JP2012037448A - Thunder impulse withstand voltage test system, reference waveform calculation program, and thunder impulse withstand voltage test method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for accurately determining the insulation resistance of an object to be tested in a thunder impulse withstand voltage test.SOLUTION: A thunder impulse withstand voltage test system according to the invention, comprises: a recorded waveform data acquisition unit 110 for acquiring recorded waveform data RD in an application of a thunder impulse voltage to an object to be tested; a core region extraction unit 112 for extracting a core region RD; a coefficient determination unit 114 for determining a wave front element β and a time origin tby performing a regression analysis on an equation (1) using data of the core region RD; a stable region extraction unit 116 for extracting a stable region RD; a reference waveform calculation unit 118 for determining a predetermined constant A and a wave rear element α by performing a regression analysis on the equation (1) using data of the stable region RD, and calculating a reference waveform function BC; and an insulation resistance determination unit 120 for calculating an overshoot ratio OSr on the basis of the reference waveform function BC and the recorded waveform data RD.

Description

  The present invention relates to a lightning impulse withstand voltage test system and a reference waveform calculation program applied to a lightning impulse withstand voltage test, and a lightning impulse withstand voltage test method.

  As one method for determining the insulation resistance of power equipment, a lightning impulse withstand voltage test based on IEC 60060-1 is adopted. In a lightning impulse withstand voltage test based on IEC 60060-1, for example, using a test device as described in Patent Document 1, a lightning impulse voltage (unipolar full-wave voltage) is applied to an object to record waveform data. (Transition data with respect to time) is acquired. When the recording waveform data is acquired, a reference waveform function is derived based on this.

At present, the reference waveform function uses data in the core region from the portion that has reached 20% or more to the peak value of the rising edge of the recorded waveform data until it drops to 40% with respect to the peak value after passing the peak value, The following equation (1) is calculated by determining four coefficients A, α, β, and t ₀ by performing regression analysis so as to approximate the data in the core region. Instead of using the above calculation method, the reference waveform is set based on experience (division amount) based on the recorded waveform data.

  When the reference waveform function (reference waveform) is obtained, the overshoot rate is calculated based on the recording waveform data and the peak value of the reference waveform function. The overshoot rate is obtained by the following equation (2). The insulation resistance of the object is determined based on the overshoot rate.

  The current IEC 60060-1 stipulates that the overshoot rate is within 5%. However, in large equipment applied to UHV (Ultra High Voltage), residual inductance (parasitic capacitance) such as electrostatic capacity and power supply lines inevitably increases, so suppression of vibration component superposition (reduction of overshoot ratio) is suppressed. It is extremely difficult. Therefore, an amendment proposal of IEC 60060-1 is being approved to reduce the overshoot rate to within 10% and introduce the k-factor method. The k-factor method is described in Non-Patent Document 1, for example.

JP 2009-168733 A

Toshiji Kato, “Determination of impulse parameters by k-factor method”, [online], Doshisha University, Faculty of Science and Technology, [Searched July 20, 2010], Internet <URL: http://kairo.doshisha.ac .jp / ~ kato / documents / temp / 080924B% 83p% 83l% 83% 8B /% 89% c1% 93% a1-Kfactor.ppt>

  In the conventional calculation method of the reference waveform function described above, the peak value tends to be calculated higher by being pulled by the overshoot portion of the recorded waveform data. The reference waveform function assumes an ideal waveform that does not overshoot due to vibration components superimposed when a lightning impulse voltage is applied to an object (because it cannot accurately grasp parasitic capacitance, etc.) Derivation is impossible), and being pulled by the overshooted part leads to a deviation from the original waveform. It should be noted that even if this ideal waveform is approximated by EMPT (Electro Magnetic Transients Program) analysis or the like, it is proved that the wave height value is calculated higher by the conventional method of calculating the reference waveform function.

  When the peak value of the reference waveform function is calculated to be high, the overshoot rate, which is a criterion for insulation resistance, is calculated to be low. As a result, the determination as to whether or not the product conforms to the standard may be unsatisfactory, which may cause unreasonableness. On the other hand, when the reference waveform is set based on experience based on the recorded waveform data, it strongly depends on the subjectivity of the personnel, and therefore the determination criterion may not be kept constant.

  The present invention has been made in view of such a problem, and is a lightning impulse withstand voltage test system capable of accurately determining the insulation resistance of an object in a lightning impulse withstand voltage test, and a standard used therefor. An object is to provide a waveform calculation program and a lightning impulse withstand voltage test method.

