EP1911134B1 - Spark-discharge gap - Google Patents

Description

The invention relates to a spark gap, in particular for the protection of supply lines or AC networks against lightning.

Spark gaps as protective elements against overvoltages are known per se. That's how it describes WO 2004/017479 A1 a hybrid overvoltage protection element in which a varistor and a surge arrester are connected in parallel. Also in JP 04065087 . JP 61281489 . JP 03121694U . DE 4318994 Surge protection elements are described. EP-A-0251010 discloses a spark gap according to the preamble of claim 1.

Especially in devices of network protection, there is a need to improve the properties of such elements, in particular with regard to the current carrying capacity and the quenching behavior. Basically suitable for use at high currents and voltages are air gaps with triggering device, which are complex, expensive and bulky.

The invention has for its object to provide an improved spark gap, especially in a compact design, with stable connection electrodes with good leadership properties, which is suitable for high current loads.

The invention solves the problem with the features of independent claim 1. Embodiments of the invention are characterized in dependent claims.

In a first embodiment of the invention, a spark gap with a cavity is proposed which is comprised of two terminal electrodes and an electrical insulator arranged therebetween. The spark gap points a protruding into a tube electrode pin electrode and cavity-side indentations or bulges of the terminal electrodes and a guide of the terminal electrodes by means of beads on the inner wall of the insulator.

This embodiment has an extremely compact construction of the spark gap with excellent overall properties. The terminal electrodes terminate the insulator at the end and together with the latter form the cavity. From the respective edge-side transition region of the connection electrodes to the insulator, bulges of the connection electrodes extend into the cavity.

In the production of this very compact spark gap, it is thereby possible for the electrodes carrying the spark discharge to be adapted very precisely to these and their bulges, both with regard to the materials used and with regard to their connection to the terminal electrodes. In addition, it is possible to connect connecting pins provided as external connections of the spark gap within the bulges with the connection electrodes in order to obtain an even more compact construction and a further optimized material adaptation.

The beads in the bulges also allow a precise and secure guidance of the terminal electrodes on the inner wall of the insulator. The connection electrodes and the insulator can therefore be adjusted very precisely to each other even in a miniaturized spark gap during assembly. It is even possible to connect the terminal electrodes self-aligned with each other with the insulator.

In one embodiment, a spark gap is provided with a cavity which is comprised of two connection electrodes and an electrical insulator arranged therebetween. The spark gap has a stylus projecting into a tube electrode and stiffening electrodes, which are each connected to one of the terminal electrodes.

This embodiment has an extremely compact construction of the spark gap with excellent overall properties. For example, the terminal electrodes are thin and made of a highly conductive material. Preferably, the terminal electrodes have a low heat capacity. The material combination of pin or tube electrode, connection electrode, stiffening electrode and possibly externally connected connection pin enables optimization of the spark gap with regard to its compactness as well as electrical, thermal and mechanical properties.

The shapes of the terminal electrodes and the stiffening electrodes are preferably matched to each other. As a result, both a stable outer electrode and a good heat dissipation in the discharge case is possible.

Even if the spark gap through the terminal electrodes alone should not have the necessary stability, the stiffening electrodes ensure the stability and integrity of the spark gap, especially if the stiffening electrodes are made of a harder material than the terminal electrodes.

The individually and in their entirety optimized elements of the claimed embodiments of the spark gap affect on the one hand in a compact design and on the other hand in particular on improved thermal and electrical properties. Thus, the current carrying capacity and the dynamic ignition conditions of the spark gap are improved.

The pin electrode as the first electrode and the tube electrode as the second electrode are arranged in the cavity of the insulator. The first and second electrodes protrude into each other and are spatially separated. The second electrode lies between the insulator and the first electrode and is spatially separated from both. This results in a simple realized nested arrangement.

The pin electrode is considered to be any type of electrode which has a pen-like or rod-like appearance according to its external appearance. This includes pipes with at least one frontal flange. Likewise, a tube electrode has a closed or partially interrupted tube shape. In the following, the terms first electrode and pin electrode and second electrode and tube electrode are used interchangeably.

