Method and system for damage identification of flange rubber joint of post composite insulator based on modal fingerprint

Abstract

The application discloses a kind of based on modal fingerprint's flange rubber mounting node damage identification method and system of support composite insulator, the method comprises: the modal fingerprint library of the rubber damage of flange rubber mounting node of composite insulator is established;Multiple dynamic characteristic tests are carried out on composite insulator, including: multiple dynamic characteristic parameters are obtained by multiple excitations of composite insulator in multiple directions respectively, and the corresponding relative frequency limit δ i，j Is calculated respectively;Maximum in multiple relative frequency limits δ a，j It is compared with the reduced height damage modal fingerprint library, and the overall damage degree is determined;The flexibility curvature amplitude mutation coefficient α ik Of the first three orders is calculated according to the node number of composite insulator, and the damage degree and damage position of each flange are determined;The natural frequency mutation value of multiple dynamic characteristic tests is compared with the reduced corner damage modal fingerprint library, and the specific corner direction of damage is determined.The application can quickly judge the damage of flange rubber mounting node.

Description

Technical Field

[0001] This invention relates to the field of power equipment damage identification technology, and in particular to a method and system for damage identification of flange glue joints of post composite insulators based on modal fingerprinting. Background Technology

[0002] High-voltage electrical equipment serves as the objective carrier and vital lifeline structure for the transmission, distribution, and use of electrical energy in substations and converter stations. Insulators and bushings, as the main load-bearing components of high-voltage electrical equipment, not only require excellent electrical insulation performance but also superior mechanical and environmental adaptability. Compared to traditional ceramic materials, glass fiber reinforced resin composite materials (hereinafter referred to as composite materials) possess various excellent mechanical properties, such as high specific stiffness, high specific strength, good toughness, and fatigue resistance. Furthermore, composite materials offer advantages such as ease of processing and molding, and strong design flexibility, making them an important alternative to electrical porcelain. With the continuous advancement of ultra-high-voltage and extra-high-voltage AC / DC transmission projects, many ultra-high-voltage and extra-high-voltage substations and converter stations in China have achieved comprehensive composite materialization of their electrical equipment.

[0003] However, the widespread use of composite insulators has also brought some problems. Ultra-high voltage (UHV) and extra-high voltage (EHV) substations and converter stations, as crucial hubs of the power transmission system, operate in harsh environments. The high-voltage electrical equipment within these stations is expensive and difficult to replace, resulting in long maintenance cycles and a wide-ranging impact from equipment failures. Furthermore, to meet the creepage distance requirements of UHV and EHV electrical equipment, long-cantilevered, post-type composite insulator structures have become more flexible, with lower natural frequencies and larger low-frequency swaying displacements at the top of the equipment. This makes them more sensitive to wind, earthquakes, and impacts and vibrations caused by maintenance and operation, leading to increasingly prominent faults caused by mechanical damage and vibration deformation.

[0004] Flange damage or failure is a major cause of failure in composite electrical equipment. A few scholars have only conducted full-process fatigue analysis on composite bushings with interference fit technology, predicting the lifespan of flange bonding joints. However, current research on the damage mechanisms of electrical equipment, both domestically and internationally, is still focused on ceramic electrical equipment; research on the damage mechanisms of flange bonding joints in composite electrical equipment is extremely scarce.

[0005] Composite bushings possess excellent fatigue resistance and vibration resistance. However, the flange joint at the base of the composite insulator is the weakest point in the overall structure, experiencing the greatest bending moment load. This leads to current failures of composite electrical equipment primarily occurring at the flange joint, rather than the composite bushing itself. Furthermore, due to the unique structural configuration of the flange joint (metal flange-glue-composite bushing), it is highly sensitive to various vibration loads, resulting in frequent mechanical damage and secondary electrical accidents (bucket leaks, tripping, etc.) caused by glue deformation and tearing. Moreover, the glue thickness at the composite insulator flange joint is extremely small, only about 1mm, and the glue is inside the metal flange, making even large-area damage to the glue difficult to detect visually. This poses significant challenges to the rapid and accurate troubleshooting of composite electrical equipment in substations and converter stations.

