CN117192313A - Optical fiber sensing system for detecting partial discharge of gas-insulated switchgear - Google Patents
Optical fiber sensing system for detecting partial discharge of gas-insulated switchgear Download PDFInfo
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Abstract
The invention provides an optical fiber sensing system for detecting partial discharge of gas-insulated switchgear, comprising: the first coupler divides laser light emitted by the laser into detection light and reference light; the optical fiber sensor detects the ultrasonic signal by using the detection light to obtain ultrasonic modulated light; the second coupler interferes the ultrasonic modulated light and the reference light which is modulated by the piezoelectric ceramic optical phase modulator and the low-frequency noise suppression module together, and divides the interference light into a first interference light and a second interference light; the balance photoelectric detector performs photoelectric conversion on the first interference light and the second interference light to obtain an alternating voltage signal corresponding to the ultrasonic signal; the noise feedback module filters the alternating voltage signal at a first preset frequency to obtain an environmental noise voltage signal; the piezoelectric ceramic optical phase modulator carries out first modulation on the phase of reference light according to an environmental noise voltage signal; the low-frequency noise suppression module performs second modulation on the phase of the reference light according to the environmental noise voltage signal.
Description
Technical Field
The invention relates to the technical field of optical fiber sensing and the technical field of partial discharge measurement, in particular to an optical fiber sensing system for detecting partial discharge of gas-insulated switchgear.
Background
The gas-insulated switchgear (Gas Insualation Switchgear, GIS) is the main stream equipment in the high-voltage power system with the advantages of compact structure, difficult influence of external environment, strong expandability, high operation reliability, convenient overhaul and maintenance, and the like.
A large number of GIS fault cases show that: the metal particles generated in the GIS production and installation process are the main reasons for reducing the GIS insulation level, and more GIS insulation faults can be caused along with the reduction of the GIS insulation level. In the GIS operation process, metal particles can be adsorbed on the surface of the GIS insulator, so that the electric field distortion of the surface of the GIS insulator is caused, and partial discharge is initiated. Partial discharge is an important sign and expression form of insulation fault, so that the GIS internal insulation state can be diagnosed and evaluated by detecting GIS partial discharge caused by metal particles, insulation fault early warning is realized, and the operation reliability of the GIS is improved.
In the related art, the detection of the GIS partial discharge phenomenon is realized by detecting different physical quantities generated by the GIS partial discharge. The existing detection method of partial discharge mainly comprises the following steps: pulse current method, ultrahigh frequency method, optical measurement method, and acoustic measurement method. The pulse current method has extremely low detection lower limit and large field interference, and cannot be detected on the GIS field; the optical measurement method needs to open a hole on a GIS cavity to install a photodiode, so as to destroy the GIS structure; the ultrahigh frequency method relies on an ultrahigh frequency built-in or external sensor, so that the field interference is large; the sensor used by the ultrasonic method is arranged on the GIS shell, the field application is simple and quick, but in the field test, the GIS equipment has complex running field environment, various system noise sources and influences the stability of the detection system. Therefore, it is needed to find a method for resisting environmental interference, ensuring a stable detection system and improving the accuracy of the detected partial discharge of the GIS.
Disclosure of Invention
In view of the above, the present invention provides an optical fiber sensing system for detecting partial discharge of a gas-insulated switchgear.
The invention provides an optical fiber sensing system for detecting partial discharge of gas-insulated switchgear, comprising:
a laser for emitting laser light of a predetermined wavelength;
a first coupler for dividing the laser into detection light and reference light with the same power;
the optical fiber sensor is used for detecting ultrasonic signals generated by partial discharge of the insulation switch equipment by using the detection light to obtain ultrasonic modulated light;
the second coupler is used for interfering the ultrasonic modulated light and the reference light with the phase frequency modulated by the piezoelectric ceramic optical phase modulator and the low-frequency noise suppression module together, and dividing interference light obtained by interference into first interference light and second interference light with the same power;
the balanced photoelectric detector is used for carrying out photoelectric conversion on the first interference light and the second interference light to obtain an alternating voltage signal corresponding to the ultrasonic signal, so that the optical fiber sensing system obtains the ultrasonic signal according to the alternating voltage signal;
the noise feedback module is used for filtering the alternating voltage signal at a first preset frequency to obtain an environment noise voltage signal, wherein the environment noise voltage signal represents a voltage signal corresponding to a noise signal in an environment where the insulating switch equipment is located;
A piezoelectric ceramic optical phase modulator connected to a reference optical fiber for transmitting the reference light, and performing a first modulation on the phase of the reference light according to the environmental noise voltage signal, so as to increase a first frequency phase in the phase of the first modulated reference light, wherein the first frequency phase represents a phase which has the same amplitude and frequency as a second frequency phase and has an opposite propagation direction, and the second frequency phase represents a phase amount which is greater than or equal to a second predetermined frequency and less than or equal to the first predetermined frequency and is used for increasing the phase of the detection light by environmental noise;
and a low-frequency noise suppression module connected to a reference optical fiber for transmitting the reference light, wherein the low-frequency noise suppression module performs second modulation on the phase of the reference light according to the environmental noise voltage signal, so as to increase a third frequency phase in the phase of the reference light subjected to the second modulation, wherein the third frequency phase is the same as the fourth frequency phase in frequency and opposite in propagation direction, the third frequency phase is determined according to the fourth frequency phase and a preset phase, and the fourth frequency phase represents the phase quantity of the increase of the phase of the detection light by the environmental noise smaller than the second preset frequency.
According to an embodiment of the present invention, the low frequency noise suppression module includes:
a voltage comparator for comparing the ambient noise voltage signal with a predetermined voltage and outputting a binary signal corresponding to the predetermined voltage;
the singlechip controller is used for outputting at least one eight-bit binary number at a third preset frequency according to the binary signal;
the digital-to-analog converter is used for respectively converting the at least one eight-bit binary number into an initial driving voltage signal to obtain at least one initial driving voltage signal;
the motor driving sub-module is used for amplifying the at least one initial driving voltage signal by a preset multiple to obtain at least one target driving voltage signal;
and the motor drives the telescopic optical fiber lead screw to be connected into the reference optical fiber for transmitting the reference light, and is used for adjusting the length of the reference optical fiber according to the at least one target driving voltage signal so as to increase the third frequency phase in the phase of the adjusted reference light.
