Electrical protection device, electrical apparatus and associated control method

Abstract

The invention relates to an electrical protection device, comprising: a mechanical switch; a switching unit (18) comprising a plurality of switching modules (32, 42) comprising at least one semiconductor element (34, 35, 44, 45) and a voltage limiting element (39, 49), each switching module having a limiting voltage (Ulim1, Ulim2), each switching module being configured to switch between a conducting configuration and a blocking configuration; and a control unit comprising a unit control module (66) configured to continuously switch each switching module to a blocking configuration, the input of the mechanical switch and the input (18a) of the switching unit, and the output of the mechanical switch and the output (18b) of the switching unit being connected to each other by non-switchable electrical connections (19a, 19b).

Description

TECHNICAL FIELD

[0001] The present invention relates to an electrical protection device, an electrical equipment and a related control method. BACKGROUND

[0002] It is known to use electrical protection devices comprising a mechanical switch and a switching unit comprising at least one switching module having a semiconductor element connected in parallel with a voltage limiting element. These protection devices are also called hybrid circuit breakers. US2022122801A1 describes a hybrid circuit breaker for high voltage direct current comprising a main circuit breaker having several switching modules connected in series. When a short circuit type fault is detected and the current needs to be interrupted, the switching modules are sequentially opened, allowing the voltage across the main circuit breaker terminals to gradually increase, preventing the main circuit breaker components from deteriorating.

[0003] However, this known hybrid circuit breaker comprises an auxiliary switch connected in series with the mechanical switch, including the assembly of the auxiliary switch and the mechanical switch connected in parallel with the main circuit breaker. The auxiliary switch generates significant electrical losses, such as losses caused by heat dissipation, and increases the number of components required to implement the hybrid circuit breaker. SUMMARY

[0004] It is an object of the present invention to propose a protection device that reduces electrical losses and limits the number of components.

[0005] To this end, the invention relates to an electrical protection device configured to be connected between a source and a load, the device comprising:

[0006] a mechanical switch configured to switch between a closed configuration in which the mechanical switch conducts an electrical current flowing between the source and the load and an open configuration in which the mechanical switch does not conduct the electrical current;

[0007] a switching unit connected in parallel with the mechanical switch, the switching unit comprising a plurality of switching modules connected to each other, each switching module comprising:

[0008] at least one semiconductor element; and

[0009] a voltage limiting element connected in parallel with the or each semiconductor element,

[0010] each switching module having a limiting voltage, each switching module being configured to transition between a conducting configuration in which the electrical current flows through the semiconductor element or one of the semiconductor elements of the switching module and a blocking configuration in which, if the electrical current flows through the switching module, it flows through the voltage limiting element;

[0011] a current sensor configured to measure a value of the electrical current;

[0012] a control unit comprising:

[0013] a detection module configured to detect a short-circuit type electrical fault based on the value of the current measured by the current sensor;

[0014] a mechanical switch control module configured to switch the mechanical switch to an open configuration when a short-circuit type electrical fault is detected; and

[0015] a unit control module configured to switch each switch module to a blocking configuration in turn, one of the switch modules being commanded from the conducting configuration to the blocking configuration when the dielectric strength of the mechanical switch is greater than or equal to the sum of the limit voltage of said switch module and the limit voltage of the switch module in the blocking configuration.

[0016] According to the invention, the input of the mechanical switch and the input of the switch unit are connected to each other by an electrically non-switchable connection, and the output of the mechanical switch and the output of the switch unit are connected to each other by an electrically non-switchable connection.

[0017] The electrically non-switchable connection means that the device does not comprise an auxiliary switch. Thus, thanks to the invention, the number of components of the electrical device is reduced and the electrical and thermal losses are minimized, thus improving the performance of the device.

[0018] Furthermore, the use of a plurality of switch modules allows the current to be immediately limited when the dielectric strength of the mechanical switch is greater than or equal to the sum of the limit voltages of said switch modules, without having to wait for the dielectric strength to be equal to the sum of all the limit voltages. Thus, the current is limited earlier, which helps to limit the increase in current caused by a short-circuit type electrical fault, and thus to limit the stress on the load, or even on the cables connecting the device, the source and the load.

[0019] According to other advantageous aspects of the invention, the device comprises one or more of the following features, alone or in any technically possible combination:

[0020] The switch modules are connected in series with each other.

[0021] Each switch module comprises two semiconductor elements connected in electrically anti-serial and unidirectional, and for each semiconductor element, a diode is connected in electrically anti-parallel with the semiconductor element.

