Experimental simulation system and method for core burr fault characteristics of oil-immersed transformer

Abstract

The invention discloses an experimental simulation system for core burr fault characteristics of an oil-immersed transformer, and the system constructs a two-dimensional axisymmetric simulation model of the transformer, sets a simulated core burr defect, and obtains electric field distribution data and voltage distribution data under a normal working condition and the simulated core burr defect through finite element simulation; a corresponding simulated iron core burr defect is arranged in an oil-immersed transformer entity, a transformer no-load test is carried out on the oil-immersed transformer entity, a partial discharge signal is obtained through partial discharge detection equipment, and the electric field distribution data and the voltage distribution data are combined through the partial discharge signal to determine the core burr defect of the oil-immersed transformer entity. And evaluating to obtain the damage degree of the burr defect of the simulated iron core. According to the invention, the diagnosis accuracy and controllability of the burr defect of the iron core of the oil-immersed transformer are improved.

Description

An experimental simulation system and method for the characteristics of burr faults in the core of an oil-immersed transformer. Technical Field

[0001] This invention relates to the field of transformer defect fault diagnosis technology, specifically to an experimental simulation system and method for the characteristics of burr faults in the core of an oil-immersed transformer. Background Technology

[0002] As a core piece of equipment in the power system, the operational reliability of oil-immersed transformers directly affects the safety and stability of the entire power grid. The internal electric field distribution of a transformer is complex, especially in the composite insulation system composed of key components such as the core, windings, insulating oil, and grounding shield. Any local electric field distortion can lead to insulation degradation, or even serious faults such as insulation breakdown. In particular, due to mechanical stress during manufacturing, transportation, or installation, the transformer core is prone to developing microscopic defects such as burrs and protrusions on its surface. These burr defects distort the surrounding electric field, causing a sharp increase in local field strength, which can then lead to serious faults such as partial discharge and even arc discharge. If not detected in time, continuous discharge will accelerate the aging of the insulation material, potentially developing into catastrophic accidents such as inter-turn short circuits or main insulation breakdown. Therefore, understanding the electric field distortion and partial discharge characteristics of burr defects in the transformer core is crucial for optimizing the insulation structure and assessing the condition of oil-immersed transformers. Summary of the Invention

[0003] The purpose of this invention is to provide an experimental simulation system and method for the fault characteristics of burrs in the core of oil-immersed transformers. This invention improves the diagnostic accuracy and controllability of burr defects in the core of oil-immersed transformers by combining simulation and experiment.

[0004] To achieve this objective, the present invention provides an experimental simulation system for the fault characteristics of core burrs in oil-immersed transformers. The system comprises: a simulation analysis module for constructing a two-dimensional axisymmetric simulation model of the transformer based on its actual structure, and setting up simulated core burr defects. Through finite element simulation, it acquires electric field distribution data and voltage distribution data of the two-dimensional axisymmetric simulation model of the transformer under normal operating conditions and simulated core burr defects, respectively. An experimental simulation module is used to set up simulated core burr defects corresponding to the two-dimensional axisymmetric simulation model of the transformer within the oil-immersed transformer entity, and to conduct a no-load test on the oil-immersed transformer entity. Partial discharge detection equipment is used to detect partial discharge in the oil-immersed transformer entity to obtain partial discharge signals. The degree of harm caused by the simulated core burr defects is assessed by combining the partial discharge signals with the electric field distribution data and voltage distribution data.

[0005] Preferably, before the finite element simulation, the simulation analysis module is also used to define the material properties of each structure in the two-dimensional axisymmetric simulation model of the transformer, and to set the boundary conditions and meshing rules of the two-dimensional axisymmetric simulation model of the transformer according to the electrostatic loop theorem.

[0006] Preferably, each structure includes an iron core, a ground shield, an oil gap, and a winding, and the material properties include dielectric constant and electrical conductivity.

[0007] Preferably, in the simulation analysis module, the specific method for setting the simulated core burr defect is as follows: The two-dimensional axisymmetric simulation model of the transformer adopts a three-phase five-column core structure. The three-phase five-column core structure consists of five parallel core columns, including three parallel main core columns and two side yoke columns. Three sets of high-voltage windings are wound on the outside of the three main core columns, and the grounding shield is arranged between the high-voltage and low-voltage windings. The three-phase five-column core structure is provided with simulated core middle burrs, simulated core top short burrs, and simulated core top long burrs. The simulated core middle burrs are set in the middle of the core column, and the simulated core top short burrs and simulated core top long burrs are both set at the top of the core column.

