EP1692751B1 - Surge suppressor - Google Patents

Abstract

An overvoltage protection means having a first electrode (1), a second electrode (2), a breakdown spark gap between the two electrodes (1, 2), and a housing (3) which holds the electrodes (1, 2). When the breakdown spark gap is ignited, an arc (4) is formed between the two electrodes (1, 2) within the discharge space (5) which connects the two electrodes (1, 2). The overvoltage protection arrangement has an especially high line follow current extinguishing capacity, but can nevertheless be easily built, and the discharge space (5) is made such that it runs at least partially transversely and/or opposite the direction of the electrical field of the prevailing line voltage so that the distance to be overcome by the arc (4) between the two electrodes (1, 2) has a transverse component relative to the electrical field.

Description

The invention relates to an overvoltage protection device, comprising a first electrode, with a second electrode, with a formed between the two electrodes breakdown spark gap and with a housing receiving the electrodes, wherein when igniting the breakdown spark gap between the two electrodes an arc within a the arises two connecting discharge space.

Electrical, but especially electronic measuring, control, regulating and switching circuits, especially telecommunications equipment and systems, are sensitive to transient overvoltages, as may occur in particular by atmospheric discharges, but also by switching operations or short circuits in power grids. This sensitivity has increased as electronic components, in particular transistors and thyristors, are used; above all, increasingly used integrated circuits are to a great extent endangered by transient overvoltages.

Electrical circuits work with the voltage specified for them, the rated voltage (usually ≅ mains voltage), normally without interference. This does not apply if surges occur. Overvoltages are all voltages that are above the upper tolerance limit of the rated voltage. These include, above all, the transient overvoltages that can occur due to atmospheric discharges, but also through switching operations or short circuits in power supply networks and can be galvanically, inductively or capacitively coupled into electrical circuits. In order to protect electrical or electronic circuits, especially electronic measuring, control, and circuits, especially telecommunications equipment and systems, wherever they are used against transient overvoltages, overvoltage protection devices have been developed and for more than twenty Known years ago.

An essential part of overvoltage protection device of the type in question here is at least one spark gap that responds at a certain overvoltage, the Ansprechspannung, and thus prevents that occur in the protected by an overvoltage protection circuit surges that are greater than the operating voltage of the spark gap.

Initially, it has been stated that the overvoltage protection device according to the invention has two electrodes and a breakdown spark gap formed between the two electrodes. In practice, such breakdown spark gaps are often referred to as air breakdown spark gaps, which in the context of the invention with breakdown spark gap should also be meant an air breakdown spark gap. However, it may be present between the electrodes other than air and another gas. The region of the overvoltage protection device in which the arc is formed when the breakdown spark gap is ignited is referred to below as the discharge space. This is usually the space between the two electrodes.

In addition to overvoltage protection devices with a breakdown spark gap, there are also overvoltage protection devices with a rollover spark gap, which occurs when responding a sliding discharge.

Overvoltage protection devices with a breakdown spark gap have the advantage over surge protection devices with a flashover spark gap the advantage of a higher surge current carrying capacity, but the disadvantage of a higher - and not very constant - Ansprechspannung. Therefore, various overvoltage protection devices have been proposed with a breakdown spark gap, which have been improved in terms of the response voltage. In this case, ignition aids have been realized in various ways in the region of the electrodes or the effective between the electrodes breakdown spark gap, z. B. such that between the electrodes at least one sliding discharge triggering ignition aid has been provided, which at least partially protrudes into the breakdown spark gap, is web-like and made of plastic (see, for DE 41 41 681 A1 or the DE 44 02 615 A1 ).

The above-mentioned in the known overvoltage protection devices, previously mentioned Zündhilfen can be called as "passive Zündhilfen", so called "passive Zündhilfen" because they do not respond "active", but respond only by an overvoltage that occurs at the main electrodes.

" EP 0251 010 A1 discloses an overvoltage protection device according to the preamble of claim 1.

