CN106294914A - A kind of converter transformer valve-side three-dimensional electric field emulation mode considering Anisotropic Nonlinear - Google Patents

Abstract

The invention belongs to electric system simulation field, especially with regard to the method for converter transformer valve-side three-dimensional electric field emulation.The method mostly concentrates on two dimensional electric field modeling analysis for the current research to converter power transformer electric field, rare three-dimensional modeling analysis, the present invention is configured to core with converter power transformer major insulation threedimensional model, propose one and consider material nonlinearity and anisotropy, for the method for the emulation of valve winding in converter transformer DC electric field.First, utilize ANSYS finite element analysis software to set up the threedimensional model of converter power transformer winding overhang, and it is carried out stress and strain model；Then, the secondary development APDL module utilizing ANSYS writes Anisotropic Nonlinear DC electric field calculation procedure；Finally, boundary condition, initial electrical resistivity, load test voltage are set, calculate three-dimensional electric field.The invention provides a kind of converter transformer valve-side three-dimensional electric field emulation mode considering Anisotropic Nonlinear, provide a method that for improving converter power transformer Electric Field Simulation precision.

Description

A kind of converter transformer valve-side three-dimensional electric field emulation mode considering Anisotropic Nonlinear

Technical field

The invention belongs to electric system simulation field, especially with regard to converter transformer valve-side three-dimensional electric field The method of emulation.

Background technology

China builds multinomial large-sized DC power transmission engineering, along with the throwing of these DC transmission engineerings at present Fortune, the stable work of direct current transportation seems and becomes more and more important, and the design of power transformer main minor insulation is High-power transformer, especially superhigh tension power transformer calculate the important component part of design, and it is not only Power-carrying and operational reliability to power transformer are significant, and the warp to transformator Ji index also has extremely important impact.

At present, large-sized converter transformer is internal typically still uses oil, paper composite insulation structure.Normal fortune In the case of row, the electric field in oil, paper compound inslation is AC and DC complex electrical field, under DC voltage Electric Field Distribution determined by electrical conductivity, and electrical conductivity shows as non-linear, with electric field intensity and Temperature exponentially relation so that electric field shows as non-linear when converter power transformer bears DC voltage, Additionally due to manufacturing process, the resistivity of cardboard there is also anisotropy.Solving converter transformer valve Need to calculate by nonlinear field during the direct current electric field of side, simultaneously need to consider material anisotropy, calculate Complexity, therefore, it is necessary to further investigate converter power transformer Electric Field Distribution.

Existing research is concentrated mainly on the research of converter power transformer two dimensional electric field, seldom has three-dimensional electric field The research analyzed, the non-linear and material anisotropy that consideration temperature and field intensity cause the most simultaneously Research.Document " valve winding in converter transformer analysis of electric field under complex electrical field effect " analyzes the change of current Voltage condition suffered by the winding of transformator valve side, it is indicated that under DC Steady voltage effect, insulant Electric field is obeyed resistive distribution and is directly proportional to its resistivity, and calculates electric field under different resistivity ratio Distribution situation, the non-linear necessity that valve side DC electric field is calculated of analytic explanation.Document " changes The FEM calculation of convertor transformer anisotropy DC electric field " utilize self-programming to converter transformer valve-side Direct current electric field is calculated, and is emulated by FEM-software ANSYS, electrical conductivity of having derived In the case of anisotropy, the mathematical model of DC electric field, gives discrete scheme, analyzes electrical conductivity pair The impact of DC electric field, and 1 500kV converter power transformer is calculated.Result of calculation table Bright, it is considered in the anisotropy back cardboard of material, field intensity reduces, in oil, field intensity increases, the amplitude of change Relevant with electrical conductivity initial value.Document " valve winding in converter transformer Anisotropic Nonlinear DC electric field Analyzing " the author uses ANSYS secondary exploitation technology, and calculate and considering that insulant resistivity is with field Non-linear DC electric field by force and under temperature variations and Anisotropic Nonlinear DC electric field.Calculate Result shows, is considering that insulant resistivity is non-linear and in the case of anisotropy, Electric Field Distribution With do not consider that the distribution under the conditions of these is very different.Document " valve winding in converter transformer end Portion's three-dimensional electric field is analyzed " herein by modeling and stress and strain model, to one ± 500kV change of current transformation Device valve side winding overhang carried out the analysis of three-dimensional DC electrical field, AC field and polarity inversion electric field with Calculate, and contrasted with traditional two-dimentional computational methods, calculating does not accounts for material nonlinearity And anisotropy.