According to an embodiment of the present invention, the predetermined voltage includes a first predetermined voltage and a second predetermined voltage, the first predetermined voltage is smaller than the second predetermined voltage, the voltage comparator is further configured to perform the comparing the ambient noise voltage signal with the predetermined voltage by:
Outputting a first binary signal if the ambient noise voltage signal is greater than a second predetermined voltage;
outputting a second binary signal in case that the ambient noise voltage signal is smaller than a first predetermined voltage;
and outputting a third binary signal when the ambient noise voltage signal is equal to or higher than the first predetermined voltage and equal to or lower than the second predetermined voltage.
According to an embodiment of the present invention, the single chip microcomputer controller is further configured to output at least one eight-bit binary number at a third predetermined frequency according to the binary signal by:
sequentially outputting eight-bit binary numbers corresponding to at least one value included in the first numerical range at a third predetermined frequency under the condition that the binary signal is the first binary signal;
sequentially outputting eight-bit binary numbers corresponding to at least one value included in the second value range at a third predetermined frequency under the condition that the binary signal is the second binary signal;
and outputting eight-bit binary numbers corresponding to at least one value included in the third numerical range at a third predetermined frequency when the binary signal is a third binary signal.
According to an embodiment of the present invention, the digital-to-analog converter is further configured to convert the at least one eight-bit binary number into an initial driving voltage signal, respectively, to obtain at least one initial driving voltage signal by:
and linearly mapping the at least one eight-bit binary number to a driving voltage signal with the value in a fourth value range to obtain at least one initial driving voltage signal, wherein the maximum value of the at least one eight-bit binary number corresponds to the maximum value in the fourth value range, and the minimum value of the at least one eight-bit binary number corresponds to the minimum value in the fourth value range.
According to an embodiment of the present invention, a noise feedback module includes:
the low-pass filter is used for carrying out low-pass filtering of a first preset frequency on the alternating voltage signal to obtain an initial environmental noise voltage signal;
and the integrator is used for carrying out accumulation processing on the initial environmental noise voltage signal to obtain the environmental noise voltage signal with the cutoff frequency of the first preset frequency.
According to an embodiment of the present invention, the first predetermined voltage is-2V, and the second predetermined voltage is 2V.
According to an embodiment of the present invention, the predetermined multiple is 20 times, and the third predetermined frequency is 1/1 us.
According to an embodiment of the invention, the first predetermined frequency is 10kHz and the second predetermined frequency is 10Hz.
According to the embodiment of the invention, the devices and modules except the optical fiber sensor in the optical fiber sensing system are packaged by using an aluminum plate with the thickness of 5mm, and the optical fiber sensor is a cylindrical optical fiber sensor with the diameter of 5 cm and packaged by epoxy resin.
According to the embodiment of the invention, the phase of the reference light is subjected to first modulation through the piezoelectric ceramic optical phase modulator, so that the first frequency phase is increased in the phase of the reference light subjected to first modulation, the low-frequency noise suppression module is used for carrying out second modulation on the phase of the reference light, so that the third frequency phase is increased in the phase of the reference light subjected to second modulation, the second coupler can filter out an optical signal corresponding to environmental noise in an ultrasonic modulated optical signal after interfering the ultrasonic modulated light and the reference light subjected to common modulation of the phase frequency by the piezoelectric ceramic optical phase modulator and the low-frequency noise suppression module, the influence of the environmental noise on the ultrasonic modulated optical signal is suppressed, the obtained first interference light and second interference light do not comprise an optical signal corresponding to the environmental noise, and then the photoelectric conversion is carried out on the first interference light and the second interference light, so that an alternating voltage signal corresponding to the ultrasonic signal, which is not influenced by the environmental noise, can be obtained, and then the ultrasonic signal, which is not influenced by the environmental noise, can be obtained according to the stable alternating voltage signal, can be analyzed by the ultrasonic signal, and the local discharge signal can be analyzed according to the high-frequency noise signal.
Drawings
The foregoing and other objects, features and advantages of the invention will be apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:
FIG. 1 shows a schematic diagram of a fiber optic sensing system for detecting partial discharge of a gas insulated switchgear according to an embodiment of the present invention;
fig. 2 shows a flowchart for controlling the single chip microcomputer controller to output a binary signal corresponding to a predetermined voltage according to an embodiment of the present invention.
Detailed Description
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be understood that the description is only illustrative and is not intended to limit the scope of the invention. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the invention. It may be evident, however, that one or more embodiments may be practiced without these specific details. In addition, in the following description, descriptions of well-known structures and techniques are omitted so as not to unnecessarily obscure the present invention.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The terms "comprises," "comprising," and/or the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.
All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It should be noted that the terms used herein should be construed to have meanings consistent with the context of the present specification and should not be construed in an idealized or overly formal manner.
Where expressions like at least one of "A, B and C, etc. are used, the expressions should generally be interpreted in accordance with the meaning as commonly understood by those skilled in the art (e.g.," a system having at least one of A, B and C "shall include, but not be limited to, a system having a alone, B alone, C alone, a and B together, a and C together, B and C together, and/or A, B, C together, etc.).
The metal particles generated in the GIS production and installation process are the main reasons for reducing the GIS insulation level, and more GIS insulation faults can be caused along with the reduction of the GIS insulation level. In the GIS operation process, metal particles can be adsorbed on the surface of the GIS insulator, so that the electric field distortion of the surface of the GIS insulator is caused, and partial discharge is initiated. Partial discharge is an important sign and expression form of insulation fault, so that the GIS internal insulation state can be diagnosed and evaluated by detecting GIS partial discharge caused by metal particles, insulation fault early warning is realized, and the operation reliability of the GIS is improved.
