CN100498347C - Three state polarization detection method for eliminating linear birefringence influence of optical current transformer - Google Patents

Abstract

This invention provides a kind of triple polarized detection method which can remove the linear birefringence influence in optic current transformer. It measures the light intensity in three direction of polarization of ellipse polarized light output by the optic current transformer, that is the data of the level polarized intensity, the uprightness polarized intensity and the 45 degree with the level direction polarized intensity, uses the triple measurement data calculates the phasic difference information between level polarized component and uprightness polarized component, separates and detect the Faraday effect and linear birefringence in real time. The triple ellipse polarized detection project of ellipse polarized light advances in this invention can realize that the measurement of the linear birefringence and the detected current be correct and in real time by using the Faraday magneto-optic effect optic current transformer, and it can be applied in more broad field of ellipse polarized light measurement.

Description

The three state polarization detection method of getting rid of optical current mutual inductor neutral line birefringence influence

(1) technical field

Inventing related is a kind of Data Detection and disposal route in the optical current mutual inductor, specifically gets rid of the Data Detection and the disposal route of linear birefrigence influence in the optical current mutual inductor of Faraday magnetooptical effect.

(2) background technology

The operating voltage of current power system increases day by day, and strong day by day to the demand of high precision, wide range, safe and reliable New type of current mutual inductor, the huge potential market of New type of current mutual inductor forms.Optical current mutual inductor (Optical Current Transformer:OCT) is the new technology in the high-voltage great-current fields of measurement, has great importance for electric-power metering and protection.Advantages such as the nothing blast that OCT showed, no magnetic saturation, nothing hysteresis, small and light have obtained many researchers' approval and concern.Though the research of relevant OCT has obtained many gratifying achievements, because gordian technique obstacles such as linear birefrigence still are not solved, the practicability OCT system of industry access is still rare.

OCT utilizes Faraday magnetooptical effect, by detecting the rotation angle measurement unknown current of output light polarization face.Signal Processing scheme commonly used is removed and detection scheme for difference, and this can overcome the influence of intensity of light source fluctuating and the dc shift of system.The birefringence of OCT neutral line is still the gordian technique obstacle of OCT practicability to the influence of system's output.Difference is removed and testing result makes the output of most OCT system do not influenced by linear birefrigence to improve, its basic reason is Faraday effect and the linear birefrigence tied up in knots in Jones matrix that electric current to be measured causes in the OCT scheme, and difference is removed and detection scheme can't be distinguished.

The difference of block glass OCT remove and the detection scheme light path as shown in Figure 1, be example with block glass OCT, the light E that light source sends _In(generally being to play inclined to one side linearly polarized light from the horizontal by 45 °) injects block glass head, through triple reflection, four pickup arms of lease making, through polarization beam apparatus PBS, exports light E behind first circle _OutOrthogonal two components (P, S component) that form are expressed as respectively: [E _Out] ₀, [E _Out] ₁Differ from after the opto-electronic conversion and remove and computing, obtain system's output $U_{\mathrm{out}}=\frac{{\left|{\left[E_{\mathrm{out}}\right]}_1\right|}^2-{\left|{\left[E_{\mathrm{out}}\right]}_0\right|}^2}{{\left|{\left[E_{\mathrm{out}}\right]}_1\right|}^2+{\left|{\left[E_{\mathrm{out}}\right]}_1\right|}^2}=2\mathrm{VI},$ V is the Field constant in the formula, and I is an electric current to be measured.Here it is, and traditional difference is removed and detection scheme.

Since the influence of factors such as linear birefrigence, the output light E of system _OutThe light vector track may be degenerated to ellipse, through behind the PBS, owing to only detected E _OutIn the intensity signal of orthogonal two polarization states, and do not detect the phasic difference information of this two-beam, caused the disappearance of the information that detects, when signal restoring, just can't calculate the accurate size of linear birefrigence and electric current to be measured like this.Thereby when linear birefrigence was influenced by temperature etc. to produce irregular variations, difference was removed with detection scheme just powerless.If γ, φ are respectively faraday's rotation angle that linear birefrigence value on the pickup arm and electric current to be measured produce, by analysis

$\left\{\begin{array}{c}A=\left|{\left[E_{\mathrm{out}}\right]}_0\right|=\sqrt{0.5-4\mathrm{\φ}\·\cos \left(2\mathrm{\γ}\right)}\\ B=\left|{\left[E_{\mathrm{out}}\right]}_1\right|=\sqrt{0.5+4\mathrm{\φ}\·\cos \left(2\mathrm{\γ}\right)}\\ \mathrm{\δ}=\arg {\left[E_{\mathrm{out}}\right]}_0-\arg {\left[E_{\mathrm{out}}\right]}_1=2\·\tan \left(2\mathrm{\γ}\right)\end{array}\right.---\left(1\right)$

Following formula shows, difference that only rely on to measure A, B numerical value is removed and detection scheme can't calculate the size of linear birefrigence γ and Faraday effect φ, because in A, B, linear birefrigence occurs with identical product form with Faraday effect and can't separate, and is not fully independently between A, the B.Only relend and help the δ value and just can calculate linear birefrigence and Faraday effect size separately.