Above-mentioned document is concentrated mainly on its two dimension of research to the research of converter transformer valve-side DC electric field The distribution of electric field, the distribution to three-dimensional electric field is studied less, and document does not considers under three-dimensional electric field Non-linear and anisotropic analytical calculation, and converter power transformer is as spatial entities, only by three Dimension module could accurately analyze the distribution of its space electric field, is therefore worth converter power transformer Electric Field Distribution Carry out deeper into research.

Accompanying drawing explanation

Fig. 1 is the Calculation of Three-Dimensional Electric Fields illustraton of model of the present invention

Fig. 2 is the stress and strain model figure of the present invention

Fig. 3 is the electrical conductivity-electric field intensity matched curve figure of the present invention

Fig. 4 is the non-linear DC electric field computing block diagram of the present invention

Summary of the invention

Two dimensional electric field modeling analysis is mostly concentrated on for the current research to converter power transformer electric field, and Converter power transformer is as spatial entities, it is necessary to carry out three-dimensional modeling analysis for converter power transformer, this Patent of invention, with the core that is configured to of converter power transformer major insulation threedimensional model, proposes one and considers material Non-linear and anisotropy, for the method for the emulation of valve winding in converter transformer DC electric field.First First, ANSYS finite element analysis software is utilized to set up the threedimensional model of converter power transformer winding overhang, and It is carried out stress and strain model；Then, the secondary development APDL module utilizing ANSYS is write non-linear Anisotropy DC electric field calculation procedure, calculates Nonlinear Electric Field by the method for iteration, and in iteration During read the component on the different directions of electric field intensity respectively, calculate each of material based on each component Anisotropy；Finally, boundary condition, initial electrical resistivity, load test voltage are set, calculate three-dimensional Electric field.

For achieving the above object, the present invention takes techniques below scheme:

1, modeling and stress and strain model.As a example by certain 500KV converter power transformer, use solid modelling Mode sets up model, models mainly for converter power transformer major insulation, it is contemplated that symmetry can only choosing Take winding overhang and set up model, and in view of actual working condition and the feature of model structure itself Model is carried out stress and strain model.

2, the electric field intensity impact on resistivity is considered.Using APDL Parametric Design Language is to pass through The method of iteration, once solves based on the field intensity obtained is by front, calculates each finite element list The resistivity of unit.Then revise the resistivity of each finite element unit, solve next time.Successively Circulation, until meeting iteration precision or reaching the maximum iteration time of regulation.

3, the temperature impact on resistivity is considered.Load Temperature Excitation herein according to experience, only consider Heat conductive process in insulating board and transformer oil, by the method setting up coupled field, by temperature Degree field result passes to electric field, utilizes the resistivity of each finite element unit of this results modification, to carry out Solving of steady-state DC electric field.

4, anisotropy DC electric field calculates.Make the in-plane of insulating board parallel when modeling or It is perpendicular to the z coordinate axle of system.When calculating Anisotropic Nonlinear steady-state DC electric field, only need to be Iterative process reads the x of electric field intensity, y, z-component, calculates the horizontal and vertical component of this point, Calculate the horizontal and vertical resistivity of correspondence again, then calculate x, y, z direction by coordinate transform Resistivity.

The present invention is to consider material nonlinearity and the calculating of anisotropic three-dimensional electric field, for converter power transformer Valve side direct current electric Field Calculation provides a method that, for exhausted by software emulation converter power transformer master Edge electric field provides corresponding basic model.

Detailed description of the invention

The present invention comprises the following steps:

1, the analysis of electric field under DC voltage effect

Converter power transformer is by caused by operating mode, and it the most singly bears the effect of AC power frequency voltage, the most also holds Acted on by DC voltage.Under the effect of DC voltage, the electric field of oil-paper combination insulation structure divides Cloth depends primarily on the resistivity of insulant, in resistive distribution.Therefore, AC and DC voltage effect Under electric field be diverse, need to use different method for solving.

