EP2006874B1 - Fuse cut-off device for voltage surge protection and device for protecting against voltage surges comprising such a cut-off device - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to a fusible cut-off device comprising an arc extinguishing chamber having a median longitudinal axis and being delimited by at least one insulating side wall extending between a first and second conductive radial wall. The arc extinguishing chamber comprises at least one conductive separator maintained within said chamber to define two expansion volumes and at least one conductive fuse element electrically connected between a first and a second electrode. Said at least one fuse element extends from the first to the second radial walls through a gap and is rigidly held in the arc extinguishing chamber by second holding means. The section of the at least one conductive fuse element in a plane perpendicular to the median longitudinal axis is elongate in shape so that the length of said section is at least three times greater than the width.

The invention also relates to an overvoltage protection device comprising an overvoltage limiter with non-linear elements variable with the voltage.

STATE OF THE PRIOR ART

It is known to associate overvoltage protection devices with disconnectors comprising at least one fuse element. Generally, said at least one fuse element is connected in series with a surge limiter with variable non-linear elements.

Said fuse disconnector is calibrated to disconnect when traversed by alternating short-circuit electric currents. In addition, however, it must be calibrated to pass lightning currents type 8/20 or 10/350.

Traditional fuses with one or more conductors placed in a ceramic envelope generally have sizes that are too large to be integrated into the surge protection devices. In addition, given their manufacture and the conductor structure, this type of fuse hardly withstands lightning strikes. The conductors are subjected to electrodynamic forces due to the passage of a lightning strike. These efforts tend to irreversibly damage the fuse.

This problem of mechanical deterioration is also encountered with the solution described in the patent FR2216667 . In addition, so-called arc reclearing phenomena can occur with this solution. These phenomena tend to reduce the arc voltage and to oppose the rapid limitation of the electric current. Finally, given the large space between the birth zone of the arc and the arc extinction chamber, the travel time of the arc from said zone to the chamber is not favorable to a break fast electric current.

The use of a fuse as described in patent DE3044153 allows to reduce the so-called phenomena of arc reclearing. However, the mechanical resistance to lightning strikes and the time required to establish a sufficient arc voltage are not yet optimal.

The document " DE 23 49 270 A1 "discloses a fusible breaking device according to the preamble of independent claim 1.

SUMMARY OF THE INVENTION

The invention therefore aims to overcome the disadvantages of the state of the art, so as to provide a fuse cutoff device of reduced size and high breaking capacity.

The fusible breaking device according to the invention comprises at least two conductive fusible elements.

According to one embodiment of the invention, said at least two conductive fusible elements are placed on either side of the median longitudinal axis so that electric arcs arising after the fusion of said fusible elements attract each other. towards the center of the extinguishing chamber.

Preferably, said at least two conductive fusible elements are placed symmetrically with respect to the longitudinal median axis of the extinguishing chamber.

Advantageously, said at least two conductive fusible elements are placed at the periphery of the separators.

Preferably, the conductive fuse elements consist of a metal conductive sheet held by the second holding means on an insulating support of gasogenic material.

Preferably, the conductive sheet is a layer of metallic material deposited on the insulating support, the layer having a thickness of less than 1 mm.

Advantageously, the support of insulating material constitutes an element of the insulating side wall.

Advantageously, the cross section of the gap through which a conductive fuse element is shaped substantially identical to that of said at least one fuse element.

Advantageously, the side wall consists of four lateral facades extending along a median longitudinal axis.

Advantageously, the side wall consists of a cylinder positioned around the at least one separator and extending along the median longitudinal axis.

Advantageously, the insulating side wall consists of a gasogenic material.

Advantageously, the side wall comprises gas evacuation holes contained in the expansion volumes.

An overvoltage protection device, according to a development mode of the invention, comprises an overvoltage limiter with non-linear elements variable with the voltage, said limiter being placed in a housing having a first and a second electrical connection range. At least one fuse cutoff device as defined above is connected in series with the surge protector. The surge protector and the fuse cut-off device are electrically connected to the connection pads.

Advantageously, the housing comprises at least two flanges of insulating material, said flanges constituting a part of the side wall of said at least one fusible breaking device.

