Power cable connection structure integrated with temperature detection function and temperature detection method

Abstract

The invention discloses a power cable connection structure integrated with a temperature detection function and a temperature detection method. The method comprises the steps of obtaining electrical parameters and thermal parameters of a cable and surface temperatures of two ends and a middle part of a cable intermediate joint; respectively calculating the calorific value of the cable conductor and the thermal resistance and thermal capacity of the two ends of the cable intermediate joint and the intermediate insulating layer, and constructing a thermal circuit equation; constructing a target optimization function, and solving cable conductor temperatures at different temperature acquisition moments; calculating an average temperature rise change rate and an average temperature change rate based on the cable conductor temperatures at different temperature acquisition moments, and correcting the thermal resistivity of an insulating layer material; and based on the updated thermal resistivity, re-determining the average temperature rise change rate, and calculating the temperature of the cable conductor at any moment within a preset duration after the current temperature acquisition moment. According to the invention, through multi-point real-time temperature acquisition, thermal circuit equation optimization solution and insulation thermal resistivity self-adaptive correction, the accuracy and reliability of power cable conductor temperature calculation and prediction are improved.

Description

Technical Field

[0001] This invention belongs to the field of power cable technology and relates to a power cable connection structure and temperature detection method with integrated temperature detection function. Background Technology

[0002] The structure of intermediate joints for interconnecting power cables is a known system. Power cable intermediate joints are coated for insulation and waterproofing. Furthermore, because the internal condition cannot be inspected without damaging the coated cable connection structure, damage to a power cable intermediate joint under normal operating conditions can lead to power supply interruptions or even severe power outages, and the abnormality may go undetected until these serious faults occur.

[0003] On the other hand, when an abnormality occurs at the intermediate joint between power cables, the internal temperature rises abnormally due to discharge or poor contact. Therefore, it is urgent to study a method to detect the temperature of the intermediate joint by monitoring the temperature at the intermediate joint location of the power cable.

[0004] Currently, existing cable temperature detection methods include: Patent CN112484874A provides a temperature sensing structure and method for conductive cooling high-temperature superconducting cables. This method involves point-distributing platinum resistance sensors on the superconducting tape, with more sensors placed at the joint, and reducing lead wire errors through thermal anchoring technology. Finally, a cubic spline interpolation method is used to fit the temperature distribution curve, achieving real-time detection of the temperature field of the high-temperature superconducting cable and providing a rapid temperature feedback signal for the quench protection system. Meanwhile, Chinese patent CN120213257A provides a cable joint temperature detection method and system. This method acquires environmental parameters, uses a trained sampling information model to determine sampling parameters and resonant frequencies, applies a fast Fourier transform to extract the final resonant frequency, calculates the joint temperature based on a temperature-frequency relationship model considering environmental factors, and provides graded warnings based on dynamic warning thresholds, achieving accurate, reliable detection and intelligent warning of cable joint temperatures.

[0005] Current methods for detecting the temperature of intermediate joints cannot directly detect the crucial conductor temperature unless the temperature sensor is placed on the conductor surface during the cable joint installation phase. Placing the temperature sensor on the conductor surface can lead to uneven electric field distribution, causing excessively large local electric fields, which can adversely affect cable operation. Furthermore, existing detection methods, without obtaining the conductor surface temperature, struggle to develop accurate conductor surface temperature estimation models. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a power cable connection structure and temperature detection method integrating temperature detection functionality. The method includes: acquiring the electrical and thermal parameters of the cable, and the surface temperatures of both ends and the middle section of the cable joint; calculating the heat generation of the cable conductor, the thermal resistance and thermal capacity of the insulation layer at both ends and the middle section of the cable joint, and constructing thermal circuit equations for each; based on the thermal circuit equations, constructing an objective optimization function and solving for the cable conductor temperature at different temperature acquisition times; based on the cable conductor temperatures at different temperature acquisition times, calculating the average temperature rise rate and the average temperature change rate, and correcting the thermal resistivity of the insulation material; based on the updated thermal resistivity, redetermining the average temperature rise rate, and calculating the cable conductor temperature at any time within a predetermined time period after the current temperature acquisition time. This invention improves the accuracy and reliability of power cable conductor temperature calculation and prediction through multi-point real-time temperature acquisition, optimized solution of the thermal circuit equation, and adaptive correction of the insulation thermal resistivity.

[0007] The present invention adopts the following technical solution.

