Method for analyzing contact resistance and equivalent heat of high-voltage vacuum interrupter

Abstract

The application discloses a high-voltage vacuum arc-extinguishing chamber contact resistance and equivalent thermal analysis method, comprising the following steps: three-dimensional equivalent modeling of the high-voltage vacuum arc-extinguishing chamber; determining the number and position of the contact piece contact points; experimentally measuring the high-voltage vacuum arc-extinguishing chamber loop resistance and calculating the contact radius; establishing a conductive bridge, and obtaining a simulation loop resistance by an electromagnetic simulation software; adjusting the contact radius so that the simulation loop resistance is consistent with the experimental measurement result, and obtaining an adjusted conductive bridge; performing electromagnetic field-thermal field-airflow field two-way coupling simulation analysis based on the high-voltage vacuum arc-extinguishing chamber equivalent model of the adjusted conductive bridge, and obtaining the high-voltage vacuum arc-extinguishing chamber temperature rise distribution. The application can more accurately simulate the current constriction effect on the large-size high-voltage vacuum contact piece and more accurately simulate the high-voltage vacuum contact piece contact resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of contact resistance simulation analysis of power equipment, and particularly relates to a high-voltage vacuum arc-extinguishing chamber contact resistance and equivalent thermal analysis method. BACKGROUND

[0002] The vacuum arc-extinguishing chamber is also called a vacuum bulb or a vacuum switch tube, and is a core device of a vacuum switch, has advantages of safety, explosion prevention, low carbon environmental protection, long service life, high insulation level, large short-circuit current breaking, easy operation, and easy maintenance, and has been widely applied in the field of medium and low voltage. With the continuous development of vacuum arc-extinguishing technology and the restriction on the use of SF6 insulating gas in high-voltage switch equipment in the Kyoto Protocol, the development in the direction of high voltage and large breaking current gradually becomes a popular research direction of the vacuum arc-extinguishing chamber. The heat generation under the through-flow state is one of the bottlenecks restricting the development of the vacuum arc-extinguishing chamber to high voltage levels. The vacuum environment inside the vacuum arc-extinguishing chamber determines that there are only two heat dissipation modes of heat conduction and heat radiation for the internal parts of the vacuum arc-extinguishing chamber. The temperature of the steady-state through-flow heat generation is low, and the radiation heat dissipation is extremely weak. The heat inside the arc-extinguishing chamber can only be transferred to the outside of the arc-extinguishing chamber through the heat conduction of the moving and static conductive rods. Because the insulation level of the high-voltage vacuum arc-extinguishing chamber is higher, the length of the conductor in the vacuum of the arc-extinguishing chamber is longer, and the heat conduction path in the vacuum is longer. Compared with the traditional SF6 insulating arc-extinguishing chamber, the internal environment of the high-voltage vacuum arc-extinguishing chamber is more severe. The risk of mechanical strength reduction of the internal conductor of the arc-extinguishing chamber caused by the temperature being too high due to the heat generation under the large current through-flow is greater. Therefore, the research on the temperature distribution inside the vacuum arc-extinguishing chamber is of great significance in the field of high-voltage vacuum arc-extinguishing chambers.

[0003] The contact resistance on the surface of the contact piece is an important factor causing the heating of the contact. The contact resistance in the vacuum environment only exists the constriction resistance. The diameter of the high-voltage and large-current vacuum contact is often large, and the change of the current path has a more significant influence on the constriction resistance. The contact points of the contacts with different structures are different in number and position, and then the current path is affected, and the current constriction effect of different sizes is generated. The existing contact resistance modeling analysis methods such as the conductive bridge method and the increased resistivity method often cannot accurately consider the influence of the number, position and actual current path of the contact points on the contact piece. The calculation method of the small contact contact resistance is not applicable in the high-voltage vacuum arc-extinguishing chamber because the macroscopic size of the contact is ignored. SUMMARY

[0004] The present application aims at overcoming the deficiencies of the prior art, and provides a high-voltage vacuum arc-extinguishing chamber contact resistance and equivalent thermal analysis method, which can more accurately simulate the position and size of the contact points on the large-size high-voltage vacuum contact, more accurately simulate the current constriction effect on the high-voltage vacuum contact piece, and make the temperature field simulation of the contact system more in line with the actual situation, thereby providing a reference for the structural design of the high-voltage vacuum contact.

