A narrow-band ultrasonic partial discharge detection system and method based on a resonant cavity

Abstract

The application discloses a narrow-band ultrasonic partial discharge detection system and method based on a resonant cavity, which comprises a controller, a driving device, a broadband ultrasonic sensor, a supporting part and a moving plate. The resonant cavity is formed by the supporting part, the moving plate and a measured surface. The broadband ultrasonic sensor is arranged on the moving plate. The detection signal transmitted from the resonant cavity is collected by the broadband ultrasonic sensor. The input end of the driving device is connected with the controller, and the output end is connected with the moving plate. The controller is connected with the broadband ultrasonic sensor. The controller is used for receiving the detection signal collected by the broadband ultrasonic sensor, calculating the signal-to-noise ratio of the detection signal, and controlling the driving device to drive the moving plate to move towards or away from the measured surface or stop moving based on the signal-to-noise ratio, so as to adjust the resonant frequency, change the frequency band of the ultrasonic wave passing through the resonant cavity, and make the ultrasonic wave of a specific narrow-band frequency be detected by the broadband ultrasonic sensor through the resonant cavity, thereby realizing narrow-band detection of the partial discharge ultrasonic wave and improving the detection sensitivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of partial discharge detection, and in particular to a narrow-band ultrasonic partial discharge detection system and method based on a resonant cavity. BACKGROUND

[0002] Power equipment ultrasonic detection of partial discharge is a common power equipment defect detection technology. When there is an insulation defect inside the power equipment, a local breakdown, i.e., partial discharge, occurs due to the concentration of the local electric field, exciting an ultrasonic signal. By detecting the ultrasonic signal, it can be effectively determined whether the equipment insulation has a defect.

[0003] However, the current power equipment ultrasonic detection of partial discharge commonly uses a contact ultrasonic sensor based on piezoelectric materials, and the frequency band characteristics of the ultrasonic sensor cannot be tuned after processing. It is mainly divided into wide-band ultrasonic sensors and narrow-band ultrasonic sensors. The advantage of using a wide-band ultrasonic sensor is to improve the coverage of the ultrasonic detection of partial discharge and avoid missing detection due to the mismatch between the sensor frequency band and the partial discharge ultrasonic signal frequency band, but at the same time, this method easily introduces wide-band noise and has low sensitivity. The advantage of using a narrow-band ultrasonic sensor is to improve the sensitivity of the ultrasonic detection of partial discharge and reduce noise, but there is a defect of missing detection due to the mismatch between the sensor frequency band and the partial discharge ultrasonic signal frequency band. SUMMARY

[0004] Therefore, the embodiments of the present application provide a narrow-band ultrasonic partial discharge detection system and method based on a resonant cavity to solve the technical problem of introducing wide-band noise and low detection sensitivity when using a wide-band ultrasonic sensor for detection in the prior art.

[0005] The technical solutions provided by the present application are as follows:

[0006] The first aspect of the embodiments of the present application provides a narrow-band ultrasonic partial discharge detection system based on a resonant cavity, comprising a controller, a driving device, a wide-band ultrasonic sensor, a support part, and a moving plate. The support part, the moving plate, and a measured surface form a resonant cavity. The wide-band ultrasonic sensor is arranged on the moving plate, and a detection signal transmitted from the resonant cavity is collected by the wide-band ultrasonic sensor. The input end of the driving device is connected with the controller, and the output end is connected with the moving plate. The controller is connected with the wide-band ultrasonic sensor. The controller is used for receiving the detection signal collected by the wide-band ultrasonic sensor, calculating the signal-to-noise ratio of the detection signal, and controlling the driving device to drive the moving plate to move towards or away from the measured surface or stop moving based on the signal-to-noise ratio.

[0007] Optionally, the resonant cavity is filled with a viscous fluid or an elastic acoustic impedance matching filler.

[0008] Optionally, the movement plate and the support part are movably connected, and the movement plate moves towards or away from the measured surface along the support part.

[0009] Optionally, the movement plate and the support part are fixedly connected, and the support part is a telescopic structure, and the movement plate moves towards or away from the measured surface by making the support part telescopic.

[0010] Optionally, the support part comprises a first support plate and a second support plate, the first support plate and the second support plate are oppositely arranged on both sides of the measured surface, the movement plate is opposite to the measured surface, and both ends of the movement plate are connected with the first support plate and the second support plate respectively, and the first support plate, the second support plate, the movement plate and the measured surface form a resonant cavity.

[0011] Optionally, the driving device comprises a motor and a lead screw, the motor is connected with the controller, one end of the lead screw is connected with an output shaft of the motor, and the other end of the lead screw is connected with the movement plate through a nut.

