EP2654065B1 - Assembly for controlling the disconnection of a line in the event of a voltage surge on said line and circuit-breaker for protecting against a voltage surge on a line - Google Patents

Description

Technical field of the invention

The invention relates to the field of overcurrent protection. More specifically, it relates to a control assembly which is of the control unit type of a cut of a line in the event of overcurrent in this line, by transmission of an electrical control signal to a control device. 'a break switch of the line.

The invention also relates to an overcurrent protection circuit breaker in a line, of the type comprising a line breaking switch, a device for operating this switch in response to an electrical control signal, and a control unit. a cut of the line in case of overcurrent in this line, by sending the electrical control signal to the operating device.

State of the art

Electromechanical circuit breakers are well known and constitute a special kind of overcurrent protection circuit breaker. An electromechanical circuit breaker conventionally comprises a coil connected in the line to be protected, and a movable ferromagnetic core which is exposed to the magnetic field produced by the coil when it is energized. The moving part of a cut-off switch of the line to be protected is mechanically coupled to the mobile core. In case of short circuit, this Mobile core is driven by the magnetic field produced by the coil and its motion is transmitted to the moving part of the switch, which is thus open.

An electromechanical circuit breaker is not flexible for use in single-use: electromechanical circuit breakers only fulfill their only protection function in the event of a short-circuit, without being able to cooperate with other devices or being triggered by a control. exterior. In addition, electromechanical circuit breakers are not equipped with a self-test, that is to say they can not conduct tests on themselves to check their condition.

There are also electronic circuit breakers, which are more flexible than electromechanical circuit breakers, but have the disadvantage of being less reliable. In these electronic circuit breakers, the current to be monitored is analyzed continuously. The current analysis is used in a test to decide whether or not to cut a line to protect.

dépasse un certain seuil. Des exemples de disjoncteurs réalisant une protection l²t sont proposés dans la demande de brevet français FR-2 540 303 et dans le brevet US-5 220 478 des Etats-Unis d'Amérique.In particular, it is known to make electronic circuit breakers digitally performing a so-called l ² t protection, which avoids a cut in the case of peaks of current sufficiently fugitive not to be sources of destructive heating. In a protection l ² t, the overcurrent protection resulting from a current i is triggered when the integral of the square of this current i over a predetermined duration d, that is to say the integral ${\displaystyle {\int }_t^{t+d}{i}^{2}dt,}$

exceeds a certain threshold. Examples of circuit breakers realizing protection l ² t are proposed in the French patent application FR-2,540,303 and in the patent US-5,220,478 United States of America.

Cette dernière valeur W recalculée en permanence, en temps réel, est comparée sans cesse à un seuil et une coupure de la ligne à protéger intervient lorsque ce seuil est dépassé. Une protection contre une surintensité n'est efficace que s'il est répondu en un temps très bref après la survenance de cette surintensité. L'élévation au carré d'un échantillonnage du courant i à surveiller et l'intégration numérique ne peuvent être effectués rapidement qu'au moyen d'une électronique qui est passablement consommatrice d'énergie et dont le coût est conséquent, en incluant le coût des dispositifs de calcul et d'acquisition des mesures d'intensité, ainsi que le coût de l'alimentation. Les disjoncteurs électroniques réalisant une protection l²t sont donc onéreux.In a protective l ² t performed digitally, is sampled and is digitized continuous measurement of the current i to be monitored. Also, we squares the sampled values continuously, then numerically calculates a value of the integral $W={\displaystyle {\int }_t^{t+d}{i}^{2}dt.}$

This last value W recalculated permanently, in real time, is constantly compared to a threshold and a cut of the line to protect occurs when this threshold is exceeded. Overcurrent protection is only effective if it is responded to in a very short time after the occurrence of this overcurrent. The squaring of a sample of the current i to be monitored and the numerical integration can be done quickly only by means of electronics that are fairly energy-consuming and cost-intensive, including the cost calculation and acquisition devices for intensity measurements, as well as the cost of power supply. Electronic circuit breakers providing protection l ² t are therefore expensive.

