Method and system for evaluating non-uniform aging degree of oil-immersed current transformer

Abstract

The invention discloses a method and a system for evaluating the non-uniform aging degree of an oil-immersed current transformer. The method comprises the following steps: acquiring real part scatter point values and imaginary part scatter point values of complex dielectric constants of overall main insulation of equipment under different frequencies; acquiring real part scatter values and imaginary part scatter values of complex dielectric constants of main insulation of the head of the equipment under different frequencies; fitting an expression of an overall major insulation complex dielectric constant by using an HN dielectric relaxation model, and fitting an expression of a head major insulation complex dielectric constant by using the HN dielectric relaxation model; in the fitting process, parameters are continuously adjusted until the value of the overall error function and the value of the head error function are minimum, fitting is stopped, and corresponding parameters are obtained; evaluating the non-uniform aging degree of the equipment main insulation and the aging condition of the equipment head main insulation; the method has the advantages that insulation aging evaluation is effectively carried out for the non-uniformly aged current transformer, and the evaluation result is more accurate.

Description

Technical Field

[0001] The invention relates to the field of current transformer insulation aging assessment, and in particular to a method and system for assessing the uneven aging degree of an oil-immersed current transformer. Background Art

[0002] As an important component of power infrastructure, current transformers play an important role in measurement and protection. During long-term operation, due to the combined effects of electrical, thermal, mechanical, chemical and other stresses, the insulation strength of current transformers will continue to decline, thus causing failures. At present, most oil-immersed current transformers at home and abroad have been in service for 20 to 30 years. The insulation status of such equipment and whether it can continue to operate are urgent issues that power managers need to solve. Therefore, it is very necessary to perform insulation diagnosis and aging status detection on current transformers.

[0003] Due to its special structure, the main insulation of the head of the oil-immersed inverted current transformer is more prone to aging than other main insulation parts after long-term operation. For example, the "Technical Specifications for Current Transformers for Power Use in Special Environments" published by standard number DB 65 / T 4665-2023 records the connection diagram of the end-screen insulation frequency domain dielectric response test. However, the end-screen insulation frequency domain dielectric response can only generally measure the overall main insulation status of the equipment. It is impossible to effectively carry out insulation aging assessment for current transformers with uneven aging. In addition, during the analysis process using the HN relaxation model, the fitting effect of the dielectric spectrum is often poor, resulting in inaccurate evaluation results. Summary of the invention

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

[0005] The present invention solves the above technical problems by the following technical means: A method for evaluating the uneven aging degree of an oil-immersed current transformer comprises the following steps:

[0006] Step 1, obtaining the real part scatter point value and the imaginary part scatter point value of the complex dielectric constant of the overall main insulation of the equipment at different frequencies;

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

[0008] Step three, based on the real and imaginary scatter values ​​of the complex dielectric constant of the overall main insulation of the equipment at different frequencies, use the HN dielectric relaxation model to fit the expression of the complex dielectric constant of the overall main insulation, based on the real and imaginary scatter values ​​of the complex dielectric constant of the main insulation of the head of the equipment at different frequencies, use the HN dielectric relaxation model to fit the expression of the complex dielectric constant of the head main insulation; construct an overall error function and a head error function, continuously adjust the parameters in the expression of the complex dielectric constant of the overall main insulation during the fitting process until the value of the overall error function is minimized, stop fitting to obtain the final expression of the complex dielectric constant of the overall main insulation and the corresponding parameters, continuously adjust the parameters in the expression of the complex dielectric constant of the head main insulation until the value of the head error function is minimized, stop fitting to obtain the final expression of the complex dielectric constant of the head main insulation and the corresponding parameters;

[0009] Step 4: Calculate the equipment uneven aging evaluation index value and the insulation paper polymerization degree based on the parameters obtained in step 3, use the equipment uneven aging evaluation index value to evaluate the uneven aging degree of the equipment main insulation, and use the insulation paper polymerization degree to evaluate the aging of the main insulation of the equipment head.

[0010] Furthermore, the real part of the complex dielectric constant of the main insulation of the equipment at different frequencies is scattered point value ε′ 1 Scattered values ​​of the real part of the complex dielectric constant ε″ at different frequencies from the main insulation of the equipment head 2 and the scatter value of the imaginary part of the complex dielectric constant ε″ at different frequencies of the main insulation of the equipment 1 Scattered values ​​of the imaginary part of the complex dielectric constant ε″ at different frequencies from the main insulation of the equipment head 2 The relationship between

[0011]

[0012] Among them, l 1 , l 2 They are the average thickness of the main insulation paper and the head insulation paper of the equipment, m 1 、m 2 They are the mass of the overall main insulation and the head-wrapped insulation paper respectively.

