阅读说明：本技术 一种输电线路杆塔空气间隙的电场分布表征方法 (Electric field distribution characterization method for air gap of power transmission line tower ) 是由 邱志斌 张楼行 廖才波 侯华胜 朱雄剑 于 2021-06-08 设计创作，主要内容包括：本发明公开了一种输电线路杆塔空气间隙的电场分布表征方法,其利用有限元法计算输电线路-杆塔空气间隙的静电场分布,以导线或均压环表面电场强度最大值所在位置为起点,以杆塔塔身或横担距离高压电极最近的一条平行线上的电场强度最大值所在位置为终点,将两点的连线作为电场特征提取路径；以导线或均压环上的电场强度最大值所在位置为顶点,顶角为θ,底面为电位等于x·U的等位面构成的锥形场域作为电场特征提取场域。在上述路径与场域内分别提取54个和19个与电场分布相关的特征量,用以表征输电线路杆塔空气间隙的三维空间结构。本发明兼顾了特征提取的效率和特征表达的完善性,可为输电工程外绝缘空气间隙放电电压预测模型提供输入参数。(The invention discloses an electric field distribution characterization method of an air gap of a power transmission line tower, which utilizes a finite element method to calculate the electrostatic field distribution of the air gap of the power transmission line tower, takes the position of the maximum value of the electric field intensity on the surface of a lead or a grading ring as a starting point, takes the position of the maximum value of the electric field intensity on a parallel line of the tower body or a cross arm closest to a high-voltage electrode as an end point, and takes the connection line of the two points as an electric field characteristic extraction path; and taking the position of the maximum value of the electric field intensity on the lead or the grading ring as a vertex, the vertex angle as theta, and the bottom surface as a conical field formed by equipotential surfaces with the potential equal to x.U as an electric field characteristic extraction field. And respectively extracting 54 and 19 characteristic quantities related to electric field distribution in the path and the field to represent the three-dimensional space structure of the air gap of the power transmission line tower. The method gives consideration to the efficiency of feature extraction and the perfection of feature expression, and can provide input parameters for the prediction model of the external insulation air gap discharge voltage of the power transmission project.)

1. The electric field distribution characterization method for the air gap of the tower of the power transmission line is characterized by comprising the following steps: establishing a three-dimensional simulation model according to the size of the transmission line tower gap structure; applying a high potential U to electrodes such as a lead, an equalizing ring, a wire clamp and an insulator high-voltage side hardware fitting, and applying a zero potential to grounding electrodes such as a tower body and a cross arm; calculating the electrostatic field distribution of the air gap between the transmission line and the tower by using a finite element method, defining an electric field distribution characteristic extraction path and an extraction field area, and respectively extracting characteristic quantities from the electric field distribution characteristic extraction path and the extraction field area;

taking the position of the maximum value of the electric field intensity on the surface of a wire or an equalizer ring of a wire clamp-containing part facing one side of a tower body or a cross arm of the tower as a starting point, taking the position of the maximum value of the electric field intensity on a parallel line of the tower body or the cross arm closest to a high-voltage electrode as an end point, and taking the connection line of the two points as an electric field distribution characteristic extraction path;

and taking a conical field formed by the maximum position of the electric field intensity on the lead or the grading ring facing one side of the tower body or the cross arm of the tower as a vertex, the vertex angle as theta and the bottom surface as an equipotential surface with the electric potential equal to x.U as an electric field distribution characteristic extraction field.

2. The electric field distribution characterization method of the air gap of the transmission line tower according to claim 1, characterized in that: equally dividing the electric field distribution characteristic extraction path into n sections, and extracting the electric field intensity E of each sampling point through post-processing_iAverage electric field intensity E of each segment_iaAnd its squared value W_iWherein i is more than or equal to 1 and less than or equal to n, and the corresponding coordinate position is used as original data, and 54 physical quantities or mathematical quantities are adopted to represent the space electric field of the air gap of the power transmission line tower on the path, and the method specifically comprises the following steps:

maximum value of electric field intensity E_maxAnd its x, y, z directional components E_xem、E_yem、E_zem(ii) a Maximum value E in x, y, z directions_xm、E_ym、E_zm(ii) a Minimum value E_min(ii) a Median E_Mid(ii) a Average value E_aveAnd average value E in x, y, z directions_xa、E_ya、E_za(ii) a Variance E_std ²And standard deviation E_std(ii) a Coefficient of variation C_v(ii) a Distortion rate E_d；

