EP3699942B1 - Operating system for a vacuum bulb - Google Patents

Description

Technical field of the invention

The present invention relates to a system for actuating a vacuum interrupter for the purpose of opening an electrical circuit in an electrical device of medium voltage or high voltage, that is to say an apparatus operating at a voltage greater than 1000V.

The invention also relates to an electrical device comprising such an actuation system for at least one of its phases. In this document, the term electrical device interchangeably includes several types of devices such as a switch, a circuit breaker, a contactor, a fuse switch, a recloser, a disconnector, etc.

State of the art

A medium voltage or high voltage electrical device of the type described in the document EP2182536 comprises a vacuum interrupter which is placed not in the main circuit comprising the main switch of one phase of the apparatus, but in a parallel branch of this main switch. When the main switch is closed, therefore, no current flows into the vacuum interrupter. This is only requested during an opening operation of the main circuit, with the aid of a main switch opening mechanism which first makes it possible to switch the current from the main circuit to the bypass, this allows the main switch to be opened while the current is flowing fully through the vacuum interrupter. This is then opened in turn by the opening mechanism.

Thanks to this architecture, the vacuum interrupter receives a current only during the opening phase of the main phase circuit, and not when the main switch is closed. In addition, the bulb is not stressed during a closing operation of the main circuit and it does not have to withstand any short-circuit current either, in particular when the electrical appliance is a switch. It just needs to be able to withstand a transient recovery voltage TTR (or Transient Recovery Voltage - TRV) after the power is cut in the main circuit.

As a result, the vacuum interrupter can advantageously be simplified and made of a much smaller size compared to a conventional architecture in which the vacuum interrupter would be placed in the main circuit of the electrical apparatus.

In addition, the opening mechanism which makes it possible to switch the current from the main circuit to the bypass and then to open the vacuum interrupter placed in the bypass must be very precise and reproducible to ensure on the one hand that, for each phase, the vacuum interrupter is only opened correctly once the main switch is already sufficiently open so as not to risk an electric arc on the main switch by re-ignition or re-ignition under the effect of voltage TTR, and on the other hand that the vacuum interrupters of the different phases of the device are open simultaneously.

The document EP3300097 already describes such an opening mechanism. It comprises in particular a device for driving the mobile electrode of the vacuum interrupter. This drive device is actuated by the movable contact of the main switch using a movable paddle. The drive device then drives the movable electrode to the open position, via an adjusting nut to precisely adjust the movement of the movable electrode. This training device however comprises a certain number of small mechanical parts which require precise adjustments to obtain good reproducibility of the system.

Furthermore, one of the challenges of such an actuation system is to achieve performance in accordance with the standards in force for the devices concerned. Another issue is to minimize the number of requests for the vacuum interrupter. Indeed, during a cut in the main circuit of the electrical appliance having such an actuation system, the vacuum interrupter should preferably open only if there is really an active load in the main circuit and that the current exceeds the breaking capacity of the main moving contact. This also avoids opening the vacuum interrupter systematically at each opening movement even in the absence of main current, which advantageously reduces its use and further simplifies its design.

Moreover, even if the main circuit is cut while there is no or little main current, there may nevertheless remain in some cases capacitive charges in the cables downstream of the electrical device, and the fact that the vacuum interrupter does not open in such a case, makes it possible to reduce the dielectric stresses linked to the capacitive loads.

The document WO 2016/169826 A1 describes a system for actuating a vacuum interrupter of an electrical appliance according to the preamble of claim 1.

One of the aims of the invention is therefore to find a simple, reliable and economical system which, on the one hand, makes it possible to avoid the constraints of precise mechanical adjustments of the parts involved in the opening of a vacuum interrupter placed in bypass. of a main circuit of an electrical appliance, and which on the other hand makes it possible to minimize the number of openings of the vacuum interrupter by opening only if necessary, that is to say only if the current flowing in the main circuit of the electrical appliance is greater than a predetermined threshold, corresponding for example to the breaking capacity of the main contact.

