IEEE Power & Energy Magazine - May/June 2015 - 64

A disaster, which usually includes a blackout,
refers to severe and rapidly changing circumstances possibly
never before experienced.

and operational measures. Hardening measures are denoted
as infrastructure reinforcement actions for making the power
system less susceptible to extreme events. In contrast, operational measures refer to "smart" control-based actions taken
to provide the assets with control capability and resources
to effectively deal with the emergency as it unfolds. In particular, the goal of the operational measures is to make the
system "bend," rather than "break," in the face of a disaster.
A cost versus effectiveness evaluation of these measures
can provide the most suitable road map for improving power
systems resilience. The costs of these resilience actions
include capital, operational, and maintenance. Figure 6 illustrates conceptually how hardening measures (also depending on the resilience metric used) might be more effective
than operational ones, but they are also likely to come at a
higher cost. A hybrid approach that allows the development
of a stronger and bigger, but also smarter at the same time,
system might offer the capability to build a more resilient
power infrastructure while optimizing the investment in the
resilience enhancement measures.

Making the Grid Stronger and Bigger
Hardening measures may refer to topology and structural
changes to make the network less vulnerable to severe events.
Table 2 shows examples of these measures, some of which
focus on dealing with extreme weather events. These constitute one of the main threats of power systems resilience,
as discussed earlier, and the uncertainty about the implications of climate change is likely to increase the importance
of weather events within the resilience debate.
Moving transmission and distribution lines underground
is considered one of the most effective measures for reducing the vulnerability to wind damage, lightning, and vegetation contact. However, the cost associated with converting
overhead systems to underground may make the widespread
table 2. Examples of network
and component hardening measures.
-Moving distribution and transmission lines underground
-Upgrading poles and structures with stronger, more robust
materials
-Elevating substations
-Relocating facilities to areas less prone to extreme weather
-Rerouting transmission lines to areas less affected by
weather
-Redundant transmission routes

64

ieee power & energy magazine

use of this measure prohibitive. The cost of burying overhead
wires ranges from US$500,000 to US$2 million per mile. An
additional challenge lies in the restoration time of the buried
cables, which is significantly higher compared to overhead
lines. This is because of the complicated nature of these systems and the inability of the repair crews to visually detect
damaged components. As mentioned earlier, this action may
actually have controversial effects on system resilience, as it
enhances the robustness of the network, on the one hand, but
it affects the response and restoration times following a disaster, on the other hand. Targeted or selective undergrounding
of overhead lines could thus be a more viable solution than
a total conversion, following a proper risk and cost/benefit
analysis. Advanced condition monitoring and fault detections techniques would also help tackle these challenges.
Upgrading the components with stronger materials constitute a further primary hardening strategy aimed at making
the components more robust to extreme weather phenomena,
such as severe winds. For distribution networks, this usually
involves the conversion of wooden poles to concrete, steel,
or any other composite material. For transmission networks,
there are several approaches under consideration worldwide,
including design and material upgrades. In the United Kingdom, for example, National Grid PLC already approved a project of US$1.6 billion for replacing the traditional steel towers
with T-pylons and underground cables while using the existing
rights of way in the southwest of England. The T-pylons are
shorter than traditional towers, have less impact on the environment, and, more importantly, are considered more robust.
Elevating substations, relocating facilities, or rerouting
transmission lines to areas less prone to extreme weather
help provide protection against flood damage and any other
type of damage caused by weather events, for instance,
tower collapses due to extreme winds and snowfalls. Additional transmission lines help increase the transmission network capacity, and they also provide operational flexibility,
as they offer the ability to bypass damaged lines, which contributes to the prevention of cascading failures.

Making the Grid Smarter
As mentioned previously, the term "smart" here refers to a
broad set of operational actions that can be taken to improve
the observability, controllability, and operational flexibility
of a power system, particularly in response to an extreme
event. This is critical in building resilience as it provides the
system (and system operators) with monitoring and control
may/june 2015



Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - May/June 2015

IEEE Power & Energy Magazine - May/June 2015 - Cover1
IEEE Power & Energy Magazine - May/June 2015 - Cover2
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IEEE Power & Energy Magazine - May/June 2015 - Cover3
IEEE Power & Energy Magazine - May/June 2015 - Cover4
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