[0008] The first aspect of the present invention provides a method for detecting the temperature of a power cable, comprising the following steps: S1. Obtain the electrical and thermal parameters of the cable, and collect the surface temperatures at both ends and the middle of the cable joint in real time. S2. Based on the data collected in S1, calculate the heat generation of the cable conductor, the thermal resistance and thermal capacity of both ends of the cable joint and the middle insulation layer, and construct the thermal circuit equations respectively. Based on the rate of change of cable conductor temperature with time in the thermal circuit equations, combine the two constructed thermal circuit equations into an equation. Based on the difference between the left and right sides of the equation, construct the objective optimization function and solve for the cable conductor temperature at different temperature collection times. S3. Based on the cable conductor temperature at different temperature acquisition times, calculate the average temperature rise rate of change at all temperature acquisition times within a predetermined time period; substitute the cable conductor temperature into the thermal circuit equation to calculate the average temperature change rate; calculate the absolute value of the difference between the average temperature rise rate and the average temperature change rate; if the value is greater than a predetermined difference threshold, correct the thermal resistivity of the insulation material. S4. Based on the updated thermal resistivity, redetermine the average temperature rise rate; based on the cable conductor temperature and average temperature rise rate at the current temperature acquisition time, calculate the cable conductor temperature at any time within a predetermined time after the current temperature acquisition time.

[0009] Preferably, the process of calculating the heat generation of the cable conductor, the thermal resistance and thermal capacity of the two ends of the cable joint and the intermediate insulation layer in S2 is as follows: Based on the current and AC resistance of the cable conductor, calculate the heat generated by the cable conductor at each temperature acquisition time. For the insulation layer at both ends or in the middle of a cable joint, the logarithm of the ratio of the insulation layer thickness to the cable conductor diameter is taken using a logarithmic function with the natural constant as the base. The result of taking the logarithm is multiplied by the thermal resistivity of the insulation material and then divided by 2π to obtain the thermal resistance of the insulation layer at the corresponding position of the cable joint. For the insulation layer at both ends or in the middle of a cable joint, the heat capacity of the insulation layer at the corresponding position is obtained by multiplying the difference between the insulation layer thickness and the conductor diameter, the specific heat capacity and mass density of the insulation material, and then multiplying by 4π.

[0010] Preferably, the process of constructing the objective optimization function in S2 is as follows: For any temperature acquisition time, the square of the difference between the two sides of the equation based on the temperatures at both ends and the middle surface of the corresponding cable joint is taken as the residual for the corresponding temperature acquisition time; the residuals corresponding to all temperature acquisition times within the predetermined time are accumulated and used as the objective optimization function.

[0011] Preferably, the process of calculating the average temperature rise rate and the average temperature change rate in S3 is as follows: Divide the difference in cable conductor temperature at adjacent temperature acquisition times by the time difference between adjacent temperature acquisition times to obtain the rate of temperature rise between the corresponding adjacent temperature acquisition times; take the average of the rate of temperature rise between all adjacent temperature acquisition times within a predetermined time period to obtain the average rate of temperature rise. For any temperature acquisition time, the cable conductor temperature at the corresponding time is substituted into the thermal circuit equation to obtain the temperature change rate at the corresponding time; the average temperature change rate is obtained by averaging all temperature change rates within a predetermined time period.

[0012] Preferably, the process of correcting the thermal resistivity of the insulating layer material in S3 is as follows: For each temperature acquisition moment, the average rate of temperature rise, the corresponding cable conductor temperature, and the surface temperatures at both ends and the middle of the cable joint are substituted into the thermal circuit equation to calculate the thermal resistivity of the insulation material at the corresponding temperature acquisition moment. The average thermal resistivity of the insulation material at all temperature acquisition moments is taken as the estimated thermal resistivity value for a predetermined time period. The reciprocal of the standard deviation of the thermal resistivity of the insulation material at all temperature acquisition moments is used as the confidence level of the thermal resistivity estimate. The confidence level is input into a sigmoid function with a predetermined exponential coefficient to obtain the adjustment weight of the thermal resistivity estimate. 1 is subtracted from the adjustment weight of the thermal resistivity estimate as the adjustment weight of the original insulation material's thermal resistivity. Based on the adjustment weight, the thermal resistivity of the original insulation material and the thermal resistivity estimate are weighted to obtain the corrected thermal resistivity.

