Method for obtaining correction coefficient in inverse power electrical lifetime model based on E-eta characteristic method

Abstract

The invention discloses a method for obtaining correction coefficients in an inverse power electrical lifetime model based on an E-eta characteristic method. The numerical values of the correction coefficients (alpha and beta) are obtained by using an electro-acoustic pulse method and E-eta characteristics of a PEA system test sample. The method comprises the steps that S1, based on the quantitative relation between a twiddle factor beta and an electric field distortion rate eta, the value of the twiddle factor beta is obtained from an Ea-eta characteristic curve obtained through a long-time pressurization test by adopting an external field intensity pressurization test of a PEA method; and S2, based on the quantitative relationship between the translation factor alpha and the electric field distortion rate eta, acquiring the short-time breakdown electric field intensity Eb of the sample by adopting a short-time breakdown experiment, and acquiring the internal electric field distortion rate eta b when the externally applied electric field intensity is the breakdown electric field intensity and the acquired twiddle factor beta in combination with an extrapolation method to obtain the value of the translation factor alpha.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of solid insulation electrical life, and in particular to a method for obtaining correction coefficients in an inverse power electrical life model based on an E-η characteristic method, specifically using an electroacoustic pulse method and a PEA system to test the E-η characteristics of a sample to obtain correction coefficients α and β. Background Art

[0002] At present, the inverse power life model is used to describe the characteristic relationship between the external DC voltage borne by the solid insulation layer and the insulation failure time, and to predict the remaining life of the solid insulation material.

[0003] In the patent "Improved method and system for inverse power electric life model considering the influence of DC field strength distortion (ZL202111644808.X)", an improved inverse power electric life model is proposed, as shown in formula (1): Where α and β are defined as the translation factor and rotation factor, respectively, which are the correction coefficients in the inverse power life model.

[0004] Patent ZL202111644808.X does not clearly provide a method for obtaining α and β, so this application provides a method for obtaining the values ​​of α and β using an electroacoustic pulse method. Summary of the invention

[0005] In order to overcome the above technical defects, the embodiment of the present application provides a method for obtaining the correction coefficient in the inverse power electrical life model based on the E-η characteristic method, and the correction coefficient includes a translation factor α and a rotation factor β. The specific scheme is as follows:

[0006] S1, based on the quantitative relationship between the rotation factor β and the electric field distortion rate η, the PEA method is used to apply an external field strength pressure test and obtain the E obtained through a long-term pressure test. a -Get the value of the rotation factor β from the η characteristic curve;

[0007] S2. Based on the quantitative relationship between the translation factor α and the electric field distortion rate η, a short-time breakdown experiment is used to obtain the short-time breakdown electric field strength E of the sample. b , and combined with the extrapolation method to obtain the internal electric field distortion rate η when the external electric field strength is the breakdown electric field strength b And the obtained rotation factor β, get the value of the translation factor α.

[0008] Specifically, it is characterized in that the quantitative relationship between the rotation factor β and the electric field distortion rate η is:

[0009]

[0010] Specifically, the quantitative relationship between the translation factor α and the electric field distortion rate η is:

[0011] or

[0012] Further optionally, the duration of the long-term pressure test is greater than or equal to 420 seconds;

[0013] The value of the rotation factor β is obtained in S1, including:

[0014] S1.1. In the experiment, i (i≥3) different external electric field strengths are selected to carry out PEA pressure test with constant external electric field strength. The total test time is t0. The E r ;

[0015] S1.2, each sampling moment E r Substitute into the following formula to calculate the field strength distortion rate η,

[0016] S1.3. Calculate the η values ​​obtained at different sampling times within the range of 420s-t0 to obtain the root mean square value η m ;

[0017] S1.4、Different E a The η obtained in the experiment m +1 for data point (E a , η m +1) into the double logarithmic coordinate system, fit the data points, and obtain E a -The equation corresponding to the η characteristic curve;

[0018] S1.5, from E a The value of the rotation factor β is obtained from the slope of the -η characteristic curve equation.

[0019] Further optionally, the duration of the short-time pressure test when the applied electric field strength obtained by the extrapolation method is the breakdown electric field strength is less than or equal to 20 seconds;

[0020] The value of the translation factor α is obtained in S2, including:

[0021] S2.1, obtain the rotation factor β of the sample under test;

[0022] S2.2. Under the condition of external DC voltage, a short-time breakdown test is performed on the sample to obtain the short-time breakdown electric field strength E of the sample. b ;

[0023] S2.3. Use the extrapolation method to obtain the internal electric field distortion rate ηb when the external applied electric field strength is the breakdown electric field strength.