[0022] The switch unit comprises two rectification branches, the input and the output of the switch unit forming respectively a midpoint of one of the rectification branches, each rectification branch comprising two diodes arranged on either side of the midpoint, the two diodes being connected in electrically anti-serial with each other;

[0023] The switch modules are connected in parallel with the rectification branches;

[0024] Each switching module comprises a single semiconductor element connected in parallel with a voltage limiting element.

[0025] The device comprises at least three switching modules.

[0026] The device further comprises an isolator connected in series with the mechanical switch and not in parallel with the switching units.

[0027] The detection module detects a short-circuit type electrical fault and a trip time between the transfer of all the switching modules to the blocking configuration is less than 1 ms, preferably less than 400 μs, preferably even less than 200 μs.

[0028] The application also relates to an electrical installation comprising a source, a load connected to the source and an electrical protection device connected between the source and the load as described above, wherein the rated voltage of the current flowing between the source and the load is less than 1500 V.

[0029] The application also relates to a method for controlling an electrical protection device, the method comprising at least the following steps:

[0030] measuring the value of the current by a current sensor;

[0031] detecting a short-circuit type electrical fault by the control unit based on the value of the current measured by the current sensor;

[0032] when a short-circuit type electrical fault is detected, commanding the mechanical switch to the open configuration by the mechanical switch control module;

[0033] commanding each switching module in turn to the blocking configuration, one of the switching modules being commanded from the conducting configuration to the blocking configuration when the dielectric strength of the mechanical switch is greater than or equal to the sum of the limit voltage of said switching module and the limit voltage of the switching module in the blocking configuration. BRIEF DESCRIPTION OF DRAWINGS

[0034] The application will become more clearly understood by reading the following description, given only by way of non-restrictive example, and with reference to the appended drawings, in which:

[0035] Figure 1 is a diagram of an electrical installation comprising an electrical protection device according to a first embodiment of the application;

[0036] Figure 2 is a diagram of a switching unit of an electrical protection device according to a first embodiment of the application;

[0037] Figure 3 is a graphical representation of the voltage and current values flowing over time in a protection device according to the application;

[0038] Figure 4 is a flowchart of a control method according to the application.

[0039] Figure 5 is a diagram of a switching unit of an electrical protection device according to a second embodiment of the invention; and

[0040] Figure 6 is a diagram of a switching unit of an electrical protection device according to a third embodiment of the invention. DETAILED DESCRIPTION

[0041] Figure 1 is a diagram of an electrical installation 1 comprising a source 3 and a load 5 electrically connected by a phase conductor 7 and a neutral conductor 8. The source 3 supplies electrical power and is for example a generator or an electrical grid, such as a mains grid. The load 5 is a device consuming electrical power, such as a household appliance, an industrial equipment such as an electric motor or a server. Thus, an electrical current flows between the source 3 and the load 5 through the phase conductor 7 and returns to the source 3 via the neutral conductor 8.

[0042] The electrical current is a low voltage current, meaning that the current voltage is less than 1500 V. The electrical current is an alternating current, or alternatively, a direct current.

[0043] The electrical installation 1 further comprises an electrical protection device 10 (hereinafter also referred to as device) connected between the source 3 and the load 5. The device 10 is configured to switch between an armed configuration, in which the device 10 conducts the electrical current flowing between the source 3 and the load 5, and a tripped configuration, in which the device 10 electrically isolates the source 3 from the load 5.

[0044] The device 10 comprises a mechanical switch 12, also called bypass switch or fast mechanical switch, also called FMS (Fast Mechanical Switch). The mechanical switch 12 is connected in series with the phase conductor 7 via an input 12a and an output 12b and is configured to switch between a closed configuration, in which it conducts the electrical current flowing between the source 3 and the load 5, and an open configuration, in which it does not conduct the electrical current. In Figure 1 In the figure, the mechanical switch 12 is shown in the open configuration. The device 10 advantageously comprises an actuator 16 which, when activated, switches the mechanical switch 12 to the open configuration.

[0045] The device 10 comprises a switching unit 18 connected in parallel with the mechanical switch 12, such that the input 12a and the output 12b of the mechanical switch 12 are connected to the input 18a and the output 18b of the switching unit 18, respectively. More specifically, the input 12a of the mechanical switch 12 and the input 18a of the switching unit 18 are connected by a non-switchable electrical connection 19a, and the output 12b of the mechanical switch 12 is connected to the output 18b of the switching unit 18 by a non-switchable electrical connection 19b. In other words, the electrical connections 19a and 19b are cables or wires, respectively; neither of the electrical connections 19a and 19b comprises a switch or, more generally, a device that switches current. The switching unit 18 is configured to allow or cut off current passing therethrough, as explained below.

