Minimum or undervoltage shunt trip for a circuit breaker, assembly and associated process

Abstract

Undervoltage / Undervoltage Shunt Release for a Circuit Breaker, Assembly and Method. The present invention relates to an undervoltage / undervoltage shunt release (1) for a circuit breaker (2). The release (1) comprises: a load block (7), electrically connected between a first terminal (3) and a second terminal (5), comprising a load (16) configured to actuate the circuit breaker (2); a protection module (9), comprising: a surge protection thyristor (27) and a varistor (29), in series with each other and in parallel with the load block (7); and a first capacitor (33), in parallel with the varistor (29); a fusible element (15) and a first resistive wire (11) in series with each other, connected between the first terminal (3) and the protection module (9); and a second resistive wire (13), connected between the protection module (9) and the second terminal (5). Figure for the abstract: Figure 1

Description

Title of the invention: Minimum or undervoltage shunt trip unit for a circuit breaker, assembly and associated method

[0001] The present invention relates to a shunt trip unit with undervoltage or undervoltage release. It also relates to an assembly comprising such a trip unit and a circuit breaker. Finally, it relates to a method for tripping such a circuit breaker.

[0002] A circuit breaker is a protective device for an electrical installation that can be remotely operated by a shunt trip actuator (also called a shunt trip actuator or close-trip actuator) according to IEC 60947-2, when this actuator detects the presence of a voltage exceeding a threshold. Such devices can be installed, in particular, at the head of an electrical installation, where the electrical power is relatively high.

[0003] When inserted into an electrical network, shunt trip releases with minimum or no-voltage operation are subjected to intermittent voltage variations of varying amplitude. These voltage variations are likely to cause the trip releases to break and result in a loss of service across the entire electrical installation.

[0004] Various techniques are known for protecting an actuator against overvoltages in an electronic device. For example, it is known to use a thyristor and a varistor in series to attenuate overvoltages. In particular, document WO202325609A1 describes a method for operating a device comprising overvoltage protection by means of a thyristor and a varistor in parallel with a capacitor and a resistor.

[0005] However, existing surge protection solutions are not suitable and optimized for minimum or no-voltage shunt releases, which have particular size and structure constraints.

[0006] The aim of the invention is then to propose a shunt trigger with minimum or no voltage exhibiting increased resistance to overvoltages from an electrical network external to the device, taking into account the constraints of size, cost and structure of such equipment.

[0007] To this end, the invention relates to a shunt trip unit with minimum or undervoltage activation for a circuit breaker, the trip unit comprising: • a first terminal and a second terminal for applying an input voltage between them; • a charging unit, electrically connected between the first terminal and the second terminal, comprising a load configured to operate opening or closing the circuit breaker by means of a mechanical actuator; • a protection module, comprising: • a surge protection thyristor, electrically connected between a first intermediate point and a second intermediate point; and • a varistor, electrically connected between the second intermediate point and a third intermediate point, in series with the surge protection thyristor, the surge protection thyristor and the varistor being in parallel with the load block; • a first capacitor, belonging to the protection module, electrically connected in parallel with the varistor; • a fusible element and a first resistive wire in series with each other, electrically connected between the first terminal and the protection module, the first resistive wire having a resistance greater than or equal to 0.5Ω; and • a second resistive wire, having a resistance greater than or equal to 0.5Q, electrically connected between the protection module and the second terminal.

[0008] Thanks to the invention, an overvoltage from the external electrical network, occurring between the first and second terminals, is partially attenuated by the thyristor and the varistor in series, so as to protect the load. In particular, the presence of the thyristor makes it possible to reduce the size of the varistor, and therefore limit the overall size of the device, while maintaining the same overvoltage attenuation capacity. Furthermore, the first capacitor and the resistive wires allow for the absorption of a residual overvoltage across the varistor. Indeed, the thyristor conducts before the varistor, which results in a very short-duration overvoltage across the varistor, which could eventually reduce the varistor's lifespan. The attenuation of the overvoltage by the first capacitor and the resistive wires limits this effect, thus extending the lifespan of the trigger.In addition, the presence of resistive wires limits the current during an overvoltage, and the fusible element reduces the risk of overheating and / or fire in the trigger in case of thyristor or varistor failure.

