A wind-induced vibration fatigue test method for composite post insulators

Abstract

The application provides a wind-induced vibration fatigue test method for a composite post insulator, comprising the following steps: determining an equivalent displacement cycle amplitude and a cumulative cycle number corresponding to the equivalent displacement cycle amplitude of a loading vibration fatigue test based on wind speed statistical information of a target station; performing a fatigue test on the composite post insulator by applying a vibration load with a preset frequency; and determining whether the composite post insulator is fatigue failed by performing a hammering test on the composite post insulator after the fatigue test. The fatigue test parameters of the composite post insulator fatigue test are calculated based on real wind field working condition data, the composite post insulator can be accurately simulated for fatigue test, the accuracy and efficiency of evaluating the long-term safe operation of the composite post insulator in different complex wind environments are realized, and the use safety of the composite post insulator in the key equipment of the converter station is ensured.

Description

Technical Field

[0001] This invention relates to the field of power equipment reliability testing technology, and specifically provides a method for wind-induced vibration fatigue testing of composite post insulators. Background Technology

[0002] Composite post insulators are key components of converter stations, and their performance directly affects the safe and stable operation of power equipment systems. Due to their slender and flexible structural characteristics, they are prone to fatigue damage under wind vibration. With the large-scale development of clean energy sources such as wind power and photovoltaic power, converter station equipment needs to operate reliably for a long time in complex wind environments, which places higher demands on the fatigue resistance of composite post insulators.

[0003] Currently, there is a lack of fatigue testing methods that can realistically simulate wind-induced vibration environments and dynamically monitor structural damage, resulting in insufficient accuracy in equipment fatigue life assessment. In other words, existing fatigue tests do not yield ideal results for wind-induced vibration testing of composite post insulators. Summary of the Invention

[0004] The purpose of this invention is to solve the problem that existing fatigue testing methods do not yield ideal results in evaluating the fatigue performance of composite post insulators.

[0005] The objective of this invention is achieved through the following technical solution: The invention provides a method for wind-induced vibration fatigue testing of composite post insulators, comprising: determining the equivalent displacement cycle amplitude and the cumulative number of cycles corresponding to the equivalent displacement cycle amplitude based on wind speed statistics of the target station; applying a vibration load of a preset frequency to the composite post insulator to conduct a fatigue test based on the equivalent displacement cycle amplitude and the cumulative number of cycles; and conducting a hammer test on the composite post insulator after the fatigue test to determine whether the composite post insulator has failed due to fatigue.

[0006] Preferably, determining the equivalent displacement cycle amplitude and the cumulative number of cycles corresponding to the equivalent displacement cycle amplitude based on the wind speed statistics of the target station includes: acquiring wind speed distribution data from the wind speed statistics, processing it using a wind field simulation method to generate a total wind speed time history; calculating the displacement time history response based on the total wind speed time history and the MDOF structural model, converting the displacement time history response into a discrete cyclic load using a rainflow counting method, and correcting the discrete cyclic load using Goodman's algorithm to obtain the equivalent displacement cycle amplitude; and determining the cumulative number of cycles corresponding to the equivalent displacement cycle amplitude within a preset service life based on the wind speed statistics and the equivalent displacement cycle amplitude.

[0007] Preferably, the step of obtaining the wind speed distribution data from the wind speed statistics and processing it using a wind field simulation method to generate the fluctuating wind speed time history includes: The equivalent wind speed in the wind speed distribution data is selected, and the pulsating wind energy distribution is calculated using the Davenport wind speed power spectrum. A vertical spatial correlation model is established by combining the Davenport coherence function. The noise covariance matrix is ​​constructed by numerical integration, and the total wind speed time history is generated by combining the Cholesky decomposition with the AR model. The formula for calculating the Davenport wind speed power spectrum is:

[0008] In the formula, S vi For spatial points where the turbulence scale remains constant along the height Horizontal fluctuating wind speed power spectrum at the location. For wind frequency, For spatial points i exist z i Average wind speed at altitude z i For spatial points At what altitude? The surface damping coefficient; The formula for establishing the vertical spatial correlation model using the Davenport coherence function is as follows:

[0009] In the formula, γ ij For Davenport's vertical spatial coherence function, z i , z j They are spatial points i and j height, C z V is the vertical attenuation coefficient. i V j They are spatial points i and j The average wind speed; The noise covariance matrix is:

[0010]

[0011] The formula for the total wind speed time history is:

[0012] In the formula, V total,i (t ) is a spatial point The total wind speed time history. V mean,i ( t () represents the average wind speed. v i ( t ) is a spatial point i The pulsed wind speed time history.

