JPH10132864A - Photo voltage sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To directly measure a high voltage without using a voltage-dividing capacitors and without losing a linearity by providing an electrode for applying a voltage to a crystal member used as a Pockels element and forming another capacitance between electrodes. SOLUTION: Light entering an optical fiber 1 is collimated into parallel light by a focusing lens 10, only a linear polarization in one direction is reflected by a polarization beam splitter(PBS) 12 and is inputted to a 1/4 wavelength plate 16 as a circular polarization. A voltage is applied between transparent electrode films 18 and 20, and circular polarization is supplied to Pockels elements 14 and 15 and is supplied to a PBS 13 as an elliptical polarization that is proportional to the application voltage. The application voltage to the Pockels elements 14 and 15 is divided by its own capacitance and the capacitance of the space between them, the output linearity of the Pockets elements 14 and 15 cannot be lost even if a high voltage is applied, and also a sufficient withstand voltage is achieved. The elliptical polarization supplied to the PBS 13 reflects only the linear polarization constituent in one direction and is applied to an optical fiber 3 by a focusing lens 11, thus emitting intensity-modulated light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical voltage sensor for detecting a voltage using an optical fiber technology, and more particularly, to a configuration in which a voltage dividing capacitor is not required and a high voltage is directly applied without impairing linearity or withstand voltage. The present invention relates to an inexpensive optical voltage sensor that can be measured quickly.

[0002]

2. Description of the Related Art An optical voltage sensor utilizing the Pockels effect is generally known as a sensor utilizing optical fiber technology. FIG. 5 is a diagram showing a schematic configuration of a conventional optical voltage sensor. As shown in FIG. 5, the optical voltage sensor includes a polarizer 2 connected to a first optical fiber 1, an analyzer 4 connected to a second optical fiber 3, the polarizer 2 and the analyzer. ４ wavelength plate 5 and BSO disposed between
(Bi ₁₂ SiO ₂₀ ) Pockels element 6.
The BSO Pockels element 6 is connected to the BSO (Bi
Transparent electrode films 8 and 9 are provided on both surfaces of a ₁₂ SiO ₂₀ ) single crystal 7, and a voltage is applied between the transparent electrode films 8 and 9. In the conventional optical voltage sensor, the polarizer 2 changes the light that has passed through the first optical fiber 1 into linearly polarized light, the quarter-wave plate 5 gives a phase difference of π / 4, Converts linearly polarized light to circularly polarized light. And the BSO
When a voltage is applied between the transparent electrode films 8 and 9 provided on both surfaces of the single crystal 7, the two axes <011> and <011> of the BSO single crystal 7 are applied.
1>, the incident circularly polarized light is changed to elliptically polarized light. The phenomenon in which the refractive index difference changes linearly with the electric field is the so-called Pockels effect. When the light converted into the elliptically polarized light passes through the analyzer 4, the intensity of the transmitted light changes as compared with when there is no voltage (circularly polarized light). . That is,
The intensity of the transmitted light is amplitude-modulated by the voltage applied between the electrodes 8 and 9. Therefore, a change in voltage can be obtained as a change in light amount. FIG. 6 shows the principle of the amplitude modulation. Here, if the input voltage is AC,
The AC component Pac is superimposed on the DC light Pdc. The characteristics of the amplitude modulation can be expressed by the following equations (1) to (4). P = Po (1 @ m) (1) m = .pi.V / V.pi.f (V) (2) f (V) = [sin {G (V)}] / G (V) (3) G ( V) = {(πV / Vπ) ² } (2θ ₀ d) ² (4) where V is the voltage applied to the BSO single crystal, Vπ is a material-specific constant called half-wave voltage, and θ ₀ is natural Optical rotation. When a wavelength of 0.87 μm is applied to a BSO single crystal, Vπ is 6800 V and θ ₀ is 10.5 ° / mm.

[0003]