[0009] According to other advantageous aspects of the invention, the trigger comprises one or more of the following features, taken individually or in all technically possible combinations:

[0010] - the trigger comprises a first resistor in series with the first capacitor, the resistor and the first capacitor being in parallel with the varistor;

[0011] - the load block includes a voltage rectifier bridge, the rectifier bridge of voltage taking as input a voltage across the terminals of the protection module and giving as output a voltage across the terminals of the load;

[0012] - the trigger a detection module, electrically connected at least to second intermediate point and to a control unit and configured to detect and transmit to the control unit an occurrence of an overvoltage event between the first terminal and the second terminal;

[0013] - the detection module comprises: • a first diode, electrically connected between the second intermediate point and a fourth intermediate point; • a second resistor, electrically connected between the fourth intermediate point and a fifth intermediate point; • a third resistor, electrically connected between the fifth intermediate point and a ground; • a second diode, electrically connected between the third intermediate point and the fourth intermediate point; • a third diode, electrically connected between the fifth intermediate point and a sixth intermediate point; • a second capacitor, electrically connected between the sixth intermediate point and ground; and • a fourth resistor, electrically connected between the sixth intermediate point and the control unit;

[0014] and the fifth intermediate point is electrically connected with the control unit;

[0015] - the load block includes a third filtering capacitor, connected electrically in parallel with the load;

[0016] - the charge includes: • a measurement module, configured to measure the voltage across the load terminals; • a call coil, configured to activate the mechanical actuator; and • a holding coil, configured to hold the mechanical actuator in position;

[0017] - the trigger is a minimum voltage shunt trigger and the actuator The mechanical system is configured for: • open the circuit breaker after activation by the call coil; or • close the circuit breaker after activation by the call coil;

[0018] - the trigger is a no-voltage shunt trigger and the actuator The mechanical system is configured for: • open the circuit breaker after activation by the call coil; and • prevent the circuit breaker from closing when the mechanical actuator is held in position by the holding coil.

[0019] The invention also relates to an assembly comprising a trigger according to the foregoing and a circuit breaker.

[0020] Such an assembly presents the same advantages as the trigger of the invention, in particular an increased trigger life.

[0021] The invention also relates to a method of operating the trigger belonging to an assembly according to the above, in the event of an overvoltage between the first terminal and the second terminal, generating an overvoltage current between the first terminal and the second terminal, the method comprising: • a flow of overvoltage current through the fusible element, the first resistive wire and the second resistive wire; • a primary deflection of at least part of the overvoltage current through the overvoltage protection thyristor and the varistor; • a secondary deflection of at least some other portion of the surge current through the first capacitor; and • activation of the mechanical actuator by the load.

[0022] This method has the advantage that the function of opening or closing the circuit breaker by the trip unit is ensured at the same time as the electrical energy due to the overvoltage is dissipated during the primary and secondary deflections, thus preserving the various components of the trip unit against overvoltages.

[0023] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawing in which:

[0024] [Fig-1] [Fig. 1] is a diagram of an assembly comprising a circuit breaker and a shunt release with minimum or no voltage according to the invention.

[0025] Figure 1 illustrates a shunt trip unit 1 for a circuit breaker 2. The trip unit 1 and the associated circuit breaker 2 form an assembly 4, intended to be inserted into an electrical installation (not shown). In particular, the assembly 4 is advantageously intended to be inserted at the head of an electrical installation and connected to an external electrical network.

[0026] In an alternative not shown, the trigger 1 is integrated into the circuit breaker 2.

[0027] The trigger 1 comprises a first terminal 3 and a second terminal 5, a block load 7, a protection module 9, a first resistive wire 11, a second wire resistive 13 and an optional fusible element 15. Advantageously, the trigger 1 further includes a detection module 19.

[0028] The trip unit 1 is connected to the external electrical network via the first terminal 3 and the second terminal 5. The external electrical network applies an input voltage U between the first terminal 3 and the second terminal 5. Thus, terminals 3 and 5 are input voltage application terminals for U of the trip unit 1. Advantageously, the purpose of the trip unit 1 is to remotely operate the circuit breaker 2, so as to interrupt or restore the flow of current in the electrical installation according to the input voltage U.

[0029] According to a first example of the invention, the trip unit 1 is a minimum-voltage shunt trip unit. In other words, the circuit breaker 1 is configured to trip the circuit breaker 2 when the input voltage U exceeds a certain predetermined maximum voltage threshold. The occurrence of the input voltage U above the predetermined maximum voltage threshold is called an overvoltage, or overvoltage event.