Maximum value of electric field gradient E_gmMinimum value E_gnAverage value E_gaMedian E_gM；

E_maxAnd E_aveThe ratio of f to f in the x, y, z directions_x、f_y、f_z；E_minAnd E_maxRatio f of_n；E_yemAnd E_xemRatio tan of_zm，E_yemAnd E_zemRatio tan of_xm，E_zemAnd E_xemRatio tan of_ym；

Sum of squares of electric field intensity W_eAnd its average value W_ea；E_ia>c·E_maxSum of squares of electric field intensities on line segment and W_eRatio E of_rscWherein c is 0.9, 0.75;

E_ia>E_Midintegral of electric field strength V over line segment_MAnd the ratio V of it to the applied voltage U_rM；E_ia>E_aveIntegral of electric field strength V over line segment_aAnd the ratio V of it to U_ra；

W_i>c·W_eLength L of line segment_scAnd the ratio L of the distance d to the gap_rsc；E_ia>c·E_maxLength L of line segment_EcAnd the ratio L of it to d_rEc；E_g>c·E_gmLength L of line segment_gcAnd the ratio L of it to d_rgc；E_max、E_xm、E_ym、E_zm、E_MidThe distance L from the high-voltage electrode end_Em、L_Exm、L_Eym、L_Ezm、L_EM。

3. The power transmission line pole of claim 1The electric field distribution characterization method of the tower air gap is characterized by comprising the following steps: extracting m grid units in the field by electric field distribution characteristics, and extracting the electric field intensity E of each grid unit by post-processing_jAnd volume V thereof_jAs original data, wherein j is more than or equal to 1 and less than or equal to m, 19 physical quantities or mathematical quantities are adopted in the field to represent the space electric field of the air gap of the power transmission line tower, and the method specifically comprises the following steps:

maximum value of electric field intensity E_mAverage value E_aMinimum value E_nMedian E_M(ii) a Distortion rate E of electric field_dis；

Electric field energy W and energy density W_d；E_j>E_aVolume ratio V of area to whole conical field_raTo energy ratio W_ra；

E_j>E_MVolume ratio V of area to whole conical field_rMTo energy ratio W_rM；

E_j>b·E_mVolume ratio V of area to whole conical field_rbTo energy ratio W_rbWherein b is 0.9, 0.75, 0.5, 0.25.

4. The electric field distribution characterization method of the air gap of the transmission line tower according to claim 1, characterized in that: according to the three-dimensional simulation calculation result of the electrostatic field, if the position of the metal conductor part of the high-voltage electrode, which is closest to the position of the maximum electric field intensity value on the tower body or the cross arm of the tower, is the equalizing ring, the position of the maximum electric field intensity value on the surface of the equalizing ring is used as the vertex of the conical feature extraction field; and if the sub-conductor of the split conductor is closest to the position of the maximum value of the electric field intensity on the tower body or the cross arm of the tower, taking the position of the maximum value of the surface electric field intensity on the sub-conductor as the vertex of the conical characteristic extraction field.

5. The electric field distribution characterization method for the air gap of the power transmission line tower according to claim 1, characterized in that: the cone vertex angle theta of the electric field characteristic extraction field can be 60 degrees, 75 degrees and 90 degrees, and the equipotential surface x & U can be 0.3U, 0.5U and 0.7U.

Technical Field

The invention belongs to the technical field of high voltage and insulation, and particularly relates to an electric field distribution characterization method of an air gap of a power transmission line tower.

