DE102007015931A1 - Encapsulated, flameproof, non-hermetically sealed, rotationally symmetric high-performance spark gap - Google Patents

Abstract

The invention relates to an encapsulated, pressure-proof, non-hermetically sealed, rotationally symmetrical high-power spark gap comprising two main electrodes positioned opposite one another at a distance, a cylindrical metallic outer housing, a gas or plasma cool-off chamber surrounded by the outer housing and connection contacts for the main electrodes, which contacts are preferably arranged on the front face. The cool-off chamber consists of a coaxial cup-shaped arrangement with an interposed meandering cooling channel. One of the main electrodes is configured as a hollow-cylindrical expulsion electrode the lateral openings of which extend into the cool-off chamber. The cooling channel comprises a plurality of independent vent openings or communicates with such openings. The invention is characterized in that a first vent opening communicates directly with the base of the arc channel, said vent opening being configured by a threaded section or a bore of one of the connection contacts. The other vent openings are located in zones where cooled gases are present which have been cooled by deviation and heat-exchanging contact with the cup-shaped arrangement. The cross-sectional area of the lateral openings of the expulsion electrode is larger than the cross-sectional area of the arc formation chamber, thereby reducing electrode consumption.

Description

The The invention relates to an encapsulated, pressure-resistant, non-hermetically sealed, rotationally symmetric high-performance spark gap with two spaced opposite main electrodes, one cylindrical metallic outer casing, a gas or plasma cooling space surrounded by the outer housing and preferably frontally arranged electrical connection contacts for the main electrodes according to the preamble of claim 1

For surge arresters on the basis of spark gaps according to the state The technology is used in low-voltage applications encapsulated to the environment endangering To avoid blowing out hot or even ionized gases.

at belonging to the prior art Ausblasenden Arresters will be the major part of energy sales to about 90% in the form of hot gas delivered to the environment. It is obvious that by avoiding blowing out in modern day Spark gaps both the thermal and the dynamic load increases. These increasing loads complicate with encapsulated arresters the necessary control of high pulse and secondary currents with the smallest possible size.

to Realization of low levels of protection in the range of less kV the arresters provided with additional triggering devices. Such a triggering device requires isolation of the additional, generally with high-voltage loaded further electrode. The additional expenditure of installation space and the additional insulation materials also lead to a further restriction the performance of such realized arrester.

According to the DE 100 08 764 A1 and the encapsulated spark gap shown there, it is known to supply the trigger potential via the metallic housing casing of the spark gap. The main electrodes provided there are isolated from each other and introduced into the spark gap in relation to the housing. Due to the small arc length and the simple division of the arc, however, only a small follow current limitation can be achieved with this solution of the prior art.

With the encapsulated arrester after DE 100 18 012 A1 the potential of the ignition electrode is also supplied via the pressure-resistant metallic shell of the spark gap. The local pressure-resistant jacket is made of one piece and it is used for the preparation of a simple forming process. The waiver of an insulated implementation of the ignition potential leads in this variant, however, to an additional burden of insulation in the interior of the spark gap, since both electrodes must be isolated not only against each other, but also with respect to the entire housing. In addition to the higher space requirement is hampered by the complex and voltage-resistant insulation in particular, the heat output from the spark gap. This leads to an increased thermal load on the insulating parts, to long cooling times and to an enormous limitation of the space available for the spark gap. All of these disadvantages ultimately limit the performance of the spark gap.

Then, if to improve certain parameters of a spark gap a additional delivery of hard gas takes place, creates a high Energy turnover, in addition to the thermal load to another Increase or a dynamic pressure load both at Pulse as well as subsequent currents leads.

In the DE 101 64 025 A1 an encapsulated triggerable spark gap is shown, which operates on the Radax flow principle. In this solution of the prior art, the existing cuboid housing of the spark gap is used for cooling the hot gases. The supply to the trigger electrode is effected by the insulating parts of the second, opposite the housing main electrode. Such a variant is very complicated due to the geometric embodiment of the housing and significantly limits the space of the active arc region with respect to the region for cooling the gases.

