Method for calculating interfacial pressure between cable accessory and body at high temperature and related device

Abstract

The invention discloses a method for calculating interfacial pressure between a cable accessory and a body at high temperature and a related device, and belongs to the technical field of power cables. The method comprises the following steps: acquiring an environment temperature, an inner diameter and an outer diameter of the cable accessory before and after assembly and related parameters of an insulating material of the cable accessory; calculating an interface pressure change caused by a thermal expansion effect through the environment temperature, the inner diameter and the outer diameter before and after the cable accessory is assembled and related parameters of an insulating material of the cable accessory; obtaining a Gough-Jule effect coefficient delta, and calculating an interface pressure change caused by the Gough-Jule effect in combination with the environment temperature, the inner diameter and related parameters of an insulating material of the cable accessory before and after the cable accessory is assembled; and acquiring an interface pressure value at room temperature after the cable accessory is assembled, and finally calculating the interface pressure between the cable accessory and the body at high temperature according to the interface pressure change caused by the thermal expansion effect and the interface pressure change caused by the Gough-Joule effect.

Description

Technical Field

[0001] The invention belongs to the technical field of power cables and relates to a method for calculating the interface pressure between a cable accessory and a body at high temperature and a related device. Background Art

[0002] Cable accessories are both an important part and a weak link in the cable system. According to statistics, about 70% of early failures in cable systems are caused by failures at the interface between cable accessories and the cable body. Sufficient interface pressure is the key to ensuring the safe operation of cable accessories. Existing calculations, measurements, and simulations of the interface pressure of cable accessories mostly focus on its changes at room temperature. However, in actual operation, since the cable accessory system is affected by the Joule heat of the current, its temperature is higher than the ambient temperature, which will greatly affect the interface pressure between the cable accessories and the cable body, causing it to deviate from the predicted and measured values ​​at room temperature.

[0003] The research on the interface pressure between cable accessories and the cable body at high temperature is currently mainly concentrated in the field of finite element simulation and offline measurement. Finite element simulation is a commonly used method to obtain the interface pressure of cable accessories at high temperature. It measures the relevant performance parameters of cable accessories at different temperatures, substitutes them into the finite element software, and calculates the interface pressure at this time as the value of the interface pressure of cable accessories at high temperature. The effectiveness and accuracy of this method need to be considered. In addition, installing a thin film pressure sensor between the cable accessories and the cable body and measuring it at high temperature is also one of the methods to study the interface pressure characteristics at high temperature. However, this method is difficult to install and destroys the close-fitting structure between the cable accessories and the cable body. The accuracy of the thin film sensor at high temperature also needs to be considered.

[0004] In summary, the results of the finite element analysis method for the current research on interface pressure at high temperatures are unreliable, and there are many different opinions on the changing trend of the interface pressure between cable accessories and cable bodies at high temperatures, and there is no final conclusion yet; while the thin film piezoresistance measurement method destroys the close adhesion of the insulation interface between the cable accessories and the cable body, and can only be applied to the surface pressure design and offline research of new products, and cannot be truly applied to the interface pressure measurement under working conditions. Therefore, it is urgent to develop a method that can accurately calculate the interface pressure under high temperature, so as to more accurately predict the interface pressure value and changing trend of cable accessories under working conditions, and ensure the safe and stable operation of the cable accessory system. Summary of the invention

[0005] The purpose of the present invention is to provide a method and related device for calculating the interface pressure between a cable accessory and a cable body at high temperature, so as to solve the technical problem that it is difficult to accurately calculate the interface pressure between a cable accessory and a cable body at high temperature in the prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for calculating the interface pressure between a cable accessory and a body at high temperature, comprising the following steps:

[0008] Obtain the ambient temperature, inner diameter and outer diameter of the cable accessories before and after assembly, as well as the relevant parameters of the insulation materials of the cable accessories;

