Note: Descriptions are shown in the official language in which they were submitted.
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SQUIRREL SHIELD DEVICE
BACRGROUND OF fiHE INVENTION
This is a divisional application of Canadian Patent Application Serial
No. 2,174,084 filed on Oct. 11, 1994.
Technical Field
This invention relates generally to devices which protect
various electrical components from contact with small animals
and, more particularly, to a device which prevents a small
animal from simultaneously contacting an energized component
and a grounded conductive structure within an electrical power
distribution substation.
It should be understood that the expression "the invention" and the
like encompasses the subject-matter of both the parent and the
divisional applications.
Description of the Prior Art
Squirrels or other small animals climbing onto electrical
equipment in power distribution substations often ground
energized equipment and cause "low-side faults." A low-side
fault generally refers to a short, circuit to ground on a low
voltage bus and/or other electrical equipment connected to a
low voltage side of a step-down transformer in a power
distribution substation. Low voltage in this context refers to
power distribution voltage levels which may be tens of
thousands of volts. When a small animal provides a conducting
path from an energized substation component to ground via a
support structure, extensive-damage both to the animal and to
electrical equipment may occur. Such an occurrence causes a
low-side fault within the substation leading to damage to
transformers, insulators, switches, feeder breakers, and other
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equipment due to high values of electrical fault current, and
electrical arcs generated by the short circuit. An explosion
or fire may result, along with interruption of electrical power
service to power consumers. Repairing the damage from a low-
side fault is costly and also requires an extended interruption
of service to customers. Thus, small animals such as squirrels
that crawl on exposed, energized components can cause extensive
damage to unprotected components within the substation and are
a nuisance to electric power producers whose ultimate goal is
to provide customers with electricity free from interruption.
A number of devices have been used in attempts to prevent
small animals from coming into contact with energized
substation components and grounded structures. Fake owls have
been placed on substation structures with the intention of
warding off squirrels or other small animals. Ultrasonic
devices and lights have been used as a deterrents to small
animals. Finally, trapping devices, animal repellents, and
screening have also been used to prevent small animals from
approaching power substations. Unfortunately, none of the
above-mentioned deterrents have proved to have a significant
effect on the number of animal-caused faults in power
distribution substations.
Other devices have been placed directly in contact with
energized contacts or support structures. Grease lubricants
have been applied to support structures to prevent animals from
climbing on power substations; however, normal weather
conditions have been known to degrade and reduce the
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lubricating effect of grease. Furthermore, greased structures
within a power substation have not presented a favorable work
environment for maintenance crews. Heat-shrinkable tape and
insulating paint have been used on supporting structures and
energized buses to prevent small animals from grounding an
energized surface or contact. Unfortunately, heat-shrinkable
tape and paint have also been found to degrade from exposure to
the weather, and thus have only limited effectiveness.
Furthermore, insulating material degrades when in direct
contact with an energized surface. This degradation has been
termed "insulation breakdown," and has limited the
effectiveness of insulating paint, heat-shrink tape, and other
cover-up devices in adequately covering energized surfaces.
Moreover, small animals climbing on substation equipment often
puncture heat-shrinkable tape and insulating paint with their
claws or nails. Cover-up devices have been used for breaker
bushings, lightening arrestor leads, and station service
transformer leads; however, spaces between switch and bus
insulators or bus insulators and steel structures remain
unprotected. Unfortunately, unprotected portions of energized
structures near bus insulators in substations have been the
primary points of contact for squirrels and other small
animals.
SIIMMARY OF THE INVENTION
While fake owls, screens, and animal repellents have been
used in an attempt to keep animals out of power distribution
substations; and while tapes, paints, and various covering
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devices have been used to protect breaker bushings and
lightening arrestor leads from contact with small animals, no
such guard or shield has been developed which would effectively
protect switch insulators, bus insulators, and various bushings
by preventing an animal from simultaneously making contact with
a grounded structure and a high voltage conductor.
