WO2015182187A1

WO2015182187A1 - Voltage measurement device and voltage measurement method

Info

Publication number: WO2015182187A1
Application number: PCT/JP2015/055259
Authority: WO
Inventors: 悟郎川上; 公平冨田
Original assignee: オムロン株式会社
Priority date: 2014-05-26
Filing date: 2015-02-24
Publication date: 2015-12-03
Also published as: JP6372164B2; JP2015224886A

Abstract

A voltage measurement device (1) is provided with first and second electrode voltage acquisition circuits (61, 62) that can be connected to and disconnected from a first ground (GND1), a capacitance detection voltage acquisition circuit (64) that is connected to a second ground (GND2) and is for acquiring a capacitance detection voltage that occurs in a first electrode (21) when voltage is applied to a second electrode (22), and a calculation unit (24) that calculates the voltage of a measurement wire (11) on the basis of the voltages of the first and second electrodes, an injection voltage, and the capacitance detection voltage.

Description

Voltage measuring device and voltage measuring method

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 insulated wire.

Conventionally, as disclosed in Patent Document 1, 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.

In the configuration described in Patent Document 1, 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 obtained AC voltage is corrected.

Specifically, the coupling capacity between the conductor of the wire and the electrode is obtained from the input signal from the electrode arranged on the insulator of the wire, and the AC voltage is obtained based on the value of this coupling capacity. 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.

Japanese Patent Publication “Japanese Patent Laid-Open No. 2004-177310 (published on June 24, 2004)”

However, in the configuration of Patent Document 1, a circuit for obtaining a phase difference between two AC voltages (reference AC voltage and dielectric loss voltage) and obtaining a dielectric loss tangent from the obtained phase difference is required. 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.

Therefore, 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 with a simple configuration.

In order to solve the above-described problems, a voltage measuring device according to 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 first electrode and a second electrode arranged around the insulating coating. And a first switching unit that switches between a first connection state in which the first electrode is electrically connected to a first ground common to the ground of the electric wire and a first non-connection state in which the first electrode is not connected, A first voltage acquisition circuit that is grounded to one ground and that can acquire a first electrode voltage induced in the first electrode by the AC voltage when the first switching unit is in the first connection state; A second switching unit that switches between a second connection state in which the second electrode is electrically connected to the first ground and a second non-connection state in which the second electrode is not connected, and is grounded to the first ground, Before by the AC voltage A second voltage acquisition circuit that can acquire a second electrode voltage induced in the second electrode when the second switching unit is in the second connection state; and a second voltage acquisition circuit that is insulated from the first ground. When the first switching unit is in the first non-connected state and the second switching unit is in the second non-connected state, an injection voltage is supplied to the second electrode. A capacitance detection voltage acquisition circuit capable of acquiring a voltage induced in the first electrode as a capacitance detection voltage, and the electric wire from the first electrode voltage, the second electrode voltage, the injection voltage, and the capacitance detection voltage. And an arithmetic unit for obtaining a voltage.

According to the configuration of the present invention, it is possible to accurately measure the voltage of the wire to be measured with a simple configuration.

It is a circuit diagram which shows the structure of the voltage measuring device of embodiment of this invention. In the circuit diagram of the voltage measuring apparatus shown in FIG. 1, the capacitance detection voltage acquisition circuit is distinguished from other circuits and is a circuit diagram indicated by a broken line. It is a circuit diagram explaining the operation | movement of the capacity | capacitance detection voltage acquisition circuit in the voltage measuring device shown in FIG. It is a circuit diagram explaining the operation | movement of the 3rd electrode voltage acquisition circuit shown in FIG. FIG. 6 is a circuit diagram illustrating an operation in the vicinity of a third electrode voltage acquisition circuit in the capacitance detection voltage acquisition circuit shown in FIG. 1. FIG. 2 is a circuit diagram illustrating operations of first and second electrode voltage acquisition circuits shown in FIG. 1. 4 is an equivalent circuit of the capacitance detection voltage acquisition circuit shown in FIG. 3. It is an equivalent circuit of the 1st electrode voltage acquisition circuit shown in FIG. It is an equivalent circuit of the 2nd electrode voltage acquisition circuit shown in FIG. 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. FIG. 2 is a circuit diagram showing the capacitance detection voltage acquisition circuit 64 in a circuit diagram of the voltage measuring apparatus 1 shown in FIG.