[0006] Currently, there are few methods for damage detection of electrical equipment based on dynamic characteristics. Generally, methods commonly used in building structures are directly adopted, involving signal processing of the equipment's dynamic characteristics to determine damage. However, this approach has many shortcomings. Damage detection of composite electrical equipment in substations and converter stations is of great significance. It is necessary to start from practical engineering considerations and find suitable dynamic sensitive parameters for composite insulator damage. Furthermore, these parameters must be correlated with the weakest link of the composite insulator (the flange bonding joint) and be able to locate the hidden damage at the joint.

[0007] In summary, due to the lack of research on the mechanical properties and damage modes of composite insulator flange glued joints, coupled with practical engineering problems such as the frequency and concealment of damage to flange glued joints, there is an urgent need to find a fast, accurate, and easy-to-implement method for identifying and assessing damage to flange glued joints that can be located and quantitatively detected simultaneously. Summary of the Invention

[0008] This invention provides a method and system for damage identification of flange glue joints of post composite insulators based on modal fingerprinting, in order to solve the technical problems of the frequency and concealment of damage to flange glue joints and the inadequacy of existing non-destructive testing.

[0009] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0010] A damage identification method for flange glued joints of post composite insulators based on modal fingerprinting includes the following steps:

[0011] Establish a modal fingerprint library of adhesive damage in flange glue joints of composite insulators, including a high-damage modal fingerprint library and a corner damage modal fingerprint library;

[0012] Multiple dynamic characteristic tests were conducted on the composite insulator, including: performing multiple excitations on the composite insulator in multiple directions to obtain multiple dynamic characteristic parameters, and calculating the corresponding relative frequency limits for each parameter. δ a,j ;

[0013] Multiple relative frequency limits δ a,j The maximum value in the database is compared with the reduced high-damage modal fingerprint database to determine the overall damage level.

[0014] Calculate the flexibility curvature amplitude abrupt change coefficient of the first three natural frequencies based on the number of sections of the composite insulator. α ik Compare the coefficient of change in flexibility curvature amplitude α at different flange bonding joint locations. i The magnitude of the value determines the degree and location of damage to each flange;

[0015] By comparing the abrupt changes in natural frequency values ​​from multiple dynamic characteristic tests with the reduced angle damage modal fingerprint database, the specific angle orientation of flange joint damage can be determined.

[0016] Preferably, establishing a modal fingerprint library of adhesive damage in flange bonding joints of composite insulators includes the following steps:

[0017] Dynamic characteristic tests were performed on the composite insulator in a non-destructive state to obtain the dynamic characteristic parameters in a single horizontal direction and the first three natural frequencies.

[0018] A refined finite element model of the composite insulator considering the bonding effect of the colloid was established. Damage was pre-set in the height and rotation directions of the colloid, and two corresponding damage factors were set for each. Each damage factor was assigned a relative frequency limit to characterize the degree of frequency drop. δ a,j The bonding strength of the flange joints was artificially reduced, thereby reducing the overall stiffness of the composite insulator. This led to the acquisition of a height damage correspondence table and a corner damage correspondence table for different values ​​of the two damage factors.

[0019] The dynamic characteristic parameters of composite insulators under different values ​​of various damage factors were obtained by two methods: direct modal calculation using a refined finite element model and simulated excitation. A modal fingerprint database of adhesive damage in the flange glue joints of composite insulators was then established.

[0020] Preferably, after establishing a modal fingerprint database of adhesive damage in flange bonding joints of composite insulators, the damage to flange bonding joints is determined by the following indicators:

[0021] Class I equipment: For equipment with a height greater than 10m or a main frequency between 0-3Hz, the decrease in the natural frequency value of any one of the first three orders exceeds the relative frequency limit. δ Ⅰ,123 The flange bonding joint was determined to be completely destroyed.

