WO1996030986A1

WO1996030986A1 - Process for making a connecting bush for high-voltage cables

Info

Publication number: WO1996030986A1
Application number: PCT/DE1996/000542
Authority: WO
Inventors: Norbert Kurda; Reinhard Schroth; Dirk Kunze; Stephan PÖHLER; Lothar Goehlich
Original assignee: Siemens Aktiengesellschaft
Priority date: 1995-03-30
Filing date: 1996-03-19
Publication date: 1996-10-03
Also published as: DE19512922A1

Abstract

To make a compact and quickly and securely fitted connecting bush for high and very high voltage cables, the insulation of which consists of cross-linked polyethylene and which are designed for voltages up to 400 kV, prefabricated, elastically expandable control components (31) are first pushed over the cable cores to be connected; an also elastically expandable screening electrode (30) is also pushed over the conductor connecting point. The surface of the control components, the control electrode and the core insulation (21) between them is then coated with a bonding agent, whereafter an insulating elastomer (32) is poured over this arrangement and cross-linked. The core insulators in region (23) of the screening electrode are preferably reduced to a wall thickness of some 5mm.

Description

description

Process for manufacturing a connecting sleeve for high-voltage cables

The invention is in the field of energy distribution and can be used in the production of connecting sleeves with which the individual lengths of plastic-insulated high-voltage cables are electrically connected to one another when a high-voltage cable system is being created. Preferred areas of application are connecting sleeves for cables insulated with crosslinked polyethylene (VPE / XLPE), the transmission voltage of which is 220 kV and more.

The technical development in the field of high-voltage cable systems was characterized in the 80s and 90s, inter alia, by the use of cross-linked polyethylene as insulation material. After the introduction of this insulating material at the 110 kV level and the commissioning of cable systems at the 220 kV and 275 kV levels, cable systems for a transmission voltage of 400 kV are now being set up. The possibility of installing such cable systems also depends on the sets available for connecting the cable systems (end closures) and for connecting individual cable lengths (connecting sleeves). Insulating bodies made of porcelain or cast resin are used for end closures, which are filled with a synthetic liquid after assembly. The electrical field control in the end closures is carried out with the aid of prefabricated, slide-on control elements made of silicone rubber, which form a relatively small component with the corresponding design of the electrically conductive part (DE-Z "ABB technology", issue 2/1994 , Pages 13 to 19 / EP-A2-0 491 447). At room temperature, the material for the control elements is vulcanizing, pourable, two-component silicon types of rubber (RTV-2 rubbers) into consideration (DE-Z "Kautschuk + Gummi.Kunststoffe", No. 1/1986, pages 33 to 36; DE-Z "Energiewirtschaft", 1991, No. 26, pages 1535 to 1545) . - In the manufacture of connecting sleeves for the cable systems mentioned, the actual insulating body of the sleeve is either constructed from crosslinkable polyethylene tapes (winding sleeve) or is produced using a casting mold by extrusion of a crosslinkable polyethylene (EMJ sleeve; DE 29 28 856 AI / magazine IEEE Electrical Insulation Magazine, May / June 1991, Vol. 7, No. 3, pages 31 to 33) or a sleeve consisting of prefabricated individual components (solid sleeve) is used, the insulating body of which is made of epoxy resin and contains a high-voltage electrode, with the two ends of the Insulating body made of conical high-voltage seals

Silicone rubber can be inserted ("ABB technology", issue 2/1994, page 17, Figure 3 with text). - In another known connecting sleeve, the cable ends, each provided with a pushed-on control element, are surrounded in the area of the conductor connection point with an electrically conductive and an electrically insulating sheath in the form of a winding and overall surrounded by a dense metal housing, which with an insulating medium in the form of the insulating gas SFg is filled (DE-Al-38 22 288). - These known connecting sleeves usually require a relatively large volume (length, diameter) and / or are possibly relatively complex to manufacture (tempering for cross-linking the insulating body) or must be monitored during operation (filling with SFg).

For the manufacture of a connecting sleeve for plastic insulated high-voltage cables with a transmission voltage of 65 kV, a prefabricated sleeve body is known, which consists of elastic material and rests on the wire insulation of the two connected cable wires. The sleeve body contains an electrically conductive shielding cylinder place surrounds at a distance and makes the space inside the shielding cylinder field-free (DE-Al-16 65 222).

