EP3331111B1 - Overvoltage protection device based on a spark gap comprising at least two main electrodes arranged in a pressure-resistant housing - Google Patents

Description

The invention relates to an overvoltage protection device based on spark gaps, comprising at least two main electrodes located in a pressure-tight housing and at least one auxiliary ignition electrode, a functional assembly for reducing the response voltage of the spark gap being connected in the housing volume, which is connected to one of the main electrodes and the auxiliary ignition electrode, according to the preamble of claim 1.

The trend in the development of electrical and electronic systems is towards greater compactness and smaller external dimensions. At the same time, however, the sensitivity to internal and external overvoltages of such systems increases. In addition, there is a desire and also the need for trouble-free operation of electrical and electronic equipment, which results in new requirements for surge protection technology.

So surge arresters with a reduced response voltage z. B. from the DE 199 52 004 A1 or the DE 198 03 636 A1 known. In order to make the systems even more compact, there has been a growing tendency in recent years to arrange lightning arresters for coarse protection and surge arresters for fine protection without the previous decoupling via cable routes or through specially dimensioned inductors.

So that the weaker fine protection element is not necessarily overloaded in such a compact arrangement, there are special requirements for the lightning current arrester or the coarse protection element.

To achieve this task, it became known to use separate and, in some cases, quite complex ignition aids, which are externally coupled to the lightning current arrester on a spark gap basis. According to DE 199 52 004 A1 take over these ignition aids also function or partial functions of the fine protection under certain conditions.

In general, the ignition aids are designed as active ignition aids for powerful surge arresters for use in low-voltage networks between L and N and also N and PE. With the help of a pulse transformer, these ignition aids generate a high ignition voltage, by means of which one of the sections is flashed over in a typical three-electrode spark gap arrangement.
A disadvantage of such a solution is on the one hand the sometimes considerable space requirement of the ignition aid, which generally consists of a large number of components, and on the other hand the resulting interference factors.

The space requirement of this ignition device limits the design options for the main functional element, namely the actual spark gap, given the relatively small dimensions of the surge arresters. This limitation does not only affect the generally available volume, but also the need for the additional contacting of a third electrode.

Compared to a simple spark gap without ignition aid, there are currently a large number of additional sources of interference.
In the spark gap itself, it is no longer only necessary to ensure the function of a separation gap, but the function of two or even three separation paths between the three-electrode arrangement. If one of these separation sections is damaged, there is a risk of the arrester failing. This can cause damage within the spark gap, but also the ignition aid itself. This can quickly destroy the entire arrester and endanger neighboring elements, especially if the ignition aid is overloaded. The same is, however, not only possible in the case of damage within the spark gap, but also in the event of faults such as vibrations, vibrations, erosion, poor installation and so on, damage or corrosion of the contacts of the ignition device with the main connections or the connectors to the spark gap.

Poor or aged contact points can lead to spark formation outside the spark gap and ultimately to external sparkover of the spark gap.

Although there are certainly ways to at least partially protect the ignition aids from overload, measures such as those in the DE 199 14 313 A1 shown, only further, costly effort and space requirements.

With all the difficulties described above, however, an ignition aid for the desired low protection level is essential. The general reduction in the spacing of the main electrodes, as was the case with older devices of the prior art, is not expedient in the case of modern arresters, since under the usual geometric conditions the required spacings cannot be achieved or these mean a significant deterioration in the achievable surge current values .

With the generic DE 101 57 817 A1 An arrangement for an isolating spark gap is presented in which a conventional active ignition aid with an impulse transmitter is integrated in a housing enclosed by the electrodes in a chamber.

However, this arrangement has the disadvantage that active ignition aid is necessary, which increases the space requirement and the susceptibility to faults. This safe functioning of active ignition aids is disturbed, for example, by changing the response values and the insulation value of the individual isolating sections. Since these phenomena increase with the number and amount of the loads, this can lead to thermal overload or even to failure of the ignition aid. In the above-mentioned arrangement, the risk of thermal overload also increases due to the lack of cooling or also due to heating due to the power conversion in the spark gap and thus the ignition device during loads.
The electrodes are designed in accordance with DE 101 57 817 A1 would also have to be relatively large so that on the one hand the ignition aid can be accommodated and on the other hand the ignition aid is protected from the temperature effect of the thermally highly stressed electrodes. There is also a need the frictional connection to produce reproducible distances between the partial spark gaps between the electrodes, whereby the ignition aid is not only loaded thermally but also by mechanical forces.
Strong dynamic loads also occur between the electrodes when the spark gap responds. There are further restrictions with this arrangement when used in a spark gap for network applications. In contrast to the isolating spark gap, network spark gaps must master and solve follow-up currents in the kA range, which means that not only further and, in particular, longer-lasting thermal loads occur, but corresponding follow-current quenching or even follow-current limiting measures must be implemented. In particular with regard to the possibilities for limiting the line follow current in conventional dimensions of the surge arresters for network use, which are generally smaller than isolating spark gaps, an arrangement as in the DE 101 57 817 A1 presented, to extreme restrictions when choosing a suitable method for current limitation.

In the DE 195 10 181 A1 An ignition aid consisting of a first spark gap, which is used to ignite a flashover, and a second spark gap, which is connected in parallel and serves to extinguish the follow-up current, is presented. Furthermore, reference is made to the integration of a passive, simple ignition aid in a spark gap. In the spark gaps shown, the first spark gap is used to set the response voltage and the spark that arises is used for pre-ionization of the second, longer and more current-carrying spark gap. As a result of the pre-ionization and the voltage drop across the impedance connected in series with the spark gap, the second spark gap is ignited. In contrast to the first spark gap, the second spark gap has a high surge current carrying capacity and good follow-current extinguishing capacity.
A disadvantage of this solution, however, is that the first spark gap is exposed to the thermal loads due to the arc and also to the contaminants due to the loads. This makes it difficult or impossible to maintain low and almost constant response voltages. With a spatially separate arrangement of the first and second spark gaps, compliance with a low response value can be ensured, but it is disadvantageous that the pre-ionization of the second spark gap to lower the response voltage is dispensed with got to. As a result, the voltage drop across the impedance must be increased until the undiminished response voltage of the second spark gap is reached. If lower response values of the entire spark gap are to be achieved, the choice and the performance of the second spark gap are considered DE 195 10 181 C1 limited.

