Method for measuring degree of aging of insulating layer of high-voltage cable, and related apparatus

Abstract

A method for measuring the degree of aging of an insulating layer of a high-voltage cable, and a related apparatus. The method comprises: on the basis of each layer of structure of a cable, establishing a steady-state thermal circuit model; on the basis of structural parameters, calculating the thermal resistance T1 of an outer sheath and the thermal resistance T2 of a buffer layer, wherein the structural parameters comprise inner diameters and outer diameters; separately measuring the surface temperature θ0 of the outer sheath, the surface temperature θ1 of an aluminum sheath and a real-time load current I of the cable; on the basis of the thermal resistance T1 of the outer sheath, the surface temperature θ0 of the outer sheath and the surface temperature θ1 of the aluminum sheath, calculating a total heat flow Q of the cable; on the basis of the surface temperature θ0 of the outer sheath, the thermal resistance T1 of the outer sheath, the thermal resistance T2 of the buffer layer and the total heat flow Q, calculating the surface temperature θ2 of an insulating layer; on the basis of the total heat flow Q, the surface temperature θ2 of the insulating layer and the real-time load current I, calculating the thermal conductivity of the insulating layer; and on the basis of the thermal conductivity of the insulating layer, determining the degree of aging of the insulating layer of the cable.

Description

Methods and related devices for testing the aging degree of high voltage cable insulation.

[0001] This application claims priority to Chinese Patent Application No. 202411761237.1, filed with the Chinese Patent Office on December 3, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of high-voltage cable insulation aging detection technology, for example, to a method and related apparatus for detecting the aging degree of high-voltage cable insulation. Background Technology

[0003] Cross-linked polyethylene (XLPE) cables possess a unique molecular and cross-linking structure, resulting in excellent electrical properties, insulation performance, heat resistance, and mechanical properties. They are widely used in high-voltage and ultra-high-voltage transmission systems. During operation, cables undergo various aging processes due to environmental influences, broadly categorized as thermal aging, water treeing, electrical treeing, and other aging. As the primary carrier of power transmission in the power grid, the aging of the cable's insulation layer directly affects the reliability and safety of power transmission. Furthermore, a significant portion of cable equipment failures are caused by insulation aging. When cables experience severe aging, the insulation layer may degrade during operation, leading to breakdown and potentially causing fires or explosions.

[0004] To address the safety issues caused by cable aging, numerous methods exist both domestically and internationally for detecting the degree of cable aging. These include thermogravimetric analysis to measure activation energy, differential scanning calorimetry (DSC) to measure XLPE crystallinity, Fourier transform infrared spectroscopy (FTIR) to detect changes in chemical groups during XLPE cable aging, dielectric spectroscopy testing, and space charge measurement. However, all these methods require damaging the cable structure. This not only damages the cable but also causes power outages and reduces the quality of power for users. Currently, low-frequency online monitoring methods cannot be directly applied to monitoring due to the suddenness, frequency, and amplitude uncertainties of low-frequency signals generated by power system oscillations. Furthermore, the experimental results lack generalizability. Some studies have also focused on using distributed optical fiber to measure conductor and cable surface temperatures to calculate current-carrying capacity and monitor cable aging; however, the accuracy of optical fiber temperature measurement remains inconclusive, and this method cannot directly and accurately measure the degree of cable aging. Summary of the Invention

[0005] This application provides a method for detecting the aging degree of high-voltage cable insulation, in order to solve the problem that the aging degree of high-voltage cable insulation cannot be directly and accurately measured.

[0006] In a first aspect, this application provides a method for detecting the aging degree of the insulation layer of a high-voltage cable, wherein the cable comprises, from the inside out, a conductor, an insulation layer, a buffer layer, an aluminum sheath, and an outer sheath, and the method for detecting the aging degree of the insulation layer of the high-voltage cable includes:

[0007] Obtain the structural parameters of each layer of the cable, including the inner diameter and the outer diameter;

[0008] Calculate the thermal resistance T1 of the outer sheath and the thermal resistance T2 of the buffer layer based on the structural parameters.

[0009] Measure the surface temperature θ0 of the outer sheath and the real-time load current I of the cable;

[0010] The total heat flow Q of the cable is calculated based on the thermal resistance T1 of the outer sheath, the surface temperature θ0 of the outer sheath, and the surface temperature θ1 of the aluminum sheath.

[0011] The surface temperature θ2 of the insulation layer is calculated based on the surface temperature θ0 of the outer sheath, the thermal resistance T1 of the outer sheath, the thermal resistance T2 of the buffer layer, and the total heat flow Q.

[0012] The thermal conductivity of the insulation layer is calculated based on the total heat flux Q, the surface temperature θ2 of the insulation layer, and the real-time load current I.

[0013] The degree of aging of the cable insulation layer is determined by the thermal conductivity of the insulation layer.