For example, the French patent application FR 2,812,965 which discloses an electromagnetic actuator of a breaking pole, comprising a magnetic circuit provided with a fixed core, an excitation coil connected in series on a current line, and a measuring component, such as a coil surrounding the fixed core . When a current flows through the excitation coil, a magnetic field is created in the magnetic circuit, and the measurement component creates an electric current proportional to the current flowing in the excitation coil, to actuate the breaking pole. But such an actuator is not reliable enough.

Summary of the invention

The object of the invention is at least to make it possible to propose a circuit breaker which provides the same or comparable protection as an I ² t protection and which, without being too expensive, is flexible in use and can be used in one or more other functions. that of protecting against overcurrent.

• un actionneur électromagnétique dont un enroulement à connecter dans la ligne est à même de produire un champ magnétique d'entraînement et dont un équipage mobile est déplaçable sous l'action de ce champ magnétique d'entraînement, depuis une zone d'attente au moins jusqu'à une zone de déclenchement,
• un organe élastique de rappel de l'équipage mobile vers la zone d'attente, dans la direction opposée à la zone de déclenchement,
• un dispositif de détection d'un passage de l'équipage mobile de la zone d'attente à la zone de déclenchement, et
• un dispositif électronique de surveillance du dispositif de détection et de commande au dispositif de manoeuvre d'actionner l'interrupteur dans le sens d'une coupure de la ligne dans le cas où le dispositif de détection a détecté le passage de l'équipage mobile de la zone d'attente à la zone de déclenchement.

According to the invention, this object is achieved by means of a control assembly which is of the aforementioned type and which comprises:

• an electromagnetic actuator having a winding to be connected in the line which is capable of producing a driving magnetic field and a movable element of which is movable under the action of this driving magnetic field, from a waiting zone at least up to 'to a trigger zone,
• an elastic member for returning the moving equipment to the waiting zone, in the direction opposite to the trigger zone,
• a device for detecting a passage of the mobile crew from the waiting zone to the trigger zone, and
• an electronic device for monitoring the device for detecting and controlling the operating device to actuate the switch in the direction of a cut of the line in the case where the detection device has detected the passage of the mobile unit of the waiting zone at the trigger zone.

En cas de surintensité, la vitesse d'accroissement de l'intensité i du courant dans la ligne surveillée influe sur le temps de déclenchement. Toutefois, quelle que soit cette vitesse d'accroissement, le niveau déterminant une coupure de la ligne est atteint par $W={\displaystyle {\int }_t^{t+d}{i}^{2}dt.}$

dès lors que l'équipage mobile s'est déplacé suffisamment pour parvenir à la zone de déclenchement et que cela peut être détecté par le dispositif de détection.As combined as specified in the above definition, the electromagnetic actuator and the elastic member together define a trigger threshold which corresponds to a globally constant value of $W={\displaystyle {\int }_t^{t+d}{i}^{2}dt.}$

In case of overcurrent, the rate of increase of the intensity i of the current in the monitored line influences the tripping time. However, regardless of this rate of increase, the level determining a break in the line is reached by $W={\displaystyle {\int }_t^{t+d}{i}^{2}dt.}$

as soon as the moving equipment has moved sufficiently to reach the trigger zone and this can be detected by the detection device.

It follows from the above that the circuit breaker defined above provides protection l ² t.

Furthermore, the operating device of the switch is controlled by an electronic device which can perform several different functions, in particular easily communicate with the outside. This electronic device can in particular receive from outside and implement orders to open or close the switch, for example in the context of an installation control applying a load shedding strategy. Thanks to its ability to exchange with the outside, the electronic device therefore allows the circuit breaker is used in a new feature.

The electronic device of the circuit breaker according to the invention does not have to perform a large sum of calculations in a very short time and can be cheap.

The control assembly defined above may incorporate one or more other advantageous characteristics, alone or in combination, in particular from those defined below.

Advantageously, the control assembly comprises a reception input of an external control and is adapted to control the operating device to actuate the switch according to this external command.

Advantageously, the detection device comprises a magnetic field variation detection coil, as well as a magnet driven by the moving element so as to modify the magnetic field inside the detection coil during a period of time. inversion of the position of the moving equipment between the waiting and trigger zones.

