JPS61221679A - Light applied measuring instrument for zero-phase component - Google Patents

Abstract

PURPOSE:To improve measurement precision by using and connecting polarization plane maintaining optical fibers, etc., in series by as many as phases and constituting a sensor head part. CONSTITUTION:Sensor heads 17u, 17v, and 17w are constituted by winding polarization plane maintaining optical fibers, etc., in a coil shape respectively. The heads 17u and 17v are connected in series through a fiber connection part 23u, a single polarization optical fiber 19, and a fiber connection part 22v and the heads 17u and 17w are connected in series through a connection part 23v, a fiber 20, and a connection part 22w to constitute the sensor head part. Further, the light output of an optical multiplexer 15 is made incident on the head 17u through a fiber 16 and a connection part 22u. Connections are made at the connection parts 22u, 22v, and 22w so that axes of propagation of polarized wave modes are aligned with one another and the connection parts 23u, 23v, and 23w make connection while the axes are slanted by 45 deg.. Consequently, a O-phase current component measured value outputted by a signal processing circuit 26 is improved in precision by correcting variation in the intensity of a light source and variation in loss on an optical transmission line.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical application measuring device for measuring zero-phase components of multiphase alternating current.

[Conventional technology]

Figure 2 shows, for example, Mitsubishi Electric Technical Report (Vot!, 57, N
010.1983) is a configuration diagram of a conventional optical application measuring device for current measurement (magnetic field sensor). In the figure, l is a light source drive circuit, 2 is a light emitting element (hereinafter abbreviated as LED) as a light source, 3 is an optical fiber, 4 is an optical connector, and 5 is a sensor head. The sensor head 5 includes a polarizer 6, a magneto-optical element 7, an analyzer 8, and a mirror 9, and is arranged, for example, in a current measuring section of an AC motor or the like.

A light receiving element 12 receives the light emitted from the sensor head 5 through the optical connector 10 and the optical fiber 11. 13
is an optical receiving circuit which separates the output of the light receiving element 12 into a DC component Vd and an AC component Va and supplies them to the division circuit 14.

Next, the operation of this device will be explained.

Light of a predetermined wavelength emitted by the LED 2 is guided to a polarizer 6 in the sensor head 5 via an optical fiber 3 and an optical connector 4. The polarizer 6 passes linearly polarized waves of incident light. While this linearly polarized light wave propagates within the magneto-optical element 7,
The plane of polarization is rotated by the alternating current magnetic field H generated by the current to be measured flowing through the conductor. This rotation angle ψ is generally represented as ψ -VR / H / L ・. Here, E is the optical path length, Vγ is the Weld constant of the magneto-optical element 7, which has wavelength dependence, and the analyzer 8 generates an optical signal with a light intensity P corresponding to the rotation angle ψ of the linearly polarized light wave.

This light intensity P is determined by the Lee current magnetic field H=Ho−s i nωt
(However, Ho is the maximum amplitude of one field under measurement, and ω is the angular frequency.) Then, P" (Po/2) (1-2V
r-Ho-sina+t)・・・・・・・■, and the light intensity P is proportional to 1 (o-sinωt).

However, the relative angle of the polarized light passing direction between the polarizer 6 and the analyzer 8 is 45''. Here, PO is the intensity of light incident on the magneto-optical element 7.

In addition, Fig. 3(a) shows the temporal change in PO, and Fig. 3(b) shows the temporal change in PO.
shows the temporal change in light intensity P.

The optical signal emitted by the analyzer 8 is changed in optical path by a mirror 9 and sent to the light receiving element 1 via an optical connector 10 and an optical fiber 11.
2, where it is converted into an electrical signal, and the electrical signal (
(analog signal) is supplied to the optical receiving circuit 13. The electrical signal is separated into a DC component Vd and an AC component Va by the optical receiver circuit 13, and the division circuit 14 calculates (Va/Vd) to calculate LED output intensity, optical fiber transmission loss, optical connector loss, etc. After removing the influence of fluctuations, this voltage ratio is output as a measured value.

[Problem that the invention seeks to solve]

By the way, when monitoring and controlling the power distribution system,
It is necessary to measure the zero-sequence component of voltage and current at the time of a ground fault or disconnection fault, but when using the above-mentioned optical measurement equipment, for example, in the case of a three-phase AC system, the
Three optical measurement devices are required to measure u, gov, and Iw.

The configuration of the sensor head described above is complicated with a large number of parts, so connecting a large number of parts to form the sensor head becomes expensive.In addition, a signal processing device is required to combine and process these parts, so the equipment cost is high. There is a problem that it becomes
Furthermore, since the zero-phase component has a very low electrical level,
High measurement accuracy is required, but in the conventional configuration described above, the optical constants included in the above equation 0 have wavelength dependence, so if the temperature environment of the light source changes, the spectrum of the emitted light will fluctuate. This causes a measurement error, and there is a problem in that it is difficult to satisfy the above-mentioned requirements for measurement accuracy.

