JP2015224933A - Device and method for measuring voltage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure voltage on an electric cable without grounding to the ground of the cable.SOLUTION: A voltage measurement device (1) includes: a reference electrode (21N); a measurement electrode (21L); a reference electrode voltage acquisition section (101N) which is grounded to a second ground insulated from a first ground of an electric cable and is configured to acquire voltage of the reference electrode (21N); a measurement electrode voltage acquisition section (101L) which is grounded to the second ground and is configured to acquire voltage of the measurement electrode (21L); a differential amplifier (102) for obtaining differential voltage of the two voltages; and a measurement voltage computation unit (103) for computing AC voltage from the differential voltage.

Description

  The present invention relates to a voltage measuring device and a voltage measuring method for measuring an alternating voltage applied to a conductor of an electric wire that is insulated.

  Conventionally, as disclosed in Patent Documents 1 to 3, a technique for measuring a voltage applied to an insulated wire without bringing a measurement electrode into contact with a conductor of the insulated wire is known.

  The configurations described in Patent Documents 1 and 2 output a detection probe having a detection electrode capable of covering a part of the surface of the insulation coating of the insulated wire and a shield electrode covering the detection electrode, and a signal having a predetermined frequency. Using an oscillator. Specifically, a signal having a predetermined frequency is output from the oscillator, the signal is supplied to the detection electrode of the detection probe, and the impedance between the detection electrode and the conductor is measured. Further, the current flowing out from the detection electrode due to the voltage applied to the conductor of the insulated wire is measured, and the voltage applied to the conductor is measured from this current and the impedance.

  Here, the characteristic of each insulation coating of an insulated wire (measurement wire) varies greatly depending on temperature and humidity. For this reason, the measurement voltage of a measurement electric wire changes a lot with temperature and humidity. Moreover, the relative dielectric constant of the insulation coating of the measuring wire has frequency characteristics, and the frequency characteristics vary depending on the material of the insulation coating. In particular, PVC (polyvinyl chloride), which is frequently used as an insulating coating, has a remarkable difference in relative dielectric constant with respect to a difference in frequency.

  Under the circumstances where the measurement voltage of the measurement wire is greatly influenced by the factors as described above, in the configurations described in Patent Documents 1 and 2, a high-frequency signal (frequency is significantly different from the measurement voltage of the measurement wire (for example, frequency 60 Hz)). For example, the impedance between the conductor of the measurement wire and the detection electrode is measured by applying a frequency of 6 kHz to the measurement wire, and the voltage (measurement voltage) of the conductor is obtained based on the impedance. For this reason, the voltage of a measurement electric wire cannot be measured correctly.

  On the other hand, in the configuration described in Patent Document 3, the AC voltage of the electric wire is obtained, and the dielectric loss tangent of the insulator covering the electric wire is obtained from the phase difference between the reference alternating current and the dielectric loss current. The AC voltage obtained previously is corrected.

  Specifically, the coupling capacitance between the conductor of the wire and the electrode is obtained from the input signal from the electrode disposed on the insulator of the wire, and the AC voltage is obtained based on the value of this coupling capacitance. Further, a reference alternating current advanced by 90 ° with respect to the alternating voltage is detected through an insulator. In addition, the dielectric loss current accompanying the dielectric loss of the insulator is detected through the insulator. Next, the phase difference between these reference AC current (reference AC voltage) and dielectric loss current (dielectric loss voltage) is obtained, and the dielectric loss tangent of the insulator is calculated from this phase difference. Further, the previously obtained AC voltage value is corrected based on the value of the dielectric loss tangent. Therefore, according to such a configuration of Patent Document 3, the above-described problem of the configurations of Patent Documents 1 and 2 can be avoided.

Japanese Patent Laid-Open No. 10-206468 (published August 7, 1998) JP 2002-365315 A (released on December 18, 2002) JP 2004-177310 A (released on June 24, 2004) JP 2014-44102 A (published March 13, 2014)

  However, all of the configurations of Patent Documents 1 to 3 are configured to ground the measuring device to a common ground with the ground (GND) of the electric wire when measuring the AC voltage of the electric wire. For this reason, the operation | work which attaches a measuring device to a distribution board, for example, is regarded as electrical work, needs to be performed by a qualified worker, and has a problem that use is restricted.

  Patent Document 4 describes a circuit that acquires a differential voltage of a voltage detected by a pair of voltage measurement probes in a circuit board inspection apparatus. Specifically, the probe is arranged in a non-contact manner with respect to the two solder ball bumps of the circuit board, the voltage generated in each solder ball bump is acquired, and these voltages are differentially amplified via the buffer circuit. The difference voltage between the two voltages is acquired by inputting to the circuit. Further, the resistance value between the two solder ball bumps is calculated based on the acquired differential voltage and the current from the probe brought into contact with the two solder ball bumps. Thus, although the structure of patent document 4 can be used for the measurement of the resistance value between two points on a circuit board, for example, it cannot be used for the measurement of the alternating voltage of an electric wire.

  Accordingly, an object of the present invention is to provide a voltage measuring device and a voltage measuring method capable of measuring the voltage of the measuring wire without being grounded to the common ground of the measuring wire.

  In order to solve the above-described problem, the voltage measuring device according to the present invention is a voltage measuring device that measures an alternating voltage supplied by a plurality of electric wires through the insulation coating of the electric wires, and is used as a reference among the plurality of electric wires. A reference electrode disposed around the insulating coating of the electric wire, a measurement electrode disposed on all the electric wires other than the electric wire serving as the reference among the plurality of electric wires, and a first ground which is a ground of the electric wire A reference electrode voltage acquisition unit configured to acquire a reference electrode voltage induced in the reference electrode by the AC voltage, and grounded to the second ground, and connected to the second ground. A measurement electrode voltage acquisition unit that acquires a measurement electrode voltage induced in the measurement electrode, a difference voltage acquisition unit that acquires a difference voltage between the reference electrode voltage and the measurement electrode voltage, and the difference voltage It is characterized in that it comprises a measurement voltage calculation unit for obtaining the alternating voltage using.

  According to said structure, a reference electrode voltage acquisition part acquires the reference electrode voltage induced by the reference electrode with the alternating voltage of an electric wire (for example, single-phase two-phase N-phase electric wire). The measurement electrode voltage acquisition unit acquires a measurement electrode voltage induced in the measurement electrode by an AC voltage of an electric wire (for example, a single-wire two-phase L-phase electric wire). The reference electrode voltage and the measurement electrode voltage are a sine wave when the reference electrode voltage acquisition unit and the measurement electrode voltage acquisition unit are grounded to a second ground that is insulated from the first ground of the electric wire. It will not be. Therefore, the difference voltage acquisition unit obtains the difference voltage of the sine wave by taking the difference between the reference electrode voltage and the measurement electrode voltage. A measurement voltage calculating part calculates | requires alternating voltage using the said differential voltage.

