FR2967293A1 - ELECTRICAL DISCONNECTING DEVICE AND PARAFOUDRE COMPRISING SUCH A DEVICE - Google Patents

Abstract

The invention relates to an electrical disconnection device (10), comprising: two fixed contacts (12, 14) spaced from each other, a movable contact (16) optionally forming a single piece with one of the two fixed contacts, the movable contact being capable of moving between: a closed position in which the movable contact is in electrical contact with the fixed contacts to electrically connect them to each other, and an open end position in which the movable contact is separated from at least one of the fixed contacts for electrically isolating the fixed contacts from each other; at least one varistor (18; 28; V1 ... V5) for limiting the voltage between the fixed contacts (12; 14) during at least part of the path of the movable contact from the closed position to the open end position; the exclusion of a last part of the journey.

Description

ELECTRICAL DISCONNECTING DEVICE AND PARAFOUDRE COMPRISING SUCH A DEVICE

The present invention relates to a device for disconnecting an electrical device with respect to an electrical line, in particular a disconnection device mounted in a surge arrester for an electrical installation supplied with DC voltage. In the field of protection of electrical installations against overvoltages, particularly overvoltages related to lightning strikes, it is usual to resort to surge arresters. It is conventional for surge arresters to include one or more varistors and possibly one or more gaps to limit transient overvoltages appearing on the power supply lines, for example due to a thunderbolt, and evacuate the shock currents to Earth. Standards require disconnecting the surge protection components of power lines when they fail. In particular, a surge arrester varistor may short circuit, in which case it bypasses the two electrical lines (for example the phase and the neutral or two phases of a very low voltage network) between which it is connected, which can lead to the explosion of the arrester or fire. Or, the leakage current of such a varistor can increase and lead to abnormal and excessive heating of the arrester (a situation called thermal runaway), which can also cause a fire. To avoid these risks, the surge arresters are equipped with disconnectors whose function is to disconnect the varistor from the power lines in the event of a short circuit or thermal runaway. With regard to short-circuit protection, these are generally fuses, circuit breakers or other breaking devices which have a high breaking capacity. With regard to the protection against thermal runaway, it is generally thermal disconnectors using a hot-melt welding releasing a prestressed contact - such as a blade or a bridge - so that it passes from the closed position to the open position. These thermal disconnectors sometimes provide themselves protection against short circuits. Of course, as long as the arrester's varistor is working properly, these disconnectors must remain closed and be able to discharge the currents of shock due to possible transient overvoltages.

In case of disconnection, the movable contact of the disconnector reaches an open end position in which it is far enough away from the fixed contact to prevent (re) creation of an electric arc for the nominal voltage considered power lines. But during the disconnection operation, especially for the case of R: 130500A30564 ABBBI30564--101104-Application.doc - 04/11/10 - 12:11 - 1/23 disconnection in case of short circuit of the varistor, the disconnector must be able to cut the electric arc that is created between its movable contact and his or her fixed contacts when opening the movable contact. The extinction of the electric arc can be obtained by stretching it between the fixed contact (s) and the movable contact which moves away from it a sufficient distance for the nominal voltage of the electric lines to be insufficient. to maintain the electric arc. Other techniques used to extinguish an electric arc include sending the electric arc into a break chamber that divides the electric arc into several small arcs to extinguish it and / or stretch the arc under its own electromagnetic force. . The extinction of such an electric arc is easier in the case of alternating currents because the sinusoidal supply voltage is periodically zeroed, which allows the extinction of the arc without reformation thereof that the distance between the movable contact and the fixed contact (s) is sufficient.

