A method and system for evaluating the non-uniform aging degree of an oil-immersed current transformer

Abstract

The application discloses a kind of oil-immersed current transformer non-uniform aging degree evaluation method and system, method includes: obtaining the real part scatter point value and imaginary part scatter point value of complex dielectric constant of different frequency under equipment whole main insulation;Obtain the real part scatter point value and imaginary part scatter point value of complex dielectric constant of different frequency under equipment head main insulation;HN dielectric relaxation model is used to fit the expression of whole main insulation complex dielectric constant, and HN dielectric relaxation model is used to fit the expression of head main insulation complex dielectric constant;Constantly adjust parameter in fitting process until the value of whole error function is minimum and the value of head error function is minimum, and stop fitting to obtain corresponding parameter;Evaluate equipment main insulation non-uniform aging degree and equipment head main insulation aging condition;The application has the advantages that: for non-uniform aging current transformer, effective insulation aging evaluation is carried out, and evaluation result is more accurate.

Description

Technical Field

[0001] This invention relates to the field of insulation aging assessment of current transformers, and specifically to a method and system for assessing the degree of uneven aging of oil-immersed current transformers. Background Technology

[0002] As a crucial component of power infrastructure, current transformers play a vital role in measurement and protection. During long-term operation, current transformers are subjected to a combination of electrical, thermal, mechanical, and chemical stresses, leading to a continuous decline in their insulation strength and ultimately, faults. Currently, most oil-immersed current transformers, both domestically and internationally, have been in service for two to three decades. The insulation condition of these devices and whether they can continue to operate are pressing issues for power managers. Therefore, insulation diagnosis and aging condition testing of current transformers are essential.

[0003] Due to its special structure, the main insulation of oil-immersed inverted current transformers is more prone to aging than other main insulation parts after long-term operation. For example, the "Technical Specification for Current Transformers for Power Use in Special Environments" published in standard DB 65 / T 4665—2023 records the connection diagram for the frequency domain dielectric response test of the end screen insulation. However, the frequency domain dielectric response of the end screen insulation can only generally measure the overall main insulation status of the equipment. It cannot effectively conduct insulation aging assessment for current transformers with uneven aging. Moreover, in the process of analysis using the HN relaxation model, the fitting effect on the dielectric spectrum is often poor, resulting in inaccurate assessment results. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the existing technology cannot effectively carry out insulation aging assessment for current transformers with uneven aging, and the assessment results are not accurate enough.

[0005] This invention solves the above-mentioned technical problems through the following technical means: a method for evaluating the uneven aging degree of an oil-immersed current transformer, comprising the following steps:

[0006] Step 1: Obtain the real and imaginary scatter plot values ​​of the complex dielectric constant of the overall main insulation of the equipment at different frequencies;

[0007] Step 2: Obtain the real and imaginary part scatter plot values ​​of the complex dielectric constant at different frequencies of the main insulation of the equipment head;

[0008] Step 3: Based on the real and imaginary scatter plot values ​​of the complex dielectric constant of the overall main insulation at different frequencies, fit the expression for the complex dielectric constant of the overall main insulation using the HN dielectric relaxation model. Similarly, based on the real and imaginary scatter plot values ​​of the complex dielectric constant of the main insulation of the equipment head at different frequencies, fit the expression for the complex dielectric constant of the main insulation head using the HN dielectric relaxation model. Construct the overall error function and the head error function. During the fitting process, continuously adjust the parameters in the expression for the complex dielectric constant of the overall main insulation until the value of the overall error function is minimized, then stop fitting to obtain the final expression for the complex dielectric constant of the overall main insulation and its corresponding parameters. Continuously adjust the parameters in the expression for the complex dielectric constant of the main insulation head until the value of the head error function is minimized, then stop fitting to obtain the final expression for the complex dielectric constant of the main insulation head and its corresponding parameters.

[0009] Step 4: Based on the parameters obtained in Step 3, calculate the evaluation index value of the equipment's uneven aging degree and the degree of polymerization of the insulating paper. Use the evaluation index value of the equipment's uneven aging degree to evaluate the uneven aging degree of the main insulation of the equipment, and use the degree of polymerization of the insulating paper to evaluate the aging condition of the main insulation at the head of the equipment.

[0010] Furthermore, the relationships between the real part scatter plot values ​​ε′1 and ε″2 of the complex dielectric constant of the main insulation of the equipment at different frequencies, and between the imaginary part scatter plot values ​​ε″1 and ε″2 of the complex dielectric constant of the main insulation of the equipment head at different frequencies, are as follows:

[0011]

[0012] Wherein, l1 and l2 are the average thicknesses of the main insulation paper and the head insulation paper of the equipment, respectively, and m1 and m2 are the masses of the main insulation paper and the head wrapping insulation paper, respectively.

