Sea cable partial discharge inversion method and device based on distributed optical fiber temperature measurement

Abstract

The present application relates to the technical field of cable partial discharge detection, and discloses a submarine cable partial discharge quantity inversion method and device based on distributed optical fiber temperature measurement. The present application obtains a first target fitting curve of the time-varying characteristics of the submarine cable outer skin surface temperature distribution under different partial discharge source parameters based on partial discharge test data; the partial discharge source is equivalent to a heat source, and based on the simulation data of the surface temperature distribution of the optical fiber unit and the temperature distribution characteristics of the submarine cable outer skin under different equivalent heat powers, a second target fitting curve of the time-varying characteristics of the submarine cable outer skin surface temperature distribution under different heat source parameters is constructed; the second target fitting curves and the first target fitting curves are fitted, and the radial position of the partial discharge defect and the partial discharge quantity corresponding to each second target fitting curve are inverted according to the obtained fitting results. The present application can effectively identify the partial discharge type, the radial position of the partial discharge defect and the severity of the partial discharge of the submarine cable.

Description

Technical Field

[0001] This invention relates to the field of partial discharge detection technology for cables, and in particular to a method and apparatus for inverting the partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement. Background Technology

[0002] As a core component of offshore power transmission networks, submarine cables play a crucial role in the safe and stable operation of the entire offshore wind farm power system, and their insulation condition is a key factor affecting the safe and reliable operation of the cables.

[0003] Insulation aging-related main insulation faults account for a significant proportion of external force damage faults in submarine cables. The insulation condition of cables is closely related to the changes and magnitude of partial discharge. Therefore, the magnitude and changes in partial discharge can serve as important indicators of cable insulation condition and safe operation. However, current submarine cable condition monitoring schemes can only provide early warning of over-temperature and locate the axial position of partial discharge defects, but cannot accurately identify the type of partial discharge, the radial location of the partial discharge defect, or the severity of the partial discharge. Summary of the Invention

[0004] This invention provides a method and apparatus for inverting the partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement, which solves the technical problem of how to accurately identify the type of partial discharge, the radial location of the partial discharge defect, and the severity of the partial discharge in submarine cables.

[0005] The first aspect of this invention provides a method for inverting the partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement, comprising:

[0006] Acquire partial discharge test data; the partial discharge test data includes monitoring data of the circumferential and axial temperature distribution of the submarine cable sheath under different partial discharge power parameters, the partial discharge power parameters include partial discharge type, radial location of partial discharge defect and partial discharge amount;

[0007] The partial discharge test data were analyzed to obtain the first target fitting curve of the temperature distribution characteristics of the submarine cable outer sheath surface changing with time under different partial discharge power parameters;

[0008] Construct a geometric simulation model of the submarine cable; the geometric simulation model of the submarine cable includes optical fiber units arranged in a distributed manner within the submarine cable;

[0009] The equivalent thermal power corresponding to different partial discharge sources is determined based on the submarine cable geometric simulation model and the partial discharge test data.

[0010] Based on simulation data of surface temperature distribution of optical fiber units and temperature distribution of submarine cable sheath under different equivalent thermal powers, a second objective fitting curve is constructed to show the change of surface temperature distribution characteristics of submarine cable sheath over time under different heat source parameters; the heat source parameters include partial discharge type, heat source location, equivalent thermal power and surface temperature of optical fiber units.

[0011] Fit each of the second target fitting curves and each of the first target fitting curves, and inversely deduce the radial position and partial discharge amount of the partial discharge defect corresponding to each of the second target fitting curves based on the obtained fitting results.

[0012] According to one aspect of the present invention, the analysis of the partial discharge test data to obtain a first target fitting curve of the temperature distribution characteristics of the submarine cable outer sheath surface changing over time under different partial discharge power parameters includes:

[0013] Construct fitting curves for the first function relationship between the surface temperature distribution characteristics of submarine cable sheath and the amount and time of partial discharge at the same radial location of partial discharge defect for different types of partial discharge;

[0014] Construct fitting curves for the second function relationship between the surface temperature distribution characteristics of submarine cable outer sheath and the amount and time of partial discharge at radial locations of different partial discharge defects of the same partial discharge type;

[0015] By combining the first functional relationship fitting curve and the second functional relationship fitting curve, the first target fitting curve is obtained.

[0016] According to one achievable method of the first aspect of the present invention, the construction of the submarine cable geometric simulation model includes:

[0017] A simplified structural model of the submarine cable is determined. The simplified structural model is obtained by simplifying the target structure of the submarine cable and the material properties of the corresponding areas. The target structure includes the insulation structure of the submarine cable core, the protective structure of the submarine cable core, and the structure of the optical fiber unit.

[0018] Based on the simplified structural model, a geometric simulation model of the submarine cable is obtained using finite element simulation.

[0019] According to one achievable method of the first aspect of the present invention, determining the equivalent thermal power corresponding to different partial discharge sources based on the submarine cable geometric simulation model and the partial discharge test data includes:

[0020] The target partial discharge power source is equivalent to a target heat source. The evolution relationship data of the maximum temperature of the cable outer sheath surface at the local defect location corresponding to the target partial discharge power source and time are obtained from the partial discharge test data. The heating power range of the target heat source is determined based on the evolution relationship data.

[0021] The lower limit of the heating power range of the target heat source is used as the initial value of the heat power of the target heat source. The step size of the heat power change is set, as well as the ambient temperature and boundary conditions of the submarine cable are set.

[0022] Heat conduction calculations are performed based on the current value of the thermal power of the target heat source to obtain the surface temperature distribution characteristics of the optical fiber at different locations. The surface temperature of each optical fiber in the surface temperature distribution characteristics data at different locations is compared with the surface temperature of the corresponding optical fiber unit at the actual measured location of the optical fiber unit to obtain the relative error ratio.