[0014] Secondly, this application provides a device for detecting the aging degree of high-voltage cable insulation, comprising:

[0015] The model building module is used to establish a steady-state thermal circuit model based on the structure of each layer of the cable. The steady-state thermal circuit model includes the thermal resistance of the insulation layer, buffer layer, outer sheath, and conductor loss heat source.

[0016] A thermal resistance calculation module is used to calculate the thermal resistance T1 of the outer sheath and the thermal resistance T2 of the buffer layer based on the structural parameters, wherein the structural parameters include the inner diameter and the outer diameter.

[0017] The data measurement module is used to measure the surface temperature θ0 of the outer sheath, the surface temperature θ1 of the aluminum sheath, and the real-time load current I of the cable, respectively.

[0018] The full-line heat flow calculation module is used to calculate the full-line heat flow Q of the cable based on the thermal resistance T1 of the outer sheath, the surface temperature θ0 of the outer sheath, and the surface temperature θ1 of the aluminum sheath.

[0019] The insulation layer surface temperature calculation module is used to calculate the insulation layer surface temperature θ2 based on the outer sheath surface temperature θ0, the outer sheath thermal resistance T1, the buffer layer thermal resistance T2, and the total heat flow Q.

[0020] The insulation layer thermal conductivity calculation module is used to calculate the thermal conductivity of the insulation layer based on the total heat flux Q, the surface temperature θ2 of the insulation layer, and the real-time load current I.

[0021] The insulation aging degree determination module is used to determine the aging degree of the cable insulation layer based on the thermal conductivity of the insulation layer.

[0022] Thirdly, this application provides an electronic device, the electronic device comprising:

[0023] At least one processor; and

[0024] A memory communicatively connected to the at least one processor; wherein,

[0025] The memory stores a computer program that can be executed by the at least one processor, which enables the at least one processor to perform the high-voltage cable insulation aging detection method described in the first aspect of this application.

[0026] Fourthly, this application provides a computer-readable storage medium storing computer instructions that, when executed by a processor, implement the high-voltage cable insulation aging detection method described in the first aspect of this application.

[0027] The high-voltage cable insulation aging detection method provided in this application establishes a steady-state thermal circuit model based on the cable's structure of each layer. This model includes the thermal resistances of the insulation layer, buffer layer, and outer sheath, as well as conductor loss heat sources. The method calculates the thermal resistance T1 of the outer sheath and the thermal resistance T2 of the buffer layer based on the structural parameters, including the inner and outer diameters. It measures the surface temperature θ0 of the outer sheath, the surface temperature θ1 of the aluminum sheath, and the real-time load current I of the cable. Based on the thermal resistance T1, surface temperature θ0, and surface temperature θ1 of the outer sheath, the method calculates the total heat flow Q of the cable. Based on the surface temperature θ0, thermal resistance T1, thermal resistance T2, and total heat flow Q, the method calculates the surface temperature θ2 of the insulation layer. Based on the total heat flow Q, surface temperature θ2, and real-time load current I, the method calculates the thermal conductivity of the insulation layer. Finally, it determines the aging degree of the cable insulation layer based on the thermal conductivity of the insulation layer. The thermal resistance of the insulation layer, buffer layer, and outer sheath is virtually constructed based on a steady-state thermal circuit model. The corresponding thermal resistance value and surface temperature are calculated using formulas and the law of thermal conduction. Furthermore, the thermal conductivity of the insulation layer is detected. The thermal conductivity of the insulation layer is highly correlated with the degree of aging of the insulation layer. Therefore, the degree of aging of the insulation layer can be determined by the thermal conductivity of the insulation layer. The degree of aging of the insulation layer is detected without damaging the insulation layer and conductor of the cable, and it will not affect the use of the cable. This can ensure the stability and reliability of the cable insulation material. Attached Figure Description

[0028] Figure 1 is a flowchart of a method for detecting the aging degree of high-voltage cable insulation layer according to an embodiment of this application;

[0029] Figure 2 is a schematic diagram of a steady-state thermal circuit model provided in an embodiment of this application;

[0030] Figure 3 is a schematic diagram of a high-voltage cable insulation aging detection device provided in an embodiment of this application;

[0031] Figure 4 is a schematic diagram of the structure of the electronic device provided in an embodiment of this application. Detailed Implementation

[0032] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of this application, and not all of them.

[0033] Figure 1 is a flowchart of a method for detecting the aging degree of high-voltage cable insulation layer according to an embodiment of this application. This embodiment is applicable to situations where the aging degree of high-voltage cable insulation layer is detected. This method can be executed by a high-voltage cable insulation layer aging degree detection device, which can be implemented in hardware and / or software and can be configured in an electronic device. As shown in Figure 1, the method for detecting the aging degree of high-voltage cable insulation layer includes:

[0034] S101. Establish a steady-state thermal circuit model based on the structure of each layer of the cable. The steady-state thermal circuit model includes the thermal resistance of the insulation layer, buffer layer, outer sheath, and conductor loss heat source.

