DE19655119C2 - Spark gap arrangement - Google Patents

Abstract

The control method is used for an overvoltage diverter device having a pair of spaced electrodes (2a,2b) contained within a housing (6) which contains an arc extinction gas, the volume of the interior (1) of the housing matched to the size of the arc current, to obtain a short-term increase in the internal pressure as a result of the arc current between the electrodes. The internal pressure may increase to between 10 and 60 bar, the overvoltage diverter device provided as a module inserted in an outer housing receiving one or more overvoltage diverter devices.

Description

The invention relates to a spark gap arrangement with two Electrodes in the interior of a pressure-resistant housing are arranged.

Spark gap arrangements are due to their large energy a preferred component for the span protection. Especially with spark gap arrangements that are in the Low voltage supply system installed, it can be used the derivation of an overvoltage to a so-called network follow current come. For this reason, for such Orders the demand for a sufficient follow-up current extinguishing power.

The subsequent current extinguishing capacity of spark gap arrangements is essentially directly proportional to the arc voltage. This leads to the objective of achieving the highest possible arc voltage. In particular, there are several approaches that can be derived from equation (1) below:

UB = (UA + UK) + L. E (1)

UB = arc tension;
UA + UK = anode drop / cathode drop voltage;
L = arc length;
E = field strength.

The UA + UK values are basic parameters of plasma technology and hardly influenceable. A first basic approach is that Influencing the arc length L. This is usually done by an expansion of the arch is achieved. The disadvantage is that the geometrical dimensions of the electrodes correspondingly large and there are limits due to the overall geometry.

The second principal option is the arc field strength E and thus the subsequent current extinguishing capacity via direct cooling influence effect. This is the case with known devices usually brought about by cooling the arc. The Cooling is usually due to the cooling effect of the insulation fabric walls and the use of gas-emitting insulating materials reached. There is also a strong flow of the extinguishing gas necessary, which in turn requires a great deal of design effort required. The hot, ionized gases from the arc will through outlets in the spark gap housing to the outside in dissipated the environment. This means that at the installation site Spark gap certain distances to other live, e.g. B. provided in the electrical distribution and combustible Parts are to be adhered to, what use only under certain enables additional specifications.

DE-OS 20 07 293 is a re-igniting spark gap for surge arresters with a spark quenching coil and with two electrodes arranged on an insulating base known. The spark gap is in a known manner on one circular plate made of ceramic material. The The plate has a recessed part that forms an extinguishing chamber. The spark gap consists of two electrodes, each of which includes a mounting part and a spark gap part. The Spark gap parts diverge away from the ignition point. Your opposite surfaces form discharge paths for the Base points of the arc occurring between the electrodes. Form the surfaces of the spark gap facing away from each other Return paths for the base points of the arc if the Arc so far under the influence of the spark quenching coil has been extended that its base points are the tops of the  Electrodes have passed. Between the return path and the Each electrode has an outlet path, one channel at a time Flow area for the ionizing gas of the arc forms. The channel can be designed as a channel in the plate and is thereby on one side of the spark gap part covered. In another embodiment, the channel consist of a hole in each electrode so that the channel lies entirely in the electrode material. The channel flows into the or in the immediate vicinity of the ignition point, where the arc is ignited when a rollover occurs.

The disadvantage of the subject of DE-OS 20 07 293 is that the opening angle of the two divergent horn-like Spark gap shares a relatively large space is needed and that also the power supply to the two electrodes of comes from the outside of the electrodes. This can lead to relatively high current-related forces that have to be dealt with mechanically.

DE-PS 29 34 236 shows a surge arrester with Spark gap, the electrodes of which by means of an insulating piece Keep a distance and which one is the area of the arch Chamber enclosing the discharge with walls made of insulating material has, which releases fire gas under the influence of heat. With this Surge arrester is the one that arises during a flashover Energy used to extinguish gas from the corresponding To produce existing insulating piece such that the arc is pushed away from the gap and the ionized Gases are released to the outside, so that after overvoltage no further ignition from the mains voltage can. The disadvantage here is a relatively high constructive Effort for the creation of gas flow and the fact that the hot gases are blown out.