  Thereby, the voltage of an electric wire can be measured, without earth | grounding to the ground common with the ground of an electric wire.

  The voltage measurement apparatus includes a first reference electrode and a second reference electrode as the reference electrode, and includes a first measurement electrode and a second measurement electrode as the measurement electrode, and the reference electrode voltage acquisition unit includes The first reference electrode voltage is induced with a phase shift of a first amount with respect to the phase of the AC voltage from the first reference electrode, and the phase is second with respect to the phase of the AC voltage from the second reference electrode The second reference electrode voltage induced by the amount of deviation is respectively obtained, and the measurement electrode voltage obtaining unit induces the phase from the first measurement electrode to be shifted by the first amount with respect to the phase of the AC voltage. A first measurement electrode voltage that is induced and a second measurement electrode voltage that is induced from the second measurement electrode with a phase shift of the second amount with respect to the phase of the AC voltage, and the differential voltage The acquisition unit is configured from the first reference electrode. A first differential voltage acquisition unit that acquires a first differential voltage between a first reference electrode voltage and a first measurement electrode voltage from the first measurement electrode; and a second reference from the second reference electrode A second differential voltage acquisition unit that acquires a second differential voltage between an electrode voltage and a second measurement electrode voltage from the second measurement electrode, wherein the measurement voltage calculation unit includes the first differential voltage And the second differential voltage, the coupling capacitance between the core of the wire and the first measurement electrode is obtained, and the alternating voltage is obtained from the obtained coupling capacitance and the first differential voltage. It is good also as a structure.

  According to the above configuration, the reference electrode voltage acquisition unit is configured to detect the first reference electrode voltage induced from the first reference electrode with a phase shift of the first amount with respect to the phase of the AC voltage, and the second reference electrode. A second reference electrode voltage that is induced with a phase shift of a second amount with respect to the phase of the AC voltage is acquired. The measurement electrode voltage acquisition unit is configured to detect the first measurement electrode voltage that is induced by a first amount shift from the first measurement electrode with respect to the phase of the AC voltage, and the AC voltage phase from the second measurement electrode. Second measurement electrode voltages that are induced with a phase shift of the second amount are obtained. The first differential voltage acquisition unit acquires a first differential voltage between the first reference electrode voltage from the first reference electrode and the first measurement electrode voltage from the first measurement electrode. The second difference voltage acquisition unit acquires a second difference voltage between the second reference electrode voltage from the second reference electrode and the second measurement electrode voltage from the second measurement electrode. The measurement voltage calculation unit obtains the coupling capacitance between the core of the electric wire and the first measurement electrode from the phase difference between the first difference voltage and the second difference voltage, and obtains the obtained coupling capacitance and the first difference. The AC voltage is obtained from the voltage.

  Therefore, a configuration for applying a voltage to the electrodes arranged around the electric wire, a configuration for acquiring a voltage generated in the electrode by the voltage applied to the electrode, and a configuration for separating a plurality of voltages generated in the electrode are not required. Thereby, a circuit structure becomes simple and a circuit board can be reduced in size. As a result, the voltage of the electric wire can be accurately measured with a simple configuration.

  The voltage measurement device includes a detection unit including the reference electrode, the measurement electrode, the reference electrode voltage acquisition unit, and the measurement electrode voltage acquisition unit, and is connected to the detection unit by a cable, and the differential voltage acquisition unit And a calculation unit including the measurement voltage calculation unit.

  According to said structure, a voltage measuring device can be appropriately comprised by a detection unit and a calculation unit.

  The voltage measuring method of the present invention is a voltage measuring method for measuring an AC voltage supplied by a plurality of electric wires through the insulating coating of the electric wires, and a reference is provided around the insulating coating of the electric wire serving as a reference among the plurality of electric wires. A reference for obtaining a reference electrode voltage induced in the reference electrode by the AC voltage in a state where the electrode is disposed and the ground is a second ground that is insulated from the first ground that is the ground of the electric wire. In the state where the measurement electrodes are arranged on all the wires other than the reference wire among the plurality of wires and the ground is the second ground, the measurement electrode is obtained by the AC voltage. A measurement electrode voltage acquisition step for acquiring a measurement electrode voltage induced by the difference, a difference voltage acquisition step for acquiring a difference voltage between the reference electrode voltage and the measurement electrode voltage, and the difference voltage And use is characterized in that it comprises a measurement voltage calculation step of obtaining the AC voltage.

  According to said structure, there exists an effect similar to the said voltage measuring device.

  According to the configuration of the present invention, the voltage of the measurement electric wire can be measured without being grounded to the ground common to the measurement electric wire.

It is a circuit diagram which shows the voltage measurement principle in the voltage measuring device of embodiment of this invention in case a measurement electric wire is a single phase 2 wire. It is a schematic diagram which shows the measurement state of the measurement voltage VS in case the measurement electric wire is a single phase 2 line | wire by the voltage measuring device of embodiment of this invention. It is a block diagram which shows the structure of the voltage measuring device shown in FIG. 1 and FIG. FIG. 4 is a circuit diagram showing an example of a specific configuration of the voltage measuring device shown in FIG. 3. FIG. 5 is a waveform diagram showing a phase relationship between a measurement voltage VS, a difference voltage V1, and a difference voltage V2 shown in FIG. FIG. 5 is a timing chart of signals at various parts shown in FIG. 4. FIG. FIG. 5 is an explanatory diagram illustrating a phase relationship among a measurement voltage VS, a difference voltage V1, and a difference voltage V2 illustrated in FIG. It is a longitudinal cross-sectional view which shows the substantive form example of the voltage measuring device shown in FIG. It is a perspective view of the detection unit shown in FIG. It is a circuit diagram which shows the other example of the specific structure of the voltage measuring device shown in FIG. It is explanatory drawing which shows the voltage waveform and phase of each part of the voltage measuring device shown in FIG. It is an equivalent circuit of the circuit G shown in FIG.

[Embodiment 1]
(Voltage measurement principle of voltage measuring device 1)
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram illustrating the voltage measurement principle when the measurement wire is a single-phase two-wire in the voltage measurement apparatus 1 according to the embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a measurement state of the measurement voltage VS when the measurement electric wire is a single-phase two-wire by the voltage measurement device 1 according to the embodiment of the present invention.

