A method for evaluating lightning impulse energy withstand capability of a resistance disc of a distribution network arrester

Abstract

This invention discloses a method for evaluating the lightning impulse energy withstand capability of surge arrester resistor elements in distribution networks. The method includes conducting a first preset test on a predetermined number of surge arrester resistor elements of various types from different manufacturers based on a first impulse current. The first preset test is continuously conducted based on the test results and preset conditions to obtain the current amplitude of the first impulse current when the resistor element fails. The current amplitude of the first impulse current is used as the starting value for the current amplitude of a second impulse current. A second preset test is conducted on a predetermined number of surge arrester resistor elements of the same type from the same manufacturer based on the second impulse current. The second preset test is continuously conducted based on the test results and preset conditions to obtain undamaged resistor elements that meet the damage quantity condition and calculate their lightning impulse withstand value. The lightning impulse withstand values ​​of various types of resistor elements from different manufacturers are normalized to obtain a withstand value per unit size, which is used to evaluate the lightning impulse withstand capability. This embodiment accurately evaluates surge arrester resistor elements of various types from different manufacturers.

Description

Technical Field

[0001] This invention relates to the field of resistance element withstand capability, and more particularly to a method for evaluating the lightning impulse energy withstand capability of resistance elements in distribution network surge arresters. Background Technology

[0002] Surge arresters are widely used in distribution networks, and the problem of them exploding due to lightning strikes is frequent. The energy withstand capability of the arrester's resistor element to lightning impulses determines its service life and its ability to protect the distribution network. Therefore, it is necessary to understand the energy withstand limit of the arrester under a lightning waveform (8 / 20μs). Although national standards specify the energy withstand capability of the arrester's resistor element under lightning impulses, this energy can only be considered a minimum requirement. According to the standard, all resistor elements should meet or exceed this requirement. In actual resistor element design and production, a certain margin is included, but the exact value of this margin is often unclear, leading to uncertainty about the energy the resistor element can withstand before failure. Calculating the energy withstand limit of the arrester or resistor element is crucial. Injecting energy exceeding this value into the resistor element will likely damage the arrester. Based on the energy value, it is possible to select a higher-performance distribution network arrester resistor element.

[0003] Currently, there are few experiments conducted on the energy limit value of the resistor under lightning impulse waveform. The existing technology obtains the energy limit value through simulation, which cannot fully take into account the actual state of the arrester resistor under lightning impulse, and cannot accurately obtain the withstand energy limit value of the arrester resistor. Summary of the Invention

[0004] This invention provides a method for evaluating the lightning impulse energy withstand capability of surge arrester resistors in distribution networks. It enables the testing and evaluation of the energy withstand capability of surge arrester resistors under lightning impulse, accurately obtains the withstand energy value of the surge arrester resistors, and effectively selects surge arrester resistors of different manufacturers and models.

[0005] To address the aforementioned technical problems, embodiments of the present invention provide a method for evaluating the lightning impulse energy withstand capability of surge arrester resistor elements in distribution networks, comprising:

[0006] Based on the first impulse current, the first resistor element is subjected to a first preset test to obtain the first test result. Based on the first preset conditions, the first test result, and the first preset test, the current amplitude of the first impulse current when the first resistor element fails is obtained. The first resistor element is a distribution network surge arrester resistor element with a first preset number of resistor elements of various types from various manufacturers.

[0007] Based on the second impulse current, the second resistor is subjected to a second preset test to obtain the second test result. Based on the second preset conditions, the second test result, and the second preset test, the current first electrical parameters of the third resistor are obtained. Based on the current second impulse current and the current first electrical parameters of the third resistor, the lightning impulse withstand value of the same type of resistor from the same manufacturer is calculated. Wherein, the starting value of the current amplitude of the second impulse current is the current amplitude of the first impulse current, the second resistor is the distribution network surge arrester resistor based on the second preset number of the same type of resistor from the same manufacturer, and the third resistor is the undamaged distribution network surge arrester resistor among the second resistors that meet the damage quantity condition.

[0008] The lightning impulse withstand values ​​of several types of resistors from several manufacturers are normalized to obtain the unit size withstand value of each type of resistor from each manufacturer. Based on the unit size withstand value, the lightning impulse withstand capability of each type of resistor from each manufacturer is evaluated.

[0009] In implementing this embodiment of the invention, a first preset test is conducted on a predetermined number of distribution network surge arrester resistors of various types from different manufacturers based on a first impulse current. The first preset test is continuously conducted based on the test results and preset conditions to obtain the current amplitude of the first impulse current when the resistor fails. Using the current amplitude of the first impulse current as the starting value of the current amplitude of the second impulse current, a second preset test is conducted on a predetermined number of distribution network surge arrester resistors of the same type from the same manufacturer based on the second impulse current. The second preset test is continuously conducted based on the test results and preset conditions to obtain the undamaged resistors among those meeting the damage quantity condition, i.e., finding the resistor closest to the withstand energy limit, and calculating the lightning impulse withstand value of the same type from the same manufacturer. Then, the lightning impulse withstand values ​​of various types of resistors from different manufacturers are normalized to obtain the withstand value per unit size, and this value is used to evaluate the lightning impulse withstand capability. By continuously changing the impulse current and test conditions, and approaching the withstand limit values ​​of various types of distribution network surge arrester resistors from different manufacturers, the energy withstand capability of distribution network surge arrester resistors under lightning impulses can be tested and evaluated. This allows for precise acquisition of the lightning impulse withstand value of the surge arrester resistors, effective selection of surge arrester resistors from different manufacturers, and mastery of the withstand limit values ​​of resistors from different manufacturers. This enables the selection of the best among the best, comparing and choosing resistors with superior performance. Furthermore, by combining the withstand energy value of the resistors with the operating conditions that the surge arrester may encounter during operation, the suitability of the surge arrester can be analyzed. This can be used in surge arrester selection work, and the lightning impulse withstand value of the surge arrester resistors can also be used as a reference for surge arrester fault analysis under lightning strikes.

