JPH07333256A - Optical current transformer - Google Patents

Abstract

PURPOSE:To provide a superior optical current transformer wherein drift of an optical axis and fluctuation of a space beam with respect to the temperature variation does not occur, the high accuracy can be stably maintained and it can be used in a power system of heavy current CONSTITUTION:A transmission optical fiber 1 and a lens 2 are united with each other by a bonding member 31 to form a fiber-lens assembly body 32. A sensor is wound around a conductor 9 to be measured to form a sensing optical fiber 34. Lenses 2 are provided to each of the input and output ends of the sensing optical fiber 34 and are united thereto by bonding members 31 to form respective fiber-lens assembly bodies 36. An optical system housing box 37 houses the fiber-lens assembly bodies 32, 36, a polarizer 3 and an analyzer 5 such that they are directly fixed thereto to form optical passages of the optical system. The optical system housing box 37 is made of a material of which thermal expansion coefficient is lower than that of each of the optical elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current measuring device for measuring a current of a power system. In particular, it relates to an improvement in the structure of an optical system in an optical current transformer that uses the Faraday effect of light.

[0002]

[Prior art]

[1] Principle of optical current transformer In recent years, optical current transformers using light are advantageous in that they have high insulation properties and can be miniaturized with the increase in power system voltage and capacity. , Its practicality is increasing rapidly. The optical current transformer is constituted by using a substance having a Faraday effect, such as lead glass or quartz, as a sensor and disposing this sensor in the vicinity of the conductor to be measured. Then, the linearly polarized light is passed through this sensor, the illuminating angle of the Faraday effect due to the magnetic field formed by the measured current flowing through the measured conductor is measured, and the measured current that is proportional to this Faraday applied angle is obtained. It is a thing. FIG. 5 is a block diagram showing the principle of such an optical current transformer. The principle of the optical current transformer will be described below with reference to FIG.

In FIG. 5, first, the optical system includes a transmission optical fiber 1, a lens 2, a polarizer 3, a sensor 4, an analyzer 5, and a mounting device 6. Of these, the transmission optical fiber 1 is used to receive the light from the light source 7 and to send two measurement lights to the two light receivers 8. Further, the lens 2 is used for converting the light from the transmission optical fiber 1 into a parallel beam and separately focusing the two linearly polarized lights from the analyzer 5 and guiding them to the individual transmission optical fibers 1. ing. And the polarizer 3
Is used to convert the parallel beam from the lens 2 into linearly polarized light, and is composed of, for example, a Glan-Thompson prism or the like. Further, the sensor 4 is arranged near the conductor 9 to be measured so as to pass the linearly polarized light from the polarizer 3, and is made of a substance having a Faraday effect such as lead glass or quartz. The arrow H shown on the sensor 4 part shows a part of the magnetic field generated by the current flowing through the conductor 9 to be measured. Further, the analyzer 5 is arranged so as to separate the linearly polarized light that has passed through the sensor 4 into two linearly polarized lights that are orthogonal to each other, and is composed of a Wollaston prism, a polarization beam splitter, and the like. Further, the attachment device 6 is a mechanism for holding each of the optical elements 1 to 5 described above, and is schematically shown in FIG.

On the other hand, the light source 7 is used to introduce light into the above optical system, and is drive-controlled by the drive control circuit 10. Further, the two light receivers 8 are used for individually receiving the two measurement lights from the optical system and converting the intensity of the measurement lights into an electric signal, and are driven by the drive circuit 11. Has become. One measuring electronic circuit 12 is connected to the two light receivers 8.
Is configured to process the electric signals obtained by the two light receivers 8 and calculate the current flowing through the conductor 9 to be measured.

When the current flowing through the conductor 9 to be measured is measured by the optical current transformer having the above structure, the following operation is performed. First, the light source 7 emits light, which propagates through the transmission optical fiber 1 and is emitted, and is converted into a parallel beam by the lens 2. This parallel beam is made into linearly polarized light by the polarizer 3 and is incident on the sensor 4. At this time, since the sensor 4 is in the magnetic field H formed by the current flowing through the conductor 9 to be measured, the linearly polarized light incident on the sensor 4 has its polarization direction rotated by the angle θf due to the Faraday effect.

In this case, the strength of the magnetic field H at the sensor 4 portion is represented by H as it is, the Verdet constant of the substance forming the sensor 4 is V, and the length of the minute portion of the light path is d.
Letting α be the angle formed by S, the electric field H and the light path, the Faraday light application angle d generated at the minute portion dS of this light path.
θf is expressed by the following equation (1).

## EQU00001 ## d.theta.f = VH.dS.cos.alpha. = VH.dS (1) In this case, the Faraday illumination angle .theta.
f is represented by the following equation (2).

