SF6 current transformer internal fault analysis method and system based on finite element method

Abstract

The invention discloses an SF6 current transformer internal fault analysis method and system based on a finite element method, and relates to the technical field of current transformer fault analysis, and the method comprises the steps: obtaining the internal structure and disassembly condition of an SF6 current transformer; analyzing the initial position of the internal fault of the SF6 current transformer according to the disassembly condition; and establishing a geometric model according to the fault initial position, and performing finite element simulation to obtain a fault reason. Through three-dimensional modeling and finite element simulation analysis, internal fault characteristics of the SF6 current transformer, such as cracks and internal bubbles of an insulating support column, can be identified carefully, the specific form of the fault is revealed, the influence of the fault on electric field distribution is quantified, the overall performance and operation safety of equipment are improved, and the method is suitable for popularization and application. And meanwhile, solid technical support is provided for long-term stable operation of a power system. A simulation technology is utilized to analyze internal insulation distribution and fault causes of equipment from a design level, and a traditional mode of utilizing experience for judgment is broken through.

Description

Technical Field

[0001] The present invention relates to the technical field of current transformer fault analysis, and in particular to a SF6 current transformer internal fault analysis method and system based on a finite element method. Background Art

[0002] As a key equipment for monitoring grid current, SF6 current transformer plays a role in ensuring the safe and stable operation of the grid. Therefore, once a current transformer fails, it will seriously affect the safety of the grid, equipment and personnel. This paper analyzes the disassembly process of an SF6 current transformer with an internal fault, measures the size of the current transformer, and reversely redraws the three-dimensional model of the transformer. The internal potential and electric field distribution of the SF6 current transformer are simulated and calculated using COMSOL finite element analysis software, pointing out the weak links of the internal insulation. Combined with the disassembly situation, the development process of the SF6 fault is reproduced, and it is analyzed that it is due to defects such as cracks or bubbles in the insulation pillars of the SF6 current transformer, which causes the local field strength to be higher than the design allowable value, causing local discharge, and ultimately leading to main insulation breakdown.

[0003] As the key main equipment in the substation that converts large current into small current, the current transformer plays the role of protecting, monitoring and controlling the power system. Once a fault occurs, it will seriously affect the power grid, equipment and personal safety. The fault cause was analyzed by dismantling the faulty SF6 current transformer and performing X-ray detection. The SF6 current transformer was simulated and analyzed using ElecNet, and corresponding countermeasures for optimizing the electric field were proposed. A three-dimensional electric field simulation calculation and analysis was performed on the typical defects of the pot-type insulator to analyze the changes in the degree of influence of different defects. The above research only conducted simulation analysis on pot-type insulators, and no equipment failure analysis research using electric field simulation technology has been conducted on SF6 current transformers.

[0004] The present invention disassembles and analyzes an SF6 current transformer with an internal fault, uses finite element software to simulate and calculate its internal potential and electric field distribution, points out the weak links in internal insulation, and reproduces the development process of the fault in combination with the disassembly situation to clarify the corresponding cause of the fault. By performing simulation technology analysis on the internal field strength distribution of the equipment and the fault development process, it can provide guidance for optimizing the field strength and improving the manufacturing process for the weak links in the internal insulation of the equipment. Summary of the invention

[0005] In view of the above-mentioned problems, the present invention is proposed.

[0006] Therefore, the problem to be solved by the present invention is: how to solve the problem that traditional fault diagnosis methods are often difficult to accurately identify the starting location of the fault, especially in the case of tiny defects in key components such as insulating pillars and conductive tubes. The existing analysis methods lack accuracy in simulating the electric field distribution and cannot effectively reveal the deep-seated causes of the fault.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for analyzing internal faults of SF6 current transformers based on the finite element method, comprising: obtaining the internal structure and disintegration condition of the SF6 current transformer; analyzing the starting position of the internal fault of the SF6 current transformer according to the disintegration condition; establishing a geometric model according to the starting position of the fault, performing finite element simulation, and obtaining the cause of the fault.

