Method, device and system for evaluating water content of insulation paper in oil-immersed transformer

Abstract

The invention discloses a method, a device and a system for evaluating water content of insulation paper in an oil-immersed transformer, and belongs to the technical field of electrical equipment monitoring. The method comprises the following steps: on the basis of a frequency spectrum set of non-oil-immersed insulation paper with respect to water content, calculating frequency spectrums of oil-immersed insulation paper in a to-be-detected transformer under different water contents by adopting a formula # imgabs0 # to form a frequency spectrum set A, and further calculating to obtain frequency spectrums of main insulation of the to-be-detected transformer under different water contents to form a frequency spectrum set B; and taking the moisture content corresponding to the frequency spectrum with the minimum deviation with the main insulation frequency spectrum of the to-be-detected transformer in the frequency spectrum set B as a moisture content evaluation result of the insulation paper in the to-be-detected transformer. According to the method, the influence of the dielectric properties of different oil on the main insulation frequency spectrum of the transformer is fully considered, the influence of the dielectric properties of different oil on the water content evaluation result is effectively eliminated, and the water content evaluation precision of the insulation paper in the oil-immersed transformer is relatively high; the applicability and the reliability of water content evaluation of the frequency domain dielectric spectrum method under the field complex condition are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrical equipment monitoring, and more specifically, relates to a method, device and system for evaluating the moisture content of insulating paper in an oil-immersed transformer. Background Art

[0002] Oil-immersed transformers are core equipment in power systems, and their insulation condition is directly related to their safety and operational lifespan. Insulation paper, the primary component of transformer insulation, exhibits a strong correlation between performance degradation and moisture content: for every 1% increase in moisture content, the breakdown voltage decreases by approximately 15%-20%, and the aging rate increases by 2-3 times. Therefore, accurately assessing the moisture content of insulation paper in oil-immersed transformers is a key technical challenge in preventing transformer insulation failures.

[0003] Frequency-domain dielectric spectroscopy is a nondestructive measurement method widely used to assess the insulation condition of electrical equipment. Existing methods for assessing moisture content in transformer insulation paper are mostly based on spectral analysis of composite oil-impregnated insulation paper. This typically assumes that the dielectric properties of oil-impregnated paper are primarily determined by its moisture content. Based on a laboratory-established spectrum set of oil-impregnated paper at different moisture contents, the transformer's main insulation spectrum is calculated and compared with the measured spectrum to assess moisture content. However, insulating oils of different types, varying degrees of aging, and operating conditions exhibit distinct dielectric properties. This results in significant differences in the spectra of oil-impregnated paper, even for the same moisture content, depending on the impregnation oil. Furthermore, the variability and unpredictability of insulating oil's dielectric properties make it difficult to pre-establish a comprehensive and universal spectrum set for oil-impregnated paper through experimental means. Consequently, existing frequency-domain dielectric spectroscopy methods significantly reduce their accuracy when applied to transformers in the field with varying oil quality conditions, impacting the reliability of the insulation paper moisture content assessment results. Summary of the Invention

[0004] In response to the above defects or improvement needs of the prior art, the present invention provides a method, device and system for evaluating the moisture content of insulating paper in an oil-immersed transformer, which are used to solve the technical problem of low accuracy in the prior art in evaluating the moisture content of insulating paper in an oil-immersed transformer.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a method for evaluating the moisture content of insulating paper in an oil-immersed transformer, comprising:

[0006] Obtain the main insulation spectrum and insulating oil spectrum ε of the transformer to be tested * oil (ω); ω represents the angular frequency; the transformer to be tested is an oil-immersed transformer to be tested;

[0007] Using the formula Calculate the spectrum of the oil-immersed insulation paper in the transformer under test at different moisture contents to form a spectrum set A; where ε * OIP (ω,x) is the spectrum of the oil-immersed insulating paper in the transformer under test at a moisture content of x; ε * paper (ω, x) is the pre-obtained spectrum of the non-oil-impregnated insulation paper at a moisture content of x; θ is the series-parallel connection coefficient of the oil and paper in the oil-impregnated insulation paper; is the volume ratio of insulating oil in oil-impregnated insulating paper; ε * air is the complex relative permittivity of air;

[0008] Substitute spectrum set A and main insulation structural parameters X and Y of the transformer under test into the transformer main insulation XY equivalent model for calculation to obtain the spectrum of the main insulation of the transformer under test at different moisture contents, forming spectrum set B;

[0009] The moisture content corresponding to the spectrum in spectrum set B that has the smallest deviation from the main insulation spectrum of the transformer to be tested is used as the moisture content evaluation result of the insulation paper in the transformer to be tested.

