阅读说明：本技术 一种126kV三相共箱盆式绝缘子界面缺陷检测方法 (126kV three-phase common-box basin-type insulator interface defect detection method ) 是由 杨旭 张长虹 黎卫国 黄忠康 高超 周福升 黄若栋 熊佳明 杨芸 王国利 郑尧 于 2021-09-08 设计创作，主要内容包括：本发明公开了一种126kV三相共箱盆式绝缘子界面缺陷检测方法,利用超声纵波反射检测系统对被测126kV三相共箱盆式绝缘子的中心导体-环氧树脂交界面进行缺陷检测,建立了界面缺陷超声传播模型,以幅值为缺陷表征量,将超声探头沿检测路径扫描,确定界面缺陷深度,利用数据三维重建得到界面缺陷的二维、三维图像,进而确定界面缺陷的大小,可用于盆式绝缘子的出厂检测也可适用于盆式绝缘子的现场装配检测。解决了使用X射线成像法进行盆式绝缘子界面缺陷检测存在的对宽度较小的缺陷灵敏度不高,且设备体积庞大,不便于携带,价格昂贵,X射线对人体存在辐射性危害的技术问题,具有检测成本低、检测精度高、体积小、对人体无X射线辐射危害的优点。(The invention discloses a method for detecting interface defects of a 126kV three-phase common-box basin-type insulator, which comprises the steps of utilizing an ultrasonic longitudinal wave reflection detection system to detect the defects of a central conductor-epoxy resin interface of the 126kV three-phase common-box basin-type insulator to be detected, establishing an interface defect ultrasonic propagation model, scanning an ultrasonic probe along a detection path by taking an amplitude value as a defect characterization quantity, determining the depth of the interface defects, utilizing data three-dimensional reconstruction to obtain two-dimensional and three-dimensional images of the interface defects, further determining the size of the interface defects, and being capable of being used for factory detection of the basin-type insulator and also being suitable for field assembly detection of the basin-type insulator. The technical problems that the defect detection of the basin-type insulator interface by using an X-ray imaging method is low in defect sensitivity to small width, large in equipment size, inconvenient to carry and high in price, and X-rays have radiation damage to a human body are solved, and the method has the advantages of being low in detection cost, high in detection precision, small in size and free of X-ray radiation damage to the human body.)

1. A126 kV three-phase common-box basin-type insulator interface defect detection method is characterized by comprising the following steps:

constructing a basin-type insulator interface defect detection platform based on ultrasonic longitudinal wave reflection detection;

placing an ultrasonic transmitting probe of a basin-type insulator interface defect detection platform on the upper epoxy insulation surface of a 126kV three-phase common-box basin-type insulator to be detected, placing an ultrasonic receiving probe on the lower surface of a basin body of the 126kV three-phase common-box basin-type insulator to be detected, building an ultrasonic propagation model for interface defect detection, and obtaining a calculation formula of an interface defect detection range and an interface defect depth based on an ultrasonic longitudinal wave reflection method detection principle;

scanning detection is carried out on each detection point in the interface defect detection range, whether the 126kV three-phase common-box basin-type insulator to be detected has an interface defect or not is judged according to the amplitude of a reflected wave signal of each detection point, and if yes, the interface defect depth is calculated according to a calculation formula of the interface defect depth;

according to the two-dimensional polar coordinates of each detection point position and the corresponding echo signal amplitude, performing three-dimensional image display of a linear difference function on the interface defect of the central conductor-epoxy resin, and determining the position of the interface defect;

scanning and sampling the interface defect area with a given step length, recording position information of the interface defect area, processing and reading a peak value through a filter, then performing time domain three-dimensional data imaging of the interface defect, and determining the boundary of the interface defect based on a bottom wave attenuation method to obtain the form and the size of the interface defect;

the calculation formula of the interface defect detection range is as follows:the calculation formula of the interface defect depth is as follows:wherein, L is the length of the epoxy insulation arc at the joint of the top of the insert, delta is the angle between the inclination and the horizontal of the pot body, and L₀For initial probe displacement position, L_jAt any position during probe movement, L_kThe probe can detect the surface position of the insulating part corresponding to the defect in the maximum range.

