EP1413027B1 - Encapsulated spark-gap based surge voltage protector - Google Patents

Description

The invention relates to an encapsulated surge arrester spark gap base with large, opposite, disc-shaped electrodes in rotationally symmetrical arrangement and an arc discharge gap located between the electrodes, which is at least partially enclosed by a baffle, according to the preamble of patent claim 1.

Encapsulated, also triggerable spark gaps as surge arresters, preferably used as N / PE spark gap, have long been state of the art. The two most essential requirements for such spark gaps, namely a high insulation capacity and very high surge current dissipation properties, result directly from their place of use for N / PE spark gaps. Decisive here is a high lightning current carrying capacity and high reliability, so that in any case harmful contact voltages can be excluded.

Known such spark gaps with a direct lightning protection capability of up to 100 kA 10/350 μs have relatively large dimensions, which is disadvantageous.

The high surge current load, the associated high material erosion, the high dynamic loads due to current forces, pressure, energy and temperature of the arc discharge make extremely high design demands in encapsulated embodiments. In the case of a triggerable N / PE spark gap, in addition to the isolating distance of the main spark gap, the insulation capacity and the response voltages of two further isolating distances must be ensured under all loads. With a reduction in the outer dimensions of the arrester, however, this leads to an increased load on the individual components or assemblies.

The DE 100 08 764 A1 discloses a principle triggerable spark gap of small dimensions, which can be used as N / PE route. This spark gap has coaxial electrodes and the connection is made from one side. conditioned the structure and local principle of the traveling arc, the performance of this spark gap is limited at burst currents due to the burning, the thermal and dynamic load, however, a considerable follow current extinguishing capability can be achieved, which is of no significant importance in N / PE spark gaps is.

The triggerable encapsulated spark gap after EP 0 305 077 A1 is an embodiment without vent opening with flat parallel main electrodes. The disadvantage of the local spark gap is based on the sliding distance between the two main electrodes whose length corresponds to the distance between the electrodes themselves. At high-current load this slide is loaded by the addition of decomposition and combustion products; which can lead to a reduction of the insulation capacity or even a short circuit.

An encapsulated Überspannungsableiter.nach the preamble of claim 1 is known from US-A-2,431,226 known.

From the foregoing, it is an object of the invention to provide a sealed overvoltage arrester on spark gap basis, in particular for use as N / PE spark gap, which has a high surge current Ableitvermögen with small dimensions and simple structure and the triggerable executable, so that already factory different over-voltage protection levels of eg 1.5, 4 or 6 kV can be set without significant changes to the spark gap are necessary. Furthermore, it should be ensured that deposits due to decomposition products in such areas, which are of minor importance for the insulating ability and thus the long-term stability of the spark gap.

The object of the invention is achieved with an encapsulated surge arrester spark gap base with large, opposite, disc-shaped electrodes according to the features of claim 1, wherein the dependent claims represent at least expedient refinements and developments.

The design of the two main electrodes as an air gap ensures a high strength of the arrangement in so-called TOV loads and long-term flows. Due to the possibility of triggering, different threshold voltages can be specified at the factory via an internal or external circuit.

The electrodes have large-area and thus erosion-resistant arc regions, wherein by means of the meander-shaped baffles arranged a deflection of the hot gas flow adjusts, which is caused by the pressure wave when igniting the spark gap. The baffle or diverting walls project partially beyond the main separation section, so that optionally occurring burn-up or decomposition products such as soot or the like can accumulate without the necessary insulation sections, which are arranged off the flow direction between the baffle walls, being contaminated. Existing small diameter vents provide slow pressure equalization in the spark gap after load.

According to the invention, a first baffle wall of one of the electrodes, projecting the main separation section, is arranged directed towards the opposite electrode and a second baffle wall is provided radially spaced from the first baffle wall in relation to the rotationally symmetrical structure. The baffles form, as already mentioned, a meander which is to be traversed by the arc discharge pressure wave. Off the flow direction are protected by deposits insulation stretches.

The baffles may have an intermeshing comb structure, which extends substantially perpendicular to the respective electrode surface.

Within the area enclosed by the first baffle, an insulating layer is provided in one of the main electrodes, and in this case, the first baffle or parts thereof are designed as a conductive auxiliary or trigger electrode.

