METHOD FOR DETECTING DEFECTION OF A SWITCHING DEVICE

Description

technical field

[0001] The present invention relates to the field of switching devices for electrical equipment, for example, for low and medium voltage electrical equipment. The switching device may, for example, be a circuit breaker. Previous technique

[0002] A low- or medium-voltage switching device may include one or more actuators, for example, electromagnetic actuators, that trigger the opening of an electrical circuit. To do this, the actuator may release a spring-loaded control mechanism, allowing a movable electrical contact to open or close the circuit. In the case of a circuit breaker, the electrical circuit is opened when a fault occurs. The fault could be, for example, a short circuit between two phases, or between a phase and earth.

[0003] When the actuator is electromagnetic, it comprises a moving magnetic core and a control coil. Under the influence of an electric current flowing through the control coil, the magnetic core moves. The magnetic core is mechanically coupled to a drive element that acts on the moving electrical contacts, thus opening or closing the electrical circuit. Closing the circuit allows a load to be energized.

[0004] To ensure the safety of the electrical grid and people, it is important to be able to verify the proper functioning of switching devices throughout their lifespan. A switching device is generally subject to the effects of aging, which can progressively degrade its electrical or mechanical functions, eventually rendering it inoperable. It is therefore important for users to be able to monitor the condition of the switching device. In particular, it is desirable to be able to monitor the condition of the control mechanism between the actuator and the moving contacts, and especially to be able to detect any degradation of this control mechanism. US patent 7,692,522 B2 is an example of such a detection method. This allows users to intervene to repair or replace the control mechanism at an opportune time during the management of the electrical grid. Summary

[0005] To this end, the invention proposes a method for detecting degradation of a switching device comprising: a movable electrical contact between a closed position of an electrical circuit and an open position of the electrical circuit, a control mechanism comprising: -- a drive element configured to move the movable electrical contact so as to open an electrical circuit, -- an elastic member linked to the drive element, -- a release member configured to move from a locked position in which the elastic member is held in a tensioned state to a release position in which the elastic member is free to relax so as to move the electrical contact from the closed position to the open position of the electrical circuit, or from the open position to the closed position, an actuator configured to move the release member from the locked position to the release position, The process includes the following steps: (i) command the actuator to move the unlocking member from the locked position to the released position, (ii) determine a first instant corresponding to a predetermined position of the unlocking member, (iii) determine a second instant corresponding to a predetermined position of the drive element, (iv) determine a time elapsed between the first instant and the second instant, (v) iterate steps (i) to (iii) for a set of successive actuator commands, so as to obtain a set of values ​​for the time elapsed between the first instant and the second instant, switching based on the evolution of the values ​​of the assembly during successive commands of the actuator.

[0006] The method for detecting degradation of the switching device is a method for detecting changes in the behavior of the switching device's control mechanism due to the aging of its components. Component aging includes, for example, wear, deformation, the effects of corrosion, and changes in the tribological properties of the components. The time elapsed between the first and second instants corresponds to the reaction time of the unlocking mechanism. Monitoring the evolution of this time value—that is, how the time changes over the lifetime of the switching device—allows for tracking the evolution of the switching device's control mechanism's behavior during its operation. When the unlocking mechanism is functioning nominally, the overall values ​​do not change significantly during successive actuations of the switching device.In other words, the various values ​​of the assembly are essentially constant. Conversely, a gradual degradation of the control mechanism tends to cause a change in values ​​during successive actuations, in particular a fluctuation of these values. The values ​​of the assembly are no longer essentially constant and exhibit significant fluctuation. This gradual change makes it possible to detect a degradation of the unlocking mechanism. The method for detecting a degradation of the switching device is also a method for anticipating the occurrence of a fault in the switching device. Indeed, an uncorrected degradation of the switching device can eventually lead to the occurrence of a fault, and this fault can thus be anticipated.

[0007] The features listed in the following paragraphs can be implemented independently of each other or in any technically possible combination:

[0008] At step (vii), the evolution of the values ​​of the assembly can be a fluctuation of the values ​​of the assembly during successive commands of the electromagnetic actuator.

[0009] In one embodiment, the electrical contact is movable between a closed position and an open position of the electrical circuit, and the release of the elastic element moves the electrical contact from the closed position to the open position. The control mechanism thus allows the flow of electric current in the circuit to be interrupted.

[0010] In another embodiment, the electrical contact is movable between an open position and a closed position of the electrical circuit, and the release of the elastic element moves the electrical contact from the open position to the closed position. The control mechanism thus allows the flow of electric current in the circuit.

[0011] The set of values ​​for the time elapsed between the first instant and the second instant is obtained by a succession of consecutive actuations of the switching device.

[0012] Each value in the set of values ​​of the time elapsed between the first instant and the second instant corresponds to a distinct actuation of the switching device.

[0013] Each actuation of the switching device corresponds to a command from the actuator.

[0014] The switching device can be a circuit breaker.

[0015] The switching device can be a switch.

[0016] The switching device can be a disconnect switch.

[0017] According to one embodiment, the actuator is an electromagnetic actuator.

[0018] The electromagnetic actuator includes an electromagnet.

[0019] The electromagnetic actuator includes a control coil and a magnetic core configured to move under the action of a magnetic field created by an electric current flowing through the control coil.

[0020] The magnetic core, for example, is mobile in translation.

[0021] The unlocking mechanism is linked to a magnetic core of the electromagnetic actuator.

[0022] According to another embodiment, the actuator includes a push button that can be manually operated by an operator.

[0023] The unlocking mechanism includes a position indicator.

[0024] The position indicator provides a two-level signal.

[0025] The position indicator is a two-state electrical contactor.

[0026] The predetermined position of the unlocking mechanism used to determine the first instant can be an equilibrium position of the unlocking mechanism.

[0027] The predetermined position of the unlocking device used to determine the first instant can be a transient position of the unlocking device.

[0028] The predetermined position of the drive element used to determine the second instant can be a transient position of the drive element.

[0029] The elastic element is configured to apply a driving force to the electrical contact.

[0030] The elastic element can be a spring, for example a spiral spring or a helical spring.

[0031] The drive element can be mobile in rotation.

[0032] The drive element can be connected to the moving contact by a connecting rod.

[0033] Measuring a current flowing in the electromagnetic actuator means measuring the intensity of the electric current flowing in the electromagnetic actuator.

[0034] The current flowing through the electromagnetic actuator can be detected by a sensor measuring the current flowing through the electromagnetic actuator.

[0035] The current flowing through the electromagnetic actuator can be sampled, for example with a sampling frequency between 1 kHz and 100 kHz.

[0036] The actuator is configured to trigger a movement of the moving electrical contact in order to open or close the electrical circuit.

[0037] When the switching device is a circuit breaker, the electromagnetic actuator is configured to trigger an opening of the electrical circuit in the event of a fault in the electrical circuit.

[0038] According to one embodiment of the proposed detection method, in which the actuator is an electromagnetic actuator, the method comprises the following substeps: - measure a current flowing in the electromagnetic actuator when the switching device is actuation, - determine the first instant corresponding to a predetermined position of the unlocking member from the time variations of the measured current.

