EP1833130A2 - Encapsulated overvoltage arrester - Google Patents

Abstract

A multipole surge-protected arrester has an internally-wired encapsulated series of parallel gaps in a housing. The gaps have facing contact surfaces connected to outer terminals and have inner contact bars or bridges. The arrester also has an electronic control or trigger circuit on a wiring support. The trough-shaped housing has dividing walls accommodating the series gaps and terminals. An insulating plate on the trough opens upwards and has openings for spring contacts. The wiring is on top of the insulating plate. The spring contact elements form an electrical connection between contact points under the wiring support and the gap cover. Also claimed is an encapsulated surge protector with series gaps and two coaxial and partially overlapping main metal electrodes forming an arc chamber. One or both electrodes has an expansion chamber and a trigger electrode extending radially or axially.

Description

The invention relates to an encapsulated surge arrester according to the preamble of claim 1.

Multi-pole surge arresters, which are resistant to surge current up to 100 kA and which contain a plurality of encapsulated spark gaps in a housing, but not in a 3 + 1 circuit, are known.

In a so-called 3 + 1 circuit, the outer conductors L1, L2, L3 are switched against N and the N conductor again against PE.

In such embodiments of multi-pole surge arresters in a housing so an internal wiring level change is required if all conductors (L1, L2, L3 and N) to be excluded from one side.

If such an internal wiring is realized by an additional bridge, at least two further screw or welded connections for electrical contacting are required. Due to the fact that such a bridge is exposed to a very high mechanical load in the mentioned possible surge currents up to the range of 100 kA, care must be taken for a corresponding dimensioning and mechanical design.

Another problem with the embodiments of multi-pole arresters with wiring level change is that, if possible, no additional space for the bridge itself should be taken in order not to change the outer dimensions of the housing or to use standard housing, which also for others Applications are suitable.

Likewise, for reasons of space minimization to integrate the trigger circuit or a drive circuit in the housing, wherein the electrical connection points are to be formed with a view to the assembly and manufacturing costs.

In low-voltage networks, so-called N-PE spark gaps are used to protect against overvoltages between the N and PE conductors.

These spark gaps must have a very high surge current capability up to 100 kA 10/350 μs, in particular for protection against direct lightning strike.

Encapsulated spark gaps with such a performance are for example from DE 196 04 947 C1 . DE 198 18 674 A1 or DE 298 10 937 U1 previously known. These spark gaps have a protection level of ≥ 2.5kV.

In certain applications, however, spark gaps with lower protection levels are required. To realize these requirements, the use of trigger circuits is expedient. Powerful N-PE spark gaps, which also have an additional effective trigger electrode with consistently high performance, are not yet available. The high current load, the associated high material erosion, the high dynamic loads due to current forces, pressure, energy and temperature make significant design demands with encapsulated arresters.

Surge arresters with coaxial electrode arrangements, which are on the production side due to the given rotational symmetry of advantage, have been described for example in the EP 0 840 413 A1 or EP 0 771 055 A1 disclosed. There is an electrode isolated on both sides passed through a tube, which simultaneously represents the outer electrode and the housing shell. The introduction of an additional trigger electrode is not possible or only with difficulty. In addition, an additional electrode would be arranged directly in the focal region of the arc and thus affect the burning behavior of the arc and subject to a strong burn. According to DE 35 28 556 A1 or EP 0 242 688 B1 coaxial electrode arrangements are formed by a single-sided protrusion of a rod electrode into a tube electrode. In the cited solutions, the introduction of a third electrode is not provided and also difficult to realize. Furthermore, in the ignition of particularly high-current or long-lasting arcs the risk that they emerge from the coaxial electrode area and permanently damage the encapsulation of the spark gap. Existing cavities outside the preferred combustion chamber can not be used for pressure relief or as an expansion space, since the heat transfer to the insulation material of the housing wall is extremely ineffective.

From the US 3,849,704 , but also the DE 198 17 063 A1 are encapsulated spark gaps with coaxial electrode arrangement previously known.

According to DE 198 17 063 A1 the electrode spacing increases with increasing distance from the flashover point. The aim here is to achieve an arc migration with arc extension to increase the extinguishing capacity at Netzfolgestrom. The extension of the arc, however, inevitably leads to higher energy conversions and stronger temperature and pressure loads, which are unnecessary in particular in N-PE spark gaps and beyond undesirable.

