Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02678541 2009-09-14
APPARATUS AND METHOD FOR REMOTELY BLOCKING AN OPEN END OF A
CONDUCTOR OF AN ENERGIZED ELECTRICAL TRANSMISSION SYSTEM
TECHNICAL FIELD
[0001] This application relates to apparatuses and methods for remotely
blocking an
open end of a conductor of an energized electrical transmission system.
BACKGROUND
[0002] Conductors of electrical transmission systems may have open ends that
afford
attractive nesting or storage cavities for various animals. An example
conductor of this type
may be part of a pipe bus.
SUMMARY
[0003] An apparatus is disclosed for remotely blocking an open end of a
conductor of
an energized electrical transmission system, the apparatus comprising: a cover
having a
cover end for blocking the open end of the conductor, the cover having an
external eyebolt;
and a dielectric hotstick with a hook at a remote end of the dielectric
hotstick, the hook being
configured to engage the external eyebolt for remote installation of the cover
end blocking
the open end of the conductor.
[0004] A method is also disclosed of remotely blocking an open end of a
conductor
of an energized electrical transmission system, the method comprising:
remotely installing a
cover end of a cover blocking the open end of the conductor using a dielectric
hotstick
operated by a user who is in a position outside a safe Limit of Approach.
[0005] An apparatus is also disclosed for remotely blocking an open end of a
conductor of an energized electrical transmission system, the apparatus
comprising: a cover
having a cover end for blocking the open end of the conductor, the cover end
comprising a
laterally expandable plug such as rubber or memory foam.
[0006] These and other aspects of the device and method are set out in the
claims,
which are incorporated here by reference.
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BRIEF DESCRIPTION OF THE FIGURES
[0007] Embodiments will now be described with reference to the figures, in
which
like reference characters denote like elements, by way of example, and in
which:
[0008] Fig. 1 is an exploded perspective view of a cover for blocking the open
end of
a conductor.
[0009] Fig. IA is a perspective view of the cover of Fig. 1 installed blocking
the
previously open end of the conductor.
[0010] Fig. 2 is a perspective view of a user installing the cover of Fig. 1
over the
open end of a conductor.
[0011] Fig. 3 is a close-up perspective view of the cover of Fig. lbeing
remotely
installed onto the open end of the conductor.
[0012] Fig. 4 is a close-up perspective view of a hook control element for
gripping
and releasing the cover of Fig. 3.
DETAILED DESCRIPTION
[0013] Immaterial modifications may be made to the embodiments described here
without departing from what is covered by the claims.
[0014] Electric poles, towers, and other electrical equipment including
substations
may have various open conductor cavities that provide attractive roosts for
birds, particularly
in treeless regions. If the wings of a bird simultaneously contact a conductor
and another
object such as an adjacent conductor, support tower or tree, the resulting
electrical short-
circuit can kill the bird and also damage the power system. The electrical
short can further
cause electrical system damage resulting in power outages. Further, the
nesting of birds in
open cavities in electrical systems increases the risk that predators will be
attracted to the
nests and cause a power fault or outage. Predators can be mammals such as
raccoons or cats,
birds such as magpies, or snakes.
[0015] Substations transform power from transmission voltages to distribution
voltages, typically ranging from 2400 volts to 37,500 volts. Distribution
voltages allow for
reduced system clearances. These reduced clearances between phase to ground
and phase to
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phase, increase station susceptibility to bird or animal caused outages.
Faults caused by
birds and other animals often trigger sensitive relay protection schemes,
resulting in
substation lockouts, interrupting service to thousands or possibly tens of
thousands of
customers and at the same time damaging expensive substation equipment.
[0016] Thus, in the field of electrical power transmission and distribution
there is a
need to protect open conductors in electrical power systems from intrusion or
occupation by
birds and other animals. The variety and number of proposed solutions for
repelling birds
and other animals from electrocution risks highlights the persistence and
magnitude of the
problems created by such undesirable intrusion.
[0017] The inventor's own prior patent document discloses protectors for
components
of electrical power transmission systems, see United States patent publication
no.
20080123254, as well as methods of making such protectors. However, in order
to install
such protectors, a power-down of the electrical system may be required, which
adds to the
cost of protecting the electrical equipment.
