US 3688155 A
A reigniting spark gap for surge diverters with magnetic blowing has electrodes arranged on an insulating base. Each electrode has a spark gap part arranged in an extinguishing chamber and the spark gap parts of the electrodes diverge from an ignition point and the surfaces of the spark gap parts face each other and form running-out paths for the foot points of the arc arising between the electrodes. At least one of the two surfaces of the spark gap parts facing away from each other forms a return path for one foot point of an arc. The return path has an end point substantially opposite the ignition point. A channel connects the running-out path and the return path and forms a through-flow channel for ionized gas from the return path to the running-out path.
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Description (OCR text may contain errors)
United States Patent Johansson et al. 1 Aug. 29, 1972  REIGNITING SPARK GAP DEVICE  References Cited INCLUDING A FLOW-THROUGH mm CH EL 2 614 232 10/ 195 QaI E PATENTS 3/ ..31 156  Inventors: Bengt Johansson- Erland Nllsson I both of Ludvika weden 3,354,345 11/1967 Stetson ..3l7/74 X  Assignee: Allmnnna Svenska Elektriska Ak- Pn'mary Examiner-Roy Lake tiebolaget, Vasteras, Sweden Assistant ExaminerPalmer C. Demeo  Filed: June 17, 1971 Attorney-Jennings Halley, Jr.  Appl. No.: 154,049  ABSTRACT Related s. Aplmcafion Data A reigniting spark gap for surge diverters with mag- I netic blowing has electrodes arranged on an insulating  Contmuatton-m-part of Ser. No. 9,706, Feb. 9, base Each electrode has a spark gap pan arranged in 1970 abandmedan extinguishing chamber and the spark gap parts of the electrodes diverge from an ignition point and the  Forelgn Appllcauon Pnonty Data surfaces of the spark gap parts face each other and Feb. 21, 1969 Sweden ..2398/69 form rumihgeut Paths for the feet points of the are arising between the electrodes. At least one of the two 52 US. Cl.; ..315/36, 313/155, 313/231, surfaces of the spark p parts facing ay from each 317 74 317 77 other forms a return path for one foot pomt of an arc. 51 int. Cl .1101, 7/44, H02h 9/06 e return p th h end P subetehtlally 1  Field of Search ..315/36; 313/155, 161, 231, p e the lgmtlen p A channel connects the 3 3 5; 3 7 9 7 77 runmng-out path and the return path and forms a through-flow channel for ionized gas from the return path to the running-out path.
a claims, 2
PATENTEDmsza m2 m/awoa save-r cram 0 BY N ERLAND A/ILSsoA/ REIGNITING SPARK GAP DEVICE INCLUDING A FLOW-THROUGH CHANNEL This application is a continuation-in-part of application Ser. No. 9,706, filed Feb. 9, 1970, and now abandoned.
BACKGROUND OF THE INVENTION 1. Field of the Invention In surge diverters which are arranged to protect installations where long duration over-voltages may arise it may be necessary to have spark gaps which give low voltage drop during the diverting process so that the heating in the spark gap will be low.
SUMMARY OF THE INVENTION The present invention relates to a reigniting spark gap for surge diverters with magnetic blowing. The surge diverter is built up of a number of spark gaps each comprising two electrodes arranged on a plate of insulating material and the plates are axially juxtaposed and thereby the two electrodes which are arranged on one side of the plate will be enclosed between two adjacent plates. The spark gap is designed so that a controlled reignition of the arc is obtained. By the influence of the magnetic blowing, the arc is extended and when it has reached a certain position it effects a reignition of the spark gap. The reignited arc is considerably shorter and thus has a lower voltage drop than the extended are, which means that the extended arc is extinguished and the reignited arc takes over the current conduction. This phenomenon is repeated until the current is so low that reignition cannot take place.
BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 of the accompanying drawing show two embodiments of a spark gap according to the invention. The two variants differ only in the position of the through-flow channel.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The spark gap is constructed on a circular plate 1 of ceramic material. The plate has two electrodes 3, 4, each comprising an attachment part 5 and a spark gap part 6. The plate has also an inset part 2 on at least one side.
As is well known, a surge diverter is composed of a number of axially juxtaposed plates with spark gaps and an inset part on at least one side. When two plates are placed close to each other there will be a closed arc extinguishing chamber between them in which the arc is lengthened and suppressed. If the plate has an inset part on only one side and the other side is flat, the volume of the extinguishing chamber will be about the same as the volume of the inset, but if the plate has an inset part on each side the volume of the extinguishing chamber will be about twice the volume of the inset part. In the last case it is not necessary for the two inset parts to be exactly opposite each other when the two adjacent plates are in place. On the contrary, the suppressing effect on the arc may be increased if the two facing inset parts are more or less displaced in relation to each other.