[0013] Preferably, the process in S4 for calculating the cable conductor temperature at any time within a predetermined time period after the current temperature acquisition time is as follows: Substitute the thermal resistivity of the insulation material and the cable conductor temperature at all temperature acquisition times into the thermal circuit equation to determine the corresponding average temperature rise rate. For any time within a predetermined time after the current temperature acquisition time, multiply the average temperature rise rate by the time difference and add the cable conductor temperature at the previous time to obtain the cable conductor temperature at the corresponding time.

[0014] A second aspect of the present invention provides a power cable connection structure with integrated temperature detection function, wherein the temperature detection function is implemented by a power cable temperature detection method; the power cable connection structure includes an intermediate connection component for connecting a first power cable 1 and a second power cable 2 that have been stripped in sections, and a temperature detection component; the power cable includes a cable conductor 5, a cable insulation layer 6, a cable semi-conductive layer 10, and a cable protective sheath arranged sequentially from the inside to the outside; and a power cable temperature detection method is used. The intermediate connection assembly includes a copper connecting pipe 11 and a waterproof protective layer 9; the copper connecting pipe 11 is fitted at the connection point of the cable conductors 5 of the first power cable 1 and the second power cable 2 to realize the electrical connection between the two power cables. The temperature detection component includes a first cable temperature sensor 3, a second cable temperature sensor 16, a data transmission module 17, and a temperature sensor power supply module 4. The first cable temperature sensor 3 is disposed on the outer surface of the waterproof protective layer 9 and located inside the tubular waterproof sheath 15, and is used to detect the cable surface temperature at both ends of the cable joint when current flows in the power cable. The second cable temperature sensor 16 is disposed on the outer surface of the waterproof protective layer 9 and is used to detect the cable surface temperature at the middle of the cable joint when current flows in the two power cables. The data transmission module 17 is disposed on the outer surface of the waterproof protective layer 9, adjacent to the second cable temperature sensor 16, and communicatively connected to the first cable temperature sensor 3 and the second cable temperature sensor 16, for transmitting the temperature detection results to an external receiving device. The temperature sensor power supply module 4 is fixed on the outer wall of the cable semiconducting layer 10. It uses the change in magnetic flux caused by the current flowing in the two power cables to generate electrical energy to drive the first cable temperature sensor 3, the second cable temperature sensor 16 and the data transmission module 17.

[0015] Preferably, the intermediate connection assembly further includes: an inner shielding tube 12, an insulating tube 8, and an outer sheath 13 for the intermediate joint; The inner shielding tube 12 wraps around the outside of the copper connecting tube 11; The insulating tube 8 is wrapped around the outside of the inner shielding tube 12; The outer sheath 13 of the intermediate joint is wrapped around the outside of the insulating tube 8; the outer sheath 13 of the intermediate joint is coated with the waterproof protective layer 9.

[0016] Preferably, a tubular waterproof sheath 15 is provided on the outside of the waterproof protective layer 9 to protect the first cable temperature sensor 3.

[0017] Preferably, the outer side of the cable protection sheath 7 of the two power cables is also covered with a cable shielding layer 14 to prevent external personnel from being electrocuted and to conduct the leakage current of the two power cables to the grounding terminal.

[0018] A third aspect of the present invention provides a terminal, including a processor and a storage medium; The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps of a power cable temperature detection method.

[0019] A fourth aspect of the invention provides a computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the steps of a method for detecting the temperature of a power cable.

[0020] Compared with the prior art, the beneficial effects of the present invention include at least the following: 1. This invention utilizes multiple temperature sensors arranged at both ends and the middle of the cable joint to collect surface temperatures at different locations in real time, and constructs a multi-node thermal circuit equation model by combining electrical and thermal parameters. Through the simultaneous solution of two types of thermal circuit equations, residual optimization, and a multi-time conductor temperature back-calculation mechanism, it achieves high-precision calculation of the actual temperature of the cable conductor, significantly outperforming traditional temperature estimation methods that rely on single-point or fixed thermal parameters. This effectively solves the problem of accurately obtaining the actual temperature of cables in existing technologies.

[0021] 2. This invention adaptively corrects the thermal resistivity of the insulating layer material by exploiting the discrepancy between the average rate of temperature change and the rate of temperature change calculated by the thermal circuit equation. Furthermore, it utilizes the standard deviation of the thermal resistivity estimates at multiple time points to construct a confidence level, and then combines this with sigmoid weight adjustment to achieve dynamic optimization and calibration of the material's thermal resistivity. This mechanism addresses the problem of temperature predictions deviating from reality due to fixed material thermal parameters and accumulated calculation errors, thereby significantly improving the reliability and robustness of the prediction model.

