CN110320274B - Three-post insulator internal defect reconstruction method based on ultrasonic scanning principle - Google Patents
Three-post insulator internal defect reconstruction method based on ultrasonic scanning principle Download PDFInfo
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Abstract
The invention discloses a three-post insulator internal defect reconstruction method based on an ultrasonic scanning principle, which comprises the following steps of: s1, building an ultrasonic detection system; s2, detecting the similar positions of the three-post insulator by an ultrasonic detection system, and recording ultrasonic reflection echo information of each detection position; s3, judging the ultrasonic reflection echo information of each detection position by using a similarity method, and determining the defect position; s4, the ultrasonic detection system carries out ultrasonic scanning near the defect position and records the ultrasonic reflection echo information of each detection position; s5, constructing the corresponding relation between the ultrasonic reflection echo information and the defect depth and the defect size, and obtaining a defect reconstruction schematic diagram based on the detection result of each scanning position. The method can efficiently, accurately and intuitively identify, position and quantify the internal defects of the three-post insulator.
Description
Technical Field
The invention relates to the field of power transmission and transformation insulating equipment, in particular to a method for reconstructing internal defects of a three-post insulator based on an ultrasonic scanning principle.
Background
The three-post insulator is a key electrical component in a gas insulated metal enclosed transmission line (GIL) and plays a role in electrical insulation and mechanical support. The three-pillar insulator is formed by mixing epoxy resin, curing agent (generally acid anhydride) and filler (alumina powder) and placing the mixture into a mold with an aluminum alloy insert for high-temperature curing, if the quality control in the curing process is not good, the defects of unshelling, interlayer, untight combination and the like (the defects are collectively called internal defects) can appear in the intersection of the epoxy material and the aluminum alloy of the three-pillar insulator, and particularly the combination part of the solid epoxy material at the column foot mold closing gap of the three-pillar insulator and the grounding insert. In the practical application process, the internal defects can cause the electric field inside the insulator to be unevenly distributed, so that the phenomena of partial discharge of the insulator, abnormal heating of the insulator and the like are caused, the aging of the insulator is accelerated, the performance of the insulator is reduced, and the normal operation of the GIL is directly threatened. Therefore, whether the three-post insulator has internal defects or not is confirmed as soon as possible, and the method has important significance for guaranteeing the safe operation of the power system.
At present, three-post insulator defect detection is generally carried out in a factory test stage by two detection methods: one method is a direct method, namely an industrial digital X-ray imaging technology is adopted, and whether the defects such as air gaps, cracks, interlayers and the like exist in the insulator or not is judged by comparing the brightness degree of X-ray penetrating waves on a display panel, so that the direct method has the advantages of visualization of the defects and higher detection efficiency, but the detection sensitivity of the direct method on the cracks with smaller width is not high, the radiation of X-rays is harmful to a human body, and an X-ray imaging machine is expensive and large in size and cannot detect the insulator in the assembling and overhauling processes; the other method is an indirect method, namely a power frequency partial discharge detection method is adopted, and comprises a pulse current method, a ultrahigh frequency method, an acoustic detection method, an optical detection method, a chemical detection method and the like, the state of the insulator is evaluated according to the size of partial discharge, the pulse current method is widely applied in practice, but the defect position and the defect shape of the insulator are difficult to accurately identify.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a three-post insulator internal defect reconstruction method based on an ultrasonic scanning principle. The invention has the advantages of low detection cost, high detection precision, convenient carrying and no radiation hazard to human bodies, and can efficiently, accurately and visually identify, position and quantify the internal defects of the GIL three-post insulator.
The purpose of the invention can be realized by the following technical scheme:
a three-post insulator internal defect reconstruction method based on an ultrasonic scanning principle comprises the following steps:
s1, building an ultrasonic detection system;
s2, detecting the similar positions of the three-post insulator by adopting an ultrasonic detection system, and recording ultrasonic reflection echo information of each detection position;
s3, judging the ultrasonic reflection echo information of each detection position by using a similarity method, and determining the defect position;
s4, performing ultrasonic scanning near the defect position by adopting an ultrasonic detection system, and recording ultrasonic reflection echo information of each detection position;
s5, constructing the corresponding relation between the ultrasonic reflection echo information and the defect shape and defect size, and obtaining a defect reconstruction schematic diagram based on the detection result of each scanning position, thereby quantifying the defect size and identifying the defect shape.
