Method and system for acquiring temperature rise time constant of oil-filled cable

Abstract

The invention relates to the technical field of high-voltage cable operation and maintenance management, and discloses a method and a system for acquiring a temperature rise time constant of an oil-filled cable, and the method comprises the steps: building a current rising and temperature measuring system, an oil pressure and oil flow system and a temperature control system, synchronously regulating and controlling the current, oil flow rate, oil pressure and environment temperature of the oil-filled cable, and obtaining the temperature rise time constant of the oil-filled cable. And acquiring temperature data of the oil-filled cable, and calculating a temperature rise time constant after fitting. The system corresponds to the method. According to the invention, by synchronously controlling current, oil flow, oil pressure and environment temperature and simulating real scenes of the oil-filled cable under different operation conditions, the temperature rise rule of each part of the cable can be comprehensively captured, and by synchronously collecting temperature data of multiple parts, the temperature rise time constant can be accurately calculated, so that a reliable basis is provided for quantitative evaluation of the thermal stability of the cable; and the safety of the testing process is ensured through the design of a sealed heat preservation box, sealed thermocouple leading-out and a closed-loop oil flow loop.

Description

Technical Field

[0001] This invention relates to the field of high-voltage cable operation and maintenance management technology, specifically a method and system for obtaining the temperature rise time constant of oil-filled cables. Background Technology

[0002] Oil-filled cables, due to their unique insulation structure and material properties, have advantages such as high electrical performance, excellent aging resistance, strong adaptability to extreme environments, and long life cycle, making them the preferred solution for harsh scenarios such as ultra-high voltage, submarine, and large elevation differences.

[0003] However, temperature has a decisive impact on the safe operation and lifespan of oil-filled cables: According to Arrhenius's law, for every 8-10°C increase in temperature, the lifespan of insulating materials, such as oil-impregnated paper, will be halved. Furthermore, prolonged exposure to overheating will cause the insulating oil to crack and the paper fibers to carbonize, directly resulting in a significant decrease in the cable's breakdown strength and seriously threatening its insulation performance. The dielectric loss factor of oil-filled cables exhibits a non-linear growth trend under high-temperature conditions. Increased temperature not only exacerbates energy loss but also easily leads to local overheating, creating potential thermal fault hazards. Excessive temperature difference between the conductor and the insulation layer can lead to a mismatch in their coefficients of thermal expansion, resulting in mechanical stress. Over time, this can cause cracks in the insulation layer, potentially leading to partial discharge or even overall failure.

[0004] With the continuous expansion of new energy grid connection, oil-filled cables need to frequently cope with load fluctuations, and their temperature rise characteristics directly affect the flexibility and reliability of operating strategies. Currently, there is no comprehensive and accurate understanding of the temperature rise characteristics of oil-filled cables under the combined effects of multiple variables (such as current, oil flow, oil pressure, and ambient temperature), making it difficult to fully support the daily operation and maintenance management and full life cycle assessment of cables. Therefore, there is an urgent need for a technical approach that can accurately control key operating variables and systematically grasp temperature rise characteristics. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for obtaining the temperature rise time constant of oil-filled cables, so as to solve the technical problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention discloses the following technical solutions: In a first aspect, the present invention discloses a method for obtaining the temperature rise time constant of an oil-filled cable, the method comprising the following steps: A current boosting and temperature measurement system for regulating the current of oil-filled cables and collecting temperature data, an oil pressure and oil flow system for regulating the oil flow rate and oil pressure of oil-filled cables, and a temperature control system for regulating the ambient temperature of the oil-filled cables are constructed. The current, oil flow rate, oil pressure, and ambient temperature of the oil-filled cable are synchronously controlled through the current boosting and temperature measurement system, the oil pressure and oil flow system, and the temperature data of the oil-filled cable are collected. The temperature data of the oil-filled cable was fitted over time to calculate the temperature rise time constant.

[0007] Preferably, the setup of the current boosting and temperature measurement system includes: A section of oil-filled cable was cut as a test specimen. Several thermocouples were placed on the outer surface of the test specimen, the oil passage of the guide rod, the end connecting rod and the surrounding environment. After the thermocouples were led out from one end of the oil-filled cable, the lead-out part was sealed. The output end of the current booster is connected to the end guide rod of the oil-filled cable through a conductor to form a current boosting circuit, and a current transformer is connected in series in the current boosting circuit; temperature data is collected by a thermocouple so that the thermocouple and the current boosting circuit work together.

