GB1603031A – Field effect devices for protection against over voltages
– Google Patents
GB1603031A – Field effect devices for protection against over voltages
– Google Patents
Field effect devices for protection against over voltages
Download PDF
Info
Publication number
GB1603031A
GB1603031A
GB13173/78A
GB1317378A
GB1603031A
GB 1603031 A
GB1603031 A
GB 1603031A
GB 13173/78 A
GB13173/78 A
GB 13173/78A
GB 1317378 A
GB1317378 A
GB 1317378A
GB 1603031 A
GB1603031 A
GB 1603031A
Authority
GB
United Kingdom
Prior art keywords
electrodes
primary
secondary electrodes
pair
pairs
Prior art date
1977-05-06
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
Application number
GB13173/78A
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.)
Italtel SpA
Original Assignee
Societa Italiana Telecomunicazioni Siemens SpA
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.)
1977-05-06
Filing date
1978-04-04
Publication date
1981-11-18
1978-04-04
Application filed by Societa Italiana Telecomunicazioni Siemens SpA
filed
Critical
Societa Italiana Telecomunicazioni Siemens SpA
1981-11-18
Publication of GB1603031A
publication
Critical
patent/GB1603031A/en
Status
Expired
legal-status
Critical
Current
Links
Espacenet
Global Dossier
Discuss
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
H01T4/10—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
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
H01T2/00—Spark gaps comprising auxiliary triggering means
H01T2/02—Spark gaps comprising auxiliary triggering means comprising a trigger electrode or an auxiliary spark gap
Description
(54) IMPROVEMENTS IN OR RELATING TO FIELD EFFECT
DEVICES FOR PROTECTION AGAINST OVER VOLTAGES
(71) We, SOCIETA ITALIANA
TELECOMUNICAZIONI SIEMENS
S.p.A., of Piazzale Zavattari 12, 20149
Milan, Italy, an Italian Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:
The present invention relates to devices for protection against over voltages. Such devices may be used, for instance, in radar systems, telecommunication lines, telesignalling lines, and circuits connected to them, and may comprise two electrodes arranged in a vacuum-sealed envelope devoid of radioactive elements and containing a gas.
Overvoltages occur along lines and across apparatus connected thereto owing to atmospheric conditions (lightning, static charges, etc.), accidental contact with, or induction due to, power transmission lines, or to other causes. Generally speaking, the most dangerous overvoltages occur along a telecommunication line and reach the terminals of the line which are generally formed by exchange apparatus, repeaters, user’s sets, etc. These overvoltages result in an electric discharge taking place, which causes damage to or malfunction of the line terminal.
To avoid such a drawback, gas-discharge protection devices are generally provided at the input of line terminals and connected to the line wires and to the earth. Such protection devices are designed to produce an electric discharge inside them when a voltage exceeding a predetermined threshold is present across the said wires.
These protection devices thus prevent the said overvoltages from reaching the line terminals, or at least ensure that overvoltages are attenuated to such a level that they are no longer dangerous for persons or for the apparatus. The above-mentioned deviced generally comprise at least two electrodes located in a vacuum-sealed envelope containing a low-pressure gas.
In the protection devices of known type, use is generally made of emission radioactive isotope designed to generate ioinic pairs in the gas contained in the envelope, such ion pairs facilitating discharge priming when overvoltages occur.
These protection devices have the disadvantage that, should the envelope break, the radioactive isotope escapes and thus contaminates the environment. This could constitute a source of danger for persons working near the protected apparatus.
Other solutions, also known, include the use of radioactive material to form at least part of the envelope (or to make radioactive at least part of the envelope). Protection devices in accordance with these solutions, although being in solid state, may become a source of risk for persons.
According to the invention there is provided a field-effect device for protecting against overvoltages, comprising at least one section disposed in an envelope containing a gas, the or each section comprising two primary electrodes and a pair of secondary electrodes arranged to generate an electric field between the secondary electrodes stronger than that existing between the primary electrodes, the secondary electrodes being provided in the same envelope in parallel via at least one capacitor with the primary electrodes, the secondary electrodes extending parallel to each other.
The invention will be further described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 illustrates a known type of protection device and its respective circuit diagram for the purpose of explaining the invention;
Figure 2 shows a Paschen curve for better illustrating the operation of the protection device of Figure 1; and
Figure 3 shows a circuit diagrams of a preferred embodiment of the invention.
Figure 1 shows a known type protection device comprising an envelope or vessel 1 through which pass two terminals 2 insulated from each other. The said terminals 2 are connected to a pair of primary electrodes 3 which are connected m parallel with a pair of secondary electrodes 4.
The secondary electrodes 4 are arranged between the said primary electrodes 3, thereby priming the ionization process in the gas present between the primary electrodes 3.
