EP1566868B1 - Overvoltage arrester element and ignition device for an overvoltage arrester element - Google Patents

Description

The invention relates to an overvoltage protection element for deriving transient overvoltages, comprising at least two electrodes, with at least one ignition element of insulating material arranged between the electrodes and an air breakdown spark gap which acts between the electrodes, wherein the air breakdown spark gap between the two electrodes create an arc. In addition, the invention also relates to an ignition element for use in an overvoltage protection element, wherein the ignition element is arranged and designed such that a region of weakened insulation (ignition region) is provided between the two electrodes.

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. Overvoltages can significantly damage electrical and electronic equipment and systems. The damage is not limited to industrial and commercial plants. Also the building technology, up to the devices of the daily use in the private household, like kitchen devices, telephone system, television sets and hi-fi systems as well as computers are affected. Without effective protection against overvoltages, high costs for repair or new acquisition of the affected systems and equipment can be expected.

Electrical circuits operate at the voltage specified for them, the nominal 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 in particular, the transient overvoltages, which can occur due to atmospheric discharges, but also by switching operations or short circuits in power supply networks and galvanically, inductively or capacitively coupled into electrical circuits. In order to protect electronic measuring, control, and switching circuits, especially telecommunications equipment and installations, wherever they are used against transient overvoltages, overvoltage protection element or overvoltage protection devices have been developed and known for more than twenty years.

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

The GB 545 677 A discloses an overvoltage protection element having two electrodes and a very thin layer of dielectric material disposed between the electrodes and coated on an electrode. When an overvoltage occurs, it comes to a large number of discharges between the two electrodes through the pores of the layer, so that a large surge current carrying capacity is given.

From the DE 23 37 743 A1 is a spark gap with two electrodes and arranged between the electrodes, the electrodes spaced insulation layer known in which the flashover between an outside of the one electrode and an outside of the other electrode is, so that the flashover no longer in a closed chamber is provided. As a result, the energy generated during the rollover can be dissipated more quickly.

Initially, it has been stated that the overvoltage protection element according to the invention has two electrodes and an air-breakdown spark gap existing between the two electrodes. With air breakdown spark gap is generally a breakdown spark gap meant; So it should also be a breakdown spark gap, in which not air, but another gas between the electrodes is present. In addition to overvoltage protection elements with an air breakdown spark gap, there are overvoltage protection elements with an air flashover spark gap, in which a sliding discharge occurs when responding.

Overvoltage protection elements with an air breakdown spark gap have over overvoltage protection elements with an air 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 elements have been proposed with an air breakdown spark gap, which have been improved with respect to 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 air breakdown spark gap, z. B. such that between the electrodes at least one of a sliding discharge triggering ignition aid has been provided, which at least partially protrudes into the air breakdown spark gap, is web-like and made of plastic (see. DE 41 41 681 A1 . DE 42 44 051 A1 or DE 44 02 615 A1 ).

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

From the German patent application 198 03 636 is an overvoltage protection element or an overvoltage protection device with two electrodes, with an effective between the two electrodes air breakdown spark gap and a starting aid known. In this known overvoltage protection device the ignition aid is designed as an "active ignition aid", 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 air 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 and the two ignition electrodes are arranged with respect to the two main electrodes such that the fact that the spark gap has addressed, the air breakdown spark gap between the two main electrodes responds. The response of the Zündschnkenstrekke leads to an ionization of existing in the air breakdown spark gap air, so that - abruptly - after response of the spark gap then the air breakdown spark gap between the two main electrodes responds.

In the known, previously described embodiments of overvoltage protection elements with ignition aids, the ignition aids lead to an improved, namely lower and more constant response voltage. A disadvantage of an active ignition aid, however, is that an additional ignition circuit with an ignition switching element required to realize a response of the spark gap. There is a risk that the Zündfunkenstrec-ke or the ignition circuit with the ignition switch are destroyed by the lightning current or the usually occurring Netzfolgestrom.

In particular, an overvoltage protection element according to the preamble of claim 1 is made DE-A-4244051 known.

The invention is therefore an object of the invention to provide a Überspannungssehutzelement of the type described above, in which in a particularly simple and effective manner a relatively low and constant as possible operating voltage can be guaranteed. The ignition element used for this purpose should be as simple and therefore inexpensive to manufacture.

The overvoltage protection element according to the invention, in which the object indicated above is achieved, is now initially and essentially characterized in that when a voltage is applied to the ignition element, a discharge on the surface of the ignition element leads to a conductive connection between the two electrodes, wherein the conductive Compound has a low current carrying capacity, so that it is at a load of this conductive connection with a leakage current due to the low current carrying capacity of the conductive connection to a "burning" of the conductive connection comes.