In order to solve the above-mentioned problems, the present inventors diligently studied and focused on the above formula (1) for calculating the reference waveform function, particularly the wave tail element α. The reference waveform function calculated by the equation (1) is that the wave head (the rear part of the waveform) is higher than the recorded waveform data as a result of the wave head (the front part of the waveform) being pulled higher by the overshooted part. Tend to be lower. On the other hand, as the value of the wave tail element α is larger, the wave head tends to be lower and the wave tail is higher. Therefore, after determining the four coefficients A, α, β, and t ₀ , in order to cancel the influence pulled by the overshoot portion, the data of the stable region after passing the peak value of the recorded waveform data is used. The present invention has been completed by considering that a predetermined constant A, which is an overall coefficient, and the wave tail element α may be determined again.

That is, a typical configuration of a lightning impulse withstand voltage test system according to the present invention includes a recording waveform data acquisition unit that acquires recording waveform data in which a lightning impulse voltage is applied to an object, and a recording waveform data that exceeds a first threshold value. A core region extraction unit that extracts a core region from the reached portion until the value drops to the second threshold after passing the peak value, and a wavefront element β by performing regression analysis so that the above equation (1) approximates the data of the core region And a coefficient determining unit for determining the time origin t ₀ , a stable region extracting unit for extracting a stable region after passing the peak value in the recorded waveform data, and a wave front element determined by the coefficient determining unit using the data of the stable region β and the above equation according to the time origin t ₀ a (1) regression analysis, a reference waveform calculation unit for calculating a reference waveform function by determining a predetermined constant a and the wave tail element α It characterized by having a a dielectric strength determining unit determines the dielectric strength of the object by calculating the overshoot ratio based on the peak value of the reference waveform function and recording waveform data.

  According to such a configuration, the predetermined constant A and the wave tail element α are determined using the data in the stable region after passing the peak value of the recorded waveform data in order to cancel the influence pulled by the overshoot portion. Since the correction is made, a more appropriate reference waveform function can be calculated. Therefore, it is possible to accurately determine the insulation resistance of the object. Note that the stable region is a convergent portion (a terminal portion that changes linearly) with almost no vibration in the recorded waveform data.

  The stable region may be from 15 to 25 μs after the standard origin to 55 to 65 μs. Thereby, as the stable region, a convergent portion having almost no vibration is extracted from the recorded waveform data, and a more appropriate reference waveform function can be calculated.

A typical configuration of a reference waveform calculation program according to the present invention is a recording waveform for acquiring recording waveform data obtained by applying a lightning impulse voltage to an object to calculate a reference waveform function used in a lightning impulse withstand voltage test. Data acquisition means, core area extraction means for extracting the core area from the portion of the recorded waveform data that has reached the first threshold value or higher until it drops to the second threshold value after passing the peak value, and the above equation (1) is the data of the core area The coefficient determination means for determining the wave front element β and the time origin t ₀ by regression analysis so as to approximate, the stable area extraction means for extracting the stable area after passing the peak value in the recorded waveform data, and the stable area data used, the applied above equation (1) the wavefront element β and the time origin t ₀ which is determined regression analysis by the coefficient determining means, a predetermined constant a and wave Characterized in that to function reference waveform calculation means for calculating a reference waveform function as, by determining the elements alpha.

  According to such a configuration, the program can be generalized as a program for calculating an appropriate reference waveform function. In addition, the component corresponding to the technical idea in the lightning impulse withstand voltage test system mentioned above and its description are applicable also to the said reference waveform calculation program.

A typical configuration of the lightning impulse withstand voltage test method according to the present invention includes a recording waveform data acquisition step for acquiring recording waveform data in which a lightning impulse voltage is applied to an object, and the recording waveform data has reached a first threshold value or more. A core region extracting step for extracting a core region from the portion until the peak value is lowered to the second threshold value, and a regression analysis so that the above equation (1) approximates the data of the core region, and the wave front element β and time A coefficient determining step for determining the origin t ₀ , a stable area extracting step for extracting a stable area after passing the peak value in the recorded waveform data, and a wave front element β determined by the coefficient determining step using the data of the stable area time origin t ₀ the applied above equation (1) a regression analysis, calculates a reference waveform function by determining a predetermined constant a and the wave tail element α And quasi waveform calculating step, characterized in that it comprises a and a dielectric strength determination step of determining the insulation resistance of the object by calculating the overshoot ratio based on the peak value of the reference waveform function and recording waveform data.

