Oil paper insulation damp state evaluation method and device based on special-shaped split ring structure

Abstract

The invention discloses an oil paper insulation damp state evaluation method and device based on a special-shaped split ring structure, and relates to the field of electrical equipment insulation state monitoring, and the method comprises the steps: building an equivalent circuit of a petal-shaped complementary split ring, and calculating the relative dielectric constant, resonant frequency and effective dielectric constant of a resonator; the coupling effect is enhanced through the coupling gaps between the split rings, and the detection sensitivity is improved; establishing a relation function between the effective dielectric constant and the resonant frequency to obtain a dielectric response curve; according to the dielectric response curve, establishing an oil paper insulation damping evaluation model containing a linear relation so as to evaluate the oil paper insulation damping state of the to-be-tested equipment, and outputting an evaluation result; the problems of low detection efficiency and poor effect caused by difficulty in effectively coping with complex equipment detection requirements due to limitation of an existing oil paper insulation detection method are solved, and the oil paper insulation damp detection efficiency and accuracy are remarkably improved.

Description

Technical Field

[0001] The invention relates to the field of insulation status monitoring of power equipment, and in particular to a method and a device for evaluating the moisture status of oil-paper insulation based on a special-shaped split ring structure. Background Art

[0002] In the power system, oil-immersed power transformers are key equipment in the power transmission and distribution network, and undertake important tasks such as voltage conversion and energy transmission. The main component of its internal insulation is oil-paper insulation. Under the influence of multi-physical field coupling, it is prone to moisture absorption and dampness, which leads to a decrease in the dielectric properties of the insulation system, increases the risk of partial discharge, and accelerates the degradation of oil-paper insulation, thus affecting the normal operation of the transformer. Once a transformer fails, it will affect the reliability of power supply, cause large-scale power outages, and cause huge economic losses. Therefore, it is particularly important to diagnose the insulation moisture of the oil-paper insulation system of oil-immersed power equipment.

[0003] At present, the commonly used methods for detecting moisture in oil-paper insulation are mainly non-destructive testing methods based on dielectric response characteristics, which are divided into time domain dielectric response technology and frequency domain dielectric response technology. Compared with the traditional time domain dielectric response technology, the frequency domain dielectric response technology (1mHz~5kHz) has the advantages of rich test information, but it can only reflect the overall moisture content and the test takes a long time. At the same time, due to the large size of the test equipment and the complex wiring, the frequency domain dielectric response method is limited in detection and cannot be effectively tested. Although the microstrip resonance dielectric response technology can realize the accurate measurement of the moisture content of the local insulation of the transformer, reduce the complexity of the wiring, and realize the rapid detection of the status of the oil-paper insulation power equipment while ensuring the effectiveness of the detection. However, due to the uncertainty of the transmission characteristics of the resonator and the high-frequency dielectric response characteristics of the damp oil-paper insulation, the test accuracy and evaluation reliability need further study. Summary of the invention

[0004] The present invention aims at the problem that the existing oil-paper insulation detection method has limitations and is difficult to effectively respond to complex equipment detection requirements, resulting in low detection efficiency and poor effect; a method and device for evaluating the moisture state of oil-paper insulation based on a special-shaped split ring structure are proposed, wherein the special-shaped split ring structure includes a ring resonator composed of a petal-shaped complementary split ring composed of at least two concentric petal-shaped rosettes, and the relative dielectric constant, resonant frequency and equivalent dielectric constant of the resonator are calculated by establishing an equivalent circuit of the petal-shaped complementary split ring; the coupling gap between the anisotropic split rings enhances the coupling effect, thereby changing the equivalent inductance and capacitance, enhancing the concentration effect of the electromagnetic field, and improving the detection sensitivity; a relationship function between the equivalent dielectric constant and the resonant frequency is established to obtain a dielectric response curve; an oil-paper insulation moisture evaluation model containing a linear relationship is established according to the dielectric response curve to evaluate the moisture state of the oil-paper insulation of the equipment to be tested, and output an evaluation result; the method overcomes the problem that the existing oil-paper insulation detection method has detection condition limitations and is difficult to balance detection efficiency and accuracy in response to complex equipment to be tested, and significantly improves the efficiency and accuracy of oil-paper insulation moisture detection.

[0005] To solve the above technical problems, according to a first aspect of an embodiment of the present application, a method for evaluating the moisture state of oil-paper insulation based on a special-shaped split ring structure is provided, wherein the special-shaped split ring structure comprises a ring resonator composed of at least two concentric petal-shaped rosettes and a petal-shaped complementary split ring, wherein the petal-shaped complementary split rings have openings of the same size at symmetrical positions of the concentric petal-shaped rosettes, and the method comprises the following steps: S1, establishing an equivalent circuit of the petal-shaped complementary split ring, and calculating the relative dielectric constant of the petal-shaped complementary split ring; S2. Calculating the resonant frequency of the ring resonator based on the relative dielectric constant; S3, obtaining an equivalent dielectric constant of the ring resonator based on the relative dielectric constants of the upper medium and the substrate of the ring resonator; S4, establishing a relationship function between the equivalent dielectric constant and the resonant frequency, and obtaining a dielectric response curve according to the relationship function; S5. Establishing an oil-paper insulation moisture assessment model including a linear relationship according to the dielectric response curve to assess the moisture state of the oil-paper insulation of the device to be tested, and outputting the assessment result.