[0022] 3. The intermediate joint structure of this invention adopts a multi-layered protective design consisting of a copper connecting pipe, an inner shielding pipe, an insulating pipe, an outer sheath, and a waterproof protective layer, achieving high-strength electrical connection and excellent insulation and protection performance. The joint integrates multiple temperature sensors, a data transmission module, and a self-powered module externally, enabling temperature measurement, data transmission, and energy acquisition to be completed entirely within the joint, eliminating the need for external power supplies or complex wiring, significantly improving installation convenience and long-term system stability; it also possesses the ability to monitor cable operating status in real time, effectively preventing safety risks such as cable overheating and insulation aging. Attached Figure Description

[0023] Figure 1 This is a side cross-sectional view of the power cable connection structure according to an embodiment of the present invention; Figure 2 This is a perspective view of the temperature sensor power supply module according to an embodiment of the present invention; Figure 3 This is a flowchart of a power cable temperature detection method provided by the present invention; Figure 4 This is a thermal diagram of the first cable temperature sensor in an embodiment of the present invention; Figure 5 This is a thermal diagram of the second cable temperature sensor in an embodiment of the present invention.

[0024] Figure descriptions: 1. First power cable; 2. Second power cable; 3. First cable temperature sensor; 4. Temperature sensor power supply module; 5. Cable conductor; 6. Cable insulation layer; 7. Cable outer sheath; 8. Insulating tube; 9. Waterproof protective layer; 10. Cable semiconductor layer; 11. Copper connecting tube; 12. Inner shielding tube; 13. Intermediate joint outer sheath; 14. Cable shielding layer; 15. Tubular waterproof sheath; 16. Second cable temperature sensor; 17. Data transmission module. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0026] Example 1 Embodiment 1 of the present invention provides a power cable connection structure with integrated temperature detection function, such as... Figure 1 As shown, it includes an intermediate connection assembly for connecting a first power cable 1 and a second power cable 2 that have been stripped in segments, and a temperature detection assembly.

[0027] The first power cable 1 and the second power cable 2 include a cable conductor 5, a cable insulation layer 6, a cable semi-conductive layer 10, and a cable protective sheath 7, arranged sequentially from the inside out; the cable insulation layer 6 is made of insulating materials such as cross-linked polyethylene and covers the outer surface of the cable conductor 5; the cable semi-conductive layer 10 is a semi-conductive layer made of materials such as cross-linked polyethylene with added carbon particles; the cable protective sheath 7 is made of polyvinyl chloride or polyethylene.

[0028] The intermediate connection assembly includes a copper connecting pipe 11, an inner shielding pipe 12, an insulating pipe 8, an intermediate joint outer sheath 13, and a waterproof protective layer 9; A copper connecting pipe 11 is fitted at the connection point of the conductors 5 of the first power cable 1 and the second power cable 2 to realize the electrical connection between the two power cables; The inner shielding tube 12 is wrapped around the outside of the copper connecting tube 11, which improves the electric field distribution. The insulating tube 8 is wrapped around the outside of the inner shielding tube 12 to enhance insulation; The outer sheath 13 of the intermediate joint is wrapped around the outside of the insulating tube 8; the outer sheath 13 of the intermediate joint is coated with a waterproof protective layer 9.

[0029] The temperature detection component includes a first cable temperature sensor 3, a second cable temperature sensor 16, a data transmission module 17, and a temperature sensor power supply module 4; The first cable temperature sensor 3 is disposed on the outer surface of the waterproof protective layer 9 and located inside the tubular waterproof sheath 15, and is used to detect the surface temperature of the cable joint at both ends of the cable joint when current flows in the two power cables. The second cable temperature sensor 16 is set on the outer surface of the waterproof protective layer 9, located in the middle section, and is used to detect the surface temperature of the cable joint in the middle of the cable joint when current flows in the two power cables. The data transmission module 17 is disposed on the outer surface of the waterproof protective layer 9, adjacent to the second cable temperature sensor 16, and is communicatively connected to the first cable temperature sensor 3 and the second cable temperature sensor 16. It uses a wireless communication device such as Bluetooth to send the temperature detection results to an external receiving device. The temperature sensor power supply module 4 is fixed to the outer wall of the cable semiconducting layer 10. It generates electrical energy to drive the temperature sensor and the data transmission module 17 by utilizing the change in magnetic flux caused by the current flowing in the first power cable 1 and the second power cable 2.

