[0001] The present invention relates to a method to provide a medium voltage interconnection
for realizing an electrical connection between a receiving connector of a first equipment
station and a receiving connector of a second equipment station.
[0002] Such an interconnection is generally known in the art. It is made of a metal conductor
at the ends of which are mounted electrical connectors. The electrical connector mates
with the receiving connector generally forming part of a "bushing" of an equipment
station. The equipment station is typically a transformer or switchgear in transformation
station and the properties of the connectors are therefore preferably standardized.
[0003] The electrical connector is moulded in polyethylene material so as to form a massive
conductive core enclosed within a screened insulating body. As a result, the interconnection
is relatively rigid and, additionally, is not available in different relative short
lengths, e.g. of about 30 cm.
[0004] A connector of this kind is described e.g. in FR-2 741 484. This document is directed
to an electrical connector for connecting e.g. two cables, and comprising a conductive
core including a metal conductor with at each end thereof, an electrical connector.
It also comprises an elastic protective sleeve made of a layer of semi-conductive
or conductive rubber. This connector is pre-fabricated by moulding a one-piece element.
[0005] An object of the present invention is to provide an interconnection of the above
known type but of which the electrical connectors are relatively more flexible, and
available in different lengths without any significant extra-cost.
[0006] According to the invention, this object is achieved due to the fact that said method
comprises the steps of:
- providing an electrical connector mating said receiving connector at each end of a
metal conductor, said metal conductor with its two connectors forming a conductive
core,
- providing a flexible tube made of at least an insulating layer of elastomeric material
and having the same length as said conductive core,
- expanding radially said flexible tube and sliding therein said conductive core, and
- releasing said flexible tube over said conductive core.
[0007] In this way, the moulding process is replaced by an extrusion process. As a result,
the conductive core is composed of a flexible conductor connected to two electrical
connectors, whole enclosed within an elastic tube or sleeve to define connection insulated
interfaces to mating the receiving connectors of the equipments. For many applications,
flexible interconnections are more adequate due to the flexibility of material and
dimensions.
[0008] The method of the present invention preferably comprises the steps of providing said
electrical connector with a substantially conical shape of which the base has a diameter
relatively larger than the diameter of said metal conductor, and of connecting said
base to an end of said metal conductor.
[0009] The so obtained interconnection best matches the standard bushings.
[0010] More particularly, the present method further comprises the step of engaging one
end of said flexible tube into an inner side of a conical bushing means made of insulating
material and provided with said receiving connector so as to bring the electrical
connector of the conductive core into contact with said receiving connector and said
insulating layer of said flexible tube into contact with said inner side of said bushing
means.
[0011] In a preferred embodiment, said method comprises the steps of providing said flexible
tube with, coaxially starting from the center:
- a first semi-conductive layer,
- an insulating layer made of elastomeric material, and
- a second semi-conductive layer.
[0012] Such an extruded 3-layer tube gives the best results with respect to flexibility
and insulation properties.
[0013] Also in a preferred embodiment, said method further comprises the steps of:
- providing an external locking ring onto at least one electrical connector of said
conductive core, and
- providing into said flexible tube at least one internal ring groove for receiving
the locking ring of said electrical connectors when the tube is released over said
conductive core.
[0014] The flexible tube or sleeve is then locked onto the electrical connectors or end-pieces
of the conductive core to prevent any relative movement. The grooves may also be used
to hold slidable outer clamps to mechanically clamp each electrical connector and
possibly to achieve the external screening continuity between the interconnection
and the mating parts.
[0015] The present invention also relates to a medium voltage interconnection obtained by
the method of the invention and adapted to electrically connect a receiving connector
of a first equipment station and a receiving connector of a second equipment station.
[0016] This medium voltage interconnection is characterized in that it comprises a conductive
core including a metal conductor with, at each end thereof, an electrical connector
adapted to mate said receiving connector, and a flexible tube having at least an insulating
layer made of elastomeric material and covering the whole conductive core.
