US2112322A - Cable - Google Patents

Description

K. s. wYATT 2,112,322

CABLE March 29, 1938.

Filed Jan. 18, 1935 19 TEE/771757 Nif/7071279 2 Z l @M0706 for L15-2 24 27g/EW DF cw. n mig? Patented Mar. 29, 1938 PATENT OFFICE CABLE Kenneth S.'Wyatt, Detroit, Mich., assignor to The Detroit Edison Company, Detroit, Mich., a corporation of New York Application January 18, 1935, Serial No. 2,328

14 Claims.

This invention relates to the insulation of elecl tric cables sothat they are able to withstand Kthe tremendous electrical stresses created during the use of the cable.

More specically this invention relates to the insulation of cables for electric current transmission having one or more centrally arranged conductors enclosed in a lead sheath and having insulating material surrounding the conductors rendered active for the adsorption of such harmful products a`s maybe formed during the use of the cable or which may be present therein when the cable is manufactured.

Cables of the type above referred to are gen- 15 erally formed by wrapping one or more electric current conductors with an insulating impreg- 'natedmateriaL oils and various types of fibrous materials such as paper tape being used for this purpose. The'tape is wound around the conduc- 9 tors to provide a pluralityof conductor insulatinglayers, and one or more conductors, which may becoated with a metal shielding tape, are surrounded with a packing material such as jute. cellulose fiber, etc., the packed conductors then being sheathed Within the customary lead covering in the well known manner. If desired an additional insulating belting may be wrapped around the jute or cellulose fiber packing and the so wrapped mass covered with the lead sheath.

In my copending application Serial No. 693,697, led October 16,-1933, which has matured to Patent 2,083,889 dated June 15, 1937 and entitled Oxidation resistant cable I have described how the harmful effects of oxidation of the insulating material can be prevented by the incorporation of anti-oxidants into the inner and outer windings of the insulation.

It now appears that other products may have Aa deleterious effect on cable operation, some of these products perhaps being present in the cable as originally manufactured, and some products undoubtedly representing combinations of some of the original materials present, some of these l combinations probably being formed as a result ofthe conditions .caused by operation of the cable.

Among these harmful products may be listed moisture, hydrogen, carbon dioxide, carbon monoxide, sulphur compounds, nitrogenous compounds, hydro-carbon acids such as the substituted acetylencs, dispersed cellulose particles carrying electric charges, metal soaps, and ions of these or other substances formed by the several forces present. 'I'he harmful effect of these products seems to be their ability to carry current, which, of course, increases the dielectric loss in the cable. Some of these products are undoubtedly deterioration or oxidation products and all of them impair the electrical characteristics 5 to some extent, particularly when they collect in large quantities.

Although voids in cable insulation, occurring as a result of expansion followed by unequal contraction tend to facilitate the collection of large 10 masses of deterioration products, it is possible` under some circumstances that any ionized molecules present could collect in the vapor state within the insulation, to form a gas pocket. Other deterioration products, forming perhaps 15 around any catalyzer which may be present, also collect in relatively large continuous bodies.

I propose to reduce the harmful effect of the several deterioration products by locating Within the insulating material agents adapted actively 20 to adsorb these products, and by preventing the collection of large bodies of these lharmful products, it is possible to minimize the amount of current which they carry and thus reduce their harmful effect on the insulating material. 25

These adsorbing agents, designed to adsorb the various harmful or deterioration products present in the cable, may b e used in'conjunction with theanti-oxidant material disclosed in my above referred to application, or they may be used by themselves, depending upon the type of product, which under various conditions, appears to be most harmful.

The use of agents of this nature will permit the use of a poorer grade of paper or oil under certain circumstances, the cable insulation then undergoing what may be called a refining action in place.

It is therefore an object of this invention to provide an electric cable with insulating material 40 'which is protected against the inuence of deterioration products present in the cable.

A further object of this invention is to make use of the adsorptive properties of certain materials for reducing the harmful effect due to 45 ionization of the insulating materials used in electric cables.

A further object of this invention is to reduce the impairment of the insulating properties of cable insulating materials by dispersing active 50 adsorbing agents throughout said materials.

Other and further objects of this invention will be apparent from the following detail description of the accompanying sheet of drawings which forms a part of this specification. 55

On the drawing:

Figure 1 is a sectional view of a three-conductor belted cable having paper insulation tape wound around the conductors with adsorbing agents dispersed between the layers of the wound tape, and with anti-oxidant material impregnated into the inner and outer windings of said tape.

