US3072815A - Spark gap arrangement for surge arresters - Google Patents

Description

Filed Oct. 5. 1960 Jan. 8, 1933 w. MKCHLER ETAL 3,072,815

SPARK GAP ARRANGEMENT FOR SURGE ARRESTERS 4 Sheets-Sheet 1 INVENTORS Werner NdchLe h clhelm ZoLler P- IJJWEJOMM ATTORNEYS 8, 1963 w. MACHLER ETAL Y 3,072,

SPARK GAP ARRANGEMENT FOR SURGE ARRESTERS Filed Oct. 5, 1960 4 Sheets-Sheet 2 I 1 I I I i x i jfi ki gfim ATTORNEY .S

Jan. 8, 1963 ;w. MACHLER ETAL 3,072,815

SPARK GAP ARRANGEMENT FOR SURGE ARRESTERS 4 Sheets-Sheet Filed Oct. 5, 1960 Werner N'achlr wL-zhem Z0146 .BY/P. J

I fwfmk Jan. 8, 1963 w. MKCHLER ETAL 3,072,815

SPARK GAP ARRANGEMENT FOR sum: ARRESTERS 4 Sheets-Sheet 4 Filed Oct. 5, 1960 Werner NdchLer Wilhelm Z l BYP 02%., wk J A'fORNEYs ning, etc. But due to the reduced 7 Filed Oct. 5, 1960, Ser. No. 60,611

Claims priority, application Switzerland Oct. 6, 1959 5 Claims. (Cl. 313-161) In connection with surge voltage arresters with a multiple spark gap and voltage-dependent resistors, increasingly lower sparkover voltages and lower residual voltages are being demanded, corresponding to the different specifications in the various countries. But with. use of lower sparkover voltages it is possible to deal with over-voltages occurring in the circuit as well as voltages caused by lightratio of sparkover voltage and the recovery voltage, the requirements, which the spark gaps have to meet with regard to the restrike voltage, also increase. The protective level is reduced by the 'low residual voltage, which reduces the costs of the in- -sulation of the apparatus. The low residual voltage can be achieved, on the one hand, by improving the voltage dependent resistors, and on the other hand, by reducing the amount of resistance. .;l 1igher'- follow-current. age. with a greater-follow-current naturally results in fresh But this must be paid for by a The required higher restrike voltrequirements for the spark gaps which the conventional plate-spark; gaps do not meet. As a suitable measure for increasing the extinguishing capacity of the spark gaps, .a method where the'follow-current arc is allowed to migrate from its origin under the influence of a magnetic blast field is used to an increasing extent. The blast field can be produced by causing the follow-current to take a suitable course in the electrodes, or by blast coils through which the follow-current flows, or by permanent magnets. Recently, the migration of the arc has been accompanied by an extension of the arc. The resulting high voltage above the arc reduces the follow-current and'thus relieves A the resistors. Thepresent invention relates to a spark gap arrange ment for surge arresters with voltages-dependent resistors gandmagnetic blast field, where the spark gaps consists of a number of axially stacked plates of insulation material,

..which"are'provided'on each side with an electrode and -whereby in eachcase an electrode on one plate together with an electrode on an adjacent plate forms-a spark gap. With this spark gap arrangement it is possible to extinguish several hundred amperes of follow-current with a high restrike voltage. At the same time, use is also made of the relief of the resistors by an extension of the arc, The spark gaps should act in closedchambers, so that acompact arrangement is possible in the arrester insulator, without increasing the danger of a breakdown in the interior of the insulator by are gases.

According to the invention the foregoing conditions are met in this way, that the two electrodes belonging to a plate extend from the center of the plate to the edge, and consist of one piece, which is inserted and fixed laterally in a slot of the plate, the entrance of the slot being closed by projections on the circumference of the adjacent plates above and underneath, and that the plates are provided with gas channels, which permit the circulation of gas from the arc of a spark gap through the plate to the sparkover distance of the spark gap above and underneath.

The invention will be described more fully on the basis of the embodiments represented in the attached figures.

FIG. 1 is a schematic representation of an active ele- United States Patent different arrangement ment of a high voltage arrester with magnetically blasted spark gaps.

FIG. 2 is a similar representation as FIG. 1, but with a of the blast coils.

FIG. 3 shows an active element of the arrester with magnetically blasted spark gaps, partly in a section and partly in an elevation.

