Safety-controlled high-voltage DC power cut-off device

Abstract

The invention relates to a high-voltage direct current switching device (1), comprising: - a main circuit (16); - a switching module (18), comprising the following branches connected in parallel: - a main branch (24) including a main switching device (26); - a switching branch (32) comprising several switching modules (34) in series, each comprising: - a switching capacitor (38) for current flow in the switching branch (32); - a switching switch (41, 42) in series with the switching capacitor (38); - a loop formed by the main branch (24) and the switching branch (32); - a control system (561) for closing the switch and discharging the switching capacitor (38) in said loop; - the switching module (18) comprising a surge arrester (30) for conduction when the main branch and the switching branch are open.Figure to be published with the abbreviation: Fig. 1.

Description

Title of the invention: Safely controlled high-voltage direct current interruption device

[0001] The invention relates to a high-voltage direct current interruption device. Such devices are intended to be implemented in HVDC networks or network units in the event of an electrical fault generating a fault current in at least one electrical conductor of the network.

[0002] HVDC networks are notably considered as a solution for interconnecting disparate or non-synchronous power generation sites. HVDC networks are particularly favored for the transmission and distribution of energy produced by offshore wind farms rather than alternating current technologies, due to lower line losses and the absence of the impact of parasitic network capacitances over long distances. Such networks typically have nominal operating voltage levels exceeding 75 kV, particularly in the range of 100 kV and above.

[0003] In the present text, a high-voltage direct current device is considered to be either a "high-voltage A" device, in which the rated continuous operating voltage is greater than 1500 V but less than or equal to 75,000 V, or a "high-voltage B" device when the rated continuous operating voltage is greater than 75,000 V. Thus, the domain of high-voltage direct current includes the domain of "high-voltage A" and that of "high-voltage B".

[0004] Power outages in such networks are a crucial safety issue directly affecting the feasibility and development of such networks.

[0005] The evolution of these networks today tends towards the interconnection of infrastructures to result in mesh networks, that is to say networks comprising several possible paths between two given points of the network.

[0006] An electrical circuit generally contains at least one voltage source and at least one voltage user, which may include any device or set of devices, or any network containing such devices, that uses electrical energy to transform it into another form of energy. An electrical circuit generally also contains at least one electrical switching device for interrupting the flow of electric current in the circuit, typically between the voltage source and the voltage user, or between the voltage source and ground.

[0007] Various types of electrical switching devices are known, designed to be interposed in an electrical conductor of an electrical circuit. For example, circuit breakers are known, which are mechanical devices for interrupting the electrical circuit and which are designed and sized to allow, in particular, opening under load or in fault conditions of the electrical circuit in which they are interposed. We also know of electrical switching devices of simpler design, such as disconnectors, which are generally not designed to perform circuit interruptions under load, but rather to ensure, in a circuit where the current flow is already interrupted by another switching device, a high level of electrical insulation predetermined between an upstream portion of a conductor of the circuit, connected for example to the voltage source, and a downstream portion of this conductor of the circuit.

[0008] In a main mechanical switching device, the current is interrupted solely by the opening of a mechanical switching element. Such a mechanical switching element comprises two conductive parts making contact which are in mechanical and electrical contact when the switching element is closed and which are mechanically separated when the switching element is opened.

[0009] In the presence of a significant direct current and / or voltage, mechanical separation can result in the formation of an electric arc between the two conductive parts, due to the substantial energy accumulated in the network that the device protects. As long as the electric arc remains established across the mechanical separation, the mechanical electrical disconnect device does not perform the electrical interruption, since a current continues to flow through the device due to the presence of the arc. Electrical interruption, in the sense of the effective interruption of the flow of electric current, is sometimes particularly difficult to achieve in a context of high direct current voltage, as these conditions tend to sustain the electric arc.

[0010] Interrupting high-voltage direct current is more complex than interrupting alternating current. This is because, when interrupting an alternating current, a zero-crossing of the current is used to perform the electrical interruption, which is not possible with a high-voltage direct current.

[0011] Hybrid circuit breakers have been developed to interrupt direct current. These hybrid circuit breakers use a main branch carrying direct current during normal operation and a parallel branch of power electronic components. The main branch typically includes a vacuum tube switch in series with a switching assistance module. During a fault, the opening of the vacuum tube generates an arc voltage. The impedance-boosting switching assistance module increases the impedance in the main branch to force current to flow through the parallel branch. The power electronic components of the parallel branch then open to interrupt the current flow.