[0010] Further preferably, the insulating oil spectrum ε * oil The expression of (ω) is:

[0011]

[0012] Where j is the imaginary number symbol; σ oil is the oil conductivity of the transformer to be tested; ε0 is the vacuum dielectric constant.

[0013] Further preferably, the spectrum of the main insulation of the transformer to be tested at a moisture content x is:

[0014]

[0015] Further preferably, the calculation formulas for the main insulation structure parameters X and Y of the transformer to be tested are respectively:

[0016]

[0017] Where m is the total number of layers of oil-immersed insulation paper in the transformer to be tested; d OIP,i is the thickness of the i-th layer of oil-immersed insulating paper in the transformer to be tested; D total is the total main insulation spacing of the transformer under test; n is the total number of braces in each layer of the transformer under test; w spacer,k is the width of the kth strut in the transformer to be tested; φ HV and φ LV They are the inner diameter of the high-voltage winding and the outer diameter of the low-voltage winding of the transformer to be tested.

[0018] Further preferably, the spectrum deviation between the main insulation spectrum of the transformer to be tested and the spectrum F at any moisture content x in the spectrum set B is:

[0019]

[0020] Where L is the total number of samples of the spectrum angular frequency in each spectrum; ω l is the lth sampling value of angular frequency ω; ε' main_mea (ω l ) and ε” main_mea (ω l ) are the real and imaginary parts of the main insulation spectrum of the transformer to be tested in ω l Dielectric response value under ε' main_cal (ω l ,x) and ε” main_cal (ω l ,x) are the real and imaginary parts of the spectrum F at ω l The dielectric response value under .

[0021] Further preferably, the moisture content ranges from 0.5% to 5.0%; the moisture content involved in spectrum set B covers the entire range of 0.5% to 5.0%.

[0022] In a second aspect, the present invention provides a device for evaluating the moisture content of insulating paper in an oil-immersed transformer, comprising:

[0023] Spectrum acquisition module, used to obtain the main insulation spectrum and insulating oil spectrum ε of the transformer under test * oil (ω); ω represents the angular frequency; the transformer to be tested is an oil-immersed transformer to be tested;

[0024] The first spectrum set acquisition module is used to use the formula Calculate the spectrum of the oil-immersed insulation paper in the transformer under test at different moisture contents to form a spectrum set A; where ε * OIP (ω,x) is the spectrum of the oil-immersed insulating paper in the transformer under test at a moisture content of x; ε * paper (ω, x) is the pre-obtained spectrum of the non-oil-impregnated insulation paper at a moisture content of x; θ is the series-parallel connection coefficient of the oil and paper in the oil-impregnated insulation paper; is the volume ratio of insulating oil in oil-impregnated insulating paper; ε * air is the complex relative permittivity of air;

[0025] The second spectrum set acquisition module is used to substitute spectrum set A and main insulation structural parameters X and Y of the transformer under test into the transformer main insulation XY equivalent model to perform calculations to obtain the spectrum of the main insulation of the transformer under test at different moisture contents to form spectrum set B;

[0026] The evaluation module is used to use the moisture content corresponding to the spectrum in spectrum set B that has the smallest deviation from the main insulation spectrum of the transformer to be tested as the moisture content evaluation result of the insulation paper in the transformer to be tested.

[0027] In a third aspect, the present invention provides a system for evaluating the moisture content of insulating paper in an oil-immersed transformer, comprising: a memory and a processor, wherein the memory stores a computer program, and the processor executes the method provided in the first aspect of the present invention when executing the computer program.

[0028] In a fourth aspect, the present invention further provides a computer-readable storage medium, which includes a stored computer program, wherein when the computer program is executed by a processor, the device where the storage medium is located is controlled to execute the method provided in the first aspect of the present invention.

[0029] In a fifth aspect, the invention further provides a computer program product, comprising a computer program / instruction, which implements the method provided in the first aspect of the invention when executed by a processor.