The invention generally relates to a shield which prevents
squirrels or other animals from causing faults on energized
equipment in power distribution substations. Switch and bus
insulators are primary points of contact when a small animal
crawls from a supporting, grounded structure across the
insulator to an energized conductor. Other points of contact
include breaker and transformer bushings. The present
invention therefore provides for a shield on intermediary
devices to prevent animal-caused faults. Generally, an
intermediary device is constructed of non-conducting material,
mounted on a grounded structure, such as a support structure or
some type of grounded housing, and supports a conductive
device. Examples of intermediary devices are switch
insulators, bus insulators, breaker bushings, transformer lead
bushings, and any other type of insulator or bushing: The
shield is mounted on an intermediary device and prevents
animals from simultaneously contacting a grounded structure and
an energized conductor, thus eliminating a ground path from the
energized conductor through the animal to the grounded
structure. This prevents damage resulting from high fault
current flowing though the contact to ground at the point where
the small animal immediately contacts the energized equipment.
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In several embodiments, a squirrel shield according to the
present invention can be constructed from any durable
nonconducting material. Preferably, a transparent material
such as UV treated Lexan (a registered trademark of General
Electric) polycarbonate sheet plastic can be used as a material
for fabricating the squirrel shield. The shield is generally
formed from two semi-circular or rectangular portions. At
least one shield portion has a slit defined by space between
two extensions and a central edge. The central edge is adapted
to conform to the intermediary device when the shield is
assembled. More specifically, the slit is adapted to fit
around a diameter of the intermediary device between skirts and
over corresponding portions of another shield portion, such
that corresponding portions of each shield portion overlap one
another. Appropriate fastening means such as bolts, pop
rivets, or plastic adhesive hold the overlapping portions
together around the intermediary device. The shield extends
radially outward and substantially perpendicular to a
longitudinal axis of the insulator or bushing. Since these
embodiments retrofit a shield to one or several intermediary
devices, the shield can be installed when substation equipment
is energized. This is not possible with many conductor
covering techniques.
In another embodiment, the shield is formed integrally
with an intermediary device so as to provide for an
intermediary device-shield combination apparatus that is formed
of only one piece. This apparatus allows maintenance crews to
install only one piece which not only provides support to a
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conductor or an energized device, but also provides for
protection against animal-caused faults.
Small animals crawling from a grounded structure across an
insulator or bushing must climb around the shield to arrive at
an energized device or conductor. The shield is of sufficient
radius or width (measured perpendicular to a longitudinal axis
of the insulator or bushing) such that the animal cannot
simultaneously contact the grounded structure and energized
conductor or device. The animal must climb from the grounded
structure over the=shield, then from the shield to the
energized conductor or vice versa, thereby eliminating the
animal as a path to ground.
In a first embodiment, a shield according to the present
invention includes two shield portions. At least one shield
portion includes a main portion substantially semi-circular in
shape with a slit defined by space between two extensions
extending from the main portion. The portions having slits are
adapted to fit around an insulator between skirts, and the
assembled shield is substantially circular in shape.
In a second embodiment, a shield according to the present
invention includes two shield portions. At least one shield
portion includes a main portion substantially rectangular in
shape with a slit defined by space between two extensions
extending from the main portion. The shield portions having
slits are adapted to fit around an insulator, and the assembled
shield is substantially rectangular in shape.
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In a third embodiment, a shield according to the present
invention includes several square shields adapted to fit over
insulators which are located close to one another. In this
embodiment, peripheral edges of each individual shield overlap
with adjacent shields, forming a larger shield over several
insulators.
In a fourth embodiment, a shield of two portions according
to the present invention is adapted to fit over a group of
insulators. In this embodiment, at least one portion of the
shield includes a main portion substantially rectangular in
shape with at least three extensions extending from the main
portion_ Slits are located between extensions and always
number one less than the number of extensions. The shield
portions having slits are adapted to fit around the insulators.
The assembled shield is substantially rectangular in shape.
In a fifth embodiment, an apparatus according to the
present invention comprises a shield which is integral with an
electrical insulator, forming a shielded insulator of unitary
construction.
In a sixth embodiment, an apparatus according to the
present invention comprises a shield which is integral with a
bushing. Such a bushing is used in a power distribution
substation to insulate an energized conductor from a grounded
housing of a transformer or breaker. The shield prevents a
small animal from simultaneously contacting a grounded housing
of a breaker or transformer and an energized conductor.
