EP2208208B1 - Surge diverter comprising a housing and at least one diverting element, especially a varistor - Google Patents

Abstract

The invention relates to a surge diverter comprising a housing, at least one diverting element, especially a varistor, and a device for disconnecting the diverting element/s from the mains. The disconnecting device encompasses an isolating point, particularly a soldered joint, which is integrated into the electrical connection path within the diverter. Via the soldered joint, a movable conductor section or a movable conducting bridge is connected to the diverting element, and the conductor section or the bridge is connected to a first external electrical connection of the diverter. The disconnecting device also encompasses a means generating a biasing force, e.g. a spring, the force vector of which acts on the conductor section or the bridge in the disconnecting direction. According to the invention, a commutation branch is provided in parallel to the disconnecting device. Said commutation branch is permanently electrically connected in parallel once a defined voltage has been reached over the disconnecting device or in accordance with a predefined disconnecting distance of the disconnecting device.

Description

The invention relates to a surge arrester having a housing and at least one diverting element, in particular a varistor, as well as a separating device for separating the diverter element or elements from the network, the divider device comprising a separating point, in particular soldering point, which leads into the electrical connection path inside the diverter is involved, wherein via the solder joint, a movable conductor portion or a movable conductive bridge with the diverter on the one hand and the conductor portion or the bridge on the other hand connected to a first electrical outer terminal of the arrester, and comprising a biasing force generating means, such as a spring, wherein the related Force vector acts on the conductor section or the bridge in the separation direction, according to the preamble of patent claim 1.

To protect overvoltage-sensitive devices, more or less compact overvoltage arresters based on varistors are often used in power and data lines. As a rule, these arresters have a limited discharge capacity and, in the case of overload, may be subject to destruction gradually but also abruptly.

Surge arresters based on varistors generally have an internal disconnecting device in the low-voltage range.

This internal separation device consists for example of a combination of a thermal separation device and a predetermined breaking point for high currents. This predetermined breaking point represents a defined reduction of the connection cross section of the varistor with a certain melting integral value.

With high pulse currents to be derived, this bottleneck melts. It is then the movable connector separated and due to a spring bias the varistor is power-free. The state of the art is here on the DE 42 41 311 A1 , the DE 38 05 889 or the DE 9305796 U directed.

The basic design of a separating device, which is often realized by a solder joint between the varistor and a movable, under spring contact pressure, is shown in the schematic diagram Fig. 1 , The disk-shaped varistor 1 shown there is in series with the separating device 2, as a switch symbolizes, switched. A biasing force F acts on the separating device. If the solder 5 melts at the connection point, then the electrical contact between the varistor connection 6 and the external connection 7 is removed via the separating strip 3. The geometric bottleneck with a defined melting integral value is symbolized by the reference numeral 4.

Basically, errors that occur with surge arresters with varistors can be described as follows.

Upon gradual heating of the varistor, e.g. due to aging or a slight increase in voltage, the thermal separation device generally responds after several seconds. A solder which fixes the separating device melts, whereby the contacts under spring force undergo an opening process. The varistor has a high resistance in this case of error, whereby the current through the varistor is severely limited. As a rule, the separating device can easily interrupt these currents and thus safely disconnect the overloaded arrester from the mains, without a further separate overvoltage protection device responding or being required. The power supply of the consumer is therefore not interrupted or disturbed. All that needs to be done is to replace the defective surge arrester during maintenance.

If, on the other hand, the arrester is overloaded by a high pulse voltage, but not destroyed or overturned, the thermal disconnecting device can, on the one hand, lead to a delayed disconnection or else the melting integral value of the constriction is reached, whereby it melts and separates the arrester from the mains.

If the arrester is destroyed or overturned within an extremely short time due to an increased line frequency voltage or a surge current, fault currents can occur which, depending on the impedance of the fault, the driving voltage and the prospective short-circuit current of the network, lie in the region of a few kiloamps. These currents often reach values that are above the switching capacity of conventional disconnecting devices. Addresses the disconnector before other overcurrent protection devices at these loads, the surge arrester can be damaged and the response of the overcurrent protection devices are given only delayed with all adverse consequences.

The latter error case is therefore problematic with regard to the safe disconnection of the surge arrester. If the arrester also this error case independently or the response of the internal disconnecting device of the arrester can not be prevented before the external overcurrent protection device responds, the disconnecting device must have a higher switching capacity.

To achieve such higher switching capability, various prior art solutions are known.