  According to such a configuration, it is possible to accurately determine the insulation resistance of the object in the lightning impulse withstand voltage test. In addition, the component corresponding to the technical idea in the lightning impulse withstand voltage test system mentioned above and its description are applicable also to the said lightning impulse withstand voltage test method.

  According to the present invention, a lightning impulse withstand voltage test system capable of accurately determining the insulation resistance of an object in a lightning impulse withstand voltage test, a reference waveform calculation program used therefor, and a lightning impulse withstand voltage test method Can be provided.

It is a block diagram which shows schematic structure of the lightning impulse withstand voltage test system concerning this embodiment. It is a flowchart explaining the lightning impulse withstand voltage test method concerning this embodiment. It is a figure explaining calculation of a reference waveform function. It is a figure explaining calculation of evaluation waveform data. It is a figure explaining determination of evaluation waveform data. It is the figure which compared the precision of the reference waveform calculation method of this embodiment, and the conventional reference waveform calculation method. It is the figure which compared the case where the vibration component to superimpose is 300 kHz, and the case where the vibration component to superimpose is 600 kHz.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  FIG. 1 is a block diagram showing a schematic configuration of a lightning impulse withstand voltage test system 100 according to the present embodiment. As shown in FIG. 1, the lightning impulse withstand voltage test system 100 is a computer system including a system control unit 102 and a storage unit 104. The system control unit 102 is a semiconductor integrated circuit including a central processing unit (CPU) and manages and controls the entire lightning impulse withstand voltage test system 100. The storage unit 104 includes a ROM, RAM, EEPROM, nonvolatile RAM, flash memory, HDD, and the like, and stores programs and various data used in the system.

  Further, the lightning impulse withstand voltage test system 100 includes an input unit 106 and an output unit 108. The input unit 106 takes in predetermined information from the outside to the system by a keyboard, a mouse, a touch panel, a file input / output device, data communication through a network, or the like. The output unit 108 includes a display, a printer, and the like, and displays information to the user and performs printing. It is also possible to save the output content as data in a recording medium, or to perform data communication or web display over a network.

  Hereinafter, the recording waveform data acquisition unit 110, the core region extraction unit 112, the coefficient determination unit 114, the stable region extraction unit 116, the reference waveform calculation unit 118, and the insulation resistance of the lightning impulse withstand voltage test system 100 will be described with reference to FIGS. The determination unit 120, residual waveform calculation unit 122, residual waveform processing unit 124, evaluation waveform calculation unit 126, and evaluation waveform determination unit 128 will be described.

  FIG. 2 is a flowchart illustrating the lightning impulse withstand voltage test method according to the present embodiment. The lightning impulse withstand voltage test system 100 determines the insulation resistance of the object through the steps of the flowchart of FIG. FIG. 3 is a diagram for explaining the calculation of the reference waveform function BC. FIG. 4 is a diagram for explaining the calculation of the evaluation waveform data ED. FIG. 5 is a diagram illustrating determination of the evaluation waveform data ED.

  In the recording waveform data acquisition step S110, the recording waveform data acquisition unit 110 acquires recording waveform data RD (transition data with respect to time) in which the lightning impulse voltage is applied to the object (see FIG. 3A). The recorded waveform data acquisition unit 110 may be a test device (circuit) that applies the above-described lightning impulse voltage to an object, or is configured as a part that receives the recorded waveform data RD output from such a device. May be.

In core region extracting step S112, the core area extracting unit 112 extracts a core region RD ₁ from the portion that reaches or exceeds the first threshold value in the recording waveform data RD of the up decreases to the second threshold value after the peak value P passes (See FIG. 3B). Here, according to IEC6000060-1, the first threshold value is set to 20% with respect to the peak value P, and the second threshold value is set to 40% with respect to the peak value P.

The coefficient decision step S114, the coefficient determining unit 114, and a regression analysis as the following equation (1) approximates the data core region RD _1, 4 single factor A, alpha, beta, to calculate the _{t 0.} That is, the reference waveform function BCp (indicated by a dotted line in FIG. 3B) based on the conventional method is calculated. In the present embodiment, the wave front element β and the time origin t ₀ among the four coefficients are employed (determined) as they are, and the predetermined constant A and the wave tail element α are re-determined through a process described later.

