Abstract
With the increasing use of electricity in the home and information technology oriented society in recent years，there are various electric appliances being implemented in the home. Therefore to design an economical and safe electrical wiring system it is necessary to fully understand the introduction of future electrical appliances，and understand their background for usage. Especially in recent years with the increase in living standards，in both houses and collective housing alike，we see an increase in the number of home electrical appliances and high capacity appliances in line with an improvement of home living. For this reason in order to meet the increasing demand for electricity year by year，it is important to proceed carefully with electrical wiring design. Especially，electric equipment design of medium and high-rise apartments with long durability must be done not by only considering the maximum power demand of each residence's present state，but also consider the future electric power demand trend to correspond to durability of the building. Hence，the collective analysis of the electric power load data based on the long-term view is indispensable to the main line design. To find the progress of each residence's main power line demand factor in collective housing，every several years the Urban Renaissance Agency （former Urban Devlopment Corporation） executes the measurement of the main line current. In this paper we have especially studied 10 main lines which are measured every 5 years to clarify their demand factor progress and its main cause.