According to the stacking radio link for medium and high voltage applications US 3,223,874 individual spark gaps have an ignition aid for pre-ionization. This arrangement can be at least partially encapsulated. However, such a type of spark gap is only designed for low surge current loads of 8/20 µs and cannot withstand the pressures and the force effects of lightning impulse currents worth mentioning. The extinguishing capacity for follow-up currents that is partially present in such an arrangement largely results from the series connection of a large number of partial spark gaps, each with an ignition aid. Such an effort is not justified for low-voltage arrangements.
The ignition aid is connected directly to the main electrodes of the spark gap. It does not have a third auxiliary electrode and there is no direct discharge directly between the main electrodes. The type of pre-ionization is based there on partial discharges that spread over both sides of the surface of an existing insulation part. There is no possibility of a spark discharge, as is usually used in modern low-voltage arresters, since the auxiliary electrodes of the ignition aid are located on opposite sides of the insulator. This form of ignition aid is sufficient for rapid ignition at high potential differences of several kV. However, if the response voltage is to be <1 kV, such an embodiment of an ignition aid is not efficient. Incidentally, the entire ignition aid is exposed to the effects of the arc without protection, which can lead to malfunctions in its function as well as complete destruction.

Versions with auxiliary spark gaps are known in which a spark discharge is possible. In such arrangements, the discharge from the auxiliary spark gap, in which the current flow is limited by various measures, is transferred to the main electrodes. In such solutions, the auxiliary spark gap with a suitable one would have to be independent of the delay time until the main spark gap is ignited Ignition aid must be equipped to reliably maintain a response voltage of, for example, <1kV.

The WO 03/021735 A1 shows a simplified ignition aid for surge arresters, which can be located at least partially in the interior of the spark gap. This ignition aid is based on a series connection of a voltage switching element and a so-called ignition element. The response voltage of the arrester is advantageously determined by the voltage switching element. The main spark gap is ignited in that a current flows over the ignition element after the ignition of the voltage-switching element, as a result of which a voltage is built up across the main spark gap. As a result of poor electrical contact between the ignition element and a main electrode, sparking should then occur. The spark travels along the ignition element and extends until the main spark gap flips over. This solution has major disadvantages due to its function. The crucial component for safe functioning is the so-called ignition element. Depending on the mode of operation, this is located directly in the combustion chamber of the arc. It is therefore not only subjected to an electrical load when it is ignited, but throughout the entire discharge process. Likewise, there is a load with possible subsequent currents. With all known materials, this leads to considerable melting. This particularly affects metals, but also polymers. Because of the strong dynamic loads, ceramics tend to break quickly or change their surface or total resistance as a result of metallic or other conductive deposits. In this way, however, the start of spark formation, the electrical load on the ignition element and the start, but also the speed of the arc migration along the ignition element, are determined to a large extent.
In addition, the ignition element in this solution is subjected to a current flow during the entire arc duration, consisting of pulse and follow current, due to the direct parallel arrangement to the main electrodes and thus to the entire arc voltage, as a result of which the electrical and thermal stress of the ignition element and u. U. of the voltage switching element is large. Another requirement for the basic function according to WO 03/021735 A1 is the necessary spark formation between parts in electrically conductive contact, namely the electrode there and the ignition element. It should be obvious that the one described there Embodiment the contact point from load to load even with a spring contact always changes due to melting phenomena or unavoidable contamination. A reproducible spark at such a contact point is therefore very difficult to set. The above-mentioned restrictions lead overall to a very complicated geometry and material selection. Furthermore, the dynamic and thermal loads caused by the arc and the follow current can quickly lead to a malfunction or a defect.
The spring used for making contact and tracking the ignition element can possibly track the ignition element when it burns off or breaks off. However, the spring can neither avoid a complete breakage of the ignition element after changes in the contact point as a result of the formation of melt on the electrode or on the ignition element or the deposits of impurities in the contact area. Of course, the spring must also be protected against erosion products and the thermal and dynamic loads caused by the arc.
If the spark formation is small or delayed, the ignition delay time of the main spark gap increases. On the one hand, this can significantly increase the electrical load on the voltage-switching element and also on the ignition element; on the other hand, the voltage across the ignition element and thus over the entire spark gap rises sharply. This also endangers the elements to be protected and the desired low residual voltage values of the lightning arrester.

Another disadvantage of the solution cited is that the distance between the main electrodes is directly connected to the length of the ignition element. However, a relatively large main electrode spacing is often advantageous, in particular for network spark gaps. However, as the distance between the main electrodes increases, the response voltage between the electrodes also increases. This means that at higher distances, a stronger pre-ionization must take place between the main electrodes so that the desired low voltages can flash over. The distance along which the spark has to travel from the poor contact point until it reaches the other main electrode is also extended. As already mentioned, this also restricts the choice of the usual means for deleting or limiting follow current.

The spark gap arrangement according to DE 199 52 004 A1 can be operated with an active as well as with a greatly simplified passive ignition aid. These ignition aids are all outside the spark gap. For the rest, the ignition aids consist of a large number of components which are to take on the task of fine protection. However, this requires relatively large and powerful components, which complicates integration into the spark gap. However, the task of fine protection also requires a relatively high power consumption and an additional thermal load.
In the case of the passive ignition aid, which advantageously consists of only a few components, the space requirement would be reduced, but the problem of the power conversion remains when the fine protection is implemented. The disadvantage of the DE 199 52 004 A1 furthermore, that the response behavior of the overall arrangement is determined by the geometric design of the spark gap. In this case, the response voltage of the shorter isolating section defines the response voltage of the entire arrester. Experience has shown that the response voltages that can be achieved in this way are not stable to aging and strongly dependent on the load condition of the spark gap.

The integration of a PTC element in the spark gap is also problematic. Such PTC elements heat up due to their mode of operation by up to several 100 K. However, such heating places very high demands on the load capacity of the insulation elements. In addition, such an application of a PTC element is made more difficult by the fact that, in order to ensure the functioning of the spark gap again, it has to be cooled relatively quickly after loading. Such cooling would be made more difficult by encapsulation.

From the above, it is therefore an object of the invention to provide an overvoltage protection device based on spark gaps, in particular for low-voltage applications, comprising at least two main electrodes located in a pressure-tight housing and with at least one auxiliary ignition electrode, which avoids possible sources of interference between the ignition aid and the spark gap, and in principle all of them Known methods for extinguishing follow current, limiting follow current or also avoiding follow current in spark gaps can be used. The solution to be provided should therefore allow universal applications, regardless of the specific electrode geometry.

The object of the invention is achieved with an overvoltage protection device based on spark gaps in accordance with the combination of features according to patent claim 1, the subclaims representing at least expedient refinements and developments.

