JP3302155B2 - Optical current measuring device - Google Patents

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 flowing through a conductor such as a gas-insulated bus, and more particularly to an optical current measuring device.

[0002]

2. Description of the Related Art Conventionally, a current measuring device for an electric power system using light, that is, an optical current transformer, uses a block of lead glass or quartz as a sensor in close proximity to a conductor, passes linearly polarized light, The principle is to measure the optical rotation angle of the Faraday effect caused by the current to be measured flowing through.

FIG. 6 shows an example of a conventional optical current transformer. G
Inside the IS tank 1, a sensor 3 made of a block of quartz or lead glass is arranged so as to surround the conductor 2. The sensor is fixed to a fixture 4 and is insulated from a ground potential by an insulating cylinder 5 made of an insulator because the conductor 2 has a high voltage. Light emitted from a light source (not shown) passes through a light transmission fiber 6 and is converted into a substantially parallel light linearly polarized beam 8 by a coupling optical system 7 composed of a lens, a polarizer, etc., and propagates through space to the sensor 3. The light enters, and after being repeatedly reflected inside, exits the sensor 3. During this time, the light passing through the sensor 3 rotates by a certain angle due to the Faraday effect induced by the current flowing through the conductor 2. The emitted light becomes a linearly polarized beam 9, propagates in space, travels again to the coupling optical system 7, passes through the analyzer and the lens, and enters the light receiving fiber 10. Note that the configuration and operation of the coupling optical system 7 described here are already well-known, and thus description thereof will be omitted.

[0004]

In the optical current transformer having the above configuration, the linearly polarized beam 8 for measuring current propagates in the high pressure insulating gas in the GIS tank. As a result, as the current in the conductor 2 increases, the conductor 2 generates heat, the insulating gas is heated, the gas density changes locally, and convection occurs. As a result, the refractive index of the propagation path of the linearly polarized beam for measurement 8 changes irregularly with time, causing beam fluctuation. The fluctuation of the beam is equivalent to a change in the optical axis of the optical system or an irregular change in the sensitivity of the sensor 3, and significantly lowers the accuracy of the current measuring device.

[0005] Further, such an optical current transformer has a drawback that an error increases with respect to a vibration or a temperature change (-20 to 90 ° C) generated on site. Amorphous solids such as glass generally used as a Faraday effect material are optically isotropic, but when an external stress is applied, the glass becomes optically anisotropic and exhibits birefringence. This contributes to the measurement error. When a temperature change occurs in the glass, stress is generated, but when the glass is firmly fixed to a substance having a different coefficient of thermal expansion or when a substance having a different coefficient of thermal expansion is firmly fixed to the glass. In the method, the stress inside the glass caused by a change in temperature becomes considerably large as compared with the case of a single glass, resulting in a measurement error. An object of the present invention is to provide an optical current measuring device capable of measuring a current with high accuracy even in an environment where vibrations and temperature changes are large.

[0006]

SUMMARY OF THE INVENTION According to the present invention, an insulating gas is filled in a sealed tank formed by joining a plurality of tubular tanks to each other via flanges provided at the ends of the respective tanks. In an optical current measuring device for measuring a current flowing through a current-carrying conductor of a gas-insulated device having a current-carrying conductor disposed in an axial direction of a tank, an annular insulating member is disposed between end flanges of the tubular tank. An optical fiber is wound around and fixed to the outer periphery of the annular insulating member so as to circumvent the current-carrying conductor, and a heat insulating member is disposed around the outer periphery of the optical fiber via an insulating member. A predetermined optical device is attached, and the energizing current is measured based on a polarization state associated with the Faraday effect of light passing through the optical fiber.

[0007]

[Function] With the above configuration, it is possible to reduce a sudden temperature change caused by vibration or direct sunlight from the outside air, to make it difficult to generate a temperature difference in the optical component, and to eliminate stress concentration due to a local temperature rise. Can be. This enables highly accurate current measurement.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. In FIG. 1, a sensing fiber section 11 is arranged outside the GIS tank 1 so as to surround the conductor 2. From the sensing fiber section 11, a light transmitting fiber 12 and a light receiving fiber 13 (actually two fibers are shown in FIG. 1) are provided, and each light source (laser diode or super luminescent diode) is provided.
14 and a detector 15 (only one channel is shown in the figure, but there are actually two channels). The output signal of the detector 15 is calculated by the signal processing circuit 16 and the result is output to the output terminal.
Output from 17. These light source / detector sections 18 are arranged at positions sufficiently distant from the sensing fiber section 11 (at least 10 m).