From the DE 198 03 636 A1 is also an overvoltage protection device with two electrodes, with an effective between the two electrodes breakdown spark gap and a starting aid known. In this known overvoltage protection device, the ignition aid, in contrast to the previously described, a sliding discharge triggering ignition aids, as "active ignition aid" formed, namely the fact that in addition to the two electrodes - there referred to as main electrodes - two ignition electrodes are provided. These two ignition electrodes form a second, serving as a spark gap breakdown spark gap. In this known overvoltage protection device belongs to the ignition aid except the spark gap nor a firing circuit with an ignition switch. When applying an overvoltage to the known overvoltage protection device, the ignition circuit with the ignition switching element ensures a response of the spark gap. The spark gap or the two ignition electrodes are arranged with respect to the two main electrodes such that the fact that the spark gap has addressed, the breakdown spark gap between the two main electrodes, called main spark gap responds. The response of the spark gap leads to an ionization of existing in the breakdown spark gap air, so that - abruptly - after response of the spark gap then the breakdown spark gap between the two main electrodes, so the main spark gap responds.

In the known, previously described embodiments of overvoltage protection devices with ignition aids, the starting aids lead to an improved, namely lower and more constant response voltage.

In overvoltage protection devices of the type in question - with or without the use of a starting aid - arises when igniting the breakdown spark gap by the resulting arc a niederimpedante connection between the two electrodes. Initially, the lightning current to be diverted flows intentionally via this low-impedance connection. When the power supply voltage but then follows this low-impedance connection of the overvoltage protection device an undesirable Netzfolgestrom, so that it is anxious to extinguish the arc as quickly as possible after completion of the discharge process. One way to achieve this goal is to increase the arc length and thus the arc voltage.

One way to erase the arc after the dissipation process, namely to increase the arc length and thus the arc voltage is in the overvoltage protection device, as it is known from DE 44 02 615 A1 is known, realized. The from the DE 44 02 615 A1 known overvoltage protection device has two narrow electrodes, which are each formed angularly and each having a sparking horn and a bent therefrom terminal leg. In addition, the spark headers of the electrodes are provided in their adjacent to the terminal legs areas with a bore. The provided in the Funkenhörnem the electrodes holes ensure that at the moment of the response of the overvoltage protection element, ie the ignition, the resulting arc by a thermal pressure effect "is set in motion", ie migrates away from its point of origin. Since the spark horns of the electrodes are arranged in a V-shape relative to one another, the distance to be bridged by the arc as the arc travels out is thus increased, as a result of which the arc voltage also increases. The disadvantage here, however, that in order to achieve the desired increase in the arc length, the geometric dimensions of the electrodes must be correspondingly large, so that the overall overvoltage protection device is bound to certain geometry specifications.

Another way to extinguish the arc after the discharge, consists in the cooling of the arc by the cooling effect of Isolierstoffwänden and the use of gas-releasing insulating materials. In this case, a strong flow of the quenching gas is necessary, which requires a high design effort.

In addition, there is still the possibility to achieve an increase in the arc voltage by increasing the pressure. This is in the DE 196 04 947 C1 proposed to choose the volume in the interior of the housing so that a pressure increase to a multiple of the atmospheric pressure is achieved by the arc. The increase in the follow current extinguishing capacity is achieved by a pressure-dependent influencing of the arc field strength. For this overvoltage protection device to function reliably, however, a very pressure-resistant housing is required, on the other hand, the height of the mains voltage must be known very precisely in order to be able to design the volume in the interior of the housing accordingly.

If the arc in question is extinguished in the case of overvoltage protection devices, the low-impedance connection between the two electrodes is first interrupted, the space between the two electrodes, ie. H. the discharge space, however, is still almost completely filled with a conductive plasma. Due to the existing plasma, the response voltage between the two electrodes is reduced so that it can come even with voltage applied to the renewed ignition of the breakdown spark gap. This problem occurs especially when the over-flow protection device has an enclosed or semi-open housing, because then cooling or volatilization of the plasma is prevented by the substantially closed housing.

To restart the overvoltage protection device, i. H. In order to prevent the breakdown spark gap, various measures have been taken so far to drive away or cool the ionized gas cloud of the ignition electrodes. For this purpose, structurally complex labyrinths and heat sinks are used, which makes the production of the overvoltage protection device more expensive.

The invention is an object of the invention to provide an overvoltage protection device of the type described above, which is characterized by a high Netzfolgestromlöschvermögen, but nevertheless can be easily realized constructively.

