High-voltage cable line operation state inversion method and system

Abstract

The invention discloses a high-voltage cable line operation state inversion method and system, and relates to the technical field of high-voltage cable line supervision, and the method comprises the steps: collecting the structure, size and material parameters of a cable accessory, and building an electromagnetic thermal multi-physical field simulation model of the cable accessory and the defect of the cable accessory; establishing a multi-physical field simulation model of the cable buffer layer and the defects thereof; establishing a multi-physical field simulation model and a field-circuit coupling model of an electromagnetic field, a temperature field and a flow field of the cable tunnel; obtaining an actual measurement value of a cable line state parameter, comparing the actual measurement value with a simulation result of large-scale and local defects of a cable tunnel space, and correcting the model according to a comparison result; and inversion of tunnel cables and typical defect faults of the cables under different working conditions is realized. According to the method, cable overall operation state simulation and typical defect simulation are integrated to realize simulation reproduction and defect inversion of a cable line state.

Description

Technical Field

[0001] The present invention relates to the technical field of high-voltage cable line supervision, and in particular to a method and system for inverting the operating status of a high-voltage cable line. Background Art

[0002] As the main transmission component of power grid equipment, high-voltage cable lines have always been the focus of power grid operation and maintenance due to their complex working conditions and changing environment. With the continuous improvement of the cableization rate of urban transmission networks and the increase in the number of cable loops, the problems of induced voltage and circulating current in the cable metal sheath caused by magnetic field coupling have become more serious; due to long-term operation under thermal, electrical, mechanical and other factors, various defects are inevitable inside or outside the cable, which eventually lead to aging or failure of cable insulation. In recent years, cable breakdown accidents have occurred frequently due to defects in cable accessories and buffer layers, seriously affecting the safe and stable operation of the power system. Therefore, in order to ensure the normal operation of the power system and reduce the accident rate, it is very important to realize the simulation inversion of the normal state and defect faults of tunnel cables under different working conditions.

[0003] Among the cable inversion methods proposed in the current invention patents, there are few studies on inversion methods for cable tunnels. In terms of typical cable defects, they are mainly aimed at defect simulations of cable terminals and intermediate joints, and defect simulations of cable buffer layers. There is no inversion method for both normal working conditions of tunnel cables and typical cable defects. Most of the existing methods are limited to a single model to achieve the inversion of the operating status of active cables, and fail to compare the simulation results of large-scale and local defects in the cable tunnel space, thereby achieving simulation reproduction of different states of cable lines under tunnel conditions and defect simulation inversion.

[0004] Patent CN118366011 A discloses a model training, underground cable pipeline defect recognition method, product and equipment, which uses target images and sample images to train the target detection model to obtain an underground cable pipeline defect recognition model, which can improve the detection accuracy of the trained underground cable pipeline defect recognition model. This method can provide a fault recognition model for underground cable pipelines at a lower cable detection cost, but its recognition method does not involve the electric field, magnetic field, and temperature distribution of the cable, and cannot detect internal defects of the cable.

[0005] Patent CN118334561 A relates to a smart panoramic inspection and monitoring method and system for high-voltage cables. The method mainly obtains a panoramic image of the high-voltage cable and obtains the three-dimensional coordinates of the cable components based on the average brightness intensity data and shadow area pixel distribution data of the panoramic image of the high-voltage cable, generates the morphological structure data of the cable components, and obtains environmental perception parameters. The patent realizes real-time and efficient panoramic inspection and monitoring of cables, but the disadvantage is that the method can only detect external defects of the cable, and its evaluation results are one-sided, and it is easy to ignore the influence of other factors on the working status of the cable.

[0006] Patent CN115079060 B invention relates to three-core cable phase current measurement technology, specifically to a three-core cable phase current spatial magnetic field inversion method based on a differential evolution algorithm, by establishing a three-core cable spatial magnetic field calculation model, using a Hall sensor on the cable surface to measure the magnetic induction intensity along the cable circumference, and using a differential evolution algorithm to solve the nonlinear equations to obtain the three-phase current value. This method realizes the three-core cable phase current, but the patent only involves the inversion of current, and does not involve the inversion of temperature field, electromagnetic field and cable defects.

