Insulation monitoring device

Abstract

To obtain a leakage current caused by insulation-to-ground resistance with good accuracy, irrespective of the disequilibrium of ground capacitance of an electrical circuit to be measured or the presence or absence of grounding resistance.SOLUTION: An insulation monitoring device according to the present invention includes leakage current value computation means 40 that obtains a leakage current value caused by insulation-to-ground resistance, on the basis of the voltage waveform of R phase of a three-phase three-wire type or a single-phase three-wire type electric circuit to be measured 2, a T-phase voltage waveform, and a zero-phase current waveform. The leakage current value computation means 40 obtains a plurality of circuit equations regarding the sine and cosine components of the zero-phase current, on the basis of the fundamental wave and plurality of odd harmonic components of the R-phase voltage waveform, T-phase voltage waveform, and zero-phase current waveform, obtains the insulation-to-ground resistance values of the R-phase and the T-phase, respectively, by matrix operation of a simultaneous equation composed of the plurality of circuit equations, and obtains a leakage current value caused by insulation-to-ground resistance from the R-phase insulation-to-ground resistance value, the T-phase insulation-to-ground resistance value, the effective value of R-phase voltage, and the effective value of T-phase voltage.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an insulation monitoring device for monitoring leakage current in a three-phase three-wire or single-phase three-wire circuit.

Background Art

[0002] Insulation monitoring devices for monitoring leakage current in a circuit are known. Leakage current includes ground fault current caused by capacitance to ground and ground fault current caused by insulation resistance. Since the cause of electric leakage fires and the like is the decrease in insulation resistance, if the leakage current caused by insulation resistance can be accurately detected, the insulation state of the circuit can be accurately grasped, and major disasters such as electric leakage fires can be prevented.

[0003] Regarding the method for measuring the leakage current caused by insulation resistance, for example, in Patent Document 1, the zero-phase current measured by a zero-phase current sensor that measures the zero-phase current of a grounded circuit and a phase determination signal having a predetermined phase according to the grounded phase of the circuit are vectorially added and subtracted to create XY vector components, and using the effective values of these vector components and the phase determination signal, it is described that the resistive ground fault current is obtained.

[0004] Also, in Patent Document 2, the zero-phase current of a three-phase circuit is measured by a zero-phase current transformer, the voltage of each phase is measured by a voltage measuring device, the fundamental wave component and the fifth harmonic component are extracted from the outputs of the zero-phase current transformer and the voltage measuring device by a band-pass filter, the phase relationship between the current and voltage of the extracted frequency components is obtained by an arithmetic processing device, and the leakage current due to capacitance to ground is removed from the leakage current of the three-phase circuit to calculate the leakage current due to the ground insulation resistance.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

[0006] However, the method described in Patent Document 1 performs leakage current monitoring under the condition that the grounding resistance is 0Ω for single-phase three-wire circuits, and under the condition that the grounding resistance is 0Ω and the capacitance to ground of each phase is balanced for three-phase three-wire circuits. Therefore, if the grounding resistance of the circuit is high or the capacitance to ground is unbalanced, the measurement error of the leakage current will be large, which may result in false alarms or failure to alarm.

[0007] The method described in Patent Document 2 can be applied even when the capacitance to ground of a three-phase three-wire circuit is unbalanced by using not only the fundamental wave component but also the fifth harmonic component. However, when the grounding resistance is high, the measurement error of the leakage current becomes large. Furthermore, because the harmonic component fluctuates greatly, it is difficult to reduce the measurement error of the leakage current by simply using the harmonic component, and improvement is needed.

[0008] Furthermore, when comparing balanced and unbalanced transmission lines, if all waveforms—line voltage, phase voltage, voltage to ground, and line current / zero-sequence current—at the commercial frequency are perfectly identical, it becomes impossible to distinguish between the two, and therefore, leakage current values ​​cannot be measured.

