CN104076180A - Dual probe-based calibration-free optical current sensor and method - Google Patents

Abstract

The invention discloses a dual probe-based calibration-free optical current sensor and a method. The sensor is composed of two magneto optical current sensing heads, a sensing head fixing support and a measuring unit. According to the method, as the sensing head fixing support is adopted, the relative distance of the two sensing head can be ensured to be fixed and is not influenced by temperature, stress and other environmental disturbance. The measuring unit receives output light intensity of the two magneto optical current sensing heads and the output light intensity is converted into electrical signals and an output measurement current value is calculated. Through demodulating the measurement values of the sensing heads, influences of the distance in relative to a cable lead on the measuring result in the case of installation can be directly eliminated, and the difficulty that power needs to be on for calibration in the case of onsite installation of the sensor can be avoided.

Description

A kind of optical current sensor and method of exempting from calibration based on two probes

Technical field

The present invention relates to a kind of optical current sensor and method of exempting from calibration based on two probes, belong to the technical field of electric measurement, calibration.

Background technology

Magneto-optic current transducer is from the many decades that begins one's study till now, and many manufacturers both domestic and external have all released product separately.Magneto-optic current transducer compared to conventional current sensor have advantages of safe, that precision is high, measurement range is wide etc. is numerous, but do not promoted fully in actual applications so far.Reason is current optical current sensor, is subject to the impact of the factors such as temperature, time, position, external magnetic field, causes sensor degree of accuracy to decline.Especially be subject to wire to be measured to the impact of sensor distance, for different conductor, different environment for use, all need before use sensor to carry out independent calibration and situ calibration, this brings huge trouble for on-the-spot installment and debugging work.In use, also need regularly to calibrate maintenance, brought difficulty and inconvenient to the application of sensor.In industry, existing self calibration technology is used complicated control circuit to carry out error correction more at present, also brought certain restriction, and calibration result is unsatisfactory when increasing cost for sensor service condition.

Correlation technique 1: use ^[1]current sensor field calibration instrument carries out error-tested.

As shown in Figure 1, electric current field calibration instrument is the current signal detecting in electrified wire 1 by Hall element or other current sensor 2, and the signal of detection connects amplifier 3 amplification outputs and obtains current measurement value by sample circuit 4.

By electric current field calibration instrument be calibrated current sensor and hang on same busbar, the same time is read two indicating values, avoids the error that the mistiming causes.By the difference that shows to being reached service precision by school sensor field adjustable.

With electric current field calibration instrument, carry out calibration current sensor, higher to the accuracy requirement of prover.By prover be calibrated sensor access wire and need to disconnect electrical network, regularly detect cumbersome.

Correlation technique 2: ^[2]the online Hall current sensor that detects, calibrates.

Chinese patent 200910241742.2 provides a kind of automatic calibration and has revised the method for Hall current sensor error, comprises measurement Hall current sensor; Be wrapped in and measure with the assisted calibration coil on Hall current sensor, be in series with the output of controllable current source and the input circuit of assisted calibration Hall current sensor; The control signal of controllable current source is connected to the control output end of measurement and control unit.

Electric current in assisted calibration coil and measurement have a fixing proportionate relationship with Hall current sensor output current.Measure with Hall current sensor with assisted calibration Hall current sensor under identical environment, by comparing assisted calibration Hall current sensor, measure the current value and the output current value of measuring with Hall current sensor of assisted calibration coil gained, can calculate the measuring error of Hall current sensor.Measurement is carried out to corresponding correction with Hall current sensor and can realize automatic calibration.

The online Hall current sensor volume that detects, calibrates is large, control circuit is comparatively complicated.

Correlation technique 3: magneto-optic current transducer.

When light beam passes through magneto-optical crystal, under the impact in magnetic field, due to Faraday effect, the polarization state of light field can rotate.The angle of rotation is relevant to the length of the Verdet constant of magneto-optical crystal, the size in magnetic field and angle and magneto-optical crystal.

