Monitoring system for improving anti-interference capability of converter transformer partial discharge ultrasonic monitoring

Abstract

The invention discloses a monitoring system for improving the anti-interference capability of converter transformer partial discharge ultrasonic monitoring. According to the system, a first coupler divides continuous narrow-band light emitted by a laser into a sensing light signal and a reference light signal; the sensing optical signal is reflected by the Faraday rotating mirror, then returns along an original optical path, and enters the second coupler through the circulator; a reference light signal generates a fixed frequency shift through an acousto-optic modulator and then enters a second coupler to interfere with the sensing light, two beams of interference light are converted by a balanced photoelectric detector for differential detection, and a measurement signal is output; the radio frequency driving signal is divided into a first driving signal and a second driving signal by the power divider, the first driving signal is used for driving the acousto-optic modulator, and the second driving signal enters the RF gain phase detector as an electrical synchronization reference signal; and the RF gain phase detector performs difference processing on the phase quantity of the measurement signal and the phase quantity of the electrical synchronous reference signal to obtain a partial discharge ultrasonic signal of the converter transformer, and outputs the partial discharge ultrasonic signal to the acquisition card system.

Description

Technical Field

[0001] The present invention relates to the technical field of power equipment status monitoring, and more specifically, to a monitoring system for improving the anti-interference capability of ultrasonic monitoring of partial discharge of a converter transformer. Background Art

[0002] As the core components of the power system, the reliable operation of high-voltage electrical equipment such as converter transformers is extremely critical to the stable operation of the power grid. Faults caused by reduced insulation level of electrical equipment account for a large proportion of electrical faults, and insulation failures often lead to more serious safety accidents. Fiber optic ultrasonic detection is a more practical method for detecting partial discharge inside converter transformers.

[0003] For ultrasonic sensors, fiber optic ultrasonic sensing technology has more advantages in weak signal detection and sensitivity, but with high sensitivity, it is also more susceptible to interference from noises such as light source noise, frequency shift noise, and circuit noise in the detection system. The thermal motion of atoms in the laser and external disturbances will cause stimulated radiation to produce photon frequency differences, resulting in light source noise. When the fiber optic ultrasonic signal is frequency shifted by the acousto-optic modulator, frequency shift noise will be introduced due to the deviation of the device manufacturing process and the external drive signal. Photoelectric detectors and acquisition cards will generate thermal noise, quantization noise, and shot noise during operation, collectively referred to as circuit noise. Therefore, there is a technical problem that noise affects the integrity and accuracy of the partial discharge signal during the ultrasonic partial discharge detection of the converter transformer. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a monitoring system for improving the anti-interference capability of ultrasonic monitoring of partial discharge of a converter transformer.

[0005] According to one aspect of the present invention, a monitoring system for improving the anti-interference capability of ultrasonic monitoring of partial discharge of a converter transformer is provided, comprising:

[0006] A laser, a first coupler, a measuring optical fiber, a reference optical fiber, a circulator, a Faraday rotator, a second coupler, an acousto-optic modulator, a balanced photodetector, a power divider, a radio frequency driving signal, an RF gain phase detector, and a signal acquisition system, wherein

[0007] The first coupler divides the continuous narrowband light emitted by the laser into two narrowband lights through the first coupler, wherein the first narrowband light enters the reference optical fiber of the interference structure, namely the reference optical signal, and the other narrowband light enters the measuring optical fiber through the circulator, namely the sensing optical signal; the sensing optical signal enters the Faraday rotator through the measuring optical fiber, returns along the original optical path after being reflected by the Faraday rotator, and enters the second coupler through the circulator; the reference optical signal enters the second coupler after generating a fixed frequency shift through the acousto-optic modulator to interfere with the sensing optical signal, and the two interfering optical signals are converted into electrical signals by the balanced photodetector for differential detection, and the electrical signals enter the RF gain phase detector as the measurement signal; the RF drive signal is divided into the first drive signal and the second drive signal through the power divider, the first drive signal is used to drive the acousto-optic modulator, and the second drive signal enters the RF gain phase detector as the electrical synchronization reference signal; the RF gain phase detector reflects the phase difference between the two signals by continuously calculating the zero-point time difference between the measurement signal and the electrical synchronization reference signal; the partial discharge ultrasonic signal of the converter transformer is obtained and output to the acquisition card system.

