JP7070680B2 - Measuring equipment and method - Google Patents

Description

The present invention relates to a measuring device and a method.

A technique is used in which a sensor installed on a distribution board monitors power consumption and current consumption waveforms, and estimates the power consumption and operating state of each electric device based on its characteristics. In order to compare and analyze the current waveform in time series, it is necessary to measure the current waveform based on the phase of the voltage. When measuring the current waveform, it is preferable to accurately grasp the phase delay with respect to the voltage waveform. It is known that when the phase delay with respect to the voltage waveform is inaccurate, the calculation cost for estimating the current waveform increases, and the estimation accuracy also decreases, which makes it impractical.

Therefore, as shown in FIG. 12, it is desirable to measure the current and the voltage at the same time. FIG. 12 schematically shows an example of a power measurement system in a three-phase four-wire connection. The current waveform and voltage waveform are monitored by an ammeter 101 and a voltmeter 102 installed in a breaker 105 of a distribution board that supplies electric power to a load 104 of an electric device or the like. Generally, as the ammeter 101, a non-contact type sensor such as a CT (Current Transformer) is used. In CT, for example, an alternating current (secondary current) corresponding to the turns ratio flows in the winding on the secondary side so as to cancel the magnetic flux generated in the magnetic core due to the alternating current flowing in the conductor (primary side), and this 2 Measure the voltage (proportional to the current flowing through the conductor) generated across the resistor by the next current. The ammeter 101 may be connected to the main trunk of the distribution board instead of the branch wiring. FIG. 13 is a diagram showing an example of a three-phase four-wire current waveform I1, I2, I3 and a voltage waveform V1, V2, V3 to a load 104 measured by an ammeter 101 and a voltmeter 102.

When the line voltage is measured by the voltmeter 102 as in the example of FIG. 12, it is difficult to measure the line voltage without touching the power supply wiring, that is, without contact and with high accuracy. Installation of the voltage measurement cable requires construction by an electrician. Although it is possible to obtain voltage information by measuring the voltage of the wiring network, distribution boards generally do not have a power outlet, and new construction work is required for measurement with a voltmeter. ..

For the problem of voltage sensor installation in a distribution board, a method of acquiring a current waveform in synchronization with a voltage waveform by a non-contact type voltage / current sensor using a stray capacitance generated between an electric wire and the sensor is known. (Patent Document 1).

In Patent Document 1, it is possible to measure the current waveform in synchronization with the voltage waveform, but the stray capacitance changes depending on the thickness and material of the wire and the mounting method, and the phase delay after the sensor is installed. It is stated that the value is constant, but the value varies depending on the installation environment. Further, there is a problem that it is difficult to know from only the non-contact measurement result because the phase delay between the current waveform and the voltage waveform is environment-dependent. To solve this problem, Patent Document 1 describes a voltage / current phase delay estimation device for estimating a phase delay between a voltage waveform and a current waveform using a non-contact type voltage / current sensor, and a method thereof. It has been disclosed. In Patent Document 1, the power factor of the measured current waveform and the voltage waveform having a phase delay is calculated, and the phase delay at which the power factor is maximized is estimated as the true value. As described above, in Patent Document 1, the voltage waveform and the current waveform are measured by using the non-contact type voltage sensor and the current sensor, and the phase delay between them is estimated.

Japanese Unexamined Patent Publication No. 2016-0334888

In order to compare and analyze the current waveform in time series, it is necessary to measure the current waveform based on the phase of the voltage.

As mentioned above, in order to measure the voltage on the distribution board, it is necessary to have a qualified person (electrical work) to install the voltage measurement cable.

In addition, distribution boards often do not have power outlets, which requires new construction.

The present invention has been devised in view of the above problems, and an object of the present invention is to provide an apparatus and a method capable of analyzing a measured current waveform without measuring a voltage.

According to one embodiment of the present invention, a device having a predetermined current pattern that appears in synchronization with the current frequency is connected to the power supply line from the distribution board.
It is characterized by being provided with a means for detecting the predetermined current pattern from the current waveform measured by the current meter for measuring the current in the distribution board and acquiring the phase information of the voltage in the distribution board. Measuring equipment is provided.

According to the present invention, a device having a predetermined current pattern that appears in synchronization with the current frequency is connected to the power supply line from the distribution board.
Measure the current in the distribution board with an ammeter and
A measuring method is provided in which a predetermined current pattern is detected from a current waveform measured by an ammeter, and phase information of a voltage in the distribution board is acquired.

