A voltage/current verifier (17e) computes, for each phase, a phase difference between phase voltage and phase current from the phase of phase voltage and the phase of phase current computed for each phase by a phase acquirer (17d), and determines conformity if all of the computed phase differences are within a preset range. A current/current verifier (17f) computes phase differences between phase currents from the phase of phase current computed for each phase by the phase acquirer (17d), and determines conformity if all of the computed phase differences are within 180°. A reporting device reports that a current transformer is incorrectly placed on a power line unless both the voltage/current verifier (17e) and the current/current verifier (17f) do not determine conformity.