[0010] As a preferred embodiment, before conducting a first preset test on the first resistor element based on the first impulse current and obtaining the first test result, the method further includes measuring the initial electrical parameters of each distribution network surge arrester resistor element based on the volt-ampere characteristic curve of each distribution network surge arrester resistor element.

[0011] The initial electrical parameters include the initial DC reference voltage of the resistor under 1mA DC, the initial leakage current under 0.75 times the initial DC reference voltage, and the initial lightning impulse residual voltage value under the nominal discharge current at 8 / 20μs.

[0012] In implementing this embodiment of the invention, the distribution network mainly refers to 10kV and 35kV power grids. The system operates with the neutral point ungrounded or grounded through an arc suppression coil. Under single-phase fault grounding, the short-circuit current is less than 10A. The operating conditions of the distribution network surge arresters are quite different from those of the main grid. It is not necessary to consider interrupting large power frequency short-circuit currents. When conducting impulse current tests on the surge arresters, using an 8 / 20μs lightning impulse waveform impulse current can more effectively simulate the actual scenario when the surge arrester is subjected to an impulse, which is conducive to accurately evaluating the lightning impulse withstand capability.

[0013] As a preferred embodiment, based on the first inrush current, the first resistor element is subjected to a first preset test to obtain a first test result. Then, based on the first preset conditions, the first test result, and the first preset test, the current amplitude of the first inrush current when the first resistor element fails is obtained, specifically as follows:

[0014] Based on the first impulse current, the first resistor is subjected to a first preset test to obtain the current second electrical parameters of the first resistor. Based on the first preset conditions, the current second electrical parameters of the first resistor, and the initial electrical parameters, it is determined whether the first resistor is damaged. The current second electrical parameters include the current second DC reference voltage of the resistor at 1mA DC, the current second leakage current at 0.75 times the current second DC reference voltage, and the current second lightning impulse residual voltage value at 8 / 20μs under the nominal discharge current.

[0015] If damaged, obtain the current amplitude of the first impact current when the first resistor element fails;

[0016] If not damaged, the current amplitude of the first inrush current is increased according to the first preset step value. The first inrush current is adjusted according to the current amplitude of the first inrush current, and the first resistor is reacquired. The first resistor is subjected to a first preset test according to the first inrush current to obtain the current second electrical parameters of the first resistor. The first resistor is judged to be damaged according to the first preset conditions, the current second electrical parameters of the first resistor, and the initial electrical parameters until the first resistor is damaged. The current amplitude of the first inrush current when the first resistor is damaged is obtained.

[0017] As a preferred option, the first preset test specifically involves applying a first impulse current three times consecutively to the first resistor within a 3-minute period.

[0018] The waveform of the first impact current is 8 / 20μs, and the initial value of the current amplitude of the first impact current is 2kA.

[0019] Implementing embodiments of the present invention, recent research results have confirmed that each ground flash often involves multiple return strokes. Statistical data shows that on average, each ground flash contains about 3 return strokes. Therefore, 3 impacts are chosen to be applied to the resistive element. In actual nature, the return stroke interval is short, only tens to hundreds of milliseconds. However, based on realistic experimental conditions, due to the charging time limitation of the impact testing equipment, a single impact test requires at least 50 to 60 seconds. By performing 3 impacts within 3 minutes, the actual natural ground flash conditions are simulated as closely as possible, improving the accuracy of calculating the lightning impulse withstand value.

[0020] As a preferred embodiment, based on the first preset conditions, the current second electrical parameters of the first resistor, and the initial electrical parameters, it is determined whether the first resistor is damaged, specifically as follows:

[0021] If the first resistor meets any of the first preset conditions, it is determined that the first resistor is damaged; otherwise, it is determined that the first resistor is not damaged.

[0022] The first preset condition includes: the first resistor element is broken or broken down;

[0023] The sum of the initial DC reference voltage of the first resistor and the change in the current second DC reference voltage exceeds the first preset value;

[0024] The initial leakage current of the first resistor and the change in the current second leakage current exceed the second preset value;

[0025] The changes in the initial lightning impulse residual voltage value and the current second lightning impulse residual voltage value of the first resistor exceed the third preset value.