[0008] As a preferred solution of the SF6 current transformer internal fault analysis method based on the finite element method described in the present invention, the internal structure of the SF6 current transformer includes an SF6 current transformer consisting of an explosion-proof device, a shell, a conductive tube, four insulating pillars, a secondary shielding cover, a lead tube and a base part, the main insulation is composed of insulating pillars, an SF6 air gap between the high potential and the ground potential, and a composite bushing, a uniform electric field, and a bushing shield II is provided inside the composite bushing and fixed on a pot-type insulator.

[0009] As a preferred solution of the SF6 current transformer internal fault analysis method based on the finite element method described in the present invention, the disintegration condition includes the insulation support column condition, the casing condition, the grounding wire and the lead tube inspection; combined with the protection recording and equipment disintegration inspection and analysis, the cause of the fault is preliminarily analyzed and the starting position of the fault is determined.

[0010] As a preferred solution of the SF6 current transformer internal fault analysis method based on the finite element method described in the present invention, wherein: the establishment of the geometric model includes determining the starting position of the fault according to the disintegration situation, performing three-dimensional modeling on the fault starting position part of the SF6 current transformer, filling the screw holes, deleting the bolts and the secondary winding and the core in the secondary shielding cover, focusing on the electric field distribution of the internal electrodes and insulating parts of the current transformer, simplifying the bushing, base and lead structure, and using Comsol software to establish a three-dimensional electric field simulation geometric model under normal conditions, cracks on the outer surface of the pillar, and bubbles inside the pillar, and performing material selection and boundary condition setting.

[0011] As a preferred solution of the SF6 current transformer internal fault analysis method based on the finite element method described in the present invention, the material selection includes that in the three-dimensional electric field simulation geometric model, the outer shell, secondary shielding cover, and conductive tube are all made of aluminum alloy materials, the insulating pillars are made of epoxy resin materials, the inside of the outer shell is filled with SF6 gas material, the inside of the outer sheath is glass fiber impregnated with epoxy resin material, and the outer sheath is made of silicone rubber.

[0012] As a preferred solution of the SF6 current transformer internal fault analysis method based on the finite element method described in the present invention, wherein: the boundary conditions include obtaining the effective value of the line voltage of the current transformer, converting the effective value of the line voltage into the peak value of the phase voltage, obtaining the corresponding lightning impulse voltage peak value, performing electric field calculations of the current transformer defect-free model, crack, and bubble defect model under the lightning impulse voltage, loading the top shell, primary winding and bushing shield I with high potential, grounding the secondary winding shielding cover and the secondary lead tube, and setting the bushing shield II with a suspended potential.

[0013] As a preferred scheme of the SF6 current transformer internal fault analysis method based on the finite element method described in the present invention, wherein: the finite element simulation includes performing finite element simulation based on an established three-dimensional electric field simulation geometric model, analyzing the crack conditions under normal operating conditions, in the case of crack defects on the outer surface of the fault starting position, and in the case of bubble defects inside the fault starting position, to obtain the cause of the fault.

[0014] Another object of the present invention is to provide a system for SF6 current transformer internal fault analysis method based on finite element method, which can solve the problem of SF6 current transformer internal fault analysis based on finite element method by constructing SF6 current transformer internal fault analysis system.

[0015] In order to solve the above technical problems, the present invention provides the following technical solutions: an SF6 current transformer internal fault analysis system based on the finite element method, comprising a structure acquisition module (100), a disassembly analysis module (200) and a finite element simulation module (300); the structure acquisition module (100) is used to acquire the internal structure and disassembly condition of the SF6 current transformer; the disassembly analysis module (200) is used to analyze the starting position of the internal fault of the SF6 current transformer according to the disassembly condition; the finite element simulation module (300) is used to establish a geometric model according to the starting position of the fault, perform finite element simulation, and obtain the cause of the fault.

