An oil-filled cable terminal moisture simulation platform

Abstract

This invention discloses a moisture simulation platform for oil-filled cable terminals, belonging to the field of power equipment condition monitoring and fault diagnosis technology. It includes a rain shower device and a terminal simulation platform. The rain shower device comprises a water tank, a water pump, a liquid flow meter, and a nozzle connected sequentially via pipelines. The terminal simulation platform includes a cable structure simulation module, a fixing cover, an angle adjustment module, a hydraulic pressure simulation module, and a temperature simulation module. The simulated conductor of the cable structure simulation module has a central oil channel, and the simulated insulation layer is surrounded by multiple layers of oil-impregnated insulating paper tape, with each layer of paper tape bonded together and gaps between adjacent paper tapes within the same layer. The fixing cover is fitted over the insulation layer and connected to the angle adjustment module. The hydraulic pressure simulation module provides controllable oil pressure to the oil channel through an oil pump and a replenishment pipeline. The temperature simulation module simulates the operating temperature through a conductor heating unit and a temperature controller. This allows for a high degree of realism in replicating the on-site moisture conditions, providing reliable data for studying moisture diffusion behavior.

Description

Technical Field

[0001] This invention relates to the field of power equipment condition monitoring and fault diagnosis technology, and in particular to a moisture simulation platform for oil-filled cable terminals. Background Technology

[0002] Oil-filled cables, especially self-contained oil-filled submarine cables, are key equipment in high-voltage and ultra-high-voltage power transmission projects. Cable terminals, serving as the electrical connection and sealing end of cable lines, are the weakest link in their insulation structure. In complex outdoor environments (especially on the seabed and in coastal areas), if the terminal seal fails due to aging, mechanical damage, or other reasons, external moisture (such as rainwater and seawater moisture) can easily penetrate, causing the oil-impregnated paper insulation to become damp and deteriorate. Moisture significantly reduces the electrical strength of the insulating paper (e.g., decreased breakdown voltage, decreased volume resistivity, increased dielectric loss) and accelerates the thermal aging of cellulose, potentially leading to serious accidents such as insulation breakdown and threatening power grid safety.

[0003] Currently, most studies on the diffusion of moisture in oil-impregnated paper insulation are conducted under ideal laboratory conditions, described using Fick's second law. However, the actual moisture environment in the field is complex and variable: cable laying angles vary (horizontal, inclined, vertical), the internal oil channels at the terminals may be under positive pressure, and the chemical composition, flow rate, and duration of water sources (such as rainfall or wave splashing) are uncontrollable. Existing laboratory platforms (such as simple immersion experiments) are insufficient to comprehensively simulate these key field factors, leading to discrepancies between the diffusion models and parameters obtained in the laboratory and actual conditions, making them unsuitable for direct guidance in accurate field assessments. Therefore, developing a technical solution that can realistically simulate on-site moisture conditions has urgent engineering needs and significant application value. Summary of the Invention

[0004] The purpose of this invention is to provide a moisture simulation platform for oil-filled cable terminals, which solves the technical problem that existing experimental devices cannot simultaneously simulate the effects of multiple factors such as rainfall, cable laying angle, internal oil channel pressure and operating temperature, resulting in deviations between the diffusion models and parameters obtained in the laboratory and the actual situation, and thus cannot be directly used to guide accurate on-site assessments.

[0005] To achieve the above objectives, the present invention provides the following solution: The present invention provides a moisture simulation platform for oil-filled cable terminals, comprising: A rain shower device includes a water tank, a water pump, a liquid flow meter, and a sprinkler head; the water tank is connected to the inlet of the liquid flow meter via the water pump, and the outlet of the liquid flow meter is connected to the sprinkler head; and... The terminal simulation platform includes a cable structure simulation module, a fixing cover, an angle adjustment module, a hydraulic pressure simulation module, and a temperature simulation module. The cable structure simulation module comprises a simulated conductor and a simulated insulation layer. The simulated conductor has a central through-hole for forming a simulated oil channel. The simulated insulation layer comprises multiple layers of oil-impregnated insulating paper tape, each layer of which is wrapped around the outer surface of the simulated conductor. The layers of oil-impregnated insulating paper tape are bonded together, with gaps between adjacent layers within the same layer. The fixing cover is fitted over the simulated insulation layer and fixed to it. The angle adjustment module includes an angle-adjustable bracket, which is fixedly connected to the fixing cover and used to adjust and lock the laying angle of the cable structure simulation module. The hydraulic pressure simulation module includes an insulating oil tank, an oil pump, and a replenishing oil pipe. One end of the replenishing oil pipe is connected to the simulated oil channel, and the other end is connected to the insulating oil tank via the oil pump. The temperature simulation module includes a conductor heating unit and a temperature controller. The conductor heating unit is disposed on the simulated conductor, and the temperature controller is electrically connected to the conductor heating unit.

[0006] Optionally, the nozzles are provided in multiples and form a nozzle array. The nozzle array is arranged in a two-dimensional plane, the spray angle of each nozzle is independently adjustable, and the overall coverage area of ​​the nozzle array is greater than the surface area of ​​the cable structure simulation module.