Thus, a completely new overvoltage protection element with an ignition element or a completely new ignition element for use in an overvoltage protection element is realized, as can be seen from the following functional description:

The ignition element is chosen or dimensioned such that when a voltage greater than the operating voltage of the overvoltage protection element is applied, a sliding discharge occurs on the surface of the ignition element which leads to a conductive connection between the two electrodes adjacent to the ignition element. If this conductive connection is loaded with a leakage current, then due to the low current-carrying capacity of the conductive connection, the conductive connection will "burn up". By this "burning" of the ignition is ionized, so that it comes - suddenly - to ignite the air breakdown spark gap between the two electrodes.

Due to the intentionally occurring conductive connection between the two electrodes of the air-Durschlag spark gap, the overvoltage protection element according to the invention differs significantly from the known overvoltage protection elements. From the prior art (see. 198 56 939 A1 Although it is known to arrange an element made of insulating material between the two electrodes, this element, however, in accordance with its function as a service holder, consists of an insulating material which permanently ensures the desired insulation between the two electrodes even in the case of a pending arc.

From the DE 42 44 051 A1 Although an overvoltage protection element is also known in which an ignition element made of insulating material is arranged between the two electrodes, in this known overvoltage protection element the ignition of the air breakdown spark gap is effected only by a sliding discharge occurring at the ignition element. In the known overvoltage protection element is characterized by the arrangement of the ignition element thus realizes an auxiliary air flashover spark gap between the two electrodes; a conductive connection between the two electrodes via the ignition element, however, is not provided.

The above-described arrangement and design of the ignition element can preferably take place in that the region of weakened insulation (ignition region) is realized by a recess in the ignition element. For example, this recess may simply be a hole made in the ignition element, in which case the ignition region is completely surrounded by the ignition element. In addition, however, it is also possible to form the ignition area at the edge in the ignition element.

The material used for the ignition element may preferably be a plastic with a relatively low CTI value (Comperative Trecking Index). By using a plastic with a low CTI value - and thus with a low tracking resistance - the desired formation of the conductive compound on the surface of the ignition element is promoted. In contrast, in known overvoltage protection elements for the spacers arranged between the electrodes, plastics, for example POM, are used with the highest possible CTI value.

According to a further preferred embodiment of the invention, the ignition element is arranged and designed such that when an arc occurs between the electrodes, a charring of the surface of the ignition element occurs. This ensures that when a renewed occurrence of an overvoltage the initial conditions of a conductive, low current carrying connection between the two electrodes on the surface of the ignition element are present again, so that it again to an initial ignition of the air-Durschlag spark gap and a "burning" the conductive connection and thus leads to an ionization of the ignition range. As a result, an overvoltage protection element is provided which has a constant response with a low response voltage even if there are several overvoltages that occur in succession.

To improve the response of the overvoltage protection element according to the invention at the first application of an overvoltage, a conductive, low current carrying coating is applied on the surface of the ignition element according to a preferred embodiment. This ensures a conductive connection between the two electrodes, which is independent of the charring which occurs due to the discharge on the surface of the ignition element. The coating can be realized, for example, by a chemical, thermal or electrothermal charring of the surface of the ignition element in the manufacture of the overvoltage protection element.

Since in the above-described overvoltage protection element according to the invention, a conductive connection between the two electrodes is realized or is realized by applying an overvoltage by discharging on the surface of the ignition element, the voltage protection element is advantageously connected in series with the overvoltage protection element. A voltage switching element can be provided in particular a gas-filled surge arrester, a varistor or a suppressor diode. By additionally connected in series voltage switching element is prevented that over the overvoltage protection element in the normal case, d. H. if there is no overvoltage, a current flows. In such an overvoltage protection device, which then consists of the overvoltage protection element according to the invention and the additional voltage switching element, the voltage switching element is selected or dimensioned so that it becomes conductive at the response voltage of the overvoltage protection device, ie "switches". As a result, the overvoltage is applied to the overvoltage protection element or to the two electrodes, which then leads to the ignition of the air breakdown spark gap previously described in detail by the initial ignition triggered by the ignition element.