Light beam is obtained to linearly polarized light by the polarizer; By magneto-optical crystal, under the impact in magnetic field, light beam polarization direction rotates again; With analyzer, detect polarization direction rotation angle, can measure the size in magnetic field.Because the magnetic effect of electric current can produce magnetic field, by measuring the large I in magnetic field, calculate corresponding size of current.

[1]. the patent No. 200910272835.1 DC high-current sensor field calibration instrument;

[2]. 200910241742.2 1 kinds of online detection and calibration method for Hall current sensor of the patent No..

Magneto-optic current transducer has good electric insulating quality than traditional current sensor, be not subject to the impact of electromagnetic radiation, antijamming capability is strong, and the plurality of advantages such as frequency response is fast, but based on Faraday effect, the measured value of magneto-optic current transducer and sensor are to the Range-based of electrified wire, and therefore, the change in location that in the individual difference of measure traverse line and installation difference and long-time use procedure, external environment causes can be brought measurement difference.

Summary of the invention

The present invention seeks to provides a kind of magneto-optic current transducer and method that avoids adjusting the distance and calibrate for the problem and blemish in background technology.

The present invention for achieving the above object, adopts following technical scheme:

A kind of optical current sensor of exempting from calibration based on two probes of the present invention, by two Magnetooptic current sensing heads, sensing head fixed support and measuring unit, formed, two Magnetooptic current sensing heads are arranged at respectively sensing head fixed support two ends, the output terminal of two Magnetooptic current sensing heads connects respectively the input end of measuring unit, and the measured value of measuring unit output and two Magnetooptic current sensing heads are to the range-independence of current carrying conductor.

Described Magnetooptic current sensing head is connected in series successively the polarizer, magneto-optic memory technique, analyzer, optical fiber collimator and conduction optical fiber by light source and forms.

The light that described light source sends is polarization irrelevant light;

The angular separation that thoroughly shakes of described polarizer starting of oscillation direction and analyzer is 45 °.

It is a kind of that based on two probes, to exempt from the detection method of optical current sensor of calibration as follows:

Near being placed in to current carrying conductor, Magnetooptic current sensing head make the magneto-optic memory technique optical direction of Magnetooptic current sensing head vertical with direction of current; The light that light source sends becomes polarized light after the polarizer; When light field continues to propagate through magneto-optic memory technique, because Faraday effect polarization direction rotates, the anglec of rotation and polarizer starting of oscillation angular separation are:

$\mathrm{\θ}=\frac{{\mathrm{\μ}}_0\mathrm{VLI}}{2\mathrm{\πr}}---\left(1\right)$

μ wherein ₀for permeability of vacuum, V is magneto-optic memory technique Field constant, and L is the distance that light is propagated in magneto-optic memory technique, and r is that magneto-optic memory technique is to the distance of current carrying conductor; Light field continues to propagate output intensity after analyzer:

P wherein ₀for the output intensity of light source, by output intensity, calculated the size of light field faraday rotation angle B.The Field constant corresponding to the light with 632.8nm wavelength of conventional high Field constant material MR4 magneto-optic glass is 110.5rad/Tm, in magneto-optic memory technique length L, be 1mm, magneto-optic memory technique is under the condition of 1cm to current carrying conductor distance, huge current flow for 10kA, light field faraday's rotation angle θ is only 0.0221rad, in practicality, is approximately the B Size Error now calculating is 0.0326%; In current carrying conductor, the relational expression of size of current and output intensity is: two Magnetooptic current sensing heads are fixed by fixed support, and its spacing is d, measures to such an extent that output intensity is respectively P ₁, P ₂, by formula (1), obtained:

$\left\{\begin{array}{c}{\mathrm{\θ}}_1=\frac{{\mathrm{\μ}}_0\mathrm{VLI}}{2{\mathrm{\πr}}_1}\\ {\mathrm{\θ}}_2=\frac{{\mathrm{\μ}}_0\mathrm{VLI}}{{2\mathrm{\πr}}_2}\\ r_2-r_1=d\end{array}\right.$

