Method for predicting power frequency electromagnetic field of ac transmission line and evaluating sound environment influence

Abstract

The present application relates to the technical field of electromagnetic environment impact prediction, and specifically discloses a power frequency electromagnetic field prediction and sound environment impact evaluation method for alternating current transmission lines.The present application builds a space geometry model, synchronously calculates the distribution of power frequency electric field intensity, power frequency magnetic induction intensity and audible noise in each discrete section along the line in three-dimensional space, calculates the electric field intensity, magnetic induction intensity and noise sound pressure level of each horizontal coordinate point at each vertical height, and identifies the compliance height interval that simultaneously satisfies the electric field intensity limit value, magnetic induction intensity limit value and noise limit value, interpolates and smooths the discrete compliance height interval set, generates a three-dimensional surface of the continuous compliance height interval of the whole space, and uses it as the environmental impact evaluation conclusion of the alternating current transmission line project.The present application solves the technical problem of large deviation in electromagnetic field and noise prediction in the vicinity of the strain tower and large span section caused by single geometry parameter modeling for the whole line in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic environment impact prediction and evaluation technology, and particularly relates to methods for predicting power frequency electromagnetic fields and evaluating the acoustic environment impact of AC transmission lines. Background Technology

[0002] During operation, AC transmission lines generate power frequency electric and magnetic fields in the space surrounding the conductors, while corona discharge on the conductor surface produces audible noise. Predicting and evaluating power frequency electric and magnetic fields and audible noise during the planning and design phase of transmission lines, in accordance with standards such as the "Technical Guidelines for Environmental Impact Assessment of Power Transmission and Transformation" (HJ24-2020), is a crucial technical step in ensuring the environmental friendliness of the project.

[0003] Currently, the standard method for predicting power frequency electric fields is the equivalent charge method, which uses the image method to handle ground boundary conditions; the standard method for predicting power frequency magnetic fields is Ampere's law, where the magnetic field calculation for parallel lines requires consideration of the phase angle between currents and synthesis according to phase vectors; the standard method for predicting audible noise uses the BPA empirical formula, estimating the sound power level through the maximum potential gradient on the conductor surface. These methods are clearly defined in industry standards and are widely used in practical engineering.

[0004] However, existing evaluation methods have the following technical shortcomings: First, the geometric modeling of the entire transmission line uses uniform parameters, that is, the entire line uses only a single representative model of straight towers, and uses a single representative sag value for electromagnetic field and noise calculation. This fails to effectively consider the impact of different locations along the line, different tower types (there are differences in the spatial coordinates of conductors between straight towers and tension towers, and there are spatial positional deviations of conductors at tension towers due to inclined insulator strings and jumpers), and sag differences caused by temperature changes in different crossing sections on the distribution of electromagnetic field and audible noise. This results in significant deviations between the evaluation conclusions of electric field, magnetic field and audible noise in the area near tension towers, long crossing sections and high-temperature operating conditions and the actual distribution.

[0005] Second, traditional environmental impact assessments are conducted only at a fixed height (e.g., 1.5m above ground), answering only the question of "whether the standard is met at this fixed height," but failing to address practical engineering decisions such as "whether the standard is met at different heights if the building is in the same horizontal position but different heights" and "how many meters should the building height be limited to in order to simultaneously meet the electric, magnetic, and acoustic standards." While existing technologies can manually estimate height limits for a few discrete points, they lack a systematic, automated method for generating continuous evaluation boundaries across the entire space that can simultaneously constrain the electric field, magnetic field, and noise standards.

[0006] Third, when evaluating the compliance of the three physical quantities of electric field, magnetic field and noise, existing technologies are usually isolated from each other, outputting compliance / exceedance conclusions separately, failing to conduct joint constraints under a unified evaluation framework, and the evaluation results remain at the level of textual description or "marking of areas exceeding the standard", which cannot directly provide a highly quantitative basis for control over land space planning and architectural design. Summary of the Invention

[0007] The purpose of this invention is to provide a method for predicting the power frequency electromagnetic field of AC transmission lines and assessing the acoustic environment impact, thereby addressing the problems mentioned in the background art.

[0008] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions: A method for predicting power frequency electromagnetic fields and assessing the acoustic environment impact of AC transmission lines, the method specifically includes the following steps: Step S101: Obtain the engineering parameters of the AC transmission line and construct a differentiated discretized geometric model; Step S102: Based on the differentiated discretized geometric model, the distribution of power frequency electric field intensity, power frequency magnetic induction intensity and audible noise in each discrete segment along the line in three-dimensional space is calculated simultaneously to generate segmented distribution data of electric field intensity, segmented distribution data of magnetic field intensity and segmented distribution data of noise. Step S103: Obtain land use type data along the transmission line, and extract the corresponding electric field strength limit, magnetic induction intensity limit and noise limit from the electromagnetic environment control standard and the acoustic environment quality standard according to the land use type. Step S104: Based on the segmented distribution data of electric field strength, magnetic field strength, and noise, starting from the ground height, scan upwards layer by layer with a preset step size, calculate the electric field strength, magnetic induction intensity, and noise sound pressure level at each horizontal coordinate point at each vertical height, and identify the qualified height intervals that simultaneously meet the electric field strength limit, magnetic induction intensity limit, and noise limit, forming a discrete set of qualified height intervals; Step S105 involves interpolating and smoothing the discrete set of acceptable height intervals to generate a three-dimensional surface that covers the entire evaluation area and simultaneously satisfies the limits for electric field strength, magnetic induction intensity, and noise. This surface serves as the environmental impact assessment conclusion for the AC transmission line project.

[0009] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention obtains tower type category data for each tower along the line and establishes a tower type category sequence according to the natural physical order. It also obtains sag variation data for each span under different temperature gradients and establishes a temperature-span-sag correlation data table. Based on the tower type category sequence, the entire line is discretized into multiple continuous discrete segments, and the phase conductor coordinates and conductor height parameters above ground are independently configured for straight tower segments and tension tower segments. This solves the technical problem of large deviations in electromagnetic field and noise prediction in the vicinity of tension towers and large span segments caused by single geometric parameter modeling of the entire line in the prior art. It realizes the technical upgrade from unified approximate modeling of the entire line to segmented differentiated high-precision geometric modeling.

[0010] 2. This invention synchronously uses the geometric parameters of each discrete segment in the differentiated discretized geometric model as inputs to the equivalent charge method, the Ampere's law complex vector superposition method, and the BPA audible noise prediction formula. For parallel line segments, it obtains the phase difference relationship of each loop and calculates the magnetic induction intensity according to the complex vector superposition. At the same time, it coordinates the maximum potential gradient of the conductor surface required by the BPA formula with the conductor height to ground parameters and voltage level parameters of each discrete segment in the differentiated discretized geometric model. This solves the problem of the isolation of electric field, magnetic field, and noise evaluation and inconsistent input parameters in the prior art, and realizes the synchronous prediction of electric field intensity, magnetic induction intensity, and audible noise under a unified refined geometric model and ensures data consistency.

[0011] 3. This invention scans upwards layer by layer with a preset step size, starting from the ground height. At each scanning height, it queries the electric field strength, magnetic induction intensity, and noise sound pressure level values ​​of the current horizontal coordinate point from the segmented distribution data of electric field strength, magnetic field strength, and noise. These values ​​are then combined with the electric field strength limit, magnetic induction intensity limit, and noise limit dynamically obtained according to the land use type to perform a ternary joint judgment. The height at which all three values ​​are simultaneously met for the first time from the ground is identified as the compliance starting height. The continuous height range from the compliance starting height to the maximum search height is defined as the compliance height interval. This invention overcomes the limitation of existing technologies that only perform binary compliance evaluation on a fixed height plane, and realizes a dimensional expansion from fixed height evaluation to continuous evaluation across the entire height space.

[0012] 4. This invention generates a continuous starting height surface and a continuous ending height surface covering the entire evaluation area by interpolating and smoothing the discrete set of acceptable height intervals. The two surfaces are then closed in the vertical direction to form a full-space acceptable envelope. The upper boundary surface of the envelope is extracted as a three-dimensional surface of the continuous acceptable height interval in the entire space and output in a three-dimensional solid model file format or a common data format of geographic information system. This solves the problem that the evaluation conclusions of the existing technology are limited to contour maps, data tables or discrete point limit tables and cannot be directly used for spatial planning. It realizes the upgrade of the evaluation conclusions from data analysis to a decision-making tool that can be directly used as the building height control red line. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention.