[0006] In this scheme, by detecting a ring resonator including at least two petal-shaped complementary split rings, it can be ensured that when the area of ​​the central resonant ring remains unchanged, the equivalent area of ​​the resonator is effectively increased by the concentric petal-shaped complementary split rings, thereby reducing the resonant fundamental frequency of the resonator and increasing the number of resonance peaks to improve the resonance information; the openings provided on the rings can enhance the coupling effect and improve the detection sensitivity of the ring resonator; by establishing an equivalent circuit of the petal-shaped complementary split rings, the relationship between the electromagnetic field and the circuit parameters can be more accurately analyzed, which helps to accurately calculate the relative dielectric constant, the equivalent dielectric constant and the resonant frequency, ensure comprehensive acquisition of the dielectric response curve, and more accurately capture the dielectric performance changes of the oil-paper insulation of the equipment to be tested caused by moisture, thereby improving the detection sensitivity, detection sensitivity and detection efficiency; the linear programming oil-paper insulation moisture assessment model can be used to perform a detailed analysis of the dielectric response curve, discover small changes and features in the curve, and extract the relationship between the dielectric response characteristic quantity and the moisture content of the oil-paper insulation, thereby improving the accuracy and reliability of the detection.

[0007] Preferably, the S1 comprises the following sub-steps: Establishing a parallel resonant circuit based on the operating characteristics of the ring resonator and using it as an equivalent circuit of the petal-shaped complementary split ring; Based on the equivalent circuit, the relative dielectric constant is calculated through the movement of charges between the gaps of the petal-shaped complementary split rings.

[0008] Preferably, the relative dielectric constant includes at least inductance and capacitance, wherein: The inductance characterization radius is R 0 The equivalent inductance of the petal-shaped complementary split ring; The calculation formula of the equivalent inductance is expressed as follows: Where L represents the equivalent inductance, Z 0 is the characteristic impedance of the resonator, c is the speed of light in vacuum, P mean is the effective length of the outer side of the equivalent outer ring of the petal-shaped complementary split ring, ε eff is the effective dielectric constant; The calculation formula of the capacitance is expressed as follows: In the formula, C 0 represents the capacitance value of the microstrip ring surface in the ring resonator, P avg It is the average effective length of the upper or lower semicircle of the petal-shaped complementary split ring.

[0009] Preferably, the resonant frequency of the ring resonator is calculated as follows: In the formula, f represents the resonant frequency, and C represents the capacitance of the microstrip ring in the ring resonator.

[0010] Preferably, the effective dielectric constant ε eff The calculation formula is as follows: In the formula, q 1 and q 2 are the structural parameters of the split ring resonator, ε pb is the relative dielectric constant of the upper medium of the ring resonator, ε sub is the relative dielectric constant of the base of the ring resonator.

[0011] Preferably, S4 includes the following sub-steps: Establishing the relationship function based on the mutual influence relationship between the resonant frequency and the effective dielectric constant; The ring resonator is used to perform a resonant dielectric response test on the medium to be tested, and an insertion loss curve and a dielectric response curve of the medium to be tested are obtained according to the resonant frequency data of the test.

[0012] Preferably, the calculation formula of the relationship function is as follows: In the formula, f res represents the mutual influence relationship between the resonant frequency and the effective dielectric constant, R 0 is the equivalent radius of the petal-shaped complementary split ring, Gap is the opening width of the petal-shaped complementary split ring, c is the speed of light in vacuum, and π is pi.

[0013] Preferably, S5 comprises the following sub-steps: Analyze the high-frequency dielectric change characteristics of the oil-paper insulation of the medium to be tested based on the insertion loss curve and the dielectric response curve to obtain a dielectric response characteristic quantity; A linear regression model is used to establish the oil-paper insulation moisture assessment model, and a fitting analysis is performed on the relationship between the moisture content of the oil-paper insulation of the medium to be tested and the dielectric response characteristic quantity to obtain a moisture prediction result of the medium to be tested; The moisture state of the oil-paper insulation of the medium to be tested is evaluated based on the moisture prediction result to obtain an evaluation result of the moisture state of the oil-paper insulation.

[0014] Preferably, the method further comprises: calculating an evaluation error based on the moisture prediction result, specifically comprising: The relative dielectric constant at each test resonance frequency is extracted based on the insertion loss characteristic curve, and the evaluation error is comprehensively calculated in combination with the actual water content and the predicted water content of the medium to be tested.