[0007] Optionally, the angle-adjustable bracket includes a base, a gear transmission mechanism, and a worm gear transmission mechanism; the base is fixed to the ground or a test bench; the input end of the gear transmission mechanism is used to receive external drive, and its output end is connected to the input end of the worm gear transmission mechanism, the output end of the worm gear transmission mechanism is connected to the fixed cover; the worm gear transmission mechanism is capable of reverse self-locking, so that the angle-adjustable bracket is automatically locked after being adjusted to any preset angle.

[0008] Optionally, the oil pressure simulation module further includes a pressure sensor, an electronically controlled regulating valve, and a controller; the pressure sensor is installed on the oil replenishment pipeline; the electronically controlled regulating valve is connected in series on the oil replenishment pipeline and located between the oil pump and the simulated oil passage; the controller is connected to the pressure sensor and the electronically controlled regulating valve respectively, and is used to control the opening degree of the electronically controlled regulating valve according to the preset target pressure curve and the real-time oil pressure collected by the pressure sensor through a PID algorithm.

[0009] Optionally, the fixed cover is equipped with a pressure relief valve; the platform also includes an oil-water separation and circulation system, which includes a liquid collection module, an oil-water separation module, a water circulation module, and an oil recovery module. The inlet of the liquid collection module is connected to the pressure relief valve via a pipe; the inlet of the oil-water separation module is connected to the outlet of the liquid collection module; the inlet of the water circulation module is connected to the water phase outlet of the oil-water separation module, and the outlet of the water circulation module is connected to the water tank of the rain shower device; the inlet of the oil recovery module is connected to the oil phase outlet of the oil-water separation module.

[0010] Optionally, the oil-water separation module is a gravity settling separator, which is internally divided into a filtration zone, a separation zone, and a liquid outlet zone by a first partition and a second partition. The inlet of the filtration zone is connected to the outlet of the liquid collection module through a switching valve. A liquid outlet is provided on the first partition, and the filtration zone is connected to the separation zone through the liquid outlet. A liquid outlet pipe is provided on the second partition, and a valve is provided on the liquid outlet pipe. The separation zone has an oil outlet on its side wall, which serves as the oil phase outlet of the oil-water separation module. A water outlet is provided on the side wall of the liquid outlet zone, which serves as the water phase outlet of the oil-water separation module.

[0011] Optionally, the water circulation module includes a water storage tank, a filter, and a delivery pump; the oil-water separation and circulation system also includes a water quality monitoring unit, which is used to monitor the conductivity, pH value, or oil content of the recycled water online; the water inlet of the water circulation module is connected to an external water supply pipeline through a switching valve, and the water quality monitoring unit controls the opening and closing of the switching valve according to the monitoring results to switch to the external water supply pipeline.

[0012] Optionally, the oil recovery module includes an oil storage tank and an oil filter; the inlet of the oil storage tank serves as the inlet of the oil recovery module, the oil filter is connected to the pipeline between the inlet and outlet of the oil storage tank, and the outlet of the oil storage tank is connected to the insulating oil tank of the terminal simulation platform via a pipeline.

[0013] Optionally, the temperature simulation module further includes multiple temperature sensors arranged on the surface of the simulated conductor and inside the simulated insulating layer; the temperature controller is connected to the temperature sensors.

[0014] Optionally, the simulated conductor is a tubular structure, and the central through hole extends along the axial direction of the simulated conductor; the conductor heating unit is integrated on the outside of the simulated conductor or embedded in the tube wall of the simulated conductor.

[0015] The present invention achieves the following technical effects compared to the prior art: This invention organically combines a rain-spraying device with a terminal simulation platform integrating angle adjustment, oil pressure simulation, and temperature simulation functions. For the first time, it achieves simultaneous coupled simulation of multiple factors, including rainfall intensity, water quality, cable laying angle, internal oil pressure, and operating temperature, highly replicating complex on-site moisture-affected conditions. This platform can simulate the moisture-affected process under various conditions, including normal cable operation, load fluctuations, and oil leakage due to faults. It provides a reliable data foundation for studying the true diffusion behavior of moisture in oil-impregnated paper insulation and establishing accurate moisture-affected assessment models, effectively improving the efficiency of research on the operational safety of oil-filled cables. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments 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.

[0017] Figure 1 This is a schematic diagram of the structure of the oil-filled cable terminal moisture simulation platform provided in the embodiments of this disclosure; Figure 2 This is a schematic diagram of the angle adjustment mechanism provided in an embodiment of this disclosure; Figure 3 This is a schematic diagram of the structure of the oil-water separation and circulation system provided in the embodiments of this disclosure; The components include: 1. Shower device; 11. Water tank; 12. Water pump; 13. Connecting pipes; 14. Liquid flow meter; 15. Sprinkler head; 2. Terminal simulation platform; 21. Simulated oil passage; 22. Simulated conductor; 23. Simulated insulation layer; 24. Fixing cover; 25. Angle-adjustable bracket; 226. Oil replenishment pipeline; 27. Oil pump; 28. Insulating oil tank; 29. ​​Pressure relief valve; 251. Base; 252. Gear transmission; 253. Worm gear transmission; 3. Oil-water separation and circulation system; 31. Liquid collection module; 32. Oil-water separation module; 33. Water circulation module; 34. Oil recovery module; 321. Connecting switching valve; 322. Filter plate; 323. Filtration zone; 324. Liquid outlet; 325. Separation zone; 326. Liquid outlet pipe; 327. Liquid outlet area; 328. Water outlet; 329. Oil outlet. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0019] The purpose of this invention is to provide a moisture simulation platform for oil-filled cable terminals, which solves the technical problem that existing experimental devices cannot simultaneously simulate the effects of multiple factors such as rainfall, cable laying angle, internal oil channel pressure and operating temperature, resulting in deviations between the diffusion models and parameters obtained in the laboratory and the actual situation, and thus cannot be directly used to guide accurate on-site assessments.