In comparison, the extinction of an electric arc in the case of a direct current requires a much greater distance between the movable contact and the fixed contact (s). From this point of view, it is recalled that the stretching of an electric arc to a certain length requires less energy than the initiation of an electric arc of the same length. In other words, the minimum voltage for initiating an electric arc between two contacts having a predetermined spacing (arc striking voltage) is greater than the minimum voltage for maintaining and stretching an electric arc to the same distance (holding voltage arc). It has emerged that the existing surge arresters based on the abovementioned technologies are unsatisfactory, particularly in the case where they are used on DC power lines, in particular on photovoltaic installations. Indeed, it has emerged that the disconnectors in the event of a short circuit of the overvoltage protection component do not always succeed in cutting the electric arc between its contacts during the disconnection. This problem is related to some peculiarities of photovoltaic installations. A peculiarity lies in the fact that photovoltaic installations generate a relatively high DC voltage, generally between 500 V and 1000 V, even up to 1500 V. As a result, it is necessary to stretch the electric arc produced during the disconnection over a very large distance to turn it off. This distance is incompatible with the size of surge arresters which are generally housed in housings intended to be mounted on DIN rails of standardized electrical panels. It is the same if it is resorted to an arc-breaking chamber by division of it because the chamber having to divide the arc into a large number of 8: 130500/30564 ABBB / 30564--101104-Request .doc - 04/11/10 - 12:11 - 2/23 segments, must include as many platelets housed one after the other parallel to each other. Another peculiarity lies in the fact that the short-circuit current of the photovoltaic installations is not predetermined, but depends on the conditions of sunshine. Indeed, while the voltage supplied by a photovoltaic installation is relatively stable whether it is night or day, the maximum current that it can provide (and therefore the short-circuit current) varies depending on the brightness and therefore varies between a null value (at night) and a maximum value (full day without a cloud). But techniques for extinguishing the electric arc by sending the arc into a breaking chamber or by stretching the arc under its own electromagnetic force can only function properly if the arc itself has some energy for send it to the room or stretch it. However, the level of energy required may not be reached in case of too little sunlight. The disconnection then does not take place and the electric current is maintained through the arrester, which leads to an excessive rise in temperature that can cause a fire. These problems may also exist in other applications than disconnection of surge arresters in the event of failure of their protection component. There is therefore a need for a disconnecting device at least partially overcoming the disadvantages of the prior art. In particular, there is a need to provide a disconnection device capable of operating for relatively large DC voltages, in particular between 500 V and 1000 V, or even 1500 V and for non-predetermined currents ranging from a few tens of milliamps up to 200 A, or even 300 A. And more particularly, there is a need for a surge arrester with an effective disconnection device in the event of a short circuit of the overvoltage protection component for installations operating under relatively high direct current, such as a photovoltaic installation. For this, the invention proposes an electrical disconnection device, comprising: two fixed contacts spaced apart from one another; a movable contact possibly forming a single piece with one of the two fixed contacts, the movable contact; being able to move between: - a closed position in which the movable contact is in electrical contact with the fixed contacts to electrically connect them to each other, and - an open end position in which the movable contact is separated by at least 1 one of the fixed contacts for electrically isolating the fixed contacts from each other; A: 130500A30564 ABBBI30564--101104 -About.doc - 04/11/10 - 12:11 - 3/23 - at least one varistor for limiting the voltage between the fixed contacts during at least part of the path of the moving contact from the closed position to the open extremal position excluding a last part of the path. According to preferred embodiments, the electrical disconnection device comprises one or more of the following characteristics: the at least one varistor is disconnected from at least one of the fixed contacts during a last part of the path of the movable contact from the closed position to the open extremal position; the at least one varistor is arranged to limit the voltage between the two fixed contacts via the moving contact; the at least one varistor is provided for continuously limiting the voltage between the fixed contacts during the path of the moving contact from the closed position to the beginning of said last portion of the path, the at least one varistor limiting said voltage to a a value which increases with moving away from the movable contact from the closed position; one of the fixed contacts and the movable contact is in frictional electrical contact with a pole surface of the at least one varistor, the movement of the movable contact from the closed position to at least the beginning of said last part the path causing a correlative displacement of said electrical contact by friction on said surface to increase the value at which the at least one varistor limits the voltage between the fixed contacts; it is the moving contact which is in electrical contact by friction with said pole surface of the at least one varistor, the movable contact being kept in electrical contact with one of the fixed contacts when the moving contact moves from the closed position in the open position, the at least one varistor having another pole connected to the other fixed contact; the at least one varistor has at least one pole electrically connected to one of the fixed contacts and the movable contact by means of frictional electrical contact during a portion of the path of the moving contact to limit the voltage between the fixed contacts have a predetermined value during this part of the path of the moving contact; it is with the moving contact that a pole of the at least one varistor is in electrical contact by friction, the movable contact being kept in electrical contact with one of the fixed contacts when the moving contact moves on said part of the path of the moving contact, the at least one varistor having another pole connected to the other fixed contact; A: 130500A30564 ABBBI30564--101104 -About.doc - 04/11/10 - 12:11 - 4/23 - several such varistors, each being provided to limit the voltage between the fixed contacts to a respective predetermined value during a portion respective path of the movable contact; - Elastic means for constraining the movement of the movable contact from the closed position to the open end position. The invention further proposes a use of the preceding electrical disconnection device for disconnecting an electrical circuit from a continuous nominal voltage supply greater than or equal to 500 V. The invention also proposes a device for protection against transient overvoltages, comprising: at least one overvoltage protection component, preferably a varistor; and a system for disconnecting the protection component in the event of a failure of the protection component, the disconnection system comprising the preceding electrical disconnection device. According to preferred embodiments, the transient overvoltage protection device comprises one or more of the following characteristics: the disconnection system is thermal triggered; the disconnection system comprises a second electrical disconnection device which comprises a movable contact held in the closed position by at least one hot-melt welding which is intended to melt when the temperature of the protection component exceeds a detection threshold of the component component failure. protection, the movable contact being resiliently biased to an open position; and the first and second disconnecting devices are connected in parallel with each other and arranged so that the opening of the movable contact of the second disconnecting device causes the coordinated opening of the movable contact of the first disconnecting device; - At least one hot melt welding maintaining the movable contact in the closed position, which hot melt welding is provided to melt when the temperature of the protection component exceeds a detection threshold of the failure of the protection component. The invention also proposes a use of the above-mentioned transient overvoltage protection device to protect an electrical installation supplied with a continuous nominal voltage preferably greater than or equal to 500 V. According to one variant, the continuous nominal voltage is delivered by a photovoltaic installation . R: 130500A30564 ABBBI30564--101104 -About.doc - 04/11/10 - 12:11 - 5/23 Other features and advantages of the invention will appear on reading the detailed description which follows of the embodiments of FIG. the invention, given by way of example only and with reference to the drawings which show: FIG. 1, a diagram of a disconnection device according to a first embodiment; Figure 2 is a diagram of a disconnection device according to a second embodiment; Figure 3 is a diagram of a disconnection device according to a third embodiment; FIG. 4 is a circuit diagram of an installation of photovoltaic modules comprising a surge arrester comprising a breaking device according to the first embodiment; FIG. 5, a diagram illustrating an exemplary implementation of the thermal disconnection device of FIG. 4; Figure 6, a diagram illustrating another example of implementation of a thermal disconnection device of a surge arrester. The electrical disconnection device according to the invention comprises two fixed contacts distant from each other and a movable contact. The movable contact is capable of moving between a closed position and an open end position. In the closed position, the movable contact is in electrical contact with the two fixed contacts to electrically connect them. In the open end position, the movable contact is separated from at least one of the fixed contacts to electrically isolate the fixed contacts from one another. The device comprises at least one varistor for limiting the voltage between the fixed contacts during at least part of the path of the movable contact from the closed position to the open end position, but which is excluded a last part of this path. In other words, the at least one varistor does not have the effect of limiting the voltage on a last part of the path of the moving contact towards the open end position, that is to say from an intermediate position of the moving contact between the closed position and the open extremal position and the open extremal position itself. The device is designed in consideration of the maximum rated operating voltage and the maximum current to be interrupted. For these conditions of use, the at least one varistor and the at least part of the path during which the voltage is thus limited, are defined to prevent the creation of an electric arc between the fixed contacts during the passage of the contact. mobile from the closed position to the open extremal position. R: 130500A30564 ABBBI30564--101104 -About.doc - 04/11/10 - 12:11 - 6/23 Alternatively, for these same conditions of use, the at least one varistor and the at least part of the path during which the voltage is thus limited, are defined to limit the energy of the electric arc or arcs formed between the fixed contact (s) from which the mobile contact separates when the transition from the closed position to the open extremal position. In this case, it is advantageous that the at least one varistor and the at least part of the path during which the voltage is so limited, are defined so that the limitation of the energy of the electric arc or arcs is sufficient for it (s) to be extinguished (s) when the movable contact reaches the open extremal position.

