B. Distribution Line Configuration The length of the distribution line was determined from the building size as shown in Fig. 1. The cross section was determined from the rated current, which is set to one and a half times as much as the maximum load current. Fig. 2 and Fig. 3 show the distribution line configurations of ac and dc system, respectively. The ac distribution voltage is AC 200 V, and the dc distribution voltage is DC±200 V. The dc voltage was determined from the dc voltages inside of air conditioners and refrigerators. The both systems have 20 residential houses, PV system (30 kW) and gas engine cogeneration (6.6 kW). It is assumed that PV output power can be