Overhead line peripheral electric field equivalence and temporary electricity experiment optimization method

Abstract

The invention relates to an overhead line peripheral electric field equivalence and temporary power experiment optimization method, and belongs to the technical field of power experiments. The method comprises the following steps: obtaining design data for indicating a corresponding lead design standard; electric field models of different wire heights are established by utilizing design data, for example, the standard design height is H, and different heights are H / 2, H / 3, H / 4 and the like; acquiring an electric field change curve in the preset research area according to the electric field model; and obtaining an electric field equivalent interval under the standard design height and different conductor heights. Therefore, the electric field model is constructed by setting the wires with different heights, so that the change condition of the electric field below the wire when only the variable of reducing the height of the wire is simulated under the condition that the rest conditions are kept consistent. The temporary electricity early warning experiment is optimized through the electric field equivalent intervals under the wires of different heights, the experiment difficulty is reduced, and the experiment precision is improved.

Description

Technical Field

[0001] The invention relates to an overhead line peripheral electric field equivalent and temporary power test optimization method, belonging to the technical field of electric power experiments. Background Art

[0002] The three-axis cubic capacitance electric field sensor is an efficient and reliable electric field signal acquisition device. Its principle is to collect the capacitance voltage of the cube in the three directions of xyz respectively, and then perform internal vector operations to obtain the comprehensive field strength to determine whether an early warning is needed. The device has the characteristics of simple and reliable structure, sensitive response, and is not affected by the movement of personnel. It is very suitable for installation in safety helmets and other portable equipment for power operations for electric field acquisition and early warning. However, the current electric field sensor experimental detection is difficult. There are great safety hazards in actual measurement near overhead lines. The distance to the conductor can only be visually observed at high altitudes, and outdoor environmental factors have a greater impact on the electric field, so a pure 10kV experimental environment needs to be established. Not only does the test and detection of the sensor need to be carried out in a temporary power environment, but also in scenarios involving scientific research on high-voltage lines, testing of electrical equipment, etc., such as before and after the overhead commissioning and transformation of superconducting overhead cables, the experiment also needs to be close to the line.

[0003] It is costly and difficult to restore the design of a tower conductor of the same height in the laboratory. Conventional methods require the construction of complex experimental equipment, which consumes a lot of manpower and material resources. The existing temporary power experimental environment simulates the electric field of standard height conductors, which mostly relies on complex and expensive devices. It does not fully explore the internal connection between the electric fields of conductors of different heights, and it is difficult to achieve accurate simulation at low cost. How to build the same electric field environment as the standard conductor in the laboratory is a technical problem that needs to be solved urgently by technicians in this field.

[0004] The preceding description is intended to provide general background information and does not necessarily constitute prior art. Summary of the invention

[0005] Based on this, the present invention proposes an electric field equivalent and temporary power test optimization method around overhead lines, aiming to solve the technical problems that the existing temporary power test environment simulates the electric field of standard height conductors, cannot fully explore the intrinsic connection between the electric fields of conductors at different heights, and is difficult to achieve accurate simulation at low cost.

[0006] The theoretical basis of the present invention is derived as follows:

[0007] The situation involved in this application is a temporary electric experiment, that is, the length of the wire is much greater than the distance from the observation point to the wire, so the wire can be approximately equivalent to an infinitely long straight wire, and the electric field near it can be calculated using Coulomb's law.

[0008] Coulomb's law is used to calculate the electric field generated by point charges. For transmission lines, their charge distribution can be discretized and approximated as multiple point charges. Assuming that the charge per unit length of the transmission line is ρ, according to Coulomb's law and the definition of electric field strength:

[0009]

[0010] Where E is the electric field strength, F is the electric field force, and q is the test charge. The electric field strength formula around an infinitely long straight wire derived from Coulomb's law is:

[0011]

[0012] Where ρ is the linear charge density, ε0 ​​is the dielectric constant of vacuum, and r is the distance to the wire.