The electrical disconnection device makes it possible to provide an effective electrical disconnection solution even for high DC voltages, in particular 500 V or more, while having a small footprint. As a result, such a device can be used in transient overvoltage protection devices to ensure, for example, the thermal disconnection of a varistor in the event of overheating thereof, while allowing the protection device to be housed in small cartridges designed to be mounted on standard DIN rail electrical panels. More generally, the electrical disconnection device of the invention is particularly suitable for disconnecting electrical circuits supplied with a DC voltage. In this case, the maximum rated operating voltage mentioned above is of a continuous nature. But the electrical disconnection device of the invention is also applicable to the disconnection of electrical circuits powered under an alternating voltage. In this case, it is possible to define a maximum nominal operating voltage of alternative nature for the same device, but which may be different - especially higher - than for the case of a DC voltage, since the extinction of the electric arcs is favored in the case of the AC voltages due to the periodic transition by the zero voltage. In order to define the at least one varistor and the at least part of the path during which the voltage is thus limited, the parameters influencing the creation and maintenance of or arcing such as the nature of the material are taken into account. contacts and the speed of movement of the moving contact. Of course, in the open end position, the movable contact is sufficiently distant from at least one of the two fixed contacts to avoid (re) creation of an electric arc between them at the maximum nominal voltage of use. Figure 1 shows a diagram of a disconnection device 10 according to the first embodiment of the invention. The disconnecting device 10 comprises a first fixed contact 12, a second fixed contact 14 and a contact R: 130500A30564 ABBBI30564--101104 -Disclaimer.doc - 04/11/10 - 12:11 - 7/23 mobile 16. The contact mobile 16 is able to move between an initial position and a final position. In the initial position, the movable contact is in electrical contact with the fixed contacts 12 and 14 and thus establishes an electrical connection between them: it is the closed position of the movable contact 16. In the final position, the moving contact 16 is separated from at least one of the two fixed contacts 12 and 14. This final position is the open end position of the movable contact 16. In the example of FIG. 1, the movable contact 16 is only separated from the fixed contact. 12, the opening of the disconnection device 10 being effected by pivoting of the movable contact 16 on the fixed contact 14 from the initial position to the final position. According to a preferred embodiment, the movable contact 16 and the fixed contact 14 are made in one piece, for example in the form of an elastic blade whose one end is held fixed which constitutes the fixed contact 14. In FIG. , the movable contact 16 is represented in solid lines in the closed position while the open end position is shown in dashed lines and referenced by the letter A. Intermediate positions of the movable contact 16 between the closed position and the open end position A are also These intermediate positions are not stable positions of the movable contact 16, but positions furtively occupied during the transition from the closed position to the open end position. They are shown only for the convenience of the description below. The disconnecting device 10 further comprises a varistor 18. A first pole of the varistor 18 is electrically connected to the fixed contact 12, for example, by welding. The varistor 18 has an arcuate surface which constitutes a second pole of the varistor 18. During its displacement from the initial position to the final position, the movable contact 16 separates from the fixed contact 12 and comes with an end in frictional contact with the arcuate surface of the varistor 18. The end of the movable contact 16 is continuously in frictional contact with the arcuate surface forming the second pole of the varistor 18 on at least a first portion of the path of the moving contact from the closed position to the open extremal position. Therefore, the varistor 18 is connected between the two fixed contacts 12, 14 via the moving contact 16. The varistor 18 is thus able to limit the voltage between the movable contact 16 and the fixed contact 12 and therefore by way of consequence between the two fixed contacts 12 and 14.