[0005] A high-voltage vacuum arc-extinguishing chamber contact resistance and equivalent thermal analysis method, comprising:

[0006] A three-dimensional equivalent model of the high-voltage vacuum arc-extinguishing chamber is established to obtain an initial high-voltage vacuum arc-extinguishing chamber equivalent model;

[0007] The number and position of the contact piece contact points are determined according to the contact structure and the closing stress analysis;

[0008] The loop resistance of the high-voltage vacuum arc-extinguishing chamber is measured experimentally, and the contact radius is calculated;

[0009] The conductive bridge is established according to the number and position of the contact points and the calculated contact radius, and the simulation loop resistance is calculated by the electromagnetic simulation software;

[0010] The contact radius is adjusted to make the simulation loop resistance consistent with the experimental measurement result, thereby obtaining an adjusted conductive bridge for calculating the contact resistance of the high-voltage vacuum arc-extinguishing chamber with the same structure;

[0011] Based on the adjusted high-voltage vacuum arc-extinguishing chamber equivalent model of the conductive bridge, electromagnetic field-thermal field-airflow field two-way coupling simulation analysis is performed to obtain the temperature rise distribution of the high-voltage vacuum arc-extinguishing chamber.

[0012] Further, when the high-voltage vacuum arc-extinguishing chamber is three-dimensionally equivalent modeled, the vacuum high-voltage contact, the conductive rod and the arc-extinguishing chamber shell are completely retained, and the structures irrelevant to the temperature rise are deleted.

[0013] Further, in the stress analysis, the static conductive rod end is fixed, the dynamic conductive rod end is subjected to the contact terminal pressure, the stress analysis is performed based on the stress finite element simulation software, the stress concentration position of the contact piece contact surface in the closing state is obtained, and the stress concentration position of the contact piece contact surface is the contact point position of the contact piece.

[0014] Further, the loop resistance of the high-voltage vacuum arc-extinguishing chamber in the closing state is obtained by a loop resistance meter or a bridge method.

[0015] Further, the formula for calculating the contact radius r is as follows:

[0016]

[0017] Wherein, F is the contact pressure; ζ is the contact condition of the contact surface; H is the Brinell hardness of the contact material.

[0018] Further, at the contact point position determined by the stress analysis, a micro cylindrical conductive bridge is established according to the calculated contact radius.

[0019] Further, based on the electromagnetic simulation software, a direct current is passed through the high-voltage vacuum arc-extinguishing chamber model after the conductive bridge is established, and the simulation loop resistance is obtained by dividing the ohmic loss by the square of the current.

[0020] Further, based on the high-voltage vacuum interrupter equivalent model adjusted by the conductive bridge, electromagnetic field-thermal field-gas flow field two-way coupling simulation analysis is carried out, including:

[0021] A1, set the initial temperature of the model as T0;

[0022] A2, the material conductivity g0 under the model temperature T0 is calculated by the electromagnetic field simulation software;

[0023] A3, electromagnetic field simulation is carried out to obtain the ohmic loss corresponding to the material conductivity g0;

[0024] A4, the obtained ohmic loss is used as a heat source for thermal flow field simulation, and the gas thermal conductivity and specific heat capacity and other parameters change with temperature in the thermal flow field simulation, and the model temperature T1 is obtained by simulation;

[0025] A5, judge whether the difference between the model temperature T1 and the model temperature T0 is less than the preset value, if yes, the temperature field reaches stability, the model temperature T1 is output and step A6 is entered, otherwise, the model temperature T1 is used as the model temperature T0, and step A2 is returned;

[0026] A6, the model temperature T1 is subtracted by the room temperature to obtain the high-voltage vacuum interrupter temperature rise distribution.