[0009] The present invention was made to solve the above problems, and aims to provide an insulation monitoring device that can accurately determine the leakage current caused by the insulation resistance to ground, regardless of the degree of imbalance in the capacitance to ground of the circuit under test or the presence or absence of grounding resistance. [Means for solving the problem]

[0010] To solve the above problems, the insulation monitoring device according to the present invention is an insulation monitoring device that monitors leakage current caused by the ground insulation resistance of a three-phase three-wire or single-phase three-wire circuit under test, comprising: a voltage R-phase acquisition means for acquiring the voltage waveform of the R-phase with respect to the S-phase or N-phase; a voltage T-phase acquisition means for acquiring the voltage waveform of the T-phase with respect to the S-phase or N-phase; a zero-sequence current acquisition means for acquiring the zero-sequence current waveform of the ground phase of the circuit under test; and a leakage current value calculation means for determining the leakage current value caused by the ground insulation resistance based on the voltage waveform of the R-phase, the voltage waveform of the T-phase, and the zero-sequence current waveform. The leakage current value calculation means is characterized in that it obtains a plurality of circuit equations relating to the sine and cosine components of the zero-sequence current based on the fundamental wave and a plurality of odd-order harmonic components of the voltage waveform of the R phase, the voltage waveform of the T phase, and the zero-sequence current waveform, and obtains the insulation resistance value of the R phase to ground and the insulation resistance value of the T phase to ground by matrix operation of the simultaneous equations composed of the plurality of circuit equations, and obtains the leakage current value caused by the insulation resistance to ground from the insulation resistance value of the R phase to ground, the insulation resistance value of the T phase to ground, the effective value of the voltage of the R phase, and the effective value of the voltage of the T phase.

[0011] According to the present invention, leakage current can be accurately determined even when the capacitance to ground of each phase of the circuit under test is unbalanced or when the grounding resistance is high. Therefore, false alarms and missed alarms in insulation monitoring can be prevented.

[0012] In the present invention, it is preferable that the leakage current value calculation means obtains the sinusoidal and cosine components of the plurality of odd-order harmonic components of the R-phase voltage, the T-phase voltage waveform, and the zero-sequence current waveform, respectively, by performing a Fourier transform on the R-phase voltage waveform, the T-phase voltage waveform, and the zero-sequence current waveform. According to the present invention, a plurality of circuit equations necessary for calculating the leakage current value can be easily generated.

[0013] In the present invention, it is preferable that the leakage current value calculation means determines eight or more of the circuit equations. This makes it possible to accurately determine the leakage current value while suppressing the influence of harmonic fluctuations.

[0014] Preferably, the leakage current value calculation means applies the maximum likelihood estimation method to the matrix operation of the system of equations consisting of the eight or more circuit equations to obtain the maximum likelihood solution for the R phase's insulation resistance to ground and the T phase's insulation resistance to ground, respectively. This makes it possible to accurately determine the leakage current value while minimizing the influence of harmonic fluctuations.

[0015] The leakage current value calculation means preferably applies ridge regression to the maximum likelihood solution obtained by the maximum likelihood estimation method to determine the insulation resistance value of the R phase to ground and the insulation resistance value of the T phase to ground, respectively. This makes it possible to obtain a stable leakage current value while minimizing the influence of harmonic fluctuations.

[0016] The aforementioned odd-order harmonic components are preferably the 5th, 7th, and 9th harmonics, and the number of circuit equations is preferably eight. The 3rd harmonic is the odd-order harmonic closest to the fundamental wave, and therefore has a strong influence on the fundamental wave distortion generated in the current transformer and circuit that constitute the zero-sequence current sensor, affecting the accuracy of the leakage current value. The absence of even-order harmonics and odd-order harmonics from the 11th order onward is due to the small size of the waveform obtained from the circuit under test, making it difficult to obtain accuracy.

[0017] The matrix operation preferably includes a weighting matrix in which the fundamental wave is weighted to 1 and the odd-order harmonics are weighted to less than 1. The effective value and phase difference of each harmonic are not constant, and the magnitude of fluctuations differs depending on the order of the harmonic. However, by weighting the harmonics, the measurement accuracy of the leakage current can be improved.

