One of a plurality of switches constituting a power system is set as a perceived switch, and n optional switches Bk (k=1 to n) in the on state among the other switches are changed to the off state, and n loop networks including the perceived switch are created, and each switch Ck (k=1 to n) constituting the loop networks is changed from the off state to the on state so as to create a plurality of network configuration candidates, and a power network configuration is decided on the basis of the plurality of network configuration candidates.