For the stable region extraction step S116, the stable region extraction unit 116 extracts a peak value P after passing through the stable region RD ₂ in the above-described recording waveform data RD (see Figure 3 (c)). The stable region is a convergent portion (a terminal portion that changes linearly) with almost no vibration in the recording waveform data RD. Here, the stable region RD ₂ is determined from 15 to 25 μs to 55 to 65 μs after the standard origin (the point where the straight line passing 30% and 90% of the peak value P intersects the time axis at the rising portion). To do. By setting the stable region RD ₂ at least in this way, vibration can extract substantially no convergent portion, it has been confirmed to be able to exclude the influence of the overshoot portion. The method for obtaining the stable region may be determined by time as described above, but the range in which the recorded waveform data RD is differentiated twice and the value is equal to or less than a predetermined value may be determined as the stable region. .

In reference waveform calculation step S118, the reference waveform calculation unit 118, by using the data of stability region RD _2, the applied above formula wavefront element β and the time origin t ₀ determined by the coefficient determining unit 114 (1) A regression analysis is performed to determine a predetermined constant A and a wave tail element α. Thereby, the reference waveform function BC (indicated by a one-dot chain line in FIG. 3C) is calculated.

When the reference waveform function BCp based on the conventional method is compared with the reference waveform function BC of the present embodiment calculated as described above, the reference waveform function BC of the present embodiment uses the data of the stable region RD ₂ and the wave tail element α. Since (predetermined constant A) is re-determined, it is possible to cancel the influence of being pulled by the overshooted portion (see FIG. 3D). That is, the reference waveform function BC can ensure higher accuracy than the reference waveform function BCp based on the conventional method.

Calculating the insulation resistance determination step S120, dielectric strength determination unit 120, a peak value P of the recording waveform data RD, based on the peak value P _BC of the reference waveform function BC, the overshoot ratio OSr the equation below (2) (See FIG. 3D). In IEC 60060-1, the overshoot rate OSr is currently within 5%, and within the revised proposal, it is within 10%. In the present embodiment, since the reference waveform function BC that is more appropriate than the conventional one (the effect of canceling the effect of being pulled to the overshoot portion) is used, it is possible to accurately determine the insulation resistance of the object.

  When the overshoot rate OSr is not within a predetermined range (for example, within 10%) (insulation resistance determination step S120 No), the insulation resistance of the object is considered to be out of the predetermined standard, and this is output to the user. (Non-conforming output step S132). When the overshoot ratio OSr is within the predetermined range (insulation resistance determination step S120 Yes), the following steps are further performed, and the tolerance of the peak value P of the recording waveform data RD, the standard wavefront length, the standard wave It is determined whether the tail length is within a predetermined range.

  In the residual waveform calculation step S122, the residual waveform calculation unit 122 calculates residual waveform data GD obtained by subtracting the reference waveform function BC from the recorded waveform data RD (see FIG. 4A). In the residual waveform processing step S124, the residual waveform processing unit 124 performs filtering processing on the residual waveform data GD based on the k-factor method, and outputs the residual waveform data GDf after the filtering processing (FIG. 4B). )reference). Since the k-factor method is well known to those skilled in the art, the description thereof is omitted.

In the evaluation waveform calculation step S126, the evaluation waveform calculation unit 126 calculates the evaluation waveform data ED by adding the residual waveform data GDf after the filtering process to the reference waveform function BC obtained above (FIG. 4C). reference). Accordingly, in the evaluation waveform determination step S128, the evaluation waveform determination unit 128 causes the tolerance (the difference between the target voltage value (specified value) and the actual measurement value) of the peak value P _ED of the evaluation waveform data ED, the standard wavefront length T. _1, standard wave tail length T ₂ is equal to or within a predetermined range.

FIG. 5 is a diagram illustrating determination of the evaluation waveform data ED. As shown in FIG. 5, the standard wavefront length T ₁ is defined as the straight line L from the standard origin O ₁ where the straight line L passing through 30% and 90% with respect to the peak value P _ED intersects the time axis at the rising portion of the waveform. It is the time to reach the peak value P _ED . The standard wave tail length T _2, the standard origin O _1, is that the time to decrease to 50% relative to the peak value P _ED after the peak value P _ED pass. According to the current standard, the tolerance of the peak value P _ED of the evaluation waveform data ED is set to + 3% to −3%. Also, standard front time _{T 1} is a 1.2Myuesu (tolerance + 30% to -30%), standard wave tail length _{T 2} are, there is a 50 [mu] s (tolerance + 20% to -20%).

