Note: Descriptions are shown in the official language in which they were submitted.
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Docket No.: 493331-0045
LINK DISCONNECT BOX FOR AN ELECTRICAL DISTRIBUTION NETWORK
PROTECTOR
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional Application No.
61/638,830, filed
April, 26, 2012, and of U.S. Provisional Application No. 61/639,302, filed
April, 27, 2012.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention generally relates to electrical power
distribution systems. In
particular, the present invention relates to a link disconnect box that allows
for the easy isolation
of a network protector switch from load side connections.
[0004] 2. Description of the Related Art
[0005] The distribution of electricity in urban centers involves medium
voltage (up to 35 kV)
electrical cables (called "feeders") connecting a power substation to the
utility customer base. In
the vicinity of the customer, connections are made from the feeder to a
transformer that reduces
the voltage to one capable of being utilized by the customer. In order to
sectionalize the feeder,
that is, to isolate the feeder in the event of an electrical fault, three
phase power breakers called
network protectors are installed on the low voltage side of the transformer.
The customer
connection side ("load side") of various network protectors can be shorted
together to create a
low voltage electrical grid ("network"), which provides reliable power service
to the utility
customer. Secondary power lines extend from the low voltage electrical grid to
the consumers,
and as a result a failure of any single transformer in the grid does not
disrupt power to the
consumers.
[0006] There are presently tens of thousands of these network protectors in
operation in urban
electrical centers throughout the world. Each network protector operates as an
automatic switch,
connecting or disconnecting the related transformer to the network based upon
the monitoring of
electrical conditions. A network protector comprises a large three phase
switch/breaker element
installed in an enclosure, which can be a submersible tank or a non-
submersible cabinet. The
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switch element is connected on one side to the low voltage side of a
transformer and on the other
side to the network. Because the load side of the network protector can be
connected to the load
side of other network protectors in a network system, there is an enormous
amount of electrical
energy available at any one network protector. Protecting utility workers from
this energy while
they are servicing network protectors is of paramount importance.
[0007] As indicated above, the network protector acts as a three-phase switch
between the low-
voltage side of a transformer and the customer. When a transformer, network
protector or both
need to be serviced, the feeder to the transformer can be isolated so as to
prevent high voltage
current from reaching the transformer using an electrical switch between the
feeder and the
transformer. However, because of the networked connections on the low voltage
side of the
network protector, it is not possible to isolate the network protector itself
from low voltage
current. Consequently, the customer side of the network protector remains
energized, and this
can present serious safety issues for linemen, particularly in the form of arc
flash when servicing
the network protector.
[0008] It is therefore desirable to provide a link disconnect box that can be
retrofitted onto the
existing terminals of a network protector so that, once installed, linemen can
readily disconnect a
network protector from a low voltage network.
SUMMARY OF THE INVENTION
[0009] In one aspect, a link disconnect box for a voltage distribution network
is disclosed. The
link disconnect box has an outer casing that define a cavity, a front face
opening, a top bus bar
opening, and a bottom bus bar opening. A top terminal is disposed over the top
bus bar opening,
while a bottom terminal is disposed over the bottom bus bar opening. The
bottom terminal is
configured to electrically and mechanically connect to an existing terminal of
a network
protector in the voltage distribution network. A face plate removably covers
the front face
opening. A top bus bar electrically couples to the top terminal and extends
through the top bus
bar opening, and a bottom bus bar electrically couples to the bottom terminal
and extends
through the bottom bus bar opening. An air gap electrically isolates the top
bus bar from the
bottom bus bar within the cavity. An electrical link connects and disconnects
the top bus bar and
the bottom bus bar by electrically bridging the air gap.
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[0010] In a preferred embodiment, the face plate sealingly covers the front
face opening, the top
terminal sealingly covers the top bus bar opening, and the bottom terminal
sealingly covers the
bottom bus bar opening. In such embodiments, the face plate may further
include an air
pressurization port for pressurizing the cavity.
[0011] In one embodiment the bottom terminal comprises through holes
configured to align with
connectors, such as bolts or threaded holes, in the existing terminal of the
network protector. In
preferred embodiments, however, the bottom terminal has threaded openings that
do not pass
through the bottom terminal.