[0015] According to another aspect of an embodiment of the present application, a device for evaluating the moisture state of oil-paper insulation based on a special-shaped split ring structure is provided, comprising: A split ring analysis module, used to establish an equivalent circuit of the petal-shaped complementary split ring; A split ring calculation module, used to calculate the relative dielectric constant of the petal-shaped complementary split ring, the resonant frequency of the ring resonator and the equivalent dielectric constant, and establish a relationship function between the equivalent dielectric constant and the resonant frequency; The oil-paper insulation moisture test module uses the ring resonator to test the medium to be tested and obtains a dielectric response curve according to the relationship function; The oil-paper insulation moisture assessment module is used to establish an oil-paper insulation moisture assessment model containing a linear relationship according to the dielectric response curve, so as to assess the moisture state of the oil-paper insulation of the equipment to be tested and output the assessment result.

[0016] Beneficial effects of the present invention: 1. The size of the resonant ring is reduced by using a petal-shaped complementary split ring resonator. Compared with a single ring, while ensuring that the area of ​​the central resonant ring remains unchanged, the use of at least two concentric petal-shaped rosettes can effectively increase the equivalent area of ​​the resonator, thereby reducing the resonant fundamental frequency of the resonator, increasing the number of resonant peaks, and effectively improving the detection sensitivity; 2. By considering the relative dielectric constants of the upper medium and the substrate of the entire device to calculate the equivalent dielectric constant, the impact of the environment in which the device is located on the detection can be comprehensively evaluated, the interference of the dielectric constant of the medium around the oil-paper insulation on the detection results can be eliminated, and the accuracy and reliability of the detection can be ensured; 3. The dielectric response curve and insertion loss curve can amplify and visualize the impact of tiny moisture changes on electromagnetic properties, so as to intuitively display the moisture state changes of oil-paper insulation. By studying the relationship between the moisture content of oil-paper insulation and the dielectric response characteristic quantity, quantitative evaluation and prediction of the moisture content of the medium to be tested can be achieved, providing an efficient and accurate solution for the detection of the moisture state of oil-paper insulation of power equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings. The drawings are only for the purpose of illustrating preferred embodiments and are not to be considered as limiting the present invention. Also, the same reference symbols are used throughout the drawings to represent the same parts.

[0018] Figure 1 The present invention is a flowchart of a method for evaluating the moisture status of oil-paper insulation based on a special-shaped split ring structure according to an embodiment of the present invention.

[0019] Figure 2The figure is a schematic diagram of a ring resonator structure according to an embodiment of the present invention.

[0020] Figure 3 Schematic diagram of a petal-shaped complementary split ring structure according to an embodiment of the present invention.

[0021] Figure 4 The figure is a schematic diagram of an equivalent circuit of a petal-shaped complementary split ring according to an embodiment of the present invention.

[0022] Figure 5 It is a schematic diagram of a three-dimensional simulation of a ring resonator according to an embodiment of the present invention.

[0023] Figure 6 The figure is a schematic diagram of an insertion loss curve of a simulation test of an embodiment of the present invention.

[0024] Figure 7 It is a schematic diagram of an insertion loss curve and a dielectric response curve according to an embodiment of the present invention.

[0025] Figure 8 The present invention is a block diagram of an oil-paper insulation moisture status assessment device based on a special-shaped split ring structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] 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 in conjunction with the accompanying drawings and embodiments. It should be understood that the specific implementation method described herein is only an optimal embodiment of the present invention, which is only used to explain the present invention and does not limit the scope of protection of the present invention. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] Example 1: Figure 1 As shown, a method for evaluating the moisture state of oil-paper insulation based on a special-shaped split ring structure, wherein the special-shaped split ring structure includes a ring resonator composed of at least two concentric petal-shaped rosettes, wherein the petal-shaped complementary split rings have openings of the same size at symmetrical positions of the concentric petal-shaped rosettes, and the method includes steps S1-S5, which are specifically as follows: S1, establishing an equivalent circuit of the petal-shaped complementary split ring, and calculating the relative dielectric constant of the petal-shaped complementary split ring; specifically comprising: Establishing a parallel resonant circuit based on the operating characteristics of the ring resonator and using it as an equivalent circuit of the petal-shaped complementary split ring; Based on the equivalent circuit, the relative dielectric constant is calculated through the movement of charges between the gaps of the petal-shaped complementary split rings.

[0028] Specifically, the relative dielectric constant includes at least inductance and capacitance, wherein: The inductance characterization radius is R 0 The equivalent inductance of the petal-shaped complementary split ring; The calculation formula of the equivalent inductance is expressed as follows: Where L represents the equivalent inductance, Z 0 is the characteristic impedance of the resonator, c is the speed of light in vacuum, P mean is the effective length of the outer side of the equivalent outer ring of the petal-shaped complementary split ring, ε eff is the effective dielectric constant; The calculation formula of the capacitance is expressed as follows: In the formula, C 0 represents the capacitance value of the microstrip ring surface in the ring resonator, P avg It is the average effective length of the upper or lower semicircle of the petal-shaped complementary split ring.