[0008] Preferably, in the simulation analysis module, the step of setting the boundary conditions and meshing rules of the two-dimensional axisymmetric simulation model of the transformer according to the electrostatic loop theorem is specifically used to: by adding the electrostatic field physics module, set the boundary conditions and meshing rules of the two-dimensional axisymmetric simulation model of the transformer according to the electrostatic loop theorem, so that the electrostatic field around the core, grounding shield, oil gap and winding components satisfies the electrostatic loop theorem.

[0009] Preferably, in the simulation analysis module, the boundary conditions of the two-dimensional axisymmetric simulation model of the transformer are specifically configured to satisfy the following: in, The interfacial potential of the oil gap; Let i be the interface potential of conductor i, where 2 ≤ i ≤ 4. When i = 2, the conductor is the iron core; when i = 3, the conductor is the ground shield; and when i = 4, the conductor is the winding. is the dielectric constant of the oil gap; Let be the dielectric constant of conductor i; Let be the interface normal vector of the interface between the oil gap and conductor i.

[0010] Preferably, in the simulation analysis module, the meshing rules for the two-dimensional axisymmetric simulation model of the transformer are specifically used as follows: for the two-dimensional axisymmetric simulation model of the transformer, different meshing rules with different precision are applied to different regions; for the contact area between the ground screen and the core at the core burr defect, the local mesh is refined with the minimum element size within D; for the area outside the core burr defect, a gradually thickening meshing strategy is adopted.

[0011] Preferably, in the experimental simulation module, the partial discharge signal obtained by partial discharge detection using a partial discharge detection device is specifically used for: partial discharge detection using a multi-channel partial discharge comprehensive analyzer. A partial discharge measuring instrument input unit is arranged on each of the high-voltage side A-phase, high-voltage side C-phase, and medium-voltage side A-phase of the winding inside the oil-immersed transformer. Channel 1 of the multi-channel partial discharge comprehensive analyzer detects the partial discharge signal on the high-voltage side A-phase, channel 2 detects the partial discharge signal on the high-voltage side C-phase, channel 3 detects the partial discharge signal on the medium-voltage side A-phase, and channel 4 detects the partial discharge signal at the core by arranging a current sensor on the grounding wire of the core grounding bushing.

[0012] Preferably, in the experimental simulation module, the step of assessing the severity of simulated core burr defects by combining partial discharge signals with electric field distribution data and voltage distribution data is specifically used for: performing correlation analysis between the electric field distribution data and voltage distribution data and the partial discharge signal; comparing the electric field distortion value and voltage distribution change value under normal operating conditions and simulated core burr defects with the electric field distribution data and voltage distribution data; extracting partial discharge characteristic parameters from the partial discharge signal; and obtaining the severity of simulated core burr defects based on the electric field distortion value, voltage distribution change value, and partial discharge characteristic parameters, combined with preset hazard level assessment rules.

[0013] This invention also provides an experimental simulation method for the fault characteristics of core burrs in oil-immersed transformers, comprising: constructing a two-dimensional axisymmetric simulation model of the transformer based on the actual structure of the oil-immersed transformer, and setting simulated core burr defects; obtaining electric field distribution data and voltage distribution data of the two-dimensional axisymmetric simulation model of the transformer under normal operating conditions and simulated core burr defects through finite element simulation; setting simulated core burr defects corresponding to the two-dimensional axisymmetric simulation model of the transformer inside the oil-immersed transformer entity, and conducting a transformer no-load test on the oil-immersed transformer entity; obtaining partial discharge signals by performing partial discharge detection on the oil-immersed transformer entity using a partial discharge detection device; and evaluating the degree of harm of the simulated core burr defects by combining the partial discharge signals with the electric field distribution data and voltage distribution data.

[0014] The present invention also provides a computer storage medium storing a computer program, which, when executed by a processor, implements the steps of an experimental simulation method for the characteristics of burr faults in an oil-immersed transformer core as described above.

[0015] The beneficial effects of this invention are as follows: This invention constructs a two-dimensional axisymmetric simulation model of a transformer that matches the actual structure and dimensions of an oil-immersed transformer. Combining the electrostatic loop theorem and regional mesh division, it accurately obtains electric field and voltage distribution data under normal operating conditions and simulated core burr defects, clarifying the influence of core burrs on electric field distortion. By simulating core burr defects with a discharge tube, and adjusting the distance between the needle and plate electrodes within the discharge tube according to the grounding voltage distribution data obtained from the two-dimensional axisymmetric simulation model of the transformer, controllable simulation of core burr defects is achieved. Furthermore, this invention employs a multi-channel partial discharge comprehensive analyzer. By analyzing the differences in partial discharge quantities across different channels, the location of core burr defects can be accurately pinpointed, solving the problem of easily missing fault signals with a single detection point.