The Briefly appreciated solutions of the prior art technology includes low-voltage, low-voltage air-gap which, due to their structural design, a per se high pressure resistance have.

In the EP 0 305 077 A1 is presented a spark gap of lower efficiency, in which a trigger electrode is passed through the existing of insulating material outer sheath of a spark gap. This non-lightning current carrying spark gap has small main electrode distances and no means for increasing the arc voltage. The power conversion and thus the associated thermal and dynamic load of this spark gap of the prior art is insufficient. For use in low-voltage networks such a spark gap is unsuitable. The dynamic load capacity of the local housing and the implementation of the trigger electrode is also low.

Out It is therefore the object of the invention to provide a further developed, encapsulated, flameproof, non-hermetic, rotationally symmetrical high-performance spark gap with two spaced opposite main electrodes, a cylindrical metallic outer casing, one from the outer casing surrounded gas or plasma cooling space and preferably arranged on the front side electrical connection contacts for the main electrodes indicate, wherein the spark gap compared to the known a Good and fast cooling of hot gases causes.

The Solution to the problem of the invention is achieved by a spark gap according to the combination of features according to claim 1, wherein the dependent claims at least expedient Represent refinements and developments.

at the encapsulation of spark gaps according to the Radax flow principle increased by the non-given blowing and the energy removal the thermal load of all spark gap parts. About that In addition, the dynamic stress of the spark gap increases, since the gas additionally generated in the Radax flow principle can not flow freely.

These thermal stress leads to faster deformation and the increased burn-up used cheaper passive insulation parts, but also the active gas-emitting substances.

As well increases the burnup of the main and possibly existing Trigger electrode. The burning particles, but also the melt are due the dynamic pressure development within the entire spark gap distributed. This also endangers the already known Prior art existing pressure equalization holes, which for the necessary pressure equalization to the surroundings of the spark gap to care. At the wear of these pressure equalization holes there is a risk of permanent damage to the spark gap with repeated loading.

The dynamic load on the spark gap due to function-related pressure surges leads at high loads to a short-term or permanent gap formation in which are in a stacked arrangement Items. This can be due to contamination or by plasma interference a Damage to the insulation and thus deterioration of the Ignition behavior of the spark gap occur. For even stronger Strains can affect the parts that make up the arc furnace limit, tend to crack, causing the function of the spark gap endangered is.

It There is therefore a need for an effective and space-saving as well as cost-effective cooling of hot Gases and a safe pressure equalization of the spark gap with to create the environment.

According to the invention the cooling space of the encapsulated, flameproof, non-hermetically sealed, rotationally symmetric high-performance spark gap from a coaxial, cup-like arrangement with intervening meandering cooling channel. The cup arrangement Can be made of a metallic material, which has a high thermal conductivity owns.

A the main electrode is formed as a hollow cylindrical Ausblaselektrode having the side openings. These side openings reach into the side cooling room.

Of the aforementioned cooling channel has several, from each other independent vents or is associated with such openings.

the The basic idea of the invention is a first vent opening indirectly or directly with the bottom of the arc channel in conjunction standing. This first vent is from a thread and a bore of one of the connection contacts educated.

The further vents are located in Areas where by deflection and heat-exchanging Contact with the cup-like arrangement already the gases of a refrigeration are subject.

Farther is the sum of the cross-sectional areas according to the invention the lateral openings of the blow-out electrode larger as the cross-sectional area of the arc combustion chamber, so that in a simple way an effective reduction of Elektrodenabbrands given is.

to Increasing the pressure resistance of the overall arrangement is included An embodiment of the invention, a surrounding the arc furnace support member in the form of a support ring, a support band, a support fabric and / or a support insert intended.

to Increasing the compressive strength is also the possibility at least parts of the open end of the cup-like arrangement with the exhaust electrode in positive or non-positive connection to bring.

In a complementary embodiment, the support ring made of an electrically conductive material and it is provided with a connection to the cup-like arrangement, wherein between the Support ring and the arc furnace a space limiting use of a gas-emitting material, eg. B. POM is located.

