Quasi-synchronous sampling algorithm and its applications I. Principle and measurement of `average´ values of periodic signal

For Pt. II, see ibid., pp. 94-98 (1993). The authors describe the principle and applications of an algorithm, i.e., shape of window, for the precise measurement of various quantities of periodic signals in power networks. Synchronous sampling is a common method with good performance. However, due to imperfect synchronization, or for a multiple frequency signal or a signal containing interharmonics, undesirable asynchronous deviations between the sampling and some components of the signal may exist. In these cases, three kinds of possibly large leakage or truncation errors mainly caused by the limited window width may occur: long-, medium- and short-range leakage. If in cases of imperfect synchronization the quasi-synchronous algorithm or a special window referred to as the quasi-synchronous window is used one can more effectively reduce the leakage errors and more accurate results can be obtained than with the traditional algorithm. The principle and its application for the precise measurement of average values are discussed in detail