Counterattack trip-out rate calculation method and system

Abstract

The invention discloses a method and a system for calculating a back-strike trip-out rate, and the method is characterized in that the method comprises the following steps: 1, collecting historical lightning monitoring data, constructing the probability distribution of lightning strike density based on the over-limit distribution characteristics of lightning activities, and calculating the average value of the lightning strike density based on the probability distribution; 2, historical lightning monitoring data are used for fitting probability distribution of lightning current amplitudes, and therefore the probability that the lightning current amplitudes exceed the pole and tower counterattack lightning resistance level is solved; and step 3, substituting the average lightning strike density value and the probability that the lightning current amplitude exceeds the counterattack lightning resistance level of the tower into a calculation formula of a regulation method, and solving the counterattack trip-out rate. According to the method, data of lightning activity rules are collected, the distribution rule of lightning current amplitude and the distribution rule of thunderbolt density are analyzed by using a large amount of data, a traditional regulation method is improved, and optimization of back-strike trip-out rate estimation is realized.

Description

Technical Field

[0001] The present invention relates to the field of power systems, and more specifically, to a method and system for calculating a back-attack trip rate. Background Art

[0002] The power grid is an important infrastructure in today's society. Its safe and stable operation is related to the efficient operation of social life. With the scale of the power grid, the occurrence of large-scale power outages has brought great impacts on people's production and life. Large-scale power outages may paralyze the transportation system, stagnate production, and affect social order. Analyzing the internal causes of large-scale power outages and finding effective early warning and prevention measures are issues that need to be solved urgently.

[0003] A blackout accident is a power outage accident caused by a continuous static overload or stability problem caused by one or more fault disturbances in the power system under specific circumstances. This accident lasts for a long time, affects a wide range, and has very serious consequences. Among the causes of blackout accidents, lightning disasters are an important one.

[0004] Lightning accidents account for as high as 40%-70% of accidents in my country's power system. Since power plants and substations are effectively protected by lightning protection facilities such as intrusion wave measures and direct lightning protection devices, the risk of being struck by lightning is greatly reduced. Currently, the risk of lightning strikes is mainly concentrated on transmission lines.

[0005] On the one hand, transmission lines are built over long distances, passing through different terrains and meteorological conditions. Different lines are located in different areas, different sections of the same line, and different towers are subject to different lightning characteristics. The risk impact of lightning tripping on different lines on the power grid is different, and the risk impact of lightning tripping on the same line at a certain time and operating mode on the power grid is also different. However, there are few in-depth studies and risk assessments of lightning impacts that are achieved based on line differentiation in the existing technology.

[0006] On the other hand, with the development of high-voltage transmission technology, the width of the line corridor and the height of the tower increase with the increase of the voltage level of the transmission line. The possibility of the line encountering lightning accidents is increasing, which increases the risk of line power outages and causes great economic losses and casualties. In order to avoid these losses, it is necessary to study the laws of regional lightning activities, accurately evaluate the lightning resistance level of the transmission line and the lightning risk of the line, and then propose reasonable lightning protection measures to reduce the losses and costs caused by lightning accidents.

[0007] Among the evaluation indicators of lightning risk, the most important one is the lightning trip rate. Combined with the above reasons, there are two main factors affecting the lightning trip rate. One is the law of lightning activity in the area where the line is located, and the other is the lightning resistance level of the line itself. The lightning trip rate of the transmission line is mainly composed of the counter-strike lightning trip rate and the bypass lightning trip rate. Among them, the counter-strike trip rate refers to the number of trips caused by reverse flashover of the conductor caused by lightning towers in 40 thunderstorm days and 100km transmission lines each year. At present, there are many problems in the calculation method of the counter-strike trip rate. For example, the calculation method does not consider the influence of the lightning activity laws in different regions on the calculation results, the influence of the lightning resistance level of the towers themselves, etc.

[0008] In view of the above problems, a new method and system for calculating the back-attack tripping rate is urgently needed. Summary of the invention

[0009] In order to solve the deficiencies in the prior art, the present invention provides a method and system for calculating the back-strike tripping rate, which improves the regulatory method by estimating the probability distribution of lightning strike density and the probability that the lightning current amplitude exceeds the back-strike lightning resistance level of the tower.

