Offshore booster station lightning arrester arrangement optimization method

Abstract

The invention relates to an offshore booster station lightning arrester arrangement optimization method, which comprises the following steps of: constructing an offshore booster station model, and calculating lightning stroke induction overvoltage of an offshore booster station; using a Monte Carlo method to estimate lightning stroke parameters of the power distribution network, estimating probability distribution of overvoltage through a Gaussian density function, and constructing a risk model of lightning arrester failure; and based on the risk model of lightning arrester failure, constructing a target function considering the protection importance and economic indexes of the nodes, and determining the optimal arrangement of the lightning arrester through particle swarm optimization of the target function. Compared with the prior art, the method has the advantages that the influence of uncertainty in a power grid can be processed, so that the robustness and reliability of a lightning arrester arrangement scheme under different operation conditions are ensured, more reliable lightning protection is provided for an offshore booster station, and the method is suitable for various complex offshore power system environments.

Description

Technical Field

[0001] The invention relates to the field of lightning protection for a booster station in a wind power plant, and in particular to a method for optimizing the arrangement of lightning arresters for an offshore booster station. Background Art

[0002] As an important hub between wind farms and land power grids, the safety and stability of offshore wind farm booster stations are crucial to the power transmission and economic benefits of the entire wind power system. Due to the particularity of the offshore environment, such as strong winds, high humidity, salt spray corrosion and waves, the power equipment of the booster station faces more severe tests. Lightning strikes, as a sudden natural phenomenon, often cause serious induced overvoltages in offshore wind farms, resulting in equipment damage, system shutdown, and even large-scale power outages. Therefore, lightning protection for offshore wind farm booster stations has become one of the key issues to ensure the safe operation of offshore wind power systems.

[0003] At present, the lightning arrester protection scheme for offshore wind farm booster stations mainly relies on traditional electrical parameter design. However, due to the complexity of the offshore environment and the randomness of lightning strikes, traditional lightning arresters often find it difficult to provide adequate protection when facing offshore lightning. On the one hand, the equipment of offshore wind farm booster stations is exposed to an open environment, and the probability of lightning strikes increases significantly; on the other hand, the high salinity and high humidity in the marine environment accelerate the aging and corrosion of the equipment, further reducing the effectiveness of the lightning arrester.

[0004] In addition, with the expansion of offshore wind farms, the structure and function of booster stations are becoming increasingly complex. Traditional lightning arrester protection systems often find it difficult to achieve efficient dynamic response and reliable protection when faced with changing marine environments and complex power transmission requirements. Therefore, how to optimize the layout and operation of lightning arresters, reduce the impact of lightning strikes on booster stations, and ensure the long-term stable operation of the system while meeting the requirements for lightning protection is an urgent problem to be solved in the current technical field. Therefore, it is necessary to accurately arrange and dynamically adjust lightning arresters for different areas and equipment in booster stations. Summary of the invention

[0005] The purpose of the present invention is to overcome the defect that the traditional lightning arrester arrangement method is difficult to fully meet the lightning protection needs of offshore booster stations due to the particularity of the offshore environment, such as humidity, high salt, strong wind and other factors, and to provide an optimized lightning arrester arrangement method suitable for offshore booster stations.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for optimizing the arrangement of lightning arresters in an offshore booster station, comprising the following steps:

[0008] Construct an offshore booster station model and calculate the lightning induced overvoltage of the offshore booster station;

[0009] The Monte Carlo method is used to estimate the lightning parameters of the distribution network, the probability distribution of overvoltage is estimated through the Gaussian density function, and the risk model of lightning arrester failure is constructed;

[0010] Based on the risk model of arrester failure, an objective function considering the protection importance of nodes and economic indicators is constructed, and the optimal arrangement of arresters is determined by particle swarm optimization of the objective function.

[0011] As a preferred technical solution, the offshore booster station model includes: lightning arrester, grounding system, oil-immersed transformer, transmission line and overvoltage caused by lightning strike, as follows:

[0012] The model of the arrester uses multi-parameter analysis to calculate the values ​​of resistance, inductance and capacitance;

[0013] Constructing a high-frequency model of the grounding system and a high-frequency surge model of the oil-immersed transformer to calculate voltage, magnetic permeability and electrical parameters;

[0014] The equivalent model of the transmission line uses a π-type equivalent circuit to represent the maximum frequency of the transmission line with a length of l.

