A Simulation Analysis Method for Electrical Stress in a 10kV Surge Arrester under Multiple Lightning Strikes

Abstract

This invention belongs to the field of surge arrester simulation technology and discloses a simulation analysis method for the electrical stress of a 10kV surge arrester under multiple lightning strikes. First, the parameters of the line, tower, and surge arrester are obtained to establish an electromagnetic transient simulation model. Then, a single lightning strike current model and a multiple lightning strike current model using a combination of the first and subsequent return stroke waveforms are established, and the return stroke frequency and time interval are set. By connecting the two lightning current models to the same distribution line model, simulation analysis is performed under three typical lightning strike conditions: direct strike, induced strike, and backflash strike, to obtain the discharge current and absorbed energy of the surge arrester. Comparing the electrical stress under single and multiple lightning strikes reveals that the surge arrester's withstand current amplitude is significantly reduced and the absorbed energy is significantly increased due to the energy accumulation effect of multiple lightning strikes. This method overcomes the shortcomings of existing simulations that only use single or two standard waveforms and ignore the waveform differences and energy accumulation of multiple lightning strikes.

Description

Technical Field

[0001] This invention belongs to the field of surge arrester simulation technology, specifically a simulation analysis method for the electrical stress of a 10kV surge arrester under multiple lightning strikes. Background Technology

[0002] In power systems, the 10kV distribution network is the end-point network directly facing users, and its power supply reliability is crucial. Zinc oxide surge arresters, as key devices for limiting lightning overvoltage, must withstand lightning current surges and absorb energy. When the absorbed energy exceeds their withstand limit, thermal breakdown or even explosion can occur. Lightning monitoring data shows that approximately 50% of lightning strikes to ground are multiple strikes, meaning a single lightning flash contains multiple return strokes. This causes the surge arrester to withstand multiple energy surges in a very short time, resulting in a significant cumulative effect.

[0003] Existing simulation design and evaluation methods for 10kV surge arresters are generally based on a single 2.6 / 50μs standard lightning current waveform. This waveform differs significantly from the waveform parameters of real multiple lightning strikes (1 / 200μs for the first return stroke and 0.25 / 100μs for subsequent return strokes) and cannot simulate the energy accumulation process of multiple return strokes. This leads to a systematic underestimation of the electrical stress (especially energy stress) that the surge arrester experiences in actual operation, resulting in insufficient selection margin for surge arresters. This is a major technical root cause of their frequent explosions in areas with frequent multiple lightning strikes.

[0004] The closest existing approach involves using a single 2.6 / 50μs standard lightning current waveform, or two such waveforms with a longer interval, to perform electromagnetic transient simulation analysis on 10kV distribution lines and surge arresters. This method establishes a simplified line model, injects one or two standard lightning currents, evaluates the current and energy stress of the surge arrester, and uses this as the basis for surge arrester selection, insulation coordination, and fault analysis. The simulation typically uses a double exponential wave to fit the lightning current, with fixed waveform parameters, and does not consider the timing control of consecutive return strokes.

[0005] The current scheme, due to significant differences in waveform parameters and return stroke modes compared to actual multiple lightning strikes, cannot accurately simulate the energy accumulation effect under multiple return strokes, leading to an overestimation of the surge arrester's withstand capability. Specifically, it cannot quantify the differences in discharge current and absorbed energy between multiple lightning strikes and a single lightning strike, cannot reveal the fact that the surge arrester's withstand current amplitude is significantly reduced under multiple lightning strikes, and lacks a systematic simulation analysis method to compare the electrical stress of single and multiple lightning strikes and guide the optimized design of surge arresters. Summary of the Invention