[0008] Preferably, in the current boosting and temperature measurement system, the rated current of the current booster covers the current range of the oil-filled cable during normal operation and overload operation; the temperature measurement accuracy of the thermocouple meets the accuracy requirements for temperature testing of the oil-filled cable; and the current transformer is used to monitor the current parameters in the current boosting circuit in real time.

[0009] Preferably, the construction of the hydraulic and oil flow system includes: Several guide oil channels connected to the guide rod oil channels are respectively set at both ends of the oil-filled cable; The oil guide channels at both ends of the oil-filled cable are sequentially connected to the inlet and outlet of the small oil pump and the connection port of the pressure oil tank through oil pipes, forming an oil pressure and oil flow control circuit that can regulate the oil flow rate and oil pressure. In the oil pressure and oil flow control circuit, the insulating oil can circulate between the oil-filled cable, the small oil pump and the pressure oil tank to simulate the oil circulation state in actual operation.

[0010] Preferably, in the oil pressure and oil flow system, the oil discharge rate of the small oil pump covers the oil flow rate range in the actual operation of the oil-filled cable, so as to simulate the circulation state of insulating oil under different working conditions; the pressure adjustment range of the pressure tank matches the oil pressure requirements of the oil-filled cable during operation.

[0011] Preferably, the temperature control system includes the following components: The oil-filled cable is placed entirely inside a sealed insulated box, the inner dimensions of which are adapted to the length of the oil-filled cable and the testing requirements. A heater for heating is installed inside the insulation box, and at least one hole is opened on the insulation box for introducing liquid nitrogen for cooling. An oil bottle containing a thermocouple is installed inside the insulation box near the oil-filled cable. The oil bottle contains oil of the same type as the insulating oil of the oil-filled cable, forming an ambient temperature control unit that can regulate ambient temperature. The thermocouple in the oil bottle is used to monitor the ambient reference temperature.

[0012] Preferably, in the temperature control system, the temperature control range of the insulation box covers the high and low temperature environment range that the oil-filled cable may encounter in actual operation, so as to simulate the operating state under cold, normal temperature and high temperature scenarios.

[0013] Preferably, the curve of the temperature data of the oil-filled cable changing over time is fitted using a first-order exponential function; the first-order exponential function is...

[0014] in, and It is a constant. It is a time constant. This is the cumulative time calculated from the start time.

[0015] Preferably, the acquisition of temperature data for the oil-filled cable includes: The temperature rise rate is calculated based on two consecutive temperature data acquisitions. The temperature rise rate is the ratio of the temperature difference to the acquisition time interval. The temperature difference is the difference between the temperature of the second acquisition and the temperature of the first acquisition. The acquisition time interval is the difference between the time of the second acquisition and the time of the first acquisition. A preset temperature rise rate threshold is set. When the temperature rise rate is not lower than the preset rate threshold, the acquisition cycle is adjusted to a preset high-speed acquisition mode; when the temperature rise rate is less than the preset rate threshold, the acquisition cycle is adjusted to a preset low-speed acquisition mode.

[0016] Secondly, the present invention discloses a system for obtaining the temperature rise time constant of an oil-filled cable, used to implement the method for obtaining the temperature rise time constant of an oil-filled cable as described above. The system includes: The component building module is used to build a current boosting and temperature measurement system for regulating the current of oil-filled cables and collecting temperature data, an oil pressure and oil flow system for regulating the oil flow rate and oil pressure of oil-filled cables, and a temperature control system for regulating the ambient temperature of the oil-filled cables. The data acquisition module is used to synchronously regulate the current, oil flow rate, oil pressure and ambient temperature of the oil-filled cable through the current boosting and temperature measurement system, the oil pressure and oil flow system and the temperature control system, and to collect temperature data of relevant parts of the oil-filled cable. The data calculation module is used to fit the curve of temperature data collected from relevant parts of the oil-filled cable over time and calculate the temperature rise time constant.