The ignition element described above, which is provided for use in the above-described overvoltage protection element, is characterized particularly simple and inexpensive to produce, that the ignition element consists of at least two electrically conductive layers and at least one interposed insulating layer, wherein the insulating layer by gluing or Press with the electrical conductive Layers is connected and has a range of weak insulation (ignition). The production of the ignition element according to the invention can be carried out according to the known manufacturing processes for multilayer printed circuit boards (multilayer printed circuit boards), which largely known materials, ie copper foils for the electrically conductive layers and polyimide films or FR4 films for the insulating layer can be used ,

The use of electrically conductive layers or foils, in particular of copper foils and of insulating foils, for example polyimide foils, makes it possible to produce very small distances between the conductive layers with very narrow dimensional tolerances. The electrically conductive layers are so far apart or insulated by the insulating layer from each other so that the electrical insulation is well above the expected in the worst case response of the overvoltage protection element. In practice, copper foils or polyimide foils or FR4 foils with standard available thicknesses of 35 μm, 50 μm, 70 μm or 100 μm can be used both for the electrically conductive layers and for the insulating layer. Of course, however, other metallic foils or electrically conductive plastic films can be used instead of copper foils.

The region of weakened insulation (ignition region) in the insulating layer, in which both the initial ignition and the actual ignition of the air breakdown spark gap takes place, can simply pass through a recess or hole in the insulating layer and optionally in one or both be realized electrically conductive layers. In this case, a hole which is formed both in the insulating layer and in the two conductive layers can be produced, for example, simply by a corresponding hole after lamination of the individual layers.

With a corresponding dimensioning of the electrically conductive layers, these can directly assume the function of the electrodes of an overvoltage protection element, so that then such an ignition element itself can function as an overvoltage protection element. In general, the However, conductive layers of the ignition element designed so that they can be contacted directly by the electrodes of the overvoltage protection element.

Fig. 1

eine Prinzipskizze eines Ausführungsbeispiels eines erfindungsgemäßen Überspannungsschutzelements,

Fig. 2

ein erstes Ausführungsbeispiel eines erfindungsgemäßen Zündelements,

Fig. 3

ein zweites Ausführungsbeispiel eines erfindungsgemäßen Zündelements,

Fig. 4

ein Ausführungsbeispiel eines Zündelements, ähnlich der Ausführung gemäß Fig. 1,

Fig. 5

ein Ausführungsbeispiel eines Zündelements mit einer Mehrzahl von elektrisch leitfähigen und isolierenden Schichten,

Fig. 6

ein weiteres Ausführungsbeispiel eines Zündelements mit einer Mehrzahl von elektrisch leitfähigen und isolierenden Schichten,

Fig. 7

ein Ausführungsbeispiel eines Zündelements für ein mehrphasiges Überspannungsschutzsystem und

Fig. 8

ein weiteres Ausführungsbeispiel eines Zündelements für ein mehrphasiges Überspannungsschutzelement.

In particular, there are a variety of ways to design and develop the overvoltage protection element according to the invention or the ignition element according to the invention. Reference is made on the one hand to the patent claims 1 and 8 subordinate claims, 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 an embodiment of an overvoltage protection element according to the invention,

Fig. 2

A first embodiment of an ignition element according to the invention,

Fig. 3

A second embodiment of an ignition element according to the invention,

Fig. 4

an embodiment of an ignition element, similar to the embodiment according to Fig. 1 .

Fig. 5

an embodiment of an ignition element having a plurality of electrically conductive and insulating layers,

Fig. 6

a further embodiment of an ignition element with a plurality of electrically conductive and insulating layers,

Fig. 7

an embodiment of an ignition element for a multi-phase overvoltage protection system and

Fig. 8

a further embodiment of a firing element for a multi-phase overvoltage protection element.

In the Fig, 1 an inventive overvoltage protection element is shown only in terms of its basic structure. The illustrated overvoltage protection element includes a first electrode 1, a second electrode 2, an ignition element 3 arranged between the two electrodes 1 and 2, and an air-breakdown spark gap 4 existing between the two electrodes 1 and 2. When the air is ignited Shock spark gap 4 is formed between the two electrodes 1 and 2 - not shown - arc over which the lightning current to be derived flows.

The ignition element 3 is now arranged so that between the two electrodes 1 and 2, a region of weakened insulation (ignition area) is formed, in which the arc is formed when igniting the air breakdown spark gap 4. According to the invention the ignition element 3 is formed so that when a voltage applied to the ignition element 3, a discharge on the surface 5 of the ignition element 3 leads to a conductive connection between the two electrodes 1 and 2, wherein the conductive connection has only a low current carrying capacity. If a leakage current then begins to flow via this conductive connection, due to the low current carrying capacity of the conductive connection, the conductive connection will burn up and thus ionize the ignition region, which leads to a sudden ignition of the air breakdown spark gap 4.

