CN112380672B - Simulation method for determining density distribution of post insulator and disc insulator - Google Patents

Simulation method for determining density distribution of post insulator and disc insulator Download PDF

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CN112380672B
CN112380672B CN202011132923.4A CN202011132923A CN112380672B CN 112380672 B CN112380672 B CN 112380672B CN 202011132923 A CN202011132923 A CN 202011132923A CN 112380672 B CN112380672 B CN 112380672B
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insulator
alumina
disc
cell
post
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梁虎成
杜伯学
李进
王泽华
张程
冉昭玉
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Tianjin University
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    • G06F2119/02—Reliability analysis or reliability optimisation; Failure analysis, e.g. worst case scenario performance, failure mode and effects analysis [FMEA]
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Abstract

The invention discloses a simulation method for determining density distribution of a post insulator and a disc insulator, which comprises the following steps: respectively determining the geometrical sizes of the post insulator and the disc insulator; and respectively carrying out finite element mesh subdivision on the post insulator and the disc insulator: carrying out one-dimensional subdivision on the post insulator, and carrying out two-dimensional subdivision on the disc insulator; determining a simulation starting condition; respectively calculating the particle movement speed of the post insulator and the disc insulator at the time t; respectively calculating inflow and outflow of each unit cell of the post insulator and the disc insulator; respectively calculating the alumina concentration of each unit cell of the post insulator and the disc insulator; if the time reaches 70 minutes, stopping calculation, and calculating the density of the insulator according to the concentration of the alumina in the cells; otherwise, the time is increased to t + dt and the above steps are repeated. The invention is an economic and effective means for obtaining insulator density distribution.