FIG. 4 is a top view of one of the insulating plates of the spark gap.

FIG. 5 is a section along the line V-V of FIG. 4.

FIG. 6 is a top view of an insulating plate of the spark gaps with built-in electrodes.

FIG. 7 is a section along the line VII-VII of FIG. 6.

'FIGS. 8 and 9 are a top view and section respectively of one of the electrode elements.

FIG. 10 shows a stack of spark gaps in the disassembled state. I

The active part of the surge arrester consists of the voltage-dependent resistors 1 and the stack of spark gaps 2 which are connected between a high voltage line 7 and the ground 8, as it can be seen from FIGS. 1-2. The resistors 1 have the function, as known, of limiting the follow-current, while the spark gaps 2, interrupt the follow-current. In order to increase the quenching capacity of the spark gaps 2, the follow-current arc in the spark gaps in blown away from its place of origin by a magnetic field, the migration of the arc resulting at the same time in an extension of the latter. The arc voltage thus achieved helps to reduce the follow-current, so that the height of theresistance stack canbe reduced, which has a favorable effect on the residual voltage. The blast field is produced on the one hand by a screw-shaped guidance of the current in the spark gaps, and on the other hand by the additional blast coils 3, the two blast fields assisting each other during the entire extinguishing process.

The blast coils 3, can be arranged at both ends of the stack of spark gaps 2, in series with the latter, as shown in FIG. 1, or they can extend as a unit around the entire stack of gaps (FIG. 2). Since the blast coils 3 have a relatively high inductivity, a nonlinear element must be connected in parallel to by-pass the surge-current with steep wave front. This can be a voltage-dependent resistor block, for example, also a resistor stack 1. In the present case, a spark gap 4, connected in parallel to the blast coil 3 is used, which has the advantage, compared to the resistance block, that it produce no additional residual voltage. This spark gap 4 can be built exactly like the extinguishing spark gap 2. For constructional reasons, however, a slightly modified form may be used, which will be described later. The spark gap 4 in parallel with the blast coil is also blasted magnetically, which has the advantage that the arc in the spark gap 4, can be extinguished much faster, due to its migration and extension. The current rises thus faster in the blast coil 3, which results in a rapid buildup of the blast field thus increasing the extinguishing effect.

The spark gap 2, consists of a number of identical spark gaps whose construction can be seen from FIGS. 3 to 9. Each spark gap has a round insulating plate 5 which consists of pressable material and which has a high electric strength, a high creeping strength, good heat stability and high mechanical strength. The plate 5, is provided with a slot 6 (FIG. 4), into which are inserted the two electrodes 24, made of one piece and belonging to one plate. FIG. 6 shows the plate 5 with electrodes 24 inserted, while FIGS. 8 and 9 respectively show the double electrode 24 alone in an elevation and section respectively. To fasten the electrodes 24, the plate 5 is provided on each side with a boss 23, which fits into the holes 9 provided in the electrodes. In the center of the plate 5 are provided, on both sides, depressions 10, which serve to increase the creep path between the two electrodes of a 3 spark gap. On the electrodes 24 are attached metal tongues 22 (FIG. 6), which press against the counterplate after the spark gaps have been assembled. These tongues 22 serve to pre-ionize the spark gaps.

The slot 6 widens toward the edge of the plate 5 in the opening 11. This opening is closed toward the outside by the bosses or projections 12 of the plates which lie above and underneath during the stacking, and is subdivided in the interior into two parts 20 and 21 (FIGS. 6 i

and 7). These bosses 12, serve at the same time to fix the insulating plates 5, so that mutal turning is prevented. The plate 5 is provided with an elevated edge 13, so that when the plates are assembled, spark chambers 14 are formed which are closed toward the outside, and the stacked plates are secured at the same time against lateral displacement. Due to the wider elevations 15, gas channels are formed on the plates (FIGS. 6 and 7).

The construction of the blast coils and of the respective spark gaps can be seen from FIG. 3, which shows an arrester, partly in a section. The voltage-dependent resistors 1 and the above described stack of spark gaps 2, are arranged in known manner in an insulator case 30. The blast coil 3, provided at each end of the stack of spark gaps 2, is attached on a coil form which consists of two parts 16 and 17, the plate-shaped part being made preferably of the same heat-resistant insulating material as the plates 5 of the quenched spark gap 2. The spark gap 4, which is connected in parallel to the blast coil, is formed by an electrode of the same form as that of the quenched spark gaps, and of a copper tube 18 which is embedded in the coil form 16, 17. This tube 18 acts at the same time as a connection from the spark gap 4 to the contact plate 19, which serves as an electric connection to the elements bearing on the stack of spark gaps 2. The entire spark gap arrangement is under the action of the compression spring 3-1.