[0023] Determine whether the current relative error ratio is less than the preset ratio; if yes, use the current value of the thermal power of the target heat source as the equivalent thermal power corresponding to the target local discharge power source; if no, increase the current value of the thermal power of the target heat source by the step size and return to the previous step.

[0024] According to one embodiment of the first aspect of the present invention, determining the equivalent thermal power corresponding to different partial discharge sources based on the submarine cable geometric simulation model and the partial discharge test data further includes:

[0025] The preset ratio is set to 20%.

[0026] According to a method achievable according to a first aspect of the present invention, the step of fitting each second target fitting curve and each first target fitting curve, and retrieving the radial position and partial discharge amount of the partial discharge defect corresponding to each second target fitting curve based on the obtained fitting results, includes:

[0027] Based on the partial discharge type in the second target fitting curve to be fitted, the corresponding first target fitting curve is extracted from each first target fitting curve and assigned to the curve cluster to be fitted.

[0028] Calculate the goodness of fit of the second target fitting curve to be fitted and each first target fitting curve in the family of curves to be fitted;

[0029] The first target fitting curve corresponding to the maximum goodness of fit in the cluster of curves to be fitted is used as the correlation curve of the second target fitting curve to be fitted. Based on the correlation curve, the radial position of the partial discharge defect and the partial discharge amount corresponding to the second target fitting curve to be fitted are obtained.

[0030] According to one achievable embodiment of the first aspect of the invention, the method further includes:

[0031] Acquire optical signal variation data of fiber unit under different equivalent thermal power;

[0032] Based on the principle of optical time-domain reflection and the Raman scattering effect, the optical signal variation data is analyzed to determine the axial position of the partial discharge defect corresponding to each second target fitting curve.

[0033] A second aspect of the present invention provides a device for inverting the partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement, comprising:

[0034] The test data acquisition module is used to acquire partial discharge test data; the partial discharge test data includes monitoring data of the circumferential and axial temperature distribution of the submarine cable sheath under different partial discharge power parameters, and the partial discharge power parameters include partial discharge type, radial location of partial discharge defect and partial discharge amount;

[0035] The first curve construction module is used to analyze the partial discharge test data and obtain the first target fitting curve of the temperature distribution characteristics of the submarine cable outer sheath surface changing with time under different partial discharge power parameters.

[0036] The model building module is used to build a geometric simulation model of the submarine cable; the geometric simulation model of the submarine cable includes optical fiber units arranged in a distributed manner within the submarine cable.

[0037] The equivalent thermal power determination module is used to determine the equivalent thermal power corresponding to different partial discharge sources based on the submarine cable geometric simulation model and the partial discharge test data.

[0038] The second curve construction module is used to construct a second target fitting curve for the change of surface temperature distribution characteristics of submarine cable sheath over time under different heat source parameters, based on simulation data of surface temperature distribution of fiber unit and temperature distribution characteristics of submarine cable sheath under different equivalent thermal power. The heat source parameters include partial discharge type, heat source location, equivalent thermal power and surface temperature of fiber unit.

[0039] The inversion module is used to fit each of the second target fitting curves and each of the first target fitting curves, and to invert the radial position and partial discharge amount of the partial discharge defect corresponding to each of the second target fitting curves based on the obtained fitting results.

[0040] According to one achievable embodiment of the second aspect of the present invention, the first curve construction module comprises:

[0041] The first curve construction unit is used to construct a fitting curve of the first function relationship between the surface temperature distribution characteristics of the submarine cable sheath and the amount and time of partial discharge under the same radial position of the partial discharge defect for different types of partial discharge.

[0042] The second curve construction unit is used to construct a fitting curve of the second function relationship between the surface temperature distribution characteristics of the submarine cable sheath and the amount and time of partial discharge under different radial positions of partial discharge defects of the same type of partial discharge.

[0043] The curve combining unit is used to combine the first function relationship fitting curve and the second function relationship fitting curve to obtain the first target fitting curve.

[0044] According to one achievable method of the second aspect of the present invention, the model building module includes:

[0045] A determining unit is used to determine a simplified structural model of the submarine cable; the simplified structural model is obtained by simplifying the target structure of the submarine cable and the material properties of the corresponding areas, the target structure including the insulation structure of the submarine cable core, the protective structure of the submarine cable core, and the structure of the optical fiber unit;

[0046] The simulation unit is used to obtain the geometric simulation model of the submarine cable using finite element simulation based on the simplified structural model.

[0047] According to one achievable method of the second aspect of the present invention, the equivalent thermal power determination module includes:

[0048] The heating power range determination unit is used to equate the target partial discharge power source to a target heat source, obtain the evolution relationship data of the maximum temperature of the cable outer sheath surface at the local defect location corresponding to the target partial discharge power source and time from the partial discharge test data, and determine the heating power range of the target heat source based on the evolution relationship data.

[0049] The initial setting unit is used to set the step size of the heat power change, and to set the ambient temperature and boundary conditions of the submarine cable, using the lower limit of the heat power range of the target heat source as the initial value of the heat power of the target heat source.

[0050] The first calculation unit is used to perform heat conduction calculations based on the current value of the thermal power of the target heat source, obtain fiber surface temperature distribution characteristic data at different locations, and compare the surface temperature of each fiber in the fiber surface temperature distribution characteristic data at different locations with the fiber unit surface temperature at the corresponding location actually measured by the fiber unit to obtain the relative error ratio.

[0051] The judgment unit is used to determine whether the current relative error ratio is less than the preset ratio; if so, the current value of the thermal power of the target heat source is used as the equivalent thermal power corresponding to the target local discharge power source; if not, the current value of the thermal power of the target heat source is increased by the step size and returned to the first calculation unit.

