A power control apparatus according to the present disclosure includes a first interconnection relay and a second interconnection relay configured to interconnect or parallel off an inverter to or from a power grid, a reference potential relay configured to set a neutral phase of an independent operation output system to a reference potential, voltage sensors respectively installed between the first interconnection relay and the inverter and between the first interconnection relay and the power grid, voltage sensors respectively installed between the second interconnection relay and the inverter and between the second interconnection relay and the power grid, and a controller configured to turn the reference potential relay on to set the neutral phase to the reference potential and then to judge whether a state of each interconnection relay is normal on the basis of voltage values measured by the voltage sensors.
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