[0039] The proposed method therefore does not require the installation of any additional sensors, such as a sensor for the displacement of the electrical contact or a sensor for the displacement of an element of the actuation mechanism.

[0040] The proposed method includes a sub-step for determining the temporal variations of the measured current.

[0041] The electromagnetic actuator comprises a control coil and a magnetic core configured to move under the influence of a magnetic field created by an electric current flowing through the control coil. The predetermined position of the unlocking element at the initial instant is a position of maximum displacement of the magnetic core.

[0042] According to one aspect of the detection process, the first instant corresponding to a predetermined position of the unlocking device is an instant corresponding to a local minimum value of the electric current flowing in the electromagnetic actuator.

[0043] The first instant can be determined from the time evolution of the intensity of the current flowing in the control coil, and coincides with the instant when the current passes through a local minimum value.

[0044] According to another embodiment of the proposed detection method, in which the actuator comprises a push button that can be manually operated by an operator and in which the unlocking element comprises a position indicator, the method comprises the following substeps: - measure an electrical signal from the position indicator, - determine the first instant corresponding to a predetermined position of the unlocking device from the time variations of the electrical signal from the position indicator.

[0045] The instant corresponds to a change in the electrical state of the position indicator. The instant is a time reference indicating that the action exerted on the push button has been successfully transmitted to the unlocking mechanism.

[0046] According to one embodiment of the detection method, the predetermined position of the drive element corresponding to the second instant is an intermediate displacement position of the drive element. This intermediate displacement position lies between a first extreme position in which the moving electrical contact is closed and a second extreme position in which the moving electrical contact is open.

[0047] An angular stroke of displacement of the drive element is for example between 40° and 60°.

[0048] According to one embodiment of the detection method, a displacement stroke of the drive element between the first extreme position and the predetermined position corresponding to the second instant is between 5% and 15% of a total displacement stroke of the drive element.

[0049] The initial part of the drive element's displacement stroke is thus used to determine the second reference instant. This improves the detection sensitivity of the proposed method.

[0050] The detection process may include the following sub-steps: - measure a position of the drive element when the switching device is actuation, - determine the second instant corresponding to the predetermined position of the drive element from the measured position of the drive element.

[0051] According to one embodiment of the proposed detection process: - the control mechanism includes a position sensor configured to detect a magnetic field, - the drive element includes a plurality of magnetic elements configured to pass successively in front of the position sensor during a displacement stroke of the drive element.

[0052] The magnetic elements can be permanent magnets.

[0053] The position sensor can be a Hall effect sensor.

[0054] For example, the magnetic elements are arranged on part of a periphery of the drive element.

[0055] The magnetic elements can be arranged in a plane perpendicular to an axis of rotation of the drive element.

[0056] The magnetic elements can be identical.

[0057] An angular separation between two consecutive magnetic elements can be constant.

[0058] The drive element includes, for example, four magnetic elements.

[0059] According to one embodiment, the unlocking mechanism comprises a rotating movable half-moon.

[0060] The half-moon is actuated by the magnetic core of the electromagnetic actuator.

[0061] The unlocking mechanism may include an intermediate lever comprising a first portion configured to cooperate with the half-moon and comprising a second portion configured to cooperate with the drive element.

[0062] According to one embodiment, the detection process comprises the substep: - calculate a value of a statistical parameter representative of a fluctuation in the values ​​of the set of values ​​of the time elapsed between the first instant and the second instant, - determine a degradation of the unlocking mechanism from the calculated value of the statistical parameter.

[0063] According to an example of the implementation of the detection process, the statistical parameter representing a fluctuation in the values ​​of the set of values ​​for the time elapsed between the first instant and the second instant comprises a difference between: - a current value of the time elapsed between the first instant and the second instant, determined for a current actuation of the switching device, and - an average value of the values ​​of the time elapsed between the first instant and the second instant obtained for a predetermined number of actuations preceding the current actuation of the switching device.

[0064] The average value can be a moving average calculated from the values ​​corresponding to the actuations preceding the current actuation, and comprising a number of values ​​equal to the predetermined number of actuations.

[0065] According to an example of implementation of the detection method, the statistical parameter representing a fluctuation in the values ​​of the set of values ​​of the time elapsed between the first instant and the second instant includes a standard deviation of the values ​​of the time elapsed between the first instant and the second instant determined for a set of actuations of the switching device carried out under reference conditions corresponding to a new state of the circuit breaker.

[0066] The set of actuations of the switching device carried out under reference conditions includes, for example, 20 successive actuations of the switching device.

[0067] The proposed method thus includes a calibration phase to quantify the nominal variations in the time elapsed between the first and second instants during the actuation of the switching device. These nominal variations correspond to the variations observed in a reference state in which the switching device exhibits neither assembly defects nor degradation due to wear.

[0068] The reference state corresponds, for example, to a new state of the switching device.

[0069] The proposed method includes a measurement phase in which the variations in the value of the time elapsed between the first instant and the second instant are analyzed.

[0070] The measurement phase follows the calibration phase.

[0071] The measurement phase is carried out throughout the entire period of use of the switching device.

[0072] According to an example of the implementation of the proposed detection method, the statistical parameter representing a fluctuation in the elapsed time between the first instant and the second instant is equal to the ratio of: - the difference between a current value of the time elapsed between the first instant and the second instant and the average value of the values ​​of the time elapsed between the first instant and the second instant obtained for a predetermined number of actuations preceding the current actuation, and - the standard deviation of the values ​​of the time elapsed between the first instant and the second instant determined for a set of actuations of the switching device carried out under reference conditions corresponding to a new state of the switching device.

[0073] The proposed statistical parameter enables robust detection of potential degradation of the switching device's unlocking mechanism, while remaining simple to implement. In particular, the necessary calculations can be easily performed in real time, allowing for rapid detection of degradation.

[0074] The statistical parameter representing a fluctuation in the time elapsed between the first instant and the second instant can thus be equal to: P i = D i − ∑ j = 1 − M j = i − 1 D j M ∑ j = 1 N D j − ∑ j = 1 j = N D j K K 2 With Di the determined value of the duration D for an actuation of rank i, P(i) the calculated value of the statistical parameter P for the actuation of rank i, M the number of actuations taken into account to determine an average value, K a number of actuations carried out under reference conditions corresponding to a new state of the switching device.

[0075] According to one aspect of the proposed detection method, a degradation of the unlocking mechanism is determined when the absolute value of the statistical parameter representing a fluctuation in the time elapsed between the first instant and the second instant is greater than a first predetermined positive threshold.

[0076] The value chosen for the first predetermined threshold allows the sensitivity of the proposed detection method to be adjusted.

[0077] The first predetermined threshold is, for example, between 2 and 3.

[0078] According to an example of the detection process, the degradation of the unlocking mechanism is classified into a first type of degradation, called minor degradation, when the absolute value of the statistical parameter representing a fluctuation in the time elapsed between the first instant and the second instant is greater than a first predetermined positive threshold and less than a second predetermined positive threshold.