As described above, an optical voltage sensor is excellent in insulation because it detects a voltage with an optical component and an optical fiber, but has a high voltage, for example, 6.6 KV high voltage, for the following reasons. The distribution line voltage could not be measured directly. (1) The voltage is too high and the linearity of the sensor deteriorates. (2) the transparent electrode 8 on the surface of the BSO single crystal 7 in the sensor,
9 and discharge occurs due to insufficient withstand voltage. Regarding the problem of linearity (1), as a Pockels element for measuring voltage, Bi ₁₂ SiO ₂₀ is generally used.
Single crystals, Bi ₁₂ GeO ₂₀ single crystals, and LiNbO ₃ single crystals are often used. However, these materials have a low half-wavelength voltage of the crystal (Bi ₁₂ SiO _{20 having} a wavelength of 8
Since the half-wave voltage at 70 nm = 6800 (V)), 6.6
In the voltage measurement of the KV high-voltage distribution line, the linearity of the voltage measurement output deteriorates. That is, as is clear from the graph showing the principle of FIG. 6, the transmitted light intensity is shown on a sin curve in proportion to the sensor input voltage. Occurs. Referring to the problem of the withstand voltage of the above (2), as shown in FIG. 8, transparent electrode films 8 and 9 are formed on the surface of the BSO single crystal 7 in the optical sensor. Electrode film 8,
Discharge occurs between 9 points. Therefore, as shown in FIG. 7, a method is generally used in which a sufficient withstand voltage is realized by dividing the input of the optical voltage sensor by the voltage dividing capacitors C ₁ and C ₂ to lower the input voltage.

In FIG. 7, the input voltage V ₂ of the optical sensor is expressed by the following equation (5). (Optical sensor input voltage) V ₂ = {C ₁ / (C ₁ + C ₂ )} × V ₁ (5) where V ₁ : Distribution line voltage V ₂ : Optical voltage sensor input voltage C ₁ : Voltage dividing capacitor Capacitance (high voltage side) C ₂ : Capacitance of voltage dividing capacitor (low voltage side) As described above, a voltage dividing capacitor is conventionally used as a solution to the problem of linearity and withstand voltage, but a high voltage side voltage dividing capacitor is very difficult. Therefore, it is difficult to produce a capacitor having good temperature characteristics because a high withstand voltage is required (it is necessary to withstand an electric impulse voltage; an electric impulse voltage (between electric wire and ground) of about 60 KV). That is, a capacitor with a high withstand voltage is generally made of ceramic, but has poor temperature characteristics and poor capacitance stability. In addition, a configuration using a series connection of film capacitors with high withstand voltage is also conceivable,
It is very large and unrealistic. Also, the price of the capacitor was expensive. The present invention has been made in view of the above circumstances, and provides an inexpensive optical voltage sensor capable of directly measuring a high voltage without impairing linearity or withstand voltage by a configuration that does not require a voltage dividing capacitor. The purpose is to do.

[0005]

In order to achieve the above object, the present invention is used as a Pockels element for transmitting light in an optical voltage sensor for detecting a change in voltage as a change in the amount of light using the Pockels effect. A crystal member, an electrode for applying an applied voltage to the crystal member, and an electrode formed between the electrodes to form a second capacitance different from the first capacitance formed by the crystal member. And a dielectric member provided. Another feature of the present invention is that the dielectric member comprises a space having a predetermined width. Another feature of the present invention is that the dielectric member is made of a glass member having a predetermined width. Another feature of the present invention is that the value of the second capacitance is larger than the value of the first capacitance. Another feature of the present invention is that the crystal member is made of Bi ₁₂ SiO ₂₀ (BSO) single crystal.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on illustrated embodiments. FIG. 1 is a configuration diagram showing an embodiment of the optical voltage sensor according to the present invention. As shown in FIG.
The optical voltage sensor includes a first condenser lens 10 connected to the first optical fiber 1, a second condenser lens 11 connected to the second optical fiber 3, and the first condenser lens. Lens 1
A first polarizing beam splitter (PBS) 12 disposed at a position where light from zero enters, and a second polarizing beam splitter disposed at a position where light is emitted to the second condenser lens 11 (PBS) 13 and the first and second P
First and second Pockels elements 14 and 15 disposed between the BSs 12 and 13 and the first Pockels element 1
4 and a 1/4 wavelength plate 16 provided between the first PBS 12. The first Pockels element 14 is formed of the first BSO (Bi ₁₂ SiO ₂₀ ) single crystal plate 1.
7, a first transparent electrode film 18 is formed on the first PBS 12 side, and the second Pockels device 15 includes a second BSO (Bi ₁₂ SiO ₂₀ ) single crystal plate 1.
9, a second transparent electrode film 20 is formed on the second PBS 13 side. And the first BS
The O single crystal plate 17 and the second BSO single crystal plate 19 are separated from each other by a predetermined space.
And an applied voltage between the second transparent electrode 20 and the second transparent electrode 20.