Specifically, in step S1, the ultrasonic detection system includes an ultrasonic pulse generator, an oscilloscope, a narrow pulse ultrasonic straight probe, a probe adaptation line, and a high impedance transmission line.
The ultrasonic pulse generator is a low-noise pulse generator with sharp pulse excitation, adjustable output pulse width and gain, and can optimize broadband response and improve the near-surface detection resolution, thereby being more beneficial to the detection and measurement application of materials with strong sound beam attenuation.
The oscilloscope is a four-channel high-performance digital storage oscilloscope with the maximum sampling frequency of 1GHz and the sampling bandwidth of 200MHz, and the input channel of the oscilloscope and the signal output end of the ultrasonic pulse generator are connected with the electric potential through a high-impedance transmission line, so that the transmitted and received ultrasonic signals can be displayed on the oscilloscope in real time.
The narrow pulse ultrasonic straight probe belongs to a cylindrical longitudinal wave straight probe, and adopts a circular composite material piezoelectric wafer, the bottom surface of the probe is circular, the circular composite material piezoelectric wafer is considered to be of a cylindrical structure, the surface of an insulator is an arc surface, the radius of the bottom surface of the probe is smaller, the detection precision is improved, the smaller the radius of the bottom surface of the probe is, the better the radius is, but the smaller the bottom surface of the probe requires the circular composite material piezoelectric wafer to be very small, the energy of ultrasonic waves emitted by the probe is also very small, the detection characteristic, the detection efficiency and the manufacturing cost are comprehensively considered, the design range of the diameter (D) of the bottom surface of the probe is 5-10mm, and the design range of the height.
Further, the narrow pulse ultrasonic straight probe is a pulse ultrasonic straight probe with good response characteristics, the higher the nominal frequency of the narrow pulse ultrasonic straight probe is, the larger the attenuation coefficient in the detected material is, the poorer the sound beam propagation characteristic effect is, and the frequency design of the narrow pulse ultrasonic straight probe is not more than 5MHz by combining with the practical measurement experience.
The probe adaptive line is a signal line matching the ultrasonic pulse generator and the narrow pulse ultrasonic straight probe, has the characteristics of high impedance, strong anti-interference capability and the like, ensures that an output electric signal of the ultrasonic pulse generator can be received by the narrow pulse ultrasonic straight probe in high quality, and simultaneously ensures that the ultrasonic signal received by the narrow pulse ultrasonic straight probe is converted into an electric signal which is 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 detection object is a three-post insulator and consists of a solid epoxy part, a central conductor and a grounding insert, wherein the solid epoxy part comprises three columns, and the column foot of each column is combined with one grounding insert; in engineering, the joint of the grounding insert and the bottom (column foot) of the column body is easy to have internal defects such as air gaps, shelling and the like; the central conductor is of a cylindrical structure made of aluminum, and the size of the three-post insulator changes along with the change of the GIL voltage level.
The ultrasonic detection system building method comprises the following steps: the narrow pulse ultrasonic straight probe is connected with the signal output end of the ultrasonic pulse generator through a probe adaptive line, and the signal synchronization end of the ultrasonic pulse generator is connected with an oscilloscope through a high-impedance transmission line.
The same-type position refers to the position of the detection position where the material type, the size and the like are completely consistent, such as any position on the circumference of the three-post insulator cylinder with the same radius.
Specifically, in step S2, the method for detecting the similar position of the three-post insulator by the ultrasonic detection system includes: and adjusting an ultrasonic pulse generator, placing a narrow pulse ultrasonic straight probe coated with a water-based ultrasonic coupling agent on the same type of position of the three-pillar insulator for detection, and recording ultrasonic reflection echo information at each same type of position. The water-based ultrasonic couplant increases the contact effect of the probe and the surface to be detected.
Specifically, in step S3, the defect position of the three-post insulator is determined by the analogy method: under the condition of no defect, all ultrasonic reflection echo waveform information (peak value, phase and the like) obtained from the same type of detection positions are consistent, and when the waveform information of the same type of detection positions is different, the defect exists below the detection positions with different ultrasonic reflection echoes. During the inspection, the influence of dimensional tolerance and surface roughness is neglected.
