IEEE Power & Energy Magazine - January/February 2022 - 30

Although a large number of these wildfires are of natural causes,
many have originated from human-related ignition sources such
as arson, vehicles, outdoor activities, and powerline faults.
Covered Conductor
As mentioned earlier, SCE has focused most of its wildfire
mitigation projects around preventing electrical faults.
A wildfire covered conductor program deployment is its
primary grid-hardening wildfire risk mitigation measure,
which was developed after detailed risk analysis and
benchmarking across other utilities in the United States
and abroad. SCE's risk analysis showed that implementing
a covered conductor represents the most prudent mitigation
measure.
While SCE's prior practice of replacing existing bare
conductors with underground cable has a greater riskreduction
benefit, reconductoring with a covered conductor
has the greatest overall value. A covered conductor effectively
mitigates several types of ignition drivers, such as
contact from an object and wire-to-wire contact and reduction
in equipment failures associated with older distribution
system equipment and hardware (e.g., cross arms), all at a
lower cost.
More importantly, a covered conductor allows SCE to
reduce the greatest amount of wildfire risk in the shortest
amount of time. A covered conductor is ~70% effective at
mitigating SCE's wildfire ignition drivers compared to ~98%
from undergrounding. Undergrounding is approximately
~8× installation cost, on average, compared to the covered
conductor. Absent the significant cost, undergrounding also
has a much longer lead time for execution (e.g., design, permitting,
construction) and may not even be feasible in certain
areas in SCE's high fire-risk area (e.g., rocky terrain).
This approach is consistent with some of California's recent
landmark legislation, namely Senate Bill 901 (SB901) in
2018 and Assembly Bill 1054 (AB1054) in 2019, which states
that electric utilities must " construct, maintain, and operate
[their] electrical lines and equipment in a manner that will
minimize the risk of catastrophic wildfire posed by those
electrical lines and equipment. "
SCE's covered conductor design is leveraging the latest
Fuel
figure 1. The fire triangle: the foundational fire science as
the key pillars of wildfire risk-reduction strategy.
technology with a three-layer design (Figures 2 and 3). The
first layer is a conductor shield that reduces the electrical
stress (i.e., voltage) and preserves the integrity of the insulation
and useful life of the covered conductor. The second
layer is more durable due to the use of cross-linked low-density
polyethylene material that can withstand high temperatures.
The cross-linking increases the high impulse strength
of the covering, which in turn increases the longevity of the
covered conductor. The third layer also uses cross-linked
high-density polyethylene material that has high impulse
strength and provides greater abrasion and impact resistance
(providing greater mitigation effectiveness from
contact from object situations). The third layer also has
additives that protect against cracking and ultraviolet rays.
Conductor
Shield
Inner Layer
Outer Layer
ACSR
Conductor
figure 2. A cross-sectional view of a covered conductor
deployed at SCE.
30
ieee power & energy magazine
figure 3. SCE's covered conductor design with its layers of
insulation. ACSR: aluminum conductor steel reinforced.
january/february 2022
Heat
Oxygen
IEEE Power & Energy Magazine - January/February 2022

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