[0013] Furthermore, the expression of the complex dielectric constant of the overall main insulation is fitted by the HN dielectric relaxation model based on the real part scatter point values ​​and the imaginary part scatter point values ​​of the complex dielectric constant of the overall main insulation of the equipment at different frequencies, and the expression of the complex dielectric constant of the head main insulation is fitted by the HN dielectric relaxation model based on the real part scatter point values ​​and the imaginary part scatter point values ​​of the complex dielectric constant of the head main insulation of the equipment at different frequencies, including:

[0014]

[0015] in, are the complex dielectric constants of the overall main insulation and the head main insulation respectively; τ m , τ n are the overall main insulation relaxation time constant and the head main insulation relaxation time constant respectively; ε s1 , ε s2 They are the static dielectric constant of the overall main insulation and the static dielectric constant of the head main insulation respectively; ε ∞ is the high frequency dielectric constant; j is the imaginary unit; α m , β m are the first and second shape parameters related to the relaxation time distribution in the overall main insulation HN relaxation model, α n , β n are the third and fourth shape parameters related to the relaxation time distribution within the head main insulation HN relaxation model.

[0016] Furthermore, the real part and imaginary part of the complex dielectric constant of the overall main insulation are separated to obtain the real part curve ε′ of the complex dielectric constant of the overall main insulation m and the imaginary part curve ε″ m ; Separate the real and imaginary parts of the complex dielectric constant of the main insulation of the head to obtain the real part curve ε′ of the complex dielectric constant of the main insulation of the head n and the imaginary part curve ε″ n .

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

[0018]

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

[0020] Furthermore, the calculation of the equipment uneven aging evaluation index value and the insulation paper polymerization degree, using the equipment uneven aging evaluation index value to evaluate the equipment uneven aging degree, and using the insulation paper polymerization degree to evaluate the aging of the main insulation of the equipment head, includes:

[0021] By formula Calculate the equipment non-uniform aging degree evaluation index value, where η is the equipment non-uniform aging degree evaluation index value;

[0022] When 1<η≤2.6, it is determined that the main insulation of the equipment has slightly uneven aging; when 2.6<η≤9.3, it is determined that the main insulation of the equipment has moderately uneven aging; when η>9.3, it is determined that the main insulation of the equipment has severely uneven aging;

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

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

[0025] The present invention also provides an evaluation system for the uneven aging degree of an oil-immersed current transformer, comprising:

[0026] The first data acquisition module is used to obtain the real part scatter point value and the imaginary part scatter point value 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 obtain the real part scatter point value and the imaginary part scatter point value of the complex dielectric constant of the main insulation of the equipment head at different frequencies;

[0028] A data fitting module is used to fit the expression of the complex dielectric constant of the overall main insulation based on the real and imaginary scatter values ​​of the complex dielectric constant at different frequencies of the overall main insulation of the equipment using the HN dielectric relaxation model, and fit the expression of the complex dielectric constant of the head main insulation based on the real and imaginary scatter values ​​of the complex dielectric constant at different frequencies of the main insulation of the head of the equipment using the HN dielectric relaxation model; construct an overall error function and a head error function, and during the fitting process, continuously adjust the parameters in the expression of the complex dielectric constant of the overall main insulation until the value of the overall error function is minimized, and stop fitting to obtain the final expression of the complex dielectric constant of the overall main insulation and the corresponding parameters, and continuously adjust the parameters in the expression of the complex dielectric constant of the head main insulation until the value of the head error function is minimized, and stop fitting to obtain the final expression of the complex dielectric constant of the head main insulation and the corresponding parameters;

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

[0030] Furthermore, the real part of the complex dielectric constant of the main insulation of the equipment at different frequencies is scattered point value ε′ 1 Scattered values ​​of the real part of the complex dielectric constant ε′ at different frequencies from the main insulation of the equipment head 2 and the scatter value of the imaginary part of the complex dielectric constant ε″ at different frequencies of the main insulation of the equipment1 Scattered values ​​of the imaginary part of the complex dielectric constant ε″ at different frequencies from the main insulation of the equipment head 2 The relationship between

[0031]

[0032] Among them, l 1 , l 2 They are the average thickness of the main insulation paper and the head insulation paper of the equipment, m 1 、m 2 They are the mass of the overall main insulation and the head-wrapped insulation paper respectively.