Proceeding from a method for producing a connecting sleeve for plastic-insulated high-voltage cables with the features of the preamble of claim 1 (DE 38 22 288), the invention is based on the object of taking measures for producing the sleeve which result in a small construction , fast and safe mountable sleeve that can also be used for transmission voltages around 400 kV.

To achieve this object it is provided according to the invention that a prefabricated, elastically expandable shielding electrode is used as the electrically conductive and electrically insulating sheathing of the conductor connection point, the ends of which are seated on the insulation of the two cable ends, and continue to follow when the shielding electrode is pushed onto the conductor connection point, the surface of the two field control elements, the cable insulation and the shielding electrode are coated with an adhesive and that subsequently a casting mold is arranged around the connection point thus prepared and this casting mold with an insulating, liquid-processable and cross-linkable elastomer filled in and the elastomer is crosslinked.

As a result of the use of prefabricated control elements and a prefabricated shielding electrode, the measures provided according to the invention lead to a sleeve which is small in the axial and radial directions and whose operational reliability is achieved by using an adhesion promoter in the border area between the prefabricated parts, including the wire insulation, and by Pouring socket body manufactured on site is guaranteed. It is expedient to use silicone rubber as the material for the field control elements and the shielding electrode; Prefabricated elements made from this material can be expanded and guaranteed relatively easily a secure elastic fit. Accordingly, a silicone rubber that crosslinks at room temperature should be used as the elastomer that can be processed in liquid form, the pot life of which is set to 1 to 5 hours by suitable additives in order to ensure that the elastomer flows into the casting mold in an amount of approximately 100 liters to enable. The use of an elastomer that crosslinks at room temperature eliminates the need for external heat to crosslink the insulating material in other sleeve constructions. A further reduction in the volume of the sleeve produced can be achieved if the wire insulation of the two connected cable wires in the area of the shielding electrode is reduced to a wall thickness of approximately 5 mm. As a result, the outer diameter of the shielding electrode, which is at high voltage potential, can be significantly reduced without leading to an electrical overloading of the sleeve body, which is also reduced in diameter.

The cavity-free contact of the socket body against the core insulation of the two cable ends can be done by a radial

Pressure are supported. A tube-like pressure sleeve made of an elastically stretchable plastic of high strength based on ethylene-propylene or on a silicone basis is suitable for this. Such a pressure sleeve expediently forms the outer area of the insulating sleeve body and is pushed over the connection point before the casting mold is arranged, a tight support in the foot area of the two control elements being sought. The outer diameter of the pressure sleeve is chosen to be smaller than the inner diameter of the casting mold, so that under the action of the filling pressure when the liquid elastomer is filled in, the pressure sleeve is expanded until it comes into contact with the casting mold. For reasons of casting technology, the inner surface of the pressure sleeve can be designed with a double cone with a larger diameter towards the ends. Two exemplary embodiments of a connecting sleeve, which were produced by the method designed according to the invention, are shown in FIGS. 1 and 2.

It shows

1 shows a schematic representation of a connecting sleeve in which the insulation of the cable cores for the purpose of producing the conductor connection is offset in one step, and FIG. 2 shows a connecting sleeve in which the insulation of the

Cable cores is conically reduced for the purpose of arranging a shielding electrode with the smallest possible diameter.

The sleeve according to Figure 1 serves to connect the two

Cable cores 1 and 4, which have a conductor 2 or 5 and an insulation 3 or 6. Inner and outer conductive layers associated with the cable insulation are not shown. The insulation is removed at the ends of the two cable wires in order to connect the conductors to the conductor connecting element 7. A potential-controlling bridge 8 is arranged above it, which establishes an electrical connection to the shielding electrode 9, which consists of an electrically conductive part 6 and an insulating sheath 11. The shielding electrode 9 is dimensioned such that its ends rest on the wire insulation 3 and 6 with elastic expansion.

Before connecting the two cable cores, the two control elements 12 and 15 were pushed onto the correspondingly prepared cable ends, each of which has a control deflector 13 as the conductive part, which is embedded in an insulating part 14.