Nor do the cited overvoltage protection elements have a third electrode for triggering. The above-cited prior art also shows no expansion spaces in which the heated gas can be effectively cooled after or during the load. However, such a measure is very important especially in N-PE spark gaps in encapsulated design, since so the pressure load, the arc voltage and thus the energy expenditure and the temperature load can be limited to a minimum.

From the DE 100 08 764 A1 In turn, an overvoltage protection device is known, which has coaxial main electrodes which are triggerable. The connection of the electrodes takes place from the same side in order to effect a directed movement of the arc to a baffle plate within the spark gap.

However, this leads to an extension and division of the arc, which is to support a deletion of Netzfolgeströmen. The extension of the arc is, as already stated, not suitable for N-PE spark gaps. Furthermore, the known spark gap has no suitable expansion spaces, which allow cooling of the hot gases. The resulting high pressure thus causes an undesirable increase in the arc voltage and claimed the housing of the spark gap in mechanical terms unnecessarily. Reducing the pressure load can only be achieved by means of large outlet openings, which are already effective during arc formation. However, there is a risk of undesirable leakage of electrically conductive gases.

The DE-AS 12 82 153 presents a spark gap that has a so-called expansion and a reflection space. The reflection space is intended by the pressure generated during the arc ignition, the arc specifically press into the expansion chamber, on the one hand to protect the ignition from excessive burn and on the other hand to extend the arc, so that the quenching behavior of the spark gap is improved.

It is therefore an object of the invention to provide a further developed encapsulated surge arrester with a spark gap arrangement, which can also be used as an N-PE arrester in a compact arrangement. The surge arrester should meet the essential requirements, namely a high insulation capacity and a very high Stoßstromableitvermögen and it should be possible to perform triggerable by means of a third electrode the surge arrester.

The solution of this object of the invention is carried out with an encapsulated surge arrester according to the features of claim 1, wherein the dependent claims comprise at least expedient refinements and developments.

In the case of the surge arrester developed according to the invention, a coaxial construction is based at least partially on overlapping metallic main electrodes which have oppositely directed connections. The main electrodes, in conjunction with at least one insulating member, include an arc combustion chamber.

According to the invention, at least one of the main electrodes has an inner expansion space and is in the region of the insulating part a preferably provided radially or axially rotationally symmetrical trigger electrode.

Preferably, the first main electrode is formed as a rod electrode with a cavity, which is connected via openings with the arc chamber on the flow side.

In the connection region of the second, hollow cylindrical outer main electrode, a further expansion space is present.

The expansion spaces may have a minimized pressure equalization opening, which is preferably formed in the region of the terminals.

In one embodiment of the invention, the rod electrode is centered and held with its connection remote end via a further insulating part within the surrounding second main electrode.

The second isolation part has return flow channels to the expansion space of the second main electrode.

Both expansion spaces can be connected on the flow side by at least one insulating channel.

Via a variation of the radial distance between the coaxially arranged, partially overlapping electrodes, a respective response voltage can be specifically predefined.

At least one of the electrodes has an arc-facing landing or step for staggered response and safe fire-extinguishing capability even in the event of triggering failure.

According to the invention, it is also possible to divide the arc combustion chamber by a circumferential web applied to the rod electrode.

The main electrodes may have groove-shaped contours, webs and / or cams for minimizing burnup on their surface facing the arc combustion chamber.

The second main electrode surrounding the first main electrode may constitute a substantial part of the encapsulation.

The first and / or second insulating part may have at least one circumferential web for supporting air punctures.

In a pressure-tight embodiment of the surge arrester, a quenching gas filling is preferably provided.

By the inventively proposed arrangement of two nested electrodes in a coaxial layer of erosion-resistant material with opposite terminals, wherein the main electrodes have internal expansion spaces, a configuration is created which allows the introduction of a rotationally symmetrical third so-called trigger electrode. The overall arrangement has a high insulation capacity with a correspondingly high surge current capability and is therefore intended in particular for use as an N-PE spark gap.

