CN201281724Y - Optical current sensor - Google Patents

Abstract

The utility model discloses an optical current sensor pertaining to the field of measuring technique for solving a problem of high-voltage current measurement. The optical current sensor consists of a current sensing unit and an optical current processing unit, the current sensing unit comprises two current sensing heads, the magneto-optic elements of the two current sensing units are thin disc type are symmetrically distributed on the two sides of a through-flow conductor, light-through directions of the two current sensing heads are parallel and are vertical to the through-flow conductor, the two current sensing heads have different materials and specific value of Verdet constant and temperature have a monotonic functional relation. Effect of temperature on Verdet constant can be compensated without introducing an outer portion standard reference source, the optical current sensor not only has long-term running stability and high measuring accuracy but also has small volume and simple process and is suitable for bulk production.

Description

A kind of optical current sensor

Technical field

The utility model relates to a kind of optical sensor that is used to measure the electric system high-voltage great-current, belongs to field of measuring technique.

Background technology

Optical current sensor (OCT) is the desirable device that high-voltage great-current is measured.From the sixties in 20th century, people's optical current sensor that just begins one's study.Power industry is generally adopted Faraday magneto-optic effect principle with optical current sensor.Through 30 years of researches, obtained remarkable progress, the report of multiple model machine linked network trial run is arranged both at home and abroad in succession.But up to the present, the steady state measurement precision of optical current sensor long-time running but still can not reach the measuring requirement of electric system, and its main cause is that the performance of sensor is subject to the influence that external environment factor (as: temperature) changes.

China Patent No. CN 1523618 has provided a kind of technical scheme of photoelectric current inductor, and it adopts the method for introducing permanent magnet and reference path, and compensation temperature is to measuring the influence of sensitive element in the light path.Can eliminate Temperature Influence on this theoretical method, but being accuracy of measurement, the weak point in the practicality depends on the stability of permanent magnet long-time running, permanent magnet and reference path are needed strict electromagnetic screen, very high to the coherence request of reference channel and measurement passage.This photoelectric current inductor is through after the long-time running, and inconsistent variation can take place the optical device parameter of two light paths of two passage and each passage, and this will produce the influence that can not be ignored to accuracy of measurement.

Summary of the invention

The purpose of this utility model is to overcome the deficiencies in the prior art, a kind of optical current sensor with long-time running stability and high measurement accuracy is provided.

The alleged problem of the utility model realizes with following technical proposals:

A kind of optical current sensor, form by current sensing unit and photoelectricity processing unit, described current sensing unit comprises two current sensing heads, and first current sensing head is made up of the first input collimating apparatus, first polarizer, first magneto-optic element, first analyzer, the first parallel component output collimator and the first vertical component output collimator that distribute successively along optical path direction; Second current sensing head is made up of the second input collimating apparatus, second polarizer, second magneto-optic element, second analyzer, the second parallel component output collimator and the second vertical component output collimator that distribute successively along optical path direction; The input collimating apparatus of each current sensing head connects light source, and output collimator connects the input end of photoelectricity processing unit through optical fiber, optical cable; The magneto-optic element of described two current sensing heads is symmetrically distributed in the both sides of through-flow conductor, and their optical direction is parallel to each other and is perpendicular with through-flow conductor, the two material difference, and have dull funtcional relationship between the ratio of Verdet constant and the temperature.

Above-mentioned optical current sensor, the magneto-optic element of described current sensing head are laminar, and its logical light length is less than 1mm.

Above-mentioned optical current sensor, the Verdet constant of the magneto-optic element of described current sensing head is greater than 10 ^-3Rad/A.

The utility model adopts the double-current sensing head be symmetrically distributed in through-flow conductor both sides that high-tension current is measured, and by the relation between sensing no-load voltage ratio and the temperature factor is accurately demarcated, but the real-Time Compensation temperature is to the influence of Verdet constant; The magneto-optic element of current sensing head adopts the sheet type structure, effectively reduces linear birefrigence in the material to the influence of measurement result; Adopt the magneto-optic element of high Verdet constant, can improve the sensitivity of measurement.But the utility model do not need to introduce the external perimysium reference reference source just compensation temperature the influence of Verdet constant is not only had long-time running stability and high measurement accuracy, and volume little, be easy to processing, be fit to batch process.

