On-site calibration device and method for built-in acoustic sensor of transformer

Abstract

The invention discloses a field calibration method and device for a built-in acoustic sensor of a transformer. The device comprises a signal generation module and a signal analysis module, the signal generation module comprises an ultrasonic transmitting module and a microcontroller; the ultrasonic transmitting module and the optical voiceprint sensor are packaged in the transformer, and the microcontroller is arranged outside the oil tank to control the ultrasonic module; the signal generation module generates ultrasonic square wave signals with fixed frequency and fixed sound intensity, the ultrasonic square wave signals and environment signals are transmitted to the optical voiceprint sensor together, the sound signals are converted into electric signals through the optical voiceprint sensor, and the electric signals pass through the filtering module to filter detection signals, so that detection and recording of discharge signals are not affected. A signal analysis module is utilized to analyze voltage signals in a limited range every three days, and the number of rising edge signals of specified trigger voltage is counted. And if the statistical result is lower than the standard value in three continuous time periods, determining that the calibration is not passed. The standards of the trigger voltage and the rising edge number are calibrated and determined through the signal generation module.

Description

Technical Field

[0001] The present invention relates to an on-site calibration method and a device thereof, and in particular to an on-site calibration device and method for a transformer built-in acoustic sensor. Background Art

[0002] As the core equipment in the power system, power transformers undertake the important functions of voltage conversion and energy transmission. During its operation, partial discharge failure may occur in the internal insulation medium, which is one of the main reasons for transformer insulation degradation. The ultrasonic and audible sound signals generated by partial discharge have strong penetrating power and can penetrate the transformer oil tank and solid insulation materials. They are an important means of detecting internal discharge failures in transformers.

[0003] Transformer optical soundprint sensing technology (Hou Zhe. Development of acoustic fiber sensor for arc discharge inside transformer and research on soundprint characteristics [D]. North China Electric Power University (Beijing), 2022. DOI: 10.27140 / d.cnki.ghbbu.2022.001675.) records the use of fiber Bragg grating as the core sensing element, which causes the bending of the fiber Bragg grating through the sound signal, thereby affecting its refractive index and causing the wavelength to change. This technology achieves accurate monitoring of the sound signal inside the transformer by monitoring the change of wavelength in the fiber Bragg grating. The key components required in the implementation process include laser light source, optical fiber, fiber circulator, fiber coupler, photodetector, filter and digital oscilloscope. This technology can effectively measure the audio frequency range of 5 to 60kHz, and has excellent anti-electromagnetic interference ability, which is suitable for applications in complex power environments.

[0004] Prior art: an optical acoustic sensor based on a Fabry-Perot interference structure (Qi Zhimei, Zhang Mengying, Ren Dipeng, et al. Optical acoustic sensor and optical acoustic sensor including the same [P]. Beijing: CN201910495620.X, 2020-12-22.), the sound pickup structure of the sensor is composed of a support, a sound pickup diaphragm and a support beam, and the sound pickup diaphragm and the end face of the optical fiber form a Fabry-Perot cavity. When the sound pickup diaphragm receives sound pressure vibration, the cavity length changes and outputs a phase modulated optical signal;

[0005] In addition, the existing technology, such as an optical acoustic sensor (Author: Yu Benli, Hao Wenliang, Wang Hui, etc. An optical acoustic sensor [P]. Anhui Province: CN202121912592.6, 2022-01-21.) has a fixed sound pickup structure, so the sound pressure detection sensitivity cannot be adjusted. At the same time, the structure of the optical detection structure is complex, and the laser measurement distance is short. Improvements have been made to use a dual air cavity structure with adjustable air cavity size to adjust the vibration amplification factor, and at the same time combine the self-mixing interference system to detect the vibration displacement of the vibrating diaphragm. The two are used together to realize the recovery of the sound vibration signal. The invention has high sensitivity and a simple device structure. It has the advantages of moisture resistance, electromagnetic interference resistance, high sensitivity and adjustability. At the same time, the laser pigtail can be used to extend the measurement distance.