[0012] A drawback of the augmentation switching assistance module The impedance issue is that it is connected in series with the main branch. This induces Joule effect losses during normal operation and requires cooling.

[0013] To limit such losses, document EP3072143 proposes connecting a reverse current injection module as a switching assistance module. A current transformer is then used to inject a reverse current into the main branch at the time of switching.

[0014] Patent FR2103336 proposes a reverse current injection module based on the discharge of a capacitor.

[0015] The invention aims to resolve one or more of these drawbacks. The invention thus relates to a high-voltage direct current interruption device comprising: -a main circuit, in which, in a conduction configuration of the switching device, an electric current flows under a high nominal continuous service voltage of the device; -a switching module, interposed in the main circuit between a first point and a second point of the main circuit, the switching module comprising the following branches connected in parallel between the first point and the second point: -a main branch including a main mechanical type electrical disconnection device interposed between the first point and the second point; -a switching branch comprising several switching modules connected in series, each switching module comprising: -a switching capacitor configured to allow current to flow in the switching branch; -at least one semiconductor-type switching switch, connected in series with the switching capacitor and configured to selectively allow or interrupt current flow in the switching branch; -a loop formed by the main branch and the switching branch of the switching module, said loop of the switching module having a switching inductance; -a control system for the switching switch and configured to control the closing of the switching switch so as to discharge the switching capacitor in said loop; -the switching module including at least one surge arrester interposed between the first point and the second point so as to ensure conduction between the first and second points when the main branch and the switching branch are open.

[0016] The invention also relates to the following variants. Those skilled in the art will understand that each of the features of the following variants can be combined independently of the above characteristics, without constituting an intermediate generalization.

[0017] According to one variant, said switching switch of each switching module includes at least two transistors connected in series.

[0018] According to one variant, said switching switch of each switching module comprises a first pair of GTO thyristors mounted in antiparallel and a second pair of GTO thyristors mounted in antiparallel, the first and second pairs being connected in series.

[0019] According to yet another variant, each switching module further includes another surge suppressor connected to the terminals of the switching capacitor.

[0020] According to another variant, the sum of the transition voltages of the other surge suppressors is less than the transition voltage of the surge suppressor of the cutoff module.

[0021] According to yet another variant, the device further comprises an electronic control unit configured to control the control systems of the control modules.

[0022] According to one variant, the device includes a pre-charge circuit for the switching capacitor.

[0023] According to yet another variant, the device further comprises an inductance connected in series with the switching modules.

[0024] According to another variant, each switching module includes a coil connected in series with the switching switch and the switching capacitor.

[0025] According to yet another variant, the device includes a surge protector for each switching module, connected in parallel to the terminals of a respective switching module.

[0026] According to one variant, each switching control system of a cutoff module is electrically powered by the switching capacitor of that cutoff module.

[0027] Other features and advantages of the invention will become clear from the following description, which is by way of example and not limitation, with reference to the accompanying drawings, in which:

[0028] [Fig-1] is a schematic representation of an example embodiment of a switching device for high voltage direct current according to the invention;

[0029] [Fig.2] is a schematic representation of a first example of a communication module mutation of a switching device;

[0030] [Fig.3] is a schematic representation of a switching module of a first type for a second example of a switching module;

[0031] [Fig.4] is a schematic representation of another example of an embodiment of an electrical cut-off device according to the invention;

[0032] [Fig.5] illustrates a variant of a switching module associated with a para- surge protector;

[0033] [Fig.6] illustrates another variant of a switching module associated with a para- surge protector;

[0034] [Fig.7] further illustrates a variant of a switching module associated with a para- surge protector.

[0035] In an electrical network, the transmission of electrical power between two given points in the network is carried out by a power transmission line which generally comprises several electrical conductors, each corresponding to an electrical pole of the power transmission line. Thus, in an HVDC network, the transmission of electrical power between two given points in the network is carried out by a power transmission line which generally has two electrical poles. In this case, the power transmission line therefore comprises two electrical conductors of different polarities, with, for example, one electrical conductor at a positive potential and one electrical conductor at a negative or neutral potential.

