US1710845A - Ments - Google Patents

Description

April 30, 1929. sm o s 1,710,845

CABLE STRUCTURE Original Filed March 19, 1925 FIE-LI. 5 13.11.

Patented Apr. 30,- 1929.

UNITED STATES DONALD m. smoNs, or osBonNE, PENNSYLVANIA, ASSIGNOR, BY MESNE AssIGN-I 1,710,845 raraia'r o-rrlcs.

MENTS, TO GENERAL CABLE CORPORATION, A QORPOBATION OF NEW JERSEY.

CABLE STRUCTURE.

Application filed um 19, 1925, Serial 1T0. 16,732. Renewed September 15, 1928.

My invention relates to improvements in the structure of and in the method of opera tion of high-tension electric cables. The nvention is illustrated in the accompanymg 5 drawings, in which Fig. I is a view in transverse section of a three-conductor cable in the use of which my invention may be employed. Fig. II similarly shows a cable in which an alternative form of structure is employed for the practice of my invention. F ig'. III diagrammatically illustrates a detail of installation.

There is known to the art a certain high-tension electrical cable characterized by having a thin and closely adherent and grounded envelope of metal, surrounding the insulated conductor within the cable sheath. Cables of this general character are in practical use, particularly multiple-conductor cables, in which each separately insulated conductor is separately surrounded by a thin, grounded envelope of metal. The efiect of the envelope is to limit voltage stresses to thebody of insulation enveloped, and to relieve bodies of insulation external to the envelope of such stresses. When such a cable is put to use spaces are likely to develop within the cable sheath and externally of the individually insulated conductors. Such spaces may develop In consequence of the bending of the cable during 1nstallation, or they may appear in consequence of temperature changes. It is primarily to prevent sparking and lowing in such spaces source of difiiculty, even though the invention just alluded to be employed; I have discovered that, when such spaces aplpear, insulating compound, particularly if it e very fluid, is liable to migrate from the body-of insulation which surrounds the individual conductor and which the envelope of thin metal immediately overlies, in order to fill these spaces. The.

thin metal envelope is ineffective to prevent this, for in the usual embodiment of the invention alluded to the envelope intentionally is made pervious to insulating compound, that the underlying body of insulation may, after ual conductor, and

(however developed) t at the invention of a flow and to occupy spaces within the cable sheath as they open, thus preventing migration of compound from the body of insulatron which immediately surrounds the indivpreventing the said tendency to break-down.

In a multiple-conductor cable the-spaces between the individually insulated conductors and the all-including cable sheath (and beneath the belt insulation, if a belt be employed.) are ordinarily filled with bodies of relatively inferior insulation, ordinarily jute. These bodies are termed fillers, and in the three-conductor cable, which is the commonest form of multi le-conductor cable, there ZLI'GiifOlII fillers,t reelaterals and one cen- These filler bodies are ordinarily theniselves pervious to a flood'of insulatin compound, and it is possible 'to cause the 00d of msulatingcompound which the practice of my invention requires, to penetrate the fillers of the otherwise normal construction. Preferably, however, I make provision for the more rapid and more effective flow of and distr bution of the flood of compound by removing one or more of the fillers of the normal assembly and by employing the space so aflorded as the conduit for the flood of insulatmg compound. I may' make no. other provision, but may allow the walls of the ad jacent cable parts to constitute the limiting walls of such conduit. Preferably, however,

I introduce into such space a conduit as a separatestructure; and where, in the ensuing claims, I emplo the word conduit-I define thereby a con uit as a separate structure. This specially prepared conduit may or may not fill the whole space; and, if it does not, jute or other suitable material may be employed to fill the'otherwise' unoccupied space.

The conduit may be circular'in cross-section or it may be particularly shaped, for example to the approximately sector shape of the lateral space in a three-conductor cable. It may be formed of flexible, and even some- -what elastic material, and so when applied and filled with liquid under pressure, it may shape itself to and enlarge to fullest extent and fully occupy the space in which it is set.

