CN111721992B - Optical fiber sensing system for measuring current intensity of three-phase high-voltage conductor - Google Patents
Optical fiber sensing system for measuring current intensity of three-phase high-voltage conductor Download PDFInfo
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- CN111721992B CN111721992B CN202010564940.9A CN202010564940A CN111721992B CN 111721992 B CN111721992 B CN 111721992B CN 202010564940 A CN202010564940 A CN 202010564940A CN 111721992 B CN111721992 B CN 111721992B
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0046—Arrangements for measuring currents or voltages or for indicating presence or sign thereof characterised by a specific application or detail not covered by any other subgroup of G01R19/00
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/24—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using light-modulating devices
- G01R15/245—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using light-modulating devices using magneto-optical modulators, e.g. based on the Faraday or Cotton-Mouton effect
- G01R15/246—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using light-modulating devices using magneto-optical modulators, e.g. based on the Faraday or Cotton-Mouton effect based on the Faraday, i.e. linear magneto-optic, effect
Abstract
The invention relates to the technical field of current detection in a high-voltage transmission line, and discloses an optical fiber sensing system for measuring the current intensity of three-phase high-voltage wires, which comprises three light sources, a wave splitter, three Faraday waveguide modules, a demodulator and a data processing terminal, wherein the three Faraday waveguide modules are respectively arranged at the same position of each high-voltage wire of the three-phase high-voltage wires; the detection lights with three different wavelengths are respectively input into the Faraday waveguide modules on three transmission wires of the three-phase transmission wires and then output into the demodulator to convert the signal light into an electric signal, the input data processing terminal obtains the total magnetic field of the three transmission wires on each transmission wire test point through Malus 'theorem and Faraday magneto-optical effect calculation, and obtains the current intensity on each transmission wire through Biao-Saval's theorem calculation. The problem of how to reduce sensor cost and reduce the sensor volume, eliminate external electromagnetic interference, realize three-phase transmission line current detection is solved.
Description
Technical Field
The invention relates to a current detection technology in a high-voltage transmission line, in particular to an optical fiber sensing system for measuring the current intensity of a three-phase high-voltage wire.
Background
The current detection mainly adopts the following schemes:
a flow divider: the current divider is usually used for low-frequency small-amplitude current measurement, but can generate larger error when 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. The ac current transformer is only suitable for measuring ac current in thousands of amperes. If the measured current is too large, the excitation current of the mutual inductor is not ignored any more.
A direct current transformer: the direct current transformer utilizes the change of the direct current to be measured to cause the iron core coil to generate inductive reactance, thereby indirectly changing the current of the auxiliary alternating current circuit to reflect the magnitude of the current to be measured. The disadvantages are large volume, high price, need of support from external power supply, etc.
A Hall current sensor: 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 current, and has the defects of large volume and heavy weight.
In summary, the existing current detection has technical defects of large volume, heavy weight, easy interference of exciting current and the like, and the existing current detection can only measure the current on a single power transmission conductor and cannot measure the current on three-phase high-voltage conductors which are influenced by magnetic fields among a plurality of power transmission conductors.
Disclosure of Invention
Aiming at the problems, aiming at overcoming the defects that the existing current detection method has large volume and heavy weight, is easy to be interfered by excitation current and can not measure the current on the three-phase high-voltage wire which is influenced by the mutual magnetic fields among a plurality of power transmission wires among the power transmission wires, the invention aims to provide the optical fiber sensing system for measuring the current intensity of the three-phase high-voltage wire.
