This paper introduces a general implementation procedure for the measurement of harmonic phase angles using Power Quality (PQ) instruments. It is intended to fill this gap of the standards IEC 61000-4-7 and IEC 61000-4-30, particular with focus on grid measurements. While measurement for a single time instant is well defined, the paper focuses on methods to aggregate the harmonic phase angles in frequency and in time. The application of the methods is illustrated with different simulated and real data. Moreover, the accuracy of the harmonic phase angle measurement and procedures for implementation test are provided.