JP3158063B2 - Non-contact voltage measurement method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring an AC voltage applied to a conductor covered with an insulator, such as a vinyl insulated wire, in a non-contact manner with the conductor.

[0002]

2. Description of the Related Art Conventionally, an AC voltmeter has been generally used for measuring a commercial AC voltage applied to an insulated wire.

However, in the conventional method using an AC voltmeter, it is necessary to bring one of the electrodes for measurement into contact with a conductor, so that a part of the coating of the insulated wire is peeled off, or a terminal for measurement is provided in advance. Had to be kept.

Therefore, in order to measure the voltage applied to the insulated wire without contacting the conductor, a pickup covering the insulating coating of the insulated wire, a shield covering the pickup, and a series connected between the pickup and the ground. And an operational amplifier whose input side is connected to the connection point of the two resistors and whose output side is connected to the shield, and whose amplification is equal to the reciprocal of the voltage division ratio of the two resistors. A contact voltage measurement device has been proposed (Japanese Utility Model Laid-Open No. 6-28748).

[0005]

However, according to the conventional non-contact voltage measuring device described above, the output of the operational amplifier is used as a measuring point, so that the output of the operational amplifier becomes equal to the voltage applied to the insulated wire. . That is, since the output of the operational amplifier becomes a high voltage such as 100 volts or 200 volts, it is necessary to configure an operational amplifier having a high withstand voltage and a high output, and there is a disadvantage that the configuration of the device becomes complicated and expensive. In addition, since it is necessary to supply a high voltage to the device, it is not suitable for portable use.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and does not require the use of a special operational amplifier having a high withstand voltage and a high output, can operate at a low voltage, and is suitable for portable use. An object of the present invention is to provide a voltage measuring method and a voltage measuring apparatus.

[0007]

According to a first aspect of the present invention, there is provided a method for measuring an AC voltage applied to a conductor coated with an insulator in a non-contact manner with the conductor.
Using a detection probe having a detection electrode capable of covering a part of the surface of the insulator and a shield electrode covering the detection electrode, and an oscillator that outputs a signal of a predetermined frequency,
By applying the signal of the oscillator to the detection electrode, measure the impedance between the detection electrode and the conductor, measure the current flowing out of the detection electrode due to the voltage applied to the conductor, A voltage applied to the conductor is measured from the current and the impedance.

According to a second aspect of the present invention, there is provided a detection electrode capable of covering a part of the surface of the insulator and electrostatically shielding a part of the conductor from the outside, and a method of keeping the detection electrode static from the outside. Using a detection probe with a shield electrode for electric shielding, and an oscillator that outputs a signal of a predetermined frequency,
The state where the detection probe is separated from the insulator and the detection
With the probe covered with the insulator.
In state, by adding to the detection electrode via a detection resistor a signal of the oscillator, the impedance between the detecting electrode and the conductor is measured, a portion of the surface of the insulator by the detecting probe In the covered state, a current flowing from the detection electrode due to a voltage applied to the conductor is measured, and a voltage applied to the conductor is measured from the current and the impedance.

According to a third aspect of the present invention, there is provided an apparatus for measuring an AC voltage applied to a conductor coated with an insulator in a non-contact manner with the conductor, wherein a surface of a part of the insulator is measured. A detection probe that includes a detection electrode that covers the conductor and electrostatically shields a part of the conductor from the outside, and a shield electrode for electrostatically shielding the detection electrode from the outside.
An oscillator that outputs a signal of a predetermined frequency, and an impedance measuring unit that measures an impedance between the detection electrode and the conductor by applying a signal of the oscillator to the detection electrode via a detection resistor. Outflow current measurement means for measuring the current flowing out of the detection electrode due to the voltage applied to the conductor, and conductor voltage measurement means for measuring the voltage applied to the conductor from the current and the impedance, It is configured to have.

