JPS58189568A - Magnetic field measuring device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic field measuring device, and particularly to a magnetic field measuring device that utilizes an optical fiber and the rotatability (Faraday rotatability) of the plane of polarization of light.

In order to prevent accidents in places where high voltage is generated such as transformers and circuit breakers where the internal structure cannot be seen, and especially for preventive maintenance of high voltage equipment that requires strong insulation and high response, it is necessary to
It is effective to monitor disturbance changes in R and the magnetic field from normal times.

Gold W4fii for measuring current and magnetic field of conventional high voltage equipment!
A device is used that detects a magnetic field by converting the strength of the magnetic field into the magnitude of the total current minus the voltage, using a magnetic field detection coil formed into a coil shape. However, placing the above-mentioned metal coil in the measurement part is good if the measurement part is very spacious and the insulation can be maintained sufficiently even if the coil is inserted, but if the measurement part is very narrow and the voltage It is dangerous and cannot be used in areas where insulation is very high and insulation is a problem. 1 million v for registration,
It cannot be used for transformers in substations that use 500,000V.

In such a case, it is possible to use an insulating medium such as an optical fiber. Using conventionally known light to generate electric current and
A typical example of a device for measuring magnetic fields is one in which a magnetic field detection element is inserted between two optical fibers, as disclosed in Japanese Patent Application Laid-Open No. 57-37277. This configuration will be explained using FIG. 1. The magnetic field detection element is, for example, λ or YI.
G(Ys l;"e, ol!) is used as a Faraday rotation element 1, which is sandwiched between a gold polarizer 2 and an analyzer 3 before and after it. Since the output from one optical fiber 4 is non-polarized, Only the linearly polarized light component is taken out by the polarizer 2 and is incident on the Faraday rotation element 1 .

It should be noted here that half of the light that passes through the optical fiber 4 and the polarizer 2 is a loss. The linearly polarized light entering the Faraday rotation element 1 undergoes rotation of its vibration plane according to the magnitude H of the magnetic field, so that, for example, the optical axis S of the analyzer 3 intersects with the optical axis of the polarizer 2 at 45 and faces it. , the intensity of light passing through the analyzer increases in proportion to the rotation of the vibrating surface.

The above is a conventional method for measuring magnetic fields using light. This method has the following problems: 1) Since there is only one magnetic field measurement point, the influence of the magnetic field other than the measurement magnetic field is entirely ff-? water.

2) There is a drawback in that output fluctuations occur if the magnetic field measurement position shifts due to crustal movements, earthquakes, etc.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic field measuring device that can measure magnetic fields in spatially narrow areas or in high-voltage areas with high accuracy, at a safe measurement position, and regardless of external magnetic fields.

In order to achieve the above object, the magnetic field measurement device of the present invention includes a light source section, a magnetic field detection section including a magnetic material equipped with a medium having Faraday rotation ability, a measurement section that measures light from the detection section,
Also, an optical transmission line optically couples the light source section, the detection section, and the measurement section, and the plurality of detection sections are optically coupled in series.

In this way, by providing a plurality of magnetic field detection units 7i and optically coupling them in series, the 19 causes of locally existing measurement errors are averaged or diluted. The influence of the measurement position and external magnetic field has been significantly reduced in the device. However, as mentioned above, in the conventional magnetic field measurement device using a Faraday (co-rotating element), the amount of light that passes through the magnetic field detection element is half of the incident light due to optical loss due to the polarizer. Therefore, when N Faraday rotation elements are coupled in series, the amount of light is limited to (1/2) H at most, and no light is emitted. For example, if four magnetic field detection units are optically coupled in series, six
% appears in the output, which seriously harms the output power.

The respective detection sections may be coupled by an optical transmission path such as an optical fiber.

In order to completely prevent the decrease in the light waves passing through the magnetic field detection section as described above, a polarizing prism is used instead of the polarizer that is used in conventional magnetic field measurement devices using Faraday rotation elements. is split into two related polarized lights, and after entering a magnetic material that is fully equipped with a medium capable of Faraday rotation, that is, a Faraday rotation element, the transverse photon all passes through the optical fiber, and the resulting light is input into an optical fiber. , the other optical sound enters the same or other Faraday rotator as the above-mentioned 7 Alladay rotator, passes through the same or other analyzer as above, and inputs into the optical fiber the 2 polarized light. It is preferable to configure them so that they are combined. That is, in this case, in the magnetic field detection section, at least the polarizing prism for incidence, the magnetic material, and the analyzer are arranged in this order between the optical fiber on the light input side and the optical fiber on the light output side. Between the optical fiber on the light input side and the optical fiber on the light output side, there is a lens, an input polarizing prism, and a magnetic material.

