CN115495944A - Method for acquiring electric-thermal-stress distribution of switch cabinet under influence of different factors - Google Patents

Method for acquiring electric-thermal-stress distribution of switch cabinet under influence of different factors Download PDF

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CN115495944A
CN115495944A CN202111118468.7A CN202111118468A CN115495944A CN 115495944 A CN115495944 A CN 115495944A CN 202111118468 A CN202111118468 A CN 202111118468A CN 115495944 A CN115495944 A CN 115495944A
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switch cabinet
temperature
stress
distribution
influence
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李鹏
贾廷波
张钟昱
郑楠
张健
何建好
朱江
吕红德
李同林
刘伟
朱传强
孙浩
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State Grid Corp of China SGCC
Rizhao Power Supply Co of State Grid Shandong Electric Power Co Ltd
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State Grid Corp of China SGCC
Rizhao Power Supply Co of State Grid Shandong Electric Power Co Ltd
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Abstract

The invention relates to a method for acquiring electric-thermal-stress distribution of a switch cabinet under the influence of different factors, which comprises the following steps: s1: establishing a three-dimensional physical model of a switch cabinet with multiple air chambers; s2: theoretical analysis of electromagnetic field, temperature conduction and solid mechanics of the switch cabinet; s3: adding electromagnetic-temperature-solid mechanics multi-physical field coupling; s4: setting corresponding parameters and boundary conditions; s5: carrying out mesh generation on the switch cabinet; s6: and (5) simulating to obtain the distribution of the electromagnetic field, the temperature field and the electric power of the switch cabinet. S7: and adding different fixed constraints to obtain different displacement amounts of the bus caused by stress. S8: the contact pressure at the joint was varied and the effect on temperature rise and stress was analyzed. The method of the invention is adopted to obtain the distribution characteristics of temperature rise, electric field intensity and electric power of the switch cabinet under different conditions. The method provides a basis for providing a theoretical basis for the optimized layout of the switch cabinet sensors, and the engineering design optimization and the heat dissipation structure design of the switch cabinet.

Description

Method for acquiring electric-thermal-stress distribution of switch cabinet under influence of different factors
Technical Field
The invention belongs to the field of research on electrical performance of key equipment of a power transmission and distribution network, and relates to a method for acquiring electric-thermal-stress distribution of a switch cabinet under the influence of different factors.
Background
The power switch cabinet is used as key equipment of a power system, is widely applied to a power transmission and distribution network, plays a role in opening and closing, controlling and protecting electric equipment, and directly influences the power supply quality and safety performance of the power system due to the operation reliability of the power switch cabinet. In order to improve the operation reliability of the switch cabinet, reduce the fault risk and reduce the economic loss caused by faults, various monitoring devices can be additionally arranged in the switch cabinet, and the operation state detection and safety early warning are realized by analyzing and processing the monitoring data so as to ensure that operation and maintenance personnel can find problems in time. In addition, under the background of intelligent power grid construction, higher requirements are put forward on the real-time and accuracy of data acquired by the switch cabinet.
However, when the switch cabinet works, the eddy current loss and the joule heat of the switch cabinet can cause temperature rise, the Lorentz force generated by electromagnetism can affect the non-fixed metal elements, the factors can affect the measurement of the characteristic quantity of the switch cabinet by the sensor, the service life of the switch cabinet is seriously affected, and the safe and stable operation of equipment is affected. Therefore, the temperature, the electromagnetic distribution and the electric power condition of the switch cabinet are researched, the position of the highest point of temperature rise and the position of the maximum electric field strength are determined, the influences of different factors on the temperature and the stress are analyzed, the position optimization layout of various sensors is guided, and the development of a real-time monitoring system of the switch cabinet is facilitated.
Disclosure of Invention
The invention aims to provide a method for acquiring electric-thermal-stress distribution of a switch cabinet under the influence of different factors, which is based on the actual structure and the operating condition of the switch cabinet, establishes a three-dimensional switch cabinet simulation model based on electromagnetic-temperature-solid mechanical coupling by adopting a finite element method, and realizes a simulation method for the temperature, the electric field intensity distribution and the stress of the switch cabinet under the influence of different factors.