And then obtain size of current in wire and be:

$I=\frac{{2\mathrm{\π\θ}}_1{\mathrm{\θ}}_{2}d}{{\mathrm{\μ}}_0\mathrm{VL}({\mathrm{\θ}}_1-{\mathrm{\θ}}_2)}---\left(3\right)$

By approximate formula $\left\{\begin{array}{c}{P}_1=\frac{1}{2}{P}_0(1-{2\mathrm{\θ}}_1)\\ P_2=\frac{1}{2}{P}_0(1-{2\mathrm{\θ}}_2)\end{array}\right.$ Substitution (2) Shi Ke get:

$I=\frac{\mathrm{\πd}(P_0-{2P}_1)(P_0-{2P}_2)}{{2\mathrm{\μ}}_0{\mathrm{VLP}}_0(P_2-P_1)}---\left(4\right)$

Measuring unit can be calculated size of current the output in current carrying conductor according to the input light intensity meter of two sensing heads thus.Now the measured value of size of current and two magneto-optical sensors are irrelevant to distance r1, the r2 of current carrying conductor.

The present invention is exactly the defect for the prior art of mentioning in background technology, apply for a kind of optical current sensor and method of exempting from calibration, this sensor has two sonde configurations, by the result of detection of two probes is done to difference computing, draw current value to be measured, measured value is insensitive to mounting distance, therefore can remove calibration process completely from.

The present invention uses Non-contact Magnetic photocurrent sensor, linked network convenience and strong interference immunity; By the computing of the measurement result of two sensing heads is obtained to current measurement value, measurement result and sensing head, to the range-independence of current carrying conductor, have been exempted the calibration of distance.In practicality is installed, sensor of the present invention is applicable to the current lead of various models, environment for use is required low, and fitting operation simply can reduce the impact on current measurement of change in location that temperature, vibrations etc. cause.

Accompanying drawing explanation

Fig. 1: electric current field calibration instrument structural representation;

Fig. 2: structural representation of the present invention;

Fig. 3: Magnetooptic current transducing head structure schematic diagram.

Embodiment

A kind of optical current sensor of exempting from calibration based on two probes of the present invention comprises two Magnetooptic current sensing heads, and two sensing head materials are identical with structure and be disposed at apart from the position that is loaded with tested current lead different distance; Sensing head fixed part, guarantees that the relative distance of two sensing heads is fixed, and is not subject to the impact of the environmental perturbations such as temperature, stress; Measuring unit, receive the output intensity of two Magnetooptic current sensing heads, be converted into electric signal and calculate output and measure current value, while installing by can directly eliminating the demodulation of two sensing head measured values, relative cable conductor, apart from the impact on measurement result, has avoided need to powering up when sensor is on-the-spot to be installed the difficulty of calibration.

Described Magnetooptic current sensing head is by light source, Output optical power, Wavelength stabilized and polarization irrelevant; The polarizer; Magneto-optic memory technique, has larger Verdet constant; Analyzer, transmission polarization direction and polarizer starting of oscillation angular separation are 45 °; Optical fiber collimator, can import to light signal in optical fiber and transmit.

Near being placed in to current carrying conductor, Magnetooptic current sensing head make magneto-optic memory technique optical direction vertical with direction of current.The light that light source sends becomes polarized light after the polarizer; When light field continues to propagate through magneto-optic memory technique, because Faraday effect polarization direction rotates, the anglec of rotation with polarizer starting of oscillation angular separation is also:

$\mathrm{\θ}=\frac{{\mathrm{\μ}}_0\mathrm{VLI}}{2\mathrm{\πr}}---\left(1\right)$

μ wherein ₀for permeability of vacuum, V is magneto-optic memory technique Field constant, and L is the distance that light is propagated in magneto-optic memory technique, and r is that magneto-optic memory technique is to the distance of current carrying conductor; Light field continues to propagate output intensity after analyzer