The overvoltage protection device according to the invention, in which the above-mentioned object is achieved, is now initially and essentially characterized in that the discharge space is designed such that it extends at least partially transversely and / or opposite to the direction of the electric field of an applied mains voltage, so that the distance to be overcome by the arc between the two electrodes has a transverse component to the electric field E. This has the consequence that the electric field or the voltage applied to the two electrodes can not accelerate continuously from one electrode to the other electrode in the free carrier contained in the plasma, whereby a Netzfolgestrom is prevented.

In known overvoltage protection devices, the unwanted conductive plasma or the free charge carriers contained therein after the actual discharge process is thereby "removed" in that the plasma is driven away from the electrodes. Such overvoltage protection devices, which are also referred to as "Ausblasende" spark gap arrangements, first have the disadvantage that for "blowing out" of the plasma, a relatively strong flow inside the surge protection device must be generated, including gas-emitting insulating materials are used in the rule. The hot plasma is then discharged through exhaust openings in the housing of the overvoltage protection device to the outside into the environment. This has the disadvantage that at the installation of the surge protection certain minimum distances to other live or combustible parts or devices must be complied with, which allows the use of such Ausblasenden overvoltage protection devices only in certain installation conditions.

In contrast, in the overvoltage protection device according to the invention can be dispensed with the "blowing out" of the hot plasma. The inventive arrangement and geometric design of the discharge space, the undesirable consequence of the presence of the plasma - formation of a Netzfolgestrom after the actual discharge - prevented without the plasma must be expelled from the electrodes or cooled.

Constructively, the discharge space can be designed such that it has at least three regions, wherein the first region is connected to the first electrode, the second region to the second electrode and the third region on the one hand to the first region and on the other hand to the second region. The third region thus establishes the connection between the first region and the second region and thus also between the first electrode and the second electrode. The third region is now structurally designed so that the free charge carriers contained in the plasma are not accelerated by the electric field of the applied mains voltage or are accelerated only slightly from the first region to the second region or vice versa. For this purpose, the third region has at least one transverse component to the electric field. In particular, the third region can be aligned obliquely, substantially perpendicularly or even partially opposite to the direction of the electric field of an applied mains voltage.

According to an advantageous embodiment of the invention, the discharge space is structurally realized in that the second electrode facing side of the first electrode and the first electrode facing side of the second electrode are each partially covered with an insulating or high-resistance material, which is not with the insulating or high-resistance material covered region of the first electrode and the second electrode are arranged offset from one another. Due to the design and arrangement of the insulating or high-resistance material on the first and the second electrode, the shape of the discharge space can be determined in a simple manner. If a high-resistance but nevertheless conductive material is applied to the two electrodes, the resistance of which is so great that no arc can form on its surface due to the current limitation, this leads, after the actual discharge process, to the effect in the discharge space between the two electrodes existing free charge carriers separated by the electric field of an applied mains voltage and "sucked" depending on the polarity of the high-resistance material on the first or the second electrode.

Due to the inventive design of the discharge chamber between the two electrodes, wherein the discharge space has at least one transverse component to the electric field is - as described above - the Forming an unwanted network follower prevents. At the same time, however, the response voltage of the breakdown spark gap is increased, which is also undesirable in the rule. Therefore, in a preferred embodiment of the overvoltage protection device according to the invention an active ignition aid for reducing the response voltage is provided. In principle, different, known from the prior art, active ignition aids can be used for this purpose. According to a preferred embodiment, however, the active ignition aid is realized in that the series connection of a Spammngsschaltelements and an ignition element is connected to the two electrodes, wherein the response voltage of the voltage switching element is below the response voltage of the breakdown spark gap and wherein the response of the voltage switching element initially a leakage over the ignition element flows.

The voltage switching element is chosen so that it becomes conductive at the response voltage of the overvoltage protection device, ie "switches". As a voltage switching element, a varistor, a suppressor diode or a gas-filled arrester can be provided. The ignition element is preferably made of a conductive plastic, a metallic material or a conductive ceramic and is in mechanical contact with the second electrode.