The Invention will be described below with reference to embodiments and explained in more detail with the aid of figures become.

in this connection demonstrate:

1 an embodiment of an efficient cooling for a flameproof executed, non-hermetically sealed rotationally symmetric high-performance spark gap with coaxial cup-like arrangement and intermediate meandering cooling channel;

1a a detailed representation of the arrangement according to 1 ;

2 an embodiment analogous to that after 1 but with additional support ring to increase the pressure resistance of the overall assembly;

3 an embodiment similar to that after 2 , but with additional screw connection between the cup-like arrangement and the discharge electrode for stabilizing and increasing the pressure resistance of the overall arrangement and

4 another embodiment with a conductive support ring, which is in communication with the cup-like arrangement which limits the cooling space.

The spark gap shown by way of example in the figures comprises a cylindrical metallic outer housing 1 and two main electrodes 2 ; 3 ,

In addition, optionally, the possibility of triggering, z. B. by an insulated introduced conductive tape 8th provided to a trigger electrode is provided.

The trigger electrode has an inner end that extends to the arc chamber 7 leads.

The isolated insertion of the trigger potential as shown in the illustration 1 discloses providing additional clearance in the lower portion of the spark gap assembly.

This space is predominantly tubular staggered metal parts 21 filled, which represent a coaxial, cup-like arrangement.

Annular column 22 between the metal parts 21 are by circumferential slots 23 or holes 24 or the like recesses interconnected so that a meandering coaxial space-saving cooling system with multiple gas deflection 25 arises.

The metallic cylindrical housing wall (the outer housing 1 ) can be included as a completion in this cooling system.

The Dimensions and location of the cooling system lead by their coaxial arrangement to no unwanted increase the space requirement over known Ausblasernden spark gaps at same performance.

The cooling system of the invention includes a plurality of completely independent pressure equalization ports 26 , which have a larger cross-section with increasing distance or residence time of the gas.

The first or innermost tubular wall 27 the cup-like arrangement is adjacent to the bottom of the main electrode 28 with gas passage as usual the refraction of the plasma jet. As a result, the hot gas in the first, inner cylindrical chamber 17 equally distributed. The wall of this chamber is hereby heavily stressed as a result of the plasma jet, therefore, the material should have a high erosion resistance or an increased thickness. In addition to metallic materials, ceramic materials, composite materials or polymers with high dynamic strength can be used. Metals are particularly suitable because of the high heat absorption capacity, if already in the first chamber 17 a strong cooling of the hot gases should be achieved.

The connection of the first cylindrical chamber 17 to the first annular gap is preferably at the upper end of the first chamber 17 via a gap or individual openings provided there.

With This measure is the flow direction of the Gas in the first chamber opposite the flow direction deflected in the arc channel and thereby the complete Surface of the cylindrical chamber for cooling exploited.

In addition, this makes the flow more diffuse and existing burn-off particles are already stored in the first chamber 17 from.

After leaving the inner, heavily loaded first chamber 17 the hot gas enters the annular gap between the outer wall of the inner chamber and the second annular metal insert. By guiding the gas in the narrow Gap is another, intense cooling. The gap is so dimensioned that a closure by burned-off particles and soot is not possible.

At need the second ring in terms of erosion resistance and the mechanical strength only made lower demands become. Furthermore, the first and the second ring can also be connected by a suitable thread. At the end of the annular gap the gas will pass through a suitable compound in the next Annealed, in which a further deflection can be done. As the last annular gap, the cavity between the last ring insert and the metallic outer sheath (Outer casing) of the spark gap can be used.

The Positioning of the independent pressure equalization holes takes place such that clogging of these openings themselves be avoided with strong burnup within the spark gap can.

The pressure compensation openings 26 are staggered according to the areas with the gas deflections from the inside out, the cross-section of these openings preferably increases from the inside to the outside.

According to the invention, in a first embodiment, a first opening directly at the bottom of the arc channel 7 created in the field of plasma deflection. In a second variant, there is no hole at the bottom, but with a connection according to the inner channel 26 to 1 consists.