Under DC voltage effect, Electric Field Distribution is not only relevant with insulation system, also with dielectric Resistivity size is relevant.The built-in electrical insulation medium of converter power transformer mainly includes transformer oil, oil-paper And cardboard, the resistivity of these media can be by the shadow of the several factors such as temperature, humidity, electric field intensity Ringing, its excursion is the biggest, and meanwhile, the manufacturing process of insulating board causes its stepped construction, makes absolutely The feature that the resistivity of edge cardboard has an anisotropy that.In the converter power transformer of actual motion, the electricity of oil Resistance rate is typically 10¹²～10¹⁴Change between Ω m, oil-paper and cardboard then 10¹²～10¹⁵Ω·m Between.According to existing data, under room temperature the ratio of oil and paper resistivity may between l:10 to 1:500, May be between 1:1 to 1:1000 under service condition.In addition, the absolute value pair of insulant resistivity Transient DC electric field also has a major impact.

2. Electric Field Distribution mathematical model

The differential form of Maxwell equation is as follows:

$\left\{\begin{array}{c}\mathrm{rotH}=J+\frac{\∂D}{\∂t}\\ \mathrm{rotE}=-\frac{\∂B}{\∂t}\\ \mathrm{div}D=\mathrm{\ρ}\\ \mathrm{div}B=0\end{array}\right.$ (formula 2.1)

Wherein H, B, E, D, J and ρ represent magnetic field intensity, magnetic induction, electric field respectively Intensity, dielectric displacement, conduction current density vector charge density；

Media material properties equation is as follows:

D=ε E (formula 2.2)

J=γ E (formula 2.3)

Wherein ε, γ represent dielectric permittivity, electrical conductivity respectively；In AC field calculates, ε and γ Constant can be regarded as, and in DC electric field, ε, γ change with the change of field intensity；

The computing formula of electric field intensity is:

$E=-\mathrm{grad}u-\frac{\∂A}{\∂t}$ (formula 2.4)

Because the length of electromagnetic wave is much larger than the field domain of computation model, therefore negligible:

E=-grad u (formula 2.5) Assume insulating board and transformer oil do not exist free charge:

$\mathrm{div}(J+\frac{\∂D}{\∂t})=0$ (formula 2.6)

$\mathrm{div}(\mathrm{\γE}+\mathrm{\ϵ}\frac{\∂E}{\∂t})=0$ (formula 2.7)

Bring E=-grad u into above formula to obtain:

$\mathrm{\γ}\mathrm{div}\mathrm{grad}u+\mathrm{\ϵ}\frac{\∂}{\∂t}\mathrm{div}\mathrm{grad}u=0$ (formula 2.8)

In Vector operation, exchange, to time derivation and the order to space derivation, obtains:

$(\mathrm{\γ}+\mathrm{\ϵ}\frac{\∂}{\∂t})\mathrm{div}\mathrm{grad}u=0$ (formula 2.9)

In cartesian coordinate system, consider ε and γ number of Three dimensional transient electric field in complex media simultaneously Model is:

(formula 2.10)

3. modeling and stress and strain model

In ANSYS finite element software, the mode of solid modelling is used to set up converter power transformer major insulation 3-D geometric model；Material Physics parameter in converter power transformer major insulation 3-D geometric model is carried out really Determine and model is carried out stress and strain model.

ANSYS, can be in software by being similar to the side that CAD draws as finite element analysis software Formula sets up various model, and inputs the material dielectric constant of each several part, initial electrical resistivity, pyroconductivity, Specific heat capacity, density, determine cell type and model is carried out stress and strain model.

The computation model herein used is single-phase four-column type structure, and the winding on middle two core limbs is adopted With parallel-connection structure, increasing by two return yokes is to dredge magnetic flux, reduces height unshakable in one's determination.Therefore, Electric Field Calculation model can choose 1/8 structure, again because of the symmetrical structure of core limb, and mainly divides Analyse is the structure of end, and actual computation model is less than 1/8.Computation model is as shown in Figure 1.

In the insulator die type of transformator end, insulating paper cylinder and square ring etc. all can be approximately cylindrical ring body, because of This can use first split surface, then scanned the subdivision of perfect aspect by body.And the pole of figure of transformer oil Irregularly, need be split into rule shape, the axial symmetry part being i.e. filled between winding and Irregularities outside winding, carries out subdivision control the most respectively.Carrying out face subdivision when, By arranging length or the segments in sideline, it is ensured that the grid between model structure can rational mistake Cross.The when of carrying out rotary body subdivision, control grid by arranging along direction of rotation signal generating unit number The precision of subdivision.Owing near fuel tank, field intensity is the least, therefore can be by arranging unit on its boundary line Number control its subdivision precision.Controlled by above-mentioned a series of subdivision, it is ensured that model structure Between Mesh Smoothing transition, and obtained the preferable FEM (finite element) model of quality.Due to winding and iron core It is intended to compose upper constant potential value, therefore need not it is carried out subdivision, only insulant is carried out grid Subdivision, grid model is as shown in Figure 2.