  In the present embodiment, for grounding, grounding to the same ground (for example, GND1 in FIG. 1; hereinafter referred to as ground connection) as the ground of the measurement wire (voltage measurement target wire) 11 and to the frame of the voltage measurement device 1 1 (for example, GND2 in FIG. 1; hereinafter referred to as frame connection). These ground connection and frame connection are electrically insulated from each other.

  The voltage measuring device 1 measures an alternating voltage of a measuring wire (electric wire) 11 that is a covered electric wire to be subjected to voltage measurement. In this case, the voltage of the measuring wire 11 can be measured by connecting the voltage measuring device 1 to the unique GND 2 (frame connection) without connecting to the same GND 1 as the measuring wire 11 (ground connection). . That is, when the measurement wire 11 is a single-phase two-wire (example in FIGS. 1 and 2), the differential voltage between the voltage obtained from the N-phase wire of the measurement wire 11 and the voltage obtained from the L-phase wire. Thus, the coupling capacitance CL between the core of the measuring wire 11 and the electrode 21 can be calculated without matching the GND of the voltage measuring device 1 and the measuring wire 11.

  As shown in FIGS. 1 and 2, the voltage measurement apparatus 1 includes a reference electrode 21N, a measurement electrode 21L, a reference electrode voltage acquisition unit 101N, a measurement electrode voltage acquisition unit 101L, a differential amplifier 102, and a measurement voltage calculation unit 103. ing. The measuring wire 11 is connected to the breaker 104.

  In FIG. 1, the reference electrode voltage acquisition unit 101N acquires the reference electrode voltage VN by a circuit that grounds (frame-connects) the reference electrode 21N via a resistor RS. Similarly, the measurement electrode voltage acquisition unit 101L acquires the measurement electrode voltage VL by a circuit that grounds the measurement electrode 21L via a resistor RS (frame connection).

  When measuring the measurement voltage VS (voltage of the measurement electric wire 11), the reference electrode 21N is arranged on the N-phase electric wire of the measurement electric wire 11, and the measurement electrode 21L is arranged on the L-phase electric wire of the measurement electric wire 11. In this case, a coupling capacitance between the core wire of the N-phase electric wire and the reference electrode 21N is a coupling capacitance CN, and a coupling capacitance between the core wire of the L-phase electric wire and the measurement electrode 21L is a coupling capacitance CL.

  The reference electrode voltage acquisition unit 101N acquires a voltage (reference electrode voltage VN) induced in the reference electrode 21N by the AC voltage of the N-phase electric wire, and inputs the voltage to the inverting input terminal of the differential amplifier 102. Similarly, the measurement electrode voltage acquisition unit 101L acquires a voltage (measurement electrode voltage VL) induced in the measurement electrode 21L by the AC voltage of the L-phase wire, and supplies the voltage to the non-inverting input terminal of the differential amplifier 102. input. The differential amplifier 102 acquires a difference voltage between the reference electrode voltage VN and the measurement electrode voltage VL and outputs the difference voltage to the measurement voltage calculation unit 103.

  In this case, since the reference electrode voltage VN and the measurement electrode voltage VL do not match GND2 (frame connection) of the reference electrode voltage acquisition unit 101N and measurement electrode voltage acquisition unit 101L with GND1 (ground connection) of the measurement electric wire 11, For example, an unstable voltage waveform as shown in FIG. Therefore, in the differential amplifier 102, the difference between the reference electrode voltage VN and the measurement electrode voltage VL is taken to obtain a stable sine wave difference voltage VLN.

  As the measurement voltage calculation unit 103, a configuration of a conventionally known method or a new method can be adopted. As the reference electrode voltage acquisition unit 101N and the measurement electrode voltage acquisition unit 101L, those corresponding to the method of the measurement voltage calculation unit 103 to be employed are adopted.

(Specific configuration of voltage measuring device)
FIG. 3 is a block diagram illustrating a configuration of the voltage measuring apparatus 1 illustrated in FIGS. 1 and 2. FIG. 4 is a circuit diagram showing an example of a specific configuration of the voltage measuring apparatus 1 shown in FIG. As shown in FIGS. 3 and 4, the measurement voltage calculation unit 103 includes a signal processing unit 111 and a calculation unit 112 configured by, for example, a CPU. The signal processing unit 111 and the calculation unit 112 constitute the measurement voltage calculation unit 103 illustrated in FIG.

  The voltage measuring device 2 shown in FIG. 4 obtains the voltage of the measuring wire 11 by the phase difference method. As shown in FIG. 4, the voltage measuring device 2 includes a first reference electrode 21 </ b> N and a second reference electrode 22 </ b> N arranged around the N-phase wire of the measurement wire 11, and the L-phase wire of the measurement wire 11. A first measurement electrode 21L and a second measurement electrode 22L are provided around. The first reference electrode 21N, the second reference electrode 22N, the first measurement electrode 21L, and the second measurement electrode 22L are, for example, arc-shaped having a predetermined width in the direction of the electric wire so that they can be arranged on the outer periphery of the corresponding electric wire. It has become. In addition, the shape of the measurement electrode 21 and the reference electrode 22 is not limited to this, For example, what is necessary is just the shape which can contact | connect the measurement electric wire 11, such as flat form.

  The voltage measuring device 2 includes the first reference electrode 21N and the second reference electrode 22N corresponding to the N-phase wire of the measurement wire 11, so that the reference electrode voltage acquisition unit 101N has the first reference electrode 21N and the second reference electrode 22N. A circuit for acquiring a voltage induced in the two reference electrodes 22N is provided. Similarly, the measurement electrode voltage acquisition unit 101L includes the first measurement electrode 21L and the second measurement electrode by including the first measurement electrode 21L and the second measurement electrode 22L corresponding to the L-phase electric wire of the measurement electric wire 11. Each circuit includes a circuit for acquiring a voltage induced in 22L. Corresponding to the configurations of the reference electrode voltage acquisition unit 101N and the measurement electrode voltage acquisition unit 101L, the differential amplifier 102 includes two differential amplifiers 102a and 102b.

  The reference electrode voltage acquisition unit 101N and the measurement electrode voltage acquisition unit 101L take into account the withstand voltages of the differential amplifier (first difference voltage acquisition unit) 102a and the differential amplifier (second difference voltage acquisition unit) 102b. The function of reducing the AC voltage of the measuring wire 11 and inputting it to the differential amplifier 102a and the differential amplifier 102b is provided.

  Between the first reference electrode 21N and the non-inverting input terminal of the differential amplifier 102a, the resistor R1 of the reference electrode voltage acquisition unit 101N, the operational amplifier 25, and the resistor R2 are provided in series. In addition, the resistor R1 of the measurement electrode voltage acquisition unit 101L, the operational amplifier 25, and the resistor R2 are provided in series between the first measurement electrode 21L and the inverting input terminal of the differential amplifier 102a.

