US3783181A - Electrical bushing having a stress relieving shield and method of constructing same - Google Patents

Electrical bushing having a stress relieving shield and method of constructing same Download PDF

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Publication number
US3783181A
US3783181A US00302329A US3783181DA US3783181A US 3783181 A US3783181 A US 3783181A US 00302329 A US00302329 A US 00302329A US 3783181D A US3783181D A US 3783181DA US 3783181 A US3783181 A US 3783181A
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US
United States
Prior art keywords
epoxy
shield
bushing
opening
mold
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00302329A
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English (en)
Inventor
P Martincic
J Quirk
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ABB Inc USA
Original Assignee
Westinghouse Electric Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Westinghouse Electric Corp filed Critical Westinghouse Electric Corp
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Publication of US3783181A publication Critical patent/US3783181A/en
Assigned to ABB POWER T&D COMPANY, INC., A DE CORP. reassignment ABB POWER T&D COMPANY, INC., A DE CORP. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: WESTINGHOUSE ELECTRIC CORPORATION, A CORP. OF PA.
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Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B17/00—Insulators or insulating bodies characterised by their form
    • H01B17/26—Lead-in insulators; Lead-through insulators
    • H01B17/28—Capacitor type
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S439/00—Electrical connectors
    • Y10S439/921—Transformer bushing type or high voltage underground connector
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49002—Electrical device making
    • Y10T29/49227—Insulator making