BRIEF DESCRIPTION OF THE FIGURES

• les figures 1 et 2 représentent des vues schématiques d'un dispositif de coupure fusible selon un premier mode de réalisation de l'invention ;
• Les figures 3 et 4 représentent des vues schématiques d'un dispositif de coupure fusible selon un second mode de réalisation de l'invention ;
• la figure 5 représente une vues éclatées en perspective d'un dispositif de coupure fusible selon un mode préférentiel de réalisation de l'invention ;
• la figure 6A représente une vue schématique en coupe d'un arc électrique dans une chambre d'extinction connue ;
• les figures 6B et 6C représentent des vues schématiques en coupe d'un arc électrique dans une chambre d'extinction selon les modes de réalisation représentés sur les figures 1 à 5 ;
• la figure 7 représente une vue schématique d'un dispositif de protection contre les surtensions comprenant un dispositif coupure fusible selon les modes de réalisation des figures 1 à 5.

Other advantages and features will emerge more clearly from the following description of particular embodiments of the invention, given by way of non-limiting examples, and represented in the accompanying drawings in which:

• the Figures 1 and 2 show schematic views of a fusible cutoff device according to a first embodiment of the invention;
• The Figures 3 and 4 represent schematic views of a fusible cut-off device according to a second embodiment of the invention;
• the figure 5 represents an exploded perspective view of a fuse cutoff device according to a preferred embodiment of the invention;
• the Figure 6A is a schematic sectional view of an electric arc in a known extinguishing chamber;
• the Figures 6B and 6C represent schematic sectional views of an electric arc in a quenching chamber according to the embodiments shown in FIGS. Figures 1 to 5 ;
• the figure 7 represents a schematic view of a surge protection device comprising a fusible cut-off device according to the embodiments of the Figures 1 to 5 .

DETAILED DESCRIPTION OF AN EMBODIMENT

As shown on the Figures 1 to 5 , the fuse cut-off device 1 comprises an arc extinction chamber 2 having a median longitudinal axis Z and being delimited by at least one insulating lateral wall 4.

The insulating side wall 4 extends between first and second conductive radial walls.

The arc extinction chamber 2 comprises at least one conductive separator 5 maintained inside said chamber to define two expansion volumes 56. Said at least one separator is positioned between the two conductive radial walls. Preferably, the first and second radial walls extend perpendicular to the longitudinal median longitudinal axis Z of said extinguishing chamber.

According to the embodiments as shown in the Figures 1 to 5 the extinguishing chamber 2 comprises a plurality of conductive separators extending preferably perpendicularly to a median longitudinal axis Z.

The arc extinction chamber 2 comprises at least one fuse element 3, 3A, 3B conductor electrically connected between a first and a second electrode 6, 7. Said at least fuse element 3, 3A, 3B extends from the first at the second radial walls 10 through a passage gap. Said at least one fuse element 3, 3A, 3B preferably extends in a direction parallel to the median longitudinal axis Z.

The section of said at least fuse element 3, 3A, 3B in a plane perpendicular to the median longitudinal axis Z of the arc extinguishing chamber 2 is of elongate shape so that the length of said section is at least three times larger than the width.

Due to the elongate shape of the passage gap of said at least fuse element 3, 3A, 3B, the electric arc 70 which naturally has a substantially circular cross section, is forced to deform and leave said gap zone. Unlike known solutions as represented in Figure 6A , the development of the arc in the spaces of relaxations is thus favored.

Said at least fuse element 3, 3A, 3B is held rigidly in the arc extinguishing chamber 2 by first holding means ensuring the rigid holding of said at least one fuse element in the event of a lightning strike. The second holding means can withstand the electrodynamic forces due to lightning strikes.

As shown on the Figures 1 and 2 The arc extinction chamber 2 comprises a fuse element 3 conductor electrically connected between the radial walls respectively acting as an electrode 6, 7. The separators respectively comprise a hole. The surface of the hole defines the size of the passage gap. The clearance between the fuse element and each of the separators is minimal in particular to ensure the rigid retention of the fuse element in case of lightning strike. The first of maintenance are then assured directly by the separators.

The cross section of the passageway through which said at least one electrical conductor 3, 3A, 3B is of substantially identical shape to that of said at least one fuse element 3, 3A, 3B.

According to another embodiment as shown in the Figures 3 and 4 said at least fuse element 3, 3A, 3B is placed on the periphery of said at least one separator 5. Said at least fuse element 3, 3A, 3B is held rigidly between said at least one separator 5 and said at least one side wall.

As illustrated on Figures 6A, 6B , the passage gap of said at least one fuse element is represented by a first hatched area 31. The dashed hatched surface 71 represents the electric arc present in the relaxation spaces 56 when said at least one fuse element has melted. The electric current then reached a significant value, greater than 1000A. The area where the dashed lines 71 and hatches 31 overlap corresponds to the space where a fraction of the electric arc is not divided by the separators. The larger this superposition area, the lower the arc voltage and the lower the short circuit current limitation. Thus, a high arc voltage will be reached more quickly with breaking devices according to the invention than with known breaking devices. Indeed, the interaction zone between the dotted zone 71 and the shaded area 31 is lower for the Figure 6B that for the Figure 6A .

