IEEE Power & Energy Magazine - March/April 2015 - 27

Quantifying the impact of DERs on reliability is a difficult
task even when the DERs are dispatchable. The analysis is
by nature probabilistic because failures have a high degree of
uncertainty. Researchers have come up with various approaches
to probabilistic planning that, for the most part, have not been
embraced by utility planners. Utility distribution planners prefer
more deterministic methods that are based on average failure
rates and assume predictable interactions among circuit components. EPRI's plan has yet to embrace a preferred method.
An overall assessment must consider the incremental
impacts-both positive and negative-that result from DER
additions. The overall assessment must also consider the interrelationship of the benefits and impacts from each of the five categories. Once the full set of assessments have been performed,
the result is a clearer picture of the full range of response that can
be expected on a distribution feeder, one that considers unique
feeder characteristics, constraints, and capabilities as well as the
location-specific impacts of DERs (see Figure 5).
Performing such a thorough analysis can be challenging.
The greatest challenge lies in analyzing all feeders within a
service territory, which is necessary to better quantify the
impacts of DERs across a planning area and/or system and
thus determine the overall costs and benefits that should be
captured in an integration study.

Systemwide Application
In 2010, EPRI began a detailed investigation into the impact
that increasing levels of DERs, specifically PVs, could
have on distribution system performance. Approximately

6 million uniquely different solar deployment cases and
the resulting feeder response outcomes have been analyzed
across 34 feeders throughout North America using the opensource distribution system simulator OpenDSS. A glimpse of
the overall hosting capacities was provided in Figure 3.
From the outset, the goal of performing such a thorough,
detailed analysis was that lessons should be learned and trends
observed to develop better methods and tools. These improved
methods would then let utilities efficiently and confidently
answer such questions as: "What level of PVs is going to affect
my system, and where will these issues occur?"
Throughout 2013 and 2014, EPRI analyzed a vast quantity
of feeder hosting capacity results to identify trends. These
trends form the basis for a streamlined method of determining, on a feeder-by-feeder basis, four important items:
✔✔ the hosting capacities for individual feeders
✔✔ the locations where PVs can be placed without requiring
system upgrades (optimal versus nonoptimal locations)
✔✔ the issues that can arise due to increased levels of PVs
✔✔ mitigation solutions for integrated DERs beyond the
base hosting capacity level.
This streamlined method for evaluating the hosting capacity of individual feeders can also be performed across an
entire distribution system in an automated fashion, as shown
in Figure 6. Efficient implementation also enables qualified
users to evaluate mitigation solutions on a feeder-by-feeder
basis. As the distribution system changes over time, the
assessment method can be repeated as needed to account for
changes to the distribution system, such as reconfigurations

Systemwide Assessment Capturing Feeder-Specific Results
Hosting Capacity Values
Feeder Level

Substation Level

Feeder Level
Feeder Level
Feeder Level

figure 6. An illustration of system-level hosting capacity results.
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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - March/April 2015