[0017] In a characterizing embodiment of the present invention, said elastomeric material
is a synthetic terpolymer of ethylene, propylene and diene [EPDM],
[0018] In a variant, said elastomeric material is a silicone.
[0019] These materials are preferred for their good flexibility and insulation qualities.
[0020] Further characterizing embodiments of the present method and medium voltage interconnection
are mentioned in the appended claims.
[0021] It is to be noticed that the term 'comprising', used in the claims, should not be
interpreted as being limitative to the means listed thereafter. Thus, the scope of
the expression 'a device comprising means A and B' should not be limited to devices
consisting only of components A and B. It means that with respect to the present invention,
the only relevant components of the device are A and B.
[0022] Similarly, it is to be noticed that the term 'coupled', also used in the claims,
should not be interpreted as being limitative to direct connections only. Thus, the
scope of the expression 'a device A coupled to a device B' should not be limited to
devices or systems wherein an output of device A is directly connected to an input
of device B. It means that there exists a path between an output of A and an input
of B which may be a path including other devices or means.
[0023] The above and other objects and features of the invention will become more apparent
and the invention itself will be best understood by referring to the following description
of an embodiment taken in conjunction with the accompanying drawings wherein:
Fig. 1 represents a longitudinal view of a conductive core 1 of a medium voltage interconnection
according to the invention;
Figs. 2a and 2b represent the left end and a sectional view of a flexible tube 5 used
in the interconnection of the invention;
Fig. 3 represents the left end of the flexible tube 5 of Fig. 2 prepared to receive
the conductive core 1 of Fig. 1;
Fig. 4 shows the left end of the whole assembly of the medium voltage interconnection
of the invention, including the conductive core 1 of Fig. 1 and the flexible tube
5 of Fig. 3; and
Fig. 5 represents the left end of the medium voltage interconnection engaged in a
bushing of an equipment station.
[0024] It is to be noted that all the views, except Fig. 2b, are cross-sectional views along
the longitudinal axis, and that although only the left end of the medium voltage interconnection
is shown in the Figs. 2a, 3, 4 and 5, the right end of this interconnection is identical
thereto. Moreover, the different views are not all drawn at the same scale.
[0025] The flexible interconnection of the present invention is intended to be used for
electrically connecting medium voltage electrical devices located in distinct equipment
stations. Such an electrical device is for instance a switchgear or a transformer
operating at voltages above 1 kVolt and enclosed in an equipment station that is a
tank or a cubical. The equipment station is filled with an insulated medium that is
oil fluid or gas, generally pressurized sulfur hexa-fluoride [SF6]. Each terminal
of the electrical device is connected to a so-called "bushing well" or "bushing" hermetically
mounted inside a hole of a wall of the equipment station.
[0026] The bushing well is an insulating molded hollow cone provided with a metallic rod
interconnecting a connector at the top of the outer side of the cone with a receiving
connector at the inner side of this cone, inside the well. The receiving connector
meets the requirements of ANSI/IEEE Standard 386-1977 as is the case of the known
bushing "K16O1PCC/K16O1PCC-R Clampable Apparatus Bushing Well with Gasket" of AMERACE™
LTD (10 Esna Park Drive Markham, Ontario, Canada L3R
1E1/1 November 1983). It is to be noted that bushing wells with other dimensions but
still matching the present interconnection may also be used.
[0027] One side of the bushing, generally the outer side of the cone, is immersed in the
insulated medium of the equipment station and electrically connected to the electrical
device, whilst the inner side of the cone is in the ambient air and provided with
the receiving connector designed to receive one end of the flexible interconnection.
[0028] In order to interconnect two bushings, the flexible interconnection comprises a conductive
core surrounded by a flexible tube that will be explained in detail below.
[0029] The conductive core, generally indicated by 1 in Fig. 1, is made of a metal flexible
conductor 2 provided at each end with an electrical connector, indicated by arrows
3 and 4. Each connector 3/4 is adapted for mating the receiving connector of the bushing.
