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Publication numberUS3845233 A
Publication typeGrant
Publication dateOct 29, 1974
Filing dateFeb 12, 1973
Priority dateFeb 12, 1973
Publication numberUS 3845233 A, US 3845233A, US-A-3845233, US3845233 A, US3845233A
InventorsBurton E
Original AssigneeDielectrics Int Ltd
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Pressurized insulant of solid and fluid for a conductor
US 3845233 A
Abstract
Electrical equipment has a conductive member surrounded by an insulant. The insulant comprises finely divided particles of a solid insulating material in an insulating fluid, which fluid acts as a discharge suppressant and is effectively in the form of a thin film. Means are provided for maintaining the fluid above atmospheric pressure and for maintaining the interparticle pressure.
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Description  (OCR text may contain errors)

1451 Oct. 29, 1974 United States Patent 1.191

Burton PRESSURIZED INSULANT OF SOLID AND L. R R R X S l 5 5 F 322 l 4 4 4 7 7771 7 l l l l t n n 7 H n H 6 cmnmm H 1 C h 85 d k n n w 0 0 h h a M .IOOM VJ T 6 4 5 l 2 5 6 6 7 7 9 9 9 9 9 l l l l l 9 0 oo 9 6 l U 7 7 6 9 3 0 0 7 ,52 1 4 l 9 0 6 5 0 0 7 7 1 3 2 3 3 3 3 FLUID FOR A CONDUCTOR [75] Inventor: Edward Arthur Burton, Guildford,

England [73] Assignee: Dielectrics International Limited,

174/25 G 174/25 G 174/25 R London, England [22] Filed: Feb. 12, 1973 [2]] Appl. No.: 331,775

SPRING MEMBER D E N m S N E T lNSULANT (FLUID+ SOLID) STRANDED CONDUCTOR I 11 17 1 13 INSULANT (FLUID+$0LID) 11 Claims, 3 Drawing Figures 2 4 1p-31t1f FLUID sulating fluid, which fluid acts as a discharge suppressant and is effectively in the form of a thin film. Means are provided for maintaining the fluid above atmospheric pressure and for maintaining the interparticle pressure.

Zb pazssuinzen ILE E MEMBRANE 2 8/FILTER IMPERMEABLE IMFERMEA MEMBRAN STRANDED CONDUCTOR EXPANSION DEVICE IMPERMEABLE MEMBRANE Bennett................................. Vogel.......... Atkins0n...............................

References Cited UNITED STATES PATENTS IN SULANT SPRING MEMBER PRESSURIZED INSULANT OF SOLID AND FLUID FOR A CONDUCTOR BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION According to this invention there is provided electrical equipment comprising a conductive member surrounded by an insulant. The insulant comprises finely divided particles of a solid insulating material in an insulating fluid, which fluid acts as a discharge suppressant and is effectively in the form of a thin film. Means are provided for maintaining the fluid above atmospheric pressure and for maintaining the interparticle pressure.

The solid insulating material may be quartz, fused silica or mica for applications requiring a low permittivity insulant or glass or porcelain for applications permitting a higher permittivity insulant.

The fluid may be either liquid or gaseous and suitable fluids are, for example, low viscosity mineral oil, fluorocarbon oil, and silicone oil. Suitable gases are, for example, nitrogen and sulphur hexafluoride.

The electrical equipment may have at least two conductive members spaced apart from each other, the space between the conductive members being filled by the insulant.

The electrical equipment may, for example, be a cable, a supertension bushing, a straight joint, a stop joint, a sealing end, a metal clad supertension busbar, or a super-tension current transformer.

The provision of means for maintaining the fluid above atmospheric pressure and for maintaining interparticle pressure is important if the highest electrical strengths are to be obtained.

A cable in accordance with this invention may comprise a stranded hollow conductor intended to be filled with the fluid, which acts as a discharge suppressant, above atmospheric pressure, a permeable membrane which surrounds the conductor, and an impermeable membrane which surrounds the permeable membrane, the space between the permeable and impermeable membranes containing particles of the solid insulating material and being intended to receive the fluid, which acts as a discharge suppressant, through the permeable membrane, the means for maintaining the fluid above atmospheric pressure and for maintaining the interparticle pressure surrounding the impermeable membrane.

