US2852596A - High voltage cable connector - Google Patents

Description

' 2 -1 N11- /1 l/N 2 SPt 16 1958 D; c. PRINCE 2,852,596

' HIGHVOLTAGE CABLE CONNECTOR Filed May 20. 1952 QTTOENEYS y apparatus.

United States Partir' f1 S-IjIIGI-I 'VOLTAGE CABLEv CONNECTOR vDavid C.4 Prince, Schenectady, N. Y.

`Application May 20,- 1952, Serial No. 288,795'

3 Claims. (Cl. 174-73) This invention'relates to improvements in high voltage cables.

i/The usual high voltage cable comprises a conducting .-v-core of strandedwire upon which is wound a plurality of layers of. paper insulating tape, the whole being enn closed in a lead or other vprotective sheath. The laying of such cable involves considerable expense, a substantialY portion of which is consumed in making joints bev tween the `ends of adjacent pieces of cable, and between the final end and the particular apparatus to which it is ,iattached, such as a transformer, pot head, etc.

= 'In order toprevent electrical breakdown of cable insufflation, it is commonepractice to cut the sheath back so as to provide a suicient creepage distance fromthe sheath over the surface `of the paper tape to the conductor- Theproblem then becomes one of securing a low enough potential gradient along the exposed paper` to prevent a surface creepage breakdown. Since the creepage-length israther considerable, it is necessary to takekv steps to insure va fairlyuniform distribution of p0- -tential along this path. Heretofore, it has been attempted to obtaingthis potentialnniformity by hand-winding adtire; expense of installation. These high labor costs are further increased when the designer makes an etort to achieve the ideal of'short cable runs between pieces of In this casethe cost of the cable ends is so vhigh that this method of construction has been virtually abandoned.

In accordance with my invention these prior difliculties are completely eliminated, so that high voltage cables may be joined together simply and efficiently, with resultant savings in labor costs. The new cable comprises the usual conductor and outer sheathing separated by insulating tape. However, this insulation is divided into insulating layers separated by concentric conducting layers. The sheathing and insulation of the cables to be joined are cut 'back on a bias such that proper potential distribution along the surfaces is obtained. A coupling structure is provided for completing the joint.

' The coupling is of substantially the same construction as the cables to be joined, but it also includes a bushing member internally threaded for engagement with complementary threads on the respective conductor cores. Upon rotation of the coupling, electrical continuity of the HCC cables 1 and 2 comprise, respectively, lead sheaths 3k and 4, insulation 5 and 6 of varnished cambric oiled paper, styrenated paper, orthe like, and conductors 7 and ln these cables 1 and 2 are a plurality of conducting tape layers indicated at 9 and 10, respectively. These tape layers, which may be'thinmetalfoil, subdivide the insulation layers 5 and 6. The conducting layers 9 and 10 are concentric with the insulating layers 5 and 6 and with the central conducting cores. As will be explained later in greater detail, the conducting layers 9 and 10 assume electrical potentials determined by their respective capacitances, so that by cutting the cable ends on a suitable bias, a uniform distribution of potential may be obtained along the'terminal surface formed by the cut.

In preparing the joint, the cable conductors 7 and 8 are bared and the cable ends are cut on a bias, as previously explained, so that they `are conical or tapered. As part of the actual joint, a coupling'structure indicated generally at 11 is used. Thiscoupling is made in the factory, so that .the time required in the tield for making the joint is greatly reduced.

As best seen in Fig. 2,v coupling structure 11 comprises a bushing member l2` mounted withinasleeve. The sleeve comprises insulation tape layers 15 alternating with conducting layers 16, the whole beingenclosed by a lead sheath 18. The sleeve ends are internally tapered so that they are complementary tothe adjacent tapered ends of the cables. The bushingk 12 is internally threaded at its ends for right and left hand threads, respectively. Similarly, the ends of the conductors 7 and 8 have cooperating threads at 113 and 14 -for engaging the threaded portions of bushing 12. The -ca-bles are thus united by rotating the coupling 11. Electrical continuity for the cables is maintained through the bushing member 12. When the mechanical. joint is completed, the lead sheaths `are splicedtogether. The joint is dried` and lled with an insulating compoundy 17 in thefusual manner.

ln high voltage cables, the radial potential gradient is very high, so that if the ca'ble were cut off at the end in a plane perpendicular to the longitudinal axis of the cable, an electrical breakdown would occur because of the short distance between the sheath and the conductor.