[0033] Furthermore, the expression of the complex dielectric constant of the overall main insulation is fitted by the HN dielectric relaxation model based on the real part scatter point values ​​and the imaginary part scatter point values ​​of the complex dielectric constant of the overall main insulation of the equipment at different frequencies, and the expression of the complex dielectric constant of the head main insulation is fitted by the HN dielectric relaxation model based on the real part scatter point values ​​and the imaginary part scatter point values ​​of the complex dielectric constant of the head main insulation of the equipment at different frequencies, including:

[0034]

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

[0036] Furthermore, the real part and imaginary part of the complex dielectric constant of the overall main insulation are separated to obtain the real part curve ε′ of the complex dielectric constant of the overall main insulation m and the imaginary part curve ε″ m ; Separate the real and imaginary parts of the complex dielectric constant of the main insulation of the head to obtain the real part curve ε′ of the complex dielectric constant of the main insulation of the head n and the imaginary part curve ε″ n .

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

[0038]

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

[0040] Furthermore, the calculation of the equipment uneven aging evaluation index value and the insulation paper polymerization degree, using the equipment uneven aging evaluation index value to evaluate the equipment uneven aging degree, and using the insulation paper polymerization degree to evaluate the aging of the main insulation of the equipment head, includes:

[0041] By formula Calculate the equipment non-uniform aging degree evaluation index value, where η is the equipment non-uniform aging degree evaluation index value;

[0042] When 1<η≤2.6, it is determined that the main insulation of the equipment has slightly uneven aging; when 2.6<η≤9.3, it is determined that the main insulation of the equipment has moderately uneven aging; when η>9.3, it is determined that the main insulation of the equipment has severely uneven aging;

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

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

[0045] The advantages of the present invention are:

[0046] (1) The present invention fits the expression of the complex dielectric constant of the overall main insulation and the expression of the complex dielectric constant of the head main insulation based on the real part scatter value and the imaginary part scatter value of the complex dielectric constant of the overall main insulation of the equipment and the head main insulation of the equipment at different frequencies. In the fitting process, constraint conditions (conditions for minimizing the overall error function and the head error function) are set to continuously adjust the parameters of the expression, and the fitting is stopped when the constraint conditions are met. The parameters obtained after the fitting are used to calculate the evaluation index value of the uneven aging degree of the equipment and the polymerization degree of the insulation paper, thereby evaluating the uneven aging degree of the main insulation of the equipment and the aging of the main insulation of the head of the equipment, and effectively carrying out insulation aging evaluation for the current transformer with uneven aging, and setting the constraint conditions makes the evaluation result more accurate.

[0047] (2) The present invention conducts a dielectric response test on the current transformer, obtains the overall frequency domain dielectric spectrum of the equipment and separates the real part and the imaginary part of the relative dielectric constant, calculates the relative dielectric constants of the head main insulation and the overall main insulation equivalently, and then adds restriction conditions (overall error function and head error function) on the basis of the HN model to obtain relevant electrical characteristic quantities, judge the degree of uneven aging of the main insulation, and achieve insulation aging evaluation of the oil-immersed inverted current transformer for uneven aging of the main insulation head.

[0048] (3) The entire scheme of the present invention adds constraints on the basis of the HN model to make the evaluation result more accurate. Compared with the traditional method, it can more accurately analyze the working status of the current transformer and more accurately judge the degree of uneven aging of the current transformer. It optimizes the traditional detection method and saves manpower. On the basis of meeting the current transformer aging detection, it achieves high efficiency and improves the reliability of equipment operation. While ensuring the economy, it can improve the evaluation accuracy to a certain extent and maximize the economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 The present invention is a flowchart of a method for evaluating the uneven aging degree of an oil-immersed current transformer disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work 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, the relationship between the complex dielectric constant of the head main insulation and the overall main insulation is obtained on the basis of experiments 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 scatter point value and imaginary part scatter point value of the complex dielectric constant of the overall main insulation of the equipment at different frequencies;

[0054] S2. Obtain the real part scatter point value and imaginary part scatter point value of the complex dielectric constant of the main insulation of the equipment head at different frequencies; the specific process of S1 and S2 is as follows:

[0055] This embodiment first develops a real model of a 220kV inverted oil-immersed current transformer, leads a test wire from the connection between the main insulating ring and the straight section, and extends it to the outside of the current transformer at the top of the expander. The primary guide rod of the prototype is short-circuited, the secondary coil is pressurized and current is passed, and the prototype is heated by electromagnetic induction to make the temperature of the oil storage cabinet on the prototype reach 120°C, and the internal heating temperature is monitored by a thermocouple placed inside the transformer.