The spark-gap parts diverge from an ignition point 7 and the surfaces 8 and 9 of the spark gap parts facing each other form running-out paths for the foot points 11 and 12 of the are 10 arising between the electrodes. The surfaces 13 and 14 of the spark-gap parts facing away from each other form return paths for the foot points of the are when the are, under the influence of the magnetic blowing, has been extended so much that its foot points 11 and 12 have passed the top of the electrodes.
Between the return path and the running-out path of each electrode is a channel 15, 16, respectively, which forms a through-flow channel for ionized gas. The channel may be in the form of a groove in the plate 1 and is then covered on one side by the spark gap part 6. The channel according to another embodiment may be in the form of a hole bored through the electrode so that the channel is completely within the electrode material.
FIG. 1 shows that the channel opens into or in the immediate vicinity of the ignition point 7 where the arc ignites when the spark gap comes into operation. FIG. 2 shows that the channel opens further up on the running-out path at a reignition point 17.
The spark gap operates in the following way: When the voltage rises above the ignition voltage determined for the gap, there is a spark-over between the electrodes at the ignition point 7. Because of the magnetic blowing, which is perpendicular to the plane of the plate, the arc is forced upwards and increases in length. If the current has sufliciently long duration the foot points of the arc are moved up the surfaces 8 and 9, pass the top of the spark gap parts 6 and continue on the return paths 13 and 14, respectively. All the time the arc presses ionized, hot gas in front of it and, when the foot points of the are come near to the channels 15 and 16, respectively, the gas rushes into the channels towards the openings of the channels into the runningout paths. In this position the arc has increased its length and the arc voltage drop has thus also increased.
When the hot and ionized gas reaches the ignition point 7 or reigiition point 17, the strength there drops to a value which is lower than the arc voltage drop. The result is that the gap reignites and the current flows through the reignited arc, whereupon the primary, extended arc will grow in the same way as the arc first ignited and the process is repeated until the current has dropped to such a low value that the gas current through the channel 15 is not sufi'iciently great to cause reignition, the arc is extinguished and the current finally broken.
It is clear from the method of operation described that the operation of the spark gap is controlled by the current through the gap. At high current a strong gas flow is driven from the are through the gas channel to the ignition point and the gap reignites rapidly. With lower currents the gas flow is weaker and finally too weak to cause reignition so that the arc can be blown out completely and can extinguish the remaining current.
In certain cases it may be suflicient to arrange a return flow channel on only one of the electrodes. Such a gap will not be so rapid in reignition, since the reignition point receives gas from only one direction. In certain cases, however, such a gap may be more suitable. In such a gap both the electrodes may be alike, as shown in the drawings, or one of the electrodes may have no return path so that the foot point of the are on this electrode stops at the top of the electrode and only the other base follows a running-out path and effects reignition.
A reigniting spark gap according to the invention gives low voltage drop at the diverting current. This means that the gap takes up a negligible amount of energy and therefore, and because the arc is always moving, the extinguishing capacity of the gap is maintained even over long periods of operation.
1. Reigniting spark gap for surge diverters comprising a number of axially juxtaposed plates, each plate having two electrodes forming said spark gap, each plate having means forming an arc extinguishing chamber between two adjacent plates, each electrode having a spark gap part (6) arranged in said extinguishing chamber (2), the spark gap parts of the electrodes diverging from an ignition point (7) and the surfaces (8, 9) of the spark gap parts facing each other forming running-out paths for the foot points of the arc arising between the electrodes, at least one of the two surfaces (13, 14) of the spark gap parts facing away from each other forming a return path for one foot point of an arc, which return path has an end point substantially opposite the ignition point, and a channel (15, 16) connecting the running-out path and the return path and forming a through-flow channel for ionized gas from the return path to the running-out path.
2. Spark gap according to claim 1, in which the two electrodes are alike and each is provided with both a running-out path and a return path.
3. Spark gap according to claim 1, in which the electrodes are different and both the electrodes have running-out paths, whereas only one electrode has a return path.
4. Spark gap according to claim 1, in which the channel (15, 16) from the return path opens into the running-out path in the vicinity of the ignition point (7 5. Spark gap according to claim 1, in which the channel (15, 16) from the return path opens into the running-out path at a reignition point (17) located at a distance from the ignition point.
6. Spark gap according to claim 1, in which the channel is formed in the electrode material.
7. Spark gap according to claim 1, in which the channel is formed in the insulating base.
8. Spark gap according to claim 1, in which the chan nel has one end at the end point and it is limited partly by the insulating base and partly by the electrode material, the electrode material providing a runningout path for the foot point of the arc.