Cycloaliphatic
from Cooper Power Systems
THE ULTIMATE GAS-FREE, OIL-FREE AND
MAINTENANCE-FREE SOLUTION FOR
AUTOMATION, PROTECTION AND SWITCHING
APPLICATIONS
O
O
CH – CH2 – O – C
CH2
O
O
C – O – CH2 – CH
CH2
NOVA Technology
Kyle Distribution Switchgear
Cycloaliphatic
NOVA Utilizes State-of-theArt Insulation Material
The use of polymeric materials is not new to the electric
power industry. It is not, however, a trivial task. To
assure optimum performance, a designer must match
material characteristics to the expected environment.
Physical properties dictated from the equipment itself
are also key to material selection. Material selection for
insulators or arresters, for example, have similar environmental requirements, but vary widely in physical
demands. Recloser and switch products are dynamic
devices in thermal, electromagnetic, and mechanical
characteristics.
Cooper Power Systems, Kyle Distribution Switchgear
manufactures economical, reliable, and compact
switchgear products that provide higher performance
and greater value. In today's electric power environment, switchgear products must also meet increasing
needs for longer life, lower maintenance, environmental safety, and adaptability to system automation, and
new technology development. The choice of materials
utilized in the insulation and structural systems of
switchgear are critical in meeting these goals.
Key elements in the selection of cycloaliphatic epoxy
for use in power interruption applications are:
Kyle’s NOVA solid insulation system features a proprietary cycloaliphatic epoxy formulation manufactured
by Ciba Geigy. A resin-hardener-filler system, this formulation is compounded to provide the optimum
physical, surface, and processing characteristics necessary to produce durable and reliable distribution
switchgear products.
• Surface tracking resistance for BIL retention.
• Superior hydrophobicity and low vapor transmission
levels.
• High ultraviolet resistance indicating material stability and property retention.
• Physical properties matched to power interruption
duty.
NOVA Development Pays Off
NOVA is the product of design experience, advanced
dynamic modeling techniques, and years of field and
laboratory life testing. When combined with Kyle’s
extensive vacuum interrupter experience, NOVA products are uniquely qualified and tested for long, troublefree service to the electric power industry.
NOVA Cycloaliphatic Epoxy
Epoxides are compounds which contain a three-member ring composed of two carbon and one oxygen molecules. The majority of epoxy rings remain closed until
they are mixed with hardener agents.
O
C
C
Epoxy molecular structure.
Hardener
The second component of the epoxy system is the hardener, or anhydride, which is the catalyst of the
crosslinking process. The epoxy rings open and
crosslink when mixed with the hardener.
Filler
The epoxy and hardener are both filled with a modified
silica flour. The silica flour filler improves the physical
properties of the molded material to provide superior
crack resistance, fracture toughness, thermal conductivity, and reduced shrinkage.
All critical components undergo finite element analysis for validation purposes.
2
Cycloaliphatic
Cycloaliphatic Advantages
samples were exposed to ionic solutions which simulate concentrated contaminants found in highly polluted locations. When compared to polyurethane,
cycloaliphatic required 50 percent more voltage before
tracking occurred. Also, once voltage was removed, the
epoxy ceased combustion while the polyurethane sample continued to burn.
Surface Tracking
To a large extent, dielectric failure of equipment
accounts for a majority of all outages on distribution
systems. NOVA’s exceptional ability to resist electrical
tracking will reduce both the flashovers and the associated cost of repairs.
Coastal Degradation
Coastal locations are typically the harshest of all environmental conditions and a significant source of contamination. The large amount of salt accumulations
severely degrade the dielectric properties of most insulating materials. Cycloaliphatic performs exceptionally
well under these conditions.
Surface tracking occurs when particulates accumulate
on the insulating surface. As a result, dielectric properties are compromised, creating a low-impedance path
for the resulting energy. The type of insulating material
employed plays a very important role in the amount of
contaminants it is able to withstand before a failure
occurs. It is under these extreme conditions that the
essential qualities of cycloaliphatic are accentuated.
NOVA field test units installed in North Carolina verify
resistance to surface degradation in seacoast locations.
After two years of exposure to date, surface roughening from erosion was minimal. There was no visuallydetectable loss of gloss and no evidence of chalking.
When installed in heavily polluted locations, standard
porcelain bushings frequently require extended creepage distances. NOVA’s ability to resist tracking allows
use of a standard module in these installations.
Production NOVA modules were independently tested
by Arizona State University to determine susceptibility
to contaminants as outlined in IEC 815, “Guide for the
Selection of Insulators in Respect of Polluted
Conditions.” No tracking or flashovers occurred even
after the contaminants applied exceeded the highest
pollution level (very heavy) as defined by IEC 815.