Background

The air gap is the main external insulation form of the high-voltage transmission line, and the discharge voltage of the air gap is the main basis of the external insulation design of the power transmission project. At present, the determination of the discharge voltage mainly depends on a discharge test with high cost and long period, and an empirical formula of the discharge voltage and the gap distance is fitted according to test data. However, it is difficult to effectively represent the three-dimensional space structure of the tower gap of the power transmission line only by the gap distance, the application range of the empirical formula is limited, and the method is difficult to be popularized to various complex engineering gap structures. The gap structure corresponds to the electrostatic field distribution one by one, the transmission line tower gap structure is described through the spatial electric field distribution with richer information, a parameterized electric field distribution characteristic set is constructed, and a feasible method is hopefully provided for establishing the relevance between the gap structure and the discharge voltage and realizing the insulation strength prediction of the engineering gap.

At present, the electric field distribution characterization method of the air gap has been researched. For example, in the disclosed technologies of "an electric field characterization method of a rod-plate gap structure" (ZL 201810069950.8), "a shortest path feature set for characterizing a spherical gap electric field distribution" (ZL 201810070448.9), etc., an electric field characterization method for an air gap of a typical structure such as a rod-plate gap, a spherical gap, etc. has been proposed. In the prior art, a characteristic quantity related to electric field distribution is defined on the shortest path between two electrodes of an air gap and is used as an input parameter of a machine learning model to predict the breakdown voltage of the air gap with a typical structure. However, for the air gap of the power transmission line tower with a complex structure in the practical engineering, if the shortest path electric field characteristic set proposed by the above-mentioned disclosure is adopted, the complex electrode structures of the conducting wire, the cross arm, the tower body and the like which affect the gap discharge and the space electric field distribution determined by the complex electrode structures cannot be fully reflected. In order to realize reasonable characterization of the gap structure, in addition to the electric field characteristic quantity on the shortest path, a characteristic extraction field needs to be further defined between a high-voltage electrode formed by a lead and a grading ring and a grounding electrode formed by a tower body or a cross arm, so as to form an electric field distribution characteristic set suitable for the gap structure of the power transmission line tower.

Disclosure of Invention

Aiming at the defects and problems in the prior art, the invention aims to provide a method for representing the electric field distribution of the air gap of the tower of the power transmission line, which provides basic characteristic parameters for reasonably representing the three-dimensional space structure of the complex engineering gap and further realizing the discharge voltage prediction of the external insulation gap of the power transmission engineering.

The invention is realized by the following technical scheme:

a method for representing electric field distribution of an air gap of a power transmission line tower is characterized in that a three-dimensional simulation model is built according to the structural size of the air gap of the power transmission line tower, high-potential U is applied to electrodes such as a lead, a grading ring, a wire clamp and an insulator high-voltage side hardware fitting, zero potential is applied to grounding electrodes such as a tower body and a cross arm, the electrostatic field distribution of the air gap of the power transmission line tower is calculated by utilizing a finite element method, an electric field distribution characteristic extraction path and an extraction field area are defined, and characteristic quantities are extracted from the electric field distribution characteristic extraction path and the extraction field area.

The position of the maximum value of the electric field intensity on the surface of a conducting wire (including a wire clamp) or an equalizer ring facing one side of a tower body or a cross arm of the tower is taken as a starting point, the position of the maximum value of the electric field intensity on a parallel line of the tower body or the cross arm closest to a high-voltage electrode is taken as an end point, and the connection line of the two points is taken as an electric field characteristic extraction path. Selecting n sampling points from the path, equally dividing the sampling points into n-1 sections, and extracting the electric field intensity E of each sampling point through post-processing_iAverage electric field intensity E of each segment_iaAnd its squared value W_i(i is more than or equal to 1 and less than or equal to n) and corresponding coordinate positions are used as original data, 54 physical quantities or mathematical quantities are adopted on the path to represent the space electric field of the air gap of the power transmission line tower, and the method specifically comprises the following steps:

maximum value of electric field intensity E_maxAnd its x, y, z directional components E_xem、E_yem、E_zem(ii) a Maximum value E in x, y, z directions_xm、E_ym、E_zm(ii) a Minimum value E_min(ii) a Median E_Mid(ii) a Average value E_aveAnd average value E in x, y, z directions_xa、E_ya、E_za(ii) a Variance E_std ²And standard deviation E_std(ii) a Coefficient of variation C_v(ii) a Distortion rate E_d；

