A power measurer measures, for each current transformer CT, electric energy supplied to equipment or electric energy supplied from the equipment based on a current measured by a current measurer and a voltage measured by a voltage measurer. A sign memory stores, for each current transformer CT, information indicating whether the electric energy measured by the power measurer when the current transformer CT is disposed in a correct direction on a power line shows a positive sign or a negative sign. A determiner determines that, when the sign stored in the sign memory differs from the sign of the electric energy measured by the power measurer, the current transformer CT is disposed in an incorrect direction on the power line.