High DC voltage current cut-off device with plasma tube

Abstract

A cut-off device for high DC voltage current with a plasma tube. The present invention proposes a DC high voltage cut-off device comprising at least one cut-off module (18), said device comprising: a main cutoff device (26) in the main branch (24); a general-purpose surge protection device (30) in the absorbing branch (28); a switching branch (32) including at least one switching capacitor (C1); Including, a first plasma tube switch (34.1) in the switching branch (32); A pre-charging circuit (48.1) for the switched capacitor (C1); a switched surge protection device (80.1) in parallel with the switched capacitor (C1) and having a protection voltage lower than the nominal operating voltage of the cut-off module; and at least one pilot enabled switch (58.1, 58a, 58b) supplying a voltage derived from the electrical voltage across the armature (C1p, C1d) of the switched capacitor (C1) to the first plasma tube switch (34.1).

Description

[Technical Field]

[0001] The present invention relates to a device for cutting off currents under high voltage DC (HVDC). Such a device is intended to be installed in an HVDC network or network unit in the event of an electrical fault occurring which generates a fault current in at least one conductor of the network.

[0002] HVDC networks are envisaged as a solution for interconnecting disparate or asynchronous power production sites, particularly for the transmission and distribution of energy produced by offshore wind farms, rather than AC current technologies, due to their lower line losses and lack of parasitic capacitance effects over long distances. Such networks generally have nominal operating voltage levels above 75 kV, especially around 100 kV or higher.

[0003] As used herein, high DC voltage devices are considered to be either "High Voltage A" devices, which have a DC nominal operating voltage greater than 1,500 V and up to 75,000 V (75 kV), or "High Voltage B" (or ultra-high voltage) devices, which have a DC nominal operating voltage greater than 75,000 V (75 kV). Thus, high DC voltage fields include "High Voltage A" fields and "High Voltage B" fields.

[0004] Current cut-off in such networks is a key issue that directly conditions the viability and development of such networks.

[0005] The current evolution of these networks is trending towards interconnected infrastructures that lead to mesh networks, i.e. networks that contain several possible paths between any two given points in the network. In these networks, electrical equipment (including, in particular, power stations or substations) has at least one electrical circuit cutoff device in the electrical circuit.

[0006] An electrical circuit generally has at least one voltage source and at least one voltage user, which may include any device or set of devices or any network having such devices that uses electrical energy and converts it into another form of energy, such as mechanical energy and / or calorific energy and / or electromagnetic energy.

[0007] An electric circuit generally has at least one electric cut-off device, which makes it possible to interrupt the flow of electric current in the circuit, generally between a voltage source and a voltage user or between a voltage source and earth.

[0008] Various types of electrical cut-off devices are known that are intended to be inserted into the conductors of an electrical circuit. For example, circuit breakers are known, which are mechanical devices that cut off an electrical circuit and are designed and scaled in particular to allow opening under fault conditions or during charging of the electrical circuit to which they are inserted. Also known are electrical cut-off devices of simpler design, such as disconnectors, which are generally not designed to perform a circuit cut-off during charging, but to ensure the safety of belongings and persons during intervention by ensuring a predetermined high level of electrical isolation between an upstream portion of a circuit conductor connected to a voltage source or the like and a downstream portion of this circuit conductor in a circuit in which the flow of current has already been interrupted by another cut-off device.

[0009] In mechanical-type main cutoff devices, current cutoff is achieved only by opening a mechanical switch element. Such a mechanical switch element includes two conductor contacts that are in mechanical and electrical contact when the switch element is closed and mechanically separated when the switch element is opened. This mechanical separation is generally achieved by movement of a movable conductor relative to a fixed conductor. These mechanical electrical cutoff devices have several drawbacks when high currents flow, especially under high DC voltages.

