Irradiation cross-linked polymeric insulated electric cable

• US 4,317,001 A
• Filed: 09/18/1980
• Issued: 02/23/1982
• Est. Priority Date: 02/23/1979
• Status: Expired due to Term

• Current Assignee: Pirelli Cable Corporation (Prysmian SPA)
• Original Assignee: Pirelli Cable Corporation (Prysmian SPA)
• Inventors: Silver, David A., Lukac, Rudolf G., Rubinstein, Solomon
• Primary Examiner(s): Kucia, Richard R.
• Application Number:
  US06/188,529
• Time in Patent Office: 523 Days
• Field of Search: 174/110 PM, 174/102 SC, 174/105 SC, 174/120 SC
• US Class Current: 174/102.0SC
• CPC Class Codes: H01B 3/004 with conductive additives or conductive layers
• CPC Class Codes: H01B 3/44 vinyl resins; acrylic resins silicones H01B3/46
• CPC Class Codes: H01B 3/46 silicones
• CPC Class Codes: H01B 9/027 composed of semi-conducting layers
• CPC Class Codes: Y10S 174/27 including a semiconductive layer

Abstract

Insulation for an electric power cable, and a power cable including such insulation, the insulation having an improved dielectric strength and being irradiation cross-linked polymeric material having mixed therewith carbon black having a particle size in the range from about 200 to about 500 millimicrons, the carbon black content being about 10% to about 40% of the weight of the mixture of carbon black and the polymeric material. Also, the cable insulation may be layers of different density polyethylene, at least one of the layers being the described mixture of polyethylene and carbon black.

Claims

1. An electric cable comprising a conductor and at least one layer of insulating material therearound, said layer comprising a radiation cross-linked, polymeric material with carbon black distributed therein, the amount and particle size of the carbon black which is present in the polymeric material being such that the volume resistivity of said layer of insulating material is at least 1×

10¹⁰ ohm-cm. but carbon black having a particle size in the range from about 200 to about 500 millimicrons being present in the polymeric material in an amount of about 10% to about 40% of the total weight of the polymeric material and the carbon black having a particle size in said range, said insulating layer being distinguished from other insulating layers comprising said radiation cross-linked, polymeric material with carbon black therein in particle sizes and amounts different from particle sizes in said range and in said amount not only by having a resistivity of at least 1×

10¹⁰ ohm-cm. but also by having a greater dielectric strength and a reduction in at least one of the number and of the size of electron trees therein as compared to such other insulating layers having lesser amounts of said carbon black.

2. An electric cable as set forth in claim 1 wherein said volume resistivity of said layer of insulating material is at least 1×

10¹⁵ ohm-cm. and said carbon black having a particle size in said range is present in an amount from 20-30%.

3. A cable as set forth in claim 2 wherein substantially all the carbon black is present in said polymeric material has a particle size in the range from 200-500 millimicrons.

4. A cable as set forth in claim 1, 2 or 3 wherein said polymeric material is selected from the group consisting of polyethylene, polyvinyl chloride, silicone rubber, styrene butadiene rubber, ethylene copolymers, ethylene terpolymers, and mixtures thereof.

5. A cable as set forth in claim 1 further comprising a further layer of radiation cross-linked, polymeric material extending around said conductor and intermediate said conductor and said first-mentioned layer.

6. A cable as set forth in claim 5 wherein the polymeric material of said first-mentioned layer is high density polyethylene and the polymeric material of said further layer is a low density polyethylene.

7. A cable as set forth in claim 5 wherein the polymeric material of said first-mentioned layer is medium density polyethylene and the polymeric material of said further layer is low density polyethylene.

8. A cable as set forth in claim 5, 6 or 7 wherein said polymeric material of said further layer comprises carbon black having a particle size in the range from 200-500 millimicrons, said carbon black being present in an amount from 10-20% of the total weight of said last-mentioned material and said last-mentioned carbon black and wherein said further layer of polymeric material has a volume resistivity of at least 1×

10¹⁰ ohm-cm.

9. A cable as set forth in claim 5 wherein said further layer is a semi-conducting layer and has a volume resistivity of less than 1×

10⁵ ohm-cm.