According to a fourth aspect of the present invention, there is provided a detection electrode capable of covering a part of the surface of the insulator and electrostatically shielding a part of the conductor from the outside, and disposing the detection electrode from the outside. A detection probe having a shield electrode for electrically shielding, an oscillator that outputs a signal having a frequency different from the frequency of the AC voltage applied to the conductor and whose output impedance is sufficiently low, and an output of the oscillator. A detection resistor connected to the detection electrode; current detection means for detecting a current flowing through the detection resistor based on a voltage appearing at both ends of the detection resistor; output from the current detection means A first filter that passes only the signal of the oscillator from among the signals, a signal output from the first filter in a state where the detection probe is separated from the insulator, and the detection probe. Ri based on the signal output from the first filter while covering a portion of the surface of the insulator,
A capacitance measuring means for measuring a capacitance C1 between the detection electrode and the conductor, and passing only a signal of a frequency of a voltage applied to the conductor from signals output from the current detecting means A second filter to be performed, based on a signal output from the second filter, an outflow current measuring unit that measures a current flowing out of the detection electrode due to a voltage applied to the conductor, And a conductor voltage measuring means for measuring a voltage applied to the conductor from the capacitance C1.

In the apparatus according to a fifth aspect of the present invention, the capacitance measuring means measures the rectifier for rectifying a signal output from the first filter, and measures the detection probe in a state where the detection probe is separated from the insulator. Further , the capacitance between the detection electrode and the shield electrode and the stray capacitance of the detection electrode
A capacitance storage unit for storing the combined capacitance C0, a signal output from the rectifier with the detection probe covering a part of the surface of the insulator, and a signal stored in the capacitance storage unit. Capacitance calculating means for calculating the capacitance C1 based on the capacitance C0, wherein the conductor voltage measuring means outputs a signal output from the integrator to the output from the capacitance measuring means. And a divider for dividing by a capacitance C1.

[0012] In the apparatus according to claim 6, the frequency of the oscillator is set higher than the frequency of the voltage applied to the conductor. According to a seventh aspect of the present invention, there is provided an electric power measuring means for measuring electric power supplied by the conductor based on the measured voltage.

[0013]

FIG. 1 is a block diagram showing the configuration of a voltage measuring device 1 according to the present invention, FIG. 2 is a front view showing an example of the structure of a detection probe 11, and FIG. Is an equivalent circuit.

In FIG. 1, a voltage measuring device 1 includes a detecting resistor R1, a detecting probe 11, an oscillator 12, a current detecting unit 13, an impedance measuring unit 14, and an outflow current measuring unit 1.
5, a conductor voltage measuring unit 16, a power measuring unit 17, and a display unit 18.

[0015] The detection probe 11 is an insulator S of the electric wire WR.
A cylindrical detection electrode 111 that covers a part of the surface of L and electrostatically shields a part of the conductor CD from the outside, and a cylindrical shield electrode for electrostatically shielding the detection electrode 111 from the outside. 112 is provided. These detection electrodes 111
The shield electrode 112 and the shield electrode 112 are both cylindrical and have the same length. Its length is for example 2-4
cm. Detection electrode 111 and shield electrode 112
A support member 113 made of an insulator is provided between the two.

As shown in FIG. 2, the detection electrode 111, the shield electrode 112, and the support member 113 are divided by a diametric plane, and each part has a shaft 115.
Arms 114, 114 that can rotate around the center are attached. A spring 116 that urges the arms 114 and 114 in a direction to open each other is mounted.

Therefore, in the free state, the detection probe 11 is in an open state as shown in FIG. 2A, and the operator grips the arms 114, 114 by hand and resists the urging force of the spring 116. By pressing down, it becomes a closed state as shown in FIG. When the detection probe 11 is in the closed state, the state is detected by the sensor SE1.

As the sensor SE1, a limit switch, a proximity sensor, a photo sensor, and other various sensors are used. Although not shown, the lead wire of the sensor SE1, the detection electrode 111, and the shield electrode 1
An electric wire or the like connected to the power supply 12 is provided.