These first opening is preferred by a bore with the Thread of the electrode terminal, which also be extended can, formed.

The second vent is from the first chamber 17 via a spiral or groove-shaped feed into the same channel of the electrode terminal or in a separate, slot-shaped channel between the electrode terminal and the extension of the baffle wall of the first chamber 17 ,

The mentioned variants for the pressure compensation can, due to their placement in the area of the highest spark gap load only with minimal cross-section and only with additional cooling, z. B. by long spirals 29 or thread 30 to avoid blowing out. In these stress areas, however, burned products are formed despite high-grade materials, which means that the vent openings are subject to the risk of undesired closure, especially at high loads.

It are therefore according to the invention further vents provided in areas where already a significant cooling of the gas has occurred and in which the probability of Deposition of burned products is lower. A first possibility this exists after the first execution of the Gas through the annular gap between the inner chamber and the first Cooling ring. The pressure compensation opening can over Grooves, but also spirals on one of the other pressure equalization holes independent way outward. An additional and independent pressure equalization opening offers itself as an opening between the metallic housing the spark gap and the outer metallic Ring for gas cooling on.

The Design of discrete pressure compensation openings or openings between the individual cooling walls can also be through porous or gas permeable structures or corresponding inserts are realized.

The resulting high efficiency of the presented solution for cooling the hot gases is shown in that the volume of the walls for deflecting and cooling the gases is approximately equal to or higher than the gas volume in the cooling space 17 is selectable. Likewise, the gas volume in the cooling space does not differ appreciably from the gas volume of the arc combustion chamber 7 ,

Next the high efficiency for the relaxation and cooling of the gases offers the design of the presented cooling system one behind the other staggered, meandering connected annular baffles further advantages.

at known spark gaps according to the Radax flow principle is through the small cross-sectional configuration of the transverse openings the main electrode with the channel for gas passage Backflow of the gas causes in the arc region. At high Pulse currents through this effect, a so-called Nozzle clogging is achieved, reducing the energy turnover of the Spark gap is reducible.

This aforementioned solution has two major disadvantages at high pulse currents and in an encapsulated embodiment. The backflow of the gas in front of the nozzle causes pressure reflections, which run directly into the arc combustion chamber and cause a change in position of the stacked items with possible damage to these parts by excessive pressure increases. The narrowing of the plasma, which is very hot in this area, leads to severe burnup at the lower main electrode even at still moderate residual current loads or pulse loads. This one will carried in the hot plasma jet and endangers the pressure equalization holes. Due to the long heating time in the plasma jet, the material remains molten and reactive for a relatively long time. This further increases the risk of rapid closure of the compensation openings and endangered by the high energy density and the thermally less stable insulation parts of the spark gap. Due to the pressure reflections in the flow channel of the main electrode such hot parts can reach into the ignition range of the spark gap.

Through an opening according to the invention 31 the flow passage in the main electrode which is larger than the cross section 32 in the arc furnace, the erosion of the electrode can be drastically reduced. To achieve the desired backflow at high pulse currents, the distance and the material properties of the first cooling ring of the cooling chamber 27 and the dimensioning of the passage opening of the gas in the other cooling rings 23 be used. By reducing the distance to the cooling ring or by reducing the heat capacity of the material of the aforementioned "nozzle clogging" equivalent effect can be achieved even with smaller pulse currents as needed.

Of the Burning of the already divided and diffusing with increasing distance Plasma jet on the surface of the ring is rather uniform and in addition, coherent enamel fronts form, which make the detachment of individual melt particles more difficult.

By the displacement of Abbranderscheinungen from the electrode in the Cooling range into the risk of damage decreases of insulating parts by entrained melt, even at Pressure reflections due to high impulse loads. This reduces also the risk of blockage of the pressure equalization openings, z. B. by loose melting particles.

As is known, all parts in the arc combustion chamber of a spark gap are particularly sensitive to pressure. Here, in particular, the running of gas-emitting materials routes 19 ; 20 between the main electrodes 2 and 3 and the optional trigger electrode are considered. As preferred low-cost material POM is used here. The strength of POM is limited and can not be significantly increased by the addition of fiber materials.

