Numerical simulation method for space charge measurement of oil-paper insulation considering composite electric field conditions

Abstract

The invention proposes a numerical simulation method for measuring space charge of oil-paper insulation considering composite electric field conditions, and relates to the technical field of simulation of space charge measurement of oil-paper insulation, including: obtaining actual operating environment parameters of a high-voltage transformer, and performing multi-physical field coupling calculations between the fluid field, electrostatic field and temperature field of the high-voltage transformer; establishing a bipolar carrier transport model, and collecting structural parameters and properties of the oil-paper insulation, and setting material parameters at the same time; setting boundary conditions of each physical field, and establishing corresponding charge transport reaction equations; initializing the system of the oil-paper insulation to configure solver-related parameters, and calculating the charge transport reaction equations through the solver to obtain simulation results; and improving the simulation results to obtain numerical simulation results of space charge measurement of the oil-paper insulation; the invention overcomes the limitations of field test conditions, solves the technical problem of low detection resolution of measuring equipment, and ensures the real-time precise observation of dynamic response of charge.

Description

Technical Field

[0001] The invention relates to the technical field of oil-paper insulation space charge measurement simulation, and in particular to a numerical simulation method for oil-paper insulation space charge measurement considering a composite electric field working condition. Background Art

[0002] High-voltage transformer equipment has the characteristics of high operating voltage level, high internal temperature, and large capacity. Its valve-side winding needs to withstand the effects of DC, power frequency fundamental wave and multiple harmonic composite electric fields at the same time. Oil-paper insulation is the main internal insulation form of high-voltage transformers. Under the continuous damage of composite voltage partial discharge and space charge accumulation, its insulation performance will continue to deteriorate and develop into insulation flashover or breakdown, which will eventually cause equipment failure. Under the action of DC electric field, space charge will move directionally inside the oil-paper insulation, and the space charge test system based on the electroacoustic pulse method can accurately measure it. Unlike the test under DC electric field, the problems of poor signal-to-noise ratio, low detection phase resolution, and difficult phase identification and recovery processing of raw data in the direct detection technology of space charge under AC electric field are technical difficulties that have not been completely solved or the processing methods have not been widely promoted and applied.

[0003] Current research on numerical simulation of space charge focuses on simulating the charge response characteristics under DC conditions, while there are few studies on the simulation of charge transport in oil-paper insulation under AC and AC / DC composite superposition electric fields. The technical problem of low detection resolution of measuring equipment has not yet been solved, and it is impossible to provide experimental and theoretical references for the subsequent defect analysis of oil-immersed paper insulation of high-voltage transformers and the optimization of insulation coordination. Summary of the invention

[0004] The purpose of the present invention is to provide a numerical simulation method for measuring space charge of oil-paper insulation taking into account composite electric field conditions, which can overcome the limitations of field test conditions, solve the technical problem of low detection resolution of measuring equipment, and ensure the real-time accuracy of accurate observation of dynamic response of charge.

[0005] The technical solution of the present invention is:

[0006] The present application provides a numerical simulation method for measuring space charge of oil-paper insulation considering a composite electric field condition, which comprises the following steps:

[0007] S1. Obtain the actual operating environment parameters of the high-voltage transformer, and perform multi-physics field coupling calculations between the fluid field, electrostatic field, and temperature field of the high-voltage transformer;

[0008] S2. Establish a bipolar carrier transport model through coupling calculation results, collect structural parameters and properties of oil-paper insulation, and set material parameters;

[0009] S3. Setting the boundary conditions of each physical field according to the structural parameters and properties of the oil-paper insulation, and establishing the charge transport reaction equation corresponding to the boundary conditions of each physical field;

[0010] S4. Initialize the oil-paper insulation system according to the bipolar carrier transport model and material parameters to configure solver related parameters, and calculate the charge transport reaction equations corresponding to the boundary conditions of each physical field through the solver to obtain the simulation results including the internal body charge;

[0011] S5. Improve the simulation results including the internal volume charge to obtain the numerical simulation results of the space charge measurement of oil-paper insulation.