[0018] It is preferable to further provide notification means for notifying the leakage current value or an alarm based on the leakage current value. This allows monitoring personnel to be notified of the monitoring results. [Effects of the Invention]

[0019] The present invention aims to provide an insulation monitoring device that can accurately determine the leakage current caused by the insulation resistance to ground, regardless of the degree of imbalance in the capacitance to ground of the circuit under test or the presence or absence of grounding resistance. [Brief explanation of the drawing]

[0020] [Figure 1] Figure 1 is a block diagram showing a schematic configuration of an insulation monitoring device according to an embodiment of the present invention. [Figure 2] Figure 2 is a detailed block diagram of the insulation monitoring device. [Figure 3] Figure 3 is an explanatory diagram of the method for calculating the leakage current of the circuit under test using an insulation monitoring device. [Figure 4] Figure 4 is an equivalent circuit diagram of the circuit under test when the S-phase's insulation resistance to ground is treated as a high resistance value. [Modes for carrying out the invention]

[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0022] Figure 1 is a block diagram showing the schematic configuration of an insulation monitoring device according to an embodiment of the present invention. Figure 2 is a detailed block diagram of the insulation monitoring device.

[0023] As shown in Figures 1 and 2, the insulation monitoring device 1 according to this embodiment monitors a three-phase three-wire (or single-phase three-wire) circuit under test 2, and is connected to the S-phase (or N-phase) line 2S and the R-phase line 2R, and the voltage waveform of the R-phase is measured with respect to the S-phase (or N-phase). R A voltage R-phase input means 10 that takes in the voltage R phase, and is connected to the S-phase (or N-phase) line 2S and the T-phase line 2T, and the voltage waveform of the T-phase is taken with the S-phase (or N-phase) as the reference. T A voltage T-phase acquisition means 20 captures the voltage, and a zero-sequence current waveform i of the ground phase of the circuit under measurement i is transmitted via a zero-sequence current sensor ZCT magnetically coupled to the S-phase ground wire 4S. OZero-phase current acquisition means 30 for acquiring a zero-phase current, voltage R-phase acquisition means 10, voltage T-phase acquisition means 20, and leakage current value calculation means 40 for extracting fundamental wave and harmonic components of the output waveforms of the zero-phase current acquisition means 30 and calculating the effective value Ior of the leakage current caused by the ground insulation resistance through the calculation of the simultaneous equations of the voltage and current of the measured circuit 2 created for each frequency component, and notification means 50 for notifying a leakage current value or an alarm based thereon.

[0024] The insulation monitoring device 1 extracts the resistive ground fault current component i O from the zero-phase current i detected by the zero-phase current sensor ZCT Or and monitors the insulation of the measured circuit 2. The leakage current of the measured circuit 2 includes the ground fault current i R caused by the capacitance to ground C S of each phase, C T and the ground fault current i OC caused by the ground insulation resistance R R of each phase, R S R T However, the cause of leakage fires and the like is the decrease in the ground insulation resistance R Or R R S R T T R R S R T Therefore, the insulation monitoring device 1 monitors the ground fault current i Or caused by the ground insulation resistance R T

[0025] As shown in FIG. 2, the voltage R-phase acquisition means 10 of the insulation monitoring device 1 includes a primary power input unit 11 on which a transformer, a protection circuit, etc. for separating the primary side and the secondary side are mounted, a filter unit 12 on which a low-pass filter (LPF) for extracting the fundamental wave is mounted, an A / D unit 13 for converting the analog waveform of the fundamental wave into a digital waveform, a filter unit 14 on which a HPF and a LPF for extracting the harmonic are mounted, and an A / D unit 15 for converting the analog waveform of the harmonic into a digital waveform.

[0026] The voltage T-phase input means 20 has the same circuit configuration as the voltage R-phase input means 10. Specifically, the voltage T-phase input means 20 includes a primary power input section 21 on which a transformer and protection circuits are mounted, a filter section 22 on which an LPF is mounted for extracting the fundamental wave, an A / D section 23 for converting the analog waveform of the fundamental wave into a digital waveform, a filter section 24 on which a HPF and LPF are mounted for extracting harmonics, and an A / D section 25 for converting the analog waveform of the harmonics into a digital waveform.

[0027] The zero-sequence current acquisition means 30 has the same configuration as the voltage R-phase acquisition means 10 and the voltage T-phase acquisition means 20, except that it is equipped with a current input unit 31 instead of primary power input units 11 and 21. Specifically, the zero-sequence current acquisition means 30 includes a current input unit 31 on which an IV conversion unit is mounted to convert the current of the zero-sequence current sensor ZCT into a voltage, a filter unit 32 on which an LPF is mounted for extracting the fundamental wave, an A / D unit 33 for converting the analog waveform of the fundamental wave into a digital waveform, a filter unit 34 on which an HPF and an LPF are mounted for extracting harmonics, and an A / D unit 35 for converting the analog waveform of the harmonics into a digital waveform.

