AU683680B2

AU683680B2 - Power cable jointing accessory and power cable equipped therewith

Info

Publication number: AU683680B2
Application number: AU72966/94A
Authority: AU
Inventors: Bernard Aladenize; Jean-Claude Assier; Jean Becker; Jose Bezille; Francois Gahungu; Hakim Janah; Alain Le Mehaute
Original assignee: Alcatel Cable SA
Current assignee: Nexans France SAS
Priority date: 1993-09-17
Filing date: 1994-09-14
Publication date: 1997-11-20
Anticipated expiration: 2014-09-14
Also published as: DK0644641T3; EP0644641B1; FR2710204B1; CN1113045A; DE69421781T2; JPH07170624A; NO943427L; EP0644641A3; EP0644641A2; NO943427D0; AU7296694A; KR950009754A; FR2710204A1; DE69421781D1

Description

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: Societe Anonyme dite: ALCATEL CABLE S Actual Inventor(s): Hakim Janah *Jean Becker *Francois Gahungu Jean-Claude Assier Bernard Aladenize Alain Le Mehaute Address for Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: POWER CABLE JOINTING ACCESSORY AND POWER CABLE EQUIPPED

THEREWITH

Our Ref: 383294 POF Code: 1501/188345 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): method of performing it known to applicants): u~gAYUDI~PPIIIB~ra*RRse~Rens~~ POWER CABLE JOINTING ACCESSORY AND POWER CABLE EOUIPPED

THEREWITH

The present invention concerns medium voltage, high voltage and very high voltage DC or AC power cables. It applies in particular to a jointing accessory for a cable of this kind and to the power cable equipped therewith.

Power cables include a conductive core, an inner semiconductor screen covering the core, an insulative dielectri layer over the innez semiconductor screen, an outer semiconductor screen over the dielectric layer and an outer protective sheath.

The insulative dielectric layer is an extruded or wrapped polymer insulator. The protective sheath can be S"".of metal, and in particular of lead in the case of buried 15 power cables, and can then also serve as a metal earthing screen, or it can be insulated in which case it is .po usually associated with an underlying metal earthing screen. The semiconductor screens are made from a polymer material containing carbon black, for example.

Jointing devices fitted to power cables include terminations for connection to the grid or to equipment, a.° "branch connections between cables or to equipment, and splices between two cables.

Prior art jointing devices include: S. 25 a connection part which is electrically and o mechanically connected to the bared core of the end part of the cable or cables concerned, a jointing accessory associated with the connection part and used to reconstitute the successive layers of the cable stripped over an adequate length and to terminate these layers. The jointing accessory covers all or part of the connection part or merely extends the connection part, in which case it can be contiguous with the latter, and constitutes an adapter or reducer on the upstream side of the connection part on the cable. It III1I~C1 ~slpBl~aa~*sraasrr~8Irase~armrr can itself protect the jointing equipment but is more usually covered with an associated outer protection sleeve which also covers all or part of the connection part.

The layers of the end part of the cable are usually stripped in stepped lengths to provide access to each of them and to the core and to cater for fitting the connection part and the associated accessory.

The accessories can additionally provide insulation, in particular where the inner and outer semiconductor screens of the cable are terminated. To this end they con be made primarily from an insulative material (in the form of a tape or a sleeve) and carry or are fitted over a semiconductor layer provided at 15 appropriate locations to reconstitute the inner semiconductor screen. To reconstitute the outer semiconductor screen they are covered with an appropriate semicondunctor layer once they have been fitted to the •el• cable.

The jointing accessories are preferably formed in the well known manner by a simple insulative sleeve whose e •inside surface is semiconductive over at least part of oo the length of the sleeve. A sleeve of this kind covers at least the bared parts of the inner semiconductor a e screen and the dielectric layer. It is relatively rigid and its inside cross-section is matched to the crosssections of the parts to be covered, or it can be shrunk onto the parts to be covered. The continuity of the outer semiconductor screen is reconstituted by wrapping a semiconductive layer over the sleeve and extending as-far as the outer semiconductor screen of the cable, for example.

To achieve homogeneous distribution of the electric field a rigid or shrinkable sleeve of this kind must procure uniform radial contact between the inner and I Ispa 8Prra~l~oaca~aa~ outer semiconductor screens of the respective semiconductor parts of its inside and outside surface- To this end the end part of the sleeve around the outer semiconductor screen is often semiconductive throughout its thickness, which is then relatively small, and the semiconductive outer surface runs from this semiconductive end part in a conical shape to form a deflector integral with the sleeve so that the electric field is homogeneously distributed at the termination of the outer semiconductor screen of the cable.

