JP2015222238A - Device and method for measuring voltage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure voltage on an electric cable using a simple configuration.SOLUTION: A voltage measurement device (1) comprises a measurement electrode voltage acquisition circuit (31), a reference electrode voltage acquisition circuit (32), and arithmetic means which computes coupling capacitance between a core of an electric cable (11) and a measurement electrode (21) from a phase difference between measurement electrode voltage and reference electrode voltage, which is out of phase with AC voltage by a certain amount, and then computing a voltage on the electric cable (11) using the computed coupling capacitance and the measurement electrode 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)

  However, the configuration of Patent Document 3 requires a circuit for obtaining a phase difference between two alternating voltages (reference alternating voltage, dielectric loss voltage) and obtaining a dielectric loss tangent from the obtained phase difference. Moreover, in order to obtain | require the coupling capacity | capacitance between the conductor of an electric wire and an electrode, the two capacitors with a known capacity | capacitance and the switch which switches these capacitors are provided. For this reason, there is a problem that the circuit configuration becomes complicated.

  Accordingly, an object of the present invention is to provide a voltage measuring device and a voltage measuring method capable of accurately measuring the voltage of a measuring wire that is a measurement target with a simple configuration.

  In order to solve the above problems, the voltage measuring device of the present invention is a voltage measuring device that measures an AC voltage of an electric wire through an insulating coating of the electric wire, and a measurement electrode and a reference electrode arranged around the insulating coating, A measurement electrode voltage acquisition circuit that acquires a measurement electrode voltage generated at the measurement electrode by the AC voltage, and a reference electrode voltage that is generated at the reference electrode by the AC voltage and is out of phase by a certain amount with respect to the phase of the AC voltage. A reference electrode voltage acquisition circuit for acquiring the reference electrode voltage, and a phase difference between the measurement electrode voltage and the reference electrode voltage to obtain a coupling capacitance between the core of the wire and the measurement electrode, and the obtained coupling capacitance and the measurement An arithmetic means for obtaining the AC voltage from the electrode voltage is provided.

  According to said structure, a measurement electrode voltage acquisition circuit acquires the measurement electrode voltage induced by a measurement electrode by the alternating voltage of an electric wire. The reference electrode voltage acquisition circuit acquires a reference electrode voltage that is induced in the reference electrode by the AC voltage of the electric wire and whose phase is shifted by a certain amount with respect to the phase of the AC voltage. The calculation means obtains a coupling capacity between the core wire of the electric wire and the measurement electrode from the phase difference between the measurement electrode voltage and the reference electrode voltage, and obtains an AC voltage from the obtained coupling capacity and the measurement electrode voltage.

  Therefore, a configuration for acquiring a voltage generated in the electrode by a voltage applied to the electrode, a configuration for separating a plurality of voltages generated in the electrode, and the like are unnecessary. 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.

  In the voltage measuring apparatus, the reference electrode voltage acquisition circuit may acquire the reference electrode voltage whose phase is shifted by 90 ° with respect to the phase of the AC voltage.

  According to the above configuration, since the reference electrode voltage acquisition circuit acquires the reference electrode voltage whose phase is shifted by 90 ° with respect to the phase of the AC voltage, signal processing using the reference electrode voltage in the subsequent circuit is performed. It becomes easy. Further, the reference electrode voltage acquisition circuit can have a simple circuit configuration excluding elements such as resistors that affect the phase of the reference electrode voltage.

  In the voltage measurement apparatus, the measurement electrode voltage acquisition circuit is an inverting amplifier circuit that includes a first operational amplifier, and the measurement electrode is connected to an inverting input terminal of the first operational amplifier via a resistor. The reference electrode voltage acquisition circuit may include a second operational amplifier, and the reference electrode may be an inverting amplifier circuit that is directly connected to an inverting input terminal of the second operational amplifier.

  According to the above configuration, the measurement electrode voltage acquisition circuit and the reference electrode voltage acquisition circuit can have a simple configuration using an operational amplifier.

  In the above-described voltage measuring apparatus, the calculating means outputs a first pulse wave output circuit that outputs a first pulse wave that is a signal obtained by binarizing the measurement electrode voltage at a zero cross point, and zero-crosses the reference electrode voltage. A second pulse wave output circuit that outputs a second pulse wave that is a signal binarized at a point; the measurement electrode voltage and the reference electrode voltage from the first pulse wave and the second pulse wave; A phase difference signal output circuit that outputs a phase difference signal indicating a phase difference of the signal, a coupling capacitance between the core of the wire and the measurement electrode is obtained from the phase difference signal, and the obtained coupling capacitance and the measurement electrode voltage It is good also as a structure provided with the calculation part which calculates | requires alternating voltage by.

