FR2752106A1 - Self supporting termination for high tension power cable - Google Patents

Abstract

The self-supporting cable termination accepts a cable with a conductive core and insulating layer, a semiconductor screen, a conductive metal screen and an external protective sheath. The termination has a tubular housing with a sealed end to accept the end of the cable. Openings (26,27) are formed in opposite ends of the chamber enclosing the stripped end of the cable, allowing the chamber (25) to be at the ambient external pressure and circulation of air in the chamber. A continuous flexible cover (12) with insulating skirts (13) is mounted on the stripped insulation (3) of the cable between the electric field deflector (11) covering the semiconductor screen and the cap (17) at the end of the termination.

Description

SELF-CARRYING ENERGY CABLE END
The present invention relates to a self-supporting end of electric cable, in particular of high or very high voltage cable, said cable comprising a conductive core, an insulation, a semiconductor screen, a conductive metal screen and an outer protective sheath.

 Such an end is more especially provided for the external connection of an energy cable from an underground line to an overhead network or to an apparatus.

 Document Fr-A-2590739 discloses such a self-supporting power cable end. This end comprises an end portion of the cable successively stripped, a support for fixing said end portion relative to the ground, a cone deflector of the electric field mounted on the stripped semiconductor screen and an adjoining portion of the stripped insulation, a connecting conductive terminal end piece mounted on the stripped conductive core and a rigid and insulating tubular body carried by said support and extending without contact around the terminal portion of the cable. This tubular body is provided with a metal end cap, opposite to said support and traversed in a sealed manner by the stripped conductive core and the connection end piece. It is made of porcelain and has a series of peripheral skirts stepped over its height, for lengthening the lines of leakage between the cap and the metallic support itself. This tubular body defines a sealed chamber, around the end portion of the cable, between said support and said cap, which is filled with.

dielectric gas under pressure, in particular SF6.

 Such an end is made self-supporting by its insulating and rigid tubular body. It thus has the advantage of avoiding the use of posts or other support structure which then necessarily has to extend over the total length of the cable end when the latter comprises an insulating but relatively flexible tubular body. On the other hand, it has the disadvantage of not avoiding the risks of explosion and projection of debris, during electrical faults such as abnormal overvoltages in the end.

 To minimize these risks and ensure better protection of people, materials and property, it is known to provide, on such self-supporting ends, a rupture zone of the chamber under dielectric gas pressure, with an associated external protection of retention of projections in the event of deflagration in the chamber and rupture of this zone. Of course, the realization of such a rupture zone makes the end more complex and more cumbersome.

 The present invention aims to solve the problems posed by the self-supporting ends of energy, energy cable, so as to avoid the aforementioned risks without however leading to a more complex and / or bulky realization.

 It relates to a self-supporting end of the type as mentioned above, characterized in that it has openings in the two opposite end parts of said chamber, for bringing the chamber to external ambient pressure and an air circulation. in the chamber, and a continuous and flexible assembly of second insulating skirts, mounted on the stripped insulation, between said deflector cone and said cap.

This end advantageously also has at least one of the following additional characteristics
- the tubular body is made of a composite material which is mechanically resistant to the surrounding external conditions
- The end comprises third insulating skirts constituted by at least one modular element with fins or spiral attached internally to the tubular body;
the end comprises a dielectric material, solid but with internal cells, for filling said chamber
- The chamber openings are provided for some in said cap and for the others in said support.

 The characteristics and advantages of the present invention will emerge from the description given below of an embodiment given by way of preferred example and illustrated in the single figure of the attached drawing.

 This single figure represents a self-supporting end of power cable, partially illustrated in section and in elevation.

 In this figure, the reference 1 designates an energy cable from an underground line, or more precisely the terminal portion of this cable which has been released from the underground line and is equipped with an end 10, according to the present invention.

 This cable comprises a central conductive core 2, an insulation 3, a semiconductor screen 4, a conductive metal screen 5 and an external protective sheath 6. This terminal portion of the cable is successively stripped over part of its length.

 The end 10 comprises this end portion of the cable and of the equipment mounted on the stripped part thereof. This equipment comprises an electric field deflector cone 11 mounted on the stripped semiconductor screen 4 and an adjoining portion of the stripped insulation 3, a continuous and flexible assembly 12 of insulating skirts 13 associated with the deflector cone and mounted on the stripped insulation 3 and a connecting conductive end piece 14 mounted on the stripped conductive core. They also comprise a rigid and insulating tubular body 15, which surrounds the deflector cone 11 and the set of insulating skirts 13 without contact, a support 16 for fixing the end portion of the cable relative to the ground and a cap 17 received on the body opposite the support.

 The mounting bracket is a horizontal metal bracket, with a passage for the cable. The terminal portion of the cable is fixed by its bare metal screen to the support 16. This fixing is made by a couple of complementary retaining rings 18 and 19, the ring 18 being generally welded under the support around the passage of the cable and the ring 19 retained on the metal screen and received and held in the ring 18. An internally shouldered ring 20 is integral and protruding above the support around the passage for the cable. It receives and retains the body 15, for maintaining the body on the support and coaxially around the stripped part of the cable, thus making the end self-supporting.

