Abstract: A support structure for a coaxial transmission line includes a plurality of groups of dielectric balls compressibly mounted between the inner and outer conductors of the coaxial transmission line, the balls being "locked" into position via recesses located in the outer face of the inner conductor with holes centrally located in the balls and aligned parallel with the longitudinal axis of the transmission line sewing to compression relieve the balls and improve the VSWR of the transmission line, and with seventy-degree V-grooves being located on either side of the recesses in longitudinal alignment with the coaxial transmission line, for further improving the VSWR by adding inductance to compensate for the capacitance added by the presence of the balls.

Abstract: A system for HVDC transmission comprises a conductor, stressed by d.c. voltage, which is insulated from a surrounded grounded casing by pressurized SF.sub.6 gas and along part of its length by at least one solid insulator supporting the conductor in the casing and in contact with the gas. By designing the solid insulator as a core of solid insulating material and a coating, provided thereon, with a high surface resistance, it is possible considerably to reduce the dimensions of the casing. The coating consists of a resinous binder containing a powdered filler in the form of chromium oxide or iron oxide, or a mixture of these substances. The coating preferably has a surface resistance between 10.sup.12 and 10.sup.18 ohm/.quadrature. at an electric field strength of 1 kV/mm.

Abstract: The invention relates to a conductor supporting apparatus for gas insulated equipment in which a high voltage conductor which is arranged in a grounded tank is insulated and supported by an insulating spacer having attaching metal fittings at both end portios. In the apparatus of the invention, a cylindrical insulating barrier having a flange portion on the side of the free end so as to be substantially perpendicular to the surface of the insulating spacer is attached by use of the attaching metal fitting of the insulating spacer on at least the side of the grounded tank. The insulating spacer is surrounded by this insulating barrier through a space. By use of the insulating barrier, the approach of conductive foreign matters to the insulating spacer can be prevented and the high dielectric strength can be maintained.

Abstract: A stub-support arrangement for a coaxial transmission line wherein the line has inner and outer conductors and the stub is in the form f oppositely disposed stubs each having a length of 1/8 wavelength at the center operating frequency or less. One of the stubs is an open-circuit stub and the other is a short-circuit stub. In the case of the stubs being of 1/8 wavelength, the characteristic admittances of the stubs are equal and in the case of the stubs being less than 1/8 wavelength the characteristic admittance of the open-circuit stub becomes larger and that of the short-circuit stub becomes smaller as the physical length of the stub is reduced.

Abstract: A gas insulated electrical apparatus comprises: a metal pipe in which an insulation gas is sealed; a conductor supported inside of the metal pipe by an insulation supporting member; and an insulation layer provided on the inner surface of the metal pipe. Strong dielectric material is mixed in the insulation layer so that its specific inductive capacity becomes ten or more.

Abstract: A high-voltage line which includes a conductor supported in a metal encapsulation which is filled with insulating gas and which consists of pipe sections, the ends of which are welded together in a gas-tight manner at specially formed annular mating surfaces. A high-voltage conductor in the interior of the metal encapsulation is supported on partitioning insulators which divide the metal encapsulation into axially spaced cylindrical spaces. Between every two partitioning insulators one or more support insulators are arranged, each of which is located in a distinctly formed annular space. The body of the support insulator is comprised of insulating material having openings in it. The mating surfaces of the two pipe ends are separated by a V-shaped annular gap and are welded together by a welding seam which fills the annular gap. The welding seam has a root which extends annularly and which is electrically in contact with the metallic outer edge of the partitioning insulator or support insulator.

Abstract: The conduit system is comprised of a corrugated inner and a corrugated outer tube with a helical spacer in between, the spacer being comprised of intertwined, stranded and/or, braided ceramic fibers.

Abstract: Two corrugated metal tubes in a low temperature conduit system are spaced apart by a ceramic spacer made of braided ceramic threads, each thread being composed of stranded or twisted together ceramic filaments, the space between adjacent loops of this spacer is filled with super-insulation being comprised of multiple metal foils spaced apart by a ceramic webbing, mesh, plaits, sheets or the like.

