JP2001050986A - Noncontact-type voltage probe device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a noncontact-type voltage probe device which can measure a voltage down to a low-frequency region of 10 kHz or lower. SOLUTION: A voltage signal, which is generated across an inner cylindrical electrode 101a and an outer cylindrical electrode 101b, is electricity-to-light- converted by an electricity-to-light conversion part 103. A light signal which is electricity-to-light-converted by the electricity-to-light conversion part 103 is input to a photoelectric conversion part 105 via an optical fiber 106 so as to be photoelectrically converted. Then, a voltage signal which is photoelectrically converted by the photoelectric conversion part 105 is detected by a voltage detection means 107.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact voltage probe device for measuring a voltage induced in an electric cable to be measured by capacitive coupling without cutting the electric cable to be measured, and to a light modulation circuit for a voltage detecting circuit. The present invention relates to a non-contact type voltage probe device using light-to-light conversion means such as a measuring instrument.

[0002]

2. Description of the Related Art In the field of electromagnetic compatibility (EMC), interference such as erroneous operation of a telephone due to CB wireless communication and mixing of a broadcast wave into the telephone is caused by an interference wave that enters a device in a common mode through a cable. The malfunction of the electronic device has become a problem. In particular, recently, malfunctions of communication devices in a low frequency range due to the inverter device have become a problem. In order to prevent conducted disturbances to communication equipment such as telephones, it is necessary to measure the voltage and current that penetrate the communication equipment and accurately understand the entry path and level of the intruded disturbance. is there. Further, in order to grasp the situation of malfunction of the communication device due to the interference wave, it is necessary to measure the voltage and current of the interference wave in the service operation state.

[0003] In order to measure the above-mentioned interference wave, a conductive interference wave transmitted through a cable connected to a communication device, particularly, a common mode voltage generated between the ground and the ground is efficiently and operationally communicated. There is a need for the development of a voltage probe device that can easily and accurately measure without affecting the signal. As this voltage probe device, a non-contact type voltage probe utilizing electrostatic coupling with a cable has been proposed (Japanese Patent Application Laid-Open No. 9-222442).

[0004]

However, in the conventional non-contact type voltage probe device, the input impedance of the voltage detection circuit for detecting the voltage of the interfering wave transmitted through the cable is as low as 1 MΩ to 10 MΩ, and the input voltage is less than 10 kHz. Voltage detection sensitivity was reduced. This 10kHz
In the following frequency bands, the waveform of an interference wave is often measured in the time domain. For this reason, a change in sensitivity of voltage detection by the conventional non-contact type voltage probe device in a low frequency band of 10 kHz or less has been a major problem in measuring the voltage of an interference wave.

The present invention has been made to solve the above problems, and has as its object to provide a non-contact type voltage probe device capable of measuring a voltage up to a low frequency region of 10 kHz or less. I have.

[0006]

According to the present invention, there is provided a non-contact type voltage probe device which is arranged near an electric cable to be measured and electrostatically couples to the electric cable; and a coupling electrode and a potential reference plane. Photoelectric conversion means for converting a voltage signal between the ground and the ground into an optical signal by photoelectric conversion, photoelectric conversion means for photoelectrically converting the optical signal into an electric signal, and voltage of the electric signal converted by the photoelectric conversion means Voltage detecting means for detecting a value. According to the present invention, the voltage signal between the coupling electrode and the ground is converted from an optical signal by the light-to-light converter to an electric signal by the photoelectric converter, and the voltage value is detected by the voltage detector from the electric signal. Therefore, the voltage applied to the electric cable is detected as a voltage value of the electric signal obtained by performing a photoelectric conversion on the voltage signal once and then performing the photoelectric conversion.

[0007] Further, since an outer electrode is newly provided so as to be spaced apart from the coupling electrode and to cover the outside of the coupling electrode and to be grounded to the ground, the outer electrode functions as an electrostatic shield. Therefore, the outer electrode can prevent the coupling between the coupling electrode and a metal body other than the electric cable around the coupling electrode. The coupling electrode may be formed in a cylindrical shape covering the periphery of the electric cable, and similarly, the outer electrode may be formed in a cylindrical shape covering the outside of the coupling electrode.

