A Defect Detection Method for Composite Insulator Core Rods Based on Radio Frequency Transmission

Abstract

The present invention provides a composite insulator core rod defect detection method based on radio frequency transmission method. In the measurement device preparation stage, the microwave transmission method composite insulator core rod detection equipment comprises: a vector network analysis instrument, a coaxial transmission line, a radio frequency transmitting port (four-port device), a radio frequency receiving port (four-port device), a defect-free core rod (diameter 30mm, length 2400mm), a defective core rod (diameter 30mm, length 2400mm), a computer and other instruments and equipment, and the scattering parameters of the composite insulator core rod are measured from both ends of the composite insulator core rod by radio frequency transmission method. Compared with the traditional defect detection method, microwaves have strong penetration in non-metallic materials and can be propagated in a specified direction according to the position of the transmitting probe. The microwave signal transceiver probe does not need to contact the composite insulator core rod itself, does not need a coupling agent, does not affect the performance of the core rod itself, is easy to operate under low pressure, and has a fast speed.

Description

Technical Field

[0001] The present invention relates to a method for detecting an insulating core rod, and in particular to a method for detecting defects in a composite insulator core rod based on a radio frequency transmission method. Background Art

[0002] Currently, methods for inspecting composite insulator core rod defects include infrared thermography, voltage detection, X-rays, ultrasound, ultraviolet light, and microwave reflectometry. Infrared thermography can detect internal defects by sensing the temperature rise caused by material discontinuities in the composite insulator core rod, but it is easily affected by environmental factors such as sunlight, temperature, wind speed, and humidity. The electric field method is a widely used inspection method that can locate internal defects by measuring the distortion level of the composite insulator's axial electric field strength. However, it cannot detect conductive defects in composite insulators at medium and high voltage levels. X-rays have strong penetrating power and can detect microcracks at interfaces and within composite insulators, but they are expensive and carry a high risk of bio-radiation. Ultrasonic methods can detect most defects by listening to the echo of an acoustic signal and analyzing its amplitude, timing, and phase shift. However, a specific chemical coupling agent must be applied to the insulator core rod before inspection. Ultraviolet detection can detect defects by sensing corona discharge at different locations on the insulator core rod, but this method can only be performed in high humidity environments. Extensive research has been conducted on microwave nondestructive testing technology both domestically and internationally, but its application has primarily been in aerospace and military fields. Limited research has been conducted on the application of microwave testing to composite insulator testing. Hinken et al. used a network analyzer to test resin flat plates, demonstrating the ability to detect pre-determined defects. Qaddoumi et al. used near-field microwaves to detect internal defects in composite insulator samples with built-in defects. While their ability to identify porosity was good, their ability to identify metal defects was poor. Professor Wang Liming of Tsinghua University and his colleagues used microwave reflectometry to identify pre-determined millimeter-level depth defects, but the large length and width resulted in low detection efficiency. Summary of the Invention

[0003] In order to overcome the deficiencies of the prior art, the present invention provides.

[0004] The present invention is implemented by the following technical solutions: A composite insulator core rod defect detection method based on radio frequency transmission method,

[0005] (1) Measuring device preparation stage

[0006] The microwave transmission method for measuring composite insulator core rod detection equipment includes: vector network analyzer, coaxial transmission line, RF transmitting port (four-port device), RF receiving port (four-port device), defect-free core rod (diameter 30mm, length 2400mm), defective core rod (diameter 30mm, length 2400mm), computer and other instruments and equipment.

[0007] (2) Measurement device connection stage

[0008] After the vector network analyzer is powered on, it is connected to the coaxial transmission line. The other end of the coaxial transmission line is connected to the RF transmitting port. The RF transmitting port is fixed at one end of the composite insulator core rod. The microwave signal is coupled into the core rod through the transmitting port. The other end of the core rod is connected to the RF receiving port to receive the microwave signal. The RF receiving port then transmits the microwave signal back to the vector network analyzer through the coaxial transmission line and displays the real-time data on the computer.

[0009] (3) Data measurement stage

[0010] A defect-free composite insulator core rod is selected, and the vector network analyzer is connected to port 1 of the RF transmitting port through a coaxial transmission line. The microwave passes through the composite insulator core rod and is transmitted back to the vector network analyzer through the coaxial line via the RF receiving port port 5. At this time, port 2, port 3, port 4, port 6, port 7, and port 8 are connected to a 50Ω matching load. After this process, the S2 of the defect-free composite insulator core rod in the direction of 15 is measured. （5） 1 （1） data.