[0007] Patent CN104776938A provides a cable joint core temperature inversion method and system based on cable surface temperature. The accurate cable core contact point temperature can be obtained by inversion and fitting the cable body surface temperature, which is simple and convenient. However, this method does not consider the situation where the electric field is distorted when there are defects in the cable accessories.

[0008] Patent CN118409163 A proposes a method and device for evaluating the performance of a high-voltage cable buffer layer. By collecting the interlayer contact resistivity, compression force, moisture content, volume resistivity and surface resistance of the cable buffer layer, it is determined whether the buffer layer meets the corresponding preset indicators, and then whether the cable to be inspected has potential ablation defects. This method has the advantages of high accuracy, but the cable model obtained by the method through input parameters can only determine the existence of defects in the buffer layer of the cable section, and does not involve the type and location of specific defects.

[0009] Patent CN118409163 A monitors the temperature of the cable and its cable accessories, performs fitting analysis on the current and temperature data, and corrects the simulation calculation results to obtain the hot spot temperature of the cable accessories, thereby determining whether the cable accessories are faulty. However, this method also does not consider the location of the defect during simulation, which may lead to the neglect of the existence of some latent defects during the inversion process. Summary of the invention

[0010] In view of the above existing problems, the present invention is proposed.

[0011] Therefore, the present invention provides a method for inverting the operating status of a high-voltage cable line. The purpose of the present invention is to provide a method for simulating and inverting the normal state of a tunnel cable and typical cable defects and faults under different working conditions. First, the simulation of the cable operating state is realized based on the multi-physical field simulation of the cable tunnel. Secondly, the simulation of typical defects or faults of the cable line is realized based on the simulation of typical cable defects. On the basis of the multi-physical field coupling simulation of the tunnel cable group and typical cable defects, the key characteristic quantities of the line operation at the key spatial calibration points and the state parameters within the interval are obtained. The overall cable operating state simulation and typical defect simulation are combined to realize the simulation reproduction of the cable line state and defect inversion.

[0012] In order to solve the above technical problems, the present invention provides the following technical solution, a method for inverting the operating state of a high-voltage cable line, comprising:

[0013] The structure, size and material parameters of cable accessories are collected to establish an electromagnetic thermal multi-physics field simulation model of cable accessories and their defects. The structure, size and material parameters of the cable buffer layer are collected to establish a multi-physics field simulation model of the cable buffer layer and its defects. The structure and size parameters of the cable tunnel and the structure, size and material parameters of the cable body are collected to establish a multi-physics field simulation model of the electromagnetic field, temperature field and flow field of the cable tunnel and a field-circuit coupling model. The actual measured values ​​of the cable line state parameters are obtained and compared with the simulation results of large-scale and local defects in the cable tunnel space, and the multi-physics field simulation model is corrected according to the comparison results. Based on the optimized simulation model and parameters, the inversion of tunnel cables and typical cable defect faults under different working conditions is realized.

[0014] As a preferred scheme of the high-voltage cable line operation status inversion method described in the present invention, wherein: the establishment of an electromagnetic thermal multi-physics field simulation model of cable accessories and their defects includes, by setting the defect size, position and material parameters, simulating and analyzing the influence of scratches, impurity residues and water seepage defects on the composite insulation interface of the cable accessories during installation or operation on the heating and partial discharge of the cable joints, and obtaining the key characteristic quantities near the accessories under different defect states.

[0015] As a preferred solution of the high-voltage cable line operation status inversion method described in the present invention, the key characteristic quantities near the attachment under different defect states include electric field and temperature.

[0016] As a preferred scheme of the high-voltage cable line operation status inversion method described in the present invention, wherein: the establishment of a multi-physical field simulation model of the cable buffer layer and its defects includes, by setting the defect size, position and material parameters, simulating and analyzing the influence of moisture in the buffer layer, precipitation of water-blocking powder, and poor contact between the buffer layer and the aluminum sheath on the cable operation status, and extracting the electric field and temperature characteristic parameters near the defects of the cable buffer layer.