For example, the shows EP 0 046 545 A1 , the DE 28 53 697 A1 or the EP 0 862 255 A1 or the EP 1 447 831 A1 the combination of a surge arrester with a mechanical switching device, which takes over the actual disconnection function. Although the switching capacity of such a separation device is sufficiently high, the effort and space required is considerable. Also, the coupling with the thermal tripping function is structurally difficult.

The DD 239 488 or the US Pat. No. 6,430,019 B1 disclose the use of an insulating slider which is moved between the two connectors upon the response of the thermal separator.

A disadvantage of this solution is that the movement of the slider can be hindered by the melting behavior and the residues of the solder of the thermal contact point, whereby the speed of the arc extension is undefined.

Furthermore, the insulating slide can be coated by the liquid solder conductive and there is a risk that the arc cuts through the slide or causes its thermal destruction before a sufficient arc extension has been achieved.

Mentioned here is still from the EP 0 905 839 A1 or the WO 2004/064213 A1 known use of double interruption with terminal contacts or solder contacts. The stroke of such a double interruption is limited. The embodiments of known double interruptions also do not allow particularly high arc voltages, since in these arrangements, the risk of direct short circuit or the formation of a single arc consists. This is because the main contacts are not isolated from each other and there is a direct influence on the arc plasma. The surge arresters of this prior art also have no bottleneck. With increased fault currents, however, it is precisely the response of the bottleneck that is more likely than the opening of the thermal separation point.

From the foregoing, it is therefore an object of the invention to provide a further developed surge arrester with a housing and at least one dissipation element, in particular a varistor, as well as a disconnecting device, which ensures that given during the overload fault currents are safely controlled without damage to the varistors occurs , in the case when the switching capacity of the integrated separating device itself is overwhelmed.

The object of the invention is achieved by the feature combination according to claim 1, wherein the dependent claims represent at least expedient refinements and developments.

The basic idea of the invention is thus to reduce the residual current which may possibly flow by deliberately commutating this fault current into a separate erase path, this erase path of the separator being connected in parallel or connected in parallel in dependence on certain conditions.

Thus, the fault current is prevented after the opening of the separation distance or commutated in the mentioned parallel branch and thus deleted.

Ausgestaltend there is the possibility in the path of movement of the conductor section or the bridge, which are part of the separation device, to arrange a conductive element, the first end comes in triggered disconnector with the conductor portion or the bridge in contact, the second end with a second external electrical connection in Connection stands and the conductive element comprises a switching device or is designed as a switching device. This embodiment leads to a safe fail-safe behavior by achieving a targeted short circuit of the discharge element. Furthermore, the aforementioned embodiment ensures that at a predetermined time, the switching device opens, whereby the fault current is interrupted. After the shutdown process, the defective overvoltage protection device is disconnected from the circuit to be protected and the power supply is maintained. The canceled short circuit allows maintenance personnel to measure a voltage and replace the arrester without danger.

The commutation branch provided parallel to the separating device can be permanently connected electrically in parallel to the separating device. But it is also ausgestaltend the possibility of parallel connection after reaching a defined To bring about voltage across the separating device or to trigger in dependence on a predetermined separation distance of the separating device.

In the Kommutierungszweig ausgestaltend a fuse or a PTC element are arranged.

For securing, at least one voltage-switching or voltage-limiting element can be connected in series.

There is also the possibility to arrange in the Kommutierungszweig another, second thermal separation device.

By means of the second disconnecting device in the commutation branch, it can be ensured that in the event of a fault complete disconnection of the network can be realized.

According to the invention, a so-called target electrode, which is connected to the commutation branch, is provided in the separation distance of the separating device arranged in series with the discharge element. In the event of an overload, an arc that arises over the separation section is led to the target electrode and thus enters the commutation branch and is deleted.

The designed to achieve a targeted short circuit ausgestaltend conductive element can also be used later in the arrester to realize in addition to a separation and the aforementioned short-circuit fail-safe function.

For selectively activating the conductive element in the sense of a disconnect-acting short-circuiter, an insulating pad may be arranged between the conductive element and the conductor section or the bridge, or the conductive element has a detachable insulating cover at least at its first end.

Likewise, there is the possibility of selectively activating the conductive element in the sense of acting in the separation case short-circuiter to make the relative distance between the conductive element and the conductor section or the bridge adjustable.

For selectively activating the conductive element, it is also possible to use an element delimiting the path of movement of the conductor section or the bridge as a pin, bolt or similar arrangement.

The conductive element may be formed as a fuse, but also have a power semiconductor or form a circuit with a power semiconductor, wherein the power semiconductor is transferred after passing a short-circuit current by means of an initial pulse in the open state.

The conductive element is further ausgestaltend in cross-section dimensioned such that after passing a short-circuit current is carried out a separation of the conductive connection.

