will be described below with reference to FIG.
First, as a first step, a diagnosis item for determining deterioration of the insulation performance of the electrical device to be diagnosed is selected, and a plurality of measurement items having a strong correlation therewith are selected.
The reason for using diagnostic items and a plurality of measurement items for insulation diagnosis will be briefly described. Insulator deterioration varies greatly depending on the type of insulator, usage environment, and external environment. Therefore, as the diagnostic items suitable for the insulation, for example, in the case of electrical measurement, the most appropriate one is selected from items such as “partial discharge”, “surface resistance”, “tanδ”, and “leakage current”, but these are measured locally. It is not easy to be affected by external noise. Therefore, a plurality of items that cause deterioration of the diagnostic items or have strong correlation and can be easily measured in the field are extracted and set as measurement items. For example, when “partial discharge” is a diagnostic item, “gloss”, “surface erosion degree”, and “decomposition gas amount” are selected as measurement items. By directly measuring the selected measurement item, the original diagnosis item is indirectly determined from a plurality of measurement items.

  Next, a large number of insulator samples of new and used products (for example, deteriorated products that have been used for many years by users) of the same insulator as that of the electrical equipment to be measured are prepared. From these insulator samples, measurement items are collected by measuring the diagnostic items under a certain environment (for example, temperature 20 ° C., humidity 50%, hereinafter referred to as reference environment). In addition, measurement data is collected from each sample for each measurement item. Next, the measurement data of each measurement item is expressed for each sample as one index (Mahalanobis distance) using the Mahalanobis Taguchi system method (hereinafter abbreviated as MT method) well known in the field of quality engineering. Then, a correlation diagram (refer to FIG. 4), which represents the correlation between this one index and the measurement result of the diagnostic item, is created, and a master curve in which the correlation is represented by a single line is obtained (S11). . In this correlation diagram, the numerical value on the horizontal axis indicating the diagnostic item value is a value in the reference environment.

  Next, as a second step, a characteristic diagram (see FIG. 5) or a characteristic equation showing the relationship between the diagnostic item and external environmental factors affecting it is created and prepared (S12). The external environmental factor here is an environmental item that is used as a reference environment when collecting diagnostic item data in Step 1, and in the above example, is the temperature and humidity. However, creating a characteristic chart for each of multiple external environmental factors for multiple diagnostic items requires a great deal of labor, so if you can identify external environmental factors (for example, humidity) that have a particularly large impact, just look at the relationship with them. Practical enough.

To create a characteristic diagram, prepare multiple insulator samples (this may not be the same as the insulator sample in Step 1), create samples with different degrees of degradation due to accelerated degradation, and create external samples for each sample. The diagnostic item is measured with the environmental factor as a parameter, and the measurement result is represented as a graph with the horizontal axis as the magnitude of the external environmental factor and the vertical axis as the measured value of the diagnostic item. By doing so, a plurality of characteristic curves of diagnostic items with different degrees of deterioration using external environmental factors as parameters can be obtained.
Alternatively, the characteristic curve may be formulated into a formula and the characteristic curve may be created using the formula. (Specific examples will be described later)
The first step to the second step described above are preparatory work that is prepared in advance prior to the insulation diagnosis of the electrical device to be diagnosed on site.

  Next, the third step will be described. After this, the measurement and diagnosis work for insulation diagnosis with the actual machine is performed. First, measurement data for diagnosis is collected for each measurement item for the insulator to be measured of the electrical device to be diagnosed. Depending on the measurement item, the insulator is usually measured directly in a power failure state, or a sample is taken from the insulator and the sample is measured. The measurement result is set as one index using the MT method. Next, the numerical value of the diagnostic item corresponding to one index is read using the master curve of the correlation diagram created in the first step (S13). Since the numerical value of the diagnostic item read here is a value in the reference environment as described above, it is possible to obtain a measurement result in a certain environment without being influenced by local external environmental factors at the time of measurement.

Next, as the fourth step, using the characteristic diagram or characteristic formula created in the second step, based on the numerical value of the diagnostic item obtained in the third step (value in the reference environment), Create a characteristic curve showing the relationship between external environmental factors and diagnostic items. A specific creation method will be described later.
This characteristic curve is a characteristic curve having an external environmental factor (for example, humidity) of a diagnostic item at the time of measurement in the field as a parameter. Therefore, for example, if the external environmental factor is humidity, the values of the diagnostic items in all of the humidity from 0% to 100% can be read from this characteristic curve (S15).