Said at least one fuse element 3, 3A, 3B consists of a metal foil conductive. The conductive sheet may be held by the second holding means on an insulating support.

According to a preferred embodiment represented on the figure 5 , the arc extinction chamber 2 comprises two fusible elements 3A, 3B conductors electrically connected between the radial walls 10 respectively acting as an electrode 6, 7. The at least two fusible elements 3A, 3B are preferably placed symmetrically with respect to the longitudinal median axis Z of the extinguishing chamber 2. In addition, the two fusible elements are placed on the periphery of the at least one separator 5.

• D'une part, compte tenu que les éléments fusibles sont placés de part et d'autre de l'axe longitudinal médian Z et que chaque élément fusible est traversé par un courant électrique circulant dans le même sens, les arcs électriques 70 qui naîtront après la fusion desdits éléments fusibles auront tendance à s'attirer mutuellement vers le centre de la chambre d'extinction 2. Comme cela a été décrit ci-dessus, le fait de placer l'arc au centre de la chambre en l'éloignant des interstices de passage permet d'augmenter encore l'efficacité de la chambre d'extinction du dispositif de coupure fusible. De préférence, les éléments fusibles sont placés symétriquement par rapport audit axe longitudinal Z et sont de préférence placés en périphérie des séparateurs 5.
• D'autre part, compte tenu que pour une section utile de conducteur, deux éléments fusibles sont utilisés au lieu d'un, on réduit par deux la section de chaque élément fusible dans un plan perpendiculaire à l'axe longitudinal Z. Cette réduction de la section de chaque élément fusible s'accompagne d'une réduction de la section des interstices de passage respectivement utilisés pour le passage desdits éléments fusibles. Comme cela a été décrit ci-dessus, la réduction des sections des interstices de passage permet d'augmenter l'efficacité de la chambre d'extinction du dispositif de coupure fusible.

The use of at least two fusible elements 3A, 3B instead of a single fusible element induces at least one new function and generates at least two additional advantages:

• On the one hand, considering that the fusible elements are placed on either side of the central longitudinal axis Z and that each fuse element is crossed by an electric current flowing in the same direction, the electric arcs 70 which will be born after the fusion of said fusible elements will tend to attract each other towards the center of the extinguishing chamber 2. As has been described above, placing the arc in the center of the chamber away from the interstices passage makes it possible to further increase the efficiency of the extinguishing chamber of the fusible cut-off device. Preferably, the fuse elements are placed symmetrically with respect to said longitudinal axis Z and are preferably placed at the periphery of the separators 5.
• On the other hand, considering that for a useful conductor section, two fusible elements are used instead of one, the section of each fuse element is reduced by two in a plane perpendicular to the longitudinal axis Z. This reduction in the section of each fuse element is accompanied by a reduction of the section of the passage interstices respectively used for the passage of said fusible elements. As has been described above, reducing the cross-sectional areas of the passageway makes it possible to increase the efficiency of the extinguishing chamber of the breaking device. fuse.

According to this preferred embodiment, the conductive sheet is a layer of metallic material deposited on the insulating support, the layer having a thickness of less than 1 millimeter. The layer of metallic material preferably has a thickness equal to 70 microns. Said at least one side wall 4 consists of four lateral facades extending along a median longitudinal axis Z. Preferably, the four lateral facades are conjoined. The extinguishing chamber 2 has a parallelepipedal shape and said at least one separator having a square or rectangular shape. The support of insulating material supporting the fusible elements constitutes an element of said at least one side wall 4. The separators 5 are held by two of the side walls. In addition, the support of insulating material of the two fusible elements 3A, 3B is of gasogenic material.

According to an alternative embodiment of the first embodiment of the invention, the extinguishing chamber may comprise a plurality of fusible elements passing through said at least one separator 5.

According to an alternative embodiment, said at least one side wall 4 is composed of a cylinder positioned around said at least one separator 5 and extending along the median longitudinal axis Z. Said at least one separator (5) preferably has the shape of a disc.

According to an alternative embodiment, said at least one side wall consists of a gasogenic material.

The presence of facades or part of the side wall 4 of gas-forming material makes it possible to push the arc or the electric arcs towards the center of the extinguishing chamber and away from the passage gap or gaps. As has been described above, this further increases the efficiency of the extinguishing chamber of the fuse cutoff device.