Abstract: A disc-type insulator for enclosed high-voltage equipment includes a cast-in electrode which is segmented and which extends peripherally and concentrically with respect to the edge surface of the disc. The cast-in electrode is connected to contact electrodes by means of contact tongues, the contact electrodes bearing against a metal mounting ring. To avoid damage to the disc-type insulator, to the contact tongues, or to the cast-in electrode during shrinkage of the disc-type insulator, following its casting, or damage resulting from thermal stresses during operation, the cast-in electrode is divided into a plurality of electrode segments which follow one another in the peripheral direction. The contact tongues are formed of bent-over extensions of the electrode segments and are "S" shaped. The electrode segments are composed of aluminum sheet which may have a smooth surface. The contact electrodes are fastened to the mounting ring by means of bolts.

Abstract: A particle trap is provided for gas insulated transmission lines having a central high voltage conductor supported within an outer coaxial conductive sheath by a dielectric support member. A cavity between the inner conductor and outer sheath is filled with a dielectric insulating gas. A cone-like particle deflector, mounted to the inner conductor, deflects moving particles away from the support member, to radially outer portions of the cavity. A conductive shield is disposed adjacent the outer sheath to form a field-free region in radially outer portions of the cavity, between the shield and the sheath. Particles traveling along the cavity are deflected by the cone-like deflector into the field-free region where they are held immobile. In a vertical embodiment, particles enter the field-free region through an upper end of a gap formed between shield and sheath members. In a horizontal embodiment, the deflector cone has a base which is terminated radially internally of the shield.

Abstract: A disk, or circular-cone-shaped insulating spacer for gas insulated equipment wherein a portion of the insulating spacer, which is secured to a metal sheath, is greater in thickness than the other portion of the spacer. The insulating spacer is brought into contact with the metal sheath through portions of the metal sheath which are outward of arcuate portions of flanges formed on said metal sheath. The distance between opposed flange surfaces which are formed in said metal sheath may be larger in the outside portion of the metal sheath than that in the inside portion of the metal sheath. The insulating spacer is brought into contact with the metal sheath through the outside portion of the metal sheath.

Abstract: The central conductor of a gas-insulated flexible cable consists of separate concentric tubes which are alternately spirally corrugated and annularly corrugated so that the corrugations will not nest relative to one another and are axially movable relative to one another.

Abstract: A metal-clad electric installation for high tension use includes a metallic housing containing a conductor supported by an insulator and surrounded by an insulating gas. The metallic housing has adjacent sections which are joined by pairs of connected flanges. The insulator has an external border which is interposed between the flanges of two successive sections of the housing and is secured thereto by bolts passing through aligned openings in the flanges and external border, thereby partitioning the housing into tight compartments. In order to dismantle a section without affecting the sealed condition of the adjacent section, the bolts are replaced by screws which are screwed into small nut plates inserted into slots provided in the interface of the external border and the flanges.

Abstract: A gas insulated transmission line includes a hollow outer conductor having an inner conductor and a support framework disposed therein. A tensioned insulating member is utilized to support the inner conductor within the outer conductor and the support framework. The insulating member is made of flexible insulating filaments which are tensioned to a predetermined amount which is greater than the tension caused by suspending the weight of the inner conductor alone.

Abstract: A gas insulated transmission line having a novel insulator for supporting an inner conductor concentrically within an outer sheath. The insulator has a recess contiguous with the periphery of one of the outer and inner conductors. The recess is disposed to a depth equal to an optimum gap for the dielectric insulating fluid used for the high voltage insulation or alternately disposed to a large depth so as to reduce the field at the critical conductor/insulator interface.

Abstract: An electrical cable for very high voltage underground power transmission comprises two or more inner conductors (2) which are twisted together and are supported within the gas-filled void of a hollow extruded plastic cable sheath (4) by means of a plurality of spacers (3) which are positioned along the length of the cable, each spacer (3) being formed of solid dielectric material with a number of angularly spaced radial webs equal to the number of conductors in the cable and being engaged with the twisted conductors with the webs extending from the cable axis radially outwardly between the conductors into contact with the inner wall of the cable sheath (4) where the outermost ends of the webs engage with complementarily shaped portions (5) of the sheath (4) providing for reduction of the electrical stresses at the spacer ends.

Abstract: A funnel-shaped support insulator is mounted by its insulator outer edge in a recess of a grounded housing and has an orifice which is provided at a distance from the housing and in which a high-voltage conductor part is retained. To prevent, in this insulator, inadmissible field increases and glow discharges associated with these in the region of the outer edge of the insulator, the insulator has a wall thickness decreasing from the orifice to the outer edge of the insulator. A plurality of lobes engaging the housing are located at the outer edge of the insulator. An insulator of this type is to be used preferably in metal-encased high-voltage switch gear.