Description of drawings

Below in conjunction with accompanying drawing the utility model is further specified.

Fig. 1 is a structural representation of the present utility model;

Fig. 2 is the structural drawing of current sensing head;

Fig. 3 is the principle assumption diagram of low-pressure side photoelectricity processing unit;

Fig. 4 is the linearity calibration process figure of optical current sensor in the present embodiment;

Fig. 5 is the temperature compensation curve calibration process figure of optical current sensor in the present embodiment;

Fig. 6 is the real-time measurement temperature compensation procedure chart of optical current sensor in the present embodiment.

Each label is among the figure: 1, through-flow conductor, 2, current sensing unit, 3, first current sensing head, 4, second current sensing head, 5, fibre bundle, 6, insulator, 7, base, 8, the joints of optical fibre, 9, optical cable, 10, the photoelectricity processing unit, 11, the first input collimating apparatus, 12, first polarizer, 13, first magneto-optic element, 14, first analyzer, 15, the first parallel component output collimator, 16, the first vertical component output collimator, 17, the second input collimating apparatus, 18, second polarizer, 19, second magneto-optic element, 20, second analyzer, 21, the second parallel component output collimator, 22, the second vertical component output collimator.

Used symbol: K in the literary composition ₁(T), the first current sensing head sensing no-load voltage ratio, K ₂(T), the second current sensing head sensing no-load voltage ratio, P ₀₁, P ₀₂, the input light intensity, P ₁₁, first current sensing head parallel component output light, P ₂₁, second current sensing head parallel component output light, u ₁₁, P ₁₁The voltage signal of output after opto-electronic conversion and processing, u ₂₁, P ₂₁The voltage signal of output after opto-electronic conversion and processing, P ₁₂, first current sensing head vertical component output light, P ₂₂, second current sensing head vertical component output light, u ₁₂, P ₁₂The voltage signal of output after opto-electronic conversion and processing, u ₂₂, P ₂₂The voltage signal of output after opto-electronic conversion and processing, q (T), temperature factor, V ₁(T), the first magneto-optic element Verdet constant, V ₂(T), the second magneto-optic element Verdet constant, l ₁, first magneto-optic element logical light length, l ₂, second magneto-optic element logical light length, i, tested electric current, P ₀₁, the input light intensity, θ ₁, the first magneto-optic element faraday rotation angle, θ ₂, the second magneto-optic element faraday rotation angle, δ ₁, linear birefrigence, T, temperature, μ ₀, permeability of vacuum, the spacing at h, current sensing head and Ampereconductors center, the magnetic induction density that B, h place current i produce, the magnetic field intensity of H, the generation of h place current i, R ₁, the first current sensing head parallel component sensing passage conversion coefficient, R ₂, the second current sensing head parallel component sensing passage conversion coefficient, R ₁', the conversion coefficient of the first current sensing head vertical component sensing passage, R ₂', the conversion coefficient of the second current sensing head vertical component sensing passage, m, degree of modulation, i _b, electric current standard value.

Embodiment

Two magneto-optic elements, 13, the 19 material differences of the utility model sensing unit 2 (material is identical just can't temperature compensation, and temperature factor is with null(NUL)) are sheet type, have high Verdet constant (in order to improve measurement sensitivity, this is very important for precision); Select two magneto-optic elements, 13,19 materials simultaneously, make to have dull funtcional relationship between the ratio of two Verdet constants and the temperature; Temperature compensation comprises the following steps:

1, in the laboratory canonical measure passage and the series connection of the optical current sensor that the utility model proposes are inserted same current return, the standard value i of electric current is provided by the canonical measure passage _b

2, calculate the sensing no-load voltage ratio of two sensing passages

$K_1\left(T\right)=i_b*\frac{u_{11}+u_{12}}{u_{11}-u_{12}}$

$K_2\left(T\right)=i_b*\frac{u_{21}+u_{22}}{u_{22}-u_{21}}$

u ₁₁, u ₂₁Be respectively two current sensing head parallel component output light P ₁₁, P ₂₁The voltage signal of output after opto-electronic conversion and processing;

u ₁₂, u ₂₂Be respectively two current sensing head vertical component output light P ₁₂, P ₂₂The voltage signal of output after opto-electronic conversion and processing.