When the tolerance of the peak value P _ED , the standard wave front length T ₁ , and the standard wave tail length T ₂ satisfy the above criteria (evaluation waveform determination step S128 Yes), the insulation resistance of the target object satisfies the predetermined standard. And the fact is output to the user (adaptation output step S130). On the other hand, when the tolerance of the peak value P _ED , the standard wave front length T ₁ , and the standard wave tail length T ₂ do not satisfy the above criteria (evaluation waveform determination step S128 No), a test for applying a lightning impulse voltage to the object. The device is adjusted (for example, the braking resistance is increased / decreased), and the lightning impulse voltage is applied to the object again to acquire the recording waveform data RD.

  As described above, according to the lightning impulse withstand voltage test system 100 described above, it is possible to calculate the reference waveform function BC that is more accurate than before, and thus it is possible to more accurately determine the insulation resistance of the object. It should be noted that the recording waveform data acquisition unit 110 (recording waveform data acquisition unit), the core region extraction unit 112 (core region extraction unit 112), the coefficient determination unit 114 (coefficient determination unit), and the stable region extraction unit 116 (stable region extraction). The reference waveform calculation method described above can be implemented using a general-purpose computer by constructing a reference waveform calculation program that functions as the means) and the reference waveform calculation unit 118 (reference waveform calculation means). Compared to the conventional reference waveform calculation method, it is clear that the reference waveform calculation method of this embodiment is superior, and since it is expected to become a new standard, such generalization has a remarkable effect. Play.

  Hereinafter, in order to confirm the effects exhibited by the present embodiment, the study methods performed by the present inventors will be described as examples.

  In this embodiment, the recording waveform data RD is simulated based on the following equation (3). Then, the reference waveform calculation method of the above embodiment and the conventional reference waveform calculation method are applied to the simulation of the recording waveform data RD, and their accuracy is compared. In Equation (3), the first term on the right side (the portion corresponding to Equation (1)) represents an ideal waveform (original waveform) excluding the vibration component, and corresponds to the second term on the right side (Formula (1)). The remaining part excluding the part that expresses) represents the vibration component superimposed on it due to the influence of the inductance. In order to confirm the accuracy, when the recorded waveform data RD actually measured by a 1000 kV class test apparatus was applied to this equation (3), it was confirmed that it could be simulated very well.

Here, the first term on the right side is the standard lightning impulse voltage (standard wavefront length 1.2 μs (allowable error + 30% to −30%), standard wave tail length 50 μs (allowable error + 20% to −20%)). Each parameter (A ₀ , α ₀ , β ₀ , t ₀ ′) was determined. Specifically, the predetermined constant A ₀ was set to 1.0373, the wave tail element α ₀ was set to 0.014659, and the wave front element β ₀ was set to 2.4689. The second term on the right side is a predetermined value (10%, 20%, 30%) of the overshoot rate OSr calculated based on the peak value of the first term on the right side and the above equation (3), that is, the simulated recording waveform data RD. Each parameter (C, f, θ, γ) was determined so that In particular, the amplitude C was fixed to a predetermined constant A ₀ and equivalent. The frequency f was set every 100 kHz between 100 kHz and 600 kHz. The phase θ and the attenuation rate γ were set so that the overshoot rate OSr had a predetermined value.

  In Table 1, the frequency f is set to 100 kHz, 200 kHz, 300 kHz, and 400 kHz, respectively, to simulate the recording waveform data RD, and the accuracy when the reference waveform calculation method of the present embodiment and the conventional reference waveform calculation method are applied thereto. Is shown. FIG. 6 is a diagram for comparing these accuracies. As shown in Table 1 and FIG. 6, when the reference waveform calculation method of the present embodiment is applied to the case where the superimposed frequency of the recording waveform data RD is simulated as 100 kHz to 400 kHz, it is far more than the conventional reference waveform calculation method. It has been proved that high accuracy can be obtained.

  Table 2 shows the accuracy when the recording waveform data RD is simulated by setting the frequency f to 500 kHz and 600 kHz, respectively, and the reference waveform calculation method of the present embodiment and the conventional reference waveform calculation method are applied thereto. . FIG. 7 is a diagram comparing the case where the superimposed vibration component is 300 kHz and the case where the superimposed vibration component is 600 kHz. As shown in Table 2, the difference in accuracy between the reference waveform calculation method of the present embodiment and the conventional reference waveform calculation method becomes smaller as the frequency f is applied. As shown in FIG. 7, as the frequency increases, the ratio (falling range) of the valleys C1 and C2 after passing the peak value increases, and even if the conventional reference waveform calculation method is applied, the influence of the overshoot portion This is thought to be offset. In any case, it has been proved that the reference waveform calculation method of this embodiment ensures high accuracy.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  The present invention can be used as a lightning impulse withstand voltage test system, a reference waveform calculation program, and a lightning impulse withstand voltage test method applied to a lightning impulse withstand voltage test.

