JP2023155635A - Insulation monitoring device - Google Patents

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

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

Insulation monitoring devices for monitoring leakage current in electrical circuits are known. Leakage current includes ground fault current caused by ground capacitance and ground fault current caused by insulation resistance. However, since the cause of leakage fires, etc. is a decrease in insulation resistance, leakage current caused by insulation resistance If this can be detected accurately, the insulation state of the electrical circuit can be accurately determined, and catastrophes such as electric leakage fires can be prevented.

Regarding a method for measuring leakage current caused by insulation resistance, for example, Patent Document 1 describes a zero-sequence current measured by a zero-sequence current sensor that measures the zero-sequence current of a grounding system electric circuit, and a predetermined method according to the grounding phase of the electric circuit. It is described that XY vector components are created by vectorial addition and subtraction of phase determination signals having a phase of .

Furthermore, Patent Document 2 discloses that the zero-phase current of a three-phase electric circuit is measured with a zero-phase current transformer, the voltage of each phase is measured with a voltage measuring device, and the output of the zero-phase current transformer and the voltage measuring device is measured. The fundamental wave component and the fifth harmonic component are extracted using a band-pass filter, and the phase relationship between the current and voltage of the extracted frequency component is determined using an arithmetic processing unit, and the ground capacitance is determined from the leakage current of the three-phase circuit. It describes a method for calculating the leakage current due to ground insulation resistance, excluding the leakage current due to the ground insulation resistance.

Japanese Patent Application Publication No. 2002-125313 Japanese Patent Application Publication No. 2004-317466

However, the method described in Patent Document 1 is based on the condition that the grounding resistance is 0Ω for a single-phase 3-wire circuit, and that the grounding resistance is 0Ω and the ground capacitance of each phase is 0Ω for a 3-phase 3-wire circuit. Since leakage monitoring is performed under the condition of balance, there is a large error in leakage current measurement when the ground resistance of the electrical circuit is high or the ground capacitance is unbalanced, which may result in false alarms or no alarms.

The method described in Patent Document 2 is applicable even when the ground capacitance of a three-phase three-wire circuit is unbalanced by using not only the fundamental wave component but also the fifth harmonic component. If the resistance is high, the leakage current measurement error will be large. Further, since the harmonic components have large fluctuations, it is difficult to reduce the leakage current measurement error by simply using the harmonic components, and improvements are needed.

In addition, when comparing a balanced line and an unbalanced line, if all waveforms at the commercial frequency of line voltage, phase voltage, ground voltage, line current, and zero-sequence current match completely, it is possible to distinguish between the two. Therefore, there is a problem that the leakage current value cannot be measured.

The present invention has been made to solve the above problems, and it is possible to accurately determine leakage current caused by ground insulation resistance, regardless of the degree of unbalance of the ground capacitance of the electrical circuit to be measured or the presence or absence of ground resistance. The purpose is to provide an insulation monitoring device that is capable of

In order to solve the above problems, an insulation monitoring device according to the present invention is an insulation monitoring device that monitors leakage current caused by the insulation resistance to ground of a three-phase three-wire system or a single-phase three-wire system to be measured, voltage R-phase capturing means for capturing an R-phase voltage waveform with reference to the S-phase or N-phase as a reference; voltage T-phase capturing means that captures a T-phase voltage waveform with the S-phase or the N-phase as a reference; A zero-sequence current capturing means that captures a zero-sequence current waveform of the ground phase of the electric circuit, and a zero-sequence current capturing means that captures leakage caused by the ground insulation resistance based on the R-phase voltage waveform, the T-phase voltage waveform, and the zero-phase current waveform. leakage current value calculating means for calculating a current value, the leakage current value calculating means calculating a fundamental wave and a plurality of odd-order harmonics of the R-phase voltage waveform, the T-phase voltage waveform, and the zero-phase current waveform. Based on the components, a plurality of circuit equations regarding the sine component and cosine component of the zero-sequence current are determined, and the ground insulation resistance value of the R phase and the T phase are calculated by matrix calculation of simultaneous equations constituted by the plurality of circuit equations. The earth insulation resistance values are calculated from the R phase earth insulation resistance value, the T phase earth insulation resistance value, the R phase voltage effective value, and the T phase voltage effective value. The present invention is characterized in that the leakage current value caused by the leakage current value is determined.

