Triggered double spark gap device

Abstract

The invention relates to a triggered double spark gap with main electrodes (1, 2), wherein a hollow cylinder (10) made of arc-resistant material is arranged in the center of the first main electrode (1), an insulating disk (7) with a hole that maximally exposes the hollow cylinder (10) is arranged on the first main electrode (1), a metal electrode (6) having a central hole is arranged on the insulating disk (7), the metal electrode (6) is electrically connected to the first main electrode (1) via an impedance (11), a first disk (5) made of low-resistance conductive material is arranged on the metal electrode (6), the disk having an inner circle of holes with several holes that largely cover the central hole of the metal electrode (6), and a second disk (4) made of insulating material having an inner circle of holes with several holes is arranged on the first disk (5).A third disc (3) made of arc-resistant, electrically conductive material is arranged on the second disc (4), which rests against the surface of the second main electrode (2).

Description

[0001] The invention relates to a triggered spark gap with a flat design for surge arresters. In known lightning arresters, multiple spark gaps are used to ensure sufficient follow current extinguishing capacity. The more spark gaps connected in series, the greater the follow current extinguishing capacity. On the other hand, however, this results in an undesirable increase in the response voltage.

[0002] The more spark gaps are used, the higher the system's response voltage becomes.

[0003] To reduce the sparkover voltage and thus the protection level, capacitive control of the spark gaps can be used, for example. However, there are technical limiting conditions that also increase the sparkover voltage when the number of spark gaps increases.

[0004] Another option is to connect a single spark gap in series with a graphite granulate system. Using a single spark gap results in a low sparkover voltage. The granulate system has a low resistance before the current flows and develops a high counter voltage, or damping, during the current flow, to enable the single spark gap to quench the follow current.

[0005] Another option is to use a spark gap with a large arc width and a narrow arc channel. Conducting arcs through narrow spaces, preferably made of cold-gassing material (POM or PTFE), increases the arc voltage and thus improves the follow current quenching behavior. Since the sparkover voltage would be very high in such a system due to the large arc width, this spark gap would require external ignition.

[0006] The principle of the triggered spark gap in question here is as follows: When the trigger spark gap is triggered, ionized gas is generated, which spreads through the corresponding system and ignites the main spark gap between the phase and neutral conductors. The trigger spark gap is connected in series with a varistor, so that only an initial current flows until the main spark gap is ignited, because the voltage across the varistor is greater than the arcing voltage of the main spark gap.

[0007] The main spark gap is also dimensioned so that the arc voltage is greater than the mains voltage, so that a mains follow current cannot occur.

[0008] The devices commonly used in this regard, which utilize this principle, are manufactured in a cylindrical design, with the main electrodes (L and N, but also N and PE) mounted axially at the ends. The cylindrical body then establishes the connection to the trigger electrode.

[0009] The triggering usually consists of a voltage-limiting varistor or a series connection of a varistor and a gas discharge tube if sufficient insulation or freedom from leakage current of the trigger spark gap is not provided.

[0010] If a sufficiently low response voltage of the trigger spark gap is not available, circuits with ignition transformers, for example, are used. This ensures a low response voltage of the entire system.

[0011] The design of surge arresters with spark gaps consisting of disc-shaped elements is known, for example, from DE 297 24 817 U1 or EP 2 916 401 A1.

[0012] The invention is based on the object of avoiding the disadvantages inherent in these systems and of creating a spark gap with a flat design that enables the standardized use of only one pitch unit (17.5 mm) in distribution boxes, so that such lightning current arresters can be easily installed in conventional distributions.

