  This letter proposes a new approach for online detection of low-quality
synchrophasor data under both normal and event conditions. The proposed
approach utilizes the features of synchrophasor data in time and frequency
domains to distinguish multiple regional PMU signals and detect low-quality
synchrophasor data. The proposed approach does not require any offline study
and it is more effective to detect low-quality data with apparently
indistinguishable profiles. Case studies from recorded synchrophasor
measurements verify the effectiveness of the proposed approach.