Advantageously, the winding of the actuator and the detection coil delimit respectively a first and a second axial passage. leading to one another. Preferably, the moving element is axially slidable in the first passage and drives the magnet towards and away from an axial inlet of the second passage.

Advantageously, the control assembly comprises first and second magnetic circuits. Preferably, the first magnetic circuit comprises at least one loop which passes through the winding of the actuator. Preferably, the second magnetic circuit comprises at least one loop which passes through the detection coil. Preferably, the or each loop of the second magnetic circuit is angularly offset from the or each loop of the first magnetic circuit, around said second axial passage, so as to be substantially magnetically decoupled from the first magnetic circuit.

Advantageously, the control assembly comprises a partition wall dividing the space locally into a first region, where the winding of the actuator is located, and a second region, where the detection coil is located. Preferably, this partition wall is made of ferromagnetic material in order to channel the driving magnetic field and a deflection of this field away from said detection coil.

Advantageously, the magnet passes the separation wall when the moving equipment passes from the waiting zone to the trigger zone.

Advantageously, said partition wall is part of a carcass which is made of ferromagnetic material, which forms part of a first magnetic circuit passing through the winding of the actuator and forms part of a second magnetic circuit passing through. in the detection coil.

Advantageously, the control assembly comprises a hollow support shaft which is engaged in the first and second passages and which supports the winding of the actuator and the detection coil.

Advantageously, the support shaft encloses the moving element.

Advantageously, the carcass comprises two parts which are fixed to one another and which retain axially between them the support shaft.

The invention also relates to a circuit breaker which is of the aforementioned type and whose control assembly is as defined above.

Brief description of the drawings

• la figure 1 est un schéma de l'architecture générale d'un disjoncteur conforme à l'invention et représente également la connexion de ce disjoncteur dans une ligne à protéger contre des surintensités,
• la figure 2 est une vue en perspective d'un sous-ensemble électromécanique constitutif du disjoncteur de la figure 1,
• la figure 3 est une vue en perspective d'une carcasse d'assemblage faisant partie du sous-ensemble de la figure 2,
• la figure 4 est une vue en perspective, avec arrachement, qui représente le même sous-ensemble que la figure 2 et sur laquelle ce sous-ensemble est dans une première configuration, au repos,
• la figure 5 est un schéma de circuits électriques présents dans le disjoncteur de la figure 1, et
• la figure 6 est une vue en perspective, avec arrachement, qui est analogue à la figure 4 et sur laquelle le sous-ensemble de la figure 2 est dans une deuxième configuration, à savoir dans une configuration déclenchée, suite à une surintensité.

Other advantages and features will emerge more clearly from the following description of a particular embodiment of the invention given by way of non-limiting example and shown in the accompanying drawings, among which:

• the figure 1 is a diagram of the general architecture of a circuit breaker according to the invention and also represents the connection of this circuit breaker in a line to be protected against overcurrent,
• the figure 2 is a perspective view of a constituent electromechanical subassembly of the circuit breaker of the figure 1 ,
• the figure 3 is a perspective view of an assembly carcass forming part of the subset of the figure 2 ,
• the figure 4 is a perspective view, with tearing, which represents the same subset as the figure 2 and on which this subset is in a first configuration, at rest,
• the figure 5 is a diagram of electrical circuits present in the circuit breaker of the figure 1 , and
• the figure 6 is a perspective view, with tearing, which is analogous to the figure 4 and on which the subset of the figure 2 is in a second configuration, namely in a triggered configuration, following an overcurrent.

Description of a preferred embodiment of the invention

On the figure 1 , reference 1 designates a circuit breaker which is in accordance with the invention and which is connected in an electrical line 2 to provide protection against accidental overcurrents.

The circuit breaker 1 comprises an electromechanical subassembly 3, whose function is to react to an overcurrent and which is under the observation of an electronic monitoring and control device. Advantageously consisting of a microcontroller 5 as in the example shown, this electronic device controls a device 6 for maneuvering a switch 7 for cutting line 2. The electromechanical subassembly 3 and microcontroller 5 are part of a set control according to the invention.

