CN113484369A - Oil paper insulation dielectric spectrum characteristic analysis method - Google Patents
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- 238000009413 insulation Methods 0.000 title claims abstract description 110
- 238000001453 impedance spectrum Methods 0.000 title claims abstract description 37
- 238000004458 analytical method Methods 0.000 title claims abstract description 12
- 230000004044 response Effects 0.000 claims abstract description 44
- 238000004364 calculation method Methods 0.000 claims abstract description 38
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 35
- 238000000034 method Methods 0.000 claims abstract description 34
- 238000004088 simulation Methods 0.000 claims abstract description 27
- 238000009792 diffusion process Methods 0.000 claims abstract description 17
- 230000008569 process Effects 0.000 claims abstract description 13
- 238000012360 testing method Methods 0.000 claims abstract description 11
- 230000009545 invasion Effects 0.000 claims abstract description 7
- 238000001035 drying Methods 0.000 claims description 40
- 238000013016 damping Methods 0.000 claims description 21
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 7
- 238000009736 wetting Methods 0.000 claims description 7
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 6
- 229910052782 aluminium Inorganic materials 0.000 claims description 6
- 239000011888 foil Substances 0.000 claims description 6
- 239000011521 glass Substances 0.000 claims description 6
- 238000010521 absorption reaction Methods 0.000 claims description 4
- 230000008859 change Effects 0.000 claims description 4
- 238000005303 weighing Methods 0.000 claims description 4
- 230000000903 blocking effect Effects 0.000 claims description 3
- 238000004140 cleaning Methods 0.000 claims description 3
- 229920006395 saturated elastomer Polymers 0.000 claims description 3
- 238000000691 measurement method Methods 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 3
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- 239000002131 composite material Substances 0.000 description 2
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- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004422 calculation algorithm Methods 0.000 description 1
- 238000003745 diagnosis Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005316 response function Methods 0.000 description 1
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Abstract
The invention provides an oiled paper insulation dielectric spectrum characteristic analysis method, which comprises the following steps: and constructing a finite element model of the uneven distribution of the water in the multi-layer oil paper insulation according to Fick's second diffusion law and COMSOL software, simulating the invasion process of the water in the insulation oil paper in the simulation sleeve layer through the model, and constructing a numerical calculation model of the simulated insulation frequency response of the uneven moisture of the oil paper insulation according to the dielectric response characteristic in the process. Preparing oil paper insulation samples with different moisture degrees to construct different unit laminated physical moisture models, carrying out frequency domain dielectric spectrum testing on the physical moisture models, and constructing physical insulation frequency response numerical value calculation models according to dielectric response characteristics tested by the frequency domain dielectric spectrum testing. And comparing whether the dielectric spectrum curves of the simulated insulation frequency response numerical calculation model and the physical insulation frequency response numerical calculation model are consistent or not, and judging the accuracy of the simulated insulation frequency response numerical calculation model. The method verifies the accuracy of the numerical calculation model for simulating the insulation frequency response.
Description
Technical Field
The invention relates to the technical field of oil paper insulation equipment state diagnosis, in particular to an oil paper insulation dielectric spectrum characteristic analysis method.
Background
As one of the most important connecting devices of a power transformer, the rapid and accurate assessment of the insulation state of a capacitive high-voltage bushing is important for the safe and stable operation of a power system, the oil-paper composite insulation is used as an insulation main component of the oil-immersed transformer, the state of the oil-paper composite insulation can seriously affect the electrical service life and the mechanical service life of the insulation of the transformer, and moisture is used as one of the most important factors influencing the operation state of the oil-paper insulation bushing and is regarded as the first threat of the bushing insulation system, so that the method has important significance for accurately assessing and diagnosing the oil-paper insulation moisture state of the transformer.