[0056] Using the dielectric response tester IDAX-300, the measurement frequency is set to 1mHz-1kHz, and the periodic dielectric response test of the head main insulation and the overall main insulation is carried out through the test wires reserved in the prototype to obtain the overall complex dielectric constant ε of the prototype at different aging stages. 1 and the complex dielectric constant ε of the prototype head 2 The real part of the complex dielectric constant of the main insulation of the prototype (ie, equipment) at different frequencies is derived by the instrument. 1 、The imaginary part of the complex dielectric constant of the main insulation of the equipment at different frequencies ε″ 1 , the scattered value of the real part of the complex dielectric constant of the main insulation of the equipment head at different frequencies ε′ 2 、The scattered value of the imaginary part of the complex dielectric constant of the main insulation of the equipment head at different frequencies ε″ 2 By comparing and analyzing the complex dielectric constants of the prototype as a whole and the prototype head with the main insulation parameters of the designed prototype, it is confirmed that their quantitative relationship is as shown in the following formula:

[0057]

[0058] Among them, l 1 , l 2 The average thickness of the main insulation paper and the head insulation paper of the equipment, in millimeters (mm); m 1 、m 2 They are respectively the mass of the overall main insulation and the head-wrapped insulation paper, in kilograms (kg).

[0059] Considering that it is not easy to directly sample the main insulation paper of the current transformer, and the oil storage cabinet of the 220kV oil-immersed inverted current transformer is small and cannot hold enough paper sample packages, the insulation paper of the same model as the main insulation is bundled into packages and placed in an oil-immersed sealed tank, and then placed in an oven and heated at the same temperature of 120°C as the head of the prototype. After each test cycle of the dielectric response, the insulation paper in the sealed tank is extracted for physical and chemical testing to obtain the degree of polymerization DP of the insulation paper, which is equivalent to the degree of polymerization of the insulation paper of the main insulation head of the current transformer. The degree of polymerization DP of the insulation paper is used in the subsequent step S4 and will not be repeated here.

[0060] S3. Based on the real and imaginary scatter values ​​of the complex dielectric constant of the overall main insulation of the equipment at different frequencies, the HN dielectric relaxation model is used to fit the expression of the complex dielectric constant of the overall main insulation. Based on the real and imaginary scatter values ​​of the complex dielectric constant of the main insulation of the head of the equipment at different frequencies, the HN dielectric relaxation model is used to fit the expression of the complex dielectric constant of the head main insulation; the overall error function and the head error function are constructed, and the parameters in the expression of the complex dielectric constant of the overall main insulation are continuously adjusted during the fitting process until the value of the overall error function is minimized, and the fitting is stopped to obtain the final expression of the complex dielectric constant of the overall main insulation and the corresponding parameters. The parameters in the expression of the complex dielectric constant of the head main insulation are continuously adjusted until the value of the head error function is minimized, and the fitting is stopped to obtain the final expression of the complex dielectric constant of the head main insulation and the corresponding parameters; the specific process is as follows:

[0061] The Havriliak–Negami (HN) dielectric relaxation model is used to express the complex dielectric constant of the entire and head main insulation as a function of the angular frequency ω, which is expressed as follows:

[0062]

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

[0064] The real part and imaginary part of the complex dielectric constant of the overall main insulation are separated to obtain the real part curve ε′ of the complex dielectric constant of the overall main insulation m and the imaginary part curve ε″ m ; Separate the real and imaginary parts of the complex dielectric constant of the main insulation of the head to obtain the real part curve ε′ of the complex dielectric constant of the main insulation of the head n and the imaginary part curve ε″ n , the relevant formula is as follows:

[0065]

[0066] The intermediate quantity

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

[0068] The above formula is just the real part curve ε′ of the complex dielectric constant of the overall main insulation m and the imaginary part curve ε″ m 、Real part curve of complex dielectric constant of head main insulation ε′ n and the imaginary part curve ε″ n The general calculation formula is: if you want to calculate the real part curve ε′ of the complex dielectric constant of the overall main insulation in practical applications m and the imaginary part curve ε″ m Then add m to the subscript in the above formula. If you want to calculate the real part curve of the complex dielectric constant of the head main insulation ε′ n and the imaginary part curve ε″ n Then add n to the subscript in the above formula, and the formula is as follows:

[0069]

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

[0071]

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

[0073] On the basis of the Havriliak–Negami dielectric relaxation model, the overall error function and the head error function are added to facilitate more accurate fitting of the real and imaginary curves of the complex dielectric constants of the overall main insulation and the head main insulation. The formulas of the overall error function and the head error function are as follows:

[0074]

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

[0076] S4. Calculate the equipment uneven aging evaluation index value and the insulation paper polymerization degree based on the parameters obtained in S3. Use the equipment uneven aging evaluation index value to evaluate the uneven aging degree of the equipment main insulation. Use the insulation paper polymerization degree to evaluate the aging of the main insulation of the equipment head. The specific process is as follows:

[0077] Under the above-mentioned restriction of S3, the real part curve of the complex dielectric constant ε′ of the overall main insulation is obtained by fitting the measured dielectric spectrum curve with the HN model. m , imaginary part curve ε″ m , real part curve of complex dielectric constant of head main insulation ε′ n , imaginary part curve ε″ n After reconstructing the real and imaginary curves of the complex dielectric constants of the two, the overall main 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 the formula Calculate the equipment uneven aging evaluation index value, where η is the equipment uneven aging evaluation index value. The larger the η value, the deeper the uneven degree of the equipment. When 1<η≤2.6, it is determined that the main insulation of the equipment has slightly uneven aging; when 2.6<η≤9.3, it is determined that the main insulation of the equipment has moderate uneven aging; when η>9.3, it is determined that the main insulation of the equipment has severely uneven aging.

[0078] Then, the formula to be fitted between the degree of polymerization DP of the insulation paper and the characteristic quantity of the main insulation at the head is established, and the specific formula is obtained by fitting using the least squares method. According to the degree of polymerization DP of the insulation paper, the aging of the insulation paper at the head of the main insulation is judged, and the degree of aging of the equipment is evaluated. The formula to be fitted is as follows:

[0079]

[0080] Among them, k 0 , k 1 , k 2 These are the coefficients to be fitted in the above formula. After fitting is completed, k 0 , k 1 , k 2 They are 0.97, 4.22 and 1.28 respectively, so the final fitting formula is as follows:

[0081]

[0082] Therefore, in practical applications, the degree of polymerization DP of the insulating paper of any device can be directly obtained according to the above relationship, so as to judge the aging of the head main insulation of the equipment according to the degree of polymerization DP of the insulating paper. Therefore, the above formula is also applicable to other types of 220kV oil-immersed inverted current transformers. When the degree of polymerization of the insulating paper is between 1000 and 1200, the head main insulation is judged to be new insulating paper; when the degree of polymerization of the insulating paper is between 650 and 1000, the head main insulation is judged to have excellent insulation performance; when the degree of polymerization of the insulating paper is between 350 and 650, the head main insulation is judged to have medium insulation performance; when the degree of polymerization of the insulating paper is less than 350, the head main insulation is judged to be aged and needs to be retired.

[0083] Through the above technical scheme, the present invention fits the expression of the complex dielectric constant of the overall main insulation and the expression of the complex dielectric constant of the head main insulation based on the real part scatter point values ​​and the imaginary part scatter point values ​​of the complex dielectric constant of the overall main insulation of the equipment and the main insulation of the head of the equipment at different frequencies. In the fitting process, constraints (conditions for minimizing the overall error function and the head error function) are set to continuously adjust the parameters of the expression, and the fitting is stopped when the constraints are met. The parameters obtained after the fitting are used to calculate the equipment uneven aging degree evaluation index value and the insulation paper polymerization degree, thereby evaluating the uneven aging degree of the main insulation of the equipment and the aging of the main insulation of the head of the equipment, effectively carrying out insulation aging evaluation for unevenly aged current transformers, and setting constraints makes the evaluation results more accurate.