[0013] For a wire with a height of h, the components of the electric field strength E at a point in space (x, y, z) can be calculated based on the coordinate transformation and the above formula. Assuming that the wire is along the Z axis, in the XY plane, the component of the electric field strength E in the X direction is E x for:

[0014]

[0015] The component E of the electric field strength E in the Y direction y for:

[0016]

[0017] For formula (3) and formula (4), x is the horizontal coordinate, y is the vertical coordinate, and h is the height of the wire.

[0018] Since the Z-direction electric field changes relatively little when the overhead wires are parallel, the Z-direction component is not considered, and it is more intuitive to analyze the electric field overlap area in a two-dimensional plane. When the heights of the two wires are h1 and h2 respectively, the generated electric field satisfies in a certain area:

[0019] E1-E2|≤ΔE (5)

[0020] Among them, E1 is the electric field strength corresponding to the conductor with a height of h1, E2 is the electric field strength corresponding to the conductor with a height of h2, and ΔE is a set allowable error value used to determine whether the electric field can be approximately considered to overlap. The range of the overlap area will be affected by factors such as the conductor height difference and the allowable error ΔE. As the conductor height difference decreases, the overlap area may increase; the larger the allowable error ΔE, the looser the calculated overlap area range may be.

[0021] To find this area, we can solve a set of inequalities. In the XY plane, let

[0022]

[0023] Among them, E 1x is the component of the electric field intensity in the X direction corresponding to the wire with a height of h1, E 2x is the component of the electric field intensity in the X direction corresponding to the wire with a height of h2, E 1y is the component of the electric field intensity in the Y direction corresponding to the wire with a height of h1, E 2y is the component of the electric field intensity in the Y direction corresponding to the wire with a height of h2.

[0024] Substituting the electric field intensity component expressions in (3) and (4) above into the inequality, we obtain a complex inequality with respect to x and y.

[0025] It is proved that the inequality has a solution, that is, it is proved that there is an equivalent interval of electric field overlap for two wires at different heights. When far away from the two wires, the electric field strength generated by the two wires will approach zero. Because in the electric field strength formula, as the distance from the space point to the wire increases, the value of the electric field strength will become smaller and smaller. When the electric field strength approaches zero, the absolute value of their difference will also approach zero. The set ΔE is a fixed positive number, so this inequality is valid at a distance far enough from the wire, which means that the inequality has a solution. Through the above theoretical derivation, it can be concluded that under certain conditions, there is an area of ​​electric field overlap for wires at different heights.

[0026] The present application solves the technical problem by adopting the following technical solution: The present application provides an optimization method for electric field equivalent and temporary power test around overhead lines, comprising the following steps:

[0027] Acquire design data of the corresponding conductor, wherein the design data of the corresponding conductor is used to indicate its design standard, and the conductor design data includes voltage level, conductor radius, conductor arrangement mode, conductor height to ground, and distance between conductors;

[0028] Using the design data of the corresponding conductors to establish electric field models at different heights;

[0029] Acquire an electric field variation curve in a preset research area according to the electric field model, wherein the preset research area is a range circled below the middle of the conductor;

[0030] According to the electric field variation curves in the preset research area under the electric field models at different heights, the electric field equivalent ranges of different conductor heights and the original design heights are obtained;

[0031] The temporary electric field experiment is optimized based on the obtained electric field equivalent interval.

[0032] The step of establishing electric field models at different heights using the design data of the corresponding conductors includes:

[0033] Calculating the height of the conductor of other electric field models according to the conductor height in the design data of the corresponding conductor;

[0034] The electric field model group is obtained by using wires of different heights set according to the simulation.

[0035] Specifically, assuming the standard height is H, the wire height of other models is H n for:

[0036]

[0037] Where n is a positive integer and 2≤n≤H / 2. All models have the same settings except for their heights.