According to the basic idea of the invention, a simplified ignition aid is assumed, which consists at least of a voltage-switching element, an impedance and a isolating section. The simplified ignition aid is preferably between two main electrodes and completely in the pressure-resistant housing of the overvoltage protection device, i.e. integrated into the spark gap itself and becomes part of it. If an overvoltage occurs in such an arrangement, which exceeds the sum of the response voltages of the switching element and the isolating distance of the series connection, the ignition aid responds, whereby a current via the voltage-switching element, the impedance and the associated isolating distance from the first main electrode to the second main electrode flows. The arc, which bridges the above-mentioned isolating gap, immediately introduces charge carriers into the spark gap when the ignition aid responds, which causes the isolating gap between the two main electrodes to ionize immediately, reducing the dielectric strength of this isolating gap and resulting from the voltage drop increasing with the current intensity The impedance finally leads to the now reduced dielectric strength of the isolating gap between the two main electrodes and thus to the ignition of the spark gap.

The integration into the pressure-resistant housing of the spark gap, but outside the arc combustion chamber, eliminates all external connection problems of the ignition device to the spark gap.
The flameproof enclosure is designed for the control of pressures up to several 10 bar due to the loads on the spark gap in the case of lightning and line follow currents.
If the ignition aid is overloaded, the damage potential is thus limited considerably by the pressure-resistant encapsulation of the spark gap. This also eliminates additional protective measures for the ignition aid itself, such as fuses or the like. Any desired evaluation of the state of the arrester is also greatly facilitated, since only the overall function, measurable at the outer terminals of the spark gap, and not individual components, connections and components need to be monitored.

It is the ignition auxiliary function module for targeted reduction of the response voltage of the spark gap from a series connection of a voltage-switching element, an impedance and a separation gap that is completely integrated in the pressure-tight housing and is located outside the arc combustion chamber, the separation gap being defined by the distance of the ignition aid electrode from nearest main electrode is defined.

The voltage switching element can be a gas arrester, for example. There is also the possibility of designing the voltage-switching element as a suppressor diode, thyristor, varistor and / or as a defined, fire-resistant air or sliding spark gap.
The auxiliary ignition electrode can itself be designed with impedance and have a complex resistance.

The auxiliary ignition electrode preferably extends partially into or is located in the arc combustion chamber.
The auxiliary ignition electrode can be made of a conductive plastic or a plastic with conductive additives, such as. B. consist of conductive fibers.

The impedance in turn consists of a material with a non-linear or linear resistance curve.

However, the impedance can also consist of a conductive plastic or a conductive ceramic.

An embodiment of the impedance as a discrete component, for. B. resistance, varistor or capacitance in the sense of the invention.

The auxiliary ignition electrode is insulated from the main electrode, the response voltages of the partial sections resulting in each case from the main electrodes being selected differently.

The response voltage e _{1 of} the first main electrode to the auxiliary ignition electrode is selected to be much greater than the response voltage of the further isolating path e ₂ .

To reduce the response voltage of the isolating gap e ₂ , it is designed as a thin, erosion-proof insulating film, as an erosion-resistant lacquer coating or other thin insulating layer.
According to the invention, the overvoltage protection device has means for flowing hard gas onto the arc.

To generate the hard gas, hard gas-emitting material surrounds at least sections of the arc combustion chamber, the hard gas-emitting material additionally having conductive properties in order to bring the potential of one of the main electrodes as far as the separation path of the auxiliary ignition electrode.

In the hard gas version, a pressure equalization opening prevents an undesirable pressure increase from accumulating over time.

According to the invention, the pressure compensation opening can be formed by the housing or by electrode materials which are at least partially gas-permeable.
For this purpose, sections of the housing can consist of a porous polymer material, porous ceramic or correspondingly porous metal.

In a further embodiment, the overvoltage protection device can have means for limiting the residual voltage.

Here, in particular, there is the possibility of designing the conductive, hard gas-emitting material, which is electrically connected to one of the main electrodes, in a defined geometry and with defined electrical properties, so that it is possible to influence the course and the level of the residual voltage in a targeted manner.

The resistance of the hard gas-emitting material to the impedance of the series connection of the functional element is preferably lower.

The conductive, hard gas-emitting material carries part of the total flowing current during the load with surge current as well as with follow currents, so that the reliability of the device according to the invention and its long-term stability are increased.

The proportion of current which is taken over by the conductive, hard gas-emitting material can be adjusted via the ratio of the resistance of this material to the resistance value of the arc.

The average value of the resistance of the conductive, hard gas-emitting material is preferably chosen to be greater than the average, average resistance value of the arc.

To protect against thermal and / or mechanical loads, the voltage-switching element and / or the discrete impedance can be integrated into one of the main electrodes in one embodiment of the invention.
For this purpose, one of the main electrodes can have a cavity that is accessible from the outside, which also ensures that the voltage-switching element can be exchanged if necessary.

The voltage-switching element is inserted into the cavity in a single-pole, insulated manner, the cavity having an internal thread for receiving a conductive screw contacting the voltage-switching element used.

In a further embodiment of the invention, the end of the auxiliary ignition electrode which extends to the arc combustion chamber is essentially at the same level as the end of the main electrode which extends into the combustion chamber and is associated with the first isolating section.

The auxiliary ignition electrode can also be arranged laterally offset and / or set back in relation to the main arc combustion chamber to protect it.

The response voltage of the overvoltage protection device can be adjusted or adjusted via an additional voltage-switching element, which is located outside the pressure-tight enclosure.

In principle, the surge protection device presented can also be implemented as a combination of a triggerable partial spark gap with a high response voltage and at least one downstream partial spark gap with a low response voltage.

In this embodiment, the partial spark gaps can have means for internal potential control.
The partial spark gaps are mechanically fixed and connected via spacers.
The spacers can consist of a conductive, field-controlling material.

In one embodiment of the invention, the spacers and the electrodes of the partial spark gaps can have a sheathing, the sheathing comprising a shield that is electrically connected on one side for targeted potential distortion, or is designed as such itself.

The distance between the electrodes, which form the partial spark gap with the auxiliary ignition electrode, is preferably chosen to be larger than the distance between the electrodes, which define the following partial spark gap.

The spacer can be designed as an integral component in the sense of production rationalization and easier assembly for the partial spark gap that cannot be triggered by the auxiliary ignition electrode.

In order to avoid an electrical flashover outside the arc combustion chamber, additional insulating sections or insulating materials, preferably in the outer area of the electrodes of the partial spark gap, are provided or arranged there.

