US2607822A - Electric cable lead with crepe paper insulation - Google Patents

Description

Aug. 19, 1952 E, CRANDALL 2,607,822

ELECTRIC CABLE LEAD WITH CREPE PAPER INSULATION- FiledMarch 31 1950 Inventor Eugene]. Pa

CREPE PAPER Patented Aug. 19, 1952 .ELE CTRIG .CABLE LEAD -WITH CREPE INSULATION Eugene L. Crandall, Schenectady, N.'Y., ass'ignor 'to:General Electric Company, a corporation or New York Application March-i1, 1950, Serial No. 153,134

This invention relates to an improved insulating fluid-filled electrical apparatus} and more particularly to apparatus 'such' 'as' transformers employing a number of interconnection {conductor; cables "having an improved insulating ma ter-ial-within the apparatus.

It is common practice in large electrical apparatus of the stationary type, such as "transformers, to employ astructure which is enclosed within atank filled with oil orother liquid dielectric such as a suitable askarel, for example, chlorinated diphenol. This'liq'uid' dielectric acts-as insulation and also as a'cooling medium which .circulatesaround the windings of the apparatus and through portions of the casing whichmay be designed especially for the dissipation of heat. .It is desirable to operate the apparatus atas high a temperature as possible, without unduly accelerating aging, .in .order to obtainomaximum utilization; ;This temperature isgenerallyallowed to range upxto 190 centigrade, with intermittent service ratings which may resultin temperatures appreciably :higher thangthis.

Interconnectionconductors are.commonly-us,ed between various :windings within. the apparatus and between the .coilsor componentsiand leadout terminals ior exterior connections to the. apparatus, and, these interconnection Lconductors arelcommonly. insulated with materials such as varnished cambric. These conductors are of necessity lbelowzthe levelyof the oil which. fills the. apparatus and are therefore directly subjected to the heat which is presentwithinthe apparatus. Under these circumstances rthe varnished .cambric insulation has :been .known to swell slightly. In apparatus :ofrthetabove description which is intended for use at high voltages,-the interconnection conductors must have insulation which is in the order of three-eighths of an inch thick, or greater, and with such a thickness this swelling or. expansion of .the varnished cambric insulation sometimes causes portions of the insulation to burst and become separated from the interconnection conductors. A further circumstance which may cause destructive swelling and bursting-of this varnished cambric insulation'is the common practice, -in the-manufacture of such apparatus, of removing -all moisture from the apparatus; before filling with the-liquiddielectric, to assure ig'ood electricalandinsulation properties, by subjecting the apparatusto a vacuum with the concurrent applicationofheat. 1

Accordingly, it is :an object ofuthis invention to provide a liquid dielectric-fllled electrical apparatus employing interconnection conductors having insulatiomwhich'will not deteriorate by swelling and bursting when subjected to normal conditions of heating.

It has been found that in apparatus of the vziclai ms. (c1. are-21s. I

above description which is filled with askarel instead of oil; the varnish in the-varnishedcambric causes a certain undesired contamination of the askarel liquid. It has therefore been the frequent practice in aska-rel-filled apparatus to employ manila paper as insulation ior these interconnection conductor cables. However, the

manila paper insulated cables are =not'.-so flexible as the varnished cambric cables and do 'n'ot possess the desirable electrical qualities 0f the varnished cambric insulated cables." Fur-ther. the lack of flexibilitylimits the-practicalthicb mess to which the manila paper insulation can be applied, thus limiting thevolt'age at which :the apparatusmaybe' used. k

It is thereforelanotherlobiect of this-invention to provide an apparatus of the above description which may be'ffilled with askarelland jemployin'g interconnection =icables which are highly flexible evenin thickness suitable for high-voltages; and having desirahlelelectrical gqualities "whlleifailing to contaminatefthe askarel'llquid.

Another object Of'lfhliilVEIltiOIl'iiS to provide an apparatus lot the above descriptionhalving' interconnection cables whichfarei suitable for :i'fnmersion in eithe'roil or ,askarel, .or in any other suitable dielectricliquid.

.A ,stillifurther object of :the invention is :to provide an apparatus .of the .above description employing interconnection .caloles which are anpreciably flower in cost, while fat thefs'ame time representing ;a technical improvement.

Further objects and advantagesof theinventicn will be a parent from 'a-t-he following spiecification. i

Accordin ly, in carrying out the objects rot thisiinvention, .a liquid;;dielectricifilled electrical appara us is'-:emp10y di-having interconnection and leadout conductorswhigch areinsulated with v bfl o ay scfi repe ak'liflif'fi 512 411 For -be t r ndwm c mp te understanding of the invention,reference ;;should 'beqhadwtogthe following specification andfthe zaccompa-rrying drawinssi in which Figure 1 {is a view; partially in section,;of an electrical;apparatusincorporatingthis invention; and Figure} is a detailgview of @a section V of interconnection -.conducter;-cable as used'in -the-apparatusYofthis invention.