[0013] Preferably, the step of calculating and obtaining the displacement time history response based on the total wind speed time history and the MDOF structural model includes: obtaining the wind load time history acting on the composite post insulator according to the total wind speed time history and the wind load calculation formula; constructing a model of the composite post insulator according to the wind load time history and the MDOF structural model; and performing numerical calculation on the constructed model to obtain the displacement sequence of the displacement time history response. The formula for the wind load time history is:

[0014] In the formula, air density, The drag coefficient is... The windward area of ​​the specimen; The formula for constructing the model is:

[0015] In the formula, M Let C be the mass diagonal matrix, C be the damping matrix obtained using the Rayleigh damping form, and K1 be the stiffness tridiagonal matrix. u(t) , , These are displacement, velocity, and acceleration vectors, respectively.

[0016] Preferably, the method of converting the displacement time history response into a discrete cyclic load using the rainflow counting method includes: extracting and reconstructing extreme points in the displacement sequence of the displacement time history response to obtain an extreme value sequence containing complete peaks and valleys at the beginning and end, wherein the displacement sequence includes amplitude and mean; establishing a stack data structure and implementing a three-point loop judgment mechanism, sequentially traversing the extreme value sequence, and pushing each extreme point onto the stack; when there are no less than three elements in the stack, extracting the three consecutive extreme points at the top of the stack and calculating adjacent amplitudes R1 and R2; if R1 is greater than R2, determining that the intermediate point forms a complete closed loop, recording the amplitude and mean, and removing the intermediate point from the stack, iterating this process until the three points at the top of the stack no longer meet the extraction conditions; after completing the traversal of the extreme value sequence, pairing the remaining extreme points in the stack to form a semi-loop, and outputting a matrix containing the amplitude, the mean, and a loop type identifier to complete the conversion of the displacement time history into the discrete cyclic load.

[0017] Preferably, the equivalent displacement cyclic amplitude is obtained by correcting the discrete cyclic load using Goodman's method, and the correction conversion relationship is as follows:

[0018] In the formula, Δ eq The equivalent displacement cyclic amplitude of the composite post insulator without initial displacement. Δ The amplitude (or initial cyclic range) in the discrete cyclic load. μ The mean (or original displacement) in the discrete cyclic load. μ μ This represents the maximum permissible displacement at the top of the composite post insulator.

[0019] Preferably, determining the cumulative number of cycles corresponding to the equivalent displacement cycle amplitude within a preset service life based on the wind speed statistics and the equivalent displacement cycle amplitude includes: obtaining the equivalent wind speed and the average annual occurrence duration corresponding to the equivalent wind speed from the wind speed statistics; counting the number of cycles experienced by the equivalent displacement cycle amplitude within a single simulation duration; and calculating the cumulative number of cycles within the preset service life based on the average annual occurrence duration and the number of cycles experienced, using the following formula:

[0020] In the formula, For the first l The cumulative number of cycles corresponding to the equivalent displacement cycle amplitude of the level. The first equivalent wind speed indivual, The total number of equivalent wind speeds simulated. N 短时,w The number of cycles experienced within the w-th equivalent displacement cycle amplitude. T 年均,,w For the first The annual average duration of occurrence of the aforementioned equivalent wind speed. T 短时,w For the first The duration of a single simulation for each equivalent wind speed, Y The preset service life is defined as follows.

[0021] Preferably, the fatigue test of applying a vibration load of a preset frequency to the composite post insulator based on the equivalent displacement cycle amplitude and the cumulative number of cycles includes: vertically fixing the composite post insulator in a test device; installing a preset mass counterweight, a displacement sensor, and a force sensor in the top region of the composite post insulator; arranging a strain sensor in the bottom region of the composite post insulator; applying a displacement load of a preset frequency to the composite post insulator; and conducting a fatigue test according to the equivalent displacement cycle amplitude and the cumulative number of cycles.

[0022] Preferably, the step of performing a hammer impact test on the composite post insulator after the fatigue test to determine whether the composite post insulator has failed due to fatigue includes: obtaining the fundamental frequency attenuation rate of the composite post insulator using the hammer impact test; if the fundamental frequency attenuation rate is ≥ a preset threshold, then the composite post insulator is determined to have failed and the test is terminated.