The invention will be explained below with reference to an embodiment and with the aid of figures.

Fig. 1

ein Prinzipschaltbild einer Reihenschaltung eines Varistors mit Abtrennvor- richtung sowie eine mögliche konstruktive Anordnung dieser Reihenschal- tung gemäß Stand der Technik;

Fig. 2a

ein Blockschaltbild der erfindungsgemäßen Lösung mit einem permanent der Abtrennvorrichtung parallel geschalteten Kommutierungszweig;

Fig. 2b

eine Anordnung ähnlich derjenigen nach Fig. 2a, jedoch mit der Möglichkeit, den Kommutierungszweig separat zuzuschalten, und

Fig. 3

eine Ausführungsform des Kommutierungszweigs mit einer Fangelektrode, d.h. nicht ständiger Parallelschaltung bezogen auf die Abtrennvorrichtung.

Hereby show:

Fig. 1

a schematic diagram of a series circuit of a varistor with separation device and a possible structural arrangement of this series circuit according to the prior art;

Fig. 2a

a block diagram of the solution according to the invention with a permanent disconnect device connected in parallel Kommutierungszweig;

Fig. 2b

an arrangement similar to that after Fig. 2a , but with the possibility to connect the commutation branch separately, and

Fig. 3

an embodiment of the Kommutierungszweigs with a target, ie, not continuous parallel circuit with respect to the separation device.

In the representations after the Fig. 2a, 2b and 3 Initially, a series connection of a diverting element, in particular a varistor 1 with a separating device 2, is assumed.

The separating device 2 comprises a solder joint, not shown in detail, which is integrated in the electrical connection path AB of the arrester, wherein via the soldering a movable conductor portion or a movable conductive bridge (symbolized as a switch) with the diverter 1 on the one hand and the conductor section or the bridge on the other hand connected to a first external electrical connection of the arrester. Furthermore, a biasing force generating means, symbolized by F, For example, a spring, present, wherein the relevant force vector acts on the conductor section or the bridge in the separation direction.

According to Fig. 2a a commutation branch or commutation path 8 is present, which comprises a series connection of a fuse 10 and a voltage-switching element 11.

The Kommutierungszweig 8 is the separator 2 constantly connected in parallel. In the case when the severing device 2 opens, the fault current commutates into the branch 8. This branch 8 carries the current until there is a sufficient separation distance and the arc is safely extinguished. Thereafter, the parallel branch is switched high impedance, e.g. by activating fuse 10, and the flowing current is finally erased.

The representation after Fig. 2b shows a variant embodiment, according to which the connection of the Kommutierungszweigs 8, for example, voltage-dependent, or else by a mechanical movement of a switch. 9

In the solutions according to the Fig. 2a and 2b the commutation branch 8 is activated at all loads which lead to the opening of the separating device. If this is undesirable or if the Kommutierungszweig 8 is to be activated only in case of overload of the separating device 2, this can according to the embodiment according to Fig. 3 will be realized.

As shown Fig. 3 the movable connecting element of the separating device 2 is passed or passed by a target electrode 12.

The target electrode 12 is arranged so that the distance between the fixed terminal of the varistor and the target electrode 12 is sufficient under conventional cut-off conditions for safe separation of the varistor 1.

On the other hand, if an emerging arc can not be reliably extinguished in the event of an overload, the current commutates to the target electrode 12 while the movable element of the severing device 1 continues to move. As a result, between the fixed terminal of the varistor 1 and the movable element of the separating device 2, an isolating distance is created, which is only partially bridged by the arc. After switching off the fault current in Kommutierungszweig 8 the arc then completely extinguished.

In the embodiment according to Fig. 3 There is a free-burning arc in the arrester, which must be controlled thermally and dynamically, at least temporarily, by the arrester, the fixed connection of the varistor and the target electrode 12.

As already stated, in the simplest case, the commutation branch 8 can be realized by a parallel connection of a fuse 10 of small size and low nominal current intensity.

In combination, it is possible to connect the fuse voltage-switching and voltage-limiting switching elements in series. The resulting fault current commutates to the fuse. This leads the fault current over a period of time which is sufficient for extinction and deionization of the switching path. After that, the fuse switches off the power. The switching voltage of the fuse 10 may in this case the dielectric strength of the actual switching path, i. the switching path of the separator, do not exceed.

As an alternative to an irreversible fuse, reversible fuses or PTC elements can be used. Also, the use of electronic components for shutdown and commutation is possible.

In these variants of the invention, a further separating device may be provided in the commutation path, which may be e.g. disconnects the PTC element when reaching a certain temperature, whereby the arrester is finally fully released from the network by a real separation distance.