[0015] As a preferred technical solution, the lightning induced overvoltage of the offshore substation under direct lightning strike is calculated as follows:

[0016]

[0017]

[0018] Where c is the speed of light in free space; h is the line height; I0 ​​is the return current; β is the ratio of the collection speed to the speed of light; d is the horizontal distance between the lightning channel and the line; h c Indicates the height of the lightning channel.

[0019] As a preferred technical solution, in the absence of a lightning arrester, the offshore booster station lightning induced overvoltage is calculated by the induced voltage generated by the circuit breaker and the T-type connection:

[0020]

[0021]

[0022] Where y is the lateral distance from the horizontal line to the vertical lightning ground terminal, v is the return stroke velocity, V IR is the residual voltage of the arrester, V max is the maximum induced voltage, T f is the impulse rise time of the lightning channel, L is the span length, I pis the peak lightning current;

[0023] When V max >1.5CFO, lightning flashover occurs, where CFO is the critical flashover voltage with a 50% probability of occurrence:

[0024]

[0025] Assumptions And N g is the average number of chronic flashovers, and the final striking point is expressed as follows:

[0026]

[0027] R g =0.9R c

[0028] Among them, R c Indicates the impulse resistance when struck by lightning; R g Indicates the ground resistance when struck by lightning.

[0029] As a preferred technical solution, the objective function considering the protection importance of nodes and economic indicators is as follows:

[0030]

[0031] Where i represents the region index, R(i) global is the system global risk of region i, T i is the technical index, E i For economic index.

[0032] As a preferred technical solution, the system global risk of region i determines the importance of all regions by the probability risk index R(i):

[0033]

[0034] Among them, R Pi is the risk of a lightning conductor being struck directly, R Gi The risk of lightning striking near a conductor;

[0035] The risk of a direct lightning strike to the conductor is expressed as:

[0036]

[0037] Where f(V) is the probability density function of lightning overvoltage, V 50％ is the overvoltage corresponding to a 50% probability density, σ is the standard deviation;

[0038] The risk of lightning striking near a conductor is expressed as:

[0039]

[0040]

[0041] Among them, f(V g ) is the probability density of overvoltage caused by indirect lightning strike, p(V g ) is the discrete probability of indirect lightning discharge; V g It is the overvoltage caused by indirect lightning discharge.

[0042] As a preferred technical solution, the technical index T i Based on the compression ratio K of the substation in the feeder pi and marine environmental conditions K hi , used to determine the protection importance of all nodes:

[0043] T i =K pi ×K hi

[0044]

[0045] K hi =w1·F wind +w2·Ft ide +w3·F salt

[0046] Among them, F wind 、F tide 、F salt They represent the influencing factors of wind speed, tide and salt spray corrosion respectively; w1, w2, w3 are the weight coefficients of wind speed, tide and salt spray corrosion respectively, and satisfy w1+w2+w3=1.

[0047] As a preferred technical solution, the economic index E i Including repair and maintenance costs C PMi and energy consumption cost C ENSi :

[0048] E i =C PM +C ENSi

[0049] C PMi =0.02C invi

[0050]

[0051] Among them, C invi is the annualized cost of investment, I R is the interest rate, Y is the operation period, C TIis the cost of component investment. As a preferred technical solution, the voltage constraint of the component position is set in the particle swarm optimization process:

[0052] V t =V p +2ST<2V p

[0053] Among them, V t is the voltage at the original position, S is the input steep front wave slope, V p Protective voltage for lightning arrester.

[0054] As a preferred technical solution, an insulation level BIL constraint is set in the particle swarm optimization process: the induced overvoltage of the power grid equipment caused by lightning strike is calculated, and the maximum induced overvoltage is constrained to be less than the set insulation level BIL.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] 1) The present invention proposes a lightning arrester optimization layout technology based on multi-objective functions, which can achieve a balance among multiple indicators such as technology, safety and risk, and economic benefits, thereby optimizing the lightning protection performance of offshore booster stations. First, the electrical components of the offshore booster station are comprehensively and accurately modeled. It can not only effectively reduce lightning-induced overvoltage and ensure the safe operation of booster station equipment, but also achieve the optimal balance in risk management and cost control, providing all-round technical guarantees for the safe and stable operation of offshore wind farms.