[0008] Optionally, the RF gain phase detector uses an AD8302 integrated chip for detecting the amplitude ratio and phase difference of the RF and IF signals.

[0009] Alternatively, the phase difference response of the RF gain phase detector is expressed as The output voltage signal is proportional to the phase difference between the two input signals, where G is the "output voltage / input phase difference" sensitivity of the RF gain phase detector. is a low-frequency signal caused by low environmental noise, Characterize the ultrasound signal.

[0010] Optionally, the laser is a semiconductor laser, and the line width of the semiconductor laser should be smaller than a preset threshold.

[0011] Optionally, the measurement signal output by the photodetector is The electrical synchronization reference signal is In the formula, is the phase noise; f1 = 200MHz, is the fixed frequency shift introduced by AOM; The phase change of the sensing light, t is the time, is the phase constant of the interference light.

[0012] According to another aspect of the present invention, a monitoring method for improving the anti-interference capability of ultrasonic monitoring of partial discharge of a converter transformer is provided, comprising:

[0013] The continuous narrow-band light emitted by the laser is evenly divided into a sensing light signal for measuring a partial discharge ultrasonic signal of a converter transformer and a reference light signal through a first coupler;

[0014] The sensing light signal after measuring the ultrasonic signal interferes with the reference light signal to obtain two interference lights;

[0015] Perform differential detection on the two interfering light beams to obtain the measurement signal;

[0016] The electrical synchronization reference signal and the measurement signal are differentially processed to obtain the partial discharge ultrasonic signal of the converter transformer.

[0017] Optionally, the continuous narrow-band light emitted by the laser is evenly divided into a sensing light signal for measuring a partial discharge ultrasonic signal of a converter transformer and a reference light signal through a first coupler, including:

[0018] The continuous narrowband light emitted by the laser is evenly divided into a first narrowband light and a second narrowband light through the first coupler, wherein the first narrowband light enters the reference optical fiber of the interference structure to obtain a sensing light signal, and the second narrowband light enters the measuring optical fiber through the circulator to obtain a reference light signal.

[0019] Optionally, the sensing light signal after measuring the ultrasonic signal interferes with the reference light signal to obtain two interference lights, including:

[0020] The sensing light containing the ultrasonic signal is reflected by a Faraday rotator and then returns along the original optical path, passes through a circulator and enters a second coupler;

[0021] The reference light signal is subjected to a fixed frequency shift by an acousto-optic modulator and then enters the second coupler to interfere with the sensing light signal to obtain two light signals.

[0022] Optionally, differential detection is performed on the two interfering light beams to obtain a measurement signal, including:

[0023] The two interfering light beams are differentially detected by a balanced photodetector and a measurement signal is output.

[0024] Optionally, performing differential processing on the electrical synchronization reference signal and the measurement signal to obtain a partial discharge ultrasonic signal of the converter transformer includes:

[0025] The radio frequency driving signal is equally divided into a first driving signal and a second driving signal by using a power divider, wherein the first driving signal is used to drive the acousto-optic modulator, and the second driving signal is used as an electrical synchronization reference signal to enter the RF gain phase detector;

[0026] The phase difference between the measurement signal and the electrical synchronization reference signal is processed by the RF gain phase detector to obtain the partial discharge ultrasonic signal of the converter transformer.

[0027] Optionally, the measurement signal is:

[0028]

[0029] The electrical synchronization reference signal is:

[0030]

[0031] In the formula, is the phase noise; f1 = 200MHz, is the fixed frequency shift introduced by AOM; The phase change of the sensing light, t is the time, is the phase constant of the interference light.

