Electromechanical impedance uniform corrosion assessment method for grounding conductor of power transmission tower

Abstract

The invention provides an electromechanical impedance uniform corrosion assessment method for a grounding conductor of a power transmission tower. The corrosion degree of the grounding conductor is assessed by taking the radius variation delta r of the grounding conductor as a corrosion parameter. Solving a model parameter km by using a finite element simulation technology and a least square method based on a model of a system electromechanical impedance real part resonance original frequency fm and a corrosion parameter delta r; and substituting the actually measured fm into the model to predict the delta r so as to evaluate the corrosion degree of the grounding conductor.

Description

Technical Field

[0001] The invention belongs to the technical field of electrical equipment repair and maintenance, and in particular relates to a method for evaluating uniform corrosion of electromechanical impedance of a grounding conductor of a transmission tower. Background Art

[0002] The grounding conductor of the transmission tower is prone to electrochemical corrosion in the soil, which causes its conductivity to decrease, affecting the normal operation of the power system and even causing large-scale power outages in the power supply area. However, the traditional grounding conductor corrosion diagnosis methods currently used, such as power grid analysis method, megohmmeter method, electromagnetic field detection method, etc., are difficult to intuitively detect the degree of corrosion of the conductor and are easily disturbed by the working environment, affecting the accuracy of the measurement results. In addition, some measuring equipment is expensive and bulky, the operation process is complicated, and a lot of manpower is required for measurement. Therefore, a method is needed to effectively and conveniently evaluate the degree of corrosion of the grounding conductor.

[0003] Electromechanical impedance technology uses a low-cost, small, sensitive, and fast-responding piezoelectric transducer to detect damage to the main structure. It is an effective ground conductor corrosion assessment technology. However, this method usually uses the root mean square difference and the average absolute percentage difference as damage indicators to conduct a qualitative analysis of the damage to the structure to be tested. It does not truly analyze the relationship between the damage indicator and the damage in theory, and does not establish a relationship model between the two, so it is impossible to perform quantitative analysis. Moreover, in rod-shaped structures, electromechanical impedance technology generally uses a symmetrical sensor arrangement method, which cannot reflect the change in rod radius caused by corrosion. So far, there is no detection technology that can truly effectively and conveniently quantitatively evaluate the change in the radius of the ground conductor caused by corrosion. Summary of the invention

[0004] Therefore, in order to overcome the shortcomings of the existing transmission tower grounding conductor corrosion detection method, the present invention proposes a new method for evaluating the uniform corrosion degree of the grounding conductor based on electromechanical impedance technology, including establishing a parametric corrosion model of the grounding conductor, establishing a system electromechanical impedance characteristic corrosion parameter model, and combining finite element simulation with least squares to solve the corrosion model parameters. The main content of the invention is: by establishing a parametric uniform corrosion model of the grounding conductor, the corrosion parameters used to characterize the corrosion degree of the grounding conductor are established; by analyzing the system electromechanical impedance and the mechanical admittance of the grounding conductor, an electromechanical impedance characteristic corrosion parameter model of the electromechanical impedance frequency characteristics and corrosion parameters is established; finite element simulation and least squares method are used to solve the electromechanical impedance characteristic corrosion model parameters.

[0005] The technical solution specifically adopted by the present invention to solve the technical problem is:

[0006] A method for evaluating uniform corrosion of electromechanical impedance of a grounding conductor of a transmission tower, characterized in that: the radius change Δr of the grounding conductor is used as a corrosion parameter to evaluate the corrosion degree of the grounding conductor; based on the original resonance frequency f of the real part of the electromechanical impedance of the system m The model with corrosion parameter Δr is simulated by finite element simulation technology and least square method to find the model parameter k m Solve it; then use the measured f m Substitute Δr into the model to predict the corrosion degree of the grounding conductor.

[0007] Furthermore, the method of using the ground conductor radius change Δr as a corrosion parameter to evaluate the corrosion degree of the ground conductor is specifically as follows:

[0008] Under natural conditions, the corrosion degree of the metal grounding conductor of the transmission tower in the soil due to electrochemical corrosion is calculated from the loss mass m l characterization, quantitative estimation through Faraday's law, and further converted into radius reduction Δr;

[0009] m l =(r1 2 -r2 2 )πlρ=(r1+r2)(r1-r2)πlρ=(2r1-Δr)Δrπlρ

[0010] Where r1 and r2 are the radii of the grounding conductor before and after corrosion, respectively; l is the conductor length; ρ is the conductor density; Δr = r1-r2.