In order to achieve the purpose, the invention provides the following technical scheme, and the method comprises the following steps:
s1: establishing a simplified physical model of an electrical switch cabinet with a plurality of air chambers;
s2: the switch cabinet relates to the theoretical analysis of electromagnetic field, temperature conduction and solid mechanics;
s3: adding a proper physical field to carry out electromagnetic-heat transfer-solid mechanics coupling analysis research;
s4: setting corresponding appropriate physical parameters and various boundary conditions based on the actual operation state of the switch cabinet;
s5: meshing the electrical chambers of the switch cabinet according to the geometric characteristics of the electrical chambers and the calculation precision requirement, setting proper simulation time and step length, and setting a solver according to the simulation requirement;
s6: and (4) simulating to obtain distribution results of the electromagnetic field and the temperature field under the steady state condition of the switch cabinet under different environmental conditions, and performing post-processing on the distribution results to obtain the distribution conditions of the temperature, the electric field intensity and the Lorentz force. Determining the position of the hottest point, and comparing and analyzing the influences of different environmental conditions on the maximum temperature and the average temperature;
s7: obtaining the change of different displacement caused by the stress of the bus due to the addition of different fixed constraints through simulation;
s8: the contact pressure at the joint is changed through simulation, and the influence of the contact pressure on temperature rise and stress is analyzed;
further, step S1 is specifically to establish a three-dimensional physical model of the switch cabinet with multiple air chambers in finite element software, where an important characteristic of an internal structure of the model is validity and invalidity, that is, some characteristics may need to be ignored sometimes according to the type of the analysis problem. The key parts of a system heat source and a switch cabinet are mainly considered, and fixing nuts and tiny electronic components which do not influence the analysis precision are omitted, so that the switch cabinet is reasonably simplified, the workload is reduced, and the efficiency is improved.
Step S2 is specifically a theoretical analysis of the electromagnetic field, temperature conduction and solid mechanics of the switch cabinet: calculating eddy current loss according to Maxwell electromagnetic theory of switch cabinet operation, and taking the loss as a heat source to carry into solid heat transfer for temperature distribution calculation; the electromotive force of the busbar of the switch cabinet is described according to the Lorentz force generated by the electromagnetic field.
(I) electromagnetic field
When the problem of the quasi-steady electromagnetic field is solved and analyzed, the magnetic field generated by the time variation of the electric field can be ignored, and the analysis is only carried out on the electric field generated by the time variation of the magnetic field, so that the electromagnetic problem is simplified. The macroscopic properties of the electromagnetic field are described by maxwell's equations, in differential form as:
Figure BDA0003276135380000021
in the formula: d is electric displacement; h is the magnetic field intensity; b is the magnetic flux density; e is the electric field strength; ρ is the charge density; j is the current density.
Figure BDA0003276135380000022
Epsilon represents the dielectric constant of the magnetic field coal quality and has the unit of F/m; mu represents the magnetic permeability of coal quality and has the unit of H/m; σ is the conductivity, with the unit of S/m; for isotropic media, ε, μ, and σ are all scalars.
(II) solid Heat transfer
Considering that the heating loss of the cabinet body is derived from eddy current loss, the heat is radiated to the surrounding environment through two modes of natural convection heat exchange and heat radiation on the surface of the cabinet body. The joule loss of the busbar comes from the resistance heating loss and induction heating of the source current, and the resistance of the busbar comprises a current-carrying conductor resistance and a contact resistance.
And (3) leading in Joule loss obtained by calculating the eddy current field as a heat source, setting corresponding radiation boundary conditions and convection heat dissipation boundary conditions, and calculating the temperature field of the switch cabinet. The governing equation of the temperature field is:
Figure BDA0003276135380000031
where ρ is the density of the material, λ and C are the thermal conductivity and specific heat of the material, respectively,
Figure BDA0003276135380000032
the internal heat source intensity.
The outer surface of the busbar should meet convection and radiation boundary conditions:
Figure BDA0003276135380000033
wherein q is a heat flux density vector, T a Is the ambient temperature; k is a radical of formula e Representing the convection heat transfer coefficient of the surface of the busbar; epsilon represents the heat generation rate of the surface of the busbar; sigma represents Stefin-glassThe number of Zeemans constants.