[0038] The step of obtaining an electric field variation curve in a preset research area according to the electric field model includes:

[0039] Get the height and field strength corresponding to multiple points in the preset study area.

[0040] The electric field variation curves in the preset research area under the electric field models at different heights are used to obtain the electric field equivalent intervals of different conductor heights and the original design height, including:

[0041] Obtain the electric field variation curves corresponding to different wire heights;

[0042] When the electric field difference between different conductors is less than a preset range, the interval where the electric field difference is less than the range is marked as an electric field equivalent interval;

[0043] When the electric field difference between different conductors is greater than a preset range, the interval in which the electric field difference is greater than the range is marked as an electric field difference interval.

[0044] Specifically, the electric field difference E Δ is defined as:

[0045]

[0046] Among them, E H is the electric field at the height of the standard wire, E H / n It is the electric field corresponding to the relative position of wires of different heights and the standard height.

[0047] The optimization of the temporary electric field experiment based on the obtained electric field equivalent interval includes:

[0048] Determine the required temporary power test type, where the temporary power test type is used to indicate the operating distance of the test;

[0049] Determine the required electric field equivalent range according to the type of temporary electric test;

[0050] Get the minimum wire height corresponding to the electric field equivalent interval.

[0051] The step of determining the minimum conductor height comprises:

[0052] When the operating distance is less than or equal to the electric field equivalent interval, the wire height of the electric field model is calibrated as the minimum wire height of the experimental situation.

[0053] Specifically, after determining the simulated minimum conductor height according to the electrical proximity distance required for the experiment, the method further includes: constructing a safe and high-precision experimental environment according to electromagnetic principles.

[0054] The embodiments of the present application have the following beneficial effects:

[0055] This application takes into account the problems that when conducting temporary power experiments near AC overhead lines, the distance cannot be accurately measured at high altitudes, and the experiment is greatly affected by external factors and is highly dangerous. Through a preliminary and brief analysis of Coulomb's law, it is found that there are areas of electric field overlap for conductors at different heights, and then an electric field model is established using conductors at different heights to determine the specific areas of electric field overlap for conductors at different heights. The inherent connection between the electric fields of conductors at different heights is fully explored, and the minimum conductor height that can simulate the electric field of conductors at standard heights is determined through the operating distance required for temporary power experiments. This allows temporary power experiments to be conducted conveniently and accurately without being affected by the height of overhead lines, saving the cost of temporary power experiments.

[0056] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented according to the contents of the specification, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following preferred embodiments are specifically cited and described in detail with the accompanying drawings. It should be understood that the above general description and the detailed description below are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0058] Figure 1 A schematic diagram of a flow chart of an overhead line peripheral electric field equivalent and temporary power test optimization method provided by an embodiment;

[0059] Figure 2 A schematic diagram of a standard height conductor provided by an embodiment;

[0060] Figure 3 A schematic diagram of a standard height wire model provided by an embodiment;

[0061] Figure 4 A schematic diagram of electric field variation curves of electric fields of wires at different heights provided by an embodiment;

[0062] Figure 5 A schematic diagram of a process flow for optimizing minimum conductor height in a temporary power test is provided in an embodiment. DETAILED DESCRIPTION

[0063] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0064] At present, temporary power experiments are generally carried out outdoors, but in actual situations, the accuracy and convenience of temporary power experiments are low; if a pole tower of the same height as that outdoors is built indoors, the space cost and construction difficulty are high. There are many problems with the existing temporary power experiment methods, but power science research, equipment insulation testing, etc. are inseparable from temporary power experiments. In order to conduct temporary power experiments more simply and accurately, this application proposes a method for optimizing the electric field equivalence and temporary power experiments around overhead lines to optimize temporary power experiments. To clearly describe the method for optimizing the electric field equivalence and temporary power experiments around overhead lines provided in this application, please refer to Figure 1-Figure 5 , including steps S110 to S150.