[0009] Calculate the interface pressure change caused by the thermal expansion effect by using the ambient temperature, inner diameter and outer diameter of the cable accessories before and after assembly, and relevant parameters of the insulating material of the cable accessories;

[0010] Obtain the Gough-Joule effect coefficient δ, and calculate the interface pressure change caused by the Gough-Joule effect by combining the ambient temperature, inner diameter and relevant parameters of the cable accessory insulation material before and after assembly of the cable accessory;

[0011] The interface pressure value at room temperature after the cable accessories are assembled is obtained. According to the interface pressure changes caused by thermal expansion effect and Gough-Joule effect, the interface pressure between the cable accessories and the body at high temperature is finally calculated.

[0012] Furthermore, the step of obtaining the ambient temperature, inner diameter and outer diameter of the cable accessories before and after assembly, and related parameters of the insulating material of the cable accessories specifically includes:

[0013] Measure the ambient temperature T0 when the cable accessories are initially assembled and the high-temperature working ambient temperature T1 by using a thermometer or temperature sensor;

[0014] The inner diameter a0 and outer diameter b0 of the cable accessories before assembly, as well as the inner diameter a1 and outer diameter b1 after assembly are measured with a caliper;

[0015] Obtain the elastic modulus E and thermal expansion coefficient α of the cable accessories insulation material through test detection or inquiry of factory parameters j And the thermal expansion coefficient α of the cable outer insulation material c .

[0016] Furthermore, the step of calculating the interface pressure change caused by the thermal expansion effect is specifically calculated by the formula:

[0017]

[0018] ΔT=T1-T0

[0019] Wherein, Δp1 is the change in interface pressure caused by thermal expansion effect; E is the elastic modulus of the insulating material of the cable accessories; v is the Poisson's ratio of the insulating material of the cable accessories; ΔT is the change in ambient temperature before and after the cable accessories are assembled; α j is the thermal expansion coefficient of the insulation material of the cable accessories; α c is the thermal expansion coefficient of the cable outer insulation material.

[0020] Furthermore, the method for obtaining the Gough-Joule effect coefficient δ specifically includes:

[0021] Cutting to obtain a rubber material sample to be tested;

[0022] The rubber material sample to be tested is fixed on a dynamic thermomechanical analyzer, the elongation rate and heating rate of the sample are set, and the change of the tensile stress in the sample is recorded; multiple elongation rates are selected and measured respectively;

[0023] According to the measurement results, the σ-T curve of tensile stress and temperature in the sample at different stretching rates is made;

[0024] The obtained σ-T curve is linearly fitted according to the formula σ=b+CT to obtain the change rate C of the tensile stress-temperature in the rubber sample at different stretching rates;

[0025] According to the change rate C of the tensile stress-temperature in the rubber sample under different stretching rates, a C-λ curve is drawn, and its slope δ is obtained by linear fitting, which is the Gough-Joule effect coefficient of the rubber material to be tested in the temperature range.

[0026] Furthermore, the step of calculating the interface pressure change caused by the Gough-Joule effect is specifically calculated by the following formula:

[0027]

[0028] Where Δp2 is the change in interface pressure caused by the Gough-Joule effect; δ is the Gough-Joule effect coefficient; ΔT is the change in ambient temperature before and after the cable accessories are assembled.

[0029] Furthermore, the method for obtaining the interface pressure value at room temperature after the cable accessories are assembled specifically includes:

[0030] The interface pressure value at room temperature after the cable accessories are assembled is obtained by calculation using a thick-walled cylinder model or by direct measurement using a thin film pressure sensor.

