CN111751596A - Distributed high-voltage transmission line current detection system - Google Patents
Distributed high-voltage transmission line current detection system Download PDFInfo
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Abstract
The invention relates to the technical field of current detection in a high-voltage transmission line, and provides a current detection system of a distributed high-voltage transmission line, which comprises: the system comprises a broadband light source, a wave separator, Faraday current sensors, a detector and a demodulator, wherein the Faraday current sensors have the same number with a plurality of wires to be detected; the broadband light source emits detection light, the detection light with a plurality of different wavelengths is formed through the wave splitter and transmitted to the Faraday current sensors arranged on the wires to be detected, the Faraday current sensors are further transmitted to the detector, optical signals are converted into electric signals and input into the demodulator, the magnetic field intensity B is obtained through Faraday magneto-optical effect and Malus theorem calculation, and the current intensity I of the wires to be detected is obtained through calculation according to the Biao-Saval theorem and the magnetic field intensity B. The method solves the problems that the current detection method of the power transmission line has large volume, heavy weight, easy excitation current interference and complex measurement system structure, and each power transmission wire needs to be detected when a power transmission system comprises a plurality of power transmission wires.
Description
Technical Field
The invention relates to the technical field of current detection in a high-voltage transmission line, in particular to a current detection system of a distributed high-voltage transmission line.
Background
The current detection methods commonly used in the prior art include the following methods:
a flow divider: the principle of the current divider is simple, and the current divider is usually used in low-frequency small-amplitude current measurement, but can generate larger error when being applied to high-frequency large-amplitude current measurement.
An alternating current transformer: the sensing principle of the alternating current transformer is simple, and the precision is high. However, the alternating current transformer is only suitable for measuring alternating current within thousands of amperes, and the measured current is too large, so that the excitation current of the transformer is not ignored any more, and the measurement error is increased.
The direct current transformer utilizes the change of the detected direct current to cause the iron core coil to generate inductive reactance, thereby indirectly changing the current of the auxiliary alternating current circuit to reflect the size of the detected current. The disadvantages are large volume, high price, need of support of external power supply, etc.
The Hall current sensor is a commonly used current measuring device, adopts a Hall element as a sensing unit, realizes the measurement of current through the size of a magnetic field generated by the measured current, is applied to the measurement of large flow, but has the defects of large volume and heavy weight.
In summary, the current detection methods in the prior art all have the disadvantages of large volume, heavy weight and easy interference from exciting current. In addition, the current detection method in the prior art generally detects one power transmission conductor, and when the whole power transmission system includes a plurality of power transmission conductors, each power transmission conductor needs to be detected, so that the operation is complex, and time and labor are consumed.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a current detection system for a distributed high voltage transmission line, which utilizes the characteristic that an optical fiber or a waveguide can eliminate the influence of an exciting current, adopts a faraday optical fiber or a faraday dielectric waveguide with an input polarizer and an output polarizer, and eliminates external electromagnetic interference by using the inherent characteristics of the optical fiber or the waveguide, thereby achieving the purposes of reducing cost and reducing volume.