DESCRIPTION OF SYMBOLS 100 ... Lightning impulse withstand voltage test system, 102 ... System control part, 104 ... Memory | storage part, 106 ... Input part, 108 ... Output part, 110 ... Recording waveform data acquisition part, 112 ... Core area extraction part, 114 ... Coefficient determination part , 116: stable region extraction unit, 118: reference waveform calculation unit, 120 ... insulation resistance determination unit, 122 ... residual waveform calculation unit, 124 ... residual waveform processing unit, 126 ... evaluation waveform calculation unit, 128 ... evaluation waveform determination Part, O ₁ ... standard origin, P, P _ED , P _BC ... peak value, T ₁ ... standard wave front length, T ₂ ... standard wave tail length, RD ... recording waveform data, RD ₁ ... core region, RD ₂ ... stable region , BC ... reference waveform function, BCp ... reference waveform function based on conventional method, GD ... residual waveform data, GDf ... residual waveform data after filtering processing, ED ... evaluation waveform data, C1, C2 ... valley

Claims (4)

A recording waveform data acquisition unit for acquiring recording waveform data obtained by applying a lightning impulse voltage to an object;
A core region extraction unit that extracts a core region from a portion that has reached a first threshold value or more in the recorded waveform data until it drops to a second threshold value after passing a peak value;
A coefficient determining unit that performs regression analysis so that the following equation (1) approximates the data in the core region to determine the wave front element β and the time origin t ₀ ;
A stable region extraction unit for extracting a stable region after passing a peak value in the recorded waveform data;
Using the data of the stable region, regression analysis is performed again on the following equation (1) to which the wave front element β determined by the coefficient determination unit and the time origin t ₀ are applied, and a predetermined constant A and a wave tail element α are obtained. A reference waveform calculation unit for calculating a reference waveform function by determining,
An insulation resistance determination unit that calculates an overshoot ratio based on the peak value of the reference waveform function and the recorded waveform data, and determines the insulation resistance of the object;
A lightning impulse withstand voltage test system.

  2. The lightning impulse withstand voltage test system according to claim 1, wherein the stable region is from after 15 to 25 μs elapses from 55 to 65 μs elapse from a standard origin. Computer to calculate the reference waveform function used for lightning impulse withstand voltage test,
Recording waveform data acquisition means for acquiring recording waveform data obtained by applying a lightning impulse voltage to an object,
A core region extracting means for extracting a core region from the portion that has reached the first threshold value or more in the recorded waveform data until it drops to the second threshold value after passing the peak value;
Coefficient determining means for determining the wave front element β and the time origin t ₀ by performing regression analysis so that the following equation (1) approximates the data of the core region:
A stable area extracting means for extracting a stable area after passing a peak value in the recorded waveform data, and a wave front element β and a time origin t ₀ determined by the coefficient determining means using the stable area data, A reference waveform calculation means for calculating a reference waveform function by performing regression analysis of the following equation (1) and determining a predetermined constant A and a wave tail element α;
Reference waveform calculation program to function as

A recording waveform data acquisition step for acquiring recording waveform data obtained by applying a lightning impulse voltage to an object;
A core region extraction step for extracting a core region from a portion that has reached a first threshold value or more in the recorded waveform data until it drops to a second threshold value after passing the peak value;
A coefficient determination step for determining the wave front element β and the time origin t ₀ by performing regression analysis so that the following equation (1) approximates the data of the core region;
A stable region extracting step for extracting a stable region after passing a peak value in the recorded waveform data;
Using the stable region data, regression analysis is performed on the following equation (1) to which the wave front element β determined by the coefficient determining step and the time origin t ₀ are applied, and a predetermined constant A and a wave tail element α are determined. A reference waveform calculation step for calculating a reference waveform function by:
An insulation resistance determination step for calculating an overshoot rate based on the peak value of the reference waveform function and the recording waveform data, and determining an insulation resistance of the object;
A lightning impulse withstand voltage test method comprising:

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