[Equation 2]

That is, the linearly polarized light incident on the sensor 4 has an angle θf proportional to the measured current which causes the magnetic field H.
Only the polarization direction is rotated and the light is emitted.

The light emitted from the sensor 4 is separated by the analyzer 5 into two linearly polarized lights having polarization directions orthogonal to each other, and travels in different directions (illustrated as 90 degrees for convenience in FIG. 5). The two lights respectively enter the two photodetectors 8 via the individual lenses 2 and the individual transmission optical fibers 1, and the intensities thereof are measured. Here, the azimuths of the two lights from the analyzer 5 are the X-axis direction and the Y-axis direction, and the polarization azimuth of the polarizer 3 is 45 degrees with respect to the XY-axis.
If the intensities of the two measurement lights divided into two by the analyzer 5 are IX and IY, the Faraday rotation angle θf can be easily obtained from the following equations (3) and (4).

(3) (IX-IY) / (IX + IY) = sin (2θf) (3)

[Equation 4] That is, the intensities IX and IY of the two measurement lights are measured by the two light receivers 8, the Faraday rotation angle θf is calculated by the measurement electronic circuit, and the current value proportional to the Faraday rotation angle θf is obtained. You can The above is the operation principle of the optical current transformer.

[2] Configuration of Conventional Optical Current Transformer Next, the configuration of an actual optical current transformer based on the above operation principle will be described with reference to FIG. This Figure 6
Of the optical current transformer of FIG. 5, the light source 7 and its drive control circuit 10,
Light receiver 8 and its drive circuit 11, and measurement electronic circuit 12
It is a figure which shows the specific structural example by the prior art of the optical system part except for. As shown in FIG. 6, the sensor 4 is arranged near the measured conductor 9 so as to surround the measured conductor 9. The sensor 4 is integrally formed in a block shape and is formed so that light can pass around the conductor 9 to be measured. In this case, a small block-shaped sensor is used because an optically homogeneous and large block is difficult and expensive to manufacture. However, in an actual power system, the ground voltage of the conductor 9 to be measured is high and the flowing current is also large, so that a sufficient insulation distance must be secured. However, since the transmission optical fiber 1 is connected to the ground potential, it is impossible to obtain the high insulation performance required for the high voltage and high power power system only by the insulation performance.

Therefore, in the conventional optical current transformer, the mounting device 6 for the optical element is specifically as shown in FIG.
The optical system storage box 21, the optical element holder 22, the sensor holder 23, the insulating holder 24, and the like are included. First,
Each optical element except the sensor 4, that is, the transmission optical fiber 1, the lens 2, the polarizer 3, and the analyzer 5 is attached to the optical element holding base 22 with a fixture and is stored in the optical system storage box 21 for insulation. It is arranged apart from the conductor 9 to be measured by a necessary distance. Then, the transmission optical fiber 1, the lens 2,
In order to maintain the positional relationship of each optical element of the optical system including the polarizer 3, the sensor 4, and the analyzer 5 and align the optical axis between the optical elements, the sensor holder 23 and the insulating holder 24
The sensor 4 and the optical system storage box 21 are mechanically connected by. In the figure, 25 is a fiber fixture for attaching the transmission optical fiber 1 to the optical element holding base 22, and 26 is a fiber fixture.
It is a lens fixing tool for attaching the lens 2 to the optical element holding base 22. Further, reference numeral 27 in the figure is a reflecting mirror for guiding light from the polarizer 3 to the sensor 4.

[3] Operation of Conventional Optical Current Transformer Next, the operation of the optical current transformer of FIG. 6 having the above-mentioned configuration will be described. In FIG. 6, light emitted from a light source (not shown) propagates through the transmission optical fiber 1 and is emitted, and is converted into a parallel beam by the lens 2. This parallel beam is converted into linearly polarized light by the polarizer 3, and enters the sensor 4 via the reflecting mirror 27. The parallel beam incident on the sensor 4 causes Faraday illuminating by the magnetic field formed by the current flowing through the conductor under measurement 9 while passing around the conductor 9 under measurement inside the sensor 4, and its polarization azimuth is angled. The light is emitted after rotating by θf. In this case, the Faraday illumination angle θf is given by Ampere's theorem.
Assuming that the number of times the light orbits the current is N and the Verdet constant of the substance forming the sensor 4 is V, it is expressed by the following equation (5).

[Mathematical formula-see original document] θf = N · V · I (5) That is, the linearly polarized light that circulates inside the sensor 4 surrounding the conductor 9 to be measured is polarized at an angle θf proportional to the current to be measured flowing through the conductor 9 to be measured. The direction is rotated and the light is emitted.