According to the present invention, it is possible to analyze the measured current waveform without measuring the voltage.

(A) and (B) are diagrams illustrating exemplary embodiments 1 and 2 of the present invention. It is a figure explaining the exemplary Embodiment 1 of this invention. It is a figure explaining the exemplary Embodiment 1 and 2 of this invention. It is a figure explaining the structure of the modification of Embodiments 1 and 2 of this invention. It is a figure explaining the application example to the three-phase four-wire system of Embodiments 1 and 2 of this invention. It is a figure explaining the output in a measuring device. It is a figure explaining the exemplary Embodiment 2 of this invention. It is a figure explaining the exemplary Embodiment 2 of this invention. It is a figure explaining the structure of Embodiment 3 of this invention. It is a figure explaining the exemplary Embodiment 3 of this invention. (A), (B), and (C) are diagrams illustrating an exemplary embodiment 3 of the present invention. It is a figure explaining an example of a power measurement system. It is a figure explaining an example of a power measurement system.

An embodiment of the present invention will be described with reference to the drawings.

<Embodiment 1>
FIG. 1 is a diagram illustrating an exemplary embodiment 1 of the present invention. FIG. 1A shows an example of a single-phase two-wire connection for ease of explanation. Referring to FIG. 1A, a non-contact ammeter 101 such as a CT (Current Transformer) detects, for example, an alternating current flowing in a power supply line from an alternating current power supply 103, and uses the alternating current as a terminal of, for example, a resistor. It is supplied to the measuring device 110 as an intercurrent voltage. In FIG. 1A, the ammeter 101 detects the current of the power supply line 106-1 of the breaker 105 of the distribution board in a non-contact manner.

A device (device) 200 having a current consumption characteristic of a predetermined pattern that appears in synchronization with the current frequency is connected to the power outlet 107 connected to the power supply line 106-2 downstream of the breaker 105. That is, by connecting (inserting) the power plug 201 of the device 200 to the power outlet 107, the device 200 is connected to the power line 106-2.

Although not particularly limited, the device 200 may be configured by an inverter or the like as shown in FIG. 1 (B). In FIG. 1B, the switching elements S1-S4 may be IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors). A load element is connected to the connection point between the switching elements S1 and S2 and the connection point between the switching elements S3 and S4. When the switching elements S1 and S4 are turned on at the same time, the switching elements S2 and S3 are turned off, a current flows from the direct current power supply ( _VDC ) in the directions of the switching elements S1, the load, and the switching element S4, and the switching elements S2 and S3 Are turned on at the same time, the switching elements S1 and S4 are turned off, and a current flows from the direct current power supply ( _VDC ) in the directions of the switching element S3, the load, and the switching element S2. In FIG. 1B, an AC (Alternate Current) -DC (Direct Current) converter or the like that converts an AC power source to a direct current power source ( _VDC ) is omitted. Although not particularly limited, the device 200 may be composed of a self-excited converter (inverter) that does not consume reactive power, an inductor element, a capacitor element, or the like. The device 200 synchronizes with the power frequency (50 Hz (Hertz) / 60 Hz) of the AC power supply 103, stores power at a predetermined timing, releases the stored power at another timing, and returns it to the AC power supply 103. It may be configured. As the current pattern of the device 200, the closer the power factor is to 0, the more the power consumption can be suppressed.

FIG. 2 is a diagram illustrating the operation of the first embodiment. In FIG. 2, the waveform 141 is an AC voltage waveform on the distribution board. The waveform 142 is a current waveform measured by the ammeter 101 (current waveform measured by the distribution board). 143 and 144 represent a predetermined current pattern in the device 200 that appears in synchronization with the current frequency. The current patterns 143 and 144 appear in the phases θa and θb from the start point of the AC current cycle, and are superimposed on the current consumption of the load 104. The pattern of the current waveform consumed by the device 200 at a predetermined timing in synchronization with the current frequency is arbitrary, such as a sine wave, a square wave, or a triangular wave, but it can be discriminated by superimposing it on the current consumption of the load 104. An isolated pattern is preferred. It should be noted that at least one current pattern peculiar to the device 200 may be arranged per cycle of the AC power supply cycle. As described above, the closer the power factor is to 0 as the current pattern 143 and 144, the more the power consumption can be suppressed.