The US 3,849,704 shows a surge arrester with a closed housing. In interaction with the impedance of a Supply cable, the deletion process is optimized, whereby the Volume of the housing of the surge arrester chosen so large  is that even with repeated triggers there are no impermissibly high ones Pressures occur. The disadvantage, however, is that the effects only then with regard to optimal surge dissipation set if a voltage limit is set via the cable impedance is given, the arrester itself on the housing side must be dimensioned large.

From the patent specification DD 279 120 A1 is one Pressure relief device for surge arresters in Medium voltage systems previously known.

This device has essentially opposite Electrodes in the interior of a pressure-resistant housing are arranged, a gas-emitting extinguishing chamber with a Pressure relief is provided. The pressure relief device consists of a spring inside a guide cylinder and a spherical closure body with corresponding Bracket. When an overvoltage arrives at the arrester and when the ignition voltage is reached within the arcing chamber there is a rollover between the electrodes of the Extinguishing spark gap along the inner surface, being a Extinguishing gas is released. This leads to a rapid Pressure increase in the quenching chamber, whereby when reaching the Response pressure of the pressure relief device blowing out of the plasma takes place via the released blow-out opening. In order to becomes a deletion if the pressures build up relatively slowly guaranteed low currents and bursting of the arcing chamber avoided due to gas evolution at high currents, however is the line follow current extinguishing capacity of such Setup especially when used in Low voltage supply systems inadequate.

The invention is therefore based on the object of a spark route arrangement with two electrodes in the interior of a flameproof housing are arranged so that an increase in the network follow-up current extinguishing capacity in none,  at least only with a small increase in volume Spark gap arrangement is achievable.

The object of the invention is achieved with an arrangement tion according to the features of claim 1, wherein the Expedient embodiments and Training includes.

According to the invention, the volume of the interior is the spark Route arrangement so dimensioned and at the level of the expected tendency mains sequence current coordinated that by the arc of the Mains sequence current a short pressure increase by a lot times the atmospheric pressure. For later slowly reduce the overpressure or to adjust the Internal pressure at atmospheric ambient pressure are channels small cross-section formed in or on the housing.

The housing preferably has a substantially cylindrical shape Shape, the end faces closed by cover elements are.

The housing is made of a metallic tubular pressure body enclosed or is formed by such a pressure body. The pressure body is flanged on the front and encompasses the Cover elements.  

The above-mentioned pressure increase in the electrode Interior is created by the arc of the grid follow current itself produced.

Accordingly, the increase in the subsequent current extinguishing capacity is not as already known and usual, through improved cooling of the arc, but through a pressure-dependent Influencing the field strength.

Due to the accompanying increase in bow tension improve in a surprisingly simple way Deletion conditions. This is due to the application of the effect attributed such that the field strength E directly the pressure of the extinguishing gas is proportional. This allows high bows reach voltages with very small dimensions of the housing. In itself, both surge current and follow current generate heat and cause an increase in pressure; however, the Heating by the line follow current. So that's the pressure increase and thus the extinguishing capacity in a direct way to the interrupting line follow current coupled. This creates a current-dependent switching behavior or switching capacity. Decide The voltage dif is the end of the size of the line follow current Reference between mains voltage on the one hand and arc voltage on the other hand. Since here both tensions affect each other in their effect the opposite direction has this for the invention the advantage that only so much pressure increase produces becomes like interrupting the current flowing necessary is. This so-called "soft switching" is in the Contrary to "hard switching" according to the state of the art. There is due to the lack of current dependence of the extinguishing power always at full capacity interrupted. This can lead to the so-called power cut. This current stall puts a load on the downstream protective systems or devices and is in the present Avoided invention.

To optimize the volume of the arc chamber or The following must be observed inside the housing. Is this  Chamber volume too small, it occurs with surge or follow current extinguishing process to a mechanical and / or thermal transfer load of the housing. If the volume is too large, the pressure is increased and thus the increase in bow tension too low.