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] like Figures 1 to 3 This invention provides a moisture simulation platform for oil-filled cable terminals, such as... Figure 1 As shown, it includes a rain shower device 1 and a terminal simulation station 2.

[0022] The rain shower device 1 is used to simulate environmental rainfall and includes a water tank 11, a water pump 12, a liquid flow meter 14, and nozzles 15. The outlet of the water tank 11 is connected to the inlet of the water pump 12 via a pipe, the outlet of the water pump 12 is connected to the inlet of the liquid flow meter 14 via a pipe, and the outlet of the liquid flow meter 14 is connected to the nozzles 15 via a pipe. The water pump 12 draws water and delivers it to the liquid flow meter 14 via a connecting pipe 13. It is understood that the water tank 11 can be used to hold deionized water or a salt solution prepared at a preset concentration to simulate different water qualities. For example, deionized water can be used to simulate rainfall conditions, and a standard-prepared NaCl solution (e.g., 3.5% concentration) can be used to simulate seawater splash conditions, thereby simulating the chemical composition of different water sources. The water pump 12 provides the power for the entire rain shower circuit, and the liquid flow meter 14 is used to monitor and adjust the volumetric flow rate of the water in real time. The water flows through the nozzles 15 and is sprayed out as a water mist. Based on the above embodiments, as a preferred example, a flow control valve can also be connected in series on the pipeline between the liquid flow meter 14 and the nozzle 15. This valve precisely adjusts the flow rate to the nozzle 15 according to the instructions of the control system, thereby achieving precise and controllable simulation of rainfall intensity and immersion duration. Thus, the rain shower device 1 of this embodiment solves the problem that existing immersion experiments cannot simulate the differentiated effects of different water qualities, rainfall intensities, and durations on the moisture absorption of terminal insulation.

[0023] The terminal simulation platform 2 is used to simulate the state of oil-filled cable terminals in a humid environment. It is equipped with a cable structure simulation module, a fixing cover 24, an angle adjustment module, an oil pressure simulation module, and a temperature simulation module.

[0024] The cable structure simulation module is used to reproduce the insulation structure of an actual cable terminal. It includes a simulated conductor 22 and a simulated insulation layer 23. The simulated conductor 22 is designed and manufactured according to the actual dimensions of a certain type of 500kV oil-filled submarine cable, and has a central through-hole, which is used to form a simulated oil channel 21. The simulated insulation layer 23 consists of multiple layers of oil-impregnated insulating paper tape, specifically DDB oil-impregnated kraft paper tape. Each layer of oil-impregnated insulating paper tape is wrapped around the outer surface of the simulated conductor 22, and the layers of oil-impregnated insulating paper tape are bonded to each other, with gaps between adjacent layers within the same layer. It can be understood that the insulation layer of an actual oil-filled cable is made by wrapping insulating paper tape strictly according to process requirements. The layers of paper tape are tightly bonded to form an insulating cylinder, but there are tiny gaps between adjacent paper tapes within the layer. These gaps are the main channels for moisture to penetrate into the interior of the insulation layer. Driven by factors such as concentration gradient and pressure gradient, moisture migrates into the depth of the insulation layer along the microchannel network formed by these gaps. Existing idealized experimental models usually use homogeneous insulating cylinders, which cannot reproduce the influence of this microstructure on the moisture diffusion path and rate. This embodiment uses the same DDB oil-impregnated kraft paper tape as the actual cable, and employs a structure in which the layers of paper tape are bonded together and there are gaps between adjacent paper tapes in the same layer. This highly replicates the material properties and microstructure of the insulation layer of the actual cable, making the diffusion behavior of moisture in the insulation layer highly consistent with the actual working conditions. This provides a reliable data foundation for establishing an accurate moisture diffusion model.

[0025] The fixing cover 24 is a cylindrical structure with openings at both ends. Its inner wall is adapted to and fastened to the outer surface of the simulated insulation layer 23, and is used to fix the cable structure simulation module into a whole.

[0026] An angle adjustment module is used to simulate different laying slopes of cables on the seabed, slopes, or vertical wells. It includes an angle-adjustable bracket 25. The angle-adjustable bracket 25 is fixedly connected to a fixed cover 24. By adjusting the tilt angle of the angle-adjustable bracket 25, the entire cable structure simulation module can be positioned horizontally, tilted, or vertically and locked. It is understood that the cable laying angle directly affects the direction and rate of gravity-driven migration of moisture within the insulation layer. In horizontal laying, moisture mainly diffuses radially inward; in tilted or vertical laying, moisture migrates directionally along the axial direction under the influence of gravity, significantly altering the moisture distribution. Existing immersion experiments are typically only conducted in horizontal conditions, making it impossible to study the impact of laying angle on moisture migration. This embodiment, by setting an angle adjustment module, can simulate various laying conditions from horizontal to vertical, enabling experimental research to cover moisture behavior in different laying scenarios such as submarine cable landing sections, seabed slope sections, and platform vertical lifting sections.