[0016] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the SF6 current transformer internal fault analysis method based on the finite element method as described above are implemented.

[0017] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the SF6 current transformer internal fault analysis method based on the finite element method as described above.

[0018] The beneficial effects of the present invention are as follows: the SF6 current transformer internal fault analysis method based on the finite element method provided by the present invention can carefully identify the fault characteristics inside the SF6 current transformer, such as cracks in the insulating pillars and internal bubbles, through three-dimensional modeling and finite element simulation analysis, which not only reveals the specific form of the fault, but also quantifies the impact of the fault on the electric field distribution. It provides an in-depth understanding of the fault mechanism, so that preventive measures can be taken during the equipment design and manufacturing process to avoid the occurrence of similar faults, thereby improving the overall performance and operational safety of the equipment, and also provides solid technical support for the long-term stable operation of the power system. The simulation technology is used to analyze the internal insulation distribution and fault causes of the equipment from the design level, breaking through the traditional way of using experience to judge. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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 labor.

[0020] Figure 1 A flow chart of a method for analyzing internal faults of SF6 current transformers based on the finite element method provided in the first embodiment of the present invention.

[0021] Figure 2 A current transformer insulation support diagram of a SF6 current transformer internal fault analysis method based on the finite element method provided in the first embodiment of the present invention.

[0022] Figure 3 Fragment diagram of insulating pillar No. 1 of the SF6 current transformer internal fault analysis method based on the finite element method provided in the first embodiment of the present invention.

[0023] Figure 4 A diagram of the inner surface of the casing of the SF6 current transformer internal fault analysis method based on the finite element method provided in the first embodiment of the present invention.

[0024] Figure 5 A diagram of a burned-out grounding wire in the SF6 current transformer internal fault analysis method based on the finite element method provided in the first embodiment of the present invention.

[0025] Figure 6 A lead tube head diagram of the SF6 current transformer internal fault analysis method based on the finite element method provided in the first embodiment of the present invention.

[0026] Figure 7A three-dimensional geometric model diagram of an SF6 current transformer according to the SF6 current transformer internal fault analysis method based on the finite element method provided in the first embodiment of the present invention.

[0027] Figure 8 A schematic diagram of applied voltage for the SF6 current transformer internal fault analysis method based on the finite element method provided in the first embodiment of the present invention.

[0028] Fig. 9 A structural diagram of an SF6 current transformer internal fault analysis system based on the finite element method provided in the second embodiment of the present invention.

[0029] Fig.10 The internal potential and electric field distribution diagram under lightning impulse voltage of the SF6 current transformer internal fault analysis method based on the finite element method provided in the third embodiment of the present invention.

[0030] Fig.11 An electric field distribution diagram of an insulating support of an SF6 current transformer internal fault analysis method based on the finite element method provided in the third embodiment of the present invention.

[0031] Fig.12 A diagram of external cracks in an insulating support according to a method for analyzing internal faults of an SF6 current transformer based on the finite element method provided in the third embodiment of the present invention.

[0032] Fig.13 The electric field distribution diagram of the external crack surface of the insulating support of the SF6 current transformer internal fault analysis method based on the finite element method provided in the third embodiment of the present invention.

[0033] Fig.14 A bubble diagram inside an insulating support of an SF6 current transformer internal fault analysis method based on the finite element method provided in the third embodiment of the present invention.

[0034] Fig.15 The electric field distribution diagram of the insulator support bubbles of the SF6 current transformer internal fault analysis method based on the finite element method provided in the third embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to make the above-mentioned objects, 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 accompanying drawings.

[0036] 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.

[0037] Example 1

[0038] Reference Figures 1 to 8 , which is the first embodiment of the present invention, provides an SF6 current transformer internal fault analysis method based on the finite element method, including: obtaining the internal structure and disintegration condition of the SF6 current transformer; analyzing the starting position of the internal fault of the SF6 current transformer according to the disintegration condition; establishing a geometric model according to the starting position of the fault, performing finite element simulation, and obtaining the cause of the fault.

[0039] S1. Obtain the internal structure and disassembly of the SF6 current transformer.

[0040] S1.1. Internal structure.

[0041] SF6 current transformer consists of explosion-proof device, shell, conductive tube, four insulating pillars (epoxy castings), secondary shield, lead tube and base. The main insulation consists of insulating pillar, SF6 air gap between high potential and ground potential and composite bushing. In order to make the electric field uniform, bushing shield II is installed inside the composite bushing and fixed on the pot insulator.

[0042] S1.2 Disintegration

[0043] Insulation support column situation: The current transformer contains a total of 4 columns, and the columns are arranged as follows Figure 2 As shown in the figure, the No. 1 pillar has been smashed, and the fragments are distributed everywhere inside the current transformer CT; the No. 2 pillar is relatively intact; the outer surfaces of the No. 3 and No. 4 pillars have obvious carbonization marks. The cracks of the No. 1 pillar fragments were pried open for inspection, and black carbonization marks were found inside the cracks, but the outer surface was white, as shown in the figure. Figure 3 As shown, it can be judged that the fault of the insulating support develops from the inside to the outside.

[0044] Shell condition: There are 4 obvious arc discharge marks on the inner surface of the shell, and 2 discharge marks on the P1 and P2 sides. The most serious one is located at the No. 1 support of the CT. Figure 4 shown.

[0045] Check the grounding wire and lead tube: The grounding wire connecting the lead tube and the lead tube shield are obviously blown. Figure 5 As shown in the figure, obvious ablation marks occur on the top of the lead tube. Figure 6 shown.

[0046] S2. Analyze the starting position of the internal fault of the SF6 current transformer based on the disintegration situation.

[0047] Combined with the protection recording and equipment dismantling inspection and analysis, a preliminary analysis of the cause of the fault was conducted and the starting location of the fault was determined.

[0048] Combined with the protection recording and equipment disassembly inspection and analysis, a total of 2 short circuits to the ground occurred. The first short circuit to the ground channel was high voltage-No. 1 insulating pillar-secondary shielding cover-lead shielding-grounding wire-lead tube-ground. The fault current was about 30kA, which eventually caused the No. 1 insulating pillar to explode. At the same time, the short-circuit current far exceeded the current-carrying capacity of the grounding wire, causing the grounding wire to fuse. After the first discharge fault, a large amount of carbide was generated inside the equipment. After the line overlapped, the high-voltage electrode short-circuited to the ground along the outer surface of the No. 3 and No. 4 insulating pillars, the inner side of the secondary shielding cover and the lead tube. Therefore, there are a lot of carbonization marks on the outer surface of the No. 3 and No. 4 insulating pillars. Combined with the disassembly situation, the preliminary analysis is that the No. 1 insulating pillar has cracks or bubbles and other defects, causing local discharge, which eventually leads to insulation breakdown after long-term operation.

[0049] In order to quantitatively analyze the partial discharge caused by defects such as cracks or bubbles, the present invention uses finite element software to carry out internal electric field simulation analysis under normal and defective conditions to clarify the development process of the fault.

[0050] S3. Establish a geometric model according to the fault starting position, perform finite element simulation, and obtain the cause of the fault.

[0051] According to the disintegration situation, the starting position of this fault is located at the insulating support. Therefore, in order to simplify the calculation, only the upper part of the SF6 current transformer is 3D modeled, the screw holes are filled, the bolts, and the secondary winding and core in the secondary shielding cover are deleted. At the same time, the electric field distribution of the internal electrodes and insulating parts of the current transformer is focused on, and the structures such as the bushing, base, and lead are simplified. The 3D electric field simulation geometric model is established using the comsol software under the normal working conditions, the cracks on the outer surface of the support, and the bubbles inside the support. Figure 7 shown.

[0052] S3.1. Material selection.

[0053] In the simulation model, the shell, secondary shielding cover and conductive tube are all made of aluminum alloy, the insulating pillars are made of epoxy resin, the shell is filled with SF6 gas, the outer sheath is made of glass fiber impregnated with epoxy resin, and the outer sheath is made of silicone rubber. The relative dielectric constants of the materials of each component are shown in Table 1[12-13].

[0054] Table 1 Relative dielectric constants of various materials

[0055]

[0056]

[0057] S3.2 Boundary conditions.

[0058] The effective value of the line voltage of the current transformer is obtained, and the effective value of the line voltage is converted into the peak value of the phase voltage to obtain the corresponding lightning impulse voltage peak value. The electric field calculation of the current transformer defect-free model, crack, and bubble defect model is performed under the lightning impulse voltage. The top shell, primary winding, and bushing shield I are loaded with high potential, the secondary winding shield and the secondary lead tube are grounded, and the bushing shield II is set to a suspended potential.

[0059] According to GB / T 20840.1-2010 "Transformers Part 1: General Technical Requirements", the power frequency voltage level of the CT is 550kV (line voltage effective value), which is converted to a phase voltage peak of 449.07kV, and the corresponding lightning impulse voltage peak is 1675kV. Under lightning impulse voltage, the electric field calculation of the CT defect-free model, crack, bubble and other defect models is performed. The top shell, primary winding and bushing shield I are loaded with high potential, the secondary winding shield and secondary lead tube are grounded, and the bushing shield II is set to a floating potential, such as Figure 8 As shown, the left side is the high voltage potential side and the right side is the ground side.

[0060] Finite element simulation is performed based on the established three-dimensional electric field simulation geometric model to analyze the crack conditions under normal working conditions, the outer surface crack defects at the fault starting position, and the internal bubble defects at the fault starting position to obtain the cause of the fault.

[0061] Example 2

[0062] Reference Fig. 9 , which is the second embodiment of the present invention, is different from the previous embodiment in that it provides an SF6 current transformer internal fault analysis system based on the finite element method, including: a structure acquisition module 100, a disassembly analysis module 200 and a finite element simulation module 300.

[0063] The structure acquisition module 100 is used to obtain the internal structure and disassembly status of the SF6 current transformer.

[0064] The disassembly analysis module 200 is used to analyze the starting position of the internal fault of the SF6 current transformer according to the disassembly situation.

[0065] The finite element simulation module 300 is used to establish a geometric model according to the fault starting position, perform finite element simulation, and obtain the cause of the fault.

[0066] 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.

[0067] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0068] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0069] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0070] Example 3

[0071] Reference Figure 10 to Figure 15 , which is the third embodiment of the present invention, and which is different from the first two embodiments in that it is used to verify and illustrate the technical effects adopted in the present invention, so as to verify the real effects of this method.

[0072] Under normal working conditions.

[0073] Under lightning impulse voltage, the overall potential distribution inside the SF6 current transformer is as follows: Fig.10 As shown on the left, since the shell, conductive tube, and bushing shield I are loaded with a high potential of 1675kV, the secondary lead tube and secondary shield are grounded at 0 potential, and the bushing shield II is a floating potential, its potential is about 1100kV. The potential distribution of the insulating support gradually decreases from the shell to the secondary winding shield. The electric field distribution inside the current transformer is as follows Fig.10 As shown on the right, the highest overall field strength is located at the secondary shielding cover, conductive tube and grounding lead tube, reaching a maximum of 13.8kV / mm.

[0074] According to the document "SF6 High Voltage Electrical Appliance Design", the surface field strength control value of metal parts under lightning impulse voltage is 24.5kV / mm, and the peak value of the surface field strength control value of insulating parts is 12kV / mm (gas pressure 0.4MPa), as shown in Table 2. The theoretical breakdown value of the air gap in the insulator under lightning impulse voltage is 3kV / mm. If the bubble field strength is greater than 3kV / mm, partial discharge will occur.

