Cable line metal sheath protector type selection optimization method based on induced overvoltage

Abstract

The invention belongs to the technical field of protector type selection optimization, and particularly relates to a cable line metal sheath protector type selection optimization method based on induced overvoltage, which comprises the following steps of: acquiring operation state data and environment state data of a cable line, analyzing and diagnosing the state of the cable line, and if the state of the cable line is abnormal, performing early warning. If the state of the cable line is normal, obtaining an initial overvoltage; correcting the initial overvoltage based on the intermittent load of the electrified railway to obtain corrected overvoltage; evaluating the insulation performance and the overvoltage hazard level of the metal sheath of each area of the current cable line; determining basic model selection indexes of the protectors based on the overvoltage hazard levels, and screening candidate protectors based on the basic model selection indexes; and performing performance evaluation on the candidate protectors, and determining an optimal protector. According to the method, the optimal protector is determined through short-term and long-term performance evaluation under multi-round screening and simulation working conditions, and reliable operation of a cable line under different working conditions is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of protector selection optimization, and in particular to a method for selecting and optimizing a cable line metal sheath protector based on induced overvoltage. Background Art

[0002] In power transmission systems, the metal sheath protector of cable lines plays a key role, protecting the metal sheath from damage caused by overvoltage and ensuring the stable operation of the cable lines. However, in actual applications, damage to cable sheath protectors often occurs due to insufficient understanding of the overvoltage levels of the metal sheath of high-voltage cable lines, improper configuration of sheath protectors, and changes in the state of the sheath protectors under multiple impacts. When lightning overvoltage and switching overvoltage occur, the overvoltage transmitted from the transmission line will generate an induced overvoltage on the metal sheath, which in turn causes the state of the sheath protector to change. Therefore, it is necessary to conduct multiple continuous impulse current tests to evaluate the impulse current tolerance capability of the sheath protector and to study the changes in performance parameters such as the residual voltage, leakage current, and power loss of the sheath protector with the number of overvoltage impacts under multiple overvoltages.

[0003] Existing cable sheath protector configuration optimization methods have obvious deficiencies in the selection process. These methods lack precise selection criteria and fail to fully consider the cable's operating status, environmental factors, the impact of intermittent loads, and changes in insulation performance. This leads to irrational protector selection and difficulty in effectively protecting cable lines. For example, although Chinese invention patent publication number CN114784777B discloses a configuration optimization method and system for high-voltage cable sheath protectors, this method primarily optimizes parameter configuration based on the real-time induced voltage of the sheath protector, and still fails to address the problem of insufficient comprehensive consideration of multiple factors during the selection process. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide a method for optimizing the selection of metal sheath protectors for cable lines based on induced overvoltage. The optimal protector is determined through multiple rounds of screening and short-term and long-term performance evaluation under simulated working conditions to ensure reliable operation of cable lines under different working conditions.

[0005] To achieve the above object, the technical solution adopted by the present invention is: The method for optimizing the selection of metal sheath protectors for cable lines based on induced overvoltage includes the following steps: Obtain the operating status data and environmental status data of the cable line, analyze and diagnose the cable line status, and issue an early warning if the cable line status is abnormal. If the cable line status is normal, obtain the initial overvoltage; Correcting the initial overvoltage based on the intermittent load of the electrified railway to obtain the corrected overvoltage; Evaluate the insulation performance of the metal sheath and the overvoltage hazard level in each area of the current cable line; Determine the basic selection index of the protector based on the overvoltage hazard level, and screen the candidate protectors based on the basic selection index; The performance of candidate protectors is evaluated to determine the optimal protector.

[0006] Preferably, the operating status data includes a core current curve , core current change rate curve and voltage fluctuation range , environmental status data includes ambient temperature change curve And the environmental humidity change curve , is the minimum value of the voltage fluctuation range, is the maximum value of the voltage fluctuation range; Analyzing and diagnosing the cable line status includes the following steps: Obtain the parameterized operating status data and parameterized environmental status data stored in the database. The parameterized operating status data includes the core current parameter curve. , core current change rate parameter curve And voltage fluctuation parameter range , parameterized environmental status data including ambient temperature change parameterized curve and ambient humidity change parameter curve , is the minimum value of the voltage fluctuation parameter range, The maximum value of the voltage fluctuation parameter range; Perform similarity processing on the operating status data and the parameter operating status data; Perform similarity processing on the environmental state data and the reference environmental state data; Determine the state coefficient based on the similarity processing result , if the state coefficient Greater than the state coefficient stored in the database The cable line status is abnormal. If the status coefficient Not greater than the state coefficient stored in the database The cable line status is normal, where the status coefficient The calculation formula is: ; in, and are all transfer functions, for and The similarity function of for and The similarity function of for and The similarity function of for and The similarity function of .