[0084] Example 2

[0085] Based on Example 1, Example 2 of the present invention further provides an evaluation system for the uneven aging degree of an oil-immersed current transformer, comprising:

[0086] The first data acquisition module is used to obtain the real part scatter point value and the imaginary part scatter point value 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 obtain the real part scatter point value and the imaginary part scatter point value of the complex dielectric constant of the main insulation of the equipment head at different frequencies;

[0088] A data fitting module is used to fit the expression of the complex dielectric constant of the overall main insulation based on the real and imaginary scatter values ​​of the complex dielectric constant at different frequencies of the overall main insulation of the equipment using the HN dielectric relaxation model, and fit the expression of the complex dielectric constant of the head main insulation based on the real and imaginary scatter values ​​of the complex dielectric constant at different frequencies of the main insulation of the head of the equipment using the HN dielectric relaxation model; construct an overall error function and a head error function, and during the fitting process, continuously adjust the parameters in the expression of the complex dielectric constant of the overall main insulation until the value of the overall error function is minimized, and stop fitting to obtain the final expression of the complex dielectric constant of the overall main insulation and the corresponding parameters, and continuously adjust the parameters in the expression of the complex dielectric constant of the head main insulation until the value of the head error function is minimized, and stop fitting to obtain the final expression of the complex dielectric constant of the head main insulation and the corresponding parameters;

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

[0090] Specifically, the real part of the complex dielectric constant of the main insulation of the equipment at different frequencies is ε′ 1 Scattered values ​​of the real part of the complex dielectric constant ε′ at different frequencies from the main insulation of the equipment head 2 and the scatter value of the imaginary part of the complex dielectric constant ε″ at different frequencies of the main insulation of the equipment 1 Scattered values ​​of the imaginary part of the complex dielectric constant ε″ at different frequencies from the main insulation of the equipment head 2 The relationship between

[0091]

[0092] Among them, l 1 , l 2 They are the average thickness of the main insulation paper and the head insulation paper of the equipment, m 1 、m 2 They are the mass of the overall main insulation and the head-wrapped insulation paper respectively.

[0093] More specifically, the expression of the complex dielectric constant of the overall main insulation is fitted using the HN dielectric relaxation model based on the real part scatter point values ​​and the imaginary part scatter point values ​​of the complex dielectric constant of the overall main insulation of the equipment at different frequencies, and the expression of the complex dielectric constant of the head main insulation is fitted using the HN dielectric relaxation model based on the real part scatter point values ​​and the imaginary part scatter point values ​​of the complex dielectric constant of the head main insulation of the equipment at different frequencies, including:

[0094]

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

[0096] More specifically, the real part and imaginary part of the complex dielectric constant of the overall main insulation are separated to obtain the real part curve ε′ of the complex dielectric constant of the overall main insulation m and the imaginary part curve ε″ m ; Separate the real and imaginary parts of the complex dielectric constant of the main insulation of the head to obtain the real part curve ε′ of the complex dielectric constant of the main insulation of the head n and the imaginary part curve ε″ n .

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

[0098]

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

[0100] More specifically, the calculation of the equipment uneven aging evaluation index value and the insulation paper polymerization degree, the evaluation of the equipment uneven aging degree using the equipment uneven aging evaluation index value, and the evaluation of the aging of the main insulation of the equipment head using the insulation paper polymerization degree include:

[0101] By formula Calculate the equipment non-uniform aging degree evaluation index value, where η is the equipment non-uniform aging degree evaluation index value;

[0102] When 1<η≤2.6, it is determined that the main insulation of the equipment has slightly uneven aging; when 2.6<η≤9.3, it is determined that the main insulation of the equipment has moderately uneven aging; when η>9.3, it is determined that the main insulation of the equipment has severely uneven aging;

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

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

[0105] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for evaluating the uneven aging degree of an oil-immersed current transformer, characterized in that: The following steps are involved: Step 1, obtaining the real part scatter point value and the imaginary part scatter point value of the complex dielectric constant of the overall main insulation of the equipment at different frequencies; Step 2: Obtain the real part scatter point value and the imaginary part scatter point value of the complex dielectric constant of the main insulation of the equipment head at different frequencies; Step three, based on the real and imaginary scatter values ​​of the complex dielectric constant of the overall main insulation of the equipment at different frequencies, use the HN dielectric relaxation model to fit the expression of the complex dielectric constant of the overall main insulation, based on the real and imaginary scatter values ​​of the complex dielectric constant of the main insulation of the head of the equipment at different frequencies, use the HN dielectric relaxation model to fit the expression of the complex dielectric constant of the head main insulation; construct an overall error function and a head error function, continuously adjust the parameters in the expression of the complex dielectric constant of the overall main insulation during the fitting process until the value of the overall error function is minimized, stop fitting to obtain the final expression of the complex dielectric constant of the overall main insulation and the corresponding parameters, continuously adjust the parameters in the expression of the complex dielectric constant of the head main insulation until the value of the head error function is minimized, stop fitting to obtain the final expression of the complex dielectric constant of the head main insulation and the corresponding parameters; Step 4: Calculate the equipment uneven aging evaluation index value and the insulation paper polymerization degree based on the parameters obtained in step 3, use the equipment uneven aging evaluation index value to evaluate the uneven aging degree of the equipment main insulation, and use the insulation paper polymerization degree to evaluate the aging of the main insulation of the equipment head.