This invention was made to solve the above problem.
It is an object of the present invention to obtain an optical application zero-phase component measuring device that can significantly improve measurement accuracy compared to the conventional one and can reduce the cost of the device.

[Means to solve the problem]

This invention was made in order to solve the above-mentioned problem, and uses two sets of light sources with different wavelengths as light sources, and uses a polarization-maintaining optical fiber as a sensor head disposed at each phase measurement site of multiphase alternating current. Alternatively, the light output of the sensor head is converted into an electrical signal, the electrical signal is separated into an alternating current component and a direct current component, and a signal processing circuit generates a first wavelength light. Then, the two DC components corresponding to the second wavelength light are used as fluctuation parameters to calculate the light intensity corresponding to the no-load state, and the high frequency component is removed from the AC component corresponding to the first wavelength light or the second wavelength light. The configuration is such that correction is performed using the amount corresponding to the light intensity during load.

[Effect]

In this invention, since the measured value is compensated for wavelength fluctuation by the signal processing circuit, it is possible to obtain a highly accurate measured value that is virtually unaffected by wavelength fluctuation, and the sensor head disposed at each phase measurement site of a polyphase alternating current can be used. Since the sensor head is inserted in series between the light source section 1 and the receiver section 1, and an optical fiber coil is used as the sensor head, the structure of the sensor head section is simple, and the device is therefore compact. ,
The equipment cost is also low.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 2a and 2b are, for example, Aj! -Ga-A
These are s-based LEDs, and output optical signals with wavelengths λa and λb, respectively. The light output from both LEDs 2a and 2b is combined by a light combiner 15. 17u, 17v, and 17w are sensor heads that connect polarization-maintaining optical fibers or single-mode optical fibers that propagate two orthogonal polarization modes. The sensor head 17u and the sensor head 17v are connected in series via the fiber connection part 23u, the single polarization optical fiber 19, and the fiber connection part 22V, and the sensor heads 17v and 17w are connected to the fiber connection part 2.
3v1 single polarization optical fiber 20 and fiber connection 2
2w to form a sensor head section, and a single polarization optical fiber 16 and a fiber connection section 2.
The light output of the light combiner 15 enters the sensor head 17u via 2U. 18u, 18v, and 18w are conductors through which three-phase AC currents 1u, Iv, and Iw flow, and they pass through the centers of the sensor heads 17u, 17V, and 17w, respectively. The light intensity modulated light output by the sensor head is transmitted to the fiber connection part 23c and the single polarization optical fiber 2.
1 to the optical demultiplexer 24. The optical demultiplexer 24 demultiplexes the incident light into light with a wavelength λa and light with a wavelength λb, and supplies each to the light receiving elements 12a and 12b. The voltage signal output by the light receiving element 12a is separated into a DC component Vda and an AC component Va by the optical receiver circuit 13a, and the AC component V
The calculation contents of the low-pass filter 25 processing circuit 26 will be described later. Fiber connection parts 22u, 22v, 22
At w, the axes through which the polarization mode propagates are aligned and connected, and at the fiber connection parts 23u, 23v, and 23w, the axes are connected at 45
It is connected at an angle.

Furthermore, "polarization-maintaining optical fiber" refers to one that propagates both two orthogonal polarization modes, and "single polarization-maintaining optical fiber" refers to one that propagates only one of the two polarization modes. ”

Next, the operation of this device will be explained.

Now, if the length of the fiber of the sensor head is l, the rotation angle θ of the plane of polarization due to the Faraday effect is expressed by the equation 0 above, but the magnetic field generated on the fiber in the case of is Then, H=1/2π·R·····■. In the fiber connection parts 23u, 23v, and 23W, the fiber axes of each are inclined by 45 degrees and connected to the single polarization optical fiber on the output side, so the alternating current 1=Io・sin
If ωt, then...■ is derived from the formula ■ and the formula 0. Since Vγ has wavelength dependence, B″
= -1o-1/π・R, then the formula ■ becomes P"(Po/
2) ・(1+Vr, B, sinωt)・・・・・・・
■ It becomes.

Measured current I of sensor heads 17u, 17v and 17w
When u, Iv and Iw are expressed by the following 0 formula, Iu=Iou-
sin ω t lv=Iov−sin (ωt+φv) ・−−■
Iw=Iow-sin (ωt+φW) However, φy w
2π/3, φw=4π/3 sensor head 17u, 17
Since v and 17w are connected in series with a single polarization optical fiber, the light intensity reaching the light receiving element 12aS12b is Q-Qe (1+Vr-Bu-s ina+t)X
(1+Vr-By-s in (ωt+φV))x
(1+Vy-13w, sin (act+φW))
It is expressed as However, Qe is the light intensity at the time of current, and Bu=
-1ou11/rtR.

B Y = I Ov・1/πR.

Bw=-1ow,j? /πR.

This equation (2) can be rewritten from the viewpoint of frequency as follows.