The resulting during ignition of the air breakdown spark gap 4 arc ensures at a suitable dimensioning of the ignition element 3 that it comes to a "charring" on the surface 5 of the ignition element 3. This ensures that, in the event of a renewed occurrence of an overvoltage, there is again a conductive, low-current-carrying connection between the two electrodes 1 and 2, which in turn causes a burn-up and thus an initial ignition of the air-breakdown spark gap 4 during a load with a leakage current and thus leads to an ignition of the overvoltage protection element.

Since in such an overvoltage protection element, even when the normal voltage is applied, a conductive connection between the two electrodes 1 and 2 is present, as desired Fig. 1 the actual overvoltage protection element, an additional voltage switching element 6, for example, a varistor and / or a gas-filled surge arrester connected in series. In such an overvoltage protection device, which consists of the overvoltage protection element according to the invention and the additional voltage switching element 6, the voltage switching element 6 is dimensioned so that it becomes conductive at the response voltage of the overvoltage protection device. If an overvoltage occurs at the overvoltage protection device, this leads to a switching of the voltage switching element 6, so that then the overvoltage is applied to the two electrodes 1 and 2, resulting in the previously described ignition of the air breakdown spark gap 4 by the current ignition triggered initial ignition of the ignition element 3 leads. On the other hand, the voltage switching element 6 prevents, in the normal case, ie when no overvoltage is applied, a - then unwanted - current flows through the overvoltage protection element.

Hereinafter, preferred embodiments of the ignition element 3 according to the invention based on the Fig. 2 to 8 explained.

That in the Fig. 2 to 4 illustrated ignition element 3 consists of two conductive layers 7, 8 and an insulating layer 9 arranged therebetween, wherein the region of weakened insulation is realized by a recess 10 in the insulating layer 9. The recess, for example, according to the Fig. 1 and 3 can be formed as a central hole can be easily prepared by drilling or milling. It can - as this is a comparison of Fig. 2 and 4 shows - the recess 10 may be formed either only in a conductive layer 7 or in both conductive layers 7, 8.

The production of the ignition element 3 according to the invention is now particularly simple in that the known from the production of multilayer printed circuit boards (multilayer printed circuit boards) manufacturing processes can be applied. Thus, the conductive layers 7, 8, which may be, for example, standardized copper foils, be connected to the insulating layer 9 by lamination. Also suitable for the insulating layer 9 are the materials known from the production of multilayer circuit boards, such as polyimide films or FR-4 films, with their default available thicknesses of 35 to 100 μm. As a result, the distance between the conductive layers 7, 8, which can be connected directly to the electrodes 1 and 2, can be set very small but nevertheless very accurately, as a result of which very low response voltages can be realized.

In a - shown in the embodiments - circular design of the ignition element 3, the insulating layer 9 has a slightly larger outer diameter than the conductive layers 7, 8, so that at the edge region 11 of the ignition element 3 is given by an extended creepage increased insulation, whereby ignition in this area is prevented.

Fig. 5 shows an embodiment of a firing element 3, which has a plurality of conductive layers 7, 8 and a plurality of insulating layers 9. In the illustrated embodiment, the three conductive layers 7, 7 'and 7 "and the three conductive layers 8, 8' and 8" are electrically connected to each other, so that although a total of six conductive layers 7, 7 ', 7 "and 8, 8 ', 8 "are present, but these have only two different potentials, wherein the two potentials are arranged alternately to each other and each separated by an insulating layer 9. Of course, instead of the six conductive layers shown, even more conductive Layers can be arranged alternately with two different potentials.

By such a multiplication of the principle in Fig. 2 shown construction of the ignition element 3 manufacturing variations due to the properties of the insulating layers 9 and consequent fluctuations in the response voltage of the ignition element 3 can be compensated. At the in Fig. 5 illustrated embodiment of the ignition element 3, the initial ignition is always triggered by the Teilzündelement 3 'that has the lowest response voltage, ie with otherwise identical properties in Teilzündelement 3' with the thinnest insulating layer. 9

Also in the embodiment according to Fig. 6 For example, the ignition element 3 has a plurality of conductive layers 7, 7 ', 8, 8' and a plurality of insulating layers 9, wherein the conductive layers 7, 7 'and 8, 8' are electrically connected to each other so that only two different potentials are present here , In contrast to the embodiment according to Fig. 5 Here, however, the two different potentials are not arranged several times alternately. The advantage of this embodiment compared to the embodiment according to Fig. 2 is that after the ignition of the air breakdown spark gap 4, the arc jumps directly on the outer conductive layers 7, 8, so that a larger arc is present.