In the related art, the detection of the GIS partial discharge phenomenon is realized by detecting different physical quantities generated by the GIS partial discharge. However, in field test, the GIS equipment has complex operation field environment, various system noise sources and can influence the stability of the detection system. Therefore, it is needed to find a method for resisting environmental interference, ensuring a stable detection system and improving the accuracy of the detected partial discharge of the GIS.
In order to at least partially solve the technical problems in the related art, the embodiment of the invention provides an optical fiber sensing system for detecting partial discharge of gas-insulated switchgear, which can be applied to the technical field of optical fiber sensing and the technical field of partial discharge measurement.
An optical fiber sensing system for detecting partial discharge of a gas-insulated switchgear according to an embodiment of the present invention will be described in detail based on fig. 1 and 2.
Fig. 1 shows a schematic diagram of a fiber optic sensing system for detecting partial discharge of a gas insulated switchgear according to an embodiment of the present invention.
As shown in fig. 1, the optical fiber sensing system for detecting partial discharge of a gas-insulated switchgear includes: the device comprises a laser 1, a first coupler 2, an optical fiber sensor 3, a second coupler 4, a balance photoelectric detector 5, a noise feedback module 6, a piezoelectric ceramic optical phase modulator 7 and a low-frequency noise suppression module 8.
A laser 1 for emitting laser light of a predetermined wavelength.
According to an embodiment of the present invention, the predetermined wavelength may be selected according to the actual situation, and is not limited herein. For example, the predetermined wavelength may be 1310nm or 1550nm.
For example, the optical fiber sensing system provided by the embodiment of the invention can detect partial discharge of the GIS based on 1550nm laser.
A first coupler 2 for dividing the laser light into detection light and reference light of the same power.
According to an embodiment of the invention, the first coupler 2 may be a 2 x 2 coupler.
According to an embodiment of the present invention, the laser 1 and the first coupler 2 are connected by an optical fiber for transmitting laser light.
According to the embodiment of the invention, an optical isolator can be added between the optical fiber for transmitting laser and the laser 1, so as to inhibit reflected light generated from the distal end face of the optical fiber or the interface of the first coupler 2 in the optical fiber line from returning to the laser, thereby ensuring the stability of the working state of the laser and reducing noise caused by the reflected light of the optical fiber sensing system.
And the optical fiber sensor 3 is used for detecting ultrasonic signals generated by partial discharge of the insulation switch equipment by using detection light to obtain ultrasonic modulated light.
According to an embodiment of the present invention, the optical fiber sensor 3 and the first coupler 2 are connected by a sensing optical fiber for transmitting detection light.
According to the embodiment of the invention, the high-sensitivity optical fiber sensor 3 is arranged on a GIS cavity to be detected, and an ultrasonic couplant is smeared on the contact surface. After the optical fiber sensor 3 receives the detection light, an ultrasonic signal generated by partial discharge of the gas-insulated switchgear modulates the detection light in the optical fiber sensor 3, so that the phase of the modulated detection light in the optical fiber sensor 3 is shifted, and ultrasonic modulated light is obtained.
And a second coupler 4 for interfering the ultrasonic modulated light and the reference light with the phase frequency modulated by the piezoelectric ceramic optical phase modulator 7 and the low-frequency noise suppression module 8 together, and dividing the interfered light into a first interfered light and a second interfered light with the same power.
According to an embodiment of the invention, the second coupler 4 may be a 2 x 2 coupler.
According to an embodiment of the invention, the connection between the second coupler 4 and the optical fiber sensor 3 is made with a sensing optical fiber for transmitting the ultrasound modulated light. The second coupler 4 and the first coupler 2 are connected by a reference fiber for transmitting reference light.
And the balance photoelectric detector 5 is used for carrying out photoelectric conversion on the first interference light and the second interference light to obtain an alternating voltage signal corresponding to the ultrasonic signal, so that the optical fiber sensing system obtains the ultrasonic signal according to the alternating voltage signal.
According to an embodiment of the present invention, the balanced photodetector 5 and the second coupler 4 are connected by optical fibers for transmitting the first interference light and the second interference light, respectively.
According to the embodiment of the present invention, the balanced photodetector 5 may perform photoelectric conversion on the first interference light and the second interference light, and then perform differential amplification on the converted output signals corresponding to the first interference light and the second interference light, so as to eliminate the direct current component, and obtain an alternating voltage signal corresponding to the ultrasonic signal.
The optical fiber sensing system of fig. 1 may also include a bandpass filter, a digital oscilloscope, and a host computer according to embodiments of the invention. After the alternating voltage signal is obtained, the band-pass filter can carry out band-pass filtering of 10 kHz-80 kHz on the alternating voltage signal, then the alternating voltage signal is collected by the digital oscilloscope, the ultrasonic signal can be obtained through measurement after recording and analysis by the upper computer, and further the partial discharge of the insulating switch equipment and the partial discharge capacity of the insulating switch equipment can be determined according to the ultrasonic signal.
And the noise feedback module 6 is used for filtering the alternating-current voltage signal at a first preset frequency to obtain an environment noise voltage signal, wherein the environment noise voltage signal represents a voltage signal corresponding to the noise signal in the environment where the insulated switchgear is located.
According to the embodiment of the present invention, the noise feedback module 6 is mainly configured to perform low-pass filtering on the ac voltage signal, so as to obtain an ac voltage signal with a frequency less than or equal to the first predetermined frequency in the ac voltage signal.
The piezoceramic optical phase modulator 7 is connected to a reference optical fiber for transmitting the reference light, and performs first modulation on the phase of the reference light according to the environmental noise voltage signal, so that a first frequency phase is added to the phase of the reference light subjected to the first modulation, wherein the first frequency phase represents a phase which has the same amplitude and frequency as those of a second frequency phase and has opposite propagation directions, and the second frequency phase represents a phase amount which is greater than or equal to a second preset frequency and less than or equal to the first preset frequency and causes the phase of the detection light to be increased by environmental noise.