[0010] The present invention adopts the following technical solution.

[0011] The first aspect of the present invention relates to a method for calculating a counter-strike tripping rate, the method comprising the following steps: step 1, collecting historical lightning monitoring data, constructing a probability distribution of lightning strike density based on the over-limit distribution characteristics of lightning activity, and calculating an average lightning strike density value based on the probability distribution; step 2, fitting the probability distribution of lightning current amplitude with historical lightning monitoring data, thereby solving the probability that the lightning current amplitude exceeds the counter-strike lightning resistance level of the pole tower; step 3, substituting the average lightning strike density value and the probability that the lightning current amplitude exceeds the counter-strike lightning resistance level of the pole tower into the calculation formula of the regulation method, and solving the counter-strike tripping rate.

[0012] Preferably, the lightning monitoring data includes a lightning strike density sequence and a lightning current amplitude sequence in a historical period.

[0013] Preferably, constructing the probability distribution of lightning density based on the out-of-limit distribution characteristics of lightning activity also includes: constructing a fitting equation for the lightning density sequence in an out-of-limit distribution manner, and derivatizing the fitting equation to obtain the probability density distribution of the lightning density.

[0014] Preferably, the probability density distribution of lightning density is:

[0015]

[0016] Where N β is the number of samples in the lightning density sequence {γ} that exceed the threshold β,

[0017] Nγ is the number of samples in the lightning density sequence {γ},

[0018] k is the lightning density parameter, and its value is positively correlated with the lightning density.

[0019] α is the scale parameter.

[0020] Preferably, the average lightning density N is calculated based on the probability density distribution. ave , also includes:

[0021]

[0022] Where γ0 is the lightning density threshold of the tower when it resists lightning strikes.

[0023] γ h is the peak value of lightning density.

[0024] Preferably, solving the probability that the lightning current amplitude exceeds the counter-strike lightning resistance level of the tower also includes: using the fitted probability distribution of the lightning current amplitude as the cumulative probability distribution of the lightning current amplitude; calculating the counter-strike lightning resistance level of the transmission line tower at different voltage levels; calculating the cumulative probability distribution value of the counter-strike lightning resistance level greater than the current tower.

[0025] Preferably, the probability distribution of the fitted lightning current amplitude is:

[0026]

[0027] Where I is the lightning current amplitude.

[0028] Preferably, the lightning strike resistance level I of the transmission line tower at different voltage levels gtF (R gt )for:

[0029] The lightning strike resistance level of the transmission line tower at 500kV is:

[0030]

[0031] The lightning strike resistance level of the 220kV transmission line tower is:

[0032]

[0033] The lightning strike resistance level of the 110kV transmission line tower is:

[0034]

[0035] In the formula, R gt is the grounding resistance of the tower.

[0036] Preferably, the calculation formula of the protocol method is:

[0037] n=N ave (b+4h)ηg P

[0038] Where n is the counter-tripping rate,

[0039] b is the distance between lightning conductors,

[0040] h is the tower height,

[0041] η is the arc building rate,

[0042] g is the stroke rate,

[0043] P is the probability that the lightning current amplitude exceeds the tower's strike-back lightning resistance level.

[0044] The second aspect of the present invention relates to a counter-attack tripping rate calculation system using the method in the first aspect of the present invention, the system comprising an acquisition module, a fitting module and a solution module; wherein the acquisition module is used to acquire historical lightning monitoring data, construct a probability distribution of lightning strike density based on the over-limit distribution characteristics of lightning activity, and calculate an average lightning strike density based on the probability distribution; the fitting module is used to fit the probability distribution of lightning current amplitude with historical lightning monitoring data, thereby solving the probability that the lightning current amplitude exceeds the counter-attack lightning resistance level of the pole tower; the solution module is used to substitute the average lightning strike density and the probability that the lightning current amplitude exceeds the counter-attack lightning resistance level of the pole tower into the calculation formula of the specification method to solve the counter-attack tripping rate.