[0017] As a preferred scheme of the high-voltage cable line operating status inversion method described in the present invention, wherein: the establishment of a multi-physics field simulation model of the electromagnetic field, temperature field and flow field of the cable tunnel and a field-circuit coupling model includes analyzing the influence of the tunnel flow field and operating conditions on the cable temperature and electromagnetic field parameters by studying the changing characteristics of the electromagnetic field and temperature field of the cable under steady-state and transient conditions.

[0018] As a preferred scheme of the high-voltage cable line operation status inversion method described in the present invention, wherein: the establishment of a multi-physics field simulation model of the electromagnetic field, temperature field and flow field of the cable tunnel and a field-circuit coupling model includes, based on the multi-physics field coupling model of the cable tunnel, obtaining key parameters and characteristic quantities of line operation; the key parameters of line operation include cable temperature and electromagnetic field.

[0019] As a preferred scheme of the high-voltage cable line operation status inversion method described in the present invention, the inversion of tunnel cables and typical cable defect faults under different working conditions includes obtaining the temperature distribution of tunnel cables under different working conditions through electromagnetic heat flow multi-physics field coupling simulation of tunnel cables; obtaining the influence of different defects on the electric field and temperature state parameters of the cable through multi-physics field simulation of typical defects of cable accessories and cable buffer layer defects, and then providing early warning for cable operation through local discharge and current state indicators, and also comparative analysis can be carried out with the local discharge, temperature and current parameters obtained from the on-site cables.

[0020] The types of defects of the typical cable faults are not limited to the above types. For example, the interface defects of the cable accessories in the embodiment may be air gap defects, scratch defects or charge accumulation in addition to copper sheet defects; the interface defects of the cable buffer layer in the embodiment may be water blocking powder precipitation defects, white spot defects and poor contact in addition to air gap defects.

[0021] As a preferred solution of the high-voltage cable line operation status inversion system described in the present invention, the system includes a data acquisition module, a data processing module, a simulation model module, and an analysis module; the data acquisition module is used to collect parameter data and transmit the collected data to the data processing module; the data processing module is used to process the data; the simulation model module is used to construct an electromagnetic thermal multi-physics field simulation model of cable accessories and their defects, a multi-physics field simulation model of a cable buffer layer and its defects, and a multi-physics field simulation model of the electromagnetic field, temperature field and flow field of a cable tunnel and a field-circuit coupling model; the analysis module is used to analyze the model output results, as well as comparative analysis between data.

[0022] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and is characterized in that when the processor executes the computer program, the steps of a method for inverting the operating status of a high-voltage cable line are implemented.

[0023] A computer-readable storage medium stores a computer program, wherein the computer program, when executed by a processor, implements the steps of a method for inverting the operating status of a high-voltage cable line.

[0024] Beneficial effects of the present invention: 1) Multi-physics field coupling simulation of cable tunnels

[0025] Considering the flow field distribution of the cable tunnel, establishing a multi-physics field coupling simulation model of the electromagnetic field, temperature field and fluid in the cable tunnel is the key to the present invention. On the basis of the multi-physics field coupling model, a field-circuit coupling model is established to simulate the operating conditions of the tunnel cable under different grounding conditions. The voltage and current parameters obtained by the circuit model are used as input parameters for the multi-physics field coupling simulation of the tunnel cable. The influence of the grounding state on the key parameters of the cable line operation is obtained, which is the difficulty and key to the simulation and reproduction of the cable line state under tunnel conditions. Tunnel cable simulation can realize multi-physics field simulation of the cable group in steady state, transient state, different tunnel conditions and different grounding conditions, and can extract key parameters such as the electromagnetic field and temperature of the cable under different conditions.

[0026] 2) Simulation of typical cable defects

[0027] Abnormal heating of cable joints, partial discharge of terminals or joints, and ablation of cable buffer layers are typical defects or faults in the operation of cable equipment. The simulation of typical cable defects is an important part of the inversion of cable tunnel operation status. The simulation model of cable accessories (intermediate joints, terminals) can realize the study of the influence of interface state, impurities and cable operation state on the electric field distortion and heating of accessories. The simulation model of cable buffer layer can realize the study of the influence of interface contact, water seepage and sheath circulation on cable buffer layer faults. It can extract characteristic parameters such as electromagnetic field and temperature near typical cable defects, and realize the simulation reproduction and simulation inversion of typical cable defects.

