A refined prediction method for ice thickness of power transmission lines in mountainous micro-terrain

Abstract

The present invention provides a method for fine prediction of ice thickness of transmission lines in mountainous micro-terrain, comprising: (1) refining the 3km×3km ice thickness prediction grid points in mountainous micro-terrain into 300m×300m grid points, and determining the category of each refined grid point: the refined grid points are divided into four categories according to the category: high-altitude grid points, ridge grid points, windward grid points and leeward grid points; (2) correcting the ice thickness prediction value of the high-altitude grid points; (3) correcting the ice thickness prediction value of the leeward grid points, windward grid points and ridge grid points; (4) correcting the ice thickness prediction value of the windward grid points and ridge grid points corrected in step (3) according to the wind direction. The present invention realizes the prediction of ice thickness at the stage level, improves the accuracy of ice thickness prediction of lines in micro-terrain areas, and has the advantages of wide applicability and fast calculation speed.

Description

Technical Field

[0001] The present invention relates to the technical field of power transmission line operation and maintenance, disaster prevention and early warning, and in particular to a method for finely predicting ice thickness of a transmission line in a mountainous micro-topography. Background Art

[0002] Icing of overhead transmission lines has always been an important natural factor threatening the safe and stable operation of power grids. Overhead transmission lines located in mountainous icing micro-topography areas are often more severely iced, causing a series of phenomena such as line overload, uneven or uneven deicing, and ice flash, resulting in a large number of power grid accidents such as line disconnection and tower collapse caused by icing. Using meteorological forecast information and combining the equivalent icing thickness calculation model for transmission lines, the icing thickness of transmission lines can be predicted, which can buy time for the formulation of emergency plans and the implementation of disaster prevention and emergency response.

[0003] However, when the transmission line section is located in mountainous micro-topography such as passes, alpine watersheds, and canyon wind channels, the microclimate characteristics are prominent. The meteorological forecast results based on large spatial resolution cannot accurately reflect the actual meteorological conditions in the micro-topography area, which brings large errors in the prediction of ice thickness on transmission lines in mountainous micro-topography areas. Summary of the invention

[0004] The purpose of the present invention is to provide a method for finely predicting ice thickness of power transmission lines in mountainous micro-terrain, so as to improve the accuracy of prediction of ice thickness of lines in micro-terrain areas, and the method has the advantages of wide applicability and fast calculation speed.

[0005] In order to achieve the above object, the present invention provides a method for finely predicting ice thickness of power transmission lines in micro-topography areas, comprising the following steps:

[0006] (1) The 3 km × 3 km ice thickness prediction grid of the mountain micro-topography is refined into 300 m × 300 m grids, and the categories of each refined grid point are determined: the refined grid points are divided into four categories: high altitude grid points, ridge grid points, windward grid points, and windward grid points;

[0007] (2) Correct the predicted ice thickness at high altitude grid points;

[0008] (3) Correct the predicted ice thickness values ​​at the backwind points, the frontwind points and the ridge grid points;

[0009] (4) The predicted ice thickness at the windward points and ridge grid points corrected according to the wind direction correction step (3).

[0010] Furthermore, in the step (1), the 3km×3km ice thickness prediction grid of the mountain micro-topography is refined into 300m×300m grids, and the step of determining the category of each refined grid point is specifically as follows: 1) according to whether the altitude of the refined grid point is greater than 2000m, it is divided into high-altitude grid points and low-altitude grid points; 2) for the low-altitude grid points, it is divided into windward slope grid points and leeward slope grid points according to whether they are located on the windward slope; (3) for the windward slope grid points, it is divided into ridge grid points and windward grid points according to whether they are located on the ridge line.

[0011] Furthermore, in the step (1), the low-altitude grid points are divided into windward slope grid points and leeward slope grid points according to whether they are located on the windward slope. Specifically, the slope direction of a refined grid point is calculated using DEM data. If the slope direction of the grid point is within the range of ±90° of the wind direction in the meteorological numerical model, the refined grid point is determined to be a windward slope grid point; otherwise, the refined grid point is determined to be a leeward slope grid point.

[0012] Furthermore, in the step (1), the windward slope grid points are divided into ridge grid points and windward grid points according to whether they are located on the ridge line, specifically: 1) positive terrain is obtained through DEM neighborhood analysis; 2) the DEM is filled and the flow direction flow is analyzed and obtained; 3) the value of the flow accumulation being zero is extracted and intersected with the positive terrain, that is, the ridge line is obtained, and the windward slope grid points are divided into ridge grid points and windward grid points according to whether they are located on the ridge line.

