CN111709153B - Oiled paper insulation moisture content evaluation method by using transfer function and weighting combination method - Google Patents
Oiled paper insulation moisture content evaluation method by using transfer function and weighting combination method Download PDFInfo
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Abstract
The invention relates to an oiled paper insulation moisture content assessment method by using a transfer function and optimal weighting combination method, which comprises the following steps: establishing a transfer function equation of an oil paper insulation series-parallel equivalent model; deducing a polar expression of a polarization branch of a series-parallel model based on a transfer function equation of the system; establishing a relational expression between the polar value and the moisture content of the sensitive polarization branch; and obtaining a composite evaluation equation of the insulation moisture content of the oil paper by combining an optimal weighted combination method. The method can improve the accuracy and reliability of the assessment result of the insulating moisture content of the oilpaper.
Description
Technical Field
The invention relates to the technical field of oiled paper insulation moisture content assessment, in particular to an oiled paper insulation moisture content assessment method by using a transfer function and optimal weighting combination method.
Background
The method for estimating the moisture content of the oil paper insulation by FDS at present mainly comprises the steps of obtaining a frequency domain dielectric spectrum curve of an oil paper insulation sample, extracting characteristic quantity according to the curve, and establishing the correlation between the characteristic quantity and the moisture content for estimation.
In the past research on the insulation spectrum of the oil paper, the used extended Debye model cannot reflect the complicated interface polarization reaction of the oil paper insulation, and the used characteristic quantity cannot exclude the influence of the thickness and the cross section area of the insulation paper.
Disclosure of Invention
In view of the above, the present invention provides an oiled paper insulation moisture content evaluation method using a transfer function and an optimal weighting combination method, which can improve the accuracy and reliability of an oiled paper insulation moisture content evaluation result.
The invention is realized by adopting the following scheme: a method for evaluating the insulation moisture content of oiled paper by using a transfer function and optimal weighting combination method specifically comprises the following steps:
establishing a transfer function equation of an oil paper insulation series-parallel equivalent model;
deducing a polar expression of a polarization branch of a series-parallel model based on a transfer function equation of the system;
establishing a relational expression between the polar value and the moisture content of the sensitive polarization branch;
and obtaining a composite evaluation equation of the insulation moisture content of the oil paper by combining an optimal weighted combination method.
Further, the method also comprises the following steps:
and (4) checking the obtained composite evaluation equation according to the new test data and the actually measured data of the induction voltage regulator.
Further, the establishing of the transfer function equation of the oil paper insulation series-parallel equivalent model specifically comprises the following steps:
step S11: and (3) deducing an admittance equation Y (w) shown as the following formula through an oil-paper insulation hybrid equivalent model:
the oil paper insulation series-parallel equivalent model sequentially comprises a geometric equivalent circuit, an RC series polarization equivalent circuit and an interface polarization equivalent circuit; in the formula (1), R g Is the insulation resistance of the system in a geometric equivalent circuit, C g Representing the overall geometric capacitance, R, of the system in a geometric equivalent circuit pi And C pi Representing the equivalent polarization resistance and polarization capacitance in the polarization process of the media with different dielectric constants in the RC series polarization equivalent circuit, C hm Representing the equivalent polarization capacitance, R, of the media with different dielectric constants in the interface polarization equivalent circuit during the polarization process h(2m-1) 、R h(2m) Representing equivalent polarization resistance of media with different dielectric constants in the interface polarization equivalent circuit in the polarization process, wherein k is the number of polarization resistance or polarization capacitance in the RC series polarization equivalent circuit, and 2n is the number of polarization resistance or polarization capacitance in the interface polarization equivalent circuit;
step S12: deriving a system transfer function from equation (1), as in equation (2):
further, the derivation of the polar expression of the polarization branch of the series-parallel model based on the system transfer function equation specifically includes the following steps:
step S21: decomposing H representing geometric equivalent circuit and RC series polarization branch by transfer function 1 (s) and H representing the interface polarization arm 2 (s), the specific expression is shown as formula (3) and formula (4);