Definitions

  • ABSTRACT PP 302,329 An electrical bushing having a corona shield and -methods of constructing such a bushing.
  • HOlb 15/00 layer Such as a layer 0f aluminum (filmed a [58] Field of Search 174/18, 31 R, 73 R, insulating layer, Such as a film P [74/73 SC 140 R 140 C 142, 143, 152 R polyethylene terephthalate.
  • the shield is wrapped 153 R; 29/ 3 I. 339/275 c 27 C 277 C, around a mold plug and then epoxy 18 disposed around 278 C the plug. After the epoxy has cured, the mold plug is withdrawn to leave the shield attached to the wall of [56] References Cited the molded opening.
  • a coating of conductive material is UNITED STATES PATENTS sprayed onto a mold plug which is placed into a mold. 2,870,524 1/1959 Klnncar 264/255 X
  • the mold plug is removed after the epoxy injected gz 'x zrg gi 22 32 into the mold has cured and the conductive material is 3:320:341 5/1967- Mackie .I.IIII,,....IIIIIII't4/255 x t fii 133115; the inside the Pening Provided FOREIGN PATENTS OR APPLICATIONS 65,960 3/1969 Germany 174/142 7 Claims, 9 Drawing Figures IE. m mn SHIELD POLYETHYLENE TEREPHTHALATE PATENTEU JAN 1 I974 SHEET 1 BF 2 FIG. 2B
  • This invention relates, in general, to electrical bushing assemblies and, more specifically, to epoxy bushing insulators having stress relieving shields and methods of constructing such insulators.
  • Electrical bushings of the draw-lead type include an insulator member with a longitudinal opening extending therethrough. The purpose of the opening is to permit the placement of a conductor lead or stud within the insulator to conduct current through the bushing.
  • the opening is provided by a hollow metal tube which also provides a mandrel on which the paper is wound.
  • the opening is provided by a suitable hollow metal tube which is encapsulated by the material comprising the bushing insulator.
  • the metal tubes are usually constructed of copper or aluminum and have sufficient rigidity to support the paper wound thereon in paper wound bushings or to maintain an opening during the casting process in epoxy bushings.
  • epoxy bushings small corona generating voids may exist between the metal tube and the epoxy material due to gas entrapment or irregularities on the surface of the metal tube.
  • a corona shield, or electrical stress relieving shield is cast into the epoxy around the metal conductor tube to eliminate the electrical discharges between the metal conductor tube and the epoxy. lt is desirable, and it is an object of this invention, to eliminate the need for the metal support tube in epoxy bushings. It is also desirable, and it is a further object of this invention, to eliminate the need for a separate shield embedded in the epoxy and to provide a bushing which is substantially corona free and unaffected by thermal expansion characteristics.
  • a shield is wrapped around a mold plug and epoxy material is cast-therearound.
  • the mold plug is withdrawn from the epoxy after the epoxy has cured, thus leaving an opening in the cast epoxy bushing insulator which is lined with the shield.
  • the shield includes a layer of film, a layer of conductive material which is vacuum deposited on the film, and a layer of adhesive on the conductive material.
  • the adhesive side of the shield is positioned adjacent to the epoxy.
  • the shield is connected to a conductor stud by a shield lead soldered to a fastener which is attached to the conductive material of the shield.
  • a conductive material is sprayed onto a mold plug which is cast into the epoxy insulator.
  • the mold plug is removed, thereby leaving a conductive material on the wall of the opening in the epoxy insulator formed by the mold plug.
  • a metal support tube is not required in bushings which are constructed as taught by this invention.
  • the opening is formed by the mold plug.
  • the electrical stress relief is provided by the conductive material. Due to the excellent adhesion of the epoxy to the shield, corona discharges are substantially reduced. Since the shield is relatively thin, the thermal expansion characteristics of the bushing are improved.
  • FIG. 1 is an elevational view, partly in section, of an electrical bushing having a corona shield attached to an opening therethrough;
  • FIG. 2A is a view of the bushing insulator and molding member
  • FIG. 2B is an enlarged view of a corona shield
  • FIG. 3 is a view of a mold plug with a corona shield partially wrapped therearound;
  • FIG. 4 is a view of a mold plug with a coating of conductive material partially sprayed thereon;
  • FIG. 5 is a view of a corona shield with a portion thereof enlarged for clarity.
  • FIGS. 6, '7 and 8 are block diagrams illustrating steps in the construction of the electrical bushings of this invention.
  • An electrical bushing assembly constructed according to this invention.
  • An insulator 10 is constructed of an epoxy material and includes the longitudinal opening 12 and the mounting flange 14.
  • a conductor stud 16 is located within the opening 12 and is secured to the end of the insulator by nuts 18 and 20 with the aid of the caps 22 and 24. It is within the contemplation of this invention that the conductor stud 16 may be replaced by a suitably flexible conductor lead since the main function of the conductor stud 16 is to carry current.
  • the shield 26 is extremely smooth and contains substantially no irregularities, thus the epoxy material of the insulator adheres uniformly to the shield 26 and corona producing voids are virtually nonexistent.
  • FIG. 2A illustrates a mold arrangement which may be used in constructing the bushing shown in FIG. 1.
  • the shield includes a layer of highly polymeric polyethylene terephthalate film 30 which is sold under the trademark of Mylar, a layer of electrically conductive material 32, such as aluminum, and a suitable epoxy adhesive 34, such as a bisphenol A type.
  • the shield 26 is constructed by vacuum depositing a thin layer of the conductive material 32 on the substrate film 30 and coating the conductive material 32 with the adhesive 34.
  • the shield is approximately 0.0015 mils thick and does not contain any significant irregularities.
  • the film 30 protects the conducting material 32 from being scuffed when the stud 16, or a lead, is drawn through the opening 12.
  • the adhesive 34 tenaciously attaches the epoxy insulator to the smooth conducting material 32 without producing any voids therebetween as the epoxy adhesive 34 cures during 4 the curing of the epoxy insulator 10.
  • the shield 26 is positioned around a mold plug 36.
  • the mold plug illustrated in FIG. 2A includes a metal shaft 38 with a tube 4t) disosed thereon for allowing easy removal of the mold plug 36.
  • the tube 40 may be constructed of polytetrafluoroethylene which is sold under the trademark of Teflon. Other arrangements for the mold plug 36 may be used, such as a solid Teflon mold plug.
  • a mold 42 is positioned around the mold plug 36 and is formed 'to properly shape the outside surface of the insulator l0.
  • the epoxy material comprising the insulator 10 is injected into the region located between the mold 42 and the mold plug 36.
  • the heat and pressures existing during the casting operation are sufficient to provide a voidless bond between the epoxy and the adhesive 34.
  • the mold plug 36 is withdrawn from the epoxy leaving the conductive material 32 in the opening 12 to provide a corona shield 26.
  • FIG. 3 The operation of wrapping the shield 26 around the mold plug 36 is shown in FIG. 3.
  • the shield 26 is folded or wrapped around the mold plug 36 with a sufficient overlapping of the shield 26 to prevent any gaps therein.
  • FIG. 3 the upper portion of the shield 26 is shown in a partially unwrapped position to illustrate the overlapping of the shield 26.
  • Other wrapping arrangements such as spiral wrapping, may be used within the contemplation of this invention.
  • FIG. 7 is a block diagram which illustrates the major steps involved in constructing a bushing according to this embodiment.
  • FIG. 4 shows a conductive material 33 being sprayed onto the mold plug 36.
  • the coating of conductive material 33 can be applied by flame or plasma spraying of a suitable material, such as tin or aluminum, or by spraying a conductive ink material onto the mold plug 36.
  • the rough external surface of the coating of conductive material 33 aids adhesion of the conductive material 33 to the epoxy when the mold plug is withdrawn.
  • FIG. 8 is a block diagram illustrating the major steps performed in constructing a bushing according to this embodiment.
  • FIG. 5 shows a portion of the shield 26 with the shield lead 28 attached thereto.
  • the lead 28 is soldered to a snap fastener 46 which is attached to the conductive material 32.
  • the enlarged portion of FIG. 5 illustrates the different layrs comprising the shield 26.
  • the process of attaching the lead 28 to the conductive material 32 involves several steps.
  • the adhesive 34 is removed from the conductive material 32 by a proper solvent, such as alcohol.
  • the lead 28 is soldered to one portion of the fastener 46.
  • a hole is punched in the conductive material 32 and in the film 30.
  • a portion of the fastener 46 is inserted through the hole and engaged with another part of the fastener 46 located on the other side of the shield.
  • FIG. 6 is a block diagram illustrating the major steps performed in connecting the lead 28 to the shield 26.
  • the embodiments of this invention provide several advantages over prior art bushings and bushing construction methods. Since the only purpose of a metal support tube was to maintain an opening through the epoxy insulator, a bushing constructed according to this invention does not require the extra cost of a metal support tube. Additionally, by elimination of the support tube, the thermal expansion characteristics of tbe bushings are improved. Corona discharges herebefore existing in voids between the support tube and the epoxy are greatly reduced due to the tight adherence of the epoxy to the corona shield and the smooth surface of the layer of conductive material. Providing the corona shield is accomplished in a manner which requires a minimum number of steps.
  • a method of constructing an epoxy bushing insulator comprising the steps of:
  • a conductive sheet wrapping a conductive sheet around a longitudinal mold plug, said conductive sheet comprising an in sulating substrate material with a conductive layer disposed thereon, with said insulating substrate material facing said mold plug; injecting epoxy between the wrapped mold plug and a mold positioned around said mold plug;
  • An electrical bushing comprising an insulator constructed of epoxy and having a longitudinal opening extending therethrough, a stress relieving shield which is tightly attached to the wall of said opening, said shield comprising a sheet of insulating material and a layer of conductive material each having first and second sides, the first sides of said insulating sheet and conductive layers being tightly adhered to each other, the second side of said sheet of insulating material facing the center of said opening, and a conducting means located in said opening for conducting current through said bushing, said conducting means being smaller than said opening thereby providing a substantial space between the conducting means and the sheet of insulating material which does not contain any other solid insulating material.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Insulators (AREA)
  • Insulating Bodies (AREA)
US00302329A 1972-10-30 1972-10-30 Electrical bushing having a stress relieving shield and method of constructing same Expired - Lifetime US3783181A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US30232972A 1972-10-30 1972-10-30

