JPH08304471A - Transformer for optical instrument - Google Patents

Abstract

PURPOSE: To provide a transformer for an optical instrument which can reduce output errors of a photoelectric field sensor even when a surface of a supporting insulator is wet or stained. CONSTITUTION: A surface of an insulator 1 incorporating an optical fiber and supporting a photoelectric field sensor 4 is coated with, e.g. a conductive glaze and turned to be conductive, so that influences by the moisture or stain at the surface of the insulator are lessened. It becomes unnecessary to separate the insulator and a sensor head by a long arm although it is required conventionally. When the photoelectric field sensor 4 is supported by an arm 5, it is preferable to arrange a lower electrode immediately below the sensor. Moreover, the photoelectric field sensor 4 is set inside rather than at an upper surface of the insulator 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer for an optical instrument used for extracting the voltage of a conductor as an optical signal in a substation or the like.

[0002]

2. Description of the Related Art As a transformer for an optical instrument used for the above purpose, one in which an optical sensor is supported by an insulator with a built-in optical fiber is known. FIG. 10 shows a conventional structure of such a transformer for an optical instrument, where 51 is an optical fiber 52.
Is an optical fiber built-in insulator, 53 is an arm horizontally provided at its upper end, 54 is a sensor head at the tip of the arm 53, and 55 is an optical voltage sensor housed in the sensor head 54. The optical sensor 55 includes an intermediate electrode 57 having a voltage dividing capacitor 56, and has a function of detecting a voltage between electrodes of the voltage dividing capacitor 56 and converting the voltage into an optical signal.

However, in such a conventional transformer for an optical instrument, the output of the optical voltage sensor 55 largely changes when the resistance value of the insulator surface changes due to the surface of the insulator 51 with a built-in optical fiber becoming wet or soiled. There was a problem. The reason is considered to be as follows.

First, the equivalent circuit of the apparatus of FIG. 10 is as shown in FIG. Here, R ₁ and R ₂ are surface resistances of the insulator 51 with a built-in optical fiber, and usually have a value of about 10 ³ MΩ. Also,
R ₃ and R ₄ are surface resistances when the insulator 51 with a built-in optical fiber is wet or soiled and has a value of about 10 ² to 10 ³ MΩ. C ₁ is a voltage dividing capacitor, C ₂ is an atmospheric capacitance formed between the intermediate electrode 57 and the ground, and the optical sensor 55 measures the voltage between the electrodes of the voltage dividing capacitor C ₁ as described above. . As is clear from this equivalent circuit, when only the resistance R ₄ is lowered due to the unequal contamination of the insulator surface, the voltage between the electrodes of the voltage dividing capacitor C ₁ changes greatly, and the sensor output changes greatly.

Therefore, in the conventional transformer for an optical instrument, the arm is
By increasing 53, the capacitance of the capacitor shown as C _{3 in} FIG. 11 has been reduced, and the influence of the resistance R ₄ on the insulator surface has been reduced. For this reason, in the transformer for a photometer that is easily installed outdoors, the fluctuation of the output of the optical voltage sensor 55 is reduced by setting the arm 53 to 70 cm or more, which causes a problem that the entire transformer for a photometer becomes large. was there.

Furthermore, in the conventional optical instrument transformer having the long arm 53 as shown in FIG.
If a piece of metal invades the space between 54 and the earth due to wind, or if a bird or the like enters this space, the atmospheric capacitance C ₂ will fluctuate, causing a large error in the output of the optical voltage sensor 55. There was also a problem.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and the first object thereof is to solve the problems that the surface of the optical fiber built-in insulator becomes wet or soiled. Another object of the present invention is to provide a transformer for an optical instrument in which an error is less likely to occur in the output of the optical sensor. A second object of the present invention is to provide a transformer for an optical instrument in which the error in the output of the optical sensor due to the intrusion of foreign matter such as metal pieces and birds is eliminated.

[0008]

A first invention made to solve the above problems is characterized in that an optical electric field sensor is held by an optical fiber built-in insulator whose surface has conductivity. To do. A second aspect of the invention is characterized in that an optical electric field sensor is attached to a portion inside the insulator surface above the insulator having a built-in optical fiber and having conductivity.

The optical instrument transformer of the first invention holds the optical electric field sensor by means of an optical fiber built-in insulator having conductivity on its surface, and therefore, when the insulator surface is soiled or wet, However, the change in the surface resistance due to this is very small, and the error of the optical electric field sensor can be reduced. Therefore, it is not necessary to take a long distance between the center of the insulator and the optical electric field sensor by a long arm as in the conventional case,
The overall size can be reduced.