[0052] According to one embodiment of the second aspect of the present invention, the equivalent thermal power determination module further includes:

[0053] A ratio setting unit is used to set the preset ratio to 20%.

[0054] According to one achievable embodiment of the second aspect of the invention, the inversion module comprises:

[0055] The curve selection unit is used to extract the corresponding first target fitting curve from each first target fitting curve and classify it into the curve cluster to be fitted, based on the partial discharge type in the second target fitting curve to be fitted.

[0056] The second calculation unit is used to calculate the goodness of fit of the second target fitting curve to be fitted and each first target fitting curve in the cluster of curves to be fitted.

[0057] The inversion unit is used to take the first target fitting curve corresponding to the maximum goodness of fit in the cluster of curves to be fitted as the correlation curve of the second target fitting curve to be fitted, and obtain the radial position and partial discharge amount of the partial discharge defect corresponding to the second target fitting curve to be fitted based on the correlation curve.

[0058] According to one embodiment of the second aspect of the invention, the apparatus further includes:

[0059] The optical signal change data acquisition module is used to acquire optical signal change data of the fiber unit under different equivalent thermal powers;

[0060] The axial position determination module is used to analyze the optical signal change data based on the principle of optical time-domain reflection and Raman scattering effect to determine the axial position of the partial discharge defect corresponding to each second target fitting curve.

[0061] A third aspect of the present invention provides a device for inverting the partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement, comprising:

[0062] A memory for storing instructions; wherein the instructions are used to implement the method for inverting partial discharge of submarine cables based on distributed optical fiber temperature measurement as described above.

[0063] A processor for executing instructions in the memory.

[0064] The fourth aspect of the present invention provides a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, it implements the method for inverting the partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement as described in any of the above embodiments.

[0065] As can be seen from the above technical solutions, the present invention has the following advantages:

[0066] This invention obtains a first target fitting curve of the temperature distribution characteristics of the submarine cable sheath surface changing over time under different partial discharge power source parameters based on partial discharge test data; constructs a submarine cable geometric simulation model, and determines the equivalent thermal power corresponding to different partial discharge power sources based on the submarine cable geometric simulation model and partial discharge test data; based on simulation data of the surface temperature distribution of optical fiber units and the temperature distribution characteristics of the submarine cable sheath under different equivalent thermal powers, constructs a second target fitting curve of the temperature distribution characteristics of the submarine cable sheath surface changing over time under different heat source parameters; fits each second target fitting curve with each first target fitting curve, and inversely derives the radial position and partial discharge quantity of the partial discharge defect corresponding to each second target fitting curve based on the fitting results; this invention can not only effectively identify the type of partial discharge and the radial position of the partial discharge defect, but also obtain key parameters characterizing the severity of partial discharge, namely the magnitude of the partial discharge quantity, which can provide important judgment basis for the insulation status and change trend of the submarine cable, thus providing important reference for the operation and maintenance of the submarine cable, and effectively improving the safety and stability of the offshore wind farm power system. Attached Figure Description

[0067] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0068] Figure 1 A flowchart of a method for inverting the partial discharge quantity of submarine cables based on distributed optical fiber thermometry, provided as an optional embodiment of the present invention;

[0069] Figure 2 A schematic diagram of a partial discharge test provided in an optional embodiment of the present invention;

[0070] Figure 3 A schematic diagram of the distributed optical fiber arrangement of a three-core submarine cable provided in an optional embodiment of the present invention;

[0071] Figure 4 The diagram below shows the structural connection of a submarine cable partial discharge inversion device based on distributed optical fiber temperature measurement, which is an optional embodiment of the present invention.

[0072] Figure label:

[0073] Figure 2 In the diagram, T1 is the first isolation transformer; T2 is the voltage regulator; C1 is the low-voltage low-pass filter; T3 is the second isolation transformer; C2 is the high-voltage low-pass filter; L1 is the first inductor; L2 is the second inductor; C V - Capacitor voltage divider; Ck - Coupling capacitor; Z m - Impedance detection; A1 - Partial discharge meter; A2 - Data acquisition system; A3 - Temperature display terminal; A4 - Surface mount temperature sensor;

[0074] Figure 4 In the module, 1-Experimental data acquisition module; 2-First curve construction module; 3-Model construction module; 4-Equivalent thermal power determination module; 5-Second curve construction module; 6-Inversion module. Detailed Implementation

[0075] This invention provides a method and apparatus for inverting the partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement, which is used to solve the technical problem of how to accurately identify the type of partial discharge, the radial location of the partial discharge defect, and the severity of the partial discharge in submarine cables.

[0076] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0077] This invention provides a method for inverting the partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement.

[0078] Please see Figure 1 , Figure 1 The flowchart illustrates a method for inverting the partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement, as provided in an embodiment of the present invention.

[0079] The present invention provides a method for inverting the partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement, including steps S1-S6.

[0080] Step S1: Obtain partial discharge test data; the partial discharge test data includes monitoring data of the circumferential and axial temperature distribution of the submarine cable sheath under different partial discharge power parameters, and the partial discharge power parameters include partial discharge type, radial location of partial discharge defect and partial discharge amount.

[0081] The partial discharge test data is obtained by conducting partial discharge tests on the cable under different partial discharge power supply parameters.

