IEEE Power & Energy Magazine - July/August 2020 - 59

decentralization fosters the introduction of ICT-dependent
functions that use fewer closed and observable ICT infrastructures. This is particularly relevant for lower voltage
levels where dedicated communication connections to the
large number of components are not feasible. An operator
has good reason to trust a remotely controlled switch to act
as demanded, and a remotely controlled switch can perform
the requested action without intensive plausibility checks for
a closed SCADA system. When functions using wide and
local area networks via fiber optic, power line, or even wireless communication like WiMAX or 5G start to increasingly appear, it gets much harder to monitor and maintain
the resilience of the ICT system and subsequently the cyberphysical power system resilience.
Even if controllable generators, controllable loads, tap
changing transformers, and automated switches in the LV
grids were connected to a dedicated and sealed ICT infrastructure, the increased complexity of the system creates a
need for local intelligence. When the number of links and
entry points rises, the number of corrupted signals rises as
well and with it the need for local plausibility checks. The
more signals a system needs to work properly, the higher the
probability of losing signals. This requires strong and reliable
plausibility checks as well as a robust fallback configuration
of many components, ideally realized in a way that prevents
oscillation and cascading.

Cyberphysical Power System Resilience

systems were designed in the early 20th century, there were
no fast coordination mechanisms, so statistical diversity of
loads was implicitly guaranteed. However, simultaneity occurs
in cases where many customers turn on or off their appliances
triggered by an event. An example is the TV pickup phenomenon in the United Kingdom triggered by the final whistle of
a soccer match (2.8 GW of additional demand in the United
Kingdom alone after the penalties of the 1990 World Cup and
2.6 GW after England versus Brazil in 2002).
More digitalization by the automation of processes at prosumer
premises and other generation sites within the distribution system
brings flexibility into the system that is necessary with large
penetrations of PV and wind energy resources. However, these
inverter-based resources can react simultaneously to discrete
steps of market prices within seconds. This behavior is already
well known for generation scheduling based on hourly spot market prices. After each time block, the ramping-up and rampingdown of generators is visible in frequency time-series measurements and brings significant disturbance to frequency stability.
Today, dedicated cyberattacks can cause high simultaneities in power demand. Furthermore, cyberattacks that do not
specifically target the electric power system might still cause
massive changes in load, which can affect system performance.
Historically, the reliability and resilience of power systems have depended heavily on hardware oversizing and
physical redundancy. With the changing energy landscape
and the trend for digitalization and decentralization, there
is the opportunity as well as the necessity to augment the
traditional reliability approaches with increased awareness, smart control, and local backup strategies. Figure 6

july/august 2020

Safety Margin

Minimal Hardware

Normal
Requirements

System Performance

Power system operational dependence on ICT requires the
combined assessment of ICT resilience and power system
resilience, called cyberphysical
power system resilience. Separate
assessments of ICT or power system performance are not enough
Hardware
Smart
More Smart
Maliciously Smart Fallback
Redundancy
Flexibility
Flexibility
Controlled After Detected
when the interconnected system
Smart
Attack
performance becomes of interest.
Flexibility
There is a discussion about possible threats. In Ukraine, the power
system suffered from a coordinated
cyberattack in 2015 that led to a
widespread blackout. The attackers
were able to infiltrate the SCADA
system to control switches, disable and destroy communication
infrastructure, and slow down restoration by damaging the backup
power supplies.
The ICT system that is explicitly used to provide beneficial services for the power system itself
Past
Present
Future?
could be corrupted, and the genFuture After Cyberattack?
eral development toward the Internet of Things comes with the risk
of increased simultaneity of load figure 6. The range of possible overall resilience in future power systems. Hardevents. When ele c t r ic p owe r ware: gray; smart flexibility: green; safety margins: orange; abused flexibility: red.

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IEEE Power & Energy Magazine - July/August 2020

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