P wherein ₀for the output intensity of light source, therefore can by output intensity, be calculated the size of light field faraday rotation angle θ, in practicality, be approximately now, in current carrying conductor, the relational expression of size of current and output intensity is

Relational expression can be found out thus, when magneto-optic memory technique is different to the distance r of current lead, calculates the relational expression difference of size of current by light intensity.Therefore, when magneto-optic current transducer is installed at the scene, need to calibrate to cable under test energising, thereby accurately measure above formula middle distance r value.Can bring unnecessary trouble and difficulty in actual applications.So proposition improvement project of the present invention: by the introducing of two probes, realized installation of sensors and can use, the r value while installing without the scene of measuring, has avoided on-the-spot energising to calibrate this step completely.

In a kind of detection method of optical current sensor of exempting from calibration based on two probes of the present invention, two sensing heads are fixed by fixed support, and its spacing is that d measures to such an extent that output intensity is respectively P ₁, P ₂, by formula (1), can set up system of equations

$\left\{\begin{array}{c}{\mathrm{\θ}}_1=\frac{{\mathrm{\μ}}_0\mathrm{VLI}}{2{\mathrm{\πr}}_1}\\ {\mathrm{\θ}}_2=\frac{{\mathrm{\μ}}_0\mathrm{VLI}}{2{\mathrm{\πr}}_2}\\ r_2-r_1=d\end{array}\right.$

Separating this system of equations can obtain size of current in wire and be:

$I=\frac{{2\mathrm{\π\θ}}_1{\mathrm{\θ}}_{2}d}{{\mathrm{\μ}}_0\mathrm{VL}({\mathrm{\θ}}_1-{\mathrm{\θ}}_2)}---\left(3\right)$

By approximate formula $\left\{\begin{array}{c}{P}_1=\frac{1}{2}{P}_0(1-{2\mathrm{\θ}}_1)\\ P_2=\frac{1}{2}{P}_0(1-{2\mathrm{\θ}}_2)\end{array}\right.$ Substitution (2) Shi Ke get:

$I=\frac{\mathrm{\πd}(P_0-{2P}_1)(P_0-{2P}_2)}{{2\mathrm{\μ}}_0{\mathrm{VLP}}_0(P_2-P_1)}---\left(4\right)$

Formula thus, measuring unit can be calculated size of current the output in current carrying conductor according to the input light intensity meter of two sensing heads, and result of calculation and sensing head have nothing to do to distance r1 and the r2 of current carrying conductor.

Embodiment

As shown in Figure 2, the magneto-optic current transducer of automatic calibration distance of the present invention is respectively [5], [6] by two Magnetooptic current sensing heads, and fixed support [7] and measuring unit [8] form.

Fig. 3 is the structural representation of sensing head [5], [6], and magneto-optic sensing head [5], [6] are comprised of light source [9], the polarizer [10], magneto-optic memory technique [11], analyzer [12], optical fiber collimator [13] and conduction optical fiber [14].The light that light source [9] sends enters conducting light [14] through the polarizer [10], magneto-optic memory technique [11], analyzer [12] and optical fiber collimator [13] from one end, the other end of conduction optical fiber [14] is as the output terminal of sensing head [5], [6].

Sensor is placed near current carrying conductor [1], makes fixed support [7] point to current carrying conductor [1], and make the magneto-optic memory technique optical direction in sensing head [5], [6] vertical with current carrying conductor [1]; The output optical fibre of two sensing heads [5], [6] is connected with the input end of measuring unit [8].Measuring unit [8] is accepted the output intensity of sensing head [5], [6], by formula (4), calculates size of current the output in current carrying conductor [1].

The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, although the present invention is had been described in detail with reference to previous embodiment, for a person skilled in the art, its technical scheme that still can record aforementioned each embodiment is modified, or part technical characterictic is wherein equal to replacement.Within the spirit and principles in the present invention all, any modification of doing, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.

