EP2096657B1 - Device for protecting against voltage surges comprising selective disconnection means - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to an overvoltage protection device comprising a disconnection device with electrical contacts. Said disconnection device comprises a first connection electrode in electrical connection with a first connection pad, a second connection electrode in electrical connection with a second pad, a third movable pad switching electrode electrically connected to the second pad and a surge protector connected in series between the third moving arc switching electrode and the second connecting pad. An actuating mechanism is provided for moving the third movable arc switching electrode to cause permanent opening of the electrical contacts.

STATE OF THE PRIOR ART

Overvoltage protection devices are known that include an overvoltage limiter with non-linear elements variable with the voltage and a contact disconnection device actuated by an actuating mechanism. The surge protector and the disconnect device are connected in series.

As described in the document EP0441722B1 ; the contact disconnection device can adopt a triggering position and a latching position respectively corresponding to the open state and the closed state of the contacts. An actuating mechanism causes the displacement of the contacts of the disconnection device to the open state, especially in the event of destruction of the surge arrester when said non-linear elements are at the end of their service life.

• d'une part pour écouler des courants électriques d'ondes de foudre de type 10/350 ou 8/20 sans que le mécanisme d'actionnement ne soit actionné, et
• d'autre part pour actionner le mécanisme d'actionnement et provoquer automatiquement l'ouverture permanente des contacts pour des courants alternatifs ou continus de court-circuit.

The disconnecting device with contacts is calibrated:

• on the one hand to sell electric currents of lightning waves of type 10/350 or 8/20 without the actuating mechanism being actuated, and
• on the other hand to actuate the actuating mechanism and automatically cause the permanent opening of the contacts for alternating currents or continuous short circuit.

The contacts can generally open (repel) and close under a lightning strike without the actuating mechanism unlocking. This repulsion (opening) of the contacts during operation of the protection device is followed by an automatic re-closing of said contacts.

The term "permanent opening" of the contacts, an opening caused by the actuating mechanism. This opening can be caused manually or due to an electrical fault. In the case of a manual opening, the re-closure of the contacts is then possible only by a voluntary external action of a user. In the case of an opening due to an electrical fault, the opening is then final.

The known protection devices are calibrated in such a way that the actuating mechanism of the disconnection device remains locked in the presence of lightning-type electric currents of the 10/350 or 8/20 type. It is generally undesirable for the actuating mechanism of the disconnecting device to unlock and cause permanent opening of the contacts each time it is crossed by an electric lightning wave current.

The triggering energy threshold is directly dependent on the electric currents of 10/350 or 8/20 type lightning waves for which the opening of the contacts of the disconnection device is not desired. In other words, said triggering energy threshold corresponds to the threshold above which electrical currents of lightning waves of the 10/350 or 8/20 type would cause the permanent opening of the electrical contacts.

In addition, alternating or short-circuit currents having an electrical energy greater than the triggering energy threshold cause the contacts of the disconnection device to open.

For electrical currents of lightning waves of the 10/350 or 8/20 type having an energy lower than the triggering threshold energy, the protection device is effective and allows the flow of said electric currents of lightning waves without their energy being responsible for material damage. In addition, the electric currents of 10/350 or 8/20 type lightning waves having an energy lower than the triggering energy threshold do not unlock the actuating mechanism of the disconnection device to cause the opening of the contacts.

However, in certain particular circumstances, the known protective devices do not have the sufficient level of protection.

Indeed, when the energy of the alternating or continuous short-circuit currents becomes lower than that of the trip threshold energy, the actuating mechanism is no longer actuated and does not cause the permanent displacement of the device contacts. disconnecting the closed state to the open state. The risk of deterioration of the components is then not negligible.

• l'impédance du limiteur de surtension devient faible après avoir reçu de nombreux chocs de foudre. Un courant alternatif de court-circuit ayant une énergie inférieure à celle de l'énergie de seuil de déclenchement circule alors dans le dispositif de protection.
• un mauvais montage de dispositif de protection est réalisé. Notamment, lorsque qu'un dispositif de protection, habituellement branché entre une phase et neutre, est branché par exemple entre deux phases. La tension appliquée entre les phases est généralement supérieure à celle que peut supporter en permanence le limiteur de surtension. Le limiteur de surtension devient alors passant et un courant alternatif de court-circuit circule dans le dispositif de protection. Ce faible courant alternatif de court-circuit peut être réduit si la puissance du transformateur d'alimentation est faible et/ou lorsque les longueurs de câbles sont grandes.