[0014] Figure 1 A flowchart of the method provided by an embodiment of the present invention is shown.

[0015] Figure 2 This is a graph showing the variation of the power frequency electric field intensity at 1.5m above the ground from the horizontal distance of the line center on a 500kV single-circuit line in the existing technology.

[0016] Figure 3 This is a graph showing the variation of the power frequency magnetic induction intensity at 1.5m above the ground and the horizontal distance from the center of the line in the existing technology for a 500kV single-circuit line. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] In view of the above, the main objective of this invention is to propose a method for predicting the power frequency electromagnetic field and assessing the acoustic environment impact of AC transmission lines, so as to solve the above-mentioned technical problems.

[0019] This invention proposes a method for predicting the power frequency electromagnetic field and assessing the acoustic environment impact of AC transmission lines, such as... Figure 1 As shown, the method specifically includes the following steps: Step S101: Obtain the engineering parameters of the AC transmission line and construct a differentiated discretized geometric model.

[0020] In a preferred embodiment of the present invention, obtaining the engineering parameters of the AC transmission line and constructing a differentiated discretized geometric model specifically includes the following steps: Step S1011: Obtain tower type category data for each tower along the AC transmission line, and establish a tower type category sequence according to the natural physical order of the towers to obtain the tower type category sequence; wherein, the tower type categories include straight-line towers and tension towers; Step S1012: Obtain the span length data between each tower, and establish a span length sequence according to the natural physical order of the spans to obtain the span length sequence. Step S1013: Obtain the sag change data of each span under the preset temperature gradient, and establish a temperature-span-sag correlation data table. Step S1014: According to the tower type category sequence, the entire line is discretized into multiple continuous discrete segments along the longitudinal direction, and a corresponding tower type category identifier is assigned to each discrete segment to obtain a set of discrete segments with tower type category identifiers. Step S1015: For discrete segments in the discrete segment set whose tower type is straight tower, construct a geometric sub-model of the straight tower based on the standard phase conductor coordinates of the straight tower. Step S1016: For discrete segments in the discrete segment set whose tower type is tension tower, a geometric sub-model of the tension tower is constructed based on the standard phase conductor coordinates of the tension tower and taking into account the spatial position deviation of the conductor caused by the inclined insulator string; wherein, the spatial position deviation of the conductor includes: the horizontal lateral offset and the vertical offset of the conductor caused by the inclined insulator string; the offset is a preset fixed value or a calculated value based on the length and angle of the insulator string; It should be noted that the inclined insulator string refers to the insulator string on the tension tower that has a spatial position deviation due to its inclined arrangement. This causes the jumper wire to have sag in the vertical direction and offset in the horizontal direction, thus affecting the spatial coordinates of the overall positional deviation of the conductor.

[0021] Step S1017: Based on the span length data corresponding to each discrete segment in the span length sequence, match the sag value of the target discrete segment at the specified ambient temperature from the temperature-span-sag correlation data table, and convert the sag value into the conductor height parameter of the target discrete segment to the ground. Step S1018: Configure the conductor height parameter to the straight tower geometric sub-model and the tension tower geometric sub-model to obtain the straight tower geometric sub-model and the tension tower geometric sub-model configured with the conductor height parameter to the ground, respectively. Step S1019: The geometric sub-model of the straight tower with configured conductor height parameters and the geometric sub-model of the tension tower with configured conductor height parameters are spliced ​​together in the order of the tower type sequence and the span length sequence to construct a differentiated discretized geometric model.

[0022] In this embodiment of the invention, a 500kV AC transmission line project is used as an example. The project includes multiple tower types along its entire length, primarily common straight-line towers and tension towers. For instance, a certain series of straight-line towers are used in general line sections, while a certain series of tension towers are installed at substation inlet / outlet points and line bends. First, the tower type category data for each tower along the line is obtained, and a tower type category sequence is established according to the natural physical order of the towers, such as: tension tower, straight-line tower, straight-line tower, tension tower, straight-line tower, etc. Then, the span length data between each tower is obtained, and a span length sequence is established. Next, the sag design data for each span section at corresponding temperatures (e.g., -10℃, 0℃, 10℃, 20℃, 30℃, 40℃) is obtained, and a temperature-span-sag correlation data table is established. Based on the tower type category sequence, the entire line is discretized longitudinally into multiple continuous discrete segments, each segment identified by the tower type categories of its starting and ending towers.

[0023] For discrete sections of a straight-line tower, a geometric sub-model of the straight-line tower is constructed based on the standard phase conductor coordinates of the straight-line tower. For example, for a double-circuit straight-line tower section, the phase conductor coordinates of the western circuit can be set as (-X1, Y1), (-X2, Y2), and (-X3, Y3), and the phase conductor coordinates of the eastern circuit can be set as (X1, Y1), (X2, Y2), and (X3, Y3). The specific coordinate values ​​are determined according to the design dimensions of the actual tower type. For discrete sections of a tension tower, a geometric sub-model of the tension tower is constructed based on the standard phase conductor coordinates of the tension tower, and the spatial position deviation of the conductor caused by the inclined insulator string is additionally taken into account. This deviation is manifested as a horizontal offset of the conductor suspension point to the outside of the line (e.g., offset of 0.3 to 0.5 meters) and a vertical descent due to the jumper sag (e.g., descent of 0.2 to 0.4 meters). Based on the span length data corresponding to each discrete segment, the sag value corresponding to the specified ambient temperature (e.g., a maximum summer temperature of 40℃) is matched from the temperature-span-sag correlation data table. This sag value is then converted into the conductor height above ground parameter for that discrete segment, where the conductor height above ground is equal to the tower suspension point height minus the sag value. Next, this conductor height above ground parameter is configured into the corresponding straight-line tower geometric sub-model or tension tower geometric sub-model, resulting in a configured sub-model. Finally, all configured sub-models are sequentially spliced ​​together according to the tower type sequence and the span length sequence to construct a complete differentiated discrete geometric model. Compared with the existing technology that uses a single representative sag (such as only taking the sag at 20℃) and a single tower type parameter for the entire line, the differentiated discretized geometric model of the present invention can accurately reflect the changes in the spatial position of the conductor near the tension tower caused by the inclined insulator string, as well as the actual operating conditions of the long span crossing section with a significant increase in sag under high temperature conditions. This makes the subsequent calculation input parameters of electric field, magnetic field and noise closer to the actual engineering situation, thereby significantly improving the accuracy of prediction and evaluation.

[0024] Step S102: Based on the differentiated discretized geometric model, the distribution of power frequency electric field intensity, power frequency magnetic induction intensity and audible noise in each discrete segment along the line in three-dimensional space is calculated simultaneously to generate segmented distribution data of electric field intensity, segmented distribution data of magnetic field intensity and segmented distribution data of noise.

[0025] In a preferred embodiment of the present invention, based on the differentiated discretized geometric model, the distribution of power frequency electric field intensity, power frequency magnetic induction intensity, and audible noise in each discrete segment along the line in three-dimensional space is calculated simultaneously to generate segmented distribution data of electric field intensity, segmented distribution data of magnetic field intensity, and segmented distribution data of noise. Specifically, this includes the following sub-steps: Step S1021: Take the geometric parameters of each discrete segment in the differentiated discretized geometric model as input, use the equivalent charge method to calculate the power frequency electric field intensity at each point in the three-dimensional space within each discrete segment, generate the electric field intensity distribution data corresponding to each discrete segment, and obtain the first electric field intensity segmented distribution dataset. Step S1022: Using the geometric parameters of each discrete segment in the differentiated discretized geometric model as input, the power frequency magnetic induction intensity at each point in the three-dimensional space within each discrete segment is calculated using Ampere's law, generating magnetic field intensity distribution data corresponding to each discrete segment, and obtaining the first magnetic field intensity segmented distribution dataset; wherein, for discrete segments with multiple parallel lines, the phase relationship of each loop is obtained, and the magnetic field intensity generated by each loop is calculated by superimposing complex vectors according to the phase relationship; Step S1023: The conductor height parameter to ground and voltage level parameter of each discrete segment in the differentiated discretized geometric model are used as inputs. The audible noise sound pressure level of each point in the three-dimensional space within each discrete segment is calculated using the BPA audible noise prediction formula. The noise distribution data corresponding to each discrete segment is generated to obtain the first noise segment distribution dataset. Step S1024: The first electric field strength segmented distribution dataset, the first magnetic field strength segmented distribution dataset, and the first noise segmented distribution dataset are longitudinally spliced ​​and smoothly transitioned according to the arrangement order in the differentiated discretized geometric model of each discrete segment, to generate electric field strength segmented distribution data, magnetic field strength segmented distribution data, and noise segmented distribution data covering the entire conductor.

