Multi-resonant-frequency partial discharge ultrasonic sensor and partial discharge ultrasonic signal detection system

Abstract

The invention relates to the technical field of sensors, and discloses a multi-resonant-frequency partial discharge ultrasonic sensor, which comprises a capillary glass tube, an optical fiber collimating mirror arranged in the capillary glass tube, and a diaphragm arranged at the end part of one side of the capillary glass tube, the capillary glass tube is provided with an optical fiber matching liquid containing cavity, the optical fiber matching liquid containing cavity is located between the optical fiber collimating mirror and the diaphragm, optical fiber matching liquid is contained in the optical fiber matching liquid containing cavity, a set of cantilever beams extending towards the center position are installed in the optical fiber matching liquid containing cavity, and the cantilever beams and the diaphragm are plated with reflecting films with certain reflectivity. The optical fiber collimating mirror is connected with the coupler through an optical fiber line penetrating through the capillary glass tube, the coupler is connected with the driving light source and the photoelectric converter, and the photoelectric converter is connected with the data acquisition terminal. According to the invention, a Michelson interferometer principle is utilized, three resonance detection frequency bands are copolymerized, and a detected ultrasonic signal is restored through the change of light intensity, so that the cantilever beam diaphragm can detect a partial discharge ultrasonic signal; and meanwhile, a common-path design is adopted, so that the problem of thermal expansion and contraction of an optical path caused by temperature can be counteracted, and the influence of temperature is eliminated.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a multi-resonance frequency partial discharge ultrasonic sensor and a partial discharge ultrasonic signal detection system. Background Art

[0002] Partial discharge (PD) is a preliminary sign of insulation degradation in large power equipment. Its detection is crucial for accurately assessing insulation status, preventing major power accidents, and ensuring safe and stable grid operation. PD is accompanied by various physical phenomena, including sound, light, electricity, and heat. PD ultrasonic signals, in particular, have attracted widespread attention due to their unique advantages in locating PD points with high accuracy, strong resistance to electromagnetic interference, and isolation of the detection frequency band from low-frequency vibrations in the field.

[0003] At present, the widely used partial discharge ultrasonic sensors mainly include piezoelectric ceramic ultrasonic sensors (PZT) and fiber optic ultrasonic sensors. Among them, fiber optic ultrasonic sensors have been widely studied by scholars at home and abroad due to their long transmission distance and strong anti-electromagnetic interference ability of the transmission signal. However, there are still two problems with fiber optic ultrasonic sensors. First, their detection performance is greatly affected by stability, resulting in unstable detection results. Second, the resonant detection method limits its detection frequency band, which easily leads to the mismatch between the sensor detection band and the intrinsic high-energy spectrum of the partial discharge ultrasonic signal, resulting in missed detection and misjudgment of partial discharge signals. This has become a technical problem that needs to be solved urgently. Summary of the Invention

[0004] Aiming at the problem of missed partial discharge detection and judgment caused by the mismatch between the sensor detection frequency band and the intrinsic high-energy spectrum of the partial discharge ultrasonic signal in optical fiber ultrasonic sensors, the present invention provides a multi-resonance frequency partial discharge ultrasonic sensor and a partial discharge ultrasonic signal detection system.

[0005] The technical solution adopted in the present invention is: A multi-resonance frequency partial discharge ultrasonic sensor comprises a capillary glass tube, a fiber optic collimator mounted within the capillary glass tube, and a diaphragm mounted at one end of the capillary glass tube. The capillary glass tube is provided with a fiber optic matching liquid chamber located between the fiber optic collimator and the diaphragm. The fiber optic matching liquid chamber is filled with fiber optic matching liquid and is provided with a group of cantilever beams extending toward the center. The cantilever beams and the diaphragm are both coated with a reflective film having a certain reflectivity. The optical fiber collimator is connected to a coupler via an optical fiber line passing through a capillary glass tube. The coupler is respectively connected to a driving light source and a photoelectric converter. The photoelectric converter is connected to a data acquisition terminal.

[0006] Furthermore, the multi-resonance frequency partial discharge ultrasonic sensor forms a common optical path through a group of cantilever beams, optical fiber collimating mirrors, optical fiber lines and couplers, that is, the Michelson interferometer principle; the common optical path can offset the thermal expansion and contraction of the optical path caused by temperature.