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

Hereby show:

1 shows a sectional view through a surge arrester with coaxial electrode structure.

Fig. 2 is a view similar to that of Fig. 1, but with a gradation of an inner surface of the second main electrode to provide a staggered response;

3 is a sectional view of a surge arrester with stepped version of the second main electrode for reducing the distance in the entire arc combustion chamber and with an additional radial isolation path to reduce the burn-off, in particular the trigger electrode. and

Fig. 4 is a sectional view of a surge arrester with a trigger electrode, which is arranged adjacent to the second main electrode in the axial direction.

FIGS. 1 to 4 start from a first main electrode 41 and a second main electrode 42, wherein the electrodes in the regions 45 have an electrical connection. This connection can be realized for example by means of a screw connection.

The first main electrode is preferably designed as a rod electrode, which has a cavity 47 in the interior. This cavity 47 represents an inner expansion space.

The cavity 47 is connected to the arc combustion chamber 48 through at least one opening 49.

The first main electrode 41 projects partially into the tubular-shaped region of the second main electrode 42 in a coaxial arrangement. Specifically, this overlap area represents the desired coaxial structure.

Due to the pot-shaped design of the second main electrode 42, this can directly form part of the encapsulation of the entire spark gap, so that the cost in terms of technology, but also material side is reduced.

To improve the guidance and adjustment, it is possible to arrange an insulation part 44 between the first main electrode 41 and the second main electrode 42. This insulating part 44 then delimits the arc combustion chamber 48 simultaneously in the axial direction.

Preferably, the insulating member 44 has suitable openings or flow channels 410, so that an additional cavity 47 within the second main electrode 42 is in communication with the arc combustion chamber 48.

In order to achieve a complete encapsulation of the electrode assembly and to further limit the combustion chamber, a (first) insulating member 43 is disposed between the first main electrode 41 and the open end of the main electrode 42.

A solution in which the encapsulation takes place outside the main electrode arrangement and in which the arc chamber is not directly delimited by insulating parts, is also within the scope of the invention.

The insulation part 43 now has an additional third electrode 46 for triggering the main line between the first and second main electrodes. This electrode or a plurality of electrodes 46 may be arranged rod-shaped, pin-shaped, but also annular.

In a preferred embodiment, a disk electrode is used which is coaxial with the first and second main electrodes is aligned.

Preferably, the described spark gap is pressed or screwed with additional insulation in a pressure-resistant metal housing.

The force is applied in the direction of the axis of symmetry. In order to largely decouple the possible rollover paths of the spark gap along the insulating parts 43 and 44 from the force effect during the joining process, these parts extend in the radial direction from the axis of symmetry. In this way it is ensured that an influence on the operating voltage of the spark gap remains low both by the joining process and under thermal stress of the pressurized insulating parts.

The operation of the arrangement will be explained below.

Upon triggering of the spark gap, one or more sparks 411 are fired from the trigger electrode 46 to one or both of the main electrodes 41 and / or 42.

Then, the arc 100 ignites between the main electrodes 41 and 42. In the case where the spark gap is made without the trigger electrode 6, the arc 100 forms via a sliding discharge along the insulation paths 43 or 44 or by an air breakdown between the main electrodes 41 and 42nd

The arc 100 is in the arc combustion chamber 48 after ignition and can rotate around the first main electrode 41 in accordance with the coaxial arrangement within this space. At the time of arc ignition occurs within the combustion chamber 48, an overpressure due to the heating of the existing gases. This overpressure would lead to increased mechanical stress on the parts and also increase the arc voltage, resulting in an unnecessarily high energy conversion within the spark gap and thus also to high thermal loads.

Also, the strong heating of all parts in the combustion chamber would make the extinction of the arc more difficult. To avoid these negative phenomena within the spark gap the expanding gas provided at least one additional cavity 47 as an expansion space, which is not directly exposed to the arc. After ignition of the arc, the heated gas can flow through the aforementioned openings or channels 49 and 410 in the expansion chamber 47. Due to the large volume there, the large heat capacity and the large surface area of the metal electrodes, the heated gas within these cavities is immediately cooled and relaxed.

The pressure increase, the Bogenbrennspannung and the energy conversion within the combustion chamber are thus limited to a minimum.