[0016] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail below with reference to the accompanying drawings. Attached Figure Description

[0017] Figure 1 is a schematic diagram of the experimental simulation system for transformer core burr fault characteristics; Figure 2 is a two-dimensional simulation model of an oil-immersed transformer; Figure 3(a) is a model of the burr defect in the middle of the transformer core, Figure 3(b) is a model of the short burr defect at the top of the transformer core, and Figure 3(c) is a model of the long burr defect at the top of the transformer core; Figure 4(a) is a diagram of the electric field distribution of the ground shield under simulated core burr defects, Figure 4(b) is a diagram of the electric field distribution of the ground shield and core under simulated core burr defects, Figure 4(c) is a diagram of the electric field distribution of the winding under simulated core burr defects, and Figure 4(d) is a diagram of the electric field distribution of the winding and core under simulated core burr defects; Figure 5 is a diagram of the induced voltage distribution of the ground shield; Figure 6 is a diagram of the mesh generation result; Figure 7 is a diagram of the partial discharge of core burrs; Figure 8 is a flowchart of the experimental simulation method for transformer core burr fault characteristics; In Figure 2, 1-core, 21-winding, 3-ground shield, 4-oil gap. Detailed Implementation

[0018] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0019] Example 1: An experimental simulation system for the core burr fault characteristics of an oil-immersed transformer, as shown in Figure 1, includes: a simulation analysis module (based on COMSOL Multiphysics simulation software) to construct a two-dimensional axisymmetric simulation model of the transformer based on the actual structure of the oil-immersed transformer (220kV oil-immersed transformer), which includes the core, grounding shield, oil gap, and windings, and to set up simulated core burr defects. Through finite element simulation (based on the solver of COMSOL Multiphysics simulation software for direct simulation calculation), the electric field distribution data and voltage distribution data of the two-dimensional axisymmetric simulation model of the transformer under normal operating conditions (normal operating conditions without core burrs) and under simulated core burr defects are obtained respectively. This design, through the construction of a two-dimensional axisymmetric simulation model of the transformer based on the actual structure of the oil-immersed transformer, sets up targeted simulated core burr defects, and ensures the scientificity and accuracy of the electric field distribution data and voltage distribution data through electrostatic loop theorem constraints and finite element simulation; and an experimental simulation module to set up a simulation model of the transformer within the actual oil-immersed transformer body. The design simulates the core burr defect and conducts a no-load test on the oil-immersed transformer. Partial discharge signals (specifically, signals generated by partial discharge caused by the core burr defect) are obtained using a partial discharge detection device. These signals are then combined with electric field and voltage distribution data to assess the severity of the simulated core burr defect. This design uses electric field and voltage distribution data from a two-dimensional axisymmetric transformer simulation model as guidance to replicate the simulated core burr defect in the physical transformer. Through no-load testing and multi-dimensional partial discharge detection, the actual partial discharge signal under the simulated core burr defect is directly obtained. This signal is then correlated with the electric field and voltage distribution data, overcoming the limitations of single simulation (lacking actual operating conditions) or single experiment (difficult to accurately control defect parameters), making the hazard assessment more closely aligned with real-world scenarios.

[0020] In the above technical solution, before the finite element simulation, the simulation analysis module is also used to define the material properties of each structure in the two-dimensional axisymmetric simulation model of the transformer, and to set the boundary conditions and mesh generation rules of the two-dimensional axisymmetric simulation model of the transformer according to the electrostatic loop theorem. The above-mentioned material property definition, boundary condition setting and mesh generation rule formulation before the finite element simulation provide a foundation for subsequent accurate simulation calculations, ensure the consistency from digital model to physical reality, and improve the reliability and practicality of experimental simulation.

[0021] In the above technical solution, each structure includes an iron core, a ground shield, an oil gap, and windings. The material properties include dielectric constant and conductivity (conductivity is directly used in COMSOL Multiphysics simulation software to calculate the electric field). The dielectric constant and conductivity in the above design are the core parameters that determine the electromagnetic properties of the material, directly affecting the calculation results of electrostatic field strength and voltage distribution. By clarifying the core components of the two-dimensional axisymmetric simulation model of the transformer, the consistency between the two-dimensional axisymmetric simulation model of the transformer and the actual structure of the oil-immersed transformer is higher, thereby improving the reliability of electric field distribution data and voltage distribution data.

[0022] Regarding the material properties of each structure in the two-dimensional axisymmetric simulation model of the transformer, some optimized technical solutions include: dielectric constant ε1=2.2 for the oil gap and conductivity σ1=10. -12 S / m; Dielectric constant of the iron core ε2=8000, conductivity σ2=10S / m; Dielectric constant of the (copper) ground shield ε3=10000, conductivity σ3=10 7 S / m; Dielectric constant ε4=8000, conductivity σ4=10 for (copper wire) windings 7 S / m.