  In the reference electrode voltage acquisition unit 101N and the measurement electrode voltage acquisition unit 101L, the resistor R1 is connected to the inverting input terminal of the operational amplifier 25, and the resistor R2 is connected between the inverting input terminal and the output terminal of the operational amplifier 25. ing. The operational amplifier 25 has a non-inverting input terminal connected to the frame. The output terminal of the operational amplifier 25 of the reference electrode voltage acquisition unit 101N is connected to the non-inverting input terminal of the differential amplifier 102a, and the output terminal of the operational amplifier 25 of the measurement electrode voltage acquisition unit 101L is the inverting input of the differential amplifier 102a. Connected to the terminal.

  An operational amplifier 27 and a resistor R0 are provided between the second reference electrode 22N and the non-inverting input terminal of the differential amplifier 102b. The second reference electrode 22N is connected to the inverting input terminal of the operational amplifier 27. An operational amplifier 27 and a resistor R0 are provided between the second measurement electrode 22L and the inverting input terminal of the differential amplifier 102b. The second measurement electrode 22L is connected to the inverting input terminal of the operational amplifier 27. In the reference electrode voltage acquisition unit 101N and the measurement electrode voltage acquisition unit 101L, the resistor R0 is connected between the inverting input terminal and the output terminal of the operational amplifier 27, and the non-inverting input terminal of the operational amplifier 27 is frame-connected. Yes.

  The signal processing unit 111 includes an XOR 24 and comparators 26 and 28. The output terminal of the differential amplifier 102 a is connected to the calculation unit 112 and the inverting input terminal of the comparator 28. As a result, the difference voltage V1 output from the differential amplifier 102a is input to the calculation unit 112 and the inverting input terminal of the comparator 28. The output terminal of the differential amplifier 102b is connected to the inverting input terminal of the comparator 28.

  The comparator 26 has a non-inverting input terminal connected to the frame via the resistor R <b> 11 and an output terminal connected to the first input terminal 24 a of the XOR 24. Between the output terminal and the non-inverting input terminal of the comparator 26, a resistor R15 and a capacitor C11 connected in series are provided.

  The comparator 28 has a non-inverting input terminal connected to the frame via the resistor R12 and an output terminal connected to the second input terminal 24b of the XOR 24. Between the output terminal and the non-inverting input terminal of the comparator 26, a resistor R16 and a capacitor C12 connected in series are provided.

  The power supply voltage Vcc is supplied to the first input terminal 24a of the XOR 24 via the resistor R13, and the power supply voltage Vcc is supplied to the second input terminal 24b of the XOR 24 via the resistor R14. A phase difference voltage Vpd is output from the XOR 24 to the calculator 23.

(Operation of voltage measuring device 2)
In the above configuration, the operation of the voltage measuring device 2 will be described below. When the measurement voltage VS is measured by the voltage measuring device 2, the first reference electrode 21N and the second reference electrode 22N are arranged around the N-phase electric wire of the measurement electric wire 11, and the first measurement electrode 21L and the second measurement electrode are arranged. The electrode 22L is arranged around the L-phase wire of the measurement wire 11. In this case, the coupling capacitance between the core wire of the N-phase electric wire and the first reference electrode 21N is CN1, the coupling capacitance between the core wire of the N-phase electric wire and the second reference electrode 22N is CN2, and the L-phase electric wire A coupling capacitance between the core wire of the electric wire and the first measurement electrode 21L is a coupling capacitance CL1, and a coupling capacitance between the core wire of the L-phase electric wire and the second measurement electrode 22L is a coupling capacitance CL2. Note that the coupling capacitors CN1 and CN2 do not need to match, and similarly, the coupling capacitors CL1 and CL2 do not need to match.

  When each electrode is arranged as described above, the voltage VN1 (relative to the phase of the measurement voltage VS) is applied from the reference electrode voltage acquisition unit 101N to the non-inverting input terminal of the differential amplifier 102a due to the voltage induced on the first reference electrode 21N. The voltage VL1 (the phase of the measurement voltage VS) is input from the measurement electrode voltage acquisition unit 101L to the inverting input terminal of the differential amplifier 102a by the voltage induced in the first measurement electrode 21L. Is input with a voltage whose phase is shifted by a first amount. As a result, the differential voltage V1 is output from the differential amplifier 102a.

  Further, due to the voltage induced in the second reference electrode 22N, the voltage VN2 (the phase is shifted by a second amount with respect to the phase of the measurement voltage VS) from the reference electrode voltage acquisition unit 101N to the non-inverting input terminal of the differential amplifier 102b. Voltage) and a voltage induced on the second measurement electrode 22L causes the voltage VL2 (the phase with respect to the phase of the measurement voltage VS to be second) from the measurement electrode voltage acquisition unit 101L to the inverting input terminal of the differential amplifier 102b. A voltage that is off by an amount is input. As a result, the differential voltage V2 is output from the differential amplifier 102b.

  In FIG. 4, the circuit on the first reference electrode 21N side including the reference electrode voltage acquisition unit 101N includes a coupling capacitor CN1 and a resistor R1 in series, and includes these coupling capacitor CN1, resistor R1, operational amplifier 25, and resistor R2. It is an inverting amplifier circuit. Similarly, in the circuit on the first measurement electrode 21L side including the measurement electrode voltage acquisition unit 101L, the coupling capacitor CL1 and the resistor R1 are in series, and the inversion includes the coupling capacitor CL1, the resistor R1, the operational amplifier 25, and the resistor R2. It is an amplifier circuit. Therefore, assuming that the coupling capacitance CN1 = CL1, the difference voltage V1 is expressed by the following equation (1).

  In this case, the phase α of the differential voltage V1 is expressed by the following formula (2), and the amplitude (absolute value) of the differential voltage V1 is expressed by the following formula (3).

  As can be seen from the equation (2), the phase α of the difference voltage V1 varies depending on the value of the coupling capacitor CL1. That is, the phase α of the difference voltage V1 is in a state shifted from the phase of the measurement voltage VS that is the voltage of the measurement wire 11 (a state shifted by a first amount).

  On the other hand, the voltage VN2 is input from the reference electrode voltage acquisition unit 101N to the non-inverting input terminal of the differential amplifier 102b by the voltage induced at the second reference electrode 22N, and the measurement is performed by the voltage induced at the second measurement electrode 22L. The voltage VL2 is input from the electrode voltage acquisition unit 101L to the inverting input terminal of the differential amplifier 102b. As a result, the differential voltage V2 is output from the differential amplifier 102b.