[0011] Furthermore, the original resonance frequency f based on the real part of the system electromechanical impedance m The model with the corrosion parameter Δr is as follows:

[0012] Under the asymmetric sensor arrangement, when the radius r of the ground conductor changes, the bending vibration natural frequency w of the ground conductor is cm Changes, thereby affecting the real part of the system electromechanical impedance Re(Z(w)) resonant original frequency f m ; Change of the original resonance frequency of the real part of the electromechanical impedance Re(Z(w)) before and after corrosion Δf m for:

[0013]

[0014] In the formula, f 0，m and f Δ，m The original resonant frequency of the electromechanical impedance system when Δr = 0 and Δr ≠ 0 respectively; m is the corresponding resonance order; E is the elastic modulus of the grounding conductor; k m is the model parameter; since the above formula is only accurate when the aspect ratio of the metal conductor is infinite, the metal conductor corrosion model is established using finite element simulation technology to obtain km value.

[0015] Furthermore, the finite element simulation technology and the least squares method are used to calculate the model parameter k m The specific solution is as follows: the grounding conductor under different Δr is established by finite element simulation software to extract its Re(Z(w)) resonant original frequency f m Then, the least square method is used to find f m Perform linear fitting with Δr to solve the model parameter k m .

[0016] Furthermore, in the measurement process, a single piezoelectric ceramic sheet is first pasted on the top of the grounding conductor of the transmission tower to be tested to form an asymmetric sensor arrangement. The grounding conductor and the piezoelectric ceramic sheet together constitute an electromechanical impedance system. Then, the electromechanical impedance of the system is measured to obtain the real part of the total impedance Re(Z(w)) of the electromechanical system, and the resonant frequency f in the uncorroded state is read through Re(Z(w)). 0，m ;

[0017] The specific parameters of the grounding conductor and the piezoelectric ceramic sheet are input into the finite element simulation software, and a finite element simulation model is established to obtain the Re(Z(w)) of the grounding conductor under different Δr. Then, its resonant frequency f is read through Re(Z(w)). m , calculate Δf under different Δr m ;

[0018] Δf m Perform the least squares linear fitting with Δr to obtain the model parameter k m , get the numerical model f m =k m Δr.

[0019] Furthermore, the specific parameters of the ground conductor and the piezoelectric ceramic sheet include:

[0020] Specific parameters of the grounding conductor to be tested, including: initial length l, initial radius r, elastic modulus E and density ρ;

[0021] And the specific parameters of the piezoelectric ceramic sheets used, including: length, width, thickness, density, piezoelectric stress coefficient and relative dielectric constant coefficient.

[0022] Furthermore, when the grounding conductor is buried in the soil for a certain number of years and its corrosion degree needs to be measured, the resonant frequency f is measured again. Δ，m , calculate Δf m ; Its Δf m Substitute it into the established model to predict its corrosion parameter Δr; and combine it with the power grid standard to determine whether the grounding conductor needs to be dug up for inspection.

[0023] And, a device for evaluating uniform corrosion of electromechanical impedance of a grounding conductor of a transmission tower, comprising an electromechanical impedance system and a measuring device: a single piezoelectric ceramic sheet is pasted on the top of the grounding conductor of the transmission tower to be tested to form an asymmetric sensor arrangement, and the grounding conductor and the piezoelectric ceramic sheet together constitute the electromechanical impedance system; the measuring device is used to measure and obtain the real part of the total impedance Re(Z(w)) of the electromechanical system, and read the resonant frequency f in the uncorroded state through Re(Z(w)). 0,m The specific parameters of the grounding conductor and the piezoelectric ceramic sheet are input into the finite element simulation software, and a finite element simulation model is established to obtain the Re(Z(w)) of the grounding conductor under different Δr. Then, the resonant frequency f is read through Re(Z(w)). m , calculate Δf under different Δr m ; Δf m Perform the least squares linear fitting with Δr to obtain the model parameter k m , get the numerical model f m =k m Δr.

[0024] Furthermore, the measuring device includes a PC and an AD5933 impedance analysis board, and the AD5933 impedance analysis board is used to measure and obtain the real part of the total impedance Re(Z(w)) of the electromechanical system.

