IEEE Power & Energy Magazine - January/February 2022 - 71

network to transport the PMU data stream of 30 to 60 frames/s
back to a substation for processing. For returned FCP tripping
commands, the controller publishes high-speed tripping
commands using the International Electrotechnical Commission
61850 Generic Object-Oriented Substation Event
(GOOSE) message packet specification. Fiber-optic connections
are installed in the substation to connect PMU-enabled
feeder relays to the PDC. Fibers along distribution circuit
paths may be available in place of radio paths in selected
service areas with high load densities.
FCP requires robust communication links that provide consistently
high data rates and low packet loss rates. Recent FCP
deployments use wideband Ethernet mesh, point-to-point, and
point-to-multipoint radio systems with repeaters. These radio
networks operate in the U.S. Federal Communication Commission-allocated
2.4- and 5.8-GHz unlicensed bands and can
transport synchrophasor streams with a latency, or time delay,
shorter than 50 ms. High-gain directional antennas boost the
signal strength and signal-to-noise ratio for penetrating foliage
and other environmental obstacles. Omnidirectional antennas
are employed where directionality is not required, due to their
ease of installation and use.
Figure 5 also shows how the high-speed radio communication
for PMU data and tripping is overlaid on SDG&E's
legacy wide-area and lower-speed distribution SCADA radio
system so that both networks can simultaneously operate as
advanced high-speed data collection and communication are
being deployed across the company's distribution system. The
lower-right portion shows a substation-based communication
hub tied to FCP controller system components, as explained
in the following. The substation hub communicates with circuit
control devices over high-speed Ethernet radio, shown as
the advanced communication system. Circuit synchrophasor
measurements and FCP system data are transferred to control
centers via a backhaul connection from a substation through
the wide area network to control centers. The traditional SCADA
communication system at the lower right includes a lowerspeed,
wide-area radio system exchanging data with circuit
devices across the service area every few seconds. The traditional
and advanced communication paths can be overlaid,
even on a single circuit.
We have pointed out that SDG&E is deploying privately
owned LTE cellular radio systems for a variety of grid
monitoring and control applications. New FCP deployments
operate over this expanding communication network. This
commercial off-the-shelf solution features flexible network
routing and the ability to integrate overlapping zones of coverage
between geographical areas for improved reliability.
The LTE solution decreases the cost of FCP deployment and
improves cybersecurity management.
Substation Processing Array
At the substation terminating each FCP-equipped circuit,
the high-speed data radio system host transceiver node is
combined on a rack with a PDC, FCP-programmed automajanuary/february
2022
tion controller, Ethernet switch, and GPS receiver for precise
system measurement and event timing (Figure 6). In newer
deployments, PDC and FCP functions are combined in a
next-generation automation controller.
Figure 7 displays the overall interconnection of components
for the FCP system. Every circuit IED installation
communicates with a host radio transceiver node in a substation,
as in Figure 5. The radio node exchanges Ethernet data
packets with the PDC and Ethernet network with a real-time
scheme automation controller, substation relay PMU, and
SCADA communication interface. In some installations, the
scheme controller directly communicates with the distribution
SCADA system, performing its own SCADA remote
terminal unit function. In some FCP installations, the PDC
concentrates and streams the entire circuit PMU data array
from across the circuit over a wideband backhaul channel
to a wide area network data center server (Figure 5). These
full PMU measurement records are available to engineers
for near-real-time circuit observation, event analysis, and
archiving as well as the development of other distribution
PMU applications, such as circuit voltage and current profile
monitoring.
Scheme Operation
The controller receives a new set of phasor frames from
across a monitored circuit 30 or 60 times/s. With each new
figure 6. The FCP substation IEDs. (Source: SDG&E.)
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