Route Planning For High Voltage Overhead Transmission Lines

The primary work of designing high-voltage overhead transmission lines is path planning. Currently, path planning method has been developed from the computer aided stage to the computer automatic path planning stage. The automatic path planning method is based on single resolution cost surface model to plan path. When use the method to plan path in continuous space, the first step is to rasterize the continuous space into cells with specific resolution. Each cell is valued in the light of the cost or impedance for crossing it, and they constitute the cost surface model. The second step is to take use of the shortest path algorithm.In the process of path planning, the cost surface is seen as a weighted network graph comprised of nodes and edges.The last step is to get a group of cells with the lowest cost from the cost surface, and these cells constitute the optimal paths. As the cost surface model adopted by the method is single-resolution, it cann't effectively express topographical variation and features edge, which leads to the low positional accuracy of the planned path, edge effect of features, low computational efficiency and a large number of redundant cells. When allocate weight for each factor, this method adopts subjective weighting method, which leads to weights susceptible to subjective preference. As large work area for transmission line path planning, the method will meet problems such as difficult to collect detail data, low reliability of path planned, etc. Confined to the range of the neighborhood, the planned path by this method is jagged, which means that the method can not guarantee the rationality of the planned path. As the method put no consideration on the validation of the path planning results by tower spotting, it can not guarantee the feasibility of the planned path.In order to solve these problems, the first step is to screen factors that affect the path planning of transmission lines, establish evaluation criteria system; the second is to research weighting methods, determine the weight of each criterion; the last is to research modelling method for cost surface model, path planning algorithms and tower spotting algorithms, use proposed path planning algorithm to calculate least-cost path on cost surface model and use tower spotting algorithm to validate the planned path. When validation fails, get regions where can not errect towers, and consider the regions as a factor, re-planning the path.In this paper, the main research work and innovation are as follows:(1) In view of problems in single resolution cost surface model, this paper researches the modelling methods of cost surface model, proposes a modelling method for variable resolution cost surface model based on the irregular mosaic and quadtree thought, and then design neighborhood patterns and calculation methods of the neighborhood moving cost for different neighborhood pattern. The proposed modelling method regards the quadtree segmentation method as the basic space partition method of cost surface model, regard the precision of the cells as the termination condition of the segmentation, divide cells in regions with dramatic terrain change and regions with dense features, to get a mosaic cost surface model which expresses the terrain and features'edge in higher precision, that is, a variable resolution cost surface model. Experimental results show that:variable resolution cost surface model can be effectively applied to a variety of geographical environment; it is better than single resolution cost surface model, it can effectively express topographical variation and features'edge, inhibit the generation of edge effect, improve the positional accuracy of the planned path, reduce data redundancy and improve computational efficiency.(2) The transmission lines path planning method is a spatial multicriteria decision making method. The importance of different factors for path planning is different. In order to weight factors, this paper analyse variety factors that influence transmission lines path planning, establish evaluation criteria system, analyse current weighting methods and propose a new combination weighting method based on principle component analysis (PCA) and analytical hierarchy process (AHP). The proposed method first builds a judgement matrix combining subjective information and objective information, then use the judgement matrix to calculate single priority vector, finally,calculate global priority vector and get each factor's weight. In this way, we can get weights containing objective and subjective information without combination of subjective and objective weights. Experimental results show that the proposed combination weighting method based on PCA and AHP solve the problem of determining the proportion of subjective weights and objective weights.(3) There are problems in traditional path planning algorithms, such as difficult to collect detail data, low reliability and low rationality of path planned, path distortion, etc. To solve these problem, propose a new multi-phase transmission line path planning algorithm. The algorithm is divided into corridor analysis, path planning and path distortion correction three stages. This algorithm adopts variable resolution cost surface which avoids the problmes of data redundancy, edge effects and so on. This algorithm use Dijkstra algorithm for corridor analysis, use A* algorithm adopting precomputation heuristics for path planning, and use proposed path distortion correction algorithm to correct distorted path. Experimental resutls show that the multi-phase transmission line path planning algorithm is effective, it gives adequate consideration in variety factors; the proposed algorithm is better than EPRI-GTC method in three aspects:efficiency, routing results and inhibitional effect on edge effect; the path distortion correction algorithm is better than traditional line simplification algorithm, Douglas-Peucker algorithm for example, it can correct the path distortion effectively, improve the rationality of the planned path; the precomputation heuristic method has higher admissibility, efficiency than traditional heuristic method, improve the reliability of results..(4) The traditional tower spotting algorithm can not interfere with the process of determining the location of each tower. To solve this problem, research transmission lines operating environment and stress sag analysis of wires, analyse various constraints in the progress of tower spotting, determine the basic equation of dynamic programming for tower spotting by studying dynamic programming and propose a tower spotting algorithm considering manual tower spotting knowledge. The algorithm sets no tower district (point) and compulsory towering district (point) as the constraint conditions. Experimental results show that:the proposed tower spotting algorithm can use tower spotting knowledge to intervene and guide the spotting progress. As current path planning method can not validate the planned path,propose a mehtod that combining the path planning method and the tower spotting method. Experimental results show that:the path planned by this method can pass the tower spotting validation, the method improve the feasibility of the path; the method can get multiple paths, which can meet different purpose; the method can get paths which are better than the artificial lines.