JP2000292459A - Optical current transformer - Google Patents

Abstract

(57) [Object] To provide an optical current transformer for obtaining a measured current value from a rotation angle of a linearly polarized light that rotates due to a magnetic field effect of a measured current.
A single optical fiber for connecting the electronic circuit unit and the current detection unit. Also, simplify the optical system of the current detection unit. An optical current transformer includes a light source and a photoelectric conversion element.
An electronic circuit unit 10 including a signal processing circuit 14 and a light branching unit 15; a current detection unit including a polarization unit 33, an optical bias unit 34, a reflection mirror 32 at the end, and a current detection optical fiber 31. Unit 30, an optical fiber 2 connecting the electronic circuit unit 10 and the current detection unit 30
0. By providing the optical biasing means 34, the rotation angle of the linearly polarized light is modulated by the polarization means 33, and the optical branching means 15 is provided inside the electronic circuit part 10, so that the electronic circuit part 10 The current detection unit 30 is connected with one optical fiber 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a current flowing through a conductor using the Faraday effect.

[0002]

2. Description of the Related Art An optical current transformer utilizing the Faraday effect in which the plane of polarization of light rotates due to the action of a magnetic field includes a circulating-integral optical current transformer using an optical fiber as a Faraday element.
The specific configuration is disclosed, for example, in Japanese Patent Application Laid-Open No. 7-248338. An example is shown in FIG.

An optical current transformer shown in FIG. 7 includes a light source 11 for emitting light of a predetermined wavelength and first and second photoelectric conversion elements 12 and 1.
3 and an electronic circuit unit 10 including a signal processing circuit 14, first, second, third, and fourth condenser lenses 44a, 44b, 44
c, 44d, polarizer 41, half mirror 43, and analyzer 4
2, a current detecting unit 40 including a current detecting optical fiber 31 having a reflecting mirror 32 at the end thereof, and a light transmitting fiber connecting the light source 11 and the current detecting unit 40. 21 and the first and second photoelectric conversion elements 1
2 and 13 and the first and second connecting the current detecting unit 40.
It is constituted by light receiving fibers 22 and 23.

The current detecting optical fiber 31 is arranged around the conductor 50 through which the current to be measured flows.

The light of a predetermined wavelength emitted from the light source 11 is transmitted to the current detecting section 40 via the light transmitting fiber 21.
The light emitted from the light transmitting fiber 21 becomes linearly polarized light in the same direction as the main axis of the polarizer 41 by the polarizer 41, becomes parallel light by the first condenser lens 44a, and passes through the half mirror 43. The light is condensed by the second condenser lens 44b, and is incident on the current detection optical fiber 31. Current detection fiber 3
For example, a lead glass fiber disclosed in JP-A-3-13177 is used for 1. The light incident on the current detecting optical fiber 31 is reflected by the terminal mirror 32, returns through the current detecting optical fiber 31, and is emitted toward the second condenser lens 44b again. At this time, the polarization direction of the emitted light is rotated by θ radians with respect to the incident light due to the magnetic field generated by the measured current. Current detection optical fiber 31
Is converted into parallel light by the second condenser lens 44b, and then guided to the analyzer 42 by the half mirror 43. The analyzer 42 has its main axis inclined at π / 4 radian with respect to the main axis of the polarizer 41, thereby modulating the rotation angle θ of the linear polarization direction depending on the current value of the measured current to the light intensity. . At this time, depending on the type and structure of the analyzer 42, there are one case and two cases of light that is intensity-modulated, and each of them has the following configuration. When two lights are intensity-modulated, the light is condensed by the third and fourth condenser lenses 44c and 44d and transmitted to the first and second photoelectric conversion elements 12 and 13 by the first and second light receiving fibers 22 and 23. Is done. The intensity-modulated light is converted into an electric signal by the first and second photoelectric conversion elements 12 and 13, and the value of the measured current is calculated by the signal processing circuit 14. When one light is intensity-modulated,
The fourth condenser lens 44d, the second light receiving fiber 23, and the second photoelectric conversion element 13 are omitted.

[0006]

In the field of electric power, an optical composite power cable obtained by combining a conventional power cable and an optical fiber cable is used as a power transmission and distribution cable. Conventionally, an optical fiber housed in an optical composite power cable has been used for communication. On the other hand, when new power is supplied to customers due to the efficiency of transmission and distribution lines, instead of constructing a new transmission and distribution line from a substation, a Y-branch connection is made to an existing transmission and distribution line near the customer. A method is adopted in which a box is cut in and a track is constructed from the junction box to a new customer. However, as the number of branches increases with the increase in consumers, it has become difficult to identify the section where a short-circuit accident or ground fault accident has occurred. For this reason, a fault section determination method using an optical current transformer has been devised, and an optical fiber housed in an optical composite power cable is used as an optical fiber connecting a current detection unit and an electronic circuit unit of the optical current transformer. That is being considered. In this case, it is necessary to install a large number of optical current transformers on one transmission and distribution line in order to specify the accident point in detail. When an accident point is specified using an optical fiber in an existing optical composite power cable according to a conventional technique, two or more optical fibers are required to connect an electronic circuit unit and a current detection unit. Therefore, a first object of the present invention is to connect an electronic circuit unit and a current detection unit with one optical fiber so that more optical current transformers can be installed in an existing optical composite power cable. An object of the present invention is to provide an optical current transformer. Another object of the present invention is to reduce the time for assembling and adjusting the optical current transformer, the number of components, and the cost by using a single optical fiber for connecting the electronic circuit unit and the current detection unit.

