An analog unit having a multiple-channel configuration among analog units included in a sequencer system is such that an AC signal as a measurement target, which is captured by a CT sensor, can be directly input to each of a plurality of channels, and the analog unit includes a setting unit that sets, in an internal memory, an abnormality-determination peak current value and an abnormal peak current duration, which are applied to the AC signal as a measurement target, for each of the channels, and a detecting unit that, when the AC signal as a measurement target includes an AC signal that maintains a state where a peak value exceeds the abnormality-determination peak current value for the abnormal peak current duration, detects generation of an abnormal alternating current in each of the channels.