[0013] The invention proposes a triggered double spark gap in a flat design, with two main electrodes connected between L and N or N and PE, wherein the main electrodes are cuboid-shaped and are mechanically connected to each other, i.e. electrically insulated from each other, wherein a hollow cylinder made of arc-resistant material is arranged in the center of the first main electrode, wherein an insulating disc with a central hole is arranged on the first main electrode on the surface facing the second main electrode, which maximally exposes the hollow cylinder, wherein a disc-shaped metal electrode is arranged on the insulating disc, which has a central hole that is larger in diameter than the central hole of the insulating disc, so that a circular space is formed up to the hollow cylinder and forms an insulating distance, wherein the metal electrode is electrically conductively connected to the first main electrode via an impedance, wherein a first disc made of low-resistance conductive material is arranged on the metal electrode, which has an inner hole circle with several holes that largely cover the center hole of the metal electrode,wherein a second disc made of insulating material is arranged on the first disc, said second disc having an inner hole circle with a plurality of holes, the position and size of which are identical to the position and size of the holes in the first disc, wherein a third disc made of arc-resistant, electrically conductive material is arranged on the second disc, said third disc being in contact with the surface of the second main electrode facing the first main electrode.

[0014] It is preferably provided that the first main electrode and the second main electrode are connected by means of screws which are surrounded by insulating sleeves and which are arranged in corner regions of the, for example, square, cuboid-shaped main electrode, which are positioned next to the insulating disc, the metal electrode and the discs without touching them.

[0015] In addition, it is preferably provided that the hollow cylinder is designed to contact the arc and to reduce the pressure inside the spark gap package.

[0016] It is also preferred that the hollow cylinder is made of tungsten copper.

[0017] Alternatively, it may also be preferred that the hollow cylinder is made of graphite.

[0018] It is also preferred that the insulating disc is made of PTFE.

[0019] It can also be provided that the insulating disc is made of POM.

[0020] Furthermore, the insulating disc can be made of Nomex or vulcanized fiber.

[0021] The function and also the flat design are beneficial because the hollow cylinder has a through opening of 3 to 5 mm.

[0022] For the same reason, it is preferred that the disc-shaped metal electrode has a material thickness of 0.4 to 1.2 mm.

[0023] For the same reason, the center hole of the metal electrode is intended to have a diameter of 17 to 23 mm.

[0024] Furthermore, it is preferred that the impedance is formed by a varistor, a suppressor diode, a gas discharge tube or a combination of these.

[0025] It can also preferably be provided that the first disc consists of PTFE with carbon or graphite.

[0026] It is also preferably provided that the first disc has an inner hole circle with 3 to 6 holes.

[0027] It is particularly preferred that the holes of the first disc have a diameter of 1.5 to 6 mm.

[0028] It is also preferred that the second disc is made of PTFE, Nomex or vulcanized fiber.

[0029] It is also preferred that the third disc is made of graphite or tungsten copper.

[0030] An embodiment of the triggered dual spark gap is shown in the drawing and described in more detail below.

[0031] It shows: Figure 1 a corresponding component in isometric view; Figure 2 the component seen in the middle cross-section; Figure 3 an exploded view of the component.

[0032] In the exemplary embodiment, the spark gap system is arranged between the first main electrode 1 and the second main electrode 2, which are mechanically connected by screws 9 and insulating sleeves 8 but are electrically insulated.

[0033] In the center of the first main electrode 1 there is a hollow cylinder 10 made of arc-resistant material, for example tungsten copper or graphite, which serves both to contact the arc and to reduce the pressure inside the spark gap.

[0034] On the first main electrode 1 lies an insulating disc 7, made of PTFE or POM, for example, with a central hole that exposes only the opening of the hollow cylinder 10. On this insulating disc 7 lies a disc-shaped metal electrode 6, made of copper, for example, with a preferred material thickness of approximately 0.5 to 1.0 mm and a center hole diameter of approximately 18 to 22 mm, forming a circular space that thus forms an insulating distance of several millimeters toward the hollow cylinder 10.

[0035] This metal electrode 6 is connected to the first main electrode 1 via an impedance 11. This impedance 11 can be formed by a varistor, a suppressor diode, or a gas discharge tube, or by a combination of these components.

[0036] A first disc 5 made of a low-resistance conductive material, for example, PTFE with carbon, rests on the metal electrode 6. It has an inner hole circle consisting of four holes with a diameter of approximately 2 to 5 mm in the illustrated embodiment. The holes in this hole circle are positioned such that, in the intended mounting position, their outer regions clearly overlap the center hole of the metal electrode 6, thus forming a large passage.