[0027] The hydraulic pressure simulation module is used to simulate the pressure state of the internal oil channels of a cable. It includes an insulating oil tank 28, an oil pump 27, and an oil replenishment pipe 26. The insulating oil tank 28 stores insulating oil, specifically dried DDB oil. One end of the oil replenishment pipe 26 is connected to the lower end of the simulated oil channel 21, and the other end is connected to the insulating oil tank 28 via the oil pump 27. Turning on the oil pump 27 provides a stable positive pressure to the simulated oil channel 21, simulating the oil replenishment state during cable operation. It is understood that the internal oil channels of an oil-filled cable terminal in actual operation are under positive pressure replenishment, and the magnitude of the internal oil pressure directly affects the driving force balance of external moisture intrusion. When the internal oil pressure is higher than the external water pressure, moisture intrusion can be effectively suppressed; when the internal oil pressure drops due to a fault, the rate of moisture intrusion will significantly accelerate. Existing experimental devices typically do not have hydraulic pressure simulation functions, making it impossible to study the mechanism by which hydraulic pressure inhibits or accelerates moisture intrusion. This embodiment uses a hydraulic simulation module to establish and maintain a set positive pressure in the simulated oil passage 21, which can realistically simulate the hydraulic pressure state under normal operation, load fluctuation or fault conditions of the cable, and provide experimental conditions for studying the coupling relationship between hydraulic pressure and moisture intrusion.

[0028] The temperature simulation module is used to simulate the operating temperature of a cable caused by load current. It includes a conductor heating unit and a temperature controller. The conductor heating unit is set on the simulated conductor 22, specifically an electric heating rod embedded inside the simulated conductor 22. The temperature controller is electrically connected to the conductor heating unit and precisely controls the heating power of the electric heating rod, thereby establishing a temperature gradient from the inside to the outside of the simulated conductor 22, realistically simulating the Joule heating and operating temperature of the cable caused by load current. It is understood that the cable operating temperature is one of the key driving forces for the diffusion and migration of moisture within the insulation layer. At the operating temperature, a temperature gradient forms inside the insulation layer from the inside to the outside. Moisture migrates from the high-temperature zone to the low-temperature zone driven by this temperature gradient, and temperature also affects the dynamic balance of moisture between oil and paper. Existing experimental setups typically do not consider the influence of temperature factors or can only provide simple uniform heating, failing to simulate the temperature gradient existing inside and outside the actual cable insulation layer. This implementation, through the temperature simulation module, achieves accurate simulation of the cable's operating thermal field, solving the problem that existing experiments cannot study moisture migration behavior under real temperature gradient conditions.

[0029] The top or side wall of the fixed cover 24 is also provided with a pressure relief valve 29, which is connected to the upper space of the simulated oil passage 21 and is used to release excess oil-water mixture during the experiment to maintain stable system pressure.

[0030] In summary, this invention, by organically combining a rain-spraying device with a terminal simulation platform integrating angle adjustment, oil pressure simulation, and temperature simulation functions, achieves for the first time the synchronous coupled simulation of multiple factors such as rainfall intensity and water quality, cable laying angle, internal oil pressure, and operating temperature, highly replicating complex on-site moisture-affected conditions. This platform can simulate the moisture-affected process under various conditions, including normal cable operation, load fluctuations, and oil leakage due to faults. It provides a reliable data foundation for studying the true diffusion behavior of moisture in oil-impregnated paper insulation and establishing accurate moisture-affected assessment models, effectively improving the efficiency of research on the operational safety of oil-filled cables.

[0031] Based on the above implementation method, multiple nozzles 15 are provided to form a nozzle array. The nozzle array is arranged in a matrix in a two-dimensional plane, and the spray angle of each nozzle 15 can be adjusted independently. The overall coverage area of ​​the nozzle array is larger than the surface area of ​​the cable structure simulation module. Based on the above implementation method, as a preferred example, water flow can be evenly distributed to each nozzle 15 through a distribution pipe to ensure that the outlet flow rate of each nozzle 15 is basically consistent, thereby forming a uniform rain curtain. It is understood that the actual effect of rainfall or wave splashing on the cable terminal is all-round spraying from all directions. The existence of local dead corners will lead to uneven moisture absorption and affect the consistency of experimental data. This implementation method, by setting a two-dimensional nozzle array and making its coverage area larger than the surface area of ​​the simulated terminal, combined with the independently adjustable spray angle of each nozzle, can achieve uniform spraying without dead corners on the surface of the terminal model, solving the problem that a single nozzle or simple spraying device cannot simulate all-round and uniform moisture absorption, and ensuring the realism and repeatability of the moisture environment simulation.