[0007] Preferably, correcting the initial overvoltage based on the intermittent load of the electrified railway to obtain the corrected overvoltage includes the following steps: Obtaining a curve of intermittent load current changing over time, and smoothing the intermittent load change data to obtain a smoothed load current change curve; The Fourier transform is used to perform spectrum analysis on the smoothed load current variation curve to obtain the current amplitude and phase at different frequencies. Determine the main frequency components , and the current amplitude of the main frequency components and phase , i is the main frequency component number; Obtain the mutual inductance M of the cable line; Calculate corrected overvoltage : ; Among them, j is the imaginary unit, e is the natural constant, is the induced voltage increment generated by the i-th main frequency component, is the initial overvoltage.

[0008] Preferably, evaluating the insulation performance of the metal sheath and the overvoltage hazard level in each area of the current cable line includes the following steps: Based on the historical operation records of the cable line, obtain historical operation characteristic data, including operation time , overvoltage times , the amplitude of each overvoltage and duration and aging coefficient ; Compare the historical operation feature data with the historical operation feature matching data stored in the database one by one to obtain the respective comparison coefficients. , determine the historical operation feature matching data corresponding to the minimum comparison coefficient, and obtain the insulation resistance prediction value corresponding to the historical operation feature matching data from the database ; Historical operation feature matching data including operation matching time , overvoltage matching times , the matching amplitude of each overvoltage and match duration and matching aging coefficients , where a is the number of each overvoltage with the maximum number of overvoltage matches in the historical operation feature matching data, and g is the number of the historical operation feature matching data; If the predicted insulation resistance value is less than the standard value of the cable insulation resistance, it is marked as abnormal insulation performance of the metal sheath; If the predicted insulation resistance value is not less than the standard value of the cable insulation resistance, it is marked as the insulation performance of the metal sheath is normal; Get the breakdown voltage of the current metal protection layer stored in the database , the corrected overvoltage and breakdown voltage Perform ratio calculation to obtain the voltage ratio factor r; The ratio of the total duration of the overvoltage amplitude exceeding the set voltage threshold to the operating time is calculated to obtain the time ratio factor p; When the predicted insulation resistance value is less than the standard value of the cable insulation resistance, , the voltage ratio factor r and the time ratio factor p are combined into a hazard level matching set; Compare the similarity between the hazard level matching set and the hazard level parameter set stored in the database to obtain the level comparison factor , determine the hazard level parameter set corresponding to the minimum level comparison factor, and obtain the overvoltage hazard level corresponding to the hazard level parameter set from the database. The overvoltage hazard level includes mild, medium and severe levels. The hazard level parameter set includes the parameter insulation resistance prediction value , parameter voltage ratio factor and the parameter time ratio factor , d is the number of the hazard level parameter set.

[0009] Preferably, the comparison coefficient The calculation method is as follows: ; in, is the transfer function, A is the maximum number of overvoltage matching times in each historical operation feature matching data; Rank comparison factor The calculation method is as follows: .

[0010] Preferably, determining the basic selection index of the protector based on the overvoltage hazard level includes the following steps: Get the maximum operating voltage and the maximum power appearing in the cable ; Cluster the duration of overvoltage and determine the first duration of overvoltage , the second duration and the third duration ,in, ; Obtain the index correction factor based on the overvoltage hazard level, and determine the rated voltage requirement of the protector based on the index correction factor and protector energy absorption capacity , x=1, 2, 3; Get the allowed number of failures per year and mean time between failures MTBF, the rated voltage requirement for the protector and protector energy absorption capacity Make corrections.

[0011] Preferably, the index correction factor includes a slight correction factor for rated voltage , slight correction factor for energy absorption , rated voltage medium correction factor , medium correction factor for energy absorption , rated voltage severe correction factor and energy absorption severity correction factor ; If the overvoltage hazard level is mild, the rated voltage requirement of the protector is , , the energy absorption capacity of the protector is , ; If the overvoltage hazard level is medium, the rated voltage requirement of the protector is , , the energy absorption capacity of the protector is , ; If the overvoltage hazard level is severe, the rated voltage requirement of the protector is , , the energy absorption capacity of the protector is , .

[0012] Preferably, the protector rated voltage requirement value and the protector energy absorption capacity are corrected, comprising the following steps: ; ; in, is the rated voltage requirement of the protector after correction, The energy absorption capacity of the corrected protector is: is the general allowable number of failures, To set the mean time between failures.

