Test device and analysis method for simulating oil flow mode of oil-filled submarine cable

Abstract

The invention relates to the technical field of high-voltage power cable detection and operation and maintenance, and discloses a test device and analysis method for simulating an oil flow mode of an oil-filled submarine cable, and the device comprises a hydraulic power system, a pipeline heating simulation system, a pipeline conveying and leakage simulation system, and a data collection control system. The pipeline conveying and leakage simulation system comprises the oil flow pipeline, a leakage point pipeline arranged on the oil flow pipeline and a flow control valve group, and the flow control valve group is configured to control the flowing direction and the leakage state of the insulating oil in the oil flow pipeline. According to the invention, a simulation means of combining physical scaling and heating temperature control is adopted, the inner diameter of a test pipeline is set as a specific proportion of an actual submarine cable, and the temperature of insulating oil is accurately adjusted by using a heater so as to change the viscosity; and the flow resistance characteristic and the pressure conduction rule of the long-distance submarine cable at different load temperatures can be truly reproduced in a limited space of a laboratory.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high-voltage power cable detection and operation and maintenance, in particular to a test device for simulating oil flow mode of oil-filled submarine cable and an analysis method. BACKGROUND

[0002] The oil-filled submarine cable is operated in a complex underwater environment for a long time. The internal insulating oil not only bears the electrical insulation function, but also carries away heat through flow. Once the submarine cable is damaged by external force or the insulating oil leaks due to aging, it will not only cause the insulating performance to decline and trigger electrical faults, but also pollute the marine ecological environment. Therefore, it is of great significance to study the oil flow dynamics of the submarine cable in the leakage state and develop a high-precision leakage point positioning method for the operation and repair of the submarine cable.

[0003] In order to study the flow and pressure conduction law of insulating oil in long-distance submarine cable, it is usually necessary to establish a simulation test platform in the laboratory. However, the actual submarine cable line length usually reaches several tens of kilometers, and it is difficult to build a full-size physical model in a limited laboratory space in terms of cost and space. The existing small-scale simulation device often directly uses a short pipe instead of a long pipe, ignoring the along-the-way resistance accumulation effect of the fluid in long-distance transportation and the obvious influence of temperature on the viscosity of insulating oil, resulting in a large deviation between the fluid mechanics characteristics of the test data and the actual working conditions on site, and it is difficult to truly reflect the pressure gradient distribution of the submarine cable in operation.

[0004] The existing simulation test device has limitations in structural flexibility. Most of them use fixed position leakage point design, which cannot conveniently adjust the position ratio of the leakage point relative to the two ends of the submarine cable, and it is also difficult to flexibly switch between different fault hydraulic conditions such as submarine cable fracture (double-end oil injection) and small leakage (single-end transportation). This structural limitation makes it difficult to systematically reproduce and algorithmically verify multiple damage scenarios on one platform.

[0005] In terms of leakage positioning algorithm, the traditional positioning method based on fluid mechanics usually relies on the absolute pressure value and flow value collected by the sensor at a time. For the small leakage condition, the pressure drop change is small, which is easily submerged by the zero point drift of the sensor, electromagnetic interference and background noise of the fluid system. The existing single-state measurement method lacks effective error elimination mechanism, resulting in low signal-to-noise ratio when processing small leakage signals, and the positioning calculation result is prone to large error, which cannot meet the demand for accurate positioning of early small insulating defects.

[0006] Therefore, the present application proposes a test device for simulating oil flow mode of oil-filled submarine cable and an analysis method to solve the deficiencies of the prior art. SUMMARY

[0007] In view of the deficiencies of the prior art, the application provides a test device and an analysis method for simulating oil flow patterns of oil-filled submarine cables, which solve the problems that the temperature variation hydrodynamic characteristics of long-distance submarine cables are difficult to be truly reproduced under existing laboratory conditions, the test device has poor flexibility in simulating multiple leakage conditions, and the traditional single-state measurement method has low positioning accuracy for small leaks.

[0008] To achieve the above object, the application provides a test device for simulating oil flow patterns of oil-filled submarine cables, which comprises a hydraulic power system, a pipeline heating simulation system, a pipeline transportation and leakage simulation system, and a data acquisition and control system.

[0009] The hydraulic power system comprises a first hydraulic pump, a first motor, a first oil tank, a second hydraulic pump, a second motor, and a second oil tank.

[0010] The pipeline heating simulation system comprises a heater wrapped around the outer wall of the oil flow pipeline.

[0011] The data acquisition and control system comprises a computer and a controller, and the computer is in communication connection with the controller.

[0012] Preferably, the data acquisition and control system further comprises a first pressure sensor, a second pressure sensor, a third pressure sensor, a first flow sensor, a second flow sensor, a third flow sensor, a fourth flow sensor, and a temperature sensor, which are all in electrical connection with the controller.

[0013] The first pressure sensor and the first flow sensor are arranged at the inlet end of the oil flow pipeline.

[0014] The third pressure sensor and the second flow sensor are arranged at the outlet end of the oil flow pipeline.

[0015] The second pressure sensor, the third flow sensor, and the fourth flow sensor are arranged near the leakage point in the middle part of the pipeline, which are used for state monitoring of the whole pipeline section in cooperation with the above-mentioned port sensors.

[0016] Preferably, the leakage point pipeline is connected to the middle part of the oil flow pipeline through a tee valve.

[0017] The leakage point pipeline comprises a leakage control valve and a replaceable simulated leakage part.

[0018] The simulated leak device is configured as a needle valve to simulate different degrees of pipe damage and gaps;

[0019] The oil flow pipeline consists of multiple standard pipe sections with detachable flange connections.

[0020] Preferably, the flow control valve assembly includes:

[0021] The first and fourth valves, located at both ends of the oil flow pipeline, are used to control the entry and exit of insulating oil.

[0022] A second valve is installed on the oil flow pipeline and located downstream of the connection point of the leaking pipeline, for connecting and blocking the flow path of the oil flow pipeline;

[0023] The third valve, installed on the simulated leakage branch, is used to control the occurrence and shut off of the leakage.

[0024] Preferably, it also includes a waste oil treatment system;

[0025] The waste oil treatment system includes a waste oil collection tank and a vacuum pump. The inlet of the waste oil collection tank is connected to the outlet of the leak point pipeline, and the vacuum pump is connected to the air port of the waste oil collection tank for negative pressure suction treatment of the oil flow pipeline after the test.