[0012] In various embodiments the bottom terminal comprises a bottom terminal
plate covering
the bottom bus bar opening and mechanically coupled to the bottom bus bar, and
a terminal
adapter plate removably connected to the bottom terminal plate. The terminal
adapter plate has a
first surface configured to mechanically and electrically engage with the
bottom plate terminal,
and a second surface configured to mechanically and electrically engage with
the existing
terminal of the network protector. Preferably, the bottom terminal plate has a
larger surface area
than the existing terminal of the network protector. In such embodiments the
terminal adapter
plate may have first through holes for coupling the terminal adapter plate to
the bottom terminal
plate, and second through holes for coupling the terminal adapter plate to the
existing terminal of
the network protector, in which the first through holes delimit a greater
surface area than a
surface area delimited by the second through holes. It may also be preferable
that the bottom
terminal plate has threaded openings that do not pass through the bottom
terminal plate, with the
first through holes aligning with the threaded openings.
[0013] In various embodiments the electrical link is configured to be
mechanically secured in a
closed position in which the air gap is bridged, and is further configured to
fall under gravity into
an open position in which the air gap is not bridged when not mechanically
secured in the closed
position. For example, the electrical link may include a swing arm for
bridging the air gap, the
swing arm having at least an opening, with the upper bus bar having a hole
corresponding to the
opening in the swing arm. A bolt can then be run through the opening in the
swing arm and
engage with the threaded hole in the upper bus bar to mechanically secure the
link in the closed
position.
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[0014] In some embodiments the top terminal may have a mechanical
configuration
corresponding to the existing terminal of the network protector, so that
secondary power lines
can be readily moved from the existing terminal of the network protector to
the top terminal. In
other embodiments the top terminal is a spade terminal. In yet other
embodiments the bottom
terminal is a spade terminal.
[0015] In another aspect, a method for the field retrofitting of a network
protector in a voltage
distribution network is disclosed. Secondary power lines from an existing
output terminal of the
network protector are removed. A link disconnect box is electrically and
mechanically coupled
to the existing terminal of the network protector, with the secondary power
lines electrically and
mechanically coupled to the link disconnect box. The link disconnect box may
have the
structure described above, with the bottom terminal of the link disconnect box
connecting to the
existing terminal of the network protector, and the top terminal of the link
disconnect box being
used to connect to secondary power lines.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The various aspects and embodiments disclosed herein will be better
understood when
read in conjunction with the appended drawings, wherein like reference
numerals refer to like
components. For the purposes of illustrating aspects of the present
application, there are shown
in the drawings certain preferred embodiments. It should be understood,
however, that the
application is not limited to the precise arrangement, structures, features,
embodiments, aspects,
and devices shown, and the arrangements, structures, features, embodiments,
aspects and devices
shown may be used singularly or in combination with other arrangements,
structures, features,
embodiments, aspects and devices. The drawings are not necessarily drawn to
scale and are not
in any way intended to limit the scope of this invention, but are merely
presented to clarify
illustrated embodiments of the invention. In these drawings:
[0017] Fig. 1 is a perspective view of an embodiment link disconnect box.
[0018] Fig. 2 is a bottom view of the link disconnect box shown in Fig. 1.
[0019] Fig. 3 is a top view of the link disconnect box shown in Fig. 1.
[0020] Fig. 4 is a front x-ray view of the link disconnect box shown in Fig.
1.
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[0021] Fig. 5 is a cross-sectional view along a line 5-5 shown in Fig. 4.
[0022] Fig. 6 is a perspective view of embodiment link disconnect boxes
coupled to a network
protector.
[0023] Figs. 7 and 8 are a detailed cross-sectional views illustrating
installation of another
embodiment link disconnect box being retrofitted onto a network protector.
[0024] Fig. 9 is a perspective x-ray view of a single link disconnect box
shown in Figs. 7 and 8
in a closed position.
[0025] Fig. 10 is a perspective x-ray view of a single link disconnect box
shown in Figs. 7 and 8
in an open position.
[0026] Figs. 11 and 12 are cross-sectional views illustrating installation of
another embodiment
link disconnect box and a related adapter.
[0027] Fig. 13 is a perspective view of another embodiment link disconnect
box.
[0028] Fig. 14 illustrates a spade-to-spade connection between a link
disconnect box and an
existing terminal of a network protector according to an embodiment of the
invention.
[0029] Figs. 15 and 16 illustrate a standoff adapter for a link disconnect box
according to an
embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] Various embodiments of the invention provide a link disconnect box that
can be field
installed, for example, on top of the existing terminals of a network
protector and that allows for
the easy isolation of the network protector from the load side connections.
