CN101285854B - Self focusing -type optical current mutual inductor - Google Patents

Abstract

The invention relates to a self-focusing optical current transformer, which comprises a light source 1, a collimator 2, a polarizer 3, an annular magnetism collector 5, an optical fiber coupler 8, a single mode polarization-preserving fiber 9, an analyzer 10 and a signal detection and processing system 11. The self-focusing optical current transformer is characterized in that: an annular magnetism collector opening 7 is provided with a sensing head 4 which adopts magneto-optic glass or crystal and has a cuboid processing shape; and the breadth of the magnetism collector opening 7 is of between 5 and 10 mm and needs to be more than that of the sensing head 4. The self-focusing optical current transformer has the advantages that: the sensitivity of a sensing system is improved; because light beam does not contact an interface when transmitted in the sensing head, the light intensity of polarized light does not have loss, thereby also overcoming the disadvantages of weak output light intensity signal and poor signal-to-noise ratio of the prior optical glass type current transformer; moreover, the self-focusing optical current transformer avoids the operation of the prior art of adopting a dual light source and reduces the cost of a sensing system.

Description

Self focusing-type optical current mutual inductor

Technical field

The present invention relates to a kind of self focusing-type optical current mutual inductor, relate to the optical current mutual inductor technical field.

Background technology

High-tension current inductor is that electric system is the little current signal of low pressure with the high-voltage great-current signal transition in the electrical network, thereby the device of the current signal of unified, standard is provided for the metering of system, monitoring, relay protection etc.Optical current mutual inductor (Optical Current Transducer, be called for short OCT) is the theoretical of the fine sensing technology of a kind of light harvesting, photoelectric technology, nonlinear optics and advanced a plurality of subjects such as signal processing technology and the new type current transformer in high voltage that is applied to one.Compare advantage such as optical current mutual inductor has good, the no magnetic saturation of insulating property, range of dynamic measurement is big, measuring accuracy is high, anti-electromagnetic interference capability is strong with traditional high-voltage great-current mutual inductor.

Optical glass type OCT adopts the monoblock optical glass with higher Fil moral (Verdet) constant to make sensing head.Because light beam will form the closed light path around current in sensing head, therefore in this process, to adopt the total reflection structure to make light generation deviation inevitably.Because during total reflection, the reflected light electric vector makes the linearly polarized light of incident become elliptically polarized light with respect to producing additional phase change (being called for short reflection phase shift, as follows) between the respective component of incident light electric vector, thereby reduced measurement sensitivity, and had a strong impact on measuring accuracy.Studies show that: if total reflection phase shift is controlled in the 0.24rad (being about 14 °), then the sensitivity of sensing head will be not less than ideal model the sensitivity theory desired value 90%.The raising of the antijamming capability of simultaneity factor and stability all will realize by reducing reflection phase shift.Find out that thus it is significant to the sensitivity, antijamming capability and the stability that improve system to reduce reflection phase shift.Therefore, how to reduce the phase differential that causes by reflection, become the key issue that needs to be resolved hurrily in this type of OCT design.

People (Sensitivity Improvement of an Optical Current Sensor with EnhancedFaraday Rotation such as Gongde Li, Journal of Lightwave Technology, VolL.15, No.12,1997) a kind of optical glass type current sensor has been proposed.This current sensor adopts annular collection chinaware to increase the current bus bar surrounding magnetic field, and rectangular parallelepiped optical glass is placed on collection chinaware opening part, utilizes Faraday effect to measure bus current.But, will inevitably introduce reflection phase shift owing to linearly polarized light in the optical glass upper and lower surface reflection process takes place repeatedly, thereby bring error to measurement result.

