Motor anti-corona structure design method and device considering voltage division proportion of anti-corona structure

Abstract

The invention discloses a motor anti-corona structure design method and device considering the voltage division proportion of an anti-corona structure, core parameters of the motor anti-corona structure can be obtained by testing and calculating specific parameters of a motor bar, the method is suitable for various motors, especially high-voltage and ultrahigh-voltage motors and high-voltage variable-frequency motors, and the motor anti-corona structure design method and device are suitable for various motors. The device can simulate stator end parts of motors of multiple models, avoids the problem that a large-scale production line needs to be used for preparing winding bars when anti-corona structures of motors of different models are tested, and also avoids the problem that the corona discharge test of an anti-corona layer is interfered by partial discharge in a main insulator by utilizing the self-repairing characteristic of insulating oil. Through cooperation of the motor anti-corona structure design method of the anti-corona structure partial pressure proportion and the motor anti-corona structure detection device, design of various motor anti-corona structures can be realized, and the motor anti-corona structure detection device has the advantages of wide application scene, low cost, easy realization and the like. And rapid, accurate, simple, convenient and economical design and evaluation of different motor anti-corona structures are facilitated.

Description

Technical Field

[0001] This invention belongs to the technical field of high-voltage motor insulation structure design, specifically relating to a motor anti-corona structure design method and device that considers the voltage division ratio of the anti-corona structure. Background Technology

[0002] Current anti-corona technology for stator bar ends in high-voltage motors mainly relies on anti-corona layers (anti-corona structures) to alter the electric field distribution and homogenize the electric field, thereby avoiding electric field concentration at the stator bar ends due to their inherent insulation structure, which could lead to surface discharge. With the continuous development of high-voltage motor technology in my country, the increase in rated voltage places higher demands on stator bar end anti-corona technology. However, the design and optimization of existing anti-corona structures still rely on engineering experience, and the lack of more scientific and effective anti-corona structure design methods limits further increases in the voltage level of high-voltage motors.

[0003] The design methods for anti-corona structures at the ends of stator bars in high-voltage motors can be divided into two categories: one is based on the traditional RC chain model, and the other is based on the finite element model and algorithm optimization. The traditional RC chain model can only calculate the maximum electric field strength at the beginning (near the slot outlet) of each segment of the anti-corona structure. Furthermore, when the number of segments exceeds two, the complexity of the equations increases exponentially, making it almost impossible to solve anti-corona structures with three or more segments. The finite element model and optimization algorithm-based design methods, on the other hand, impose unrealistic requirements on material properties, such as requiring nonlinear anti-corona materials with extremely high nonlinear coefficients that are impossible to manufacture, thus making the anti-corona design unfeasible.

[0004] In view of the above factors, a design method and device for motor anti-corona structure considering the voltage division ratio of the anti-corona structure is provided. This method can more effectively improve the design of the anti-corona structure at the end of the motor stator bar. While achieving anti-corona, it can not only significantly shorten the length of the anti-corona structure, but also design a multi-segment anti-corona structure to further improve the anti-corona efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a method and device for designing an anti-corona structure for a motor that takes into account the voltage distribution ratio of the anti-corona structure, so as to solve the problems mentioned in the background art.

[0006] The objective of this invention is achieved through the following technical solution: a method for designing a motor anti-corona structure considering the voltage division ratio of the anti-corona structure, comprising the following steps;

[0007] Step 1: Test and obtain the main insulation material parameters and geometric parameters of the motor rod, and calculate its insulation parameters per unit length;

[0008] Among them, the material parameters, geometric parameters, and insulation parameters per unit length of the main insulation of the motor bar, including the relative permittivity per unit length, the unilateral thickness of the main insulation of the bar, the length and width of the rectangle formed by the cross-section of the internal winding of the bar, the capacitance value (specific capacitance) per unit length of the main insulation of the bar, and its capacitive reactance X

[0014] , ;

[0009] Step 2: Given a resistivity increase rate k, satisfying 1 < k < 10, substitute k and the insulation parameters per unit length of the motor bar into the formula , where η is the voltage division ratio of the grading structure, and M is the resistance-capacitance ratio . When calculating the voltage division ratio of the low-resistance layer, R is the resistivity of the low-resistance layer, which is numerically equal to the resistivity value ρ n ;

[0010] Among them, the expression of the voltage division ratio of the grading structure is , where U1 is the voltage of the main insulation to the ground, and η1 is the voltage division ratio of the low-resistance layer

[0011] Step 3: According to the maximum length of the grading structure allowed by the end structure of the motor bar, given a grading structure length L1, divide it into n finite segments with a length of x, where n is a positive integer greater than or equal to 1. Define the segment closest to the slot opening of the stator bar as the first segment, and the subsequent segments as the second segment, … until the nth segment. Let the resistivity of the nth segment be ρ n , and the resistivity of the (n - 1)th segment be , and so on, to determine the resistivity of all segments

[0012] Step 4: Establish a finite element model according to the end structure of the motor bar. According to the grading structure parameters determined in Step 3, including the number of segments n and the resistivity ρ n corresponding to the number of segments n, assign corresponding parameters to the grading structures of each segment, and calculate the electric field distribution of the grading structure

[0013] Step 5: Observe whether the maximum value E1 of the electric field strength on the surface of the grading structure and the maximum value E2 of the electric field strength on the surface of the exposed main insulation at the end of the grading structure are both lower than the allowable value E of the electric field strength on the surface of the end of the motor stator bar a . If both are yes, shorten the grading structure length L1, and repeat Steps 3 and 4 until the maximum value E1 of the electric field strength on the surface of the grading structure and the maximum value E2 of the electric field strength on the surface of the exposed main insulation at the end of the grading structure are exactly equal to the allowable value Ea of the electric field strength on the surface of the end of the motor stator bar

[0014] If the maximum value E1 of the surface electric field strength of the corona prevention structure or the maximum value E2 of the electric field strength on the exposed main insulation surface at the end of the corona prevention structure is higher than the allowable value Ea of the electric field strength on the end surface of the motor stator bar, increase the length L1 of the corona prevention structure, and repeat steps three and four until the maximum value E1 of the surface electric field strength of the corona prevention structure and the maximum value E2 of the electric field strength on the exposed main insulation surface at the end of the corona prevention structure are exactly equal to the allowable value Ea of the electric field strength on the end surface of the motor stator bar.

[0015] In particular, the more segments the corona prevention structure has, the closer the distribution of the resistance-capacitance ratio on the surface of the corona prevention structure is to the expression , where d is the distance ratio, x is the distance from the starting end of the corona prevention structure, l is the total length of the corona prevention structure, and it needs to satisfy 0 < x < l. For example, when , the expression is .

[0016] Furthermore, the range of the voltage division ratio of the low-resistance layer in step two is 1% - 12.5%.

[0017] Furthermore, when the maximum value E1 of the surface electric field strength of the corona prevention structure is too high, reduce the electric field strength by changing the resistivity on the segments of the length L1 of the corona prevention structure.

[0018] Furthermore, the resistivity values determined in step three include the resistivity values of conventional corona prevention materials, the values of the linear resistivity regions corresponding to non-linear corona prevention materials, and the non-linear resistivity values of non-linear corona prevention materials when bearing the allowable electric field strength on the end surface of the motor bar.

[0019] Furthermore, the calculation and analysis of the electric field distribution of the corona prevention structure in the finite element model in steps four and five include the calculation and analysis of the electric field strength modulus, loss distribution, and potential distribution on the surface of the corona prevention structure and the exposed main insulation surface at the end of the corona prevention structure when the corona prevention structure L1 changes.

[0020] A device for testing a motor corona prevention structure design method considering the voltage division ratio of the corona prevention structure includes a grading ball, which is tightly connected to the test main electrode through a fixed thread pair. The grading ball has an external thread on the side rod end that cooperates with the test main electrode, and the test main electrode has an internal thread inside that matches the external thread of the rod end of the grading ball;

[0021] It also includes a circular bare end, and the circular bare end is connected to a transmission line to introduce voltage to the test main electrode. The exposed part of the test main electrode between the circular bare end and the main body shell is wrapped with an epoxy resin insulating sleeve;

[0022] The test main electrode is arranged inside the main body shell, and the main body shell is threadedly and tightly fitted with the shell assembly through a shell thread pair;

[0023] The test electrode is connected to the electrode assembly disposed within the housing assembly via threads.

[0024] Furthermore, the outer casing assembly and the main casing form an insulating oil tank, and the test main electrode passes through one side of the main casing, with a threaded connection between the test main electrode and the main casing.

[0025] Furthermore, the right side of the main electrode has an internal thread hole that mates with the external thread on the left side of the electrode assembly;

[0026] The cavity formed by the outer shell assembly and the main shell is filled with insulating oil. The main shell has a sealing cover, and an insulating sealing gasket is placed between the main shell and the sealing cover when they are fitted together.

[0027] The main shell and the main electrode are fitted together, and the gaps between them are completely filled and bonded by epoxy resin adhesive.

[0028] Furthermore, the outer shell of the outer shell assembly is made of epoxy resin, the main electrode and electrode assembly are made of brass, and the equalizing ball is made of stainless steel or brass.

[0029] An application of a device for testing the anti-corona structure is presented, which considers the voltage division ratio of the anti-corona structure in the design of a motor anti-corona structure. By designing and simulating the structure of the main insulation and anti-corona layer at the end of the motor bar in a real environment, and utilizing the self-healing properties of insulating oil, the device avoids the problem of indistinguishable partial discharge caused by minor defects inside the main insulation due to process issues from the corona discharge on the surface of the anti-corona layer during the testing of the bar, thus interfering with the corona discharge test of the anti-corona layer.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] This invention can significantly shorten the length of the anti-corona layer (anti-corona structure) and reduce the size of the motor end, effectively improving the power density of the motor, without changing the main insulation structure at the end of the stator bar.

[0032] This invention proposes for the first time a method for precisely controlling the surface electric field strength of the stator bar ends, which has extremely high application value in various products that have strict requirements for the surface electric field strength of the stator bar ends, such as ultra-high voltage motors, high voltage variable frequency motors, high altitude motors, explosion-proof motors, and high-speed rail traction motors.

[0033] This invention achieves excellent anti-corona effect using conventional anti-corona materials with fixed resistivity, and can replace nonlinear anti-corona materials in most scenarios, greatly reducing the cost of motor anti-corona. Moreover, the anti-corona structure of this invention is easier to implement than that using nonlinear anti-corona materials.

[0034] This invention establishes a platform for testing the anti-corona performance of motors. Referring to the end structure of the stator bars of a real high-voltage motor, the main electrodes and electrode assemblies are used to represent the motor bars. Insulating oil is used to represent the main insulation of the motor bars, along with sealing structures and supporting components. The outer shell is made of epoxy resin sheet, providing both insulation performance and excellent mechanical strength support. In normal anti-corona performance testing structures, the main insulation is limited by factors such as processing technology, which can interfere with the test results due to potential defects in the main insulation. In contrast, because liquids are fluid, insulating oil can flow and self-repair after a discharge or breakdown occurs, reducing material loss. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the circuit model at the end of the stator bar of the motor of the present invention;

[0036] Figure 2 This is a diagram showing the relationship between the resistance-capacitance ratio and the voltage division coefficient of the anti-corona structure in the unit circuit of this invention.

[0037] Figure 3 This is a schematic diagram of the resistance-capacitance ratio distribution of the anti-corona structure of the present invention;

[0038] Figure 4 This is a diagram showing the electric field intensity and resistivity distribution at the end of the stator bar of the motor designed in this invention;

[0039] Figure 5 This is the flowchart corresponding to step five of the present invention;

[0040] Figure 6 This is a schematic diagram of the motor anti-corona structure testing device of the present invention;

[0041] Figure 7 This is a partial schematic diagram of the motor anti-corona structure testing device of the present invention;

[0042] Figure 1 In the diagram, 1-Equalizing ball; 2-Circular bare end; 3-Epoxy resin insulating sleeve; 4-Sealing cap; 5-Electrode thread pair; 6-Insulating sealing gasket; 7-Fixing thread pair; 8-Shell thread pair; 9-Main electrode; 10-Electrode assembly; 11-Insulating oil; 12-Shell assembly; 13-Main shell;

[0043] Figure 7 In the middle, 21-insulating oil, 22-tin foil, 23-anti-corona layer 1, 24-anti-corona layer 2, 25-anti-corona layer 3. Detailed Implementation

[0044] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0045] In the description of the present invention, it should be noted that, unless otherwise clearly defined and limited, the terms "installed", "connected", and "connected" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be directly connected, or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0046] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0047] As Figure 1-4 shown, a method for designing an anti-corona structure of a motor considering the voltage division ratio of the anti-corona structure includes the following steps;

[0048] Step 1, test and obtain the material parameters and geometric parameters of the main insulation material of the motor wire bar, and calculate the insulation parameters per unit length thereof;

[0049] Among them, the material parameters, geometric parameters, and insulation parameters per unit length of the main insulation of the motor wire bar include the relative permittivity per unit length, the single-sided thickness of the main insulation of the wire bar, the length and width of the rectangle formed by the cross-section of the internal winding of the wire bar, the capacitance value (specific capacitance) per unit length of the main insulation of the wire bar, and its capacitive reactance X C ; [[ID=2|1]]

[0050] Step 2, given a resistivity rise rate k, satisfying 1 < k < 10, substitute k and the insulation parameters per unit length of the motor wire bar into the formula , where η is the voltage division ratio of the anti-corona structure, and M is the resistance-capacitance ratio, , when calculating the voltage division ratio of the low-resistance layer, R is the resistivity of the low-resistance layer, and its numerical value is equal to the resistivity value ρ n ;

[0051] Among them, the expression of the voltage division ratio of the anti-corona structure is Where U1 is the voltage of the main insulation to ground, and η1 is the voltage division ratio of the low-resistivity layer.

[0052] Step 3: Based on the maximum allowable length of the anti-corona structure at the end of the motor rod, a given anti-corona structure length L1 is established. This structure is then divided into n equal segments of length x, where n is a positive integer greater than or equal to 1. The segment closest to the stator rod slot is defined as segment 1, followed by segment 2, and so on until segment n. Let the resistivity of segment n be ρ. n The resistivity of the (n-1)th segment is ...and so on, to determine the resistivity of all segments;

[0053] Step four: Establish a finite element model based on the end structure of the motor rod, according to the anti-corona structure parameters determined in step three, including the number of segments n and the resistivity ρ corresponding to segment n. n Each segment of the anti-corona structure is assigned corresponding parameters, and the electric field distribution of the anti-corona structure is calculated.

[0054] Step 5: Observe whether the maximum electric field strength E1 on the surface of the anti-corona structure and the maximum electric field strength E2 on the exposed main insulation surface at the end of the anti-corona structure are both lower than the allowable value E of the electric field strength on the surface of the motor stator bar end. a If both are true, then shorten the length L1 of the anti-corona structure and repeat steps three and four until the maximum electric field strength E1 on the surface of the anti-corona structure and the maximum electric field strength E2 on the exposed main insulation surface at the end of the anti-corona structure are exactly equal to the allowable value Ea of the electric field strength on the end surface of the motor stator bar.

[0055] If the maximum electric field strength E1 on the surface of the anti-corona structure or the maximum electric field strength E2 on the exposed main insulation surface at the end of the anti-corona structure is higher than the allowable electric field strength Ea on the end surface of the motor stator bar, then increase the length L1 of the anti-corona structure and repeat steps three and four until the maximum electric field strength E1 on the surface of the anti-corona structure and the maximum electric field strength E2 on the exposed main insulation surface at the end of the anti-corona structure are exactly equal to the allowable electric field strength Ea on the end surface of the motor stator bar.

[0056] In step two, the voltage division ratio of the low-resistivity layer ranges from 1% to 12.5%.

[0057] When the maximum electric field strength E1 on the surface of the anti-corona structure is too high, the electric field strength is reduced by changing the resistivity of the segments along the length L1 of the anti-corona structure.

[0058] The resistivity values ​​determined in step three include the resistivity values ​​of conventional anti-corona materials, the resistivity values ​​of nonlinear anti-corona materials in the linear region, and the nonlinear resistivity values ​​of nonlinear anti-corona materials within the allowable electric field strength range of the motor rod end surface.

[0059] Steps four and five involve the calculation and analysis of the electric field distribution of the anti-corona structure using the finite element model, including the calculation and analysis of the electric field strength modulus, loss distribution, and potential distribution on the surface of the anti-corona structure and the exposed main insulation surface at the end of the anti-corona structure when the anti-corona structure L1 changes.

[0060] like Figure 5-7 As shown, a device for testing the anti-corona structure is a design method for motor anti-corona structure considering the voltage distribution ratio of the anti-corona structure. The device includes an equalizing ball 1, which is fastened to the test main electrode 9 through a fixed threaded pair 7. The end of the equalizing ball 1 that mates with the test main electrode 9 has an external thread, and the test main electrode 9 has an internal thread that mates with the external thread of the end of the equalizing ball 1.

[0061] It also includes a circular bare end 2, which is matched with the equalizing ball 1. The circular hole in the middle of the circular bare end 2 is fitted into the screw. The circular bare end 2 of the test main electrode 9 is connected to a power transmission line to introduce voltage to the test main electrode 9. The exposed part of the test main electrode 9 between the circular bare end 2 and the main body shell 13 is wrapped with an epoxy resin insulating sleeve 3.

[0062] The test electrode 9 is disposed inside the main body shell 13, and the main body shell 13 is threadedly fastened to the shell assembly 12 via the shell thread pair 8.

[0063] The test electrode 9 is connected to the electrode assembly 10 disposed within the housing assembly 12 by a thread.

[0064] The outer casing assembly 12 and the main casing 13 form an insulating oil tank. The test main electrode 9 passes through one side of the main casing 13 and is threadedly connected to the main casing 13.

[0065] The main electrode 9 has an internal thread hole on its right side that mates with the external thread on the left side of the electrode assembly 10;

[0066] The cavity formed by the outer shell assembly 12 and the main shell 13 is filled with insulating oil 11. The main shell 13 has a sealing cover 4. When they are fitted together, an insulating sealing gasket 6 is placed between the outer shell and the sealing cover.

[0067] The main body shell 13 and the main body electrode 9 are mutually matched, and the gaps between the two are completely filled and bonded by epoxy resin adhesive.

[0068] The circular bare end is clamped by an equalizing ball and the main electrode. A high-voltage AC transmission line is connected below the circular bare end. The transmission line is located below the overall device and is wrapped with an insulating sleeve on the outside. The test main electrode is connected to the main shell by adhesive. The adhesive used in the adhesive process is an epoxy resin adhesive with good insulation properties, so that the main electrode and the main shell form a whole. The sealing cover is equipped on the main shell by internal and external thread matching. The sealing cover has internal thread and the main shell has external thread. An insulating sealing gasket is placed between the two when they are matched.

[0069] The right side of the main shell is trapezoidal. The internal thread hole is machined at the thickened part of the main shell using a machine tool. The shape of the shell component is similar to that of a PET bottle. External threads are machined on the outside of the narrow opening using a lathe. The external threads can be mated with the internal threads of the main shell. When the internal and external threads are mated, an insulating sealing gasket should be placed between them.

[0070] The outer shell assembly has a circular hole in the center of its external thread, with a diameter larger than that of the electrode assembly. The main electrode and the electrode assembly are connected using internal and external threads. The fixed end is machined with an internal thread on a lathe. The internal and external threads require precision machining. When mating, a small amount of conductive grease should be applied to the external thread of the electrode assembly and the bottom plane of the external thread. After connection, epoxy resin sealant should be applied to the interface to prevent insulating oil from seeping into the gaps, and the surface should be polished smooth. The insulating oil fills the entire main shell and the interior of the outer shell assembly. The insulating oil is added through the sealing cap. After the main shell and the outer shell assembly are fastened, the insulating oil enters the interior of the outer shell assembly through the central circular hole and the gap between the electrode assembly, filling the internal space.

[0071] The outer shell 13 of the outer shell assembly 12 is made of epoxy resin, the main electrode 9 and the electrode assembly 10 are both made of brass, and the equalizing ball 1 is made of stainless steel or brass.

[0072] A method for designing a motor anti-corona structure considering the voltage divider ratio of the anti-corona structure, and a device for verifying the anti-corona structure, comprising the following steps:

[0073] Step 1: Select an insulating oil with a consistent dielectric constant based on the dielectric constant of the main insulation, and determine the amount of insulating oil to use based on the structural parameters of the main insulation.

[0074] Step 2: Make electrode assembly and corresponding housing assembly models according to the actual shape of the wire rod. Both have external threads that match the corresponding internal thread holes.

[0075] Step 3: Connect the electrode assembly to the main electrode. Before connecting, apply a certain amount of conductive paste to the external thread of the electrode assembly and the bottom plane of the external thread to ensure good conductivity. After connecting, apply epoxy resin sealant to the interface to ensure that insulating oil does not seep into the joint. Connect the outer shell assembly to the main shell, and place an insulating sealing coil between the two during the connection.

[0076] Step 4: Open the sealing cap and inject insulating oil into the cavity. The insulating oil should be injected slowly to ensure that it fills the cavity of the device and that there are no air bubbles.

[0077] Step 5: Wrap a layer of tin foil around the outer shell interface, and place a ground wire between the tin foil and the outer shell for grounding; wrap the anti-corona material to be tested around the part of the outer shell assembly that is not covered by tin foil. The anti-corona material has the same composition parameters as the actual anti-corona layer. Wrap the outer shell assembly with a low-resistance layer, a medium-resistance layer, and a high-resistance layer.

[0078] Step 6: With the power off, align the center hole of the bare circular end with the threaded hole of the electrode, and fasten the equalizing ball rod end to the main electrode and the bare circular end through the threaded engagement.

[0079] Step 7: Connect the power supply. The test voltage should be AC ​​with a frequency of 50Hz and a sine waveform. The voltage applied during the test should start from no more than half of the corona initiation voltage value specified in formula (1) or formula (2), and then be increased uniformly to the full value. The time for the voltage to increase from half the value to the full value should not be less than 10s.

[0080] The corona initiation voltage of the motor coil (or rod) should not be lower than the value calculated by formula (1):

[0081] Equation (1):

[0082]

[0083] In the formula:

[0084] U BS - The corona initiation voltage of a coil (or bar), in kV;

[0085] U N - The rated voltage of the motor, in kV;

[0086] K – The rate of decrease in corona initiation voltage with increasing altitude, where K is taken as 0.1, and the unit is km. -1

[0087] H S - The altitude of the motor installation site, in km;

[0088] H A - The altitude of the motor installation site, in km;

[0089] The corona initiation voltage of the motor winding should not be lower than the calculated value of formula (2):

[0090]

[0091] In the formula:

[0092] U IS - Corona initiation voltage of motor windings, in kV;

[0093] U φ - Rated phase voltage of the motor, in kV;

[0094] Step 8: Observe under full voltage, using a high-speed ultraviolet camera to photograph the surface of the anti-corona layer and infrared thermography to measure the surface temperature to confirm whether corona discharge has occurred. Confirm the test results; the time should not exceed 1 minute. After the test observation is completed, uniformly reduce the voltage to half the test voltage, then quickly reduce it to zero. After disconnecting the power supply, discharge the sample to ground to evaluate the anti-corona performance of the anti-corona structure.

[0095] Taking the stator bars of a certain type of 24kV gas turbine as an example, the measured length of the bars is 8.146m, the capacitance to ground is 11nF, and the capacitance per unit length of the bars is 1.36×10⁻⁶. -9 F / m, capacitive reactance X C 2.3×10 11 Ω / m. The anti-corona layer is divided into 10 segments, with the partial pressure ratio at the end of the anti-corona layer set to 10%, and k set to 1.43. , The calculated resistivity of each anti-corona layer is shown in the table.

[0096]

[0097] Based on the above data, a finite element model was established to observe whether the maximum electric field strength on the surface of the anti-corona structure was exactly lower than the allowable value of 0.31 kV / mm on the surface of the stator bar end of the motor, and whether the maximum electric field strength on the exposed main insulation surface at the end of the anti-corona structure was higher than the electric field strength on the surface of the stator bar end of the motor. Verification showed that when the anti-corona structure L1 = 300 mm, the maximum electric field strength on the surface of the anti-corona structure was approximately 0.237 kV / mm, lower than the electric field strength on the surface of the stator bar end of the motor (0.31 kV / mm), and the maximum electric field strength on the exposed main insulation surface at the end of the anti-corona structure was not higher than the allowable value of the electric field strength on the surface of the stator bar end. Figure 4 As shown.

[0098] Based on the motor's main insulation design, the main electrode (32mm wide, 61mm long) and the main outer shell (36.8mm wide, 65.8mm long) were installed on the motor anti-corona structure testing device. Insulating oil with a relative permittivity of 4 was injected, and the device was left to stand for 12 hours to ensure that the insulating oil was free of air bubbles. A layer of tin foil was wrapped around the outer shell interface, and a grounding wire was fixed between the tin foil and the outer shell. After grounding, anti-corona tapes made of 10 different anti-corona materials with different resistivities (as shown in the table) were tightly wrapped around the outer surface of the main shell (not covered by tin foil) in order of number 1-10, with a standard width of 30mm, from near to far. The center hole of the circular bare end was aligned with the threaded hole of the electrode. The equalizing ball end was fastened to the main electrode via a threaded connection with the round bare end, thus connecting to the power supply. The power was then turned on and boosted to the test voltage of 24kV. Following the DL / T 298-2011 standard, visual inspection in a darkroom showed no corona discharge, proving the anti-corona design was successfully implemented and achieved its anti-corona effect. At this point, the length of the anti-corona structure was still approximately 10% shorter than the minimum length of existing 24kV motor rod anti-corona structures (330mm to 400mm).

[0099] In this process, inspectors can visually inspect experimental phenomena using a high-speed ultraviolet camera and an infrared thermal imager. Testers entering a dark room or dark place should allow their vision to adapt to the dark environment for at least 5 minutes. During the test, three experienced testers with good vision should simultaneously observe the sample; the results of at least two observations are considered valid. The high-speed ultraviolet camera can be used to detect and record corona discharge phenomena in high-voltage equipment. By capturing the ultraviolet radiation emitted during corona discharge, infrared thermal imaging can measure the localized heating caused by energy loss when the anti-corona layer has defects and generates corona or increased leakage current. The high-speed ultraviolet camera and infrared thermal imager can be used to characterize the anti-corona status of equipment.

[0100] An application of a device for testing the anti-corona structure is presented, which considers the voltage division ratio of the anti-corona structure in the design of a motor anti-corona structure. By designing and simulating the structure of the main insulation and anti-corona layer at the end of the motor bar in a real environment, and utilizing the self-healing properties of insulating oil, the device avoids the problem of indistinguishable partial discharge caused by minor defects inside the main insulation due to process issues from the corona discharge on the surface of the anti-corona layer during the testing of the bar, thus interfering with the corona discharge test of the anti-corona layer.

[0101] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0102] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for designing a motor anti-hunting structure considering the partial pressure ratio of the anti-hunting structure, characterized in that: It comprises the following steps: Step one, test the motor wire bar main insulation material parameters and geometric parameters, calculate the insulation parameters per unit length; Wherein, the material parameters, geometric parameters, insulation parameters per unit length of the main insulation of the motor bar, including the relative permittivity per unit length, the single side thickness of the main insulation of the bar, the length and width of the rectangular section constituted by the internal winding of the bar, the capacitance value (specific capacitance) per unit length of the main insulation of the bar and its reactance X C ; Step two, given a resistivity rising rate k, satisfying 1 < k < 10, put k and the insulation parameter of the motor wire rod unit length into the formula , to calculate the end voltage division ratio of the anti-balling structure. Wherein, η is the anti-balling structure voltage division ratio, wherein, M is the resistance-capacitance ratio, , when calculating the voltage division ratio, R is the resistivity of the corresponding position of the anti-balling structure, which is equal in value to the resistivity value ρ n ; The anti-halo structure is expressed by a partial pressure ratio formula as Wherein, U1 is the voltage of the main insulation to ground, and η1 is the partial pressure ratio of the low-resistance layer. Step three, according to the maximum length of the anti-bucking structure allowed by the end structure of the motor wire bar, a length L1 of the anti-bucking structure is given, which is equally divided into a finite n segments with a length of x, where n is a positive integer greater than or equal to 1, the segment closest to the stator wire bar slot is defined as the first segment, followed by the second segment, and so on until the nth segment, and the resistivity of the nth segment is defined as n , the resistivity of the n-1th segment is , and so on, to determine the resistivity of all segments. Step four, according to the resistivity of each segment, the length of each segment, and the length of the anti-bucking structure, the length of the anti-bucking structure is determined as L1 = x + x + x + … + x Step five, according to the length of the anti-bucking structure, the length of each segment, and the length of the anti-bucking structure, the length of the anti-bucking structure is determined as L1 = x + x + x + … + x Step six, according to the length of the anti-bucking structure, the length of each segment, and the length Step four, according to the motor wire bar end structure to establish a finite element model, in accordance with the step three determined anti-blooming structure parameters, including the number of segments n, and the number of segments n corresponding to the resistivity p n , respectively, each segment of the anti-blooming structure is given corresponding parameters, and the anti-blooming structure electric field distribution is calculated; Step five, observe whether the maximum surface electric field intensity E1 of the anti-hunting structure and the maximum surface electric field intensity E2 of the exposed main insulation surface at the end of the anti-hunting structure are both lower than the allowable value Ea of the surface electric field intensity of the end surface of the motor stator bar a If both are yes, shorten the length L1 of the anti-hunting structure, and repeat steps three and four until the maximum surface electric field intensity E1 of the anti-hunting structure and the maximum surface electric field intensity E2 of the exposed main insulation surface at the end of the anti-hunting structure are exactly equal to the allowable value Ea of the surface electric field intensity of the end surface of the motor stator bar. If the maximum surface electric field strength E1 of the anti-corona structure or the maximum surface electric field strength E2 of the anti-corona structure end exposed main insulation is higher than the allowable value Ea of the surface electric field strength of the motor stator wire bar end, the length L1 of the anti-corona structure is increased, and steps three and four are repeated until the maximum surface electric field strength E1 of the anti-corona structure and the maximum surface electric field strength E2 of the anti-corona structure end exposed main insulation are equal to the allowable value Ea of the surface electric field strength of the motor stator wire bar end.