[0031] Furthermore, the step of finally calculating the interface pressure between the cable accessory and the body at high temperature is specifically calculated by the following formula:

[0032] p=p0+Δp1+Δp2

[0033] Where, p is the interface pressure between the cable accessory and the body at high temperature; p0 is the interface pressure value at room temperature after the cable accessory is assembled; Δp1 is the interface pressure change caused by thermal expansion effect; Δp2 is the interface pressure change caused by Gough-Joule effect;

[0034] Substituting the specific calculation formulas of the interface pressure change caused by thermal expansion effect and the interface pressure change caused by Gough-Joule effect into the above formula, we get:

[0035]

[0036] Where, E is the elastic modulus of the cable accessory insulation material; v is the Poisson's ratio of the cable accessory insulation material; ΔT is the change in ambient temperature before and after the cable accessory is assembled; α j is the thermal expansion coefficient of the insulation material of the cable accessories; α c is the thermal expansion coefficient of the cable outer insulation material.

[0037] In a second aspect, the present invention provides a system for calculating the interface pressure between a cable accessory and a body at high temperature, comprising:

[0038] A parameter acquisition module is used to obtain the ambient temperature, inner diameter and outer diameter of the cable accessories before and after assembly, as well as relevant parameters of the insulation materials of the cable accessories;

[0039] An expansion effect calculation module, used to calculate the interface pressure change caused by the thermal expansion effect through the ambient temperature, inner diameter and outer diameter of the cable accessories before and after assembly, and relevant parameters of the cable accessories insulation material;

[0040] The Gough-Joule effect calculation module is used to obtain the Gough-Joule effect coefficient δ and calculate the interface pressure change caused by the Gough-Joule effect in combination with the ambient temperature, inner diameter and relevant parameters of the cable accessory insulation material before and after the cable accessory is assembled;

[0041] The interface pressure calculation module is used to obtain the interface pressure value at room temperature after the cable accessories are assembled. According to the interface pressure changes caused by thermal expansion effect and Gough-Joule effect, the interface pressure between the cable accessories and the body at high temperature is finally calculated.

[0042] In a third aspect, the present invention provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above method when executing the computer program.

[0043] In a fourth aspect, the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the above method are implemented.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention discloses a method and a related device for calculating the interface pressure between a cable accessory and a body at high temperature, which comprehensively considers the influence of thermal expansion effect and Gough-Joule effect on the interface pressure of cable accessories at high temperature, and can quantitatively calculate the change of interface pressure when the temperature rises, which can be applied to select the design value of interface pressure in early product design. In addition, the method does not use invasive measurement equipment throughout the process, so for cable accessories in actual working conditions, it is only necessary to measure their temperature, related materials and dimensional parameters, and the interface pressure change caused by the temperature rise can be calculated in real time, which is convenient for on-site monitoring of interface pressure. Compared with the prior art, the calculation result is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0047] Figure 1 is a flow chart of the method of the present invention;

[0048] Figure 2 is a schematic diagram of the system of the present invention;

[0049] Figure 3 This is a schematic diagram of a simplified thick-walled cylindrical plane axisymmetric model of a cable accessory according to an embodiment of the present invention;

[0050] Figure 4 Schematic diagram of a thin film piezoresistive measurement system for cable accessory interface pressure at high temperature according to an embodiment of the present invention;

[0051] Figure 5 This is a schematic diagram of measuring the Gough-Joule effect parameters of a rubber material according to an embodiment of the present invention;

[0052] Among them: 201-cable accessories; 202-piezoresistive film sensor; 203-alloy mold; 204-film pressure testing system; 205-first measurement computer; 206-constant temperature box; 301-silicon rubber sample; 302-measuring fixture; 303-dynamic thermomechanical analyzer; 304-second measurement computer. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0054] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0056] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0057] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0058] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0059] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0060] See also Figure 1 The embodiment of the present invention discloses a method for calculating the interface pressure between a cable accessory and a body at high temperature, comprising the following steps:

[0061] Step 1, obtaining the ambient temperature, inner diameter and outer diameter of the cable accessories before and after assembly, and relevant parameters of the insulating materials of the cable accessories;

[0062] The ambient temperature T0 when the cable accessories are initially assembled and the high-temperature working ambient temperature T1 are measured by a thermometer or a temperature sensor; the temperature difference between the two environments ΔT=T1-T0 is calculated.