[0012] Optionally, the controller comprises: a signal processing unit, configured to perform envelope detection on the detection signal, and generate an amplitude distribution histogram according to the envelope detection result; a calculation unit, configured to acquire a noise amplitude and a maximum signal amplitude according to the amplitude distribution histogram, and calculate a signal-to-noise ratio according to the noise amplitude and the maximum signal amplitude, wherein the noise amplitude is the highest frequency amplitude in the amplitude distribution histogram, and the maximum signal amplitude is the maximum amplitude appearing in the amplitude distribution histogram; and a driving control unit, configured to control the driving device to drive the movement plate to move towards or away from the measured surface when the signal-to-noise ratio is less than a set threshold, and stop the movement when the signal-to-noise ratio is greater than or equal to the set threshold.

[0013] The second aspect of the embodiment of the present application provides a narrow-band ultrasonic partial discharge detection method based on a resonant cavity, comprising the following steps: installing a support part on a measured surface, installing a movement plate on the support part, and making the support part, the movement plate and the measured surface form a resonant cavity; installing a wide-band ultrasonic sensor on the movement plate, and collecting a detection signal transmitted from the resonant cavity through the wide-band ultrasonic sensor; receiving, by a controller, the detection signal collected by the wide-band ultrasonic sensor, calculating a signal-to-noise ratio of the detection signal, and controlling the driving device to drive the movement plate to move towards or away from the measured surface or stop the movement based on the signal-to-noise ratio.

[0014] Optionally, before the movement plate is installed on the support part, the method further comprises the following steps: applying a viscous flow state or elastic acoustic impedance matching filler on the measured surface; and when the movement plate is installed on the support part, making the side of the movement plate, which is towards the measured surface, contact the acoustic impedance matching filler.

[0015] Optionally, the signal-to-noise ratio of the detection signal is calculated, and the driving device is controlled to drive the moving plate to move towards or away from the measured surface based on the signal-to-noise ratio, including: envelope detection is performed on the detection signal, and an amplitude distribution histogram is generated according to the envelope detection result; the noise amplitude and the maximum signal amplitude are obtained according to the amplitude distribution histogram, and the signal-to-noise ratio is calculated according to the noise amplitude and the maximum signal amplitude, wherein the noise amplitude is the amplitude with the highest frequency in the amplitude distribution histogram, and the maximum signal amplitude is the maximum amplitude in the amplitude distribution histogram; when the signal-to-noise ratio is less than a set threshold, the driving device is controlled to drive the moving plate to move towards or away from the measured surface, and when the signal-to-noise ratio is greater than or equal to the set threshold, the moving is stopped.

[0016] From the above technical solutions, it can be seen that the embodiments of the present application have the following advantages:

[0017] The narrow-band ultrasonic partial discharge detection system and method based on a resonant cavity provided by the embodiments of the present application include a controller, a driving device, a wideband ultrasonic sensor, a support part, and a moving plate. A resonant cavity is formed by the support part, the moving plate, and a measured surface. The wideband ultrasonic sensor is arranged on the moving plate. The detection signal transmitted from the resonant cavity is collected by the wideband ultrasonic sensor. The input end of the driving device is connected with the controller, and the output end is connected with the moving plate. The controller is connected with the wideband ultrasonic sensor. The controller is used to receive the detection signal collected by the wideband ultrasonic sensor, calculate the signal-to-noise ratio of the detection signal, and control the driving device to drive the moving plate to move towards or away from the measured surface or stop moving based on the signal-to-noise ratio. The length of the resonant cavity is adjusted by controlling the moving plate to move towards or away from the measured surface based on the signal-to-noise ratio, so as to adjust the resonant frequency. The frequency band of the ultrasonic wave passing through the resonant cavity is changed, so that the ultrasonic wave with a specific narrow-band frequency can be detected by the wideband ultrasonic sensor through the resonant cavity. The narrow-band ultrasonic partial discharge detection is realized, and the detection sensitivity is improved. Meanwhile, the narrow-band frequency can be tuned through the resonant cavity, which solves the defect that the detection frequency band cannot be tuned when a narrow-band ultrasonic sensor is directly used, and avoids the missed detection caused by the mismatch between the frequency band of the narrow-band ultrasonic sensor and the frequency band of the partial discharge ultrasonic signal. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly express the technical solutions of the embodiments of the present application, the drawings needed for the description of the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0019] Figure 1Schematic diagram of the structure of a narrow-band ultrasonic partial discharge detection system based on a resonant cavity in an embodiment of the present invention;