[Outline of voltage measuring device 1]
The voltage measuring device 1 according to the present embodiment is a method for measuring the voltage of the measuring wire 11 (hereinafter referred to as a measured voltage VL) by the following procedure. That is, the voltage (injection voltage) Vin, voltage (capacitance detection voltage) V2, voltage V (first electrode voltage) 11, and voltage V (second electrode voltage) 12 shown in FIG. 1 are measured. Next, based on the voltage Vin and the voltage V <b> 2, a coupling capacitance CL <b> 1 between the first electrode 21 and the measuring wire 11 and a coupling capacitance CL <b> 2 between the second electrode 22 and the measuring wire 11 are obtained. Next, the measurement voltage VL is obtained based on the coupling capacitors CL1 and CL2 and the voltages V11 and V12. Details of the procedure for obtaining the measurement voltage VL will be described later.

Here, in the present embodiment, with respect to grounding, grounding to the same ground as the ground of the voltage measurement target wire (for example, GND1 (first ground) in FIG. 1; hereinafter referred to as ground connection), and voltage measuring device 1 is distinguished from grounding to one frame (for example, GND2 (second ground) in FIG. 1; hereinafter referred to as frame connection). These ground connection and frame connection are electrically insulated from each other.

[Configuration of Voltage Measuring Device 1]
The voltage measuring device 1 measures the voltage of a measuring wire (electric wire) 11 that is a covered wire for voltage measurement. As shown in FIGS. 1 and 2, the voltage measuring apparatus 1 includes a first electrode 21, a second electrode 22, a third electrode 23, a calculation unit (calculation unit) 24, a voltage Vin (injection voltage) to the calculation unit 24, Each circuit that supplies voltage V2 (capacitance detection voltage), voltage V11 (first electrode voltage), and voltage V12 (second electrode voltage), and a power supply circuit 44 are provided. The first electrode 21 to the third electrode 23 have an arc shape having a predetermined width in the direction of the measurement electric wire 11 so that the first electrode 21 to the third electrode 23 can be arranged on the outer periphery of the measurement electric wire 11. In addition, the shape of the 1st electrode 21 and the reference electrode 22 is not limited to this, What is necessary is just a shape which can contact | connect the measurement electric wire 11, such as flat form, for example. The first electrode 21 is grounded via a resistor R11 and a switch (first switching unit) SW1 connected in series.

The circuit from the first electrode 21 to the calculation unit 24 includes the first and second circuits in parallel. In the first circuit, an operational amplifier 31, a resistor R2, an A / D converter 32, and an insulating circuit 41 are provided in series. In the second circuit, an operational amplifier 33 and an A / D converter 34 are provided in series.

The circuit including the resistor R 11 and the switch SW 1 connected to the first electrode 21 and the second circuit constitute a first electrode voltage acquisition circuit (first voltage acquisition circuit) 61.

In the first circuit, the resistor R2 is connected between the inverting input terminal 31a and the output terminal 31c of the operational amplifier 31. The non-inverting input terminal 31b of the operational amplifier 31 is frame-connected (GND2).

The second electrode 22 is grounded (GND1) via a resistor R12 and a switch (second switching unit) SW2 connected in series. In the circuit from the second electrode 22 to the calculation unit 24, an operational amplifier 35 and an A / D converter 36 are provided in series. The circuit including the resistor R12 and the switch SW2 and the circuit including the operational amplifier 35 and the A / D converter 36 connected to the second electrode 22 are a second electrode voltage acquisition circuit (second voltage acquisition circuit) 62. Is configured.

In the circuit from the third electrode 23 to the calculation unit 24, an operational amplifier 37, a resistor Rf1, a resistor RF2, a photocoupler (signal transmission unit) 42, an operational amplifier 38, an A / D converter 39, and an insulation circuit 43 are connected in series. Is provided. The second electrode 22 is connected between the operational amplifier 38 and the A / D converter 39.

Insulation circuits

41 and 43 are those that cause the A /

D converters

32 and 39 to output their inputs to the calculation unit 24 and insulate the left and right circuits of the

insulation circuits

41 and 43. Conventionally known general-purpose circuits and components can be used.

The resistor Rf1 is connected between the inverting input terminal 37a and the output terminal 37c of the operational amplifier 37. A non-inverting input terminal 37 b of the operational amplifier 37 is connected to the DC offset circuit 40. The DC offset circuit 40 applies a DC offset voltage (Voffset) to the operational amplifier 37 so as to increase the negative voltage so that the sine wave voltage induced in the third electrode 23 changes in the positive polarity region. It is.

The photocoupler 42 has anode 42a, cathode 42b, collector 42c, and emitter 42 terminals. A resistor RF2 is connected to the anode 42a of the photocoupler 42, and a cathode 42b is connected to ground (GND1). The collector 42c is connected to the operational amplifier 38, and the emitter 42d is frame-connected (GND2). A power supply voltage Vcc2 is supplied from the power supply circuit 44 to the collector 42c via the resistor Rt1.