Suitably the means for maintaining the fluid above atmospheric pressure and for maintaining interparticle pressure comprises a further impermeable membrane which surrounds the first mentioned impermeable membrane, the space between the impermeable membranes being intended to be filled with fluid under pressure.

Alternatively the means for maintaining the fluid above atmospheric pressure and for maintaining interparticle pressure comprises metal tape under tension wound around the impermeable membrane.

Each particle, is of course, in contact with ticles.

A bushing in accordance with this invention may comprise a conductor surrounded by a casing, and a corona shield of sheet material which surrounds the central part of the conductor and is secured to the casing so as to define a space which is filled with the fluid, which acts as a discharge suppressant, above atmospheric pressure, the remainder of the space within the casing being filled with the said insulant, there being formed a passage permeable to the said fluid but not to the particles of insulating material between the first mentioned space and the remainder of the space within the casing.

DESCRIPTION OF THE DRAWINGS Embodiments of this invention will now be described, by way of example only, with reference to the accompanying drawings of which:

FIG. I is a sectional view of a first supertension cable in accordance with this invention;

FIG. 2 is a sectional view of a second supertension cable in accordance with this invention; and

FIG. 3 is a longitudinal sectional view of a supertension bushing in accordance with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 the cable shown therein has a stranded conductor 1 which is hollow, the duct 2 formed within it being filled with mineral oil under pressure. It will be appreciated that oil from the duct 2 can pass through the stranded conductor 1. Suitable conducting or semiconducting filter paper, e.g. carbon paper tape, is wound onto the conductor 1 to form a layer 3 which acts as a membrane permitting passage therethrough of mineral oil. A concentric impermeable membrane 4 surrounds the layer 3 of carbon paper tape, the space in between the membrane 4 and the layer 3 being filled with an insulant 5 which comprises particles of a solid insulating material in mineral oil. The membrane 4 is surrounded by a further impermeable membrane 6 and the space between the membranes 4 and 6 is filled by a fluid 7 under pressure.

As the membrane 3 is permeable, the mineral oil in the duct 2 exerts a pressure on the insulant 5, say the pressure P,. The pressure of the fluid 7 in the space formed between the membranes 4 and 6 also acts on the insulant 5 at a pressure of, say, P so that the net pressure acting on the insulator 5 is P P The cable may be manufactured by extruding a suitably wetted powdered solid insulating material within the space between the layer 3 and the membrane 4 and mineral oil is then supplied under pressure to the duct 2 and passes through the layer 3 into the powdered insulating material to form the insulant 5.

The cable shown in FIG. 2 is similar to that shown in FIG. 1 and only the differences will be explained. In this cable the impermeable membrane 6 and the fluid under pressure in the space or duct 7 is omitted and instead metal tape under tension is helically wound around the membrane 4 as indicated at 8. This layer of metal tape 8 exerts an inward radial force on the impermeable membrane 4 and has the same effect as the fluid 7 under pressure P in the cable shown in FIG. 1.

other par- The supertension bushing shown in FIG. 3 has a central metal conductor which is at a high potential, the conductor 10 being surrounded by a hollow cylinder 11 of insulating material. An end plate 12 is provided at each end of the cylinder 11 and is preferably of an insulating material. At the inner end and outer edges of the end plates 12, seals 13 are provided which engage the central conductor 10 and the cylinder 11. Each end of the conductor 10 is threaded and, at each end, a nut 14 is used to hold a spring member 15 against the end plate 12. On the inner side of each of the end plates 12, a corona shield 16 surrounds the central conductor 10 and rests against the end plate 12. The corona shield 16 at each end of the bushing is connected to the central conductor 10 by a lead 17. An earthed corona shield 18 surrounds the central part of the conductor 10 and is in the form of a hollow cylinder of sheet metal having a narrow central portion 19 at each end of which there is an outwardly flared portion 20. At each end of the outwardly flared portion 20 there is provided a further cylindrical portion 21, the outer ends of the cylindrical portions 21 being bent back on themselves as indicated at 22. The ends of the portions 22 are joined to the hollow cylinder 11 by an impermeable supports 24. The annular space 25 enclosed by the corona shield 18 and the annular supports 24 is filled with oil under pressure and contains oil expansion elements 26. The space 27 between the central conductor 10 and the hollow cylinder 11 other than the space 25 is filled with an insulant consisting of particles of a solid insulating material and oil. A filter 28 extends through one of the supports 24 and is permeable to oil but not to the particles of the solid insulating material. Consequently the pressure of the oil in the space 25 is applied to the insulator in the space 27 and it will be seen that the insulant in the space 27 is present between the corona shield 18, and the central conductor 10. The central conductor 10 is at the high tension whereas the corona shield is earthed and the insulant has been found to operate satisfactorily.