[0012] Furthermore, in step S1, the calculation formula of the multi-physics field coupling calculation includes:

[0013] , , , where Sa represents the sum of the changes in the concentration of various carriers caused by the physical processes of space charge trapping, detrapping and recombination, and is regarded as the reaction source term. a represents the carrier type, x represents the location of the charge in the medium, n a for t The carrier concentration at time j ɑ For time t The current formed by the diffusion and migration of carriers at time E for t The electric field strength at the time, ρ all for t The algebraic sum of all carrier densities at the moment, is the dielectric constant of vacuum, is the relative dielectric constant, µ a For the carrier t The mobility of the moment, D f is the diffusion rate.

[0014] Furthermore, in step S3, the calculation formulas of the charge transport reaction equations corresponding to the boundary conditions of the above-mentioned physical fields include: , , , , where j i is the injected current density, T a is the temperature at the electrode, A is the Richardson constant, arepresents the carrier type, e is the electron charge, k is the Boltzmann constant, E a is the electric field strength at the electrode, is the dielectric constant of vacuum, is the relative dielectric constant, ω i is the Schottky injection barrier at the interface, is the free electron concentration, is the trapped hole concentration, is the trapped electron concentration, is the free hole concentration, j o is the hole extraction current, C is the extraction rate, µ µ is the charge mobility, n µ is the charge concentration, E is the electric field strength, is the free electron coefficient, is the free hole coefficient, is the trapped electron coefficient, is the trap hole coefficient, is the recombination coefficient between free electrons and trapped holes, is the recombination coefficient between free holes and trapped electrons, is the recombination coefficient between trapped electrons and trapped holes, h µ is a free hole, e µ For free electrons, h t For the trap hole, e t Trapped electrons, B e is the electron trapping rate, B h is the hole penetration rate, is the electron trap concentration, is the hole trap concentration.

[0015] Furthermore, in step S4, the solver adopts a transient solver, and solves the charge transport reaction equations corresponding to the boundary conditions of each physical field through the backward difference formula of the transient solver to obtain the simulation results including the internal body charge.

[0016] Furthermore, in step S5, the calculation process of improving the simulation results including the internal body charge includes:

[0017] , , where g(x) is the interface induced charge peak with Gaussian normal distribution characteristics, x is the position of the charge in the medium, ω is the half peak width, cd 1 is the total charge, f ( x ) is the space charge distribution after perfect processing.

[0018] Compared with the prior art, the present invention has at least the following advantages or beneficial effects:

[0019] (1) The present invention provides a numerical simulation method for measuring the space charge of oil-paper insulation considering the composite electric field conditions. By establishing a bipolar carrier transport model for describing the charge behavior of oil-paper insulation for high-voltage transformers, the model is based on the coupling of the convection-reaction equation, the Poisson equation and the carrier transport equation, taking into account the charge conservation law, injection, extraction, trapping, detrapping and recombination and other charge microscopic physical processes, as well as the technical difficulties of phase recognition and data storage in the direct detection technology of space charge under AC electric field. Through numerical simulation, iterative calculation between multiple physical fields such as dilute material transfer, electric field and temperature field is realized, overcoming the limitations of field test conditions, and performing high phase resolution space charge dynamic response detection simulation on oil-paper insulation under AC electric field and AC / DC composite electric field, significantly improving the accuracy of space charge measurement of oil-paper insulation under composite electric field conditions, solving the technical problem of low detection resolution of measurement equipment, and ensuring the real-time accurate observation of charge dynamic response.