This situation may arise in particular when:

• the impedance of the surge protector becomes low after receiving many lightning strikes. An alternating current of short circuit having a lower energy than that of the trip threshold energy then flows in the protection device.
• bad mounting of protective device is realized. In particular, when a protection device, usually connected between a phase and neutral, is connected for example between two phases. The voltage applied between the phases is generally greater than that which the surge protector can withstand permanently. The surge protector then turns on and an alternating current of short circuit flows in the protection device. This low AC short circuit current can be reduced if the power transformer power is low and / or when the cable lengths are large.

In the two situations described above, the short-circuit current having a energy lower than that of the triggering energy threshold, can cause material damage.

The document " FR-A-2,846,478 "discloses a protection device according to the preamble of claim 1.

SUMMARY OF THE INVENTION

The invention therefore aims to overcome the drawbacks of the state of the art, so as to provide an overvoltage protection device comprising effective means of disconnection against short circuits.

The overvoltage protection device according to the invention comprises, at least first, a thermal disconnector against alternating or continuous short-circuit currents connected in series with the surge protector between the third movable arc switching electrode and the second connection. Said thermal disconnector comprises at least one fusible element extending through a passage gap, between a first and second conductive radial walls, inside an insulating side wall extending from an extinguishing chamber. arc, said arc extinction chamber comprising at least one conductive separator maintained inside the insulating side wall to define two expansion volumes. Said thermal disconnector is off when an electric arc is switched between the first connection electrode and the second connection electrode. Disconnection of said said disconnector is performed when traversed by alternating or short-circuit electrical currents having an energy lower than a triggering energy threshold, said triggering energy threshold corresponding to the threshold beyond which electrical currents of 10/350 or 8/20 lightning waves cause permanent opening of the electrical contacts.

Preferably, the fusible element fuse element has a section of substantially identical shape to the section of the passage gap.

Preferably, the section of said at least fuse element in a plane perpendicular to a median longitudinal axis is of elongate shape so that the length of said section is at least three times greater than the width.

Advantageously, the thermal disconnector comprises two arc extinguishing chambers crossed respectively by a fuse element.

Advantageously, said at least one conductive fuse element consists of a conductive metal sheet.

Advantageously, the metal sheet is held by holding means on an insulating support constituting an element of the insulating side wall.

Preferably, said at least one conductive fuse element is placed on the edges of said at least one separator.

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

Advantageously, comprises a housing having at least two flanges of insulating material, said flanges forming part of the side wall of the thermal disconnector.

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

According to a first particular embodiment of the invention, the surge protector is electrically connected in series with the disconnection device by at least one fusible link, drive means exert a displacement force displacing the surge protector in case melting said at least one fusible link, moving said limiter acting directly on the actuating mechanism to move the third movable arc switching electrode and cause permanent opening of the contacts.

Preferably, the surge protector is electrically connected to the second connection pad by a first fusible link fused upon overheating of said limiter.

Preferably, the surge protector is electrically connected to the second connection pad by a second fusible link acting as a thermal disconnector.

According to a second particular embodiment of the invention, a second electromagnetic disconnector against alternating currents or continuous short circuits is connected in series with the thermal disconnector and the surge protector between the third mobile arc switching electrode and the second connection range.

Preferably, the electromagnetic disconnector comprises electromagnetic tripping means intended to act on the actuating mechanism to cause the permanent opening of the electrical contacts.

According to a development mode, a high-energy disconnector is connected in series between the first connection electrode and the first connection pad, the high-energy disconnector being calibrated to disconnect when it is traversed by electric currents having an energy greater than the triggering energy threshold.

Advantageously, the high energy disconnector comprising an arc extinction chamber being delimited by an insulating side wall extending between a first and second conductive radial wall, the arc extinguishing chamber comprising 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 extending from the first to the second radial walls through a interstice and being rigidly held in the arc extinguishing chamber by holding means, the section of said at least one fuse element being of elongate shape so that the length of said section is at least three times greater than the width.

According to a development mode, a closure stop is intended to maintain directly or indirectly the third mobile arc switching electrode at a separation distance from the first electrode of connection when the electrical contacts are closed.

Preferably, the closure abutment has two parts, a first portion of insulating material is placed in contact with the fixed contact and a second portion of conductive material placed adjacent to the first part and is in contact with the movable contact when the two contacts are closed.

Advantageously, the thickness of the first insulating portion is equal to the separation distance.