[0023] In the above technical solution, the specific method for setting the simulated core burr defect is as follows: The two-dimensional axisymmetric simulation model of the transformer adopts a three-phase five-column core structure, as shown in Figure 2. The three-phase five-column core structure includes three parallel main core columns (each main core column is fitted with a high-voltage winding) and side yoke columns on both sides. The three sets of high-voltage windings are respectively wound on the outside of the three main core columns. The grounding screen is arranged between the high-voltage and low-voltage windings to improve the electric field distribution. The three-phase five-column core structure is equipped with two simulated cores. The simulated core has two short burrs (5cm long) and two long burrs (10cm long) at the top. For the middle burrs of the simulated core, one burr is located between the left side yoke and the adjacent ground screen, and is situated in the middle of the left side yoke. The other burr is located between the main core column and the adjacent winding, and is situated in the middle of the main core column, as shown in Figure 3(a). For the short burrs at the top of the simulated core, one burr... The real iron core has a short burr at the top, which is located between the left side yoke and the adjacent grounding screen, and at the top of the left side yoke. The other simulated iron core has a short burr at the top, which is located between the main iron core column and the adjacent winding, and at the top of the main iron core column, as shown in Figure 3(b). For the simulated iron core has a long burr at the top, one simulated iron core has a long burr at the top, which is located between the left side yoke and the adjacent grounding screen, and at the top of the left side yoke. The other simulated iron core has a short burr at the top, which is located between the main iron core column and the adjacent winding, and at the top of the main iron core column, as shown in Figure 3(c). In the above design, by setting simulated iron core middle burrs, simulated iron core top short burrs, and simulated iron core top long burrs, the different defect morphologies of iron core burrs can be simulated, making the simulated defects more consistent with the fault scenarios in actual production and improving the practicality of the simulation. By setting the simulated iron core burrs in the key areas where burrs are easily generated and electric field distortion is easily caused in actual operation, the targeting of the simulated defects is ensured.

[0024] For the three sets of high-voltage windings, some optimized technical solutions include: In the two-dimensional axisymmetric simulation model of the transformer, the potential of the high-voltage winding closest to the left side column core (with the core burr set on the left side) is set to (220 / 1.73)×sin90°=127 kV, and the potential of the other two high-voltage windings is set to 220 / 1.73*sin(90±120)=-63.5kV. The core is grounded, and the potential is set to 0.

[0025] For the aforementioned electric field distribution data and voltage distribution data, some optimized technical solutions include: the electric field distribution data includes the ground shield electric field distribution data shown in Figure 4(a), the ground shield-core electric field distribution data shown in Figure 4(b), the winding electric field distribution data shown in Figure 4(c), and the winding-core electric field distribution data shown in Figure 4(d); the voltage distribution data is the ground shield induced voltage distribution data shown in Figure 5. As can be seen from Figures 4(a), 4(b), and 4(d), the electric field strength at the simulated core burr defect is significantly greater than the electric field strength under normal operating conditions. The burr defect affects the ground shield electric field, the ground shield-core electric field, and the winding-core electric field. The distortion of the electric field has a significant impact. At the same location (top), the electric field distortion caused by long burrs at the top of the simulated iron core is more severe than that caused by short burrs. In Figure 4(b), the electric field strength of the ground screen-iron core is the highest at the burr defect of the simulated iron core, indicating that the burr defect of the simulated iron core has the most severe distortion of the electric field of the ground screen-iron core (therefore, the structure of the ground screen-iron core should be optimized). As shown in Figure 4(c), the burr defect of the simulated iron core has almost no effect on the winding electric field. As shown in Figure 6, the ground screen voltage is about 29kV. Therefore, the distance between the needle and plate electrodes is set to a discharge gap of 20-25kV to ensure stable discharge.

[0026] In the above technical solution, the step of setting the boundary conditions and meshing rules of the two-dimensional axisymmetric simulation model of the transformer according to the electrostatic loop theorem is specifically used as follows: In the COMSOL Multiphysics simulation software, by adding an electrostatic field physics module, the boundary conditions and meshing rules of the two-dimensional axisymmetric simulation model of the transformer are set according to the electrostatic loop theorem, so that the electrostatic field around the core, grounding shield, oil gap, and winding components must satisfy the electrostatic loop theorem, as shown in the following formula: in, Electric field strength (unit: V / m). This indicates that a line integral is performed over a closed loop L. Represents the basic unit that constitutes a closed loop L; in, Here are the dielectric constants of each structure. The electric displacement vector is used. The above design is based on COMSOL Multiphysics simulation software and the electrostatic loop theorem to set boundary conditions and mesh generation rules, ensuring that the electric field distribution of the two-dimensional axisymmetric simulation model of the transformer satisfies the physical laws, thus improving the scientificity and accuracy of the simulation results.