[0035] In this application, the thermal resistance of each structural layer is calculated based on a steady-state thermal circuit model and Fourier's law of heat transfer. Fourier's law states that the heat flux density Q is equal to the product of the temperature difference ΔT and the thermal resistance R, i.e., Q = ΔT / R. This law describes that during heat conduction, the amount of heat passing through a given cross-section per unit time is directly proportional to the rate of temperature change perpendicular to that cross-section and the cross-sectional area, and the direction of heat transfer is opposite to the direction of temperature increase.

[0036] In an optional example, the schematic diagram of the steady-state thermal circuit model is shown in Figure 2. Taking the conductor as the heat source and also the innermost structure, the steady-state thermal circuit model of the cable consists of the conductor, insulation layer, buffer layer, aluminum sheath, and outer sheath from the inside out. Correspondingly, the insulation layer, buffer layer, and outer sheath are provided with thermal resistances of T3, T2, and T1, respectively. Thermal resistance will hinder the transfer of temperature, which will cause the temperature to decrease during heat transfer. Therefore, the surface temperature of the conductor θ3, the surface temperature of the insulation layer θ2, the surface temperature of the buffer layer θ1, and the surface temperature of the outer sheath θ0 must decrease in that order.

[0037] Among them, aluminum has relatively low thermal resistance. Therefore, in the steady-state thermal circuit model of this embodiment, the thermal resistance of the aluminum sheath is not shown (considered as 0). The inner and outer sides of the aluminum sheath can be regarded as isothermal nodes, that is, the temperature of the two nodes is the surface temperature θ1 of the buffer layer.

[0038] S102. Calculate the thermal resistance T1 of the outer sheath and the thermal resistance T2 of the buffer layer based on the structural parameters.

[0039] The structural parameters include the inner diameter and the outer diameter, specifically referring to the inner and outer diameters excluding the insulation layer, buffer layer, aluminum sheath, and outer sheath.

[0040] Specifically, the aluminum sheath is a corrugated metal sheath, and the thermal resistance T1 of the outer sheath is calculated using the following formula:

[0041] ρ T D is the thermal resistance coefficient of the insulating layer material. it D is the diameter of an imaginary concentric cylinder tangent to the inner surface of the corrugated metal sleeve trough. oc The diameter of an imaginary concentric cylinder tangent to the crest of the corrugated metal sleeve; t s t3 represents the thickness of the corrugated metal sleeve, and t3 represents the thickness of the outer protective layer.

[0042] The formula for calculating the thermal resistance T2 of the buffer layer is as follows;

[0043] Where λ1 is the thermal conductivity of the buffer layer material, and D and d are the outer and inner diameters of the buffer layer, respectively. The thermal conductivity of the buffer layer material can also be obtained in advance.

[0044] S103. Measure the surface temperature θ0 of the outer sheath, the surface temperature θ1 of the aluminum sheath, and the real-time load current I of the cable.

[0045] The real-time load current I of the cable can be obtained by measuring a current sensor. Temperature (cable surface temperature, aluminum sheath surface temperature) is measured using a temperature sensor. Specifically, the surface temperature θ0 of the outer sheath can be obtained by measuring the temperature of the aluminum sheath, while the surface temperature θ1 of the aluminum sheath can be obtained by drilling holes in the outer sheath and then measuring the surface temperature of the aluminum sheath using a temperature sensor. Measuring the aluminum sheath temperature by drilling holes, and sealing the drilled holes after measurement, will not damage the cable structure or affect its use. Specifically, the temperature sensor is properly connected to the cable surface to measure the cable surface temperature θ0. For measuring the temperature of the aluminum sheath, a hole is drilled to the outside of the aluminum sheath using an electric drill. The diameter of the hole should not exceed 3 mm. The temperature sensor is then placed in good contact with the outer surface of the aluminum sheath to measure the surface temperature θ1.

[0046] In an optional embodiment, before measuring the cable surface temperature, aluminum sheath surface temperature, and conductor load current value corresponding to each of the resistor branches, the method further includes: acquiring the reading deviation of the temperature sensor; determining whether the reading deviation of the temperature sensor is less than a preset deviation range; if so, then performing the step of measuring the cable surface temperature, aluminum sheath surface temperature, and conductor load current value corresponding to each of the resistor branches. To ensure the accuracy of the temperature sensor measurement data, before using the sensor, connect the temperature sensor to the same experimental instrument to observe whether there is a deviation in the reading and the specific reading deviation. Temperature sensors with large deviations are replaced in a timely manner to reduce detection errors.

[0047] S104. Calculate the total heat flow Q of the cable based on the thermal resistance T1 of the outer sheath, the surface temperature θ0 of the outer sheath, and the surface temperature θ1 of the aluminum sheath.

[0048] Specifically, based on Fourier's heat transfer law and the steady-state thermal circuit model, the formula for calculating the total heat flux Q is as follows;

[0049] θ1 and θ0 are the surface temperatures of the outer sheath and the aluminum sheath, respectively, and T1 is the thermal resistance of the outer sheath.