[0032] Therefore, the present invention proposes a method for improving the anti-interference ability of ultrasonic monitoring of partial discharge of converter transformers. By analyzing the noise interference of the light transmission process in the system, an interference phase hardware demodulation method based on electrical synchronization reference is proposed. The measurement signal and the reference signal are directly demodulated by the RF gain phase detector. The signal output waveform is directly an ultrasonic waveform, and no data processing is required. While eliminating the frequency shift noise interference, the sampling rate is reduced from hundreds of MHz to hundreds of kHz (ultrasonic frequency band), ensuring the real-time acquisition of partial discharge signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0034] Figure 1 It is a schematic diagram of the structure of a monitoring system for improving the anti-interference capability of ultrasonic monitoring of partial discharge of a converter transformer provided by an exemplary embodiment of the present invention;

[0035] Figure 2 is a schematic diagram of a phase difference response characteristic curve provided by an exemplary embodiment of the present invention;

[0036] Figure 3 It is a flow chart of a monitoring method for improving the anti-interference capability of ultrasonic monitoring of partial discharge of a converter transformer provided by an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0037] Below, the exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments of the present invention, and it should be understood that the present invention is not limited to the exemplary embodiments described here.

[0038] It should be noted that the relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.

[0039] Those skilled in the art can understand that the terms "first" and "second" in the embodiments of the present invention are only used to distinguish different steps, devices or modules, etc., and neither represent any specific technical meaning nor indicate the necessary logical order between them.

[0040] It should also be understood that, in the embodiments of the present invention, “plurality” may refer to two or more than two, and “at least one” may refer to one, two or more than two.

[0041] It should also be understood that any component, data or structure mentioned in the embodiments of the present invention can generally be understood as one or more, unless explicitly limited or otherwise indicated in the context.

[0042] In addition, the term "and / or" in the present invention is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects before and after are in an "or" relationship.

[0043] It should also be understood that the description of the various embodiments of the present invention focuses on the differences between the various embodiments, and the same or similar aspects thereof can be referenced to each other, and for the sake of brevity, they will not be described one by one.

[0044] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0045] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0046] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0047] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0048] Figure 1 1 is a schematic diagram of the structure of the monitoring system for improving the anti-interference capability of ultrasonic monitoring of partial discharge of converter transformers according to the first aspect of the present invention. Figure 1 As shown in the figure, the monitoring system for improving the anti-interference capability of ultrasonic monitoring of partial discharge of converter transformers includes:

[0049] A laser, a first coupler, a measuring optical fiber, a reference optical fiber, a circulator, a Faraday rotator, a second coupler, an acousto-optic modulator, a balanced photodetector, a power divider, a radio frequency driving signal, an RF gain phase detector, and a signal acquisition system, wherein

[0050] The first coupler divides the continuous narrowband light emitted by the laser into two narrowband lights through the first coupler, wherein the first narrowband light enters the reference optical fiber of the interference structure, namely the reference optical signal, and the other narrowband light enters the measuring optical fiber through the circulator, namely the sensing optical signal; the sensing optical signal enters the Faraday rotator through the measuring optical fiber, returns along the original optical path after being reflected by the Faraday rotator, and enters the second coupler through the circulator; the reference optical signal enters the second coupler after generating a fixed frequency shift through the acousto-optic modulator to interfere with the sensing optical signal, and the two interfering optical signals are converted into electrical signals by the balanced photodetector for differential detection, and the electrical signals enter the RF gain phase detector as the measurement signal; the RF drive signal is divided into the first drive signal and the second drive signal through the power divider, the first drive signal is used to drive the acousto-optic modulator, and the second drive signal enters the RF gain phase detector as the electrical synchronization reference signal; the RF gain phase detector reflects the phase difference between the two signals by continuously calculating the zero-point time difference between the measurement signal and the electrical synchronization reference signal; the partial discharge ultrasonic signal of the converter transformer is obtained and output to the acquisition card system.

