PROBLEM TO BE SOLVED: To recover the function of an original distribution system at an early stage, by surely separately specifying the abnormalities of automatic voltage regulators and quickly separating the automatic voltage regulator with the abnormality from a distribution line. SOLUTION: The representative configuration of an abnormality detector 150 has a first current transformer 152 detecting a current at a power-supply side terminal, in a second switching section 144 of a switching unit 140; a second current transformer 154 detecting the current at a load-side terminal in a third switching section 146; and a difference-detecting section 156 for comparing the current value detected by the first current transformer, with the current value detected by the second current transformer and setting a changeover flag, when there is a difference which is larger than a fixed value and a switching operating section 158 closing a first switching section, opening the second switching section and the third switching section and separating the automatic voltage regulator 130 from the distribution line after the changeover flag is set. COPYRIGHT: (C)2009,JPO&INPIT