3, accounting temperature factor q (T)=K ₁(T)/K ₂(T).

Temperature information and two magneto-optic element 13,19 Verdet constant V of q (T) reflection sensing unit ₁(T), V ₂(T) pass is q (T)=V ₂(T) * l ₂/ (V ₁(T) * l ₁), l ₁, l ₂Be respectively the logical light length of magneto-optic element 13,19, when the two is equal, two magneto-optic element 13,19 Verdet constant V ₁(T), V ₂(T) ratio is q (T).

4, the sensing unit 2 of the optical current sensor that the utility model proposes is put into temperature control box, according to electronic current mutual inductor international standard IEC60044-8 and electronic mutual inductor national standard, optical current sensor is applied the temperature cycles of intensification-cooling-intensification, in the laboratory to K ₁(T)--q (T) and K ₂(T)--q (T) demarcates.

Calculate when 5, measuring in real time $q\left(T\right)=\frac{u_{11}+u_{12}}{u_{11}-u_{12}}*\frac{u_{22}-u_{21}}{u_{22}+u_{21}},$ By calibration curve K ₁(T)--q (T) and K ₂(T)--q (T) provides actual no-load voltage ratio K ₁(T), K ₂(T), calculate tested electric current

$i=K_1\left(T\right)*\frac{u_{11}-u_{12}}{u_{11}+u_{12}}$ Or $i=K_2\left(T\right)*\frac{u_{22}-u_{21}}{u_{22}+u_{21}}$

Or the two is carried out digital averaging can further improve measuring accuracy

$i=\frac{1}{2}*(K_1\left(T\right)*\frac{u_{11}-u_{12}}{u_{11}+u_{12}}+K_2\left(T\right)*\frac{u_{22}-u_{21}}{u_{22}+u_{21}})$

Because the magneto-optic element in the sensing unit is a sheet type, the linear birefrigence in the material can be ignored, and can utilize the influence of calibrating method compensation temperature described in the utility model to Verdet constant.

Be the influence of explanation linear birefrigence, suppose that magneto-optic element 13 is strip, its logical light length is greater than the diameter of through-flow conductor 1, and when considering bigger linear birefrigence, it is output as

$P_{11}=\frac{P_{01}}{2}(1+2{\mathrm{\θ}}_1\frac{\sin {\mathrm{\δ}}_1}{{\mathrm{\δ}}_1})$

$P_{12}=\frac{P_{01}}{2}(1-2{\mathrm{\θ}}_1\frac{\sin {\mathrm{\δ}}_1}{{\mathrm{\δ}}_1})$

P ₁₁, P ₁₂Be respectively the output intensity of parallel component and vertical component; P ₀₁Be the input light intensity; θ ₁Be the faraday's rotation angle that is directly proportional with electric current; δ ₁Be linear birefrigence.

The existence of linear birefrigence reduces sensing sensitivity as can be seen, brings than mistake.Linear birefrigence owing to magneto-optic element be heated or cooling procedure in the internal stress skewness cause that magneto-optic element is the poor conductor of temperature, material produces the temperature difference along optical path direction and causes the internal stress skewness in temperature changing process.Linear birefrigence has uncertainty, is difficult to carry out calibration compensation.

Because linear birefrigence is directly proportional with the length of material along optical path direction, so the sheet type material that the utility model proposes (length＜1mm) can regard a space infinitesimal as, can ignore by linear birefrigence.For guaranteeing sensitivity, the magneto-optic element of selecting high Verdet constant is (generally greater than 10 ^-3Rad/A).