[0028] 3) Inversion of cable line status under tunnel conditions

[0029] The key to this patent is the simulation and reproduction of the normal state of the cable line under tunnel conditions and the inversion of defect simulation. Through the multi-physics field coupling simulation of the cable tunnel, the key parameters and characteristic quantities of the line operation under normal conditions are obtained; through the simulation of typical defects of the cable, the key characteristic quantities and influencing factors of the cable failure are obtained; by comparing the simulation results of the cable state parameters with the measured state parameter results, the multi-physics field simulation model and simulation parameters of the cable can be optimized. Based on the optimized simulation model and parameters, the inversion of tunnel cables and typical defect faults of cables under different working conditions can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0031] Figure 1 A schematic flow chart of a method for inverting the operating status of a high-voltage cable line is provided for one embodiment of the present invention.

[0032] Figure 2 A schematic diagram of a cable accessory simulation model for a high-voltage cable line operating status inversion method provided by an embodiment of the present invention.

[0033] Figure 3 A schematic diagram of a simulation of metal defects at the interface of cable accessories for a method for inverting the operating status of a high-voltage cable line provided by an embodiment of the present invention, wherein (a) is a copper sheet defect and (b) is a local electric field distribution.

[0034] Figure 4 A schematic diagram of electric field distribution when a cable buffer layer and an aluminum sheath are in good contact in a high-voltage cable line operation status inversion method provided by an embodiment of the present invention.

[0035] Figure 5 A schematic diagram of simulation of an air gap defect in a cable buffer layer of a high-voltage cable line operation status inversion method provided by an embodiment of the present invention.

[0036] Figure 6 A schematic diagram of a three-dimensional model of a tunnel cable group of a method for inverting the operating status of a high-voltage cable line provided by an embodiment of the present invention.

[0037] Figure 7 A schematic diagram of temperature distribution of a tunnel cable group of a high-voltage cable line operation status inversion method provided by an embodiment of the present invention, wherein (a) is the tunnel profile temperature distribution, and (b) is the tunnel temperature distribution. DETAILED DESCRIPTION

[0038] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0039] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0040] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0041] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0042] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0043] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] Example 1, reference Figure 1 , which is the first embodiment of the present invention, and provides a method for inverting the operating state of a high-voltage cable line, comprising:

[0045] S1: Collect the structure, size and material parameters of cable accessories, and establish an electromagnetic thermal multi-physics field simulation model of cable accessories and their defects.

[0046] S2: Collect the structure, size and material parameters of the cable buffer layer, and establish a multi-physics field simulation model of the cable buffer layer and its defects.

[0047] S3: Collect the cable tunnel structure and size parameters as well as the cable body structure, size and material parameters, and establish a multi-physics simulation model of the cable tunnel electromagnetic field, temperature field and flow field and a field-path coupling model.

[0048] S4: Obtain the actual measured values ​​of the cable line state parameters, compare them with the simulation results of large-scale and local defects in the cable tunnel space, and modify the multi-physics field simulation model based on the comparison results.

[0049] S5: Based on the optimized simulation model and parameters, the inversion of tunnel cables and typical cable defect faults under different working conditions is realized.

[0050] The electromagnetic thermal multi-physics field simulation model of the cable accessories and their defects is established, including setting the defect size, position and material parameters, simulating and analyzing the influence of scratches, impurity residues and water seepage defects on the composite insulation interface of the cable accessories during installation or operation on the heating and partial discharge of the cable joints, and obtaining key characteristic quantities near the accessories under different defect states.

[0051] The key characteristic quantities near the attachment under different defect states include electric field and temperature.

[0052] The model is built based on the coupling analysis model of electromagnetic field and temperature field. The mathematical model is shown in equations (1)-(3).