[0050] S105. Calculate the surface temperature θ2 of the insulation layer based on the surface temperature θ0 of the outer sheath, the thermal resistance T1 of the outer sheath, the thermal resistance T2 of the buffer layer, and the total heat flow Q.

[0051] According to Fourier's heat transfer law and steady-state thermal circuit model, the surface temperature θ2 of the insulation layer is calculated as follows: θ2=Q(T2+T1)+θ0.

[0052] S106. Calculate the thermal conductivity of the insulation layer based on the total heat flow Q, the surface temperature θ2 of the insulation layer, and the real-time load current I.

[0053] Specifically, it includes:

[0054] A1. Calculate the AC resistance of the conductor based on the total heat flow Q and the real-time load current I.

[0055] The formula for calculating the AC resistance of a conductor is:

[0056] A2. Calculate the conductor temperature θ3 based on the conductor's AC resistance.

[0057] The formula for calculating the AC resistance of a conductor is: R = R0[1 + α] 20 (θ3-20)][1+y s +y p ];

[0058] Based on this formula, the formula for calculating the conductor temperature θ3 is as follows:

[0059] In the above formula, Q is the total heat flux, R is the AC resistance of the conductor, I is the real-time load current, and R0 and α are the total heat flux. 20 These represent the DC resistance and temperature coefficient of the conductor at 20℃, respectively. s y p These are the known skin effect factor and proximity effect factor, respectively. The temperature coefficient of standard soft copper is taken as 0.00392. The cable in this application is a single-core cable, meaning it has only one conductor. For a single-core cable, the proximity effect factor is 0.

[0060] Since the AC resistance of a conductor can be calculated based on the total heat flow and load current, this value can be substituted into the formula for calculating the conductor temperature θ3 to obtain the conductor temperature θ3.

[0061] A3. Calculate the thermal resistance T3 of the insulation layer based on the conductor temperature θ3, the surface temperature θ2 of the insulation layer, and the total heat flow Q.

[0062] Similarly, according to Fourier's heat transfer law and the steady-state thermal circuit model, the formula for calculating the thermal resistance T3 of the insulation layer is:

[0063] A4. Calculate the thermal conductivity of the insulation layer based on the thermal resistance T3 of the insulation layer.

[0064] The formula for calculating the thermal conductivity of the insulation layer is as follows:

[0065] λ2 is the thermal conductivity of the insulating layer, d1 and d2 are the radii of the conductor surface and the insulating layer surface, respectively. The radius of the conductor surface is also the inner diameter of the insulating layer, and the radius of the insulating layer surface is the outer diameter of the insulating layer.

[0066] S107. Determine the degree of cable aging based on the thermal conductivity of the insulation layer.

[0067] The aging of the insulation layer significantly affects its thermal conductivity. Prolonged exposure to heat reduces the flexural and tensile strength of the insulation material, making it more susceptible to damage and potentially leading to insulation breakdown. Furthermore, moisture and other contaminants can form weak dielectrics, increasing conductivity and dielectric loss, further accelerating the thermal aging process. Therefore, the thermal conductivity of the insulation layer is the primary indicator for assessing its aging degree.

[0068] Temperature sensors and experimental instruments are used to monitor the real-time surface temperature θ0 of the cable and the temperature θ1 of the aluminum sheath, and the thermal parameters of the insulation layer are measured using a thermal circuit model. By comparing the thermal conductivity database from aging experiments, a non-destructive testing method for the aging degree of the cable is achieved.

[0069] Specifically, determining the degree of cable aging based on the thermal conductivity of the insulation layer includes:

[0070] A thermal conductivity database is obtained through aging experiments. The thermal conductivity database includes the thermal conductivity of the cable insulation layer at different aging levels. The thermal conductivity of the current cable insulation layer is compared with the data in the thermal conductivity database to determine the aging level of the current cable insulation layer.

[0071] A thermal conductivity database is pre-established, and then the thermal conductivity of the current cable insulation layer is compared with the data in the thermal conductivity database. Specifically, the aging degree corresponding to the current thermal conductivity is matched as the aging degree of the current cable insulation layer.

[0072] Specifically, a thermal conductivity database was established based on aging experiments. This database established a database of thermal conductivity coefficients corresponding to different aging degrees of cable insulation layers from different manufacturers. The process is as follows:

[0073] B1. Establish an electrothermal combined aging test platform.

[0074] The high-voltage generator was placed at the center of the electrothermal combined aging test, with six and four cable terminals placed on either side, respectively, ensuring safe distances between equipment and between buildings. A through-core transformer was placed on each cable circuit as an independent current generator.

[0075] B2. Using appropriate temperature as a reference, cables with different service years are subjected to constant temperature heating at 90℃ and thermal cycling heating aging methods to simulate two actual operating conditions: constant load and load fluctuation.

[0076] Cables with different service years have different degrees of insulation aging, which makes it easy to obtain the thermal conductivity of insulation layers with different aging degrees.