According to the invention is therefore proposed, the dynamic pressure resistance of the aforementioned materials by at least one outer support ring 33 according to 2 or 3 to increase. 2 shows the execution of a spark gap with a support ring 33 , which consists of an electrically conductive or non-conductive material and worked to fit the active part. As an alternative to a support ring, re-tensioning or wrapping with threads or fabrics is also possible. Of course, the aforementioned support elements or support parts can also be integrated in the manufacturing process in the outer, generally non-active part of the gas-emitting material.

Through the support ring 33 not only does that get in the arc channel 7 located part 34 stabilized, but it is also a distribution of the compressive forces on the entire circumference of the part and also on the other parts lying behind the ring, z. B. insulation parts 35 causes. As a result, even with asymmetrical pressure distribution on the parts, which the arc combustion chamber 7 limit exposed outside of the arc furnace parts of a uniform pressure load. Thus, by the above technical solution, not only the compressive strength of the arc channel 7 Limiting sensitive parts increases, but also the radially more distant parts are protected against a critical asymmetric pressure distribution. This is especially true for the maintenance of the voltage-proof insulation and the trigger potential 6 . 8th as well as the isolated introduced main electrode 3 necessary.

At high pulse currents, the pressure in the combustion channel increases in areas in which, in particular in the preferred constructive variant of stacked and compressed individual parts of the spark gap, they can separate from one another in the event of pressure reflections. However, this poses a great danger to the insulation distances 36 and 37 as well as the trigger electrode 6 ( 2 On the one hand, damage is to be expected from penetrating plasma and, on the other hand, from burning particles and soot.

to Avoiding these negative phenomena can be several Countermeasures are taken.

When maintaining a stacking solution of individual parts, these are to be designed in such a way that when the parts are lifted off by approx. 1 mm, no continuous free spaces can arise between these parts with different potentials. Likewise, a continuous gap to the outer sheath of the spark gap is to be avoided. This can be z. B. by bends, bulges and entanglements of the individual parts of the arc channel 36 . 6 . 37 . 34 . 2 . 3 , like in the 2 shown, done. This is the same with the isolation part 35 and the isolation ring 38 possible. The isolation ring 38 serves the thermal and mechanical decoupling of the active part 34 from the main electrode 2 and the cooling room 17 ,

at Another design variant is also a catch of the Individual parts possible. An advantageous solution is also the encapsulation or encapsulation of parts with insulating material, which lead to the possibly necessary trigger potential. This can be added later or directly during production be made. Another advantage is the joint spraying of the different polymers to form a composite part, creating a lift of Parts can be excluded.

3 shows an arrangement in which as a further measure to relieve pressure or to equalize the pressure screwing the outermost cooling ring 39 with the lower main electrode 2 or other suitable parts.

By this measure, the pressure in the intermediate chamber (Abkühlraum 17 ), evenly distributed to the gas-emitting parts and the parts of the trigger area. Likewise, under heavy loads and a possible gap formation between the parts, a secondary gas flow between the arc combustion chamber and the cooling space is prevented.

In addition to the high pressure load also represents the energy converted in the spark gap, a thermal load on the insulating parts and the gas-emitting parts, in particular the low-melting POM. Especially the parts that the arc furnace 7 are strongly heated and must be rapidly cooled after exposure to avoid both further gas delivery and permanent deformation. A thermal and mechanical decoupling of the parts which limit the combustion channel (arc combustion chamber) laterally, from the strongly heated electrode with gas passage through temperature-stable insulating materials, eg. As high-temperature polymers or ceramics, with the aid of an insulating ring 38 be achieved.

One Another problem especially at high pulse loads and thus high current and voltage gradients is the maintenance of a low Protection level and a low ignition delay of the spark gap.

