JP4215313B2 - Light current transformer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical current transformer for measuring a current flowing through a conductor using a Faraday effect type optical fiber having a property that the plane of polarization of light passing therethrough rotates in proportion to the strength of a magnetic field. Of high current transformer.
[0002]
[Prior art]
By using an optical current transformer using a Faraday effect type optical fiber for current measurement, there is no saturation phenomenon of the iron core and it is easy to insulate compared with a conventional current transformer in which a winding is wound around the iron core. Therefore, it is possible to reduce the size. In addition, there is an advantage that an optical station can be totally optically controlled by an optical current transformer in the future.
[0003]
FIG. 3 is a perspective view showing a configuration of a conventional optical current transformer. The Faraday effect type optical fiber 2 is wound around the outer periphery of the winding frame 3 having no magnetism, and the input optical fiber 7 is connected to the input end 2A of the Faraday effect type optical fiber 2 via the polarizer 4, so that the Faraday effect is achieved. An output optical fiber 8 is connected to an output end 2B of the type optical fiber 2 via an analyzer 5 and a lens 6. A conductor to be measured 1 through which a current is measured passes through the inside of the winding frame 3. The input end 2A and the output end 2B of the Faraday effect type optical fiber 2 are housed in a magnetic shield box 10 made of ferrite or the like for the polarizer 4, the analyzer 5 and the lens 6. In FIG. 3, the magnetic shield box 10 is indicated by a dotted line so that the internal configuration of the magnetic shield box 10 can be seen.
FIG. 4 is a side view showing the configuration of the optical current transformer of FIG. The Faraday effect type optical fiber 2 circulates around the conductor 1 to be measured, the input end 2A is arranged above the output end 2B, and the input optical fiber 7 and the output optical fiber 8 are drawn out to the near side of the figure. ing.
[0004]
Returning to FIG. 3, the Faraday effect type optical fiber 2 has a property that the polarization plane of the light passing therethrough rotates in proportion to the strength of the magnetic field, and is composed of, for example, lead glass (quartz glass containing a large amount of lead oxide). Optical fiber. The Faraday effect is a phenomenon in which, when light passes through lead glass or the like placed in a magnetic field, the plane of polarization of the light rotates by a rotation angle θ = V · H · L. Here, V is a Verde constant, H is a magnetic field in the traveling direction of light, and L is a path length of light. Lead glass has a Verde constant V of about 6 times larger than that of general quartz glass containing no lead oxide, and the rotation angle θ of the polarization plane of light with respect to the magnetic field H is large. However, the input optical fiber 7 and the output optical fiber 8 are ordinary silica glass optical fibers or plastic optical fibers not containing lead oxide.
[0005]
When the current I flows through the conductor 1 to be measured, a magnetic field H that increases or decreases in proportion to the current I is formed around the current I. When the incident light P1 is injected into the input optical fiber 7 in this state, the incident light P1 is linearly polarized in one direction by the polarizer 4, and enters the input end 2A of the Faraday effect type optical fiber 2. When the light P passes through the Faraday effect type optical fiber 2, the plane of polarization of the light P is rotated by the rotation angle θ by the magnetic field H. The light P inclined by the rotation angle θ reaches the output end 2B of the Faraday effect type optical fiber 2 and is injected into the analyzer 5. The analyzer 5 transmits only the light component in the passable direction of the light P, is condensed by the lens 6, and is emitted to the output optical fiber 8 as transmitted light P2. Since the amount of change in the light amount of the transmitted light P2 when the current of the conductor to be measured 1 flows is proportional to the rotation angle θ with respect to the light amount of the transmitted light P2 when no current flows through the conductor 1 to be measured, The current I can be known by obtaining the amount of change in the amount of light P2. The amount of change in the amount of transmitted light P2 is converted into an electrical signal by a converter (not shown) and output.