ln all three embodiments, the insulant consists of particles of an insulating material in a fluid discharge suppressant and it has been foundthat this operates satisfactorily. It is believed that the reason for the satisfactory operation of the insulant results from the fact that the fluid is effectively in the form of a thin film and when a fluid insulant is in the form ofa thin film its specific electrical strength is increased.

Suitable fluids are, for example, low viscosity mineral oil, fluorocarbon oil, silicone oil, nitrogen and sulphur hexafluoride. Suitable solid insulating materials are, for example, quartz, silica, mica, glass and porcelain which are inorganic materials and polythene, polypropylene, P.T.F.E., P.V.C. and hydrocarbons (e.g. sugar) which are organic materials. The particle size of the solid insulating material, its compaction and porosity, affect its characteristics.

Suitable materials for use as impermeable membranes are, by way of example, lead, aluminum, copper, stainless steel, polyethylene, etc.

The purpose of maintaining interparticle pressure is to inhibit particle movement and to prevent sedimentation so as to ensure thin film condition in the fluid insulant, i.e. the fluid discharge suppressant.

The particles may be of any shape.

I claim:

1. Electrical equipment comprising:

a conductive member; an insulant surrounding said conductive member; said insulant comprising finely divided particles of a solid insulating material in an insulating fluid, said insulating fluid acting as a discharge suppressant; first pressure applying means for applying pressure to said insulating fluid to maintain said insulating fluid at above atmospheric pressure, said first pressure applying means including a fluid passage means for placing the insulating fluid in fluid flow communication with a source of pressurized fluid, said fluid passage means being permeable to said insulating fluid and impermeable to said solid insulating material; and second pressure applying means for applying pressure to said solid insulating material to maintain interparticle pressure to inhibit particle movement and prevent particle sedimentation and thereby maintain the insulating fluid as a thin film.

2. The electrical equipment as claimed in claim 1 and further comprising an impermeable membrane surrounding the insulant, the insulant supporting the conductive member in spaced relationship with respect to said surrounding impermeable membrane member.

3. The electrical equipment claimed in claim 1 and further comprising an impermeable membrane surrounding the insulant, the second pressure applying means being in contact with said surrounding impermeable membrane and applying pressure to the particles through the impermeable membrane.

4. Electrical equipment as claimed in claim 1 wherein said conductive member is a stranded hollow conductor, said hollow conductor including pressurized insulating fluid, said fluid passage means comprising a fluid permeable membrane surrounding said conductor, and further comprising a first impermeable membrane which surrounds the insulant.

5. Electrical equipment as claimed in claim 4 wherein the second pressure applying means comprises a second impermeable membrane which surrounds and is spaced from the first impermeable membrane, and fluid under pressure in the space between the first and second impermeable membranes.

6. Electrical equipment as claimed in claim 4 wherein the second pressure applying means comprises metal tape under tension wound around the first impermeable membrane.

7. Electrical equipment as claimed in claim 1 in the form of a bushing and further comprising a casing surrounding the conductive member and spaced therefrom, a corona shield of sheet material within the easing which surrounds the central part of the conductive member and is spaced therefrom, said corona shield being secured to the casing and dividing said casing into a first space defined by the corona shield and casing and a remaining space, said remaining space containing said insulant, said first pressure applying means comprising insulating fluid under pressure in said first space and said fluid passage means which is permeable to said insulating fluid and impermeable to said solid insulating material connecting said first space and remammg space.

8. Electrical equipment as claimed in claim 7 wherein said second pressure applying means is in contact with said casing and applies pressure to the particles through said casing.

9. Electrical equipment as claimed in claim 1 wherein the solid insulating material is selected from the group gen and sulphur hexafluoride.

11. Electrical equipment as claimed in claim 1 having at least two conductive members spaced apart from each other, the space between the conductive members being filled by the insulant.

