抄録
The electric power distribution systems in densely-populated areas have been gradually replaced from 6kV-class systems to 20kV-class ones. It is likely that the 20kV-class systems become more common because the systems are more suitable to supply power in the cities, especially when the load demand become heavier in the future. But, in order for the 20kV-class systems to be really promoted, the reduction of the size and the cost of the 20kV-class equipments are crucial.
Including this issue, we describe the problems and solutions for 20kV-class systems promotion.