[0036] Still within an HVDC network unit, the transmission of electrical power between two given points in the network can also be achieved via a three-pole power transmission line comprising three electrical conductors, with, under load, one electrical conductor at a positive potential, one electrical conductor at a negative potential, and one electrical conductor at a neutral potential. In some cases, the transmission of electrical power between two given points in the network can be achieved via a single-pole power transmission line, with one electrical conductor at the line potential and with an electrical return to earth.

[0037] Figure 1 illustrates a first example of an embodiment of a switching device 10 for interrupting a high-voltage direct current flowing in an electrical conductor 11. The electrical conductor 11 may, for example, belong to a power transmission line in an HVDC network unit operating at a nominal continuous service voltage exceeding 1500 V, or even exceeding 75,000 V (75 kV). The switching device 10 is therefore interposed in the electrical conductor 11, between a primary point 12 of the device 10 and a secondary point 14 of the device 10. The primary point 12 and the secondary point 14 may be connection terminals of the device 10, respectively. The switching device 10 thus divides the electrical conductor 11 into two sections, one first section 111 which is connected to primary point 12, and a second section 112 which is connected to secondary point 14.

[0038] The switching device 10 therefore comprises a main circuit 16, between the primary point 12 of the device 10 and the secondary point 14 of the device 10. In a conduction configuration of the switching device 10, an operational electric current flows under a high nominal operating voltage of the switching device 10. This is the operational electric current flowing in the conductor 11, and the intensity of which is less than or equal to the nominal current for the device. Indeed, in the event of an electrical fault, the current intensity through the switching device may exceed this nominal intensity for a brief time.

[0039] The switching device 10 is configured to fulfill the role of a circuit breaker, namely that it has the capacity to interrupt a current of lower intensity than its breaking capacity, therefore either under load at the nominal or partial intensity, or in the presence of a fault current.

[0040] The switching device 10 includes at least one switching module 18 interposed in the main circuit 16 between a first point 20 and a second point 22. In the example of [Fig.1] (which includes only one switching module 18), the first point 20 and a second point 22 of the main circuit 16 are points of the main circuit 16 which are respectively at the same electrical potential as, respectively, the primary point 12 and the secondary point 14 of the switching device 10 which delimit the main circuit 16 of the switching device 10.

[0041] The switching device may include several switching modules which may be arranged electrically in series in the main circuit 16, between the primary point 12 and the secondary point 14 of the switching device 10.

[0042] A switching module 18 comprises three branches which are electrically in parallel with each other between the first point 20 and the second point 22.

[0043] A switching module 18 comprises a main branch 24, between the first point 20 and the second point 22, with at least one main switching device 26, which is interposed in the main branch 24 between the first point 20 and the second point 22, and which is of the mechanical type to ensure electrical switching in the main branch 24. The main switching device 26 can switch between a closed state, in which it allows the flow of electric current in the main branch 24, and an open state in which it ensures electrical switching in the main branch 24 by interrupting the flow of electric current at the moment of a zero crossing of the current in the main branch 24. The main branch 24 of the module 18 is the one in which the operational current flows in normal operation of the network when the switching device 10 is in its conduction configuration.In normal network operation, when the cutoff device 10 is in its confi. Conduction configuration, the main switching device 26 is therefore traversed by the operational current flowing in the electrical conductor 11, according to a regime which can be permanent, or quasi-permanent.

[0044] The main switching device 26 can, for example, be a disconnector, a load switch, or a circuit breaker.

[0045] In the main mechanical switching device 26, the electrical interruption is achieved by displacement, in particular by separation, of one or more pairs of electrical contacts. The displacement of the electrical contacts is generally carried out by mechanical, pneumatic, hydraulic, or electrical operating elements or actuators. This displacement can be controlled electronically, for example by an electronic control unit 100. In the presence of a high current and / or voltage, the mechanical separation of the electrical contacts can result in the formation of an electric arc between the two electrical contacts of the device. As long as the electric arc remains established across the mechanical separation, the main switching device 26 does not perform the electrical interruption since a current continues to flow through the switch due to the presence of the arc.

