ELECTRICAL DISTRIBUTION SYSTEM PLANNING

Abstract

An electric distribution system is an important link between the power transmission system and the consumer. Its function is to take power from the bulk or grid sub-stations and delivering it to the consumer. The effective-ness with which a distribution system fulfills this func-tion depends on the soundness of its planning. The distri-bution system consists of six main interrelated components, namely, subtransmission, distribution substations, primary feeders, distribution transformers, secondary distributors and consumer service lines. In planning a distribution system for a given load area, all the system components should be considered so that savings in one component will not be exceeded by a resulting increase in cost elsewhere in the system. In this dissertation, the various factors to be considered in distribution system planning and the approaches to the planning problem are briefly discussed. The study dwells at length on distribution sub-station planning. Methods of locating distribution sub-stations in sparse and dense load areas are presented. The need for selecting a basic scheme and physical layout of a particular substation to suit reliability requirements, local site conditions and economy is brought out. The main substation equipment, safety clearances and auxiliary (iv) facilities are discussed highlighting the necessity for selection of the various equipment to suit the type of physical layout adapted. A practical problem of expanding and reinfor-cing a typical existing distribution substation to meet increased load and reliability requirements has been presented. A three phased reinforcement is suggested giving the basic schemes and equipment requirements for each phase. Considering that the largest portion of power loss in a distribution system occurs in primary feeders, the methods of reducing power losses in high voltage pri-mary distribution feeders are presented.