US1830533A - Terminal for fluid filled cables - Google Patents

Description

Nov. 3, 1931. E. D. EBY

TERMINAL FOR FLUID FILLED CABLES F'ild Nov.

Patented Nov. 3, 1931 UNITED STATES PATENT OFFICE EUGENE D. EBY, OF PITTSFIELD, MASSACHUSETTS, ASSIGNOB '10 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK TERMINAL FOE FLUID FILLED CABLES Application filed November 21, 1930. Serial No. 497,220.

The present invention relates to cable of the type comprising three separately insulated conductors contained in one sheath which is filled with oil or equivalent fluid insulation at a pressure not less than that of the atmosphere and preferably somewhat above it. In a cable installation of this character it is not only of the utmost importance that all air and other gases be removed from the .1 interior of the sheath and from the fluid insulation, but that this condition be permanently maintained at all times. In order that the individual conductors of the cable may be properly connected to other conductors, it is necessary to provide an arrangement of parts sheath. It is also necessary to provide means whereby the terminals subsequent to installation may be opened for inspection or repair without admitting air to the cable, and that such air as enters a terminal be removed prior to putting the cable into service. It is also necessary to provide an arrangement of parts whereby the terminals and parts associated therewith may first be evacuated and then filled with degasified oil or its equivalent.

The object of my invention is the provision of an improved terminal structure for fluid filled cables, which fulfills all of the exacting requirements specified above, and one which is of such character that it may be readily installed b such men as are commonly available for t is class of work.

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

In the attached drawing, Fig. 1 is a view in elevation of a cable spreader and terminals for the conductors; Fig. 2 is a view partly in elevation and partly in section of the spreader; Fig. 3 is a side view of the same; Flg. 4 is a detail view of the valve which controls the flow of oil between the cable proper and the terminals; and Fig. 5 is a cross section of the cable.

5 lndicates the sheath which is common to and encloses three separately insulated conductors 6. Above the cable and connected thereto by a wiped soldered or other fluid tight joint 7 is a spreader box or casing 8. The casing is secured to a supporting structure by means of lugs 9 and suitable bolts. The casing enlarges from the bottom upward and has three openings through which extend the individual conductors as will appear more fully later on. Each conductor above the spreader is enclosed in its own sheath 10 made of lead or equivalent material which is slipped endwise over the same, and the lower end of each sheath is independently connected to the casing by a wiped soldered joint 11. The upper end of each conductor is enclosed by an insulator 12 which is supported upon flanged upper end of base member 15, the latter being carried by any suitable support 14, shown in dotted lines. Bolted to the flanged lower end of the base member is a wiping sleeve to which the upper end of sheath 10 is connected. The casing is provided with suitable fittings 16 by means of which the interior of the metal casing and insulator may be evacuated and filled with degasified oil. Mounted on top of each insulator is a metal cap 17 which makes a fluid tight joint therewith. The conductor terminates in the cap and from the latter connection is made by suitable conductors and insulating supports to the electrical apparatus receiving current from or delivering it to the cable. The specific construction of the insulators 12 and their supports is not material to the present invention, but however constructed they must be of such character as to prevent the entrance of air to the cable system and the escape of oil therefrom.

Referring now more especially to Figs. 2 and 3, the lower end of the casing is of such size as to closely surround or be enclosed by the lead sheath of the cable and the two are carefully united. The cable proper comprises three insulated conductors 6, each having a metallic electrostatic shield 19 and tubes 19 between the surfaces of the conductors and the wall of the sheath which form oil passages or conduits, 1 The lead sheath is first removed from the cable for a length great enough to form the terminal connections. The conductors diverge from the end of the sheath and pass outwardly through tubular sockets or extensions 20 of the casing. Around each conductor and outside of the casing is slipped a lead sheath 10 of smaller diameter than the main sheath 5, and in turn is Wipe jointed at its lower end to a socket 20, the upper end being similarly connected to the wiping sleeve which is bolted to the metallic member 15 of a terminal.

Assumin the cable to be filled with oil and a suita le valve controlled reservoir 21 for supplying additional oil attached to the end opposite from the terminals, the seal at the end of the cable is broken and sufficient sheath removed to expose the desired length of conductors. By opening the valve 22 on the reservoir a limited quantity of oil will be forced out at the cut end of the cable which prevents air and moisture from entering. The casing is then slipped into place and suitably jointed to the cable sheath, after which the other parts are assembled. \Vhile the easing is being ointed to the sheath the valve 22 of the reservoir had best be closed.

As previously indicated the cable itself is filled with oil and this must be prevented from escapin while the terminals are being mounted in p ace, and also air must be prevented from entering the cable. This is done by providing each individual conductor where it passes from the oil chamber 23 in the spreader casing 8 with what may be termed a semi-stop 'oint. structed as follows: he base of each socket 20 is provided with an internal shoulder 24 anda screw threaded portion 25. On the shoulder is seated a gasket 26, in this instance of laminated form and made of cork. Because of possible injur to the gaskets or the conductor coverings i they were threaded down over the conductors, which may be and usually are several feet long, the elements'of the asket are split, which permits of slipping them over the conductors at points near the casing. The joints in the various elements shou d be staggered in the assembly. Above and below the gaskets are metal washers which prevent injury to the gasket when put under compression. The gasket is held under sufiicient pressure by the nut 27 to cause the walls of its bore to engage the conductor covering and the periphery to engage the wall of the socket to prevent the passa e of oil at both points. The nut is seate by a suitable wrench inserted from above and prior to mounting the sheath 10 in'place. During this operation oil pres- These are con sure is maintained on the cable by the reservoir 21 or equivalent means.