[0018] Power downs for the purpose of measuring electrical equipment for
protective
covers can keep a system down for a half a day or longer time period, at great
cost. Some
systems are operated under the direction of a regulatory and scheduling
authority that
controls the system's downtime scheduling. In locations with minimal spare
power
transmission capacity, it can be a challenge for a system to get the downtime
needed to
access its equipment. Because electrical systems are usually scheduled for
maintenance
downtime on a fairly short notice (typically a week for non-emergency
situations), and
because scheduled downtime may be cancelled by the Regulatory Authority on an
extremely
short notice, there is no guarantee that personnel will be available to
install the required
component during a system's available downtime period. As a result, a system
can
experience significant delays in protecting their equipment.
[0019] Thus, there is a need for installing conductor end covers on energized
equipment by a person positioned outside the Limits of Approach.
[0020] Referring to Fig. 2, an apparatus 10 for remotely blocking an open end
12 of a
conductor 14 of an energized electrical transmission system 16 is disclosed.
Referring to Fig.
3, apparatus 10 may comprise a cover 18, such as a plug, and a dielectric
hotstick 20. Cover
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CA 02678541 2009-09-14
18 may have a cover end 22 for blocking the open end 12 of the conductor 14.
The cover end
22 may insert into the open end 12 as shown, or slip at least partially over
and around the
external circumferential surface area 25 of the conductor 14, or both. Open
end 12 of
conductor 14 is illustrated as having a circular cross-section, although this
is not required and
other cross-section shapes are possible such as polygon shapes. Cover 18 may
have an
external eyebolt 24, which may extend from an external end 26 opposite the
cover end 22.
Eyebolt 24 may extend along an insertion axis 28 of the cover as shown, or
eyebolt 24 may
be at a suitable angle to axis 28. Referring to Fig. 1, external eyebolt 24
may comprise an
eyelet 30 and a zbolt 32. Bolt 32 may be positioned through aligned bores in
the other
components of the cover 18 as shown, securing the components together with a
nut 34 at the
cover end 22. Referring to Fig. lA, the eyebolt 24 may extend from the
external end 26.
External end 26 may be adapted to be outset from the open end 12, for example
if the
external end 26 is flat across the open end 12 as shown, when installed
blocking the open
end 12. Outset in this context is understood to be the opposite of inset, in
order to exclude
the provision of a cavity in external end 26 of cover 18 of which animals
would be able to
occupy.
[0021] Between nut 34 and eyelet 30 may be various components, for example
external and internal washers 36 and 38, respectively, and plug material 40.
The nut 34 and
eyebolt 24 together form an exemplary means for compressing the plug material
40
longitudinally and thus providing lateral expansion of the plug material 40.
External washer
36 may act as a lid or cap. At least part of cover 18 may be magnetic, in
order to
magnetically secure to conductor 14. Plug material 40 may have a cross-section
that is
slightly larger than the bore of the conductor 14 and may be compressible,
with varying
degree of elasticity, to fit within the conductor 14 under compression. This
ensures a tight fit
within open end 12. Plug material 40 may comprise, for example memory foam,
rubber or
other compressible material. Suitable memory foam may have a range of density
of 3-6
pounds per cubic foot. Memory foam may be advantageous because it is easily
compressed
and returns slowly to its original shape in order to fill and seal the open
end 12 of the
conductor 14. Thus, the memory foam may be compressed by an operator, by for
example
turning one or both of the nut 34 and eyelet 30 in relation to each other, and
the cover 18
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installed before full expansion has taken place. Memory foam is also adept at
forming a
suitable seal, which does not have to be a fluid-tight seal. In other
embodiments, rubber may
be used, for example with a density range from 0.945 - 1.2 grams per cubic
centimeter.
Suitable rubber may have a Poisson's ratio of 0.5, although materials
exhibiting other values
of Poisson's ratio may produce acceptable results. Other suitable materials
may be used,
such as polymers and elastomers. Suitable materials may have acceptable
transverse profile
deformation and maintain such deformation over time, when compressed
longitudinally.
Suitable materials such as rubber may also have a durometer range from 60 A to
90 A. For
all ranges provided herein, materials with values outside the ranges are
possible.
