Overhead line lightning stroke electromagnetic transient calculation method considering lightning channel coupling
By combining the PEEC and MTL methods with the Monte Carlo method and electrical geometry model, the problem of inaccurate electromagnetic radiation coupling of lightning channels and inter-conductor coupling in lightning electromagnetic transient calculations was solved, achieving more accurate lightning electromagnetic transient calculations and protection design.
Patent Information
- Application Number
- CN202511557625.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-28
- Publication Date
- 2026-02-27
AI Technical Summary
Existing methods for calculating the electromagnetic transients of lightning strikes fail to accurately characterize the electromagnetic radiation coupling effect of lightning channels and the complex coupling between conductors, resulting in insufficient accuracy in the calculation and modeling of direct lightning strikes and induced lightning.
The overhead line system is modeled using the Partial Component Equivalent Circuit (PEEC) and Multi-Conductor Transmission Line (MTL) methods. The mutual coupling coefficient matrix between the lightning channel and the conductor is constructed by combining the Monte Carlo method and the electrical geometry model. The time-domain response is solved by implicit integration, taking into account the nonlinear effects and electromagnetic coupling of the lightning channel.
It achieves accurate modeling of electromagnetic radiation coupling effects and complex coupling between conductors in lightning channels, improves the accuracy and reliability of electromagnetic transient calculations of lightning strikes, and optimizes lightning protection design.
Smart Images
Figure CN121580948A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of power system overvoltage protection and electromagnetic transient calculation, and in particular to an overhead line lightning electromagnetic transient calculation method considering lightning channel coupling. BACKGROUND
[0002] Lightning activity is the most important external natural factor threatening the safe and stable operation of overhead distribution lines. The transient overvoltage caused by lightning may cause line insulation flashover, leading to tripping accidents and affecting the reliability of the power grid. Accurate lightning electromagnetic transient calculation of overhead distribution line systems has important scientific value and engineering significance for line overvoltage and flashover risk distribution research, overhead line lightning protection evaluation and protection design, and improvement of power supply reliability.
[0003] The traditional lightning electromagnetic transient overvoltage calculation method for overhead transmission line and distribution line systems is usually based on equivalent circuit model as the main body of commercial software for calculation modeling. The transient process of lightning directly hitting the line in nature is equivalent to a simple circuit of an ideal current source in parallel with impedance parameters directly injected into the lightning attachment point of the conductor system. It cannot consider the electromagnetic radiation characteristics of the lightning channel itself during the lightning transient process, resulting in the superposition of the lightning surge injection effect and the channel electromagnetic field-line induced coupling effect during the analysis of the lightning transient process of directly hitting the line. The electromagnetic transient of the line system caused by the electromagnetic wave incident field effect of the induced lightning near the line conductor system is ignored in the past induced lightning calculation of overhead distribution line overvoltage, and the coupling between the multiple short line conductors and the long line conductors of the line system, as well as the coupling of the channel radiation electromagnetic field to the short line conductors of the line system, is also ignored. In addition, the influence of the geometric shape of the lightning channel (such as the inclination angle, height, corona effect, etc.) on the overvoltage also needs to be further modeled in detail, and the most commonly used lightning channel engineering model (assuming that the channel is a vertical structure in space and the lightning current distribution is regulated by a mathematical function) cannot consider the calculation influence of the channel geometric shape. The above-mentioned simplification of the conductor line modeling and the treatment of the lightning channel model result in obvious calculation modeling accuracy and rationality problems in the numerical calculation and evaluation of the line system electromagnetic transient caused by the lightning direct hit process and the induced coupling process, and therefore need to be improved. SUMMARY
[0004] The purpose of the present application is to provide an overhead line lightning electromagnetic transient calculation method considering lightning channel coupling, to solve the problem of inaccurate lightning electromagnetic transient calculation in the prior art, which cannot accurately represent the lightning channel electromagnetic radiation coupling effect and the complex coupling between conductors.
