JPS59151065A - Optical current transformer - Google Patents

Abstract

PURPOSE:To enable stable measurement of electric current with high accuracy by coating the entire reflection surface of the Faraday effect glass of an optical current transformer with a reflection film or covering the surface thereof with a protective cover to avoid direct contact of said surface with the atm. CONSTITUTION:When the light linearly polarized by a polarizer 1 is made incident to Faraday effect glass 2, the linearly polarized light s totally reflected twice each by the respective angle parts of the glass 2 and is changed to elliptically polarized light. The rotating angle of the plane of polarization thereof is detected and the intensity of the magnetic field is measured, by which the electric current flowing in a primary conductor 6 is measured. A reflection film 7 such as multilayered film of silver, aluminum and dielectric material is formed by means such as vacuum deposition or the like on the reflection surface of the glass 2 to avoid direction contact of the glass 2 with the atm. The stable measurement is thus made possible without sticking of water drops and the contaminated material in the atm. on the reflection surface even if the current transformer is used in a climatic environment of adverse temp. and humidity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to optical current transformers, and more particularly to optical current transformers that transmit normal original polarized light.

[Prior art]

When polarized light passes through a glass exhibiting the Faraday effect such as lead glass (hereinafter referred to as Faraday effect glass) placed in a magnetic field caused by an electric current, the plane of polarization is at an angle θ given by the following equation.
only rotates.

1=Ve-H-,L However, Ve: Guerde constant H: Strength of the magnetic field parallel to the optical path L Length of the optical path inside the glass Detect this rotation angle θ using a well-known method and calculate the strength of the magnetic field H. Current transformers that measure the current flowing near the glass are common. Figure 1 shows the structure of an applied example of Faraday effect glass, which consists of a polarizer 1, a Faraday effect glass 2, an analyzer 3, a condenser lens 4, an optical eyeper 5, and a primary conductor 6 through which the current to be measured flows. , the light travels in this order ('). When light linearly polarized by the gold polarizer 1 is incident on the Faraday effect glass 2,
This directly a-polarized light is totally reflected twice at each corner of the glass 2, changing the linearly polarized light into elliptically polarized light, so that the amount of rotation of the Noah Arab rotation angle decreases, and at the same time, the output sensitivity does not decrease. It has a structure. This principle is described in the University of Tokyo Production Technology Research Report Vol.

It was made public by ``Fundamental Research on Power Current and Voltage Measuring Devices Using Lasers'' by Mr. Saito and three others published in 28A5 (March 1980). The rotation of the polarization plane of linearly polarized light due to the Faraday effect is proportional to the strength of the magnetic field parallel to the optical path and the length of the optical path, so the linearly polarized light incident from a goes around the human sensitive body 6 and exits from b. , the Noah 2-day rotation angle θ is proportional only to the current of the single sensitive body 6 interlinked with the optical path, as shown in the following equation.

θ=Ve'/H-dt=Ve'I However, (-1y e/: Weerde's constant I (: Strength of magnetic field parallel to the optical path t Nigarasu's optical path length ■: Current interlinking with the optical path Therefore, one person The influence of the current flowing in other conductors in the vicinity of 6 can be ignored because the integration along the optical path becomes zero.In this way, the optical current transformer using Faraday effect glass is a very good special consideration. Lead glass, heavy flint glass, magnetic glass, quartz glass, etc. are used as the glass material.In order to maintain linearly polarized light as described above, 7. It is necessary to carry out total reflection twice at a time, and total reflection takes place six times for linearly polarized light to go around the seven Alladay effect glass 2. In the normal case, the shape of the Faraday effect glass 2 shown in FIG. However, when used under harsh conditions, i.e., in environments with poor weather conditions such as temperature and humidity, dirty substances from water droplets may adhere to the reflective surface. There is a risk that the total internal reflection efficiency will not only decrease, but also that the optical axis will shift.

[Purpose of the invention]

The present invention has been made in view of the above points, and an object thereof is to provide an optical current transformer that can perform stable and highly accurate current measurement.

[Summary of the invention]

The present invention achieves the intended purpose by coating the total reflection surface of the Faraday effect glass of the optical current transformer with a reflective film or covering it with a protective cover to prevent direct contact with the atmosphere. This is what I did.

[Embodiments of the invention]

An embodiment of the optical current transformer according to the present invention will be described below with reference to the drawings.

The overall structure of the Faraday effect glass of the optical current transformer is the same as that described in the conventional example, but as shown in Figure 2, the Faraday effect glass 20 has a reflective surface made of silver, aluminum, dielectric multilayer, etc. A film 7 is formed by means such as vacuum deposition, and blocks the reflective surface of the Faraday effect glass 2 from coming into direct contact with the atmosphere.

FIG. 3 shows another embodiment of the present invention, in which the reflective surface of the Faraday effect glass 20 remains in total reflection, and a protective cover 8 with a gap g formed therein so as not to touch the reflective surface is fixed to the reflective surface. However, the portion other than this gap g is bonded to the reflective surface. Even in this case, the reflective surface of the Faraday effect glass 2 is shielded from the atmosphere.

As described above, according to the embodiment of the present invention, the reflective surface of the 7 Allade effect glass is shielded from the atmosphere, and it is possible to prevent the reflection efficiency from decreasing or the optical axis from shifting due to the influence of dew condensation or dust in the atmosphere. normal linear deflection and optical path are maintained under any harsh weather conditions, ensuring accurate measurements.

〔Effect of the invention〕

As described above, according to the present invention, a reflective film or a protective cover is provided on the reflective surface of the Faraday effect glass, thereby providing an optical current transformer that can stably measure current with a high f*If under any weather conditions. The effect that can now be done is a dog.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the structure of an optical current transformer using Faraday effect glass, FIG. 2 is an explanatory view showing an example of Faraday effect glass used in the optical current transformer of the present invention, and FIG. It is an explanatory view showing another example of the same 772 day effect glass. 1... Polarizer, 2... Faraday effect gas, 3...
...Analyzer, 5...Optical fiber, 6...-Primary conductor, 7...Reflection film, 8...Protective cover, a...Linearly polarized incident light, b...Linearly polarized light emitted. Salmon 10 3F

Claims (1)

[Claims] 1. A Faraday effect glass is interlinked with a primary conductor through which the current to be measured flows, and a reflective film is provided on the total reflection surface of the Faraday effect glass around which the optical path circulates. An optical current transformer characterized by having a structure that blocks the single rotation glass and the atmosphere. 2. The reflective film is a protective cover having the same or equivalent expansion coefficient as the Faraday effect glass, and the protective cover 2. The optical current transformer according to claim 1, wherein the total reflection surface and the atmosphere are shielded from each other, and the total reflection surface in a portion corresponding to the optical path does not come into contact with the protective cover.