The circuit including the operational amplifier 37 connected to the third electrode 23, the resistor Rf1, the resistor RF2, the LED of the photocoupler 42, and the DC offset circuit 40 is a third electrode voltage acquisition circuit (third voltage acquisition circuit) 63. Is configured. The operational amplifier 33, the operational amplifier 35, and the operational amplifier 38 constitute a voltage follower and have a function as a buffer.

Of the first circuit connected to the first electrode 21, the operational amplifier 31, the resistor R 2, the A / D converter 32, the insulating circuit 41, and the transistor of the photocoupler 42 and the insulating circuit 43 A circuit between them (including the insulation circuit 43), that is, the transistor of the photocoupler 42, the resistor Rt1, the operational amplifier 38, the A / D converter 39, and the insulation circuit 43 constitute a capacitance detection voltage acquisition circuit 64.

The first to third electrode voltage acquisition circuits 61 to 63 are grounded, while the capacitance detection voltage acquisition circuit 64 is frame-connected, and the capacitance detection voltage acquisition circuit 64 is connected to the first to third electrode voltage acquisition circuits 61 to 63 is electrically insulated.

The calculation part 24 is based on the voltage V2, the voltage V11, V12, and the voltage Vin which are input from the circuit between the measurement electric wire 11 and the calculation part 24, the core wire of the measurement electric wire 11, the first electrode 21 and the second electrode. 22 is obtained, and the measurement voltage VL is obtained from these coupling capacitors CL1 and CL2. The calculator 24 is supplied with the power supply voltage Vcc1 from the power supply circuit 44.

The power supply circuit 44 supplies the power supply voltage Vcc1 or the power supply voltage Vcc2 to each unit as described above.

In the circuits shown in FIGS. 1 and 2, the calculation unit 24 is configured to be supplied with the power supply voltage Vcc1 and connected to the ground (GND1). However, the configuration is not limited to this, and the calculation unit 24 may be configured to be supplied with the power supply voltage Vcc2 and to be frame-connected (GND2). In this case, the calculation unit 24 is configured to be insulated from the circuit connected to the ground (GND1).

[Operation of Voltage Measuring Device 1]
In the above configuration, the operation of the voltage measuring apparatus 1 will be described below.
When the measurement voltage VL is measured by the voltage measurement device 1, the first electrode 21 to the third electrode 23 are arranged on the outer peripheral surface of the insulation coating of the measurement wire 11. In this case, the coupling capacities generated between the core of the measuring wire 11 and the first electrode 21 to the third electrode 23 are defined as CL1 to CL3, respectively.

(Operation of the capacitance detection voltage acquisition circuit 64)
FIG. 3 is a circuit diagram for explaining the operation of the capacitance detection voltage acquisition circuit in the voltage measuring apparatus shown in FIG. In the state where the first electrode 21 to the third electrode 23 are arranged as described above, when the switches SW1 and SW2 are turned off by the calculation unit 23 (first unconnected state and second unconnected state), the capacitance detection voltage In the acquisition circuit 64, as shown in FIG. 3, a current flows along a path indicated by a two-dot chain line. Thereby, the capacitance detection voltage acquisition circuit 64 acquires the voltage Vin and the voltage V2.

Specifically, the signal acquired from the third electrode 23 by the third electrode voltage acquisition circuit 63 is input to the capacitance detection voltage acquisition circuit 64 via the photocoupler 42. This signal is a signal having the same frequency as the measurement voltage VL. In the capacitance detection voltage acquisition circuit 64, current flows through the path shown in FIG. 3, signal injection is performed on the second electrode 22, and the voltage V <b> 2 can be obtained from the first electrode 21. At this time, since the capacitance detection voltage acquisition circuit 64 is electrically insulated from the first to third electrode voltage acquisition circuits 61 to 63, the first electrode 21 and the second electrode are connected to the capacitance detection voltage acquisition circuit 64. The signal due to the measurement voltage VL of the measurement wire 11 does not flow directly through 22. Therefore, the voltage V2 does not become a mixed wave but can be taken out as an output voltage corresponding to the signal injected from the third electrode 23.

(Operation of Photocoupler 42, DC Offset Circuit 40, and Peripheral Circuit)
Here, operations of the photocoupler 42, the DC offset circuit 40, and peripheral circuits thereof will be described. FIG. 4 is a circuit diagram for explaining the operation of the third electrode voltage acquisition circuit 63 (the circuit on the LED side of the photocoupler 42). FIG. 5 is a circuit diagram for explaining the operation of the capacitance detection voltage acquisition circuit 64 (circuit on the transistor side of the photocoupler 42).

