ELECTRIC-QUANTITY MEASURING APPARATUS AND ELECTRIC-QUANTITY MEASURING METHOD

A frequency-coefficient calculating unit calculates, as a frequency coefficient (fc), a value ((v21+v23)/(2v22)) obtained by normalizing, with a differential voltage instantaneous value (v22) at intermediate time, an average ((v21+v23)/2) of a sum (v21+v23) of differential voltage instantaneous values at time other than the intermediate time among differential voltage instantaneous value data (v21, v22, and v23) at three points representing an inter-distal end distance between voltage instantaneous value data at adjacent two points in voltage instantaneous value data at continuous at least four points extracted, out of voltage instantaneous value data obtained by sampling a measurement target alternating-current voltage at a predetermined data collection sampling frequency, at a gauge sampling frequency lower than the data collection sampling frequency and equal to or higher than a frequency of the alternating-current voltage.