[0030] The electrical connector 3/4 has a central blind hole 5/6 for connecting to a respective
receiving connector of the bushing and has a conical shape of which the base 7/8 is
respectively connected to an end of the metal flexible conductor 2. This base 7/8
has a diameter that is larger than the diameter of the metal conductor 2. The electrical
connector 3/4 is further provided with an external locking ring 9/10 mating in an
internal ring groove of the flexible tube.
[0031] The conductive core 1 is covered, protected and insulated by a flexible tube, generally
indicated by 11 in the Figs. 2a, 2b and 3, and preferably made of up to three layers
of material.
[0032] The flexible tube 11 is a moulded or extruded tube made of a first semi-conductive
layer 12 (at the inside), an insulating layer 13 made of elastomeric material, and
a second semi-conductive layer 14 (at the outside). In order to improve the elasticity
of the flexible tube 11, the elastomeric material of the insulating layer 13 is preferably
a synthetic terpolymer of ethylene, propylene and diene [EPDM]. Additionally, this
EPDM may be recycled and is thus friendly for the environment. The tube 11 preferably
has the same length as the conductive core 1.
[0033] The flexible tube 11 is then prepared for receiving the conductive core 1, as shown
at Fig. 3. Therefore, each end of the second semi-conductive layer 14 is removed at
a certain distance up to the insulation material 13. At the same time, an internal
ring groove 15 is provided at each end in the first semi-conductive layer 12 and partially
in the insulating layer 13 of the flexible tube 11. The flexible tube 11 is then radially
expanded and the conductive core 1 is slided therein.
[0034] Afterwards, the flexible tube is released over the conductive core 1 in order to
obtain a resulting medium voltage interconnection as shown at Fig. 4. The flexible
tube 11 has now taken the shape of the underlying conductive core 1 and the latter
is prevented to move therein owing to the mating external locking ring 9/10 of the
conductive core and the internal ring groove 15 of the tube. The first semi-conductive
layer 12 of the tube is in contact with the metal flexible conductor 2 and the connectors
3/4.
[0035] As shown at Fig. 5, each end of the so obtained interconnection may then be engaged
into an inner side 16 of a conical bushing, generally indicated by an arrow 17, as
described above, and mounted in a hole of a wall 18. The receiving connector 19 of
the bushing 17 is so brought into contact with the electrical connector 3 of the conductive
core via its hole 5, whilst the insulating layer 13 of the interconnection is brought
into contact with the inner side 16 of the bushing. In order to give the necessary
pressure on the expanded tube to ensure a contact with a tight fit between mating
parts of the bushing and the interconnection, a fixing ring, indicated by arrow 20,
is provided over the conductive core at each end thereof. On the left side of the
interconnection, the fixing ring 20 abuts against the base 7 of the conical electrical
connector 3 covered by the flexible tube and is mechanically fixed (not shown) to
the bushing 17.
[0036] As an option, a metal flexible protection (not shown) can be mounted on the outside
of the tube to take the short-circuit currents.
[0037] It is finally to be noted that the insulating layer of the bushing device may also
be a molded elastomeric material, preferably a synthetic terpolymer of ethylene, propylene
and diene [EPDM] as for the insulating layer 13 of the flexible tube 11.
[0038] While the principles of the invention have been described above in connection with
specific apparatus, it is to be clearly understood that this description is made only
by way of example and not as a limitation on the scope of the invention, as defined
in the appended claims.
1. Method to provide a medium voltage interconnection for realizing an electrical connection
between a receiving connector of a first equipment station and a receiving connector
of a second equipment station,
characterized in that said method comprises the steps of:
- providing an electrical connector (3, 4) mating said receiving connector (19) at
each end of a metal conductor (2), said metal conductor with its two connectors forming
a conductive core (1),
- providing a flexible tube (11) made of at least an insulating layer (13) of elastomeric
material,
- expanding radially said flexible tube and sliding therein said conductive core,
and
- releasing said flexible tube over said conductive core.