Referring again to FIG. 1, the oscillator 12 has a frequency sufficiently higher than the commercial AC frequency of 50 Hz or 60 Hz, and a frequency sufficiently higher than a frequency of about 500 Hz which may be supplied from an inverter or the like. A signal of a constant voltage Es of a sine wave having a frequency of, for example, about 10 times the frequency of 5 KHz is output. The output impedance of the oscillator 12 is sufficiently lower than that of the detection resistor R1, so that the output of the oscillator 12 and the detection resistor R1
Is equivalent to being grounded when viewed from the detection electrode 111 side. Also, for the conductor CD,
Seen from the side of the oscillator 12, this is equivalent to being grounded.

The current detector 13 detects a current flowing into the detection electrode 111 and a current flowing out of the detection electrode 111, and outputs a signal S1. In the present embodiment, the current I flowing through the detection resistor R1 is detected based on the voltage Er that appears at both ends of the detection resistor R1.

The current I includes a current component Is flowing toward the detection electrode 111 by the signal Es of the oscillator 12, and
And a current component Ix flowing out of the detection electrode 111 toward the oscillator 12. Therefore, voltage component Ers generated due to signal Es of oscillator 12 is included in voltage Er.
And a voltage component Erx caused by the voltage Ex applied to the conductor CD. These voltage components Ers,
Erx is discriminated by using a filter or the like, utilizing characteristics due to different frequencies f.

The impedance measuring section 14 includes the oscillator 12
Of the detection electrode 111 via the detection resistor R1.
, The impedance Zw between the detection electrode 111 and the conductor CD is measured.

The outflow current measuring unit 15 measures a current Ix flowing out of the detection electrode 111 due to the voltage Ex applied to the conductor CD. The conductor voltage measuring unit 16 measures the voltage Ex applied to the conductor CD from the current Ix and the impedance Zw.

The power measuring unit 17 calculates the measured voltage Ex
And the power supplied to the load by the conductor CD based on the current and a separately input current. The display unit 18 displays the measured voltage Ex or the measured power. The display unit 18
An analog type using a meter or a digital type using a liquid crystal may be used.

The voltage measuring device 1 is intended to measure the voltage of a commercial AC power supply (including inverter application equipment). For this reason, the frequency fs of the signal Es of the oscillator 12 is made different from the frequency fx of the voltage Ex supplied to the conductor CD, and the current component due to them is discriminated using a filter. This simplifies the processing and simplifies the configuration. However, the frequency fs of the signal Es of the oscillator 12 is changed to the frequency fx of the voltage Ex.
It is also possible to measure the impedance Zw by periodically varying the voltage value of the signal Es of the oscillator 12, for example.

Since the measured values of the impedance Zw, the current Ix, the voltage Ex, and the like can be easily converted into numerical values or units, it is only necessary to obtain information relating to those phenomenon values. , Amps, or volts need not be obtained.

The impedance measuring unit 14, the outflow current measuring unit 15, the conductor voltage measuring unit 16 and the like can be realized by executing an appropriate program using a microprocessor, a ROM, a RAM and the like.

Next, another embodiment of the voltage measuring device will be described. FIG. 3 is a block diagram showing a configuration of a voltage measuring device 1A according to another embodiment of the present invention.

The voltage measuring device 1A includes a detecting resistor R1,
Detection probe 11, oscillator 12, current detector 13, first
Bandpass filter 21 as filter, rectifier 2
2, a capacitance calculation unit 23, a stray capacitance detection unit 24, a switch 25, a low-pass filter 26 as a second filter,
It comprises an integrator 27 and a divider 28. Rectifier 2
2. The capacitance calculation unit 23 and the stray capacitance detection unit 24 constitute a capacitance measurement unit 20 as capacitance measurement means.

Since the impedance Zw between the detection electrode 111 and the conductor CD is mainly the reactance XC1 due to the capacitance C1 between them, the reactance XC1, that is, the capacitance C1, is measured instead of Zw. Shall be.