[0077] During the combined electrothermal aging experiment, samples of the experimental cable were taken at different aging times, and current-carrying temperature rise tests were conducted on the samples. Temperature data for each layer of the cable were recorded. The thermal conductivity of the insulation layer was calculated using the following formula.

[0078] Where d1 and d2 are the radii of the conductor surface (inner diameter of the insulation layer) and the radius of the XLPE insulation layer (outer diameter of the insulation layer), respectively. Q1 is the total heat flux detected during the aging test, θ3 is the detected conductor temperature, and θ2 is the detected surface temperature of the insulation layer during the aging test.

[0079] It should be noted that during the aging test, since the cable does not need to be connected to the power grid, holes can be drilled in the cable to obtain the conductor temperature θ3 and the surface temperature θ2 of the insulation layer. To ensure the accuracy of the temperature sensor measurements, before using the sensors, connect them to the same experimental instrument and observe for any deviations in the readings. Replace any temperature sensors with significant deviations promptly to reduce experimental errors.

[0080] B3. After obtaining the thermal conductivity of the insulation layer, organize the data to obtain the correlation between thermal conductivity and aging degree, and store the correlation in the thermal conductivity database.

[0081] Based on the thermal conductivity database, the thermal conductivity of the insulation layer is detected by using the detected cable surface temperature θ0 and aluminum sheath surface temperature θ1, combined with the derivation process of S101-S107. The aging degree of the insulation layer is obtained by comparing with the database, thus realizing non-destructive detection of the aging degree of the cable insulation layer.

[0082] The high-voltage cable insulation aging detection method provided in this application establishes a steady-state thermal circuit model based on the cable's structure of each layer. This model includes the thermal resistances of the insulation layer, buffer layer, and outer sheath, as well as conductor loss heat sources. The method calculates the thermal resistance T1 of the outer sheath and the thermal resistance T2 of the buffer layer based on the structural parameters, including the inner and outer diameters. It measures the surface temperature θ0 of the outer sheath, the surface temperature θ1 of the aluminum sheath, and the real-time load current I of the cable. Based on the thermal resistance T1, surface temperature θ0, and surface temperature θ1 of the outer sheath, the method calculates the total heat flow Q of the cable. Based on the surface temperature θ0, thermal resistance T1, thermal resistance T2, and total heat flow Q, the method calculates the surface temperature θ2 of the insulation layer. Based on the total heat flow Q, surface temperature θ2, and real-time load current I, the method calculates the thermal conductivity of the insulation layer. Finally, it determines the aging degree of the cable insulation layer based on the thermal conductivity of the insulation layer. The thermal resistance of the insulation layer, buffer layer, and outer sheath is virtually constructed based on a steady-state thermal circuit model. The corresponding thermal resistance value and surface temperature are calculated using formulas and the law of thermal conduction. Furthermore, the thermal conductivity of the insulation layer is detected. The thermal conductivity of the insulation layer is highly correlated with the degree of aging of the insulation layer. Therefore, the degree of aging of the insulation layer can be determined by the thermal conductivity of the insulation layer. The degree of aging of the insulation layer is detected without damaging the insulation layer and conductor of the cable, and it will not affect the use of the cable. This can ensure the stability and reliability of the cable insulation material.

[0083] Corresponding to the high-voltage cable insulation aging degree detection method in this application, this application also provides a high-voltage cable insulation aging degree detection device. Figure 3 is a structural schematic diagram of a high-voltage cable insulation aging degree detection device provided in an embodiment of this application. As shown in Figure 3, the high-voltage cable insulation aging degree detection device includes:

[0084] The model building module 301 is used to establish a steady-state thermal circuit model based on the structure of each layer of the cable. The steady-state thermal circuit model includes the thermal resistance of the insulation layer, buffer layer, outer sheath, and conductor loss heat source.

[0085] The thermal resistance calculation module 302 is used to calculate the thermal resistance T1 of the outer sheath and the thermal resistance T2 of the buffer layer based on the structural parameters, wherein the structural parameters include the inner diameter and the outer diameter.

[0086] The data measurement module 303 is used to measure the surface temperature θ0 of the outer sheath, the surface temperature θ1 of the aluminum sheath, and the real-time load current I of the cable, respectively.

[0087] The full-line heat flow calculation module 304 is used to calculate the full-line heat flow Q of the cable based on the thermal resistance T1 of the outer sheath, the surface temperature θ0 of the outer sheath, and the surface temperature θ1 of the aluminum sheath.

[0088] The insulation layer surface temperature calculation module 305 is used to calculate the surface temperature θ2 of the insulation layer based on the surface temperature θ0 of the outer sheath, the thermal resistance T1 of the outer sheath, the thermal resistance T2 of the buffer layer, and the total heat flow Q.

[0089] The insulation layer thermal conductivity calculation module 306 is used to calculate the thermal conductivity of the insulation layer based on the total heat flow Q, the surface temperature θ2 of the insulation layer and the real-time load current I.