in the formula, N 1 (s) and N 2 (s) represents a polynomial containing s, P pi Representing the poles of the series-polarized branches, P hm Representing an interface polarization branch pole; r g Is the insulation resistance of the system in a geometric equivalent circuit, C g Representing the overall geometric capacitance, R, of the system in a geometric equivalent circuit pi And C pi Representing the equivalent polarization resistance and polarization capacitance in the polarization process of the media with different dielectric constants in the RC series polarization equivalent circuit, C hm Representing the equivalent polarization capacitance, R, of the media with different dielectric constants in the interface polarization equivalent circuit during the polarization process h(2m-1) 、R h(2m) Representing equivalent polarization resistance of media with different dielectric constants in the interface polarization equivalent circuit in the polarization process, wherein k is the number of polarization resistance or polarization capacitance in the RC series polarization equivalent circuit, and 2n is the number of polarization resistance or polarization capacitance in the interface polarization equivalent circuit;
step S22: deriving expressions of a series polarization branch pole and an interface polarization branch pole respectively according to the expressions (3) and (4), specifically expressed by the expressions (5) and (6):
further, the establishing of the relation between the polar value and the moisture content of the sensitive polarization branch specifically comprises the following steps:
step S31: testing the oiled paper insulation system by using a DIRANA dielectric response analyzer to obtain corresponding frequency domain dielectric spectrum data, wherein the frequency domain dielectric spectrum data comprises a dielectric loss factor tan delta, a real part C 'and an imaginary part C' of a complex capacitor; identifying the parameters of the parallel-series equivalent circuit model based on the data to obtain the pole of the polarization branch;
step S32: fitting the curve between the polarization branch pole and the moisture content obtained in the step S31, and screening out two sensitive polarization branch poles having a significant exponential function relation with the moisture content;
step S33: and reversely deducing a mathematical relation between the water content MC and the poles of the two sensitive polarization branches to obtain a single characteristic quantity evaluation equation.
Further, the method for obtaining the composite assessment equation of the insulation moisture content of the oil paper by combining the optimal weighted combination method specifically comprises the following steps:
step S41: combining the prediction deviation e of the submodel shown in the formula (8) with the combined prediction model Y shown in the formula (7) jt Obtaining a fitted deviation matrix E shown in equation (9):
in the formula, l is the number of single evaluation equation, w j For the weight corresponding to the jth single evaluation equation,
is the predicted value of the jth single evaluation equation;
where t is 1,2,. n is the number of samples, y is jt The true value of the t-th sample corresponding to the j-th single evaluation equation,
expressing the predicted value of the jth single evaluation equation of the tth sample;
step S42: converting the solved weight problem into a constraint equation shown as a formula (10), and substituting R ═ 1,1 T Converting formula (10) to formula (11):
in the formula, e t Representing the deviation of the true value and the predicted value of the t sample;
step S43: obtaining the optimal weight by using a Lagrange method for the formula (11), wherein a specific expression is shown as a formula (12), and a Q minimum value expression is shown as a formula (13):
step S44: combining data of two sensitive polarization branch poles with a single characteristic water content evaluation value, then obtaining a fitting deviation matrix E by using a formula (9), and finally obtaining an optimal weight value by using a formula (12);
step S45: and (4) obtaining a composite evaluation equation of the moisture content by combining the optimal weight value with the combined prediction model Y formula (7).
Further, the step of checking the obtained composite evaluation equation by the new test data and the actually measured induction voltage regulator data specifically comprises the following steps:
step S51: preparing four new groups of oiled paper insulation samples with different moisture contents, obtaining polar values of two sensitive polarization branches, and then substituting a single characteristic quantity evaluation equation and a composite evaluation equation to obtain the oiled paper insulation moisture contents under different evaluation equations;
step S52: three values of average absolute percentage error, root mean square error and correlation coefficient are introduced as evaluation indexes;
step S53: and (4) combining the insulation moisture content of the oiled paper under different evaluation equations obtained in the step S51 with each evaluation index in the step S52, and obtaining the composite evaluation equation through comparison, wherein the composite evaluation equation has higher accuracy.