In this case, the resistor R corresponding to the resistor R1 does not exist in the circuit on the second reference electrode 22N side including the reference electrode voltage acquisition unit 101N and the circuit on the second measurement electrode 22L side including the measurement electrode voltage acquisition unit 101L. . Therefore, assuming that the coupling capacitance CN2 = CL2, the phase β of the difference voltage V2 is tan ⁻¹ ∞, asymptotically approaching 90 °, because the resistance R1 = 0 in the equation (2). Thereby, the phase β of the difference voltage V2 is not affected by the coupling capacitance CL2 (= CN2), and is fixed to a state advanced by 90 ° (a constant amount) with respect to the phase of the measurement voltage VS.

  FIG. 5 shows the phase relationship of the measurement voltage VS, the difference voltage V1, and the difference voltage V2. FIG. 5 is a waveform diagram showing the phase relationship between the measurement voltage VS, the difference voltage V1, and the difference voltage V2.

  In FIG. 5, Δα indicates a phase difference between the difference voltage V1 and the difference voltage V2. Therefore, taking into account that the phase of the difference voltage V2 is advanced by 90 ° from the phase of the measurement voltage VS, the phase difference Δα is expressed by the equation (4) by the coupling capacitor CL1 and the resistor R1.

  FIG. 6 is a timing chart of the difference voltage V1, the difference voltage V2, the output signal COMP1 of the comparator 26, the output signal COMP2 of the comparator 28, and the phase difference voltage Vpd output from the XOR 24.

  As shown in FIG. 6, there is a phase difference ΔT (corresponding to the phase difference Δα) between the difference voltage V1 and the difference voltage V2. The comparator 26 receives the difference voltage V1 and outputs a pulse wave output signal COMP1 to the XOR 24. Similarly, the comparator 28 outputs a pulse wave output signal COMP2 to the XOR 24 when the difference voltage V2 is input. The rising level of the output signals COMP1 and COMP2 is the power supply voltage Vcc.

  The XOR 24 receives the output signal COMP1 and the output signal COMP2, and generates a phase difference voltage Vpd that is an exclusive OR of the output signals COMP1 and COMP2, and outputs the phase difference voltage Vpd to the calculation unit 23. The phase difference voltage Vpd is a pulse signal including a pulse having a width (time ΔT) corresponding to the phase difference Δα between the difference voltage V1 and the difference voltage V2.

  Here, the phase difference between the measurement voltage VS and the difference voltage V2 is 90 °, the phase difference between the difference voltage V1 and the difference voltage V2 is Δα, and the phase difference between the measurement voltage VS and the difference voltage V1 is 90 ° −Δα. Therefore, referring to equation (4), the phase relationship among the measurement voltage VS, the difference voltage V1, and the difference voltage V2 is arranged as shown in FIG.

  First, the calculation unit 23 obtains the phase difference Δα from the phase difference voltage Vpd input from the XOR 24 according to Expression (5). Note that f is the frequency of the measurement voltage VS.

Δα = ΔT × f × 360 (5)
Next, the calculation unit 23 obtains an unknown coupling capacitance CL1 from Expression (4) using the obtained phase difference Δα. Further, the calculation unit 23 obtains the measurement voltage VS using the obtained coupling capacitance CL1.

  In this case, the phase of the difference voltage V1 is Equation (2), and the amplitude of the difference voltage V1 is Equation (3). The calculation unit 23 performs A / D conversion on the difference voltage V1 input from the output terminal of the operational amplifier 25 to obtain the value of the difference voltage V1.

  Further, when formula (3) is arranged for measurement voltage VS, formula (6) is obtained.

  In equation (6), the coupling capacitance CL1 and the difference voltage V1 are known. Therefore, the calculation unit 23 can calculate the measurement voltage VS from Expression (6).

  As described above, the voltage measuring device 2 can measure the voltage of the measurement electric wire 11 without being grounded to the ground common to the measurement electric wire 11 (GND1).

  Further, the voltage measuring device 2 acquires a differential voltage V2 whose phase is shifted by a certain value (second amount, for example, 90 °) with respect to the phase of the measured voltage VS. Further, the phase difference Δα between the difference voltage V1 and the difference voltage V2 is obtained by the comparators 26 and 28 and the XOR 24. Next, the coupling capacitance CL1 (= CN1) generated between the core of the measurement wire 11 and the first reference electrode 21N and the first measurement electrode 21L is obtained from the obtained phase difference Δα. Further, the value of the differential voltage V1 is obtained by the calculation unit 23. Further, the calculation unit 23 obtains the measurement voltage VS from the known coupling capacitance CL1 and the difference voltage V1.

  Therefore, a configuration for applying a voltage to the electrode arranged on the outer peripheral surface of the measuring wire 11, a configuration for acquiring a voltage generated in the electrode by the voltage applied to the electrode, a configuration for separating a plurality of voltages generated in the electrode, and the like. It is unnecessary. Therefore, the circuit configuration is simplified and the circuit board can be reduced in size. Thereby, the measurement voltage VS can be accurately measured with a simple configuration.

  In the voltage measuring device 2, the first reference electrode 21N and the first measurement electrode 21L are arranged in contact with the outer peripheral surface of the insulating coating of the measurement wire 11, while the second reference electrode 22N and the second measurement electrode 22L are It is preferable that the measurement electric wire 11 is arranged in a state where it is lifted, for example, 1 to 2 mm from the measurement electric wire 11 without being brought into contact with the outer peripheral surface of the measurement electric wire 11. That is, when the first and second reference electrodes 22N and 22L are floated from the surface of the insulation coating of the measuring wire 11 so that a space exists between the insulation coating and the first and second reference electrodes 22N and 22L. In this case, the electrical resistance between the insulating coating and the first and second reference electrodes 22N and 22L becomes infinite. This prevents the phase of the differential voltage V2 from changing due to a change in the resistance value of the surface of the insulating coating due to the influence of environmental changes, and the amount of phase shift of the differential voltage V2 with respect to the phase of the measured voltage VS It becomes easy to fix.

  The voltage measuring device 2 uses operational amplifiers 25 and 27 and an XOR 24 in order to easily obtain the phase difference Δα, that is, ΔT from the difference voltage V1 and the difference voltage V2. That is, the voltage measuring device 2 includes the operational amplifiers 25 and 27 and the XOR 24, so that the burden on the CPU constituting the calculation unit 23 can be reduced and high-speed processing can be performed in order to obtain the phase difference Δα, that is, ΔT. The calculation unit 23 can be configured by an inexpensive CPU instead of an expensive CPU.