Abstract: A gas-insulated transmission line includes a corrugated outer conductor, an inner conductor disposed within and insulated from the outer conductor by means of support insulators and an insulating gas, and a non-binding transport device for supporting and permitting movement of the inner conductor/insulating support assembly axially along the corrugated outer conductor without radial displacement and for moving without binding along corrugations of any slope less than vertical. The transport device includes two movable contacts, such as skids or rollers, supported on a common pivot lever, the pivot lever being rotatably disposed about a pivot lever axis, which pivot lever axis is in turn disposed on the periphery of a support insulator or particle trap if one is used.

Abstract: A non-binding particle trap to outer sheath contact for use in gas insulated transmission lines having a corrugated outer conductor. The non-binding feature of the contact according to the teachings of the invention is accomplished by having a lever arm rotatably attached to a particle trap by a pivot support axis disposed parallel to the direction of travel of the inner conductor/insulator/particle trap assembly.

Abstract: A particle trap to outer elongated conductor or sheath contact for gas-insulated transmission lines. The particle trap to outer sheath contact of the invention is applicable to gas-insulated transmission lines having either corrugated or non-corrugated outer sheaths. The contact of the invention includes an electrical contact disposed on a lever arm which in turn is rotatably disposed on the particle trap and biased in a direction to maintain contact between the electrical contact and the outer sheath.

Abstract: A gas-insulated transmission line includes a corrugated outer conductor, an inner conductor disposed within and insulated from the outer conductor by means of support insulators and an insulating gas, and a transport device for supporting and permitting movement of the inner conductor/insulating support assembly axially along the corrugated outer conductor without radial displacement. The transport device includes two movable contacts, such as skids or rollers, supported on a common pivot lever, the pivot lever being rotatably disposed about a pivot lever axis, which pivot lever axis is in turn disposed on the periphery of a support insulator or particle trap if one is used. The movable contacts are separated axially a distance equal to the axial distance between the peaks and valleys of the corrugations of the outer conductor and separated radially a distance equal to the radial distance between the peaks and valleys of the corrugations of the outer conductor.

Abstract: Gas insulated electrical apparatus having first and second conductors separated by an insulating support within an insulating gas environment, and particle traps disposed along the surface of the high potential conductor for trapping and inactivating foreign particles which may be present within the insulating gas medium. Several embodiments of the invention were developed which are particularly suited for vertically aligned gas insulated transmission lines. The particle traps are grooves or cavities formed into the walls of the tubular inner conductor, without extending into the hollow portion of the conductor. In other embodiments, the traps are appendages or insert flanges extending from the inner conductor, with the insulator supports contacting the appendages instead of the inner conductor.

Abstract: A gas-insulated high voltage cable for submersion in water has an increased internal gas pressure in the interior of the outer cable housings which are to be at a depth greater than 100 feet. The wall thickness of the housings may be the same as that of housing sections which are at external ambient pressure or at an external pressure given by immersion in water at a depth of less than 100 feet. The increased pressure is applied to the housings through the central conductor which is continuous for the cable.

Abstract: A gas-insulated transmission line includes an outer enclosure, an inner conductor insulatably supported within the outer conductor, and an insulating gas providing electrical insulation of the inner conductor. The outer enclosure includes a cylindrical insulating pipe or sheath with a separate electrostatic shield disposed on the sheath. The pressure containing function is separated from the electrostatic shielding function, thereby minimizing the use of the more expensive electrostatic shielding material for the pressure containing function.

Abstract: A soft silicone rubber insert is compressed between the interior surface of an insulator support in a gas-insulated cable and the outer surface of a soft aluminum central conductor which is supported within the interior surface of an opening in the insulator. The flexible rubber insert prevents scratching of the surface of the aluminum conductor and the production of aluminum particles during relative movement between the insulator and the aluminum tube.

Abstract: A gas-insulated bus bar, wherein each end of a plurality of support arms for holding bus conductors substantially in the center of a case which faces the inner peripheral wall of the case is fitted with a metal member whose end spatially faces the inner peripheral wall of the case; an annular groove is formed in the end portion of the metal member; an annular sliding member prepared from an elastic electrically insulating synthetic resin capable of easily sliding over the inner peripheral wall of the case is inserted into the annular groove in a state to project from the end of the metal member to be pressed against the inner peripheral wall of the case; a radially extending hole open to the inner peripheral wall of the case is formed in said end of the metal member; a metal button is inserted into said hole in a state urged toward the inner peripheral wall of the case; and the support arms are elastically pressed against the inner peripheral wall of the case.