[0079] The second predetermined threshold is, for example, between 4 and 5.

[0080] According to an example of the implementation of the detection process, the degradation of the unlocking mechanism is classified into a second type of degradation, called major degradation, when the criterion representing a fluctuation in the time elapsed between the first instant and the second instant is greater than the second predetermined threshold.

[0081] The statistical parameter P used thus allows a quantification of the degradation, and not just the presence or absence of degradation.

[0082] The detection process may include a step of emitting an alert signal in response to a determination of degradation of the unlocking device.

[0083] The alert signal emitted allows users to plan and carry out maintenance or replacement of the switching device.

[0084] No warning signal is issued when no damage has been detected. In other words, no alert is issued when the proposed procedure indicates that the unlocking mechanism is free from damage.

[0085] The invention also relates to a switching device comprising: a movable electrical contact between a closed position of an electrical circuit and an open position of the electrical circuit, a control mechanism comprising: -- a drive element configured to move the movable electrical contact so as to open an electrical circuit, -- an elastic member linked to the drive element, -- a release member configured to move from a locked position in which the elastic member is held in a tensioned state to a release position in which the elastic member is free to relax so as to move the electrical contact from the closed position to the open position of the electrical circuit, an actuator configured to move the release member from the locked position to the release position, an electronic control unit configured to implement the degradation detection method as described above.

[0086] The switching device can be a circuit breaker, or a switch, or a disconnector. Brief description of the drawings

[0087] Other features, details, and advantages will become apparent upon reading the detailed description below and analyzing the attached drawings, on which: [ Fig. 1 ] is a schematic view of an electrical circuit equipped with a switching device, the electrical circuit being in the closed position, [ Fig. 2 ] is a schematic view of an electrical circuit equipped with a switching device, the electrical circuit being in the open position, [ Fig. 3 ] is a schematic view of the control mechanism of a switching device according to a first embodiment, the electrical circuit being in the closed position, [ Fig. 4 [ ] is a schematic view of the control mechanism of the switching device of the figure 3 , with the electrical circuit in the open position, , Fig. 5] illustrates the temporal evolution of several operating parameters of the switching device figures 3 and 4 , when it is activated, [ Fig. 6 ] is a time-domain diagram illustrating the process according to the invention, [ Fig. 7 ] is a block diagram illustrating different stages of the process according to the invention, [ Fig. 8 ] is a schematic view of the control mechanism of a switching device according to a second embodiment, the electrical circuit being in the closed position, [ Fig. 9 [ ] is a schematic view of the control mechanism of the switching device of the figure 7 the electrical circuit being in the open position. Description of the implementation methods :

[0088] To facilitate the reading of the figures, the different elements are not necessarily drawn to scale. In these figures, identical elements bear the same references. Some elements or parameters may be indexed, that is, designated, for example, as first element or second element, or first parameter and second parameter, etc. This indexing aims to differentiate similar, but not identical, elements or parameters. This indexing does not imply any priority of one element or parameter over another, and the designations can be interchanged. When it is specified that a subsystem contains a given element, this does not exclude the presence of other elements in that subsystem. Similarly, when it is specified that a subsystem includes a given element, it is understood that the subsystem includes at least that element.

[0089] We have schematically represented on the figure 1an electrical circuit 50. The electrical circuit 50 comprises three electrical conductors 20, 21, 22, each conductor corresponding to one phase of a medium voltage three-phase network.

[0090] The electrical circuit 50 includes a switching device 30.

[0091] The switching device 30 can be a circuit breaker. Alternatively, the switching device 30 can be a switch. According to another application example, the switching device 30 can be a disconnect switch.

[0092] There figure 1 and the figure 2 illustrate, schematically, two states of the switching device 30.

[0093] The switching device 30 includes a movable electrical contact 10 between a closing position F of an electrical circuit 50 and an opening position O of the electrical circuit 50.

[0094] The switching device 30 also includes a control mechanism 4 comprising: - a drive element 9 configured to move the movable electrical contact 10 so as to open an electrical circuit 50, - an elastic member 7 linked to the drive element 9, - a release member 8 configured to move from a locking position V in which the elastic member 7 is held in a tension state to a release position L in which the elastic member 7 is free to relax so as to move the electrical contact 10 from the closing position F to the opening position O of the electrical circuit 50. The switching device 30 further includes an actuator 1 configured to move the unlocking member 8 from the locking position V to the release position L. The switching device 30 also includes an electronic control unit 25 configured to implement the degradation detection process which will be described in detail below.

[0095] The elastic element 7 is configured to apply a driving force to the electrical contact 10. The elastic element 7 can be a spring, for example a spiral spring or a helical spring.

[0096] The actuator 1 is configured to trigger a movement of the movable electrical contact 10 in order to open or close the electrical circuit 50. Indeed, the actuator 1 allows the control mechanism 4 to be unlocked in order to move the movable contact 10 and thus open or close the electrical circuit 50.

[0097] On the figure 1The moving contacts 10, 11, and 12 are in the closed position, meaning that an electric current can flow in the electrical circuit 50. The symbol F indicates the closed position of the moving contact 10. The elastic element 7 is in the extended state. The elastic element 7 is held in the extended state by the release element 8. The drive element 9 is blocked by the release element 8.

[0098] The opening of the electrical circuit 50 is achieved as follows: Under the action of the actuator 1, the unlocking member 8 is moved to a release position L in which the drive element 9 is no longer blocked by the unlocking member 8. The drive element 9 can move under the action of the drive force applied by the elastic member 7, which was in a tensed state and is now free to relax. The drive element 9 thus moves the electrical contact 10 from the closed position F to the open position O of the electrical circuit 50. The three movable contacts 10, 11, 12 are mechanically coupled, so that all three contacts 10, 11, 12 simultaneously move to the open position when the control mechanism 4 is unlocked. figure 2 diagram shows the position of the different elements once the moving contacts 10, 11, 12 have been moved to the opening position of the electrical circuit 50.

[0099] According to the embodiment illustrated on the figure 1 and the figure 2 , actuator 1 is an electromagnetic actuator.

[0100] The electromagnetic actuator 1 includes an electromagnet. The electromagnetic actuator 1 includes a control coil 2 and a magnetic core 3 configured to move under the action of a magnetic field created by an electric current flowing through the control coil 2. The magnetic core 3 is, for example, free to move in translation.

[0101] The unlocking member 8 is linked to the magnetic core 3 of the electromagnetic actuator 1. A displacement of the magnetic core 3 of the electromagnetic actuator 1 therefore causes a displacement of the unlocking member 8.

[0102] When the switching device 30 is a circuit breaker, the electromagnetic actuator 1 is configured to trigger an opening of the electrical circuit 50 in the event of a fault on the electrical circuit 50.

[0103] According to another embodiment, illustrated on the figures 8 And 9 The actuator 1 includes a push button 32 that can be manually operated by an operator. When the operator wishes to trigger an opening of the electrical circuit 50, the operator presses the push button 32, which is mechanically linked to the unlocking element 8. The unlocking element 8 is thus unlocked by the operator's action on the push button 32.