(III) mechanics of solids
The differential equation describing the motion of the object with the damping forced vibration system under the action of disturbance force is as follows:
Figure BDA0003276135380000034
wherein m is the total mass of the vibration system, C represents the viscous damping coefficient for supporting the vibration isolator when the object moves, and K represents the acting force of the unit deformation of the spring stiffness. F 0 sin ω t represents the disturbance force applied to the system, and the coordinate axis is placed at the static equilibrium position O of the object. x, x,
Figure BDA0003276135380000035
Respectively representing the displacement, the speed and the acceleration of the node under the global coordinate system.
And S3, adding a relevant physical field, and performing electromagnetic-temperature-solid mechanics multi-physical field coupling. Based on the theoretical analysis, the physical fields corresponding to the control equations are selected, namely Maxwell equation sets corresponding to the electromagnetic field, convection, conduction and radiation of the temperature of the switch cabinet correspond to the solid heat transfer physical field, and the stress of the equipment corresponds to the solid mechanical physical field under the excitation of external large current. The electromagnetic field and the temperature field are coupled based on temperature and electromagnetic thermal effects; solid heat transfer and solid mechanics are coupled based on Lorentz force and thermal expansion effect, so that direct coupling of multiple physical fields is realized;
step S4 specifically includes setting corresponding parameters and boundary conditions based on the actual operating state of the switchgear: the parameters comprise relevant parameters of electromagnetism, temperature and solid mechanics such as conductivity, magnetic conductivity, resistivity, heat conductivity coefficient and the like of each part of the switch cabinet; boundary conditions include external stress and environmental constraints such as pressurization, grounding, current excitation, temperature boundaries, mechanical fixation constraints, and the like. The bidirectional coupling of the temperature and the material resistivity is added, so that the simulation precision is improved;
step S5 specifically is to carry out mesh generation on the switch according to the geometric characteristics of the switch, and set simulation time and step length: setting the size of a global grid, further refining the grid according to local geometric characteristics, then constructing all grids, setting simulation time and step length, starting calculation until a time condition is met, and converging a simulation result;
step S6 is specifically to firstly simulate to obtain the distribution results of the electromagnetic field, the temperature field and the time-averaged lorentz force of the switch cabinet under the steady state condition, determine the position of the hottest point and obtain the average temperature rise and the maximum temperature rise of the switch cabinet when the environmental temperatures are 293K,298K,303K,308K and 313K under the rated working condition. And (4) comparing and analyzing the influence of different environmental temperatures on the highest temperature and the average temperature of the switch cabinet.
And S7, specifically, different fixing constraints are added through simulation, different parts are fixed, the deformation condition caused by the stress change of the bus under different conditions is analyzed, and reference is provided for fixing the bus of the switch cabinet. Different changes of the stress of the bus are respectively analyzed through three parts, namely a fixed breaker, an insulator, the end part of the bus and the like;
step S8 specifically, the contact pressure of the corresponding connection position in the switch cabinet can affect the temperature rise and the stress of the connection position, the contact impedance is changed by changing the contact pressure of the connection position, and the influence degree of the contact impedance on the temperature rise and the influence on the stress are analyzed;
the invention has the beneficial effects that: by adopting the method, the characteristics of temperature distribution, electric field distribution characteristic and stress of the switch cabinet under the influence of different factors can be obtained, and reliable theoretical basis can be provided for product design of the switch cabinet and optimal arrangement of sensors of the switch cabinet through analysis of different factors.
Drawings
FIG. 1 is a flow chart of an electric-thermal-force simulation of a switchgear of the present invention;
FIG. 2 is a three-dimensional physical model of the switchgear of the present invention;
FIG. 3 is a diagram of the distribution of the overall temperature field and the position of the highest point of the temperature rise of the switch cabinet according to the embodiment of the invention;
FIG. 4 is a distribution diagram of the overall electric field strength and current density of the switch cabinet according to the embodiment of the present invention;
FIG. 5 is a distribution diagram of the Lorentz forces of the switch cabinet in the X, Y and Z directions according to the embodiment of the present invention;
FIG. 6 is a graph comparing the average and maximum temperature of a switchgear cabinet at different ambient temperatures according to an embodiment of the present invention;
FIG. 7 is a bus bar displacement distribution diagram under different fixed constraints for a switchgear in accordance with an embodiment of the present invention;
FIG. 8 is a graph of the temperature profile at different pressures at a switchgear connection in accordance with an embodiment of the present invention;
FIG. 9 is a graph of stress distribution at different pressures at a switchgear connection in accordance with an embodiment of the present invention;
the specific implementation mode is as follows:
the present invention will be described in detail below with reference to the accompanying drawings.