Abstract: A gas-insulated transmission line includes an outer enclosure, an inner conductor insulatably supported within the outer conductor, and an insulating gas providing electrical insulation of the inner conductor. The outer enclosure includes a cylindrical insulating pipe or sheath with a separate electrostatic shield disposed on the sheath. The pressure containing function is separated from the electrostatic shielding function, thereby minimizing the use of the more expensive electrostatic shielding material for the pressure containing function.

Abstract: A gas-insulated transmission line includes an outer enclosure, an inner conductor insulatably supported within the outer conductor, and an insulating gas providing electrical insulation of the inner conductor. The outer enclosure includes a cylindrical insulating pipe or sheath with a separate electrostatic shield disposed on the sheath. The pressure containing function is separated from the electrostatic shielding function, thereby minimizing the use of the more expensive electrostatic shielding material for the pressure containing function.

Abstract: This invention provides a novel high voltage gas insulated transmission line utilizing insulating supports spaced at intervals with snap-in means for supporting a continuous trapping apparatus and said trapping apparatus having perforations and cutouts to facilitate trapping of contaminating particles and system flexibility.

Abstract: A transmission line assembly including a mechanism for reducing vibrations and a method of making the same is provided which includes an outer tubular sheath having an inner surface forming an inner diameter, an inner tubular wall member firmly frictionally fixed to the inner surface of the outer tubular sheath, a transmission line disposed within the inner tubular wall for transmitting energy, a plurality of radially contracted tubular sections having axial lengths at regularly spaced axial intervals formed in the inner tubular wall member and contiguously surrounding the transmission line for protecting, centering and supporting the transmission line within the outer tubular sheath and a plurality of radially enlarged sections formed in the inner tubular wall member having axial lengths greater than the axial lengths of the radially contracted tubular sections and having outer diameters radially compressed by the outer tubular sheath.

Abstract: A gas-insulated transmission line includes an outer sheath, an inner conductor, an insulating gas electrically insulating the inner conductor from the outer sheath, and insulating supports insulatably supporting the inner conductor within the outer sheath. The inner conductor is provided with flexibility by the use of main conductor sections which are joined together through a conductor hub section and flexible flexing elements. Stress shields are provided to control the electric field at the locations of the conductor hub sections where the insulating supports are contacting the inner conductor.The flexing elements are formed by sandwiching together, by fusing, a pair of thin hollow discs which are fixedly secured to both the main conductor sections and the conductor hub section.

Abstract: A gas-insulated power transmission line includes an outer enclosure containing an inner conductor and insulating supports for insulatably supporting the inner conductor within the outer enclosure. An electrically insulating gas electrically insulates the inner conductor from the outer enclosure. The outer enclosure is comprised of two separate components; an outer sheath made of carbon steel, a grounded inner sheath disposed within the outer sheath and made of aluminum. The inner sheath, containing the inner conductor and the insulating supports, is assembled separately from the outer sheath and then the inner sheath assemblage is inserted within the outer sheath at the final field location.

Abstract: A gas insulated transmission line having radially flexible field control means for reducing the electric field along the periphery of the inner conductor at predetermined locations wherein the support insulators are located. The radially flexible field control means of the invention includes several structural variations of the inner conductor, wherein careful controlling of the length to depth of surface depressions produces regions of reduced electric field. Several embodiments of the invention dispose a flexible connector at the predetermined location along the inner conductor where the surface depressions that control the reduced electric field are located.

Abstract: A gas-insulated transmission line includes an outer sheath, an inner conductor, an insulating gas electrically insulating the inner conductor from the outer sheath, and insulating supports insulatably supporting the inner conductor within the outer sheath. The inner conductor is provided with flexibility by main conductor sections which are joined together through a conductor hub section and flexible flexing elements. Stress shields are provided to control the electric field at the locations of the conductor hub sections where the insulating supports are contacting the inner conductor. A plug and socket arrangement is utilized for joining adjacent sections of the inner conductor, and a protection tube is utilized inside the hollow plug to maintain proper alignment of the joint when the transmission line is bent.