[0022] Class II equipment: For equipment with a height greater than 5m but less than 10m or a principal frequency between 3-10Hz; the decrease in the natural frequency value of any one of the first two orders exceeds the relative frequency limit. δ Ⅱ,12 The flange bonding joint was determined to be completely destroyed.

[0023] Class III equipment: For equipment with a height less than 5m or a main frequency greater than 10Hz, the decrease in the first-order natural frequency exceeds the relative frequency limit. δ Ⅲ,1 The flange bonding joint was determined to be completely destroyed.

[0024] Preferably, the relative frequency limit δ a,j The calculation formula is as follows:

[0025]

[0026] in, a Indicates the first a Such devices, and a=Ⅰ, Ⅱ, Ⅲ ; j Indicates the first j First-order frequency, and j=1, 2, 3 ; f 0 represents the natural frequency of the composite insulator under undamaged conditions. f This is the natural frequency of the composite insulator.

[0027] Preferably, the coefficient of change in the amplitude of the flexibility curvature α ik The calculation is performed using the following formula:

[0028] For a single-section composite insulator, the degree of damage is determined by the ratio of the flexibility curvature values ​​at two points:

[0029]

[0030] The flexibility curvature value is calculated using the central difference method:

[0031]

[0032] Where: F ″ F ″ d F represents the flexibility curvature before and after structural damage. i,k +1 and F di,k +1 Fi,k and F di,k and F i,k -1 and F di,k -1 Δh represents the i-th mode flexibility coefficient at the k+1, k, and k-1 measuring points before and after structural damage, respectively; Δh is the distance between adjacent measuring points, which are arranged as adjacent flange glued joints.

[0033] Preferably, the composite insulator in its undamaged state has a centrally symmetrical structure and a cantilever structure with a circular or annular cross-section.

[0034] Preferably, the damage factor ranges from 0 to 1, with an interval of 0.1.

[0035] The present invention also provides a computer system, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of any of the above methods.

[0036] The present invention has the following beneficial effects:

[0037] This invention relates to a damage identification method and system for flange glued joints of post composite insulators based on modal fingerprinting. Targeting the damage characteristics of flange glued joints in composite insulators, it combines glue modal fingerprinting and compliance matrix discrimination methods for damage identification. It features fast identification speed, high accuracy, and the ability to identify hidden damage. Furthermore, it is a damage identification method specifically tailored to the structural characteristics of composite insulators and the damage characteristics of flange glued joints, overcoming the shortcomings of traditional modal fingerprinting methods that cannot accurately locate damage. It also eliminates the need for identifying parameters such as mode shape, transfer function, and modal curvature, directly obtaining the damage location of the flange glued joint by repeatedly measuring the insulator's natural frequency. Simultaneously, this invention is simple to implement; at most three accelerometers are required for rapid damage identification of flange glued joints in post composite electrical equipment of most voltage levels.

[0038] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0039] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0040] Figure 1 This is a flowchart illustrating the damage identification method for flange glued joints of post composite insulators based on modal fingerprinting, according to a preferred embodiment of the present invention.

[0041] Figure 2This is a flowchart illustrating the damage identification method for flange glued joints of post composite insulators based on modal fingerprinting, according to a preferred embodiment 2 of the present invention.

[0042] Figure 3 This is Table 1 of the preferred embodiment 2 of the present invention: Correspondence table of height damage (taking 200mm colloid as an example);

[0043] Figure 4 This is Table 2 of the preferred embodiment 2 of the present invention: Correspondence table of corner damage;

[0044] Figure 5 This is a schematic diagram of three types of composite electrical equipment according to a preferred embodiment 2 of the present invention;

[0045] Figure 6 This is a schematic diagram of the finite element model and mode shape of the preferred embodiment 3 of the present invention. (a) is the geometric model; (b) is the finite element model; (c) is the first mode shape.

[0046] Figure 7 This is Table 3 of the preferred embodiment 3 of the present invention: natural frequency verification table;

[0047] Figure 8 This is a graph showing the relationship between the damage factor and the decrease in natural frequency in the preferred embodiment 3 of the present invention;

[0048] Figure 9 This is a schematic diagram of obtaining the dynamic characteristics of a damaged composite electrical device by striking it, according to a preferred embodiment 3 of the present invention.

