JP2000221214A - Photovoltaic sensor for high voltage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photovoltaic sensor for high voltages having a superior withstand voltage characteristic, a superior temperature characteristic and the like by arranging a transparent electrode of an electro-optic element having a natural rotary polarization to a nearly central part of a transmission face and eliminating process distortions generated to a peripheral edge part of the transmission face. SOLUTION: The photovoltaic sensor includes a polarizer for converting an incident light to a linearly polarization, a 1/4 wave plate for converting the linearly polarization to a circularly polarized light, an electro-optic element for passing the circularly polarized light and phase modulating the light in accordance with an impressed high voltage, and an analyzer for detecting the light passing the electro-optic element. The electro-optic element 5 is an electro-optic element having a natural rotary polarization. Layered electrodes 6a-6c are disposed to a nearly central part of each light transmission face of the electro-optic element. A predetermined creeping distance is obtained between the layered electrodes on the basis of a distance L between a peripheral edge part of the layered electrodes and a peripheral edge part of the light transmission face of the electro-optic element, and a thickness d of the electro-optic element. Moreover, influences of process distortions to the peripheral edge part of the light transmission face are eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-voltage optical voltage sensor, and more particularly, to a high-voltage optical sensor which eliminates the influence of processing distortion formed on the periphery of a transmission surface of an electro-optical element having natural optical rotation. .

[0002]

2. Description of the Related Art FIG. 6 shows a conventional optical voltage sensor. In the figure, 1 is an optical fiber for introducing incident light, 2 is a light transmitting collimator, 3 is a polarizer for converting incident light into linearly polarized light, and 4 is a quarter wavelength plate for converting the linearly polarized light into circularly polarized light. . 5 is an electro-optical element (Pockels effect element) using a single crystal such as BGO (Bi ₁₂ GeO ₂₀ ), 6 is a conductive transparent electrode disposed on each light transmitting surface of the electro-optical element,
7 is a voltage application terminal for applying a voltage to be detected to the conductive transparent electrode, 8 is an analyzer for detecting the polarization of the transmitted light transmitted through the electro-optical element, and 9 is a light receiving device for receiving the polarization detected by the analyzer. The collimator unit 10 is an optical fiber unit that sends out to a voltage detection unit (not shown).

Light emitted from a light emitting diode or the like is incident on a light transmitting collimator unit 2 via an optical fiber 1, and the light transmitting collimator unit 2 converts the incident light into a parallel light beam and converts the incident light into a polarizer 3.
To supply. The polarizer 3 converts the incident parallel light into linearly polarized light, and the quarter-wave plate converts the linearly polarized light into circularly polarized light.

The electro-optical element 5 converts the circularly polarized light incident through the quarter-wave plate 4 into elliptically polarized light according to the electric field intensity applied to the electro-optical element. The light-receiving collimator 9 receives the elliptically polarized P-polarized light and S-polarized light, and sends the elliptically polarized light to the voltage detector (not shown) via the optical fiber 10.

Since a high voltage obtained by dividing the transmission voltage of the power system is applied to the transparent electrode of the electro-optical element, a predetermined withstand voltage characteristic is required. Methods for improving the withstand voltage characteristics are described in Japanese Patent Application Laid-Open Nos.
As disclosed in Japanese Patent No. 4379 and Japanese Patent Application Laid-Open No. Hei 5-188091, the conductive transparent electrode is disposed only at the center part of the light transmission surface, avoiding the peripheral part, thereby securing a sufficient creepage distance, and A method to prevent dielectric breakdown due to high voltage surges and other accidents. Or, as described in JP-A-10-13
As disclosed in Japanese Patent No. 2863, a method of arranging a conductive transparent electrode only at a central portion of a light transmitting surface and further covering the conductive transparent electrode with an insulating film to limit an electrically exposed portion of the conductive transparent electrode. It has been known.

Further, in the peripheral portion of the electro-optical element, the flatness of the electro-optical crystal is often lost due to processing distortion in manufacturing the electro-optical element, and the electrode is formed only in the central portion of the light transmitting surface. This is also advantageous for forming a uniform and strong electrode.

[0007]

The electro-optical element used in the optical voltage sensor for high voltage needs to reduce the temperature dependence and the manufacturing cost in addition to the withstand voltage characteristic described above. Also, the electro-optical element having a natural optical rotation such as the BGO described above prevents the detection sensitivity from being lowered by the natural optical rotation as described in the information research committee "Optical Fiber Sensor" P106 issued in 1985. It is common to shorten the optical path length in order to reduce the length. Therefore, even in a sensor for high voltage use, the creepage distance cannot be increased by increasing the thickness of the electro-optical element in order to improve the withstand voltage characteristics.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and eliminates the influence of processing distortion generated at the peripheral portion of the transmission surface of an electro-optical element having natural optical rotation, thereby improving withstand voltage characteristics, temperature characteristics, and the like. Provide an excellent optical sensor for high voltage.