[0005] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme: an overhead line lightning electromagnetic transient calculation method considering lightning channel coupling, comprising the following steps:
[0006] S1, a partial element equivalent circuit (PEEC) method is used to establish a model for a short-line conductor in an overhead line system, the short-line conductor including a tower, a cross arm, a down lead and a distributed grounding device; a multi-conductor transmission line (MTL) method is used to establish a model for an overhead parallel line, the overhead parallel line including a horizontal phase line and a lightning conductor; based on the PEEC principle, electromagnetic coupling coefficients between long-line conductors and short-line conductors are calculated, and a long-line-short-line mutual coupling coefficient matrix is constructed;
[0007] S2, a three-phase power frequency power supply model, an insulator flashover model and a lightning arrester action model of a distribution system are established;
[0008] S3, a lightning channel is discretized into multiple segments, and parameters of a corona size, a length, an equivalent radius, an inclination angle and a transmission charge amount are set for each segment, so as to establish a PEEC model of the lightning channel;
[0009] S4, based on the PEEC model of the lightning channel established in step S3, electromagnetic coupling relationships between the lightning channel at different heights and each conductor of the ground conductor system in step S1 are calculated, and a channel-conductor mutual coupling coefficient matrix is constructed;
[0010] S5, an equivalent model of the overhead line system and surrounding pointed conductors is established, and a Monte Carlo method and an electrical geometric model (EGM) are combined to evaluate a probability of lightning attachment to the line, the ground or the surrounding conductors;
[0011] S6, a node analysis method is used to integrate the PEEC model, the MTL model and the mutual coupling coefficient matrix established in steps S1 to S4 into a system equivalent electrical network matrix, and an implicit integration method is used to solve the matrix in a time domain, and transient overvoltage and current responses of each conductor node of the overhead line are output.
[0012] Further, in step S1, the PEEC method is used to model the short-line conductor, including: dividing the tower and the grounding down lead conductor into multiple units, and calculating partial inductance and partial capacitance parameters of each unit; in the parameter calculation, a nonlinear mirror effect of a non-ideal ground is introduced for correction.
[0013] Further, in the calculation of the partial inductance and the partial capacitance parameters, a vector fitting technique is used to represent the frequency variation characteristics of the impedance of the thin-line conductor.
[0014] Further, in steps S3 and S4, the PEEC model of the lightning channel includes resistance, inductance and capacitance parameters of the channel segment itself; the channel-conductor mutual coupling coefficient matrix is obtained by calculating mutual inductance and mutual capacitance coefficients between the channel segment and the conductor.
[0015] Further, in step S5, the surrounding pointed conductors include building steel structures, lightning rods, communication pole towers and tall trees.
[0016] Further, in step S6, in the time domain solving process, time delay effects are introduced in the channel-conductor mutual coupling coefficient matrix and the long line-short line mutual coupling coefficient matrix to simulate the spatial time delay of electromagnetic wave propagation.
[0017] Further, in step S6, a sparse matrix acceleration algorithm is used to solve the equivalent electric network matrix of the system.
[0018] Compared with the prior art, the overhead line lightning electromagnetic transient calculation method considering lightning channel coupling provided by the application models the short line conductors (including pole towers, cross arms, downlead lines, distributed grounding devices, coaxial cables and other conductor types) in the overhead distribution line system by using the partial element equivalent circuit (PEEC) method, models the overhead parallel lines (including horizontal phase lines, lightning conductors and the like) by using the multi-conductor transmission line (MTL) method, and then derives the coupling coefficients of each long line conductor and short line conductor and establishes a mutual coupling coefficient matrix based on the PEEC principle, so that the electromagnetic coupling effect of long lines, short lines and other different scale and type conductors of the line system can be accurately modeled.
[0019] By discretizing the lightning channel, assuming the channel corona size, length, equivalent radius, inclination angle, transmission charge and the like, the calculation of the bending degree and the nonlinear effect of the discharge process of the lightning channel are realized; on this basis, the electromagnetic effect mutual coupling coefficient matrix of the lightning channel of different heights on the long line-short line of the ground overhead line conductor system is derived and solved based on the PEEC principle, so that the multi-scale calculation of the lightning channel on the long line and short line of the conductor system can be realized.
[0020] By modeling the overhead distribution line system and the surrounding building steel structures, lightning rods, communication pole towers, tall trees and other pointed conductors, combined with the Monte Carlo method and the electrical geometric model (EGM), the probabilistic evaluation problem of the lightning strike position of different conductor systems can be completed, so that the correction consideration of the influence of the lightning strike point probability distribution is realized.