[0046] As will be seen later, the invention provides means for ensuring electrical interruption, in the sense of the effective interruption of the flow of electric current. The main interruption device 26 may consist of a single main interruption device, or may consist of several main electrical interruption devices arranged electrically in series and / or in parallel. The main interruption device 26 may be a so-called "metal-enclosed" device where the electrical contacts are enclosed in a sealed chamber filled with an insulating fluid, or, more preferably, a "vacuum" device (sometimes called a "vacuum bulb") where the electrical contacts are enclosed in a sealed chamber in which the pressure is lower than atmospheric pressure, in particular less than 100 millibars, in particular less than 10 microbars.The main switching device 26 will advantageously be capable of interrupting the electric arc of a current exhibiting, at the moment of a zero crossing of the current, a high rate of change of current (di / dt), typically with a rate of change of current greater than or equal to 100 A per microsecond.

[0047] A cutoff module 18 also includes an absorption branch 28, which is electrically arranged in parallel with the main branch 24 between the first point 20 and the second point 22 of the cutoff module 18 considered, with at least one general surge suppressor 30 interposed in the absorption branch 28 between the first point 20 and the second point 22 of the module considered.

[0048] Such a general surge suppressor 30 makes it possible to limit the amplitude of the potential difference across the terminals of any component or set of components in parallel with which or those with which it is arranged. A surge protector is therefore a device that limits voltage peaks across its terminals. A surge protector generally comprises an electrical component whose resistance varies according to the electrical voltage across its terminals. The surge protector acts as a voltage limiter across its terminals within the current range for which it was selected. It applies the protection voltage when the highest current for which the surge protector was designed is applied. Below the transition voltage, it tends to prevent current flow. Above the transition voltage, it allows current to flow through the surge protector for a small increase in the voltage across its terminals. As is known, the transition voltage is generally not a precise value but rather corresponds to a range of transition voltages.However, in this text, the transition voltage of a surge protector is defined as the voltage at which the surge protector allows a current of 1 ampere (A) to flow. The protection voltage is the voltage across the surge protector when it is carrying the highest current for which it was designed. Surge protectors are well-known, including surge arresters, which may include varistors and TVS (Transient Voltage Suppressor) diodes, such as Transil™ diodes. Specifically, within the scope of this invention, a surge protector, particularly the general surge protector 30, may include a metal oxide varistor (MOV).

[0049] In the example illustrated in [Fig. 1], the absorption branch 28 does not have a switch. Therefore, it is necessary to select the general surge protector 30 such that its transition voltage is greater than the voltage likely to appear across the terminals of the switching module 18 when the switching device 10 is in operation and in its electrically open configuration under the nominal operating voltage of the network. For example, the general surge protector 30 is selected such that its protection voltage is between 1.2 and 2 times, for example 1.6 times, the nominal operating voltage of the module 18, which is the voltage under which the switching module 18 operates when the switching device 10 is in operation under the nominal operating voltage of the network.

[0050] Due to the presence of the general surge suppressor 30 interposed in the absorption branch 28, and due to the choice of its transition voltage value, it can be considered that, in normal operation of the network when the switching device 10 is in its conduction configuration, no electric current flows in the absorption branch 28.

[0051] A switching module 18 according to the invention also comprises a switching branch 32 which is electrically arranged in parallel with the main branch 24 and of the absorption branch 28 between the first point 20 and the second point 22 of the cutoff module 18 considered.

[0052] Several switching modules 34 are found electrically interposed in series in the switching branch 32, between the first point 20 and the second point 22. The switching modules 34 are controlled by the electronic control unit 100.

[0053] A sufficient number of switching modules 34 are connected in series to allow high currents (e.g. greater than 500 A, e.g. on the order of 10000 A) to be interrupted under a DC voltage equal to or greater than 50 kV in branch 32. The number of switching modules 34 connected in series can also be adapted to allow this high current interruption even if the control or operation of one of the modules 34 were to fail.

[0054] To control the switching modules 34, the electronic control unit 100 allows them to be switched either in their open state or in their closed state.

[0055] As detailed below, the switching modules 34 are intended to be controlled to their closed state only during switching phases of the main switching device 26, in particular during a switching phase of the main switching device 26 from its closed state to its open state. Outside of these switching phases (in particular during a nominal conduction phase when the main switching device 26 is held in its closed state or during an isolation phase in which the main switching device 26 is held in its open state), the switching modules 34 are intended to be held in their open state, so that no current flows in the switching branch 32.

[0056] For each switching module 34, a switching capacitor 38 is mounted in series with at least one semiconductor switch.