[0026] As a preferred embodiment, based on the second inrush current, the second resistor is subjected to a second preset test to obtain the second test result. Then, based on the second preset conditions, the second test result, and the second preset test, the current first electrical parameters of the third resistor are obtained, specifically:

[0027] Based on the second impulse current, the second resistor is subjected to a second preset test to obtain the current first electrical parameters of the second resistor. Based on the second preset conditions, the current first electrical parameters of the second resistor, and the initial electrical parameters, it is determined whether the second resistor is damaged. The number of damaged second resistors in the second preset number of resistors is counted to obtain the damage amount. It is then determined whether the damage amount meets the damage quantity condition. The waveform of the second impulse current is 8 / 20μs. During the first preset test, the second impulse current is applied to the second resistor three times consecutively within 3 minutes. The current first electrical parameters include the current first DC reference voltage of the resistor at 1mA DC, the current first leakage current at 0.75 times the current first DC reference voltage, and the current first lightning impulse residual voltage value at 8 / 20μs under the nominal discharge current.

[0028] If the damage quantity condition is not met, the current amplitude of the second inrush current is adjusted according to the second preset step value. The second inrush current is adjusted according to the current amplitude of the second inrush current, and the second resistor is reacquired. According to the second inrush current, the second resistor is subjected to the second preset test to obtain the current first electrical parameters of the second resistor. According to the second preset conditions, the current first electrical parameters of the second resistor and the initial electrical parameters, it is determined whether the second resistor is damaged. The number of damaged second resistors in the second preset number of resistors is counted to obtain the damage quantity. It is determined whether the damage quantity meets the damage quantity condition until the damage quantity meets the damage quantity condition, and the current first electrical parameters of the third resistor are obtained.

[0029] If the damage quantity condition is met, the current first electrical parameters of the distribution network surge arrester resistors that are not mechanically damaged in the second resistor are counted to obtain the current first electrical parameters of the third resistor.

[0030] In implementing this invention, national and industry standards, as well as the technical parameters of surge arresters provided by manufacturers, only require that the surge arrester resistor element withstands an impulse amplitude or energy exceeding a certain value. They do not specify or display the actual limit or critical value of the impulse energy that the surge arrester resistor element can withstand. That is, when the resistor element is subjected to this energy, the probability of damage or non-damage is 50% each. By designing a second preset test and setting the conditions for the number of damages, the impulse current amplitude in the second preset test is continuously adjusted to gradually approach the limit value of the resistor element's withstand energy, thereby accurately calculating the lightning impulse withstand value of the same type of resistor element from the same manufacturer.

[0031] As a preferred embodiment, based on the second preset conditions, the current first electrical parameters and initial electrical parameters of the second resistor, it is determined whether the second resistor is damaged, specifically as follows:

[0032] If the second resistor meets any of the second preset conditions, it is determined that the second resistor is damaged; otherwise, it is determined that the second resistor is not damaged.

[0033] The second preset condition includes: the second resistor element is cracked or broken down;

[0034] The sum of the initial DC reference voltage of the second resistor and the change in the current first DC reference voltage exceeds the fourth preset value;

[0035] The initial leakage current of the second resistor and the change in the current first leakage current exceed the fifth preset value;

[0036] The change between the initial lightning impulse residual voltage value and the current first lightning impulse residual voltage value of the second resistor exceeds the sixth preset value.

[0037] As a preferred option, based on the current second impulse current and the current first electrical parameters of the third resistor, the lightning impulse withstand value of the same type of resistor from the same manufacturer is calculated, specifically as follows:

[0038] Based on the current second impulse current and the current residual voltage value of the first lightning impulse of the third resistor, the withstand energy value of each third resistor is calculated using the following formula:

[0039]

[0040] Where E is the withstand energy value of each third resistor, u is the current residual voltage value of the first lightning impulse, i is the current second impulse current, and T is the duration of the current second impulse current;

[0041] Based on the withstand energy value of each third resistor, the average withstand energy is calculated. Based on the current amplitude of the current second impulse current and the average withstand energy, the lightning impulse withstand value of the same type of resistor from the same manufacturer is obtained.

[0042] As a preferred approach, the lightning impulse withstand values ​​of various types of resistors from different manufacturers are normalized to obtain the unit size withstand value for each type of resistor. Based on the unit size withstand value, the lightning impulse withstand capability of each type of resistor from different manufacturers is evaluated. Specifically:

[0043] Divide the current amplitude of the second impulse current by the average cross-sectional area of ​​the third resistor to obtain the impulse current amplitude per square centimeter of the same type of resistor from the same manufacturer.

[0044] Divide the average withstand energy by the average volume of the third resistor to obtain the energy withstand value per cubic centimeter of the same type of resistor from the same manufacturer.

[0045] The lightning impulse withstand capability of various types of resistors from different manufacturers is evaluated by comparing the impulse current amplitude per square centimeter of cross-section and the energy withstand value per cubic centimeter of resistor.

[0046] In implementing this invention, due to differences in material formulations, pressing processes, firing techniques, and dimensions, resistors from different manufacturers exhibit varying residual voltages under the same impulse current. This typically makes an objective and fair comparison of the energy withstand capabilities of resistors from different manufacturers impossible (e.g., two resistors, A with a diameter of 30mm and B with a diameter of 35mm, may absorb more energy under the same impulse current, but B's larger cross-sectional area does not necessarily indicate superior performance). Therefore, by considering the cross-sectional area and volume of the resistors and normalizing the calculation to obtain the impulse current amplitude and energy withstand value of the resistors under average area and volume, it is possible to practically compare the merits of resistors from different manufacturers and effectively evaluate the lightning impulse withstand capabilities of different types of resistors from different manufacturers.