The method for detecting moisture of the oil paper insulation of the transformer mainly comprises an electrical measurement method and a chemical measurement method, the traditional electrical measurement method mainly comprises insulation resistance measurement, tan delta measurement and the like, and cannot be used for quantitatively analyzing the moisture content of the insulation, in recent years, a dielectric response method is favored, the principle is to judge the insulation state by obtaining and analyzing a dielectric response function, and compared with the traditional electrical measurement method, the method can obtain more insulation information, so that the insulation state can be better reflected. Establishing an internal relation between branch parameters of an extended Debye model and an FDS curve by using a GA-LMA algorithm, and evaluating the moisture degree of the oilpaper insulation by extracting characteristic quantity representing the moisture content; and a functional relation between the real part of the complex dielectric constant and the water content and FDS curve can be constructed, and a database of epsilon is formed through curve fitting, so that the water content of the oilpaper insulation is judged based on the Euclidean distance.
The assessment is mainly performed around the main insulation of the transformer, the study on the sleeve mainly aims at uniform damping, the study on the non-uniform damping state of the sleeve is rarely performed, the sleeve mainly aims at non-uniform damping when being actually damped, and the assessment on the non-uniform damping state of the oil paper insulation sleeve is still to be further studied through a frequency domain dielectric spectrum test.
In summary, in order to overcome the problems of the methods, a frequency domain dielectric spectrum characteristic curve of uneven moisture of the oil paper insulation needs to be analyzed, a numerical calculation model of insulation frequency response of uneven moisture needs to be constructed, and a fick's second diffusion law and a COMSOL finite element model are adopted to simulate and study the transient diffusion process of the water in the sleeve, so that an oil paper insulation dielectric spectrum characteristic analysis method is provided.
Disclosure of Invention
Accordingly, the present invention is directed to a method for analyzing dielectric spectrum characteristics of oiled paper insulation, so as to solve at least the above problems.
A method of analysis of oil paper insulation dielectric spectral characteristics, the method comprising the steps of:
s1, constructing a finite element model of the uneven distribution of the insulating moisture of the multilayer oiled paper according to Fick' S second diffusion law and COMSOL software, simulating the insulating oiled paper moisture invasion process in the simulation sleeve layer through the finite element model, and constructing a simulation insulation frequency response numerical calculation model of uneven moisture of the oiled paper insulation according to the dielectric response characteristic in the process;
s2, constructing different unit laminated physical damping models by preparing oil paper insulation samples with different damping degrees, carrying out frequency domain dielectric spectrum test on the physical damping models, and constructing physical insulation frequency response numerical value calculation models according to dielectric response characteristics tested by the frequency domain dielectric spectrum test;
and S3, judging the accuracy of the simulated insulation frequency response numerical calculation model by comparing whether the dielectric spectrum curves of the simulated insulation frequency response numerical calculation model and the real object insulation frequency response numerical calculation model are consistent.
Further, in step S1, the aluminum foil is contained between the insulating paper layers in the actual sleeve layer, and due to the blocking of the aluminum foil, the moisture in the insulating paper will diffuse only along the y-axis direction, but not along the x-axis direction, so that the fick' S second diffusion law is expanded:
where D is the diffusion coefficient and Dx is 0.
Further, in the moisture invasion process of the insulating paper in the simulation sleeve layer of step S1, the moisture content of the interface between the insulating oil and the insulating paper is kept constant, the boundary of the insulating paper is set to be the equilibrium moisture content, and the calculation formula of the moisture equilibrium of the oil-paper interface is as follows:
wherein, CequilDenotes equilibrium moisture in the insulating paper, pvIs the moisture pressure and T is the simulated temperature.
Further, p isvThe calculation formula of (a) is as follows:
wherein HR is relative humidity, ppm is moisture content in the insulating oil, pv,sat and ppmsatRespectively the pressure and the moisture content under the saturated state, and then solving through the following formulas:
log(ppmsat)＝A-B/T
wherein, A is 742, B is 1670,
wherein p iscThe critical pressure of water, T the simulation temperature, Δ T the difference between the critical temperature of water and the simulation temperature, a ═ 3.24, b ═ 5.87 × 10-3, c ═ 1.17 × 10-8, and d ═ 2.19 × 10-3.