[0024] The embodiment of the present application adopts the above technical solution to obtain the values ​​of correction coefficients α and β by testing the E-η characteristics of the sample using the electroacoustic pulse method and the PEA system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings exemplarily illustrate the embodiments and constitute a part of the specification, and together with the text description of the specification, are used to explain the exemplary implementation of the embodiments. The embodiments shown are for illustrative purposes only and do not limit the scope of the claims. In all drawings, the same reference numerals refer to similar but not necessarily identical elements.

[0026] Figure 1 Schematic diagram of the internal electric field formed by space charge accumulation;

[0027] Figure 2 Schematic diagram of the mathematical meaning of the translation factor α;

[0028] Figure 3 Schematic diagram of the mathematical meaning of the rotation factor β;

[0029] Figure 4 A schematic diagram of a process for obtaining the translation factor α and the rotation factor β in the inverse power electrical lifetime model based on the E-η characteristic method in this application. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0031] It should be noted that the descriptions involving "first", "second", etc. in the embodiments of the present application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0032] In the description of the present application, it should be understood that the numerical labels before the steps do not indicate the order in which the steps are executed, but are only used to facilitate the description of the present application and to distinguish each step, and therefore should not be understood as a limitation on the present application.

[0033] like Figure 1 As shown, in the internal electric field formed by the accumulation of space charges, there is a clear quantitative relationship between the translation factor α, the rotation factor β and the electric field distortion rate η.

[0034] The expression of electric field distortion rate η is: Where E r With E a The meaning and relationship are: if the external DC electric field strength acting on the XLPE sheet sample is E a , then the electric field distortion caused by the accumulation of space charge makes the actual electric field strength in the body higher than E a . r Represents the maximum value of the actual electric field strength. a With E r have the same direction.

[0035] The distorted electric field strength E sc Represents E r With E a The difference is E a 、E r 、E sc The relationship satisfied is shown in Formula 3: r =E a +E sc (3).

[0036] 1) Quantitative relationship between translation factor α and electric field distortion rate η

[0037] On the lnE-lnt plane, the translation factor α reflects the value of E a -t curve and E r The difference between the vertical intercepts of the E-t curves due to electric field distortion. a -t curve parameters can be obtained by changing E r- The corresponding parameters of the t curve are obtained by multiplying the correction coefficients α and β, that is, C a =C r α , n a =βn r Therefore, we can use α=ln(C a ) / ln(C r ) to obtain the mathematical expression of α.

[0038] If the inverse power life model is expressed as:

[0039] t=C×E -n (4)

[0040] In formula (4), n is the voltage withstand index (VEC), and C is a constant that characterizes the amount of cumulative electrical damage required for material insulation failure.

[0041] For the expression of lnC, equation (4) can be rewritten as equation (5):

[0042] lnC=nlnE+lnt(5),

[0043] If the point (E a1 , t1) and (E r1 , t1) are substituted into formula (5) to obtain:

[0044]

[0045] When t1 = 1s, lnt1 in equation (6) = 0. Figure 2 As shown, when lnt1 = 0, E a -t curve and E r The -t curve will intersect with the horizontal axis. The electric field strength values ​​at the intersection are the external electric field strength E when the voltage is applied for a time of t1 = 1s. a-1s The actual electric field strength E in the dielectric r-1s , as shown in formula (7):

[0046]

[0047] In formula (2), E a-1s It is the external electric field strength required when the insulation life of the tested sample is 1s, E r-1s The strength of the external electric field is E a-1s The actual electric field strength inside the sample is a-1s , a short-time breakdown test of 1s is required for the sample under test. In this process, the space charge test (electroacoustic pulse method, PEA) is also required to be performed on the sample under test and E is calculated. r-1s However, such an experimental scheme is difficult to implement. Therefore, based on the ASTM-D149 standard referenced by a large number of short-time breakdown test results, the test time can be extended from 1s to 20s. b The actual electric field strength E r-b After substituting into formula (7), α can be expressed as formula (8):

[0048]

[0049] like Figure 2 As shown, when t1 = t b = 20s, the α value calculated by equation (8) will only cause a negligible deviation to the α value calculated by equation (7) when t1 = 1s. Therefore, the method of expressing the α value by equation (8) is valid.

[0050] The expression of field intensity distortion rate η is shown in formula (2). Substituting it into formula (8), we can construct the functional relationship expression of η and α. a =βn r , so we can get:

[0051]

[0052] The functional relationship between α and η is established. The parameters that determine the value of α include the rotation factor β, the breakdown field strength E b , Field strength distortion rate η when breakdown occurs b .