[0013] Furthermore, the method of fitting the expression for the complex dielectric constant of the overall main insulation using the HN dielectric relaxation model based on the real and imaginary scatter plot values ​​of the complex dielectric constant at different frequencies of the main insulation of the equipment head, and the method of fitting the expression for the complex dielectric constant of the main insulation of the equipment head using the HN dielectric relaxation model based on the real and imaginary scatter plot values ​​of the complex dielectric constant at different frequencies of the main insulation of the equipment head, includes:

[0014]

[0015] in, These are the overall main insulation complex dielectric constant and the head main insulation complex dielectric constant, respectively; τ m τ n These are the overall main insulation relaxation time constant and the head main insulation relaxation time constant, respectively; εs1 ε s2 These are the static dielectric constants of the overall main insulation and the head main insulation, respectively; ε ∞ α is the high-frequency dielectric constant; j is the imaginary unit; α m β m α represents the first and second shape parameters related to the relaxation time distribution within the overall main insulation HN relaxation model. n β n The third and fourth shape parameters are related to the relaxation time distribution within the HN relaxation model of the head main insulation.

[0016] Furthermore, by separating the real and imaginary parts of the overall primary insulation complex permittivity, the real part curve ε′ of the overall primary insulation complex permittivity is obtained. m and the imaginary part curve ε″ m The real part curve ε′ of the complex permittivity of the main head insulation is obtained by separating the real and imaginary parts of the complex permittivity. n and the imaginary part curve ε″ n .

[0017] Furthermore, the construction of the overall error function and the head error function includes:

[0018]

[0019] Among them, S m S n These are the overall error function and the head error function, respectively.

[0020] Furthermore, the calculation of the equipment's uneven aging degree assessment index value and the degree of polymerization of the insulating paper, using the equipment's uneven aging degree assessment index value to evaluate the equipment's uneven aging degree, and using the degree of polymerization of the insulating paper to evaluate the aging condition of the main insulation at the equipment head, includes:

[0021] Through formula Calculate the evaluation index value of the uneven aging degree of the equipment, where η is the evaluation index value of the uneven aging degree of the equipment;

[0022] When 1 < η ≤ 2.6, the main insulation of the equipment is judged to have slight uneven aging; when 2.6 < η ≤ 9.3, the main insulation of the equipment is judged to have moderate uneven aging; when η > 9.3, the main insulation of the equipment is judged to have severe uneven aging.

[0023] Through formula Calculate the degree of polymerization of the insulating paper, where Δε n =ε s2 -ε ∞ DP represents the degree of polymerization of the insulating paper;

[0024] When the degree of polymerization of the insulating paper is between 1000 and 1200, the main insulation at the head is considered to be new insulating paper. When the degree of polymerization of the insulating paper is between 650 and 1000, the main insulation at the head is considered to have excellent insulation performance. When the degree of polymerization of the insulating paper is between 350 and 650, the main insulation at the head is considered to have medium insulation performance. When the degree of polymerization of the insulating paper is less than 350, the main insulation at the head is considered to be aged and needs to be retired.

[0025] This invention also provides a system for evaluating the uneven aging degree of an oil-immersed current transformer, comprising:

[0026] The first data acquisition module is used to obtain the real part and imaginary part of the complex dielectric constant of the overall main insulation of the equipment at different frequencies.

[0027] The second data acquisition module is used to acquire the real part and imaginary part of the complex dielectric constant of the main insulation of the equipment head at different frequencies.

[0028] The data fitting module is used to fit the expression for the complex dielectric constant of the overall main insulation of the equipment based on the real and imaginary scatter points of the complex dielectric constant at different frequencies using the HN dielectric relaxation model. Similarly, it fits the expression for the complex dielectric constant of the head insulation based on the real and imaginary scatter points of the complex dielectric constant at different frequencies using the HN dielectric relaxation model. It constructs an overall error function and a head error function, continuously adjusting the parameters in the expression for the overall main insulation complex dielectric constant until the overall error function is minimized, at which point the fitting stops, yielding the final expression for the overall main insulation complex dielectric constant and its corresponding parameters. The same module continuously adjusts the parameters in the expression for the head insulation complex dielectric constant until the head error function is minimized, yielding the final expression for the head insulation complex dielectric constant and its corresponding parameters.

[0029] The aging assessment module is used to calculate the evaluation index value of the equipment's uneven aging degree and the degree of polymerization of the insulating paper based on the parameters obtained by the data fitting module. The evaluation index value of the equipment's uneven aging degree is used to evaluate the uneven aging degree of the main insulation of the equipment, and the degree of polymerization of the insulating paper is used to evaluate the aging condition of the main insulation at the head of the equipment.

[0030] Furthermore, the relationships between the real part scatter plot values ​​ε′1 and ε′2 of the complex dielectric constant of the main insulation of the equipment at different frequencies, and between the imaginary part scatter plot values ​​ε″1 and ε″2 of the complex dielectric constant of the main insulation of the equipment head at different frequencies, are as follows:

[0031]

[0032] Wherein, l1 and l2 are the average thicknesses of the main insulation paper and the head insulation paper of the equipment, respectively, and m1 and m2 are the masses of the main insulation paper and the head wrapping insulation paper, respectively.