[0006]
FIG. 3 shows an example in which the Faraday effect type optical fiber 2 is circulated by one turn, but in general, the Faraday effect type optical fiber 2 may be circulated continuously in positive integer turns. By rotating the Faraday effect type optical fiber 2 for a plurality of turns, the light path length L increases, so that the detection sensitivity of the optical current transformer can be increased. When the Faraday effect type optical fiber 2 is wound around the winding frame 3 for a plurality of turns, the Faraday effect type optical fiber 2 may be spirally wound around the winding frame 3 or may be wound into a disk shape. The detection sensitivity of the optical current transformer is the same.
[0007]
Moreover, in FIG. 3, the magnetic shield box 10 is for eliminating the influence of the magnetic field formed by the electric current which flows into another phase conductor. If the Faraday effect type optical fiber 2 passing through the conductor to be measured 1 forms a closed loop, the amount of change in the amount of transmitted light P2 is proportional to the current I of the conductor to be measured 1 based on Ampere's law. And the relative position between the Faraday effect type optical fiber 2 and the current flowing through the other-phase conductor not intersecting with the Faraday effect type optical fiber 2 are irrelevant. However, if the magnetic flux formed by the current flowing through the other-phase conductor enters the input end 2A and the output end 2B of the Faraday effect optical fiber 2, a measurement error occurs. Therefore, the input end 2A and the output end 2B of the Faraday effect type optical fiber 2 are magnetically shielded by the magnetic shield box 10, and the optical current transformer is not affected by the other phase conductor.
[0008]
[Problems to be solved by the invention]
However, in the conventional apparatus as described above, since the input end and the output end of the Faraday effect type optical fiber are housed in the magnetic shield box, the Faraday effect type optical fiber cannot be completely circulated, resulting in a measurement error. There was a problem that occurred.
That is, if the rotation of the Faraday effect type optical fiber is completely closed, the polarization plane of the light passing through the Faraday effect type optical fiber is rotated by exactly one rotation angle θ from the law of ampere's rotation integration, The current of the conductor to be measured that penetrates the Faraday effect type optical fiber is accurately detected. However, since the magnetic shield box 10 is not integrated because the magnetic field is not formed in the magnetic shield box 10, a corresponding measurement error occurs. Conventionally, as a countermeasure against this problem, as described above, the measurement error is reduced by making the magnetic shield box itself as small as possible. However, if the loop diameter of the Faraday effect type optical fiber is reduced, the ratio of the part that is not loop-integrated to the total loop length increases accordingly, and the measurement error increases.
An object of the present invention is to provide a highly accurate optical current transformer that does not cause a measurement error even if the circular diameter of the Faraday effect type optical fiber is small.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a Faraday effect type optical fiber having a property that the plane of polarization of light passing therethrough rotates in proportion to the strength of a magnetic field is circulated around a conductor to be measured and the Faraday Passes light from the input end to the output end of the effect type optical fiber, outputs a signal proportional to the rotation angle of the polarization plane of the light passing through the Faraday effect type optical fiber, and the current flowing from this signal to the conductor to be measured in the optical current transformer for measuring the said Faraday effect optical fiber a positive integer turns covering from orbiting is allowed position to inputs and outputs in the magnetic shield Utotomoni, the input side of the Faraday effect optical fiber output A contact portion in which the Faraday effect type optical fibers are in direct contact with each other may be formed on the side .
[0010]
Thereby, the passing light completely circulates in the Faraday effect type optical fiber by a positive integer turn. Moreover, the magnetic flux generated by the other phase conductor current from the input and output terminals of the Faraday effect optical fiber by the magnetic shield can also be shielded by the contact portion, and the input side of the Faraday effect optical fiber and the output side There is no gap between them, and there is no room for the magnetic flux generated by the conductor current of the other phase to enter.
[0011]
In this configuration, the magnetic shield may be a conductor. Thereby, an eddy current is generated in the magnetic shield by the magnetic flux from the conductor current of the other phase, and the energy of the magnetic flux is consumed. Therefore, the magnetic flux which penetrates into the input end and the output end of the Faraday effect type optical fiber is weakened.