[0023] Preferably, the preset threshold value ranges from 5% to 15%.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a method for wind-induced vibration fatigue testing of composite post insulators, comprising: determining the equivalent displacement cycle amplitude and the cumulative number of cycles corresponding to the equivalent displacement cycle amplitude based on wind speed statistics of the target station; applying a vibration load of a preset frequency to the composite post insulator for fatigue testing based on the equivalent displacement cycle amplitude and the cumulative number of cycles; and conducting a hammer impact test on the composite post insulator after the fatigue test to determine whether the composite post insulator has failed due to fatigue. By calculating the fatigue test parameters of the composite post insulator fatigue test from real wind field operating data, accurate simulation fatigue testing of the composite post insulator can be performed, realizing the accuracy and efficiency of evaluating the long-term safe operation of the composite post insulator under different complex wind environments, thereby ensuring the safety of the composite post insulator in the use of key equipment in converter stations. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the loading of the post insulator during the fatigue test of this invention; Figure 2 This is a schematic diagram showing the arrangement of fatigue test data acquisition points on the post insulator in the fatigue test of this invention; Figure 3 for Figure 2 Schematic diagram of strain gauge arrangement at section AA; Figure 4 for Figure 2 Schematic diagram of the position sensor arrangement at the BB section; Figure 5This is a flowchart of the main steps of the wind-induced vibration fatigue test method for composite post insulators of the present invention.

[0026] Reference numerals: 1-Dynamic actuator; 2-Actuator connector; 3-Specimen connector; 4-Insulator specimen; 5-Machining support; 6-Out-of-plane protective frame; 7-First displacement sensor; 8-Second displacement sensor; 9-Accelerometer; 10-Force sensor; 11-First strain gauge; 12-Second strain gauge; 13-Third strain gauge; 14-Fourth strain gauge. Detailed Implementation

[0027] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0028] It should be noted that in the description of this invention, terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," indicating directional or positional relationships, are based on the directional or positional relationships shown in the accompanying drawings. These are merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0029] like Figure 5 As shown, the present invention provides a method for wind-induced fatigue testing of composite post insulators, comprising: S1. Based on the wind speed statistics of the target station, determine the equivalent displacement cycle amplitude and the cumulative number of cycles corresponding to the equivalent displacement cycle amplitude in the loading vibration fatigue test. S2. Based on the equivalent displacement cycle amplitude and cumulative cycle number, fatigue tests are conducted on composite post insulators by applying a vibration load of a preset frequency. S3. After the fatigue test, a hammer test is performed on the composite post insulator to determine whether the composite post insulator has failed due to fatigue.

[0030] By extrapolating fatigue test parameters for composite post insulators from real wind farm operating data, accurate wind-induced fatigue testing of composite post insulators can be conducted. This enables the assessment of the accuracy and efficiency of long-term safe operation of composite post insulators under different complex wind environments, thereby ensuring the safety of composite post insulators in key equipment of converter stations.

[0031] Specifically, step S1 includes: S11. Obtain wind speed distribution data from wind speed statistics and use wind field simulation methods to generate total wind speed time history; S12. Based on the total wind speed time history and the MDOF (Multiple Degrees of Freedom) structural model, the displacement time history response is calculated and obtained. The displacement time history response is transformed into a discrete cyclic load using the rainflow counting method. The equivalent displacement cyclic amplitude is obtained by correcting the discrete cyclic load using Goodman. S13. Based on wind speed statistics and equivalent displacement cycle amplitude, determine the cumulative number of cycles corresponding to the equivalent displacement cycle amplitude within the preset service life.

[0032] In step S11, the equivalent wind speed from the wind speed statistics of the target station is selected, the Davenport wind speed power spectrum is used to calculate the fluctuating wind energy distribution, and a vertical spatial correlation model is established by combining the Davenport coherence function. The noise covariance matrix is ​​constructed by numerical integration, and after Cholesky decomposition, the total fluctuating wind speed time history is generated by combining the AR model (AutoRegressive Model).

[0033] First, the average wind speed at a given height is calculated using the exponential law:

[0034] In the formula, V ref For reference height z ref The average wind speed at a point (usually 10m) is taken. α The surface roughness coefficient is 0.12 for Class A landforms in this case.

[0035] The formula for calculating the Davenport wind speed power spectrum is:

[0036] In the formula, S vi For spatial points where the turbulence scale remains constant along the height Horizontal fluctuating wind speed power spectrum at the location. For wind frequency, For spatial points i exist z i Average wind speed at altitude z i For spatial points At what altitude? is the surface damping coefficient.

[0037] The formula for establishing the vertical spatial correlation model using the Davenport coherence function is as follows:

[0038] In the formula, γ ij For Davenport's vertical spatial coherence function, z i , z j They are spatial points i and j height, C z V is the vertical attenuation coefficient. i V j They are spatial points i and j The average wind speed.

[0039] For each spatial point i Its autocorrelation function R i (τ) is obtained through the inverse Fourier transform of the power spectral density:

[0040] In the formula, This refers to time lag. This is the cutoff frequency, typically 2Hz.

[0041] spatial point i and j cross-covariance function between R N,ij for:

[0042] S vj For spatial points where the turbulence scale remains constant along the height The horizontal fluctuating wind speed power spectrum at the location, and the cross-covariance between all spatial points constitute the noise covariance matrix. .