[0046] The device 10 advantageously comprises a first isolator 23 and optionally a second isolator 24 connected to the phase conductor 7 and to the neutral conductor 8, respectively. In particular, the isolator 23 is connected in series with the mechanical switch 12 to the phase conductor 7, without being connected in parallel with the switching unit 18. Moreover, the isolator 23 is connected in series with the neutral conductor 8. The isolators 23 and 24 are configured to be switched between a closed configuration, in which the isolators 23 and 24 conduct current, and an open configuration, in which the isolators 23 and 24 do not conduct current. Advantageously, and as shown, the device 10 comprises an actuator 25 for the first isolator 23 and an actuator 26 for the second isolator 24, which, when activated, interact with the first isolator 23 and the second isolator 24, respectively, to switch them to the open configuration. The actuators 25 and 26 are, for example, coils and are activated when a current flows through the turns of the coils. Figure 1

[0047] The isolators 23 and 24 are configured to be switched to the open position, in particular when no current flows between the source 3 and the load 5, in other words when the current has been interrupted by the mechanical switch 12 and / or the switching unit 18.

[0048] The switching unit 18 comprises a plurality of switching modules, for example two switching modules 32 and 42, as can be seen in Figure 2 Alternatively, the number of switching modules is three or more, as indicated by the dashed lines in Figure 2 .

[0049] The switching modules 32 and 42 are connected in series with each other. Each switching module 32 and 42 comprises at least one switchable semiconductor element, for example at least one thyristor or at least one transistor, such as a field effect transistor (also known as FET (field effect transistor)), an insulated gate field effect transistor (also known as MOSFET (metal oxide semiconductor field effect transistor)), an insulated gate bipolar transistor or IGBT (insulated gate bipolar transistor), or a combination of these different semiconductor elements.

[0050] In​Figure 2 In the example of Fig. 2, each switch module 32 comprises two unidirectional current transistors 34 and 35, for example two IGBTs. The conduction direction of the transistors 34 and 35 is indicated by the arrows on each transistor 34, 35. The transistors 34 and 35 are connected anti-serial to each other, meaning that the transistors 34 and 35 are connected in series but head to tail, so that they do not conduct current at the same time. Two diodes 36 and 37 are connected to the transistors 34 and 35, respectively. The diode 36 is connected anti-parallel to the transistor 34, meaning that the diode 36 and the transistor 34 do not conduct current at the same time: if the transistor 34 is conducting, the diode 36 is blocked, and vice versa. In other words, the transistor 34 and the diode 36 are connected head to tail in parallel. The same applies to the transistor 35 and the diode 37. This arrangement allows each switch module 32 and 42 to conduct alternating current without interruption at each change of sign of the current.

[0051] The switch module 32 comprises a voltage limiting element 39. The voltage limiting element 39 is connected in parallel to the group formed by the transistors 34 and 35 and is for example a metal oxide varistor or MOV, a transistor or a gas discharge tube. The voltage limiting element 39 has a limiting voltage U lim1 , the limiting voltage U lim1 corresponding to the voltage across its terminals when the current between the source 3 and the load 5 flows through this element. It can also be said that the switch module 32 has a limiting voltage U lim1 .

[0052] Similarly, the switch module 42 comprises two transistors 44 and 45 and two diodes 46 and 47, which are at least functionally similar to the transistors 34, 35 and the diodes 36 and 37 and are connected in a similar manner as described for the transistors 34, 35 and the diodes 36 and 37. The switch module 42 comprises a voltage limiting element 49, which is at least functionally similar to the voltage limiting element 39 and is connected in parallel to the transistors 44 and 45. The voltage limiting element 39 has a limiting voltage U lim2 , or in other words, the switch module 42 has a limiting voltage U lim2 .

[0053] The limiting voltages U lim1 and U lim2 are advantageously different, for example, the limiting voltage U lim1 equals 520 V and the limiting voltage U lim2 equals 600 V. Alternatively, the limiting voltages U lim1 and U lim2 are identical.

[0054] The switching modules 32 and 42 are configured to switch between a conducting configuration and a blocking configuration. In the conducting configuration, the current flows through the switching module 32 either through the transistor 34 and the diode 37 or through the transistor 35 and the diode 36, and through the switching module 42 either through the transistor 44 and the diode 47 or through the transistor 45 and the diode 46. In particular, when the current flowing through the device 10 is alternating, the transistor 34, the diode 37, the transistor 44 and the diode 47 first conduct the current, and then, when the current changes direction, the transistor 35, the diode 36, the transistor 45 and the diode 46 conduct the current. More generally, in the conducting configuration, at least one of the transistors 34, 35 and at least one of the transistors 44, 45 conduct the current.

