A method for estimating the operating life of porcelain insulators

Abstract

The present invention discloses a method for estimating the operating life of porcelain insulators. By using fewer test samples, the weighted geometric mean is calculated based on the actual tensile force and the tensile force value at which rapid fracture occurs, shortening the failure time of the test to the range of several hours to several months, and extrapolating the failure time under the actual tensile force based on this failure time. The method of the present invention has a relatively long test time, and the longest test time for a group is nearly one year, so the accuracy of life estimation is high.

Description

Technical Field

[0001] The present invention belongs to the application technology of materials science and engineering, and particularly relates to a method for estimating the service life of ceramic insulators. Background Art

[0002] Ceramic insulators are the most widely used insulators at present. Insulators play a role in mechanically supporting transmission wires and providing electrical insulation. After a fault occurs inside a ceramic insulator, its appearance often remains unchanged, making the detection work time-consuming and laborious. However, if a fault occurs in the insulator, it will endanger the safe and stable operation of the power grid and affect social production. If the service life of the insulator can be predicted, the detection personnel can reasonably formulate a detection plan and determine the detection period. Estimating the service life of ceramic insulators not only ensures the safety of the power grid but also reduces the detection workload.

[0003] Ceramic insulators have stable chemical properties and a long aging time. Most failures are caused by long-term stress. Estimating the life according to the actual tensile force is a reasonable choice. However, the failure time under the actual tensile force is as long as ten or dozens of years. The present invention calculates the weighted geometric mean based on the actual tensile force and the tensile force value for rapid fracture, shortening the test failure time to the range of several hours to several months, and extrapolating the failure time under the actual tensile force based on this failure time. Summary of the Invention

[0004] The object of the present invention is to provide a method for estimating the service life of ceramic insulators, which determines the test tensile force value according to the actual tensile force and the tensile force value for rapid fracture of the ceramic insulator, and extrapolates the failure time under the actual tensile force based on the failure time under the test tensile force, with high accuracy in life estimation.

[0005] The technical solution of the present invention is as follows:

[0006] A method for estimating the service life of ceramic insulators includes the steps:

[0007] (1) For a certain type of ceramic insulator, investigate and confirm the tensile force it actually bears during long-term operation, denoted as S 0 ;

[0008] (2) Take multiple ceramic insulators for tensile fracture tests, calculate the average value of the tensile fracture forces, denoted as S 1 ;

[0009] (3) According to the tensile force S 0 that the ceramic insulator bears during long-term operation and the average value S 1 of the tensile fracture forces of multiple ceramic insulators, calculate the test tensile force F k ;

[0010] (4) At each test tensile force F kUnder the following conditions, M groups of tests are carried out; each group of tests is an insulator string composed of N porcelain insulators connected in series, and both ends of the insulator string bear a tensile force of F k The tensile force is recorded, and the failure time when each insulator string is broken by the tensile force is recorded and sorted from small to large. Denote the tensile force borne by the insulator string as F k After sorting, the m-th failure time is T(k,m), where ;

[0011] (5)Calculate the derivative values p m , f k , t(k,m):

[0012] ;;

[0013] ;

[0014] ;

[0015] where ln(*) is the function to calculate the natural logarithm;

[0016] (6)Use the above derivative values t(k,m), p m , f k to perform multiple linear fitting, and fit to obtain the values of coefficients A, B, and C;

[0017] (7)According to the coefficients A, B, and C, calculate the operating life T 0 when the long-term tensile force S 0 .

[0018] Preferably, the method for calculating the operating life T 0 when the long-term tensile force S 0 is as follows:

[0019] ;

[0020] where exp[*] is the exponential function with the natural logarithm as the base, A, B, and C are the coefficients obtained from the multiple linear fitting in step (6), P 0 is the failure probability of a single insulator, N is the number of insulators in each insulator string in the test in step (4), and N 0 is the number of insulators in a certain insulator string during actual use.

[0021] Preferably, the method for the breaking test in step (2) is: when the porcelain insulator is produced and assembled, a metal connecting piece with higher mechanical strength is used to ensure that the metal connecting piece is not damaged. At this time, the measured breaking value reflects the performance of the porcelain part.

[0022] Preferably, in step (3), calculate the test tensile force Fk The method is as follows:

[0023] ;

[0024] where k ranges from 0.7 to 0.9.

[0025] Preferably, in step (4), the values of M and N are N = 5 and M = 10.

[0026] Preferably, in step (7), it is required that P 0 ≤5 / 10 5 .

[0027] The advantages of the present invention are:

[0028] The method for estimating the service life of porcelain insulators proposed by the present invention uses fewer test samples, calculates the weighted geometric mean based on the actual tensile force and the tensile force value at rapid fracture, shortens the test failure time to the range of several hours to several months, and extrapolates the failure time under the actual tensile force based on this failure time. The method of the present invention has a relatively long test time, and the longest test time for one group is nearly one year, so the accuracy of life estimation is high. Detailed implementation manners

[0029] Taking a certain type of disc suspension porcelain insulator as an example, the method for estimating the service life of the porcelain insulators of the present invention specifically includes the following steps.

[0030] (1) Investigate and confirm that the tensile force actually borne by this type of porcelain insulator during long-term operation is S 0 = 200 kN.