Maximum value of electric field gradient E_gmMinimum value E_gnAverage value E_gaMedian E_gM；

E_maxAnd E_aveThe ratio of f to f in the x, y, z directions_x、f_y、f_z；E_minAnd E_maxRatio f of_n；E_yemAnd E_xemRatio tan of_zm，E_yemAnd E_zemRatio tan of_xm，E_zemAnd E_xemRatio tan of_ym；

Sum of squares of electric field intensity W_eAnd its average value W_ea；E_ia>c·E_max(c 0.9, 0.75) the sum of the squares of the electric field intensities on the line segment and W_eRatio E of_rsc；

E_ia>E_MidIntegral of electric field strength V over line segment_MAnd the ratio V of it to the applied voltage U_rM；E_ia>E_aveIntegral of electric field strength V over line segment_aAnd the ratio V of it to U_ra；

W_i>c·W_eLength L of line segment_scAnd the ratio L of the distance d to the gap_rsc；E_ia>c·E_maxLength L of line segment_EcAnd the ratio L of it to d_rEc；E_g>c·E_gmLength L of line segment_gcAnd the ratio L of it to d_rgc；E_max、E_xm、E_ym、E_zm、E_MidThe distance L from the high-voltage electrode end_Em、L_Exm、L_Eym、L_Ezm、L_EM。

And taking a conical field formed by the maximum position of the electric field intensity on the lead or the grading ring facing one side of the tower body or the cross arm of the tower as a vertex, the vertex angle as theta and the bottom surface as an equipotential surface with the electric potential equal to x.U as an electric field characteristic extraction field. The number of grid units in the field is m, and each grid is extracted through post-processingElectric field intensity E of the cell_jAnd volume V thereof_jAs original data (j is more than or equal to 1 and less than or equal to m), 19 physical quantities or mathematical quantities are adopted in the field to represent the space electric field of the air gap of the power transmission line tower, and the method specifically comprises the following steps:

maximum value of electric field intensity E_mAverage value E_aMinimum value E_nMedian E_M(ii) a Distortion rate E of electric field_dis(ii) a Electric field energy W and energy density W_d；E_j>E_aVolume ratio V of area to whole conical field_raTo energy ratio W_ra；E_j>E_MVolume ratio V of area to whole conical field_rMTo energy ratio W_rM；E_j>b·E_m(b is 0.9, 0.75, 0.5, 0.25) area of the whole conical field area_rbTo energy ratio W_rb。

According to the electric field three-dimensional simulation calculation result, if the position of the maximum electric field intensity value on the metal conductor part of the high-voltage electrode, which is away from the tower body or the cross arm of the tower, is the nearest grading ring, the position of the maximum electric field intensity value on the surface of the grading ring is used as the vertex of the conical feature extraction field; and if the sub-conductor of the split conductor is closest to the position of the maximum value of the electric field intensity on the tower body or the cross arm of the tower, taking the position of the maximum value of the surface electric field intensity on the sub-conductor as the vertex of the conical characteristic extraction field.

In the electric field distribution characterization method for the air gap of the power transmission line tower, the cone vertex angle theta of the electric field characteristic extraction field can be 60 degrees, 75 degrees and 90 degrees, and the equipotential surface x.U can be 0.3U, 0.5U and 0.7U.

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention describes the three-dimensional space structure of the air gap of the power transmission line tower by adopting the conical space field between the electrified conductor and the grounding electrode and the electric field distribution characteristic set on the path, can replace simple geometric parameters such as gap distance and the like, and realizes reasonable representation of the complex engineering gap structure.

(2) Compared with the prior art that the shortest path is only adopted for the characteristic definition of the electric field distribution, the electric field distribution characterization method of the air gap of the power transmission line tower, provided by the invention, has the advantages that the efficiency of characteristic extraction and the perfection of characteristic expression are both considered, and the method can be suitable for being used as an input parameter of a power transmission project external insulation air gap discharge voltage prediction model.