Various embodiments
of a link disconnect box may include a submersible box with one or more bolted
links. When
unbolted, the links fall and thereby isolate each phase of the network
protector. The links may
be unbolted using an extended insulated wrench to add distance between the
worker and the
electrical energy. The link disconnect box can be configured for mounting, for
example, on
existing spade or stud type terminals that are commonly used with network
protectors. The link
disconnect box may also be wall mounted. The link disconnect box can
advantageously be
mounted on network protectors already operating in the field, thus allowing a
utility to gain a
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measure of protection for its workers without replacing equipment. Terminal
adapters may be
used to conform the terminals of the link disconnect box with the existing
terminals of the
network protector and with the secondary power lines that form the low voltage
network.
[0031] Reference is initially drawn to Figures 1-5, which illustrate a first
embodiment link
disconnect box 100 that may be field-installed on a conventional network
protector, and in
particular on existing electric terminals of a network protector. Link
disconnect box 100
includes an outer casing 110 that defines an internal cavity 140, which is
preferably a monolithic,
molded structure made from any suitably durable and electrically insulating
material, such as
polyester glass, or epoxy, and having a front face opening 112, a bottom bus
bar opening 114 and
a top bus bar opening 116. A face plate 120 is used to cover the front face
opening 112, with a
gasket 122, such as made from rubber, interposed between the face plate 120
and the rim of front
face opening 112 to ensure that the front face plate 120 makes a liquid-tight
seal with the outer
casing 110. The face plate 120 may be made from the same material as that used
for the outer
casing 110, or from any other suitable, electrically insulating material.
Bolts 121 are used to
secure front face plate 120 to the outer casing 110, the bolts 121 engaging
with corresponding
threaded openings 111 set in the rim of front face opening 112. Brass inserts
or the like may be
used to provide the corresponding threading within the openings 111. To reduce
the chances of
ingress of liquids into cavity 140, preferably the only openings in outer
casing 110 are front face
opening 112, bottom bus bar opening 114 and top bus bar opening 116.
[0032] The rim of front face opening 112 may be substantially square having,
for example, a
height 113 and a width 115 of 9 inches. Of course, other dimensions for the
width 115 and
height 113 are possible, but dimensions are preferred that provide sufficient
access room for a
lineman while remaining sufficiently small to ensure adequate spacing of the
boxes 100 when
mounted on a network protector. Hence, preferred embodiment widths 115 may be
from 7 to 10
inches, and heights 113 may be from 7 to 12 inches.
[0033] A top surface 117 of the outer casing 110 is formed so as to provide a
recess 131 for a top
terminal 130. Recess 131, which may be substantially circular, surrounds top
bus bar opening
116. Top terminal plate 132, which may be made from copper, optionally plated
with silver or
tin, is disposed within recess 131. Preferably, universal top terminal plate
132 forms a liquid-
tight seal with outer casing 110. In certain preferred embodiments, the outer
casing 110 is
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molded around universal top terminal plate 132 to ensure such a liquid-tight
seal. Top terminal
plate 132 is preferably shaped to be compatible with existing infrastructure,
and in particular
with standard connections used for the low voltage grid of an electrical power
distribution
system, such as spade terminals or the like. In a preferred embodiment, top
terminal plate 132
has eight threaded holes 134 equidistantly aligned along a circle 133 having a
diameter 136 of 3
and 3/4 inches. Holes 134 preferably do not pass all the way through top
terminal plate 132.
Threaded holes 134 are preferably sized to engage with 1/2 inch bolts. Recess
131 itself may
therefore have a diameter 139 of, for example, 4 and 5/8 inches, with top
terminal plate 132 then
sized to fit snugly within, or be molded within, recess 131. Top terminal
plate 132 may have a
thickness of about 1 inch.
[0034] A back surface 141 of the cavity 140 defined by outer casing 110 is
shaped to have a top
recess 142 aligned with top bus bar opening 116, and within which is disposed
a top bus bar 150
that extends through top bus bar opening 116 to physically and electrically
contact top terminal
plate 132. Top bus bar 150 preferably makes a liquid-tight seal with top bus
bar opening 116.
Although the term "bus bar" is used, it should be understood that here and in
the following such
electrical components are not limited to bar-like shapes, and that other
shapes are possible,
including tubes, rods or any other suitable shape. Hence, it should be
understood that the term
"bus bar" includes any suitable shape that is capable of carrying the currents
intended for the link
disconnect box. Top bus bar 150 may be, for example, brazed to the top
terminal plate 132. Top
terminal plate 132 may include a recess 137 within which top bus bar 150 may
be disposed to
provide greater contact surface area between the electrical bus components
132, 150. Top bus
bar 150 may be made from silver-plated copper, for example, and have a
thickness of 5/8 of an
inch to 2 inches, preferably about 1 inch, and a width of 3 to 4 inches. The
depth of top recess
142 may be such that the top bus bar 150 lies flush with the back surface 141
when disposed
within the recess 142. Top bus bar 150 also preferably includes one or more
threaded holes 152,
which are discussed below.
