| In this paper, methods of optimal substation positioning and optimal selection and location of switching devices in distribution power system are studied. Main works as following. 1. Method of optimal substation positioning in power network planningAs modern power system is becoming more highly complex and paying more attention on its performance as a whole, more reasonable power planning is required to achieve more secure and economic power network operation, and to ensure power network construction along a scientific and reasonable direction. With the development of computer technique, more methods appear in optimal planning of power network.The optimization of network configuration is the main content of power network planning. And location of substations will influence network structure. So in this paper optimal substation positioning is studied together with the network configuration optimization. A new method is proposed for those purposes and is realized by computer visual programming. Satisfactory results are obtained when applying the method to power network planning of one county in Henan province.In essence, optimal network planning is a cosmic, dynamic, nonlinear, mixed and integral planning. Because large system scale involved in and the consumed time for solutions are limited when applied to practical power system, and the difficulty to obtain the optimal solutions, it is required to simplify the model. In this article, after linearization, the original optimal model of network planning is simplified as a minimum cost and maximum flow model (MCMFM). The MCMFM is summarized as following. First, suppose a source point and a sink point. Second, draw a unilateral line from source point to every substation node. The line's capacity is set as corresponding substation's allowable load value and the line cost is set as the substation's unit load cost. Third, draw a unilateral line from every load node to the sink point. The line's capacity is the load value of the node and the cost is zero. Last, use the minimum cost and maximum flow method in graph theory to solve the problem. The result got is relatively accurate and the solving process is quite fast and simple.The problem of optimal substation position is finding the best geographical coordinates of substation to be built to optimize the objective function (e.g. annualsynthetical cost or power loss, etc.) with physical constraints, such as load demand, line's capacity, substation's capacity etc. As we know, it is difficult to get differential function of a nonlinear objective function, so for simplifying the problem, a layered optimal strategy for multi-constrained substation positioning is proposed. The inside arithmetic is for optimal network planning with given substation sites applying the minimum cost and maximum flow method. Based on the optimal network-planning arithmetic, the outside arithmetic is for the optimal coordinates of substation position by using one of the nonlinear optimization methods-direct optimization. Therefore, it can realize not only optimize substation position but also the network configuration.Though the method is not always to get the best solutions in the whole scope, it can always provide the secondary best solutions within certain range. Compared with the traditional location methods, it removes the people factors and ensures the result unification of optimal substation position and optimal network structure. So, it is simple and practical.2. Method of optimal selection and location of switching devices in distribution power systemDistribution automation is the inevitable result of technical advancement. It is impossible without any fault and blackout in power system, but it is absolutely possible to reduce the number and time of fault and restore the power supply quickly. The switchers can isolate the faulted branch, restrict the faulted scale and ensure the supply of non-interruptions such that the reliability of distribution power system is improved. At the same time, the switchers are...
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