Study And Application Of Integrated Evaluation Methods Of Distribution Systems

With the rapid development of power systems,the power system planning plays an important role at the development of power system as the key foundation of power system decision. As a crucial part of power syatem planning, the evaluation of power distribution grids,has been used for making a decision,optimizing the distribution of resources and promoting the rapid development of a power system.In connection with the evaluation of an existing high voltage grid,as the grid is not complicated and the involved data is easy to obtain, relevant load flow and short circuit calculation and qualitative analysis are used to find out the weaknesses and improvement measures of a high voltage power system. Also, a method of quasi-dynamic optimization ordering for high voltage substation/line planning projects is proposed based on the single project optimization ordering, with the research results of distribution network evaluation being made full use of and extraneous factors impacting on planning projects being considered. In the proposed method, the traditional optimization method of benefit-cost rate is employed. This method have been used by a municipal electric power supply bureau of china Southern Power grid. For the evaluation of an existing medium voltage power system,a contrastive analysis is performed to find out the difference between two typical distribution network evaluation methods in Zhejiang Power Grid and China Southern Power Grid in terms of an indicator system, evaluative standards, weights and differentiation . Furthermore,some corresponding opinions are recommended.Considering the grid features of a distribution grid under planning,load flow analysis, short circuit calculation and energy loss computation are employed to verify the planning grid. For the evaluation of a medium voltage planning grid,considering the features of uncertain loads and topological structure, some effectiveness indicators (such as the energy losses and reliability rate) are proposed to verify the planning effect by using some Guidelines.Considering the features of a medium voltage feeder under planning,an electric distribution network may be simply divided into several typical network configurations. In this paper, based on the fault-spreading- analyses–method, a simplified evaluation model of various typical configurations is presented. Moreover, a correction evaluation model is proposed based on the known reliability indexes of an existing network. Considering the features of high,middle and low voltage distribution network planning,the methods for estimating the energy loss rate are presented.Especially,regarding the complicated middle and low voltage distribution networks,a loss coefficient method and a factor correction method of allowable loss rate are proposed to overcome the problems of data deficiency of feeders and fuzzy load distribution information.Presently,estimation methods of energy loss and reliability for distribution network planning are applied into many engineering projects of China Southern Power Grid and State Grid Corp.