[0030] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0031] 1. The present invention provides a method for evaluating the moisture content of insulating paper in oil-immersed transformers, based on the spectrum set of moisture content of non-oil-immersed insulating paper, using the formula The spectra of the oil-impregnated insulating paper in the transformer under test at different moisture contents are calculated to form a spectrum set A. The spectra of the main insulation of the transformer under test at different moisture contents are then calculated to form a spectrum set B. The moisture content corresponding to the spectrum in spectrum set B that has the smallest deviation from the spectrum of the main insulation of the transformer under test is used as the moisture content assessment result of the insulating paper in the transformer under test. The present invention establishes a spectrum conversion relationship from un-oiled insulating paper to oil-impregnated insulating paper, fully considering the impact of the dielectric properties of different oil qualities on the spectrum of the transformer's main insulation, effectively eliminating the impact of different oil dielectric properties on the moisture content assessment result. The moisture content assessment accuracy of the insulating paper in the oil-impregnated transformer is high, and the applicability and reliability of the frequency domain dielectric spectroscopy method for moisture content assessment under complex on-site conditions are improved.

[0032] 2. Furthermore, the method for evaluating the moisture content of insulating paper provided by the present invention is based on the formula To obtain the insulating oil spectrum, transformer insulating oil, a weakly polar dielectric, has a constant real part of its spectrum of 2.2, while the imaginary part is determined by DC conductivity. At high frequencies, insulating oil has extremely low dielectric loss. Using the above formula effectively avoids measurement errors caused by insufficient equipment accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A flow chart for evaluating the moisture content of insulating paper in an oil-immersed transformer provided in an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of the frequency spectrum of non-oil-impregnated insulating paper with different moisture contents provided by an embodiment of the present invention;

[0035] Figure 3 The embodiment of the present invention provides Figure 2 The spectrum set of non-oil-impregnated insulation paper with respect to moisture content obtained through interpolation;

[0036] Figure 4 A schematic structural diagram of a transformer main insulation scale model and a corresponding physical diagram provided in an embodiment of the present invention;

[0037] Figure 5 A schematic diagram of the frequency spectrum of the main insulation of the transformer to be tested under different moisture contents x provided by an embodiment of the present invention;

[0038] Figure 6 A spectrum deviation distribution diagram between the 46 main insulation spectra in spectrum set B provided in an embodiment of the present invention and the main insulation spectrum of the transformer to be tested;

[0039] Figure 7 This is a comparison diagram of the main insulation spectrum of the transformer to be tested and the spectrum with the smallest deviation from the main insulation spectrum of the transformer to be tested in spectrum set B provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0041] To achieve the above objectives, in a first aspect, the present invention provides a method for evaluating the moisture content of insulating paper in an oil-immersed transformer, comprising:

[0042] Obtain the main insulation spectrum and insulating oil spectrum ε of the transformer to be tested * oil(ω); ω represents the angular frequency; the transformer to be tested is an oil-immersed transformer to be tested;

[0043] Using the formula Calculate the spectrum of the oil-immersed insulation paper in the transformer under test at different moisture contents to form a spectrum set A; where ε * OIP (ω,x) is the spectrum of the oil-immersed insulating paper in the transformer under test at a moisture content of x; ε * paper (ω, x) is the pre-obtained spectrum of the non-oil-impregnated insulation paper at a moisture content of x; θ is the series-parallel connection coefficient of the oil and paper in the oil-impregnated insulation paper; is the volume ratio of insulating oil in oil-impregnated insulating paper; ε * air is the complex relative permittivity of air, specifically, ε * air = 1. θ and It is related to the specific material. For oil-immersed transformer paper, θ is generally taken as 0.69. The general value is 0.28.

[0044] Substitute spectrum set A and main insulation structural parameters X and Y of the transformer under test into the transformer main insulation XY equivalent model for calculation to obtain the spectrum of the main insulation of the transformer under test at different moisture contents, forming spectrum set B;

[0045] The moisture content corresponding to the spectrum in spectrum set B that has the smallest deviation from the main insulation spectrum of the transformer to be tested is used as the moisture content evaluation result of the insulation paper in the transformer to be tested.