[0030] The cable protective sheaths 7 of the two power cables are also covered with cable shielding layers 14, which are made of materials such as copper strips and copper mesh. The cable shielding layer 14 is a conductive layer set up to prevent external personnel from being electrocuted and to allow the leakage current of the first power cable 1 and the second power cable 2 to flow, and is used to conduct the leakage current of the two power cables to the grounding end.

[0031] The tubular waterproof sheath 15 is wrapped around the outside of the waterproof protective layer 9, which serves to protect the first cable temperature sensor 3 and ensure the stability of the surface temperature of the cable sheath.

[0032] Figure 2 A schematic diagram of the temperature sensor power supply module is provided. The device features two locking latches that can be fixed vertically, securing the power supply module around the first power cable 1 and the second power cable 2. The device contains multiple coils for electromagnetic induction, which generate electrical energy to power the temperature sensor and data transmission module. This eliminates the need for batteries or third-party power sources, resulting in more stable and reliable operation.

[0033] Example 2 Currently, the thermal resistance method is generally used to estimate the temperature of the cable conductor by testing the surface temperature of the cable. The accuracy of this method mainly depends on the thermal resistance and heat capacity of the cable insulation material. However, the insulation material of the cable is dispersed, and the actual thermal resistance and specific heat capacity of the insulation material will inevitably differ from the calculated thermal resistance and specific heat capacity. This will cause an error between the calculated conductor temperature and the actual conductor temperature when calculated using the standard algorithm.

[0034] Embodiment 2 of the present invention provides a method for detecting the temperature of power cables, see below. Figure 3 This includes the following steps: S1. Obtain the electrical and thermal parameters of the cable, and collect the surface temperatures at both ends and the middle of the cable joint in real time.

[0035] In this embodiment, two temperature sensors are used to monitor the temperature at different locations of the cable joint. The temperature at these two locations differs, and since all other parameters of the two temperature sensors are the same, this difference is only caused by the different thicknesses of the insulation layers.

[0036] S2. Based on the data collected in S1, calculate the heat generation of the cable conductor, the thermal resistance and thermal capacity of both ends of the cable joint and the intermediate insulation layer, and construct the thermal circuit equations respectively. Based on the rate of change of cable conductor temperature with time in the thermal circuit equations, combine the two constructed thermal circuit equations into an equation. Based on the difference between the left and right sides of the equation, construct the objective optimization function and solve for the cable conductor temperature at different temperature collection times.

[0037] Based on the current and AC resistance of the cable conductor, the heat generated by the cable conductor at each temperature acquisition time is calculated; the specific calculation formula is as follows: ; In the formula, Q is the heat generated by the cable conductor; I is the current in the cable conductor; It is the AC resistance of the cable conductor; like Figure 4 and Figure 5 As shown, For environmental thermal resistance, For environmental heat capacity, The ambient temperature is used; the heat channels of the first cable temperature sensor 3 and the second cable temperature sensor 16 are almost identical, except that their insulation layer thicknesses differ. For the insulation layer at both ends or in the middle of the cable joint, the logarithm of the ratio of the insulation layer thickness to the cable conductor diameter is taken using a logarithmic function with the natural constant as the base. The result of the logarithm is multiplied by the thermal resistivity of the insulation material and then divided by 2π to obtain the thermal resistance of the insulation layer at the corresponding position of the cable joint. The specific formula is as follows: ; ; In the formula, The thermal resistance per unit length of the insulation layer at both ends of the cable joint; The thermal resistivity of the insulating material; The thickness of the insulation layer at both ends of the cable intermediate joint; The diameter of the cable conductor; The thermal resistance per unit length of the intermediate insulation layer of the cable joint; The thickness of the intermediate insulation layer of the cable joint; For the insulation layer at both ends or in the middle of a cable joint, the heat capacity of the insulation layer at the corresponding location is obtained by multiplying the difference between the insulation layer thickness and the conductor diameter, the specific heat capacity and mass density of the insulation material, and then multiplying by 4π. The specific calculation formula is as follows: ; ; In the formula, ρ is the heat capacity of the insulation layers at both ends of the cable joint; c is the specific heat capacity of the insulation material, in J / (kg·K); The mass density of the insulating material is expressed in kg / m³. The heat capacity of the intermediate insulation layer of the cable joint; For the insulation layers at both ends or in the middle of a cable joint, thermal circuit equations are constructed based on the surface temperature, heat capacity, and thermal resistance of the corresponding insulation layers, combined with the heat generation of the cable conductor; the specific formulas are as follows: ; ; In the formula, For cable conductor temperature; The surface temperatures at both ends of the cable joint; t represents time. This refers to the surface temperature at the center of the cable joint. Based on the rate of change of cable conductor temperature over time By combining the two constructed thermal circuit equations into an equation, we can obtain: ; For any temperature acquisition moment, the square of the difference between the two sides of the equation relating the temperatures at both ends and the surface of the corresponding cable joint is taken as the residual for that temperature acquisition moment. The residuals corresponding to all temperature acquisition moments within a predetermined time period are summed up and used as the objective optimization function. The specific formula is as follows: ; In the formula, This represents the residual corresponding to the i-th temperature acquisition time. Let be the temperature of the cable conductor at the i-th temperature acquisition time; This represents the total number of temperature measurements taken within the predetermined time period. Let be the heat generated by the cable conductor at the i-th temperature acquisition time. The temperature of the middle surface of the cable joint at the i-th temperature acquisition time; Let be the surface temperature of both ends of the cable joint at the i-th temperature acquisition time.

