Electric DC-cable with an insulation system

Inactive Publication Date: 2002-04-04
GUSTAFSSON BILL +7
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

0017] It is an object of the present invention to provide an insulated DC-cable with an electrical insulation system suitable for use as a transmission and distribution cable in networks and installations for DC transmission and distribution of electric power. The cable shall comprise a solid extruded conductor insulation that can be applied and processed without the need for any lengthy time consuming batch-treatment such as impregnation or degassing, i.e. vacuum treatment of the cable. Thereby reducing the production time and thus the production costs for the cable and thereby offering the possibility for an essentially continuous or at least semi-continuous production of the cable insulation system. Further, the reliability, low maintena

Problems solved by technology

Against these very significant advantages has to be weighed the high cost of the terminal equipment for conversion of the AC to DC and for inversion of the DC back again to AC.
However, for a given transmission power, the terminal costs are constant and therefore, DC transmission systems were rendered economical for the schemes involving long distances.
However, it has not been possible to obtain the full potential of these materials for full size cables.
Such space charges distort the stress distribution and persist for long periods because of the high resistivity of the polymers.
Thus the design for a cable insulation must include a safety factor taking account for this considerably higher field resulting in the use of thicker and/or more expensive materials in the cable insulation.
The build up of the space charge accumulation is a slow process, therefore this problem is accentuated when the polarity of the cable after being operated for a long period of time at same polarity is reversed.
To date it has not been possible to match the

Method used

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  • Electric DC-cable with an insulation system
  • Electric DC-cable with an insulation system
  • Electric DC-cable with an insulation system

Examples

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Effect test

example 1

[0066] Comparative Tests

[0067] Test plates with compositions as used in prior art insulated AC-cables and in accordance with the present invention for use in insulated DC-cables were produced, processed and subjected to an evaluation of the tendency for space charge accumulation by recording space charge profiles using the Pulsed ElectroAccoustic (PEA) technique. The PEA technique is well known within the art and described by Takada et al. in IEEE Trans. Electr. Insul. Vol. EI-22(No.4). pp 497-501(1987).

[0068] a,A 2 mm thick test plate of a polyethylene composition comprising:

[0069] about 98% by weight of low density polyethylene (922 kg / m.sup.3) of melt flow rate 0.8 g / 10 min.

[0070] about 0,4% by weight of an antioxidant SANTONOX R.RTM. (Flexsys Co) with the chemical designation 4,4'-thio-bis-(6-tert-butyl-m-cresol), and about 1,6% by weight of a cross linking agent, DICUP R.RTM. (Hercules Chem) with the chemical designation dicumyl peroxide, was molded at 130.degree. C.

[0071] Two ...

example 2

[0092] a polyethylene based resin composition was compounded as described in the following. to a low density polyethylene resin with a MFR of 1.2 g / 10 min following additions were made,

[0093] a peroxide cross-linking agent in the form of dicumyl peroxide was added in an amount of 1.7% by weight,

[0094] a scorch retarding agent in the form of compound (D), 2,4-diphenyl-4-methyl-pentene-1, was added in an amount of 0.3% by weight, and an antioxidant system consisting of

[0095] compound (B) in the form of DSTDP, di-stearyl-thio-dipropianate and

[0096] compound (C), a diester of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionicacid and thiodiglycol, was added to the polyethylene resin in a total amount of 0.3% by weight. The ratio of compound B to compound C was 1:3. The compounded resin composition was extruded to a 8 mm insulation on a shielded, stranded multi-wire conductor and cross-linked at a product temperature of 225.degree. C. and for a limited processing time of 5 minutes.

[0097] No...

example 3

[0100] A polyethylene based resin composition was compounded as described in the following. To a low density polyethylene resin with a MFR of 1 g / 10 min the following additions were made,

[0101] a peroxide cross-linking agent in the form of dicumyl peroxide was added in an amount of 1.4% by weight,

[0102] a scorch retarding agent in the form of compound (D), 2,4-diphenyl-4-methyl-pentene-1, was added in an amount of 0.4% by weight, and an antioxidant system consisting of compound (C), a diester of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionicacid and thiodiglycol, only was added to the polyethylene resin in an amount of 0.3% by weight. The compounded resin composition was extruded and cross-linked at a temperature of 300.degree. C.

[0103] The tendency for space charge accumulation was, when tested, low and substantially reduced in relation to the space charge accumulation normally detected in conventional extruded cross-linked polyethylene based compositions as used for AC-cables. Th...

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Abstract

An insulated DC-cable and method for production of an insulated DC-cable with an insulating system comprising an extruded cross-linked polyethylene based insulation disposed around the conductor. The extruded polyethylene based compound comprises additives such as cross-linking agent, scorch retarding agent and antioxidant. The scorch retarding agent comprises a compound (D), 2,4-diphenyl-4-methyl-pentene-1 and the antioxidant comprises a compound (C), a diester of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionicacid and thiodiglycol. The compounded polyethylene based resin composition is extruded and cross-linked at a temperature and for a period of time sufficient enough to cross link the insulation. The temperature and the period of time upon extrusion and cross-linking are limited so as to substantially suppress or essentially avoid undesired polar by-products being formed in the cross-linked composition.

Description

[0001] The present invention relates to an insulated electric direct current cable, a DC-cable, with a current- or voltage-carrying body, i.e. a conductor and an insulation system disposed around thc conductor, wherein the insulation system comprises an extruded and cross-linked polyethylene composition.[0002] The present invention relates in particular to an insulated electric DC cable for transmission and distribution of electric power. The extruded insulation system comprises a plurality of layers, such as an inner semi-conductive shield, an insulation and an outer semi-conductive shield. At least the extruded insulation comprises a cross-linked polyethylene based electrically insulating composition with a system of additives such as cross-linking agent, scorch retarding agent and anti-oxidant.[0003] Although many of the first electrical supply systems for transmission and distribution of electrical power were based on DC technology, these DC systems were rapidly superseded by sy...

Claims

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Application Information

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IPC IPC(8): C08K5/01C08K5/134C08K5/375H01B3/44
CPCC08K5/01C08K5/1345C08K5/375H01B3/441Y10T428/2933C08L23/04
Inventor GUSTAFSSON, BILLNILSSON, ULFCAMPUS, ALFREDCARSTENSEN, PETERGUSTAFSSON, ANDERSFARKAS, ANDREASERICSSON, ANDERSBOSTROM, JAN-OVE
Owner GUSTAFSSON BILL
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