The operation of the above described protection device will be described with reference to the Paschen curve shown in
Figure 2.
The Paschen curve is characteristic of the type of gas used and of the material of which the electrodes are made. Such a curve is obtained by indicating, against a double logarithmical scale, in the abscissa the product of the distance d between two electrodes contained in a gaseous environment at a pressure p by the pressure itself, and in the ordinate the corresponding priming or breakdown voltage V across the two electrodes.
It will be noted that the priming or breakdown voltage V gradually decreases as the product p.d. decreases until it reaches a minimum value at the point A.
A further decrease in the product p.d.
results in the priming or breakdown voltage
V increasing again.
Since the said electrodes 3 and 4 are contained in the same envelope or vessel 1, the pressure p is the same for both of them, and thus it is possible to vary the priming voltage V by modifying only the distance d between each pair of electrodes.
Once the pressure p0 inside the envelope is known, the distance d2 between the primary electrodes 3 is chosen so that the said electrodes operate in the conditions indicated at A in the characteristic curve.
For the secondary electrodes, the working point is B which is determined by the product po.dl and the voltage V’.
The operating point A is characterized in that it has a negligible field-effect and a low priming voltage V. The operating point B is instead characterised in that it has a high field-effect and a priming voltage greater than the voltage at the point A.
Should an overvoltage with slow increase occur, the protection device operates under the conditions existing at the point A, and thus priming occurs between the said primary electrodes 3.
In the case of a rapidly increasing overvoltage, the primary electrodes, in the absence of ion pairs would prime with a delay such that part of the overvoltage impulse would pass through, which could result in damage to or malfunction of the line terminal downstream.
The usefulness of the said secondary electrodes 4 resides in that, when an overvoltage impulse has a value V’ such that
V’/d1 exceeds the emission threshold of the electrode material, electron emission occurs. In this condition, owing to acceleration due to the electric field, a sufficient number of ion pairs are generated to immediately prime a discharge between the secondary electrodes, or to facilitate a discharge between the primary electrodes. The secondary electrodes thus perform the function that in the conventional protection devices is performed by a radioactive isotope.
In order for electron emission from the secondary electrodes to occur at lower voltages V, the distance between the electrodes being the same, the electrodes may be coated with, or made of, an electropositive material or a high-emission material (e.g. caesium or rubidium).
The same results i.e. an abundant emission of electrons, may be obtained by increasing the strength of the electric field, by giving the secondary electrodes 4 a suitable configuration (such as pointed configuration), and/or a suitable surface treatment (e.g. shot-blasting).
In the above described protection device, a discharge due to an overvoltage impulse prevailingly occurs between the secondary electrodes 4. When the impulse energy involved is rather large, particularly when the secondary electrodes are covered with, or made of, low-melting material, the secondary electrodes could be destroyed or damaged. To avoid this drawback, according to the invention, the secondary electrodes 4 are connected to the primary electrodes 3 by way of a capacitative junction diagrammatically illustrated in the form of capacitors 5 in
Figure 3. Without departing from the scope of the invention, it is possible to limit the capacitative connection to one secondary electrode 4 only.
With reference to the diagram of Figure 3, the capacitors 5 limit the energy in the electric circuit in parallel with the primary electrodes 3.
In order not to negatively affect the discharge priming mechanism described above between the primary electrodes 3, it is necessary to effect a capacitative junction in such a way that the capacitance of the capacitors 5 is much higher than the capacitance between the secondary electrodes 4.
The voltage across the terminals 2 is distributed in a way inversely proportional to the capacitances of the members 4 and 5.
By way of example, if the said capacitors 5 have a hundred times the capacitance of the capacitor 4, the voltage across the secondary electrode 4 is about 98%, that applied across the terminals 2.
Protection devices have been described above, which comprise a pair of electrodes.
Without departing from the scope of the invention, it is possible to provide protection devices comprising a plurality of pairs of electrodes (e.g. multiple self-controlled discharges) by adopting the above described constructional and/or technological measures for each line electrode-earth electrode pair.
WHAT WE CLAIM IS:
1. A field-effect device for protecting against overvoltages, comprising at least one section disposed in an envelope containing a gas, the or each section comprising two primary electrodes and a pair of secondary electrodes arranged to generate an electric field between the secondary electrodes stronger than that existing between the primary electrodes, the secondary electrodes being provided in the same envelope in parallel via at least one capacitor with the primary electrodes, the secondary electrodes extending parallel to each other.
2. A device as claimed in claim 1, in which the secondary electrodes are separated from each other by a distance smaller than the distance between the primary electrodes.
3. A device as claimed in claim 1, in which the primary and secondary electrodes are coated with an electropositive material.