Disclosure of the invention

• un contact de dérivation qui est connecté à un contact mobile du circuit principal lors d'un mouvement d'ouverture de l'appareil électrique,
• un électroaimant dont la bobine est raccordée entre l'électrode mobile et le contact de dérivation, et dont le noyau est mécaniquement lié à l'électrode mobile, de sorte que le noyau entraîne l'électrode mobile vers la position ouverte seulement quand la valeur du courant qui traverse la bobine atteint un seuil prédéterminé.

For this, the invention describes a system for actuating a vacuum interrupter of an electrical device, the vacuum interrupter being connected by branching from a main circuit of a phase of the electrical apparatus and comprising a movable electrode and a fixed electrode, the movable electrode being movable between a closed position in which the two electrodes are in contact with each other and an open position in which the two electrodes are separated. The actuation system includes:

• a bypass contact which is connected to a movable contact of the main circuit during an opening movement of the electrical device,
• an electromagnet whose coil is connected between the movable electrode and the bypass contact, and whose core is mechanically linked to the movable electrode, so that the core drives the movable electrode to the open position only when the value of the current flowing through the coil reaches a predetermined threshold.

According to one characteristic, the core drives the movable electrode towards the open position when the current passes through the coil for at least a predetermined time.

According to another characteristic, the core is mechanically linked to the mobile electrode by means of a buffer device.

According to another characteristic, the buffer device comprises a pusher connected to the core and cooperating with a drive part connected to the movable electrode.

According to another characteristic, during the opening movement of the electrical device, the pusher drives the drive part after having first made a distance D between the pusher and one side of the drive part. Said predetermined duration is determined by the distance D.

According to another characteristic, the actuation system comprises an electronic circuit placed as a bypass from the coil and comprising an electronic switch, so that the electronic switch is in the closed position and bypasses the coil as long as the value of the current flowing through the coil. electronic circuit does not reach the predetermined threshold.

According to another characteristic, the actuation system also comprises a short-circuit device which short-circuits the coil on itself when the vacuum interrupter is in the open position.

The invention also describes an electrical device comprising at least one main phase switch and a vacuum interrupter placed bypassing the main phase switch, and comprising such a system for actuating the vacuum interrupter.

In the case of a multiphase electrical device (for example three-phase) therefore having a main switch for each of the phases, the device preferably comprises a vacuum interrupter bypassing each main switch and therefore a system for actuating the bulb. empty for each phase.

Brief description of the figures

• [FIG.1] la figure 1 représente, en position fermée, un schéma simplifié d'un premier mode de réalisation du circuit interrupteur d'une phase d'un appareil électrique avec un système d'actionnement selon l'invention,
• [FIG.2] [FIG.3] [FIG.4] [FIG.5] [FIG.6] les figures 2 à 6 montrent le système d'actionnement de la figure 1, durant les différentes étapes successives du mouvement d'ouverture du circuit interrupteur,
• [FIG.7] la figure 7 représente, en position fermée, un schéma simplifié d'un autre mode de réalisation du système d'actionnement selon l'invention.

Other characteristics will appear in the following detailed description given with reference to the appended drawings in which:

• [ FIG. 1 ] the figure 1 shows, in the closed position, a simplified diagram of a first embodiment of the switch circuit of a phase of an electrical device with an actuation system according to the invention,
• [ FIG. 2 ] [ FIG. 3 ] [ FIG. 4 ] [ FIG.5] [FIG.6 ] the figures 2 to 6 show the actuation system of the figure 1 , during the various successive stages of the opening movement of the switch circuit,
• [ FIG. 7 ] the figure 7 shows, in the closed position, a simplified diagram of another embodiment of the actuation system according to the invention.

detailed description

The figure 1 shows a switch circuit of a phase of an electrical appliance comprising a main circuit 10, a main fixed contact 12 and a main movable contact 14 (also called the movable knife 14 below).