[0045] The beneficial effect of the present invention is that, compared with the prior art, the method and system for calculating the counter-attack tripping rate in the present invention improves the regulatory method by estimating the probability distribution of the lightning density and the probability that the lightning current amplitude exceeds the counter-attack lightning resistance level of the tower. The present invention collects data on the laws of lightning activity, uses a large amount of data to analyze the distribution law of the lightning current amplitude and the distribution law of the lightning density, and realizes the optimization of the counter-attack tripping rate estimation.

[0046] The beneficial effects of the present invention also include:

[0047] 1. Methods An improved calculation method for the counter-attack tripping rate is proposed. The calculation result is more in line with the actual situation than the regulation method and is highly consistent with the actual tripping rate.

[0048] 2. Since the strike-back tripping rate is an important factor in the assessment of lightning strike risk, the present invention can help assess the risk of lightning strikes and improve the assessment accuracy of the risk of different lines being struck by lightning and the risk of the same line being struck by lightning at different times. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A schematic flow chart of a method for calculating a back-attack tripping rate according to the present invention;

[0050] Figure 2 The present invention is a schematic diagram of the module structure of a back-attack trip rate calculation system. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in the present invention are only embodiments of a part of the present invention, not all embodiments. Based on the spirit of the present invention, all other embodiments not recorded in the present invention obtained by ordinary technicians in this field according to the embodiments recorded in the present invention without making creative work should belong to the protection scope of the present invention.

[0052] Figure 1 The first aspect of the present invention relates to a method for calculating a back-attack tripping rate, characterized in that the method comprises the following steps:

[0053] Step 1: Collect historical lightning monitoring data, construct a probability distribution of lightning density based on the over-limit distribution characteristics of lightning activities, and calculate the average value of lightning density based on the probability distribution;

[0054] Preferably, the lightning monitoring data includes a lightning strike density sequence and a lightning current amplitude sequence in a historical period.

[0055] In the present invention, the main influencing parameters of lightning activity are lightning current amplitude and lightning density. The present invention conducts research based on the monitoring data of lightning location system in a certain area in the south. The lightning location data analysis of the area from 2003 to 2009 is shown in Table 1.

[0056]

[0057] Table 1 Lightning location data analysis table

[0058] Specifically, according to relevant measurements at home and abroad, negative polarity lightning currents account for the vast majority, and negative polarity impulse overvoltages have low attenuation when propagating through lines, which poses a greater threat to equipment. Therefore, negative polarity is generally considered in lightning protection calculations. Therefore, when performing data statistics, negative polarity data is generally counted.

[0059] At present, the lightning location system can directly monitor the density of ground lightning, that is, the density of lightning strikes. Taking the statistics of ground lightning in a certain area in the south obtained in Table 1 as an example, the average ground lightning density in the area is a single-peak distribution, which conforms to the characteristics of extreme value distribution. Since the law of lightning conforms to the characteristics of extreme value distribution of climate events, it is essentially a certain probability distribution of lightning events. The extreme value theory is the most targeted for the analysis of this probability characteristic, and there are suitable analysis models for extreme values ​​of different time scales. After multiple fitting comparisons and analyses, this paper uses the generalized Pareto distribution function (GPD) to fit and analyze the ground lightning data.

[0060] The generalized Pareto distribution (GPD) is a probability distribution specifically used to analyze all observation data sets that exceed a certain critical value (threshold). In fact, it is necessary to use the extreme observations that exceed the threshold, which is called the threshold exceedance number. When using the GPD model to fit the ground flash density distribution, it is necessary to use each extreme sample that exceeds a certain threshold as an analysis sample to fit the GPD, obtain the lightning distribution under this special situation, and calculate the lightning trip rate. It can provide a theoretical basis for more reasonable configuration of transmission line lightning protection facilities and early warning and other protection measures.