The measuring device 110 detects the current patterns 143 and 144 of the device 200 from the current waveform 142 on the distribution board measured by the ammeter 101.

The current patterns 143 and 144 unique to the device 200 are in phase synchronized with the alternating current period and are periodic. Therefore, the current patterns 143 and 144 are in phase with each other with respect to the AC voltage cycle. From the current pattern 143 (144), the start point of the AC current cycle is calculated, and the AC voltage waveform 141 on the distribution board (breaker 105) is obtained (estimated). The appearance timing of the current pattern peculiar to the device 200 may be measured in advance by a measuring device (not shown) and stored in a storage unit (not shown) of the measuring device 110.

FIG. 3 is a diagram illustrating the configuration of the first embodiment. In the current meter 101, an alternating current (secondary current) corresponding to the turns ratio is applied to the winding on the secondary side so as to cancel the magnetic flux generated in the magnetic core 1011 due to the alternating current flowing in the power supply line 106 (primary side). The current flows, and the voltage generated across the resistor RL by this secondary current is output as the detected current. In the measuring device 110, the amplifier 111 amplifies the voltage (AC voltage) between the terminals of the resistor RL. The analog digital converter (ADC) 112 converts the voltage from the amplifier 111 into a digital signal.

The current pattern detection unit 113 analyzes the digital signal from the ADC 112, detects the current pattern peculiar to the device 200, and acquires the timing information thereof. That is, the current pattern detection unit 113 calculates the position in one cycle (360 degrees) of the current waveform of the current pattern peculiar to the device 200. It is assumed that the delay (phase) of the AC voltage waveform from the zero crossing point is known for the current pattern peculiar to the device 200 (may be configured to be measured in advance and stored and set in the measuring device 110). That is, the appearance timing information (delay, phase information) in the AC current cycle of the current patterns 143 and 144 is measured in advance and stored in the measuring device 110.

The phase detection unit 114 calculates the start point of the alternating current cycle based on, for example, the timing information (phase information) of the appearance of the detected current pattern 143 (144), and the alternating current and the unmeasured distribution board. Estimate the phase difference of the AC voltage waveform in. In this case, the AC voltage may be generated with the start point of the AC current cycle as the start point (zero cross point) of the AC voltage cycle (phase difference is 0). Alternatively, the AC voltage waveform that maximizes the power factor may be calculated for the AC current waveform for which the start point of the cycle has been calculated, and the phase difference from the AC current waveform may be obtained. According to this embodiment, the AC voltage can be estimated without measuring the AC voltage, and the AC current waveform synchronized with the AC voltage can be analyzed.

FIG. 4 is a diagram illustrating a modified example of the first embodiment. In the modified example of FIG. 4, in addition to the configuration of FIG. 3, a voltage generation unit 115 that generates an AC voltage having a calculated phase difference is provided. The voltage generation unit 115 generates and outputs a voltage waveform (digital signal waveform) having a phase difference detected by the phase detection unit 114 with respect to the current waveform acquired by the ammeter 101. The voltage generation unit 115 may generate an AC voltage waveform that maximizes the power factor. The current waveform is output by delaying the digital signal from the ADC 112 by the delay circuit 116. The delay circuit 116 has a delay time corresponding to the processing delay in the current pattern detection unit 113, the phase detection unit 114, and the voltage generation unit 115. The voltage generation unit 115 may be configured to output a voltage converted into an analog signal by a digital-to-analog converter. In this case, the current waveform may be configured to be output from the output of the amplifier 111 via the delay circuit 116. According to the first embodiment, the measuring device 110 is configured as a battery-powered device.

FIG. 5 is a diagram showing an example of a three-phase four-wire current measurement system. In FIG. 5, non-contact ammeters 101-1 to 101-3 are arranged on the power supply lines L1, L2, and L3 of the three-phase power supply, and the current waveforms Ii are generated from the measuring devices 110-1 to 110-3. (I = 1 to 3) and the voltage waveform Vi (i = 1 to 3) phase-synchronized with the current waveform Ii are output.

FIG. 6 shows a three-phase current waveform Ii (i = 1 to 3) output from the measuring devices 110-1 to 110-3 and a three-phase voltage waveform generated by the measuring devices 110-1 to 110-3. Vi (i = 1 to 3) is shown.