The capacitance between the detection electrode 111 and the shield electrode 112, the stray capacitance due to the wiring to the detecting resistor R1, and the combined capacitance due to other stray capacitances are C0, and the reactance due to this is XC0. I do. The capacitance C0 may be referred to as “floating capacitance C0”. The value of the capacitance C1 is about several tenths pF to several pF, and the value of the stray capacitance C0 is about several pF to several tens pF.

The value of the detection resistor R1 is the reactance X
C1 and XC0 should be small enough to be ignored.
For example, it is 10 to 1000 KΩ. In the present embodiment, it is 100 KΩ.

As described above, the current flowing from the oscillator 12 to the detection electrode 111 through the detection resistor R1 is Is
And the current flowing from the detection electrode 111 toward the oscillator 12 is Ix.

Of the current Is, the current flowing into the ground pole (earth pole) via the stray capacitance C0 is Is ₀ , and the current flowing into the ground pole via the capacitance C1 and the conductor CD is Is.
_Set to ₁ .

The detecting resistor R1, the detecting probe 11, the oscillator 12, and the current detecting section 13 are the same as those described in relation to the voltage measuring device 1, and the description is omitted here.

The band-pass filter 21 includes the current detector 1
3 out of the signal S1 output from the signal E3. Therefore, the center frequency is 5 KHz, which is the same as the frequency fs of the oscillator 12, and
The blocking characteristic is 18 dB / oct or more.

The rectifier 22 rectifies the signal S2 output from the band-pass filter 21 and outputs a signal S3 corresponding to the amplitude.
Is output. The stray capacitance detection unit 24 includes the detection probe 11
Is separated from the electric wire WR (the state shown in FIG. 2A), the stray capacitance C0 is measured and stored. Specifically, immediately before the detection probe 11 closes, the switch 2
5, the stray capacitance C0 is measured based on the output signal S3 of the rectifier 22 at that moment, and the value is stored.

The capacitance calculation unit 23 includes the detection probe 11
Then, the capacitance C1 is calculated based on the signal S3 output from the rectifier 22 while covering the surface of the insulator SL and the stray capacitance C0 stored in the stray capacitance detection unit 24. The obtained capacitance C1 is output to the divider 28 as a signal S4.

The low-pass filter 26 is connected to the current detector 13
From the signal S1 output from the terminal A, only the signal due to the voltage Ex applied to the conductor CD is passed. Therefore, the cutoff frequency is 800 Hz, which is higher than the highest frequency (500 Hz) supplied to the conductor CD, and the cutoff characteristic is 18 dB / oct or more.

If the voltage E applied to the conductor CD is
If the frequency of x is even higher than above, the oscillator 1
By lowering the frequency fs of the signal Es2 so as to be about one tenth thereof and changing the low-pass filter 26 to a high-pass filter, the two currents Is and Ix can be discriminated.

The integrator 27 integrates the signal S5 output from the low-pass filter 26. Thus, the phase of the signal waveform is corrected. The integrator 27 corresponds to the outflow current measuring means in the present invention. FIG. 5 shows an example of the circuit of the integrator 27.

The divider 28 obtains the voltage Ex by dividing the signal S6 (Erx) output from the integrator 27 by the signal S4 (electrostatic capacitance C1) output from the capacitance calculator 23. The divider 28 corresponds to the conductor voltage measuring means in the present invention.

Next, an example of calculation in the voltage measuring device 1A will be described with reference to FIG. First, detection probe 1
1 is opened (the state shown in FIG. 2A), the stray capacitance C0 is measured.

When viewed from the oscillator 12, the detection resistor R
1 and the impedance Z0 of the circuit reaching the ground through the stray capacitance C0 is as follows: Z0 = R1 + jXC0 where j is an imaginary unit. However, since the detection resistor R1 is smaller than the reactance XC0 and can be ignored, Z0 = XC0 Good.