[0029] In this embodiment, if Figure 2 A ring resonator is shown, h 1 is the substrate thickness, h 2 is the total thickness of the device after superimposing the upper dielectric layer, w is the width of the microstrip line, and g is the width of the coupling gap between the microstrip line and the split ring. The ring resonator reflects the change in the dielectric properties of the material to be tested through the shift of the resonance peak. The dielectric properties of the medium to be tested are derived by superimposing the change in the resonant frequency before and after the medium to be tested and the insertion loss value at the resonant frequency. Combining the split ring with two microstrip lines and designing an opening on the ring can enhance the coupling effect; the number of split rings can be increased, and the number of coupling gaps can be increased in a nested manner.

[0030] Among them, Figure 3 As shown, the split ring structure is a petal-shaped complementary type, R 0 is the equivalent radius of the petal-shaped complementary split ring, r 0 is the average radius of a single petal, Gap is the width of the wreath opening, g 0 is the distance between the two rings. Under a certain working voltage excitation, the microstrip ring will generate a current around the ring and generate a magnetic field through the ring. This phenomenon can be equivalent to the effect of inductance. The impedance discontinuity part on the ring, the gap between the two rings and the opening of the complementary split ring are capacitors. Therefore, the equivalent circuit of the petal-shaped complementary split ring can be regarded as a parallel resonant circuit, such as Figure 4 shown.

[0031] Furthermore, the capacitance of the complementary split ring is generated by the charges of equal magnitude and opposite polarity induced at the gap, and both the upper and lower surfaces of the microstrip ring contribute to the capacitance of the equivalent circuit. Therefore, Figure 4 Two C's 0Respectively represent the capacitance values ​​of the upper and lower surfaces of the microstrip loop, C = C 0 / 2, L represents the equivalent radius R 0 The equivalent inductance of the petal-shaped complementary split ring. According to the structural characteristic parameters of the ring resonator and the split ring, the relative dielectric constant of the resonator can be accurately calculated, which provides accurate data support for the subsequent calculation of the resonant frequency and equivalent dielectric constant, and further lays the premise for obtaining the insertion loss curve and dielectric response curve of the medium to be tested.

[0032] Furthermore, the effective length P of the outer side of the equivalent outer ring of the petal-shaped complementary split ring is mean and the average effective length P of the upper or lower semicircle of the petal-shaped complementary split ring avg The calculation formula is as follows: p avg =3π[(R 0 ×sin15°+0.5g)+(R 0 ×sin15°-0.5g)]-Gap (3) p mean =6π[(R 0 ×sin15°+w+g)+(R 0 ×sin15°-wg)]-Gap (4)

[0033] In this embodiment, by constructing an equivalent circuit, the electrical characteristics of the petal-shaped complementary split ring can be quantified and the relative dielectric constant can be accurately calculated, which in turn helps to determine the electromagnetic response characteristics of the split ring in different dielectric environments and can reflect the tiny electrical parameter changes caused by moisture in the oil-paper insulation, laying a data foundation for detection sensitivity.

[0034] S2. Calculate the resonant frequency of the ring resonator based on the relative dielectric constant; the calculation formula is as follows: In the formula, f represents the resonant frequency, and C represents the capacitance of the microstrip ring in the ring resonator.

[0035] In this embodiment, the resonant frequency is calculated by the relative dielectric constant, which can indirectly reflect the moisture state of the oil-paper insulation. When the oil-paper insulation is damp, its dielectric constant will change, causing the resonant frequency to shift. When the resonant frequency shifts to a certain degree in a certain direction, it can be judged that the moisture degree of the oil-paper insulation has reached a certain threshold; in this way, the change state of the dielectric constant is obtained through the resonant frequency, and even the slightest moisture change can be captured, thereby improving the sensitivity of the detection. At the same time, by calculating the resonant frequency, the necessary characteristic parameters are provided for the subsequent establishment of the relationship function to ensure the accuracy of the dielectric response curve, making the entire detection process more systematic.

[0036] S3, based on the relative dielectric constants of the upper dielectric layer and the substrate of the ring resonator, obtaining the equivalent dielectric constant of the ring resonator; the effective dielectric constant ε eff The calculation formula is as follows: In the formula, q 1 and q 2 are the structural parameters of the split ring resonator, ε pb is the relative dielectric constant of the upper medium of the ring resonator, ε sub is the relative dielectric constant of the base of the ring resonator.

[0037] Furthermore, the equivalent dielectric constant ε of the entire device is eff Relative dielectric constant ε with the upper medium pb and substrate relative permittivity ε sub The relationship can be expressed as:

[0038] In this embodiment, the equivalent dielectric constant comprehensively considers the influence of the upper dielectric and the substrate of the entire device. When the oil-paper insulation is damp, the change in its dielectric constant will be reflected in the equivalent dielectric constant. Therefore, by calculating the equivalent dielectric constant, the change in dielectric properties caused by dampness can be more comprehensively captured, including the coupling effect of the upper dielectric and the substrate on the dampness of the oil-paper insulation, thereby improving the detection sensitivity. At the same time, in the subsequent detection process, the dampness state of the oil-paper insulation can be quickly evaluated by monitoring the change in the equivalent dielectric constant, without the need to perform complex analysis on the dielectric constants of the upper dielectric, the substrate, and the oil-paper insulation, thereby improving the detection efficiency.