However, the end of the movable contact 16 sweeps the arcuate surface forming the second pole of the varistor 18. In other words, the location of the frictional contact on the arcuate surface changes with the displacement of the movable contact 16. As a result, the value at which the varistor 18 limits the voltage between the movable contact 16 and the fixed contact 12 increases as and when the moving the movable contact 16 on this first part of the path to the open end position. This variation of the limiting voltage is related to the increase in the constituent portion of the varistor 18 between the first pole and the second pole of the varistor 18 which is subject to the potential difference existing between the fixed contact 12 and the movable contact 16. The varistor 18 is advantageously designed so that the limitation voltage it imposes for any position of the movable contact 16 during at least part of its displacement between the closed position towards the open end position, is lower at the electric arc striking voltage between the fixed contact 12 and the movable contact 16 in the position considered, for the maximum current to be interrupted. Preferably, this property of the varistor 18 is verified as soon as the movable contact 16 is separated from the fixed contact 12 and this up to the position of the moving contact 16 from which the ignition voltage of the electric arc between the contact fixed 12 and the movable contact 16 exceeds the maximum nominal voltage of use. In this way, no electric arc is created between the fixed contact 12 and the movable contact 16 during the transition from the closed position to the open end position. Thus, when the movable contact 16 is at the intermediate position B, the limiting voltage imposed by the varistor 18 is less than the starting voltage of an electric arc between the movable contact 16 and the fixed contact 12. intermediate C, the movable contact 16 is further away from the fixed contact 12 than the intermediate position B. In this intermediate position C, the ignition voltage of an electric arc between the fixed contact 12 and the movable contact 16 is therefore greater than that at the position B and the limiting voltage imposed by the varistor 18 is also greater than that in the position B. The largest value of the limiting voltage imposed by the varistor 18 is at the intermediate position D after which the movable contact 16 is separated from the varistor 18. Therefore, when opening the movable contact 16, a current flows through the path formed by the fixed contact 14, the contact m obile 16, the varistor 18 and the fixed contact 12 as the movable contact 16 is in frictional contact with the varistor 18 and the limiting voltage imposed by the varistor 18 is lower than the voltage across the fixed contacts 12 and 14 As illustrated, it is preferable that the movable contact 16 ceases to be in contact with the second pole of the varistor 18 on a last part of the path of the moving contact to prevent it having to actively oppose the establishment. current when the moving contact is in the open end position. In this way, there is no risk that a leakage current likely to be established through the varistor 18 passes through the device in the disconnected position. R: 130500A30564 ABBBI30564--101104-Application.doc - 04/11/10 - 12:11 - 9/23 The variation curve of the limiting voltage imposed by the varistor 18 as a function of the location of the friction contact on its arcuate surface forming the second pole is preferably defined to avoid the creation of an electric arc between the movable contact 16 and the varistor 18 during the separation of the movable contact 16 with the varistor 18. In particular, the limiting voltage imposed by the varistor 18 at the last position of contact friction of the movable contact 16 on the varistor 18 before separating (the intermediate position D), is greater than the maximum nominal voltage of use. The disconnection, that is to say the interruption of current, takes place for the position of the movable contact 16 for which the limiting voltage imposed by the varistor 18 becomes greater than the voltage existing between the fixed contacts 12 and 14. Alternatively, this curve of variation of the limiting voltage is defined to ensure that the electric arc which is created between the movable contact 16 and the varistor 18 is extinguished when the movable contact 16 reaches the open end position. In this case, the disconnection is definitive only when the electric arc has gone out. This curve of variation of the limiting voltage imposed by the varistor 18 is obtained for example by choosing a suitable geometry for the varistor 18, in particular by appropriately defining the evolution of its section along its friction contact surface, that is, the arcuate surface in the example described. Many variants are possible for this first embodiment. According to a first variant, the movable contact 16 is not pivotally mounted, but is mounted in translation to move from a closed position to an open end position. In this case, the movable contact 16 may be provided to separate from the two fixed contacts 12 and 14 during passage to the open end position. The arcuate surface of the second pole of the varistor 18 is replaced by a flat surface against which the movable contact 16 comes into frictional contact while its first pole is connected to the fixed contact 12 as before. The operation remains the same as above, except to take into account the separation distance between the fixed contact 14 and the movable contact 16 which increases gradually during the passage of the movable contact 16 from the closed position to the open end position. Again, the varistor 18 limits the voltage between the two fixed contacts 12 and 14 during at least part of the path of the movable contact 16 from the closed position to the extreme open position, through the movable contact 16. Alternatively, it may also be provided a second varistor similar to the first, the second varistor being connected between the fixed contact 14 and the movable contact 16. R: 130500A30564 ABBBI30564--101104-Demande.doc - 04/11/10 - 12 According to another variant, the varistor 18 is integral with the movable contact 16 and thus moves with it. In this case, a first pole of the varistor 18 is connected to the movable contact 16 and it is the fixed contact 12 which comes into frictional contact with a surface of the varistor 18 forming a second pole thereby providing a variation of the voltage limiting the varistor when moving the moving contact. According to another variant, the varistor 18 is integral with the movable contact 16, but none of its poles is electrically connected to the moving contact 16. In this case, it may have two surfaces each forming a respective pole of the varistor 18. Each of the contacts fixed 12 and 14 comes into frictional contact with a respective one of the two pole surfaces of the varistor 18 during the displacement of the movable contact 16. The varistor 18 then directly limits the voltage between the two fixed contacts 12 and 14, and not more through the movable contact 16. In another variant, the varistor 18 is arranged at a distance from the movable contact 16 in the closed position. When the movable contact 16 leaves the closed position, an electric arc is likely to be created between the movable contact 16 and the fixed contact 12. The electric arc is extinguished as soon as the movable contact 16 comes into frictional contact with the surface arcuate forming the second pole of the varistor 18 because of the limitation voltage it imposes between the fixed contact 12 and the movable contact 16. The operation on the rest of the path of the movable contact 16 to the open end position is identical to that described previously. In this case, the varistor 18 does not prevent the creation of an electric arc, but allows its extinction.