4. A device as claimed in claim 1, in which the primary and secondary electrodes are made of or coated with caesium or rubidium.
5. A device as claimed in claim 1, further comprising a plurality of line electrode-earth electrode pairs, a respective pair of secondary electrodes being connected via a respective at least one capacitor in parallel with each of the said pairs.
6. A device substantially as hereinbefore described, with reference to and as illustrated in Figure 3 of the accompanying drawings.
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (6)
**WARNING** start of CLMS field may overlap end of DESC **. By way of example, if the said capacitors 5 have a hundred times the capacitance of the capacitor 4, the voltage across the secondary electrode 4 is about 98%, that applied across the terminals 2. Protection devices have been described above, which comprise a pair of electrodes. Without departing from the scope of the invention, it is possible to provide protection devices comprising a plurality of pairs of electrodes (e.g. multiple self-controlled discharges) by adopting the above described constructional and/or technological measures for each line electrode-earth electrode pair. WHAT WE CLAIM IS:
1. A field-effect device for protecting against overvoltages, comprising at least one section disposed in an envelope containing a gas, the or each section comprising two primary electrodes and a pair of secondary electrodes arranged to generate an electric field between the secondary electrodes stronger than that existing between the primary electrodes, the secondary electrodes being provided in the same envelope in parallel via at least one capacitor with the primary electrodes, the secondary electrodes extending parallel to each other.
2. A device as claimed in claim 1, in which the secondary electrodes are separated from each other by a distance smaller than the distance between the primary electrodes.
3. A device as claimed in claim 1, in which the primary and secondary electrodes are coated with an electropositive material.
4. A device as claimed in claim 1, in which the primary and secondary electrodes are made of or coated with caesium or rubidium.
5. A device as claimed in claim 1, further comprising a plurality of line electrode-earth electrode pairs, a respective pair of secondary electrodes being connected via a respective at least one capacitor in parallel with each of the said pairs.
6. A device substantially as hereinbefore described, with reference to and as illustrated in Figure 3 of the accompanying drawings.
GB13173/78A
1977-05-06
1978-04-04
Field effect devices for protection against over voltages
Expired
GB1603031A
(en)
Applications Claiming Priority (1)
Application Number
Priority Date
Filing Date
Title
IT23269/77A
IT1115469B
(en)
1977-05-06
1977-05-06
FIELD-EFFECT DEVICE FOR OVERVOLTAGE PROTECTION
Publications (1)
Publication Number
Publication Date
GB1603031A
true
GB1603031A
(en)
1981-11-18
Family
ID=11205484
Family Applications (1)
Application Number
Title
Priority Date
Filing Date
GB13173/78A
Expired
GB1603031A
(en)
1977-05-06
1978-04-04
Field effect devices for protection against over voltages
Country Status (9)
Country
Link
BE
(1)
BE863395A
(en)
BR
(1)
BR7802133A
(en)
ES
(1)
ES467208A1
(en)
FR
(1)
FR2389994B1
(en)
GB
(1)
GB1603031A
(en)
IT
(1)
IT1115469B
(en)
NL
(1)
NL7802238A
(en)
NO
(1)
NO781561L
(en)
SE
(1)
SE7805024L
(en)
Cited By (3)
* Cited by examiner, † Cited by third party
Publication number
Priority date
Publication date
Assignee
Title
GB2200243A
(en)
*
1987-01-27
1988-07-27
English Electric Valve Co Ltd
Overvoltage protection device
DE19818674A1
(en)
*
1998-04-27
1999-10-28
Phoenix Contact Gmbh & Co
Surge protection element
DE102018133389A1
(en)
*
2018-12-21
2020-06-25
Phoenix Contact Gmbh & Co. Kg
Surge arresters
Families Citing this family (1)
* Cited by examiner, † Cited by third party
Publication number
Priority date
Publication date
Assignee
Title
IT1108971B
(en)
*
1978-02-16
1985-12-16
Sits Soc It Telecom Siemens
OVERVOLTAGE PROTECTION DEVICE
Family Cites Families (5)
* Cited by examiner, † Cited by third party
Publication number