Due to the nested arrangement, the pin electrode preferably engages the tube electrode such that the inner wall of the insulator surrounding the electrodes, which is preferably tubular, is partially shaded by the pin electrode by the tube electrode.

A shading of the insulator of the pin-shaped electrode by means of the tubular electrode allows the ignition of the spark gap advantageously compliance the structural integrity of the insulator and optionally applied thereon ignition aids, such as graphite, and the stability of the insulating property of the insulator.

The interior of the spark gap is preferably filled with gas, in particular a gas mixture containing noble gas. On the one hand, this positively supports the extinguishing behavior of the spark gap and, on the other hand, ensures uniformized dynamic ignition conditions during repeated ignition of the spark gap.

According to another embodiment of the spark gap, the ends of one or both electrodes are chamfered in the discharge space. It is preferred that the ends have rounded or smoothed outer surfaces, so that local electric Feldüberhöhungen be avoided.

It is also advantageous if at least one of the electrodes has an activation mass. With the activation mass, a higher AC load capacity of the spark gap can be ensured. This is particularly possible if the activation mass is arranged on the free end of the pin electrode and / or on the bottom of the pipe electrode.

The preferably mounted on each end side of the insulator each a connection electrode allows electrical connection of the spark gap to the outside. In this case, in each case one connection electrode is connected to the pin or tube electrode. The contacting of the electrodes is carried out so that each electrode is on the one hand exactly positioned and on the other hand the occurring currents can be safely dissipated.

To form the preferably hermetic, i. In the gas-tight, sealed-off interior of the spark gap, the connecting electrodes can completely cover the front sides of the insulator.

Particularly advantageous are the two embodiments of the invention combine.

The individually and in their entirety optimized elements of the claimed embodiments of the spark gap affect on the one hand in a compact design and on the other hand in particular on improved thermal and electrical properties. Thus, the current carrying capacity and the dynamic ignition conditions of the spark gap are improved.

The invention will be explained in more detail with reference to the Ausführungsbei.spiele and the figures of the drawings.

Figur 1

einen Schnitt durch eine erste erfindungsgemäße Funkenstrecke,

Figur 2

einen Schnitt durch eine Funkenstrecke, gemäß Stand der Tecknik mit zwei versteifungselektroden.

Figur 3

einen Schnitt durch eine zweite erfindungsgemäße Funkenstrecke,

Figur 4

einen Schnitt durch eine dritte erfindungsgemäße Funkenstrecke und

Figur 5

eine dreidimensionale Ansicht einer Funkenstrecke gemäß Figur 1 mit stirnseitigen Anschlussbolzen.

Showing:

FIG. 1

a section through a first spark gap according to the invention,

FIG. 2

a section through a spark gap, according to the Tecknik with two stiffening electrodes.

FIG. 3

a section through a second spark gap according to the invention,

FIG. 4

a section through a third spark gap according to the invention and

FIG. 5

a three-dimensional view of a spark gap according to FIG. 1 with frontal connection bolts.

FIG. 1 shows a spark gap, in particular as a high-current spark gap, which contains a tubular insulator 2, in particular made of ceramic. At the front, the spark gap has connection electrodes 7a and 7b. The terminal electrodes have cavity-side bulges, as in the embodiment of FIG. 1 cup-shaped. They serve alone or, as in FIG. 1 shown in conjunction with stiffening electrodes 12a, 12b, inter alia for electrical connection to the network to be protected.

In the interior of the housing formed by the insulator and the terminal electrodes of the spark gap is a filled with gas, preferably a gas mixture with inert gas, sealed outward cavity 3. In the cavity, a first electrode 4 and a second electrode 5 are arranged, each attached to one of the terminal electrodes 7a and 7b and are electrically connected thereto. The first electrode 4, shown as a partial section, is preferably pin-shaped and the second electrode 5 is preferably tubular. The spark gap preferably has a height and a diameter of between 25 mm to 35 mm, in particular 30 mm.

