WO2003019744A1

WO2003019744A1 - Encapsulated secondary-current-limiting voltage surge diverter based on a spark gap

Info

Publication number: WO2003019744A1
Application number: PCT/EP2002/009232
Authority: WO
Inventors: Arnd Ehrhardt; Peter Zahlmann; Michael Waffler; Stefan Hierl
Original assignee: Dehn + Söhne Gmbh + Co. Kg
Priority date: 2001-08-21
Filing date: 2002-08-17
Publication date: 2003-03-06
Also published as: ATE391355T1; EP1419565A1; DE50212026D1; EP1419565B1

Abstract

The invention relates to an encapsulated secondary-current-limiting voltage surge diverter based on a spark gap, for low-voltage applications, comprising two main electrodes and with insulating pieces which release gas on temperature loading, whereby one of the main electrodes is at least part of the capsule and/or the spark gap housing. According to the invention, the capsule or the spark gap housing has an essentially elongated parallelepiped form, with an arc chamber and at least two separate expansion chambers embodied in the parallelepiped, such as to extend over the total height of the parallelepiped. The expansion chambers are connected to the arc chamber by means of channels and the arc chamber and the expansion chambers run essentially parallel to each other. The arc chamber is defined in the head region by one of the main electrodes and an insulating piece and, in the opposing base region, is formed by an arc extending piece, electrically connected to the other main electrode. The channels run laterally from the arc extending piece to the expansion chambers. In at least one channel and/or one expansion chamber, further insulating pieces or insulating sections may be provided, which on arcing and temperature rise give off gas to produce a back pressure.

Description

Encapsulated surge arrester limiting line follow current

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description

The invention relates to an encapsulated surge arrester surge arrester based on spark gap for low-voltage applications with two main electrodes and with gas-emitting insulating parts, one of the main electrodes being at least part of the encapsulation and / or of the spark gap housing, according to the preamble of claim 1.

It is known to use surge arresters on the basis of self-extinguishing spark gaps in low-voltage networks to protect against overvoltages between the N-L conductors.

These spark gaps have particular have for protection against direct lightning strike on a high surge current up to 25 kA and 10/350 are up to 25 kA interrupt automatically ^'and the line follow currents occur in the region. Furthermore, such spark gaps should limit the line follow current so strongly during the arcing phase that upstream overcurrent protection devices do not switch off the power supply of the end user, with all the disadvantageous consequences that then arise.

Due to the developments in recent years, there is a tendency to encapsulate the spark gaps with small dimensions, so that no hot, electrically conductive gases or combustion particles are blown out into the surrounding area of the arresters.

An encapsulated spark gap with an optimized line follow current extinguishing capacity is known for example from DE 196 04 947 Cl. There, a spark gap arrangement is described, which comprises two electrodes, which are arranged within a housing and, in addition, there is the possibility of providing an extinguishing gas. To increase the follow-up current extinguishing capacity with none, or at least only with a small increase in volume To achieve an overall arrangement, a coordination of the size of the follow-up current to be deleted to the volume of the interior of the housing is proposed, the aim being to bring about a brief increase in the internal pressure of the housing to a multiple of the atmospheric pressure. The pressure increase in the interior containing the electrodes is produced by the arc of the follow-up current itself.

DE 198 17 063 AI discloses an overvoltage protection element with arcing, in which an inner electrode is arranged in an outer electrode. One end of the inner electrode projects freely into the outer electrode, the cross section of the inner electrode decreasing towards the free end and an arc distance between the inner electrode and the outer electrode increasing towards the free end. Concretely, it is also taught that it is desirable if the surface area of the inner electrode over which arcs are distributed is enlarged with a compact construction volume and causes the arcs formed to migrate away more quickly. An opening for pressure equalization is also provided in the part of the housing forming one of the electrodes there. The arrangement itself is rotationally symmetrical and has a cylindrical shape.

EP 0 860 918 B1 presents a drain on a spark gap basis, in which a second space is arranged after the actual spark gap, which is separated from the space of the spark gap by a plate with openings and in which baffle and cooling surfaces are present, as well as a blow-out opening is provided. The design of the second room is intended to deflect and cool the hot gases so that they can escape without endangering the environment.

The blow-out tube spark gap according to DE-PS 897.444 works according to the so-called extinguishing tube principle, where a blow chamber connected in series is arranged to reduce the risk of blow-out, in which the heated gases are deflected and cooled before they leave the corresponding chamber. The overvoltage protection device with improved network sequence estrom extinguishing capacity according to DE 100 08 764 AI is based on a concentric arrangement of a first spark plug and a second spark plug having first and second electrodes, air breakdown spark gaps being formed between the spark horns. In the construction there, the lowest possible overall height is to be achieved, namely in that the first spark plug is frustoconical and the second spark plug is arranged concentrically around the first spark plug.