Since the chamber 23 in the spreader casing is in direct communication with the end of the cable it follows'that it is filled with oil from the cable due to the action of the reservoir 21 on the far end. Since it is necessar to keep the sheaths 10' of the cable terminals as well as the insulators filled with oil durin use, and since the cable has to be filled witi de asified oil at all times, the source of supply for the cable is utilized to fill these parts as well. At the same time means must be provided whereby any one or all of the terminals may be 0 ened or removed at will for the purpose 0 repair without affecting the cable. For this purpose the semi-stop joints form an important part. It is also necessary for normal 0 rating conditions to by-pass the stop joints in order to get oil on the upper side thereof. This is accomplished by a very simple and inexpensive means in the form of by-pass connections. A wall of the casing is tapped andscrew threaded and into the opening thus formed is inserted a fitting 28 which contains a shut-off valve 29. From the upper side of the fitting extend three small by-pass pipes 30, one for each of the individual terminals. These pipes may be made of soft copper or other suitable material. The outer end of each pipe is connected by a suitable nipple 31 to a tubular extension or socket at a point above the stop joint. By means of the central passage 32 opening into chamber 23, the branch connections to the extensions and the valve 29, the supply of oil to the terminals may be shut off or admitted at will. If only one terminal requires attention its pipe 30 may be pinched b a suitable clamp to stop the flow of oil. ter a new ipe will be substituted for the one so pinc ed.

Assuming the parts to be pro rly assembled with the valve 29 adjuste to shut off oil to all of the terminals, the sheath 10 of each conductor and the interior of its insulator are evacuated b attaching a vacuum pump, first to one and then to the other terminals, for example, to one of the fittings 16. After this is properly done degasified oil is admitted from the cable and its reservoir by proper adjustment of the valves 29 and 22. In making the original installation a separate source of oil supply may be used if desired. After all the terminals have been properly evacuated and filled with degasified oil, the valve 29 is fully opened to supply oil from the chamber 23 to all of the lndlvidual terminals which is the normal operating condition, and the reservoir or reservoirs on the main cable will take care of expansion and contraction of the oil, and also of any temporary leakage, should such occur. Under normal conditions of operation all of the stop joints are rendered ineffective by reason of the by-pass connections 30 around them. The fitting 28 is also provided with a conduit 33 which 0 ens into the chamber therein on the side 0 the valve seat opposite the by-pass connections. The conduit is connected to a suitable reservoir 34 located at a suitable elevation to supply oil to the cable, or other means may be employed for obtaining the desired pressure to ensure the proper supply of oil to the cable. It will thus be seen that the spreader box or casing is utilized as a central source from which oil is supplied to the main cable and also to the individual conductors and their terminals. Such an arrangement tends to simplication of the system as a whole and reduces the number of joints which have to be made. To prevent leakage around the valve stem it is covered by a screw' threaded cap 34, under which is a gasket 35.

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

1. A terminal structure for a multiple conductor, fluid filled cable comprisinga chambered spreader casing attached to the cable sheath and having openings through which the conductors individually extend, an insulated terminal member attached to the outer end of each conductor, a sheath for each conductor connectedat one end to the casing and at the other end to its terminal member, a semi-stop joint for each conductor for shutting off the free flow of insulating fluid from the chamber of the spreader to its sheath and terminal member, and a by-pass around each of said joints whereby the flow of fluid into the terminal members may be controlled. a

2. A terminal structure for amultiple conductor, fluid filled cablecomprisin'g a chambered spreader casing attached to the cable sheath and provided with sockets containing openings through which the conductors individually extend, an insulated terminal member attached to the outer end of each conductor, a sheath for each conductor which conveys fluid from the casing to the terminal member, semi-stop joints located in the sockets to prevent the free flow of fluid from the chamber in the casing to the several terminal members, a byass for each stop joint connected at one en to said chamber and at the other end above the sto -'joint, and valve means for controlling the ow of fluid through the b -passes-.

3. A sprea er for fluid filled cable comprising a chamber casing provided with sockets containing openings through which the conductors individually extend, said chamber being in open communication with one end of the cable, a fluid stop joint located in each of the sockets and surrounding the conductor therein, a by-pass for each conductor that by-passes flu1d from one side of its stop-joint to the other, a fitting that is common to all of said by-passes and which opens into the chamber in the casing, a fluid supply conduit connected to the fitting, and a valve in the fitting to admit fluid from the supply conduit to said chamber and by-passes and to shut ofl the fluid supply at will.

at. A terminal structure for multiple conductor fluid filled cable comprisin a chambered spreader casing attached to t e sheath of the cable and through which the individual conductors extend, an insulated terminal for each conductor, a stop-joint for each conductor located within the casing, a bypass for each joint, a fitting mounted on the casing and to which one end of each bypass is connected, the opposite end thereof being connected to the casing the other side of a stop-joint, a valve mounted in the fitting which controls the passage of fluid from the chamber in the casing to the b -passes, a fluid supply reservoir, and a con u1t connecting the reservoir to the fittin to supply the terminals and the cable wit fluid under pres-

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