A power supply system is structured, which has a server disposed so that it is capable of communicating through redundant communication media with a user terminal at a user site which is capable of receiving power from one power supply system selected by making a switchover among a plurality of power supply systems; the server collects information about abnormalities caused in the plurality of power supply systems through other redundant communication media from abnormality detectors disposed in a plurality of power generating plants, each of which is part of one of the plurality of power supply systems, and on a plurality of electric transmission/distribution lines, each of which is also part of one of the plurality of power supply systems; the server determines whether the power supply system from which the user is currently receiving power is normal or abnormal; if the power supply system is abnormal, the server sends, to the user terminal, information about normal power supply systems from which the user is able to receive power.