According to this embodiment, it is possible to analyze the measured current waveform without measuring the AC voltage. According to this embodiment, it is possible to calculate (estimate) the AC voltage from the measured current waveform without measuring the AC voltage, and it is possible to measure the current at the timing synchronized with the AC voltage. The embodiment for enabling the analysis of the measured current waveform without measuring the voltage is not limited to the above, and the following method can also be applied.

<Embodiment 2>
An exemplary embodiment 2 of the present invention will be described. The basic configuration is the same as in FIG. 1 (A). However, in the first embodiment, the device 200 connected to the power outlet 107 is configured to output a predetermined current pattern at a timing synchronized with the alternating current cycle, whereas in the second embodiment, the device 200 is connected to the power outlet 107. The connected device 200 consumes current in a desired pattern in synchronization with the AC voltage frequency. The device 200 may be an inverter or the like. Alternatively, the device 200 may be a self-excited converter (inverter or the like) that does not consume reactive power, an inductor element, a capacitor element, or the like. Similar to the first embodiment, the desired current pattern is such that the power factor is closer to 0, the power consumption can be suppressed.

FIG. 7 is a diagram illustrating the operation of the second embodiment. In FIG. 7, the waveform 131 is a voltage waveform (AC voltage waveform) supplied to the distribution board from the power supply 103. The waveform 132 is a current waveform measured by an ammeter 101. Reference numeral 133 and 134 represent a current pattern having a predetermined shape in the device 200 that appears at the timing synchronized with the AC voltage waveform 131. In the second embodiment, the current patterns 133 and 134 appear in the phases θa and θb from the start point of the AC voltage cycle. The pattern of the current waveform consumed by the device 200 in synchronization with the phase of the voltage is arbitrary, such as a sine wave, a square wave, or a triangular wave, but an isolated pattern that can be discriminated by superimposing it on the current consumption of the load 104 is preferable. .. It should be noted that at least one current pattern peculiar to the device 200 may be arranged per cycle of the AC power supply cycle.

The measuring device 110 detects the current pattern of the device 200 from the current waveform on the distribution board measured by the current meter 101, and from the current pattern, the phase information of the AC voltage on the distribution board (breaker 105) ( (Progress with respect to current) is calculated. The phase difference between the AC voltage at the power outlet 107 in FIG. 1A and the AC voltage at the distribution board is 0.

In FIG. 7, it is assumed that the current patterns 133 and 134 unique to the device 200 are phase-locked with respect to the AC voltage. The current patterns 133 and 134 are periodic. Therefore, by detecting the appearance positions of the current patterns 133 and 134, the AC voltage waveform in the distribution board can be estimated. For example, as shown in FIG. 8, in the case of the measured position (phase) θc of the current pattern 133, it is based on the difference (θa−θc) from the phase θa of the original current pattern 133 from the start point of the AC cycle. , It is possible to estimate the phase difference between the AC voltage waveform and the AC current waveform on the distribution board. As in the first embodiment, the appearance timing of the current pattern peculiar to the device 200 may be measured in advance by a measuring device (not shown) and stored in a storage unit (not shown) of the measuring device 110.

The basic configuration of the measuring device 110 of the second embodiment is the same as that of the first embodiment shown in FIG. Referring to FIG. 4, in the measuring device 110, the amplifier 111 amplifies the voltage between terminals (AC voltage) of the resistor RL through which the current detected by the ammeter 101 flows. The ADC 112 converts the voltage from the amplifier 111 into a digital signal. The current pattern detection unit 113 analyzes the digital signal from the ADC 112, detects the current pattern peculiar to the device 200, and acquires the timing information (phase information) thereof.

It is assumed that the delays (phases θa, θb, etc. in FIG. 7) in the current cycles of the current patterns 133 and 134 are known in advance. That is, it is assumed that the phase information such as the phases θc and θd of the current patterns 133 and 134 in FIG. 8 is measured in advance and set in the measuring device 110.

The phase detection unit 114 has, for example, a current waveform 132 measured by the distribution board and a voltage waveform on the distribution board based on the timing information (phase information) of the appearance of the current pattern 133 (134) of the detected device 200. Calculate the phase difference of 131 (not measured, calculated based on the current waveform 132). According to this embodiment, it is possible to analyze the current waveform synchronized with the AC voltage without measuring the AC voltage.

