Invited PaperA New Technique For Design Of Layout ForLooped Distribution Systems

An algorithm based on evolution principles is proposed for the design of layout of looped networks on rectilinear grids. The technique is similar in concept to genetic algorithms and evolution strategies which operate iteratively on a population of solutions to produce progressively better solutions. A key feature of the technique is a new solution coding scheme which overcomes some of the difficulties associated with the generation of infeasible solutions. This solution coding scheme uses continuous numbers on a [0-1] interval to represent the preference for links in a layout. The algorithm then finds a threshold value that selects the minimal number of links that will produce a feasible looped network. The method is demonstrated by application to an example problem. 1 Scope of the Research Considerable research has been done in recent years on methods to determine optimal layout geometry for branched water and natural gas distribution systems (Cembrowicz, 1992; Davidson and Coulter, 1991a; 1991b; Walters and Lohbeck, 1993). However, little work has been directed towards the development of methods for determining the optimal geometry of looped systems. This paper describes research concerned specifically with the issue of layout geometry of looped distribution systems. It should be noted that the focus of this research on the issue of layout geometry is based upon the need to develop a technique which is able to generate 'optimal' layouts which can then be modified to accommodate the related issues of optimal component sizing, reliability and operating costs. Due to the complexity of the layout problem, particularly in terms of the looping requirements which are a key feature of the problem, a number of simplifying assumptions have to be made. The simplified problem consists of determining the optimal geometry of single source rectilinear distribution systems under the constraint that the network layouts must remain contiguous in the event of any single link failing. Three additional assumptions have been made as follows: Transactions on Ecology and the Environment vol 7, © 1994 WIT Press, www.witpress.com, ISSN 1743-3541