Synchrophasor time skew: Formulation, detection and correction

The most critical part of the synchrophasor technology is the availability of accurate UTC time. Usually an external GPS clock device feeds PMU with 1 pulse per second time signals. During the second, PMU´s internal clock keeps the pace until the next time signal arrives. Because of various reasons, time skews have been observed in some real life synchrophasor data. Two fundamental types of time skews are identified in this paper. Synchrophasor time skew problem is fundamentally different from that in SCADA system, because time shift is translated into error in phase angle measurements and subsequent errors in frequency and rate of change of frequency measurements. Algorithms are developed to automatically detect time skews online and to estimate the time errors. A correction method is also provided. Both simulated data and real life data are used to verify that the proposed methods are effective and accurate.