US2368097A - Electric cable system - Google Patents

Description

\ Jan. 30, 1945. Q E, BENNETT E 2,368,097

ELECTRIC CABLE SYSTEM Filed sept. 1:5, i941 INVEN'TOR Cfr/Mms .BfA/NE Tr BY v f W%TCEYS j .ceedingly dicult to remove this moisture.

Patented jan. 30, i945 riesen ELECTRIC CABLE SYSTEM Charles E. Bennett, Rldgewood,-N. J., assigner to The Okonite-Callender Cable Company, Incorporated, Paterson, N. J., a corporation of New Jersey Application September 13, 1941, Serial No. 4l0,654

(Cl. li74-25) 3 Claims.

This invention relates to improvements in elec tric cable systems and is particularly directed to high tension cable systems wherein insulated conductors are loosely enclosed in a pipe line which is filled with an insulating fluid under pressure.

In one well known cable system such as disu closed, for example, in my prior Patent No. 2,615,063the conductors are insulated with oil pervious, oil impregnated paper and enclosed in a steel pipe line which is kept lled With oil or other insulating fluid under pressure.

Certain diiculties and inconveniences have been experienced in manufacturing, shipping and installing this prior system. For example, in shipping, because of the fact that the cable is insulated with oil pervious, oil impregnated paper, it has been necessary to either ship the cable in. a sealed drum or to sheath the cable with a temporary lead sheath in order to protect the cable against contamination with wateror other deleterious materials and `to prevent loss of the insulating oil. if the cable is shipped in a temporary lead sheath it is necessary to remove the sheath in the held as the cable is being drawn into the pipe line and should the sheath be removed in damp weather there is danger of moisture being absorbed by the cable, and it is ex- The method generally employed for removing this moisture from the system involves considerable installation disadvantages; for instance, in the case of a long line oil is pumped through the line into a tank, and then the oil is treated to remove Broadly the present invention provides for insulating the cable with fluid impervious material lli the moisture picked up. This is done over and over again until the oil comes through free of moisture.

Other objections to shipping in a temporary sheath are (l) the space required at the site of installation by the construction forceto strip ofi the lead sheath as the cables are being drawn into the pipe line and the necessity in inclement weather for housing to protect the cable; (2) the weight of the lead itself. In many instances this is halff the weight of the cable. This adds to the cost of shipment to the job, to which must be added the cost of return of the scrap lead to the factory.

Where these cables are shipped in oil containers instead of in a lead sheath, considerable money must be spent for duplicate reels of a special design which are costly. Then again these reels are very heavy when filled with oil which increase the shipping costs.

The present invention presents an improvement over the prior cable system mentioned above and overcomes the disadvantages outlined.

and shipping the cable dry to the installation site. This eliminates the necessity of shipping in a temporary lead sheath or special reels and automatically eliminates the disadvantages above re ferred to inherent in such systems.

The insulating vmaterial employ may be the usual paper tape employed for insulating high tension paper insulated power cables but under the present invention this tape is `treated with Wax or other suitable material to render the same impervious to oil, water and like fluids.

After the cable has been insulated with this fluid impervious insulation it is wrapped with the usual metal shielding tape and then covered with a moistureproof covering. This covering is readily applied by dipping or drawing the cable through aparaiiin bath, i or example.

lt will be appreciated that up to this point the cable has not been evacuated nor has it been iilled with oil or any other insulating fluid.

The cable is shipped inthis condition to the installation site, and after the pipe line has been dried out the cable is drawn in.

By reason of the 'fact that the covering of the cable is moistureproo the cable can be drawn in without danger of contamination with moisture. and any moisture collecting on the covering can ybe wiped on without-difculty. After the cable is drawn in the same is evacuated and dried out thoroughly by electrically heating the conductor, after which the insulating iluid, such as degasiiied oil, is introduced and vplaced under a substantial pressure, for example, seventy-ve pounds per square inch minimum. v

in the accompanying drawing I have illustrated a cable system made and installed in accordance with my invention.

in the drawing:

Fig. 1 is a sectional view of my improved cable; and

Fig. 2 is an enlarged elevational view of one of the insulated conductors.