According to an alternative embodiment, said at least one side wall 4 has gas evacuation holes contained in the expansion volumes 56.

The invention also relates to 100 surge protection device. As shown on the figure 7 the overvoltage protection device 100 comprises an overvoltage limiter 20 with non-linear elements variable with the voltage. Said limiter is placed in a housing 101 having a first and a second electrical connection area 41, 51. In addition, the protection device 100 comprises at least one fusible cut-off device 1 as described above. The surge protector 20 is connected in series with said at least one fuse cut-off device 1. The surge protector and the fuse cut-off device are connected to connection pads 41, 51. According to an example embodiment, the surge protector overvoltage 20 has a varistor.

According to an alternative embodiment of the protection device 100, the housing 101 comprises at least two flanges of insulating material. Said flanges may constitute a part of the side wall 4 of said at least one fusible cut-off device 1. Preferably, the housing 101 is made of molded plastic material and consists of two parallel side flanges of insulating material placed on each side other of a median longitudinal plane. Part of the side flanges constitutes part of the side wall 4 of the at least one fusible cut-off device 1.

Claims (14)

1. A fuse switchgear device (1) comprising an arc extinguishing chamber (2) having a longitudinal centre line (Z) and being delineated by an insulating side wall (4) extending between a first and second conductive radial walls (10), the arc extinguishing chamber (2) comprising:

   - at least one conductive separator (5) secured inside said chamber to define two expansion volumes (56),

   - at least one conductive fuse element (3A,3B) electrically connected between a first and second electrodes (6,7), said at least one fuse element (3A,3B) extending from the first to the second radial wall (10) through a gap and being rigidly secured in the arc extinguishing chamber (2) by second securing means, the cross-section of said at least one conductive fuse element (3A,3B) in a plane perpendicular to the longitudinal centre line (Z) being of elongate shape so that the length of said cross-section is at least three times larger than the width,

   a device characterized in that it comprises at least two conductive fuse elements (3A,3B).
2. The switchgear device according to claim 1, characterized in that said at least two conductive fuse elements (3A,3B) are placed on each side of the longitudinal centre line (Z) so that the electric arcs (70) arising after said fuse elements have melted attract one another towards the centre of the arc extinguishing chamber (2).
3. The switchgear device according to claim 1 or 2, characterized in that said at least two conductive fuse elements (3A,3B) are placed symmetrically with respect to the longitudinal centre line (Z) of the arc extinguishing chamber (2).
4. The switchgear device according to claim 3, characterized in that said at least two conductive fuse elements (3A,3B) are placed at the periphery of the separators (5).
5. The switchgear device according to any one of the foregoing claims, characterized in that the conductive fuse elements (3A,3B) are composed of a metal conducting foil secured by the second securing means on an insulating support made from gas-generating material.
6. The fuse switchgear device according to claim 5, characterized in that the conducting foil is a layer of metallic material deposited on the insulating support, the layer having a thickness of less than 1 mm.
7. The fuse switchgear device according to claim 6, characterized in that the support made from insulating material constitutes an element of the insulating side wall (4).
8. The fuse switchgear device according to any one of the foregoing claims, characterized in that the cross-section of the gap through which a conductive fuse element (3A,3B) passes is of substantially identical shape to that of said at least one fuse element.
9. The fuse switchgear device according to any one of the foregoing claims, characterized in that the side wall (4) is composed of four lateral front surfaces extending along a longitudinal centre line (Z).
10. The fuse switchgear device according to any one of claims 1 to 8, characterized in that the side wall (4) is composed of a cylinder positioned around said at least one separator (5) and extending along the longitudinal centre line (Z).
11. The fuse switchgear device according to any one of the foregoing claims, characterized in that the insulating side wall (4) is composed of a gas-generating material.
12. The fuse switchgear device according to any one of the foregoing claims, characterized in that the side wall (4) comprises holes for removal of the gases contained in the expansion volumes (56).
13. A voltage surge protection device (100) comprising a voltage surge limiter (2) with non-linear elements variable with the voltage, said limiter being placed in a casing (101) having a first and second electric connection strips (41, 51), characterized in that it comprises at least one fuse switchgear device (1) according to claims 1 to 12 connected in series with the voltage surge limiter (2), the surge limiter (2) and said at least one fuse switchgear device (1) being electrically connected to the connection strips (41, 51).
14. The voltage surge protection device according to claim 13, characterized in that the casing (101) comprises at least two flanges made from insulating material, said flanges constituting part of the side wall (4) of said at least one fuse switchgear device (1).

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