EP0278612B1 - Protection device - Google Patents
Protection device Download PDFInfo
- Publication number
- EP0278612B1 EP0278612B1 EP19880300542 EP88300542A EP0278612B1 EP 0278612 B1 EP0278612 B1 EP 0278612B1 EP 19880300542 EP19880300542 EP 19880300542 EP 88300542 A EP88300542 A EP 88300542A EP 0278612 B1 EP0278612 B1 EP 0278612B1
- 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.)
- Expired
Links
Images
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 including a sealed chamber having a first conductor passing through it and a second conductor which constitutes part of the wall of the chamber, the two conductors together constituting an electrical transmission line having a substantially constant characteristic impedance.
- a protection device is known from GB-A 2 083 945. Protection devices of this kind are arranged to become conductive when a transient excess voltage appears between two electrodes which form part of it. Typically, 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 in which the first conductor is tapered so that it has a reducing cross section within the chamber, and the second conductor is shaped so that 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. 0.13 Pa (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 2666 Pa (20 Torr) to in excess of 1 bar (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 Q , 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)
Description
- This invention relates to a protection device including a sealed chamber having a first conductor passing through it and a second conductor which constitutes part of the wall of the chamber, the two conductors together constituting an electrical transmission line having a substantially constant characteristic impedance. Such a protection device is known from GB-A 2 083 945. Protection devices of this kind are arranged to become conductive when a transient excess voltage appears between two electrodes which form part of it. Typically, 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 in which the first conductor is tapered so that it has a reducing cross section within the chamber, and the second conductor is shaped so that 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.
- Advantageously, 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. However, 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.
- The invention is further described by way of example with reference to the accompanying drawings, in which:
- Figure 1 illustrates a transient protection device in accordance with the present invention, and
- Figure 2 shows a modification.
- Referring to the drawing, 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 achamber 4. An inner solid conductor 3 passes through thechamber 4 so formed and is sealed to the twoend 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 thechamber 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 ashaped 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 alead 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. 0.13 Pa (10-4) Torr after which the chambers are filled with 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 2666 Pa (20 Torr) to in excess of 1 bar (760 Torr). - During operation, it is assumed that a relatively modest potential difference exists between the two conductors 1 and 3 which is such so as not to cause electrical breakdown in the region 9. 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 thepower 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. - When a high voltage transient appears so as to raise the potential difference between the conductors 1 and 3 above a threshold value, electrical discharge in the region of the gap 9 occurs, and this breakdown is initiated by the presence of free electrons. It is the contribution and effect of these free electrons that ensures a reliable and very prompt breakdown. In the absence of any'free electrons, electrical breakdown would occur eventually, provided that the potential difference is large enough, but at a much slower and indeterminate rate.
- In order to ensure that the electrical breakdown occurs very rapidly indeed it is necessary that the gap 9 is small, and since the
chamber 4 is evacuated the spacing between the two conductors can be made much smaller within the chamber than it is possible to space the two conductors 1 and 3 in a normal atmosphere. Consequently, in order to permit the conductors to carry high frequency signals, the inner conductor 3 is also tapered so as to provide a constant impedance transmission line. By ensuring that the relative diameters of the conductor 3 and the conductor 1, as modified by theextension portion 8, is constant, then the characteristic impedance is preserved. A typical characteristic impedance is 50 Q , 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 theportion 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. - Instead of the gap 9, 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 chamber 22. Electrical breakdown occurs across thesurface 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 thechamber 22.