[0039] S4, establishing a relationship function between the equivalent dielectric constant and the resonant frequency, and obtaining a dielectric response curve according to the relationship function; specifically comprising: Establishing the relationship function based on the mutual influence relationship between the resonant frequency and the effective dielectric constant; The ring resonator is used to perform a resonant dielectric response test on the medium to be tested, and an insertion loss curve and a dielectric response curve of the medium to be tested are obtained according to the resonant frequency data of the test.

[0040] Specifically, the calculation formula of the relationship function is as follows: In the formula, f res represents the mutual influence relationship between the resonant frequency and the effective dielectric constant, R 0is the equivalent radius of the petal-shaped complementary split ring, Gap is the opening width of the petal-shaped complementary split ring, c is the speed of light in vacuum, and π is pi.

[0041] In this embodiment, the mutual influence of the effective dielectric constant and the resonant frequency can be clearly known through the relationship function between the resonant frequency and the effective dielectric constant, which provides a basis for quantitatively analyzing the degree of moisture in the oil-paper insulation. During the detection process, the dielectric response curve is constructed through the relationship function, which can intuitively display the changes in the physical properties of the medium to be tested; the insertion loss curve can intuitively reflect the changes in the loss characteristics of the medium to be tested, and combined with the changes in physical properties, it can more comprehensively reflect the changes in the moisture state of the oil-paper insulation, thereby more accurately judging the current moisture state of the oil-paper insulation.

[0042] S5. Establishing an oil-paper insulation moisture assessment model including a linear relationship according to the dielectric response curve to assess the moisture state of the oil-paper insulation of the device to be tested, and outputting the assessment result; specifically comprising: Analyze the high-frequency dielectric change characteristics of the oil-paper insulation of the medium to be tested based on the insertion loss curve and the dielectric response curve to obtain a dielectric response characteristic quantity; A linear regression model is used to establish the oil-paper insulation moisture assessment model, and a fitting analysis is performed on the relationship between the moisture content of the oil-paper insulation of the medium to be tested and the dielectric response characteristic quantity to obtain a moisture prediction result of the medium to be tested; The moisture state of the oil-paper insulation of the medium to be tested is evaluated based on the moisture prediction result to obtain an evaluation result of the moisture state of the oil-paper insulation.

[0043] In some embodiments, standard curves of the dielectric response curve and the insertion loss curve of the medium to be tested in an unmoistened state are established respectively, and the dielectric response curve and the insertion loss curve obtained by the test are compared with the standard curves respectively, and the change state of the oil-paper insulation is reflected according to the overall offset or shape change of the curve. Among them, the key characteristic points on the dielectric response curve and the insertion loss curve, such as the peak point of the dielectric constant corresponding to the resonant frequency, the minimum point of the insertion loss curve, etc., can be used to intuitively reflect the moisture state of the oil-paper insulation and obtain preliminary evaluation results. For example, the peak value of the dielectric constant corresponding to the resonant frequency may decrease, and the frequency corresponding to the minimum point of the insertion loss curve may shift and the loss value will increase. Based on the change amount of these characteristic points, the degree of moisture of the oil-paper insulation can be determined.

[0044] In another embodiment, by analyzing the changes in the insertion loss curve and the dielectric response curve in the high frequency band, the characteristic that moisture has a more significant effect on the dielectric properties of oil-paper insulation in a high-frequency electric field can be utilized to make the polarization and migration process of water molecules under the action of the electric field more active, and the slight changes in the initial stage of oil-paper insulation being damp can be captured more accurately, so as to comprehensively obtain the dielectric response characteristics of oil-paper insulation being damp. By constructing a linear oil-paper insulation dampness assessment model, for example, a linear regression model, the dielectric response characteristic quantities that have a significant effect on the moisture content of oil-paper insulation can be automatically screened out. For complex detection environments and complex dielectric response data, the oil-paper insulation dampness assessment model can be simplified through linear regression, focusing on key factors to effectively avoid overfitting problems.

[0045] Furthermore, by fitting and analyzing the relationship between the moisture content of the oil-paper insulation of the test medium and the dielectric response characteristic quantity, the detection data such as the dielectric response curve and the insertion loss curve can be converted into a quantitative description of the actual moisture degree of the oil-paper insulation, that is, the moisture content, thereby realizing the key transformation from electromagnetic property detection to moisture state assessment, and then obtaining the moisture prediction result, which provides a quantitative measurement standard for the moisture state of the oil-paper insulation.