[0013] Preferably, the performance evaluation of candidate protectors and determination of the optimal protector comprises the following steps: Perform a round of screening on the candidate protectors, screen out the candidate protectors whose response time is greater than the response time threshold, and screen out the candidate protectors whose heat resistance level is lower than the required heat resistance level; After a round of screening, the performance of the candidate protectors is evaluated under simulated working conditions: Using circuit simulation software, the candidate protectors after a round of screening are connected to the simulated cable system model. According to different operating conditions, the simulated performance indicators of the candidate protectors after a round of screening are simulated and calculated. The simulated performance indicators include simulated residual voltage , simulated energy absorption and the number of successful simulated actions ; Obtain the short-term performance evaluation factor of each candidate protector based on the simulated performance index and the required performance index , the required performance indicators include the required residual pressure , energy absorption required and the required number of successful actions ; Based on the long-term simulation operation, the performance index change data of the candidate protectors after a round of screening is obtained. The performance index change rate includes the increase in the simulated residual pressure. , Simulated energy absorption reduction and the reduction in the number of successful simulated actions ; Obtain long-term stability evaluation factors based on performance index change data ; Based on short-term performance evaluation factors and long-term stability assessment factors Determine comprehensive evaluation factors , determine the minimum comprehensive evaluation factor The candidate protector after the corresponding round of screening is taken as the optimal protector.

[0014] Preferably, comprehensive evaluation factors The method to obtain is as follows: .

[0015] The present invention has the following beneficial effects: The present invention comprehensively collects cable line operation and environmental data, combines historical information to evaluate line status, insulation performance and overvoltage hazard level, and considers the impact of intermittent loads on overvoltage in electrified railways. Based on the evaluation results, the present invention determines the protector selection index, conducts multiple rounds of screening and performance evaluation on candidate protectors, and comprehensively considers short-term and long-term performance to select the optimal protector. This solves the problem in the prior art that the selection of metal sheath protectors for cable lines lacks precise basis, cannot fully consider the cable operation status, environmental factors, intermittent load effects and insulation performance changes, resulting in unreasonable protector selection and difficulty in effectively protecting cable lines.

[0016] This invention determines basic protector selection criteria based on the overvoltage hazard level, taking into account factors such as maximum operating voltage, maximum cable power, and overvoltage duration. Different hazard levels correspond to different correction factors, which determine the appropriate protector rated voltage requirement and energy absorption capacity. The selection criteria are also corrected based on the allowable annual number of failures and mean time between failures, ensuring that the selected protector is more in line with actual needs and effectively protecting the cable line.

[0017] The present invention evaluates the performance of candidate protectors, first screening out products whose response time and heat resistance level do not meet the requirements, and then evaluating the performance of the remaining candidate protectors under simulated working conditions. By simulating and calculating indicators such as simulated residual pressure, simulated energy absorption, and simulated number of successful actions, a short-term performance evaluation factor is obtained in combination with the required performance indicators; through long-term simulation operation, performance indicator change data is obtained to obtain a long-term stability evaluation factor; finally, a comprehensive evaluation factor is determined based on the short-term and long-term evaluation factors, and the candidate protector with the smallest comprehensive evaluation factor is selected as the optimal protector. The multi-dimensional evaluation method comprehensively considers the performance of the protector, ensuring that the selected protector can operate reliably under different working conditions and effectively protect the cable line. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0019] The embodiments of the present invention are further described below with reference to the accompanying drawings: like Figure 1 As shown in FIG, the method for optimizing the selection of a metal sheath protector for a cable line based on induced overvoltage includes the following steps: Obtain the operating status data and environmental status data of the cable line, analyze and diagnose the cable line status, and issue an early warning if the cable line status is abnormal. If the cable line status is normal, obtain the initial overvoltage; Correcting the initial overvoltage based on the intermittent load of the electrified railway to obtain the corrected overvoltage; Evaluate the insulation performance of the metal sheath and the overvoltage hazard level in each area of the current cable line; Determine the basic selection index of the protector based on the overvoltage hazard level, and screen the candidate protectors based on the basic selection index; The performance of candidate protectors is evaluated to determine the optimal protector.

[0020] The initial overvoltage can be calculated using existing calculation methods or directly measured using a measuring device.