The second baffle may be part of a spacer which fixes the opposing main electrodes, which preferably is orientated in the flow direction and has said at least one pressure equalization opening.

The spacer itself can be designed so that further meander forming baffle or deflection walls arise.

The insulating layer has a circumferential rotationally symmetrical extension, which extends beyond the surface of the corresponding main electrode that a rollover path for an auxiliary discharge between the trigger electrode and the main electrode is formed, which is simultaneously oriented to the opposite main electrode.

To excite diffuse arc-base points, the ratio between distance and diameter of the main electrodes is ≥ 1:10.

Starting from the spacer radially inward and parallel and gap-forming extending to the main electrode surface, a so-called Bedampfungssperre be provided, which may additionally have an optional offset at its free end.

Within the area enclosed by the first baffle, in the alternative embodiment it is possible to embed an insulating trigger electrode in one of the main electrodes.
This isolated trigger electrode may be formed as a ring or pin electrode which is substantially flush with or recessed from the respective main electrode surface, the insulation additionally surrounding a part of the pin electrode in a circular ring in the latter embodiment.

To further optimize the burn-off behavior, the main electrode surfaces can be structured. Furthermore, one of the main electrodes can form part of the arrester housing, so that simplifies the structure of the flameproof enclosure.

The invention will be explained below with reference to exemplary embodiments and with the aid of figures.

Fig. 1

eine erste Ausführungsform des gekapselten Überspannungsableiters auf Funkenstreckenbasis mit Hilfs- oder Triggerelektrode;

Fig. 2a und 2b

eine Ausführungsform analog derjenigen nach Fig. 1, jedoch mit zusätzlichen parallel zu einer der Hauptelektroden verlaufenden Bedampfungssperren;

Fig. 3a und 3b

verschiedene Ausführungsformen von im Zentrum einer der Hauptelektroden angeordneter Hilfs- oder Triggerelektroden;

Fig. 4a und 4b

eine Ausführungsform einer Funkenstrecke mit besonders hohem Leistungsvermögen durch Kombination einer Gleitstrecke mit einer Luftüberschlagsstrecke bzw. eine Ausgestaltung einer der Hauptelektroden, welche von elektrisch halbleitendem Material mit oder ohne Luftspalt umgeben ist, so daß sich hier die erwähnte Gleitfunkenstrecke ausbildet; und

Fig. 5

ein gekapselter Überspannungsableiter mit Mäanderprallwänden, jedoch ohne Hilfs- oder Triggerelektrode.

Hereby show:

Fig. 1

a first embodiment of the encapsulated surge arrester with auxiliary or trigger electrode;

Fig. 2a and 2b

an embodiment analogous to that after Fig. 1 but with additional evaporation barriers running parallel to one of the main electrodes;

Fig. 3a and 3b

various embodiments of auxiliary or trigger electrodes arranged in the center of one of the main electrodes;

Fig. 4a and 4b

an embodiment of a spark gap with a particularly high performance by combining a slide with an air raid distance or a configuration of one of the main electrodes, which is surrounded by electrically semiconductive material with or without an air gap, so that here forms the mentioned Gleitfunkenstrecke; and

Fig. 5

an encapsulated surge arrester with meander impact walls, but without auxiliary or trigger electrode.

In the figures, the main electrodes are designated by the reference numerals 1 and 2. These main electrodes 1, 2 are formed substantially rotationally symmetrical and are opposite. The main electrodes 1, 2 may have a mutually directed extension whose parallel course and distance defines the main spark gap 6.

In the embodiment according to Fig. 1 accepts a specially trained baffle 3 not only the function of the flow deflection, but also that of an auxiliary electrode, so that adjusts an initial flashover 11 between the fed with trigger voltage auxiliary electrode 3 and the main electrode 2 via the insulation gap 9.

The main discharge 12 takes place exclusively between the electrodes 1 and 2, in the area marked 6.

The (first) baffle from the part 3 causes the pressure wave, which forms when the spark gap between the two main electrodes, is broken and deflected, whereby the pressure surge in the downstream Areas that serve to ensure isolation, can be reduced.