[0063] The inner diameter a0 and outer diameter b0 of the cable accessories before assembly, as well as the inner diameter a1 and outer diameter b1 after assembly are measured with a caliper;

[0064] Obtain the elastic modulus E and thermal expansion coefficient α of the cable accessories insulation material through test detection or inquiry of factory parameters j And the thermal expansion coefficient α of the cable outer insulation material c .

[0065] Step 2, calculating the interface pressure change caused by the thermal expansion effect according to the ambient temperature, inner diameter and outer diameter of the cable accessory before and after assembly, and relevant parameters of the insulating material of the cable accessory;

[0066] See also Figure 3 In applied elastic-plastic mechanics, a cylinder with a ratio of outer radius to inner radius greater than 1.2 is called a thick-walled cylinder. By referring to the inner and outer diameter dimensions of common cable accessories, it can be seen that it meets the definition of a thick-walled cylinder. When the thick-walled cylinder is in an elastic state, the stress method or displacement method can be used to solve the stress and strain. Considering the actual situation of the cable accessory system, it can be considered that its distribution along the axial direction is almost unchanged, so it can be analyzed as a plane axisymmetric problem. Figure 1 As shown. Plane problems can be divided into two categories: plane stress problems and plane strain problems. Obviously, the solution of cable accessories belongs to the plane strain problem, and the subsequent derivation of surface pressure is based on the plane strain model.

[0067] First, the influence of thermal expansion effect on interface pressure is analyzed, and the term describing thermal expansion is introduced into the stress-strain relationship (constitutive equation) of the microelement to obtain:

[0068]

[0069] Among them, α j represents the thermal expansion coefficient of the cable accessory insulation material, E and v represent the elastic modulus and Poisson's ratio of the cable accessory insulation material, ΔT represents the temperature change, ε r ~ε zRepresent the radial, tangential and axial strains respectively, σ r ~σ z They represent the stresses in these three directions respectively.

[0070] According to the basic assumption of plane strain problem, it can be considered that ε z =0, so (1) can be transformed into

[0071]

[0072] The equilibrium equations and geometric equations for plane axisymmetric problems are:

[0073]

[0074] Among them, u represents the radial displacement of the infinitesimal element, and r represents the radial coordinate of the infinitesimal element.

[0075] Take u as the unknown function and r as the independent variable, and substitute equations (2) and (4) into (3) to obtain the following equation:

[0076]

[0077] Solve this equation and substitute the expression of u into equations (2) and (4), and we get:

[0078]

[0079] Among them, C1′ and C2′ represent constants and are related to the boundary conditions.

[0080] At the initial temperature T0, the inner and outer diameters of the cable accessories before assembly are a0 and b0 respectively, while the inner and outer diameters after assembly become a1 and b1. The interface pressure at this time is p0. Then the temperature rises to T1=T0+ΔT. Affected by thermal expansion, the inner and outer diameters of the cable accessories become a2 and b2. The interface pressure at this time becomes p0+Δp1.

[0081] So we can get the following boundary conditions:

[0082]

[0083] Among them, Δσ r Represents the change in the axial stress of the microelement at r before and after the temperature rises.

[0084] Substituting (7) into (6), we can find the values ​​of C1′ and C2′, and then we can get the change Δσ of the axial stress of the microelement at r: r The expression is as follows:

[0085]

[0086] In addition, the expression for the axial displacement at the interface before and after heating (i.e., at r=a1) can be calculated as follows:

[0087]

[0088] In the operating temperature range of cable accessories (40 to 90 degrees Celsius), the elastic modulus of the cable outer insulation material (general cross-linked polyethylene XLPE) is much greater than that of the silicone rubber material, so it can be considered to be free to expand thermally without restraint. The axial displacement at the interface is equal to the change in the outer diameter of the cable accessory outer insulation caused by thermal expansion, that is:

[0089]

[0090] Among them, α c Represents the thermal expansion coefficient of the cable's outer insulation material.