Referring to the drawing in detail: 2 designates the conductor. This conductor is of usual construction, say of the standard stranded type. About this conductor I apply the insulating material 4. 'Ihis material is preferably paper tape treated with Wax to make it fluid impervious. It must have a aow power factor around .5% at rooml temperature, a relatively low power factor as `compared with a power factor of 5% which is that of varnished cambric and which unfits the cable for my purpose which is high tension power 2 escalier transmission. The wax or other material employed to render the cable fluid impervious must be capable of withstanding temperatures in excess of 90 C. which is about the maximum temperature encountered lin cable practice.

B designates the usual shielding tape applied about the fluid impervious insulation, while u designates D-shaped protective armor applied about the cable exterior to kprotect the cable against injury when being pulled into the pipe line, and to reduce the friction between the cable and pipe line, thus facilitating `drawing in. After the cable is made up it is treated with paraiin or some other moistureproof material, by drawing the cable through a suitable bath of the moistureproofing material, or in other coureu-J ient-fashion. This moistureprooflng material is only a temporary coating to protect the cable against the entry of moisture during handling, shipping and installing, andior this reason .has a melting point below 90 C., which, as above pointed out, is maximum temperature usually met with in cable operation, so that after the cable is installed the parafn will be melted and will no longer prevent the passage of insulating iluid to between the layers composing the insulating wall 4.

I'he cable or cables is or are drawn into the pipe line I0 which is of steel or other suitable material which is capable of withstanding high internal pressures of the order of several hundred pounds per square inch, the pipe having first been thoroughly dried.

The cable is next heated electrically,v by suitably connectingy the conductor to a source of power, thoroughly to evacuate and dry the cable. As previously pointed out, the wax or other material with which the cable insulation is pretreated to render it tluid impervious has a high melting point, in excess oi' 90 C., and in this connection I wish to note itsmelting point must be above that reached by the cable in the evacuating and drying stage just referred to. Y

Finally the pipe line isV filled with oil or other insulating fluid which is placed under pressure,

preferably not less than seventy-five pounds per square inch.

` By placing the oil under pressure it will be apparent that while no oil can pass into the liusulating paper because the same is fluid im pervious, the oil will be forced into and ill all of the spaces between the laminations of the fluid. impervious insulation.

Itlwill be 'apparent that'the pressure will promote connection between adjacent paper layers.

In addition to the `several advantageous features above referred to, it will be armrest to those skilled in this art that the t cil or other iluid insulation ein much reduced in volume as compe with prior structures employing fluid parviens n `rterial, and as a consequence the expansion difficulties in herent in the usual cable w i employs all pervious paper and oil are el" l have illustrated my inve multi-conductor cable syste stood, of course, that i; equally well to single cour what l. claim is:

l. in electric cable tion a conductor, pape:w terial rendering the having a higher meltih operating temperature Y rally layer upon lavez icl conductor to build up an electri l insulating wall the conductor1 a coating i moistureprooi material about said insulating wail, inoisttuejproof material having a melting point iower than the maximum operating temperature of "the cable, a body of insulating fluid under superatmospheric l is ver!! applied to will be under is applicable ale systems.

sing in combina "'reated with a nia- 'Jpet spipressure surrounding the insulated conductor, an

enclosure for the insulating iiuid and the insulaiing conductor, loading of 'the cable disintegrating the said inoistureprooi` material and permitting access oi the insulating iiuid between 'the layers of paper composing said insulating wall.

2. An electric cable comprising a conductor insulated/with laminated paper treated with a material rendering the paper uiddmpervious and having a higher melting pointthan the maximum operating temperature of the cable, the insulated conductor havingl a coating of a moistureproof material which has a. melting point lower than the maximum operating temperature of the cable, a body of insulating liquid under pressure surrounding the insulated conductor, an enclosure for the insulating liquid and the insulated conductor, loading of the cable disintegrating the moistureproof material andpermitting access ci the insulating liquid between the layers ci paper.

lin electric cable comprising a conductor insulated with laminated paper treated with wax having a melting point above 90 C and the insulated conductor' having an exterior seating of paraffin wax having a melting point between roma temperature and 90 C., a body o! insulating fluid under pressure surrounding said conductor, and

an enclosure for the fluid and conductor loosely surrounding the latter.

CHARLES E. BENNE'IT.

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