Fig. 1 is based on an embodiment of separate expansion chambers 47, but it is also possible to connect the two chambers along the axis of symmetry by one or more channels which are insulated.

In the region of the contacting 45 or at a location within the expansion chambers 47, the arrangement shown can additionally have minimum pressure equalization openings, which provide pressure compensation with the environment after the decay of the pressure-side load. This is particularly advantageous when it comes to the decomposition of the materials used and thus the eventual additional gas formation within the spark gap by the action of the arc. Due to the location and the size of the pressure compensation openings, a rapid pressure equalization in the millisecond range or a slow pressure reduction in the range over minutes can take place.

Due to the positioning of the electrodes 41, 42 and 46 after the formation of the spark between the electrodes 42 and 46, which overtops only a part of the overall arrangement, the arrangement according to FIG. 1 still requires a considerable input of energy until the entire separation distance between the electrodes 41 and 42 ionizes and thus a flashover between the main electrodes can take place. The possibility of tuning this energy requirement, however, advantageously allows easy coordination of the N-PE arrester downstream protective devices.

As a result of a corresponding design of the electrode arrangement as a whole, triggerable arresters with a high requirement for trigger energy can thus be created, as a result of which a response of the main spark gap of the arrester only takes place in the case of high-energy surges.

The above increases the noise immunity of the network and ensures better utilization of the performance of the downstream protection devices. On the other hand, however, can also be created by a design of the electrode assembly, as shown in Fig. 4, an arrester, which responds even at extremely low power surges and thus can be used as a single device.

In case of failure of the trigger electrode 46, the spark gap due to the central arrangement of the trigger electrode 46 and the resulting double insulation distance quite high thresholds.

In order to achieve a certain emergency running property of the spark gap here, according to FIG. 2, the insulation part 44 is shortened by a step or step 412 in the electrode 42. This causes, in addition to the triggerable spark gap, a further independent spark gap with triggering independent response, which is significantly smaller than the response voltage of the sliding or air gap between the first and second main electrode 41 and 42 in the triggering available stands.

At the same time arises in this construction, the possibility of a staggered response of the spark gap at different voltage slopes. This allows a decoupling of the behavior of the spark gap just at these different slopes of the voltage. For small slopes, the spark gap is controlled by the trigger circuit and the corresponding trigger path. In contrast, an overhead ignition of the spark gap can be obtained, especially at high voltage gradients, which is characterized in that the trigger unit of the spark gap itself remains uninvolved. The spark gap ignites then, so to speak, automatically in the area grading 412 without stressing the trigger unit.

By not shown attaching a high circumferential web of insulating material on the first main electrode 41 in the arc furnace this can be divided, in a region with trigger electrode and a region without trigger electrode. With this arrangement there is the advantage that in normal operation only the combustion chamber is loaded with the trigger electrode and the other combustion chamber remains unloaded, whereby in an emergency, i. E. in case of failure of the triggering, the desired emergency running properties can be guaranteed, since no impairment of these combustion chambers by burnup, temperature or pollution just up to the given emergency is done. Such an operation can also be realized with two completely independent and separate combustion chambers.

Fig. 3 shows a similar arrangement as Fig. 2, but here the paragraph or the gradation is extended so far that results in a significant reduction in space in the entire arc combustion chamber 48 between the first and second main electrode 41/42. An additional axial isolation path 413 also reduces the burnup on the insulation part 43 and the trigger electrode 46, since direct contact between these parts and the arc 100 can be avoided. Of course, this isolation section 413 may be provided independently of the paragraph 412 as in an embodiment of FIG. 1.

An arrangement in which the trigger electrode 46 of the second main electrode 42 has been arranged downstream in the axial direction, Fig. 4.

This arrangement ensures both the protection of the trigger electrode against excessive burnup and a reduction of the response voltage without triggering. Furthermore, with this arrangement, the required trigger energy can be reduced to a minimum. The ignition spark generated in response of the trigger circuit between the trigger electrode 46 and the second main electrode 42 can, in particular with a minimum in the combustion chamber 48 protruding insulation part 414 and a smaller distance of the Main electrodes 41 and 42 already touch the first main electrode 41 when it is formed. As a result, the insulation gap between the main electrodes 41 and 42 is bridged abruptly and the trigger energy is kept to a minimum.