[0033] Furthermore, the method of fitting the expression for the complex dielectric constant of the overall main insulation using the HN dielectric relaxation model based on the real and imaginary scatter plot values ​​of the complex dielectric constant at different frequencies of the main insulation of the equipment head, and the method of fitting the expression for the complex dielectric constant of the main insulation of the equipment head using the HN dielectric relaxation model based on the real and imaginary scatter plot values ​​of the complex dielectric constant at different frequencies of the main insulation of the equipment head, includes:

[0034]

[0035] in, These are the overall main insulation complex dielectric constant and the head main insulation complex dielectric constant, respectively; τ m τ n These are the overall main insulation relaxation time constant and the head main insulation relaxation time constant, respectively; ε s1 ε s2 These are the static dielectric constants of the overall main insulation and the head main insulation, respectively; ε ∞ α is the high-frequency dielectric constant; j is the imaginary unit; α m β m α represents the first and second shape parameters related to the relaxation time distribution within the overall main insulation HN relaxation model. n β n The third and fourth shape parameters are related to the relaxation time distribution within the HN relaxation model of the head main insulation.

[0036] Furthermore, by separating the real and imaginary parts of the overall primary insulation complex permittivity, the real part curve ε′ of the overall primary insulation complex permittivity is obtained. m and the imaginary part curve ε″ m The real part curve ε′ of the complex permittivity of the main head insulation is obtained by separating the real and imaginary parts of the complex permittivity. n and the imaginary part curve ε″ n .

[0037] Furthermore, the construction of the overall error function and the head error function includes:

[0038]

[0039] Among them, S m S n These are the overall error function and the head error function, respectively.

[0040] Furthermore, the calculation of the equipment's uneven aging degree assessment index value and the degree of polymerization of the insulating paper, using the equipment's uneven aging degree assessment index value to evaluate the equipment's uneven aging degree, and using the degree of polymerization of the insulating paper to evaluate the aging condition of the main insulation at the equipment head, includes:

[0041] Through formula Calculate the evaluation index value of the uneven aging degree of the equipment, where η is the evaluation index value of the uneven aging degree of the equipment;

[0042] When 1 < η ≤ 2.6, the main insulation of the equipment is judged to have slight uneven aging; when 2.6 < η ≤ 9.3, the main insulation of the equipment is judged to have moderate uneven aging; when η > 9.3, the main insulation of the equipment is judged to have severe uneven aging.

[0043] Through formula Calculate the degree of polymerization of the insulating paper, where Δε n =ε s2 -ε ∞ DP represents the degree of polymerization of the insulating paper;

[0044] When the degree of polymerization of the insulating paper is between 1000 and 1200, the main insulation at the head is considered to be new insulating paper. When the degree of polymerization of the insulating paper is between 650 and 1000, the main insulation at the head is considered to have excellent insulation performance. When the degree of polymerization of the insulating paper is between 350 and 650, the main insulation at the head is considered to have medium insulation performance. When the degree of polymerization of the insulating paper is less than 350, the main insulation at the head is considered to be aged and needs to be retired.

[0045] The advantages of this invention are:

[0046] (1) This invention fits the expressions for the complex dielectric constant of the overall main insulation and the head main insulation at different frequencies based on the real and imaginary scatter values ​​of the complex dielectric constant of the overall main insulation and the head main insulation. During the fitting process, constraints are set (the condition of minimizing the overall error function and the head error function) and the parameters of the expressions are continuously adjusted. When the constraints are met, the fitting stops. The parameters obtained after the fitting is completed are used to calculate the evaluation index value of the uneven aging degree of the equipment and the degree of polymerization of the insulating paper, thereby evaluating the uneven aging degree of the main insulation of the equipment and the aging condition of the head main insulation. It effectively carries out insulation aging evaluation for unevenly aged current transformers, and the constraint conditions make the evaluation results more accurate.

[0047] (2) This invention performs dielectric response tests on current transformers, obtains the overall frequency domain dielectric spectrum of the equipment and separates the real and imaginary parts of the relative permittivity, performs equivalent calculations on the relative permittivity of the head main insulation and the overall main insulation, and then adds constraints (overall error function and head error function) to the HN model to obtain relevant electrical characteristic quantities, judges the degree of uneven aging of the main insulation, and achieves insulation aging assessment for oil-immersed inverted current transformers with uneven aging of the head main insulation.