[0082] As a specific implementation method, based on such Figure 2 The test platform shown was used to conduct partial discharge tests under different partial discharge power supply parameters. Figure 2The test platform shown includes a first isolation transformer T1, a voltage regulator T2, a low-voltage low-pass filter C1, a second isolation transformer T3, a high-voltage low-pass filter C2, a first inductor L1, a second inductor L2, and a capacitive voltage divider C. V Coupling capacitor C k Detection impedance Z m The test platform consists of a partial discharge instrument A1, a data acquisition system A2, and a temperature display terminal A3. It is used to test a submarine cable with a pre-existing defect. A patch-type temperature sensor A4 is installed on the submarine cable with the pre-existing defect.

[0083] In this design, assuming the length direction of the submarine cable is the z-direction and the axial position of the partial discharge defect is zero, patch-type temperature sensors A4 can be uniformly attached to the circumferential surface of the submarine cable sheath within the axial region (-z, z). For example, patch-type temperature sensors A4 are uniformly arranged along the circumference and axial direction, with each pair of patch-type temperature sensors A4 at the same axial position and the angle between them and the center of the circle set to 60°, resulting in six temperature sensors uniformly arranged along the entire circumference, forming one group. Simultaneously, using the axial position of the partial discharge defect as a reference position, five groups of temperature sensors are arranged at the reference position along the axis and at ±10cm and ±20cm, forming a 5×6 temperature sensor array.

[0084] It should be noted that, in order to improve the accuracy of temperature distribution measurement, more patch-type temperature sensors A4 can be appropriately arranged.

[0085] It should be noted that the test platform for partial discharge testing can also refer to other existing partial discharge test platforms; correspondingly, the test method for partial discharge testing can also refer to other existing partial discharge test methods.

[0086] Step S2: Analyze the partial discharge test data to obtain the first target fitting curve of the temperature distribution characteristics of the submarine cable outer sheath surface changing with time under different partial discharge power parameters.

[0087] In one feasible approach, the process of constructing the first target fitting curve includes:

[0088] Construct fitting curves for the first function relationship between the surface temperature distribution characteristics of submarine cable sheath and the amount and time of partial discharge at the same radial location of partial discharge defect for different types of partial discharge;

[0089] Construct fitting curves for the second function relationship between the surface temperature distribution characteristics of submarine cable outer sheath and the amount and time of partial discharge at radial locations of different partial discharge defects of the same partial discharge type;

[0090] By combining the first functional relationship fitting curve and the second functional relationship fitting curve, the first target fitting curve is obtained.

[0091] As a specific implementation method, based on Figure 2 When the experimental platform shown conducts partial discharge tests under different partial discharge power supply parameters, the process of constructing the first target fitting curve may include:

[0092] (1) Temperature distribution characteristics of the surface of the submarine cable are obtained by arranging patch-type temperature sensors A4 in the circumferential and axial directions of the submarine cable.

[0093] (2) For different types of partial discharge, the characteristics of partial discharge quantity and surface temperature distribution and their evolution over time were obtained through partial discharge experiments with different partial discharge quantities.

[0094] After completing the wiring of each component of the test platform, the partial discharge quantity is calibrated using a calibration pulse generator before the test officially begins, and then the test is started according to the submarine cable partial discharge test procedure.

[0095] (3) For different types of partial discharge, at the same radial position, different partial discharge amounts were used to conduct experiments. For example, partial discharge amounts of 50 pC, 100 pC, 150 pC, 200 pC, 250 pC, and 300 pC were used to obtain the functional relationship between the temperature distribution characteristics of the outer skin surface and time under different partial discharge amounts. in The partial discharge quantity is represented by Q. n The surface temperature of the submarine cable sheath changes with time t along the circumferential direction α and the axial direction z. m represents the type of partial discharge, i.e., the partial discharge type. m = 1, 2, 3 represent the partial discharge types as air gap discharge, surface discharge, and corona discharge, respectively.

[0096] (4) For different radial positions P1, P2, ..., P of the same type of partial discharge, i The partial discharge test was conducted with the same magnitude of partial discharge as in (3). For example, the partial discharge magnitude was still 50pC, 100pC, 150pC, 200pC, 250pC and 300pC respectively, in order to obtain the relationship between the temperature distribution characteristics of the outer skin surface and time t under different partial discharge magnitudes.

[0097] (5) Combining the data obtained in (3) and (4), the functional relationship between the surface temperature distribution of the submarine cable sheath and time t under different partial discharge types, different radial locations of partial discharge defects, and different magnitudes of partial discharge can be obtained, denoted as: The representative partial discharge type is m, and the radial location of the partial discharge defect is P. i The partial discharge quantity is Q nThe surface temperature of the submarine cable sheath varies with time t along the circumferential direction α and the axial direction z.

[0098] In this embodiment of the invention, by using partial discharge test data, the distribution characteristics of the temperature field along the circumference and axial direction on the cable sheath surface and the evolution relationship with time under different partial discharge quantities, partial discharge types and partial discharge defect locations are obtained. The method is simple and convenient.

[0099] Considering that for different types of partial discharge, the temperature rise characteristic curve of the partial discharge point over time is different under the same discharge magnitude, the type of partial discharge can be determined by the characteristics of the temperature rise characteristic curve of the submarine cable sheath changing over time. Similarly, the type of partial discharge can also be determined based on the changing characteristics of the fitted curve of temperature versus time measured by the optical fiber unit. Based on this, the present invention performs the following steps S3-S5.

[0100] Step S3: Construct a geometric simulation model of the submarine cable; the geometric simulation model of the submarine cable includes optical fiber units arranged in a distributed manner within the submarine cable.

[0101] In one feasible manner, constructing the submarine cable geometric simulation model includes:

[0102] A simplified structural model of the submarine cable is determined. The simplified structural model is obtained by simplifying the target structure of the submarine cable and the material properties of the corresponding areas. The target structure includes the insulation structure of the submarine cable core, the protective structure of the submarine cable core, and the structure of the optical fiber unit.