[0035] In a similar vein, a bottom surface 119 of outer casing 110 is formed
so as to provide a
recess 161 for a bottom terminal 160. Recess 161, which may be substantially
rectangular but
with semi-circular ends, surrounds bottom bus bar opening 114. Note that both
recess 131 on top
surface 117 and recess 161 on bottom surface 119 may be set within respective
protrusions 138,
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168, such as circular or elliptical protrusions, extending from top surface
117 and bottom surface
119, respectively, of outer casing 110, as indicated in the figures for this
specific embodiment.
These protrusions 138, 168 may give the outer casing 110 a total height 102
of, for example,
about 12 inches. This is not, however, a requirement of the invention.
However, such
protrusions 138, 168 do provide the benefit of providing a standoff distance
from the surface of
the network protector upon which link disconnect box 100 is mounted, which may
make for
easier installation of link disconnect box 100 onto the existing terminals of
a network protector.
[0036] Bottom terminal plate 162, which may be made from silver-plated copper,
is disposed
within recess 161 of protrusion 168 of outer casing 110. Preferably, bottom
terminal plate 162 is
sealed within the recess 161 so as to provide a liquid-tight seal between
bottom terminal plate
162 and outer casing 110. By way of example, an adhesion promoter may be used
so that the
polyester glass bonds to the copper when molded. Bottom terminal plate 162 may
be shaped to
be compatible with existing infrastructure, and in particular with standard
connections used for
network protectors or shaped to properly mate with a specific make and/or
model of network
protector. In a preferred embodiment, bottom terminal plate 162 has six
threaded holes 164,
three of which are equidistantly spaced along a first semi-circular end 163 of
the bottom terminal
plate 162, and three of which are equidistantly spaced along an opposing
second semi-circular
end 166 of bottom terminal plate 162. The threaded holes 164 are preferably
sized to engage
with 1/2 inch bolts. Protrusion 168 within which recess 161 is set may be
elliptical, having a
major axis 169 of, for example, 9 and 3/4 inches, and a minor axis 167 of 9
inches. Bottom
terminal plate 162 may have a thickness of about 1 inch, and a length 165 of
about 8 and 3/4
inches.
[0037] The back surface 141 of cavity 140 is further shaped to have a bottom
recess 146 aligned
with bottom bus bar opening 114, and within which is disposed a bottom bus bar
170 that
extends through bottom bus bar opening 114 to physically and electrically
contact bottom
terminal plate 162. Bottom terminal plate 162 may include a recess 167 within
which bottom
bus bar 170 may be disposed to provide greater contact surface area between
the components
162, 170. Bottom bus bar 170 may be made from silver-plated copper, for
example, and have a
thickness of from 5/8 of an inch to 2 inches, preferably 1 inch, and a width
of 3 to 4 inches,
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similar to that of top bus bar 150. The depth of bottom recess 146 may be such
that bottom bus
bar 170 lies flush with the back surface 141 when disposed within the recess
146.
[0038] Top bus bar 150 extends down from top terminal plate 132, through top
bus bar opening
116 and to a top edge of a central recess 144 in back surface 141. Similarly,
bottom bus bar 170
extends up from bottom terminal plate 162, through bottom bus bar opening 114
and to the
bottom edge of central recess 144. Central recess 144 is located within a
central region of back
surface 141, and has a depth and width that preferably exceeds those of top
recess 142 and
bottom recess 146. Central recess 144 provides a suitable air gap between top
bus bar 150 and
bottom bus bar 170 to electrically isolate top bus bar 150 from bottom bus bar
170.
[0039] In one embodiment, top terminal plate 132 is first braised to top bus
bar 150, bottom
terminal plate 162 is braised to bottom bus bar 170, and then these components
are set into a
suitable mold so that molding material forming outer casing 110 is molded
around top terminal
plate 132, top bus bar 150, bottom terminal plate 162 and bottom bus bar 170,
thereby ensuring
that these components are held firmly into position in a liquid- and air-tight
manner.