[0030] According to a second embodiment of the invention, the trip 1 is a no-voltage shunt trip. In other words, the trip 1 is configured to operate the circuit breaker 2 when the input voltage U falls below a predetermined minimum voltage threshold.

[0031] In the following description, the case of the shunt release with minimum voltage is described, the case of the shunt circuit breaker with no voltage can be deduced by analogy.

[0032] The load block 7 is electrically connected between the first terminal 3 and the second terminal 5 and includes a load 16, configured to actuate an opening or closing of the circuit breaker 2. Advantageously, the load block 7 further includes a voltage rectifier bridge 17.

[0033] The load 16 advantageously comprises a measuring module 21, a pull coil 23 and a holding coil 25.

[0034] The measuring module 21a has the role of measuring the voltage U' across the terminals of the load 16 and comparing this voltage U' to the predetermined maximum voltage threshold.

[0035] The pull coil 23 is configured to activate a mechanical actuator 24. The mechanical actuator 24 is advantageously configured to open the circuit breaker 2 after activation by the pull coil 23, thereby interrupting the current flowing in the electrical installation. Alternatively, the mechanical actuator 24 is configured to close the circuit breaker 2 after activation by the pull coil 23. The mechanical actuator 24 is, for example, a mechanical finger which, by translation between an extended and a retracted position, acts on a mechanism of the circuit breaker 2 so as to open or close the circuit breaker 2.

[0036] The holding coil 25 is configured to hold the mechanical actuator 24 in the extended or retracted position. Advantageously, the mechanical actuator 24 is configured to release the circuit breaker 2 when the mechanical actuator 24 is no longer held by the holding coil 25, so as to allow the circuit breaker 2 to return to its initial open or closed state.

[0037] In the case of a shunt release with no voltage, the mechanical actuator 24 is configured to open the circuit breaker 2 after activation by the pull coil 23 and to prevent the circuit breaker 2 from closing when the mechanical actuator 24 is held in position by the holding coil 25.

[0038] The voltage rectifier bridge 17 takes as input the voltage U across the terminals of the protection module 9 and outputs a voltage U' across the terminals of the load 16. The voltage rectifier bridge 17 is advantageous when the electrical network supplies an alternating input voltage U. The voltage rectifier bridge 17 then allows the conversion of the alternating input voltage U into a direct current voltage U' across the terminals of the load 16.

[0039] The protection module 9 has the role of protecting the trigger 1 against overvoltages occurring in the external electrical network, i.e. overvoltages of the input voltage U. The protection module includes an overvoltage protection thyristor 27, a varistor 29 and a first capacitor 33.

[0040] The varistor 29 is electrically connected between a second intermediate point 35 and a third intermediate point 67. The varistor 29 exhibits a resistance that varies depending on the voltage across its terminals. When the voltage across the varistor 29 is low, i.e., in the absence of an overvoltage, the varistor 29 exhibits a first, relatively high resistance value, and thus carries a relatively low current. When the voltage across the varistor 29 exceeds a certain threshold, the resistance of the varistor 29 drops drastically until it reaches a second resistance value, allowing a relatively large current to flow through the varistor 29, dissipating some of the electrical energy of the overvoltage. The varistor 29 is then considered to be conducting.

[0041] By way of non-limiting example, the first resistance value is greater than 10 megaohms for an input voltage U, for example, of the order of 200 to 250V, while the second resistance value is less than 0.5 ohms in the presence of an overvoltage.

[0042] The surge protection thyristor 27 is electrically connected between a first intermediate point 65 and a second intermediate point 35, in series with the varistor 29. The presence of the surge protection thyristor 27 makes it possible to limit the size of the varistor 29 required to withstand overvoltages from the external electrical network, to limit a leakage current flowing in the varistor 29 in the absence of an overvoltage, and to reduce the risk of a short circuit occurring in the event of failure of varistor 29, as well as to ensure reliable current deflection in case of significant overvoltage.

[0043] Advantageously, the overvoltage protection thyristor 27 is an assembly consisting of two thyristors and protection diodes.