  On the other hand, the voltage measuring device 2 does not include the operational amplifiers 25 and 27 and the XOR 24, and the calculation unit 23 performs A / D conversion on the difference voltage V1 and the difference voltage V2, and a zero cross point between the difference voltage V1 and the difference voltage V2. The phase difference Δα, that is, ΔT may be calculated from the time difference.

  In the example of the voltage measurement device 2 described above, the measurement wire 11 corresponds to the case of the single-phase two-wire, and the first reference electrode 21N, the second reference electrode 22N, the first measurement electrode 21L, and the second measurement electrode 22L are connected. The configuration provided is described. On the other hand, the voltage measuring device 2 can cope with a case where the number of the measuring wires 11 is three or more and single phase three wires, such as single phase three wires or three phase three wires. In this case, a reference line (reference line) is set, a difference voltage between the reference line and another line is acquired, a phase difference voltage Vpd is acquired from the acquired difference voltage, and a measurement voltage VS is obtained. What is necessary is just composition.

(Substantial form of voltage measuring device)
FIG. 8 is a longitudinal sectional view showing a substantial form example of the voltage measuring device 2, and FIG. 9 is a perspective view of the detection unit shown in FIG. Note that the configurations shown in FIGS. 8 and 9 are the same for the voltage measurement devices of the other embodiments. In the following description, the measurement electrode 21 and the reference electrode 22 are the first reference electrode 21N and the second reference electrode 22N, or the first measurement electrode 21L and the second measurement electrode 22L.

  As shown in FIG. 8, the voltage measurement device 2 includes a detection unit 41 and an arithmetic unit 51. The detection unit 41 includes a housing part 42 that is separated into an upper housing part 43 and a lower housing part 44. The upper housing part 43 and the lower housing part 44 are connected by a hinge 45, and the upper housing part 43 can be opened and closed with respect to the lower housing part 44. A shield plate 46 is provided on the inner surface of the housing portion 42.

  The reference electrode 22 is disposed on the upper surface portion of the lower housing portion 44, and the measurement electrode 21 is disposed on the lower surface portion of the upper housing portion 43 so as to face the reference electrode 22. The measurement electrode 21 and the reference electrode 22 are formed in a semi-cylindrical shape obtained by vertically dividing a cylinder. Therefore, when the upper housing portion 43 is closed with respect to the lower housing portion 44, a cylinder is formed by the measurement electrode 21 and the reference electrode 22, and the measurement electric wire 11 is connected between the measurement electrode 21 and the reference electrode 22. It can be arranged. In FIG. 8, reference numeral 12 denotes a core wire of the measurement electric wire 11, and reference numeral 13 denotes an insulation coating of the measurement electric wire 11.

  A detection circuit board 47 is disposed inside the lower housing part 44. The detection circuit board 47 is connected to an arithmetic unit 51 disposed outside the housing unit 42 via a connector 48 provided on the lower housing unit 44 and a cable 49. The detection circuit board 47 is provided with, for example, a voltage acquisition unit 101, and the arithmetic unit 51 is provided with, for example, differential amplifiers 102a and 102b, a signal processing unit 111, and a calculation unit 112.

  When the measurement wire 11 is a single-layer two-wire, two sets of detection units 41 are used, and one set of calculation unit 51 is used. That is, the detection unit 41 is used for the number of lines, and the arithmetic unit 51 is usually used by one CPU because it corresponds by one CPU. The number of sets used for the arithmetic unit 51 is not particularly limited. This also applies to voltage measuring devices according to other embodiments described below.

  When the measurement electric wire 11 is a single-layer two-wire, one of the two detection units 41 is arranged on the N-phase electric wire, and the other one is arranged on the L-phase. In this case, the voltage acquisition unit 101 of the detection circuit board 47 arranged on the N-phase electric wire is the reference electrode voltage acquisition unit 101N, and the voltage acquisition unit 101 of the detection circuit board 47 arranged on the L-phase electric wire is This is the measurement electrode voltage acquisition unit 101L.

[Embodiment 2]
Another embodiment of the present invention will be described below with reference to the drawings. In the voltage measurement device 3 of the present embodiment, the integration method is used for the voltage processing for obtaining the voltage of the measurement wire 11. In addition, the same code | symbol is attached | subjected to the means which has the same function as the means shown to the said embodiment, and description is abbreviate | omitted.

(Configuration of voltage measuring device 3)
FIG. 10 is a circuit diagram showing another example of the specific configuration of the voltage measuring apparatus 1 shown in FIG. The voltage measurement device 3 is replaced with the reference electrode voltage acquisition unit 121N, the measurement unit voltage acquisition unit 101L, the signal processing unit 111, and the calculation unit 112 of the voltage measurement device 2 shown in FIG. An electrode voltage acquisition unit 121L, a signal processing unit 131, and a calculation unit 132 are provided.

  Note that the reference electrode voltage acquisition unit 121N and the measurement electrode voltage acquisition unit 121L reduce the AC voltage of the measurement wire 11 in consideration of the withstand voltages of the differential amplifier 102a and the differential amplifier 102b, and the differential amplifier 102a and the differential amplifier 102L. It has a function of inputting to the amplifier 102b.

  An operational amplifier 25 constituting a buffer is provided between the first reference electrode 21N and the non-inverting input terminal of the differential amplifier 102a and between the first measurement electrode 21L and the inverting input terminal of the differential amplifier 102a. It has been.

  An operational amplifier 27 and a resistor R0 are respectively provided between the second reference electrode 22N and the non-inverting input terminal of the differential amplifier 102b and between the second measurement electrode 22L and the inverting input terminal of the differential amplifier 102b. Is provided. The second reference electrode 22N and the second measurement electrode 22L are connected to the inverting input terminal of the corresponding operational amplifier 27. The resistor R0 is connected between the inverting input terminal and the output terminal of the operational amplifier 27, and the non-inverting input terminal of the operational amplifier 27 is frame-connected.

  The signal processing unit 131 includes comparators 141 and 142, first and second integration circuits 143 and 144, and a phase shift circuit 145.

  The output section of the differential amplifier 102b is connected to the input section of the second integration circuit 144 via the comparator 142 and is also connected to the input section of the phase shift circuit 145. The output unit of the phase shift circuit 145 is connected to the input unit of the calculation unit 132 and is connected to the input unit of the first integration circuit 143 via the comparator 141. The output units of the first and second integration circuits 143 and 144 are connected to the input unit of the calculation unit 132.

  Furthermore, the output part of the phase shift circuit 145 is connected to the first reference electrode 21N and the first measurement electrode 21L via each resistor R31.