2. The method for detecting the interface defect of the 126kV three-phase common-box basin-type insulator according to claim 1, wherein the platform for detecting the interface defect of the basin-type insulator comprises an ultrasonic flaw detector, an oscilloscope, a PC (personal computer) and the 126kV three-phase common-box basin-type insulator to be detected, wherein the ultrasonic flaw detector is connected with an ultrasonic transmitting probe and an ultrasonic receiving probe through probe connecting wires;

the ultrasonic transmitting probe and the ultrasonic receiving probe adopt ultrasonic longitudinal wave straight probes with the frequency of 2.5MHz and the diameter of the bottom surface of 6 mm.

3. The method for detecting the interface defect of the 126kV three-phase common-box basin-type insulator according to claim 2, wherein the contact surfaces of the ultrasonic transmitting probe and the ultrasonic receiving probe with the 126kV three-phase common-box basin-type insulator to be detected adopt a water-based ultrasonic coupling agent.

4. The method for detecting the interface defect of the 126kV three-phase common-box basin-type insulator according to claim 2, wherein the oscilloscope is a high-input-impedance four-channel high-performance digital storage oscilloscope with the bandwidth of 100MHz, the sampling rate of 2.5GS/s and the recording length of 10M.

5. The method for detecting the interface defect of the 126kV three-phase common-box basin-type insulator according to claim 1, wherein the given step length is 1 mm.

6. The method for detecting the interface defect of the 126kV three-phase common-box basin-type insulator according to claim 1, wherein judging whether the 126kV three-phase common-box basin-type insulator to be detected has the interface defect according to the amplitude of the reflected wave signal of each detection point comprises the following steps:

and judging whether the amplitude of the reflected wave signal of each detection point is smaller than a reference value, if the detection point with the amplitude of the reflected wave signal smaller than the reference value exists, determining that the detected 126kV three-phase common-box basin-type insulator has an interface defect, and if not, determining that the detected 126kV three-phase common-box basin-type insulator does not have an interface defect.

7. The 126kV three-phase common-box basin-type insulator interface defect detection method according to claim 1, wherein scanning detection is performed on each detection point within an interface defect detection range, and the method comprises the following steps:

scanning paths along different directions of a tested 126kV three-phase common box basin-type insulator basin body within an interface defect detection range, and carrying out scanning type detection on detection points on the scanning paths at detection point intervals of 5 mm.

8. The method for detecting the interface defect of the 126kV three-phase common-box basin-type insulator according to claim 1, wherein the step of displaying a three-dimensional image of a linear difference function of the interface defect of the central conductor and the epoxy resin according to the two-dimensional polar coordinates of each detection point and the corresponding echo signal amplitude value to determine the position of the interface defect comprises the following steps of:

projecting the detection points into a two-dimensional polar coordinate system to obtain two-dimensional coordinates of the detection points;

performing noise reduction processing on the echo signal by using a wavelet filtering algorithm based on a wavelet transformation theory, and extracting the amplitude of the echo signal;

and forming a three-dimensional array by the two-dimensional polar coordinates of the positions of the detection points and the amplitude of the echo signal of each detection point, and forming a three-dimensional graph by adopting a linear interpolation function to obtain the position of the interface defect.

9. The 126kV three-phase common-box basin-type insulator interface defect detection method according to claim 1, wherein scanning sampling of a given step length is performed on an interface defect region, position information of the interface defect region is recorded, time domain three-dimensional data imaging of the interface defect is performed after peak values are read through filter processing, the interface defect boundary is determined based on a bottom wave attenuation method, the form and the size of the interface defect are obtained, and then:

and projecting the bottom surface of the three-dimensional image imaged by the time domain three-dimensional data into a two-dimensional image of the interface defect area to obtain the two-dimensional interface defect form and size.