Patent Citations
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Referenced by
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US4132084 *Oct 29, 1976Jan 2, 1979Francisco Arnold Richard DSubmarine conductor for the deep sea transmission of high voltage electrical power
US4850672 *Feb 19, 1988Jul 25, 1989Siecor CorporationStrain compensated fiber optic cable
US5221709 *Oct 8, 1991Jun 22, 1993Associated Electrical Industries LimitedSealing composition and a mineral insulated electric cable termination employing such composition
US7494355Feb 20, 2007Feb 24, 2009Cooper Technologies CompanyThermoplastic interface and shield assembly for separable insulated connector system
US7568927Apr 23, 2007Aug 4, 2009Cooper Technologies CompanySeparable insulated connector system
US7572133Mar 20, 2007Aug 11, 2009Cooper Technologies CompanySeparable loadbreak connector and system
US7578682Feb 25, 2008Aug 25, 2009Cooper Technologies CompanyDual interface separable insulated connector with overmolded faraday cage
US7632120Mar 10, 2008Dec 15, 2009Cooper Technologies CompanySeparable loadbreak connector and system with shock absorbent fault closure stop
US7633741Apr 23, 2007Dec 15, 2009Cooper Technologies CompanySwitchgear bus support system and method
US7661979Jun 1, 2007Feb 16, 2010Cooper Technologies CompanyJacket sleeve with grippable tabs for a cable connector
US7666012Mar 20, 2007Feb 23, 2010Cooper Technologies CompanySeparable loadbreak connector for making or breaking an energized connection in a power distribution network
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US7695291Oct 31, 2007Apr 13, 2010Cooper Technologies CompanyFully insulated fuse test and ground device
US7811113Mar 12, 2008Oct 12, 2010Cooper Technologies CompanyElectrical connector with fault closure lockout
US7854620Dec 22, 2008Dec 21, 2010Cooper Technologies CompanyShield housing for a separable connector
US7862354Oct 2, 2009Jan 4, 2011Cooper Technologies CompanySeparable loadbreak connector and system for reducing damage due to fault closure
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US7901227Nov 20, 2008Mar 8, 2011Cooper Technologies CompanySeparable electrical connector with reduced risk of flashover
US7905735Feb 25, 2008Mar 15, 2011Cooper Technologies CompanyPush-then-pull operation of a separable connector system
US7909635Dec 22, 2009Mar 22, 2011Cooper Technologies CompanyJacket sleeve with grippable tabs for a cable connector
US7950939Feb 22, 2007May 31, 2011Cooper Technologies CompanyMedium voltage separable insulated energized break connector
US7950940Feb 25, 2008May 31, 2011Cooper Technologies CompanySeparable connector with reduced surface contact
US7958631Apr 11, 2008Jun 14, 2011Cooper Technologies CompanyMethod of using an extender for a separable insulated connector
US8038457Dec 7, 2010Oct 18, 2011Cooper Technologies CompanySeparable electrical connector with reduced risk of flashover
US8056226Feb 25, 2008Nov 15, 2011Cooper Technologies CompanyMethod of manufacturing a dual interface separable insulated connector with overmolded faraday cage
US8109776Feb 27, 2008Feb 7, 2012Cooper Technologies CompanyTwo-material separable insulated connector
US8152547Oct 3, 2008Apr 10, 2012Cooper Technologies CompanyTwo-material separable insulated connector band
US8749951Mar 26, 2010Jun 10, 2014Lawrence Livermore National Security, LlcTwo-phase mixed media dielectric with macro dielectric beads for enhancing resistivity and breakdown strength
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Classifications
U.S. Classification174/24, 174/25.00G, 174/31.00R, 174/25.00R, 174/17.0SF, 174/142
International ClassificationH01F38/28, H02G15/24, H02G15/00, H01F27/32, H01B17/26, H01B13/30, H02G15/25, H01B13/06, H01B7/02
Cooperative ClassificationH01B13/06, H01F38/28, H01F27/321, H01B17/26, H01B7/02, H02G15/25, H01B13/30, H02G15/24
European ClassificationH02G15/24, H01B7/02, H01F38/28, H02G15/25, H01B17/26, H01F27/32A, H01B13/30, H01B13/06