An insulating part 4 is used for electrical insulation and at the same time represents the Überschlagsweg between the baffle / auxiliary electrode 3 and the main electrode 2. A spacer 5 holds the two main electrodes 1, 2 at a distance. This spacer 5 comprises a plurality of baffles 10, vents 8 and insulation sections 7. The vents 8 lead after extinguishing the arc to reduce the increased internal pressure within the spark gap.

From the schematic representation of the respective figures it can be seen that the baffles form a quasi-meandering or intermeshing comb structure, so that there is a multiple deflection of the gas flow. The actual insulation sections 7, which are relevant for the relevant electrical properties, are protected outside the flow area. Unavoidable deposits due to electrode erosion do not affect the properties of these insulation sections 7.

It is in the constructive implementation of the above teaching to ensure that the distances between the baffles and the respective opposite portion of the corresponding main electrode are greater than the distance 6 of the active main electrode surfaces.

In a passive ignition of the spark gap, the auxiliary electrode 3 can be interconnected inductively or with high impedance to the main electrode 1 internally or externally. In this way, the auxiliary electrode 3 performs the same potential as the main electrode 1. After flashover along the path 9, a small current flows through the auxiliary electrode, whereby the dielectric strength of the separation distance between the main electrodes is reduced, so that the arc between the main electrodes 1 and 2 for Ignition comes. This in turn relieves the auxiliary electrode 3. The auxiliary electrode 3 can be made of electrically conductive or semiconducting material.

In a further embodiment of the aforementioned passive ignition, the parts 3 and 5 may be made of a single part or consist, here on semiconducting material is used. In passive ignition, the insulation section 9 determines the response voltage and thus essentially the protection level of the entire spark gap.

In this passive ignition, the distance 6 between the opposing main electrode surfaces may be a multiple of the distance 9, however, the length of the path 9 is to be selected as a function of the desired response voltage of the spark gap.

With an active triggering, it is possible to choose the distances or distances 9 and 6 almost arbitrarily, wherein the maximum possible length of the path 9 is limited by the output voltage of the trigger circuit and the maximum possible distance 6 is dependent on the energy input of the trigger circuit.

With an active triggering of the spark gap, the distance 6 between the surfaces of the main electrodes 1 and 2 can thus be designed significantly higher than in the case of spark gaps without auxiliary electrode with a comparable overvoltage protection level. This and the selected design as an air gap ensure a high insulation capacity and a constant overvoltage protection level even under heavy loads.

After the ignition of the discharge by means of the triggering via the insulating section 9, the dielectric strength of the main line 6 is so greatly reduced by formed charge carriers that the arc discharge 12 ignites after a delay time, whereby the trigger circuit and thus the insulation section 9 are immediately relieved.

The smaller the distance 6 and the higher the amount of trigger energy introduced, the lower is the delay time until complete ignition of the main line 12 after the insulation section 9 has rolled over.

In region 9, the insulating part is preferably provided with a projection, whereby the length and thus the energy of the spark is increased. At the same time the resulting charge carriers are brought closer to the opposite main electrode 1, whereby the ignition of the arc 12 improves.

The wiring for the passive ignition is possible inside or outside the spark gap. Corresponding high-resistance conductive or semiconducting materials, such as, for example, electrically conductive polymers or ceramics, but also resistance materials, are conceivable as an internal wiring.
In the case of an external circuit, varistors, gas arresters, capacitors, coils, as well as their combinations can additionally be used.
In an active trigger circuit, which is preferably mounted outside the spark gap, the distance of the insulation section 9 can be selected independently of the desired overvoltage protection level.

The central extension on one or both of the main electrodes 1, 2 forms the preferred focal surface of the arc. The main electrodes 1 and 2 are made of tungsten / copper, graphite or similar erosion-resistant materials.

The large-area electrodes with a distance / diameter ratio of substantially 1:10 are characterized by diffuse and thus low-burning arc base points. As a result, the pressure or current load of the overall arrangement remains very low, which in turn is of decisive advantage for the desired small design.

The tendency to form a diffuse arc can be supported in another embodiment by lowering the pressure, by utilizing natural or foreign magnetic fields and by high-melting electrical materials such as graphite, silicon carbide, tungsten, molybdenum and their compounds.