The spacers have an insulation coating or insulation sheathing on their side remote from the arc combustion chamber, which is a supplementary measure to avoid undesired flashovers.

It is possible to replace the first, triggerable partial spark gap with a gas arrester, which determines the response voltage of the overall arrangement, without thereby abandoning the basic idea of the invention.

In principle, the spark gap according to the invention can be designed as a horn spark gap or as a stacked spark gap.

The invention will be explained in more detail below with the aid of exemplary embodiments and with the aid of figures.

Fig. 1

eine Prinzip-Schnittdarstellung durch eine in einer gekapselten Funkenstrecke befindlichen Zündhilfe;

Fig. 2

eine Ausführungsform ähnlich Fig. 1, jedoch mit zusätzlichem hartgasabgebenden Material, welches den Lichtbogen-Brennraum umgibt;

Fig. 3

eine weitere Ausführungsform der Überspannungsschutzeinrichtung ähnlich wie in Fig. 2 dargestellt, jedoch mit variierter Heranführung des Potentials der Hauptelektrode an die Zündhilfselektorde;

Fig. 4

eine Darstellung einer Überspannungsschutzeinrichtung mit einem spannungsschaltenden Element, integriert in eine der Hauptelektroden;

Fig. 5

eine Ausführungsform mit spezieller höhenmäßiger Zuordnung einer der Hauptelektroden zur Zündhilfselektrode;

Fig. 6

eine weitere Ausführungsform der Zuordnung von Zündhilfselektode und benachbarter Hauptelektrode;

Fig. 7

eine Darstellung mit einem spannungsschaltenden Element außerhalb der druckfesten Kapselung der Funkenstrecke;

Fig. 8

eine Funkenstrecke, umfassend mehrere Teilfunkenstrecken;

Fig. 9

eine Darstellung ähnlich Fig. 8, jedoch mit einem gemeinsamen Distanzhalter für die nicht triggerbaren Teilfunkenstrecken und

Fig. 10

eine Darstellung einer Funkenstrecke ähnlich den Fig. 8 und 9, jedoch mit zusätzlichen Maßnahmen zur Isolation zum Zweck des Vermeidens von unerwünschten äußeren Durchschlägen.

Here show:

Fig. 1

a schematic sectional view through an ignition aid located in an encapsulated spark gap;

Fig. 2

an embodiment similar Fig. 1 , but with additional hard gas-emitting material that surrounds the arc combustion chamber;

Fig. 3

a further embodiment of the overvoltage protection device similar to that in Fig. 2 shown, but with varying approach of the potential of the main electrode to the auxiliary ignition electrode;

Fig. 4

an illustration of an overvoltage protection device with a voltage switching element, integrated into one of the main electrodes;

Fig. 5

an embodiment with a special height assignment of one of the main electrodes to the auxiliary ignition electrode;

Fig. 6

a further embodiment of the assignment of auxiliary ignition electrode and adjacent main electrode;

Fig. 7

a representation with a voltage switching element outside the flameproof encapsulation of the spark gap;

Fig. 8

a spark gap, comprising a plurality of partial spark gaps;

Fig. 9

a representation similar Fig. 8 , but with a common spacer for the non-triggerable partial spark gaps and

Fig. 10

a representation of a spark gap similar to that Fig. 8 and 9 , but with additional insulation measures to avoid unwanted external breakdowns.

The passive ignition aid 100 accordingly Fig. 1 is integrated in the flameproof enclosure 5 of the spark gap, which has two main electrodes 1 and 2. These main electrodes 1 and 2 are kept insulated with respect to, for example, metallic encapsulation 5.

The ignition aid 100 consists of a voltage-switching element 4, preferably a gas arrester, although suppressor diodes, thyristors, varistors, defined, erosion-resistant isolating sections or a combination of these elements are also suitable. Furthermore, the ignition aid 100 has an ignition aid electrode 3 with impedance. There is also the possibility that a discrete impedance 3a is present as a separate element.

Elements or materials such as plastics or ceramics with linear but also with non-linear resistances or characteristics are suitable as impedance 3a. When using a discrete impedance 3a, this can e.g. as a resistor, as a varistor, as a capacitance or also from materials with the corresponding characteristics of such components.

The auxiliary ignition electrode or ignition electrode 3 is insulated from the two main electrodes 1 and 2. However, the response voltages of the resulting spark gaps e ₁ and e ₂ are designed differently.

The response voltage of the path e ₁ , ie the main electrode 1 to the auxiliary ignition electrode 3, is much greater than the response voltage of the path e ₂ , formed by the distance between the main electrode 2 and the auxiliary ignition electrode 3.

The response voltage of the path e ₁ is at least the same, but generally higher than the response voltage of the voltage-switching element 4 of the ignition aid 100.
In contrast, the response voltage of the path e ₂ is at most the same, but generally lower than the response voltage of the voltage-switching element 4 of the ignition aid 100.

In this way it is ensured that the response voltage of the entire arrester is essentially determined by the response voltage of the voltage-switching element 4 and can thus be selected independently of the usual geometric conditions of the main spark gap. Advantageously, all parts which are functionally relevant for the response behavior are not exposed to the direct action of the arc. Only one end of the auxiliary ignition electrode 3, which preferably itself has impedance, e.g. can be designed as a conductive plastic, is located partially in the arc combustion chamber and is insulated from the two main electrodes 1, 2.

If the auxiliary ignition electrode 3 is made of a low-resistance material, e.g. As already mentioned, copper or the like is used, a separate impedance 3a is used, which is then completely outside the direct arcing effect.

The unavoidable erosion of all parts in the arc combustion chamber can only partially damage the auxiliary ignition electrode 3. Since the arcing of the arc takes place on all sides in the entire combustion chamber of the spark gap, all parts delimiting the combustion chamber, that is to say also the ignition auxiliary electrode 3, with their adjacent insulation parts are gradually burned down.
This ensures that the geometric proportions of all components remain largely the same after each load.
As a result of an uneven erosion or as a result of contamination, this geometry can also damage or bridge the short insulation distance e ₂ . In particular with almost all active external ignition aids, this would virtually lead to a short circuit in the pulse transmitter and thus to failure or overloading of the ignition aid. At However, the design proposed here according to the exemplary embodiment is not the case. The resulting impurities and the usually only partial contact bridges, which are formed by melting phenomena and are only minor due to the design of the components, have a comparatively high resistance and are eliminated by a low current flow.