Further, in step S2, the unit laminated physical damping model includes a two-unit laminated damping model, a three-unit laminated damping model, and a multi-unit laminated damping model.
Further, in step S2, before preparing the oiled paper insulation samples with different moisture degrees, the insulation paper and the transformer oil are dried, and the specific steps are as follows:
drying the insulating paper: firstly, wiping a cavity and a glassware in a vacuum oven clean by using alcohol, placing the vacuum oven in the vacuum oven, continuously drying for several hours to ensure that no residual moisture exists in the drying oven, then placing the rolled insulating paper into the glassware in a laminated manner for dispersed arrangement, placing the glass into the vacuum oven for drying for several hours, then opening the oven, wiping off water drops on the inner wall of the oven, continuously drying, and measuring the moisture content in the paper by using a Switzerland Karl Fischer moisture meter KFT831 after drying;
drying the transformer oil: firstly, cleaning the inner cavity and glassware of a vacuum oven by using alcohol, placing the vacuum oven and the glassware in the vacuum oven, continuously drying for several hours to ensure that no residual moisture exists in the drying oven, then placing transformer oil into the glassware for dispersed arrangement, placing the glass ware and the vacuum oven for drying for several hours, then opening the oven, wiping off water drops on the inner wall of the oven, continuously drying, and measuring the moisture content in the transformer oil by using a Switzerland Karl Fischer moisture meter KFT831 after drying.
Further, the specific steps of wetting the oiled paper are as follows:
taking out the dried oil-impregnated paper sample, immediately placing the oil-impregnated paper sample in a high-precision electronic balance for weighing, preparing a plurality of oil-impregnated paper insulation samples with different water contents by controlling the weight change during natural moisture absorption, and then placing the prepared sample in an oil-containing sealed bottle for standing for a plurality of hours to enable bubbles in the insulation paper to overflow.
Further, in step S3, the insulation conductivity and dielectric constant of the oiled paper in the simulated insulation frequency response numerical calculation model and the physical insulation frequency response numerical calculation model are regarded as nonlinear arbitrary changes, and are calculated as follows:
wherein Z (f) is the complex impedance of the entire medium, Zi(f) For each layer of mediumComplex impedance of (G), (f) complex conductance of the medium, Gi(f) For complex conductivity, σ, of each layer of dielectriciIs the conductivity, ε, of each layer of the mediumiIs a relative dielectric constant,. epsilon0In terms of vacuum dielectric constant, ω is frequency, Δ x is the thickness of each layer of dielectric, and S is the area of each layer of dielectric.
When x is infinitely small:
wherein σ x and ε x are the electrical conductivity and relative permittivity corresponding to when x is infinitesimally small,
the complex capacitance versus complex impedance is expressed as:
then, after the conductivity and the relative permittivity of each sheet are known, the relative permittivity is calculated by the above equation.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides an oil paper insulation dielectric spectrum characteristic analysis method, which simulates the water transient diffusion process of a sleeve by adopting a Fick second diffusion law and a COMSOL finite element model, simplifies the simulation model by calculating the average water content of insulation paper so as to be convenient for verifying experiments, deduces a relation between complex conductivity and complex dielectric constant based on a frequency domain dielectric spectrum method, constructs an insulation frequency response numerical value calculation model with uneven moisture, analyzes the influence of uneven water distribution on the dielectric response characteristic of the oil paper insulation model, and provides a reliable basis for accurately evaluating the insulation performance of oil paper insulation power equipment.
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In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is apparent that the drawings in the following description are only preferred embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without inventive efforts.
Fig. 1 is a non-uniform moisture distribution diagram of a method for analyzing dielectric spectrum characteristics of oiled paper insulation according to an embodiment of the present invention.
Fig. 2 is a numerical model diagram of an analysis method of dielectric spectrum characteristics of oiled paper insulation according to an embodiment of the present invention.