[0103] Based on the simplified structural model, a geometric simulation model of the submarine cable is obtained using finite element simulation.

[0104] Although partial discharge points can be treated as virtual heat sources, analytical solutions are extremely difficult due to the complexity of the submarine cable structure and the complexity of the paths when partial discharge points couple to optical fibers at different locations. Without proper simplification of the submarine cable structure, finite element modeling and simulation will also suffer from complex mesh generation and long solution times. Based on these considerations, this embodiment first determines a simplified structural model of the submarine cable, and then uses finite element simulation to obtain a geometric simulation model of the submarine cable based on this simplified structural model.

[0105] As a specific implementation method, the simplification process of submarine cable structures may include:

[0106] 1) The thin conductor shielding layer, the thick XLPE insulation layer (i.e., cross-linked polyethylene insulation layer), and the thin insulation shielding layer of the wire core are combined and simplified into a single insulation layer, and its material properties such as specific heat capacity and thermal conductivity are set to equivalent material properties.

[0107] 2) The thinner anti-corrosion layer and the PE sheath layer (taking polyethylene sheath) are equivalent to the sheath layer, and its material properties are set to the equivalent material properties;

[0108] 3) The structure of the optical fiber unit is simplified to optical fiber, HDPE sheath (i.e., high-density polyethylene sheath) and stainless steel tube.

[0109] To more accurately obtain the temperature distribution characteristics across the cross-section and along the axis of the submarine cable, the fiber optic units can be arranged symmetrically. For example, a schematic diagram of the arrangement method for a commonly used three-core submarine cable is shown below. Figure 3 As shown, three distributed optical fibers are arranged at a 120° angle between each pair of fibers on the cross-section of a three-core submarine cable to measure temperature information at different locations.

[0110] When obtaining the geometric simulation model of a submarine cable using finite element simulation based on a simplified structural model, the corresponding geometric simulation model can be established in COMSOL (multiphysics simulation software). Regions without equivalents are set to the actual material parameters of the corresponding submarine cable, while equivalent layers are set to the equivalent material parameters.

[0111] Step S4: Determine the equivalent thermal power corresponding to different partial discharge sources based on the submarine cable geometric simulation model and the partial discharge test data.

[0112] In one feasible approach, determining the equivalent thermal power corresponding to different partial discharge sources based on the submarine cable geometric simulation model and the partial discharge test data includes:

[0113] The target partial discharge power source is equivalent to a target heat source. The evolution relationship data of the maximum temperature on the surface of the cable outer sheath at the local defect location corresponding to the target partial discharge power source and time are obtained from the partial discharge test data. The heating power range of the target heat source is determined based on the evolution relationship data.

[0114] The lower limit of the heating power range of the target heat source is used as the initial value of the heat power of the target heat source, the step size of the heat power change is set, and the ambient temperature and boundary conditions of the submarine cable are set.

[0115] Heat conduction calculations are performed based on the current value of the thermal power of the target heat source to obtain the surface temperature distribution characteristics of the optical fiber at different locations. The surface temperature of each optical fiber in the surface temperature distribution characteristics data at different locations is compared with the surface temperature of the corresponding optical fiber unit at the actual measured location of the optical fiber unit to obtain the relative error ratio.

[0116] Determine whether the current relative error ratio is less than the preset ratio; if yes, use the current value of the thermal power of the target heat source as the equivalent thermal power corresponding to the target local discharge power source; if no, increase the current value of the thermal power of the target heat source by the step size and return to the previous step.

[0117] According to the embodiments of this application, in specific implementation, the partial discharge type is m and the partial discharge quantity is Q. n The partial discharge power source is equivalent to a heat source. Among them W n The corresponding partial discharge quantity is Q n The heating power of the heat source at that time, P N P is the location of the heat source. N The radial location of the partial discharge defect corresponds to the partial discharge source. Based on the evolution relationship between the maximum temperature of the cable sheath and time on the radial location profile of the partial discharge defect obtained from the experiment, i.e., the temperature rise characteristics, the heat W generated by the partial discharge at this defect per unit time is estimated. If the estimated partial discharge amount is Q... n If the range of the heat source's heating power is W1 to W2, then W1 to W2 is divided into multiple segments, the initial heating power is set to W1, the step size is ΔW, and the input power of the heat source is parametrically scanned to determine the equivalent heat power corresponding to the partial discharge power source.

[0118] The ambient temperature and boundary conditions of the submarine cable in the simulation model can be set according to the actual operating environment. These ambient temperature and boundary conditions include the temperature range at the cable laying location and the range of voltage and current applied to the cable.

[0119] The formula for calculating the relative error ratio can be set according to the actual situation. For example, when comparing the surface temperature of each fiber in the surface temperature distribution characteristic data of the fiber at different locations with the actual measured surface temperature of the fiber unit at the corresponding location, the maximum temperature error can be obtained. The relative error ratio is obtained by dividing the maximum temperature error by the actual measured surface temperature of the fiber unit at the corresponding location.

[0120] When performing heat conduction calculations based on the current thermal power of the target heat source, the mesh can be appropriately refined near the heat source and at the interface of the medium to improve the calculation accuracy.

[0121] It should be noted that the preset ratio can be set according to actual conditions. In one feasible approach, the preset ratio is set to 20%.

[0122] Step S5: Based on simulation data of the surface temperature distribution of the optical fiber unit and the temperature distribution characteristics of the submarine cable sheath under different equivalent thermal powers, construct a second target fitting curve of the surface temperature distribution characteristics of the submarine cable sheath changing with time under different heat source parameters; the heat source parameters include partial discharge type, heat source location, equivalent thermal power and surface temperature of the optical fiber unit.