[0090] The insulation layer aging degree determination module 307 is used to determine the aging degree of the cable insulation layer based on the thermal conductivity of the insulation layer.

[0091] Optionally, the thermal conductivity calculation module 306 for the insulating layer includes:

[0092] The conductor AC resistance calculation submodule is used to calculate the AC resistance of the conductor based on the total heat flow Q and the real-time load current I.

[0093] The conductor temperature calculation submodule is used to calculate the conductor temperature θ3 based on the conductor's AC resistance.

[0094] The insulation layer thermal resistance calculation submodule is used to calculate the thermal resistance T3 of the insulation layer based on the conductor temperature θ3, the surface temperature of the insulation layer θ2, and the total heat flow Q.

[0095] The insulation layer thermal conductivity calculation submodule is used to calculate the thermal conductivity of the insulation layer based on the thermal resistance T3 of the insulation layer.

[0096] Optionally, the insulation aging degree determination module 307 includes:

[0097] A thermal conductivity database acquisition submodule is used to acquire a thermal conductivity database, which is obtained through aging experiments and includes the thermal conductivity of the cable insulation layer under different aging degrees.

[0098] The aging degree determination submodule is used to compare the thermal conductivity of the current cable insulation layer with the data in the thermal conductivity database to determine the aging degree of the current cable insulation layer.

[0099] Optionally, the aluminum sheath is a corrugated metal sheath, and the thermal resistance T1 of the outer sheath is calculated using the following formula:

[0100] ρ T D is the thermal resistance coefficient of the insulating layer material. it D is the diameter of an imaginary concentric cylinder tangent to the inner surface of the corrugated metal sleeve trough. oc The diameter of an imaginary concentric cylinder tangent to the crest of the corrugated metal sleeve; t s t3 is the thickness of the corrugated metal sleeve, and t3 is the thickness of the outer protective layer.

[0101] The formula for calculating the thermal resistance T2 of the buffer layer is as follows;

[0102] Where λ1 is the thermal conductivity of the buffer layer material, and D and d are the outer and inner diameters of the buffer layer, respectively.

[0103] Specifically, the buffer layer includes the buffer layer body and the air gap;

[0104] The outer diameter of the buffer layer, D = D i +2·d r +d air ;

[0105] Where D i d is the outer diameter of the insulating layer. r d represents the thickness of the buffer layer body. air The thickness of the air gap.

[0106] Optionally, the formula for calculating the total heat flux Q is as follows;

[0107] θ1 and θ0 are the surface temperatures of the outer sheath and the aluminum sheath, respectively, and T1 is the thermal resistance of the outer sheath.

[0108] Optionally, the surface temperature θ2 is calculated using the following formula: θ2=Q(T2+T1)+θ0;

[0109] The parameters include the surface temperature θ0 of the outer sheath, the thermal resistance T1 of the outer sheath, the thermal resistance T2 of the buffer layer, and the total heat flux Q.

[0110] Optionally, the formula for calculating the AC resistance of a conductor is:

[0111] The formula for calculating the conductor temperature θ3 is:

[0112] The formula for calculating the thermal resistance T3 of the insulation layer is:

[0113] Where Q is the total heat flux, R is the AC resistance of the conductor, I is the real-time load current, and Q is the total heat flux; R0, α 20 These represent the DC resistance and temperature coefficient of the conductor at 20℃, respectively. s y p These are the known skin effect factor and the proximity effect factor, respectively.

[0114] Optionally, the formula for calculating the thermal conductivity of the insulating layer is as follows:

[0115] λ2 is the thermal conductivity of the insulating layer, and d1 and d2 are the radii of the conductor surface and the insulating layer surface, respectively.

[0116] The high-voltage cable insulation aging detection device provided in this application embodiment can execute the high-voltage cable insulation aging detection method provided in any embodiment of this application, and has the corresponding functional modules and beneficial effects of the method.

[0117] Figure 4 illustrates a schematic diagram of an electronic device 40 that can be used to implement embodiments of this application. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processors, cellular phones, smartphones, wearable devices (e.g., helmets, glasses, watches, etc.), and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely illustrative and are not intended to limit the implementation of the application described and / or claimed herein.

[0118] As shown in Figure 4, the electronic device 40 includes at least one processor 41 and a memory, such as a read-only memory (ROM) 42 or a random access memory (RAM) 43, communicatively connected to the at least one processor 41. The memory stores computer programs executable by the at least one processor. The processor 41 can perform various appropriate actions and processes based on the computer program stored in the ROM 42 or loaded into the RAM 43 from storage unit 48. The RAM 43 can also store various programs and data required for the operation of the electronic device 40. The processor 41, ROM 42, and RAM 43 are interconnected via a bus 44. An input / output (I / O) interface 45 is also connected to the bus 44.