By using eigen- or external magnetic fields, which are oriented in the axial or radial direction, based on the Stromflußrichtung in the arc, there is the possibility to force the arc to a desirable rotation. This rotation supports the diffuse arc approach, improves follow-up current behavior and reduces electrode wear. In addition, the diffuse arc approach reduces the arc voltage and thus reduces the energy turnover within the spark gap.

Under heavy load, in particular with metallic main electrodes, molten beads are formed. As a result of the arc discharge pressure, these molten pearls are transported away from the discharge area and settle on or behind the baffle wall, as a result of which the opposing main electrode surfaces in the active region can be kept free of burnup material with the spacing 6 as far as possible. The Abbrandfläche is in the range of substantially 75 mm ² to 1000 mm ² , wherein the distance between the two main electrodes 1 and 2 is substantially between 0.2 mm and 4 mm.

The (first) baffle protrudes with its flank at least 0.5 mm to a maximum of 5 mm beyond the discharge gap with the distance 6, so that the pressure, which arises in the discharge gap, can not propagate directly radially, but only undergoes a deflection.

Larger erosion particles, which do not slide on the flanks of the main electrodes 1, 2, are thus thrown against the first baffle wall on part 3. Smaller particles are transported along as stated and can deposit on the further (second) baffles 10.

In the spacer 5, a region 7 is formed, which remains almost unaffected by the pressure wave and the deposits and thus serves as the main insulation route.

Existing vents 8 ensure after load a rapid reduction of the increased pressure, which is caused by the heated gases, but also by the decomposition products, whereby the response of the spark gap can be kept constant.

As in the Fig. 2a and 2b can be provided between the main electrodes 1 and 2, starting from the spacer 5, evaporation barriers. The purpose of this vapor barrier is to provide as long and thin a gap 13 between the spacer 5 and at least one of the main electrodes, which lies outside the main direction of propagation of the pressure and flow wave. This gap may also contain deflections by a cranked embodiment of the vapor barrier, as this Fig. 2a shows. The risk of contamination of this gap is thus extremely low, which a further isolation route is created. The width of the gap should be in the range ≤ 0.2 mm, the length has to be at least 2 mm.

With lower requirements for the performance of the spark gap can be dispensed with a well-defined rear backing or undercut in the spacer 5 with a correspondingly dimensioned Bedampfungsperre. In this case, the spacer is only used to fix the two main electrodes 1, 2 and the vent or the pressure equalization.
It should be noted at this point that the venting of the spark gap can of course also be done through openings on or through the electrodes or the auxiliary electrode.

The above-mentioned functions can also be taken over by this housing with the removal of a separate spacer 5 with a corresponding design of the outer casing of the surge arrester.

In an embodiment with special auxiliary electrodes according to the Fig. 3a and 3b these are quasi-centric in one of the main electrodes, in the example shown the main electrode 2. The example pin electrode 16 is electrically isolated by an insulation 15 from the potential of the main electrode 2. According to Fig. 3a Closes the pin electrode 16 with the surface of the main electrode 2 almost, with the insulating portions 15 projecting.

In the embodiment with a reset trigger electrode 16, the insulating part 15, the upper end of the pin electrode 16 is formed annularly, formed. In the embodiment according to Fig. 3a can be ignited with an appropriate design of the trigger circuit and the distance 6 instead of the adjacent main electrode 2 and the opposite main electrode 1. This has the advantage that almost the entire separation distance between the main electrodes 1 and 2 is rollover, thereby minimizing the delay time for igniting the arc 12.

After the Fig. 4a and 4b In the case of spark gaps with particularly high performance, the sliding section 9 (FIG. Fig. 1 ) by a combination with an air gap in series between the parts 3 and the main electrode 2 before heavier loads to be protected. In a further variant, the main electrode 2 can also be surrounded by electrically semiconducting material, eg conductive plastic 14 with or without an air gap, via which the spark then slides from the auxiliary electrode 3 to the main electrode 2.