Technical Field

The invention relates to the technical field of basin-type insulator interface defect detection, in particular to a 126kV three-phase common-box basin-type insulator interface defect detection method.

Background

The basin-type insulator is a key part of a gas insulated metal-enclosed switchgear (GIS), is composed of a metal insert, an epoxy insulator and a metal flange, plays roles of electrically insulating, isolating a gas chamber and supporting a conductor, and is the weakest insulating link in the gas insulated metal-enclosed switchgear. The fault caused by the basin-type insulator accounts for a considerable proportion of the insulation fault of the gas insulated metal-enclosed switchgear, wherein the interface defect generated at the interface of the basin-type insulator central conductor and the epoxy insulation material is mainly caused by human error or mechanical movement of the gas insulated metal-enclosed switchgear central conductor and the like in the assembling process, the central conductor-epoxy insulation interface is an area with concentrated electric, thermal and force ratios, the structure is complex, the interface has prominent effect, the interface defect is easy to occur, the partial discharge and the insulation damage of the basin-type insulator are caused, and the normal operation of the gas insulated metal-enclosed switchgear is directly threatened. Therefore, the detection of whether the defect exists at the interface between the basin-type insulator central conductor and the epoxy resin is of great significance for guaranteeing the safe operation of the power system.

The existing methods applied to the detection of the interface defects of the basin-type insulator include an electrical detection method and a non-electrical detection method. The electrical detection method is mainly used for judging the type of a fault defect by detecting an electromagnetic physical signal generated along with partial discharge aiming at the partial discharge phenomenon caused by the defect, but the strength of the detection signal is related to the amount of the partial discharge and is easily interfered by other signals. The non-electric detection method detects the GIS equipment with a non-running object, wherein an X-ray imaging method is mature in technology and high in detection efficiency, but has low sensitivity to defects with small width, the equipment is large in size, inconvenient to carry and high in price, and X-rays have radiation hazard to a human body. Therefore, the invention provides a 126kV three-phase common-box basin-type insulator interface defect detection method which is used for solving the problem of basin-type insulator interface defect detection by an X-ray imaging method.

Disclosure of Invention

The invention provides a 126kV three-phase common-box basin-type insulator interface defect detection method, which is used for solving the technical problems of low sensitivity to defects with small width, large equipment size, inconvenience in carrying and high price in the process of basin-type insulator interface defect detection by using an X-ray imaging method, and radiation damage of X-rays to a human body.

In view of the above, the invention provides a 126kV three-phase common-box basin-type insulator interface defect detection method, which includes:

constructing a basin-type insulator interface defect detection platform based on ultrasonic longitudinal wave reflection detection;

placing an ultrasonic transmitting probe of a basin-type insulator interface defect detection platform on the upper epoxy insulation surface of a 126kV three-phase common-box basin-type insulator to be detected, placing an ultrasonic receiving probe on the lower surface of a basin body of the 126kV three-phase common-box basin-type insulator to be detected, building an ultrasonic propagation model for interface defect detection, and obtaining a calculation formula of an interface defect detection range and an interface defect depth based on an ultrasonic longitudinal wave reflection method detection principle;

scanning detection is carried out on each detection point in the interface defect detection range, whether the 126kV three-phase common-box basin-type insulator to be detected has an interface defect or not is judged according to the amplitude of a reflected wave signal of each detection point, and if yes, the interface defect depth is calculated according to a calculation formula of the interface defect depth;

according to the two-dimensional polar coordinates of each detection point position and the corresponding echo signal amplitude, performing three-dimensional image display of a linear difference function on the interface defect of the central conductor-epoxy resin, and determining the position of the interface defect;

scanning and sampling the interface defect area with a given step length, recording position information of the interface defect area, processing and reading a peak value through a filter, then performing time domain three-dimensional data imaging of the interface defect, and determining the boundary of the interface defect based on a bottom wave attenuation method to obtain the form and the size of the interface defect;

the calculation formula of the interface defect detection range is as follows:the calculation formula of the interface defect depth is as follows:wherein, L is the length of the epoxy insulation arc at the joint of the top of the insert, delta is the angle between the inclination and the horizontal of the pot body, and L₀For initial probe displacement position, L_jAt any position during probe movement, L_kThe probe can detect the surface position of the insulating part corresponding to the defect in the maximum range.