  According to the above configuration, the first pulse wave output circuit outputs a first pulse wave that is a signal obtained by binarizing the measurement electrode voltage at the zero cross point. The second pulse wave output circuit outputs a second pulse wave that is a signal obtained by binarizing the reference electrode voltage at the zero cross point. The phase difference signal output circuit outputs a phase difference signal indicating the phase difference between the measurement electrode voltage and the reference electrode voltage from the first pulse wave and the second pulse wave. A calculation part calculates | requires the coupling capacity between the core wire of an electric wire and a measurement electrode from a phase difference signal, and calculates | requires alternating voltage by the calculated | required coupling capacity and measurement electrode voltage.

  As described above, since the arithmetic means includes the first pulse wave output circuit, the second pulse wave output circuit, the phase difference signal output circuit, and the calculation unit, the calculation unit is configured by a relatively inexpensive CPU. In addition, a general-purpose inexpensive circuit other than the calculation unit can be configured. As a result, an expensive CPU capable of high-speed processing is required when the entire arithmetic means is constituted by a CPU, and the arithmetic means becomes an expensive configuration, whereas the arithmetic means can be made inexpensive. .

  The voltage measuring method of the present invention is a voltage measuring method for measuring an AC voltage of an electric wire through an insulating coating of the electric wire, wherein a measuring electrode is arranged around the insulating coating of the electric wire, and the measuring electrode generated at the measuring electrode by the AC voltage A measurement electrode voltage acquisition step for acquiring a voltage, and a reference electrode is arranged around the insulation coating of the electric wire, and the phase is shifted by a certain amount with respect to the phase of the AC voltage generated in the reference electrode by the AC voltage. Based on a reference electrode voltage acquisition step for acquiring a reference electrode voltage, and a phase difference between the measurement electrode voltage and the reference electrode voltage, a coupling capacitance between the core of the wire and the measurement electrode is obtained, and the obtained coupling capacitance And a calculation step of obtaining the AC voltage from the measurement electrode voltage.

  According to said structure, the voltage of the electric wire which is a measuring object can be measured correctly with a simple structure similarly to said voltage measurement apparatus.

  In the voltage measurement method, the reference electrode may be arranged so as not to contact the insulating coating of the electric wire and to have a space between the insulating coating.

  According to the above configuration, the electrical resistance between the insulating coating and the reference electrode is infinite by arranging the reference electrode so as not to contact the insulating coating of the electric wire and having a space between the insulating coating and the insulating coating. Become big. Therefore, it is possible to prevent the phase of the reference electrode voltage from changing due to the resistance value of the surface of the insulation coating being affected by the environmental change, and the amount of deviation of the phase of the reference electrode voltage from the phase of the AC voltage of the wire It becomes easy to fix.

  According to the structure of this invention, the voltage of the electric wire which is a measuring object can be measured correctly with a simple structure.

It is a circuit diagram which shows the structure of the voltage measuring device of embodiment of this invention. FIG. 2 is a circuit diagram including a measurement electrode voltage acquisition circuit and a reference electrode voltage acquisition circuit from the measurement wire in FIG. 1 to the preceding stage of both comparators. It is a wave form diagram which shows the relationship of the phase of measurement voltage VL, measurement electrode voltage V1, and reference electrode voltage V2 which were shown in FIG. 2 is a timing chart of a measurement electrode voltage V1, a reference electrode voltage V2, a comparator output signal COMP1, 2 and a phase difference signal Vpd shown in FIG. It is explanatory drawing which shows the relationship of the phase of the measurement voltage VL shown in FIG. 1, the measurement electrode voltage V1, and the reference electrode voltage V2. FIG. 6 is a circuit diagram showing another example of the measurement electrode voltage acquisition circuit and the reference electrode voltage acquisition circuit shown in FIG. 1. It is a longitudinal cross-sectional view which shows the substantive example of the voltage measuring device shown in FIG. It is a perspective view of the detection unit shown in FIG.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of a voltage measuring apparatus 1 according to an embodiment of the present invention.