Q=Qe (FO+F1+F2+F3)l HI l
■However, F1=Vr (Bu-s inωt+By-s in
(ωt+φv) +Bw−s in (ωt+φ
W) F2=-Ten (Bu-Bvcos (2ωt+φV)
+Bv・Bwcos (2ait) +BwIBucos (2ωt+φW)], and the above F1 is the zero-sequence voltage component of three-phase AC 100=■u+■v+
■Wl...--Corresponds to ■. The low-pass filter 25 blocks high frequency components F2 and F3 corresponding to 2ω and 3ω.

Here, the Weld constant Vγa for the wavelength λa, the wavelength λ
Expressed by the Weld constant 4vγb for b, and assuming that the DC voltage corresponding to the light intensity Qe (corresponding to the no-load light intensity) is Ve, Vda= ......[Phase] Vd b= ...... ■ holds true. However, it is assumed that the amplification gains of the optical receiving circuits 13a and 13b are adjusted so that the Weld constants for the wavelengths λa and λb are the same.

From equations 01 and 0, the above Ve becomes (, λ3 − αlb >. VTa & Vyb can be measured in advance for wavelengths λa1λb. On the other hand, ■a=Ve−Vra (Bu, rina+t=+Bv−
sin(ωt+φU) +Bw−s l n ((1) t+φW)] ・・・
... is 0.

The signal processing circuit 26 calculates the zero-sequence current component V a /V c''V r a by performing a circular operation on the above [phase] formula. This Ve×vγa is a wavelength fluctuation compensation coefficient, and the output of the signal processing circuit 26 The zero-phase current component measurement value is a highly accurate measurement value that has been corrected for intensity fluctuations in the light source and loss fluctuations in the optical transmission line.Of course, the value obtained by removing the high frequency component from the AC component for wavelength λb is The correction may be made using VeXVγb.

In the above embodiment, two sets each of the light receiving element and the light receiving circuit are provided, but the light receiving element and the light receiving circuit may be combined into one set to serve two wavelengths, and the LEDs 2a and 2b may be configured to emit light alternately. Good too.

Furthermore, although the above embodiment has been described in the case of three-phase alternating current, the present invention can be implemented in the case of polyphase alternating current other than three-phase, and similar effects can be obtained.

〔Effect of the invention〕

As explained above, the present invention configures a sensor head section by connecting sensor heads arranged at each phase measurement site of a polyphase AC circuit in series, and inserts this between a light source section and a receiving section.
Since an optical fiber coil is used as the sensor head, the configuration is simple and the equipment cost can be reduced.In addition, the system uses light sources with different wavelengths to compensate for wavelength fluctuations in the measured values. Therefore, the measurement accuracy of the zero-phase component can be significantly improved.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a block diagram of a conventional optical applied measurement device, and Fig. 3 is a diagram showing temporal changes in light intensity. be. In the figure, 2a, 2b - light source, 12a, 12b - light receiving element, 13a, 13b - optical receiving circuit, 15 - optical combiner, 24 - optical demultiplexer, 16 - 21 - single polarization optical fiber, 17u - 17W. -Sensor head, 22u ~ 22w
and 23 u ~ 23 W - fiber connection, and 4 = 6 colors 4 days filter 1.25 - low pass filter, 26...-
signal processing circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (3)

[Claims] (1) A light source unit comprising a light source whose emitted light has a first wavelength and a light source whose emitted light has a second wavelength different from the wavelength; A sensor head section that modulates light intensity, a light receiving element that receives the light emitted from the sensor head section, and an electric signal outputted by the light receiving element that is separated into a DC component and an AC component that correspond to the first wavelength light received by the light receiving element. an optical receiving circuit that outputs a DC component, an AC component, and a DC component corresponding to the second wavelength light, and a signal processing circuit that receives the two DC components and the AC component from which a high frequency component has been removed by a low-pass filter. ,
The sensor head section is made by winding a polarization-maintaining optical fiber or a single-mode optical fiber into a coil that propagates two orthogonal polarization modes. The signal processing circuit calculates the no-load light intensity corresponding to the two DC components as a fluctuation parameter, and calculates the no-load light intensity corresponding to the AC component and the fiber output. An optical application zero-phase component measuring device characterized by performing correction using a de-constant. (2) The incident light and the output light to the sensor head section are propagated through a single constant polarization optical fiber, and the axes of the input side of the sensor head and the single constant polarization optical fiber are aligned, and the output side of the sensor head section and the single constant wave direction are aligned. The axis of optical fiber is 45
2. The optical zero-phase component measuring device according to claim 1, wherein the device is connected at an angle. (3) The signal processing circuit sets the DC outputs of the optical receiving circuit to Vda and Vdb, respectively, to the first wavelength λa and the second wavelength λb, and the AC outputs of the optical receiving circuit to Va and Vdb, respectively.
First wavelength λa, second wavelength λb When the Weld constants for the first wavelengths λa and λb are Vγa and Vγb, respectively, the no-load light intensity corresponding Ve: (V^2γa・Vab−V^2γb・Vdb )/(V^
2γa-V^2γb), Va/Vγ, a・Ve
The optical application zero-phase component measuring device according to any one of claims 1 to 2, characterized in that the multi-phase alternating current zero-phase component is calculated by calculating the following.