Specifically, in step S4, the ultrasonic inspection system ultrasonic scanning method near the defect position: and detecting the narrow pulse ultrasonic straight probe according to the ultrasonic scanning path and position, and recording ultrasonic reflection echo information of each scanning position. The ultrasonic scanning paths and positions are scanning point sets which are near the defect and cover the whole defect in area, the detection positions are determined by setting different step lengths on each scanning path, and all the detection positions are listed to be a scanning lattice set of the whole defect. The number of ultrasonic scanning paths and the number of positions are set according to specific conditions.
Specifically, in step S5, a method for constructing a correspondence relationship between the ultrasonic reflection echo information and the defect shape and the defect size is as follows: according to the principle of an ultrasonic pulse reflection method, the peak value of an ultrasonic initial wave corresponds to time t0, when a defect-free object is detected, a bottom echo B appears on an oscilloscope, the peak value corresponds to time t1, the depth of a detection surface to the bottom surface is H, when a defect object is detected, a defect echo F appears between the initial wave and the bottom surface, the peak value corresponds to time t2, the depth of the detection surface to the bottom surface is d, namely t0 is less than t2 and less than t1, the sound velocities are the same in the same medium, and the relation between d and H can be expressed as
Assume that 2n +1 scanning position coordinates on any one scanning path m in step S3 are L(m,-n)、L(m,-n+1)…L(m,0)…L(m,n-1)、L(m,n)Substituting the ultrasonic detection echo information of the position into the formula (1) to obtain the depth d of the position(m,-n)、d(m,-n+1)…d(m,0)…d(m,n-1)、d(m,n)Then these depth values are all divided by
(d(m,-n)、d(m,n)The position is a defect-free position, the position and the position are theoretically equal, and the average value of the position and the position is taken for eliminating measurement deviation), so that all detection position results on the scanning path m are normalized, and the normalized result is subjected to cubic spline interpolation to obtain a curve for representing the defect length and the defect depth on the scanning path m; similarly, other scanning paths are processed according to the method, and curves of all the scanning paths representing lengths and defect depths can be obtained; and obtaining a reconstruction schematic diagram of the internal defects of the three-post insulator by fitting the curves according to a least square surface fitting method.
Compared with the prior art, the invention has the following beneficial effects:
1. the method comprises the steps of utilizing an ultrasonic detection system to detect the three-post insulator, firstly determining the general position of a defect by comparing ultrasonic reflection echo information of the same detection position, then carrying out scanning detection near the defect according to a variable step scanning method, recording the ultrasonic reflection echo information of different detection positions under each scanning path, constructing the corresponding relation between the ultrasonic reflection echo information and the shape and size of the defect, and finally identifying the shape and the size of the defect according to the corresponding relation. The invention has the advantages of low detection cost, high detection precision, convenient carrying, no radiation to human body and the like, and can efficiently, accurately and intuitively identify, position and quantify the internal defects of the three-post insulator.
Drawings
Fig. 1 is a schematic diagram of a system for detecting internal defects of a three-post insulator based on an ultrasonic scanning principle in this embodiment;
fig. 2 is a schematic structural diagram of a narrow pulse ultrasonic straight probe in the embodiment: wherein, a) is a front view of the narrow pulse ultrasonic straight probe, b) is a bottom schematic view of the narrow pulse ultrasonic straight probe;
FIG. 3 is a schematic diagram of three similar positions of the three-post insulator in this embodiment;
fig. 4 is a schematic diagram illustrating operation steps of a method for reconstructing internal defects of a three-post insulator based on an ultrasonic scanning principle according to the present embodiment;
fig. 5 is a schematic diagram illustrating a position of a three-post insulator pedestal detected by the ultrasonic detection system in this embodiment; wherein, a) is a sectional view of a detection process of the column base I, b) is a top view of the detection process of the column base I, c) is a sectional view of a detection process of the column base II, and d) is a top view of the detection process of the column base II;
FIG. 6 is a waveform of ultrasonic testing of the position of the three post insulator stub in the present embodiment; wherein, a) is a detection result graph of four positions of a column base I, and b) is a detection result graph of four positions of a column base II;
FIG. 7 is a schematic diagram of an ultrasonic scanning lattice set in this embodiment;
FIG. 8 is a schematic diagram illustrating reconstruction of an internal defect of a three-post insulator according to the present embodiment; wherein, a) is a defect characterization curve on each scanning path, and b) is a schematic diagram for reconstructing internal defects of the three-post insulator.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited thereto.