The above object of the present invention is achieved by the following technical solutions:
an optical fiber sensing system for measuring current intensity of three-phase high-voltage wires comprises a light source, wave splitters, three Faraday waveguide modules, a demodulator and a data processing terminal, wherein the three Faraday waveguide modules are respectively arranged at the same position of each high-voltage wire of the three-phase high-voltage wires;
the faraday waveguide module specifically comprises: the optical fiber comprises an input optical fiber, an input lens, an input polaroid, magneto-optical materials, an output polaroid, an output lens and an output optical fiber, wherein the magneto-optical materials comprise any one of a Faraday optical fiber and a Faraday waveguide;
the light source is connected with the wave separator through an optical fiber, the wave separator is connected with the Faraday waveguide module through an optical fiber, the Faraday waveguide module is connected with the demodulator through an optical fiber, and the demodulator is further connected with the data processing terminal;
when the current on the three-phase power transmission conductor is measured, the light source emits detection light, the detection light forms three detection lights with different wavelengths after passing through the wave splitter, the three detection lights with different wavelengths are respectively input into the Faraday waveguide modules on the three power transmission conductors of the three-phase power transmission conductor through the input optical fibers, pass through the Faraday waveguide modules and then are output into the demodulator through the output optical fibers, the signal light containing the magnetic field intensity is converted into an electric signal, and the electric signal is converted into a format for communicating with the data processing terminal and then is input into the data processing terminal; the data processing terminal obtains the total magnetic field of the three transmission conductors on each transmission conductor test point through the Malus theorem and the Faraday magneto-optical effect, and obtains the current intensity on each transmission conductor through the calculation of the Biot-Saval theorem.
Further, the specific detection process of the faraday waveguide module is as follows:
the detection light with the wavelength corresponding to each Faraday waveguide module is guided into a magneto-sensitive area as incident light through the input optical fiber, is focused by the input lens and then is changed into linearly polarized light through the input polarizer, and is incident into the magneto-optical material, and the polarization plane of the incident light is deflected;
the incident light passing through the magneto-optical material is focused by the output lens into the output optical fiber after passing through the output polarizer;
after the incident light passes through the magneto-optical material, the light intensity of the incident light is determined by the input intensity I 0 Becomes output light intensity I 1 。
Further, the polarization directions of the input polarizer and the output polarizer are perpendicular to each other, and the intensity of the transmitted light measured is proportional to the rotation angle of the polarization plane of the light in the magneto-optical crystal and proportional to the intensity of the component of the magnetic field intensity along the crystal axis direction.
Further, the faraday waveguide module further includes: and the glass tube is used for wrapping the structure comprising the input lens, the input polaroid, the magneto-optical material, the output polaroid and the output lens in the Faraday waveguide module in the glass tube.
Furthermore, a detector is also arranged on the demodulator;
the detector further comprises a diode, a preamplification circuit and an active band-pass filtering device;
the diode is used for converting an optical signal into an electrical signal;
the pre-amplification processing circuit is used for carrying out operational amplification on the electric signal;
and the active band-pass filtering is used for filtering the electric signal to obtain an electric signal containing magnetic field intensity information.
Further, the data processing terminal is used for analyzing, calculating and displaying the electric signal provided by the demodulator.
Further, the total magnetic field of three transmission conductors on each transmission conductor test point is obtained through the Malus theorem and the Faraday magneto-optical effect, and the current intensity on each transmission conductor is obtained through the calculation of the Biot-Saval theorem, which specifically comprises the following steps:
by utilizing the Faraday magneto-optical effect, when linearly polarized light is transmitted in a medium, a magnetic field is generated on a transmission line in a direction parallel to the transmission direction of light, the vibration direction of the light is deflected, and the deflection angle theta is formed F Proportional to the product of magnetic induction B and the length d of the light traversing the faraday medium:
θ F ＝VBd
the proportionality coefficient V is called Verdet constant, and is related to the property of the medium and the frequency of the light wave;
deflection angle theta F Input light intensity I by measuring signal 0 And the intensity I of the light generated by the Faraday fiber or waveguide with the polaroid under the action of the magnetic field 1 Comparison results, according to the malus theorem:
I 1 ＝I 0 ·sin 2 θ F
according to the biot-savart theorem, for an infinite straight wire, at a vertical distance r from the wire, the magnetic field strength perpendicular to the wire is as follows:
wherein, mu 0 4 π × 10 is magnetic permeability in vacuum -7 H/m; r is the distance between the measured point and the axis of the conducting wire, and the unit is m; i is the magnitude of the current to be measured, unit A;
for a group of horizontal three-phase wireless straight conductors 1, 2 and 3, the current in the same direction passing through the three transmission conductors is I 1 ，I 2 ，I 3 The distance between the transmission wires is R, the length of the test point from the wire 1 is R, and the test point is in the horizontal direction outside the wire 1. According to the Biao-Saval theorem, the magnetic field of the test point on the lead 1 is as follows:
when R "R, the magnitude of the magnetic field experienced by the wire 2 at the test point can be approximated as:
the magnitude of the magnetic field experienced by the test point by the wire 3 can be approximated by:
the total magnetic field experienced by the test point is therefore:
finishing to obtain:
similarly, the total magnetic field intensity of the test point at r in the horizontal direction from the wire 2 and facing the direction of the wire 1 is:
finishing to obtain:
similarly, the total magnetic field strength received by the test points at r in the horizontal direction outside the distance wire 3 is:
finishing to obtain:
solving the ternary linear equation set for the two-form after finishing to obtain:
from this, the magnetic field strength B of the three-phase current lead group measured by each of the three-phase current leads is determined 1 ，B 2 ，B 3 Calculating the current intensity I by using the distance parameter R between the high-voltage straight conductor groups and the distance R between the test points and the straight conductor R 1 ，I 2 ,I 3 。
Compared with the prior art, the invention has the beneficial effects that:
(1) the optical fiber sensing system for the current intensity of the three-phase high-voltage wires is characterized by comprising three light sources, wave splitters, Faraday waveguide modules, demodulators and a data processing terminal, wherein the three Faraday waveguide modules are respectively arranged at the same position of each high-voltage wire of the three-phase high-voltage wires; when the current on the three-phase power transmission conductor is measured, the light source emits detection light, the detection light forms three detection lights with different wavelengths after passing through the wave splitter, the three detection lights with different wavelengths are respectively input into the Faraday waveguide modules on the three power transmission conductors of the three-phase power transmission conductor through the input optical fibers, are output into the demodulator through the Faraday waveguide modules and the output optical fibers, convert the signal light containing the magnetic field intensity into an electric signal, convert the electric signal into a format for communicating with the data processing terminal, and input the electric signal into the data processing terminal; the data processing terminal obtains the total magnetic field of the three transmission conductors on each transmission conductor test point through the Malus theorem and the Faraday magneto-optical effect, and obtains the current intensity on each transmission conductor through the calculation of the Biot-Saval theorem. The advantages that the exciting current can be eliminated by the optical fiber or the waveguide, the external electromagnetic interference is eliminated by the inherent characteristics of the optical fiber or the waveguide, the purposes of reducing cost and volume are achieved, and the purpose of detecting the current of the three-phase high-voltage transmission line among the transmission conductors under the mutual influence of the magnetic fields among a plurality of transmission conductors is effectively realized.
(2) The invention preferably adopts the scheme that the input polaroid and the output polaroid are perpendicular to each other, and the measured intensity of the transmitted light is in direct proportion to the rotation angle of the polarization plane of the light in the magneto-optical crystal and in direct proportion to the light intensity of the component of the magnetic field intensity along the axial direction of the crystal. And when measuring current, sensitivity is higher, and is more sensitive to magnetic field.
Drawings
Fig. 1 is a block diagram of an optical fiber sensing system of the present invention for detecting current levels in a three-phase power conductor.
Figure 2 is a schematic view of the faraday waveguide module installation of the present invention detecting current intensity of a three phase power conductor.
Figure 3 is a schematic diagram of the structure of a faraday waveguide with a polarizer.
Fig. 4 is a diagram illustrating the principle of the magneto-optical effect.
Fig. 5 is a cross-sectional view of the current sensor of the present invention as measured by a set of horizontal three-phase electrical high voltage straight conductors.
FIG. 6 shows magnetic field intensity B and deflection angle θ F The relationship between them.
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, this embodiment provides an optical fiber sensing system for measuring current intensity of three-phase high-voltage wires, including a light source, a wave splitter, three faraday waveguide modules, a demodulator, and a data processing terminal, where the three faraday waveguide modules are respectively disposed at the same position of each high-voltage wire of the three-phase high-voltage wires. Fig. 2 is a schematic diagram of a faraday waveguide module of the present invention mounted on each of three-phase high-voltage conductors.
