US3579163A - Liquid-filled transformer with foamed insulation - Google Patents

Liquid-filled transformer with foamed insulation Download PDF

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Publication number
US3579163A
US3579163A US860688A US3579163DA US3579163A US 3579163 A US3579163 A US 3579163A US 860688 A US860688 A US 860688A US 3579163D A US3579163D A US 3579163DA US 3579163 A US3579163 A US 3579163A
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United States
Prior art keywords
liquid
gap
oil
gaps
insulating
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Expired - Lifetime
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US860688A
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English (en)
Inventor
John C Cronin
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Westinghouse Electric Corp
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Westinghouse Electric Corp
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Publication date
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/02—Casings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/28—Coils; Windings; Conductive connections
    • H01F27/30—Fastening or clamping coils, windings, or parts thereof together; Fastening or mounting coils or windings on core, casing, or other support
    • H01F27/303—Clamping coils, windings or parts thereof together
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/28—Coils; Windings; Conductive connections
    • H01F27/32—Insulating of coils, windings, or parts thereof
    • H01F27/324—Insulation between coil and core, between different winding sections, around the coil; Other insulation structures

Definitions

  • the invention relates in general to electrical inductive apparatus, such as transformers, and more specifically to electrical inductive apparatus of the type having a magnetic corewinding assembly immersed in liquid-insulating means.
  • Certain types of electrical inductive apparatus such as transformers and reactors, include magnetic core-winding assemblies immersed in a liquid-insulating and cooling medium, such as mineral oil.
  • a liquid-insulating and cooling medium such as mineral oil.
  • the breakdown stress in volts per mil of an oil gap in such apparatus decreases, as the gap spacing is increased.
  • liquid-insulating and cooling dielectric such as mineral oil
  • transformer 10 includes a metallic tank 12 having sidewall, bottom and top portions, with the tank 12 being filled to a level 14 with an insulating and cooling liquid dielectric, such as mineral oil.
  • a magnetic core-winding assembly I6 is disposed in the tank 12, and immersed in the liquid dielectric.
  • the electrical bushings associated with transformer l 10 are not shown in the FIGURE, in order to simplify the drawing.
  • the tank 12 has a plurality of openings 18 at the level 14 of the liquid dielectric, which openings are in communication with coolers or heat exchangers (not shown) mounted outside the tank 12. The liquid dielectric flows into the heat exchangers, is colled, and collected in suitable headers, and then allowed to flow back into the tank 16 near the bottom thereof, either by natural thermal siphon effect, or
  • the oil impregnated pressboard has a higher dielectric constant than the oil, which transfers electrical stress from the pressboard barriers or spacers to the liquidfilled gaps between the barriers.
  • Completely solid barriers are usually avoided as it requires extreme care to avoid an oil gap in series with the solid barrier, between the electrode surfaces adjacent the gap. This is important, as the higher dielectric constant solid material would transfer electrical stress to the series oil gap which may be greater than the breakdown stress of the gap, creating corona which breaks down and degrades the solid and liquid insulation adjacent thereto, eventually causing complete failure of the insulation in this area.
  • the present invention is a new and improved electri cal inductive apparatus, such as transformers or reactors, having a magnetic core-winding assembly disposed in a tank containing a liquid-insulating and cooling dielectric, such as mineral oil.
  • the high stress oil gaps in the apparatus such as those between phase winding assemblies, those between the high and low voltage windings of a phase winding assembly, the areas adjacent the static plate, and the gaps between the phase winding assemblies and the tank walls, are subdivided into a large plurality of minute oil gaps by using an open cell foam material disposed in the gaps.
  • the open cells of the foam material allow the material to become completely filled with the liquid dielectric, with the resulting liquid'filled structure having substantially the same dielectric constant as the liquid itself, due to the thin membranelike walls of the cells, and with the gap having a breakdown stress in volts per mil which is based more nearly on the cell dimensions, rather than on the dimensions of the gap in which the foam material is placed.
  • FIGURE is a perspective view of a transformer, partially cutaway, and partially in section, constructed according to the teachings of the invention.
  • FIGURE is a perspective view of a transformer 10 constructed according to the teachings of the invention.
  • Transformer I0 is illustrated as being of polyphase core-form construction, but the apparatus may be single of polyphase, shell of core-form, and in general by a suitable pump.
  • Transformer 10 may have a plurality of heat exchangers, as required by the specific application.
  • Magnetic core-winding assembly 16 includes a three phase magnetic core 22 having winding legs 24, 26 and 28 connected by'upper and lower yoke portions 30 and 32, respectively.
  • Magnetic core 22 is formed of a plurality of stacks of magnetic, metallic laminations, such as grain-oriented silicon steel, with the winding legs being illustrated as having a cruciform cross-sectional configuration, in order to more effectively couple windings having round openings therein.
  • the stacked laminations are held in assembled relation by upper and lower end frames 34 and 36, respectively.
  • the magnetic core-winding assembly 16 also includes phase winding assemblies 38, 40 and 42, disposed about winding legs 24, 26 and 28, respectively.
  • Each of the phase winding assemblies includes concentrically disposed low and high voltage windings, such as low and high voltage windings 44 and 46 illustrated in phase winding assembly 38.
  • the low and high voltage windings are separated by insulating means 48 in the highlow space between the concentrically disposed windings, and static plates, such as a static plate 50, may be disposed at the line end, or ends, of the winding structure, to more evenly distribute surge potentials across the line end pancake coil of the plurality of pancake type coils of which the high voltage winding may be formed.