[0046] It should be noted that oil-impregnated insulation paper is a composite insulation formed by insulating oil filling the pores of the insulation paper, which can be regarded as a two-phase composite insulation of dense cellulose and oil gaps. According to the two-phase inhomogeneous dielectric theory, the complex relative dielectric constant of oil-impregnated insulation paper can be expressed as:

[0047]

[0048] Where, ε * OIP , ε * oil and ε * cellulose are the complex relative permittivities of oil-impregnated insulating paper, insulating oil, and dense cellulose, respectively; is the volume ratio of insulating oil in oil-immersed insulating paper, θ is the geometric microtopological coefficient of oil-immersed insulating paper, representing the series-parallel connection coefficient of oil and paper.

[0049] Similarly, non-oil-impregnated insulation paper can be regarded as a two-phase composite insulation of dense cellulose and air pores, and its complex relative dielectric constant can be expressed as:

[0050]

[0051] Where, ε * paper and ε * air are the complex relative permittivities of non-oil-impregnated insulating paper and air, respectively;

[0052] Furthermore, by combining the above two equations at different frequencies, the frequency spectrum of oil-impregnated insulating paper can be obtained as follows:

[0053]

[0054] This formula establishes the spectrum conversion relationship from non-oil-impregnated insulation paper to oil-impregnated insulation paper, and realizes the quantitative calculation of the influence of impregnation oil.

[0055] It should be noted that the main insulation spectrum of the transformer to be tested may be a main insulation spectrum measured in real time using a dielectric impedance spectrometer, or may be a main insulation spectrum measured in advance, which is not limited here.

[0056] Get the insulating oil spectrum ε * oil There are many ways to calculate (ω). For example, in one optional embodiment, it can be measured using a dielectric impedance spectrometer. In another optional embodiment, it can also be calculated. Specifically, in the second optional embodiment, the insulating oil spectrum ε * oil The expression of (ω) is:

[0057]

[0058] Where j is the imaginary number symbol; σ oil is the oil conductivity of the transformer to be tested; ε0 is the vacuum dielectric constant, which is 8.854×10 -12 F / m.

[0059] It should be noted that the XY equivalent model of the transformer main insulation is:

[0060]

[0061] In an optional implementation manner, the calculation formulas for the main insulation structure parameters X and Y of the transformer to be tested are respectively:

[0062]

[0063] Where m is the total number of layers of oil-immersed insulation paper in the transformer to be tested; d OIP,i is the thickness of the i-th layer of oil-immersed insulating paper in the transformer to be tested; D totalis the total main insulation spacing of the transformer under test; n is the total number of braces in each layer of the transformer under test; w spacer,k is the width of the kth strut in the transformer to be tested; φ HV and φ LV They are the inner diameter of the high-voltage winding and the outer diameter of the low-voltage winding of the transformer to be tested.

[0064] In an optional implementation manner, the spectrum deviation between the main insulation spectrum of the transformer to be tested and the spectrum F at any moisture content x in the spectrum set B is:

[0065]

[0066] Where L is the total number of samples of the spectrum angular frequency in each spectrum; ω l is the lth sampling value of the angular frequency ω (i.e. ω=ω l );ε' main_mea (ω l ) and ε” main_mea (ω l ) are the real and imaginary parts of the main insulation spectrum of the transformer to be tested in ω l Dielectric response value under ε' main_cal (ω l ,x) and ε” main_cal (ω l ,x) are the real and imaginary parts of the spectrum F at ω l The dielectric response value under .

[0067] It should be noted that there are many ways to measure the spectral deviation between spectra, which are not limited here. The above is only one of them. Euclidean distance, cosine similarity and other methods can also be used for measurement.

[0068] It should be noted that the value of moisture content (i.e., mass-to-weight ratio moisture content) x can be determined by the user and is generally an empirical value, determined based on the possible moisture content values ​​of the insulating paper in the oil-immersed transformer. Preferably, in one optional embodiment, the value range of moisture content x is 0.5% to 5.0%, which is also the general range of moisture content values ​​for the insulating paper in oil-immersed transformers. The moisture content involved in spectrum set B covers the full range of 0.5% to 5.0%. In this example, a step size of 0.1% is used to obtain a total of 46 different moisture content values.