4. consider the electric field intensity impact on resistivity

4.1 consider the nonlinear iterative formula of electric field intensity

When nonlinear analysis, the electrical conductivity-electric-field strength of oil in Fig. 3 with exponential function again matching Degree nonlinear curve, as shown in formula 5.1, the electrical conductivity of vertical paper-electric field intensity non-linear relation Still represent by traditional mode, as shown in formula 5.2:

${\mathrm{\γ}}_{\mathrm{oil}}={\mathrm{\γ}}_{0\mathrm{oil}}\exp \left(\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{a}_i{E}^{i-1}\right)$ (formula 4.1)

γ_paper=γ_0paper(β E) (formula 4.2)

In formula, E is electric field intensity value kV/mm；γ_0oilAnd γ_0paperIt is room temperature (20 DEG C) respectively, E=0 Time oil and the estimated value of vertical cardboard direction electrical conductivity.Calculate in Chinese style and take N=7, coefficient a_i(i=1,2 ... 7) value obtains according to the electrical conductivity-electric field strength profile matching of Fig. 3, cardboard in formula 5.2 Nonlinear factor β=0.017.

4.2 consider the nonlinear computational methods of electric field intensity

NONLINEAR CALCULATION uses secondary development program APDL of ANSYS software, i.e. ANSYS joins Numberization design language, can be directly utilized APDL command operating ANSYS mastery routine, and be circulated by DO. Basic thought is through the method for iteration, utilizes * VGET order by the front field intensity once solving and obtaining Save as array, utilize this array to calculate the resistivity of each finite element unit.Then utilize The resistivity of each finite element unit is revised in EMODIF order, solves next time.Circulate successively, Until meeting iteration precision or reaching the maximum iteration time of regulation.The flow chart of nonlinear solution is shown in Fig. 4.

4.3 convergence criterion

Multiple choices are had in paper oil insulation electric Field Calculation:

Choose from field amount (criterion object), the rate of change of desirable current potential, field intensity, region electrical conductivity etc.；From Various ways is had again on algorithm.Here, owing to field intensity E is the emphasis being concerned about, therefore with E for criterion pair As, it is considered to the independence of criterion, the maximum rate of change that algorithm takes each unit field intensity E is foundation, it may be assumed that

$\max \left\{\frac{E_{n+1}^{\′}-E_n}{E_n}{|}_{k=1\→N}\right\}\%\≤E_{\max }$ (formula 4.3)

In formula: E_nIt is each unit n-th field intensity result of calculation；K is iterations；N is subdivision Unit sum；E_maxFor the maximum field strength rate of change set.

5. consider the temperature impact on resistivity.

The determination of 5.1 end region temperatures

When this patent calculates the Temperature Distribution of winding overhang, use the method that temperature value is empirically set. Adding Temperature Excitation at winding and electrostatic ring surface, its value is 30 DEG C.Ambient temperature is set to 20 DEG C. Winding overhang temperature is simulated by single Temperature calculating.Resistance to tested owing to executing DC voltage outside In testing, the flow velocity of transformer oil is almost negligible.Only consider that heat is in insulating board and transformation Conductive process in device oil, does not consider heat convection and the heat radiation on winding surface.

5.2 coupling process

After completing winding overhang solution of Temperature, read the temperature value of each unit with * VGET, so The temperature of each unit is saved in a text by the rear * of utilization VWRITE order.Straight when calculating During stream steady-state field, * VREAD order is utilized to read the data in text and be saved in array, Utilize this array to revise the resistivity of each finite element unit, revise in each NONLINEAR CALCULATION iteration γ in formula 4.1 and formula 4.2_0oilAnd γ_0paperValue be oil during E=0 under corresponding temperature and vertical cardboard The estimated value of direction electrical conductivity, to carry out solving of steady-state DC electric field.