In the transformer for an optical instrument according to the second aspect of the invention, the optical electric field sensor is attached to a portion inside the insulator surface at the upper part of the insulator with a built-in optical fiber whose surface has conductivity. As in the first aspect of the present invention, even if the insulator surface is soiled or wet, there is no effect, and the error in the output of the optical electric field sensor due to foreign matter in the surroundings can be reduced.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below in more detail with reference to the drawings. In FIG. 1, 1 is an insulator with a built-in optical fiber, 2 is an optical fiber inside thereof, 3 is a sensor head provided above the insulator with built-in optical fiber 1, 4 is an optical electric field sensor provided at the center thereof, and 5 is an optical field sensor. It is an arm connecting the fiber-embedded insulator 1 and the sensor head 3. In the present invention, the insulator 1 with a built-in optical fiber has a surface having conductivity, for example, a surface having a conductive glaze layer.

Here, the conductive glaze is a glaze component containing iron or other conductive component, and as such, it is described, for example, in "NGK Review" May 1979 issued by the applicant company. It is known. It is known that when such a layer of conductive glaze is formed on the insulator surface, corona discharge on the insulator surface, which causes noise such as television and radio, can be prevented.

In the present invention, by forming such a layer of conductive glaze on the surface of the optical fiber built-in insulator 1,
If the surface resistances R ₃ and R ₄ in the equivalent circuit of FIG.
Reduce to about ² MΩ. On the other hand, since the surface resistance due to wetting and fouling is about 10 ³ MΩ as described above,
Even if the surface resistance changes due to wetting or fouling, the voltage between the electrodes of the voltage dividing capacitor C ₁ hardly changes. By decreasing the surface resistance of the insulator, the surface of the optical fiber built-in insulator 1 due to wetting or unequal fouling It is extremely unlikely to be affected by the change in the resistance value of.

FIG. 3 is a graph showing the fluctuation rate of the sensor output when the surface of the insulator 1 with a built-in optical fiber is glazed by ordinary glaze and when it is glazed by conductive glaze.
As is clear from this graph, in the case of ordinary glaze, if the surface becomes wet or soiled, the sensor output will drop significantly,
When glazed with a conductive glaze as in the present invention, an error in sensor output due to wetting or stain can be suppressed to less than -4%.

As described above, when the optical fiber built-in insulator 1 whose surface has conductivity is used, the fluctuation of the sensor output due to wetting or stain is reduced. Therefore, in the first aspect of the invention, it is not necessary to avoid the influence of wetting and stains by increasing the distance between the optical fiber built-in insulator 1 and the sensor head 3 by using the conventional long arm. FIG. 4 shows this relationship, and shows that even if the distance between the optical fiber built-in insulator 1 and the sensor head 3 is made small, the fluctuation of the sensor output becomes much smaller than in the conventional case.

FIG. 5 shows a modification of the first invention.
A lower electrode 7 is attached to the lower part of the insulator 1 with a built-in optical fiber. The lower electrode 7 is made of a conductor such as aluminum, and is provided directly below the sensor head 3 provided at the tip of the arm 5 above the insulator 1 with a built-in optical fiber. The lower electrode 7 may be attached to the lower metal fitting of the optical fiber built-in insulator 1 as shown in FIG. 5, or may be mounted between the lower metal fitting and the pedestal 6. In the case of FIG. 1 that does not have such a lower electrode 7, C ₂ (optical field sensor 4 to ground capacity) shown in the equivalent circuit of FIG. 2 changes depending on the distance between the ground and the optical field sensor 4. In addition, the output of the optical electric field sensor 4 changes depending on the installation height, and it is necessary to perform calibration every installation. On the other hand, if the lower electrode 7 is attached directly below the sensor head 3 as shown in FIG. 5, the size of C ₂ can be made constant, so the output of the optical electric field sensor 4 changes depending on the installation height. There is nothing to do. The lower electrode 7 has chamfered peripheral corners to prevent corona generation.

In addition, in the example of FIG. 5, an LN electric field sensor is used as the optical electric field sensor 4, electrodes 8 and 8 are applied on the upper and lower surfaces thereof, and lead wires 9 and 9 electrically connect the arm 5 and the intermediate electrode 10 to each other. Adopted the structure connected to. Then, these are housed inside the sensor package 11 to form the sensor head 3. With such a structure, a divided voltage can be applied to both ends of the optical electric field sensor 4, and a stable output can be obtained.