If according to a further embodiment of the invention in the event of a fault, the varistor is short-circuited, there is a risk that in a permanent short circuit in the case of application of such a surge arrester in transformerless inverters in photovoltaic applications problems result, due to flowing back currents. In addition, the replacement of a short-circuited surge arrester can cause an arc hazard, since in the aforementioned photovoltaic applications, a current flow from the generator takes place.

To avoid these disadvantages, a switching device is present in the short circuit branch. In the case of an overload of the varistor, the actual thermal separation device is actuated and moves the separation contact to the conductive element, with the result of reaching a short-circuit state. The resulting arc is guided by the contact elements and extinguishes automatically on reaching the short-circuit contact. After a predetermined time, the switching device provided in the short-circuit path then opens and interrupts the fault current. As a switching device mechanical switching devices, fuses, but also power semiconductors can be used. The use of spark gaps as a switching device is conceivable. After the shutdown of the switching device, which is located in the short circuit path, the defective surge arrester arrangement is separated from the actual circuit and it remains the supply.

LIST OF REFERENCE NUMBERS

1

Discharge element / varistor

2

cut-off

3

movable ladder section or movable conducting bridge

4

geometric bottleneck

5

solder joint

6, 7

varistor

8th

commutation

9

switch

10

fuse

11

voltage-switching element

12

collecting electrode

Claims (10)

1. Surge arrester having a housing and at least one arrester element, specifically a varistor (1), and a disconnection device (2) for disconnecting the arrester element(s) (1) from the mains, the disconnection device (2) comprising a point of separation, specifically a soldering joint, which is incorporated into the electrical connection path (A, B) inside the arrester, wherein a movable conductor section or a movable conductive bridge (3) is connected via the soldering joint, on the one hand, to the arrester element (1) and, on the other hand, the conductor section or the bridge (3) is connected to a first electrical outer terminal of the arrester, and comprising a means for generating a prestressing force, such as a spring, wherein the force vector (F) in this regard acts on the conductor section or the bridge (3) in the disconnecting direction,
   characterized in that
   a commutation branch (8) is provided in parallel to the disconnection device (1), which commutation branch (8) is electrically connected in parallel in dependence on a predefinable isolating distance of the disconnection device (2), wherein a collecting electrode (12) is provided in the isolating distance of the disconnection device (2) arranged in series with the arrester element (1) which is connected to the commutation branch (8), wherein, in the event of an overload, an arc generated over the isolating distance gets to the collecting electrode (12) and thus to the commutation branch (8) and is quenched.
2. Surge arrester according to claim 1,
   characterized in that
   a fuse (10) is located in the commutation branch (8).
3. Surge arrester according to one of the preceding claims,
   characterized in that
   a conductive element is arranged in the movement path of the conductor section or the bridge (3), whose first end contacts the conductor section or the bridge (3) if the disconnection device is triggered, wherein the second end thereof is connected to a second electrical outer terminal and the conductive element comprises a switching device or is designed as a switching device.
4. Surge arrester according to claim 1,
   characterized in that
   the conductive element can be inserted into the arrester subsequently in order to realize a short-circuit fail safe function in addition to a disconnecting function.
5. Surge arrester according to claim 1 or 4,
   characterized in that
   for optionally activating the conductive element in terms of a short-circuiting device acting in the event of a disconnection an insulating plate can be arranged between the conductive element and the conductor section or the bridge (3), or the conductive element comprises a removable insulating coating at least on its first end.
6. Surge arrester according to claim 3 or 4,
   characterized in that
   for optionally activating the conductive element in terms of a short-circuiting device acting in the event of a disconnection the relative distance between the conductive element and the conductor section or the bridge is adjustable.
7. Surge arrester according to claim 3 or 4,
   characterized in that
   for optionally activating the conductive element in terms of a short-circuiting device acting in the event of a disconnection an element in the form of a pin, bolt or the like device can be inserted to limit the movement path of the conductor section or the bridge.
8. Surge arrester according to one of claims 1 to 7,
   characterized in that
   the conductive element is designed as a fuse.
9. Surge arrester according to one of claims 1 to 7,
   characterized in that
   the conductive element comprises a power semiconductor or forms an electric circuit with a power semiconductor, wherein the power semiconductor, after carrying a short-circuit current, is transferred into the open state by means of an initial impulse.
10. Surge arrester according to one of claims 1 to 8,
    characterized in that
    the conductive element is dimensioned with respect to its cross-section such that, after carrying a short-circuit current, the conductive connection is disconnected.

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