[0047] As a preferred embodiment, before conducting a first preset test on the first resistive element based on the first impact current and obtaining the first test result, the method further includes:

[0048] The diameters of several distribution network surge arrester resistors from several manufacturers and models are classified to obtain the types of resistors for each manufacturer and model. The types of resistors include Class I distribution network surge arrester resistors and Class II distribution network surge arrester resistors. Attached Figure Description

[0049] Figure 1 : A schematic flowchart of an embodiment of a method for evaluating the lightning impulse energy withstand capability of a surge arrester resistor element provided by the present invention;

[0050] Figure 2 : A flowchart of a resistance element test according to an embodiment of the method for evaluating the lightning impulse energy withstand capability of a distribution network surge arrester resistance element provided by the present invention. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Example 1

[0053] Please refer to Figure 1This is a flowchart illustrating a method for evaluating the lightning impulse energy withstand capability of surge arrester resistor elements in a distribution network, as provided in an embodiment of the present invention. The evaluation method of this embodiment is applicable to surge arrester resistor elements of different manufacturers and models. This embodiment evaluates the energy withstand capability of the surge arrester resistor elements under lightning impulse by testing, accurately obtaining the withstand energy value of the surge arrester resistor elements, and effectively selecting surge arrester resistor elements of different manufacturers and models. The evaluation method includes steps 101 to 105, each step as follows:

[0054] Step 101: Classify the diameters of several distribution network surge arrester resistors from several manufacturers and models to obtain the types of resistors for each manufacturer and model. The types of resistors include Class I distribution network surge arrester resistors and Class II distribution network surge arrester resistors.

[0055] In this embodiment, the test samples were distribution network surge arrester resistors produced by different manufacturers, applied to 10kV and 35kV surge arresters, with a nominal discharge current of 5kA. They were classified as A, B, C, and D according to different manufacturers. The diameter, height, and weight of the resistors were measured and recorded. The resistors were also classified according to the diameter of the distribution network surge arrester resistors of each manufacturer's model. Those with a diameter of 40mm or less were classified as Class I distribution network surge arrester resistors, and those with a diameter of 40mm or more were classified as Class II distribution network surge arrester resistors.

[0056] Step 102: Measure the initial electrical parameters of each distribution network surge arrester resistor element according to the volt-ampere characteristic curve of each distribution network surge arrester resistor element; wherein, the initial electrical parameters include the initial DC reference voltage of the resistor element at 1mA DC, the initial leakage current at 0.75 times the initial DC reference voltage, and the initial lightning impulse residual voltage value at 8 / 20μs under the nominal discharge current.

[0057] In this embodiment, the initial electrical parameters of each surge arrester resistor sample are measured. Three representative points are selected on the resistor's volt-ampere characteristic curve: the initial DC reference voltage of the resistor at 1mA DC, the initial leakage current at 0.75 times the initial DC reference voltage, and the initial lightning impulse residual voltage at the nominal discharge current for 8 / 20μs.

[0058] Step 103: Based on the first impulse current, perform the first preset test on the first resistor to obtain the first test result, and based on the first preset conditions, the first test result and the first preset test, obtain the current amplitude of the first impulse current when the first resistor is damaged; the first resistor is the distribution network surge arrester resistor based on the first preset number of resistors of various types from various manufacturers.

[0059] Optionally, the first preset test is as follows: the first resistor is subjected to a first impulse current three times in a 3-minute period; wherein the waveform of the first impulse current is 8 / 20μs and the initial value of the current amplitude of the first impulse current is 2kA.

[0060] Optionally, step 103 specifically involves: conducting a first preset test on the first resistor based on the first impulse current to obtain the current second electrical parameters of the first resistor; and determining whether the first resistor is damaged based on the first preset conditions, the current second electrical parameters of the first resistor, and the initial electrical parameters; wherein the current second electrical parameters include the current second DC reference voltage of the resistor under 1mA DC, the current second leakage current under 0.75 times the current second DC reference voltage, and the current second lightning impulse residual voltage value under the nominal discharge current at 8 / 20μs.

[0061] If damaged, obtain the current amplitude of the first impact current when the first resistor element fails;

[0062] If not damaged, the current amplitude of the first inrush current is increased according to the first preset step value. The first inrush current is adjusted according to the current amplitude of the first inrush current, and the first resistor is reacquired. The first resistor is subjected to a first preset test according to the first inrush current to obtain the current second electrical parameters of the first resistor. The first resistor is judged to be damaged according to the first preset conditions, the current second electrical parameters of the first resistor, and the initial electrical parameters until the first resistor is damaged. The current amplitude of the first inrush current when the first resistor is damaged is obtained.

[0063] Optionally, based on the first preset conditions, the current second electrical parameters of the first resistor, and the initial electrical parameters, it is determined whether the first resistor is damaged, specifically as follows:

[0064] If the first resistor meets any of the first preset conditions, it is determined that the first resistor is damaged; otherwise, it is determined that the first resistor is not damaged.

[0065] The first preset condition includes: the first resistor element is broken or broken down;

[0066] The sum of the initial DC reference voltage of the first resistor and the change in the current second DC reference voltage exceeds the first preset value;

[0067] The initial leakage current of the first resistor and the change in the current second leakage current exceed the second preset value;

[0068] The changes in the initial lightning impulse residual voltage value and the current second lightning impulse residual voltage value of the first resistor exceed the third preset value.