[0069] It should be noted that the spectrum ε of non-oil-impregnated insulation paper at moisture content x * paper(ω, x) is obtained in advance and also involves a variety of different moisture contents, which are the same as the moisture content values ​​involved in spectrum set B. The spectra of non-oil-impregnated insulation paper at different moisture contents constitute an non-oil-impregnated insulation paper spectrum set. This spectrum set can be an existing spectrum set or pre-collected before obtaining spectrum set A. In an optional implementation manner, the spectra of non-oil-impregnated insulation paper at different moisture contents can be obtained by the following method:

[0070] Unimpregnated insulation paper used in oil-immersed transformers is selected as the measurement object; the unimpregnated insulation paper is placed in M ​​different humidity environments to absorb moisture. After reaching moisture equilibrium, M types of unimpregnated insulation paper with different moisture contents are obtained. The frequency spectra of the M types of unimpregnated insulation paper with different moisture contents are measured using a dielectric impedance spectrometer. At each angular frequency (i.e., frequency point) of the obtained spectrum, the moisture content is interpolated to obtain frequency spectra of N types of unimpregnated insulation paper with different moisture contents, where N>M. Preferably, the moisture content ranges from 0.5% to 5.0%, with a step size of 0.1%, resulting in 46 different moisture content values, i.e., N is 46.

[0071] In summary, this method comprehensively considers the dielectric properties of both insulating paper and insulating oil, avoiding the limitations of traditional methods that ignore the influence of oil quality, significantly improving the accuracy and versatility of moisture content assessment. Furthermore, based on frequency-domain dielectric spectroscopy measurements, this method eliminates the need for transformer disassembly or destructive testing, enabling non-destructive testing of the moisture content of insulating paper in transformers.

[0072] In order to further illustrate the method for evaluating the moisture content of insulating paper in an oil-immersed transformer provided by the present invention, a specific embodiment is described in detail below:

[0073] like Figure 1 As shown, in this embodiment, the method for evaluating the moisture content of insulating paper in an oil-immersed transformer includes the following parts:

[0074] Part 1:

[0075] Construct a spectrum set of non-oil-impregnated insulation paper, including: spectrum of non-oil-impregnated insulation paper at different moisture contents;

[0076] In this embodiment, a non-oiled cellulose-based insulating cardboard with a thickness of 1 mm was selected as the test object to ensure that the surface of the sample was clean and free of pollution. The insulating cardboard sample was placed in a constant temperature and humidity chamber at a temperature of 45°C, and different humidity environments were set to allow the sample to reach moisture balance under constant temperature and humidity conditions. By controlling the ambient humidity, the water content of the sample was adjusted to cover a range of 0.5% to 5%. A dielectric impedance spectrometer was used to measure the spectrum (frequency domain dielectric spectrum) of the sample. The test voltage was 5V. peakThe measurement frequency range is 1mHz-5kHz, covering 6 orders of magnitude frequency bands to fully reflect the dielectric properties of the insulating paper. When measuring, it is necessary to ensure that the ambient temperature and humidity are constant to avoid the influence of temperature and humidity fluctuations on the measurement results. The measurement results are as follows: Figure 2 As shown in the figure, the spectrum of non-oil-impregnated insulation paper with different moisture contents at 45°C (i.e., the frequency domain dielectric spectrum data of complex relative permittivity) is shown, including the real part (such as Figure 2 ) and the imaginary part (as shown in the figure below) Figure 2 (as shown in the figure above).

[0077] In order to ensure the accuracy of subsequent moisture assessment, the measurement results need to be further processed to generate a high-resolution spectrum set. Since the moisture content interval in laboratory measurements is large and difficult to use for accurate moisture assessment, the cubic spline interpolation method is used to generate the spectrum of unimpregnated insulation paper with a moisture content of 0.5% to 5.0% and an interval of 0.1%, which is denoted as ε * paper (ω,x), used for subsequent water content evaluation; specifically, Figure 3 Shown is the Figure 2 The spectrum set of moisture content of non-oil-impregnated insulating paper obtained by interpolation; the spectrum in the figure shows data with a moisture content of 0.5% to 5.0% from left to right, and the moisture interval of each spectrum is 0.1%. The left figure is the real part of the spectrum, and the right figure is the imaginary part of the spectrum.