NOVA VCS-1 switch at environmental test station in Kure Beach, North
Carolina.
NOVA cycloaliphatic epoxy material (left) and polyurethane material (right)
after incline plane track testing.
Furthermore, ASTM test simulating harsh seacoast conditions were independently performed to validate the
performance of the epoxy. No tracking was evidenced
after exposure to very heavy contaminants typical of
coastal conditions and sea-spray as described by
IEC 815.
The industry standard incline plane test (ASTM D2303:
Test Methods for Liquid-Contaminant Tracking and
Erosion of Insulating Materials) is often used as the
benchmark for comparison of insulating materials in
outdoor applications. Cycloaliphatic and polyurethane
3
Cycloaliphatic
Flashover Failures
Hydrophobicity
Flashovers result from objects making contact with
energized portions of the equipment, causing an arc
which often results in significant material damage. A
large number of flashovers are a direct result of wildlife
contact. NOVA minimizes the effect of these occurrences with its remarkable physical resilience and
extraordinary arc-quenching properties. These attributes permit the unit to withstand the enormous forces
experienced during faults without wholesale damage
to the modules. The cycloaliphatic epoxy’s self-healing
ability also permits re-energizing after external
flashover without cleaning or removal of resulting
residue.
NOVA cycloaliphatic material and mold
design provide superior moisture protection.
These abilities were demonstrated in tests performed on
modules at Cooper Power Systems’ Edison Technical
Institute. A fault was established across a NOVA module
and then re-energized at rated voltage. No dielectric
breakdown occurred even though no repairs or cleaning
was performed on the unit between tests.
when heated by continuous flow, create
a dry band path that
further deteriorates
the creepage withstand level. Surface
arcing and pitting
are byproducts of
this activity and will
eventually lead to
complete breakdown
or flashover.
NOVA cycloaliphatic epoxy maintains
excellent hydrophobicity, a property
characterized by
water “beading”
into isolated drops,
and resisting moisture absorption into
the material. These
isolated drops prevent continuous
sheets of water from
forming leakage current paths which,
NOVA module during thermal shock testing.
NOVA cycloaliphatic epoxy also has a high resistance to
moisture absorption that causes the bonds of the material to break the exposed surfaces. As a result, NOVA
resists surface degradation and increases it’s useful life.
The lower the absorption rate, the lower the effect on
dielectric and mechanical property characteristics.
NOVA module undergoing staged fault test
(video still).
Water Absorption Level
Polyurethane = .23%
NOVA module after staged fault test. Unit
remained intact without physical damage
and was successfully re-energized
(video still).
Water Absorption Level
Cycloaliphatic Epoxy = .14%
Comparison of water absorption levels between cycloaliphatic epoxy and
polyurethane.
4
Cycloaliphatic
Ultraviolet Resistance
Physical Properties
Ultraviolet light will break down electrical bonds of
most materials over time. This molecular bond breakdown appears as chalking and cracking on exposed surfaces, decreasing the material’s hydrophobicity.
Cycloaliphatic’s tight, cross-linked bonding structure
increases the resistance to decomposing in intense ultraviolet environments.
As a result, NOVA
maintains a smooth,
self-cleansing,
unblemished surface
with low adhesion
to contaminants. To
date, NOVA has
been subjected to
more than two years
of testing to confirm
the impact of high
ultraviolet radiation
levels on
cycloaliphatic epoxy.
Results show only
minimal chalking
NOVA VCS-1 switch at environmental test
and no surface
station near Phoenix, Arizona.
degradation.
Outdoor switchgear will likely see extreme temperature
fluctuation during its installed life. Materials used in
these applications must have outstanding physical properties which will withstand severe thermal shock. In
addition, designers must consider the high thermal
shock during duty cycle tests (per ANSI C37.60) as a
four-shot, 12 kA sequence will conduct additional heat
through the insulation system.
NOVA Reduces Thermal Expansion
NOVA’s low expansion coefficient significantly reduces
thermal expansion to one-fifth the level of polyurethane
formulations. Thermal expansion is a major consideration in reducing fracture potential. Conversely, higher
coefficients in thermal expansion result in increased
forces on the internal components, and stress the bond
between components and the solid insulation.
COEFFICIENT OF LINEAR
THERMAL EXPANSION
-5
15 x 10
Polyurethane is nearly
five times more likely
to fracture due to thermal
stress and expansion.
Shed Design
-5
3.5 x 10
By careful design, NOVA uses alternate-sized skirts to
enhance material properties of hydrophobicity and
ultraviolet resistance. NOVA’s major shed extension
shields and protects the minor sheds from moisture and
ultraviolet exposure, eliminating the formation of microcracks, and ensuring extra protected creepage against
surface degradation. The sheds are designed with sharp
edges to direct water away. This is more dramatically
apparent in freezing conditions where ice formations are
broken and eliminated. Creepage distance is designed in
accordance with IEC 815 to exceed 25mm per kV, meeting the requirement for “heavy” contaminant levels.