[0048] (3) The entire scheme of this invention adds constraints to the HN model to make the evaluation results more accurate. Compared with the traditional method, it analyzes the working state of the current transformer more accurately and can more accurately judge the degree of uneven aging of the current transformer. It optimizes the traditional detection method, saves manpower, and achieves high efficiency and improves the reliability of equipment operation on the basis of satisfying the aging detection of the current transformer. While ensuring economy, it can improve the evaluation accuracy to a certain extent and maximize economic benefits. Attached Figure Description

[0049] Figure 1 This is a flowchart of a method for evaluating the uneven aging degree of an oil-immersed current transformer, as disclosed in an embodiment of the present invention. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] Example 1

[0052] like Figure 1 As shown, Embodiment 1 of the present invention provides a method for evaluating the uneven aging degree of an oil-immersed current transformer. First, based on experiments, the relationship between the complex dielectric constant of the head main insulation and the overall main insulation is obtained to form an aging evaluation method. Then, the current transformer is evaluated according to the aging evaluation method, including the following steps:

[0053] S1. Obtain the real part and imaginary part of the complex dielectric constant of the overall main insulation of the equipment at different frequencies;

[0054] S2. Obtain the real and imaginary part scatter plot values ​​of the complex dielectric constant of the main insulation of the equipment head at different frequencies; the specific processes of S1 and S2 are as follows:

[0055] This embodiment first develops a full-scale model of a 220kV inverted oil-immersed current transformer. A test conductor is led out from the connection between the main insulation ring and the straight section, extending from the top of the expansion joint to the outside of the current transformer. The primary conductor of the prototype is short-circuited, and the secondary coil is pressurized and current is passed through it. The prototype is heated using electromagnetic induction, raising the temperature of the oil tank on the prototype to 120°C. The internal heating temperature is monitored by a thermocouple placed inside the transformer.

[0056] Using an IDAX-300 dielectric response tester, with a measurement frequency of 1mHz-1kHz, periodic dielectric response tests were conducted on the main insulation of the head and the overall main insulation through the test leads pre-installed in the prototype. The overall complex dielectric constant ε1 and the head complex dielectric constant ε2 of the prototype were obtained at different aging stages. The instrument was used to derive the real part scatter plot values ​​ε′1 and ε″1 of the overall main insulation of the prototype (i.e., the equipment) at different frequencies, and the real part scatter plot values ​​ε′2 and ε″2 of the head complex dielectric constant at different frequencies. By comparing and analyzing the overall and head complex dielectric constants of the prototype with the designed main insulation parameters, the quantitative relationship was confirmed as shown in the following formula:

[0057]

[0058] Wherein, l1 and l2 are the average thicknesses of the main insulation paper and the head insulation paper of the entire equipment, respectively, in millimeters (mm); m1 and m2 are the masses of the main insulation paper and the head wrapping insulation paper, respectively, in kilograms (kg).

[0059] Considering that it is not easy to directly sample the insulating paper of the main insulation of the current transformer, and that the oil tank of the 220kV oil-immersed inverted current transformer is small and cannot hold a sufficient number of paper sample bundles, the insulating paper of the same model as the main insulation is bundled into separate packages and placed in an oil-immersed sealed container, which is then placed in an oven and heated at the same temperature as the sample head (120℃). After each test cycle of dielectric response, the insulating paper in the sealed container is extracted for physicochemical testing to obtain the degree of polymerization (DP) of the insulating paper, which is equivalent to the degree of polymerization of the insulating paper at the head of the main insulation of the current transformer. The degree of polymerization (DP) of the insulating paper is used in subsequent step S4, and will not be elaborated here.

[0060] S3. Based on the real and imaginary scatter plot values ​​of the complex dielectric constant of the overall main insulation at different frequencies, the expression for the complex dielectric constant of the overall main insulation is fitted using the HN dielectric relaxation model. Similarly, based on the real and imaginary scatter plot values ​​of the complex dielectric constant of the main insulation at different frequencies, the expression for the complex dielectric constant of the main insulation at the equipment head is fitted using the HN dielectric relaxation model. An overall error function and a head error function are constructed. During the fitting process, the parameters in the expression for the complex dielectric constant of the overall main insulation are continuously adjusted until the value of the overall error function is minimized, at which point the fitting stops, yielding the final expression for the complex dielectric constant of the overall main insulation and its corresponding parameters. The specific process is as follows:

[0061] Using the Havriliak–Negami (HN) dielectric relaxation model, the complex dielectric constant of the overall and head main insulation is expressed as a function of angular frequency ω, and its expression is:

[0062]

[0063] in, These are the overall main insulation complex dielectric constant and the head main insulation complex dielectric constant, respectively; τ m τ n These are the overall main insulation relaxation time constant and the head main insulation relaxation time constant, respectively; ε s1 ε s2 These are the static dielectric constants of the overall main insulation and the head main insulation, respectively; ε ∞ α is the high-frequency dielectric constant; j is the imaginary unit; α m β m α represents the first and second shape parameters related to the relaxation time distribution within the overall main insulation HN relaxation model. n β n The third and fourth shape parameters are related to the relaxation time distribution within the HN relaxation model of the head main insulation.

