Electricity: conductors and insulators – With fluids or vacuum – Conduits – cables and conductors
Reexamination Certificate
1999-05-14
2001-03-06
Kincaid, Kristine (Department: 2831)
Electricity: conductors and insulators
With fluids or vacuum
Conduits, cables and conductors
Reexamination Certificate
active
06198039
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a pipeline section of a gas-insulated pipeline. Gas-insulated pipelines are used advantageously in population centers since they are installed underground and can be created or expanded without any significant negative influence on the traffic, water and gas supply and sewer infrastructure.
BACKGROUND OF THE INVENTION
A pipeline section of a gas-insulated pipeline is known, for example, from patent document 0 789 438 A2. This document describes a pipeline section of a gas-insulated pipeline in which a high voltage-conducting current conductor is arranged in a pipe that is filled with compressed SF
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and is made from an insulating material, typically polyethylene. The insulating pipe carries on its mantle surface a layer that is field-controlling and, if needed, conducts any occurring return current and is comprised of a conductive or semi-conductive material. The high voltage-conducting current conductor is constructed in tubular form and is arranged centrically in the capsule pipe by means of post insulators. The post insulators may include insulation legs that are aligned radially or are constructed as an isosceles triangle which are kept in one of several longitudinal grooves undercut in the mantle surface of the current conductor. Because of the current conductor that is undercut and provided with longitudinal grooves and the post insulators that are comprised of a high number of insulation legs, such a pipeline section is relatively complicated.
U.S. Pat. No. 4,018,978 A and U.S. Pat. No. 4,132,855 A describe post insulators for a high voltage-conducting current conductor of a metal-capsulated, gas-insulated pipeline, each of which support themselves via support arches or with a support ring on the inside surface of the capsule.
SUMMARY
The invention relates to a pipeline section of a gas-insulated pipeline which is characterized by good di-electric properties and at the same time can be produced in a simple and cost-efficient manner.
In the pipeline section according to the invention, only a relatively small part of the material of the post insulators reaches up near the capsule pipe. Because of this small amount of material with a di-electricity constant that is higher than that of the insulating gas, relatively small electric field intensities occur in gaps between the inside surface of the capsule pipe and the outer surfaces of the support elements of the post insulators. For this reason, and because the post insulators are also arranged practically without an edge at the inside surface of the capsule pipe, di-electric weak points in the area of the capsule pipe are substantially avoided.
In the pipeline section according to the invention, the encapsulation is constructed as a capsule pipe on the one side, and the current conductor and post insulators on the other side, first can be manufactured as systems that are separated from each other. Since the encapsulation is first empty during the assembly of the pipe section, it can be produced without much expenditure by welding capsule pipe sections to each other. The welding seams formed in the process are easily finished and can be easily checked for tightness and strength. In addition, the encapsulation produced in this manner can be easily cleaned before the current conductor and post insulators are installed, e.g. with a robot. Then the current conductor and the post insulators can be pulled into the encapsulation. It is hereby a special advantage that the friction between the post insulators and the capsule is kept low by a suitable shaping of the post insulators, and/or that the diameter of the capsule pipe can be greater than the diameter of the post insulator, since the pulling can then be performed with little force. Because of the low friction and small diameter of the post insulators, the generation of a di-electrically undesirable abrasion is also avoided during assembly and during operation.
For this reason also, the pipeline section displays a favorable di-electric behavior. In addition, the arch- and trapezoid-shaped construction of the support elements resting on the post insulators cause the support forces to be exerted in a favorable manner on the encapsulation, so that there is practically no danger that the load of the post insulators on the capsule pipe is too high which could possibly deform it. Due to the arch- or trapezoid-shaped design of the support elements, the cantilever strength of the post insulators is at the same time increased significantly, and in this way negative effects on the di-electric properties of the pipeline section are avoided.
An electrode, which may be arranged in the inside surface of the support ring of each of the post insulators, is able to di-electrically discharge the triple points (common to current conductor, post insulator and insulating gas) without any problems.
REFERENCES:
patent: 3864507 (1975-02-01), Fox et al.
patent: 3996414 (1976-12-01), Artbauer et al.
patent: 4018978 (1977-04-01), Bacvarov et al.
patent: 4132855 (1979-01-01), Clark et al.
patent: 4160119 (1979-07-01), Artbauer
patent: 4415763 (1983-11-01), Cookson
patent: 5571989 (1996-11-01), Thuries et al.
patent: 2347927C3 (1981-07-01), None
patent: 0789438A2 (1997-08-01), None
patent: 1073606 (1967-06-01), None
Bruhl Bodo
Mendik Michael
Worzyk Thomas
Asea Brown Boveri AG
Burns Doane Swecker & Mathis L.L.P.
Kincaid Kristine
Nguyen Chau N.
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