PCT / EP99 / 06962 describes a spark gap-based surge conductor that can be completely encapsulated and whose function is based on the principle of hard gas generation. The drain there has a cooling chamber which is large in relation to the combustion chamber and in which the generated and heated gases pass through a nozzle to control the mass flow rate. The large cooling room is intended to hold the amount of gas generated and cool it down as quickly as possible. The disadvantages of such an arrangement are that the absorbed energy of the gas entering the cooling chamber is no longer used to influence the arc behavior, so that the arc can penetrate into the cooling chamber and that if the cooling capacity of the cooling chamber is overwhelmed, there is no pressure difference remains between the cooling space and the separating space, as a result of which the necessary current flow to the arc comes to a standstill, particularly when the encapsulation is complete. The result is that the arc voltage drops suddenly and the limitation of the follow current is undesirably reduced. In addition, comparatively large amounts of hard gas must be released in order to generate a high arc burning voltage.

In contrast to the known blow-out rooms, DE 195 06 057 AI discloses an extinguishing spark gap arrangement in an encapsulated form, in which flow of the arc is achieved by pressure differences in the individual rooms and thus the blow-out rooms have a direct influence on the arc combustion chamber. However, this is only achieved if the pressure in the combustion chamber is comparatively low and, in addition, quite large volumes of the cooling rooms are available. In general, the extinguishing capacity has increased

Follow-up current limitation for surge arresters the flow of hard arc through the arc has proven itself.

In order to be able to implement the blowing effect as optimally as possible for extinguishing the follow current, Abieiter were regularly used with these spark gaps to blow out.

Due to the fact that it is necessary to protect neighboring system parts from the hot and electrically conductive gas jet of the arresters, the active area of the spark gaps are followed by chambers for deflecting and cooling the gases, as is shown in the prior art, these chambers being the Blow out the temperature of the exhaust gases below a critical range. In the case when the cooling chambers are to be completely closed, considerable volumes are required which go well beyond the actual volume of the active part of the drain, which runs counter to the general objective mentioned at the beginning.

The large pressure difference in the high and low pressure section of the spark gap is necessary for the system, since a pressure drop between the active area and the blow-out area is necessary for the exact functioning of the drain in the case of follow-up flow. If the pressure drop and thus the flow are eliminated, the efficiency of the arc cooling is significantly reduced. This undesirably leads to the performance of the surgeon being restricted.

The pressure drop between the active area and the cooling chambers can, however, only be maintained in the case of the drains according to the prior art by means of a comparatively large and complexly cooled blow-out space and, if appropriate, by means of nozzles, which are used for rapid gas relaxation, between the active area and the cooling chamber. The aim of the cooling chambers is therefore only to achieve that the energy supplied to the gas is broken down as quickly as possible in order to ensure the necessary pressure drop between the arc chamber and the blow-out space during the entire follow-up current quenching. In the aforementioned approach to achieving the desired flow limitation, considerable gas generation is required, which means that correspondingly large blow-out volumes or cooling chambers are necessary. The implementation of the previous approaches is difficult with small dimensions but comparable performance, among other things, because there is not enough volume available for blow-out rooms or deflection and cooling rooms. Furthermore, the volume for providing hard gas, which is necessary for flowing the arc, is also reduced. With smaller volumes, therefore, fewer hard gas reserves are available and the cooling volume of the blow-out spaces is limited.

If the hard gas consumption is high, this not only reduces the lifespan of the drain, but also threatens its failure if the cooling capacity is overloaded.

From the foregoing, it is therefore an object of the invention to provide a further developed encapsulated surge arrester based on spark gap for low-voltage applications, which has an effective sequence current limitation, which in principle can also be triggered and which has a low overall volume and high reliability.

The object of the invention is achieved by an overvoltage arrester with the features according to claim 1, the subclaims comprising at least expedient refinements and developments.

According to the invention, the build-up of pressure by the arc itself and by the hard gas in the pressure-resistant housing of the discharge pipe and, in addition, the radial flow through the arc in this area is used to limit the follow current. The maintenance of the pressure difference necessary for the flow and the extension of the arc with follow current despite small dimensions and a low pressure reduction within the entire drain is achieved by the fact that at least one of the two electrodes includes two independent expansion spaces, in which there are alternately different pressures, which are caused by the Spark gap and in particular the arc itself are generated and controlled and their pressure difference to support the desired Rotational movement and blowing at least one arc approach is used.