According to the present invention, even when the ground capacitance of each phase of the electrical path to be measured is unbalanced or the ground resistance is high, leakage current can be determined with high accuracy. Therefore, false alarms and non-alarms in insulation monitoring can be prevented.

In the present invention, the leakage current value calculation means performs a Fourier transform on the R-phase voltage waveform, the T-phase voltage waveform, and the zero-phase current waveform to calculate the R-phase voltage, the T-phase voltage, and the zero-phase current waveform. It is preferable to obtain a sine component and a cosine component of each of the plurality of odd harmonic components of the zero-sequence current. According to the present invention, it is possible to easily generate a plurality of circuit equations necessary for calculating a leakage current value.

In the present invention, it is preferable that the leakage current value calculating means calculates eight or more of the circuit equations. Thereby, it is possible to suppress the influence of harmonic fluctuations and obtain the leakage current value with high accuracy.

The leakage current value calculation means applies a maximum likelihood estimation method to the matrix calculation of the simultaneous equations composed of the eight or more circuit equations, and calculates a maximum likelihood solution of the R-phase ground insulation resistance value and the T-phase It is preferable to find the maximum likelihood solution of each ground insulation resistance value. Thereby, it is possible to minimize the influence of harmonic fluctuations and obtain the leakage current value with high accuracy.

Preferably, the leakage current value calculating means applies ridge regression to the maximum likelihood solution obtained by the maximum likelihood estimation method to obtain the R-phase ground insulation resistance value and the T-phase ground insulation resistance value, respectively. This makes it possible to minimize the influence of harmonic fluctuations and obtain a stable leakage current value.

Preferably, the plurality of odd harmonic components are a fifth harmonic, a seventh harmonic, and a ninth harmonic, and the number of the plurality of circuit equations is eight. Since the third harmonic is the odd harmonic closest to the fundamental wave, the harmonic has a strong influence on the fundamental wave distortion generated in the current transformer and circuit that constitute the zero-sequence current sensor, and the accuracy of the leakage current value is affected. By influencing. Furthermore, the reason why there are no even-order harmonics or odd-order harmonics after the 11th order is that the waveform obtained from the electrical circuit under test is small and it is difficult to obtain accuracy.

Preferably, the matrix calculation includes a weighting matrix in which the fundamental wave is weighted at 1 and the odd harmonics are weighted at less than 1. The effective value and phase difference of each harmonic do not remain constant, and the magnitude of fluctuation varies depending on the order of the harmonic. However, when the harmonics are weighted, the measurement accuracy of the leakage current value can be improved.

It is preferable to further include a notification means for notifying the leakage current value or an alarm based on the leakage current value. This allows the monitoring results to be reported to the monitoring staff.

According to the present invention, there is provided an insulation monitoring device that can accurately determine leakage current caused by insulation resistance to ground, regardless of the degree of unbalance of ground capacitance of the electrical circuit to be measured or the presence or absence of ground resistance. With the goal.

FIG. 1 is a block diagram showing a schematic configuration of an insulation monitoring device according to an embodiment of the present invention. FIG. 2 is a detailed block diagram of the insulation monitoring device. FIG. 3 is an explanatory diagram of a method for calculating leakage current in a measured electrical circuit by the insulation monitoring device. FIG. 4 is an equivalent circuit diagram of the electrical circuit to be measured when the S-phase ground insulation resistance is treated as a high resistance value.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a schematic configuration of an insulation monitoring device according to an embodiment of the present invention. Moreover, FIG. 2 is a detailed block diagram of the insulation monitoring device.

As shown in FIGS. 1 and 2, the insulation monitoring device 1 according to the present embodiment monitors a three-phase, three-wire (or single-phase, three-wire) electrical circuit 2 to be measured. A voltage R-phase capturing means 10 is connected to the line 2S of the N-phase) and the line 2R of the R-phase, and captures the voltage waveform _vR of the R-phase with the S-phase (or N-phase) as a reference; ) is connected to the line 2S of the T-phase and the line 2T of the T-phase, and a voltage T-phase capturing means 20 that captures the voltage waveform _vT of the T-phase with the S-phase (or N-phase) as a reference, and a magnetic A zero-phase current capturing means 30 that captures the zero-phase current waveform _iO of the ground phase of the electrical circuit under test 2 via the coupled zero-phase current sensor ZCT, a voltage R-phase capturing means 10, and a voltage T-phase capturing means. 20, and the fundamental wave and harmonic components of the output waveform of the zero-sequence current acquisition means 30, and calculate the simultaneous equations of the voltage and current of the circuit under test 2 created for each frequency component to determine the cause of the ground insulation resistance. The leakage current value calculation means 40 calculates the effective value Ior of the leakage current, and the notification means 50 reports the leakage current value or an alarm based on the leakage current value.