[0026] In this embodiment of the invention, based on the differentiated discretized geometric model constructed above, the three-dimensional spatial distribution of electric field, magnetic field, and noise is calculated for each discrete segment. For the electric field calculation, the equivalent charge method is used, and the conductor voltage is set to 1.05 times the rated voltage, i.e., 525kV. For discrete segments with parallel lines, such as the parallel line segment (current carrying capacity 4056 amperes) of the Zhiliao-Dianbai 500kV line disconnection and connection to the Gaozhou switch station line project, the center-line distance between the two lines is 50 meters. The phase relationship between the two lines is obtained (the phase difference between adjacent circuits is fixed at 180 degrees), and the magnetic field strength generated by each circuit is calculated by complex vector superposition according to the phase difference.

[0027] For noise calculation, the BPA formula is used. The maximum potential gradient on the conductor surface in the formula is calculated segment by segment based on the differentiated geometric parameters (conductor height to ground, phase distance, split spacing, and sub-conductor diameter) and voltage level parameters of each discrete segment. After the calculation of each discrete segment is completed, the segmented distribution data of electric field strength, magnetic field strength, and noise are longitudinally spliced ​​according to the arrangement order of the discrete segments in the model. Linear interpolation is used at the connection between segments to smooth the transition, generating continuous distribution data covering the entire conductor. Compared with the existing technology that models the electric field, magnetic field, and noise independently with inconsistent input parameters, this invention achieves synchronous calculation and data linkage of the three physical fields under the same refined geometric model, ensuring the inherent consistency of the evaluation conclusions and avoiding contradictory conclusions caused by model mismatch.

[0028] In a preferred embodiment of the present invention, the geometric parameters of each discrete segment in the differentiated discretized geometric model are used as input, and the power frequency electric field intensity at each point in the three-dimensional space within each discrete segment is calculated using the equivalent charge method to generate electric field intensity distribution data corresponding to each discrete segment, thereby obtaining a first electric field intensity segmented distribution dataset. The specific steps include the following: Step S10211: Based on the tower type category identifier, phase conductor coordinate data, conductor height parameters above ground and temperature-span-sag correlation data table of each discrete segment in the differentiated discretized geometric model, each discrete segment is decomposed into a preset number of sag micro-elements according to the span length in the span length sequence, and each sag micro-element is assigned an actual height value above ground that matches the temperature conditions of the target discrete segment, so as to obtain the sag micro-element height sequence above ground for each discrete segment. Step S10212: Combine the split conductors of each phase contained in each discrete segment into a single equivalent conductor according to the equivalent radius formula, and calculate the equivalent radius of the split conductor for each sag element according to the ground height sequence of the sag element, so as to obtain the equivalent radius sequence of the sag element corresponding to each discrete segment. It should be noted that the formula for the equivalent radius is as follows: the equivalent radius is equal to the product of the sub-conductor radius and the split circle radius (the number of splits minus one power) raised to the power of the split number; when the number of splits is 1, the equivalent radius is equal to the sub-conductor radius.

[0029] Step S10213: Arrange all sag micro-elements in each discrete segment according to the direction of the conductor trajectory to form a chain of sag micro-elements corresponding to each discrete segment; take the ground as the zero potential surface, establish a corresponding mirror micro-element between the ground and the bottom of each sag micro-element in the chain of sag micro-elements, and input the position coordinates and equivalent radius parameters of all sag micro-elements and their corresponding mirror micro-elements into a preset potential coefficient matrix according to the equivalent radius parameters of each sag micro-element in the equivalent radius sequence of sag micro-elements, solve for the equivalent charge of each sag micro-element, and obtain the charge distribution sequence of sag micro-elements corresponding to each discrete segment; Step S10214: For any spatial coordinate point within the three-dimensional spatial range covered by each discrete segment, calculate the distance between the spatial coordinate point and each sag element in the sag element chain based on the equivalent charge of each sag element in the sag element charge distribution sequence. Substitute the distance between the spatial coordinate point and each sag element in the sag element chain, as well as the equivalent charge of each sag element, into the electric field intensity superposition formula to calculate the electric field intensity component generated by each sag element at the spatial coordinate point. Then, perform vector summation on the electric field intensity components generated by all sag elements to obtain the composite electric field intensity at the spatial coordinate point. Based on the composite electric field intensity, generate the segmented distribution data of the electric field intensity corresponding to each discrete segment. Step S10215: The electric field intensity segment distribution data corresponding to each discrete segment is labeled according to the arrangement order of each discrete segment in the differentiated discretized geometric model, forming an electric field intensity segment distribution data set with discrete segment index identifier, which serves as the first electric field intensity segment distribution dataset.

[0030] In a preferred embodiment of the present invention, the distance between the spatial coordinate point and each sag element in the sag element chain, as well as the equivalent charge of each sag element, are substituted into the electric field strength superposition formula. The corresponding relationship is as follows: ; ; in, Represents the coordinates of a point in space The horizontal component of the electric field intensity at that location, Represents the ordinate of a point in space The perpendicular component of the electric field intensity at that location Represents pi (π). Represents the vacuum permittivity. This represents the total number of sag elements in the sag element chain. Indicates the index number of the sag element. Indicates the first The equivalent charge of a sag element Indicates the first The horizontal coordinates of the sag element Indicates the first The vertical coordinates of a sag element Represents the spatial coordinates from the point to the th The straight-line distance of a sag element Represents the spatial coordinates from the point to the th The straight-line distance between the mirror image elements corresponding to each sag element.

[0031] In this embodiment of the invention, taking a discrete segment of a straight tower as an example, with a span of 378 meters, the discrete segment is decomposed into 76 sag micro-elements, each with a length of 5 meters. Each sag micro-element is assigned an actual ground height value calculated based on the catenary equation. The sag is largest at the center of the span (approximately 9.1 meters) and gradually decreases towards both ends. In the calculation of the equivalent radius of the split conductor, the radius of the split circle is 250 mm, the radius of the sub-conductor is 18.115 mm, the number of splits is 4, and the equivalent radius is approximately 183.4 mm. Then, a chain of sag micro-elements is formed, and mirror micro-elements are established with the ground as the zero potential surface. A potential coefficient matrix is ​​constructed, and the equivalent charge of each micro-element is solved. For a spatial point (8 meters from the edge conductor, 5 meters high), the distance from it to each micro-element is calculated, and the distance is substituted into Coulomb's law to obtain the complex vector of the electric field intensity contributed by each micro-element. The summation of all micro-element contributions as complex vectors and the modulus are taken to obtain the composite electric field intensity. The above steps are repeated to generate the three-dimensional electric field distribution of the entire discrete segment. Compared with the simplified calculation method in the prior art that uses a uniform sag value across the entire line and does not divide into infinitesimal elements, the present invention uses the fine division of sag infinitesimal element chains and mirror infinitesimal elements to make the solution of equivalent charge based on the actual geometric position of each infinitesimal element rather than the average position of the entire segment, thereby significantly improving the accuracy of electric field prediction, especially in the long span section and the area near the tension tower.

