JP3347449B2 - 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 a power system, and more particularly, to an optical current transformer used for a tubular insulating 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, is generally arranged such that a block of lead glass or quartz is used as a sensor in close proximity to a conductor to allow linearly polarized light to pass therethrough. The principle is to measure the optical rotation angle of the Faraday effect by the magnetic field created by the current. To guide the light from the light source to the sensor, use an optical fiber,
Alternatively, it is directly incident as a light beam. As is well known, an optical fiber is an insulator. In an aerial line, light is guided by an optical fiber because the distance between conductors and the ground is large. It has been considered that it is difficult to ensure insulation between a conductor and a ground potential even for an optical fiber because the distance between the ground and the gas-insulated bus is short. As a result, a portion close to the inner conductor of the optical paths in the optical current transformer for a conventional gas-insulated bus is allowed to propagate light as a beam, and ensures insulation with a gas such as SF _6.

The above will be described with reference to the drawings in the case of an optical current transformer for a GIS line. FIG. 4 shows a conventional GI.
It is an example of the optical current transformer for S lines. In FIG. 4, 1 is G
The IS tank 3 is a sensor made of a block of quartz or lead glass. This sensor has a reflection surface so that a light beam passing therethrough outside the input / output surface surrounds the conductor. 15 is a fixture for mounting the sensor, and 16 is an insulating cylinder made of an insulator for mounting the sensor insulated from the ground potential. Light emitted from a light source (not shown) passes through a light transmission fiber 11-1 and travels through space as an almost parallel linearly polarized light beam 18 in an optical system including a coupling lens 12 and a polarizer 13. The light enters the sensor 3 and repeats reflection inside, and exits the sensor via an optical path that goes around the conductor. During this time, the light passing through the sensor is rotated by a certain angle due to the Faraday effect induced by the magnetic field generated by the current flowing through the conductor 7. The emitted light becomes a beam 18, propagates in space, travels again to the optical system, is split by the analyzer 14 into two lights having polarization planes orthogonal to each other, and then passes through the lens 12 to two light receiving fibers 11-2. Incident and airtight optical terminal 17
, And passes through a fiber provided in the atmosphere to reach a light receiver (not shown). The light intensity is measured by this light receiver, and the rotation angle of the polarization plane generated by the sensor 3 is known from the value, and the value of the current flowing through the conductor 7 is obtained. Note that the configuration and function of the optical system described here and the method of obtaining the current value are already known matters, and thus detailed description is omitted.

[0004]

SUMMARY OF THE INVENTION The G having the above structure
In an optical current transformer for an IS line, light 18 for current measurement propagates in the form of a spatial beam in a high-pressure insulating gas in a GIS tank. As a result, there are the following problems. That is, as the conductor current increases, the conductor 7 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 measuring light beam 18 changes irregularly with time, and irregular fluctuation of the beam occurs. This 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, and significantly lowers the accuracy of the current measuring device. In addition, the overall dimensions must be large, and a current transformer having a diameter greater than the tank diameter and a length that cannot be ignored is inserted in the middle of the line as shown in FIG. This is a major obstacle to downsizing GIS equipment.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical current measuring device capable of accurately measuring a current flowing through a conductor of a tubular gas insulated device without increasing the size of the device.

[0006]

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 a flange provided at each of the tank ends. In an optical current measuring device for measuring a current flowing through a current-carrying conductor of a gas-insulated device in which a current-carrying conductor is disposed in an axial direction of a closed tank, an annular insulating member is provided between end flanges of the tubular tank. A hollow concentric groove surrounding the current-carrying conductor is provided in the annular insulating member,
A fiber sensor is wound and fixed in a fiber winding provided in the groove, and a predetermined optical device is attached to both ends of the fiber sensor, and polarization caused by the Faraday effect of light passing through the fiber sensor. The energizing current is measured based on a state.

[0007]

With the above-described means, the optical system including the sensor is all placed on the atmospheric pressure side, and the light beam does not propagate through the high-pressure insulating gas, and the beam fluctuates. Disappears. In addition, an airtight optical terminal or the like that requires precise optical alignment is not required. Furthermore, since the fiber sensor is held by an insulator, even if a current flows through the GIS tank due to a ground fault or the like, the current flows through a joint outside the circuit light path created by the sensor. Therefore, the sensor can always measure only the conductor current. Further, since the fiber sensor is held by an annular flat plate whose diameter is not so different from that of the GIS tank and is sandwiched between the tank flanges, the size can be reduced without requiring a large-sized welded structure.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an illustrative view showing an example of a cross-section when the optical current transformer according to the present invention is mounted on a gas-insulated bus. FIG. 2 shows FIG.
FIG. FIG. 3 is an optical path diagram showing only the optical system of the present invention. In FIG. 1, 1 is a GIS tank, and 7 is a conductor. A fiber winding 4 is disposed in a hollow concentric groove formed in the insulating sensor holding plate 2, and the fiber sensor 3 is wound and fixed in the winding 4. The sensor holding plate 2 is pressed from both sides by coupling bolts 8 with a metal annular intermediate plate 5 having an O-ring groove. The coupling bolt 8 tightens the intermediate plate 5 and the sensor holding plate 2 outside the fiber sensor as shown in the figure. The intermediate plate 5 is further mounted on a flange of the GIS tank 1 by mounting bolts 9. The O-ring groove of the annular intermediate plate 5 is provided on the inner peripheral side of the groove for accommodating the sensor. The O-ring 6 is for sealing a high-pressure insulating gas filled in the GIS tank 1.