The light emitted from the sensor 4 is separated by the analyzer 5 into two linearly polarized lights whose polarization directions are orthogonal to each other, and in different directions (illustrated as 90 degrees for convenience in FIG. 6). move on. The two lights are incident on a light receiver (not shown) via the individual lens 2 and the individual transmission optical fiber 1, and the intensities thereof are measured. That is, the light reaching the light receiver is converted into an electric signal proportional to each intensity, and the measurement electronic circuit (not shown) calculates the above equation (4) to obtain a signal proportional to the current. To be

[0013]

As can be seen from the above description, in the conventional optical current transformer shown in FIG. 6, the light emitted from the emission end of the transmission optical fiber 1 on the light source side is on the light receiver side. A long distance to the entrance end of the transmission optical fiber propagates as a spatial beam. The core diameter of the transmission optical fiber is several microns to several tens of microns. Therefore, there is a possibility that light may not reach the light receiver or the amount of light reaching the light receiver may be significantly reduced due to a slight optical axis shift between the optical elements.

Further, among the optical elements between the emission end of the transmission optical fiber on the light source side and the incidence end of the transmission optical fiber on the light receiver side, the optical elements except the sensor 4 and the reflecting mirror 27, that is, Lens 2, Polarizer 3, and Polarizer 5
Are stored inside the optical system storage box 21. In this case, these optical elements are attached to the inside of the optical system storage box 21 by being held by the optical element holding base 22 via the fixtures. The positional relationship between the transmission optical fiber 1 and the sensor 2 is determined by a plurality of optical elements 2, 3, 5 housed in the optical system housing box 21, an insulating holder 24, a sensor holder 23, and an optical member. It is held by a large number of members such as a reflecting mirror 27 arranged outside the system storage box 21.

Therefore, when the conductor to be measured is heated by a large current and the temperature changes due to a change in ambient temperature, the position and orientation of the optical element change due to the difference in thermal expansion between the members, and the optical axis shifts between the optical elements. Is likely to occur. Also, since the distance that light propagates as a spatial beam is long, if the density of air or insulating gas in the optical path fluctuates due to a local temperature change such as a sudden temperature change or conductor heat generation, the spatial beam will change. There is a large fluctuation, and a deviation similar to the deviation of the optical axis appears. Any of these optical axis shifts and spatial beam fluctuations deteriorates the accuracy of the optical current transformer or makes measurement impossible.

Further, as described above, the sensor 4 is generally formed of a lead glass or quartz block, and a reflecting surface is formed on each part so that the light beam reflects the inside thereof and goes around. In such an orbiting optical path, the beam deviates from a predetermined position even if a slight optical axis deviation occurs, and the light cannot be orbited. That is,
Such a sensor has a very high possibility that it becomes impossible to measure light as an optical current transformer because the light cannot be circulated due to temperature fluctuations.

As described above, in the conventional optical current transformer, there is a possibility that accuracy may be significantly reduced or measurement may not be possible due to a change in ambient temperature or a change in ambient temperature of the optical system due to heat generation of the conductor due to conduction of a large current. is there. If the change in accuracy with temperature is linear, it can also be corrected by the measuring electronics. However, these changes in accuracy are non-linear with respect to temperature, and correction in the measurement electronic circuit is extremely difficult, which is practically impossible. Therefore, by the conventional optical current transformer,
It is difficult to reliably prevent the decrease in accuracy and the occurrence of measurement inability due to the temperature change. Therefore, the conventional optical current transformer, from the problem of reliability against such temperature changes,
Its use in high current power systems is severely limited.

By the way, as described above, the cause of the reliability problem with respect to the temperature change in the conventional optical current transformer is the optical axis shift of the optical system and the fluctuation of the spatial beam caused by the temperature change. . The fundamental causes of such optical axis shift and spatial beam fluctuation are that the optical paths are held by many members and that light propagates as a spatial beam over a long distance, as described above. It is in.

Therefore, an object of the present invention is to hold the optical path with a small number of members and to minimize the distance that light propagates as a spatial beam, so that the optical axis shifts and the space even when the temperature changes. It is an object of the present invention to provide an excellent optical current transformer that does not generate beam fluctuations, maintains stable high accuracy, and can be used in a large-current power system.