[0027] In the above technical solution, the boundary conditions of the two-dimensional axisymmetric simulation model of the transformer are specifically used to satisfy the following: in, This represents the interfacial potential of the oil gap (where the oil gap is an insulating medium). Let i be the interface potential of conductor i (the conductor includes the core, winding and ground), 2≤i≤4. When i=2, the conductor is the core; when i=3, the conductor is the ground; when i=4, the conductor is the winding. is the dielectric constant of the oil gap; Let be the dielectric constant of conductor i; The interface normal vector is the interface between the oil gap and conductor i. The above design quantifies the relationship between the interface potential, dielectric constant and interface normal vector of the oil gap and each conductor (core, grounding, winding), making the setting of boundary conditions more accurate and operable, avoiding simulation errors caused by fuzzy settings, and improving the reliability of electric field distribution data.

[0028] In the above technical solution, the meshing rules for the two-dimensional axisymmetric simulation model of the transformer are specifically used as follows: For the two-dimensional axisymmetric simulation model of the transformer, a meshing rule with different precision is adopted for different regions, as shown in Figure 6. For the contact area between the ground screen and the core at the core burr defect location, a local mesh refinement process is performed with a minimum unit size within D (D is 1 mm). For the non-core burr defect area ("non-core burr defect area" refers to the area in the two-dimensional axisymmetric simulation model of the transformer that is not directly related to the location of the core burr defect, has a relatively uniform electric field distribution, and does not require high-precision calculation (areas not directly affected by the electric field distortion caused by the core burr, and do not play a key role in the calculation accuracy of defect characteristics (electric field distribution, voltage distribution)) a gradually thickening meshing strategy is adopted. This design, by clearly defining the minimum unit size of the mesh at the core burr defect location, enables the electric field changes in the core burr defect area to be accurately captured, improving the local accuracy of the simulation results. The gradually thickening meshing strategy for the non-core burr defect area effectively controls the amount of simulation computation and shortens the simulation time.

[0029] For simulating core burr defects corresponding to the two-dimensional axisymmetric simulation model of the transformer inside the physical body of an oil-immersed transformer, some optimized technical solutions include: simulating core burr defects by using a discharge tube, adjusting the distance between the needle and plate electrodes in the discharge tube according to the grounding screen induced voltage distribution data, connecting the needle electrode end to the core, and connecting the plate electrode end to the output terminal of the A-phase winding on the medium voltage side.

[0030] In the above technical solution, the partial discharge signal obtained by partial discharge detection using a partial discharge detection device is specifically used for: the windings of the oil-immersed transformer are designed as a three-phase AC A phase, a three-phase AC B phase, and a three-phase AC C phase. The high-voltage side A phase refers to the output terminal of the high-voltage winding corresponding to the three-phase AC A phase; the high-voltage side C phase refers to the output terminal of the high-voltage winding corresponding to the three-phase AC C phase; and the medium-voltage side A phase refers to the output terminal of the medium-voltage winding corresponding to the three-phase AC A phase. Partial discharge is detected using a multi-channel partial discharge comprehensive analyzer, and a partial discharge detector is arranged on each of the high-voltage side A phase, high-voltage side C phase, and medium-voltage side A phase of the windings inside the oil-immersed transformer. The discharge measurement unit, the multi-channel partial discharge comprehensive analyzer, detects the partial discharge signal at phase A on the high-voltage side through channel 1, the partial discharge signal at phase C on the high-voltage side through channel 2, the partial discharge signal at phase A on the medium-voltage side through channel 3, and the partial discharge signal at the core through channel 4 by arranging a current sensor on the grounding wire of the core grounding bushing. The detected partial discharge signals are shown in Figure 7. The channel 3 connected to phase A on the medium-voltage side shows the largest partial discharge, because the simulated core burr defect is set on phase A on the medium-voltage side, so the discharge signal of phase A on the medium-voltage side is the most obvious. Secondly, the channel 4 connected to the core shows a relatively obvious discharge phenomenon. The high-voltage side phase A and phase C are far from the simulated core burr defect, and the partial discharge signals of channels 1 and 2 are relatively small. This indicates that when the oil-immersed transformer has a core burr defect, strong discharge will occur at both the location of the core burr defect and the core. The core burr defect can be diagnosed according to the discharge location and discharge amount. The above design, through a multi-channel, multi-location detection strategy (high-voltage side phase A, high-voltage side phase C, medium-voltage side phase A, and core grounding bushing), ensures that all key partial discharge signals caused by the simulated core burr defect can be captured, avoiding signal omissions caused by single-location detection, and improving the reliability and comparability of partial discharge signals.