BRIEF DESCRIPTION OF THE FIGURES

• la figure 1 à 3 représentent des vues schématiques d'un dispositif de protection contre les surtensions selon un mode préférentiel de réalisation de l'invention ;
• les figures 4A et 4B représentent des vues schématiques d'un déconnecteur thermique selon un premier mode de réalisation de l'invention ;
• Les figures 5A et 5B représentent des vues schématiques d'un déconnecteur thermique selon un second mode 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 d'un déconnecteur thermique selon les modes de réalisation représentés sur les figures 1 à 3 ;
• les figures 7 à 9 représentent, dans différentes positions de fonctionnement, des vues schématiques d'un dispositif de protection contre les surtensions selon un premier mode particulier de réalisation de l'invention selon la figure 1 ;
• la figure 10 représente une variante de réalisation du dispositif de protection selon les figures 7 à 9 ;
• la figure 11 représente une vue schématique d'un second mode particulier de réalisation du dispositif de protection selon la figure 1 ;
• les figures 12A et 12B représentent des vues schématiques de variantes de réalisation du dispositif de protection selon les différents modes de réalisation de l'invention ;
• la figure 13 représente une vue schématique d'une autre variante de réalisation du dispositif de protection contre les surtensions.

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 figure 1 to 3 represent schematic views of an overvoltage protection device according to a preferred embodiment of the invention;
• the Figures 4A and 4B represent schematic views of a thermal disconnector according to a first embodiment of the invention;
• The Figures 5A and 5B represent schematic views of a thermal disconnector according to a second 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 of a thermal disconnector according to the embodiments shown in FIGS. Figures 1 to 3 ;
• the Figures 7 to 9 represent, in different operating positions, schematic views of a surge protection device according to a first particular embodiment of the invention according to the figure 1 ;
• the figure 10 represents an alternative embodiment of the protection device according to the Figures 7 to 9 ;
• the figure 11 represents a schematic view of a second particular embodiment of the protection device according to the figure 1 ;
• the Figures 12A and 12B show schematic views of alternative embodiments of the protection device according to different embodiments of the invention;
• the figure 13 is a schematic view of another alternative embodiment of the overvoltage protection device.

DETAILED DESCRIPTION OF AN EMBODIMENT

As shown on Figures 1 to 3 , the overvoltage protection device 1 comprises an overvoltage limiter 2 with non-linear elements variable with the voltage and a disconnecting device 3 with electrical contacts 30, 31. The surge protector 2 and the disconnecting device 3 are electrically arranged. serial.

The surge protector 2 preferably comprises a varistor 21. In some embodiments of the invention not shown, a spark gap can also be placed in series with the varistor 21.

The disconnection device 3 comprises a first connection electrode 40 in electrical connection with a first connection pad 41 and a second connection electrode 50 in electrical connection with a second connection pad 51.

If the protection device 1 is connected between phase and ground, the connection pads 41, 51 are intended to be connected respectively to a phase and earth or vice versa.

The disconnection device 3 comprises a third movable arc switching electrode 60 electrically connected to the second connection pad 51.

A first electrical contact 30 is placed on the first connection electrode 40 and a second electrical contact 31 is positioned on the third movable arc switching electrode 60.

As shown on Figures 1 to 3 according to a preferred embodiment, the surge protector 2 is connected in series between the third movable arc switching electrode 60 and the second connection pad 51.

The third movable arc switching electrode 60 is in contact with the first connection electrode 40 when the electrical contacts 30, 31 are closed.

The disconnecting device 3 further comprises an actuating mechanism 7. Said mechanism is intended to be actuated to move the third movable arc switching electrode 60 and mechanically cause the permanent opening of the electrical contacts 30, 31.

The disconnecting device 3 with contacts 30, 31 is calibrated firstly to discharge electric currents of lightning waves of the type 10/350 or 8/20 without the actuating mechanism 7 being actuated, and of on the other hand to actuate the actuating mechanism 7 and cause permanent opening of the contacts 30, 31 for alternating currents or continuous short circuit.

The protection devices 1 are calibrated in such a way that the actuating mechanism 7 of the disconnection device 3 remains locked in the presence of lightning-type electric currents of the 10/350 or 8/20 type. Indeed, the actuating mechanism 7 does not cause permanent opening of the contacts each time it is crossed by an electric current of lightning wave.

The trigger energy threshold is directly dependent on the currents 10/350 or 8/20 type lightning-type electric waves for which the opening of the contacts 30, 31 of the disconnection device 3 is not performed. In other words, said triggering energy threshold corresponds to the threshold above which electrical currents of lightning waves of the 10/350 or 8/20 type would cause the permanent opening of the electrical contacts 30, 31.

When the protective device is traversed by electric currents having an energy greater than a triggering energy threshold, the actuating mechanism 7 is actuated and moves the third movable arc switching electrode 60 and mechanically causes the permanent opening of the electrical contacts 30, 31. The electric currents responsible for actuating the actuating mechanism 7 are generally alternating currents or continuous short circuit.

