PURPOSE: To prevent the expansion of a power failure range due to a short- circuiting accident, etc., during changing-over by suppressing the loop power flow at the time of uninterruptible switching (loop change-over).
CONSTITUTION: This method is related to a system change-over method for changing-over the power supply system of an nuloaded sub-station 300 in uninterruptible state by an upper-level sub-station with a constitution of a plurality of buses in normal and spare system secondary sub stations 210 and 220 receiving power from a same power supply 101. When power supply systems are changed-over, transmission lines 401 and 402 existing at the power supply path of the load sub-station 300 and buses B12 and B21 and transformers Tr12 and Tr21 within the normal and spare system secondary sub-stations 210 and 220 are turned into exclusive use, thus separating them from other load systems and hence reducing phase difference of both power supplies when viewed from the load sub-station 300.
HIROSE FUMIHIKO
KOIDE TETSUYA
OKUMURA RYOHEI
TAWARA YUJI
NAKAYAMA KOICHI
NIPPON KOKAN KK