The Fig. 7 and 8th Finally, two embodiments of an ignition element 3 with three horizontally one above the other ( Fig. 7 ) or four horizontally juxtaposed potentials ( Fig. 8 ). Such ignition elements 3 are thus suitable for use in an overvoltage protection element which is used in a three-phase network. In contrast to the embodiment according to Fig. 2 is in accordance with the ignition element 3 Fig. 7 a third conductive layer 13 is provided, which is separated from the second conductive layer 8 by a second insulating layer 14, so that the three conductive layers 7, 8, 13 have three different potentials.

In the ignition element 3, as in Fig. 8 are shown, in addition to a circular conductive layer 7 and a likewise circular insulating Layer 9 further conductive layers 8, 13, 15 and 16 are provided, which are each not electrically connected to each other. The conductive layers 8, 13, 15 and 16 are each formed in a segment of a circle and arranged side by side, wherein the circular conductive layer 7 is arranged opposite to all. In the event of a pending overvoltage between the first conductive layer 7 and one of the other conductive layers 8, 13, 15 or 16, initial firing of the respective air breakdown spark gap 4 occurs, due to the arrangement of the individual conductive layers 8, 13 , 15 and 16 to each other or to the conductive layer 7 ignition of all air breakdown spark gap 4 takes place. In a corresponding circuit of the overvoltage protection element thereby the desired level of protection is ensured not only between the active phase conductors (L1, L2, L3) and the neutral conductor (N) or between the neutral conductor (N) and the ground (PE) but between all line branches.

Claims (13)

1. Overvoltage protection element for discharging transient overvoltages comprising at least two electrodes (1, 2), having at least one ignition element (3) of insulating material located between the electrodes (1, 2) and an air breakdown spark gap (4) which acts between the electrodes (1, 2), wherein an arc being formed when the air breakdown spark gap (4) between the two electrodes (1, 2) is ignited, and
   wherein the ignition element (3) is arranged and designed so that an area with weakened insulation, i.e. ignition area, is provided between the two electrodes (1, 2),
   characterized in,
   that when a voltage is applied to the ignition element (3), a discharge on the surface (5) of the ignition element (3) leads to a conductive connection between the two electrodes (1, 2), wherein the conductive connection has a low current-carrying capacity,
   so that when this conductive connection is loaded with a discharge current the conductive connection "bums out" due to the low current-carrying capacity of the conductive connection.
2. Overvoltage protection element according to claim 1, characterized in that the area with weakened insulation is realized by a recess (10) in the ignition element (3).
3. Overvoltage protection element according to claim 1 or 2, characterized in that the ignition element (3) consists of plastic or another insulating material with a relatively low CTI value.
4. Overvoltage protection element according to any one of claims 1 to 3, characterized in that the conductive connection is formed only on the surface (5) of the ignition element (3).
5. Overvoltage protection element according to any one of claims 1 to 4, characterized in that the ignition element (3) is arranged and designed so that when there is an arc between the electrodes (1, 2), a "carbonization" of the surface (5) of the ignition element (3) occurs.
6. Overvoltage protection element according to any one of claims 1 to 5, characterized in that a conductive coating with low current-carrying capacity is applied to the surface (5) of the ignition element (3).
7. Overvoltage protection element according to claim 6, characterized in that the coating is realized by a chemical, thermal or electro-thermal carbonization.
8. Ignition element for use in an overvoltage protection element according to any one of claims 1 to 7,
   characterized in
   that the ignition element (3) consists of at least two electrically conductive layers (7, 8) and at least one insulating layer (9) located between them, wherein the insulating layer (9) is connected to the electrically conductive layers (7, 8) by adhesion or, respectively, by pressing and having an area with weakened insulation (5), i.e. ignition area.
9. Ignition element according to claim 8, characterized in that the area with weakened insulation is realized by a recess (10) or, respectively a hole in the insulating layer (9) and, where applicable, additionally in the electrically conductive layer (7) or, respectively, in the electrically conductive layers (7, 8), in particular by means of drilling or milling.
10. Ignition element according to claim 8 or 9, comprising at least three electrically conductive layers (7, 7', 8, 8') and at least two insulating layers (9), characterized in that at least two electrically conductive layers (7, 7', 8, 8') are electrically connected to one another.
11. Ignition element according to any one of claims 8 to 10, characterized in that copper foils are used as electrically conductive layers (7, 8) and polyimide film or FR4 film is used as an insulating layer (9).
12. Ignition element according to any one of claims 8 to 11, characterized in that conductive components, for example, fibers or metal particles are located insulated in the insulating layer (9).
13. Ignition element according to any one of claims 8 to 12, characterized in that the electrically conductive layers (7, 8) and/or the insulating layer (9) have a thickness of less than 0.2 mm, preferably from 35 µm to 70 µm.

Images