[0026] A second aspect of the present invention provides an analysis method for simulating oil flow patterns in oil-filled submarine cables, comprising the following steps:

[0027] S1. Based on the parameters of the submarine cable to be simulated, set the heating temperature of the heater and open the leak point pipe;

[0028] S2. Control the hydraulic power system and the flow control valve group to make the device operate in a bidirectional oil flow leakage condition or a unidirectional oil flow leakage condition. When performing high-precision positioning analysis, under the unidirectional oil flow leakage condition, change the system oil injection pressure to perform at least two independent measurements and obtain the first set of measurement data and the second set of measurement data respectively.

[0029] S3. The data acquisition and control system acquires the first pressure value, the second pressure value, the first flow rate value, the second flow rate value, and the temperature value at both ends of the oil flow pipeline under stable conditions.

[0030] S4. Based on the collected data, calculate the location of the leak point in the submarine cable using fluid dynamics calculation logic;

[0031] S5. After the test, start the waste oil treatment system and use the vacuum pump in conjunction with the waste oil collection box to recycle the insulating oil in the pipeline.

[0032] Preferably, the specific control logic for running in the bidirectional oil flow leakage condition in the S2 step is as follows:

[0033] opening the first valve and the fourth valve at both ends of the oil flow pipeline, opening the second valve at the middle of the oil flow pipeline, and opening the third valve on the leakage point pipeline;

[0034] simultaneously starting the first hydraulic pump and the second hydraulic pump, and controlling the first hydraulic pump and the second hydraulic pump to pressurize the oil flow pipeline, so that the pressure at both ends of the oil flow pipeline is greater than the pressure at the outlet end of the leakage point pipeline, so that the insulating oil flows out from both ends of the oil flow pipeline to the leakage point pipeline to simulate the bidirectional leakage state when the submarine cable is broken.

[0035] Preferably, the specific control logic for running in the unidirectional oil flow leakage condition in the S2 step is as follows:

[0036] opening the first valve and the fourth valve at both ends of the oil flow pipeline, opening the second valve at the middle of the oil flow pipeline, and opening the third valve on the leakage point pipeline;

[0037] controlling the first hydraulic pump to pressurize the first oil tank, and controlling the pressure of the first oil tank to be greater than the pressure of the second oil tank, so that part of the insulating oil flows out through the leakage point pipeline during the process of flowing from the first oil tank to the second oil tank through the oil flow pipeline.

[0038] Preferably, the S1 step further comprises a pipeline flow resistance coefficient calibration step before the S1 step:

[0039] closing the third valve on the leakage point pipeline, and controlling the device to run in a normal conveying condition;

[0040] measuring the pressure difference value between the inlet end and the outlet end of the oil flow pipeline at a set temperature, and measuring the flow value in the oil flow pipeline;

[0041] calculating the product of the flow value and the total length of the oil flow pipeline, and dividing the obtained product by the pressure difference value to obtain the pipeline flow resistance coefficient at the current temperature.

[0042] Preferably, the specific operation logic for calculating the leakage point position in the S4 step is as follows:

[0043] obtaining the first group of measurement data and the second group of measurement data measured in the S2 step;

[0044] calculating the product of the pipeline flow resistance coefficient and the total pressure difference sum, the total pressure difference sum being the sum of the pressure difference at both ends of the first group of data and the pressure difference at both ends of the second group of data;

[0045] adding the product to a length flow product, the length flow product being obtained from the multiplication of the total length of the oil flow pipeline and a flow variation value, the flow variation value being the outlet flow of the second set of measurement data minus the outlet flow of the first set of measurement data;

[0046] calculating a flow sum difference, the flow sum difference being obtained from the inlet flow of the first set of data plus the outlet flow of the second set of data, minus the outlet flow of the first set of data and the inlet flow of the second set of data;

[0047] dividing the molecular value by the flow sum difference to obtain the distance of the leakage point from the inlet end of the oil flow pipeline.

[0048] The present application provides a test device and an analysis method for simulating the oil flow mode of an oil-filled submarine cable.

[0049] 1. The present application adopts a simulation method combining physical scaling and temperature control, sets the inner diameter of the test pipeline to a specific proportion of the actual submarine cable, and uses a heater to accurately adjust the temperature of the insulating oil to change the viscosity, which can truly reproduce the flow resistance characteristics and pressure conduction rules of long-distance submarine cables under different load temperatures in a limited laboratory space. The present application solves the problem of building a full-size submarine cable of several kilometers long for fluid mechanics experiments in a land-based laboratory, and provides a low-cost, high-precision experimental platform for studying the complex oil flow mode of oil-filled submarine cables.

[0050] 2. The present application can flexibly build two typical leakage conditions of bidirectional confluence and unidirectional transportation through the cooperation of the flow control valve group and the double-end hydraulic drive system. By changing the physical position of the leakage point by replacing the standard pipe segment length on both sides of the three-way valve, and combining with the needle-type regulating valve to change the leakage aperture, the device can comprehensively cover various damage scenarios from small crack leakage to complete cable rupture. This enables the detection personnel to systematically study the oil flow dynamics characteristics under different leakage distances and different leakage degrees, and verify the effectiveness of the leakage positioning algorithm.

[0051] 3. The present application proposes a differential positioning analysis method based on variable pressure double measurement. In the unidirectional small leakage simulation, the method obtains two independent state data by changing the system operating pressure, and uses a difference calculation model to process the changes of pressure and flow. This algorithm uses the differential combination of numerator and denominator, effectively eliminates the systematic steady-state error caused by sensor zero drift, temperature fluctuation and fluid pulsation, improves the positioning calculation accuracy of small leakage points, and improves the reliability of submarine cable health state evaluation. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 The present application is a schematic diagram of a simulation test device;

[0053] Figure 2 Schematic diagram of simulation of operation of bidirectional leakage oil flow of the application;

[0054] Figure 3 Schematic diagram of simulation of operation of unidirectional leakage oil flow of the application;

[0055] Figure 4 Schematic diagram of simulation of operation of un-leakage oil flow of the application;

[0056] Figure 5 Schematic diagram of simulation of operation of un-leakage oil flow of the application;

[0057] 1, computer; 2, controller; 3, first hydraulic pump; 4, second hydraulic pump; 5, first electric motor; 6, second electric motor; 7, first oil tank; 8, second oil tank; 9, first valve; 10, second valve; 11, third valve; 12, fourth valve; 13, first pressure sensor; 14, second pressure sensor; 15, third pressure sensor; 16, first flow sensor; 17, second flow sensor; 18, third flow sensor; 19, fourth flow sensor; 20, leakage point pipeline; 21, temperature sensor; 22, heater; 23, waste oil collection tank; 24, vacuum pump; 25, oil flow pipeline. DETAILED DESCRIPTION

[0058] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the accompanying drawings of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0059] Please refer to the accompanying drawings of the application Figure 1 The embodiment discloses a test device for simulating oil flow mode of a filled submarine cable, comprising a hydraulic power system, a pipeline heating simulation system, a pipeline transportation and leakage simulation system, and a data acquisition and control system. The pipeline transportation and leakage simulation system comprises an oil flow pipeline 25, a leakage point pipeline 20 arranged on the oil flow pipeline 25, and a flow control valve group. The flow control valve group is configured to control the flow direction and leakage state of the insulating oil in the oil flow pipeline 25.