[0057] 2) In order to accurately simulate the impact of lightning strikes on the power grid, the present invention proposes a high-frequency transient mathematical model suitable for offshore booster stations. These models include modeling of key components such as lightning arresters, oil-immersed transformers, overhead lines, and lightning induced voltage. By modeling and analyzing these components, the voltage distribution and electromagnetic coupling effect of each component during a lightning strike can be accurately predicted, thereby providing a scientific basis for the layout of lightning arresters.

[0058] 3) The optimization method based on multi-objective functions proposed in the present invention comprehensively considers multiple key indicators such as technology, safety and risk, and economic benefits, and optimizes and solves them through particle swarm optimization (PSO) and Monte Carlo (MC) technology. The PSO algorithm can quickly search for the optimal solution, while the MC technology is used to deal with the impact of uncertainty in the power grid, thereby ensuring the robustness and reliability of the lightning arrester layout scheme under different operating conditions. The present invention can provide more reliable lightning protection for offshore substations, while taking into account economy and safety, and is suitable for various complex offshore power system environments. In the future, the method of the present invention can also be further promoted and applied to other types of power systems, such as lightning protection for land substations and transmission lines, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 It is a structural schematic diagram of the present invention;

[0060] Figure 2 This is a schematic diagram of the arrester model of the present invention;

[0061] Figure 3 is a lumped parameter equivalent circuit diagram of the grounding electrode of the present invention;

[0062] Figure 4 is an equivalent circuit diagram of the transformer winding of the present invention;

[0063] Figure 5 This is a schematic diagram for calculating direct lightning overvoltage. DETAILED DESCRIPTION

[0064] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0065] Example 1

[0066] The present invention proposes a lightning arrester optimization layout method suitable for offshore booster stations, aiming to cope with the lightning threat faced by offshore booster stations and their complex power system environment. As an important hub of offshore wind farms, the safety of offshore booster stations is crucial to the stable operation of the entire wind farm. Due to the particularity of the offshore environment, such as humidity, high salt, strong wind and other factors, the traditional lightning arrester layout method is difficult to fully meet the lightning protection requirements of offshore booster stations. In response to this problem, the present invention proposes a lightning arrester optimization layout technology based on multi-objective functions, which can achieve a balance between multiple indicators such as technology, safety and risk, and economic benefits, thereby optimizing the lightning protection performance of offshore booster stations. First, the electrical components of the offshore booster station are comprehensively and accurately modeled. In order to accurately simulate the impact of lightning strikes on the power grid, the invention proposes a high-frequency transient mathematical model suitable for offshore booster stations. These models include modeling of key components such as lightning arresters, oil-immersed transformers, overhead lines and lightning induced voltage. By modeling and analyzing these components, the voltage distribution and electromagnetic coupling effect of each component during a lightning strike are accurately predicted, thereby providing a scientific basis for the layout of the lightning arrester. An optimization method based on multi-objective functions is proposed. This method comprehensively considers multiple key indicators such as technology, safety and risk, and economic benefits, and optimizes and solves them through particle swarm optimization (PSO) and Monte Carlo (MC) technology. The PSO algorithm can quickly search for the optimal solution, while the MC technology is used to deal with the impact of uncertainty in the power grid, thereby ensuring the robustness and reliability of the lightning arrester layout scheme under different operating conditions. The present invention can provide more reliable lightning protection for offshore substations, while taking into account economy and safety, and is suitable for various complex offshore power system environments. In the future, the method of the present invention can also be further promoted and applied to other types of power systems, such as lightning protection for land substations and transmission lines, and has broad application prospects.

[0067] The technical solution of the present invention is: a method for optimizing the arrangement of lightning arresters in offshore booster stations, comprising the following three steps:

[0068] Step 1: An accurate model of the offshore substation was constructed, including the earth, oil-immersed transformers, overhead lines, and overvoltages caused by lightning strikes, and the Heidler model was used to simulate the lightning current. The arrester model was determined according to IEEE standards and manufacturer data, and multi-parameter analysis was used to calculate the values ​​of resistance, inductance, and capacitance. The high-frequency model of the grounding system and the high-frequency surge model of the oil-immersed transformer were also optimized to achieve accurate calculations of voltage, permeability, and electrical parameters. By establishing an equivalent model of the transmission line, efficient lightning protection in a complex marine environment is ensured, and the safety and reliability of the system are improved.