[0032] like Figure 2As shown, the angle-adjustable bracket 25 includes a base 251, a gear transmission mechanism 252, and a worm gear transmission mechanism 253. The base 251 is fixed to the ground or experimental platform, providing stable support for the entire bracket. The gear transmission mechanism 252 consists of a driving gear and a driven gear. Its input end receives external drive, such as a handwheel or motor, and transmits the driving action through gear meshing. Its output end is connected to the input end of the worm gear transmission mechanism 253. The output end of the worm gear transmission mechanism 253 is connected to the fixed cover 24, enabling it to drive the cable structure simulation module to rotate around a horizontal axis to change its tilt angle. The worm gear transmission mechanism 253 has a reverse self-locking characteristic, so that the angle-adjustable bracket 25 is automatically locked after being adjusted to any preset angle, preventing angle changes due to gravity or vibration without the need for additional braking or locking devices. Understandably, during long-term moisture experiments, the experimental period may last for hundreds of hours. If the angle cannot be stably locked, it may drift due to environmental vibrations or the weight of the cable model itself, affecting the accuracy and repeatability of the experimental data. This implementation utilizes the reverse self-locking characteristic of the worm gear transmission mechanism to achieve automatic locking after angle adjustment. It can accurately simulate different laying slopes of the cable on the seabed, slopes, or vertical wells, ensuring that the laying angle parameters remain constant throughout the entire experimental period.

[0033] The hydraulic simulation module also includes a pressure closed-loop control system, which comprises a pressure sensor, an electronically controlled regulating valve, and a controller. The pressure sensor is installed on the replenishment pipeline 26, near the inlet of the simulated oil passage 21, to collect real-time hydraulic pressure data within the simulated oil passage 21. The electronically controlled regulating valve is a servo valve, connected in series on the replenishment pipeline 26, located between the oil pump 27 and the simulated oil passage 21, and is used to linearly adjust the flow area according to the control signal to control the replenishment flow rate. The controller is an embedded microprocessor; its signal input is connected to the pressure sensor, and its control output is connected to both the electronically controlled regulating valve and the oil pump 27. The controller has a pre-stored pressure control program configured to: receive the real-time hydraulic pressure signal from the pressure sensor, compare it with the user-defined target pressure curve, calculate the control quantity using a PID algorithm, and output the corresponding control signal to the electronically controlled regulating valve to dynamically adjust the replenishment action. Understandably, in actual cable operation, the oil pressure in the oil passage is not constant but fluctuates due to load changes causing thermal expansion and contraction, the operation of the oil replenishment system, and even drops sharply in the event of seal failure. Existing experimental devices can typically only provide constant pressure through an oil pump, and cannot simulate the impact of these dynamic oil pressure changes on the moisture intrusion process. This embodiment uses a pressure closed-loop control system to ensure that the oil pressure in the simulated oil passage 21 accurately follows and stabilizes on a preset target pressure curve. It can simulate the constant oil pressure during normal cable operation, oil pressure fluctuations caused by load changes, or the oil pressure drop process during fault leakage, providing a technical means for studying moisture intrusion behavior under dynamic oil pressure conditions.

[0034] In one embodiment, a pressure relief valve 29 is provided on the top or side wall of the fixed cover 24. This valve 29 communicates with the upper space of the simulated oil passage 21 and is used to release excess oil-water mixture during the experiment to maintain stable system pressure. The platform also includes an oil-water separation and circulation system 3, such as... Figure 3As shown, the oil-water separation and circulation system 3 includes a liquid collection module 31, an oil-water separation module 32, a water circulation module 33, and an oil recovery module 34. The inlet of the liquid collection module 31 is connected to a pressure relief valve 29 via a pipe to collect all overflow and seepage of the oil-water mixture from the experiment. The inlet of the oil-water separation module 32 is connected to the outlet of the liquid collection module 31 to separate the insulating oil and water in the mixture. The inlet of the water circulation module 33 is connected to the water phase outlet of the oil-water separation module 32, and the outlet of the water circulation module 33 is connected to the water tank 11 of the rain shower device 1 to return the separated water to the rain shower device for recycling. The inlet of the oil recovery module 34 is connected to the oil phase outlet of the oil-water separation module 32 to recover or purify the separated insulating oil. It is understandable that long-term dampness during experiments will generate a large amount of oil-water mixture. Direct discharge not only pollutes the environment but also wastes insulating oil and water. Especially for experiments using special insulating oils such as DDB oil, continuous replacement of the oil will lead to high experimental costs. This embodiment integrates an oil-water separation and circulation system, which reuses the separated water in the rain shower device to achieve water resource recycling. The separated insulating oil is recovered or purified and sent back to the insulating oil tank for reuse, which greatly reduces experimental consumables and waste liquid discharge, forming an environmentally friendly and economical closed-loop experimental process and significantly reducing the experimental cost of long-term moisture aging research.

[0035] The oil-water separation module 32 is a gravity settling separator, internally divided from top to bottom by a first and second partition into a filtration zone 323, a separation zone 325, and an outlet zone 327. The inlet of the filtration zone 323 is connected to the outlet of the collection module 31 via a switching valve 321. A filter plate 322 can be installed within the filtration zone 323 to remove large particulate impurities from the mixture. A drain port 324 is located on the right side of the first partition, through which the filtration zone 323 connects to the separation zone 325. Three outlet pipes 326 are located at the bottom of the second partition, each equipped with a valve. The separation zone 325 connects to the outlet zone 327 via the outlet pipes 326. An oil outlet 329 is provided on the left side wall of the separation zone 325, serving as the oil phase outlet of the oil-water separation module 32. A water outlet 328 is provided on the right side wall of the liquid outlet zone 327, serving as the water phase outlet of the oil-water separation module 32. It is understood that insulating oil has a lower density than water. Utilizing this basic physical property, a gravity settling structure can achieve efficient and continuous oil-water separation. Furthermore, this structure has no moving parts, ensuring reliable operation and low maintenance costs. During oil-water separation, the oil-water mixture flows into the filtration zone 323 through the switching valve 321. After preliminary filtration to remove large particulate impurities, it enters the separation zone 325 through the liquid outlet 324. Within the separation zone 325, it settles, and gravity separation is achieved using the density difference between oil and water. The lighter insulating oil floats and is discharged from the left oil outlet 329, while the heavier water sinks. After opening the valve on the liquid outlet pipe 326, the water is discharged through the liquid outlet zone 327 and then from the right water outlet 328. Each outlet pipe 326 is set at a different height position. The corresponding outlet pipe 326 can be opened according to the actual position of the oil-water interface to ensure that water is discharged instead of oil, thereby improving the separation efficiency.