When the protection device is traversed by electric currents of lightning waves of type 10/350 or 8/20 having an energy lower than the trigger threshold energy, the protection device is effective and allows the flow of electrical currents of lightning waves without their energy being responsible for material damage. In addition, said electric currents of lightning waves do not unlock the actuating mechanism 7 of the disconnection device to cause the opening of the contacts 30, 31.

The overvoltage protection device comprises at least a first disconnector against the AC or DC short-circuit currents 9, 10. The at least first disconnector is a thermal disconnector 9.

As shown on Figures 1 to 3 according to the embodiments, the thermal disconnector 9 is electrically connected in series with the overvoltage limiter 2 between the third movable arc switching electrode 60 and the second connection pad 51.

When the protection device is traversed by electric currents of lightning waves of the 10/350 or 8/20 type, an electric arc 100 is very quickly switched between the first connection electrode 40 and the second connection electrode 50. surge protector 2 and the thermal disconnector 9 are then simultaneously placed out of circuit and are lightly traversed by the lightning wave. Said limiter and said thermal disconnector are thus protected and are not damaged by lightning strikes. The protection device comprises an extinction chamber 101 of the electric arc 100. The first connection electrode 40 and the second connection electrode 50 are arranged facing the arc extinction chamber 101 and define the mouth of said arc extinguishing chamber 101. Said arc extinguishing chamber 101 comprises deionization fins 102 for cooling an electric arc 100 and extinguishing it.

As shown on Figures 5A to 6B according to a first preferred embodiment, the thermal disconnector 9 comprises at least one fuse element 91 extending through a passage gap inside an insulating side wall 92 of an arc extinguishing chamber 99. The arc extinguishing chamber 99 has a median longitudinal axis Z. The insulating side wall 92 of the arc extinguishing chamber 99 extends between first and second conductive radial walls 90. The arc extinguishing chamber 99 comprising at least one conductive separator 95 held inside the insulating lateral wall 92 to define two expansion volumes 97. Said at least one separator is positioned between the two conductive radial walls 90. preferably, the first and second radial walls 90 extend perpendicular to the longitudinal median longitudinal axis Z of said extinguishing chamber.

The section of said at least one fuse element 91 in a plane perpendicular to the median longitudinal axis Z is of elongate shape. In addition, said section is substantially identical to that of the passage gap. Preferably, the length of said section is at least three times greater than the width.

The fuse element 91 extends from the first to the second radial wall 90 through the passage gap and is held rigidly in the arc extinguishing chamber 99 by holding means. Said holding means guarantee the rigid holding of said at least one fuse element 91 in the event of a lightning strike. They make it possible to withstand the electrodynamic forces caused by lightning strikes.

Advantageously, as shown on the Figures 5A, 5B the fuse element 91 is placed on the periphery of the at least one separator 95. The fuse element 91 is held rigidly between the at least one separator 95 and the at least one insulating side wall 92. The clearance between the fuse element 91 and each of the separators 95 is minimal in particular to ensure the rigid retention of the fuse element in the event of a lightning strike. The means maintained are then provided directly by the separators 95 and the insulating wall 92.

Preferably, the conductive fuse element 91 consists of a conductive sheet of metal. The conductive sheet is preferably held by holding means on an insulating support which can constitute an element of the insulating lateral wall 92.

When the fuse element 91 melts, an electric arc arises at the passage gap. Due to the elongated shape of said passage gap, said electric arc which naturally has a substantially circular cross section, is forced to deform and leave said gap zone. Thus, the development of the arc in the expansion volumes 97 is thus favored, which makes it possible to achieve a sufficient arc voltage for a satisfactory limitation of the short-circuit currents. In addition, said arc tends to be laminated within said passage gap. This rolling of the electric arc in the passage gap tends to rapidly raise its voltage for a satisfactory limitation of the short-circuit currents.

As illustrated on Figures 6B to 6C , the passage gap of said at least one fuse element is represented by a first hatched area 73. The dashed hatched surface 74 represents the electric arc present in the expansion spaces 97 when said at least one fuse element has melted. The electric current then reached a significant value, greater than 1000A. The area where the dotted lines 74 and the first shaded area 73 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 faster with cutoff devices according to the invention with known cutting devices. Indeed, the zone of interaction between the dotted zone 74 and the shaded area 73 is lower for the Figure 6B that for the Figure 6A .

As represented on the Figures 4A to 5B the extinguishing chamber 99 comprises a plurality of conductive separators 95 extending preferably perpendicular to a median longitudinal axis Z.

Said at least one side wall 92 is preferably composed of four lateral facades extending along a median longitudinal axis Z. The four lateral facades are conjoined. The extinguishing chamber 99 has a parallelepipedal shape and the separators 95 have a square or rectangular shape. The protection device 1 against overvoltages comprises a housing made of molded plastic material and consisting of two parallel side flanges of insulating material placed on either side of a median longitudinal plane. Said flanges may constitute part of two facades of the side wall 92. A portion of the side flanges then constitutes a portion of the side wall 92 of the extinguishing chamber 99 of the thermal disconnector 9. The separators 95 are held by two of the facades side.