[0104] In this embodiment, the unlocking member 8 includes a position indicator 33.

[0105] The proposed method aims to detect degradation of the switching device 30, that is, to detect a change in the behavior of the control mechanism 4 of the switching device 30, and in particular of the unlocking element 8, due to the aging of its components. Component aging includes, for example, wear, deformation, changes in magnetic performance, and changes in the tribological properties of the components.

[0106] A method for detecting degradation of a switching device 30 is therefore proposed, comprising: an electrical contact 10 movable between a closed position F of an electrical circuit 50 and an open position O of the electrical circuit 50, a control mechanism 4 comprising: -- a drive element 9 configured to move the movable electrical contact 10 so as to open an electrical circuit 50, -- an elastic member 7 linked to the drive element 9, -- a release member 8 configured to move from a locking position V in which the elastic member 7 is held in a tensioned state to a release position L in which the elastic member 7 is free to relax so as to move the electrical contact 10 from the closed position F to the open position O of the electrical circuit 50, or from the open position O to the closed position F, an actuator 1 configured to move the release member 8 from the locking position V to the release position L, The process includes the following steps: (i) control the actuator 1, (ii) determine a first instant t1 corresponding to a predetermined position P1 of the unlocking member 8, (iii) determine a second instant t2 corresponding to a predetermined position P2 of the drive element 9, (iv) determine a time D elapsed between the first instant t1 and the second instant t2, (v) iterate the steps (i) to (iii) for a set of successive commands of the actuator 1, so as to obtain a set E of values ​​of the time D elapsed between the first instant t1 and the second instant t2, (vi) determine a degradation of the unlocking member 8 of the switching device 30 from the evolution of the values ​​of the set E during the successive commands of the actuator 1.

[0107] The time interval D between the first instant t1 and the second instant t2 corresponds to the reaction time of the unlocking element 8. Monitoring the evolution of the value of time D, that is, how time D changes over the lifetime of the switching device 30, allows us to track the behavior of the unlocking element of the control mechanism 4 during its use. When the unlocking element of the control mechanism 4 operates nominally, the values ​​of the entire E' set do not change significantly during successive actuations of the switching device 30. In other words, the various values ​​of the entire E' set remain essentially constant.Conversely, a gradual degradation of the unlocking element of the control mechanism 4 during the service life of the switching device 30 tends to cause changes in the values ​​of the E assembly during successive actuations, in particular a fluctuation of these values. The values ​​of the E assembly are thus no longer essentially constant and exhibit a significant change. This gradual change makes it possible to detect a degradation of the unlocking element 8 of the control mechanism 4. The method for detecting a degradation of the switching device 30 is also a method for detecting a fault in the switching device 30. Indeed, an uncorrected degradation of the switching device 30 can eventually lead to the occurrence of a fault, and this fault can also be detected.

[0108] The opening and closing movements of the movable electrical contact can be achieved in a similar manner. In one example, the electrical contact 10 is movable between a closed position F of the electrical circuit 50 and an open position O of the electrical circuit 50, and the release of the elastic element 7 moves the electrical contact 10 from the closed position F to the open position O of the electrical circuit 50. The control mechanism 4 thus interrupts the flow of electric current in the circuit 50.

[0109] According to another example of implementation, the electrical contact 10 is movable between an open position O of an electrical circuit 50 and a closed position F of the electrical circuit 50, and a release of the elastic element 7 moves the electrical contact 10 from the open position O to the closed position F of the electrical circuit 50. The control mechanism 4 thus makes it possible to establish a flow of electric current in the circuit 50.

[0110] The set E of values ​​of the time D elapsed between the first instant t1 and the second instant t2 is obtained by a succession of consecutive actuations of the switching device 30. Each value of the set E of values ​​of the time D elapsed between the first instant t1 and the second instant t2 corresponds to a distinct actuation of the switching device 30.

[0111] Each actuation of the switching device 30 corresponds to a command from the actuator 1. An actuation of the switching device 30 is understood to mean a passage of the electrical contact 10 from the closing position F of the electrical circuit 50 to the opening position O of the electrical circuit 50 in response to a command from the actuator 1.

[0112] When actuator 1 is an electromagnetic actuator, actuation of the switching device 30 is obtained by circulating current in the control coil 2. When actuator 1 is a push button, actuation of the switching device 30 is obtained by the operator pressing the push button.

[0113] The predetermined position P1 of the unlocking member 8 is a first characteristic position allowing the definition of a first time reference for characterizing the operation of the control mechanism 4. The predetermined position P2 of the drive element 9 is a second characteristic position allowing the definition of a second time reference for characterizing the operation of the control mechanism 4. More precisely, the time interval between these two time references can be a parameter for determining a degradation of the control mechanism 4 of the switching device 30.

[0114] According to the illustrated example, the predetermined position P1 of the unlocking member 8 allowing the determination of the first instant t1 can be an equilibrium position of the unlocking member 8. In other words, the unlocking member 8 has a zero velocity when the unlocking member 8 is in the predetermined position P1 allowing the determination of the first instant t1.

[0115] According to an embodiment not shown, the predetermined position P1 of the unlocking member 8, which determines the first instant t1, can be a transient position of the unlocking member 8. In this case, the unlocking member 8 has a non-zero velocity when it is in the predetermined position P1, which determines the first instant t1. The first instant t1 corresponds to the unlocking member 8 passing through the first position P1.

[0116] The predetermined position P2 of the drive element 9, which determines the second time t2, can be a transient position of the drive element 9. In other words, the drive element 9 has a non-zero velocity when it is in the predetermined position P2, which determines the second time t2. The second time t2 corresponds to the drive element 9 passing through the second position P2.

[0117] The duration D elapsed between the first instant t1 and the second instant t2 corresponds to the duration separating the first instant t1 and the second instant t2.

[0118] The method for determining the first instant t1 depends on the type of actuator 1. When actuator 1 is an electromagnetic actuator, the determination of the first instant t1 is based on a measurement of the current in the electromagnetic actuator 1.

[0119] Measuring a current C flowing in the electromagnetic actuator 1 means measuring the intensity of the electric current flowing in the electromagnetic actuator 1. The current C flowing in the electromagnetic actuator 1 can be detected by a current measurement sensor 6. The current C flowing in the electromagnetic actuator 1 can be sampled, for example with a sampling frequency between 1 kHz and 100 kHz.

[0120] In the embodiment in which the actuator 1 is an electromagnetic actuator, the method comprises the following substeps: - measure a current C flowing in the electromagnetic actuator 1 when the switching device 30 is actuation, - determine the first instant t1 corresponding to a predetermined position P1 of the unlocking member 8 from the time variations of the measured current C.

[0121] The proposed method therefore does not require the installation of any additional sensors, such as a sensor for the displacement of the electrical contact or a sensor for the displacement of an element of the actuation mechanism.

[0122] The proposed method can therefore include a sub-step of determining the temporal variations of the measured current C.