According to the embodiment of the present invention, the reference optical fiber is wound on the piezoelectric ceramic in the piezoelectric ceramic optical phase modulator 7, and in the case of applying the environmental noise voltage signal to the piezoelectric ceramic optical phase modulator 7, the piezoelectric ceramic optical phase modulator 7 is deformed, causing the refractive index and the length of the inside of the reference optical fiber wound on the piezoelectric ceramic optical phase modulator 7 to change, thereby realizing the first modulation of the phase of the reference light, and increasing the first frequency phase in the phase of the first modulated reference light.
According to the embodiment of the invention, the piezoelectric ceramic optical phase modulator 7 is connected into the reference optical fiber for transmitting the reference light, and the phase of the reference light is subjected to first modulation according to the environmental noise voltage signal, so that the phase of the reference light subjected to first modulation is increased by a first frequency phase, the first frequency phase represents a phase which is identical in amplitude and frequency and opposite in propagation direction to the second frequency phase, the second frequency phase represents a phase quantity which is greater than or equal to a second preset frequency and less than or equal to the first preset frequency and is used for increasing the phase of the detection light by environmental noise, the second coupler 4 is used for enabling the phase of the reference light subjected to the modulation of the phase frequency by the piezoelectric ceramic optical phase modulator 7 to offset phase offset caused by a high-frequency signal in the environmental noise signal in the ultrasonic modulation light after interference of the ultrasonic modulation light and the reference light subjected to the modulation of the phase frequency by the piezoelectric ceramic optical phase modulator 7, and the influence of the high-frequency signal in the environmental noise signal on the optical fiber sensing system is inhibited.
According to the embodiment of the invention, the piezoelectric ceramic optical phase modulator 7 can inhibit high-frequency noise signals in environmental noise signals, and the piezoelectric ceramic optical phase modulator 7 has the characteristics of short response time (a few microseconds), accurate phase adjustment and the like, and can effectively realize small-amplitude phase adjustment particularly aiming at the high-frequency signals.
The low-frequency noise suppression module 8 is connected to the reference optical fiber for transmitting the reference light, and performs second modulation on the phase of the reference light according to the environmental noise voltage signal, so that a third frequency phase is added to the phase of the reference light subjected to the second modulation, wherein the third frequency phase is the same as the fourth frequency phase in frequency and opposite in propagation direction, the third frequency phase is determined according to the fourth frequency phase and the preset phase, and the fourth frequency phase represents the phase quantity of the phase increase of the detection light caused by the environmental noise smaller than the second preset frequency.
According to the embodiment of the present invention, the predetermined phase may be selected according to the actual situation, which is not limited herein. For example, the predetermined phase may be 0.5 pi.
According to the embodiment of the present invention, since the piezoelectric ceramic in the piezoelectric ceramic optical phase modulator 7 has a poor response to the low frequency excitation signal and a hysteresis effect, the input voltage signal of the piezoelectric ceramic optical phase modulator 7, i.e., the ambient noise voltage signal, and the output phase modulation amount, i.e., the first frequency phase, are not in a standard linear relationship. Under the combined action of voltage signals corresponding to the high-frequency noise signal and the low-frequency noise signal respectively, namely under the action of the environmental noise voltage signal, the piezoelectric ceramic optical phase modulator 7 can accumulate low-frequency phase modulation quantity deviation, and cannot eliminate the deviation only by means of feedback regulation of the piezoelectric ceramic optical phase modulator, so that the control failure of the phase working point of the alternating-current voltage signal output by the whole grating sensing system can be caused, and the stability of the optical fiber sensing system is affected.
According to the embodiment of the present invention, the third frequency phase can be regarded as the deviation of the low frequency phase modulation amount accumulated by the piezoceramic optical phase modulator 7. Since the low-frequency noise suppression module 8 can perform the second modulation on the phase of the reference light, a third frequency phase is added to the phase of the reference light subjected to the second modulation, the third frequency phase is the same as the fourth frequency phase in frequency and opposite in propagation direction, the third frequency phase is determined according to the fourth frequency phase and the predetermined phase, and the fourth frequency phase represents a phase amount by which the phase of the detection light is increased by the environmental noise smaller than the second predetermined frequency. After the second coupler is used for interfering the ultrasonic modulated light and the reference light with the phase frequency modulated by the piezoelectric ceramic optical phase modulator and the low-frequency noise suppression module, the low-frequency noise suppression module 8 can be used for eliminating the low-frequency phase error accumulated by the high-frequency noise suppression module and enabling the optical fiber sensing system to stably work at the quadrature working point.
According to the embodiment of the invention, the phase of the reference light is subjected to first modulation by the piezoelectric ceramic optical phase modulator 7, so that the first frequency phase is increased in the phase of the reference light subjected to first modulation, the low-frequency noise suppression module 8 is used for performing second modulation on the phase of the reference light, and the third frequency phase is increased in the phase of the reference light subjected to second modulation, so that the second coupler 4 can filter out an optical signal corresponding to environmental noise in an ultrasonic modulated optical signal after interference is performed on the ultrasonic modulated optical signal and the reference light subjected to common modulation of the phase frequency by the piezoelectric ceramic optical phase modulator and the low-frequency noise suppression module, the influence of the environmental noise on the ultrasonic modulated optical signal is suppressed, the obtained first interference light and second interference light do not comprise an optical signal corresponding to the environmental noise, and then the balanced photoelectric detector 5 can obtain an alternating voltage signal corresponding to the ultrasonic signal which is not influenced by the environmental noise after photoelectric conversion is performed on the first interference light and the second interference light, and then the optical fiber sensing system can work in a stable state, and further can obtain an ultrasonic signal which is not influenced by the environmental noise and an ultrasonic signal which is not influenced by the local discharge signal according to the stable alternating voltage signal, and the local discharge precision of the ultrasonic device can be analyzed.