The switch circuit also comprises a branch circuit 11 which is connected in parallel with the main circuit 10, between an upstream connection point 15 and a branch contact 13. This branch circuit 11 comprises a vacuum interrupter 20 having a fixed electrode 21 conductive (also called fixed rod) and a movable conductive electrode 22 (also called movable rod).

In the closed position of the main circuit 10, the movable knife 14 is in contact only with the main contact 12 and allows current to flow through the main circuit. No current therefore passes through the branch circuit 11. The opening movement of the main circuit 10 takes place in several successive stages. During a first step, the movable knife 14 comes into contact with the bypass contact 13 while also remaining in contact with the main contact 12, as indicated in figure 2 . Then in a following step, the movable knife 14 separates from the main contact 12 and remains in contact with the bypass contact 13, as indicated in the figures 3 and 4 . Then in a last step, to reach the open position of the main circuit 10, the movable knife 14 also separates from the bypass contact 13, as shown in figure 5 .

Optionally, for example in the case of a three-position phase switch, the switch circuit could also include an earthing contact (not shown in the figures) that the movable knife 14 would reach at the end of the open position.

The electrode 22 of the vacuum interrupter 20 is movable along a longitudinal axis X between a closed position in which the two electrodes 21, 22 are in contact with each other and an open position in which the two electrodes 21 , 22 are separated. The fixed electrode 21 is connected with the upstream connection point 15. Conventionally, the vacuum interrupter 20 also comprises a return spring (not shown in the figures) to effect the closing movement of the ampoule, c 'that is to say return the movable electrode 22 to its closed position.

According to the invention, the vacuum interrupter actuation system comprises an electromagnet having an excitation coil 30 surrounding a metallic movable core 31 which is actuated when a current passes through the coil 30. The coil 30 is connected to it. '' one side to the bypass contact 13 and the other side to the movable electrode 22 at a so-called intermediate connection point 24 (see figure 2 ). Thus, the coil 30 receives current if the vacuum interrupter is in the closed position and if the movable knife 14 is in contact with the bypass contact 13. In the presence of current in the coil, the core moves along the longitudinal axis X in the direction of the opening of the vacuum interrupter 20. In the absence of current in the coil 30, a return spring (not shown in the figures) returns the core 31 to an initial rest position.

The movable core 31 of the electromagnet is mechanically linked to the movable electrode 22, such that it drives the movable electrode 22 towards the open position when a sufficient current flows in the coil 30. According to one embodiment , this mechanical connection is made by means of a buffer device 25 which is designed so that the core 31 effectively drives the movable electrode 22 only when a sufficient current, greater than a predetermined threshold, has flowed in the coil 30 for a predetermined duration, so as to confer sufficient kinetic energy on the mobile core. The intermediate connection point 24 is located between the mobile electrode 22 and this buffer device 25. The conductor which connects the intermediate connection point 24 to the coil 30 can be flexible to facilitate the movement of the mobile electrode 22.

According to the embodiment presented in the figures 2 to 6 , the buffer device is of mechanical design and comprises a pusher 26 connected to the core 31 and a drive part 27 connected to the movable electrode 22 which cooperates with the pusher 26. The drive part 27 is for example rectangular in shape. and comprises a first transverse side 28 and a second transverse side 29 opposite, forming a space in which is housed one end of the pusher 26. The first transverse side 28 is connected to the movable electrode 22. The second transverse side 29 is recessed in its middle to allow the pusher 26 to slide along the longitudinal axis X relative to the part 27.