, divides the cable into a plurality of concentric condensers` cables is accomplished. The joint is then completed in the usual manner by drying and lling any air pockets with an insulating compound.

A better understanding of the invention may Ibe had from the following description taken in conjunction with the accompanying drawings, in which:

positioned between the sheath and the core. These conducting layers assume potentials determined by the capacitances between the cable sheath, the metallic layersy and the conductor. By cutting the cable end on a suitable bias, ya uniform distribution of potential between. the sheath and the core may be obtained Without any necessity for applying `additional insulating tape along the surface of the cut.

When the cable is to terminate in a pot head, the porcewise have been the entrance bushing. Since the bushings represent a rather large part of the cost of both circuit breakers land transformers, this construction will materially reduce such cost and lead to a type of sub-station design very much less costly than prior designs.

The quality of the cable joint made in accordance with my invention is superior to present designs. Since the coupling structure is prepared in the factory, few manual operations are required of the workman in the lield. The opportunity for human error is thus substantially reduced, so that the cable joints are of unifoim high quality throughout the installation.

The ease with which the cable union may be accomplished in the lield reduces the time within which the cable insulation is exposed to the moisture in the atmosphere. The time required by the drying process will therefore be considerably reduced. The nal results of these measures make for both lower costs and higher quality cable joints.

When the cable joint unites cables having the conducting layers 9 and 10, the conducting layers 16 may be omitted from the coupling structure 11. Conversely, a4

coupling structure 11 having the conducting layers 16 can be used with cables not having the conducting layers 9 and 10, and the full benets obtained.

In Fig. 3, I have shown a further embodiment of the invention in which the coupling structure 19 is a central conducting bushing 12 surrounded by insulating layers 15 alternating with conducting layers 16, and an outer sheathing 18. One end of the sleeve 15-16-18 is externally tapered to form a male portion while the other end is internally tapered to form a female portion 21. The cable 1 in this case does not include the conducting layers 9. The cable conductor 7, where it protrudes at the end of the cable, is threaded into the bushing 12 at the female end of the coupling structure 19. A short central conductor 22 is threaded or otherwise secured in the opposite end of bushing 12 and protrudes somewhat from the end of the male portion 20. The male part 20 can be inserted in a coupling structure similar to the structure 11 shown in Figs. 1 and 2, and the effect is just as though the entire cable 1 were made with the conducting layers 9 of Figs. 1 and 2. In this case, the proper bias of the tapered portions Will be slightly different in order to produce the same result as in the embodiment of Figs. 1 and 2.

I claim:

l. For connecting with the end of a high voltage cable having insulation which tapers conically from a central conductor to an outer sheath, a coupling comprising a central conducting member for electrically connecting with the central conductor of the cable, an outer sheath of substantially the sarne diameter as the sheath of the cable, a plurality of layers of a high voltage tape wound about said conducting member to act as insulation in the space between said conducting member and said sheath, the exposed ends of tape being tapered from the conducting member to form an extended and continuous creepage path between said conducting member and said sheath, said taper being of the opposite conforming taper to that of the cable, concentric layers of a metallic conducting material of low electrical resistivity interposed between selected layers of the tape with the ends thereof exposed by the continuous taper of the insulation to obtain a potential gradient along the tapers which is substantially uniform, and an insulating compound interposed between the taper of the coupling and the taper of the connected cable.

2. A coupling according to claim l wherein is provided a female taper to mate with a corresponding male taper upon the cable.

3. A coupling according to claim 1 wherein the central conducting member is a bushing having threads for engaging corresponding threads upon the end of the central conductor of the cable.

References Cited in the tile of this patent UNITED STATES PATENTS 477,951 Mezger June 28, 1892 483,327 Purcell Sept. 27, 1892 952,513 Dow Mar. 22, 1910 1,129,460 Farnsworth Feb. 23, 1915 1,508,373 Lightfoot Sept. 9, 1924 2,142,625 Zoethout Jan. 3, 1939 2,222,718 Phillips Nov. 26, 1940 2,288,969 Kirkwood July 7, 1942 2,449,983 Devol Sept. 28, 1948 2,451,868 Quackenbush et al. Oct. 19, 1948 2,523,313 Lee Sept. 26, 1950 2,650,334 Skeats Aug. 25, 1953 FOREIGN PATENTS 204,706 Great Britain Oct. 9, 1924

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