[0053] J=σE+jωε0ε′(1-jtanδ)E (1)

[0054]

[0055] Where: J is the current density; σ is the material conductivity; E is the electric field intensity; ω is the current angular frequency; ε0 is the dielectric constant of vacuum; ε′ is the dielectric constant of the material; δ is the dielectric loss angle. The heat transfer process of the cable is the synergistic effect of the core heat source, internal solid heat transfer, and external air convection / radiation heat dissipation. Its electric-thermal coupling control equation and boundary conditions are:

[0056]

[0057]

[0058] Where: ρ is the material density; C p is the constant pressure heat capacity; T is the temperature; k is the thermal conductivity of the material; h is the air convection heat transfer coefficient; γ is the surface radiation coefficient; ψ is the Stefan-Boltzmann constant; T amb is the external ambient temperature.

[0059] The multi-physics field simulation model of the cable buffer layer and its defects is established by setting the defect size, position and material parameters, simulating and analyzing the influence of the buffer layer moisture, water blocking powder precipitation, and poor contact between the buffer layer and the aluminum sheath on the cable operation state, and extracting the electric field and temperature characteristic parameters near the cable buffer layer defects. The mathematical model based on which the cable buffer layer is simulated is the same as formulas (1)-(4).

[0060] The establishment of a multi-physics field simulation model of the electromagnetic field, temperature field and flow field of the cable tunnel and a field-circuit coupling model includes studying the electromagnetic field and temperature field variation characteristics of the cable under steady-state and transient conditions, and analyzing the influence of the tunnel flow field and operating conditions on the cable temperature and electromagnetic field parameters.

[0061] The establishment of a multi-physics field simulation model of the electromagnetic field, temperature field and flow field of the cable tunnel and a field-circuit coupling model includes obtaining key parameters and characteristic quantities of line operation based on the multi-physics field coupling model of the cable tunnel.

[0062] The key parameters of line operation include cable temperature and electromagnetic field.

[0063] Considering the electric field difference caused by the phase difference of the three-phase cable, the potential of the three-phase cables A, B, and C are set as:

[0064] V A =252kV

[0065] V B =252e 120[deg]j kV

[0066] V C =252e -120[deg]j kV (5)

[0067] Also considering the magnetic field difference caused by the phase difference of the three-phase cable, the currents of the three-phase cables A, B, and C are set as:

[0068] I A =1783.7A

[0069] I B =1783.7e 120[deg]j A

[0070] I C =1783.7e -120[deg]j A (6)

[0071] Where [deg] represents the degree of phase; the electromagnetic field equation is used to input the solved electromagnetic loss as a heat source into the heat transfer equation to realize electromagnetic-thermal coupling. The fluid equation is constrained by using inflow and outflow conditions at the entrance and exit of the cable tunnel, as shown in equations (7)-(9):

[0072] -n·q=ρΔHu·n (7)

[0073]

[0074] -n·q=0 (9)

[0075] Equations (7) and (8) describe the boundary heat flux caused by fluid flow, where q is the heat flux; H is the constant pressure enthalpy change; u is the velocity field; T ustr is the upstream temperature. Equation (9) is the outflow condition boundary constraint.

[0076] The non-isothermal flow interface is used to achieve the coupling of heat and flow fields, as shown in equations (10) and (11). In the calculation, the fluid viscosity dissipation heat source, the upstream heat source and the boundary heat flux caused by the fluid flow are considered at the same time.

[0077]

[0078] Where: Q vd is the non-isothermal heat transfer heat source; Q turb is the upstream heat source; τ is the viscous stress tensor; u is the velocity field; q is the heat flux.

[0079] The actual measured values ​​of the cable line state parameters are obtained, compared with the simulation results of large-scale and local defects in the cable tunnel space, and the multi-physics simulation model is corrected according to the comparison results. For example, infrared imaging temperature measurement can be used to obtain the temperature distribution of the cable tunnel, and compared with the simulation results of the multi-physics field of the tunnel cable, and then the tunnel air velocity, cable material and model parameters can be adjusted for optimization.