1. a) En figure 1, correspondant à la position fermée du circuit principal 10, le couteau 14 est déconnecté du contact de dérivation 13. Donc, aucun courant ne circule dans la bobine 30. Le noyau 31 est rappelé dans sa position repos par son ressort de rappel, le poussoir 26 n'est pas en contact avec le second côté transversal 29 mais s'en trouve éloigné d'une certaine distance D.
2. b) En figure 2, le couteau mobile 14 entre en contact avec le contact de dérivation 13 et l'ampoule à vide 20 est toujours fermée. Le circuit de dérivation passant par l'ampoule à vide 20 et la bobine 30 est donc désormais alimenté. Néanmoins, tant que le couteau mobile 14 reste en contact avec le contact principal 12, le courant continue de passer principalement dans le circuit principal 10, à cause de l'impédance de la bobine 30.
3. c) En figure 3, le couteau mobile 14 continue son mouvement et quitte le contact principal 12 pour ne rester connecté qu'avec le contact de dérivation 13. Le courant passe donc désormais dans le circuit de dérivation. La bobine 30 est alimentée et va être capable d'entraîner le noyau 31. Quand le noyau 31 commence son déplacement pour effectuer un mouvement d'ouverture, il entraîne le poussoir 26 qui va commencer par parcourir la distance D avant d'entrer en contact avec le second côté transversal 29. Donc le poussoir 26 n'entraîne pas encore la pièce d'entraînement 27 ce qui fait que, tant que la distance D n'est pas franchie, l'ampoule à vide 20 reste fermée, ce qui est le cas dans la figure 3.
   On voit ainsi que s'il n'y a pas de courant circulant dans le circuit principal 10 lors de l'ouverture du circuit principal, le poussoir 26 ne bouge pas et l'ampoule à vide 20 n'est avantageusement pas actionnée, ce qui limite son utilisation aux cas où c'est nécessaire.
   De plus, la distance D fournit avantageusement un seuil qui joue un rôle de tampon permettant de s'assurer que le courant circule dans la bobine 30 de l'électroaimant avec une intensité suffisante et pendant un temps suffisant avant de commencer l'ouverture de l'ampoule à vide 20. La bobine 30 de l'électroaimant et la valeur de la distance D, qui est par exemple de l'ordre de quelques millimètres, sont configurés pour :
   1. i) s'assurer que l'ampoule à vide 20 ne s'ouvre pas tant que le couteau mobile 14 ne s'est pas éloigné suffisamment du contact principal 12,
   2. ii) définir un seuil de courant prédéterminé, par exemple de l'ordre de 30 A correspondant au pouvoir de coupure du couteau mobile 14, avant de commencer le mouvement d'ouverture de l'ampoule à vide. De plus, il faut préférentiellement que ce courant suffisant circule aussi durant une durée suffisante. En effet, on veut éviter que l'électrode mobile 22 démarre son mouvement d'ouverture sans pouvoir aller rapidement jusqu'en position ouverte, ce qui pourrait arriver si le courant circule dans la bobine 20 avec une amplitude faible ou seulement pendant un temps très court, par exemple à cause d'éventuelles impulsions de courant générées par des charges capacitives à vide lors d'une ouverture du circuit principal.
   