[0037] The holes of the hole circle are located for the most part in the area covered by the center hole of the metal electrode 6, so that the resulting plasma can easily leave this area.

[0038] On top of the first disc 5 lies a thin insulating second disc 4, made of PTFE, vulcanized fiber, or Nomex, which has the same hole pattern as the first disc 5. The second disc 4 has a thickness of approximately 0.2 to 0.4 mm.

[0039] On top of the second disc 4 there is a third disc 3 made of arc-resistant material, for example graphite or tungsten copper, whose diameter is significantly larger than the diameter of the hole circles of the discs 4 and 5.

[0040] The four holes, together with the metal electrode 6 and the discs 3 to 5, form the trigger spark gaps for igniting the main spark gap.

[0041] The third disc 3 contacts directly with the second main electrode 2. In the installation situation, the mains voltage UN is applied to the main electrodes 1 and 2.

[0042] It works as follows: When an overvoltage occurs that is greater than the response voltage of the spark gap system, a current initially flows through the series circuit of impedance 11, metal electrode 6, low-resistance disc 5, and third disc 3. A flashover between the first disc 5 and the third disc 3 creates an initial arc. The response voltage is determined by the insulating second disc 4. It is arbitrary which of the four holes in the trigger spark gaps in the hole circle triggers the arc. An initial response directly across the path from the third disc 3 to the hollow cylinder 10 is not possible due to the large arcing distance.

[0043] After the spark gap between the first disc 5 and the third disc 3 is triggered, an initial current flows through the material of the low-resistance conductive first disc 5. Shortly thereafter, the current leaves the material of the first disc 5 as an arc, forming an external flashover or a sliding flashover. This lengthens the arc between the metal electrode 6 and the third disc 3 by the material thickness of the first disc 5, leading to an increase in the converted power. This temporal progression results in a highly nonlinear residual voltage curve due to the current load.

[0044] The higher arc power creates more plasma to ignite the main spark gap between the hollow cylinder 10 and the holes / trigger spark gaps to the third disc 3. The plasma created in the holes now begins to fill the space formed by the center hole of the metal electrode 6 and the volume of the holes in the trigger spark gaps. As soon as the plasma reaches the hollow cylinder 10 located in the main electrode 1, the discharge of the surge current from the free areas of the third disc 3 to the hollow cylinder begins. Since the entire space is now filled with conductive plasma, all areas of the disc 3 are included in the discharge process. Therefore, the diameters of the holes in discs 4 and 5 can be relatively small without causing overload.

[0045] Since the counter voltage / arc voltage is smaller here than in the parallel path with impedance 11 and the trigger spark gaps, the surge current now flows through the main spark gap. The counter voltage / arc voltage is sufficiently large to prevent or significantly reduce a line follow current.

[0046] To prevent the surge protection device from being reignited, the plasma is ejected through the hole in the hollow cylinder 10 and additionally cooled in the flat space of the disk 6 by disks 5 and 7. The following explanation should be added: The graphite disk 3, together with the copper electrode 6, forms the spark gap of the trigger spark gap, which is connected in series with the impedance 11 (varistor). The plasma of the spark gap is generated in one of the four trigger spark gaps and then ignites the main spark gap with the hollow copper cylinder 10 as the second main electrode. The offset holes in disks 4 and 5 and the material thickness of the copper electrode 6 create a flat area for the arc. This increases the countervoltage and limits or prevents the follow current. The hollow copper cylinder 10 allows the plasma to exit the spark gap and thus the necessary pressure peak to be released from the spark gap.

[0047] Due to the large arc width (PTFE disc 4 + PTFE disc with carbon), the arc of the trigger spark gap is extended by the thickness of the PTFE ring or the PTFE disc with carbon 5, which increases the electrical power and creates more plasma to ignite the main spark gap.