[0060] In one embodiment, the oil flow pipe 25 and the leakage pipe 20 are both made of high-pressure 304 stainless steel seamless pipe, and the pipes are connected by high-pressure flanges to withstand the high oil pressure generated during the test. Considering the actual size of the submarine cable (the length can reach tens of kilometers), this embodiment is based on the principle of fluid similarity to construct a scaled-down model. The leakage speed of the oil is related to the radius, length and viscosity of the pipe. Therefore, the inner diameter of the oil flow pipe 25 is set to be 0.1 times the inner diameter of the actual single-core oil-filled submarine cable oil pipe. According to the Hagen-Poiseuille law, the flow rate is proportional to the fourth power of the radius. In the case of controlling the test oil pressure difference to be about 10 times the field oil pressure difference, this physical scaling can achieve a length equivalence of about 1:1000 in fluid mechanics characteristics between the test pipe and the field submarine cable, so as to be able to simulate the oil flow dynamics of the long-distance submarine cable in the laboratory limited space.

[0061] The hydraulic power system includes a first hydraulic pump 3, a first motor 5, a first oil tank 7, a second hydraulic pump 4, a second motor 6 and a second oil tank 8. The input end of the first hydraulic pump 3 is connected to the first oil tank 7, and the output end of the first hydraulic pump 3 is connected to the inlet end of the oil flow pipe 25. The input end of the second hydraulic pump 4 is connected to the second oil tank 8, and the output end of the second hydraulic pump 4 is connected to the outlet end of the oil flow pipe 25.

[0062] In one embodiment, the first hydraulic pump 3 and the second hydraulic pump 4 are variable plunger pumps, which can provide stable output pressure, and the rated pressure range covers 0 to 10 MPa. The first motor 5 and the second motor 6 are variable frequency motors, which can accurately control the flow output of the hydraulic pump by adjusting the motor speed. The first oil tank 7 and the second oil tank 8 are both transparent or visualized stainless steel containers, which are provided with a liquid level meter on the side and an air filter on the top to prevent external impurities from entering the hydraulic system.

[0063] The pipe heating simulation system includes a heater 22 wrapped around the outer wall of the oil flow pipe 25.

[0064] The data acquisition and control system includes a computer 1 and a controller 2, and the computer 1 is in communication connection with the controller 2.

[0065] In one embodiment, the heater 22 is a flexible silicone rubber heating tape, which is spirally wound around the outer wall of the oil flow pipe 25, and the outer part of the heating tape is further wrapped with a thermal insulation cotton layer to reduce heat loss. The controller 2 is a PLC programmable logic controller, which is connected to the computer 1 through an industrial Ethernet interface. The computer 1 runs a host computer monitoring software, which can display the pressure curve and temperature value of each point of the pipe in real time, and send control instructions to the PLC to adjust the heating power and the speed of the pump.

[0066] The data acquisition control system further comprises a first pressure sensor 13, a second pressure sensor 14, a third pressure sensor 15, a first flow sensor 16, a second flow sensor 17, a third flow sensor 18, a fourth flow sensor 19 and a temperature sensor 21, all of which are electrically connected to the controller 2.

[0067] The first pressure sensor 13 and the first flow sensor 16 are arranged at the inlet end of the oil flow pipeline 25.

[0068] The third pressure sensor 15 and the second flow sensor 17 are arranged at the outlet end of the oil flow pipeline 25.

[0069] The second pressure sensor 14, the third flow sensor 18 and the fourth flow sensor 19 are arranged near the leakage point in the middle of the pipeline, for monitoring the state of the entire pipeline section in cooperation with the above-mentioned port sensors.

[0070] In one specific embodiment, the first pressure sensor 13, the second pressure sensor 14 and the third pressure sensor 15 are all selected to be diffusion silicon pressure transmitters, with a precision level not less than 0.5 level and a response time less than 10 milliseconds. The first flow sensor 16, the second flow sensor 17, the third flow sensor 18 and the fourth flow sensor 19 are all selected to be oval gear flowmeters or turbine flowmeters suitable for medium-high viscosity fluids, with straight pipe sections in front and behind the installation position reserved in accordance with the requirements of fluid mechanics. The temperature sensor 21 is selected to be a PT100 platinum resistance, with the probe directly inserted into the pipeline interior to contact the insulating oil, so as to obtain the true fluid temperature.

[0071] The leakage point pipeline 20 is connected to the middle of the oil flow pipeline 25 through a three-way valve;

[0072] The leakage point pipeline 20 comprises a leakage control valve and a replaceable simulated leakage piece;

[0073] The simulated leakage piece is configured as a needle type regulating valve, for simulating different degrees of pipeline damage gaps;

[0074] The oil flow pipeline 25 is composed of multiple standard pipe sections connected by detachable flanges.

[0075] In one specific embodiment, the standard pipe sections are pre-fabricated in multiple length specifications (for example, 1 meter, 2 meters, 5 meters). The test personnel assemble different numbers or lengths of standard pipe sections on the left and right sides of the three-way valve according to the test requirements, so as to physically reconstruct the position proportion of the leakage point (such as the leakage point being located at 10%, 30% or 50% of the entire length of the pipeline). The simulated leakage piece is selected to be a needle type valve with a fine scale dial, and the flow area of the valve port is changed by rotating the valve stem, so as to quantitatively simulate different degrees of damage conditions of the submarine cable, such as a small crack, a moderate damage or a complete rupture.

[0076] The flow control valve group comprises:

[0077] The first valve 9 and the fourth valve 12 arranged at both ends of the oil flow pipeline 25 are used to control the inflow and outflow of the insulating oil;

[0078] The second valve 10 arranged on the oil flow pipeline 25 and located downstream of the connection point of the leakage point pipeline 20 is used to connect and block the flow path of the oil flow pipeline 25;

[0079] The third valve 11 arranged on the leakage simulation branch is used to control the occurrence and cutoff of the leakage.