[0044] The first capacitor 33 is electrically connected in parallel with the varistor 29. In combination with the resistive wires 11 and 13, the first capacitor 33 protects the varistor 29 in the event of a high overvoltage, also dissipating some of the electrical energy of the overvoltage. The presence of the resistive wires 11 and 13 and the first capacitor 33 thus increases the service life of the trip unit 1, and in particular of the varistor 29, in the context of an unstable external electrical network.

[0045] In the example shown in [Fig.1], the protection module 9 further comprises a first resistor 31 in series with the first capacitor 33, the first resistor 31 and the first capacitor 33 being in parallel with the varistor 29. The first resistor 31 and the first capacitor 33 thus form an RC loop in parallel with the varistor 29, providing increased protection to the varistor 29 in the event of a high overvoltage.

[0046] However, the first resistance 31 is optional since, as explained above, its role can be assumed by the resistive wires 11 and 13, allowing a saving of space in the trigger 1.

[0047] By way of non-limiting example, the first resistor 31 has a resistance value between 0 and 63 ohms (the case at 0 Ohms corresponding to the absence of the first resistor 31), while the first capacitor 33 has a capacitance value between 10 picofarads and 100 nanofarads, for an input voltage U for example of the order of 200 to 250V.

[0048] In addition, the protection module 9 has an overall capacity improving electromagnetic compatibility of the trigger 1, i.e. providing the trigger 1 with low sensitivity to electromagnetic disturbances.

[0049] The first resistive wire 11 is connected in series with the fuse element 15. The assembly consisting of the first resistive wire 11 and the fuse element 15 in series is electrically connected between the first terminal 3 and the protection module 9. In the example shown in [Fig. 1], the fuse element 15 is electrically connected to the first terminal 3 and the first resistive wire 11 is electrically connected to the protection module 9. In an alternative configuration not shown, the fuse element 15 is electrically connected to the protection module 9 and the first resistive wire 11 is electrically connected to the first terminal 3.

[0050] The first resistive wire 11 is a conducting wire having a resistance greater than or equal to 0.5Q, preferably equal to 1.5Q for an input voltage U, for example in the range of 200 to 250V. The choice of a resistive wire 11 allows for space savings and simplification compared to a conductor wire connected to a separate resistive element.

[0051] Similarly, the second resistive wire 13 connects the second terminal 5 to the protection module 9 and is a conductive wire having a resistance greater than or equal to 0.5Q, preferably equal to 1.5Q for an input voltage U for example of the order of 200 to 250V.

[0052] Advantageously, the first and second resistive wires 11 and 13 have substantially equal resistances. This symmetry improves the electromagnetic compatibility of the trigger 1.

[0053] Alternatively, the resistive wires 11 and 13 are conducting wires connected to a respective resistive element, as shown in Figures 1 and 2.

[0054] The resistive wires 11 and 13 allow dissipation of part of the electrical overvoltage energy without requiring much space.

[0055] The fusible element 15 is configured to melt when it is traversed by a current exceeding a predetermined critical current, thereby protecting all the components of the trip unit 1 in the event of an electrical failure and thus extending their service life. Furthermore, the presence of the resistive wires 11 and 13 and the fusible element 15 dissipates electrical energy in the event of a failure of the overvoltage protection thyristor 27 and / or the varistor 29, thereby reducing the risk of overheating and / or fire in the trip unit 1.

[0056] The detection module 19 is optional.

[0057] The detection module 19 takes advantage of the architecture presented previously by detecting overvoltages, for the purpose of monitoring overvoltage events and predictive maintenance of the components of the trigger 1, and in particular of the varistor 29. Indeed, knowing the number of occurrences of overvoltage events, by means of the detection module 19, and the number of switching events during the lifetime of the varistor 29, by means of charts provided by the varistor manufacturer, it is possible to predict the remaining lifetime of the varistor 29. In addition, the detection module 19 makes it possible to detect a short circuit at the second intermediate point 35, revealing a failure of the varistor 29 and the overvoltage protection thyristor 27.

[0058] The detection module 19 is electrically connected at least to the second intermediate point 35 and to a control unit 37 internal to the trigger 1 and the circuit breaker 2.

[0059] In an alternative not shown, the control unit 37 is integrated into the circuit breaker 2.

[0060] The detection module 19 includes a first diode 39, a second resistor 41, a third resistor 43, a second diode 53, a third diode 55, a second capacitor 49 and a fourth resistor 59.