[0048] The example shown in the drawing does not correspond to the actual dimensions. In reality, the edge length of the cuboid is Figure 1 approximately 3 cm. The height is approximately 15 mm. The dimensions of the individual components have already been specified above. Overall, the flat and narrow design ensures the standardized use of only one pitch unit (17.5 mm) in distribution enclosures.

[0049] Installation in standard fuse boxes with a 17.5 mm pitch is easily possible.

[0050] The invention is not limited to the embodiment, but is defined by the claims.

Claims

1. A triggered double spark gap in a flat design with main electrodes (1, 2), which are connected between electrical conductors L and N or N and PE, the main electrodes (1, 2) being of cuboidal design and being mechanically connected to one another, but electrically insulated from one another, - wherein a hollow cylinder (10) made of arc-resistant material is arranged in the center of the first main electrode (1), - wherein an insulating disc (7) having a central hole is arranged on the first main electrode (1) on the surface facing the second main electrode (2), said central hole releasing the maximum of the hollow cylinder (10), - wherein a disc-shaped metal electrode (6) is arranged on the insulating disc (7) and has a central hole, which has a larger diameter than the central hole of the insulating disc (7), so that a circular space is formed up to the hollow cylinder (10) and forms an insulating gap, - wherein the metal electrode (6) is electrically conductively connected to the first main electrode (1) via an impedance (11), - wherein a first disc (5) of low-impedance conductive material is arranged on the metal electrode (6) and has an inner hole circle with a plurality of holes, which cover the central hole of the metal electrode (6) for the most part, - wherein a second disc (4) made of insulating material is arranged on the first disc (5) and has an inner hole circle with a plurality of holes, the position and size of which equals the position and size of the holes of the first disc, - wherein a third disc (3) made of an arc-resistant, electrically conductive material is arranged on the second disc (4) and bears against the surface of the second main electrode (2) facing the first main electrode (1).

2. The spark gap of claim 1, characterized in that the first main electrode (1) and the second main electrode (2) are connected by means of screws (9), which are surrounded by insulating sleeves (8) and which are arranged in corner regions of the main electrodes (1, 2), which are positioned next to the insulating disc (7), the metal electrode (6) and the discs (5, 4, 3) without touching them.

3. The spark gap of claim 1 or 2, characterized in that the hollow cylinder (10) is designed as contacting the electric arc and for reducing the pressure in the interior of the spark gap package.

4. The spark gap of one of claims 1 to 3, characterized in that the hollow cylinder (10) consists of tungsten-copper.

5. The spark gap of one of claims 1 to 3, characterized in that the hollow cylinder (10) consists of graphite.

6. The spark gap of one of claims 1 to 5, characterized in that the insulating disc (7) consists of PTFE.

7. The spark gap of one of claims 1 to 5, characterized in that the insulating disc (7) consists of POM.

8. The spark gap of one of claims 1 to 5, characterized in that the insulating disc (7) consists of Nomex, or vulcanized fiber.

9. The spark gap of one of claims 1 to 8, characterized in that the hollow cylinder (10) has a through-opening of 3 to 5 mm.

10. The spark gap of one of claims 1 to 9, characterized in that the disc-shaped metal electrode (6) has a material thickness of 0.4 to 1.2 mm.

11. The spark gap of one of claims 1 to 10, characterized in that the central hole of the metal electrode (6) has a diameter of 17 to 23 mm.

12. The spark gap of one of claims 1 to 11, characterized in that the impedance (11) is formed by a varistor, a suppressor diode, a gas arrester, or a combination thereof.

13. The spark gap of one of claims 1 to 12, characterized in that the first disc (5) consists of PTFE with carbon or graphite.

14. Spark gap of one of claims 1 to 13, characterized in that the first disc (5) has an inner hole circle with 3 to 6 holes.

15. The spark gap of one of claims 1 to 14, characterized in that the holes of the first disc (5) have a diameter of 1.5 to 6 mm.

16. The spark gap of one of claims 1 to 15, characterized in that the second disc (4) consists of PTFE, Nomex, or vulcanized fiber.

17. The spark gap of one of claims 1 to 16, characterized in that the third disc (3) consists of graphite or tungsten-copper.

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