Therefore, the current Is ₀ flowing into the stray capacitance C 0 by the signal Es output from the oscillator 12 is: Is ₀ = Es / Z 0 = Es / XC 0 (1) The voltage across the detection resistor R 1 Er _{is, Er = is 0 × R1 =} (Es × R1) / XC0 ... (2) Therefore, XC0 = (Es × R1) / Er C0 = (Es × R1) / ωs · Er ... (3) However, ωs Is the angular frequency of the signal Es of the oscillator 12 (ωs =
1 / 2πfs).

The stray capacitance C obtained by the equation (3)
The value of 0 is stored in the stray capacitance detection unit 24. Next, a state in which the detection probe 11 is closed (a state shown in FIG. 2B).
Then, the capacitance C1 is measured.

As the detection electrode 111 covers the electric wire WR, the capacitance C1 is added. Therefore, the impedance Zw seen from the oscillator 12 is as follows: Zw = R1 + jXCc (4) Cc = C0 + C1 Since the detection resistor R1 is smaller than the reactance XCc and can be ignored, Zw = XCc.

Therefore, the current Is flowing into the detection resistor R1 by the signal Es output from the oscillator 12
Is = Es / Zw = Es / XCc (5) The voltage Er across the detection resistor R1 is: Er = Is × R1 = (Es × R1) / XCc (6) Therefore, XCc = (Es × R1) / Er Also, since XCc is ωs (C0 + C1), C0 + C1 = (Es × R1) / ωs · Er (7) The capacitance (C0 + C1) obtained by the equation (7)
Is input to the capacitance calculator 23 as the signal S3.

The capacitance calculator 23 calculates the capacitance C1 by subtracting the value of the stray capacitance C0 stored in the stray capacitance detector 24 from the value of the input capacitance (C0 + C1). Are output to the divider 28.

Next, with the detection probe 11 closed,
The voltage Er across the detection resistor R1 due to the voltage Ex applied to the conductor CD is determined. The impedance Zx of the circuit passing through the detection resistor R1 viewed from the conductor CD side
Zx = R1 + jXC1 (8) Since the detection resistor R1 is small compared to the reactance XC1 and can be ignored, Zx = XC1.

Therefore, the voltage E applied to the conductor CD
The current Ix flowing into the detection resistor R1 due to x is: Ix = Ex / Zx = Ex / XC1 (9) The voltage Er across the detection resistor R1 is Er = Ix × R1 = (Ex × R1) / XC1 = ωx × C1 × (Ex × R1) (10) where ωx is the angular frequency of the voltage Ex applied to the conductor CD (ωx = 2πfx).

The voltage Er obtained by the equation (10)
The value of (Ers) is input to the divider 28 as a signal S6. The divider 28 obtains the voltage Ex by dividing the input voltage Er by a coefficient including the capacitance C1 output from the capacitance calculator 23. That is, Ex = Er / (ωx × C1 × R1) (11)

The obtained voltage Ex is output from the divider 28 and is displayed by a display unit (not shown).
Further, the determined voltage Ex and the separately detected electric wire WR
Is calculated on the basis of the current I flowing through the device, and the result is displayed on the display unit.

Further, instead of or in addition to the display on the display unit, an input may be made to a computer (not shown) so that various operations or digital processing can be performed in the computer.

The measurement of the capacitance C1 when the detection probe 11 is closed, the calculation of the voltage Er across the detection resistor R1 due to the voltage Ex, and the calculation of the voltage Ex are as follows.
This is executed at the moment when the detection probe 11 is closed.

Using the above-described voltage measuring devices 1 and 1A, the voltage Ex applied to the electric wire WR can be easily measured from above the insulator SL. Therefore, there is no need to peel off part of the insulator SL or to provide a measurement terminal in advance.

Furthermore, since the measurement of the voltage Er or the currents Ix and Is can be performed at a low voltage, it is not necessary to use a special operational amplifier or circuit having a high withstand voltage or a high output.
Further, since the power supply may be at a low voltage, the power supply can be easily obtained with a commercially available dry battery or the like, and is suitable for portable use.