According to an alternative embodiment, the side wall 92 is preferably composed of a gasogenic plastic material. As shown on the Figure 6C , the presence of gasogenic material makes it possible to push the electric arc towards the center of the extinguishing chamber and away from the passage gap. As has been described above, this further increases the efficiency of the extinguishing chamber of the fuse cutoff device.

In addition, in some applications not shown, the insulating side wall can be made of glass or ceramic.

According to an alternative embodiment, said at least one side wall 92 has gas evacuation holes contained in the expansion volumes 97.

According to another variant embodiment, filters are positioned at the drainage holes, preferably outside the extinguishing chambers arc. These filters make it possible to strongly limit the external manifestations of the protection device. Indeed, the hot cutoff gases present in the arc extinguishing chamber are greatly cooled as they pass through the filters. The inside of the protection device against overvoltages is thus less polluted.

According to a first particular mode of development of the preferred embodiment, the surge protector 2 is electrically connected in series with the disconnection device 3 by at least one fuse link 8, 91. As shown in FIGS. Figures 7 to 9 drive means 22 permanently exert the displacement force Fd on said surge protector. If at least one of the fuse links 8, 91 is destroyed, the surge protector 2 then moves under the action of the displacement force Fd. The displacement of said limiter acts directly on the actuating mechanism 7. Said mechanism unlocks and moves the third movable arc switching electrode 60 and causes permanent and permanent opening of the electrical contacts 30, 31.

Preferably, the drive means 22 comprise a spring. According to the particular embodiment as represented on the Figures 7 to 9 , this helical type spring is stretched to exert the displacement force Fd directly on the varistor 21 of the surge limiter 2. According to another particular mode not shown, this helical type spring is compressed.

The surge protector 2 may be electrically connected to the second connection pad 51 by two fusible links 8, 91. By way of example, a first fusible link 8 is melted in the event of overheating of said surge protector. A second fuse link 91 plays the role of the thermal disconnector 9. When at least one of the fusible links melts 8, 91, the varistor 21 moves under the action of the displacement force Fd to act directly on the actuating mechanism 7. As shown on Figures 7 to 9 the varistor 21 is connected in series with the disconnecting device 3 through two terminals. A first terminal is connected to the disconnection device 3 by a flexible metal braid 15, and a second terminal is connected to the second connection range 51.

The metal conductive foil constitutes the fuse element 91 of the thermal disconnector 9. The conductive metal sheet then maintains the varistor in a first position. The metal conductive sheet connecting the varistor 21 to the second connection pad 51 then comprises a section calibrated to melt when said sheet is traversed for a given time by short-circuit electrical currents whose energy is below the tripping threshold. . In addition, the metal conductive foil connecting the varistor 21 to the second connection pad 51 is soldered to the second terminal of the varistor by a low temperature solder forming the first fusible link 8.

The operation remains unchanged if the varistor 21 is placed in a carriage or in a mobile housing, forming a single block with the varistor 21. The displacement force Fd could then be applied to the carriage or to the mobile housing in place of apply directly to the varistor. In addition, the carriage or the mobile housing could act directly on the trigger bar 71 of the actuating mechanism 7.

According to an alternative embodiment as represented on the figure 10 the thermal disconnector 9 comprises two arc extinguishing chambers 99 placed side by side. Each arc extinguishing chamber 99 is traversed by a fuse element 91. This particular arrangement of the two arc extinguishing chambers 99 is optimized for an internal volume of an overvoltage protection device as shown in FIG. figure 10 . In addition, the fact of having two arc extinction chambers 99 connected in series makes it possible to double the arc voltage and thus to better limit the short-circuit currents. The fuse elements 91 passing respectively through the two arc extinguishing chambers 99 are not calibrated identically. Indeed, the first fuse element 91 which is directly connected to the varistor 21 via the metal sheet is calibrated to melt before the second fuse element. This configuration makes it possible to ensure that, in the presence of a short-circuit current, the melting of the first fusible element will systematically release said varistor. The varistor will move under the effect of the displacement force Fd to actuate the actuating mechanism 7 and cause permanent and permanent opening of the electrical contacts 30, 31.