[0020] (2) The present invention takes into account the actual working conditions that the valve side winding needs to withstand the AC and DC composite superposition electric field at the same time and the carrier mobility is affected by the temperature electric field. Through numerical simulation, the multi-physical field coupling cycle iteration of fluid field, electric field and temperature field is realized, and the distribution of spatial charge and electric field intensity distribution are calculated, which provides experimental and theoretical references for the later analysis of oil-immersed paper insulation defects and optimization of insulation coordination of high-voltage transformers. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 A step diagram of a numerical simulation method for measuring space charge of oil-paper insulation considering a composite electric field condition according to the present invention;

[0023] Figure 2Schematic diagram of the transfer mechanism of the bipolar carrier model;

[0024] Figure 3 It is a schematic diagram of polarization voltage waveform under AC / DC superposition composite electric field;

[0025] Figure 4 (a) is the spatial charge distribution result diagram of oil-paper insulation before AC / DC ratio 1:1 composite voltage polarization, (b) is the spatial charge distribution result diagram of oil-paper insulation after AC / DC ratio 1:1 composite voltage polarization. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0028] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0029] It should be noted that, in this article, the term "include" or any other variation thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "include..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0030] In the description of this application, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "disposed" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0031] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0032] Example 1

[0033] See also Figure 1 , Figure 1 Shown is a step diagram of a numerical simulation method for measuring space charge of oil-paper insulation taking into account composite electric field conditions provided in an embodiment of the present application.

[0034] The present application provides a numerical simulation method for measuring space charge of oil-paper insulation considering a composite electric field condition, which comprises the following steps:

[0035] S1. Obtain the actual operating environment parameters of the high-voltage transformer, and perform multi-physics field coupling calculations between the fluid field, electrostatic field and temperature field of the high-voltage transformer; S2. Establish a bipolar carrier transmission model based on the coupling calculation results, collect the structural parameters and properties of the oil-paper insulation, and set the material parameters;

[0036] S3. Setting the boundary conditions of each physical field according to the structural parameters and properties of the oil-paper insulation, and establishing the charge transport reaction equation corresponding to the boundary conditions of each physical field;

[0037] S4. Initialize the oil-paper insulation system according to the bipolar carrier transport model and material parameters to configure solver related parameters, and calculate the charge transport reaction equations corresponding to the boundary conditions of each physical field through the solver to obtain the simulation results including the internal body charge;

[0038] S5. Improve the simulation results including the internal volume charge to obtain the numerical simulation results of the space charge measurement of oil-paper insulation.

[0039] It should be noted that the bipolar carrier transport model is a fluid transport model, which is established by coupling calculation through the actual operating environment of the high-voltage transformer. Figure 2, the model comprehensively considers multiple physical processes such as carrier injection, transport, trapping, recombination, and extraction. Space charges will migrate to both sides of the oil-paper insulation along the thickness direction under the action of electric field force. In this process, some charges may be captured by traps to form trapped charges. This process is called the trapping process (the dotted arrows are the trapping process); at a certain trap energy level in the medium, when the trapped charges are excited by energy, they will escape from the traps and become free charges again. This process is called the detrapping process (the solid arrows next to the dotted lines are the detrapping process). At the same time, recombination will also occur between charges of opposite polarities, including free charges and trapped charges. During the charge transfer process, part of it migrates in the conduction band, and part of it migrates by hopping conductance. There is also a probability of being captured by deep traps or recombining with neighboring electrons and holes and then releasing energy and disappearing. In fact, this model can be used to describe the migration of any type of carriers under an electric field and the interactions between the carriers, such as trap capture, recombination of positive and negative carriers, etc. By setting different model boundary conditions, it can characterize various physical processes such as charge injection from the plate to the medium and charge deposition from the electrode under different mechanisms.

[0040] The set material parameters mainly include material properties such as relative dielectric constant, density, thermal conductivity, constant-pressure heat capacity of oil-paper insulation materials, as well as parameters such as injection barrier, extraction rate, mobility, diffusion coefficient, recombination coefficient, trapping and detrapping rates of electron holes.