Fig. 3 is a simplified simulation model of an analysis method for dielectric spectrum characteristics of oiled paper insulation according to an embodiment of the present invention.
FIG. 4 is a graph of a simulation and a frequency domain dielectric spectrum of a sample of a method for analyzing the dielectric spectrum characteristics of the oiled paper insulation according to an embodiment of the present invention.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, the illustrated embodiments are provided to illustrate the invention and not to limit the scope of the invention.
Referring to fig. 1 and 2, the present invention provides a method for analyzing the dielectric spectrum characteristics of oiled paper insulation, the method comprising the steps of:
s1, constructing a finite element model of uneven distribution of the multi-layer oiled paper insulation moisture according to Fick' S second diffusion law and COMSOL software, simulating the insulating oiled paper moisture intrusion process in a simulation sleeve layer through the finite element model, and constructing a simulation insulation frequency response numerical calculation model of uneven moisture of oiled paper insulation according to dielectric response characteristics in the process, wherein the specific construction process is as follows: selecting model parameters, establishing two-dimensional axisymmetric geometry, setting material parameters, selecting a physical field, wherein the physical field adopts a dilute substance transfer module, and finally selecting a transient study equation to perform analog simulation analysis.
S2, constructing different unit laminated physical damping models by preparing oil paper insulation samples with different damping degrees, carrying out frequency domain dielectric spectrum test on the physical damping models, and constructing physical insulation frequency response numerical calculation models according to dielectric response characteristics tested by the frequency domain dielectric spectrum test, wherein the concrete test steps are as follows: and applying voltage excitation signals with variable frequencies at two ends of the sample, measuring response current in a loop, and analyzing the obtained voltage and current signals according to the basic principle of the frequency domain dielectric spectrum to obtain a frequency domain dielectric spectrum curve of the sample.
And S3, judging the accuracy of the simulated insulation frequency response numerical calculation model by comparing whether the dielectric spectrum curves of the simulated insulation frequency response numerical calculation model and the real object insulation frequency response numerical calculation model are consistent.
In step S1, the aluminum foil is contained between the insulating paper layers in the actual sleeve layer, and due to the blocking of the aluminum foil, the moisture in the insulating paper will diffuse only along the y-axis direction, but not along the x-axis direction, expanding the fick' S second diffusion law:
where D is the diffusion coefficient and Dx is 0.
Illustratively, the dielectric response characteristic of the oiled paper insulation when the oiled paper insulation is uneven and is affected by moisture is calculated through simulating the moisture invasion process of a sleeve layer model, the equilibrium moisture of an oiled paper interface is 6.25% through calculation, and the experimental temperature is 70 ℃. The moisture diffusion time was set at 200h, 500h, 800h, 1000h, where the x-axis represents the axial direction of the sleeve, the y-axis represents the radial direction of the sleeve, and the z-axis represents the moisture content of the insulating paper in this region. With the increase of the diffusion time, the moisture content of the insulating paper inside the sleeve gradually rises, and the whole insulating paper is distributed in a step shape. The initial damp point of the end screen has the highest water content because the water exchange with the external insulating oil is always balanced. And the insulating water content distribution of the sleeve corresponding to 800h and 1000h has no obvious difference, and the water diffusion reaches a steady state.
In the moisture invasion process of the insulating paper in the simulation sleeve layer of the step S1, the moisture content of the interface between the insulating oil and the insulating paper is kept constant, the boundary of the insulating paper is set as the equilibrium moisture content, and the calculation formula of the moisture equilibrium of the oil-paper interface is as follows:
wherein, CequilDenotes equilibrium moisture in the insulating paper, pvIs the moisture pressure and T is the simulated temperature.
pvThe calculation formula of (a) is as follows:
wherein HR is relative humidity, ppm is moisture content in the insulating oil, pv,satAnd ppm ofsatRespectively the pressure and the moisture content under the saturated state, and then solving through the following formulas:
log(ppmsat)＝A-B/T
wherein, A is 742, B is 1670,
wherein p iscThe critical pressure of water, T the simulation temperature, Δ T the difference between the critical temperature of water and the simulation temperature, a ═ 3.24, b ═ 5.87 × 10-3, c ═ 1.17 × 10-8, and d ═ 2.19 × 10-3.