For example, there is a brief increase in the interior pressure of the housing to 10 to 60 bar. So that can be Quadruple follow current extinguishing capacity, the advantage a very small volume of the interior of the housing given is.

As stated, the arc in the housing Surge current and the arc of the follow current Overpressure is slowly reduced, reducing the overpressure preferably within 3 to 5 hours. Because everyone Surge current causes a follow current and the follow current an increase in internal pressure due to its heat development in the spark gap arrangement is caused by the existing which channels reliably avoided that the respective over add up and destroy the spark gap arrangement. Rather, given the features of the invention a slow, continuous equalization of the internal pressure of the Housing reached to the outside atmosphere. Because the Can reduce pressure, the response voltage of the sparks remains route arrangement almost constant, even in the case when multiple deletions at intervals take place.

When using the described quasi-pressure tight Housing has the disadvantage given in the prior art blowing out the hot gases generated by the arc. Consequently there is no risk of endangering People and / or damage to neighboring components or the like.

Generally it should be noted that an important synergistic effect is that a reduction in Volume of the interior of the housing at an assumed Size of the line follow current is a corresponding one and for that  Deletion advantageous increase in internal pressure in the housing Consequence, so that it is not necessary to increase the Arc voltage to ver the length of the follow current arc enlarge. This is an undesirable increase in volume of the above not mentioned, the electrode receiving housing interior necessary.

The spark gap arrangement according to the invention can be used as a module in single or multi-pole housing variants for indoor and Outdoors, including explosions protected spark gaps.

When using an outer pressure body, which has the advantages of a Has inexpensive manufacture, no mechanical Requirements placed on the surrounding plastic element. By means of a result of differences in diameter Coverage can also be a pressure relief valve for the sparks route arrangement can be realized, the cover elements, the z. B. made of plastic, at the flanges shear off and the respective electrode foot to abut the Flanging comes. Because of the larger gaps that appear the overpressure into the atmosphere is released very quickly.

To equalize the pressure in the interior are to adjust the Internal pressure of the housing arrangement to the atmospheric Normal pressure ventilation channels provided, so be dimensioned so that the reduction of overpressure ver different times is adjustable. In the spirit of improving the Deletion behavior can internal plastic elements and / or Insulator made of a gas-emitting material.

The invention is intended below from exemplary embodiments as well are explained in more detail with the aid of figures.

Here show:

Fig. 1 shows a first embodiment of the Funkenstreckenanord voltage in longitudinal section;

Fig. 2, 2a is a view of a NH-Fuse housing with inserted bauter spark gap arrangement in the closed and open state,

Fig. 3, 3a is a view of an outer housing with three built-in spark gap arrangements in the closed and open state and

Fig. 4 shows another embodiment of the spark gap arrangement in longitudinal section.

The first embodiment of the spark gap arrangement is shown in longitudinal section in FIG. 1. In the interior 1 there are two electrodes 2 a and 2 b, which are kept at a necessary distance a by an insulating piece 3 . This distance also determines the response voltage of the spark gap. The distance a can be changed by means not shown in detail so that different response voltages can be set, an increase in the distance a increasing the response voltage and this leading to a higher arc voltage.

The insulator 3 can advantageously be made of a gas-releasing plastic (eg. B. POM) and be designed such that the ignition of the arc is initiated b as creeping discharge at the mutually facing ends of the electrodes cone 2 a and 2. This causes the arc to expand in accordance with the opening angle caused by the cone shape of the electrodes 2 a and 2 b and thus to produce more favorable thermal and quenching properties.

The arc jumps within the small gap a and is then guided radially outward along the electrode surfaces 20 extending from this gap a. Since these electrode surfaces together form an outwardly widening cone, this results in a corresponding extension of the arc and thus an increase in the arc voltage. In the embodiment of the spark gap arrangement according to FIG. 1, but shown in FIG. 4 and in the here given dimensions of approximately one third of the size of the display on the figures is given a pressure increase of the internal pressure in the range of about 30 to 50 bar.

