Patent ID: 7006935

Claim:
A synchronous vector measuring device comprising: a voltage measuring part that measures the voltage of an electric power system in a period equal to ¼N (N being a positive integer) of one period of a reference wave; a voltage root-mean-square value calculation part that calculates, at each of timings at which said voltage is measured, a voltage root-mean-square value at a specific timing from said voltages measured at past 4N timings including said specific timing; and an absolute phase angle calculation part that calculates an absolute phase angle of a synchronous vector at each of said timings according to the following expression β = cos - 1 ⁢ { v re 2 ⁢ V } (where β is the absolute phase angle, v re is the voltage measured at the specific timing, and V is the voltage root-mean-square value calculated at the specific timing).