Lightning arrester service life evaluation method

Abstract

The lightning arrester service life evaluation method comprises health state evaluation and residual service life evaluation. The health state evaluation judges the current state by measuring the direct current reference voltage and the leakage current; in the residual life evaluation, an accelerated aging test is carried out on the whole lightning arrester, a zinc oxide resistor disc and a silicon rubber umbrella skirt, a life model is established, and the residual service life is predicted. According to the invention, the service life of the lightning arrester under the real working condition can be scientifically evaluated, and a basis is provided for operation and maintenance and replacement cycle formulation of an electric locomotive.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power equipment state monitoring and life prediction, and particularly relates to a life evaluation method for a lightning arrester of an electric locomotive. BACKGROUND

[0002] The operating condition of the lightning arrester of the electric locomotive is relatively special. The main circuit breaker of the locomotive needs to be operated for splitting and combining when the locomotive frequently passes through a sub-phase, and an operating overvoltage is generated during the operation. Meanwhile, the lightning arrester of the locomotive is operated outdoors and is easily subjected to a lightning overvoltage generated by lightning, and both of them will form an impact on the lightning arrester. The frequent vibration, high temperature, wind and sand in the process of operation of the locomotive will also affect the performance of the lightning arrester body and the umbrella skirt, resulting in failure of the lightning arrester. In order to avoid locomotive operation accidents and reduce maintenance costs, a scientific and economic replacement cycle of the lightning arrester should be formulated, and therefore it is necessary to evaluate the state and life of the lightning arrester under the existing operating condition.

[0003] At present, the evaluation methods of the lightning arrester of the electric locomotive mainly include online monitoring and power-off detection. The online monitoring system collects performance data in real time and continuously through the sensors installed on the lightning arrester, and transmits the performance data to the background system for analysis and early warning. The power-off detection mainly refers to that the lightning arrester is taken out of operation according to the maintenance plan, and the performance is checked regularly.

[0004] In view of the current state evaluation method of the lightning arrester of the electric locomotive, only the existing equipment problems can be found, the current safe operation of the lightning arrester is ensured, and the life of the lightning arrester under the existing operating condition cannot be estimated, and the operation and maintenance are planned in advance. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a lightning arrester life evaluation method, which can comprehensively evaluate the health state of the lightning arrester and predict the remaining service life, and provide a basis for operation and maintenance decision.

[0006] In order to solve the above technical problems, the technical scheme of the present application is as follows: a lightning arrester life evaluation method, comprising the following steps: Performing health state evaluation, selecting lightning arresters with different service times, measuring the direct current reference voltage and the leakage current under 0.75 times the direct current reference voltage of the lightning arrester, and comparing them with the preset threshold value to obtain the current state and state change of the lightning arrester; Performing remaining life evaluation, including performing accelerated aging test on the lightning arrester as a whole, zinc oxide resistance sheet and silicon rubber umbrella skirt respectively, establishing a life attenuation model, and selecting the weak part with faster life attenuation as the remaining life of the lightning arrester; Comprehensive health state and remaining life evaluation results.

[0007] As an improvement, the threshold value of the direct current reference voltage is not less than 58kV, and the threshold value of the leakage current is not higher than 50μA.

[0008] As an improvement, the accelerated aging test of the whole arrester is carried out at 135 DEG C, and the termination condition is that the leakage current reaches 2 times of the initial value or the test time reaches 7 days.

[0009] As an improvement, the accelerated aging test of the zinc oxide resistor disc is carried out at 115 DEG C and under the condition of continuous operating voltage, and the termination condition is that the resistor disc fails or the test time reaches 1000 hours.

[0010] As an improvement, the establishment of the life model of the zinc oxide resistor disc comprises: collecting the change data of power loss with aging time; selecting the optimal model by fitting linear, logarithmic, exponential or power function model; calculating the aging time based on the optimal model and the failure threshold, and converting the actual working condition into the remaining life according to the Arrhenius law.

[0011] As an improvement, the optimal model is a linear model, which has the highest goodness of fit R² and the smallest root mean square error RMSE.

[0012] As an improvement, the accelerated aging test of the silicone rubber umbrella skirt comprises heating the test sample at multiple temperatures, monitoring the tensile strength and elongation at break, until the elongation at break decreases to 50%, and calculating the remaining life accordingly.

