US2050888A - Oil filled high voltage cable - Google Patents

Description

Aug. 11, 1936. E, KIRCH 2,050,888

OIL FILLED HIGH VOLTAGE CABLE Filed Dec. I4, 1952 @ma mi His Att Orrweu Patented ug. 1l, 1936 UNITED STATES on. FILLED HIGH VOLTAGE CABLE Ernst Kirch, Berlin-Oberschoneweide, Germany,

assignor toGeneral Electric Company, a corporation of New York Application December 14,

1932, Serial No. 647,200

In Germany January 9, 1932 13 Claims.

Oil lled high voltage cables now in service are provided with feeding and compensating containers or reservoirs for the compensation of temperature-produced variations in the volume of the oil iilling. Tl.e containers are located at suitable points on the line as in manholes, for example, and are in communication with the oil vfilled space of the cable through the medium of receptacles known as joint casings or boxes. It

has been proposed to combine the oil-feeding container and the cable ttings in one unit, but known fittings of this kind have disadvantages which render their use impossible, either from a technical or an industrial point of view. In one construction, air is immediately above the oil in adomed chamber of the container and it is taken for granted that the oil within the cable is fully saturated with this gas. It is, however, common knowledge that the use of oil containing dissolved gases is detrimental, so that the actual practice is to use degasied oils only, that is to say oils which are freed to a high degree from their dissolved gas. Since, however, highly degasied oils are capable of absorbing a volume of gas approximately equal to that of the oil, the air contained in the chamber cfrthe expansion vessel would be absorbed by this oil within a very short time so that the expected result is lost. Another known construction, provided with metal partitions acting as diaphragms avoids the disadvantage above noted but involves such large dimensions for a compensating chamber of a capacity of only a few litres that the construction is too costly and therefore uneconomical as compared with the arrangement of separate boxes and compensating containers. Moreover, reliability is imperiled by the circumstance that the sheet metal partitions are subjected to very high bending stresses as a resultof the breathing effect l .of the cable.

The present invention has for its object to obviate these disadvantages and to provide an improved arrangement of an expansion vessel with a cable fitting wherein a non-metallic,` resili ient and/or collapsible oilproof partition is disposed between the impregnating agent of the cable and the pressure-compensating medium.

The partition is suitably made from a rubberlike oil insoluble and very elastic insulating agent comprising the products of polymerization of an acrylic acid or a product of polymerization of its derivative, or again a product of polymerization of homologues alone or in a mixture, if necessary with an additional material such as paper, mica,

r etc. O ther synthetic and equivalent insulating agents may also be used of which vinapas may be taken as an example. Vinapas is a material comprising polymerized vinyl compounds, particularly ,poly-vinyl compounds. When used alone, these materials may be formed into cylin- 5, drically or otherwise shaped elements by dipping, adhesion, compression, rolling or other processes; when used in combination with reinforcements, for example fabrics, the latter are impregnated and coated with the said materials and are therel0 by rendered impermeable. The materials above referred t0 are rubber-like in the sense that they are capable of stretching under the inuence of applied pressure and are capable of self contracting when the pressure is removed. They are unl5y like rubber in that they are not affected by the oil contained in the cable.

With cables containing oil in their unoccupied spaces or on the surface of the cores, the expansion vessels are merely sleeve-shaped members which may be disposed at any point along the length of the cable and surrounding a suitable opening or openings in the lead sheath thereof. In .cables in-which the oil is Within the cores, the expansion vessels may be combined with the known junction or joint boxes. The expansion vessels just described may be used not only on cables having very thin insulation oils but also with cables containing viscous impregnating materials, whether oils or compositions. Greater .0 viscosity makes it necessary to use a large number of such vessels or to work them under higher pressure.

Constructional examples of the subject matter of the invention are illustrated in the accompany- 5 ing drawing, in which Fig. 1 illustrates an expansion vessel surrounding the sheath of a cable; Fig. 2 illustrates a modified form of the Vessel in longitudinal section taken on line 2--2 of Fig. 3; Fig. 3 is a sectional view taken on line 3--3 of Fig. 2; Fig. 4 illustrates a further modification of the expansion vessel; Fig. 5 illustrates the application` of a vessel of the type shown in Fig. 1 to a joint; Fig. 6 illustrates a cable terminal, and Fig. 7 is a detail view illustrating one of the automatic valves for controlling the flow of oil through the sheath.