[0025] Compared with the prior art, the present invention and its preferred embodiments have at least the following beneficial effects:

[0026] 1. The electrochemical corrosion model of the grounding conductor established in the present invention converts the mass loss of the metal into the radius loss, establishes Δr as a parameter to characterize the corrosion degree of the grounding conductor, and establishes a theoretical basis for the parametric corrosion assessment of the grounding conductor;

[0027] 2. The system electromechanical impedance resonance frequency f under the asymmetric sensor layout established by the present invention m The mathematical relationship model with the corrosion parameter Δr realizes the resonant frequency f of the slave electrical impedance m The conversion from the original data to the corrosion parameter Δr provides a theoretical support for the quantitative evaluation of the corrosion parameter Δr.

[0028] 3. The present invention combines finite element simulation technology with the least squares method to obtain the model parameter k simply and accurately. m , easy to implement in engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0030] Figure 1 1 is a diagram of the measurement process and main equipment in an embodiment of the present invention.

[0031] Figure 2 4 is a finite element model diagram of the electromechanical impedance of the grounding conductor under the asymmetric sensor in an embodiment of the present invention.

[0032] Figure 3 3 is a simulation diagram of Re(Z(w)) corresponding to different Δr in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the features and advantages of the present invention more clearly understood, the following embodiments are specifically described in detail as follows:

[0034] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0035] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0036] The present invention provides a new method for evaluating the uniform corrosion degree of the grounding conductor of a transmission tower based on electromechanical impedance technology. According to the corrosion characteristics of the grounding conductor, an electrochemical corrosion model of the grounding conductor is established, and Δr is used as a corrosion parameter to evaluate the corrosion degree of the grounding conductor; an electromechanical impedance resonance frequency f is established. m The mathematical model between the corrosion parameter Δr and the model parameter k is simulated by finite element simulation technology and least square method. m Solve; using the measured f m Substitute the mathematical model to predict Δr and evaluate the corrosion degree of the grounding conductor. The specific implementation process includes the following steps:

[0037] Step S1: The measurement process and main equipment of this embodiment are as follows: Figure 1 As shown. First, a single piezoelectric ceramic sheet needs to be pasted on the top of the grounding conductor of the transmission tower to be tested to form an asymmetric sensor arrangement. The grounding conductor and the piezoelectric ceramic sheet together constitute an electromechanical impedance system. Then the electromechanical impedance of the system is measured, where the measuring equipment consists of a computer and an AD5933 impedance analysis board. The computer is connected to the AD5933 impedance analysis board via a USB interface, and the upper computer software is used to control the AD5933 development board to measure the real part of the total impedance Re(Z(w)) of the electromechanical system. The resonant frequency f in the uncorroded state is read through Re(Z(w)). 0,m.

[0038] Step S2: Find the specific parameters of the ground conductor to be tested: initial length l; initial radius r; elastic modulus E; density ρ. And the specific parameters of the piezoelectric ceramic sheet to be used: length; width; thickness; density; piezoelectric stress coefficient; relative dielectric constant coefficient. Input the specific parameters of the ground conductor and the piezoelectric ceramic sheet into the finite element simulation software to establish a finite element simulation model, such as Figure 2 As shown. Obtain the Re(Z(w)) of the grounding conductor under different Δr, as Figure 3 As shown. Then read its resonant frequency f through Re(Z(w)) m , calculate Δf under different Δr m . m Perform the least squares linear fitting with Δr to obtain the model parameter k m , get the numerical model f m =k m Δr

[0039] Step S3: When the grounding conductor has been buried in the soil for a certain number of years and its corrosion degree needs to be measured, its resonant frequency f is measured again. Δ,m , calculate Δf m . Set its Δf m Substitute it into the model established in step 2 to predict its corrosion parameter Δr. And combine it with the power grid standard to determine whether the grounding conductor needs to be dug up for maintenance.