[0020] Figure 2 Schematic diagram of the structure of the resonant cavity in an embodiment of the present invention;

[0021] Figure 3 Schematic diagram of the effect of adjusting the resonant cavity length to achieve frequency selection of transmitted ultrasound in an embodiment of the present invention;

[0022] Figure 4 is the original waveform diagram of the detection signal in the embodiment of the present invention;

[0023] Figure 5 This is a waveform diagram of the detection signal after envelope detection in an embodiment of the present invention;

[0024] Figure 6 is an amplitude distribution histogram of the detection signal in an embodiment of the present invention;

[0025] Figure 7 Flowchart of a narrowband ultrasonic partial discharge detection method based on a resonant cavity in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0027] The embodiment of the present invention provides a narrowband ultrasonic partial discharge detection system based on a resonant cavity, such as Figure 1 As shown, it includes a controller 5, a driving device 6, a broadband ultrasonic sensor 4, a support part 1 and a moving plate 2. The support part 1, the moving plate 2 and the measured surface 3 form a resonant cavity. The broadband ultrasonic sensor 4 is arranged on the moving plate 2. The detection signal transmitted from the resonant cavity is collected by the broadband ultrasonic sensor 4. The input end of the driving device 6 is connected to the controller 5, and the output end is connected to the moving plate 2. The controller 5 is connected to the broadband ultrasonic sensor 4. The controller 5 is used to receive the detection signal collected by the broadband ultrasonic sensor 4, calculate the signal-to-noise ratio of the detection signal, and control the driving device 6 to drive the moving plate 2 to move toward or back to the measured surface 3 or stop moving based on the signal-to-noise ratio.

[0028] In particular, the narrow-band ultrasonic partial discharge detection system based on the resonant cavity is used to detect internal defects of power equipment. When there is an insulation defect inside the power equipment, a local breakdown, i.e., a partial discharge, occurs due to a local electric field concentration, exciting an ultrasonic signal. By measuring the ultrasonic signal, it can be effectively determined whether the equipment insulation has a defect. The detection signal is an ultrasonic signal that enters the broadband ultrasonic sensor 4 through the resonant cavity. The driving device 6 adopts a linear motor, an air cylinder, or a screw rod structure to drive the linear motion of the motion plate 2. The measured surface 3 is the outer surface of various power equipment housings. One end of the support part 1 is fixed to the measured surface 3 by magnetic adsorption, bolts, a bandage, or gravity. The fixing method can be selected according to the actual working conditions on site. The other end of the support part 1 is connected to the motion plate 2, so that the motion plate 2, the support part 1, and the measured surface 3 form a cavity, which is the resonant cavity, as shown in Figure 2 The bottom of the resonant cavity is the measured surface 3, and the top is the motion plate 2. The support part 1 between the measured surface 3 and the motion plate 2 forms the side of the resonant cavity. The resonant cavity can be a closed cavity or a cavity with one or more openings on the side, so that the ultrasonic wave moves back and forth between the measured surface 3 and the motion plate 2 after entering the resonant cavity from the power equipment housing. The resonant cavity can be filled with a filler to increase the acoustic impedance, or no filler can be provided, and the air in the environment can be used as a filler to automatically fill through the side openings. In this case, the filler can also be understood as air, but it does not need to be filled manually.

[0029] The principle of the resonant cavity formed by the support part 1, the motion plate 2, and the measured surface 3 is as follows:

[0030] Let the distance between the motion plate 2 and the measured surface 3 be d, and the intensity of the ultrasonic signal inside the power equipment be P1. Then the ultrasonic signal that enters the resonant cavity through the power equipment housing can be represented as:

[0031] P2 = t 12 P1 (1)

[0032] where P1 is the amplitude of the ultrasonic signal inside the power equipment, P2 is the amplitude of the ultrasonic signal inside the resonant cavity, t 12 is the transmission coefficient of the ultrasonic wave from the inside of the power equipment through the housing into the inside of the resonant cavity.

[0033] The ultrasonic signal inside the resonant cavity continues to transmit through the motion plate 2 and enters the broadband ultrasonic sensor 4, which is represented as:

[0034] P 30 = t 23 P2e -iδ (2)

[0035] where P 30 is the amplitude of the ultrasonic signal inside the resonant cavity after transmitting through the motion plate 2, t 23is the transmission coefficient of the ultrasonic wave from the resonant cavity into the broadband ultrasonic sensor 4, i is an imaginary number, and δ is the additional phase generated by the ultrasonic wave propagating from the power equipment housing to the moving plate 2. The calculation formula of this additional phase is:

[0036]

[0037] Wherein f is the ultrasonic frequency, v is the ultrasonic velocity, and d is the distance between the moving plate 2 and the housing of the power equipment.