The follow current limitation is designed in such a way that the maximum prospective short-circuit current that can be controlled by the spark gap is reduced to a twentieth or less of its peak value.

Accordingly, the encapsulation or the spark gap housing, contrary to the prior art known to date, has an essentially elongated cuboid shape, an arc combustion chamber and at least two separate expansion spaces, each essentially extending over the entire cuboid height, being formed in the cuboid.

The expansion spaces are connected to the arc combustion chamber via channels and the chambers and the expansion spaces run essentially parallel to one another.

The arc combustion chamber is delimited in the head region by one of the main electrodes and by an insulating part and in the opposite foot region by an arcing attachment part which is connected to the further main electrode. The channels extend laterally from the arc attachment part to the aforementioned expansion rooms.

In at least one channel and / or an expansion space, further insulating parts or insulating sections, which emit gas when the arc is ignited and the temperature rises, build up a counterpressure.

The arc column, which is formed between the head and foot area, ie between the main electrodes and the intended arc attachment part, executes a base point movement in the area of the arc attachment part. This base point movement alternately closes one of the connecting channels to the expansion spaces, so that different pressure and flow conditions build up in each case. A trigger electrode can be easily guided through the insulating part in the head region of the arc combustion chamber, so that the task is also fulfilled from this point of view.

The expansion spaces and the arc combustion chamber extend essentially over the entire height of the cuboid body.

The channels run essentially at right angles to the longitudinal axis of the combustion chamber or the expansion spaces. Furthermore, the connecting channels can consist of a gas-emitting insulating material.

The cuboid or cuboid body has cavities which form the arc combustion chamber and the expansion spaces and the channels according to the invention.

However, one of the main electrodes can also have cavities which comprise at least the expansion spaces, the expansion spaces each having almost the same volume as the arc combustion chamber.

The cross section of the expansion rooms is essentially the same as that of the

Channels and the arc combustion chamber. The expansion spaces are oriented essentially opposite to the direction of flow within the arc combustion chamber.

In an embodiment, the transition area between the arc combustion chamber and the respective channel can have an expansion in order to ensure that the gases flow into one or both of the expansion spaces even when the combustion chamber is completely filled by the arc or arc column.

The inside of the expansion spaces preferably have means for effective gas cooling. These means can include cooling plates, cooling plates or also surface structures, for example in the manner of knobs. It is also advantageous if the expansion spaces consist of copper or copper alloy material. Furthermore, the expansion rooms have ventilation openings with a small diameter or cross-section for gradual pressure equalization to the environment.

In a further embodiment of the invention, there is the possibility of forming a plurality of electrically switchable arc combustion chambers in the encapsulation, each with associated channels and expansion spaces.

Likewise, an arc combustion chamber manufactured as a separate component can be introduced into an encapsulation which contains the channels and the expansion spaces and forms the counterelectrode and the arc attachment part.

In one embodiment of the invention, a semiconductor resistor with positive temperature coefficients, i.e. a semiconductor resistor, is connected between the further main electrode or the arc attachment part and the trigger electrode or an electrode equivalent thereto. switched a PTC element. A PTC element or PTC thermistor has a low resistance at low temperatures. The electrical resistance of the PTC thermistor rises abruptly at the Curie temperature of the ferroelectric. Below the Curie temperature there is spontaneous polarization between the individual grains of the PTC thermistor material. This shields the negative grain boundary charge. This lowers the potential barriers between the grains at low temperatures below the Curie temperature. The dielectric constant is significantly lower above the Curie temperatures than below. There is no ferroelectric order above and no spontaneous polarization. The shielding of the space charge zones becomes much more ineffective and the potential barriers increase. As a result, the resistance at the transition from low to high temperatures increases by three to six orders of magnitude.

The PTC resistor is relieved by the PTC thermistor connected between the auxiliary electrode or trigger electrode and the other main electrode. The PTC thermistor takes over a larger part of the current with increasing load on the spark gap, which, as mentioned above, reduces the load within the spark gap itself and also extends the arc can be limited by reducing the pressure and the current forces. In the case of long-term discharges, for example also with follow-up currents, there is a further advantage. After a large part of the arc current has been taken over by the PTC thermistor, it heats up and its resistance increases. As a result, the follow current is reduced and the power consumption and thus the wear within the spark gap are reduced. In this way, the PTC thermistor or the PTC element can make a significant contribution to the reduction and deletion of follow-up currents. The proposed measure also has a very positive effect on the re-consolidation of the insulation section after the load. Due to the proposed partial parallel connection of the spark gap and the PTC thermistor, the risk of overloading the PTC thermistor is negligible, especially due to high surge currents.