FIG. 2 shows an optical system diagram of the present embodiment.
The laser light emitted from the light source 14 is
2 and the combined optical box 1 in the sensing fiber unit 11
9 is incident. The container of the coupling optical box 19 is made of a low expansion coefficient optical material such as Zerodur in order to minimize a change due to a temperature change. The laser beam incident on the coupling optical box is converted into a parallel beam by the lens 20a,
The light is linearly polarized by 1a and reaches the lens 20b. The laser beam focused by the lens 20b is applied to the sensing fiber 2 wound around the conductor 2 via the holder 22.
3 (one winding in the figure may be used a plurality of times to increase the sensitivity), and returns to the original optical path again by the reflector 24 disposed at the end of the fiber. Normally, reflective material 2
No. 4 can be made by coating the end of the sensing fiber with aluminum. The returned laser light is reflected by the beam splitter 25a, and further divided into two by the beam splitter 25b, and the respective laser lights are arranged at right angles to the analyzers 21b and 2b.
After passing through 1c, the light is guided to the light receiving fiber 13 by the lenses 20c and 20d. Here, the orientation of the polarizer 21a is set to be exactly the angle between the analyzers 21b and 21c. The output from the light receiving fiber 13 is calculated by a signal processing circuit 16 received by the detectors 15a and 15b, and the result is output from an output terminal 17. Since the method of signal processing and the like are known, they are omitted here.

Next, a specific structure of the sensing fiber section 11 of the present invention will be described with reference to FIG. FIG.
Shows a vertical sectional view of the GIS tank 1. An insulating spacer 26 for fixing the sensing fiber 23 is connected to a joint of the GIS tank 1. The insulating spacer 26 is firmly fixed to the GIS tank 1 by a bolt 29 insulated by an insulating collar 28 while maintaining airtightness by an O-ring 27.

The sensing fiber 23 is an insulating spacer 26
Is wound one or more times by digging a V-shaped groove on the upper surface of. By setting the angle between the V-shaped grooves to be from 75 degrees to 135 degrees, the amount of birefringence induced in the sensing fiber 23 is minimized. The sensing fiber 23 is adhered (fixed) to the insulating spacer by an easily deformable adhesive material 30, for example, silicon rubber, gel or the like. Insulation spacer
An insulating cover 31 that can be divided into a plurality of pieces in the circumferential direction for protecting the sensing fiber 23 is attached to the upper surface of the 26 while maintaining the space 32. In addition, insulation cover 31
A GIS tank is surrounded by a conductive cover 34 with a heat insulating material 33 (such as styrene foam) interposed therebetween. The coupling optical box 19 is attached to the outside of the insulating cover 31 via an adhesive 35 such as silicone rubber.

FIGS. 4 and 5 show another embodiment of the optical system. In FIG. 4, the laser light emitted from the light source 14 passes through the transmission / reception fiber 36, is linearly polarized by the polarizer 37 of the sensing fiber unit 11, and is incident on the depolarizer 38a.
After being guided to 3 and passing through the depolarizer 38b again, the light returns to the original optical path again by the reflector 24 disposed at the end of the fiber. The returned laser light passes through the transmission / reception fiber 36, is branched at the fiber branch point 39, is received by the detector 15c, is calculated by the signal processing circuit 16a,
The result is output from the output terminal 17. Here, the polarizer 3
If a laminated polarizer (for example, Ramipol (registered trademark) of Sumitomo Osaka Cement Co., Ltd.) is used as 7, the optical system can be made into all fibers, and higher functionality can be achieved. The feature of this system is that the light intensity at the detector 15c is generated by the measured current and the Faraday rotation angle lock is generated.
represented by _t of the cosine function (cos @ 2閘_t), it is that it is accurate measurement. Also in this embodiment, the laser light is turned back and forth by the reflector 24. Further, the number of turns of the sensing fiber is one rotation or more.

