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A digital phase meter (DPM) for power frequencies with a very low measurement uncertainty of 1 μrad was developed at Japan Electric Meters Inspection Corporation (JEMIC) to establish a power and energy calibration system. We also developed a phase meter calibrator (PMC) for calibrating the DPM. Since the DPM and PMC are synchronized with a single clock, the DPM can be calibrated by a very simple measurement method, which no longer requires extra standards. The DPM has been employed as an instrument for the primary standard of power and energy in Japan to achieve precise phase angle measurement. Since the error in the power measurement at power factor 0 is equal to the error in the phase angle measurement, we verified the performance of the DPM by calibrating a standard power meter using the power calibrators at JEMIC and Physikalische-Technische Bundesanstalt (PTB), and comparing the test results at power factor 0. According to the measurement, the phase angle difference between JEMIC and PTB is within 7 μrad. [ABSTRACT FROM AUTHOR]