IEEE Power & Energy Magazine - September/October 2014 - 83

A recent congressional study estimates the average
annual cost of outages related to severe weather at between
US$25 billion and US$70 billion.

* whose assets-utility assets, customer assets, or those
of a third party-should protection relays protect first?
* how can we effectively detect short circuits in the
presence of many dc-based sources such as Pv
and storage?
✔ the business case for utilities to invest in utility-owned
distributed resources to improve resilience, vis-à-vis
hardening the distribution grid itself
✔ issues related to data and communication security
and reliability
✔ issues related to the islanding of microgrids, such as:
* standard designs for microgrid controllers
* the detection of Der-based islands and the visibility
of islands to the utility.

Summary and Conclusions
Based on the previous discussion, distributed resources
could play the following roles in resilient operation:
✔ Distributed resources by and large can provide many
of the same energy and ancillary services that central
resources can provide.
✔ since most distributed resources are geographically
and electrically closer to loads, they could be less vulnerable to grid component failures during a vLse.
✔ some leading utilities have already begun to leverage
distributed resources during outage conditions. such
applications are mostly limited to utility-owned distributed resources, however, and do not extend to distributed resources owned by customers or third-party
service providers.
✔ customer-owned distributed resources are generally
shut down during outage conditions and are not leveraged during vLses. the only exception is when the
customer can be islanded, in which case it can use its
distributed resources for its own individual benefit.
Given the significant amount of distributed resources
already interconnected at many utilities and the forecast
for substantial growth in distributed resources, it is prudent
to explore whether utilities could further leverage these
resources to increase resilience with respect to vLses.
Opportunities to do so may grow as the redundancy in distribution grids increases as a result of network upgrades. It
is conceivable that many of today's distribution grids will
evolve away from their current radial configurations, supplying power from substations, into meshed networks that
will primarily serve as "interconnection" services among
september/october 2014

customers, distributed resources, microgrids, and utilities.
In this case, it will become even more important to understand the potential applications of distributed resources in
response to vLses.
a key motivation for many customers when installing
distributed resources is to protect themselves individually
against grid outages. For a number of good reasons, these
distributed resources are at present not fully leveraged in a
way that would better serve the grid in response to vLses.
In the future, however, a number of things may change: technology may ease the inherent difficulties in safely coordinating Ders; society may expect more tangible value for
the grid from individual Ders; and vLses may increase
in frequency and severity. significant additional research is
needed to explore suitable solutions if the value of distributed resources is to be maximized for resilience.

For Further Reading
"economic benefits of increasing electric grid resilience to
weather outages," executive Office of the President, the
white house Office of science and technology, aug. 2013.
m. mcGranaghan, m. Olearczyk, and c. Gellings, "enhancing distribution resiliency-Opportunities for applying
innovative technologies," white paper, electric Power research Institute, Palo alto, ca, Jan. 2013.
D. Q. stocker, "climate change 2013: the physical science
basis," in Working Group I Contribution to the Fifth Assessment
Report of the Intergovernmental Panel on Climate Change,
Summary for Policymakers, IPCC, 2013.

Biographies
Reza Arghandeh is with the california Institute for energy
and environment (cIee), University of california, Berkeley.
Merwin Brown is with the california Institute for energy
and environment (cIee), University of california, Berkeley.
Alberto Del Rosso is with the electric Power research
Institute, tennessee.
Girish Ghatikar is with Lawrence Berkeley national
Laboratory, california.
Emma Stewart is with Lawrence Berkeley national Laboratory, california.
Ali Vojdani is with GridBright, Inc., california.
Alexandra von Meier is with the california Institute for
energy and environment (cIee), University of california,
Berkeley.
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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - September/October 2014