[0031] In the above technical solution, the assessment of the hazard level of simulated core burr defects by combining partial discharge signals with electric field distribution data and voltage distribution data is specifically performed as follows: The electric field distribution data and voltage distribution data are correlated with the partial discharge signal; the electric field intensity distortion value and voltage distribution change value under normal operating conditions and simulated core burr defects are compared with the electric field distribution data and voltage distribution data; partial discharge characteristic parameters (including peak discharge quantity and discharge phase characteristic parameters) are extracted from the partial discharge signal; based on the electric field intensity distortion value, voltage distribution change value, and partial discharge characteristic parameters, and combined with preset hazard level assessment rules (based on a comprehensive judgment of low, medium, and high risk according to the degree of electric field distortion and discharge characteristics), the hazard level of simulated core burr defects is obtained. This design, through the correlation analysis of electric field distribution data and voltage distribution data with partial discharge signals, achieves a quantitative assessment of the hazard level of simulated core burr defects, avoiding the one-sidedness of assessment caused by a single data dimension (such as only looking at the partial discharge signal).

[0032] Example 2, as shown in Figure 8, provides an experimental simulation method for the fault characteristics of core burrs in an oil-immersed transformer. The method includes the following steps: S1. Constructing a two-dimensional axisymmetric simulation model of the transformer based on its actual structure, setting up simulated core burr defects, defining the material properties of each structure in the two-dimensional axisymmetric simulation model, and setting the boundary conditions and mesh generation rules of the two-dimensional axisymmetric simulation model based on the electrostatic loop theorem. Through finite element simulation, obtaining the electric field distribution data and voltage distribution data of the two-dimensional axisymmetric simulation model of the transformer under normal operating conditions and simulated core burr defects, specifically including: 1.1 Setting up simulated core burr defects... The process of simulating burr defects in the core is as follows: The two-dimensional axisymmetric simulation model of the transformer adopts a three-phase five-column core structure. The three-phase five-column core structure consists of five parallel core columns, including three parallel main core columns and two side yoke columns. Three sets of high-voltage windings are wound on the outside of the three main core columns, and the grounding shield is arranged between the high-voltage and low-voltage windings. Simulated burrs in the middle of the core, simulated short burrs at the top of the core, and simulated long burrs at the top of the core are set in the three-phase five-column core structure. The simulated middle burrs are set in the middle of the core column, and the simulated short burrs and simulated long burrs at the top of the core column are both set at the top of the core column.

[0033] 1.2 The boundary conditions and meshing rules of the two-dimensional axisymmetric simulation model of the transformer are set according to the electrostatic loop theorem. The specific process is as follows: By adding the electrostatic field physics module, the boundary conditions and meshing rules of the two-dimensional axisymmetric simulation model of the transformer are set according to the electrostatic loop theorem, so that the electrostatic field around the core, grounding shield, oil gap and winding components satisfies the electrostatic loop theorem.

[0034] 1.3 Boundary conditions for the two-dimensional axisymmetric simulation model of the transformer, the specific process is as follows: The boundary conditions of the two-dimensional axisymmetric simulation model of the transformer satisfy: in, The interfacial potential of the oil gap; Let i be the interface potential of conductor i, where 2 ≤ i ≤ 4. When i = 2, the conductor is the iron core; when i = 3, the conductor is the ground shield; and when i = 4, the conductor is the winding. is the dielectric constant of the oil gap; Let be the dielectric constant of conductor i; Let be the interface normal vector of the interface between the oil gap and conductor i.

[0035] 1.4 Mesh generation rules for the two-dimensional axisymmetric simulation model of the transformer. The specific process is as follows: The two-dimensional axisymmetric simulation model of the transformer adopts a mesh generation rule with different precision for different regions. The contact area between the ground screen and the core at the core burr defect is subjected to local mesh refinement processing with the minimum element size within D. The region outside the core burr defect adopts a gradually thickening mesh generation strategy.

[0036] S2. Simulated core burr defects corresponding to the two-dimensional axisymmetric simulation model of the transformer are set inside the oil-immersed transformer body, and a transformer no-load test is carried out on the oil-immersed transformer body. Partial discharge signals are obtained by partial discharge detection equipment. The degree of harm of the simulated core burr defects is evaluated by combining the partial discharge signals with the electric field distribution data and voltage distribution data. Specifically, this includes: 2.1 Obtaining partial discharge signals by partial discharge detection equipment. The process is as follows: Partial discharge detection is performed by a multi-channel partial discharge comprehensive analyzer. A partial discharge measuring instrument input unit is arranged on the high-voltage side A phase, high-voltage side C phase, and medium-voltage side A phase of the winding inside the oil-immersed transformer body. Channel 1 of the multi-channel partial discharge comprehensive analyzer detects the partial discharge signal on the high-voltage side A phase, channel 2 detects the partial discharge signal on the high-voltage side C phase, channel 3 detects the partial discharge signal on the medium-voltage side A phase, and channel 4 detects the partial discharge signal at the core by arranging a current sensor on the grounding wire of the core grounding bushing.