[0038] In addition, when the ultrasonic signal inside the resonant cavity propagates to the moving plate 2, it will also be reflected. After reaching the measured surface 3, the reflected ultrasonic wave is reflected back to the moving plate 2 and transmits through the moving plate 2 to reach the broadband ultrasonic sensor 4. The transmitted ultrasonic signal is expressed as:

[0039] P 31 =t 23 (r 21 e -iδ r 23 e -iδ P2e -iδ ) (4)

[0040] Among them, P 31 is the amplitude of the ultrasonic signal inside the resonant cavity after being reflected once and then transmitted through the moving plate 2, r 23 is the reflection coefficient of the moving plate 2, r 21 is the reflection coefficient of the power equipment casing.

[0041] Similarly, when the ultrasonic signal inside the resonant cavity propagates to the moving plate 2, the ultrasonic signal that is reflected twice by the moving plate 2 and the outer casing of the power equipment and then transmitted through the moving plate 2 is expressed as:

[0042] P 32 =t 23 ((r 21 e -iδ r 23 e -iδ ) 2 P2e -iδ ) (5)

[0043] Therefore, the final synthetic sound field transmitted through the moving plate 2 is:

[0044]

[0045] From the resonance characteristics of formula (6), it can be seen that the support part 1, the moving plate 2 and the measured surface 3 form a resonant cavity. The resonant frequency can be adjusted by adjusting the length d of the resonant cavity, thereby filtering the ultrasonic frequency range entering the broadband ultrasonic sensor 4. Specifically, Figure 3 As shown, Figure 3is the relationship between ultrasonic frequency and transmission coefficient in resonant cavities of different lengths d calculated according to formula (6), where t 12 , t 23 is 0.05, r 21 and r 23 =0.95, and v is set to 1500 m / s. It can be seen that when the resonant cavity length is adjusted to 3 mm, only ultrasound waves of 165 kHz can pass through the resonant cavity. When the resonant cavity length is adjusted to 5 mm, only ultrasound waves of 100 kHz and 200 kHz can pass through the resonant cavity. When the resonant cavity length is adjusted to 8 mm, only ultrasound waves of 60 kHz, 120 kHz, 180 kHz, and 240 kHz can pass through the resonant cavity.

[0046] It can be seen from the characteristics of the resonant cavity that the frequency of the ultrasonic wave penetrating the resonant cavity can be changed by changing the length of the resonant cavity. After the broadband ultrasonic sensor 4 collects the detection signal transmitted from the resonant cavity, the controller 5 calculates the signal-to-noise ratio of the detection signal. If the signal-to-noise ratio is large, it means that the transmission coefficient of the ultrasonic signal generated by the local discharge inside the power equipment is large. If the signal-to-noise ratio is low, it means that the transmission coefficient of the ultrasonic signal generated by the local discharge inside the power equipment is small. It is necessary to change the length of the resonant cavity to increase the transmission coefficient of the ultrasonic signal generated by the local discharge inside the power equipment. The controller 5 controls the driving device 6 to drive the moving plate 2 toward or away from the measured surface 3, thereby adjusting the length of the resonant cavity to increase the transmission coefficient of the ultrasonic signal generated by the local discharge inside the power equipment, thereby improving the detection sensitivity.

[0047] In one example, the moving plate 2 is initially positioned against the surface to be measured 3. The controller 5 controls the actuator to gradually move the moving plate 2 outward from the surface to be measured 3. During this process, the controller 5 collects the detection signal output by the broadband ultrasonic sensor 4 in real time and calculates the signal-to-noise ratio. When the signal-to-noise ratio reaches a certain set value, such as a maximum signal-to-noise ratio, the controller 5 stops the actuator 6. When the frequency of the partial discharge signal within the power equipment changes, causing the signal-to-noise ratio to drop to a set threshold, such as below 2:1, the controller 5 re-controls the actuator 6 to cause the moving plate 2 to continue moving. This movement is a continuous reciprocating process toward and away from the surface to be measured 3. When the movement away from the surface to be measured reaches its maximum range (e.g., 5 mm is sufficient for frequencies of 80 kHz to 200 kHz), the moving plate 2 resumes its movement toward the surface to be measured 3 until a signal with a high signal-to-noise ratio, such as a signal-to-noise ratio greater than 2:1, is detected during the reciprocating motion. The moving plate 2 then remains in this position. If the signal disappears (e.g., due to interference that disappears quickly), the process is repeated until the signal-to-noise ratio of the signal waveform output by the broadband ultrasonic sensor 4 increases to above 2:1.