The electrical parameters of the components integrated in the spark gap are predefined on the one hand by the geometric dimensions. On the other hand, the power conversion is also limited in favor of a simple construction of the contact points and also the thermal load on the insulation sections. The performance of the ignition aid in the present embodiment is limited to small pulse powers.

In the presentation used for the general description of the function Fig. 1 a basic, simplified geometry of a possible spark gap arrangement is shown. In this arrangement, which only affects the ignition range, no measures for limiting the follow current are included for the sake of simplicity.

The main electrodes 1 and 2 are manufactured in a manner known per se from erosion-resistant, electrically conductive materials such as metals, metallic alloys, sintered metals, graphite, ceramics or composite ceramics.

With regard to the auxiliary ignition electrode 3, it should also be noted that, as explained, it is either made of a material with increased impedance, e.g. Resistance material, electrically conductive plastic, plastic with filler material or is connected to a separate impedance 3a in the form of a resistor.

In order to set the desired impedance properties, not only soot or graphite elements or metal or carbon fibers can be contained in the plastic material of the auxiliary ignition electrode, but it is also possible to incorporate microvaristors or nanotubes.

The main electrode 1 is above the voltage-switching element 4, which is a gas discharge arrester, a gas discharge arrester with a microgap; a spark gap, a isolating gap, a suppressor diode, a varistor or a combination of the aforementioned elements can be connected to the impedance 3a or the auxiliary ignition electrode 3 within the outer pressure-resistant encapsulation 5 of the spark gap.

As explained, the three electrodes form two partial separation sections e ₁ and e ₂ , e ₂ having a significantly lower response voltage than the separation section e ₁ .
The response voltage of the section e ₂ is equal to or less than the response voltage of the voltage-switching element 4. Since the DC response voltage of the entire arrester should be equal to or less than 1 kV, there are special requirements for the design of the isolating section e ₂ .
This separation distance e ₂ can be realized, for example, by means of thin films made of erosion-resistant materials or by means of temperature-resistant coatings, but also by means of special erosion-resistant lacquers.

After the voltage-switching element 4 and the isolating gap e _{2 have} responded, a spark arises between the auxiliary ignition electrode 3 and the main electrode 2. The current flows from the main electrode 1 via the impedance 3a, the auxiliary ignition electrode 3 and the spark to the main electrode 2. This spark brings charge carriers into the interior of the spark gap, whereby the dielectric strength of the separation gap e ₁ is reduced very quickly.
According to the main electrode 1 and the auxiliary ignition electrode 3 Fig. 1 there is a voltage difference, which is essentially determined by the level of the current in the ignition circuit and the impedance 3a. If this voltage difference exceeds the dielectric strength of the isolating distance e ₁ , which is reduced by the charge carrier entry, then this ignites, takes over the current and relieves the ignition circuit. The partial arcs over the separating distances e ₁ and e ₂ connect and the spark gap ignites between the main electrodes 1 and 2.

Fig. 2 shows a spark gap for network applications, especially between L and N. This spark gap is able to withstand higher arcing voltages to create. In the present case, these are achieved by flowing hard gas on the arc.

A hard gas-releasing substance 10, for example POM, polytetrafluoroethylene on a polymer or mineral basis, for example CaCO ₃ or BaCO ₃ , is used for the flow of hard gas.

The effect can also be used to bring the potential of the main electrode 2 to the separation path of the auxiliary ignition electrode 3 by means of electrically conductive additives, such as metal fibers, carbon black, carbon fibers, microvaristors, nanotubes, metal particles, semiconductor particles or even per se conductive polymers.
This measure does not change the response voltage of the isolating sections e ₁ and e ₂ ; however, the effective arc length between the main electrodes 1 and 2 is increased.

The ignition spark arises between the auxiliary ignition electrode 3 and the conductive hard gas-emitting material 10 and can then extend very quickly to the main electrode 2 already or only after the separation distance e _{1 has} flipped over.
On the one hand, this increases the length of the arc and, on the other hand, the arc is cooled and flowed through by the hard gas.

Both measures increase the arc voltage, which is known to be able to limit the current in line follow currents. Due to the generation of hard gas and the flow through the arc, a pressure rise occurs which can be derived through the pressure compensation opening 11. This prevents a gradual pressure increase in the pressure-tightly closed volume via the generated gas, which could possibly cause the bursting strength of the spark gap to be exceeded after repeated loads.

Constructed channels with a small cross-section can be used to equalize the pressure. Likewise, there is the possibility according to the invention, also porous, for gases or for certain types of gases permeable housing materials, such as. B. porous polymers, metals or ceramics, alternatively to constructive channels.

The response voltage of the spark gap is from a pressure increase z. B. not affected when using gas discharge arresters as voltage-switching element 4.

Referring to the illustration after Fig. 3 the potential of the main electrode 1 can also be brought to the auxiliary ignition electrode 3 in an analogous manner.

As already explained, the distance between the two main electrodes can be extended without influencing the response voltage by using correspondingly conductive materials 10. The size of the conductive, hard gas-emitting part 10 is preferably chosen to be larger than the dimensions of the separation distance e ₁ .

As is known, the residual voltage of an arrester, which occurs only after the arrester has responded and thus when current flows through the arrester, loads downstream devices. This is particularly important in the new generation of surge arresters, since, as already explained at the beginning, it is intended to protect the downstream devices at an overall low protection level without additional decoupling.

The amount of the residual voltage in the spark gap arrangement corresponding to the Fig. 1 and 2nd can be classified into three areas. A first time period begins, so to speak, after the voltage-switching element has responded and the separation distance e _{2 has} flashed over. A current flows through the voltage-switching element 4, the impedance 3 and the electrically conductive part 3 ( Fig. 2 ).
The impedance of all these elements determines the voltage drop across the arrester. If the strength of the distance e ₁ , which is reduced by the pre-ionization, is exceeded, the main electrode 1 and the part 10 roll over. This relieves the ignition circuit and reduces the residual voltage by the voltage drop across the ignition circuit. Now the residual stress is essentially determined by the part 10. As the ionization between the two main electrodes 1 and 2 progresses and the arc moves along part 10, the flashover occurs between the main electrodes 1 and 2. At this point in time, the residual voltage is determined by the arc between the main electrodes.

Of course, the first arcing can also take place over the part 10 and only then can the separation distance e ₁ . According to the invention, this can be avoided by a corresponding geometric design. In this way, the load on the ignition circuit is prevented from increasing.