[0061] Therefore, in the present invention, it is assumed that the sequence of lightning density γ collected over time is {γ}, where the number of samples is N r , the distribution function is F(γ). Then the method can be defined It is the conditional excess distribution function (CEDF), which is the conditional distribution function of the variable exceeding the threshold β, expressed as:

[0062]

[0063] According to the conditional probability formula, we can get

[0064]

[0065] In order to obtain the distribution function F(γ) of lightning γ, we only need to Expand the analytical calculation. When β is large enough, the conditional over-limit distribution function There is a GPD distribution function

[0066]

[0067] Substituting into the formula F(γ), we have

[0068]

[0069] Therefore, this method constructs a fitting equation for the lightning density series in a transfinite distribution manner.

[0070] Preferably, constructing the probability distribution of lightning density based on the out-of-limit distribution characteristics of lightning activity also includes: constructing a fitting equation for the lightning density sequence in an out-of-limit distribution manner, and derivatizing the fitting equation to obtain the probability density distribution of the lightning density.

[0071] The probability density distribution f(γ) is the derivative of F(γ), so the probability density distribution of lightning density is preferably:

[0072]

[0073] Where N β is the number of samples in the lightning density sequence {γ} whose values ​​exceed the threshold β,

[0074] N γ is the number of samples in the lightning density sequence {γ},

[0075] k is the lightning density parameter, and its value is positively correlated with the lightning density.

[0076] α is the scale parameter.

[0077] Next, we need to solve the model. First, we need to select a threshold. When selecting a threshold, the threshold must be high enough, but not too high that there is not enough sample data to estimate reasonable distribution parameters. Therefore, the average excess function method can be used to estimate the threshold.

[0078] The average transfinite function method is:

[0079]

[0080] Where k = min{i|γ i >β|}, the method of selecting the threshold β is to select a sufficiently large β so that when γ≥β, e(β) is an approximate linear function.

[0081] In order to further reduce the calculation errors caused by lightning randomness, lightning monitoring system and unpredictable external disturbances, the average value of lightning density is used to calculate the lightning density.

[0082] Preferably, the average value N of the lightning density (times / 100km*year) is calculated based on the probability density distribution. ave , also includes:

[0083]

[0084] Where γ0 is the lightning density threshold of the tower when it strikes back against lightning, γ h is the peak value of lightning density.

[0085] Step 2: Fit the probability distribution of lightning current amplitude with historical lightning monitoring data to solve the probability that the lightning current amplitude exceeds the tower's strike-back lightning resistance level.

[0086] IEEE recommends a formula for the cumulative probability distribution of lightning current amplitude. However, this formula is not accurate for regional lightning conditions that are not universal. Therefore, this method can fit the probability distribution of lightning current amplitude through historical lightning monitoring data.

[0087] The statistical data monitored by the lightning location system found in step 1 can be fitted to obtain an approximate curve distribution. Considering that the lightning current amplitude has different distribution patterns in different intervals, the lightning current amplitude can be fitted in sections.

[0088] This article does not elaborate on the fitting process, and the fitting results are:

[0089] The probability distribution of lightning current amplitude is:

[0090]

[0091] Where I is the lightning current amplitude.

[0092] Preferably, solving the probability that the lightning current amplitude exceeds the counter-strike lightning resistance level of the tower also includes: using the fitted probability distribution of the lightning current amplitude as the cumulative probability distribution of the lightning current amplitude; calculating the counter-strike lightning resistance level of the transmission line tower at different voltage levels; calculating the cumulative probability distribution value of the counter-strike lightning resistance level greater than the current tower.

[0093] The factors that affect the lightning resistance level of the tower include the tower grounding resistance, tower height, insulator flashover criterion, conductor arrangement, arrester installation method, etc. Among them, there are physical factors that affect the lightning resistance level of the tower itself, and there are also human factors. For example, the insulator flashover criterion is not perfect, which leads to the calculated lightning resistance level not being consistent with the actual value. However, after years of operating experience, the most important factor affecting the lightning resistance level of the tower is the tower grounding resistance. By directly studying the relationship between the grounding resistance and the tower lightning resistance level, the calculation process of the entire counter-tripping rate can be simplified, avoiding the influence of the calculation results being too dependent on the calculation model and the human calculation error.