The microcontroller 5 can communicate with the outside. In the example shown, this microcontroller 5 has indeed an input 8 for receiving an external control, which it is able to apply to the operating device 6 and which can be the order to cut the line 2 or the reverse order to close this line 2.

The operating device 6 may have several forms. For example, the assembly that it forms with the switch 7 may be constituted by an electromechanical relay. In the example shown, the maneuvering device 6 comprises an electromechanical actuator known in itself and shown schematically, the coil and the movable magnetic circuit are respectively referenced 10 and 11.

Always at the figure 1 , reference 12 designates the connection terminals of circuit breaker 1 in line 2.

The electromechanical subassembly 3 is shown alone at figure 2 . It comprises a hollow support shaft 20, made of polymer and mounted in an assembly casing 21. With a longitudinal axis X-X ', this hollow shaft 20 supports a winding 22 and a detection coil 23 offset axially one. on the other and substantially coaxial, being centered on the axis X-X '.

Represented alone at figure 3 , the assembly carcass 21 results from the attachment of two parts 24 and 25 to one another. Each of the pieces 24 and 25 is obtained by U-folding a blank of ferromagnetic material, for example of suitable steel. Each wing of the U defined by the piece 25 is crimped or welded or otherwise assembled on one of two opposite edges of a partition wall 26 that forms one of the wings of the U defined by the piece 24. The wings of the 24 are traversed by the axis X-X ', which passes through the bottom of the U formed by the part 25.

The partition wall 26 locally divides the space: on one side of this partition wall 26 is a first region, which the part 24 partially surrounds and where there is the winding 22. On the other side of the partition wall 26 is a second region that the part 25 partially surrounds and where there is the detection coil 23. The partition wall 26 provides a magnetic isolation function of the first and second regions relative to one another. other, by channeling any field magnetic sensor generated from one of these first and second regions and radially deflecting it towards the rest of the assembly carcass 21.

The part 24 forms part of a first magnetic circuit, which is referenced C ₁ and symbolized by a broken line at the figure 3 . In the example shown, this first magnetic circuit C ₁ has only one loop passing through the winding 22.

The partition wall 26 is common to the first magnetic circuit C ₁ and to a second magnetic circuit, which further comprises the part 25. This second magnetic circuit is referenced C ₂ and symbolized by a broken line at the figure 3 . In the example shown, it comprises two loops passing through the detection coil 23. The magnetic circuit C ₂ may also comprise only one loop passing through the detection coil 23.

Each loop of the magnetic circuit C ₂ is angularly offset by 90 ° with respect to the loop of the magnetic circuit Ci, around the axis X-X ', so as to be substantially magnetically decoupled from this magnetic circuit C ₁ .

The winding 22 and the part 24 constitute the static part of an actuator, of which a movable plunger core 27 is visible at the figure 4 . Intervening in the detection of a possible overcurrent, this actuator does not have to be powerful and its winding 22 may advantageously comprise only a single turn, as in the example shown, or a few turns.

Made of a ferromagnetic material such as steel, the plunger core 27 is part of a moving element which is slidably mounted along the axis X-X ', in the axial passage delimited internally by the winding 22. coil compression spring 28 forms a resilient member reminding said moving element towards the detection coil 23, against a stop constituted by an internal shoulder 29 of the support shaft 20.

The plunger core 27 has an end which is directed towards the axial passage delimited by the detection coil 23 and which carries a permanent magnet 30.

The support shaft 20 encloses the spring 28, the magnet 30, as well as the plunger 27, of which it guides the axial sliding.

In addition to the piece 24, the magnetic circuit C ₁ comprises the plunger core 27 and a fixed core 31 engaged in one end of the support shaft 20.

In addition to the partition wall 26 and the part 25, the magnetic circuit C ₂ comprises a static core 32 of ferromagnetic material. This static core 32 is engaged in one end of the support shaft 20, so as to extend in the axial passage delimited by the detection coil 23.