Abstract: A gas-insulated transmission line includes an outer sheath, an inner conductor, an insulating gas electrically insulating the inner conductor from the outer sheath, and insulating supports insulatably supporting the inner conductor within the outer sheath. The inner conductor is provided with flexibility by use of main conductor sections which are joined together through a conductor hub section and flexible flexing elements. Stress shields are provided to control the electric field at the locations of the conductor hub sections where the insulating supports are contacting the inner conductor.The flexing elements and the stress shields may also be utilized in connection with a plug and socket arrangement for providing electrical connection between main conductor sections.

Abstract: A composite profile spacer for use in compressed gas insulated co-axial electrical cables. The cables have a central conductor and an outer envelope conductor and an insulating gas contained therebetween. The spacer comprises a composite profile shaped body formed of an electrically insulating material and extends radially between the central conductor and the envelope conductor to support the central conductor substantially concentric with the envelope conductor. The body has a disc section configuration in a first support section adjacent the central conductor, and a cone-section configuration in a remaining support section extending to the envelope conductor whereby to obtain substantially uniform field distribution and low field intensity on the opposed surfaces of the spacer. The contact angle between the opposed surfaces and the central conductor is approximately 75.degree. and the insulating material is an epoxy having a relative dielectric constant of 5 or higher.

Abstract: It has been discovered that the transient voltage which develops on the outer sheath of a coaxial cable under pulse voltage excitation is a result of the inequality between the self inductance of the sheath and the mutual inductance between the sheath and the center conductor. The self inductance of the sheath is always less than the mutual inductance by a small amount because of the finite thickness of the sheath. By manipulating the design of the outer sheath, an equality between the sheath self inductance and the sheath to inner conductor mutual inductance can be achieved which results in a cancellation of the transient voltage on the sheath when the cable is pulsed.

Abstract: A gas insulated transmission line includes an elongated outer sheath, a plurality of inner conductors disposed within and extending along the outer sheath, and an insulating gas which electrically insulates the inner conductors from the outer sheath. A support insulator insulatably supports the inner conductors within the outer sheath, with the support insulator comprising a main body portion including a plurality of legs extending to the outer sheath, and barrier portions which extend between the legs. The barrier portions have openings therein adjacent the main body portion through which the inner conductors extend.

Abstract: Electrical apparatus including an enclosure, an electrode disposed within the enclosure, and supports for insulatably supporting the electrode within the enclosure has a permanently sticky adhesive material which is disposed on the interior surface of the outer enclosure. A high-vapor-pressure sublimable material is disposed on the permanently sticky adhesive material, with the sublimable material capable of subliming away in the presence of a vacuum. The presence of the sublimable material enables the apparatus to be non-sticky during assembly and handling operations, while being rendered sticky upon commissioning of the apparatus.

Abstract: The invention relates to an installation for transmitting electrical power which includes a safety device for providing protection against the effects of electric arcs, said installation including a metal casing (5) filled with a dielectric gas under pressure and having a coaxial central conductor (1,2). In such an installation, where a conductor (1,2) and a casing (5) are held in position relative to each other by a transverse insulator (8), said safety device comprises a tubular electrode (9) situated close to the casing (5) and to the insulator (8) and upstream therefrom relative to the direction of power transmission. The tubular electrode is electrically connected to the casing (5) by conductors (12) which are disposed at a small number of points around its periphery. The invention applies to protecting high-tension electric installations contained in metal casings.

Abstract: A gas-insulated transmission line includes a cylindrical outer sheath, an inner conductor within the outer sheath, an insulating gas, and support insulators for insulatably supporting the inner conductor within the outer sheath. The support insulators have a pair of circumferentially spaced apart openings therein, and a wheel assembly is disposed within each of the support insulator openings. Each wheel assembly includes a rotatable wheel which extends outwardly of the support insulator opening and contacts the outer sheath. With such an arrangement, insertion or movement of the inner conductor within the outer sheath is done on wheels instead of with a sliding motion to thereby minimize the generation of conducting contamination particles.

Abstract: A gas-insulated transmission line includes an outer sheath, an inner conductor within the outer sheath, insulating supports supporting the inner conductor within the outer sheath, and an insulating gas electrically insulating the inner conductor from the outer sheath. An apertured particle trapping electrode is disposed within the outer sheath, and the electrode has a pair of dielectric members secured at each longitudinal end thereof, with the dielectric members extending outwardly from the apertured electrode.

