Remaining fatigue life assessment method and storage medium for temperature compensation bellows of GIS pipelines

Abstract

This invention belongs to the field of material performance evaluation, and relates to a method and storage medium for assessing the remaining fatigue life of a temperature-compensated corrugated pipe for GIS pipelines. Based on finite element simulation analysis data of the temperature-compensated corrugated pipe under internal pressure and axial tensile-compressive loads, the method calculates the fatigue damage caused by daily thermal expansion and contraction of the corrugated pipe using stress fatigue life data of the corrugated pipe material and measured GIS pipeline temperature or axial deformation of the corrugated pipe, thus assessing its residual fatigue life. This invention uses the finite element method to pre-calculate the stress components in the critical area of ​​the corrugated pipe under internal pressure loads and axial deformation loads caused by thermal expansion and contraction, effectively avoiding the problem of difficulty in installing stress sensors to obtain measured data due to structural limitations.

Description

Technical Field

[0001] This invention belongs to the field of material performance evaluation, and in particular to a method and storage medium for assessing the remaining fatigue life of a temperature-compensated corrugated pipe for GIS pipelines. Background Technology

[0002] GIS pipelines are widely used in power grid transmission and transformation projects due to their compact structure, convenient installation, and ease of monitoring and maintenance. Most GIS pipelines are installed outdoors, and they will undergo significant thermal expansion and contraction due to environmental factors. Temperature compensation corrugated pipes are usually used to absorb the axial thermal expansion and contraction deformation caused by daily temperature rises and falls. However, due to insufficient estimation of thermal expansion and contraction deformation caused by environmental changes during the product design stage, temperature compensation corrugated pipes develop fatigue cracks prematurely, leading to internal SF6 gas leakage, which seriously threatens power supply safety. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for assessing the remaining fatigue life of GIS pipeline temperature compensation corrugated pipes. This method can predict the remaining life of GIS pipeline temperature compensation corrugated pipes, allow for timely replacement, prevent SF6 gas leakage, and ensure power supply safety.

[0004] The technical solution adopted by this invention to solve the technical problem is:

[0005] This invention is based on finite element simulation analysis data of GIS pipeline temperature-compensated corrugated pipe under internal pressure and axial tensile and compressive loads, stress fatigue life data of corrugated pipe material, and measured GIS pipeline temperature or axial deformation of corrugated pipe to calculate the fatigue damage caused by thermal expansion and contraction of temperature-compensated corrugated pipe every day, and evaluate its residual fatigue life.

[0006] The first aspect of this invention is to provide a method for assessing the remaining fatigue life of a temperature-compensated corrugated pipe for GIS pipelines, comprising the following steps:

[0007] 1) The radial membrane stress σ3 and radial bending stress σ4 at the crest of the temperature-compensated bellows under internal pressure were calculated using the finite element method.

[0008] 2) The finite element method was used to simulate the tensile and compressive deformation of the temperature-compensated bellows to obtain the radial membrane stress σ5 and radial bending stress σ6 at the wave crest for different deformation amounts.

[0009] 3) The finite element method was used to simulate the temperature-compensated bellows by first applying an internal pressure load and then performing tensile and compressive deformation calculations to obtain the radial membrane stress σ at the crest for different deformation amounts. 35 and radial bending stress σ 46 ;

[0010] 4) Compare the σ values ​​of the bellows under the same tensile or compressive deformation.t1 and σ t2 , where σ t1 =0.7(σ3+σ4)+(σ5+σ6),σ t2 =σ 35+ σ 46 Take the larger stress value σ t , i.e. σ t =Max(σ t1 , σ t2 );

[0011] 5) Establish the deformation amount and σ within the limit deformation range of the temperature-compensated bellows. t The data table shows that the deformation increment is set to 0.1mm to 1mm based on the calculation accuracy.