[0055] In the blocking configuration, the transistors 34, 35, 44 and 45 do not conduct the current, and if a current flows through the switching modules 32 and 42, the current flows through the voltage limiting elements 39 and 49. Thus, in the blocking configuration, the voltage across the switching modules 32 and 42 is respectively the limiting voltage U lim1 and the limiting voltage U lim2 .

[0056] The control device 10 further comprises a current sensor 52. This current sensor 52 is configured to measure the value I of the current flowing between the source and the load, in particular the current flowing in the phase conductor 7. The current sensor 52 is for example a Rogowski coil.

[0057] The control device 10 comprises a control unit 60 comprising a detection module 62 connected to the current sensor 52 and configured to detect a short-circuit type electrical fault based on the value of the current I measured by the current sensor 52. Hereafter, the term short-circuit will be used to designate a short-circuit type electrical fault.

[0058] The control unit 60 further comprises a mechanical switch control module 64, a cell control module 66, and advantageously an isolator control module 68, connected to the detection module 62 and configured to control respectively the mechanical switch 12, the switching cell 18 and the isolators 23 and 24.

[0059] The mechanical switch control module 64 and the isolator control module 68 are advantageously configured to actuate respectively the actuators 16, 25 and 26 to switch the switch 12 and the isolators 23 and 24 to the open configuration.

[0060] The control unit 60 is an electronic circuit designed to manipulate and / or transform data represented by electronic or physical quantities in the registers of the control unit 60 and / or of a memory, into similar data corresponding to physical data in a memory register or other type of display device, transmission device or storage device.

[0061] As a particular example, the control unit 60 is implemented as a programmable logic component, for example an FPGA (Field Programmable Gate Array) or an integrated circuit such as an ASIC (Application Specific Integrated Circuit).

[0062] In a variant not shown, the control unit 60 comprises an information processing unit formed for example by a memory and a processor associated with the memory. The detection module 62, the mechanical switch control module 64, the cell control module 66 and the isolator control module 68 are each implemented as software or as a block of software executable by the processor. The memory of the control unit 60 is then able to store the detection software, the mechanical switch control software, the cell control software and the isolator control software. The processor is then able to execute each of the software between the detection software, the mechanical switch control software, the cell control software and the isolator control software.

[0063] In a variant not shown, the detection module 62, the mechanical switch control module 64, the cell control module 66 and the isolator control module 68 are each implemented as a programmable logic component such as an FPGA (Field Programmable Gate Array), an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or even as an analog component.

[0064] Advantageously, the device 10 also comprises a power supply module 70 connected to the conductors 7 and 8 and to the control unit 60 to supply the control unit 60 with electrical power. In a variant not shown, the power supply module 70 is connected to an external circuit not connected to the conductors 7 and 8. In a variant not shown, the power supply module 70 is supplied with power by the transformer effect from the current flowing in the conductors 7 and 8.

[0065] The operation of the device 10 will now be explained with reference to Figure 3 and 4

[0066] Initially, advantageously, the device 10 is in the armed configuration, which means that the isolators 23 and 24 are in the closed configuration, the mechanical switch 12 is in the closed configuration and the transistors 34, 35, 44 and 45 are conducting. However, since the internal resistance is lower than the internal resistance of the transistors 34, 35, 44 and 45, the mechanical switch 12 conducts the entire current flowing in the device 10. The voltage U across the terminals of the device 10 is substantially zero.

[0067] At step S102, the current sensor 52 measures the value I of the current flowing in the phase conductor 7.

[0068] ​At step S104, the control unit 60 receives the current measurement value I and detects, via the detection module 62, whether a short-circuit exists between the source 3 and the load 5. If no short-circuit is detected, the current sensor 52 performs again step S102, continuing the measurement of the value I of the current. An iterative operation is then implemented. If a short-circuit is detected, corresponding to the instant A in Figure 3 , at step S106, the control unit 60 commands, via the mechanical switch control module 64, the mechanical switch 12 to switch to its open configuration. The opening of the mechanical switch 12 corresponds to the instant B in Figure 3 .

[0069] When a short-circuit exists between the source 3 and the load 5 or in the load 5, the value I of the current increases significantly and rapidly, for example, by tens of amperes per microsecond. Thus, a short-circuit is detected, for example, when the value I of the current is greater than a predetermined threshold, or when the derivative of the value of the current I is greater than a predetermined threshold, or when a combination of conditions of the value of the current I and of its derivative is satisfied.

