US1986843A - Terminal or pothead for electric cables - Google Patents

Description

Jan. 8, 1935. F. c. MEYER ET AL 1,986,843

TERMINAL OR POTHEAD FOR ELECTRIC CABLES Filed Sept. l2, 1932 W INVENT()R. 2 8 BY w W MW wms.

Patented Jan. 8, 1935 UNITED STATES PATENT OFFICE TERMINAL R POTHEAD FOR ELECTRIC CABLES Application September 12, 1932, Serial No. 632,755

1 Claim.

This invention relates to a terminal or pothead construction for electric cables and is more specifically directed to an improved terminal or pothead construction for cables of the type in which the insulated conductor is maintained at all times submerged in oil under high pressure as disclosed for example in Charles E. Bennett application Serial No. 563,714, filed July 29, 1931.

The drawing shows an embodiment of the invention in sectional elevation. Y

Referring to the drawing in detail, 1 designates the end of the sheath enclosing the cable, this sheath to be maintained filled with oil under pressure at all times. The sheath 1 is made up of an inner and outer lead sheath 2 and 3, respectively, and an intermediate layer or layers of canvas or other suitable fabric 4 provided for the purpose of permitting of expansion of the inner sheath 2 under the pressure of the oil and also for preventing bursting of the sheath. As will be understood this sheath construction is part of the cable system rather than a part of the terminal or pothead constituting the present invention.

Secured to the outside of this sheath construction is a sleeve or gland 5 rigidly attached to the cable sheath by a wipe joint 6. The insulated and shielded conductor of the cable passes out Y of the end of the sheath 1 and upwardly as 30 viewed in the drawing through the gland 5, the

metal shielding 7 terminating at 8 on the drawing. The gland 5 is tapered on the inside as shown to gradually change the electrostatic stress from the conductor outward. The interior of the gland 5 is maintained in communication with the interior of the sheath structure of the,

cable by slight mechanical clearance between the gland and the conductor of the cable. Pipe 9 is an oil supply line to take care of contraction and expansion of the oil due to thermal conditions.

Screwed into the upper end of the gland 5 is a pressure tube 10 of insulating material such as a phenolic condensation product, porcelain or other suitable material, having a specific inductive capacity dillerent from-that of the insulation of the conductor, the insulated conductor extending upwardly through this tube and terminating adjacent the upper end thereof as will be described presently. The pressure tube closely fits the insulation of the conductor so as to reduce as much as possible the electrostatic stress on the oil in the tube.

Mounted on the upper end of the gland 5 is a metal shielding cone 11 secured to the gland 5 by a wipe joint 12, the outward taper of this cone being practically a continuation of the taper provided by tapering the upper end of the gland 5 above referred to. The gland 5 is also provided adjacent its upper end with an annular flange 13, and bolted to this flange by bolts 14 is a metal cone 15 for supporting the terminal insulator 16.

The upper end 1'7 of the insulated but unsheathed conductor of the cable is equipped with a connector 18 attached rigidly thereto in any suitable fashion, this connector 18 having a. stem 19 which extends to the outside of the terminal through the top thereof.

The upper end of the pressure tube 10 is provided with a metal sleeve 20 screwed in place thereon, the connector 18 just referred to passing through this sleeve. Bolted to the sleeve 20 by bolts 21 is a cap plate or ring 22 through which passes the stem 19 of the connector 18, the top of the connector being drawn up to this plate by a nut 23. This structure seals the upper end of the pressure tube 10.

The metal cone 15 as above mentioned supports the insulator 16 of the terminal. The lower end of this porcelain is cemented as shown at 24 to a metal ring 25 secured to the cone 15 by the bolts 26. A washer 27 insures a liquid-tight joint.

The upper end of the insulator 16 is provided with a cap plate 28 bolted to a ring 29 cemented or otherwise rigidly secured to the upper end of the insulator. This cap plate'is provided with a vent 30 for permitting of the escape of air from the interior of the terminal when the same is being filled with oil through the filler opening 31, this oil being maintained under gravity pressure as distinguished from the high pressures maintained on the oil in the cable pipe and within the pressure tube 10. A vent tube 32 is also provided in the cap plate 22 of the pressure tube for initially venting the tube.

The cone 6r grounding shield 11 supports a plurality of tubes 33 of suitable insulating material such as a phenolic condensation product, paper, etc. concentrically disposed with respect to each other and with respect to the pressure tube 10 and its contained conductor. These tubes as will be seen from'the drawing are supported by the shielding cone 11.

It is to be understood that while the sheath of *the cable has been describedas composed of an inner and outer sheath with an intermediate fabric or other material for the purpose of this invention the sheath may be of the fluted lead type.

It will be seen from all the foregoing that the pressure tube 10 is in communication with the interior of the cable sheath 1 so that the high pressure maintained on the oil in the cable pipe or sheath is maintained on the oil within the pressure tube while the oil of the terminal exterior of the pressure tube is only under gravity pressure, whereby the advantages accruing to the use of oil under high pressure in direct contact with the exterior of the insulation of the cable are available to the extreme outer end of the cable, without subjecting the porcelain insulator 16 to any unusual pressure, this insulator being sealed off from the pressure tube and simply filled with oil under gravity pressure.

What is claimed is:

A terminal for high tension electric cables of the oil filled pressure type wherein the insulated cable conductor is enclosed in a tubular casing filled with oil maintained under high pressure, said terminal comprising in combination a sleeve fitting over the end of the cable casing and wiped thereto, said sleeve constituting a continuation of the cable casing to receive the insulated cable conductor, and flaring outwardly on its interior adjacent the upper end of the sleeve gradually to change the electrostatic stress from the conductor outwardly, a pressure tube of insulating material for receiving the insulated cable conductor, said tube being screwed into the upper end of said sleeve to provide a continuation thereof,

means for sealing the upper end of said pressure tube, a connector secured to the outer end of the conductor and projecting through the upper end of the pressure tube, a shielding cone surrounding the lower end of the pressure tube and wiped to the outer end of said sleeve, the outward taper of this cone being a substantial continuation of the outwardly flaring interior of said sleeve, tubes of insulating material surrounding the pressure tube and concentrically disposed with respect thereto and with respect to each other, said tubes resting upon said shielding cone to be supported thereby, said sleeve being provided with an annular flange, a conical metal member surrounding said shielding cone and bolted to said annular flange, an insulator sealed to and supported by said conical metal member and enclosing said shielding cone, said tubes and said pressure tube, a plate for sealing the upper end of said insulator, a vent for said plate, a vent pipe for said pressure tube extending through said plate, an insulating fluid under gravity pressure within said insulator and surrounding said pressure tube, said pressure tube and sleeve permanently separating the said liquid insulation in the insulator from the; high pressure liquid insulation in the pressure tube.

FRED c. MEYER. GEORGE E. om.

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