US 2222932 A
Description (OCR text may contain errors)
C. E. BENNETT ELECTRIC CABLE Nov. 26, 1940.
Filed Sept. 11, 1937 NOM- MEGA ENC M57414 5 72PM W W W/ W a L w w v 0 g 0 m 7 we r M Z 4 2 WM M 1 M 5 1 6 I W 0/1. //VPEE6 M475; PAPEe 85g; INVENTOR mwm Patented Nov. 26, 1940 UNITED STATE FFIE 2.222.932 istccrnio one Jersey Application September ill, 193?, Serial No. 163,372
This invention relates to an improvement in electric cables, particularly to high voltage cables which are installed in pipe lines.
These cables as heretofore constructed are 5 usually composed of copper conductors insulated with laminated paper insulation. Over this insulation a suitable electrostatic shielding tape is applied and then some kind of protective covering such as braid, canvas tape or similar materials. This outer covering protects the paper insulation against abrasion when pulling the cable into the pipe line.
It has been found that the frictional resistance to pulling such cables into a pipe when a canvas or similar covering is used makes it ditficult to pull long lengths, of the order of several thousand feet for example.
I have found that by installing a metallic covering instead of the canvas the frictional resistance to pulling in is very materially reduced. Actual tests have indicated a. coeflicient of friction one-half that of a non-metallic covering. It has been suggested to concentric armor the exterior of the cable, but this requires considerable material and the added weight tends to offset the gain in lessening the coeflicient of friction.
In the proposed construction of this invention I employ a half round high resistance or 80 non-magnetic metal strip wound spirally about the cable with gaps say of one-half inch between successive turns. When the shielding tape is installed a very thin cotton or paper tape is interlocked between successive turns of the shield- 85 ing tape, the D section or half round outer nonmagnetic strip touching and making contact with the shielding tape wherever the two metallic surfaces come together. This construction therefore short circuits the shielding tape at 40 numerous intervals, the half round strip contacting the wall of the pipe line in which the cable is installed. The shielding tape in efiect, therefore, is grounded continuously throughout its length.
Where shielding tape is installed with a paper or other insulated space between successive turns and then covered with canvas, as above.
5 be of such value that damage may be done to the cable insulation. Under some conditions a sparking voltage continuously induced would sooner or later deteriorate the insulation.
The disadvantages and drawbacks referred to in the preceding paragraph are overcome by the present invention.
An embodiment of the invention is illustrated in the accompanying drawing, wherein:
Fig. 1 is a cross sectional view of a three phase cable of the present invention, installed in a pipe line; and
Fig. 2 is an elevational view of one of the ca bles of Fig. 1 with parts broken away at different levels "for clarity of illustration.
Referring to the drawing in detail, 2 designates an iron or steel pipe line in which the cable is to be installed. A three phase system has been illustrated, the separate cables being designated i, 6 and 8 respectively.
These cables are alike and one has been illustrated in detail and on a larger scale in Fig. 2.
With reference to this figure of the drawing, ll] designates the conductor. which is insulated with oil impregnated oil filled paper tape l2. About this insulation is spirally wound electrostatic shielding tape I4. This tape may be thin copper for example, and it may if desired be interlocked with a very thin cotton or paper tape.
Over the shielding tape II and contacting therewith, I spirally apply a half round or D section non-magnetic metal strip Hi. This is applied with its convex'face outward, the flat face lying in contact with the shielding tape I4.
Extending lengthwise of the cable over the strip I6 is a. crlmped piano wire l8, and about the whole assembly is applied an outer sheath, as for example a thin lead sheath 20. This sheath is removed by ripping the same open with the piano wire l8 as the cable is drawn into the pipe line 2.
After the three phases have been pulled into the pipe line the latter is filled with oil under pressure designated 22.
It will be appreciated that by crimping the piano wire l8 the cable may be reeled for shipment without endangering the wire. It will be apparent also that by employing a half round strip over the shielding tape the frictional resistance to pulling the cable into the pipe line is very materially reduced as compared with canvas and the like, with the added advantage that, inasmuch as this half-round strip contacts the metal pipe line and the shielding tape, the latuously throughout its entire length.
ter will be short circuited substantially contin- It is to be understood that changes may be made in the details of construction and arrangement of parts above described within the purview 01' this invention.
What I claim is:
1. An electric cable comprising in combination an insulated conductor, electrostatic shielding tape interlocked with a non-metallic tape wrapped about the insulation, and a solid metal strip of substantially halt-round cross section wrapped about the said electrostatic shielding with its flat face in contact with the shielding.
said wire to remove the same from the cable 1 when the latter is installed.
CHARLES E. BENNETT.