[0013] Compared with the prior art, the present application has the following beneficial effects: The current performance check is used as a basic means to verify the state of the arrester with different mileage and time, to ensure the safe operation of the equipment, and the remaining life evaluation is used as a core means to obtain the remaining service life of the arrester under the existing working condition, to provide a basis for the operation and maintenance of electric locomotives. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The flow chart of the life evaluation of the arrester.

[0015] Figure 2 The scatter plot of the DC reference voltage of the arrester.

[0016] Figure 3 The scatter plot of the leakage current under 0.75 times the DC reference voltage.

[0017] Figure 4 The trend chart of the DC reference voltage of the accelerated aging of the whole arrester.

[0018] Figure 5 The trend chart of the leakage current under 0.75 times the DC reference voltage of the accelerated aging of the whole arrester.

[0019] Figure 6This is a scatter plot of power loss data for zinc oxide resistor samples during accelerated aging.

[0020] Figure 7 This is a power loss-aging time curve. Detailed Implementation

[0021] The present invention will now be further described with reference to the accompanying drawings.

[0022] A method for assessing the lifespan of surge arresters for electric locomotives mainly comprises two parts: a health status assessment based on data analysis and a remaining lifespan assessment based on aging analysis.

[0023] Health status assessment involves selecting surge arresters with different service durations, measuring and analyzing status data such as DC reference voltage and leakage current at 0.75 times the DC reference voltage, to determine the current status and changes in status of the surge arresters.

[0024] like Figure 2 As shown, the DC reference voltage of most surge arresters is concentrated in the range of 61 to 66 kV, and there is no obvious linear trend with the increase of service life, indicating that the service life has no significant impact on the DC reference voltage within this sample range. All data points are higher than the lower limit threshold of 58 kV, indicating that the DC reference voltage performance of all 43 surge arresters meets the requirements and there are no failures below the threshold.

[0025] like Figure 3 As shown, all data points are below the upper limit threshold of 50uA, indicating that the leakage current performance of all 43 surge arresters at 0.75 times the DC reference voltage meets the requirements and there is no risk of failure exceeding the threshold. The leakage current of most surge arresters is concentrated in the range of 0-20uA, with a few exceeding 20uA. Moreover, there is no obvious linear growth trend with the increase of service life, indicating that the service life has no significant impact on the leakage current.

[0026] Figure 3 , Figure 4 The leakage current performance of the surge arrester was verified to be generally stable under different operating periods, DC reference voltage, and 0.75 times DC reference voltage, and no performance degradation due to aging was observed.

[0027] The remaining life assessment covers the surge arrester as a whole, zinc oxide resistor elements, and silicone rubber sheds. Accelerated aging and characteristic parameter testing are performed on the assessment objects, and the test data is obtained, followed by statistical analysis and calculation to determine the corresponding remaining life. Details are as follows:

[0028] 1) Overall surge arrester – A certain number of surge arrester samples were placed in a 135℃ oven for accelerated aging until the leakage current value reached twice the initial value or the test time reached 7 days. During this period, the changes in leakage current under DC reference voltage and 0.75 times DC reference voltage were tested and recorded to obtain the DC reference voltage and leakage current change curves.

[0029] like Figure 4 , 5 As shown, the DC reference voltage and leakage current at 0.75 times the DC reference voltage of surge arresters samples 1#, 2#, 3#, 4#, and 6# remained stable within a stable range, without any obvious increasing or decreasing trend. This indicates that the overall performance of these samples remained stable during accelerated aging and did not show significant deterioration. Sample 5#, however, showed a rapid and significant decrease in reference voltage and a significant increase in leakage current over aging time, exhibiting obvious deterioration characteristics. It is considered an abnormal sample, and the analysis suggests that the performance degradation was caused by an accidental collision during the test.

[0030] Figure 4 , Figure 5 It was verified that temperature has no significant effect on the DC reference voltage and 0.75 times the reference voltage of the surge arrester, and no significant degradation of the surge arrester was observed.

[0031] 2) Zinc oxide resistance sheet – Three zinc oxide resistance sheet samples were selected and subjected to thermoelectric accelerated aging at a temperature of 115℃ and continuous operating voltage until the resistance sheet failed or the test time reached 1000h. The power loss of the resistance sheet was recorded at different aging times to obtain the power loss change curve over time. The time taken to age to failure was also recorded and multiplied by the aging acceleration factor. Finally, the remaining life of the resistance sheet under ambient temperatures of 40℃ and 80℃ was calculated.