Occurs in the overvoltage protection device with the above-described active ignition aid on an overvoltage which is equal to or greater than the predetermined by the voltage switching element operating voltage, so the voltage switching element, so that via the series connection of the first electrode - voltage switching element - ignition element - second electrode to a leakage current begins to flow. The current generated by an initial ignition conductive plasma that can be introduced into the discharge space, resulting in an ignition of the breakdown spark gap between the first electrode and the second electrode and thus to form an arc in the discharge space. For further details of such an active ignition aid, which may also be referred to as "current ignition" is on the DE 101 46 728 A1 directed.

Fig. 1

eine Prinzipskizze eines ersten Ausführungsbeispiels einer erfin- dungsgemäßen Überspannungsschutzeinrichtung,

Fig. 2

eine Prinzipskizze eines zweiten Ausführungsbeispiels einer er- findungsgemäßen Überspannungsschutzeinrichtung,

Fig. 3

eine Prinzipskizze eines weiteren Ausführungsbeispiels einer er- findungsgemäßen Überspannungsschutzeinrichtung,

Fig. 4

eine Prinzipskizze eines vieiten Ausführungsbeispiels einer er- findungsgemäßen Überspannungsschutzeinrichtung,

Fig. 5

eine Prinzipskizze eines weiteren Ausführungsbeispiels einer er- findungsgemäßen Überspannungsschutzeinrichtung, und

Fig. 6

eine Prinzipskizze eines letzten Ausführungsbeispiels einer er- findungsgemäßen Überspannungsschutzeinrichtung,

In particular, there are a variety of ways to design and develop the overvoltage protection device according to the invention. For this purpose, it is proven on the one hand to the claims subordinate to claim 1, on the other hand, to the following description of preferred embodiments in conjunction with the drawings. In the drawing show

Fig. 1

a schematic diagram of a first embodiment of an inventive overvoltage protection device,

Fig. 2

a schematic diagram of a second embodiment of an inventive overvoltage protection device,

Fig. 3

1 is a schematic diagram of a further exemplary embodiment of an overvoltage protection device according to the invention,

Fig. 4

1 is a schematic diagram of a preferred embodiment of an overvoltage protection device according to the invention;

Fig. 5

a schematic diagram of another embodiment of an inventive overvoltage protection device, and

Fig. 6

1 is a schematic diagram of a last embodiment of an inventive overvoltage protection device,

In the figures, various embodiments of an overvoltage protection device according to the invention are shown. To the overvoltage protection device - which is shown only in terms of their basic structure - each include a first electrode 1, a second electrode 2 and the electrodes 1, 2 receiving housing 3. Between the two electrodes 1 and 2 there is a breakdown spark gap, wherein the Igniting the breakdown spark gap between the two electrodes 1 and 2, an arc 4 is formed.

According to the invention, a discharge space 5 is provided between the two electrodes 1 and 2, wherein the discharge space 5 is inclined at least partially (FIG. Fig. 2 ), partly across ( Fig. 1 . 5 and 6 ), partly opposite ( Fig. 3 ) or partly transversely and oppositely ( Fig. 4 ) to the direction of the electric field of an applied mains voltage shown by arrows 6 runs. In all embodiments, the discharge space 5 thus has at least one transverse component to the electric field. In contrast to the known overvoltage protection device, therefore, not the entire space between the electrodes 1, 2 functions as the discharge space 5.

As can be seen from the figures, the discharge space 5 can be divided into three areas 7, 8 and 9. In this case, the first region 7 is connected to the first electrode 1, the second region 8 to the second electrode 2 and the first region 7 to the second region 8 via the third region 9. In the embodiments illustrated in the figures, the first region 7 and the second region 8 extend substantially parallel to the direction of the electric field. In contrast, the third region 9 extends in the embodiment according to the Fig. 1 . 5 and 6 substantially perpendicular or transverse to the direction of the electric field. In the embodiment according to Fig. 2 the third region 9 of the discharge space 5 extends obliquely and according to the exemplary embodiment Fig. 3 obliquely opposite to the direction of the electric field, ie the longitudinal direction of the third region 9 of the discharge space 5 has a transverse component to the direction of the electric field. According to the overvoltage protection device according to the invention Fig. 4 For example, the third region 9 of the discharge space 5 has both regions which are perpendicular to the direction of the electric field and a region which is opposite to the direction of the electric field.