[0017] Compared with the prior art, the method and system for obtaining the temperature rise time constant of oil-filled cables of the present invention have the following advantages: 1. By synchronously controlling key operating variables such as current, oil flow rate, oil pressure and ambient temperature, the real-world scenarios of oil-filled cables under different operating conditions such as normal operation, overload operation and high and low temperature environments can be accurately simulated. This effectively overcomes the limitations of single-variable analysis in existing technologies and can more comprehensively and realistically capture the temperature rise patterns of key parts such as the cable outer surface, guide rod oil passages, and end connecting rods, providing a data foundation that is more in line with actual operating conditions for subsequent thermal characteristic analysis. 2. By using thermocouples to synchronously collect temperature data from multiple parts of the oil-filled cable and fitting the temperature-time change curve with a first-order exponential function, the temperature rise time constant can be accurately calculated. This time constant can provide a reliable basis for quantitatively assessing the thermal stability of the cable, directly supporting the optimization of oil-filled cable operation and maintenance strategies (such as load adjustment intervals and overheat protection threshold settings) and full-cycle life management (such as insulation life prediction). 3. The sealed insulation box design enables stable control of ambient temperature, the thermocouple lead-out area is sealed to prevent insulation oil leakage, and the closed-loop oil flow circuit design ensures the safety of insulation oil circulation. The multi-dimensional safety design ensures the stability and safety of the entire testing process and avoids safety hazards caused by oil leakage, temperature runaway and other issues during the testing process.

[0018] In summary, this invention provides a clear system setup process (the setup steps for the current booster and temperature measurement system, the oil pressure and oil flow system, and the temperature control system are clearly defined), the parameter adjustment range closely matches actual needs (e.g., the rated current of the current booster covers the normal and overload ranges, the oil pump discharge rate matches the actual oil flow range, and the temperature of the insulation box covers high and low temperature environments), the overall operation is easy to repeat, and the results obtained can directly guide the insulation performance evaluation, life prediction, and operation and maintenance strategy formulation of high-voltage oil-filled cables. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A flowchart illustrating the method for obtaining the temperature rise time constant of an oil-filled cable according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the platform architecture of the current boosting and temperature measurement system provided in an embodiment of the present invention; Figure 3This is a schematic diagram of the fitting curve for the temperature rise test data of the oil-filled cable provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the fitting curve for the cooling test data of the oil-filled cable provided in an embodiment of the present invention; Figure 5 The structural block diagram of the system for obtaining the temperature rise time constant of an oil-filled cable provided in an embodiment of the present invention.

[0021] Attached reference numerals: 1. Current booster; 2. Current transformer; 3. Oil guide channel; 4. Oil-filled cable; 5. Insulation box; 6. Oil bottle. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In this document, the term "comprising" is intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0024] This embodiment provides a method such as Figure 1 The method for obtaining the temperature rise time constant of oil-filled cables, as shown, is applicable to the analysis of insulation performance, cycle life, and operation and maintenance strategies for high-voltage oil-filled cables. It aims to examine the temperature rise time constant of oil-filled cables under different conditions by controlling key variables such as current, oil flow, oil pressure, and ambient temperature, providing a basis for formulating operation and maintenance strategies and full-cycle life management. Specifically, the method includes: Step 1: Setting up the current boosting and temperature measurement system: Combining Figure 2 As shown, a 5m section of high-voltage oil-filled cable 4 is cut. Its insulation structure consists of oil-impregnated paper and insulating oil, and the conductor cross-section meets the 4000A current-carrying requirement. Several thermocouples are arranged on the outer surface of the oil-filled cable 4, the oil channels of the guide rod, the end connecting rod, and in the environment. The thermocouples are led out from one end of the oil-filled cable 4, and the lead-out holes are sealed with sealant to prevent insulating oil leakage.

[0025] The output terminal of current booster 1 is connected to the end guide rod of oil-filled cable 4 via a conductor to form a current boosting circuit. The current boosting circuit includes current booster 1, conductor, end guide rod, current transformer 2, and cable conductor. The circuit path is: current booster 1 → conductor → end guide rod → cable conductor → other end guide rod → conductor → current booster 1. Temperature data is collected by thermocouples to form a current boosting and temperature measurement circuit in conjunction with the current boosting circuit.