[0021] The calculation modeling method provided by the application significantly optimizes the overhead line system, especially the technical tool for accurate modeling and evaluation of direct lightning and induced lightning of the overhead distribution line system. The overhead line lightning electromagnetic transient calculation model and method obtained by calculating the electromagnetic radiation coupling effect of the lightning channel have important theoretical contribution and reference value for the risk evaluation and optimization problems required for the demonstration of the electromagnetic effect basic research and lightning protection design of the lightning power overhead distribution line. BRIEF DESCRIPTION OF DRAWINGS
[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings described below only show some embodiments of the present application, and other drawings can also be obtained by those skilled in the art based on these drawings.
[0023] Figure 1 The overhead line lightning electromagnetic transient calculation flowchart of lightning channel electromagnetic radiation coupling effect provided by the embodiment of the present application;
[0024] Figure 2 The lightning channel and electromagnetic coupling effect schematic diagram when lightning strikes different positions provided by the embodiment of the present application;
[0025] Figure 3 The conductor top surge current calculation comparative waveform graph of the proposed model and the simplified consideration of the direct lightning current source model provided by the embodiment of the present application;
[0026] Figure 4 The conductor top overvoltage calculation comparative waveform graph of the proposed model and the simplified consideration of the direct lightning current source model provided by the embodiment of the present application. DETAILED DESCRIPTION
[0027] In order to make those skilled in the art better understand the technical solutions of the present application, the present application will be further described in detail below with reference to the drawings.
[0028] As shown in the accompanying Figure 1 to the accompanying Figure 4 drawings:
[0029] Embodiment one:
[0030] The present application provides an overhead line lightning electromagnetic transient calculation method considering lightning channel coupling, including the following steps:
[0031] S1, constructing a hybrid numerical model of the ground conductor system: for the short line conductors in the overhead line system, including the towers, cross arms, down conductors and distributed grounding devices, the partial element equivalent circuit (PEEC) method is used for modeling; for the overhead parallel lines, including the horizontal phase lines and the lightning conductors, the multi-conductor transmission line (MTL) method is used for modeling; based on the PEEC principle, the electromagnetic coupling coefficients between each long line conductor and the short line conductor are derived, and a long line-short line mutual coupling coefficient matrix is established.
[0032] S2, establishing a line system steady-state power supply and a nonlinear device model: a three-phase power frequency power supply model of a distribution system, an insulator flashover model, a lightning arrester protection action model and a transformer equivalent frequency variable circuit model are established, which are used for simulating the normal operation condition of the line and the nonlinear breakdown process when lightning strikes.
[0033] S3, PEEC model of lightning channel: discretize the lightning channel, set the corona size, length, equivalent radius, tilt angle, and transmission charge parameters of the channel to construct the PEEC model of the lightning channel to consider the bending degree and nonlinear effects of the discharge process; the model includes the resistance, inductance, and capacitance parameters of the channel itself.
[0034] S4, calculation of electromagnetic coupling effect of lightning channel and line system: based on the PEEC principle, deduce the electromagnetic coupling effect of lightning channels at different heights on each type of conductor of the ground overhead line conductor system, calculate the mutual inductance and mutual capacitance coefficients between the channel segments and the conductors, and establish the channel-conductor mutual coupling coefficient matrix.
[0035] S5, evaluate the lightning strike position probability distribution: establish the equivalent model of the overhead distribution line system and the surrounding building steel structure, lightning rod, communication tower, and tall trees, etc. sharp conductors, combine the Monte Carlo method and the electrical geometric model (EGM), and evaluate the probability of lightning attaching to the line, ground, or surrounding conductors.
[0036] S6, solve the time-domain response of the system: use the node analysis method to construct the equivalent electric network matrix of the integrated PEEC-MTL hybrid numerical model, and use the implicit integration method for time-domain solving; in the solution, introduce time delay effect in the channel-conductor mutual coupling coefficient matrix and the long-line-short-line mutual coupling coefficient matrix to simulate the space propagation time delay of electromagnetic waves; finally obtain the transient overvoltage and current response of each conductor node of the overhead line.
[0037] Embodiment two:
[0038] This embodiment is basically the same as the previous embodiment, the difference is that the PEEC modeling in steps S1 and S3 is refined.
[0039] In S1, when modeling the tower, frame, grounding down conductor and other short line conductors using the PEEC method, specifically: divide the above-mentioned size and wavelength comparable conductors into multiple units, and deduce and calculate the partial inductance and partial capacitance parameters of each unit under the PEEC model. In the parameter calculation, the influence of the nonlinear mirror effect of the non-ideal ground on the calculation parameters is considered. At the same time, the vector fitting technology is used to represent the frequency variation characteristics of the impedance of the thin line conductor.