The insulation monitoring device 1 extracts a resistive ground fault current component i _Or from the zero-sequence current i _O detected by the zero-sequence current sensor ZCT, and monitors the insulation of the electrical circuit under test 2 . The leakage current of the circuit under test 2 includes a ground fault current i OC caused by the ground capacitance C _R , C _S , _CT of each phase and a ground fault current i _OC caused by the ground insulation resistance R _R , R _S , _RT of each phase. Although the ground fault current i _Or is included, the cause of electric leakage fires, etc. is a decrease in the ground insulation resistances R _R , R _S , _RT , so the insulation monitoring device 1 measures the ground insulation resistances R _R , R _S , _RT Monitor the ground fault current i _Or caused by

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

The voltage T-phase acquisition means 20 has the same circuit configuration as the voltage R-phase acquisition means 10 described above. That is, the voltage T-phase acquisition means 20 includes a primary power input section 21 in which a transformer, a protection circuit, etc. are mounted, a filter section 22 in which an LPF for extracting the fundamental wave is mounted, and an analog waveform of the fundamental wave. an A/D section 23 that converts the harmonic into a digital waveform, a filter section 24 equipped with an HPF and an LPF for extracting harmonics, and an A/D section 25 that converts the analog waveform of the harmonic into a digital waveform. It is equipped with

The zero-phase 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 includes a current input section 31 instead of the primary power supply input sections 11 and 21. have. That is, the zero-sequence current acquisition means 30 includes a current input section 31 equipped with an IV conversion section that converts the current of the zero-phase current sensor ZCT into a voltage, and a filter section equipped with an LPF for extracting the fundamental wave. 32, an A/D section 33 that converts the analog waveform of the fundamental wave into a digital waveform, a filter section 34 that is equipped with an HPF and an LPF for extracting harmonics, and converts the analog waveform of the harmonics into a digital waveform. It also includes an A/D section 35 for conversion.

The leakage current value calculation means 40 includes a coefficient matrix setting section 41 that sets a coefficient matrix based on the fundamental wave and harmonic components of the voltage waveform and current waveform of each phase, and a coefficient matrix setting section 41 that sets a coefficient matrix based on the fundamental wave and harmonic components of the voltage waveform and current waveform of each phase, and a coefficient matrix setting section 41 that sets a coefficient matrix based on the ground insulation resistance and ground capacitance of each phase. a constant term vector setting section 42 that sets a constant term based on the above, a weight matrix setting section 43 that sets a weight matrix for each harmonic, and a matrix calculation section 44 that calculates a leakage current value I _Or by calculating a matrix equation. We are prepared. Although not particularly limited, the notification means 50 includes a server output 51 for remotely notifying the calculated leakage current value, a monitor output 52 for displaying the leakage current value using a tool such as a PC, and an insulation monitoring device. It is equipped with a 7-segment display output 53 for checking the leakage current value on the main body, and a lamp output 54 for notifying that the leakage current value exceeds a threshold value.

Next, with reference to FIG. 3, a method of calculating the leakage current _Ior of the electrical circuit under test 2 using the insulation monitoring device 1 will be described.

Since harmonics occurring in the electric circuit are used, each waveform can be defined as shown below in FIG. The subscript k represents the fundamental wave (commercial frequency) when k=1, the 5th harmonic when k=5, and the 7th harmonic when k=7. As a general term, the fundamental wave and the k-th harmonic will be hereinafter expressed as the k-th frequency. Furthermore, the currents i _oc and i _or without subscripts represent fundamental wave currents.