[0007] Furthermore, the optical signal emitted by the driving light source enters the optical fiber collimator after passing through the coupler and the optical fiber line. The optical fiber collimator converts the divergent optical signal into a parallel beam and injects it into the optical fiber matching liquid. The upper and lower halves of the parallel light beam in the matching liquid are blocked by a set of cantilever beams respectively, and the light signal is reflected by the reflective film on the end face of the cantilever beam; the middle part of the parallel light beam is directly incident on the diaphragm and reflected by the reflective film on the diaphragm; The optical signal forms a fixed optical path difference during this transmission process, and interferes after being reflected back to the fiber collimator. The interfering optical signal is sent to the data acquisition and analysis terminal after passing through the optical fiber line, coupler and photoelectric converter.

[0008] Furthermore, the group of cantilever beams includes a first cantilever beam and a second cantilever beam; the first cantilever beam, the second cantilever beam and the diaphragm have different resonant frequencies.

[0009] Furthermore, the first cantilever beam, the second cantilever beam, and the diaphragm have different resonant frequencies. When a broadband local discharge ultrasonic signal acts on the sensor, the first cantilever beam, the second cantilever beam, and the diaphragm will respectively generate large vibrations within their respective resonant frequency ranges. The vibration causes the optical path difference of the optical signal to change during transmission, resulting in a change in the interference intensity of the optical signal reflected back to the fiber collimator. Based on the change in interference intensity, after photoelectric conversion, a corresponding electrical signal will be output, and these changed electrical signals will be collected and analyzed by a data acquisition terminal.

[0010] A partial discharge ultrasonic signal detection system, which is based on the above-mentioned multi-resonance frequency partial discharge ultrasonic sensor and includes a multi-resonance frequency partial discharge ultrasonic sensor, a sensor driving and demodulation system, and a data acquisition terminal; The multi-resonance frequency partial discharge ultrasonic sensor is placed in the transformer oil of the transformer to be tested and is connected to the sensor drive and demodulation system; the sensor drive and demodulation system is connected to the data acquisition terminal, which includes a 1-to-2 coupler, a laser, and a photoelectric converter; The multi-resonance frequency partial discharge ultrasonic sensor detects partial discharge ultrasonic signals. The partial discharge ultrasonic signals act on the first cantilever beam, the second cantilever beam and the diaphragm to cause them to vibrate in their respective resonant frequency ranges, thereby changing the optical path difference of the light beam carrying the deformation information of the cantilever beam and the diaphragm. The reflected light interferes through the fiber collimator, and the interference signal light is output to the photoelectric converter through a 1-to-2 coupler. The photoelectric converter converts the optical signal into an electrical signal and sends it to the data acquisition terminal. The acquisition terminal obtains the partial discharge ultrasonic signals received by the first cantilever beam, the second cantilever beam and the diaphragm.

[0011] The beneficial effects of the present invention are: This multi-resonance frequency partial discharge ultrasonic sensor uses the principle of Michelson interferometer and has three resonant detection frequency bands. It takes advantage of the different resonant frequencies of two cantilever beams and one diaphragm. When measuring partial discharge ultrasonic signals, the cantilever beam and the diaphragm both vibrate in their respective resonant frequency ranges, causing the optical path difference of the light signal to change, and ultimately causing the interference intensity of the reflected light signal to change. The measured ultrasonic signal is restored through the change in light intensity, so that both the cantilever beam and the diaphragm can detect the partial discharge ultrasonic signal.

[0012] This multi-resonance frequency partial discharge ultrasonic sensor adopts a common optical path design. Since the optical paths of the optical signals in the sensor are all in the same path, when the ambient temperature changes, the optical paths of the optical signals will increase or decrease simultaneously, so the optical path difference of the optical signals does not change, that is, the interference phase does not change. Therefore, the common optical path design can offset the thermal expansion and contraction problem of the optical path caused by temperature, thereby eliminating the influence of temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic structural diagram of a multi-resonance frequency partial discharge ultrasonic sensor according to the present invention; Figure 2 Schematic diagram of the structure of the partial discharge ultrasonic signal detection system of the present invention; Figure 3 This is the detection effect diagram of the traditional PZT sensor; Figure 4 This is a diagram showing the detection effect of the multi-resonance frequency partial discharge ultrasonic sensor of the present invention; In the figure, 1 is a capillary glass tube, 2 is a diaphragm, 3 is a fiber matching liquid cavity, 4 is a fiber matching liquid, 5 is a fiber collimator, 6 is a fiber line, 7 is a coupler, 8 is a driving light source, 9 is a photoelectric converter, 10 is a data acquisition terminal, 11 is a first cantilever beam, 12 is a second cantilever beam, 13 is a multi-resonance frequency partial discharge ultrasonic sensor, 14 is a sensor driving and demodulation system, 15 is a transformer oil, and 16 is a PZT sensor. DETAILED DESCRIPTION