  The phase shift circuit 145 shifts the phase of the voltage input from the differential amplifier 102b to generate a phase shift voltage (applied voltage, voltage Vin). The generated phase shift voltage is compared with the comparator 141, the calculation unit 132, and the phase shift circuit 145. Output toward the resistor R31. In the present embodiment, the phase shift circuit 145 advances the phase of the input voltage by 90 °.

  The output section of the differential amplifier 102a is connected to the input sections of the first and second integrating circuits 143 and 144. Based on the voltage V1 output from the first integration circuit 143, the voltage V2 output from the second integration circuit 144, and the phase shift voltage (Vin) output from the phase shift circuit 145, the calculation unit 132 measures the measurement wire. 11 voltages are calculated.

(Operation of voltage measuring device 3)
In the above configuration, the operation of the voltage measuring device 3 will be described below. FIG. 11 is an explanatory diagram showing voltage waveforms and phases of each part of the voltage measuring device 3 shown in FIG.

  When the first reference electrode 21N is arranged around the N-phase electric wire of the measurement electric wire 11 and the first measurement electrode 21L is arranged around the L-phase electric wire, the core of the measurement electric wire 11, the first reference electrode 21N and the first electric wire A voltage corresponding to the measurement voltage VS is induced in the first reference electrode 21N and the first measurement electrode 21L by the coupling capacitance Cs between the first measurement electrode 21L and a current Ix flows through each resistor R31. As a result, an induced voltage V31 (see FIG. 11C) is generated at both ends of each resistor R31. The induced voltage V31 has a phase advanced by 90 ° with respect to the phase of the measurement voltage VS by setting the resistance R31 to a value sufficiently smaller than the impedance of the coupling capacitor Cs (for example, about 1 MΩ).

  Further, when the second reference electrode 22N is arranged around the N-phase electric wire of the measurement electric wire 11 and the second measurement electrode 22L is arranged around the L-phase electric wire, the core of the measurement electric wire 11 and the second reference electrode 22N are arranged. Due to the coupling capacitance Cs between the second measurement electrode 22L and the second measurement electrode 22L, an induced voltage corresponding to the measurement voltage VS is generated at the second reference electrode 22N and the second measurement electrode 22L. These induced voltages have a phase advanced by 90 ° with respect to the phase of the measurement voltage VS. Next, these induced voltages are input to the inverting input terminal and the non-inverting input terminal of the differential amplifier 102b, whereby the differential voltage V21 is output from the differential amplifier 102b.

  In the present embodiment, the coupling capacity between the core wire of the measurement wire 11 and the first reference electrode 21N and the second reference electrode 22N, and the core wire of the measurement wire 11 and the first measurement electrode 21L and the second measurement wire. The coupling capacitance between the electrode 22L and the electrode 22L may not be the same. Due to the presence of the coupling capacitance, the first reference electrode 21N and the second reference electrode 22N, and the first measurement electrode 21L and the second measurement electrode 22L are predetermined. It is only necessary to obtain a level voltage.

  The difference voltage V21 is input to the phase shift circuit 145, and the phase shift circuit 145 advances the phase of the input difference voltage V21 by 90 °, so that the phase shift voltage whose phase is advanced by approximately 180 ° with respect to the measurement voltage VS. (Voltage Vin) is output.

  When the phase shift voltage is applied to the first reference electrode 21N and the first measurement electrode 21L via the resistor R31, the phase shift voltage between the first reference electrode 21N and the first measurement electrode 21L and the core wire of the measurement wire 11 is obtained. Due to the coupling capacitance Cs, a voltage corresponding to the phase shift voltage is induced in the first reference electrode 21N and the first measurement electrode 21L, and a current Is flows through the resistor R31. As a result, an induced voltage V33 (see FIG. 11C) is generated at both ends of the resistor R31. The induced voltage V33 has substantially the same phase as the phase shift voltage by setting the resistance R31 to a value sufficiently smaller than the impedance of the coupling capacitor Cs (for example, 1 MΩ). That is, the phase of the induced voltage V33 is advanced by approximately 180 ° with respect to the measurement voltage VS, and the phase is advanced by 90 ° with respect to the induced voltage V31.

  Therefore, the voltage at the point A connected to the first reference electrode 21N and the first measurement electrode 21L (hereinafter referred to as the first electrode voltage) is the induced voltage V31 and the induced voltage as shown in FIG. It becomes a mixed voltage in which V33 is mixed. By inputting the first electrode voltage to the inverting input terminal and the non-inverting input terminal of the differential amplifier 102a, the differential voltage V11 is output from the differential amplifier 102a. The difference voltage V11 is input to the first integration circuit 143 and the second integration circuit 144.

  The phase shift voltage output from the phase shift circuit 145 is input to the first integration circuit 143 as COMP1 through the comparator 141. Further, the differential voltage V21 is input to the second integration circuit 144 as COMP2 via the comparator 142. COMP2 and COMP1 are shown in FIGS. 11A and 11B, respectively.

  The first integration circuit 143 integrates the difference voltage V11 (first electrode voltage) for the period during which COMP1 is on, thereby extracting only the induced voltage V33 from the difference voltage V11 (first electrode voltage), and integrating the induced voltage V33. The voltage value V1, which is a value, is output to the calculation unit 132.

  The second integration circuit 144 integrates the difference voltage V11 (first electrode voltage) for the ON period of COMP2 to extract only the induced voltage V31 from the difference voltage V11 (first electrode voltage), and integrate the induced voltage V31. The voltage value V <b> 2 that is a value is output to the calculation unit 132.

  Next, a method for obtaining the voltage value V2 in the second integration circuit 144 and a method for obtaining the voltage value V1 in the first integration circuit 143 will be described.

The difference voltage V11 (first electrode voltage) is
V11 = A · sin (ωt) + B · cos (ωt) (7)
A · sin (ωt): induced voltage V33
B · cos (ωt): induced voltage V31
It becomes.

  Here, in the differential voltage V11 (first electrode voltage), the induced voltage V31 is eliminated if the differential voltage V11 is integrated over the ON period of COMP1. Thereby, only the induced voltage V33 can be taken out.

  Further, in the difference voltage V11 (first electrode voltage), the induced voltage V33 is erased if the difference voltage V11 is integrated over the ON period of COMP2. Thereby, only the induced voltage V31 can be taken out.

  Therefore, the voltage V1 is obtained by integrating the differential voltage V11 from 0 to π as in the following equation (8), and V11 is integrated to π / 2 to 3π / 2 as in the following equation (9). Thus, the voltage V2 is acquired. In this case, the voltages V1 and V2 have only amplitude.