Optionally, the basin-type insulator interface defect detection platform comprises an ultrasonic flaw detector, an oscilloscope, a PC and a 126kV three-phase common-box basin-type insulator to be detected, wherein the ultrasonic flaw detector is connected with an ultrasonic transmitting probe and an ultrasonic receiving probe through probe connecting wires;

the ultrasonic transmitting probe and the ultrasonic receiving probe adopt ultrasonic longitudinal wave straight probes with the frequency of 2.5MHz and the diameter of the bottom surface of 6 mm.

Optionally, the contact surfaces of the ultrasonic transmitting probe and the ultrasonic receiving probe and the 126kV three-phase common-box basin-type insulator to be tested adopt a water-based ultrasonic coupling agent.

Optionally, the oscilloscope is a high-input-impedance four-channel high-performance digital storage oscilloscope with a bandwidth of 100MHz, a sampling rate of 2.5GS/s and a recording length of 10M.

Alternatively, the step size is given as 1 mm.

Optionally, judging whether the 126kV three-phase common-box basin-type insulator to be tested has an interface defect according to the amplitude of the reflected wave signal at each detection point, including:

and judging whether the amplitude of the reflected wave signal of each detection point is smaller than a reference value, if the detection point with the amplitude of the reflected wave signal smaller than the reference value exists, determining that the detected 126kV three-phase common-box basin-type insulator has an interface defect, and if not, determining that the detected 126kV three-phase common-box basin-type insulator does not have an interface defect.

Optionally, the scanning detection of each detection point in the interface defect detection range includes:

scanning paths along different directions of a tested 126kV three-phase common box basin-type insulator basin body within an interface defect detection range, and carrying out scanning type detection on detection points on the scanning paths at detection point intervals of 5 mm.

Optionally, the three-dimensional image display of the linear difference function is performed on the interface defect of the central conductor and the epoxy resin according to the two-dimensional polar coordinates of each detection point position and the corresponding echo signal amplitude, and the determining of the position of the interface defect includes:

projecting the detection points into a two-dimensional polar coordinate system to obtain two-dimensional coordinates of the detection points;

performing noise reduction processing on the echo signal by using a wavelet filtering algorithm based on a wavelet transformation theory, and extracting the amplitude of the echo signal;

and forming a three-dimensional array by the two-dimensional polar coordinates of the positions of the detection points and the amplitude of the echo signal of each detection point, and forming a three-dimensional graph by adopting a linear interpolation function to obtain the position of the interface defect.

Optionally, scanning and sampling the interface defect region with a given step length, recording position information of the interface defect region, performing time domain three-dimensional data imaging of the interface defect after processing and reading a peak value by a filter, determining an interface defect boundary based on a bottom wave attenuation method, and obtaining a form and a size of the interface defect, and then:

and projecting the bottom surface of the three-dimensional image imaged by the time domain three-dimensional data into a two-dimensional image of the interface defect area to obtain the two-dimensional interface defect form and size.