[0020]

An optical current transformer according to the present invention comprises an optical system, and an optical current transformer for measuring a current flowing through a conductor to be measured from a Faraday rotation angle of light passing through the optical system, The optical system is characterized by being configured as follows. First, the optical current transformer according to claim 1 comprises a sensor, a transmission optical fiber on the light source side and the light receiving side, a lens on the light source side and the light receiving side, a polarizer, an analyzer, and an optical system storage box. There is. The sensor is made of a substance having a Faraday effect and is placed in a magnetic field generated by a current flowing through the conductor to be measured. The transmission optical fiber on the light source side transmits the light from the light source to the sensor, and the transmission optical fiber on the light receiver side transmits the light from the sensor to the light receiver. The lens on the light source side is optically coupled to the emission end of the transmission optical fiber on the light source side, and the lens on the light receiver side is optically coupled to the incidence end of the transmission optical fiber on the light receiver side. The polarizer is arranged between the lens on the light source side and the sensor and converts light from the lens into linearly polarized light. The analyzer is arranged between the sensor and the lens on the side of the light receiver, and separates the linearly polarized light passing through the sensor into two linearly polarized light. The optical system storage box
The end of the transmission optical fiber, the lens, the polarizer, and the analyzer are attached and housed so as to form the optical path of the optical system. According to the optical current transformer of claim 1, in addition to the above configuration, each optical fiber for transmission and each lens optically coupled to the end thereof are assembled as an integrated fiber / lens assembly. , A coupling member attached to the optical system storage box.

An optical current transformer according to a second aspect is the optical current transformer according to the first aspect, characterized in that it has the following mounting structure. That is, in the optical current transformer according to claim 2, the fiber / lens assembly in which the transmission optical fiber and the lens are assembled by the coupling member, the polarizer, and the analyzer are directly attached to the optical system storage box. .

The optical current transformer according to claim 3 is the optical current transformer according to claim 1 or 2, wherein the sensor and its mounting structure have the following features. That is, in the optical current transformer according to a third aspect of the present invention, the sensor is a sensor optical fiber, and further includes lenses that are optically coupled to an incident end and an emitting end of the sensor optical fiber. The individual coupling member includes a coupling member that assembles the optical fiber for sensor and each lens coupled to the incident end and the emission end thereof as a fiber-lens assembly having an integral structure.

The optical current transformer according to a fourth aspect is the optical current transformer according to the third aspect, and has the following features in the mounting structure of the optical fiber for sensor. That is, in the optical current transformer according to claim 4, a fiber / lens assembly in which the sensor optical fiber and the lens are assembled by a coupling member is provided.
It can be attached directly to the optical system storage box.

The optical current transformer according to claims 5 and 6 is the optical current transformer according to claim 1, wherein the configuration of the optical system storage box has the following features. That is, in the optical current transformer according to claim 5, the optical system storage box includes an optical fiber, a lens,
It is composed of a polarizer and a material having a coefficient of thermal expansion equal to or lower than that of the analyzer. Further, in the optical current transformer according to claim 6, the optical system storage box is made of a material having a large thermal conductivity.

An optical current transformer according to a seventh aspect is the optical current transformer according to the first aspect, wherein the analyzer has the following features. That is, in the optical current transformer according to claim 7,
The analyzer is composed of two polarizers and a beam splitter arranged so that their optical axes are orthogonal to each other.

[0026]

The optical current transformer of the present invention as described above has the following actions. First, according to the first aspect of the present invention, the optical fiber for transmission and the lens are assembled by a single coupling member as a fiber / lens assembly having an integrated structure, so that the optical system for storing the optical fiber for transmission and the lens is housed. Attachment to the box can be done by a single coupling member. Therefore, as compared with the case where the transmission optical fiber and the lens are attached by separate fixtures, the optical axis shift between the transmission optical fiber and the lens due to the temperature change can be reduced.

According to the second aspect of the invention, by directly attaching each optical element to the optical system storage box, the optical path of the optical system can be held by as few members as possible.
Therefore, even if a temperature change occurs, it is possible to reduce the change in the position and orientation of the optical element caused by the difference in thermal expansion of each member, and to minimize the optical axis deviation between the optical elements.

According to the third aspect of the present invention, since the sensor optical fiber is used as the sensor, even if a slight optical axis deviation occurs, compared with the case where the block-shaped sensor is used, the optical Can be circulated, and there is no risk of measurement failure. Further, by assembling the end portion of the optical fiber for sensor as a fiber lens assembly having an integral structure with a single coupling member, the optical fiber for lens and the lens can be attached to the optical system storage box in a single unit. This can be done by a connecting member. Therefore, the optical axis shift between the sensor optical fiber and the lens due to temperature change can be reduced as compared with the case where the sensor optical fiber and the lens are attached by separate fixtures.

According to a fourth aspect of the present invention, there is provided a fiber / lens assembly formed at an end of an optical fiber for sensor,
By directly attaching to the optical system storage box, the incident end and the output end of the sensor optical fiber are arranged in contact with or close to the optical system storage box. Therefore, the distance that light propagates as a spatial beam can be shortened as much as possible, and the fluctuation of the spatial beam due to temperature change can be reduced.