According to the embodiment of the invention, the phase of the reference light is subjected to first modulation through the piezoelectric ceramic optical phase modulator 7, so that the first frequency phase is added in the phase of the reference light subjected to first modulation, the low-frequency noise suppression module 8 is used for carrying out second modulation on the phase of the reference light, and the third frequency phase is added in the phase of the reference light subjected to second modulation, so that the second coupler 4 is used for suppressing the phase fading phenomenon in the ultrasonic modulated light caused by environmental noise after interfering the ultrasonic modulated light and the reference light subjected to common modulation of the phase frequency by the piezoelectric ceramic optical phase modulator and the low-frequency noise suppression module, the interference problem of low-frequency and high-frequency signals in the environmental noise on the ultrasonic modulated light is solved, the overall environment interference resistance of the sensing optical fiber system is improved, the system can stably work for a long time, the continuous stable working time can reach a preset number of days, the long-term use requirement of the sensing optical fiber system is met, and the high-precision online monitoring of GIS partial discharge is realized.
According to an embodiment of the invention, the first predetermined frequency may be 10kHz and the second predetermined frequency may be 10Hz.
According to an embodiment of the present invention, the low-frequency noise signal in the environmental noise characterizes the environmental noise signal having a frequency of 0Hz or more and less than 10Hz. The high-frequency noise signal in the environmental noise characterizes the environmental noise signal with the frequency of more than or equal to 10Hz and less than or equal to 10 kHz.
According to an embodiment of the present invention, after the balanced photodetector 5 performs photoelectric conversion on the first interference light and the second interference light, the obtained alternating voltage signal corresponding to the ultrasonic signal may be expressed as. Wherein,U AC representing the maximum amplitude of the alternating voltage signal, +.>The phase change of the reference light in the sensing optical fiber caused by the high-frequency ultrasonic signal generated by the characteristic partial discharge is a high-frequency small signal.And->The phase changes of the reference light in the sensing fiber caused by the high frequency signal and the low frequency signal in the ambient noise signal are characterized, respectively.
Phase drift caused by ambient noise signals in general, i.e.Will be greater than pi, wherein ∈>Phase drift caused by high frequency ambient noise signal of 10Hz to 10kHz，/>A low frequency ambient noise signal of 0 to 10 Hz. In the case where the ultrasonic signal modulates the phase of the reference light, the reference light for detecting the ultrasonic signal is simultaneously modulated by the environmental noise so that the phase of the reference light is shifted +>After that, will continue to shift +.>And->。
In generalIs much higher than +.>But at +.>Where m is an integer greater than or equal to 1, the detected ac voltage signal is small in a short time, i.e., the fiber optic sensing system operates in an insensitive area, where the duration of the short time is greater than the period of the ultrasonic signal and much less than the period of the noise signal. And at In the short term, the detected ac voltage signal is relatively large. In order to ensure the stability and sensitivity of the optical fiber sensing system, measures have to be taken to make +.>At this time, the optical fiber sensing system stably operates at the orthogonal operating point.
According to the embodiment of the invention, since the piezoceramic optical phase modulator 7 performs the first modulation on the phase of the reference light, the reference of the first modulationThe first frequency phase is added in the phase of the light, the low-frequency noise suppression module 8 adds the third frequency phase in the phase of the reference light after the second modulation is carried out on the phase of the reference light, so that the second coupler 4 can counteract the phase offset in the ultrasonic modulation light after the ultrasonic modulation light and the reference light with the phase frequency modulated by the piezoelectric ceramic light phase modulator and the low-frequency noise suppression module are interferedThe third frequency phase in the reference light can counteract the phase offset in the ultrasound modulated light>And the preset phase offset of 0.5 pi is added in the final interference light, so that the alternating voltage signal finally obtained according to the interference light is relatively large, the optical fiber sensing system stably works at an orthogonal working point, and the stability and the sensitivity of the optical fiber sensing system are ensured.
As shown in fig. 1, the noise feedback module 6 includes: a low pass filter 61 and an integrator 62.
A low-pass filter 61 for performing low-pass filtering of a first predetermined frequency on the ac voltage signal to obtain an initial ambient noise voltage signal;
and an integrator 62 for accumulating the initial ambient noise voltage signal to obtain an ambient noise voltage signal having a cutoff frequency of a first predetermined frequency.
According to an embodiment of the present invention, the low-pass filter 61 may filter out a high frequency component above 10kHz in the ac voltage signal, which is generally considered to be caused by the ultrasonic signal, without performing phase compensation, to obtain an initial ambient noise voltage signal corresponding to the ambient noise signal, and the integrator 62 may smooth the initial ambient noise voltage signal output from the previous stage low-pass filter 61 and amplify low frequency, ultra-low frequency and high frequency signals in the initial ambient noise voltage signal to obtain an ambient noise voltage signal with a cut-off frequency of 10 kHz.
As shown in fig. 1, the low frequency noise suppression module 8 includes a voltage comparator 81, a single chip controller 82, a digital-to-analog converter 83, a motor drive sub-module 84, and a motor drive retractable fiber optic screw 85.
A voltage comparator 81 for comparing the ambient noise voltage signal with a predetermined voltage and outputting a binary signal corresponding to the predetermined voltage;
a single chip microcomputer controller 82 for outputting at least one eight-bit binary number at a third predetermined frequency according to the binary signal;
a digital-to-analog converter 83 for converting at least one eight-bit binary number into an initial driving voltage signal, respectively, to obtain at least one initial driving voltage signal;
a motor driving sub-module 84 for amplifying the at least one initial driving voltage signal by a predetermined multiple to obtain at least one target driving voltage signal, respectively;
the motor drives the telescopic optical fiber screw rod 85, which is connected into the reference optical fiber for transmitting the reference light, and is used for adjusting the length of the reference optical fiber according to at least one target driving voltage signal, so that the phase of the adjusted reference light is increased by a third frequency phase.
According to an embodiment of the present invention, the predetermined multiple may be 20 times and the third predetermined frequency may be 1/1 us.
