JPH05344663

PURPOSE:To shorten a power interruption time as much as possible when a power supply source is switched in a power distribution system for supplying power from a plurality of power sources. CONSTITUTION:Couplers 1, controllers 2a, 2b are mounted in substations 3a and 3b, and couplers 4, and controllers 5a, 5b, 5t are respectively mounted in switches Sa, Sb, St. The couplers 1, 4 are all coupled among the same phases of power sources, and a carrier signal synchronized with the power source is injected or extracted by the coupler. When the controller 2a confirms that a preparation for switching the controllers 5a, 5t is completed, it sends a switching designation signal. The controller 5a opens the switch Sa when the designation signal is finished at a voltage '0' point where a predetermined period of a power source frequency is finished. The controller 5t closes the switch St at a slight delay therefrom. As a result, power is supplied from the substation 3b to a zone A2 to complete the switching.