In an alternative, the arc attachment part is insulated from the surrounding further main electrode and between the arc attachment part and the main electrode there is a semiconductor resistor with a positive temperature coefficient, i.e. a PTC element.

Another exemplary embodiment is also based on an insulated arrangement of the arc attachment part, in which case the PTC thermistor or the PTC element is connected to ground and the further main electrode also has ground potential. In these embodiments, too, the advantages mentioned above arise in the sense of loading the spark gap and reducing spark gap wear.

It is within the scope of the invention that other nonlinear impedances can also be used instead of a PTC thermistor. Inductors, varistors or series connections of gas arresters and varistors are conceivable here. However, in the case of a PTC thermistor, a considerable partial current can be taken over much more easily and with comparatively lower arc impedances. On the other hand, the risk of overloading the PTC thermistor is extremely low due to the self-protection function of this element. The invention will be explained in more detail below using an exemplary embodiment and with the aid of figures.

Here show:

Figure 1 - a sectional view and a sectional plan view of a first

Embodiment of the surge arrester in a cuboid shape;

Figure 2 - an arrangement similar to that of Figure 1 but with additional cooling plates or webs within the expansion rooms;

2a-2c an embodiment with partial parallel connection of the spark gap and a PTC thermistor;

Figure 3 - an embodiment with different arrangements of

Combustion chambers and expansion rooms, which are also partially connected to one another;

Figure 4 - an embodiment of the surge arrester with

Expansion rooms that extend from the arc attachment part both upwards and downwards, in the head and foot area;

Figure 5 - a surge arrester with two arc combustion chambers, each of which two expansion rooms are assigned, with the possibility of connecting the arc combustion chambers and

Figure 6 - a sectional view through an Abieiter, in which a prefabricated spark gap according to the hard gas principle can be screwed into an encapsulation which comprises at least expansion spaces. The spark gap according to the figures, in particular FIG. 1, is based on a cuboid shape which is adapted to the usual dimensions of so-called row housings, the width and the height being chosen to be significantly greater than the depth.

The spark gap is in its simplest form, i.e. untriggered from the first main electrode 1, a first insulating part 2 and the second main electrode 3.

The main electrode 3 accommodates the arc combustion chamber 5 in the interior and two expansion spaces 6 extend from an arc attachment part 4 which is preferred in the event of a follow current load.

In a triggerable embodiment, a trigger or auxiliary electrode 7 is integrated in the first insulating part 2. The insulating part 2 emits extinguishing gas when exposed to temperature from the arc.

After the insulation gap on the insulating part 2 has flashed over, the arc ignites along the shortest separation gap 8 between the main electrodes 1 and 3.

Thereafter, the arc base moves on the inside of the arc chamber 5 due to the pressure difference that arises as a result of the arc ignition and the additional gas emission through the insulating part 2 and the consequent flow between the combustion chamber 5 and the expansion spaces 6 along the part 3 within the combustion chamber 5 for the preferred Arc approach area, ie to the arc attachment part 4.

The length achieved with the reference symbol 9, which corresponds to the distance between the main electrode 1 and the part 4, is equal to an arc length which is maintained over the almost entire arc duration.

The ability of the spark gap to limit, extinguish or even avoid line follow currents increases with the length of the arc, which can be achieved by modifying the length of the arc combustion chamber and with Time period but also the amount of gas emission and the type of gas, preferably hydrogen, ie the properties of the first insulating part 2. Another variation is the possibility of reducing the cross section of the arc combustion chamber 5, which includes an increase in the intensity of the gas flow of the arc cooling and a pressure increase in of the combustion chamber, which can increase the arc voltage and thus also limit the follow current.

In the embodiment according to FIG. 2a, the spark gap is relieved by using a PTC thermistor 17.

The PTC thermistor 17 is connected between the trigger electrode 7 or an equivalent electrode and the arc attachment part 4. The discharge of the spark gap is achieved as follows. The arc is ignited between the main electrodes 1 and 3. At this point in time, the arc voltage, the arc length, the pressure and the temperature within the spark gap are still low. This results in a comparatively low arc impedance. In contrast, the cold resistance of the PTC thermistor is comparatively high and the current through the PTC thermistor 17 is negligible. The build-up of pressure and the lengthening of the arc increase the arc impedance. The PTC thermistor 17 thus takes over a larger part of the current with increasing load on the spark gap, as a result of which the load within the spark gap itself is reduced and the lengthening of the arc can also be limited by reducing the pressure and the current forces.