[0123] The electromagnetic actuator 1 comprises a control coil 2 and a magnetic core 3 configured to move under the action of a magnetic field created by an electric current flowing in the control coil 2. The predetermined position P1 of the unlocking member 8 corresponding to the first instant t1 is a position of maximum displacement of the magnetic core 3.

[0124] In other words, the first instant t1 corresponds to an instant when the magnetic core 3 reaches its position of maximum displacement.

[0125] The first instant t1 corresponding to a predetermined position P1 of the unlocking member 8 is an instant corresponding to a local minimum value of the electric current flowing in the electromagnetic actuator 1.

[0126] The first instant t1 can thus be determined from the time evolution of the intensity of the current flowing in the control coil 2, and coincides with the instant when the current passes through a local minimum value.

[0127] There figure 5 illustrates the evolution of several parameters during the actuation of the switching device. On the figure 5Curve G2 illustrates the temporal evolution of the electric current in the electromagnetic actuator 1 during its activation. Curve G2 comprises a first, continuously increasing portion z1, a second, continuously decreasing portion z2, the second portion z2 following the first portion z1, a third, continuously increasing portion z3, the third portion z3 following the second portion z2. The instant t1, corresponding to the local minimum of the current, is the instant separating the third portion z3 from the second portion z2. The electromagnet activation is deactivated at time tf, and the portion z4 corresponds to a phase of current decay until it reaches a zero value. The current remains zero until the next activation, or activation, of the electromagnet.

[0128] A local maximum current value i1 is obtained at a time tm between a time t0, when the electric current begins flowing in the electromagnetic actuator 1, and a time t1 corresponding to a local minimum of the electric current flowing in the electromagnetic actuator 1. The local maximum current value i1 is the current value obtained at the transition from the first segment z1 to the second segment z2. The decrease in current between time tm and time t1 is related to the change in the air gap between the moving and fixed parts. Once the air gap stops changing, the current begins to increase again, corresponding to segment z3 of the curve G2. From time t1 onward, the electromagnetic actuator 1 has reached its maximum travel, and the position of the magnetic core 3 no longer changes. However, the electrical control is maintained until time tf to ensure a holding force.

[0129] When actuator 1 is a purely mechanical push-button type actuator, the determination of the first instant t1 is based on the signal from a position indicator, also called a position sensor.

[0130] The unlocking mechanism 8 includes a position indicator 33. The position indicator 33 can provide a two-level signal. The position indicator 33 is a two-state electrical contactor. In other words, the signal from the position indicator 33 switches from a first level to a second level when the locking mechanism reaches a certain threshold position.

[0131] Thus, in the proposed embodiment of the detection method, in which the actuator 1 comprises a push button 32 that can be manually operated by an operator and in which the unlocking member 8 comprises a position indicator 33, the method comprises the following substeps: - measure an electrical signal from the position indicator 33, - determine the first instant t1 corresponding to a predetermined position P1 of the unlocking member 8 from the time variations of the electrical signal from the position indicator 33.

[0132] The instant t1 corresponds to a change of electrical state of the position indicator 33. The instant t1 is a time reference indicating that the action exerted on the push button by the operator has been transmitted to the unlocking element 8.

[0133] There figure 3 and the figure 4 The figures illustrate one embodiment of the control mechanism 4 of the switching device 30, in which the actuator 1 is an electromagnetic actuator. To simplify the figure, the elastic element 7 is represented as a helical spring. The elastic element 7 can also be a spiral spring.

[0134] On the figure 3The unlocking member 8 is in the locked position V and the spring 7 is held in a compressed state. One end of the spring 7 exerts a force on a fixed stop 18, the other end of the spring exerts a force on the drive element 9.

[0135] The drive element 9 is free to rotate. The drive element 9 is connected to the moving contact 10 by a connecting rod 19. The connecting rod 19 is rigid. The connecting rod 19 is pivotally connected to the drive element 9. The connecting rod 19 is pivotally connected to the moving contact 10.

[0136] The unlocking mechanism 8 comprises a rotatable half-moon 16. The half-moon 16 has a general semi-cylindrical shape and includes a flat surface 16-1 extending parallel to the axis of the semi-cylinder. The half-moon 16 is actuated by the magnetic core 3 of the electromagnetic actuator 1. "Actuated" means that the half-moon 16 can rotate in response to the movement of the magnetic core 3. The electromagnetic actuator 1 includes a connecting element 13 linking the movable magnetic core 3 and the half-moon 16.

[0137] The unlocking member 8 also includes an intermediate lever 17 comprising a first portion 17-1 configured to cooperate with the half-moon 16 and comprising a second portion 17-2 configured to cooperate with the drive element 9.

[0138] On the figure 3where the unlocking member 8 is in the locking position V, the driving force of the elastic member 7 applied to the drive element 9 is transmitted to the intermediate lever 17 of the unlocking member 8. The half-moon 16 is in the locking position, and blocks the rotation of the intermediate lever 17 because the first portion 17-1 of the intermediate lever 17 interferes with the surface 16-1 of the half-moon 16. The second portion 17-2 blocks the drive element 9, which is thus held in place. The spring 7 is kept compressed between the drive element 9 and the fixed stop 18. When the half-moon 16 leaves its locking position, the first portion 17-1 is no longer held and the force applied at the level of the second portion 17-2 causes the intermediate lever 17 to pivot. The intermediate lever 17 can thus pivot under the action of the driving force of the elastic element 7.The drive element 9 can thus move under the action of the drive force of the elastic member 7. The connecting rod 19, integral with the drive element 9, rotates the movable contact 10.

[0139] On the figure 4 The unlocking mechanism 8 is in the release position L. The spring 7, in its relaxed state, after rotating the drive element 9 and thus moving the movable electrical contact 10, is in the open position O. On the figure 4 , the half-moon 16 of the unlocking organ 8 is represented in position P1 used to define the first time reference t1.

[0140] According to the illustrated embodiment, the predetermined position of the drive element 9 corresponding to the second instant t2 is an intermediate displacement position of the drive element 9. The intermediate displacement position lies between a first extreme position B1 in which the movable electrical contact 10 is in the closed position F and a second extreme position B2 in which the movable electrical contact 10 is in the open position O. The figure 3 diagram shows the first extreme position B1 and the figure 4 diagram the second extreme position B2.

[0141] According to the illustrated example, the displacement of the drive element 9 between the first extreme position B1 and the predetermined position P2 corresponding to the second time t2 is between 5% and 15% of the total displacement CT of the drive element 9. The initial portion of the drive element 9's displacement is thus used to determine the second reference time. The detection sensitivity of the proposed method is thereby improved.

[0142] The total displacement stroke CT is the distance between the first extreme position B1 and the second extreme position B2 of the drive element 9. In the case where the drive element 9 is rotationally mobile, the total displacement stroke CT is an angular distance.

[0143] The angular stroke CT of the drive element 9 is, for example, between 40° and 60°. The symbol L0 designates a reference indicating the initial position B1 of the drive element 9, and the symbol L1 designates the position of this reference after a complete rotation of the drive element 9, when it is in position B2. The difference between L0 and L1 indicates the rotational stroke CT. The symbol L2 designates the position of the reference L0 at the moment when the drive element 9 is in the predetermined position P2, corresponding to the second instant t2.