[0036] In one embodiment, the water circulation module 33 includes a water storage tank, a filter, and a delivery pump. The inlet of the water storage tank serves as the inlet of the water circulation module 33, and the outlet of the water storage tank is connected to the water tank 11 of the rain shower device 1 via the delivery pump. The filter can be installed inside the water storage tank or on the pipeline between the inlet and outlet of the water storage tank. Specifically, it can be an activated carbon filter or a multi-layer filter cartridge, used for deep purification of the recycled water, further removing any residual oil and ions that may be present, ensuring that the recycled water quality meets experimental requirements. Furthermore, the oil-water separation and circulation system 3 also includes a water quality monitoring unit, which is used to monitor the conductivity, pH value, or oil content of the recycled water online. The inlet of the water circulation module 33 is connected to the external water supply pipeline 36 via a switching valve 35, and the water quality monitoring unit controls the opening and closing of the switching valve 35 based on the monitoring results. In some cases, when the water quality monitoring unit detects that the conductivity, pH value, or oil content of the recycled water is within the preset normal range, the switching valve 35 remains closed, and the system continues to circulate the recycled water. In other cases, when the water quality monitoring unit detects that the purity of the recycled water does not meet the experimental requirements, the switching valve 35 is opened, and the system automatically switches to the external water supply pipeline 36 to supply fresh deionized water to ensure that the water quality of the spray water is not affected by cumulative pollution and to ensure the consistency of experimental conditions throughout the entire experimental cycle.

[0037] The oil recovery module 34 includes an oil storage tank and an oil filter. The inlet of the oil storage tank serves as the inlet of the oil recovery module 34. The oil filter is connected to the pipeline between the inlet and outlet of the oil storage tank. The outlet of the oil storage tank is connected to the insulating oil tank 28 of the terminal simulation platform 2 via a pipeline. It is understood that the insulating oil separated from the oil-water separation module 32 may still contain trace amounts of moisture, gas, and solid impurities. If directly reused in experiments, these impurities will affect the electrical and physicochemical properties of the insulating oil, thus affecting the accuracy of the moisture test results. This embodiment uses an oil filter, specifically a vacuum oil filter, to dehydrate, degas, and filter solid impurities from the recovered insulating oil, fully restoring its performance indicators. The purified insulating oil is transported back to the insulating oil tank 28 via pipeline for reuse. This ensures that the quality of the oil used in experiments always meets requirements and achieves closed-loop recycling and reuse of the insulating oil, significantly reducing the consumption and replacement costs of the insulating oil during experiments.

[0038] The temperature simulation module also includes multiple temperature sensors. These sensors are positioned on the surface of the simulated conductor 22 and at key points inside the simulated insulation layer 23. Specifically, they can be multiple thermocouple temperature sensors embedded at different radial depths within the insulation layer 23. A temperature controller is connected to each temperature sensor to monitor and record the temperature field data within the insulation layer 23 in real time. Understandably, during cable operation, due to the Joule heat generated by the conductor's current and the relatively low external environment, a decreasing temperature gradient forms inside the insulation layer from the inside out. This gradient is one of the key driving forces for moisture migration within the insulation layer; moisture migrates from high-temperature areas to low-temperature areas under this temperature gradient. By arranging temperature sensors at different radial depths, the temperature distribution inside the insulation layer can be accurately obtained. This provides precise temperature boundary conditions for calculating the temperature gradient and studying its impact on the moisture diffusion rate and equilibrium distribution, allowing experimental data to more realistically reflect the moisture absorption behavior of actual cables under different load conditions.

[0039] In one embodiment, the simulated conductor 22 is a tubular structure with a central through-hole extending along its axial direction, forming a simulated oil channel 21. A conductor heating unit is integrated outside the simulated conductor 22 or embedded within its tubular wall, used to apply controllable electrical power to the conductor to simulate the Joule heat generated by the cable load current. It is understood that the conductor of an actual oil-filled cable has an oil channel at its center for the flow of insulating oil, which circulates within the channel. Simultaneously, the Joule heat generated by the conductor's current is transferred from the inside out, creating a temperature gradient within the insulation layer. This embodiment, through the tubular structure and embedded heating unit, simultaneously simulates both the oil channel and the heat source, making the cable structure simulation module as close as possible to a real cable in terms of structural form and thermal field distribution, providing accurate geometric and thermal boundary conditions for moisture experiments.

