IEEE Power & Energy Magazine - September/October 2014 - 79

consequences of disturbances or
disruptive events are time depenGrid
dent, as are the system's adaptive
Identification
responses and its recovery speed.
vulnerability analysis therefore
requires taking into account system response before, during, and
after disturbances.
Vulnerability
Resilient Distributed
resilience operation is another
Analysis
Resources Operation
part of the system resilience
framework. the ultimate goal of
a resilient system is to maintain
system functionality after disturbing events. resilience operation control defines new settings
Before
During
After
Grid Recovery
Grid Absorbing
and equilibrium points for the
Disturbance Disturbance Disturbance
Potential
Potential
distributed resources. It has two
main components: "grid recovery
potential" and "grid absorbing figure 3. A resilience assessment framework for power T&D networks.
potential." this means that the
system can absorb disturbances, adapt itself to the disturb- Ders include resources such as solar Pv that are typically
ing events, then recover fast enough to mitigate disturb- installed by electric customers on their side of the meter,
ing event consequences. Figure 3 illustrates this resilience either to increase reliability or to partially supply the cusassessment framework for the electric grid.
tomer's own load to reduce the electric bill. their operation
Disturbance absorption in t&D networks depends on a is subject to an interconnection agreement with the local
range of factors that include component design characteristics, electric utility. most such agreements require compliance
system topology, control philosophy, and protection coordina- with applicable engineering standards (primarily Ieee
tion. the recovery potential is also characterized by the speed 1547) and are intended to ensure that the Der interconnecof the power system's return to its normal or restorative state.
tion is safe, does not adversely affect power quality for other
as mentioned above, the majority of physical vulnerabili- customers, and is compliant with regulatory rules. the exact
ties are related to the disruption of overhead distribution and requirements vary by resource size and are more restrictive
transmission lines following severe weather. Faults caused for larger resources. the Ieee 1547 standard and many of
by contact between conductors and ground are a major the regulations related to interconnection of Der are evolvsource of service interruptions, safety hazards, and fires; ing in reaction to the increased penetration of Ders and the
transformers are second among the most vulnerable compo- emergence of smart grid technology. Interconnections that
nents in t&D networks. hardening the t&D system is one fall under federal jurisdiction because they sell into wholeapproach to prevent or mitigate the catastrophic impact of sale markets, even if connected at the distribution level, are
weather-related disruptions. structural reinforcements and subject to standard procedures and agreements established
vegetation management are thus among the most effective in the United states by the Federal energy regulatory
actions that can be taken to increase robustness.
commission (Ferc)-for example, the small Generator
Beyond robustness, however, system resilience involves Interconnection Procedures. all of the above standards and
active adaptation to conditions during and after disruptive procedures are vitally important because they define what
events. By introducing a vast range of new possibilities for Ders can and cannot do in response to grid disturbances.
operating and control actions that can be taken at the distriDers also include small-scale generation and storage
bution level, the presence of distributed resources brings a technologies owned and operated by utilities or service profundamentally new complexity to resilience analysis. these viders at the distribution voltage level. such resources may be
possibilities need to be studied carefully so that existing either stationary or mobile. moreover, Dr can be considered
assets can be leveraged for maximal advantage-not if but as a Der source. so-called "emergency Dr" is employed to
when the next vLse occurs.
avoid involuntary service interruptions during times of supply
scarcity. this could be one strategy employed during vLses.
For customers and distributed resources interested in particiOverview of Distributed Energy
pating in Dr programs and receiving notifications of emerResource Technologies
In this article we use the term distributed resources to gency and load change requests during vLses, the key will
refer to distributed energy resources (Ders) as well as be providing reliable data and communication that are secure
demand response (Dr) resources. On the generation side, and can interoperate efficiently with electric grid systems.
september/october 2014

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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - September/October 2014