[0046] Furthermore, the moisture state of the oil-paper insulation of the medium to be tested is evaluated according to the moisture prediction result, and the moisture degree level can be formulated according to the historical moisture information, for example, dry, slightly damp, moderately damp, and severely damp; each moisture degree level corresponds to a moisture content numerical range, and the moisture prediction result is matched with the moisture content numerical range to determine the moisture degree level of the oil-paper insulation of the medium to be tested.

[0047] In some examples, a risk warning mechanism can be established for power equipment based on the assessment results of the moisture status of oil-paper insulation to ensure the safe and stable operation of the power equipment.

[0048] In this embodiment, the relationship between the moisture content of oil-paper insulation and the dielectric response characteristic quantity is analyzed by the oil-paper insulation moisture assessment model, so that slight changes and characteristics in the curve can be found, and quantitative assessment and prediction of the moisture content of the medium to be tested can be achieved, thereby improving the accuracy and sensitivity of detection; by utilizing the linear programming model, the dielectric response curve can be quickly analyzed, key characteristic quantities can be automatically extracted and a relationship with the moisture content can be established, thereby improving the analysis speed and thus improving the detection efficiency.

[0049] Specifically, the method further includes: calculating an evaluation error based on the moisture prediction result, specifically including: The relative dielectric constant at each test resonance frequency is extracted based on the insertion loss characteristic curve, and the evaluation error is comprehensively calculated in combination with the actual water content and the predicted water content of the medium to be tested.

[0050] In this embodiment, if Figure 5As shown, the sensitivity of the ring resonator to the dielectric properties of the test material is tested through a simulation model. The ring resonator, also known as a microstrip lobe-shaped complementary split ring resonator (MPCSRR), consists of a double-open lobe-shaped ring and two microstrip lines, with two SMA interfaces designed at both ends. In this embodiment, HFSS simulation software is used to establish a simulation model of the microstrip lobe-shaped complementary split ring resonator at a ratio of 1:1. Using a mode-driven solution method, ideal conductor boundary conditions are set for the reference ground, microstrip ring, and microstrip line. The entire device is placed in an "air box" and set as a radiation boundary. Lumped excitation ports are set at both ends of the device; the network partitioning mode is used to measure the insertion loss S of the entire resonator device in the 1-6 GHz frequency band. 21 , air medium was selected as the control, and insulating paperboard (εr = 2.5, tanδ = 0.0442) and NX9320 (ε r =3.3, tanδ=0.0025) as test materials. At the same time, under the same conditions, the traditional microstrip ring resonator (MRR) is simulated and compared to obtain the insertion loss curves of different test materials, such as Figure 6 shown.

[0051] Furthermore, the average value of the resonant frequency of the corresponding medium to be tested is calculated, and compared with air, the offset value of the resonant frequency after superimposing the insulating cardboard or NX9320 material to be tested is calculated, and then the sensitivity is calculated. The calculation formula is as follows: In the formula, △f is the offset value of the resonant frequency after the insulation cardboard or NX9320 to be tested is superimposed compared with air, and S represents the sensitivity; The results are shown in Tables 1 and 2. Table 1 MPCSRR performance analysis Table 2 MRR performance analysis It can be seen from the table that MPCSRR can sensitively distinguish the materials to be tested with different dielectric parameters, and the offset of the resonant frequency is about 3 to 4 times that of the traditional microstrip ring resonator, with higher test sensitivity.

[0052] As a specific example analysis, seven kinds of insulation paperboard samples were prepared, including dry (water content less than 0.5%) and 1.06%, 2.01%, 3.10%, 3.96%, 4.94%, and 6.03% moisture content. All samples were calibrated with Karl Fischer moisture. The seven kinds of insulation paperboard samples were subjected to microstrip resonant dielectric response tests in the frequency range of 1 to 6 GHz. The insertion loss curves and dielectric response curves were obtained, as shown in the figure. Figure 7Observe the insertion loss curve without superimposing the medium to be tested, that is, the substrate curve, and Figure 6 Compared with the simulation results shown in the figure, the resonant peak of the MPCSRR insertion loss curve is slightly shifted, and the curve smoothness is slightly lower than the simulation results, which is mainly related to the processing accuracy of the resonator.

[0053] It should be noted that from the insertion loss characteristic curve, it can be found that with the increase of moisture content, the resonance peak shifts to the left, indicating that the relative dielectric constant of the insulating paperboard continues to increase. In the 1-6 GHz frequency band, the last two resonance peaks have obvious attenuation. This is because the increase in frequency will make the parasitic effects (such as parasitic capacitance) more obvious, which may cause the resonance peak to decrease, causing signal distortion, phase shift and other problems. In order to avoid introducing errors, the first seven resonance peaks from 1 to 6 GHz are selected to study the dielectric properties of the insulating paperboard.

[0054] Furthermore, a linear regression model was used to construct an oil-paper insulation moisture assessment model to analyze the relationship between the moisture content of oil-paper insulation and the dielectric response characteristic quantity, and combined with cross-validation to obtain the optimal moisture prediction result. The comparison results of the moisture prediction value of linear regression and the original value of the test are shown in Table 3. Table 3 Moisture assessment prediction results In Table 3, R 2 It expresses the degree of explanation of the relationship between the independent variable and the dependent variable. The larger the R2, the better the model fit. 2 The value is 0.999, which indicates that the fitting effect is good.