By aligning the third region 9 of the discharge space 5 obliquely, transversely or opposite to the direction of the electric field of an applied mains voltage is achieved that the free charge carriers contained in the plasma no longer consistently from the first electrode 1 to the second electrode 2 - or vice versa - be accelerated, whereby the formation of a network follow current is prevented.

To realize the discharge space 5, an insulating or high-resistance material 12 is applied to the second electrode 2 side 10 of the first electrode 1 and an insulating or high-resistance material 13 is applied to the side 11 of the second electrode 2 facing the first electrode 1. As can be seen from the figures, the insulating or high-resistance material 12 and 13 is not applied over the entire area on the first electrode 1 and the second electrode 2, respectively, but there is a region 14 or 15 on the first electrode 1 and the second electrode, respectively 2 recessed, which is not covered with the insulating or high-resistance material 12 and 13 respectively. In this case, as can be seen directly from the figures, the two regions 14 and 15 of the first electrode 1 and the second electrode 2 not covered by the insulating or high-resistance material 12 and 13, respectively, are offset relative to one another.

From a comparison of the in the Fig. 1, 2 and 3 illustrated embodiments of an overvoltage protection device according to the invention is thereby seen that by a corresponding choice of the dimensions of the material 12, 13, the course of the discharge chamber 5 can be set in a simple manner. Has the material 12, 13 over its length a constant thickness, as in the embodiment according to Fig. 1 the fur is, this leads to a region 9 of the discharge space 5, which is transverse or perpendicular to the direction of the electric field. If the thickness of the material 12, 13 changes over its length ( Fig. 2 and 3 ), this leads to an oblique ( Fig. 2 ) or partially opposite ( Fig. 3 ) extending to the direction of the electric field discharge space. 5

As in the embodiment according to Fig. 4 can be seen, by an appropriate design and arrangement of the materials 12, 13 on the electrodes 1, 2 almost any gradients of the discharge space 9 can be realized. The optimal for the particular application of the discharge space 5 depends on the one hand, after the required Netzfolgestromlöschvermögen on the other hand according to the level of the desired operating voltage of the overvoltage protection device. However, the latter can also be determined by providing a suitable starting aid, in particular an active starting aid.

The overvoltage protection devices according to Fig. 1 and 5 differ from each other in that in the overvoltage protection device according to Fig. 1 an insulating material 12, 13 is applied to the electrodes 1, 2, while in the overvoltage protection device according to Fig. 5 a high-resistance but conductive material 12, 13 is used. The arrangement of a high-resistance, yet conductive material 12, 13 directly on the one side 10 of the first electrode 1 and the one side 11 of the second electrode 2 causes the present in the discharge space 5 free charge carrier after the actual discharge adjacent mains voltage and - depending on the polarity - "sucked" by the material 12 or the material 13. By reducing the number of free charge carriers in the discharge space 5, the impedance of the discharge space 5 increases, whereby the occurrence of a follow-on current is prevented even when mains voltage is applied. Instead of a - known in the art - mechanical "blow-out" of the plasma or the free charge is carried out here an electrical "suction" of the free charge carriers, which, however, also prevents the unwanted Netzfolgestrom while avoiding the disadvantages of the known "blow-out".

In Fig. 6 a further variant of an overvoltage protection devices is shown. In this embodiment is first - comparable to the filling according to Fig. 1 - An insulating material 12, 13 applied to the electrodes 1, 2. However, the discharge space 5 is not only by the shape of the insulating material 12, 13, but primarily by additionally on the insulating material 12, 13 applied high-resistance material 17, 18 - comparable to the embodiment according to FIG Fig. 5 - certainly. The high-resistance material 17 is at a distance from the region 14 with the first electrode 1 and the high-resistance material 18 spaced from the region 15 to the second electrode 2 electrically connected. The two regions 19, 20, in which the first electrode 1 is connected to the high-resistance material 17 and the second electrode 2 is connected to the high-resistance material 18, are likewise arranged offset from one another. By the high-resistance material 17, 18 is first achieved that after the breakdown in the discharge space 5 located free charge carriers are "sucked". In this case, flows through the high-resistance material 17, 18, a current, resulting in a voltage drop along the high-resistance material 17, 18 leads. This voltage drop along the high-resistance material 17, 18 produces an electric field whose field lines 6 'have a component opposite to the direction of the arc 4. This results in a distortion of the electric field in the discharge space 5, whereby the "transverse character" of the discharge space 5 is amplified. However, this amplification of the "cross character" takes place here - in contrast to the exemplary embodiment according to FIG Fig. 3 - not geometric but electric.

Finally, it can be seen from the figures that the housing 3, which is preferably designed as a metallic pressure housing, has an inner insulating housing 16, wherein in the exemplary embodiments according to FIGS Fig. 1 to 4 the insulating material 12, 13 is connected to the insulating housing 16 or to parts of the insulating housing 16.

Claims (12)

1. Overvoltage protection means, having a first electrode (1), having a second electrode (2), having a breakdown spark gap which has been formed between the two electrodes (1, 2), and a housing (3) which holds the electrodes (1, 2), wherein when the breakdown spark gap is ignited, an arc (4) being formed between the two electrodes (1, 2) within a discharge space (5) that connects the two electrodes (1, 2),
   characterized in
   that the discharge space (5) is made such that it runs at least partially transversely and/or opposite the direction of an electrical field of a prevailing line voltage so that the distance to be overcome by the arc (4) between the two electrodes (1, 2) when the breakdown spark gap is ignited, has a transverse component to the electrical field E.
2. Overvoltage protection means according to claim 1, characterized in that the discharge space (5) has at least three regions (7, 8, 9), the first region (7) being connected to the first electrode (1), the second region (8) being connected to the second electrode (2) and the third region (9) being connected, on the one hand, to the first region (7) and, on the other hand, to the second region (8).
3. Overvoltage protection means according to claim 2, characterized in that the third region (9) runs essentially perpendicularly to the direction of the electrical field of a prevailing line voltage.
4. Overvoltage protection means according to claim 2, characterized in that the third region (9) runs obliquely to the direction of the electric field of a prevailing line voltage.
5. Overvoltage protection means according to claim 2, characterized in that the third region (9) runs partially opposite to the direction of the electric field of a prevailing line voltage.
6. Overvoltage protection means according to any one of claims 1 to 5, characterized in that the side (10) of the first electrode (1) facing the second electrode (2) and the side (11) of the second electrode (2) facing the first electrode (1) are partially covered with an insulating or high-resistance material (12, 13), the region (14) of the first electrode (1) not covered with the insulating or high-resistance material (12) and the region (15) of the second electrode (2) not covered with the insulating or high-resistance material (13) being arranged offset to one another.
7. Overvoltage protection means according to any one of claims 1 to 5, characterized in that the side (10) of the first electrode (1) facing the second electrode (2) and the side (11) of the second electrode (2) facing the first electrode (1) are partially covered with an insulating material (12, 13) the region (14) of the first electrode (1) not covered with the insulating material (12) and the region (15) of the second electrode (2) not covered with the insulating material (13) being arranged offset to one another, wherein the side of the insulating material (12) facing the second electrode (2) and the side of the insulating material (12) facing the first electrode (1) are at least partially covered with a high-resistance material (17, 18), the first electrode (1) spaced away from the region (14) being electrically conductively connected to the high-resistance material (17) and the second electrode (2) spaced away from the region (15) being electrically conductively connected to the high-resistance material (18).
8. Overvoltage protection means according to any one of claims 1 to 7, characterized in that there is an active ignition aid.
9. Overvoltage protection means according to claim 8, characterized in that a series connection of a voltage switching device and an ignition element is connected to the two electrodes (1, 2), the sparkover voltage of the voltage switching device being below the sparkover voltage of the breakdown spark gap, and at first a diversion current flowing via the ignition element when the voltage switching device responds.
10. Overvoltage protection means according to claim 9, characterized in that there is a varistor, a suppressor diode or a gas-filled voltage arrester as the voltage switching device.
11. Overvoltage protection means according to claim 9 or 10, characterized in that the ignition element consists of a conductive plastic, a metal material or a conductive ceramic and is in mechanical contact with the second electrode (2).
12. Overvoltage protection means according to any one of claims 1 to 11, characterized in that the housing (3) is made as a metal pressure housing and has an inner insulation housing (16).

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