Ignore the influence of linear birefrigence, temperature mainly is to cause that magneto-optic element Field constant changes to the influence of the utility model current sensing head.Faraday's rotation angle of magneto-optic element is directly proportional with electric current:

${\mathrm{\&theta;}}_1=V_1\left(T\right){\mathrm{<figure-callout\; id="1"\; label="Bl"\; filenames="Y200820105641E00152.png,Y200820105641E00153.png"\; state="\{\{state\}\}">Bl</figure-callout>}}_1=V_1\left(T\right){\mathrm{\&mu;}}_0{\mathrm{<figure-callout\; id="1"\; label="Hl"\; filenames="Y200820105641E00152.png,Y200820105641E00153.png"\; state="\{\{state\}\}">Hl</figure-callout>}}_1=V_1\left(T\right){\mathrm{\&mu;}}_0\frac{i}{2\mathrm{\&pi;<figure-callout\; id="1"\; label="h\; l"\; filenames="Y200820105641E00152.png,Y200820105641E00153.png"\; state="\{\{state\}\}">h</figure-callout>}}{l}_{}{}_1$

${\mathrm{\&theta;}}_2=V_2\left(T\right)(-B){\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">l</figure-callout>}}_2=V_2\left(T\right){\mathrm{\&mu;}}_0{(-H)\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">l</figure-callout>}}_2={-V}_2\left(T\right){\mathrm{\&mu;}}_0\frac{i}{2\mathrm{\&pi;<figure-callout\; id="2"\; label="h\; l"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">h</figure-callout>}}{l}_{}{}_2$

In the formula, V ₁(T), V ₂(T) being the Verdet constant of magneto-optic element, is the function of temperature T; I is an electric current to be measured; μ ₀Be permeability of vacuum; H is the spacing at current sensing head 3,4 and Ampereconductors 1 center; B and H are magnetic induction density and the magnetic field intensity that h place current i produces; Negative sign represents direction opposite.

Verdet constant varies with temperature has definite relation, and the chamber is demarcated and compensated by experiment.

The utility model sensing unit volume is little, be easy to processing, be fit to produce in batches, and the double-current sensing head is standby each other, the reliability height.Can adopt the digital averaging method to improve measuring accuracy.

The utility model can carry out the inconsistent variation of sensing passage parameter and proofread and correct in real time.

When each current sensing head parallel component and vertical component sensing passage parameter are inconsistent, current sensing head parallel component output light P ₁₁, P ₂₁The voltage signal u of output after opto-electronic conversion and processing ₁₁, u ₂₁, vertical component output light P ₁₂, P ₂₂The voltage signal u of output after opto-electronic conversion and processing ₁₂', u ₂₂' be respectively:

$u_{11}=\frac{R_1{P}_{01}}{2}(1+\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">sin</figure-callout>}2{\mathrm{\&theta;}}_1)$

$u_{12}\&prime;=\frac{{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="Y200820105641E00152.png,Y200820105641E00153.png"\; state="\{\{state\}\}">R</figure-callout>}}_1\&prime;P_{01}}{2}(1-\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">sin</figure-callout>}2{\mathrm{\&theta;}}_1)$

$u_{21}=\frac{R_2{P}_{02}}{2}(1+\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">sin</figure-callout>}2{\mathrm{\&theta;}}_2)$

$u_{22}\&prime;=\frac{{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">R</figure-callout>}}_2\&prime;P_{02}}{2}(1-\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">sin</figure-callout>}2{\mathrm{\&theta;}}_2)$

R ₁, R ₂, R ₁', R ₂' be respectively the conversion coefficient of current sensing head 3,4 parallel components and vertical component sensing passage, relevant with the coupling situation of photoelectric detector parameter and each optical device.

During normal steady-state operation, θ ₁, θ ₂The variation of reflection alternating current i, thus in above four formulas the 2nd be AC compounent, the 1st is DC component, is made as u respectively _11DC, u _12DC', u _21DC, u _22DC'.Order

$u_{12}=\frac{u_{11\mathrm{DC}}}{u_{12\mathrm{DC}}^{\&prime;}}\&CenterDot;u_{12}\&prime;$

$u_{22}=\frac{u_{21\mathrm{DC}}}{u_{22\mathrm{DC}}^{\&prime;}}\&CenterDot;u_{22}\&prime;$

Current sensing head parallel component u then ₁₁, u ₂₁Respectively with vertical component u ₁₂, u ₂₂Have identical sensing passage conversion coefficient, be called passage and have consistance, be i.e. passage trim.Just can remove with computing after the passage trim and find the solution electric current according to difference: $i=K_1\left(T\right)*\frac{u_{11}-u_{12}}{u_{11}+u_{12}}$ Or $i=K_2\left(T\right)*\frac{u_{22}-u_{21}}{u_{22}+u_{21}}$ Or $i=\frac{1}{2}*(K_1\left(T\right)*\frac{u_{11}-u_{12}}{u_{11}+u_{12}}+K_2\left(T\right)*\frac{u_{22}-u_{21}}{u_{22}+u_{21}}).$ Difference is removed and computing is used to eliminate the influence of light source intensity fluctuation, the DC component of electric current in the time of simultaneously again can demodulation transient state fault.