[0070] When the mechanical switch 12 is in the open configuration, the current is diverted from the mechanical switch 12 to the switch unit 18, however, the opening of the mechanical switch 12 generates an arc and ionization of the medium between the contacts of the mechanical switch 12. This reduces the dielectric strength of the mechanical switch 12. Thus, before reducing or interrupting the current flowing between the source 3 and the load 5, it is necessary to wait for a sufficient recovery of the dielectric strength of the mechanical switch 12, otherwise a rebreakdown at the mechanical switch 12 can occur, which means a re-ignition of the current through the contacts of the mechanical switch 12 while it is in the open configuration, and the reduction or interruption of the current cannot be achieved.

[0071] The waiting time T is measured from the instant at which the mechanical switch 12 is switched to the open configuration.

[0072] In a variant not shown, the waiting time T is measured from the instant at which the short-circuit is detected, in other words from the instant A.

[0073] When the waiting time T becomes greater than or equal to a first waiting threshold T1, also called Paschen time, the dielectric strength of the mechanical switch 12 is sufficient to withstand a voltage equal to the limiting voltage U lim1 across its terminals. The first waiting threshold T1 is advantageously determined and programmed beforehand by the manufacturer of the device 10, based on for example the characteristics of the mechanical switch 12 and of the limiting voltage U lim1 , or determined by the control unit 60, for example based on the value I of the current at the instant at which the mechanical switch 12 is switched to the open configuration and on the limiting voltage U lim1 .

[0074] At step S108, the control unit 60 determines whether the waiting time T is greater than or equal to the first waiting threshold T1. If not, the control unit 60 waits for a predetermined time and then executes again step S108. If the waiting time T is greater than or equal to the first waiting threshold T1, the unit control module 66 commands, at step S110, the switching module 32 to the blocking configuration, which corresponds to Figure 3 the instant C. The transistors 36 and 37 are blocked and do not conduct current, the current then flowing through the voltage limiting element 39 and the switching module 422. The voltage U at the terminals of the device 10 and therefore across the terminals of the mechanical switch 12 is then equal to the limiting voltage U lim1 . The passage of current through the voltage limiting element 39 allows an increase in the value of the current I caused by the short-circuit limitation, according to the following formula:

[0075]

[0076] where TA is the rate of increase of the value of the current I;

[0077] U is the voltage across the terminals of the device 10; and

[0078] U S is the nominal voltage of the current, also called mains voltage.

[0079] In practice, the voltage caused by the resistances of the conductors 7 and 8 and the fault is considered negligible, so the rate of increase TA is considered equal to .

[0080] In Figure 3 , the limiting voltage U lim1 is approximately equal to the nominal voltage of the current U S , for example approximately 520 V. Thus, when the switching module 32 is commanded to the blocking configuration, the voltage U across the terminals of the device 10 is approximately 520 V and the value of the current I stops increasing.

[0081] The control unit 60 also determines whether the waiting time T is greater than or equal to the second waiting threshold T2. The second waiting threshold T2 is also measured from the instant at which the mechanical switch 12 is switched to the open configuration when the dielectric strength of the mechanical switch 12 is equal to the sum of the limiting voltages U lim1 and U lim2 of the switching modules 32 and 42.

[0082] Therefore, in step S112, the control unit 60 determines whether the waiting time T is greater than or equal to the second waiting threshold T2. If the waiting time T is less than the second waiting threshold T2, the control unit 60 waits for a predetermined time and then executes step S112 again. Then, an iterative operation is performed. If the waiting time T is greater than or equal to the second waiting threshold T2, the unit control module 66 commands the switch module 42 to the blocking configuration in step S114, which corresponds to Figure 3 Moment D in the

[0083] The second waiting threshold T2 is advantageously predetermined and programmed by the manufacturer of the device 10 , for example, based on the mechanical switch 12 and the limiting voltage U lim2 characteristics, or determined by the control unit 60, for example, based on the value of the current I and the limiting voltage U at the moment when the mechanical switch 12 is switched to the open configuration lim2 .

[0084] During step S114, in addition to transistors 34 and 35, transistors 44 and 45 are blocked, and the current then passes through voltage limiting element 39 and voltage limiting element 49. Therefore, the voltage U across the device 10 is equal to the limiting voltage U lim1 and U lim2 The sum of .

[0085] The voltage across the device 10 is greater than the network voltage, and the value I of the current flowing in the device 10 decreases until it becomes zero, as Figure 3 As can be seen in region E of FIG. 1 , when the current value I becomes zero, the current is interrupted between the source 3 and the load 5 and the voltage across the terminals of the device 10 becomes equal to the network voltage U S , as shown at the instant F. Advantageously, the tripping time Td between the instant of detecting the short circuit and the instant all switching modules have switched to the blocking configuration, meaning the time between instants A and D, is less than 1 ms, preferably less than 400 μs, preferably even less than 200 μs.