The light-to-light conversion means may comprise a light source, and a light modulator for intensity-modulating light emitted from the light source with a voltage signal and outputting a light signal. The light modulating section is composed of a substrate made of LiNbO ₃ , two parallel waveguides made of a core formed by introducing Ti into the substrate, and connected to the input ends of the two waveguides to form a light modulating section. An input waveguide for splitting input light into two waveguides,
An output waveguide connected to the output ends of the two waveguides to combine the output lights of the two waveguides into one, and a first and a second formed outside the two waveguides on the substrate, respectively. A voltage signal is applied to the first and second electrodes, and light emitted from the light source enters the input waveguide,
An optical signal is emitted from the output waveguide. Also,
The light modulating section extracts an electro-optic crystal made of a crystal of LiNbO ₃ to which a voltage signal is applied and a linearly polarized light component inclined by 45 ° with respect to the optical axis of the electro-optic crystal from light emitted from a light source. And a polarizer to be introduced into the electro-optic crystal. The light-to-light conversion means may be constituted by a semiconductor laser. When light-to-light conversion is performed using this semiconductor laser, the voltage signal can be light-to-light converted to an optical signal without using a new light source. In addition, an optical fiber for transmitting an optical signal is provided, and the optical signal is transmitted through the optical fiber.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a non-contact type voltage probe according to the present invention is first formed in a cylindrical shape through which a cable to be measured passes in the center, and directly connected to a cable 108 to be measured passing through the inside of the cylinder. An electrode (coupling electrode) 101a is provided. Further, an outer cylinder formed around the inner cylindrical electrode 101a in a cylindrical shape covering the inner cylindrical electrode 101a and serving as an electrostatic shield for preventing coupling of the surrounding metal body and the inner cylindrical electrode 101a. A shape electrode (outer electrode) 101b is provided. The inner cylindrical electrode 101a and the outer cylindrical electrode 101b are coaxial cylindrical electrodes composed of two semi-cylindrical coaxial conductors used for non-contact detection of a voltage applied to the cable 108 to be measured. is there. In addition, the outer cylindrical electrode 10
1b is connected to a potential reference plane 110 such as the ground via a ground wire 109.

A jig 102 made of an insulator for fixing a cable 108 to be measured is arranged inside the inner cylindrical electrode 101a. The inner cylindrical electrode 101a and the outer cylindrical electrode 101b are connected to input terminals of the electro-optical converter 103 via connection wires, respectively, and the inner cylindrical electrode 101a and the outer cylindrical electrode 101b are connected.
The voltage signal generated between b and b is electro-optically converted by the electro-optical conversion unit 103. The optical signal that has been electro-optically converted by the electro-optical conversion unit 103 is transmitted through the optical fiber 106 to the photoelectric conversion unit 10.
5 and photoelectrically converted. Then, the photoelectric conversion unit 10
The voltage signal photoelectrically converted in 5 is detected by a voltage detecting means 107 such as a level meter or an oscilloscope.

Using this non-contact type voltage probe, a case where a voltage V is generated between the cable 108 and the ground (potential reference plane 110) in a state where the cable 108 passes through the inside of the inner cylindrical electrode 101a. Think. When the voltage V is generated, coupling occurs between the cable 108 and the inner cylindrical electrode 101a due to electrostatic coupling. The ratio of the coupling caused by the electrostatic coupling, that is, the capacitance C between the cable 108 and the inner cylindrical electrode 101a can be approximated by the following equation (1).

C = 2πε ₀ ε _r Llog _e (b / a) (1)

Here, ε ₀ is the dielectric constant in a vacuum, ε _r is the relative dielectric constant of the jig 102 for fixing the cable 108, a
Is the outer shape of the conductor portion of the cable 108, b is the inner diameter of the inner cylindrical electrode 101a, and L is the length of the inner cylindrical electrode 101a.

Assuming that the input resistance and the input capacitance of the electro-optical conversion unit 103 are R _P and C _P , respectively, the non-contact type voltage probe of this embodiment is represented by an equivalent circuit as shown in FIG. . In FIG. 2 showing this equivalent circuit, the voltage V generated in the cable 108 is simulated by the voltage source 201. The capacitance C between the cable 108 and the inner cylindrical electrode 101a shown in FIG.
It is C shown in the equation. Further, the stray capacitance generated between the earth, which is an internal cylindrical electrode 101a and the potential reference plane 110 is indicated by C _S. As shown in the equivalent circuit of FIG. 2, the input impedance of the electro-optical conversion unit 103 is represented by a parallel circuit of an input resistance R _P and an input capacitance C _P.
Then, from the equivalent circuit shown in FIG.
The voltage V ₀ applied to the input terminal of No. 3 is expressed by the following equation (2). Note that j indicates an imaginary unit, and ω indicates an angular frequency.

