A method for calculating the water pressure rejection threshold of disc-type suspension porcelain insulators

Abstract

The present invention discloses a method for calculating the internal water pressure rejection threshold of a disc-type suspension porcelain insulator. (1) n samples of porcelain insulators are extracted and subjected to a destructive internal water pressure test. The water pressure values of the damaged samples are sorted from small to large; (2) a probability value of the destructive water pressure is estimated to obtain a data set of damaged samples; (3) the products with the first k% proportion of the destructive water pressure are set as defective products, and the first k% of the data are rejected from the data set D0 to obtain a data set D0 of qualified products. k ; (4) Data set D for qualified products k Calculate the significance Pr(k); (5) Select different k%, repeat steps (3) and (4), calculate the corresponding Pr(k), and find k best ; (6) Calculate the water pressure rejection threshold S selected on the production line th The present invention divides defective products and qualified products according to the significance of the Weibull distribution fitting correlation coefficient, and determines the rejection threshold of the internal water pressure test of the disc-type suspension porcelain insulator. This method scientifically rejects defective products and improves the quality of factory products.

Description

Technical Field

[0001] The invention belongs to material science and engineering application technology, and particularly relates to a method for calculating a water pressure rejection threshold value in a disc-type suspension porcelain insulator. Background Art

[0002] Disc-type suspension porcelain insulators play a role in mechanical support and electrical insulation for transmission lines, and are widely used in power grid systems such as high-voltage transmission lines and substations. The raw materials used to produce porcelain insulators contain some natural minerals, which inevitably introduce impurities. On the other hand, fluctuations in process parameters during production can also cause defects inside porcelain insulators. How to detect and remove products with internal impurities or defects is an important issue that porcelain insulator manufacturers need to consider in order to improve product quality.

[0003] The internal water pressure test is a test item carried out one by one for the porcelain parts of disc-type suspension porcelain insulators. It has a high rejection rate and is currently the most advanced detection and rejection method. The internal water pressure test is to seal and pressurize the concave part of the porcelain part with water. Porcelain parts with defects often cannot withstand the water pressure and are destroyed and rejected. The higher the water pressure value, the more defective products are rejected, but qualified products may also be destroyed by excessive water pressure, resulting in waste. Determining a reasonable internal water pressure rejection threshold is the key to this test method. Due to the different production levels of each manufacturer, the proportion of defective products is different. In addition, the formulas, structural dimensions and intrinsic strength of porcelain parts used by different manufacturers are different. The rejection threshold should not be selected as a fixed value. The present invention proposes a method for calculating the internal water pressure rejection threshold of disc-type suspension porcelain insulators. The core principle is to divide defective products and qualified products according to the significance of the Weibull distribution correlation coefficient, and further determine the internal water pressure rejection threshold. Summary of the invention

[0004] The purpose of the present invention is to provide a method for calculating the water pressure rejection threshold of disc-type suspension porcelain insulators, which allows disc-type suspension porcelain insulator manufacturers to determine whether there are defects in the porcelain parts and classify defective products and qualified products; determine the rejection threshold, reasonably reject defective products, and improve the quality of factory products.

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

[0006] A method for calculating the water pressure rejection threshold of a disc-type suspension porcelain insulator comprises the following steps:

[0007] (1) Take n samples of porcelain insulators and conduct a destructive internal water pressure test. The maximum water pressure value S before the failure of each sample is recorded. i , record that m samples among n samples are destroyed, record the water pressure value of the destroyed samples when destroyed, and the water pressure values ​​are sorted from small to large as {S1, S2, … S m};

[0008] (2) For the breaking water pressure {S1, S2, …S m}Estimated probability values ​​{P1,P2,…P m}, and obtain the data set of the damaged sample: D0={(S1,P1),(S2,P2),…,(S m ,P m )};

[0009] (3) Set the first k% of products that break the water pressure as defective products, remove the first k% of data from the data set D0, and obtain the data set D0 of qualified products. k = {(S nk ,P nk ), (S nk+1 ,P nk+1 ), … ,(S m ,P m )};

[0010] (4) Data set D for qualified products k Calculate the significance Pr(k);

[0011] (5) Select different k%, repeat steps (3) and (4) to calculate the corresponding Pr(k); among multiple sets of discrete {k, Pr(k)} values, when Pr(k) takes a minimum value, or when ln[Pr(k)] takes a minimum value, the corresponding k value is recorded as k best , the front k best % of the products are defective;

[0012] (6) Calculate the water pressure rejection threshold S selected on the production line th .

[0013] Preferably, in step (1), the value of the destruction quantity m is required to be m ≥ 100;

[0014] If the above conditions are not met, increase the sample size n so that the above conditions are met.