[0038] The cable conductor temperature at different temperature acquisition times was obtained by using methods such as the Gauss-Newton method and the Levenberg-Marquardt method.

[0039] S3. Based on the cable conductor temperature at different temperature acquisition times, calculate the average temperature rise rate of change at all temperature acquisition times within a predetermined time period; substitute the cable conductor temperature into the thermal circuit equation to calculate the average temperature change rate; calculate the absolute value of the difference between the average temperature rise rate of change and the average temperature change rate; if this value is greater than a predetermined difference threshold, correct the thermal resistivity of the insulation material.

[0040] The temperature difference between adjacent temperature sampling times is divided by the time difference between adjacent temperature sampling times to obtain the temperature rise rate between corresponding adjacent temperature sampling times; the average temperature rise rate is obtained by averaging the temperature rise rates between all adjacent temperature sampling times within a predetermined time period; the specific calculation formula is as follows: ; In the formula, This represents the average rate of change of temperature. This represents the time difference between adjacent temperature acquisition times. For any temperature acquisition moment, substitute the cable conductor temperature at that moment into the thermal circuit equation to obtain the temperature change rate at that moment; average all temperature change rates over a predetermined time period to obtain the average temperature change rate; the specific calculation formula is as follows: ; In the formula, The average rate of temperature change; Calculate the absolute value of the difference between the average rate of temperature rise and the average rate of temperature change. If the value is greater than a predetermined difference threshold, the thermal resistivity of the insulating layer material is corrected; if it is not greater than the predetermined difference threshold, the thermal resistivity is not changed.

[0041] As a preferred embodiment, the process of correcting the thermal resistivity of the insulating layer material is as follows: For each temperature acquisition moment, the average rate of temperature rise, the corresponding cable conductor temperature, and the surface temperatures at both ends and the middle of the cable joint are substituted into the thermal circuit equation to calculate the thermal resistivity of the insulation material at the corresponding temperature acquisition moment. The average thermal resistivity of the insulation material at all temperature acquisition moments is taken as the estimated thermal resistivity value for a predetermined time period. The reciprocal of the standard deviation of the thermal resistivity of the insulation material at all temperature acquisition moments is used as the confidence level of the thermal resistivity estimate. The confidence level is input into a sigmoid function with a predetermined exponential coefficient to obtain the adjustment weight of the thermal resistivity estimate. 1 is subtracted from the adjustment weight of the thermal resistivity estimate as the adjustment weight of the original insulation material's thermal resistivity. Based on the adjustment weight, the thermal resistivity of the original insulation material and the thermal resistivity estimate are weighted to obtain the corrected thermal resistivity. The specific calculation formula is as follows: ; ; In the formula, This is the corrected thermal resistivity; This is an estimated value for thermal resistivity; The confidence level for the thermal resistivity estimate; This represents the standard deviation of the thermal resistivity of the insulating material at all temperature acquisition times during the calculation. To prevent the minimum value where the denominator is zero, this embodiment takes... ; is the exponential coefficient of the sigmoid function.

[0042] S4. Based on the updated thermal resistivity, redetermine the average temperature rise rate; based on the cable conductor temperature and average temperature rise rate at the current temperature acquisition time, calculate the cable conductor temperature at any time within a predetermined time after the current temperature acquisition time.