It is preferable that the analyzer and the lens be arranged at 11@ in the magnetic field detection section.

The incident polarizing prism includes the well-known polarizing beam sifter, Rochon prism, Wollaston frism,
A Tual Nicol prism, a Cenamon prism, a Grantiller prism, or the like can be used. In particular, it is common to use a polarizing beam splitter.

The analyzer may be a conventional one, but the polarizing prism kumquat has the function of an analyzer and the function of combining two polarized lights. It is convenient to have it do double duty. In this case, as a prism for analysis,
Any of the above-mentioned incident polarizing prisms can be used, and polarizing beam nuplitters are particularly common. The polarizing prism for incidence and the polarizing prism for analysis are made of a medium fJ! having Faraday rotation ability. ! It is convenient to make the magnetic field detecting section compact by arranging them to face each other through the magnetic bodies provided therein.

In addition, it is generally preferable that the polarizing prism for incidence and the polarizing prism for analysis are symmetrically opposed to each other, or they are opposed to each other with an optical angle of 45, but this is not limited to this. Not done.

The magnetic material having the bride material that undergoes the Faraday rotation is given the general formula RB (Fe, -z M* ] O as a medium that undergoes the Faraday rotation iie'fr:M
1t (However, RUY, La, Sm
,F,u.

At least one element selected from the group consisting of Gd, Tm, Yb, Lu, Ca, and ↓UBi, and M is Qa.

At least one element selected from the group consisting of n and Cr, and the value of X is 0≦X≦1.5) in the direction of light transmission. It is preferable to use one having at least one magnetized magnetic Carnet thin film, but the present invention is not limited thereto.

Adding the element Mk brings about effects such as matching the lattice constant with the substrate and completely changing the magnitude of saturation magnetization, making it possible to detect ^^ in the low magnetic field region, but the value of If it exceeds 1.5 degrees, the Curie temperature will drop below room temperature, making it unstable as a ferromagnetic material, which is not desirable.

The above magnetic garnet thin film is made of cadrium gallium garnet (Qcl, Qa, 0
□), neodymium potassium garnet (NdsG
asO+t) or samarium potassium garnet (
The above-mentioned garnet thin film is deposited on both sides or one side of a paramagnetic substrate such as Sm3Ga1l oat ) (hereinafter referred to as GGG, NdGG, and smooth, respectively, for simplicity) so that the magnetization direction is perpendicular to the above-mentioned surface. It is formed by a dispersed phase growth method or a vapor phase method (('VD method), and is coupled to an optical fiber so that the original propagation coincides with the direction of the output power.

In addition to the above error, a plurality of magnetic field detection sections are optically coupled in series to the magnetic field measurement wave R of the present invention, and these plurality of magnetic field detection sections are connected in a loop shape around the magnetic field generation source. It is desirable to set it in For example, a magnetic field generated by a wire carrying current? For measurement, it is preferable to arrange magnetic field detection units in a loop around the wire. In this case, it is preferable to configure the magnetic field detection unit so that the direction perpendicular to the surface of the magnetic body is the connecting direction of the circumference of a circle that is perpendicular to the wire and has the entire center of the wire. .

The magnetic field measurement device of the present invention configured as described above has a plurality of magnetic field detection units ft connected in series in one direction with low optical loss, and such magnetic field detection units are installed around the object to be measured. This enables stable measurement regardless of the position of the magnetic field detection section.

Note that the configuration other than the above may follow the conventional technology (for example, the magnetic field measuring device described in Japanese Patent Publication No. 1983-37277).

The present invention will be described in detail below by way of examples with reference to the drawings.

Embodiment FIG. 2 is an explanatory diagram showing the configuration of an embodiment of the magnetic field measuring device according to the present invention.
1 consists of optical transmission lines B, , B, , B, . . . and magnetic field detection sections C 1 , C, , C 5 .

Measurement unit Afl has the same configuration as a general optical measurement system, and the light emitted from the light source 7 is adjusted by the lens 8 so that the maximum amount of light can enter the optical fiber 6. The light from the lens 8 is partially coupled to the optical fiber 6 via the half mirror 9 and guided to the first detection section C1. The other part is guided to the light receiving section 10 and becomes an output electric signal P1. Ten thousand,
An<, detection portions Ct, Ct, Cs... described later
The light from... is guided to the receiver 11 by the optical fiber 6.
Output electricity (becomes Q Pt.