FIG. 2 represents an electrical diagram of a disconnection device 20 according to a second embodiment. The description made of the first embodiment in relation with FIG. 1 also applies to this second embodiment, except for the varistor 18 which is replaced by another varistor 28. In particular, the fixed and movable contacts 12, 14 and 16 are similar to those of the first embodiment. Unlike the first embodiment, the varistor 28 does not include a surface forming a second pole to provide a variable limiting voltage depending on the location of the contact therewith. The varistor 28 is of a conventional type comprising two poles, one of which is connected to the fixed contact 12 and the other to a fixed contact 29 made in the form of an arcuate plate of conductive material. This arched fixed contact 29 is placed along a portion of the path of the end of the movable contact 16 as it passes from the closed position to the open end position. The end of the movable contact 16 thus comes into contact with friction with the arcuate contact 29 for this portion of the path. FIG. Therefore, the varistor 28 limits the voltage between the fixed contact 12 and the movable contact 16 during this portion of the path. The varistor 28 always applies the same limiting voltage regardless of the position of the friction contact of the movable contact 16 on the arcuate contact 29. The limiting voltage of the varistor 28 and the part of the path during which it is connected between the fixed contact 12 and the movable contact 16 are chosen to avoid the initiation of an electric arc under the maximum nominal operating voltage and the maximum current to be interrupted throughout the path of the movable contact from the closed position to the open end position . It is possible not to start an electric arc during the passage of the movable contact 16 from the closed position to the moment of coming into frictional contact with the arcuate contact 29 if the distance between the fixed contact 12 and the beginning of the arcuate surface 29 is small and the moving speed of the movable contact 16 is high.

Alternatively, the varistor 28 and the part of the path during which it is connected between the fixed contact 12 and the moving contact 16 are chosen to extinguish the electric arc that may be created between the fixed contact 12 and the moving contact 16 before the latter frictionally contacts the arcuate contact 29 and that the electric arc, if any, created between the arcuate contact 29 and the movable contact 16 after breaking the contact by friction between them, is extinguished when the moving contact 16 arrives at the position extremal open.

FIG. 3 represents an electrical diagram of a disconnection device 30 according to a third embodiment. This third embodiment is similar to the second embodiment described with reference to FIG. 2, except that it comprises several varistors V1, V2, V3, V4 and V5 instead of just one. One pole of each of the varistors is connected to the fixed contact 12 while the other pole is connected to a respective fixed contact P1, P2, P3, P4 and P5 each made in the form of an arcuate plate of conductive material. The end of the movable contact 16 successively comes into frictional contact with each of the arched contacts during the transition from the closed position to the open end position. Each of the varistors therefore limits the voltage between the fixed contact 12 and the movable contact 16 for a respective portion of the path of the movable contact between the closed position and the open end position.

The limiting voltage imposed by each of the varistors can be advantageously chosen different from those of the others. More precisely, the limiting voltage is chosen higher as the greater distance of the respective arcuate contact relative to the fixed contact 12 is moved away. Application.doc - 04/11/10 - 12:11 - 12/23 is possible to approach the operating mode of the first embodiment described with reference to FIG. 1, except to have a progression in steps of the value of the limiting voltage and interstices without voltage limitation on the path of the movable contact 16 between the closed position and the open end position. The limiting voltage of each varistor and the part of the path during which it is connected between the fixed contact 12 and the movable contact 16 are chosen as before to prevent the initiation of an electric arc at the maximum nominal voltage for the maximum current. to interrupt or alternatively to ensure that the electric arc or arcs created - whether between the fixed contact 12 and the movable contact 16 or between each of the arcuate contacts and the movable contact 16 - are extinguished when the movable contact 16 reaches the position extremal open.