Examples
As shown in fig. 1, the ultrasonic detection system includes an ultrasonic pulse generator 1, an oscilloscope 2, a narrow pulse ultrasonic straight probe 3, a probe adapting line 4 and a high impedance transmission line 5, and the system detection object is a three-post insulator 6.
The three post insulator 6 is comprised of a solid epoxy 61, a center conductor 62 and a ground insert 63. The solid epoxy piece comprises three columns, each column is combined with one grounding insert, and the joint of the grounding insert and a column base is easy to have defects such as air gaps and unshelling. The central conductor is of an aluminum annular structure. The size of the three post insulator varies with the GIL voltage level.
Fig. 2 is a schematic structural diagram of a narrow pulse ultrasonic straight probe. The narrow pulse ultrasonic straight probe adopts a circular composite material piezoelectric wafer, the bottom surface 32 of the probe is circular, considering that a three-pillar insulator is of a cylindrical structure, the surface of the insulator is an arc surface, in order to increase the contact effect of the probe and the measured position of the insulator and improve the detection precision, the smaller the diameter D of the bottom surface of the probe is, the better the diameter D is, but the smaller the bottom surface of the probe requires the circular composite material piezoelectric wafer to be very small, the ultrasonic energy emitted by the probe is also very small, the detection characteristic, the detection efficiency and the manufacturing cost are comprehensively considered, the diameter D of the bottom surface of the probe in the embodiment is 6mm, and.
The higher the frequency of the narrow pulse ultrasonic straight probe is, the larger the attenuation coefficient of the detected material is, and the poorer the sound beam propagation characteristic effect is, and in combination with actual measurement experience, the frequency of the narrow pulse ultrasonic straight probe in the embodiment is set to be 5 MHz.
As shown in fig. 3, the schematic diagram of the similar positions of the three-post insulators indicates that the material types, sizes, and the like of the detection positions are completely consistent, and the three-post insulators can be divided into three types of positions: the first type of location is at the bottom of the body (at the column foot), where it consists of the solid epoxy and the ground insert, and any point on the circumference of equal body radius belongs to the first type of location, such as locations w11, w12, w13, w14, w15, w16 in fig. 3 where the body radius is the same. The second type of location is in the middle of the body, where only solid epoxy is contained, and any point on the circumference of equal body radius belongs to the second type of location, such as w21, w22, w23, w24, w25, w26 with the same cylinder radius in fig. 3. The third type of location is on the pillar base, where such location is comprised of a solid epoxy and a center conductor, and any point on the pillar base of the same curvature belongs to the third type of location, such as the same curvature locations w31, w32, w33 in fig. 3.
In engineering, internal defects such as air gaps and unshelling are most likely to occur in the first-class similar positions (namely, at the joint of the grounding insert and the column base), so that the defect reconstruction is performed on a 550kV three-post insulator in China based on the ultrasonic detection system, as shown in fig. 4, a specific step flow chart includes the steps of:
s1, building an ultrasonic detection system;
specifically, the narrow pulse ultrasonic straight probe is connected with the emitting end of the ultrasonic pulse generator through a probe adaptive line, and the oscilloscope is connected with the synchronous end of the ultrasonic pulse generator through a high-impedance transmission line.