In such a configuration, the magnetic shield may be a magnetic body. As a result, the magnetic flux entering the input end and the output end of the Faraday effect type optical fiber from the conductor current of the other phase is shielded.
[0012]
In this configuration, the magnetic shield may be formed of a sheet-like magnetic material and may be wound around the outer periphery of the Faraday effect type optical fiber. Thereby, even if the length and diameter of the Faraday effect type optical fiber are different, magnetic shielding can be performed immediately, and the Faraday effect type optical fiber can be easily magnetically shielded.
In this configuration, the magnetic shield may be made of a paint containing a magnetic material, and may be coated on the outer periphery of the Faraday effect type optical fiber. Thereby, even if the length and diameter of the Faraday effect type optical fiber are different, magnetic shielding can be performed immediately, and the Faraday effect type optical fiber can be easily magnetically shielded.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on examples. FIG. 1 is a perspective view showing a configuration of an optical current transformer according to an embodiment of the present invention. A contact portion 2C in which the Faraday effect type optical fibers 2 are brought into direct contact with each other is formed on the input side 2A and the output side 2B of the Faraday effect type optical fiber 2. The outer periphery of the Faraday effect type optical fiber 2 between the contact portion 2C and the input end 2A and between the contact portion 2C and the output end 2B is covered with a magnetic shield 9. The other parts are the same as those of the conventional optical current transformer shown in FIG.
[0014]
FIG. 2 is a plan view of the main part of FIG. The magnetic shield 9 is formed so that the Faraday effect type optical fiber 2 completely circulates. That is, the surrounding portion of the Faraday effect type optical fiber 2 and the contact portion 2 </ b> C are left, and the other portions are covered with the magnetic shield 9.
Returning to FIG. 1, the magnetic shield 9 is arranged so as not to interfere with the circulation of the Faraday effect type optical fiber 2, and the Faraday effect type optical fiber 2 completely circulates through the contact portion 2 </ b> C. As a result, the polarization plane of the light P passing through the Faraday effect type optical fiber 2 is accurately rotated by a rotation angle θ for one round, and the current I of the conductor 1 to be measured penetrating the Faraday effect type optical fiber 2 is highly accurate. Can be detected. Further, since the magnetic shield 9 magnetically shields between the contact portion 2C and the input end 2A, and between the contact portion 2C and the output end 2B, it is not magnetically affected by the conductor current of the other phase that is not the conductor 1 to be measured. It is like that.
[0015]
In FIG. 1, the magnetic shield 9 may be a conductor such as an aluminum material. Thereby, an eddy current is generated in the magnetic shield 9 by the magnetic flux from the conductor current of the other phase, and the energy of the magnetic flux is consumed. Accordingly, the magnetic flux entering the input end 2A and the output end 2B of the Faraday effect type optical fiber 2 is weakened and magnetically shielded. The smaller the conductivity of the conductor, the greater the magnetic shielding effect.
In FIG. 1, the magnetic shield 9 may be a magnetic material. As a result, the magnetic flux entering the input end 2A and the output end 2B of the Faraday effect type optical fiber 2 from the conductor current of the other phase is shielded.
[0016]
In FIG. 1, the magnetic shield 9 may be formed of a sheet-like magnetic material and may be wound around the outer periphery of the Faraday effect type optical fiber 2. As a result, even if the length and diameter of the Faraday effect type optical fiber 2 are different, the magnetic shielding can be performed immediately and the magnetic shielding becomes easy.
In FIG. 1, the magnetic shield 9 may be made of a paint containing a magnetic material and may be painted on the outer periphery of the Faraday effect type optical fiber. Also by this, even if the length and diameter of the Faraday effect type optical fiber 2 are different, the magnetic shielding can be performed immediately, and the Faraday effect type optical fiber 2 can be easily magnetically shielded.