The parts 24 and 25 of the assembly carcass 21 hold together the support shaft 20, in the direction defined by the axis X-X '. In addition to this, the fixed core 31 and the static core 32 laterally retain the ends of this support shaft 20, each having a pin which is engaged through the corresponding part 24 or 25 and which is crimped or welded or fastened by fitting by force to this piece.

It follows from the foregoing that the assembly carcass 21, the fixed core 31 and the static core 32 maintain assembled the components of the electromechanical subassembly 3, at the same time that they form the major part of two magnetic circuits. In doing so, they fill simultaneously two functions, which is advantageous in particular in terms of simplification, lightening, reduced size, ease of industrial assembly and lower cost.

In a first step of assembling the electromechanical subassembly 3, the support shaft 20 is provided with the detection coil 23 and with different components that this support shaft 20 is intended to enclose, and among which notably include the core plunger 27 provided with the magnet 30, as well as the spring 28. The assembly thus formed is engaged through the partition wall 26 and then in the winding 22, and it is put in place in the part 24 already provided with the core fixed 31, but not yet of the piece 25. The installation of this piece 25 and its attachment to the piece 24 take place only then. Alternatively, the part 25 can be assembled at one end of the support shaft 20 before the latter is put in place in the part 24.

From the above, it follows that the assembly of the electromechanical subassembly 3 is an operation that the arrangement of this subset 3 greatly simplifies, which is advantageous.

As can be seen at figure 1 , the winding 22 is intended to be connected in the line 2 to be monitored. For this purpose, this winding 22 and the cutoff switch 7 are connected in series between the two terminals 12 for connecting the circuit breaker 1 in the line 2.

Visibly at the figure 1 as at the figure 5 , the terminals of the detection coil 23 are connected to an input of the microcontroller 5, which monitors the voltage between them.

The microcontroller 5 is further adapted to perform itself, at regular intervals, an automated continuity check test. electrical coil of the detection coil 23, for which there is provided a test circuit shown in FIG. figure 5 . In this test circuit, the detection coil 23 and a bias resistor 40 of this coil 23 are connected in series between two points to which different electrical potentials V ₀ and V _ref are applied.

The detection coil 23 has a much lower electrical resistance than that of the bias resistor 40. Therefore, when there is a break in the electrical continuity of the detection coil 23, the potential at a point between this coil of detection 23 and the bias resistor 40 changes significantly, passing substantially from V ₀ to V _ref in the example shown, which monitors the automated test.

Also represented at figure 5 , a supply circuit of the coil 10 of the operating device 6 comprises two electronic cut-off switches controlled by the microcontroller 5 and each of which may be in the form of a transistor 41 or 42. The transistor 41 and the coil 10 are connected in series in a branch connected to a DC power supply. In a branch connected in parallel with the coil 10, a freewheeling diode 43 and a zener diode 44 are connected in series, so as to be in opposite directions. The transistor 42 and the zener diode 44 are connected in parallel.

In the absence of overcurrent, the electromechanical subassembly 3 is as illustrated in FIG. figure 4 , on which the compressed spring 28 holds the immobilized plunger 26 in abutment against the shoulder 29, in a waiting zone. The magnet 30 is then within the magnetic circuit C ₂ passing through the detection coil 23. The magnetic field that it produces therefore reigns inside this detection coil 23.

In case of overcurrent in line 2, the current flowing in the winding 22 produces a magnetic field such that it manages to drive the plunger 27 against the action of the spring 28, to its position of the figure 6 , where this plunger 27 has reached a trigger zone of the protection.

More specifically, when he moves from his position of figure 4 to that of the figure 6 , the plunger core 27 carries with it the magnet 30 away from the magnetic circuit C ₂ , by causing it to cross the partition wall 26 and bringing it into the first aforementioned region, that is to say in a region where the magnetic field produced by this magnet 30 is not or almost not present inside the detection coil 23. The passage of the plunger 27 between its position of the figure 4 and that of the figure 6 thus results in a variation of the magnetic flux generated by the magnet 30 through the detection coil 23.

The drop of the magnetic flux through the detection coil 23 leads to the fact that, at its terminals, this coil 23 produces a voltage that detects the microcontroller 5 thus informed about the occurrence of the overcurrent.