[0022] Although material 40 has been described with relation to the embodiment
of
cover end 22 being a plug, it should be understood that material 40 may also
be used in other
arrangements, for example if material 40 is arranged to surround the external
circumferential
surface area 25 of conductor 14. In this example, the material 40 would have a
bore for
receiving conductor and the bore would be dimensioned to be slightly larger
than the outer
diameter of the conductor 14 so that the material 40 would fit with a
compressed fit on the
outside of the conductor 14.
[0023] Referring to Fig. 2, dielectric hotstick 20 may have a hook 42 at a
remote end
44 of the dielectric hotstick 20. Referring to Fig. 3, in use, the hook 42
engages the external
eyebolt 24 for remote installation of the cover end 22 blocking the open end
12 of the
conductor 14. The cover 18 is configured so that the external eyebolt 24
extends externally
when the cover 18 is installed on the conductor. Referring to Figs. 3 and 4,
the dielectric
hotstick 20 comprises a hook control element 46, for example a hand grip as
shown, at an
end 48 of the dielectric hotstick 20 opposed to the remote end 44. The hook
control element
46 may be connected to open and close the hook 42 to grip and release,
respectively, the
eyebolt 24. Control element 46 may operate a dielectric control rod 47 that
opens and closes
the hook 42. Hotstick 20 may be used to grip the cover 18, place the cover end
18 blocking
the open end 12, and then release the cover 18 in place. In some embodiments,
the hotstick,
for example a shotgun hotstick, may be telescopic. The construction of hot
stick stock 20
should meet regulatory requirements and may have a length sufficient to
provide limit of
approach protection for high voltage power equipment energized at more than
750 V. The
CA 02678541 2009-09-14
use of hook 42 and eyebolt 24 allows the insertion axis 28 of the cover 18 to
be angled
relative to the hotstick 20 shaft, in order to allow cover 18 to be easily
installed in elevated
conductors from the ground level, or from other generally awkward positions.
[0024] Referring to Fig. 2, an exemplary method of remotely blocking an open
end
12 of a conductor 14, for example a sliding pipe bus, of an energized
electrical transmission
system 16 is illustrated. Cover end 22 is remotely installed blocking the open
end 12 of the
conductor 14 using dielectric hotstick 20 operated by a user 50 who is in a
position outside a
safe Limit of Approach, for example limit of approach 52D. Remotely installing
may be
carried out with hook 42 removably connected to the external eyebolt 24.
Standard limits of
approach are generally set by the IEEE for live electrical systems. It should
be understood
that the limits of approach may vary according to region. The limits of
approach 52 around
energized equipment generally widens as the voltage increases. In the
illustration of Fig. 2,
the limits of approach 52 correspond to increasing voltages, and thus
increasing radii, from
limits of approach 52A-52D. For this purpose, hotstick 20 may be provided in a
length that is
suitable for the various limits of approach standards in all jurisdictions. In
some
embodiments, the conductor 14 comprises non-energized, for example grounded,
electrical
equipment that is located in close proximity to energized equipment of the
energized
electrical transmission system, and thus the conductor 14 lies within the
Limit of Approach
of the adjacent energized equipment.
[0025] The dielectric material which constitutes at least a part of the hot
stick 20 may
comprise a single part material or multiple part material mixed before
application, and may
be formulated from a combination of liquid and semi-solid or solid components.
Electrical
transmission system may refer to any apparatus intended to transmit power. It
will be
understood that the teachings equally apply and may be adapted to any
commercially used
voltage range or any suitable transmission system. In another embodiment the
hot stick
dielectric control rod 47 may be replaced with a different driving system,
such as a pulley
system. The driving system may be internal or external to the hotstick 20. Hot
stick 20 may
be separated into more than one part, for ease of transport. For example, hot
stick 10 may
collapse into three parts. For further example, hot stick 10 may be provided
as a multi-part
kit.
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[0026] In the claims, the word "comprising" is used in its inclusive sense and
does
not exclude other elements being present. The indefinite article "a" before a
claim feature
does not exclude more than one of the feature being present. Each one of the
individual
features described here may be used in one or more embodiments and is not, by
virtue only
of being described here, to be construed as essential to all embodiments as
defined by the
claims.
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