6. anisotropy DC electric field calculates

Converter power transformer uses cardboard and the oil-paper of stacking, and their resistivity is along parallel paper There is anisotropy in direction and vertical paper direction, this character can be expressed as:

$\mathrm{\σ}=\left(\begin{array}{cc}{\mathrm{\σ}}_h& 0\\ 0& {\mathrm{\σ}}_t\end{array}\right)$ (formula 6.1)

σ_hResistivity for horizontal paper direction；

σ_tFor being perpendicular to the resistivity in paper direction.

In Fig. 1 transformator 1/8 overhang insulation model, insulating paper cylinder and square ring etc. all can be approximately round Annular solid, with cylindrical ring body cross section as x during modeling, z-plane, with the cylindrical ring body longitudinal axis as y-axis, Now with cardboard with the angle in y-axis direction is as θ, then the coordinate of cardboard arbitrfary point a is (x_a,y_a,z_a) Vertical paper direction is expressed as:

$\stackrel{\→}{a_h}=(x_a,\tan \mathrm{\θ}\sqrt{{x_a}^2+{z_a}^2},z_a)$ (formula 6.2)

Assume that the electric field intensity that now a point reads is expressed as E_a=(E_x,E_y,E_z), then E_aVertical paper Component be:

$E_h=\frac{\stackrel{\→}{E_a}\·\stackrel{\→}{a_h}}{\left|\stackrel{\→}{a_h}\right|}=\frac{E_x{x}_a+E_y\tan \mathrm{\θ}\sqrt{{x_a}^2+{z_a}^2}+E_z{z}_a}{\sqrt{{x_a}^2+{\tan }^2\mathrm{\θ}({x_a}^2+{z_a}^2)+{z_a}^2}}$ (formula 6.3)

E_aThe component of horizontal paper is:

$E_t=\sqrt{{E_a}^2-{E_h}^2}=\sqrt{({E_x}^2+{E_y}^2+{E_z}^2)-\frac{{(E_x{x}_a+E_y\tan \mathrm{\θ}\sqrt{{x_a}^2+{z_a}^2}+E_z{z}_a)}^2}{{x_a}^2+{\tan }^2\mathrm{\θ}({x_a}^2+{z_a}^2)+{z_a}^2}}$ (formula 6.4)

Then according to E_hAnd E_tBring the non-linear of cardboard vertically and horizontally resistivity in 4.1 respectively into Fitting formula, calculates σ_hAnd σ_t。

Through more corresponding mathematic(al) manipulations, it can be deduced that as a (x in arbitrfary point on cardboard_a,y_a,z_a) and and coordinate When there is angle theta in axle y:

$\left(\begin{array}{c}{\mathrm{\σ}}_r\\ {\mathrm{\σ}}_y\end{array}\right)=\left(\begin{array}{cc}{\mathrm{\σ}}_{\mathrm{rr}}& {\mathrm{\σ}}_{\mathrm{ry}}\\ {\mathrm{\σ}}_{\mathrm{yr}}& {\mathrm{\σ}}_{\mathrm{yy}}\end{array}\right)$ (formula 6.5)

Wherein:

$\left\{\begin{array}{c}{\mathrm{\σ}}_{\mathrm{rr}}={\mathrm{\σ}}_h{\cos }^2\mathrm{\θ}+{\mathrm{\σ}}_t{\sin }^2\mathrm{\θ}\\ {\mathrm{\σ}}_{\mathrm{ry}}={\mathrm{\σ}}_h\cos \mathrm{\θ}\sin \mathrm{\θ}-{\mathrm{\σ}}_t\cos \mathrm{\θ}\sin \mathrm{\θ}\\ {\mathrm{\σ}}_{\mathrm{yr}}={\mathrm{\σ}}_{\mathrm{ry}}\\ {\mathrm{\σ}}_{\mathrm{yy}}={\mathrm{\σ}}_h{\sin }^2\mathrm{\θ}+{\mathrm{\σ}}_t{\cos }^2\mathrm{\θ}\end{array}\right.$ (formula 6.6)

In like manner:

$\left(\begin{array}{c}{\mathrm{\σ}}_x\\ {\mathrm{\σ}}_z\end{array}\right)=\left(\begin{array}{cc}{\mathrm{\σ}}_{\mathrm{xx}}& {\mathrm{\σ}}_{\mathrm{xz}}\\ {\mathrm{\σ}}_{\mathrm{zx}}& {\mathrm{\σ}}_{\mathrm{zz}}\end{array}\right)$ (formula 6.7)

Wherein:

(formula 6.8)

Wherein σ_x,σ_y,σ_z,σ_rIt is respectively x, y, z direction and a point resistivity component along radial direction,For y-axis with a place plane with the angle of x-axis Yu y-axis place plane, and

In sum:

(formula 6.9)

Obtained σ_x,σ_y,σ_zIt is the cardboard of correspondence respectively to resistivity component.