Claims (5)
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 EP0278612A1 (en) | 1988-08-17 |
EP0278612B1 true EP0278612B1 (en) | 1990-09-26 |
Family
ID=10611278
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19880300542 Expired EP0278612B1 (en) | 1987-01-27 | 1988-01-22 | Protection device |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0278612B1 (en) |
DE (1) | DE3860668D1 (en) |
GB (1) | GB2200243B (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH09120880A (en) * | 1995-10-26 | 1997-05-06 | Shinko Electric Ind Co Ltd | Lighting tube |
Family Cites Families (13)
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. |
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 |
GB895577A (en) * | 1958-06-30 | 1962-05-02 | Gen Electric Co Ltd | Improvements in or relating to gas filled electric discharge tubes |
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 (en) * | 1977-05-06 | 1986-02-03 | Sits Soc It Telecom Siemens | FIELD-EFFECT DEVICE FOR OVERVOLTAGE PROTECTION |
EP0044894B1 (en) * | 1980-07-30 | 1985-05-08 | Reliance Electric Company | Surge voltage arrester with ventsafe feature |
GB2083945B (en) * | 1980-09-19 | 1984-07-11 | M O Valve Co Ltd | Excess voltage arresters |
GB2095466B (en) * | 1981-03-25 | 1984-12-12 | M O Valve Co Ltd | Gas-filled excess voltage arresters |
FR2520951A1 (en) * | 1982-02-04 | 1983-08-05 | Commissariat Energie Atomique | ELECTROMAGNETIC PULSE GENERATOR OF HIGH VOLTAGE |
-
1987
- 1987-01-27 GB GB8701757A patent/GB2200243B/en not_active Expired - Lifetime
-
1988
- 1988-01-22 EP EP19880300542 patent/EP0278612B1/en not_active Expired
- 1988-01-22 DE DE8888300542T patent/DE3860668D1/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
EP0278612A1 (en) | 1988-08-17 |
GB8701757D0 (en) | 1987-03-04 |
GB2200243B (en) | 1990-09-05 |
DE3860668D1 (en) | 1990-10-31 |
GB2200243A (en) | 1988-07-27 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
Bloess et al. | The triggered pseudo-spark chamber as a fast switch and as a high-intensity beam source | |
US2331398A (en) | Electronic discharge device | |
US3702952A (en) | Gas tube surge protective device and method for making the device | |
GB1222841A (en) | A surge protection device | |
US4604554A (en) | Triggered spark gap discharger | |
US2373175A (en) | Electron discharge apparatus | |
GB1190957A (en) | Triggerable Vacuum Gap Devices | |
EP0278612B1 (en) | Protection device | |
US1930088A (en) | Electrical discharge device | |
US4293887A (en) | Surge arrester with improved impulse ratio | |
US3207947A (en) | Triggered spark gap | |
US3267321A (en) | Electron discharge device having cathode protective means within the envelope | |
US3818259A (en) | Gas-filled discharge tube for transient protection purposes | |
US3093766A (en) | Gas generating electric discharge device | |
US2457102A (en) | Spark gap | |
US3290542A (en) | Triggered vacuum discharge device | |
US4187526A (en) | Gas-Discharge surge arrester with concentric electrodes | |
US3581142A (en) | Triggered vacuum gap device with means for reducing the delay time to arc-over the main gap | |
US4126808A (en) | High voltage two stage triggered vacuum gap | |
JPS5998488A (en) | Gas-filled arrester tube | |
US3292049A (en) | Spark gap | |
US2790923A (en) | Gaseous electric discharge tubes and electrodes | |
US2422659A (en) | Spark gap discharge device | |
US3636407A (en) | Gas-discharge device with magnetic means for extinguishing the discharge | |
US4245197A (en) | Radar receiver protector with auxiliary source of electron priming |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): CH DE FR LI SE |
|
17P | Request for examination filed |
Effective date: 19880920 |
|
17Q | First examination report despatched |
Effective date: 19891114 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): CH DE FR LI SE |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: SE Effective date: 19900926 Ref country code: LI Effective date: 19900926 Ref country code: CH Effective date: 19900926 |
|
REF | Corresponds to: |
Ref document number: 3860668 Country of ref document: DE Date of ref document: 19901031 |
|
ET | Fr: translation filed | ||
REG | Reference to a national code |
Ref country code: CH Ref legal event code: PL |
|
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
26N | No opposition filed | ||
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Effective date: 19910930 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Effective date: 19911001 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST |