CN-121543359-B - Transformer structure response calculation and grading operation maintenance strategy considering nonlinear characteristics of winding cushion block materials

CN121543359BCN 121543359 BCN121543359 BCN 121543359BCN-121543359-B

Abstract

The invention belongs to the technical field of non-electric variable prediction of power equipment, and relates to a transformer structure response calculation and grading operation and maintenance strategy taking nonlinear characteristics of a winding cushion block material into consideration, wherein a real stress state is simulated and residual moisture interference is eliminated through cushion block sample preparation and pretreatment; the method comprises the steps of realizing accurate simulation of environmental humidity through dynamic humidity regulation and verification, obtaining high-precision stress-strain data through a nonlinear compression test, dividing an elasticity, plasticity platform and densification key strain stage based on local slope and change rate, establishing a segmented power law constitutive model to represent mechanical characteristics of each stage, combining three-dimensional modeling and multi-physical-field simulation, improving the reliability of the model through vibration measurement and boundary condition adjustment, formulating a grading operation and maintenance strategy based on cushion plastic deformation calculation under a short-circuit working condition, improving the prediction precision of the structural response of the transformer, and solving the problem of prediction deviation of the structural response caused by neglecting cushion nonlinearity, humidity influence and insufficient coupling of multiple physical fields in the traditional method.

Inventors

LIU CHENGXIANG
REN BO
ZHANG LINZHI
Yi Wanshuang
Zhong Zhuoyan
TIAN GUODONG
WANG JIANLAN
XU LANLAN
YU FANG
CHEN YUAN
WANG JUNQING
XU BO
RAN YICHUAN
LI YOUPING
TANG ZHENGYANG
XUE BING
ZHANG CHUNHUI
LIU JINGTAO

Assignees

中国长江电力股份有限公司

Dates

Publication Date: 20260505
Application Date: 20260119

Claims (9)

1. The transformer structure response calculation and grading operation and maintenance strategy taking nonlinear characteristics of winding cushion block materials into consideration is characterized by comprising the following steps: S1, preparing and preprocessing a cushion block sample; s2, dynamic humidity regulation and verification; s3, nonlinear compression testing; s4, dividing key strain stages; s5, establishing a segmented power law constitutive model; s6, three-dimensional modeling; S7, normal working condition simulation calculation; s8, measuring vibration acceleration under normal working conditions; s9, boundary condition adjustment; S10, simulating and calculating short-circuit working conditions; s11, formulating a grading operation maintenance strategy; in S4, specifically includes: S4-1, calculating local slope point by point for the processed stress-strain data And local slope change rate : Wherein the method comprises the steps of And Represent the first Strain and stress of the point; s4-2, identifying the end point of the elastic phase in the loading process Finding local slope change rate Corresponding to a strain value of ; S4-3, identifying end points of plastic platform areas in loading process Calculating local slope change rate The point at which the mean value of (2) reaches the threshold value is the plateau end point, the corresponding strain is The threshold value is the sum of the mean value and the standard deviation; in S2, specifically includes: s2-1, preparing saturated salt solution, placing the saturated salt solution in a constant temperature tank, and introducing dry nitrogen into the solution to generate gas with humidity; S2-2, placing the insulating cushion block into a sealed container, setting target humidity according to the actual running environment of the transformer, introducing the gas, feeding back data in real time through a high-precision temperature and humidity sensor, and dynamically adjusting the proportion of dry/wet nitrogen, wherein the humidity fluctuation is +/-0.1%; s2-3, maintaining the humidity at a constant temperature for 24 hours under the target humidity, scanning the internal humidity distribution by adopting a near infrared spectrometer, and sampling and titrating to verify that the humidity error is less than 0.1%; In S5, specifically includes: S5-1, intercepting loading process Fitting elastic phase coefficients using a first order polynomial And initial residual stress Obtaining a cushion block elasticity stage constitutive equation: Wherein the method comprises the steps of And Respectively representing stress and strain; s5-2, intercepting loading process Is optimized using the Levenberg-Marquardt algorithm ~ Obtaining a cushion block plastic platform stage constitutive equation: Wherein the method comprises the steps of And Respectively the stress and strain are indicated, ~ The proportional coefficient, the index coefficient and the constant term of the plastic platform stage are respectively; S5-3, intercepting the loading process Is optimized using the Levenberg-Marquardt algorithm ~ Obtaining a cushion block densification stage constitutive equation: Wherein the method comprises the steps of And Respectively the stress and strain are indicated, And For the plastic plateau phase end point stresses and strains, ~ The proportion coefficient and the index coefficient of the cushion block densification stage are respectively; S5-4, intercepting experimental data of an unloading stage, and optimizing the coefficients of the unloading stage by using a Levenberg-Marquardt algorithm to obtain an unloading stage constitutive equation: Wherein the method comprises the steps of And Respectively the stress and strain are indicated, Representing the residual stress after the final unloading, Indicating the load-off start point strain, And Representing the unloading stage coefficients.
2. The transformer structural response calculation and hierarchical operation and maintenance strategy taking into account the nonlinear characteristics of the winding spacer material according to claim 1, wherein in S1, specifically comprises: s1-1, preparing test blocks with the dimensions of 8 mm long, 8 mm wide and 6 mm thick by adopting a directional hot-pressing process, and controlling hot-pressing parameters to be 10+/-0.1 MPa at 75+/-2 ℃ for 20 minutes so as to simulate the actual stress distribution of a transformer cushion block; s1-2, quick dehydration in a first stage, namely dehydration in a vacuum drying oven for 12 hours, and free moisture removal; s1-3, the second stage is stable drying, namely, high-purity nitrogen is introduced, the temperature is maintained at 60+/-1 ℃, and the vacuum degree is kept below 5 kPa for continuous drying for 12 hours; s1-4, judging an end point, namely, through an online mass spectrometer, the required resolution is less than or equal to 0.001 mg/(g.h), monitoring the moisture release rate in real time to be less than 0.01 mg/(g.h), and ensuring the initial humidity to be less than or equal to 0.5%.
3. The transformer structural response calculation and hierarchical operation and maintenance strategy taking into account the nonlinear characteristics of the winding spacer material according to claim 1, wherein in S3, specifically comprises: S3-1, using a material mechanical testing device, wherein the measuring range is more than or equal to 10MPa, the precision is less than or equal to +/-0.1% of full-scale FS, loading to 10MPa at a strain rate of 0.05%/S, unloading to 0.3MPa at the same rate after 10 seconds, recording stress-strain data, and sampling frequency is 100 Hz, and repeating 5 times of experiments for each group of conditions to average; s3-2, extracting discrete data points from the experimental curve image by using data processing software, wherein the discrete data points comprise two columns of data of strain mm/mm and stress MPa; s3-3, preprocessing data, namely adopting a Savitzky-Golay filter, wherein the window width is 5, and the polynomial order is 2, so that high-frequency noise is eliminated.
4. The transformer structural response calculation and grading operation and maintenance strategy considering the nonlinear characteristics of the winding cushion block materials according to claim 1 is characterized in that in S6, solidWorks is used for building a three-dimensional model of the transformer, the three-dimensional model comprises a high-low voltage winding, a pressing plate, a cushion block and an iron core main structure, ANSYS Workbench is led in to generate a hexahedral leading grid, the hexahedral leading grid is locally encrypted to 0.3 mm, and the Jacobian ratio is more than 0.6.
5. The transformer structural response calculation and hierarchical operation and maintenance strategy taking into account the nonlinear characteristics of the winding spacer material according to claim 1, wherein in S7, the method specifically comprises: S7-1, setting winding and iron core magnetic fields to calculate material parameters, wherein the B-H curve of the silicon steel sheet uses factory parameters; S7-2, calculating normal operation conditions, and current under no-load closing and rated operation Obtaining excitation of magnetic field calculation; S7-3, calculating Lorentz force applied to the winding by solving magnetic field distribution through ANSYS Maxwell; deriving a control equation of the magnetic field according to Maxwell's equation set, the equation and the magnetic vector potential Correlation: ; Wherein, the Is the current density vector which is used to determine the current density, Is the magnetic permeability of the material, Is the conductivity; S7-4, analyzing the response of the normal working condition structure; The magnitude of the normal operating mode current density vector is defined as current Cross-sectional area with wires in transformer windings Ratio of (3): Wherein, the As a unit vector, indicating the tangential direction at the winding; further, winding stress is calculated according to the lorentz force law: Wherein, the Is the magnetic induction intensity; Calculating the structural response of the transformer, wherein the solid mechanics motion differential equation is as follows: Wherein, the Indicating that the winding is stressed, , And Respectively representing the mass matrix, the damping matrix and the deformation of the transformer winding, , And Representing acceleration, velocity and displacement, respectively.
6. The transformer structural response calculation and hierarchical operation and maintenance strategy taking into account the nonlinear characteristics of the winding spacer material according to claim 1, wherein in S8, the method specifically comprises: And arranging an acceleration sensor and a stress sensor on the upper pressing plate and the lower pressing plate of the winding, arranging 2 sensors respectively in the circumferential direction, and measuring the stress and the acceleration under the same normal working condition and the simulation working condition.
7. The transformer structural response calculation and hierarchical operation and maintenance strategy taking into account the nonlinear characteristics of the winding spacer material according to claim 1, wherein in S9, the method specifically comprises: and (3) comparing the result obtained by measurement in the step (S8) with the simulation result of the corresponding position in the step (S7), and if the simulation and experimental error of the acceleration amplitude is more than 5%, adjusting the key boundary condition in the step (S7), namely the prestress of the pressing plate, until the simulation and actual measurement results of the acceleration amplitude are less than 5%.
8. The transformer structural response calculation and hierarchical operation and maintenance strategy taking into account the nonlinear characteristics of the winding spacer material according to claim 1, wherein in S10, specifically comprises: S10-1, setting winding and iron core magnetic fields to calculate material parameters, wherein the B-H curve of the silicon steel sheet uses factory parameters; s10-2, calculating short circuit current: Wherein, the Is the short-circuit current which is applied to the circuit, Is the effective value of the steady state current; The time is represented by the time period of the day, And Respectively representing equivalent resistance and equivalent leakage inductance, Is the initial phase angle and, Is the angular frequency; s10-3, solving magnetic field distribution through ANSYS Maxwell to derive Lorentz force density; deriving a control equation of the magnetic field according to Maxwell's equation set, the equation and the magnetic vector potential Correlation: ; Wherein, the Is the current density vector which is used to determine the current density, Is the magnetic permeability of the material, Is the conductivity; Further, the magnitude of the short circuit current density vector is defined as the ratio of the short circuit current to the cross-sectional area of the individual wires in the transformer winding: Wherein, the As a unit vector, indicating the tangential direction at the winding; further, winding stress is calculated according to the lorentz force law: S10-4, analyzing the structure response of the short-circuit working condition; Setting material parameters of a winding, an iron core and a cushion block for structural response analysis in finite element simulation software, wherein a copper conductor uses a linear elastic model, the elastic modulus is 110 GPa, an iron core silicon steel sheet uses factory parameters, the elastic modulus is 200GPa, setting the cushion block material to adopt a sectional constitutive model by using an experimental result obtained in the step S5, setting a pressing plate prestress boundary condition, and setting according to a determined value of the step S9; The differential equation of motion of solid mechanics is: Wherein, the Indicating that the winding is stressed, , And Respectively representing the mass matrix, the damping matrix and the deformation of the transformer winding, , And Representing acceleration, velocity and displacement, respectively.
9. The transformer structure response calculation and hierarchical operation and maintenance strategy taking into account the nonlinear characteristics of the winding pad material according to claim 1, wherein in S11, the method specifically comprises: According to the calculated plastic deformation result of the transformer cushion block, a grading operation and maintenance overhaul strategy is formulated as follows: if the maximum plastic deformation of the cushion block is smaller than a, the transformer can be put into operation normally and the running state can be observed continuously; If the maximum plastic deformation of the cushion block is greater than or equal to a and less than c th , the transformer is put into operation for 15min and vibration data are observed, if the vibration data are abnormal, the operation is stopped and the oil is discharged for inspection; if the maximum plastic deformation of the cushion block is greater than or equal to c th , the operation cannot be performed, oil is discharged, and the transformer winding is inspected; the critical values a and c th are determined according to the maximum oil passage height of the transformer.

Description

Transformer structure response calculation and grading operation maintenance strategy considering nonlinear characteristics of winding cushion block materials Technical Field The invention belongs to the technical field of non-electric variable prediction of power equipment, and relates to a transformer structure response calculation and grading operation maintenance strategy considering the non-linear characteristic of a winding cushion block material. Background When the power transformer is short-circuited, transient electromagnetic force born by the winding can reach hundreds of kilonewtons, and insulation breakdown can be caused by compression failure of the cushion block and displacement of the winding. Conventional structural response analysis has significant limitations, mainly including: (1) The material model has the defects that the cushion block is compressed to present the nonlinear characteristics of three stages of elasticity, a plastic platform and densification, the traditional linear elasticity assumption cannot represent the real relationship of stress and strain, so that the displacement prediction error is very large, and when compression cycles under multiple impact loads occur, the cushion block generates permanent thickness loss, so that the clamping pressure is continuously reduced; (2) Environmental factors are ignored, namely the mechanical property of the cushion block is obviously changed after moisture absorption, but the existing method does not realize humidity dynamic regulation and quantitative analysis; (3) Experiment and simulation disjoint that in the prior art, although the cushion block compression curve is measured through a static experiment, nonlinear characteristics are not integrated into a dynamic structure response model, and high-precision detection and feedback mechanisms of key parameters such as humidity, strain and the like are lacked, so that precise coupling of multiple physical fields (electromagnetic field-structural mechanics) cannot be realized; (4) The operation and maintenance quantization basis is insufficient, namely, after the transformer is short-circuited, the capability of judging the state of the transformer by an off-line method is very limited, and a transformer state quantization analysis method based on high-precision simulation calculation is absent. The limitations directly lead to the fact that whether the transformer can be continuously put into operation or not can not be judged only by means of offline means such as short-circuit impedance test after the transformer is short-circuited, so that a high-precision modeling and simulation method is needed, reliable test and test data verification are matched, influences of material nonlinearity and environmental factors on structural response of the transformer are comprehensively considered, and a transformer grading operation, maintenance and overhaul strategy after the short-circuit is realized. Disclosure of Invention The technical problem to be solved by the invention is to provide a transformer structure response calculation and grading operation and maintenance strategy considering the nonlinear characteristics of a winding cushion block material, and solve the problem of structure response prediction deviation caused by insufficient cushion block nonlinear modeling, humidity sensitivity neglect and multi-physical field coupling in the traditional method. In order to solve the technical problems, the technical scheme adopted by the invention is that the transformer structure response calculation and grading operation and maintenance strategy taking the nonlinear characteristics of the winding cushion block material into consideration comprises the following steps: S1, preparing and preprocessing a cushion block sample; s2, dynamic humidity regulation and verification; s3, nonlinear compression testing; s4, dividing key strain stages; s5, establishing a segmented power law constitutive model; s6, three-dimensional modeling; S7, normal working condition simulation calculation; s8, measuring vibration acceleration under normal working conditions; s9, boundary condition adjustment; S10, simulating and calculating short-circuit working conditions; s11, formulating a grading operation maintenance strategy; in S4, specifically includes: S4-1, calculating local slope point by point for the processed stress-strain data And local slope change rate: Wherein the method comprises the steps ofAndRepresent the firstStrain and stress at the point. S4-2, identifying the end point of the elastic phase in the loading processFinding local slope change rateCorresponding to a strain value of; S4-3, identifying end points of plastic platform areas in loading processCalculating local slope change rateThe point at which the mean value of (2) reaches the threshold value is the plateau end point, the corresponding strain isThe threshold value is the sum of the mean value and the standard deviation; In S5, s