Optical elements other than the fiber sensor are mounted inside the optical system storage box 10, and are connected to a light source and a light receiver (not shown) by a multi-core optical fiber cable 11. The fiber sensor 3 includes a loop portion and a lead portion wound once or a plurality of times. The loop portion and the lead portion are all in the same plane and form an arc having the same radius of curvature. Light from a light source (not shown) exits the light transmitting fiber 11-1 and is converted into a substantially parallel light flux by the coupling lens 12 to pass through the polarizer and become linearly polarized light. Then, the fiber sensor 3 is
Incident on. When propagating through the fiber sensor 3, it receives Faraday rotation by a magnetic field generated by a current flowing through the conductor 7, and emits a polarization plane rotated by a certain angle. The emitted light is converted into a substantially parallel light beam by the coupling lens 12 and enters the analyzer 14 such as a Wollaston prism. The analyzer 14 separates the incident light into two linearly polarized lights whose polarization planes are orthogonal to each other. These two lights are respectively incident on the light transmitting fiber 11-2 by the coupling lens 12 and reach two light receivers (not shown), and the intensities thereof are measured. 8 shows the positions of several of the connecting bolts in FIG. Here, the operation of the polarizer and the analyzer and the method of obtaining the current value from the above-mentioned two received light intensities are already known matters, and therefore detailed description is omitted.

In this embodiment, since the fiber sensor 3 and other optical systems are isolated from the high-pressure insulating gas in the GIS tank by an O-ring as shown in FIGS. 1 and 2, they must be placed in an atmospheric pressure atmosphere. become. Since no metal passes through the loop formed by the fiber sensor 3, the current passing through the loop is only the current flowing through the conductor 7. Also,
The whole sensor part has an annular shape with a relatively thin thickness,
It is attached so as to be sandwiched in the flange portion of the S tank. Further, since the fiber sensor 3 forms an arc having the same radius of curvature over its entire length, the direction of the principal axis, which is the same as the magnitude of birefringence caused by bending, is the same at any position of the fiber sensor.

[0011]

According to the present invention, no error occurs due to the fluctuation of light caused by the change in the density of the insulating gas caused by the increase in the current. Also, no error occurs due to the current flowing through the tank at the time of ground fault or the like. Further, the dimensional ratio of the GIS can be significantly reduced. Therefore, it can greatly contribute to downsizing of the entire GIS. Further, since the birefringence and the direction of its main axis are the same everywhere over the entire length of the fiber sensor, improvement in accuracy can be greatly expected.

[Brief description of the drawings]

FIG. 1 is an illustrative view showing an example of mounting an optical current transformer device according to an embodiment of the present invention.

FIG. 2 is a top plan view of FIG. 1;

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

FIG. 4 is a diagram showing the basic configuration of a conventional optical current transformer device.

FIG. 5 is a top plan view of FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... GIS tank 2 ... Sensor holding plate 3 ... Fiber sensor 4 ... Fiber winding 5 ... Intermediate plate 6 ... O-ring 7 ... Conductor 8 ... Coupling bolt 9 ... Mounting bolt 10 ... Optical storage box 11 ... Optical fiber cable 12 ... Coupling Lens 13 ... Polarizer 14 ... Analyzer 11-1 ... Transmission fiber 11-2 ... Reception fiber

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kiyoto Terai 2-1 Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Hamakawasaki Plant of Toshiba Corporation (72) Keiko Niwa 2-1 Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture No. Toshiba Hamakawasaki Plant (72) Inventor Hiroshi Miura 2-1 Ukishima-cho, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Toshiba Hamakawasaki Plant (56) References JP-A-3-225282 (JP, A) JP Hei 3-191871 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01R 15/24 G01R 33/032 G01R 19/00

Claims (2)

(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 an end of each of the tanks. In an optical current measuring device for measuring a current flowing through the current-carrying conductor of a gas-insulated device, a ring-shaped insulating member is provided between end flanges of the tubular tank, and the ring-shaped insulating member is provided in the ring-shaped insulating member. A hollow concentric groove surrounding the current-carrying conductor is provided, a fiber sensor is wound and fixed in a fiber winding provided in the groove, and a predetermined optical device is attached to both ends of the fiber sensor. An optical current measurement device, wherein the current is measured based on a polarization state of light passing through the fiber sensor due to the Faraday effect. 2. The optical current measuring device according to claim 1, wherein the end flanges are electrically connected to each other by a conductive connecting member penetrating the annular insulating member.