Cycloaliphatic
Epoxy
TENSILE STRENGTH
MPa (psi)
Major Shed
8
(1200)
Glazed
Porcelain
Minor Shed
NOVA shed design utilizes major and minor sheds for maximum creepage
protection from ultraviolet light and contamination.
5
Polyurethane
Formulations
80
(12000)
14
(2000)
Polyurethane
Formulations
Cycloaliphatic
Epoxy
Cycloaliphatic
Field Experience
NOVA Tensile Strength Provides Long Life
NOVA modules are tough and non-fragmenting because
they possess outstanding tensile and flexural strength
characteristics. A 12-gauge shotgun test supports the
non-fragmenting performance and displays
the ability of NOVA to
thwart vandalism
attempts by successfully passing a highpotential withstand
test. Polyurethane and
porcelain insulation
materials, in comparison, have relatively
low tensile strength.
Cycloaliphatic is superior and withstands a
greater severity of
mechanical loads from
wind, snow, and ice
NOVA module after being shot twice
loading without failure.
Cycloaliphatic epoxy bushings, installed in 1986 at a
substation subject to severe pollution from a paper mill,
show promising results. The cycloaliphatic epoxy has
shown excellent resistance to insulator flashover in this
contaminated environment. Prior to use of cycloaliphatic bushings in that substation, flashovers of bus insulators and equipment bushings caused periodic interruptions in service. The cycloaliphatic bushings have not
required cleaning since installation in 1986. The success
of these cycloaliphatic bushings in preventing flashover
in a contaminated environment, over ten years, is
strong evidence that cycloaliphatic epoxy is an exceptional insulating material.
European experience with cycloaliphatic epoxy has
been extensive and long-term with millions of insulators in service. Virtually no maintenance was required
on insulators in environments with severe surface contamination. In addition, the insulators experienced
extremely low failure rates. More than 1,000,000
cycloaliphatic epoxy insulators are in service in Finland.
After nearly 25 years of service, no failures have been
attributed to the mechanical characteristics of the
cycloaliphatic epoxy.
with 12-gauge shotgun.
NOVA’s proprietary material composition results in superior, trouble-free, and
maintenance-free operation. Testing and field-experience verify that
Cooper Power Systems’ NOVA cycloaliphatic epoxy is the “shape of things to come.”
CYCLOALIPHATIC EPOXY
POLYURETHANE
EXCELLENT
Poor
Electrical Properties
OUTSTANDING
Poor
Mechanical Strength
EXCELLENT
Adequate
Track Resistance
EXCELLENT
Poor
Weatherability
EXCELLENT
Adequate
Hydrophobic Properties
EXCELLENT
Adequate
.14%
.23%
UV Ozone Resistance
Water Absorption (in percent)
Source: Conference on Polymeric Material Notes 1990 - Chicago, IL USA
6
Cycloaliphatic
NOVA Cycloaliphatic Epoxy
Outperforms Other Insulating
Materials in Outdoor
Switchgear Applications
NOVA is the Shape of Things
to Come
Cooper Power Systems, Kyle Distribution Switchgear
NOVA switchgear products (reclosers, switches, sectionalizers) incorporate a state-of-the-art cycloaliphatic
epoxy solid insulation system.
Cooper Power Systems, Kyle Distribution Switchgear
has invested in extensive field and laboratory testing to
validate the performance of the NOVA cycloaliphatic
epoxy. Comparisons between NOVA cycloaliphatic
epoxy and other insulating materials provide solid evidence that cycloaliphatic epoxy is superior in outdoor
switchgear applications.
NOVA combines Kyle’s 55 years of design experience,
advanced modeling and testing tools, years of field
experience, and unparalleled vacuum interrupter
expertise. Designed for extended life, reliability, and
maintenance-free operation, NOVA is “the shape of
things to come.”
NOVA cycloaliphatic epoxy excels in tracking and erosion resistance, ultraviolet resistance, hydrophobicity,
chemical and physical properties. Polyurethanes possess relatively low insulation resistance, high dielectric
loss, and susceptibility to ultraviolet radiation and acid
rain. Porcelain has poor tracking characteristics which
require extra creepage distances in high-contaminant
areas, and low tensile strength.
7
Cycloaliphatic
©1998 Cooper Power Systems, Inc.
Kyle® is a registered trademark of Cooper Industries, Inc.
NOVA™ is a trademark of Cooper Industries, Inc.
Bulletin 98009 • March 1998 • New Issue
P.O. Box 1640
Waukesha, WI 53187 USA
www.cooperpower.com
KTM
3/98