[0011] The RF receiving port remains unchanged, the transmitting port is changed to port2, and port1 is connected to a 50Ω matching load. The S2 of the defect-free composite insulator core rod in the 25 direction can be measured. （5） 1 （2） Then change the transmitting port to port3 and connect port2 to a 50Ω matching load to measure the S2 of the core rod 35 of the defect-free composite insulator. （5） 1 （3） Similarly, the transmitting port is changed to port4, and port3 is connected to a 50Ω matching load, and the S2 of the defect-free composite insulator core rod in the 45 direction can be measured. （5） 1 （4） Through this process, a total of 4 sets of measurement data of the receiving port of the defect-free composite insulator core rod 5 can be obtained;

[0012] Similarly, the RF receiving ports port 6, port 7, and port 8 are connected to the coaxial transmission line in sequence, and the RF transmitting ports port 1, port 2, port 3, and port 4 are connected to the coaxial transmission line in turn. The ports not connected to the coaxial line are connected to a 50Ω matching load. This way, the remaining 12 groups of defect-free composite insulator core rod data are obtained.

[0013] Similarly, the same data measurements are performed on the defective composite insulator core rods to obtain another 16 sets of data.

[0014] Entering the data processing stage, the data of the four transmitting ports in different port directions of the same receiving port are superimposed to simulate the simultaneous excitation of RF signals with equal amplitude and phase. Taking RF receiving port 5 as an example, the expression is:

[0015] S2 (5) 1 （1+2+3+4） =S2 （5） 1 （1） + S2 （5） 1 （2） + S2 （5） 1 （3） + S2 （5） 1 （4）

[0016] Similarly, we can get S2 (6) 1 （1+2+3+4） 、S2 (7) 1 （1+2+3+4） 、S2 (8) 1 （1+2+3+4） The 16 sets of data of defective composite insulator core rods can be processed in the same way to obtain another four S2 (5) 1 （1+2+3+4） 、S2 (6) 1 （1+2+3+4） 、S2 (7) 1 （1+2+3+4） 、S2 (8) 1 （1+2+3+4） . With S2 (7) 1 （1+2+3+4） and S2 (5) 1 （1+2+3+4） The difference between the two is used to characterize the vertically polarized RF signal excited by the four-port equal amplitude and in-phase signals at the same time. Similarly, S2 (8) 1 （1+2+3+4） and S2 (6) 1 （1+2+3+4） The difference between the two is used to characterize the horizontally polarized RF signal excited by the four-port equal-amplitude and in-phase signals simultaneously.

[0017] Conversely, if a vertically polarized RF signal or a horizontally polarized RF signal is used as the excitation source at the RF input, the high-order modes excited by them can also be received at the receiving end. That is, at the RF input port, port 2 and port 4 are used as the excitation source respectively. The difference between the two is equivalent to equal-amplitude and anti-phase signals, which can be regarded as horizontally polarized RF signal excitation. At the RF receiving port, the sum of the signals at ports 5, 6, 7, and 8 simulates the high-order modes excited by the vertically polarized RF signal. The expression is:

[0018] S2 （5+6+7+8） 1 （2） - S2 （5+6+7+8） 1 （4） =S2（5） 1 （2） + S2 （6） 1 （2） + S2 （7） 1 （2） + S2 （8） 1 （2）

[0019] - S2 （5） 1 （4） -S2 （6） 1 （4） - S2 （7） 1 （4） - S2 （8） 1 （4）

[0020] The defective core rod is treated in the same way, and the vertical polarization signal when it is excited by the four-port equal-amplitude and in-phase signals and the high-order signal when it is excited by the horizontal polarization signal can be obtained.

[0021] Compared with the existing technology, the present invention uses a radio frequency transceiver to measure the scattering parameters of the composite insulator core rod from both ends through the radio frequency transmission method. Compared with traditional defect detection methods, microwaves have strong penetration in non-metallic materials and can propagate in a specified direction according to the position of the transmitting probe. The microwave signal transceiver probe does not need to be in contact with the composite insulator core rod itself, does not require a coupling agent, will not affect the performance of the core rod itself, and does not require strict control of environmental temperature, humidity, light, wind speed and other conditions. It is easy to operate under low voltage and has a high speed. Compared with the currently proposed radio frequency reflection method, the composite insulator core rod defect detection method based on the radio frequency transmission method has faster data acquisition and data processing speeds and is more convenient to operate. It only needs to measure data in different directions to evaluate the integrity of the composite insulator core rod. The transmission detection method based on radio frequency microwaves can effectively reflect the anomalies between defective core rods and non-defective core rods, improves the method of radio frequency transmission measurement of composite insulator core rods, and provides effective reference data for composite insulator manufacturers. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a simulation structure diagram of the composite insulator core rod.