  • the high and low voltage windings are mechanically held at each end of its associated phase assembly by pressure'rings or plates, such as pressure plates 52 and 54 illustrated in assembled relation with the phase winding assembly 40.
  • Suitable means such as bolts 56 and 58 connected to the end frames, apply pressure at discrete points about the pressure plates of each phase winding assembly, to provide the necessary force to prevent the windings from distorting during short circuit conditions.
  • High voltage electrical inductive apparatus has many areas of high electrical stress, which areas must be adequately insulated to prevent corona discharges and breakdown of insulation.
  • high stress areas are the high-low insulation, such as insulating means 48, disposed between the high and low voltage windings of a phase winding assembly, the space between adjacent phase winding assemblies, the insulation between the static plate and pressure ring, and the space between the phase winding assemblies and the adjacent metallic tank walls.
  • the breakdown stress in volts per mil of an oil gap decreases as the gap spacing is increased. Therefore, the breakdown stress of an given gap can be increased by breaking the oil gap into a plurality of series oil gaps, which substantially increases the volts per mil which the gap will withstand before a breakdown occurs.
  • the prior art discloses structures which divide or break up an oil gap into a plurality of series oil gaps, which structures are formed of a plurality of pressboard barriers. The number of series oil gaps which can be created is seriously limited, however, when using pressboard, due to mechanical limitations. Further, oil impregnated pressboard has a higher dielectric constant than the oil in the gaps between the pressboard layers.
  • the dimensions of the cells of the foam are not critical. It is important, however, that the. cells of the foam material selected beopen and interconnected. It is also important that I all of the air be removed from the cells of the foam before it is impregnated with the liquid dielectric. It may be necessary to compress flexible foam to break any cells which may not be completely open, to remove any air entrapped therein, and also to insure complete impregnation of the foam by the liquid in the electrical apparatus.
  • the foam material selected must be able to withstand the maximum operating temperature to which it will be subjected in the electrical apparatus. Further, it must be nonfriable and nondusting, and it must be able to withstand attack from the specific liquid used for the cooling and insulating dielectric medium. While thermosetting materials are preferable, thermoplastic foam materials having a softening temperature well above the maximum operating temperature of the apparatus would be suitable.
  • Flexible urethane foams have been found to be excellent in mineral oil, as they are made up of interconnecting cells separated by thin broken walls.
  • the urethane foams have a high mechanical strength, even at low densities, and have a low compression set and a high degree of resiliency.
  • urethane foam is preferable because it can be economically foamed in place, sprayed, or preformed in molds to special shapes
  • other insulating foams may be equally as suitable.
  • low density silicone foams are open celled, they have good chemical resistance, and they have a very high maximum service temperature.
  • the open-celled phenolic foams are nonflexible and thermosetting, but they are not as desirable as they become friable at low densities.
  • Flexible polyvinychloride foams are open celled and have a good chemical resistance, but they are thermoplastic, with a F. maximum service temperature. Since the production of foams is well known, as is the various methods of foaming the resins, it is not necessary to discuss specific foaming techniques in detail.
  • the Handbook of Foamed Plastics, Rene J Bender, Lake Publishing Corporation, Libertyville, Illinois, 1965 describes suitable foams which may be used, as well as techniques for their production.
  • Transformer 10 shown in the FIGURE may advantageously utilize open cell insulating foam structures in its highly stressed areas, such as the high-low insulation 48.
  • the high and low voltage windings may be assembled with suitable mechanical spacers, and the foam insulation applied by foaming in place, or a rectangular section or sheet of preformed foam insulation may be disposed between the windings when the phase assembly is being manufactured.
  • foam insulation is between the static plate, such as the static plate 50, and the adjacent pressure plate.
  • the foam in this area may be sprayed on the pressure plate, or applied as a discrete section of insulation.
  • phase barriers may be formed of large sections of open-celled foam, such as barrier 60 between phase assemblies 38 and 40, and barrier 62 between phase assemblies 40 and 42. Sections of foam insulation may also be placed between the phase winding assemblies and the adjacent walls of the tank 12, such as barrier 64 between phase assembly38 and the adjacent tank wall, and barrier 66 between phase assembly 42 and the adjacent tank wall.
  • the invention has been described as being used with a mineral oil-cooling and insulating medium, it will be understood that the invention is applicable to any type of liquid coolant, such as the synthetic transformer oils. Care should be taken to insure that the foam material selected will be compatible-with the specific liquid dielectric used. For example, certain of the foams, such as the urethanes, are compatible with mineral oil, but may severely swell when being subjected to coolants which contain chlorinated products.
  • Electrical inductive apparatus comprising:
  • foamed insulating means disposed between predetermined points of different electrical potential in said magnetic core-winding assembly, said foamed insulating means being of the open cell type, with the cells of the foamed insulating means being impregnated with said liquid-insulating means.
  • the magnetic core-winding assembly is of the core-form type, having a plurality of phase winding assemblies disposed on spaced leg portions of the magnetic core, and wherein the foamed insulating means includes members disposed between adjacent phase winding assemblies.
  • foamed insulating means includes members disposed between the phase winding assemblies and the casing.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Insulating Of Coils (AREA)
US860688A 1969-09-24 1969-09-24 Liquid-filled transformer with foamed insulation Expired - Lifetime US3579163A (en)