[0021] Operating status data including core current curve , core current change rate curve and voltage fluctuation range , environmental status data includes ambient temperature change curve And the environmental humidity change curve , is the minimum value of the voltage fluctuation range, is the maximum value of the voltage fluctuation range; Analyzing and diagnosing the cable line status includes the following steps: Obtain the parameterized operating status data and parameterized environmental status data stored in the database. The parameterized operating status data includes the core current parameter curve. , core current change rate parameter curve And voltage fluctuation parameter range , parameterized environmental status data including ambient temperature change parameterized curve and ambient humidity change parameter curve , is the minimum value of the voltage fluctuation parameter range, The maximum value of the voltage fluctuation parameter range; Perform similarity processing on the operating status data and the parameter operating status data; Perform similarity processing on the environmental state data and the reference environmental state data; Determine the state coefficient based on the similarity processing result , if the state coefficient Greater than the state coefficient stored in the database The cable line status is abnormal. If the status coefficient Not greater than the state coefficient stored in the database The cable line status is normal, where the status coefficient The calculation formula is: ; in, and are all transfer functions, for and The similarity function of for and The similarity function of for and The similarity function of for and The similarity function of .

[0022] This method obtains the specified operating status data and specified environmental status data stored in the database, performs similarity processing on them against the actual operating status data and environmental status data, and then determines the status coefficient based on the processing results. This coefficient is then compared with the threshold to determine the cable line status. This method quantifies the judgment of cable line status and is more scientific and accurate than subjective judgment or simple threshold judgment. For example, when judging the core current curve, the similarity function comprehensively considers multiple factors such as the curve shape and amplitude changes to produce a more convincing judgment result, avoiding the potential safety hazards that may be overlooked due to misjudgment of a single factor.

[0023] The similarity function can be implemented by existing technologies such as cosine similarity and Euclidean distance similarity.

[0024] Correcting the initial overvoltage based on the intermittent load of the electrified railway to obtain the corrected overvoltage includes the following steps: Obtaining a curve of intermittent load current changing over time, and smoothing the intermittent load change data to obtain a smoothed load current change curve; Data smoothing effectively removes these interferences, preserving the true trend of load current changes and providing a more reliable data foundation for subsequent spectrum analysis. For example, during the starting and braking phases of electric locomotives, current changes dramatically. Smoothing can avoid analysis errors caused by excessive data fluctuations, making the subsequent determination of the main frequency components more accurate.

[0025] The Fourier transform is used to perform spectrum analysis on the smoothed load current variation curve to obtain the current amplitude and phase at different frequencies. Converting the time-domain current signal to the frequency domain can clearly reveal the frequency composition of intermittent load current. Different electric locomotive operating conditions will produce current fluctuations with different frequency characteristics. Through spectrum analysis, the main frequency components and their corresponding current amplitudes and phases can be determined. This information is crucial for understanding the essential characteristics of intermittent loads and provides key parameters for calculating the induced voltage increment. For example, under certain operating conditions, the high-frequency current components generated by electric locomotives will induce higher voltages on the cable metal sheath. Accurately capturing these high-frequency components can help more accurately assess overvoltage conditions.

[0026] Determine the main frequency components , and the current amplitude of the main frequency components and phase , i is the main frequency component number; Obtain the mutual inductance M of the cable line; Calculate corrected overvoltage : ; Among them, j is the imaginary unit, e is the natural constant, is the induced voltage increment generated by the i-th main frequency component, is the initial overvoltage.

[0027] By taking into account the frequency characteristics of intermittent loads and the electromagnetic parameters of the cable, the calculation method is more consistent with actual operating conditions. The formula incorporates imaginary units, pi, natural constants, and comprehensively considers the phase relationship in electromagnetic induction and the connection between physical quantities. Compared to simple calculation methods that do not consider intermittent load characteristics, this method can more accurately reflect actual overvoltage conditions.

[0028] Corrected overvoltage data is an important basis for evaluating the insulation performance of cable metal sheaths and determining the selection criteria for protectors. Accurate overvoltage data can more precisely assess the degree of damage to cable metal sheath insulation, providing strong support for developing a reasonable protector selection strategy.