  Next, how to calculate the measurement voltage VS in the calculation unit 132 will be described. When the circuit G of FIG. 10 is shown by an equivalent circuit, it is as shown in FIG. From FIG. 12, the voltage V1 is obtained by dividing the voltage Vin (applied voltage) by the coupling capacitor Cs and the resistor R31.

  In equation (10), when jωCs is applied to the denominator and numerator of the fractional part, equation (11) is obtained.

  If the amplitude of V1 is calculated | required from Formula (11), it will become Formula (12).

  When Expression (12) is solved for the coupling capacitance Cs, Expression (13) is obtained.

  In Expression (13), since the right side is all known variables in the calculation unit 132, the coupling capacitance Cs can be calculated.

  Furthermore, the equation (14) is established for the measurement voltage VS from the separately obtained voltage V2.

  Therefore, the measurement voltage VS can be obtained by substituting Cs in the equation (11) for Cs in the equation (14).

  As described above, the voltage measuring device 3 can measure the voltage of the measuring wire 11 without being grounded to the ground common to the ground (GND1) of the measuring wire 11.

  Moreover, in the voltage measuring device 3, the voltage acquired from the measuring wire 11 by the second reference electrode 22N and the second measuring electrode 22L, that is, the voltage having the same frequency as the voltage of the measuring wire 11 is used as the first reference electrode 21N and the first measuring electrode. The coupling capacitance Cs between the core wire 12 of the measurement electric wire 11 and the first reference electrode 21N and the first measurement electrode 21L is obtained by applying the measurement electric wire 11 from 21L, and the voltage of the measurement electric wire 11, that is, the measurement voltage VS is obtained. Looking for. As a result, the measurement voltage VS can be accurately measured without being affected by the change in the relative dielectric constant of the insulating coating 13 of the measurement wire 11 due to the difference in frequency, and without being affected by changes in temperature and humidity. it can.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention. Furthermore, a new technical feature can be formed by combining the technical means disclosed in each embodiment.

  The present invention can be used as an AC voltage measuring device such as a commercial power source supplied to various devices.

DESCRIPTION OF SYMBOLS 1 Voltage measuring device 2 Voltage measuring device 3 Voltage measuring device 11 Measuring electric wire 12 Core wire 13 Insulation coating 21N Reference electrode, 1st reference electrode 21L Measurement electrode, 1st measurement electrode 22N 2nd reference electrode 22L 2nd measurement electrode 23 Calculation part (Measurement voltage calculation means)
41 detection unit 47 detection circuit board 49 cable 51 arithmetic unit 101N reference electrode voltage acquisition unit 101L measurement electrode voltage acquisition unit 102 differential amplifier (differential voltage acquisition unit)
102a Differential amplifier (differential voltage acquisition unit, first differential voltage acquisition unit)
102b Differential amplifier (differential voltage acquisition unit, second differential voltage acquisition unit)
103 Measurement Voltage Calculation Unit 111 Signal Processing Unit 112 Calculation Unit 121N Reference Electrode Voltage Acquisition Unit 121L Measurement Electrode Voltage Acquisition Unit 131 Signal Processing Unit 132 Calculation Unit CL1 Coupling Capacitance CL2 Coupling Capacitance CN1 Coupling Capacitance CN2 Coupling Capacitance Cs Coupling Capacitance

Claims (4)

In the voltage measuring device that measures the AC voltage supplied by a plurality of electric wires through the insulation coating of the electric wires,
A reference electrode disposed around the insulation coating of the electric wire serving as a reference among the plurality of electric wires;
Measurement electrodes arranged on all the wires other than the reference wire among the plurality of wires,
A reference electrode voltage acquisition unit that acquires a reference electrode voltage that is grounded to a second ground that is insulated from a first ground that is the ground of the electric wire and is induced in the reference electrode by the AC voltage;
A measurement electrode voltage acquisition unit that acquires a measurement electrode voltage that is grounded to the second ground and is induced in the measurement electrode by the AC voltage;
A differential voltage acquisition unit for acquiring a differential voltage between the reference electrode voltage and the measurement electrode voltage;
A voltage measurement apparatus comprising: a measurement voltage calculation unit that obtains the AC voltage using the differential voltage. The reference electrode includes a first reference electrode and a second reference electrode,
The measurement electrode includes a first measurement electrode and a second measurement electrode,
The reference electrode voltage acquisition unit is configured to induce a first reference electrode voltage whose phase is shifted by a first amount with respect to a phase of the AC voltage from the first reference electrode, and the AC voltage from the second reference electrode. A second reference electrode voltage that is induced with a phase shift of a second amount with respect to the phase of
The measurement electrode voltage acquisition unit is configured to induce a first measurement electrode voltage whose phase is shifted by the first amount with respect to a phase of the AC voltage from the first measurement electrode, and the AC from the second measurement electrode. Obtaining a second measurement electrode voltage that is induced with a phase shift of the second amount with respect to the phase of the voltage,
The differential voltage acquisition unit acquires a first differential voltage acquisition that acquires a first differential voltage between a first reference electrode voltage from the first reference electrode and a first measurement electrode voltage from the first measurement electrode. And a second difference voltage acquisition unit that acquires a second difference voltage between the second reference electrode voltage from the second reference electrode and the second measurement electrode voltage from the second measurement electrode. ,
The measurement voltage calculation unit obtains a coupling capacitance between the core of the wire and the first measurement electrode from a phase difference between the first difference voltage and the second difference voltage, and obtains the obtained coupling capacitance. The voltage measuring device according to claim 1, wherein the AC voltage is obtained from the first differential voltage. A detection unit including the reference electrode, the measurement electrode, the reference electrode voltage acquisition unit, and the measurement electrode voltage acquisition unit;
The voltage measuring device according to claim 1, further comprising: an arithmetic unit that is connected to the detection unit by a cable and includes the differential voltage acquisition unit and the measurement voltage arithmetic unit. In the voltage measurement method for measuring the AC voltage supplied by a plurality of electric wires through the insulation coating of the electric wires,
In a state where a reference electrode is disposed around the insulating coating of the reference electric wire among the plurality of electric wires, and the ground is a second ground insulated from the first ground which is the ground of the electric wire. A reference electrode voltage acquisition step of acquiring a reference electrode voltage induced in the reference electrode by the AC voltage;
The measurement electrode is induced in the measurement electrode by the AC voltage in a state where the measurement electrode is arranged on all the wires other than the reference wire among the plurality of wires, and the ground is the second ground. A measurement electrode voltage acquisition step of acquiring a voltage;
A differential voltage acquisition step of acquiring a differential voltage between the reference electrode voltage and the measurement electrode voltage;
A voltage measurement method comprising: a measurement voltage calculation step for obtaining the AC voltage using the differential voltage.

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