[0006] However, in practical applications, the failure rate of fiber Bragg grating acoustic sensors is relatively high. In particular, since the sensors are in a harsh environment of high temperature and high pressure for a long time, performance drift or failure may occur easily, resulting in inaccurate detection signals. Such problems seriously affect the judgment and location of discharge faults and increase the risk of equipment operation. This not only increases maintenance costs, but also makes it difficult to judge the status of the sensor in real time. Once a sensor fails, the discharge fault may not be discovered in time, further exacerbating the safety hazards of transformer operation. Therefore, how to effectively perform real-time calibration of the fiber Bragg grating acoustic sensor built into the transformer to ensure its normal working condition has become a technical problem that needs to be solved urgently. Summary of the invention

[0007] In order to solve the defects existing in the prior art, the present invention discloses a transformer built-in acoustic sensor on-site calibration device, and its technical solution is as follows:

[0008] A transformer built-in acoustic sensor on-site calibration device, comprising a signal generating module and a signal analyzing module, and having the following characteristics:

[0009] The signal generating module generates an ultrasonic square wave signal with a fixed frequency and fixed sound intensity through a microcontroller, and transmits it together with the environmental signal to the optical voiceprint sensor, after which it is converted into an electrical signal and filtered out by the filtering module without affecting the detection and recording of the discharge signal;

[0010] The signal analysis module has a function of counting the rising edges of fixed trigger level signals, and performs counting detection on the rising edges of fixed trigger voltages of signals processed by the optical voiceprint sensor, thereby realizing on-site verification of the sound monitoring system.

[0011] Preferably: the signal generating module includes an ultrasonic module, a microcontroller

[0012] The square wave signal generation program is loaded into the microcontroller, and the microcontroller generates a level signal at a fixed frequency according to the set requirements. The generated level signal is transmitted to the ultrasonic sensor module through the output port, and the driver module emits an ultrasonic square wave signal according to the specified pulse width.

[0013] Preferably: the signal analysis module includes a storage module, an analog-to-digital converter, a logic analyzer, an LED indicator light, and a band-stop filter; the analog signal output by the photoelectric demodulator is transmitted in two paths, one path is transmitted to the band-stop filter module, the band-stop filter filters out the additional standard reference signal in the input signal, outputs the signal, transmits it to the oscilloscope, outputs the waveform, and is used for transformer sound signal detection; the other path is transmitted to the storage module for storage, the storage module outputs data to the analog-to-digital conversion module, the analog-to-digital conversion module converts the analog signal exceeding the trigger level into a digital signal, the output digital signal is transmitted to the logic analyzer, the logic analyzer counts the rising edge of the digital signal at a fixed time (set by the operator), and if it exceeds 90% of the number of times the standard sound signal is sounded, the output signal is transmitted to the logic analyzer. L , or higher than 90% of the standard sound signal sound frequency n H , the logic analyzer outputs a high-level signal, indicating that the sensor is faulty.

[0014] The invention also discloses a method for on-site calibration of a transformer built-in acoustic sensor.

[0015] Beneficial Effects

[0016] Signal generation module: It is composed of a microcontroller and an ultrasonic generation module. The microcontroller has the advantages of being small in size and low in price. By changing the program written in it, the ultrasonic generator can be controlled to emit different ultrasonic signals (sounding time, sounding frequency...) to adapt to the calibration of different types of fiber grating voiceprint sensors in different application scenarios.

[0017] Signal analysis module: The signal information module includes a storage module, which can solve the problem of mismatched signal transmission speeds between different devices; the analog-to-digital converter used only converts signals that exceed the trigger level into digital signals. The sound intensity of the standard sound signal is set to be higher than the background sound signal during normal operation of the transformer, which can effectively avoid interference from background sound signals and ensure the accuracy of the calibration system.

[0018] The fixed frequency sound signal emitted by the ultrasonic module and the microcontroller will be used as a detection means for analysis and judgment through filters, storage modules, analog-to-digital converters, and logic analyzers; it has a longer service life than other optical acoustic sensors; it has high stability, as shown in that the Bragg grating is usually engraved inside the fiber grating sensor, so it has high stability to changes in the external environment (such as temperature, vibration, etc.). In the event of a discharge failure in the transformer, the temperature and pressure in the oil tank will change significantly. In contrast, the Fabry-Perot interferometer used in the present invention is more susceptible to external factors because it involves multiple optical surfaces. It has a high degree of integration, as shown in that the Bragg grating can be written directly into the optical fiber, which is convenient for integration with other optical fiber components to form a compact photonic device. However, the Fabry-Perot interferometer usually requires additional alignment and fixing devices, and has a low degree of integration.