In the case of long-lasting discharges, for example also with follow currents, a large part of the arc current is taken over by the PTC thermistor, which heats it up and automatically increases its resistance. As a result, the follow current is reduced and the power conversion and thus the wear within the spark gap are reduced. The Kaltieiter 17 can thus make a significant contribution to the reduction and deletion of follow-up currents. In addition, this embodiment also has a very positive effect on the re-consolidation of the insulation section after loading. Due to the partial parallel connection of spark gap and PTC thermistor 17, the risk of overloading the PTC thermistor 17, in particular due to high surge currents, is negligible.

Figures 2b and 2c show similar arrangements with a comparable mode of operation. Here, however, an insulation 16 is formed between the electrode 3 and the arc attachment part 4. According to FIG. 2b, the PTC thermistor 17 is connected both to the main electrode 3 and to the insulated arc attachment part 4.

In the embodiment according to FIG. 2c, the arc attachment part 4 is also insulated from the main electrode 3 via the section 16. The PTC thermistor 17 is connected on the one hand to the arc attachment part 4 and on the other hand is connected to a ground connection. The main electrode 3 also leads to ground.

Due to the high thermal loads and the high pressures, it is expedient to protect the spark gap and in particular the expansion spaces 6 from direct and long-term exposure to arcing, an additional reduction in the energy conversion within the arc combustion chamber 5, which is surprisingly easier with the approaches according to FIGS. 2a to 2c Way succeeds.

However, it is not desirable to further reduce the cross section of the arc combustion chamber 5, since this leads to a deterioration in the surge current carrying capacity.

Due to the small dimensions of the arc chamber and the expansion spaces, as well as the desired long service life, it makes sense to minimize the amount of gas generated in the spark gap according to the invention. For this purpose, the length or the dimensions of the hard gas-emitting material, preferably POM, are limited to a minimum, specifically in a range from diameter to length less than 1: 2. The inner cross section of the insulating part 2 is preferably circular and has a radius of 1 to 5 mm. As a result, both the amount of gas generated with follow-up current and with surge currents is reduced.

In order to prevent an extension of the arc and thus a high power conversion in the event of surge currents, it is necessary to reduce the pressure difference and thus the flow between the arc combustion chamber 5 and the expansion spaces 6. This is achieved according to the invention in that hard gas-emitting insulating material 15 can also be introduced into the expansion spaces 6 and / or into the connecting channels 10.

Since the level of the surge currents through the spark gap cannot be reduced, since this is an impressed current, the entire cross section of the combustion channel is filled by the arc when the surge current is applied. The level of the current, the pressure, the power conversion and the temperature of the plasma are a multiple of the values compared to the follow-up current. A significantly larger and more heated amount of gas compared to the subsequent current load thus penetrates directly and suddenly into the expansion spaces. As a result, hard gas is additionally produced by the parts 15 outside the combustion chamber. Since the volume of the expansion spaces is anyway small according to the invention, a counterpressure is built up in relation to the combustion chamber within the short period of time, as a result of which an arc-extending flow comes to a standstill. As a result, the energy conversion in the event of surge currents within the arrester can be limited.

Suitable positioning, the specification of a certain quantity and the type of gas-emitting material within the channels 10 or the expansion spaces 6 can be used to control very well at which loads and temperatures additional gas is to be emitted.

The closer the hard gas-emitting material 15 is positioned to the arc combustion chamber 5 and the lower the temperature at which the material begins to gases, the lower the loads at which additional gas is released outside the combustion chamber.

In the case when the connecting channels 10 are also made of gas-emitting insulation material, there is a better separation of the Combustion chamber from the expansion rooms 6. In a further embodiment, the expansion rooms 6 and also a part of the arrester housing can thus be insulated from the main electrode 3.

In the case of network follow currents, the power input into the gas and into the expansion chambers is significantly lower, so that the cooling capacity of the expansion chambers 6 is sufficient to prevent the release of hard gas, such as occurs during surge currents, within the expansion spaces 6 or the connecting channels 10.

The positive effects of shortening or limiting the arc length and thus the energy conversion in the case of surge currents would, however, lead to a less-energized and cooled arc in the case of follow-up current. A deterioration in the subsequent current extinguishing capacity would be the immediate consequence. The extension of the arc for compensation is also only possible to a limited extent with the dimensions desired to be reduced. In order to achieve the desired current-limiting extinguishing capacity, the arc voltage must be increased by a stronger and faster pressure build-up within the combustion chamber. However, this can be achieved in a simple manner by reducing the volume of the combustion chamber and the expansion spaces.

This and the relatively small available volume of the spark gaps, in particular of the expansion spaces 6, as well as the avoidance of the release of hot ionized gases and thus a large part of the energies through the intended encapsulation, lead to an excessive adjustment of pressure between the combustion chamber and the expansion space and possibly also supported by pressure reflection, the gas flow necessary for cooling and extending the arc is very strongly prevented or comes to a complete standstill. This then leads to a lowering of the arc voltage and thus to a possible failure of the spark gap due to insufficient cooling, by reducing the arc length or by burning the arc.

