US2196026A - Fluid filled cable - Google Patents

Description

April c. A. PIERCY 2,196,0 6

FLUID FILLED CABLE Filed Aug. 6, 1936 Inventor:

Carl A Hero Attorney.

Patented Apr. 2, 1940 FLUID FILLED CABLE Carl A. Piercy, Ballston Lake, N. Y., assignor to General Electric Company, a corporation of New York Application August 6, 1936, Serial No. 94,621

6 Claims.

In the manufacture of fluid filled cable of the single conductor type, it is desirable in order to reduce the overall diameter of the cable to compact the strandsas fully as possible. As a result of this, the usual spaces between strands are practically non-existent with the result that radial movement of the fluid between the strands is largely or wholly prevented. It is also desirable in very large conductors to divide the total cross-sectional area into segments, all operating at the same potential, so as to reduce eddy current and other losses in the conductor itself. After the segments have been assembled in a socalled closing machine to form a cable, an insuld lating covering comprising many layers of paper or other fibrous insulation is tightly applied. In order to form a channel for the impregnating fluid, such as oil, an axially extending opening is provided. Because the segments are all operating at the same potential, they need not for that reason be insulated one from the other, and because the spaces which exist between strands where round wires are used are no longer present due to the compacting, the problem is.presented u of providing suitable means for conveying the. oil or other fluid contained in the channel or core to the body of pervious insulation surrounding the conductor without the application of an abnormally high pressure .on the fluid which would be 30 injurious to the sheath.

The object of my invention is the provision of an improved single conductor cable of the fluid filled type having channel means located between adjacent segments adequate to convey fluid from a the core or central channel into the surrounding insulation so that the latter will be fully impregnated under all operating conditions.

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

In the drawing which is illustrative of my in vention, Fig. 1 is a cross-section of a multi-segment single conductor cable; Fig. 2 is a partial section of a modified form of my invention; Fig. 3 is a detail view of a spacer located between adjacent segments; Fig. 4 is a further modification in which. special channel means are formed in the strands of the conductors; Fig. 5 is a detail 50 view of the channel means of Fig. 4, and Fig. 6

illustrates a modified form of the partitions illustrated in Fig. 2.

Referring to Fig. 1, 5 indicates segments of the same conductor of which six are shown. The uninsulated strands 8 of each segment are compacted to such an extent that as a practical matter, there are no open spaces between strands through which fluid could pass from the center channel I to the layers of permeable insulation 8 surrounding them. To reduce losses in the 5 cable due to so-called proximity eflect, the wires or strands are so arranged that each strand instead of occupying the same radial position throughout the cable is changed by a definite plan, flrst appearing as a bottom or inner strand m and later as an outer strand and then as an inner strand, etc. There is nothing new in this feature, it being old in the cable art. In the center of the assembly is a core 9 made of narrow metal stock wound in the form of a coiled extension spring with spaces between turns to permit oil to pass. This core is primarily of use in assembling the segments ina closing. machine to the end that each segment will occupy its proper radial position with respect to the axis. Under certain conditions, the use of this core as a guiding or centering means may be omitted.

Because the segments are operating at the same potential, they do not for that reason need to be insulated from each other but in order to attain the advantages of the strand relation previously referred to, the segments should be insulated from each other. Since the segments all carry current at the same voltage, the insulation between them 'need not be very thick. It is the 3 insulation 8 which insulates the conductors from ground. In order to carry fluid such as thin degasified oil from the center channel 1 to 'the surrounding body or belt of insulation and vice versa, thin bodies of permeable material ID are 35 located between segments. These bodies which are thin may be wrapped entirely around each segment or they may be located only between adjacent surfaces. In a radial direction, the

bodies should extend between the segments from o the center channel to any permeable covering over said segments. As illustrated in this figure.

the bodiesextend entirely around each segment and in each case the covering so applied is of the order of 14 mils in thickness. However, when 5 the segments are assembled in the closing machine, the pressure exerted thereby on the bodies or coverings will compress them to say 20 mils total between each two segments. A metal binding tape i2 arranged with rather widely spaced turns is desirable to prevent the segments from spreading or bird-caging when the cable is bent as in reeling and unreeling. Because it is im-- portant to prevent short circuiting of the segments andthereby nullify to an extent the advantages of segmentalconst-ruction, one or two layers of permeable material I 3, such as paper, are wound over the segments and under the binding tape. The outer corners of each segment are slightly rounded and in the approximately triangular spaces thus formed, there are .or may be laid soft cotton, paper or equivalent cord H for the purpose of making the assembly circular in form and at the same time preventing concentration of electrical stresses in said spaces. Surrounding the binding-tape is a body 8 of permeable insulation in the form of relatively narrow tapes or ribbons applied layer by layer in such manner that the joint between turns on one layer is covered by the tape of the next outer layer. Enclosing the body of insulation is a lead sheath N3 of ordinary construction. As a result of the construction described, the radial or partition portions of the bodies l0 serve to convey by capillary action oil from the center channel to the surrounding body of insulation 8 and maintain it in a fully impregnated condition.