  As described above, according to the first to fourth steps, determination is made based on a plurality of diagnosis items having a strong correlation with the diagnosis item, so that the diagnosis item can be determined from various aspects, and external environmental factors at the time of measurement Regardless of the condition, the characteristic curve of the diagnostic item value with the external environmental factor as a parameter can be obtained, so the diagnostic item value corresponding to any external environmental value can be obtained, and the deterioration state of the insulator can be accurately grasped .

  Furthermore, a method for accurately performing the life diagnosis based on the above results will be described. First, a life estimation diagram showing the correlation between the diagnosis item and the year of use (age) is prepared, and the initial value of the diagnosis item (that is, the value at the time of a new item, which is measured in the first step) And the diagnostic item value at the time of measurement obtained in the fourth step, connecting two points as a deterioration tendency line, and from the intersection of this line and the threshold line for the diagnostic item obtained in advance The lifetime is estimated (S15). That is, the aging from the new time to the intersection is the life, and the aging from the measurement to the intersection is estimated as the remaining life (see FIG. 7, details will be described later).

  As described above, according to this method, the lifetime can be estimated using the diagnostic item value at an arbitrary external environment value at the time of measurement, so that it is possible to estimate the lifetime by predicting various external environments.

Next, a specific diagnosis method will be described by taking as an example the case where the above-described insulation diagnosis method for electrical equipment is applied to insulation diagnosis for power receiving and distribution equipment.
The main types of insulators used in power distribution facilities are polyester resin insulators, epoxy resin insulators, phenol resin insulators, and the like. As the deterioration process of these insulators, contamination of the insulator surface → moisture absorption → reduction of insulation resistance, increase of leakage current → formation of dryness (micro dry gap formed when the insulator surface is wet) by Joule heat → Scintillation discharge (creeping discharge) → Tracking discharge (local discharge) due to carbonization of the surface → Progress → Recent research has revealed that it progresses like all-way destruction. Therefore, it is known that it is effective to measure and judge the surface resistance of an insulator as a deterioration diagnosis item.

  First, as a first step, diagnostic items and measurement items are selected. The diagnostic item is the “surface resistance value of the insulator” that is effective for the deterioration determination of the insulator as described above. However, electrical measurements such as surface resistance are easily affected by external environmental noise such as humidity. For example, even if the same insulator deteriorates to the same extent, there is a measurement error of up to 5 digits if the humidity is different. . Therefore, we decided to directly measure the cause of deterioration that is less likely to receive noise from the external environment and cause changes in surface resistance. In consideration of the ease of on-site measurement, there is a strong correlation with surface resistance as a measurement item. The chemical measurement items “ion amount” and “color difference gloss amount” were selected. As the types of ions, there are nitrate ions, sulfate ions, chlorine ions, sodium ions, fluorine ions and the like, and there are also colors (lightness), colors (yellow) and the like regarding color differences. If the strength of the correlation with the insulator to be measured is known in advance, it may be selected as appropriate, but in the present embodiment, the optimum measurement items are narrowed down from each item by the following method.

  FIG. 2 is a flowchart for selecting a measurement item from measurement item candidates, and FIG. 3 is a factor effect diagram for determining the effectiveness of the measurement item. This will be described with reference to the drawings. In FIG. 2, first, 15 items such as color, gloss, component (hydrocarbon, etc.), ion adhesion amount, etc. were selected as a plurality of measurement item candidates that seem to be correlated with the surface resistance value as a diagnostic item (S21). . Those listed on the horizontal axis in FIG. 3 are measurement item candidates.

  Next, using a sample of an insulator, for each of these items, the degree of effectiveness (effectiveness) when the item is used or not used is expressed as an SN ratio using the MT method (S22). ). In FIG. 3, for each item candidate, the vertical axis represents the SN ratio with “Yes” when the item is used for diagnosis and “No” when the item is not used. It can be seen that the effect of “Yes” becomes more remarkable as the difference decreases to the right.

  Next, the invalid measurement item candidates are excluded, the items that are more effective are extracted from the valid measurement item candidates, and are selected as the measurement items (S23). Based on FIG. 3, three items of color (yellow), nitrate ion and sulfate ion having a high S / N ratio were extracted and selected as measurement items.

