JP2020122671A - Lightning arrester failure determination method and lightning arrester failure determination apparatus - Google Patents

Abstract

To provide a lightning arrester failure determination method and a lightning arrester failure determination apparatus that are highly accurate based on a stable determination criterion.SOLUTION: A failure determination method for determining whether a lightning arrester in which lightning arrester elements are connected in series is a normal product or a defective product, includes: a reference value calculation process for seeking a frequency characteristic of equivalent series resistance of the lightning arrester from a theoretical formula expressing an equivalent circuit of the lighting arrester apparatus and for using it as a reference value; a target value measurement process for measuring the frequency characteristic of the equivalent series resistance of the lightning arrester that is a determination target and for using it as a target value; a comparison process for comparing the reference value with the target value; and a determination process for determining, as a result of the comparison, that the target lightning arrester is a defective product when a difference between the reference value and the target value exceeds a threshold.SELECTED DRAWING: Figure 7

Description

The present invention relates to a failure determination method and a failure determination device for a lightning arrester mainly used in overhead power transmission equipment.

Lightning is the most frequent cause of failure in overhead power transmission equipment, and for that reason, lightning arresters have been introduced in many transmission lines. A general lightning protection device has a structure in which lightning protection elements made of zinc oxide (ZnO) are connected in series and housed in an outer tube, and this is installed in an insulator device of a power transmission line. When there is a lightning strike on a tower or an electric wire, the lightning protection device allows only the lightning current to pass and interrupts the AC follow-up current, thereby preventing flashover of the insulator device and preventing power failure.

By the way, such a lightning arrester may fail due to a large current of lightning strike. The faulty lightning arrester does not have the original performance, and the risk of power failure increases if it is left as it is, so it is necessary to find and replace the faulty product by inspection. However, even in the case of a lightning arrester that is a defective product, there is no abnormality in the outer tube and only the internal lightning arrester element may be damaged. In that case, it is impossible to visually determine whether or not there is a failure. Therefore, as shown in Patent Documents 1 and 2, by measuring the frequency characteristic of the equivalent series resistance of the target lightning arrester that is the determination target, and comparing the measured value with the same measured value of the normal lightning arrester, the target A failure determination method for determining whether the lightning arrester is a normal product or a malfunctioning product (a complete failure product in which all lightning protection devices have failed and a partial failure product in which some lightning protection devices have failed) has been proposed. There is.

More specifically, the method of Patent Document 1 judges that the target is a completely defective product when a difference of 1 kHz or less and a predetermined threshold value or more is confirmed as a result of comparing the measured value of the target and the measured value of the normal product. If the difference is not confirmed at 1 kHz or less and the difference is confirmed at 100 kHz or more, it is determined as a partially defective product. Further, in the method of Patent Document 2, the intersection of the frequency characteristic of the equivalent series resistance of the completely failed product and the frequency characteristic of the equivalent series resistance of the normal product is obtained in advance, and the measured value of the target is compared with the measured value of the normal product. As a result, if a difference of more than a predetermined threshold is confirmed in the frequency band that exceeds the intersection, it is determined as a defective product, and if a difference is confirmed in the frequency band below the intersection, it is determined as a completely defective product. However, other than that, it is determined as a partially defective product.

JP, 2011-202956, A JP, 2014-13164, A

In these conventional methods, the measured value of the frequency characteristic of the equivalent series resistance of a normal lightning arrester is used as a criterion for determination. However, there is a possibility that the accuracy of the failure determination may decrease because the measured values have large variations and the determination criteria are not stable.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a highly accurate lightning arrester failure determination method and a lightning arrester failure determination apparatus based on stable determination criteria.

The invention according to claim 1 of the present invention is a failure determination method for determining whether a lightning arrester in which lightning arresters are connected in series is a normal product or a defective product, and is based on a theoretical formula representing an equivalent circuit of the lightning arrester. A reference value calculation process that obtains the frequency characteristic of the equivalent series resistance of the lightning arrester and sets it as a reference value, and a target value measurement process that measures the frequency characteristic of the equivalent series resistance of the target lightning arrester that is the determination target and sets it as the target value. It is characterized by comprising a comparison process of comparing the reference value and the target value, and a determination process of determining the target lightning arrester as a defective product when the difference between the reference value and the target value exceeds a threshold as a result of the comparison. The equivalent circuit of the lightning arrester is obtained by replacing each component of the lightning arrester with a circuit element, and the equivalent circuit is replaced with an equivalent series circuit consisting of an equivalent series resistance and an equivalent series reactance to obtain a theoretical formula. It is what is done.