The arrangement of the pin and tube electrodes is chosen so that the pin electrode 4 protrudes partially with its free end into the tube electrode 5 or inserted. As a result, the tube electrode 5 partially overlaps the pin electrode 4 and shadows the pin electrode in this area from the inner wall of the insulator. This arrangement forms a nested geometry.

The pin electrode and the tube electrode are preferably concentrically positioned in their nested region so that there is a space 8 between the peripheral surface of the pin electrode and the inner surface of the tube electrode. The space 8 serves as a primary electrical discharge space, with secondary discharges also taking place in other spaces between the first and second electrodes 4 and 5.

The pin and the tube electrode each have free ends lying in the cavity. The respective other end of the pin or tube electrode is firmly connected to a connection electrode 7a or 7b, in particular by means of a hypereutectic brazing.

The edges 4a and 5a preferably of all ends of the electrodes are chamfered or rounded off, thus avoiding excesses of the electric fields at these edges. As a result, a more uniform current discharge in the cavity 3, in particular in the discharge space 8, is achieved. Thus, locally highly concentrated electromagnetic fields and thus the formation of accompanying temperature peaks are avoided. In particular, the current load for the pin and the tube electrode is reduced. Non-chamfered electrodes, on the other hand, can cause impermissibly high current densities at the edges of the electrodes, which can lead to unwanted melting of the electrodes.

The preferred materials of the pin electrode and the tube electrode are copper, iron or a tungsten-copper mixture or at least portions of these materials. The Electrodes may also contain different materials relative to each other, such as a tungsten-copper stud electrode and a copper rod electrode. In this case, the expensive tungsten copper has the lowest burnup at surge current loads, so that this material is also preferred for both electrodes. Electrodes of iron or copper show a higher burnup, but are cheaper and therefore also advantageous.

Depending on the requirements, the interleaved construction of the first and second electrodes 4 and 5 allows materials which are unsuitable for a reliable ceramic-metal compound per se, such as iron or tungsten-copper, to be used in the discharge region.

A suitable ceramic for the insulator 2 is alumina (Al ₂ O ₃ ). The insulator is dimensioned with a wall thickness of 4 mm to 6 mm, but preferably with a wall thickness of 5 mm, to safely master the enormous pressure wave during a surge discharge in the interior of the spark gap, without the insulator bursting or cracking.

On the inner wall 2a of the insulator ignition aids 9, for example, one or more graphite-containing ignition marks are applied, which ensure above all the good dynamic ignition behavior (eg ignition at <1500 V with a rise time of 5 kV / μsec). Furthermore, such stable characteristic values, such as, for example, ignition voltage and insulation resistance, are ensured. Due to the shading effect of the pipe electrode, the ignition strips are effectively protected against burning.

An optimal ceramic-metal connection between the insulator 2 and the terminal electrode 7a or 7b is given if the thermal expansion coefficients of the two materials are the same or similar. In an alumina insulator, the ceramic-metal compound is preferably made by FeNi alloy or copper. In a composite electrode according to the embodiment, the pin and the tube electrode are made of current-resistant materials and fixed to the connection electrode, for example, welded or brazed. Therefore, the terminal electrode contains a material that can be connected well with the material of the pin and tube electrode as well as with that of the insulator. Composite electrodes each of first and second electrode, terminal electrode and, as in the embodiment of FIG. 1 , Stiffening electrode with their respective optimized materials and shapes contribute significantly to a mechanical and electrical optimization of the spark gap.

Preferably, the pin electrode and / or the tube electrode are provided with an activation mass to a high. Safely handle AC load. It is according to FIG. 1 an activation mass is disposed on the free end of the pin electrode. It is also possible to apply an activation mass between the walls of the tubular electrode 5 to the inside of the connecting electrode 7b connected to the tubular electrode, that is to say to the bottom of the tubular electrode. The activation compound is preferably a silicate coating, which is applied in recesses at the free end 4a of the inner pin electrode, for example in the form of a wafer pattern.