  Note that the correlation is confirmed by the selected measurement item, and if the correlation is not sufficient, another measurement item candidate is given and the operations of S21 to S23 are performed again. Further, it goes without saying that the method of determining effectiveness from this SN ratio and finding a measurement candidate can be applied to other than the above example.

  According to the operation for determining the measurement item based on the SN ratio as described above, there is an effect that the measurement item can be objectively extracted and the main deterioration factor can be clarified.

  Next, prepare a number of insulation samples of the same insulation as the object to be measured and a product with a different usage period. From these samples, three items of color (yellow), nitrate ion amount and sulfate ion amount are prepared. Measure about. For the color, for example, the density of yellow is measured with a simple dye meter. The amount of each ion is measured by, for example, measuring the concentration of ions transferred to the ion test paper using an ion test paper and a high-sensitivity reflection photometer. Color and ion content are almost unaffected by temperature and humidity and can be measured at room temperature. Next, the surface resistance value is measured using the same sample as described above. However, since the surface resistance value is greatly affected by humidity, for example, using a noise shield room in which noise from the external environment is shut out, the temperature 20 Measure under a constant environment (standard environment) such as ℃ and humidity 50%. Next, using the MT method, the color measured above and the two types of ions are obtained as one index (Mahalanobis distance), and the correlation between the surface resistance value and the Mahalanobis distance as shown in FIG. And a master curve is obtained. In FIG. 4, a plurality of clusters in the lower right indicates a new article, and the difference between the new article and the new article increases as the Mahalanobis distance increases. If the Mahalanobis distance is known, the surface resistance value can be determined from the master curve. The surface resistance value obtained here is a value in the reference environment.

Next, as a second step, work is performed to see the influence of humidity as an external environment that affects the surface resistance value, that is, the humidity dependence of the surface resistance. The surface resistance value varies greatly depending on humidity even for the same deteriorated product. When color and ion content are used as measurement items, temperature is not considered because temperature does not affect much.
First, a plurality of insulator samples are prepared. After drying the sample exposed to the vapor of nitric acid aqueous solution for one day or two days at room temperature for a period of time, etc., change the temperature from 20 ° C. and humidity to 5% to 95% stepwise in the environmental chamber. The surface resistance value at each time point is measured. FIG. 5 is a characteristic curve diagram showing the relationship between humidity and surface resistance. In the figure, a broken line indicates a curve obtained from the measurement result, and the measurement result is plotted and smoothly connected. A indicates a new curve, and B, C, D and lower curves are characteristic curves of an insulator having a higher degree of deterioration. It can be seen that the more deteriorated, the more susceptible to humidity.

In creating a characteristic curve, if you prepare many samples with different degrees of deterioration, many curves with different degrees of deterioration can be obtained, resulting in detailed characteristic curve diagrams. It takes time and effort. Therefore, if this curve can be mathematically expressed, humidity correction can be easily performed with any surface resistance value. Since the characteristic curve obtained by the measurement is similar to a part of the normal distribution curve as shown in FIG. 5, a technique for fitting this curve with a Gaussian distribution function and formulating it using the Gaussian distribution curve is available. , And disclosed in Japanese Patent Application Laid-Open No. 2003-9316. Therefore, a characteristic curve drawn by using this technique and using a characteristic expression expressed by a Gaussian distribution function is indicated by a solid line in FIG. a to d are characteristic curves obtained from the characteristic equation corresponding to the characteristic curves A to E obtained from actual measurement. If this characteristic equation is used, a characteristic curve can be drawn if one point of the surface resistance value where the humidity is specified is known, so that the surface resistance value at an arbitrary humidity can be easily read.
The steps up to here are preparatory work prior to actual diagnosis.