A second aspect of the present invention is a failure determination method for determining whether a lightning arrester in which lightning arresters are connected in series is a normal product or a defective product, and is a normal lightning arrester having an equivalent series resistance of A reference value measurement process in which the frequency characteristics are measured and an approximated curve of the measured values is obtained as a reference value, and a target value measurement process in which the frequency characteristics of the equivalent series resistance of the target lightning arrester that is the determination target is measured and set as the target value And a comparison step of comparing the reference value and the target value, and a comparison step, when the difference between the reference value and the target value exceeds a threshold value, a determination step of determining the target lightning arrester as a defective product, To do. Various known methods can be used as a method for obtaining the approximated curve of the measured value.

The invention according to claim 3 of the present invention is characterized by including a smoothing process for smoothing a target value. Smoothing is a process of averaging or removing values that are largely different from other values among the values for each frequency, so that there is no overall protruding value. .. As a method of smoothing the target value, various known methods can be used in addition to the method of passing a low-pass filter.

According to a fourth aspect of the present invention, it is determined whether the lightning arrester in which lightning arresters are connected in series is a normal product or a defective product, based on the method for determining a failure of the lightning arrester according to the first, second or third aspect. A failure determination device, which is a target value measuring means for measuring the frequency characteristic of the equivalent series resistance of the target lightning arrester to be determined as a target value, and a prestored reference value and the measured target value. It is characterized by comprising a comparing means for comparing and a determining means for determining the target lightning arrester as a defective product when the difference between the reference value and the target value exceeds a threshold as a result of the comparison. It should be noted that it may include a smoothing means for smoothing the target value.

According to the first aspect of the present invention, the reference value for failure determination is the reference value for the failure determination, which is obtained by obtaining the frequency characteristic of the equivalent series resistance of the lightning protection device from the theoretical expression representing the equivalent circuit of the lightning protection device. Since there is no variation in the value of the frequency characteristics of the equivalent series resistance of the normal lightning arrester, the accuracy of failure determination is improved.

According to the second aspect of the present invention, the frequency characteristic of the equivalent series resistance of the normal lightning arrester is measured, and the approximate curve of the measured value is obtained as the reference value for failure determination. Since there is no variation in the measured value of the frequency characteristic of the equivalent series resistance of the normal lightning arrester, the accuracy of failure determination is improved.

According to the invention of claim 3 of the present invention, it can be obtained from the measurement results so far that the closer the target lightning arrester is to a normal product (the smaller the failure ratio of the lightning arrester), the greater the variation of the target value. Therefore, there is a possibility that a normal product may be determined to be a defective product due to variations. However, by smoothing the measured values, the accuracy of failure determination is further improved.

According to the invention of claim 4 of the present invention, the target is a normal product by the method of claim 1, 2 or 3 only by measuring the frequency characteristic of the equivalent series resistance of the target lightning arrester to be judged. It can be easily and highly accurately determined whether the product is defective or defective.

It is a schematic diagram which shows the structure of a lightning arrester. It is a circuit diagram which shows the equivalent circuit of a lightning arrester. It is a graph which shows the standard value calculated from the theoretical formula showing the equivalent circuit of a lightning arrester. It is a graph which shows the standard value and the target value of three target lightning arresters collectively. 6 is a graph showing target values before and after smoothing. 6 is a graph showing a difference between a reference value and a target value (target value/reference value). It is a block diagram showing composition of a failure judging device of a lightning arrester. It is a graph which shows the measured value of an equivalent series resistance of a normal lightning arrester, and its approximate curve.

The specific contents of the present invention will be described below. The failure determination method of the present invention determines whether a lightning arrester in which lightning arresters are connected in series is a normal product or a defective product. Then, the first embodiment of the present invention is a reference value calculation process of determining a frequency characteristic of an equivalent series resistance of a lightning arrester as a reference value from a theoretical expression representing an equivalent circuit of the lightning arrester, and a target lightning arrester that is a determination target. The target value measurement process of measuring the frequency characteristics of the equivalent series resistance of to be the target value, the smoothing process of smoothing the target value, the comparison process of comparing the reference value and the target value, the result of the comparison, the reference When the difference between the target value and the target value exceeds the threshold value, the target lightning arrester is determined to be a defective product.