The above object of the present invention is achieved by the following technical solutions:
a current detection system of a distributed high-voltage transmission line comprises: the device comprises a broadband light source, a wave separator, a plurality of Faraday current sensors with the same number as that of a plurality of wires to be measured, at least one detector, a demodulator and a data analysis display terminal, wherein each Faraday current sensor is respectively arranged on each wire to be measured and used for simultaneously measuring the plurality of wires to be measured;
the broadband light source is connected with the wave separator through an optical fiber, the wave separator is simultaneously connected with a plurality of Faraday current sensors through the optical fiber, each Faraday current sensor is respectively connected with the corresponding detector, the detector is connected with the demodulator through the optical fiber, and the demodulator is further connected with the data analysis display terminal;
when the current on a plurality of leads to be measured is measured simultaneously, the broadband light source emits detection light, the detection light with the same number of different wavelengths as the wires to be detected is formed after passing through the wave splitter, the detection light with the different wavelengths is respectively transmitted to the Faraday current sensors arranged on the wires to be detected, the detection light with the different wavelengths passes through the corresponding Faraday current sensors and is transmitted to the detector corresponding to each Faraday current sensor through an optical fiber, the detector converts the optical signal into an electric signal, inputs the electric signal into the demodulator, calculates through Faraday magneto-optical effect and Malus theorem to obtain the magnetic field intensity B, calculating the current intensity I of the plurality of wires to be tested according to the Biao-savart theorem and the magnetic field intensity B, and displaying the current intensity I through the data analysis display terminal;
the Faraday current sensor specifically comprises: optical fibers, lenses, polarizers, and magneto-optical media; the optical fiber comprises an input optical fiber and an output optical fiber, the lenses comprise a convex flat lens and a plano-convex lens, the polaroids comprise the input polaroid and the output polaroid, and the magneto-optical medium comprises any one form of magneto-optical fiber and magneto-optical waveguide; the detection light with a plurality of different wavelengths formed by the broadband light source after passing through the wave splitter is guided into a magneto-sensitive area as incident light through the input optical fiber, is focused by the convex flat lens and then is changed into linearly polarized light through the input polaroid, and the linearly polarized light is incident into the magneto-optical medium, so that the polarization plane of the incident light is deflected; after passing through the magneto-optical medium and the output polarizer, light is focused into the output optical fiber; after the incident light passes through the Faraday current sensor, the light intensity of the incident light is determined by the input intensity I0Becomes output light intensity I1。
Further, the current detection system of distributed high-voltage transmission line still includes:
when the number of the detectors is multiple, configuring an adaptive detector for each Faraday current sensor, wherein the optical signal output by each Faraday current sensor is converted into an electrical signal by the adaptive detector;
when the number of the detectors is one, a combiner is arranged between the Faraday current sensors and the detectors, the optical signal output by each Faraday current sensor is subjected to sum and parallel by the combiner, and then the combined optical signal is input into the detectors by the combiner to be converted into an electrical signal.
Further, calculating to obtain a magnetic field strength B through a faraday magneto-optical effect and a malus theorem, and calculating to obtain the current strength I of the wire to be tested according to a bioto-savart theorem and the magnetic field strength B, specifically:
according to the Faraday magneto-optical effect, when linearly polarized light propagates in a medium and a magnetic field generated by a high-voltage wire is arranged in a direction parallel to the propagation direction of the light, the polarization plane of the light is deflected by an angle thetaFProportional to the product of magnetic induction B and the length d of the light traversing the faraday medium:
θF＝VBd (1)
wherein, the proportionality coefficient V is called as Welch constant and is related to the property of the medium and the frequency of the light wave;
deflection angle thetaFAccording to the intensity I of the light generated by the Faraday current sensor with the polaroid under the action of the magnetic field1And a maximum light intensity I0The comparison shows that according to the Malus theorem:
I1＝I0·sin2θF(2)
according to the biot-savart theorem, for an infinitely long straight wire, at a vertical distance r from the wire, the magnetic field strength perpendicular to the wire is as follows:
wherein, mu04 π × 10-7H/m; r is the distance between the measured point and the axis of the lead to be measured, and the unit is m; i is the magnitude of the measured current, in units A.
Theta is obtained by calculation through formula (2)FAnd substituting the magnetic field B into a formula (1) to obtain the magnetic field B, and calculating the current intensity I through a formula (3).
Further preferably, the input polarizer and the output polarizer are perpendicular to each other.
Further preferably, the faraday current sensor is an ultra short length of the faraday optical fiber and the faraday waveguide.
Further, the detector further comprises: a pre-amplification circuit and active band-pass filtering;
the preamplification circuit converts the optical signal into an electric signal and performs operational amplification;
and the active band-pass filtering filters noise in the electric signal to obtain the electric signal containing magnetic field intensity information.
Further, the demodulator is used for shaping and limiting the electric signal, converting the electric signal into a format capable of being communicated with the data analysis display terminal, and sending the electric signal to the data analysis display terminal.