[0012] 6) Different σ values ​​can be obtained depending on the corrugated pipe material. t The corresponding fatigue life N f ;

[0013] 7) The axial displacement change of the temperature-compensated bellows is calculated once every 24 hours.

[0014] 8) Based on the daily length change, the corresponding σ can be obtained from the data table in step 5). t The value, and then based on N obtained in step 6). f The calculated damage to the bellows on this day is ΔS = 1 / N. f If N f More than 10 7 When the damage ΔS for that day is 0, the total damage S of the bellows can be obtained by accumulating the damage ΔS of each day.

[0015] 9) Remaining fatigue life N of the bellows r =([S]-S) / ΔS a [S] is the permissible damage value, ΔS a This represents the historical daily damage average.

[0016] Furthermore, the change in bellows length is calculated using data directly measured by a displacement sensor installed on the bellows.

[0017] Furthermore, the displacement sensor collects data over 24 hours each day, and the difference between the maximum and minimum values ​​is the daily length change ΔD.

[0018] Furthermore, the change in bellows length is calculated using data directly measured by a temperature sensor installed on the bellows.

[0019] Furthermore, the temperature sensor collects the temperature of the GIS pipeline cylinder over 24 hours each day, calculates the circumferential temperature average, and calculates the difference between the maximum and minimum average temperature values ​​as the daily temperature change ΔT. Based on the compensation length L of the temperature-compensated corrugated pipe and the linear expansion coefficient α of the GIS cylinder material, the theoretical length change ΔD can be calculated, ΔD=α·L·ΔT.

[0020] A second aspect of the present invention is to provide a computer-readable storage medium having a computer program stored thereon, the computer program being used to cause the computer to execute the method for assessing the remaining fatigue life of a temperature-compensated corrugated pipe for GIS pipelines.

[0021] The advantages and positive effects of this invention are:

[0022] 1) This invention uses the finite element method to pre-calculate the stress components of the critical area of ​​the temperature-compensated bellows under the action of internal pressure load and axial deformation load caused by thermal expansion and contraction, effectively avoiding the problem of difficulty in installing stress sensors to obtain measured data due to structural reasons.

[0023] 2) This invention can obtain the displacement amplitude of the temperature-compensated bellows within a 24-hour thermal expansion and contraction cycle based on both measured displacement and measured temperature data.

[0024] 3) This invention only requires transmitting temperature and / or displacement data to the server for subsequent damage calculations and residual life assessments. Data analysis, display, and early warning can all be performed on the server side. Furthermore, for all corrugated pipes on GIS pipelines within the same substation, damage calculations and residual life assessments can be performed using only one or a few sets of temperature data, making it highly economical and practical. Attached Figure Description

[0025] Figure 1 This is a cloud map showing the axial deformation and maximum principal stress distribution of a section of GIS pipeline under internal pressure load and temperature rise expansion, where a) is the axial displacement and b) is the maximum principal stress;

[0026] Figure 2 To compensate for the maximum principal stress distribution of the bellows under different degrees of compression, a) is a cloud map of deformation and maximum principal stress distribution of the bellows under axial compression of 2.274 mm; b) is a cloud map of deformation and maximum principal stress distribution of the bellows under axial compression of 4.7 mm; c) is a cloud map of deformation and maximum principal stress distribution of the bellows under axial compression of 8.96 mm.

[0027] Figure 3 A schematic diagram of a displacement sensor for measuring the distance between flanges on both sides of a bellows;

[0028] Figure 4for Figure 3 Enlarged view of part A;

[0029] Figure 5 This is a schematic diagram of temperature measurement in a GIS cylinder.

[0030] The diagram is marked as follows:

[0031] 1 is the corrugated pipe, 2 is the waterproof cover plate, 3 is the temperature sensor, 4 is the signal transmission device, and 5 is the cylinder. Detailed Implementation

[0032] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0033] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0034] A method for assessing the remaining fatigue life of a temperature-compensated corrugated pipe for GIS pipelines includes the following steps:

[0035] 1) The radial membrane stress σ3 and radial bending stress σ4 at the crest of the temperature-compensated bellows under internal pressure are calculated using the finite element method; (The inside of the GIS pipeline is filled with SF6 gas, and there is a certain gas pressure inside. Here, internal pressure refers to the internal gas pressure).