[0006] This invention provides a simulation analysis method for the electrical stress of a 10kV surge arrester under multiple lightning strikes, which solves the problem that existing simulations do not consider the energy accumulation and waveform differences of multiple lightning strikes, leading to inaccurate assessment of the electrical stress of the surge arrester.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a simulation analysis method for the electrical stress of a 10kV surge arrester under multiple lightning strikes, comprising: acquiring parameters of a 10kV distribution line, towers, and surge arresters; establishing an electromagnetic transient simulation model of the 10kV distribution line based on the parameters; establishing a single lightning strike current model and a multiple lightning strike current model, wherein the multiple lightning strike current model uses a combination of the initial return stroke waveform and subsequent return stroke waveforms, and sets the return stroke frequency and return stroke time interval; and connecting the single lightning strike current model and the multiple lightning strike current model to the 10kV distribution line. An electromagnetic transient simulation model of a V-type power distribution line was established, with three lightning strike conditions: direct strike, induced strike, and backflash strike. Electromagnetic transient simulation analysis models for single and multiple lightning strikes under each condition were created. Using these models, the electrical stress of a 10kV line arrester under single and multiple lightning strike conditions was simulated and analyzed. The electrical stress of the arrester obtained from the simulations under single and multiple lightning strike conditions was compared, and the results of the comparison of the impact of multiple lightning strikes on the arrester's withstand capability were output.

[0008] According to one embodiment of the present invention, the multiple lightning strike current model adopts a negative polarity first return stroke waveform and a negative polarity subsequent return stroke waveform, and the return stroke frequency includes multiple return strokes; the single lightning strike current model adopts a negative polarity standard lightning current waveform.

[0009] According to one embodiment of the present invention, both the single lightning strike and multiple lightning strike current models are fitted using a double exponential wave, and the formula for fitting using a double exponential wave is as follows:

[0010] in, For time, This represents the amplitude of the lightning current. and These are the fitting parameters; different waveforms correspond to different fitting parameter values. This represents the instantaneous value of the lightning current.

[0011] According to one embodiment of the present invention, when establishing a multiple lightning strike current model, the continuous process of multiple lightning strikes is simulated. Specifically, the continuous process of multiple lightning strikes is simulated by setting an independent circuit breaker for each return stroke in the electromagnetic transient simulation software, and controlling the closing duration, opening duration and switching sequence of each circuit breaker through a time logic module to simulate the continuous return stroke process of multiple lightning strikes.

[0012] According to one embodiment of the present invention, the circuit breaker is initially in an open state, and each circuit breaker operates twice; the circuit breaker corresponding to the first return stroke closes at the start time and opens at the end of the first return stroke discharge; the circuit breakers corresponding to subsequent return strokes close sequentially at the end of the previous return stroke discharge and open at the end of their respective return stroke discharge, and so on until all return strokes are completed.

[0013] According to one embodiment of the present invention, in setting up three lightning strike conditions—direct strike, induced strike, and backflashover—the equivalent method for the direct strike condition is as follows: the lightning current is used as a current source and connected in parallel with the equivalent wave impedance between the thundercloud and the ground to a conductor; the equivalent method for the induced strike condition is as follows: the induced voltage component generated on the conductor by the lightning impact energy is used as a voltage source, and its high-voltage end is connected to the conductor; the equivalent method for the backflashover condition is as follows: the lightning current component is used as a current source connected to the top of the tower, and the induced voltage component on the conductor is used as a voltage source, and its high-voltage end is connected to the conductor.

[0014] According to one embodiment of the present invention, the electromagnetic transient simulation model is built using electromagnetic transient simulation software, the line conductor is modeled using a frequency-dependent model, the tower is simulated using a single wave impedance, and the insulator is determined by the leader development method and the flashover process is simulated by an ideal controllable switch.

[0015] According to one embodiment of the present invention, the simulation analysis sets a range of lightning current amplitude variation to make the surge arrester reach its nominal discharge current limit or maximum absorbed energy limit, and records the lightning current amplitude, discharge current and absorbed energy when the surge arrester reaches its withstand limit under different operating conditions.

[0016] According to one embodiment of the present invention, the comparison of the electrical stress of the surge arrester obtained by simulation under different operating conditions of single lightning strike and multiple lightning strikes includes: comparing the lightning current amplitude, surge arrester discharge current and absorbed energy when the surge arrester reaches the discharge current limit or the energy absorption limit under the same lightning strike conditions, respectively, by single lightning strike and multiple lightning strikes.