[0023] Figure 2 This is a schematic diagram of the RF transmitting port.

[0024] Figure 3 This is a schematic diagram of the RF receiving port. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0026] Composite insulator core rod defect detection method based on radio frequency transmission method,

[0027] (1) Measuring device preparation stage

[0028] The microwave transmission method for measuring composite insulator core rod detection equipment includes: vector network analyzer, coaxial transmission line, RF transmitting port (four-port device), RF receiving port (four-port device), defect-free core rod (diameter 30mm, length 2400mm), defective core rod (diameter 30mm, length 2400mm), computer and other instruments and equipment.

[0029] (2) Measurement device connection stage

[0030] After the vector network analyzer is powered on, it is connected to a coaxial transmission line. The other end of the coaxial transmission line is connected to the RF transmitter port. The RF transmitter port is fixed to one end of the composite insulator core rod. Microwave signals are coupled into the core rod through the transmitter port. The other end of the core rod is connected to the RF receiver port, which receives the microwave signal. The RF receiver port then transmits the microwave signal back to the vector network analyzer via the coaxial transmission line, and the real-time data is displayed on the computer.

[0031] (3) Data measurement stage

[0032] A defect-free composite insulator core rod is selected, and the vector network analyzer is connected to port 1 of the RF transmitting port through a coaxial transmission line. The microwave passes through the composite insulator core rod and is transmitted back to the vector network analyzer through the coaxial line via the RF receiving port port 5. At this time, port 2, port 3, port 4, port 6, port 7, and port 8 are connected to a 50Ω matching load. After this process, the S2 of the defect-free composite insulator core rod in the direction of 15 is measured. （5） 1 （1） data.

[0033] The RF receiving port remains unchanged, the transmitting port is changed to port2, and port1 is connected to a 50Ω matching load. The S2 of the defect-free composite insulator core rod in the 25 direction can be measured. （5） 1 （2） Then change the transmitting port to port3 and connect port2 to a 50Ω matching load to measure the S2 of the core rod 35 of the defect-free composite insulator. （5） 1 （3） Similarly, the transmitting port is changed to port4, and port3 is connected to a 50Ω matching load, and the S2 of the defect-free composite insulator core rod in the 45 direction can be measured.（5） 1 （4） Through this process, a total of 4 sets of measurement data of the receiving port of the defect-free composite insulator core rod 5 can be obtained;

[0034] Similarly, the RF receiving ports port 6, port 7, and port 8 are connected to the coaxial transmission line in sequence, and the RF transmitting ports port 1, port 2, port 3, and port 4 are connected to the coaxial transmission line in turn. The ports not connected to the coaxial line are connected to a 50Ω matching load. This way, the remaining 12 groups of defect-free composite insulator core rod data are obtained.

[0035] Similarly, the same data measurements are performed on the defective composite insulator core rods to obtain another 16 sets of data.

[0036] Entering the data processing stage, the data of the four transmitting ports in different port directions of the same receiving port are superimposed to simulate the simultaneous excitation of RF signals with equal amplitude and phase. Taking RF receiving port 5 as an example, the expression is:

[0037] S2 (5) 1 （1+2+3+4） =S2 （5） 1 （1） + S2 （5） 1 （2） + S2 （5） 1 （3） + S2 （5） 1 （4）

[0038] Similarly, we can get S2 (6) 1 （1+2+3+4） 、S2 (7) 1 （1+2+3+4） 、S2 (8) 1 （1+2+3+4） The 16 sets of data of defective composite insulator core rods can be processed in the same way to obtain another four S2 (5) 1 （1+2+3+4） 、S2 (6) 1 （1+2+3+4） 、S2 (7) 1 （1+2+3+4） 、S2 (8) 1 （1+2+3+4） . With S2 (7) 1 （1+2+3+4） and S2 (5) 1 （1+2+3+4） The difference between the two is used to characterize the vertically polarized RF signal excited by the four-port equal amplitude and in-phase signals at the same time. Similarly, S2 (8) 1 （1+2+3+4） and S2 (6) 1 （1+2+3+4） The difference between the two is used to characterize the horizontally polarized RF signal excited by the four-port equal-amplitude and in-phase signals simultaneously.