[0036] 2) The finite element method was used to simulate the tensile and compressive deformation of the temperature-compensated bellows to obtain the radial membrane stress σ5 and radial bending stress σ6 at the wave crest for different deformation amounts.

[0037] 3) The finite element method was used to simulate the temperature-compensated bellows by first applying an internal pressure load and then performing tensile and compressive deformation calculations to obtain the radial membrane stress σ at the crest for different deformation amounts. 35 and radial bending stress σ 46 ;

[0038] 4) Compare the σ values ​​of the bellows under the same tensile or compressive deformation. t1 and σ t2 , where σ t1 =0.7(σ3+σ4)+(σ5+σ6),σ t2 =σ 35+ σ 46 Take the larger stress value σ t , i.e. σ t =Max(σ t1 , σ t2 );

[0039] 5) Establish the deformation amount and σ within the limit deformation range of the temperature-compensated bellows. t The data table shows that the deformation increment is set to 0.1mm to 1mm based on the calculation accuracy.

[0040] Figure 1 This is a cloud map showing the axial deformation and maximum principal stress distribution of a section of GIS pipeline under internal pressure load and temperature increase expansion, where a) is the axial displacement and b) is the maximum principal stress.

[0041] Figure 2 To compensate for the maximum principal stress distribution of the bellows under different degrees of compression, a) is a cloud map of deformation and maximum principal stress distribution of the bellows under axial compression of 2.274 mm; b) is a cloud map of deformation and maximum principal stress distribution of the bellows under axial compression of 4.7 mm; c) is a cloud map of deformation and maximum principal stress distribution of the bellows under axial compression of 8.96 mm.

[0042] 6) Different σ values ​​can be obtained depending on the corrugated pipe material. t The corresponding fatigue life N f The horizontal axis of the SN characteristic curve of the material is the stress σ. t The vertical axis is N f According to σ t Then you can query the corresponding N. f value.

[0043] 7) The axial displacement change of the temperature-compensated bellows is calculated once every 24 hours.

[0044] The change in the length of the bellows can be calculated directly from the data measured by the displacement sensor installed on the bellows. Specifically, the data collected over 24 hours each day is used to calculate the difference between the maximum and minimum values, which is the change in length ΔD for that day.

[0045] like Figure 3 , Figure 4 The diagram shows a displacement sensor for measuring the distance between the flanges on both sides of the corrugated pipe. The displacement sensor can be a pull rope, pull rod, or other type. The displacement sensor and signal transmission module are both installed below the waterproof cover plate 2.

[0046] The length change can also be calculated by directly measuring the data from the temperature sensors installed on the corrugated pipe. The specific method is to collect the temperature of the GIS pipeline cylinder over 24 hours each day, calculate the average circumferential temperature (it is recommended to have 4 or 8 temperature sensors evenly distributed around the cylinder), and calculate the difference between the maximum and minimum average temperature values ​​as the temperature change ΔT for that day. Based on the compensation length L of the temperature-compensated corrugated pipe (the distance between the nearest fixed supports on both sides of the corrugated pipe) and the linear expansion coefficient α of the GIS cylinder material, the theoretical length change ΔD can be calculated, ΔD=α·L·ΔT;

[0047] Figure 5 This is a schematic diagram of temperature measurement in a GIS cylinder. Eight temperature sensors 3 are evenly distributed inside the cylinder 5, and the temperature sensors are connected to a signal transmission device 4.