[0091] By comparing equations (9) and (10), the change in interface pressure Δp1 caused by thermal expansion can be obtained as follows:

[0092]

[0093] Wherein, Δp1 is the change in interface pressure caused by thermal expansion effect; E is the elastic modulus of the insulating material of the cable accessories; v is the Poisson's ratio of the insulating material of the cable accessories; ΔT is the change in ambient temperature before and after the cable accessories are assembled; α j is the thermal expansion coefficient of the insulation material of the cable accessories; α c is the thermal expansion coefficient of the cable outer insulation material.

[0094] Step 3, obtaining the Gough-Joule effect coefficient δ, and calculating the interface pressure change caused by the Gough-Joule effect in combination with the ambient temperature, inner diameter and relevant parameters of the cable accessory insulation material before and after the cable accessory is assembled;

[0095] A silicone rubber sample for cable accessories was taken and its Gough-Joule effect coefficient δ within the working temperature range was measured using a dynamic thermal mechanical analyzer.

[0096] Consider the change in interfacial pressure caused by the Gough-Joule effect. The so-called Gough-Joule effect refers to the phenomenon that the tensile stress of a rubber material in a stretched state increases when it is heated. This effect satisfies the following formula:

[0097]

[0098] Among them, λ1~λ3 represent the elongation of the rubber sample in three directions, σ represents the tensile stress of the rubber sample in the λ1 direction, and δ represents the Gough-Joule effect parameter. For a certain material, this value is fixed and can be measured using a dynamic thermomechanical analyzer.

[0099] Since the silicone rubber material used in cable accessories is always in a tensile state after installation, when its temperature rises, the Gough-Joule effect will increase the tensile stress therein, thereby causing the interface pressure to rise. Since the Poisson's ratio of the cable accessory material is 0.49, it can be basically considered that its volume does not change before and after stretching, so λ1λ2λ3=1, and since the cable accessories are in a plane strain state, λ3=1, then formula (12) can be transformed into:

[0100]

[0101] Therefore, when the temperature rises by ΔT, the change of tangential stress in the cable accessories caused by the Gough-Joule effect is:

[0102]

[0103] Among them, λ1 is the radial expansion rate of the cable accessories, and its value is approximately

[0104] Using the plane strain condition, the radial stress change in the cable accessories caused by the Gough-Joule effect can be obtained from equation (14), that is, the change in interface pressure caused by the Gough-Joule effect is:

[0105]

[0106] Step 4, obtain the interface pressure value at room temperature after the cable accessories are assembled, and finally calculate the interface pressure between the cable accessories and the body at high temperature based on the interface pressure change caused by thermal expansion effect and the interface pressure change caused by Gough-Joule effect.

[0107] The interface pressure value p0 at room temperature after the cable accessories are assembled is obtained by calculation using a thick-walled cylinder model or by direct measurement using a thin film pressure sensor.

[0108] Finally, the interface pressure between the cable accessories and the body at high temperature is calculated:

[0109] p=p0+Δp1+Δp2 (16)

[0110] Where, p is the interface pressure between the cable accessory and the body at high temperature; p0 is the interface pressure value at room temperature after the cable accessory is assembled; Δp1 is the interface pressure change caused by thermal expansion effect; Δp2 is the interface pressure change caused by Gough-Joule effect;

[0111] Substituting equation (11) and equation (15) into equation (16), we obtain:

[0112]

[0113] Where, E is the elastic modulus of the cable accessory insulation material; v is the Poisson's ratio of the cable accessory insulation material; ΔT is the change in ambient temperature before and after the cable accessory is assembled; α j is the thermal expansion coefficient of the insulation material of the cable accessories; α c is the thermal expansion coefficient of the cable outer insulation material.

[0114] In a feasible implementation manner of the present invention, the method for measuring the Gough-Joule effect coefficient δ in step 3 comprises the following steps:

[0115] (1) Cut the rubber material sample to be tested into a suitable size (the size is determined according to the measurement mold size of the thermomechanical analyzer used).