[0043] right R N Perform symmetry transformation and ensure positive definiteness:

[0044] In the formula, ε Small positive number, I It is an identity matrix.

[0045] The lower triangular matrix is ​​obtained through Cholesky decomposition. :

[0046] usep An autoregressive model describes the time history of fluctuating wind speed:

[0047] In the formula, v i (t) is a spatial point i At any moment t The pulsed wind speed time-course. ψ i,k For AR coefficient vectors, w i (t) represents the white noise at each spatial point i , Δt For time step.

[0048] Solving the AR coefficient vector using the Yule-Walker equation :

[0049] spatial point i residual variance σ i 2 for:

[0050] Set the initial time step so that the fluctuating wind speed at all spatial points is zero at t=0. For time steps n>p+1, perform the following steps: 1. For each spatial point Calculate AR predictions based on historical data:

[0051] 2. Generate a noise vector with a specified covariance. :

[0052] in η (n) is a vector consisting of independent standard normal random variables.

[0053] 3. Update the pulsed wind speed time history for each spatial point:

[0054] To verify the accuracy of the simulated fluctuating wind speed time history, the power spectral density of the simulated time history needs to be compared with the target Davenport spectrum. Specifically, the power spectral density of the simulated fluctuating wind speed time history needs to be calculated. With the target Davenport spectrum The comparison needs to be performed, and the spatial coherence function of the simulated time histories needs to be calculated. Coherence function with the target The comparison is made using the following specific evaluation indicators:

[0055]

[0056] The above indicators reflect the relative error between the simulated spectrum and the target spectrum in terms of overall energy distribution; the smaller the value, the higher the matching degree. E spectral This refers to the relative error of the power spectrum. E coh total The relative error of the spatial coherence function; N pair This represents the total number of point pairs in space.

[0057] After verification, the accuracy requirements were met. The formula for obtaining the total wind speed time history by superimposing the average wind speed is as follows:

[0058] In the formula, V total,i For spatial points Total wind speed time history V mean,i ( t () represents the average wind speed.

[0059] In step S12, the displacement time history response is calculated based on the total wind speed time history and the MDOF model, including: Based on the total wind speed time history and wind load calculation formula, the wind load time history acting on the composite post insulator is obtained. A model of the composite post insulator is constructed based on the wind load time history and MDOF. The displacement sequence of the displacement time history response is obtained by numerically solving the constructed model.

[0060] First, based on the total wind speed time history and wind load calculation formula, the wind load time history acting on the specimen is obtained, and its calculation formula is as follows:

[0061] In the formula, air density, The drag coefficient is... The windward area of ​​the specimen.

[0062] The MDOF model formula for constructing post insulators is as follows:

[0063] In the formula, M Let C be the mass diagonal matrix, C be the damping matrix obtained using the Rayleigh damping form, and K1 be the stiffness tridiagonal matrix. u(t) , , These are displacement, velocity, and acceleration vectors, respectively.

[0064] More specifically, M=diag(m 1 ,m 2 ,...,m N ) ,in m N For the first N Concentrated mass of the floors N This represents the total number of degrees of freedom in the system. Where C = α M+ β K1, where α For mass damping coefficient, β This is the stiffness damping coefficient. α and β The specific calculation formulas are as follows:

[0065]

[0066] In the formula, For the damping ratio, The first The angular frequencies of the mode shapes are usually taken as the angular frequencies of the first and second mode shapes. This invention uses these two frequencies to determine the damping parameters.

[0067] in

[0068] In the formula, k N This refers to the interlayer stiffness.

[0069] Then, to numerically solve the dynamic equations of this structure, a velocity vector is introduced. The second-order differential equation system of the above model formula can be rewritten in first-order form:

[0070] Considering the initial static wind load effect, calculate the initial displacement. u 0= K -1 F(0), set the initial state The state equation is solved numerically by using the variable step-size Runge-Kutta method to obtain the state vector. The time history is used to extract the displacement time history response at the top of the specimen. u top (t) That is, discrete time series This displacement response sequence contains complete dynamic information such as amplitude and frequency, which can be directly used as input for subsequent stress analysis, rainflow counting, and fatigue life assessment.