[0086] Advantageously, when the current value I has reached zero, the isolator control module 68 activates the actuators 25 and 26 to switch the isolators 23 and 24 to the open configuration at step S116. For example, if the actuators 25 and 26 are coils, the isolator control module 68 sends an electrical pulse to the actuators 25 and 26. This generates a magnetic field that interacts with the isolators 23 and 24 and allows them to switch to the open configuration. The device 10 is then in the tripped configuration.

[0087] The disconnect connectors 23 and 24 are switched to the disconnect configuration only when the current is cut off and serve to galvanically isolate the source 3 and the load 5 but do not participate in the cutting off of such current.

[0088] More generally, in the case where the device 10 comprises other switching modules, each waiting threshold is determined based on the switching module and the order in which the switching modules are switched to the blocking configuration. Indeed, when the waiting time T is greater than or equal to the time required for the dielectric strength to become greater than or equal to the sum of the limit voltage of the given switching module and the limit voltage of the switching modules already in the blocking configuration, the given switching module is commanded to open.

[0089] This process is described in the case where the switching module 32 is commanded before the switching module 42. Alternatively, the switching module 42 is commanded before the switching module 32. In this case, the first waiting threshold is calculated based on the dielectric strength required for the mechanical switch 12 to withstand the limit voltage U lim2 without breakdown occurring, in other words based on the limit voltage U lim2 The first waiting threshold is calculated.

[0090] Thus, the successive command of the switching modules 32 and 42 allows the current to be limited earlier, in this case as soon as the first waiting threshold T1 is reached, whereas without this, the current would be cut off only after the second waiting threshold T2 is reached, and the current value I is allowed to increase as long as the second waiting threshold T2 has not elapsed. This significantly allows the increase in the current value I to be limited, thereby avoiding overheating of the conductors 7 and 8, and also allows the transistors 34, 35, 44 and 45 to be chosen whose current rating is lower than that of an equivalent device which does not employ a switching module into the blocking configuration for the first control.

[0091] Figure 5 is a diagram of a switching unit 118 of an electrical protection device 10 according to a second embodiment of the application as a variant of the switching unit 18. The switching unit 118 is similar to the switching unit 18, connected in parallel to the mechanical switch 12, such that the input 12a and the output 12b of the mechanical switch 12 are connected to the input 118a and the output 118b of the switching unit 118, respectively. More particularly, the input 12a of the mechanical switch 12 and the input 118a of the switching unit 118 are connected by an electrically non-switchable connection 19a, and the output 12b of the mechanical switch 12 is connected to the output 118b of the switching unit 118 by an electrically non-switchable connection 19b. The switching unit 118 comprises two rectifying branches 120 and 122. Each rectifying branch 120 and 122 comprises diodes 146 and 147 for the rectifying branch 120, and 136 and 137 for the rectifying branch 122, respectively. The diodes 136 and 137 are connected anti-serially to each other, meaning that the diodes 136 and 137 are connected in series and cannot conduct current at the same time. The same applies to the diodes 146 and 147.

[0092] The input 118a and the output 118b of the switching unit 118 correspond to the midpoints of the rectification branches 120 between the diodes 136 and 137 and of the rectification branches 122 between the diodes 146 and 147, respectively. The switching unit 118 is thus connected in parallel with the mechanical switch 12 through the midpoints of each rectification branch 120 and 122.

[0093] The switching unit 118 comprises two switching modules 132 and 142, but in a variant not shown, more than two switching modules. The switching modules 132 and 142 are connected in parallel with the rectification branches 120 and 122 and in series with each other. Alternatively, the switching unit 118 comprises more than two switching modules, which are connected in series with the switching module 142 and in parallel with the branches 120 and 122.

[0094] The switching modules 132 and 142 comprise a switchable semiconductor element, here a transistor 134 and 144, and a voltage limiting element 139 and 149, respectively. The voltage limiting element 139 is connected in parallel with the transistor 134 and the voltage limiting element 149 is connected in parallel with the transistor 144. In the example shown, the transistors 134 and 144 are unidirectional current transistors, the direction of which is indicated by the arrow on each transistor. The voltage limiting elements 139 and 149 are at least functionally similar to the voltage limiting elements 39 and 49 and have a limiting voltage U Figure 5 , respectively. The limiting voltage U lim1 and U lim12 are advantageously different from the limiting voltage U lim1 , but alternatively, these voltages are identical. lim12

[0095] The switching unit 118 is configured to be independent of the current direction through the diodes 136, 137, 146 and 147, so that the unidirectional switching modules 132 and 142 can be used bidirectionally. The arrangement of the diodes 136, 137, 146 and 147 allows to limit the number of diodes in the switching unit 118 to four. Thus, even when the switching unit 118 comprises more than two switching modules, only four diodes 136, 137, 146 and 147 are necessary for their operation, thus limiting the number of diodes required compared to the switching unit 18.