The voltage detected by the microcontroller 5 depends on the rate of variation of the magnetic flux and therefore on the speed of the moving element, which is itself a function of the rate of increase di / dt of the intensity i of the current in line 2. The detection coil 23 is dimensioned such that the voltage induced in this coil 23 is sufficiently high, for example of the order of a volt, to be detected by the microcontroller 5 without having to be amplified beforehand, which allows the economy of an expensive amplification.

The plunger core 27 is driven axially from the waiting zone to the trigger zone by compression of the spring 28 and the storage 28. Under these conditions, its driving to the trip zone implies the satisfaction of a condition, which is generally the triggering condition of a protection l ² t.

doit atteindre une valeur minimale qui est sensiblement constante quelle que soit l'évolution de l'intensité i du courant dans la ligne 2 sur la durée fixe d'intégration d. Etant sensiblement constante, cette valeur minimale est assimilable à un seuil et elle est considérée comme constituant un tel seuil dans la définition et l'utilisation de la protection conférée par le disjoncteur 1.Specifically, for the plunger 27 to reach the trigger zone, the integral ${\displaystyle {\int }_t^{t+d}{i}^{2}dt}$

must reach a minimum value that is substantially constant irrespective of the change in intensity i of the current in line 2 over the fixed duration of integration d. Being substantially constant, this minimum value is comparable to a threshold and is considered to constitute such a threshold in the definition and use of the protection conferred by the circuit breaker 1.

To set the tripping threshold of the protection conferred by the circuit breaker 1, one can play on the stiffness of the spring 28.

As long as the two transistors 41 and 42 are closed, that is to say, passers, the coil 10 is energized and the operating device 6 holds the switch 7 in the closed position.

In response to detection of an overcurrent, the microcontroller 5 opens the switch 7. When it thus results in the detection of an overcurrent in the line 2, the opening of the switch 7 must be performed very quickly after this detection.

If a fast opening of the switch 7 is desired as in the case of detection of an overcurrent, the microcontroller 5 simultaneously opens the transistors 41 and 42. In this way, a strong counter-voltage is established across the coil 10, which leads to a rapid demagnetization of the latter. It follows a prompt displacement of the mobile magnetic circuit 11 under the action of a spring, not shown, returning the switch 7 to its open position.

A quick opening of the switch 7 is also brutal for the hardware. It may not be useful to quickly open this switch 7, for example when the command to cut the line 2 comes from the outside through the input 8 and does not result in detection of an overcurrent. The microcontroller 5 can control a slower opening of the switch 7. To do this, it opens the transistor 42 and leaves the transistor 41 closed, so that the zener diode is bypassed and the coil 10 can be discharged slowly because the low counter-tension imposed by the freewheeling diode 43.

Advantageously, the transistor 41 can also be used to regulate the supply current of the coil 10 by chopping the supply voltage, which can then be wide range, that is to say likely to fluctuate over a wide range.

The circuit breaker 1 has the advantage of being designed to provide protection against low overcurrent, for example against overcurrent of less than ten amperes. The circuit breaker 1 has other advantages of having high reliability, low cost and space saving.

The invention is not limited to the embodiment described above. In particular, the detection of a passage of the plunger core 27 from the waiting zone to the trip zone can be performed by a device other than that described above. For example, this detection can be performed by means of a microswitch, or a Hall effect sensor, or even any other electronic or mechanical sensor capable of detecting a position. However, the detection device comprising the magnet 30 and the detection coil 23 as shown in FIGS. Figures 2, 4 and 6 has the advantages of being reliable and being able to be tested automatically so that its state of operation is verified, as was explained above.

In addition, the electronic device controlling the operating device 6 is a control logic that can have various forms, in particular not be in the form of a microcontroller 5. For example, a customer integrated circuit, also designated by the acronym CIC and still called "specific application integrated circuit" (named ASIC or "Application-Specific Integrated Circuit" in English), can be used in place of the microcontroller 5. A programmable gate-end IC (designated by the terms "field programmable gate array And by the acronym FPGA in English) may also be suitable for the same purposes. According to yet another possibility, the microcontroller 5 can be replaced or supplemented by comparators associated with logic.