[0040] As a preferred solution of this embodiment, the parameterized uniform corrosion model of the grounding conductor is constructed as follows: Under natural conditions, the grounding metal conductor generally undergoes electrochemical corrosion in the soil, and the electrochemical corrosion degree of the metal conductor is generally determined by its loss mass m l The loss mass m can be quantitatively estimated by Faraday's law. l ;

[0041]

[0042] In the formula, M is the mass of metal atoms; I is the current applied to the conductor; t is the time of current flow; z is the charge number corresponding to the metal cation generated by corrosion; F = 96500 (A / S) is the Faraday constant. Since the length-to-diameter ratio of the rod-shaped grounded metal conductor is large, the effect of corrosion on its length is smaller than that on its radius. If the density of the uncorroded part of the conductor does not change, the degree of corrosion of the grounded conductor can be calculated by the loss mass m l It is converted into the radius reduction Δr to characterize;

[0043] m l =(r1 2 -r2 2)πlρ=(r1+r2)(r1-r2)πlρ=(2r1-Δr)Δrπlρ

[0044] In the formula, r1 and r2 are the radii of the grounded conductor before and after corrosion, respectively; l is the conductor length; ρ is the conductor density; Δr = r1-r2. This formula indicates that the corrosion loss mass of the metal conductor is related to the reduction in the conductor radius. Therefore, the corrosion loss mass m can be evaluated by detecting the change in Δr. l , which is the basic technology of corrosion assessment.

[0045] As a preferred solution of this embodiment, the electromechanical impedance characteristic corrosion parameter model is constructed as follows: under the asymmetric sensor arrangement, when the radius r of the ground conductor changes, the bending vibration natural frequency w of the ground conductor will change. cm , thus affecting the real part of the system electromechanical impedance Re(Z(w)) resonant original frequency f m . The natural frequency of the ground conductor is w cm for:

[0046]

[0047] Where m is the corresponding resonance order; E is the elastic modulus of the grounding conductor. When the grounding conductor is corroded, the conductor radius changes, and the natural frequency difference Δw of the conductor before and after corrosion is cm for:

[0048]

[0049] Where r1 and r2 are the radii of the grounded conductor before and after corrosion. The natural frequency of the metal conductor w cm Re(Z(w)) resonant original frequency f of the electromechanical impedance system m The relationship is:

[0050]

[0051] Then there is

[0052] In the formula, f 0,m and f Δ,m The original resonant frequency of the electromechanical impedance system when Δr=0 and Δr≠0 respectively; k m is the model parameter. When m is constant, Δf m It is linearly related to Δr, and k m As m increases, it increases. Since the above formula is only accurate when the aspect ratio of the metal conductor is infinite, it is impossible to use the above formula to directly obtain k m The present invention uses finite element simulation technology to establish a metal conductor corrosion model and obtains k m Value is the key technology.

[0053] As a preferred solution of this embodiment, the model parameter k is solved by finite element simulation and least square method. m Specifically, the finite element simulation software is used to establish the grounding conductor under different Δr and extract its Re(Z(w)) resonant original frequency f m Then, the least square method is used to find f m Perform linear fitting with Δr to solve the model parameter k m .

[0054] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0055] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

[0056] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of electromechanical impedance uniform corrosion evaluation methods for grounding conductors of transmission towers under the inspiration of the present invention. All equivalent changes and modifications made within the scope of the invention application of the present invention should fall within the scope of the present invention.

Claims

1. A method for evaluating uniform corrosion of electromechanical impedance of a grounding conductor of a transmission tower, characterized in that: The change in the radius of the grounding conductor Δr is used as a corrosion parameter to evaluate the corrosion degree of the grounding conductor. Based on the original resonance frequency f of the real part of the system electromechanical impedance m The model with corrosion parameter Δr is simulated by finite element simulation technology and least square method to find the model parameter k m Solve it; then use the measured f m Substitute Δr into the model to predict the corrosion degree of the grounding conductor.

2. The method for evaluating uniform corrosion of electromechanical impedance of a transmission tower grounding conductor according to claim 1, characterized in that: The method of using the ground conductor radius change Δr as a corrosion parameter to evaluate the corrosion degree of the ground conductor is specifically: Under natural conditions, the corrosion degree of the metal grounding conductor of the transmission tower in the soil due to electrochemical corrosion is calculated from the loss mass m l characterization, quantitatively estimated by Faraday’s law, and further converted into radius reduction Δr; Where r1 and r2 are the radii of the grounding conductor before and after corrosion, respectively; l is the conductor length; ρ is the conductor density; Δr = r1-r2.

