Actuation system for vacuum bottles

Abstract

The invention relates to a 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 one phase of the electrical device and comprising a movable electrode (22) and a fixed electrode (21). The actuation system comprises a shunt contact (13) and an electromagnet, the shunt contact (13) being connected to a movable contact (14) of the main circuit (10) during movement to disconnect the electrical device, the coil (30) of the electromagnet being connected between the movable electrode (22) and the shunt contact (13), and the magnetic core (31) of the electromagnet being mechanically linked to the movable electrode (22), so that the magnetic core (31) drives the movable electrode (22) to the disconnected position only when the value of the current passing through the coil (30) reaches a predetermined threshold.

Description

Technical Field

[0001] The invention relates to a system for actuating a vacuum bottle for the purpose of opening an electrical circuit in a medium or high voltage electrical device, ie a device operating at a voltage higher than 1000 Volts.

[0002] 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 indiscriminately includes several types of devices such as switches, circuit breakers, contactors, switch-fuses, reclosers, disconnectors and the like. Background Art

[0003] A medium or high voltage electrical device of the type described in document EP2182536 comprises a vacuum bottle which is not placed in a main circuit comprising a main switch of one phase of the device, but in a shunt circuit connected in parallel with the main switch. When the main switch is closed, no current therefore flows in the vacuum bottle. The vacuum bottle is called upon only during the operation of disconnecting the main circuit, by means of a disconnection mechanism of the main switch, which first makes it possible to switch the current from the main circuit to the shunt, which makes it possible to disconnect the main switch while the current flows completely in the vacuum bottle. The vacuum bottle is then disconnected in turn by the disconnection mechanism.

[0004] Due to this structure, the vacuum bottle receives current only during the disconnection phase of the main phase circuit, not when the main switch is closed. In addition, the vacuum bottle is not called upon during the operation of closing the main circuit, and it also does not have to withstand possible short-circuit currents, especially when the electrical device is a switch. The vacuum bottle just has to be able to withstand the transient recovery voltage TRV (TRV stands for transient recovery voltage) after cutting off the current in the main circuit.

[0005] As a result, the vacuum bottle can be advantageously simplified and designed to be much smaller in size compared to a conventional structure in which the vacuum bottle is placed in a main circuit of an electrical device.

[0006] Furthermore, the disconnection mechanism making it possible to switch the current from the main circuit to the shunt circuit and subsequently disconnect the vacuum bottles placed in the shunt circuit must be very precise and reproducible in order to ensure, on the one hand, that for each phase the disconnection of the vacuum bottles is actually only carried out when the main switch has been sufficiently opened to avoid the risk of arcing on the main switch by reignition or restriking under the effect of the TRV voltage, and, on the other hand, that the vacuum bottles of the different phases of the installation are actually disconnected simultaneously.

[0007] Document EP3300097 has described such a disconnection mechanism. It comprises in particular a device for driving the movable electrode of the vacuum bottle. The drive device is driven by the movable contact of the main switch via a movable blade. The drive device then drives the movable electrode towards the disconnection position through the intermediary of an adjustment nut for precisely adjusting the movement of the movable electrode. However, the drive device comprises a certain number of small mechanical parts which need to be precisely adjusted in order to obtain good system reproducibility.

[0008] Furthermore, one of the problems of such an actuation system is to obtain a performance that complies with the current standards of the device in question. Another problem is to minimize the number of times the vacuum bottle is called up. In fact, during disconnection in the main circuit of an electrical device having such an actuation system, the vacuum bottle should preferably be disconnected only if there is indeed a valid load in the main circuit and the current exceeds the disconnection capacity of the main movable contacts. This also avoids systematically disconnecting the vacuum bottle at each disconnection movement, even in the absence of main current, which advantageously reduces the use of the vacuum bottle and further simplifies its design.

[0009] Furthermore, even if the main circuit is cut off and there is little or no main current, capacitive charge may still remain in the cable downstream of the electrical equipment in some cases, and the fact that the vacuum bottle is not disconnected in this case can reduce the dielectric stress associated with the capacitive charge.