Since the process takes a certain amount of time to flash over between the two main electrodes, the residual voltage rises during this period depending on the currently effective impedance and the pulse current. In the event of high voltage steepness or surge currents, the residual voltage may therefore assume values that are too high, which can result in a hazard or even overload of the downstream elements.

According to the invention, the conductive, hard gas-emitting part 10 is additionally given the task of effective residual voltage limitation. According to the exemplary embodiment, a certain dimensioning of the resistance of the part 10 is required for this.
A targeted influencing of the course and the level of the residual voltage can also be done by the geometric in addition to the electrical design of the part 10. If the resistance of the part 10 is chosen to be relatively high-impedance in relation to the impedance 3a, the residual voltage continues to increase even after the separation distance e _{1 has} overturned. There would therefore be a risk of excessive residual voltage with large pulse currents, particularly in the case of large dimensions (length) of part 10 (longer ignition delay time). If, on the other hand, the resistance of the part 10 to the impedance 3a is chosen to be low, the increase in the residual voltage after the overlap of the isolating distance e ₁ can be reduced, as a result of which the risk of excessive residual voltage can be significantly reduced.

The effective effective resistance of the part 10 can be influenced by the material, the geometry of the part and the respective contact surface of the part 10 on the electrode 2. However, the design of the transition region between the part 10 and the auxiliary ignition electrode 10 and the positioning of the main electrode 1 are equally effective. B. executed with a larger inner diameter than the part 10, it is compared to the part quasi reset, there is a practically larger contact area on the part 10 for the spark between the main electrode 1st and the part 10 itself, which results in a lower effective resistance of the part 10.
If the auxiliary ignition electrode is practically in the arc combustion chamber, the resistance increases. It is also possible to carry out geometric design measures in the direction of the axes.

When influencing the residual voltage, it should also be borne in mind that the material of part 10 experiences a corresponding electrical and thermal load through the assumption of a significant current component of up to several kA with pulse current loading and must be designed accordingly. A thermal preload of part 10 during the ignition phase is, however, also to be seen positively, since POM materials in particular release the hard gas accelerated at a higher temperature. This leads to an overall better extinguishing behavior with possible follow currents, which of course also flow partially over the material of the part 10 and stress it electrically and thermally.

The level of resistance of part 10 e.g. as a hollow cylinder with an outer diameter of 18 mm, an inner diameter of 4 mm and a height of 5 mm, you can practically vary between several hundred kΩ and values down to approx. 1 Ω without negative effects on the extinguishing capacity of the spark gap and the Material selection result. As explained, the maximum limitation of the residual voltage results from the lowest resistance values.

• Z_{Teil 10} > Mittelwert des Widerstands des Lichtbogens bei Impuls- und Folgeströmen
• Mittelwert des Widerstands des Lichtbogens bei Impulströmen < Z_{Teil 10} < Mittelwert des Widerstands des Folgestrom-Lichtbogens
• Z_{Teil 10} < Mittelwert des Widerstands des Lichtbogens bei Impuls- und Folgeströmen.

Any reduction is not possible, however, since the overall properties of the spark gap do not change advantageously from certain values. In principle, three dimensioning ranges can be recorded for the average value of the resistance of the conductive, gas-emitting part 10:

• Z _{Part 10} > Average value of the resistance of the arc with pulse and follow currents
• Average value of the resistance of the arc with pulse currents <Z _{part 10} <Average value of the resistance of the follow-current arc
• Z _{Part 10} <mean value of the resistance of the arc with pulse and follow currents.

The resistance value of the part 10 of a spark gap according to the Fig. 2 or 3rd However, it is of particular importance not only in terms of residual voltage, but also due to its effect on subsequent current quenching. In the arrangements described, part 10 is basically parallel to the arc or at least to sections of the arc. This applies to all loads at which the spark gap between the main electrodes 1 and 2 is ignited. Part 10 always assumes a portion of the total current both when loaded with surge currents and when loaded with follow-up currents. The level of this portion depends on the level of the resistance of the part 10 and the quasi-resistance of the arc.

As is known, the current-voltage characteristic curve of an arc is not linear, but of numerous factors, including depending on the composition of the gas, pressure, temperature and so on. These sizes are used in a real spark gap, among other things. determined by the geometry, the materials used and the electrical load. The fact that all of these sizes vary greatly due to aging, even with a fixed spark gap geometry, means that the exact arc characteristic curve cannot be predicted adequately. Looking at the follow current arc with AC voltage, however, it is also known that the resistance of the arc is significantly increased at the time of ignition and at the time of extinguishing. In this time range, the parallel resistance of part 10 thus assumes a correspondingly higher current component or even the total current at low values <10 Ω. This naturally removes charge carriers from the arc, which greatly reduces ionization. This leads to the premature extinguishing of the arc. Part 10 here leads the follow-up current to the current zero crossing.

The low resistance value of the part 10 can also serve to avoid a line follow current arc. The mains voltage is comparatively low in relation to the driving voltage of the pulse current and also depends on the phase position. Among other things, this leads in practice to the fact that the pulse current arc often does not pass directly into the line follow current arc, but rather can only ignite as a result of the reduced dielectric strength of the switching path as a result of the pulse load.

The parallel resistance of part 10, however, quasi reduces the voltage load of the switching path due to its electrical conductivity, as a result of which the ignition of the line follow current arc can be prevented. In such a case, the mains follow current can on the one hand be completely prevented or, on the other hand, only a limited follow current flows via the part 10 to the current zero crossing. With this mode of operation, the extinguishing tip and the ignition tip of the arc are avoided. This effect is a positive side effect, with the rest, there is still no risk of damage to the part 10 regardless of the selected conductive material.

However, if the resistance of part 10 corresponds approximately to the resistance of the follow-current arc, a strong current load on part 10 must be expected over the entire arc phase. For this reason, only materials are used that cannot be damaged by prolonged exposure to electricity and temperature. For spark gaps where a very effective follow current limitation is to be achieved, i.e. at which the level of the arc voltage, which reaches the mains voltage after one millisecond at the latest, the arc resistance at follow current has a value essentially between 0.5 and 1 Ω. If this value is undershot by part 10, on the one hand this leads to a heavy load on part 10, but on the other hand the arc can be extinguished more quickly or ignition can be prevented.

When choosing a very low resistance value of part 10, it must be taken into account that the follow current limitation decreases and that both the isolating distance e ₁ and the voltage-switching element 4 have to master the occurring follow currents and also the erosion several times.
A reduction in the resistance of part 10 in spark gaps according to, for example Fig. 2 under the generally significantly lower resistance of the arc (approx. <1/10) with pulse currents, a desired strong follow current limitation disproportionately hinders. The strong difference between the resistance of the arc with impulse currents and with follow currents results accordingly in arrangements Fig. 2 inter alia from the delayed delivery of hard gas from part 10 used for this.