[0069] In this embodiment, the resistor test procedure is as follows: Figure 2As shown, based on the first preset number of resistors for various types of resistors from different manufacturers, the first preset number of resistors is 1. The first preset test involves applying three consecutive first impulse currents of the same amplitude to the first resistor within a 3-minute timeframe. The waveform of the first impulse current is 8 / 20 μs, and the amplitude of the first impulse current is I. start The initial current of the first impact current is 2kA. After the first preset test, the current test results are obtained, i.e., the current electrical parameters are obtained. Based on the current electrical parameters and initial electrical parameters of the first resistor, and the first preset conditions, it is determined whether the first resistor is damaged. If any of the first preset conditions is met, it is determined that the first resistor is damaged. The first preset conditions mainly include four:

[0070] (1) The resistor element is broken or broken down;

[0071] (2) DC reference voltage U of the resistor 1mA The change exceeds ±5% (first preset value);

[0072] (3) Leakage current I of the resistor 0.75U1mA Increase by more than 10 μA (second preset value);

[0073] (4) Lightning impulse residual voltage U of the resistor element res The change exceeds ±5% (third preset value).

[0074] If the first resistor is not damaged, then the amplitude I of the first impact current will be... start Increase the current by 500A (first preset step value), reacquire the first resistor, and continue the first preset test. Then determine if the first resistor is damaged. Repeat the first preset test and determine if the first resistor is damaged until the first resistor is damaged. Obtain the current amplitude I of the first inrush current when the first resistor is damaged. con .

[0075] Step 104: Based on the second impulse current, conduct a second preset test on the second resistor to obtain the second test result. Based on the second preset conditions, the second test result, and the second preset test, obtain the current first electrical parameters of the third resistor. Based on the current second impulse current and the current first electrical parameters of the third resistor, calculate the lightning impulse withstand value of the same type of resistor from the same manufacturer. Wherein, the initial value of the current amplitude of the second impulse current is the current amplitude of the first impulse current, the second resistor is the distribution network surge arrester resistor based on the second preset number of resistors of the same type from the same manufacturer, and the third resistor is the undamaged distribution network surge arrester resistor among the second resistors that meet the damage quantity condition.

[0076] Optionally, step 104 specifically involves: conducting a second preset test on the second resistor based on the second inrush current to obtain the current first electrical parameters of the second resistor; determining whether the second resistor is damaged based on the second preset conditions, the current first electrical parameters of the second resistor, and the initial electrical parameters; counting the number of damaged second resistors in the second preset number of resistors to obtain the damage amount; and determining whether the damage amount meets the damage quantity condition. The waveform of the second inrush current is 8 / 20μs. During the first preset test, the second resistor is continuously subjected to the second inrush current three times within a 3-minute period. The current first electrical parameters include the current first DC reference voltage of the resistor at 1mA DC, the current first leakage current at 0.75 times the current first DC reference voltage, and the current first lightning impulse residual voltage value at 8 / 20μs under the nominal discharge current.

[0077] If the damage quantity condition is not met, the current amplitude of the second inrush current is adjusted according to the second preset step value. The second inrush current is adjusted according to the current amplitude of the second inrush current, and the second resistor is reacquired. According to the second inrush current, the second resistor is subjected to the second preset test to obtain the current first electrical parameters of the second resistor. According to the second preset conditions, the current first electrical parameters of the second resistor and the initial electrical parameters, it is determined whether the second resistor is damaged. The number of damaged second resistors in the second preset number of resistors is counted to obtain the damage quantity. It is determined whether the damage quantity meets the damage quantity condition until the damage quantity meets the damage quantity condition, and the current first electrical parameters of the third resistor are obtained.

[0078] If the damage quantity condition is met, the current first electrical parameters of the distribution network surge arrester resistors that are not mechanically damaged in the second resistor are counted to obtain the current first electrical parameters of the third resistor.

[0079] Optionally, based on the second preset conditions, the current first electrical parameters and initial electrical parameters of the second resistor, it is determined whether the second resistor is damaged, specifically as follows:

[0080] If the second resistor meets any of the second preset conditions, it is determined that the second resistor is damaged; otherwise, it is determined that the second resistor is not damaged.

[0081] The second preset condition includes: the second resistor element is cracked or broken down;

[0082] The sum of the initial DC reference voltage of the second resistor and the change in the current first DC reference voltage exceeds the fourth preset value;

[0083] The initial leakage current of the second resistor and the change in the current first leakage current exceed the fifth preset value;

[0084] The change between the initial lightning impulse residual voltage value and the current first lightning impulse residual voltage value of the second resistor exceeds the sixth preset value.

[0085] In this embodiment, a second set of 10 distribution network surge arrester resistors of the same type and model from the same manufacturer are used. The second preset test involves applying three consecutive second impulse currents of the same amplitude to the second resistor within a 3-minute period. The waveform of the second impulse current is 8 / 20 μs. The starting value of the current amplitude of the second impulse current is I, which is the current amplitude of the first impulse current. con After the first second preset test, the current test results are obtained, i.e., the current electrical parameters are obtained. Based on the current electrical parameters and initial electrical parameters of the second resistor, and the second preset conditions, it is determined whether the second resistor is damaged. If any of the second preset conditions is met, it is determined that the second resistor is damaged. The second preset conditions mainly include four conditions:

[0086] (1) The resistor element is broken or broken down;

[0087] (2) DC reference voltage U of the resistor 1mA The change exceeds ±5% (fourth preset value);

[0088] (3) Leakage current I of the resistor 0.75U1mA Increase by more than 10 μA (fifth preset value);

[0089] (4) Lightning impulse residual voltage U of the resistor element res The change exceeds ±5% (sixth preset value).