[0041] As a preferred implementation, in step S1, the calculation formula for multi-physics field coupling calculation includes:

[0042] Convection-reaction equation:

[0043] , Poisson's equation: , carrier transport equation:

[0044] , where Sa represents the sum of the changes in the concentration of various carriers caused by the physical processes of space charge trapping, detrapping and recombination, and is regarded as the reaction source term. a represents the carrier type, x represents the location of the charge in the medium, n a for t The carrier concentration at time j ɑ For time t The current formed by the diffusion and migration of carriers at time E for t The electric field strength at the time, ρ all for t The algebraic sum of all carrier densities at the moment, is the dielectric constant of vacuum, is the relative dielectric constant, µ a For the carrier t The mobility of the moment, D f is the diffusion rate.

[0045] It should be noted that in the process of multi-physics field coupling between fluid field, electric field and temperature field, fluid mechanics theory is used to deal with continuous convection reaction equation and carrier transport equation. The first convection-reaction equation is used to simulate the transport of various carriers. The left side is the reaction term describing carrier trapping and recombination, and the right side is the convection term describing the transport process. The equation involved in electrostatic induction theory is Poisson's equation, which describes the quantitative relationship between charge density and electric field distribution. The third carrier transport equation represents the instantaneous current density of each carrier and describes the migration and diffusion process in detail. The transport reaction of various carriers and current fluxes will cause temperature changes and electric field changes. Temperature changes and electric field distortion will also affect mobility and thus affect carrier transport.

[0046] As a preferred implementation, in step S3, the calculation formula of the charge transport reaction equation corresponding to the boundary conditions of each physical field includes:

[0047] , , , where j i is the injected current density, T a is the temperature at the electrode, A is the Richardson constant, a represents the carrier type, e is the electron charge, k is the Boltzmann constant, E a is the electric field strength at the electrode, is the dielectric constant of vacuum, is the relative dielectric constant, ω i is the Schottky injection barrier at the interface, is the free electron concentration, is the trapped hole concentration, is the trapped electron concentration, is the free hole concentration, j o is the hole extraction current, C is the extraction rate, µ µ is the charge mobility, nµ is the charge concentration, E is the electric field strength, is the free electron coefficient, is the free hole coefficient, is the trapped electron coefficient, is the trap hole coefficient, is the recombination coefficient between free electrons and trapped holes, is the recombination coefficient between free holes and trapped electrons, is the recombination coefficient between trapped electrons and trapped holes, h µ is a free hole, e µ For free electrons, h t For the trap hole, e t Trapped electrons, B e is the electron trapping rate, B h is the hole penetration rate, is the electron trap concentration, is the hole trap concentration.

[0048] It should be noted that by setting different model boundary conditions, various physical processes such as charge injection from the plate to the medium and charge deposition from the electrode under different mechanisms can be characterized. The electrostatic field sets the electrode potential boundary conditions on both sides, calculates the Poisson equation, and sets the potential to the AC / DC composite voltage. The schematic diagram of the simulation environment of the AC / DC composite electric field can be found in Figure 3 , the horizontal axis T is the polarization time, the vertical axis V nis the magnitude of polarization voltage; the boundary conditions of the fluid field need to be determined by the injection and precipitation of carriers at the interface between the electrode and the dielectric: the injection adopts the Schottky injection model that considers the attraction of image charges on the plate and the electric field to reduce the metal-insulator interface barrier. For precipitation, it is assumed that the electrode has no blocking effect on the precipitation of carriers, that is, there is no precipitation barrier. At this time, the carrier will be precipitated from the electrode in the form of ohmic contact, and the charge reaction equation and the transport equation are edited. It is worth noting that under the AC / DC superposition composite voltage condition, the oil-paper insulation will be subjected to alternating voltage polarity, and it is no longer like the DC electric field where the electrodes on both sides always maintain an injection or extraction state. The space charge at the electrodes on both sides is repeatedly injected and extracted, and the change of space charge with time before and after the polarity reversal under the AC / DC composite voltage of different proportions is not mirrored with time 0 as the symmetry axis. The charge accumulated on the electrode side will dissipate to varying degrees at the next moment. In order to adapt to such changes, starting from the mechanism of dielectric charge movement, the polarization voltage phase characteristics are used to measure the space charge of certain specific phases to study the space charge characteristics under AC electric field and AC / DC superposition electric field. The instantaneous voltage is collected and the voltage phase information is calculated by inverse trigonometric function. The motion state of the space charge on the two electrode sides is determined in real time by phase detection at the positive and negative alternation of the polarization voltage at a certain moment.