Further, the distance r between the measured point and the axis of the lead to be measured is a constant input in advance in the demodulator.
Further, the magneto-optical medium comprises: a high concentration terbium-doped glass or ceramic or crystal waveguide or a high concentration terbium-doped glass or ceramic or crystal waveguide containing a thin metal film that contributes to a field constant enhancement.
Compared with the prior art, the invention has the beneficial effects that:
(1) through establishing a distributed high tension transmission line's current detection system, include: the device comprises a broadband light source, a wave separator, a plurality of Faraday current sensors with the same number as that of a plurality of wires to be measured, at least one detector, a demodulator and a data analysis display terminal, wherein each Faraday current sensor is respectively arranged on each wire to be measured and used for simultaneously measuring the plurality of wires to be measured; the broadband light source is connected with the wave separator through an optical fiber, the wave separator is simultaneously connected with a plurality of Faraday current sensors through the optical fiber, each Faraday current sensor is respectively connected with the corresponding detector, the detector is connected with the demodulator through the optical fiber, and the demodulator is further connected with the data analysis display terminal; when the current on a plurality of leads to be measured is measured simultaneously, the broadband light source emits detection light, the detection light with the same number of different wavelengths as the wires to be detected is formed after passing through the wave splitter, the detection light with the different wavelengths is respectively transmitted to the Faraday current sensors arranged on the wires to be detected, the detection light with the different wavelengths passes through the corresponding Faraday current sensors and is transmitted to the detector corresponding to each Faraday current sensor through an optical fiber, the detector converts the optical signal into an electric signal, inputs the electric signal into the demodulator, calculates through Faraday magneto-optical effect and Malus theorem to obtain the magnetic field intensity B, and calculating the current intensity I of the plurality of wires to be tested according to the Biao-Saval theorem and the magnetic field intensity B, and displaying the current intensity I through the data analysis display terminal. The technical scheme utilizes the characteristic that the optical fiber or the waveguide can eliminate the influence of exciting current, adopts the Faraday optical fiber or the Faraday dielectric waveguide with the input polarizing film and the output polarizing film, and utilizes the inherent characteristics of the optical fiber or the waveguide to eliminate external electromagnetic interference, thereby achieving the purposes of reducing cost and reducing volume.
(2) The distributed voltage sensing system for the high-voltage transmission line can simultaneously detect a plurality of wires to be detected, the detection light for detection is emitted by the same light source and is finally displayed by the same data analysis display terminal, and detection personnel can acquire the current conditions of all the transmission lines at one time, so that the operation is simple, and the time and labor consumption is reduced.
(3) According to the invention, by adopting the scheme that the input polaroid is perpendicular to the output polaroid, the sensitivity of the current sensor is higher during measurement, and the current sensor is more sensitive to a magnetic field.
Drawings
FIG. 1 is a block diagram of a distributed high voltage transmission line current sensing system with multiple detectors in accordance with the present invention;
FIG. 2 is a block diagram of a distributed high voltage transmission line current sensing system with a detector according to the present invention;
FIG. 3 is a schematic diagram of the structure of a Faraday waveguide with polarizer according to the present invention;
FIG. 4 is a diagram illustrating the magneto-optical effect of the present invention;
FIG. 5 is a schematic view of magnetic induction at a distance r from a wire to be measured according to the present invention;
FIG. 6 shows the current I and deflection angle θ in a high voltage transmission lineFSchematic diagram of the relationship between;
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments that can be derived by a person skilled in the art from the embodiments given herein without making any inventive work are intended to be within the scope of the present disclosure.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Example one
As shown in fig. 1 and fig. 2, the present embodiment provides a current detection system for a distributed high-voltage transmission line, including: the device comprises a broadband light source, a wave separator, a plurality of Faraday current sensors with the same number as that of a plurality of wires to be measured, at least one detector, a demodulator and a data analysis display terminal, wherein each Faraday current sensor is arranged on each wire to be measured and used for measuring the plurality of wires to be measured simultaneously.
