An evaluating hierarchy for distribution network based on fuzzy evaluation

To solve the problem of lacking of effective quantitative evaluation methods to the connection modes of distribution network, a comprehensive evaluating hierarchy is introduced in this paper. Security, reliability, economic profit, supply capability and derivative capability are included in this hierarchy. Maximal short circuit current, maximal voltage drop, voltage shift, average service availability index (ASAI), system average interruption duration index (SAIDI) and annual cost for unit load are selected as evaluating indices. Functions of fuzzy membership grade are constructed according to the above indices. Satisfaction degree of each index of a certain connection mode is then evaluated quantitatively by these functions. Weighing coefficients of each index are set according to the certain phase of the local distribution network. The final degree, or comprehensive satisfaction degree, is determined by weighted average of each index and is used to evaluate the certain connection mode. The method can be used not only in comparing the planning network with the current one but also in evaluating the planning alternatives. The 10kV distribution network planning of a district in Shanghai, China is selected as an actual example, in which several planning alternatives are evaluated based on this method. The results of the example show that the method proposed in this paper can not only evaluate the connection modes quantitatively in an effective way, but also fully reflect the key elements influencing the characteristics of network planning.