In a conventional optical current transformer, an optical fiber for connecting an electronic circuit unit and a current detecting unit, a light transmitting fiber for transmitting light from a light source to a current detecting unit, and a current detecting unit for a photoelectric conversion element. A light receiving fiber for transmitting light is used.
In the current detection section, the light emitted from the light transmission fiber is made incident on the current detection optical fiber, and the light reflected by the mirror provided at the tip of the current detection optical fiber is made incident again on the light reception fiber. At least three condenser lenses, a polarizer, a half mirror, and an analyzer are used as components, and these optical components are housed in an optical box. Since the arrangement of the optical components in the optical box is a two-dimensional arrangement centered on the half mirror, the operation of adjusting the optical axis of each optical component is very complicated. Therefore, a second object of the present invention is to provide an optical current transformer that facilitates adjustment of an optical axis by unitizing optical components and that has a compact current detection unit.

[0008]

According to claim 1 of the present invention,
A current detection unit comprising an optical path that circumvents the outer periphery of the conductor through which the current to be measured flows and that has a reflection unit at the peripheral end thereof, and a polarization unit that allows linearly polarized light to enter the optical path; And an electronic circuit unit including a photoelectric conversion element that supplies light having a predetermined wavelength from a light source, converts light emitted from the current detection unit into an electric signal, and a signal processing circuit that performs arithmetic processing on the electric signal. An optical current transformer for obtaining the measured current value from a rotation angle of the linearly polarized light rotated by the magnetic field effect of the measured current, wherein the optical path is formed by a first Faraday element; By providing an optical bias unit using a second Faraday element for rotating the polarization direction of light by π / 8 radian between the optical path and the optical path, and providing an optical branching unit in the electronic circuit unit, Electronic circuit Characterized by connecting the single light guide means and said current detecting unit and.

According to a second aspect of the present invention, an optical fiber coupler is used for the optical branching means.

A third aspect of the present invention is characterized in that a half mirror is used for the light branching means.

In the optical current transformer having the above-described structure, the optical bias means for rotating by π / 8 radian is provided to reciprocate the azimuth of the main axis of the polarizing means and the optical path provided on the outer periphery of the conductor. Since an optical bias of π / 4 radian is generated between the azimuth of the linearly polarized light incident on the means and the polarization means, the rotation angle of the linearly polarized light depending on the measured current value can be modulated to the light intensity by the polarizing means. It becomes possible. Therefore, using an optical path for transmitting the light of the light source to the polarizing means,
The intensity-modulated light can be transmitted to the electronic circuit unit. In addition, it is possible to split the intensity-modulated light by an optical splitting unit provided in the electronic circuit unit and transmit the split light to the photoelectric conversion element. Therefore, according to the present invention, the conventional optical current transformer requires two or more optical paths for connecting the electronic circuit unit and the current detection unit, but the present invention can reduce the number of optical paths to one.

According to a fourth aspect of the present invention, a thin film polarizer is used as the polarizing means, and a garnet crystal and a permanent magnet are used as the optical biasing means.

In the optical current transformer having the above configuration, the optical components in the current detecting section can be made compact and the adjustment of the optical axis can be facilitated.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a configuration of an optical current transformer according to a first embodiment of the present invention. In the following description, in the drawings referred to in the above-mentioned conventional technology, the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted.

The optical current transformer shown in FIG. 1 includes an electronic circuit section 10 having a light source 11 for emitting light of a predetermined wavelength, a photoelectric conversion element 12, a signal processing circuit 14, and an optical branching means 15,
A current detecting unit 30 including an optical bias means 34 using a third Faraday element and a current detecting optical fiber 31 serving as a first Faraday element having a reflection mirror 32 at the end; Unit 10 and the current detection unit 30
And an optical fiber 20 connecting the two.

A current detecting optical fiber 31 as a first Faraday element is connected to a conductor 50 through which a current to be measured flows.
It is arranged around.