Compared with the prior art, the invention has the following beneficial effects:
1. according to the invention, a series-parallel equivalent model is introduced on the basis of expanding a Debye model, so that the complex interface polarization reaction of the oil paper insulation can be better reflected, and the extracted characteristic quantity can more fully represent the insulation information carried by a branch circuit;
2. according to the invention, a new characteristic quantity irrelevant to the thickness and the cross sectional area of the oilpaper is extracted by combining the transfer function and the parallel equivalent model, so that the influence of the size of a test sample on a detection result can be eliminated, and the insulation information carried by a branch can be more fully reflected;
3. according to the method, the single characteristic quantity evaluation equation is subjected to weight combination by using an optimal weighting combination method, the obtained composite evaluation equation can linearly fuse branch insulation information carried by two single characteristic quantities, the error of the single characteristic quantity evaluation equation can be effectively avoided, and the evaluation precision of the composite evaluation equation is higher than that of the single characteristic quantity evaluation equation.
Drawings
Fig. 1 is a novel series-parallel equivalent circuit of the oiled paper insulation system according to the embodiment of the invention.
FIG. 2 is a graph of different moisture content paper insulation samples according to an embodiment of the present invention.
FIG. 3 is a graph showing the relationship between the pole of the sense branch and the moisture content according to an embodiment of the present invention.
Fig. 4 shows a test spectrum of the oil-immersed induction voltage regulator according to the embodiment of the present invention.
Detailed Description
The invention is further explained below with reference to the drawings and the embodiments.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The embodiment provides an oiled paper insulation moisture content assessment method by using a transfer function and optimal weighting combination method, which specifically comprises the following steps:
step S1: establishing a transfer function equation of an oil paper insulation series-parallel equivalent model;
step S2: deducing a polar expression of a polarization branch of a series-parallel model based on a transfer function equation of the system;
step S3: establishing a relational expression between the polar value and the moisture content of the sensitive polarization branch;
step S4: and obtaining a composite evaluation equation of the insulation moisture content of the oil paper by combining an optimal weighted combination method.
In this embodiment, the method further comprises the steps of:
step S5: and (4) checking the obtained composite evaluation equation according to the new test data and the actually measured data of the induction voltage regulator.
In this embodiment, the establishing of the transfer function equation of the oil paper insulation series-parallel equivalent model specifically includes the following steps:
step S11: an admittance equation Y (w) shown in the following formula is derived through an oil-paper insulation hybrid equivalent model:
the oil paper insulation series-parallel equivalent model sequentially comprises a geometric equivalent circuit, an RC series polarization equivalent circuit and an interface polarization equivalent circuit; in the formula (1), R g Is the insulation resistance of the system in a geometric equivalent circuit, C g Representing the overall geometric capacitance, R, of the system in a geometric equivalent circuit pi And C pi Representing the equivalent polarization resistance and polarization capacitance in the polarization process of the media with different dielectric constants in the RC series polarization equivalent circuit, C hm Representing the equivalent polarization capacitance, R, of the media with different dielectric constants in the interface polarization equivalent circuit during the polarization process h(2m-1) 、R h(2m) Representing different dielectric constants in an interface polarization equivalent circuitThe equivalent polarization resistance of a plurality of media in the polarization process, k is the number of polarization resistances or polarization capacitances in the RC series polarization equivalent circuit, and 2n is the number of polarization resistances or polarization capacitances in the interface polarization equivalent circuit;
step S12: deriving a system transfer function from equation (1), as in equation (2):
in this embodiment, the derivation of the polar expression of the polarization branch of the series-parallel model based on the system transfer function equation specifically includes the following steps:
step S21: decomposition of H representing a geometric equivalent circuit and an RC series polarization branch from a transfer function 1 (s) and H representing the interface polarization arm 2 (s), the specific expression is shown as formula (3) and formula (4);