In order to avoid such consequences, even with extremely low volumes and high pressures within the spark gaps, it is necessary to do so with follow current high pressure difference between the combustion chamber and the expansion chamber to ensure that a continuous flow through the arc is achieved.

For the above According to the invention, the aforementioned independent expansion spaces 6, which e.g. can be arranged within the main electrode 3 used. So that a gas flow necessary for the extension and cooling can be maintained under the aforementioned conditions, the at least two, ideally almost the same size expansion spaces are embedded in an electrode, which is at the same time an integral part of the housing or the encapsulation of the drain. The expansion rooms have almost the same volume as the active area of the drain, namely the arc combustion chamber. In the preferred embodiment according to FIG. 1, there is no appreciable widening or reduction of the cross section within the expansion spaces compared to the channels 10 and towards the arc combustion space or the combustion chamber 5. That is, the cross section of the expansion spaces also corresponds approximately to that of the arc combustion chamber 5.

However, design variants are also conceivable here in which an exclusive reduction in the cross section of the arc combustion chamber 5 for drastic follow-up current limitation or avoidance is sought, or even in the case of a larger number of expansion spaces, there is the possibility of the ratio of the volumes and the cross sections of the arc combustion chamber 5 to the To design expansion rooms 6 differently, e.g. higher than 2 but less than 20.

As can be seen in FIG. 1, the expansion spaces 6 are connected to the arc combustion chamber at the level of the preferred arc base, namely at the arc attachment part, each with a channel 10, the cross section of which deviates only slightly from the cross section of the arc combustion chamber 5, in order to prevent unwanted pressure reflection and nozzle formation or but also to avoid nozzle clogging if the load is too low. The channels 10 in two expansion rooms are in the same plane and face each other. Furthermore, the expansion spaces are designed such that they preferably extend opposite to the flow direction within the arc combustion chamber 5. After the arc has been ignited, the arc is extended, as shown, by the rapidly arising overpressure along the main electrode 3 to the arc attachment part 4. The heated gas flows into the expansion spaces 6 and, in contrast to known solutions, also very rapidly brings about a considerable pressure rise within these subspaces, which deviates only minimally from the pressure within the arc combustion chamber 5. This pressure in turn has an effect on the outflow behavior from the arc combustion chamber 5. In order to avoid a complete pressure equalization, through which the necessary gas flow comes to a standstill and as a result of which the spark gap would almost lose its ability to limit the current due to the drastic reduction in the arc burning voltage, the specificity of the base point movement of arcs and furthermore the Take advantage of independent expansion chambers.

The arc base and thus also the arc moves continuously in the preferred area of part 4. This results in the basic behavior that with the selected small diameters of the channels 10 of a few millimeters, these are mutually completely or partially closed off by the arc column in the case of network follow currents. As a result, the gas supply from the arc combustion chamber 5 into the respective expansion space 6 is mutually interrupted or restricted to different extents. This now leads to the pressure being reduced due to the cooling of the gases within the closed expansion space compared to the other expansion chamber 6, in which an unrestricted gas supply continues and in particular with respect to the arc combustion chamber.

To support the different inflow behavior of the chambers, the inlet openings of the channels 10 between the arc combustion chamber 5 and the expansion spaces 6 can be widened or designed such that an outflow of the gases is ensured even when the arc combustion chamber is almost completely filled by the arc in the event of follow-up current loads. The changing pressure conditions in the area of part 4 or the specificity of the arc foot point movement lead to the release of the respective outflow channel 10 into the room with reduced pressure. As a result, the further or other expansion space is relieved or closed, as a result of which the pressure in it can now be reduced. The different pressure between the expansion spaces 6 can also lead to a flow between the expansion spaces 6 themselves when the two (outflow) channels 10 are released for a short time, as a result of which the base point movement or the arc rotation in the region of part 4 is supported.

Due to the changing pressure conditions in the expansion rooms, both the flow in the combustion channel and a continuous arc movement can be ensured in the range of up to over 100 bar despite extremely high pressures in the combustion chamber and the expansion rooms, thus preventing the channels from clogging up to the largest subsequent flows. The pressure difference between the combustion chamber and the expansion spaces in the solution according to the exemplary embodiment is preferably only a few percent or bar. However, the pressure in the expansion rooms corresponds to at least 50% of the mean pressure that prevails within the arc combustion chamber.