As shown on the figure 11 according to a second particular mode of development of the preferred embodiment, a second disconnector against the AC or DC short-circuit currents 10 is connected in series with the surge protector 2 between the third movable arc switching electrode 60 and the second connection pad 51. The second disconnector is an electromagnetic disconnector 10. The electromagnetic disconnector 10 comprises electromagnetic tripping means 12 for acting on the actuating mechanism 7 and causing the permanent opening of the electrical contacts 30, 31. According to FIG. a first exemplary embodiment, the electromagnetic trigger means 12 comprise a plunger core. Circulation of short-circuit currents through the electromagnetic disconnector 10 causes the displacement of the plunger to act on the actuating mechanism 7. In fact, this plunger core comprises a striker which releases the attachment of the actuating mechanism 7 The mass of the plunger is calibrated so that the core does not move in the passage of the lightning impulse currents in the protection device. Preferably, this electromagnetic plunger disconnector 10 also comprises its own hooking system to prohibit the reset of the actuating mechanism 7 when it is unlocked. According to a second exemplary embodiment, the electromagnetic triggering means 12 comprise a pallet. As before, the mass of the pallet is calibrated so that it does not move to the passage of the lightning shock currents in the protection device. Preferably, this pallet also has a hooking system which prevents the reset of the actuating mechanism 7 so the pallet has been actuated by a fault current. The electromagnetic disconnector 10 is also calibrated to actuate the actuating mechanism 7 when it is crossed by alternating or continuous short circuit electrical currents whose energy is greater than the disconnection threshold. The electromagnetic trigger means 12 act on the mechanism actuator 7 to cause permanent and permanent opening of the electrical contacts 30, 31.

The operation of the overvoltage protection device 1 comprising at least a first thermal disconnector 9 is as follows:

When the protection device is traversed by electric currents of lightning waves of the 10/350 or 8/20 type, an electric arc 100 is very quickly switched between the first connection electrode 40 and the second connection electrode 50. thermal disconnector 9 is placed out of circuit and is no longer crossed by the lightning wave. The thermal disconnector 9 is then protected and is not damaged by lightning strikes.

Given that said disconnector is slightly subject to lightning strikes, its calibration is essentially dependent on the energy of the short-circuit currents for which it is intended to disconnect.

When the protection device 1 against overvoltages is traversed by alternating currents or short-circuit currents having an energy lower than the triggering energy threshold, said currents pass through the first connection electrode 40, the third connection electrode 60 and the thermal disconnector against the alternating or continuous short-circuit currents 9, 10. The repulsion of the movable contact 31 is then limited. The arc voltage between the contacts 30, 31 remains low and switching of the arc 100 is not possible or is very late. By low arc voltage is meant a voltage lower than the mains voltage, for example less than 100 volts.

The thermal disconnector 9 is nevertheless calibrated to disconnect when it is crossed by alternating or continuous short circuit electrical currents whose energy is greater than a disconnection threshold. For example, the electric currents responsible for the disconnection of said disconnector have an intensity greater than 100A.

The fuse element 91 of the thermal disconnector 9 is calibrated to then go into a closed electrical state to an open electrical state under the effect of the thermal stress generated by the passage of short-circuit currents. The voltage generated by the quenching chamber 99 of the thermal disconnector 9 is important because of the splitting in the separators 95 and / or the rolling of the arc. Thus, for these short-circuit current values, the limitation will essentially be ensured by the thermal disconnector 9. In addition, the melting of the fuse element 91 causes the overvoltage limiter 2 to move and the mechanism to be actuated. actuation 7 to cause permanent and permanent opening of the electrical contacts 30, 31.

When the overvoltage protection device 1 is traversed by strong alternating or short-circuit currents whose intensity is greater than that of those described above, especially whose intensity is greater than 6000 A, the repulsion of the third movable arc switching electrode 60 is important. The voltage of the arc 100 rises rapidly and its switching on the second connection electrode 50 is done quickly. This switching speed is a function of the level of the short-circuit current. After switching, the arc voltage increase is ensured by the breaking chamber 101. Despite this rapid opening of the electrical contacts 30, 31, a residual current can flow in the third movable arc switching electrode 60 and cause the fusion of the fuse element 91 of the thermal disconnector 9 or the actuation of the electromagnetic disconnector 10. Said fusion or said actuation then causes the displacement of the surge limiter 2 and the actuation of the actuating mechanism 7 to cause the permanent and permanent opening of the electrical contacts 30, 31.