After the control elements 12 and 15 and the shield electrode 10 had been arranged, the surfaces of these clothing parts became and the exposed wire insulation are coated with an adhesion promoter and then surrounded with a casting mold into which a liquid, crosslinkable insulating material has been filled. This casting process and the crosslinking process formed the insulating body 17, to which the conductive layer 18 was subsequently applied. The conductive layer 18 is usually electrically connected to the electrical shields of the cable wires to be connected. For the purpose of potential separation, this conductive layer can have an interruption 19.

Figure 2 shows the connection of two high-voltage cables, only one half of the sleeve being shown. Each of the two cables 20 is provided with insulation 21, which is reduced to a region 23 of small wall thickness by means of a conical step 22. The shielding electrode 30 lies in the area of the reduced wall thickness on the wire insulation of the two cables.

Each cable is surrounded by an aluminum corrugated jacket 24, which in turn carries a plastic jacket 25. In the area of the point of deposit of the cable jacket, a piece of pipe 27 is attached to the metal jacket, on which the foot of the respective control element 31 is seated. The earth clamp 26 is also attached to the pipe section. This grounding terminal 26 is provided with a connector 28 to which an earth rail 29 is attached. The earth rail 29 is electrically connected at the other end of the sleeve to the metal sheath of the other cable or to an outcrossing device. The insulating sleeve body 32 also bears against the earth rail 29 and is provided with an outer conductive layer (not designated in any more detail).

A sleeve housing 33 is also arranged around the connecting sleeve, which essentially consists of the shielding electrode 30, the control elements 31 and the insulating sleeve 32 For the purpose of moisture-proof encapsulation of the sleeve as a whole is cast with resin.

Control elements and shielding electrodes made of silicone rubber were used in the manufacture of the sleeve. An adhesion promoter based on polysiloxane, as is customary in the trade, was used to coat the surfaces prior to the production of the insulating body. For the manufacture of the insulating sleeve body 17 or 32, a silicone rubber vulcanizing at room temperature by addition crosslinking, which was offered by the company Wacker-Silicon, was used for this purpose.

Claims

claims

1.Method for producing a connecting sleeve for plastic-insulated high-voltage cables, in which, before connecting the conductor ends, a prefabricated, elastically expandable field control element (12, 15) is pushed onto each of the two cable wires to be connected, in which the interconnected conductor ends are made with a plastic one , electrically conductive sheathing and with an insulating sheathing also made of plastic and in which the sheathed conductor connection point (7, 8) and the field control elements are surrounded by an insulating medium, characterized in that the electrically conductive and electrically insulating sheathing of the Conductor connection point a prefabricated, elastically expandable shielding electrode (9) is used, the ends of which are seated on the insulation (6) of the two cable ends (1, 4) that after the shielding electrode (9) has been pushed onto the conductor connection point Surfaces (16) of the two field control elements (12, 15) of the cable insulation (6) and the shielding electrode (9) are coated with an adhesion promoter and that subsequently a casting mold is arranged around the connection point thus prepared and this casting mold is coated with an insulating, liquid-processable and crosslinkable elastomer (17) is filled and the elastomer is crosslinked.

2. The method according to claim 1, characterized in that after the crosslinking of the insulating elastomer on the sleeve body (17) thus produced, a conductive coating (18) is applied.

3. The method of claim 2, d a d u r c h g e k e n n z e i c h n e t that the conductive coating is only electrically connected to the cable shield of one of the two cable cores.

4. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that the field control elements (12, 15) and the shielding electrode (9) consist of silicone rubber and that as a liquid-processable elastomer, a cold-curing silicone rubber with a pot life of 1 to 5 hours. is used.

5. The method of claim 1 or 2, d a d u r c h g e k e n n z e i c h n e t that a polysiloxane or a mixture of several polysiloxanes is used as an adhesion promoter.

6. The method according to claim 1, so that the wall thickness of the wire insulation (21) in the region (23) of the shielding electrode is reduced to approximately 5 mm before the shielding electrode (30) is pushed on.

7. The method according to any one of claims 1 to 6, characterized in that a prefabricated, tubular pressure sleeve is arranged above the connection point before arranging the casting mold, the pressure sleeve consisting of an elastically stretchable plastic, sealingly abuts the control elements and an outer diameter has that is smaller than the inner diameter of the mold.