The traditional difference of this explanation is removed the influence that can not get rid of linear birefrigence with detection scheme, be subject to influences such as temperature owing to linear birefrigence irregular variation takes place, thereby the electric current to be measured that difference is removed and detection scheme is calculated will be subjected to the influence of external environment factors such as temperature, Here it is one of OCT gordian technique obstacle.Yet difference is except that being still the present topmost detection scheme of industry with detection scheme and being widely used.

(3) summary of the invention

The object of the present invention is to provide a kind ofly can solve linear birefrigence, reduce the three state polarization detection method that temperature effect is promptly got rid of optical current mutual inductor neutral line birefringence influence.

The object of the present invention is achieved like this: the light intensity of measuring three polarised directions of elliptically polarized light of optics current transformer systems output simultaneously, be horizontal polarization intensity, vertical polarization intensity and with the data of level direction polarization intensity at 45, utilize ternary measurement data, calculate the phasic difference information between elliptically polarized light horizontal polarization component and the vertical polarization component, in real time separation detection Faraday effect and linear birefrigence.

The present invention can also comprise:

1, the described light intensity of measuring three polarised directions of elliptically polarized light of optics current transformer systems output simultaneously is the light E that light source sends _InInject the sensing head of sensor, output light E behind the first circle of sensing or a few circle _OutBy being divided into two bundles behind the no polarization effect beam splitter NPBS, one is injected polarization beam apparatus PBS, and it is A that emergent light is divided into amplitude ²P light and amplitude be B ²S light, after the PIN opto-electronic conversion, deliver to computing machine; Another road is through 45 ° of analyzers, its output intensity

After opto-electronic conversion, deliver to computing machine, in computing machine, use $\left\{\begin{array}{c}{I}_{\mathrm{out}}\left(0\right)={\left|{\left[E_{\mathrm{out}}\right]}_0\right|}^2=A^2\\ I_{\mathrm{out}}\left(\frac{\mathrm{\π}}{2}\right)={\left|{\left[E_{\mathrm{out}}\right]}_1\right|}^2=B^2\\ I_{\mathrm{out}}\left(\frac{\mathrm{\π}}{4}\right)=\frac{A^2+B^2}{2}+\mathrm{AB}\cos \mathrm{\δ}\end{array}\right.$ Formula is calculated the size of the phase shift delta between P, the S light; Use then $\left\{\begin{array}{c}\mathrm{\γ}=\frac{1}{2}\arctan \frac{\mathrm{\δ}}{2}\\ I=\frac{1}{V\sqrt{4-{\mathrm{\δ}}^2}}\·\frac{B^2-A^2}{B^2+A^2}\end{array}\right.$ Formula is calculated the value of linear birefrigence and electric current to be measured in real time.

2, the light E that sends of described light source _InBe to play inclined to one side linearly polarized light from the horizontal by 45 °.

3, described optical current mutual inductor is block vitreous electricity flow sensor or fibre optic current sensor.

By formula $\left\{\begin{array}{c}A=\left|{\left[E_{\mathrm{out}}\right]}_0\right|=\sqrt{0.5-4\mathrm{\φ}\·\cos \left(2\mathrm{\γ}\right)}\\ B=\left|{\left[E_{\mathrm{out}}\right]}_1\right|=\sqrt{0.5+4\mathrm{\φ}\·\cos \left(2\mathrm{\γ}\right)}\\ \mathrm{\δ}=\arg {\left[E_{\mathrm{out}}\right]}_0-\arg {\left[E_{\mathrm{out}}\right]}_1=2\·\tan \left(2\mathrm{\γ}\right)\end{array}\right.$ As can be known, as long as measure three values of A, B, δ in the elliptic parameter equation, just can calculate the value of φ, γ.As output elliptical light E _OutThrough forming with horizontal direction

Behind the analyzer at angle, detected light intensity For:

So $\left\{\begin{array}{c}{I}_{\mathrm{out}}\left(0\right)={\left|{\left[E_{\mathrm{out}}\right]}_0\right|}^2=A^2\\ I_{\mathrm{out}}\left(\frac{\mathrm{\π}}{2}\right)={\left|{\left[E_{\mathrm{out}}\right]}_1\right|}^2=B^2\\ I_{\mathrm{out}}\left(\frac{\mathrm{\π}}{4}\right)=\frac{A^2+B^2}{2}+\mathrm{AB}\cos \mathrm{\δ}\end{array}\right.$

This shows, only need to analyzer three specific angles (

) carry out analyzing measurement (being ternary analyzing), just can calculate the value of A, B, δ.

The present invention proposes with the ternary detection scheme of the ellipse polarisation of output.From detecting the problem of tangling mutually that principle solves Faraday effect and linear birefrigence, for the practicability of OCT provides feasible detection method.