[0064] By separating the real and imaginary parts of the overall primary insulation complex permittivity, the real part curve ε′ of the overall primary insulation complex permittivity is obtained. m and the imaginary part curve ε″ m The real part curve ε′ of the complex permittivity of the main head insulation is obtained by separating the real and imaginary parts of the complex permittivity. n and the imaginary part curve ε″ n The relevant formulas are as follows:

[0065]

[0066] intermediate quantities in the formula

[0067] Where ε′ and ε″ are the real and imaginary parts of the complex permittivity after separation, respectively; j is the imaginary unit; α and β are shape parameters related to the relaxation time distribution, 0 << α and β << 1; Δε = ε s ε ∞ , ε s and ε ∞ Let represent the static dielectric constant and the high-frequency dielectric constant, respectively, and τ be the relaxation time constant.

[0068] The above formula is only the real part curve of the overall principal insulation complex permittivity ε′. m and the imaginary part curve ε″ m The real part curve of the complex permittivity of the head main insulation ε′ n and the imaginary part curve ε″ n The general calculation formula is used to calculate the real part curve ε′ of the overall main insulation complex permittivity in practical applications. m and the imaginary part curve ε″ m Then simply add 'm' to the subscripts in the above formula. To calculate the real part curve ε′ of the complex dielectric constant of the main head insulation... n and the imaginary part curve ε″ n Simply add 'n' to the subscript in the above formula, as shown in the formula below:

[0069]

[0070] In the formula, Δε m =ε s1 -E ∞ .

[0071]

[0072] In the formula, Δε n =ε s2 -ε ∞ .

[0073] Based on the Havriliak–Negami dielectric relaxation model, an overall error function and a head error function are added to facilitate a more accurate fitting of the real and imaginary parts of the complex dielectric constant curves of the overall main insulation and the head main insulation. The formulas for the overall error function and the head error function are as follows:

[0074]

[0075] Among them, S m S n These are the overall error function and the head error function, respectively.

[0076] S4. Based on the parameters obtained in S3, calculate the evaluation index value of the equipment's uneven aging degree and the degree of polymerization of the insulating paper. Use the evaluation index value of the equipment's uneven aging degree to evaluate the uneven aging degree of the main insulation of the equipment, and use the degree of polymerization of the insulating paper to evaluate the aging condition of the main insulation at the equipment head. The specific process is as follows:

[0077] Under the constraints of S3 described above, the real part curve of the overall main insulation complex dielectric constant ε′ is obtained by fitting the dielectric spectrum curve using the HN model. m Imaginary part curve ε″ m The real part curve of the complex permittivity of the head main insulation ε′ n Imaginary part curve ε″ n After reconstructing the real and imaginary parts of the complex permittivity curves, the overall principal insulation relaxation characteristic α is obtained. m β m τ m , Δε m Head main insulation characteristic α n β n τ n , Δε n Through formula The evaluation index value for the degree of uneven aging of equipment is calculated, where η is the evaluation index value for the degree of uneven aging of equipment. The larger the value of η, the deeper the degree of unevenness of the equipment. When 1 < η ≤ 2.6, the main insulation of the equipment is judged to have slight uneven aging; when 2.6 < η ≤ 9.3, the main insulation of the equipment is judged to have moderate uneven aging; when η > 9.3, the main insulation of the equipment is judged to have severe uneven aging.

[0078] Then, a fitting formula is established to determine the relationship between the degree of polymerization (DP) of the insulating paper and the characteristic quantity of the main insulation at the head. The specific formula is obtained by fitting using the least squares method. Based on the degree of polymerization (DP) of the insulating paper, the aging condition of the main insulation head insulating paper is judged, and the degree of equipment aging is evaluated. The fitting formula is as follows:

[0079]

[0080] Where k0, k1, and k2 are the coefficients to be fitted in the above formula. After fitting, k0, k1, and k2 are 0.97, 4.22, and 1.28 respectively, resulting in the final fitting formula as follows:

[0081]

[0082] Therefore, in practical applications, the degree of polymerization (DP) of the insulating paper can be directly obtained from the above formula, and the aging status of the main insulation at the head of the equipment can be judged based on the degree of polymerization (DP). Therefore, the above formula is also applicable to other models of 220kV oil-immersed inverted current transformers. When the degree of polymerization of the insulating paper is between 1000 and 1200, the main insulation at the head is considered to be new insulating paper; when the degree of polymerization is between 650 and 1000, the main insulation at the head has excellent insulation performance; when the degree of polymerization is between 350 and 650, the main insulation at the head has medium insulation performance; and when the degree of polymerization is less than 350, the main insulation at the head is considered to be aged and needs to be decommissioned.