For a consideration of what I believe to be novel and my invention, attention is directed to the accompanying description and to the claims apr pended thereto.

Fig. 1 shows a sleeve-shaped expansion vessel which may be tted at any point of the cable,

whether of the multiple conductor type with oil channels in the outer unoccupied spaces, or of the single conductor type with oil channels directly under the lead covering. Oil outlets or radial ports 'I are made in the lead sheath of the cable 8 and are screened for example by a perforated metal sleeve 9 forming the inner limiting surface and a support for a nonmetallic resilient partition I0, said partition dening a compensating vessel. Instead of making the ports in the sheath itself they may be made in a device generally similar to the connector shown in Fig. 5, and referred to later. Such a vessel may take the form of a tube applied over the sheath or the sheath may be interrupted to receive it. 'Ihe initial position of the partition I0 is determined by the metal screen 9 which prevents the said partition from being damaged when air in the space between the cable and partition is exhausted through the connection nipple |0. The nipple may also be used if it be desired to deliver degasied oil to the chamber within the vessel dened by the elastic partition I0. In Fig. 1, the partition is secured, for example, by wire ligatures II and I2, to the two ends of the metal screen 9 which at these points form soldered fluid-tight joints with the lead covering of the cable. The partition may also be directly .and hermetically secured to the cable sheath.

This assembly is surrounded, at a certain distance, by an air-tight sleeve or casing I3 and the space I4 between the latter and the resilient partition I0 forms an expansion chamber preferably filled with a neutral or easily dissolved gas under more or less high pressure. ,To permit introduction of such gas into the chamber, the said sleeve is provided with a suitable fitting I3, The tting also permits of access to the nipple I0".

The compensating vessels are more easily mounted in position when the oil ports 1 in the cable covering are closed as for example by valves. Ball or conical valves 22, Fig. '7, may be used for this purpose and are so arranged that they are pressed upon their seats as long as the cable is under pressure, i. e., as long as it is closed to the outside. Any suitable means may be employed to retain the valves in proximity to their respective seats. In this gure 8 may be taken as indicating the sheath of the cable or a split tube surrounding it and sealed thereto at its ends and along the joint. As illustrated herein the opening operation of the valves is carried out by making the pressure outside the valve equal to or higher than the internal pressure of the cable so that a suitable number of the closing balls or cone valves will drop by gravity and allow the oil to ow out through the ports. The valves may of course be of other forms and be actuated in any desired manner. As will be evident, these valves are only used once and that while the installation is being made. After the external pressure is applied to open them, they remain in said position and therefore exert no controlling effect on the insulating fluid in its passage between the cable and the exterior thereof.

Other constructional examples of the expansion vessel are illustrated in Figs. Z and 4. The casing I3 of Fig. 2 encloses a compressible sackshaped element I5 which appears in cross section as an annular hollow body and which is made of the hereinbefore mentioned material. The longitudinal division, Fig. 3, is provided to simplify the assembly. 'I'he resilient tubular element I6 of Fig. 4 is coiled within the casing I3 and around the cable. In these cases, the resilient element contains the compressible medium and both are made of the material referred to above which is not affected by the impregnating oil or compound.

It may be desirable to give to one or the other form of chamber of the expansion vessel a greater 5 or lesser capacity, according to the cross section of the parts; this may be done without difficulty by connecting to the chamber an additional gas chamber Il (Fig. 2). These chambers may be formed in metal walled casings.

Fig. 5 shows a joint or casing used with hollow conductor cables and provided with an expansion vessel. The two ends I8 and I9 of the hollow conductor of the cable are conductively united by means of a tube 20 having end sockets l5 for the conductors and provided with axial slots or ports 1 in order that the oil may ilow out of the said hollow conductor into the expansion chamber proper through the wound insulating means 2I or along the latter. These ports may be provided with suitable valve means, as shown in Fig. 7, to prevent oil from escaping from the core during the assembly operations. They may be opened automatically or manually prior to the application of the nal winding of insulating 25 material.