[0019] Bragg grating: Advantages: It has the characteristics of high sensitivity, strong anti-electromagnetic interference ability, small size, high temperature resistance, etc., and is suitable for accurate measurement in harsh environments; Working principle: The periodic modulation of the refractive index in the optical fiber is used to make the incident light Bragg reflected at a specific wavelength, which is related to the grating period of the fiber grating. By monitoring the change in the wavelength of the reflected light, external parameters such as strain and temperature can be detected; Application scenario: In sensors, Bragg gratings are used to accurately measure physical quantities (such as temperature and strain), and the signal analysis is stable and sensitive.

[0020] Fabry-Perot interferometer: Advantages: It has the characteristics of high resolution, high stability and wide wavelength range, and can be used for fine measurement and multi-parameter measurement; Structure: It is composed of a cavity composed of two high-reflectivity parallel lenses, and achieves high-precision signal detection through interference effect; Working principle: When light waves are reflected multiple times between two mirrors, light waves of different paths interfere with each other to form interference fringes. Changes in external factors (such as pressure, vibration, temperature) will cause changes in the cavity length or refractive index, thereby causing the deviation of the interference fringes. By demodulating the fringes, the change information of the external environment can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A transformer built-in acoustic sensor on-site calibration method and device system workflow diagram;

[0022] Figure 2 It is a schematic diagram of the on-site calibration method and device system of the transformer built-in acoustic sensor in the example;

[0023] In the attached figure, 1. ultrasonic module; 2. microcontroller; 3. fiber grating sensor; 4. photoelectric demodulator; 5. filter; 6. storage module; 7. analog-to-digital converter; 8. logic analyzer; 9. LED indicator light; 10. oscilloscope. DETAILED DESCRIPTION

[0024] A transformer built-in acoustic sensor on-site calibration device, comprising a signal generating module and a signal analyzing module, and having the following characteristics:

[0025] The signal generating module generates an ultrasonic square wave signal with a fixed frequency and fixed sound intensity through a microcontroller, and transmits it together with the environmental signal to the optical voiceprint sensor, after which it is converted into an electrical signal and filtered out by the filtering module without affecting the detection and recording of the discharge signal;

[0026] The signal analysis module has a function of counting the rising edge of a fixed trigger level signal, and counts and detects the rising edge of a fixed trigger voltage of the signal processed by the optical voiceprint sensor to realize on-site verification of the sound monitoring system; the signal generation module includes an ultrasonic module and a microcontroller; the square wave signal generation program is loaded in the microcontroller, and the microcontroller generates a level signal at a fixed frequency according to the set requirements, and the generated level signal is transmitted to the ultrasonic sensor module through the output port, and the driving module emits an ultrasonic square wave signal according to the specified pulse width; the signal analysis module includes a storage module, an analog-to-digital converter, a logic analyzer, an LED indicator, and a band-stop filter; the analog signal output by the photoelectric demodulator is transmitted in two ways, one of which is transmitted to the band-stop filter module, and the band-stop filter filters the additional standard reference signal in the input signal, outputs the signal, and transmits it to the oscilloscope to output the waveform for transformer sound signal detection; the other is transmitted to the storage module for storage, and the storage module outputs data to the analog-to-digital conversion module, and the analog-to-digital conversion module converts the analog signal exceeding the trigger level into a digital signal, and the output digital signal is transmitted to the logic analyzer, and the logic analyzer counts the digital rising edge at a fixed time. If it exceeds 90% of the number of times the standard sound signal is sounded, the output signal is transmitted to the oscilloscope, and the waveform is output for transformer sound signal detection. L , or higher than 90% of the standard sound signal sound frequency n H , the logic analyzer outputs a high-level signal, indicating that the sensor is faulty; the ultrasonic module uses a piezoelectric ceramic ultrasonic sensor without a metal structure, which is required to be able to emit a frequency of 30kHZ or above, and the sound intensity is required to reach 100dB or above; the ultrasonic module and the optical voiceprint sensor are packaged and placed inside the transformer, and the microcontroller is placed outside the fuel tank to control the ultrasonic module; the signal generating module generates an ultrasonic square wave signal with a fixed frequency and fixed sound intensity, and transmits it to the optical voiceprint sensor together with the ambient signal.