Applications Claiming Priority (1)

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US86068869A 1969-09-24 1969-09-24

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BE (1) BE756562A (fr)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4133970A (en) * 1975-12-30 1979-01-09 Joslyn Mfg. And Supply Co. Electrical insulation system
WO1996004347A1 (fr) * 1994-08-03 1996-02-15 Henkel Kommanditgesellschaft Auf Aktien Adhesif de reaction a un ou deux composant(s)
US6429765B1 (en) * 1996-05-23 2002-08-06 Abb Ab Controllable inductor
US20100101879A1 (en) * 2007-02-14 2010-04-29 Mcvickers Jack C Motor Battery Systems
US20100246093A1 (en) * 2009-03-26 2010-09-30 Steven Falabella Two-phase mixed media dielectric with macro dielectric beads for enhancing resistivity and breakdown strength
US20100279153A1 (en) * 2009-04-30 2010-11-04 Lg Chem, Ltd. Battery systems, battery module, and method for cooling the battery module
US20110027625A1 (en) * 2009-07-29 2011-02-03 Lg Chem, Ltd. Battery module and method for cooling the battery module
US20120126923A1 (en) * 2009-05-19 2012-05-24 Siemens Ltda. Submersible dry distribution transformer
DE102017206348A1 (de) * 2017-04-12 2018-10-18 Siemens Aktiengesellschaft Geräuscharmes elektrisches Gerät für die Serienkompensation, Kurzschlussstrombegrenzung oder Gleichstromglättung
EP3654354A1 (fr) * 2018-11-14 2020-05-20 ABB Schweiz AG Supports internes pour transformateurs en forme de coque
US10902996B2 (en) * 2015-10-30 2021-01-26 Jiangsu Huapeng Transformer Co., Ltd. Self-clamping structure for solving short-circuit resistance problem of amorphous alloy transformers