(Configuration of voltage measuring device 1)
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. As shown in FIG. 1, the voltage measurement apparatus 1 includes a measurement electrode 21, a reference electrode 22, a calculation unit 23, and a circuit that supplies the measurement electrode voltage V1 and the phase difference signal Vpd to the calculation unit 23. The measurement electrode 21 and the reference electrode 22 have an arc shape having a predetermined width in the direction of the measurement electric wire 11 so that the measurement electrode 21 and the reference electrode 22 can be arranged on the outer periphery of the measurement electric wire 11. 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.

  An output terminal of an XOR (exclusive OR, phase difference signal output circuit) 24 is connected to the calculation unit 23. Between the measurement electrode 21 and the first input terminal 24a of the XOR 24, a resistor (resistor) R1, an operational amplifier 25 and a resistor R2, and a comparator (comparator, first pulse wave output circuit) 26 are provided in series. It has been. Among these, the resistor R1, the operational amplifier (first operational amplifier) 25, and the resistor R2 constitute a measurement electrode voltage acquisition circuit 31.

  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. The operational amplifier 25 has a non-inverting input terminal grounded and an output terminal connected to the inverting input terminal of the comparator 26. In addition, the output terminal of the operational amplifier 25 is connected to the calculation unit 23, whereby the measurement electrode voltage V <b> 1 is input to the calculation unit 23. The comparator 26 has a non-inverting input terminal grounded via the resistor R11 and an output terminal connected to the first input terminal 24a of the XOR 24.

  An operational amplifier (second operational amplifier) 27, a resistor R0, and a comparator (comparator, second pulse wave output circuit) 28 are provided in series between the reference electrode 22 and the second input terminal 24b of the XOR 24. ing. Among these, the operational amplifier 27 and the resistor R 0 constitute a reference electrode voltage acquisition circuit 32.

  The resistor R0 is connected between the inverting input terminal and the output terminal of the operational amplifier 27. The operational amplifier 27 has a non-inverting input terminal grounded and an output terminal connected to the inverting input terminal of the comparator 28. The comparator 28 has a non-inverting input terminal grounded via the resistor R12 and an output terminal connected to the second input terminal 24b of the XOR 24.

  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 signal Vpd is output from the XOR 24 to the calculator 23. The comparators 26 and 28, the resistors R11 and R12, the XOR 24, and the calculation unit 23 constitute an arithmetic unit.

(Operation of voltage measuring device 1)
In the above configuration, the operation of the voltage measuring apparatus 1 will be described below. FIG. 2 is a circuit diagram including the measurement electrode voltage acquisition circuit 31 and the reference electrode voltage acquisition circuit 32 from the measurement wire 11 to the preceding stage of the comparators 26 and 28 in FIG.

  When the measurement voltage VL is measured by the voltage measurement device 1, the measurement electrode 21 and the reference electrode 22 are arranged on the outer peripheral surface of the insulation coating of the measurement wire 11. In this case, the coupling capacitance between the core wire of the measurement electric wire 11 and the measurement electrode 21 is defined as a coupling capacitance CL1, and the coupling capacitance between the core wire of the measurement electric wire 11 and the reference electrode 22 is defined as a coupling capacitance CL2. Note that the coupling capacitance CL1 and the coupling capacitance CL2 do not need to match.

  By arranging the measurement electrode 21 and the reference electrode 22 around the measurement wire 11, the measurement electrode voltage V <b> 1 is obtained from the measurement electrode 21, and the reference electrode voltage V <b> 2 is obtained from the reference electrode 22.

  In FIG. 2, the circuit on the measurement electrode 21 side including the measurement electrode voltage acquisition circuit 31 includes a coupling capacitor CL1 and a resistor R1 in series, and an inverting amplification including these coupling capacitor CL1, resistor R1, operational amplifier 25, and resistor R2. Circuit. Therefore, the measurement electrode voltage V1 is represented by the following formula (1).

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

  As can be seen from Equation (2), the phase α of the measurement electrode voltage V1 varies depending on the value of the coupling capacitance CL1. That is, the phase α of the measurement electrode voltage V1 is shifted from the phase of the measurement voltage VL that is the voltage of the measurement wire 11.