[0119] Multiple components in electronic device 40 are connected to I / O interface 45, including: input unit 46, such as keyboard, mouse, etc.; output unit 47, such as various types of monitors, speakers, etc.; storage unit 48, such as disk, optical disk, etc.; and communication unit 49, such as network card, modem, wireless transceiver, etc. Communication unit 49 allows electronic device 40 to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0120] Processor 41 can be a variety of general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of processor 41 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various special-purpose artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, a digital signal processor (DSP), and any suitable processor, controller, microcontroller, etc. Processor 41 performs the various methods and processes described above, such as the method for detecting the aging degree of high-voltage cable insulation.

[0121] In some embodiments, the high-voltage cable insulation aging detection method can be implemented as a computer program tangibly contained in a computer-readable storage medium, such as storage unit 48. In some embodiments, part or all of the computer program can be loaded and / or installed on electronic device 40 via ROM 42 and / or communication unit 49. When the computer program is loaded into RAM 43 and executed by processor 41, one or more steps of the high-voltage cable insulation aging detection method described above can be performed. Alternatively, in other embodiments, processor 41 can be configured to perform the high-voltage cable insulation aging detection method by any other suitable means (e.g., by means of firmware).

[0122] Various embodiments of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), systems-on-a-chip (SoCs), complex programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments may include implementations in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which may be a dedicated or general-purpose programmable processor, capable of receiving data and instructions from a storage system, at least one input device, and at least one output device, and transmitting data and instructions to the storage system, the at least one input device, and the at least one output device.

[0123] Computer programs used to implement the methods of this application may be written in any combination of one or more programming languages. These computer programs may be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, such that when executed by the processor, the computer programs cause the functions / operations specified in the flowcharts and / or block diagrams to be performed. The computer programs may be executed entirely on a machine, partially on a machine, or as a standalone software package, partially on a machine and partially on a remote machine, or entirely on a remote machine or server.

[0124] In the context of this application, a computer-readable storage medium can be a tangible medium that may contain or store a computer program for use by or in conjunction with an instruction execution system, apparatus, or device. A computer-readable storage medium can be, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. Alternatively, a computer-readable storage medium can be a machine-readable signal medium. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing. The storage medium can be a non-transitory storage medium.

[0125] To provide interaction with a user, the systems and techniques described herein can be implemented on an electronic device having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and pointing device (e.g., a mouse or trackball) through which the user provides input to the electronic device. Other types of devices can also be used to provide interaction with the user; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including sound input, voice input, or tactile input).

[0126] The systems and technologies described herein can be implemented in computing systems that include backend components (e.g., as data servers), or computing systems that include middleware components (e.g., application servers), or computing systems that include frontend components (e.g., user computers with graphical user interfaces or web browsers through which users can interact with implementations of the systems and technologies described herein), or any combination of such backend, middleware, or frontend components. The components of the system can be interconnected via digital data communication of any form or medium (e.g., communication networks). Examples of communication networks include local area networks (LANs), wide area networks (WANs), blockchain networks, and the Internet.

[0127] A computing system can include clients and servers. Clients and servers are generally located far apart and typically interact through communication networks. The client-server relationship is created by computer programs running on the respective computers and having a client-server relationship with each other. The server can be a cloud server, also known as a cloud computing server or cloud host, which is a hosting product within the cloud computing service system to address the shortcomings of traditional physical hosts and VPS services, such as high management difficulty and weak business scalability.

[0128] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this application can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this application can be achieved, and this is not limited herein.

[0129] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for detecting the aging degree of high-voltage cable insulation, wherein, The cable, from the inside out, comprises a conductor, an insulation layer, a buffer layer, an aluminum sheath, and an outer sheath. The method for detecting the aging degree of the insulation layer of the high-voltage cable includes: A steady-state thermal circuit model is established based on the structure of each layer of the cable. The steady-state thermal circuit model includes the thermal resistance of the insulation layer, buffer layer, outer sheath, and conductor loss heat source. Calculate the thermal resistance T1 of the outer sheath and the thermal resistance T2 of the buffer layer based on the structural parameters, where the structural parameters include the inner diameter and the outer diameter. The surface temperature θ0 of the outer sheath, the surface temperature θ1 of the aluminum sheath, and the real-time load current I of the cable were measured respectively. The total heat flow Q of the cable is calculated based on the thermal resistance T1 of the outer sheath, the surface temperature θ0 of the outer sheath, and the surface temperature θ1 of the aluminum sheath. The surface temperature θ2 of the insulation layer is calculated based on the surface temperature θ0 of the outer sheath, the thermal resistance T1 of the outer sheath, the thermal resistance T2 of the buffer layer, and the total heat flow Q. The thermal conductivity of the insulation layer is calculated based on the total heat flux Q, the surface temperature θ2 of the insulation layer, and the real-time load current I. The degree of aging of the cable insulation layer is determined based on the thermal conductivity of the insulation layer.