The light having a predetermined wavelength emitted from the light source 11 is transmitted to the current detector 30 via the optical fiber 20 after passing through the light branching means 15. The light emitted from the optical fiber 20 is turned into linearly polarized light having the same direction as the main axis of the polarizing means 33 by the polarizing means 33, and then the linearly polarized light direction is changed to π by the optical bias means 34 using the second Faraday element. After rotating by / 8 radians, the light enters the current detection optical fiber 31.
The current detecting fiber 31 includes, for example,
No. 77 lead glass fiber is desirable. The light incident on the current detection optical fiber 31 is reflected by the mirror 3 at the end.
The light is reflected by the optical fiber 2, returns to the optical fiber 31 for current detection, and is emitted again toward the optical bias unit 34.
At this time, the linear polarization direction of the light is rotated by θ radians due to the magnetic field generated by the measured current. The light emitted from the current detecting optical fiber 31 has its linear polarization direction rotated by π / 8 radian by the optical bias means 34, and
3 is incident. At this time, the polarization direction of the linearly polarized light incident on the polarization unit 33 is π with respect to the main axis direction of the polarization unit 33.
Since a bias of / 4 radian is included, the rotation angle θ of the direction of the linearly polarized light generated by the measured current can be modulated to the light intensity. The light whose intensity has been modulated by the polarizing means 33 is
After being transmitted to the optical branching means 15 by the optical fiber 20,
The light enters the photoelectric conversion element 12. After the light incident on the photoelectric conversion element 12 is converted into an electric signal, the signal processing circuit 14 calculates the value of the measured current.

The optical current transformer having the above configuration can use one optical fiber for connecting the electronic circuit section and the current detecting section. Therefore, in the power field, when fault location is performed using the optical fiber of the existing optical composite power cable, it is possible to install more than twice the number of optical current transformers compared to the conventional type, and more detailed fault The section can be specified. Further, by using only one optical fiber for connecting the electronic circuit unit and the current detecting unit, the time required for assembling and adjusting the optical current transformer and the number of components can be reduced, so that the cost can be reduced.

FIG. 2 is a block diagram showing an optical current transformer according to a second embodiment of the present invention. In this figure, parts that are the same as or correspond to those in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted. The half mirror 16 is used as a light branching unit, and the half mirror 16 is connected to the light source 11 and the optical fiber 20.
Are arranged at an angle of about π / 4 radian with respect to the optical path connecting Further, first and second condenser lenses 17a and 17b are provided before and after the half mirror 16. The photoelectric conversion element 12
The current detection optical fiber 31 is emitted and the half mirror 16
Is disposed at a position where the light reflected by the light enters the light receiving surface of the photoelectric conversion element 12. With this configuration, of the light emitted from the light source 11, the light amount that reaches the half mirror 16 is about 1 /
2 is transmitted to the current detecting unit 30 via the optical fiber 20, and about の of the amount of light incident on the half mirror 16 via the optical fiber 20 is guided from the current detecting unit 30 to the photoelectric conversion element 12. The electronic circuit unit 1
0 and the current detection unit 30 can be connected by one optical fiber 20.

FIG. 3 is a block diagram showing an optical current transformer according to a third embodiment of the present invention. In this figure, parts that are the same as or correspond to those in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted. As a light branching means, a one-to-two branch optical fiber coupler 18 is used. One end of the optical fiber coupler 18 on the two branch side is connected to the light source 11 and the other end is connected to the photoelectric conversion element 1.
2 and one branch side of the optical fiber coupler 18 is used as the optical fiber 20 or connected to the optical fiber 20. With this configuration, a part of the light emitted from the light source 11 enters the current detection unit 30 and
A part of the light emitted from the current detection unit 30 is
2 can be led. In the light splitting means having this configuration, since there is no space in the light splitting portion, the connection efficiency can be kept high and stable.

FIGS. 4 to 6 show the configuration of an optical current transformer according to a fourth embodiment of the present invention. In this figure, parts that are the same as or correspond to those in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted. The current detector 30 of the optical current transformer in FIG.
A thin film polarizer 35, first and second condenser lenses 39a, 3
9b, an optical bias means 38 using a garnet crystal 36 and a permanent magnet 37, a case 60, and a current detection optical fiber 31 provided with a mirror 32 at the end. Thin-film polarizer 35, first and second condenser lenses 39
a, 39b and the garnet crystal 36 are housed in the case 60, and the case 6
The structure is such that a permanent magnet 37 is attached to the outside of 0 so that a magnetic field is applied in parallel to the optical axis of the garnet crystal 36. The case 60 is desirably in a pipe shape. The thin-film polarizer 35 can be directly bonded and fixed to the end face of the optical fiber 20, for example, Ramipol (trade name, manufactured by Sumitomo Cement Co., Ltd.) or Polar Core (trade name, manufactured by Corning Incorporated).
Is desirable. Further, it is desirable to use a method (fiber collimator) in which the second condenser lens 39b is directly fixed to the end face of the current detecting fiber 31. Thin film polarizer 35
The first and second condenser lenses 39a and 39b, the garnet crystal 36 and the permanent magnet 37 are previously housed and fixed in the case 60, and the first condenser lens 39a and the second condenser lens 3 are fixed.
9b can be handled as one optical component 70 by adjusting the optical axes to coincide with each other. In this configuration, it is only necessary to install and fix the optical component 70 on a straight optical path connecting the optical fiber 20 and the current detection optical fiber 31, so that the configuration of the current detection unit can be made compact and the optical axis at the time of assembly can be reduced. Adjustment can be facilitated. Although the permanent magnet 37 is arranged outside the case 60 in FIG. 4, the same effect can be obtained by disposing the permanent magnet 37 inside the case 60.