V ₀ = jωCR _P / {1 + jωR _P C + C _P + C _S )} × V (2)

In the equation (2), ωR _P ((C +
In the frequency range in which C _P ) >> 1, the light-to-light conversion unit 1
The voltage V ₀ applied to the input terminal 03 can be approximated by the following equation (3).

V ₀ = C / (C + C _P + C _S ) × V (3)

As is apparent from equation (3), ωR _P
If (C + C _P ) >> 1 holds, a constant sensitivity can be obtained regardless of the frequency. If R _P becomes infinitely large, ωR _P (C +
C _P ) >> 1 holds, and the light-to-light conversion unit 1
The voltage V ₀ applied to the input terminal of the input terminal 03 can be approximated. In the non-contact type voltage probe of this embodiment, the cable 10
Since the signal from the inner cylindrical electrode 101a and the signal from the outer cylindrical electrode 101b coupled to the light-to-electrode converter 8 are converted to light by the light-to-light conversion unit 103, the input resistance R _P
Becomes almost infinite. Therefore, ωR _P (C + C _P )>
> 1 also holds in the low frequency region. in this way,
In the non-contact voltage probe of this embodiment, since the light-to-light conversion unit 103 is used, the voltage can be measured with a certain sensitivity even in a low frequency region.

[0019]

EXAMPLE 1 Hereinafter, a non-contact type voltage probe of this embodiment will be described in more detail with reference to examples. Example 1
Next, as shown in FIG. 3, a non-contact type voltage probe using an optical modulator for an electro-optical converter will be described. The non-contact type voltage probe according to the first embodiment includes an inner cylindrical electrode 301a formed of a copper plate and an inner cylindrical electrode 30a.
An outer cylindrical electrode 301b composed of a copper plate that covers the first electrode 1a at predetermined intervals is provided. These inner cylindrical electrode 301a and outer cylindrical electrode 301b
Are fixed at equal intervals by the support member 330. In addition, the outer cylindrical electrode 301b
Are grounded to the earth as a potential reference plane. In addition,
The inner cylindrical electrode 301a and the outer cylindrical electrode 301b
Not only the copper plate but also other conductive members having high conductivity may be used.

A fixing jig 302 for fixing a cable 308 to be measured is disposed inside the inner cylindrical electrode 301a. This fixing jig 302
Is made of an insulating elastic material such as a foamed polystyrene or a foamed polyurethane. By using the insulating material that is elastically deformed in this way, the cable 308 is fixed near the center of the inner cylindrical electrode 301a regardless of the outer diameter of the cable 308, even if the cable 308 has various outer diameters. it can.
The fixing jig 302 fixes the cable 308 to the center of the inner cylindrical electrode 301a in the cylinder. The fixing jig 302 is not limited to an elastically deformable insulating material, and may be formed of a plastic leaf spring. Good.

In the electrode portion composed of the inner cylindrical electrode 301a and the outer cylindrical electrode 301b, a wiring 30 is provided.
The light modulator 303 is connected via 3a and 303b. As shown in FIG. 4, the light modulation unit 303 includes a Mach-Zehnder (Mach-Z
ehnder) type optical modulator. This optical modulator has L
A waveguide 33 composed of a core formed by diffusing Li on a substrate 331 of iNbO ₃ and branched once and then coupled again
2 is provided. The waveguide 332 includes two parallel waveguides. The input waveguide is connected to input ends of the two waveguides and splits light input to the optical modulator into two waveguides. An output waveguide is connected to the output ends of the two waveguides to combine the output lights of the two waveguides into one. Further, two electrodes 333a and 333b are provided so as to sandwich two parallel waveguide portions of the waveguide 332. Further, the two electrodes 32 arranged on the substrate 331
2a and 333b are connected to voltage terminals 334a and 334b exposed to the outside of the housing 330.