[0028] The leakage current value calculation means 40 includes a coefficient matrix setting unit 41 that sets a coefficient matrix based on the fundamental and harmonic components of the voltage waveform and current waveform of each phase, a constant term vector setting unit 42 that sets a constant term based on the insulation resistance to ground and capacitance to ground of each phase, a weight matrix setting unit 43 that sets a weight matrix for each harmonic, and calculates the leakage current value I by calculating the matrix equation. Or The system includes a matrix operation unit 44 for calculating the leakage current value. The notification means 50 includes, but is not limited to, a server output 51 for remotely notifying the calculated leakage current value, a monitor output 52 for displaying the leakage current value on a tool such as a PC, a 7-segment display output 53 for checking the leakage current value on the insulation monitoring device itself, and a lamp output 54 for indicating that the leakage current value has exceeded a threshold.

[0029] Next, referring to Figure 3, the leakage current I of the circuit under measurement by the insulation monitoring device 1 is measured. or This explains how to perform the calculation.

[0030] Since we use the harmonics generated in the circuit, we can define each waveform in Figure 3 as follows. The subscript k represents the fundamental wave (commercial frequency) when k=1, the 5th harmonic when k=5, the 7th harmonic when k=7, and so on. As a general term, the fundamental wave and the kth harmonic will be referred to as the kth frequency from now on. Also, the current i without a subscript oc Ya i or This indicates that it is the fundamental wave current.

[0031] V Rk : Voltage R-phase RMS value, V Tk : Voltage T-phase RMS value, β Rk : Theoretical phase of the voltage R phase, β Tk : Theoretical phase of voltage T phase, α Rk : The inherent phase error of the R-phase voltage, α Tk If defined as the inherent phase error of the T-phase voltage, then the R-phase and T-phase voltage waveforms at the k-th frequency v Rk , v Tk It will be as follows:

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[0032] Also, the current waveforms i of the R, S, and T phases at the k frequency Rk , i Sk , i Tk It will be as follows:

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[0033] Furthermore, the zero-sequence current i of the kth frequency Ok This can be expressed as follows:

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[0034] These equations (1) to (6) can be summarized as follows.

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[0035] Next, when the measurable voltage and current waveforms are Fourier transformed, the following results are obtained.

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[0036] Substituting these into the original equation yields the following two relationships.

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[0037] If we set the harmonic order k=1 (fundamental wave), the number of equations is insufficient for the number of unknown parameters, so we cannot determine the unknown parameters unless we provide conditions. Therefore, by increasing the number of equations by setting k=1, 5, 7, and 9, we obtain the following eight equations.

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[0038] r(1 / R R +1 / R S +1 / R T For the solution to ), the vector (I C1 , I S1 , I C5 , I S5 , I C7 , I S7 , I C9 , I S9 Since the )' is parallel, it becomes a trivial solution that does not depend on the measured value, and it is not possible to obtain a normal solution. (Here, the prime symbol '' means the transpose of the matrix.) In other words, this shows that the S phase's insulation resistance to ground cannot be theoretically determined using the Ior method.

[0039] For example, a simple example is the following system of equations.

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[0040] Next, we will explain a method of calculating the Ior method using harmonics, in which the insulation resistance of the ground phase to ground is treated as a high resistance.

[0041] The insulation resistance R of the S phase of the circuit under measurement 2 S The equivalent circuit when treated as a high resistance value is shown in Figure 4. As mentioned above, the subscript k represents the fundamental wave (commercial frequency) when k=1, the 5th harmonic when k=5, the 7th harmonic when k=7, and so on. As a general term, the fundamental wave and harmonics will be expressed as the kth frequency from now on. Also, currents ioc and ior without a subscript indicate that they are the fundamental wave currents.

[0042] Therefore, the above eight equations become as follows.

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[0043] The unknown parameters can be set using the following five options.

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[0044] The reason there are eight equations for five unknown parameters is that harmonics constantly fluctuate compared to the fundamental wave, and it is necessary to find an average solution. The absence of the third harmonic is because it is the odd-numbered harmonic closest to the fundamental wave, and therefore its influence on the fundamental wave distortion generated in the current transformer and circuit that make up the zero-sequence current sensor is strong and affects the accuracy. The absence of even-numbered harmonics and odd-numbered harmonics from the 11th order onward is because the harmonics obtained from the circuit are small and it is difficult to obtain accuracy.