Respectively bring above-mentioned cardboard into 4.2 cardboard nonlinear resistivity change to resistivity component computing formula For computing, according to all directions field intensity value obtained in calculating, calculate all directions resistive component, and pass through EMODIF instruction modification cardboard unit is respectively to resistivity component, as the parameter of next iteration computing, Anisotropy can be considered the most simultaneously.

Claims (5)

1. consider a converter transformer valve-side three-dimensional electric field emulation mode for Anisotropic Nonlinear, including Following steps:

1), in ANSYS finite element software, the mode of solid modelling is used to set up converter power transformer major insulation three-dimensional several What model, is determined Material Physics parameter in converter power transformer major insulation 3-D geometric model and model is carried out net Lattice divide；2), secondary development program APDL of ANSYS software is used to be programmed, by the method for iteration, profit Carry out computing next time with the front results modification resistivity of material once calculated, until result restrains, calculate electric field with this The intensity impact on resistivity；3), the method that temperature value is empirically set is used to add temperature at winding and electrostatic ring surface Excitation, simulates winding overhang temperature by single Temperature calculating, according to temperature computation result in iterative computation, The calculating parameter of amendment corresponding units, to calculate the temperature field impact on electric field；4), derivation anisotropy computing formula, Obtain electric field all directions component the most respectively, calculate all directions resistive component, and repaiied by EMODIF instruction Change cardboard unit respectively to resistivity component, as the parameter of next iteration computing, with consider the most simultaneously each to The opposite sex.

2. according to the converter transformer valve-side three-dimensional electric field emulation side of the consideration Anisotropic Nonlinear described in claim l Method, it is characterised in that: described step 1) in modeling use computation model be single-phase four-column type structure, model includes Iron core, winding, paper oil insulation, the winding on middle two core limbs uses parallel-connection structure, and increasing by two return yokes is In order to dredge magnetic flux, reduce height unshakable in one's determination；1/8 structure chosen by electric Field Calculation model；

The first split surface of stress and strain model employing, then the subdivision of perfect aspect is scanned by body, first it is split into rule Shape, the irregularities outside the axial symmetry part being i.e. filled between winding and winding, distinguish the most again Carry out subdivision control, carrying out face subdivision when, by arranging length or the segments in sideline, it is ensured that mould Grid between type structure can reasonably transition.

3. according to the converter transformer valve-side three-dimensional electricity of the consideration Anisotropic Nonlinear described in claim l Emulation mode, it is characterised in that: described step 2) in consider that electric field intensity is non-linear；

(1) the nonlinear iterative formula of electric field intensity is considered

Electrical conductivity-electric field intensity nonlinear curve with exponential function matching oil is as follows:

${\mathrm{\γ}}_{\mathrm{oil}}={\mathrm{\γ}}_{0\mathrm{oil}}\exp \left(\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{a}_i{E}^{i-1}\right)$

Electrical conductivity-electric field intensity the non-linear relation of vertical paper is still as follows by traditional mode:

γ_paper=γ_0paper(βE)

In formula, E is electric field intensity value kV/mm；γ_0oilAnd γ_0paperIt is room temperature (20 DEG C) respectively, during E=0 The estimated value of oily and vertical cardboard direction electrical conductivity；Calculate in Chinese style and take N=7, coefficient a_i(i=1,2 ... 7) value Obtain according to electrical conductivity-electric field strength profile matching, nonlinear factor β=0.017 of cardboard；

(2) the nonlinear computational methods of electric field intensity are considered

NONLINEAR CALCULATION uses the secondary exploitation technology of ANSYS software, i.e. ANSYS Parametric designing Language；Basic thought is through the method for iteration, utilizes * VGET order front once solving to be obtained Field intensity saves as array, utilizes this array to calculate the resistivity of each finite element unit, then utilizes The resistivity of each finite element unit is revised in EMODIF order, solves next time, circulates successively, directly To meeting iteration precision or reaching the maximum iteration time of regulation；

(3) convergence criterion

Multiple choices are had in paper oil insulation electric Field Calculation:

With E for criterion object, it is considered to the independence of criterion, algorithm takes the maximum change of each unit field intensity E Rate is foundation, i.e. $\max \left\{\frac{E_{n+1}^{\′}-E_n}{E_n}{|}_{k=1\→N}\right\}\%\≤E_{\max }$

In formula: k is iterations；N is subdivision unit sum；E_maxFor the maximum field strength rate of change set.