[0069] Step 2: Construct a method to calculate the lightning-induced overvoltage of offshore substations based on the Chowdhuri-Gross formula. Lightning strikes are one of the destructive phenomena in distribution networks and may cause permanent or transient faults. By using the direct lightning overvoltage equation of Chowdhuri and Gross, key parameters such as line height, horizontal distance between the lightning channel and the line, and return stroke current are modeled, and the maximum overvoltage amplitude caused by lightning strikes is calculated to be 1.5×10 5 kV. In addition, the calculation formula of the induced voltage without a lightning arrester was analyzed through a circuit breaker and a T-type connection, and the effect of the increase in the lightning strike distance on the overvoltage was considered. This method can accurately assess the lightning strike risk of offshore substations and provide effective protection strategies.

[0070] Step 3. Construct a risk modeling method for offshore wind farm booster stations, and estimate the risk of insulation failure caused by lightning overvoltage through the normal distribution probability density function. The Monte Carlo (MC) method is used to calculate the magnitude of lightning overvoltage at the distribution network node, and the probability distribution of overvoltage is estimated through the Gaussian density function. Construct a risk model for arrester failure, considering complex factors such as arrester parameters, lightning strike area, and lightning characteristics. Introduce the normal density function, calculate the probability density of lightning energy, and use the Weibull cumulative distribution to approximate the probability of arrester failure. Construct a global risk model, comprehensively consider the protection ratio of multiple components and the maximum lightning current determined by the Monte Carlo method, evaluate the overall risk of offshore wind farm booster stations, and provide an effective lightning protection strategy for the system.

[0071] Step 4. An intelligent protection measure is constructed to minimize the number of lightning arresters in the power grid by optimizing the objective function. Particle swarm optimization (PSO) technology and Monte Carlo (MC) method are used to determine the optimal layout of lightning arresters and their distance from grid components. PSO, as a heuristic optimization algorithm, effectively deals with complex engineering problems, while the MC method is used to estimate lightning strike parameters. In the method of the present invention, the results of MC are used as input to PSO to optimize the global risk and economic indicators of the system. The technical index takes into account marine environmental conditions such as wind speed, tide, and salt spray corrosion. The economic index covers installation, operation, maintenance and investment costs. In order to ensure that the lightning arrester provides optimal protection under surge conditions and avoid damage to components due to overvoltage, BIL=125kV is used as a constraint to achieve comprehensive intelligent lightning protection.

[0072] Specifically, in step 1, an accurate model of the offshore booster station is constructed, including the earth, oil-immersed transformers, overhead lines, and overvoltages caused by lightning strikes. It should be noted that since the length and impedance of the vertical grounding wire of the lightning arrester are too small compared to other distribution network components, its modeling is ignored. For lightning strike modeling of offshore booster stations, in the IEEE standard (standard C62.45), a double exponential waveform and a triangular waveform are used to represent the lightning return current. In the present invention, the test waveform provided in the IEEE standard C62.45 is used as follows:

[0073] I(t)=I0(e -at -e -bt ) (1)

[0074] Among them, I0 is the maximum value of lightning current, a is the first strike time, and b is the second strike time. The mathematical model Heilder model that simulates the lightning current waveform is as follows:

[0075]

[0076] Among them, I p is the peak current, η is the correction factor for the peak current, χ=t / τ1, τ1 is the time constant for determining the current rise. In order to deal with the probability distribution, the following expression is used based on the (Anderson) probability. In IEEE Standard C62.45, the probability expression for the peak current I0 of the first lightning strike exceeding a certain value i0 is:

[0077]

[0078] Where P(I0>i0) is the probability that the peak value of the first return stroke current I0 exceeds i0, and i0 is the expected peak value of the first return stroke current (kA). Construct a flashover rate calculation model, and the ground flashover density N in the temperate zone g It can be estimated according to IEEE standard C62.45 as follows:

[0079]

[0080] Among them, N g is the number of ground flashovers per square kilometer per year, T d The number of days with thunder each year. According to IEEE arrester modeling, the parameters include L1 and R1, and L0, R0 and C are determined based on the technical data and equations provided by the manufacturer. The equation is as follows:

[0081] L1=15nμH (5)

[0082] R1=65dμΩ (6)

[0083] L0=0.2dnμH (7)

[0084] R0=100dnΩ (8)

[0085] C=100n / dPF (9)

[0086] Where d is the height of the arrester and n is the number of protection modules in the arrester. Figure 2 shown.