[0055] Further, from the analysis of Table 3, it can be seen that the predicted moisture content is retained, and the final oil-paper insulation moisture assessment model formula is: In order to verify the accuracy of the model, insulation paperboard samples with moisture contents of 1.51%, 3.01%, 4.01%, and 5.17% were prepared, and the dielectric response test of MPCSRR was carried out. The relative dielectric constant at each resonant frequency of the insertion loss characteristic curve was extracted and substituted into formula (10). The actual moisture content and predicted moisture content are shown in Table 4, where y represents the actual moisture content, represents the predicted moisture content, E represents the evaluation error, and its calculation formula is: Table 4 Validation results of moisture assessment model It can be seen from Table 4 that the error between the predicted moisture content and the actual moisture content is less than 4%, indicating that the above evaluation model has a small error and can accurately evaluate the moisture state of oil-paper insulation with a moisture content of less than 6%.

[0056] Embodiment 2, as Figure 8 As shown, a device for evaluating the moisture state of oil-paper insulation based on a special-shaped split ring structure comprises: A split ring analysis module, used to establish an equivalent circuit of the petal-shaped complementary split ring; A split ring calculation module, used to calculate the relative dielectric constant of the petal-shaped complementary split ring, the resonant frequency of the ring resonator and the equivalent dielectric constant, and establish a relationship function between the equivalent dielectric constant and the resonant frequency; The oil-paper insulation moisture test module uses the ring resonator to test the medium to be tested and obtains a dielectric response curve according to the relationship function; The oil-paper insulation moisture assessment module is used to establish an oil-paper insulation moisture assessment model containing a linear relationship according to the dielectric response curve, so as to assess the moisture state of the oil-paper insulation of the equipment to be tested and output the assessment result.

[0057] Beneficial effects of the embodiment: By optimizing the design of the resonator, improving the circular ring structure to a petal-shaped complementary split ring structure, and designing a ring resonator containing at least two petal-shaped complementary split rings for detection, the number of resonance peaks in the 1-6GHz frequency band is increased from five to nine, which can ensure that the equivalent area of ​​the resonator is effectively increased by two concentric petal-shaped complementary split rings while the area of ​​the central resonance ring remains unchanged, thereby reducing the resonant fundamental frequency of the resonator, increasing the number of resonance peaks, and improving the richness of the resonance information. By setting an opening on the ring and flexibly increasing the coupling gap between the rings in the ring resonator, the coupling effect can be enhanced, thereby changing the equivalent inductance and capacitance, enhancing the concentration effect of the electromagnetic field, and being more sensitive to small changes in moisture distribution and dielectric properties, significantly improving the detection sensitivity. By constructing an equivalent circuit, the electrical performance of the resonator and the internal energy storage and transmission mechanism are reflected, the electromagnetic field distribution of the MPCSRR is revealed, and the relationship between the electromagnetic field and the circuit parameters can be analyzed more accurately, which helps to accurately calculate the relative dielectric constant, equivalent dielectric constant and resonant frequency, ensure the comprehensive acquisition of the dielectric response curve, and more accurately capture the dielectric performance changes of the oil-paper insulation of the equipment under test caused by moisture, thereby improving the detection sensitivity, detection sensitivity and detection efficiency; the linear programming oil-paper insulation moisture assessment model can be used to perform a detailed analysis of the dielectric response curve, discover the subtle changes and features in the curve, and extract the relationship between the dielectric response characteristic quantity and the moisture content of the oil-paper insulation, thereby improving the accuracy and reliability of the detection.

[0058] The above specific embodiments are preferred embodiments of the present invention, and are not intended to limit the specific implementation scope of the present invention. The scope of the present invention includes but is not limited to the present specific embodiments. All equivalent changes made in accordance with the shape, structure, and method of the present invention are within the protection scope of the present invention.

Claims

1. A method for evaluating the moisture state of oil-paper insulation based on a special-shaped split ring structure, wherein the special-shaped split ring structure comprises a ring resonator composed of at least two concentric petal-shaped rosettes, wherein the petal-shaped complementary split rings have openings of the same size at symmetrical positions of the concentric petal-shaped rosettes, and the method is characterized in that: The method comprises the following steps: S1, establishing an equivalent circuit of the petal-shaped complementary split ring, and calculating the relative dielectric constant of the petal-shaped complementary split ring; S2. Calculating the resonant frequency of the ring resonator based on the relative dielectric constant; S3, obtaining an equivalent dielectric constant of the ring resonator based on the relative dielectric constants of the upper medium and the substrate of the ring resonator; S4, establishing a relationship function between the equivalent dielectric constant and the resonant frequency, and obtaining a dielectric response curve according to the relationship function; S5. Establishing an oil-paper insulation moisture assessment model including a linear relationship according to the dielectric response curve to assess the moisture state of the oil-paper insulation of the device to be tested, and outputting the assessment result.