[0080] In a specific embodiment, the first valve 9, the second valve 10, the third valve 11 and the fourth valve 12 are all electric ball valves. The controller 2 outputs on-off signals to control the opening and closing of the above valves according to the preset test mode logic. For example, when the bidirectional oil flow leakage simulation is performed, the controller 2 controls the first valve 9, the fourth valve 12 and the third valve 11 to be opened, and the second valve 10 to be kept in an open state, so as to form a flow path structure converging from both ends to the middle and leaking.

[0081] Waste oil treatment system;

[0082] The waste oil treatment system comprises a waste oil collection tank 23 and a vacuum pump 24. The inlet of the waste oil collection tank 23 is connected with the outlet of the leakage point pipeline 20, and the vacuum pump 24 is connected with the gas port of the waste oil collection tank 23 and is used to perform negative pressure suction treatment on the oil flow pipeline 25 after the test.

[0083] In a specific embodiment, the waste oil collection tank 23 is a sealed metal tank. The vacuum pump 24 is a rotary vane vacuum pump 24. When the test is completed, the system is closed to the hydraulic pump and is opened to the waste oil treatment system. The vacuum pump 24 performs air suction on the waste oil collection tank 23 to form a negative pressure inside the waste oil collection tank 23. The negative pressure acts on the leakage point pipeline 20 and the oil flow pipeline 25 through the connecting pipeline to suck the insulating oil remaining in the pipelines into the waste oil collection tank 23, so as to realize the centralized recovery of the waste oil and avoid the pollution of the laboratory environment when the pipelines are disassembled.

[0084] Referring to the accompanying drawings Figure 5 In another aspect, the embodiment provides an analysis method of simulating the oil flow mode of the submarine cable based on the above test device. The method is based on the pressure conduction characteristics of the fluid in the closed pipeline and the law of conservation of mass to realize the physical simulation and numerical calculation of the leakage point position of the pipeline. The method comprises the following steps:

[0085] Step S1, initialization setting and leakage point opening

[0086] According to the rated voltage, the core section and the load current parameters of the oil-filled submarine cable to be simulated, the corresponding insulation oil working temperature range is determined; the target heating temperature of the heater 22 is set by the controller 2, so that the insulation oil in the oil flow pipeline 25 reaches the predetermined viscosity state; at the same time, the valve arranged on the leakage point pipeline 20 is opened, and the physical leakage channel connecting the oil flow pipeline 25 and the external environment is communicated.

[0087] Step S2, working condition establishment and measurement execution

[0088] The output power of the hydraulic power system and the on-off state of the flow control valve group are adjusted by the controller 2 to establish a bidirectional oil flow leakage working condition or a unidirectional oil flow leakage working condition; when the system operates in the unidirectional oil flow leakage working condition and executes the positioning analysis, the overall oil injection pressure of the system is changed by adjusting the output pressure of the first hydraulic pump 3, and independent measurements are performed at at least two different pressure levels to establish a first measurement state and a second measurement state respectively, so as to obtain the differential data set required to eliminate system errors.

[0089] Step S3, data acquisition

[0090] In each measurement state, the fluid flow in the pipeline is waited to reach a stable state; the pressure values detected by the first pressure sensor 13 and the third pressure sensor 15 arranged at the inlet end and the outlet end of the oil flow pipeline 25, the flow values detected by the first flow sensor 16 and the second flow sensor 17, and the temperature value detected by the temperature sensor 21 are synchronously read and recorded by the data acquisition control system.

[0091] Step S4, position solving

[0092] The controller 2 or the computer 1 calls the internal stored fluid mechanics operation logic to extract the pressure values and flow values collected in step S3; by establishing a fluid equation set about the leakage point position, the specific length value of the leakage point from the inlet end of the oil flow pipeline 25 is calculated.

[0093] Step S5, waste oil recovery and system reset

[0094] After the test and calculation are completed, the hydraulic power system is stopped; the waste oil treatment system is started, and the vacuum pump 24 is started to perform negative pressure suction on the waste oil collection tank 23 and the pipeline system, so that the residual insulation oil in the oil flow pipeline 25 and the leakage point pipeline 20 is recovered into the waste oil collection tank 23.

[0095] Reference to the accompanying Figure 4 In order for those skilled in the art to more clearly understand the specific operation details and operation principles in the above steps, the control logic and calculation method of each key step will be described in detail below.

[0096] Before conducting leakage location analysis of oil-filled submarine cables, in order to eliminate the influence of ambient temperature, batch differences in insulating oil, and pipe processing tolerances on the accuracy of fluid dynamics calculations, this embodiment first executes a system parameter setting and pipe flow resistance coefficient calibration procedure before entering the formal leakage simulation. This process specifically includes the following sub-steps:

[0097] Step S11: Establish the temperature and viscosity corresponding environment

[0098] At the start of the test, the target oil temperature required for the test was determined based on the actual operating load of the submarine cable to be simulated and the marine ambient temperature. Controller 2 sent a control command to heater 22, located on the outer wall of oil flow pipe 25, to initiate the heating operation. Due to the dynamic viscosity of the insulating oil (… The temperature decreases as the temperature rises. Temperature sensor 21 monitors the temperature of the fluid inside the pipe in real time and feeds it back to controller 2. Controller 2 uses feedback control logic to adjust the heating power so that the temperature of the insulating oil in the entire section of the oil flow pipe 25 is uniformly maintained at the preset value, so that the viscosity characteristics of the fluid in the pipe are consistent with the actual operating conditions of the submarine cable.

[0099] Step S12: Construct a closed DC calibration loop

[0100] Before officially starting the leak simulation, the system needs to obtain the pipeline flow resistance coefficient under the current temperature and oil conditions. Controller 2 controls the third valve 11, located on the leak point pipeline 20, to be fully closed, physically cutting off the leak branch; simultaneously, it controls the first valve 9 and the fourth valve 12 at both ends of the oil flow pipeline 25, as well as the second valve 10 located in the middle, to be fully open. The first hydraulic pump 3 in the hydraulic power system is started, injecting insulating oil from the first oil tank 7, allowing it to flow through the oil flow pipeline 25 to the second oil tank 8. At this point, the system forms a single series flow path, simulating a leak-free standard submarine cable transmission state.