Referring to Fi I of the drawings, a three-conductor ca 1e is shown. The conductor is indicated at 1; 2 is the body of insulation applied immediately to the conductor. Ordinarily it takes the form of wrappedon paper tape, impregnated with insulating compound. 3 is the metal envelope, pervious to the passage of com ound, which immediatel I surrounds the ndividually insulated con uctor. 4 is the cable sheath, ordinarily of lead. Within the sheath and externally of the individually insulated and metal-enveloped conductors the spaces are filled with bodies 7, commonly called fillers, and these bodies ordinarily are formed of such relatively inferior material as jute. The fillers may be com sed of materlal so porous and so penetra 1e by a flood of insulating compotmd that my invention may be practiced upon the cable without structural change. The spaces in which the fillers are containedmay constitute a conduit, in which, in spite of the presence of the filler bodies themselves, the flood of insulating material: under pressure, in which my invention centers, may be maintained.

Alternately, as illustrated in Fig. II, one or more of the fillers may be omitted, and in its place a conduit 8 may be introduced, hav-" ing the characteristics tobe s ecified below,

and through this conduit the 00d of insulating compound may be maintained, available to correct injury and to revent damage at V anypoint throughout the ength of the cable.

Since in the cable withwhich I have to do the voltage stresses are limited by the metallic envelope which immediately overlies the body of insulation surrounding the individual conductor, the conduit which I may employ in the practice of my invention, may be of conducting or. of non-conducting material; it may be of metal, for instance; it may be. simply a metal pipe arranged in one of the lateral spaces or in the central space. In any case, it should be pervious, and if therefore it be formed of metal, the metal wall will be perforated and the perforations will be of suflicient size and frequency to render the flood of liquid res onsive to the danger conditions already in icated. Instead of a metal pipe with perforated walls, a conduit formed of porous material may be employed,

through whose pores the flood of liquid will flow to achieve the end in View. Textile material, for example, may be employed, of fine woven wire or of thread formed of plant fibre; or paper or cardboard may be employed.

sure. Fig. IIIshows a reservoir 9 arranged at a cable joint. The joint casing is indicated at 10, and with the space within, the reservoir has connection. Within the reservoir a supply of compound may be maintained, and pressure, due to head, or due to special pressure-imparting means, may be transmitted from the body of compound within the reservoir to the flood of insulatin compound within the cable, throughout al the extent of the cable. 7 i

Whatever specific provision be made for the presence of a. flood. insulating compound, such bodyof insulating compound present within the cable sheath may at all times whlle the cable continues in service,

andzif'desired while installation is being effooted, be maintained under pressure. When conditions transpire which otherwise would result in the openin of a space, the flood of msulatmgcompoun migrating under pressure will occupy and prevent the openin of ,such space. If a space has opened, the 00d of compound under pressure will occupy and close the space, and prevent migration of compounds from the insulation which surrounds the conductors individually. Myinvention, then, makes for reater and better efliciency o'f a cable of t e type described above and characterized by an envelope of metal foil or equivalent material applied immediately upon the insulation surrounding the individual conductor. I

It will beremarked of the structure of my invention that the conductor 1 with the body of insulation ;.2 envelo ed in the per'vious layer 3 constitutes a unit which is accessible to a flood of liquid under pressure over its exterior surface only, and that from the exterlor surface only of this unit can there be escape of liquid. Elsewhere, the unit is' closed to liquid flow.

I. have used in this specification the term insulating compound, and the term has specific meaning in the art, and signifies an oil or a mixture of oils' and other substances, such as are commonly used in such cases. The invention is applicable, as will be perceived. whatever be the particular liquid employed:

I claim as my invention: 1. In a multiple-conductor cable the combmatlon of a plurality of individually insulated metal elweloped conductors cabled within a sheath with filler spaces between,

the metal envelope of each insulated conductor being penetrable by liquid insulating material, and the insulation immediately surrounding each conductor and within the metal envelope consisting of permeable material filled with liquid insulating material, vidually insulated metal sheathed conductors 10 and a flood of liquid under pressure mainso as to form filler space therebetween, a contained within the filler spaces. duit in the filler space, the wall of said con- 2. In a multiple conductor cable the comduit being penetrable by liquid material, and

5-Ibination of a plurality of individually insuliquid insulating material under pressure lated conductors, a metal envelope surroundfilling the conduit and the filler space.

in each insulated conductor, the said en- .In testimony whereof I have hereunto set ve opes being penetrable by liquid material, my hand.

an imperforate sheath surrounding the indi- DONALD M. SIMONS.

Images