In FIG. 4, since the measurement voltage VL is a sine wave (alternating current), the voltage (signal) induced in the third electrode 23, the total current I flowing through the coupling capacitance CL3 of the third electrode 23, and the LED of the photocoupler 42 The current I1 flowing through is also a sine wave (AC). On the other hand, the LED of the photocoupler 42 does not react to a negative voltage. Therefore, the DC offset circuit 40 applies a DC offset voltage (Voffset) to the operational amplifier 37 so that the sine wave changes in the positive polarity region, and increases the negative voltage component induced in the third electrode 23. is doing.

In this case, assuming that the forward voltage of the LED of the photocoupler 42 is Vf and the output voltage of the operational amplifier 37 is Vo, the output voltage Vo and the current I1 flowing through the LED are
Vo = Voffset−Rf1 × I
I1 = (Vo−Vf) / Rf2
It becomes.

Next, in FIG. 5, when the current flowing through the transistor of the photocoupler 42 is I2, and the output voltage of the operational amplifier 38 is Vbuf, the current I2 and the output voltage Vbuf are
Vbuf = Vcc2-Rt1 × I2
I2 = a × I1 (a is the amplification factor of the photocoupler 42 transistor)
It becomes. Note that Vbuf = Vin.

Next, rewriting the expression of the output voltage Vbuf using the above expressions,
Vbuf = Vcc2-Rt1 × a × I1
= Vcc2− (Rt1 / Rf2) × a × (Vo−Vf)
= Vcc2− (Rt1 / Rf2) × a × (Voffset−Rf1 × I−Vf)
It becomes.

In the above Vbuf equation, the current I is a sine wave, and elements other than the current I are fixed values. Therefore, Vbuf (= Vin) is a sine wave having the same frequency as the entire current I flowing through the coupling capacitor CL3.

(Operations of the first and second electrode voltage acquisition circuits 61 and 62)
FIG. 6 is a circuit diagram for explaining the operation of the first electrode voltage acquisition circuit 61 and the second electrode voltage acquisition circuit 62.

On the other hand, in the voltage measuring apparatus 1, when the calculation unit 23 turns on the switches SW1 and SW2 (first connection state and second connection state), as shown in FIG. In the second electrode voltage acquisition circuit 62, a current flows along a path indicated by a one-dot chain line. The first electrode voltage acquisition circuit 61 acquires V11, and the second electrode voltage acquisition circuit 62 acquires V12.

Specifically, when the switch SW1 is turned on by the calculation unit 23, in a loop from the first electrode 21 to the first electrode 21 via the resistor R11, the switch SW1, and the measurement wire 11 connected to the ground. Current flows. Further, when the switch SW2 is turned on by the calculation unit 23, a current flows in a loop from the second electrode 22 to the second electrode 22 via the resistor R12, the switch SW2, and the measurement wire 11 connected to the ground. .

In the first electrode voltage acquisition circuit 61, a voltage V11 is induced in the first electrode 21 by the measurement voltage VL, and this voltage V11 is input to the calculation unit 24 via the operational amplifier 33 and the A / D converter 34. Similarly, in the second electrode voltage acquisition circuit 62, a voltage V12 is induced on the second electrode 22 by the measurement voltage VL, and this voltage V12 is input to the calculation unit 24 via the operational amplifier 35 and the A / D converter 36. The

(Operation of the calculation unit 24)
First, the calculation unit 24 uses the voltage Vin and the voltage V2 input from the capacitance detection voltage acquisition circuit 64, the coupling capacitance CL1 between the first electrode 21 and the core of the measurement wire 11, and the second electrode 22 and the measurement wire 11. The coupling capacitance CL2 with the core wire is calculated. In this case, the calculation unit 24 obtains a combined capacitance CL of the coupling capacitance CL1 and the coupling capacitance CL2 based on the circuit shown in FIG. FIG. 7 is an equivalent circuit of the capacitance detection voltage acquisition circuit 64 shown in FIG.

In FIG. 7, since the composite capacitor CL and the resistor R2 are connected in series, the absolute value of the impedance Z of the circuit of FIG. 7 is expressed by Expression (1).

Since the voltage V2 is a voltage at both ends of the resistor R2 when the voltage Vin is divided by the combined capacitor CL and the resistor R2, the equation (2) is obtained.

When formula (2) is arranged by combined capacitance CL, formula (3) is obtained.