[0009]

The present invention employs the following means in order to solve the above-mentioned problems.

A polarizer for converting incident light into linearly polarized light, a quarter-wave plate for converting the linearly polarized light into circularly polarized light, and an optical phase modulation transmitting the circularly polarized light and corresponding to a high voltage applied An electro-optical element that performs the following, an analyzer that detects transmitted light transmitted through the electro-optical element, and a light receiving unit that detects the applied voltage by detecting transmitted light transmitted through the analyzer. Is a light voltage sensor comprising a laminated electrode in which a conductive transparent electrode and a non-reflective coating film are laminated on each light transmitting surface, wherein the electro-optical element is an electro-optical element having natural optical rotation, and the laminated electrode is It is arranged at a substantially central portion of each light transmitting surface of the electro-optical element, and the respective laminations are performed based on a distance between a peripheral portion of the laminated electrode and a light transmitting surface peripheral portion of the electro-optical element, and a thickness of the electro-optical element. The specified distance between the electrodes With distance obtaining, characterized in that the removal of the influence of working strain that can be on the periphery of the light transmitting surface.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing an optical voltage sensor according to the present embodiment, FIG. 2 is a diagram showing an assembly of the electro-optical element shown in FIG. 1, FIG. 2 (a) is a top view, and FIG. FIG. 2C is a side view.

In FIG. 1, 1 is an optical fiber for introducing incident light, 2 is a collimator for transmitting light, 3 is a polarizer for converting incident light into linearly polarized light, and 4 is a quarter for converting the linearly polarized light into circularly polarized light. Wave plate. Reference numeral 5 denotes an electro-optical element (Pockels effect element) using a single crystal such as BGO (Bi ₁₂ GeO ₂₀ ), 6 denotes a laminated electrode disposed on each light transmitting surface of the electro-optical element, and 7 denotes a conductive transparent electrode. A voltage application terminal for applying a voltage to be detected, 8 is an analyzer for detecting the polarization of the transmitted light transmitted through the electro-optical element, 9 is a light receiving collimator for receiving P-polarized light and S-polarized light detected by the analyzer, 10
Is an optical fiber for transmitting P-polarized light and S-polarized light to a voltage detecting unit (not shown), and 11 is a reflecting prism. Light emitted from a light emitting diode or the like is incident on a light transmitting collimator unit 2 via an optical fiber 1, and the light transmitting collimator unit 2 converts the incident light into a parallel light beam and supplies the parallel light beam to a polarizer 3. The polarizer 3 converts the incident parallel light into linearly polarized light, and the quarter-wave plate converts the linearly polarized light into circularly polarized light.

The electro-optical element 5 converts the circularly polarized light incident through the quarter-wave plate 4 into elliptically polarized light according to the electric field intensity applied to the electro-optical element. The light-receiving collimator 9 receives the elliptically polarized P-polarized light and S-polarized light, and sends the elliptically polarized light to the voltage detector (not shown) via the optical fiber 10.

In FIG. 2, 5 is BGO (Bi ₁₂ GeO).
₂₀ ) An electro-optical element (Pockels effect element) having a natural optical rotation using a single crystal, such as ₂₀ ), 5a is a light transmitting surface of the electro-optical element, 6a is a conductive transparent electrode disposed on both sides of the electro-optical element 1, 6b Is an insulating non-reflective coating film disposed on each of the conductive transparent electrodes, and the laminated electrode 6 is formed by the conductive transparent electrode 6a and the anti-reflective coating film 6b.
Is configured. Reference numeral 6c denotes a part of the conductive transparent electrode exposed from the antireflection coating film, and a lead wire for supplying a voltage to be measured is attached to the exposed part of the conductive transparent electrode. In the drawing, d is the thickness of the electro-optical element, and L is the distance between the peripheral edge of the electrode 6a and the light transmitting surface peripheral edge of the electro-optical element. Then, the creeping distance when the voltage to be measured is applied between the two transparent electrodes 6a arranged on both surfaces of the electro-optical element can be expressed by (d + 2L).

The thickness d of the electro-optical element having the natural optical rotation cannot be increased in order to improve the withstand voltage characteristic as described above. Also,
Since the conductive transparent electrode forms a light transmitting surface of the electro-optical element widely, the distance L needs to be small. Further, in order to reduce the cost of the electro-optical element, it is advantageous that the distance is small.

On the other hand, in order to eliminate the influence of the processing distortion existing at the peripheral portion of the electro-optical element, it is necessary to secure the distance L by a predetermined amount.