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2313379A (en) * 1940-12-30 1943-03-09 Cleef Bros Van Mounting means for electrically operated units
US2999222A (en) * 1957-10-22 1961-09-05 Gen Electric Electric control unit
US3163838A (en) * 1962-03-28 1964-12-29 Gen Electric Inductive device employing foamed resin thermal barrier
US3302149A (en) * 1964-09-30 1967-01-31 Westinghouse Electric Corp Electrical insulating structure

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2313379A (en) * 1940-12-30 1943-03-09 Cleef Bros Van Mounting means for electrically operated units
US2999222A (en) * 1957-10-22 1961-09-05 Gen Electric Electric control unit
US3163838A (en) * 1962-03-28 1964-12-29 Gen Electric Inductive device employing foamed resin thermal barrier
US3302149A (en) * 1964-09-30 1967-01-31 Westinghouse Electric Corp Electrical insulating structure

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4133970A (en) * 1975-12-30 1979-01-09 Joslyn Mfg. And Supply Co. Electrical insulation system
WO1996004347A1 (fr) * 1994-08-03 1996-02-15 Henkel Kommanditgesellschaft Auf Aktien Adhesif de reaction a un ou deux composant(s)
US5962540A (en) * 1994-08-03 1999-10-05 Henkel Kommanditgesellschaft Auf Aktien One-component or two-component reactive adhesive
US6429765B1 (en) * 1996-05-23 2002-08-06 Abb Ab Controllable inductor
US20100101879A1 (en) * 2007-02-14 2010-04-29 Mcvickers Jack C Motor Battery Systems
US20100246093A1 (en) * 2009-03-26 2010-09-30 Steven Falabella Two-phase mixed media dielectric with macro dielectric beads for enhancing resistivity and breakdown strength
US8749951B2 (en) 2009-03-26 2014-06-10 Lawrence Livermore National Security, Llc Two-phase mixed media dielectric with macro dielectric beads for enhancing resistivity and breakdown strength
US8663828B2 (en) * 2009-04-30 2014-03-04 Lg Chem, Ltd. Battery systems, battery module, and method for cooling the battery module
US20100279153A1 (en) * 2009-04-30 2010-11-04 Lg Chem, Ltd. Battery systems, battery module, and method for cooling the battery module
US20120126923A1 (en) * 2009-05-19 2012-05-24 Siemens Ltda. Submersible dry distribution transformer
US8614614B2 (en) * 2009-05-19 2013-12-24 Siemens Ltda. Submersible dry distribution transformer
US20110027625A1 (en) * 2009-07-29 2011-02-03 Lg Chem, Ltd. Battery module and method for cooling the battery module
US8703318B2 (en) * 2009-07-29 2014-04-22 Lg Chem, Ltd. Battery module and method for cooling the battery module
US20140186661A1 (en) * 2009-07-29 2014-07-03 Lg Chem, Ltd. Battery module and method for cooling the battery module
US9196937B2 (en) * 2009-07-29 2015-11-24 Lg Chem, Ltd. Battery module and method for cooling the battery module
US10902996B2 (en) * 2015-10-30 2021-01-26 Jiangsu Huapeng Transformer Co., Ltd. Self-clamping structure for solving short-circuit resistance problem of amorphous alloy transformers
DE102017206348A1 (de) * 2017-04-12 2018-10-18 Siemens Aktiengesellschaft Geräuscharmes elektrisches Gerät für die Serienkompensation, Kurzschlussstrombegrenzung oder Gleichstromglättung
EP3654354A1 (fr) * 2018-11-14 2020-05-20 ABB Schweiz AG Supports internes pour transformateurs en forme de coque
WO2020099517A1 (fr) * 2018-11-14 2020-05-22 Abb Schweiz Ag Supports internes pour transformateurs en forme de coque
US12046402B2 (en) 2018-11-14 2024-07-23 Hitachi Energy Ltd Internal supports for shell form transformers

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Publication number Publication date
BE756562A (fr) 1971-03-24

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