[0096] Figure 6 is a circuit diagram of a switching unit 218 of an electrical protection device 10 according to a third embodiment of the application, as an alternative embodiment to the switching units 18 and 118.

[0097] ​The switch unit 218 comprises an input 218a and an output 218b and is connected in parallel with the mechanical switch 12, such that the input 12a and the output 12b of the mechanical switch 12 are connected to the input 118a and the output 118b of the switch unit 118, respectively. More specifically, the input 12a of the mechanical switch 12 and the input 218a of the switch unit 218 are connected by an electrically non-switchable connection 19a, and the output 12b of the mechanical switch 12 is connected to the output 118b of the switch unit 118 by an electrically connection 19b.

[0098] The switch unit 218 comprises two switch modules 232 and 242. The switch module 232 is similar to the switch module 32 and comprises two semiconductor elements, here two transistors 234, 235, connected to each other in anti-series, as indicated by the arrows on each transistor 234, 235. The switch module 232 comprises a diode 236 connected in anti-parallel with the transistor 234, and a diode 237 connected in anti-parallel with the transistor 235. The switch module 232 comprises a voltage limiting element 239, which is at least functionally similar to the voltage limiting element 39, having a limiting voltage U lim21 , and is connected in parallel with the group formed by the transistors 234 and 235.

[0099] The switch module 242 also comprises two transistors 244 and 245 connected to each other in anti-series, which are advantageously unidirectional in current, as indicated by the arrows on each transistor 244, 245. A diode 246 is connected in anti-parallel with the transistor 244, and a diode 247 is connected in anti-parallel with the transistor 245. The switch module 242 comprises a voltage limiting element 249, which is at least functionally similar to the voltage limiting element 49, having a limiting voltage U lim22 . The limiting voltage U lim22 is advantageously different from the limiting voltage U lim21 , but alternatively, the limiting voltages U lim21 and U lim22 are the same.

[0100] In the on configuration, when the current flowing through the device 10 is alternating, the current flows, on the one hand, successively through the transistor 234, the diode 237, the transistor 244 and the diode 247, and, on the other hand, through the transistor 235, the diode 236, the transistor 245 and the diode 246, when the current changes direction.

[0101] Unlike the voltage limiting element 49, the voltage limiting element 249 is connected in parallel with the group formed by the four transistors 234, 235, 244 and 245. Thus, the switch modules 232 and 242 are not connected in series with each other.

[0102] The description of the method of operation of the device 10 comprising the switching unit 18 also applies to the device 10 comprising the switching unit 118 or to the device 10 comprising the switching unit 218.

[0103] When the switching module 232 is the only one commanded to the blocking configuration, the switching unit 218 allows the voltage obtained across the terminals of the device 10 to be equal to the limiting voltage of the voltage limiting element 239. When the switching module 242 is switched to the blocking configuration, independently of the command of the switching module 232, the voltage across the terminals of the device 10 is equal to the voltage of the voltage limiting element 249. Thus, the limiting voltage across the terminals of the device 10 can be U lim21 or U lim22 In a variant not shown, the source 3 and the load 5 are connected by a single-phase conductor or by a plurality of, for example three, phase conductors. In this case, for each phase conductor, the device 10 advantageously comprises a mechanical switch and a switching unit connected in parallel with the mechanical switch.

[0104] Optionally, the mechanical switch is connected to a neutral conductor, with the switching unit being connected in parallel with the mechanical switch.

[0105] In a variant not shown, the source 3 and the load 5 are connected by only one, possibly a plurality of, phase conductors, and / or the electrical installation 1 does not comprise a neutral conductor 8.