The invention relates to a method for acquiring electric-thermal-stress distribution of a switch cabinet under the influence of different factors, which is shown in figure 2, and establishes a three-dimensional simulation model of the switch cabinet based on electromagnetic-temperature-solid mechanics multi-physical field coupling by adopting a finite element method based on the actual structure of the switch cabinet, wherein eddy current loss of an electromagnetic field is used as a heat source for temperature conduction, the temperature distribution and the hottest temperature position of the switch cabinet are obtained by simulation based on heat conduction, heat convection and heat radiation theories, and the influence of Lorentz force on metal in the electromagnetic field is considered, so that the simulation of the electric force of the switch cabinet is realized. The method comprises the following specific steps:
1. establishing three-dimensional physical model of switch cabinet
When a three-dimensional physical model of a switch cabinet is drawn in finite element software, as shown in fig. 2, when coupling analysis is carried out, an important characteristic of the internal structure of the model is effective and ineffective, namely, certain characteristics sometimes need to be ignored according to the type of an analysis problem. Therefore, the three-dimensional modeling is carried out by taking a high-current switch cabinet of 10kV/3150A as a prototype on the basis of the following assumptions:
(1) The insulator only plays a role of insulation support, so that the shape characteristics of the insulator are simplified;
(2) Thin elements at the joints of screws and the like are simplified;
(3) The simplified circuit breaker is cylindrical;
2. adding physical fields, setting up coupling with multiple physical fields
Adding three physical fields of an electromagnetic field, solid heat transfer and structural mechanics, and performing coupling calculation:
(I) electromagnetic field
When the problem of the quasi-steady electromagnetic field is solved and analyzed, the magnetic field generated by the time variation of the electric field can be ignored, and the analysis is only carried out on the electric field generated by the time variation of the magnetic field, so that the electromagnetic problem is simplified. The differential equation of the finite element method for processing the electromagnetic field problem can be deduced through the differential form of the Maxwell equation system:
Figure BDA0003276135380000051
in the formula: d is a potential shift; h is the magnetic field intensity; b is the magnetic flux density; e is the electric field strength; ρ is the charge density; j is the current density.
Figure BDA0003276135380000052
In the formula: epsilon represents the dielectric constant of the magnetic field coal quality and has the unit of F/m; mu represents the magnetic permeability of coal quality and has the unit of H/m; sigma is the conductivity, and the unit is S/m; for isotropic media, ε, μ, σ are all scalars.
(II) solid Heat transfer
Considering that the heating loss of the cabinet body comes from eddy current loss, the heat is diffused to the surrounding environment through two modes of natural convection heat exchange and heat radiation on the surface of the cabinet body. The joule loss of the busbar comes from the resistance heating loss and induction heating of the source current, and the resistance of the busbar comprises a current-carrying conductor resistance and a contact resistance.
And (3) leading in Joule loss obtained by calculating the eddy current field as a heat source, setting corresponding radiation boundary conditions and convection heat dissipation boundary conditions, and calculating the temperature field of the switch cabinet. The governing equation of the temperature field is:
Figure BDA0003276135380000053
where ρ is the density of the material, λ and C are the thermal conductivity and specific heat of the material, respectively,
Figure BDA0003276135380000054
the strength of the internal heat source.
Wherein the conductivity of the material changes with the change of temperature, and the resistivity of copper at 20 ℃ is 17.2 (m omega mm) 2 /m), the temperature coefficient of resistivity α was selected to be 0.004. The expression for resistance versus temperature is:
ρ(t)＝ρ 0 (1+0.004(t-20)) ⑼
in the above formula, t is the current ambient temperature, ρ 0 Which is the resistivity of copper at 20 c.
The influence of the skin effect and the proximity effect of the busbar is synthesized, and the resistance expression of the copper bar is summarized as follows:
Figure BDA0003276135380000061
wherein R is a bus bar resistance rho 0 Copper resistivity at 20 ℃, L is the length of the busbar, S represents the sectional area of the busbar, K J Denotes the skin Effect coefficient, K L Representing the proximity effect coefficients.