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Alternatively, a shield of several portions may also be placed
over an existing bushing between skirts. At least one shield
portion includes a main portion with a slit defined by space
between two extensions extending from the main portion. The
shield portions having slits are adapted to fit around a
bushing, and the assembled shield may be square, rectangular,
or circular in shape.
The present invention is inexpensive, easy to install,
allows maintenance crews to visually inspect various components
of the substation if transparent, and is not prone to
insulation break-down since the shield is attached to an
insulator or bushing rather than an energized surface.
Moderate shield thickness provides for physical strength, a
rugged barrier to small animals, and high voltage insulating
properties between the conductor and the supporting grounded
structure.
Accordingly, it is an object of the present invention to
provide a shield which prevents animal-caused faults in the
vicinity of any insulator in a power distribution substation.
It is another object of the present invention to provide a
shield for use in power distribution substations which prevents
animal-caused faults in the vicinity insulating bushings.
It is another object of the present invention to provide a
shield on an insulator or bushing for use in power distribution
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substations which is transparent and allows maintenance crews
to visually inspect nearby components when installed.
Still another object of the present invention is to
provide a shield which prevents animal-caused faults in power
distribution substations which requires no specialized tools
for installation.
Still another object of the present invention is to
provide a shield which prevents animal-caused faults in power
distribution substations that is not prone to insulation break
down.
Finally, another object of the invention is to provide for
a shield in power distribution substations which is durable and
thus performs as an insulating barrier without being affected
by temperature, moisture, debris, or excessive sunlight.
According to an aspect of the present invention there
is provided for use in an electrical power distribution
substation including a grounded supporting structure, an
intermediary device, and an energized conductor, a shield
for preventing small animals from simultaneously contacting
the supporting structure and the energized conductor
comprising a first shield portion and a second shield
portion, the first shield portion partially overlapping
corresponding portions of the second shield portion,
wherein the intermediary device is an insulator or a
bushing containing skirts, each of the skirts having a
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first peripheral edge and wherein at least one of the
shield portions is formed of a substantially transparent
material and comprises a second peripheral edge, a slit
adapted to engage the insulator including, a central edge
conforming to an outside surface of the intermediary device
between skirts, and fastening means for fastening the
overlapping portions of each the shield portion together
around the intermediary device between the skirts, wherein
the fastening means is selected from the group consisting
of bolts and nuts, pop rivets, screws, and adhesive,
wherein the minimum distance between the first edge of the
skirt and the second peripheral edge at any point of each
the shield portion is sufficient to prevent a small animal
from simultaneously contacting the grounded supporting
structure the intermediary device and the conductor
supported by the intermediary device_
According to a further aspect of the present invention
there is provided for use in an electrical power
distribution substation including a grounded supporting
structure, an insulator, and an energized conductor, a
shield for preventing animals from simultaneously
contacting the grounded supporting structure and energized
conductor comprising:
a first shield portion and a second shield portion,
wherein at least one of said portions is configured to fit
around at least two insulators such that portions of said
first shield portion partially overlap corresponding
portions of said second shield portion.
According to a further aspect of the present invention
there is provided for use in an electrical power
distribution substation including a grounded structure, and
an energized conductor, an apparatus for preventing an
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animal having a defined length approximately equal to that
of an average-sized squirrel from simultaneously contacting
the grounded supporting structure and the energized
conductor comprising an electrically non-conducting main
body including, a first end coupled to the grounded
structure, a second end coupled to the conductor, a medial
portion including a main body peripheral edge portion
disposed between the first portion and second ends, a first
shield element constructed of nonconducting material and
including front and back planar surfaces, a second shield
element constructed of nonconducting material and including
front and back plariar surfaces, means for fastening the
first shield element to the second shield element to form a
shield assembly around the main body without requiring
disassembly of the main body from the grounded structure or
the energized conductor, wherein the front surface of the
first shield element partially overlaps the back surface of
the second shield element to form the shield assembly, and
wherein the shield assembly extends radially outward from
the main body, the means for fastening selected from the
group consisting of elongated slots on the first shield
element and corresponding holes on the second shield
element, pop rivets, and adhesive applied to each the
shield element, and the shield assembly having a peripheral
shield edge portion bordering the front and back planar
surfaces of the first and second shield elements, wherein
the peripheral shield edge portion is spaced apart from the
main body peripheral edge portion, such that a sum of a
first distance from the main body first end to the
peripheral shield edge and a second distance from the
peripheral shield edge to the main body.second end is
greater than the defined length of the animal, thereby
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preventing the animal from simultaneously contacting the
grounded structure and the conductor.