[0075] Table 2 Field strength control values ​​at various locations

[0076]

[0077] from Fig.11It can be seen that under the lightning impulse voltage, when there are no defects, the electric field distribution of the four insulating pillars is similar, and the maximum calculated field strength is about 10.1kV / mm. The maximum field strength is located near the connection between the shed and the cylinder near the secondary winding shielding cover. The field strength in the middle section is relatively uniform, about 5-7kV / mm, and the field strength near the conductive tube is relatively small, about 1-2kV / mm. The field strength at each position meets the field strength control value.

[0078] The maximum calculated field strength of the insulating support, secondary shielding cover, conductive tube and lead tube under normal conditions is compared with the field strength control value, and all meet the requirements, as shown in Table 3. However, from the safety factor calculation results, it can be seen that the safety margin of the insulating support is the lowest.

[0079] Table 3 Insulation safety factor of each part

[0080]

[0081]

[0082] In the case of crack defects on the outer surface of the pillar.

[0083] A vertical crack with a depth of 1 mm, a width of 1 mm, and a height of 5 mm is applied to the outer surface of one of the pillar insulation. Fig.12 The simulation results are shown in Fig.13 As shown, it can be seen that the electric field strength near the crack will be distorted, and its value is significantly higher than the case where no crack defect occurs. The maximum field strength of the entire insulating pillar also exists in the cracks on the outer surface, with a maximum value of about 13kV / mm, which exceeds the field strength control value of the insulator of 12kV / mm. Therefore, local discharge will occur in the pillar insulation, which is consistent with the disintegration of the black carbonization marks inside the gap.

[0084] In the case of bubble defects inside the pillar.

[0085] Apply a bubble with a radius of 1 mm inside one of the pillar insulation, such as Fig.14 The simulation results are shown in Fig.15 As shown in the simulation result diagram, it can be seen that the internal bubbles are filled with air, and the maximum electric field strength on the air gap surface reaches 10.1 kV / mm, which exceeds the theoretical breakdown value of air of 3 kV / mm. Therefore, local discharge will also occur in the bubbles inside the insulating pillar, further causing insulation breakdown of the insulating pillar.

[0086] The present invention uses COMSO finite element software to carry out simulation analysis of SF6 current transformer under normal and defective conditions under lightning impulse voltage, and the conclusions are as follows:

[0087] After comprehensive calculation of the internal insulation distribution of the SF6 current transformer, it was found that the insulation margin at the insulating support was the lowest, about 1.19, which also corresponded to the starting point of the fault.

[0088] For the preset cracks or bubble defects in the insulating pillar, the simulation results show that the maximum electric field strength at the crack defect reaches 13kV / mm, exceeding the control value of 12kV / mm; the maximum field strength on the surface of the bubble defect reaches 10kV / mm, exceeding the breakdown field strength of air by 3kV / mm. Therefore, local discharge will occur in the insulating pillar when there are defects such as cracks or bubbles.

[0089] This invention uses simulation technology to analyze the internal insulation distribution and fault causes of the equipment from the design level, breaking through the traditional way of using experience to judge. However, it does not consider the influence of factors such as internal insulation aging and special operating environment after long-term operation of the equipment. Further research is needed on the equipment status assessment method under insulation aging and special operating environment.

[0090] In order to improve the safety and reliability of the equipment, the following suggestions are put forward. The field strength optimization at the insulating pillar should be strengthened, and the electric field strength at the insulating pillar should be reduced by changing the electrode shape and optimizing the internal inserts. It is recommended that manufacturers strengthen the quality control of the insulating pillars in the future, and conduct partial discharge, withstand voltage, X-ray and other tests on all the insulating pillars entering the factory to ensure product quality. Improve the mechanical strength of the insulating pillars and improve the transportation conditions to avoid defects in the insulating pillars caused by improper transportation or installation.

[0091] 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.