S2, detecting the joint of the grounding insert and the column base of the three-column insulator by an ultrasonic detection system;
specifically, as shown in fig. 5, the ultrasonic detection system detects two different column bases of the three-column insulator, where fig. 5a) is a sectional view of a column base I detection process, fig. 5b) is a top view of the column base I detection process, fig. 5c) is a sectional view of a column base II detection process, and fig. 5d) is a top view of the column base II detection process; starting an ultrasonic detection system, adjusting an ultrasonic pulse generator, placing a narrow pulse ultrasonic straight probe coated with a water-based ultrasonic couplant on 8 different positions (w11, w12, w17, w18, w13, w14, w19 and w20) of two different column bases (column base I and column base II) of a three-column insulator for detection, and recording ultrasonic reflection echo information at each position, wherein the result is shown in figure 6;
s3, determining ultrasonic reflection echo information of a defect-free position and defective ultrasonic reflection echo information by using a similarity method, thereby determining a defective position;
specifically, as shown in fig. 6(a) and 6(B), in the waveform diagram of ultrasonic detection at the column base position of the three-post insulator in the embodiment, an ultrasonic initial wave F is vertically incident into the solid epoxy, reaches the interface between the solid epoxy and the ground insert, the acoustic impedances of the materials at the two sides of the interface are different, a part of the ultrasonic wave is reflected, reaches the probe along the original path, and is displayed as a first echo B1 after the initial wave in the received waveform; the other part of ultrasonic waves are transmitted into the grounding insert and are totally reflected when reaching the interface between the grounding insert and the air, at the moment, the reflected waves are transmitted and reflected again through the grounding insert and the epoxy interface, the transmitted waves return to the probe, and a second echo B2 after the initial wave is displayed in the received waveform; b1 arrives at the probe and is reflected again at the contact surface, and the above steps are repeated, so that a secondary reflection echo B3 of the epoxy and ground insert interface appears after B2 in the received waveform.
In contrast to the detection waveforms at the four positions w11, w12, w17 and w18 of the column base I and the three positions w14, w19 and w20 of the column base II which are substantially identical in shape, peak value, phase and the like, the peaks of echoes B1, B2 and B3 at the position w13 of the column base II are only small, particularly the peak value at the position B1 is much smaller than those at other positions, and the time span of the B1 wave is also large. Therefore, the states of the w13 position of the column base II position can be classified into one type, the other seven positions can be classified into one type, and the defect in the w13 position of the column base II position can be preliminarily judged according to the reverse theory and experience.
S4, the ultrasonic detection system carries out ultrasonic scanning near the defect position and records the ultrasonic reflection echo information of each detection position;
specifically, ultrasonic scanning detection is performed near the w13 position of the pedestal II, and the scanning path and the scanning position are as shown in fig. 7, where a small circle represents the ultrasonic scanning detection position, the origin represents the w13 position of the pedestal II, the x axis represents the axial direction along the w13 position of the pedestal II, the y axis represents the tangential direction along the w13 position of the pedestal II, 6 ultrasonic scanning paths are provided, that is, x is 0, x is 1, x is 2, x is 3, x is 4, and x is 5, and 13 ultrasonic scanning paths are provided on each path, that is, y is-8, y is-6, y is-4, y is-3, y is-2, y is-1, y is 0, y is 1, y is 2, y is 3, y is 4, y is 6, and y is 8; the ultrasonic scanning lattice set is (0, -8), (0, -6), (0, -4), (0, -3), (0, -2), (0, -1), (0,0), (0,1), (0,2), (0,3), (0,4), (0,6), (0,8), (1, -6), (1, -4), (1, -3), (1, -2), (1, -1), (1,0), (1,1), (1,2), (1,3), (1,4), (1,6), (1,8), (2, -6), (2, -4), (2, -3), (2, -2), (2, -1), (2,0) (2,1), (2,2), (2,3), (2,4), (2,6), (2,8), (3, -6), (3, -4), (3, -3), (3, -2), (3, -1), (3,0), (3,1), (3,2), (3,3), (3,4), (3,6), (3,8), (4, -6), (4, -4), (4, -3), (4, -2), (4, -1), (4,0), (4,1), (4,2), (4,3), (4,4), (4,6), (4,8), (5, -6), (5, -4), (5, -3), (5, -2), (5, -1), (5,0), (5,1), (5,2), (5,3), (5,4), (5,6), (5, 8); starting an ultrasonic detection system, adjusting an ultrasonic pulse generator, sequentially placing the centers of narrow pulse ultrasonic straight probes coated with water-based ultrasonic couplants on the ultrasonic scanning lattice set, and recording ultrasonic echo information B1 of each scanning point.
S5, constructing the corresponding relation between the ultrasonic reflection echo information and the defect shape and defect size, and obtaining a defect reconstruction schematic diagram based on the detection result of each scanning position, thereby quantifying the defect size and identifying the defect shape.