[0043] Substituting the thermal resistivity of the insulation material and the cable conductor temperature at all temperature acquisition moments into the thermal circuit equation, the corresponding average temperature rise rate is determined. For any moment within a predetermined time interval after the current temperature acquisition moment, the average temperature rise rate is multiplied by the time difference, and then the cable conductor temperature at the previous moment is added to obtain the cable conductor temperature at that moment. The specific calculation formula is as follows: ; In the formula, Let t be the temperature of the cable conductor at time t; The temperature of the cable conductor at time t-1 is given; the temperature of the cable conductor at the current temperature acquisition time is obtained by solving the objective optimization function.

[0044] In this embodiment, if thermal resistivity correction is required based on the content of S3 at the current temperature acquisition time, then the corrected thermal resistivity is substituted into the thermal circuit equation in S4.

[0045] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0046] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0047] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0048] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for detecting the temperature of a power cable, characterized in that, Includes the following steps: S1. Obtain the electrical and thermal parameters of the cable, and collect the surface temperatures at both ends and the middle of the cable joint in real time. S2. Based on the data collected in S1, calculate the heat generation of the cable conductor, the thermal resistance and thermal capacity of both ends of the cable joint and the intermediate insulation layer, and construct the thermal circuit equations respectively. Based on the rate of change of cable conductor temperature with time in the thermal circuit equation, the two constructed thermal circuit equations are combined into an equation; Based on the difference between the left and right sides of the simultaneous equation, an objective optimization function is constructed, and the cable conductor temperature at different temperature acquisition times is solved. S3. Based on the cable conductor temperature at different temperature acquisition times, calculate the average rate of temperature rise change at all temperature acquisition times within a predetermined time period; Substitute the cable conductor temperature into the thermal circuit equation to calculate the average temperature change rate; Calculate the absolute value of the difference between the average temperature rise rate and the average temperature change rate. If the value is greater than a predetermined difference threshold, correct the thermal resistivity of the insulating layer material. S4. Based on the updated thermal resistivity, redetermine the average temperature rise rate; based on the cable conductor temperature and average temperature rise rate at the current temperature acquisition time, calculate the cable conductor temperature at any time within a predetermined time after the current temperature acquisition time.

2. The method for detecting the temperature of a power cable according to claim 1, characterized in that: The process of calculating the heat generation of the cable conductor, the thermal resistance and thermal capacity of the two ends and the intermediate insulation layer of the cable joint in S2 is as follows: Based on the current and AC resistance of the cable conductor, calculate the heat generated by the cable conductor at each temperature acquisition time. For the insulation layer at both ends or in the middle of a cable joint, the logarithm of the ratio of the insulation layer thickness to the cable conductor diameter is taken using a logarithmic function with the natural constant as the base. The result of taking the logarithm is multiplied by the thermal resistivity of the insulation material and then divided by 2π to obtain the thermal resistance of the insulation layer at the corresponding position of the cable joint. For the insulation layer at both ends or in the middle of a cable joint, the heat capacity of the insulation layer at the corresponding position is obtained by multiplying the difference between the insulation layer thickness and the conductor diameter, the specific heat capacity and mass density of the insulation material, and then multiplying by 4π.

3. The method for detecting the temperature of a power cable according to claim 1, characterized in that: The process of constructing the objective function in S2 is as follows: For any temperature acquisition time, the square of the difference between the two sides of the equation based on the temperatures at both ends and the middle surface of the corresponding cable joint is taken as the residual for the corresponding temperature acquisition time; the residuals corresponding to all temperature acquisition times within the predetermined time are accumulated and used as the objective optimization function.

4. The method for detecting the temperature of a power cable according to claim 1, characterized in that: The process for calculating the average rate of change of temperature rise and the average rate of change of temperature in S3 is as follows: Divide the difference in cable conductor temperature at adjacent temperature acquisition times by the time difference between adjacent temperature acquisition times to obtain the rate of temperature rise between the corresponding adjacent temperature acquisition times; take the average of the rate of temperature rise between all adjacent temperature acquisition times within a predetermined time period to obtain the average rate of temperature rise. For any temperature acquisition time, the cable conductor temperature at the corresponding time is substituted into the thermal circuit equation to obtain the temperature change rate at the corresponding time; the average temperature change rate is obtained by averaging all temperature change rates within a predetermined time period.

