EP0278612A1 - Schutzvorrichtung - Google Patents

Schutzvorrichtung Download PDF

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Publication number
EP0278612A1
EP0278612A1 EP88300542A EP88300542A EP0278612A1 EP 0278612 A1 EP0278612 A1 EP 0278612A1 EP 88300542 A EP88300542 A EP 88300542A EP 88300542 A EP88300542 A EP 88300542A EP 0278612 A1 EP0278612 A1 EP 0278612A1
Authority
EP
European Patent Office
Prior art keywords
chamber
conductor
protection device
conductors
section
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.)
Granted
Application number
EP88300542A
Other languages
English (en)
French (fr)
Other versions
EP0278612B1 (de
Inventor
David John Mellor
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.)
Teledyne UK Ltd
Original Assignee
English Electric Valve Co Ltd
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 English Electric Valve Co Ltd filed Critical English Electric Valve Co Ltd
Publication of EP0278612A1 publication Critical patent/EP0278612A1/de
Application granted granted Critical
Publication of EP0278612B1 publication Critical patent/EP0278612B1/de
Expired legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T4/00—Overvoltage arresters using spark gaps
    • H01T4/08—Overvoltage arresters using spark gaps structurally associated with protected apparatus
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T4/00—Overvoltage arresters using spark gaps
    • H01T4/10—Overvoltage arresters using spark gaps having a single gap or a plurality of gaps in parallel
    • H01T4/12—Overvoltage arresters using spark gaps having a single gap or a plurality of gaps in parallel hermetically sealed

Definitions

  • This invention relates to a protection device of the kind which is arranged to become conductive when a transient excess voltage appears between two electrodes which form part of it.
  • a protection device of the kind which is arranged to become conductive when a transient excess voltage appears between two electrodes which form part of it.
  • such a device is to withstand a large potential difference without breaking down into conduction between the two electrodes, but it can be brought rapidly into conduction when required so that typically a current of several thousand amps can flow between the two electrodes for a short period.
  • a device of this kind can be used to protect relatively delicate electronic equipment or the like from the effect of transient over-voltages which can be induced onto the conductors by external events.
  • the invention provides a protection device including a sealed chamber having a first conductor projecting into it; a second conductor which constitutes part of the wall of the chamber; the first conductor being tapered so that it has a reducing cross section within the chamber, and the second conductor being shaped so that the two conductors together constitute an electrical transmission line having a substantially constant characteristic impedance and so that the distance between the two conductors is least in the region of smallest cross section of the first conductor.
  • a rise in potential difference between the two conductors above a threshold value causes electrical breakdown to occur between them.
  • the shaping of the conductors to provide an electrical transmission line of substantially constant characteristic impedence enables the protection device to handle the transmission of high frequency signals without causing reflections which would result from variation in line impedence.
  • a radioactive source or a separate chamber region connecting with the first chamber and having a source of free electrons, is provided to release electrons into the chamber in a controlled manner.
  • the source of free electrons is such that electrons are released into that region of the chamber where electrical discharge between the two conductors is to be achieved at a reasonably slow rate so as not to initiate breakdown below the desired threshold value.
  • the release of electrons should be sufficiently large to ensure that there is always at least one free electron in the vicinity of the discharge region so as to promptly initiate discharge the moment an over-voltage occurs.
  • a first envelope consists of an outer cylindrical wall 1 formed of an electrically conductive material carrying a circular disc 2 at each end, these discs being formed of an electrically insulating material such as ceramic and being sealed around their outer peripheral edges to the wall 1 to enclose a chamber 4.
  • An inner solid conductor 3 passes through the chamber 4 so formed and is sealed to the two end discs 2 where it passes through them.
  • the central inner conductor 3 is a relatively robust and substantial conductor but it is of tapered section within the chamber 4, tapering smoothly to a mid-point 5 which is adjacent to an opening 6 in a second chamber 7.
  • the inner walls of the outer conductor 1 are provided with a shaped portion 8 which is dimensioned to form a relatively small gap 9 in the region of the opening 6.
  • a typical dimension for gap 9 is 0.5 mm.
  • the second chamber 7 constitutes a source of free electrons and it consists of a conductive outer wall 10 having an inner central electrode 11 which is connected via a lead 12 to a d.c. power supply 13.
  • the two chambers 4 and 7 are, of course, inter­connected via the opening 6 but both are hermetically sealed from the atmosphere.
  • the chambers are initially evacuated to a fairly high level of vacuum, e.g. 10 ⁇ 4 Torr after which the chambers are filled with an inert gas, such as argon or neon or a mixture of these.
  • an inert gas such as argon or neon or a mixture of these.
  • the gas type and pressure are chosen to determine the breakdown voltage, but the pressure is expected to be in the range 20 Torr to in excess of 760 Torr.
  • Electrons are generated at the second chamber 7, particularly in the region of the opening 6 where an electron plasma exists. Free electrons from this plasma are randomly distributed in the region of the opening 6 and the gap 9, but it is arranged that the electron density is very low indeed, in principle it being sufficient to ensure that at least one free electron exists within the gap at any one time.
  • the electron plasma is generated by striking a glow discharge between the electrodes 10 and 11 under the action of the power supply 13. The resulting ions as well as the electrons assist in the rapid electrical breakdown.
  • the d.c. current in the glow discharge is typically of the order of a few tens of microamps.
  • the inner conductor 3 is also tapered so as to provide a constant impedance transmission line.
  • a typical characteristic impedance is 50 ⁇ , with the maximum diameter of the conductors 1 and 3 being 10 mm and 4.35mm respectively, reducing to 1.84 mm and 0.8mm respectively in the region of the gap 9.
  • the provision of the tapered section greatly enhances the reliability and speed of operation and for certain applications the free electon source may not always be necessary.
  • the two conductors 1 and 3, together with the portion 8, therefore constitute an electrical transmission line having a characteristic impedance which does not alter at different points along the conductors. This enables the protection device to handle the transmission of high frequency signals without causing signal reflections which would result from variations in the line impedance.
  • the benefit of the tapered conductor sections to give a constant characteristic impedance can also be obtained with a conventional radioactive source of electrons and/or ions, such as Tritium or other radioactive isotope.
  • one of the insulating discs can be placed at the point where the separation between the two electrodes is least.
  • Such an arrangement is shown in Figure 2, in which two insulating discs 20 and 21 are provided to define the walls of a gas filled chamber 22. Electrical breakdown occurs across the surface 23, and a cathodic electron source can be included (in a manner similar to Figure 1) to initiate electrical breakdown, or a radioactive isotope can be included in the gas which fills the chamber 22.