2. The method for designing the de-buzzing structure of the motor considering the pressure ratio of the de-buzzing structure according to claim 1, characterized in that: The range of the voltage division ratio of the anti-corona structure end in step two is 1%-12.5%.

3. The method for motor anti-hunting structure design considering the proportion of partial pressure of anti-hunting structure according to claim 2, characterized in that: When the maximum surface electric field strength E1 of the anti-corona structure is too high, the electric field strength is reduced by changing the length L1 of the anti-corona structure and its resistivity, wherein the way to change the length L1 of the anti-corona structure includes increasing the length L1 of the anti-corona structure, and the way to change the resistivity includes increasing or decreasing the resistivity rising rate k.

4. The method for designing the anti-hunting structure of the motor considering the pressure ratio of the anti-hunting structure according to claim 3, characterized in that: The value of the resistivity determined in step three includes the resistivity value of the conventional anti-corona material, the value of the linear region of the resistivity corresponding to the nonlinear anti-corona material, and the nonlinear resistivity value of the nonlinear anti-corona material when it withstands the allowable electric field strength range of the motor wire bar end surface.

5. The method for designing the de-buzzing structure of the motor considering the pressure ratio of the de-buzzing structure according to claim 4, characterized in that: The finite element model anti-corona structure electric field distribution calculation and analysis in steps four and five include the calculation and analysis of the electric field strength modulus, loss distribution, and potential distribution of the anti-corona structure surface and the anti-corona structure end exposed main insulation when the anti-corona structure L1 changes.

6. A device for checking the anti-hunting structure of the motor according to the method of claim 5, characterized in that it comprises: It comprises a voltage equalizing ball (1) which is fastened to a test main electrode (9) through a fixed threaded pair (7), and the voltage equalizing ball (1) and the test main electrode (9) are matched on one side of the bar end with external threads, and the test main electrode (9) has internal threads in the inside which are matched with the external threads of the bar end of the voltage equalizing ball (1); It also comprises a circular bare end (2) which is connected to a power transmission line to introduce voltage to the test main electrode (9), and the exposed part of the test main electrode (9) between the circular bare end (2) and the main shell (13) is wrapped with an epoxy resin insulation sleeve (3); The test main electrode (9) is arranged in the main shell (13), and the main shell (13) is threadedly fastened to a shell assembly (12) through a shell threaded pair (8); The test main electrode (9) is connected to an electrode assembly (10) arranged in the shell assembly (12) through threads.

7. The device for testing the anti-hunting structure of the method for designing the anti-hunting structure of the motor considering the pressure ratio of the anti-hunting structure according to claim 6, characterized in that: The shell assembly (12) and the main shell (13) form an insulation oil tank, and the test main electrode (9) passes through one side of the main shell (13), and the test main electrode (9) is threadedly connected to the main shell (13).

8. The device for checking the anti-hunting structure of the method for designing the anti-hunting structure of the motor considering the pressure ratio of the anti-hunting structure according to claim 7, characterized in that: The main electrode (9) has an internal threaded hole on the right side which is matched with the external threads on the left side of the electrode assembly (10); The cavity formed by the shell assembly (12) and the main shell (13) is filled with insulation oil (11), and the main shell (13) has a sealing cover (4), and an insulation sealing gasket (6) is placed between the shell and the sealing cover when they are matched; The main body shell (13) cooperates with the main body electrode (9), and the cooperation apertures are completely filled and adhered by epoxy resin adhesive.

9. The device for checking the anti-hunting structure of the method for designing the anti-hunting structure of the motor considering the pressure ratio of the anti-hunting structure according to claim 8, characterized in that: The main body shell (13) of the shell assembly (12) is made of epoxy resin, the main body electrode (9) and the electrode assembly (10) are both made of brass, and the equalizing ball 1 is made of stainless steel or brass.

10. The application of the device for checking the anti-corona structure of the motor anti-corona structure design method considering the pressure distribution ratio of the anti-corona structure according to claim 9, by designing and simulating the structure of the main insulation and the anti-corona layer at the end of the motor wire rod in the real environment, and using the self-repairing property of the insulating oil, the problem that the partial discharge caused by the internal slight defects of the main insulation and the corona discharge on the surface of the anti-corona layer cannot be distinguished due to process problems during the test process of the wire rod, and further interfere with the corona discharge test of the anti-corona layer is avoided.

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