[0071] Then, the rainflow counting method is used to perform cyclic amplitude statistics on the above displacement time history response. The purpose is to decompose the complex displacement time history response into simple displacement cycles and statistically obtain discrete cyclic loads. The specific steps include: Step a: Extract and reconstruct extreme points from the displacement sequence of the input displacement time history response to obtain an extreme value sequence containing complete peaks and valleys at the beginning and end, ensuring that the data starts and ends at extreme points to meet the boundary condition requirements of the rainflow counting method. Step b: Establish a stack data structure and implement a three-point loop judgment mechanism, sequentially traversing the extreme value sequence and pushing each point onto the stack. Here, the stack is a data container used to temporarily store extreme points and implement the reverse extraction of nested loops. When there are at least three elements in the stack, extract the top three consecutive extreme values ​​and calculate the adjacent amplitudes. R 1 and R 2, if R 1 greater than R If the intermediate points form a complete closed loop, record the amplitude and mean of the loop and remove the intermediate points from the stack. Iterate this process until the three points at the top of the stack no longer meet the extraction conditions. Specifically, the extreme value sequence obtained in step a is traversed sequentially, and each extreme point (displacement value) is pushed onto the stack in turn. Here, the stack is a data container used to temporarily store extreme points and implement the reverse extraction of nested loops. When there are at least three elements in the stack, the top three consecutive extreme points are extracted. P n-2 (recorded as) P n-2 , P n-1 , P n , P (The displacement value at the extreme point) is used to calculate the adjacent amplitudes. R 1=| P n - P n-1 |、 R 2=| P n-1 - P n-2 |; like R 1> R 2. Then determine the midpoint. P n-1 With the two points before and after P n-2 , P nA complete closed loop is formed, wherein: the cyclic amplitude is taken from the displacement difference between the extreme points at both ends of the closed loop (| P n - P n-2 |), the mean is taken from the average displacement of the extreme points at both ends of the closed loop ( P n + P n-2 After recording the amplitude and mean of the loop () / 2, remove the intermediate point from the stack. P n-1 Iterate this process until the top three points of the stack are no longer satisfied. R 1> R Extraction conditions for 2.

[0072] Step c: After completing the extreme value sequence traversal, if the remaining extreme points in the stack cannot form a complete closed loop through the three-point cycle determination in step b, then these remaining extreme points are paired adjacently to form a semi-cycle. A semi-cycle refers to a single peak-valley or valley-peak fluctuation process consisting of only two adjacent extreme points, which does not complete a complete load closure and is counted as half a cycle. Simultaneously, the complete cycles identified in step b are integrated. A complete cycle refers to a closed peak-valley-peak or valley-peak-valley fluctuation process consisting of three or more extreme points, which completes a complete loading-unloading-reverse loading-reverse unloading load cycle. The output is a matrix containing amplitude, mean, and cycle type identifiers. The cycle type identifiers indicate that a complete cycle is marked as 1 and a semi-cycle as 0.5, achieving a complete conversion from displacement time history response to discrete cyclic load. The amplitude, mean, and cycle type identifiers are all detailed data of non-zero average stress cycles.

[0073] Finally, the Goodman linear correction criterion is used to convert the above non-zero mean stress cycles into equivalent displacements under equivalent zero mean stress conditions. The final equivalent displacement cycle amplitude is then output for fatigue test loading. The conversion relationship is expressed as:

[0074] In the formula, Δ eq The equivalent displacement cycle amplitude of the specimen without initial displacement. Δ The amplitude (initial loop range) output in step c above. μ The average value (original displacement) output from step c above. μ μ This represents the maximum permissible displacement at the top of the specimen.

[0075] Step S13 specifically includes: S131. Obtain the equivalent wind speed and the annual average occurrence duration corresponding to the equivalent wind speed from the wind speed statistics; S132. Statistical analysis of the number of cycles experienced by the equivalent displacement cyclic amplitude within a single simulation duration; S133. Calculate the cumulative number of cycles within the preset service life based on the average annual occurrence duration and the number of cycles experienced. The calculation formula is as follows:

[0076] In the formula, For the first l The cumulative number of cycles corresponding to the equivalent displacement cycle amplitude. The equivalent wind speed of the first indivual, The total number of equivalent wind speeds simulated. N 短时,w Let w be the number of cycles experienced within the w-th equivalent displacement cycle amplitude. T 年均,,w For the first The average annual duration of occurrence of an equivalent wind speed, T 短时,w For the first The duration of a single simulation for an equivalent wind speed (10 minutes is taken by default for any wind speed). Y The preset service life.

[0077] After the above steps, the equivalent displacement cycle amplitude and the cumulative number of cycles corresponding to the equivalent displacement cycle amplitude can be calculated for the fatigue test of the composite post insulator under the working conditions of the target station.

[0078] When the equivalent wind speed in the wind speed statistics of the target station includes multiple levels, the equivalent displacement cycle amplitude of each level corresponds to the cumulative cycle number of the corresponding level.

[0079] For example, take the wind speed statistics of a ±800kV converter station in a certain area. Table 1 shows the wind speed range at a height of 10m above the ground in this area from 2022 to 2024.