[0039] Conversely, using a vertically polarized RF signal or a horizontally polarized RF signal as the excitation source at the RF input port will also allow the receiver to receive the excited high-order modes. Specifically, at the RF input port, port 2 and port 4 are used as the excitation source, and the difference between the two is equivalent to equal-amplitude, inverted signals, which can be considered as horizontally polarized RF signal excitation. At the RF receiving port, the sum of the signals at ports 5, 6, 7, and 8 simulates the high-order modes excited by the vertically polarized RF signal. The expression is:

[0040] S2 （5+6+7+8） 1 （2） - S2 （5+6+7+8） 1 （4） =S2 （5） 1 （2） + S2 （6） 1 （2） + S2 （7） 1 （2） + S2 （8） 1 （2）

[0041] - S2 （5） 1 （4） -S2 （6） 1 （4） - S2 （7） 1 （4） - S2 （8） 1 （4）

[0042] The defective core rod is treated in the same way, and the vertical polarization signal when it is excited by the four-port equal-amplitude and in-phase signals and the high-order signal when it is excited by the horizontal polarization signal can be obtained.

[0043] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A composite insulator core rod defect detection method based on radio frequency transmission method, characterized in that: (1) Measurement device preparation stage The microwave transmission method for measuring composite insulator core rod detection equipment includes: vector network analyzer, coaxial transmission line, RF transmitting port four-port device, RF receiving port four-port device, defect-free core rod with diameter of 30mm and length of 2400mm, defective core rod with diameter of 30mm and length of 2400mm, and computer equipment; (2) Measurement device connection stage After the vector network analyzer is powered on, it is connected to the coaxial transmission line. The other end of the coaxial transmission line is connected to the RF transmitting port. The RF transmitting port is fixed at one end of the composite insulator core rod. The microwave signal is coupled into the core rod through the transmitting port. The other end of the core rod is connected to the RF receiving port to receive the microwave signal. The RF receiving port then transmits the microwave signal back to the vector network analyzer through the coaxial transmission line and displays the real-time data on the computer. (3) Data measurement phase Select a defect-free composite insulator core rod, connect the vector network analyzer to port 1 of the RF transmitting port through a coaxial transmission line, and transmit the microwave through the composite insulator core rod and transmit it back to the vector network analyzer through the coaxial line through the RF receiving port port 5. At this time, port 2, port 3, port 4, port 6, port 7, and port 8 are connected to a 50Ω matching load. After this process, the S2 of the defect-free composite insulator core rod 15 direction is measured. （5） 1 （1） data; The RF receiving port remains unchanged, the transmitting port is changed to port2, and port1 is connected to a 50Ω matching load, so that the S2 of the core rod 25 of the defect-free composite insulator can be measured. （5） 1 （2） Then change the transmitting port to port3, connect port2 to a 50Ω matching load, and measure the S2 of the core rod 35 of the defect-free composite insulator. （5） 1 （3） Similarly, the transmitting port is changed to port4, and port3 is connected to a 50Ω matching load, and the S2 of the core rod of the defect-free composite insulator in the 45 direction can be measured. （5） 1 （4） Data, through this process, a total of 4 groups of measurement data of the receiving port of the defect-free composite insulator core rod 5 can be obtained; By analogy, the RF receiving ports port6, port7, and port8 are connected to the coaxial transmission line in turn, and the RF transmitting ports port1, port2, port3, and port4 are connected to the coaxial transmission line in turn, and the port not connected to the coaxial line is connected to a 50Ω matching load, and the remaining 12 groups of defect-free composite insulator core rod data can be obtained; Similarly, the same data measurements are performed on defective composite insulator core rods to obtain another 16 sets of data.

