Electricity: conductors and insulators – Insulators – Combined
Reexamination Certificate
2001-01-22
2002-05-21
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Insulators
Combined
C439S921000, C174S07000A, C174S07100B, C174S0720TR
Reexamination Certificate
active
06392157
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for bus coupling between enclosed switchboards with an insulating gas sealed therein, such as cubicle type gas-insulated switchgear.
2. Description of the Related Art
FIG. 3
shows a schematic construction of a known conventional cubicle type gas-insulated switchgear
100
employing a square container. The switchgear
100
includes a plurality of cubicles
101
,
102
,
103
, and
104
. The cubicles
101
,
102
,
103
, and
104
accommodate devices for each unit circuit, such as a circuit breaker, a disconnector, and a transformer for measuring instruments. Power is supplied to the switchgear
100
through a power receiving cable
105
. The cubicles
101
,
102
,
103
, and
104
are electrically connected via T-shaped bushings
31
by insulated coupling buses
35
for establishing communication between switchboards.
FIG. 4
shows an example of a specific structure of the conventional known T-shaped bushing
31
used in the gas-insulated switchgear
100
. The T-shaped bushing
31
is disclosed, for example, in FIG. 8 of Japanese Laid-open Patent Application No. 60-160309.
As shown in
FIG. 4
, the conventional T-shaped bushing
31
includes a T-shaped bushing mold
41
with a substantially T-shaped current-carrying conductor
32
integrally formed therein. The T-shaped bushing mold
41
is normally molded using an epoxy resin. The current-carrying conductor
32
is formed to have a substantially T shape by a cylindrical shielding electrode
32
a
and a conductor drawing-out rod
32
b
that juts out perpendicularly in a radial direction from a central outer periphery of the shielding electrode
32
a
. A contact
39
is disposed on an inner periphery of the shielding electrode
32
a
. The contact
39
is formed such as by inserting an elastic conductive plate, which has many punched holes, along an inner periphery of a concave groove
42
provided in an inner periphery of the shielding electrode
32
a.
To connect the cubicles
101
,
102
,
103
, and
104
by the T-shaped bushings
31
constructed as set forth above, the coupling buses
35
formed of a bridging polyethylene insulated cable that has been cut to a predetermined length are used.
First, both ends of the coupling bus
35
are stripped to expose a conductor
43
and an insulator
44
(only one end is shown in FIG.
4
). Then, a stress cone
46
for relieving the electric field of a shielding layer
45
, a pressing member
47
such as a spring that presses the stress cone
46
toward a connection port
40
of the coupling bus
35
, a protective tube
48
for protecting the end of the coupling bus
35
, etc. are attached to an outer periphery of the exposed insulator
44
.
Subsequently, a conductive plug
49
which has an outside diameter substantially equal to or greater than an outside diameter D of the coupling bus before the coupling bus
35
is stripped and which is to be closely fitted to the contact
39
is attached to the end of the conductor
43
. The plug
49
is disposed such that it is closely fitted to the contact
39
, and the required components, including the stress cone
46
, that have been attached in advance, are disposed at predetermined positions, and these components are then assembled by common means. In
FIG. 4
, reference numeral
104
denotes a cubicle, which is identical to the one shown in
FIG. 3
, reference numeral
50
denotes a blank cap, reference numeral
51
denotes a seal, reference numeral
52
denotes an external semiconductive layer, and reference numeral
53
denotes a shield.
However, since the conventional device for bus coupling between the enclosed switchboards with an insulating gas sealed therein uses the bridging polyethylene insulated cable cut to a predetermined length as the coupling bus
35
, the stripping process is cumbersome and it is also difficult to improve machining accuracy. Furthermore, as the ends of the coupling bus
35
are stripped, the seal
51
, the protective tube
48
, the stress cone
46
, etc. are required. This results in a complicated structure, a cumbersome assembly process, a prolonged assembly time, and an increased cost.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made with a view toward solving the problems with the prior art, and it is an object of the invention to provide an inexpensive device for bus coupling between enclosed switchboards with an insulating gas sealed therein that has a simpler structure and permits a shortened time for assembly.
To this end, according to one aspect of the present invention, there is provided a device for bus coupling between enclosed switchboards with an insulating gas sealed therein, comprising: a coupling bus for establishing communication between switchboards that have an insulating gas sealed therein and which accommodate electric units; a T-shaped bushing that has a current-carrying conductor integrally molded therein, a connection port for the coupling bus, and a contact for making connection between the coupling bus and the current-carrying conductor; and a fixture for securing an end of the coupling bus that has been inserted in the connection port of the T-shaped bushing, wherein a bore shape of the connection port for the coupling bus in the T-shaped bushing is a conical shape in which the diameter thereof increases outwardly, the coupling bus has a central conductor composed of a one-wire conductor, an insulating rubber member covering an outer peripheral surface of the central conductor, and a conductive layer formed on the outer peripheral surface of the insulating rubber member, in which both end portions of the insulating rubber member are formed into conical portions that fit to the connection port, a portion between both end portions is formed into a cylindrical portion having a uniform diameter, and a boundary portion between the cylindrical portion and the conical portions is formed into a stepped portion so that the outside diameter of the cylindrical portion is smaller than the outside diameters of the conical portions, the fixture secures the coupling bus by pressing the stepped portion into the connection port, and the conductive layer is provided only on an outer peripheral surface of the cylindrical portion, and further, is grounded.
The coupling bus according to the present invention may have a conductive layer between an inner surface of the insulating rubber member and the outer peripheral surface of the central conductor.
The device for bus coupling between enclosed switchboards with an insulating gas sealed therein according to the present invention may be provided with an air unit coupling bushing at one of the connection ports of the T-shaped bushing. In this case, the air unit coupling bushing is equipped with a central conductor and an insulating rubber member covering the central conductor. One end of the insulating rubber member is formed into a conical portion that fits to the connection port, and an outer peripheral surface on an outer side of the connection port in the insulating rubber member is provided with ribs that have an outside diameter larger than the outside diameter of the conical portion.
REFERENCES:
patent: 4032820 (1977-06-01), Oishi et al.
patent: 4865559 (1989-09-01), Clabburn
patent: 6002085 (1999-12-01), Utsumi et al.
patent: 6042407 (2000-03-01), Scull et al.
patent: 195 02 048 (1996-07-01), None
patent: 0 624 924 (1994-05-01), None
patent: 60-160309 (1985-08-01), None
patent: 7-230731 (1995-08-01), None
Arioka Masahiro
Isoya Hiroshi
Lee Jinhee
Mitsubishi Denki & Kabushiki Kaisha
Reichard Dean A.
Sughrue & Mion, PLLC
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