[0049] Figure 10 This is a schematic diagram showing the specific location and actual extent of damage of the damaged flange in the preferred embodiment 3 of the present invention;

[0050] Figure 11 The coefficient of change in the amplitude of the flexibility curvature in the preferred embodiment of the present invention is α. ik (108°) Schematic diagram. Detailed Implementation

[0051] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0052] Example 1:

[0053] See Figure 1 The damage identification method for flange glued joints of post composite insulators based on modal fingerprinting according to embodiments of the present invention includes the following steps:

[0054] Establish a modal fingerprint library of adhesive damage in flange glue joints of composite insulators, including a high-damage modal fingerprint library and a corner damage modal fingerprint library;

[0055] Multiple dynamic characteristic tests were conducted on the composite insulator, including: performing multiple excitations on the composite insulator in multiple directions to obtain multiple dynamic characteristic parameters, and calculating the corresponding relative frequency limits for each parameter. δ a,j ;

[0056] Multiple relative frequency limits δ a,j The maximum value in the database is compared with the reduced high-damage modal fingerprint database to determine the overall damage level.

[0057] Calculate the flexibility curvature amplitude abrupt change coefficient of the first three natural frequencies based on the number of sections of the composite insulator. α ik Compare the coefficient of change in flexibility curvature amplitude α at different flange bonding joint locations. i The magnitude of the value determines the degree and location of damage to each flange;

[0058] By comparing the abrupt changes in natural frequency values ​​from multiple dynamic characteristic tests with the reduced angle damage modal fingerprint database, the specific angle orientation of flange joint damage can be determined.

[0059] Example 2:

[0060] See Figure 2 The damage identification method for flange glued joints of post composite insulators based on modal fingerprinting according to embodiments of the present invention includes the following steps:

[0061] I. Establishment of a modal fingerprint database based on flange colloidal damage, the specific contents of which are as follows:

[0062] (1) By conducting on-site dynamic characteristic testing on a certain type of composite insulator in a non-destructive state, since the cross-section of the composite insulator is circular or annular and is a centrally symmetrical structure, the dynamic characteristic parameters in a single horizontal direction can be directly obtained. The composite insulator is a cantilever structure, and the vibration is mainly contributed by the first three vibration modes (determined according to the height of the free end of the composite insulator; generally, the contribution rate of the first vibration mode is over 90%), so the natural frequencies of the first three modes can be obtained.

[0063] (2) Establish a refined finite element model of the insulator considering the bonding effect of the colloid, and pre-set damage in the height and rotation directions of the colloid, and set damage factors (0-1, with an interval of 0.1, and each damage factor corresponds to a relative frequency limit). δ a,j (This is used to characterize the degree of frequency descent). Artificially reducing the bonding strength of the flange joints reduces the overall stiffness of the composite insulator. Each damage factor corresponds to a relative frequency limit value used to characterize the degree of frequency descent. δ a,jArtificially reducing the bonding strength of flange joints reduces the overall stiffness of the composite insulator. This leads to the acquisition of height damage and corner damage correspondence tables for different values ​​of the two damage factors. (See [reference]). Figure 3 (Table 1 Correspondence Table of Height Damage (Taking 200mm Colloid as an Example)) and Figure 4 (Table 2 Correspondence Table of Corner Damage).

[0064] (3) The dynamic characteristic parameters of composite insulators under various damage factors were obtained by two methods: direct modal calculation using finite element model and simulated excitation. The modal fingerprint database of adhesive damage of composite insulator flange joint was established.

[0065] II. Damage assessment criteria for flange bonding joints based on modal parameter variations, specifically:

[0066] (1) For equipment with a height greater than 10m or a main frequency between 0-3Hz, it is considered that its vibration is affected by the combination of the first three mode shapes, and the stiffness is relatively small. During vibration, the horizontal displacement at the top, midpoint, and third points will all cause damage to the glued joint of the root flange. Therefore, for this type of equipment, we use the first three modal parameters to determine the damage of the composite insulator, and the natural frequency value of any one of the first three frequencies decreases beyond the relative frequency limit. δ Ⅰ,123 The flange bonding joint is considered completely destroyed. This embodiment defines such composite electrical equipment as Class I equipment. See also... Figure 5 .