As shown in fig. 3, the faraday waveguide module specifically includes: the optical fiber comprises an input optical fiber, an input lens, an input polaroid, a magneto-optical material, an output polaroid, an output lens and an output optical fiber, wherein the magneto-optical material comprises any one form of Faraday optical fiber and Faraday wave guide;
the light source is connected with the wave separator through an optical fiber, the wave separator is connected with the Faraday waveguide module through an optical fiber, the Faraday waveguide module is connected with the demodulator through an optical fiber, and the demodulator is further connected with the data processing terminal;
when the current on the three-phase power transmission conductor is measured, the light source emits detection light, the detection light forms three detection lights with different wavelengths after passing through the wave splitter, the three detection lights with different wavelengths are respectively input into the Faraday waveguide modules on the three power transmission conductors of the three-phase power transmission conductor through the input optical fibers, pass through the Faraday waveguide modules and then are output into the demodulator through the output optical fibers, the signal light containing the magnetic field intensity is converted into an electric signal, and the electric signal is converted into a format for communicating with the data processing terminal and then is input into the data processing terminal; the data processing terminal obtains the total magnetic field of the three transmission conductors on each transmission conductor test point through the Malus theorem and the Faraday magneto-optical effect, and obtains the current intensity on each transmission conductor through the calculation of the Biot-Saval theorem.
Further, the specific detection process of the faraday waveguide module is as follows:
the detection light with the wavelength corresponding to each Faraday waveguide module is guided into a magneto-sensitive area as incident light through the input optical fiber, is focused by the input lens and then is changed into linearly polarized light through the input polaroid, and the linearly polarized light is incident into the magneto-optical material, so that the polarization plane of the incident light is deflected;
the incident light passing through the magneto-optical material is focused by the output lens into the output optical fiber after passing through the output polarizer;
after the incident light passes through the magneto-optical material, the light intensity of the incident light is determined by the input intensity I 0 Becomes output light intensity I 1 。
Further, the polarization directions of the input polarizer and the output polarizer are perpendicular to each other, and the intensity of the transmitted light measured is proportional to the rotation angle of the polarization plane of the light in the magneto-optical crystal and proportional to the intensity of the component of the magnetic field intensity along the axial direction of the crystal.
Further, the faraday waveguide module further includes: and the glass tube is used for wrapping the structure comprising the input lens, the input polaroid, the magneto-optical material, the output polaroid and the output lens in the Faraday waveguide module in the glass tube.
Furthermore, a detector is also arranged on the demodulator;
the detector further comprises a diode, a preamplification circuit and an active band-pass filtering device;
the diode is used for converting an optical signal into an electrical signal;
the pre-amplification processing circuit is used for carrying out operational amplification on the electric signal;
and the active band-pass filtering is used for filtering the electric signal to obtain an electric signal containing magnetic field intensity information.
Specifically, the detector converts the optical signal into an electrical signal to obtain a spot signal containing the magnetic field strength. The detector converts the optical signal into the electrical signal, but the optical signal and the electrical signal are very weak, so the circuit is designed to be an amplifying circuit with low noise and high gain. The weak optical signal received by the photoelectric detector is converted into an electric signal and is subjected to operational amplification, the signal and noise are amplified by using the operational amplifier, and new noise is introduced into the amplifier, so that a signal containing magnetic field intensity information can be obtained by active band-pass filtering. It should be noted that the design of the above circuit has many implementation schemes, and this embodiment is not described in detail.
Further, the data processing terminal is used for analyzing, calculating and displaying the electric signal provided by the demodulator.