V _Rk : Voltage R phase effective value, V _Tk : Voltage T phase effective value, β _Rk : Theoretical phase of voltage R phase, β _Tk : Theoretical phase of voltage T phase, α _Rk : Specific voltage R phase α _Tk : Defining the phase error inherent in the voltage T phase, the voltage waveforms v Rk and v _Tk of the R phase and _T phase of the k-th frequency are as follows.

Further, the current waveforms i _Rk , i _Sk , i _Tk of the R phase, S phase, and T phase of the k-th frequency are as follows.

Furthermore, the zero-sequence current i _Ok at the k-th frequency can be expressed as follows.

These formulas (1) to (6) can be summarized as follows.

Next, when the measurable voltage and current waveforms are Fourier transformed, they become as follows.

By substituting these into the original equation, the following two relational equations are obtained.

If the harmonic order k=1 (fundamental wave), the number of equations is insufficient for the number of unknown parameters, so the unknown parameters cannot be found unless conditions are given. Therefore, by increasing the number of equations by setting k=1,5,7,9, the following eight equations will be created.

For the solution of r(1/R _R +1/R _S +1/R _T ), the vector (I _C1 , I _S1 , I _C5 , I _S5 , I _C7 , I _S7 , I _C9 , I _S9 )' is Since they are parallel, the solution becomes obvious and does not depend on the measured value, and a normal solution cannot be found. (Here, the prime sign "'" means the transposition of the matrix.) In other words, it is shown that the S-phase ground insulation resistance cannot be determined theoretically using the Ior method.

ここで、a, b, c, dは測定値とし、x, yは求める解とする。この解は、x=0 , y=-1となるが、明らかにa , b , c , dの値とは無関係に成立している。したがって、r(1/R_R+1/R_S+1/R_T)は正常に求まらないため、以降はr(1/R_R+1/R_S+1/R_T)=0と近似する。実際、接地抵抗より対地絶縁抵抗のほうが十分に大きいのでゼロ近似の影響は少ないと言える。 For example, a simple example is the following simultaneous equations.

Here, a, b, c, and d are measured values, and x and y are the solutions to be obtained. This solution becomes x=0, y=-1, but it clearly holds true regardless of the values of a, b, c, and d. Therefore, r(1/R _R +1/R _S +1/R _T ) cannot be found correctly, so from now on, r(1/R _R +1/R _S +1/R _T )=0. Approximate. In fact, since the ground insulation resistance is sufficiently larger than the ground resistance, it can be said that the influence of zero approximation is small.

Next, as an Ior method calculation method using harmonics, a method in which the ground insulation resistance of the ground phase is treated as a high resistance will be described.

FIG. 4 shows an equivalent circuit when the S-phase ground insulation resistance R _S of the electrical circuit under test 2 is treated as a high resistance value. As mentioned above, the subscript k represents the fundamental wave (commercial frequency) when k=1, the 5th harmonic when k=5, and the 7th harmonic when k=7. Hereafter, the fundamental wave and harmonics will be collectively expressed as the k-th frequency. Also, currents ioc and ior without subscripts indicate fundamental wave currents.

Therefore, the above eight equations become as follows.

The following five unknown parameters can be set.

The reason why there are 8 equations for 5 unknown parameters is that harmonics constantly fluctuate compared to the fundamental wave, and it is necessary to find an average solution. In addition, since there is no third harmonic, it is the odd harmonic closest to the fundamental wave, so the harmonics have a strong influence on the fundamental wave distortion generated in the current transformer and circuit that make up the zero-phase current sensor, resulting in poor accuracy. By influencing. Further, the reason why there are no even harmonics or odd harmonics after the 11th order is because the harmonics obtained from the electric circuit are small and it is difficult to obtain precision.

The above eight equations can be expressed as a matrix and vector as follows.

のように最尤解を得ることができる。ここでプライム記号「'」は行列の転置を意味する。この最尤解は不偏推定量でありクラメール・ラオの下限に達していることから、分散は最小化される。つまり、揺らぎの度合いは理論上最小となる。 This equation becomes a multiple regression model under the condition that the error follows a normal distribution, and when the maximum likelihood estimation method is performed,

The maximum likelihood solution can be obtained as follows. Here, the prime sign "'" means transposition of the matrix. This maximum likelihood solution is an unbiased estimator and reaches the Cramer-Rao lower bound, so the variance is minimized. In other words, the degree of fluctuation is theoretically minimum.