According to the technical scheme, the embodiment of the invention has the following advantages:

the invention provides a method for detecting interface defects of a 126kV three-phase common-box basin-type insulator, which is characterized in that an ultrasonic longitudinal wave reflection detection system is utilized to detect the defects of a central conductor-epoxy resin interface of the 126kV three-phase common-box basin-type insulator to be detected, an interface defect ultrasonic propagation model is established, an ultrasonic probe is scanned along a detection path by taking an amplitude value as a defect characterization quantity, the depth of the interface defects is determined, a two-dimensional image and a three-dimensional image of the interface defects are obtained by utilizing data three-dimensional reconstruction, and then the size of the interface defects is determined. The 126kV three-phase common-box basin-type insulator interface defect detection method provided by the invention solves the technical problems of low sensitivity to a defect with a small width, large equipment size, inconvenience in carrying and high price in the basin-type insulator interface defect detection by using an X-ray imaging method, and the technical problems of radioactive damage of X-rays to a human body, and has the advantages of low detection cost, high detection precision, small size and no X-ray radiation damage to the human body.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other related drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic flow chart of a 126kV three-phase common-box basin-type insulator interface defect detection method provided in an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a basin-type insulator interface defect detection platform based on ultrasonic longitudinal wave reflection detection and built in the embodiment of the invention;

fig. 3 is a schematic structural diagram of an ultrasound transmitting probe and an ultrasound receiving probe provided in an embodiment of the present invention;

FIG. 4 is a schematic diagram of an ultrasonic propagation model for interface defect detection constructed in an embodiment of the present invention;

FIG. 5 is a comparison of a defect-free interface inspection schematic and a defective interface inspection schematic provided in an embodiment of the present invention;

fig. 6 is a schematic diagram of a 126kV three-phase common-box basin-type insulator interface ultrasonic detection point position provided in the embodiment of the present invention;

FIG. 7 is a schematic view of the polar coordinates of the detection points of the interface corresponding to FIG. 6;

FIG. 8 is a schematic diagram of an interface detection echo of a 126kV three-phase common-box basin-type insulator without interface defects, provided in an embodiment of the present invention;

FIG. 9 is a schematic diagram of an echo detected by a 126kV three-phase common-box basin-type insulator interface with interface defects according to an embodiment of the present invention;

fig. 10 is a time domain three-dimensional imaging diagram for 126kV three-phase common-box basin-type insulator interface detection provided in the embodiment of the present invention;

fig. 11 is a schematic diagram of a position of a detection point for scanning and sampling a probe moving by a step length of 1mm in a defective region of a 126kV three-phase common-box basin-type insulator provided in the embodiment of the present invention;

fig. 12 is a three-dimensional time domain imaging diagram of a defective region of a 126kV three-phase common-box basin-type insulator provided in the embodiment of the present invention;

fig. 13 is a two-dimensional image map projected onto the bottom surface of the three-dimensional time domain image map of fig. 12.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

For easy understanding, please refer to fig. 1, an embodiment of a method for detecting an interface defect of a 126kV three-phase common-box basin-type insulator in the present invention includes:

step 101, a basin-type insulator interface defect detection platform based on ultrasonic longitudinal wave reflection detection is built.

As shown in fig. 2, the ultrasonic testing object in the embodiment of the present invention is a 126kV three-phase common-box basin insulator 7, which is composed of a metal insert 71 (central conductor), an epoxy insulator 72 and a metal flange 73, an interface defect generated at an interface between the central conductor and the epoxy insulator is mainly caused by human error in an assembling process or mechanical movement of the GIS central conductor, and the interface between the central conductor and the epoxy insulator is an area where electric, thermal and force are concentrated, and has a complex structure, an outstanding interface effect, and an interface defect is easy to occur, and the size of the basin insulator changes with the change of the GIS voltage level.

The basin-type insulator interface defect detection platform based on ultrasonic longitudinal wave reflection detection is constructed as shown in fig. 2 and comprises an ultrasonic flaw detector, an oscilloscope, a PC (personal computer) and a 126kV three-phase common-box basin-type insulator to be detected, wherein the ultrasonic flaw detector is connected with an ultrasonic transmitting probe and an ultrasonic receiving probe through probe connecting wires, the two probes are connected with the ultrasonic flaw detector through the probe connecting wires, and a signal synchronization end of the ultrasonic flaw detector is connected with the oscilloscope through a high-impedance transmission line. In one embodiment. In order to enhance the contact effect, the contact surface of the probe and the sample is coupled by using a water-based ultrasonic coupling agent.