Claims (5)

1. based on two probes, exempt from the optical current sensor of calibrating for one kind, it is characterized in that being formed by two Magnetooptic current sensing heads, sensing head fixed support and measuring unit, two Magnetooptic current sensing heads are arranged at respectively sensing head fixed support two ends, the output terminal of two Magnetooptic current sensing heads connects respectively the input end of measuring unit, and the measured value of measuring unit output and two Magnetooptic current sensing heads are to the range-independence of current carrying conductor.

2. a kind of optical current sensor of exempting from calibration based on two probes according to claim 1, is characterized in that described Magnetooptic current sensing head is connected in series successively the polarizer, magneto-optic memory technique, analyzer, optical fiber collimator and conduction optical fiber by light source and forms.

According to claim 2 a kind of based on two probes exempt from calibration optical current sensor, it is characterized in that the light that described light source sends is polarization irrelevant light.

According to claim 2 a kind of based on two probes exempt from calibration optical current sensor, it is characterized in that the angular separation that thoroughly shakes of described polarizer starting of oscillation direction and analyzer is 45 °.

5. based on an a kind of detection method of exempting from the optical current sensor of calibration based on two probes described in claim 1, it is characterized in that described method is as follows:

Near being placed in to current carrying conductor, Magnetooptic current sensing head make the magneto-optic memory technique optical direction of Magnetooptic current sensing head vertical with direction of current; The light that light source sends becomes polarized light after the polarizer; When light field continues to propagate through magneto-optic memory technique, because Faraday effect polarization direction rotates, the anglec of rotation and polarizer starting of oscillation angular separation are:

$\mathrm{\θ}=\frac{{\mathrm{\μ}}_0\mathrm{VLI}}{2\mathrm{\πr}}---\left(1\right)$

μ wherein ₀for permeability of vacuum, V is magneto-optic memory technique Field constant, and L is the distance that light is propagated in magneto-optic memory technique, and r is that magneto-optic memory technique is to the distance of current carrying conductor; Light field continues to propagate output intensity after analyzer:

P wherein ₀for the output intensity of light source, by output intensity, calculated the size of light field faraday rotation angle θ, in practical application, be approximately now, in current carrying conductor, the relational expression of size of current and output intensity is:

Two Magnetooptic current sensing heads are fixed by fixed support, and its spacing is d, measures to such an extent that output intensity is respectively P ₁, P ₂, by formula (1), obtained:

$\left\{\begin{array}{c}{\mathrm{\θ}}_1=\frac{{\mathrm{\μ}}_0\mathrm{VLI}}{2{\mathrm{\πr}}_1}\\ {\mathrm{\θ}}_2=\frac{{\mathrm{\μ}}_0\mathrm{VLI}}{{2\mathrm{\πr}}_2}\\ r_2-r_1=d\end{array}\right.$

And then obtain size of current in wire and be:

$I=\frac{{2\mathrm{\π\θ}}_1{\mathrm{\θ}}_{2}d}{{\mathrm{\μ}}_0\mathrm{VL}({\mathrm{\θ}}_1-{\mathrm{\θ}}_2)}---\left(3\right)$

By approximate formula $\left\{\begin{array}{c}{P}_1=\frac{1}{2}{P}_0(1-{2\mathrm{\θ}}_1)\\ P_2=\frac{1}{2}{P}_0(1-{2\mathrm{\θ}}_2)\end{array}\right.$ Substitution (2) Shi Ke get:

$I=\frac{\mathrm{\πd}(P_0-{2P}_1)(P_0-{2P}_2)}{{2\mathrm{\μ}}_0{\mathrm{VLP}}_0(P_2-P_1)}---\left(4\right)$

Measuring unit is calculated size of current the output in current carrying conductor according to the input light intensity meter of two sensing heads thus.