[0087] Based on the technical data provided by Pars and the proposed arrester model, in the Fernandez arrester modeling, the following determinations were made based on the technical data provided by the manufacturer under the 8 / 20μs test waveform:

[0088]

[0089]

[0090] Through formulas (11) and (12) and the technical data provided by the manufacturer, V and are provided by the manufacturer; these determined parameters are most similar to the standard model presented in EMTP / 2018 and PSCAD / 4.5 software, which is used as the default model. In addition, the parameters L1 and L0 (unit: μH) are determined according to the Pinceti-Giannettoni arrester model as follows:

[0091]

[0092]

[0093] Among them, V n is the rated voltage of the arrester, V r1 / T2 is the arrester voltage (in kV) at 10KA and 8 / 20μs waveform, and R1 = 1MΩ. In the model presented, according to the IEEE model, the capacitance C is calculated as follows:

[0094]

[0095] Construct a high-frequency model of the grounding system. The grounding electrode model circuit is as follows: Figure 3 shown.

[0096] The calculation formula for the ground rod assembly in the circuit is as follows:

[0097]

[0098] Among them, R is the resistance, L is the inductance, and C is the capacitance, all corresponding to the ground electrode. l is the length, a is the diameter of the ground electrode, ρ is the resistivity of the material around the ground electrode, μ0 is the magnetic permeability of the vacuum, and ε is the dielectric constant of the medium around the ground electrode.

[0099] A model of oil-immersed distribution transformer under high-frequency surge is constructed, and the model based on layered winding of single-phase transformer is extended to three-phase transformer. The calculation formula of capacitance C0 at both ends of the winding part is as follows:

[0100]

[0101] Among them, C r Indicates the capacitance value at both ends of the winding part, and n indicates the number of turns. In this process, the primary and secondary sides of the transformer can be considered as transmission line models with capacitance C and inductance L. The equivalent model is as follows Figure 4 As shown:

[0102] Where L0 and C0 are the equivalent (simplified) inductance and capacitance between nodes, respectively. For the three-phase oil-immersed transformer model, according to equations (18)-(20), all parameters are phase multiples. The capacitance between two phase conductors is expressed as equation (19), and the number of conductors relative to each other in each node is (n-1) times.

[0103] C=(n-1)εε0πDb / d (19)

[0104] Where ε is the relative dielectric constant of the turn-to-turn insulation, ε0 is the dielectric constant of vacuum, D is the average winding diameter, b is the axial conductor width, and d is the turn-to-turn insulation thickness. L is given by n / 2 turns:

[0105] L=(n / 2)μ0πDd / b (20)

[0106] where μ0 is the magnetic permeability of vacuum.

[0107] To construct an equivalent model of a transmission line, a π-type equivalent circuit can be used to represent the maximum frequency of a transmission line with a length of , as shown below:

[0108]

[0109] Where L and C are the inductance and capacitance per unit length respectively. The length of the transmission line should be less than the following value:

[0110]

[0111] Among them, θ is the speed of electromagnetic waves, and the calculation formula is as follows:

[0112]

[0113] Step 2: Use the Chowdhuri-Gross formula to calculate the lightning induced overvoltage of the offshore substation. One of the destructive phenomena in the distribution network is lightning strike, which can cause permanent or transient failures. Due to the sensitivity and importance of loads and grid equipment to overvoltage. Figure 5 As shown, h is the height of the line and d is the horizontal distance between the lightning channel and the line. The closed form solution proposed by Chowdhuri and Gross (Chowdhuri-Gross model) is obtained through the coupling model they developed themselves. The coupling equation is shown below:

[0114]

[0115] In order to solve the coupled equations (24) and (25), the following processing is performed:

[0116]

[0117] Where c is the speed of light in free space (3×10 8 m / s), h is the line height (the cable system indicates the burial depth or the distance from the ground), I0 is the return stroke current, β is the ratio of the convergence speed to the speed of light, d is the horizontal distance between the lightning channel and the line, h c is the height of the lightning channel. The maximum overvoltage amplitude of a direct lightning strike is calculated to be 1.5×10 5 KV, and the increase in lightning strike distance is equivalent to a decrease in direct lightning overvoltage.