According to further aspect of the present invention
there is provided for use in an electrical power
distribution substation including a first conductor, a
second conductor, and an intermediary device having a first
end connected to the first conductor, a second end
connected to the second conductor, and a medial portion
including a main body peripheral edge portion, wherein the
intermediary device insulates the first conductor from the
second conductor, a shield assembly for a preventing an
animal having a defined length approximately equal to that
of an average-sized squirrel from simultaneously contacting
the first andsecond conductors, the shield assembly
comprising a first shield element constructed of
nonconducting material and including front and back planar
surfaces, a second shield element constructed of
nonconducting material and including front and back planar
surfaces, means for fastening the first shield element to
the second shield element to form a shield assembly around
the intermediary device without requiring disassembly of
the intermediary device from the first or second
conductors, wherein one front surface of the first shield
element partially overlaps one back surface of the second
shield element to form the shield assembly, and wherein the
shield assembly extends radially outward from the
intermediary device, the means for fastening including at
least one of a) bolts, pop rivets.or screws each extending
through an elongated slot in one of the first shield
elements and a corresponding hole in the other of the first
and second shield elements and b) adhesive applied to each
of the first and second shield elements, and the shield
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assembly having a peripheral shield edge portion bordering
the front and back planar surfaces of the first and second
shield elements, wherein the peripheral shield edge portion
is spaced apart from-a peripheral edge portion of the
intermediary device such that a sum of a first distance
from the first end of the intermediary device to the
-peripheral shield edge portion and a second distance from
the peripheral shield edge portion to the second end of the
intermediary device is greater than the defined length of
the animal, thereby preventing the animal from
simultaneously contacting the first and second conductors.
According to a further aspect of the present invention
there is provided for use in an electrical power
distribution substation including a grounded supporting
structure, an energized conductor, and a plurality of
insulators, each having a peripheral edge portion, wherein
the insulators connect the conductor to the grounded
supporting structure, a shield assembly for preventing an
animal having a defined length equal to that of an average-
sized squirrel from simultaneously contacting the grounded
supporting structure and the energized conductor
comprising:
a first shield element constructed of nonconducting
material and including front and back planar surfaces;
a second shield element constructed of nonconducting
material and including front and back planar surfaces;
means for fastening said first shield element to said
second shield element around the insulators without
requiring disassembly of the grounded structure or the
conductor from the insulators, wherein said front surface
of said first shield element partially overlaps said back
surface of said second shield element to form said shield
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assembly, wherein said shield assembly extends radially
outward from the insulators;
said shield assembly having a peripheral shield edge
portion bordering said front and back planar surfaces of
said first and second shield elements, wherein said
peripheral shield edge portion is spaced apart from the
insulator peripheral edge portion such that a sum of a
first distance from the first end of the insulator to said
peripheral shield edge portion and a second distance from
said peripheral shield edge portion to the second end of
the insulator is greater than the defined length of the
animal, thereby preventing the animal from simultaneously
contacting the grounded structure and the conductor; and
wherein at least one of said shield elements is
configured to fit around at least two insulators.