[0048] Since the ultrasonic signal generated by the partial discharge inside the power equipment varies with the frequency of the discharge signal, the position of the moving plate 2 needs to be adjusted repeatedly during the detection process to make the moving plate 2 stay at a position with a high signal-to-noise ratio. The embodiment of the present application realizes frequency-selective partial discharge narrowband ultrasonic measurement through a resonant cavity and a wideband ultrasonic sensor, solving the defect that the frequency band of the narrowband ultrasonic sensor cannot be tuned directly.

[0049] The narrowband ultrasonic partial discharge detection system based on a resonant cavity provided by the embodiment of the present application comprises a controller 5, a driving device 6, a wideband ultrasonic sensor 4, a support part 1 and a moving plate 2. The resonant cavity is composed of the support part 1, the moving plate 2 and the measured surface 3. The wideband ultrasonic sensor 4 is arranged on the moving plate 2. The detection signal transmitted from the resonant cavity is collected through the wideband ultrasonic sensor 4. The input end of the driving device 6 is connected with the controller 5, and the output end is connected with the moving plate 2. The controller 5 is connected with the wideband ultrasonic sensor 4. The controller 5 is used for receiving the detection signal collected by the wideband ultrasonic sensor 4, calculating the signal-to-noise ratio of the detection signal, and controlling the driving device 6 to drive the moving plate 2 to move towards or away from the measured surface 3 or stop moving based on the signal-to-noise ratio, so as to adjust the resonant frequency, change the frequency band of the ultrasonic wave passing through the resonant cavity, and make the ultrasonic wave of a specific narrowband frequency be detected by the wideband ultrasonic sensor 4 through the resonant cavity, realizing narrowband detection of the partial discharge ultrasonic wave, improving the detection sensitivity, and at the same time, the narrowband frequency can be tuned through the resonant cavity, solving the defect that the frequency band of the narrowband ultrasonic sensor cannot be tuned directly, and avoiding the missed detection caused by the mismatch between the frequency band of the narrowband ultrasonic sensor and the frequency band of the partial discharge ultrasonic signal.

[0050] In an embodiment, the resonant cavity is filled with a viscous flow state or elastic acoustic impedance matching filler 7. The acoustic impedance matching filler 7 is a viscous flow state or elastic semi-cured encapsulation glue, silicone grease or the like. Since the actual stroke of the moving plate 2 only needs to be in the order of millimeters, for example, less than 5 mm can completely cover the frequency selection range of 80 kHz-200 kHz, the viscous flow state or elastic acoustic impedance matching filler 7 will shrink and expand with the reciprocating motion of the moving plate 2, which can improve the transmission coefficient of the resonant cavity compared with directly using air.

[0051] In an embodiment, the moving plate 2 and the support part 1 are movably connected, and the moving plate 2 moves along the support part 1 towards or away from the measured surface 3. Exemplarily, the support part 1 is a cylinder with a polygonal or circular cross section. The support part 1 is internally provided with a slide rail perpendicular to the moving plate 2. The two ends of the moving plate 2 are connected with the slide rail, and the moving plate 2 can move along the slide rail towards or away from the measured surface 3, so as to adjust the length of the resonant cavity.

[0052] In an embodiment, the motion plate 2 is fixedly connected with the support part 1, the support part 1 is a telescopic structure, and the motion plate 2 moves towards or away from the measured surface 3 by making the support part 1 telescopic. Exemplarily, the support part 1 is made of elastic material, the two ends of the motion plate 2 are connected with the support part 1, the controller 5 controls the driving device 6 to drive the motion plate 2, and the motion plate 2 moves towards or away from the measured surface 3 by extruding the support part 1, so as to adjust the length of the resonant cavity, or the support part 1 is a telescopic plate, and the motion plate 2 moves towards or away from the measured surface 3 by extruding the telescopic plate.

[0053] In an embodiment, as shown in Figure 2 the support part 1 comprises a first support plate 11 and a second support plate 12, the first support plate 11 and the second support plate 12 are oppositely arranged on both sides of the measured surface 3, the motion plate 2 is opposite to the measured surface 3, and the two ends of the motion plate 2 are respectively connected with the first support plate 11 and the second support plate 12, and the first support plate 11, the second support plate 12, the motion plate 2 and the measured surface 3 form a resonant cavity. Specifically, the first support plate 11 and the second support plate 12 are parallel to each other and perpendicular to the measured surface 3 and the motion plate 2, and the two ends of the motion plate 2 are movably connected with the first support plate 11 and the second support plate 12 respectively and can move along the length direction of the first support plate 11 or the second support plate 12. In this embodiment, the side surface of the resonant cavity has an opening, which facilitates filling the acoustic impedance matching filler 7 into the resonant cavity.