[0057] Figure 2 illustrates an example of an embodiment of a switching module 34. A switching capacitor 38 is connected in series between unidirectional semiconductor switches 41 and 42. The switching capacitor 38 generates an oscillating current in the switching branch 32 to inject a counter-current into the main branch 24, thereby facilitating the extinction of the electric arc that may appear between the electrodes of the main switching device 26 when it opens. The device 1 according to the invention makes it possible to perform the opening functions of the switch 26 with switching capacitors 38 having a voltage rating much lower than the nominal operating voltage of the switching module 18, and therefore much lower than the nominal operating voltage of the network in which the electrical conductor 11 is inserted.

[0058] Several unidirectional switches 41 and 42 can be connected in parallel to increase the capacity of the system.

[0059] The switching capacitor 38 also serves as a power supply for a control system 561. By using several modules 34 connected in series, the voltage across the individual capacitors 38 can be sufficiently reduced to approach the supply voltage of the control systems 561. Alternatively, the control system 561 advantageously includes a pre-charge circuit for the switching capacitor 38. This pre-charge circuit allows a predetermined electrical voltage to be applied between the two plates of the switching capacitor 38 before any switching of the main switching device 26. In the example, the pre-charge circuit includes a DC voltage source 501 that selectively applies a voltage across the switching capacitor 38. This voltage is applied here through a resistor 531 and through another resistor 551.The resistors 531 and 551 of the pre-charge circuit may have the same resistance value, or they may have different values. In practice, only one of the two resistors may suffice. The role of resistor(s) 531 and 551 is to limit the charge / discharge current supplied by the DC voltage source 501. In order to allow the control system 561 to be powered by its capacitor 38, a DC / DC converter may be interposed between the control system 561 and this capacitor 38, or it may be contained within the control system 561.

[0060] Module 34 includes, electrically in parallel with the switching capacitor 38, a switching surge suppressor 801. This switching surge suppressor 801 is connected by its two terminals to two points respectively on the first section of the switching branch 32, on either side of the switching capacitor 38. The switching surge suppressor 801 limits the voltage across the switching capacitor 38, thus allowing the use of lower voltage capacitors. Such a surge suppressor 801 is, for example, of the ZnO type. Typically, in a switching device 1 intended for a very high voltage network, the voltage across the switching capacitor 38 can thus be limited by the first switching surge suppressor 801, to a level dependent on the number of modules 34 connected in series. For example, at least 8 modules 34 can be connected in series.

[0061] Switches 41 and 42 are of the IGBT (Insulated Gate Bipolar Transistor) type. IGBTs 41 and 42 are oriented in opposite directions. IGBTs 41 and 42 form a bidirectional switch capable of selectively conducting or blocking current in both directions. The use of two IGBTs 41 and 42 provides a bidirectional switch in both current and voltage.

[0062] Each IGBT 41, 42 has a freewheeling diode mounted antiparallel to the IGBT. In operation, both IGBTs 41 and 42 are normally open. IGBTs 41, 42 are switched to their closed state to initiate the discharge of capacitor 38.

[0063] The IGBTs 41 and 42 are controlled by the control system 561. The control system 561 is dedicated to the module 34 and is powered by the capacitor 38. This configuration avoids the problems of a common power supply for the control systems 561 with corresponding galvanic isolation. The control systems 561 are controlled via the electronic control unit 100.

[0064] As detailed below, the generation of a switching current oscillation in the switching branch 32, when the modules 34 are in their closed state, results from a modulation of the current in the loop formed by the main branch 24 and the switching branch 32 of the switching module 18. This loop, which includes the switching capacitors 38, necessarily and naturally exhibits, like any loop, a certain inductance, so that the loop forms an LC circuit that generates a current ripple during transient phases. This current ripple is used to interrupt an electric arc that may form in the main switching device 26 in its open state.

[0065] The switching inductance may result from the self-inductance of the components that make up the loop, in particular the self-inductance of the main branch 24 and / or the self-inductance of the switching branch 32. However, if the self-inductance of the components is not sufficient, the loop formed by the main branch 24 and the switching branch 32 may include a coil 82. This coil is preferably arranged in the switching branch 32. The switching inductance will be sized to limit the rate of change of current through the main switching device 26, a change that occurs when the switching branch 32 becomes conducting.The rate of change of current in the loop formed by the switching branch 32 and the main branch 24 must be limited by the components in the switching branch 32 to a value corresponding to the capacity of the main switching device 26 to interrupt the electric arc. The device is thus sized so that it ensures the interruption of the arc in the main switching device 26 when the current through this main electrical switching device 26 passes through a value of zero.