The current detector 30 of the optical current transformer of FIG.
The positions of the thin film polarizer 35 and the first condenser lens 39a are interchanged. In this case, the first condenser lens 39a
It is desirable to use a method (fiber collimator) that is directly fixed to the end face of the optical fiber 20. Even with this configuration,
The same effect as the embodiment shown in FIG. 4 can be obtained.

The current detector 30 of the optical current transformer of FIG.
The first and second condenser lenses 39a and 39b are excluded. Although the connection efficiency is slightly reduced as compared with the configuration of FIG. 4, the number of parts can be reduced, the size can be reduced, and the optical axis can be easily adjusted at the time of assembly.

[0024]

As described above, according to the present invention,
Forming an optical path in the current detector with the first Faraday element;
An optical bias unit using a second Faraday element for rotating the polarization direction of light by π / 8 radian is provided between the polarizing unit and the optical path, and a light branching unit is provided in the electronic circuit unit. An optical current transformer comprising a single light guide means for connecting the current detector with the current detector can be provided. Further, it is possible to reduce the time for assembling and adjusting the optical current transformer, the number of parts, and the cost. Further, the optical components are unitized using a thin-film polarizer as the polarizing means and a garnet crystal and a permanent magnet as the optical biasing means, so that the adjustment of the optical axis is facilitated and the current detecting section is made compact. be able to.

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram of an optical current transformer according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of an optical current transformer according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of an optical current transformer according to a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram illustrating another example of an optical current transformer according to a fourth embodiment of the present invention.

FIG. 6 is a configuration diagram showing another example of the optical current transformer according to the fourth embodiment of the present invention.

FIG. 7 is a configuration diagram illustrating an example of a conventional optical current transformer.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 electronic circuit section 11 light source 12 photoelectric conversion element 13 photoelectric conversion element 14 signal processing circuit 15 optical branching means 16 half mirror 18 optical fiber coupler 20 optical fiber 30 current detection section 31 current detection optical fiber 32 mirror 33 polarizing means 34, 38 Optical biasing means 35 Thin film polarizer 36 Garnet crystal 37 Permanent magnet 39a First condenser lens 39b Second condenser lens 50 Conductor 60 Case 70 Optical component

 ──────────────────────────────────────────────────の Continuing on the front page (72) Eiji Itakura 3-1-1, Yoshino-machi, Nishibiwajima-cho, Nishi-Kasugai-gun, Aichi Prefecture Inside the Technical Development Center, Takatake Works Co., Ltd. 3-chome Yoshino-cho No.1 Takatake Manufacturing Co., Ltd. Technology Development Center F-term (reference) 2G025 AA04 AA05 AA17 AB10 AB13 AC06 2G035 AA12 AA15 AB08 AC01 AD19 AD35 AD37

Claims (4)

[Claims] 1. A current detecting section comprising: an optical path which goes around the outer periphery of a conductor through which a current to be measured flows and has a reflection means at the end thereof; and a polarization means for entering linearly polarized light into the optical path. A light source having a predetermined wavelength supplied to the current detection unit from a light source, a photoelectric conversion element that converts light emitted from the current detection unit into an electric signal, and a signal processing circuit that performs arithmetic processing on the electric signal An optical current transformer having an electronic circuit portion, wherein the measured current value is obtained from a rotation angle of the linearly polarized light rotated by the magnetic field effect of the measured current, wherein the optical path is formed by a first Faraday element. Optical bias means using a second Faraday element for rotating the polarization direction of light by π / 8 radian is provided between the polarizing means and the optical path, and an optical branching means is provided in the electronic circuit section. By providing Optical current transformer which is characterized by connecting the single light guide means and said current detecting unit and the electronic circuit unit. 2. An optical current transformer according to claim 1, wherein an optical fiber coupler is used for said optical branching means. 3. An optical current transformer according to claim 1, wherein a half mirror is used as said light branching means. 4. The method according to claim 1, wherein a thin film polarizer is used as said polarizing means, and a garnet crystal and a permanent magnet are used as said optical biasing means. Light current transformer.