[0045] The above eight equations can be expressed using matrices and vectors as follows.

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[0046] This equation becomes a multiple regression model under the condition that the errors follow a normal distribution, and when maximum likelihood estimation is performed,

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[0047] 1 / R obtained in this way R and 1 / R T Multiplying each by its RMS voltage,

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[0048] Next, we will explain the application of ridge regression. When ridge regression is applied to the above maximum likelihood solution, using the L2 regularization parameter λ and the identity matrix I,

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[0049] The reason for applying ridge regression is to obtain stable leakage current values. Depending on the RMS values ​​and phase patterns of the voltage and current at each frequency, |A'A| may be close to 0. This means the denominator is close to 0, which leads to unstable results. By using the L2 regularization parameter of ridge regression, the denominator can be prevented from becoming 0, thus achieving stability.

[0050] For example, in a single-phase three-wire circuit, the voltage phase difference between the RN and TN phases is 180°. However, if not only the fundamental wave but also each harmonic is close to the ideal environment of 180°, multicollinearity can occur when applying multiple regression, affecting accuracy. To prevent this, the L2 regularization parameter is used to improve accuracy.

[0051] If not only the fundamental wave but also each harmonic is 180°, even if the above ridge regression is applied, stability cannot be obtained unless the L2 regularization parameter λ is increased. However, if the L2 regularization parameter λ is increased too much, a phenomenon occurs where it deviates from the true value. To solve this, the phase difference of each voltage is set to 180°, and 1 / R R -1 / R T and ωC R -ωC T If we give the premise that each of these is an unknown parameter, we can do the following.

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[0052] By doing so, the phenomenon of multicollinearity is eliminated, and a significantly more stable system is obtained that takes into account the imbalance between grounding resistance and capacitance to ground.

[0053] The effective values ​​and phase differences of each harmonic do not remain constant compared to the fundamental wave, and their fluctuations are large. Therefore, weighting is applied to the harmonics to improve accuracy. The weighting can be defined as follows. Since the fundamental wave has higher accuracy than the harmonics, its weight is fixed at 1.

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[0054] One way to determine each component of the weight matrix is ​​to use the following method (Neyman allocation method): the time representation of the current cosine and current sine values ​​of each harmonic.

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[0055]

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[0056]

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[0057] The capacitance between the R phase and the T phase to ground is calculated using the following method: ωC R YaωC TSince this can be determined, the capacitance to ground itself can also be determined, making it possible to evaluate the degree of imbalance.

[0058] Regarding the calculation method for the S-phase capacitance to ground, if the ground resistance r is known by measuring the voltage to ground, then r RST =rω(C R +C S +C T ) is found, C S =r RST / rω-C R -C T Therefore, it becomes possible to determine the capacitance of the S phase to ground.

[0059] As described above, the insulation monitoring device 1 according to this embodiment includes a leakage current value calculation means 40 that calculates the leakage current value due to the insulation resistance to ground based on the voltage waveform of the R phase, the voltage waveform of the T phase, and the zero-sequence current waveform, and the leakage current value calculation means 40 calculates the capacitance to ground C based on the voltage waveform of the R phase, the voltage waveform of the T phase, and the zero-sequence current waveform. R ,C T ,C S The fundamental wave and 5th, 7th, and 9th harmonic components of the zero-sequence current, as well as the ground insulation resistance R, are related to this. R ,R T Multiple circuit equations relating to the fundamental wave and the 5th, 7th, and 9th harmonic components of the zero-sequence current caused by this are obtained, and the R phase's insulation resistance to ground R is calculated by matrix operations on the system of equations composed of these multiple circuit equations. R and the T-phase's insulation resistance value R to ground T Determine each of these, and the R phase's insulation resistance to ground R R R, the insulation resistance value of the T phase to ground. T The effective value V of the R phase voltage R1 and the effective value V of the T-phase voltage T1 R from the insulation resistance to ground R ,R T To determine the effective value Ior of the leakage current caused by this, we need to find the capacitance C to ground of the circuit under test 2. R ,C T ,C S Regardless of the degree of imbalance or the presence or absence of grounding resistance r, the insulation resistance to ground R R ,R T The leakage current caused by this can be determined with high accuracy.