The first and second Pockels elements 1
FIG. 2 shows an equivalent circuit of the voltage application portions 4 and 15. Here, the first and second Pockels elements 1
Assuming that the capacitances of ₄ and 15 are C ₁ and C ₃ , the capacitance of the space (air) between the first and second Pockels elements 14 and 15 is C _2, and that C 1 = C 3, voltage 2Vo applied to the first and second Pockels cell 14, _{15, 2Vo = {C 2 / (} C 1/2 + C 2)} a × V (6). Next, the operation of the optical voltage sensor having the above configuration will be described. When light is incident on the first optical fiber 1 in a state of random polarization, the light is collimated by the first condenser lens 10. Next, the parallel light from the first condenser lens 10 is reflected by the first PBS 12 in the direction of the quarter-wave plate 16 only in one direction of linearly polarized light component.
Light of other components is transmitted (reflected light is linearly polarized). The linearly polarized light from the first PBS 12 is converted into circularly polarized light by the quarter-wave plate 16 (state of circularly polarized light). Next, the first and second transparent electrode films 18, 2
In the state where the applied voltage is applied during 0,
When circularly polarized light is supplied from the お よ び wavelength plate 16 to the first and second Pockels elements 14 and 15, the circularly polarized light is proportional to the applied voltage in the first and second Pockels elements 14 and 15. The second PB becomes elliptically polarized light.
It is supplied to S13.

The voltage applied to the first and second Pockels elements 14 and 15 is, as shown in FIG. 2, the capacitance C of the first and second Pockels elements 14 and 15. ₁ , C ₃ and the capacitance C due to the space (air) between the first and second Pockels elements 14, 15
_It is divided by _two . Note that the above capacitance ratio is C ₁
+ C ₃ <C ₂ . Therefore, even if the applied voltage is a high voltage, the divided voltage is applied to the Pockels elements 14 and 15, so that the linearity of the output characteristics of the optical voltage sensor is not impaired. As shown in FIG. 1, the distance D1 between the first and second transparent electrode films 18 and 20 is equal to the distance between the first and second BSO single crystal plates 1 and 2.
7 and 19 and the first and second BSOs
Since the width is the sum of the width of the space between the single crystal plates 17 and 19, a sufficient withstand voltage can be obtained even when the applied voltage is high. Next, the elliptically polarized light supplied to the second PBS 13 is reflected by the second PBS 13 in the direction of the second condenser lens 11 while only the linearly polarized light component in one direction is transmitted, and the other component light is transmitted. You. Then, the linearly polarized light from the second PBS 13 is transmitted to the second condenser lens 11 by the second condenser lens 11.
And the intensity-modulated light is emitted from the second optical fiber 3.

Next, a second embodiment of the optical voltage sensor according to the present invention will be described with reference to FIGS. FIG. 3 is a configuration diagram of a second embodiment of the optical voltage sensor according to the present invention, and FIG. 4 is a diagram illustrating an equivalent circuit of a voltage application portion of the Pockels element illustrated in FIG. As shown in FIG. 3, the optical voltage sensor includes a first condenser lens 10 connected to the first optical fiber 1 and a second condenser lens 11 connected to the second optical fiber 3. , The first condenser lens 10
A first polarizing beam splitter (PBS) 12 disposed at a position where light from
1, a second polarizing beam splitter (PBS) 13 disposed at a position where light is emitted to the first and second PBs.
A Pockels element 21 disposed between S12 and S13,
A quarter-wave plate 16 is provided between the Pockels element 21 and the first PBS 12.

The Pockels element 21 is a BSO (Bi
_A first transparent electrode film 23 is formed on the side of the first PBS _{12 of the 12} SiO ₂₀ ) single crystal plate 22, and a first transparent electrode film 23 is formed on the side of the second PBS 13 of the BSO single crystal plate 22 via a glass member 24 having a predetermined thickness. In this configuration, two transparent electrode films 25 are formed. An applied voltage is applied between the first transparent electrode film 23 and the second transparent electrode film 25. The Pockels element 21
FIG. 4 shows an equivalent circuit of the voltage application portion. Here, the capacitance of the Pockels element 21 is C ₄ ,
Assuming that the capacitance of the glass member 24 is C ₅ , the voltage Vo applied to the Pockels element 21 is as follows: Vo = {C ₅ / (C ₄ + C ₅ )} × V (7)