[0078] Part II:

[0079] Obtain the structural parameters X and Y of the main insulation of the transformer to be tested (the transformer to be tested in this embodiment is an oil-immersed transformer): This embodiment uses a transformer main insulation scale model built in the laboratory as the research object to simulate the main insulation structure of the actual transformer, such as Figure 4 shown; among them, Figure 4 The left picture is a structural diagram of the transformer main insulation scale model, and the right picture is the corresponding actual picture; the moisture content of its internal insulation paper was measured by Karl Fischer titrator and was 2.2%, which was used to verify the accuracy of the subsequent evaluation results.

[0080] The transformer's main insulation structural parameters, X and Y, refer to the structural parameters of the oil-impregnated paper between the transformer's high- and low-voltage windings. Parameter X is the ratio of the total thickness of the oil-impregnated paper layers within the transformer to the total spacing between the main insulation layers. Parameter Y is the ratio of the total width of the braces within the transformer to the average circumference of the high- and low-voltage windings. Specifically, for two-winding transformers, the main insulation is the oil-impregnated paper between the high- and low-voltage windings. For three-winding transformers, the main insulation is the oil-impregnated paper between the high- and high-voltage windings, or between the medium- and low-voltage windings.

[0081] according to and The structural parameters of the main insulation of the transformer to be tested are calculated to be X=0.325 and Y=0.199.

[0082] Part III:

[0083] Measure the oil conductivity and main insulation spectrum of the transformer under test;

[0084] The transformer main insulation scale model is sealed and the whole device is placed in a constant temperature box at 45℃ for 48 hours. After the temperature and moisture are fully balanced, the main insulation spectrum ε of the transformer to be tested is measured. * main_mea (ω). Then take an oil sample from the main insulation model and measure the oil conductivity σ oil It is 0.66pS / m, and the test temperature is consistent with the main insulation dielectric measurement, both of which are 45°C.

[0085] Part 4:

[0086] Calculate the spectrum ε of the main insulation of the transformer under test at different moisture contents x * main_cal (ω,x):

[0087] According to the transformer oil conductivity σ obtained in the third part oil , calculate the insulating oil spectrum ε of the transformer to be tested * oil (ω) (i.e., the frequency domain dielectric spectrum of the complex relative permittivity), the specific expression is:

[0088] The spectrum of the insulating oil and the spectrum of the non-oiled insulating paper are then combined using the formula Calculate the spectrum ε of the oil-immersed insulation paper in the transformer under test at different moisture contents x * OIP (ω,x), constitute the spectrum set A;

[0089] Then, according to the main insulation structure parameters X and Y, the transformer main insulation XY equivalent model is used Calculate the spectrum ε of the main insulation of the transformer under test at different moisture contents * main_cal (ω, x), constitutes spectrum set B; spectrum set B contains 46 spectra, namely the spectra of the main insulation of the transformer under test at 46 different moisture contents, such as Figure 5 As shown, the left figure is the real part of the spectrum, and the right figure is the imaginary part of the spectrum. The spectrum in the figure is data with a moisture content of 0.5% to 5.0% from left to right, and the moisture interval of each spectrum is 0.1%.

[0090] Part 5:

[0091] The main insulation spectrum of the transformer under test obtained in the third part is compared with the spectrum in spectrum set B obtained in the fourth part to obtain the moisture content of the insulation paper in the transformer under test.

[0092] According to the following formula, calculate the 46 main insulation spectra in spectrum set B and the main insulation spectrum ε of the transformer to be tested: * main_mea The distribution diagram of the spectrum deviation λ between (ω) is as follows: Figure 6 shown.

[0093]

[0094] Where L is the total number of samples of the spectrum angular frequency in each spectrum; ω l is the lth sampling value of angular frequency ω; ε' main_mea (ω l ) and ε” main_mea (ω l ) are the real and imaginary parts of the main insulation spectrum of the transformer to be tested in ω l Dielectric response value under ε' main_cal (ω l ,x) and ε” main_cal (ω l ,x) are the real and imaginary parts of the spectrum F at ω l The dielectric response value under .

[0095] The minimum value in the spectrum deviation λ distribution diagram is selected as the group that best matches the actual situation. The corresponding moisture content is the moisture content of the insulation paper in the transformer to be tested. The evaluation result is 2.1%, which is basically consistent with the measured moisture content of 2.2%, verifying the effectiveness of the method proposed in the present invention. Figure 7 As shown, Figure 7 The comparison diagram of the spectrum corresponding to 2.1% water content in spectrum set B and the main insulation spectrum of the transformer under test is shown (the left figure is the real part of the spectrum, and the right figure is the imaginary part of the spectrum).