[0060] Although preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the invention, and these modifications are also included within the scope of the present invention. [Explanation of Symbols]

[0061] 1. Insulation monitoring device 2 Electrical circuit under test 2R R-phase railway 2S S-phase railway 2T T-phase railway 4S S-phase grounding wire 10 Voltage R phase input means 11 Primary power input section 12 Filter section 13 A / D section (fundamental wave) 14 Filter section 15 A / D section (harmonic) 20 Voltage T-phase input means 21 Primary power input section 22 Filter section 23 A / D section (fundamental wave) 24 Filter section 25 A / D section (harmonic) 30 Zero-sequence current acquisition means 31 Current Input Section 32 Filter section 33 A / D section (fundamental wave) 34 Filter section 35 A / D section (harmonic) 40 Leakage current value calculation means 41 Coefficient matrix setting section 42 Constant Term Vector Setting Unit 43 Weight matrix setting section 44 Matrix operation section 50. Notification methods 51 Server Output 52 Monitor Outputs 53 7-segment display output 54 Lamp Output ZCT Zero-Sequence Current Sensor

Claims

1. An insulation monitoring device for monitoring leakage current caused by the ground-to-ground insulation resistance of a three-phase three-wire or single-phase three-wire circuit under test, A voltage R-phase acquisition means that acquires the voltage waveform of the R-phase with respect to the S-phase or N-phase, A voltage T-phase acquisition means for acquiring the voltage waveform of the T-phase with reference to the S-phase or the N-phase, A zero-sequence current acquisition means for acquiring the zero-sequence current waveform of the ground phase of the circuit under measurement, The system includes a leakage current value calculation means that determines the leakage current value caused by the ground insulation resistance based on the voltage waveform of the R phase, the voltage waveform of the T phase, and the zero-sequence current waveform. The leakage current value calculation means is Based on the R-phase voltage waveform, the T-phase voltage waveform, and the zero-sequence current waveform, and the fundamental wave and multiple odd-order harmonic components, multiple circuit equations, including the sinusoidal and cosine component circuit equations, are obtained for each of the fundamental wave and multiple odd-order harmonic components of the zero-sequence current. The insulation resistance values ​​of the R phase to ground and the T phase to ground are determined by matrix operations on a system of equations constructed using the circuit equations with a number greater than or equal to the number of unknown parameters. An insulation monitoring device characterized by determining the leakage current value caused by the ground insulation resistance from the ground insulation resistance value of the R phase, the ground insulation resistance value of the T phase, the effective value of the voltage of the R phase, and the effective value of the voltage of the T phase.

2. The insulation monitoring device according to claim 1, wherein the leakage current value calculation means determines the sinusoidal and cosine components of the plurality of odd-order harmonic components of the R-phase voltage, the T-phase voltage waveform, and the zero-sequence current waveform by performing a Fourier transform on each of them.

3. The insulation monitoring device according to claim 2, wherein the leakage current value calculation means determines eight or more of the circuit equations.

4. The insulation monitoring device according to claim 3, wherein the leakage current value calculation means applies the maximum likelihood estimation method to the matrix operation of the system of linear equations composed of eight or more circuit equations to obtain the maximum likelihood solution for the R phase's insulation resistance to ground and the T phase's insulation resistance to ground, respectively.

5. The insulation monitoring device according to claim 4, wherein the leakage current value calculation means applies ridge regression to the maximum likelihood solution of the maximum likelihood estimation method to determine the insulation resistance value of the R phase to ground and the insulation resistance value of the T phase to ground, respectively.

6. The insulation monitoring device according to any one of claims 1 to 5, wherein the plurality of odd-order harmonic components are the 5th harmonic, the 7th harmonic, and the 9th harmonic, and the number of the plurality of circuit equations is 8.

7. The insulation monitoring device according to any one of claims 1 to 5, wherein the matrix operation includes a weighting matrix in which the weighting for the fundamental wave is 1 and the weighting for the odd-order harmonics is less than 1.

8. The insulation monitoring device according to any one of claims 1 to 5, further comprising notification means for notifying the leakage current value or an alarm based on the leakage current value.

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