R e ri more p ti ula y; ;t0 ;F sure themis shown atransformer generally designated 'as ;whi h- -e W a casin -.an omprises a magnetic core 7 .-3 having three a :vertical core membersyor-legsA. Threewindings M and,lcarelwound around magnetic core membe'r'sIAI Terminal members 8 are provided .ior making lexte'rior electrical .connections t6"tlie transformer; A" multiplicity of nterconnection and "leado'ut conductor cable's 9 are provided" to connect terminals 8 to windings 5, 6 and I and to establish interconnections between the windings themselves.

Each of these conductors 9 is insulated with layers of crepe paper insulation. The paper of the insulation used is preferably entirely untreated; that is, this paper is not filled with insulating varnishes or insulating filling materials of any kind. The insulating oil, or askarel or other liquid dielectric, which will be generally referred to below as oil, with which the apparatus is filled, completely penetrates this paper insulation within a very brief interval of time after filling. The oil itself thus performs the ofiice of an insulating impregnant. V g a The crepe paper insulation is formed of a kraft paper which has been creped and then cut into tape of appropriate width, with lines of creping preferably running at an angle to the longitudinal dimension of the tape. This angle corresponds generally to the angle at which the tape is applied to the cable or conductor, so that after the tape is applied, the lines of crepe form rings around the conductor in planes perpendicular to the axis thereof. This structure is shown in the enlarged detail view of Figure 2, where the tape is designated as H, and the angle of these crepe lines [2a is shown and designated at l2.

The crepe paper insulation for conductors having such an angle of crepe is shown and described and forms a portion of the subject matter of a copending patent application entitled, ,Crepe Paper Cable Insulation, Serial No. 118,292, filed September 28, 1949, by Guglielmo Camilli and Leo Mulligan, and assigned to the same assignee as this application. In that application it is pointed out that such a crepe paper insulation has a number of advantages, including ease and economy in assembly in the cable structure and in a high degree of flexibility resulting in a capability for unusually short-radius conductor bends without injury to the insulation.

It has also been found desirable to additionally crepe the paper of tape II with lines of crepe in a direction transverse to the above-described crepe angle disclosed in the Camilli et al. cable structure. This additional creping permits greater ease in applying the tape and adds further flexibility to the cable. The additional lines of creping are indicated by broken lines in the drawing at I3.

- The above described crepe kraft paper is preferably of the secondary crepe variety wherein the creping is done as a separate operation after manufacture of the paper, as distinguished from primary crepe in which the creping is formed at the time of manufacture.

A braided fibre or cloth sheath [4 may be added to the exterior of the conductor to serve as an outer protective covering. This sheath I4 must be porous for the admission of oil.

It has been found that, in apparatus of the above description, where the crepe kraft paper has been used, no further difliculties were encountered from swelling and bursting of the insulation due to heating, either in the vacuum drying process, or in subsequent operation of the apparatus. Higher operating temperatures of the apparatus are therefore possible, with longer interconnection cable life. This interconnection cable insulation also provides excellent electrical properties; that is, low power factor, good dielectric strength, and so on. Further, no contamination of the fluid filling the apparatus is encountered and the interconnection cables are more flexible '4 than either those insulated with manila paper or varnished cambric, providing greater ease in the manufacture of the apparatus.

It will be seen from the above description that in addition to the above enumerated advantages of the new structure of the invention, the cost of apparatus produced according to the invention is appreciably lower than prior art apparatus. This is due to the greater flexibility of the interconnection cable, providing greater ease and lower labor costs in installation, and because the interconnection cable insulating material itself is less expensive. Also, the apparatus employing the above interconnection cable may be filled with either oil or askarel, permitting greater standardization.

While a particular embodiment of the invention has been shown and described above, it will be understood that the following claims are intended to cover all modifications which fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a high voltage electrical apparatus comprising an enclosing casing substantially filled with an insulating liquid, an electrical device contained within said enclosing casing and immersed in said insulating liquid, short flexible connection leads for said electrical device, said connection leads being immersed in said insulating liquid, said connection leads including as substantially their only solid insulation a plurality of layers of crepe paper insulation positioned on said respective leads, said insulating liquid penetrating said crepe paper insulation.

2. In combination, a high voltage electrical apparatus comprising anenclosing casing substantially filled with an insulating liquid, an electrical device contained within said enclosing casing and immersed in said insulating liquid, short flexible connection leads for said electrical device, said connection leads being immersed in said insulating liquid, said connection leads including as substantially their only solid insulation a plurality of layers of crepe paper positioned on said respective leads, said layers of crepe paper being surrounded by an abrasion-resistant liquid-permeable sheath having a radial thickness which is small compared to the total radial thickness of said plurality of layers of crepe paper, said insulating liquid penetrating said sheath and said crepe paper insulation.

EUGENE L. CRANDALL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,886,786 Branthwaite Nov. 8, 1932 1,890,254 Frederickson 1 Dec. 6, 1932 1,994,911 Ford Mar. 19, 1935 2,029,140 Treanor Jan. 28, 1936 2,038,935 Hunter et al A r. 28, 1936 2,048,849 Di Lustro et a1. 'July 28, 1936' 2,097,501 Reichelt Nov. 2. 1937 2,377,689 Hyde June 5, 1945 FOREIGN PATENTS Number Country Dat r 19,951 England Sept. 7, 1901

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