US2462770A - Electric cable - Google Patents

Description

W. T. PEIRCE ELECTRIC CABLE Feb. 22, 1949.

Filed Jan. 15. 1946 INVENTORI M 7 5@ /Df/E,

,d-MYex/Xh HIS ATTORNEY.

III Il l l l ll l l l l l l l l l l. l l ll l l l Of/ll lll n n n n r n n n n 4 r r n f n r f l n r i f n r f n 4 J f n r r r a r r r r n r r r r n r r r r r r n f r n n f n f r n r r II.

Patented Fb.422,1949

ELECTRIC CABLE Walter 'I'. leirce, Worcester, Mass., assigner to The American Steel and Wire Company of New Iersey,

l. corporation of New Jersey Application January 15, 1946, Serial No. 641,204

7 Claims. 1

This invention relates to an electric cable oi the type shown in my co-pending application, Serial No. 507,693, led October 26, 1943, now Patent No. 2,398,447, dated April 16, 1946, of which this application is a continuation-in-part. In this type of cable, the electrical `conductors and insulation are enclosed in an oil tight sheath. Due to temperature changes the pressure within the cable will vary if compensating means are not provided. This causes trouble due to ionization and also distortion and breakage of the sheath. Various compensating means have been proposed, but they have not proved satisfactory' sibility that the pressure within the cable will fall belowatmospheric. This condition is undesirable and it is an object of this invention to provide an electric cable in which the pressure oi' the oil will always be above atmospheric.

Another object is to provide an electric cable having means for keeping the'pressure throughout the length of the cable constant.

Still another object is to provide pressure compensating means which can be easily incorporated in various types of cables having oil saturated insulation.

These and other objects will be more apparent afterreferring to the following specification and attached drawings, in which:

Figure 1 is a cross sectional view of the cable;

Figure 2 is a schematic drawing showing one pair of tubes within the cable with joints between successive lengths of cable;

Figure 2a is a fragmentary view similar to Figure 2, but showing a modification of my invention; and

Figure 3 is a view similar to Figure 1, but showing a modification of my invention.

Referring more particularly to the drawings,

i the reference numeral 2 indicates the metallic conductors of the cable, each of which is surrounded by oil impregnated insulation 4. A metallic tape 8 surrounds the insulation l and a metallic and fibrous binder 8 holds the three conductors 2 together and makes contact between .the conductors 2 are a plurality of concentric tubes I2 and I l. The space in the interstices between the conductors not occupied by the concentric tubes I2 and Il is filled with fibrous material I6.

Figure 2 is a schematic representation drawn out of scale to illustrate the operation of the system when several lengths of cable constructed as in Figure 1 are joined together. The conductors and insulation are omitted from'the drawing for the sake of simplicity. The outer tube I2 is provided with openings I8 at spaced apart intervals for a purpose which will appear later. The lengths of cable are spliced together at the enlarged section 20. Within this enlarged section 20 Iis a manifold 22 which joins the ends of the two adjacent sections of the outer tube I2. The ends of the inner tubes I4 are open to the manifold 22. Instead of using a separate manifold 22, the contiguous outer tubes ILof each length of cable may be spliced together by means of a splicing sleeve 23 and the inner tubes Il broken at the splice as shown in Figure 2a so that the gas therein will have access to the space between the tubes. In other words the splice acts as the manifold.

In the manufacture of the cables, the inner tube I4 is iirst extruded from copper or other flexible material and the outer tube I2 is then extruded from similar material around the outside of tube I4 and perforated at intervals. The conductors l2 are covered with the insulation l which may be helically applied paper tape. The three conductors 2 and the three pairs of tubes I2, Il are put on separate cradles and cabled together in the usual manner by rotating the cradles as the cabled conductors are advanced. The assembly is then placed in a tank and the inner tube Il is flushed out with an inert gas such as nitrogen and sealed ofi'. Heat and vacuum are applied to the cable to remove all gas and moisture and the tank is illled with an insulating oil to impregnate the insulation 4. This oil will enter the openings lIII and ll completely the space between the tubes I2 and Il, as well as all other voids within the cable structure. The protective sheath I0, which is generally made of lead, is then extruded over the cable. The cable is made up in lengths convenient to handle, such as 500 feet, and several such lengths are fastened together to provide the total length required. At each joint 20 the outer tubes I2 are connected to the common manifold The sealsffare removed from the ends of the inner tubesi u which are then open to the manifold z2.