Fig. 6 shows the arrangement of an expansion vessel within the casing of a single conductor cable stop end or terminal. The expansion vessel may be combined in a similar manner with an 30 oil stop joint which is more or less equivalent to two oil immersed terminals or stop ends. In this ligure I3 indicates a casing which is soldered to the sheath of the cable at its lower end as indicated at 25, and the upper end has an out-turned 35 ange which is united with that on the ring 26. Rising above the ring is an insulator 21 through the upper end of which projects a part 28 connected to the cable conductor` The expansion vessel takes the form illustrated in Figs. 2 and 3. At one end of the vessel is a perforated metal screen 9 which protects it when the chambered interior of the insulator is evacuated preparatory to lling it with degasied oil. The cable sheath may have valved ports such as those hereinafter described, or other means to permit oil from the interior of the cable to enter the chamber in the insulator. The interior of the expansion vessel may be iilled with -gas under super-atmospheric pressure through the nipple I0, the same as in 50 Figs. 2 to 4.

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

1. A cable ,comprising a. conductor, insulation thereon, an enclosing metal sheath and a body of insulating uid lling the spaces within the sheath, a casing surrounding the sheath and sealed thereto to dene a chamber, means establishing communication between the interior of the sheath and the chamber, and a sealed expansion vessel located within the casing and substantially lling it under an operating condition and having a unitary wall made of a rubber-like material capable of expanding and contracting but which is insoluble in the fluid filling of the cable, said wall being moved by change in volume of the fluid within the cable and casing and limited in its expansive movements by the casing.

2. A cable comprising a conductor, insulation thereon, an enclosing metal sheath and a body 70 of insulating fluid filling the spaces within the sheath, said sheath having an outlet port, a casing surrounding the sheath and sealed thereto to denne a chamber normally in free communication with the port, and a sealed expansion vessel .enveloping the sheath and located within the chamber and substantially filling it to compensate for changes in volume of the fluid in the cable, said vessel comprising a body of rubberlike material but which is insoluble in the insulating fluid yet capable of stretching and contracting with changes in the volume of the fluid within the cable and casing to compensate for such changes and prevent excessive pressures therein, the stretching of the vessel being limited by the inner wall of the casing.

3. A cable comprising a conductor, insulation thereon, an enclosing metal sheath and a body of insulating fluid filling the spaces within the sheath, said sheath having a port through which the uid is free to flow when the cable is in service, a rigid walled casing surrounding the sheath and sealed thereto to define a chamber of xed size, a sealed expansion vessel enveloping the sheath and located within the casing and substantially filling the chamber under an operating condition, said vessel having a non-metallic wall made of a material which is expansible and contractible, one side of which is acted upon by fluid issuing from the port, the other side being acted upon by gas under pressure, and means through which the gas is supplied.

4. A cable comprising a conductor, insulation thereon, an enclosing metal sheath having an opening therein, and a body of liquid insulation filling the spaces within the sheath not occupied by the conductor and its insulation, a casing surrounding the sheath and sealed thereto on opposite sides of the opening to define a chamber, a vessel within the chamber surrounding the sheath and sealed at its ends around the sheath, said vessel having a non-metallic expansible and contractible wall, a perforated support between the sheath and wall to limit the inward movement thereof, and means for filling the portion of chamber outside of the wall with elastic fluid.

5. A cable comprising a conductor, insulation thereon, an enclosing metal sheath having a lateral port, and a body of insulating liquid filling the spaces within the sheath, an inwardly opening valve for the port, a casing surrounding the sheath and sealed thereto to define a chamber, a sealed expansion vessel within the casing enveloping the sheath and having a non-metallic wall made of a material which is expansible and contractible and is moved by the liquid issuing from the port after the valve has been opened to compensate for changes in volume thereof, and means for imposing a superior pressure outside of the sheath to cause the valve to open.

6. A pair of hollow liquid filled cables, a connector unitingv the ends of the conductors thereof, ports in the connector through which liquid from the cable flows in and out, a body of insulationv surrounding the cable ends and the connector, a perforated annular support surrounding the body of insulation and supported at its ends by the sheaths, a tubular vessel surrounding the support and sealed to the sheath at its ends, said vessel having an elastic non-metallic wall, a metallic casing enclosing the vessel and sealed to the sheathvand defining a chamber, and a filling of elastic fluid between the wall of the vessel and the adjacent wall of the casing.