[0051] Specifically, the present invention is based on the ultrasonic signal generated during the partial discharge process of the converter transformer, and proposes an anti-interference method based on the partial discharge optical fiber ultrasonic detection system for the light source noise, circuit noise, and frequency shift noise in the optical fiber ultrasonic sensing system, which relates to the field of online monitoring of partial discharge of transformers.

[0052] The fiber optic ultrasonic sensing system includes a laser, a coupler, a circulator, a Faraday rotator, an acousto-optic modulator (AOM), a balanced photodetector, a power divider, a driving signal, an RF gain phase detector, a signal acquisition system, a reference optical fiber, and a measurement optical fiber.

[0053] The laser uses a semiconductor laser with an ultra-narrow line width to improve the stability of the output optical frequency. The smaller the line width, the smaller the tiny fluctuations of the laser output optical frequency.

[0054] The balanced photodetector has a built-in differential amplifier that can perform differential operations on two input signals and effectively reduce common-mode noise.

[0055] The acquisition system uses a high ADC resolution acquisition card to reduce acquisition noise.

[0056] The driving signal of the AOM is a non-ideal single-frequency signal containing frequency noise. During the demodulation process, the frequency noise will be converted into phase noise. It can be expressed as This noise is broadband noise and is difficult to eliminate through filtering circuits. It increases the noise level of the demodulation system and has an adverse effect on the detection of ultrasonic signals.

[0057] The measurement signal output by the photodetector is:

[0058]

[0059] The power divider will carry frequency fluctuation information The driving signal is divided into two paths, one for driving AOM and the other for electrical synchronization reference signal. The electrical synchronization reference signal can be expressed as:

[0060]

[0061] The RF gain phase detector uses the AD8302 integrated chip, which can be used to detect the amplitude ratio and phase difference of RF and IF signals. AD8302 has three main working modes: measurement, control and level comparison. In the measurement mode, its output signal is proportional to the phase difference of the two input signals.

[0062] The reference optical fiber and the measuring optical fiber are both wound from single-mode optical fiber. The optical signal in the measuring optical fiber is the measuring signal, and the optical signal in the reference optical fiber is the reference signal.

[0063] The function of the circulator is as follows: the optical signal passes through the circulator, enters the Faraday rotator through the measuring optical fiber, and after reflection, returns through the measuring optical fiber and enters the coupler through the circulator.

[0064] The measured signal and the reference signal are continuously calculated through the RF gain phase detector to obtain the phase difference of the input signal by the zero point time difference of the two input signals. The phase difference response of the RF gain phase detector is expressed as:

[0065]

[0066] Where G is the "output voltage / input phase difference" sensitivity of the RF gain phase detector. The output voltage of the RF gain phase detector corresponds to the phase change of the interference light intensity. in It is a low-frequency signal caused by low environmental noise, which can be eliminated by high-pass filtering. The result of high-pass filtering is Directly characterize the ultrasonic signal, thereby realizing fast hardware demodulation and frequency shift noise filtering of the ultrasonic signal. After testing, the phase difference response characteristic curve of the RF gain phase detector is as follows: Figure 2 shown.

[0067] like Figure 1The topology diagram of the interference phase hardware demodulation method based on electrical synchronous reference. During the propagation of fiber-optic ultrasonic signals, the laser emits a continuous narrowband light of 1550nm, which is evenly divided into two beams after passing through the coupler. One beam enters the reference optical fiber of the interference structure, and the other beam enters the measurement optical fiber through the circulator. The sensing light is reflected by the Faraday rotator and returns along the original optical path, passing through the circulator and entering the coupler; the reference optical signal enters the coupler after a fixed frequency shift after passing through the AOM to interfere with the sensing light, and finally the balanced photodetector converts the optical signal into an electrical signal, and differentially detects the two interfering optical signals. The RF drive signal is divided into two by the power divider, one is used to drive the AOM, and the other is used as a reference signal to enter the RF gain phase detector. The acquisition card system is used to process the output electrical signal of the RF gain phase detector to achieve reliable ultrasonic signal sensing and hardware demodulation.