[0027] The present invention discloses a method for on-site calibration of a transformer built-in acoustic sensor. The method is based on the on-site inspection device according to claim 1 and comprises the following steps:

[0028] Step 1, equipment installation: The ultrasonic module is installed inside the transformer and near the fiber grating voiceprint sensor so that the sensor can receive the sound signal. The rest of the devices are installed outside the transformer casing. After the installation is completed, the program is written into the microcontroller, and the microcontroller controls the ultrasonic transmitter to send out ultrasonic signals. The signal frequency is required to be within the measurable range of the optical sound sensor. A lower frequency should be selected as much as possible, and the fault signal monitoring will not be affected after filtering.

[0029] Step 2, equipment debugging: control the microcontroller to send out ultrasonic signals, and the signal frequency is required to be within the measurable range of the optical acoustic sensor (5kHz-60kHz). After adjusting the signal frequency and strength, use the adjusted signal to calibrate the acoustic sensor field calibration system. The calibration process must first start with the ultrasonic signal. The ultrasonic signal is converted into an electrical signal by the optical voiceprint sensor and the demodulator. The storage module in the signal analysis module stores the signal. According to the stored signal upper and lower amplitudes and frequency information, set the trigger level of the analog-to-digital converter and the lower and upper limits of the rising edge count of the logic analyzer. The rising edge count cycle is set to T, and the total signal transmission time is t. Considering the counting error of 10%, the lower limit of the count number is calculated using the following formula:

[0030]

[0031] The upper limit of the count is calculated using the following formula:

[0032]

[0033] A filter module is installed between the demodulator and the oscilloscope to remove the influence of the detection signal on the partial discharge detection. The band-stop filter is adjusted according to the set signal frequency. The filter center frequency is the electrical signal frequency and the bandwidth is 100Hz.

[0034] Step 3, parameter setting: select a lower frequency, which will not affect the fault signal monitoring after filtering, and is convenient for subsequent counting. The signal strength is required to be greater than 100dB. Use the adjusted signal to calibrate the fiber Bragg grating voiceprint sensor field verification system. According to the upper and lower amplitudes and frequency information of the calibration signal response, set the trigger level of the analog-to-digital converter and the lower and upper limits of the rising edge count of the logic analyzer. Set the trigger level of the system response voltage count according to 90% and 110% of the actual number of times;

[0035] Step 4: During operation, if the noise intensity of the normal operating environment is lower than the detection signal, and the corresponding electrical signal amplitude is smaller than the trigger voltage, the signal analysis module will not count. The logic analyzer only counts the rising edge of the signal generated by the square wave check signal. If the count number is n L With n H If the value is between 0 and 1, the logic analyzer outputs a 0 signal, otherwise it outputs a 1 signal.

[0036] Step 5, setting the detection cycle: set every three days as a cycle, and start sending ultrasonic signals to detect the fault of the fiber Bragg grating voiceprint sensor when there is no obvious fluctuation in the detection discharge signal; each fault detection is repeated three times, and if there is no abnormal signal, it is considered that the fiber Bragg grating voiceprint sensor is not faulty;

[0037] Step 6: Distinguishing abnormal signals: The signal output port is connected to the LED indicator light. If the logic signal is one and lasts for three cycles, the indicator light will light up, indicating that there is a problem with the fiber Bragg grating or a discharge fault occurs in the transformer. Use an oscilloscope to analyze the filtered signal and the full-wave signal. Combined with the output signal of the optical voiceprint sensor, the above two faults can be distinguished and the maintenance target can be determined.

[0038] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A transformer built-in acoustic sensor on-site calibration device, comprising a signal generating module and a signal analyzing module, characterized in that: The signal generating module generates an ultrasonic square wave signal with a fixed frequency and fixed sound intensity through a microcontroller, and transmits it together with the environmental signal to the optical voiceprint sensor, after which it is converted into an electrical signal and filtered out by the filtering module without affecting the detection and recording of the discharge signal; The signal analysis module has a function of counting the rising edges of fixed trigger level signals, and performs counting detection on the rising edges of fixed trigger voltages of signals processed by the optical voiceprint sensor, thereby realizing on-site verification of the sound monitoring system.

2. The transformer built-in acoustic sensor on-site calibration device according to claim 1 is characterized by: The signal generating module comprises an ultrasonic module and a microcontroller; a square wave signal generating program is loaded into the microcontroller, and the microcontroller generates a level signal at a fixed frequency according to the setting requirements. The generated level signal is transmitted to the ultrasonic sensor module through the output port, and the driving module emits an ultrasonic square wave signal according to the specified pulse width.