[0053] 2) Quantitative relationship between rotation factor β and electric field distortion rate η

[0054] On the lnE-lnt plane, the rotation of a line can be characterized by the value of its slope. The quantitative relationship between the rotation factor β and η can be derived from the slope formula of the line. Let E a The slope of the -t curve is -n a , E r The slope of the -t curve is -n r , from the slope mathematical expression we can get:

[0055]

[0056] Substituting equation (2) into equation (10), the field intensity distortion rate η can be introduced into the expression of the straight line slope, and the result is:

[0057]

[0058] From formula (10), we can know that: lnt1-lnt2=-n a (lnE a1 -lnE a2 ), which can be substituted into formula (11) to obtain:

[0059]

[0060] Because n a =βn r , so from formula (12) we can get:

[0061]

[0062] From the mathematical expression of the slope, it can be seen that the β-1 value can be expressed as the slope of the straight line shown in formula (14) in the lnE-ln(η+1) coordinate system:

[0063] ln(η+1)=(β-1)lnE a +A(14)

[0064] In formula (14), A is a constant. The slope of the straight line β-1 can also be regarded as the field distortion rate η with the external electric field strength E a Increased rate of change, such as Figure 3 shown.

[0065] Therefore, the mathematical expression of β can be simplified to formula (15):

[0066]

[0067] Formula (15) establishes a clear quantitative relationship between β and η. It can be seen that the factors affecting the value of β are: a The rate of change of change.

[0068] Based on the above construction, there is a clear quantitative relationship between the translation factor α, rotation factor β and electric field distortion rate η. The method for obtaining the values ​​of α and β is as follows: Figure 4 As shown, including:

[0069] S1, based on the quantitative relationship between the rotation factor β and the electric field distortion rate η, the PEA method is used to apply an external field strength pressure test and obtain the E obtained through a long-term pressure test. a -η characteristic curve to obtain the value of the rotation factor β.

[0070] Specifically, the quantitative relationship between the rotation factor β and the electric field distortion rate η is shown in the above formula (15). From formula (15), it can be seen that the experimental acquisition of the rotation factor β requires the following value:

[0071] ① The field distortion rate η changes with the external electric field strength E a Increased rate of change: d[ln(η+1)] / d[ln(E a )].

[0072] More specifically, the duration of the long-term pressure test is greater than or equal to 420 seconds.

[0073] S2. Based on the quantitative relationship between the translation factor α and the electric field distortion rate η, a short-time breakdown experiment is used to obtain the short-time breakdown electric field strength E of the sample. b , and combined with the extrapolation method to obtain the internal electric field distortion rate η when the external electric field strength is the breakdown electric field strength b And the obtained rotation factor β, get the value of the translation factor α.

[0074] Specifically, the quantitative relationship between the translation factor α and the electric field distortion rate η is shown in the above formula (9).

[0075] From formula (9), we can see that the experimental acquisition of the translation factor α requires the following three values:

[0076] ①The value of the rotation factor β;

[0077] ②Short-time breakdown electric field strength E of the sample to be tested b ;

[0078] ③ When the external electric field strength is the short-time breakdown strength, the distortion rate η of the internal electric field strength of the sample to be tested after being affected by the space charge b .

[0079] More specifically, the duration of the short-time pressure test when the applied electric field strength obtained by the extrapolation method is the breakdown electric field strength is less than or equal to 20 seconds.

[0080] Because the quantitative relationship between α, β and η contains space charge characteristic and failure characteristic parameters, the developed plan should include two aspects: space charge characteristic test and failure characteristic test. Figure 4 As shown, the plan can be formulated into the following steps in the order of execution:

[0081] The value of the rotation factor β is obtained in S1, including:

[0082] S1.1. In the experiment, i (i≥3) different external electric field strengths are selected to carry out PEA pressure test with constant external electric field strength. The total test time is t0. The E r ;

[0083] S1.2, each sampling moment E r Substitute into formula (2) to calculate the field intensity distortion rate η;

[0084] S1.3. Calculate the η values ​​obtained at different sampling times within the range of 420s-t0 to obtain the root mean square value η m ;

[0085] S1.4、Different E a The η obtained in the experiment m +1 for data point (E a , η m +1) into the double logarithmic coordinate system, fit the data points, and obtain E a -The equation corresponding to the η characteristic curve;

[0086] S1.5, from E a The value of the rotation factor β is obtained from the slope of the -η characteristic curve equation.