Further, the total magnetic field of the three transmission conductors on each transmission conductor test point is calculated by the malus theorem and the faraday magneto-optical effect (shown in fig. 4), and the current intensity on each transmission conductor is calculated by the biot-savart theorem, which specifically includes:
by utilizing the Faraday magneto-optical effect, when linearly polarized light is transmitted in a medium, a magnetic field is generated on a transmission line in a direction parallel to the transmission direction of the light, and the vibration direction of the light isIs deflected by a deflection angle theta F Proportional to the product of the magnetic induction B and the length d of the light traversing the faraday medium:
θ F ＝VBd
the proportionality coefficient V is called Verdet constant, and is related to the property of the medium and the frequency of the light wave;
deflection angle theta F Input light intensity I by measuring signal 0 And the intensity I of the light generated by the Faraday fiber or waveguide with polarizer and acted by magnetic field 1 Comparison results, according to the malus theorem:
I 1 ＝I 0 ·sin 2 θ F
according to the biot-savart theorem, for an infinite straight wire, at a vertical distance r from the wire, the magnetic field strength perpendicular to the wire is as follows:
wherein, mu 0 4 π × 10 is magnetic permeability in vacuum -7 H/m; r is the distance between the measured point and the axis of the wire, and is the unit m; i is the magnitude of the current to be measured, unit A;
as shown in FIG. 5, for a group of horizontal three-phase wireless long straight conductors 1, 2, 3, the current magnitude in the same direction passing through three transmission conductors is I 1 ，I 2 ，I 3 The distance between the transmission wires is R, the length of the test point from the wire 1 is R, and the test point is in the horizontal direction outside the wire 1. According to the Biao-Saval theorem, the magnetic field of the test point on the lead 1 is as follows:
when R > R, the magnitude of the magnetic field experienced by the test point on the wire 2 can be approximated as:
the magnitude of the magnetic field experienced by the wire 3 at the test point can be approximated as:
the total magnetic field experienced by the test point is therefore:
finishing to obtain:
similarly, the total magnetic field intensity of the test point at r in the horizontal direction from the wire 2 and facing the direction of the wire 1 is:
finishing to obtain:
similarly, the total magnetic field strength received by the test points at r in the horizontal direction outside the distance wire 3 is:
the finishing can be carried out as follows:
solving the ternary linear equation set for the two-form after finishing to obtain:
from this, the magnetic field strength B of the three-phase electric wire set measured separately is obtained 1 ，B 2 ，B 3 Calculating the current intensity I by the distance parameter R between the high-voltage straight conductor groups and the distance R between the test points and the straight conductor R 1 ，I 2 ,I 3 。
It should be noted that the installation positions of the three faraday waveguides shown in fig. 5 (the first and second faraday waveguides are installed on the left side of the conductor, and the third faraday waveguide is installed on the right side of the conductor) are only an example, and in the actual installation, the faraday waveguides can be installed at any position of the conductor, and it is only necessary to ensure that the three faraday waveguides are located at the same position of each high-voltage conductor of the three-phase high-voltage conductor. Correspondingly, if the installation positions are different, the calculation formula for calculating the magnetic field needs to be adjusted correspondingly.
Example two
The present embodiment now considers the actual situation of the measured currents on a set of three-phase electric high voltage dc conductors as shown in fig. 5.
The Faraday waveguide with a polarizing plate used a 65-wt% terbium-doped silicate fiber as a Faraday fiber, with a length d of 0.04m and a Verdet constant V of 32 rad/(T.m).
As shown in fig. 4, it is known from the faraday magneto-optical effect that when linearly polarized light propagates through a medium, if a magnetic field is applied in a direction parallel to the propagation direction of the light, the vibration direction of the light is deflected, and the deflection angle θ is changed F Proportional to the product of the magnetic induction B and the length d of the light traversing the faraday medium:
θ F ＝VBd
with the known length d and Verdet constant V, the deflection angle θ F The relationship with the magnetic field strength B is:
θ F ＝VBd＝32rad/(T.m)·0.04m·B＝1.28B(rad)
wherein the unit of the magnetic field strength B is tesla (T). Further, it is found that the magnetic field intensity B and the deflection angle θ F In proportion:
B＝0.78θ F
wherein the deflection angle theta F Can be based on the reference light intensity I 0 And the intensity I of the light generated by the Faraday fiber with polaroid under the action of magnetic field 1 The comparison shows that according to the Malus theorem:
I 1 ＝I 0 ·sin 2 θ F
as shown in FIG. 6, θ can be calculated F Value according to the deflection angle theta F And the magnitude of the magnetic field intensity B can be calculated according to the relation between the magnetic field intensity B and the magnetic field intensity.