It is of course within the scope of the invention to design the shape of the electrode surfaces and also the electrodes as such and their holder differently than shown in FIGS. 1 and 4.

For example, the electrode surface 20 from the insulating piece 3 to the outer circumference of the electrodes 2 a, 2 b at a distance a can be designed to run radially outwards, the inner end face of which can adjoin the insulating piece. The interior 1 having the electrodes is surrounded by a pressure-resistant housing arrangement 5 . This housing arrangement 5 is limited by two cover elements 4 a and 4 b on the end faces. The entire arrangement is guided and closed to the side surfaces by an inner plastic element 5 a. These parts 4 a, 4 b and 5 isolate the spark gap from an external pressure body 6 provided in this exemplary embodiment, which encloses parts 4 a, 4 b and 5 a in such a way that a pressure-resistant cohesion is produced.

Preferably, the outer pressure body 6 consists of a metallic pipe piece, which can be manufactured inexpensively by flanging its two ends lying on the covers 4 a, 4 b. In one embodiment of the invention, the inner plastic element 5 a can also consist of a gas-emitting material (e.g. POM).

High mechanical and thermal requirements are placed on the cover elements 4 a and 4 b, which consist of an electrically non-conductive material. They withstand the corresponding forces that are generated by the pressure in the interior 1 or housing arrangement 5 during the surge current discharge process and during the follow-up current quenching.

Since thermally highly resilient plastics are generally very brittle and are therefore not optimally suitable for the application for the cover elements 4 a and 4 b, a function separation is carried out here. The thermal insulation of the hot electrodes 2 a and 2 b between the cover elements 4 a and 4 b can take over a thermal cutting disc 7 . A mechanical relief of the lid elements 4 a and 4 b can be achieved by supporting them on the above-mentioned edges of the pressure body 6 .

The special design of an electrode foot 8, whose diameter d1 is larger than the inside diameter d2 of the pressure body 6, b reaches a relief of the lid members 4 a and 4 and the forces acting evenly distributed. The overlap x is of great importance for the mechanical stability of the overall arrangement (see FIG. 2)

x = (d1 - d2) / 2.

For a long-term, minutes-long adjustment of the stationary internal pressure in the housing arrangement 5 to the ambient conditions, ventilation channels 9 are provided, which have the above-mentioned adjustment, correspondingly small passage cross sections. The channels 9 go into the threaded bore of the connecting rods 2 'and the screw thread pairing provided there. The thread pairing shown in Figs. 1 and 4 forms a channel small cross-section without additional openings or holes in the housing are required.

Due to the fact that the proposed arrangement is a self-contained, non-blowing spark gap and therefore no force is exerted on another outer housing (e.g. NH fuse housing, Fig. 2), there are many possible applications also in correspondingly less stable outer housings.

The spark gap module according to the invention can be integrated as a standard assembly in various housing variants, as will be described and explained in more detail below with reference to FIGS. 2 and 3.

It should be noted at this point that with the inven tion compared to the prior art, the spark gap arrangement can be relatively small. For example, the illustration of the spark gap arrangements in FIGS. 1 and 4 is drawn approximately on a 3: 1 scale. In the practical version, the spark gaps are correspondingly smaller than can be seen in the figures.

Another advantage of the arrangement is the possibility of supplying current via the connecting rods 2 ′ of the electrodes 2 a, 2 b running axially in the direction of the longitudinal central axis 19-19 . This avoids harmful power-related forces.

For the sake of completeness it should be mentioned that the housing arrangements 5 of the invention must be so pressure-resistant that they can also withstand the short-term internal pressure due to the relatively high surge current; whereas, on the other hand, the internal pressure is significantly lower due to the explained follow-up current. In contrast, the further outer housings 11 , 13 explained below do not have to withstand any internal pressure, since this is practically taken over by the spark gap arrangement.