[0087] The value of the translation factor α is obtained in S2, including:

[0088] S2.1, obtain the rotation factor β of the sample under test;

[0089] S2.2. Under the condition of external DC voltage, a short-time breakdown test is performed on the sample to obtain the short-time breakdown electric field strength E of the sample. b ;

[0090] S2.3. Use the extrapolation method to obtain the internal electric field distortion rate ηb when the external applied electric field strength is the breakdown electric field strength.

[0091] The PEA system is used to perform i (i≥3) groups of pressurization tests at an electric field strength lower than the breakdown electric field strength of the sample being tested. The pressurization time should preferably not exceed 20 seconds, or the experimental data of the pressurization test data not exceeding the first 20 seconds should be used. The internal electric field strength is calculated from the charge density distribution, and the E sc-b or E r-b With E b-DC By substituting the breakdown electric field strength value of the sample under test into the expression, the actual electric field strength E that the sample is subjected to at the time of breakdown can be extrapolated. r-b , and calculate the field strength distortion rate ηb at this time.

[0092] During the execution of the above scheme, the pressurized electric field strength in the PEA test is an experimental parameter that needs to be designed. In the experiment, the pressurized electric field strength can be set closer to the breakdown electric field strength of the sample under test based on the obtained breakdown electric field strength value and the actual situation of the test equipment.

[0093] Because the E-η characteristics of the PEA system test samples were used in the process of obtaining the correction coefficients α and β, the method designed in this section can be defined as the "E-η characteristic method".

[0094] Obviously, those skilled in the art should understand that the modules or steps of the above-mentioned embodiments of the present application can be implemented by general-purpose computer devices, they can be concentrated on a single computer device, or distributed on a network composed of multiple computer devices, optionally, they can be implemented by executable program codes of computer devices, so that they can be stored in a storage device and executed by the computer device, and in some cases, the steps shown or described can be executed in a different order from that herein, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. In this way, the embodiments of the present application are not limited to any specific combination of hardware and software.

[0095] It should be noted that the above are only preferred embodiments of the present application, and the patent protection scope of the present application is not limited thereto. Any equivalent structure or equivalent process transformation made using the contents of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for obtaining a correction coefficient in an inverse power electrical life model based on an E-η characteristic method, wherein the correction coefficient includes a translation factor α and a rotation factor β, characterized in that: The method comprises: S1, based on the quantitative relationship between the rotation factor β and the electric field distortion rate η, the PEA method is used to apply an external field strength pressure test and obtain the E obtained through a long-term pressure test. a -Get the value of the rotation factor β from the η characteristic curve; S2. Based on the quantitative relationship between the translation factor α and the electric field distortion rate η, a short-time breakdown experiment is used to obtain the short-time breakdown electric field strength E of the sample. b , and combined with the extrapolation method to obtain the internal electric field distortion rate η when the external electric field strength is the breakdown electric field strength b And the obtained rotation factor β, get the value of the translation factor α.

2. The method according to claim 1, characterized in that The quantitative relationship between the rotation factor β and the electric field distortion rate η is:

3. The method according to claim 1, characterized in that The quantitative relationship between the translation factor α and the electric field distortion rate η is: or 4. The method according to claim 1, characterized in that: The duration of the long-term pressure test is greater than or equal to 420s; the value of the rotation factor β is obtained in S1, including: S1.

1. In the experiment, i (i≥3) different applied electric field intensities are selected to carry out PEA pressure test with constant applied electric field intensity. The total test time is t0. The E r ; S1.2, each sampling moment E r Substitute into the following formula to calculate the field strength distortion rate η, S1.

3. Calculate the η values ​​obtained at different sampling times within the range of 420s-t0 to obtain the root mean square value η m ; S1.4、Different E a The η obtained in the experiment m +1 for data point (E a , η m +1) into the double logarithmic coordinate system, fit the data points, and obtain E a -The equation corresponding to the η characteristic curve; S1.5, from E a The value of the rotation factor β is obtained from the slope of the -η characteristic curve equation.

5. The method according to claim 1, characterized in that The duration of the short-time pressure test when the applied electric field strength obtained by the extrapolation method is the breakdown electric field strength is less than or equal to 20s; The value of the translation factor α is obtained in S2, including: S2.1, obtain the rotation factor β of the sample under test; S2.

2. Under the condition of external DC voltage, a short-time breakdown test is performed on the sample to obtain the short-time breakdown electric field strength E of the sample. b ; S2.

3. Use the extrapolation method to obtain the internal electric field distortion rate ηb when the external applied electric field strength is the breakdown electric field strength.

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