[0026] In this embodiment, a total of 14 thermocouples are arranged on the outer surface of the oil-filled cable 4, the guide rod oil passage, the end connecting rod, and the environment. Among them, 7 measuring points are arranged on the outer surface of the cable (i.e., Figure 2 The measuring points shown are 7-13, and five measuring points are arranged in the guide rod oil passage (i.e., Figure 2 The measurement points 1-5 shown in the figure), and one measurement point is arranged on the end connecting rod (i.e. Figure 2 One measurement point is set up at measurement point 6 shown in the diagram and at oil bottle 6 in the environment (i.e., Figure 2 (See measurement point 14 shown). Secondly, the rated current of current booster 1 is 4000A, and the temperature measurement accuracy of the thermocouple is ±0.1℃.

[0027] Step 2: Construction of the Hydraulic Pressure and Flow System: Two guide oil channels 5 (8mm in diameter) are machined at both ends of the oil-filled cable 4, connecting to the guide rod oil channels. The guide oil channels 5 at both ends of the oil-filled cable 4 are sequentially connected to the inlet and outlet of the small oil pump and the connection port of the pressure oil tank via oil pipes, forming an hydraulic pressure and flow control circuit. This circuit includes the guide oil channels 5, oil pipes, the small oil pump, and the pressure oil tank, which is pre-filled with insulating oil of the same type as the cable. The hydraulic pressure and flow control circuit forms a closed-loop circulation through the oil pipes, allowing the insulating oil to circulate between the oil-filled cable 4, the small oil pump, and the pressure oil tank, simulating the oil circulation state in actual operation.

[0028] In this embodiment, the small oil pump has an oil discharge rate of 0~10L / min, a pressure tank capacity of 100L, and a maximum pressure of 4bar.

[0029] Step 3: Temperature Control System Setup: Place the oil-filled cable 4 entirely within the sealed insulated box 5. The oil-filled cable 4 refers to the entire set of test components directly connected to it and required to be under a uniform ambient temperature. Its specific composition is as follows: Oil-filled cable 4 body: that is, a section of oil-filled cable 4 to be tested, which includes core structures such as conductor, oil-impregnated paper insulation layer, guide rod oil channel (internal flow of insulating oil) and outer sheath; End guide rod; Thermocouple measuring ends attached to the cable: Thermocouples arranged on the outer surface of the oil-filled cable 4, inside the oil passage of the guide rod and on the end connecting rod are used to directly collect temperature data of various parts of the cable; The oil pipes directly connected to both ends of the cable: In the oil pressure and oil flow system, the oil pipes connecting the guide oil channel 5 at the end of the cable to the small oil pump / pressure oil tank (the section located inside the insulation box 5) ensure that the insulating oil flows in the cable and oil pipes under a uniform ambient temperature, avoiding external temperature interference with the heat dissipation characteristics of the oil flow.

[0030] The internal dimensions of the insulation box 5 are adapted to the length of the oil-filled cable 4 and the testing requirements. It is equipped with a heater for heating and at least one hole for introducing liquid nitrogen for cooling. An oil bottle 6 with a thermocouple is placed inside the insulation box 5 near the oil-filled cable 4 to monitor the ambient reference temperature, forming an ambient temperature control unit that can control the ambient temperature. The oil bottle 6 contains oil of the same type as the insulating oil of the oil-filled cable 4.

[0031] In this embodiment, the temperature control range of the insulation box 5 is -20℃ to 60℃. The dimensions of the insulation box 5 are 5m in length, 0.5m in width, and 0.5m in height.

[0032] Step 4: Calculation of Temperature Rise Time Constant: The output current of current booster 1 is controlled by the current booster circuit; the oil flow rate of the small oil pump and the oil pressure of the pressure tank are controlled by the oil pressure and oil flow regulation circuit; and the ambient temperature inside the insulation box 5 is controlled by the ambient temperature regulation unit. Temperature data from each thermocouple are collected simultaneously. Based on thermodynamic principles, a first-order exponential function is used to fit the curve of temperature data changing with time to calculate the temperature rise time constant. The first-order exponential function is: ,in and It is a constant. This is the time constant (used to characterize the rate at which the oil-filled cable 4 reaches thermal equilibrium under corresponding operating conditions). The smaller the value, the faster the temperature rises or falls to a steady state. This is the cumulative time calculated from the start time.