Also in the second embodiment, as in FIG. 5, the configuration may include a voltage generation unit 115 that generates an AC voltage having a detected phase difference. In this case, the AC voltage waveform that maximizes the power factor may be generated. Further, also in the second embodiment, the measuring device 110 may be configured as a battery-powered device.

<Embodiment 3>
FIG. 9 is a diagram illustrating the configuration of the third embodiment of the present invention. Referring to FIG. 9, in the third embodiment, the device 200 (connected to the power outlet) of FIG. 1 (A) is deleted. The measuring device 110 Fourier transforms the current waveform acquired by the ammeter 101 and converts it into a frequency domain. Then, the measuring device 110 adjusts the entire phase component so that the AC power supply frequency component becomes 0 with respect to the phase component of the frequency spectrum, and inverse Fourier Transforms the frequency spectrum obtained by adjusting the entire phase component. The current waveform in the time region is acquired, and the current waveform (I) is output. In the following, the Fast Fourier Transform (FFT) is used as the Fourier transform, but the Discrete Fourier Transform (DFT) may be used.

FIG. 10 is a diagram illustrating the configuration of the third embodiment. Referring to FIG. 10, in the current meter 101, an alternating current corresponding to the turns ratio is applied to the winding on the secondary side so as to cancel the magnetic flux generated in the magnetic core 1011 due to the alternating current flowing in the power supply line 106 (primary side). (Secondary current) flows, and the voltage generated across the resistor RL by this secondary current is output as the value of the detected current. In the measuring device 110, the amplifier 111 amplifies the voltage (AC voltage) between the terminals of the resistor RL. The analog-to-digital converter (ADC) 112 converts the voltage from the amplifier 111 into a digital signal. The FFT calculation unit 117 refers to the digital signal sequence x (0), x (T), x (2T), x ((N-1) T) from the ADC 112 (T is the sampling period, N is the number of sampling points). FFT calculation is performed. If the sampling frequency is Fs, it is given by Fs = 1 / T.

・・・(1)

と表したとき（ｊ^２＝－１）、位相成分は、

・・・(2)
で与えられる。The number of FFT points is N, and the result of FFT calculation of the digital signal sequence x (nT) (n = 0, ..., N-1) (Fourier coefficient): X (ω _k ): ω _k = 2πk / ( In N × T) (k = 0, ..., N-1), it is expressed as X (k). Divide X (k) into real part and imaginary part,

・ ・ ・ (1)

When expressed as (j ² = -1), the phase component is

・ ・ ・ (2)
Given in.

・・・(3)

で与えられる。The amplitude component (gain) is

・ ・ ・ (3)

Given in.

The phase adjusting unit 118 calculates the phase component of the frequency spectrum for each frequency component so that the phase component of the AC power frequency (f ₀ = 50 Hz / 60 Hz) becomes 0.

Specifically, the following is calculated for the AC power frequency (f ₀ = 50 Hz / 60 Hz) and the phase component of the harmonic component thereof.

・・・(4)

（ｉ＝１，・・・，Ｍ，ただし、Ｍ×ｆ_０≦ナイキスト周波数＝Ｆｓ／２）。

···(Four)

(I = 1, ..., M, where M × f ₀ ≤ Nyquist frequency = Fs / 2).

Here, assuming that the AC power frequency f ₀ is q times (f ₀ = q × Fs / N) of 1 / N of the sampling frequency Fs, ψ (i × f ₀ ) in the equation (4) has a coefficient X (ω). _i ): Corresponds to the phase component of ω _i = 2πq × i / (N × T) (i = 1, ..., M, where M ≦ q / 2).

・・・（５）
（ｋ＝０，・・・，Ｎ－１）
に対して、ＩＦＦＴ演算を施して時間領域の波形（時系列データ）に戻す。The IFFT calculation unit 119 is a frequency spectrum in which the AC power frequency (f ₀ ) and the phase component of its harmonic component are adjusted.

... (5)
(K = 0, ..., N-1)
Then, the Fourier operation is performed to return the waveform (time series data) in the time domain.

FIG. 11 is a diagram illustrating the third embodiment. In FIG. 11A, the waveform 131 is an AC voltage waveform supplied to the distribution board from the power supply 103. The waveform 132 is a current waveform measured by an ammeter 101.

