Electrical interconnections

Details Electrical interconnections Electrical interconnections

1997-07-14

1999-05-04

Kincaid, Kristine

Electricity: conductors and insulators

Conduits, cables or conductors

Combined

174 75R, 174 76, H02G 1508

Patent

active

059005858

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

This invention relates to the protection of electrical interconnections. Such interconnections may be between two or more electrical cables (i.e. in-line or branch joints), between two or more pieces of other electrical equipment such as transformers and switchgear, but which may also include another cable or between cable and equipment, including cable adapters and terminations. Such an interconnection usually needs to be protected against ingress of moisture to interconnected conductors, and to provide electrical insulation therearound. Additionally, at voltages above about 10 kV, some form of electrical stress control is usually also desired. The invention is generally applicable to electrical interconnections at low voltage, typically around 1 to 10 kV, at medium voltage, typically around 10 to 36 kV, and also at high voltage, typically greater than 36 kV.


DESCRIPTION OF RELATED ART

Various technologies exist for protecting such interconnections, some of which are more applicable to one voltage range rather than another, and some applicable to cables, for example, of one material, for example polymeric, then another, for example paper. Amongst these technologies may be mentioned polymeric heat shrink, elastomeric push -on and roll-on, elastomeric hold-out, tape winding, hot bitumen filling, and cold-pour resin systems. Yaworski et al., U.S. Pat. No. 5,606,149 (1997), the contents of which also published in International Application Publication No. WO 95/11543, discloses a power cable joint which is filled by a compressible sealant material such as gel, which has been found to have surprisingly good performance.


BRIEF SUMMARY OF THE INVENTION

The present invention is particularly concerned with an interconnection between an electric cable and other electrical equipment in which a compressible, and preferably oil-extended polymeric, sealant material is employed to seal and to provide electrical insulation around the connection.
Thus, in accordance with one aspect of the present invention, there is provided an enclosure arranged to enclose a connection between a screened electric power cable and another piece of electrical equipment, the enclosure comprising a housing, at least one electrical stress cone contained within the housing, and a quantity of compressible sealant material that is contained by the housing and that substantially fills the housing when enclosing the interconnection, wherein the or each stress cone comprises resilient aperture means that is arranged to change its volume in response to a change of volume of the sealant material thereby, in operation, to maintain substantially complete filling of the housing around the interconnection without the formation of voids therein.
The resilient aperture can thus adapt to the volume of the sealant material as it changes in response to change in temperature of the substrate or of its ambient surroundings or to other external pressure. The sealant material advantageously adheres to the resilient means so as to minimise the likelihood of a void forming as a result of movement of the material.
The aperture means may expand, or stretch, as the sealant expands, or it may be arranged to be in a relaxed configuration when the sealant is in its expanded state, which is expected to be the state it occupies most of its time in operation.
In many applications of the present invention, it is advantageous for the resilient aperture means to exert a continuous pressure on the sealant material. However, when the sealant material comprises a combination of solid and a liquid component, such as a gel comprising an oil-filled polymer for example, the pressure should not be such as to urge the liquid component significantly out of the complete system.
The aperture means may be provided by a void or gaseous entrapment contained completely within a resilient portion of the stress cone, or located between a resilient portion of the cone and a non-resilient portion of the housing.
A spring and plunger arrangement may be provided so as to

REFERENCES:
patent: 3571783 (1971-03-01), Lusk
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patent: 4079189 (1978-03-01), Troccoli
patent: 4377547 (1983-03-01), Hervig
patent: 4852646 (1989-08-01), Dittmer et al.
patent: 4863535 (1989-09-01), More
patent: 4868967 (1989-09-01), Holt et al.
patent: 5079300 (1992-01-01), Dubrow et al.
patent: 5606149 (1997-02-01), Yaworski et al.
patent: 5804767 (1998-09-01), Windfield et al.
Derwent Abstract No. 78-L0695A/51 (Abstract of FR 2,394,197) (Jan. 1979), Abs only.

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