[0033] A feasible approach is to fit the temperature data to the time curve using a first-order exponential function, including: The temperature data curve was fitted using MATLAB software. The MATLAB software programs used for fitting include: , where kt is the temperature data.

[0034] In this embodiment, the temperature data is acquired in real time and continuously, and the acquisition period is dynamically adjusted according to the rate of temperature change in order to capture key change nodes in the temperature rise curve.

[0035] Furthermore, the data acquisition cycle is dynamically adjusted based on the rate of temperature change, including: The temperature rise rate is calculated based on two consecutive temperature data acquisitions. The temperature rise rate is the ratio of the temperature difference to the acquisition time interval. The temperature difference is the difference between the temperature of the second acquisition and the temperature of the first acquisition, and the acquisition time interval is the difference between the time of the second acquisition and the time of the first acquisition. When the temperature rise rate is not lower than the preset rate threshold (e.g., 1℃ / min), the acquisition cycle will be adjusted to the preset high-speed acquisition mode (e.g., acquisition will be performed every 5~10s). When the temperature rise rate is less than the preset rate threshold, the sampling period will be adjusted to the preset low-speed sampling mode (e.g., sampling once every 30~60 seconds).

[0036] This embodiment sets the following experimental parameters: Booster 1 output current: 815A (simulating medium load conditions); Small oil pump discharge rate: 3L / min (simulating the normal circulation speed of insulating oil); Oil pressure in the pressure tank: 2.9 bar (actual operating oil pressure of the matching cable); Insulation box 5 ambient temperature: 30℃ (maintained by heater, fluctuation controlled within ±0.5℃).

[0037] The experimental procedure is as follows: Heating Phase: Start the current booster 1, small oil pump, and heater in insulation box 5, and simultaneously record the temperature data of each thermocouple. Dynamic adjustment of the acquisition cycle: In the initial hour (temperature rise rate ≥ 1℃ / min), acquire data every 10 seconds; after 1 hour (temperature rise rate < 1℃ / min), acquire data every 30 seconds, until the temperature of each part of the cable tends to stabilize (temperature change ≤ 0.5℃ within 30 minutes), then stop the heating test, which lasts for approximately 1200 minutes.

[0038] Cooling phase: Turn off the current booster 1, keep the ambient temperature of the small oil pump, pressure oil tank and insulation box 5 constant, continue to collect temperature data, the collection period is the same as the heating phase, until the cable temperature drops to the difference between the ambient temperature and ≤1℃, stop the test, the duration is about 1320min.

[0039] The data processing and result analysis process is as follows: The collected temperature data (time-temperature curve) was imported into MATLAB software, fitted using the aforementioned first-order exponential function, and the time constant was extracted to obtain the following result: Figure 3 and 4 The fitting results of the heating test data are shown.

[0040] Experimental conclusion: The method and system for obtaining the temperature rise time constant of the oil-filled cable in this embodiment accurately captures the temperature rise and fall characteristics of the oil-filled cable 4 by controlling the current 815A, oil flow 3L / min, oil pressure 2.9bar and ambient temperature 30℃. The calculated time constant τ can quantitatively characterize its thermal response speed, providing direct data support for the operation and maintenance strategy (such as load adjustment interval and overheat protection threshold) of this type of cable under medium load and normal temperature environment.

[0041] Specifically: Heating stage: The fitting curve shows that the highest temperature of the oil passage of the guide rod of the oil-filled cable reaches 78℃, the highest temperature of the outer surface reaches 62℃, and the time constant τ is 320min, indicating that the cable reaches thermal stability at a moderate rate under this working condition.

[0042] The corresponding time constant is calculated as follows: A1. Determine the fitting constants a and b: During the heating stage, the cable temperature eventually tends to stabilize. The stable temperature is the highest temperature of the guide rod oil passage, which is 78℃. Therefore, the fitting constant b = 78 (stable temperature value). At the initial moment, x = 0, the cable temperature is the same as the ambient temperature, which is 30℃. Substituting x = 0 and T(0) = 30 into the first-order exponential function, we can solve for a = 30 - 78 = -48.