[0080] Table 1

[0081] According to step S11, four levels of equivalent wind speed are selected: 5m / s, 10m / s, 15m / s, and 20m / s. The total wind speed time history is obtained after processing and calculation.

[0082] Based on step S12, the displacement time history response of the composite post insulator under 10-minute wind load is obtained based on the total wind speed time history and the MDOF structural model. The equivalent displacement cycle amplitude is obtained by rainflow counting and Goodman correction.

[0083] Finally, according to step S13, during the simulation of pulsating wind, the number of cycles obtained is the result of the simulation duration under the corresponding wind speed time history, thus obtaining the data in Table 2.

[0084] Table 2 is a comparison table of the number of cycles of the top displacement amplitude of the composite post insulator under 10-minute wind load, obtained from wind field simulation.

[0085] Table 2

[0086] Finally, based on steps S131-S132, the number of cycles the post insulator needs to withstand within a typical preset service life is calculated according to the average annual occurrence duration and the number of cycles experienced, i.e., the cumulative number of cycles.

[0087] Table 3

[0088] Table 3 is a comparison table of the equivalent displacement cycle amplitude and the corresponding cumulative number of cycles required for fatigue testing of composite post insulators at the preset service life.

[0089] Furthermore, step S2 specifically includes: S21. The composite post insulator is vertically fixed in the test device. A preset mass counterweight is installed on the top of the composite post insulator. Displacement sensors and force sensors are arranged at the top of the composite post insulator, and strain sensors are arranged at the root of the composite post insulator. S22. Apply a displacement load of a preset frequency to the composite post insulator and perform a fatigue test according to the equivalent displacement cycle amplitude and cumulative cycle number.

[0090] It should be noted that a hammer test was performed on the composite post insulator before the fatigue test was performed to obtain the initial fundamental frequency of the composite post insulator.

[0091] Specifically, such as Figure 1 As shown, during the wind-induced vibration fatigue test of the composite post insulator of the present invention, the insulator specimen 4 is specifically installed in the test device as follows: the bottom end of the insulator specimen 4 is vertically fixed by the processing support 5 at the bottom of the device, and the top of the insulator specimen 4 is connected to the dynamic actuator 1 via the actuator connector 2 of the test device. A preset mass counterweight is installed on the insulator specimen 4 to replace the mass of the equalizing ring in actual service. An external protective frame 6 is vertically installed between the insulator specimen 4 and the dynamic actuator 1. After installation, the coordinate system of the insulator specimen 4 is as follows: the X-axis is along the direction of the post insulator generatrix of the insulator specimen 4; the Y-axis is parallel to the actuator load direction in the horizontal plane; and the Z-axis is perpendicular to the Y-axis in the horizontal plane.

[0092] like Figure 2 and Figure 3 As shown, at the top BB section position of the insulator specimen 4, a first displacement sensor 7 and an accelerometer 9 are set on the left side of the Y-axis of the coordinate system, a second displacement sensor 8 is set on the Z-axis, and a force sensor 10 is set at the actuator connector 2.

[0093] like Figure 2 and Figure 4 As shown, four sets of strain gauges—first strain gauge 11, second strain gauge 12, third strain gauge 13, and fourth strain gauge 14—are equidistantly arranged in a ring at the AA section of the root of the insulator specimen 4. The first strain gauge 11 and the third strain gauge 13 are symmetrically arranged along the Z-axis of the coordinate system, while the second strain gauge 12 and the fourth strain gauge 14 are symmetrically arranged along the Y-axis of the coordinate system.

[0094] It should be noted that the first displacement sensor 7, the second displacement sensor 8, the accelerometer 9, the force sensor 10, the first strain gauge 11, the second strain gauge 12, the third strain gauge 13, and the fourth strain gauge 14 are all electrically connected to the information acquisition module in the test device to collect the corresponding data information in the fatigue test in real time.

[0095] Based on the installation of the aforementioned insulator specimen 4 on the test apparatus, a pre-set frequency, constant amplitude half-sine wave displacement load was applied to the composite post insulator. Wind-induced vibration fatigue tests were conducted according to the determined equivalent displacement cycle amplitude and cumulative cycle number. The pre-set frequency was based on the initial fundamental frequency of the insulator specimen measured by the hammer impact test. Considering the common vibration frequency range of insulators under wind load in engineering practice, the selectable range for the pre-set frequency was determined to be 1.0Hz–2.0Hz. Taking into account the dynamic output characteristics of the test loading equipment and the fatigue performance testing requirements of the specimen, the final pre-set frequency was selected as 1.4Hz. This frequency is within the pre-set frequency range and deviates from the initial resonant frequency of the specimen.

[0096] When the equivalent displacement cycle amplitude and cumulative cycle number include multiple levels, fatigue testing should begin with the level with the smaller equivalent displacement cycle amplitude.