[0123] Among them, the second target fitting curve can be as follows: To express, This indicates that the partial discharge type is m and the heat source location is P. N And the surface temperature of the fiber unit is T fibre The functional relationship between the surface temperature of the outer sheath of the submarine cable along the circumferential direction α and the axial direction z and time t.

[0124] Step S6: Fit each of the second target fitting curves and each of the first target fitting curves, and inversely deduce the radial position and partial discharge amount of the partial discharge defect corresponding to each of the second target fitting curves based on the obtained fitting results.

[0125] In one feasible manner, fitting each of the second target fitting curves and each of the first target fitting curves, and retrieving the radial position and partial discharge amount of the partial discharge defect corresponding to each of the second target fitting curves based on the obtained fitting results, includes:

[0126] Based on the partial discharge type in the second target fitting curve to be fitted, the corresponding first target fitting curve is extracted from each first target fitting curve and assigned to the curve cluster to be fitted.

[0127] Calculate the goodness of fit of the second target fitting curve to be fitted and each first target fitting curve in the family of curves to be fitted;

[0128] The first target fitting curve corresponding to the maximum goodness of fit in the cluster of curves to be fitted is used as the correlation curve of the second target fitting curve to be fitted. Based on the correlation curve, the radial position of the partial discharge defect and the partial discharge amount corresponding to the second target fitting curve to be fitted are obtained.

[0129] Based on the embodiments of this application, assuming the variation characteristics of the temperature versus time fitting curve measured by the fiber optic unit, the partial discharge type is determined to be air gap discharge, i.e., m=1. The second target fitting curve to be fitted is then... When fitting the curve to the first target curve of the family of curves to be fitted, it was found that... Fitted curve with the first target If the goodness-of-fit value is the largest, then it can be determined that at this time... The corresponding partial discharge type is air gap discharge, the magnitude of the partial discharge power source is Q2, and the radial position of the partial discharge defect is P3.

[0130] In one feasible implementation, the method further includes:

[0131] Acquire optical signal variation data of fiber unit under different equivalent thermal power;

[0132] Based on the principle of optical time-domain reflection and the Raman scattering effect, the optical signal variation data is analyzed to determine the axial position of the partial discharge defect corresponding to each second target fitting curve.

[0133] It should be noted that the method for determining the axial position of partial discharge defects based on the principle of optical time-domain reflection and Raman scattering effect is existing technology. In this embodiment, the optical signal change data can be analyzed by referring to existing methods to obtain the axial position of the partial discharge defect corresponding to each second target fitting curve.

[0134] Existing distributed fiber optic temperature measurement systems can only achieve over-temperature early warning and axial position location, but cannot identify the type of partial discharge, the radial location of insulation defects, or the severity of partial discharge. The embodiments of this invention can effectively achieve online monitoring of key parameters of the partial discharge state of submarine cables, effectively solving the aforementioned technical problems. It can not only effectively identify the type of partial discharge and the specific radial location of insulation defects, but also obtain key parameters characterizing the severity of partial discharge, i.e., the magnitude of the partial discharge. Therefore, it can provide important judgment criteria for the insulation status and changing trends of submarine cables, provide important reference for the operation and maintenance of submarine cables, and effectively improve the safety and stability of offshore wind farm power systems.

[0135] The present invention also provides a device for inverting the partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement, which can be used to perform the method for inverting the partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement as described in any of the above embodiments of the present invention.

[0136] Please see Figure 4 , Figure 4 The diagram shows a structural connection block diagram of a submarine cable partial discharge inversion device based on distributed optical fiber temperature measurement according to an embodiment of the present invention.

[0137] This invention provides a device for inverting the partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement, comprising:

[0138] The test data acquisition module 1 is used to acquire partial discharge test data; the partial discharge test data includes monitoring data of the temperature distribution of the outer circumferential surface and axial direction of the submarine cable under different partial discharge power parameters, and the partial discharge power parameters include partial discharge type, radial location of partial discharge defect and partial discharge amount;

[0139] The first curve construction module 2 is used to analyze the partial discharge test data and obtain the first target fitting curve of the temperature distribution characteristics of the submarine cable outer sheath surface changing with time under different partial discharge power parameters.

[0140] Model building module 3 is used to build a submarine cable geometric simulation model; the submarine cable geometric simulation model includes optical fiber units distributed within the submarine cable;

[0141] The equivalent thermal power determination module 4 is used to determine the equivalent thermal power corresponding to different partial discharge sources based on the submarine cable geometric simulation model and the partial discharge test data.

[0142] The second curve construction module 5 is used to construct a second target fitting curve of the surface temperature distribution characteristics of the submarine cable sheath under different heat source parameters as a function of time, based on simulation data of the surface temperature distribution of the optical fiber unit and the temperature distribution characteristics of the submarine cable sheath under different equivalent thermal power. The heat source parameters include partial discharge type, heat source location, equivalent thermal power and surface temperature of the optical fiber unit.

[0143] The inversion module 6 is used to fit each of the second target fitting curves and each of the first target fitting curves, and to invert the radial position and partial discharge amount of the partial discharge defect corresponding to each of the second target fitting curves based on the obtained fitting results.

[0144] In one feasible manner, the first curve construction module 2 includes:

[0145] The first curve construction unit is used to construct a fitting curve of the first function relationship between the surface temperature distribution characteristics of the submarine cable sheath and the amount and time of partial discharge under the same radial position of the partial discharge defect for different types of partial discharge.

[0146] The second curve construction unit is used to construct a fitting curve of the second function relationship between the surface temperature distribution characteristics of the submarine cable sheath and the amount and time of partial discharge under different radial positions of partial discharge defects of the same type of partial discharge.