According to a further aspect of the present invention
there is provided for use in an electrical power
distribution substation including a grounded supporting
structure, an energized conductor, and a plurality of
insulators, each having a peripheral edge portion, wherein
the insulators connect the conductor to the grounded
supporting structure, a shield assembly for preventing an
animal having a defined length equal to that of an average-
sized squirrel from simultaneously contacting the grounded
supporting structure and the energized conductor
comprising:
a first shield element constructed of nonconducting
material;
a second shield element constructed of nonconducting
material;
means for fastening said first shield element to said
second shield element around the insulators without
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requiring disassembly of the grounded structure or the
conductor from the insulators, wherein said first shield
element partially overlaps said second shield element to
form said shield assembly, wherein said shield assembly
extends radially outward from the insulators;
said shield assembly having a peripheral shield edge
portion bordering said front and back planar surfaces of
said first and second shield elements, wherein said
peripheral shield edge portion is spaced apart from the
insulator peripheral edge portion such that a sum of a
first distance from the first end of the insulator to said
peripheral shield edge portion and a second distance from
said peripheral shield edge portion to the second end of
the insulator is greater than the defined length of the
animal, thereby preventing the animal from simultaneously
contacting the grounded structure and the conductor; and
wherein at least one of said shield elements is
configured to fit around at least two insulators.
These and other objects are accomplished by the present
invention which is more particularly set forth in the remainderN
of the specification.
BRIEF DESCRIPTION OP THE DRAWINGS
The accompanying drawings illustrate the preferred
embodiment of the invention, -and serve to aid in_the
explanation of the principles of the invention_
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Fig. 1 is a perspective, exploded view of a first
embodiment of a shield according to the present invention.
Fig. 2 is a perspective, exploded view of a second
embodiment of a shield according to the present invention.
Fig. 3 is a perspective, exploded view of a third
embodiment of a shield according to the present invention.
Fig. 4 is a perspective, exploded view of a fourth
embodiment of a shield according to the present invention.
Fig. 5 is a perspective and partial cut-away view of a
fifth embodiment of a shield according to the present
invention.
Fig. 6 is a perspective and partial cut-away view of a
sixth embodiment of a shield according to the present
invention.
Other objects, features and aspects of the present
invention are discussed in greater detail below.
DETAILED DESCRIPTION OF THE INVENTION
Figure 1 illustrates a first embodiment of the present
invention situated within a portion of a power distribution
substation. Grounded supporting structure 102, shown
generically, provides support for various conducting devices
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through insulating components within the power distribution
substation. As shown in Fig. 1, ceramic insulators 108 and 112
extend from structure 102 horizontally and vertically,
respectively. Insulators 108 and 112 support conducting
devices 104 and 106. Conducting devices 104 and 106 may
comprise a myriad of components including breakers, buses,
switches, bare conducting cable, or any other electrically
conducting device. Conducting devices 104 and 106 are normally
energized at high voltage levels, making the conductors
dangerous to small animals climbing in a power distribution
substation.
Shield 114 is exploded in view in order to show relevant
details. In this particular embodiment, the shield 114 is
comprised of shield portions 122 and 124. Each portion of
shield 114 has several additional portions. A main portion 126
of shield portion 122 is substantially semicircular in shape.
Extensions 128 and 134 extend from main portion 126. Extension
128 is bordered longitudinally by outer edge 130 and inner edge
132. Similaily, extension 134 is bordered longitudinally by
outer edge 136 and inner edge 138. Outer edges 130 and 136 are
continuous with peripheral edge 140. Peripheral edge 140 is
semicircular and is concentric with central edge 148. Inner
edges 132 and 138 and central edge 148 form a slit 156.
Shield portions 122 and-124 are essentially identical
except for the location of fastening means. Holes 168 and 164
on shield portion 122 line up with elongated slots 170 and 166
on shield portion 124. This fastening arrangement allows for
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longitudinal adjustment of the shield portions when placed onto
an insulator. Shield 118, identical to shield 114 and shown
assembled on insulator 112, illustrates fasteners 186 and 188
placed through the elongated holes and slots at overlapping
portion 194. Fasteners 186 and 188 may be df any suitable type
including bolts and nuts, screws, and pop rivets.
Slits 156 and 157 of shield portions 122 and 124,
respectively, are adapted to be mounted over insulator 108
between skirts 109 as shown more clearly by assembled shield
118. The width of slits 156 and 157 is greater than a diameter
of the insulator 108 between skirts 109 but less than an outer
diameter of skirts 109. This allows for the shield to be
supported between skirts such that extensions from portion 122
match.with and overlap extensions from portion 124 between
skirts 109. The shield is adapted to be placed between any two
skirts on an insulator, but is usually placed between first and
second or second and third skirts from the supporting structure
while power is on. The shield is mounted on the insulator
close to the supporting structure since protection devices,
used on conductors 104 and 106 while power is on, allow little
or no room for the shield to be placed in the middle portion of
the insulator. However, when power is turned off, the shield
may be placed between any two skirts.