[0017] According to one embodiment of the present invention, the parameters of the 10kV distribution line include conductor type, line length, span, sag, conductor height and phase spacing; the parameters of the tower include tower type, tower height, soil resistivity, grounding resistance, insulator type and insulation length; and the parameters of the surge arrester include surge arrester type, rated voltage and volt-ampere characteristic curve parameters.

[0018] Compared with existing technologies, this invention has the following advantages: This invention provides a simulation analysis method for the electrical stress of a 10kV surge arrester under multiple lightning strikes. First, it obtains the parameters of the line, tower, and surge arrester to establish an electromagnetic transient simulation model. Then, it establishes a single lightning strike current model and a multiple lightning strike current model using a combination of the first and subsequent return stroke waveforms, setting the return stroke frequency and time interval. By connecting the two lightning current models to the same distribution line model and performing simulation analysis under three typical lightning strike conditions—direct strike, induced strike, and backflash strike—the discharge current and absorbed energy of the surge arrester are obtained. Comparing the electrical stress under single and multiple lightning strikes reveals that the energy accumulation effect of multiple lightning strikes significantly reduces the surge arrester's withstand current amplitude and significantly increases its absorbed energy. This method overcomes the shortcomings of existing simulations that only use single or double standard waveforms and ignore the differences in waveforms and energy accumulation of multiple lightning strikes. It makes the simulation results closer to the real lightning environment and can accurately assess the actual electrical stress of the surge arrester under multiple lightning strikes. This provides a reliable basis for surge arrester design, selection and insulation coordination, thereby improving the operational reliability of surge arresters in areas with frequent multiple lightning strikes and reducing the explosion accident rate. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart illustrating a simulation analysis method for the electrical stress of a 10kV surge arrester under multiple lightning strikes, according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the maximum electrical stress under direct lightning strike conditions according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the maximum electrical stress under the counter-lightning condition according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the maximum electrical stress under induced lightning conditions according to an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0023] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0024] Before introducing the technical content of this invention, the relevant terms will be explained: Multiple lightning strikes: refers to the phenomenon where a single lightning strike includes multiple (usually 3 to 4) consecutive return strikes, with the time interval between each return strike typically being tens of milliseconds.

[0025] Electrical stress: In this invention, it specifically refers to the key electrical load parameters applied to the surge arrester, mainly including the peak current under the nominal discharge current and the absorbed lightning energy.

[0026] Electromagnetic transient simulation: a numerical simulation technique used to analyze rapidly changing electromagnetic processes in power systems at the microsecond to millisecond level caused by lightning strikes, switching operations, etc. Commonly used software includes PSCAD / EMTDC and ATP-EMTP.

[0027] Double exponential wave: A mathematical expression commonly used to simulate lightning current waveforms, in the form of... ,in denoted as peak value of lightning current, and a and b are fitting parameters that determine the timing of wavefront and wave tail.

[0028] Direct lightning strike: Lightning strikes a power line or tower directly.

[0029] Induced lightning: When lightning strikes the ground or an object near a power line, it induces an overvoltage in the conductor through electromagnetic induction.

[0030] Backflash lightning: When lightning strikes a tower or lightning protection wire, the tower's potential rises sharply, causing insulator flashover and thus introducing the high potential into the conductor.

[0031] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0032] like Figure 1 As shown, this invention provides a simulation analysis method for the electrical stress of a 10kV surge arrester under multiple lightning strikes, including: S1: Obtain the parameters of the 10kV distribution line, tower and surge arrester, and establish an electromagnetic transient simulation model of the 10kV distribution line based on the parameters; S2: Establish a single lightning strike current model and a multiple lightning strike current model respectively. The multiple lightning strike current model adopts a combination of the first return stroke waveform and subsequent return stroke waveforms, and sets the return stroke frequency and return stroke time interval. S3: Connect the single lightning strike current model and the multiple lightning strike current model to the electromagnetic transient simulation model of the 10kV distribution line, and set up three lightning strike conditions: direct strike, induction, and backflash, to establish electromagnetic transient simulation analysis models for single lightning strike and multiple lightning strike under each condition. S4: Using the electromagnetic transient simulation analysis models of single and multiple lightning strikes under various working conditions, the electrical stress of the 10kV line arrester under different working conditions of single and multiple lightning strikes is simulated and analyzed respectively. S5: Compare the electrical stress of the surge arrester obtained from simulations under different operating conditions of single lightning strike and multiple lightning strikes, and output the comparison results of the impact of multiple lightning strikes on the surge arrester's withstand capability.