2. The method for evaluating the uneven aging degree of an oil-immersed current transformer according to claim 1, characterized in that: The relationship between the real part scatter value ε′1 of the complex dielectric constant of the main insulation of the equipment at different frequencies and the real part scatter value ε′2 of the complex dielectric constant of the main insulation of the equipment head at different frequencies, and the relationship between the imaginary part scatter value ε″1 of the complex dielectric constant of the main insulation of the equipment at different frequencies and the imaginary part scatter value ε″2 of the complex dielectric constant of the main insulation of the equipment head at different frequencies are as follows: Among them, l1 and l2 are the average thickness of the main insulation paper and head insulation paper of the equipment, respectively, and m1 and m2 are the masses of the main insulation and head wrapping insulation paper of the equipment, respectively.

3. The method for evaluating the uneven aging degree of an oil-immersed current transformer according to claim 2, characterized in that: The expression of fitting the complex dielectric constant of the overall main insulation by using the HN dielectric relaxation model based on the real part scatter point values ​​and the imaginary part scatter point values ​​of the complex dielectric constant of the overall main insulation of the equipment at different frequencies, and the expression of fitting the complex dielectric constant of the head main insulation by using the HN dielectric relaxation model based on the real part scatter point values ​​and the imaginary part scatter point values ​​of the complex dielectric constant of the head main insulation of the equipment at different frequencies, include: in, are the complex dielectric constants of the overall main insulation and the head main insulation respectively; τ m , τ n are the overall main insulation relaxation time constant and the head main insulation relaxation time constant respectively; ε s1 , ε s2 They are the static dielectric constant of the overall main insulation and the static dielectric constant of the head main insulation respectively; ε ∞ is the high frequency dielectric constant; j is the imaginary unit; α m , β m are the first and second shape parameters related to the relaxation time distribution in the overall main insulation HN relaxation model, α n , β n are the third and fourth shape parameters related to the relaxation time distribution within the head main insulation HN relaxation model.

4. The method for evaluating the uneven aging degree of an oil-immersed current transformer according to claim 3, characterized in that: The real part and imaginary part of the complex dielectric constant of the overall main insulation are separated to obtain the real part curve ε′ of the complex dielectric constant of the overall main insulation m and the imaginary part curve ε″ m ; Separate the real and imaginary parts of the complex dielectric constant of the main insulation of the head to obtain the real part curve ε′ of the complex dielectric constant of the main insulation of the head n and the imaginary part curve ε″ n .

5. The method for evaluating the uneven aging degree of an oil-immersed current transformer according to claim 4, characterized in that: The constructing of the overall error function and the head error function comprises: Among them, S m , S n They are the overall error function and the head error function respectively.

6. The method for evaluating the uneven aging degree of an oil-immersed current transformer according to claim 5, characterized in that: The method of calculating the uneven aging evaluation index value of the equipment and the polymerization degree of the insulation paper, evaluating the uneven aging degree of the equipment by using the uneven aging evaluation index value of the equipment, and evaluating the aging of the main insulation of the equipment head by using the polymerization degree of the insulation paper includes: By formula Calculate the equipment non-uniform aging degree evaluation index value, where η is the equipment non-uniform aging degree evaluation index value; When 1<η≤2.6, it is determined that the main insulation of the equipment has slightly unevenly aged; when 2.6<η≤9.3, it is determined that the main insulation of the equipment has moderately unevenly aged; when η>9.3, it is determined that the main insulation of the equipment has severely unevenly aged; By formula Calculate the degree of polymerization of insulating paper, where Δε n =ε s2 -ε ∞ , DP is the degree of polymerization of insulating paper; When the degree of polymerization of the insulation paper is between 1000 and 1200, the main insulation of the head is judged to be new insulation paper; when the degree of polymerization of the insulation paper is between 650 and 1000, the main insulation of the head is judged to have excellent insulation performance; when the degree of polymerization of the insulation paper is between 350 and 650, the main insulation of the head is judged to have medium insulation performance; when the degree of polymerization of the insulation paper is less than 350, the main insulation of the head is judged to be aged and needs to be retired.