3. The method for evaluating uniform corrosion of electromechanical impedance of a grounding conductor of a transmission tower according to claim 1, characterized in that: The original resonance frequency f based on the real part of the system electromechanical impedance m The model with the corrosion parameter Δr is as follows: Under the asymmetric sensor arrangement, when the radius r of the ground conductor changes, the bending vibration natural frequency w of the ground conductor is cm Changes, thereby affecting the real part of the system electromechanical impedance Re(Z(w)) resonant original frequency f m ; Change of the original resonance frequency of the real part of the electromechanical impedance Re(Z(w)) before and after corrosion Δf m for: In the formula, f 0，m and f Δ，m The original resonant frequency of the electromechanical impedance system when Δr = 0 and Δr ≠ 0 respectively; m is the corresponding resonance order; E is the elastic modulus of the grounding conductor; k m is the model parameter; since the above formula is only accurate when the aspect ratio of the metal conductor is infinite, the metal conductor corrosion model is established using finite element simulation technology to obtain k m value.

4. The method for evaluating uniform corrosion of electromechanical impedance of a transmission tower grounding conductor according to claim 1, characterized in that: The finite element simulation technology and the least square method are used to calculate the model parameter k m The specific solution is as follows: the grounding conductor under different Δr is established by finite element simulation software to extract its Re(Z(w)) resonant original frequency f m Then, the least square method is used to find f m Perform linear fitting with Δr to solve the model parameter k m .

5. The method for evaluating uniform corrosion of electromechanical impedance of a grounding conductor of a transmission tower according to claim 1, characterized in that: During the measurement process, a single piezoelectric ceramic sheet is first pasted on the top of the grounding conductor of the transmission tower to be tested to form an asymmetric sensor arrangement. The grounding conductor and the piezoelectric ceramic sheet together constitute an electromechanical impedance system. Then, the electromechanical impedance of the system is measured to obtain the real part of the total impedance Re(Z(w)) of the electromechanical system. The resonant frequency f in the uncorroded state is read through Re(Z(w)). 0，m ; The specific parameters of the grounding conductor and the piezoelectric ceramic sheet are input into the finite element simulation software, and a finite element simulation model is established to obtain the Re(Z(w)) of the grounding conductor under different Δr. Then, its resonant frequency f is read through Re(Z(w)). m , calculate Δf under different Δr m ; Δf m Perform the least squares linear fitting with Δr to obtain the model parameter k m , get the numerical model f m =k m Δr.

6. The method for evaluating uniform corrosion of electromechanical impedance of a grounding conductor of a transmission tower according to claim 5, characterized in that: The specific parameters of the grounding conductor and the piezoelectric ceramic sheet include: Specific parameters of the grounding conductor to be tested, including: initial length l, initial radius r, elastic modulus E and density ρ; And the specific parameters of the piezoelectric ceramic sheets used, including: length, width, thickness, density, piezoelectric stress coefficient and relative dielectric constant coefficient.

7. The method for evaluating uniform corrosion of electromechanical impedance of a grounding conductor of a transmission tower according to claim 5, characterized in that: When the grounding conductor is buried in the soil for a certain number of years and its corrosion degree needs to be measured, the resonant frequency f is measured again. Δ，m , calculate Δf m ; Its Δf m Substitute it into the established model to predict its corrosion parameter Δr; and combine it with the power grid standard to determine whether the grounding conductor needs to be dug up for inspection.

8. An electromechanical impedance uniform corrosion assessment device for a transmission tower grounding conductor, characterized in that: The invention comprises an electromechanical impedance system and a measuring device: a single piezoelectric ceramic sheet is pasted on the top of the grounding conductor of the transmission tower to be tested to form an asymmetric sensor arrangement, and the grounding conductor and the piezoelectric ceramic sheet together constitute the electromechanical impedance system; the measuring device is used to measure the real part of the total impedance Re(Z(w)) of the electromechanical system, and read the resonant frequency f in the uncorroded state through Re(Z(w)). 0,m The specific parameters of the grounding conductor and the piezoelectric ceramic sheet are input into the finite element simulation software, and a finite element simulation model is established to obtain the Re(Z(w)) of the grounding conductor under different Δr. Then, the resonant frequency f is read through Re(Z(w)). m , calculate Δf under different Δr m ; Δf m Perform the least squares linear fitting with Δr to obtain the model parameter k m , get the numerical model f m =k m Δr.

9. The method for evaluating uniform corrosion of electromechanical impedance of a grounding conductor of a transmission tower according to claim 8, characterized in that: The measuring equipment includes a PC and an AD5933 impedance analysis board, and the AD5933 impedance analysis board is used to measure and obtain the real part of the total impedance Re(Z(w)) of the electromechanical system.

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