[0147] The curve combining unit is used to combine the first function relationship fitting curve and the second function relationship fitting curve to obtain the first target fitting curve.

[0148] In one feasible implementation, the model building module 3 includes:

[0149] A determining unit is used to determine a simplified structural model of the submarine cable; the simplified structural model is obtained by simplifying the target structure of the submarine cable and the material properties of the corresponding areas, the target structure including the insulation structure of the submarine cable core, the protective structure of the submarine cable core, and the structure of the optical fiber unit;

[0150] The simulation unit is used to obtain the geometric simulation model of the submarine cable using finite element simulation based on the simplified structural model.

[0151] In one feasible manner, the equivalent thermal power determination module 4 includes:

[0152] The heating power range determination unit is used to equate the target partial discharge power source to a target heat source, obtain the evolution relationship data of the maximum temperature of the cable outer sheath surface at the local defect location corresponding to the target partial discharge power source and time from the partial discharge test data, and determine the heating power range of the target heat source based on the evolution relationship data.

[0153] The initial setting unit is used to set the step size of the heat power change, and to set the ambient temperature and boundary conditions of the submarine cable, using the lower limit of the heat power range of the target heat source as the initial value of the heat power of the target heat source.

[0154] The first calculation unit is used to perform heat conduction calculations based on the current value of the thermal power of the target heat source, obtain fiber surface temperature distribution characteristic data at different locations, and compare the surface temperature of each fiber in the fiber surface temperature distribution characteristic data at different locations with the fiber unit surface temperature at the corresponding location actually measured by the fiber unit to obtain the relative error ratio.

[0155] The judgment unit is used to determine whether the current relative error ratio is less than the preset ratio; if so, the current value of the thermal power of the target heat source is used as the equivalent thermal power corresponding to the target local discharge power source; if not, the current value of the thermal power of the target heat source is increased by the step size and returned to the first calculation unit.

[0156] In one feasible implementation, the equivalent thermal power determination module 4 further includes:

[0157] A ratio setting unit is used to set the preset ratio to 20%.

[0158] In one feasible implementation, the inversion module 6 includes:

[0159] The curve selection unit is used to extract the corresponding first target fitting curve from each first target fitting curve and classify it into the curve cluster to be fitted, based on the partial discharge type in the second target fitting curve to be fitted.

[0160] The second calculation unit is used to calculate the goodness of fit of the second target fitting curve to be fitted and each first target fitting curve in the cluster of curves to be fitted.

[0161] The inversion unit is used to take the first target fitting curve corresponding to the maximum goodness of fit in the cluster of curves to be fitted as the correlation curve of the second target fitting curve to be fitted, and obtain the radial position of the partial discharge defect and the partial discharge amount corresponding to the second target fitting curve to be fitted based on the correlation curve.

[0162] In one feasible embodiment, the device further includes:

[0163] The optical signal change data acquisition module is used to acquire optical signal change data of the fiber unit under different equivalent thermal powers;

[0164] The axial position determination module is used to analyze the optical signal change data based on the principle of optical time-domain reflection and Raman scattering effect to determine the axial position of the partial discharge defect corresponding to each second target fitting curve.

[0165] The present invention also provides a device for inverting the partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement, comprising:

[0166] A memory is used to store instructions; wherein the instructions are used to implement the method for inverting the partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement as described in any of the above embodiments;

[0167] A processor for executing instructions in the memory.

[0168] The present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the method for inverting the partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement as described in any of the above embodiments.

[0169] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the devices, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and the specific beneficial effects of the devices, modules, and units described above can be referred to the corresponding beneficial effects in the foregoing method embodiments, and will not be repeated here.

[0170] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another device, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or modules may be electrical, mechanical, or other forms.

[0171] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical modules; that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0172] Furthermore, the functional modules in the various embodiments of the present invention can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module. The integrated modules described above can be implemented in hardware or as software functional modules.

[0173] If the integrated module is implemented as a software functional module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes: USB flash drives, portable hard drives, read-only memory (ROM), and various other media capable of storing program code.

[0174] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for inverting partial discharge quantity in submarine cables based on distributed optical fiber thermometry, characterized in that, include: Acquire partial discharge test data; the partial discharge test data includes monitoring data of the circumferential and axial temperature distribution of the submarine cable sheath under different partial discharge power parameters, the partial discharge power parameters include partial discharge type, radial location of partial discharge defect and partial discharge amount; The partial discharge test data were analyzed to obtain the first target fitting curve of the temperature distribution characteristics of the submarine cable outer sheath surface changing with time under different partial discharge power parameters; Construct a geometric simulation model of the submarine cable; the geometric simulation model of the submarine cable includes optical fiber units arranged in a distributed manner within the submarine cable; The equivalent thermal power corresponding to different partial discharge sources is determined based on the submarine cable geometric simulation model and the partial discharge test data. Based on simulation data of surface temperature distribution of optical fiber units and temperature distribution of submarine cable sheath under different equivalent thermal powers, a second objective fitting curve is constructed to show the change of surface temperature distribution characteristics of submarine cable sheath over time under different heat source parameters; the heat source parameters include partial discharge type, heat source location, equivalent thermal power and surface temperature of optical fiber units. Fit each of the second target fitting curves and each of the first target fitting curves, and inversely deduce the radial position and partial discharge amount of the partial discharge defect corresponding to each of the second target fitting curves based on the obtained fitting results.