[0015] Preferably, in step (2), the breaking water pressure {S1, S2, ... S m}Estimate the probability value and use the Ross function as the estimated value:

[0016] ;

[0017] Where i is the breaking water pressure S i The sequence numbers are sorted from small to large, i ≥ 1 and i ≤ m, and n is the total number of samples in step (1).

[0018] Preferably, in step (3), the sequence number n k The calculation method is:

[0019] ;

[0020] The function Represents the floor function.

[0021] Preferably, in step (4), the method for calculating the significance Pr(k) is:

[0022] First, calculate the following parameters LP k LS k , r k :

[0023] ;

[0024] ;

[0025] ;

[0026] Then calculate the significance Pr(k):

[0027] ;

[0028] Calculate LP k LS k , r k The summation in the formula is performed on the index i, and the summation range is from arrive ; represents the logarithm with natural logarithm as base; calculate the Pr(k) formula is the circumference of a circle, is the gamma function:

[0029] ;

[0030] In the above formula, e is the natural logarithm.

[0031] Preferably, in step (5), the value of k is close to the first value, and when m<200, the interval is 1; if m≥200, the interval is reduced to 0.5.

[0032] Preferably, in step (6), the water pressure rejection threshold S selected on the production line is calculated according to the following equation: th :

[0033] ;

[0034] ;

[0035] ;

[0036] ;

[0037] calculate The summation in the above is performed on index i, and the summation range of i is from arrive ; Calculate S th In the formula, exp(·) is an exponential function with natural logarithm as base.

[0038] Preferably, the method further includes step (7): in order to further improve the yield rate, increase the rejection rate by 0.5-1%, and calculate S th In the formula, k is used best +0.5 or k best +1 for replacing k best Perform calculations.

[0039] The advantages of the present invention are:

[0040] The method for calculating the water pressure rejection threshold of disc-type suspension porcelain insulators proposed in the present invention obtains the defective rate and the rejection threshold based on a small number of several hundred samples. This method allows disc-type suspension porcelain insulator manufacturers to determine whether there are defects in porcelain parts, classify defective products and qualified products, determine the rejection threshold, reasonably reject defective products, improve the quality of factory products, and facilitate the reasonable rejection of a large number of subsequent samples from the same production line. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0042] Figure 1 Schematic diagram of the relationship between significance ln[Pr(k)] under different elimination rates k%. DETAILED DESCRIPTION

[0043] The present invention proposes a method for calculating the water pressure rejection threshold of a disc-type suspension porcelain insulator, the steps of which are as follows:

[0044] (1) For a batch of porcelain insulators produced, approximately 1% of the total production volume of the batch is selected for destructive internal water pressure test, and the number of samples selected is recorded as n. Destructive internal water pressure test means that the internal water pressure value is continuously increased until the sample is destroyed, and the maximum water pressure value S before destruction is recorded for each sample. i Due to the upper limit of the water pressure that the internal water pressure tester can generate, some products may not be destroyed. Record that m samples out of n samples are destroyed, and record the water pressure value of the destroyed samples at the time of destruction. The water pressure values ​​are sorted from small to large as {S1, S2, …S m}. Requirements for the value of the destruction quantity m

[0045] m ≥ 100;

[0046] If the above conditions are not met, the sample size n needs to be increased so that the above conditions are met.

[0047] (2) For the breaking water pressure {S1,S2,…S m}Estimate the probability value and use the Ross function as the estimated value:

[0048] ;

[0049] Where i is the breaking water pressure S i The serial numbers are sorted from small to large, i≥1 and i≤m, and n is the total number of samples in step 1. The data set D0 of the damaged samples is obtained ={(S1,P1),(S2,P2),…,(S m ,P m )}.

[0050] (3) Assume that the first k% of products with the breaking water pressure are defective, and the first possible value of k% is 5%. The breaking water pressure value of defective products is lower than the expected Weibull distribution. Remove the first k% of data from the data set D0 to obtain the qualified product data set D k = {(S nk ,P nk ), (S nk+1 ,P nk+1 ), … ,(S m ,P m )}, where the sequence number n k The calculation method is:

[0051] ;

[0052] The function Represents the floor function.

[0053] (4) Data set D for qualified products k Calculate the following parameters LP k LS k , r k And the significance Pr(k).

[0054] ;

[0055] ;

[0056] ;

[0057] ;

[0058] Calculate LP k LS k , r k The summation in the formula is performed on the index i, and the summation range is from arrive . represents the logarithm with natural logarithm as base. is the circumference of a circle, is the gamma function. The gamma function is defined as:

[0059] ;

[0060] In the above formula, e is the natural logarithm.