Therefore, by setting the dimensional relationship between the electro-optical element and the electrode thereof optimally, the influence of processing distortion formed on the peripheral portion of the transmission surface of the electro-optical element having natural optical rotation can be eliminated, and the withstand voltage characteristic can be improved. A high-voltage optical sensor having excellent temperature characteristics and the like can be obtained. Note that the length of each side of the electro-optical element 1 in the present embodiment is 10 mm,
The thickness d is 5 mm, the length of each side of the transparent electrode is 5 mm, and the distance L is 2.5 mm.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a plan view showing an assembly of the electro-optical element according to the present embodiment. In the figure, 21 is BGO
An electro-optical element (Pockels effect element) having a natural optical rotation using a single crystal such as (Bi ₁₂ GeO ₂₀ ). Reference numeral 22 denotes a conductive transparent electrode disposed on the surface of the electro-optical element 21 and disposed on the conductive transparent electrode. The laminated electrode 23 made of the insulating non-reflective coating film is a position where the conductive transparent electrode is attached to the lead wire.

In this embodiment, the length of each side of the electro-optical element is 10 mm, the thickness d is 5 mm, the diameter of the laminated electrode is 5 mm, and the shortest distance between the periphery of the electro-optical element and the laminated electrode is 2 mm. 0.5 mm, and the diameter of the light beam transmitted through the electro-optical element is 3 mm.

Table 1 is a table showing the withstand voltage characteristics of the optical voltage sensor according to the first embodiment. Satisfactory results were obtained in any of the AC withstand voltage test, the impulse withstand voltage test, and the impulse limit test.

[0021]

[Table 1]

FIG. 4 is a diagram showing the temperature characteristics of the optical voltage sensor according to the first embodiment. The temperature dependence of P-polarized light is shown as P-wave, and the temperature dependence of S-polarized light is shown as S-wave. In the present invention, the differential operation result (differential output) of the P-polarized light and the S-polarized light is set as the optical voltage sensor output. The variation of the ratio error is about ± 0.1% in a temperature range of −20 to 60 ° C., which is a very small temperature-dependent characteristic as compared with ± 1% which is a criterion.

FIG. 5 is a view showing the result of measuring the surface distribution of the extinction ratio of the electro-optical element. In the figure, the portion that looks white is the portion where the processing distortion exists, and it can be seen that it is concentrated on the peripheral edge of the electro-optical element. By not disposing the conductive transparent electrode about 2 mm from the peripheral edge where the processing strain is concentrated, the influence of the processing strain can be removed, and the temperature dependency can be significantly reduced.

[0024]

As described above, according to the present invention,
Since the transparent electrode of the electro-optical element having natural optical rotation is arranged at the approximate center of the transmission surface, the effects of processing distortion at the periphery of the transmission surface are eliminated, and high voltage with excellent withstand voltage characteristics, temperature characteristics, etc. The optical sensor for use can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a view showing an assembly of the electro-optical element shown in FIG.

FIG. 3 is a view showing an assembly of an electro-optical element according to a second embodiment of the present invention.

FIG. 4 is a diagram illustrating temperature characteristics of the high-voltage sensor according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a result of measuring a surface distribution of an extinction ratio of the electro-optical element.

FIG. 6 is a diagram showing a conventional optical voltage sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Transmitting collimator part 3 Polarizer 4 1/4 wavelength plate 5, 21 Electro-optical element 6, 22 Stacked electrode 7 Voltage application terminal 8 Analyzer 9 Light receiving collimator part 10 Optical fiber

Continued on the front page (72) Inventor Yoshiyuki Kubota 7-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in the Electric Power & Electronics Development Division, Hitachi, Ltd. 2G025 AA08 AA17 AB11 AC06

Claims (1)

[Claims] 1. A polarizer that converts incident light into linearly polarized light, a quarter-wave plate that converts the linearly polarized light into circularly polarized light, and a light that transmits the circularly polarized light and corresponds to an applied high voltage. An electro-optical element that performs phase modulation; an analyzer that detects transmitted light transmitted through the electro-optical element; and a light receiving unit that detects the applied voltage by detecting transmitted light transmitted through the analyzer. The optical element is a light voltage sensor including a laminated electrode in which a conductive transparent electrode and an anti-reflection coating film are laminated on each light transmitting surface thereof, wherein the electro-optical element is an electro-optical element having natural optical rotation, The electrode is arranged at a substantially central portion of each light transmitting surface of the electro-optical element, the distance between the peripheral portion of the laminated electrode and the light transmitting surface peripheral portion of the electro-optical element, and the thickness of the electro-optical element. Predetermined between each laminated electrode Characterized in that the creeping distance of the light transmitting surface is obtained and the influence of processing distortion generated at the peripheral portion of the light transmitting surface is removed.