[0040] An electrical link 180 is used to selectively electrically connect and
disconnect top bus
bar 150 and bottom bus bar 170 by electrically bridging air gap 144 existing
between bus bars
150 and 170. When electrically disconnecting top bus bar 150 from bottom bus
bar 170, link
180 with central recess 144 together ensure that an adequate air gap exists
between these
components 150 and 170. Link 180 includes a base 182 that is firmly affixed,
such as bolted, to
bottom bus bar 170, back surface 141 or both, and which is made from, for
example, brass. A
swing arm 184 is pivotally connected to base 182, which may also be made from,
for example,
brass. Swing arm 184 is pivoted so as to swing up and down along the vertical
direction as
defined by bus bars 150 and 170, with a pivot point 185 of swing arm 184 being
at the lower end
of swing arm 184. When swung into the up, closed, position, swing arm 184 is
substantially
parallel to bus bars 150 and 170; when swung into the down, open, position,
swing arm 184 is
substantially perpendicular to bus bars 150, 170 and points towards front face
opening 112. A
bus bar bridge 186 is fixedly connected, such as bolted, to the surface of
swing arm 184 that
faces bus bars 150 and 170 and at a position that is above pivot point 185.
Bus bar bridge 186
may be made, for example, from silver-plated copper and have a thickness from
5/8 of an inch to
1 inch, and preferably of about 1 inch. When link 180 is in the closed
position, upper and lower
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ends of bus bar bridge 186 respectively contact upper bus bar 150 and lower
bus bar 170 to
electrically connect bus bars 150 and 170 together. Also, when in the closed
position, one or
more openings 187 in swing arm 184 align with one or more threaded holes 152
in upper bus bar
150, so that one or more respective bolts 188 may run through openings 187 to
threadedly
engage with threaded holes 152 so as to bolt link 180 into the closed
position. Nuts 189 may be
disposed on each bolt 188 between swing arm 184 and top bus bar 150 to prevent
bolts 188 from
falling out of openings 187 when link 180 is in the open position. An
electrical pathway
provided by bottom terminal plate 162, bottom bus bar 170, bus bar bridge 186,
top bus bar 150
and top terminal plate 132 is designed to safely support the maximum
electrical power load
needed from the respective phase output port of the network protector. For
example, the
electrical pathway may be constructed so as to support current ranges from 800
Amperes to 5100
Amperes.
[0041] In use, face plate 120 may be unbolted from outer casing 110 so that a
lineman can gain
access to link 180. Then, using an extended insulated wrench, the lineman can
unscrew the one
or more bolts 188 so that they disengage from threaded holes 152. Swing arm
184 then swings
down, opening link 180 and thus de-energizing one phase of the network
protector from the low
voltage network. Further, as pivot point 185 of swing arm 184 is positioned to
be well below the
center of mass of swing arm 184, swing arm 184 will naturally tend to swing
down into the open
position and remain there, ensuring a naturally open position of link 180 to
ensure the safety of
the lineman. Once servicing of the network protector, transformer or both has
been completed,
link 180 may be once more bolted into the closed position by way of bolt(s)
188 and face plate
120 put back into place, thereby sealing shut cavity 140.
[0042] In some embodiments, face plate 120 may include an air pressurization
port 124, of any
suitable known design, that can be releasably connected to a pressurized air
source to pressurize
cavity 140 so as to further prevent ingress of any liquids into cavity 140.
Air pressurization port
124 may be any suitable one-way valve or the like, as known in the art, such
as a ball valve,
needle valve or the like, and may optionally be threaded.
[0043] Fig. 6 illustrates a network protector 1 employing alternate embodiment
link disconnect
boxes 200. Each link disconnect box 200 is substantially similar to link
disconnect box 100
discussed above, but does not include the air pressurization port 124 and has
a slightly modified
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bottom terminal plate 262 for bottom terminal 260. Three link disconnect boxes
200 are
installed on the top surface 3 of network protector 1, one for each of the
three phases output by
network protector 1 on respective output terminals 5. That is, network
protector 1 has three
existing output terminals 5 respectively for the three-phase power provided
over the low voltage
network. The protrusion 268 and related bottom terminal 260 of each link
disconnect box 200 is
installed onto a respective existing output terminal 5 of network protector 1.
As shown in Fig. 6,
when the face plate 220 is removed, a lineman can gain access to the link 280
within each link
disconnect box 200 to electrically connect and disconnect the respective
terminal 5 of network
protector 1 from the low voltage network.