   La distance D permet donc de garantir un effet de seuil en deçà duquel le contact mobile de l'ampoule ne bouge pas, et au-delà duquel le contact mobile terminera complètement son mouvement d'ouverture.
   Par ailleurs, l'effort du ressort de rappel de l'électrode mobile 22 et du ressort de rappel du noyau, l'inertie mécanique des différentes pièces et la différence de pression entre la pression dans l'environnement externe de l'ampoule et le vide de l'ampoule, font que le courant circulant dans la bobine 30 doit être suffisamment élevé pour vaincre ces différents efforts mécaniques et effectuer le mouvement d'ouverture.
4. d) En figure 4, la distance D a été franchie, le poussoir 26 et le second côté transversal 29 sont donc en contact, et le noyau mobile 31 entraîne désormais le dispositif tampon 25 et l'électrode mobile 22, provoquant l'ouverture de l'ampoule à vide.
   Lorsque l'électrode mobile 22 se séparera de l'électrode fixe 21, le courant circulant dans la bobine 30 va cependant cesser quand il n'y aura plus d'arc dans l'ampoule et le noyau mobile 31 ne sera plus maintenu. Néanmoins, l'électroaimant est conçu, notamment grâce à sa propre inductance, pour se décharger suffisamment lentement de façon à ce que le noyau mobile 31 puisse maintenir l'ampoule à vide 20 ouverte suffisamment longtemps après que le couteau mobile 14 se sépare du contact de dérivation 13.
5. e) De plus, l'invention prévoit optionnellement un dispositif de mise en court-circuit de la bobine 30 de l'électroaimant. Ce dispositif prévoit un contact de fin d'ouverture 32 qui est mécaniquement et électriquement lié au noyau mobile 31. En position fermée de l'ampoule à vide, le contact 32 n'est pas raccordé. En fin de position ouverte représentée en figure 5, le contact de fin d'ouverture 32 vient en contact avec une borne de fin d'ouverture 16 laquelle est reliée au contact de dérivation 13 et donc à une extrémité de la bobine 30. Dans cette configuration, les éléments 26 et 27 sont réalisés en matériau conducteur, par exemple en métal. Pour améliorer le contact électrique, des pastilles de contacts peuvent bien sûr être prévues sur les parties du poussoir 26 et du second côté transversal 29 qui sont en contact les unes avec les autres durant le mouvement d'ouverture. Par ailleurs, pour assurer un bon contact électrique entre le contact 32 et la borne 16, on peut évidemment utiliser un mécanisme de ressort de pression de contact classique.
   Ainsi, comme indiqué en figure 5, ce dispositif de mise en court-circuit a pour effet de court-circuiter le circuit d'alimentation de la bobine 30, lorsque l'ampoule à vide 20 est en position ouverte. En effet, le circuit d'auto alimentation de la bobine 30 est le suivant : borne de fin d'ouverture 16, bobine 30, point de connexion intermédiaire 24, poussoir 26, noyau 31, contact de fin d'ouverture 32. Grâce à ce dispositif, on rallonge le maintien de l'ampoule à vide 20 en position ouverte et stable (environ 1 seconde avec le dispositif au lieu de 200-300 msec) avant que, sous l'effet de son ressort de rappel, le noyau mobile 31 revienne à sa position initiale et l'électrode mobile 22 referme l'ampoule à vide 20.
6. f) la figure 6 montre la position finale du mouvement d'ouverture du circuit principal, à savoir circuit principal ouvert et retour de l'ampoule à vide 20 dans sa position fermée, lorsque l'action du ressort de rappel du noyau 31 est supérieure à la force d'ouverture de l'électroaimant sous l'action du courant résiduel circulant dans la bobine 30. Le contact de fin d'ouverture 32 est alors séparé de la borne de fin d'ouverture 16 et le poussoir 26 se trouve de nouveau à une distance D du second côté transversal 29.

During the opening of the main circuit 10, the operating sequence of the actuation system is then as follows:

1. a) In figure 1 , corresponding to the closed position of the main circuit 10, the knife 14 is disconnected from the bypass contact 13. Therefore, no current flows in the coil 30. The core 31 is returned to its rest position by its return spring, the pusher 26 is not in contact with the second transverse side 29 but is away from it by a certain distance D.
2. b) In figure 2 , the movable knife 14 comes into contact with the bypass contact 13 and the vacuum interrupter 20 is still closed. The branch circuit passing by the vacuum interrupter 20 and the coil 30 is therefore now supplied. However, as long as the movable knife 14 remains in contact with the main contact 12, current continues to flow mainly through the main circuit 10, due to the impedance of the coil 30.
3. c) In figure 3 , the movable knife 14 continues its movement and leaves the main contact 12 to remain connected only with the bypass contact 13. The current therefore now flows in the bypass circuit. The coil 30 is powered and will be able to drive the core 31. When the core 31 begins its movement to perform an opening movement, it drives the pusher 26 which will begin by traveling the distance D before coming into contact. with the second transverse side 29. Therefore the pusher 26 does not yet drive the driving part 27 so that, as long as the distance D is not crossed, the vacuum interrupter 20 remains closed, which is the case in the figure 3 .
   It can thus be seen that if there is no current flowing in the main circuit 10 when the main circuit is opened, the pusher 26 does not move and the vacuum interrupter 20 is advantageously not actuated, this which limits its use to cases where it is necessary.
   In addition, the distance D advantageously provides a threshold which acts as a buffer making it possible to ensure that the current flows in the coil 30 of the electromagnet with sufficient intensity and for a sufficient time before starting to open the l. 'vacuum interrupter 20. The coil 30 of the electromagnet and the value of the distance D, which is for example of the order of a few millimeters, are configured for:
   1. i) make sure that the vacuum interrupter 20 does not open until the movable knife 14 has moved far enough away from the main contact 12,
   2. ii) define a predetermined current threshold, for example of the order of 30 A corresponding to the breaking capacity of the movable knife 14, before starting the opening movement of the vacuum interrupter. In addition, this sufficient current must preferably also flow for a sufficient duration. In fact, we want to prevent the movable electrode 22 from starting its opening movement without being able to go quickly to the open position, which could happen if the current flows in the coil 20 with a low amplitude or only for a very long time. short, for example due to any current pulses generated by capacitive no-load loads when the main circuit is opened.
   