  Next, as a third step, measurement of three items of color (yellow), nitrate ion amount, and sulfate ion amount from the surface deposit of the insulator to be measured at the site where the power distribution facility to be diagnosed is installed To implement. For the color, for example, the density of yellow is measured with a simple dye meter. The amount of each ion is measured by, for example, measuring the concentration of ions transferred to the ion test paper using an ion test paper and a high-sensitivity reflection photometer. The measured color and the two kinds of ions are set as one index (Mahalanobis distance) using the MT method. Then, the surface resistance value with respect to the Mahalanobis distance is read from the master curve of the correlation diagram prepared in the first step. This resistance value is a value at a humidity of 50%. That is, according to the steps so far, a surface resistance value of a temperature of 20 ° C. and a humidity of 50% can always be obtained from the insulator to be measured at the site regardless of the measurement conditions. Therefore, when diagnosing the deterioration tendency from the measurement results measured in time series, the measurement results can be used as they are without correction.

Next, humidity correction is performed as a fourth step. FIG. 6 is a diagram for explaining a method of using the characteristic curve. The surface resistance value obtained from the correlation diagram in the third step is plotted (point P) on the 50% humidity line in the figure. When a characteristic curve prepared in advance is used, if the point P is on the curve, the curve is a humidity-dependent curve of the measured surface resistance of the insulator. When not on the curve, a new curve passing through the point P may be created from the distance between the curves above and below the point P.
If the above characteristic equation is used, it is not necessary to prepare a characteristic diagram in advance, and a curve can be drawn by a characteristic equation based on a Gaussian distribution function based on the surface resistance value of the point P. This curve becomes the humidity dependence curve of the surface resistance value obtained by the measurement. As indicated by a thick arrow in the figure, assuming that the surface resistance value at a humidity of 50% is 11 (log ρΩ), a humidity dependence curve like a thick curve is obtained from the equation based on this value. Therefore, the surface resistance value at the time of measurement at an arbitrary humidity can be known.

Next, the lifetime is estimated based on the above result. FIG. 7 is a life estimation diagram by the electrical equipment insulation diagnosis method according to the present embodiment. The life estimation diagram is created as follows. The vertical axis is the surface resistance value (logarithmic scale), the horizontal axis is the year of use (age), and the insulation resistance value at the time of a new article is plotted on the leftmost vertical axis (point a). Next, the surface resistance value of 50% humidity read from the correlation diagram in the third step is plotted (point A). In addition, a value at an arbitrary humidity as a reference for estimating the lifetime is obtained from the characteristic curve obtained in the fourth step and plotted (point c). Since point a is always a value at a humidity of 50%, a constant diagnosis can be made regardless of the weather or the like when, for example, a tendency is compared with the value at another measurement time point. If the point C is a value at a humidity of 100%, for example, the life described later can be determined under the most severe conditions. Usually, it is practical to use humidity during the rainy season or typhoon. Next, if a straight line connecting points A and U is drawn, this line becomes a deterioration tendency line of the insulator to be measured.
In addition, when performing life estimation periodically, it is possible to see a deterioration tendency that matches the actual situation by drawing a deterioration tendency line starting from the previous result.

  Next, in order to estimate the life, a preset threshold value of the surface resistance value is drawn parallel to the horizontal axis. For example, the threshold value may be determined on the basis of a rule, derived from a past case, or calculated by a formula obtained in the second embodiment described later. The use year corresponding to the intersection (point d) of the threshold line and the deterioration tendency line is estimated as the life. Therefore, the estimated remaining life can be obtained by subtracting the aging from the life to the time of measurement. The reason why the deterioration trend line suddenly drops to the right of point (D) in FIG. 7 is that the deterioration progresses rapidly thereafter, and the probability of a ground fault / short circuit increases rapidly.

As described above, according to the invention according to the first embodiment, it is possible to obtain diagnostic data in a fixed environment that eliminates the influence of noise received from the external environment, and the external environmental factor can be determined regardless of the external environmental factor at the time of measurement. Since the characteristic curve of the diagnostic item value as a parameter is obtained, a measurement item value corresponding to an arbitrary external environment value is obtained, and the deterioration state of the insulator can be accurately grasped.
Further, since the determination is made based on a plurality of diagnosis items having a strong correlation with the diagnosis items, the diagnosis items can be determined from various aspects, and the measurement accuracy is improved.
Moreover, when estimating a lifetime using a measurement result, since the diagnostic item value in arbitrary external environment values can be used, it is possible to estimate the lifetime by predicting various external environments.
Furthermore, an external environment factor dependency curve based on the measurement result can be easily created by using the characteristic formula to obtain a correction value using the external environment factor as a parameter from the measurement result.