According to the embodiment of the invention, the predetermined multiple is 20 times, so that at least one target driving voltage signal obtained by the motor driving sub-module 84 can be ensured, and the motor in the motor-driven telescopic optical fiber screw 85 can be driven, so that the motor-driven telescopic optical fiber screw 85 can work normally.
According to the embodiment of the invention, after the environmental noise voltage signal is sequentially processed by the voltage comparator 81, the singlechip controller 82 and the digital-to-analog converter 83 to obtain at least one initial driving voltage signal, the motor driving submodule 84 amplifies the at least one initial driving voltage signal by 20 times to obtain at least one target driving voltage signal, so that the at least one target driving voltage signal can drive the motor in the telescopic optical fiber screw rod 85 by the motor, and the motor moves left and right to stretch/compress and wind the telescopic optical fiber screw rod 85 driven by the driving motorThe reference optical fiber on the condensed optical fiber lead screw 85 changes the phase of the reference light due to the elasto-optical effect, so that the phase of the adjusted reference light is added with a third frequency phase to realize the low-frequency modulation of the phase of the reference light, and after the second coupler 4 is utilized to interfere the ultrasonic modulated light and the reference light with the phase frequency modulated by the piezoelectric ceramic optical phase modulator and the low-frequency noise suppression module together, the influence of the low-frequency signal in the environmental noise signal on the optical fiber sensing system can be suppressed, namely, the cancellation of the low-frequency signal in the environmental noise signalPhase offset for the ac voltage signal.
According to an embodiment of the present invention, the motor-driven retractable fiber-optic screw 85 may achieve suppression of low-frequency noise signals in an ambient noise signal, such as 0 to 10 Hz. The motor-driven telescopic optical fiber lead screw 85 has the characteristics of simple control, large adjustable range and the like, and can be used for solving the problem of poor response of piezoelectric ceramics in the piezoelectric ceramic optical phase modulator 7 to low-frequency excitation.
According to an embodiment of the present invention, the predetermined voltage includes a first predetermined voltage and a second predetermined voltage, the first predetermined voltage being smaller than the second predetermined voltage.
According to an embodiment of the present invention, the first predetermined voltage may be-2V, and the second predetermined voltage may be 2V.
According to the embodiment of the invention, the first preset voltage is-2V, the second preset voltage is 2V, and the threshold value of the environmental noise voltage signal in the phase modulation process can enable the ultrasonic modulation light and the reference light which is subjected to common modulation of the phase frequency by the piezoelectric ceramic light phase modulator 7 and the low-frequency noise suppression module 8 to be interfered, and the environmental noise voltage signal stabilized at-2V to 2V can be obtained after the first interference light and the second interference light are subjected to photoelectric conversion and low-pass filtering, so that the stable optical fiber sensing system working at the orthogonal working point can be obtained.
As shown in fig. 1, the voltage comparator 81 is also configured to compare the ambient noise voltage signal with a predetermined voltage by:
outputting a first binary signal in case the ambient noise voltage signal is greater than a second predetermined voltage;
outputting a second binary signal in case the ambient noise voltage signal is less than the first predetermined voltage;
And outputting a third binary signal when the ambient noise voltage signal is greater than or equal to the first predetermined voltage and less than or equal to the second predetermined voltage.
According to the embodiment of the invention, under the condition that the environmental noise voltage signal is larger than or equal to the first preset voltage and smaller than or equal to the second preset voltage, the influence of the environmental noise voltage signal on the optical fiber sensing system for partial discharge of the gas-insulated switchgear provided by the embodiment of the invention is small, and at the moment, the optical fiber sensing system for partial discharge of the gas-insulated switchgear provided by the embodiment of the invention is stable and works in a sensitive area.
According to an embodiment of the present invention, the first binary signal, the second binary signal, and the third binary signal may be selected according to actual situations, which is not limited herein. For example, the first binary signal may be 01, the second binary signal may be 10, and the third binary signal may be 00.
According to an embodiment of the present invention, by outputting a first binary signal in case the ambient noise voltage signal is greater than a second predetermined voltage; outputting a second binary signal in case the ambient noise voltage signal is less than the first predetermined voltage; when the environmental noise voltage signal is greater than or equal to the first predetermined voltage and less than or equal to the second predetermined voltage, a third binary signal is output, so that different binary signals can be output according to the relation between the environmental noise voltage signal and the second predetermined voltage, and then the regulation and control direction of the phase of the reference light by the piezoelectric ceramic optical phase modulator 7 and the low-frequency noise suppression module 8 can be controlled according to the different binary signals.
According to an embodiment of the present invention, the single-chip controller 82 is further configured to output at least one eight-bit binary number at a third predetermined frequency according to the binary signal by:
sequentially outputting eight-bit binary numbers corresponding to at least one numerical value included in the first numerical value range at a third predetermined frequency under the condition that the binary signal is the first binary signal;
sequentially outputting eight-bit binary numbers corresponding to at least one value included in the second value range at a third predetermined frequency under the condition that the binary signal is the second binary signal;
in the case that the binary signal is a third binary signal, eight-bit binary numbers corresponding to at least one value included in the third numerical value range are output at a third predetermined frequency, respectively.
According to an embodiment of the invention, the first range of values may be a range of values from 0 to 120, wherein the first range of values comprises 0 and 120. The second range of values may be a range of values from 120 to 0, where the second range of values includes 0 and 120. The third numerical range may be 0.
Fig. 2 shows a flowchart for controlling the single chip microcomputer controller to output a binary signal corresponding to a predetermined voltage according to an embodiment of the present invention.
As shown in fig. 2, at step S210, an ambient noise voltage signal is received.
In step S220, it is determined whether the ambient noise voltage signal is greater than 2V or less than-2V.
In the case where the environmental noise voltage signal is greater than 2V, eight-bit binary numbers from 0 to 120 are sequentially output at a frequency of 1/1 us at step S221.