Priority date
Publication date
Assignee
Title
GB353924A
(en)
*
1930-01-29
1931-07-29
Edison Swan Electric Co Ltd
Improvements in protecting devices for electric circuits
FR1052741A
(en)
*
1952-03-24
1954-01-26
Arc transfer surge arrester
CH313669A
(en)
*
1953-07-23
1956-04-30
Bbc Brown Boveri & Cie
Pre-ionized spark gap, especially for surge arresters
GB1085032A
(en)
*
1964-09-11
1967-09-27
English Electric Co Ltd
Improvements in or relating to protective spark gap devices
US3845345A
(en)
*
1973-07-05
1974-10-29
Gen Electric
Frequency sensitive preionizer
1977
1977-05-06
IT
IT23269/77A
patent/IT1115469B/en
active
1977-10-06
FR
FR7730048A
patent/FR2389994B1/fr
not_active
Expired
1978
1978-01-27
BE
BE184689A
patent/BE863395A/en
unknown
1978-02-22
ES
ES467208A
patent/ES467208A1/en
not_active
Expired
1978-03-01
NL
NL7802238A
patent/NL7802238A/en
not_active
Application Discontinuation
1978-04-04
GB
GB13173/78A
patent/GB1603031A/en
not_active
Expired
1978-04-06
BR
BR7802133A
patent/BR7802133A/en
unknown
1978-05-02
SE
SE7805024A
patent/SE7805024L/en
unknown
1978-05-03
NO
NO781561A
patent/NO781561L/en
unknown
Cited By (7)
* Cited by examiner, † Cited by third party
Publication number
Priority date
Publication date
Assignee
Title
GB2200243A
(en)
*
1987-01-27
1988-07-27
English Electric Valve Co Ltd
Overvoltage protection device
GB2200243B
(en)
*
1987-01-27
1990-09-05
English Electric Valve Co Ltd
Protection device
DE19818674A1
(en)
*
1998-04-27
1999-10-28
Phoenix Contact Gmbh & Co
Surge protection element
US6392862B1
(en)
1998-04-27
2002-05-21
Phoenix Contact Gmbh & Co.
Overvoltage protection element system
US6529360B2
(en)
1998-04-27
2003-03-04
Phoenix Contact Gmbh & Co.
Overvoltage protection element system
DE19818674B4
(en)
*
1998-04-27
2004-04-29
Phoenix Contact Gmbh & Co. Kg
Snubber
DE102018133389A1
(en)
*
2018-12-21
2020-06-25
Phoenix Contact Gmbh & Co. Kg
Surge arresters
Also Published As
Publication number
Publication date
SE7805024L
(en)
1978-11-07
FR2389994B1
(en)
1981-06-19
NL7802238A
(en)
1978-11-08
IT1115469B
(en)
1986-02-03
ES467208A1
(en)
1978-11-16
BE863395A
(en)
1978-05-16
NO781561L
(en)
1978-11-07
FR2389994A1
(en)
1978-12-01
BR7802133A
(en)
1979-05-29
Similar Documents
Publication
Publication Date
Title
US3710191A
(en)
1973-01-09
Overvoltage arrester with several electrodes
US2089555A
(en)
1937-08-10
Electrical discharge device
US3339112A
(en)
1967-08-29
Voltage limiting protective arrangement for high voltage power circuits
GB1603031A
(en)
1981-11-18
Field effect devices for protection against over voltages
US4680665A
(en)
1987-07-14
Gas discharge arrester
US3045143A
(en)
1962-07-17
Spark gap protector
US1962062A
(en)
1934-06-05
Electrical protective system
US20050063118A1
(en)
2005-03-24
Multipole overvoltage protection system and method for the reliable operation of a multipole overvoltage protection system
US2469215A
(en)
1949-05-03
Protective device
US3683234A
(en)
1972-08-08
Protective device comprising a plurality of serially connected spark gaps
EP0060530A1
(en)
1982-09-22
Electrical circuit protector
US1271794A
(en)
1918-07-09
Protective device.
US4029997A
(en)
1977-06-14
Surge voltage arrester arrangement
GB2179214A
(en)
1987-02-25
Surge voltage protection arrangement
US3393338A
(en)
1968-07-16
Surge suppressor for protecting a high voltage dc power circuit
US3411040A
(en)
1968-11-12
Voltage-fault absorbing device including gas tubes and carbon arrestors
US4375661A
(en)
1983-03-01
Overvoltage protection circuit for a television
US3760227A
(en)
1973-09-18
Gas tube protector having an internal fuse link
JPS5998488A
(en)
1984-06-06
Gas-filled arrester tube
US3353059A
(en)
1967-11-14
Series multiple spark gap switch with a triggering terminal
US3816802A
(en)
1974-06-11
Lightning arrester
US4924346A
(en)
1990-05-08
Gas discharge surge suppressor for a telephone line
US1966083A
(en)
1934-07-10
Lightning arrester
WO1985002723A1
(en)
1985-06-20
Balanced dual-gap protector
US2663817A
(en)
1953-12-22
Lightning arrester
Legal Events
Date
Code
Title
Description
1982-02-10
PS
Patent sealed [section 19, patents act 1949]
1982-11-03
PCNP
Patent ceased through non-payment of renewal fee