People (New Design of Optical Electric-Current Sensor for SensitivityImprovement such as Benshun Yi, IEEE Translations on Instrumentation and Measurement, Vol.49, No.2,2000) a kind of optical glass type current sensor that proposes has also adopted an annular collection chinaware that opening arranged to increase magnetic field around the current bus bar.They become the inclination angle with the front end face grinding and polishing of rectangular parallelepiped optical glass is the inclined-plane of critical angle, rear end face plating reflectance coating, and be placed on the opening part of annular collection chinaware, linearly polarized light is perpendicular to inclined-plane incident, and repeatedly reflection at critical takes place at the upper and lower surface place of optical glass, when arriving the glass rear end face, in the metallic reflective coating reflected back glass on rear end face, pass through the repeatedly reflection at critical of upper and lower surface again, finally from the incident end face outgoing.And then they (Magneto-optical electric-current sensor with enhanced sensitivity, MeasurementScience and Technology, Vol.13,2002, N61-N63) again above-mentioned sensing head is improved.But no matter be before improving or the sensing head after improving, because light beam can not be strict with inclined-plane incident in the restriction of machining precision and the practical application, thereby make that the reflection that linearly polarized light takes place in upper and lower surface is not strict reflection at critical, therefore can introduce reflection phase shift equally and reduce the sensitivity of sensor.

Summary of the invention

The technical matters that solves

For fear of the deficiencies in the prior art part, the present invention proposes a kind of self focusing-type optical current mutual inductor.Utilize the self-focusing principle of graded index type magneto-optic glass or crystal to make sensing head, since light arrive glass or the crystal upper and lower surface before will bend, avoided total reflection from the teeth outwards, thereby can eliminate reflection phase shift fully, thereby improve sensitivity, antijamming capability and the stability of system.

Technical scheme

A kind of self focusing-type optical current mutual inductor, comprise light source 1, collimating apparatus 2, the polarizer 3, annular collection chinaware 5, fiber coupler 8, single-mode polarization maintaining fiber 9, analyzer 10 and acquisition of signal and disposal system 11, it is characterized in that: at annular collection chinaware opening 7 position of sound production sensing heads 4, described sensing head adopts magneto-optic glass or crystal, the processing type shape is a rectangular parallelepiped, the width of described collection chinaware opening 7 be 5mm to 10mm, must be greater than the width of sensing head 4.

The width of described sensing head 4 must be greater than 2c, wherein: c is the thickness of gradient index layers.

The angle γ of the plane of light incidence of described sensing head 4 and incident light ₀Should satisfy:

Wherein: n ₀Be sensing head 4 intermediate refractive index layers, n ₂Be sensing head 4 upper and lower surface place refractive indexes.

The external diameter of described annular collection chinaware 5 is less than 40mm, and width R is more than or equal to the length L of sensing head, wherein L poor less than the external diameter of annular collection chinaware 5 and tested current bus bar radius.

Two logical light faces of described sensing head are become parallel plane by grinding and polishing, and fiber coupler 8 is connected the side that sensing head 4 is positioned at annular collection chinaware 5 internal diameters.

The end face that described sensing head 4 is positioned at annular collection chinaware 5 external diameters is polished polishing, and at rear end face plating protective eccentric reflective film 12 in parallel, fiber coupler 8 is connected the side that sensing head 4 is positioned at annular collection chinaware 5 external diameters.

Sensing head 4 is made according to light beam self-focusing principle, the sensing head material is magneto-optic glass or crystal, adopt ion exchange process or technologies such as sol-gal process or chemical vapour deposition technique that the refractive index of described sensing head material is prepared into Gradient distribution, thereby light is propagated forward with curvilinear path in sensing head inside, do not contacted with air interface with sensing head.

The annular collection chinaware 5 of band opening, from be in order to form magnetic line of force path, make that the sensing head magnetic circuit is closed as far as possible and increase magnetic flux in the magnetic circuit.The wall thickness of annular collection chinaware, openings of sizes depends on the size of rectangular build sensing head, the size in promptly annular collection chinaware opening part space will be fit to sensing head and put into wherein.Opening is big more simultaneously, and opening part magnetic field is more little, and homogeneity is poor more.When collection chinaware A/F is 5mm during to 10mm, the magnetic field intensity of its opening part is about 2 times that do not add electric current produces in the collection chinaware bus magnetic field intensity; And when collection chinaware A/F during greater than 16mm, the magnetic field intensity of its opening part even the magnetic field intensity that electric current produces in the bus when not adding the collection chinaware.Secondly, the diameter of collection chinaware should be less than 80mm, because the toroidal magnetic field that current bus bar produced is just very faint at distance bus 40mm place, and it is very inhomogeneous, if therefore the external diameter of collection chinaware surpasses this scope, the distortion in magnetic field be will cause, thereby sensitivity and the stability measured reduced.