The major obstacle of OCT practicability is the temperature stability problem of system.The present invention has overcome that difference is removed and the incompleteness of detection scheme, difference remove and detection scheme owing to, on principle, can not distinguish linear birefrigence and Faraday effect to the disappearance (having lost the phasic difference between P, the S light) of output light detection information.The ternary detection scheme of elliptically polarized light proposed by the invention is measured so can realize the accurately real-time of linear birefrigence and electric current to be measured owing to obtained the full detail of output light.And can be applicable to elliptically polarized light detection range more widely.

(4) description of drawings

Fig. 1 is that the difference of block glass OCT is removed and the detection scheme block diagram;

Fig. 2 is the ternary detection scheme block diagram of block glass OCT output elliptically polarized light;

Fig. 3 is the ternary detection scheme block diagram of optical fiber OCT output elliptically polarized light.

(5) embodiment

For example the present invention is done description in more detail below in conjunction with accompanying drawing:

Experimental light sources adopts the LED3S403 type SLD of Wuhan telecommunications, centre wavelength 1290nm; Sensing head is a ZF-7 glass, and the reflecting surface plating is protected inclined to one side deielectric-coating with individual layer; Adopt PMS-2 type light power meter to measure the analyzing light intensity; Strong current generator output 1KA.Adopt local electrical heating to realize temperature control to optical sensing head.The sensing head temperature six values of 24.2 ℃ to 42.6 ℃, is built system according to light path shown in Figure 2 respectively, 45 ° the polarisation E that light source sends _InInject the sensing head of sensor, through triple reflection, four pickup arms of lease making, around the first circle of sensing back output light E _OutBy being divided into two bundles behind the no polarization effect beam splitter NPBS, one is injected polarization beam apparatus PBS, and it is A that emergent light is divided into amplitude ²P light and amplitude be B ²S light, through the PIN opto-electronic conversion; Another road is through 45 ° of analyzers, its output intensity

Through opto-electronic conversion, adopt PMS-2 type light power meter to measure ternary analyzing light intensity value.δ by $\left\{\begin{array}{c}{I}_{\mathrm{out}}\left(0\right)={\left|{\left[E_{\mathrm{out}}\right]}_0\right|}^2=A^2\\ I_{\mathrm{out}}\left(\frac{\mathrm{\π}}{2}\right)={\left|{\left[E_{\mathrm{out}}\right]}_1\right|}^2=B^2\\ I_{\mathrm{out}}\left(\frac{\mathrm{\π}}{4}\right)=\frac{A^2+B^2}{2}+\mathrm{AB}\cos \mathrm{\δ}\end{array}\right.$ Formula is calculated.In 24.2 ℃ to 42.6 ℃ scope of experiments, the electric current of ternary analyzing scheme output relative deviation varies with temperature scope in 0.5%-1%, difference remove and the output relative deviation of detection scheme with the variation of temperature scope more than 4%.As seen ternary polarization analyzing method has solution linear birefrigence, reduces the practical function of temperature effect.

Claims (1)

1, the three state polarization detection method of getting rid of optical current mutual inductor neutral line birefringence influence, it is characterized in that: the light intensity of measuring three polarised directions of elliptically polarized light of optics current transformer systems output simultaneously, be horizontal polarization intensity, vertical polarization intensity and with the data of level direction polarization intensity at 45, utilize ternary measurement data, calculate the phasic difference information between elliptically polarized light horizontal polarization component and the vertical polarization component, in real time separation detection Faraday effect and linear birefrigence; The described light intensity of measuring three polarised directions of elliptically polarized light of optics current transformer systems output simultaneously is 45 ° the polarisation E that light source sends _InInject the sensing head of sensor, output light E behind the first circle of sensing or a few circle _OutBy being divided into two bundles behind the no polarization effect beam splitter NPBS, one is injected polarization beam apparatus PBS, and it is A that emergent light is divided into amplitude ²P light and amplitude be B ²S light, after the PIN opto-electronic conversion, deliver to computing machine; Another road is through 45 ° of analyzers, its output intensity

After opto-electronic conversion, deliver to computing machine, in computing machine, use $\left\{\begin{array}{c}{I}_{\mathrm{out}}\left(0\right)={\left|{\left[E_{\mathrm{out}}\right]}_0\right|}^2=A^2\\ I_{\mathrm{out}}\left(\frac{\mathrm{\π}}{2}\right)={\left|{\left[E_{\mathrm{out}}\right]}_1\right|}^2=B^2\\ I_{\mathrm{out}}\left(\frac{\mathrm{\π}}{4}\right)=\frac{A^2+B^2}{2}+\mathrm{AB}\cos \mathrm{\δ}\end{array}\right.$ Formula is calculated the size of the phase shift delta between P, the S light; Use then $\left\{\begin{array}{c}\mathrm{\γ}=\frac{1}{2}\arctan \frac{\mathrm{\δ}}{2}\\ I=\frac{1}{V\sqrt{4-{\mathrm{\δ}}^2}}\·\frac{B^2-A^2}{B^2+A^2}\end{array}\right.$ Formula is calculated the value of linear birefrigence γ and electric current I to be measured in real time.

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