The invention has the greatest advantage that the invention is suitable for simultaneously detecting a plurality of wires to be detected, the detection light for detection is emitted by the same light source and is finally displayed by the same data analysis display terminal, and the detection personnel can acquire the current conditions of all power transmission wires at one time, thereby having the advantages of simple operation and time and labor consumption reduction.
The faraday current sensor of the present invention may comprise any one of a faraday fiber and a faraday waveguide, or other alternative materials, and the present invention is not limited in any way.
The broadband light source is connected with the wave separator through an optical fiber, the wave separator is simultaneously connected with a plurality of Faraday current sensors through the optical fiber, each Faraday current sensor is respectively connected with the corresponding detector, the detector is connected with the demodulator through the optical fiber, and the demodulator is further connected with the data analysis display terminal;
when the current detection system of the distributed high-voltage transmission line is used for simultaneously measuring the current on a plurality of wires to be detected, the broadband light source emits detection light, the detection light with a plurality of different wavelengths is formed after passing through the wave splitter, the number of the detection light with the different wavelengths is the same as that of the wires to be detected, the detection light with the different wavelengths is respectively transmitted to the Faraday current sensors arranged on the wires to be detected, the detection light with the different wavelengths passes through the corresponding Faraday current sensors and is transmitted to the detector corresponding to each Faraday current sensor through the optical fiber, the detector converts a magneto-optical signal into an electric signal and inputs the electric signal into the demodulator, the magnetic field intensity B is obtained through the Faraday effect and the Malus theorem, and the current intensity I of the wires to be detected is obtained according to the Piao-Saval theorem and the magnetic field intensity B, and the data is displayed through the data analysis display terminal.
The detection light emitted from the broadband light source may be any one of laser light, X-ray, r-ray, y-ray, and the like, which can be used to detect light of the power transmission line.
The technical scheme of the current detection system of the distributed high-voltage transmission line utilizes the characteristic that the optical fiber or the waveguide can eliminate the influence of exciting current, adopts the Faraday optical fiber or the Faraday dielectric waveguide with the input polarizing film and the output polarizing film, and utilizes the inherent characteristics of the optical fiber or the waveguide to eliminate external electromagnetic interference, thereby achieving the purposes of reducing cost and reducing volume.
Further, the current detection system of the distributed high-voltage transmission line of the present invention further includes:
when the number of the detectors is multiple, as shown in fig. 1, for each faraday current sensor, an adapted detector is configured, and the optical signal output from each faraday current sensor is converted into an electrical signal by the adapted detector;
when there is one detector, as shown in fig. 2, a combiner is directly disposed between the faraday current sensors and the detector, and the optical signal output from each faraday current sensor is summed and summed by the combiner, and then the combined optical signal is input into the detector by the combiner, so as to convert the optical signal into an electrical signal.
The two schemes are preferable schemes, and in addition, the Faraday current sensors can be grouped, and each group is combined through a combiner and then transmitted to the same detector.
Further, the magnetic field strength B is calculated through the faraday magneto-optical effect and the malus theorem, and the current strength I of the wire to be tested is calculated according to the bioto-savart theorem and the magnetic field strength B, and the specific principle is as follows:
as shown in FIG. 4, according to Faraday magneto-optical effect, linearly polarized light is in the mediumWhen a magnetic field is applied to the power transmission line in the direction parallel to the propagation direction of light during medium propagation, the polarization plane of the light is deflected by an angle thetaFProportional to the product of magnetic induction B and the length d of the light traversing the faraday medium:
θF＝VBd (1)
wherein, the proportionality coefficient V is called as Welch constant and is related to the property of the medium and the frequency of the light wave;
deflection angle thetaFAccording to the input light intensity I0(reference intensity) and intensity of magnetic field I generated by the Faraday current sensor with polarizing plate1The comparison shows that according to the Malus theorem:
I1＝I0·sin2θF(2)
according to the biot-savart theorem, for an infinitely long straight wire, at a vertical distance r from the wire, the magnetic field strength perpendicular to the wire is as follows:
wherein, mu04 π × 10-7H/m; r is the distance between the measured point and the axis of the lead to be measured, and the unit is m; i is the magnitude of the measured current, in units A.