[0010] In the presence of DC currents and / or high voltages, mechanical separation can cause an electric arc to be established between two conductors due to high energy buildup in the network the device is protecting. Mechanical electrical cutoff devices do not perform an electrical cutoff, since the presence of the arc causes current to continue to flow through the device as long as the electric arc remains established by the mechanical separation. Electrical cutoff, in the sense that the flow of current is actually interrupted, can be particularly difficult to achieve in the context of high DC currents, as these conditions tend to maintain the electric arc. Furthermore, this electric arc can, on the one hand, deteriorate the contact between the two conductors by erosion, and, on the other hand, deteriorate the medium surrounding the conductor where the arc is established by ionization. This requires restrictive and costly maintenance work on the cutoff device.

[0011] Achieving cutoff of current under high DC voltage (HVDC) is more complicated than cutoff of current under alternating current (AC) voltage. In fact, while cutting off current under AC voltage, the zero crossing of the current can be utilized to perform electrical cutoff that cannot be achieved with current under HVDC voltage.

[0012] The use of such electrical cutoff devices, particularly mechanical devices, does not provide the desired performance in terms of electrical cutoff without some additional means to facilitate cutoff.

[0013] Furthermore, an object of the present invention is to enable current interruption regardless of the magnitude of the fault current intensity to be cut off, including when the fault current intensity value is low. In fact, in some prior art techniques based on reverse current injection, interruption of low intensity fault currents can be prevented or hindered by injecting a reverse current of too high a value, in particular because the zero crossing of the current at the open switch is performed with a derivative of intensity that is too large to enable interruption at the moment of this zero crossing. [Background technology]

[0014] To that end, many cutoff devices are known that assist the main electrical cutoff apparatus with additional specific means to facilitate cutoff, which can be classified into various distinct families according to their mode of assisting the main cutoff.

[0015] In the first of these families, the additional specific means for facilitating cutoff is the generation of a reverse current through the main cutoff device after it has been mechanically opened, which reverse current must be in the opposite direction to the fault current and of a magnitude greater than the fault current to offset it.

[0016] An example of such a device is described in document EP 3091626 A1, which comprises: · Main branch including main electrical cut-off device of mechanical type, an absorbing branch electrically parallel with the main branch between the first point and the second point and including at least one general-purpose surge protection device; A switched branch electrically parallel with the main branch and the absorbing branch, the switched branch including a switched capacitor, an inductor, and a switch.

[0017] The device of document EP 3091626 A1 includes a circuit for precharging a switched capacitor: if an arc exists between its electrodes after the main cut-off device has been mechanically opened, the arc is cut off by injecting a reverse current into the main branch, which is generated by closing a change-over switch, thereby discharging the pre-charged switched capacitor in the loop formed by the main branch and the change-over branch.

[0018] Document US2014299579 describes a similar device based on the same principle of generating a reverse current, but comprising several banks of pre-charged capacitors: depending on the current strength to be cut off, this device generates an adaptable reverse current strength, thereby inserting an appropriate capacitance into the circuit by selective closure of capacitor switches, so as to have a sufficiently low magnitude derivative to allow interruption at this zero crossing moment.

[0019] In document WO2015166600, capacitor 10 is recharged by auxiliary DC voltage source 20 before closing change-over switch 17. Inductive bypass switches 15 and 16 are selectively closed to vary the inductance of the LC circuit formed by the change-over branch, and the amplitude of the resulting oscillating current is monitored. To cover a wide range of intensity values ​​at which current interruption can be guaranteed, such a device would involve a large number of inductive bypass switches.

[0020] In this first family, it is understood that the energy that makes it possible to cut off the electric arc is stored in advance in a pre-charged capacitor.

[0021] Documents WO2015185096, US3758790, and US4442469 describe cutoff modules that include at least two cutoff devices in series in the main branch of the module, creating an oscillating current through these switches, thereby creating a loop intended to interrupt the current. These three devices have the disadvantage that the switching capacitor must be able to withstand a voltage higher than the nominal operating voltage of the electrical network into which they are inserted, typically at least 1.6 times this nominal operating voltage. This requires expensive and bulky capacitors. Additionally, the presence of a switching switch in the switching branch requires an undescribed auxiliary energy source for its operation. Furthermore, these cutoff modules still have a relatively long arcing time in the main branch cutoff devices. Furthermore, arc extinction can only be achieved after the separation of the contacts allows the arc to travel a distance long enough to withstand a voltage higher than the nominal operating voltage. This arcing time is generally longer than several milliseconds, representing a relatively long time during which the arc is likely to cause significant heating and erosion of the electrodes.