[0032] In a preferred embodiment of the present invention, the geometric parameters of each discrete segment in the differentiated discretized geometric model are used as input, and the power frequency magnetic induction intensity at each point in the three-dimensional space within each discrete segment is calculated using Ampere's law to generate magnetic field intensity distribution data corresponding to each discrete segment, thereby obtaining a first magnetic field intensity segmented distribution dataset. The specific steps include the following: Step S10221: Based on the tower type category identifier, phase conductor coordinate data, conductor height parameter to ground, and the initial values ​​of current amplitude and phase angle of each loop in the differentiated discretized geometric model, generate a sequence of associated pairs of conductor spatial coordinates and current parameters corresponding to each discrete segment. Step S10222: For any spatial coordinate point in each discrete segment where the magnetic induction intensity needs to be calculated, according to the parameters in the correlation pair sequence of the conductor spatial coordinates and current parameters, calculate the straight-line distance between the spatial coordinate point and the conductor corresponding to each correlation pair in the correlation pair sequence in turn, so as to obtain the distance sequence from the spatial point corresponding to each discrete segment to each phase conductor. Step S10223: According to Ampere's law, substitute the current amplitude of each phase conductor in the distance sequence from the spatial point to each phase conductor into the Ampere's law formula, and calculate the magnetic field strength vector value generated by each phase conductor at the spatial point, so as to obtain the magnetic field strength vector sequence of each phase conductor corresponding to each discrete segment. Step S10224: For each vector value in the magnetic field intensity vector sequence of each phase conductor corresponding to each discrete segment, perform complex domain decomposition on the magnetic field intensity vector according to the phase angle of each phase conductor in the discrete segment to obtain the complex component sequence of the magnetic field intensity corresponding to each discrete segment. Step S10225: For each discrete segment, sum the complex components in the sequence of complex magnetic field strength components to obtain the total complex magnetic field strength vector for each discrete segment. Multiply the total complex magnetic field strength vector by a preset vacuum permeability to obtain the magnetic flux density vector value for each discrete segment. Generate a three-dimensional spatial magnetic flux density distribution matrix for each discrete segment based on the magnetic flux density vector value. Obtain the magnetic field strength distribution data for each discrete segment based on the three-dimensional spatial magnetic flux density distribution matrix for each discrete segment. Step S10226: Determine whether the current discrete segment belongs to the parallel walking line segment. If the discrete segment belongs to the parallel walking line segment, obtain the phase difference relationship of each loop in the parallel walking line segment, and traverse each loop contained in the parallel walking line segment in sequence. For each loop, execute steps S10222 to S10225 respectively, and perform complex vector superposition of the magnetic induction intensity vector values ​​generated by each loop according to the phase difference relationship to obtain the magnetic induction intensity distribution correction matrix of the parallel walking line segment. Use the correction matrix to update the magnetic field intensity segmented distribution data to obtain the updated magnetic field intensity distribution data. Step S10227: The updated magnetic field strength distribution data corresponding to each discrete segment is labeled according to the arrangement order of each discrete segment in the differentiated discretized geometric model to form a set of magnetic field strength segmented distribution data with discrete segment index identifier, which serves as the first magnetic field strength segmented distribution dataset.

[0033] In a preferred embodiment of the present invention, according to Ampere's law, the current amplitude of each phase conductor in the distance sequence from the spatial point to each phase conductor is substituted into the formula of Ampere's law to calculate the vector value of the magnetic field strength generated by each phase conductor at the spatial point. The corresponding relationship is as follows: ; in, This represents the vector value of the magnetic field strength generated by a single conductor at a spatial coordinate point. Represents the permeability of free space. Indicates magnetic field strength. This indicates the current amplitude in each phase conductor. This represents the straight-line distance from a spatial coordinate point to the traverse line.

[0034] In this embodiment of the invention, taking a discrete section of a single-circuit line as an example, the coordinates of a certain spatial point are (8 meters from the outer edge conductor, 9 meters above the ground). First, the straight-line distances from this point to the three-phase conductors A, B, and C are calculated (e.g., 15.8 meters, 16.2 meters, and 14.5 meters). According to Ampere's law, the magnitude of the magnetic field intensity vector generated by each phase at this point is calculated, with the direction perpendicular to the line connecting the point and the conductor. Then, based on the phase angles of the currents in each phase (e.g., phase A 0°, phase B -120°, phase C 120°), the three vectors are decomposed into complex domains to obtain the real and imaginary parts. Summing the real and imaginary parts yields the total magnetic field intensity complex vector, which, after taking the modulus, is multiplied by the permeability of free space to obtain the resultant magnetic induction intensity at this spatial point (approximately 32.1 μT).

[0035] For parallel line segments, such as two parallel lines with an adjacent loop phase difference of 180°, the magnetic flux density vectors of the two loops are calculated separately. The vector of the second loop is then rotated 180° in the complex domain and added to the vector of the first loop to obtain the corrected composite magnetic flux density. Compared with the existing method of simply adding the magnetic field values ​​of each loop algebraically, the complex vector superposition method of this invention can accurately reflect the magnetic field enhancement or cancellation effect caused by the phase difference, avoiding significant errors caused by algebraic addition in close-range sections of parallel lines.

[0036] In a preferred embodiment of the present invention, the conductor height parameter to ground and voltage level parameter of each discrete segment in the differentiated discretized geometric model are used as inputs. The audible noise sound pressure level at each point in the three-dimensional space within each discrete segment is calculated using the BPA audible noise prediction formula, generating noise segment distribution data corresponding to each discrete segment, and obtaining the first noise segment distribution dataset. The specific steps include the following: Step S10231: Based on the tower type category identifier, conductor type data, splitting method data, sub-conductor diameter and splitting spacing data of each discrete segment in the differentiated discretized geometric model, and the conductor height to ground parameter of each discrete segment at a specified ambient temperature in the temperature-span-sag correlation data table, generate the set of split conductor geometric parameters corresponding to each discrete segment. Step S10232: Based on the geometric parameters of the split conductor in the set of geometric parameters of the split conductor corresponding to each discrete segment, the maximum potential gradient on the surface of each split sub-conductor is calculated by the mirror method to obtain the maximum potential gradient sequence on the surface of the split sub-conductor corresponding to each discrete segment. Step S10233: Substitute each potential gradient value in the maximum potential gradient sequence on the surface of the split sub-conductor into the BPA audible noise prediction formula to calculate the A-weighted sound power level of the audible noise per unit length of each split sub-conductor, and obtain the sound power level sequence of the split sub-conductor corresponding to each discrete segment. In a preferred embodiment of the present invention, each potential gradient value in the maximum potential gradient sequence on the surface of the split sub-conductor is substituted into the BPA audible noise prediction formula to calculate the A-weighted sound power level of the audible noise per unit length of each split sub-conductor. The corresponding relationship in this process is as follows: ; in, Indicates the first A-weighted sound power level of audible noise per unit length of phase conductor. Represents the logarithmic function. Indicates the first Maximum potential gradient value on the surface of the phase conductor. Indicates the number of wire splits. Indicates the diameter of the sub-conductor.

[0037] Step S10234: For any spatial coordinate point within the three-dimensional spatial range covered by each discrete segment, calculate the spatial straight-line distance from the spatial coordinate point to each split sub-conductor, and combine the A-weighted sound power level of each split sub-conductor with the sound wave energy superposition formula to calculate the total noise sound pressure level contributed by all split sub-conductors at the spatial coordinate point, so as to obtain the three-dimensional spatial noise sound pressure level distribution matrix corresponding to each discrete segment, and use it as the noise distribution data corresponding to each discrete segment; Step S10235: The noise distribution data corresponding to each discrete segment is labeled according to the arrangement order of each discrete segment in the differentiated discretization geometric model to form a noise segment distribution data set with discrete segment index identifier, which serves as the first noise segment distribution dataset.

[0038] In this embodiment of the invention, taking a discrete section of a straight-line tower as an example, the conductor type is 4×JL / LB20A-720 / 50, and the cross-sectional area of ​​a single conductor is 720 mm². 2Each phase conductor consists of four sub-conductors with a split spacing of 500mm. Based on the conductor height parameter (approximately 25.5 meters) and voltage level (525kV) of the discrete segment in the differentiated discretized geometric model, the maximum potential gradient gmax on the surface of each split sub-conductor is calculated using the mirror method and substituted into the BPA formula. For a spatial point (8 meters from the edge conductor and 9 meters above the ground), the distance from that point to each split sub-conductor is calculated, and the total noise sound pressure level is obtained using the sound wave energy superposition formula. Unlike the existing technology where the potential gradient input of the BPA formula uses a uniform and constant conductor height value (such as only taking the design representative value), the potential gradient input value of this invention comes from the actual ground height parameter of each discrete segment in the differentiated discretized geometric model (which already includes tower type differences and temperature sag differences). This allows the audible noise prediction to dynamically reflect the influence of geometric structure changes and temperature changes along the line, significantly improving the accuracy of the acoustic environment assessment.

