US3911384A - Increasing the dielectric strength in metal electrodes - Google Patents

Increasing the dielectric strength in metal electrodes Download PDF

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Publication number
US3911384A
US3911384A US480929A US48092974A US3911384A US 3911384 A US3911384 A US 3911384A US 480929 A US480929 A US 480929A US 48092974 A US48092974 A US 48092974A US 3911384 A US3911384 A US 3911384A
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US
United States
Prior art keywords
layer
dielectric constant
increasing
field strength
metal electrodes
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Expired - Lifetime
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US480929A
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English (en)
Inventor
Olle Andersson
Ellerth Ericsson
Svante Forsberg
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ABB Norden Holding AB
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ASEA AB
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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
    • H01F27/28—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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • 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
    • H01B17/56—Insulating bodies
    • H01B17/62—Insulating-layers or insulating-films on metal bodies
    • 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
    • H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/005—Impregnating or encapsulating

Definitions

  • electrodes must here be taken in its broad sense, and in this context it comprises construction parts for electric machines and apparatus which have high voltage to earth or other live parts or earth-connected parts which are located in the vicinity of live parts. As examples of what is meant may be mentioned the iron core with relevant parts, splash rings for live parts and the like.
  • the sheets will display small irregularities in the cut edges. Even such construction parts as press beams, lifting devices and the like cannot be made absolutely smooth, and even after a normal grinding there will be irregularities which, in normal cases, are of no significance.
  • a conductor with high voltage passes in the vicinity of an earthed object displaying such insignificant irregularities on the surface, the electric field between the conductor and the earthed object will be affected very strongly quite close to the irregularities, and the insulating material just outside even an almost microscopic elevation will be exposed to a considerably increased field strength with a resultant risk of glow discharge appearing there.
  • Such a seemingly insignificant partial discharge can easily increase and will eventually give rise to a flash-over in the liquid insulating agent between the earthed object and the live conductor.
  • the problem of avoiding partial discharges on the electrode surfaces referred to above has been solved by applying a layer of a resin with a dielectric constant which is high in comparison with the dielectric constant of the transformer oil to the electrode by means of electrostatic spraying.
  • Electrostatic spray painting as such is well-known, but so far it has not been known to employ this method for strengthening the capacity of the electrodes to endure strong electrical fields in electrical apparatus.
  • the method according to the invention makes use of the tendency of the applied material to accumulate mostly where the electrical field strength is highest, which is where the strongest insulation is required.
  • FIG. 1 shows a sharp corner 'in a metallic construction part coated with an insulating-agent according to the invention
  • FIG. 2 shows a vertical section through a toroidal splash ring on the line II-II of FIG. 3.
  • FIG. 3 is a view from above of the splash ring accord- 0 ing to FIG. 2.
  • FIG. 4 shows an enlarged cross-section of the area IV in FIG. 2 and also an enlarged view of the encircled area II in FIG. 6.
  • FIG. 5 shows a time-temperature curve for the application of a coating according to the invention.
  • FIG. 6 shows a schematic view of a transformer to which the invention is applied.
  • FIG. 1 shows a sharp corner in a metallic construction part 1 in an electrical apparatus.
  • This may be, for example, the iron core in a transformer.
  • burrs will always appear and these will have a particular importance at the corners of the construction, with a resultant risk of glow phenomena.
  • an insulating layer 2 is applied by means of electrostatic spraying of a powdered resin or a resinous solution. Because of the increased field strength at the corner 3, an extra thick coating will appear there. This means that a coating is obtained, the thickness of which is related to the risk of flash-over between the construction part and a live conductor in the vicinity thereof.
  • FIG. 2 shows a vertical section through a toroidal splash ring 4, which is placed on that end of a transformer bushing which is located in the oil in a transformer tank. The lower end of the bushing is indicated at 5. The splash ring is supported by the bushing by means of stays 6.
  • FIG. 3 shows the splash ring from above.
  • Such splash rings are manufactured of a thin material, and the field strength will thus be high along the edges 7 with a subsequent risk of glow discharge.
  • FIG. 4 shows a section through the edge 7 on an enlarged scale, after the splash ring has been treated according to the invention. The figure shows that the said edge is coated with a layer 8 of insulating material so that the otherwise sharp edge has a considerably increased radius of curvature. The risk of glow discharge and flash-over at the edge is thus considerably reduced.
  • the treatment with resin according to the invention causes all sharp edges to acquire a smooth curvature with a definable radius. This decreases the field strength and reduces the risk of glow discharge and flash-over.
  • FIG. 5 shows the time temperature curve during the process of coating an object.
  • the straight part 10 indicates the temperature of the object before the start of the spraying.
  • the object is removed from the heating furnace and the spraying commences. While the spraying is going on, the temperature decreases, which is marked by the downward curve part 12.
  • the spraying is finished and the applied resin must be cured and this curing can be performed under a continuing temperature drop in the object according to one of the curve parts 14 or 15. It is also possible to place the object in a furnace so that the curing continues at constant temperature, as shown by the curve part 16. In any event it mustbe ensured that the temperature does not rise after the spraying has been finished.
  • FIG. 6 shows a transformer having a tank filled with oil.
  • An iron core 21 with windings 22 is in the tank.
  • the lower end of each bushing situated in the tank has a splash ring 4, and each bushing is connected to a winding by a conductor 24.
  • the encircled area II at the lower end of the bushing is shown on an enlarged scale in FIG. 2.
  • the encircled area I at the upper righthand corner is shown in FIG, 1 and explained in connection with the description of said Figure,