An essential quantity, which is the time for the flashover of the distance between the main electrodes 2 . 3 determined, is the length of this route. However, this can not be chosen independently of the material used of the fuel channel, the pulse current carrying capacity and the current limit. In order to limit the voltage across the spark gap, therefore, only the time required for the flashover can be reduced or the voltage during this period of time must be limited by other possibilities.

to Shortening the required period of time can the geometric design or the flow conditions the spark gap changed or even the available standing ignition energy can be increased. Likewise the voltage until ignition by external parallel elements, z. B. varistors are limited. These elements can both part of the trigger circuit and separately in parallel be arranged to the spark gap.

According to the invention, both the thermal relief of the parts of the combustion chamber and the stress load to the flashover of the arc between the two main electrodes by an advantageous design variant of the support ring 33 and the POM parts of the fuel channel can be realized. For this purpose, as shown 4 the support ring 33 electrically conductive and with one or more cooling rings 33 of the cooling room 17 or the lower main electrode 2 connected. This connection with the lower main electrode is particularly effective when the main electrode has sufficient mass or cooling.

By the measure explained above, the gas-emitting parts bounding the arc combustion chamber are cooled more directly and more intensively than by a support ring which is not connected 33 and an isolation ring 38 (please refer 3 ) is possible. This cooling is so intense that partly due to the known thermal decoupling (component 38 according to 3 ) can be omitted.

Due to the electrical contacting of the gas-emitting parts depending on the embodiment of the gas-emitting substances (insulating or electrically conductive material), the electric field or the current distribution in the gas-emitting substance 34 to be controlled. Thus, both a shortening of the Zündverzugszeit and a reduction of the voltage drop to the ignition of the main spark gap is possible. The current flow through an electrically conductive gas-emitting material can be controlled by means of these approaches independently of the respective polymer mixture in a wide range. The current flow increases with decreasing ring strength of the gas-emitting substance 34 and with increasing height of the electrically conductive support ring 33 , This significantly reduces the voltage until the flashover between the main electrodes. In this advantageous design variant, it should be noted that, in particular in the case of a strong overlap between the gas-emitting part and the support ring, measures must be taken which prevent a flashover between the upper main electrode 3 and the support ring 33 prevent.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10008764 A1 [0005]
• - DE 10018012 A1 [0006]
• - DE 10164025 A1 [0008]
• EP 0305077 A1 [0010]

Claims (5)

Encapsulated, flameproof, non-hermetically sealed, rotationally symmetric high-performance spark gap with two spaced-apart main electrodes, a cylindrical metallic outer housing, a gas or plasma cooling space surrounded by the outer housing, and preferably frontally arranged electrical connection contacts for the main electrodes, wherein the cooling space ( 17 ) from a coaxial cup-like arrangement ( 21 ) with intermediate meandering cooling channel, one of the main electrodes as a hollow cylindrical Ausblaselektrode ( 3 ) is formed, the lateral openings ( 31 ) in the cooling room ( 17 ), as well as the cooling channel ( 17 ) a plurality of independent vents ( 26 ; 30 ) or is in communication with such openings, characterized in that a first vent opening ( 26 ; 30 ) directly with the arc channel ( 32 ), which is formed by a thread or a bore of one of the terminal contacts, and the other vents ( 26 ) in areas by deflection and heat-exchanging contact with the cup-like arrangement ( 21 ) already cooled gases are located. Spark gap according to Claim 1, characterized in that, in order to increase the pressure resistance of the overall arrangement, the arc combustion chamber ( 7 ) surrounding support element in the form of a support ring, a support band, a support fabric and / or a support insert is provided. Spark gap according to claim 1 or 2, characterized in that to increase the compressive strength of the overall arrangement at least parts of the open end of the cup-like arrangement ( 21 ) with the exhaust electrode in positive or non-positive connection. Spark gap according to claim 2, characterized in that the support ring ( 33 ) consists of an electrically conductive material and with the cup-like arrangement ( 21 ), wherein between the support ring ( 33 ) and the arc furnace ( 7 ) a use limiting this space ( 34 ) is located from a gas-emitting material. Spark gap according to one of the preceding claims, characterized in that the added cross-sectional area of the lateral openings ( 31 ) of the blow-off electrode is greater than the cross-sectional area ( 32 ) of the arc combustion chamber ( 7 ) is to reduce electrode burnup.