[0048] 8) Based on the daily change in length, the corresponding σ can be obtained from the data table in 5). t The value, and then based on N obtained in 6). f The calculated damage to the bellows on this day is ΔS = 1 / N. f If N f More than 10 7 When the damage ΔS for that day is 0, the total damage S of the bellows can be obtained by accumulating the damage ΔS of each day.

[0049] 9) Remaining fatigue life N of the bellows r =([S]-S) / ΔS a [S] is the permissible damage value, ΔS a The remaining fatigue life N is the historical daily damage average. Since the GIS pipeline undergoes thermal expansion and contraction once a day, corresponding to one thermal fatigue cycle, the remaining fatigue life is... r The unit is times or days.

[0050] 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 assessing the remaining fatigue life of a temperature-compensated corrugated pipe for GIS pipelines, comprising the following steps: 1) The radial membrane stress σ3 and radial bending stress σ4 at the crest of the temperature-compensated bellows under internal pressure were calculated using the finite element method. 2) The finite element method was used to simulate the tensile and compressive deformation of the temperature-compensated bellows to obtain the radial membrane stress σ5 and radial bending stress σ6 at the wave crest for different deformation amounts. 3) The finite element method was used to simulate the temperature-compensated bellows by first applying an internal pressure load and then performing tensile and compressive deformation calculations to obtain the radial membrane stress σ at the crest for different deformation amounts. 35 and radial bending stress σ 46 ; 4) Compare the σ values ​​of the bellows under the same tensile or compressive deformation. t1 and σ t2 , where σ t1 =0.7(σ3+σ4)+(σ5+σ6),σ t2 =σ 35+ σ 46 Take the larger stress value σ t , i.e. σ t =Max(σ t1 , σ t2 ); 5) Establish the deformation amount and σ within the limit deformation range of the temperature-compensated bellows. t The data table shows that the deformation increment is set to 0.1mm to 1mm based on the calculation accuracy. 6) Different σ values ​​can be obtained depending on the corrugated pipe material. t The corresponding fatigue life N f ; 7) The axial displacement change of the temperature-compensated bellows is calculated once every 24 hours. 8) Based on the daily length change, the corresponding σ can be obtained from the data table in step 5). t The value, and then based on N obtained in step 6). f The calculated damage to the bellows on this day is ΔS = 1 / N. f If N f More than 10 7 When the damage ΔS for that day is 0, the total damage S of the bellows can be obtained by accumulating the damage ΔS of each day. 9) Remaining fatigue life N of the bellows r =([S]-S) / ΔS a [S] is the permissible damage value, ΔS a This represents the historical daily damage average.

2. The method for assessing the remaining fatigue life of temperature-compensated corrugated pipes for GIS pipelines according to claim 1, characterized in that, The change in bellows length is calculated from data directly measured by a displacement sensor installed on the bellows.

3. The method for assessing the remaining fatigue life of GIS pipeline temperature-compensated corrugated pipes according to claim 2, characterized in that, The displacement sensor collects data over 24 hours each day, and the difference between the maximum and minimum values ​​is the daily length change ΔD.

4. The method for assessing the remaining fatigue life of temperature-compensated corrugated pipes for GIS pipelines according to claim 1, characterized in that, The change in bellows length is calculated using data directly measured by a temperature sensor installed on the bellows.

5. The method for assessing the remaining fatigue life of temperature-compensated corrugated pipes for GIS pipelines according to claim 4, characterized in that, Temperature sensors collect the temperature of the GIS pipeline cylinder over 24 hours each day, calculate the circumferential temperature average, and the difference between the maximum and minimum average temperature values ​​is the daily temperature change ΔT. Based on the compensation length L of the temperature-compensated corrugated pipe and the linear expansion coefficient α of the GIS cylinder material, the theoretical length change ΔD can be calculated, ΔD=α·L·ΔT.

6. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program for causing the computer to execute the method for assessing the remaining fatigue life of a GIS pipeline temperature-compensated corrugated pipe according to any one of claims 1-5.

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