According to first variants of the embodiments, a high-energy disconnector 11 is connected in series between the first connection electrode 40 and the first connection pad 41. Said high-energy disconnector 11 is calibrated to disconnect when it is crossed. by electric currents having an energy higher than the triggering energy threshold. Preferably, said high-energy disconnector is intended to act on the actuating mechanism 7 to move the third movable arc switching electrode 60 and cause the permanent opening of the electrical contacts 30, 31. The high-energy disconnector 11 is then calibrated to unlock the actuating mechanism 7 when traversed by electric currents having an energy higher than the triggering energy threshold. Said high-energy disconnector then comprises means for acting on the actuating mechanism 7 to cause permanent opening of the electrical contacts 30, 31. As an exemplary embodiment, the high-energy disconnector 11 is an electromagnetic disconnector comprising electromagnetic triggering means. As shown on the Figures 12A and 12B , as an exemplary embodiment, the high-energy disconnector 11 is a thermal disconnector. Said disconnector comprises an arc extinguishing chamber 99 having a median longitudinal axis Z and being delimited by an insulating side wall 92. Said wall extends between a first and second conductive radial wall 90. The arc extinguishing chamber 99 comprises at least one conductive separator 95 held inside said chamber to define two expansion volumes 97. At least one fuse element 91 is electrically connected between a first and a second electrode 96 and extending from the first to the second radial wall 90 through a passage gap. Said at least one fuse element 91 is rigidly held in the arc extinguishing chamber 99 by holding means. The section of the at least one fuse element 91 in a plane perpendicular to the median longitudinal axis Z is elongate in shape so that the length of said section is at least three times greater than the width. Thus, although the limitation is essentially provided by the breaking chamber 101, said breaking chamber 101 does not allow to reach a sufficient arc voltage for a satisfactory limitation of the short-circuit currents. The additional arc voltage is then supplied by the quenching chamber 99 of the high-energy thermal disconnector 11. The addition of these two voltages then makes it possible to limit the current very rapidly.

According to a second variant embodiment of the various preferred embodiments of the invention, the device comprises a closing abutment 80 intended to directly or indirectly hold the third movable arc switching electrode 60 at a distance D from the first electrode connection 40 when the electrical contacts 30, 31 are closed. This separation distance D of the electrical contacts in the closed position acts as a spark gap 22 electrically positioned in series with the varistor 21 of the surge protector 2. As described in the applicant's patent application WO 04/042762 as an exemplary embodiment, the closing abutment 80 comprises a conductive fixed pellet having a face constituting a fixed electrode facing the first connecting electrode 40 and an opposite face constituting a contact electrode on which the third electrode of mobile arc switching 60. According to another embodiment example as shown in FIG. figure 13 , the closing abutment 80 has two parts 81, 82. A first portion 80 of insulating material is placed in contact with the fixed contact 30. A second portion 82 of conductive material is placed adjacent to the first portion 81 and is in contact with the movable contact when the two contacts 30, 31 are closed. The thickness of the first insulating part determines the distance D. In the event of a lightning strike, the thermal disconnector 9 is out of circuit when an electric arc 100 is switched between the first connection electrode 40 and the second connection electrode 50.

According to another variant embodiment, the disconnecting device comprises resetting means 72. The resetting means 72 allow the displacement of said third electrode from the so-called switching position to the so-called service position. In other words, thanks to the resetting means 72, it is possible to mechanically cause the closing of the contacts 30, 31 after permanent opening of said contacts. In addition, the resetting means 72 also act on the actuating mechanism 7 to cause the permanent opening of the electrical contacts 30, 31. The resetting means 72 are no longer operational as soon as a disconnector against the currents alternating or continuous short circuits 9, 10 has caused the definitive opening of the electrical contacts 30, 31 following a short-circuit fault.

Claims (20)

1. A voltage surge protection device (1) comprising:

   - a disconnection device (3) with electric contacts (30, 31) comprising:

   - a first connecting electrode (40) in electric connection with a first connecting strip (41),

   - a second connecting electrode (50) in electric connection with a second connecting strip (51),

   - a third movable arc switching electrode (60) in electric connection with the second connecting strip (51),

   - an actuating mechanism (7) designed to move the third movable arc switching electrode (60) to cause permanent opening of the electric contacts (30, 31),

   - a surge arrestor (2) connected in series between the third movable arc switching electrode (60) and the second connecting strip (51),

   characterized in that it comprises at least a first thermal disconnector (9) for protection against AC or DC short-circuit currents connected in series with the surge arrestor (2) between the third movable arc switching electrode (60) and the second connecting strip (51), said thermal disconnector comprising at least one fuse element (91) extending through a passage gap between first and second conducting radial walls (90) inside an insulating side wall (92) of an arc extinguishing chamber (99), said arc extinguishing chamber (99) comprising at least one conducting separator (95) secured inside the insulating side wall (92) to define two pressure relief volumes (97),

   - said thermal disconnector (9) being out of circuit when an electric arc (100) is switched between the first connecting electrode (40) and the second connecting electrode (50);