[0067] (2) For equipment with a height greater than 5m but less than 10m or a main frequency between 3-10Hz, it is assumed that its vibration is affected by the combination of the first two mode shapes, and the stiffness is moderate. During vibration, the horizontal displacement of the top and midpoint will cause damage to the glued joint of the root flange. Therefore, for this type of equipment, we use the first two modal parameters to determine the damage to the composite insulator. Similarly, if the decrease in the natural frequency value of any one of the first two frequencies exceeds the relative frequency limit, the damage is considered to be caused by the first two mode shapes. δ Ⅱ,12 This assumes the flange bonding joint is completely destroyed. For this type of composite electrical equipment, this embodiment defines it as Class II equipment. See also... Figure 5 .

[0068] (3) For equipment with a height of less than 5m or a main frequency greater than 10Hz, it is assumed that its vibration is only affected by the first mode shape and has a large stiffness. During vibration, only the horizontal displacement at the top can be considered to cause damage to the glued joint of the root flange. Therefore, for this type of equipment, we use the first mode parameter to determine the damage of the composite insulator, that is, the drop in the first natural frequency value exceeds the relative frequency limit. δ Ⅲ,1 This assumes the flange bonding joint is completely destroyed. For this type of composite electrical equipment, this embodiment defines it as Class III equipment. See also... Figure 5 .

[0069] See Table 3 for relative frequency limits. δ a,j for:

[0070]

[0071] in, a Indicates the first a Class of equipment ( a=Ⅰ, Ⅱ, Ⅲ ), j Indicates the first j First frequency ( j=1, 2, 3 ); f 0 represents the natural frequency of the composite insulator under undamaged conditions. f This is the natural frequency of the composite insulator.

[0072] Table 3 Frequency drop limits for composite post insulators of different heights δ a,j

[0073]

[0074] Note: when δ a,j When the range is defined, a constant value is obtained by linear interpolation based on the fundamental frequency value.

[0075] III. Damage diagnosis of adhesive joints in composite insulator flanges based on flexibility matrix characteristics.

[0076] The above establishes the criteria for determining adhesive damage at flange bonding joints and a modal fingerprint database. However, for multi-section composite insulators, it is impossible to determine which flange section is damaged. Therefore, this embodiment also supplements the method for locating damage using modal fingerprints.

[0077] Compared to single modal parameters such as frequency or mode shape, the compliance matrix is ​​more sensitive to structural damage identification, and it simultaneously considers changes in frequency and curvature modes, and can also include the compliance curvature amplitude abrupt change coefficient α. i As a sensitive parameter for damage identification, α was compared at different flange bonding node locations. i The magnitude of the value can quickly determine the degree and location of the damage. Finally, by combining the corner damage assessment, the specific corner orientation of the flange bonding node can be determined.

[0078] The applicability of this embodiment to the flange glued joint of composite insulators lies in the fact that the composite bushing itself has sufficient strength and is not easily damaged, while the flange glued joint is extremely easy to be damaged. By properly arranging the sensors and utilizing the overall flexibility matrix characteristics of the insulator, the damage to the flange glued joint of each section can be amplified, and the damage of each flange section can be compared.

[0079] The compliance matrix of the original structure in the undamaged state can be expressed as:

[0080]

[0081] Where F is the compliance matrix, ω i The natural frequency of the composite insulator in a lossless state. Φ i This is the mode shape vector (considering the first three frequencies, i=1,2,3).

[0082] The compliance matrix after structural damage can be expressed as:

[0083]

[0084] Among them, F d For the flexibility matrix, ω di The natural frequency of the composite insulator under conditions of adhesive damage at the flange bonding joint. Φ di This is the mode shape vector after damage (considering the first three frequencies, i=1,2,3).