[0049] As a preferred implementation, in step S4, the solver adopts a transient solver, and solves the charge transport reaction equations corresponding to the boundary conditions of each physical field through the backward difference formula of the transient solver to obtain the simulation results including the internal body charge.

[0050] As a preferred implementation, in step S5, the calculation process of improving the simulation results including the internal body charge includes:

[0051] , , where g(x) is the interface induced charge peak with Gaussian normal distribution characteristics, x is the position of the charge in the medium, ω is the half peak width, cd 1 is the total charge, f ( x ) is the space charge distribution after perfect processing.

[0052] It should be noted that in the process of improving the simulation results containing internal volume charge, it is necessary to first artificially expand the surface charge SCD into a wave packet with the same resolution as the measurement result after simulating the internal volume charge density of the medium and the interface induced surface charge density respectively, and then alias the surface charge SCD with the volume charge, and convolute the total charge with the interface induced charge peak with Gaussian normal distribution characteristics to obtain the space charge in the form of a wave packet similar to the actual measurement result; the surface charge SCD calculation formula is:

[0053] , where SCD 0 is the electrode surface charge density, SCD d is the surface charge density of the electrode on the other side, is the dielectric constant of vacuum, is the relative dielectric constant, E 0 is the electrode electric field strength, E d is the electric field strength of the electrode on the other side; where the surface charge SCD is SCD 0 and SCD d A general term for .

[0054] Example 2

[0055] According to Example 1, the AC / DC composite field is set to be a 1:1 superposition of AC and DC, each field component is 15 kV / mm, 8 different phases are selected to collect space charge, and the simulated polarization time is 3000 s. Under the AC / DC composite voltage, due to the superposition of a certain amount of DC component, the waveform of the space charge is no longer symmetrical, and the phases in the positive half cycle are more than the phases in the negative half cycle. See Figure 4 It can be seen that the charge density peak on the electrode is positive only at 270°, while the other phases are negative, and the peak increases successively at -36° / 216°, 0° / 180°, 36° / 144°, and 90° phases. After polarization, there is obvious accumulation of opposite polarity charges near the electrode.

[0056] It can be understood that the structure shown in the figure is only for illustration, and the numerical simulation method for measuring space charge of oil-paper insulation considering the composite electric field condition may also include more or fewer components than those shown in the figure, or have a different configuration than those shown in the figure. Each component shown in the figure can be implemented by hardware, software or a combination thereof.

[0057] In the embodiments provided in the present application, it should be understood that the disclosed method can also be implemented in other ways. The embodiments described above are merely schematic, for example, the flowchart or block diagram in the accompanying drawings shows the possible implementation architecture, functions and operations of the method and computer program product according to multiple embodiments of the present application. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the module, a program segment or a part of a code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or the flowchart, and the combination of the boxes in the block diagram and / or the flowchart can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0058] In addition, the functional modules in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

[0059] If the function is implemented in the form of a software function 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 application can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. 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, and other media that can store program codes.

[0060] In summary, the numerical simulation method for measuring the space charge of oil-paper insulation considering the composite electric field conditions provided in the embodiment of the present application establishes a bipolar carrier transport model for describing the charge behavior of oil-paper insulation for high-voltage transformers. The model is based on the coupling of the convection-reaction equation, the Poisson equation and the carrier transport equation, and takes into account the charge conservation law, injection, extraction, trapping, detrapping and recombination and other charge microscopic physical processes, as well as the technical difficulties of phase recognition and data storage in the direct detection technology of space charge under AC electric field. Through numerical simulation, iterative calculation between multiple physical fields such as dilute material transfer, electric field and temperature field is realized, which overcomes the limitations of field test conditions, solves the technical problem of low detection resolution of measuring equipment, and ensures the real-time precise observation of dynamic response of charge.