4. according to the converter transformer valve-side three-dimensional electric field of the consideration Anisotropic Nonlinear described in claim l Emulation mode, it is characterised in that: described step 3) the middle consideration temperature impact on resistivity, first basis Empirical hypothesis temperature value, then calculate the temperature impact on resistivity by the method for coupling；

(1) determination of end region temperature

Adding Temperature Excitation at winding and electrostatic ring surface, its value is 30 DEG C, and ambient temperature is set to 20 DEG C, Flow velocity is ignored, and only considers heat conductive process in insulating board and transformer oil, do not consider around The heat convection on group surface and heat radiation；

(2) coupling process

After completing winding overhang solution of Temperature, the temperature value reading each unit with * VGET, then utilize * the temperature of each unit is saved in a text by VWRITE order, when calculating DC Steady electricity During field, utilize * VREAD order read the data in text and be saved in array, utilize this array Revise the resistivity of each finite element unit, to carry out solving of steady-state DC electric field.

5. according to the converter transformer valve-side three-dimensional electricity of the consideration Anisotropic Nonlinear described in claim l Emulation mode, it is characterised in that: described step 4) in anisotropy DC electric field calculate:

(1) there is anisotropy in paper direction, and this character can be expressed as:

$\mathrm{\σ}=\left(\begin{array}{cc}{\mathrm{\σ}}_h& 0\\ 0& {\mathrm{\σ}}_t\end{array}\right)$

σ_hResistivity for horizontal paper direction；

σ_tFor being perpendicular to the resistivity in paper direction；

In transformator 1/8 overhang insulation model, insulating paper cylinder and square ring etc. all can be approximately cylindrical ring body, during modeling With cylindrical ring body cross section as x, z-plane, with the cylindrical ring body longitudinal axis as y-axis, now with cardboard with the folder in y-axis direction Angle is θ, then the coordinate of cardboard arbitrfary point a is (x_a,y_a,z_a) vertical paper direction be expressed as:

$\stackrel{\→}{a_h}=(x_a,\tan \mathrm{\θ}\sqrt{{x_a}^2+{z_a}^2},z_a)$

Assume that the electric field intensity that now a point reads is expressed as E_a=(E_x,E_y,E_z), then E_aThe component of vertical paper is:

$E_h=\frac{\stackrel{\→}{E_a}\·\stackrel{\→}{a_h}}{\left|\stackrel{\→}{a_h}\right|}=\frac{E_x{x}_a+E_y\tan \mathrm{\θ}\sqrt{{x_a}^2+{z_a}^2}+E_z{z}_a}{\sqrt{{x_a}^2+{\tan }^2\mathrm{\θ}({x_a}^2+{z_a}^2)+{z_a}^2}}$

E_aThe component of horizontal paper is:

$E_t=\sqrt{{E_a}^2-{E_h}^2}=\sqrt{({E_x}^2+{E_y}^2+{E_z}^2)-\frac{{(E_x{x}_a+E_y\tan \mathrm{\θ}\sqrt{{x_a}^2+{z_a}^2}+E_z{z}_a)}^2}{{x_a}^2+{\tan }^2\mathrm{\θ}({x_a}^2+{z_a}^2)+{z_a}^2}}$

Then according to E_hAnd E_tBring cardboard nonlinear fitting formula vertically and horizontally in 5.1 respectively into and calculate σ_h And σ_t；

Obtain through more corresponding mathematic(al) manipulations:

Obtained σ_x,σ_y,σ_zIt is the cardboard resistivity initial anisotropy component of iteration next time；

Cardboard is respectively brought into resistivity component computing formula the interative computation of cardboard nonlinear resistivity again, and passes through EMODIF instruction modification cardboard unit is respectively to resistivity component, as the parameter of next iteration computing, and can be in emulation Middle consider anisotropy simultaneously.