7. A system for evaluating the uneven aging degree of an oil-immersed current transformer, characterized in that: include: The first data acquisition module is used to obtain the real part scatter point value and the imaginary part scatter point value of the complex dielectric constant of the overall main insulation of the equipment at different frequencies; The second data acquisition module is used to obtain the real part scatter point value and the imaginary part scatter point value of the complex dielectric constant of the main insulation of the equipment head at different frequencies; A data fitting module is used to fit the expression of the complex dielectric constant of the overall main insulation based on the real and imaginary scatter values ​​of the complex dielectric constant at different frequencies of the overall main insulation of the equipment using the HN dielectric relaxation model, and fit the expression of the complex dielectric constant of the head main insulation based on the real and imaginary scatter values ​​of the complex dielectric constant at different frequencies of the main insulation of the head of the equipment using the HN dielectric relaxation model; construct an overall error function and a head error function, and during the fitting process, continuously adjust the parameters in the expression of the complex dielectric constant of the overall main insulation until the value of the overall error function is minimized, and stop fitting to obtain the final expression of the complex dielectric constant of the overall main insulation and the corresponding parameters, and continuously adjust the parameters in the expression of the complex dielectric constant of the head main insulation until the value of the head error function is minimized, and stop fitting to obtain the final expression of the complex dielectric constant of the head main insulation and the corresponding parameters; The aging assessment module is used to calculate the equipment uneven aging assessment index value and the insulation paper polymerization degree based on the parameters obtained by the data fitting module, use the equipment uneven aging assessment index value to evaluate the uneven aging degree of the equipment main insulation, and use the insulation paper polymerization degree to evaluate the aging of the equipment head main insulation.

8. The system for evaluating the uneven aging degree of an oil-immersed current transformer according to claim 7, characterized in that: The relationship between the real part scatter value ε′1 of the complex dielectric constant of the main insulation of the equipment at different frequencies and the real part scatter value ε′2 of the complex dielectric constant of the main insulation of the equipment head at different frequencies, and the relationship between the imaginary part scatter value ε″1 of the complex dielectric constant of the main insulation of the equipment at different frequencies and the imaginary part scatter value ε″2 of the complex dielectric constant of the main insulation of the equipment head at different frequencies are as follows: Among them, l1 and l2 are the average thickness of the main insulation paper and head insulation paper of the equipment, respectively, and m1 and m2 are the masses of the main insulation and head wrapping insulation paper of the equipment, respectively.

9. The system for evaluating the uneven aging degree of an oil-immersed current transformer according to claim 8, characterized in that: The expression of fitting the complex dielectric constant of the overall main insulation by using the HN dielectric relaxation model based on the real part scatter point values ​​and the imaginary part scatter point values ​​of the complex dielectric constant of the overall main insulation of the equipment at different frequencies, and the expression of fitting the complex dielectric constant of the head main insulation by using the HN dielectric relaxation model based on the real part scatter point values ​​and the imaginary part scatter point values ​​of the complex dielectric constant of the head main insulation of the equipment at different frequencies, include: in, are the complex dielectric constants of the overall main insulation and the head main insulation respectively; τ m , τ n are the overall main insulation relaxation time constant and the head main insulation relaxation time constant respectively; ε s1 , ε s2 They are the static dielectric constant of the overall main insulation and the static dielectric constant of the head main insulation respectively; ε ∞ is the high frequency dielectric constant; j is the imaginary unit; α m , β m are the first and second shape parameters related to the relaxation time distribution in the overall main insulation HN relaxation model, α n , β n are the third and fourth shape parameters related to the relaxation time distribution within the head main insulation HN relaxation model.

10. The system for evaluating the uneven aging degree of an oil-immersed current transformer according to claim 9, characterized in that: The real part and imaginary part of the complex dielectric constant of the overall main insulation are separated to obtain the real part curve ε′ of the complex dielectric constant of the overall main insulation m and the imaginary part curve ε″ m ; Separate the real and imaginary parts of the complex dielectric constant of the main insulation of the head to obtain the real part curve ε′ of the complex dielectric constant of the main insulation of the head n and the imaginary part curve ε″ n .

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