Embodiment 2. FIG.
The electrical device insulator diagnostic method according to the second embodiment is characterized by theoretically obtaining a threshold value for life estimation. Until the measurement data is obtained from the insulation of the electrical equipment to be diagnosed, the surface resistance value is read using the correlation diagram, the humidity dependence curve is obtained from the correction curve, and the deterioration trend line is obtained from the life estimation diagram to estimate the life Since it is the same as that of Embodiment 1, detailed description is abbreviate | omitted. The threshold value according to the present embodiment is obtained as follows.

  FIG. 8 is a diagram showing an electrical equivalent circuit of an insulator of an electrical device according to Embodiment 2 of the present invention. As shown in the drawing, an insulator 3 made of, for example, an epoxy resin cast product is provided between the conductive portion 1 and the conductive portion 2 in order to insulate and support them. There are various shapes of insulators used in electrical equipment, but the drawings are schematically shown for explanation. The description of the symbols will be described later.

  Next, a threshold value calculation method will be described. The insulation creepage distance of the insulator 3 is L, and the applied voltage between the conductive parts 1 and 2 is V. The capacitance per unit length of the insulator 3 is C1 to Cn, and the surface resistance is R1 to Rn. Strictly speaking, it is necessary to consider the insulation resistance R inside the insulator 3, but at the commercial frequency (50/60 Hz), the impedance of the insulator 3 is dominated by the capacitance (R >> 1 / C, where C Is neglected because it is the total capacitance of the insulator 3).

  Here, as described in the first embodiment, the process from the deterioration of the insulator 3 to the formation of tracking on the surface leading to dielectric breakdown is as follows. → Drivand formation → Scintillation discharge generation → Tracking discharge generation / progress → All road destruction.

  In FIG. 8, the capacitance of the insulator in the dry is shown as Cg and the surface resistance as Rg. The impedance Zd of the dry portion and the impedance Zp per unit length of the other portions are expressed by Equation 1 and Equation 2.

  Assuming that the impedance of the entire insulator 3 being charged is Z, since Z = Zd + Zp · n, Expressions 1 and 2 are substituted into Z to obtain Expression 3.

  Here, since n is a number obtained by dividing the insulation creepage distance L of the insulator 3 into unit lengths, it is a coefficient proportional to the insulation creepage distance L. Now, when calculating the conditions under which scintillation discharge occurs on the surface of the insulator 3, since the surface resistance Rg of the dry portion shown in FIG. 8 is sufficiently high, the potential sharing of the surface of the insulator 3 is the capacitance Cg. Determined by the impedance. Therefore, Z can be approximated by Equation 4 below.

  The relationship between the applied voltage V applied to the insulator 3 and the voltage vg applied to the dry ground is given by the following equation (5).

  Here, if the condition of the applied voltage V at which vg exceeds the spark start voltage vi is obtained, the scintillation discharge generation voltage Vi can be calculated by the following equation 6.

  Cg depends on the length t of the dry band gap, and vi likewise depends on t. vi is given by the so-called Paschen spark start voltage, and vi of atmospheric pressure air can be approximated by the following equation (7).

From Equation 6, if the equation is arranged with Rn as the left side and the discharge generation surface resistance value Rs is obtained, then Rs becomes Equation 8.
Rs (MΩ) ≈a × E ^b / (L × T) (8)
Where E: Rated voltage (kV), L: Insulation creepage distance L (mm), T: Insulation thickness (mm)
Note that a and b are constants determined by the frequency and the type of insulator. From Equation 8, it was found that the discharge initiation surface resistance value Rs is inversely proportional to the product of the insulation creepage distance and the insulation thickness. The discharge start surface resistance value Rs indicates a point at which discharge may occur depending on the material, shape, and use conditions of the insulator. When a discharge occurs, the ions in the atmospheric environment cause a chemical reaction to generate a compound that promotes deterioration of the performance of the insulator, and thus progresses from tracking to all-path destruction. Therefore, this discharge start surface resistance value Rs is a threshold value. Set as value.

  As described above, according to the invention of the second embodiment, the threshold value is logically obtained from the numerical value of the insulator to be diagnosed and the discharge start voltage, such as the type and shape of the insulator, the operating voltage, etc. An objective and accurate threshold value can be obtained, and based on this, it is possible to estimate an accurate life and remaining life.