2. The composite insulator core rod defect detection method based on radio frequency transmission method according to claim 1 is characterized in that: Entering the data processing stage, the data of the four transmitting ports in different port directions of the same receiving port are superimposed to simulate the simultaneous excitation of RF signals with equal amplitude and phase. The expression of RF receiving port 5 is: <h2 style=";text-align:left;direction:ltr">S2<h2 style=";text-align:left;direction:ltr"> (5) <h2 style=";text-align:left;direction:ltr"> 1<h2 style=";text-align:left;direction:ltr"> （1+2+3+4） <h2 style=";text-align:left;direction:ltr"> =S2<h2 style=";text-align:left;direction:ltr"> （5） <h2 style=";text-align:left;direction:ltr"> 1<h2 style=";text-align:left;direction:ltr"> （1） <h2 style=";text-align:left;direction:ltr"> + S2<h2 style=";text-align:left;direction:ltr"> （5） <h2 style=";text-align:left;direction:ltr"> 1<h2 style=";text-align:left;direction:ltr"> （2） <h2 style=";text-align:left;direction:ltr"> + S2<h2 style=";text-align:left;direction:ltr"> （5） <h2 style=";text-align:left;direction:ltr"> 1<h2 style=";text-align:left;direction:ltr"> （3） <h2 style=";text-align:left;direction:ltr"> + S2<h2 style=";text-align:left;direction:ltr"> （5） <h2 style=";text-align:left;direction:ltr"> 1<h2 style=";text-align:left;direction:ltr"> （4） Similarly, S2 (6) 1 （1+2+3+4） 、S2 (7) 1 （1+2+3+4） 、S2 (8) 1 （1+2+3+4） , the 16 sets of data of the defective composite insulator core rod can be processed in the same way to obtain another four S2 (5) 1 （1+2+3+4） 、S2 (6) 1 （1+2+3+4） 、S2 (7) 1 （1+2+3+4） 、S2 (8) 1 （1+2+3+4） , with S2 (7) 1 （1+2+3+4） and S2 (5) 1 （1+2+3+4） The difference between the two is used to characterize the vertically polarized RF signal excited by the four-port equal-amplitude and in-phase signals at the same time. Similarly, S2 (8) 1 （1+2+3+4） and S2 (6) 1 （1+2+3+4） The difference is used to characterize the horizontally polarized RF signal excited by the four-port equal-amplitude and in-phase signals simultaneously. On the contrary, when a vertically polarized RF signal or a horizontally polarized RF signal is used as the excitation source of the RF input end, the high-order mode excited by it can also be received at the receiving end. That is, port 2 and port 4 are used as excitation at the RF input port respectively, and the difference between the two is equivalent to an equal-amplitude anti-phase signal, which can be regarded as a horizontally polarized RF signal excitation. At the RF receiving port, the sum of the port 5, port 6, port 7, and port 8 signals is used to simulate the high-order mode excited by the vertically polarized RF signal. The expression is: <h2 style=";text-align:left;direction:ltr">S2<h2 style=";text-align:left;direction:ltr"> （5+6+7+8） <h2 style=";text-align:left;direction:ltr"> 1<h2 style=";text-align:left;direction:ltr"> （2） <h2 style=";text-align:left;direction:ltr"> - S2<h2 style=";text-align:left;direction:ltr"> （5+6+7+8） <h2 style=";text-align:left;direction:ltr"> 1<h2 style=";text-align:left;direction:ltr"> （4） <h2 style=";text-align:left;direction:ltr"> =S2<h2 style=";text-align:left;direction:ltr"> （5） <h2 style=";text-align:left;direction:ltr"> 1<h2 style=";text-align:left;direction:ltr"> （2） <h2 style=";text-align:left;direction:ltr"> + S2<h2 style=";text-align:left;direction:ltr"> （6） <h2 style=";text-align:left;direction:ltr"> 1<h2 style=";text-align:left;direction:ltr"> （2） <h2 style=";text-align:left;direction:ltr"> + S2<h2 style=";text-align:left;direction:ltr"> （7） <h2 style=";text-align:left;direction:ltr"> 1<h2 style=";text-align:left;direction:ltr"> （2） <h2 style=";text-align:left;direction:ltr"> + S2<h2 style=";text-align:left;direction:ltr"> （8） <h2 style=";text-align:left;direction:ltr"> 1<h2 style=";text-align:left;direction:ltr"> （2） <h2 style=";text-align:left;direction:ltr">- S2<h2 style=";text-align:left;direction:ltr"> （5） <h2 style=";text-align:left;direction:ltr"> 1<h2 style=";text-align:left;direction:ltr"> （4） <h2 style=";text-align:left;direction:ltr"> -S2<h2 style=";text-align:left;direction:ltr"> （6） <h2 style=";text-align:left;direction:ltr"> 1<h2 style=";text-align:left;direction:ltr"> （4） <h2 style=";text-align:left;direction:ltr"> - S2<h2 style=";text-align:left;direction:ltr"> （7） <h2 style=";text-align:left;direction:ltr"> 1<h2 style=";text-align:left;direction:ltr"> （4） <h2 style=";text-align:left;direction:ltr"> - S2<h2 style=";text-align:left;direction:ltr"> （8） <h2 style=";text-align:left;direction:ltr"> 1<h2 style=";text-align:left;direction:ltr"> （4） The defective core rod is treated in the same way, and the vertical polarization signal excited by the four-port equal-amplitude and in-phase signals and the high-order signal generated when excited by the horizontal polarization signal can be obtained.

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