Further, the combined capacitance CL, the coupling capacitance CL1, and the coupling capacitance CL2 have the relationship of the formula (4).

Next, the calculation unit 24 calculates the ratio between the coupling capacitance CL1 and the coupling capacitance CL2 from the voltage V11 input from the first electrode voltage acquisition circuit 61 and the voltage V12 input from the second electrode voltage acquisition circuit 62. To do. FIG. 8 is an equivalent circuit of the first electrode voltage acquisition circuit 61 shown in FIG. 6, and FIG. 9 is an equivalent circuit of the second electrode voltage acquisition circuit 62 shown in FIG.

In FIG. 8, since the coupling capacitor CL1 and the resistor R11 are connected in series, the absolute value of the impedance Z of the circuit of FIG. 8 is expressed by Equation (5).

Since the voltage V11 is a voltage across the resistor R11 when the measurement voltage VL is divided by the coupling capacitor CL1 and the resistor R11, the voltage V11 is expressed by Equation (6).

Since the circuit in FIG. 9 has the same configuration as the circuit in FIG. 8, the voltage 12 is expressed by Equation (7) in the same manner as the voltage 11.

Further, when formula (6) is arranged for the measurement voltage VL, formula (8) is obtained.

From Equations (6) and (7), if R11 = R12 and V12 / V11, the unknown VL can be eliminated, and Equation (9) is obtained.

Next, the calculation part 24 calculates | requires measurement voltage VL by the following calculation. First, the combined capacitance CL is calculated from the input voltage V2 by the equation (3). Next, the coupling capacity CL2 is calculated from the calculated combined capacity CL and Expression (4). The calculation of the coupling capacitance CL2 in this case is as follows.

CL2 = (1-CL) / (CL-1) × CL1
Next, when the calculated CL2 is substituted into the equation (9), the unknown amount becomes only the coupling capacitance CL1, and the coupling capacitance CL1 can be calculated. Next, the measured coupling voltage CL1 is substituted into the equation (8) to calculate the measurement voltage VL.

As described above, in the voltage measuring apparatus 1, when the switches SW1 and SW2 are turned off by the calculation unit 23, the capacitance detection voltage acquisition circuit 64 is formed, and the switches SW1 and SW2 are turned on by the calculation unit 23. In this case, the first electrode voltage acquisition circuit 61 and the second electrode voltage acquisition circuit 62 are formed. Further, the capacitance detection voltage acquisition circuit 64 and the first to third electrode voltage acquisition circuits 61 to 63 are electrically insulated from each other.

Therefore, in the capacitance detection voltage acquisition circuit 64, a signal (injection signal) induced in the third electrode 23 by the measurement voltage VL is injected into the second electrode 22, and from the third electrode 23, injection into the second electrode 22 is performed. Only the voltage V2 induced in the first electrode 21 by the signal can be taken out. In the first electrode voltage acquisition circuit 61 and the second electrode voltage acquisition circuit 62, the voltage V11 induced in the first electrode 21 by the measurement voltage VL and the voltage V12 induced in the second electrode 22 by the measurement voltage VL, respectively. Can be taken out. The calculation unit 24 obtains coupling capacitances CL1 and CL2 between the core wire of the measurement electric wire 11 and the first electrode 21 and the second electrode 22 based on the voltage Vin and the voltage V2. Further, the calculation unit 24 obtains the measurement voltage VL from the coupling capacitors CL1 and CL2, the voltage V11, and the voltage V12.

Thereby, in order to obtain the voltage V2, the voltage measuring device 1 does not require a means for separating the mixed wave, and a measurement value error due to separation accuracy does not occur. Therefore, the voltage measuring apparatus 1 can accurately measure the measurement voltage VL with a simple configuration.

[Substantial form of voltage measuring apparatus 1]
FIG. 10 is a longitudinal sectional view showing a substantial form of the voltage measuring apparatus 1, and FIG. 11 is a perspective view of the detection unit shown in FIG. The configurations shown in FIGS. 4 and 5 are the same for the voltage measuring devices of the other embodiments.

As shown in FIG. 10, the voltage measurement device 1 includes a detection unit 141 and a calculation unit 24. 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 second electrode 22 and the third electrode 23 are disposed on the upper surface portion of the lower housing portion 144, and the first electrode 21 is disposed on the lower surface portion of the upper housing portion 143 so as to face the second electrode 22. ing. The first electrode 21, the second electrode 22, and the third electrode 23 are formed in a semi-cylindrical shape in which a cylinder is vertically divided. Therefore, when the upper housing part 143 is closed with respect to the lower housing part 144, a cylinder is formed by the first electrode 21 and the second electrode 22, and the first to third electrodes 21 are formed around the measurement wire 11. To 23 can be arranged. In FIG. 10, 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.