[0083] Through the above technical solutions, this invention fits the expressions for the complex dielectric constant of the overall main insulation and the head main insulation at different frequencies using the real and imaginary scatter points of the complex dielectric constant. During the fitting process, constraints (the condition of minimizing the overall error function and the head error function) are set, and the parameters of the expressions are continuously adjusted. The fitting stops when the constraints are met. The parameters obtained after the fitting are completed are used to calculate the evaluation index value of the uneven aging degree of the equipment and the degree of polymerization of the insulating paper, thereby evaluating the uneven aging degree of the main insulation and the aging condition of the head main insulation. This invention effectively conducts insulation aging evaluation for unevenly aged current transformers, and the constraint conditions make the evaluation results more accurate.

[0084] Example 2

[0085] Based on Embodiment 1, Embodiment 2 of the present invention also provides a system for evaluating the degree of uneven aging of an oil-immersed current transformer, comprising:

[0086] The first data acquisition module is used to obtain the real part and imaginary part of the complex dielectric constant of the overall main insulation of the equipment at different frequencies.

[0087] The second data acquisition module is used to acquire the real part and imaginary part of the complex dielectric constant of the main insulation of the equipment head at different frequencies.

[0088] The data fitting module is used to fit the expression for the complex dielectric constant of the overall main insulation of the equipment based on the real and imaginary scatter points of the complex dielectric constant at different frequencies using the HN dielectric relaxation model. Similarly, it fits the expression for the complex dielectric constant of the head insulation based on the real and imaginary scatter points of the complex dielectric constant at different frequencies using the HN dielectric relaxation model. It constructs an overall error function and a head error function, continuously adjusting the parameters in the expression for the overall main insulation complex dielectric constant until the overall error function is minimized, at which point the fitting stops, yielding the final expression for the overall main insulation complex dielectric constant and its corresponding parameters. The same module continuously adjusts the parameters in the expression for the head insulation complex dielectric constant until the head error function is minimized, yielding the final expression for the head insulation complex dielectric constant and its corresponding parameters.

[0089] The aging assessment module is used to calculate the evaluation index value of the equipment's uneven aging degree and the degree of polymerization of the insulating paper based on the parameters obtained by the data fitting module. The evaluation index value of the equipment's uneven aging degree is used to evaluate the uneven aging degree of the main insulation of the equipment, and the degree of polymerization of the insulating paper is used to evaluate the aging condition of the main insulation at the head of the equipment.

[0090] Specifically, the relationships between the real part scatter plot values ​​ε′1 and ε′2 of the complex dielectric constant of the main insulation of the equipment at different frequencies, and between the imaginary part scatter plot values ​​ε″1 and ε″2 of the complex dielectric constant of the main insulation of the equipment head at different frequencies, are as follows:

[0091]

[0092] Wherein, l1 and l2 are the average thicknesses of the main insulation paper and the head insulation paper of the equipment, respectively, and m1 and m2 are the masses of the main insulation paper and the head wrapping insulation paper, respectively.

[0093] More specifically, the method of fitting the expression for the complex dielectric constant of the overall main insulation using the HN dielectric relaxation model based on the real and imaginary scatter plot values ​​of the complex dielectric constant at different frequencies of the main insulation of the equipment head, and the method of fitting the expression for the complex dielectric constant of the main insulation of the equipment head using the HN dielectric relaxation model based on the real and imaginary scatter plot values ​​of the complex dielectric constant at different frequencies of the main insulation of the equipment head, includes:

[0094]

[0095] in, These are the overall main insulation complex dielectric constant and the head main insulation complex dielectric constant, respectively; τ m τ nThese are the overall main insulation relaxation time constant and the head main insulation relaxation time constant, respectively; ε s1 ε s2 These are the static dielectric constants of the overall main insulation and the head main insulation, respectively; ε ∞ α is the high-frequency dielectric constant; j is the imaginary unit; α m β m α represents the first and second shape parameters related to the relaxation time distribution within the overall main insulation HN relaxation model. n β n The third and fourth shape parameters are related to the relaxation time distribution within the HN relaxation model of the head main insulation.

[0096] More specifically, the real and imaginary parts of the overall primary insulation complex permittivity are separated to obtain the real part curve ε′ of the overall primary insulation complex permittivity. m and the imaginary part curve ε″ m The real part curve ε′ of the complex permittivity of the main head insulation is obtained by separating the real and imaginary parts of the complex permittivity. n and the imaginary part curve ε″ n .

[0097] More specifically, the construction of the overall error function and the head error function includes:

[0098]

[0099] Among them, S m S n These are the overall error function and the head error function, respectively.

[0100] More specifically, the calculation of the equipment's uneven aging degree assessment index value and the degree of polymerization of the insulating paper, using the equipment's uneven aging degree assessment index value to evaluate the degree of uneven aging of the equipment, and using the degree of polymerization of the insulating paper to evaluate the aging condition of the main insulation at the equipment head, includes:

[0101] Through formula Calculate the evaluation index value of the uneven aging degree of the equipment, where η is the evaluation index value of the uneven aging degree of the equipment;

[0102] When 1 < η ≤ 2.6, the main insulation of the equipment is judged to have slight uneven aging; when 2.6 < η ≤ 9.3, the main insulation of the equipment is judged to have moderate uneven aging; when η > 9.3, the main insulation of the equipment is judged to have severe uneven aging.