In the case where the ambient noise voltage signal is less than-2V, eight-bit binary numbers from 120 to 0 are sequentially output at a frequency of 1/1 us in step S222.
In the case where the ambient noise voltage signal is equal to or greater than-2V and equal to or less than 2V, in step S223, an eight-bit binary number corresponding to 0 is output at a frequency of 1/1 us.
In the case where all binary numbers are output, in step S230, an end statement is executed.
According to an embodiment of the present invention, by sequentially outputting eight-bit binary numbers corresponding to at least one value included in the first numerical range at a third predetermined frequency in a case where the binary signal is the first binary signal; sequentially outputting eight-bit binary numbers corresponding to at least one value included in the second value range at a third predetermined frequency under the condition that the binary signal is the second binary signal; in the case that the binary signal is a third binary signal, outputting an eight-bit binary number corresponding to at least one value included in the third value range at a third predetermined frequency, so as to realize corresponding regulation and control of the phase frequency and the phase direction of the reference light by the piezoelectric ceramic optical phase modulator 7 and the low-frequency noise suppression module 8 according to the phase regulation and control directions corresponding to the first binary signal, the second binary signal and the third binary signal respectively.
According to an embodiment of the present invention, the digital-to-analog converter 83 is further configured to convert at least one eight-bit binary number into an initial driving voltage signal, respectively, to obtain at least one initial driving voltage signal by:
at least one initial driving voltage signal is obtained by linearly mapping at least one eight-bit binary number to a driving voltage signal with a value in a fourth value range, wherein the maximum value in the at least one eight-bit binary number corresponds to the maximum value in the fourth value range and the minimum value in the at least one eight-bit binary number corresponds to the minimum value in the fourth value range.
According to the embodiment of the present invention, the fourth numerical range may be selected according to practical situations, which is not limited herein.
For example, the fourth numerical range may be a numerical range of 0.1V or more and 6.1V or less. The fourth numerical range may be a numerical range of 0V or more and 6V or less.
For example, an eight-bit binary number corresponding to a value of 0 to 120, respectively, may be linearly mapped onto a 0V to 6V drive voltage signal, where a value of 0 corresponds to a 0V drive voltage signal and a value of 120 corresponds to a 6V drive voltage. Alternatively, eight binary numbers corresponding to values of 0 to 120, respectively, may be linearly mapped onto the 0.1V to 6.1V drive voltage signal, where the value 0 corresponds to the 0.1V drive voltage signal and the value 120 corresponds to the 6.1V drive voltage.
Similarly, eight binary numbers corresponding to values of 120 to 0, respectively, can be linearly mapped onto the 6V to 0V drive voltage signal. Or linearly map eight-bit binary numbers corresponding to the values of 120 to 0, respectively, onto the driving voltage signal of 6.1V to 0.1V.
According to an embodiment of the present invention, at least one initial driving voltage signal is obtained by linearly mapping at least one eight-bit binary number to a driving voltage signal having a value within a fourth value range, in preparation for driving a motor of the retractable fiber optic screw 85 according to the initial driving voltage signal.
According to the embodiment of the invention, all devices and modules except the optical fiber sensor 3 in the optical fiber sensing system are packaged by using an aluminum plate with the thickness of 5mm, and the optical fiber sensor 3 is a cylindrical optical fiber sensor with the diameter of 5 cm and packaged by epoxy resin.
According to the embodiment of the invention, the field operation environment of the GIS is complex, and particularly, factors such as high voltage level, complex equipment, extremely many wires and the like of a transformer substation where the GIS is located can bring strong interference to an electrical sensing system. Meanwhile, all devices and modules except the optical fiber sensor 3 in the optical fiber sensing system in fig. 1 are packaged by using an aluminum plate with the thickness of 5mm, all wires used for transmitting signals in an external environment in the optical fiber sensing system are transmitted by adopting optical fibers, a built-in power supply module is designed according to measurement requirements, and power is supplied by adopting a battery, so that electromagnetic shielding is realized.
According to the embodiment of the invention, the cylindrical optical fiber sensor with the diameter of 5 cm packaged by epoxy resin can be selected as the optical fiber sensor 3 in consideration of the voltage class and the diversity of the outer diameter size of different substations, and the size is suitable for all existing GIS equipment, so that the universality and the wide applicability of the optical fiber sensor 3 are ensured. And the epoxy resin is selected as a sensor material, so that effective insulation can be realized, and the safety of the optical fiber sensing system is further ensured.
According to an embodiment of the present invention, the operation steps of the optical fiber sensing system provided in the embodiment of the present invention are: the various electrical control devices in fig. 1 are powered on to place the various devices in operation. And then the high-sensitivity optical fiber sensor 3 is arranged on the GIS cavity to be detected, and the ultrasonic couplant is smeared on the contact surface. The laser 1 is turned on to output laser light, and the GIS partial discharge is detected by the laser light.
It should be noted that, unless there is an execution sequence between different operations or an execution sequence between different operations in technical implementation, the execution sequence between multiple operations may be different, and multiple operations may also be executed simultaneously.
Some of the block diagrams and/or flowchart illustrations are shown in the figures. It will be understood that some blocks of the block diagrams and/or flowchart illustrations, or combinations of blocks in the block diagrams and/or flowchart illustrations, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the instructions, when executed by the processor, create means for implementing the functions/acts specified in the block diagrams and/or flowchart.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature.
Those skilled in the art will appreciate that the features recited in the various embodiments of the invention and/or in the claims may be combined in various combinations and/or combinations, even if such combinations or combinations are not explicitly recited in the invention. In particular, the features recited in the various embodiments of the invention and/or in the claims can be combined in various combinations and/or combinations without departing from the spirit and teachings of the invention. All such combinations and/or combinations fall within the scope of the invention.
The embodiments of the present invention are described above. However, these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Although the embodiments are described above separately, this does not mean that the measures in the embodiments cannot be used advantageously in combination. The scope of the invention is defined by the appended claims and equivalents thereof. Various alternatives and modifications can be made by those skilled in the art without departing from the scope of the invention, and such alternatives and modifications are intended to fall within the scope of the invention.
