CN2762147Y - Double-light-path optical current transformer - Google Patents

Abstract

The utility model discloses a double-light-path optical current sensing head. Light emitted by light-emitting diodes are converted into parallel light through a collimation self-focusing lens, the parallel light is converted into linear polarized light through a polarizer, and the linear polarized light enters a sensitive element; after the light travels a circle by encircling a detected conductor in a center hole in the sensitive element, the light is emitted, and the polarized surface of entering linear polarized light beams generates deflection under the action of the detected current; besides, emitted modulated light is output to an analyzer, reflected light and transmitted light of the analyzer is output to two coupling self-focusing lenses, and after the coupling self-focusing lenses focus and couple the light beams, the light beams are transmitted to a photo detector. The utility model utilizes the reflected light and the transmitted light, and the reflected light and the transmitted light are split from the analyzer after modulation; the sensitivity and the signal noise ratio are raised; in view of the same detected signal, an interference signal is reduced after modulation, a useful signal is doubled, and the anti-common mode interference ability is enhanced.

Description

Double light path optical current sensing head

Technical field

The utility model relates to a kind of double light path optical current sensing head, can be used for optical current mutual inductor.

Background technology

The optical current mutual inductor (OCT) that utilizes the Faraday magnetooptical effect principle to make has many advantages than traditional induction current transformer (CT).Its measurement bandwidth, the primary current changing condition in the time of correctly reflecting electric power system fault, insulation is simple relatively, anti-electromagnetic interference capability is strong, is the substitute products of traditional CT.At present optical current mutual inductor has two kinds, and is a kind of for light transmission type is active formula optical current mutual inductor, and another kind is the passive type optical current mutual inductor for sensing type, and the former is with traditional CT number of winning the confidence, and the latter is with numbers of winning the confidence such as optical material such as flint glasses.The passive type optical current mutual inductor adopts block flint glass to do sensing head mostly and is the structure on monochromatic light road, though this structure can be obtained signal, signal to noise ratio (S/N ratio) is lower, is subject to disturb.Current in wire changes in the electric system, and mutual inductor is except that need are measured rated current; Also to measure 1% and 5% of rated current, require to satisfy certain accuracy.If sensing head is the monochromatic light line structure, the sensitivity of measurement and signal to noise ratio (S/N ratio) are difficult to satisfy the measurement requirement under a small amount of journey rated current situation.

Summary of the invention

The utility model at existing monochromatic light road sensing head defective, a kind of double light path optical current sensor is provided.This sensing head can improve the noise anti-interference level of system when of measuring.

A kind of double light path optical current sensor provided by the invention, the light that light emitting diode sends becomes directional light through the collimation GRIN Lens, directional light becomes linearly polarized light through the polarizer, linearly polarized light is incident to responsive unit, the measured conductor that light centers in responsive unit in the center pit is propagated week back ejaculation, and the plane of polarization of the linear polarized beam of incident is deflected under the effect of tested electric current; The modulated light that penetrates exports analyzer to, the transmitted light of analyzer exports the first coupling GRIN Lens to, the first coupling GRIN Lens focuses on coupling back, back by Optical Fiber Transmission to the first photodetector with light beam, it is characterized in that: this sensing head also is provided with the second coupling GRIN Lens, be used to receive the reflected light of analyzer, the second coupling GRIN Lens focuses on coupling back, back by Optical Fiber Transmission to the second photodetector with light beam.

The dissimilarity of the utility model and monochromatic light road optical current sensing head is: the optical current sensing head on monochromatic light road is that modulated light beam is only got wherein one road light beam (generally being transmitted light beam) behind analyzer, and another light beam does not utilize.And reflected light and transmitted light that the utility model has utilized modulated back to be told by analyzer.Respectively export photodetector to through GRIN Lens becomes electric signal to the two-way light beam.These two electric signal amplitudes are identical, and 180 ° of phase phasic differences by data processing, with two signal subtractions, can obtain doubling the output signal on monochromatic light road like this.Particularly, the utility model has following technique effect:

1, improved sensitivity and signal to noise ratio (S/N ratio), to same measured signal, its output signal of modulation back doubles.

2, improved anti-common mode interference ability,, after the modulated two-beam of double light path becomes electric signal, subtracted each other during data processing when disturbing to two optical path signal sizes, when direction is consistent.Like this, undesired signal can be deducted, and useful signal doubles.