[0065] Step S110: Acquire design data of the corresponding conductor, wherein the design data of the corresponding conductor is used to indicate its design standard, and the conductor design data includes voltage level, conductor radius, conductor arrangement, conductor height to the ground, and distance between conductors.

[0066] In one embodiment, the present application is aimed at temporary power experiments with different requirements, and there must be differences in experimental conditions and experimental environments. In order to clearly understand the electric field changes in the corresponding situation, it is necessary to obtain the design data of different conductors to determine the type of electric field and the research area that need to be studied. For ease of understanding, the electric field cited in this application is a 10kV overhead line situation. And the 10kV overhead line is a single-loop bare conductor, and the conductors are arranged in a triangle. As for how to determine the source of the corresponding conductor design data, it must first be determined based on the existing conductor data. There is no restriction on the acquisition means, which can be point cloud data obtained by lidar or obtained through a design manual.

[0067] Step S120: establishing electric field models at different heights using the design data of the corresponding conductive wires.

[0068] In one embodiment, establishing a synthetic electric field model using design data of the conductor includes: obtaining a standard height electric field model according to the required voltage level, conductor thickness, conductor type, conductor arrangement, etc. of the conductor.

[0069] In one embodiment, assuming that the standard height is H, the wire heights of other models are H n for:

[0070]

[0071] Where n is a positive integer and 2≤n≤H / 2. All models have the same settings except for their heights.

[0072] If the distance between the corresponding conductor towers is too long, the corresponding connected wires will not be in a straight line, but curved, with sag. However, since it is a temporary power experiment, the test point is close to the conductor and it is generally regarded as a long straight conductor.

[0073] The standard height of the wire according to an embodiment of the present application can be referred to Figure 2 , Figure 2 This is a schematic diagram of standard height conductors when the 10kV line is arranged in a triangle. The corresponding relationship between various parameters and voltage levels can be found in Table 1.

[0074] Table 1 shows some conductor design data

[0075]

[0076] In Table 1, the line spacing of 10kV overhead lines is determined by the span length. The corresponding span requirements are in brackets in the fifth row. In the simulation design, the line spacing of 10kV lines is 60m, and the line spacing corresponds to 0.7m, that is, the horizontal projection distance and vertical projection distance of 10kV overhead lines are both 0.7m. The line spacing of other voltage levels is 100. The three values ​​in a row of the line spacing of 35kV overhead lines correspond to three different conductor arrangements. The line spacing of 110kV lines is calculated according to the formula in the fourth column of Table 1, where K i is the suspension insulator string coefficient, which is 0.4, D is the distance between the horizontal lines of the conductors, L K is the length of the suspension insulator string, U is the system nominal voltage, f c is the maximum sag of the conductor.

[0077] Furthermore, after setting up the corresponding conductors, the influence of other factors needs to be considered. For details, please refer to the description below for setting. The earth is regarded as an infinitely large conductor with zero electric potential; the split conductor is equivalent to one, and in the same span, the equivalent radius of the same type of conductors is equal and parallel to each other, and the surface of the conductor is equipotential; only the electric field generated by the conductor is considered, while the effects of nearby targets such as towers, hardware and insulators, as well as the terminal effects of the conductors and overhead ground wires are ignored; there is no distortion of charge distribution along the length of the conductor, and it is irrelevant to the change in the electric potential on the conductor. The electric field model of different conductor heights is obtained according to the corresponding conductors set up in the simulation. Figure 3 This is a schematic diagram of a standard height wire model provided in an embodiment, so that finite element software can be used to simulate and design it to obtain electric field change data in the study area.

[0078] Step S130: obtaining an electric field variation curve in a preset study area according to the electric field model, wherein the preset study area is a range circled below the middle of the conductor.