The probe connecting wire is a signal wire matched with the ultrasonic flaw detector and the ultrasonic probe, has the characteristics of high impedance, strong anti-interference capability and the like, ensures that an output electric signal of the ultrasonic flaw detector can be received by the ultrasonic probe in high quality, and ensures that an electric signal converted from an ultrasonic signal received by the ultrasonic probe can be returned to a receiving end of the ultrasonic pulse generator in high quality.

The high-impedance transmission line is a transmission line with small stray inductance and resistance, phase delay of high-frequency signals in the transmission process is shortened, real-time identical potential and same phase of electric signals received by the oscilloscope and electric signals at the signal output end of the ultrasonic pulse generator are guaranteed, detection errors are greatly reduced, and detection precision is guaranteed.

The ultrasonic flaw detector is an ultrasonic transmitting and receiving device with adjustable negative square wave excitation, square wave amplitude and width, low noise response and adjustable gain, can adjust broadband response and detect near-surface resolution, and can be used for detecting and measuring the defects of materials with strong sound velocity attenuation.

The structure of the ultrasonic transmitting probe and the ultrasonic receiving probe is shown in fig. 3, a circular composite material piezoelectric wafer 11 is adopted, the bottom surface of the probe is circular, the diameter of the probe is D, the diameter D of the bottom surface of the probe is considered to be an arc surface, in order to increase the contact effect of the probe and the measured position of an insulator and improve the detection precision, the smaller the diameter D of the bottom surface of the probe is, the better the diameter D of the bottom surface of the probe is, but the smaller the bottom surface of the probe is required to be, the circular composite material piezoelectric wafer is very small, and the energy of ultrasonic waves emitted by the probe is also very small. The higher the frequency of the ultrasonic probe is, the larger the attenuation coefficient of the detected material is, the poorer the sound beam propagation characteristic effect is, the detection characteristic, the detection efficiency and the manufacturing cost are comprehensively considered, and in one embodiment, the diameter D of the bottom surface of the ultrasonic probe is 6mm, and the frequency is 2.5 MHz.

102, placing an ultrasonic transmitting probe of a basin-type insulator interface defect detection platform on the upper epoxy insulation surface of a 126kV three-phase common-box basin-type insulator to be detected, placing an ultrasonic receiving probe on the lower surface of a basin body of the 126kV three-phase common-box basin-type insulator to be detected, building an ultrasonic propagation model for interface defect detection, and obtaining a calculation formula of an interface defect detection range and an interface defect depth based on an ultrasonic longitudinal wave reflection method detection principle.

An ultrasonic propagation model for detecting the interface defects built in the embodiment of the invention is shown in fig. 4, an ultrasonic emission probe is arranged on the upper surface of an epoxy insulation, ultrasonic waves are incident in a way of being vertical to the epoxy insulation and reach the interface between the epoxy insulation and a central conductor insert, a part of the ultrasonic waves are reflected on the interface according to Snell's law, and reflected waves are received by a probe arranged on the lower surface of a pot body. When a defect interface is detected, the lengths of ultrasonic propagation paths of all detection positions on the inclined plane are equal due to the symmetrical geometric structure of the three-phase box-shared basin-type insulator. As shown in FIG. 4, M is the extension line of the outer side of the metal insert (extension line of line NO) and line L_k L₀The intersection of the extension lines for the purpose of constructing the MNL_jCalculating the defect position in a triangular mode; p is that the probe is placed at L₀When the probe is positioned at the uppermost edge detection position, the ultrasonic waves emitted are incident to the position on the metal insert interface, namely the uppermost edge detection position of the corresponding insert interface when the probe is positioned at the uppermost edge detection position; o is the uppermost point position of the junction of the metal insert and the epoxy insulation; q is the probe placed at L_kWhen the probe is positioned at the lowest edge detection position, the ultrasonic waves emitted are incident to the position on the metal insert interface, namely the lowest edge detection position of the corresponding insert interface when the probe is positioned at the lowest edge detection position; the probe head is moved from a starting position L in the detection direction₀Move to L_iIn this range, a defect-free ultrasonic receiving wave (denoted as B in FIG. 5) is set₁F in fig. 5 indicates that the probe emits a wave) is less attenuated; the probe head is driven by L_iMove to L_jIn the process, the interface in the range is set to have defects, the ultrasonic waves are reflected at the defect and the epoxy interface, the energy attenuation is large, and the ultrasonic receiving waves (marked as B in figure 5)₂) Amplitude compared to received wave B without defect₁Is small. Under the detection path, the depth H of the defect can be according to the triangular MNL_jThe trigonometric function relationship of each side yields:

the interface defect depth is:

wherein L is the length of the epoxy insulation arc at the joint of the top of the insert, L can take the value of 7mm, delta is the angle of the basin body inclined to the horizontal, delta can take the value of 45 degrees, and L₀For initial probe displacement position, L₀Can be 0mm, L_jAt any position during probe movement, L_kThe probe can detect the surface position of the insulating part corresponding to the defect in the maximum range.

It should be noted that the above calculation formula is suitable for the situation that the basin body is inclined at a horizontal angle δ of not more than 45 °, and in practical application, the inclination of the basin body of the three-phase common-box basin-type insulator is 35 °, so that the above calculation formula can be suitable for the common 126kV three-phase common-box basin-type insulator. When the basin body is applied to a special scene, and the horizontal angle delta is larger than 45 degrees, the calculation formula can be additionally deduced according to the ultrasonic reflection principle and the geometric relation, and the method is the same and is not repeated.

And 103, performing scanning type detection on each detection point within the interface defect detection range, judging whether the 126kV three-phase common-box basin-type insulator to be detected has an interface defect according to the amplitude of the reflected wave signal of each detection point, and if so, calculating the depth of the interface defect according to a calculation formula of the depth of the interface defect.

Scanning paths of the probe in different directions are arranged along the pot body, the interval between detection points in the detection direction is set to be 5mm in consideration of the size constraint of the probe, and as shown in figure 6, a straight line in figure 6 is a scanning path of the probe. And (3) carrying out scanning type detection on each detection point along the detection path, recording the position of each detection point, projecting the detection points into a two-dimensional polar coordinate system, acquiring two-dimensional coordinates (shown in figure 7) of the detection points, and acquiring the amplitude of the reflected wave signal of each detection point through an ultrasonic receiving probe. The 126kV three-phase common-box basin-type insulator is provided with three central conductors (namely three metal inserts 71 in figure 2), so that three interfaces of the central conductors and epoxy insulation are provided, and in the embodiment of the invention, a defective interface is set to be a No. 2 interface, and a non-defective interface is set to be a No. 1 interface and a No. 3 interface. The method is used for detecting the defect-free interface of the three-phase common-box basin-type insulator, and the original detection echo signals at four positions with polar angles of 0 degree (360 degrees), 270 degrees, 180 degrees and 90 degrees (A, B, C, D) in FIG. 7 are selected for analysis because the amplitude and the phase of the echo signals at all positions of the interface are basically the same.

Fig. 8 is a detected echo of a defect-free central conductor insert of the three-phase common-box basin-type insulator and an epoxy insulation interface, amplitude and phase of echo signals at four positions in fig. 8 are consistent, attenuation of transmitted waveform and received echo amplitude is small, loss of sound wave energy is small, and it is indicated that the interfaces of the three-phase common-box basin-type insulator inserts 2 and 3 are defect-free, and epoxy materials in all directions of the basin-type insulator are uniformly mixed.