[0029] Evaluate the insulation performance of the metal sheath and the overvoltage hazard level in each area of the current cable line, including the following steps: Based on the historical operation records of the cable line, obtain historical operation characteristic data, including operation time , overvoltage times , the amplitude of each overvoltage and duration and aging coefficient ; Compare the historical operation feature data with the historical operation feature matching data stored in the database one by one to obtain the respective comparison coefficients. , determine the historical operation feature matching data corresponding to the minimum comparison coefficient, and obtain the insulation resistance prediction value corresponding to the historical operation feature matching data from the database ; Historical operation feature matching data including operation matching time , overvoltage matching times , the matching amplitude of each overvoltage and match duration and matching aging coefficients , where a is the number of each overvoltage with the maximum number of overvoltage matches in the historical operation feature matching data, and g is the number of the historical operation feature matching data; If the predicted insulation resistance value is less than the standard value of the cable insulation resistance, it is marked as abnormal insulation performance of the metal sheath; If the predicted insulation resistance value is not less than the standard value of the cable insulation resistance, it is marked as the insulation performance of the metal sheath is normal; Get the breakdown voltage of the current metal protection layer stored in the database , the corrected overvoltage and breakdown voltage Perform ratio calculation to obtain the voltage ratio factor r; The ratio of the total duration of the overvoltage amplitude exceeding the set voltage threshold to the operating time is calculated to obtain the time ratio factor p; When the predicted insulation resistance value is less than the standard value of the cable insulation resistance, , the voltage ratio factor r and the time ratio factor p are combined into a hazard level matching set; Compare the similarity between the hazard level matching set and the hazard level parameter set stored in the database to obtain the level comparison factor , determine the hazard level parameter set corresponding to the minimum level comparison factor, and obtain the overvoltage hazard level corresponding to the hazard level parameter set from the database. The overvoltage hazard level includes mild, medium and severe levels. The hazard level parameter set includes the parameter insulation resistance prediction value , parameter voltage ratio factor and the parameter time ratio factor , d is the number of the hazard level parameter set.

[0030] Comparison coefficient The calculation method is as follows: ; in, is the transfer function, A is the maximum number of overvoltage matching times in each historical operation feature matching data; The historical operation characteristic data and the historical operation characteristic matching data are quantitatively processed, making it more objective and accurate when evaluating the similarity of the historical operation characteristics of the cable line.

[0031] By collecting historical operating characteristic data of the cable line, such as operating time, number of overvoltages, amplitude and duration of each overvoltage, and aging coefficient, and comparing it with the historical operating characteristic matching data in the database, the insulation resistance prediction value is obtained. This method utilizes a large amount of historical data and fully considers the cumulative impact of various factors in the long-term operation of the cable. Compared with a single real-time detection, it can more comprehensively and accurately evaluate the insulation performance of the metal sheath.

[0032] Rank comparison factor The calculation method is as follows: .

[0033] This embodiment not only considers the predicted insulation resistance value but also the ratio of the corrected overvoltage to the breakdown voltage (voltage ratio factor) and the ratio of the total duration that the overvoltage amplitude exceeds the set threshold to the operating time (time ratio factor). This multi-factor comprehensive assessment more accurately reflects the actual degree of damage caused by overvoltage to the cable. Accurate insulation performance assessment and determination of overvoltage hazard levels lay a solid foundation for protector selection. Different hazard levels correspond to different protector performance requirements. Based on the assessment results, a protector with appropriate parameters such as rated voltage and energy absorption capacity can be selected to avoid inappropriate selection.

[0034] Determining the basic selection criteria for a protector based on the overvoltage hazard level includes the following steps: Get the maximum operating voltage and the maximum power appearing in the cable The maximum operating voltage determines the upper limit of the normal operating voltage that the protector must withstand and is an important reference for determining the protector's rated voltage. The maximum power that can be applied to a cable is related to its energy absorption capacity. The greater the power, the more energy is generated in abnormal conditions such as overvoltage, requiring the protector to have a stronger energy absorption capacity to cope with it.

[0035] Cluster the duration of overvoltage and determine the first duration of overvoltage , the second duration and the third duration ,in, Overvoltage durations are clustered to identify different duration intervals (primary, secondary, and tertiary). Overvoltages of varying durations pose varying degrees of damage to cables. Longer durations accumulate more energy, placing greater strain on cable insulation and protectors. By categorizing overvoltage durations, the performance requirements for protectors can be more specifically determined.

[0036] Obtain the index correction factor based on the overvoltage hazard level, and determine the rated voltage requirement of the protector based on the index correction factor and protector energy absorption capacity , x = 1, 2, 3; based on the overvoltage hazard level, an indicator correction factor is derived to determine the required rated voltage and energy absorption capacity of the protector. Different correction factors correspond to different hazard levels, reflecting the impact of the degree of overvoltage hazard on protector selection. For the mild level, the rated voltage and energy absorption capacity requirements of the protector are relatively low; for the moderate and severe levels, the requirements are higher. This method of adjusting selection indicators based on hazard level enables more accurate protector selection, ensuring that protection requirements are met while avoiding resource waste caused by overselection.

[0037] Get the allowed number of failures per year and mean time between failures MTBF, the rated voltage requirement for the protector and protector energy absorption capacity Considering the reliability requirements of the cable system, if the number of annual failures is allowed to be small and the mean time between failures is long, it means that the reliability requirements of the protector are high, and its performance indicators such as rated voltage and energy absorption capacity need to be appropriately improved to reduce the probability of failure.