The magnetic field H can be calculated from the values of Pl and P, but it is convenient to find the relationship between H and P t / P t in advance in a preliminary experiment, store this in all measurement units, and calculate the actual P.
, and P from the values of , and P.

mffj part c+, Ct, Cs... (G, σ) An example is shown in FIG. Further, on the other end surface of the magnetic garnet 15, there is a polarizing beam splitter 1 which is the same as the polarizing beam splitter 13 but whose reflecting surface is in the opposite direction.
4. The condensing lens 16 is in close contact. Here, each polarizing beam splitter is shown in FIG. 4 to clearly show its function. The polarizing beam splitter has a laminated polarizer surface 17 and a total reflection surface 18, and the unpolarized light UPk of the optical fiber is perpendicular to the laminated polarizer surface 17.
It plays the role of dividing into a linearly polarized light wave HP and a linearly polarized light wave parallel to it P.

In this forgery, the light enters the magnetic garnet 15 into two linearly polarized components VP and HP.

If there is no magnetic field in the detection parts c, l c, I..., the light passing through all the magnetic garnets 15 will be in the same polarization state and will not pass through other polarization peaks.
The beam enters the beam splitter 14, is combined again by the polarizing beam splitter 14, and enters the optical fiber 6 by the converging lens 16.

As an example, the magnetic garnet 15 has a magnetic garnet thin film having a thickness d on at least one end surface of a GGG substrate having a thickness h=0.35. The <111> direction of the crystal on the substrate serves as a terminal portion. Later, a magnetic garnet thin film is formed by a liquid phase epitaxy (LPE method) or a vapor phase method (CVD method). The magnetization direction of this thin film is oriented in the direction in which light travels, that is, in a direction perpendicular to the end face. An example of the composition of a magnetic garnet thin film is (YSmLuCa)s (FeGe)s OIt
(YSm)s (FeGa)s 01! Y3FelO1
! (BiSm)3(FeGa)sOtt was featured. Here (YSmLuCa)s(FeGe)sO
The case of +t will be explained. We investigated how the outputs P,' change when a magnetic field is applied perpendicularly to the surface of the magnetic Kernet 15, as indicated by symbol H in FIG. 3, in the direction in which the light travels. When a magnetic field is applied to the magnetic guard 15, the two optical surfaces VP and HP rotate due to the Faraday effect. Due to this rotation, the direction of the light HP passing through the polarization plane 17 of the polarizing beam splitter 14 changes, and the direction of light reflected at the tip VP changes.

The i-warning sound that changes here was measured and the wavelength of light was 0.633.
The results shown in FIG. 5 were obtained by measurement in μm.

The numbers in parentheses in the figure represent the depth d of the thin film in microns. All of the obtained properties increase rapidly with small magnetic field strengths, and decrease with a change from a certain magnetic field strength (assumed Ho0e). The tl of the 9 magnetic garnets used in H8, which differs depending on the material used, is 3000e.

At saturation magnetic field H8 or lower, the ratio of power that disappears due to the 7 Alladay effect due to the magnetic field (output ratio with respect to incidence) η, = 1 - (VeH, L)''...
(1) becomes. Here, Ve is a constant (Verdet constant) specific to the material that gives it a 7-Alade rotation ability, Hl is the strength of the magnetic field, and L is the thickness of the magnetic garnet.

All of this one magnetic field detection section is combined in series as shown in FIG. If the number of combinations is kN, then the total output change η when a magnetic field is applied is as follows. The total power entering the optical fiber from the light source 7 is Ppm, and the output power received by the optical receiver 11 is Psa.
If t, then P @II l ” P I mη ・・・・・・・・・
...(3).

Now, such a loop system is used as a power transmission bus 19 shown in Fig. 2.
Suppose that it is placed around . Here, the generatrix 19 is oriented perpendicularly to the winning surface. When t#L flows through the bus bar, a magnetic field is generated around the bus bar. Since this is in the same direction as the optical fiber loop, the magnetic field is detected by the magnetic field detection section. The main reason for adopting this method is as follows. The t-wave I flowing to the busbar is expressed by the magnification of the magnetic field H generated around it.

1, -fH-dl・・・・・・・・・・・・(4
) However, dt is a line element of an arbitrary closed loop taken at the center of the busbar.

Therefore, if a large number of magnetic field detections S are arranged in a loop,
No matter where the magnetic field detection section is installed, circular integration is performed, and one magnetic field sensor is installed around the bus bar 19 as in the conventional method. It has the great advantage of being independent of the installation position of the cell/seat.

In this embodiment, the polarizing beam splitters were arranged opposite to each other in 'c, but if the laminated polarizer surfaces 17 in FIG.
In the case of FIG. 3, the output changes according to the square of the i-field H, whereas it changes according to the first power of the magnetic field H, that is, in a direct manner.