Theta is obtained by calculation through formula (2)FAnd substituting the magnetic field B into a formula (1) to obtain the magnetic field B, and calculating the current intensity I through a formula (3).
Further, as shown in fig. 3, the faraday current sensor further includes: optical fibers, lenses, polarizers, and magneto-optical media;
the optical fiber comprises an input optical fiber and an output optical fiber, the lenses comprise a convex flat lens and a plano-convex lens, the polaroids comprise the input polaroid and the output polaroid, and the magneto-optical medium comprises any one form of magneto-optical fiber and magneto-optical waveguide;
the broadband light source is guided into a magneto-sensitive area as incident light by the input optical fiber after passing through the wave splitter, the incident light is focused by the convex flat lens and then is changed into linearly polarized light by the input polaroid, the linearly polarized light is incident into the magneto-optical medium, and the polarization plane of the incident light is deflected;
after passing through the magneto-optical medium and the output polarizer, light is focused into the output optical fiber;
after the incident light passes through the Faraday current sensor, the light intensity of the incident light is determined by the input intensity I0Becomes output light intensity I1。
Further, preferably, the input polarizer and the output polarizer are perpendicular to each other, and since the polarization directions of the two polarizers are perpendicular, the measured intensity of the transmitted light is proportional to the rotation angle of the polarization plane of the light in the faraday current sensor, that is, proportional to the component of the magnetic field intensity along the crystal axis direction. The current sensor has higher sensitivity and is more sensitive to a magnetic field during measurement. Of course, the mutually perpendicular solution is only a preferred solution, and it still falls within the scope of the present invention if only the polarization directions of the input polarizer and the output polarizer are simply changed.
Further, preferably, the faraday current sensor adopts the faraday optical fiber and the faraday waveguide with ultra-short length, so that the current sensor can be integrated into an ultra-small sensor which is hung on a transmission wire, the pressure on the optical fiber is small, and the influence is smaller. Of course, the choice of the ultra-short length faraday fiber and faraday waveguide is only a preferred method, and in the implementation, the sensor does not necessarily need to be hung on the transmission line whether the ultra-short length faraday medium or other faraday media not having the ultra-short length, and the method belongs to the protection scope of the present invention as long as the design concept is the same as that of the present invention.
Further, the detector further comprises: a pre-amplification circuit and active band-pass filtering;
the preamplification circuit converts the optical signal into an electric signal and performs operational amplification; and the active band-pass filtering filters noise in the electric signal to obtain the electric signal containing magnetic field intensity information. Specifically, the pre-amplifier circuit converts an optical signal into an electrical signal, but the optical signal and the electrical signal are very weak, so the circuit is designed to be a low-noise and high-gain amplifier circuit. Namely, weak optical signals received by the photoelectric detector are converted into electric signals, and the electric signals are subjected to operational amplification. The use of the operational amplifier not only amplifies the signal but also amplifies noise, and the amplifier itself introduces new noise, so that an electric signal containing magnetic field strength information can be obtained through active band-pass filtering.
Further, the demodulator is used for shaping and limiting the electric signal, converting the electric signal into a format capable of being communicated with the data analysis display terminal, and sending the electric signal to the data analysis display terminal. The demodulator specifically includes: a band-pass filter circuit, a phase-sensitive detection circuit, a phase-shifting circuit and a low-pass filter circuit;
the band-pass filter circuit and the low-pass filter circuit are used for shaping and limiting the pulse of the electric signal;
the phase-sensitive detection and phase-shifting circuit is used for detecting the phase and repairing the phase.
The data analysis display terminal is specifically used for displaying relevant performance parameters of the power transmission line acquired by the sensor and has a real-time early warning function.
Further, the distance r between the measured point and the axis of the lead to be measured is a constant input in advance. The design of the constant is a preferable scheme, and the method is particularly suitable for designing the current sensor into an ultra-short length Faraday optical fiber or Faraday waveguide and directly hanging the current sensor on a lead to be measured for measurement.