[0027] Further, when the electromagnetic field-thermal field-gas flow field two-way coupling simulation analysis is carried out based on the high-voltage vacuum interrupter equivalent model adjusted by the conductive bridge, an air domain is established around the high-voltage vacuum interrupter in the thermal flow field simulation, and the contact boundary between the interrupter and the air domain is set as a coupling boundary condition; if the calculation device and time conditions are limited, no air domain is set outside the high-voltage vacuum interrupter, and a convection heat dissipation or mixed heat dissipation boundary condition is used for the boundary.

[0028] Further, when the electromagnetic field-thermal field-gas flow field two-way coupling simulation analysis is carried out based on the high-voltage vacuum interrupter equivalent model adjusted by the conductive bridge, no air domain is set in the vacuum region inside the high-voltage vacuum interrupter, and an adiabatic or only radiation heat dissipation boundary condition is set for the boundary of the vacuum region.

[0029] The beneficial effects of the present application are as follows:

[0030] The present application determines the number and position of contact points based on stress analysis, and the model calibrated by experimental data can accurately simulate the current constriction effect on the high-voltage vacuum contact piece, and then accurately simulate the contact resistance of the high-voltage vacuum interrupter, based on the electromagnetic field-thermal field-gas flow field two-way coupling simulation, a more realistic temperature rise distribution can be obtained, which provides a reference for the design of high-voltage vacuum contact structure. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1A principle flow chart of a high-voltage vacuum arc-extinguishing chamber contact resistance and equivalent thermal analysis method of the application;

[0032] Figure 2 A complete high-voltage vacuum arc-extinguishing chamber equivalent model schematic diagram;

[0033] Figure 3 A principle flow chart of bidirectional coupling simulation in the high-voltage vacuum arc-extinguishing chamber contact resistance and equivalent thermal analysis method of the application.

[0034] In the drawings, 1 is an arc-extinguishing chamber shell, 2 is a conductive rod, 3 is a high-voltage vacuum contact, and 4 is a conductive bridge. DETAILED DESCRIPTION

[0035] The application will be further described below in combination with specific embodiments:

[0036] As shown in the drawings, the embodiment provides a high-voltage vacuum arc-extinguishing chamber contact resistance and equivalent thermal analysis method, which comprises the following steps: Figure 1

[0037] S1, three-dimensional equivalent modeling is performed on the high-voltage vacuum arc-extinguishing chamber to obtain an initial high-voltage vacuum arc-extinguishing chamber equivalent model;

[0038] During modeling, the vacuum high-voltage contact, the conductive rod and the arc-extinguishing chamber shell are completely retained, and structures irrelevant to temperature rise, such as a shielding cover and a bellows, are deleted.

[0039] S2, the number and position of contact piece contact points are determined according to the contact structure and closing stress analysis;

[0040] During stress analysis, the static conductive rod end is fixed, and the dynamic conductive rod end is subjected to a contact terminal pressure, stress analysis is performed based on ANSYS finite element simulation software, the stress concentration position of the contact piece contact surface under the closing state is obtained, and the stress concentration position of the contact piece contact surface is the contact piece contact point position. In the embodiment, the contact is a cup-shaped longitudinal magnetic contact with a support seat, and the stress concentration position of the contact piece is the center of the contact piece, which is circular in shape.

[0041] S3, a loop resistance meter is used to pass a direct current I to the high-voltage vacuum arc-extinguishing chamber to be measured, an experimental resistance R is measured, and a contact radius is calculated;

[0042] The formula for calculating the contact radius r is as follows:

[0043]

[0044] Wherein, F is the contact pressure of the contact, ζ is the contact condition of the contact surface, and H is the Brinell hardness of the contact material.