[0022] In the second family of devices, the additional specific means for facilitating the cut-off comprise a bypass branch in parallel with the main branch, which includes a bypass switch, and an additional switch, often of electronic type, in the main branch in series with the main cut-off device, whose role in the open state is to generate a voltage at its terminals. In this family, there is no need to provide a capacitor in the bypass branch. In some documents of the prior art, for example in document EP 2 502 248, the bypass switch is designed as an array of electronic switches in parallel with the main cut-off device and in parallel with the absorbing branch.

[0023] Documents EP 3522194 and EP 3522196 both describe devices of this second family, respectively, in which the bypass switch is designed as a plasma tube switch, or, since the plasma tube switch is essentially a unidirectional switch, as two plasma tube switches installed electrically in parallel and opposite to each other.

[0024] In both documents, the cutoff devices include a control system for each plasma tube switch. Such a control system, intended to ensure control and operation of the plasma tube switches, requires a source of electrical energy. In document EP 3522194, this source of electrical energy includes a first electrical coil located in the main circuit and a second electrical coil inductively coupled to the first electrical coil, which generates electrical energy and provides it to the plasma tube switch control system. In document EP 3522196, the source of electrical energy includes a capacitor located in direct electrical parallel with an electronic cutoff switch located in the main branch of the device. This capacitor is connected to the control system via a power converter to provide the power required for its operation. The required power is high and depends on the amplitude of the fault current that must be interrupted. In these devices, the control system must provide a voltage of several kV, e.g., 1 to 10 kV, and a current of a magnitude comparable to the fault current being interrupted. In practice, such control systems must therefore provide pulsed powers of the order of tens of kilowatts for closing commands and up to tens of megawatts (MW) for opening commands. Consequently, these solutions require coils and capacitors to provide very high powers, which inevitably increases the volume and cost of these components and complicates the solution.

[0025] In both cases, the source of electrical energy required for the operation of the plasma tube switch is found to be at least one electronic cutoff switch and, optionally, an electrical coil, interposed in the device's main branch, or even in the main circuit. However, both the main branch and the main cutoff device are subject to a current at high DC voltage during nominal operation of the installation, with a nominal current of very high magnitude, for example, greater than 1,000 A or even greater than 5,000 A. Accordingly, electrical and electronic components interposed in the main branch or main circuit are permanently subjected to this nominal current during network operation. As such, they must be scaled to withstand this nominal current permanently. Additionally, regardless of the quality of these components, their presence inevitably represents a source of electrical energy loss during nominal operation. Finally, because these electrical components are subject to a nominal current at very high voltages, potentially very high magnitudes, they generally must be cooled, thereby increasing the cost of the installation.

[0026] In the third family of devices, a specific additional means for facilitating cutoff is to generate an oscillating current of increasing amplitude in an oscillating branch parallel to the main branch after the main cutoff device is mechanically opened. After several oscillations, the oscillating current reaches a sufficient value, and then a reverse current is generated through the main device, capable of offsetting the fault current. Document US2017178844 describes an example of such a device. This device proposes implementing a specially piloted IGBT converter that generates and amplifies electrical oscillations in an LC circuit parallel to the main cutoff device. It is understood that this IGBT converter must generate a current of a high intensity, similar to the fault current, and therefore is bulky and expensive. Additionally, the capacitance of the LC circuit must be able to withstand a high voltage, higher than the nominal operating voltage, typically greater than 1.6 times the nominal operating voltage.

[0027] Also known is the document US Pat. No. 5,379,014 A, which describes a vacuum circuit breaker with an external coil arranged outside the vacuum switch.