When a voltage is applied to the electrodes 322a and 333b on the substrate 331 via the voltage terminals 334a and 334b, the waveguide 33 sandwiched between the electrodes 322a and 333b is applied.
An electric field is applied to 2. When an electric field is applied to the waveguide 332, the refractive index of the waveguide 332 changes due to the electro-optic effect, and a phase difference occurs between the two branched branches of the waveguide 332. Due to this phase difference, when an optical signal from the light source 304 is input from one end (input end) of the waveguide 332, an optical output (optical signal) whose intensity is reduced in proportion to the phase difference generated by the electro-optic effect Is obtained from the other end (output end) of the waveguide 332. Note that the half-wave voltage of the optical output obtained from the output end of the waveguide 332 is
Electrodes 322a and 333b when the phase difference between the two parallel waveguide portions that are branched is exactly π / 2.
Is the voltage applied during

The light modulation section 303 includes the light source 30
4 is input via the optical fiber 306a. The optical signal obtained from the optical fiber 306a is coupled to the input end of the waveguide 332 formed on the substrate 331 by the connector 315a for connecting the optical fiber. The optical signal output from the optical modulator 303 is transmitted to the photoelectric converter 3 via the optical fiber 306b.
05 is input. The optical fiber 306b is connected to the output end of the waveguide 332 formed on the substrate 331 via the connector 315b. The optical signal input to the photoelectric conversion unit 305 via the optical fiber 306b is photoelectrically converted by the photoelectric conversion unit 305, and the voltage of the photoelectrically converted electric signal is detected by the level meter 307.

Here, the Machtz of the light modulator 303 is described.
In the end-type optical modulator, voltage terminals 334a and 334b
Input resistance R between_PIs 14MΩ and the input capacitor
C_PIs 15 pF. Therefore, the light modulator 30
3 voltage V input to the voltage terminals 334a and 334b.₀
Is ωR in any frequency range_P((C +
C _P) >> 1 holds, the level meter 30
Voltage V detected at 7₀Is, as described above, the equation (3)
It becomes what is shown by. Further, C, C in the equation (3)
_P, C_SIs a constant that can be obtained in advance.

In the first embodiment, the light modulator 30
Since V ₀ input to 3 is photoelectrically converted and then photoelectrically converted and detected by the level meter 307, the above equation (3)
As a result, the voltage V generated between the inner cylindrical electrode 301a and the grounded outer cylindrical electrode 301b, that is, the cable 3 electrostatically coupled to the inner cylindrical electrode 301a
The voltage V generated between the voltage 08 and the ground can be obtained with a certain sensitivity regardless of the frequency. Also,
Since most of the signals are transmitted as optical signals through optical fibers, measurement can be performed without receiving any electric disturbance.

Second Embodiment In the first embodiment, a Mach-Zehnder optical modulator is used as an optical modulator. Instead, a bulk optical modulator having the configuration shown in FIG. 5 is used. You may do so. In the second embodiment, a bulk modulator described below is used in place of the Mach-Zehnder optical modulator of the first embodiment.
Other configurations are the same as those in the first embodiment, and a duplicate description will be omitted.

As shown in FIG. 5, the optical modulator according to the second embodiment has a LiNbO ₃
Two electro-optic crystals 501 and 502 made of crystals are arranged in a state where the optical axes of the crystals are tilted by 90 ° with respect to each other.
Further, in the housing 330, the polarizers 501a, 502a,
Phase compensator 503 and graded lens 5
04a and 504b are arranged. The two electro-optic crystals 501 and 502 are connected to voltage terminals 334a and 334, respectively.
b.

In this optical modulator, an optical signal incident through an optical fiber 306a is first converted into parallel light by a graded lens 504a, and the light is made parallel to the optical axis of the electro-optic crystal 501 by a polarizer 501a. Only the linearly polarized light component inclined by 45 ° is extracted. The signal light from which only the linearly polarized light component is extracted passes through the electro-optic crystal 501 and the electro-optic crystal 502. Here, the electro-optic crystal 50
1 is applied with a voltage input from the voltage terminals 334a and 334b, an electric field is generated in the crystal of the electro-optic crystal 501 and the electro-optic crystal 5 is proportional to the intensity of the generated electric field.
01 and x component of the optical signal input from the optical input terminal
A phase difference occurs between the directional components.