[0013] Furthermore, the step (2) of correcting the predicted value of ice thickness at a high altitude grid point is specifically as follows: the ice thickness at a certain high altitude grid point is calculated using the following formula, where D 预报冰厚 is the predicted ice thickness at a 3km×3km grid, and A is the average altitude of the grid; ICE 高海拔 is the predicted value of the revised ice thickness at the high altitude grid point, and B is the altitude of the high altitude grid point:

[0014]

[0015] Furthermore, the step (3) of correcting the predicted ice thickness values ​​of the backwind points, the windward points and the ridge points is specifically as follows: in the 3km×3km grid points divided into 100 300m×300m grid points, the number of backwind points is a, the number of windward points is b, and the number of ridge points is c, and the ice thickness correction value of the subdivided grid points is calculated using the following formula:

[0016]

[0017] ICE 背风 ICE 迎风 ICE 山脊 are the corrected values ​​of ice thickness at the backwind point, the wind-facing point and the ridge grid point, respectively. 预报冰厚 It is the predicted value of ice thickness at a large grid of 3km×3km.

[0018] Furthermore, the step (4) of correcting the predicted ice thickness of the windward point and the ridge grid point according to the wind direction is specifically as follows: for the windward point and the ridge grid point, the predicted ice thickness is corrected using the following formula, that is, the corrected predicted ice thickness value ICE of the windward point and the ridge grid point 迎风修正 and ICE 山脊修正 They are:

[0019]

[0020] ICE 迎风 ICE 山脊 are the ice thickness correction values ​​of the windward point and the ridge grid point, respectively, and k is the correction coefficient. The calculation formula is:

[0021] k=0.013α+0.5862

[0022] Where α∈[0°,90°] is the angle between the conductor and the wind direction.

[0023] The advantages of the present invention are:

[0024] 1. The present invention divides the 3km×3km grid into 100 300m×300m refined grids, and solves the problem that the current ice thickness prediction value cannot accurately reflect the ice thickness of the transmission line in the mountainous micro-topography without improving the prediction accuracy of meteorological elements;

[0025] 2. The present invention divides the micro-topography grid points in the mountainous area into four categories: high-altitude grid points, ridge grid points, windward grid points and windward grid points, and classifies and corrects the predicted value of ice thickness. The calculation workload is small, the result is accurate, and the needs of on-site work are met. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the classification of micro-topography refinement grid points in the mountainous area of ​​the present invention;

[0027] Figure 2 It is a schematic diagram of the ridge grid point determination in the present invention;

[0028] Figure 3 This is an ice thickness prediction map for the application case of the present invention;

[0029] Figure 4 Satellite imagery of the application case in the present invention;

[0030] Figure 5 The present invention is a flow chart of a method for finely predicting ice thickness of power transmission lines in mountainous micro-terrain. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention.

[0032] like Figure 5 As shown, the embodiment of the present invention provides a method for finely predicting ice thickness of transmission lines in mountainous micro-terrain, including the following steps:

[0033] Step P101: refine the 3km×3km ice thickness prediction grid of the mountain micro-topography into 300m×300m grids, and determine the category of each refined grid point.

[0034] Specifically, the refined grid points are divided into high-altitude grid points and low-altitude grid points according to whether their altitude is greater than 2000m; low-altitude grid points are divided into windward slope grid points and leeward slope grid points according to whether they are located on the windward slope; windward slope grid points are divided into ridge grid points and windward grid points according to whether they are located on the ridge line. In summary, the refined grid points are divided into four categories: high-altitude grid points, ridge grid points, windward grid points, and leeward grid points. The classification process is as follows: Figure 1 shown.

[0035] Among them, the low-altitude grid points are divided into windward slope grid points and leeward slope grid points according to whether they are located on the windward slope, specifically:

[0036] The slope aspect of a refined grid point is calculated using DEM data. If the slope aspect of the grid point is within the range of ±90° of the wind direction in the meteorological numerical model, the refined grid point is determined to be a windward slope grid point; otherwise, the refined grid point is determined to be a leeward slope grid point.

[0037] Among them, the windward slope grid points are divided into ridge grid points and windward grid points according to whether they are located on the ridge line, specifically:

[0038] Since the ridge line belongs to positive terrain, the positive terrain is obtained through DEM neighborhood analysis; the ridge line is equivalent to the watershed line and is the origin of the water flow. The water flow direction of these grid points only has the outflow direction but not the inflow direction, so the confluence accumulation is zero, so the DEM is filled and the flow direction flow is analyzed; the value of the flow accumulation of zero is extracted and intersected with the positive terrain to obtain the ridge line, and the windward slope grid points are divided into ridge grid points and windward grid points according to whether they are located on the ridge line. The specific judgment process is as follows Figure 2 shown.