FIG. shows the various main parts of a stack of spark gaps corresponding to the arrangement in FIG. 1, in the order of their assembly, namely, from the top to the bottom, starting from the left, the upper blast coil 3, the respective spark gap 4, the extinguishing spark gap 2, the lower spark gap 4 and the lower blast coil 3, as well as the voltage-dependent resistance 1. The various spark gaps 2 are formed during the stacking of two insulating plates 5 from the lower electrode of the upper plate and the upper electrode of the lower plate. When stacking completely identical plates 5, the latter are turned each by 90 so that the two electrodes 24 forming a spark gap form an angle of 90. In this way an arc space is formed between two adjoining plates, which extends over about 270 and of the plate cross section respectively.

The method of operation of the spark gap is as follows: The electric surge causes an arc to strike across the spark gap, the spark-over point being located in the center of the insulating plate 5, or a little outside thereof in the direction of the arc space. The follow-current maintains the arc and produces in the magnet coils a blast field under whose influence the arc moves to the edge of the arc chamber 14. The moving arc displaces the gas in the chamber 14 through the opening 20 of the lower plate downward and through the opening 21 of the upper plate upward (see FIG. 7). After passing through the openings 20 and '21, the gases flow through the channels 26 to the sparkover points of the upper and lower spark gaps and consolidate them electrically.

In the arrangement according to the invention a pressure equalization is achieved between the spark gap chambers, so thatall arcs travel uniformly. The are blow each other out. There is also the additional advantage that, right after the start of the migration of the arc, the characteristic field, produced by the screw-like flow of the current in the electrodes, supports the magnetic fields produced by the blast coils. In addition, the pressure which is formed by high current impulses, is offset by the superposed sparkover distances. Besides, the inductivity is very low during the flow of the discharge current and has a favorable effect on the residual voltage.

We claim:

1. Spark gap arrangement for surge arresters with voltage-dependent resistors and magnetic blast field, where the spark gap comprises a plurality of axially stacked plates of insulating material, which have an electrode on each side, one electrode of one plate forming a spark gap with the electrode of the adjoining plate; characterized in that the two electrodes which belong to one plate and which extend from the plate center to the edge, are made of one piece, which is inserted from the side into a slot of the plate and fixed there, the entrance of the slot being closed by projections on the circumference of the adjacent plates above and underneath, and that the plates are provided with gas channels which permit the circulation of gas from the arc of a spark gap, through the plate behind to the sparkover distance of the spark gap above and underneath.

2. Spark gap arrangement according to claim 1, characterized in that the plates are stacked, offset by each, so that the arc extends over 270 in the various chambers formed between adjoining plates.

3. Spark gap arrangement according to claim 1, characterized in that a blast coil is connected in series at each end of the stack of spark gaps, to which one spark gap each is connected in parallel, said parallel connected spark gaps being of the same construction as the other spark gaps of the arrester.

4. Spark gap arrangement according to claim 1, characterized in that the stack of spark gaps is surrounded by a blast coil which is connected in parallel to one of the spark gaps of the stack.

5. Spark gap arrangement according to claim 1, characterized in that the electrodes are provided each with a preionizing element which presses against the adjoining insulating plate.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. SPARK GAP ARRANGEMENT FOR SURGE ARRESTERS WITH VOLTAGE-DEPENDENT RESISTORS AND MAGNETIC BLAST FIELD, WHERE THE SPARK GAP COMPRISES A PLURALITY OF AXIALLY STACKED PLATES OF INSULATING MATERIAL, WHICH HAVE AN ELECTRODE ON EACH SIDE, ONE ELECTRODE OF ONE PLATE FORMING A SPARK GAP WITH THE ELECTRODE OF THE ADJOINING PLATE, CHARACTERIZED IN THAT THE TWO ELECTRODES WHICH BELONG TO ONE PLATE AND WHICH EXTEND FROM THE PLATE CENTER TO THE EDGE, ARE MADE OF ONE PIECE, WHICH IS INSERTED FROM THE SIDE INTO A SLOT

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