[0101] Step S13: Calibration Status Confirmation and Data Acquisition

[0102] After the fluid flow in the pipeline reaches a stable state, controller 2 first compares the readings of the first flow sensor 16 at the inlet end of the oil flow pipeline 25 with those of the second flow sensor 17 at the outlet end. When the difference between the two flow values ​​is less than a preset threshold, it is determined that there is no leakage in the pipeline and the flow is stable. Subsequently, synchronous sampling is performed: the inlet pressure value is collected through the first pressure sensor 13. The outlet pressure value is collected by the third pressure sensor 15. The value collected by the first flow sensor 16 is used as the total pipe flow rate. The data is then transmitted to the storage unit of controller 2.

[0103] Step S14, pipeline flow resistance coefficient reverse calculation

[0104] The controller 2 uses the measured data to reverse calculate the pipeline flow resistance coefficient based on the laminar flow characteristics of the fluid in the closed circular pipe. In this embodiment, the comprehensive hindering effect of the fluid viscosity, the pipe inner diameter and the geometry on the flow is defined as the pipeline flow resistance coefficient .

[0105] The calculation logic is that the controller 2 calls the internal operation module to calculate the full pipe flow value , the product of the known total length of the oil flow pipeline 25 , the difference between the inlet pressure value and the outlet pressure value , and finally the product is divided by the pressure difference value to solve the pipeline flow resistance coefficient under the current working condition .

[0106] The corresponding calculation formula is expressed as:

[0107] ;

[0108] The value obtained in this step directly reflects the viscosity influence under the current actual oil temperature and the fourth power effect of the actual pipe inner diameter, The acquisition of the value replaces the dependence on the theoretical viscosity parameter and the theoretical pipe diameter , and eliminates the systematic error required for calculation in step S4.

[0109] Step S15, switch to the leakage standby state

[0110] After the calculation and storage of the flow resistance coefficient , the controller 2 controls the opening of the third valve 11 on the leakage point pipeline 20 to connect the oil flow pipeline 25 and the external environment. By adjusting the opening size of the third valve 11, the flow area of the leakage passage is changed, which is used to simulate different sizes of micro-cracks or damaged apertures that may occur in the actual operation of the oil-filled submarine cable. At this time, the device completes the initialization preparation and is in standby state, ready to enter the subsequent leakage condition simulation step.

[0111] After the system parameter initialization is completed by using step S1, step S2, i.e. the working condition establishment and measurement execution phase, is entered. In this step, the hydraulic power source and the pipeline valve matrix are accurately controlled to reproduce the two typical leakage forms of submarine cable double-end injection and single-end transmission at the physical level, and a variable pressure difference measurement mechanism is introduced for the small leakage scenario. This step specifically includes the following sub-steps:

[0112] Step S21, build a bidirectional oil flow leakage condition

[0113] This working condition is used to simulate the state that the oil-filled submarine cable has a large aperture damage or breakage, and the oil supply stations at both ends of the cable supplement the insulating oil to the fault point at the same time.

[0114] The controller 2 sends a command to start the hydraulic power system, and adjusts the opening degree of the first valve 9 at the inlet end and the fourth valve 12 at the outlet end of the oil flow pipeline 25. The system control logic is set so that the fluid pressures at both ends of the oil flow pipeline 25 are in a high pressure state, and are both greater than the sum of the pressure at the leakage point pipeline 20 and the ambient pressure. 、 ).

[0115] In this state, the insulating oil converges from both ends to the middle of the leakage point, and flows out through the third valve 11 that is opened. The data acquisition system monitors and records the inlet pressure , the outlet pressure , and the bidirectional flow velocity vector in the pipeline in real time. This is the bidirectional oil flow leakage defined in the specification, and its physical characteristics meet the confluence model in fluid dynamics.

[0116] Step S22, constructing a unidirectional oil flow leakage working condition

[0117] This working condition is used to simulate the state that the oil-filled submarine cable has a small leakage during normal transmission, and the main body of the insulating oil flows axially, and part of the fluid seeps out through the damage point.

[0118] The controller 2 adjusts the hydraulic power system so that the first oil tank 7 serves as the main pressure source, and the second oil tank 8 serves as the receiving end. By increasing the opening degree of the first valve 9 and appropriately closing or adjusting the throttling opening degree of the fourth valve 12, a linear pressure gradient that decreases from the inlet to the outlet is established inside the oil flow pipeline 25 (i.e. ).

[0119] At this time, the insulating oil is split when flowing through the connection of the leakage point pipeline 20: the main oil flow continues to flow to the outlet end, and part of the branch oil flow enters the leakage channel under the action of the static pressure difference.

[0120] Step S23, performing a variable-pressure double-time measurement strategy

[0121] In order to eliminate the influence of sensor zero drift and fluid pulsation on the positioning accuracy of small leakage in single measurement, the embodiment performs a pressure state switching and double-time data sampling strategy on the basis of the unidirectional oil flow working condition established in step S22. The specific operation is as follows:

[0122] First measurement sub-step: the controller 2 controls the first hydraulic pump 3 to output a first set pressure, and after the flow field in the pipeline is stabilized, the acquisition system synchronously records: a first inlet pressure , a first outlet pressure , and a first inlet flow and the first outlet flow rate .

[0123] Second measurement sub-step: while strictly maintaining the position of the leak point pipe 20, the opening of the third valve 11 and the fluid temperature, the controller 2 sends instructions to change the output power of the first hydraulic pump 3 or adjust the throttling degree of the fourth valve 12, so as to switch the overall system operating pressure to a second pressure level different from the first set pressure. After the flow field is stabilized again, the system synchronously records: the second inlet pressure , the second outlet pressure , the second inlet flow rate and the second outlet flow rate .

[0124] Through the above steps, the system obtains two independent data sets describing the same leak distance but different pressure boundary conditions. These two sets of data will be used as input parameters in the subsequent differential positioning model:

[0125] ;

[0126] wherein, is the total length of the pipe, is the pipe flow resistance coefficient obtained in step S1. The physical meaning of this measurement strategy is that the ratio of the flow rate change to the pressure change in the two measurements eliminates the system steady-state error which is difficult to measure directly, thereby supporting the subsequent step for high-precision solution of the leak distance .