[0090] The number of damaged second resistors is counted, i.e., the damage amount Z, and the condition for the damage amount is 4≤Z≤6.

[0091] If the damage amount satisfies 4≤Z≤6, then the current first electrical parameters of the third resistor are calculated. The third resistor is the distribution network surge arrester resistor that has not been mechanically damaged among the second resistors. Mechanical damage refers to visible mechanical damage to the resistor such as cracking, perforation, and flashover. The resistors without mechanical damage among the second resistors (10 resistors) are counted for the next step of withstand energy calculation.

[0092] If the damage amount Z < 4, the current amplitude of the second impact current is increased by 100A (second preset step value), the second resistor is reacquired, the second preset test is continued, the damage amount is obtained, the damage of the second resistor is judged, and the test is continuously adjusted according to the condition met by the damage amount until the damage amount meets the damage quantity condition, and the current first electrical parameters of the third resistor are obtained.

[0093] If the damage amount Z > 6, then the current amplitude of the second impact current is reduced by 100A (second preset step value), the second resistor is reacquired, the second preset test is continued, the damage amount is obtained, the damage judgment of the second resistor is performed, and the test is continuously adjusted according to the condition met by the damage amount until the damage amount meets the damage quantity condition, and the current first electrical parameters of the third resistor are obtained.

[0094] Optionally, based on the current second impulse current and the current first electrical parameters of the third resistor, calculate the lightning impulse withstand value of the same type of resistor from the same manufacturer, specifically:

[0095] Based on the current second impulse current and the current residual voltage value of the first lightning impulse of the third resistor, the withstand energy value of each third resistor is calculated using the following formula:

[0096]

[0097] Where E is the withstand energy value of each third resistor, u is the current residual voltage value of the first lightning impulse, i is the current second impulse current, and T is the duration of the current second impulse current;

[0098] Based on the withstand energy value of each third resistor, the average withstand energy is calculated. Based on the current amplitude of the current second impulse current and the average withstand energy, the lightning impulse withstand value of the same type of resistor from the same manufacturer is obtained.

[0099] In this embodiment, when the damage quantity condition is met, a third resistor is obtained. Based on the current impulse current amplitude (the current second impulse current) on each third resistor and the residual voltage value on the resistor (the current first lightning impulse residual voltage value corresponding to the current second impulse current), the energy withstand value of each third resistor is calculated (for cases of resistor breakage or breakdown, due to abnormal residual voltage values, they are not included in the calculation), using the following formula:

[0100]

[0101] Where E is the withstand energy value of each third resistor element, u is the current residual voltage value of the first lightning impulse, i.e., the voltage across the resistor element of the surge arrester, i is the current second impulse current, i.e. the impulse current flowing through the resistor element of the surge arrester, and is the duration of the current second impulse current, i.e. the duration of resistor element damage. The duration of resistor element damage can be obtained by recording the impulse current waveform or residual voltage waveform during the resistor element test. The average withstand energy value of each resistor element in the third resistor element is calculated. This energy value is the impulse energy withstand capability value E0 of the 8 / 20μs lightning impulse waveform of this type of resistor element of this manufacturer.

[0102] Step 105: Normalize the lightning impulse withstand values ​​of several types of resistors from several manufacturers to obtain the unit size withstand value of each type of resistor from each manufacturer. Based on the unit size withstand value, evaluate the lightning impulse withstand capability of each type of resistor from each manufacturer.

[0103] Optionally, step 105 specifically involves: dividing the current amplitude of the second impulse current by the average cross-sectional area of ​​the third resistor to obtain the impulse current amplitude per square centimeter of the same type of resistor from the same manufacturer; dividing the average withstand energy by the average volume of the third resistor to obtain the energy withstand value per cubic centimeter of the same type of resistor from the same manufacturer; and evaluating the lightning impulse withstand capability of each type of resistor from each manufacturer by comparing the impulse current amplitude per square centimeter of the cross-section and the energy withstand value per cubic centimeter of the resistor from each type of resistor from each manufacturer.

[0104] In this embodiment, since the structures and dimensions of the surge arrester resistors from different manufacturers vary, the results need to be normalized to compare the energy withstand capabilities of resistors from different manufacturers. The current amplitude of the second impulse current is divided by the cross-sectional area of ​​the resistor to obtain the impulse current amplitude per square centimeter of cross-section, denoted as I. acd The unit is A / cm 2 Divide the obtained impact energy withstand value E0 by the volume of the resistor element to obtain the energy withstand value per cubic centimeter of resistor element, denoted as E. mfe The unit is kJ / cm 3 Finally, with I acd E is the horizontal axis. mfe Using the vertical axis, points are plotted on the Class I and Class II resistors from various manufacturers. This allows for a clear comparison of the energy withstand capability of different manufacturers' resistor models under an 8 / 20μs lightning strike, thereby evaluating the lightning strike withstand capability of various types of resistors from different manufacturers.