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Holders For Apparel And Elements Relating To Apparel (AREA)
  • Insulating Bodies (AREA)
US480929A 1973-06-20 1974-06-19 Increasing the dielectric strength in metal electrodes Expired - Lifetime US3911384A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE7308658A SE382715B (sv) 1973-06-20 1973-06-20 Forfarande for okning av den elektriska overslaghallfastheten hos metalliska elektroder.

Publications (1)

Publication Number Publication Date
US3911384A true US3911384A (en) 1975-10-07

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ID=20317824

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Application Number Title Priority Date Filing Date
US480929A Expired - Lifetime US3911384A (en) 1973-06-20 1974-06-19 Increasing the dielectric strength in metal electrodes

Country Status (7)

Country Link
US (1) US3911384A (enrdf_load_stackoverflow)
BR (1) BR7405004A (enrdf_load_stackoverflow)
CA (1) CA1049338A (enrdf_load_stackoverflow)
DE (1) DE2427474B2 (enrdf_load_stackoverflow)
NO (1) NO134885C (enrdf_load_stackoverflow)
SE (1) SE382715B (enrdf_load_stackoverflow)
ZA (1) ZA743884B (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4320437A (en) * 1980-06-23 1982-03-16 General Electric Company Capacitor with edge coated electrode
WO1998022958A1 (en) * 1996-11-22 1998-05-28 Abb Research Ltd. Electrode for field control
CN104634898A (zh) * 2013-11-08 2015-05-20 中国石油天然气股份有限公司 电热混合场下评定变压器油产气趋势的试验方法及装置
US10449648B2 (en) 2016-08-04 2019-10-22 Robert Bosch Tool Corporation Transferring rotation torque through isolator for table saw

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4030806A1 (de) * 1990-09-28 1992-04-02 Siemens Ag Verfahren zur erhoehung der spannungsfestigkeit und verbesserung des kriechstromverhaltens von isolationsstrecken und anwendung dieses verfahrens auf vakuumschalter

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2730461A (en) * 1953-02-19 1956-01-10 Ransburg Electro Coating Corp Electrostatic coating method
US3265998A (en) * 1964-04-14 1966-08-09 Charles W Park Compact high voltage transformer having more uniform equipotential line spacing

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2730461A (en) * 1953-02-19 1956-01-10 Ransburg Electro Coating Corp Electrostatic coating method
US3265998A (en) * 1964-04-14 1966-08-09 Charles W Park Compact high voltage transformer having more uniform equipotential line spacing

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4320437A (en) * 1980-06-23 1982-03-16 General Electric Company Capacitor with edge coated electrode
WO1998022958A1 (en) * 1996-11-22 1998-05-28 Abb Research Ltd. Electrode for field control
US6432524B1 (en) 1996-11-22 2002-08-13 Abb Research Ltd. Electrode for field control
CN104634898A (zh) * 2013-11-08 2015-05-20 中国石油天然气股份有限公司 电热混合场下评定变压器油产气趋势的试验方法及装置
US10449648B2 (en) 2016-08-04 2019-10-22 Robert Bosch Tool Corporation Transferring rotation torque through isolator for table saw

Also Published As

Publication number Publication date
ZA743884B (en) 1975-06-25
CA1049338A (en) 1979-02-27
DE2427474B2 (de) 1979-07-19
NO134885B (enrdf_load_stackoverflow) 1976-09-20
SE382715B (sv) 1976-02-09
SE7308658L (enrdf_load_stackoverflow) 1974-12-23
DE2427474A1 (de) 1975-01-23
NO742180L (enrdf_load_stackoverflow) 1975-01-13
NO134885C (enrdf_load_stackoverflow) 1976-12-29
BR7405004A (pt) 1976-02-24

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