First, the structure of the target lightning arrester will be described. As shown in FIG. 1, this lightning arrester 1 has a plurality of substantially cylindrical lightning arresters 11 (10 in this example) made of zinc oxide (ZnO) connected in series. A disc-shaped partition plate 12 made of aluminum is sandwiched between adjacent lightning protection elements 11, and the center portion of the lightning protection elements 11 arranged further (the fifth lightning protection element 11 and the sixth lightning protection element 11 from the end). In the space), a columnar spacer 13 made of aluminum is provided in place of the partition plate 12. A pressing member 14 made of a coil spring is provided at one end of the lightning arresting elements 11 arranged side by side. Then, terminals 15 are provided at both ends of the lightning arresting elements 11 (and the pressing member 14) arranged side by side. The terminal 15 has a cylindrical base portion 151 and a connecting portion 152 extending from the end surface of the base portion 151 in the direction of the central axis of the base portion 151. 151 is connected to the pressing member 14, and at the other end, the base 151 of the terminal 15 is connected to the lightning protection element 11. The pressing member 14 formed of a coil spring is sandwiched between the lightning protection element 11 and the base 151 of the terminal 15 in a compressed state, and presses the lightning protection element 11 connected in series. The lightning arrester 11, the partition plate 12, the spacer 13 and the base 151 of the terminal 15 have substantially the same diameter and are located on the same axis. The lightning protection element 11, the partition plate 12, the spacer 13, the pressing member 14, and the terminal 15 arranged side by side in this manner are housed in the outer tube 16. However, only the base 151 of the terminal 15 is housed in the outer pipe 16, and the connecting portion 152 projects outward from the outer pipe 16. The outer tube 16 is made of fiber reinforced plastic and has a cylindrical shape. The inner diameter of the outer tube 16 is such that the lightning arrester element 11, the partition plate 12, the spacer 13, the pressing member 14 and the base portion 151 of the terminal 15 can be accommodated. Further, on the outer peripheral surface of the outer tube 16, a projection 161 for enhancing the stain resistance performance is formed over the entire surface.

Next, an equivalent circuit of the lightning arrester 1 having such a structure will be described. As shown in FIG. 2, the equivalent circuit is obtained by replacing each component of the lightning arrester 1 with a circuit element. More specifically, the lightning arrester element 11 has resistors n (resistance values r ₁ ,..., R _n ) and capacitors (capacitance values c ₁ ,..., cn) connected in parallel with the number _n. Represented as The number of partition plates 12 is n, which is the same as that of the lightning protection element 11, and is expressed as resistance (resistance values r _b1 ,..., R _bn ). The spacer 13 is represented as _a resistance (resistance value ra). The pressing member 14 is represented as a resistor (resistance value r _s ) and an inductor (inductance value L _s ) connected in series. The terminal 15 is represented as a resistance (resistance value r _t ). The outer tube 16 is represented as a capacitor (capacitance value c _g ). The lightning protection element 11, the partition plate 12, the spacer 13, and the pressing member 14 are connected in series, and the outer tube 16 is connected in parallel, and terminals 15 are connected in series at both ends thereof.

次に、式（１）で表される回路と外管１６が並列接続された回路（図２の二点鎖線で囲まれた部分）について、等価直列抵抗Ｒ_２と等価直列リアクタンスＸ_２からなる等価直列回路Ｒ_２＋ｊＸ_２に置き換えられ、Ｒ_２とＸ_２は次の式（２）で表される。

次に、式（２）で表される回路と端子１５が直列接続された回路（図２の全体）、すなわち避雷装置１の等価回路について、等価直列抵抗Ｒ_３と等価直列リアクタンスＸ_３からなる等価直列回路Ｒ_３＋ｊＸ_３に置き換えられ、Ｒ_３とＸ_３は次の式（３）で表される。

Further, the equivalent circuit of the lightning arrester 1 is replaced with an equivalent series circuit including an equivalent series resistance and an equivalent series reactance, and is represented by the following theoretical formula. First, regarding the circuit in which the lightning arrester 11, the partition plate 12, the spacer 13 and the pressing member 14 are connected in series (the portion surrounded by the alternate long and short dash line in FIG. 2), the equivalent series resistance R ₁ and the equivalent series reactance X ₁ It is replaced by the series circuit R ₁ +jX ₁ , and R ₁ and X ₁ are represented by the following formula (1). However, the resistance value and the electrostatic capacitance value of the lightning protection element 11 are all set to the same value, and are set to r (=r ₁ =...=r _n ) and c (=c ₁ =...=c _n ), respectively. .. Further, the resistance values of the partition plates 12 are all set to the same value and set to r _b (=r _b1 =...=r _bn ).