Next, the operation of the optical voltage sensor having the above configuration will be described. When light enters the first optical fiber 1 in a state of random polarization, the first condensing lens 10
Is collimated. Next, the parallel light from the first condenser lens 10 is reflected by the first PBS 12 in the direction of the quarter-wave plate 16 while only the linearly polarized light component in one direction is transmitted, and the light of the other components is transmitted. (Reflected light is in a state of linearly polarized light). The linearly polarized light from the first PBS 12 is converted into circularly polarized light by the quarter-wave plate 16 (state of circularly polarized light). Next, the first and second transparent electrode films 23, 2
5 while the applied voltage is applied between
When circularly polarized light is supplied from the ポ wavelength plate 16 to the Pockels element 21, the circularly polarized light becomes elliptically polarized light in the Pockels element 21 in proportion to the applied voltage.
To the PBS 13. Here, the voltage applied to the Pockels cell 21, as shown in FIG. 4, it is divided by the electrostatic capacitance C ₅ of the capacitance C ₄ and the glass member 24 of the Pockels element 21. Note that the ratio of the capacitances is C ₄ <C ₅ . Therefore, even when the applied voltage is a high voltage, the Pockels element 21
Is applied with a divided voltage, so that the linearity of the output characteristics of the optical voltage sensor is not impaired. FIG.
As shown in the figure, the first and second transparent electrode films 23, 2
5 is the sum of the width of the BSO single crystal plate 22 and the width of the glass member 24, so that a sufficient withstand voltage can be obtained even when the applied voltage is high. Next, the elliptically polarized light supplied to the second PBS 13 is applied to the second PBS 13.
The PBS 13 reflects only the linearly polarized light component in one direction toward the second condenser lens 11 and transmits the other component light. Then, the linearly polarized light from the second PBS 13 is
The light is incident on the second optical fiber 3 by the second condenser lens 11, and the light whose intensity is modulated is emitted from the second optical fiber 3.

[0012]

As described above, the optical voltage sensor of the present invention has a configuration capable of directly measuring a high voltage (for example, a 6.6 KV distribution line voltage), and therefore does not require a voltage dividing capacitor or an insulating transformer. Sufficient insulation from the measuring instrument can be maintained. Further, since the Pockels effect is used, the frequency characteristics are good. The withstand voltage can be easily changed by the insulator used for the distance between the electrodes and the voltage division, high voltage measurement is possible, and no voltage dividing capacitor, insulation transformer, or measurement transformer is required. There is no need to pay attention to the temperature characteristics. Further, the role of the voltage dividing capacitor is incorporated in the optical voltage sensor, and the cost is totally reduced because an insulating transformer is not required.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of an optical voltage sensor according to the present invention.

FIG. 2 is a diagram showing an equivalent circuit of a voltage application portion of the first and second Pockels elements shown in FIG.

FIG. 3 is a configuration diagram of a second embodiment of an optical voltage sensor according to the present invention.

FIG. 4 is a diagram showing an equivalent circuit of a voltage application portion of the Pockels device shown in FIG. 3;

FIG. 5 is a diagram showing a schematic configuration of a conventional optical voltage sensor.

FIG. 6 is a diagram illustrating the principle of amplitude modulation of the optical voltage sensor illustrated in FIG.

FIG. 7 is a configuration diagram of an optical voltage sensor using a voltage dividing capacitor.

FIG. 8 is an explanatory diagram showing a problem of the withstand voltage of the optical voltage sensor shown in FIG. 5;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... 1st optical fiber, 2 ... Polarizer, 3 ... 2nd optical fiber, 4 ... Analyzer, 5, 16 ... 1/4 wavelength plate, 6, 14, 15, 21
... Pockels element, 7 ... BSO single crystal, 8, 9, 1
8, 20, 23, 25: transparent electrode film, 10: first condenser lens, 11: second condenser lens, 1
2 ... first polarizing beam splitter, 13 ... second polarizing beam splitter, 17, 19, 22 ... BSO single crystal plate,
24 ... glass member,

Claims (5)

[Claims] 1. An optical voltage sensor for detecting a change in voltage as a change in the amount of light using the Pockels effect, comprising: a crystal member used as a Pockels element that transmits light; and a voltage member for applying an applied voltage to the crystal member. And a dielectric member formed between the electrodes to form a second capacitance different from the first capacitance formed by the crystal member. Optical voltage sensor. 2. The optical voltage sensor according to claim 1, wherein said dielectric member comprises a space having a predetermined width. 3. The optical voltage sensor according to claim 1, wherein the dielectric member is made of a glass member having a predetermined width. 4. The method according to claim 1, wherein the value of the second capacitance is larger than the value of the first capacitance.
Or the optical voltage sensor according to 3. 5. The method according to claim 1, wherein the crystal member is Bi ₁₂ SiO ₂₀ (BS
O) A single crystal, characterized in that it comprises a single crystal.
3. The optical voltage sensor according to 3 or 4.