[0066] The device 1 may include or be associated with one or more electronic control unit(s) 100 for controlling / driving the modules 34. An electronic control unit 100 typically includes at least one processor and at least An electronic memory unit 100 may include or be connected to one or more electronic communication circuits, for example, for communication with one or more computer networks, and / or one or more electronic interface circuits, and / or one or more electronic input / output circuits. An electronic control unit 100 may include or be associated with one or more displays. An electronic control unit may include or be associated with one or more sensors, for example, one or more current sensors and / or one or more voltage sensors, configured to measure a value of a physical parameter in the switching device 1 or in the electrical installation in which the device 1 is intended to be integrated. The electronic control unit(s) is / are programmed to implement all or part of a device opening method as described above.Advantageously, it can be provided that the electronic control unit(s) 100 communicate(s) their control / pilot commands, in particular to the control system(s) 561, by signals galvanically isolated from the high voltage. These signals could be optical signals carried by optical fibers. They could be electrical signals isolated by transformers. These signals could be electromagnetic signals carried by wireless communication links.

[0067] The electrical switching device 1 as described above therefore forms a current circuit breaker particularly suitable for high-voltage direct currents, especially high-voltage direct currents exceeding 75 kV. This device 1 makes it possible to obtain sufficient breaking performance with components that, overall, have a reduced size and cost, with minimal energy losses during normal operation.

[0068] The operating sequence of device 1 in case of a fault is as follows. In operation, the switches of modules 34 are open and switch 26 is closed. Upon detection of the fault (for example, by information or detection at the electronic control unit 100), a command to open switch 26 is sent by the electronic control unit 100. Due to the presence of an arc when opening switch 26, the interruption of the current through this switch 26 is not yet effective. A command to generate a switching event is sent synchronously to the modules 34.The switching time of the current from the main branch 24 to the switching branch 32 is equal to a maximum of three-quarters of the oscillation period of the current in the loop formed by the main branch 24 and the switching branch 32, knowing that this oscillation can be likened to the discharge of capacitors in an LC or RLC circuit. After a time delay or after verifying the effective interruption of the current through switch 26, the switches of the modules 34 are opened again. The . The surge protector 30 then attenuates the fault current and absorbs residual energy from the network.

[0069] The invention advantageously reduces Joule effect losses in the main branch 24 while limiting the risk of failure in the switching branch 32. Indeed, due to the presence of several modules 34 connected in series, switching can still be achieved even if the control of one of the modules 34 fails. Furthermore, such a device 1 maintains the effective switching speed in the main branch 24, thereby limiting erosion of the electrodes of the switch 26.

[0070] The switching module 341 illustrated in [Fig. 3] is based on the use of symmetrical GTO thyristors, mounted in anti-parallel. Module 341 incorporates components 38, 501, 801, 531, and 551, which will not be described in further detail. The control system 561 drives the gates of GTO thyristors 81 and 83, positioned in opposite directions on either side of capacitor 38. GTO thyristors 85 and 87 are mounted in anti-parallel to GTO thyristors 81 and 83, respectively. Thyristors 85 and 87 are driven by control circuits 91 and 93, respectively. Another block is connected in series with capacitor 38 and the above-mentioned switching system. This other block includes a capacitor 75. A switching surge suppressor 77 and a DC voltage source 79 are connected in parallel across the terminals of the capacitor 75. The DC voltage source 79 is connected across the terminals of the capacitor 75 via resistors 71 and 73.Capacitor 75 is used in particular to power control circuit 91 and possibly control circuit 93. The power supply for control circuit 93 is not illustrated here for the sake of simplicity.

[0071] The operating sequence of device 1 according to this embodiment in the event of a fault is similar to that of the previous embodiment. In operation, the switches of modules 34 are open and switch 26 is closed. Upon detection of the fault, a command to open switch 26 is sent by the electronic control unit 100. A command to generate a switching event is sent synchronously to the modules 34. After a time delay or after verifying that the current has effectively been interrupted through switch 26, the switches of modules 34 are opened again. The surge protector 30 then attenuates the fault current and absorbs residual energy from the network.