[0061] The first diode 39 is electrically connected between the second intermediate point 35 and a fourth intermediate point 69. The second resistor 41 is electrically connected in series with the first diode 39, between the fourth intermediate point 69 and a fifth intermediate point 45. The third resistor 43 is electrically connected in series with the second resistor 41, between the fifth intermediate point 45 and ground 47. The fifth intermediate point 45 is electrically connected to the control unit 37. Depending on a voltage value between the fifth intermediate point 45 and ground 47 of the trigger 1, the control unit 37 is able to detect an occurrence of an overvoltage event.

[0062] By way of non-limiting example, the second resistor 41 and the third resistor 43 each have a resistance value between 10 ohms and several megaohms, for an input voltage U for example of the order of 200 to 250V.

[0063] By way of non-limiting example, the second capacitor 49 has a capacitance value between 10 picofarads and 100 microfarads, while the fourth resistor 59 has a resistance value between 10 ohms and several megohms, for an input voltage U for example of the order of 200 to 250V.

[0064] The second diode 53 is electrically connected between the third intermediate point 67 and the fourth intermediate point 69. The third diode 55 is electrically connected between the fifth intermediate point 45 and a sixth intermediate point 63. The second capacitor 49 is electrically connected between the sixth intermediate point 63 and ground 47. The fourth resistor 59 is electrically connected between the sixth intermediate point 63 and the control unit 37. This second connection of the detection module 19 to the control unit 37 allows the control unit 37 to detect, in addition to the occurrence of the overvoltage event, the level of this overvoltage.

[0065] Advantageously, the load block 7 further includes a third capacitor 61, electrically connected in parallel with the load 16. The third capacitor 61 filters the voltage U' across the load 16, in order to improve the measurement of this voltage by the measuring module 21.

[0066] A method for tripping a circuit breaker 2 by means of a trip 1 conforming to the above is described in the remainder of the description.

[0067] The triggering process is executed automatically, due to the electronic architecture of the trigger 1 described above, in the event of an overvoltage occurring between the first terminal 3 and the second terminal 5.

[0068] The overvoltage generates an overvoltage current between the first terminal 3 and the second terminal 5. The overvoltage current necessarily flows through the fuse element 15, the first resistive wire 11 and the second resistive wire 13. As soon as the overvoltage occurs, the method includes a primary diversion of at least a portion of the overvoltage current through the overvoltage protection thyristor 27 and the varistor 29 of the protection module 9. In other words, the current no longer flows entirely through the load block 7. This makes it possible to protect the load 16 against the overvoltage.

[0069] In addition to the primary deflection, the method includes a secondary deflection of at least another portion of the surge current through the first capacitor 33. In other words, the portion of the surge current flowing through the protection module 9 is divided between the varistor 29 on the one hand, and the first capacitor 33 on the other. This secondary deflection, in combination with the flow of the surge current through the resistive wires 11 and 13, makes it possible to protect the varistor 29 from premature degradation due to repeated high surges. In particular, since the varistor 29 generally becomes conducting a few nanoseconds after the surge protection thyristor 27, the secondary deflection protects the varistor 29 during this interval.

[0070] In addition, if the overvoltage current remains too high despite the aforementioned deviations, the fusible element 15 melts in order to protect the trigger 1 from excessive heating or even a fire.

[0071] Along with the primary and secondary deflections, the method includes an activation of the mechanical actuator 24 by the load 16, advantageously resulting in an opening or closing of the circuit breaker 2. More specifically, the overvoltage of the input voltage U is reflected on the voltage U' across the terminals of the load 16, which is measured by the measuring module 21. The measuring module 21 performs a comparison of the measured voltage with the predetermined maximum voltage threshold.

[0072] The method advantageously includes overvoltage event detection by means of the detection module 19. More specifically, the overvoltage of the input voltage U is transmitted at the second intermediate point 35, and then at the fifth intermediate point 45, which is connected to the control unit 37. Through this input, the control unit 37 is able to register an occurrence of an overvoltage event. Overvoltage event detection enables monitoring of overvoltage events by the control unit 37, as well as, as explained previously, predictive maintenance of the trip components 1.

[0073] Any feature described above for one embodiment or variant can also be implemented in the other embodiments and variants described above, as far as technically possible.