[0085] When damage occurs at the glued joint of a composite insulator flange, the stiffness at the damaged area decreases, and the corresponding flexibility value also changes. The flexibility curvature can reflect the degree of this change, and it can be calculated using the central difference method.

[0086]

[0087] In the formula: F ″ F ″ d F represents the flexibility curvature before and after structural damage. i,k +1 and F di,k +1 F i,k and F di,k and F i,k -1 and F di,k -1 , are the i-th mode flexibility coefficients of the k+1, k, and k-1 measuring points before and after structural damage; Δh is the distance between adjacent measuring points, and the measuring points are arranged as adjacent flange glued joints.

[0088] For a single-section composite insulator, the number of measuring points is at most three. In this case, the flexibility curvature is directly calculated from the difference between two measuring points.

[0089]

[0090] Based on the known flexibility curvature of the damaged insulator, in order to further establish the relationship between flexibility curvature and damage to the insulator flange bonding joint, the flexibility curvature amplitude mutation coefficient α can be used. ik It can be expressed as follows:

[0091]

[0092] Among them, F ″ di,k F ″ di,k+1 With F ″ di,k-1 , i and k are the flexibility curvature values ​​of the damage point and two adjacent points, respectively, where i is the mode order and k is the measurement point number.

[0093] For a single-section composite insulator, the degree of damage is directly determined by the ratio of the flexibility curvature values ​​at two points, i.e.:

[0094]

[0095] IV. Implementation process for identifying damage at flange bonding joints.

[0096] In this embodiment, a modal fingerprint of adhesive damage at the flange bonding joint was established at the beginning, including damage in the height and angular directions, and the corresponding damage factors. However, observing only one type of damage makes it difficult to simultaneously obtain the damage degree and location. Therefore, it is necessary to combine damage in the height and angular directions for judgment. In actual engineering, the damage of the two types of adhesives is coupled, meaning that damage in the height and angular directions occurs simultaneously in a certain area, forming an adhesive tear band. However, the coupling degree of damage magnitude is relatively small; that is, damage in the height direction has the greatest impact on the stiffness of the flange bonding joint, while angular damage is only a companion to height damage. Therefore, we simplify the two types of damage, considering the damage degree (i.e., δ a,j All damage fingerprints are derived from the height-direction damage fingerprint database after reduction processing, while the damage location is controlled by the corner damage fingerprint database.

[0097] Therefore, the specific implementation process of this embodiment is as follows:

[0098] (1) Dynamic characteristic testing of composite insulators is carried out. Taking the hammer method as an example, hammer excitation is performed in ten directions on the top of the composite insulator to obtain ten dynamic characteristic parameters, and the corresponding parameters are calculated respectively. δ a,j .

[0099] (2) δ a,j The maximum value in the database is compared with the reduced high-damage modal fingerprint database to determine the overall damage level.

[0100] (3) Calculate the coefficient of change of flexibility curvature amplitude of the first three natural frequencies based on the number of insulator sections. α ik Determine the extent of damage to each flange.

[0101] (4) Find the mutation values ​​of the ten dynamic characteristic tests and the reduced corner damage modal fingerprint database (one is a single-sided damage; two symmetrically distributed ones are bilateral vibration damage), draw the damage location map, determine the damage direction, and carry out node damage investigation.

[0102] Example 3:

[0103] This invention relates to a method for damage identification of flange glued joints in post composite insulators based on modal fingerprinting. Taking a 200kV composite insulator as an example, its height is 2.4m, fundamental frequency is greater than 10Hz, and it has two flange glued joints. (See attached diagram.) Figure 6 The implementation is based on Example 2:

[0104] (1) Based on its height and natural frequency, this composite electrical equipment is classified as Class III equipment; see [link to relevant documentation]. Figure 7 .

[0105] (2) Establish the relationship between damage factors and frequency decrease to form a high-level damage database; see [link to relevant documentation]. Figure 8 .