[0045] ​S4, establish the conductive bridge according to the number, position of contact points and the calculated contact radius, and calculate the simulation loop resistance by electromagnetic simulation software;

[0046] To reduce the error of the conductive bridge body resistance, the height of the conductive bridge should be as small as possible, and in the simulation of the embodiment, the height is set to 0.1mm, and the conductivity of the conductive bridge should be as high as possible, and in the simulation of the embodiment, the conductivity is two orders of magnitude higher than the conductivity of the contact material;

[0047] Pass a direct current I through the simulation loop, simulate the ohmic loss P of the entire loop, and obtain the simulation loop resistance R by the following formula S :

[0048]

[0049] S5, adjust the contact radius to make the simulation loop resistance R S consistent with the experimental measurement result R, so as to obtain the adjusted conductive bridge for calculating the contact resistance of the high-voltage vacuum arc chamber with the same structure;

[0050] S6, based on the adjusted high-voltage vacuum arc chamber equivalent model of the conductive bridge (as shown in Figure 2 ), perform electromagnetic field-thermal field-gas flow field two-way coupling simulation analysis to obtain the temperature rise distribution of the high-voltage vacuum arc chamber.

[0051] As shown in Figure 3 , the specific process of this step includes:

[0052] A1, set the initial temperature of the model to T0;

[0053] A2, calculate the material conductivity g0 at the model temperature T0 by electromagnetic field simulation software;

[0054] A3, perform electromagnetic field simulation to obtain the ohmic loss corresponding to the material conductivity g0;

[0055] A4, the obtained ohmic loss is used as a heat source for thermal flow field simulation, and the gas thermal conductivity and specific heat capacity and other parameters change with temperature in the thermal flow field simulation, and the model temperature T1 is simulated;

[0056] A5, judge whether the difference between the model temperature T1 and the model temperature T0 is less than a preset value, if yes, the temperature field reaches stability, output the model temperature T1 and enter step A6, otherwise, take the model temperature T1 as the model temperature T0, and return to step A2;

[0057] A6, subtract the room temperature from the model temperature T1 to obtain the temperature rise distribution of the high-voltage vacuum arc chamber.

[0058] In the above, when the electromagnetic field-thermal field-airflow field two-way coupling simulation analysis is carried out based on the adjusted equivalent model of the high-voltage vacuum interrupter with the conductive bridge, an air domain is established around the high-voltage vacuum interrupter in the thermal flow field simulation, and the contact boundary between the interrupter and the air domain is set as a coupling boundary condition (the coupling boundary condition is a software automatically calculated heat dissipation coefficient); if the calculation equipment and time conditions are limited, no air domain is set outside the high-voltage vacuum interrupter, and a convection heat dissipation or mixed heat dissipation boundary condition is adopted for the boundary of the high-voltage vacuum interrupter. No air domain is set in the vacuum region inside the high-voltage vacuum interrupter, and an adiabatic or only radiation heat dissipation boundary condition is set for the boundary of the vacuum region.

[0059] The above-mentioned embodiments are only the preferred embodiments of the present application, and are not intended to limit the scope of the present application. Any changes made according to the shape and principle of the present application should be covered within the protection scope of the present application.