[0037] 2.2 The severity of the simulated core burr defect is assessed by combining the partial discharge signal with the electric field distribution data and voltage distribution data. The specific process is as follows: The electric field distribution data and voltage distribution data are correlated with the partial discharge signal. By comparing the electric field intensity distortion value and voltage distribution change value under normal operating conditions and simulated core burr defects with the electric field distribution data and voltage distribution data, the partial discharge characteristic parameters in the partial discharge signal are extracted. Based on the electric field intensity distortion value, voltage distribution change value, and partial discharge characteristic parameters, and in combination with the preset hazard level assessment rules, the severity of the simulated core burr defect is obtained.

[0038] Example 3 This example provides a computer storage medium that stores a computer program. When the computer program is executed by a processor, it implements the steps of the method described in Example 2.

[0039] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0040] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a system for implementing the functions specified in one or more blocks of the flowchart illustrations and / or one or more blocks of the block diagrams.

[0041] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including an instruction system that implements the functions specified in one or more flowcharts and / or one or more block diagrams.

[0042] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide steps for implementing the functions specified in one or more flowcharts and / or one or more block diagrams.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

[0044] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. An experimental simulation system for the fault characteristics of burr faults in the core of an oil-immersed transformer, characterized in that, include: The simulation analysis module is used to construct a two-dimensional axisymmetric simulation model of the oil-immersed transformer based on its actual structure, and to set up simulated core burr defects. Through finite element simulation, it obtains electric field distribution data and voltage distribution data of the two-dimensional axisymmetric simulation model of the transformer under normal operating conditions and simulated core burr defects, respectively. The experimental simulation module is used to set up simulated core burr defects corresponding to the two-dimensional axisymmetric simulation model of the transformer inside the oil-immersed transformer entity, and to conduct a transformer no-load test on the oil-immersed transformer entity. Partial discharge detection equipment is used to detect partial discharge on the oil-immersed transformer entity to obtain partial discharge signals. By combining the partial discharge signals with the electric field distribution data and voltage distribution data, the severity of the simulated core burr defects is evaluated.

2. The experimental simulation system for the fault characteristics of burr in the core of an oil-immersed transformer according to claim 1, characterized in that: Before the finite element simulation, the simulation analysis module is also used to define the material properties of each structure in the two-dimensional axisymmetric simulation model of the transformer, and to set the boundary conditions and meshing rules of the two-dimensional axisymmetric simulation model of the transformer according to the electrostatic loop theorem.

3. The experimental simulation system for the fault characteristics of burr in the core of an oil-immersed transformer according to claim 2, characterized in that: The structures include an iron core, a ground shield, an oil gap, and windings, and the material properties include dielectric constant and electrical conductivity.

4. The experimental simulation system for the fault characteristics of burr in the core of an oil-immersed transformer according to claim 3, characterized in that: In the simulation analysis module, the specific method for setting simulated core burr defects is as follows: The two-dimensional axisymmetric simulation model of the transformer adopts a three-phase five-column core structure. The three-phase five-column core structure consists of five parallel core columns, including three parallel main core columns and two side yoke columns. Three sets of high-voltage windings are wound on the outside of the three main core columns, and the grounding shield is arranged between the high-voltage and low-voltage windings. Simulated core middle burrs, simulated core top short burrs, and simulated core top long burrs are set in the three-phase five-column core structure. The simulated core middle burrs are set in the middle of the core column, and the simulated core top short burrs and simulated core top long burrs are both set at the top of the core column.

5. The experimental simulation system for the fault characteristics of burr in the core of an oil-immersed transformer according to claim 3, characterized in that, In the simulation analysis module, the setting of boundary conditions and meshing rules for the two-dimensional axisymmetric simulation model of the transformer according to the electrostatic loop theorem is specifically used to: by adding the electrostatic field physics module, set the boundary conditions and meshing rules for the two-dimensional axisymmetric simulation model of the transformer according to the electrostatic loop theorem, so that the electrostatic field around the core, grounding shield, oil gap and winding components satisfies the electrostatic loop theorem.

6. The experimental simulation system for the fault characteristics of burr in the core of an oil-immersed transformer according to claim 5, characterized in that, The boundary conditions of the two-dimensional axisymmetric simulation model of the transformer are specifically defined as follows: The boundary conditions of the two-dimensional axisymmetric simulation model of the transformer satisfy the following: in, The interfacial potential of the oil gap; Let i be the interface potential of conductor i, where 2 ≤ i ≤ 4. When i = 2, the conductor is the iron core; when i = 3, the conductor is the ground shield; and when i = 4, the conductor is the winding. is the dielectric constant of the oil gap; Let be the dielectric constant of conductor i; Let be the interface normal vector of the interface between the oil gap and conductor i.