[0079] In one embodiment, obtaining the electric field variation curve in a preset study area according to the synthetic electric field model includes: obtaining the heights and field strengths corresponding to multiple points in the preset study area; obtaining the electric field variation curve according to the height and field strength plot; and obtaining the electric field variation curves of wires at different heights.

[0080] In one embodiment, the preset study area is the range defined by the center of the conductor, specifically, it can be the line segment from the ground directly below the middle of the conductor to a certain distance from the conductor. It can be understood that in reality, in the middle of the corresponding conductor extension direction, the electric field is less affected by other factors such as poles and towers, and then the preset study area can be selected in the middle of the conductor. At the same time, it can be understood that all areas from the ground at the center of the conductor to the conductor need to be calculated. Because the attenuation of the electric field is very small within the distance range that is too close to the conductor, there must be an area where the electric field overlaps. Therefore, the range of the preset study area is very important. In the 10kV single-circuit overhead line of this application, the preset study area can be specifically the line segment from the ground in the middle of the 10kV overhead line along the extension direction of the line to 0.001m away from the conductor. It is worth noting that the preset study area needs to be set according to the actual temporary power experiment scene. According to the sensor temporary power detection requirements, the preset study area is the line segment from the ground directly below the middle of the edge conductor to a certain distance from the conductor.

[0081] Step S140: obtaining the electric field equivalent intervals of different conductor heights and the original design height according to the electric field variation curves preset in the study area under the electric field models at different heights.

[0082] In one embodiment, the electric field difference of the relative positions of different models is obtained. If the ratio of the electric field difference is less than 10% of the relative position of the standard model, the area where the electric field difference is less than 10% is defined as the electric field equivalent interval, and the other areas are the electric field difference intervals.

[0083] In one embodiment, the relative positions of different models are within a preset research area, and the relative positions are the distances to the conductors. For ease of explanation, the 12m 10kV overhead line and the 4m 10kV overhead line models are used as examples. The preset research area of ​​the 12m 10kV overhead line is 0-12m in the middle of the conductor, and the preset research area of ​​the 4m 10kV overhead line is 0-4m in the middle of the conductor. The research areas of the two models should correspond, that is, the relative positions are the same, then the electric field of 0-4m in the 4m model should correspond to the electric field of 8-12m in the 12m model. The relative positions corresponding to different conductor heights are realized based on this, and the electric field change curves of the electric fields of conductors at different heights are shown as follows. Figure 4 .by Figure 4 The electric field equivalent interval distances corresponding to wires of different heights are calculated using the data, see Table 2.

[0084] Table 2 The electric field equivalent interval distance corresponding to the wires of different heights

[0085] high 12m 6m 4m 3m 2m Overlap interval (10%) 11.17m 4.03m 2.54m 1.88m 0.46m Overlap interval (5%) 11.17m 3.57m 2.3m 1.76m 0.17m Overlap interval (3%) 11.17m 3.27m 2.16m 0.63m 0m Overlap interval (1%) 11.17m 2.7m 1.94m 0m 0m

[0086] In Table 2, the numbers in the brackets in the first column represent different values ​​of the electric field difference. After the electric field equivalent interval distances corresponding to the conductors of different heights are calculated by the above method, they can be used in the optimization of the temporary power test. However, different temporary power tests have different requirements for the operating distance of the experiment, and different electric field equivalent intervals need to be selected.

[0087] Step S150: Optimizing the temporary electric field experiment based on the obtained electric field equivalent interval. The specific steps are:

[0088] S151: Determine the required temporary power test type, where the temporary power test type is used to indicate the operating distance of the test.

[0089] In one embodiment, according to the above-described method for optimizing the electric field equivalent and temporary power test around overhead lines, it can be seen that the electric field at different conductor heights is different from the electric field equivalent range at the standard height. For more accurate experiments, it is necessary to obtain the corresponding operating distance of the experiment according to different experimental types.

[0090] S152: Determine the required electric field equivalent range according to the type of temporary electrical experiment;

[0091] S153: Obtain the minimum wire height corresponding to the electric field equivalent interval.