7. A cable comprising a conductor, insulation thereon, an enclosing metal sheath and a body of insulating liquid filling the spaces within the sheath, a casing surrounding the sheath and sealed thereto at its ends and defining a chamber, means permitting egress of fluid from the cable into the chamber, and a sealed expansion vessel located in the chamber and having a movable wall acting in opposition to the body ofl liquid, said vessel having a non-metallic elastic wall made of synthetic material which is impervious to said liquid,` said wall being secured at its ends only around the sheath.

8. A cable comprising a metallic sheathed insulated conductor, an enclosing casing for a portion of the cable which is sealed at its ends to for'm a chamber, a vessel located within the chamber of the casing and having an elastic wall, the ends of which are sealed about the cable, and aligned nipples for the enclosing casing and the elastic wall by means of which different fluids may be admitted to the space inside of the elastic wall and to that between the wall and the casing.

9. A cable comprising a pair of metal sheathed insulated conductors, a connector for uniting them, insulating fluid within the sheaths, insulation applied over the connector and adjacent ends of the conductors, a metallic casing, the shape of which approximates that of the applied insulation, said casing being sealed at its ends to the sheaths, a perforated metal member enclosing the applied insulation and approximating the shape thereof, and a vessel having an expansible and contractible wall, which is located between the perforated member and the Wall of the casing, said member limiting the inward movement of the wall and the casing the outward movement.

l0. A cable comprising an insulated conductor, an enclosing metal sheath, a body of insulating fluid lling the spaces within the sheath, a chambered casing surrounding the cable and having tapered ends sealed to the sheath, means normally establishing free communication between the interior of the sheath and the chamber, a sealed vessel of non-metallic material located within the chamber, surrounding the sheath and extending into the tapered ends of the casing and substantially lling the casing under certain conditions of operation, the wall of said vessel being capable of stretching and contracting and in so doingito compensate for changes of volume of the fluid in the sheath and casing and being insoluble in said fluid, said casing limiting the movements of the wall in one direction, and other means for limiting its movements in the opposite direction.

1l. A cable comprising ,a conductor, insulation thereon, an enclosing metal sheath and a body of insulating fluid filling the spaces within the sheath, a tubular casing surrounding the sheath and sealed thereto and defining an annular chamber, means permitting the fluid to flow from the sheath into the chamber, a tubular expansion vessel located inside the casing comprising a nonmetallic expansible and contractible wall scaled at its ends to the sheath and dening an annular partition, the inner surface of which is acted upon by the fluid from the cable, and by its movements compensates for changes in volume of the uid, the outward movement of the wall being limited by the inner surface of the annular casing, a support located between the cable and the wall to limit the inward movement thereof, and a body of gas under pressure acting on the outer surface of the wall in opposition to the fluid from the 7 cable.

12. A cable comprising a conductor, insulation thereon, an enclosing metal sheath and a body of insulating liquid filling the spaces within the sheath, an annular casing surrounding the sheath and sealed thereto at its ends to define a chamber,

means permitting liquid to iow from the cable into the chamber, and a sealed expansion vessel located within the chamber and conried in Place by the inner Wall of the casing and the cable and. acting in opposition to the body of insulating liquid` as its volume increases, said vessel having a wall made of synthetic material. capable of stretching and contractingand which is insolublev in the liquid acting thereon.

13. A cable installation comprising an insulated conductor, an enclosing sheath therefor, a body of insulating iuidtllling the spaces within the sheath, a casing surrounding the sheath and connected theretoand dening a sealed chamber, communicating means between the cable and casing for the iluid. a sealed vessel having a. wall made of non-metallic material which is expan- CERTIFICATE OF CORRECTION.

Patent No. 2,050,888. August l1, 1936.

ERNST KIRCH.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, second column, line 59, claim 1l for "scaled" read sealed;' and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 13th day of' October, A. D. 1936.

Henry Van Arsdale (Seal) Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION.

Patent No. 2,050,888. August ll, 1956.

ERNST KIRCH.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, second column, line 59, claim ll for "scaled" read sealed;' and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 13th day of October, A. D. 1936.

Henry Van Aradale (Seal) Acting Commissioner of Patents.

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