FIG. 4 represents an electrical diagram of a photovoltaic installation producing electrical energy from sunlight or the like. The installation includes photovoltaic panels 60 producing electricity from the light. The photovoltaic panels 60 produce an electric current under the same DC voltage, for example a voltage of 1000V, whatever the sunlight. The current generated by the photovoltaic panels 60 is provided on two lines 62 and 64 which serve to supply electrical installations (not shown). In the case of installations operating on alternating current, the photovoltaic panels 30 supply them via an inverter 70 to transform the direct current into alternating current having the required voltage level.

A transient overvoltage protection device 40, also called surge arrester, is connected to the power lines 62, 64 under direct voltage, as well as to earth. The arrester 40 comprises two terminals 42, 44 for connecting the surge arrester 40 to the power lines 62, 64 and a third terminal 52 to connect the surge arrester 40 to the ground.

The arrester 40 comprises two varistors 46, 48 and a spark gap 50. In known manner, the two varistors 46, 48 serve to maintain the voltage between the lines 42 and 44 below a certain level in the event of a thunderbolt or other electrical disturbance so as not to damage the electrical installations connected to the lines 62, 64 while the spark gap 50 serves to evacuate the lightning currents or the like to the ground. Each varistor 46, 48 has two poles, one of which is connected to a respective one of the two terminals 42, 44. The other pole of each varistor 46, 48 is connected to each other. 04/11/10 - 12:11 - 13/23 at the same pole of the spark gap 50 while the other pole of the spark gap 50 is connected to the third terminal 52. The arrester 40 is provided with disconnection systems varistors in case of failure thereof by short circuit or by thermal runaway.

Thus, the arrester 40 comprises a respective fuse 46A, 48A in series with each varistor 46, 48. The fuses 46A, 48A are both calibrated to melt in the event of a short circuit of the corresponding varistor and not to melt in case shock current (such as a lightning current) not exceeding the limits for which surge arrester 40 is provided. However, the short circuit current depending on the sun, it may be too weak to melt the respective fuse 46A or 48A and therefore it does not cause a sufficiently fast disconnection of the corresponding varistor. Fuses 46A, 48A also do not provide disconnection in case of thermal runaway of the corresponding varistor related to a leakage current thereof which is insufficient to melt. In these two cases, the disconnection is ensured by the thermal disconnection system described below. Alternatively, the fuses 46A, 48A may be replaced by other disconnection systems in the event of a short circuit, for example a circuit breaker. Alternatively, the fuses 46A, 48A are omitted, protection against short circuits being provided by the thermal disconnection system. This is possible because a short-circuit has the effect of causing thermal heating which can trigger the thermal disconnection system. The arrester 40 comprises a respective thermal disconnection system for each of the varistors 46, 48. The thermal disconnection system for each of the varistors 46, 48 is identical. Therefore, only that of the varistor 46 is described in detail below, its description also valid for that of the varistor 48. The disconnection system of the varistor 46 comprises a first electrical disconnection device 54 which is thermal trigger. This first device comprises a normally closed mobile contact arranged in series between two fixed contacts. One of the fixed contacts and the movable contact may be in one piece, for example an elastic blade whose one end is held fixed. This first disconnect device is connected in series with the varistor 46. Its movable contact is, at rest, kept in the closed position and goes to the open state when the temperature of the varistor 46 exceeds a temperature threshold. This temperature threshold is generally between 115 ° C. and 150 ° C. This first disconnection device may be of a type known per se. For example, its movable contact is elastically biased towards the opening and is kept closed by a low-temperature hot-melt weld R: 130500A30564 ABBBI30564--101104 -Object.doc - 04/11/10 - 12:11 - 14/23 This hot-melt welding is in thermal connection with the varistor 46, for example, by serving to maintain one end of the movable contact in electrical contact with an electrode of a pole of the varistor 46. In the event of overheating of the varistor 46, the hot melt weld melts and the movable contact moves to the open position. For example, the movable contact may be constituted by a prestressed elastic blade in the normally closed position, one end of the blade being held fixed to form one of the two fixed contacts of the first disconnecting device. The movable contact can also be kept in the closed state by a respective hot-melt welding on each of the fixed contacts of the first disconnecting device, for example in the case where the movable contact is constituted by a bridge of conductive material which is resiliently biased by a spring. The disconnection system of the varistor 46 also comprises a second electrical disconnection device which is according to the invention. In the example shown, this second disconnecting device is according to the first embodiment described with reference to FIG. 1, for which reason it is referenced 10, but it may be any other embodiment of the invention. disconnection device according to the invention. This second disconnection device is connected in parallel with the first disconnection device. The second disconnecting device 10 is also in the normally closed state. The thermal disconnection system of the varistor 48 similarly comprises a second disconnecting device according to the invention, but this is not shown in Figure 4 for convenience. The varistor 16 is therefore connected to the lines 63, 64 both through the first and second disconnecting devices 54 and 10. The opening of the second disconnecting device 10 is coordinated with the opening of the first disconnector 54 to avoid the formation of arcing between the movable contact and the fixed contacts of the first disconnector 54 and between the movable contact and the fixed contacts of the second disconnecting device 10, or so that the electric arc or arcs susceptible to be created between them are extinguished when they arrive in their respective open extremal position. The operation of the second disconnection device 10 to achieve this effect has been described above. This effect is also obtained for the first disconnecting device 54 due to the parallel connection of the second disconnector device 10 to the first and appropriate coordination of the opening of the two. Indeed, due to the parallel connection, the voltage across the first disconnector 54 remains zero as the first disconnection device R: 130500A30564 ABBBI30564--101104-Application.doc - 04/11/10 - 12:11 - 15/23 10 is closed and the voltage limitation imposed by the varistors or varistors of the second disconnecting device during the movement of its movable contact from the closed position to the open end position is found between the fixed contacts of the first disconnecting device 54. Therefore, it is sufficient to adequately coordinate the passage of the movable contact of the first disconnector 54 from the closed position to the open position with the passage of the movable contact of the second disconnector 10 from the closed position to the open position to get this effect. In the simplest cases, the coordination consists in causing the opening of the second disconnection device 10 only when the moving contact of the first disconnector device 54 has reached either its open end position or an intermediate position sufficiently distant from the contact (s). fixed to prevent the initiation of an electric arc. Thus, in the event of a thermal runaway of the varistor 46, the hot-melt weld (s) of the first disconnect device 54 melt and cause the opening of its movable contact and thus also the coordinated opening of the second disconnecting device 10. It results in an effective disconnection of the varistor 46 without creating an electric arc or by ensuring the extinction of the arcs or arcs possibly created.