[0118] On the other hand, without a lightning arrester, the induced voltage generated by the circuit breaker and the T-connection can be calculated by the following formula:

[0119]

[0120] Where y is the lateral distance from the horizontal line to the vertical lightning ground terminal, and v is the return stroke velocity (3×10 8 m / s), V IR is the residual voltage of the arrester, V max is the maximum induced voltage, T f is the impulse rise time of the lightning channel, L is the span length (or the distance between the lightning strike point and the power grid equipment), I p is the peak current of lightning strike. According to IEEE standard IEEE1410, when V max >1.5CFO, lightning flashover occurs, where CFO is the critical flashover voltage with a 50% probability of occurrence.

[0121]

[0122] Assumptions And N g is the average number of chronic flashovers. According to IEEE 1410-2004, the final striking point is expressed as follows:

[0123]

[0124] Among them, R c Indicates the impulse resistance when struck by lightning; R g Indicates the ground resistance when struck by lightning.

[0125] Step 3, risk modeling. In practice, many random phenomena follow the normal distribution probability density function. First, the risk of insulation failure is estimated. The present invention proposes a method for estimating the risk of insulation failure in a distribution network caused by lightning overvoltage. The lightning overvoltage at the distribution network node is calculated using equation (26) and the Monte Carlo MC method. Since the probability density function of the lightning overvoltage in the distribution network is a Gaussian density function, it can be estimated by the mean value and standard deviation, as shown below:

[0126]

[0127] Where f(V) is the probability density function of lightning overvoltage, V 50％ is the overvoltage corresponding to a 50% probability density, and σ is the standard deviation. In other words, V is the voltage at which partial discharge begins to occur in the insulation, and V 50％ is the voltage at which this discharge reaches its maximum value. The discrete probability of lightning discharge is as follows:

[0128]

[0129] Among them, σ=0.7576.

[0130] Therefore, the risk of a direct lightning strike to a conductor can be calculated using the following formula:

[0131]

[0132] The risk of lightning striking near a conductor can be calculated using the following formula:

[0133]

[0134] Among them, f(V g ) is the probability density of overvoltage caused by indirect lightning strike, p(V g ) is the discrete probability of indirect lightning discharge;

[0135]

[0136] Among them, V g It is the overvoltage caused by indirect lightning discharge.

[0137] To construct the risk model of arrester failure, the arrester parameters, grid components, lightning strike area and lightning strike characteristics are complex, critical and probabilistic parameters. In order to estimate the risk of arrester failure, the induced overvoltage is introduced into the grid components, and the risk formula (42) can be replaced by (43) and (44). In addition, the lightning energy has the following normal density function:

[0138]

[0139] Where F(E) is the probability density of energy events, E 50％ is the energy that occurs with a 50% probability, and σ is the standard deviation. The probability of arrester failure can be approximated by the Weibull cumulative distribution as:

[0140]

[0141] Among them, E R is the rated energy capacity, E s It is the energy value of tolerance.

[0142] The calculation formula for the global risk of arrester failure in the constructed calculation network is as follows:

[0143]

[0144] Among them, R G is the global risk of arrester failure in the computing network, R i is the risk calculated for each node, determined according to different risk types, and n is the number of nodes.

[0145] In order to protect the expensive and critical components in different grid nodes, a weighted risk estimation method is proposed to accurately calculate the global risk, which is shown in Equation (46). In this method, more expensive and more critical components are given larger weights.

[0146]

[0147] Among them, k i and C i is a key and economic indicator that shows the weight of the connected nodes corresponding to the most important nodes.

[0148] To construct a global risk calculation model, for the proposed multi-component protection of the feeder, its protection ratio must be considered. Therefore, the allowable value of insulation failure of each component is determined according to its importance. According to equations (44) and (45), combined with the maximum lightning current determined by the Monte Carlo method, multiple risk factors are integrated, and the contribution of multiple component failures and risks and sources is summarized to determine the global risk of the system.

[0149]

[0150] Among them, R1 to R n is the risk value in the proposed area. The probability risk index R(i) of a specific area determines the importance of all areas:

[0151]

[0152] Step 4: Construct intelligent protection measures. The Monte Carlo MC method is used to estimate the lightning parameters as the input of the particle swarm optimization PSO algorithm and is used to optimize the objective function F through the PSO algorithm to determine the optimal distance between lightning arresters, that is, the optimal arrangement of lightning arresters:

[0153]

[0154] Where i represents the region index, R(i) glotal is the global risk of region i, and the technical index T i Determine the importance of protecting all nodes based on other indicators such as marine environmental conditions such as wind speed, corrosion and meteorological conditions K hi And the compression ratio K of the substation in the feeder pi ,This index is normalized according to the total number of substations.