[0038] Index correction factors include a slight correction factor for rated voltage , slight correction factor for energy absorption , rated voltage medium correction factor , medium correction factor for energy absorption , rated voltage severe correction factor and energy absorption severity correction factor ; If the overvoltage hazard level is mild, the rated voltage requirement of the protector is , , the energy absorption capacity of the protector is , ; If the overvoltage hazard level is medium, the rated voltage requirement of the protector is , , the energy absorption capacity of the protector is , ; If the overvoltage hazard level is severe, the rated voltage requirement of the protector is , , the energy absorption capacity of the protector is , .

[0039] Corresponding rated voltage correction factors and energy absorption correction factors are specified for different overvoltage hazard levels (mild, moderate, and severe). This clearly categorized calculation method allows the protector selection criteria to more accurately match the actual protection needs of cable lines under different overvoltage hazard levels, avoiding resource waste or insufficient protection caused by improper selection. In areas with less severe overvoltage hazards, protectors with lower rated voltage and energy absorption capacity requirements are used to reduce equipment costs. In areas with more severe overvoltage hazards, higher-performance protectors are used to ensure safe cable operation.

[0040] Correcting the rated voltage requirement and energy absorption capacity of the protector includes the following steps: ; ; in, is the rated voltage requirement of the protector after correction, The energy absorption capacity of the corrected protector is: is the general allowable number of failures, To set the mean time between failures.

[0041] Accurately selecting the right protector helps improve cable system stability. An appropriate rated voltage ensures reliable operation of the protector during both normal operation and overvoltage conditions, preventing damage due to insufficient voltage tolerance. Sufficient energy absorption capacity ensures that when overvoltage occurs, the protector can promptly absorb excess energy, preventing damage to the cable. Clear selection criteria for different hazard levels ensure effective protection of the entire cable system under varying operating conditions, reducing failures caused by overvoltage and ensuring the continuity and stability of power transmission.

[0042] By revising the selection indicators, we ensure both cable line safety and economic efficiency. In practical applications, blindly pursuing high-parameter protectors is not necessarily the best choice. Excessively high rated voltage and energy absorption capacity will increase costs. The correction formula can reasonably adjust the protector parameters according to the system's fault requirements.

[0043] Perform a round of screening on the candidate protectors to eliminate those with a response time greater than the response time threshold and those with a heat resistance level lower than the required heat resistance level. By eliminating those with a response time greater than the response time threshold and those with a heat resistance level lower than the required heat resistance level, products that clearly do not meet the basic performance requirements can be quickly eliminated.

[0044] The performance of candidate protectors is evaluated to determine the optimal protector, including the following steps: Perform a round of screening on the candidate protectors, screen out the candidate protectors whose response time is greater than the response time threshold, and screen out the candidate protectors whose heat resistance level is lower than the required heat resistance level; After a round of screening, the performance of the candidate protectors is evaluated under simulated working conditions: Using circuit simulation software (such as ATP-EMTP, PSCAD, etc.), the candidate protectors after a round of screening are connected to the simulated cable system model. According to different operating conditions, the simulated performance indicators of the candidate protectors after a round of screening are simulated and calculated. The simulated performance indicators include simulated residual voltage , simulated energy absorption and the number of successful simulated actions The simulated operating conditions simulate various conditions encountered by cable systems during actual operation, including normal operation, overvoltage, and varying loads. By simulating and calculating these performance indicators, we can fully understand the performance of candidate protectors under different conditions.

[0045] Obtain the short-term performance evaluation factor of each candidate protector based on the simulated performance index and the required performance index , the required performance indicators include the required residual pressure , energy absorption required and the required number of successful actions ; Based on the long-term simulation operation, the performance index change data of the candidate protectors after a round of screening is obtained. The performance index change rate includes the increase in the simulated residual pressure. , Simulated energy absorption reduction and the reduction in the number of successful simulated actions ; Obtain long-term stability evaluation factors based on performance index change data ; Based on short-term performance evaluation factors and long-term stability assessment factors Determine comprehensive evaluation factors , determine the minimum comprehensive evaluation factor The candidate protector after the corresponding round of screening is taken as the optimal protector.

[0046] Comprehensive evaluation factors The method to obtain is as follows: .