The connection electrodes 7a and 7b are particularly preferably made of copper. They have at the periphery a plurality, preferably six beads 11. These lead the terminal electrodes within the ceramic tube 2 precisely and safely, without the terminal electrodes must be completely against the entire ceramic inner wall. Each terminal electrode is mechanically or electrically connected to either the pin or tube electrode, e.g. connected by means of a hypereutectic brazing.

The connection electrodes are made of copper and can in principle be so thick that they correspond to the resulting pressure and thermal loads. Comparatively thin connection electrodes are possible, according to FIG. 1 additional stiffening electrodes 12a and 12b are provided, which in particular contain an iron-nickel alloy. The additional stiffening electrodes 12a, 12b are brazed to the associated terminal electrodes 7a, 7b quasi in sandwich construction and form composite electrodes. The stiffening electrodes may for example be about 1 mm thick.

The stiffening electrodes preferably have a form complementary to the terminal electrodes, so that they also have indentations and are adapted to the shape of the terminal electrodes. The stiffening is provided in the case of thin connection electrodes in order to prevent bursting of the spark gap or pressing out of the connection electrodes during a rush current discharge.

For low surge current requirements of less than 50 kA, however, the stiffening electrodes 12a, 12b may be omitted if the terminal electrodes are correspondingly boosted, eg to 1 mm, see also FIG. 4 , In this case, it is preferable to choose copper or an FeNi alloy coppered before assembly as the electrode material. During the execution, the reliability of the gas-tight ceramic-metal connection must be maintained.

The interior 3 of the spark gap is filled with a gas mixture, which preferably contains an argon content of about 35 to 95%, a hydrogen content of 5 to 20% and a neon content of up to 40%. This achieves a dynamic ignition voltage and a safe extinguishing behavior. With this gas mixture can be set at a distance of 2 mm between the pin and the tube electrode or the width of the discharge chamber 8, a static ignition voltage of about 600 V safely.

Discharge through the spark gap typically proceeds as follows. The current flows from the stiffening electrode 12a and the terminal electrode 7a to the pin electrode 4, via the spark discharge of the discharge space 8 to the tube electrode 5 and to the terminal electrode 7b. It leaves the spark gap at the stiffening electrode 12b to be further derived there, for example by means of an external line. In the discharge space 8, the surge current discharge takes place mainly in a radial manner, wherein the insulator 2 is largely shielded from the pin electrode by means of the tube electrode.

A current flow in the reverse direction is also possible, with current flowing through the electrodes 12b, 7b into the tube electrode 5 flows, from there via the discharge space 8 to the pin electrode 4 and finally to the electrodes 7a and 12a.

FIG. 2 shows an embodiment of a spark gap according to the Tecknik. In the hollow space 23 formed by the insulator 22 and the terminal electrodes 27a, 27b, a pin electrode 24 and a tube electrode 25 which are nested and define the main discharge space 28 extend. On the free end of the pin electrode 24, an activation mass 26 is attached, for example in a waffle-like surface structure. The inner wall of the insulator carries applied Zündstriche 29. Sandwich-like stiffening electrodes 27c and 27d are fixedly connected to the terminal electrodes 27a and 27b, for example by soldering. With regard to the choice of materials and the choice of gases to avoid repetition on the versions FIG. 1 directed. The embodiment leads to an extremely compact design with excellent electrical, thermal and mechanical properties.

The execution according to FIG. 2 differs from the structure according to FIG. 1 on the one hand by an even lower overall height. On the other hand, the terminal and stiffening electrodes are flat and have no cavity-side protrusions. Overall, the structure with a height of 10 mm is extremely compact, the diameter of, for example, 30 mm of the FIG. 1 equivalent. This construction is suitable for switching several, in particular 3 or 4, spark gaps electrically in series. On a 230 V mains without current-limiting components, such as resistors or varistors, it is possible to strike lightning the streaming stream will be deleted directly. A lowered ignition voltage of about 200 V is ensured with a gas mixture of neon-argon-hydrogen (Ne / Ar / H ₂ ) in a ratio of 89/11/10 and an electrode gap 8 of 1 mm.