[0010] One of the objects of the present invention is therefore to find a simple, reliable and economical system which, on the one hand, avoids the constraints of precise regulation of the components involved in disconnecting a vacuum bottle placed in a circuit branching off a main circuit of an electrical device and, on the other hand, minimizes the number of disconnections of the vacuum bottle by performing disconnection only when necessary, that is to say when the current flowing in the main circuit of the electrical device is greater than a predetermined threshold value (corresponding, for example, to the disconnection capacity of the main contacts). Summary of the invention

[0011] To this end, the invention describes a system for actuating a vacuum bottle of an electrical device, the vacuum bottle being connected in a circuit branching off a main circuit of one phase of the electrical device 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 comprises:

[0012] - shunt contacts, which are connected to the movable contacts of the main circuit during the movement of disconnecting the electrical device,

[0013] An electromagnet whose coil is connected between the movable electrode and the shunt contact and whose magnetic core is mechanically coupled to the movable electrode so that the magnetic core drives the movable electrode to the open position only when the value of the current passing through the coil reaches a predetermined threshold.

[0014] According to one feature, the magnetic core drives the movable electrode to the open position when current is passed through the coil during at least a predetermined period of time.

[0015] According to another feature, the magnetic core is mechanically linked to the movable electrode through the intermediary of a buffer device.

[0016] According to another feature, the damping device comprises a push rod connected to the magnetic core and cooperating with a drive member connected to the movable electrode.

[0017] According to another feature, during the movement to switch off the electrical device, the push rod drives the drive member after previously having travelled a distance D between the push rod and one side of the drive member.

[0018] According to another feature, the actuation system comprises an electronic circuit placed in parallel with the coil and comprises an electronic switch such that the electronic switch is in a closed position and shunts the coil as long as the value of the current passing through the electronic circuit does not reach a predetermined threshold.

[0019] According to another feature, the actuation system also comprises a short-circuiting device which short-circuits the coil when the vacuum bottle is in the disconnected position.

[0020] The invention also describes an electrical device comprising at least one main phase switch and a vacuum bottle placed in parallel with the main phase switch, and comprising such a system for actuating the vacuum bottle.

[0021] In the case of a multiphase electrical installation (eg three-phase) thus having a main switch for each phase, the installation preferably comprises a vacuum bottle in parallel with each main switch and thus comprises a vacuum bottle actuation system for each phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other features will become apparent from the following detailed description given with reference to the accompanying drawings, in which:

[0023] Figure 1 a simplified circuit diagram showing a first embodiment of a switching circuit of a phase of an electrical device having an actuation system according to the invention in a closed position,

[0024] Figures 2 to 6 shows the movement during different successive steps of opening the switching circuit Figure 1 Actuation system,

[0025] Figure 7A simplified circuit diagram of another embodiment of an actuation system according to the invention is shown in a closed position. DETAILED DESCRIPTION

[0026] Figure 1 A switching circuit of one phase of an electrical device including a main circuit 10, a main fixed contact 12, and a main movable contact 14 (hereinafter also referred to as a movable blade 14) is shown.

[0027] The switch circuit further comprises a shunt circuit 11 connected in parallel with the main circuit 10 between the upstream connection point 15 and the shunt contact 13. The shunt circuit 11 comprises a vacuum bottle 20 having a fixed conductive electrode 21 (also called a fixed rod) and a movable conductive electrode 22 (also called a movable rod).

[0028] In the closed position of the main circuit 10, the movable blade 14 is in contact only with the main contact 12 and allows current to flow in the main circuit. Therefore, no current flows through the shunt circuit 11. The movement for opening the main circuit 10 occurs in several consecutive steps. During the first step, the movable blade 14 is in contact with the shunt contact 13, while also maintaining contact with the main contact 12, as shown in FIG. Figure 2 Then, in the next step, the movable blade 14 is separated from the main contact 12 and remains in contact with the shunt contact 13, as shown in FIG. Figure 3 and Figure 4 Then, in the last step, in order to enter the disconnected position of the main circuit 10, the movable blade 14 is also separated from the shunt contact 13, as shown. Figure 5 shown.