   The distance D therefore makes it possible to guarantee a threshold effect below which the mobile contact of the bulb does not move, and beyond which the mobile contact will completely complete its opening movement.
   Furthermore, the force of the return spring of the movable electrode 22 and of the return spring of the core, the mechanical inertia of the various parts and the pressure difference between the pressure in the external environment of the bulb and the vacuum of the bulb, cause the current flowing in the coil 30 to be high enough to overcome these various mechanical forces and perform the opening movement.
4. d) In figure 4 , the distance D has been crossed, the pusher 26 and the second transverse side 29 are therefore in contact, and the movable core 31 now drives the buffer device 25 and the movable electrode 22, causing the opening of the vacuum interrupter .
   When the movable electrode 22 separates from the fixed electrode 21, the current flowing in the coil 30 will however cease when there is no longer an arc in the bulb and the movable core 31 will no longer be maintained. Nevertheless, the electromagnet is designed, in particular by virtue of its own inductance, to discharge sufficiently slowly so that the movable core 31 can keep the vacuum interrupter 20 open long enough after the movable knife 14 separates from the contact. bypass 13.
5. e) In addition, the invention optionally provides a device for short-circuiting the coil 30 of the electromagnet. This device provides for an end-of-opening contact 32 which is mechanically and electrically linked to the movable core 31. In the closed position of the vacuum interrupter, the contact 32 is not connected. At the end of the open position shown in figure 5 , the end of opening contact 32 comes into contact with an end of opening terminal 16 which is connected to the bypass contact 13 and therefore to one end of the coil 30. In this configuration, the elements 26 and 27 are made made of a conductive material, for example metal. To improve the electrical contact, contact pads may of course be provided on the parts of the pusher 26 and of the second transverse side 29 which are in contact with each other during the opening movement. Furthermore, to ensure good electrical contact between contact 32 and terminal 16, one can obviously use a conventional contact pressure spring mechanism.
   Thus, as indicated in figure 5 , this short-circuiting device has the effect of short-circuiting the supply circuit of the coil 30, when the bulb at vacuum 20 is in the open position. In fact, the self-power supply circuit for coil 30 is as follows: end of opening terminal 16, coil 30, intermediate connection point 24, push-button 26, core 31, end of opening contact 32. Thanks to This device, the holding of the vacuum interrupter 20 in the open and stable position is extended (approximately 1 second with the device instead of 200-300 msec) before, under the effect of its return spring, the mobile core 31 returns to its initial position and the movable electrode 22 closes the vacuum interrupter 20.
6. f) the figure 6 shows the final position of the opening movement of the main circuit, namely the main circuit open and return of the vacuum interrupter 20 to its closed position, when the action of the return spring of the core 31 is greater than the force of opening of the electromagnet under the action of the residual current flowing in the coil 30. The end of opening contact 32 is then separated from the end of opening terminal 16 and the push-button 26 is again at a distance D of the second transverse side 29.