Next, regarding the circuit represented by the formula (1) and the circuit in which the outer tube 16 is connected in parallel (the portion surrounded by the chain double-dashed line in FIG. 2), the equivalent series resistance R ₂ and the equivalent series reactance X _{2 are used.} The equivalent series circuit R ₂ +jX ₂ is replaced, and R ₂ and X ₂ are represented by the following equation (2).

Next, the circuit represented by the equation (2) and the circuit in which the terminal 15 is connected in series (the whole of FIG. 2), that is, the equivalent circuit of the lightning arrester 1, is composed of an equivalent series resistance R ₃ and an equivalent series reactance X _3. The equivalent series circuit R ₃ +jX ₃ is replaced, and R ₃ and X ₃ are represented by the following equation (3).

The reference value calculation process is executed based on the theoretical formula of the equivalent series resistance R ₃ of the equivalent circuit of the lightning arrester thus obtained. In the reference value calculation process, parameters (frequency characteristics) such as a resistance value, an electrostatic capacitance value, and an inductance value are measured over a wide band (for example, 1 kHz to 1 MHz) for each component of a normal lightning arrester, and the value is measured as described above. Substituting into each equation of, the frequency characteristic of the equivalent series resistance of the equivalent circuit of the lightning arrester is obtained, and this is used as the reference value. FIG. 3 is a graph showing the reference value thus obtained, and is a logarithmic graph in which the horizontal axis represents frequency [Hz] and the vertical axis represents equivalent series resistance [Ω]. As described above, the reference value obtained from the theoretical formula that represents the equivalent circuit of the lightning arrester is represented by a line that is close to a straight line descending to the right on the log-log graph. For reference, the graph also shows the measured value of the equivalent series resistance obtained by actually measuring a normal lightning arrester. However, this measured value is an average value of the measured values of a plurality of (12 samples) lightning arresters. As described above, it can be seen that the measured values have large variations even if they are averages of a plurality of values.

Subsequently, the target value measurement process is executed. In the process of measuring the target value, the frequency characteristic of the equivalent series resistance is actually measured for the target lightning arrester to be determined, and this is set as the target value. The measurement is performed by an impedance analyzer over a wide band (for example, 1 kHz to 1 MHz). FIG. 4 is a graph showing the reference value and the target value together. Although three values are displayed as target values, a target lightning arrester with 10% lightning arrestor failure, a target lightning arrester with 50% lightning arrestor failure, and a target lightning arrester with 100% lightning arrester failure Showing.

Then, the smoothing process is performed. In the smoothing process, the target value obtained in the target value measuring process is smoothed. From the measurement results obtained so far, the measured value (target value) of the equivalent series resistance varies as the target lightning arrester is closer to a normal product (the smaller the failure ratio of the lightning arrester), as shown in FIG. Is obtained. This is due to the normal characteristics of the lightning protection device. Then, due to this variation, a normal product may be determined to be a defective product. Therefore, the target value is smoothed through a low pass filter. FIG. 5 is a graph showing the effect of such smoothing. This graph shows target values (before smoothing and after smoothing) for two normal lightning arresters, but it can be seen that smoothing reduces extreme variations.

Subsequently, the comparison process is performed. In the comparison process, the reference value and the target value obtained as described above are compared over a wide band. As a comparison method, here, a value (target value/reference value) obtained by dividing the target value by the reference value is calculated, and this is used as the difference between the reference value and the target value.

Then, the determination process is executed. In the determination process, when the difference between the reference value and the target value exceeds the threshold value in response to the result of the comparison, the target lightning arrester is determined to be a defective product. Here, the threshold value is set to 3, and if there is even one point where the difference between the reference value and the target value exceeds the threshold value in a wide band (1 kHz to 1 MHz), the target lightning arrester is determined to be a defective product, If there is no point where the difference between the reference value and the target value exceeds the threshold value, the target lightning arrester is determined to be a normal product. FIG. 6 is a graph showing reference values for a plurality of target lightning arresters (different from those shown in FIG. 4) and values of differences between the target values (target value/reference value) together with threshold values. , This judgment is visually represented. The triangle mark indicates the target lightning arrester that has been determined to be a defective product because it has a point that exceeds the threshold line, and the circle mark indicates a normal lightning arrestor because there is no point that exceeds the threshold line. It is a target lightning arrester that is determined to be.

