| Power System Relaying
Technologies: Synchronized
sampling, wide-area protection.
Description: Synchronized
phasor technology has been used primarily in Phasor Measurement Units
(PMUs); synchronized sampling technology has been recognized only
recently. The two technologies look much alike. The main difference is
in their focus: synchronized phasors are obtained by time stamping
calculated phasors obtained from an IED using GPS time reference;
synchronized sampling clocks in IEDs use the Pulse per Second (PPS)
time reference from the GPS receivers. The difference is in the
applications, synchronized samples allow for straightforward
differentiation of phase differences among channels, while determining
the same from scanned values may be quite involved. This prevents
scanned data from Remote Terminal Units (RTUs) of Supervisory Control
and Data Acquisition System (SCADA) to be easily utilized for fault
detection and classification, which require phase angle differentiation
among the three phases. Typical examples of synchronized sampling are
Digital Fault Recorders (DFRs), Digital Protective Relays (DPRs) and
Circuit Breaker Monitors (CBMs). Since synchronized sampling may be
used to calculate synchronized phasors, it may be considered a broader
concept than synchronized phasors.
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