in the formula, N 1 (s) and N 2 (s) represents a polynomial containing s, P pi Representing the poles of the series-polarized branches, P hm Representing an interface polarization branch pole; r is g Is the insulation resistance of the system in a geometric equivalent circuit, C g Representing the overall geometric capacitance, R, of the system in a geometric equivalent circuit pi And C pi Representing the equivalent polarization resistance and polarization capacitance in the polarization process of the media with different dielectric constants in the RC series polarization equivalent circuit, C hm Representing the equivalent polarization capacitance, R, of the media with different dielectric constants in the interface polarization equivalent circuit during the polarization process h(2m-1) 、R h(2m) Representing equivalent polarization resistance of media with different dielectric constants in the interface polarization equivalent circuit in the polarization process, wherein k is equivalent polarization resistance in the RC series polarization equivalent circuit2n is the number of the polarization resistors or polarization capacitors in the interface polarization equivalent circuit;
step S22: deriving expressions of a series polarization branch pole and an interface polarization branch pole respectively according to the expressions (3) and (4), specifically expressed by the expressions (5) and (6):
in this embodiment, the establishing of the relation between the polar value and the moisture content of the sensitive polarization branch specifically includes the following steps:
step S31: testing the oiled paper insulation system by using a DIRANA dielectric response analyzer to obtain corresponding frequency domain dielectric spectrum data, wherein the frequency domain dielectric spectrum data comprises a dielectric loss factor tan delta, a real part C 'and an imaginary part C' of a complex capacitor; identifying the parameters of the series-parallel equivalent circuit model based on the data through an intelligent optimization algorithm to obtain the pole of the polarization branch;
step S32: fitting the curve between the polarization branch pole and the moisture content obtained in the step S31, and screening out two sensitive polarization branch poles having a significant exponential function relation with the moisture content;
step S33: and reversely deducing a mathematical relation between the water content MC and the poles of the two sensitive polarization branches to obtain a single characteristic quantity evaluation equation.
In this embodiment, the obtaining of the composite estimation equation of the insulation moisture content of the oilpaper by combining the optimal weighted combination method specifically includes the following steps:
step S41: combining the prediction deviation e of the submodel shown in the formula (8) with the combined prediction model Y shown in the formula (7) jt Obtaining a fitted deviation matrix E shown in equation (9):
in the formula, l is the number of single evaluation equation, w j For the weight corresponding to the jth single evaluation equation,
is the predicted value of the jth single evaluation equation;
where t is 1,2,. n is the number of samples, y is jt The true value of the t-th sample corresponding to the j-th single evaluation equation,
expressing the predicted value of the jth single evaluation equation of the tth sample;
step S42: converting the solved weight problem into a constraint equation shown as a formula (10), and substituting R ═ 1,1 T Converting formula (10) to formula (11):
in the formula, e t Representing the deviation of the real value and the predicted value of the t sample;
step S43: obtaining the optimal weight by using a Lagrange method for the formula (11), wherein a specific expression is shown as a formula (12), and a Q minimum value expression is shown as a formula (13):
step S44: combining data of two sensitive polarization branch poles with a single characteristic water content evaluation value, then obtaining a fitting deviation matrix E by using a formula (9), and finally obtaining an optimal weight value by using a formula (12);
step S45: and (4) obtaining a composite evaluation equation of the moisture content by combining the optimal weight value with the combined prediction model Y formula (7).
In this embodiment, the step of checking the obtained composite evaluation equation by using the new test data and the actually measured data of the induction voltage regulator includes the following steps:
step S51: preparing four new groups of oiled paper insulation samples with different moisture contents, obtaining polar values of two sensitive polarization branches through steps S1, S2 and S3, and then substituting a single characteristic quantity evaluation equation and a composite evaluation equation to obtain the oiled paper insulation moisture contents under different evaluation equations;
step S52: three values of average absolute percentage error, root mean square error and correlation coefficient are introduced as evaluation indexes and are respectively shown as formulas (14) to (16):
in the above three indexes, n is the number of samples, y i 、
Are respectively as followsActual, estimated and mean values of the book;
step S53: and (4) combining the oiled paper insulation moisture contents under different evaluation equations obtained in the step S51 with each evaluation index in the step S52, and obtaining the composite evaluation equation through comparison, wherein the composite evaluation equation has higher accuracy.