Specifically, the ultrasonic echo information of the scan positions (0, -8), (0, -6), (0, -4), (0, -3), (0, -2), (0, -1), (0,0), (0,1), (0,2), (0,3), (0,4), (0,6), and (0,8) at the scan path where x is 0 in step S4 is substituted into formula (1) to calculate the depth value of each scan position, which is denoted as d(0,-8)、d(0,-6)、d(0,-4)、d(0,-3)、d(0,-2)、d(0,-1)、d(0,0)、d(0,1)、d(0,2)、d(0,3)、d(0,4)、d(0,6)And d(0,8)Then these depth values are all divided by
(d(0,-8)、d(0,8)The position is a defect-free position, the position and the defect are theoretically equal, and the average value of the position and the defect is taken for eliminating measurement deviation), so that all detection position results under the scanning path where x is 0 are normalized, and cubic spline interpolation is carried out on the normalized results, so that a curve representing the defect length and the defect depth under the scanning path where x is 0 can be obtained; similarly, the remaining scanning points can obtain curves representing the defect length and the defect depth under the scanning paths of which x is 1, x is 2, x is 3, x is 4 and x is 5 according to the theory; as shown in fig. 8 a).
As shown in fig. 8(b), it can be seen that the closer to x ═ 0 (the closer to the bottom surface of the column foot), the larger the range of the defect boundary is, the defect width at x ═ 0 is about 6mm, the defect width decreases nonlinearly along the x axis, and the defect width at x ═ 4 is about 2 mm; the total length of the defect is about 4mm, and the whole defect is in a wedge shape of a wide head and a narrow tail.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (5)
1. A three-post insulator internal defect reconstruction method based on an ultrasonic scanning principle is characterized by comprising the following steps:
s1, building an ultrasonic detection system;
s2, detecting the similar positions of the three-post insulator by adopting an ultrasonic detection system, and recording ultrasonic reflection echo information of each detection position;
the similar positions refer to the material types and the sizes of the detection positions which are completely consistent, and comprise any position on the circumference with the same radius of the three-post insulator cylinder;
s3, judging the ultrasonic reflection echo information of each detection position by using a similarity method, and determining the defect position;
in step S3, the principle of determining the defect position of the three-post insulator by using the similarity method is as follows: under the condition of no defect, all the ultrasonic reflection echo waveform information obtained from the same type of detection positions are consistent, and when the waveform information of the same type of detection positions is different, the defect exists below the detection positions with different ultrasonic reflection echoes; in the detection process, the influence of the dimensional tolerance and the surface roughness is neglected;
s4, performing ultrasonic scanning near the defect position by adopting an ultrasonic detection system, and recording ultrasonic reflection echo information of each detection position;
s5, constructing a corresponding relation between ultrasonic reflection echo information and a defect shape and a defect size, and obtaining a defect reconstruction schematic diagram based on a detection result of each scanning position, so that the defect size is quantized, and the defect shape is identified;
in step S5, a method for constructing a correspondence between ultrasound reflection echo information and a defect shape and a defect size is provided: according to the principle of an ultrasonic pulse reflection method, the peak value of an ultrasonic initial wave corresponds to time t0, when a defect-free object is detected, a bottom echo B appears on an oscilloscope, the peak value corresponds to time t1, the depth of a detection surface to the bottom surface is H, when a defect object is detected, a defect echo F appears between the initial wave and the bottom echo, the peak value corresponds to time t2, the depth of the detection surface to the bottom surface is d, namely t0< t2< t1, the sound velocities are the same in the same medium, and the relation between d and H can be expressed as
Assume that 2n +1 scanning position coordinates on any one scanning path m in step S3 are L(m,-n)、L(m,-n+1)…L(m,0)…L(m,n-1)、L(m,n)Substituting the ultrasonic detection echo information of the position into the formula (1) to obtain the depth d of the position(m,-n)、d(m,-n+1)…d(m,0)…d(m,n-1)、d(m,n)Then these depth values are all divided by
Thus, all detection position results on the scanning path m are normalized, and the normalized results are subjected to cubic spline interpolation to obtain curves representing the defect length and the defect depth on the scanning path m;
processing other scanning paths in sequence according to the method to obtain curves of all the scanning paths representing lengths and defect depths; and obtaining a reconstruction schematic diagram of the internal defects of the three-post insulator according to the obtained curve by a least square surface fitting method.