Claims (12)

1. Control unit commanding interruption of a line (2), in case of a voltage surge occurring on this line (2), by transmitting an electric control signal to an operating device (6) of a switch (7) interrupting the line (2), the control unit comprising:

   - an electromagnetic actuator (22, 24, 27, 31) having a winding (22) to be connected in the line and able to produce a magnetic drive field, and a movable assembly (27) movable by the action of this magnetic drive field from a waiting area at least to a tripping area,

   - flexible means (28) biasing the movable assembly (27) to the waiting area in the opposite direction to the tripping area,

   characterized in that the control unit comprises:

   - a detection device (23, 25, 30, 32) of movement of the movable assembly (27) from the waiting area to the tripping area, and

   - an electric device (5) for monitoring the detection device (23, 25, 30, 32) and for commanding the operating device (6) to actuate the switch (7) in the direction of interruption of the line (2) in the event of the detection device (23, 25, 30, 32) having detected movement of the movable assembly (27) from the waiting area to the tripping area.
2. Control unit according to claim 1, characterized in that the control unit comprises an input (8) receiving an external command, and is designed to order the operating device (6) to actuate the switch (7) according to this external command.
3. Control unit according to any one of the foregoing claims, characterized in that the detection device (23, 25, 30, 32) comprises a coil (23) for detecting a magnetic field variation, and a magnet (30) driven by the movable assembly (27) so as to modify the magnetic field inside the detection coil (23) when a reversal of position of the movable assembly (27) takes place between the waiting and tripping areas.
4. Control unit according to claim 3, characterized in that the winding (22) of the actuator and the detection coil (23) respectively demarcate a first and second axial passage opening onto one another, the movable assembly (27) being axially sliding in the first passage and moving the magnet (30) towards/away from an axial entrance of the second passage.
5. Control unit according to claim 4, characterized in that it comprises first and second magnetic circuits (C₁, C₂), the first magnetic circuit (C₁) comprising at least one loop which passes through the winding (22) of the actuator, the second magnetic circuit (C₂) comprising at least one loop which passes through the detection coil (23), the or each loop of the second magnetic circuit (C₂) being angularly offset from the or each loop of the first magnetic circuit (C₁) around said second axial passage so as to be substantially magnetically disconnected from this first magnetic circuit (C₁).
6. Control unit according to either one of claims 4 and 5, characterized in that it comprises a separating partition (26) locally dividing the space into a first area where the winding (22) of the actuator is located and a second area where the detection coil (23) is located, this separating partition (26) being made from ferromagnetic material in order to perform channelling of the magnetic drive field and diversion of this field away from said detection coil (23).
7. Control unit according to claim 6, characterized in that the magnet (30) passes the separating partition (26) when the movable assembly (27) moves from the waiting area to the tripping area.
8. Control unit according to either one of claims 6 and 7, characterized in that said separating partition (26) forms part of a yoke frame (21) which is made from ferromagnetic material, which forms a part of the first magnetic circuit (C₁) passing through the winding (22) of the actuator and which forms a part of the second magnetic circuit (C₂) passing through the detection coil (23).
9. Control unit according to any one of claims 4 to 8, characterized in that it comprises a hollow support shaft (20) which is engaged in the first and second passages and which supports the winding (22) of the actuator and the detection coil (23).
10. Control unit according to claim 9, characterized in that the support shaft (20) encloses the movable assembly (27).
11. Control unit according to claim 8 and to either one of claims 9 and 10, characterized in that the yoke frame (21) comprises two parts (24, 25) which are fixed to one another and which secure the support shaft (20) axially between them.
12. Circuit breaker performing protection against a voltage surge in a line (2), comprising:

    - a switch (7) for interrupting power supply of the line (2),

    - an operating device (6) of this switch (7) in response to an electronic control signal, and

    - a control unit commanding interruption of the line (2) in case of a voltage surge occurring in this line (2), by transmitting the electronic control signal to the operating device (6),

    characterized in that the control unit is according to any one of the foregoing claims.

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