Note that the arrangement form of the first to third electrodes 21 to 23 in the detection unit 141 is not limited to the above, and the measurement electric wire is obtained when the upper casing 143 is closed with respect to the lower casing 144. It is only necessary that the first to third electrodes 21 to 23 can be arranged around 11.

A detection circuit board 147 is arranged inside the lower housing part 144. The detection circuit board 147 is provided with circuits other than the first to third electrodes 21 to 23 and the calculation unit 24 in the voltage measuring apparatus 1 shown in FIG. The detection circuit board 147 is connected to the calculation unit 24 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 10 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.

In the present embodiment, the voltage (measurement voltage) VL of the measurement wire 11 is applied to the first electrode 21 and the second electrode 22 via the third electrode 23. However, instead of this, a voltage may be applied to the first electrode 21 and the second electrode 22 from an AC voltage generation source (frequency is 1 kHz or less) independent of the measuring wire 11 to obtain the voltage Vin and the voltage V2. . In this case, the AC voltage generated by the AC voltage generation source is preferably close to the frequency of the voltage (measurement voltage) VL of the measuring wire 11, and is more preferably, for example, 200 Hz or less. The AC voltage generation source may be connected to the GND 2 so as to generate AC from the output terminal of the operational amplifier 38. In this case, the third electrode 23, the operational amplifier 37, the photocoupler 42, and the power supply voltage Vcc2 (power supply that supplies Vcc2) are not required.

In the present embodiment, the calculation unit 24 is configured to turn on and off the switches SW1 and SW2, but the switches SW1 and SW2 may be controlled from the outside. In this case, the calculation unit 24 obtains information on the on / off control of the switches SW1 and SW2 (information on which timing is turned on and at which timing is turned off), and acquires the voltage at an appropriate timing.

[Summary]
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 the first electrode and the second electrode arranged around the insulating coating, and the first electrode is connected to the electric wire. A first switching unit that switches between a first connection state that is electrically connected to a first ground common to the first ground and a first non-connection state that is not connected, and is grounded to the first ground, and the AC A first voltage acquisition circuit capable of acquiring a first electrode voltage induced in the first electrode by a voltage when the first switching unit is in the first connection state; and A second switching unit that switches between a second connection state that is electrically connected to the ground and a second non-connection state that is not connected, and is grounded to the first ground and connected to the second electrode by the AC voltage Induced second electrode A second voltage acquisition circuit that can acquire a pressure when the second switching unit is in the second connection state, and a second ground that is insulated from the first ground, and the first When the switching unit is in the first disconnected state and the second switching unit is in the second disconnected state, the switching unit is induced in the first electrode by supplying an injection voltage to the second electrode. A capacitance detection voltage acquisition circuit that can acquire a voltage as a capacitance detection voltage; and a calculation unit that calculates the voltage of the electric wire from the first electrode voltage, the second electrode voltage, the injection voltage, and the capacitance detection voltage. It is a configuration.

According to the above configuration, the first voltage acquisition circuit is grounded to the first ground common to the ground of the electric wire. The first voltage acquisition circuit includes a first electrode that is induced in the first electrode by an AC voltage when the first switching unit is in a first connection state in which the first electrode is electrically connected to the first ground. Get the voltage. The second voltage acquisition circuit is grounded to the first ground. The second voltage acquisition circuit includes a second electrode that is induced in the second electrode by an AC voltage when the second switching unit is in a second connection state in which the second electrode is electrically connected to the first ground. Get the voltage. The capacitance detection voltage acquisition circuit is grounded to a second ground that is insulated from the first ground. The capacitance detection voltage acquisition circuit is in a first non-connected state in which the first switching unit does not electrically connect the first electrode to the first ground, and the second switching unit electrically connects the second electrode to the first ground. In the second non-connected state in which the connection is not performed, the voltage induced in the first electrode is obtained as the capacitance detection voltage by supplying the injection voltage to the second electrode. The calculation unit obtains the voltage of the electric wire from the first electrode voltage, the second electrode voltage, the injection voltage, and the capacitance detection voltage.

This makes it possible to accurately measure the voltage of the electric wire to be measured with a simple configuration.

In the voltage measuring device, the capacitance detection voltage acquisition circuit may supply an AC injection voltage having the same frequency as the AC voltage of the electric wire.