When this phase difference occurs, the signal light that has been incident as a linearly polarized light component inclined at 45 ° is emitted as an elliptically polarized light from the light output end of the electro-optic crystal 501. The signal light, which has been converted into the linearly polarized light component inclined at 45 ° and converted into elliptically polarized light, is returned at an inclination of 45 ° by the polarizer 502a and is condensed on the optical fiber 306b by the graded lens 504b. As a result of the elliptically polarized light in this manner, the optical output of the entire signal light is reduced. However, since the optical output is reduced in proportion to the voltage applied to the electro-optic crystal 501, the graded type The intensity of the optical signal collected and output by the lens 504b is
The voltage is inversely proportional to the voltage applied to the electro-optic crystal 501. Note that the electro-optic crystal 502 is arranged with the optical axes of the crystals tilted at 90 ° with respect to the electro-optic crystal 501. The phase compensator 503 is provided on the output side of the device. The electro-optic crystal 502 and the phase compensator 503 are used to compensate for a change in dielectric constant due to a temperature change.

The optical signal output from the graded lens 504b of the optical modulator 303 is input to the photoelectric converter 305 via the optical fiber 306b.
The optical signal input to the photoelectric conversion unit 305 is photoelectrically converted by the photoelectric conversion unit 305, and the voltage of the photoelectrically converted electric signal is detected by the level meter 307.

Here, in the bulk type optical modulator of the second embodiment, the input resistance R between the voltage terminals 334a and 334b is
_{Since P} is infinite, the voltage terminal 33 of the light modulator 303
4a, the voltage V ₀ to be input to 334b are any even frequency range _{ωR P ((C + C P} ) >> 1 is satisfied. Therefore, the voltage V ₀ to be detected by the level meter 307 Is represented by the above-described equation (3).
Further, C, C _P and C _S in Expression (3) are constants that can be obtained in advance. In the second embodiment as well, since V ₀ input to the light modulation unit 303 is electro-optically converted, photoelectrically converted and detected by the level meter 307, the internal cylindrical electrode is calculated by the above equation (3). The voltage V generated between the outer cylindrical electrode 301a and the grounded outer cylindrical electrode 301b, that is, the voltage V generated between the cable 308 electrostatically coupled to the inner cylindrical electrode 301a and the ground, is independent of the frequency. It can be obtained with a certain sensitivity.

FIG. 6 shows the frequency characteristic (a) of the detection sensitivity in the non-contact type voltage probe using the Mach-Zehnder optical modulator of the first embodiment and the bulk optical modulator of the second embodiment. 6 shows the frequency characteristic (b) of the detection sensitivity of the non-contact type voltage probe. In FIG. 6,
At the same time, the frequency characteristic (c) of the detection sensitivity in the conventional non-contact type voltage probe is also shown. As is clear from FIG. 6, it is already difficult to measure at 10 kHz with the conventional non-contact voltage probe, but at 1 kHz with the non-contact voltage probe using the Mach-Zehnder optical modulator of the first embodiment. Could be measured. The non-contact type voltage probe using the bulk-type optical modulator of Example 2 can measure from 10 Hz, and this frequency was the limit value of the equipment used for the measurement.

Embodiment 3 Next, a non-contact type voltage probe of this embodiment will be described in more detail using Embodiment 3. In the above,
Although an optical modulator is used as the light-to-light conversion unit, in the third embodiment, a semiconductor laser is used as the light-to-light conversion unit. The non-contact type voltage probe of the third embodiment is
As shown in FIG. 7, first, an inner cylindrical electrode 701a formed of a copper plate and an outer cylindrical electrode 701b formed of a copper plate that covers the inner cylindrical electrode 701a at a predetermined interval. It has electrodes. Although not shown, the inner cylindrical electrode 701a and the outer cylindrical electrode 701b are fixed to each other at equal intervals by a support member. In addition, the outer cylindrical electrode 701b
Is a grounding means 709 (FIG. 7)
Grounded by (a)).

A fixing jig 702 for fixing a cable to be measured is arranged inside the inner cylindrical electrode 701a. The fixing jig 702 is made of, for example, an elastic body having an insulating property, such as a foamed polystyrene or a foamed polyurethane. By using such an elastically deformable insulating material,
Even if the cable has various outer diameters, the cable can be fixed near the center of the inner cylindrical electrode 701a regardless of the outer diameter of the cable.