This ensures that the independent expansion spaces 6 have different pressures and that their pressure, despite their small size, is always below the pressure within the arc combustion chamber 5, which ensures that a continuous flow and thus the functional principle of the spark gap for the interruption of the follow-up current flow are maintained can be.

Since the time for the gases to cool in the expansion rooms, i.e. the dwell time is only a few microseconds due to the rapid movement of the base and the pressure difference must be maintained for several milliseconds in the case of follow-up flows, it is necessary to effectively increase the gases within the expansion rooms despite the small volume cool. In particular, copper or its alloys is used as the material for this. In addition, the surface of the expansion rooms can be increased by roughening, grooving, elevations, cooling plates or the like. The use of such materials with lower arc resistance becomes possible because the current-carrying part of the arc does not spread beyond the area near the part 4 into the expansion spaces of the main electrode 3, which is composed in this case.

The expansion spaces 6 have pressure equalization openings, not shown in the drawing, of small cross-section, which ensure gradual pressure equalization, thereby ensuring a reproducible response behavior of the spark gap after it has been loaded.

The spark gap according to the exemplary embodiment has low wear despite its high ability to limit follow current and a high surge current carrying capacity. A comparatively small amount of hard gas is required to generate a high combustion chamber pressure and a high arc voltage, as a result of which the burn-off of the gas-emitting insulating part 2 remains limited.

The increased flow and thus movement of the arc due to the pressure differences within all rooms leads to less burning in the arc combustion chamber 5 (main electrode 1, 3; insulating part 2) but also in the area of the arc attachment part 4.

According to FIG. 1, the first main electrode 1 is introduced into the second main electrode 3 in an insulated manner. The insulated 2 is used for this. The insulating part 2 consists of a material which emits hard gas under the influence of an arc. To shorten the rollover distance, the insulating part 2 can also consist of a layering of insulating parts and electrically semiconducting or conductive parts.

As already mentioned, a further auxiliary electrode 7, which is used for the targeted external triggering of the conductor, can additionally be introduced inside the insulating part 2, insulated from the main electrodes 1 and 3.

According to FIG. 1, the main electrode 3 contains the two expansion spaces 6 and the arc combustion chamber 5. The electrode 3 can be completely off arc-resistant material, such as tungsten / copper, chrome / steel alloys, graphite or the like, or are only partially made of such a material in the combustion chamber 5 and in the area of part 4 for cost reasons. The area of part 4 is raised in relation to the surrounding electrode area towards the head, ie towards the opposite main electrode 1.

Within the expansion spaces 6, but also within the channels 10, hard gas-emitting material 15 can be arranged if necessary to limit the energy conversion in the event of surge currents.

FIG. 2 shows an arrangement similar to that shown in FIG. 1, but the expansion spaces 6 are provided with a selection of different options for attaching cooling plates 11 or webs 12. The aim of these means is to create the largest possible ratio of surface area to volume of the heat sink with maximum volume utilization.

In the top view of various arrangements of combustion chambers 5 and expansion spaces 6 according to FIG. 3, design options are disclosed in which the expansion spaces can also be at least partially connected to one another or to one another.

The sectional view of a surge arrester according to a further exemplary embodiment according to FIG. 4 discloses expansion spaces which refer to the arc attachment part 4 in the electrode both upwards and downwards, i.e. extend to the head and foot area.

With an appropriate design, arrangements are also conceivable in which the expansion space is predominantly located only at the level of the arc base around the arc combustion chamber, e.g. extends in coaxial form or in segments.

FIG. 5 shows an arrester in which two arc combustion spaces correspond to two expansion spaces each. The arc combustion chambers or arc combustion chambers 5.1 and 5.2 can be electrically connected. Depending on the connection of the arc combustion chambers, the surge current carrying capacity (parallel connection) or the follow current limitation can also be carried out at higher voltages (Series connection) can be improved. FIG. 5 shows only one example of a higher number of combustion chambers or arc combustion chambers, which should not be interpreted as limiting the inventive idea. In a similar way, arrangements for a three-phase connection of the individual drain paths can also be implemented.

In the embodiment according to FIG. 6, an arrester is shown in which a prefabricated spark gap 13 is screwed into a likewise prefabricated or prefabricable housing 14 according to the hard gas principle. This housing 14 comprises at least the expansion spaces 6 described and, in the example shown, also the arc attachment part 4 for the arc base.