[0068] Specifically, the measurement signal output from the photodetector is The electrical synchronization reference signal is At this time, the phase information of the measurement signal measured by the system and the electrical synchronization reference signal also have the phase noise of frequency f1 and AOM. By performing phase difference processing on the measured signal and the electrical synchronization reference signal, the phase change of the sensing light in the interference light can be obtained. That is, the ultrasonic signal sensed by the sensor arm and the phase noise caused by the AOM frequency shift will also be eliminated.

[0069] Specifically, the RF gain phase detector uses the AD8302 integrated chip to detect the amplitude ratio and phase difference of the RF and IF signals. The phase difference response of the RF gain phase detector is expressed as The output voltage signal is proportional to the phase difference between the two input signals. G is the "output voltage / input phase difference" sensitivity of the RF gain phase detector. It is a low-frequency signal caused by low environmental noise, which can be eliminated by high-pass filtering. The result of high-pass filtering is Directly characterize the ultrasonic signal. The phase difference response characteristic curve is as follows Figure 2 shown.

[0070] Preferably, a semiconductor laser with an ultra-narrow line width is used to improve the stability of the output optical frequency. The smaller the line width, the smaller the tiny fluctuation δf of the laser output optical frequency, which reduces the light source phase noise.

[0071] Preferably, on the premise of meeting the measurement requirements, a data acquisition device with a small range and high ADC resolution is selected to reduce acquisition noise.

[0072] Preferably, a balanced photodetector is used for photoelectric signal conversion. The balanced photodetector has a built-in differential amplifier, which can perform differential operations on two input signals and effectively reduce common mode noise.

[0073] In this embodiment, in order to quantify the influence of the noise reduction technology proposed in this method on the noise level of the fiber optic ultrasonic sensor system, the background noise of the sensor system before and after the noise reduction is analyzed in the time domain and frequency domain through the test case. The experiment proves that the average background noise amplitude of the fiber optic ultrasonic sensor system is reduced from 5mV to 1mV through the noise reduction method proposed in the present invention. The system noise level is reduced by 80%, which improves the anti-interference ability of weak partial discharge signals.

[0074] Therefore, the present invention proposes a system for improving the anti-interference ability of ultrasonic monitoring of partial discharge of converter transformers. By analyzing the noise interference of the light transmission process in the system, an interference phase hardware demodulation method based on electrical synchronization reference is proposed. The measurement signal and the reference signal are directly demodulated by the RF gain phase detector. The signal output waveform is directly an ultrasonic waveform, and no data processing is required. While eliminating the interference of frequency shift noise, the sampling rate is reduced from hundreds of MHz to hundreds of kHz (ultrasonic frequency band), ensuring the real-time acquisition of partial discharge signals. Among them, the interference of laser noise is reduced by using a semiconductor laser with an ultra-narrow linewidth; the interference of circuit noise is reduced by using a high-resolution data acquisition device and a balanced photodetector; and the interference of frequency shift noise is eliminated by using a phase hardware demodulation method based on an RF gain phase detector.

[0075] also, Figure 3 This is a flow chart of a monitoring method for improving the anti-interference capability of ultrasonic monitoring of partial discharge of a converter transformer according to the second aspect of the present invention, with reference to Figure 3 As shown, the method 300 includes the following steps:

[0076] Step 301: Split the continuous narrow-band light emitted by the laser into a sensing light signal for measuring a partial discharge ultrasonic signal of a converter transformer and a reference light signal through a first coupler;

[0077] Step 302: the sensing light signal after measuring the ultrasonic signal interferes with the reference light signal to obtain two interference lights;

[0078] Step 303: performing differential detection on the two interfering light beams to obtain a measurement signal;

[0079] Step 304: Perform differential processing on the electrical synchronization reference signal and the measurement signal to obtain a partial discharge ultrasonic signal of the converter transformer.