[0029] Optionally, for example in the case of a three-position phase switch, the switching circuit may additionally comprise a ground contact (not shown in the figures) to which the movable blade 14 will reach at the end of the disconnected position.

[0030] The electrode 22 of the vacuum bottle 20 is movable along the 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 to the upstream connection point 15. Conventionally, the vacuum bottle 20 also includes a return spring (not shown in the figures) in order to perform the movement of closing the vacuum bottle, that is, to return the movable electrode 22 to its closed position.

[0031] According to the invention, the actuation system of the vacuum bottle comprises an electromagnet having an excitation coil 30 surrounding a movable metal core 31, which is actuated when a current passes through the coil 30. The coil 30 is connected at one end to the shunt contact 13 and at the other end to the movable electrode 22 at a connection point called the intermediate connection point 24 (see Figure 2). Thus, if the vacuum bottle is in the closed position and if the movable blade 14 is in contact with the shunt contact 13, the coil 30 receives current. In the presence of current in the coil, the magnetic core moves along the longitudinal axis X in the direction of disconnecting the vacuum bottle 20. In the absence of current in the coil 30, a return spring (not shown in the figure) returns the magnetic core 31 to the initial rest position.

[0032] The movable core 31 of the electromagnet is mechanically coupled to the movable electrode 22 so that when sufficient current flows in the coil 30, the movable core 31 drives the movable electrode 22 to the disconnected position. According to one embodiment, the mechanical coupling is formed through the mediation of a buffer device 25, which is designed so that the core 31 actually drives the movable electrode 22 only when sufficient current greater than a predetermined threshold has flowed in the coil 30 during a predetermined period of time, so as to provide sufficient kinetic energy for the movable core. An intermediate connection point 24 is located between the movable electrode 22 and the buffer device 25. The conductor connecting the intermediate connection point 24 to the coil 30 may be flexible so as to facilitate the movement of the movable electrode 22.

[0033] according to Figure 2 – Figure 6 In the embodiment shown, the buffer device is of a mechanical design and comprises a push rod 26 connected to a core 31 and a drive member 27 connected to a mobile electrode 22 cooperating with the push rod 26. The drive member 27 has, for example, a rectangular shape and comprises a first lateral side 28 and an opposite lateral side 29 forming a space in which one end of the push rod 26 is housed. The first lateral side 28 is connected to the mobile electrode 22. The second lateral side 29 is hollowed out in its center so as to allow the push rod 26 to slide relative to the member 27 along the longitudinal axis X.

[0034] Therefore, during the opening of the main circuit 10, the operating sequence of the actuation system is thus as follows:

[0035] a) In Figure 1 In the closed position corresponding to the main circuit 10, the blade 14 is disconnected from the shunt contact 13. Therefore, no current flows in the coil 30. The magnetic core 31 is reset to its rest position by its reset spring, and the push rod 26 is not in contact with the second lateral side 29, but is separated from the second lateral side 29 by a certain distance D.

[0036] b) Figure 2 In the embodiment of the present invention, the movable blade 14 is in contact with the shunt contact 13, and the vacuum bottle 20 is still closed. Therefore, the shunt circuit through the vacuum bottle 20 and the coil 30 is powered from then on. However, as long as the movable blade 14 remains in contact with the main contact 12, the current continues to flow mainly in the main circuit 10 due to the impedance of the coil 30.

[0037] c) Figure 3, the movable blade 14 continues its movement and leaves the main contact 12 so as to remain connected only to the shunt contact 13. Therefore, the current flows from now on in the shunt circuit. The coil 30 is powered and will be able to drive the magnetic core 31. When the magnetic core 31 starts its movement in order to perform the disconnection movement, it drives the push rod 26, which starts from the travel distance D before coming into contact with the second lateral side 29. Therefore, the push rod 26 does not yet drive the drive member 27, which means that as long as D is not passed, the vacuum bottle 20 remains closed, as shown in FIG. Figure 3 shown.