In theory, if the target lightning arrester is a normal product, the reference value and the target value should be the same value, that is, the difference between the reference value and the target value (target value/reference value) should be 1. .. However, the measured value (target value) of the frequency characteristic of the equivalent series resistance still has a variation even after being smoothed through a low-pass filter, so that the difference value may be greater than 1 depending on the frequency. As described above, when the difference value is larger than 1 due to the variation, a threshold value is used so that the target lightning arrester is not determined to be a defective product. It is empirically determined based on various experiments and demonstrations as the minimum value that absorbs the variation in the measured value (target value) of the frequency characteristic of the resistance.

According to the first embodiment of the method for determining the failure of the lightning arrester of the present invention, the reference value for the failure determination is obtained by obtaining the frequency characteristic of the equivalent series resistance of the lightning arrester from the theoretical formula representing the equivalent circuit of the lightning arrester. Therefore, there is no variation in the value compared with the measured value of the frequency characteristic of the equivalent series resistance of the normal lightning arrester, which was used as the reference value in the past. This is also clear from the graph shown in FIG. Then, by using the reference value having no variation in the value, the accuracy of the failure determination is improved.

Here, the results of actually executing the conventional failure determination method and the failure determination method of the present invention and comparing their accuracies are shown. The target lightning arrester (17 samples) that failed on a trial basis was judged by both methods. As a result, in the conventional failure determination method, the failure determination rate was 76% (13/17), whereas in the failure determination method of the present invention, the failure determination rate was 100% (17/17). .. Thus, it was confirmed that the failure determination method of the present invention improves the accuracy of failure determination.

The failure determination method of the present invention is for determining whether the target lightning arrester is a normal product or a defective product, and whether the defective product is a completely defective product in which all the lightning protection devices have failed, Although it is not judged whether or not there is a partially defective product in which some lightning protection elements have failed, it is acceptable in practical use. In most cases, if the product is a completely defective product, not only the lightning protection device but also the outer pipe is damaged, so it is not necessary to use the failure determination method of the present invention. The reason is that it is sufficient to determine whether the internal lightning protection element is damaged (=partially failed product) or undamaged (=normal product).

Next, the failure determination device of the lightning arrester of the present invention will be described. The failure determination device of the present invention determines whether a lightning arrester in which lightning arresters are connected in series is a normal product or a defective product based on the above-described failure determination method for a lightning arrester. As shown in FIG. 7, the failure determination device 2 includes a reference value calculation unit 21, a target value measurement unit 22, a smoothing unit 23, a plotting unit 24, a comparison unit 25, and a determination unit 26. However, with respect to the reference value calculating means 21, the plotting means 24, the comparing means 25 and the judging means 26, one computer C functions as each means.

The computer C is an input device including a keyboard and a mouse, an output device including a display, a CPU that sequentially executes program instructions, and a storage device that stores the program, data necessary for executing the program, calculation results, and the like. It is a standard one having M as a component (components other than the storage device M are not shown).

The target value measuring means 22 is composed of an impedance analyzer, has a probe connected to a terminal of the target lightning arrester 1a, and has an output end connected to the smoothing means 23. Then, the target value measuring means 22 measures the frequency characteristic of the equivalent series resistance of the target lightning arrester 1a to obtain the target value, and outputs the data of the target value to the smoothing means 23.

The smoothing means 23 is composed of a low-pass filter, and has an input end connected to the target value measurement means 22 and an output end connected to the computer C. Then, the smoothing means 23 cuts high-frequency components from the input data of the target value, smoothes it, and outputs it to the computer C.

The above is the configuration of the failure determination device for the lightning arrester of the present invention. Then, in the computer C, the lightning arrester failure determination program is executed to operate the apparatus. Based on the lightning arrester failure determination method of the present invention, is a lightning arrester in which lightning arresters are connected in series is a normal product? It is to determine whether or not the product is defective.

More specifically, when this program is executed by the computer C, the computer C executes each step (reference value calculation step, target value measurement step, smoothing step, plotting step, comparison step, determination step). Functions as various means (reference value calculating means 21, plotting means 24, comparing means 25, determining means 26), and performs failure determination together with other means (target value measuring means 22, smoothing means 23).