[0043] A2. Select temperature data at an intermediate moment during the heating phase, such as x=320min. Combine this with the final fitting results to deduce that the temperature at this moment is close to the critical node of the thermal equilibrium process. Assume the temperature at this moment... Based on the fitting results with a time constant τ of 320 min during the heating phase, we substitute τ=320 into the formula for verification: The temperature value of ℃ is highly consistent with the temperature data collected at the midpoint of the actual time, further confirming that τ=320min.

[0044] A3. Import all temperature-time data collected during the heating phase into MATLAB software, and set the model according to the fitting procedure: The initial parameters StartPoint=[-48,320,78] were set, and the fitting command [fitresult,gof]=fit(x,kt,fit_model,'StartPoint',[0,0,0]) was executed (where kt is the temperature data). The fitting results show that the goodness of fit R is... 2 The value is close to 1, indicating that the fitting accuracy is extremely high. The final extracted time constant τ = 320 min is consistent with the conclusion, indicating that the cable reaches thermal stability at a moderate rate under this working condition.

[0045] Cooling stage: The fitting curve shows that it takes about 900 minutes for the guide rod oil passage temperature to drop from 78℃ to 35℃ (ambient temperature 30℃), and the time constant τ is 450 minutes, indicating that the cooling process has a large thermal inertia.

[0046] The corresponding time constant is calculated as follows: B1. During the cooling stage, the final difference between the cable temperature and the ambient temperature (30℃) is ≤1℃. Take the stable temperature b'=31 (close to the stable value of the ambient temperature). At the initial moment, x'=0, the cable temperature is the highest temperature of the heating stage, 78℃. Substitute x'=0 and T'(0)=78 into the first-order exponential function to get a'=78-31=47.

[0047] B2. Select key data points during the cooling phase (e.g., x'=450min, corresponding to the fitting result of a cooling phase time constant τ of 450min), at which point the temperature... Substituting τ=450 into the formula for verification: The temperature value is consistent with the actual measured temperature of the guide rod oil passage, which dropped from 78℃ to 35℃ in about 900 minutes, and conforms to the thermal change law of the cooling process.

[0048] B3. Similarly, import the temperature-time data from the cooling phase into MATLAB, set the parameters according to the fitting model described above, and the fitting results show the goodness of fit R. 2 The value is close to 1, and the extracted time constant τ = 450 min is consistent with the conclusion, indicating that the cable has a large thermal inertia during the cooling process and the thermal equilibrium rate is slower than that during the heating stage.

[0049] It should be noted that this invention is not limited to the single operating condition described above. By adjusting the current of the booster 1 (e.g., 1000A, 3000A), oil flow rate (e.g., 1L / min, 8L / min), oil pressure (e.g., 1bar, 4bar), or ambient temperature (e.g., -10℃, 50℃), the above test procedure can be repeated to analyze the temperature rise time constant under different combinations of variables, further verifying the universality of the method. For example, under the operating condition of ambient temperature -10℃ and current 4000A, the thermal stability of the cable under extreme low temperature and heavy load can be analyzed in detail, and the results can guide the selection and operation and maintenance of oil-filled cables 4 in cold regions.

[0050] In a second aspect, this embodiment provides a system for obtaining the temperature rise time constant of an oil-filled cable, used to implement the method for obtaining the temperature rise time constant of an oil-filled cable as described above, such as... Figure 5 As shown, the system includes: The component building module is used to build a current boosting and temperature measurement system for regulating the current of oil-filled cables and collecting temperature data, an oil pressure and oil flow system for regulating the oil flow rate and oil pressure of oil-filled cables, and a temperature control system for regulating the ambient temperature of the oil-filled cables. The data acquisition module is used to synchronously regulate the current, oil flow rate, oil pressure, and ambient temperature of the oil-filled cable through the current boosting and temperature measurement system, oil pressure and oil flow system, and temperature control system, and to collect temperature data of relevant parts of the oil-filled cable. The data calculation module is used to fit the curve of temperature data collected from relevant parts of the oil-filled cable over time and calculate the temperature rise time constant.