[0116] (2) According to the actual working conditions, select the appropriate temperature range, heating rate and rubber material elongation λ.

[0117] (3) Fix the rubber sample to a dynamic mechanical analyzer (DMA), set the measurement program to a fixed sample elongation, heat at a given heating rate, and record the change in tensile stress in the sample. Select multiple elongation rates and measure them separately.

[0118] (4) After the measurement is completed, a relationship curve (σ-T curve) between the tensile stress (σ) and the temperature (T) in the sample at different stretching rates is made based on the measurement results.

[0119] (5) The σ-T curves at different stretching rates obtained in step (4) are linearly fitted according to the formula σ=b+CT to obtain the change rate C of the tensile stress-temperature in the rubber sample at different stretching rates.

[0120] (6) Using the change rate C of the tensile stress-temperature in the rubber sample at different stretching rates obtained in step (5), a C-λ curve is drawn, and its slope δ is obtained by linear fitting, which is the Gough-Joule effect parameter of the material in the temperature range.

[0121] (7) Using the Gough-Joule effect parameters obtained by this method, it is possible to calculate the change in tensile stress due to the Gough-Joule effect when the temperature rises for a rubber material with a given elongation.

[0122] Example:

[0123] This example takes the 8.7 / 10k cable intermediate joint provided by Guangzhou Gaoli Cable Accessories Co., Ltd. as an example, and cuts a section of it for actual measurement. The specific test includes the following steps:

[0124] S1. Measured by vernier caliper, the inner radius of the connector before assembly is 11.35mm and the outer radius is 23.35mm. Checking the factory parameters of the cable accessories shows that within the elastic deformation range of the connector set (strain less than 150%), the nominal elastic modulus of the rubber insulation is E = 0.95MPa, and the thermal expansion coefficient is about 8×10 -4 K -1 .

[0125] S2. Cut off about 10 cm of the main insulation section of the cable joint and fit it with the alloy mold 203 with a variable radius to achieve different expansion rates of the cable accessories. The elastic modulus of the mold is much larger than that of the cable accessory material, and its thermal expansion coefficient is 1.7×10 -5 K -1 .

[0126] S3. Build the interface pressure measurement system as follows Figure 4 As shown, the assembled cable accessory 201 is connected to the piezoresistive film sensor 202 , placed in a constant temperature box 206 to simulate a high temperature environment, and measured by a film pressure testing system 204 and a first measurement computer 205 .

[0127] S4. Use Figure 5 The Gough-Joule effect coefficient measurement system shown in the figure measures the Gough-Joule effect parameters of silicone rubber materials used in cable accessories. The cut silicone rubber sample 301 is mounted on the measuring fixture 302 of the dynamic thermomechanical analyzer. The specific size parameters of the silicone rubber sample 301 are determined according to the measuring fixture 302. Appropriate measurement conditions (including elongation, temperature range, and heating rate) are selected according to actual application requirements. The measurement program of the dynamic thermomechanical analyzer 303 is set to a fixed elongation and a uniform heating rate. The second measurement computer 304 is used to record the tensile stress changes in the silicone rubber sample 301. Finally, the Gough-Joule effect coefficient is obtained by fitting the above formula to be 5.491×10 -4 MPa / K.

[0128] S5. Substitute the above data into formula (17) to calculate the theoretical values ​​of the interface pressure of the cable accessories at different temperatures, and compare them with the measured values ​​of the actual film pressure sensor. Table 1 lists the piezoresistive film measurement results of the interface pressure of the cable accessories and the theoretical derivation values ​​of the present invention, and the results are basically consistent. Therefore, the present invention can better calculate the interface pressure value between the cable accessories and the cable body at high temperature.

