SE506172C2 - Device for insulation of high voltage conductors - Google Patents

Abstract

The invention relates to a device known as an insulator for electrically separating from one another a high voltage conductor and earth while providing sufficient creepage path length. The device consists of a tube (1) which is welded without additives to a bottom or attachment member (2) and to a top member (3), all of which are made from a thermoplastic weldable material. A number of pre-fabricated bushings (4) are applied, partly overlapping, about the tube (1), said bushings (4) being configured in such a manner that their extension along the external surface essentially exceeds their axial extension. The bushings (4) are made from a rubber-like material, such as e.g. silicone rubber, and possess a remaining mechanical tension radially after mounting.

Description

BNSÛCCIÜ 506 10 15 20 25 30 35 5C ~ 6l72C2 l: »172 2 Another disadvantage of porcelain insulators is that the manufacture of large ceramic bodies always gives a product with a large spread in mechanical strength. This in turn leads to an increase in the requirements for higher pressures during test printing. All in all, this means high costs for manufacturing insulators from porcelain, as they must contain insulating gas with high pressure, eg 6 bar.

US-A-4217466 and US-A-44144429 disclose insulators for suspending a high voltage line. The insulator in this case consists of an insulating rod, which has cuffs of elastic material on the outside.

From SE-C-457397 a device is known, which consists of a pair of cuffs, one stepped on the other. Both cuffs are then threaded over a conductor. The cuffs form a closed space filled with insulating gas.

Disadvantages of polymeric insulators, which have glass-reinforced hard plastic pipes, are partly that the cost is high due to several time-consuming process steps, and partly that the connection of metallic end elements is complicated and costly due to high mechanical requirements and high demands on the gas seal.

The invention will be explained in more detail below with reference to the accompanying drawings, in which Fig. 1 is a side view of the device according to the invention and Fig. 2 shows a longitudinal section through the device.

The device consists of a tube 1 with a end piece at each end, one of which constitutes a bottom or fastening part 2 and the other a top part or insulator top 3. All parts 1,2 and 3 consist of weldable thermoplastic, eg polyethylene or polypropylene . The bottom or fastening part 2 and the top part 3 are then welded to the pipe. The heat-welded joints are gas-tight around the entire circuit. The thickness of the tube 1 should be at least that. large, that the pipe l withstands an internal overpressure of at least 3 bar for 30 years, without the pipe l at room temperature increasing its diameter by more than 10%.

Cuffs 4 are arranged around the tube 1, which are formed with a disc 5 with a substantially greater extent radially than axially.

The cuffs 4 have one or more sheets and are made of elastomer, for example silicone rubber or EPDM rubber. The cuffs 4 have a hole diameter which is slightly smaller than the outer diameters of the tube 1.

BN S DLK; L ǤE 10 15 20 25 30 35 3 506 172 The cuffs 4 can thus be threaded onto the pipe only after a hand. elongation, and they are applied, as shown in Fig. 2, partially wrapped. The elastic tension can last for fl your decades. The clamping force together with friction between cuff 4 and tube 1 keeps the cuff in place without any additional device or to facilitate mounting of cuffs on the tube, it is convenient to have silicone grease on the surface of the tube.

Since the curing temperature is generally also significantly higher for elastomers than for thermoplastics, such as polyethylene, direct casting of the outer elastomeric casing cannot be done together with the tube 1. f The method of prefabricated cuffs 4 solves the problem which otherwise constitutes an obstacle to using melting point together with materials that are processed at high temperature.

To describe the use of the invention, it can be assumed that the device is mounted on a grounded wall 6 of a transformer box or a gas-insulated switchgear, from which a central conductor 7 emanates.

A connector is first mounted on the conductor 7, which consists of a sleeve part 9, which is fastened over the end of the conductor 7. When mounting the device, a rod 8 is threaded through a central opening in the top part 3. A seal, preferably an O-ring 10, separates the gas-tight pipe; 1 cavity from atmospheric air. The splicer is fastened to the top part 3 by means of a screw connection 11, an end 12 on the splice forming a stop against the inside of the top part 3. At the bottom of ñg 2 the device is fastened by means of a pair of second screw connections 13. A creeping current catcher 14 is suitably arranged between the rod 8 and the upper sleeve 4.

The device according to the invention forms a sufficient insulator case for high-voltage connections in an outdoor environment and at the same time has great advantages over prior art. In comparison with glass-reinforced thermoset pipes, the invention has the advantage of achieving the same function at a much lower cost, as a polyethylene pipe can be manufactured at a fraction of the cost of glass-reinforced pipes, due to a significantly lower material price and simpler manufacturing process.

BNSÛGCID -zSE 506 172 4 506172C2 I: - A further advantage is that the connecting axes 2 and 3 of the end shafts 2 and 3 can be easily gas-welded to the pipe l without any complicated attachment of metallic fl-ends, as is the case with glass pipe. Since the flanges constitute insulating material, the length of the insulator can be smaller while maintaining the compressive strength.

The invention is not limited to the embodiment shown and described, but can of course be varied in your ways within the scope of the appended claims.

Claims (4)

BNSÜCQICAL »<5? 10 15 20 5 ses 172 PATENKRAV Device for electrically isolating from each other at least two conductors, which at some point have different electrical potential, for example a high-voltage line from a grounded connection of a measuring transformer, characterized in amber, that the device consists of a tube (1 ), around which is arranged partially wrapped a number of cuffs (4) of elastic rubber material, for example silicone rubber, which have a disc-shaped part, which has a substantially greater extent in radial direction than in joint, and which are held in place around the tube (1) in that the manholes (4) in a mechanically stress-free state have a holding diameter which is smaller than the outer diameter of the pipe (1), that the pipe (1) has a bottom or fixed part (2) and a top part (3) and that the pipe (1) and said parts (2,3) are made of thermoplastic material and that the pipe (1) is joined to the bottom part (2) and the top part (3) by welding without additives. Device according to claim 1, k ä n n e t e c k n a d d âïlïfl; v, that the cuffs (4) are creep current resistant through the rubber material, which includes aluminum trihydrate. in Device according to claim 1, characterized in that the cuffs (4) are stretchable, so that their hole diameter can increase by about 20%. The device according to claim 1, characterized in that the cuffs (4) have a curing temperature which is substantially higher than the melting point of the material in the tube (1).