2. Method according to claim 1,
characterized in that it further comprises the steps of:
- providing said electrical connector (3) with a substantially conical shape of which
the base (7) has a diameter relatively larger than the diameter of said metal conductor
(2), and
- connecting said base to an end of said metal conductor.
3. Method according to anyone of claims 1 or 2, characterized in that said method further comprises the step of engaging one end of said flexible tube
into an inner side (16) of a conical bushing means (17) made of insulating material
and provided with said receiving connector (19) so as to bring the electrical connector
(3) of the conductive core (1) into contact with said receiving connector and said
insulating layer (13) of said flexible tube (11) into contact with said inner side
of said bushing means.
4. Method according to anyone of claims 1 to 3
characterized in that it comprises the steps of providing said flexible tube (11) with, coaxially starting
from the center:
- a first semi-conductive layer (12),
- an insulating layer (13) made of elastomeric material, and
- a second semi-conductive layer (14).
5. Method according to the claims 3 and 4, characterized in that said method further comprises the step of removing partially said second semi-conductive
layer (14) at the end of said flexible tube (11) prior to the step of engaging said
end of said flexible tube into said bushing means (17).
6. Method according to anyone of claims 4 or 5,
characterized in that said method comprises the steps of:
- providing a ring groove into said first semi-conductive layer (12), and
- providing a ring groove partially into said insulating layer (13).
7. Method according to anyone of claims 1 to 6,
characterized in that said method further comprises the steps of:
- providing an external locking ring (9, 10) onto at least one electrical connector
(3, 4) of said conductive core (1), and
- providing into said flexible tube (11) at least one internal ring groove (15) for
receiving the locking ring of said electrical connector when the tube is released
over said conductive core.
8. Method according to anyone of claims 1 to 7 characterized in that said flexible tube (11) has the same length as said conductive core (1).
9. Medium voltage interconnection characterized in that it is made according to anyone of claims 1 to 8 and adapted to electrically connect
a receiving connector of a first equipment station and a receiving connector of a
second equipment station, said interconnection comprising a conductive core (1) including
a metal conductor (2) with, at each end thereof, an electrical connector (3, 4) adapted
to mate said receiving connector (15), and a flexible tube (11) having at least an
insulating layer (13) made of elastomeric material and covering the whole conductive
core.
10. Medium voltage interconnection according to claim 9, characterized in that said elastomeric material is a synthetic terpolymer of ethylene, propylene and diene
[EPDM].
11. Medium voltage interconnection according to claim 9, characterized in that said elastomeric material is a silicone.
12. Medium voltage interconnection according to anyone of claims 9 to 11, characterized in that said electrical connector (3) has a substantially conical shape of which the base
(7) is connected to said metal conductor (2), said base having a diameter relatively
larger than the diameter of said metal conductor.
13. Medium voltage interconnection according to claim 12, characterized in that one end of said flexible tube (11) is adapted to be engaged into an inner side (16)
of a conical bushing means (17) made of insulating material and provided with said
receiving connector (15), the electrical connector (3) of said conductive core (1)
being adapted to be brought into electrical contact with said receiving connector,
and said insulating layer (13) of said flexible tube being adapted to be brought into
contact with said inner side of said bushing means.
14. Medium voltage interconnection according to claim 13, characterized in that said interconnection is provided with a fixing ring (20) located over said conductive
core (1) and over said flexible tube (11), said fixing ring being adapted to abut
against the base (7) of the conical electrical connector (3) and to be fixed to said
bushing means (17).
15. Medium voltage interconnection according to anyone of claims 9 to 14, characterized in that said flexible tube (11) is a multi-layer tube comprising, coaxially starting from
the center, a first semi-conductive layer (12), an insulating layer (13) made of elastomeric
material, and a second semi5 conductive layer (14).
16. Medium voltage interconnection according to anyone of claims 9 to 15, characterized in that the electrical connector (3, 4) of said conductive core (1) is provided with an external
locking ring (9, 10) mating in an internal ring groove (15) in the insulating layer
(13) of said flexible tube (11).