[0080] Optionally, the continuous narrow-band light emitted by the laser is evenly divided into a sensing light signal for measuring a partial discharge ultrasonic signal of a converter transformer and a reference light signal through a first coupler, including:

[0081] The continuous narrowband light emitted by the laser is evenly divided into a first narrowband light and a second narrowband light through the first coupler, wherein the first narrowband light enters the reference optical fiber of the interference structure to obtain a sensing light signal, and the second narrowband light enters the measuring optical fiber through the circulator to obtain a reference light signal.

[0082] Optionally, the sensing light signal after measuring the ultrasonic signal interferes with the reference light signal to obtain two interference lights, including:

[0083] The sensing light containing the ultrasonic signal is reflected by a Faraday rotator and then returns along the original optical path, passes through a circulator and enters a second coupler;

[0084] The reference light signal is subjected to a fixed frequency shift by an acousto-optic modulator and then enters the second coupler to interfere with the sensing light signal to obtain two light signals.

[0085] Optionally, differential detection is performed on the two interfering light beams to obtain a measurement signal, including:

[0086] The two interfering light beams are differentially detected by a balanced photodetector and a measurement signal is output.

[0087] Optionally, performing differential processing on the electrical synchronization reference signal and the measurement signal to obtain a partial discharge ultrasonic signal of the converter transformer includes:

[0088] The radio frequency driving signal is equally divided into a first driving signal and a second driving signal by using a power divider, wherein the first driving signal is used to drive the acousto-optic modulator, and the second driving signal is used as an electrical synchronization reference signal to enter the RF gain phase detector;

[0089] The phase difference between the measurement signal and the electrical synchronization reference signal is processed by the RF gain phase detector to obtain the partial discharge ultrasonic signal of the converter transformer.

[0090] Optionally, the measurement signal is:

[0091]

[0092] The electrical synchronization reference signal is:

[0093]

[0094] In the formula, is the phase noise; f1 = 200MHz, is the fixed frequency shift introduced by AOM; The phase change of the sensing light, t is the time, is the phase constant of the interference light.

[0095] Therefore, the present invention proposes a method for improving the anti-interference ability of ultrasonic monitoring of partial discharge of converter transformers. By analyzing the noise interference of the light transmission process in the system, an interference phase hardware demodulation method based on electrical synchronization reference is proposed. The measurement signal and the reference signal are directly demodulated by the RF gain phase detector. The signal output waveform is directly an ultrasonic waveform, and no data processing is required. While eliminating the frequency shift noise interference, the sampling rate is reduced from hundreds of MHz to hundreds of kHz (ultrasonic frequency band), ensuring the real-time acquisition of partial discharge signals.

[0096] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present invention to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. A monitoring system for improving the anti-interference capability of ultrasonic monitoring of partial discharge of converter transformers, characterized in that: include: A laser, a first coupler, a measuring optical fiber, a reference optical fiber, a circulator, a Faraday rotator, a second coupler, an acousto-optic modulator, a balanced photodetector, a power divider, a radio frequency driving signal, an RF gain phase detector, and a signal acquisition system, wherein The first coupler divides the continuous narrowband light emitted by the laser into two narrowband lights through the first coupler, wherein the first narrowband light enters the reference optical fiber of the interference structure, i.e., the reference optical signal, and the other narrowband light enters the measuring optical fiber through the circulator, i.e., the sensing optical signal; the sensing optical signal enters the Faraday rotator through the measuring optical fiber, returns along the original optical path after being reflected by the Faraday rotator, and enters the second coupler through the circulator; the reference optical signal generates a fixed frequency shift through the acousto-optic modulator, enters the second coupler to interfere with the sensing optical signal, and the balanced photodetector converts the two interference optical signals into electrical signals for differential detection, and the electrical signals enter the RF gain phase detector as the measurement signal; the RF drive signal is divided into a first drive signal and a second drive signal through the power divider, the first drive signal is used to drive the acousto-optic modulator, and the second drive signal enters the RF gain phase detector as an electrical synchronization reference signal; The RF gain phase detector reflects the phase difference between the measurement signal and the electrical synchronization reference signal by continuously calculating the zero-point time difference between the two signals; the partial discharge ultrasonic signal of the converter transformer is obtained and output to the acquisition card system.

