Abstract
Local DC distribution systems are designed, and the voltage drop and the distribution loss of which are evaluated. First, the DC system for heavily populated area is designed. Entire DC power is supplied from the conversion station located at the center of the service area through long-length, low-voltage distribution lines. 4 V maximum voltage drop is assumed and all line sizes and routings are determined. With this design, the daily energy loss of the DC system is calculated and it is shown that the total loss is almost the same as that for the traditional AC system. Though the large part of the loss consists of the transformers loss, the line loss for DC system is relatively large, especially in winter and summer. When connected with the photovoltaic generations, the current in the line decreases during the day. Then, both the voltage drop and the distribution loss decrease, especially for the DC system. If the house density is low, the line length becomes long and the voltage drop or distribution loss greatly increases. This will be solved by using large-sized wires but it leads to the increased cost. To avoid this, the reduction of the service area is effective.