FIG. 5 schematically illustrates such a method of coordinating the second disconnecting device 10 with the first disconnector device 54. The first disconnecting device 54 comprises a movable contact 54a secured to a pivoting axis 54c. The movable contact 54a is held in closed contact by a hot-melt weld 13 on a pole of the varistor 46. The movable contact 54a is prestressed towards the open position by a spring 54d. The movable contact 16 of the second disconnecting device 10 is secured to a pivoting axis 16c which is electrically connected to the aforementioned pole of the varistor 46. The coordination is obtained by the cooperation of two arm 16b, 54b shaped `L '. The arm 54b is integral with the movable contact 54a, the arm 54b being in this case mounted on the pivoting axis 54c. The arm 16b is integral with the movable contact 16. A spring 16b urges the contact 16 towards the opening, in this case by pushing on the arm 16b. As long as the hot melt welding 13 is intact, the movable contacts 54a and 16 are closed, the movable contact 16 being held in closed position by the arm 54b which cooperates with the arm 16b. After fusion of the hot melt weld 13 (due to the overheating of the varistor 46), the movable contact 54a and the arm 54b pivot under the action of the spring 54d. After a certain degree of pivoting, the arm 54b releases the arm 16b. From that moment, the movable contact 16 moves towards the open position under the action of the spring 16d.I1 is advantageous for the system of R: 130500A30564 ABBBI30564--101104-Application.doc - 04/11 / 10 - 12:11 - 16/23 thermal disconnection of a varistor to include two disconnect devices as described above. On the one hand, the first disconnector 54 makes it possible to effectively discharge the shock currents by essentially crossing the first disconnection device because of the low resistance opposed by the hot-melt weld or seals maintaining its moving contact compared to the simple support of the movable contact on a fixed contact in the second disconnecting device 10. Thus, it avoids the risk of damage to the second disconnection device 10 by the shock currents. On the other hand, since it is not the moving contact of the first disconnector 54, but that of the second disconnecting device 10 which provides a frictional contact to make contact with the voltage limiting varistor (s) during the transition from the closed position to the open position, this prevents the material of the hot-melt weld or welds - after melting - of the first disconnector device 54 to pollute these contact surfaces by friction.

Alternatively, the thermal disconnection system comprises only an electrical disconnection device according to the invention. This case is illustrated schematically in FIG. 6. In this case, its movable contact 16 is held in the closed position by a heat-fusible weld 13 intended to melt when the temperature of the varistor exceeds a threshold which is indicative of a failure thereof. this. As a variant, two hot-melt welds may be used if the movable contact forms a bridge movable with respect to the two fixed contacts 12, 14. The movable contact 16 is also biased towards the extreme opening position by any appropriate means, for example example a spring 17 or its intrinsic elasticity. However, it is preferable in this case that the portion 16a of the movable contact 16 which ensures the frictional electrical contact to make contact with the varistors or varistors during its movement, is remote from the part or parts of the movable contact on which are placed the hot melt welds, in this case the weld 13. In this way, it avoids or minimizes the risk of pollution of the contact surfaces by friction with the weld material after melting during the displacement of the movable contact. In the example shown, the fixed contact 12 is constituted by the connection pad of the varistor 46 which preferably comes from material with an electrode 246 of the varistor 46, its other electrode being referenced 146. The set of components of the device transient overvoltage protection 40 are preferably housed in the same housing on which the connection terminals 42, 44 and 52 are accessible. This housing can be advantageously sized and designed to be mounted on the DIN rails of standardized electrical panels. As such, the transient overvoltage protection device R: 130500A30564 ABBBI30564--101104-Application.doc - 04/11/10 - 12:11 - 17/23 can be housed in an interior volume cartridge having for maximum dimensions 30x42x43 mm. Furthermore, the thermal disconnection system described above can be used in other transient overvoltage protection devices, for example which has only one varistor 46 or which has no spark gap. It can also be used in transient overvoltage protection devices to protect AC voltage lines. More generally, the electrical disconnection devices according to the invention can be used in various applications, whenever it is desirable to avoid the creation of an electric arc upon disconnection or at least to ensure its extinction, and particularly advantageous in the case of applications operating under DC voltage. They are particularly suitable for applications requiring a single disconnection.