Description of drawings

Fig. 1 is a double light path optical current sensing head structural representation.

Fig. 2 is responsive first synoptic diagram of optical compensation method.

Fig. 3 is the synoptic diagram of geometric compensation method.

Fig. 4 is responsive first synoptic diagram of geometric compensation method.

Fig. 5 is to be the responsive first synoptic diagram that adopts whole block material to make.

Fig. 6 is flow chart of data processing figure.

Embodiment:

As shown in Figure 1, the utility model comprises responsive unit 1, collimation GRIN Lens 2, the polarizer 4, analyzer 5, two coupling GRIN Lens 6,6 '.The utility model can be set up two 90 ° of corner prisms 3,3 ', changes the travel path of light, makes the sensing head structure more compact.

Responsive unit 1 is used to make the plane of polarization of the linear polarized beam of incident to deflect under the effect of tested electric current.The material of responsive unit adopts block optical glass (for example flint glass), there is a center pit at center in responsive unit, this hole and responsive first upper and lower Surface Vertical, the size in hole should make measured conductor to pass, incident light carries out repeatedly total reflection in responsive unit, the measured conductor that light centers in responsive unit in the center pit is propagated week back ejaculation.The existing in the prior art report of the responsive unit of this structure, its implementation has multiple, enumerates two kinds of modes below and is specified.

For incident light polarization state after the total reflection in responsive unit remains unchanged, when the responsive unit of design, need eliminate differing of total reflection introducing, two kinds of methods are generally arranged: optical compensation method and geometric compensation method.One of typical implementation method of optical compensation method is a plated film on each reflecting surface, makes that its reflection on reflecting surface is not total reflection but reflection at critical state, so that catoptrical linear polarization remains unchanged.As shown in Figure 2, get a square flint glass material, centre-drilling hole can therefrom be passed conductor, and any three of four angles are wherein cut, and makes the tangent plane and the length of side in angle of 45 degrees, then plated film on three tangent planes.The geometric compensation ratio juris is to allow light through twice total reflection, and the plane of incidence of twice total reflection in front and back is vertical mutually, can not produce phase differential between two components through the light after twice such total reflection.As shown in Figure 3, two rectangular optical glass hexahedrons cut out an inclined-plane that becomes miter angle with the bottom surface respectively as reflecting surface, and these two hexahedron quadratures are stacked and with the gluing jail of optics.Linearly polarized light is along axis incident, arrives behind first reflecting surface total reflection light and rolls over behind 90 degree vertically upward, arrives second reflecting surface again, through after the total reflection for the second time along the axis direction outgoing, the plane of incidence of twice total reflection is vertical.Fig. 4 is the responsive first synoptic diagram that adopts the geometric compensation method, is made up of 4 optical glass parallelepipedons, and wherein two both sides end face all is the plane that becomes 45 degree with edge direction; Two other at one end has the end face of 90 degree, and the inclined-plane of 45 degree is arranged at the other end.Latter two forms the top and the terminal of light transmission, and two 90 degree end faces are respectively the plane of incidence and exit facet.These four parts are bonded to an integral body as shown in Figure 4.This sensitivity unit also can adopt the monoblock optical glass material to make.As shown in Figure 5, light divides two-layer propagated up and down in this sensitivity unit, and lower floor is I, III arm, and lower floor is II, IV arm.At a, b, place, c angle, it all is the total reflection of 45 degree that light has experienced twice incident up and down respectively.

The light beam that collimation GRIN Lens 2 is used for entering is transformed into directional light.The one 90 ° of corner prism 3 changes the travel path of light beam, makes the structure of sensing head become compact more.The effect of the polarizer is that the light that will go into to inject responsive unit is transformed into linearly polarized photon.Analyzer is used for the variation from the linear polarization polarization surface of the first outgoing of sensitivity is transformed into the light beam intensity variations, and is divided into reflected light and transmitted light two tunnel outputs.The coupling GRIN Lens is to be coupled into optical fiber and to transfer to photodetector after light beam is focused on.The effect of photodetector is to convert light signal to electric signal, so that carry out data processing.