For example, after the conductivity and the relative dielectric constant of each sheet are known, the relative dielectric constant can be calculated through a numerical model, and after the conductivity and the relative dielectric constant of each sheet are known, the relative dielectric constant can be calculated through the numerical model, in order to verify the dielectric response characteristic when the water of the sleeve is unevenly distributed by using an experimental model, the model is simplified by calculating the average water content of each layer of insulating paper in a simulation model, and the distribution of the water content is from top to bottom: 4%, 3%, 2%, and an equivalent water content I of 3%.
In step S2, the unit laminated physical damping model includes a two-unit laminated damping model, a three-unit laminated damping model, and a multi-unit laminated damping model.
In step S2, before preparing the oiled paper insulation samples with different moisture degrees, the insulation paper and the transformer oil are dried, and the specific steps are as follows:
drying the insulating paper: firstly, wiping a cavity and a glassware in a vacuum oven clean by using alcohol, placing the vacuum oven in the vacuum oven, continuously drying for several hours to ensure that no residual moisture exists in the drying oven, then placing the rolled insulating paper into the glassware in a laminated manner for dispersed arrangement, placing the glass into the vacuum oven for drying for several hours, then opening the oven, wiping off water drops on the inner wall of the oven, continuously drying, and measuring the moisture content in the paper by using a Switzerland Karl Fischer moisture meter KFT831 after drying;
drying the transformer oil: firstly, cleaning the inner cavity and glassware of a vacuum oven by using alcohol, placing the vacuum oven and the glassware in the vacuum oven, continuously drying for several hours to ensure that no residual moisture exists in the drying oven, then placing transformer oil into the glassware for dispersed arrangement, placing the glass ware and the vacuum oven for drying for several hours, then opening the oven, wiping off water drops on the inner wall of the oven, continuously drying, and measuring the moisture content in the transformer oil by using a Switzerland Karl Fischer moisture meter KFT831 after drying.
The specific steps of wetting the oiled paper are as follows:
taking out the dried oil-impregnated paper sample, immediately placing the oil-impregnated paper sample in a high-precision electronic balance for weighing, preparing a plurality of oil-impregnated paper insulation samples with different water contents by controlling the weight change during natural moisture absorption, and then placing the prepared sample in an oil-containing sealed bottle for standing for a plurality of hours to enable bubbles in the insulation paper to overflow.
Illustratively, to simulate uneven wetting of a simulated bushing, a laminated sample of insulating paper with a thickness of 1.04mm, a length of 600mm and a width of 100mm was prepared under laboratory conditions, the inner cavity and glassware of a vacuum oven were wiped clean with alcohol before the experiment, and the sample was placed in the vacuum oven and continuously dried for 5 hours at a temperature of 105 ℃/100Pa to ensure that no residual moisture remained in the oven. And (3) placing the rolled insulating paper into a glassware for dispersed arrangement, placing the glassware in a vacuum oven, and drying for 24h at the temperature of 105 ℃/100 Pa. After 24h, the oven was opened, the inner wall of the oven was wiped off, and drying was continued for 48h at 105 ℃/100 Pa. After drying, the water content in the paper was measured using a Switzerland Karl Fischer moisture meter KFT831, at which time the water content was less than 0.5%; drying 25# Claritya transformer oil for 72h at 105 ℃/100Pa by the same process, taking out the dried oil-impregnated paper sample during experiment, immediately placing the sample on a high-precision electronic balance for weighing, preparing 55 groups of oil-impregnated paper insulation samples with initial water content of 0.41-6.82% by controlling weight change during natural moisture absorption, wherein the sample with water content of more than 6% is obtained by humidifying a sprayer, then placing the prepared sample in an oil-containing sealed bottle for standing for 48h to enable bubbles in the insulation paper to overflow, laminating uniformly-moistened real models by the prepared units, realizing the construction of the non-uniformly-moistened real models by utilizing a stacking mode, and carrying out FDS test on the manufactured non-uniformly-moistened samples by using DIRANA developed by Omicron company of Austria.