According to said structure, a capacity | capacitance detection voltage acquisition circuit acquires the voltage induced by the 1st electrode as a capacity | capacitance detection voltage by supplying the AC injection voltage of the same frequency as the AC voltage of an electric wire to a 2nd electrode. . As a result, it is no longer affected by the difference in the relative dielectric constant of the insulation of the wire due to the difference between the frequency of the AC voltage of the wire and the frequency of the injection voltage, and the voltage of the wire is affected by changes in temperature and humidity. Without being able to measure accurately.

The voltage measuring device includes a third electrode disposed around the insulating coating, and a third electrode that is grounded to the first ground and that is induced in the third electrode by the AC voltage. A voltage proportional to the third electrode voltage is applied as the injection voltage to the capacitance detection voltage acquisition circuit, and the third voltage acquisition circuit and the capacitance detection voltage acquisition circuit are insulated from each other. It is good also as a structure provided with the signal transmission part.

According to the above configuration, the third voltage acquisition circuit acquires the third electrode voltage induced in the third electrode by the AC voltage. The signal transmission unit applies a voltage proportional to the third electrode voltage as an injection voltage to the capacitance detection voltage acquisition circuit, and is grounded to the third voltage acquisition circuit and the second ground that are grounded to the first ground. It is insulated from the capacitance detection voltage acquisition circuit.

Thus, the third voltage acquisition circuit provides the capacitance detection voltage acquisition circuit with the same voltage and frequency as those of the electric wire without providing a supply power supply for the injection voltage. Can do.

In the voltage measuring device, the signal transmission unit may be a photocoupler.

According to the above configuration, since the signal transmission unit is a photocoupler, the signal transmission unit can be configured simply and inexpensively.

In the above voltage measuring device, the third voltage acquisition circuit is connected to the light-emitting diode of the photocoupler, and the third electrode is such that the polarity of the third electrode voltage that is an AC voltage is always positive. It is good also as a structure provided with the offset circuit which raises a voltage.

According to the above configuration, the third electrode voltage, which is an AC voltage, is raised by the offset circuit so that the polarity is always positive. As a result, when the signal transmission unit is a photocoupler, the light-emitting diode of the photocoupler can be appropriately driven to exhibit a good signal transmission function by the photocoupler.

In the voltage measuring device, the capacitance detection voltage and the injection voltage may be input to the arithmetic unit via the photocoupler.

According to the above configuration, since the capacitance detection voltage and the injection voltage are input to the calculation unit via the photocoupler, the capacitance detection voltage and the injection voltage are grounded to the first ground between the capacitance detection voltage acquisition circuit and the calculation unit. Even if a circuit is present, it is possible to ensure insulation between the circuit grounded to the first ground and the capacitance detection voltage acquisition circuit.

In the voltage measuring apparatus, the calculation unit obtains each capacitance between the core wire of the electric wire and the first electrode and the second electrode from the capacitance detection voltage and the injected voltage, It is good also as a structure which calculates | requires the voltage of the said electric wire from an electrostatic capacitance, the said 1st electrode voltage, and a 2nd electrode voltage.

According to the above configuration, the calculation unit can easily obtain the voltage of the electric wire from the first electrode voltage, the second electrode voltage, the injection voltage, and the capacitance detection voltage.

In the voltage measuring device, the injection voltage may have a frequency of 1 kHz or less.

According to the above configuration, the capacitance detection voltage acquisition circuit can supply a suitable injection voltage whose frequency is close to the frequency of the AC voltage of the electric wire to the second electrode.

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 first electrode is disposed around the insulating coating of the electric wire, and the first electrode is connected to a ground of the electric wire. A first electrode voltage acquisition step of acquiring a first electrode voltage induced in the first electrode by the AC voltage as a state of being electrically connected to a common first ground; A second electrode for obtaining a second electrode voltage induced in the second electrode by the AC voltage, with the second electrode disposed in a state where the second electrode is electrically connected to the first ground. In a voltage acquisition step, the first electrode and the second electrode are not electrically connected to the first ground, and an injection voltage is supplied to the second electrode, thereby being insulated from the first ground. A capacitance detection voltage acquisition step of acquiring a voltage induced at the first electrode as a capacitance detection voltage in a circuit grounded to the second ground, the first electrode voltage, the second electrode voltage, and the injection And a calculation step of obtaining the voltage of the electric wire from the voltage and the capacitance detection voltage.

According to the above configuration, the voltage of the wire to be measured can be accurately measured with a simple configuration, similar to the above voltage measuring device.