2. The converter transformer partial discharge ultrasonic monitoring system according to claim 1, characterized in that: The RF gain phase detector adopts the AD8302 integrated chip and is used for detecting the amplitude ratio and phase difference of the radio frequency and intermediate frequency signals.

3. The converter transformer partial discharge ultrasonic monitoring system according to claim 1, characterized in that: The phase difference response of the RF gain phase detector is expressed as The output voltage signal is proportional to the phase difference between the two input signals, where G is the output voltage / input phase difference sensitivity of the RF gain phase detector. is a low-frequency signal caused by low environmental noise, Characterize the ultrasound signal.

4. The converter transformer partial discharge ultrasonic monitoring system according to claim 1, characterized in that: The laser is a semiconductor laser, and the line width of the semiconductor laser should be smaller than a preset threshold.

5. The converter transformer partial discharge ultrasonic monitoring system according to claim 1, characterized in that: The measurement signal output by the photodetector is The electrical synchronization reference signal is In the formula, is the phase noise; f1 = 200MHz, is the fixed frequency shift introduced by AOM; The phase change of the sensing light, t is the time, is the phase constant of the interference light.

6. The method for partial discharge ultrasonic monitoring of converter transformers implemented by the partial discharge ultrasonic monitoring system for converter transformers according to claims 1-5 is characterized in that: include: The continuous narrow-band light emitted by the laser is evenly divided into a sensing light signal for measuring a partial discharge ultrasonic signal of a converter transformer and a reference light signal through a first coupler; The sensing light signal after measuring the ultrasonic signal interferes with the reference light signal to obtain two interference lights; Performing differential detection on the two interfering light beams to obtain a measurement signal; The electrical synchronization reference signal and the measurement signal are differentially processed to obtain a partial discharge ultrasonic signal of the converter transformer.

7. The method according to claim 6, characterized in that The continuous narrow-band light emitted by the laser is evenly divided into a sensing light signal and a reference light signal for measuring the ultrasonic signal of partial discharge of the converter transformer through a first coupler, including: The continuous narrowband light emitted by the laser is divided into a first narrowband light and a second narrowband light through a first coupler, wherein the first narrowband light enters a reference optical fiber of an interference structure to obtain the sensing light signal, and the second narrowband light enters a measuring optical fiber through a circulator to obtain the reference light signal.

8. The method according to claim 6, characterized in that The sensing light signal after measuring the ultrasonic signal interferes with the reference light signal to obtain two interference lights, including: The sensing light containing the ultrasonic signal is reflected by a Faraday rotator and then returned along the original optical path, passing through a circulator and entering a second coupler; The reference light signal is subjected to a fixed frequency shift by using an acousto-optic modulator, and then enters a second coupler to interfere with the sensing light signal, thereby obtaining the two light signals.

9. The method according to claim 6, characterized in that Performing differential detection on the two interfering light beams to obtain a measurement signal includes: The two interfering lights are differentially detected by a balanced photodetector to output the measurement signal.

10. The method according to claim 6, characterized in that The electrical synchronization reference signal and the measurement signal are differentially processed to obtain a partial discharge ultrasonic signal of the converter transformer, including: Using a power divider to equally divide the radio frequency drive signal into a first drive signal and a second drive signal, wherein the first drive signal is used to drive the acousto-optic modulator, and the second drive signal is used as an electrical synchronization reference signal to enter the RF gain phase detector; The RF gain phase detector performs difference processing on the phase quantity of the measurement signal and the electrical synchronization reference signal to obtain the partial discharge ultrasonic signal of the converter transformer.

11. The method according to claim 6, characterized in that The measurement signal is: The electrical synchronization reference signal is: In the formula, is the phase noise; f1 = 200MHz, is the fixed frequency shift introduced by AOM; The phase change of the sensing light, t is the time, is the phase constant of the interference light.

Images