[0080] The inversion of tunnel cables and typical cable defect faults under different working conditions includes obtaining the temperature distribution of tunnel cables under different working conditions through electromagnetic heat flow multi-physics field coupling simulation of tunnel cables; obtaining the influence of different defects on the electric field and temperature state parameters of the cable through multi-physics field simulation of typical defects of cable accessories and cable buffer layer defects, and then providing early warning for cable operation through local discharge and current state indicators. At the same time, it can also be compared and analyzed with the local discharge, temperature and current parameters obtained from the on-site cables.

[0081] Example 2, reference Figure 2-Figure 7 , which is an embodiment of the present invention, provides a method for inverting the operating status of a high-voltage cable line. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through experiments.

[0082] 1) Input the actual structure and size of the cable accessories, as shown in Table 1, establish a multi-physics field simulation model of the cable accessories, input the dielectric and thermal parameters of each layer of the cable accessories, set the boundary conditions, and mesh the cable accessories simulation model, as shown in Table 1. Figure 2 shown.

[0083] Table 1 Cable accessories structure and size

[0084]

[0085]

[0086] 2) Set the cable operating voltage parameters, use a two-dimensional profile model and add defects, set defects at the interface between the cable main insulation layer and the stress cone, and determine the defect size and location parameters. Figure 3 The figure shows the simulation diagram of the metal defect at the interface of the cable accessories. The defect size is set to 0.05*0.2cm in the two-dimensional plane, with a length of 0.2cm and a thickness of 0.05cm. The defect location is at the interface between the cable insulation layer and the stress cone. The height of the defect is 20.5cm, and the material of the defect is a copper sheet. The working condition of the existence of metal impurities at the interface of the cable accessories is simulated to obtain the electric field distribution diagram of the cable accessories.

[0087] 2. Electric field simulation implementation plan for cable buffer layer air gap defects

[0088] 1) According to the actual structure and size of the cable, a multi-physics simulation model of the cable buffer layer is established, and the dielectric and thermal parameters of each layer of the cable material are input. The cable core voltage is set to 112kV, the aluminum sheath is grounded, and the cable model of the contact state between the cable buffer layer and the aluminum sheath is established as follows: Figure 4 As shown. As can be seen from the figure, the field strength is mainly concentrated in the cable insulation layer, and the field strength of the cable core, inner and outer semi-conductive layers, buffer layer, armor layer and outer sheath is basically zero. At the junction of the cable aluminum armor layer and the buffer layer, the field strength is slightly increased. From the radial electric field distribution of the cable, it can be clearly seen that the field strength in the cable insulation layer gradually decreases from the inside to the outside, and the field strength at the interface between the armor layer and the buffer layer is about 1.2MV / m. The axial electric field distribution along the interface between the cable buffer layer and the armor layer shows that the field strength is significantly distorted at the contact point between the armor layer trough and the buffer layer, and the maximum field strength is about 1.8MV / m.

[0089] 2) Set the cable core voltage and ground the aluminum sheath. Set an air gap defect between one of the corrugated aluminum sheath troughs and the buffer layer. Obtain the electric field distribution when there is an air gap defect between the cable buffer layer and the aluminum sheath, such as Figure 5As shown in the figure, when there is an air gap between a corrugated aluminum sheath trough and the buffer layer, the maximum field strength inside the cable increases from 9.04MV / m to 14.6MV / m; from the local electric field distribution near the air gap, it can be seen that the maximum field strength is distributed at the junction of the air gap, buffer layer and armor layer. The electric field distribution of the cable radially and along the axial direction of the interface shows that the maximum field strength is distributed near the air gap, and the field strength with air gap defects is about 6 times higher than the field strength of good contact, and is also higher than the maximum field strength inside the cable insulation.

[0090] 3. Implementation plan for electromagnetic thermal-fluid coupling simulation of tunnel cables

[0091] 1) Input the actual structure and size of the tunnel and cable, as shown in Table 2. The established three-dimensional model of the tunnel cable group is as follows: Figure 6 shown.