[0106] (3) Determine the ratio of the number of sensors to the flexibility curvature value based on the number of flange glue joints. Arrange acceleration sensors at the two flange glue joints and the middle of the insulator to test the dynamic characteristics of the damaged equipment (obtain the dynamic characteristics by tapping the damaged composite electrical equipment, see...). Figure 9 (The location of the accelerometer is determined), and the first three modal parameters of the insulator are obtained (see Table 4). Then: 1) The ratio of flexibility curvature values ​​in each direction is calculated (see Table 5) to determine which flange section is damaged; 2) The degree of flange damage is obtained by matching the relative frequency decrease value with the flange height damage factor (see Table 5). Figure 10 ); 3) Simultaneously obtain frequency mutation values ​​(see Figure 11 ).

[0107] Table 4. First three natural frequencies of composite insulators at various measuring points

[0108]

[0109] Table 5. Compliance curvature of the first three modes of composite insulators (108°) / 10 -7

[0110]

[0111] (4) Match the ratio of flexibility curvature value with the damaged flange, match the abrupt change location with the position (corner) damage factor, and match the abrupt change value with the height damage factor to complete the identification of adhesive damage at the flange bonding node.

[0112] The abrupt change in the ratio of flexibility curvature values ​​indicates that, for example Figure 11As shown, the damaged flange of the composite insulator is the lower flange of section #1 (considering the bushing is undamaged and the maximum abrupt change occurs at the first mode); the location and extent of damage to the root insulator's adhesive can be determined by the location of the abrupt change. Figure 10 As shown, with a damage factor of 0.1, the colloid damage height is 10mm, and the relative frequency decrease is 4.1%, which is less than the limit of 40%. The flange adhesive joint is not damaged, but there is slight damage.

[0113] Example 4:

[0114] The present invention also provides a computer system, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of any of the above embodiments.

[0115] In summary, this invention provides a rapid, accurate, and easy-to-implement field-based technology and method for assessing damage at flange glued joints. It features clear technical principles, convenient operation, low cost, and high identification accuracy. This invention combines the damage characteristics of composite insulator flange glued joints to establish a modal fingerprint database based on glue damage; it also determines the frequency descent limit after glue damage according to the structural characteristics of composite insulators; finally, it determines the damage amount and location of the joint through the modal fingerprints of two types of damage. Its technical advantages are mainly reflected in the following aspects:

[0116] Firstly, this invention can directly determine whether the flange adhesive joint is damaged, as well as the location and extent of damage to the adhesive inside the flange adhesive joint. It also classifies the equipment by height and natural frequency band, making it suitable for most voltage levels and multi-section composite electrical equipment.

[0117] Secondly, this invention can accurately locate the damaged flange joints of insulators with any number of sections, rather than the overall damage of the composite insulator.

[0118] Third, the technical route of this invention is clear and the actual operation is simple. It does not require analysis of other modal parameters, but only simple processing of frequency values. In addition, fewer acceleration sensors are required on site, which greatly improves the detection speed.

[0119] In summary, this invention overcomes the shortcomings of traditional detection methods that cannot simultaneously quantitatively and locally detect adhesive damage at the flange bonding joints of composite insulators. Furthermore, the detection process is simple and easy to operate, making it suitable for troubleshooting flange bonding joint damage in most composite electrical equipment in converter stations and substations.

[0120] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for damage identification of flange glued joints in post composite insulators based on modal fingerprinting, characterized in that, Includes the following steps: Establish a modal fingerprint library of adhesive damage in flange glue joints of composite insulators, including a high-damage modal fingerprint library and a corner damage modal fingerprint library; Multiple dynamic characteristic tests were conducted on the composite insulator, including: performing multiple excitations on the composite insulator in multiple directions to obtain multiple dynamic characteristic parameters, and calculating the corresponding relative frequency limits for each parameter. δ a,j ; Multiple relative frequency limits δ a,j The maximum value in the database is compared with the reduced high-damage modal fingerprint database to determine the overall damage level. Calculate the flexibility curvature amplitude abrupt change coefficient of the first three natural frequencies based on the number of sections of the composite insulator. α ik Compare the coefficient of change in flexibility curvature amplitude α at different flange bonding joint locations. i The magnitude of the value determines the degree and location of damage to each flange; By comparing the abrupt changes in natural frequency values ​​from multiple dynamic characteristic tests with the reduced angle damage modal fingerprint database, the specific angle orientation of flange joint damage can be determined.