Claims

1. An electrical protection device (10) configured to be connected between a source (3) and a load (5), the device (10) comprising: a mechanical switch (12) configured to switch between a closed configuration and an open configuration, wherein in the closed configuration, the mechanical switch (12) conducts current flowing between the source (3) and the load (5), and in the open configuration, the mechanical switch (12) does not conduct current; A switch unit (18; 118; 218) is connected in parallel with the mechanical switch (12), wherein the switch unit (18; 118; 218) includes a plurality of switch modules (32, 42; 132, 142; 232, 242) connected to each other, and each switch module (32, 42; 132, 142; 232, 242) includes: at least one semiconductor element (34, 35, 44, 45; 134, 144; 234, 235, 244, 245); and A voltage limiting element (39, 49; 139, 149; 239, 249) is connected in parallel with each semiconductor element (34, 35, 44, 45; 134, 144; 234, 235, 244, 245), Each switch module (32, 42; 132, 142; 232, 242) has a limiting voltage (U lim1 , U lim2 ;U lim11 , U lim12 ;U lim21 , U lim22 ), each switching module (32, 42; 132, 142; 232, 242) is configured to switch between a conducting configuration and a blocking configuration, in which, in the conducting configuration, current flows through one or each semiconductor element (34, 35, 44, 45; 134, 144; 234, 235, 244, 245) of the switching module (32, 42; 132, 142; 232, 242), and in the blocking configuration, if current flows through the switching module (32, 42; 132, 142; 232, 242), the current flows through the voltage limiting element (39, 49; 139, 149; 239, 249); a current sensor (52) configured to measure a value of a current (I); A control unit (60) comprising: a detection module (62) configured to detect a short-circuit type electrical fault based on a value (I) of the current measured by the current sensor (52); a mechanical switch control module (64) configured to command the mechanical switch (12) to the open configuration upon detecting a short-circuit type electrical fault; The unit control module (66) is configured to: when the dielectric strength of the mechanical switch (12) is greater than or equal to the limiting voltage (U lim1 , U lim2 ;U lim11 , U lim12 ;U lim21 , U lim22 ) and the limiting voltage (U lim1 , U lim2 ;U lim11 , U lim12 ;U lim21 , U lim22 ), each switch module (32, 42; 132, 142; 232, 242) is switched to the blocking configuration in sequence, Characterized in that the input (12a) of the mechanical switch (12) and the input (18a; 118a; 218a) of the switching unit (18; 118; 218) are connected to each other via a non-switchable electrical connection (19a), and the output (12b) of the mechanical switch (12) and the output (18b; 118b; 218b) of the switching unit (18; 118; 218) are connected to each other via a non-switchable electrical connection (19b).

2. The device (10) according to claim 1, wherein the switching modules (32, 42; 132, 142; 232, 242) are connected in series with each other.

3. The device (10) according to claim 2, wherein each switching module (32, 42) comprises two semiconductor elements (34, 35, 44, 45), the current of the two semiconductor elements is unidirectional and connected in anti-series with each other, and for each semiconductor element (34, 35, 44, 45), a diode (36, 37, 46, 47) is connected in anti-parallel with the semiconductor element (34, 35, 44, 45).

4. The device (10) according to claim 2, wherein: The switch unit (118) includes two rectifier branches (120, 122), the input (118a) and the output (118b) of the switch unit (118) respectively form the midpoint of one of the rectifier branches (120, 122), each rectifier branch (120, 122) includes two diodes (136, 137, 146, 147) arranged on both sides of the midpoint, and the two diodes are connected in anti-series with each other; The switch modules (132, 142) are connected in parallel with the rectifier branches (120, 122); Each switching module (132, 142) includes a single semiconductor element (132, 142) connected in parallel with the voltage limiting element (139, 149).

5. The device (10) according to claim 4, comprising at least three switch modules (132, 42).

6. The device (10) according to claim 1, further comprising an isolator (23) connected in series with the mechanical switch (12) and not connected in parallel with the switching unit (18; 118; 218).

7. The device (10) of claim 1, wherein a trip time (T d ) is less than 1ms.

8. The device (10) of claim 1, wherein a trip time (T d ) is less than 400μs.

9. The apparatus (10) of claim 1, wherein a trip time (T d ) is less than 200μs.

10. An electrical device (1) comprising a source (3), a load (5) connected to the source (3), and an electrical protection device (10) according to claim 1 connected between the source (3) and the load (5), wherein the rated voltage of the current flowing between the source (3) and the load (5) is less than 1500V.

11. A method for controlling an electrical protection device (10) according to claim 1, the method comprising at least the following steps: The current sensor (52) measures (S102) the value (I) of the current; Based on the value (I) of the current measured by the current sensor (52), the control unit (60) detects (S104) a short-circuit type electrical fault; When a short-circuit type electrical fault is detected, the mechanical switch control module (64) commands (S106) the mechanical switch (12) to the open configuration; and When the dielectric strength of the mechanical switch (12) is greater than or equal to the limiting voltage (U lim1 , U lim2 ;U lim11 , U lim12 ;U lim21 , U lim22 ) and the limiting voltage (U lim1 , U lim2 ;U lim11 , U lim12 ;U lim21 , U lim22 ), sequentially commanding (S110, S114) each switching module (32, 42; 132, 142; 232, 242) to the blocking configuration, one of the switching modules (32, 42; 132, 142; 232, 242) being commanded from the conducting configuration to the blocking configuration.

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