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Country Status (3)

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US (1) US3783181A (enrdf_load_stackoverflow)
JP (1) JPS4993896A (enrdf_load_stackoverflow)
CA (1) CA959951A (enrdf_load_stackoverflow)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2312094A1 (fr) * 1975-05-22 1976-12-17 Westinghouse Electric Corp Traversee electrique moulee a condensateur incorpore et methode de fabrication de celle-ci
DE2925764A1 (de) * 1979-06-26 1981-01-15 Siemens Ag Einstueckiger giessharzdurchfuehrungsisolator
US5903209A (en) * 1998-08-07 1999-05-11 Thomas & Betts International, Inc. Encapsulated fuse with corona shield
FR2786943A1 (fr) * 1998-12-07 2000-06-09 Soule Materiel Electr Dispositif de coupure electrique pour moyenne et haute tension
US6702973B2 (en) * 2000-01-11 2004-03-09 Mcgraw-Edison Company Method of sealing a stud in a bushing
US6783401B2 (en) * 1997-07-02 2004-08-31 The Regents Of The University Of California Apparatus for improving performance of electrical insulating structures
US20050077994A1 (en) * 2003-10-10 2005-04-14 G&W Electric Co. Encapsulated fuse with corona shield
US20070181324A1 (en) * 2006-01-24 2007-08-09 Arnaud Allais Electrical bushing
US20100089617A1 (en) * 2006-08-31 2010-04-15 Abb Research Ltd. High voltage shield
WO2017101992A1 (de) * 2015-12-16 2017-06-22 Siemens Aktiengesellschaft Hochspannungsvorrichtung und verfahren zu deren herstellung
EP3648121A1 (en) * 2018-10-31 2020-05-06 ABB Schweiz AG Condenser core, bushing, high voltage application and method of producing bushing

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DD65960A (enrdf_load_stackoverflow) *
GB430076A (en) * 1933-11-07 1935-06-07 Hermsdorf Schomburg Isolatoren Improvements in or relating to bushing insulators for electrical conductors
CH320903A (fr) * 1955-04-07 1957-04-15 Gardy Particip App Isolateur de traversée
US2870524A (en) * 1953-05-18 1959-01-27 Elliott Brothers London Ltd Manufacture of waveguide components
DE1105018B (de) * 1959-04-22 1961-04-20 Koch & Sterzel Kommanditgesell Verfahren zur Herstellung einer dichten Verbindung zwischen einem Giessharzisolierkoerper und einem darin eingegossenen starken Durchfuehrungsbolzen bei einer Hochspannungsdurchfuehrung
US3025201A (en) * 1957-07-15 1962-03-13 Lamtex Ind Inc Electrically non-conductive structural element
US3085295A (en) * 1957-04-30 1963-04-16 Michael A Pizzino Method of making inlaid circuits
US3320341A (en) * 1960-02-24 1967-05-16 William L Mackie Method of manufacturing a lightweight microwave antenna
GB1159205A (en) * 1966-04-29 1969-07-23 Felten & Guilleaume Carlswerk Electrical Insulating Bodies Incorporating Electrodes