[0014] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Example 1

[0015] To address the problem of missed PD detection caused by mismatch between the sensor detection frequency band and the intrinsic high-energy spectrum of the PD ultrasonic signal in optical fiber ultrasonic sensors, this embodiment provides a multi-resonance frequency PD ultrasonic sensor.

[0016] like Figure 1 As shown, the multi-resonance frequency partial discharge ultrasonic sensor includes a capillary glass tube 1, a fiber optic collimator 5 installed in the capillary glass tube 1, and a diaphragm 2 installed at one end of the capillary glass tube 1. The capillary glass tube 1 is provided with a fiber optic matching liquid chamber 3, which is located between the fiber optic collimator 5 and the diaphragm 2. The fiber optic matching liquid chamber 3 is filled with fiber optic matching liquid 4 and is equipped with a set of cantilever beams extending toward the center. The cantilever beams and the diaphragm 2 are both coated with a reflective film with a certain reflectivity. The fiber optic collimator 5 is connected to a coupler 7 via an optical fiber line 6 passing through the capillary glass tube 1. The coupler 7 is respectively connected to a driving light source 8 and a photoelectric converter 9, and the photoelectric converter 9 is connected to a data acquisition terminal 10. The driving light source 8 is a 1550nm narrowband light source, and the coupler 7 is a 1-to-2 coupler.

[0017] The working principle of the multi-resonance frequency partial discharge ultrasonic sensor is as follows: The optical signal emitted by the driving light source 8 enters the optical fiber collimator after passing through the 1-to-2 coupler 7 and the optical fiber line 6. The optical fiber collimator converts the divergent optical signal into a parallel light beam, which is then injected into the optical fiber matching liquid 4.

[0018] The optical fiber matching liquid 4 can effectively reduce the light signal reflected by the end face of the optical fiber collimator 5 and reduce the light signal propagation loss. Since the optical fiber matching liquid cavity 3 is equipped with a group of cantilever beams extending toward the center position and the diaphragm 2 at the end of one side of the capillary glass tube 1, the cantilever beams and the diaphragm 2 are both coated with a reflective film with a certain reflectivity; therefore, the upper and lower halves of the parallel light beam in the matching liquid are respectively blocked by a group of cantilever beams, and the light signal is reflected by the reflective film on the end face of the cantilever beam; the middle part of the parallel light beam is directly incident on the diaphragm 2 and reflected by the reflective film of the diaphragm 2.

[0019] The three light signals form a fixed optical path difference during this transmission process and interfere with each other after being reflected back to the fiber collimator. The interfering light signal is sent to the data acquisition and analysis terminal through the optical fiber line 6, coupler 7 and photoelectric converter 9, and finally the partial discharge ultrasonic signal received by the cantilever beam and diaphragm 2 is obtained.

[0020] The multi-resonance frequency partial discharge ultrasonic sensor forms a common optical path through a group of cantilever beams, a fiber collimator 5, an optical fiber line 6 and a coupler 7, that is, the Michelson interferometer principle; the Michelson interferometer principle is a common optical path design, which can offset the thermal expansion and contraction problem of the optical path caused by temperature, thereby eliminating the influence of temperature. This is because the optical paths of the three light signals in the sensor are all in the same path. When the ambient temperature changes, the optical paths of the three light signals will increase or decrease at the same time, so that the optical path difference of the three light signals does not change, that is, the interference phase does not change.

[0021] In addition, a group of cantilever beams in this embodiment are respectively a first cantilever beam 11 and a second cantilever beam 12; the first cantilever beam 11, the second cantilever beam 12 and the diaphragm 2 have different resonant frequencies. Based on the first cantilever beam 11, the second cantilever beam 12 and the diaphragm 2, the three have different resonant frequencies; when a broadband local discharge ultrasonic signal acts on the sensor, the first cantilever beam 11, the second cantilever beam 12, and the diaphragm 2 will respectively generate large vibrations within their respective resonant frequency ranges. This vibration will cause the optical path difference of the three light signals to change during transmission, resulting in a change in the interference intensity of the light signal reflected back to the fiber collimator; based on the change in interference intensity, after photoelectric conversion, a corresponding electrical signal will be output, and finally these changed electrical signals will be collected and analyzed by the data acquisition terminal 10.