The gain 301 and the phase 302 in FIG. 11B are diagrams schematically explaining the result of FFT calculation of the waveform 132 (the gain is given by the equation (3) and the phase is given by the equation (2)).

The gain 301 in FIG. 11 (C) is the same as the gain 301 in FIG. 11 (B). The phase 303 of FIG. 11C schematically shows the result of adjusting the overall phase of the phase 302 of FIG. 11B so that the phase of the power supply frequency component becomes 0. In FIG. 11C, the phase calculation in the above equation (4) is shown for the harmonic frequency component of the AC power supply frequency f ₀ , but it depends on the sampling frequency and is the harmonic of the AC power supply frequency. The phase of the above equation (4) may be calculated for frequencies other than the components. That is, for the phase component of each frequency spectrum below the Nyquist frequency (= Fs / 2), the value obtained by subtracting the phase component of the AC power supply frequency f ₀ may be used as the phase component.

According to the third embodiment, the phase of the AC current is known by shifting the phase of the AC power supply frequency component from the current waveform to a known value (for example, 0) by level-shifting the entire phase component in the frequency region. It can be set to the value of. The FFT calculation unit 117, the phase adjustment unit 118, and the Fourier calculation unit 119 may be realized by a processor such as a DSP (Digital Signal Processor). According to the third embodiment, the measuring device 110 can be configured as a battery-powered device.

It is also possible to generate an AC voltage that maximizes the power factor with respect to the AC current waveform obtained by performing an IFFT calculation on the frequency spectrum in which the phase component of the entire frequency region is adjusted based on the phase component of the AC power supply frequency component. ..

The disclosure of Patent Document 1 described above shall be incorporated into this document by citation. Within the framework of the entire disclosure (including the scope of claims) of the present invention, it is possible to change or adjust the embodiments or examples based on the basic technical idea thereof. Further, various combinations or selections of various disclosure elements (including each element of each claim, each element of each embodiment, each element of each drawing, etc.) are possible within the scope of the claims of the present invention. .. That is, it goes without saying that the present invention includes all disclosure including claims, various modifications and modifications that can be made by those skilled in the art in accordance with the technical idea.

101, 101-1 to 101-3 Ammeter 102 Voltmeter 103 Power supply (AC power supply)
104 Load 105 Breaker 105-1 Main breaker 105-2 Branch breaker 106, 106-1, 106-2 Power line 107 Power outlet 110 Measuring device 111 Amplifier 112 ADC
113 Current pattern detection unit 114 Phase detection unit 115 Voltage generation unit 116 Delay circuit 117 FFT calculation unit 118 Phase adjustment unit 119 IFFT calculation unit 131, 141 Voltage waveform (AC voltage waveform)
132, 142 Current waveform (alternating current waveform)
133, 134, 143, 144 Current pattern 200 device (device)
201 Plug 301 Gain
302, 303 Phase
1011 magnetic core

Claims (6)

Connect a device with a predetermined current pattern that appears in synchronization with the current frequency to the power supply line from the distribution board.
A means for detecting the predetermined current pattern from the current waveform measured by an ammeter for measuring the current in the distribution board and acquiring the phase information of the voltage in the distribution board is provided.
The device is a measuring device characterized in that, as the predetermined current pattern, a pattern that suppresses power consumption as the power factor approaches 0 is output . The predetermined current pattern in the device is
The appearance position of the AC power frequency in one cycle is preset, and
The measuring device according to claim 1, wherein the measuring device has a shape that can be discriminated by being superimposed on the current consumption of the load connected to the power supply line. The measuring device according to claim 1 or 2 , wherein the ammeter measures the current in the distribution board in a non-contact manner. Connect a device with a predetermined current pattern that appears in synchronization with the current frequency to the power supply line from the distribution board.
The predetermined current pattern is detected from the current waveform measured by the ammeter that measures the current in the distribution board, and the phase information of the voltage in the distribution board is acquired.
The measuring method is characterized in that the device outputs, as the predetermined current pattern, a pattern that suppresses power consumption as the power factor approaches zero . The predetermined current pattern in the device is
The appearance position of the AC power frequency in one cycle is preset, and
The measuring method according to claim 4, wherein the shape is superposed on the current consumed by the load connected to the power supply line so that the shape can be discriminated. The measuring method according to claim 4 or 5, wherein the ammeter measures the current in the distribution board in a non-contact manner.

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