[0054] In an embodiment, the driving device 6 comprises a motor 61 and a lead screw 62, the motor 61 is connected with the controller 5, one end of the lead screw 62 is connected with the output shaft of the motor 61, and the other end of the lead screw 62 is connected with the motion plate 2 through a nut. The controller 5 can drive the motor 61 to move the lead screw 62 and drive the motion plate 2 to move towards or away from the direction of the power equipment shell. The motor 61 is a high-precision stepping motor, and the structure of the lead screw 62 and the motor 61 realizes high-precision control of the position of the motion plate 2.

[0055] In an embodiment, the controller 5 comprises: a signal processing unit, configured to perform envelope detection on a detection signal and generate an amplitude distribution histogram according to the envelope detection result; a calculation unit, configured to acquire a noise amplitude and a maximum signal amplitude according to the amplitude distribution histogram, and calculate a signal-to-noise ratio according to the noise amplitude and the maximum signal amplitude, wherein the noise amplitude is the amplitude with the highest frequency in the amplitude distribution histogram, and the maximum signal amplitude is the maximum amplitude appearing in the amplitude distribution histogram; and a driving control unit, configured to control the driving device 6 to drive the motion plate 2 to move towards or away from the measured surface 3 when the signal-to-noise ratio is less than a set threshold, and stop the motion when the signal-to-noise ratio is greater than or equal to the set threshold.

[0056] Referring to Figure 4 , Figure 5 and Figure 6The controller 5 processes the envelope detection of the original ultrasonic signal waveform, and then counts the amplitude distribution histogram of the envelope. The y-axis of the histogram is the frequency of each signal amplitude, and the highest frequency amplitude is the noise amplitude. The x-axis is the signal amplitude, and the maximum amplitude is the maximum signal amplitude. The signal-to-noise ratio is the maximum signal amplitude divided by the noise amplitude, that is, the highest frequency amplitude divided by the maximum amplitude in the amplitude distribution histogram. After obtaining the signal-to-noise ratio, the driving device 6 is controlled to drive the motion plate 2 to move towards or away from the measured surface 3 according to the signal-to-noise ratio. When the signal-to-noise ratio is less than the set threshold, such as 2:1, the driving device 6 is controlled to drive the motion plate 2 to move towards or away from the measured surface 3. When the signal-to-noise ratio is greater than or equal to the set threshold, the motion is stopped.

[0057] The narrow-band ultrasonic partial discharge detection system based on the resonant cavity of the embodiment can quickly calculate the signal-to-noise ratio through envelope detection and counting of the amplitude distribution histogram of the envelope. The driving device 6 is controlled to drive the motion plate 2 to move towards or away from the measured surface 3 according to the signal-to-noise ratio, thereby improving the detection sensitivity and avoiding missed detection.

[0058] The embodiment of the application also provides a narrow-band ultrasonic partial discharge detection method based on a resonant cavity, as shown in Figure 7 , comprising:

[0059] Step S100, installing a support part 1 on the measured surface 3, and installing a motion plate 2 on the support part 1, so that the support part 1, the motion plate 2 and the measured surface 3 form a resonant cavity.

[0060] Step S200, installing a wideband ultrasonic sensor 4 on the motion plate 2, and collecting detection signals transmitted from the resonant cavity through the wideband ultrasonic sensor 4.

[0061] Step S300, receiving the detection signals collected by the wideband ultrasonic sensor 4 through the controller 5, calculating the signal-to-noise ratio of the detection signals, and controlling the driving device 6 to drive the motion plate 2 to move towards or away from the measured surface 3 or stop moving based on the signal-to-noise ratio.