[0040] In S3 and S4, the establishment of the PEEC model of the lightning channel and the coupling calculation, specifically include: regarding the lightning channel as a radiation source with specific geometric shape and electrical characteristics, and describing it through its segment length, tilt angle, height, cloud transfer charge, corona effect, etc. The channel model considers its own resistance, inductance, and capacitance parameters. For electromagnetic coupling, the channel segment and each conductor of the ground conductor system are calculated to construct the channel-conductor mutual coupling coefficient matrix.
[0041] Example Three:
[0042] This example is basically the same as the previous example, the difference is that the lightning strike position probability evaluation in S5 is refined.
[0043] The Monte Carlo method not only considers the influence of the protruding part of the overhead distribution line tower beyond the line height, the system conductor such as overhead lightning conductor, etc. on the lightning strike flashover, but also considers the shielding and attracting effect of the conductor tips such as building steel structure, lightning rod, communication tower and tall trees around the overhead distribution line on the lightning strike. By shielding analysis of all these pointed conductors through the electrical geometric model (EGM), the evaluation and calculation of the lightning strike position are corrected to obtain a more realistic lightning strike point probability distribution. Figure 2 In (A), the lightning strike position (0) of the line system refers to the lightning directly hitting the line, Figure 2 In (B), the line system is all induced lightning, and the lightning strike positions (1), (2), (3) and (4) refer to the lightning striking the ground, trees, buildings and lightning rods or communication towers near the overhead line system, respectively.
[0044] Example Four:
[0045] This example is basically the same as the previous example, the difference is that the time domain solving and result output in S6 are refined.
[0046] In the time domain solving process, the improved node analysis method is used to construct the equivalent electric network matrix of the PEEC-MTL hybrid numerical model. Since the lightning channel and most of the conductors of the overhead distribution line system are in a spatial vertical relationship, each sub-parameter matrix involved in the model is mainly a sparse matrix, and the coefficient matrix acceleration algorithm is used to complete the model solving acceleration in the calculation.
[0047] After the calculation is completed, the time domain overvoltage and current waveform diagram of the full-line conductor node, the transient overvoltage peak value distribution cloud diagram, and the lightning flashover state parameter matrix of each tower are output through the post-processing module. Figure 3 and Figure 4 The proposed model and the simplified direct lightning current source model are compared in the calculation of the conductor top surge current and overvoltage.
[0048] Comparative Example:
[0049] The specific implementation of the prior art is as follows:
[0050] Line modeling: The phase conductors and lightning protection conductors of overhead lines are modeled using a multi-conductor transmission line (MTL) model to simulate the propagation process of lightning surges along the line. Towers are typically represented as lumped-parameter circuits, either concentrated or composed of a few π-type circuit units, whose parameters (resistance, inductance) are estimated using empirical formulas based on structural dimensions.
[0051] Lightning source modeling: The direct lightning strike process is simplified as an ideal current source. This current source is typically described using standard waveforms (such as a 1.2 / 50μs double exponential wave, Heidler function, etc.). In direct lightning strike simulation, this ideal current source is directly injected into the struck conductor (such as the top of a tower or a lightning rod).
[0052] Coupling effects are considered: This method ignores the characteristic of the lightning channel itself as a distributed electromagnetic radiation source, that is, it does not consider the induced coupling effect of the time-varying electromagnetic field generated by the lightning channel current on nearby conductors that have not been directly struck by lightning. For the coupling between conductors inside the line, the electromagnetic coupling between phase lines and between phase lines and lightning protection wires is only considered through the constants, uniform mutual impedance and mutual admittance matrix in MTL theory.
[0053] Lightning strike location: The lightning strike attachment point (i.e. the current source injection point) is pre-specified, usually based on engineering experience assuming the most severe situation (such as lightning striking the top of the tower or the center of the span), without conducting a probabilistic assessment based on the electric field distortion of the surrounding environment.
[0054] Solution calculation: The above model is solved in the time domain using the Dommel algorithm (an implicit integration method based on the trapezoidal rule) in an electromagnetic transient calculation program (such as EMTP, ATP-EMTP) to finally obtain the overvoltage and current at the key points of the line.