[0038] It follows that, during disconnection of the main circuit, no current flows in the main circuit 10 , the drive member 27 does not move and the vacuum bottle 20 is advantageously not activated, which limits its use to necessary cases.

[0039] Furthermore, the distance D advantageously provides a threshold value that acts as a buffer, so that it is possible to ensure that the current flows in the coil 30 of the electromagnet for a sufficient time and with a sufficient amplitude before starting to disconnect the vacuum bottle 20. The coil 30 of the electromagnet and the value of the distance D (e.g., of the order of a few millimeters) are configured for:

[0040] i) ensuring that the vacuum bottle 20 will not disconnect as long as the movable blade 14 is not sufficiently separated from the main contact 12,

[0041] ii) defining a predetermined current threshold before starting the movement to disconnect the vacuum bottle, for example of the order of 30 A corresponding to the cutting capacity of the active blade 14. Moreover, preferably, it is also necessary for this sufficient current to flow for a sufficiently long time. In fact, it is desirable to prevent the active electrode 22 from starting its disconnection movement in the case where it cannot quickly enter its disconnection position, which may occur in the case where the current flows in the coil 20 with a low amplitude or only for a very short time, for example due to current pulses that may be generated by unloaded capacitive charges during disconnection of the main circuit.

[0042] The distance D thus ensures a threshold effect, below which the movable contact of the vacuum bottle will not move, and above which the movable contact will completely end its movement to open.

[0043] Furthermore, the forces of the return springs of the movable electrode 22 and of the magnetic core, the mechanical inertia of the different components and the pressure difference between the pressure in the environment outside the bottle and the vacuum of the bottle mean that the current flowing in the coil 30 must be high enough to overcome these different mechanical forces and perform the disconnection movement.

[0044] d) Figure 4 In the embodiment of FIG. 1 , the distance D has been exceeded, the push rod 26 and the second lateral side 29 are therefore in contact, and the movable magnetic core 31 thereafter drives the buffer device 25 and the movable electrode 22 , resulting in disconnection of the vacuum bottle.

[0045] However, when the movable electrode 22 is separated from the fixed electrode 21, the current flowing in the coil 30 will stop when there is no longer an arc in the vacuum bottle and the movable magnetic core 31 is no longer held. However, the electromagnet is designed to discharge slowly enough, especially due to its own inductance, so that the movable magnetic core 31 can keep the vacuum bottle 20 disconnected for a long enough time after the movable blade 14 is separated from the shunt contact 13.

[0046] e) Furthermore, the invention optionally provides a device for short-circuiting the coil 30 of the electromagnet. This device provides the end of a disconnect contact 32 mechanically and electrically connected to the movable magnetic core 31. The contact 32 is not connected in the closed position of the vacuum bottle. Figure 5 At the end of the disconnect position shown, the end of the disconnect contact 32 contacts the end of the disconnect terminal 16, which is connected to the shunt contact 13 and is therefore connected to one end of the coil 30. In this configuration, the components 26 and 27 are made of a conductive material, such as metal. In order to improve the electrical contact, the contact pads can of course be arranged on the push rod 26 and the second lateral side 29 (which are in contact with each other during the disconnection movement). In addition, in order to ensure good electrical contact between the contact 32 and the terminal 16, it is obvious that a conventional contact pressure spring mechanism can be used.

[0047] Therefore, if Figure 5 As shown, when the vacuum bottle 20 is in the disconnected position, the short-circuit device has the effect of short-circuiting the power supply circuit of the coil 30. In fact, the self-powered circuit of the coil 30 is as follows: the end of the disconnected terminal 16, the coil 30, the intermediate connection point 24, the push rod 26, the magnetic core 31, the end of the disconnected contact 32. Thanks to this device, the vacuum bottle 20 remains in the disconnected and stable position for a longer time (about 1 second with this device, instead of 200-300 milliseconds) before the movable magnetic core 31 is reset to its initial position under the action of its return spring and the movable electrode 22 closes the vacuum bottle 20 again.