3. The transformer built-in acoustic sensor on-site calibration device according to claim 1 is characterized by: The signal analysis module includes a storage module, an analog-to-digital converter, a logic analyzer, an LED indicator light, and a band-stop filter. The analog signal output by the photoelectric demodulator is transmitted in two paths. One path is transmitted to the band-stop filter module. The band-stop filter filters out the additional standard reference signal in the input signal, outputs the signal, and transmits it to the oscilloscope to output a waveform for transformer sound signal detection. The other path is transmitted to the storage module for storage. The storage module outputs data to the analog-to-digital conversion module. The analog-to-digital conversion module converts the analog signal exceeding the trigger level into a digital signal. The output digital signal is transmitted to the logic analyzer. The logic analyzer counts the rising edge of the digital signal at a fixed time. If it exceeds 90% of the number of times the standard sound signal is sounded, the output signal is transmitted to the logic analyzer. L , or higher than 90% of the standard sound signal sound frequency n H , the logic analyzer outputs a high-level signal, indicating that the sensor is faulty.

4. The transformer built-in acoustic sensor on-site calibration device according to claim 2 is characterized by: The ultrasonic module uses a piezoelectric ceramic ultrasonic sensor without a metal structure, which is required to be able to emit a frequency of 30 kHz or above, and a sound intensity of 100 dB or above.

5. The transformer built-in acoustic sensor on-site calibration device according to claim 2, characterized in that: The ultrasonic module and the optical soundprint sensor are packaged and placed inside the transformer, and the microcontroller is placed outside the oil tank to control the ultrasonic module; the signal generating module generates an ultrasonic square wave signal with a fixed frequency and fixed sound intensity, and transmits it to the optical soundprint sensor together with the environmental signal.

6. A method for on-site calibration of a transformer built-in acoustic sensor, the method being based on the on-site calibration device for a transformer built-in acoustic sensor as claimed in claim 1, characterized in that: The steps include: Step 1, equipment installation: The ultrasonic module is installed inside the transformer and near the fiber grating voiceprint sensor so that the sensor can receive the sound signal. The rest of the devices are installed outside the transformer casing. Step 2, equipment debugging: control the microcontroller to send out ultrasonic signals, and the signal frequency is required to be within the measurable range of the optical acoustic sensor, 5kHz-60kHz; after adjusting the signal frequency and strength, use the adjusted signal to calibrate the acoustic sensor field verification system. The calibration process must first start with the ultrasonic signal, which is converted into an electrical signal by the optical voiceprint sensor and the demodulator. The storage module in the signal analysis module stores the signal. According to the stored signal upper and lower amplitudes and frequency information, set the trigger level of the analog-to-digital converter and the lower and upper limits of the rising edge count of the logic analyzer. The rising edge count cycle is set to T, and the total signal transmission time is t. Considering the counting error of 10%, the lower limit of the count number is calculated using the following formula: The upper limit of the count is calculated using the following formula: Step 3, parameter setting: select a low frequency, which will not affect the fault signal monitoring after filtering, and is convenient for subsequent counting. The signal strength is required to be greater than 100dB. Use the adjusted signal to calibrate the fiber grating voiceprint sensor field verification system. According to the upper and lower amplitudes and frequency information of the calibration signal response, set the trigger level of the analog-to-digital converter and the lower and upper limits of the rising edge count of the logic analyzer. Set the trigger level of the system response voltage count according to 90% and 110% of the actual number of times; Step 4: During operation, if the noise intensity of the normal operating environment is lower than the detection signal, and the corresponding electrical signal amplitude is smaller than the trigger voltage, the signal analysis module will not count. The logic analyzer only counts the rising edge of the signal generated by the square wave check signal. If the count number is n L With n H If the value is between 0 and 1, the logic analyzer outputs a 0 signal, otherwise it outputs a 1 signal. Step 5, setting the detection cycle: set every three days as a cycle, and start sending ultrasonic signals to detect the fault of the fiber Bragg grating voiceprint sensor when there is no obvious fluctuation in the detection discharge signal; each fault detection is repeated three times, and if there is no abnormal signal, it is considered that the fiber Bragg grating voiceprint sensor is not faulty; Step 6: Distinguishing abnormal signals: If the logic signal is one and lasts for three cycles, the indicator light will light up, indicating that there is a problem with the fiber Bragg grating or a discharge fault occurs in the transformer. Use an oscilloscope to analyze the filtered signal and the full-wave signal, and combine the output signal of the optical voiceprint sensor to distinguish the above two faults and determine the maintenance target.

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