FIG. 9 is a detected echo of the interface between the center conductor insert and the epoxy insulation of the three-phase common-box basin-type insulator with defects. The checkpoint echo amplitude at D is significantly smaller compared to the checkpoint amplitude without defects. The propagation attenuation amplitude of the ultrasonic waves in the epoxy composite insulation is about 10% -14%. A. B, C, the amplitudes, phases and time domain widths of the ultrasonic echoes at the three positions are consistent, the amplitude of the echo at the position D of the defective interface is about 50% of the amplitude of the echo at the position D of the inserts 2 and 3, the defect of the interface at the position D of the insert 1 is judged according to the echo amplitudes, and the interface defect depth is calculated according to the calculation formula of the interface defect depth in the step 102.

And 104, displaying a three-dimensional image of a linear difference function of the interface defect of the central conductor and the epoxy resin according to the two-dimensional polar coordinates of each detection point position and the corresponding echo signal amplitude value, and determining the position of the interface defect.

In order to enable defect detection data to be displayed more visually, in the embodiment of the invention, the detection data is subjected to three-dimensional processing, a wavelet filtering algorithm based on a wavelet transform theory is adopted to perform noise reduction processing on echo signals, the amplitude of the echo signals is extracted, a three-dimensional array is formed by two-dimensional polar coordinates of the positions of the detection points and the amplitude of the echo signals of each detection point, a three-dimensional graph is formed based on a linear interpolation function, and three-dimensional display of the detection amplitude and the position data of the basin-type insulator interface is realized, as shown in figure 10, the amplitude of secondary echoes at the interface defect position and the peripheral area is smaller, and as shown in figure 10, an obvious recess is a defect area. And (4) corresponding the calculated data to the detection position of the actual insulating part, and determining that the defect is positioned at the interface with the polar angle of 90 degrees, namely D in figure 7.

And 105, scanning and sampling the interface defect area with a given step length, recording position information of the interface defect area, processing and reading a peak value through a filter, then performing time domain three-dimensional data imaging on the interface defect, and determining the boundary of the interface defect based on a bottom wave attenuation method to obtain the form and the size of the interface defect.

After determining the defect position by the interface detection data, moving the probe by 1mm step length in the defect area for scanning and sampling, as shown in fig. 11, and recording the position information of the sampling point, processing the echo signal by a filter and reading the amplitude. And (3) performing time domain three-dimensional data imaging on the defect by taking the defect center as the original point of a Cartesian coordinate system, the X axis as the defect width, the Y axis as the defect length and the Z axis as the amplitude of the detected echo signal, and determining the defect boundary based on the principle of a bottom wave attenuation method (6 dB-drop).

According to the established rectangular coordinate system, the echo signals are subjected to noise reduction processing and then amplitude values are read, the defect boundary is determined by utilizing the principle of a bottom wave attenuation method, and a three-dimensional image of the defect position and the amplitude values is established, as shown in fig. 12. In order to determine the length and width of the defect, the defect size was directly observed by projecting the bottom surface of the three-dimensional image to obtain a two-dimensional map of the defect area, as shown in fig. 12, and the actual interface size was measured to be 4mm × 6mm in fig. 13.

The 126kV three-phase common-box basin-type insulator interface defect detection method provided by the embodiment of the invention utilizes an ultrasonic longitudinal wave reflection detection system to detect the defect of the center conductor-epoxy resin interface of the 126kV three-phase common-box basin-type insulator to be detected, establishes an interface defect ultrasonic propagation model, scans an ultrasonic probe along a detection path by taking the amplitude as a defect characterization quantity, determines the depth of the interface defect, obtains two-dimensional and three-dimensional images of the interface defect by utilizing three-dimensional reconstruction of data, further determines the size of the interface defect, can be used for factory detection of the basin-type insulator and can also be suitable for field assembly detection of the basin-type insulator. The 126kV three-phase common-box basin-type insulator interface defect detection method provided by the invention solves the technical problems of low sensitivity to a defect with a small width, large equipment size, inconvenience in carrying and high price in the basin-type insulator interface defect detection by using an X-ray imaging method, and the technical problems of radioactive damage of X-rays to a human body, and has the advantages of low detection cost, high detection precision, small size and no X-ray radiation damage to the human body.

The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.