IEEE Power & Energy Magazine - March/April 2022 - 44

An annual hourly profile must be investigated to understand
the hourly duration of the potential kilowatt overload
on the peak day.
values. Second, the LMV calculation must be operationalized
to provide the DER rebate value. Third, the measurement
and verification of the DER response in real
time need to be recorded.
Planning and Engineering
There are multiple practical aspects to implementing a VDER
computation in the planning and engineering process. These
include 1) the need to perform an 8,760-h time series analysis,
2) a node-branch circuit mode, and 3) adjusted planning
cycles for short-term projects.
To implement this methodology, ComEd developed a
software tool based on this framework. The tool integrates
with existing distribution planning processes and is based on
sound engineering and financial analyses.
The 8,760-h Time Series Analysis
Planning studies normally identify and investigate a peak
hour for traditional capacity planning needs and high solar
production hour in a spring or fall shoulder month for DER
interconnection studies. However, an annual hourly profile
must be investigated to understand the hourly duration of the
potential kilowatt overload on the peak day or days. LMVs
are calculated on an hourly basis for each node in the system
to provide this result.
While some commercial software tools used in planning
are capable of this analysis, there are issues with input data
to consider:
✔ Feeder-level kilowatt, kilovar, or ampere loading and
weather data obtained for use in planning contain
anomalous, missing, or erroneous values that can be
caused by feeder rollover, outages, and other factors.
ComEd uses data filtering and repair methods to identify
anomalous readings that require engineering review
as well as make corrections and impute missing
data based on traditional peak-load and distribution
system planning needs.
✔ Planning generates a weather-adjusted load forecast
per feeder that leverages recent peak-hour
data and feeder weather-sensitivity factor to account
for worst-case weather scenarios (e.g., a onein-10-years
weather event). Adjusting the 8,760-h
data for a hot year can affect the temporal aspects
of the LMV results. ComEd scales only a oneweek
window around the peak based on the worstcase
weather and keeps the rest of the 8,760-h
data intact.
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ieee power & energy magazine
✔ If feeder-level data are used, the loads along the
feeder are scaled to the forecast peak according to
their customer type profile. The entire feeder load
profile must be adjusted to conform to the 8,760-h
time series. If advanced metering infrastructure
data are used as the basis for capacity planning
instead, data preparation would require the usual
cleanup of missing data and other data anomalies
but also the reconciliation of data from different
sources.
✔ The feeder level and advanced metering infrastructure
data are " net " figures of the actual load less the PV
production. For forecasting and the VDER calculations,
the data must be separated either by estimating
PV production from the installed capacity or, ideally,
via submetering information.
Node-Branch Circuit Model
The LMV analysis requires a circuit model that is node
branch in form. All load and DER injection are at nodes,
and all branches have nonzero impedances, so there is a
feasible power flow solution. In existing conventional distribution
planning software tools, the load is often associated
with sections (branches) instead of nodes. In these tools, the
distribution equipment (e.g., a reconfiguration switch) is represented
with zero impedance. A zero-impedance circuit is
unrealistic in the real world and, as modeled, incapable of
localizing the DER benefit. Our model relies upon impedances
because they influence the DER's ability to alleviate
a constraint.
Planning Cycle Adjustments for Short-Term Projects
Currently, electric utilities like ComEd use an annual planning
cycle for short-term needs. At summer's end, ComEd
reviews operations for pressing issues, and the system load
forecast is updated for the next few years as the basis for
studies of grid conditions. ComEd then identifies and plans
projects based on the problems uncovered, and engineering
designs are completed to budget these projects. Once
reviewed and approved, projects proceed to construction
that must be completed before the next summer peak. This
schedule also should account for the DER adoption based
on the VDERs at specific locations, construction, and
the date the DER enters service. However, there must be
enough time to proceed with grid construction solutions
if the DER requirements are not satisfied at locations of
urgent need.
march/april 2022
IEEE Power & Energy Magazine - March/April 2022

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