のように対地静電容量の平衡不平衡によらず、対地絶縁抵抗に起因した漏洩電流実効値を得ることができる。 Multiplying 1/R _R and 1/R _T obtained in this way by the effective voltage value, we get

As shown in the figure, it is possible to obtain the effective value of the leakage current caused by the ground insulation resistance, regardless of the balance/unbalance of the ground capacitance.

のように最尤解を得ることができる。L2正則化パラメータλは十分な数のフィールドデータから教師データを得て決められる学習パラメータのことである。 Next, the application of ridge regression will be explained. When ridge regression is applied to the above maximum likelihood solution, using the L2 regularization parameter λ and the identity matrix I,

The maximum likelihood solution can be obtained as follows. The L2 regularization parameter λ is a learning parameter determined by obtaining training data from a sufficient number of field data.

The reason for applying ridge regression is to obtain a stable leakage current value. Depending on the effective value and phase pattern of voltage and current at each frequency, |A'A| may be close to 0. This means that the denominator is close to 0, so it will give unstable results. Therefore, by using the L2 regularization parameter of ridge regression, stability can be achieved by preventing the denominator from becoming 0.

For example, in a single-phase three-wire electric circuit, the voltage phase difference between the RN phase and the TN phase is 180°, but if not only the fundamental wave but also each harmonic is close to the ideal environment of 180°, multiple regression can be used. Multicollinearity may occur in the application and affect accuracy. To prevent this, L2 regularization parameters are used to improve accuracy.

If not only the fundamental wave but also each harmonic wave is 180°, stability cannot be obtained even if the above ridge regression is applied unless the L2 regularization parameter λ is increased. However, if the L2 regularization parameter λ is made too large, a phenomenon occurs in which it deviates from the true value. In order to solve this problem, if we set the preconditions that each voltage phase difference is 180° and that 1/R _R -1/R _T and ωC _R -ωC _T are each one unknown parameter, we can do the following.

By doing this, the phenomenon of multicollinearity is eliminated and significant stability can be obtained as a method that takes into account the unbalance between ground resistance and ground capacitance.

これを重み行列として、この各成分平方根をとった行列をAとbにそれぞれ左から掛けると、以下のように表すことができる。

The effective value and phase difference of each harmonic do not remain constant compared to the fundamental wave, and the fluctuations are large, so harmonics are weighted to improve accuracy. The weighting method can be defined as follows. Since the fundamental wave has higher accuracy than the harmonics, the weight is fixed at 1.

By using this as a weight matrix and multiplying A and b from the left by a matrix obtained by taking the square root of each component, it can be expressed as follows.

で表し、

のように更新する。分母は最新m周期分の平均を意味する。 For example, the following method (Neyman distribution method) can be used to determine each component of the weight matrix. The time expression of the current cosine value and current sine value of each harmonic is

Represented by

Update like this. The denominator means the average of the latest m cycles.

のように標本標準偏差を算出する。

Calculate the sample standard deviation as follows.

のようにすれば、揺らぎが大きい高調波成分の重み付けが小さくなり、安定している高調波の重み付けを大きくして、より良い高調波を演算に反映させることができる。

By doing this, the weighting of harmonic components with large fluctuations is reduced, and the weighting of stable harmonics is increased, so that better harmonics can be reflected in calculations.

Regarding the calculation method for the ground capacitance of the R phase and T phase, since ωC _R and ωC _T can be determined, the ground capacitance itself can also be found, and it is also possible to evaluate the degree of unbalance.

Regarding the calculation method for the ground capacitance of the S phase, if the ground resistance r is known by measuring the ground voltage, r _RST = rω(C _R +C _S +C _T ) can be found, and C _S = r _RST Since /rω-C _R -C _T , it is also possible to find the ground capacitance of the S phase.