A safe working method and a hardly restricted choice of material for the part 10 is given in particular when the average resistance of part 10 is generally higher than the average resistance of the arc.
For special spark gap arrangements, however, designs can also be expedient in which an arc with a follow-up current is to be largely avoided by lowering the mean value of the resistance of the part 10 below the mean value of the resistance of the follow-up current arc. However, due to the high electrical and thermal loads, such an arrangement requires a special material selection and design of part 10. Conductive ceramics, composite materials, varistor material or the use of PTC material are conceivable here.

The 4 to 7 show further design variants of the integrated ignition aid in combination with a spark gap with follow current extinguishing according to the hard gas principle.

According to Fig. 4 the voltage-switching element 4 is integrated directly into a recess of the main electrode 1 for protection against, in particular, thermal and mechanical loads. This recess can be designed, for example, in the form of a hole in the power supply to the main electrode. This bore can have an internal thread. By screwing in a conductive screw, the voltage-switching element 4 located in the cavity can then be securely mechanically attached and contacted.

Although not shown in the drawing, there is also the possibility of accommodating a separate impedance 3a in a corresponding recess in the main electrode 1, so that this element is also better protected against static and dynamic mechanical loads during manufacture and during operation.

It should also be pointed out that one side of the voltage-switching element 4 is insulated from the main electrode 1 and that there is an insulated conductive connection or such a connection to the auxiliary ignition electrode 3.

According to Fig. 5 the auxiliary ignition electrode 3 is introduced into the arc combustion chamber at virtually the same height as the end of the main electrode 1 which extends to the arc combustion chamber.

After the main spark gap is ignited, this causes the current in the ignition circuit to go out very quickly, since this is practically no longer exposed to a potential difference. The auxiliary ignition electrode 3 is thus protected against direct arc foot erosion.

Fig. 6 shows a representation in which the auxiliary ignition electrode 3 is arranged laterally offset from the arc combustion chamber, which likewise results in a particularly protected embodiment of the electrode 3.

According to the presentation Fig. 7 there is the possibility of arranging an additional, voltage-switching element 4 outside the pressure-resistant encapsulation 5 of the spark gap.
This allows the pickup voltage of the arrester to be freely selected, regardless of the spark gap, even after installation in the application environment or to be adapted to the application environment and conditions.

In principle, the ignition aid explained and described in the exemplary embodiment can also be used with other extinguishing principles or electrode arrangements. Known follow-current extinguishing methods for low-voltage arresters in addition to the variants explained is e.g. B. the use of horn-shaped electrodes for arc extension, often in combination with quenching plate arrangements, or the generation of high pressures to increase the arc field strength. A series connection of several spark gaps for multiplying the electrode drop voltage is also conceivable.

The use for arrangements with horn-shaped electrodes requires no further explanation, since both a basic solution accordingly Fig. 1 , but also arrangements with an electrode gap extended by electrically conductive substances, e.g. B. accordingly Fig. 2 , can be provided in a known manner with horn-like spark gaps in a symmetrical or asymmetrical arrangement. As is known, the resulting follow-up electric arcs can be fed to a wide variety of extinguishing systems after being extended on the horns.

However, effective follow-up current limitation can also be achieved through a strong build-up of pressure inside the spark gap. Here, for example, on the DE 196 04 947 C1 referred. Although this is also realized in the production of hard gas, it can also be found as an individual measure. The same is e.g. B. is advantageous for spark gaps, in which the effort that is necessary with regard to the flow and cooling of the released gas should be limited, or also for spark gaps in which the least possible aging is of interest.

Arrangements according to the DE 196 04 947 C1 are basically realizable with an ignition aid according to the invention. Hard gas-releasing substances can be partially or completely replaced by electrically conductive substances with a linear but also with a non-linear characteristic. This can e.g. B. pressure-resistant conductive ceramics, fiber ceramics or composite materials with conductive components or, for example, materials with a varistor characteristic or a PTC characteristic. The pressure build-up is due to the limited internal volume z. B. realized in a cylinder. With a partial use of hard gas z. B. a sandwich solution can be used.
However, it is also possible to use a porous basic structure, e.g. B. from conductive ceramic with gas-releasing substances, for. B. Fill POM.

Design variants with active triggering for the introduction of charge carriers into one or more partial spark gaps for use in low-voltage systems show the 8 to 10 .

According to Fig. 8 the ignition aid explained above can also be used in an embodiment with several partial spark gaps and does not restrict the use of the generally known methods for potential control of the partial spark gaps.

However, it should be noted that arresters with a series connection of partial spark gaps usually also have externally connected means for potential control. These can be impedances, capacitances, linear and non-linear resistances, their combinations or additional external spark gaps, which are also used for potential control.

Regardless of what type of discrete elements are also used for potential control, these elements and their contact points to the individual partial spark gaps represent a risk factor, because due to very high pulse steepness or poor or aged contact, there are partial or complete flashovers and thus to Destruction of the arrester can occur. If a surge arrester of the type mentioned is to be safely ignited with an ignition aid and a response value <1 kV, not only the actual ignition aid but also the potential control must be carried out more safely than usual.

According to the exemplary embodiment, this can be achieved in that, instead of potential control with external and discrete elements, components which are necessary anyway are modified in such a way that adequate internal potential control is possible.

For this purpose, individual electrodes of the partial spark gaps 20 are separated by spacers 21. The material of these spacers 21 can be made of conductive or field-controlling material except for the route or routes which are provided with an ignition aid.
Alternatively or additionally, an outer sheathing of the actual spark gaps can be connected to an insulated, one-sided screen for potential distortion 22.

The partial spark gap with the ignition aid from parts 3, 3a and 4 is designed in such a way that despite possible contamination, in particular due to the ignition of the ignition electrode, it is able to control the load caused by the recurring mains voltage only after the spark gap has responded .
For this purpose, the distance between the electrodes 22 and 23 of the partial spark gap triggerable via the ignition aid is increased compared to the distance between the other partial spark paths. In addition, for better control of the recurring voltage for the material of the main electrodes of the triggerable partial spark gaps, a material with high instant hardening can be selected. The material of the other sections, on the other hand, should have a low erosion and a high electrode drop voltage.

The spacers 21 can consist of electrically conductive polymers or ceramics. Their resistance characteristics can be linear, but also non-linear.