Claims (10)
1. An optical fiber sensing system for detecting partial discharge of a gas insulated switchgear, comprising:
a laser for emitting laser light of a predetermined wavelength;
a first coupler for dividing the laser into detection light and reference light with the same power;
the optical fiber sensor is used for detecting ultrasonic signals generated by partial discharge of the insulation switch equipment by utilizing the detection light to obtain ultrasonic modulated light;
the second coupler is used for interfering the ultrasonic modulated light and the reference light with the phase frequency modulated by the piezoelectric ceramic light phase modulator and the low-frequency noise suppression module together, and dividing the interference light obtained by interference into first interference light and second interference light with the same power;
The balanced photoelectric detector is used for carrying out photoelectric conversion on the first interference light and the second interference light to obtain an alternating voltage signal corresponding to the ultrasonic signal, so that the optical fiber sensing system obtains the ultrasonic signal according to the alternating voltage signal;
the noise feedback module is used for filtering the alternating-current voltage signal at a first preset frequency to obtain an environment noise voltage signal, wherein the environment noise voltage signal represents a voltage signal corresponding to a noise signal in an environment where the insulated switchgear is located;
a piezoelectric ceramic optical phase modulator connected to a reference optical fiber for transmitting the reference light, and performing first modulation on the phase of the reference light according to the environmental noise voltage signal, so as to increase a first frequency phase in the phase of the first modulated reference light, wherein the first frequency phase represents a phase which is the same as the amplitude and the frequency of a second frequency phase and has an opposite propagation direction, and the second frequency phase represents a phase amount which is greater than or equal to a second preset frequency and less than or equal to the first preset frequency and is used for increasing the phase of the detection light by environmental noise;
the low-frequency noise suppression module is connected into a reference optical fiber for transmitting the reference light, and carries out second modulation on the phase of the reference light according to the environmental noise voltage signal, so that a third frequency phase is added to the phase of the reference light subjected to the second modulation, wherein the third frequency phase is the same as a fourth frequency phase in frequency and opposite in propagation direction, the third frequency phase is determined according to the fourth frequency phase and a preset phase, and the fourth frequency phase represents the phase quantity of the increase of the phase of the detection light by environmental noise smaller than a second preset frequency.
2. The system of claim 1, wherein the low frequency noise suppression module comprises:
a voltage comparator for comparing the ambient noise voltage signal with a predetermined voltage and outputting a binary signal corresponding to the predetermined voltage;
the singlechip controller is used for outputting at least one eight-bit binary number at a third preset frequency according to the binary signal;
the digital-to-analog converter is used for respectively converting the at least one eight-bit binary number into an initial driving voltage signal to obtain at least one initial driving voltage signal;
the motor driving sub-module is used for amplifying the at least one initial driving voltage signal by a preset multiple to obtain at least one target driving voltage signal;
and the motor drives a telescopic optical fiber lead screw, is connected into a reference optical fiber for transmitting the reference light, and is used for adjusting the length of the reference optical fiber according to the at least one target driving voltage signal so as to increase the third frequency phase in the phase of the adjusted reference light.
3. The system of claim 2, wherein the predetermined voltages comprise a first predetermined voltage and a second predetermined voltage, the first predetermined voltage being less than the second predetermined voltage, the voltage comparator further configured to perform the comparing the ambient noise voltage signal with the predetermined voltage by:
Outputting a first binary signal in case the ambient noise voltage signal is greater than a second predetermined voltage;
outputting a second binary signal in case the ambient noise voltage signal is less than a first predetermined voltage;
outputting a third binary signal when the ambient noise voltage signal is greater than or equal to the first predetermined voltage and less than or equal to a second predetermined voltage.
4. A system according to claim 3, wherein said single-chip controller is further configured to implement said outputting at least one eight-bit binary number at a third predetermined frequency from said binary signal by:
sequentially outputting eight-bit binary numbers corresponding to at least one numerical value included in the first numerical value range at a third predetermined frequency under the condition that the binary signal is the first binary signal;
sequentially outputting eight-bit binary numbers corresponding to at least one numerical value included in the second numerical value range at a third predetermined frequency under the condition that the binary signal is the second binary signal;
and outputting eight-bit binary numbers corresponding to at least one numerical value included in the third numerical value range at a third preset frequency under the condition that the binary signal is a third binary signal.
5. The system of claim 4, wherein the digital-to-analog converter is further configured to perform the converting the at least one eight-bit binary number into an initial drive voltage signal by:
and linearly mapping the at least one eight-bit binary number to a driving voltage signal with the value in a fourth value range to obtain at least one initial driving voltage signal, wherein the maximum value of the at least one eight-bit binary number corresponds to the maximum value in the fourth value range, and the minimum value of the at least one eight-bit binary number corresponds to the minimum value in the fourth value range.
6. The system of claim 1, wherein the noise feedback module comprises:
the low-pass filter is used for carrying out low-pass filtering of a first preset frequency on the alternating voltage signal to obtain an initial environmental noise voltage signal;
and the integrator is used for carrying out accumulation processing on the initial environmental noise voltage signal to obtain the environmental noise voltage signal with the cutoff frequency of the first preset frequency.
7. The system of any one of claims 3 to 5, wherein the first predetermined voltage is-2V and the second predetermined voltage is 2V.
8. The system of any one of claims 2 to 5, wherein the predetermined multiple is 20 times and the third predetermined frequency is 1/1 us.
9. The system of any of claims 1 or 6, wherein the first predetermined frequency is 10kHz and the second predetermined frequency is 10Hz.
10. The system of any one of claims 1 to 6, wherein each device and module of the optical fiber sensing system other than the optical fiber sensor is encapsulated by using a 5mm thick aluminum plate, and the optical fiber sensor is a cylindrical optical fiber sensor with a diameter of 5 cm encapsulated by epoxy resin.
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