Abstract: A gas insulated transmission line includes an outer sheath, an inner condor within the outer sheath, insulating supports supporting the inner conductor within the outer sheath, and an insulating gas electrically insulating the inner conductor from the outer sheath. An apertured particle trapping ring is disposed within the outer sheath, and the trapping ring has a pair of dielectric members secured at each longitudinal end thereof, with the dielectric members extending outwardly from the trapping ring along an arc. A support sheet having an adhesive coating thereon is secured to the trapping ring and disposed on the outer sheath within the low field region formed between the trapping ring and the outer sheath. A conditioning method used to condition the transmission line prior to activation in service comprises applying an AC voltage to the inner conductor in a plurality of voltage-time steps, with the voltage-time steps increasing in voltage magnitude while decreasing in time duration.

Abstract: A gas-insulated transmission line includes an outer sheath, an inner conductor, insulating supports and an insulating gas. A particle-trapping ring is secured to each insulating support, and it is comprised of a central portion and two tapered end portions. The ends of the particle trapping ring have a smaller diameter than the central portion of the ring, so as to enable the use of the particle trapping ring in a curved transmission line.

Abstract: A gas insulated transmission line includes an inner conductor disposed within an outer sheath, with an insulating gas providing electrical insulation and insulating supports holding the inner conductor within the outer sheath. A particle trapping ring is disposed within but spaced apart from the outer sheath, and a flexible insulating sheet is secured to the particle trapping ring. The insulating sheet has an adhesive coating disposed thereon facing the ring, and the insulating sheet is positioned on the interior surface of the outer sheath. An insulating leaf spring, preformed along the radius of curvature of the outer sheath, is secured to the ring and is positioned between the insulating sheet and the ring, with the leaf spring loading the insulating sheet against the outer sheath. A stiffener spring is also secured to the ring and is disposed intermediate the ring and the leaf spring.

Abstract: An electric busbar installation comprises at least one busbar comprising a rigid bare elongate conductor housed within and rigidly secured to and spaced from a rigid tube, arranged with its axis substantially vertical by longitudinally spaced rigid insulators, the space between the busbar and the tube containing an electrically insulating fluid which is in direct contact with the bare conductor of the busbar, at least one duct which is in thermal association with the bare conductor throughout the length of the busbar and which forms part of a closed circulatory system for evaporable refrigerant; and interconnected in the circulatory system, condensing means for receiving evaporated refrigerant from, and for delivering liquid refrigerant to, the duct.

Abstract: A multi-core power cable (1) in which the conductors comprise a central conductor (2) and two or more tubular conductors (4, 6) coaxial with the central conductor (2), at least the tubular conductors forming the cores. The conductors (2, 4, 6) are isolated from one another by insulating layers (3, 5, 7). A sheath (8) and armoring (9, 10) may also be provided.

Abstract: A gas-insulated transmission line is formed of a plurality of outer sheath sections joined together lengthwise, with a conductor disposed therein. A two leg insulating spacer supports the conductor within the sheath sections, and axially extending grooves on said sheath sections receive the ends of the insulating spacer.

Abstract: A partition insulator is disclosed having a seating in at least one insulator holder. A specific predetermined rupture behavior is provided for the partition insulator as a result of outside forces acting on the insulator at a specific quantity and direction such as, for example, gas pressure. A corresponding support (or gripping or solid gripping) of the partition insulator is provided whereby at least on the insulator, on the insulator holder or between these two parts, bearing points (or bearings) are arranged in a suitably distributed manner. The gripping of the partition insulator is accomplished herewith by the insulator holder alone or by both the insulator holder and a fastening ring which holds the partition insulator together by both threaded bolts and nuts. The partition insulator is preferably used as a pressure relief device in pressurized gas-insulated high-voltage switchgears having a metal switchgear casing.

Abstract: A gas-insulated transmission line includes a cylindrical outer sheath, an inner conductor within the outer sheath, an insulating gas, and support insulators for insulatably supporting the inner conductor within the outer sheath. The support insulators have a pair of circumferentially spaced apart openings therein, and a wheel assembly is disposed within each of the support insulator openings. Each wheel assembly includes a rotatable wheel which extends outwardly of the support insulator opening and contacts the outer sheath. With such an arrangement, insertion or movement of the inner conductor within the outer sheath is done on wheels instead of with a sliding motion to thereby minimize the generation of conducting contamination particles.