 A grounding connector 21 is mounted on the bare metal screen 5, just below the fixing support 16 and the retaining rings 18 and 19.

 The cap 17 is also conductive and generally metallic. I1 has a passage provided in a known manner to allow axial guidance of the core of the cable on which the connection end piece 14 is mounted and to ensure sealing around the stripped core and the rear part of the end piece of connection. To this end, a sealing sleeve 22 surrounds the rear part of the connection end piece and is heard on the stripped core up to the assembly 12 of the insulating skirts 13. It carries a metal centering ring 23, which is capable of sliding axially in the passage of the cap, and an outer sealing ring 24, which forms a sealing bellows maintained on the one hand on the periphery of the sleeve 22 and on the other hand on the periphery of the passage of the cap 17.

 The rigid insulating body 15 defines with the support 16 and the cap 17 an interior chamber 25 around the deflector cone 11 and the assembly 12 of the insulating skirts 13 in place on the cable.

 This chamber 25 communicates with the outside via sets of openings 26 and 27 provided in its upper part and its lower part, preferably in the cap 17 and the support 16, respectively, for bringing the chamber to ambient pressure. outside and free air circulation in it.

 The insulating body 15 advantageously has a tubular set of insulating skirts stepped externally 28 and also preferably another set of insulating skirts stepped internally 29, over its entire height, for an elongation resulting from the lines of flight externally and internally, between the cap and the metal support.

 This insulating and rigid body 15 may be constituted by a tube of porcelain or of composite material mechanically resistant over time to even severe environmental conditions. The composite material is in particular an epoxy resin filled with glass fibers. The exterior and interior skirts are in the form of insulator fins. They can be made in one piece or by fin modules. As a variant, the internal skirts 29 are formed by rings, or else by spirals which are attached and placed with or without discontinuity on the tube. In particular, the tube is manufactured by presenting its outer skirts while the inner skirts are attached. The latter are then advantageously made of silicone. The outer skirts can also be made of silicone and then also be attached to the initially smooth tube externally.

 Such a self-supporting end solves the problems posed by the self-supporting ends of the known art. In fact, it confines in chamber 25 the potential dangers in the event of a fault, without however requiring a special rupture zone since this chamber is brought to external ambient pressure with the air circulating freely in the chamber. This air circulation prevents any condensation of humidity in the room.

 In addition, the end may comprise a solid dielectric material for filling the chamber, consisting of a cellular compound or by individual elements at least partially filling the chamber. Such a dielectric material is chosen to have a high thermal conductivity. It is in particular formed of silica or alumina beads. The air circulation in the room promotes heat exchange with the outside.

Claims (11)

 1) Self-supporting end of power cable, of which said cable comprises a conductive core, an insulation, a semiconductor screen, a conductive metal screen and an external protective sheath, comprising a terminal portion successively stripped of said cable, a electric field deflector cone on the stripped semiconductor screen and an adjoining portion of the stripped insulation, a conductive terminal connection piece on the stripped core, a fixing support which passes through the stripped end portion and to which the l stripped metal screen and a rigid and insulating peripheral tubular body provided with first outer insulating skirts, held on said support extending without contact around said field deflection cone and up to the connection endpiece and provided with a cap terminal sealed through by the conductive core and the connection end piece, said body mounted on said support and provided with said capuc hon thus defining a longitudinal chamber around the stripped end portion of said cable, characterized in that it has openings (26, 27) in the two opposite end portions of said chamber (25), for bringing the chamber to the external ambient pressure and air circulation in the chamber, and a continuous and flexible assembly (12) of second insulating skirts (13), mounted on the exposed insulation (3), between said deflector cone (11) and said cap (17).  2) End according to claim 1, characterized in that said tubular peripheral body (15) comprises a tube of insulating composite material and mechanically resistant to the surrounding external conditions.  3) End according to claim 2, characterized in that said composite material tube is made of epoxy resin loaded with glass fibers.  4) End according to one of claims 1 to 3, characterized in that it comprises third interior insulating skirts (29) on said tubular peripheral body (15).  5) End according to claim 4, characterized in that said third insulating skirts (29) are constituted by fin modules attached internally to said tubular peripheral body (14).  6)) end according to claim 4, characterized in that said third insulating skirts (29) are constituted by at least one spiral element attached internally to said tubular peripheral body (14).  7) End according to one of claims 4 to 6, characterized in that said third inner insulating skirts (29) are made of silicone.  8) End according to one of claims 1 to 7, characterized in that it comprises a solid dielectric material with internal cells for filling said chamber (25).  9) end according to claim 8, characterized in that said dielectric filling material is a thermally conductive material.  10) End according to claim 9, characterized in that said filling material consists of silica or alumina beads.  11) End according to one of claims 1 to 10, characterized in that said openings (26, 27) are provided for some in said support (16) and for the others in said cap (17).