[0144] The detection process may include the following sub-steps: - measure a position of the drive element 9 during the actuation of the switching device 30, - determine the second instant t2 corresponding to the predetermined position P2 of the drive element 9 from the measured position of the drive element 9.

[0145] According to the implementation method illustrated here: - the control mechanism 4 includes a position sensor 14 configured to detect a magnetic field, - the drive element 9 includes a plurality of magnetic elements 15 configured to pass successively in front of the position sensor 14 during a displacement stroke of the drive element 9.

[0146] When the drive element 9 moves from the first extreme position B1, in which the movable electrical contact 10 is in the closed position F, to a second extreme position B2, in which the movable electrical contact 10 is in the open position O, the passage of a magnetic element 15 in front of the position sensor 14 generates a change in the electrical state of the position sensor 14. When this magnetic element 15 moves away from the sensor 14, the position sensor 15 returns to its initial electrical state. The rotation of the drive element 9 therefore generates a signal consisting of a succession of pulses, each pulse corresponding to a distinct magnetic element 15. The magnetic elements 15 can be permanent magnets. The position sensor 14 can be a Hall effect sensor.

[0147] The magnetic elements 15 are arranged on a portion of the periphery of the drive element 9. The magnetic elements 15 are arranged in a plane perpendicular to an axis of rotation of the drive element 9. The magnetic elements 15 are identical in the illustrated example. The magnetic elements 15 may also be different. An angular separation T between two consecutive magnetic elements 15 is constant here. The magnetic elements may also be arranged with an angular separation T between two consecutive magnetic elements 15 that is not constant from one magnetic element to another.

[0148] The drive element 9, as illustrated, comprises four magnetic elements 15. The four magnetic elements 15 are permanent magnets. On the figure 3 and the figure 4 The 4 permanent magnets are designated by the symbols 15-1, 15-2, 15-3, 15-4. A different number of magnetic elements can of course be used.

[0149] On the figure 5 Curve G3 illustrates the signal provided by position sensor 14 during the movement of drive element 9. Time t2 corresponds to the beginning of the passage of the first magnet 15-1 in front of position sensor 14. Time t3 corresponds to the beginning of the passage of the second magnet 15-2 in front of position sensor 14. Similarly, time t4 corresponds to the beginning of the passage of the third magnet 15-3 and time t5 corresponds to the beginning of the passage of the fourth magnet 15-4. The time between the passage of two consecutive magnets is not constant because the speed of movement is not constant. On the figure 5Curve G1 indicates the signal delivered by a high-resolution position sensor. In other words, this sensor delivers a substantially continuous signal, not a discrete one. This sensor was mounted solely for experimental purposes to validate the proposed method and is not part of the switching device 30 when used nominally. Therefore, the signal from curve G1 is not used by the proposed method. Up to time td, the signal is constant, indicating that the drive element 9 is stationary. The drive element 9 begins to rotate at the time designated by td. The time t2 at which the position sensor 14 changes its electrical state due to the passage of the magnet 15-1 is later than time td because of the travel required for the magnet 15-1 to be in a position opposite the position sensor 14.

[0150] As illustrated on the figure 5The predetermined position of the drive element 9 defining the second instant t2 corresponds to the position of the first magnet 15-1 passing in front of the position sensor 14. The predetermined position P1 of the unlocking member 8 defining the first instant t1 is the final pivoting position of the half-moon 16. The time lag between instant t1 and instant t2 defines a duration D.

[0151] There figure 8 and the figure 9 illustrate one embodiment of the control mechanism 4 of the switching device 30, in which the actuator 1 is a mechanical actuator of the push button type.

[0152] This method of implementation differs from that of figures 3 and 4by the nature of the actuator 1 and by the presence of the position indicator 33. The push button 32 is connected to the half-moon 16 by a connecting element 13B. For example, the push button 32 is integral with a connecting element 13B attached to the half-moon 16. This connecting element 13B can move the half-moon 16 in a manner analogous to that described in the embodiment with electromagnetic actuator, figures 3 and 4 .

[0153] Time t1 is determined from the electrical signal delivered by the position indicator 33. The position indicator 33 comprises a pivoting tab 34 held at a distance from a contactor 35 by a spring, not shown. When the half-moon 16 is distant from the pivoting tab 34, as is the case on the figure 8The tab is itself a distance from the contactor 35, which is in its released state. The position indicator 33 outputs a first signal level. Once the half-moon 16 has rotated sufficiently, it moves the pivoting tab 34, which presses on the contactor 35 and causes it to leave its released state. The position indicator 33 then outputs a second signal level. The instant corresponding to a transition between the first and second signal levels allows us to determine the first instant t1. In this embodiment, the rest of the control mechanism 4 is identical to the embodiment of the figures 3 and 4 and the determination of the second instant t2 is carried out in the same way.

[0154] The determined duration D is the physical parameter on which the method for detecting a degradation of the control mechanism 4 is based. Statistical processing is applied to this physical parameter.

[0155] The detection process thus includes the following sub-step: - calculate a value of a statistical parameter P representative of a fluctuation of the values ​​of the set E of values ​​of the time D elapsed between the first instant t1 and the second instant t2, - determine a degradation of the unlocking organ 8 from the calculated value of the statistical parameter P.

[0156] According to an example of the implementation of the detection process, the statistical parameter P representing a fluctuation in the values ​​of the set E of values ​​over the time D elapsed between the first instant t1 and the second instant t2 comprises a difference between: - a current value of the time D elapsed between the first instant t1 and the second instant t2, determined for a current actuation of the switching device 30, and - an average value Moy of the values ​​of the time D elapsed between the first instant t1 and the second instant t2 obtained for a predetermined number M of actuations preceding the current actuation of the switching device 30.

[0157] The average value Moy can be a moving average calculated from the values ​​corresponding to the actuations preceding the current actuation, and comprising a number of values ​​equal to the predetermined number M of actuations.

[0158] According to an example of implementation of the detection method, the statistical parameter P representing a fluctuation of the values ​​of the set E of values ​​of the time D elapsed between the first instant t1 and the second instant t2 includes a standard deviation of the values ​​of the time D elapsed between the first instant t1 and the second instant t2 determined for a set of actuations of the switching device 30 carried out under reference conditions corresponding to a new state of the circuit breaker 30.

[0159] The set of actuations of the switching device 30 carried out under reference conditions includes, for example, 20 successive actuations of the switching device 30.

[0160] The proposed method thus includes a calibration phase to quantify the nominal variations in the value of the time interval D elapsed between the first instant t1 and the second instant t2 during the actuation of the switching device 30. These nominal variations correspond to the variations observed in a reference state in which the switching device 30 exhibits neither assembly defects nor degradation due to wear. The reference state corresponds, for example, to a new state of the switching device 30.

[0161] The proposed method includes a measurement phase in which the variations in the value of the time interval D elapsed between the first instant t1 and the second instant t2 are analyzed. The measurement phase follows the calibration phase. The measurement phase is carried out throughout the entire operating time of the switching device 30.