The light beam that sends when light emitting diode 7 enters collimation GRIN Lens 2 and becomes directional light, through the one 90 ° of corner prism 3, enter the polarizer 4 again, become linearly polarized light, after entering sensing unit 1, after the current-modulation on the tested current 8, export analyzer 5 to, behind analyzer 5, light beam after modulated is divided into the two-way light beam, wherein one road transmitted light enters the first coupling GRIN Lens 6 through the 2 90 ° of corner prism 3 ', reaches second photodetector 10 through optical fiber and converts light signal to electric signal laggard line data processing.Another road reflected light enters the second coupling GRIN Lens 6 ', through optical fiber first photodetector 9 to the data processing.

According to Faraday magnetooptical effect, the magnetic field of tested electric current and light action make modulated θ angle of linearly polarized light rotation.

$\mathrm{\θ}=V{\∫}_L\stackrel{\→}{H}\·d\stackrel{\→}{l}...\left(1\right)$

The Verdet constant of V-flint glass sensing unit 1

The magnetic field intensity that the tested current i of H-is encouraged

The path that the L-light beam passes through in sensing unit 1

According to Ampere circuit law

$\mathrm{\θ}=V{\∫}_L\stackrel{\→}{H}\·d\stackrel{\→}{l}=\mathrm{Vi}...\left(2\right)$

V is the Verdet constant of responsive unit in the formula, and the θ angle is directly proportional with tested electric current.According to Malus law, transmission, the reflection output intensity of rotation angle θ after the analyzer analyzing is respectively again:

I ₀Be constant initial light intensity before the process analyzer

I ₁Be the output intensity of transmitted light path behind analyzer 5

I ₂Be the output intensity of reflected light path behind analyzer 5

I ₁, I ₂Two optical path signals are through the photodetector PIN of optical fiber to data processing unit ₁10, PIN ₂9, with data processing unit electric signal to be handled, alternating current-direct current can get after separating:

$I_{A{C}_1}=\frac{-I_0}{2}\sin 2\mathrm{\θ},I_{D{C}_1}=\frac{I_0}{2}...\left(4\right)$

${i_1}^{\′}=\frac{I_{{\mathrm{AC}}_1}}{I_{D{C}_1}}-\sin 2\mathrm{\θ}...\left(5\right)$

$I_{A{C}_2}=\frac{-I_0}{2}\sin \mathrm{\θ},I_{D{C}_2}=\frac{I_0}{2}...\left(6\right)$

${i_2}^{\′}=\frac{I_{A{C}_2}}{I_{D{C}_2}}\sin 2\mathrm{\θ}...\left(7\right)$

i ₂, i ₁Behind subtracter 16, export and then obtain

i′＝i ₂′-i ₁′＝2sin2θ (8)

When θ is very little, i '=i ' ₂-i ' ₁=4 θ (9)

Wherein, I _AC1, I _DC1Be of ac and the DC quantity that obtains after the transmitted light path alternating current-direct current separates, I _AC2, I _DC2Be of ac and the DC quantity that obtains after the reflected light path alternating current-direct current separates.So just, can be in the hope of θ, again by and the comparison and the demarcation of normalized current obtain the size of the scale-up factor between θ and the tested electric current, thereby obtain the size of tested current i.Can find out thus if only can only obtain being proportional to the size of current of 2 θ with the monochromatic light road.Flow chart of data processing is referring to Fig. 6.

Claims (3)

1. double light path optical current sensing head, the light that light emitting diode sends becomes directional light through collimation GRIN Lens (2), directional light becomes linearly polarized light through the polarizer (4), linearly polarized light is incident to responsive unit (1), one week of the measured conductor propagation back that light centers in responsive unit (1) in the center pit is penetrated, and the plane of polarization of the linear polarized beam of incident is deflected under the effect of tested electric current; The modulated light that penetrates exports analyzer (5) to, the transmitted light of analyzer (5) exports coupling GRIN Lens (6) to, the first coupling GRIN Lens (6) focuses on coupling back, back by Optical Fiber Transmission to the first photodetector (10) with light beam, it is characterized in that: this sensing head also is provided with the second coupling GRIN Lens (6 '), be used to receive the reflected light of analyzer (5), the second coupling GRIN Lens (6 ') focuses on coupling back, back by Optical Fiber Transmission to the second photodetector (9) with light beam.

2, sensing head according to claim 1 is characterized in that: be provided with the one 90 ° of corner prism (3) between the collimation lens (2) and the polarizer (4), change the travel path of light.

3, sensing head according to claim 1 and 2 is characterized in that: be provided with the 2 90 ° of corner prism (3 ') between the analyzer (5) and the first coupling GRIN Lens (6), change the travel path of light.

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