Next, in FIG. 5, after the laser light emitted from the light source 14 passes through the fiber branch point 40,
It is incident on 41. Polarizer 42 and phase modulator in optical integrated circuit
The phase modulators 43a and 43b are provided with modulation signals by a modulation circuit 44. The two laser beams emitted from the optical integrated circuit 41 pass through the quarter-wave plates 45a and 45b, respectively, pass through the sensing fiber 23 which also functions as a transmitting / receiving fiber, reach the sensing fiber unit 11, and reach the conductor 2
After returning to the optical integrated circuit 41 through different optical paths after passing through the
15d. This system is a so-called interference type optical current transformer, and detects a phase difference due to the Faraday effect of a laser beam rotating clockwise and counterclockwise around the conductor 2 by light intensity. After the output of the detector 15d is calculated by the control / signal processing circuit 16b, the result is output from the output terminal 17. Also in this embodiment, the light source / detector section 18 and the sensing fiber section are installed separately.

The embodiment having the above configuration has the following operation.
GIS tank 1 covering the conductor 2 with the sensing fiber 23
The need to pass the measuring beam through the heated gas in the tank is eliminated. Further, since the sensing fiber 23 can be kept away from a region where the temperature changes rapidly, a change in the temperature environment can be reduced.

By forming the structure around the sensing fiber 23 with the insulating spacer 26 and preventing the return current from flowing inside the loop formed by the sensing fiber 23, the current flowing through the sensing fiber loop is measured through the conductor 2 Since only current is used, highly accurate current measurement can be performed according to Ampere's law.

Since the surroundings of the sensing fiber 23 are covered with the conductive cover 34 for supplying a return current, a potential difference between the tanks around the sensor can be eliminated, and unnecessary dielectric breakdown can be prevented. .

By providing a layer made of a heat insulating material 33 between the insulating spacer 26 covering the surroundings of the sensing fiber 23 and the insulating cover 31 and the conductive cover 34 through which the return current flows, the layer can be abruptly exposed to direct sunlight from the outside air or the like. To reduce the temperature change inside the optical component
Stress concentration due to a local temperature rise can be eliminated.

By arranging the light source / detector section 18 at a position away from the installation location of the sensing fiber section 11,
Light sources and detectors that are vulnerable to environmental changes can be kept away from areas where temperature changes, vibration, and electrical noise are severe. Further, by connecting the two with the light transmitting fiber 12 and the light receiving fiber 13, the transmission beam can be hardly affected by the outside and the electrical insulation can be facilitated.

The insulating structural material is directly under the insulating cover covering the sensing fiber 23.
By providing the space portion 32 so as not to touch the 23, generation of stress in the sensing fiber 23 caused by vibration can be suppressed, and induction of birefringence which causes an error can be suppressed.

By forming the periphery of the sensing fiber 23 with the easily deformable adhesive material 30 such as silicone rubber or gel, the sensing fiber 23 can be less affected by the vibration.

By arranging the reflector 24 (FIGS. 2 and 4) at the end of the sensing fiber so that the light reciprocates through the sensing fiber 23, the rotation action of the polarization plane of the light due to the optical rotation having a temperature dependency is canceled. As a result, accuracy can be improved.

As shown in FIG. 5, light is propagated through the sensing fiber 23 from both the clockwise and counterclockwise directions, and the amount of current is measured from the phase difference between the two lights.
Since light in both directions propagates in the same environment, the influence of a temperature change can be offset, and the accuracy of the current measuring device can be improved. As described above, according to the embodiment of the present invention, it is possible to prevent a decrease in accuracy due to a beam fluctuation caused by an increase in current, and to measure a current with high accuracy even in an environment where vibration and temperature change are large. Become like In the embodiment described above, the winding direction of the sensing fiber 23 in FIG. 3 is the outer peripheral surface of the insulating spacer 26, but in a plane perpendicular to that surface, that is, the side surface (G
V faces spirally on the surface facing the end flange of IS tank 1).
This embodiment is also applicable to a case in which a sensing groove is formed and a sensing fiber is bonded with a soft adhesive material similarly to the present embodiment, and an insulating cover and a heat insulating material are provided through a space so as not to directly apply a stress to the sensing fiber. Has the same effect as.