These sleeves are relatively time" consuming and costly to manufacture. Fitting them, including the :.preliminary operation of stripping the end part of the Scable, is also time consuming. Furthermore, it is S 15 difficult to position long sleeves correctly, especially on cable joints, and this can lead to deterioration of the functions to be provided.

An object of the present invention is to avoid ee these drawbacks by simplifying the manner in which the functions of the jointing accessories are achieved, by reducing the time required to fit them correctly and by making them easier to fit. '7he invention 4e\provide improved insulation.

To this end the present invention proposes a power 25 cable jointing accessory adapted to be fitted to a stripped end part of said cable and to provide insulation around said stripped end part, said cable including a conductive core and, in succession around said cc,, an inner semiconductor screen, a dielectric layer, an outer semiconductor screen and an outer protective sheath and said accessory including a first part adapted to reconstitute said dielectric layer, associated second and third parts adapted to reconstitute said inner semiconductor screen and said outer semiconductor screen, respectively,

I

1~Bs~Q~E~iG~ar~ st-1\ said first and scon parts of said jointing accessory are nt rialdleateuy from an insulative polymer matrix containing at least one conductive polymer incorporated into said polymer matrix in a concentration by weight such that the resulting direct current electrical conductivity of said first and second parts is less than 14 S/cm and their resulting alternating current electrical conductivity is less than 10- 10 S/cm, and ia ~slah-said third part has an electrical conductivity less than 1 S/cm.

Because of the invention it is no longer necessary to manufacture a jointing accessory in three separate parts. The jointing accessory of the invention has only S 15 two separate parts, which simplifies manufacturing it and fitting it.

Because of the specific material used to manufacture the first and second parts of the accessory the electrical conductivity of the latter varies locally with the electric field so that near the inner semiconductor screen of the cable the accessory behaves as a semiconductor screen and near the insulative dielectric layer of the cable the accessory behaves substantially as an insulator.

S 25 Also, the accessory of the invention avoids the need to strip the cable completely; it is sufficient to bare the conductive core and the outer semiconductor screen by making a straight (or possibly slantwise) cut through the various layers between these two parts.

To achieve the required conductivities, the insulative polymer matrix advantageously incorporates not more than 20% by weight of a conductive polymer selected from undoped and dedoped polymers; if the conductive polymer used is an autodoped polymer, it is present in the polymer matrix in a proportion by weight of not more

I

I~UP"OY~Y-- IY~ l--l I than The accessory of the invention can advantageously have at least one of the following additional features: it forms a sleeve with shoulders inside the bore surrounding at least part of the semiconductor screen and the underlying dielectric layer of said cable and having in a first end portion of said bore an inside crosssection substantially identical to the outside crosssection of one of the peripheral layers of the cable, defined by said outer semiconductor screen and said outer protective sheath of said cable, to cover:said peripheral *.layer, said sleeve having in a second portion of said S. bore an inside cross-.section substantially identical to *the cross-section of the cable core, there being a single 15 shoulder between said first and second portions of said bore, said single shoulder between said first and second portions of said bore is at right angles or c~eo frustoconical.

The invention also consists in a power cable equipped with an accessory of this kind characterised in 2" that said end part of said cable is bared continuously and simultaneously through at least said outer semiconductor screen, said dielectric layer and said S. 25 inner semiconductor screen, as far as said core, and carries said accessory whose inside cross-section is matched to the bared end part.

This cable connected by a connection member to another power cable whose end part is also stripped is advantageously characterised in that said accessory is moulded directly onto said connection member and at either end thereof onto the bared end parts of said cables.

Other features and advantages of the present invention will emerge from the following description of I- s -I

II~

embodiments of the invention shown in the appended drawings. In the drawings: figure 1 is a part-sectional view in elevation of a jointing accessory of the invention fitted to a power cable, figures 2 and 3 are views analogous to figure 1 for variants of the figure 1 embodiment, figure 4 is a part-sectional view in elevation of a power cable joint and its jointing accessory of the invention.

Referring to figures 1 through 4, the various component parts of each power cable shown are identical .in all the figures and are identified by the same *reference numbers, these reference numbers simply bearing S 15 the suffix A or B in figure 4. The cables are each •identified by the generic reference number 10, with the suffix A for one of the cables and the suffix B for the other in figure 4.