[0061] (5) Select different k%, repeat steps 3 and 4, and calculate the corresponding Pr(k). The value of k is close to the first value. If m<200, the interval is 1, for example, the following value range is used:

[0062] ;

[0063] If m ≥ 200, the interval can be reduced to 0.5, such as:

[0064] ;

[0065] Among multiple sets of discrete {k, Pr(k)} values, when Pr(k) takes a minimum value, or when ln[Pr(k)] takes a minimum value, the corresponding k value is denoted as k best . As attached Figure 1 Confirm k based on the k - ln[Pr(k)] relationship shown best The above steps complete the classification of defective and qualified products. best % of the products are defective.

[0066] (6) Calculate the water pressure rejection threshold S selected on the production line according to the following equation: th :

[0067] ;

[0068] ;

[0069] ;

[0070] ;

[0071] calculate The summation in the above is performed on index i, and the summation range of i is from arrive Calculate S th In the formula, exp(·) is an exponential function with natural logarithm as base.

[0072] (7) To further improve the yield rate, the rejection rate can be appropriately increased by 0.5~1%. Calculate S th In the formula, k is used best+0.5 or k best +1 for replacing k best Perform calculations.

[0073] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any modifications made according to the spirit of the main technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating the water pressure rejection threshold of a disc-type suspension porcelain insulator, characterized in that: Includes steps: (1) Take n samples of porcelain insulators and conduct a destructive internal water pressure test. The maximum water pressure value S before the destruction of each sample is recorded. i , record that m samples among n samples are destroyed, record the water pressure value of the destroyed samples when destroyed, and the water pressure values ​​are sorted from small to large as {S1, S2, … S m }; (2) For the breaking water pressure {S1, S2, …S m }Estimated probability values ​​{P1,P2,…P m }, and obtain the data set of the damaged sample: D0 = {(S1, P1), (S2, P2), …, (S m ,P m )}; (3) The first k% of products that break the water pressure are set as defective products, and the first k% of data are removed from the data set D0 to obtain the qualified product data set D k ={(S nk ,P nk ),(S nk+1 ,P nk+1 ),…,(S m ,P m )}; (4) Data set D for qualified products k Calculate the significance Pr(k); the method for calculating the significance Pr(k) is: First, calculate the following parameters LP k LS k , r k : Then calculate the significance Pr(k): Calculate LP k LS k , r k The summation in the formula is performed on the index i, and the summation range is from i = n k to i=m; ln(*) represents the logarithm with natural logarithm as the base; π in the formula for calculating Pr(k) is pi, and Γ(*) is the gamma function: In the above formula, e is the natural logarithm; (5) Select different k%, repeat steps (3) and (4), and calculate the corresponding Pr(k); when Pr(k) takes a minimum value or ln[Pr(k)] takes a minimum value among multiple discrete sets of {k, Pr(k)} values, the corresponding k value is recorded as k best , the front k best % of the products are defective; (6) Calculate the water pressure rejection threshold S selected on the production line th ; Calculate the water pressure rejection threshold S selected on the production line according to the following equation th : The summation in calculating Δ, A, and B is performed on index i, and the summation range of i is from To i = m; calculate S th In the formula, exp(·) is an exponential function with natural logarithm as base.

2. The method for calculating the water pressure rejection threshold of a disc-type suspension porcelain insulator according to claim 1, characterized in that: In step (1), the value of the destruction quantity m is required to be m ≥ 100; If the above conditions are not met, increase the sample size n so that the above conditions are met.

3. The method for calculating the water pressure rejection threshold of a disc-type suspension porcelain insulator according to claim 1, characterized in that: In step (2), the breaking water pressure {S1, S2, ... S m }Estimate the probability value and use the Ross function as the estimated value: Where i is the breaking water pressure S i The sequence numbers are sorted from small to large, i≥1 and i≤m, and n is the total number of samples in step (1).

4. The method for calculating the water pressure rejection threshold of a disc-type suspension porcelain insulator according to claim 1, characterized in that: In step (3), sequence number n k The calculation method is: n k =floor(n×k%); The function floor(*) represents the floor rounding function.

5. The method for calculating the water pressure rejection threshold of a disc-type suspension porcelain insulator according to claim 1, characterized in that: In step (5), the value of k is close to the first value, and when m<200, the interval is 1; if m≥200, the interval is reduced to 0.

5.

6. The method for calculating the water pressure rejection threshold of a disc-type suspension porcelain insulator according to claim 1, characterized in that: The step (7) is also included: in order to further improve the yield rate, the rejection rate is increased by 0.5-1%, and S is calculated. th In the formula, k is used best +0.5 or k best +1 for replacing k best Perform calculations.

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