[0039] Step P102: Correct the predicted value of ice thickness at high altitude grid points.

[0040] Specifically, the following formula is used to calculate the ice thickness at a certain high altitude grid point, where D 预报冰厚 is the predicted ice thickness at a 3km×3km grid, and A is the average altitude of the grid; ICE 高海拔 is the predicted value of ice thickness at the high altitude grid point, and B is the altitude of the high altitude grid point.

[0041]

[0042] For example, the predicted ice thickness value of a grid point in a 3km×3km area is 20mm, and the average altitude of the area is A (1500m). For the 100 300m×300m subdivided grid points in the area, assuming that the altitude of a grid point is B (2600m), the corrected ice thickness prediction value of the high-altitude grid point is 22.1mm after calculation.

[0043] Step P103: Correct the predicted ice thickness values ​​at the backwind points, the headwind points and the ridge grid points.

[0044] Specifically, in the case where the 3km×3km grid is subdivided into 100 300m×300m grids, the number of leeward grids is a, the number of windward grids is b, and the number of ridge grids is c. The following formula is used to calculate the corrected ice thickness value of the subdivided grids, where ICE is: 背风 ICE 迎风 ICE 山脊 They are the corrected values ​​of ice thickness at the backwind point, the wind-facing point and the ridge grid point:

[0045]

[0046] For example, the grid forecast ice thickness in a 3km×3km area is 20mm. Among the 100 grid points divided into 300m×300m, the number of leeward slope grid points a is 70, the number of windward slope grid points b is 20, and the number of ridge grid points c is 10. According to the above formula, the predicted ice thickness of the ridge grid points is 42.6mm, the predicted ice thickness of the leeward slope grid points is 12.7mm, and the predicted ice thickness of the windward slope grid points is 34.2mm.

[0047] Step P104: Correct the predicted ice thickness values ​​at the windward points and ridge grid points according to the wind direction.

[0048] Specifically, for windward points and ridge grid points, the correction factor k is used to correct the predicted ice thickness:

[0049]

[0050] k=0.013α+0.5862

[0051] Where k is the correction coefficient, α∈[0°,90°] is the angle between the conductor and the wind direction.

[0052] For example, the angle between the conductor of the above-mentioned wind-facing point and the wind direction is 45°, then k = 0.013×45+0.5862=1.17, and the predicted value of ice thickness at this grid point after correction is 34.2×1.17=40.1 mm.

[0053] Application example: In the analysis of a 220kV line tripping due to ice damage, the forecast data of the corresponding time of the ice cover forecast model is retrieved, such as Figure 3 The predicted ice thickness of the 3km×3km grid at the fault point is 12.4mm. This prediction is based on the ice coverage prediction of the 3km×3km grid. The ice thickness of the #1 to #10 towers of the line is 12.4mm.

[0054] Figure 4 This is a satellite image of towers #1-#10 of the line. The two towers #6-#7 belong to obvious mountainous micro-topography. The predicted value of ice thickness is corrected according to the technical solution of the present invention.

[0055] Among the 100 refined grid points, there are no high-altitude grid points, 59 leeward grid points, 36 windward grid points, and 5 ridge grid points. The predicted values ​​of ice thickness on the tower after correction are shown in Table 1 below.

[0056] Table 1

[0057] Tower number Wind-friendly features Back style Ridge Grid Corrected ice thickness (mm) 1 √ 7.2 2 √ 7.2 3 √ 7.2 4 √ 7.2 5 √ 7.2 6 √ 24.1 7 √ 19.3 8 √ 7.2 9 √ 7.2 10 √ 19.3

[0058] The operation and maintenance personnel investigated the on-site conductor icing situation and reported that the icing on the conductors near towers #6, #7 and #10 was significantly more serious than in other parts. It is estimated that the ice thickness of the #6-#7 conductors is about 20mm, which is consistent with the predicted ice thickness.