[0051] It should be noted that the system for obtaining the temperature rise time constant of the oil-filled cable in this embodiment corresponds to the aforementioned method for obtaining the temperature rise time constant of the oil-filled cable. Therefore, for the parts of the system for obtaining the temperature rise time constant of the oil-filled cable that are not described in detail in this embodiment (including but not limited to specific technical means, technical effects, etc.), you can refer to the relevant descriptions in the aforementioned method for obtaining the temperature rise time constant of the oil-filled cable. This text will not repeat them here.

[0052] In summary, the method and system for obtaining the temperature rise time constant of the oil-filled cable in this embodiment, by synchronously controlling key variables such as current, oil flow, oil pressure, and ambient temperature, can simulate real-world scenarios of the oil-filled cable 4 under different operating conditions, overcoming the limitations of single-variable analysis and more comprehensively capturing the temperature rise patterns of various parts of the cable (guide rod oil passages, outer surface, end connecting rods, etc.). Secondly, the rated current of the current booster 1 covers 0~4000A, simulating different load fluctuations; the adjustable range of oil flow rate (0~10L / min) and oil pressure (0~4bar) matches the actual operating conditions of insulating oil circulation; and the ambient temperature... With a control range of -20℃ to 60℃, it can adapt to extreme high and low temperature environments, ensuring the applicability of calculation results to complex scenarios. Simultaneously, it uses thermocouples with an accuracy of ±0.1℃ to synchronously collect temperature data from multiple locations. Combined with MATLAB software for fitting the first-order exponential function of the temperature rise curve, it can accurately calculate the temperature rise time constant, providing a reliable basis for quantitatively evaluating the thermal stability of the cable and directly supporting the optimization of operation and maintenance strategies and full-cycle life management. Furthermore, the design of a sealed insulation box 5, sealed thermocouple leads, and a closed-loop oil flow circuit ensures the safety of the testing process. The system setup and parameter control process is clear and easy to repeat.

[0053] In the embodiments provided by this invention, it should be understood that the embodiments described herein can be implemented in hardware, software, firmware, middleware, code, or any suitable combination thereof. For hardware implementation, the processor can be implemented in one or more of the following: application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, other electronic units designed to implement the functions described herein, or combinations thereof. For software implementation, some or all of the processes of the embodiments can be performed by a computer program instructing the associated hardware. During implementation, the program can be stored in a computer-readable storage medium or transmitted as one or more instructions or code on a computer-readable storage medium. Computer-readable storage media include computer storage media and communication media, wherein communication media include any medium that facilitates the transmission of a computer program from one place to another. Storage media can be any available medium accessible to a computer. Computer-readable storage media can include, but are not limited to, RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code having the form of instructions or data structures and accessible to a computer.

[0054] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for obtaining the temperature rise time constant of an oil-filled cable, characterized in that, The method includes the following steps: A current boosting and temperature measurement system for regulating the current of oil-filled cables and collecting temperature data, an oil pressure and oil flow system for regulating the oil flow rate and oil pressure of oil-filled cables, and a temperature control system for regulating the ambient temperature of the oil-filled cables are constructed. The current, oil flow rate, oil pressure, and ambient temperature of the oil-filled cable are synchronously controlled through the current boosting and temperature measurement system, the oil pressure and oil flow system, and the temperature data of the oil-filled cable are collected. The temperature data of the oil-filled cable was fitted over time to calculate the temperature rise time constant.

2. The method for obtaining the temperature rise time constant of an oil-filled cable according to claim 1, characterized in that, The construction of the current boosting and temperature measurement system includes: A section of oil-filled cable was cut as a test specimen. Several thermocouples were placed on the outer surface of the test specimen, the oil passage of the guide rod, the end connecting rod and the surrounding environment. After the thermocouples were led out from one end of the oil-filled cable, the lead-out part was sealed. The output end of the current booster is connected to the end guide rod of the oil-filled cable through a conductor to form a current boosting circuit, and a current transformer is connected in series in the current boosting circuit; temperature data is collected by a thermocouple so that the thermocouple and the current boosting circuit work together.

3. The method for obtaining the temperature rise time constant of an oil-filled cable according to claim 1, characterized in that, In the current boosting and temperature measurement system, the rated current of the current booster covers the current range of the oil-filled cable during normal operation and overload operation; the temperature measurement accuracy of the thermocouple meets the accuracy requirements for temperature testing of the oil-filled cable; and the current transformer is used to monitor the current parameters in the current boosting circuit in real time.

