Note: Descriptions are shown in the official language in which they were submitted.
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GROUNDING STUD ASSEMBLY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an apparatus for
grounding electrical equipmant and, more particularly, to
a grounding stud assembly for providing a safe method of
grounding a bus system.
2. Description of the Prior Art
During the inspection or repair of equipmentl
such as switchgear, safety practices require that all
potentially "live" circuits be grounded using appropriate
grounding devices and methodsu If the switchgear is
inadvertently energized during the inspection or repair
and the equipment is not grounded, an operator may be
seriously injured and the equipmenk may be damaged.
To connect the equipment to ground, a plurality
of grounding studs are connected to the bus system of the
equipment. To comply with applicable standards, such as
creep or strike distances, the equipment to the
environment may have to be mounted staggered or installed
with barriers.
The grounding studs are insulated rom the
environment to prevent any inadvertent discharges from the
equipment to the environment. To apply the grounding
clamp to the grounding stud for grounding the equipment,
the insulation must be removed from the grounding stud to
expose the bare bus for applying the safety grounds. If
the insulation utilized is tape, an operator must cut the
.
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tape from the bus joint exposing the operator to poten-
tially live circuits.
There are several types of groundiny studs and
insulated covers. One such device is disclosed in U.S.
Patent 4,941,834 issued July 17, 1990 to DeLeo entitled
"Universal High Voltage Ground Stud Insulating System".
The ground stud insulating system comprises a ground stud
for receiving a ground clamp and having a threaded shank
for fastening to a bus. A first insulative cylinder is
arranged over the ground stud on one side of the load
terminal bus and has an eyelet to facilitate the use of a
"hotstick" by an operator to remove the first insulative
cylinder from the ground stud. A second insulative
cylinder is attached to the ground stud on the opposite
side of the load terminal bus to prevent the formation of
a discharge when the bus is energized. The first and the
second cylinders having internal threads are attached to
the ground stud by utiliæing a plurality of washers having
threads. However, to fully insulate the system, an
insulated cylinder must be utilized on each side of the
load terminal bus. Also, to remova the insulated cylinder
to attach the ground clamp, the insulated cylinder must be
unthreaded from the ground stud.
Therefore, what is ~leeded is a grounding stud
assembly which com~lies with the strike and creep distance
requirements of the applicable standards, which can be
utilized at either a cable termination or at a bus splice
joint, and which conveniently facilitates grounding the
equipment at a safe working distance~
SUMMARY OF THE INVENTION
The grounding stud assembly for grounding
electrical equipment comprises a grounding stud having one
end for connection to a grounding clamp and an opposite
end for connection to a bus system at either a bus splice
joint or cable termination. An insulated elongated
portion is positioned between the ends of the grounding
stud. A cover is positioned over the grounding clamp
receiving end of the grounding stud for insulating the
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grounding stud to prevent inadvertent discharge into the
environment during non-grounding periods. The cover
comprises an annular r.ing for engagement with an annular
retaining collar posikioned on the elongated portion for
securing together the cover and grounding stud, enabling
the cover to be installed on an inverted grounding stud.
The cover includas an eyelet for facilitating removal of
the cover from a safe working distance.
A mounting member is utilized for securing the
grounding stud to the bus system, thereby eliminating the
need to insulate each side of the grounding stud, which is
necessary when installing the grounding stud through an
insulated bus.
Due to an overlap of the insulating material of
the elongated portion o~ the grounding stud and of the
cover, the grounding stud assembly provides an extension
of the creep or strike distance between adjacent grounding
studs, enabling the grounding stud assembly to comply with
the applicable standards without requiring khe grounding
studs to be mounted staggered or installed with barriers.
When properly installed, the insulated ground stud
maintains the insulating systems integriky by meeting the
phase-to-phase and phase-to-ground strike diskances as
required in the applicable standards.