[0044] Figs. 7 and 8 provide detailed views of connecting the link disconnect
box 200 to a
respective existing terminal 5 of the network protector 1. A benefit of the
design of various
embodiment link disconnect boxes is that they can be readily retrofitted onto
the existing
terminals of any network protector 1 in the field, without any need to change
or replace the
existing terminal 5 of network protector 1. Output terminal 5 of network
protector 1 typically
includes a top terminal plate 7 that has threaded holes 9 on an upper surface
thereof and is used
for the connection of secondary power lines for the low voltage network. The
exact
configuration of top terminal plate 7 may vary from manufacturer to
manufacturer of network
protectors 1. Bottom protrusion 268 of link disconnect box 200 is shaped to
accept existing top
terminal plate 7 of network protector 1. More specifically, the recess 261,
within which is
disposed the bottom terminal plate 262 of link disconnect box 200, is shaped
to accept and
engage with existing terminal 5 of network protector 1. As shown in Figures 7
and 8, upper
terminal plate 7 of network protector 1 fits snugly, and is entirely disposed
within, recess 261 of
link disconnect box 200 to abut against bottom terminal plate 262. Holes 264
in bottom terminal
plate 262 are designed to align with threaded holes 9 of top terminal plate 7,
and the terminal
plates 7 and 262 rest snugly in direct physical contact with each other, as
shown in Fig. 8. A
rubber 0-ring or gasket 11 may be disposed between the rim of recess 261 as
provided by
bottom protrusion 268 and the housing 13 of the terminal 5 so as to ensure a
liquid-tight seal
between link disconnect box 200 and network protector 1. Bolts 15 are then
disposed through
each of the holes 264 in bottom terminal plate 262 to engage with threaded
holes 9 in top
terminal plate 7 of network protector 1, thereby firmly mechanically and
electrically coupling the
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terminal plates 262 and 7 together, and thus mechanically and electrically
coupling link
disconnect box 200 to network protector 1.
[0045] Figures 9 and 10 present perspective views of link disconnect box 200
installed on
network protector 1 while in the closed position and open position,
respectively. While in the
normal operating condition so that network protector 1 is energized and
connected to the low
voltage network, front face plate 220 is bolted and sealed against gasket 222
to ensure cavity 240
remains sealed against the ingress of both air and liquids. Link 280 is bolted
in the closed
position, so that bus bar bridge 286 electrically connects top bus bar 250
with bottom bus bar
270, and thus top terminal plate 232 with bottom terminal plate 262. A spade
terminal 20 may
be bolted to top terminal plate 232 to provide for the electrical connection
of secondary power
lines of the low voltage network. Hence, top terminal plate 232, as discussed
above, is
preferably formed as to mechanically correspond to spade terminal 20, and in
some embodiments
may have the same mechanical configuration as output terminal 5 of network
protector 1 ¨ i.e.,
of top terminal plate 7.
[0046] To de-energize network protector 1 from the low voltage network, face
plate 220 is
removed to expose and gain access to cavity 240. An extended insulated wrench
is used to
unbolt link 280 from top bus bar 250, and link 280 subsequently falls into the
open position, thus
creating an air gap between bus bars 250 and 270 and thereby de-energizing
network protector 1
from the low voltage network. A lineman may thereafter safely work on network
protector 1
without concern of energy from the low voltage network. Further, because each
link disconnect
box 200 de-energizes its respective phase terminal 5, the lineman also does
not need to worry
about phase-to-phase arcing within network protector 1, thereby further
ensuring the safety of the
lineman when servicing network protector 1. Similar advantages are obtained by
use of first
embodiment link disconnect box 100, as well.
[0047] A potential drawback of the embodiment link disconnect box 200 is that
securing bolts 15
require access to cavity 240, which may be inconvenient, particularly when
working around bus
bars 250 and 270. Also, through holes 264 through which bolts 15 pass to
mechanically engage
with network protector 1 may permit the unwanted ingress of air, liquids or
both into cavity 240,
despite the presence of 0-ring 11.
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[0048] Embodiment 300 depicted in Figures 11 and 12 avoids these drawbacks by
having a
bottom terminal plate 362 that has no through holes, unlike bottom terminal
plate 262 in the
embodiment link disconnect box 200 discussed above. Also, embodiment link
disconnect box
300 makes use of a terminal adapter plate 390 that permits link disconnect box
300 to be field
installed onto the existing terminal of any network protector, regardless of
make or model. It
will be appreciated that suitable terminal adapter plates 390 may also be made
for the
embodiment link disconnect boxes 100, 200 or any other embodiment link
disconnect box.
[0049] Link disconnect box 300 is substantially the same as first embodiment
link disconnect
box 100 and includes a lower protrusion 368 on the outer casing 310 that
defines a recess 361
within which is disposed the bottom terminal plate 362. Bottom terminal plate
362 may include
a recess, protrusion or the like around its outer periphery, as shown in Figs.