[0103] Through formula Calculate the degree of polymerization of the insulating paper, where Δε n =ε s2 -ε ∞ DP represents the degree of polymerization of the insulating paper;

[0104] When the degree of polymerization of the insulating paper is between 1000 and 1200, the main insulation at the head is considered to be new insulating paper. When the degree of polymerization of the insulating paper is between 650 and 1000, the main insulation at the head is considered to have excellent insulation performance. When the degree of polymerization of the insulating paper is between 350 and 650, the main insulation at the head is considered to have medium insulation performance. When the degree of polymerization of the insulating paper is less than 350, the main insulation at the head is considered to be aged and needs to be retired.

[0105] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of evaluating the degree of non-uniform aging of an oil-immersed current transformer, characterized by, Includes the following steps: Step 1: Obtain the real and imaginary scatter plot values ​​of the complex dielectric constant of the overall main insulation of the equipment at different frequencies; Step 2: Obtain the real and imaginary part scatter plot values ​​of the complex dielectric constant at different frequencies of the main insulation of the equipment head; Step 3: Based on the real and imaginary scatter plot values ​​of the complex dielectric constant of the overall main insulation at different frequencies, fit the expression for the complex dielectric constant of the overall main insulation using the HN dielectric relaxation model. Also, based on the real and imaginary scatter plot values ​​of the complex dielectric constant of the main insulation at different frequencies, fit the expression for the complex dielectric constant of the main insulation at the equipment head using the HN dielectric relaxation model, including: in, These are the overall main insulation complex dielectric constant and the head main insulation complex dielectric constant, respectively. These are the overall main insulation relaxation time constant and the head main insulation relaxation time constant, respectively. These are the static dielectric constants of the overall main insulation and the static dielectric constants of the head main insulation, respectively. It is the high-frequency dielectric constant; The imaginary unit; The first and second shape parameters are related to the relaxation time distribution within the overall main insulation HN relaxation model. The third and fourth shape parameters are related to the relaxation time distribution within the relaxation model of the head main insulation HN; Construct the overall error function and the head error function. During the fitting process, continuously adjust the parameters in the expression of the overall main insulation complex dielectric constant until the value of the overall error function is minimized, and stop fitting to obtain the final expression of the overall main insulation complex dielectric constant and the corresponding parameters. Continuously adjust the parameters in the expression of the head main insulation complex dielectric constant until the value of the head error function is minimized, and stop fitting to obtain the final expression of the head main insulation complex dielectric constant and the corresponding parameters. Step 4: Based on the parameters obtained in Step 3, calculate the evaluation index value of the equipment's uneven aging degree and the degree of polymerization of the insulating paper. Use the evaluation index value of the equipment's uneven aging degree to evaluate the overall uneven aging degree of the main insulation of the equipment, and use the degree of polymerization of the insulating paper to evaluate the aging condition of the main insulation at the head of the equipment. The device non-uniform aging degree evaluation index value is calculated by the formula The device non-uniform aging degree evaluation index value is calculated by the formula The device non-uniform aging degree evaluation index value is calculated by the formula when At that time, it was determined that the overall main insulation of the equipment had undergone slight uneven aging; when When the overall main insulation of the equipment is determined to have undergone moderate uneven aging; when At that time, it was determined that the overall main insulation of the equipment had undergone severe uneven aging; The insulation paper polymerization degree is calculated by the formula wherein, , DP is the insulation paper polymerization degree; When the degree of polymerization of the insulating paper is between 1000 and 1200, the main insulation at the head is considered to be new insulating paper. When the degree of polymerization of the insulating paper is between 650 and 1000, the main insulation at the head is considered to have excellent insulation performance. When the degree of polymerization of the insulating paper is between 350 and 650, the main insulation at the head is considered to have medium insulation performance. When the degree of polymerization of the insulating paper is less than 350, the main insulation at the head is considered to be aged and needs to be retired.

2. The method for evaluating the non-uniform aging degree of the oil-immersed current transformer according to claim 1, characterized in that, The real part scatter plot values ​​of the complex permittivity of the overall main insulation of the equipment at different frequencies. Scattered values ​​of the real part of the complex permittivity at different frequencies compared to the main insulation of the equipment head The relationship between the two and the scatter plot values ​​of the imaginary part of the complex permittivity of the overall main insulation of the equipment at different frequencies. Scattered values ​​of the imaginary part of the complex permittivity at different frequencies compared to the main insulation of the equipment head The relationship between them is as follows: wherein, l 1, l 2 are the average thicknesses of the insulation paper of the overall main insulation and of the head insulation, respectively, m 1, m 2 are the masses of the insulation paper of the overall main insulation and of the head wrapping insulation, respectively.