[0033] This method overcomes the shortcomings of existing simulations that only use single or double standard waveforms and ignore the differences in waveforms and energy accumulation of multiple lightning strikes. It makes the simulation results closer to the real lightning environment and can accurately assess the actual electrical stress of the surge arrester under multiple lightning strikes. This provides a reliable basis for surge arrester design, selection and insulation coordination, thereby improving the operational reliability of surge arresters in areas with frequent multiple lightning strikes and reducing the explosion accident rate.

[0034] The detailed steps are as follows: Obtain typical parameters for 10kV distribution lines, towers, and surge arresters. Line parameters include conductor type, line length, span, sag, conductor height of each phase, and phase spacing; tower parameters include tower type, tower height, soil resistivity, grounding resistance, insulator type, and insulation length; surge arrester parameters include surge arrester type, rated voltage, and volt-ampere characteristic curve parameters.

[0035] Based on the obtained parameters, an electromagnetic transient simulation model of a 10kV distribution line was established in the electromagnetic transient simulation software.

[0036] Specifically, the line conductors are modeled using a frequency-dependent model, the towers are simulated using a single wave impedance, and the insulators are identified using the leader development method for flashover detection. An ideal controllable switch is used to simulate the flashover process of the insulator string. Surge arresters are connected to the line model in a base-by-base installation manner.

[0037] A single lightning strike current model and a multiple lightning strike current model were established. The single lightning strike current model adopted a negative polarity standard lightning current waveform. The multiple lightning strike current model adopted the combination of the first return stroke waveform and subsequent return stroke waveforms recommended by the national standard, and set the return stroke frequency and return stroke time interval. For example, the first return stroke waveform is different from the subsequent return stroke waveforms, the return stroke frequency is multiple, and the return stroke time interval is in the millisecond range.

[0038] All lightning current models are fitted using a double exponential wave. The amplitude parameter in the fitting formula is set according to different simulation scenarios, and the fitting parameters are determined based on the selected waveform.

[0039] The formula for double-exponential lightning current is:

[0040] in, For time, This represents the amplitude of the lightning current. and These are the fitting parameters; different waveforms correspond to different fitting parameter values. This represents the instantaneous value of the lightning current.

[0041] In the electromagnetic transient simulation software, independent circuit breakers are set for each return stroke in the multiple lightning strike current model. The closing duration, opening duration, and switching sequence of each circuit breaker are controlled by a time logic module to simulate the continuous return stroke process of multiple lightning strikes. Specifically, the circuit breakers are initially in the open state, and each circuit breaker operates twice. The circuit breaker corresponding to the first return stroke closes at the start of the stroke and opens at the end of the first return stroke discharge; the circuit breakers corresponding to subsequent return strokes close sequentially at the end of the previous return stroke discharge and open at the end of their respective return stroke discharge, and so on until all return strokes are completed.

[0042] Next, three lightning strike scenarios—direct strike, induced strike, and backflashover—were set up, and the single-strike lightning current model and the multiple-strike lightning current model were respectively connected to the electromagnetic transient simulation model of the 10kV distribution line. Wherein: The equivalent method for direct lightning strike is to use the lightning current as a current source, connect it in parallel with the equivalent wave impedance between the thundercloud and the ground, and then connect it to a conductor. The equivalent method for induced lightning conditions is as follows: the induced voltage component generated on the conductor by the lightning impulse energy is used as a voltage source, and its high-voltage end is connected to the conductor. The equivalent method for backflashover is as follows: the lightning current component is connected to the top of the tower as a current source, and the induced voltage component on the conductor is connected to the conductor as a voltage source, with its high-voltage end connected to the conductor.

[0043] Therefore, electromagnetic transient simulation analysis models for single and multiple lightning strikes under various operating conditions are established.