When the cable changes in temperature due to atmospheric changes or heating, the components of'the cable expand. The pressure developed causesgthe liquid with which the cable was impregnated to enter the openings IB and iiow along the space'between the tubes I2 and I4 toward manifold 22 which will ll with oil coming from both directions and nally enter the open ends of tubes i4. Since tube i4 is small, the oil will block the cross section of the tube due to the wetting tension between it and the wall of the tube and prevent the gas from escaping. Additional oil will gradually compress the gas originally in tube Il between the oil blocks entering both ends. Thus the gas in the tube Il will act as a cushion to provide space in the cable structure to take care of the expanding liquid without undue pressureA change.` When the cable cools oil?, the compressed gas in tube I4 will force the liquid back to the manifold'22, through the space between tubes I2 and I4, andthrough the openings I8 back into the cable'structure.

Figure 3 shows a pair of tubes 24 and 26 which description of Figure 2 is equally applicable to this' second embodiment if reference numerals 24 and 26 are substituted for reference numerals i2 and i4. The description of the operation of the pressure compensating means for Figures 1 and 2 is equally applicable to this embodiment.

While two embodiments of my invention have been shown and described, it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

I claim: "1

i. A cable comprising a conductor. insulation about the conductor including a liquid, a duidtight sheath about the insulation, a tube containing gas disposed within said sheath, an outer tube surrounding and substantially parallel to the rst tube and providing a space therebetween, said outer tube having an opening therein for admitting liquid thereto, and a manifold, said outer tube terminating in said manifold, said inner tube opening intosaid manifold whereby the liquid upon expansion will venter into said inner tube and compress the gas-therein.

2. A cable comprising a conductor, insulation about the conductor including a liquid, a fluidtight'sheath about the insulation, a. tube containing gas disposed within said sheath, an outer tube surrounding and substantially parallel to the first tube and providing a space therebetween, said outer tube having openings therein at spaced intervals for admitting liquid thereto, and a manifold at each end of the outer tube, said inner tube opening into said manifold whereby the liquid upon expansion will enter into said inner tube and compress the gas therein.-

3. A cable comprising a conductor, insulation about the conductor including a liquid, a fluidtight sheath about the insulation, a plurality oi tubes containing gas disposed within said sheath, an outer tube surrounding each of said tubes and substantially parallel thereto and providing a space therebetween, said outer tubes having openings therein at spaced intervals for admitting liquid thereto, and a manifold at each end of the outer tubes, said inner tubes opening into said manifold whereby the liquid upon expansion will enter into said inner tubes and compress the gas therein.

A cable comprising a conductor, insulation about the conductor including a liquid, a fluidtight sheath about the insulation, a tube containing gas disposed within said sheath, a second tube adjacent said rst' tube, said second tube having an opening therein for `admitting liquid thereto, and amanifold, said second tube terminating in said manifold, said first tube opening into said manifold whereby the liquid upon expansion will enter into said first tube and compress the gas therein.

5. A cable comprising a conductor, insulation about the conductor including a liquid, a uidtight sheath about the insulation, a tube containing gas disposed within said sheath, a second tube adjacent said first tube, said second tube having openings therein at spaced intervals for admitting liquid thereto, and a manifold at each end of the second tube, the rst tube opening into said manifold whereby the liquid upon expansion will enter into said first tube and compress the gas therein.

6. A cable comprising `a conductor, insulation about the conductor including a liquid, a fluidtight sheath about the insulation, a plurality of tubes containing gas disposed within said sheath, a tube adjacenteach of said first named tubes, each of said last named tubes having openings therein at spaced intervals for admitting liquid thereto, and a manifold at each 'end of the last named tubes, the rst tubes opening into said manifold whereby the liquid upon expansion will enter into said nrst tubes and compress the gas therein.

7. A system for the transmission of electrical energy comprising at least two lengths of cable spliced together, each of such lengths of cable comprising a conductor, insulation about the conductor including a liquid, a iluid tight sheath about the insulation, a tube containing gas disposed within said sheath, an outer tube surrounding and substantially parallel to the rst tube and providing a space therebetween, said outer tube having an opening therein for admitting liquid thereto, and a splice between the contiguous outer tubes of each length of cable, the inner tube being broken at said splice so that the gas therein has access to the space between the tubes at the splice.

WALTER T. PE.

REFERENCES CITED ille of this patent:

UNITED STATES PATENTS Name 'Date Peirce Apr. 16, 1946 Number

Images