Next, the present embodiment will be further described with reference to specific parameters.
According to step S1, the admittance equation shown in formula (1) is derived by using the oiled paper insulation hybrid model shown in fig. 1, and then the system transfer function is derived by using formula (1), wherein the specific expression is shown in formula (2).
According to step S2, H representing the geometric equivalent circuit and the RC series polarization branch is decomposed by equation (2) 1 (s) and H representing the interface polarization arm 2 (s), the specific expressions are shown as formulas (3) and (4), and the expressions of the series polarization branch pole and the interface polarization branch pole are respectively deduced according to the formulas (3) and (4), and are specifically shown as formulas (5) and (6);
according to step s3, in order to obtain the relation between the polar values and the moisture content of the two sensitive polarization branches, namely a single characteristic quantity evaluation equation, the evaluation is carried out in three steps:
1) testing the oiled paper insulation system by using a DIRANA dielectric response analyzer, and acquiring corresponding frequency domain dielectric spectrum data: the dielectric loss factor tan δ, the real part of the complex capacitance C' and the imaginary part C ". And identifying the parameters of the series-parallel equivalent circuit model through an intelligent optimization algorithm based on the data to obtain the pole P of the polarization branch pi 、P hm (ii) a The frequency domain dielectric spectrum is shown in fig. 2, where (a) in fig. 2 is dielectric loss factor data, (b) is complex capacitance real part C' data, and (C) is complex capacitance imaginary part C ″ data.
2) Fitting the curve between the polarization branch pole and the moisture content obtained in the step S31, and screening out two sensitive polarization branch poles having a significant exponential function relation with the moisture content; fitting image as shown in fig. 3, (a) and (b) in fig. 3 are schematic diagrams of fitting curves of two sensitive polarization branch poles, respectively.
3) And (3) reversely deducing a mathematical relation between the moisture content MC and the poles of the two sensitive polarization branches, namely a single characteristic quantity evaluation equation, wherein the specific expression is shown in formulas (17) and (18):
in the above formula, MC represents moisture content, P TC-Max Representing the large time constant sensitive polarization branch pole.
In the above formula, MC represents moisture content, P TC-Min Representing the small time constant sensitive polarization branch pole.
According to step S4, a fitting deviation matrix shown in formula (9) is obtained by combining the prediction deviation of the submodel shown in formula (8) with the combined prediction model shown in formula (7), the solved weight problem is converted into a constraint equation shown in formula (10), and the constraint equation is substituted into R ═ 1,1 T And (3) converting the formula (10) into a formula (11), and obtaining the optimal weight of the formula (11) by using a Lagrange method, wherein a specific expression is shown as a formula (12). The data in table 1 are substituted into the formula (17) and the formula (18) to obtain a moisture content evaluation value, then a fitting deviation matrix E is obtained by using the formula (9), as shown in the formula (19), then an optimal weight value expression is obtained by using the formula (12), as shown in the formula (20), and finally a composite evaluation equation of the moisture content is obtained by combining the optimal weight value with the formula (7), as shown in the formula (21).
TABLE 1 polar values of polarization branches of used oil paper insulation test articles
Table 1 Value of pole of branch of old oil-paper insulation test product
According to step S5, to verify that the composite evaluation equation is accurate and feasible, the verification will be performed in two steps:
1) preparing four new groups of oiled paper insulation samples with different moisture contents, screening out two sensitive polarization branch polar values according to the step S3, as shown in table 2, calculating the moisture contents corresponding to the single characteristic quantity evaluation equation and the composite evaluation equation through the formulas (17), (18) and (21), and comparing the results with the actually measured moisture contents to know that the composite evaluation equation has more accuracy, as shown in table 3.
