US2219910A - Termination or joint for high tension electrical cables - Google Patents

Description

TERMINATION OR JOINT FOR HIGH TENSION ELECTRICAL GABLES Oct. 29, 1940. J. K WEBB ET AL Filed Aug. 12, 1956 F ig. 2.

RC. M/LD/VEA WW Patented Oct. 29, 1940 UNITED STATES PATENT OFFICE TERMINATION OR JOINT FOR HIGH TENSION ELECTRICAL CABLES York, N. Y.

Application August 12, 1936, Serial No. 95,544

1 Claim.

This invention relates to terminations or joints for high tension cables and is a modification of the invention disclosed in United States Patent No. 1,935,820, issued November 21, 1933. In that 5 patent we have described a condenser stress cone arrangement for grading the stress between the core and the sheath of the cable in which the cone is located with its base directed towards the end of the cable on which the cone is applied, the conductive layer at the base being at core potential.

Difliculty is sometimes experienced in applying this arrangement to existing types of terminations in which the porcelain sealing chamber is of conical form. with its base directed away from the end of the cable owing to the fact that there is insufficient room in the apex of the sealing chamber to accommodate the base of the cone. Moreover in making joints with the bases of the cones directed towards the centre of the joint there is difilculty in applying insulation to the joint by the usual process of applying an overall insulating roll.

The above objections are overcome by the pres- 25 ent invention which provides a high tension cable joint or termination in which a hollow self-supporting conical condenser comprising insulation separated conductive layers is fitted over the end of the cable insulation with its base directed away from the cable end towards the sheath but spaced therefrom. The conductive layer at the apex of the cone may be connected to the core and that at the base of the cone may be connected to earth through a low impedance connection whereby an effective grading of the potential is obtained. The conditions for uniform gradient with this arrangement of cone are somewhat different from those set forth in the prior patent, and to obtain optimum results the design of the cone must be slightly modified in respect of the number and size of the foils.

The invention will be better understood by reference to the accompanying drawing in which: 45 Fig. 1 is a sectional diagram of a cable termination constructed according to the invention;

Fig. 2 is a sectional diagram of a cable joint constructed according to the invention.

Referring to Fig. 1 the cable sheath is indicated at I which is cut away to expose the cable insulation 2 in the usual manner and 3 is the cable core or conductor connected to the terminal device 4 mounted on the porcelain sealing bell 5.

The condenser cone 8 comprises a metal tube 55 former I at the apex end supporting a. number of insulation separated conductive layers 8 01 gradually increasing diameter as described in our aforesaid patent specification. The metal tube former is slipped over the cable insulation 2 so that the cone 6 extends with its base 9 directed away from the conductor 3 and towards the cable 5 sheath I as shown. The conductive layer at the base of the cone is maintained at earth or low potential whereas the conductive layer or metal former at the apex is at high potential, thus securing a capacity grading effect within the ter- 10 mination. As indicated in the drawing electrical connections In and I I may be provided respec tively between the conductor 3 and the metal former I and between the sheath I and the conductive layer at the base of the cone.

The sealing bell would be filled with insulating compound in the usual manner and if desired polymerised styrene may be applied to insulate the cone and isolate the compound in the termination from that in the cable by the methods forming the subject matter of our application United States application Ser. No. 35,960, filed August 13, 1935.

The construction of the joint illustrated in Fig. 2 will be apparent from the drawing in which 2 the parts already described in connection with Fig. 1 are indicated by the same reference numerals. In this joint the conductors 3 are joined by means of a ferrule I2 in the usual manner after the condenser cones 6 have been applied and paper insulation I3 is lapped on to extend over the cones. The joint is completed by a lead sleeve I4 in the usual manner and if desired polymerised styrene may be applied to insulate the joint and the cones in accordance with the methods forming the subject matter of our Patent No. 2,105,567.

What is claimed is:

A high tension cable comprising a conductor, an insulating layer and a metallic sheath about said insulating layer, said conductor, insulating layer and sheath each being of substantially uniform cross-secti0n, a potential grading means for said cable consisting of a hollow self-supporting frusto conical condenser comprising insula- 4 tion separated conductive layers, the small end of said condenser fitting snugly over said insulating layer, and being arranged with the base of said frusto-conical condenser directed away from the end of said conductor and toward said sheath, but spaced therefrom, and means for connecting the end layers of said condenser to the conductor and the cable sheath, respectively.

JOHN KRAUSS WEBB. RAYMOND CHARLES LIIIIDNER.

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