[0017]
In FIG. 1, the input side 2A and the output side 2B of the Faraday effect type optical fiber 2 are in direct contact with each other at the contact portion 2C. However, the input side 2A and the output side 2B are not necessarily in contact with each other. Although a slight gap is interposed between the input side 2A and the output side 2B, the influence from the other-phase conductor is slightly affected, but this is determined in view of the required measurement accuracy. If the required measurement accuracy is much higher, the contact portion 2C is also required, but if the required measurement accuracy is low, even a slight gap is allowed. In addition, as the number of turns of the Faraday effect type optical fiber 2 increases, the influence of the other-phase conductor on the current detection sensitivity of the conductor to be measured decreases, so that the allowable gap between the input side 2A and the output side 2B increases. .
[0018]
【The invention's effect】
As described above, the present invention covers the input end and the output end from the position where the Faraday effect type optical fiber is rotated around a positive integer turn with a magnetic shield, and is provided on the input side and the output side of the Faraday effect type optical fiber. Since the contact portion is formed by directly contacting the Faraday effect type optical fibers, the passing light completely circulates in the Faraday effect type optical fiber by a positive integer turn, and the current of the conductor to be measured Can be detected with high accuracy. In addition, the magnetic shield can shield the magnetic flux generated by the conductor current of the other phase from the input end and the output end of the Faraday effect type optical fiber, and the influence of the other phase can be eliminated. In addition, the contact portion eliminates a gap between the input side and the output side of the Faraday effect type optical fiber, so that there is no room for the magnetic flux generated by the conductor current of the other phase to enter. The current can be detected with higher accuracy.
[0019]
Further, in this configuration, the magnetic shield is made of a conductor so that an eddy current is generated by a magnetic flux from a conductor current of another phase, and the energy of the magnetic flux is consumed. As a result, the magnetic flux entering the input end and output end of the Faraday effect type optical fiber is weakened.
Further, in such a configuration, the magnetic shield is made of a magnetic material, so that the magnetic flux entering the input end and the output end of the Faraday effect type optical fiber from the conductor current of the other phase is shielded.
[0020]
Further, in this configuration, the magnetic shield is made of a sheet-like magnetic material, and the Faraday effect type optical fiber is easily magnetically shielded by being wound around the outer circumference of the Faraday effect type optical fiber. be able to.
In this configuration, the magnetic shield is made of a paint containing a magnetic material, and is coated on the outer periphery of the Faraday effect optical fiber, thereby easily magnetically shielding the Faraday effect optical fiber. be able to.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a configuration of an optical current transformer according to an embodiment of the present invention. FIG. 2 is a plan view of a main part of FIG. 1. FIG. 3 is a perspective view showing a configuration of a conventional optical current transformer. 4] Side view showing the configuration of the optical current transformer of FIG.
1: conductor to be measured, 2: Faraday effect type optical fiber, 2A: input end, 2B: output end, 2C: contact portion, θ: rotation angle, I: current, 7, 8: optical fiber, 9: magnetic shield
more than

Claims (5)

The Faraday effect type optical fiber having the property that the polarization plane of the passing light rotates in proportion to the strength of the magnetic field circulates around the conductor to be measured and passes light from the input end to the output end of the Faraday effect type optical fiber. In the optical current transformer that outputs a signal proportional to the rotation angle of the polarization plane of the light passing through the Faraday effect type optical fiber and measures the current flowing from the signal to the measured conductor, the Faraday effect type light is measured. Utotomoni covered by a magnetic shield the fiber from positive integers turns orbiting is allowed position to inputs and outputs, direct the contacted the Faraday effect optical fiber to each other on the input side and the output side of the Faraday effect optical fiber An optical current transformer in which a contact portion is formed . 2. The optical current transformer according to claim 1, wherein the magnetic shield is a conductor . The optical current transformer of Claim 1 WHEREIN: The said magnetic shield is a magnetic body , The optical current transformer characterized by the above-mentioned. 4. The optical current transformer according to claim 3 , wherein the magnetic shield is made of a sheet-like magnetic material and is wound around an outer periphery of a Faraday effect type optical fiber . 2. The optical current transformer according to claim 1 , wherein the magnetic shield is made of a paint containing a magnetic material and is coated on an outer periphery of a Faraday effect type optical fiber.

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