7. The experimental simulation system for the fault characteristics of burr in the core of an oil-immersed transformer according to claim 5, characterized in that, In the simulation analysis module, the mesh generation rules for the two-dimensional axisymmetric simulation model of the transformer are specifically used as follows: different mesh generation rules with different precision are applied to different regions of the two-dimensional axisymmetric simulation model of the transformer; local mesh refinement processing with a minimum element size of D is performed on the contact area between the ground screen and the core at the core burr defect; and a gradually thickening mesh generation strategy is adopted for the area outside the core burr defect.

8. The experimental simulation system for the fault characteristics of burr in the core of an oil-immersed transformer according to claim 1, characterized in that, In the experimental simulation module, the partial discharge signal obtained by partial discharge detection equipment is specifically used for: partial discharge detection by a multi-channel partial discharge comprehensive analyzer. A partial discharge measuring instrument input unit is arranged on each of the high-voltage side A phase, high-voltage side C phase, and medium-voltage side A phase of the winding inside the oil-immersed transformer. Channel 1 of the multi-channel partial discharge comprehensive analyzer detects the partial discharge signal on the high-voltage side A phase, channel 2 detects the partial discharge signal on the high-voltage side C phase, channel 3 detects the partial discharge signal on the medium-voltage side A phase, and channel 4 detects the partial discharge signal at the core by arranging a current sensor on the grounding wire of the core grounding bushing.

9. The experimental simulation system for the fault characteristics of burr in the core of an oil-immersed transformer according to claim 1, characterized in that, In the experimental simulation module, the assessment of the severity of simulated core burr defects by combining the partial discharge signal with the electric field distribution data and voltage distribution data is specifically used to: perform correlation analysis between the electric field distribution data and voltage distribution data and the partial discharge signal; compare the electric field intensity distortion value and voltage distribution change value under normal working conditions and simulated core burr defects using the electric field distribution data and voltage distribution data; and extract the partial discharge characteristic parameters in the partial discharge signal. Based on the electric field strength distortion value, voltage distribution change value, and partial discharge characteristic parameters, and in conjunction with the preset hazard level assessment rules, the hazard level of the simulated iron core burr defect is obtained.

10. An experimental simulation method for the characteristics of burr faults in the core of an oil-immersed transformer, characterized in that, Includes the following steps: A two-dimensional axisymmetric simulation model of the transformer was constructed based on its actual structure. Simulated core burr defects were then set up. Finite element simulation was used to obtain electric field and voltage distribution data for the two-dimensional axisymmetric simulation model of the transformer under normal operating conditions and simulated core burr defects. Simulated core burr defects corresponding to the two-dimensional axisymmetric simulation model of the transformer were then set up inside the actual oil-immersed transformer. A no-load test was conducted on the actual oil-immersed transformer. Partial discharge signals were obtained by using a partial discharge detection device. The severity of the simulated core burr defects was assessed by combining the partial discharge signals with the electric field and voltage distribution data.

11. The experimental simulation method for the core burr fault characteristics of an oil-immersed transformer according to claim 10, characterized in that, The boundary conditions of the two-dimensional axisymmetric simulation model of the transformer include: the boundary conditions of the two-dimensional axisymmetric simulation model of the transformer satisfy: in, The interfacial potential of the oil gap; Let i be the interface potential of conductor i, where 2 ≤ i ≤ 4. When i = 2, the conductor is the iron core; when i = 3, the conductor is the ground shield; and when i = 4, the conductor is the winding. is the dielectric constant of the oil gap; Let be the dielectric constant of conductor i; Let be the interface normal vector of the interface between the oil gap and conductor i.

12. The experimental simulation method for the fault characteristics of burr in the core of an oil-immersed transformer according to claim 10, characterized in that, The partial discharge signal obtained by partial discharge detection equipment includes: partial discharge detection by a multi-channel partial discharge comprehensive analyzer. A partial discharge measuring instrument input unit is arranged in the high-voltage side A phase, high-voltage side C phase, and medium-voltage side A phase of the winding inside the oil-immersed transformer. Channel 1 of the multi-channel partial discharge comprehensive analyzer detects the partial discharge signal in the high-voltage side A phase, channel 2 detects the partial discharge signal in the high-voltage side C phase, channel 3 detects the partial discharge signal in the medium-voltage side A phase, and channel 4 detects the partial discharge signal at the core by arranging a current sensor on the grounding wire of the core grounding bushing.

13. A computer storage medium, wherein the computer-readable storage medium stores a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the experimental simulation method for the burr fault characteristics of an oil-immersed transformer core as described in any one of claims 10-12.

Images