BRIEF DESCRIPTION OF THE DRAWINGS
While the specificat:ion concludes with claims
particularly pointing out and distinctly claiming the
subject matter of the invention, it is believed khe
invention will be better understood from the following
description, taken in conjunction with the accompanying
drawings, wherein:
Figure 1 is a front view, partially in section,
of a grounding stud assembly including a grounding stud
and a removable insulated cover; and
Figure 2 is a sectional side view of the
grounding skud assembly illustrated in Figure 1 and
connected at a bus splice joint of a bus system.
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DESCRIPTION OF THE PREFERRED_EMBODIMENT
The invention described herein provides a
grounding stud assembly which utilizes a grounding stud
having an elongated portion for compliance with the
applicable standards and a cover for insulating the
grounding stud, which is easily removable for exposing the
grounding ~tud for grounding the equipment. The grounding
stud assembly may be used, for example, in medium voltage
metal clad switchgear with insulated bus systems at cable
termination or at bus splice joints.
R~ferring to Figure 1, a grounding stud
assembly, r~ferred to generally as 10 includes a grounding
stud 20. The grounding stud 20 has a first end 22 for
receiving a grounding clamp and a second ~nd 24 ~or
connection to a mounting member 25. The first end 22 is a
grounding stud ball for use with a corresponding ground
clamp (not shown), such as an AB Chance Ground Clamp Style
#C600-2100, which may be rated for 30,000 amps for 30
cycles and 43,000 amps for 15 cycles. The dimensions and
2U type of the grounding stud used in the grounding stud
assembly 10 may vary to allow utilization of the grounding
stud with the various grounding clamps available on the
market~
Referring to Figures 1 and 2, an elongated
portion 26 is positioned between the first end 22 and the
second end 24. The elongated portion ~6 is a cylindrical
shaft, which may be made from a metal, such as copper. A
standard ground clamp may be clamped onto the elongated
portion 26 beneath the stud ball for grounding the
equipment. The elongated portion 26 is insulated, such as
by using bed fluidized insulation 28 with a dielectric
rating of lkV per mil and a minimum applied thickness of
95 mils. The elongated portion 26 further comprises an
annular retaining collar 30. The retaining collar 30 is a
spring retaining ring having a slot lnot shown) for
installation of the retaining collar 30 onto the elongated
portion 26. Alternativelyl the retaining collar 30 may be
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integrally formed with the shaft of the elongated portion
26 or may be integrally formed with the insulation 28.
Referring to Figure 2, the second end 24 o~ the
grounding stud 20 is attached to the mounting member 25,
5such as by a brazing process. The mounting member 25 has
a first end 32 and a second end 34 and is bent at approxi-
mately 90 degrees therebetween for providing a surface, or
first end 32l to attach the grounding stud assembly 10 to
a conductor of a bus system 36, such as one ~onnected with
10switchgear equipment, and for providing a surface, or
second end 34, to attach the grounding stud 20 to the
mounting member 25. The angle between the first end 32
and the second end 34 of the mounting member 25 may be any
angle sufficient to facilitate the attachment of a
15grounding clamp onto the grounding stud 20.
The first end 32 of the mounting member 25 has a
plurality of openings 3~, which are slotted holes sized
for installation of the grounding stud 20 on standard
Æ.N.S~I. drilled bus systems. Figure 2 illustrates the
20first end 32 of the mounting member 25 fastened to a bus
splice joint of the bus system 36. The second end 34 of
the mounting member 25 has a recess for receiving the
second end 24 of the grounding stud 20 for attaching the
grounding stud 20 to the mounting member 25. A portion of
25the second end 34 is insulated with the insulation 2~.
Referring again to Figures 1 and 2, the ground-
ing stud assembly 10 also comprises a cover 40. The cover
40 is a cylindrical shell having a closed end and an open
end. The cover 40 is positioned over the first end 22 and
- 30over the elongated portion 26 of the grounding stud 20.
The cover 40 is made from an insulating material, such as
a self extinguishing PVC material, for insulating the
grounding stud 20 to prevent inadvertent discharge from
the grounding stud 20 to the environment.