11 and 12, to better
ensure rigid coupling with the walls of recess 361. Bottom terminal plate 362
forms an air and
liquid tight seal with lower protrusion 368 and includes a plurality of
threaded holes 364
disposed in a predetermined pattern across the exterior surface of bottom
terminal plate 362, for
example in a pattern as discussed previously with respect to first embodiment
link disconnect
box 100. These threaded holes 364 do not pass all the way through bottom
terminal plate 362
but extend upwards only partially into bottom terminal plate 362. Preferably,
link disconnect
box 300 is designed so that bottom terminal plate 362 spans a larger surface
area than an output
terminal 5 of a target network protector 1, or of most or even all known
network protectors, and
in particular is preferably designed so that threaded holes 364 delimit a
greater surface area than
that spanned by top terminal plate 7 of network protector 1.
[0050] Adapter plate 390 is designed to fit within recess 361 and engage with
bottom terminal
plate 362. Adapter plate 390 may be made from, for example, silver-plated
copper and have a
thickness of from 5/8 of an inch to 2 inches, preferably about 1 inch. Adapter
plate 390 includes
a first side 391 that is configured to abut immediately against bottom
terminal plate 362, and
includes through holes 394 (or other suitable connector type) that align with
threaded holes 364
(or other suitable corresponding connector type) of bottom terminal plate 362.
Bolts 17
(typically in conjunction with corresponding washers) may be passed through
through holes 394
to threadedly engage with threaded holes 364 so as to securely mechanically
and electrically
connect adapter plate 390 to bottom terminal plate 362. Adapter plate 390 has
a second side 392
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that is configured to abut immediately against top terminal plate 7 of output
terminal 5 of
network protector 1, and includes through holes 399 that align with connectors
on top terminal
plate 7 that are on terminal 5 of network protector 1. Such connectors are
typically threaded
holes 9, although they may also include, by way of example, all-thread, bolts
or the like. Hence,
the shape of the first side 391 of adapter plate 390 preferably corresponds to
the shape of bottom
terminal plate 362 of link disconnect box 300, and has a pattern of through
holes 394 that
correspond with the pattern of threaded holes 364 in the bottom terminal plate
362. Similarly,
the shape of the second side 392 of adapter plate 390 preferably corresponds
to the shape of top
terminal plate 7 of network protector 1, and has a pattern of through holes
399 that correspond
with threaded holes 9 in the top terminal plate 7 of network protector 1. In
preferred
embodiments, the through holes 399 for the second surface 392 are configured
so that bolts 15
may be completely disposed within the through holes 399 to extend from second
side 392. As
such, through holes 399 preferably include a larger-diameter portion 398 that
descends from first
side 391, and a smaller-diameter portion 397 that extends up from second side
392; larger-
diameter portions 398 are slightly larger and deeper than the diameter and
height, respectively, of
the heads of bolts 15, while small-diameter portions 397 are smaller that the
heads of bolts 15 but
accept the shafts of bolts 15. Bolts 15 (typically in conjunction with
corresponding washers)
may be passed through holes 399 to threadedly engage with threaded holes 9 in
top plate
terminal 7 of network protector 1 so as to securely mechanically and
electrically connect adapter
plate 390 to top terminal plate 7.
[0051] To field install link disconnect box 300 onto an existing terminal 5 of
network protector
1, a lineman selects the proper terminal adapter plate 390 that corresponds to
output terminal 5 of
network protector 1. The lineman removes the secondary power lines from
existing output
terminal 5, and then installs the appropriate adapter plate 390 onto this
existing output terminal 5
by placing the second surface 392 against the top plate terminal 7, aligning
the holes 9 and 399
with each other, and then passing bolts 15 (preferably with respective
washers) through holes
399 to engage with threaded holes 9 of output terminal 5. There is no need to
exchange the
existing output terminal 5 of network protector 1 for a new or different
output terminal. Bolts 15
are selected so that their heads rest entirely within larger-diameter holes
398 and thus do not
protrude above second surface 392, and firmly mechanically and electrically
connect adapter
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plate 390 to existing top terminal 9. Link disconnect box 300 is then lowered
onto adapter plate
390 so that bottom terminal plate 362 aligns with top surface 391 of adapter
plate 390. Because
through holes 394 of adapter plate 390 extend outside output terminal 5 of
network protector 1,
bolts 17 (preferably in conjunction with washers) may be easily passed through
through holes
394 to engage with threaded holes 364 in bottom plate terminal 362. Output
terminal 5 of
network protector 1 is thereby firmly mechanically and electrically connected
to bottom plate
terminal 362 of link disconnect box 300 via terminal adapter plate 390.
Secondary power lines
from the low voltage network may then be coupled to the top terminal plate 332
by, for example,
coupling a spade terminal to top terminal plate 332 using threaded holes 334,
and then coupling
the secondary power lines to the spade terminal.