[0032] like Figure 6 The figure shows the scatter plot trend of power loss data for sample #1 zinc oxide resistor during accelerated aging.

[0033] according to Figure 6 By simultaneously fitting multiple curve models, including linear, logarithmic, exponential, and power curves, and comparing the goodness of fit (R²) and significance (ANOVA results) of different models, the optimal curve model for "power loss-aging time" was finally determined. The fitted curve models are shown below. Figure 7 As shown in Table 1, the comparison results of various statistical indicators of different models are presented.

[0034] Table 1

[0035] from Figure 7 It can be seen that the R-squared of the linear model 2With a high RMSE and a significant P-value, the linear model can be identified as the optimal curve model.

[0036] After determining the optimal curve model, the model parameters can be calculated using the least squares method. The "power loss - aging time" model for sample #1 zinc oxide resistor is y = 0.00008592ln(x) + 0.76. Substituting the power loss at the failure of resistor #1 (1.1 times the initial value, i.e., 1.1 x 0.9251) into the model, the aging failure time x = 1922 h is obtained.

[0037] According to Arrhenius's law, the lifespan of the resistor at 40°C is estimated to be 1,854,730 hours (equivalent to 212 years) with an aging acceleration factor of 965, and 48,050 hours (equivalent to 5 years) with an aging acceleration factor of 25.

[0038] 3) Silicone rubber umbrella skirt - Take a sample of the silicone rubber umbrella skirt from the surge arrester, cut the umbrella skirt into a certain number of sample strips, and then select 4 temperatures to heat and age the sample strips until the elongation at break reaches 50%. During this period, test and record the tensile strength and elongation at break to obtain the remaining life of the silicone rubber umbrella skirt at 40℃ and 80℃.

[0039] Based on the aging data of the surge arrester as a whole, zinc oxide resistors, and silicone rubber skirts, a life decay model was established for each of them, and the weak parts with faster life decay were selected as the remaining life of the surge arrester.

[0040] Based on the combined results of health status assessment and remaining life assessment, the surge arrester is analyzed from different dimensions (status, time) to output the final conclusion on the remaining life of the surge arrester. For example, "healthy and with sufficient remaining life" or "sub-healthy and with less than 50% remaining life".

Claims

1. A method for evaluating the service life of a surge arrester, characterized by, The method comprises the following steps: Performing health state assessment, selecting the arrester with different service time, comparing the DC reference voltage and the leakage current under 0.75 times of the DC reference voltage of the arrester with preset threshold, obtaining the current state and state change of the arrester; Performing residual life assessment, including performing accelerated aging test on the arrester as a whole, zinc oxide resistor and silicon rubber umbrella skirt respectively, establishing life attenuation model, and selecting the weak part with faster life attenuation as the residual life of the arrester; Comprehensively assessing the health state and residual life assessment results.

2. The method of claim 1, wherein: The threshold of the DC reference voltage is not less than 58 kV, and the threshold of the leakage current is not higher than 50 μA.

3. The method of claim 1, wherein: The accelerated aging test of the arrester as a whole is performed at 135 ℃, and the termination condition is that the leakage current reaches 2 times of the initial value or the test time reaches 7 days.

4. The method of claim 1, wherein: The accelerated aging test of the zinc oxide resistor is performed at 115 ℃ and under the condition of continuous operating voltage, and the termination condition is that the resistor fails or the test time reaches 1000 hours.

5. The method of claim 4, wherein: The establishment of the life model of the zinc oxide resistor comprises: Collecting the change data of power loss with aging time; Selecting the optimal model by fitting linear, logarithmic, exponential or power function model; Based on the optimal model and failure threshold, the aging time is calculated, and the actual working condition is converted into the residual life by Arrhenius law.

6. The method of claim 5, wherein: The optimal model is a linear model, which has the highest goodness of fit R² and the smallest root mean square error RMSE.

7. The method of claim 1, wherein: The accelerated aging test of the silicon rubber umbrella skirt comprises heating the test sample at multiple temperatures, monitoring the tensile strength and elongation at break, until the elongation at break decreases to 50%, and the residual life is calculated accordingly.

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