On the other hand, the circuit on the reference electrode 22 side including the reference electrode voltage acquisition circuit 42 does not have the resistor R corresponding to the resistor R1. Therefore, the phase β of the reference electrode voltage V2 is tan ⁻¹ ∞, asymptotically approaching 90 °, since the resistance R1 = 0 in the equation (2). As a result, the phase β of the reference electrode voltage V2 is not affected by the coupling capacitance CL2, and is fixed at a state advanced by 90 ° (a constant amount) with respect to the phase of the measurement voltage VL.

  FIG. 3 shows the phase relationship of the measurement voltage VL, the measurement electrode voltage V1, and the reference electrode voltage V2. FIG. 3 is a waveform diagram showing the phase relationship between the measurement voltage VL, the measurement electrode voltage V1, and the reference electrode voltage V2.

  In FIG. 3, Δα represents the phase difference between the measurement electrode voltage V1 and the reference electrode voltage V2. Therefore, taking into account that the phase of the reference electrode voltage V2 is advanced by 90 ° from the phase of the measurement voltage VL, and expressing the phase difference Δα by the coupling capacitance CL1 and the resistor R1, the following equation (4) is obtained.

  FIG. 4 is a timing chart of the measurement electrode voltage V1, the reference electrode voltage V2, the output signal COMP1 of the comparator 26, the output signal COMP2 of the comparator 28, and the phase difference signal Vpd output from the XOR 24.

  As shown in FIG. 4, there is a phase difference ΔT (corresponding to the phase difference Δα) between the measurement electrode voltage V1 and the reference electrode voltage V2. The comparator 26 receives the measurement electrode voltage V1 and outputs a pulse wave output signal COMP1 to the XOR 24. Similarly, the comparator 28 receives the reference electrode voltage V2 and outputs the pulse wave output signal COMP2 to the XOR 24.

  The output signal COMP1 is a signal in which the measurement electrode voltage is binarized at the zero cross point, and the output signal COMP2 is a signal in which the reference electrode voltage is binarized at the zero cross point. The rising level of these 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 signal Vpd that is an exclusive OR of the output signals COMP1 and COMP2, and outputs the phase difference signal Vpd to the calculation unit 23. The phase difference signal Vpd is a pulse signal including a pulse having a width (time ΔT) corresponding to the phase difference Δα between the measurement electrode voltage V1 and the reference electrode voltage V2.

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

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

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 VL using the obtained coupling capacitance CL1.

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

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

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

  As described above, in the voltage measuring apparatus 1, the measurement electrode voltage acquisition circuit 31 acquires the reference electrode voltage V2 whose phase is deviated from the phase of the measurement voltage VL by a certain value (for example, 90 °). Further, the comparators 26 and 28 and the XOR 24 obtain the phase difference Δα between the measurement electrode voltage V1 obtained from the measurement electrode voltage acquisition circuit 31 and the reference electrode voltage V2. Next, the coupling capacitance CL1 generated between the core wire of the measurement wire 11 and the measurement electrode 21 is obtained from the obtained phase difference Δα. Further, the calculation unit 23 obtains the value of the measurement electrode voltage V <b> 1 input from the measurement electrode voltage acquisition circuit 31. Further, the calculation unit 23 obtains the measurement voltage VL from the known coupling capacitance CL1 and measurement electrode voltage V1.

  Therefore, a configuration for obtaining the dielectric loss tangent, 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, and a plurality of voltages generated in the electrode The structure etc. which isolate | separate are unnecessary. Therefore, the circuit configuration is simplified and the circuit board can be reduced in size. Thereby, the measurement voltage VL can be accurately measured with a simple configuration.

  In the voltage measuring device 1, the measurement electrode 21 is arranged in contact with the outer peripheral surface of the insulation coating of the measurement electric wire 11, while the reference electrode 22 is not brought into contact with the outer peripheral surface of the measurement electric wire 11. It is preferable to arrange in a state of floating by 1 to 2 mm. That is, when the reference electrode 22 is floated from the surface of the insulation coating of the measurement electric wire 11 so that a space exists between the insulation coating and the reference electrode 22, the electricity between the insulation coating and the reference electrode 22 is Resistance becomes infinite. As a result, it is possible to prevent the phase of the reference electrode voltage V2 from changing due to a change in the resistance value of the surface of the insulating coating due to the influence of the environmental change, and the phase of the reference electrode voltage V2 relative to the phase of the measurement voltage VL. It becomes easy to fix the shift amount.