In step S3, the oiled paper insulation conductivity and the dielectric constant in the simulated insulation frequency response numerical calculation model and the real insulation frequency response numerical calculation model are regarded as nonlinear arbitrary changes, and are calculated as follows:
wherein Z (f) is the complex impedance of the entire medium, Zi(f) Is the complex impedance of each layer of the medium, G (f) the complex conductance of the medium, Gi(f) For complex conductivity, σ, of each layer of dielectriciIs the conductivity, ε, of each layer of the mediumiIs a relative dielectric constant,. epsilon0In terms of vacuum dielectric constant, ω is frequency, Δ x is the thickness of each layer of dielectric, and S is the area of each layer of dielectric.
When x is infinitely small:
wherein σ x and ε x are the electrical conductivity and relative permittivity corresponding to when x is infinitesimally small,
the complex capacitance versus complex impedance is expressed as:
then, after the conductivity and the relative permittivity of each sheet are known, the relative permittivity is calculated by the above equation.
Exemplarily, as shown in fig. 4, it can be seen from the simulation curve and the real object curve that the tan δ -f curve of the dual-unit laminated uniform wetting model obtained by the finite element model simulation is overlapped with the real object curve obtained in the laboratory, and the two curves are well matched because the complex dielectric constant of the simulation model is obtained from the unit laminated uniform wetting oil-impregnated paper, and in the unit laminated uniform wetting model, the moisture distribution is uniform, the internal structure of the medium is simple, and the simulation insulation frequency response numerical value calculation model and the real object insulation frequency response numerical value calculation model have higher similarity in structure, so the simulation result is matched with the real object result.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (8)
1. A method for analyzing the insulating dielectric spectrum characteristics of oiled paper, which is characterized by comprising the following steps:
s1, constructing a finite element model of the uneven distribution of the insulating moisture of the multilayer oiled paper according to Fick' S second diffusion law and COMSOL software, simulating the insulating oiled paper moisture invasion process in the simulation sleeve layer through the finite element model, and constructing a simulation insulation frequency response numerical calculation model of uneven moisture of the oiled paper insulation according to the dielectric response characteristic in the process;
s2, constructing different unit laminated physical damping models by preparing oil paper insulation samples with different damping degrees, carrying out frequency domain dielectric spectrum test on the physical damping models, and constructing physical insulation frequency response numerical value calculation models according to dielectric response characteristics obtained by the frequency domain dielectric spectrum test;
and S3, judging the accuracy of the simulated insulation frequency response numerical calculation model by comparing whether the dielectric spectrum curves of the simulated insulation frequency response numerical calculation model and the real object insulation frequency response numerical calculation model are consistent.
2. A dielectric spectrum analysis method of oil paper insulation according to claim 1, wherein in step S1, the insulation paper in the actual sleeve layer contains aluminum foil, and the moisture in the insulation paper will diffuse only along the y-axis direction but not along the x-axis direction due to the blocking of the aluminum foil, so that the fick' S second diffusion law is extended:
where D is the diffusion coefficient and Dx is 0.
3. The method for analyzing insulation dielectric spectrum characteristics of oiled paper according to claim 1, wherein during the invasion of moisture into the insulation paper in the simulation sleeve layer of step S1, the moisture content of the interface between the insulation oil and the insulation paper is kept constant, the boundary of the insulation paper is set to equilibrium moisture content, and the calculation formula of the moisture equilibrium of the oiled paper interface is as follows:
wherein, CequilDenotes equilibrium moisture in the insulating paper, pvIs the moisture pressure and T is the simulated temperature.