On the basis of the above-mentioned finding that the use of the optical fiber built-in insulator 1 having a conductive surface reduces the fluctuation of the sensor output due to wetting and stains without using the long arm 5. In the invention of FIG. 6, as shown in FIG. 6, a portion inside the insulator surface of the upper portion of the optical fiber built-in insulator 1,
More preferably, the optical electric field sensor 4 is attached on the center line of the insulator 1 with a built-in optical fiber. With this configuration,
Since there is no possibility of foreign matter entering between the sensor head and the ground as in the conventional case, there is an advantage that the error in the sensor output can be further reduced. However, when the mounting position of the optical electric field sensor 4 is brought close to the lower part of the insulator 1 with a built-in optical fiber,
It is not preferable because it is likely to be affected by disturbance of equipotential lines due to foreign matter.

7 and 8 are equipotential diagrams in the case where a foreign substance having a relative dielectric constant ε _r = 80 (corresponding to an object containing water) enters between the sensor head and the ground. FIG. 7 shows the case of the conductive glazed insulator of the present invention, and FIG. 8 shows the case of the conventional ordinary glazed insulator. In any case, the electric field at point B is disturbed by the object. On the other hand, the electric field at the point A increases in FIG. 8 due to the object inside the insulator, but in FIG. 7 the electric field is relaxed by the conductive glaze layer on the insulator surface, and the inside of the insulator maintains a uniform electric field. Not easily affected. FIG. 9 is a graph obtained by calculating the variation rate of the electric field at the point B depending on the relative permittivity of the object, and it can be seen that the variation rate of the electric field is very small in the case of the conductive glaze insulator.

[0020]

As described above, according to the present invention, it is possible to reduce the error in the output of the optical electric field sensor even when the surface of the optical fiber built-in insulator is wet or soiled. Further, by providing the lower electrode as shown in FIG. 5, a stable output can be obtained without being affected by the installation height. Further, according to the present invention, since it is not necessary to use a long arm as in the conventional case for avoiding the influence of wetting and stains, it is possible to reduce the size of the whole, and at the same time, foreign matter such as metal pieces and birds enter in the vicinity. However, there is an advantage that the error in the output of the optical voltage sensor can be reduced.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of FIG.

FIG. 3 is a graph showing the sensor output fluctuation rate when the surface of the insulator is glazed with conductive glaze and when it is glazed with normal glaze.

FIG. 4 is a graph showing the relationship between the distance between the insulator and the sensor head and the sensor output fluctuation rate.

FIG. 5 is a side view showing a modified example of FIG.

FIG. 6 is a side view showing an embodiment of the second invention.

FIG. 7 is an equipotential diagram when a foreign matter enters between the sensor head of the present invention and the ground.

FIG. 8 is an equipotential diagram in the case where a foreign matter has entered between the conventional sensor head and the ground.

FIG. 9 is a graph showing the relationship between the relative permittivity of a foreign substance and the variation rate of the electric field at point B.

FIG. 10 is a side view showing a conventional example.

FIG. 11 is an equivalent circuit diagram of a conventional example.

[Explanation of symbols]

1 insulator with built-in optical fiber, 2 optical fibers, 3 sensor head, 4 optical electric field sensor, 5 arms, 6 stand for insulator with built-in optical fiber, 7 lower electrode, 8 electrodes, 9 lead wires, 10 intermediate electrode, 11 sensor package

Claims (5)

[Claims] 1. A transformer for an optical instrument, characterized in that an optical electric field sensor is held by an optical fiber built-in insulator whose surface has conductivity. 2. The transformer for an optical instrument according to claim 1, wherein the insulator with a built-in optical fiber has a conductive glaze layer formed on the surface thereof. 3. The optical electric field sensor is supported by an upper arm of the optical fiber built-in insulator, and a lower electrode is provided below the optical fiber built-in insulator so as to face the optical electric field sensor. Light meter transformer. 4. A transformer for an optical instrument, wherein an optical electric field sensor is attached to an upper portion of an insulator with a built-in optical fiber, the surface of which is electrically conductive, and a portion inside the insulator surface. 5. The transformer for an optical instrument according to claim 4, wherein the optical electric field sensor is provided on the center line of the insulator with a built-in optical fiber.