35An eyelet 42 is integrally formed on the cover
40 from the insulating material and is positioned at the
closed end of the cover 40. Alternatively, the eyelet 42
may be attached to the cover 40. The eyelet 42 facili-
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tates removal of the cover 40 from the grounding stud 20.
A removal tool tnot shown) is inserted through the eyelet
42 and lifts the cover 40 from the grounding stud 20,
thereby enabling an operator to remove the cover 40 from a
safe working distance.
The cover 40 further comprises an annular ring
44 positioned on the inside diameter of the cover 40O The
ring 44 may be integrally formed with the cover 44 or may
be attached to the cover 44. As the cover 40 is pO5 i-
tioned over the grounding stud 20, the annular ring 44
snaps over the retaining collar 30 securing together the
cover 40 and the grounding stud 20. The engagement of the
grounding stud 20 and the cover 40 enables the grounding
stud 20 to be mounted inverted without the cover 40
separating from the grounding stud 20. Alternatively, the
cover 40 may comprise an annular groove (not shown)
positioned on the inside diameter of the cover 40 cor
responding to the annular retaining collar 30 of the
elongated portion 26. An erigagement of the retaining
collar 30 within the groove would secure together the
cover 40 and the grounding stud 20.
The second end 34 of the mounting member 25 is
larger than the second end 24 of the grounding stud 20.
When the cover 40 is installed on the grounding stud 20,
the insulation 28 covering the portion of the second end
34 of the mounting member 25 overlaps the insulating
material of the cover 40. Also, the insulating material
of the cover 40 overlaps the insulation 28 on the
elongated portion 26.
The strike distance, which is measured through
air, and the creep distance, which is measured across the
surface, are determined by measuring the distance from a
first grounding stud exposed conductor, along the length
of a first insulated post, under the edge of a first
cover, through the air or along the surface to the next
phase, under the edge of a second cover of an adjacent
grounding stud, across the length of a second insulated
post, and to a second grounding stud exposed conductor.
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The creep or strike distance between adjacent grounding
studs is extended by utilizing the elongated portion 26
and the overlap of insulation of the cover 40 and of the
elongated portion 26 when the cover 40 is installed on the
grounding stud 20. With an extended creep distance across
the surface of the insulated post in addition to the in
air distance between the phases, the grounding stud
assembly 10 complies with the strike and creep distances
as re~uired in the applicable standards, such as A.N.S.I.
For a particular application, a specific
quantity of grounding studs are required. Due to the
extended creep distance, the grounding studs can be
installed closer to one another, thereby reducing the
overall size of the assembly and meeting existing standard
switchgear design dimensions.
OPERATION
Referring to Figures 1 and 2, the second end 24
of the grounding stud 20 is attached to the second end 34
o~ the mounting member 25. The second end 34 of the
mounting member 25 is installed on a bus system 36 by
utilizing the plurality of openings 38. After the
grounding stud 20 is attached to the bus system 36, the
point of installation to the bus system 36 is retaped or
insulated employing standard practices used on a bus
joint splice or cable termination.
To utilize the grounding stud assembly 10 to
gxound the bus system 36, from a safe working distance, an
operator inserts a removal tool (not shown), such as a hot
stick, into the eyelet 42 of the cover 40. The operator
lifts the cover 40 disengaging the retaining collar 30
from the annular ring 44. The dangerous procedure of
cutting insulation tape away from the point of ground
application to expose bare potentia]ly "live" circuits is
eliminated. Using standard grounding tools, the operator
applies the safety grounds from a safe working distance.
When the grounding clamp is removed from the
grounding stud 20, the cover 40 is positioned over the
first end 22 and over the elongated portion 26 of the
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grounding stud 20 to insulate the grounding stud 20 for
prPventing inadvertent discharge into the environment.
Therefore, the invention provides A groundiny
stud assembly which complies with the applicable stan-
dards, which can be installed in various bus systems, andwhich can be safety used to facilitate grounding of the
equipment.
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