2. The method for inverting partial discharge of submarine cables based on distributed optical fiber thermometry according to claim 1, characterized in that, The analysis of the partial discharge test data yields a first target fitting curve of the temperature distribution characteristics of the submarine cable outer sheath surface over time under different partial discharge power parameters, including: Construct fitting curves for the first function relationship between the surface temperature distribution characteristics of submarine cable sheath and the amount and time of partial discharge at the same radial location of partial discharge defect for different types of partial discharge; Construct fitting curves for the second function relationship between the surface temperature distribution characteristics of submarine cable outer sheath and the amount and time of partial discharge at radial locations of different partial discharge defects of the same partial discharge type; By combining the first functional relationship fitting curve and the second functional relationship fitting curve, the first target fitting curve is obtained.

3. The method for inverting partial discharge of submarine cables based on distributed optical fiber thermometry according to claim 1, characterized in that, The construction of the submarine cable geometric simulation model includes: A simplified structural model of the submarine cable is determined. The simplified structural model is obtained by simplifying the target structure of the submarine cable and the material properties of the corresponding areas. The target structure includes the insulation structure of the submarine cable core, the protective structure of the submarine cable core, and the structure of the optical fiber unit. Based on the simplified structural model, a geometric simulation model of the submarine cable is obtained using finite element simulation.

4. The method for inverting partial discharge of submarine cables based on distributed optical fiber thermometry according to claim 1, characterized in that, The step of determining the equivalent thermal power corresponding to different partial discharge sources based on the submarine cable geometric simulation model and the partial discharge test data includes: The target partial discharge power source is equivalent to a target heat source. The evolution relationship data of the maximum temperature on the surface of the cable outer sheath at the local defect location corresponding to the target partial discharge power source and time are obtained from the partial discharge test data. The heating power range of the target heat source is determined based on the evolution relationship data. The lower limit of the heating power range of the target heat source is used as the initial value of the heat power of the target heat source, the step size of the heat power change is set, and the ambient temperature and boundary conditions of the submarine cable are set. Heat conduction calculations are performed based on the current value of the thermal power of the target heat source to obtain the surface temperature distribution characteristics of the optical fiber at different locations. The surface temperature of each optical fiber in the surface temperature distribution characteristics data at different locations is compared with the surface temperature of the corresponding optical fiber unit at the actual measured location of the optical fiber unit to obtain the relative error ratio. Determine whether the current relative error ratio is less than the preset ratio; if yes, use the current value of the thermal power of the target heat source as the equivalent thermal power corresponding to the target local discharge power source; if no, increase the current value of the thermal power of the target heat source by the step size and return to the previous step.

5. The method for inverting partial discharge of submarine cables based on distributed optical fiber thermometry according to claim 4, characterized in that, The step of determining the equivalent thermal power corresponding to different partial discharge sources based on the submarine cable geometric simulation model and the partial discharge test data also includes: The preset ratio is set to 20%.

6. The method for inverting partial discharge quantity of submarine cables based on distributed optical fiber thermometry according to claim 1, characterized in that, The process of fitting each second target fitting curve and each first target fitting curve, and then retrieving the radial position and partial discharge amount of the partial discharge defect corresponding to each second target fitting curve based on the obtained fitting results, includes: Based on the partial discharge type in the second target fitting curve to be fitted, the corresponding first target fitting curve is extracted from each first target fitting curve and assigned to the curve cluster to be fitted. Calculate the goodness of fit of the second target fitting curve to be fitted and each first target fitting curve in the family of curves to be fitted; The first target fitting curve corresponding to the maximum goodness of fit in the cluster of curves to be fitted is used as the correlation curve of the second target fitting curve to be fitted. Based on the correlation curve, the radial position of the partial discharge defect and the partial discharge amount corresponding to the second target fitting curve to be fitted are obtained.

7. The method for inverting partial discharge of submarine cables based on distributed optical fiber thermometry according to claim 6, characterized in that, The method further includes: Acquire optical signal variation data of fiber unit under different equivalent thermal power; Based on the principle of optical time-domain reflection and the Raman scattering effect, the optical signal variation data is analyzed to determine the axial position of the partial discharge defect corresponding to each second target fitting curve.

8. A device for inverting partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement, characterized in that, include: The test data acquisition module is used to acquire partial discharge test data; the partial discharge test data includes monitoring data of the circumferential and axial temperature distribution of the submarine cable sheath under different partial discharge power parameters, and the partial discharge power parameters include partial discharge type, radial location of partial discharge defect and partial discharge amount; The first curve construction module is used to analyze the partial discharge test data and obtain the first target fitting curve of the temperature distribution characteristics of the submarine cable outer sheath surface changing with time under different partial discharge power parameters. The model building module is used to build a geometric simulation model of the submarine cable; the geometric simulation model of the submarine cable includes optical fiber units arranged in a distributed manner within the submarine cable. The equivalent thermal power determination module is used to determine the equivalent thermal power corresponding to different partial discharge sources based on the submarine cable geometric simulation model and the partial discharge test data. The second curve construction module is used to construct a second target fitting curve for the change of surface temperature distribution characteristics of submarine cable sheath over time under different heat source parameters, based on simulation data of surface temperature distribution of fiber unit and temperature distribution characteristics of submarine cable sheath under different equivalent thermal power. The heat source parameters include partial discharge type, heat source location, equivalent thermal power and surface temperature of fiber unit. The inversion module is used to fit each of the second target fitting curves and each of the first target fitting curves, and to invert the radial position and partial discharge amount of the partial discharge defect corresponding to each of the second target fitting curves based on the obtained fitting results.

9. A device for inverting partial discharge quantity of submarine cables based on distributed optical fiber temperature measurement, characterized in that, include: A memory for storing instructions; wherein the instructions are used to implement the method for inverting partial discharge of submarine cables based on distributed optical fiber temperature measurement as described in any one of claims 1-7; A processor for executing instructions in the memory.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the method for inverting partial discharge of submarine cables based on distributed optical fiber temperature measurement as described in any one of claims 1-7.

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