[0092] In one embodiment, the minimum height of the simulated conductor is determined according to the working distance required for the experiment, including: obtaining the working distance required for different temporary electric experiments; when the working distance is greater than the electric field equivalent interval, the model cannot be calibrated to the minimum conductor height under the temporary electric experiment; when the working distance is less than or equal to the electric field equivalent interval, the model conductor height is calibrated to the minimum conductor height under the experimental situation. It can be understood that the electric field overlap area is an equivalent area of ​​the electric field of the simulated standard height conductor, and it is meaningless when the temporary electric experiment is performed outside the electric field equivalent interval.

[0093] In one embodiment, the electric field equivalent interval will be used as the final minimum conductor height. Continuing the example of the corresponding conductor being a 10kV triangular overhead line, when the temporary power distance required for the experiment is 0.7m, the electric field equivalent interval distance should be greater than 0.7m. In other words, as long as the electric field equivalent interval distance is greater than 0.7m, the tower height can be used for temporary power experiments, but according to the difficulty, the minimum conductor height should be selected to build the indoor conductor. Figure 5 A schematic diagram of a process flow for optimizing minimum conductor height in a temporary power test is provided in an embodiment.

[0094] The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for optimizing electric field equivalent and temporary power test around overhead lines, characterized in that: The following steps are involved: Acquire design data of the corresponding conductor, wherein the design data of the corresponding conductor is used to indicate its design standard, and the conductor design data includes voltage level, conductor radius, conductor arrangement mode, conductor height to ground, and distance between conductors; Using the design data of the corresponding conductors to establish electric field models at different heights; Acquire an electric field variation curve in a preset research area according to the electric field model, wherein the preset research area is a range circled below the middle of the conductor; According to the electric field variation curves in the preset research area under the electric field models at different heights, the electric field equivalent ranges of different conductor heights and the original design heights are obtained; The temporary electric field experiment is optimized based on the obtained electric field equivalent interval.

2. The method for optimizing the electric field equivalent and temporary power test around overhead lines as claimed in claim 1, characterized in that: The step of establishing electric field models at different heights using the design data of the corresponding conductors includes: Calculating the height of the conductor of other electric field models according to the conductor height in the design data of the corresponding conductor; The electric field model group is obtained by using wires of different heights set according to the simulation.

3. The method for optimizing the electric field equivalent and temporary power test around overhead lines as claimed in claim 1, characterized in that: The step of obtaining an electric field variation curve in a preset research area according to the electric field model includes: Get the height and field strength corresponding to multiple points in the preset study area.

4. The method for optimizing the electric field equivalent and temporary power test around overhead lines as claimed in claim 1, characterized in that: The electric field variation curves in the preset research area under the electric field models at different heights are used to obtain the electric field equivalent intervals of different conductor heights and the original design height, including: Obtain the electric field variation curves corresponding to different wire heights; When the electric field difference between different conductors is less than a preset range, the interval where the electric field difference is less than the range is marked as an electric field equivalent interval; When the electric field difference between different conductors is greater than a preset range, the interval in which the electric field difference is greater than the range is marked as an electric field difference interval.

5. The method for optimizing the electric field equivalent and temporary power test around overhead lines as claimed in claim 1, characterized in that: The optimization of the temporary electric field experiment based on the obtained electric field equivalent interval includes: Determine the required temporary power test type, where the temporary power test type is used to indicate the operating distance of the test; Determine the required electric field equivalent range according to the type of temporary electric test; Get the minimum wire height corresponding to the electric field equivalent interval.

6. The method for optimizing the electric field equivalent and temporary power test around overhead lines as claimed in claim 5, characterized in that: The step of determining the minimum conductor height comprises: When the operating distance is less than or equal to the electric field equivalent interval, the wire height of the electric field model is calibrated as the minimum wire height of the experimental situation.

Images