[0039] Step S103: Obtain land use type data along the transmission line, and extract the corresponding electric field strength limit, magnetic induction intensity limit and noise limit from the electromagnetic environment control standard and the acoustic environment quality standard according to the land use type.

[0040] In a preferred embodiment of the present invention, land use type data along the transmission line is obtained, and corresponding electric field strength limits, magnetic induction intensity limits, and noise limits are extracted from electromagnetic environment control standards and acoustic environment quality standards according to the land use types. Specifically, the process includes the following steps: Step S1031: Obtain land use type classification data corresponding to each horizontal coordinate point along the transmission line, and establish a land use type spatial distribution matrix according to the land use categories in the land use type classification data to obtain the first land use type spatial distribution matrix; wherein, the land use types include at least residential areas, cultivated land, orchards, pastureland, livestock and poultry breeding land, aquaculture water surfaces and roads; Step S1032: Based on the land use type of each horizontal coordinate point in the first land use type spatial distribution matrix, find the public exposure control limit of electric field intensity corresponding to the land use type under the frequency of 50Hz from the electromagnetic environment control limit to generate the electric field intensity limit spatial distribution matrix corresponding to each horizontal coordinate point. Based on the electric field intensity limit spatial distribution matrix, obtain the first electric field intensity limit spatial distribution matrix. Step S1033: Based on the land use type of each horizontal coordinate point in the first land use type spatial distribution matrix, find the public exposure control limit of magnetic induction intensity corresponding to the target land use type under the frequency of 50Hz from the electromagnetic environment control limit to generate a magnetic induction intensity limit spatial distribution matrix corresponding to each horizontal coordinate point. Based on the magnetic induction intensity limit spatial distribution matrix, obtain the first magnetic induction intensity limit spatial distribution matrix. Step S1034: Based on the land use type of each horizontal coordinate point in the first land use type spatial distribution matrix, find the daytime or nighttime noise limit of the acoustic environment functional zone to which the target land use type belongs from the corresponding acoustic environment quality standard, so as to generate a noise limit spatial distribution matrix corresponding to each horizontal coordinate point, and obtain the first noise limit spatial distribution matrix based on the noise limit spatial distribution matrix. Step S1035: The spatial distribution matrix of the first electric field strength limit, the spatial distribution matrix of the first magnetic induction intensity limit, and the spatial distribution matrix of the first noise limit are associated and summarized according to the horizontal coordinate points, so that each horizontal coordinate point contains a triplet of electric field strength limit, magnetic induction intensity limit, and noise limit, forming a triplet spatial distribution dataset. Based on the triplet spatial distribution dataset, the corresponding electric field strength limit, magnetic induction intensity limit, and noise limit are extracted.

[0041] In this embodiment of the invention, taking a certain horizontal location along a transmission line as an example, this point is located 8 meters outside the edge conductor, and the land use type is residential area. According to the "Electromagnetic Environment Control Limits" (GB8702-2014), the public exposure control limit for electric field intensity in residential areas at a frequency of 50Hz is 4kV / m, and the public exposure control limit for magnetic induction intensity is 100μT. According to the "Environmental Quality Standard for Noise" (GB3096-2008), this area belongs to Class 2 acoustic environment functional zone, and the daytime or nighttime noise limit is 55dB(A). These limits are used as the triplet limit values ​​for this point. Another horizontal location is located 30 meters outside the edge conductor, and the land use type is cultivated land, with an electric field limit of 10kV / m, a magnetic field limit of 100μT, and a noise limit of 55dB(A).

[0042] It should be noted that (A) in 55dB(A) refers to A-weighting. dB(A) is the decibel value after A-weighting. The noise limit is the sound pressure level measured by A-weighting, and the unit is dB(A).

[0043] Following the above method, a spatial distribution matrix of limit triplets is established for all horizontal coordinate points. Compared with the existing technology that uses a single fixed limit (such as uniformly taking 4kV / m) for the entire evaluation area, the dynamic limit spatial distribution matrix of this invention enables the limit comparison to accurately reflect the differentiated requirements of different land use types, avoiding misjudgments caused by improper limit selection.

[0044] Step S104: Based on the segmented distribution data of electric field strength, magnetic field strength, and noise, starting from the ground height, scan upwards layer by layer with a preset step size, calculate the electric field strength, magnetic induction intensity, and noise sound pressure level at each horizontal coordinate point at each vertical height, and identify the qualified height intervals that simultaneously meet the electric field strength limit, magnetic induction intensity limit, and noise limit, forming a discrete set of qualified height intervals.

[0045] In a preferred embodiment of the present invention, based on segmented distribution data of electric field strength, segmented distribution data of magnetic field strength, and segmented distribution data of noise, starting from ground height, the system scans upwards layer by layer with a preset step size to calculate the electric field strength, magnetic induction intensity, and noise sound pressure level at each horizontal coordinate point at each vertical height. It then identifies the acceptable height intervals that simultaneously meet the limits of electric field strength, magnetic induction intensity, and noise, forming a discrete set of acceptable height intervals. Specifically, the process includes the following steps: Step S1041: Using the projection line of the center line of the transmission line on the ground as the longitudinal reference line, the horizontal direction perpendicular to the longitudinal reference line as the transverse reference line, and the height above the ground as the vertical direction, establish a three-dimensional spatial evaluation coordinate system; in the horizontal plane of the three-dimensional spatial evaluation coordinate system, generate a horizontal grid point array with preset transverse and longitudinal intervals to obtain the first horizontal grid point array. Step S1042: Select the first unscanned horizontal grid point from the first horizontal grid point array as the current horizontal coordinate point; Step S1043: Load the segmented distribution data of electric field intensity, segmented distribution data of magnetic field intensity, segmented distribution data of noise, and triplet spatial distribution dataset into the three-dimensional spatial evaluation coordinate system according to the correspondence of spatial coordinate points. Substitute the horizontal coordinate value of the current horizontal coordinate point into the segmented distribution data of electric field intensity, segmented distribution data of magnetic field intensity, and segmented distribution data of noise. At the same time, set the current scanning height to the ground height. At the current scanning height, query the electric field intensity value of the current horizontal coordinate point at the current scanning height from the segmented distribution data of electric field intensity to obtain the electric field intensity value at the current height. Step S1044: Query the magnetic induction intensity value of the current horizontal coordinate point at the current scanning height from the segmented distribution data of the magnetic field intensity to obtain the magnetic induction intensity value at the current height; Step S1045: Query the noise sound pressure level value of the current horizontal coordinate point at the current scanning height from the noise segment distribution data to obtain the noise sound pressure level value at the current height; Step S1046: From the triplet spatial distribution dataset, query the electric field strength limit, magnetic induction intensity limit, and noise limit corresponding to the current horizontal coordinate point, and obtain the electric field strength limit, magnetic induction intensity limit, and noise limit of the current horizontal coordinate point, respectively. Step S1047: Determine whether the current height electric field strength value is less than the current horizontal coordinate point electric field strength limit, the current height magnetic induction intensity value is less than the current horizontal coordinate point magnetic induction intensity limit, and the current height noise sound pressure level value is less than the current horizontal coordinate point noise limit. If the current height electric field strength value, current height magnetic induction intensity value, and current height noise sound pressure level value all meet the conditions, then proceed to step S1048; if any one of the current height electric field strength value, current height magnetic induction intensity value, and current height noise sound pressure level value does not meet the conditions, then proceed to step S1049. Step S1048: Record the current scanning height as the target starting height of the current horizontal coordinate point to obtain the target starting height value corresponding to the current horizontal coordinate point, and then execute step S10410. Step S1049: Increase the current scanning height by a preset vertical scanning step to obtain the updated scanning height, and use the updated scanning height as the new current scanning height, and then re-execute step S1045. Step S10410: Using the target starting height value as the new starting height, continue to increase the scanning height layer by layer according to the preset vertical scanning step size. Repeat steps S1045 to S1047 at each new scanning height until the preset maximum search height is reached. Record the continuous height range from the target starting height to the maximum search height that meets the limit conditions of the current height electric field strength value, the current height magnetic induction intensity value, and the current height noise sound pressure level value. Use the continuous height range as the target height interval corresponding to the current horizontal coordinate point. Step S10411: Determine whether there are any unscanned horizontal grid points in the first horizontal grid point array. If so, return to step S1042 to select the next unscanned horizontal grid point as the new current horizontal coordinate point, and repeat steps S1042 to S10410. If all horizontal grid points have been scanned, organize the target height intervals corresponding to all horizontal coordinate points according to the spatial arrangement order of each horizontal coordinate point to form a discrete set of target height intervals.