As shown in fig. 5, a cross-sectional view of a three-phase high-voltage straight conductor for measuring current is shown, the distance R between the faraday waveguides with the polarizing plates in the current sensor from the central axis of the conductor is 0.01m, and the distance R between the axes of the conductor is 1 m. According to the biot-savart law, for an infinite straight wire, at a vertical distance r from the wire, the magnetic field strength perpendicular to the wire is as follows:
wherein, mu 0 4 π × 10 is the permeability in vacuum -7 H/m; r is the distance between the measured point and the axis of the wire, and is the unit m; i is the magnitude of the measured current, in units A.
The Biao-Saval law is applied to three-phase high-voltage straight conductors to calculate the current I in the three conductors 1 ,I 2 ,I 3 The magnitude of the magnetic field B measured by the corresponding wire sensor 1 ,B 2 ,B 3 The relationships between the two are respectively:
the three-phase electric specific value in the embodiment is substituted to calculate the current I of the three conducting wires 1 ,I 2 ,I 3 The size B of the magnetic field applied to the Faraday waveguide with the polaroid in the current sensor 1 ,B 2 ,B 3 BetweenThe relationship of (1) is:
when the Faraday waveguide with the polaroid in the current sensor arranged on the three-phase high-voltage line is subjected to the magnetic field intensity of B 1 ＝0.04T,B 2 ＝0.03T,B 3 When the voltage is equal to 0.04T, the currents of three leads of the three-phase power are respectively measured as I 1 ＝1975.12A,I 2 ＝1500A,I 3 ＝1975.12A。
The present invention has been described in terms of specific examples, which are provided to aid understanding of the invention and are not intended to be limiting. For a person skilled in the art to which the invention pertains, several simple deductions, modifications or substitutions may be made according to the idea of the invention.
Claims (6)
1. An optical fiber sensing system for measuring current intensity of three-phase high-voltage wires is characterized by comprising three light sources, wave splitters, Faraday waveguide modules, demodulators and a data processing terminal, wherein the three Faraday waveguide modules are respectively arranged at the same position of each high-voltage wire of the three-phase high-voltage wires;
the faraday waveguide module specifically comprises: the optical fiber comprises an input optical fiber, an input lens, an input polaroid, a magneto-optical material, an output polaroid, an output lens and an output optical fiber, wherein the magneto-optical material comprises any one form of Faraday optical fiber and Faraday wave guide;
the light source is connected with the wave separator through an optical fiber, the wave separator is connected with the Faraday waveguide module through an optical fiber, the Faraday waveguide module is connected with the demodulator through an optical fiber, and the demodulator is further connected with the data processing terminal;
when the current on the three-phase high-voltage wire is measured, the light source emits detection light, the detection light forms three detection lights with different wavelengths after passing through the wave splitter, the three detection lights with different wavelengths are respectively input into the Faraday waveguide modules on the three power transmission wires of the three-phase high-voltage wire through the input optical fibers, pass through the Faraday waveguide modules and then are output into the demodulator through the output optical fibers, the signal light containing the magnetic field intensity is converted into an electric signal, and the electric signal is converted into a format for communicating with the data processing terminal and then is input into the data processing terminal; the data processing terminal obtains the total magnetic field of three transmission conductors on each transmission conductor test point through the Malus theorem and the Faraday magneto-optical effect, and obtains the current intensity on each transmission conductor through the calculation of the Biot-Saval theorem;
the method comprises the following steps of calculating the total magnetic field of three transmission conductors on each transmission conductor test point through the Malus theorem and the Faraday magneto-optical effect, and calculating the current intensity on each transmission conductor through the Biot-Saval theorem, wherein the method specifically comprises the following steps:
by utilizing the Faraday magneto-optical effect, when linearly polarized light is transmitted in a medium, a magnetic field is generated on a transmission line in a direction parallel to the transmission direction of the light, the vibration direction of the light is deflected, and the deflection angle theta is changed F Proportional to the product of the magnetic induction B and the length d of the light traversing the faraday medium:
θ F ＝VBd
the proportionality coefficient V is called Verdet constant, and is related to the medium property and the light wave frequency;
deflection angle theta F Input light intensity I by measuring signal 0 And the intensity I of the light generated by the Faraday fiber or waveguide with polarizer and acted by magnetic field 1 Comparison results, according to the malus theorem:
I 1 ＝I 0 ·sin 2 θ F
according to the biot-savart theorem, for an infinite straight wire, at a vertical distance r from the wire, the magnetic field strength perpendicular to the wire is as follows:
wherein, mu 0 4 π × 10 is the permeability in vacuum -7 H/m; r is the distance between the measured point and the axis of the conducting wire, and the unit is m; i is the magnitude of the current to be measured, unit A;
for a group of horizontal three-phase wireless straight conductors 1, 2 and 3, the current in the same direction passing through the three transmission conductors is I 1 ，I 2 ，I 3 The distance between the transmission wires is R, the distance between the test points and the wire 1 is R, and the test points are arranged in the horizontal direction outside the wire 1, and according to the Biot-Saval theorem, the magnetic field of the wire 1 on the test points is as follows:
when R > R, the magnitude of the magnetic field experienced by the test point on the wire 2 can be approximated as:
the magnitude of the magnetic field experienced by the test point by the wire 3 can be approximated by:
the total magnetic field experienced by the test point is therefore:
finishing to obtain:
similarly, the total magnetic field intensity of the test point at r in the horizontal direction from the wire 2 and facing the direction of the wire 1 is:
finishing to obtain:
similarly, the total magnetic field intensity received by the test point at r in the horizontal direction from the outer side of the wire 3 is:
finishing to obtain:
solving a ternary linear equation set for the two-form solution after finishing to obtain:
from this, the magnetic field strength B of the three-phase current lead group measured by each of the three-phase current leads is determined 1 ，B 2 ，B 3 Calculating the current intensity I by the distance parameter R between the high-voltage straight conductor groups and the distance R between the test points and the straight conductor R 1 ，I 2 ,I 3 。
2. The fiber optic sensing system according to claim 1, wherein the faraday waveguide module is configured to perform the following steps:
the detection light with the wavelength corresponding to each Faraday waveguide module is guided into a magneto-sensitive area as incident light through the input optical fiber, is focused by the input lens and then is changed into linearly polarized light through the input polaroid, and the linearly polarized light is incident into the magneto-optical material, so that the polarization plane of the incident light is deflected;
the incident light passing through the magneto-optical material is focused by the output lens into the output optical fiber after passing through the output polarizer;
after the incident light passes through the magneto-optical material, the light intensity of the incident light is determined by the input intensity I 0 Becomes output light intensity I 1 。
3. The fiber optic sensing system according to claim 1, wherein the input polarizer and the output polarizer have polarization directions perpendicular to each other, and the intensity of the transmitted light is measured in proportion to the rotation angle of the polarization plane of the light in the magneto-optical crystal and in proportion to the intensity of the component of the magnetic field along the axial direction of the crystal.
4. The fiber optic sensing system for measuring current strength of a three-phase high voltage conductor of claim 1, wherein the faraday waveguide module further comprises: and the glass tube is used for wrapping the structure comprising the input lens, the input polaroid, the magneto-optical material, the output polaroid and the output lens in the Faraday waveguide module in the glass tube.
5. The fiber optic sensing system for measuring current levels of a three-phase high voltage conductor of claim 1 wherein a detector is further disposed on said demodulator;
the detector further comprises a diode, a preamplification circuit and an active band-pass filtering device;
the diode is used for converting an optical signal into an electrical signal;
the pre-amplification processing circuit is used for carrying out operational amplification on the electric signal;
the active band-pass filtering is used for filtering the electric signal to obtain an electric signal containing magnetic field intensity information.
6. The fiber optic sensing system according to claim 1, wherein the data processing terminal is adapted to analyze, calculate and display the electrical signals provided by the demodulator.
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