IEEE Power & Energy Magazine - March/April 2017 - 36

tion provides operational flexibility
(OpFlex), is a desirable feature of
Normal
OpFlex
radial system design, and helps
13.6
14
13.1 13.2 13.4
12.9
12.7
maintain reliable service for all
12.6
12.1 12.4 12.5
customers. To do this, a tie switch
12
is opened to isolate a portion of
10
feeder/load while another tie switch
8.8
8.8
8.8
8.8
8.8
8.8
8.8
8.8
8.8
8.8
is closed to connect that portion of
8
feeder back into the system. If lo6
cated properly, employing DERs is
a mitigation alter native that could
4
potentially maintain (or enhance)
2
the system operational flexibility
while alleviating the need for the
0
new feeder.
2016 2017 2018 2019 2020 2021 2022 2023 2024 2025
Figure 9 summarizes the total
Year
amount of DERs required each
year by locating them near the
figure 9. The total DER output required to eliminate all violations of limits for norfeeder
head for both the normal
mal and OpFlex configurations.
and OpFlex configurations. Over
the study period, the analysis indicates
that
13.6
MW
of
DERs
are required to eliminate violatraditional upgrades and employing DERs, 14.7 cents/kWh
and 15.7 cents/kWh, respectively. To provide the 10% head- tions due to load growth while also maintaining OpFlex. If
room typically provided by conventional utility assets, the only considering the normal configuration, a total of 8.8 MW
would be needed. In effect, an additional 4.8 MW of DERs
cost of DERs would increase to 20 cents/kWh.
are needed to maintain operational flexibility. For each of the
feeders, the amount of DERs allocated is below the hosting
Radial System Study Results
The anticipated load growth for the SCE study system also capacity at that location and alleviates all thermal violations
results in thermal overloads. The traditional mitigation for seen through the ten-year planning horizon. (Hosting capacity
these overloads would require reconfiguring feeders served is the amount of DERs that can be accommodated without
from four separate substations and building an addition- adversely impacting power quality or reliability under current
al feeder in year one (2016) to offset load. A distinctive configurations and without requiring infrastructure upgrades.)
Figure 10 illustrates the economic analysis of the radial
characteristic of the SCE system design is that feeder sections can be reconfigured, as needed, to reroute power system studied, comparing reconfiguration of the feeder and
flows from one feeder to another for maintenance, emer- installing an additional feeder to accommodate load growth
gencies, or other operational considerations. Reconfigura- with that of two DER alternatives-normal and OpFlex

(a)

(b)

90
80
70
60
50
40
30
20
10
0

59.2

Dist. Equip.
Energy
Losses
Carbon
Capacity
DER Cost
DER Energy
DER Losses
DER Capacity
DER Carbon
Total

41.1

Incremental Cost (cents/kWh)

90
80
70
60
50
40
30
20
10
0

Dist. Equip.
Energy
Losses
Carbon
Capacity
DER Cost
DER Energy
DER Losses
DER Capacity
DER Carbon
Total

15.5

Incremental Cost (cents/kWh)

90
80
70
60
50
40
30
20
10
0

Dist. Equip.
Energy
Losses
Carbon
Capacity
DER Cost
DER Energy
DER Losses
DER Capacity
DER Carbon
Total

Incremental Cost (cents/kWh)

Total DER Output at Peak (MW)

(c)

figure 10. The cost to meet load growth (radial): (a) a traditional utility solution, (b) a DER solution with a normal configuration, and (c) a DER solution with an OpFlex configuration.
36

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march/april 2017

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