[0097] For example, as shown in Table 3, fatigue tests are first conducted with an equivalent displacement cycle amplitude of ±10 mm, according to the corresponding equivalent displacement cycle amplitude and cumulative number of cycles.

[0098] Furthermore, step S3 includes: A hammer impact test was performed on the composite post insulator to obtain the fundamental frequency attenuation rate of the composite post insulator, and the structural state of the composite post insulator after the hammer impact test was checked. If the fundamental frequency attenuation rate is greater than or equal to the preset threshold, or if visible cracks or fractures appear in the composite post insulator, the composite post insulator is deemed to have failed and the test is terminated. The preset threshold ranges from 5% to 15%.

[0099] If the equivalent displacement cycle amplitude and cumulative cycle count include multiple levels, then proceed to step S21 to continue the fatigue test for the next level of equivalent displacement cycle amplitude until all levels of cycles are completed.

[0100] For example, after each fatigue test of the composite post insulator is completed, measuring the equivalent displacement cycle amplitude and cumulative number of cycles, a hammer impact test is performed to detect the fundamental frequency attenuation rate and to check the structural condition of the specimen. The preset threshold is 10%. If the fundamental frequency attenuation rate is ≥10% or visible cracks or fractures appear, the composite post insulator is judged to have failed due to fatigue and the test is terminated.

[0101] Otherwise, continue to the next level of loading until all cycles are completed. That is, according to the equivalent displacement cycle amplitude levels of ±20mm, ±30mm, ±40mm, ±50mm, and ±60mm, jump to step S21 in sequence to continue loading the corresponding equivalent displacement cycle amplitude and cumulative number of cycles for fatigue testing until all cycles are completed.

[0102] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of the claims of the present invention pending approval.

Claims

1. A method for wind-induced vibration fatigue testing of composite post insulators, characterized in that, Includes the following steps: Based on the wind speed statistics of the target station, the equivalent displacement cycle amplitude and the cumulative number of cycles corresponding to the equivalent displacement cycle amplitude are determined for the loading vibration fatigue test. Based on the equivalent displacement cycle amplitude and the cumulative number of cycles, a vibration load of a preset frequency is applied to the composite post insulator to conduct a fatigue test. After the fatigue test, the composite post insulator is subjected to a hammer impact test to determine whether the composite post insulator has failed due to fatigue.

2. The method for wind-induced vibration fatigue testing of composite post insulators according to claim 1, characterized in that, The determination of the equivalent displacement cycle amplitude and the cumulative number of cycles corresponding to the equivalent displacement cycle amplitude based on the wind speed statistics of the target station includes: Obtain the wind speed distribution data from the wind speed statistics, and use a wind field simulation method to process and generate the total wind speed time history; The displacement time history response is obtained by solving the total wind speed time history and the MDOF structural model. The displacement time history response is converted into a discrete cyclic load using the rainflow counting method. The equivalent displacement cyclic amplitude is obtained by correcting the discrete cyclic load using Goodman. Based on the wind speed statistics and the equivalent displacement cycle amplitude, the cumulative number of cycles corresponding to the equivalent displacement cycle amplitude within a preset service life is determined.

3. The method for wind-induced vibration fatigue testing of composite post insulators according to claim 2, characterized in that, The step of obtaining wind speed distribution data from the wind speed statistics and processing it using a wind field simulation method to generate a fluctuating wind speed time history includes, The equivalent wind speed in the wind speed distribution data is selected, and the pulsating wind energy distribution is calculated using the Davenport wind speed power spectrum. A vertical spatial correlation model is established by combining the Davenport coherence function. The noise covariance matrix is ​​constructed by numerical integration, and the total wind speed time history is generated by combining the Cholesky decomposition with the AR model. The formula for calculating the Davenport wind speed power spectrum is: In the formula, S vi For spatial points where the turbulence scale remains constant along the height Horizontal fluctuating wind speed power spectrum at the location. For wind frequency, For spatial points i exist z i Average wind speed at altitude z i For spatial points Altitude, The surface damping coefficient; The formula for establishing the vertical spatial correlation model using the Davenport coherence function is as follows: In the formula, γ ij For Davenport's vertical spatial coherence function, z i , z j They are spatial points i and j height, C z V is the vertical attenuation coefficient. i V j They are spatial points i and j The average wind speed; The noise covariance matrix is: The formula for the total wind speed time history is: In the formula, V total,i ( t ) is a spatial point The total wind speed time history. V mean,i ( t () represents the average wind speed. v i ( t ) is a spatial point i The pulsed wind speed time history.