4. A method for analysis of dielectric properties of oiled paper according to claim 3, characterized in that pvThe calculation formula of (a) is as follows:
wherein HR is relative humidity, ppm is moisture content in the insulating oil, pv,satAnd ppm ofsatRespectively the pressure and the moisture content under the saturated state, and then solving through the following formulas:
log(ppmsat)＝A-B/T
wherein, A is 742, B is 1670,
wherein p iscThe critical pressure of water, T the simulation temperature, Δ T the difference between the critical temperature of water and the simulation temperature, a ═ 3.24, b ═ 5.87 × 10-3, c ═ 1.17 × 10-8, and d ═ 2.19 × 10-3.
5. The method for analyzing the dielectric spectrum characteristics of the oiled paper insulation according to claim 1, wherein in step S2, the unit laminated physical moisture model comprises a two-unit laminated moisture model, a three-unit laminated moisture model and a multi-unit laminated moisture model.
6. The method for analyzing insulation dielectric spectrum characteristics of oiled paper according to claim 1, wherein in step S2, before preparing oiled paper insulation samples with different moisture degrees, the insulation paper and transformer oil are dried, and the method comprises the following steps:
drying the insulating paper: firstly, wiping a cavity and a glassware in a vacuum oven clean by using alcohol, placing the vacuum oven in the vacuum oven, continuously drying for several hours to ensure that no residual moisture exists in the drying oven, then placing the rolled insulating paper into the glassware in a laminated manner for dispersed arrangement, placing the glass into the vacuum oven for drying for several hours, then opening the oven, wiping off water drops on the inner wall of the oven, continuously drying, and measuring the moisture content in the paper by using a Switzerland Karl Fischer moisture meter KFT831 after drying;
drying the transformer oil: firstly, cleaning the inner cavity and glassware of a vacuum oven by using alcohol, placing the vacuum oven and the glassware in the vacuum oven, continuously drying for several hours to ensure that no residual moisture exists in the drying oven, then placing transformer oil into the glassware for dispersed arrangement, placing the glass ware and the vacuum oven for drying for several hours, then opening the oven, wiping off water drops on the inner wall of the oven, continuously drying, and measuring the moisture content in the transformer oil by using a Switzerland Karl Fischer moisture meter KFT831 after drying.
7. The method for analyzing the insulation dielectric spectrum characteristics of the oiled paper according to claim 6, wherein the specific steps of wetting the oiled paper are as follows:
taking out the dried oil-impregnated paper sample, immediately placing the oil-impregnated paper sample in a high-precision electronic balance for weighing, preparing a plurality of oil-impregnated paper insulation samples with different water contents by controlling the weight change during natural moisture absorption, and then placing the prepared sample in an oil-containing sealed bottle for standing for a plurality of hours to enable bubbles in the insulation paper to overflow.
8. The method for analyzing insulation dielectric spectrum characteristics of oiled paper according to claim 1, wherein in step S3, the insulation conductivity and dielectric constant of oiled paper in the simulation insulation frequency response numerical calculation model and the physical insulation frequency response numerical calculation model are regarded as nonlinear arbitrary changes, and are calculated by:
wherein Z (f) is the complex impedance of the entire medium, Zi(f) Is the complex impedance of each layer of the medium, G (f) the complex conductance of the medium, Gi(f) For complex conductivity, σ, of each layer of dielectriciIs the conductivity, ε, of each layer of the mediumiIs a relative dielectric constant,. epsilon0In terms of vacuum dielectric constant, ω is frequency, Δ x is the thickness of each layer of dielectric, and S is the area of each layer of dielectric.
When x is infinitely small:
wherein σ x and ε x are the electrical conductivity and relative permittivity corresponding to when x is infinitesimally small,
the complex capacitance versus complex impedance is expressed as:
then, after the conductivity and the relative permittivity of each sheet are known, the relative permittivity is calculated by the above equation.
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| CN117454064A (en) * | 2023-09-18 | 2024-01-26 | 国网宁夏电力有限公司电力科学研究院 | Quantitative analysis method, medium and system for transformer drying process |
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