[0048] f) Figure 6 The final position of the movement to open the main circuit is shown, i.e. the main circuit is opened and the vacuum bottle 20 is reset to its closed position, when the action of the return spring of the magnetic core 31 is stronger than the disconnection force of the electromagnet under the effect of the residual current flowing in the coil 30. Then, the end of the disconnection contact 32 is separated from the end of the disconnection terminal 16, and the push rod 26 is again at a distance D from the second lateral side 29.

[0049] Alternatively, the present invention provides Figure 7Another embodiment is shown. In this embodiment, the buffer device is of electronic design and comprises an electronic circuit 33 connected in parallel with the coil 30, which is connected, for example, between the shunt contact 13 and the intermediate connection point 24. This electronic circuit 33 controls the power supply of the coil 30, since it comprises an electronic switch, for example of the thyristor type, which makes it possible to shunt or not shunt the coil 30, depending on whether the electronic switch is closed or open.

[0050] When the main circuit of the device is closed, the switch of the electronic circuit 33 is closed and therefore the coil 30 is shunted because its impedance is higher. Therefore, during the movement of opening the main circuit 10, the shunt current that starts to flow in the shunt circuit will mainly flow directly in the electronic circuit 33, without passing through the coil 30.

[0051] Then, if the electronic circuit 33 detects that the value of the shunt current reaches a predetermined sufficient threshold, it commands the opening of its electronic switch. The coil 30 is then powered, which will make it possible to drive the magnetic core 31 and disconnect the vacuum bottle 20. Therefore, the electronic circuit 33 is designed to power the coil 30 with a command to open its electronic switch only when a certain sufficient current value is reached. In addition, it can wait for the current to flow in the shunt circuit for a sufficient time to allow switching in the shunt circuit.

[0052] Only when the movement opening the main circuit reaches the final position, the switch of the electronic circuit 33 is reset to its closed position.

[0053] The electronic circuit 33 may indifferently be self-powered, powered during switching and therefore normally closed, or it may be powered by an external power source.

Claims

1. A 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 one 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 movable electrode and the fixed electrode are in contact with each other and an open position in which the movable electrode and the fixed electrode are separated, characterized in that: The system comprises: - a shunt contact (13) which is connected to a movable contact (14) of the main circuit (10) during the movement of disconnecting the electrical device, - an electromagnet whose coil (30) is connected between the movable electrode (22) and the shunt contact (13) and whose magnetic core (31) is mechanically linked to the movable electrode (22) so that the magnetic core (31) drives the movable electrode (22) to the open position only when the value of the current passing through the coil (30) reaches a predetermined threshold value.

2. The system according to claim 1, characterized in that When current passes through the coil (30) during at least a predetermined period of time, the magnetic core (31) drives the movable electrode (22) to the open position.

3. The system according to claim 2, characterized in that The magnetic core (31) is mechanically connected to the movable electrode (22) through the mediation of the buffer device (25).

4. The system according to claim 3, characterized in that The buffer device (25) comprises a push rod (26) connected to a magnetic core (31) and cooperating with a drive member (27) connected to a movable electrode (22).

5. The system according to claim 4, characterized in that During the movement to disconnect the electrical device, the push rod (26) drives the drive member (27) after previously having travelled a distance (D) between the push rod (26) and the side (29) of the drive member (27).

6. The system according to claim 5, characterized in that The predetermined time period is determined by the distance (D).

7. The system according to claim 2, characterized in that It comprises an electronic circuit (33) placed in parallel with the coil (30) and comprises an electronic switch such that as long as the value of the current passing through the electronic circuit (33) does not reach a predetermined threshold, the electronic switch is in a closed position and shunts the coil (30).

8. The system according to any one of claims 1 to 7, characterized in that It also includes a short-circuit device which short-circuits the coil (30) when the vacuum bottle (20) is in the disconnected position.

9. An 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 claims 1 to 7.

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