According to the fifth and sixth aspects of the invention, the optical system housing box for mounting the plurality of optical elements is made of a material having a coefficient of thermal expansion equal to or lower than the coefficient of thermal expansion of the optical elements, or a material having high thermal conductivity. With this structure, thermal expansion of the optical system storage box due to temperature change can be reduced. Therefore, when the temperature changes, changes in the positions and orientations of the plurality of optical elements attached to the optical system storage box can be reduced, and the optical axis shift between the optical elements can be minimized.

According to the invention of claim 7, the analyzer is
By configuring the two polarizers and the beam splitter arranged such that their optical axes are orthogonal to each other, the angle of the beam splitter can be appropriately adjusted to freely change the arrangement of the optical system. Since the arrangement of the optical system can be freely changed in this way, the entire optical system can be downsized, and the distance that light propagates as a spatial beam can be shortened as much as possible. Therefore, the fluctuation of the spatial beam due to the temperature change can be reduced.

[0032]

【Example】

[1] First Embodiment [1-1] Configuration of Embodiments FIGS. 1 and 2 FIG. 1 is a diagram showing a typical embodiment of an optical current transformer according to the present invention, and particularly, an optical system portion. Shows a specific configuration of. That is, in FIG. 1, the optical fibers 1 for transmission on the light source side and the optical receiver side and the corresponding lenses 2 are assembled by an individual coupling member 31 as a fiber / lens assembly 32 having an integrated structure. That is, in this fiber / lens assembly 32, as shown in FIG. 2, the optical fiber 1 for transmission and the lens 2 are attached to the tubular coupling member 31.
It is configured by being attached by a known means such as an adhesive or a stopper 33. In this case, the distance between the end face of the transmission optical fiber 1 and the lens 2 is set to be substantially equal to the focal length of the lens 2.

Further, in this embodiment, the sensor is also configured as the sensor optical fiber 34,
The sensor optical fiber 34 is wound around a ring-shaped sensor holder 35 arranged around the conductor 9 to be measured. Then, the lenses 2 are arranged at the entrance end and the exit end of the optical fiber 34 for sensor,
Similar to the transmission optical fiber 1, it is assembled by a separate coupling member 31 as an integrated fiber / lens assembly 36. The distance between the end surface of the sensor optical fiber 34 and the lens 2 is set to be substantially equal to the focal length of the lens 2.

On the other hand, in the optical system storage box 37 of this embodiment,
The fiber / lens assemblies 32, 36, the polarizer 3, and the analyzer 5 as described above are directly attached and housed so as to form the optical path of the optical system. For example,
The fiber / lens assemblies 32 and 36 are the optical system storage box 3
It is attached to the attachment hole provided on the side surface of the member 7 by a known means such as adhesion or fitting. Further, the polarizer 3 and the analyzer 5 are attached to predetermined positions on the bottom surface of the optical system storage box 37 by a known means such as an adhesive. Further, the optical system storage box 37 is made of a material having a thermal expansion coefficient equal to or slightly lower than the thermal expansion coefficient of the optical element. For example, the optical system storage box 37
Is made of quartz, Invar, low expansion glass, ceramics, or the like.

[1-2] Operation of the Embodiment The operation of the optical current transformer of the present embodiment having the above-mentioned structure is as follows. First, a single coupling member 31 is used to integrate the optical fiber 1 for transmission and the lens 2 into a single fiber.
Since the lens assembly 32 is assembled, the transmission optical fiber 1 and the lens 2 can be attached to the optical system storage box 37 by the single coupling member 31. Therefore, compared to the case where the transmission optical fiber 1 and the lens 2 are individually attached by the fiber fixture 25 and the lens fixture 26 as in the conventional example shown in FIG. 6,
The optical axis shift between the transmission optical fiber 1 and the lens 2 due to temperature change can be reduced.

Further, since the fiber / lens assemblies 32, 36, the polarizer 3 and the analyzer 5 are directly attached to the optical system housing box 37, the optical path of the optical system can be made with a smaller number of members than the conventional example shown in FIG. Can be held. Therefore,
Even if the temperature changes, the change in the position and orientation of the optical element caused by the difference in thermal expansion of each member can be made smaller than that in the conventional example of FIG. 6, and the optical axis deviation between the optical elements can be minimized. can do. Further, even when these optical elements are attached by an adhesive, since the adhesive only intervenes in a small amount between the components to be adhered, the change in the position and the posture of the optical element does not become so large as to cause a problem.