5. The method for detecting the temperature of a power cable according to claim 1, characterized in that: The process of correcting the thermal resistivity of the insulating layer material in S3 is as follows: For each temperature acquisition moment, the average rate of temperature rise, the corresponding cable conductor temperature, and the surface temperatures at both ends and the middle of the cable joint are substituted into the thermal circuit equation to calculate the thermal resistivity of the insulation material at the corresponding temperature acquisition moment. The average thermal resistivity of the insulation material at all temperature acquisition moments is taken as the estimated value of thermal resistivity over a predetermined time period. The reciprocal of the standard deviation of the thermal resistivity of the insulating material at all temperature acquisition times is used as the confidence level of the thermal resistivity estimate; the confidence level is input into the sigmoid function with a predetermined exponential coefficient to obtain the adjustment weight of the thermal resistivity estimate. The adjustment weight of the original insulating layer material is obtained by subtracting the adjustment weight of the thermal resistivity estimate from 1. Based on the adjusted weights, the thermal resistivity of the original insulating layer material and the estimated thermal resistivity are weighted to obtain the corrected thermal resistivity.

6. The method for detecting the temperature of a power cable according to claim 1, characterized in that: The process in S4 for calculating the cable conductor temperature at any time within a predetermined time period after the current temperature acquisition time is as follows: Substitute the thermal resistivity of the insulation material and the cable conductor temperature at all temperature acquisition times into the thermal circuit equation to determine the corresponding average temperature rise rate. For any time within a predetermined time after the current temperature acquisition time, multiply the average temperature rise rate by the time difference and add the cable conductor temperature at the previous time to obtain the cable conductor temperature at the corresponding time.

7. A power cable connection structure integrating temperature detection function, wherein the temperature detection function is implemented by the method described in any one of claims 1-6; characterized in that: The power cable connection structure includes an intermediate connection assembly for connecting a first power cable (1) and a second power cable (2) that have been stripped in sections, and a temperature detection assembly. The power cable includes, from the inside out, a cable conductor (5), a cable insulation layer (6), a cable semi-conductive layer (10), and a cable protective sheath (7). Its characteristics are: The intermediate connection assembly includes a copper connecting pipe (11) and a waterproof protective layer (9); the copper connecting pipe (11) is fitted at the connection point of the cable conductors (5) of the first power cable (1) and the second power cable (2) to realize the electrical connection between the two power cables; The temperature detection component includes a first cable temperature sensor (3), a second cable temperature sensor (16), a data transmission module (17), and a temperature sensor power supply module (4). The first cable temperature sensor (3) is disposed on the outer surface of the waterproof protective layer (9) and located inside the tubular waterproof sheath (15) for detecting the cable surface temperature at both ends of the cable joint when current flows in the power cable. The second cable temperature sensor (16) is disposed on the outer surface of the waterproof protective layer (9) and is used to detect the cable surface temperature at the middle of the cable joint when current flows in the two power cables. The data transmission module (17) is disposed on the outer surface of the waterproof protective layer (9), adjacent to the second cable temperature sensor (16), and is communicatively connected to the first cable temperature sensor (3) and the second cable temperature sensor (16), and is used to send the temperature detection result to an external receiving device. The temperature sensor power supply module (4) is fixed on the outer wall of the cable semiconducting layer (10). It uses the change in magnetic flux caused by the current flowing in the two power cables to generate electrical energy to drive the first cable temperature sensor (3), the second cable temperature sensor (16) and the data transmission module (17).

8. A power cable connection structure with integrated temperature detection function according to claim 7, characterized in that: The intermediate connection assembly also includes: an inner shielding tube (12), an insulating tube (8), and an outer sheath (13) for the intermediate joint. The inner shielding tube (12) is wrapped around the outside of the copper connecting tube (11); The insulating tube (8) is wrapped around the outside of the inner shielding tube (12); The outer sheath (13) of the intermediate joint is wrapped around the outside of the insulating tube (8); the outer sheath (13) of the intermediate joint is coated with the waterproof protective layer (9).

9. A power cable connection structure with integrated temperature detection function according to claim 8, characterized in that: A tubular waterproof sheath (15) is provided on the outside of the waterproof protective layer (9) to protect the first cable temperature sensor (3).

10. A power cable connection structure with integrated temperature detection function according to claim 7, characterized in that: The cable protection sheaths (7) of the two power cables are also covered with cable shielding layers (14) to prevent external personnel from being electrocuted and to conduct the leakage current of the two power cables to the grounding end.

11. A terminal, comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps of the method according to any one of claims 1-6.

12. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the program implements the steps of the method according to any one of claims 1-6.

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