[0105] By implementing this invention, the initial electrical parameters of the surge arrester resistor element before and after the impulse energy injection test are compared. Based on the comparison results, it can be determined whether the resistor element is damaged. The impulse current amplitude is adjusted accordingly, and an impulse test is conducted to further approach the impulse energy tolerance limit of the resistor element. By continuously changing the impulse current and test conditions, the tolerance limit value of various types of distribution network surge arrester resistor elements from different manufacturers is continuously approached. This allows for the testing and evaluation of the energy tolerance capability of distribution network surge arrester resistor elements under lightning impulse, accurately obtaining the lightning impulse tolerance value of the surge arrester resistor element, effectively selecting surge arrester resistor elements from different manufacturers, mastering the tolerance limit values ​​of resistor elements from different manufacturers, and selecting the best among the best. Furthermore, by combining the resistor element's tolerance energy value with the operating conditions that the surge arrester may encounter during operation, the suitability of the surge arrester can be analyzed. This can be used in surge arrester selection work, and the lightning impulse tolerance value of the surge arrester resistor element can also be used as a reference for surge arrester fault analysis under lightning strikes.

[0106] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention in detail. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A method for evaluating the lightning impulse energy withstand capability of surge arrester resistor elements in a distribution network, characterized in that, include: Based on the first impulse current, the first resistor is subjected to a first preset test to obtain the first test result. Based on the first preset conditions, the first test result, and the first preset test, the current amplitude of the first impulse current when the first resistor is damaged is obtained. The first resistor is a distribution network surge arrester resistor based on the first preset number of resistors of various types from various manufacturers. Based on the second impulse current, the second resistor is subjected to a second preset test to obtain the second test result. Based on the second preset conditions, the second test result, and the second preset test, the current first electrical parameters of the third resistor are obtained. Based on the current second impulse current and the current first electrical parameters of the third resistor, the lightning impulse withstand value of a resistor of the same type and model from the same manufacturer is calculated. Wherein, the initial value of the current amplitude of the second impulse current is the current amplitude of the first impulse current; the second resistor is the distribution network surge arrester resistor of the same type and model from the same manufacturer, based on a second preset number of such resistors; and the third resistor is the undamaged second resistor among those meeting the damage quantity condition. The lightning impulse withstand values ​​of several types of resistors from several manufacturers are normalized to obtain the unit size withstand value of each type of resistor from each manufacturer. Based on the unit size withstand value, the lightning impulse withstand capability of each type of resistor from each manufacturer is evaluated.

2. The method for evaluating the lightning impulse energy withstand capability of the resistor element of a distribution network surge arrester as described in claim 1, characterized in that, Before conducting a first preset test on the first resistor element based on the first impulse current and obtaining the first test result, the method further includes measuring the initial electrical parameters of each of the distribution network surge arrester resistor elements based on the volt-ampere characteristic curves of each of the distribution network surge arrester resistor elements. The initial electrical parameters include the initial DC reference voltage of the resistor at 1mA DC, the initial leakage current at 0.75 times the initial DC reference voltage, and the initial lightning impulse residual voltage at 8 / 20μs under the nominal discharge current.

3. The method for evaluating the lightning impulse energy withstand capability of the resistor element of a distribution network surge arrester as described in claim 2, characterized in that, The process involves performing a first preset test on the first resistor based on the first inrush current, obtaining a first test result, and then, based on the first preset conditions, the first test result, and the first preset test, obtaining the current amplitude of the first inrush current when the first resistor is damaged. Specifically: Based on the first impulse current, the first resistor is subjected to the first preset test to obtain the current second electrical parameters of the first resistor. Based on the first preset conditions, the current second electrical parameters of the first resistor, and the initial electrical parameters, it is determined whether the first resistor is damaged. The current second electrical parameters include the current second DC reference voltage of the resistor at 1mA DC, the current second leakage current at 0.75 times the current second DC reference voltage, and the current second lightning impulse residual voltage value at 8 / 20μs under the nominal discharge current. If damaged, obtain the current amplitude of the first impact current when the first resistor is damaged; If not damaged, the current amplitude of the first inrush current is increased according to the first preset step value. The first inrush current is adjusted according to the current amplitude of the first inrush current, and the first resistor is reacquired. The first resistor is subjected to the first preset test according to the first inrush current to obtain the current second electrical parameter of the first resistor. The first resistor is determined to be damaged according to the first preset condition, the current second electrical parameter of the first resistor, and the initial electrical parameter. The process continues until the first resistor is damaged, and the current amplitude of the first inrush current when the first resistor is damaged is obtained.

4. The method for evaluating the lightning impulse energy withstand capability of the resistor element of a distribution network surge arrester as described in claim 3, characterized in that, The first preset test specifically involves applying the first impulse current to the first resistor three times consecutively within a 3-minute period. The waveform of the first impact current is 8 / 20μs, and the initial value of the current amplitude of the first impact current is 2kA.

5. The method for evaluating the lightning impulse energy withstand capability of the resistor element of a distribution network surge arrester as described in claim 3, characterized in that, The step of determining whether the first resistor is damaged based on the first preset condition, the current second electrical parameter of the first resistor, and the initial electrical parameter is as follows: If the first resistor meets any of the first preset conditions, it is determined that the first resistor is damaged; otherwise, it is determined that the first resistor is not damaged. The first preset condition includes: the first resistor sheet is broken or broken down; The change in the initial DC reference voltage and the current second DC reference voltage of the first resistor exceeds a first preset value; The changes in the initial leakage current and the current second leakage current of the first resistor exceed a second preset value; The change in the initial lightning impulse residual voltage value and the current second lightning impulse residual voltage value of the first resistor exceeds a third preset value.