[0092] Table 2 Cable body structure and dimensions

[0093] Serial number Cable structure Thickness(mm) Outer diameter(mm) Remark 1 conductor - 61.2 Split copper conductor 2 Conductor shielding 2 65.2 Ultra-smooth cross-linked semi-conductive material 3 insulation 24 113.2 Ultra-clean cross-linked polyethylene insulation 4 Insulation shielding 1.0 115.2 Ultra-smooth cross-linked semi-conductive material 5 Semi-conductive water layer 5 125.2 Semi-conductive buffer water blocking tape 6 Corrugated aluminum sheath 7.5 140 Aluminum + Cable Asphalt 7 Non-metallic sheath 5 150 Polyethylene + graphite

[0094] 2) Construct a set of partial differential equations for electromagnetic-thermal-fluid coupling and solve the problem. Input the operating voltage and current of different loop cables as input conditions, input the solved electromagnetic loss as a heat source into the heat transfer equation to achieve electromagnetic-thermal coupling, and analyze the impact of the tunnel on the cable operation status by changing the air flow rate in the tunnel. Set the potential of the three-phase cables A, B, and C to 225kV, 225e 120[deg]j kV, 225e -120[deg]j kV; set the A, B, and C three-phase cable currents to: 1783.7A, 1783.7e 120[deg]j A. 1783.7e 120[deg]j A.

[0095] 3) Establish a multi-physics field and circuit coupling model of the tunnel cable group, analyze the influence of the cable grounding method on the induced voltage and circulating current of the cable metal sheath, use the voltage and current obtained by the circuit model as the input of the multi-physics field simulation of the tunnel cable group, and analyze the influence of the grounding condition on the electromagnetic field and temperature field of the tunnel cable. The temperature distribution inside the cable tunnel is obtained as follows: Figure 7 As shown. Since the heat source of the cable is mainly caused by the current conducted by the conductor, and the thermal conductivity of the XLPE insulation, outer sheath and other layer structures is low, the maximum hot spot temperature is located in the conductor core, and the temperature distribution gradually decreases from the conductor core to the outer surface. Considering the air convection heat flux, the hot spot temperature of the cable conductor and the temperature of the cable outer sheath are 56.6℃ and 29℃ respectively, which are basically consistent with the temperature obtained by infrared temperature measurement of tunnel cables under the same conditions.

[0096] 4) Obtain the temperature distribution of the tunnel cable in operation on site, compare it with the simulated tunnel cable temperature, correct the simulation model and parameter settings, and simulate and invert the operation status of the tunnel cable through simulation of different working conditions.

[0097] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0098] Embodiment 3, the third embodiment of the present invention, is different from the first two embodiments in that:

[0099] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.

[0100] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0101] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0102] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0103] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0104] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

[0105] Embodiment 4 is the fourth embodiment of the present invention. This embodiment provides a high-voltage cable line operation status inversion system, including: the system includes a data acquisition module, a data processing module, a simulation model module, and an analysis module.

[0106] The data acquisition module is used to collect on-site cable operation parameters and transmit the collected data to the data processing module; the data processing module is used to process the data; the simulation model module is used to build an electromagnetic thermal multi-physics field simulation model of cable accessories and their defects, a multi-physics field simulation model of the cable buffer layer and its defects, and a multi-physics field simulation model of the electromagnetic field, temperature field and flow field of the cable tunnel and a field-circuit coupling model; the analysis module is used to analyze the model output results and the comparative analysis between data.

[0107] In actual production, when tunnel cables are in operation, they will be affected by voltage and current to generate electric and magnetic fields. The current will generate heat loss on the conductor and generate a thermal field. The air flows in the tunnel and there is a flow field. Therefore, the operation of tunnel cables involves multiple physical fields such as electricity, magnetism, heat, and flow, and there is a certain coupling relationship between the fields, especially the electromagnetic field and the thermal field, and the thermal field and the flow field. There is a strong coupling relationship. When the lengths of the three cross-connected small sections of cable are not equal and the metal sheath forms a loop, there will also be sheath circulation, which involves circuit problems. The system of the present invention can further solve this technical problem based on the setting of the method.

[0108] Specifically, after the data acquisition module obtains the operating parameters of the on-site cable, the data processing module further obtains accurate and effective operating parameters. At the same time, the data processing module can also compare the local discharge, temperature, current and other parameters obtained by the on-site cable. The analysis module compares and analyzes the local discharge, temperature, current and other parameters obtained by the on-site cable, and modifies the multi-physical field simulation model according to the comparison results.