[0062] The narrow-band ultrasonic partial discharge detection method based on the resonant cavity provided by the embodiment of the application comprises the following steps: a support part 1, a moving plate 2 and a measured surface 3 form a resonant cavity; a broadband ultrasonic sensor 4 is arranged on the moving plate 2; the detection signal transmitted from the resonant cavity is collected by the broadband ultrasonic sensor 4; the input end of a driving device 6 is connected with a controller 5, and the output end is connected with the moving plate 2; the controller 5 is connected with the broadband ultrasonic sensor 4; the controller 5 is used for receiving the detection signal collected by the broadband ultrasonic sensor 4, calculating the signal-to-noise ratio of the detection signal, and controlling the driving device 6 to drive the moving plate 2 to move towards or away from the measured surface 3 or stop moving based on the signal-to-noise ratio, so as to adjust the resonant frequency, change the frequency band of the ultrasonic wave passing through the resonant cavity, and enable the ultrasonic wave of a specific narrow-band frequency to be detected by the broadband ultrasonic sensor 4 through the resonant cavity, thereby realizing narrow-band ultrasonic partial discharge detection and improving the detection sensitivity; meanwhile, the narrow-band frequency can be tuned through the resonant cavity, the defect that the frequency band cannot be tuned when the narrow-band ultrasonic sensor is directly used for detection is solved, and the problem of missed detection caused by the mismatch between the frequency band of the narrow-band ultrasonic sensor and the frequency band of the partial discharge ultrasonic signal is avoided.

[0063] In an embodiment, before the moving plate 2 is installed on the support part 1, the following step is further included: the measured surface 3 is coated with a viscous flow state or elastic acoustic impedance matching filler 7; when the moving plate 2 is installed on the support part 1, the side of the moving plate 2 facing the measured surface 3 is in contact with the acoustic impedance matching filler 7. When the moving plate 2 is installed, the moving plate 2 and the support part 1 are tightly attached, the side of the moving plate 2 facing the measured surface 3 is in contact with the acoustic impedance matching filler 7, and the acoustic impedance matching filler 7 covers the resonant cavity. The viscous flow state or elastic acoustic impedance matching filler 7 will shrink and expand with the reciprocating movement of the moving plate 2, and the transmission coefficient of the resonant cavity can be improved compared with directly using air.

[0064] In an embodiment, the signal-to-noise ratio of the detection signal is calculated, and the driving device 6 is controlled to drive the moving plate 2 to move towards or away from the measured surface 3 based on the signal-to-noise ratio, which comprises the following steps: envelope detection is performed on the detection signal, and an amplitude distribution histogram is generated according to the envelope detection result; the noise amplitude and the maximum signal amplitude are obtained according to the amplitude distribution histogram, and the signal-to-noise ratio is calculated according to the noise amplitude and the maximum signal amplitude, wherein the noise amplitude is the amplitude with the highest frequency in the amplitude distribution histogram, and the maximum signal amplitude is the maximum amplitude in the amplitude distribution histogram; when the signal-to-noise ratio is less than a set threshold, the driving device 6 is controlled to drive the moving plate 2 to move towards or away from the measured surface 3; and when the signal-to-noise ratio is greater than or equal to the set threshold, the moving plate 2 is stopped.

[0065] The narrow-band ultrasonic partial discharge detection method based on the resonant cavity is characterized in that: a resonant cavity is formed by a support part 1, a moving plate 2 and a measured surface 3; a broadband ultrasonic sensor 4 is arranged on the moving plate 2; the detection signal transmitted from the resonant cavity is collected by the broadband ultrasonic sensor 4; the input end of a driving device 6 is connected with a controller 5, and the output end is connected with the moving plate 2; the controller 5 is connected with the broadband ultrasonic sensor 4; the controller 5 is used for receiving the detection signal collected by the broadband ultrasonic sensor 4, calculating the signal-to-noise ratio of the detection signal, and controlling the driving device 6 to drive the moving plate 2 to move towards or away from the measured surface 3 or stop moving based on the signal-to-noise ratio, so as to adjust the resonant frequency, change the frequency band of the ultrasonic wave passing through the resonant cavity, and make the ultrasonic wave of a specific narrow-band frequency be able to pass through the resonant cavity and be detected by the broadband ultrasonic sensor 4, thereby realizing narrow-band detection of the partial discharge ultrasonic wave, improving the detection sensitivity, and simultaneously tuning the narrow-band frequency through the resonant cavity, so as to solve the defect that the detection frequency band cannot be tuned when the narrow-band ultrasonic sensor is directly used.

[0066] The above, the above embodiment is only to illustrate the technical solutions of the present application, rather than limit it; although the present application is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A narrowband ultrasonic partial discharge detection system based on a resonant cavity, characterized in that: include: A controller, a driving device, a broadband ultrasonic sensor, a support part and a moving plate, wherein the support part, the moving plate and the measured surface form a resonant cavity, the broadband ultrasonic sensor is arranged on the moving plate, and the detection signal transmitted from the resonant cavity is collected by the broadband ultrasonic sensor. The input end of the driving device is connected to the controller, and the output end is connected to the moving plate. The controller is connected to the broadband ultrasonic sensor. The controller is used to receive the detection signal collected by the broadband ultrasonic sensor, calculate the signal-to-noise ratio of the detection signal, and control the driving device to drive the moving plate to move toward or away from the measured surface or stop moving based on the signal-to-noise ratio.