[0028] Also known is document US Pat. No. 4,805,062 A, which relates to a DC circuit breaker and a method for switching it, or more specifically to a system for inserting a reverse current by using a switched capacitor that can be charged directly from the DC line. Summary of the Invention [Problem to be solved by the invention]

[0029] The object of the present invention is to propose a current cut-off device under high DC voltage, which is based on generating a reverse current through the main device by using energy pre-stored in a switched capacitor after mechanically opening the main cut-off device, which is economical, has reduced space requirements and does not generate electrical losses during the nominal operation of the installation. [Means for solving the problem]

[0030] For the above purpose, the present invention proposes a cut-off device for current under high DC voltage, the cut-off device comprising: a main circuit through which current flows under the high DC nominal operating voltage of the cutoff device in a conducting configuration of the cutoff device; at least one cutoff module interposed in the main circuit between a first point and a second point in the main circuit relative to the cutoff module, the cutoff module comprising: a main branch between the first point and the second point of the cutoff module, with at least one main electrical cutoff device of a mechanical type interposed in the main branch between the first point and the second point; an absorbing branch electrically in parallel with the main branch between the first point and the second point of the cutoff module, at least one general-purpose surge protector being interposed in the absorbing branch between the first point and the second point; a switching branch electrically parallel to the main branch and the absorption branch between the first point and the second point of the cutoff module, wherein at least a first switching capacitor is disposed in the switching branch between the first point and the second point of the cutoff module, and a switching switch is capable of allowing current flow in the switching branch; a loop formed by the main branch and the switching branch of the cutoff module, the loop of the cutoff module having a switching inductance.

[0031] The present invention provides the following: the changeover switch includes at least a first plasma tube switch including an anode, a cathode, and a control grid, the first plasma tube switch being interposed in the changeover branch between the first point and the second point of the cutoff module, thereby separating the changeover branch into a first section coupled to the cathode of the first plasma tube switch and a second section coupled to the anode of the first plasma tube switch, the first changeover capacitor being disposed in the first section of the changeover branch coupled to the cathode of the first plasma tube switch; a control system for the first plasma tube switch is powered by the first switched capacitor; the first switched capacitor includes a proximal armature coupled to the cathode of the first plasma tube switch and a distal armature on an opposite side of the cathode of the first plasma tube switch from the proximal armature; the device including circuitry for precharging the first switched capacitor; the cutoff module includes a first switched surge protector, the first switched surge protector having a protection voltage lower than a nominal operating voltage of the cutoff module and electrically connected in parallel with the first switched capacitor; The control system of the first plasma tube switch includes at least a first pilotable switch, which, when closed, supplies a voltage derived from the electrical voltage across the armature of the first switched capacitor to the control grid of the first plasma tube switch.

[0032] The device according to the invention may further have one or more of any of the following characteristics, either alone or in combination:

[0033] In some cases, during the opening of the cutoff device, the first pilotable switch is piloted according to a first closing pulse to control the closing of the first plasma tube switch after the main electrical cutoff device is partially mechanically opened, and according to a second closing pulse to control the opening of the first plasma tube switch after reversing the charge polarity of the first switched capacitor, thereby defining the conduction time of the first plasma tube switch between the closing and opening of the first plasma tube switch.

[0034] In some cases, the first pilotable switch, in a closed state, electrically couples the control grid of the first plasma tube switch to the distal armature of the first switched capacitor.

[0035] In some cases, the first pilotable switch is a two-way switch capable of conducting and blocking current in both directions between the control grid of the first plasma tube switch and the distal armature of the first switched capacitor. In some variations of such cases, the first pilotable switch is designed as two one-way electronic switches interleaved in series and in opposite directions between the control grid of the first plasma tube switch and the distal armature of the first switched capacitor, each one-way electronic switch including a freewheeling diode disposed anti-parallel to the one-way electronic switch.

[0036] In some cases, the control system of the first plasma tube switch includes a feed branch that feeds an activation electrode of the first plasma tube switch, the feed branch connecting the activation electrode of the first plasma tube switch to the distal armature of the first switched capacitor. In some variations of such cases, the feed branch includes a feed switch capable of conducting and blocking current in the feed branch and a resistor interposed in the feed branch. In some versions of such variations, the feed switch is piloted to close after receiving a current interrupt command from the cutoff device.