TABLE 2 polar values of sensitive polarization branch of new oilpaper insulation sample
Table 2 Value of pole of branch of new oil-paper insulation test product
TABLE 3 evaluation values of different evaluation equations of new oil paper insulation test articles
Table 3 Estimation of different evaluation equations for new oil-paper insulation samples
Wherein, the evaluation value 1, the evaluation value 2 and the evaluation value 3 are respectively formed by MC ═ f (P) TC-Max )、MC＝f(P TC-Min ) And evaluating a composite evaluation equation.
2) Actually measuring an induction voltage regulator to obtain a frequency domain dielectric spectrum shown in fig. 4, combining data in fig. 4 (wherein (a) in fig. 4 is a dielectric loss factor, (b) is a complex capacitance real part, and (c) is a complex capacitance imaginary part) with step S3, obtaining a single characteristic quantity evaluation equation and a composite evaluation equation in step S4 and step S51, obtaining the moisture content, obtaining the real moisture content by using DIRANA own software, and comparing the moisture content values obtained by different evaluation equations with the real moisture content value to obtain the composite evaluation equation with feasibility as shown in table 4.
TABLE 4 comparison of the present methods with the results of the DIRANA software evaluation
Table 4 Comparison of the evaluation results between the method of this paperand DIRANA software
The foregoing is directed to preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.
Claims (5)
1. A method for evaluating the insulation moisture content of oiled paper by using a transfer function and weighting combination method is characterized by comprising the following steps of:
establishing a transfer function equation of an oil paper insulation series-parallel equivalent model;
deducing a polarization branch pole expression of the series-parallel equivalent model based on a transfer function equation of the system;
establishing a relational expression between the polar value and the moisture content of the sensitive polarization branch;
obtaining a composite evaluation equation of the insulation moisture content of the oil paper by combining an optimal weighted combination method;
the method for establishing the transfer function equation of the oil paper insulation series-parallel equivalent model specifically comprises the following steps:
step S11: and (3) deducing an admittance equation Y (w) shown as the following formula through an oil-paper insulation hybrid equivalent model:
the oil paper insulation series-parallel equivalent model sequentially comprises a geometric equivalent circuit, an RC series polarization equivalent circuit and an interface polarization equivalent circuit; in the formula (1), R g Is the insulation resistance of the system in a geometric equivalent circuit, C g Representing the overall geometric capacitance, R, of the system in a geometric equivalent circuit pi And C pi Representing the equivalent polarization resistance and polarization capacitance in the polarization process of the media with different dielectric constants in the RC series polarization equivalent circuit, C hm Representing the equivalent polarization capacitance, R, of the media with different dielectric constants in the interface polarization equivalent circuit during the polarization process h(2m-1) 、R h(2m) Representing equivalent polarization resistance of media with different dielectric constants in the interface polarization equivalent circuit in the polarization process, wherein k is the number of polarization resistance or polarization capacitance in the RC series polarization equivalent circuit, and 2m is the number of polarization resistance or polarization capacitance in the interface polarization equivalent circuit;
step S12: deriving a system transfer function from equation (1), as in equation (2):
the method for deducing the polar expression of the polarization branch of the series-parallel equivalent model based on the system transfer function equation specifically comprises the following steps:
step S21: decomposing H representing geometric equivalent circuit and RC series polarization branch by transfer function 1 (s) and H representing the interface polarization arm 2 (s), the specific expression is shown as formula (3) and formula (4);
in the formula, N 1 (s) and N 2 (s) represents a polynomial containing s, P pi Representing the poles of the series-polarized branches, P hm Representing an interface polarization branch pole; r g Is the insulation resistance of the system in a geometric equivalent circuit, C g Representing the overall geometric capacitance, R, of the system in a geometric equivalent circuit pi And C pi Representing the equivalent polarization resistance and polarization capacitance in the polarization process of the media with different dielectric constants in the RC series polarization equivalent circuit, C hm Representing the equivalent polarization capacitance, R, of the media with different dielectric constants in the interface polarization equivalent circuit during the polarization process h(2m-1) 、R h(2m) Representing equivalent polarization resistance of media with different dielectric constants in the interface polarization equivalent circuit in the polarization process, wherein k is the number of polarization resistance or polarization capacitance in the RC series polarization equivalent circuit, and 2m is the number of polarization resistance or polarization capacitance in the interface polarization equivalent circuit;
step S22: deriving expressions of a series polarization branch pole and an interface polarization branch pole respectively according to the expressions (3) and (4), specifically expressed by the expressions (5) and (6):
2. the method for estimating the moisture content of oiled paper insulation by using a combination of transfer function and weighting as claimed in claim 1, further comprising the steps of:
and (4) checking the obtained composite evaluation equation according to the new test data and the actually measured data of the induction voltage regulator.