[0047] Based on the simulated performance indicators and required performance indicators, the short-term performance evaluation factor of each candidate protector is obtained. Based on the long-term simulated operation, the performance indicator change data is obtained, and then the long-term stability evaluation factor is obtained. Finally, the comprehensive evaluation factor is determined based on these two factors. This comprehensive consideration of short-term and long-term performance evaluates the performance of the protector more comprehensively. The short-term performance evaluation factor reflects the performance of the protector under the current operating conditions, while the long-term stability evaluation factor takes into account the performance changes of the protector during long-term operation, such as the increase in simulated residual pressure, the decrease in simulated energy absorption, and the decrease in the number of simulated successful actions. Through comprehensive evaluation, a protector that can operate stably and reliably in both the short and long term can be selected to ensure the long-term safe operation of the cable line.

[0048] During calculation, each formula in this embodiment may be dimensionless as needed to simplify the calculation.

[0049] The algorithm involved in this embodiment can be executed by an electronic device. The electronic device includes a memory, a processor, and a computer program stored in the memory and run on the processor. The above-mentioned algorithm calculation is implemented by executing the software through the processor.

Claims

1. A cable line metal sheath protector selection optimization method based on induced overvoltage, characterized in that: The following steps are involved: Obtain the operating status data and environmental status data of the cable line, analyze and diagnose the cable line status, and issue an early warning if the cable line status is abnormal. If the cable line status is normal, obtain the initial overvoltage; Correcting the initial overvoltage based on the intermittent load of the electrified railway to obtain the corrected overvoltage; Evaluate the insulation performance of the metal sheath and the overvoltage hazard level in each area of the current cable line; Determine the basic selection index of the protector based on the overvoltage hazard level, and screen the candidate protectors based on the basic selection index; The performance of candidate protectors is evaluated to determine the optimal protector.

2. The cable line metal sheath protector selection optimization method based on induced overvoltage according to claim 1 is characterized in that: The operating status data includes a core current curve , core current change rate curve and voltage fluctuation range , environmental status data includes ambient temperature change curve And the environmental humidity change curve , is the minimum value of the voltage fluctuation range, is the maximum value of the voltage fluctuation range; Analyzing and diagnosing the cable line status includes the following steps: Obtain the parameterized operating status data and parameterized environmental status data stored in the database. The parameterized operating status data includes the core current parameter curve. , core current change rate parameter curve And voltage fluctuation parameter range , parameterized environmental status data including ambient temperature change parameterized curve and ambient humidity change parameter curve , is the minimum value of the voltage fluctuation parameter range, The maximum value of the voltage fluctuation parameter range; Perform similarity processing on the operating status data and the parameter operating status data; Perform similarity processing on the environmental state data and the reference environmental state data; Determine the state coefficient based on the similarity processing result , if the state coefficient Greater than the state coefficient stored in the database The cable line status is abnormal. If the status coefficient Not greater than the state coefficient stored in the database The cable line status is normal, where the status coefficient The calculation formula is: ； in, and are all transfer functions, for and The similarity function of for and The similarity function of for and The similarity function of for and The similarity function of .

3. The cable line metal sheath protector selection optimization method based on induced overvoltage according to claim 1 is characterized in that: Correcting the initial overvoltage based on the intermittent load of the electrified railway to obtain the corrected overvoltage includes the following steps: Obtaining a curve of intermittent load current changing over time, and smoothing the intermittent load change data to obtain a smoothed load current change curve; The Fourier transform is used to perform spectrum analysis on the smoothed load current variation curve to obtain the current amplitude and phase at different frequencies. Determine the main frequency components , and the current amplitude of the main frequency components and phase , i is the main frequency component number; Obtain the mutual inductance M of the cable line; Calculate corrected overvoltage : ； Among them, j is the imaginary unit, e is the natural constant, is the induced voltage increment generated by the i-th main frequency component, is the initial overvoltage.

4. The cable line metal sheath protector selection optimization method based on induced overvoltage according to claim 3 is characterized in that: Evaluate the insulation performance of the metal sheath and the overvoltage hazard level in each area of the current cable line, including the following steps: Based on the historical operation records of the cable line, obtain historical operation characteristic data, including operation time , overvoltage times , the amplitude of each overvoltage and duration and aging coefficient ; Compare the historical operation feature data with the historical operation feature matching data stored in the database one by one to obtain the respective comparison coefficients. , determine the historical operation feature matching data corresponding to the minimum comparison coefficient, and obtain the insulation resistance prediction value corresponding to the historical operation feature matching data from the database ; Historical operation feature matching data including operation matching time , overvoltage matching times , the matching amplitude of each overvoltage and match duration and matching aging coefficients , where a is the number of each overvoltage with the maximum number of overvoltage matches in the historical operation feature matching data, and g is the number of the historical operation feature matching data; If the predicted insulation resistance value is less than the standard value of the cable insulation resistance, it is marked as abnormal insulation performance of the metal sheath; If the predicted insulation resistance value is not less than the standard value of the cable insulation resistance, it is marked as the insulation performance of the metal sheath is normal; Get the breakdown voltage of the current metal protection layer stored in the database , the corrected overvoltage and breakdown voltage Perform ratio calculation to obtain the voltage ratio factor r; The ratio of the total duration of the overvoltage amplitude exceeding the set voltage threshold to the operating time is calculated to obtain the time ratio factor p; When the predicted insulation resistance value is less than the standard value of the cable insulation resistance, , the voltage ratio factor r and the time ratio factor p are combined into a hazard level matching set; Compare the similarity between the hazard level matching set and the hazard level parameter set stored in the database to obtain the level comparison factor , determine the hazard level parameter set corresponding to the minimum level comparison factor, and obtain the overvoltage hazard level corresponding to the hazard level parameter set from the database. The overvoltage hazard level includes mild, medium and severe levels. The hazard level parameter set includes the parameter insulation resistance prediction value , parameter voltage ratio factor and the parameter time ratio factor , d is the number of the hazard level parameter set.