Claims

1. The internal fault analysis method of SF6 current transformer based on finite element method is characterized by: include, Obtain the internal structure and disassembly of SF6 current transformer; Analyze the starting position of the internal fault of the SF6 current transformer according to the disassembly situation; A geometric model is established according to the fault starting position, and finite element simulation is performed to obtain the cause of the fault.

2. The SF6 current transformer internal fault analysis method based on the finite element method according to claim 1, characterized in that: The internal structure of the SF6 current transformer includes an explosion-proof device, a shell, a conductive tube, four insulating pillars, a secondary shielding cover, a lead tube and a base. The main insulation is composed of insulating pillars, an SF6 air gap between high potential and ground potential, and a composite bushing. The electric field is uniform, and a bushing shield II is provided inside the composite bushing and fixed on a pot-type insulator.

3. The SF6 current transformer internal fault analysis method based on the finite element method as claimed in claim 2, characterized in that: The disassembly condition includes the condition of the insulating support column, the condition of the shell, the grounding wire and the lead tube inspection; Combined with the protection recording and equipment dismantling inspection and analysis, a preliminary analysis of the cause of the fault was conducted and the starting location of the fault was determined.

4. The SF6 current transformer internal fault analysis method based on the finite element method as claimed in claim 3, characterized in that: The establishment of the geometric model includes determining the starting position of the fault according to the disintegration situation, performing three-dimensional modeling on the fault starting position part of the SF6 current transformer, filling the screw holes, deleting the bolts and the secondary winding and the core in the secondary shielding cover, focusing on the electric field distribution of the internal electrodes and insulating parts of the current transformer, simplifying the bushing, base and lead structure, and using Comsol software to establish a three-dimensional electric field simulation geometric model under normal conditions, cracks on the outer surface of the support, and bubbles inside the support, and performing material selection and boundary condition setting.

5. The SF6 current transformer internal fault analysis method based on the finite element method as claimed in claim 4, characterized in that: The material selection includes that in the three-dimensional electric field simulation geometric model, the shell, secondary shielding cover, and conductive tube are all made of aluminum alloy materials, the insulating pillars are made of epoxy resin materials, the shell is filled with SF6 gas materials, the inside of the outer sheath is glass fiber impregnated with epoxy resin materials, and the outer sheath is made of silicone rubber.

6. The SF6 current transformer internal fault analysis method based on the finite element method as claimed in claim 5, characterized in that: The boundary conditions include obtaining the effective value of the line voltage of the current transformer, converting the effective value of the line voltage into the peak value of the phase voltage, obtaining the corresponding lightning impulse voltage peak value, performing electric field calculations of the current transformer defect-free model, crack, and bubble defect model under the lightning impulse voltage, loading the top shell, primary winding, and bushing shield I with high potential, grounding the secondary winding shielding cover and the secondary lead tube, and setting the bushing shield II with a suspended potential.

7. The SF6 current transformer internal fault analysis method based on the finite element method as claimed in claim 6, characterized in that: The finite element simulation includes performing finite element simulation based on an established three-dimensional electric field simulation geometric model, analyzing the crack conditions under normal working conditions, the outer surface crack defect conditions at the fault starting position, and the internal bubble defect conditions at the fault starting position, to obtain the cause of the fault.

8. A system using the SF6 current transformer internal fault analysis method based on the finite element method as claimed in any one of claims 1 to 7, characterized in that: It includes a structure acquisition module (100), a disassembly analysis module (200) and a finite element simulation module (300); The structure acquisition module (100) is used to acquire the internal structure and disintegration status of the SF6 current transformer; The disassembly analysis module (200) is used to analyze the starting position of the internal fault of the SF6 current transformer according to the disassembly situation; The finite element simulation module (300) is used to establish a geometric model according to the fault starting position, perform finite element simulation, and obtain the cause of the fault.

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 SF6 current transformer internal fault analysis method based on the finite element 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 SF6 current transformer internal fault analysis method based on the finite element method according to any one of claims 1 to 7 are implemented.

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