Consider that light no longer contacted with air interface with medium when light was propagated in the graded index medium, but in medium, periodically propagate forward by curvilinear path.Vertex position in curvilinear path, light still can be regarded as total reflection has taken place, and the phase shift of introducing is known as crooked phase shift, but all is pi/2 to the crooked phase shift of TE ripple and TM ripple here, so this total reflection does not change the linear polarization polarization state of light, therefore just to not influence of measurement result yet.

Beneficial effect

The invention has the beneficial effects as follows: linearly polarized light is propagated periodically forward with curvilinear path in described sensing head, does not reflect, and has therefore avoided the influence to the linearly polarized light polarization state of the reflection phase shift introduced by total reflection, the sensitivity that has improved sensor-based system; Because light does not contact with the interface when propagating in sensing head, the light intensity of polarized light does not have loss, so has overcome in the existing optical glass type current transformer a little less than the output intensity signal shortcoming of poor signal to noise yet; Avoid the way of the two light sources of available technology adopting, reduced the cost of sensor-based system.

Description of drawings

Fig. 1 is the structural representation of self focusing-type optical current mutual inductor first embodiment of the present invention;

Fig. 2 is the self focusing-type optical current mutual inductor first embodiment sensing head refractive index profile of the present invention;

Fig. 3 is the structural representation of self focusing-type optical current mutual inductor second embodiment of the present invention;

Fig. 4 is the self focusing-type optical current mutual inductor second embodiment sensing head refractive index profile of the present invention;

The 1-light source; The 2-collimating apparatus; The 3-polarizer; The rectangular build sensing head of 4-; 5-annular collection chinaware; 6 tested current bus bars; 7-annular collection chinaware opening; The 8-fiber coupler; The 9-single-mode polarization maintaining fiber; The 10-analyzer; 11-acquisition of signal and disposal system; The 12-sensing head; 13-protective eccentric reflective film.

Embodiment

Now in conjunction with the accompanying drawings the present invention is further described:

Embodiment 1: consult accompanying drawing 1, Fig. 2, comprising: light source 1, collimating apparatus 2, the polarizer 3, rectangular build sensing head 4, annular collection chinaware 5, tested current bus bar 6, fiber coupler 8, single-mode polarization maintaining fiber 9, analyzer 10, acquisition of signal and disposal system 11.

Described light source 1 is a helium-neon laser.

Described collimating apparatus 2 is used for changing the light beam of light source outgoing into parallel beam.

The effect of the described polarizer 3 is that the light beam with the collimating apparatus outgoing is transformed into linearly polarized light.

Described annular collection chinaware 5 can be for having very high magnetic permeability and very little coercitive soft magnetic material, and its external diameter is 30mm.Its effect is to form magnetic line of force path, and increases the magnetic flux in the magnetic circuit.

Described fiber coupler 8 effects are that light beam coupling is entered optical fiber.

The effect of described single-mode polarization maintaining fiber 9 is to keep the linear polarization polarization state of light of the information of carrying in the optical fiber constant, detects for analyzer.

Described analyzer 10 is used to detect the variation from the linearly polarized light plane of polarization of sensing head outgoing.

The effect of described acquisition of signal and disposal system 11 is that the light signal that will detect converts electric signal to and carries out the signal demodulation.

Described rectangular build sensing head 4 places opening 7 places of described annular collection chinaware 5, and the width of collection chinaware opening 7 is 7mm.