Claims

1. A method for inverting the operating status of a high-voltage cable line, characterized in that: include, Collect the structure, size and material parameters of cable accessories, and establish an electromagnetic thermal multi-physics field simulation model of cable accessories and their defects; Collect the structure, size and material parameters of the cable buffer layer and establish a multi-physics field simulation model of the cable buffer layer and its defects; Collect the cable tunnel structure and size parameters as well as the cable body structure, size and material parameters, and establish a multi-physics simulation model of the cable tunnel electromagnetic field, temperature field and flow field and a field-circuit coupling model; Obtain the actual measured values ​​of the cable line state parameters, compare them with the simulation results of large-scale and local defects in the cable tunnel space, and modify the multi-physics field simulation model based on the comparison results; Based on the optimized simulation model and parameters, the inversion of tunnel cables and typical cable defect faults under different working conditions is realized.

2. A high-voltage cable line operating status inversion method according to claim 1, characterized in that: The electromagnetic thermal multi-physics field simulation model of the cable accessories and their defects is established, including setting the defect size, position and material parameters, simulating and analyzing the influence of scratches, impurity residues and water seepage defects on the composite insulation interface of the cable accessories during installation or operation on the heating and partial discharge of the cable joints, and obtaining key characteristic quantities near the accessories under different defect states.

3. A high-voltage cable line operating state inversion method as claimed in claim 2, characterized in that: The key characteristic quantities near the attachment under different defect states include electric field and temperature.

4. A method for inverting the operating status of a high-voltage cable line according to claim 3, characterized in that: The multi-physics field simulation model of the cable buffer layer and its defects is established, including setting the defect size, position and material parameters, simulating and analyzing the influence of moisture on the buffer layer, precipitation of water-blocking powder, and poor contact between the buffer layer and the aluminum sheath on the cable operation state, and extracting the electric field and temperature characteristic parameters near the cable buffer layer defects.

5. A method for inverting the operating status of a high-voltage cable line according to claim 4, characterized in that: The establishment of a multi-physics field simulation model of the electromagnetic field, temperature field and flow field of the cable tunnel and a field-circuit coupling model includes studying the electromagnetic field and temperature field variation characteristics of the cable under steady-state and transient conditions, and analyzing the influence of the tunnel flow field and operating conditions on the cable temperature and electromagnetic field parameters.

6. A high-voltage cable line operating status inversion method as claimed in claim 5, characterized in that: The establishment of a multi-physics field simulation model of electromagnetic field, temperature field and flow field of the cable tunnel and a field-circuit coupling model includes obtaining key parameters and characteristic quantities of line operation based on the multi-physics field coupling model of the cable tunnel; The key parameters of line operation include cable temperature and electromagnetic field.

7. A method for inverting the operating status of a high-voltage cable line according to claim 6, characterized in that: The inversion of the tunnel cable and the typical defect faults of the cable under different working conditions includes obtaining the temperature distribution of the tunnel cable under different working conditions through electromagnetic heat flow multi-physics field coupling simulation of the tunnel cable; Through multi-physics field simulation of typical defects in cable accessories and cable buffer layer defects, the influence of different defects on the electric field and temperature state parameters of the cable is obtained, and then early warning of cable operation is given through electric field and temperature indicators. At the same time, comparative analysis can also be carried out with the local discharge, temperature and current parameters obtained from the on-site cables.

8. A system using a high-voltage cable line operating state inversion method as claimed in any one of claims 1 to 7, characterized in that: The system includes a data acquisition module, a data processing module, a simulation model module, and an analysis module; The data acquisition module is used to collect on-site cable operation parameters and transmit the collected data to the data processing module; The data processing module is used to process the data; The simulation model module is used to construct an electromagnetic thermal multi-physics field simulation model for establishing cable accessories and their defects, a multi-physics field simulation model for establishing a cable buffer layer and its defects, and a multi-physics field simulation model for establishing an electromagnetic field, temperature field and flow field of a cable tunnel and a field-path coupling model; The analysis module is used to analyze the model output results and compare the data.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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