[0127] Referring to the accompanying Figure 2 -attached Figure 3 , after establishing different simulation conditions in step S2, in order to ensure that the physical parameters input into the positioning model truly reflect the characteristics of the working conditions and eliminate the influence of the system transient response on the measurement accuracy, the system performs step S3, which includes the following sub-steps:

[0128] Step S31, flow field transient disturbance filtering

[0129] When the system adjusts the working condition due to the change of the hydraulic pump power or the adjustment of the valve opening, the fluid insulating oil in the pipe will produce non-steady-state pressure fluctuations. The controller 2 controls the data acquisition card to continuously read the original signals of the first pressure sensor 13, the third pressure sensor 15 and the corresponding flow rate sensors at a preset high-frequency sampling rate (for example, 10Hz-50Hz).

[0130] In order to eliminate the transient pressure oscillation and high-frequency mechanical noise caused by the valve action in the fluid pipeline, the controller 2 constructs a length of (for example, a first-in-first-out (FIFO) data buffer queue with a maximum capacity of 50. The system employs a moving average filter algorithm, in which each time a new sample point is read in by the sensor, the oldest data point in the queue is removed, and the arithmetic average of the current queue is calculated as the valid observation value at that time.

[0131] Step S32, executing steady state determination logic

[0132] The system executes a steady state self-check procedure based on the filtered data, the purpose of which is to ensure that the fluid flow has fully transitioned to a laminar state, thus satisfying the physical applicability prerequisite of the Hagen-Poiseuille law and its derivative formulas.

[0133] The determination logic is as follows: a continuous determination time window (e.g. 30 seconds) is set , and the controller 2 calculates the real-time variance or standard deviation of the inlet pressure , outlet pressure , and total pipe flow within the window in real time. Only when the standard deviation of the pressure data continuously remains less than the pressure stability threshold , and the standard deviation of the flow data continuously remains less than the flow stability threshold , does the controller 2 determine that the current working condition has reached a state of balance in thermodynamics and fluid mechanics.

[0134] Step S33, simultaneous acquisition and locking of physical quantities

[0135] Once the system determines that it has entered a steady state, the controller 2 immediately triggers a data acquisition instruction to ensure that the pressure and flow data at the same time are time-synchronized. The specific objects of acquisition include:

[0136] the inlet pressure value measured by the first pressure sensor 13 ;

[0137] the inlet flow value measured by the first flow sensor 16 ;

[0138] the outlet pressure value measured by the third pressure sensor 15 ;

[0139] the outlet flow value measured by the second flow sensor 17 .

[0140] The acquisition points of the above-mentioned physical quantities are explicitly corresponding to the physical inlet and outlet boundaries of the oil flow pipe 25, ensuring the accuracy of the boundary conditions for subsequent pressure drop calculations.

[0141] Step S34, data validity verification and storage

[0142] In the two-way oil flow leakage working condition, the system directly stores the above set of steady-state data .

[0143] In the variable pressure double measurement of the one-way oil flow leakage working condition, the system needs to perform the steady-state acquisition process of S31 to S33 once in the first measurement state and the second measurement state respectively, and obtain the first set of data and the second set of data .

[0144] After the acquisition is completed, the controller 2 automatically calculates the absolute value of the inlet pressure difference between the two measurements . If the difference is less than the preset minimum effective difference threshold, the system will determine that the measurement is invalid and issue an alarm. This is because in the subsequent differential calculation model, the pressure difference will appear as the denominator or a key divisor factor. If the difference is too small, it will result in a very low signal-to-noise ratio, thereby causing the calculation result to diverge or produce a large error.

[0145] All the data verified are associated and stored in the database of the controller 2 as an input parameter set for the leakage point positioning calculation of step S4, in combination with the corresponding working condition mode identifier, the flow resistance coefficient calibrated in step S1 and the oil temperature parameter.

[0146] After obtaining the high-credibility steady-state flow field data by using step S3, step S4 is entered. In this step, the acquired pressure and flow data are associated with the inherent flow resistance characteristics of the pipeline, and the specific position of the submarine cable leakage point is solved by establishing a set of fluid dynamics equations.

[0147] Step S41, loading of calculation model parameters and physical definition

[0148] The system first retrieves the pipeline physical parameters pre-stored in the database, including the total length of the pipeline and the pipeline flow resistance coefficient obtained in step S1 through the calibration experiment .

[0149] The fluid mechanics model used in this embodiment is based on the Hagen-Poiseuille law. According to the law, in the laminar flow state of a circular pipe, the volume flow satisfies the following relationship with the fluid properties and the geometric dimensions of the pipeline:

[0150] ;

[0151] wherein, is the radius of the pipeline; is the dynamic viscosity of the insulating oil; is the pressure difference.

[0152] In order to facilitate engineering calculation and real-time solving, the present application associates all geometric dimensions ( ) and fluid properties ( ) related constant term is merged into flow resistance coefficient , whose physical definition is:

[0153] ;

[0154] wherein, is pipe diameter.

[0155] The coefficient has been calibrated in step S14 by measured flow rate and pressure drop ratio. The system loads the value, which is equivalent to loading the real viscosity pipe diameter comprehensive characteristics at the current temperature, thereby supporting subsequent high-precision calculation.

[0156] Step S42, positioning calculation under bidirectional confluence working condition

[0157] When the system is in bidirectional high-pressure injection mode (i.e. simulating fracture or large aperture leakage), the fluid converges to the leakage point from both ends of the submarine cable at the same time. At this time, the leakage velocity is formed by superimposing the flow rates from both ends. The system establishes a balance equation based on the uniqueness of the leakage point pressure.

[0158] Let the distance from the leakage point to the inlet end be .

[0159] The inlet side pipe section satisfies the pressure drop equation: ;

[0160] The outlet side pipe section satisfies the pressure drop equation: .

[0161] It should be noted that in this working condition, the in the formula is defined as the flow rate flowing into the pipe from the outlet end (i.e. taking the absolute value of the flow rate sensor).

[0162] Eliminate the leakage point pressure , get the leakage distance calculation formula under bidirectional working condition:

[0163] ;

[0164] The formula shows that in the bidirectional oil injection working condition, the leakage distance mainly depends on the distribution ratio of the flow rates injected from both ends and the pressure difference established at both ends.

[0165] Step S43, positioning calculation under unidirectional differential working condition

[0166] When the system is in one-way conveying mode (i.e. simulating a small leakage), the measurement data in a single state often contains sensor zero drift and fluid pulsation noise. To solve this problem, the system uses a variable pressure differential positioning model.

[0167] The model uses two sets of independent state data (state one: ; state two: ) obtained in step S34 to construct a differential equation set.

[0168] When the oil injection pressure of the system is changed, the flow field distribution in the pipeline changes equivalently. By synthesizing the results of two tests, systematic errors can be eliminated.