6. The method for evaluating the lightning impulse energy withstand capability of the resistor element of a distribution network surge arrester as described in claim 2, characterized in that, The process involves conducting a second preset test on the second resistor based on the second inrush current, obtaining a second test result, and then obtaining the current first electrical parameters of the third resistor based on the second preset conditions, the second test result, and the second preset test. Specifically: Based on the second inrush current, the second resistor is subjected to the second preset test to obtain the current first electrical parameters of the second resistor. Based on the second preset conditions, the current first electrical parameters of the second resistor, and the initial electrical parameters, it is determined whether the second resistor is damaged. The number of damaged second resistors in the second preset number of resistors is counted to obtain the damage amount. It is determined whether the damage amount meets the damage quantity condition. The waveform of the second inrush current is 8 / 20μs. During the first preset test, the second resistor is subjected to the second inrush current three times in a 3-minute period. The current first electrical parameters include the current first DC reference voltage of the resistor at 1mA DC, the current first leakage current at 0.75 times the current first DC reference voltage, and the current first lightning impulse residual voltage value at 8 / 20μs under the nominal discharge current. If the damage quantity condition is not met, the current amplitude of the second inrush current is adjusted according to the second preset step value. The second inrush current is adjusted according to the current amplitude of the second inrush current, and the second resistor is reacquired. The second resistor is subjected to the second preset test according to the second inrush current to obtain the current first electrical parameter of the second resistor. According to the second preset condition, the current first electrical parameter of the second resistor and the initial electrical parameter, it is determined whether the second resistor is damaged. The number of damaged second resistors in the second preset number of resistors is counted to obtain the damage quantity. It is determined whether the damage quantity meets the damage quantity condition until the damage quantity meets the damage quantity condition, and the current first electrical parameter of the third resistor is obtained. If the damage quantity condition is met, the current first electrical parameters of the distribution network surge arrester resistors that are not mechanically damaged in the second resistor are counted to obtain the current first electrical parameters of the third resistor.

7. The method for evaluating the lightning impulse energy withstand capability of the resistor element of a distribution network surge arrester as described in claim 6, characterized in that, The step of determining whether the second resistor is damaged based on the second preset condition, the current first electrical parameter of the second resistor, and the initial electrical parameter is as follows: If the second resistor meets any of the second preset conditions, it is determined that the second resistor is damaged; otherwise, it is determined that the second resistor is not damaged. The second preset condition includes: the second resistor sheet is cracked or broken down; The sum of the initial DC reference voltage and the change in the current first DC reference voltage of the second resistor exceeds a fourth preset value; The changes in the initial leakage current and the current first leakage current of the second resistor exceed a fifth preset value; The change in the initial lightning impulse residual voltage value and the current first lightning impulse residual voltage value of the second resistor exceeds a sixth preset value.

8. The method for evaluating the lightning impulse energy withstand capability of the resistor element of a distribution network surge arrester as described in claim 6, characterized in that, The lightning impulse withstand value of a resistor of the same type and model from the same manufacturer is calculated based on the current second impulse current and the current first electrical parameters of the third resistor. Specifically: Based on the current second impulse current and the current first lightning impulse residual voltage value of the third resistor, the withstand energy value of each third resistor is calculated using the following formula: Where E is the withstand energy value of each of the third resistors, u is the current residual voltage value of the first lightning impulse, i is the current second impulse current, and T is the duration of the current second impulse current; Based on the withstand energy value of each of the third resistor pieces, the average withstand energy is calculated. Based on the current amplitude of the second impulse current and the average withstand energy, the lightning impulse withstand value of the same type of resistor piece from the same manufacturer is obtained.

9. The method for evaluating the lightning impulse energy withstand capability of the resistor element of a distribution network surge arrester as described in claim 8, characterized in that, The lightning impulse withstand values ​​of each type of resistor from each manufacturer are normalized to obtain the unit size withstand value of each type of resistor from each manufacturer. Based on the unit size withstand value, the lightning impulse withstand capability of each type of resistor from each manufacturer is evaluated, specifically as follows: Divide the current amplitude of the second impact current by the average cross-sectional area of ​​the third resistor to obtain the impact current amplitude per square centimeter of the same type of resistor from the same manufacturer. Divide the average withstand energy by the average volume of the third resistor to obtain the energy withstand value per cubic centimeter of the same type of resistor from the same manufacturer. The lightning impulse withstand capability of various types of resistors from various manufacturers is evaluated by comparing the impulse current amplitude per square centimeter and the energy withstand value per cubic centimeter of resistors for each type of resistor from each manufacturer.

10. The method for evaluating the lightning impulse energy withstand capability of the resistor element of a distribution network surge arrester as described in claim 1, characterized in that, Before performing a first preset test on the first resistive element according to the first impact current and obtaining the first test result, the method further includes: The diameters of several distribution network surge arrester resistors from several manufacturers and models are classified to obtain resistors of various types from each manufacturer and model. The resistor types include Class I distribution network surge arrester resistors and Class II distribution network surge arrester resistors.

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