[0096] In summary, the present invention is based on the spectrum set of moisture content of un-oiled insulating paper, further fully considers the influence of the dielectric properties of different oil qualities on the spectrum of the transformer main insulation, effectively eliminates the influence of different oil dielectric properties on the moisture content assessment results, and improves the applicability of the frequency domain dielectric spectroscopy method for moisture content assessment under complex on-site conditions.

[0097] In a second aspect, the present invention provides a device for evaluating the moisture content of insulating paper in an oil-immersed transformer, comprising:

[0098] Spectrum acquisition module, used to obtain the main insulation spectrum and insulating oil spectrum ε of the transformer under test * oil(ω); ω represents the angular frequency; the transformer to be tested is an oil-immersed transformer to be tested;

[0099] The first spectrum set acquisition module is used to use the formula Calculate the spectrum of the oil-immersed insulation paper in the transformer under test at different moisture contents to form a spectrum set A; where ε * OIP (ω,x) is the spectrum of the oil-immersed insulating paper in the transformer under test at a moisture content of x; ε * paper (ω, x) is the pre-obtained spectrum of the non-oil-impregnated insulation paper at a moisture content of x; θ is the series-parallel connection coefficient of the oil and paper in the oil-impregnated insulation paper; is the volume ratio of insulating oil in oil-impregnated insulating paper; ε * air is the complex relative permittivity of air;

[0100] The second spectrum set acquisition module is used to substitute spectrum set A and main insulation structural parameters X and Y of the transformer under test into the transformer main insulation XY equivalent model to perform calculations to obtain the spectrum of the main insulation of the transformer under test at different moisture contents to form spectrum set B;

[0101] The evaluation module is used to use the moisture content corresponding to the spectrum in spectrum set B that has the smallest deviation from the main insulation spectrum of the transformer to be tested as the moisture content evaluation result of the insulation paper in the transformer to be tested.

[0102] The related technical solution is the same as the insulation paper moisture content evaluation method provided in the first aspect of the present invention, and will not be described in detail here.

[0103] In a third aspect, the present invention provides a system for evaluating the moisture content of insulating paper in an oil-immersed transformer, comprising: a memory and a processor, wherein the memory stores a computer program, and the processor executes the method provided in the first aspect of the present invention when executing the computer program.

[0104] The related technical solution is the same as the insulation paper moisture content evaluation method provided in the first aspect of the present invention, and will not be described in detail here.

[0105] In a fourth aspect, the present invention further provides a computer-readable storage medium, which includes a stored computer program, wherein when the computer program is executed by a processor, the device where the storage medium is located is controlled to execute the method provided in the first aspect of the present invention.

[0106] The related technical solution is the same as the insulation paper moisture content evaluation method provided in the first aspect of the present invention, and will not be described in detail here.

[0107] In a fifth aspect, the invention further provides a computer program product, comprising a computer program / instruction, which implements the method provided in the first aspect of the invention when executed by a processor.

[0108] The related technical solution is the same as the insulation paper moisture content evaluation method provided in the first aspect of the present invention, and will not be described in detail here.

[0109] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for evaluating the moisture content of insulating paper in an oil-immersed transformer, characterized in that: include: Obtain the main insulation spectrum and insulating oil spectrum ε of the transformer to be tested * oil (ω); ω represents the angular frequency; The transformer to be tested is an oil-immersed transformer to be tested; Using the formula Calculate the spectrum of the oil-immersed insulating paper in the transformer under test at different moisture contents to form a spectrum set A; where ε * OIP (ω,x) is the spectrum of the oil-immersed insulating paper in the transformer under test at a moisture content of x; ε * paper (ω, x) is the pre-obtained spectrum of the non-oil-impregnated insulation paper at a moisture content of x; θ is the series-parallel connection coefficient of the oil and paper in the oil-impregnated insulation paper; is the volume ratio of insulating oil in oil-impregnated insulating paper; ε * air is the complex relative permittivity of air; Substituting the spectrum set A and the main insulation structural parameters X and Y of the transformer to be tested into the transformer main insulation XY equivalent model for calculation, the spectrum of the main insulation of the transformer to be tested at different moisture contents is obtained to form a spectrum set B; The moisture content corresponding to the spectrum in the spectrum set B that has the smallest deviation from the main insulation spectrum of the transformer to be tested is used as the moisture content evaluation result of the insulation paper in the transformer to be tested.