Drawings

FIG. 1 is a schematic diagram of an electric field distribution characteristic extraction path and an extraction field in the present invention;

FIG. 2 is a model diagram of an air gap of a pole tower of a + -660 kV direct-current transmission line in the embodiment of the invention;

fig. 3 is a cloud diagram of the distribution of the air gap electric field of the pole tower of the +/-660 kV direct-current transmission line in the embodiment of the invention.

Detailed Description

The present invention is further described in the following examples, which should not be construed as limiting the scope of the invention, but rather as providing the following examples which are set forth to illustrate and not limit the scope of the invention.

First, the concrete method principle of the invention

The invention provides a method for representing electric field distribution of an air gap of a power transmission line tower, which is used for quantitatively describing a three-dimensional space structure and electric field distribution of an external insulation gap of a power transmission project and laying a foundation for further realizing discharge voltage prediction of a complex project gap.

The invention adopts the following technical scheme:

for the air gap of the transmission line tower, a split conductor, a wire clamp, a grading ring, an insulator high-voltage side hardware fitting and the like of the transmission line are electrified conductors, the transmission line tower is a grounding conductor, a simulation model of the transmission line-tower gap can be established according to the structural size of related parts, a high potential U is applied to high-voltage side metal conductors such as the split conductor, the wire clamp, the grading ring and the like, a zero potential is applied to the tower, and electrostatic field distribution is calculated by using a finite element method.

Firstly, defining an electric field characteristic extraction path 1 in a gap between a transmission line and a tower, and taking the position of the maximum value of the surface electric field intensity of a lead (including a wire clamp) or an equalizer ring facing one side of a tower body or a cross arm of the tower as a starting point, taking the position of the maximum value of the electric field intensity on a parallel line of the tower body or the cross arm closest to a high-voltage electrode as an end point, and taking the connection line of the two points as the electric field characteristic extraction path, as shown in fig. 1. Equally dividing the path into n segments, extracting the electric field intensity E of each sampling point through post-processing_iAverage electric field intensity E of each segment_iaAnd its squared value W_i(1. ltoreq. i. ltoreq.n) and the corresponding coordinate position as raw data, where E_ia＝(E_i+E_i+1) And/2, adopting 54 physical quantities or mathematical quantities to represent the space electric field of the air gap of the power transmission line tower on the path, wherein the concrete steps are as follows:

maximum value of electric field intensity E_maxAnd its x, y, z directional components E_xem、E_yem、E_zem(ii) a Maximum value E in x, y, z directions_xm、E_ym、E_zm(ii) a Minimum value E_min(ii) a Median E_Mid(ii) a Average value E_aveAnd average value E in x, y, z directions_xa、E_ya、E_za(ii) a Variance E_std ²And standard deviation E_std(ii) a Coefficient of variation C_v(ii) a Distortion rate E_d. The corresponding calculation formula is:

maximum value of electric field gradient E_gmMinimum value E_gnAverage value E_gaMedian E_gM：

E_maxAnd E_aveThe ratio of f to f in the x, y, z directions_x、f_y、f_z；E_minAnd E_maxRatio f of_n；E_yemAnd E_xemRatio tan of_zm，E_yemAnd E_zemRatio tan of_xm，E_zemAnd E_xemRatio tan of_ym. The corresponding calculation formula is:

sum of squares of electric field intensity W_eAnd its average value W_ea；E_ia>c·E_max(c 0.9, 0.75) the sum of the squares of the electric field intensities on the line segment and W_eRatio E of_rsc. The corresponding calculation formula is:

E_ia>E_Midintegral of electric field strength V over line segment_MAnd the ratio V of it to the applied voltage U_rM；E_ia>E_aveIntegral of electric field strength V over line segment_aAnd the ratio V of it to U_ra. The corresponding calculation formula is:

W_i>c·W_elength L of line segment_scAnd the ratio L of the distance d to the gap_rsc；E_ia>c·E_maxLength L of line segment_EcAnd the ratio L of it to d_rEc；E_g>c·E_gmLength L of line segment_gcAnd the ratio L of it to d_rgc；E_max、E_xm、E_ym、E_zm、E_MidThe distance L from the high-voltage electrode end_Em、L_Exm、L_Eym、L_Ezm、L_EM。