Figure 2 is a vertical cross-sectional view of a three-conductor H-type cable having oil impregnated paper tape surrounding each conductor with adsorbing agents dispersed between the windings of the tape, and with anti-oxidant material impregnated into the inner and outer windings of said tape. i

Figure 3 is a vertical cross-sectional view of one of the insulated conductors shown in Figure l having oil impregnated paper tape wound therearound with an adsorbing agent dispersed between the inner and outer layers only of the insulation windings.

Figure 4 is a vertical cross-sectional view of one of the conductors shown in Figure 1 having oil impregnated insulation paper tape wound therearound with an adsorbing agent dispersed between each of the layers of tape.

As shown on the drawing:

In Figure l, the reference numerals Il, I I, and I2 indicate respectively the three sets of wires forming the three cable conductors. Each conductor III, II, and I2 is surrounded with a covering of mineral oil impregnated paper tape I4 wound therearound. The rst few inner windings IB of the paper tape I4 are treated with an anti-oxidant material such as hydroquinone, camphor or the like, in accordance with the invention disclosed in my application Serial No. 693,697. 'I'he last few outer windings I6 are similarly treated with anti-oxidant material.

In accordance with this invention an active adsorbing agent such as activated charcoal, de-

hydrated silicic acid (silica gel), dehydrated ferric hydroxide gel, exploded cellulose bers or similar material I1 capable of adsorbing ions is dispersed between the windings of the paper tape I4. This adsorbing agent is readily applied, in dry comminuted form, to the oil impregnated insulation tape by dusting the adsorbing agent over the oil soaked tape. The oil lm on the tape acts as an adhesive and retains a sufiicient amount of adsorbing agent thereon.

Alternatively the brous insulating tape itself may be made, in a dry atmosphere, of exploded cellulose fibre or other similar material capable of adsorbing ions and other deterioration products. Instead of dusting the adsorbing agent over the tape, the agent may be mechanically entangled in the ber of the paper itself, this process also being carried on in the absence of moisture, the tape thereafter being immediately wound on the conductor in order to minimize the adsorption of moisture by the agents.

A ller material I8 such as jute or cellulose fiber is packed around the outside of the paper tape I4 and the entire mass is wrapped in an insulation belting I9. A lead sheath forms the outside of the cable and surrounds the insulation belting I9.

The cable disclosed in Figure 1 is thus composed of three conductors for electric current having paper tape insulation to separate the conductors. The insulation is impregnated in the inner and outer windings with anti-oxidant material and an y adsorbing agent is dispersed between the windings of the tape to actively adsorb any ions or other deterioration products that are formed during use of the cable, or that are present originally.

In Figure 2, the reference numerals 2i, 22, and 23 indicate respectively the wires forming the three conductors of an H-type cable. Each conductor 2l, 22, and 23 is surrounded by an insulation covering comprising a plurality of layers of oil impregnated insulation paper 24. The inner windings 25 of the insulation paper are treated with anti-oxidant material to minimize the harmful e'ects of oxidation of the paper or of the oil. Likewise the outer windings 2l are also impregnated with an anti-oxidant material. In ac-V cordance with this invention materials capable of adsorbing deterioration products, such as ions etc., are dispersed between the windings of the paper insulation 24 as shown at 21.

A copper shielding tape 2l is then wound around the paper insulations in each conductor and the three conductors are packed together in a lead sheathing 29. Filler material such as cellulose fibers 3|! are provided to ll up the spaces between the insulated conductor and the outside lead sheath.

The cable disclosed in Figure 2 is thus composed of three conductors having windings of paper insulation separating the same from each other. Anti-oxidant material is impregnated into the, inner and outer insulation windings of each conductor and an agent capable of adsorbing ions is dispersed between the windings of each paper insulation. A shielding tape then surrounds the windings of each conductor and the three conductors are packed together in a lead sheath.

In Figure 3 the conductor 33 has wrapped therearound a plurality of windings of paper insulation 34. The rst few inner windings li have dispersed therebetween an ion adsorbing material or agent 31 such as is described above. Likewise the last few windings 36 have the ion adsorbing material 31 dispersed therebetween. I'he insulation 24 thus has the adsorbing agent dispersed between the inner and outer windings only, since the ionization occurs more at these positions.

In Figure 4 the reference numeral 4B indicates a conductor for electrical current having insulation paper 4I wrapped therearound. Adsorbing material such as activated charcoal, hydrated silicio acid or exploded cellulose bers 42 are dispersed between the layers of the paper insulation 4I. These materials can be used alone or together in any manner required by the type of impurities present.