2. The method for evaluating moisture content of insulating paper according to claim 1, wherein: The insulating oil spectrum ε * oil The expression of (ω) is: Where j is the imaginary number symbol; σ oil is the oil conductivity of the transformer to be tested; ε0 is the vacuum dielectric constant.

3. The method for evaluating moisture content of insulating paper according to claim 1, wherein: The spectrum of the main insulation of the transformer under test at a moisture content x is:

4. The method for evaluating moisture content of insulating paper according to claim 3, wherein: The calculation formulas for the main insulation structure parameters X and Y of the transformer to be tested are: Wherein, m is the total number of layers of oil-immersed insulating paper in the transformer to be tested; d OIP,i is the thickness of the i-th layer of oil-immersed insulating paper in the transformer to be tested; D total is the total main insulation spacing of the transformer under test; n is the total number of braces in each layer of the transformer under test; w spacer,k is the width of the kth strut in the transformer under test; φ HV and φ LV are respectively the inner diameter of the high-voltage winding and the outer diameter of the low-voltage winding of the transformer to be tested.

5. The method for evaluating moisture content of insulating paper according to claim 1, wherein: The spectrum deviation between the main insulation spectrum of the transformer to be tested and the spectrum F at any moisture content x in the spectrum set B is: Where L is the total number of samples of the spectrum angular frequency in each spectrum; ω l is the lth sampling value of angular frequency ω; ε' main_mea (ω l ) and ε” main_mea (ω l ) are the real and imaginary parts of the main insulation spectrum of the transformer to be tested in ω l Dielectric response value under ε' main_cal (ω l ,x) and ε” main_cal (ω l ,x) are the real and imaginary parts of the spectrum F at ω l The dielectric response value under .

6. The method for evaluating moisture content of insulating paper according to any one of claims 1 to 5, characterized in that: The moisture content ranges from 0.5% to 5.0%; The moisture content involved in the spectrum set B covers the entire range of 0.5% to 5.0%.

7. A device for evaluating the moisture content of insulating paper in an oil-immersed transformer, characterized in that: include: Spectrum acquisition module, used to obtain the main insulation spectrum and insulating oil spectrum ε of the transformer under test * oil (ω); ω represents the angular frequency; the transformer to be tested is an oil-immersed transformer to be tested; The first spectrum set acquisition module is used to use the formula Calculate the spectrum of the oil-immersed insulating paper in the transformer under test at different moisture contents to form a spectrum set A; where ε * OIP (ω,x) is the spectrum of the oil-immersed insulating paper in the transformer under test at a moisture content of x; ε * paper (ω, x) is the pre-obtained spectrum of the non-oil-impregnated insulation paper at a moisture content of x; θ is the series-parallel connection coefficient of the oil and paper in the oil-impregnated insulation paper; is the volume ratio of insulating oil in oil-impregnated insulating paper; ε * air is the complex relative permittivity of air; A second spectrum set acquisition module is configured to substitute the spectrum set A and the main insulation structural parameters X and Y of the transformer to be tested into the transformer main insulation XY equivalent model to perform calculations to obtain the spectrum of the main insulation of the transformer to be tested at different moisture contents to form a spectrum set B; An evaluation module is configured to use the moisture content corresponding to the spectrum in the spectrum set B that has the smallest deviation from the main insulation spectrum of the transformer to be tested as an evaluation result of the moisture content of the insulation paper in the transformer to be tested.

8. A system for evaluating the moisture content of insulating paper in an oil-immersed transformer, characterized in that: include: A memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the method for evaluating the moisture content of insulating paper according to any one of claims 1 to 6 is executed.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium includes a stored computer program, wherein when the computer program is executed by a processor, the device where the storage medium is located is controlled to execute the insulation paper moisture content evaluation method according to any one of claims 1 to 6.

10. A computer program product, characterized in that The method comprises a computer program / instruction, which, when executed by a processor, implements the method for evaluating moisture content of insulating paper according to any one of claims 1 to 6.

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