[0031] (2) Take 20 pieces of this type of porcelain insulator, and measure the fracture strength of the porcelain parts in a short time with a tensile testing machine. When assembling 20 porcelain insulators, metal connectors with higher mechanical strength are used to ensure that the metal connectors are not damaged. At this time, the measured fracture value reflects the performance of the porcelain parts. The test results are: {1063, 1075, 976, 999, 1028, 1055, 1106, 1036, 1113, 1074, 1109, 1056, 1017, 976, 1058, 1091, 1035, 1023, 1035, 995}. Calculate its average value as S 1 = 1050 kN.

[0032] (3) Calculate the test tensile force F according to the following formula k :

[0033] ;

[0034] Take the parameter , and obtain the test tensile force as 。

[0035] (4) Conduct M = 10 groups of tests with the above tensile forces. Each insulator string is composed of N = 5 porcelain insulators connected in series. For each group of tests, record the time when the insulator string is broken and sort them from small to large. Record the breaking time T(k,m), in hours, where 。The data is recorded in the following table:

[0036]

[0037] Among them, when the test is carried out with F k = 694 kN, there are three groups of tests that have not been damaged after more than 8000 hours, so the breaking time is not recorded. The lack of a small amount of data does not affect the use of the method of the present invention. Similarly, when the test is carried out with F k = 753 kN, one data is missing.

[0038] (5) Calculate the derived values p m , f k , t(k,m);

[0039] ;

[0040] ;

[0041] ;

[0042] where ln(*) is the function to calculate the natural logarithm. The calculation results are shown in the following table:

[0043]

[0044] (6) Use the above-derived values t(k,m), p m , f k to conduct multiple linear fitting, and the fitting . Common numerical analysis software such as Excel, MATLAB, etc. have ready-made multiple linear fitting functions that can be used. Obtain the coefficients A = 176.7672, B = 2.520903, C = -25.664762.

[0045] (7) Calculate the operating life T 0 when the long-term tensile force S 0 :

[0046] ;

[0047] where exp[*] is the exponential function with the natural logarithm as the base, A, B, and C are the coefficients obtained from the multiple linear fitting in step (6), and P 0 is the failure probability of a single insulator. Usually, it is required that P0 ≤5 / 10 5 , where N is the number of insulators in each insulator string tested in step (4), and N 0 is the number of insulators in a certain insulator string during actual use.

[0048] The failure probability of a single insulator is taken as P 0 = 5 / 10 5 , considering a string of insulators connected by N 0 = 25 insulators on the UHV transmission line, calculate the service life T 0 = 77245 hours, that is, 8.8 years.

[0049] The method for estimating the service life of the porcelain insulator of the present invention calculates the weighted geometric mean according to the actual tensile force and the tensile force value of rapid fracture, shortens the failure time of the test to the range of several hours to several months, and extrapolates the failure time under the actual tensile force based on this failure time. The test time of the method of the present invention is relatively long, and the longest time for a group of tests is nearly one year, so the accuracy of life estimation is high.

[0050] The above embodiments are only used to illustrate the technical concept and characteristics of the present invention, and their purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and cannot be used to limit the protection scope of the present invention. All modifications made according to the spirit of the main technical solution of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for estimating the service life of a porcelain insulator, characterized in that: Includes steps: (1) For a certain type of porcelain insulator, the actual tensile force it bears during long-term operation is confirmed by investigation, which is recorded as S0; (2) Take multiple porcelain insulators for breaking test and calculate the average breaking force, which is recorded as S1; (3) Calculate the test tensile force F based on the tensile force S0 that the porcelain insulator bears during long-term operation and the average breaking force S1 of multiple porcelain insulators. k ; (4) In each test tension F k Under the condition of M groups of tests, each group of tests is to connect N porcelain insulators in series to form an insulator string, and the two ends of the insulator string are subjected to F k The tensile force is recorded, and the failure time of each group of insulator strings being broken by the tensile force is recorded, and the order is arranged from small to large. k The tensile force, the mth failure time after sorting is T(k,m), where ; (5) Calculate the derivative value p m , f k , t(k,m): ； ； ； Where ln(*) is a function that calculates the natural logarithm; (6) Using the above derivative values ​​t(k,m), p m , f k Perform multivariate linear fitting, fitting , get the values ​​of coefficients A, B, and C; (7) Based on the coefficients A, B, and C, calculate the service life T0 when subjected to long-term tensile force S0.

2. The method for estimating the service life of a porcelain insulator according to claim 1, characterized in that: The method for calculating the service life T0 when subjected to long-term tensile force S0 in step (7) is: ； Where exp[*] is an exponential function with natural logarithm as base, A, B, C are the coefficients obtained by multivariate linear fitting in step (6), P0 is the probability of damage to a single insulator, N is the number of insulators contained in each insulator string tested in step (4), and N0 is the number of insulators contained in a certain insulator string when actually used.

3. The method for estimating the service life of a porcelain insulator according to claim 1, characterized in that: The method of the tensile test in step (2) is as follows: when producing and assembling porcelain insulators, metal connectors with higher mechanical strength are used to ensure that the metal connectors are not damaged. The tensile value measured at this time reflects the performance of the porcelain parts.

4. The method for estimating the service life of a porcelain insulator according to claim 1, characterized in that: Calculate the test tension F in step (3) k The method is: ； The value of k is 0.7 to 0.

9.

5. The method for estimating the service life of a porcelain insulator according to claim 1, characterized in that: The values ​​of M and N in step (4) are N = 5 and M = 10.

6. The method for estimating the service life of a porcelain insulator according to claim 2, characterized in that: Step (7) requires P0≤5 / 10 5 .

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