[0040] When the simulation platform provided by this invention is used, firstly, the adjustable bracket 25 is adjusted to the target angle according to the experimental requirements. Then, the oil pump 27 is started to establish and maintain the set oil pressure within the simulated oil channel 21. Next, the rain shower device 1 is started, and a moisture experiment is conducted on the terminal simulation platform according to a preset program. The oil-water mixture generated during the experiment is treated by the oil-water separation and circulation system. The water and oil are purified and reused at the front end of the system, forming an environmentally friendly and economical closed-loop experimental process. During the experiment, moisture, under the influence of gravity, concentration gradient, and other factors, simulates a real-world scenario of intruding into the terminal insulation. Simultaneously, the entire platform can operate continuously, providing the possibility for long-term moisture aging research.

[0041] To verify the platform's ability to simulate different moisture-affected conditions and to obtain quantitative data on moisture intrusion into the insulation layer, the following three sets of typical tests were designed. In the tests, the insulation layer of the terminal simulation station was made of DDB oil-impregnated insulating paper, the same as that used in actual 500kV oil-filled submarine cables, with an initial average moisture content of 0.5% (mass fraction). A micro-moisture meter and a resistive moisture sensor embedded in the insulation layer were used to monitor moisture changes.

[0042] Experiment 1: Steady-state long-term immersion condition Simulated scenario: The cable terminal is subjected to continuous moderate rain under constant slope and operating temperature.

[0043] Control logic: Based on the "steady-state long-term immersion" mode.

[0044] The laying angle is 30°, the conductor temperature is 70℃, the oil pressure is 0.3MPa, the spray flow rate is 2.0L / min, which is equivalent to a rainfall intensity of about 15mm / h, and the spray solution is a 3.5% NaCl solution to simulate seawater.

[0045] Experimental process and results: The system was operated continuously for 500 hours. Moisture content was measured every 100 hours via radial sampling points in the insulation layer. The test results are recorded in Table 1 (Changes in radial moisture content of the insulation layer under steady-state long-term immersion conditions).

[0046] Table 1

[0047] Results analysis: The data show that under constant temperature and humidity conditions, moisture diffuses steadily from the outside to the inside. After 500 hours, the outer side is nearly saturated, and the moisture content on the inner side also increases significantly, demonstrating the risk of moisture penetrating the insulation layer due to long-term immersion.

[0048] Experiment 2: Alternating thermo-mechanical load condition Simulation scenario: Simulates the periodic fluctuations in cable load and oil pressure caused by diurnal temperature differences or tidal changes.

[0049] Control logic: Based on the "alternating heat-mechanical load" mode, with a cycle of 12 hours.

[0050] The laying angle is 45°, the conductor temperature (stage A) is 90℃, the conductor temperature (stage B) is 40℃, the oil pressure (stage A) is 0.4MPa, the oil pressure (stage B) is 0.15MPa, and the spraying procedure is: spraying for 2 hours in each cycle (starting from stage A) and stopping for 4 hours; the spraying flow rate is 3.0L / min, and the rainfall intensity is about 22mm / h.

[0051] Experimental process and results: The test was run for 20 cycles (240 hours in total). The change in moisture content at the outermost point of the insulation layer was monitored over the cycle and compared with steady-state conditions. The test results are recorded in Table 2 (comparison of moisture content on the outer side of the insulation layer under alternating load and steady-state conditions).

[0052] Table 2

[0053] Results analysis: Under the same cumulative immersion time, the water intrusion rate under alternating load conditions was significantly higher than that under steady-state conditions. This indicates that the periodic changes in temperature and pressure produce a "pumping effect," accelerating the migration of moisture deeper into the insulation layer, revealing that dynamic operating environments are more harmful than static environments.

[0054] Test 3: Sudden Seal Failure Failure Condition Simulated scenario: The terminal seal suddenly fails, internal oil pressure is lost, and the external environment is hit by a strong water flow.

[0055] Control logic: Based on the "sudden seal failure" mode.

[0056] Initial normal operating conditions: laying angle 0°, conductor temperature (stage A) 60℃, oil pressure (stage A) 0.3MPa, spray flow rate 1.0L / min, 100 hours of operation. After the fault is triggered: the oil pressure drops to atmospheric pressure (0MPa) within 10 minutes, and the spray flow rate increases to 10.0L / min (simulating strong water flow).

[0057] Experimental process and results: Record the rapid changes in moisture content on the outer side of the insulation layer and the changes in conductivity of the outlet water of the oil-water separation system before and after the fault is triggered. The test results are recorded in Table 3 (accelerated moisture intrusion under fault conditions).

[0058] Table 3

[0059] Results Analysis: After the failure occurred, the rate of moisture intrusion increased dramatically, and the insulation layer reached saturation within 2 hours. Simultaneously, the conductivity of the separated water rapidly increased and stabilized, indicating that a large number of ions (from simulated seawater) rapidly intruded with the moisture. This demonstrates that after seal failure, moisture damage can cause serious consequences in a very short time.

[0060] Any adaptive changes made according to actual needs are within the scope of protection of this invention.