Note that all electrical conductivities referred to are at room temperature.

Each cable includes a conductive core 1 and, in o. succession, an inner semiconductor screen 2, an insulative dielectric layer 3, an outer semiconductor screen 4 and an outer protective sheath 5. The protective sheath is made of metal, for example lead or lead alloy, or can be insulative in which case it is usually associated with a directly underlying metal screen (not shown).

Figure 1 shows the component parts of the cable stripped in succession over stepped lengths along theend part of the cable which, prepared in this way, carries an adapter (or reducer) 7 of the invention around the partially stripped outer semiconductor screen 4, the stripped dielectric layer 3 and the stripped inner semiconductor screen 2. A semiconductor layer 11 over I I the adapter 7 reconstitutes the outer semiconductor screen 4 to re-establish the insulation at this level, for which purpose it extends as far as and partly surrounds the screen 4. The combination of the adapter 7 and the semiconductor layer 11 constitutes a jointing accessory 12 of the invention.

The adapter 7 of the invention is made from a material comprising an insulative polymer matrix containing a dedoped or undoped conductive polymer in a concentration of not more than 20% by weight.

In an equally advantageous variant of the invention, the adapter 7 is made from a material %oooe •comprising an insulative polymer matrix containing not S' more than 5% by weight of an autodoped conductive S. 15 polymer.

a *S The AC and DC conductivity of the semiconductor layer 11 is less than 1 S/cm. This layer can be made from a material of the type described in document eo :EP-A-0O 507 676, for example, i.e. it can comprise an insulative polymer matrix containing 5% to 70% by weight, preferably from 20% to 30%, of a dedoped or undoped conductive polymer or more than 5% and preferably from to 40% of an autodoped conductive polymer.

The layer 11 can equally well be made from a standard semiconductor material.

The adapter 7 forms a sleeve covering the stripped ends of the outer semiconductor screen 4 (in part), the dielectric layer 3 and the inner semiconductor screel 2.

It is moulded directly onto only the parts to be covered, or is premoulded and fitted over these parts, and possibly fastened mechanically at the ends, for example by heating the corresponding end of the sleeve and/or that of the outer semiconductor screen 4 in situ. It has a central bore 17 whose length and whose stepped crosssection match the respective lengths and the respective Ilql -s~-W II~ P~Plln~-~ I ~slll 8 cross-sections of the parts that it covers.

Alternatively, the adapter 7 can be made up from an extruded strip having the same composition as the aforementioned sleeve which is wound around the parts to be covered and mechanically fastened to them.

Referring to figure 2, the end part of the cable is prepared by a str.aight cut through the inner semiconductor screen 2, the dielectric layer 3 and the outer semiconductor screen 4 around the core 1, the outer protective sheath 5 being partially removed to bare a part of the outer semiconductor screen 4.f The end part prepared in this way carries an adapter 8 of the invention covered with a semiconductor layer 13 identical ':to the layer 11, the adapter 8 and the layer 13 forming a 15 jointing accessory 14 of the invention.

The adapter 8 has the same composition as the adapter 7 from figure i. It covers a short length of the :.-bared core and the bared outer semiconductor screen 4.

It constitutes a sleeve which is moulded in situ or is premoulded, fitted to the prepared end part of the cable S.10 and advantageously caused to adhere to the right-angle 01go cut surface for good contact of the sleeve with the latter.

The bore 18 in the adapter 8 has a single right- 25 angle shoulder. Its cross-section to either side of this shoulder matches the respective cross-sections of the outer semiconductor screen 4 and the core i.

The semiconductor layer 13 covers the adapter 8 in part and extends as far as the outer semiconductor screen 4 which it covers in part.

Referring to figure 3, the end part of the cable is prepared, not with a straight cut as in figure 2 but with a slantwise cut through the outer semiconductor screen 4 and the dielectric layer 3 continuous with a straight cut through the inner semiconductor screen 2 to -r r I- 1 '1111 '41 pi bare the core 1. It carries an adapter 9 of the invention, similar to the adapter 8, the bore 19 in which has end portions at opposite ends whose cross-sections match those of the outer semiconductor screen 4 and the core 1, respectively, with a frustoconical intermediate shoulder matching the slantwise cut which bares the core i.

This slantwise cut ensures better contact of the adapter 9 and better adhesion to the frustoconical cut surface.