[0094] To this end, in the present invention, the lightning strike resistance level I of the transmission line tower at different voltage levels is calculated. gtF (R gt ) was calculated. Among them, the relationship between the actual grounding resistance value and the tower's lightning strike resistance level can be obtained by fitting a large amount of data.

[0095] The lightning strike resistance level of the transmission line tower at 500kV is:

[0096]

[0097] The lightning strike resistance level of the 220kV transmission line tower is:

[0098]

[0099] The lightning strike resistance level of the 110kV transmission line tower is:

[0100]

[0101] In the formula, R gt is the grounding resistance of the tower.

[0102] Step 3: Substitute the average value of lightning density and the probability that the lightning current amplitude exceeds the tower's counter-strike lightning resistance level into the calculation formula of the regulatory method to solve for the counter-strike tripping rate.

[0103] In the present invention, the lightning activity and lightning resistance level are comprehensively considered, and the counter-attack tripping rate is calculated by using an improved procedure method. The lightning tripping rate of a transmission line is mainly composed of the counter-attack lightning tripping rate and the bypass lightning tripping rate. The present invention improves the calculation of the counter-attack tripping rate of the tower by studying the distribution law of lightning parameters and analyzing the factors affecting the counter-attack lightning resistance level of the tower.

[0104] In engineering, the regulations method and EMTP method are commonly used to calculate the lightning strike tripping rate. However, since the parameters of the EMTP method are too complicated and the amount of calculation is too large, it is difficult to apply it in actual engineering. Therefore, the regulations method is generally used for calculation. The calculation formula is as follows:

[0105] n=N·g·P·η

[0106] Where n is the strike-back tripping rate, N is the total number of lightning strikes, η is the arcing rate, g is the pole striking rate, and P is the probability that the lightning current amplitude exceeds the tower's strike-back lightning resistance level.

[0107] This paper improves the tripping rate of lightning strike based on the regulations. The improved calculation formula of the tripping rate of lightning strike is:

[0108] n=N ave (b+4h)ηgP

[0109] Where N ave is the average lightning density, b is the distance between lightning conductors, and h is the tower height. Therefore, (b+4h) is the relative lightning area of ​​the tower. P is the probability of the lightning current exceeding the lightning strike resistance level of the tower, where the calculation method of the probability density of lightning strike and the lightning strike resistance level of the tower has been given above.

[0110] By adopting the above method, the calculation accuracy is greatly improved.

[0111] First, the method verifies that the lightning amplitude probability density curve calculated by data fitting is more accurate than the standard method and the IEEE recommended curve. The method calculates the error between the fitting curve and the measured value and compares them. The error of the three methods is shown in the following table:

[0112]

[0113]

[0114] Table 2 Schematic diagram of lightning amplitude probability density curve error

[0115] Secondly, the method verifies that the lightning density curve calculated by the generalized Pareto distribution is more accurate than the standard method and the IEEE recommended curve. The error between the fitting curve and the measured value is calculated and compared. The error of the three methods is shown in the following table:

[0116]

[0117] Table 3 Error diagram of lightning density curve

[0118] It can be seen from the table that the lightning density calculated by the GPD method has a lower error, so it is feasible to improve the procedure method using the GPD method.

[0119] Figure 2 The module structure diagram of a counter-tripping rate calculation system of the present invention. The second aspect of the present invention relates to a counter-tripping rate calculation system of the method in the first aspect of the present invention, the system includes an acquisition module, a fitting module and a solution module; wherein the acquisition module is used to collect historical lightning monitoring data, construct a probability distribution of lightning density based on the over-limit distribution characteristics of lightning activity, and calculate the average value of lightning density based on the probability distribution; the fitting module is used to fit the probability distribution of lightning current amplitude with historical lightning monitoring data, so as to solve the probability that the lightning current amplitude exceeds the counter-lightning resistance level of the tower; the solution module is used to substitute the average value of lightning density and the probability that the lightning current amplitude exceeds the counter-lightning resistance level of the tower into the calculation formula of the regulation method, and solve the counter-tripping rate.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for calculating a counter-tripping rate, characterized in that: The method comprises the following steps: Step 1: Collect historical lightning monitoring data, construct a probability distribution of lightning density based on the over-limit distribution characteristics of lightning activities, and calculate the average value of lightning density based on the probability distribution; Step 2, fitting the probability distribution of lightning current amplitude with historical lightning monitoring data, so as to solve the probability that the lightning current amplitude exceeds the lightning strike resistance level of the tower; Step 3: Substitute the average value of the lightning density and the probability that the lightning current amplitude exceeds the tower's counter-strike lightning resistance level into the calculation formula of the regulatory method to solve for the counter-strike tripping rate.