Description

Simulation method for determining density distribution of post insulator and disc insulator
Technical Field
The invention relates to a simulation method, in particular to a simulation method for determining density distribution of a post insulator and a disc insulator.
Background
Gas Insulated switchgear (gas Insulated switchgear) is widely used in power systems due to its advantages of high reliability and small floor space. Insulators are important parts of GIS, and perform the functions of supporting conductors, isolating gas chambers, and electrical insulation. In industrial production, the GIS insulator is cast by epoxy resin/alumina composite insulating material. During the solidification process, the alumina particles are settled by gravity, so that the density of the insulator is changed in the gravity direction. Various mechanical parameters and electrical parameters of the insulator, such as an elastic model, mechanical strength, thermal conductivity, dielectric constant and the like, are closely related to the density. The density distribution of the GIS insulator is determined, so that the mechanical and electrical states of the insulator in operation can be mastered more accurately, and the method has very important significance.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, provides a simulation method for determining the density distribution of a post insulator and a disc insulator, and is an economic and effective means for obtaining the density distribution of the insulator.
The purpose of the invention is realized by the following technical scheme.
The invention discloses a simulation method for determining density distribution of post insulators and disc insulators, which comprises the following steps:
firstly, parameter preparation: respectively determining the geometrical sizes of the post insulator and the disc insulator; wherein the post insulator and the disc insulator are both cast by mixed liquid of epoxy resin and alumina;
secondly, respectively carrying out finite element mesh subdivision on the post insulator and the disc insulator: carrying out one-dimensional subdivision on the post insulator, and carrying out two-dimensional subdivision on the disc insulator;
thirdly, determining the simulation starting conditions: the initial volume fraction of the alumina particles, the proportion of the alumina particles of different particle sizes and the initial viscosity of the epoxy resin/alumina mixed solution;
fourthly, respectively calculating the particle movement speed of the post insulator and the disc insulator at the time t according to the following formula (2);
Figure GDA0003523774450000011
v＝v0(1-C)n (2)
wherein v is the disturbing settling velocity of the alumina in the solidification process of the insulator; v. of0Is the free settling velocity of the alumina particles in m/s; c is the volume fraction of alumina particles; n is a correction coefficient; dfIs the particle size of the alumina particles in m; g is the acceleration of gravity; rhoepAnd ρfAre respectivelyThe density of the epoxy resin and the alumina is in kg/m3(ii) a Eta is the viscosity of the epoxy resin/alumina mixed solution, and the unit is Pa.s;
fifthly, respectively calculating inflow and outflow of each unit cell of the post insulator and the disc insulator according to a formula (3), wherein the inflow and outflow of the unit cells on the boundary of the disc insulator are calculated according to a formula (4);
Figure GDA0003523774450000021
Figure GDA0003523774450000022
in the formula, Fin[i+1]Is the inflow of cell i + 1; fout[i]Is the outflow of cell i; c [ i ]]The alumina concentration for cell i; dt is the time step, in units of s; l iseleIs the cell size, in m; note that for the last cell, its outflow is 0; fouts[i,k]Is a boundary cell [ i, k](iii) outflow of (ii); c [ i, k ]]Is a boundary cell [ i, k]The alumina concentration of (a); v. oftIs the speed of movement of the alumina particles tangential to the boundary of the mold in m/s;
sixthly, respectively calculating the alumina concentration of each unit cell of the post insulator and the disc insulator according to a formula (5);
C[i]t＝C[i]t-dt+Fin[i]-Fout[i] (5)
wherein, C [ i ]]tAnd Cj]t-dtAlumina concentration, F, of unit i at time t and time t-dt, respectivelyin[i]And Fout[i]Inflow and outflow of cell i, respectively;
seventhly, stopping calculation if the time reaches 70 minutes, and calculating the density of the insulator according to the concentration of the alumina in the cells; otherwise, increasing the time to t + dt, and repeating the fourth step to the sixth step.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
as can be seen from the attached figure 6, the simulation calculation result of the invention is highly consistent with the experimental measurement, and has rationality. The simulation method of the invention is an economic and effective means for obtaining insulator density distribution, as shown in fig. 7.
Drawings
Fig. 1 is a schematic casting diagram of a disc insulator in industrial production.
Figure 2 is a schematic view of the casting and slicing of a small post insulator.
FIG. 3 is a graph showing the particle size distribution of alumina and the viscosity change of the epoxy resin/alumina mixture during curing.
Fig. 4 is a schematic diagram of mesh division of post and disc insulators.
Fig. 5 is a flow chart of the simulation.
Fig. 6 is a comparison of simulation and measurement results of post insulator density distribution.
Fig. 7 is a simulation result of the disc insulator density distribution.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
The invention discloses a simulation method for determining density distribution of a post insulator and a disc insulator, which comprises the following steps:
firstly, parameter preparation:
the geometrical dimensions of the post insulator and the disc insulator are determined separately. The present invention will use the disc insulator shown in figure 1 and the post insulator shown in figure 2 as models to perform simulation calculations. The viscosity change curve of the epoxy resin/alumina mixed solution and the particle size distribution of alumina in the curing process are shown in figure 3.
The post insulator and the disc insulator are both cast by mixed liquid of epoxy resin and alumina. FIG. 1 is a schematic diagram showing the pouring of a disc insulator in industrial production, in which a mixture of epoxy resin and alumina is poured into a mold from a gate and then cured at a high temperature of 130 ℃ for 8 hours. In the process, the alumina particles are settled under the action of gravity, so that the alumina at different parts of the insulator is different, and the density distribution of the insulator is changed. Fig. 2 is a schematic diagram of casting and slicing of a small post insulator, which is intended to facilitate measurement of density distribution and thereby verify simulation reliability.
And secondly, respectively carrying out finite element mesh subdivision on the post insulator and the disc insulator.
And (3) performing one-dimensional subdivision on the post insulator, for example: for a cylindrical insulator with the height of 20mm, the cylindrical insulator can be divided into 20 cells with the length of 1mm in one dimension. For a disc insulator, a more detailed two-dimensional subdivision of the cells is performed, for example, as shown in fig. 4.
Thirdly, determining simulation initial conditions
The starting volume fraction of the alumina particles was set at 42% according to industry standards. The ratio of the alumina particles of different sizes and the initial viscosity of the epoxy/alumina mixture can be obtained from FIG. 3.
And fourthly, respectively calculating the particle movement speed of the post insulator and the disc insulator at the time t according to the following formula (2).
The alumina particles are subjected to a combination of gravity, buoyancy and viscous forces in the liquid epoxy resin. Ignoring the short acceleration of the particles, the free settling velocity of the alumina particles can be expressed as:
Figure GDA0003523774450000041
in the formula, v0Is the free settling velocity of the alumina particles in m/s; dfIs the particle size of the alumina particles in m; g is the acceleration of gravity; rhoepAnd ρfThe densities of the epoxy resin and the alumina are respectively, and the unit is kg/m3(ii) a Eta is the viscosity of the epoxy resin/alumina mixture, and the unit is Pa · s. Considering that the content of alumina particles is very high, interaction and oxidation occur during the sedimentation processThe disturbing settling velocity of aluminum during insulator solidification can be expressed as:
v＝v0(1-C)n (2)
wherein v is the disturbing settling velocity of the alumina in the solidification process of the insulator; c is the volume fraction of alumina particles; n is a correction coefficient, and the invention takes 2.22.
And fifthly, respectively calculating inflow and outflow of each unit cell of the post insulator and the disc insulator according to a formula (3), wherein the inflow and outflow of the unit cells on the boundary of the disc insulator are calculated according to a formula (4).
The outflow of cell i is equal to the inflow of cell i +1,
Figure GDA0003523774450000042
in the formula, Fin[i+1]Is the inflow of cell i + 1; fout[i]Is the outflow of cell i; c [ i ]]The alumina concentration for cell i; dt is the time step, in units of s; l iseleIs the cell size in m. Note that for the last cell, its outflow is 0. The time step length of the invention is 1s, and the size of the cell is 1 mm.
For disc insulators, the calculation method is the same as for post insulators, but the boundary conditions are slightly different. For cells [ i, k ] on the boundary, their outflow due to particle sliding should be expressed as
Figure GDA0003523774450000043
In the formula, Fouts[i,k]Is a boundary cell [ i, k](iii) outflow of (ii); c [ i, k ]]Is a boundary cell [ i, k]The alumina concentration of (a); v. oftIs the speed of movement of the alumina particles tangential to the boundary of the mold in m/s. For cells on the border, their inflow should include sliding inflow of adjacent border cells in addition to the sinking inflow of the directly above cells.
And sixthly, respectively calculating the alumina concentration of each unit cell of the post insulator and the disc insulator according to a formula (5).
Fig. 4 is a schematic diagram of mesh division of post and disc insulators. The post insulator can be regarded as a one-dimensional structure and is divided into N unit cells. For the ith cell, the concentration of alumina can be expressed as
C[i]t＝C[i]t-dt+Fin[i]-Fout[i] (5)
Wherein, C [ i ]]tAnd Cj]t-dtAlumina concentration, F, of unit i at time t and time t-dt, respectivelyin[i]And Fout[i]Respectively inflow and outflow of cell i.
Seventhly, stopping calculation if the time reaches 70 minutes, and calculating the density of the insulator according to the concentration of the alumina in the cells; otherwise, increasing the time to t + dt, and repeating the fourth step to the sixth step.
Fig. 5 is a flow chart of the simulation, and the programming is performed by using Matlab or C language according to the flow chart shown in fig. 5. Fig. 6 shows the comparison of the simulation and measurement results of the density distribution of the post insulators, which verifies the rationality of the simulation. Fig. 7 shows the simulation result of the density distribution of the disc insulator.
While the present invention has been described in terms of its functions and operations with reference to the accompanying drawings, it is to be understood that the invention is not limited to the precise functions and operations described above, and that the above-described embodiments are illustrative rather than restrictive, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined by the appended claims.