The voltage Ex applied to the single wire WR can be easily measured using the voltage measuring device 1.1A described above. For example, a plurality of voltage measuring devices 1.1A can be used to measure two wires. It is also possible to measure the voltage applied in between, or the voltage of each phase of the three-phase electric wire. In addition, various electric wires, for example, low voltage, high voltage,
Voltage, power, and the like applied to indoor wiring, distribution lines, power lines, wiring in control panels, or electrical devices, circuit elements, and the like can be measured.

In the above embodiment, the oscillator 12 has a constant voltage output, but may have a constant current output. FIG. 6 shows an example of a circuit of the main part. In the above embodiment, the frequency fs of the signal Es of the oscillator 12
Is different from the frequency fx of the voltage Ex supplied to the conductor CD, but when these frequencies fx and fs are equal, it can be measured, for example, as follows.

That is, in order to obtain the capacitance C1,
The output voltage of the oscillator 12 is two types of Es1 and Es2,
These voltages Es1 and Es2 are applied to the detection resistor R1 in a time division manner. In this case, the currents Is1 and Is2 flowing through the detection resistor R1 are: Is1 = Es1 / [X · (C0 + C1)] + Ex / XC1 (12) Is2 = Es2 / [X · (C0 + C1)] + Ex / XC1 (13) From these equations (12) and (13), Is1−Is2 = Es1 / [X · (C0 + C1)] − Es2 / [X · (C0 + C1)] = jωs (C0 + C1) (Es1−Es2) (14) When the capacitance C1 is obtained from the equation (14), C1 = (Is1-Is2) / [ωs (Es1-Es2)] − ωsC0 (15) Since the stray capacitance C0 is obtained by the same method as described above, it is possible to measure the voltage Ex therefrom.
However, the operation is more complicated than described above.

The structure and shape of the detection probe 11 described above
The material, the configuration of the whole or each part of the voltage measuring devices 1 and 1A, the constants, the order of operation, the contents, the timing, and the like can be appropriately changed according to the gist of the present invention.

[0062]

According to the first to seventh aspects of the present invention,
There is no need to use a special high-voltage and high-output operational amplifier, and it is possible to provide a non-contact voltage measurement method and apparatus which can operate at a low voltage and are suitable for portable use.

According to the fourth and fifth aspects of the present invention, the processing is simplified and the configuration is simplified. According to the invention of claim 6, the voltage of the commercial AC power supply or the power supply supplied by the inverter can be easily measured.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a voltage measuring device according to the present invention.

FIG. 2 is a front view showing an example of the structure of a detection probe.

FIG. 3 is a block diagram illustrating a configuration of a voltage measurement device according to another embodiment of the present invention.

FIG. 4 is an equivalent circuit of a main part of the voltage measuring device.

FIG. 5 is a diagram illustrating an example of a circuit of an integrator.

FIG. 6 is a diagram showing an example of a circuit of a main part when the oscillator has a constant current output.

[Explanation of symbols]

Reference Signs List 1, 1A voltage measurement device 11 detection probe 12 oscillator 13 current detection unit (current detection unit) 14 impedance measurement unit (impedance measurement unit) 15 outflow current measurement unit (outflow current measurement unit) 20 capacitance measurement unit (capacitance) Measurement unit) 21 Band-pass filter (first filter) 22 Rectifier 23 Capacitance calculation unit (capacitance calculation unit) 24 Stray capacitance detection unit (capacitance storage unit) 26 Low-pass filter (second filter) 27 Integrator (Outflow current measurement means) 28 Divider (conductor voltage measurement means) 111 Detection electrode 112 Shield electrode R1 Detection resistor CD Conductor SL Insulator

Claims (7)