Specifically, in this embodiment, as shown in fig. 5, a scheme that a faraday sensor with an ultra-short length is hung on a wire to be measured for measurement is adopted, and the distance between a measured point and the axis of the wire to be measured is fixed, so that the distance r can be input into a system in advance without measurement each time, thereby reducing the workload of current detection and improving the accuracy of measurement.
Further, the magneto-optical medium may preferably employ the following materials: a high concentration terbium-doped glass or ceramic or crystal waveguide or a high concentration terbium-doped glass or ceramic or crystal waveguide containing a thin metal film that contributes to a field constant enhancement.
Example two
The embodiment provides a specific embodiment of calculating the current intensity after measuring a wire to be measured by using the current detection system of the distributed high-voltage transmission line, which specifically comprises the following steps:
using 65-wt% ytterbium-doped silicate fiber as the faraday fiber, the length d is 0.01m, the Verder constant is V is 32rad/(T · m), and the deflection angle θ is known from the faraday magneto-optical effect, with the length d and the Verder constant V knownFThe relationship with the magnetic field strength B is:
θF＝VBd＝32rad/(T.m)·0.01m·B＝0.32B(rad)
wherein the unit of the magnetic field strength B is tesla (T). It is also known that the magnetic field strength B and the deflection angle θFIn proportion:
B＝3.12θF
wherein the deflection angle thetaFCan be based on the reference light intensity I0And the intensity I of the light generated by the Faraday waveguide or optical fiber with polaroid1The comparison shows that according to the Malus theorem:
I1＝I0·sin2θF
then theta can be calculatedFValue according to the deflection angle thetaFThe relationship with the magnetic field strength B allows the magnitude of the magnetic field strength B to be calculated.
When the distance between the Faraday fiber or waveguide and the high-voltage straight conductor in the sensor is r 0.05m, the magnetic permeability is mu0＝4π×10-7H/m, known from the Biot-savart law:
the calculation shows that the current I in the high-voltage straight conductor is in direct proportion to the magnetic field intensity B:
therefore, the current I in the high-voltage straight conductor and the deflection angle thetaFProportional to each other (as shown in fig. 6):
I＝7.8×105θF
from the calculated deflection angle thetaFThe current I in the final high-voltage straight conductor can be calculated.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.
Claims (9)
1. A current detection system of a distributed high-voltage transmission line is characterized by comprising: the device comprises a broadband light source, a wave separator, a plurality of Faraday current sensors with the same number as that of a plurality of wires to be measured, at least one detector, a demodulator and a data analysis display terminal, wherein each Faraday current sensor is respectively arranged on each wire to be measured and used for simultaneously measuring the plurality of wires to be measured;
the broadband light source is connected with the wave separator through an optical fiber, the wave separator is simultaneously connected with a plurality of Faraday current sensors through the optical fiber, each Faraday current sensor is respectively connected with the corresponding detector, the detector is connected with the demodulator through the optical fiber, and the demodulator is further connected with the data analysis display terminal;
when the current on a plurality of leads to be measured is measured simultaneously, the broadband light source emits detection light, the detection light with the same number of different wavelengths as the wires to be detected is formed after passing through the wave splitter, the detection light with the different wavelengths is respectively transmitted to the Faraday current sensors arranged on the wires to be detected, the detection light with the different wavelengths passes through the corresponding Faraday current sensors and is transmitted to the detector corresponding to each Faraday current sensor through an optical fiber, the detector converts the optical signal into an electric signal, inputs the electric signal into the demodulator, calculates through Faraday magneto-optical effect and Malus theorem to obtain the magnetic field intensity B, calculating the current intensity I of the plurality of wires to be tested according to the Biao-savart theorem and the magnetic field intensity B, and displaying the current intensity I through the data analysis display terminal;