Claims (1)

1. A simulation method for determining density distribution of a post insulator and a disc insulator is characterized by comprising the following steps:
firstly, parameter preparation: respectively determining the geometrical sizes of the post insulator and the disc insulator; wherein the post insulator and the disc insulator are both cast by mixed liquid of epoxy resin and alumina;
secondly, respectively carrying out finite element mesh subdivision on the post insulator and the disc insulator: carrying out one-dimensional subdivision on the post insulator, and carrying out two-dimensional subdivision on the disc insulator;
thirdly, determining the simulation starting conditions: the initial volume fraction of the alumina particles, the proportion of the alumina particles of different particle sizes and the initial viscosity of the epoxy resin/alumina mixed solution;
fourthly, respectively calculating the particle movement speed of the post insulator and the disc insulator at the time t according to the following formula (2);
Figure FDA0003523774440000011
v＝v0(1-C)n (2)
wherein v is the disturbing settling velocity of the alumina in the solidification process of the insulator; v. of0Is the free settling velocity of the alumina particles in m/s; c is the volume fraction of alumina particles; n is a correction coefficient; dfIs the particle size of the alumina particles in m; g is the acceleration of gravity; ρ is a unit of a gradientepAnd ρfThe densities of the epoxy resin and the alumina are respectively, and the unit is kg/m3(ii) a Eta is the viscosity of the epoxy resin/alumina mixed solution, and the unit is Pa.s;
fifthly, respectively calculating inflow and outflow of each unit cell of the post insulator and the disc insulator according to a formula (3), wherein the inflow and outflow of the unit cells on the boundary of the disc insulator are calculated according to a formula (4);
Figure FDA0003523774440000012
Figure FDA0003523774440000013
in the formula, Fin[i+1]Is the inflow of cell i + 1; fout[i]Is the outflow of cell i; c [ i ]]The alumina concentration for cell i; dt is the time step, in units of s; l is a radical of an alcoholeleIs the cell size, in m; note that for the last cell, its outflow is 0; fouts[i,k]Is a boundary cell [ i, k](iii) outflow of (ii); c [ i, k ]]Is a boundary cell [ i, k]The alumina concentration of (a); v. oftIs the speed of movement of the alumina particles tangential to the boundary of the mold in m/s;
sixthly, respectively calculating the alumina concentration of each unit cell of the post insulator and the disc insulator according to a formula (5);
C[i]t＝C[i]t-dt+Fin[i]-Fout[i] (5)
wherein, C [ i ]]tAnd Cj]t-dtAlumina concentration, F, of unit i at time t and time t-dt, respectivelyin[i]And Fout[i]Inflow and outflow of cell i, respectively;
seventhly, stopping calculation if the time reaches 70 minutes, and calculating the density of the insulator according to the concentration of the alumina in the cells; otherwise, increasing the time to t + dt, and repeating the fourth step to the sixth step.
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CN104483043A (en) * 2014-12-19 2015-04-01 深圳供电局有限公司 Stress measurement device and method for knob insulator
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WO2008124706A2 (en) * 2007-04-06 2008-10-16 Arizona Board Of Regents Acting For And On Behalf Of Arizona State University Devices and methods for target molecule characterization
CN104483043A (en) * 2014-12-19 2015-04-01 深圳供电局有限公司 Stress measurement device and method for knob insulator
CN109408885A (en) * 2018-09-19 2019-03-01 上海电力学院 A kind of insulator space charge density model optimization method under high voltage direct current
CN110489864A (en) * 2019-08-20 2019-11-22 国网天津市电力公司电力科学研究院 Meter and wind speed, filth, partial size anti-snow slush insulator antifouling properties analysis method
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