Claims

1. A high-voltage vacuum interrupter contact resistance and equivalent thermal analysis method, characterized in that: include: Conduct three-dimensional equivalent modeling of the high-voltage vacuum interrupter to obtain an initial high-voltage vacuum interrupter equivalent model; Determine the number and location of contact points based on contact structure and closing stress analysis; Experimentally measure the loop resistance of the high-voltage vacuum interrupter and calculate the contact radius; A conductive bridge is established based on the number and position of contact points and the calculated contact radius, and the simulated loop resistance is calculated by electromagnetic simulation software; The contact radius is adjusted so that the simulated loop resistance matches the experimental measurement result, thereby obtaining an adjusted conductive bridge for contact resistance calculation of a high-voltage vacuum interrupter with the same structure; Based on the equivalent model of the high-voltage vacuum interrupter after the conductive bridge adjustment, a bidirectional coupled simulation analysis of the electromagnetic field, thermal field, and airflow field was performed to obtain the room temperature rise distribution of the high-voltage vacuum interrupter. Based on the equivalent model of the high-voltage vacuum interrupter after the conductive bridge adjustment, a bidirectional coupled simulation analysis of the electromagnetic field, thermal field, and airflow field is performed, including: A1. Set the initial temperature of the model to T0; A2. Calculate the material conductivity g0 at the model temperature T0 using electromagnetic field simulation software; A3. Perform electromagnetic field simulation to obtain the ohmic loss corresponding to the material conductivity g0; A4. The obtained ohmic loss is used as the heat source for the heat flow field simulation. In the heat flow field simulation, the gas thermal conductivity and specific heat capacity parameters change with temperature, and the model temperature T1 is obtained by simulation; A5. Determine whether the difference between the model temperature T1 and the model temperature T0 is less than a preset value. If so, the temperature field is stable, the model temperature T1 is output, and the process proceeds to step A6. Otherwise, the model temperature T1 is used as the model temperature T0, and the process returns to step A2. A6. Subtract room temperature from model temperature T1 to obtain the room temperature rise distribution of high voltage vacuum arc extinguishing room temperature; When performing stress analysis, the end of the static conductive rod is fixed, and the end of the dynamic conductive rod applies the final contact pressure. Stress analysis is performed based on stress finite element simulation software to obtain the stress concentration position of the contact surface in the closed state. The stress concentration position of the contact surface is the contact point position of the contact; When performing a bidirectional coupled simulation analysis of the electromagnetic field, thermal field, and airflow field based on the equivalent model of the high-voltage vacuum interrupter after the conductive bridge adjustment, no air domain is set in the vacuum area inside the high-voltage vacuum interrupter, and the boundary of the vacuum area is set to adiabatic or with only radiation heat dissipation boundary conditions.

2. A high-voltage vacuum interrupter contact resistance and equivalent thermal analysis method according to claim 1, characterized in that: When performing three-dimensional equivalent modeling of the high-voltage vacuum interrupter, the vacuum high-voltage contacts, conductive rods and interrupter shell are completely retained, and structures that are not related to temperature rise are deleted.

3. A high-voltage vacuum interrupter contact resistance and equivalent thermal analysis method according to claim 1, characterized in that: The loop resistance of the high-voltage vacuum interrupter in the closed state is obtained by a loop resistance meter or the bridge method.

4. A high-voltage vacuum interrupter contact resistance and equivalent thermal analysis method according to claim 1, characterized in that: The formula for calculating the contact radius r is as follows: Where F is the contact pressure; ζ is the correlation coefficient of the contact surface contact condition; H is the Brinell hardness of the contact material.

5. A high-voltage vacuum interrupter contact resistance and equivalent thermal analysis method according to claim 1, characterized in that: At the contact point position determined by stress analysis, a tiny cylindrical conductive bridge is established according to the calculated contact radius.

6. A high-voltage vacuum interrupter contact resistance and equivalent thermal analysis method according to claim 1, characterized in that: Based on electromagnetic simulation software, a DC current is passed through the high-voltage vacuum interrupter model after the conductive bridge is established, and the simulated loop resistance is obtained by dividing the ohmic loss by the square of the current.

7. A high-voltage vacuum interrupter contact resistance and equivalent thermal analysis method according to claim 1, characterized in that: When performing bidirectional coupled simulation analysis of the electromagnetic field, thermal field, and airflow field based on the equivalent model of the high-voltage vacuum interrupter after conductive bridge adjustment, an air domain is established around the high-voltage vacuum interrupter in the thermal flow field simulation, and the contact boundary between the interrupter and the air domain is set as a coupled boundary condition. If the computing equipment and time conditions are limited, no air domain is set outside the high-voltage vacuum interrupter, and its boundary adopts convection heat dissipation or mixed heat dissipation boundary conditions.

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