Figure 2 illustrates a second embodiment of the present
invention. Shields 214 and 218 are rectangular in shape after
assembly. Shield portions 222 and 224 are similar in shape.
Shield portion 222 is comprised of main portion 226 which is
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rectangular in shape and bordered by-peripheral edges 240, 242,
and 244. Extensions 228 and 234 extend from main portion 226.
Extension 228 is bordered longitudinally by outer and inner
edges 230 and 232, respectively. Similarly, extension 234 is
bordered by outer and inner edges 236 and 238, respectively.
Inner edges 232 and 238 and central edge 248 define slit 256
which is adapted to fit over insulator 208 between skirts 209
in a manner identical to the first embodiment illustrated in
Fig. 1. Fig. 2 also illustrates adhesive 286 as fastening
means between shield portions 222 and 224. Any appropriate
fastening means including screws, bolts and nuts, or pop rivets
placed through drilled holes in overlapping area 294 can fasten
the shield portions together. Shield 218, shown fully
assembled, provides a barrier between grounded structure 202
and conductor 206. Shield 218 includes overlapping portion 294
which fits between skirts of insulator 212 in a manner similar
to the first embodiment.
Fig. 3 represents a third embodiment of the present
invention. In this particular embodiment, two or more
insulators may.be located close to each other on grounded
structure 302. Shields 314 and 316 are mounted vertically
between skirts of insulators 308 and 310, respectively, to form
larger shield 321. In this embodiment, the shield pairs are
fastened together using adhesive 386, although any fastening
means may be used. A distance between insulators 308 and 310
is less than one half the width of shields 314 and 316.
Similar shields 315 and 317 are mounted horizontally on
insulators 312 and 313, fastened at overlapping portions 393
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and 394, respectively, and form a larger shield 323. A
distance between insulators 312 and 313 is less than one half
the width of shields 315 and 317. Due to the close proximity
of insulators in each pair, shield portions from separate
shield assemblies form an overlap portion 319. According to
this embodiment, a continuous shield may be created between any
number of closely spaced insulators. Furthermore, overlapping
portions may be created on any peripheral edge of a particular
shield; such an arrangement creates a continuous barrier across
a group of insulators which are not necessarily collinear.
Furthermore, peripheral edges from separate shields which form
overlapping portions 319 may also be fastened together, if
needed, by any appropriate fastening means such as adhesive
386.
Figure 4 illustrates a fourth embodiment of the present
invention in which single shields 414 and 418 are adapted to
fit onto any number of insulators which are close to one
another on grounded structure 402. Fig. 4 illustrates two
pairs of insulators; insulators 408 and 410 support conductor
404, and insulators 412 and 415 support separate conductors.
This embodiment can include adaptations to accommodate any
number of closely placed insulators by varying the number of
slits in each portion. Shield 414 is rectangular in shape
after assembly. Shield portions 422 and 424 are similar in
shape. Shield portion 422 includes main portion 426 which is
rectangular in shape and bordered by peripheral edges 440, 442,
and 444. Figure 4 illustrates horizontally mounted insulators
408 and 410 located in a vicinity of each other, therefore
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three extensions 428, 434 and 460 extend from main portion 426.
Extension 428 is bordered longitudinally by outer and inner
edges 430 and 432, respectively. Extension 434 is bordered by
inner edges 438 and 456. Extension 460 is bordered by inner
edge 458 and outer edge 462. Inner edges 432 and 438 and
central edge 448 define slit 450 which is adapted to fit over
insulator 408 between skirts 409 in a manner identical to the
first embodiment illustrated in Fig.'l. Similarly, inner edges
456 and 458 and central edge 464 define slit 454 which is
adapted to fit over insulator 410 between skirts 409. Fig. 4
also illustrates hole 465 and matching slot 466, hole 468 and
matching slot 470 as well as hole 472 and matching slot 474 as
fastening means between shield portions 422 and 424 at
overlapping portion 494. Shield 418, shown mounted on vertical
insulators 412 and 415 is secured by fasteners 488, 490, and
492 in hole-slot pairs on overlapping portion 494. Any
appropriate fastening means may be used including screws, bolts
and nuts, or pop rivets. Also, adhesive may be used to fasten
shield portions together.