[0046] In this embodiment of the invention, taking a horizontal grid point (8 meters away from the edge conductor, longitudinal mileage K10+000 of the line) as an example, the land use type of this point is a residential area, the electric field limit is 4kV / m, the magnetic field limit is 100μT, and the noise limit is 55dB(A). The scan begins at ground height Z=0: At Z=0, the electric field strength is 5.49kV / m > 4kV / m, which does not meet the requirements; increasing the step size by 0.5 meters to Z=0.5 meters, the electric field strength is 5.38kV / m, still exceeding the limit; continuing the scan to Z=4 meters, the electric field strength is 4.41kV / m, still exceeding the limit; at Z=8 meters, the electric field strength is 4.08kV / m, still exceeding the limit; at Z=9 meters, the electric field strength is 3.95kV / m ≤ 4kV / m, while the magnetic induction intensity is 32.1μT ≤ 100μT, and the noise sound pressure level is 40dB(A) ≤ the noise limit of 55dB(A). For the first time, all three items meet the standards simultaneously, and the starting height for meeting the standards is recorded as 9 meters. The scan continues upwards to 100 meters, and the electric field strength, magnetic induction intensity, and noise all consistently meet the limit requirements. Therefore, the acceptable height range for this point is [9 meters, 100 meters]. By sequentially scanning all horizontal grid points, a discrete set of acceptable height intervals is obtained. Compared with the existing technology that only judges compliance at 1.5 meters above the ground, this invention, through vertical scanning layer by layer from the ground and ternary joint judgment, achieves for the first time a dimensional expansion from "fixed height evaluation" to "continuous evaluation of the entire height space". It can automatically output the minimum lifting height required for the building at each horizontal position, providing a precise quantitative basis for building height restrictions.

[0047] Step S105 involves interpolating and smoothing the discrete set of acceptable height intervals to generate a three-dimensional surface that covers the entire evaluation area and simultaneously satisfies the limits for electric field strength, magnetic induction intensity, and noise. This surface serves as the environmental impact assessment conclusion for the AC transmission line project.

[0048] In a preferred embodiment of the present invention, the discrete set of acceptable height intervals is interpolated and smoothed to generate a three-dimensional surface covering the entire evaluation area and simultaneously satisfying the limits of electric field strength, magnetic induction intensity, and noise. This surface serves as the environmental impact assessment conclusion for the AC transmission line project. The specific steps include: Step S1051: Based on the discrete set of acceptable height intervals, extract the acceptable starting height value corresponding to each horizontal coordinate point to form a discrete set of acceptable starting height points; Step S1052: Perform triangulation or inverse distance weighted interpolation on the discrete points of the standard starting height in the set of standard starting height discrete points to generate a continuous standard starting height surface covering the entire horizontal evaluation area. Step S1053: Extract the standard termination height value corresponding to each horizontal coordinate point in the standard starting height discrete point set to form the standard termination height discrete point set. Step S1054: Perform triangulation or inverse distance weighted interpolation on the discrete points of the standard termination height in the set of standard termination height discrete points to generate a continuous standard termination height surface covering the entire horizontal evaluation area. Step S1055: Close the continuous target start height surface and the continuous target end height surface in the vertical direction to form a closed three-dimensional space. Define the three-dimensional space as the full-space target envelope, which serves as the first full-space target envelope. The height of any point in the three-dimensional space is between the target start height and the target end height corresponding to the horizontal coordinate of that point. Step S1056: Extract the upper boundary surface of the first full-space compliance envelope, and use the upper boundary surface as the three-dimensional surface of the continuous compliance height interval in the full space to obtain the three-dimensional surface of the first full-space continuous compliance height interval; wherein, the upper boundary surface of the first full-space compliance envelope is: a surface composed of the compliance termination height of each horizontal coordinate point; Step S1057: Output the three-dimensional surface of the first full-space continuous compliance height interval in the form of a three-dimensional solid model file or a geographic information system general data format as the environmental impact assessment conclusion of the AC transmission line project.

[0049] In this embodiment of the invention, based on a discrete set of acceptable height intervals, the acceptable starting height value of each horizontal coordinate point is extracted to form a discrete point set of acceptable starting heights. Inverse distance weighted interpolation (where the weight is inversely proportional to the square of the distance) is used to interpolate this discrete point set, generating a continuous acceptable starting height surface covering the entire horizontal evaluation area. Similarly, the acceptable ending height value (i.e., the maximum search height of 100 meters) of each horizontal coordinate point is extracted to form a discrete point set of acceptable ending heights, and inverse distance weighted interpolation is also used to generate a continuous acceptable ending height surface. The continuous acceptable starting height surface and the continuous acceptable ending height surface are closed in the vertical direction to form a closed three-dimensional space. The height of any point in this space lies between the acceptable starting height and the acceptable ending height corresponding to that point's horizontal coordinate. This three-dimensional space is defined as the full-space acceptable envelope. The upper boundary surface of this envelope (i.e., the surface formed by the acceptable ending heights of each horizontal coordinate point) is extracted as the three-dimensional surface of the continuous acceptable height interval in the full space. Finally, the 3D surface is output in a 3D solid model file format (such as STL format) or a common data format for geographic information systems (such as GeoTIFF format). Taking the horizontal coordinates (8 meters outside the boundary traverse, longitudinal mileage K10+000) as an example, the output surface data indicates that the building height limit at this point is 9 meters. Compared with the existing technology of outputting contour maps, data tables, or discrete point limit tables, the continuous 3D surface output by this invention can be directly imported into the land spatial planning system as a technical reference for building height control, realizing a qualitative leap from "analysis data" to "decision-making tool".

[0050] It should be noted that the existing methods for calculating ground voltage and equivalent radius of split conductors recommended in the "Technical Guidelines for Environmental Impact Assessment of Power Transmission and Transformation" (HJ24-2020) both assume a constant conductor height above ground and uniform tower parameters for the entire transmission line in electric field prediction, without considering the impact of variations in tower type and temperature sag along the line on the electric field distribution. This invention, while retaining the basic framework of the equivalent charge method, solves the aforementioned problems by introducing a differentiated discretized geometric model, configuring voltage and charge distributions that conform to the actual geometric parameters of each discrete segment. Figure 2 and Figure 3 The graphs show the changes in power frequency electric field intensity and magnetic induction intensity at a height of 1.5m above the ground from the center of the line in the prior art.

[0051] Therefore, existing technologies can only express the field distribution at a fixed height (1.5m) on the ground, outputting contour maps or two-dimensional curves. They cannot address the issue of building height control that simultaneously satisfies the limits for electric field, magnetic field, and noise at different vertical heights. This invention, by scanning vertically layer by layer from the ground upwards and identifying the compliant height intervals that simultaneously meet all three limits, ultimately generates a three-dimensional surface representing a continuous compliant height interval across the entire space. This upgrades the evaluation conclusions from planar to spatial, and from data to a decision-making tool.

[0052] It should be understood that although the steps in the flowcharts of the various embodiments of the present invention are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the various embodiments may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least a portion of the sub-steps or stages of other steps.