In the embodiment of ``1 fc or more, a polarizing beam splitter was used to separate the randomly polarized light into two ikg @ line polarized beams, but for example, the well-known Rochon prism, Wolast prism, dual Nicol prism, and Cenamon prism were used. The light may be split into two orthogonally linearly polarized lights using a polarizing prism such as a Grass/Taylor prism, and then converged again.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the configuration of a conventional magnetic field detection section, Figure 2
3 is an enlarged view of the magnetic field detection section of the device shown in FIG. 2, FIG. 4 is an explanatory view of the operation of the polarizing beam splitter,
FIG. 5 is a graph showing the relationship between the strength of the magnetic field and the amount of change in output when the magnetic field detection section of FIG. 3 is used. 1... Faraday rotation element, 2... polarizer, 3...
・Analyzer, 4.5', 6... Optical fiber, 7... Light source, 8... Lens, 9... Semi-transparent film, 10.11.
...Receiver, 12°16...Lens, 13.14...
・Polarizing beam splitter 117...Laminated polarizer surface,
18... Total reflection surface, 1st (2) y] 2 mouth 3rd figure 1δ 4th figure 8

Claims (1)

[Claims] 1. A light source section, a magnetic field detection section including a magnetic material equipped with a medium having Faraday rotation ability, a measurement section that measures light from the run-in section, and the light source section and the detection section. What is claimed is: 1. A magnetic field measuring device comprising an optical transmission line optically coupling the measuring sections, characterized in that a plurality of the detecting sections are optically coupled in series. 2. The patent characterized in that the magnetic field detection unit includes at least an incident polarizing prism, the magnetic body, and an analyzer arranged in this order between an optical fiber on the light input side and an optical fiber on the light output side. A magnetic field measuring device according to claim 1. 3. The magnetic field detection section is characterized in that a lens, an incident polarizing prism, the magnetic body, an analyzer, and a lens are arranged in this order between an optical fiber on the light input side and an optical fiber on the light output side. A magnetic field measuring device according to claim 2. 4. Separate the two polarized lights from the incident polarizing prism VC, pass through the analyzer to the magnetic material, and then send it to the optical fiber on the light distribution and output side. By making the other of the two polarized lights enter the optical fiber through the magnetic material or other magnetic material and the analyzer or other analyzer, the outgoing light of the -10,000 polarized light and the outgoing light of the other polarized light are separated. The magnetic field measuring device according to claim 2 or 3, characterized in that the magnetic field measuring device is formed so as to be combined with each other.5. The magnetic field measuring device according to claim 2, 3 or 4, characterized in that the magnetic field measuring device is a de-aluminum prism, a Cenamon prism, or a Glantiller prism.6. The medium having Faraday rotation ability has a composition represented by the general formula R3(Fes--M-)O+t (where R is Y, I, a, 3m, Eu, Gd, Tm, Yb, Lu, Ca, and At least one element selected from the group consisting of Bi, M is Qa, Qe
At least one element selected from the group consisting of , At, Si, i9c, and In-processed Cr, and the value of X is O≦X≦
1.5) and is magnetized in the direction of light transmission. The magnetic field measuring device described. 7. The magnetic material is gadolinium potassium garnet or neodymium gallium garnet. Alternatively, the magnetic garnet thin film t is formed on at least one end surface of a paramagnetic substrate made of samarium gallium carnet so that its magnetization direction is perpendicular to the end surface. The magnetic field measuring device described in Section 1. 8. The magnetic field measuring device according to any one of claims 2 to 7, characterized in that the analyzer is comprised of a polarizing prism for analysis that completely combines two separated polarized lights. 9. Any one of claims 2 to 8m, characterized in that the polarizing prism for incidence and the polarizing prism for analysis are oriented toward each other via the magnetic material. The magnetic field measuring device described in . 10. The magnetic field measuring device according to claim 9, wherein the incident polarizing prism and the analyzing polarizing prism intersect with each other at 45 degrees. 11. Claims 2 to 10, characterized in that the incident polarizing prism is an incident polarizing splitter, and the analyzing prism is an analyzing polarizing splitter.
The magnetic field measuring device described in any of the paragraphs. 12. Claim 1, wherein the plurality of magnetic field detection units are provided in a loop around the magnetic field generation source.
The magnetic field measuring device according to any one of items 1 to 111"11. 13. A plurality of the magnetic field detection parts are arranged in a loop around an electric wire, and the direction perpendicular to the surface of the magnetic body is 13. The magnetic field measuring device according to claim 12, wherein the magnetic field measuring device is configured to be tangential to the circumference of a circle centered on the electric wire on a plane perpendicular to Ichihara.