  This invention is applied to diagnosis of insulators used in switch gears of power distribution equipment widely used in chemical companies, electric gas companies, food companies, etc., and accurately diagnoses the deterioration of insulation. Therefore, it is possible to prevent a major accident such as a ground fault or a short circuit.

3 is a flowchart illustrating an electrical equipment insulation diagnosis method according to Embodiment 1; 3 is a flowchart for selecting measurement items of the electrical device insulation diagnosis method according to the first embodiment. It is a factor effect figure which judges the effectiveness of the measurement item of the insulation diagnostic method of the electric equipment by Embodiment 1. It is a correlation diagram which shows the correlation with the surface resistance value of the insulation diagnostic method of the electric equipment by Embodiment 1, and the distance of Mahalanobis. It is a characteristic curve figure which shows the relationship between the humidity and surface resistance value of the insulation diagnostic method of the electric equipment by Embodiment 1. FIG. It is a figure explaining the utilization method of the characteristic curve of the insulation diagnosis method of the electric equipment by Embodiment 1. FIG. 6 is a life estimation diagram by the electrical equipment insulation diagnosis method according to Embodiment 1. FIG. It is a figure which shows the electrical equivalent circuit of the insulator of the insulation diagnostic method of the electric equipment by Embodiment 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive part 2 Conductive part 3 Insulator.

Claims (6)

Select diagnostic items for diagnosing deterioration of insulators used in electrical equipment and multiple measurement items that have a strong correlation with these diagnostic items. Collect measurement data of the above diagnostic items, collect measurement data for each of the above measurement items in a normal environment, and express the measurement data of each of the above measurement items as one index using the MT (Mahalanobis Taguchi System) method. A first step of creating a correlation diagram representing a correlation between the one index and the measurement data of the diagnostic item;
A second step of preparing a characteristic diagram or characteristic equation showing a relationship between the diagnostic item and an external environmental factor affecting the diagnostic item;
For the insulator to be measured for insulation diagnosis, the measurement data for diagnosis measured for each measurement item is represented by one index using the MT method, and the numerical value of the diagnosis item corresponding to this one index is expressed by the first method. A third step to read from the correlation diagram created in advance in step;
Using the characteristic diagram or characteristic equation prepared in advance in the second step, create a characteristic curve indicating the relationship between the numerical value of the diagnostic item obtained in the third step and the external environmental factor, A fourth step of acquiring a correction value of the diagnostic item at the time of insulation diagnosis in consideration of the influence of the external environmental factor, and diagnosing the deterioration state of the insulator using the correction value Insulation diagnosis method for electrical equipment.   2. The insulation diagnosis method for an electrical device according to claim 1, wherein the diagnosis of the deterioration state in the fourth step is obtained by a new value of the diagnosis item measured in the first step and the fourth step. The correction value of the diagnostic item is plotted on a life estimation diagram showing the correlation between the diagnostic item and the aging, and a deterioration trend line is created, and the lifetime is estimated from the intersection with the threshold value of the diagnostic item obtained in advance. An insulation diagnosis method for electrical equipment.   3. The electrical equipment insulation diagnosis method according to claim 2, wherein the threshold value is obtained from a calculation formula created based on a discharge generation voltage at which a spark is generated due to deterioration of the insulator. .   4. The electrical equipment insulation diagnosis method according to claim 1, wherein the selection of the measurement item in the first step includes a plurality of measurement items that are considered to be correlated with the diagnosis item. 5. An insulation diagnosis method for electrical equipment, comprising: collecting measurement data from a candidate, obtaining an SN ratio using an MT method, and selecting a measurement item candidate having a strong correlation as a measurement item.   5. The electrical equipment insulation diagnosis method according to claim 1, wherein the second step measures the diagnosis item from a plurality of insulation samples in advance using the external environment factor as a parameter. An electrical equipment insulation diagnosis method characterized in that the relationship between the diagnostic item and the external environmental factor is represented by a characteristic curve, and the characteristic curve is expressed by a Gaussian distribution function.   6. The electrical equipment insulation diagnosis method according to claim 1, wherein the diagnostic item is a surface resistance value of an insulator, the measurement item is a color difference and a plurality of ion amounts, and the external environment is used. An insulation diagnosis method for electrical equipment, characterized in that the factor is humidity.

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