EP0654798A1 - Elektrischer Hochspannungsvorrichtung mit hochfrequenz Isolator - Google Patents

Elektrischer Hochspannungsvorrichtung mit hochfrequenz Isolator Download PDF

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Publication number
EP0654798A1
EP0654798A1 EP94402648A EP94402648A EP0654798A1 EP 0654798 A1 EP0654798 A1 EP 0654798A1 EP 94402648 A EP94402648 A EP 94402648A EP 94402648 A EP94402648 A EP 94402648A EP 0654798 A1 EP0654798 A1 EP 0654798A1
Authority
EP
European Patent Office
Prior art keywords
electrical
high voltage
insulating material
high frequency
cellular structure
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.)
Withdrawn
Application number
EP94402648A
Other languages
English (en)
French (fr)
Inventor
Claude Fougeron
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.)
Centre National de la Recherche Scientifique CNRS
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Original Assignee
Centre National de la Recherche Scientifique CNRS
Commissariat a lEnergie Atomique CEA
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 Centre National de la Recherche Scientifique CNRS, Commissariat a lEnergie Atomique CEA filed Critical Centre National de la Recherche Scientifique CNRS
Publication of EP0654798A1 publication Critical patent/EP0654798A1/de
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B11/00—Communication cables or conductors
    • H01B11/18—Coaxial cables; Analogous cables having more than one inner conductor within a common outer conductor
    • H01B11/1834—Construction of the insulation between the conductors
    • H01B11/1839—Construction of the insulation between the conductors of cellular structure

Definitions

  • the present invention relates generally to a high voltage electrical device with insulator comprising at least two electrical conductors to be insulated from one another.
  • high frequency high voltage such as for example particle accelerators, controlled fusion systems of the Tokomaks type, high frequency heating or telecommunications.
  • high voltage is meant a voltage greater than 1 kV and by high frequency a frequency greater than 100 KHz.
  • Teflon (registered name) is particularly used in connection applications where connection terminals often have to be isolated.
  • the surface of the insulator in contact with the conductive metal can be metallized.
  • the known insulators are then generally destroyed by short circuits which seem to occur along their surface, despite the usual precautions of dissection and varnishing.
  • An object of the invention is to provide an isolation means for a high voltage and high frequency device which does not have these drawbacks of known insulators and which withstand very high voltages without being destroyed.
  • the invention relates more precisely to a high voltage and high frequency electrical device comprising at least first and second electrical conductors, kept separated from each other by at least one insulating means.
  • electric, means for applying a high frequency high voltage between the first and second conductors characterized in that the insulating means comprises at least one part having a cellular structure, the cellular structure comprising cells having walls made of an insulating material electric and containing a gas which has a dielectric constant close to the air dielectric constant.
  • cellular structure is meant either a porous structure such as that of certain ceramics or a honeycomb structure as in expanded materials.
  • the dielectric constant of the gas is preferably between 1.2 and 1.
  • the invention starts from the observation that in the devices, the destruction of the insulators is not strictly speaking due to a simple "breakdown" or even to an overall heating of the insulating structure.
  • sparks appear between one of the conductors brought to a high voltage and the insulating material. These sparks reflect electric arcs which locally increase the temperature of the insulation until the combustion or fusion of the latter.
  • the gas contained in the cells gives the cell structure a dielectric constant close to that of air insofar as it itself has a dielectric constant close to that of air. This property does not prevent the formation of sparks but moves the threshold of their appearance towards a range of voltages much higher than the voltages which imply the destruction of known insulators.
  • Expanded polystyrene and polyurethane, for example, are both economical and effective.
  • a polymethacrylic imide such as the rigid foam sold under the trade name Rohacell is particularly indicated as a cellular structure in the context of the present invention.
  • a porous ceramic structure can also be retained.
  • the gas contained in the cells or the pores is air, nitrogen or carbon dioxide.
  • the insulation means may also comprise a part made of a conventional solid and compact insulator lined with one or more parts with a cellular structure at one or more of its ends facing one of the conductors subjected at high voltage.
  • the insulation means comprises, for example, insulating parts with a cellular structure which can be adapted to the solid part and which cover and surround the contact regions.
  • It may consist of a conventional insulating bar of generally parallelepiped shape and covered at its ends by caps of material with cellular structure.
  • the insulator may not have only one end furnished with the cellular structure.
  • the experimental device of FIG. 1 comprises a first conductor 103 connected to ground. On this conductor 103 is placed a sample 105 of insulating material with a thickness of 10 mm and finally a copper ball 107 is placed on the sample 105.
  • a high voltage is applied to the copper ball 107 by means of an HF cavity 108, the value of which is increased until the appearance of sparks.
  • FIG. 2 illustrates the device of the invention in an application to accelerating cavities where it is a question of supporting copper bars brought to an alternating high voltage potential.
  • a first conductor 203 is connected to ground.
  • shims 205 made of polyurethane foam and finally bars conductors 207 made of copper are arranged on the shims 205.
  • the shims have a thickness of around 2 cm and allow the bars 207 to be separated from the first conductor 203, allowing a potential difference with respect to the conductor 203 of for example 20 kV.
  • the potential is applied to the bars 207 by means of a high-frequency high-frequency source 208.
  • the shims 205 can also be made of another cellular material according to the invention, for example expanded polystyrene or a foam known under the name Rohacell.
  • the material 210 comprises walls 206 of electrically insulating material, in l occurrence of polyurethane, containing a gas 202 which is here essentially carbon dioxide.
  • FIG. 3 illustrates a variant of the invention where a first conductor 303 and a second conductor 307 between which a high voltage is applied from a source 308 are kept separated by an insulator 305 in several parts.
  • the insulator comprises a block 311 of a traditional solid and compact insulating material, such as, for example, glass, and is capped at its two ends 313, 315 directed towards the conductors 303 and 307 respectively of two parts 305a, 305b in a cell structure according to the invention.
  • a traditional solid and compact insulating material such as, for example, glass
  • the parts 305a, 305b each have a rim 317, 319 laterally enveloping the respective end 313, 315 of the block 311 so as to avoid an electric arc in this region.
  • Parts 305a, 305b are made of expanded polystyrene or of polymethacrylic imide.
  • FIG. 4 represents a particular application of an insulating part according to the invention in a connector of the "SPINER" type.
  • the connector 400 comprises an external metallic conductive sheath 403 called “ground” and connected for example to an earth connection, and a conductive core 407 connected to a generator 408 of high voltage at high frequency.
  • the core 407 is coaxial and concentric with the conductor 403 while a part 401 made of a cellular insulating material is interposed so as to isolate them.
  • Part 405 advantageously replaces the Teflon insulator (registered name) that is traditionally found on these connectors. Tests at high voltage and at a frequency of 1 kHz show that the destruction of part 405 made of polymethacrylic imide occurs for a voltage of 18 kV while the traditional Teflon insulator (registered name) is destroyed by a voltage of only 12 kV.
  • the invention it is finally possible to significantly reduce the threshold for the appearance of sparks and therefore the destruction of the insulators.
  • the materials corresponding to the characteristics of the invention are for the most part very inexpensive, which allows their use in a number of high voltage electrical devices.

