Electrical cable for high voltage direct current transmission, and insulating composition
a technology of high-voltage direct current transmission and electric cables, applied in the direction of plastic/resin/waxes insulators, organic insulators, electrical appliances, etc., can solve the problems of increased pressure exerted on the metal screen, decreased pressure within the cable, and risk of electrical discharge and therefore perforation of the insulation, so as to reduce the local accumulation of space charges, improve electrical performance, and easy dispersibility
Inactive Publication Date: 2013-01-03
PRYSMIAN CAVI E SISTEMI ENERGIA
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- Summary
- Abstract
- Description
- Claims
- Application Information
AI Technical Summary
Benefits of technology
The use of polyethylene with unsaturated fatty acids in the insulating layer effectively decreases local space charge accumulation, improving electrical performance and reducing the risk of electrical discharges and insulation perforation in high voltage direct current transmission cables.
Problems solved by technology
Mass impregnated cables, although characterized by high reliability in operation even with very high voltages (in excess of 150 kV) have certain drawbacks, principally related to the migration of insulating fluid within the cable.
This results in a migration of the fluid from the insulating layer towards the exterior, and consequently an increase of the pressure exerted on the metal screen which is deformed in the radial direction.
Thus a decrease of the pressure within the cable is caused, and this leads to the formation of micro-cavities in the insulating layer, with a consequent risk of electrical discharges and therefore of perforation of the insulation.
The risk of perforation increases with an increase in the thickness of the insulating layer, and therefore with an increase in the maximum voltage for which the cable has been designed.
Although this solution is highly effective in preventing the formation of micro-cavities in the cable insulation, it has various drawbacks, mainly related to the complexity of construction and, in particular, it imposes a limitation on the maximum permissible length of the cable.
This limitation on the maximum length is a major drawback, particularly in the case of use in submarine installations, where the lengths required are usually very great.
However, it has not yet been possible to make adequate and complete use of said insulating materials, particularly for direct current transmission.
The accumulation of the space charges is a slow process: however, the problem is accentuated if the direct current transported by the cable is reversed (in other words, if there is a reversal of polarity).
However, a prolonged degassing treatment evidently leads to an increase in production times and costs.
Method used
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Effect test
example 1
[0048]99.5 g of low-density polyethylene (LDPE LE 4210 S, produced by Borealis) / containing 2.1% by weight of dicumyl peroxide (99% purity), and 0.7 g of oleic acid (Aldrich) were placed in a 200 ml flask, and the whole was stirred continuously.
[0049]The temperature was then raised to 50° C. and the mixture was kept at this temperature, with stirring, for three hours, until the oleic acid had been completely absorbed.
[0050]Films by press moulding at 130° C. and subsequent cross-linking at 180° C. were prepared from the mixture so obtained.[0051]The moulding conditions were as follows:[0052]press dimensions: 20×20 cm;[0053]pressure: 170 bar;[0054]quantity of material: 4.5 g;[0055]thermoforming temperature: 130° C.;[0056]duration of thermoforming: 5 mins.;[0057]cross-linking temperature: 180° C.;[0058]duration of cross-linking: 30 mins.;[0059]cooling time: 30 mins.[0060]The films produced as described above had dimensions of 20×20 cm and a thickness of approximately 120 μm.
[0061]Test s...
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Abstract
Cable for high voltage direct current transmission, comprising at least one conductor and at least one extruded insulating layer consisting of a polymeric composition comprising a polyethylene and at least one unsaturated fatty acid. Insulating composition, comprising a polyethylene and at least one unsaturated fatty acid.
Description
CROSS-REFERENCE TO RELATED APPLICATION[0001]This is a continuation of application Ser. No. 10 / 343,515, filed Aug. 21, 2003, which is the national phase application of PCT / EP01 / 08084, filed Jul. 12, 2001, which claims the benefit of European Patent Application No. 00116643.8, filed Aug. 2, 2000, which claims the benefit of U.S. Provisional Application No. 60 / 223,476, filed Aug. 7, 2000, all of which are incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a cable for high voltage direct current transmission, and to the insulating composition used therein.[0004]More particularly, the present invention relates to a cable for high voltage direct current transmission, suitable for either terrestrial or submarine installations, comprising a conductor and an extruded insulating layer consisting of a polymer composition comprising a polyethylene and at least one unsaturated fatty acid.[0005]The present invention al...
Claims
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IPC IPC(8): H01B3/44
CPCH01B3/441Y10T428/2927Y10T428/2947Y10T428/2933Y10T428/294
Inventor PEREGO, GABRIELEALBIZZATI, ENRICO
Owner PRYSMIAN CAVI E SISTEMI ENERGIA