The cover elements 4 a and 4 b can be designed as overpressure relief or pressure protection in order to avoid an undesirable risk of explosion of the entire arrangement. For this purpose, an inadmissible increase in the internal pressure by means of the feet 8 of the electrodes 2 a and 2 b causes the inner parts of the plastic covers 4 a and 4 b to be sheared off approximately along the wavy lines 18 .

After these parts have been sheared off, the insulating washers 7 come to rest against the flanges 6 ′ of the pressure body 6 and prevent the electrodes 2 a and 2 b from being pressed out. With the shearing off of the above-mentioned parts along the lines 18 , a larger passage opening is created between the interior 1 and the environment, so that the excess pressure created in the interior is reduced very quickly.

According to FIG. 2 and 2a, the spark gap device 10 in a NH-Fuse housing 11 is installed, which state is shown in the closed (FIG. 2) and opened (Fig. 2a). The fuse housing 11 consists of two half-shells 11 a and 11 b and has pull-out tabs 12 . The electrical contacting of the live conductor or earth is carried out by standardized NH contact blades, which are designated 2a and 2b.

In Fig. 3, 3a, the multi-pole variant of spark gap arrangements 10 is shown in a special outer housing 13 . Since in the spark gap arrangements according to the invention the blowing out required in the prior art is omitted, the spark gap can be arranged closer and an outer housing surrounding it can be made less stable. As shown in FIG. 3, for example, three spark gap assemblies 10 are integrated in a space-saving, spatial arrangement. This results in a more favorable utilization factor of the inner volume of the outer housing 13 . The earth-side connection of the individual elements can be realized by an inexpensive, common earth plate 17 . The outer housing 13 can, as shown in Fig. 3a, be mounted on a standard wire rail via snap fasteners 14 . There may be connection options for cable feed 15 ( FIG. 3a) or a comb rail 16 ( FIG. 3). The connection options for the current-carrying conductors are constructed in a modular distance dimension such that three connections 15 and 16 are provided for the current-carrying conductors on one side and the earth connection 21 on the opposite side.

In the embodiment according to FIG. 4, the outer pressure body 6 provided for a hermetic seal is not present. This requires that the inner plastic element 5 a and the two cover elements 4 a and 4 b are to be designed so that these parts 5 a, 4 a and 4 b replace the function of the outer pressure body 6 insofar as the required pressure-resistant cohesion about this Parts is achieved. For this purpose, either the cover elements 4 a and 4 b are glued along the common surface (section AF) or the partial areas (section BC or DE) are provided with a fine thread and screwed. Instead of this, riveting or pinning is also conceivable. Of course, the aforementioned connection techniques can also be used in combination.

Metal or a correspondingly highly stable plastic lends itself as the material for the cover elements 4 a and 4 b. When using plastic covers 4 a and 4 b, there is the advantage that an insulating outer shell is created which offers protection against contact.

Overall, the invention succeeds in creating a spark gap order to propose which has a high network sequence current extinguishing capacity and which has a constant response tension causes. According to the invention, the volume of the inside dimensioned to the expected line follow current, d. H. minimized, with a through the arc of the line follow current there is a brief increase in pressure. The constant response voltage even if there are several, spaced apart Deletions arise due to the possibility of slow Relieving the excess pressure and adjusting the internal pressure to the atmospheric pressure.

Claims (4)

1. Spark gap arrangement with two electrodes located inside space of a pressure-resistant housing are arranged, in which the volume of the interior so dimensioned and to the height of the expected line follow current is matched by that Arc of the line follow current a brief pressure increase is a multiple of atmospheric pressure and whereby to slowly reduce the overpressure or adjust the Internal pressure at the atmospheric pressure channels small cross are trained. 2. spark gap arrangement according to claim 1, characterized in that the housing is cylindrical and on the end faces is closed by cover elements. 3. spark gap arrangement according to claim 1 or 2, characterized in that the housing of a metallic, tubular pressure body is enclosed. 4. spark gap arrangement according to claim 3, characterized in that the pressure body is flanged on the front and the cover encompasses elements.