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 the embodiments are also included. It is included in the technical scope of the present 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 Measurement electric wire 21 1st electrode 22 2nd electrode 23 3rd electrode 24 Calculation part (calculation part)
31 operational amplifier 33 operational amplifier 40 DC offset circuit 41 insulation circuit 42 photocoupler (signal transmission unit)
43 Insulation circuit 44 Power supply circuit 61 First electrode voltage acquisition circuit (first voltage acquisition circuit)
62 Second electrode voltage acquisition circuit (second voltage acquisition circuit)
63 Third electrode voltage acquisition circuit (third voltage acquisition circuit)
64 Capacitance detection voltage acquisition circuit V2 voltage (capacitance detection voltage)
V11 voltage (first electrode voltage)
V12 voltage (second electrode voltage)
Vin voltage (injection voltage)
VL Measurement voltage CL1 Coupling capacitor CL2 Coupling capacitor GND1 First ground GND2 Second ground SW1 Switch (first switching unit)
SW2 switch (second switching part)

Claims

In a voltage measuring device that measures the AC voltage of a wire through the insulation of the wire,
A first electrode and a second electrode disposed around the insulating coating;
A first switching unit that switches between a first connection state in which the first electrode is electrically connected to a first ground common to the ground of the electric wire and a first non-connection state in which the first electrode is not connected; A first voltage acquisition circuit capable of acquiring a first electrode voltage grounded to ground and induced in the first electrode by the AC voltage when the first switching unit is in the first connection state;
A second switching unit that switches between a second connection state in which the second electrode is electrically connected to the first ground and a second non-connection state in which the second electrode is not connected, and is grounded to the first ground; A second voltage acquisition circuit capable of acquiring a second electrode voltage induced in the second electrode by an AC voltage when the second switching unit is in the second connection state;
When grounded to a second ground that is insulated from the first ground, the first switching unit is in the first non-connected state, and the second switching unit is in the second non-connected state A capacitance detection voltage acquisition circuit capable of acquiring a voltage induced in the first electrode by supplying an injection voltage to the second electrode as a capacitance detection voltage;
A voltage measuring device comprising: an arithmetic unit that obtains the voltage of the electric wire from the first electrode voltage, the second electrode voltage, the injection voltage, and the capacitance detection voltage.
The voltage measuring device according to claim 1, wherein the capacitance detection voltage acquisition circuit supplies an AC injection voltage having the same frequency as the AC voltage of the electric wire.
A third electrode disposed around the insulating coating;
A third voltage acquisition circuit that is grounded to the first ground and acquires a third electrode voltage induced in the third electrode by the AC voltage;
A signal transmission unit that applies a voltage proportional to the third electrode voltage as the injection voltage to the capacitance detection voltage acquisition circuit and insulates the third voltage acquisition circuit from the capacitance detection voltage acquisition circuit; The voltage measuring device according to claim 2, wherein
4. The voltage measuring device according to claim 3, wherein the signal transmission unit is a photocoupler.
The third voltage acquisition circuit is connected to a light emitting diode of the photocoupler, and includes an offset circuit for raising the third electrode voltage so that the polarity of the third electrode voltage, which is an AC voltage, is always positive. The voltage measuring device according to claim 4, wherein the voltage measuring device is provided.
The voltage measuring device according to claim 4, wherein the capacitance detection voltage and the injection voltage are input to the arithmetic unit via the photocoupler.
The calculation unit obtains each capacitance between the core wire of the electric wire and the first electrode and the second electrode from the capacitance detection voltage and the injection voltage, and each of the capacitance, the first The voltage measuring device according to claim 1, wherein the voltage of the electric wire is obtained from an electrode voltage and a second electrode voltage.
The voltage measuring device according to claim 1, wherein the injection voltage has a frequency of 1 kHz or less.
In the voltage measurement method that measures the AC voltage of the wire through the insulation of the wire,
A first electrode is disposed around the insulation coating of the electric wire, and the first electrode is electrically connected to a first ground common to the electric wire ground, and the first electrode is connected to the first electrode by the AC voltage. A first electrode voltage acquisition step of acquiring an induced first electrode voltage;
A second electrode which is induced in the second electrode by the AC voltage in a state where a second electrode is arranged around the insulation coating of the electric wire and the second electrode is electrically connected to the first ground. A second electrode voltage acquisition step of acquiring a voltage;
The first electrode and the second electrode are not electrically connected to the first ground, and an injection voltage is supplied to the second electrode, so that the second electrode is insulated from the first ground. A capacitance detection voltage acquisition step of acquiring a voltage induced in the first electrode as a capacitance detection voltage in a circuit grounded to ground;
A voltage measuring method comprising: a calculation step of obtaining a voltage of the electric wire from the first electrode voltage, the second electrode voltage, the injection voltage, and the capacitance detection voltage.