4. The method for obtaining the temperature rise time constant of an oil-filled cable according to claim 1, characterized in that, The construction of the hydraulic and oil flow system includes: Several guide oil channels connected to the guide rod oil channels are respectively set at both ends of the oil-filled cable; The oil guide channels at both ends of the oil-filled cable are sequentially connected to the inlet and outlet of the small oil pump and the connection port of the pressure oil tank through oil pipes, forming an oil pressure and oil flow control circuit that can regulate the oil flow rate and oil pressure. In the oil pressure and oil flow control circuit, the insulating oil can circulate between the oil-filled cable, the small oil pump and the pressure oil tank to simulate the oil circulation state in actual operation.

5. The method for obtaining the temperature rise time constant of an oil-filled cable according to claim 4, characterized in that, In the oil pressure and oil flow system, the oil discharge rate of the small oil pump covers the oil flow rate range in the actual operation of the oil-filled cable, so as to simulate the circulation state of insulating oil under different working conditions; the pressure adjustment range of the pressure tank matches the oil pressure requirements of the oil-filled cable during operation.

6. The method for obtaining the temperature rise time constant of an oil-filled cable according to claim 1, characterized in that, The construction of the temperature control system includes: The oil-filled cable is placed entirely inside a sealed insulated box, the inner dimensions of which are adapted to the length of the oil-filled cable and the testing requirements. A heater for heating is installed inside the insulation box, and at least one hole is opened on the insulation box for introducing liquid nitrogen for cooling. An oil bottle containing a thermocouple is installed inside the insulation box near the oil-filled cable. The oil bottle contains oil of the same type as the insulating oil of the oil-filled cable, forming an ambient temperature control unit that can regulate ambient temperature. The thermocouple in the oil bottle is used to monitor the ambient reference temperature.

7. The method for obtaining the temperature rise time constant of an oil-filled cable according to claim 6, characterized in that, In the temperature control system, the temperature control range of the insulation box covers the high and low temperature environment range that the oil-filled cable may encounter in actual operation, so as to simulate the operating state under cold, normal temperature and high temperature scenarios.

8. The method for obtaining the temperature rise time constant of an oil-filled cable according to claim 1, characterized in that, The temperature data of the oil-filled cable over time was fitted using a first-order exponential function; the first-order exponential function is... in, and It is a constant. It is a time constant. This is the cumulative time calculated from the start time.

9. The method for obtaining the temperature rise time constant of an oil-filled cable according to claim 1, characterized in that, The acquisition of temperature data for relevant parts of the oil-filled cable includes: The temperature rise rate is calculated based on two consecutive temperature data acquisitions. The temperature rise rate is the ratio of the temperature difference to the acquisition time interval. The temperature difference is the difference between the temperature of the second acquisition and the temperature of the first acquisition. The acquisition time interval is the difference between the time of the second acquisition and the time of the first acquisition. A preset temperature rise rate threshold is set. When the temperature rise rate is not lower than the preset rate threshold, the acquisition cycle is adjusted to a preset high-speed acquisition mode; when the temperature rise rate is less than the preset rate threshold, the acquisition cycle is adjusted to a preset low-speed acquisition mode.

10. A system for obtaining the temperature rise time constant of an oil-filled cable, used to implement the method for obtaining the temperature rise time constant of an oil-filled cable as described in any one of claims 1-9, characterized in that, The system includes: The component building module is used to build a current boosting and temperature measurement system for regulating the current of oil-filled cables and collecting temperature data, an oil pressure and oil flow system for regulating the oil flow rate and oil pressure of oil-filled cables, and a temperature control system for regulating the ambient temperature of the oil-filled cables. The data acquisition module is used to synchronously regulate the current, oil flow rate, oil pressure and ambient temperature of the oil-filled cable through the current boosting and temperature measurement system, the oil pressure and oil flow system and the temperature control system, and to acquire the temperature data of the oil-filled cable. The data calculation module is used to fit the curve of the temperature data of the oil-filled cable over time and calculate the temperature rise time constant.

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