[0169] The derivation process is as follows:

[0170] Calculate the total pressure difference (ΔP) and (ΔP'): combine the pressure differences at both ends of the two sets of measurement data:

[0171] ;

[0172] Calculate the length flow product (Q*L) : introduce the total length of the pipeline Weight the flow variation:

[0173] ;

[0174] Calculate the total flow difference (Q) : build the denominator item to reflect the overall variation of the system flow:

[0175] ;

[0176] Final solution: substitute the flow resistance coefficient , to get the positioning formula after eliminating errors:

[0177] ;

[0178] This algorithm effectively eliminates common-mode interference in absolute pressure measurement by differential combination of numerator and denominator, achieving high sensitivity detection based on fluid dynamics.

[0179] Step S44, result verification and output

[0180] After obtaining the calculation value , the system performs physical constraint verification to determine whether it is within the interval .

[0181] If the verification is passed, it means that the calculation result conforms to the physical law, and the system outputs the leakage distance information through the human-computer interaction interface. The specific form is that the leakage point is located at a distance of​​​ meters.

[0182] If the check fails (for example or ), it indicates that the measurement data is affected by transient interference or sensor failure, the system will automatically prompt the positioning calculation divergence, and suggest the operator to re-execute step S2 for data sampling.

[0183] After completing the positioning calculation of step S4, the controller 2 enters step S5 according to the preset program. This step realizes environmental protection recycling by building the pressure difference between the inside and outside of the pipeline, and pressing the insulation oil leaked into the collection device into the waste oil tank.

[0184] Step S51, hydraulic power system unloading and isolation

[0185] The controller 2 sends a shutdown signal to the first hydraulic pump 3, so that the main oil flow circulation loop pressure is zero. Then, the controller 2 sends a closing instruction to the first valve 9 and the fourth valve 12.

[0186] After the first valve 9 and the fourth valve 12 are closed, the test pipe section where the leakage point is located is completely disconnected from the first oil tank 7, the second oil tank 8 and the hydraulic power source in the fluid passage. This isolation operation prevents the clean insulation oil in the main oil tank from being mistakenly sucked into the waste oil recycling pipeline during the subsequent establishment of negative pressure, ensuring the singularity of the recycling object.

[0187] Step S52, establishing a gas phase negative pressure gradient

[0188] The controller 2 starts the vacuum pump 24 connected to the gas phase space at the top of the waste oil collection tank 23. The vacuum pump 24 continuously pumps out the gas inside the waste oil collection tank 23, so that the gas pressure gradually decreases.

[0189] The controller 2 monitors the tank pressure in real time through the gas pressure sensor, and when it detects that the preset vacuum working point (for example, lower than -0.05 MPa) is reached, the controller 2 opens the fifth valve (i.e. the recycling control valve) set between the oil outlet at the bottom of the oil collection tray and the oil inlet of the waste oil collection tank 23.

[0190] At this time, the oil collection tray is in an atmospheric environment, while the waste oil collection tank 23 is in a negative pressure environment. Under the driving of the pressure difference , the waste insulation oil accumulated in the oil collection tray is automatically pressed into the recycling pipeline and flows to the waste oil collection tank 23.

[0191] Step S53, physical impurity removal

[0192] The waste insulating oil flows through the recovery pipeline under the differential pressure, and must pass through the filter preset in front of the fifth valve. The filter integrates a metal filter screen and adsorbed cotton inside, which is used to intercept external dust, metal debris and moisture mixed in the oil during leakage and collection. The oil liquid filtered of impurities enters the waste oil collection tank 23 for storage. This design of filtering first and then entering the tank protects the internal components of the waste oil collection tank 23 from contamination and facilitates subsequent centralized treatment of waste oil.

[0193] Step S54, liquid level closed-loop monitoring and shutdown

[0194] During the recovery operation, the liquid level sensor arranged in the waste oil collection tank 23 continuously feeds back the real-time liquid level signal to the controller 2. The controller 2 compares the real-time liquid level signal with the pre-stored high-level alarm threshold.

[0195] When the liquid level signal is lower than the threshold and the flow sensor detects fluid flow, the controller 2 maintains the running state of the vacuum pump 24; when the liquid level signal reaches the threshold, or the flow sensor shows that the flow is zero (indicating that the oil collection tray is empty), the controller 2 automatically executes the shutdown logic, closes the fifth valve in turn and cuts off the power supply of the vacuum pump 24, to prevent waste oil overflow or overheating of the vacuum pump 24.

[0196] For the above-mentioned vacuum pump 24, liquid level sensor and other hardware selection, those skilled in the art can select mature products with standard industrial communication interface, and the specific circuit connection belongs to the known technology in the art.

[0197] Step S55, pipeline residual liquid purging

[0198] After the test process is completely finished, in order to avoid the residual oil in the oil flow pipeline 25 from deteriorating due to long-term standing, the system performs emptying operation on the test pipe section. The controller 2 opens the vent valve to make the test pipe section communicate with the atmosphere, and uses the gravity guiding process or an auxiliary low-pressure gas source to blow the residual oil in the pipeline to the waste oil collection tank 23 through a specific blow-off branch, to complete the reset of the test bench.

Claims

1. A test apparatus for simulating oil flow patterns in oil-filled submarine cables, comprising a hydraulic power system, a pipeline heating simulation system, a pipeline transportation and leakage simulation system, and a data acquisition and control system, characterized in that, The pipeline transportation and leakage simulation system includes an oil flow pipeline (25), a leakage point pipeline (20) set on the oil flow pipeline (25), and a flow control valve group. The flow control valve group is configured to control the flow direction and leakage state of the insulating oil in the oil flow pipeline (25). The hydraulic power system includes a first hydraulic pump (3), a first electric motor (5), a first oil tank (7), a second hydraulic pump (4), a second electric motor (6), and a second oil tank (8). The input end of the first hydraulic pump (3) is connected to the first oil tank (7), and the output end of the first hydraulic pump (3) is connected to the inlet end of the oil flow pipeline (25). The input end of the second hydraulic pump (4) is connected to the second oil tank (8), and the output end of the second hydraulic pump (4) is connected to the outlet end of the oil flow pipeline (25). The pipeline heating simulation system includes a heater (22) wrapped around the outer wall of the oil flow pipeline (25); The data acquisition and control system includes a computer (1) and a controller (2), wherein the computer (1) and the controller (2) are communicatively connected.