The adapter 9 is covered with a semiconductor layer 15 identical to the semiconductor layer 13 and extending as far as the outer semiconductor screen 4 which it e covers in part. The adapter 9 and the layer 15 form a jointing accessory 16 of the invention.

o Referring to figure 4, which shows a splice between two cables 10A and 10B, the end parts of the cables to be spliced are stripped in succession over stepped lengths Sor can be stripped by means of a slantwise cut. A connection member 20 joins the ends of the stripped cores A and lB. A sleeve or adapter 21 of the invention, with "the same composition as the adapters from figures 1 to 3, is moulded onto the connection member 20 and at each end thereof onto the stripped parts and the end portions of 25 the semiconductor screens 4A and 4B of the two cables and 10B. It strengthens the mechanical jointing of the cores 1A and lB so that the connection member 20 can be a mechanical jointing and electrical connection part or merely a weld to provide the electrical connection but which is relatively weak mechanically.

The sleeve 21 is covered with a semiconductor layer 22 which extends over the semiconductor screens 4A and 4B to render them continuous.

As an alternative to this, the sleeve 21 mounded in situ can be replaced by a tape winding with the same ~IP I composition over the parts to be covered.

Of course, the joint can further comprise, in a known manner which is not shown, a heat dissipator fitted around the connection part and extending from either side of the latter over the stripped cores, together with two reducers fitted at opposite ends of the dissipator over the stripped dielectric layers 3A and 3B of the two cables.

The sleeve 21 advantageously combines the functions of a heat dissipator of this kind and of the two reducers so that the latter are not needed.

S. The composition of the jointing accessory of the invention and its main function resulting from this composition are described below.

The insulative polymer matrix and the conductive Spolymer of the accessory are polymers identical to those used in the manufacture of the semiconductor screen described in document EP-A-0 507 676.

The polymer matrix of the accessory therefore comprises at least one thermoplastic polymer selected from acrylic resin, styrenic resin, vinyl resin, cellulosic resin, polyolefins, fluoropolymers, polyethers, polyimides, polycarbonates, polyv"ethanes, silicones, their copolymers, mixtures of homopolymers and mixtures of homopolymers and copolymers.

In particular, the thermoplastic polymer is selected from polypropylene polyethylene (PE), ethylene-vinyl acetate copolymer (EVA), ,'thylenepropylene-dienmonomer (EPDM), fluoropclyvinylidene (PVDF), ethylene-butylacrylate (EBA) and mixtures thereof.

As an alternative to this, the polymer matrix comprises at least one thermosetting polymer selected from polyesters, epoxy resins and phenolic resins.

The undoped or doped and then dedoped conductive I I Lml -~49 1 I~ I~LI polymers incorporated into the polymer matrix are selected from the group comprising polyauiline, polythiophene, polypyrrole, polyacetylene, polyparaphenylene, polyalkyltiophenes, derivatives thereof and mixtures thereof.

These undoped and dedoped polymers do not contain ionic groups. Their intrinsic DC electrical conductivity is very low and in the order of 10-1 0 S/cm to 10 9 S/cm.

The low field strength DC conductivity of the accessory made from this polymer matrix containing not more than by weight of undoped or dedoped polymer is in the order of 10- 14 S/cm and its low field strength AC aconductivity is in the order of 1010 S/cm. It can be locally in the order of 10 S/cm at high levels of 15 electric field strength.

If autodoped polymers are incorporated into the matrix they are selected from the group comprising autodoped polyanilines having benzine or benzine and quinone some wi ;h grafts constituted either by a hydrocarbon radical comprising two to eight carbon atoms interrupted by at least one heteroatom or by a strong acid function or one of its salts, said heteroatom being either O and S and the strong acid function being chosen from sulphonic, phosphonic and phosphoric acid functions S 25 or their salts.

The intL'nsic DC electrical conductivity of the autodoped polymers is in the order of 10 3 S/cm to 10-2 S/cm on average. It can be varied at will between 5 S/cm and 1 S/cm by varying the molecular ratio of the two types of graft. The electrical conductivity of the accessory made from the above polymer matrix to which not more than 5% by weight of this autodoped polymer is added can itself be adjusted and at low electric field strengths is in the order of or less than 10 14 S/cm (DC) or in the order of or less than 10-1 0 S/cm (AC).