2. The resonant cavity-based narrowband ultrasonic partial discharge detection system according to claim 1, characterized in that: The resonant cavity is filled with a viscous flow or elastic acoustic impedance matching filler.

3. The resonant cavity-based narrowband ultrasonic partial discharge detection system according to claim 1, characterized in that: The moving plate is movably connected to the supporting portion, and the moving plate moves along the supporting portion toward or away from the measured surface.

4. The resonant cavity-based narrowband ultrasonic partial discharge detection system according to claim 1, characterized in that: The moving plate is fixedly connected to the supporting portion, and the supporting portion is a retractable structure. The moving plate moves toward or away from the measured surface by causing the supporting portion to retract or retract.

5. The resonant cavity-based narrowband ultrasonic partial discharge detection system according to claim 1, characterized in that: The supporting part includes a first supporting plate and a second supporting plate, which are arranged opposite to each other on both sides of the measured surface. The moving plate is opposite to the measured surface, and the two ends of the moving plate are respectively connected to the first supporting plate and the second supporting plate. The first supporting plate, the second supporting plate, the moving plate and the measured surface form a resonant cavity.

6. The resonant cavity-based narrowband ultrasonic partial discharge detection system according to claim 1, characterized in that: The driving device includes a motor and a screw rod. The motor is connected to the controller. One end of the screw rod is connected to the output shaft of the motor, and the other end of the screw rod is connected to the moving plate through a nut.

7. The resonant cavity-based narrowband ultrasonic partial discharge detection system according to claim 1, characterized in that: The controller includes: a signal processing unit, configured to perform envelope detection on the detection signal and generate an amplitude distribution histogram according to the envelope detection result; a calculation unit, configured to obtain a noise amplitude and a maximum signal amplitude according to the amplitude distribution histogram, and calculate a signal-to-noise ratio according to the noise amplitude and the maximum signal amplitude, wherein the noise amplitude is the amplitude with the highest frequency in the amplitude distribution histogram, and the maximum signal amplitude is the maximum amplitude appearing in the amplitude distribution histogram; A driving control unit is used to control the driving device to drive the moving plate to move toward or away from the measured surface when the signal-to-noise ratio is less than a set threshold, and to stop the movement when the signal-to-noise ratio is greater than or equal to the set threshold.

8. A resonant cavity-based narrowband ultrasonic partial discharge detection method, applied to the resonant cavity-based narrowband ultrasonic partial discharge detection system according to any one of claims 1 to 7, characterized in that: include: Installing a support portion on the measured surface, and installing a moving plate on the support portion, so that the support portion, the moving plate and the measured surface form a resonant cavity; Mounting a broadband ultrasonic sensor on the moving plate to collect a detection signal transmitted from the resonant cavity by the broadband ultrasonic sensor; The controller receives the detection signal collected by the broadband ultrasonic sensor, calculates the signal-to-noise ratio of the detection signal, and controls the driving device based on the signal-to-noise ratio to drive the moving plate to move toward or away from the measured surface or stop moving.

9. The resonant cavity-based narrowband ultrasonic partial discharge detection method according to claim 8, characterized in that: Before the moving plate is mounted on the support portion, the method further comprises: applying a viscous or elastic acoustic impedance matching filler on the measured surface; When the moving plate is mounted on the support portion, the side of the moving plate facing the measured surface is in contact with the acoustic impedance matching filler.

10. The resonant cavity-based narrowband ultrasonic partial discharge detection method according to claim 8, characterized in that: The calculating the signal-to-noise ratio of the detection signal and controlling the driving device to drive the moving plate to move toward or away from the detected surface based on the signal-to-noise ratio includes: Performing envelope detection on the detection signal, and generating an amplitude distribution histogram according to the envelope detection result; Obtaining a noise amplitude and a maximum signal amplitude according to the amplitude distribution histogram, and calculating a signal-to-noise ratio according to the noise amplitude and the maximum signal amplitude, wherein the noise amplitude is the amplitude with the highest frequency in the amplitude distribution histogram, and the maximum signal amplitude is the maximum amplitude in the amplitude distribution histogram; When the signal-to-noise ratio is less than a set threshold, the driving device is controlled to drive the moving plate to move toward or away from the measured surface; when the signal-to-noise ratio is greater than or equal to the set threshold, the movement is stopped.

Images