  Further, in the voltage measuring apparatus 1, operational amplifiers 25 and 27 and an XOR 24 are used in order to easily obtain the phase difference Δα, that is, ΔT from the measurement electrode voltage V1 and the reference electrode voltage V2. That is, the voltage measuring apparatus 1 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 apparatus 1 does not include the operational amplifiers 25 and 27 and the XOR 24, and the calculation unit 23 performs A / D conversion on the measurement electrode voltage V1 and the reference electrode voltage V2 to measure the measurement electrode voltage V1 and the reference electrode voltage V2. Alternatively, the phase difference Δα, that is, ΔT may be calculated from the time difference between the zero cross points.

(Modification)
In the voltage measuring apparatus 1, the measurement electrode voltage acquisition circuit 31 that acquires the measurement electrode voltage V1 from the measurement electrode 21 and the reference electrode voltage acquisition circuit 32 that acquires the reference electrode voltage V2 from the reference electrode 22 are shown in FIG. The electrode voltage acquisition circuit 41 and the reference electrode voltage acquisition circuit 42 may be used. FIG. 6 is a circuit diagram showing another example of the measurement electrode voltage acquisition circuit 31 and the reference electrode voltage acquisition circuit 32 shown in FIG.

  In the measurement electrode voltage acquisition circuit 31 shown in FIG. 1, the operational amplifiers 25 and 27 are used as inverting amplifier circuits, whereas in the measurement electrode voltage acquisition circuit 41 shown in FIG. 6, the operational amplifiers 25 and 27 are not inverted. Used as an amplifier circuit. Even in such a circuit, the measurement electrode voltage V1 and the reference electrode voltage V2 can be obtained similarly.

  In the measurement electrode voltage acquisition circuit 41, the measurement electrode voltage V1 is expressed by the following equation (7).

  In this case, the phase α of the measurement electrode voltage V1 is expressed by the following formula (8), and the amplitude (absolute value) of the measurement electrode voltage V1 is expressed by the following formula (9).

In the reference electrode voltage acquisition circuit 42, the equation (8) (provided that the phase difference between the phase of the measurement voltage VL and the phase of the reference electrode voltage V2 is 90 ° (the phase of the reference electrode voltage V2 is advanced by 90 °)). The expression R21 is read as R22), and the value of the resistor R22 is set. Specifically, with respect to the impedance (for example, 300 to 500 MΩ) of the coupling capacitor CL2, the value of the resistor R22 is set to a level that can be ignored (for example, about 1 MΩ), and is set to tan ⁻¹ ∞ in Expression (8).

  On the other hand, since the measurement electrode voltage acquisition circuit 41 wants to change the phase of the measurement electrode voltage V1 according to the value of the coupling capacitance CL1, the resistance R21 is set to a large value (for example, the impedance of the coupling capacitance CL2 (for example, 300 to 500 MΩ)). Set to about 500 MΩ).

  However, since the coupling capacitance CL1 is normally about 10 PF (= about 300 MΩ), increasing the resistance R1 increases the voltage at the point A (for example, a voltage about ½ of the measurement voltage VL is applied). For this reason, when the measurement voltage VL is high and the voltage at the point A exceeds the power supply voltage of the operational amplifier 25, this circuit is difficult to use.

(Substantial form example of the voltage measuring device 1)
FIG. 7 is a longitudinal sectional view showing a substantial form of the voltage measuring apparatus 1, and FIG. 8 is a perspective view of the detection unit shown in FIG.

  As shown in FIG. 7, the voltage measurement device 1 includes a detection unit 141 and a calculation unit 23. The detection unit 141 includes a housing part 142 separated into an upper housing part 143 and a lower housing part 144. The upper housing part 143 and the lower housing part 144 are connected by a hinge 145, and the upper housing part 143 can be opened and closed with respect to the lower housing part 144. A shield plate 146 is provided on the inner surface of the housing 142.

  The reference electrode 22 is disposed on the upper surface portion of the lower housing portion 144, and the measurement electrode 21 is disposed on the lower surface portion of the upper housing portion 143 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 part 143 is closed with respect to the lower housing part 144, a cylinder is formed by the measurement electrode 21 and the reference electrode 22, and the first and second electrodes 21, 22 around the measurement electric wire 11. Can be placed. 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 147 is disposed inside the lower housing part 144. The detection circuit board 147 is provided with circuits other than the first and second electrodes 21 and 22 and the calculation unit 23 in the voltage measurement apparatus 1 shown in FIG. The detection circuit board 147 is connected to the calculation unit 23 disposed outside the housing unit 142 via the connector 148 provided in the lower housing unit 144 and the cable 149.