Claims

claims

1. Encapsulated, line follow current limiting surge arrester based on spark gaps for low voltage applications with two main electrodes and with _. Thermal stress gas-emitting insulating parts, wherein one of the main electrodes is at least part of the encapsulation and / or the spark gap housing, characterized in that

- The encapsulation or the spark gap housing has an essentially elongated cuboid shape, wherein in the cuboid an arc combustion chamber and at least two separate expansion spaces are formed, each extending essentially over the entire cuboid height, the expansion spaces are connected to the arc combustion chamber via channels and the chamber and the Expansion spaces are essentially parallel to each other,

the arc combustion chamber is delimited in the head region by one of the main electrodes and by an insulating part and is formed in the opposite foot region by an arc attachment part which is connected to the further main electrode,

- The channels extend laterally from the arc attachment part to the expansion rooms and

- The arc column between the head and foot area, i.e. forms between the main electrode and the intended arc attachment part, with the foot movement on the arc attachment part alternately one or at times both connecting channels to the expansion spaces from the

^{■ The} arc column is / are at least partially closed, so that different pressure and flow conditions build up.

2. Encapsulated surge arrester according to claim 1, characterized in that a trigger electrode is guided through the insulating part in the head region of the arc combustion chamber.

3. Encapsulated surge arrester according to claim 1 or 2, characterized by the fact that the expansion spaces and the arc combustion chambers extend substantially over the entire height of the cuboid and the expansion spaces are preferably located in the end regions of the longitudinal narrow sides of the cuboid.

4. Encapsulated surge arrester according to one of the preceding claims, dad u rch g eke n nzei chnet that the channels are substantially perpendicular to the longitudinal axis of the combustion chamber or the expansion spaces.

5. Encapsulated surge arrester according to claim 4, dadu rch geke n nzei chnet that the connecting channels consist of a gas-emitting insulating material.

6. Encapsulated surge arrester according to one of the preceding claims, dad u rch geken nzei chnet that the cuboid has cavities that form the arc chambers and the expansion spaces and the channels.

7. Encapsulated surge arrester according to one of the preceding claims, dadu rch geken nzei c'hnet that one of the main electrodes has cavities which comprise at least the expansion spaces, the expansion spaces each having almost the same volume as the arc combustion chamber.

8. Encapsulated surge arrester according to claim 7, dad u rch marked that the cross-section of the expansion rooms essentially corresponds to that of the channels and the arc combustion chamber.

9. Encapsulated surge arrester according to one of the preceding claims, characterized by the fact that the expansion spaces extend essentially opposite to the flow direction within the arc combustion chamber.

10. Encapsulated surge arrester according to one of the preceding claims, dad urch g eken nzei ch net that the transition region between the arc combustion chamber and the respective channel has a widening to ensure an outflow of the gases even when the combustion chamber is completely filled by the arc.

11. Encapsulated surge arrester according to one of the preceding claims, characterized in that the inside of the expansion spaces comprise means for gas cooling.

12. Encapsulated surge arrester according to claim 11, so that the surface of the expansion spaces is structured and / or cooling plates or surfaces are provided.

13. Encapsulated surge arrester according to claim 11 or 12, characterized g e ken nzei c'h net that the expansion spaces consist of copper or copper alloy material.

14. Encapsulated surge arrester according to one of the preceding claims, dad u rch g eken nzei chnet that the expansion spaces ventilation openings small cross-section to the gradual

Have pressure equalization to the environment.

15. Encapsulated surge arrester according to one of the preceding claims, characterized in that in an encapsulation there are a plurality of electrically switchable arc combustion chambers, each with associated channels and expansion spaces.

16. Encapsulated surge arrester according to one of the preceding claims, characterized in that an arc combustion chamber manufactured as a separate component can be introduced into an encapsulation which contains the channels and the expansion spaces and which forms the counterelectrode and the arc attachment part.

17. Encapsulated surge arrester according to one of the preceding claims, characterized in that at least one channel and / or an expansion space is provided with further insulation parts or insulation sections which emit gas when the temperature rises and builds up a counterpressure.

18. Encapsulated surge arrester according to one of claims 2 to 17, dad u rch g eke n nzeich net that on the other main electrode (3) or the arc attachment part (4) and the trigger electrode (7) or an equivalent electrode, a semiconductor resistor with positive Temperature coefficient (17) is connected.

19. Encapsulated surge arrester according to one of claims 1 to 17, dad u rch g eken nzei ch net that the arc extension part (4) against the surrounding further main electrode (3) isolated via a part (16) and between the main electrode (3) and the Arc attachment part (4) a semiconductor resistor with a positive temperature coefficient (17) is connected.

20. Encapsulated surge arrester according to one of claims 1 to 17, characterized in that the arc attachment part (4) is insulated from the surrounding further main electrode (3) via a part (16) and on the arc attachment part (4) is a semiconductor resistor with a positive temperature coefficient (17 ) is connected to ground, the further main electrode (3) also being at ground potential.