5. The cable line metal sheath protector selection optimization method based on induced overvoltage according to claim 4 is characterized in that: Comparison coefficient The calculation method is as follows: ； in, is the transfer function, A is the maximum number of overvoltage matching times in each historical operation feature matching data; Rank comparison factor The calculation method is as follows: 。 6. The cable line metal sheath protector selection optimization method based on induced overvoltage according to claim 4 is characterized in that: Determining the basic selection criteria for a protector based on the overvoltage hazard level includes the following steps: Get the maximum operating voltage and the maximum power appearing in the cable ; Cluster the duration of overvoltage and determine the first duration of overvoltage , the second duration and the third duration ,in, ; Obtain the index correction factor based on the overvoltage hazard level, and determine the rated voltage requirement of the protector based on the index correction factor and protector energy absorption capacity , x=1, 2, 3; Get the allowed number of failures per year and mean time between failures MTBF, the rated voltage requirement for the protector and protector energy absorption capacity Make corrections.

7. The cable line metal sheath protector selection optimization method based on induced overvoltage according to claim 6, characterized in that: The index correction factor includes a slight correction factor for rated voltage , slight correction factor for energy absorption , rated voltage medium correction factor , medium correction factor for energy absorption , rated voltage severe correction factor and energy absorption severity correction factor ; If the overvoltage hazard level is mild, the rated voltage requirement of the protector is , , the energy absorption capacity of the protector is , ; If the overvoltage hazard level is medium, the rated voltage requirement of the protector is , , the energy absorption capacity of the protector is , ; If the overvoltage hazard level is severe, the rated voltage requirement of the protector is , , the energy absorption capacity of the protector is , .

8. The cable line metal sheath protector selection optimization method based on induced overvoltage according to claim 7, characterized in that: Correcting the rated voltage requirement and energy absorption capacity of the protector includes the following steps: ； ； in, is the rated voltage requirement of the protector after correction, The energy absorption capacity of the corrected protector is: is the general allowable number of failures, To set the mean time between failures.

9. The cable line metal sheath protector selection optimization method based on induced overvoltage according to claim 1, characterized in that: The performance of candidate protectors is evaluated to determine the optimal protector, including the following steps: Perform a round of screening on the candidate protectors, screen out the candidate protectors whose response time is greater than the response time threshold, and screen out the candidate protectors whose heat resistance level is lower than the required heat resistance level; After a round of screening, the performance of the candidate protectors is evaluated under simulated working conditions: Using circuit simulation software, the candidate protectors after a round of screening are connected to the simulated cable system model. According to different operating conditions, the simulated performance indicators of the candidate protectors after a round of screening are simulated and calculated. The simulated performance indicators include simulated residual voltage , simulated energy absorption and the number of successful simulated actions ; Obtain the short-term performance evaluation factor of each candidate protector based on the simulated performance index and the required performance index , the required performance indicators include the required residual pressure , energy absorption required and the required number of successful actions ; Based on the long-term simulation operation, the performance index change data of the candidate protectors after a round of screening is obtained. The performance index change rate includes the increase in the simulated residual pressure. , Simulated energy absorption reduction and the reduction in the number of successful simulated actions ; Obtain long-term stability evaluation factors based on performance index change data ; Based on short-term performance evaluation factors and long-term stability assessment factors Determine comprehensive evaluation factors , determine the minimum comprehensive evaluation factor The candidate protector after the corresponding round of screening is taken as the optimal protector.

10. The cable line metal sheath protector selection optimization method based on induced overvoltage according to claim 9, characterized in that: Comprehensive evaluation factors The method to obtain is as follows: 。

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