Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Reexamination Certificate
1999-12-17
2001-07-03
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
C174S142000
Reexamination Certificate
active
06255589
ABSTRACT:
The invention relates to a hermetically sealed current feedthrough for gas-insulated outdoor electrical gear, and more particularly to a current feedthrough for connecting a bare conductor to a metal-clad piece of gear whose metal cladding is grounded.
BACKGROUND OF THE INVENTION
There exist current feedthroughs for outdoor electrical gear that are made of molded synthetic material. An example of such a feedthrough is shown in
FIG. 1
, said feedthrough comprising a central conductor
1
having insulating resin
2
overmolded thereon and including a molded fixing flange
3
of the same material. A field-controlling screen
4
is generally embedded in the resin between the flange and the conductor in the zone where the feedthrough is mounted in the opening provided for it in a wall
5
of the metal cladding of a piece of gear. The flange is fixed to the wall by bolts in a manner that is not shown herein, and it possesses an annular groove for a sealing gasket
6
enabling the feedthrough to be mounted on the wall in hermetically sealed manner. That type of feedthrough suffers from the drawbacks of using a material that is relatively fragile, of requiring the use of a gasket which is difficult to assemble, and of a field-controlling screen whose positioning is critical. In addition, the conical outside shape of the feedthrough in the stress zone that lies between the flange and the fins
7
is unsuitable for receiving a toroidal current transformer.
There also exist composite type feedthroughs, an example of which is shown in FIG.
2
. Such a feedthrough has a core of molded resin
9
about a central conductor
8
and a fixing flange
10
that is integrally molded with the core. The outside surface of the flange and of a cylindrical portion
10
A of the core immediately adjacent to the flange is covered in a conductive covering
11
that is designed to be grounded when the feedthrough is in place. The metal-covered cylindrical portion
10
A is suitable for enabling at least one toroidal current transformer
12
to be installed thereon in the vicinity of the fixing flange. An electric field distributing cone
13
is threaded onto the core after the current transformer(s) and before a series of fins
14
of elastomer material which are stacked on the core one after the other. Functionally, the cone is equivalent to the conical stress zone included in the feedthrough shown in
FIG. 1
, and it serves to control the field at the end of the metal covering, overlying the cylindrical portion
10
A and a portion of itself following said cylindrical portion when the feedthrough is assembled. The desired electrical creepage distance is obtained by means of the stack of fins
14
in a manner that is known to the person skilled in the art. This second type of feedthrough is fixed on the wall
15
of the metal cladding of piece of gear in the same manner as is the first type described above, and it requires the same type of sealing gasket to be installed, so it suffers from the same drawbacks in this respect. It also suffers from the drawback of using a relatively large number of different parts so that manufacture and assembly thereof gives rise to a succession of operations, and in particular of manual operations. Finally, if ever it is necessary to replace a toroidal transformer, e.g. following a failure, it is necessary to dismantle the fins and the electric field distributing cone.
SUMMARY OF THE INVENTION
The invention thus proposes a hermetically sealed current feedthrough for gas-insulated outdoor electrical gear, the feedthrough being intended more particularly to provide connection to a bare conductor of a piece of gear housed inside metal cladding including a wall provided with an opening designed to put a conductive element of the gear into connection with one end of a conductive element housed axially inside the feedthrough.
According to the invention the current feedthrough includes a metal link and screen piece of cylindrical appearance that is held coaxially about the conductive element by a body of molded insulating material covering it in part and forming a plug that is impermeable to gas, and said link piece is terminated by a cylindrical portion projecting from the body, with said piece being welded to the periphery of the opening via the end of said cylindrical portion.
REFERENCES:
patent: 3018318 (1962-01-01), Franklin
patent: 3178505 (1965-04-01), Van Sickle
patent: 3318995 (1967-05-01), Buckley et al.
patent: 3523157 (1970-08-01), Bauer et al.
patent: 3705281 (1972-12-01), Luehring
patent: 4431859 (1984-02-01), Kishida
patent: 4670625 (1987-06-01), Wood et al.
patent: 32 08 358 A1 (1983-09-01), None
patent: 2 729 785 A1 (1996-07-01), None
Johnson Kenneth
Starck Thierry
Alstom
Nguyen Chau N.
Reichard Dean A.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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