The electrode portion composed of the inner cylindrical electrode 701a and the outer cylindrical electrode 701b is divided into two parts, as shown in the sectional view of FIG. Thus, the inner cylindrical electrode 7
By dividing the electrode portion composed of the inner cylindrical electrode 701a and the outer cylindrical electrode 701b, it is easy to arrange the cable in the inner cylindrical electrode 701a. Note that the electrode portion including the inner cylindrical electrode 701a and the outer cylindrical electrode 701b that are openably divided into two parts with the hinge 740 as a fulcrum is fixed in a closed state with a stopper 741.

An electro-optical conversion unit 703 is connected to an electrode portion composed of the inner cylindrical electrode 701a and the outer cylindrical electrode 701b via wirings 703a and 703b. As shown in FIG. 8, the light-to-light converter 703 includes an attenuator 801, a voltage detection circuit 802, and a semiconductor laser 803 in a housing of the light-to-light converter 703. Further, a power supply 704 for supplying power to the voltage detection circuit 802 and the semiconductor laser 803 is provided in the electro-optical conversion unit 703 so as to be detachable. The attenuator 801 has the wiring 70
The inner cylindrical electrode 701a and the outer cylindrical electrode 701b are connected via 3a, 703b and a voltage terminal (not shown) exposed outside the housing.

In the cylinder of the inner cylindrical electrode 701a,
When a voltage V is generated in the fixed cable with the cable to be measured fixed with the fixing jig 702, the inner cylindrical electrode 701a electrostatically coupled to the cable and the outer cylindrical electrode 701b grounded are connected. The signal of the voltage V ₀ is applied to the input terminal of the attenuator 801 connected to. The signal applied to the attenuator 801 is
, And the voltage of the signal is detected by the voltage detection circuit 802. Then, the semiconductor laser 803 emits laser light whose intensity changes correspond to changes in the voltage detected by the voltage detection circuit 802.

An optical connector 705 is connected to an optical output end of the semiconductor laser 803.
5 outputs the laser light emitted from the semiconductor laser 803. Then, for example, the optical fiber 107 shown in FIG. 1 may be connected to the output end of the optical connector 705, and laser light from the semiconductor laser 803 may be input to the photoelectric conversion unit 105 via the optical fiber 107. The laser light input to the photoelectric conversion unit 105 is an optical signal obtained by electro-optically converting a signal applied to the input terminal of the attenuator 801, and this optical signal is photoelectrically converted by the photoelectric conversion unit 105 to become a voltage signal. . The voltage signal obtained by the photoelectric conversion is detected by the voltage detecting means 107 as V ₀ shown in Expression (3).

As described above, in the third embodiment,
Since the semiconductor laser is used for the light-to-light converter, a light source for light modulation is not required. If the light source becomes unnecessary in this manner, an optical fiber for introducing light from the light source becomes unnecessary, so that the configuration of the entire apparatus can be further simplified.

[0040]

As described above, according to the present invention, the coupling electrode disposed near the electric cable to be measured and electrostatically coupled to the electric cable, and the coupling electrode and the ground as the potential reference plane are connected to each other. Electro-optical conversion means for converting the voltage signal between the light and light into an optical signal, photoelectric conversion means for converting the optical signal into an electric signal by photoelectric conversion, and a voltage for detecting the voltage value of the electric signal converted by the photoelectric conversion means And a detecting means. Therefore, according to the present invention, the voltage signal between the coupling electrode and the ground is converted from an optical signal by the light-to-electric conversion means to an electric signal by the photoelectric conversion means, and the voltage value is detected by the voltage detection means from the electric signal. Therefore, the voltage applied to the electric cable is detected as a voltage value of an electric signal obtained by performing a photoelectric conversion on the voltage signal once and then performing a photoelectric conversion. As a result, according to the present invention, since the voltage signal between the coupling electrode and the ground is input to the electro-optical conversion means having an infinitely large input impedance, the voltage can be measured up to a low frequency region of 10 kHz or less. Has an effect. Also, if an optical signal is transmitted through an optical fiber, 10
Voltage can be measured up to a low-frequency region of kHz or less without receiving electric disturbance.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a basic configuration of a non-contact voltage probe device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an equivalent circuit of the non-contact voltage probe device of FIG.

