POWER March 2022 - 32

TRANSMISSION & DISTRIBUTION
Composite Insulator Application
and Design for a Growing and
Evolving Transmission Grid
The need to integrate renewable energy resources, and prepare for increased
demand for power as electrification takes hold in transportation and other sectors,
creates challenges for an aging grid. Some problems are being solved with the
introduction of innovative equipment to upgrade the distribution network.
Favad Janjua
T
he U.S. power transmission grid will
need to solve a multitude of challenges
over the next few decades.
It's a period that will experience the integration
of large-scale renewable generation
to the grid, while operators are
dealing with year-over-year load growth
projections, a boom in electric vehicle
charging stations, and commonly occurring
environmental disturbances that
threaten reliability and resilience.
The U.S. and other countries have
accelerated the installation of new renewable
energy resources, in large part
due to the global concern with climate
change. The power transmission grid is
facing a major challenge as power producers
work to reduce emissions of
carbon dioxide while also meeting the
demand for interconnecting these new
sources of generation.
There are many roadblocks. Grid operators
face the challenge of upgrading the
capacity of current transmission lines,
and gaining regional regulatory approval
for any grid projects. There's resistance
from landowners with rights-of-way concerns,
and opposition due to unknowns
about the long-term effects from electromagnetic
fields near transmission lines.
These roadblocks impact the design
and construction of overhead power
lines and transmission towers, and grid
operators are looking for solutions to
tackle these issues. Some challenges
are being met with the introduction of
innovative equipment to upgrade the
power grid. One innovation is the use of
a composite insulator, both as a structure
and insulator, in what's known as a Double-V
Composite Insulated Cross Arm
(CICA). The technology has emerged as
a novel approach to tackle the technical,
and also financial, challenges presented
by today's ever-changing power grid.
32
1. A composite insulated cross arm (CICA) is composed of cable insulators, post insulators,
metal coupling connection, voltage equalization shielding devices, and suspend fitting strings
for conductors. CICA replaces the combination of " traditional iron cross arm + hanging insulated
string " in overhead transmission lines, and acts as an insulating support for high-voltage
wires. It has more excellent electric insulation performance and mechanical performance than
traditional solutions. Courtesy: SHEMAR Power
The CICA (Figure 1) can be used in
both new and existing overhead transmission
line projects. The traditional steel
cross-arm and insulator strings increase
both vertical overhang (suspension insulator)
and horizontal swing (cross arm).
The Double-V CICA allows for compaction
where its single integrated modular
assembly (Figure 2) reduces both vertical
length and horizontal swing.
Double-V CICA Overview
The Double-V assembly replaces the
two-dimensional horizontal single Vee, a
technology developed for compaction decades
ago to optimize transmission tower
geometry. However, with compaction,
the single Vee still has limitations in bending
stiffness and compression. Double-V
has been found to provide like-for-like
performance, with superior strength-toweight
ratio, elastic ability to withstand
shock loads (such as during a broken conductor
condition), and resilience against
pollution-induced flashovers through the
use of silicone rubber composite insulators
making them the most suitable
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choice for insulated cross arms.
The Double-V CICA is a combination
of composite line post insulators and
suspension insulators. The composite
line post insulator functions as a support
for compression and bending loads while
the suspension insulator functions as a
support for vertical/tension loads.
In addition to these insulator elements,
the CICA also features the high-voltage
(HV) end metallic connection node, conductor
fitting components, tower side
connection hardware, and electric field
grading devices, all while eliminating
overhang length and horizontal swing
common with conventional suspension
insulator strings. The Double-V CICA is
one design type from the CICA family, a
group that also includes the fixed/pivoting
braced line-post, tetrahedron, and tripod.
The type of CICA design is decided
upon after analyzing operating/loading
conditions,
and environmental
conditions.
The elements of the Double-V
CICA are similar to the remaining CICA
family, and cover the majority of transmission
lines (<765 kV) in use in the U.S.
POWER | March 2022

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POWER March 2022

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