Further, in this embodiment, since the sensor optical fiber 34 is used as the sensor, even if a slight optical axis deviation occurs compared to the block-shaped sensor 4 in the conventional example of FIG. Can be circulated, and there is no risk of measurement failure. Further, since the sensor optical fiber 34 and the lens 2 are assembled by the single coupling member 31 into a fiber / lens assembly 36 having an integral structure,
Optical system storage box 3 including optical fiber 34 for sensor and lens 2
Attachment to 7 can be done by a single coupling member 31. Therefore, the sensor optical fiber 34
The optical axis shift between the sensor optical fiber 34 and the lens 2 due to a temperature change can be reduced as compared with the case where the lens 2 and the lens 2 are individually attached.

The fiber / lens assembly 36 formed at the entrance end and the exit end of the sensor optical fiber 34 is directly attached to the optical system storage box 37.
In addition, in the fiber / lens assembly 36, the distance between the sensor optical fiber 34 and the lens 2 is set to be substantially equal to the focal length of the lens 2.
Since this distance is specifically several millimeters to several tens of millimeters, the sensor optical fiber 34 enters and emits light at a position in contact with the optical system storage box 37 or a very close position. Therefore, as compared with the conventional example of FIG. 6, the distance that light propagates as a spatial beam can be significantly shortened, so that fluctuations of the spatial beam due to temperature changes hardly occur.

On the other hand, since the optical system storage box 37 is made of a material having a thermal expansion coefficient equal to or slightly lower than the thermal expansion coefficient of the optical element, the thermal expansion of the optical system storage box 37 due to temperature change is reduced. be able to. In particular, when the coefficient of thermal expansion is close to the coefficient of thermal expansion of the optical element, the entire optical system exhibits uniform thermal expansion, so that the change in the position and posture of the optical element can be minimized, and the light between the optical elements can be minimized. The axis deviation can be minimized.

[1-3] Effects of the Embodiment As can be seen from the above description, according to this embodiment, the following effects can be obtained. That is, firstly, since the optical paths are formed by holding the plurality of optical elements by a small number of parts as much as possible, even if the temperature changes, the positions and postures of the plurality of optical elements do not change so much that the optical axis shifts. Is unlikely to occur. Secondly, since the distance that light propagates as a spatial beam is much shorter than that of conventional optical current transformers, the fluctuation of the beam is small with respect to temperature changes and density changes of air and insulating gas. The effect is small enough not to be a problem. Therefore, according to the present embodiment, the optical axis shift and the fluctuation of the spatial beam do not occur even with the temperature change, the stable high accuracy is maintained, and the excellent optical current transformer that can be used for the large current power system is provided. Can be provided.

[2] Second Embodiment FIG. 3 FIG. 3 is a diagram showing a second embodiment of the optical current transformer according to the present invention, and particularly shows a specific configuration of the optical system portion.
That is, in FIG. 3, the sensor optical fiber 3
One end of the optical fiber 4 is assembled with the lens 2 by the coupling member 31 into a fiber / lens assembly 36 having an integral structure, and the other end of the optical fiber 34 for sensor is provided with a reflecting mirror 38. This reflecting mirror 38
The light propagating in the sensor optical fiber 34 is arranged so as to enter from the end face thereof, be reflected at 180 degrees, and be returned to the sensor optical fiber 34 as light in the opposite direction. On the other hand, a beam splitter 39 is provided between the fiber / lens assembly 36 of the sensor optical fiber 34 and the polarizer 3. This beam splitter 39
Is arranged so that the light emitted from the polarizer 3 is transmitted and is incident on the fiber lens assembly 36, and the light in the opposite direction emitted from the fiber lens assembly 36 is reflected and incident on the analyzer 5. Has been done. The other parts are configured in the same manner as in the first embodiment described above.

In the optical current transformer of the present embodiment having the above-mentioned structure, the light is propagated in the sensor optical fiber 34,
The light whose polarization azimuth is rotated by the Faraday effect is reflected by the reflecting mirror 38 and then propagates through the optical fiber for sensor 34 again to undergo the Faraday effect. And
Fiber / lens assembly 36 to beam splitter 39
Is reflected by the beam splitter 39 and is sent to the analyzer 5. As described above, the configuration in which the light is reflected at the terminal end of the sensor optical fiber 34 is a known technique. Since the light travels back and forth in the same sensor optical fiber 34, a double Faraday effect is given to this light. The measurement sensitivity can be doubled and the natural birefringence generated in the sensor optical fiber 34 can be eliminated. Since the configuration of the other parts is the same as that of the first embodiment described above, it is obvious that the same operation as that of the first embodiment described above can be obtained.