The utility model can also reduce the adjacent electromagnetic interference effect of current conductor when the big electric current of transient state fault that communicate.

The distance of current sensing head and the adjacent current conductor that communicates equates that suffered electromagnetic interference (EMI) can be regarded common mode component as, adopts and asks difference operation to suppress.

Referring to Fig. 1, the optical current sensor system that the utility model proposes comprises: high voltage side current sensing unit 2, low-pressure side photoelectricity processing unit 10, fibre bundle 5 and optical cable 9.Fibre bundle 5 places insulator 6, and by the joints of optical fibre in the base 78 and optical cable 9 couplings, fibre bundle 5 and optical cable 9 are used for transmitting optical signal.Through-flow conductor 1 links to each other with tested Ampereconductors during use, and through-flow conductor 1 is a copper rod in the utility model.Sensing unit 2 is fixed on the through-flow conductor 1 by insulating bodies.On high-tension side two current sensing heads, 3,4 common formation sensing units 2.Low-pressure side photoelectricity processing unit 10 is finished opto-electronic conversion, current signal is separated the mediation temperature compensation algorithm.

Referring to Fig. 2, be distributed with input collimating apparatus 11 or 17, the polarizer 12 or 18, magneto-optic element 13 or 19, analyzer 14 or 20, parallel component output collimator 15 or 21, vertical component output collimator 16 or 22 successively respectively along optical path direction in two current sensing heads; Two magneto-optic elements 13 are different with 19 materials, and (material is identical just can't temperature compensation, temperature factor is with null(NUL)), be designed to sheet type to suppress the influence of linear birefrigence, selection has high Verdet constant in the hope of obtaining high sensitivity, be symmetrically distributed in the both sides of through-flow conductor 1, the two optical direction is parallel to each other and is perpendicular with through-flow conductor 1; Select two magneto-optic elements to make and have dull funtcional relationship between the ratio of two Verdet constants and the temperature, so that carry out temperature compensation.Magneto-optic element can adopt garnet crystal (because of it has high Verdet constant), the cross section can be square also can be circular.Magneto-optic element can be selected rare earth iron garnet class material, as: yttrium iron garnet crystal Y ₃Fe ₅O ₁₂(YIG) and the yttrium iron garnet crystal of various doping, comprising: bismuth doping YIG (Bi:YIG), gadolinium doping YIG (Gd:YIG), codope YIG (BiGd:YIG) etc.Magneto-optic element 13 is YIG (a yttrium iron garnet crystal) in the present embodiment, and sectional area is 1mm ²Square, logical light length is 0.5mm; Magneto-optic element 19 is Gd:YIG (the yttrium iron garnet crystal that gadolinium mixes), and sectional area is 1mm ²Square, logical light length is 0.1mm.

Enter the input light P of current sensing head 3,4 by fibre bundle 5 ₀₁, P ₀₂Become directional light through input collimating apparatus 11,17, the polarizer 12,18 becomes linearly polarized light with directional light, according to the Faraday magnetooptical effect principle, under the action of a magnetic field that through-flow conductor 1 produces, linearly polarized light will rotate by magneto-optic element 13,19 its plane of polarizations of back, and the angle of rotation is called faraday's rotation angle θ ₁, θ ₂, proportional with electric current:

${\mathrm{\&theta;}}_1=V_1\left(T\right){\mathrm{<figure-callout\; id="1"\; label="Bl"\; filenames="Y200820105641E00152.png,Y200820105641E00153.png"\; state="\{\{state\}\}">Bl</figure-callout>}}_1=V_1\left(T\right){\mathrm{\&mu;}}_0{\mathrm{<figure-callout\; id="1"\; label="Hl"\; filenames="Y200820105641E00152.png,Y200820105641E00153.png"\; state="\{\{state\}\}">Hl</figure-callout>}}_1=V_1\left(T\right){\mathrm{\&mu;}}_0\frac{\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">i</figure-callout>}}{2\mathrm{\&pi;<figure-callout\; id="1"\; label="h\; l"\; filenames="Y200820105641E00152.png,Y200820105641E00153.png"\; state="\{\{state\}\}">h</figure-callout>}}{l}_{}{}_1$