[0155] T i =K pi ×K hi (50)

[0156]

[0157] K hi =w1·F wind +w2·F tide +w3·F salt (52)

[0158] Among them, w1, w2, and w3 are the weight coefficients of wind speed, tide, and salt spray corrosion, respectively, and they satisfy w1+w2+w3=1. wind 、F tide 、F salt Respectively represent the influencing factors of wind speed, tide and salt spray corrosion.

[0159] Economic Index E i Determines installation and operating costs, including repair and maintenance costs C PMi And, energy consumption cost C ENS :

[0160] E i =C PMi +C ENSi (53)

[0161] in:

[0162] C PMi =0.02C invi (54)

[0163]

[0164] Among them, C invi is the annualized cost of investment, I R is equal to the interest rate of 19%, Y is the operation period of 30 years, C TI is the cost of component investment in US dollars; C PM is the maintenance cost, C inv is the annual investment in US dollars.

[0165] Lightning arresters must be installed close to grid equipment, especially when the facilities are not adequately protected and the substation is located at the end of the feeder. In this case, the probability of a direct lightning strike is high because the traveling wave voltage can be distributed between the lines. After the surge protector enters the traveling wave of the substation or grid component, the voltage at the location of the surge protector reaches the maximum amplitude of the surge. In addition, the initial input wave (lightning) growth rate will continue in the surge protector. The initial peak value of the input wave (lightning) is twice the surge voltage. In other aspects, the increase in the distance from the network component to the point may cause the surge residual voltage at the component location to double or even exceed the surge peak.

[0166] The voltage constraint of the component location is set during the optimization of the lightning arrester layout. If 2T>T0, T is the time for the surge to travel from the arrester to the grid component, and T0 is the time required for the arrester to reach its voltage protection, then the voltage constraint of the component location is:

[0167] V t =V p +2ST<2V p (56)

[0168] Among them, V t is the voltage at the component location, S is the input steep front wave slope, V p Protective voltage for lightning arrester.

[0169] In the present invention, the basic insulation level BIL (Basic Insulation Level) is regarded as the second constraint. In this embodiment, the constraint is set to BIL = 125KV, and the induced overvoltage of the power grid equipment caused by lightning is calculated according to formulas (34) and (35). The maximum induced overvoltage should be less than the insulation level.

[0170] Example 2

[0171] As a second aspect of the present invention, the present application also provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the above-mentioned offshore booster station lightning arrester layout optimization method. In addition to the above-mentioned processor, memory and interface, any device with data processing capability in which the device in the embodiment is located may also include other hardware according to the actual function of the device with data processing capability, which will not be described in detail.

[0172] Example 3

[0173] As a third aspect of the present invention, the present application also provides a computer-readable storage medium having computer instructions stored thereon, which, when executed by a processor, implements the above-mentioned offshore booster station arrester layout optimization method. The computer-readable storage medium may be an internal storage unit of any device with data processing capability described in any of the aforementioned embodiments, such as a hard disk or a memory. The computer-readable storage medium may also be an external storage device, such as a plug-in hard disk, a smart memory card (Smart Media Card, SMC), an SD card, a flash card (Flash Card), etc. equipped on the device. Further, the computer-readable storage medium may also include both an internal storage unit and an external storage device of any device with data processing capability. The computer-readable storage medium is used to store the computer program and other programs and data required by any device with data processing capability, and may also be used to temporarily store data that has been output or is to be output.

[0174] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for optimizing the arrangement of lightning arresters in offshore booster stations, characterized in that the steps include: Construct an offshore booster station model and calculate the lightning induced overvoltage of the offshore booster station; The Monte Carlo method is used to estimate the lightning parameters of the distribution network, the probability distribution of overvoltage is estimated through the Gaussian density function, and the risk model of lightning arrester failure is constructed; Based on the risk model of arrester failure, an objective function considering the protection importance of nodes and economic indicators is constructed, and the optimal arrangement of arresters is determined by particle swarm optimization of the objective function.