In the arrangement of FIG. 4, a partial insulation of the main electrode 41 within the combustion chamber 48 along the axis of symmetry and adjacent to the insulating members 43 and 44 to protect against Abbranderscheinungen to the respective insulating parts or at the trigger electrode may be useful.

In support of the desired arc rotation and to avoid over-deposition of fusible material, one or more circumferential contours, e.g. be formed or introduced as grooves or patch webs. Likewise, individual patch nubs or other elevations for controlling the response voltage in the case of air breakdowns or for controlling the burn-up behavior can be realized.

In order to support air punctures, the insulating parts 43 and 44 may additionally be provided with at least one circumferential web (not shown) projecting into the combustion chamber 48.

LIST OF REFERENCE NUMBERS

41 first main electrode

42 second main electrode

43 outer insulation part

44 inner insulation part

45 connections

46 trigger electrode

47 expansion space

48 arc furnace

49 openings

410 flow channels

411 spark

100 arc

412 paragraph or grading

413 axially extending insulating part

414 protruding insulation part

Claims (17)

An encapsulated surge arrester having a spark gap arrangement, comprising two coaxial, at least partially overlapping metallic main electrodes with oppositely directed terminals, the main electrodes forming an arc chamber in conjunction with at least one insulating member,
characterized in that
at least one of the main electrodes has an inner expansion space and that in the region of an outer insulating part a preferably radially or axially rotationally symmetrical trigger electrode is provided. Encapsulated surge arrester according to claim 1,
characterized in that
the first main electrode is designed as a rod electrode having a cavity, wherein the latter is connected via openings to the arc combustion chamber on the flow side. Enclosed surge arrester according to claim 2,
characterized in that
in the connection region of the second, hollow cylindrical main electrode, a further expansion space is present. Encapsulated surge arrester according to one of claims 1 to 3,
characterized in that
the expansion chamber or spaces have a minimized pressure equalization opening, which is preferably formed in the region of the terminals. Encapsulated surge arrester according to one of claims 2 to 4,
characterized in that
the rod electrode is centered and held with its connection remote end via a further, inner insulating part within the surrounding second main electrode. Enclosed surge arrester according to claim 5,
characterized in that
the second, inner insulating part has flow-through channels towards the expansion space. Encapsulated surge arrester according to one of claims 3 to 6,
characterized in that
both expansion spaces are connected by at least one insulating channel. Encapsulated surge arrester according to one of claims 1 to 7,
characterized in that
via a variation of the radial distance between the coaxially arranged, partially overlapping electrodes, the respective response voltage can be predetermined. Encapsulated surge arrester according to one of claims 1 to 8,
characterized in that
at least one of the electrodes has a directed to the arc combustion chamber paragraph or a gradation for a staggered response and safe fire fighting capacity even in the event of failure of the triggering. Encapsulated surge arrester according to one of claims 2 to 9,
characterized in that
the arc combustion chamber is divisible by a circumferential web applied to the rod electrode. Encapsulated surge arrester according to one of Claims 1 to 10,
characterized in that
the main electrodes have groove-shaped contours, webs and / or nubs on their surface facing the arc combustion chamber. Encapsulated surge arrester according to one of claims 1 to 11,
characterized in that
the second main electrode surrounding the first main electrode forms part of the surge arrester encapsulation. Encapsulated surge arrester according to one of claims 1 to 12,
characterized in that
the electrodes of erosion-resistant material, in particular tungsten-copper or graphite and the insulating parts consist of a gas-emitting plastic. Encapsulated surge arrester according to one of claims 1 to 13,
characterized in that
the first and / or second insulating part having at least one circumferential ridge in support of air blows. Encapsulated surge arrester according to one of claims 1 to 3,
marked by
a pressure-tight version with extinguishing gas filling. Encapsulated surge arrester according to one of claims 1 to 15,
characterized in that
When pressure-tight connection by means of pressing, screwing or the like, the effective forces are oriented in the symmetry axis direction. An encapsulated surge arrester according to any one of claims 1 to 16,
marked by
its use as N-PE spark gap.

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