[0022] To summarize, the multi-resonance frequency partial discharge ultrasonic sensor is based on the principle of Michelson interferometer and utilizes the characteristics that the resonant frequencies of two cantilever beams and one diaphragm 2 are different, so that when measuring the partial discharge ultrasonic signal, the cantilever beam and the diaphragm 2 both vibrate in their respective resonant frequency ranges, causing the optical path difference of the three light signals to change, and ultimately causing the interference intensity of the reflected light signal to change. The measured ultrasonic signal is restored by the change in light intensity, so that the first cantilever beam 11, the second cantilever beam 12, and the diaphragm 2 can all detect the partial discharge ultrasonic signal. Among them, the common optical path design can offset the thermal expansion and contraction problem of the optical path caused by temperature, thereby eliminating the temperature influence. Example 2

[0023] Based on the multi-resonance frequency partial discharge ultrasonic sensor provided in Example 1, this embodiment provides a partial discharge ultrasonic signal detection system.

[0024] like Figure 2 As shown, the PD ultrasonic signal detection system includes a multi-resonance frequency PD ultrasonic sensor 13, a sensor drive and demodulation system 14, and a data acquisition terminal 10. The multi-resonance frequency PD ultrasonic sensor 13 is placed in the transformer oil 15 of the transformer to be tested and is connected to the sensor drive and demodulation system 14. The sensor drive and demodulation system 14 is connected to the data acquisition terminal 10 and includes a 1-to-2 coupler 7, a laser, and a photoelectric converter 9.

[0025] The multi-resonance frequency partial discharge ultrasonic sensor 13 detects the partial discharge ultrasonic signal. The partial discharge ultrasonic signal acts on the first cantilever beam 11, the second cantilever beam 12 and the diaphragm 2 to make them vibrate in their respective resonant frequency ranges, so that the optical path difference of the light beam carrying the deformation information of the cantilever beam and the diaphragm 2 changes. The reflected light interferes through the optical fiber collimator, and the interference signal light is output to the photoelectric converter 9 through the 1-to-2 coupler 7. The photoelectric converter 9 converts the optical signal into an electrical signal and sends it to the data acquisition terminal 10. The acquisition terminal obtains the partial discharge ultrasonic signal received by the first cantilever beam 11, the second cantilever beam 12 and the diaphragm 2.

[0026] Since the partial discharge ultrasonic signal detection system uses a multi-resonance frequency partial discharge ultrasonic sensor 13 to monitor the partial discharge ultrasonic signal, it has high stability and is not affected by changes in ambient temperature. After the ambient temperature changes, the optical paths of the three light signals reflected back by the first cantilever beam 11, the second cantilever beam 12 and the diaphragm 2 will increase or decrease at the same time, so that the optical path difference of the three light signals does not change, that is, the interference phase does not change.

[0027] Furthermore, in order to test the effect of the multi-resonance frequency partial discharge ultrasonic sensor 13 and the partial discharge ultrasonic signal detection system, as shown in FIG. Figure 2 As shown, a partial discharge ultrasonic signal detection system is built to compare the effects of the multi-resonance frequency partial discharge ultrasonic sensor 13 and the traditional PZT sensor 16.

[0028] During the test, an 80kVA transformer body was used as an acoustic barrier inside the fuel tank to simulate the actual propagation process of a partial discharge ultrasonic signal. The partial discharge source was a standard plate-plate electrode. A traditional PZT sensor 16 was connected to the data acquisition terminal 10 via a 40dB amplifier. The time domain and frequency domain test results of the traditional PZT sensor 16 are shown in Figure 1. Figure 3 As shown, the time domain and frequency domain detection results of the multi-resonance frequency partial discharge ultrasonic sensor 13 are as follows Figure 4 As shown in the figure, it can be seen from the experimental results that the multi-resonance frequency partial discharge ultrasonic sensor 13 can effectively detect partial discharge ultrasonic signals, and the three structures of the first cantilever beam 11, the second cantilever beam 12 and the diaphragm 2 can detect partial discharge ultrasonic signals at different resonant frequencies. Its detection sensitivity is significantly higher than that of the traditional PZT sensor 16.