[0129] Table 1

[0130]

[0131] See also Figure 2 The embodiment of the present invention discloses a system for calculating the interface pressure between a cable accessory and a body at high temperature, including a parameter acquisition module, an expansion effect calculation module, a Gough-Joule effect calculation module and an interface pressure calculation module:

[0132] The parameter acquisition module is used to obtain the ambient temperature, inner diameter and outer diameter before and after the cable accessories are assembled, as well as the relevant parameters of the cable accessories insulating materials; the expansion effect calculation module is used to calculate the interface pressure change caused by the thermal expansion effect through the ambient temperature, inner diameter and outer diameter before and after the cable accessories are assembled, as well as the relevant parameters of the cable accessories insulating materials; the Gough-Joule effect calculation module is used to obtain the Gough-Joule effect coefficient δ, and calculate the interface pressure change caused by the Gough-Joule effect in combination with the ambient temperature, inner diameter and relevant parameters of the cable accessories insulating materials before and after the cable accessories are assembled; the interface pressure calculation module is used to obtain the interface pressure value at room temperature after the cable accessories are assembled, and finally calculate the interface pressure between the cable accessories and the body at high temperature based on the interface pressure change caused by the thermal expansion effect and the interface pressure change caused by the Gough-Joule effect.

[0133] In one embodiment of the present invention, a computer device is provided, the computer device comprising a processor and a memory, the memory is used to store a computer program, the computer program comprises program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc., which are the computing core and control core of the terminal, which are suitable for implementing one or more instructions, and are specifically suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used for the operation of the method for calculating the interface pressure between the cable accessories and the body at high temperature.

[0134] The present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It is understandable that the computer-readable storage medium here can include both built-in storage media in the computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory (non-volatile memory), such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the method for calculating the interface pressure between the cable accessory and the body at high temperature in the above embodiment.

[0135] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0136] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0137] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0138] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for calculating the interface pressure between a cable accessory and a body at high temperature, characterized in that: The following steps are involved: Obtain the ambient temperature, inner diameter and outer diameter of the cable accessories before and after assembly, as well as the relevant parameters of the insulation materials of the cable accessories; Calculate the interface pressure change caused by the thermal expansion effect by using the ambient temperature, inner diameter and outer diameter of the cable accessories before and after assembly, and relevant parameters of the insulating material of the cable accessories; Obtain the Gough-Joule effect coefficient δ, and calculate the interface pressure change caused by the Gough-Joule effect by combining the ambient temperature, inner diameter and relevant parameters of the cable accessory insulation material before and after assembly of the cable accessory; The interface pressure value at room temperature after the cable accessories are assembled is obtained. According to the interface pressure changes caused by thermal expansion effect and Gough-Joule effect, the interface pressure between the cable accessories and the body at high temperature is finally calculated.

2. The method for calculating the interface pressure between a cable accessory and a body at high temperature according to claim 1, characterized in that: The step of obtaining the ambient temperature, inner diameter and outer diameter of the cable accessories before and after assembly, and related parameters of the insulating material of the cable accessories specifically includes: Measure the ambient temperature T0 when the cable accessories are initially assembled and the high-temperature working ambient temperature T1 by using a thermometer or temperature sensor; The inner diameter a0 and outer diameter b0 of the cable accessories before assembly, as well as the inner diameter a1 and outer diameter b1 after assembly are measured with a caliper; Obtain the elastic modulus E and thermal expansion coefficient α of the cable accessories insulation material through test detection or inquiry of factory parameters j And the thermal expansion coefficient α of the cable outer insulation material c .

3. The method for calculating the interface pressure between a cable accessory and a body at high temperature according to claim 1, characterized in that: The step of calculating the change in interface pressure caused by the thermal expansion effect is specifically calculated by the following formula: ΔT=T1-T0 Wherein, Δp1 is the change in interface pressure caused by thermal expansion effect; E is the elastic modulus of the insulating material of the cable accessories; v is the Poisson's ratio of the insulating material of the cable accessories; ΔT is the change in ambient temperature before and after the cable accessories are assembled; α j is the thermal expansion coefficient of the insulation material of the cable accessories; α c is the thermal expansion coefficient of the cable outer insulation material.