This rectangular build sensing head 4 adopts block magneto-optic memory technique to make, and the thickness c of the gradient index layers of this material is 1mm, and then the width of sensing head 4 is 5mm.Two logical light faces of this sensing head are polished respectively is polished to parallel plane, makes that light beam can be from this incident of two logical light faces and outgoing, and fiber coupler 8 is connected the side that sensing head 4 is positioned at annular collection chinaware 5 internal diameters.Described block magneto-optic memory technique adopts mode such as ion-exchange to make its refractive index distribution gradient.Here becoming the square law graded profile with refractive index is that example is illustrated.Upper and lower surface at block magneto-optic memory technique is carried out ion-exchange simultaneously, at ion exchange layer, the refractive index of magneto-optic memory technique becomes the square law graded profile, in the middle layer of not carrying out ion-exchange, its refractive index is still equally distributed, and the final distribution of refractive index in the xoz plane satisfied:

n ²(x)=n ₀ ²[1-d ²(x ± b) ²] x≤b or x 〉=-b

n ²(x)＝n ₀ ² -b≤x≤b

N in the formula ₀Be the refractive index of middle conforming layer,

n ₂Be the refractive index at sensing head upper and lower surface place, c is the thickness of graded-index layer, as shown in Figure 1.

Utilizing equations of light ray to find the solution light becomes the propagation trajectories in the square-law graded profile medium to be in refractive index

$x\left(z\right)=\frac{\tan {\mathrm{\γ}}_0}{d}\sin \left(\frac{\mathrm{dz}}{\cos {\mathrm{\γ}}_o}\right)$

γ in the formula ₀Angle for light and z axle.Hence one can see that, and light is pressed the sinusoidal pattern propagated in medium, and its propagation cycle is

Amplitude

The beam Propagation of sending from described light source 1 becomes directional light to collimating apparatus 2, be transformed into linearly polarized light behind the polarizer 3, more at a certain angle through a surface feeding sputtering of rectangular build sensing head 4.Enter the incident light of sensing head 4, in the sensing head graded-index layer, propagate forward with the sinusoidal pattern path, but in conforming layer still with rectilinear propagation, so just can reflect once more and enter the graded index layer with identical angle.So periodically propagate final other end outgoing from sensing head.Be coupled to single-mode polarization maintaining fiber 9 through fiber coupler 8, detect the variation of its plane of polarizations, export acquisition of signal at last to and disposal system 11 is carried out opto-electronic conversion and signal demodulation by analyzer 10.

Because magnetic direction is perpendicular to the axis direction of described sinusoidal pattern travel path in the described sensing head.Therefore, effective light path of this optical current mutual inductor is 4M a times of periodically curvilinear path amplitude, and M is the periodicity that light is propagated in this sensing head.Can obtain the cycle by calculating If the length of this sensing head on the light ray propagation direction is L, the periodicity propagated therein of light then

$M=\frac{L}{T^{\′}}=\frac{L*d*\tan {\mathrm{\γ}}_0}{2\mathrm{\π}\sin {\mathrm{\γ}}_0+4\mathrm{db}\cos {\mathrm{\γ}}_0}$

So the effective light path that is parallel to magnetic direction is

$L^{\&prime;}=4M*(B+b)=\frac{4L\sin {\mathrm{\&gamma;}}_0({\sin \mathrm{\&gamma;}}_0+\mathrm{db}\cos {\mathrm{\&gamma;}}_0)}{{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="H2008100174578E00011.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2{\mathrm{\&gamma;}}_0(2\mathrm{\&pi;}\sin {\mathrm{\&gamma;}}_0+4\mathrm{db}\cos {\mathrm{\&gamma;}}_0)}$

As can be seen from the above equation, increase incident angle γ ₀Can increase effective light path.Simultaneously, incident angle γ ₀Be subjected to the restriction of sensing head size and refractive index degree of irregularity etc.Calculate incident angle γ ₀Should satisfy:

$\tan {\mathrm{\&gamma;}}_0\&le;\frac{\sqrt{{{\mathrm{<figure-callout\; id="0"\; label="n"\; filenames="H2008100174578E00022.png"\; state="\{\{state\}\}">n</figure-callout>}}_0}^2-{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="H2008100174578E00011.png"\; state="\{\{state\}\}">n</figure-callout>}}_2}^2}}{{\mathrm{<figure-callout\; id="0"\; label="n"\; filenames="H2008100174578E00022.png"\; state="\{\{state\}\}">n</figure-callout>}}_0}$

Embodiment 2: consult accompanying drawing 2, comprising: light source 1, collimating apparatus 2, the polarizer 3, annular collection chinaware 5, sensing head 4, analyzer 10, fiber coupler 8, single-mode polarization maintaining fiber 9, protective eccentric reflective film 13, acquisition of signal and disposal system 11.