${\mathrm{\&theta;}}_2=V_2\left(T\right)(-B){\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">l</figure-callout>}}_2=V_2\left(T\right){\mathrm{\&mu;}}_0{(-H)\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">l</figure-callout>}}_2={-V}_2\left(T\right){\mathrm{\&mu;}}_0\frac{\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">i</figure-callout>}}{2\mathrm{\&pi;<figure-callout\; id="2"\; label="h\; l"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">h</figure-callout>}}{l}_{}{}_2.$

Angle between two light transmission shafts of analyzer 14,20 and the light transmission shaft of the polarizer 12,18 is respectively ± and 45 °, angle value is converted into parallel component output intensity P ₁₁, P ₂₁With vertical component output intensity P ₁₂, P ₂₂:

$P_{11}=\frac{P_{01}}{2}(1+\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">sin</figure-callout>}2{\mathrm{\&theta;}}_1)$

$P_{12}=\frac{P_{01}}{2}(1-\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">sin</figure-callout>}2{\mathrm{\&theta;}}_1)$

$P_{21}=\frac{P_{02}}{2}(1+\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">sin</figure-callout>}2{\mathrm{\&theta;}}_2)$

$P_{22}=\frac{P_{02}}{2}(1-\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">sin</figure-callout>}2{\mathrm{\&theta;}}_2)$

P ₁₁, P ₂₁And P ₁₂, P ₂₂Be coupled into fibre bundle 5 through parallel component output collimator 15,21 and vertical component output collimator 16,22.

Referring to Fig. 3, low-pressure side photoelectricity processing unit comprises light source and signal processing.Light source employing wavelength is the laser instrument (LD) of 1550nm in the present embodiment, and light source driving circuit is that constant current output is to reduce the fluctuation of light intensity.Signal processing comprises four photoelectric detectors, four preposition amplifications and filtering circuit and digital processing system.Digital processing system is made of microprocessor, A/D modular converter, memory module, display module and communication module.

The light process optical cable 9 that light source sends is sent to the joints of optical fibre 8 of base 7, is sent to sensing unit 2 by two uplink optical fibers in the fibre bundle 5 respectively after beam split, becomes the input light P of current sensing head 3,4 ₀₁, P ₀₂

Four road light signal P by sensing unit 2 outputs ₁₁, P ₂₁And P ₁₂, P ₂₂Send four photoelectric detectors to through fibre bundle 5 and optical cable 9, photoelectric detector is converted to light signal and the proportional electric signal of light intensity, passes through output voltage signal u after preposition amplification and the filtering again ₁₁, u ₂₁And u ₁₂, u ₂₂Digital processing system is with u ₁₁, u ₂₁And u ₁₂, u ₂₂Carry out A/D conversion, separate the mediation temperature compensation algorithm by microprocessor to what digital signal corresponding was carried out current information, and finish storage, demonstration and the communication function of information.Microprocessor can adopt dsp chip, also can adopt industrial computer.

Referring to Fig. 4, optical current sensor was finished the laboratory staking-out work before delivery test.Concrete demarcation content comprises that the linearity is demarcated and temperature compensation curve is demarcated.

Regulate high-current signal generator, electric current to be measured is changed in 5%～120% scope of ratings, canonical measure passage and optical current sensor synchro measure carry out the linearity to optical current sensor and demarcate.Concrete steps are as follows:

(1) no-load voltage ratio that multiply by standard channel by the output of canonical measure passage is calculated the standard value i of electric current _b

Each parts of standard channel need be through strict tracing to the source, and the precision of standard channel must satisfy the slight error principle, promptly compares and can ignore with the measuring error of being measured passage by verification, and then the measurement result of standard channel can be used as " true value " and treats.In the present embodiment, the whole measuring error of standard channel is not more than by 1/5th of the measuring error of verification passage.