When this program is executed, the reference value calculation step is first executed, and the computer C functions as the reference value calculation means 21. The reference value calculation means 21 receives input of measured values of parameters (frequency characteristics) of each component of the normal lightning arrester. The input may be one in which data measured by a measuring device (impedance analyzer or the like) connected to the computer C is captured, or one in which data separately measured and stored in a storage medium is read. Alternatively, the separately measured data may be manually input by the input device. The input measured value is stored in the storage device M. Then, the reference value calculation means 21 reads the measured value and the expressions (1) to (3) stored in advance from the storage device M, substitutes the measured value into each expression, and equivalent series of the equivalent circuit of the lightning arrester. Obtain the frequency characteristic of the resistor and use this as the reference value. The reference value is stored in the storage device M.

Next, the target value measuring step and the smoothing step are executed, and the computer C receives the input of the target value data measured by the target value measuring means 22. However, the data of the target value that is smoothed by the smoothing means 23 is input. The input target value is stored in the storage device M. The low-pass filter as the smoothing means 23 may be implemented as software on the computer C. In that case, after the data of the target value is input to the computer C, the smoothing step is executed. Then, the data of the target value is smoothed.

Next, the plotting step is executed, and the computer C functions as the plotting means 24. The plotting means 24 reads the reference value and the target value from the storage device M and displays them as a graph on the output device (display) of the computer C.

Next, the comparison step is executed, and the computer C functions as the comparison means 25. The comparison unit 25 reads the reference value and the target value from the storage device M, calculates a value (target value/reference value) obtained by dividing the target value by the reference value for each frequency having data, and uses this as the reference value. The difference in the target value is stored in the storage device M.

Next, the determination step is executed, and the computer C functions as the determination means 26. The determination means 26 reads the difference between the reference value and the target value from the storage device M, and if there is at least one point where the difference between the reference value and the target value exceeds a predetermined threshold value in the wide band, the target lightning arrester. Is determined to be a defective product, and if the difference between the reference value and the target value does not exceed the threshold value, the target lightning arrester is determined to be a normal product. The determination result is stored in the storage device M and displayed on the output device of the computer C. With the above, the program ends, and the failure determination by the failure determination device is completed.

Note that the calculated reference value can be used in common for lightning arresters of the same type.Therefore, when performing a failure determination for a type of lightning arrester whose reference value has been calculated in the past, It suffices to omit the value calculation step and execute the target value measurement step and subsequent steps.

The lightning arrester failure determination program may be executed as dedicated software or may be executed on general-purpose spreadsheet software, or may be executed by another program or system. It may be incorporated.

As described above, according to the failure determination device for a lightning arrester of the present invention, by simply measuring the frequency characteristic of the equivalent series resistance of the target lightning arrester that is the determination target, the failure determination method for the lightning arrester described above allows the target to be normal. It is possible to easily and highly accurately determine whether the product is a defective product or a defective product.

Next, a second embodiment of the lightning arrester failure determination method of the present invention will be described. The second embodiment also determines whether the lightning arrester in which the lightning arrester is connected in series is a normal product or a defective product, but the method of obtaining the reference value is different from that in the first embodiment. That is, the first embodiment has a reference value calculation process of determining the frequency characteristic of the equivalent series resistance of the lightning arrester as a reference value from the theoretical formula representing the equivalent circuit of the lightning arrester, but the second embodiment is Instead of this reference value calculation process, there is a reference value measurement process in which the frequency characteristic of the equivalent series resistance of a normal lightning arrester is measured and an approximated curve of the measured value is obtained and used as the reference value. In the second embodiment, the target value measurement process, the comparison process, and the determination process after the reference value measurement process are the same as those in the first embodiment. Therefore, in the following, only the reference value measuring process different from the first embodiment will be described.

In the reference value measuring process executed in the second embodiment, the frequency characteristic of the equivalent series resistance of the normal lightning arrester is measured, and the approximate curve of the measured value is obtained and used as the reference value. The measurement is performed by an impedance analyzer over a wide band (for example, 1 kHz to 1 MHz). The approximate curve is obtained by the least square method. As shown in FIG. 3, the frequency characteristic of the equivalent series resistance is close to a straight line descending to the right on the log-log graph, that is, the power approximation has the highest correlation, and the approximation curve is y=ax ^b . Be in shape. The coefficients a and b are determined so that the sum of squares of the difference between each measurement point and the approximate curve is minimized. However, if the measured value (y) includes a negative value that is a measurement result with poor accuracy, it cannot be expressed in the form of y=ax ^b . In that case, the frequency x corresponding to the negative measured value y is Exclude and find the approximate curve. FIG. 8 is a graph showing the measured value of the frequency characteristic of the equivalent series resistance of the normal lightning arrester and the approximate curve (reference value) obtained by the above method for the measured value.