the Faraday current sensor specifically comprises: optical fibers, lenses, polarizers, and magneto-optical media; the optical fiber comprises an input optical fiber and an output optical fiber, the lenses comprise a convex flat lens and a plano-convex lens, the polaroids comprise the input polaroid and the output polaroid, and the magneto-optical medium comprises any one form of magneto-optical fiber and magneto-optical waveguide; the detection light with a plurality of different wavelengths formed by the broadband light source after passing through the wave splitter is guided into a magneto-sensitive area as incident light through the input optical fiber, is focused by the convex flat lens and then is changed into linearly polarized light through the input polaroid, and the linearly polarized light is incident into the magneto-optical medium, so that the polarization plane of the incident light is deflected; after passing through the magneto-optical medium and the output polarizer, light is focused into the output optical fiber; after the incident light passes through the Faraday current sensor, the light intensity of the incident light is determined by the input intensity I0Becomes output light intensity I1。
2. The current sensing system of a distributed high voltage power transmission line according to claim 1, further comprising:
when the number of the detectors is multiple, configuring an adaptive detector for each Faraday current sensor, wherein the optical signal output by each Faraday current sensor is converted into an electrical signal by the adaptive detector;
when the number of the detectors is one, a combiner is arranged between the Faraday current sensors and the detectors, the optical signal output by each Faraday current sensor is subjected to sum and parallel by the combiner, and then the combined optical signal is input into the detectors by the combiner to be converted into an electrical signal.
3. The current detection system of the distributed high-voltage transmission line according to claim 1, wherein the magnetic field strength B is calculated by a faraday magneto-optical effect and a malus theorem, and the current strength I of the wire to be measured is calculated according to a biot-savart theorem and the magnetic field strength B, specifically:
according to the Faraday magneto-optical effect, when linearly polarized light propagates in a medium and a magnetic field generated by a high-voltage wire is arranged in a direction parallel to the propagation direction of the light, the polarization plane of the light is deflected by an angle thetaFProportional to the product of magnetic induction B and the length d of the light traversing the faraday medium:
θF＝VBd (1)
wherein, the proportionality coefficient V is called as Welch constant and is related to the property of the medium and the frequency of the light wave;
deflection angle thetaFAccording to the intensity I of the light generated by the Faraday current sensor with the polaroid under the action of the magnetic field1And a maximum light intensity I0The comparison shows that according to the Malus theorem:
I1=I0·sin2θF(2)
according to the biot-savart theorem, for an infinitely long straight wire, at a vertical distance r from the wire, the magnetic field strength perpendicular to the wire is as follows:
wherein, mu0Permeability in vacuum, 4 π × 10-7H/m; r is the distance between the measured point and the axis of the lead to be measured, and the unit is m; i is the magnitude of the measured currentBit a.
Theta is obtained by calculation through formula (2)FAnd substituting the magnetic field B into a formula (1) to obtain the magnetic field B, and calculating the current intensity I through a formula (3).
4. The system of claim 1, wherein the input polarizer and the output polarizer are perpendicular to each other.
5. The current detection system of the distributed high voltage transmission line of claim 1, wherein the faraday current sensor is the faraday optical fiber and the faraday waveguide in ultra short lengths.
6. The system of claim 1, wherein the detector further comprises: a pre-amplification circuit and active band-pass filtering;
the preamplification circuit converts the optical signal into an electric signal and performs operational amplification;
and the active band-pass filtering filters noise in the electric signal to obtain the electric signal containing magnetic field intensity information.
7. The system of claim 1, wherein the demodulator is configured to shape and clip the electrical signal, convert the electrical signal into a format that can be communicated with the data analysis display terminal, and send the electrical signal to the data analysis display terminal.
8. The current sensing system of the distributed high voltage transmission line of claim 3, further comprising: the distance r between the measured point and the axis of the lead to be measured is a constant input in advance in the demodulator.
9. The current sensing system of the distributed high voltage transmission line of claim 1, wherein the magneto-optical medium comprises: a high concentration terbium-doped glass or ceramic or crystal waveguide or a high concentration terbium-doped glass or ceramic or crystal waveguide containing a thin metal film that contributes to a field constant enhancement.
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