JPS59198359A - Optical current transformer apparatus - Google Patents

Abstract

PURPOSE:To enhance accuracy by avoiding the influence of an external magnetic field, by providing a core with a gap inlaid with and inserted into a conductor being a current detecting object and a magnetooptical effect element arranged in the gap of said core. CONSTITUTION:A current transformer apparatus is constituted so that magnetic flux phim proportional to the density of a current flowing through a conductor passes a core 7 by said current and the magnetic field thereof is applied to the Faraday element 9 arranged in the gap 8 of said core 7. In this case, electromotive force is also induced in coils 10, 11 by the magnetic flux phim but, because both coils 10, 11 are same in winding numbers and subjected to inverse polarity connection, no current flows and, therefore, magnetic flux due to the coil 10 is not generated and no influence is exerted upon the Faraday element 9. As a result, the influence of an external magnetic field can be avoided and accuracy can be enhanced.

Description

[Detailed description of the invention] The present invention relates to an optical current transformer.

As is well known, various current transformation devices of this type using a magneto-optic effect element, such as a Faraday element, have been proposed.

For example, in order to measure the current of a high-voltage conductor disposed in a closed container filled with an insulating medium such as SF6 gas, a ring-shaped core made of a magnetic material is provided so as to surround the high-voltage conductor, A Faraday element is disposed in a cap provided on the core to apply an induced magnetic field to the core,
An optical cable drawn from outside the sealed container is connected to this Faraday element, and light is supplied via a polarizer.
Using the principle that the polarization angle of a Faraday element changes in proportion to the external magnetic field, changes in the current flowing through the high-voltage conductor are converted into changes in the polarization angle of light, which are further changed into intensity of light via an analyzer. It has been proposed that the source cable is led out of the sealed container and converted into a digital signal by a source-to-electrical converter in an electric station, for example.

When this optical current transformer is applied to a three-phase line, high voltage conductors 2 to 2 are placed in a container 1 corresponding to each line as shown in Fig.
4, and the core 6 (only one conductor 3 is shown) having the Faraday element 5 is fully inserted into each of the high voltage conductors 2 to 4. However, the Faraday element 5 in one high-voltage conductor 3 has all the effects of the magnetic flux φ□゛ (Fig. 2) due to the donors 2 and 4 of the other phases, and the magnetic flux φ□ φn is applied.

As a result, a current measurement error occurs, causing a problem regarding the height. This problem is not limited to other phases, but also occurs when a magnetic shield is not provided or when the device is installed in a location where it may be affected by an external AI field.

Therefore, an object of the present invention is to provide an optical current transformer that can avoid the effects of other phase magnetic flux and the like and can improve sensitivity.

An embodiment of the present invention is shown in FIG. 3, that is, in this optical current transformer, a geared core 7 is inserted into a current detection conductor (not shown), a Faraday element 9 is arranged in a gap i8, Furthermore, the gap portion 8 and the gap portion 8
Coils 10 and 11 having the same number of turns are wound around portions of the core 7 that are symmetrical to each other, and are connected to each other with opposite polarities.

As the current flows through the conductor, a flux radiation proportional to the magnitude of the current passes through the core 7, and the magnetic field is applied to the Faraday element 9 disposed in the gap 8.

At this time, coil 10. An electromotive force is also induced in II by the magnetic flux φ, but both coils ] 0 , ] ] ViF
[Because of the number and reverse polarity connections, no current flows, so no magnetic flux is generated by the coil 10, and there is no effect on the Faraday element 9.]
k is not applied, and the optical fiber 12a is connected to the Faraday element 9.
The light supplied from K is polarized in proportion to the magnitude of the magnetic field, is supplied to a light receiving circuit (not shown) through an optical fiber 12b, and is converted into an electrical signal. On the other hand, the external magnetic flux φ passing through the Faraday element 9. is a pair of coils 10.1
1 in common and in the same direction, and the interlinking magnetic fluxes can be considered to be substantially the same because the coils are in symmetrical positions, so that the same electromotive force is generated at 0°11 in each coil. Also, each coil 10°]
Since 1 is connected with opposite polarity, current flows through the coil JO due to the electromotive force of the coil 11, and a magnetic flux φ is generated in the coil 0.

' occurs. This φ. ′ is φ□−φ. ′, and since φ□ and φ□′ are in opposite directions, the Faraday element 9
This means that they were offset against each other.

Therefore, the Faraday element 9 is no longer influenced by magnetic fields caused by currents of other phases.

As described above, the optical current transformer of the present invention has a magneto-optic effect element in the gap part of the core. Along with placing
The external magnetic field erasing coil is fully wound around the gap, and the external magnetic field detection coil is fully wound around the core at a symmetrical position in the gap, and both coils are connected with opposite polarity to avoid the effects of external magnetic fields. This has the effect of improving accuracy and improving overall sensitivity.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a conventional example, FIG. 2 is an explanatory drawing showing the state of magnetic flux of other phases, and FIG. 3 is a schematic explanatory drawing of an embodiment of the present invention. 7... Core, 8... Gap portion, 9... Faraday element (magneto-optical effect element), 10... Coil (for external magnetic field erasure), 11... Coil (for external magnetic field detection) first
Page continued 0 Author Masaya Yoshikawa Inside Nissin Electric Co., Ltd., 47 Umezu Takaune-cho, Ukyo-ku, Kyoto City 0 Author: Akio Nakahashi At Nissin Electric Co., Ltd., 47 Umezu Takaune-cho, Ukyo-ku, Kyoto City Author: Sumitomo Electric Kogyo Co., Ltd. 5-15 Kitahama, Higashi-ku, Osaka City @ Applicant Nissin Electric Co., Ltd. 47-Umezu Takaune-cho, Ukyo-ku, Kyoto City

Claims (1)

[Claims] A core with a gap inserted into a conductor for current detection, a magneto-optic effect element disposed within the gap of the core, an external magnetic field erasing coil wound around the magneto-optic effect element, and the core. an optical current transformer comprising: an external magnetic field detecting coil wound with the same number of turns as the external magnetic field erasing coil at a symmetrical position of the magneto-optic effect element and connected with the opposite polarity to the coil; .