It is within the meaning of the invention that, taking into account the response voltage and the distance 6, a non-triggerable spark gap, as in Fig. 5 is shown, can be realized. In this case, it is possible, in particular to fulfill the baffle and deflection function with the extension 2 ', which is part of the main electrode 2. Here, by appropriate measures, such as distances or insulating covers, to ensure that even with heavy loads, the response distance is located in the gap marked 6 with the gap.

The selected rotationally symmetrical construction of the opposing main electrodes 1 and 2 advantageously allows the attachment of electrical connections on opposite sides. The trigger electrode can be made accessible via an insulated bushing on or in the housing for external wiring. One of the main electrodes may form part of the arrester housing which is preferably crimped or bolted to achieve the desired mechanical strengths for encapsulated spark gaps.

Claims (15)

1. Encapsulated surge diverter on a spark gap basis having large-area, opposite, disc-shaped electrodes (1, 2) in a rotationally symmetric arrangement as well as an arc discharge gap located between the electrodes, which is at least partially enclosed by an impact wall,
   characterized in that
   a first impact wall (3) is arranged from one of the electrodes in a direction toward the opposite electrode by rising above the principal separating distance,
   a second impact wall (10) is provided with respect to the rotationally symmetric structure radially and outwardly spaced away from the first impact wall, the impact walls (3, 10) forming a meander which is passed through by the arc discharge pressure wave, and that insulation distances (7) protected against deposits are situated away from the flow direction.
2. Encapsulated surge diverter according to claim 1,
   characterized in that
   the impact walls (3, 10) have an engaging comb structure which extends substantially perpendicularly to the electrode surface.
3. Encapsulated surge diverter according to claim 1 or 2,
   characterized in that
   within the region enclosed by the first impact wall (3) an insulating section (4) is provided in one of the main electrodes (1, 2) and that the first impact wall (3) or parts thereof is configured as a conductive auxiliary or trigger electrode.
4. Encapsulated surge diverter according to one of the preceding claims
   characterized in that
   the second impact wall (10) forms part of a spacer (5) fixing the main electrodes, which may comprise at least one pressure-compensation hole (8) oriented in the flow direction.
5. Encapsulated surge diverter according to claim 4,
   characterized in that
   the spacer (5) comprises additional meander-forming impact and deflection walls.
6. Encapsulated surge diverter according to claim 3,
   characterized in that
   the insulating layer (4) comprises a surrounding, rotationally symmetric extension which extends beyond the surface of the corresponding main electrode so as to form a spark-over section (11) for an auxiliary discharge between the trigger electrode (3) and the main electrode (2), which is simultaneously oriented toward the opposite main electrode (1).
7. Encapsulated surge diverter according to one of the preceding claims,
   characterized in that
   for exciting diffuse roots of an arc the ratio between the distance and the diameter of the main electrodes (1, 2) is ≥ 1:10.
8. Encapsulated surge diverter according to one of claims 4 to 7,
   characterized in that
   starting from the spacer (5), an evaporation barrier is provided which extends radially inwardly and in parallel with respect to the surface of the main electrode by forming a gap and which may be complemented at its free end with an offset or a bending.
9. Encapsulated surge diverter according to claim 1 or 2,
   characterized in that
   an insulated trigger electrode (16) is arranged in the main electrode (2) within the region enclosed by the first impact wall (3).
10. Encapsulated surge diverter according to claim 9,
    characterized in that
    the insulated trigger electrode (16) is a pin electrode which is substantially flush or retreats with respect to the surface of the respective main electrode, wherein in the latter embodiment the insulation (15) additionally surrounds an upper portion of the pin electrode in the form of an annulus.
11. Encapsulated surge diverter according to one of the preceding claims,
    characterized in that
    the surfaces of the main electrodes are structured.
12. Encapsulated surge diverter according to one of the preceding claims,
    characterized in that
    the insulating part(s) (4, 14, 15) is/are made of a gas-releasing plastic material.
13. Encapsulated surge diverter according to one of the preceding claims,
    characterized in that
    one of the main electrodes (1, 2) simultaneously forms a part of the diverter housing.
14. Encapsulated surge diverter according to one of claims 3 to 13,
    characterized in that
    the auxiliary or trigger electrode (16) is made of a semi-conducting material.
15. Encapsulated surge diverter according to one of the preceding claims,
    characterized by
    its use as N/PE spark gap.

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