2. The method for reconstructing the internal defect of the three-post insulator based on the ultrasonic scanning principle according to claim 1, wherein in step S1, the ultrasonic detection system comprises an ultrasonic pulse generator, an oscilloscope, a narrow pulse ultrasonic straight probe, a probe adaptive line and a high-impedance transmission line;
the ultrasonic detection system building method comprises the following steps: the narrow pulse ultrasonic straight probe is connected with the signal output end of the ultrasonic pulse generator through a probe adaptive line, and the signal synchronization end of the ultrasonic pulse generator is connected with an oscilloscope through a high-impedance transmission line;
the ultrasonic pulse generator is a pulse generator which is excited by sharp pulses, has adjustable output pulse width and gain and low noise;
the oscilloscope is a four-channel high-performance digital storage oscilloscope with the maximum sampling frequency of 1GHz and a sampling broadband of 200 MHz;
the narrow pulse ultrasonic straight probe belongs to a cylindrical longitudinal wave straight probe, and adopts a circular composite material piezoelectric wafer, the bottom surface of the probe is circular, the surface of an insulator is an arc surface, the diameter design range of the bottom surface of the probe is 5-10mm, and the height design range of the probe is 15-20 mm; the frequency of the narrow pulse ultrasonic straight probe is not more than 5 MHz.
3. The method for reconstructing the internal defect of the three-post insulator based on the ultrasonic scanning principle as claimed in claim 1, wherein in step S2, the ultrasonic detection system detects the similar position of the three-post insulator by: and adjusting an ultrasonic pulse generator, placing a narrow pulse ultrasonic straight probe coated with a water-based ultrasonic coupling agent on the same type of position of the three-pillar insulator for detection, and recording ultrasonic reflection echo information at each same type of position.
4. The method for reconstructing the internal defect of the three-post insulator based on the ultrasonic scanning principle as claimed in claim 1, wherein in step S4, the ultrasonic inspection system performs ultrasonic scanning around the defect position: and detecting the narrow pulse ultrasonic straight probe according to the ultrasonic scanning path and position, and recording ultrasonic reflection echo information of each scanning position.
5. The method for reconstructing the internal defect of the three-post insulator based on the ultrasonic scanning principle as claimed in claim 4, wherein the ultrasonic scanning paths and positions are scanning point sets with areas covering the whole defect, the detection positions are determined by setting different step lengths on each scanning path, and all the detection positions are listed to be a scanning lattice set of the whole defect.
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| CN111812461A (en) * | 2020-06-08 | 2020-10-23 | 天津大学 | Three-post insulator latent defect detection method based on ultrasonic propagation characteristics |
| CN111896605B (en) * | 2020-06-22 | 2022-01-21 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | GIL equipment three-support insulator surface charge measuring device and test method thereof |
| CN112034040A (en) * | 2020-08-12 | 2020-12-04 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | Defect detection method, device and system for column base of three-column insulator |
| CN112066920A (en) * | 2020-08-31 | 2020-12-11 | 南方电网科学研究院有限责任公司 | Method and device for detecting strain of three-post insulator column foot and medium |
| CN112461070B (en) * | 2020-09-10 | 2023-03-31 | 河南平高电气股份有限公司 | Three-post insulator detection tool |
| CN112630611B (en) * | 2020-12-14 | 2022-04-22 | 华南理工大学 | Test method for detecting uniformity of basin-type insulator by ultrasonic longitudinal wave reflection method |
| CN113310610B (en) * | 2020-12-31 | 2022-12-16 | 华南理工大学 | Ultrasonic detection method for peripheral epoxy stress of three-post insulator insert |
| CN113639912A (en) * | 2021-07-30 | 2021-11-12 | 华南理工大学 | Method, device and system for detecting column leg stress under radial load of three-column insulator |
| CN113899815B (en) * | 2021-09-08 | 2023-09-19 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | 126kV three-phase common-box basin-type insulator interface defect detection method |
| CN113945814B (en) * | 2021-11-09 | 2024-01-19 | 广东电网有限责任公司电力科学研究院 | GIL insulator internal temperature field on-line monitoring method |
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