4. The method for wind-induced vibration fatigue testing of composite post insulators according to claim 3, characterized in that, The process of calculating and obtaining the displacement time history response based on the total wind speed time history and the MDOF structural model includes: Based on the total wind speed time history and wind load calculation formula, the wind load time history acting on the composite post insulator is obtained. Based on the wind load time history and the MDOF structural model, a model is constructed for the composite post insulator. The displacement sequence of the displacement time history response is obtained by numerically solving the constructed model. The formula for the wind load time history is: In the formula, air density, The drag coefficient is... The windward area of ​​the specimen; The formula for constructing the model is: In the formula, M Let C be the mass diagonal matrix, C be the damping matrix obtained using the Rayleigh damping form, and K1 be the stiffness tridiagonal matrix. u(t) , , These are displacement, velocity, and acceleration vectors, respectively.

5. The method for wind-induced vibration fatigue testing of composite post insulators according to claim 4, characterized in that, The method of converting the displacement time history response into a discrete cyclic load using the rainflow counting method includes: Extreme points in the displacement sequence of the displacement time history response are extracted and reconstructed to obtain an extreme value sequence containing complete peaks and valleys at the beginning and end. The displacement sequence includes amplitude and mean. A stack data structure is established and a three-point loop judgment mechanism is implemented. The extreme value sequence is traversed sequentially, and each extreme value point is pushed into the stack. When there are no less than three elements in the stack, the three consecutive extreme value points at the top of the stack are extracted and the adjacent amplitudes R1 and R2 are calculated. If R1 is greater than R2, it is determined that the intermediate point forms a complete closed loop. The amplitude and mean are recorded and the intermediate point is removed from the stack. This process is iterated until the three points at the top of the stack no longer meet the extraction conditions. After completing the extreme value sequence traversal, the remaining extreme value points in the stack are paired adjacently to form a semi-loop, and a matrix containing the amplitude, the mean, and the loop type identifier is output, thus completing the transformation of the displacement time history into the discrete cyclic load.

6. The method for wind-induced vibration fatigue testing of composite post insulators according to claim 5, characterized in that, The equivalent displacement cyclic amplitude is obtained by correcting the discrete cyclic load using Goodman's method, and the correction conversion relationship is as follows: In the formula, Δ eq This represents the equivalent displacement cyclic amplitude of the composite post insulator without initial displacement. Δ The amplitude in the discrete cyclic load. μ The mean value in the discrete cyclic load. μ μ This represents the maximum permissible displacement at the top of the composite post insulator.

7. The method for wind-induced vibration fatigue testing of composite post insulators according to claim 1, characterized in that, The step of determining the cumulative number of cycles corresponding to the equivalent displacement cycle amplitude within a preset service life based on the wind speed statistics and the equivalent displacement cycle amplitude includes: Obtain the equivalent wind speed and the annual average duration of occurrence corresponding to the equivalent wind speed from the wind speed statistics; The number of cycles the equivalent displacement cyclic amplitude experiences within a single simulation duration is counted. The cumulative number of cycles within the preset service life is calculated based on the average annual occurrence duration and the number of cycles experienced. The calculation formula is as follows: In the formula, For the first l The cumulative number of cycles corresponding to the equivalent displacement cycle amplitude of the level. The first equivalent wind speed indivual, The total number of equivalent wind speeds simulated. N 短时,w The number of cycles experienced within the w-th equivalent displacement cycle amplitude. T 年均,,w For the first The annual average duration of occurrence of the aforementioned equivalent wind speed. T 短时,w For the first The duration of a single simulation for each equivalent wind speed, Y The preset service life is defined as follows.

8. The method for wind-induced vibration fatigue testing of composite post insulators according to claim 1, characterized in that, The fatigue test, which applies a preset frequency vibration load to the composite post insulator based on the equivalent displacement cycle amplitude and the cumulative number of cycles, includes: The composite post insulator is vertically fixed in the test device. A preset mass counterweight, displacement sensor and force sensor are installed in the top area of ​​the composite post insulator, and a strain sensor is arranged in the bottom area of ​​the composite post insulator. A displacement load of a preset frequency is applied to the composite post insulator, and a fatigue test is conducted according to the equivalent displacement cycle amplitude and the cumulative number of cycles.

9. The method for wind-induced vibration fatigue testing of composite post insulators according to claim 1, characterized in that, The step of performing a hammer impact test on the composite post insulator after the fatigue test to determine whether the composite post insulator has failed due to fatigue includes: The fundamental frequency attenuation rate of the composite post insulator was obtained using a hammer impact test. If the fundamental frequency attenuation rate is greater than or equal to a preset threshold, the composite post insulator is deemed to have failed and the test is terminated.

10. The method for wind-induced vibration fatigue testing of composite post insulators according to claim 9, characterized in that, The preset threshold value ranges from 5% to 15%.

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