FIG. 3 shows a second embodiment of the invention with a spark gap 30. In the cavity 33, which is formed by the insulator 32 and the terminal electrodes 37a, 37b, extend a pin electrode 34 and a tube electrode 35 which are nested and nested Define main discharge space 38. On the free end of the pin electrode 34, an activation mass 36 is applied, for example in a waffle-like surface structure. The inner wall of the insulator carries applied ignition strips 39, which are largely shadowed by the tube electrode 35 from the pin electrode 34.

The terminal electrodes 37a, 37b on the end faces of the cylindrical insulator 32 have on the outer edge of the cavity 33 annular bulges 31, wherein a series of beads in the bulges of the terminal electrodes takes the lead. The tube electrode 35 is welded or soldered to the bulge of the terminal electrode 37b, while the pin electrode 34 is welded or soldered thereto in the central area of the terminal electrode 37a.

Sandwich-like are with the terminal electrodes 37a and 37b Stiffening electrodes 40a and 40b firmly connected, eg welded or soldered. Possibly. Provided connecting bolts are preferably arranged in the bulges of the stiffening electrodes 40a, 40b. Regarding the materials and the selection of the gases is to avoid repetition on the versions FIG. 1 directed.

The embodiment achieves a very compact design of the spark gap with optimized properties. This allows the electrode materials to be tailored to specific requirements and to prefabricate the complete electrodes. Through the beads a self-adjusting or easy to adjust mounting is possible. Further advantages result in the same way as in the corresponding features of the other figures.

FIG. 4 shows a third solution form of the task. The spark gap 50 has a cavity 43 formed by the insulator 42 and the terminal electrodes 47a, 47b. In the cavity 43, a pin electrode 44 and a tube electrode 45 extend, which are nested and define the discharge space 48. On the free end of the pin electrode 44, an activation mass 46 is attached, for example in a waffle-like surface structure. On the bottom of the tube electrode 45, an activation mass 19 is attached. The inner wall of the insulator carries applied ignition strips 29.

The terminal electrodes 47a and 47b have annular bulges 41. The bulges are shaped that a series of beads in the bulges of the terminal electrodes takes the lead. The tube electrode 45 is welded or soldered to the bulge of the terminal electrode 47b, while the pin electrode 44 is welded or soldered thereto in the central area of the terminal electrode 47a.

Regarding the selection of the electrode materials and the selection of the gases is to avoid repetition on the statements to FIG. 1 directed. In contrast, the material thickness of the terminal electrodes is larger and selected so that the pressures and temperatures occurring during a discharge are safely controlled. The embodiment leads to an extremely compact design with excellent electrical, thermal and mechanical properties. The functionality of the spark gap corresponds to that of FIG. 2 shown spark gap. The embodiments of the invention according to FIGS. 1 . 3 and 4 form the essential solutions of the invention.

The spark gap according to FIG. 5 is shown in three-dimensional view. It corresponds in terms of their construction according to a spark gap FIG. 1 and has additional connection bolts 13a, 13b. These can either be connected directly to the connection electrodes 7a, 7b or to the stiffening electrodes 12a, 12b, preferably in their respective indentations. The connection can be carried out by soldering or welding.

The spark gaps described are preferably used for deriving direct lightning currents. They can also be used as a device or separating spark gap for the corrosion protection of gas, water and oil lines. Furthermore they can be used as arresters for network protection in home installations.

The spark gaps according to the invention have a very compact design of eg 30 mm diameter and 30 mm height or less. They have AC carrying capacities of, for example, 300 amps for a period of 0.2 seconds and can dissipate lightning currents of up to 200 kiloamps. They are suitable for the load with surge current waves of the normalized curve of 8/20 (rise time 8 μsec and back half-life 20 μsec) and 10/350. They also respond quickly, such as at a voltage of less than 1500 volts with a slope of about 5 kV / μsec before and after current loads. The static ignition voltage is for example between 600 and 900 volts. The spark gaps have a good extinguishing behavior at an alternating voltage of 255 volts, whereby reticule currents in the range of about 100 amperes can be safely extinguished after the first half cycle.