The embodiments disclosed in Figs. 1 to 4 illustrate each
portion of a single shield to be substantially symmetrical.
However, it should be noted that a single shield does not
necessarily have to made from symmetrical portions. For
example, a first shield portion may have longer extensions and
deeper slits while a corresponding second shield portion may
not have any slits. Furthermore, this shield may be
rectangular, square, circular, or any other desired shape.
Furthermore, any known means may fasten the portions around one
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or more insulators, thus the shield portions may or may not
have hole-slot pairs on overlapping portions.
Figure 5 illustrates a fifth embodiment of the present
invention. In this embodiment, an electrical insulator and a
nonconducting shield are integrated into a unitary
construction. Shielded insulators 508 and 512 have main bodies
510 and 513, respectively. Each of the main bodies 510 and 513
has a first end mounted on grounded structure 502 and a second
end mounted on energized conductors 504 and 506, respectively.
Between the first and second ends, shields 514 and 518 extend
from the main bodies 510 and 513, respectively. Additionally,
shielded insulators 508 and 512 also have radially extending
skirts 509 extending from main bodies 510 ano 513. Although
shields 514 and 518 in Fig. 5 are circular, the radially
extending shields 514 and 518 may have any shape. For example,
shields 514 and 518 may be square, rectangular, octagonal,
oval, or any other shape best suited for the particular
environment in which the shielded insulators are used. Shields
514 and 518 are bordered by peripheral edges 540 and 542,
respectively.
Figure 6 illustrates a sixth embodiment of the present
invention. In this embodiment, a shield 614 is provided on a
bushing between a conductor 604 and a grounded housing 696 of a
breaker or transformer. A bushing differs from an insulator in
that a bushing has a conductive core. Generally, a bushing is
used to feed a cable lead into some device. For example
bushing 608, provides an electrical connection 605 between a
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conductor 604 and a transformer or breaker (not shown) within
housing 696, and insulates cable leads from a grounded housing
696 of the breaker or transformer. In this particular
embodiment, a nonconducting bushing having a main body 610 and
nonconducting shield 614 form an integrated, shielded bushing
608 having a unitary construction. The main body 610 has a
first end mounted on grounded housing 696. The conductor 604
is mounted on a second end of main body.610..;Between the first
and second ends, shield 614 extends from the main body 610.
Additionally, shielded bushing 608 has radially extending
skirts 609 extendinq from main body 610. Although shield 614
in Fig. 6 is circular, it may be of any shape. For example,
shield 614 may be square, rectangular, octagonal, oval, or any
other shape best suited for the particular environment in which
the shielded bushing is used.
Also as shown in Fig. 6, a shield of two portions may also
be mounted onto a standard bushing 612. Bushing 612 has a
first end mounted on grounded housinq 698. A conductor 606 is
mounted a second end of. bushing 612. Conductor 606 is
electrically connected to a breaker or transformer (not shown)
within housing 698 via connector 607. Shield 618 includes two
portions which are adapted to fit around bushing 612 between
skirts 609. Overlapping portion 694 provides adequate space to
fasten the two portions together by any known means.
Although shielded insulators 508 and 512 and shielded
breaker 608 can be constructed from any durable, non-conducting
material, they are preferably fabricated from a strong,
17
CA 02604429 2007-09-21
moisture resistant polymer. The polymer must also be capable
of resisting degradation from ultraviolet radiation associated
with sunlight. Additionally, the polymer must withstand high
temperatures for short durations should occasional arcing
between the conductor and grounded structure occur. Also, the
shielded insulator may be fabricated from a fiber reinforced
polymer composite for added strength. Moreover, a polymer
which exhibits compliance near the peripheral edges 540, 542,
and 640 is desirable since shield overlapping may occur when
several shielded insulators are mounted close to one another.