Based on the reference value obtained in this way, the failure determination is subsequently performed as in the first embodiment. Then, according to the second embodiment of the method for determining the failure of the lightning arrester of the present invention, the frequency characteristic of the equivalent series resistance of the normal lightning arrester is measured, and the approximation curve of the measured value is obtained. It is used as a reference value for determination, and compared with the measured value of the frequency characteristic of the equivalent series resistance of the normal lightning arrester, which is the reference value in the past, there is no variation in the value, so the accuracy of failure determination is improved.

Further, also in the second embodiment of such a failure determination method, as in the first embodiment, the method is executed by the failure determination device, and at that time, the failure determination is performed in the computer. The program runs. Also in the apparatus and the program, the difference from the case of the first embodiment is only the method of obtaining the reference value, and the difference is the same as the difference in the method, so description will be omitted.

The present invention is not limited to the above-described embodiment, but can be modified as appropriate within the scope of the spirit of the invention. For example, the lightning arrester targeted for failure determination is not limited to the above-described structure, and may be a device without some components. In that case, in the first embodiment, the values of the corresponding parameters in Expressions (1) to (3) may be set to zero. Further, in the above embodiment, in the determination process, it is determined whether or not there is a point where the difference between the reference value and the target value exceeds the threshold value in a wide band, but instead, there is a difference in a specific frequency or frequency band. It may be determined whether or not there is a point exceeding the threshold value, or whether or not the total value of the differences of several points or all points exceeds the threshold value. Furthermore, in the second embodiment, various known methods can be used as a method for obtaining an approximated curve of measured values.

DESCRIPTION OF SYMBOLS 1 Lightning arrester 11 Lightning arrester 12 Partition plate 13 Spacer 14 Pressing member 15 Terminal 151 Base 152 Connection part 16 Outer tube 161 Protrusion 2 Failure determination device 21 Reference value calculation means 22 Target value measurement means 23 Smoothing means 24 Plotting means 25 Comparison means 26 Judgment means

Claims (4)

A method for determining whether a lightning arrester in which lightning arresters are connected in series is a normal product or a defective product,
A reference value calculation process of obtaining a frequency characteristic of the equivalent series resistance of the lightning arrester as a reference value from a theoretical formula representing an equivalent circuit of the lightning arrester, and
A target value measurement process of measuring the frequency characteristics of the equivalent series resistance of the target lightning arrester that is the determination target and setting the target value,
A comparison process of comparing the reference value and the target value,
A failure determination method for a lightning arrester, comprising: a determination step of determining a target lightning arrester as a defective product when a difference between a reference value and a target value exceeds a threshold value as a result of comparison. A method for determining whether a lightning arrester in which lightning arresters are connected in series is a normal product or a defective product,
A reference value measurement process in which the frequency characteristics of the equivalent series resistance of a normal lightning arrester are measured, and an approximated curve of the measured values is obtained as a reference value.
A target value measurement process of measuring the frequency characteristics of the equivalent series resistance of the target lightning arrester that is the determination target and setting the target value,
A comparison process of comparing the reference value and the target value,
A failure determination method for a lightning arrester, comprising: a determination step of determining a target lightning arrester as a defective product when a difference between a reference value and a target value exceeds a threshold value as a result of comparison. The method of determining a failure of a lightning arrester according to claim 1, further comprising a smoothing process of smoothing the target value. A failure determination device for determining whether a lightning arrester in which lightning arresters are connected in series is a normal product or a defective product, based on the method for determining a failure of a lightning arrester according to claim 1, 2, or 3.
Target value measuring means for measuring the frequency characteristic of the equivalent series resistance of the target lightning arrester that is the determination target and the target value,
Comparing means for comparing the reference value stored in advance with the measured target value,
A failure determination device for a lightning arrester, comprising: a determination unit that determines the target lightning arrester as a defective product when the difference between the reference value and the target value exceeds a threshold value as a result of comparison.

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