IEEE Power & Energy Magazine - March/April 2017 - 38

Neighboring
Transformer

Key Takeaways
Transformer
Overload-63 kVA
153 kW of DER Needed
If Optimally Located
340 kW of DER Needed
with 10-kW Limitation

Network System:
Multidirectional
Power Flows

Neighboring
Transformer

DER Location

figure 12. The impact of dispersion in a network system.

proportionally more DERs because more distant load nodes
were needed but were also less effective at mitigating that
violation. In some cases, the DER capacity required was
over five times greater than the size of the violation.
For radial systems, DERs located downstream from a
capacity-constrained asset (relative to the substation) can
contribute directly to relieving the violation, even at a distance. However, radial systems are often reconfigured to
meet new load growth, maintenance, or other operational
considerations, to the point where the DERs could have little
or even an adverse impact. Future operational flexibility
could be limited if the full impact of employing DERs as an
alternative to traditional utility-system resources is not accurately considered. Under the assumptions used in this study,
the SCE results illustrated a reconfiguration scenario where
more than 50% additional DERs would be needed to provide
the same capacity relief as that provided for the normal configuration (see Figure 13).

This study illustrates the complexity and implications of
incorporating DERs into the distribution system to address
distribution loading issues and provide capacity relief. DER
impacts on distribution can be either beneficial or adverse,
depending on a wide variety of contextual circumstances.
Distribution systems are geographically and electrically
distinct, and their characteristics vary from utility to utility and within each utility. The results from the case studies suggests that the value of DERs is not uniform across
a distribution system and cannot be simply determined by
applying generalities about feeder characteristics like megawatts served or any other single performance metric. Comprehensive, objective, and transparent methods are required
for consistent and sensible results.
The net benefits of employing DERs as an alternative
to conventional grid upgrades depends on a complex set of
parameters. Case studies reveal the importance of the physical characteristics of the feeder in valuing DERs and the
complexity of substituting portfolios of DERs for traditional
distribution equipment. The study illustrated that the most
cost-effective choice is significantly influenced by multiple
parameters, including local-area load-growth rates, peak-day
load profile, types of available DERs and capabilities, power
system design, the time and location of the grid upgrades,
and customer-adopted DERs. DERs may provide benefit in
some instances, but it may not always be the best alternative.
To maximize benefits and reduce costs, increased resource
visibility will be required beyond what is available today.
The effectiveness of DERs to provide deferral benefits
is highly dependent on the location of the DERs relative to
a system constraint, and these considerations vary by the
topology of the system. Individual DERs, and a portfolio comprised of multiple DER technologies, have different and complex interactions with the system. Engineering
analyses can establish the DER attributes needed for resolving a system capacity constraint, and this study reveals the
importance of location for DER
solutions to be effective.

Overloaded
Transformer

Moving Forward
A

Overloaded
Transformer

Neighboring
Transformer
A

Open

Closed

Flexible Radial System:
Multidirectional Power
Flows
50% More DER
Needed to Provide the
Same Capacity Relief in
Both Configurations

Neighboring
Transformer

figure 13. The impact of reconfiguration in a flexible radial system.
38

ieee power & energy magazine

The case studies suggest that distribution planning is also becoming more complex, requiring a high
degree of granularity, data, and
analysis to ensure that cost-effective
solutions are deployed while planning for the future. New distribution
power models, and the data they require, are needed to accommodate
an improved understanding of system impact. Through the effective
modeling of the distribution system,
a broad range of benefits are realized
such as improved confidence in
march/april 2017

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - March/April 2017