[0052] It will be appreciated that various types of terminal adapter plates
390 may be
manufactured, each corresponding to a different make, model or both of network
protector so
that all makes and models of network protectors can be supported and used with
any
embodiment link disconnect box. Further, use of terminal adapter plates
provides for more
flexibility in the design of bottom terminal plates in the link disconnect
boxes, so that a
proprietary pattern or design may be used for the bottom terminal plates of
the link disconnect
boxes, yet these link disconnect boxes can still be easily and readily
retrofitted and field installed
onto the existing terminals of network protectors.
[0053] Not all network protectors include a relatively flat, horizontal
surface for the output
terminal. Some, for example, may have a spade-type terminal for an existing
output terminal. In
such situations, it may be desirable to employ a spade-to-spade connection to
electrically connect
an embodiment link disconnect box to such a network protector. An embodiment
link
disconnect box 400 is depicted in Figure 13 for such a connection, and
includes a bottom spade
terminal 22 and a top spade terminal 20. Top spade terminal 20 may be used for
connection to
the secondary power lines of the low voltage network, while bottom spade
terminal 22 may be
used to mechanically and electrically connect to the existing spade terminal
on the output port of
a network protector. A suitably designed adapter plate may be used, for
example, to connect
bottom spade terminal 22 to the bottom plate terminal of link disconnect box
400. Alternatively,
the bottom plate terminal of link disconnect box 400 may be shaped in the form
of a spade
terminal or a standard spade terminal may be bolted to the bottom terminal
plate.
NY 74373699
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[0054] Figure 14 is a cross-sectional view, illustrating the link disconnect
box 400 being
installed onto an existing output spade terminal 5 of network protector 1. An
adapter plate 490
can be used, which is bolted to the bottom terminal plate 462 of link
disconnect box 400. The
adapter plate 490 has a first surface 491 shaped to mate with bottom terminal
plate 462 of link
disconnect box 400, and a second surface 492 shaped to mate with a bottom face
of spade
terminal 22, which may have a conventional shape. The top face of spade
terminal 22 is used to
electrically and mechanically connect to the output spade terminal 5 of
network protector 1, in
which the faces of the spade terminals 22, 5 are bolted to each other, thereby
mechanically and
electrically connecting link disconnect box 400 to network protector 1.
[0055] For some network protectors, the existing terminal 5 and its related
surrounding
insulation are flush with respect to each other and the surrounding areas of
the network protector,
as shown in Figure 15. To permit a lineman sufficient access to existing
terminal 5 while
connecting a link disconnect box 500, a standoff adapter plate 590 may be
used. Standoff
adapter plate 590 has a relatively tall profile, which, as shown in Figure 16,
provides adequate
room for a lineman to install mounting bolts 599 when connecting the link
disconnect box 500 to
existing terminal 5 of the network protector. Preferably, the standoff height
H of adapter plate
590 exceeds the length of mounting bolts 599 so that mounting bolts 599 may be
easily inserted
between existing terminal 5 of the network protector and the first face 591
that bolts onto bottom
terminal plate 562 of link disconnect box 500. The standoff height H may be
measured, for
example, from the bottom surface of first surface 591 that contacts bottom
terminal plate 562 and
second surface 592 that contacts the existing terminal 5 of the network
protector. Preferably, the
standoff height H is greater that 1 inch, more preferably still between 2.5
and 2.5 inches, more
preferably still from 1.75 to 2.0 inches.
[0056] Those skilled in the art will recognize that the present invention has
many applications,
may be implemented in various manners and, as such is not to be limited by the
foregoing
embodiments and examples. Any number of the features of the different
embodiments described
herein may be combined into a single embodiment, the locations of particular
elements can be
altered and alternate embodiments having fewer than or more than all of the
features herein
described are possible. Functionality may also be, in whole or in part,
distributed among
multiple components, in manners now known or to become known.
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[0057] It will be appreciated by those skilled in the art that changes could
be made to
the embodiments described above without departing from the broad inventive
concept
thereof. It is understood, therefore, that this invention is not limited to
the particular
embodiments disclosed, but it is intended to cover modifications within the
scope of the
present invention. While there has been shown and described fundamental
features of
the invention as applied to being exemplary embodiments thereof, it will be
understood
that omissions and substitutions and changes in the form and details of the
disclosed
invention may be made by those skilled in the art without departing from the
scope of
the invention. Moreover, the scope of the present invention covers
conventionally
known, future developed variations and modifications to the components
described
herein as would be understood by those skilled in the art.
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