2. The experimental apparatus for simulating oil flow patterns in oil-filled submarine cables according to claim 1, characterized in that, The data acquisition and control system also includes a first pressure sensor (13), a second pressure sensor (14), a third pressure sensor (15), a first flow sensor (16), a second flow sensor (17), a third flow sensor (18), a fourth flow sensor (19), and a temperature sensor (21), all of which are electrically connected to the controller (2). The first pressure sensor (13) and the first flow sensor (16) are located at the inlet end of the oil flow pipe (25); The third pressure sensor (15) and the second flow sensor (17) are located at the outlet end of the oil flow pipe (25); The second pressure sensor (14), the third flow sensor (18), and the fourth flow sensor (19) are located near the leak point in the middle of the pipeline to cooperate with the aforementioned port sensors to achieve status monitoring of the entire pipeline section.

3. The experimental apparatus for simulating oil flow patterns in oil-filled submarine cables according to claim 1, characterized in that, The leak point pipe (20) is connected to the middle of the oil flow pipe (25) via a three-way valve; The leak point pipeline (20) includes a leak control valve and replaceable simulated leak components; The simulated leak device is configured as a needle valve to simulate different degrees of pipe damage and gaps; The oil flow pipeline (25) consists of multiple standard pipe sections with detachable flange connections.

4. The experimental apparatus for simulating oil flow patterns in oil-filled submarine cables according to claim 1, characterized in that, The flow control valve assembly includes: The first valve (9) and the fourth valve (12) installed at both ends of the oil flow pipe (25) are used to control the entry and exit of insulating oil; The second valve (10) is installed on the oil flow pipeline (25) and located downstream of the connection point of the leakage point pipeline (20) for connecting and blocking the flow path of the oil flow pipeline (25); The third valve (11) installed on the leakage simulation branch is used to control the occurrence and shut-off of leakage.

5. The experimental apparatus for simulating oil flow patterns in oil-filled submarine cables according to claim 1, characterized in that, It also includes waste oil treatment systems; The waste oil treatment system includes a waste oil collection tank (23) and a vacuum pump (24). The inlet of the waste oil collection tank (23) is connected to the outlet of the leak point pipeline (20). The vacuum pump (24) is connected to the air port of the waste oil collection tank (23) for negative pressure suction treatment of the oil flow pipeline (25) after the test.

6. An analytical method for simulating oil flow patterns in oil-filled submarine cables, characterized in that, The experimental apparatus for simulating oil flow patterns in oil-filled submarine cables according to any one of claims 1-5 includes the following steps: S1. Based on the parameters of the submarine cable to be simulated, set the heating temperature of the heater (22) and open the leak point pipe (20). S2. Control the hydraulic power system and the flow control valve group to make the device operate in a bidirectional oil flow leakage condition or a unidirectional oil flow leakage condition. When performing high-precision positioning analysis, under the unidirectional oil flow leakage condition, change the system oil injection pressure to perform at least two independent measurements and obtain the first set of measurement data and the second set of measurement data respectively. S3. The data acquisition and control system acquires the first pressure value, second pressure value, first flow rate value, second flow rate value and temperature value at both ends of the oil flow pipeline (25) under stable conditions. S4. Based on the collected data, calculate the location of the leak point in the submarine cable using fluid dynamics calculation logic; S5. After the test, start the waste oil treatment system and use the vacuum pump (24) in conjunction with the waste oil collection box (23) to recycle the insulating oil in the pipeline.

7. The analytical method for simulating oil flow patterns in oil-filled submarine cables according to claim 6, characterized in that, The specific control logic for the bidirectional oil flow leakage condition in step S2 is as follows: Open the first valve (9) and the fourth valve (12) at both ends of the oil flow pipeline (25), open the second valve (10) in the middle of the oil flow pipeline (25) and the third valve (11) on the leak point pipeline (20); Simultaneously start the first hydraulic pump (3) and the second hydraulic pump (4), and control the first hydraulic pump (3) and the second hydraulic pump (4) to pressurize the oil flow pipe (25), so that the pressure at both ends of the oil flow pipe (25) is greater than the pressure at the outlet end of the leakage point pipe (20), so that the insulating oil flows out from both ends of the oil flow pipe (25) to the leakage point pipe (20) to simulate the bidirectional leakage state when the submarine cable breaks.

8. The analysis method for simulating oil flow patterns in oil-filled submarine cables according to claim 6, characterized in that, The specific control logic for the unidirectional oil flow leakage condition in step S2 is as follows: Open the first valve (9) and the fourth valve (12) at both ends of the oil flow pipeline (25), open the second valve (10) in the middle of the oil flow pipeline (25) and the third valve (11) on the leak point pipeline (20); The first hydraulic pump (3) is controlled to pressurize the first oil tank (7), and the pressure of the first oil tank (7) is controlled to be greater than the pressure of the second oil tank (8), so that during the process of the insulating oil flowing from the first oil tank (7) through the oil flow pipe (25) to the second oil tank (8), part of the insulating oil is diverted out through the leakage point pipe (20).

9. The analysis method for simulating oil flow patterns in oil-filled submarine cables according to claim 6, characterized in that, The pipeline flow resistance coefficient calibration step is included before step S1: The third valve (11) on the leak point pipeline (20) is closed, and the control device operates in normal conveying conditions; Measure the pressure difference between the inlet and outlet of the oil flow pipe (25) at a set temperature, and the flow rate within the oil flow pipe (25); Calculate the product of the flow rate value and the total length of the oil flow pipeline (25), divide the product by the pressure difference value, and obtain the pipeline flow resistance coefficient at the current temperature.

10. The analysis method for simulating oil flow patterns in oil-filled submarine cables according to claim 6, characterized in that, The specific calculation logic for determining the location of the leakage point in step S4 is as follows: Obtain the first set of measurement data and the second set of measurement data obtained from the two measurements in step S2; Calculate the product of the pipe flow resistance coefficient and the total pressure difference, where the total pressure difference is the sum of the pressure differences at both ends of the first set of data and the pressure differences at both ends of the second set of data; Add the length-flow product to the product to obtain the numerator value. The length-flow product is obtained by multiplying the total length of the oil flow pipe (25) with the flow variation value. The flow variation value is the outlet flow of the second set of measurement data minus the outlet flow of the first set of measurement data. The total flow difference is calculated by adding the inflow of the first set of data to the outflow of the second set of data, and then subtracting the outflow of the first set of data and the inflow of the second set of data. Divide the numerator value by the total difference in flow rate to obtain the distance from the leak point to the inlet end of the oil flow pipe (25).

Images