[0059] The present invention divides mountain micro-topography into two categories: high-altitude mountainous areas and low-altitude mountainous areas. For each type of micro-topography area, a quantitative correction model for ice thickness is established based on factors such as altitude, slope aspect, ridge line and saddle point. Based on the transmission line ice thickness model forecast product with a spatial resolution of 3km×3km in the micro-topography area, the 3km×3km grid points are evenly divided into 100 300m×300m refined grid points, and the ice thickness is calculated for each refined grid point to achieve high-precision transmission line ice thickness prediction of 300m×300m in the micro-topography area. Considering that the average span of 220kV and 500kV transmission lines in mountainous areas is about 300m, the present invention can realize the prediction of ice thickness at the segment level, improve the accuracy of ice thickness prediction of lines in micro-topography areas, and has the advantages of wide applicability and fast calculation speed.

[0060] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by technicians in this technical field within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A refined prediction method for ice thickness of transmission lines in mountainous micro-topography, characterized in that The steps include: (1) The 3 km × 3 km ice thickness prediction grid of the mountain micro-topography is refined into 300 m × 300 m grids, and the categories of each refined grid point are determined: the refined grid points are divided into four categories: high altitude grid points, ridge grid points, windward grid points, and windward grid points; (2) Correct the predicted ice thickness at high altitude grid points; (3) Correct the predicted ice thickness values ​​at the backwind points, the frontwind points and the ridge grid points; (4) The predicted ice thickness at the windward points and ridge grid points corrected according to the wind direction correction step (3); The step (2) of correcting the predicted value of ice thickness at a high altitude grid point is specifically as follows: the ice thickness at a certain high altitude grid point is calculated using the following formula, where D 预报冰厚 is the predicted ice thickness at a 3km×3km large grid, and A is the average altitude of the large grid; ICE 高海拔 is the predicted value of the corrected ice thickness at the high altitude grid point, and B is the altitude of the high altitude grid point: The step (3) of correcting the predicted ice thickness values ​​of the backwind points, the windward points and the ridge points is specifically as follows: in the 3km×3km grid points, 100 300m×300m grid points are divided, and the number of backwind points is a, the number of windward points is b, and the number of ridge points is c. The following formula is used to calculate the ice thickness correction value of the subdivided grid points: ICE 背风 ICE 迎风 ICE 山脊 are the corrected values ​​of ice thickness at the backwind point, the wind-facing point and the ridge grid point, respectively. 预报冰厚 It is the predicted value of ice thickness at a large grid of 3km×3km; The step (4) of correcting the predicted ice thickness values ​​of the windward points and the ridge grid points according to the wind direction is specifically as follows: for the windward points and the ridge grid points, the predicted ice thickness values ​​are corrected using the following formula, i.e., the corrected predicted ice thickness values ​​ICE of the windward points and the ridge grid points are: 迎风修正 and ICE 山脊修正 They are: ICE 迎风 ICE 山脊 are the ice thickness correction values ​​of the windward point and the ridge grid point, respectively, and k is the correction coefficient. The calculation formula is: k＝0.013α+0.5862 Where α∈[0°,90°] is the angle between the conductor and the wind direction.

2. The method for finely predicting ice thickness of transmission lines in mountainous micro-terrain as claimed in claim 1 is characterized by: The step (1) refines the 3km×3km ice thickness prediction grid of the mountain micro-topography into 300m×300m grids, and the step of determining the category of each refined grid point is specifically as follows: 1) according to whether the altitude of the refined grid point is greater than 2000m, it is divided into high-altitude grid points and low-altitude grid points; 2) for the low-altitude grid points, it is divided into windward slope grid points and leeward slope grid points according to whether they are located on the windward slope; (3) for the windward slope grid points, it is divided into ridge grid points and windward grid points according to whether they are located on the ridge line.

3. The method for finely predicting ice thickness of transmission lines in mountainous micro-terrain as claimed in claim 2 is characterized by: In the step (1), the low-altitude grid points are divided into windward slope grid points and leeward slope grid points according to whether they are located on the windward slope. Specifically, the slope direction of a certain refined grid point is calculated by using DEM data. If the slope direction of the grid point is within the range of ±90° of the wind direction in the meteorological numerical model, the refined grid point is determined to be a windward slope grid point; otherwise, the refined grid point is determined to be a leeward slope grid point.

4. The method for finely predicting ice thickness of transmission lines in mountainous micro-terrain as claimed in claim 2 is characterized by: In the step (1), the windward slope grid points are divided into ridge grid points and windward grid points according to whether they are located on the ridge line, specifically: 1) positive terrain is obtained through DEM neighborhood analysis; 2) the DEM is filled with depressions, and the flow direction flow is analyzed and obtained; 3) the value of the flow accumulation of zero is extracted and intersected with the positive terrain, that is, the ridge line is obtained, and the windward slope grid points are divided into ridge grid points and windward grid points according to whether they are located on the ridge line.

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