[0061] It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0062] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. An oil-filled cable termination moisture exposure simulation platform, characterized by, include: A rain shower device includes a water tank, a water pump, a liquid flow meter, and a sprinkler head; the water tank is connected to the inlet of the liquid flow meter via the water pump, and the outlet of the liquid flow meter is connected to the sprinkler head; and... The terminal simulation platform includes a cable structure simulation module, a fixing cover, an angle adjustment module, a hydraulic pressure simulation module, and a temperature simulation module. The cable structure simulation module comprises a simulated conductor and a simulated insulation layer. The simulated conductor has a central through-hole for forming a simulated oil channel. The simulated insulation layer comprises multiple layers of oil-impregnated insulating paper tape, each layer of which is wrapped around the outer surface of the simulated conductor. The layers of oil-impregnated insulating paper tape are bonded together, with gaps between adjacent layers within the same layer. The fixing cover is fitted over the simulated insulation layer and fixed to it. The angle adjustment module includes an angle-adjustable bracket, which is fixedly connected to the fixing cover and used to adjust and lock the laying angle of the cable structure simulation module. The hydraulic pressure simulation module includes an insulating oil tank, an oil pump, and a replenishing oil pipe. One end of the replenishing oil pipe is connected to the simulated oil channel, and the other end is connected to the insulating oil tank via the oil pump. The temperature simulation module includes a conductor heating unit and a temperature controller. The conductor heating unit is disposed on the simulated conductor, and the temperature controller is electrically connected to the conductor heating unit.

2. The oil-filled cable terminal moisture simulation platform according to claim 1, characterized in that, The nozzles are provided in multiples and form a nozzle array. The nozzle array is arranged in a two-dimensional plane. The spray angle of each nozzle is independently adjustable, and the overall coverage area of ​​the nozzle array is greater than the surface area of ​​the cable structure simulation module.

3. The oil-filled cable termination moisture simulation platform of claim 1, wherein, The angle-adjustable bracket includes a base, a gear transmission mechanism, and a worm gear transmission mechanism; the base is fixed to the ground or a test bench; the input end of the gear transmission mechanism is used to receive external drive, and its output end is connected to the input end of the worm gear transmission mechanism, the output end of the worm gear transmission mechanism is connected to the fixed cover; the worm gear transmission mechanism is capable of reverse self-locking, so that the angle-adjustable bracket is automatically locked after being adjusted to any preset angle.

4. The oil-filled cable termination moisture simulation platform of claim 1, wherein, The oil pressure simulation module also includes a pressure sensor, an electronically controlled regulating valve, and a controller; the pressure sensor is installed on the oil replenishment pipeline; the electronically controlled regulating valve is connected in series on the oil replenishment pipeline and located between the oil pump and the simulated oil passage; the controller is connected to the pressure sensor and the electronically controlled regulating valve respectively, and is used to control the opening degree of the electronically controlled regulating valve according to the preset target pressure curve and the real-time oil pressure collected by the pressure sensor through a PID algorithm.

5. The oil-filled cable termination moisture simulation platform of claim 1, wherein, The fixed cover is equipped with a pressure relief valve; the platform also includes an oil-water separation and circulation system, which includes a liquid collection module, an oil-water separation module, a water circulation module, and an oil recovery module. The inlet of the liquid collection module is connected to the pressure relief valve via a pipe; the inlet of the oil-water separation module is connected to the outlet of the liquid collection module; the inlet of the water circulation module is connected to the water phase outlet of the oil-water separation module, and the outlet of the water circulation module is connected to the water tank of the rain shower device; the inlet of the oil recovery module is connected to the oil phase outlet of the oil-water separation module.

6. The oil-filled cable termination moisture simulation platform of claim 5, wherein, The oil-water separation module is a gravity settling separator, internally divided into a filtration zone, a separation zone, and a liquid outlet zone by a first partition and a second partition. The inlet of the filtration zone is connected to the outlet of the liquid collection module via a switching valve. A liquid outlet is provided on the first partition, through which the filtration zone communicates with the separation zone. A liquid outlet pipe is provided on the second partition, with a valve on the pipe, through which the separation zone communicates with the liquid outlet zone. An oil outlet is provided on the side wall of the separation zone, serving as the oil phase outlet of the oil-water separation module. A water outlet is provided on the side wall of the liquid outlet zone, serving as the water phase outlet of the oil-water separation module.

7. The oil-filled cable termination moisture simulation platform of claim 5, wherein, The water circulation module includes a water storage tank, a filter, and a delivery pump; the oil-water separation and circulation system also includes a water quality monitoring unit, which is used to monitor the conductivity, pH value, or oil content of the recycled water online; the water inlet of the water circulation module is connected to an external water supply pipeline through a switching valve, and the water quality monitoring unit controls the opening and closing of the switching valve according to the monitoring results to switch to the external water supply pipeline.

8. The oil-filled cable termination moisture simulation platform of claim 5, wherein, The oil recovery module includes an oil storage tank and an oil filter; the inlet of the oil storage tank serves as the inlet of the oil recovery module, the oil filter is connected to the pipeline between the inlet and outlet of the oil storage tank, and the outlet of the oil storage tank is connected to the insulating oil tank of the terminal simulation platform through a pipeline.

9. The oil-filled cable termination moisture simulation platform of claim 1, wherein, The temperature simulation module also includes multiple temperature sensors arranged on the surface of the simulated conductor and inside the simulated insulating layer; the temperature controller is connected to the temperature sensors.

10. The oil-filled cable termination moisture simulation platform of claim 1, wherein, The simulated conductor is a tubular structure, and the central through hole extends along the axial direction of the simulated conductor; the conductor heating unit is integrated on the outside of the simulated conductor or embedded in the tube wall of the simulated conductor.

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