IEEE Power & Energy Magazine - September/October 2015 - 21

values has also made possible to integrate direct measurements
into energy management system (emss) to enhance supervisory control and data acquisition based state estimation through
the deployment of linear state estimation.
benefits already realized by transmission operators asset
owners using this technology include
✔ observing the dynamic performance of renewable
generation
✔ a quicker line restoration
✔ faster system restoration during weather events
✔ the assessment of transformer health
✔ the monitoring of geomagnetically induced currents.
with more than 600 PmUs installed throughout the wecc
and more to come, synchronized measurement technology will
take an ever-increasing role in grid reliability. as users gain
experience with the technology and tools, new applications will
be identified.
benefits of deployed synchrophasor applications throughout the wecc region (see Figure 2) can be summarized
as follows.
✔ Data analysis of system events: significant benefits have
been achieved with the installed systems.
✔ System modeling: more accurate models (particularly
dynamic) have provided significant benefits to operations
and system planning under complex grid conditions.
✔ Visualization, situational awareness, and restoration: the tracking of phenomena such as voltage, angle, frequency instability, angle pairs across two geographically diverse interconnected systems, thermal

overloads, and low-frequency oscillations (requiring
high reporting rates) assist with system reliability, including the prevention of cascading outages and minimization of their impact, as well as faster restoration.
✔ Market operations: For example, an energy imbalance market (eim) and, more precisely, a congestion
management platform provide the potential for realizing large financial benefits.
some of the real-time benefits already observed are
described in more detail below.

Postevent Analysis
in mid-afternoon on 8 september 2011, a large power outage occurred in parts of the wecc affecting 7 million
people. the entire event unfolded in about 11 min and
included dozens of switching actions clustered at four
stages of the event. time-synchronized wide-area measurements from PmUs were instrumental in reconstructing the sequence of events, which is essential
in determining causal relationship between switching
actions. reconstructing the sequence of events took a
few hours in contrast to months of extensive review of
sequential event recordings after the 14 august 2003 outage, where no PmU data was available.
Figure 3 is one feature of a production-grade tool used for
postevent analysis. in late spring of 2013, a sudden loss of
the dc intertie and immediate automated system adjustments
such as remedial actions schemes resulted in some voltage
and damping oscillations.

Oscillation Modes

"F" Hz Oscillation with % Damping

figure 3. A ring down analysis.
september/october 2015

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