From the above description of the drawing it is evident that cables can be prepared according to this invention with insulation tape wound around the conductors and having adsorbing agents irnpregnated between some or all of the layers of the tape. In addition specic anti-oxidant material can be incorporated or impregnated into the inner and outer windings of the insulaton tape as shown in Figures 1 and 2.

These adsorbing agents as a class have extended surfaces capable of holding, by surface attraction, the ions and other particles of deterioration products. Substances having a high adsorptive ability coupled with a low power factor such as activated charcoal, dehydrated silicio acid and dehydrated ferrie hydroxide, are suitable adsorbing agents for these materials. I also propose to use freshly exploded paper. pulp, or textile bers. These materials are exploded in much the same manner as cereal grains are exploded to form the weliknown puffed cereals. In other words the textile bers or pulp are-subjected to high steam pressure and then shot into the atmosphere where they burst or expand and develop extended surfaces. Other means, well known in the art for separating the micelles may also be used. The extended surfaces of these fibrous portions are capable of adsorbing ions and the other deterioration products mentioned above.

By dlspersing the adsorbing agents between the layers of the insulation tape it is possible to adsorb the ions in the layers of adsorbing agents as they are formed and prevent their accumulation in any given spot as might otherwise occur, such accumulation of the :fons Gauting breakdown of the cable insulation.

When adsorbing agents are used with insulating paper or oil material which is rich in harmful products, the agents will, by removing them from the ber of the paper or from the oil, tend further to rene the insulating material so that such material can, in spite of impurities present in the original cable, yet give adequate service in operation.

Since the electrical stresses are greatest at the conductor and again in the vicinity of the sheath, ions in the liquid and solid phase occur in greatest numbers at these points and consequently it is desirable in some circumstances to concentrate ion adsorbing materials at these points. Ions in the gas phase, however, are formed in that zone of the cable insulation which, after operation, contains the most voids. Since the location of the voids varies with the type and manufacture of the cable, although usually it occurs in the inner third of the insulation, adsorbers for ions in the vapor phase will be located in accordance with the requirements of the individual cable.

I am aware that numerous details of the process and apparatus may be varied through a wide range without departing from the principles of this invention, and I, therefore, do not propose limiting the patent granted hereon otherwise than necessitated by the prior art.

I claim as my invention:

1. A cable comprising conductors, insulation wound around each conductor and a non-conductor ion adsorbing agent dispersed between the windings of said insulation.

2. A cable comprising a conductor for electric current, insulating means wound around said conductor and a non-conductor ion adsorbing agent dispersed between the windings of said insulating means. t

3. An electrical cable comprising an electrical conductor, layers of insulating material surrounding said conductor, a non-conductor ion adsorbing agent dispersed between the layers of insulating material and an outside covering for said cable.

4. In an insulated electrical cable, oil impregnated paper tape insulation wound around the current conductors having a non-conductor ion 6. A cable comprising a plurality of conductors for electrical current, oil impregnated paper wound around each of said conductors, a nonconductor ion adsorbing agent dispersed between the inner windings and between the outer windings of said tape, and means for covering the so insulated conductors.

7. A cable comprising a plurality of conductors for electrical current, insulating material wound around each of said conductors, activated charcoal dispersed between the layers of said insulating material and a sheath for the so insulated conductors.

8. A cable comprising a, plurality of conductors for electrical current, insulation material wound around each of said conductors, dehydrated silicic acid dispersed between the layers of said insulation material and means for sheathing the so insulated conductors.

9. A cable comprising a plurality of conductors for electric current, insulating material wound around each of said conductors, exploded brous material dispersed between the layers of said insulation material and means for sheathing the so insulated conductors.

10. A cable for transmitting electric current comprising three conductors, oil impregnated paper tape wound around each of said conductors to form a plurality of layers therearound, a nonconductor ion adsorbing agent dispersed between said layers, a filler surrounding the insulation material and a lead sheathing enclosing the insulated conduits.

ll. A cable having a conductor for electric current and a non-conductor ion adsorbing insulating means surrounding said conductor.

l2. A cable comprising a conductor, insulating material surrounding the conductor, and nonconducting ion adsorbing insulation refining material dispersed between adjacent portions of said insulating material, said refining material being insoluble in said insulating material.

13. The process of refining the insulating material of a cable which includes the step of refining said material after the assembly of said cable with a non-conducting ion adsorbing agent.

14. In an electrical cable having a plurality of conductors, oil impregnated insulation tape wound around each of said conductors, and activated charcoal disposed between the layers of said tape.

KENNETH S. WYA'I'I.

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