(57) [Claims] 1. A method for measuring an AC voltage applied to a conductor covered with an insulator in a non-contact manner with the conductor, the detection electrode being capable of covering a partial surface of the insulator. And a detection probe having a shield electrode covering the detection electrode, and an oscillator that outputs a signal of a predetermined frequency. By applying a signal of the oscillator to the detection electrode, a gap between the detection electrode and the conductor is obtained. Measuring the current flowing out of the detection electrode due to the voltage applied to the conductor, and measuring the voltage applied to the conductor from the current and the impedance. Non-contact voltage measurement method. 2. A method for measuring an AC voltage applied to a conductor covered with an insulator in a non-contact manner with the conductor, wherein the conductor covers a part of the insulator and partially covers the conductor. Using a detection electrode capable of electrostatically shielding the external electrode from the outside, a detection probe having a shield electrode for electrostatically shielding the detection electrode from the external world, and an oscillator that outputs a signal of a predetermined frequency; said analyzing and to be apart probes from said insulator
With the probe covered with the insulator.
In state, by adding to the detection electrode via a detection resistor a signal of the oscillator, the impedance between the detecting electrode and the conductor is measured, a portion of the surface of the insulator by the detecting probe In a covered state, a current flowing out of the detection electrode due to a voltage applied to the conductor is measured, and a voltage applied to the conductor is measured from the current and the impedance. Non-contact voltage measurement method. 3. An apparatus for measuring an AC voltage applied to a conductor coated with an insulator in a non-contact manner with the conductor, the AC voltage covering a part of the insulator and partially covering the conductor. A detection electrode capable of electrostatically shielding the external electrode from the outside, a detection probe having a shield electrode for electrostatically shielding the detection electrode from the external world, an oscillator for outputting a signal of a predetermined frequency, and a signal of the oscillator Is applied to the detection electrode via a detection resistor to measure the impedance between the detection electrode and the conductor, and flows out of the detection electrode due to a voltage applied to the conductor. Outflow current measuring means for measuring a current to flow, and conductor voltage measuring means for measuring a voltage applied to the conductor from the current and the impedance. Non-contact voltage measurement device for. 4. An apparatus for measuring an AC voltage applied to a conductor covered with an insulator in a non-contact manner with the conductor, the AC voltage covering a part of the insulator and partially covering the conductor. A detection electrode capable of electrostatically shielding the external electrode from the outside and a detection probe including a shield electrode for electrostatically shielding the detection electrode from the external world; and a frequency different from a frequency of an AC voltage applied to the conductor. An oscillator having a sufficiently low output impedance and a detection resistor connecting the output of the oscillator and the detection electrode; and a detection resistor based on a voltage appearing at both ends of the detection resistor. Current detection means for detecting a current flowing through a resistor; a first filter for passing only the signal of the oscillator from signals output from the current detection means; The detection electrode and the detection electrode based on a signal output from the first filter in a state separated from the first filter and a signal output from the first filter in a state where a part of the surface of the insulator is covered by the detection probe. A capacitance measuring means for measuring a capacitance C1 between the conductor and a second signal for passing only a signal having a frequency of a voltage applied to the conductor from signals output from the current detecting means;
A filter, based on a signal output from the second filter, an outflow current measuring unit that measures a current flowing out of the detection electrode due to a voltage applied to the conductor, the outflow current and the capacitance A contact voltage measuring means for measuring a voltage applied to the conductor from C1; and a non-contact voltage measuring device. Wherein said capacitance measuring means, said a first rectifier for rectifying the signal outputted from the filter was measured in a state where the detection probe is released from the insulating material, the said detection electrode shield Electrostatic capacitance between electrodes
Capacitance storage means for storing a combined capacitance C0 of the amount and the stray capacitance of the detection electrode; and a signal output from the rectifier in a state where the detection probe covers part of the surface of the insulator. Capacitance calculating means for obtaining the capacitance C1 based on the capacitance C0 stored in the capacitance storage means, wherein the conductor voltage measuring means is output from the outflow current measuring means. 5. The non-contact voltage measurement device according to claim 4, further comprising: a divider that divides the output signal by a capacitance C <b> 1 output from the capacitance measurement unit. 6. The non-contact voltage measuring device according to claim 3, wherein the frequency of the oscillator is set higher than the frequency of the voltage applied to the conductor. 7. The non-contact voltage measurement according to claim 3, further comprising a power measurement unit that measures power supplied by the conductor based on the measured voltage. apparatus.