[0162] The values ​​acquired under these reference conditions allow us to determine the nominal variability of the time interval D elapsed between the first instant t1 and the second instant t2. This nominal variability is characterized here by the mathematical quantity equal to the standard deviation of the time interval D elapsed between the first instant t1 and the second instant t2, calculated for all measurements taken under the reference conditions. This nominal variability is characterized based on a predetermined number of values ​​corresponding to a predetermined number of actuations. For example, 20 successive actuations performed when the switching device 30 is new can be used to characterize the nominal variability of the quantity used to determine a degradation of the switching device 30.

[0163] There figure 6This illustrates the values ​​of the duration D between the first instant t1 and the second instant t2, for different actuations of the switching device 30. Part A schematically represents the measurements taken at a first instant t_A. Part B of the figure schematically represents the measurements taken at a second instant t_B, which is later than t_A.

[0164] The measurement points enclosed within the frame designated J0 are those taken under reference conditions corresponding to a new state of the switching device 30. To simplify the figure, only 7 measurement points are shown. It can be observed that the dispersion of the values ​​of the quantity D is small. The symbol Ec0 denotes the standard deviation of the values ​​corresponding to the set of actuations of the switching device 30 performed under reference conditions and taken into account for the calibration phase.

[0165] On part A of the figure 6The measurement points enclosed within the frame designated J1 are the points used at time t_A for the measurement phase. As before, to simplify the figure, only 10 measurement points for the duration D are shown. The value Dn, determined at time t_A, is the current value at time t_A, that is, the most recent value. The horizontal dashed line indicates the average value avg_A of the values ​​taken into account, that is, those present within frame J1. The arrow designated e_A ​​illustrates the difference between the current value Dn and the average value avg_A calculated in this example from the 10 measurement points preceding the current measurement Dn.

[0166] On part B of the figure 6The measurement points enclosed within the frame designated J2 are the points used at time t_B for the measurement phase. As before, 10 measurement points are used in the figure. The value determined at time t_B is the current value at time t_B, that is, the most recent value. Compared to time t_A, 4 new measurements have been acquired, and the 4 oldest values ​​in frame J1 are not used at time t_B and are not part of frame J2. The horizontal dashed line indicates the average value avg_B of the values ​​taken into account, that is, those present in frame J2. The arrow designated e_B illustrates the difference between the current value Dn+4 and the average value avg_B.

[0167] More precisely, the statistical parameter P representing a fluctuation in the duration D elapsed between the first instant t1 and the second instant t2 is equal to the ratio of: - the difference between a current value Di of the time D elapsed between the first instant t1 and the second instant t2 and the average value Moy of the values ​​of the time D elapsed between the first instant t1 and the second instant t2 obtained for a predetermined number M of actuations preceding the current actuation, and - the standard deviation Ec of the values ​​of the time D elapsed between the first instant t1 and the second instant t2 determined for a set of actuations of the switching device 30 carried out under reference conditions corresponding to a new state of the switching device 30.

[0168] The proposed statistical parameter P enables robust detection of potential damage to the unlocking mechanism 8 of the control mechanism 4 of the switching device 30, while remaining simple to implement. In particular, the necessary calculations can easily be performed in real time, allowing for rapid detection of damage.

[0169] The statistical parameter P representing a fluctuation in the duration D elapsed between the first instant t1 and the second instant t2 is thus equal to: P i = D i − ∑ j = 1 − M j = i − 1 D j M ∑ j = 1 N D j − ∑ j = 1 j = N D j K K 2 With Di the determined value of the duration D for an actuation of rank i, P(i) the calculated value of the statistical parameter P for the actuation of rank i, M the number of actuations taken into account to determine an average value, K the number of actuations carried out under reference conditions corresponding to a new state of the switching device 30.

[0170] The calculation of the statistical parameter P allows us to conclude on the state of the control mechanism 4. A degradation of the unlocking member 8 is determined when the absolute value of the statistical parameter P representing a fluctuation of the time D elapsed between the first instant t1 and the second instant t2 is greater than a first predetermined positive threshold S1.

[0171] The value chosen for the first predetermined threshold S1 allows the sensitivity of the proposed detection method to be adjusted. The first predetermined threshold S1 is, for example, between 2 and 3.

[0172] According to an example embodiment of the detection method, the degradation of the unlocking element 8 is classified into a first type of degradation, called minor degradation, when the absolute value of the statistical parameter P representing a fluctuation in the time D elapsed between the first instant t1 and the second instant t2 is greater than a first predetermined positive threshold S1 and less than a second predetermined positive threshold S2. The second predetermined positive threshold S2 is, for example, between 4 and 5.

[0173] The degradation of the unlocking mechanism 8 is classified into a second type of degradation, called major degradation, when the absolute value of the parameter D representing a fluctuation of the duration D elapsed between the first instant t1 and the second instant t2 is greater than the second predetermined threshold S2.

[0174] The statistical parameter P used thus allows a quantification of the degradation, and not just a determination of the presence or absence of degradation.

[0175] The detection process may include a step of emitting an alert signal in response to a determination of degradation of the unlocking device 8. The alert signal emitted allows users to plan and carry out a maintenance or replacement operation of the switching device 30.

[0176] The warning signal can be, for example, a code stored in an electronic control unit. Alternatively, or in addition, the warning signal can be an indicator light. Another alternative, or additional, is the display of a message on a control screen. Other types of alerts are, of course, possible.

[0177] No warning signal is issued when no degradation has been detected. In other words, no alert is issued when the proposed method indicates that control mechanism 4 is free from degradation.

Claims

1. A method for detecting a degradation of a switching device (30) comprising: - an electrical contact (10) movable between a closing position (F) of an electrical circuit (50) and an opening position (O) of the electrical circuit (50), - a control mechanism (4) comprising: -- a driving element (9) configured to move the movable electrical contact (10) so as to open an electrical circuit (50), -- an elastic member (7) linked to the driving element (9), -- an unlocking member (8) configured to pass from a locking position (V) wherein the elastic member (7) is kept in a state of tension to a release position (L) wherein the elastic member (7) is free to relax so as to move the electrical contact (10) from the closing position (F) to the opening position (O) of the electrical circuit (50) or from the opening position (O) to the closing position (F), - an actuator (1) configured to move the unlocking member (8) from the locking position (V) to the release position (L), the method comprising the steps of: (i) controlling the actuator (1) so as to move the unlocking member (8) from the locking position (V) to the release position (L), characterised in that the method furthermore comprises the steps of: (ii) determining a first instant (t1) corresponding to a predetermined position (P1) of the unlocking member (8), (iii) determining a second instant (t2) corresponding to a predetermined position (P2) of the driving element (9), (iv) determining a duration (D) elapsed between the first instant (t1) and the second instant (t2), (v) iterating steps (i) to (iii) for a set of successive commands of the actuator (1), so as to obtain a set (E) of values of the duration (D) elapsed between the first instant (t1) and the second instant (t2), (vi) determining a degradation of the unlocking member (8) of the switching device (30) from the evolution of the values of the set (E) in the course of the successive commands of the actuator (1).