FIG. 3 is a configuration diagram illustrating a partial configuration of a non-contact voltage probe device according to the first embodiment.

4 is a configuration diagram showing a configuration of a light modulation unit 303 of the non-contact type voltage probe device of FIG.

FIG. 5 is a configuration diagram illustrating a configuration of an optical modulation unit of a non-contact voltage probe device according to a second embodiment.

FIG. 6 shows a frequency characteristic (a) of detection sensitivity in the non-contact voltage probe of the first embodiment, a frequency characteristic (b) of detection sensitivity in the non-contact voltage probe of the second embodiment, and a conventional non-contact voltage. FIG. 4 is a characteristic diagram illustrating frequency characteristics (c) of detection sensitivity in a probe.

FIG. 7 is a configuration diagram illustrating a partial configuration of a non-contact voltage probe device according to a third embodiment.

8 is a configuration diagram illustrating a configuration of an electro-optical conversion unit in FIG. 7;

[Explanation of symbols]

101a: inner cylindrical electrode, 101b: outer cylindrical electrode, 102: jig, 103: light-to-light converter, 105: photoelectric converter, 106: optical fiber, 107: voltage detecting means, 108: cable, 109: ground wire, 110: potential reference plane.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Ryuichi Kobayashi 2-3-1, Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Nobuo Kuwahara 2-3-3, Otemachi, Chiyoda-ku, Tokyo No. 1 F-term in Nippon Telegraph and Telephone Corporation (reference) 2G025 AA17 AB07 AC06 2G035 AA08 AA12 AA18 AB04 AB08 AC13 AD34 AD39

Claims (9)

[Claims] 1. A coupling electrode disposed near an electric cable to be measured and electrostatically coupled to the electric cable, and a voltage signal between the coupling electrode and the ground as a potential reference plane is subjected to light-to-light conversion to generate light. A photoelectric conversion unit that converts the optical signal into an electric signal by photoelectrically converting the optical signal; and a voltage detection unit that detects a voltage value of the electric signal converted by the photoelectric conversion unit. Non-contact type voltage probe device. 2. The non-contact type voltage probe device according to claim 1, further comprising: an outer electrode that is newly disposed to be spaced apart from the coupling electrode so as to cover the outside of the coupling electrode and grounded to the ground. A non-contact type voltage probe device comprising: 3. The non-contact voltage probe device according to claim 1, wherein the coupling electrode is formed in a cylindrical shape that covers the periphery of the electric cable. 4. The non-contact voltage probe device according to claim 3, wherein the outer electrode is formed in a cylindrical shape covering the outside of the coupling electrode. 5. The non-contact type voltage probe device according to claim 1, wherein the light-to-light conversion unit modulates intensity of light emitted from the light source by the voltage signal. A non-contact voltage probe device comprising: an optical modulator for outputting the optical signal. 6. The non-contact type voltage probe device according to claim 5, wherein the light modulating section includes two parallel waveguides each including a substrate made of LiNbO ₃ and a core formed by introducing Ti into the substrate. An input waveguide connected to input ends of the two waveguides and branching light input to the optical modulator into the two waveguides; and an input waveguide connected to the output ends of the two waveguides. An output waveguide that combines the output lights of the two waveguides into one, and first and second electrodes formed outside the two waveguides on the substrate, respectively. The first and second electrodes are connected to the coupling electrode and the ground, respectively, the voltage signal is applied, light emitted from the light source is incident on the input waveguide, and the output waveguide is Non-contact, characterized in that an optical signal is emitted Voltage probe apparatus. 7. The non-contact type voltage probe device according to claim 5, wherein the light modulating unit is formed of a LiNbO ₃ crystal to which the voltage signal is applied, and a light emitted from the light source. A polarizer for extracting a linearly polarized light component inclined by 45 ° with respect to the optical axis of the electro-optic crystal and introducing the component to the electro-optic crystal. 8. The non-contact voltage probe device according to claim 1, wherein said electro-optical conversion means is a semiconductor laser. 9. The non-contact voltage probe device according to claim 1, further comprising an optical fiber for transmitting the optical signal.