I p-sl Ib 61'-ell 118U4 A jointing accessory with this composition is intrinsically insulative, except locally, if required, when it is subjected to a high. electric field whereupon it becomes substantially conductive to provide an integral deflector better ruited to the existing electric field distributed in this way.

Other advantages of the jointing accessory of the present invention include: the simplicity and speed of the preliminary operation to strip the end part of the cable or cables, the easy and fast manufacture of the sletve or the tape and the possibility for direct use of the accessory by moulding it onto the prepared end part of the cable or cables, the enhanced reliability of the accessory, o the heat dissipator and reducer functions provided simultaneously in a joint which is itself simplified.

Of course, the invention is not limited to the embodiments that have just been described.

In particular, the accessory of the invention can Sbe manufactured by a conventional process, possibly "mineral charges, stabilising agents, cross-linking agents, etc added to the various materials used.

The semiconductor layers which reconstitute tlh outer semiconductor screens can be made of an v of the standard semiconductor materials.

An outer protective sheath can be fitted over the accessory of the invention in the usual manner.

Claims

1. Power cable jointing accessory adapted to be Ji to a stripped end part of said cable and to provide insulation around said stripped end part, said cable including a conductive core and, in succession around said core, an inner semiconductor screen, a dielectric layer, an outer semiconductor screen and an outer protective sheath and said accessory including a first part adapted to reconstitute said dielectric layer and associated second and third parts adapted to reconstitute said inner semiconductor screen and said outer semiconductor screen, respectively, wherein said first and second parts of said jointing accessory are integrally formed from an insulative polymer matrix containing at least one conductive polymer incorporated into said polymer matrix in a concentration by weight such that the resulting direct current electrical conductivity of said first and second parts is less than 1014 S/cm and their resulting alternating current electrical conductivity is less than 10 10 S/cm, and wherein said third part has an electrical conductivity less than 1 S/cm.

2. Accessory according to claim 1 and constituting a sleeve with an internally shouldered bore surrounding at least the outer semiconductor screen in part and the underlying dielectric layer of said cable and having in a first end portion of said bore an inside cross-section substantially identical to the outside cross- •o section of said outer semiconductor screen of said cable, wherein said sleeve has over a second end portion of said bore an inside cross-section substantially identical to the cross-section of said core and a single shoulder between said first and second portions of said bore. 0•

3. Accessory according to claim 2 characterised in that it has a single right- angle shoulder between said first and second portions of said bore.

4. Accessory according to claim 2 characterised in that it has a single frustoconical shoulder between said first and second portions of said bore.

Power cable fitted with the accessory according to any one of claims 2 to 4 characterised in that said end part of said cable is stripped continuously and simultaneously from at least said outer semiconductor screen to said core and EP C \WI AORD'ELLEWSPECLRLT\72%6-94 DOC r II Is -14- carries said accessory of appropriate .nside cross-section in contact with the stripped end part.

6. Power cable according to claim 5 and connected by a connection member to another power cable with a stripped end part, wherein said accessory is moulded directly onto said connection member and at each end thereof onto the stripped end parts of said cables and constitutes with said connection member a joint between said cables.

7. Power cable jointing accessory substantially as herein described with reference to the accompanying drawings.

8. Power cable substantially as herein described with reference to the accompanying drawings. DATED: 5 February, 1996 PHILLIPS ORMONDE FITZPATRICK Attorneys for: SOCIETE ANONYME DITE: ALCATEL CABLE *9 o *oo ft MJP C;\WINWORDOMARIE\RLTNOOEL\72966C DOC ABSTRACT Power cable jointing accessory adapted to be fitted to a stripped end part of said cable and to provide insulation around said stripped end part, said cable including a conductive core and, in succession around said core, an inner semiconductor screen, a dielectric layer, an outer semiconductor screen and an outer protective sheath and said accessory including a first part adapted to reconstitute said dielectric layer and associated second and third parts adapted to reconstitute said inner S semiconductor screen and said outer semiconductor screen, respectively, characterised in that said first and second parts of said jointing accessory are made identically and simultaneously from an insulative polymer matrix 0. containing at least one conductive polymer incorporated into said polymer matrix in a concentration by weight such that the resulting direct current electrical conductivity of said first and second parts is less than 'nsf 10 1 4 S/cm and their resulting alternating current electrical conductivity is less than 10-10 S/cm, and in 5*50 that said third part has an electrical conductivity less than 1 S/cm. Figure to publish: Figure 4 ~s L I