Therefore, according to the present embodiment, similarly to the first embodiment, the optical axis shift and the fluctuation of the spatial beam do not occur even with the temperature change, the stable high accuracy is maintained, and the power of the large current is large. It is possible to provide an excellent optical current transformer that can be used in a system. In particular, in this embodiment, since the light is reciprocated in the optical fiber for sensor 34, the measurement sensitivity and the measurement accuracy can be improved as compared with the first embodiment.
Arranging the reflecting mirror at the end of the sensor optical fiber and arranging the beam splitter in the optical path can be realized by a known technique, and do not affect the essence of the present invention at all. .

[3] Third Embodiment FIG. 4 FIG. 4 is a diagram showing a third embodiment of the optical current transformer according to the present invention, and particularly shows a specific configuration of the optical system portion.
The third embodiment is an example in which only the structure of the analyzer 5 is changed from the structure of the second embodiment. That is, in FIG. 4, the analyzer 5 is composed of a Wollaston prism and a polarization beam splitter, but instead of the polarizer 3 of the first and second embodiments, second and third polarizers having the same structure. It is composed of 41 and 42 and a second beam splitter 43. In this case, the second and third polarizers 41,
42 are arranged so that their directions are orthogonal to each other and form an angle of 45 degrees with the azimuth of the first polarizer 3.
The other parts are configured in the same manner as the second embodiment described above.

In the current transformer of the present embodiment having the above-mentioned structure, the light propagating in the optical fiber for sensor 34 and the polarization direction of which is rotated by the Faraday effect is reflected by the reflecting mirror 38 and then again. The light propagates through the sensor optical fiber 34 and receives the Faraday effect. Then, it enters the first beam splitter 39 from the fiber / lens assembly 36, is reflected by the beam splitter 39, and enters the second beam splitter 43. The light that has entered the second beam splitter 43 is split into two lights and respectively enter the second and third polarizers 41 and 42. In this case, since the directions of the second and third polarizers 41 and 42 are orthogonal to each other and form an angle of 45 degrees with the azimuth of the first polarizer 3, these polarizers 41 and 42 are
The intensity of the two lights passing through 42 is 2 from the analyzer 5 described in the section [1] Principle of optical current transformer in the section of the prior art.
It corresponds to two measurement light intensities IX and IY.

Then, in this way, in order to obtain the intensities IX and IY of the two measuring lights, the second and third polarizers 41 and 4 are obtained.
In this embodiment using the second and second beam splitters 43, the arrangement of the optical system can be freely changed by appropriately changing the angles of the two beam splitters 39 and 43. Therefore, the entire optical system can be downsized, and the distance that light propagates as a spatial beam can be shortened as much as possible. As a result, fluctuations of the spatial beam due to temperature changes can be reduced. Since the other parts of the configuration are the same as those of the second embodiment described above, the same operation as that of the second embodiment described above can be obtained.

Therefore, according to this embodiment, similarly to the first and second embodiments, the optical axis shift and the spatial beam fluctuation do not occur even with the temperature change, and stable and high accuracy is maintained.
It is possible to provide an excellent optical current transformer that can be used in a high-current power system. Since the light is reciprocated in the sensor optical fiber 34 as in the second embodiment, the measurement sensitivity and the measurement accuracy can be improved as in the second embodiment. Moreover, in this embodiment, since the analyzer is composed of two polarizers and a beam splitter,
Since the distance that light propagates as a spatial beam can be made as short as possible to minimize the fluctuation of the spatial beam due to temperature change, the measurement accuracy can be further improved.

[4] Other Embodiments The optical current transformer according to the present invention is not limited to the above-described embodiments. For example, the material of the optical system storage box is not more than the coefficient of thermal expansion of the optical element. Not only a material having a low coefficient of thermal expansion but also a material having a large thermal conductivity can be used. As such a material, for example, an aluminum alloy can be used. In this case, when a temperature change occurs, the optical system storage box sufficiently radiates heat according to the thermal conductivity, and the thermal expansion of the optical system storage box can be reduced as much as possible. The excellent action and effect of can be obtained.

Further, the specific structure of the coupling member for coupling the optical fiber and the lens can be selected as appropriate, and the mounting structure of the fiber / lens assembly constituted by this coupling member to the optical system storage box can also be selected as appropriate. Is.

Further, in the present invention, it is possible to use a conventional block-shaped sensor as the sensor. In this case, the distance between the block-shaped sensor and the optical system storage box cannot be shortened, but at least the optical axis does not shift inside the optical system storage box. By aligning the optical axes of, it is possible to obtain a certain effect.