  The voltage measuring device 1 shown in FIGS. 1 and 7 is used in one set when the measuring wire 11 is a single-layer two-wire. Moreover, when the measurement electric wire 11 is a three-phase three-wire, three sets are used.

  The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope shown in the claims, and the present invention is also applied to an embodiment obtained by appropriately combining technical means disclosed in the embodiment. It is included in the technical scope of the invention.

  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 11 Measuring wire 21 Measuring electrode 22 Reference electrode 23 Calculation part (calculation means)
24 XOR (phase difference signal output circuit, calculation means)
25 operational amplifier (first operational amplifier)
26 comparator (first pulse wave output circuit, calculation means)
27 Operational amplifier (second operational amplifier)
28 comparator (second pulse wave output circuit, calculation means)
31 measurement electrode voltage acquisition circuit 32 reference electrode voltage acquisition circuit 41 measurement electrode voltage acquisition circuit 42 reference electrode voltage acquisition circuit CL1 coupling capacitance CL2 coupling capacitance R0 resistance R1 resistance (resistor)
R2 resistor R11 resistor (calculation means)
R12 resistance (calculation means)

Claims (6)

In a voltage measuring device that measures the AC voltage of a wire through the insulation of the wire,
A measurement electrode and a reference electrode disposed around the insulating coating;
A measurement electrode voltage acquisition circuit for acquiring a measurement electrode voltage generated in the measurement electrode by the alternating voltage;
A reference electrode voltage acquisition circuit that acquires a reference electrode voltage that is generated in the reference electrode by the AC voltage and that is out of phase by a certain amount with respect to the phase of the AC voltage;
Arithmetic means for obtaining a coupling capacity between the core of the electric wire and the measurement electrode from a phase difference between the measurement electrode voltage and the reference electrode voltage, and obtaining the AC voltage from the obtained coupling capacity and the measurement electrode voltage. And a voltage measuring device.   The voltage measurement apparatus according to claim 1, wherein the reference electrode voltage acquisition circuit acquires the reference electrode voltage whose phase is shifted by 90 ° with respect to the phase of the AC voltage. The measurement electrode voltage acquisition circuit is an inverting amplification circuit including a first operational amplifier, and the measurement electrode is connected to an inverting input terminal of the first operational amplifier via a resistor.
3. The inverting amplifier circuit according to claim 2, wherein the reference electrode voltage acquisition circuit is an inverting amplifier circuit including a second operational amplifier, and the reference electrode is directly connected to an inverting input terminal of the second operational amplifier. Voltage measuring device. The calculation means includes a first pulse wave output circuit that outputs a first pulse wave that is a signal obtained by binarizing the measurement electrode voltage at a zero cross point;
A second pulse wave output circuit that outputs a second pulse wave that is a signal obtained by binarizing the reference electrode voltage at a zero cross point;
A phase difference signal output circuit that outputs a phase difference signal indicating a phase difference between the measurement electrode voltage and the reference electrode voltage from the first pulse wave and the second pulse wave;
And a calculation unit that obtains a coupling capacity between the core of the electric wire and the measurement electrode from the phase difference signal, and obtains an AC voltage from the obtained coupling capacity and the measurement electrode voltage. Item 4. The voltage measuring device according to any one of Items 1 to 3. In the voltage measurement method that measures the AC voltage of the wire through the insulation of the wire,
A measurement electrode is disposed around the insulation coating of the electric wire, and a measurement electrode voltage acquisition step of acquiring a measurement electrode voltage generated in the measurement electrode by the alternating voltage;
A reference electrode voltage acquisition step of arranging a reference electrode around the insulation coating of the electric wire and acquiring a reference electrode voltage that is generated in the reference electrode by the AC voltage and whose phase is shifted by a certain amount with respect to the phase of the AC voltage. When,
A calculation step of obtaining a coupling capacity between the core of the electric wire and the measurement electrode from a phase difference between the measurement electrode voltage and the reference electrode voltage, and obtaining the AC voltage from the obtained coupling capacity and the measurement electrode voltage. And a voltage measuring method.   The voltage measurement method according to claim 5, wherein the reference electrode is disposed so as not to contact the insulation coating of the electric wire and to have a space between the reference coating and the insulation coating.

Images