Then, an electric field distribution characteristic extraction field 2 is defined in the gap between the transmission line and the tower, as shown in fig. 1, so as to face the towerThe maximum position of the electric field intensity on the lead or the equalizing ring at one side of the tower body or the cross arm is a vertex, the vertex angle 3 of the cone is theta, and the bottom surface is a conical field formed by an equipotential surface 4 with the potential equal to x.U and is used as an electric field characteristic extraction field. Wherein the cone vertex angle theta can be 60 degrees, 75 degrees and 90 degrees, and the equipotential surface x.U can be 0.3U, 0.5U and 0.7U. M grid cells in the field are extracted through post-processing, and the electric field intensity E of each grid cell is extracted_jAnd volume V thereof_jAs original data (j is more than or equal to 1 and less than or equal to m), 19 physical quantities or mathematical quantities are adopted in the field to represent the space electric field of the air gap of the power transmission line tower, and the details are as follows:

maximum value of electric field intensity E_mAverage value E_aMinimum value E_nMedian E_M(ii) a Distortion rate E of electric field_dis(ii) a Electric field energy W and energy density W_d. Let ε be the dielectric constant, the corresponding calculation formula is:

E_j>E_avolume ratio V of area to whole conical field_raTo energy ratio W_ra；E_j>E_MVolume ratio V of area to whole conical field_rMTo energy ratio W_rM；E_j>b·E_m(b is 0.9, 0.75, 0.5, 0.25) area of the whole conical field area_rbTo energy ratio W_rb。

Second, example

The electric field distribution characterization method of the air gaps of the power transmission line tower is described by taking the air gaps of the upper layers of +/-660 kV common-tower double-circuit direct-current line towers as an example. The simulation model of the air gap of the transmission line tower is shown in figure 2. In this example, the gap distance d is 5.3m, the upper cross arm of the simulation tower head is 24m long and 3.4m wide, the lower cross arm is a trapezoid, the widest part is 4.5m, the narrowest part is 1m, the total length is 20.4m, an included angle of 15 degrees is kept with the horizontal plane, and the included angle of the V-shaped insulator is 90 degrees. A three-dimensional electric field simulation model is established according to the structural size of the air gap of the power transmission line tower, the tower body is replaced by a steel plate for simplifying and calculating, the split conductor and the high-voltage end hardware are loaded with the potential of 1kV, zero potential is applied to the metal surfaces of the tower, the low-voltage end hardware (connecting pieces, pull rods) and the like and the external air boundary, the spatial electric field distribution of the tower, the low-voltage end hardware (connecting pieces, pull rods) and the like can be calculated by adopting a finite element method, and the electric field simulation result is shown in figure 3.

And (3) selecting n sampling points at equal intervals on the electric field characteristic extraction path 1, wherein the more the sampling points are, the higher the precision is, and the longer the time consumption of data extraction is. In this embodiment, n is 10001, and original data such as coordinates and electric field intensity of n sampling points are extracted and stored in a text. In the cone-shaped feature extraction field 2, in this embodiment, the cone vertex angle 3 is taken as θ being 90 °, and the equipotential surface 4 is taken as 0.3U, and the original data of the grid cell in the region, the electric field intensity thereof, the cell volume thereof, and the like are extracted and stored in the text.

According to the electric field simulation calculation result and the original data, the electric field distribution characteristic set of the air gap on the upper layer of the same-tower double-circuit direct current line tower of +/-660 kV with d being 5.3m in the embodiment can be calculated by using the definition and calculation formula of each characteristic quantity, and the table 1 shows.

TABLE 1 characteristic set of electric field distribution of this example

Therefore, the space electric field distribution characteristic set of the air gap of the transmission line tower arranged in the structure can be obtained, and the elements in the set are the 73 electric field distribution characteristic quantities.

The foregoing merely represents preferred embodiments of the invention, which are described in some detail and detail, and therefore should not be construed as limiting the scope of the invention. It should be noted that, for those skilled in the art, various changes, modifications and substitutions can be made without departing from the spirit of the present invention, and these are all within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.