In the case of a potential-controlling embodiment, the material of the spacers 21 can also be provided with microvaristors in addition to certain dielectric properties, as a result of which capacitive control is possible, which results in a better potential-controlling effect, in particular in the case of steep slopes. Alternatively, the individual electrically conductive contact holders can also be provided or designed on one or both sides with a thin insulation layer or a defined poor contact. Although this requires a minimum response voltage of z. B. some 10 V, but promotes the ionization of the partial spark gap and thus the ignition of the entire spark gap by the faster emergence of the arc from the material and sparking.
Of course, the described measures for potential control can also be used to reduce the response voltage of the partial spark gaps 20 by measures known from the field of gas discharge arresters, eg. B. the use of special gases or activation measures.

According to Fig. 9 the individual spacers 21 of the non-triggerable partial spark gaps can be replaced by a common spacer. In the case of an electrically conductive design of the spacers 21, care must be taken that the conductive material is not overloaded by the flowing partial current. This can be influenced on the one hand by the choice of material and on the other hand by the geometric design in terms of the thickness and the contact area.

Fig. 10 shows a design variant in which jointly or alternatively applicable measures are used to further reduce the likelihood of an undesired external rollover.
For this purpose, additional insulation measures are carried out in the outer area of the electrodes. The electrodes of the partial spark gaps can be provided with insulation material 25 in the outer region. The inside diameter of the insulated area is to be chosen larger than the inside diameter of the spacers 21. The spacers 21 can also be surrounded on the outer circumference with a ring made of insulation material 26.

Will with an arrangement according to the 8 to 10 If the follow currents are limited to a few hundred amperes or less, instead of the triggerable partial spark gaps, it is also possible to use a powerful gas arrester, which then determines the response voltage of the overall arrangement.

Claims (18)

1. Overvoltage protection device, based on spark gaps, in particular for low voltage applications, comprising at least two main electrodes arranged in a pressure-tight housing, as well as at least one auxiliary ignition electrode, wherein a functional assembly is accommodated in the housing volume for reducing the response voltage of the spark gap, which functional assembly is associated with one of the main electrodes and the auxiliary ignition electrode,
   wherein
   the functional assembly for reducing the response voltage of the spark gap is comprised of a series connection of a voltage-switching element (4), an impedance (3a) and a separating gap (e₂), which series connection is completely integrated in the housing and located outside the arc combustion chamber, wherein the separating gap (e₂) is formed by the distance of the auxiliary ignition electrode (3) to the nearest main electrode (2),
   so that, when an overvoltage arises which exceeds the sum of the response voltages of the switching element (4) and the separating gap (e₂), a current flows from the first main electrode (1) to the second main electrode (2) with the effect that the arc bridging the separating gap (e₂) provides charge carriers for the immediate ionization of the separating gaps between the main electrodes (1, 2), whereby the withstand voltage of this separating gap is reduced and, due to the voltage drop at the impedance (3a) increasing with the rising current strength, an excess of the reduced withstand voltage of the separating gap between the main electrodes occurs, whereby the desired ignition of the spark gap takes place, moreover means for flushing the electric arc with hard gas and for generating the hard gas, a hard gas emitting material surrounds at least portions of the arc combustion chamber, wherein the hard gas emitting material in addition has conductive properties so as to lead the potential of one of the main electrodes to the spark gap of the auxiliary ignition electrode,
   at least one pressure compensation opening being provided for preventing a pressure increase accumulating with time, wherein the pressure compensation opening is formed by housing and electrode materials that are gas permeable.
2. Overvoltage protection device according to claim 1,
   characterized in that
   the voltage switching element is a gas arrester.
3. Overvoltage protection device according to claim 1,
   characterized in that
   the voltage switching element is a suppressor diode, a thyristor, a varistor and/or an air spark gap or a sliding spark gap of a defined combustion resistance.
4. Overvoltage protection device according to any one of the claims 1 to 3,
   characterized in that
   the auxiliary ignition electrode itself is realized to have an impedance and exhibits a complex resistance.
5. Overvoltage protection device according to any one of the preceding claims,
   characterized in that
   the auxiliary ignition electrode is partially arranged within the arc combustion chamber or extends into the arc combustion chamber.
6. Overvoltage protection device according to claim 4,
   characterized in that
   the auxiliary ignition electrode is composed of a conductive plastic material.
7. Overvoltage protection device according to any one of the claims 1 to 3,
   characterized in that
   the impedance is composed of a material having a non-linear or linear resistance curve.
8. Overvoltage protection device according to claim 7,
   characterized in that
   the impedance is composed of a conductive material or conductive ceramics.
9. Overvoltage protection device according to claim 7,
   characterized in that
   the impedance is realized discretely as a resistor, a varistor or a capacitance.
10. Overvoltage protection device according to any one of the preceding claims,
    characterized in that
    the auxiliary ignition electrode is isolated with respect to the main electrodes, wherein the response voltages of the partial distances respectively arising to the main electrodes are selected to be different.
11. Overvoltage protection device according to claim 10,
    characterized in that
    the response voltage of the first main electrode to the auxiliary ignition electrode is much higher than the response voltage of the separating gap (e₂).
12. Overvoltage protection device according to any one of the preceding claims,
    characterized in that
    for reducing the response voltage of the separating gap (e₂), the separating gap (e₂) is configured as a thin isolating film that is resistant to combustion, a lacquer coating that is resistant to combustion or another thin isolating layer.
13. Overvoltage protection device according to any one of the preceding claims,
    characterized in that
    at least portions of the housing are composed of a porous polymer material, ceramics and/or metal.
14. Overvoltage protection device according to claim 1 or 13,
    characterized in that
    during the load both by surge currents and follow currents, the conductive hard gas emitting material carries a part of the respectively flowing overall current.
15. Overvoltage protection device according to claim 14,
    characterized in that
    the current portion carried by the conductive hard gas emitting material is adjustable via the ratio of the resistance of this material to the resistance value of the electric arc.
16. Overvoltage protection device according to claim 15,
    characterized in that
    the mean value of the resistance of the conductive hard gas emitting material is larger than the average mean resistance value of the electric arc.
17. Overvoltage protection device according to any one of the preceding claims,
    characterized in that
    the auxiliary ignition electrode is arranged to be laterally offset and/or, with respect to the arc combustion chamber, is arranged to be retracted.
18. Overvoltage protection device according to any one of the preceding claims,
    characterized in that
    a complementary voltage-switching element is located outside the pressure-tight enclosure for subsequently setting and/or adjusting the response voltage.

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