IEEE Power & Energy Magazine - May/June 2017 - 66

Challenges at Distribution Systems
Distribution systems face many challenges due to the introduction of new agents (e.g., distributed energy resources),
enablers (e.g., remote monitoring), and requirements (e.g.,
better reliability standards, new pricing alternatives, and
energy decarbonization). This new framework increases the
need for new attributes and technical solutions at the distribution level. One of these attributes is system resilience,
which is the capability of the system to react, resist, and
recover under low-probability, high-consequence events,
such as earthquakes and floods. Compared with the other
segments of the electricity supply chain, recovery times at
the distribution system are longer than those for transmission and generation.
After the Chilean earthquake of 2010, the Chilean Central Interconnected System, which provides electricity to
over 93% of the population, suffered an immediate loss of
4,522 MW (the peak demand of the system was 6,145 MW).
A total of 693 MW of existing power plants (6.1% of the
installed generating capacity) was forced out of service for
repairs. Sufficient energy supply remained to serve load but
operated with an N-0 security condition in several places.
Most of the main grid level was recovered within a few hours

of the event. Two electrical islands operated, with the central
part of the country separated from the south due to damage
at some substations and isolated problems in transmission
structures. Two days later, the two islands were interconnected. In contrast, there was major damage at the distribution level. Although repairs were made, it took weeks to
recover supply at the end user level. For instance, coastal
networks were completely destroyed due to the resulting tsunami after the earthquake.
This experience clearly shows that major changes are
required at the distribution system level, and technological
and social tools should be used to increase the capability of
distribution systems to react/resist/recover under high-impact
events. In this context, lessons from microgrids and community
participation are key tools in providing a resilient feature for
smart grids (i.e., resilient smart grids). There have been several
experiences of microgrid development for remote locations
that identify the resilience characteristic as a major challenge,
as shown in Figure 1.

Resilience in Microgrids

Microgrids are planned and operated to account for expected
system states (i.e., the amount of charging in the battery storage system) and to deal with
uncontrollable disturbances
(i.e., intermittency in the
renewable energy sources
and load changes). If an
Social
unexpected system disturbance occurs, the microgrid
reacts to maintain grid reliCultural Heritage
ability by keeping voltage
magnitude and frequency at
Lack of Human Capital
Development
predisturbance conditions
Migration
(these variables provide a
External Actors
Local Organization
measure of security and
adequacy). Once the disPa
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tri
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aging the resources returns
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to standard procedures.
i
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Water Bus and
s
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High-impact, low-probScarcity De
Resilience
Dispatch + Reservers =
ability events could evenf(Uncertainty)
tually collapse a particular
Land Use
Local
microgrid. A microgrid
Communications
Conditions
Infrastructure
could potentially have the
(Weather)
Wildlife
capability to recover quV and F Control
ickly and prioritize which
Dispersion
load to connect (i.e., critical
Other Impacts
Existing Technologies
loads) if full recovery is
(Visual, Noise,
not possible due to infraEmissions)
Protection Schemes
structure damage. Thus, the
resilience framework can
Environmental
Technical/Economical
be applied to microgrids,
with a resilient microgrid
figure 1. Isolated microgrid challenges.
able to
66

ieee power & energy magazine

may/june 2017

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - May/June 2017