   - disconnection of said disconnector (9) being performed when AC or DC short-circuit electric currents having a lower energy than a tripping energy threshold flow through the latter, said tripping energy threshold corresponding to the threshold above which electric surge currents of 10/350 or 8/20 type cause permanent opening of the electric contacts (30, 31).
2. The voltage surge protection device according to claim 1, characterized in that the fuse element (91) comprises a cross-section of substantially identical shape to the cross-section of the passage gap.
3. The voltage surge protection device according to claim 1 or 2, characterized in that the cross-section of said at least one fuse element (91) in a plane perpendicular to a longitudinal mid-line (Z) is of elongate shape so that the length of said cross-section is at least three times greater than the width.
4. The voltage surge protection device according to any one of the foregoing claims, characterized in that the thermal disconnector (9) comprises two arc extinguishing chambers (99) through which a fuse element (91) respectively passes.
5. The voltage surge protection device according to any one of the foregoing claims, characterized in that said at least one conducting fuse element (91) is composed of a conducting metal foil.
6. The voltage surge protection device according to claim 5, characterized in that the metal foil is secured by securing means on an insulating support forming an element of the insulating side wall (92).
7. The voltage surge protection device according to any one of the foregoing claims, characterized in that said at least one conducting fuse element (91) is placed on the edges of said at least one separator (95).
8. The voltage surge protection device according to any one of the foregoing claims, characterized in that the side wall (92) comprises holes for removal of the gases contained in the pressure relief volumes (97).
9. The voltage surge protection device according to any one of the foregoing claims, characterized in that it comprises a case having at least two flange-plates made from insulating material, said flange-plates constituting a part of the side wall (92) of the thermal disconnector (9).
10. The voltage surge protection device according to any one of the foregoing claims, characterized in that the insulating side wall (92) is composed of a gas-generating material.
11. The voltage surge protection device according to any one of the foregoing claims, characterized in that the surge arrestor (2) is electrically connected in series with the disconnection device (3) by at least one fuse link (8, 91), drive means (22) exerting a displacement force (Fd) displacing the surge arrestor (2) in the event of melting of at least one fuse link, displacement of said arrestor acting directly on the actuating mechanism (7) to move the third movable arc switching electrode (60) and cause permanent opening of the contacts (30, 31).
12. The voltage surge protection device according to claim 11, characterized in that the surge arrestor (2) is electrically connected to the second connecting strip (51) by a first fuse link (8) that melts in the event of overheating of said surge arrestor.
13. The voltage surge protection device according to claim 11 or 12, characterized in that the surge arrestor (2) is electrically connected to the second connecting strip (51) by a second fuse link (91) acting as thermal disconnector (9).
14. The voltage surge protection device according to any one of claims 1 to 10, characterized in that a second electromagnetic disconnector (10) protecting against AC or DC short-circuit currents is connected in series with the thermal disconnector (9) and the surge arrestor (2) between the third movable arc switching electrode (60) and the second connecting strip (51).
15. The voltage surge protection device according to claim 14, characterized in that the electromagnetic disconnector (10) comprises electromagnetic tripping means (12) designed to act on the actuating mechanism (7) to cause permanent opening of the electric contacts (30, 31).
16. The voltage surge protection device according to any one of the foregoing claims, characterized in that a high-energy disconnector (11) is connected in series between the first connecting electrode (40) and the first connecting strip (41), the high-energy disconnector (11) being calibrated to disconnect when it has electric currents having a greater energy than the tripping energy threshold flowing through it.
17. The voltage surge protection device according to claim 16, characterized in that the high-energy disconnector (11) comprises an arc extinguishing chamber (99) being delineated by an insulating side wall (92) extending between a first and second conducting radial wall (90), the arc extinguishing chamber (2) comprising at least one conducting separator (95) secured inside said chamber to define two pressure relief volumes (97) and at least one conducting fuse element (91) electrically connected between a first and second electrode, said at least one fuse element (91) extending from the first to the second radial wall (90) through a gap and being rigidly secured in the arc extinguishing chamber (99) by securing means, the cross-section of said at least one fuse element (91) being of elongate shape so that the length of said cross-section is at least three times greater than the width.
18. The voltage surge protection device according to any one of the foregoing claims, characterized in that it comprises a closing stop (80) designed to maintain the third movable arc switching electrode (60) directly or indirectly at a separation distance (D) from the first connecting electrode (40) when the electric contacts (30, 31) are closed.
19. The voltage surge protection device according to claim 18, characterized in that the closing stop (80) comprises two parts (81, 82), a first part (80) made of insulating material placed in contact with the stationary contact (30) and a second part (82) made of conducting material placed in adjacent manner to the first part (81) and in contact with the movable contact when the two contacts (30, 31) are closed.
20. The voltage surge protection device according to claim 19, characterized in that the thickness of the first insulating part (81) is equal to the separation distance (D).

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