[0037] In some cases, the control system of the first plasma tube switch includes a DC-DC power converter having a source side coupled to the distal armature of the first switched capacitor and a control side feeding the control grid of the first plasma tube switch via the first pilotable switch. In some variations of such cases, the control side of the power converter includes a positive terminal and a negative terminal, and the first pilotable switch includes a first pilotable start switch interposed between the positive terminal and the control grid of the first plasma tube switch and a second pilotable stop switch interposed between the negative terminal and the control grid of the first plasma tube switch. In some versions of such variations, the control system of the first plasma tube switch includes a supply branch feeding an activation electrode of the first plasma tube switch, the supply branch coupling the activation electrode of the first plasma tube switch to the positive terminal of the control side of the DC-DC power converter.

[0038] In some cases, the voltage at the terminals of the first switched capacitor is limited by the first switched surge protector to a protection voltage of less than 10% of the nominal operating voltage of the cutoff module.

[0039] In some cases, the first switched capacitor has a capacitance greater than 100 microfarads.

[0040] In some cases, the precharge voltage and switching inductance of the first switched capacitor of the cutoff module are scaled to limit the rate of change of current through the main cutoff device when the plasma tube switch is closed causing the switched branch to become conductive to current, to a value corresponding to the rate at which the main cutoff device can interrupt the electric arc.

[0041] In some cases, the conduction time of the first plasma tube switch during opening of the cutoff device is less than 1 millisecond, preferably less than 300 microseconds, and more preferably less than 100 microseconds.

[0042] In some cases, the changeover switch includes a second plasma tube switch including an anode, a cathode, and a control grid, the second plasma tube switch being interposed in the changeover branch between the first point and the second point of the cutoff module in electrical parallel with and in an opposite direction to the first plasma tube switch, whereby the cathode of the second plasma tube switch is coupled to the second section of the changeover branch and the anode of the second plasma tube switch is coupled to the first section of the changeover branch; a second switched capacitor disposed in the second section of the switched branch coupled to the cathode of the second plasma tube switch; a control system for the second plasma tube switch is powered by the second switched capacitor; the second switched capacitor includes a proximal armature coupled to the cathode of the second plasma tube switch and a distal armature on an opposite side of the cathode of the second plasma tube switch from the proximal armature; the device including a pre-charging circuit for the second switched capacitor; the cut-off module includes a second switching surge protector, the second switching surge protector having a protection voltage such that a sum of the protection voltages of the first switching surge protector and the second switching surge protector is lower than the nominal operating voltage of the cut-off module, and the second switching surge protector is electrically connected in parallel with the second switching capacitor; The control system of the second plasma tube switch includes at least a second pilotable switch which, when closed, supplies a voltage derived from the electrical voltage across the armature of the second switched capacitor to the control grid of the second plasma tube switch.

[0043] In some variations of such cases, the second pilotable switch, in a closed state, electrically couples the control grid of the second plasma tube switch to the distal armature of the second switched capacitor. In other variations of such cases, the control system of the second plasma tube switch includes a second DC-DC power converter having a source side coupled to the distal armature of the second switched capacitor and having a control side that supplies power to the control grid of the second plasma tube switch via the second pilotable switch.

[0044] In some cases, the control system of the second plasma tube switch includes a supply branch that supplies an activation electrode of the second plasma tube switch. In some variations of such cases, the supply branch connects the activation electrode of the second plasma tube switch to the positive terminal of the control side of the second DC-DC power converter.

[0045] In some cases, the at least one cutoff module includes at least one auxiliary switching branch electrically parallel to the switching branch, the absorption branch, and the main branch between the first point and the second point of the cutoff module, together with at least a first auxiliary plasma tube switch including an anode, a cathode, and a control grid, the first auxiliary plasma tube switch being interposed in the auxiliary switching branch between the first point and the second point of the cutoff module, thereby separating the auxiliary switching branch into a first section coupled to the cathode of the first auxiliary plasma tube switch and a second section coupled to the anode of the first auxiliary plasma tube switch, and at least a first auxiliary switched capacitor being disposed in the first section of the auxiliary switching branch coupled to the cathode of the first plasma tube switch.