[0053] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0054] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for predicting power frequency electromagnetic fields and assessing the acoustic environment impact of AC transmission lines, characterized in that, The method specifically includes the following steps: Obtain the engineering parameters of AC transmission lines and construct differentiated discretized geometric models; Based on the aforementioned differentiated discretized geometric model, the distribution of power frequency electric field intensity, power frequency magnetic induction intensity, and audible noise in each discrete segment along the line in three-dimensional space is calculated simultaneously, generating segmented distribution data of electric field intensity, segmented distribution data of magnetic field intensity, and segmented distribution data of noise. Obtain land use type data along the transmission line, and extract corresponding electric field strength limits, magnetic induction intensity limits, and noise limits from electromagnetic environment control standards and acoustic environment quality standards according to the land use type; Based on the segmented distribution data of electric field strength, magnetic field strength, and noise, starting from the ground height, the system scans upwards layer by layer with a preset step size to calculate the electric field strength, magnetic induction intensity, and noise sound pressure level at each horizontal coordinate point at each vertical height. It also identifies the qualified height intervals that simultaneously meet the limits of electric field strength, magnetic induction intensity, and noise, forming a discrete set of qualified height intervals. Interpolation and smoothing are performed on the discrete set of acceptable height intervals to generate a three-dimensional surface that covers the entire evaluation area and simultaneously meets the limits of electric field strength, magnetic induction intensity, and noise. This surface is then used as the environmental impact assessment conclusion for the AC transmission line project.

2. The method for predicting power frequency electromagnetic fields and assessing the acoustic environment impact of AC transmission lines according to claim 1, characterized in that, Obtaining the engineering parameters of AC transmission lines and constructing differentiated discretized geometric models includes the following steps: Data on the tower type categories of each tower along the AC transmission line are obtained, and a tower type category sequence is established according to the natural physical order of the towers to obtain the tower type category sequence; wherein, the tower type categories include straight-line towers and tension towers; Obtain the span length data between each tower, and establish a span length sequence according to the natural physical order of the spans to obtain the span length sequence; Acquire sag change data for each span under a preset temperature gradient, and establish a temperature-span-sag correlation data table. Based on the tower type category sequence, the entire line is discretized into multiple continuous discrete segments along the longitudinal direction, and a corresponding tower type category identifier is assigned to each discrete segment to obtain a set of discrete segments with tower type category identifiers. For discrete segments in the set of discrete segments that are classified as straight towers, a geometric sub-model of the straight tower is constructed based on the standard phase conductor coordinates of the straight tower. For discrete segments in the discrete segment set that are classified as tension towers, a geometric sub-model of the tension tower is constructed based on the standard phase conductor coordinates of the tension tower and taking into account the spatial position deviation of the conductor caused by the inclined insulator string. Based on the span length data corresponding to each discrete segment in the span length sequence, the sag value of the target discrete segment at the specified ambient temperature is matched from the temperature-span-sag correlation data table, and the sag value is converted into the conductor height parameter of the target discrete segment to the ground. The conductor height parameter above ground is configured into the straight tower geometric sub-model and the tension tower geometric sub-model, respectively, to obtain the straight tower geometric sub-model and the tension tower geometric sub-model with the conductor height parameter above ground configured. The geometric sub-models of straight towers and tension towers with configured conductor height parameters are spliced ​​together according to the tower type sequence and the span length sequence to construct a differentiated discretized geometric model.

3. The method for predicting power frequency electromagnetic fields and assessing the acoustic environment impact of AC transmission lines according to claim 2, characterized in that, Based on the aforementioned differentiated discretized geometric model, the distribution of power frequency electric field intensity, power frequency magnetic induction intensity, and audible noise in each discrete segment along the line in three-dimensional space is calculated simultaneously, generating segmented distribution data of electric field intensity, magnetic field intensity, and noise. This process includes the following sub-steps: Using the geometric parameters of each discrete segment in the differentiated discretized geometric model as input, the power frequency electric field intensity at each point in the three-dimensional space within each discrete segment is calculated using the equivalent charge method, generating electric field intensity distribution data corresponding to each discrete segment, and obtaining the first electric field intensity segmented distribution dataset. Using the geometric parameters of each discrete segment in the differentiated discretized geometric model as input, the power frequency magnetic induction intensity at each point in the three-dimensional space within each discrete segment is calculated using Ampere's law, generating magnetic field intensity distribution data corresponding to each discrete segment, and obtaining the first magnetic field intensity segmented distribution dataset. Using the conductor height to ground parameter and voltage level parameter of each discrete segment in the differential discretized geometric model as input, the audible noise sound pressure level at each point in the three-dimensional space within each discrete segment is calculated to generate noise distribution data corresponding to each discrete segment, thus obtaining the first noise segment distribution dataset. The first electric field strength segmented distribution dataset, the first magnetic field strength segmented distribution dataset, and the first noise segmented distribution dataset are longitudinally spliced ​​and smoothly transitioned according to the arrangement order in the differentiated discretized geometric model of each discrete segment, to generate electric field strength segmented distribution data, magnetic field strength segmented distribution data, and noise segmented distribution data covering the entire conductor.

4. The method for predicting power frequency electromagnetic fields and assessing the acoustic environment impact of AC transmission lines according to claim 3, characterized in that, Using the geometric parameters of each discrete segment in the differentiated discretized geometric model as input, the power frequency electric field intensity at each point in the three-dimensional space within each discrete segment is calculated using the equivalent charge method, generating electric field intensity distribution data corresponding to each discrete segment, and obtaining the first electric field intensity segmented distribution dataset. The specific steps include the following: Based on the tower type identification, phase conductor coordinate data, conductor height parameters above ground, and temperature-span-sag correlation data table of each discrete segment in the differential discretized geometric model, each discrete segment is decomposed into a preset number of sag micro-elements according to the span length in the span length sequence, and each sag micro-element is assigned an actual height value above ground that matches the temperature conditions of the target discrete segment, thus obtaining the sag micro-element height sequence above ground for each discrete segment. Each discrete segment contains a split conductor of each phase, which is then combined into a single equivalent conductor according to the equivalent radius formula. Based on the ground height sequence of the sag element, the equivalent radius of the split conductor is calculated for each sag element, thus obtaining the equivalent radius sequence of the sag element corresponding to each discrete segment. Arrange all the sag elements in each discrete segment according to the direction of the conductor trajectory to form a chain of sag elements corresponding to each discrete segment. Using the ground as the zero potential surface, a corresponding mirror image element is established between the ground and the bottom of each sag element in the sag element chain. Based on the equivalent radius parameters of each sag element in the sag element equivalent radius sequence, the position coordinates and equivalent radius parameters of all sag elements and their corresponding mirror images are input into a preset potential coefficient matrix to solve for the equivalent charge of each sag element, thereby obtaining the sag element charge distribution sequence corresponding to each discrete segment. For any spatial coordinate point within the three-dimensional spatial range covered by each discrete segment, the distance between the spatial coordinate point and each sag element in the sag element chain is calculated based on the equivalent charge of each sag element in the sag element charge distribution sequence. The distance between the spatial coordinate point and each sag element in the sag element chain, as well as the equivalent charge of each sag element, are substituted into the electric field intensity superposition formula to calculate the electric field intensity component generated by each sag element at the spatial coordinate point. The electric field intensity components generated by all sag elements are then vector-summed to obtain the composite electric field intensity at the spatial coordinate point. Based on the composite electric field intensity, the segmented distribution data of the electric field intensity corresponding to each discrete segment is generated. The electric field intensity segment distribution data corresponding to each discrete segment is labeled according to the arrangement order of each discrete segment in the differentiated discretized geometric model, forming a set of electric field intensity segment distribution data with discrete segment index identifiers, which serves as the first electric field intensity segment distribution dataset.

5. The method for predicting power frequency electromagnetic fields and assessing the acoustic environment impact of AC transmission lines according to claim 4, characterized in that, Substituting the spatial coordinates, the distance between each sag element in the chain of sag elements, and the equivalent charge of each sag element into the formula for superposition of electric field strength, the corresponding relationship is as follows: ； ； in, Represents the coordinates of a point in space The horizontal component of the electric field intensity at that location, Represents the ordinate of a point in space The perpendicular component of the electric field intensity at that location Represents pi (π). Represents the vacuum permittivity. This represents the total number of sag elements in the sag element chain. Indicates the index number of the sag element. Indicates the first The equivalent charge of a sag element Indicates the first The horizontal coordinates of the sag element Indicates the first The vertical coordinates of a sag element Represents the spatial coordinates from the point to the th The straight-line distance of a sag element Represents the spatial coordinates from the point to the th The straight-line distance between the mirror image elements corresponding to each sag element.