In those cases where a more rapid or freer transfer of fluid such as thin degasified oil between the channel and the surrounding body 8 is desired, the construction of Fig. 2 may advantageously be employed. In this case, the segments are not initially provided with a covering of any sort but are left bare just as they come from the compacting rolls. To simplify the i1- lustration the individual strands of which the conductor is composed are not shown but in practice they will resemble those of Fig. 1. In order to transfer fluid between the center channel T and the body 8, non-conducting partitions or spacing strips I! are placed radially between adjacent faces of the segments and held in such positions by the sidewise pressure of the segments. These may be made from fibre or equivalent material and are inserted in the form of longitudinal strips as the segments pass through the closing machine. Each of the strips is provided with shallow grooves I8 in one or both of the side faces so that when the segments are assembled, the grooves form numerous passages or auxiliary channels for the transfer of 011, said auxiliary channels being fed in parallel from the main channel. As shown, the grooves are radially disposed but they may be arranged diagonally as shown in Fig. 6. However they are made, they should all receive oil in parallel from the central channel and convey it to and from the surrounding insulation 8. The lower edges of the strips should have access to the oil in the channel and the outer ends should terminate at some point near the layer or layers of paper under the binding tape. The said outer ends desirably terminate in the substantially triangular spaces formed by the rounded corners of the segments. The arrangement of the binding band, insulation 8 and sheath is the same as described in connection with Fig. 1. In this instance, instead of relying upon capillary action to convey the fluid between the central channel and the insulation, the pressure exerted on the fluid in the main or central channel suffices for the purpose.

In Figs. 4 and 5, a generally similar arrangement is provided but differing therefrom in that the strips or partitions I! are smooth on both sides and the radial grooves or auxiliary passages l9 are formed in the surfaces of the conductor segments on opposite sides of the strips. It is advantageous to make the partitions between segments as thin as possible so as to reduce the overall diameter of the cable. By making the grooves in the conductors instead of in the partitions, it follows that this advantage is attained. The use of thin partitions also reduces the losses in the conductor. The grooves I9 can readily be formed by the same dies or rolls which compact the strands by proper shaping of the rolls forming the sides of the segment.

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

1. A fluid filled cable comprising segmental bodies of densely compacted strands of bare wire without appreciable strand spaces, the bodies operating at the same potential and forming a single conductor of cylindrical form, a member located within and engaging the inner surfaces of the segments which acts as a centering means for the segments and with them defines an unrestricted central channel for fluid, a covering of dense permeable insulation for the segments, radial partitions of non-conducting material located between'the side faces of adjacent segments and held under compression by said segments, the partitions serving as segmental spacers and also having grooves serving as means for conveying fluid between the central channel and the insulation, and an impermeable sheath surrounding the insulation for confining the fluid.

2. A fluid filled cable comprising segmental bodies of densely compacted strands of bare wire without appreciable strand spaces arranged to form a single conductor of cylindrical form and defining a central channel for fluid, there being radial grooves formed in certain of the side faces of the segmental bodies forming parallel fluid passages communicating with the central chan nel, a dense body of permeable insulation surrounding the segments, non-conducting radial partitions having smooth side surfaces located between the side faces of each pair of segments, certain of said faces defining walls of the grooves in the segments, and an impermeable sheath surrounding the insulation to confine the fluid.

3. A fluid filled cable comprising segmental bodies of densely compacted strands of bare wire without appreciable strand spaces assembled to form a single conductor of cylindrical form and defining a free open channel filled with liquid insulation under positive pressure, athin metallic binding tape exerting inward pressure on the segmental bodiesfor firmly holding the segmental bodies and preventing them from separating, a body of non-conducting material located between the peripheral surfaces of the bare conductors and the tape of suflicient thickness to prevent short circuiting of the segments but not to insulate them from ground, a dense body of permeable insulation arranged in layers and surrounding the tape for insulating the segments from ground, partitions of non-conducting material between the adjacent faces of the segments held in firm contact therewith and occupying radial positions, the said partitions and one of each 1|) sulation for confining the fiuid.

5. A liquid filled cable comprising segmental bodies of stranded wires compacted to such an extent as to prevent free radial movement of liquid between the strands, the segmental bodies 15 operating at the same potential, a central open channel defined by the inner portions of the seg- ,mental bodies containing liquid insulation under positive pressure, a body of dense permeable insulation common to the segmental bodies and M surrounding them, radially disposed partitions located between adjacent faces of the segmental bodies and firmly held in their respective positions by the sidewise pressure exerted thereon by the bodies, each partition and one of the adjacent 25 side walls of the bodies defining free passages open at both ends and arranged to receive liquid in parallel at their inner ends from the channel and freely to convey it to and from the surrounding permeable insulation, and an impermeable 6. A liquid filled cable comprising bare segmental bodies, each composed of wires stranded to reduce losses due to proximity effects and as sembled to form a single conductor of cylindrical form, the segments operating at the same potential, a central opening channel containing liquid insulation under positive pressure, the wires being so densely compacted as practically to shut off the radial passage of liquid insulation between the open channel and the periphery ofthe assembled segmental bodies, a thin metallic binding tape exerting inward pressure on the segmental bodies for firmly holding them in their assembled positions, non-conducting material 10- cated between the binding tape and the bodies to prevent short circuiting thereof by the band, a dense body of permeable insulation arranged in" layers and surrounding the tape, radially dis-' posed partitions located between adjacent faces of the segmental bodies and held in their respective positions by the sidewise pressure exerted thereon by the bodies, each partition and one 80 sheath surrounding the insulation for confining the liquid. w

of the segmental bodies defining free passages open at both ends arranged to receive liquid in parallel from the channel and convey it to and from the surrounding permeable insulation, and an impermeable sheath surrounding the insulation for confining the liquid.

CARL A. PIERCY. 80

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