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  • Organic Insulating Materials (AREA)
  • Insulating Bodies (AREA)
EP94402648A 1993-11-23 1994-11-21 Elektrischer Hochspannungsvorrichtung mit hochfrequenz Isolator Withdrawn EP0654798A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9313990 1993-11-23
FR9313990A FR2713011B1 (fr) 1993-11-23 1993-11-23 Dispositif électrique de haute tension avec isolateur notamment en haute fréquence.

Publications (1)

Publication Number Publication Date
EP0654798A1 true EP0654798A1 (de) 1995-05-24

Family

ID=9453138

Family Applications (1)

Application Number Title Priority Date Filing Date
EP94402648A Withdrawn EP0654798A1 (de) 1993-11-23 1994-11-21 Elektrischer Hochspannungsvorrichtung mit hochfrequenz Isolator

Country Status (2)

Country Link
EP (1) EP0654798A1 (de)
FR (1) FR2713011B1 (de)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH537110A (de) * 1972-08-17 1973-05-15 Sprecher & Schuh Ag Metallgekapselte Hochspannungs-Schaltanlage
WO1993015512A1 (en) * 1992-01-29 1993-08-05 W.L. Gore & Associates, Inc. Coaxial electric signal cable having a composite porous insulation

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH537110A (de) * 1972-08-17 1973-05-15 Sprecher & Schuh Ag Metallgekapselte Hochspannungs-Schaltanlage
WO1993015512A1 (en) * 1992-01-29 1993-08-05 W.L. Gore & Associates, Inc. Coaxial electric signal cable having a composite porous insulation

Also Published As

Publication number Publication date
FR2713011A1 (fr) 1995-06-02
FR2713011B1 (fr) 1996-02-16

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