2. The method for evaluating the moisture state of oil-paper insulation based on a special-shaped split ring structure according to claim 1 is characterized in that: The S1 comprises the following sub-steps: Establishing a parallel resonant circuit based on the operating characteristics of the ring resonator and using it as an equivalent circuit of the petal-shaped complementary split ring; Based on the equivalent circuit, the relative dielectric constant is calculated through the movement of charges between the gaps of the petal-shaped complementary split rings.

3. The method for evaluating the moisture state of oil-paper insulation based on a special-shaped split ring structure according to claim 2 is characterized in that: The relative dielectric constant includes at least inductance and capacitance, wherein: The inductance represents the equivalent inductance of the petal-shaped complementary split ring with a radius of R0; The calculation formula of the equivalent inductance is expressed as follows: Where L is the equivalent inductance, Z0 is the characteristic impedance of the resonator, c is the speed of light in vacuum, and P is mean is the effective length of the outer side of the equivalent outer ring of the petal-shaped complementary split ring, ε eff is the effective dielectric constant; The calculation formula of the capacitance is expressed as follows: Where C0 represents the capacitance value of the microstrip ring surface in the ring resonator, P avg It is the average effective length of the upper or lower semicircle of the petal-shaped complementary split ring.

4. The method for evaluating the moisture state of oil-paper insulation based on a special-shaped split ring structure according to claim 3 is characterized in that: The resonant frequency of the ring resonator is calculated as follows: In the formula, f represents the resonant frequency, and C represents the capacitance of the microstrip ring in the ring resonator.

5. The method for evaluating the moisture state of oil-paper insulation based on a special-shaped split ring structure according to claim 1 is characterized in that: The effective dielectric constant ε eff The calculation formula is as follows: Where q1 and q2 are the structural parameters of the split ring resonator, ε pb is the relative dielectric constant of the upper medium of the ring resonator, ε sub is the relative dielectric constant of the base of the ring resonator.

6. The method for evaluating the moisture state of oil-paper insulation based on a special-shaped split ring structure according to claim 5 is characterized in that: The S4 comprises the following sub-steps: Establishing the relationship function based on the mutual influence relationship between the resonant frequency and the effective dielectric constant; The ring resonator is used to perform a resonant dielectric response test on the medium to be tested, and an insertion loss curve and a dielectric response curve of the medium to be tested are obtained according to the resonant frequency data of the test.

7. The method for evaluating the moisture state of oil-paper insulation based on a special-shaped split ring structure according to claim 6 is characterized in that: The calculation formula of the relationship function is as follows: In the formula, f res represents the mutual influence relationship between the resonant frequency and the effective dielectric constant, R0 is the equivalent radius of the petal-shaped complementary split ring, Gap is the opening width of the petal-shaped complementary split ring, c is the speed of light in a vacuum, and π is pi.

8. The method for evaluating the moisture state of oil-paper insulation based on a special-shaped split ring structure according to claim 6 is characterized in that: The S5 comprises the following sub-steps: Analyze the high-frequency dielectric change characteristics of the oil-paper insulation of the medium to be tested based on the insertion loss curve and the dielectric response curve to obtain a dielectric response characteristic quantity; A linear regression model is used to establish the oil-paper insulation moisture assessment model, and a fitting analysis is performed on the relationship between the moisture content of the oil-paper insulation of the medium to be tested and the dielectric response characteristic quantity to obtain a moisture prediction result of the medium to be tested; The moisture state of the oil-paper insulation of the medium to be tested is evaluated based on the moisture prediction result to obtain an evaluation result of the moisture state of the oil-paper insulation.

9. The method for evaluating the moisture state of oil-paper insulation based on a special-shaped split ring structure according to claim 8, characterized in that: The method further includes: calculating an evaluation error based on the moisture prediction result, specifically including: The relative dielectric constant at each test resonance frequency is extracted based on the insertion loss characteristic curve, and the evaluation error is comprehensively calculated in combination with the actual water content and the predicted water content of the medium to be tested.

10. An oil-paper insulation moisture state assessment device based on a special-shaped split ring structure, applicable to the oil-paper insulation moisture state assessment method based on a special-shaped split ring structure as described in any one of claims 1 to 9 above, characterized in that: include: A split ring analysis module, used to establish an equivalent circuit of the petal-shaped complementary split ring; A split ring calculation module, used to calculate the relative dielectric constant of the petal-shaped complementary split ring, the resonant frequency of the ring resonator and the equivalent dielectric constant, and establish a relationship function between the equivalent dielectric constant and the resonant frequency; The oil-paper insulation moisture test module uses the ring resonator to test the medium to be tested and obtains a dielectric response curve according to the relationship function; The oil-paper insulation moisture assessment module is used to establish an oil-paper insulation moisture assessment model containing a linear relationship according to the dielectric response curve, so as to assess the moisture state of the oil-paper insulation of the equipment to be tested and output the assessment result.

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