2. The method for optimizing the arrangement of lightning arresters in an offshore booster station according to claim 1, characterized in that: The offshore booster station model includes: lightning arrester, grounding system, oil-immersed transformer, transmission line and overvoltage caused by lightning, as follows: The model of the arrester uses multi-parameter analysis to calculate the values ​​of resistance, inductance and capacitance; Constructing a high-frequency model of the grounding system and a high-frequency surge model of the oil-immersed transformer to calculate voltage, magnetic permeability and electrical parameters; The equivalent model of the transmission line uses a π-type equivalent circuit to represent the maximum frequency of the transmission line with a length of l.

3. The method for optimizing the arrangement of lightning arresters in an offshore booster station according to claim 2, characterized in that: The calculation of the lightning induced overvoltage of the offshore substation under direct lightning strike is as follows: Where c is the speed of light in free space; h is the line height; I0 ​​is the return current; β is the ratio of the collection speed to the speed of light; d is the horizontal distance between the lightning channel and the line; h c Indicates the height of the lightning channel.

4. The method for optimizing the arrangement of lightning arresters in offshore booster stations according to claim 2, characterized in that: In the absence of a lightning arrester, the offshore booster station lightning induced overvoltage is calculated through the induced voltage generated by the circuit breaker and T-type connection: Where y is the lateral distance from the horizontal line to the vertical lightning ground terminal, v is the return stroke velocity, V IR is the residual voltage of the arrester, V max is the maximum induced voltage, T f is the impulse rise time of the lightning channel, L is the span length, I p is the peak lightning current; When V max >1.5CFO, lightning flashover occurs, where CFO is the critical flashover voltage with a 50% probability of occurrence: Assumptions And N g is the average number of chronic flashovers, and the final striking point is expressed as follows: R g =0.9R c Among them, R c Indicates the impulse resistance when struck by lightning; R g Indicates the ground resistance when struck by lightning.

5. The method for optimizing the arrangement of lightning arresters in an offshore booster station according to claim 1, characterized in that: The objective function considering the protection importance of the node and the economic index is as follows: Where i represents the region index, R(i) global is the system global risk of region i, T i is the technical index, E i For economic index.

6. The method for optimizing the arrangement of lightning arresters in offshore booster stations according to claim 5, characterized in that: The system global risk of the region i is determined by the probability risk index R(i) to determine the importance of all regions: Among them, R Pi is the risk of a lightning conductor being struck directly, R Gi The risk of lightning striking near a conductor; The risk of a direct lightning strike to the conductor is expressed as: Where f(V) is the probability density function of lightning overvoltage, V 50％ is the overvoltage corresponding to a 50% probability density, σ is the standard deviation; The risk of lightning striking near a conductor is expressed as: Among them, f(V g ) is the probability density of overvoltage caused by indirect lightning strike, p(V g ) is the discrete probability of indirect lightning discharge; V g It is the overvoltage caused by indirect lightning discharge.

7. The method for optimizing the arrangement of lightning arresters in offshore booster stations according to claim 5, characterized in that: The technical index T i Based on the compression ratio K of the substation in the feeder pi and marine environmental conditions K hi , used to determine the protection importance of all nodes: T i =K pi ×K hi K hi =w1·F wind +w2·F tide +w3·F salt Among them, F wind 、F tide 、F salt They represent the influencing factors of wind speed, tide and salt spray corrosion respectively; w1, w2, w3 are the weight coefficients of wind speed, tide and salt spray corrosion respectively, and satisfy w1+w2+w3=1.

8. The method for optimizing the arrangement of lightning arresters in offshore booster stations according to claim 6, characterized in that: The economic index E i Including repair and maintenance costs C PMi and energy consumption cost C ENSi : E i =C PMi +C ENSi C PM =0.02C invi Among them, C invi is the annualized cost of investment, IR is the interest rate, Y is the operating period, C TI It is the cost of component investment.

9. The method for optimizing the arrangement of lightning arresters in offshore booster stations according to claim 1, characterized in that: The particle swarm optimization process sets the voltage constraints of the component locations: V t =V p +2ST<2V p Among them, V t is the voltage at the original position, S is the input steep front wave slope, V p Protective voltage for lightning arrester.

10. The method for optimizing the arrangement of lightning arresters in an offshore booster station according to claim 1, characterized in that: Insulation level BIL constraints are set in the particle swarm optimization process: the induced overvoltage of the power grid equipment caused by lightning strike is calculated, and the maximum induced overvoltage is constrained to be less than the set insulation level BIL.

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