Of course, the present invention is not limited to the examples and to the embodiment described and shown, but it is capable of numerous variants accessible to those skilled in the art. R: 130500A30564 ABBBI30564--101104-Request.doc - 04/11/10 - 12:11 - 18/23

Claims (4)

REVENDICATIONS1. Electrical disconnect device (10), comprising CLAIMS. Electrical disconnection device (10), comprising: - two fixed contacts (12, 14) spaced from each other, - a movable contact (16) optionally forming a single piece with one of the two fixed contacts, the mobile contact being able to move between: a closed position in which the movable contact is in electrical contact with the fixed contacts to electrically connect them to each other, and an open end position in which the movable contact is separated from at least one of the fixed contacts for electrically isolating the fixed contacts from each other; at least one varistor (18; 28; V1 ... VS) for limiting the voltage between the fixed contacts (12; 14) during at least part of the path of the movable contact from the closed position to the open end position excluding one last part of the journey. An apparatus according to claim 1, wherein the at least one varistor is disconnected from at least one of the fixed contacts (12; 14) during a last portion of the moving contact path from the closed position to the open end position. Device according to claim 1 or 2, wherein the at least one varistor is arranged to limit the voltage between the two fixed contacts via the movable contact. Device according to any one of claims 1 to 3, wherein the at least one varistor is provided to continuously limit the voltage between the fixed contacts during the path of the movable contact from the closed position to the beginning of said last part of the path, the at least one varistor limiting said voltage to a value which increases with the distance of the movable contact from the closed position. R: 130500A30564 ABBBI30564--101104-Application.doc - 04/11/10 - 12:11 - 19/23 1. 15 20 2. 25 3. 30 A device according to claim 4, wherein at least one of the stationary contacts and the movable contact is in electrical frictional contact with a pole surface of the at least one varistor (18), moving the movable contact. from the closed position at least to the beginning of said last portion of the path causing a correlative displacement of said electrical contact by friction on said surface to increase the value at which the at least one varistor limits the voltage between the fixed contacts. Device according to claim 5, in which: - it is the movable contact (16) which is in frictional electrical contact with said pole surface of the at least one varistor, - the moving contact is kept in electrical contact with the one of the fixed contacts (14) when the moving contact moves from the closed position to the open position, the at least one varistor having another pole connected to the other fixed contact (12). Device according to any one of claims 1 to 3, wherein the at least one varistor (28) has at least one pole electrically connected to one of the fixed contacts and the movable contact by means of an electrical contact. by friction during a portion of the path of the moving contact to limit the voltage between the fixed contacts to a predetermined value during this portion of the path of the moving contact. Device according to claim 7, in which: - it is with the movable contact (16) that a pole of the at least one varistor is in electrical contact by friction, and - the moving contact is kept in electrical contact with the one of the fixed contacts (14) when the moving contact is moving on said part of the path of the moving contact, the at least one varistor having another pole connected to the other fixed contact (12). Device according to claim 7 or 8, comprising a plurality of such varistors (V 1 ... V5), each being provided for limiting the voltage between the fixed contacts to a respective predetermined value during a respective portion of the path of the moving contact. A: 130500A30564 ABBBI30564--101104-Request.doc - 04/11/10 - 12:11 - 20/235. An apparatus according to any one of claims 1 to 9, comprising resilient means for constraining movement of the movable contact from the closed position towards the open extremal position. Use of an electrical disconnection device according to any one of claims 1 to 10 for disconnecting an electrical circuit from a supply of continuous nominal voltage greater than or equal to 500 V. Transient overvoltage protection device, comprising: - at minus an overvoltage protection component, preferably a varistor (46); and a system for disconnecting the protection component in the event of a failure of the protection component, the disconnection system comprising an electrical disconnection device (10) according to any one of claims 1 to 10. Device according to claim 12, in which which the disconnection system is thermal trip. Device according to claim 12 or 13, wherein: - the disconnection system comprises a second electrical disconnection device (54) which comprises a movable contact held in closed position by at least one hot melt welding which is intended to melt when the temperature of the protection component exceeds a detection threshold of the failure of the protection component, the movable contact being elastically prestressed to an open position; and - the first and second disconnecting devices are connected in parallel with each other and designed so that the opening of the moving contact of the second disconnecting device (54) causes the coordinated opening of the movable contact of the first disconnecting device (10). 15. Device according to claim 12 or 13, comprising at least one hot-melt weld maintaining the movable contact (16) in the closed position, which hot-melt weld is provided to melt when the R: 130500A30564 ABBBI30564--101104 -Application.doc - 04 / 11/10 - 12:11 - 21 / 23The protective component temperature exceeds a detection threshold of the protection component failure. 16. Use of a transient overvoltage protection device according to any one of claims 12 to 15 for protecting an electrical installation supplied with a continuous nominal voltage preferably greater than or equal to 500 V. 17. Use according to claim 16 , in which the DC rated voltage is delivered by a photovoltaic system. 8: 130500/30564 ABBB / 30564--101104-Application.doc - 04/11/10 - 12:11 - 22/23