[0051]

As described above, according to the present invention,
An optical fiber and a lens are integrated structure, a plurality of optical elements are directly attached to an optical system storage box, and a sensor optical fiber is used as a sensor. The end of this sensor optical fiber is also integrated with the lens. By directly attaching to the optical system storage box, and by constructing the optical system storage box with a material with a low coefficient of thermal expansion or a material with a high thermal conductivity, the optical path is held by as few members as possible, and the light is a spatial beam. The propagation distance can be minimized. Therefore, even if the temperature changes, the optical axis does not shift and the spatial beam does not fluctuate, maintaining stable high accuracy,
It is possible to provide an excellent optical current transformer that can be used in a high-current power system.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an optical system portion of a first embodiment of an optical current transformer according to the present invention.

FIG. 2 is a block diagram showing the fiber / lens assembly 32 of FIG.

FIG. 3 is a configuration diagram showing an optical system portion of a second embodiment of an optical current transformer according to the present invention.

FIG. 4 is a configuration diagram showing an optical system portion of a third embodiment of the optical current transformer according to the present invention.

FIG. 5 is a block diagram showing the principle of an optical current transformer.

FIG. 6 is a configuration diagram showing an example of an optical system portion of a conventional optical current transformer.

[Explanation of symbols]

 1 ... Optical fiber for transmission 2 ... Lens 3 ... Polarizer 4 ... Sensor 5 ... Analyzer 6 ... Mounting device 7 ... Light source 8 ... Photoreceiver 9 ... Conductor under test 10 ... Drive control circuit 11 ... Drive circuit 12 ... Measuring electronic circuit 21 ... Optical system storage box 22 ... Optical element holding base 23 ... Sensor holding tool 24 ... Insulation holding tool 25 ... Fiber fixing tool 26 ... Lens fixing tool 27 ... Reflecting mirror 31 ... Coupling member 32 ... Fiber / lens assembly 33 ... Adhesion Agent or stopper 34 ... Optical fiber for sensor 35 ... Sensor holder 36 ... Fiber / lens assembly 37 ... Optical system storage box 38 ... Reflector 39 ... Beam splitter 41, 42 ... Polarizer 43 ... Beam splitter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyotoshi Terai 2-1, Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Stock company Toshiba Hamakawasaki Plant (72) Hiroshi Miura Second, Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa No. 1 in stock company Toshiba Hamakawasaki factory (72) Inventor Keiko Niwa No. 2 Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Stock company Toshiba Hamakawasaki factory

Claims (7)

[Claims] 1. An optical system and a light source for sending light to the optical system,
And an optical current transformer having a light receiver for receiving light from the optical system, wherein the current flowing through the conductor to be measured is measured from the Faraday rotation angle of light passing through the optical system, wherein the optical system is a substance having a Faraday effect. A sensor disposed in a magnetic field generated by a current flowing through a conductor to be measured, and a light source side and a light receiver for transmitting light from the light source to the sensor and transmitting light from the sensor to the light receiver. Side transmission optical fiber, the light source side and the light receiver side lens optically coupled to the emission end of the light source side transmission optical fiber and the incident end of the light receiver side transmission optical fiber, respectively, A polarizer arranged between the lens on the light source side and the sensor to convert light from the lens into linearly polarized light, and arranged between the sensor and the lens on the light receiver side to pass through the sensor. An optical system for attaching and storing an analyzer for separating linearly polarized light into two linearly polarized lights, and an end portion of the optical fiber for transmission, a lens, a polarizer, and an analyzer so as to form an optical path of the optical system. A storage box; and a coupling member that is assembled into the optical system storage box by assembling the transmission optical fibers and the lenses optically coupled to the ends thereof into a fiber / lens assembly having an integrated structure. An optical current transformer characterized by that. 2. A fiber / lens assembly formed by assembling the transmission optical fiber and a lens by the coupling member, the polarizer, and the analyzer are directly attached to the optical system storage box. The optical current transformer according to claim 1. 3. The sensor is an optical fiber for a sensor, further comprising lenses that are optically coupled to an incident end and an emitting end of the optical fiber for sensor, respectively, and the individual coupling member is for the sensor. 3. The optical current transformer according to claim 1, further comprising a coupling member for assembling the optical fiber and each lens coupled to the incident end and the emission end thereof as an integrated fiber / lens assembly. 4. The optical variable according to claim 3, wherein a fiber / lens assembly in which the sensor optical fiber and the lens are assembled by the coupling member is directly attached to the optical system storage box. Sink. 5. The optical system storage box includes the optical fiber,
The lens, the polarizer, and the analyzer are made of a material having a coefficient of thermal expansion equal to or less than that of the analyzer.
The described optical current transformer. 6. The optical current transformer according to claim 1, wherein the optical system storage box is made of a material having high thermal conductivity. 7. The optical current transformer according to claim 1, wherein the analyzer comprises two polarizers and a beam splitter arranged such that their optical axes are orthogonal to each other.