2. The method as described in claim 1, wherein, The aluminum sheath is a corrugated metal sheath. The thermal resistance T1 of the outer sheath is calculated using the following formula: ρ T is the thermal resistance coefficient of the insulating layer material, D it is the diameter of the imaginary concentric cylinder tangent to the inner surface of the trough of the corrugated metal jacket; D oc is the diameter of the imaginary concentric cylinder tangent to the crest of the corrugated metal jacket; t s is the thickness of the corrugated metal jacket, t3 is the thickness of the outer protective layer; The formula for calculating the thermal resistance T2 of the buffer layer is as follows; Where λ1 is the thermal conductivity of the buffer layer material, and D and d are the outer and inner diameters of the buffer layer, respectively.

3. The method as described in claim 1, wherein, The formula for calculating the total heat flux Q is as follows; θ1 and θ0 are the surface temperatures of the outer sheath and the aluminum sheath, respectively, and T1 is the thermal resistance of the outer sheath.

4. The method of claim 1, wherein, The surface temperature θ2 of the insulation layer is calculated based on the surface temperature θ0 of the outer sheath, the thermal resistance T1 of the outer sheath, the thermal resistance T2 of the buffer layer, and the total heat flow Q. The calculation formula is as follows: θ2=Q(T2+T1)+θ0.

5. The method of claim 1, wherein, The calculation of the thermal conductivity of the insulation layer based on the total heat flux Q, the surface temperature θ2 of the insulation layer, and the real-time load current I includes: The AC resistance of the conductor is calculated based on the total heat flow Q and the real-time load current I. Calculate the conductor temperature θ3 based on the conductor's AC resistance; Calculate the thermal resistance T3 of the insulation layer based on the conductor temperature θ3, the surface temperature θ2 of the insulation layer, and the total heat flow Q. The thermal conductivity of the insulation layer is calculated based on the thermal resistance T3 of the insulation layer.

6. The method of claim 5, wherein, The formula for calculating the AC resistance of a conductor is: The formula for calculating the conductor temperature θ3 is: The formula for calculating the thermal resistance T3 of the insulation layer is: Wherein, Q is the total line heat flow, R is the AC resistance of the conductor, I is the real-time load current, Q is the total line heat; R0, a 20 respectively, the DC resistance of the conductor at 20°C, the temperature coefficient, y s , y p respectively, the known skin effect factor, the proximity effect factor.

7. The method as described in any one of claims 1-2, wherein, The formula for calculating the thermal conductivity of the insulation layer is as follows: λ2 is the thermal conductivity of the insulating layer, and d1 and d2 are the radii of the conductor surface and the insulating layer surface, respectively.

8. The method according to any one of claims 1-7, wherein, The method of determining the aging degree of the cable insulation layer based on the thermal conductivity of the insulation layer includes: A thermal conductivity database is obtained through aging experiments, and the thermal conductivity database includes the thermal conductivity of the cable insulation layer under different aging degrees. The thermal conductivity of the current cable insulation layer is compared with the data in the thermal conductivity database to determine the degree of aging of the current cable insulation layer.

9. A device for detecting the aging degree of high-voltage cable insulation, used to perform the method for detecting the aging degree of high-voltage cable insulation as described in any one of claims 1-8, comprising: The model building module is set to establish a steady-state thermal circuit model based on the structure of each layer of the cable. The steady-state thermal circuit model includes the thermal resistance of the insulation layer, buffer layer, outer sheath, and conductor loss heat source. The thermal resistance calculation module is configured to calculate the thermal resistance T1 of the outer sheath and the thermal resistance T2 of the buffer layer based on the structural parameters, wherein the structural parameters include the inner diameter and the outer diameter. The data measurement module is set to measure the surface temperature θ0 of the outer sheath, the surface temperature θ1 of the aluminum sheath, and the real-time load current I of the cable, respectively. The full-line heat flow calculation module is set to calculate the full-line heat flow Q of the cable based on the thermal resistance T1 of the outer sheath, the surface temperature θ0 of the outer sheath, and the surface temperature θ1 of the aluminum sheath. The insulation layer surface temperature calculation module is set to calculate the insulation layer surface temperature θ2 based on the outer sheath surface temperature θ0, the outer sheath thermal resistance T1, the buffer layer thermal resistance T2, and the total heat flow Q. The insulation layer thermal conductivity calculation module is set to calculate the thermal conductivity of the insulation layer based on the total heat flux Q, the surface temperature θ2 of the insulation layer and the real-time load current I. The insulation aging degree determination module is set to determine the aging degree of the cable insulation layer based on the thermal conductivity of the insulation layer.

10. An electronic device, comprising: At least one processor; as well as A memory communicatively connected to the at least one processor; wherein, The memory stores a computer program that can be executed by the at least one processor, the computer program being executed by the at least one processor to enable the at least one processor to perform the high-voltage cable insulation aging detection method according to any one of claims 1-8.

11. A computer-readable storage medium, wherein, The computer-readable storage medium stores computer instructions that cause a processor to execute the method for detecting the aging degree of high-voltage cable insulation layer as described in any one of claims 1-8.

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