The formula fully considers the influence of temperature on the resistivity, and sets the bidirectional coupling relation between the temperature and the resistivity, so that the resistivity in the simulation process continuously changes along with the temperature, and the result is more accurate.
The outer surface of the busbar should meet convection and radiation boundary conditions:
Figure BDA0003276135380000062
wherein q is a heat flux density vector, T a Is the ambient temperature; k is a radical of e Representing the convection heat transfer coefficient of the surface of the busbar; ε representsHeat generation rate of the busbar surface; σ represents the Stefan-Boltzmann constant.
(III) mechanics of solids
The differential equation describing the motion of the object with the damping forced vibration system under the action of disturbance force is as follows:
Figure BDA0003276135380000063
wherein m is the total mass of the vibration system, C represents the viscous damping coefficient for supporting the vibration isolator when the object moves, and K represents the acting force of the unit deformation of the spring stiffness. F 0 sin ω t represents the disturbance force applied to the system, and the coordinate axis is placed at the static equilibrium position O of the object. x, x,
Figure BDA0003276135380000064
Respectively representing the displacement, the speed and the acceleration of the node under the global coordinate system.
3. Setting parameters and boundary conditions according to actual operation conditions
Electromagnetic field: rated currents of 3.15kA are applied to the A-phase bus, the B-phase bus and the C-phase bus respectively, the phase difference is 120 degrees, and the three-phase bus outgoing lines output by the cable chamber are grounded. The contact impedance is set by changing the contact surfaces of the moving and static contacts and the tulip contact and the conductivity of the contact surface of the circuit breaker, and force calculation is added.
Solid heat transfer: setting the environmental temperature T to be 293K, and setting different convection heat transfer coefficients for different parts according to the actual operating condition of the switch cabinet; according to the surface air flow velocity, the convection cooling surface is divided into three parts:
the first part is a bus chamber with sufficient air circulation in the cabinet, and the convective heat transfer coefficient is 4W/(m) 2* * K) (ii) a The second part is the internal part of the circuit breaker, and the convective heat transfer coefficient is 3W/(m) 2 * K) (ii) a The third group is a cabinet body and a base, and the convective heat transfer coefficient is 5W/(m) 2 K)。
Arranging the busbar for heat conduction; and meanwhile, the surface heat radiation is set, the radiation factor of the bus is set to be 0.4, and the radiation factor of the insulator is set to be 0.8.
Solid mechanics: and selecting the whole switch cabinet as an action area, and respectively setting the breaker base, the insulator support and the bus end part as fixed constraints.
The material parameters of the present invention are shown in table 1.
TABLE 1 table of various material parameters
Material Copper (Cu) Epoxy resin Galvanized steel sheet
Thermal conductivity (W/m. K) 392 0.276 46
Density (g/cm) 3 ) 8.9 0.98 7.8
Specific heat capacity (J/(g. K)) 0.39 1.4 0.5
Emissivity 0.4 0.8 0.8
4. Carrying out mesh subdivision on the model based on a finite element method, and setting simulation time and step length: setting the size of the global grid, further refining the grid according to local geometric characteristics, then constructing all grids, setting simulation time and step length, starting calculation until a time condition is met, and converging a simulation result.
5. Based on the research of the frequency domain-steady state of the switch cabinet, the invention firstly simulates the temperature distribution in the steady state as shown in figure 3: the higher temperature points are concentrated at the circuit breakers and tulip contacts where the ventilation is not very good. Where the hottest point occurs at the connection of the circuit breaker.
The distribution of the electric field intensity is shown in fig. 4 (1): the electric field intensity at the contact and the bending part of the busbar is relatively high. The current density distribution is shown in fig. 4 (2): the current is most concentrated at the connection part of the circuit breaker, the current density at the bending part of the tulip contact and the busbar is higher, the skin effect of the busbar can be clearly seen, and the current is mostly concentrated on the surface of the busbar.
The distribution of the homolorentz forces in the three planes X, Y, Z is shown in fig. 5: the parts with large time-average Lorentz force are also bending parts of the concentrated circuit breaker, the plum blossom contact and the busbar, the parts need to be reinforced, accidents caused by electrodynamic force are prevented, stress conditions of other parts can be further explored through simulation, adjustment is carried out, and safety and stability of the switch cabinet are improved.