LIST OF REFERENCE NUMBERS

1, 21, 30, 50

radio link

2, 22, 32, 42

insulator

3, 23, 33, 43

cavity

4, 24, 34, 44

Pin electrode / first electrode

4a, 44a

chamfered end of the pin electrode

5, 25, 35, 45

Pipe electrode / second electrode

5a

chamfered end of the tube electrode

6, 19, 26, 36, 46

activating compound

7a, 27a, 37a, 47a

first connection electrode

7b, 27b, 37b, 47b

second connection electrode

8, 28, 3-8, 48

discharge space

9, 2, 39, 49

ignition strips

10

Indentation of a stiffening electrode

11

Beading of a connection electrode

12a, 27c, 40a

first stiffening electrode

12b, 27d, 40b

second stiffening electrode

13a, 13b

connecting bolt

14

gas

Claims (14)

1. Spark gap (1; 30; 50) comprising a cavity (3; 33; 43) which is surrounded by two connection electrodes (7a, 7b; 37a, 37b; 47a, 47b) and an electrical insulator (2; 32; 42) arranged between said connection electrodes, comprising a pin electrode (4; 34; 44) which projects into a tube electrode (5; 35; 45), comprising indentations (10; 31; 41) in the connection electrodes on the side of the cavity (3; 33; 43), and comprising guidance for the connection electrodes (7a, 7b; 37a, 37b; 47a, 47b) on the inner wall of the insulator (2; 32; 42), characterized in that the guidance is effected by means of beads (11) in the indentations (10; 31; 41).
2. Spark gap according to Claim 1, in which connection bolts (13a, 13b) are mounted on the connection electrodes (7a, 7b; 37a, 37b; 47a, 47b).
3. Spark gap (1; 30) according to Claim 1 or 2, comprising two stiffening electrodes (12a, 12b; 40a, 40b), each of which is connected to one of the two connection electrodes (7a, 7b; 37a, 37b).
4. Spark gap (1; 30) according to Claim 3, the connection electrodes (7a, 7b; 37a, 37b) and the stiffening electrodes (12a, 12b; 40a, 40b) having indentations (10, 31, 41).
5. Spark gap (1; 30; 50) according to one of the preceding claims, in which the insulator (2; 32; 42) is cylindrical, and a connection electrode (7a, 7b; 37a, 37b; 47a, 47b) is arranged on each end face of the insulator (2; 32; 42).
6. Spark gap (1; 30; 50) according to one of the preceding claims, in which the pin electrode (4; 34; 44) is connected to a first connection electrode (7a; 34; 44) and the tube electrode (5; 35; 45) is connected to a second connection electrode (7b; 37b; 47b).
7. Spark gap (1; 30; 50) according to one of the preceding claims, in which the inner surface (2a) of the insulator (2; 32; 42) comprises starting aids (9; 39; 49).
8. Spark gap (1; 30; 50) according to one of the preceding claims, in which the cavity (3; 33; 43) is hermetically sealed with respect to the outside.
9. Spark gap (1; 30; 50) according to Claim 8, in which the connection electrodes (7a, 7b; 37a, 37b; 47a, 47b) terminate the insulator (2; 32; 42) in a gas-tight manner.
10. Spark gap (1; 30; 50) according to one of the preceding claims, in which the cavity (3; 33; 43) is filled with gas (14).
11. Spark gap (1; 30; 50) according to Claim 10, in which the gas (14) contains at least one of the following constituents: between 35 and 95% argon, between 5 and 15% hydrogen and between 0 and 40% neon.
12. Spark gap (1; 30; 50) according to one of the preceding claims, in which the tube electrode (5; 35; 45) and the insulator (2; 32; 42) are spaced apart from one another.
13. Spark gap (1; 30; 50) according to Claim 6, in which the pin and tube electrodes (4, 5; 34, 35; 44, 45) each have ends (4a, 5a) which are in the cavity (3; 33; 43) and are chamfered.
14. Spark gap (1; 30; 50) according to Claim 6 or 13, in which an activation compound (6; 36; 46) is applied to the pin electrode (4; 34; 44) and/or to the tube electrode (5; 35; 45).

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