2. A method for calculating the back-attack tripping rate according to claim 1, characterized in that: The lightning monitoring data includes a lightning density sequence and a lightning current amplitude sequence in a historical period.

3. A method for calculating the counter-attack trip rate according to claim 2, characterized in that: The method of constructing a probability distribution of lightning density based on the over-limit distribution characteristics of lightning activity also includes: A fitting equation is constructed for the lightning density sequence in a transfinite distribution mode, and the fitting equation is differentiated to obtain the probability density distribution of the lightning density.

4. A method for calculating the counter-attack trip rate according to claim 3, characterized in that: The probability density distribution of the lightning density is: Where N β is the number of samples in the lightning density sequence {γ} whose values ​​exceed the threshold β, N γ is the number of samples in the lightning density sequence {γ}, k is the lightning density parameter, and its value is positively correlated with the lightning density. α is the scale parameter.

5. A method for calculating the counter-attack trip rate according to claim 4, characterized in that: The average value N of the lightning density is calculated based on the probability density distribution ave , also includes: Where γ0 is the lightning density threshold of the tower when it resists lightning strikes. γ h is the peak value of lightning density.

6. A method for calculating the counter-attack trip rate according to claim 5, characterized in that: The step of solving the probability that the lightning current amplitude exceeds the tower's strike-back lightning resistance level also includes: Using the fitted probability distribution of the lightning current amplitude as the cumulative probability distribution of the lightning current amplitude; Calculate the lightning strike resistance level of transmission line towers at different voltage levels; Calculate the cumulative probability distribution value of the counter-strike lightning resistance level that is greater than the current tower.

7. A method for calculating the counter-attack trip rate according to claim 6, characterized in that: The probability distribution of the lightning current amplitude obtained by fitting is: Where I is the lightning current amplitude.

8. A method for calculating the counter-attack trip rate according to claim 7, characterized in that: The lightning strike resistance level of the transmission line tower under different voltage levels I gtF (R gt )for: The lightning strike resistance level of the transmission line tower at 500kV is: The lightning strike resistance level of the 220kV transmission line tower is: The lightning strike resistance level of the 110kV transmission line tower is: In the formula, R gt is the grounding resistance of the tower.

9. A method for calculating the counter-attack trip rate according to claim 8, characterized in that: The calculation formula of the protocol method is: n=N ave (b+4h)ngP Where n is the counter-tripping rate, b is the distance between lightning conductors, h is the tower height, η is the arc building rate, g is the stroke rate, P is the probability that the lightning current amplitude exceeds the tower's strike-back lightning resistance level.

10. A system for calculating a back-attack trip rate using the method according to any one of claims 1 to 9, characterized in that: The system includes an acquisition module, a fitting module and a solution module; wherein, The acquisition module is used to collect historical lightning monitoring data, construct a probability distribution of lightning density based on the over-limit distribution characteristics of lightning activities, and calculate an average value of lightning density based on the probability distribution; The fitting module is used to fit the probability distribution of lightning current amplitude with historical lightning monitoring data, so as to solve the probability that the lightning current amplitude exceeds the lightning strike resistance level of the tower; The solution module is used to substitute the average value of the lightning density and the probability that the lightning current amplitude exceeds the tower counter-strike lightning resistance level into the calculation formula of the regulation method to solve the counter-strike tripping rate.

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