Further, in this embodiment, the current transformer having both the optical current transformer for measurement and the optical current transformer for protection flowing in the conductor 2 is shown. However, in order to increase the dynamic range of the optical current transformer for measurement. , Two optical current transformers equivalent to this embodiment are arranged side by side,
The number of windings (the number of loops) of the sensing fiber 23 on the measurement optical current transformer side may be increased. Further, the optical system for measurement and for protection may be changed.

[0024]

According to the present invention, it is possible to provide an optical current measuring device capable of measuring a current with high accuracy even in an environment where vibrations and temperature changes are large.

[Brief description of the drawings]

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

FIG. 2 is an illustrative view of one embodiment of an optical system according to the present invention.

FIG. 3 is an exemplary illustration of an optical fiber mounting structure according to an embodiment of the present invention.

FIG. 4 is an illustrative view showing another embodiment of the optical system according to the present invention;

FIG. 5 is an illustrative view showing still another embodiment of the optical system according to the present invention;

FIG. 6 is a configuration diagram of a conventional optical current measuring device.

[Explanation of symbols]

 1 GIS tank 2 Conductor 11 Sensing fiber part 18 Light source / detector part 23 Sensing fiber 24 Reflective material 26 Insulating spacer 30 Adhesive material 31 Insulating cover 32 Space 33 Thermal insulation 34 Conductive Sex cover

Continued on the front page (72) Inventor Sakae Ikuta 2-1 Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Hamakawasaki Plant, Toshiba Corporation (72) Keiko Niwa 2-1 Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Co., Ltd. Toshiba Hamakawasaki Plant (72) Inventor Hiroshi Miura 2-1 Ukishima-cho, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Toshiba Corporation Hamakawasaki Plant (56) References JP-A-3-225282 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G01R 15 / 24,31 / 00,33 / 032 H02B 13/035-13/065

Claims (7)

(57) [Claims] An insulating gas is filled in a sealed tank formed by joining a plurality of tubular tanks to each other via a flange provided at each tank end, and a current-carrying conductor is provided in an axial direction of the sealed tank. In an optical current measuring device for measuring a current flowing through a current-carrying conductor of a gas-insulated device, an annular insulating member is provided between end flanges of the tubular tank, and an outer periphery of the annular insulating member is provided. An optical fiber is wound around and fixed around the current-carrying conductor, a heat-insulating member is provided around the optical fiber via an insulating member, and a predetermined optical device is attached to both ends of the optical fiber. An optical current measuring device, wherein the current is measured based on a polarization state of light passing through an optical fiber due to a Faraday effect. 2. The end flanges are electrically connected to each other by a conductive cover disposed on the outer periphery of the heat insulating member covering the outer periphery of the optical fiber.
The optical current measuring device as described in the above. 3. The optical current measuring device according to claim 1, wherein a predetermined space is provided between said optical fiber and said insulating member. 4. The optical current measuring device according to claim 1, wherein a reflecting material is provided at an end of said optical fiber, and the transmitted light is reflected and transmitted through the same light transmitting path again. 5. The optical current measuring device according to claim 1, wherein the optical device detects a phase difference caused by a Faraday effect of light transmitted from both ends of the optical fiber and transmitted through the same light transmission path in the opposite direction. 6. A sealed tank formed by joining a plurality of tubular tanks to each other via a flange provided at each tank end is filled with an insulating gas, and a current-carrying conductor is passed in the axial direction of the sealed tank. An optical current measuring device for measuring a current flowing through the current-carrying conductor of a gas-insulated device, wherein an annular insulating member is provided between end flanges of the tubular tank, and the flange of the annular insulating member is provided. A groove surrounding the current-carrying conductor is provided on a surface facing the optical fiber, an optical fiber is wound around the groove, and a heat insulating member is provided around the outer periphery of the optical fiber via an insulating member. Optical current measurement, wherein a predetermined optical device is attached to the optical fiber, and the energizing current is measured based on a polarization state associated with the Faraday effect of light passing through the optical fiber. apparatus. 7. The optical current measuring device according to claim 6, wherein a predetermined space is provided between the optical fiber and the insulating member.