IEEE Power & Energy Magazine - May/June 2015 - 65

assets for dealing with the unfolding disaster in a timely and
efficient way. A possible set of smart intervention categories
is discussed below.
Distributed Energy Systems
and Decentralized Control

Decentralized energy systems with the large-scale deployment of distributed energy resources (and distributed generation and storage, in particular) and decentralized control can
play a key role in providing resilience to external shocks. In
fact, generating, storing, and controlling energy locally without the need for long transmission lines can make the network
less vulnerable to disasters and the response to an emergency
much faster and more efficient. Restoration times can also
be improved in smaller balancing areas. Localized protection and control assets, however, are required for achieving a
more resilient decentralized operation, which is to be considered in the wider picture of the smart grid evolution.
Microgrids

A microgrid can be simply defined as the subset of the grid
(typically at low-voltage and medium-voltage levels) that can
be islanded and still supply, in a controlled coordinated way,
all or part of its customers during emergencies, thus intrinsically enhancing system resilience. A microgrid requires the
smart technologies mentioned above to continue delivering
power to the customers in islanded mode. Several projects
worldwide aim to develop microgrids, as they are seen as one
of the most promising measures for enhancing future power
systems resilience during emergencies.
Adaptive Wide-Area Protection and Control Schemes

The majority of the existing wide-area protection and control
schemes are event based, which means that they will operate once the predetermined criteria are fulfilled. For instance,
they usually follow the logic of "if A AND B is true, then
apply C," where A and B are the electrical events that the
scheme is designed to provide protection against and C is
the protection and control actions to be implemented. These
schemes have been very effective in maintaining a high level
of security even during stressed conditions. However, the
increasing complexity of power systems and uncertainty
in the events that might occur call for the development of
smarter, more adaptive protection schemes capable of adapting to the evolving system conditions and dynamically determine the best course of actions based on the unfolding events,
and not on predetermined criteria. Nevertheless, adaptive
protections have not been widely implemented yet due to
concerns about the reliability of these schemes themselves.
It has to be kept in mind, though, that the use of these
wide-area protection schemes does not eliminate completely the need for transmission network expansion, which
might be ultimately needed for coping with future operational challenges. In the United Kingdom, for example, an
operational intertripping scheme is in place for controlling
may/june 2015

the Anglo-Scottish interconnector, but National Grid PLC
(within its "strategic wider works") plans to build submarine
high-voltage dc links for connecting Scotland to England, as
this is considered necessary for the resilience of the future
U.K. transmission network. This practical example points to
the direction that "hybrid" measure might be consider optimal to improve resilience.
Advanced Visualization
and Situation Awareness Systems

Electrical utilities often have a set of incomplete information on the state of their own network, resulting in delayed
and inefficient responses. The development of adequate situation awareness tools that enables the effective and timely
decision-making could thus play a key role in preserving
resilience during emergencies. For instance, user-friendly
visualization technologies including color contours, animated
arrows, dynamically sized pie-charts, and three-dimensional
representation of the power system could enable transmission and distribution operators to perform more effective system monitoring and develop adequate cognition of evolving
conditions during extreme events. In addition, the reliability
and functionality of the relevant communication and information systems is critical to enable an effective information
exchange and coordination between system operators and
field/repair crews. It can thus be seen that human resilience
also plays a key role in preserving power system resilience.
Disaster Response and Risk Management

These smart and operational measures can improve the
emergency and preparedness procedures that enhance
disaster response and risk management. This helps mitigate
resilience degradation during the event (i.e., R o - R pe, see
Figure 1), which is critically important in enabling fast
recovery and restoration.
This response of the system to a disaster is an additional
resilience feature that distinguishes it from reliability, as the
focus is not only on impact on customers (e.g., evaluating the
duration of interruptions or the energy not supplied) but also
on the infrastructure being able to rapidly and effectively
recover to its predisaster operational state. A resilient network should be able to achieve a resilience level that is close
or equal to R o (see Figure 1) as quickly as possible following
the disaster by possessing adequate operational and infrastructure resilience features. In this respect, recovering from
a state of degraded performance and resilience ( R pe, see Figure 1) requires an effective postdisaster restoration process.
This should describe how the system can "bounce back" to a
state similar to the predisaster functionality.
There are two aspects that drive the development of this
procedure: the time required to restore each of the damaged
components and the criticality of each component in restoring resilience. The former is strongly related to the infrastructure
resilience and depends on several factors, such as availability of
backup components, accessibility to the affected areas, and the
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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - May/June 2015