Secondly, through simulation, comparative analysis shows that the ambient temperature under rated conditions is 293k,298k,303k,308k and 313k, and the average temperature and the maximum temperature of the switch cabinet are shown in fig. 6: the distribution trend that the change of the environmental temperature does not affect the temperature under the same heat source and condition only affects the temperature rise, and the comparison of the calculated related data shows that: with the rise of the environment temperature, the maximum temperature rise and the average temperature of the switch cabinet rise, and the maximum temperature rise and the average temperature rise are approximately in a linear relation.
6. S7, setting different fixed constraints through a solid mechanical interface, and analyzing the influence of the fixed constraints on the displacement change of the busbar caused by stress;
from coupled analysis of multiple physical fields, coupling solid heat transfer and solid mechanics, it can be seen that the effect of displacement due to thermal expansion is shown in FIG. 7: (1) When the circuit breaker is fixed, the bus bar deformation of the cable chamber and the bus bar chamber is obvious, and the maximum displacement can reach 1.7mm; (2) When the insulator is fixed, the deformation of the bus supported by the insulator is smaller, but the deformation of the breaker and the bus which is not supported is more obvious, and the maximum displacement can reach 1.43mm; (3) When the bus bar end of the bus bar chamber and the cable chamber are fixed, the bending part of the circuit breaker and the bus bar is obviously deformed. The maximum displacement can reach 1.08mm.
In conclusion, fixing the above parts is very important for the safe and stable operation of the switch cabinet, and the deformation of the busbar can be reduced to the greatest extent. Meanwhile, different fixed positions can be set, and the improvement of the stability of the busbar is further explored.
7. Step S8, specifically, the contact pressure at the joint is changed through simulation, so that the contact impedance is changed, and the influence degree of the contact impedance on temperature rise and the influence on stress are analyzed; as shown in fig. 8: no matter the contact impedance is changed at the plum blossom contact or the breaker to change the pressure, the average temperature of the part is approximately in a linear relation with the change of the contact impedance, and the graph shows that when the contact pressure is increased, the temperature rise of the part can be reduced by a small amplitude, thereby being beneficial to the stable operation of the switch cabinet;
similarly, as shown in fig. 9, two locations with different contact resistances are provided, and as the contact conductance increases, the average stress decreases as the contact pressure increases, which indicates that the stress variation of the busbar can be reduced by appropriately increasing the contact pressure.
By adopting the method, the distribution characteristics of temperature rise, electric field intensity and electric force of the switch cabinet under different conditions can be obtained through simulation by modifying the characteristics of current excitation and materials. The operation condition of the switch cabinet can be analyzed through the calculation result, a theoretical basis can be provided for the optimized layout of the switch cabinet sensor, and a foundation is provided for the engineering design optimization and the heat dissipation structure design of the switch cabinet.
The above preferred embodiments are merely illustrative of the technical solutions of the present invention, and are not limited thereto, and it will be apparent to those skilled in the art that various changes in form, detail, and the like can be made without departing from the scope of the claims. The method can obtain the distribution characteristics of the electric field intensity, the hottest temperature and the electric power of the switch cabinet under the influence of different factors.

Claims (9)

1. A method for acquiring the distribution of electric-thermal-stress of a switch cabinet under the influence of different factors is characterized by comprising the following steps:
s1: establishing a simplified physical model of an electric medium-voltage switch cabinet with a plurality of air chambers;
s2: the switch cabinet relates to the theoretical analysis of electromagnetic field, temperature conduction and solid mechanics;
s3: adding a physical field, and performing electromagnetic-heat transfer-solid mechanics coupling analysis research;
s4: setting corresponding appropriate physical parameters and various boundary conditions based on the actual operation state of the switch cabinet;
s5: meshing the electrical chambers of the switch cabinet according to the geometric characteristics of the electrical chambers and the calculation precision requirement, setting proper simulation time and step length, and setting a solver according to the simulation requirement;
s6: and (4) simulating to obtain distribution results of the electromagnetic field and the temperature field under the steady state condition of the switch cabinet under different environmental conditions, and performing post-processing on the distribution results to obtain the distribution conditions of the temperature, the electric field intensity and the electric power. Determining the position of the hottest point, and comparing and analyzing the influences of different environmental conditions on the maximum temperature and the average temperature;
s7: the variation of different displacement caused by adding different fixed constraints and stress on the bus is obtained through simulation, and the influence on the stability of the bus is analyzed;
s8: the contact pressure at the joint is changed through simulation, and the influence of the contact pressure on temperature rise and stress is analyzed.