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4419951Y1 (enrdf_load_stackoverflow) * 1967-08-22 1969-08-27

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DD65960A (enrdf_load_stackoverflow) *
GB430076A (en) * 1933-11-07 1935-06-07 Hermsdorf Schomburg Isolatoren Improvements in or relating to bushing insulators for electrical conductors
US2870524A (en) * 1953-05-18 1959-01-27 Elliott Brothers London Ltd Manufacture of waveguide components
CH320903A (fr) * 1955-04-07 1957-04-15 Gardy Particip App Isolateur de traversée
US3085295A (en) * 1957-04-30 1963-04-16 Michael A Pizzino Method of making inlaid circuits
US3025201A (en) * 1957-07-15 1962-03-13 Lamtex Ind Inc Electrically non-conductive structural element
DE1105018B (de) * 1959-04-22 1961-04-20 Koch & Sterzel Kommanditgesell Verfahren zur Herstellung einer dichten Verbindung zwischen einem Giessharzisolierkoerper und einem darin eingegossenen starken Durchfuehrungsbolzen bei einer Hochspannungsdurchfuehrung
US3320341A (en) * 1960-02-24 1967-05-16 William L Mackie Method of manufacturing a lightweight microwave antenna
GB1159205A (en) * 1966-04-29 1969-07-23 Felten & Guilleaume Carlswerk Electrical Insulating Bodies Incorporating Electrodes

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2312094A1 (fr) * 1975-05-22 1976-12-17 Westinghouse Electric Corp Traversee electrique moulee a condensateur incorpore et methode de fabrication de celle-ci
DE2925764A1 (de) * 1979-06-26 1981-01-15 Siemens Ag Einstueckiger giessharzdurchfuehrungsisolator
US6783401B2 (en) * 1997-07-02 2004-08-31 The Regents Of The University Of California Apparatus for improving performance of electrical insulating structures
US5903209A (en) * 1998-08-07 1999-05-11 Thomas & Betts International, Inc. Encapsulated fuse with corona shield
FR2786943A1 (fr) * 1998-12-07 2000-06-09 Soule Materiel Electr Dispositif de coupure electrique pour moyenne et haute tension
EP1009002A1 (fr) * 1998-12-07 2000-06-14 Soule Materiel Electrique Dispositif de coupure électrique pour moyenne et haute tension
US6702973B2 (en) * 2000-01-11 2004-03-09 Mcgraw-Edison Company Method of sealing a stud in a bushing
US7327213B2 (en) 2003-10-10 2008-02-05 G & W Electric Co. Encapsulated fuse with corona shield
US20050077994A1 (en) * 2003-10-10 2005-04-14 G&W Electric Co. Encapsulated fuse with corona shield
US20070181324A1 (en) * 2006-01-24 2007-08-09 Arnaud Allais Electrical bushing
US7825331B2 (en) * 2006-01-24 2010-11-02 Arnaud Allais Electrical bushing
US20100089617A1 (en) * 2006-08-31 2010-04-15 Abb Research Ltd. High voltage shield
WO2017101992A1 (de) * 2015-12-16 2017-06-22 Siemens Aktiengesellschaft Hochspannungsvorrichtung und verfahren zu deren herstellung
US10366808B2 (en) 2015-12-16 2019-07-30 Siemens Aktiengesellschaft High-voltage apparatus and method for producing same
EP3648121A1 (en) * 2018-10-31 2020-05-06 ABB Schweiz AG Condenser core, bushing, high voltage application and method of producing bushing
WO2020088833A1 (en) * 2018-10-31 2020-05-07 Abb Schweiz Ag Condenser core, bushing, high voltage application and method of producing bushing
US11942742B2 (en) 2018-10-31 2024-03-26 Hitachi Energy Ltd Condenser core, bushing, high voltage application and method of producing bushing

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Publication number Publication date
JPS4993896A (enrdf_load_stackoverflow) 1974-09-06
CA959951A (en) 1974-12-24

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Owner name: ABB POWER T&D COMPANY, INC., A DE CORP., PENNSYLV

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:WESTINGHOUSE ELECTRIC CORPORATION, A CORP. OF PA.;REEL/FRAME:005368/0692

Effective date: 19891229