2. The detection method according to claim 1, wherein the actuator (1) is an electromagnetic actuator, and wherein the method comprises the sub-steps of: - measuring a current (C) circulating in the electromagnetic actuator (1) during the actuation of the switching device (30), - determining the first instant (t1) corresponding to a predetermined position (P1) of the unlocking member (8) from the temporal variations of the measured current (C).

3. The detection method according to claim 2, wherein the electromagnetic actuator (1) comprises a control coil (2) and a magnetic core (3) configured to move under the action of a magnetic field created by a circulation of electrical current in the control coil (2), and wherein the predetermined position (P1) of the unlocking member (8) corresponding to the first instant (t1) is a maximum displacement position of the magnetic core (3).

4. The detection method according to claim 2 or 3, wherein the first instant (t1) corresponding to a predetermined position (P1) of the unlocking member (8) is a instant (tm) corresponding to a local minimum value of the electrical current circulating in the electromagnetic actuator (1).

5. The detection method according to claim 1, wherein the actuator (1) comprises a push button (32) that can be manually actuated by an operator and wherein the unlocking member (8) comprises a position indicator (33), wherein the method comprises the sub-steps of: - measuring an electrical signal of the position indicator (33), - determining the first instant (t1) corresponding to a predetermined position (P1) of the unlocking member (8) from the temporal variations of the electrical signal of the position indicator (33).

6. The detection method according to one of the preceding claims, wherein the predetermined position of the driving element (9) corresponding to the second instant (t2) is an intermediate displacement position of the driving element (9), the intermediate displacement position being between a first extreme position (B1) wherein the movable electrical contact (10) is in the closed position (F) and a second extreme position (B2) wherein the movable electrical contact (10) is in the opening position (O).

7. The detection method according to the preceding claim, wherein a displacement stroke of the driving element (9) between the first extreme position (B1) and the predetermined position (P2) corresponding to the second instant (t2) is comprised between 5% and 15% of a total displacement stroke (CT) of the driving element (9).

8. The detection method according to one of the preceding claims, comprising the substeps of: - measuring a position of the driving element (9) during the actuation of the switching device (30), - determining the second instant (t2) corresponding to the predetermined position (P2) of the driving element (9) from the measured position of the driving element (9).

9. The detection method according to one of the preceding claims, wherein: - the control mechanism (4) comprises a position sensor (14) configured to detect a magnetic field, - the driving element (9) comprises a plurality of magnetic elements (15) configured to pass successively in front of the position sensor (14) during a displacement stroke of the driving element (9).

10. The detection method according to one of the preceding claims, comprising the sub-step of: - calculating a value of a statistical parameter (P) representative of a fluctuation of the values of the set (E) of values of the duration (D) elapsed between the first instant (t1) and the second instant (t2), - determining a degradation of the unlocking member (8) from the calculated value of the statistical parameter (P).

11. The detection method according to the preceding claim, wherein the statistical parameter (P) representative of a fluctuation of the values of the set (E) of values of the duration (D) elapsed between the first instant (t1) and the second instant (t2) comprises a difference (X) between: - a current value of the duration (D) elapsed between the first instant (t1) and the second instant (t2), determined for a current actuation of the switching device (30), and - an average value (Moy) of the values of the duration (D) elapsed between the first instant (t1) and the second instant (t2) obtained for a predetermined number (M) of actuations preceding the current actuation of the switching device (30).

12. The detection method according to claim 10 or 11, wherein the statistical parameter (P) representative of a fluctuation of the values of the set (E) of values of the duration (D) elapsed between the first instant (t1) and the second instant (t2) comprises a standard deviation of the values of the duration (D) elapsed between the first instant (t1) and the second instant (t2) determined for a set of actuations of the switching device (30) carried out under reference conditions corresponding to a new condition of the circuit breaker (30).

13. The detection method according to one of claims 10 to 12, wherein the statistical parameter (P) representative of a fluctuation of the duration (D) elapsed between the first instant (t1) and the second instant (t2) is equal to the ratio of: - the difference (X) between a current value (Di) of the duration (D) elapsed between the first instant (t1) and the second instant (t2) and the average value (Moy) of the values of the duration (D) elapsed between the first instant (t1) and the second instant (t2) obtained for a predetermined number (M) of actuations preceding the current actuation, and - the determined standard deviation of the values of the duration (D) elapsed between the first instant (t1) and the second instant (t2) determined for a set of actuations of the switching device (30) carried out under reference conditions corresponding to a new condition of the switching device (30).

14. The detection method according to one of claims 10 to 13, wherein the statistical parameter (P) representative of a fluctuation of the duration (D) elapsed between the first instant (t1) and the second instant (t2) is equal to: P i = D i − ∑ j = 1 − M j = i − 1 D j M ∑ j = 1 N D j − ∑ j = 1 j = N D j K K 2 Where Di is the determined value of the duration D for an actuation of rank i, P(i) is the calculated value of the statistical parameter P for the actuation of rank i, M is the number of actuations taken into account in order to determine an average value, K is the number of actuations carried out under reference conditions corresponding to a new condition of the switching device 30.

15. The detection method according to one of claims 10 to 14, wherein a degradation of the unlocking member (8) is determined when the absolute value of the statistical parameter (P) representative of a fluctuation of the duration (D) elapsed between the first instant (t1) and the second instant (t2) is greater than a first positive predetermined threshold (S1).

16. The method according to the preceding claim, wherein: - the degradation of the unlocking member (8) is classified as a first type of degradation, referred to as minor degradation, when the absolute value of the statistical parameter (P) representative of a fluctuation of the duration (D) elapsed between the first instant (t1) and the second instant (t2) is greater than a first positive predetermined threshold (S1) and less than a second positive predetermined threshold (S2), and wherein: - the degradation of the unlocking member (8) is classified as a second type of degradation, referred to as major degradation, when the absolute value of the statistical parameter (P) representative of a fluctuation of the duration (D) elapsed between the first instant (t1) and the second instant (t2) is greater than the second positive predetermined threshold (S2).

17. The detection method according to claim 15 or 16, comprising a step of transmitting an alert signal in response to a determination of a degradation of the unlocking member (8).

18. A switching device (30) comprising: - an electrical contact (10) movable between a closing position (F) of an electrical circuit (50) and an opening position (O) of the electrical circuit (50), - a control mechanism (4) comprising: -- a driving element (9) configured to move the movable electrical contact (10) so as to open an electrical circuit (50), -- an elastic member (7) linked to the driving element (9), -- an unlocking member (8) configured to pass from a locking position (V) wherein the elastic member (7) is kept in a state of tension to a release position (L) wherein the elastic member (7) is free to relax so as to move the electrical contact (10) from the closing position (F) to the opening position (O) of the electrical circuit (50), - an actuator (1) configured to move the unlocking member (8) from the locking position (V) to the release position (L), - an electronic control unit (25) configured to implement the method for detecting degradation according to one of the preceding claims, the switching device (30) being a circuit breaker, or a switch, or a disconnector.