2. The simulation method for obtaining the distribution of the electric-thermal-stress of the switch cabinet under the influence of different factors according to claim 1, wherein: s1, the three-dimensional physical model of the switch cabinet with the multiple air chambers is established, key components such as a circuit breaker, a conductive busbar and a plum blossom contact are mainly considered, fixing nuts and small electronic components which do not influence analysis accuracy are omitted, and the switch cabinet is reasonably simplified.
3. The simulation method for obtaining the distribution of the electric-thermal-stress of the switch cabinet under the influence of different factors according to claim 1, wherein: step S2 is specifically a theoretical analysis of the electromagnetic field, temperature conduction and solid mechanics of the switch cabinet: according to Maxwell electromagnetic theory, heat conduction, heat convection, heat radiation and solid mechanics theory analysis of the operation of the switch cabinet, selecting a simulation core physical field-electromagnetic field and solid heat transfer; and simultaneously, the influence of stress on a mechanical structure is considered, and a solid mechanical physical field is selected.
4. The method for obtaining the distribution of the electric-thermal-stress of the switch cabinet under the influence of different factors according to claim 1, wherein the method comprises the following steps: and S3, adding a relevant physical field, and performing electromagnetic-temperature-solid mechanics multi-physical field coupling. Three physical fields of an electromagnetic field, solid heat transfer and solid mechanics are added based on the theoretical analysis. The electromagnetic field and the temperature field are coupled based on temperature and electromagnetic thermal effect; solid heat transfer and solid mechanics are coupled based on thermal expansion effects.
5. The method for obtaining the distribution of the electric-thermal-stress of the switch cabinet under the influence of different factors according to claim 1, wherein the method comprises the following steps: step S4 specifically includes setting corresponding parameters and boundary conditions based on the actual operating state of the switchgear: the parameters comprise relevant parameters such as electric conductivity, magnetic conductivity, resistivity, heat conductivity coefficient and the like of each part of the switch cabinet, such as electromagnetism, temperature, solid mechanics and the like; the boundary conditions include external stress and environmental constraints such as pressurization, grounding, current excitation, temperature boundary, mechanical fixation constraints, and the like. The bidirectional coupling of the temperature and the resistivity of the material is added, so that the simulation precision is improved.
6. The method for obtaining the distribution of the electric-thermal-stress of the switch cabinet under the influence of different factors according to claim 1, wherein the method comprises the following steps: step S5 specifically is to carry out mesh generation on the switch according to the geometric characteristics of the switch, and set simulation time and step length: setting the size of the global grid, further refining the grid according to local geometric characteristics, then constructing all grids, setting simulation time and step length, starting calculation until a time condition is met, and converging a simulation result.
7. The method for obtaining the distribution of the electric-thermal-stress of the switch cabinet under the influence of different factors according to claim 1, wherein the method comprises the following steps: step S6 is specifically to obtain the distribution result of the electromagnetic field and the temperature field in the steady state of the switch cabinet through simulation, and perform post-processing on the distribution result to obtain the distribution conditions of the temperature, the electric field strength and the electric power. And determining the position of the hottest point, and comparing and analyzing the influence of the environmental conditions on the hottest point temperature and the average temperature.
8. The method for obtaining the distribution of the electric-thermal-stress of the switch cabinet under the influence of different factors according to claim 1, wherein the method comprises the following steps: and S7, specifically, adding different fixed constraints through simulation, and analyzing the change of the displacement caused by the stress of the bus.
9. The method for obtaining the distribution of the electric-thermal-stress of the switch cabinet under the influence of different factors according to claim 1, wherein the method comprises the following steps: and S8, specifically, changing the contact pressure at the joint through simulation, further changing the contact impedance, and analyzing the influence degree of the contact impedance on temperature rise and the influence on stress.
CN202111118468.7A 2021-09-24 2021-09-24 Method for acquiring electric-thermal-stress distribution of switch cabinet under influence of different factors Pending CN115495944A (en)

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