Claims

Demands

1. A minimum or undervoltage shunt release (1) for a circuit breaker (2), the release (1) comprising: • a first terminal (3) and a second terminal (5) for applying an input voltage (U) between them; • a load block (7), electrically connected between the first terminal (3) and the second terminal (5), comprising a load (16) configured to actuate the opening or closing of the circuit breaker (2) by means of a mechanical actuator (24); and • a protection module (9), comprising: • a surge protection thyristor (27), electrically connected between a first intermediate point (65) and a second intermediate point (35); and • a varistor (29), electrically connected between the second intermediate point (35) and a third intermediate point (67), in series with the overvoltage protection thyristor (27), the overvoltage protection thyristor (27) and the varistor (29) being in parallel with the load block (7); characterized in that the trigger (1) further comprises: • a first capacitor (33), belonging to the protection module (9), electrically connected in parallel with the varistor (29); • a fusible element (15) and a first resistive wire (11) in series with each other, electrically connected between the first terminal (3) and the protection module (9), the first resistive wire (11) having a resistance greater than or equal to 0.5Q; and • a second resistive wire (13), having a resistance greater than or equal to 0.5Q, electrically connected between the protection module (9) and the second terminal (5).

2. Trigger (1) according to claim 1, comprising a first resistor (31) in series with the first capacitor (33), the resistance (31) and the first capacitor (33) being in parallel with the varistor (29).

3. Trigger (1) according to any one of the preceding claims, wherein the load block (7) comprises a voltage rectifier bridge (17), the voltage rectifier bridge (17) taking as input a voltage (U) across the terminals of the protection module (9) and giving as output a voltage (U') across the terminals of the load (16).

4. Trigger (1) according to any one of the preceding claims, comprising a detection module (19), electrically connected at least to the second intermediate point (35) and to a control unit (37) and configured to detect and transmit to the control unit (37) an occurrence of an overvoltage event between the first terminal (3) and the second terminal (5).

5. Trigger (1) according to claim 4, wherein the detection module (19) comprises: • a first diode (39), electrically connected between the second intermediate point (35) and a fourth intermediate point (69); • a second resistor (41), electrically connected between the fourth intermediate point (69) and a fifth intermediate point (45); • a third resistor (43), electrically connected between the fifth intermediate point (45) and ground (47); • a second diode (53), electrically connected between the third intermediate point (67) and the fourth intermediate point (69); • a third diode (55), electrically connected between the fifth intermediate point (45) and a sixth intermediate point (63); • a second capacitor (49), electrically connected between the sixth intermediate point (63) and ground (47);and • a fourth resistor (59), electrically connected between the sixth intermediate point (63) and the control unit (37); and in which the fifth intermediate point (45) is electrically connected with the control unit (37).

6. Trigger (1) according to any one of the preceding claims, wherein the load block (7) includes a third filtering capacitor (61) electrically connected in parallel with the load (16).

7. Trigger (1) according to any one of the preceding claims, wherein the load (16) comprises: • a measuring module (21), configured to measure the voltage (U') across the terminals of the load (16); • a pull coil (23), configured to activate the mechanical actuator (24); and • a hold coil (25), configured to hold the mechanical actuator (24) in position.

8. Trip unit (1) according to claim 7, wherein the trip unit (1) is a minimum voltage shunt trip unit and the mechanical actuator (24) is configured to: • open the circuit breaker (2) after activation by the pull coil (23); or • close the circuit breaker (2) after activation by the pull coil (23).

9. Trip unit (1) according to claim 7, wherein the trip unit (1) is a no-voltage shunt trip unit and the mechanical actuator (24) is configured to: • open the circuit breaker (2) after activation by the pull coil (23); and • prevent the circuit breaker (2) from closing when the mechanical actuator (24) is held in position by the hold coil (25).

10. Assembly (4), comprising: • a trigger (1) according to any one of the preceding claims, and • a circuit breaker (2).

11. Method of operating the trigger (1) belonging to an assembly (4) according to claim 10, in the event of an overvoltage between the first terminal (3) and the second terminal (5), generating a current overvoltage between the first terminal (3) and the second terminal (5), the method comprising: • a flow of overvoltage current through the fusible element (15), the first resistive wire (11) and the second resistive wire (13); • a primary deflection of at least part of the overvoltage current through the overvoltage protection thyristor (27) and the varistor (29); • a secondary deflection of at least one other portion of the overvoltage current through the first capacitor (33); and • activation of the mechanical actuator (24) by the load (16).