4. The method for calculating the interface pressure between a cable accessory and a body at high temperature according to claim 1, characterized in that: The method for obtaining the Gough-Joule effect coefficient δ specifically includes: Cutting to obtain a rubber material sample to be tested; The rubber material sample to be tested is fixed on a dynamic thermomechanical analyzer, the elongation rate and heating rate of the sample are set, and the change of the tensile stress in the sample is recorded; multiple elongation rates are selected and measured respectively; According to the measurement results, the σ-T curve of tensile stress and temperature in the sample at different stretching rates is made; The obtained σ-T curve is linearly fitted according to the formula σ=b+CT to obtain the change rate C of the tensile stress-temperature in the rubber sample at different stretching rates; According to the change rate C of tensile stress-temperature in the rubber sample under different stretching rates, a C-λ curve is drawn, and its slope δ is obtained by linear fitting, which is the Gough-Joule effect coefficient of the rubber material to be tested in the temperature range.

5. The method for calculating the interface pressure between a cable accessory and a body at high temperature according to claim 1, characterized in that: The specific calculation formula for the step of calculating the interface pressure change caused by the Gough-Joule effect is: Where Δp2 is the change in interface pressure caused by the Gough-Joule effect; δ is the Gough-Joule effect coefficient; ΔT is the change in ambient temperature before and after the cable accessories are assembled.

6. The method for calculating the interface pressure between a cable accessory and a body at high temperature according to claim 1, characterized in that: The method for obtaining the interface pressure value at room temperature after the cable accessories are assembled specifically includes: The interface pressure value at room temperature after the cable accessories are assembled is obtained by calculation using a thick-walled cylinder model or by direct measurement using a thin film pressure sensor.

7. The method for calculating the interface pressure between a cable accessory and a body at high temperature according to claim 1, characterized in that: The step of finally calculating the interface pressure between the cable accessory and the body at high temperature is specifically calculated as follows: p=p0+Δp1+Δp2 Where, p is the interface pressure between the cable accessory and the body at high temperature; p0 is the interface pressure value at room temperature after the cable accessory is assembled; Δp1 is the interface pressure change caused by thermal expansion effect; Δp2 is the interface pressure change caused by Gough-Joule effect; Substituting the specific calculation formulas of the interface pressure change caused by thermal expansion effect and the interface pressure change caused by Gough-Joule effect into the above formula, we get: Where, E is the elastic modulus of the cable accessory insulation material; v is the Poisson's ratio of the cable accessory insulation material; ΔT is the change in ambient temperature before and after the cable accessory is assembled; α j is the thermal expansion coefficient of the insulation material of the cable accessories; α c is the thermal expansion coefficient of the cable outer insulation material.

8. A system for calculating the interface pressure between a cable accessory and a body at high temperature, characterized in that: include: A parameter acquisition module is used to obtain the ambient temperature, inner diameter and outer diameter of the cable accessories before and after assembly, as well as relevant parameters of the insulation materials of the cable accessories; An expansion effect calculation module, used to calculate the interface pressure change caused by the thermal expansion effect through the ambient temperature, inner diameter and outer diameter of the cable accessories before and after assembly, and relevant parameters of the insulating material of the cable accessories; The Gough-Joule effect calculation module is used to obtain the Gough-Joule effect coefficient δ and calculate the interface pressure change caused by the Gough-Joule effect in combination with the ambient temperature, inner diameter and relevant parameters of the cable accessory insulation material before and after the cable accessory is assembled; The interface pressure calculation module is used to obtain the interface pressure value at room temperature after the cable accessories are assembled. According to the interface pressure changes caused by thermal expansion effect and Gough-Joule effect, the interface pressure between the cable accessories and the body at high temperature is finally calculated.

9. A computer device 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, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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