[0029] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A multi-resonance frequency partial discharge ultrasonic sensor, characterized in that: It includes a capillary glass tube, a fiber optic collimator installed in the capillary glass tube, and a diaphragm installed at one end of the capillary glass tube; the capillary glass tube is provided with a fiber optic matching liquid chamber, the fiber optic matching liquid chamber is located between the fiber optic collimator and the diaphragm, the fiber optic matching liquid chamber is filled with fiber optic matching liquid, and a group of cantilever beams extending toward the center are installed, and the cantilever beams and the diaphragm are coated with a reflection film with a certain reflectivity; The optical fiber collimator is connected to a coupler through an optical fiber line passing through a capillary glass tube, the coupler is respectively connected to a driving light source and a photoelectric converter, and the photoelectric converter is connected to a data acquisition terminal.

2. The multi-resonance frequency partial discharge ultrasonic sensor according to claim 1, characterized in that: The multi-resonance frequency partial discharge ultrasonic sensor forms a common optical path through a group of cantilever beams, optical fiber collimators, optical fiber lines and couplers, that is, the Michelson interferometer principle; the common optical path can offset the thermal expansion and contraction of the optical path caused by temperature.

3. The multi-resonance frequency partial discharge ultrasonic sensor according to claim 1, characterized in that: The optical signal emitted by the driving light source enters the optical fiber collimator after passing through the coupler and the optical fiber line. The optical fiber collimator converts the divergent optical signal into a parallel light beam and injects it into the optical fiber matching liquid. The upper and lower parts of the parallel light beam in the matching liquid are blocked by a group of cantilever beams respectively, and the light signal is reflected by the end reflective film of the cantilever beam; the middle part of the parallel light beam is directly incident on the diaphragm and reflected by the reflective film of the diaphragm; The optical signal forms a fixed optical path difference during this transmission process, and interferes after being reflected back to the fiber collimator. The interference optical signal is sent to the data acquisition and analysis terminal after passing through the optical fiber line, coupler and photoelectric converter.

4. The multi-resonance frequency partial discharge ultrasonic sensor according to claim 1, characterized in that: The group of cantilever beams includes a first cantilever beam and a second cantilever beam; the first cantilever beam, the second cantilever beam and the diaphragm have different resonant frequencies.

5. The multi-resonance frequency partial discharge ultrasonic sensor according to claim 4, characterized in that: Based on the first cantilever beam, the second cantilever beam and the diaphragm, the resonant frequencies of the three are different; when the broadband partial discharge ultrasonic signal acts on the sensor, the first cantilever beam, the second cantilever beam and the diaphragm will respectively generate large vibrations in their respective resonant frequency ranges, and the vibration causes the optical path difference of the optical signal to change during the transmission process, resulting in changes in the interference intensity of the optical signal reflected back to the fiber collimator; based on the change in interference intensity, after photoelectric conversion, the corresponding electrical signal will be output, and these changed electrical signals will be collected and analyzed through the data acquisition terminal.

6. A partial discharge ultrasonic signal detection system, the partial discharge ultrasonic signal detection system is based on the multi-resonance frequency partial discharge ultrasonic sensor according to any one of claims 1 to 5, characterized in that: It includes a multi-resonance frequency partial discharge ultrasonic sensor, a sensor driving and demodulation system and a data acquisition terminal; The multi-resonance frequency partial discharge ultrasonic sensor is placed in the transformer oil of the transformer to be tested, and is connected to the sensor driving and demodulation system; the sensor driving and demodulation system is connected to the data acquisition terminal, which includes a 1-to-2 coupler, a laser and a photoelectric converter; A multi-resonance frequency partial discharge ultrasonic sensor detects partial discharge ultrasonic signals. The partial discharge ultrasonic signals act on the first cantilever beam, the second cantilever beam and the diaphragm to make them vibrate in their respective resonant frequency ranges, so that the optical path difference of the light beam carrying the deformation information of the cantilever beam and the diaphragm changes, and the reflected light interferes through the fiber collimator. The interference signal light is output to the photoelectric converter through a 1-to-2 coupler. The photoelectric converter converts the optical signal into an electrical signal and sends it to the data acquisition terminal. The acquisition terminal obtains the partial discharge ultrasonic signals received by the first cantilever beam, the second cantilever beam and the diaphragm.

Images