As explained above, the insulation monitoring device 1 according to the present embodiment calculates the leakage current value caused by the ground insulation resistance based on the R-phase voltage waveform, the T-phase voltage waveform, and the zero-sequence current waveform. The leakage current value calculating means 40 calculates the zero-phase value regarding the ground capacitances C _R , C _T , and C _S based on the R-phase voltage waveform, the T-phase voltage waveform, and the zero-sequence current waveform. A plurality of circuits related to the fundamental wave and the 5th, 7th, and 9th harmonic components of the current, and the fundamental wave and the 5th, 7th, and 9th harmonic components of the zero-sequence current caused by the earth insulation resistances R _R and R _T Find the equation, and calculate the R-phase ground insulation resistance value R _R and the T-phase ground insulation resistance value R _T by matrix calculation of simultaneous equations composed of multiple circuit equations, and calculate the R-phase ground insulation resistance value R _R , find the effective value Ior of the leakage current due to the earth insulation resistance R _R and RT from the T-phase earth insulation resistance value _R T , the R-phase voltage effective value _VR1 , and the _T -phase voltage effective value V _T1 Therefore, regardless of the degree of unbalance of the ground capacitances C _R , _CT , and _CS of the circuit under test 2 and the presence or absence of the ground resistance r, the leakage current caused by the ground insulation resistances R _R and R _T can be determined with high accuracy. be able to.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention. Needless to say, it is included within the scope.

1 Insulation monitoring device 2 Electrical circuit to be measured 2R R-phase line 2S S-phase line 2T T-phase line 4S S-phase grounding line 10 Voltage R-phase intake 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 acquisition 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-phase 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 section 43 Weight matrix setting section 44 Matrix calculation section 50 Notification means 51 Server output 52 Monitor output 53 7 segment display output 54 Lamp output ZCT Zero phase current sensor

Claims (8)

An insulation monitoring device that monitors leakage current caused by insulation resistance to ground of a three-phase three-wire or single-phase three-wire electrical circuit to be measured,
Voltage R-phase capturing means for capturing an R-phase voltage waveform with the S-phase or N-phase as a reference;
Voltage T-phase capturing means for capturing a T-phase voltage waveform with the S-phase or the N-phase as a reference;
zero-sequence current capturing means for capturing a zero-sequence current waveform of the ground phase of the electrical circuit under test;
Leakage current value calculation means for calculating a leakage current value due to the earth insulation resistance based on the R-phase voltage waveform, the T-phase voltage waveform, and the zero-sequence current waveform,
The leakage current value calculation means includes:
A plurality of circuit equations regarding the sine component and cosine component of the zero-phase current are calculated based on the R-phase voltage waveform, the T-phase voltage waveform, the fundamental wave and the plurality of odd-order harmonic components of the zero-phase current waveform. seek,
Determining the ground insulation resistance value of the R phase and the ground insulation resistance value of the T phase by matrix calculation of simultaneous equations constituted by the plurality of circuit equations, respectively;
The leakage current value due to the ground insulation resistance is determined from the R-phase ground insulation resistance value, the T-phase ground insulation resistance value, the R-phase voltage effective value, and the T-phase voltage effective value. An insulation monitoring device characterized by: The leakage current value calculating means calculates the R-phase voltage, the T-phase voltage, and the zero-sequence current by Fourier transforming the R-phase voltage waveform, the T-phase voltage waveform, and the zero-sequence current waveform. The insulation monitoring device according to claim 1, wherein a sine component and a cosine component of each of the plurality of odd harmonic components are determined. 3. The insulation monitoring device according to claim 2, wherein the leakage current value calculating means calculates eight or more of the circuit equations. The leakage current value calculation means applies a maximum likelihood estimation method to the matrix calculation of the simultaneous equations composed of the eight or more circuit equations, and calculates a maximum likelihood solution of the R-phase ground insulation resistance value and the T-phase 4. The insulation monitoring device according to claim 3, wherein a maximum likelihood solution of each of the ground insulation resistance values is obtained. 5. The leakage current value calculation means applies ridge regression to the maximum likelihood solution obtained by the maximum likelihood estimation method to obtain the R-phase ground insulation resistance value and the T-phase ground insulation resistance value, respectively. insulation monitoring device. Any one of claims 1 to 5, wherein the plurality of odd harmonic components are a fifth harmonic, a seventh harmonic, and a ninth harmonic, and the number of the plurality of circuit equations is eight. Insulation monitoring device described in . The insulation monitoring device according to any one of claims 1 to 5, wherein the matrix calculation includes a weighting matrix that gives a weight of 1 to the fundamental wave and a weight of less than 1 to the odd harmonics. The insulation monitoring device according to any one of claims 1 to 5, further comprising a notification means for notifying the leakage current value or an alarm based on the leakage current value.

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