2. The damage identification method for flange glued joints of post composite insulators based on modal fingerprinting according to claim 1, characterized in that, Establishing a modal fingerprint library of adhesive damage in flange bonding joints of composite insulators includes the following steps: Dynamic characteristic tests were performed on the composite insulator in a non-destructive state to obtain the dynamic characteristic parameters in a single horizontal direction and the first three natural frequencies. A refined finite element model of the composite insulator considering the bonding effect of the colloid was established. Damage was pre-set in the height and rotation directions of the colloid, and two corresponding damage factors were set for each. Each damage factor was assigned a relative frequency limit to characterize the degree of frequency drop. δ a,j The bonding strength of the flange joints was artificially reduced, thereby reducing the overall stiffness of the composite insulator. This led to the acquisition of a height damage correspondence table and a corner damage correspondence table for different values ​​of the two damage factors. The dynamic characteristic parameters of composite insulators under different values ​​of various damage factors were obtained by two methods: direct modal calculation using a refined finite element model and simulated excitation. A modal fingerprint database of adhesive damage in the flange glue joints of composite insulators was then established.

3. The damage identification method for flange glued joints of post composite insulators based on modal fingerprinting according to claim 1, characterized in that, After establishing a modal fingerprint database of adhesive damage in flange glued joints of composite insulators, the following indicators are used to determine the damage of flange glued joints: Class I equipment: For equipment with a height greater than 10m or a main frequency between 0-3Hz, the decrease in the natural frequency value of any one of the first three orders exceeds the relative frequency limit. δ Ⅰ,123 The flange bonding joint was determined to be completely destroyed. Class II equipment: For equipment with a height greater than 5m but less than 10m or a principal frequency between 3-10Hz; the decrease in the natural frequency value of any one of the first two orders exceeds the relative frequency limit. δ Ⅱ,12 The flange bonding joint was determined to be completely destroyed. Class III equipment: For equipment with a height less than 5m or a main frequency greater than 10Hz, the decrease in the first-order natural frequency exceeds the relative frequency limit. δ Ⅲ,1 The flange bonding joint was determined to be completely destroyed.

4. The damage identification method for flange glued joints of post composite insulators based on modal fingerprinting according to claim 3, characterized in that, Relative frequency limit δ a,j The calculation formula is as follows: in, a Indicates the first a Such devices, and a=Ⅰ, Ⅱ, Ⅲ ; j Indicates the first j First-order frequency, and j=1, 2, 3 ; f 0 represents the natural frequency of the composite insulator under undamaged conditions. f This is the natural frequency of the composite insulator.

5. The damage identification method for flange glued joints of post composite insulators based on modal fingerprinting according to claim 1, characterized in that, coefficient of change in flexibility curvature amplitude α ik The calculation is performed using the following formula: For a single-section composite insulator, the degree of damage is determined by the ratio of the flexibility curvature values ​​at two points: The flexibility curvature value is calculated using the central difference method: Where: F ″ F ″ d F represents the flexibility curvature before and after structural damage; i,k +1 and F di,k +1 F i,k and F di,k and F i,k -1 and F di,k -1 Δh represents the i-th mode flexibility coefficient at the k+1, k, and k-1 measuring points before and after structural damage, respectively; Δh is the distance between adjacent measuring points, which are arranged as adjacent flange glued joints.

6. The damage identification method for flange glued joints of post composite insulators based on modal fingerprinting according to claim 2, characterized in that, The composite insulator in the undamaged state is a centrally symmetrical structure and a cantilever structure with a circular or annular cross-section.

7. The damage identification method for flange glued joints of post composite insulators based on modal fingerprinting according to claim 2, characterized in that, The damage factor has a value range of 0-1, with an interval of 0.

1.

8. A computer system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 7.

Images