3. The method for evaluating the non-uniform aging degree of the oil-immersed current transformer according to claim 1, characterized in that, Separating the complex permittivity of the bulk main insulation into real and imaginary parts yields a curve of the real part of the complex permittivity of the bulk main insulation and a curve of the imaginary part Separating the complex permittivity of the head main insulation into real and imaginary parts yields a curve of the real part of the complex permittivity of the head main insulation and a curve of the imaginary part .

4. The method for evaluating the non-uniform aging degree of the oil-immersed current transformer according to claim 3, characterized in that, The construction of the overall error function and the head error function includes: wherein Etotai and Ehead are the overall error function and the head error function, respectively.

5. An evaluation system of non-uniform aging degree of an oil-immersed current transformer, characterized by, include: The first data acquisition module is used to obtain the real part and imaginary part of the complex dielectric constant of the overall main insulation of the equipment at different frequencies. The second data acquisition module is used to acquire the real part and imaginary part of the complex dielectric constant of the main insulation of the equipment head at different frequencies. The data fitting module is used to fit the expression for the complex dielectric constant of the overall main insulation using the HN dielectric relaxation model, based on the real and imaginary scatter plot values ​​of the complex dielectric constant at different frequencies of the main insulation of the equipment. It also fits the expression for the complex dielectric constant of the head insulation using the HN dielectric relaxation model, based on the real and imaginary scatter plot values ​​of the complex dielectric constant at different frequencies of the main insulation of the equipment head. This includes: in, These are the overall main insulation complex dielectric constant and the head main insulation complex dielectric constant, respectively. These are the overall main insulation relaxation time constant and the head main insulation relaxation time constant, respectively. These are the static dielectric constants of the overall main insulation and the static dielectric constants of the head main insulation, respectively. It is the high-frequency dielectric constant; The imaginary unit; The first and second shape parameters are related to the relaxation time distribution within the overall main insulation HN relaxation model. The third and fourth shape parameters are related to the relaxation time distribution within the relaxation model of the head main insulation HN; Construct the overall error function and the head error function. During the fitting process, continuously adjust the parameters in the expression of the overall main insulation complex dielectric constant until the value of the overall error function is minimized, and stop fitting to obtain the final expression of the overall main insulation complex dielectric constant and the corresponding parameters. Continuously adjust the parameters in the expression of the head main insulation complex dielectric constant until the value of the head error function is minimized, and stop fitting to obtain the final expression of the head main insulation complex dielectric constant and the corresponding parameters. The aging assessment module is used to calculate the evaluation index value of the equipment's uneven aging degree and the degree of polymerization of the insulating paper based on the parameters obtained by the data fitting module. The evaluation index value of the equipment's uneven aging degree is used to evaluate the overall uneven aging degree of the main insulation of the equipment, and the degree of polymerization of the insulating paper is used to evaluate the aging condition of the main insulation at the head of the equipment. Through formula The evaluation index value for the uneven aging degree of the calculation equipment is as follows: The value is used to assess the degree of uneven aging of equipment. When the device overall main insulation occurs slight uneven aging; when the device overall main insulation occurs moderate uneven aging; when the device overall main insulation occurs serious uneven aging; The insulation paper polymerization degree is calculated by the formula wherein, , DP is the insulation paper polymerization degree; When the degree of polymerization of the insulating paper is between 1000 and 1200, the main insulation at the head is considered to be new insulating paper. When the degree of polymerization of the insulating paper is between 650 and 1000, the main insulation at the head is considered to have excellent insulation performance. When the degree of polymerization of the insulating paper is between 350 and 650, the main insulation at the head is considered to have medium insulation performance. When the degree of polymerization of the insulating paper is less than 350, the main insulation at the head is considered to be aged and needs to be retired.

6. The system for evaluating the degree of non-uniform aging of an oil-immersed current transformer according to claim 5, characterized in that, The real part scatter plot values ​​of the complex permittivity of the overall main insulation of the equipment at different frequencies. Scattered values ​​of the real part of the complex permittivity at different frequencies compared to the main insulation of the equipment head The relationship between the two and the scatter plot values ​​of the imaginary part of the complex permittivity of the overall main insulation of the equipment at different frequencies. Scattered values ​​of the imaginary part of the complex permittivity at different frequencies compared to the main insulation of the equipment head The relationship between them is as follows: in, l 1. l 2 represents the average thickness of the main insulation paper and the head insulation paper of the entire equipment. m 1. m 2 refers to the quality of the overall main insulation and the head wrapping insulation paper, respectively.

7. The system for evaluating the degree of non-uniform aging of an oil-immersed current transformer according to claim 5, characterized in that, The real part curve of the overall main insulation complex permittivity is obtained by separating the real and imaginary parts of the overall main insulation complex permittivity. and imaginary curve The real part curve of the complex permittivity of the main head insulation is obtained by separating the real and imaginary parts of the complex permittivity. and imaginary curve .

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