[0061] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0062] It will be apparent to those skilled in the art that the present application is not limited to the details of the exemplary embodiments described above, and that the present application can be implemented in other specific forms without departing from the spirit or essential features of the present application. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the present application is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present application. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A numerical simulation method for measuring space charge of oil-paper insulation considering composite electric field conditions, characterized in that: The following steps are involved: S1. Obtaining actual operating environment parameters of the high-voltage transformer, and performing multi-physical field coupling calculation between the fluid field, electrostatic field and temperature field of the high-voltage transformer; wherein the calculation formula of the multi-physical field coupling calculation includes: Where Sa represents the sum of the changes in the concentration of various carriers caused by the trapping, detrapping and composite physical processes of space charge, a represents the type of carrier, x represents the position of the charge in the medium, and n represents the carrier type. a is the carrier concentration at time t, j ɑ is the current formed by the diffusion and migration of carriers at time t, E is the electric field strength at time t, ρ all is the algebraic sum of all carrier densities at time t, ε0 is the vacuum dielectric constant, ε r is the relative dielectric constant, μ a is the carrier mobility at time t, D f is the diffusion rate; S2. Establish a bipolar carrier transport model through coupling calculation results, collect structural parameters and properties of oil-paper insulation, and set material parameters; S3. Setting the boundary conditions of each physical field according to the structural parameters and properties of the oil-paper insulation, and establishing the charge transport reaction equation corresponding to the boundary conditions of each physical field; wherein the calculation formula of the charge transport reaction equation corresponding to the boundary conditions of each physical field includes: j o =Cμ μ n μ |Y| In the formula, j i is the injected current density, T a is the electrode temperature, A is the Richardson constant, a represents the carrier type, e is the electron charge, k is the Boltzmann constant, E a is the electric field strength at the electrode, ε0 is the vacuum dielectric constant, ε r is the relative dielectric constant, ω i is the Schottky injection barrier at the interface, is the free electron concentration, is the trapped hole concentration, is the trapped electron concentration, is the free hole concentration, j o is the hole extraction current, C is the extraction rate, μ μ is the charge mobility, n μ is the charge concentration, E is the electric field strength, is the free electron coefficient, is the free hole coefficient, is the trapped electron coefficient, is the trap hole coefficient, is the recombination coefficient between free electrons and trapped holes, is the recombination coefficient between free holes and trapped electrons, is the recombination coefficient between trapped electrons and trapped holes, h μ is a free hole, e μ is a free electron, h t is the trap hole, e t Trapped electrons, B e is the electron trapping rate, B h is the hole penetration rate, is the electron trap concentration, is the hole trap concentration; S4. Initialize the oil-paper insulation system according to the bipolar carrier transport model and material parameters to configure solver related parameters, and calculate the charge transport reaction equations corresponding to the boundary conditions of each physical field through the solver to obtain the simulation results including the internal body charge; S5. The simulation results including the internal volume charge are improved to obtain the numerical simulation results of the space charge measurement of the oil-paper insulation; wherein the calculation process of improving the simulation results including the internal volume charge includes: f(x)=cd1*g(x) Where g(x) is the interface induced charge peak with Gaussian normal distribution characteristics, x is the position of the charge in the medium, ω is the half-peak width, cd1 is the total charge, and f(x) is the spatial charge distribution after perfect processing.

2. The numerical simulation method for measuring space charge of oil-paper insulation considering composite electric field conditions as claimed in claim 1 is characterized in that: In step S4, the solver adopts a transient solver, and solves the charge transport reaction equation corresponding to the boundary conditions of each physical field through the backward difference formula of the transient solver to obtain the simulation result including the internal body charge.

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