3. The method for estimating the moisture content of the oiled paper insulation by using the transfer function and weighting combination method according to claim 1, wherein the step of establishing the relation between the polar value and the moisture content of the sensitive polarization branch specifically comprises the following steps:
step S31: testing the oiled paper insulation system by using a DIRANA dielectric response analyzer to obtain corresponding frequency domain dielectric spectrum data, wherein the frequency domain dielectric spectrum data comprises a dielectric loss factor tan delta, a real part C 'and an imaginary part C' of a complex capacitor; identifying the parameters of the parallel-series equivalent circuit model based on the data to obtain the pole of the polarization branch;
step S32: fitting the curve between the polarization branch pole and the moisture content obtained in the step S31, and screening out two sensitive polarization branch poles having a significant exponential function relation with the moisture content;
step S33: and reversely deducing a mathematical relation between the water content MC and the poles of the two sensitive polarization branches to obtain a single characteristic quantity evaluation equation.
4. The oiled paper insulation moisture content evaluation method by using a transfer function and weighting combination method according to claim 1, wherein the obtaining of the oiled paper insulation moisture content composite evaluation equation by combining the optimal weighting combination method specifically comprises the following steps:
step S41: combining the prediction deviation e of the submodel shown in the formula (8) with the combined prediction model Y shown in the formula (7) jt Obtaining a fitted deviation matrix E shown in equation (9):
in the formula, l is the number of single evaluation equation, w j For the weight corresponding to the jth single evaluation equation,
is the predicted value of the jth single evaluation equation;
where t is 1,2,. n is the number of samples, y is jt The true value of the t-th sample corresponding to the j-th single evaluation equation,
expressing the predicted value of the jth single evaluation equation of the tth sample;
step S42: converting the solved weight problem into a constraint equation shown as a formula (10), and substituting R ═ 1,1 T Converting formula (10) to formula (11):
in the formula, e i Representing the deviation of the real value and the predicted value of the ith sample;
step S43: obtaining the optimal weight by using a Lagrange method for the formula (11), wherein a specific expression is shown as a formula (12), and a Q minimum value expression is shown as a formula (13):
step S44: combining data of two sensitive polarization branch poles with a single characteristic water content evaluation value, then obtaining a fitting deviation matrix E by using a formula (9), and finally obtaining an optimal weight value by using a formula (12);
step S45: and (4) obtaining a composite evaluation equation of the moisture content by combining the optimal weight value with the combined prediction model Y formula (7).
5. The method for estimating the moisture content of the oiled paper insulation by using the transfer function and weighting combination method according to claim 2, wherein the step of testing the obtained composite estimation equation by using the new test data and the actually measured induction voltage regulator data specifically comprises the following steps:
step S51: preparing four new groups of oiled paper insulation samples with different moisture contents, obtaining polar values of two sensitive polarization branches, and then substituting a single characteristic quantity evaluation equation and a composite evaluation equation to obtain the oiled paper insulation moisture contents under different evaluation equations;
step S52: three values of average absolute percentage error, root mean square error and correlation coefficient are introduced as evaluation indexes;
step S53: and (4) combining the insulation moisture content of the oiled paper under different evaluation equations obtained in the step S51 with each evaluation index in the step S52, and obtaining a composite evaluation equation through comparison.
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