(2) by the degree of modulation m of signal processing unit calculating optical current sensor:

Each current sensing head as the angle between the light transmission shaft of two light transmission shafts of the polarizing prism of analyzer and the polarizer be respectively ± 45 °, the output signal that is recorded current sensing head 3,4 by signal processing unit is respectively (u ₁₁, u ₁₂) and (u ₂₁, u ₂₂), try to achieve degree of modulation m:

${\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="Y200820105641E00152.png,Y200820105641E00153.png"\; state="\{\{state\}\}">m</figure-callout>}}_1=\frac{u_{11}-u_{12}}{u_{11}+u_{12}}$

${\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="Y200820105641E00131.png,Y200820105641E00152.png"\; state="\{\{state\}\}">m</figure-callout>}}_2=\frac{u_{22}-u_{21}}{u_{21}+u_{22}}$

(3) no-load voltage ratio of each sensing passage of optical current sensor is:

K ₁(T)＝i _b/m ₁

K ₂(T)＝i _b/m ₂

Referring to Fig. 5, the sensing unit 2 of optical current sensor is put into temperature control box, according to electronic current mutual inductor international standard IEC60044-8 and electronic mutual inductor national standard, optical current sensor is applied the temperature cycles of intensification-cooling-intensification, optical current sensor is carried out temperature compensation curve demarcate.Concrete steps are as follows:

(1), calculates the no-load voltage ratio K of sensing passage for each step among each temperature spot repetition Fig. 4 that stipulates in the standard ₁(T) and K ₂(T).

(2) accounting temperature factor q (T)=K ₁(T)/K ₂(T).

(3) in the laboratory to K ₁(T)--q (T) and K ₂(T)--q (T) demarcates.

Referring to Fig. 6, (1) is respectively (u by the output signal that signal processing unit records current sensing head 3,4 ₁₁, u ₁₂) and (u ₂₁, u ₂₂), calculate in real time $q\left(T\right)=\frac{u_{11}+u_{12}}{u_{11}-u_{12}}*\frac{u_{22}-u_{21}}{u_{22}+u_{21}}.$

(2) by calibration curve K ₁(T)--q (T) and K ₂(T)--q (T) provides actual no-load voltage ratio K ₁(T), K ₂(T).

(3) calculate tested electric current

$i=K_1\left(T\right)*\frac{u_{11}-u_{12}}{u_{11}+u_{12}}$ Or $i=K_2\left(T\right)*\frac{u_{22}-u_{21}}{u_{22}+u_{21}}$

Or $i=\frac{1}{2}*(K_1\left(T\right)*\frac{u_{11}-u_{12}}{u_{11}+u_{12}}+K_2\left(T\right)*\frac{u_{22}-u_{21}}{u_{22}+u_{21}}).$

Claims (3)

1, a kind of optical current sensor, it is characterized in that, it is made up of current sensing unit (2) and photoelectricity processing unit (10), described current sensing unit (2) comprises two current sensing heads, wherein, first current sensing head (3) is made up of the first input collimating apparatus (11), first polarizer (12), first magneto-optic element (13), first analyzer (14), the first parallel component output collimator (15) and the first vertical component output collimator (16) that distribute successively along optical path direction; Second current sensing head (4) is made up of the second input collimating apparatus (17), second polarizer (18), second magneto-optic element (19), second analyzer (20), the second parallel component output collimator (21) and the second vertical component output collimator (22) that distribute successively along optical path direction; The input collimating apparatus of each current sensing head connects light source, and output collimator connects the input end of photoelectricity processing unit (10) through optical fiber, optical cable; The magneto-optic element of described two current sensing heads is symmetrically distributed in the both sides of through-flow conductor (1), their optical direction is parallel to each other and is perpendicular with through-flow conductor (1), both material differences, and have dull funtcional relationship between ratio of both Verdet constants and the temperature.

According to the described optical current sensor of claim 1, it is characterized in that 2, the magneto-optic element of described current sensing head is laminar, its logical light length is less than 1mm.

According to the described optical current sensor of claim 1, it is characterized in that 3, the Verdet constant of the magneto-optic element of described current sensing head is greater than 10 ^-3Rad/A.

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