IEEE Power & Energy Magazine - May/June 2018 - 30

µPMUs provide voltage and current measurements at higher
resolution and precision to facilitate a level of visibility into the
distribution grid that is currently not achievable.

selection for electricity market participation on the demand
side. While the suite of applications is growing, the requirements for analytics around data quality, communication, and
computational power continue to be major challenges for industry
and academia.

high-resolution measurements collected by a few µPMus and
distinguish between different types of equipment failures. the
collected data can lead to the identification of anomalies not
yet significant enough to cause a fault or customer interruption
but, if not addressed, likely to cause failures in the near future.

Predictive Analytics

Example 4

descriptive analytics is tremendously useful for managing
the existing distribution grid. the input of high-fidelity data,
such as µPMu data, is an important leap forward. on the
other hand, grid modernization has made a significant push
toward predictive and prescriptive analytics.
solar power forecasting, for example, has long been hindered by a lack of measurements at the distribution grid level
and, more often than not, relies on either direct sensing of the
generator or a forecasting approach that may use weather sensors and capacity estimates per feeder. similar, and arguably
more challenging, forecasting needs now arise at the millisecond scale and transient level, e.g., with respect to the operation
of solar panel inverters, transformers, and capacitor banks.
µPMus and related data-driven techniques can help greatly in
such applications.
In this section, we discuss two predictive analytics examples based on real-world µPMu data. Both examples are
related to the monitoring and maintenance of grid equipment and assets. this is motivated by the fact that a typical
distribution feeder may have thousands of devices, such as
transformers, capacitor banks, fuses, relays, and switches. It
is too cost-inefficient to install a dedicated asset-monitoring
sensor on each device. Interestingly, it is possible to monitor a large number of grid assets using the synchronized and

a distribution feeder includes a three-phase switched capacitor bank rated at 900 kvar. the capacitor bank is switched
on and off by a vacuum switch. the timing of the switching is controlled by a volt-var controller. a transient limiting
inductors device is installed in series with each phase of the
switched-capacitor bank to limit transient currents during
switching events or faults. the capacitor bank is installed a
few miles away from the substation on a lateral.
however, its operation can be observed remotely using
a µPMu installed at the feeder head at the substation. a
switch-off event of the capacitor bank is captured and shown
in figure 4. first, using the voltage magnitude measurements, one can confirm that switching off the capacitor
results in a permanent drop in voltage, as one would expect
and as shown in figure 4(a). Importantly, there is also a
severe current overshoot on phase a and a severe current
undershoot on phase c during such a capacitor bank switchoff event, as shown in figure 4(b). We can conclude that the
capacitor bank is switched off at zero crossing of phase B.
Repeated current synchrophasor measurements on multiple days show a very similar switching-off signature. the
overshoot and undershoot on phases a and c last for about
200 ms (a relatively long time). It appears that the capacitor
bank is not initially de-energized on phases a and c at the
time of switching until several cycles later, as shown by the
current phase angle measurements in figure 4(c). this may
indicate some hardware or control malfunction, while the
large magnitude and the long duration of the current overshoot and undershoot could be a power quality concern
for customers. this type of event analysis allows proactive crew dispatch for repair or replacement with minimal
customer interruption.

Voltage Magnitude (V)

7,260
Feeder 1

7,240

2

7,220
7,200

3

Feeder 2

7,180

1

7,160
7,140

4

0

Example 5
1

2
Time (s)

3

4

figure 3. Four voltage transient events marked on synchronized voltage measurements at two feeders.
30

ieee power & energy magazine

a distribution substation transformer has an incipient failure not
yet detected. µPMus are installed in nonoptimal locations, i.e.,
with no primary intention to monitor the operation of the transformer. during a typical on-load tap changer (oltc) action
(commonly utilized for voltage regulation across the united
may/june 2018



Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - May/June 2018

Contents
IEEE Power & Energy Magazine - May/June 2018 - Cover1
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