[0055] Comparative Analysis Table:
[0056]
[0057]
[0058] Conclusion: The existing technology represented by this comparative example oversimplifies the lightning channel, the fine structure of the line, and the physical process of lightning strikes. This results in an inability to accurately characterize the electromagnetic radiation coupling effect of the lightning channel, the complex coupling between short-circuit conductors, and the true distribution of the lightning strike point when analyzing the electromagnetic transients of lightning strikes, thus leading to insufficient accuracy in computational modeling. The present invention, through the technical solution provided in Embodiment 1, effectively overcomes these shortcomings, providing a more accurate and realistic computational model and method.
[0059] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.
Claims
1. A method for calculating the electromagnetic transients of overhead lines under lightning strikes considering lightning channel coupling, characterized in that, Includes the following steps: S1. A partial equivalent circuit (PEEC) model is established for the short conductors in the overhead line system, wherein the short conductors include towers, crossarms, down conductors and distributed grounding devices; a multi-conductor transmission line (MTL) model is established for the overhead parallel lines, wherein the overhead parallel lines include horizontal phase lines and lightning protection lines. Based on the PEEC principle, the electromagnetic coupling coefficient between the long conductor and the short conductor is calculated, and the long-short conductor mutual coupling coefficient matrix is constructed. S2. Establish a three-phase power frequency power supply model, an insulator flashover model, and a surge arrester operation model for the power distribution system; S3. Discretize the lightning channel into multiple segments, and set parameters such as corona size, length, equivalent radius, tilt angle and transported charge for each segment to establish a PEEC model of the lightning channel. S4. Based on the PEEC model of the lightning channel established in step S3, calculate the electromagnetic coupling relationship between the lightning channel and each conductor of the ground conductor system in step S1 at different heights, and construct the channel-conductor mutual coupling coefficient matrix. S5. Establish an equivalent model of the overhead line system and its surrounding pointed conductors, and combine the Monte Carlo method with the electrical geometric model (EGM) to assess the probability of lightning strikes attaching to the line, the ground, or surrounding conductors. S6. The PEEC model, MTL model and mutual coupling coefficient matrix established in steps S1 to S4 are integrated into the equivalent electrical network matrix of the system using the nodal analysis method. The matrix is then solved in the time domain using the implicit integration method to output the transient overvoltage and current response of each conductor node of the overhead line.
2. The method for calculating the electromagnetic transients of overhead lines under lightning strikes considering lightning channel coupling as described in claim 1, characterized in that, In step S1, the modeling of the short conductor using the PEEC method includes: dividing the tower and grounding down conductor into multiple units and calculating the partial inductance and partial capacitance parameters of each unit; in the parameter calculation, the nonlinear mirror effect of the non-ideal ground is introduced for correction.
3. The method for calculating the electromagnetic transients of overhead lines under lightning strikes considering lightning channel coupling as described in claim 2, characterized in that, When calculating the parameters of some inductance and some capacitance, vector fitting technology is used to characterize the frequency-varying characteristics of the impedance of the thin wire conductor.
4. The method for calculating the electromagnetic transients of overhead lines under lightning strikes considering lightning channel coupling as described in claim 1, characterized in that, In steps S3 and S4, the lightning channel PEEC model includes the resistance, inductance, and capacitance parameters of the channel segment itself; the channel-conductor mutual coupling coefficient matrix is obtained by calculating the mutual inductance and mutual capacitance coefficients between the channel segment and the conductor.
5. The method for calculating the electromagnetic transients of overhead lines under lightning strikes considering lightning channel coupling as described in claim 1, characterized in that, In step S5, the surrounding pointed conductors include building steel structures, lightning rods, communication towers, and tall trees.
6. The method for calculating the electromagnetic transients of overhead lines under lightning strikes considering lightning channel coupling as described in claim 1, characterized in that, In step S6, during the time-domain solution process, a time delay effect is introduced into the channel-conductor mutual coupling coefficient matrix and the long-line-short-line mutual coupling coefficient matrix to simulate the spatial time delay of electromagnetic wave propagation.
7. The method for calculating the electromagnetic transients of overhead lines under lightning strikes considering lightning channel coupling as described in claim 1, characterized in that, In step S6, a sparse matrix acceleration algorithm is used to solve for the equivalent electrical network matrix of the system.