6. The method for predicting power frequency electromagnetic fields and assessing the acoustic environment impact of AC transmission lines according to claim 3, characterized in that, Using the geometric parameters of each discrete segment in the differentiated discretized geometric model as input, the power frequency magnetic induction intensity at each point in the three-dimensional space within each discrete segment is calculated using Ampere's law, generating magnetic field intensity distribution data corresponding to each discrete segment, and obtaining the first magnetic field intensity segmented distribution dataset, specifically including the following steps: S10221. Based on the tower type category identifier, phase conductor coordinate data, conductor height parameter to ground, and the initial values ​​of current amplitude and phase angle of each loop in each discrete segment of the differentiated discretized geometric model, generate a sequence of associated pairs of conductor spatial coordinates and current parameters corresponding to each discrete segment. S10222. For any spatial coordinate point in each discrete segment where the magnetic induction intensity needs to be calculated, according to the parameters in the correlation pair sequence of the conductor spatial coordinates and current parameters, calculate the straight-line distance between the spatial coordinate point and the conductor corresponding to each correlation pair in the correlation pair sequence in turn, so as to obtain the distance sequence from the spatial point corresponding to each discrete segment to each phase conductor. S10223. According to Ampere's law, substitute the current amplitude of each phase conductor in the distance sequence from the space point to each phase conductor into the Ampere's law formula, and calculate the magnetic field strength vector value generated by each phase conductor at the space point to obtain the magnetic field strength vector sequence of each phase conductor corresponding to each discrete segment. S10224. For each vector value in the magnetic field intensity vector sequence of each phase conductor corresponding to each discrete segment, the magnetic field intensity vector is decomposed into complex domain according to the phase angle of each phase conductor in the discrete segment to obtain the magnetic field intensity complex component sequence corresponding to each discrete segment. S10225. For each discrete segment, sum the complex components in the sequence of complex magnetic field strength components to obtain the total complex magnetic field strength vector for each discrete segment. Multiply the total complex magnetic field strength vector by a preset vacuum permeability to obtain the magnetic induction intensity vector value for each discrete segment. Generate a three-dimensional spatial magnetic induction intensity distribution matrix for each discrete segment based on the magnetic induction intensity vector value. Obtain the magnetic field strength distribution data for each discrete segment based on the three-dimensional spatial magnetic induction intensity distribution matrix for each discrete segment. S10226. Determine whether the current discrete segment belongs to the parallel walking line segment. If the discrete segment belongs to the parallel walking line segment, obtain the phase difference relationship of each loop in the parallel walking line segment, and sequentially traverse each loop contained in the parallel walking line segment. For each loop, execute steps S10222 to S10225 respectively, and perform complex vector superposition of the magnetic induction intensity vector values ​​generated by each loop according to the phase difference relationship to obtain the magnetic induction intensity distribution correction matrix of the parallel walking line segment. Use the correction matrix to update the magnetic field intensity segmented distribution data to obtain the updated magnetic field intensity distribution data. S10227. The updated magnetic field strength distribution data corresponding to each discrete segment is labeled according to the arrangement order of each discrete segment in the differentiated discretized geometric model, forming a set of magnetic field strength segmented distribution data with discrete segment index identifiers, which serves as the first magnetic field strength segmented distribution dataset.

7. The method for predicting power frequency electromagnetic fields and assessing the acoustic environment impact of AC transmission lines according to claim 6, characterized in that, According to Ampere's law, by substituting the current amplitude of each phase conductor in the distance sequence from the spatial point to each phase conductor into the Ampere's law formula, the vector value of the magnetic field strength generated by each phase conductor at the spatial point can be calculated. The corresponding relationship is as follows: ； in, This represents the vector value of the magnetic field strength generated by a single conductor at a spatial coordinate point. Represents the permeability of free space. Indicates magnetic field strength. This indicates the current amplitude in each phase conductor. This represents the straight-line distance from a spatial coordinate point to the traverse line.

8. The method for predicting power frequency electromagnetic fields and assessing the acoustic environment impact of AC transmission lines according to claim 7, characterized in that, Obtain land use type data along the transmission line, and extract corresponding electric field strength limits, magnetic induction intensity limits, and noise limits from electromagnetic environment control standards and acoustic environment quality standards based on the land use types. Specifically, this includes the following steps: Obtain land use type classification data corresponding to each horizontal coordinate point along the transmission line, and establish a land use type spatial distribution matrix according to the land use category in the land use type classification data to obtain the first land use type spatial distribution matrix. Based on the land use type of each horizontal coordinate point in the first land use type spatial distribution matrix, the public exposure control limit of electric field intensity corresponding to the land use type under the frequency of 50Hz is found from the electromagnetic environment control limit to generate the electric field intensity limit spatial distribution matrix corresponding to each horizontal coordinate point. Based on the electric field intensity limit spatial distribution matrix, the first electric field intensity limit spatial distribution matrix is ​​obtained. Based on the land use type of each horizontal coordinate point in the first land use type spatial distribution matrix, the public exposure control limit of magnetic induction intensity corresponding to the land use type under the frequency of 50Hz is found from the electromagnetic environment control limit to generate the magnetic induction intensity limit spatial distribution matrix corresponding to each horizontal coordinate point. Based on the magnetic induction intensity limit spatial distribution matrix, the first magnetic induction intensity limit spatial distribution matrix is ​​obtained. Based on the land use type of each horizontal coordinate point in the first land use type spatial distribution matrix, the daytime or nighttime noise limit of the acoustic environment functional zone to which the target land use type belongs is found from the corresponding acoustic environment quality standard to generate a noise limit spatial distribution matrix corresponding to each horizontal coordinate point. Based on the noise limit spatial distribution matrix, the first noise limit spatial distribution matrix is ​​obtained. The spatial distribution matrix of the first electric field strength limit, the spatial distribution matrix of the first magnetic induction intensity limit, and the spatial distribution matrix of the first noise limit are associated and summarized according to the horizontal coordinate points, so that each horizontal coordinate point contains a triplet of electric field strength limit, magnetic induction intensity limit, and noise limit, forming a triplet spatial distribution dataset. Based on the triplet spatial distribution dataset, the corresponding electric field strength limit, magnetic induction intensity limit, and noise limit are extracted.

9. The method for predicting power frequency electromagnetic fields and assessing the acoustic environment impact of AC transmission lines according to claim 8, characterized in that, Interpolation and smoothing are performed on the discrete set of acceptable height intervals to generate a three-dimensional surface covering the entire evaluation area and simultaneously satisfying the limits for electric field strength, magnetic induction intensity, and noise. This surface serves as the environmental impact assessment conclusion for the AC transmission line project, and specifically includes the following steps: Based on the discrete set of acceptable height intervals, the acceptable starting height value corresponding to each horizontal coordinate point is extracted to form a discrete set of acceptable starting height points; For the discrete points of the standard starting height in the set of standard starting height discrete points, triangulation or inverse distance weighted interpolation is performed to generate a continuous standard starting height surface covering the entire horizontal evaluation area. Extract the standard termination height value corresponding to each horizontal coordinate point in the set of discrete points of the standard starting height, and form a set of discrete points of the standard termination height. For the discrete points of the target termination height in the set of target termination height discrete points, perform triangulation or inverse distance weighted interpolation to generate a continuous target termination height surface covering the entire horizontal evaluation area. The continuous target achievement start height surface and the continuous target achievement end height surface are closed in the vertical direction to form a closed three-dimensional space. The three-dimensional space is defined as the full-space target achievement envelope, which serves as the first full-space target achievement envelope. The height of any point in the three-dimensional space is between the target achievement start height and the target achievement end height corresponding to the horizontal coordinate of that point. Extract the upper boundary surface of the first full-space compliance envelope, and use the upper boundary surface as the three-dimensional surface of the continuous compliance height interval in the full space to obtain the three-dimensional surface of the first full-space continuous compliance height interval; wherein, the upper boundary surface of the first full-space compliance envelope is: a surface composed of the compliance termination height of each horizontal coordinate point; The three-dimensional surface of the first continuous compliance height range in the entire space is output in the format of a three-dimensional solid model file or a common data format of a geographic information system, and used as the environmental impact assessment conclusion of the AC transmission line project.

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