Landscapes

  • Emergency Protection Circuit Devices (AREA)
EP19880300542 1987-01-27 1988-01-22 Schutzvorrichtung Expired EP0278612B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8701757A GB2200243B (en) 1987-01-27 1987-01-27 Protection device
GB8701757 1987-01-27

Publications (2)

Publication Number Publication Date
EP0278612A1 true EP0278612A1 (de) 1988-08-17
EP0278612B1 EP0278612B1 (de) 1990-09-26

Family

ID=10611278

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19880300542 Expired EP0278612B1 (de) 1987-01-27 1988-01-22 Schutzvorrichtung

Country Status (3)

Country Link
EP (1) EP0278612B1 (de)
DE (1) DE3860668D1 (de)
GB (1) GB2200243B (de)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09120880A (ja) * 1995-10-26 1997-05-06 Shinko Electric Ind Co Ltd 避雷管

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB191328894A (en) * 1913-12-15 1914-05-28 Western Electric Co Ltd Improvements in Vaccum Lightning Arresters.
GB895577A (en) * 1958-06-30 1962-05-02 Gen Electric Co Ltd Improvements in or relating to gas filled electric discharge tubes
GB2083945A (en) * 1980-09-19 1982-03-31 M O Valve Co Ltd Excess Voltage Arresters

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB378059A (en) * 1931-04-02 1932-08-02 Jakob Bader Device to prevent lag of spark between electrodes
GB666414A (en) * 1949-01-18 1952-02-13 Ferranti Ltd Improvements relating to electric spark discharge devices
GB853192A (en) * 1957-03-29 1960-11-02 British Thomson Houston Co Ltd Improvements in and relating to enclosed spark gaps
US3290542A (en) * 1963-07-26 1966-12-06 Gen Electric Triggered vacuum discharge device
US3845345A (en) * 1973-07-05 1974-10-29 Gen Electric Frequency sensitive preionizer
US3949260A (en) * 1975-04-14 1976-04-06 Hughes Aircraft Company Continuous ionization injector for low pressure gas discharge device
IT1115469B (it) * 1977-05-06 1986-02-03 Sits Soc It Telecom Siemens Dispositivo ad effetto di campo per la protezione da sovratensioni
EP0044894B1 (de) * 1980-07-30 1985-05-08 Reliance Electric Company Überspannungsableiter mit Betriebssicherheitsvorrichtung im Falle eines Gaslecks
GB2095466B (en) * 1981-03-25 1984-12-12 M O Valve Co Ltd Gas-filled excess voltage arresters
FR2520951A1 (fr) * 1982-02-04 1983-08-05 Commissariat Energie Atomique Generateur d'impulsions electromagnetiques de haute tension

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB191328894A (en) * 1913-12-15 1914-05-28 Western Electric Co Ltd Improvements in Vaccum Lightning Arresters.
GB895577A (en) * 1958-06-30 1962-05-02 Gen Electric Co Ltd Improvements in or relating to gas filled electric discharge tubes
GB2083945A (en) * 1980-09-19 1982-03-31 M O Valve Co Ltd Excess Voltage Arresters

Also Published As

Publication number Publication date
EP0278612B1 (de) 1990-09-26
GB2200243A (en) 1988-07-27
GB8701757D0 (en) 1987-03-04
GB2200243B (en) 1990-09-05
DE3860668D1 (de) 1990-10-31

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