[0072] Figure 4 schematically illustrates another embodiment of a switching device 1 according to the invention. In this example, the absorption branch 28 is replaced by a set of surge suppressors 30. Each surge suppressor 30 is connected in parallel with a respective module 34.

[0073] Figure 5 illustrates an example of module 34 dedicated to a parallel connection with a surge protector 30. Module 34 here includes a coil 80 connected in series with the switch (including IGBTs 41 and 42) and the capacitor 38. The surge protector is here connected in parallel with the branch of module 34 including the coil 80, the switch and the capacitor 38.

[0074] Fig. 6 illustrates another example of module 34. In this example, capacitor 38 is not connected between switches 41 and 42.

[0075] Fig. 7 illustrates another example of module 34. In this example, module 34 comprises only a switch 41 in series with capacitor 38. This example allows unidirectional operation.

[0076] Each switching surge suppressor (801 or 77 in the examples) is sized in relation to the voltage of the switching capacitor 38 and has a transition voltage less than or equal to the transition voltage of the general surge suppressor 30.

[0077] In all the examples above, it has been seen that the power supply and control of the modules 34 located in the switching branch 32 is achieved with a control system that does not require any electrical or electronic components in the main branch 24 of the switching module 18. Consequently, in the conduction configuration, there are no components belonging to the control system(s) that dissipate electrical energy continuously during normal network operation. Thus, no cooling system is necessary to cool such components.

Claims

Demands

1. High-voltage direct current switching device (1), characterized in that it comprises: - a main circuit (16), in which, in a conduction configuration of the switching device (10), an electric current flows under a high nominal continuous service voltage of the device; - a switching module (18), interposed in the main circuit (16) between a first point (20) and a second point (22) of the main circuit (16), the switching module comprising the following branches connected in parallel between the first point and the second point: - a main branch (24) including a main electrical switching device (26) of mechanical type interposed between the first point (20) and the second point (22);- a switching branch (32) comprising several switching modules (34) connected in series, each switching module (34) comprising: - a switching capacitor (38) configured to allow current flow in the switching branch (32); - at least one semiconductor-type switching switch (41, 42) connected in series with the switching capacitor (38) and configured to selectively allow or interrupt current flow in the switching branch (32); - a loop formed by the main branch (24) and the switching branch (32) of the switching module, said loop of the switching module having a switching inductance; - a control system (561) for the switching switch (41, 42) and configured to control the closing of the switching switch so as to discharge the switching capacitor (38) in said loop;-the switching module (18) comprising at least one surge arrester (30) interposed between the first point (20) and the second point (22) so as to ensure conduction between the first and second points when the main branch and the switching branch are open.;

2. Switching device (1) according to claim 1, wherein said switching switch of each switching module (34) includes at least two transistors (41, 42) connected in series (38).

3. A cutting device (1) according to claim 1 or 2, wherein said switching switch of each switching module (34) includes a first pair of GTO thyristors mounted in antiparallel and a second pair of GTO thyristors mounted in antiparallel, the first and second pairs being connected in series.

4. Switching device (1) according to any one of the preceding claims, wherein each switching module (34) further comprises another surge suppressor (801, 77) connected to the terminals of the switching capacitor (38, 75).

5. Switching device (1) according to any one of the preceding claims, wherein the sum of the transition voltages of the other surge suppressors (801, 77) is less than the transition voltage of the surge suppressor (30) of the switching module.

6. Disconnecting device (1) according to any one of the preceding claims, further comprising an electronic control unit (100) configured to drive the control systems (561) of the control modules (34).

7. Switching device (1) according to any one of the preceding claims, wherein the device includes a pre-charge circuit (501) for the switching capacitor (38).

8. Switching device (1) according to any one of the preceding claims, further comprising an inductor (82) connected in series with the switching modules (34).

9. Switching device (1) according to any one of claims 1 to 8, wherein each switching module (34) comprises a coil (80) connected in series with the switching switch and the switching capacitor (38).

10. Switching device (1) according to claim 1 to 9, comprising a surge arrester (30) for each switching module (34), connected in parallel to the terminals of a respective switching module.

11. Disconnecting device (1) according to any one of the preceding claims, wherein each control system (561) of the switching switch (41, 42) of a disconnecting module is electrically powered by the switching capacitor (38) of that disconnecting module.

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