Furthermore, shielded insulators and shielded bushings can be
manufactured having several possible axial locations for the
shield. Shielded insulators and shielded bushings having
dissimilar axial shield locations can be mounted close to one
another to eliminate physical shield interference. As
illustrated by Fig. 5, the shielded insulators 508 and 512 may
be opaque or transparent. Finally, shielded bushing 608 may
also be transparent or opaque.
The shield embodiments illustrated in Figs 1 through 4 are
adapted to be placed on existing switch and bus insulators
since switch and bus insulators are primary points of contact
when small animals climb on power distribution substations.
These embodiments therefore provide for a barrier on,existing
switch and bus insulators and prevent animals from
simultaneously contacting a grounded structure and an energized
conductor, thus eliminating a ground path from the energized
conductor through the animal to the grounded structure. The
shielded insulators disclosed in Fig. 5 replace existing
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CA 02604429 2007-09-21
insulators in a substation, can be used in the construction of
a new substation, and also prevent a small animal from
simultaneously contacting a grounded structure and a conductor.
Similarly, shielded bushing 608 disclosed in Fig. 6 replaces
existing bushings in a substation and may be used in the
construction of a new substation.
When a small animal such as a squirrel traverses grounded
structure 102 of Fig. 1 and approaches insulator 108, the
squirrel must also traverse the shield 114 to come into contact
with conductor 104. =The distance between the peripheral edge
140 of shield 114 and a peripheral edge of the skirt 109 is
sufficient to force the squirrel to break contact with the
grounded structure to move from the shield 114 to the conductor
104. In other words, the shield prevents the squirrel from
making contact with the grounded structure and a conductor
simultaneously. Since the shields are constructed of
nonconducting material fastened to a porcelain insulator, no
path to ground is provided whenever the squirrel is in contact
with either the grounded structure and shield or the shield and
conductor. If the squirrel attempts to reverse its path, the
squirrel must break contact with the conductor to traverse from
the shield to the grounded structure. Additionally, square
shield 214 illustrated in Fig. 2 is of sufficient width so as
to prevent the squirrel from contacting both the conductor 204
and the grounded structure 202 simultaneously. Also, the
embodiment illustrated in Fig. 3 provides an even wider barrier
for a squirrel or small animal to traverse since peripheral
edges of adjacent shields overlap at portions 319. For
19
CA 02604429 2007-09-21
example, the overlapping arrangement of adjacent shields
embodied in Fig. 3 is very useful for providing a barrier
between the grounded supporting structure and a disconnect
switch mounted on two insulators. Moreover, the embodiment
illustrated in Fig. 4 also provides for a widened barrier
across multiple insulators using only two portions 422 and 424.
In the embodiment illustrated in Fig. 5, shields 514 and 518
provide a barrier between grounded structure 502 and conductors
504 and 506. Similarly, edges 640 and 642 of the embodiment
disclosed in Fig. 6 also are of adequate distance from skirts
609 to present a sma=11 animal from simultaneously contacting
the grounded housing and the conductor. Finally, in all
embodiments, any peripheral edge of a shield is a sufficient
distance from any peripheral edge of an insulator or bushing
skirt to prevent an animal from simultaneously contacting a
grounded structure and a conductor.
It should be apparent to those skilled in the art that the
shield disclosed in each embodiment of the present invention
may have any shape. With regard to the embodiments illustrated
in Figs. 1 through 4 and 6, any fastening means can be utilized
to attach each portion of each shield around an insulator or
bushing. Furthermore, any number of slits may be provided in
each portion of a shield regardless of overall shield shape.
Moreover, each embodiment may be transparent, opaque or
translucent. In addition, although the invention has
particular applicability to power distribution substations, its
principles could be embodied in other devices which contain
exposed, electrically energized surfaces in close proximity to
CA 02604429 2007-09-21
grounded, conductive structures. It should also should be
understood that various changes to the present invention may be
made by the ordinarily skilled artisan, without departing from
the spirit and scope of the present invention which is set
forth in the claims below. The ordinarily skilled artisan will
understand that this disclosure represents an example of the
invention and is not meant to limit the invention, as presented
in the claims, in any way whatsoever.
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