[0044] Using the established electromagnetic transient simulation analysis models of single and multiple lightning strikes under various operating conditions, the electrical stress of the 10kV line surge arrester under different operating conditions of single and multiple lightning strikes was simulated and analyzed.

[0045] In the simulation, the lightning current amplitude was set to vary within a certain range, causing the surge arrester to reach its nominal discharge current limit or maximum absorbed energy limit. The lightning current amplitude, surge arrester discharge current, and absorbed energy were recorded when the surge arrester reached its withstand limit under different operating conditions.

[0046] The electrical stress of the surge arrester obtained from simulations under different operating conditions of single and multiple lightning strikes was compared. The comparison included: the lightning current amplitude, surge arrester discharge current, and absorbed energy when the surge arrester reached the discharge current limit or energy absorption limit under the same lightning strike conditions, respectively, for single and multiple lightning strikes.

[0047] By comparison, the results of the impact of multiple lightning strikes on the surge arrester's withstand capability are presented. These results clearly reveal that, under the same lightning strike conditions, multiple lightning strikes, compared to a single lightning strike, result in a lower lightning current amplitude at the surge arrester's withstand limit, while absorbing a higher amount of energy. In other words, the energy accumulation effect of multiple lightning strikes poses a greater threat to the surge arrester.

[0048] Example: Taking a typical 10kV distribution line as the object, a simulation analysis is performed according to the above steps.

[0049] The specific steps for collecting and statistically analyzing typical parameters of typical 10kV distribution lines, towers, and surge arresters to establish an electromagnetic transient simulation model of a 10kV distribution line include: (1) Collect and statistically analyze typical parameters of typical 10kV distribution lines, towers, and surge arresters. Line-related parameters include conductor type, line length, span, sag, conductor height of each phase and phase spacing. Other related parameters include tower type, tower height, tower soil resistivity, tower grounding resistance, insulator type and insulation length. Surge arrester-related parameters include surge arrester type, rated voltage and surge arrester VI curve parameters.

[0050] (2) Based on the typical parameters of 10kV distribution lines, an electromagnetic transient simulation model of 10kV distribution lines is established. In this embodiment, the base tower of the 10kV distribution line is selected as the research object, and the simulation model is built in the electromagnetic transient simulation program PSCAD / EMTDC.

[0051] a. The line uses LGJ-50 type conductors with a radius of 16.8mm, a DC resistance of 0.04608Ω / km, and a sag of 1m. A frequency-dependent (phase) model is used in the PSCAD / EMTDC simulation program.

[0052] b. The tower is supported by a reinforced concrete tower. In the PSCAD / EMTDC simulation program, a single wave impedance is used for simulation, with the wave impedance set to 250Ω. The tower grounding resistance is set to 10Ω. The average span is set to 50m.

[0053] c. The line insulator model is S-270, and the insulation distance of the insulator is 0.49m. The pilot development method is used to determine whether the insulator flashover occurs. In the PSCAD / EMTDC simulation calculation program, an ideal controllable switch is used to simulate the flashover process of the insulator string. The controllable switch is controlled by the insulator flashover criterion and the voltage across the insulator.

[0054] d. The line surge arrester model is YH5CJ5-17 / 50Z, with a rated voltage of 17kV, and the surge arrester is installed at a base-by-base density.

[0055] 2) The specific steps for establishing lightning current models for single and multiple lightning strikes, as well as electromagnetic transient simulation analysis models for typical 10kV distribution lines subjected to single or multiple lightning strikes, including direct strikes, induced strikes, and backflashovers, include: (1) In the PSCAD / EMTDC simulation calculation program, a lightning current model of a single lightning strike is built and fitted using a double exponential lightning current wave. The fitting formula is shown in equation (1). (2) In the PSCAD / EMTDC simulation program, a lightning current model of multiple lightning strikes was built, and a double exponential lightning current wave was used for fitting. The fitting formula is shown in Equation (1). The return stroke time interval was set to 1ms, and the frequency of consecutive lightning strikes was set to 4 times, namely 1 negative polarity first return stroke and 3 negative polarity subsequent return strokes. The fitting formula is:

[0056] In the formula, t represents time, and I m Let a be the amplitude of the lightning current, and b be the fitting parameters. This represents the instantaneous value of the lightning current. In this embodiment, the values ​​of a and b in the single lightning strike current of 2.6 / 50μs are 16000 and 1040800, respectively. The values ​​of a and b in the initial negative polarity lightning current of 1 / 200μs are 3500 and 2500000, respectively. The values ​​of a and b in the subsequent negative polarity return stroke of 0.25 / 100μs are 6986 and 10850000, respectively. In PSCAD / EMTDC software, a circuit breaker module is added to the lightning current model for each return stroke. The circuit breakers in the four return stroke lightning current models are numbered BRK1, BRK2, BRK3, and BRK4, respectively. A time logic module is used to control the closing duration, opening duration, and switching sequence of each circuit breaker to simulate the occurrence of multiple lightning strikes. Each circuit breaker is initially set to open, and each circuit breaker operates twice. Since the lightning current waveform of each return stroke is different, different circuit breaker closing durations need to be set. Assuming that multiple lightning strikes occur at time 0, the waveform of the first return stroke is 1 / 200μs, and the discharge ends after 1.2ms, then circuit breaker BRK1 is set to close at 0ms and open at 1.2ms. The subsequent return stroke waveform is 0.25 / 100μs. After 1ms of discharge, the circuit breaker BRK2 is set to close at 1.2ms and open at 2.2ms; circuit breaker BRK3 is set to close at 2.2ms and open at 3.2ms; and BRK4 is set to close at 3.2ms and open at 4.2ms. At this time, the four return stroke discharges are completed.

[0057] (3) Construct simulation models for single lightning strikes and multiple lightning strikes under different lightning strike conditions. In this embodiment, the simulation process for different lightning strike conditions is as follows: a. Lightning strike conductor: In this embodiment, the amplitude of the lightning current for a single lightning strike is set to vary from 5 to 10 kA, and the amplitude of the lightning current for each return strike in multiple lightning strikes is set to vary from 5 to 10 kA. The lightning current source is connected to the C-phase conductor of tower #3, and the electrical stress of the C-phase arrester of tower #3 is simulated and analyzed. b. Lightning-struck tower: In this embodiment, the amplitude of a single lightning strike is set to vary from 15 to 20 kA, and the amplitude of each return strike from multiple lightning strikes is set to vary from 5 to 10 kA. The backflashover energy is equivalent to two parts: one part serves as a lightning current source connected to the top of the tower, and the other part serves as an induced voltage source connected to the high-voltage end of the conductor. The formula for the equivalent voltage source is as follows:

[0058] In the formula This refers to the induced voltage component during counterattack. This is the instantaneous value of the lightning current. For the steepness of the lightning current, The ratio of the main discharge velocity to the speed of light, c. The suspension height of the conductor at the tower. The average height of the conductor above the ground. This is the average height of the ground wire relative to the ground. For the length of the head-on arrival, The coupling coefficient is... For the tower height, For time.

[0059] c. Ground near the lightning strike conductor: In this embodiment, the amplitude of the single lightning strike current is set to vary from 10 to 15 kA, and the amplitude of the return lightning current after multiple lightning strikes is set to vary from 5 to 10 kA. Induced lightning is used as a voltage source connected to the high-voltage end of the conductor. The electrical stress of the C-phase arrester on tower #3 is simulated and analyzed. The equivalent voltage source formula is as follows:

[0060] In the formula Where S is the tower height, S is the lightning strike distance, and K is the correction factor. This is the instantaneous value of the lightning current. For time.

[0061] The specific steps for simulating and analyzing the electrical stress of a typical 10kV line surge arrester under different operating conditions of single and multiple lightning strikes in this embodiment include: 3) Based on the electromagnetic transient models of a typical 10kV surge arrester subjected to single and multiple lightning strikes established in this embodiment, electrical stress simulation analysis of the 10kV surge arrester under typical conditions such as direct strike, induced strike, and backflashover is performed. The specific electrical stress simulation results are as follows: Table 1 Maximum electrical stress of surge arrester under different operating conditions

[0062] (1) Direct lightning strike condition: Under a single lightning strike, when the lightning current amplitude increases to 8kA, the surge arrester will soon exceed its discharge current limit. At this time, the surge arrester current amplitude is 4.82kA, and the energy absorption is 3.60kJ. Under multiple lightning strikes, when the lightning current amplitude increases to 5kA, the surge arrester will soon exceed its discharge current limit. At this time, the surge arrester current amplitude is 4.28kA, and the energy absorption is 19.53kJ. As shown in Table 1. The maximum electrical stress under the direct lightning strike condition is as follows: Figure 2 As shown.

[0063] (2) Backflash lightning condition: Under a single lightning strike, when the lightning current amplitude increases to 19kA, the surge arrester will soon exceed its discharge current limit. At this time, the surge arrester current amplitude is 4.93kA, and the energy absorption is 21.77kJ. Under multiple lightning strikes, when the lightning current amplitude increases to 8kA, the surge arrester will soon exceed its energy absorption limit. At this time, the surge arrester current amplitude is 1.93kA, and the energy absorption is 30.41kJ, as shown in Table 1. The maximum electrical stress under the backflash lightning condition is as follows: Figure 3 As shown.

[0064] (3) Induced lightning conditions: Under a single lightning strike, when the lightning current amplitude increases to 10kA, the surge arrester will soon exceed its discharge current limit. At this time, the surge arrester current amplitude is 4.82kA, and the energy absorption is 6.17kJ. Under multiple lightning strikes, when the lightning current amplitude increases to 8kA, the surge arrester will soon exceed its energy absorption limit. At this time, the surge arrester current amplitude is 3.13kA, and the energy absorption is 30.05kJ, as shown in Table 1. The maximum electrical stress under induced lightning conditions is as follows: Figure 4 As shown.

[0065] 4) The specific steps for comparing the maximum electrical stress of line surge arresters under different operating conditions of single and multiple lightning strikes, and outputting the comparative results of the impact of multiple lightning strikes on the surge arrester's withstand capability, include: The results of comprehensive electrical stress simulation analysis show that under different lightning strike conditions, including single and multiple lightning strikes, the electrical stress of the 10kV surge arrester will reach its withstand limit (discharge current 5kA, energy absorption 30kJ) as the lightning current amplitude increases. Furthermore, under each condition, without exceeding the withstand limit of the 10kV surge arrester's electrical stress, the maximum withstandable amplitude of the multiple lightning strike current is less than that of the single lightning strike current. Obviously, multiple lightning strikes are more likely to cause the surge arrester to exceed its withstand capacity, thus causing damage. Therefore, when designing the insulation coordination and surge arrester for 10kV distribution lines, the impact of multiple lightning strikes on the surge arrester should be considered.

[0066] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or basic characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects.

[0067] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A simulation analysis method for the electrical stress of a 10kV surge arrester under multiple lightning strikes, characterized in that, include: Obtain the parameters of 10kV distribution lines, towers, and surge arresters, and establish an electromagnetic transient simulation model of the 10kV distribution lines based on the parameters; A single lightning strike current model and a multiple lightning strike current model are established respectively. The multiple lightning strike current model adopts a combination of the first return stroke waveform and subsequent return stroke waveforms, and sets the return stroke frequency and return stroke time interval. The single lightning strike current model and the multiple lightning strike current model are respectively connected to the electromagnetic transient simulation model of the 10kV distribution line, and three lightning strike conditions, namely direct strike, induction and backflash, are set respectively to establish electromagnetic transient simulation analysis models of single lightning strike and multiple lightning strike under each condition. Using the electromagnetic transient simulation analysis models of single and multiple lightning strikes under various operating conditions, the electrical stress of the 10kV line arrester under different operating conditions of single and multiple lightning strikes is simulated and analyzed. The electrical stress of the surge arrester obtained from simulations under different operating conditions of single lightning strike and multiple lightning strikes is compared, and the comparison results of the impact of multiple lightning strikes on the surge arrester's withstand capability are output.

2. The simulation analysis method for electrical stress of a 10kV surge arrester under multiple lightning strikes according to claim 1, characterized in that, The multiple lightning strike current model uses a negative polarity first return stroke waveform and a negative polarity subsequent return stroke waveform, and the return stroke frequency includes multiple returns; the single lightning strike current model uses a negative polarity standard lightning current waveform.

3. The simulation analysis method for electrical stress of a 10kV surge arrester under multiple lightning strikes according to claim 1, characterized in that, Both the single-strike and multiple-strike lightning current models are fitted using a double exponential wave. The formula for fitting using a double exponential wave is as follows: in, For time, This represents the amplitude of the lightning current. and These are the fitting parameters; different waveforms correspond to different fitting parameter values. This represents the instantaneous value of the lightning current.

4. The simulation analysis method for electrical stress of a 10kV surge arrester under multiple lightning strikes according to claim 1, characterized in that, When establishing a multiple lightning strike current model, the continuous process of multiple lightning strikes is simulated. The specific simulation of the continuous process of multiple lightning strikes is as follows: In the electromagnetic transient simulation software, an independent circuit breaker is set for each return stroke, and the closing duration, opening duration and switching sequence of each circuit breaker are controlled by the time logic module.

5. The simulation analysis method for electrical stress of a 10kV surge arrester under multiple lightning strikes according to claim 4, characterized in that, The circuit breaker is initially in the open state, and each circuit breaker operates twice; the circuit breaker corresponding to the first return strike closes at the start of the first return strike and opens at the end of the first return strike discharge; the circuit breakers corresponding to subsequent return strikes close sequentially at the end of the previous return strike discharge and open at the end of their respective return strike discharge, and so on until all return strikes are completed.

6. The simulation analysis method for electrical stress of a 10kV surge arrester under multiple lightning strikes according to claim 1, characterized in that, The three lightning strike scenarios (direct strike, induced strike, and backflashover) are described below. The equivalent method for the direct strike scenario is as follows: the lightning current is used as a current source and connected in parallel with the equivalent wave impedance between the thundercloud and the ground, and then connected to a conductor. The equivalent method for the induced strike scenario is as follows: the induced voltage component generated on the conductor by the lightning impulse energy is used as a voltage source, and its high-voltage end is connected to the conductor. The equivalent method for the backflashover scenario is as follows: the lightning current component is used as a current source and connected to the top of the tower, while the induced voltage component on the conductor is used as a voltage source, and its high-voltage end is connected to the conductor.

7. The simulation analysis method for electrical stress of a 10kV surge arrester under multiple lightning strikes according to claim 1, characterized in that, The electromagnetic transient simulation model was built using electromagnetic transient simulation software. The line conductors were modeled using a frequency-dependent model, the towers were simulated using a single wave impedance, and the insulators were identified using the leader development method to determine flashover and the flashover process was simulated using an ideal controllable switch.

8. The simulation analysis method for electrical stress of a 10kV surge arrester under multiple lightning strikes according to claim 1, characterized in that, The simulation analysis sets the range of lightning current amplitude variation, so that the surge arrester reaches its nominal discharge current limit or maximum absorbed energy limit respectively, and records the lightning current amplitude, discharge current and absorbed energy when the surge arrester reaches its withstand limit under different operating conditions.

9. The simulation analysis method for electrical stress of a 10kV surge arrester under multiple lightning strikes according to claim 1, characterized in that, The comparison of the electrical stress of the surge arrester obtained from simulations under different operating conditions of single lightning strike and multiple lightning strikes includes: comparing the lightning current amplitude, surge arrester discharge current and absorbed energy when the surge arrester reaches the discharge current limit or energy absorption limit under the same lightning strike conditions, respectively, for single lightning strike and multiple lightning strikes.

10. The simulation analysis method for electrical stress of a 10kV surge arrester under multiple lightning strikes according to claim 1, characterized in that, The parameters of the 10kV distribution line include conductor type, line length, span, sag, conductor height and phase spacing; the parameters of the tower include tower type, tower height, soil resistivity, grounding resistance, insulator type and insulation length; and the parameters of the surge arrester include surge arrester type, rated voltage and volt-ampere characteristic curve parameters.

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