APPLICATION OF LOW VOLTAGE DC-DISTRIBUTION SYSTEM - A TECHNO- ECONOMICAL STUDY

Today’s electricity distribution networks construct mainly of the three-phase AC-systems. Consumer voltage in traditional distribution system is 230/400 V and the nominal frequency in Europe is 50 Hz. The European Union (EU) low voltage directive (LVD 72/23/EEC) [1] defines the boundaries for the low voltage (LV) levels used in public distribution systems. According to the directive any electrical equipment designed to be used with a voltage rating between 50-1000 V AC and between 75-1500 V DC is a low voltage instrument. The utilization of the 1 kV AC-distribution system takes full advantage of the LVD 73/23/EEC directive’s AC-definition. However, the DC voltage rating is still unexploited in public distribution systems. As the weight of cost efficiency and reliability requirements of distribution networks are expected to increase in the future, with the utilization of distributed generation, there will be demand for novel distribution techniques. The utilisation of the LV-DCdistribution opens new possibilities for network development. In this paper, the basic concepts and the techno-economical potential of the LV-DC-systems are discussed. Also aspects of developing required power electronic equipment for LV-DC-systems are introduced.