Alternatively, the invention provides another embodiment shown in figure 7 . In this mode, the buffer device is of electronic design and comprises an electronic circuit 33 in parallel with the coil 30 connected for example between the bypass contact 13 and the intermediate connection point 24. This electronic circuit 33 controls the power supply to the coil. coil 30 because it comprises an electronic switch, for example of the thyristor type, which makes it possible to shunt coil 30 or not, depending on whether the electronic switch is closed or open.

When the main circuit of the device is closed, the electronic circuit switch 33 is closed and the coil 30 is therefore bypassed, because its impedance is higher. Thus, during the opening movement of the main circuit 10, the bypass current which begins to flow in the bypass circuit will mainly flow directly in the electronic circuit 33, without passing through the coil 30.

Then, if the electronic circuit 33 detects that the value of the bypass current reaches a predetermined sufficient threshold, it commands the opening of its electronic switch. The coil 30 is then supplied, which will make it possible to drive the core 31 and to open the vacuum interrupter 20. Thus, the electronic circuit 33 is designed to supply the coil 30, via an opening command of its. electronic switch, only when a certain sufficient current value is reached. It can also wait for current to flow through the branch circuit. for a sufficiently long period of time thus allowing switching in the branch circuit.

The electronic circuit switch 33 will then return to its closed position only once the final position of the opening movement of the main circuit has been reached.

The electronic circuit 33 can be either self-powered, powered during switching and therefore be normally closed, or alternatively be powered by an external source.

Claims (9)

1. System for actuating a vacuum bottle (20) of an electrical device, the vacuum bottle being connected in a circuit shunting a main circuit (10) of a phase of the electrical device and comprising a movable electrode (22) and a fixed electrode (21), the movable electrode being movable between a closed position in which the two electrodes are in contact with each other and an open position in which the two electrodes are separated, the actuating system comprising:

   - a shunt contact (13) which is connected to a movable contact (14) of the main circuit (10) during a movement of opening the electrical device,

   characterized in that the actuating system comprises:

   - an electromagnet whose coil (30) is connected between the movable electrode (22) and the shunt contact (13), and whose core (31) is mechanically linked with the movable electrode (22), such that the core (31) drives the movable electrode (22) to the open position only when the value of the current which passes through the coil (30) reaches a predetermined threshold.
2. Actuating system according to Claim 1, characterized in that the core (31) drives the movable electrode (22) to the open position when the current passes through the coil (30) during at least a predetermined period of time.
3. Actuating system according to Claim 1 or 2, characterized in that the core (31) is mechanically linked with the movable electrode (22) by the intermediary of a buffer device (25).
4. Actuating system according to Claim 3, characterized in that the buffer device (25) comprises a push rod (26) connected to the core (31) and cooperating with a drive part (27) connected to the movable electrode (22).
5. Actuating system according to Claim 4, characterized in that, during the movement of opening the electrical device, the push rod (26) drives the drive part (27) after having previously travelled a distance (D) between the push rod (26) and a side (29) of the drive part (27).
6. Actuating system according to Claim 5, characterized in that said predetermined period of time is determined by the distance (D).
7. Actuating system according to Claim 1 or 2, characterized in that it comprises an electronic circuit (33) placed in parallel with the coil (30) and comprising an electronic switch, such that the electronic switch is in the closed position and shunts the coil (30) as long as the value of the current which passes through the electronic circuit (33) does not reach the predetermined threshold.
8. Actuating system according to one of the preceding claims, characterized in that it also comprises a short-circuiting device which short-circuits the coil (30) when the vacuum bottle (20) is in the open position.
9. Electrical device comprising a main phase switch and a vacuum bottle placed in parallel with the main phase switch, characterized in that the electrical device comprises a system for actuating the vacuum bottle according to one of the preceding claims.

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