Described light source 1 is the solid state laser of semiconductor laser pumping.

The described sensing head 4 of present embodiment is in a kind of improvement of a last embodiment, the front end face that is about to square sensing head 4 is polished polishing, at rear end face plating protective eccentric reflective film 12 in parallel, fiber coupler 8 is connected the side that sensing head 4 is positioned at annular collection chinaware 5 external diameters.The light beam that sends from described light source 1 becomes directional light through after the collimating apparatus 2, is transformed into linearly polarized light behind the polarizer 3, enters described sensing head 4 again.Incident light incides the front end face of sensing head 4 at a certain angle, and incident beam is propagated forward with the sinusoidal pattern path in the graded-index layer of sensing head 4, in the refractive index conforming layer still along rectilinear propagation.So periodically propagate, finally reflect at the rear end face that is coated with protective eccentric reflective film 12, the reflected ray polarized light is propagated in sensing head in an identical manner, finally from former incident end face outgoing.Be coupled to single-mode polarization maintaining fiber 9 through fiber coupler 8, detect the variation of its plane of polarizations, export acquisition of signal at last to and disposal system 11 is carried out opto-electronic conversion and signal demodulation by analyzer 10.

Embodiment 2 is with the difference of embodiment 1: the rear end face of sensing head 4 plating protective eccentric reflective film 12 among the embodiment 2.Linearly polarized light is twice propagation back and forth in described sensing head 4, and effectively light path doubles.Because incident light and emergent light be in the same side of described sensing head 4, and spatially be separated from each other, therefore can reduce the overall dimension of sensing head.But may produce certain influence to sensor performance owing to introduce reflection configuration in this sensing head.

Self focusing-type optical current mutual inductor of the present invention utilizes the self-focusing principle to propose two kinds of optical current mutual inductor structures, and described two kinds of structures have all overcome existing optical glass type current transformer has reduced system's antijamming capability and stability because of the inevitable reflection phase shift of sensing head shortcoming.Because linearly polarized light is propagated periodically forward along curvilinear path in sensing head, avoided and the contacting of air and sensing head interface, eliminated the influence of the reflection phase shift that total reflection produced to measurement result.And, also avoided in the existing optical glass type current transformer a little less than the output intensity signal shortcoming of poor signal to noise because the light intensity of polarized light does not have loss.In addition, the rectangular build sensing head among the described embodiment 2 is than the rectangular build sensing head among the embodiment 1, and effectively light path doubles, and can reduce the overall dimension of sensing head.

Claims (2)

1. self focusing-type optical current mutual inductor, comprise light source (1), collimating apparatus (2), the polarizer (3), annular collection chinaware (5), fiber coupler (8), single-mode polarization maintaining fiber (9), analyzer (10) and acquisition of signal and disposal system (11), it is characterized in that: at annular collection chinaware opening (7) position of sound production sensing head (4), described sensing head adopts magneto-optic glass or crystal, machining shape is a rectangular parallelepiped, the width of described collection chinaware opening (7) be 5mm to 10mm, must be greater than the width of sensing head (4); The width of described sensing head (4) must be greater than 2c, wherein: c is the thickness of gradient index layers; The plane of light incidence of described sensing head (4) and the angle γ of incident light ₀Should satisfy:

Wherein: n ₀Be sensing head (4) intermediate refractive index layer, n ₂Be sensing head (4) upper and lower surface place refractive index.

2. self focusing-type optical current mutual inductor according to claim 1, it is characterized in that: the external diameter of described annular collection chinaware (5) is less than 40mm, width R is more than or equal to the length L of sensing head, and wherein L collects the poor of the external diameter of chinaware (5) and tested current bus bar radius less than annular.

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