[0046] In a particular variation of such a case, the anode of the first auxiliary plasma tube switch is coupled to the same point among the first point and the second point of the cutoff module as the anode of the first plasma tube switch of the at least one cutoff module; the at least one cutoff module includes a control system for the first auxiliary plasma tube switch supplied by the first auxiliary switched capacitor; the first auxiliary switched capacitor includes a proximal armature coupled to the cathode of the first auxiliary plasma tube switch and a distal armature on an opposite side of the cathode of the first auxiliary plasma tube switch relative to the proximal armature; the device includes a pre-charging circuit for the first auxiliary switched capacitor; the device includes a first auxiliary switching surge protector, the first auxiliary switching surge protector having a protection voltage lower than the nominal operating voltage of the cutoff module and electrically connected in parallel with the first auxiliary switching capacitor; The pre-charge circuit of the first switched capacitor and the pre-charge circuit of the first auxiliary switched capacitor include a common voltage source supplying the first switched capacitor and the first auxiliary switched capacitor in parallel.

[0047] In some cases, the at least one cutoff module is interposed in parallel and opposite directions in the auxiliary switching branch and includes two auxiliary plasma tube switches.

[0048] In some cases, the device includes several cut-off modules interposed in series in the main circuit, each between a first point and a second point in the main circuit relative to the cut-off module under consideration. [Brief explanation of the drawings]

[0049] [Figure 1] 1 is a schematic diagram illustrating one exemplary embodiment of a one-way cutoff device according to the present invention. [Figure 2-1] 2A-2E illustrate various embodiments of a first family of pilots for a system for controlling a plasma tube switch of a cutoff device according to the present invention. [Figure 2-2] 2F-2H illustrate various embodiments of a second family of pilots for a system for controlling a plasma tube switch of a cutoff device according to the present invention. [Figure 3] 1 is a schematic diagram illustrating one exemplary embodiment of a two-way cutoff device according to the present invention. [Figure 4] 4A to 4H are diagrams illustrating the changes in various physical quantities of the cutoff device according to FIG. 3 for a first scenario of electrical cutoff by the cutoff device. [Figure 5] 5A to 5H are diagrams illustrating the changes in various physical quantities of the cutoff device according to FIG. 3 for a second scenario of electrical cutoff by the cutoff device. [Figure 6]1 is a schematic diagram illustrating one exemplary embodiment of a two-way cutoff device according to the present invention having an auxiliary switching branch. [Figure 7] 1 is a schematic diagram showing one exemplary embodiment of a cut-off device according to the invention having several cut-off modules arranged in series in the main circuit; DETAILED DESCRIPTION OF THE INVENTION

[0050] In an electrical network, the transmission of power between two given points of the network is carried out by a transmission line, which generally comprises several conductors, each corresponding to a transmission tower of the line. In all cases, within the meaning of this specification, a conductor can be in the form of a single conductor extending between two distinct points of the network considered, or in the form of a set of conductors extending in electrical parallel between the same two distinct points of the network considered, all conductors of the set being at the same potential at any instant.

[0051] Thus, in an HVDC network, the transmission of power between two given points of the network is performed by a transmission line, which often includes two transmission towers, each tower including a conductor extending between the two given points of the network. Thus, in this case, the transmission line includes two conductors of opposite polarity, including one conductor that is at, for example, a positive potential and one conductor that is at a negative or neutral potential during charging. Furthermore, in an HVDC network unit, the transmission of power between two given points of the network can also be performed by a transmission path having three transmission towers including three conductors, including one conductor that is at a positive potential, one conductor that is at a negative potential, and one conductor that is at a neutral potential during charging. In some cases, the transmission of power between two given points of the network can be performed by a transmission line on a single transmission tower including a conductor at the potential of the transmission line and an earth return.

[0052] 1 shows a first exemplary embodiment of a cut-off device 10 for interrupting a current under a high direct current voltage flowing in a conductor 11, which may belong to a power transmission line of an HVDC network unit operating under a DC nominal operating voltage of, for example, more than 1,500 V or even more than 75,000 V (75 kV). The cut-off device 10 is therefore interposed in the conductor 11 between a primary point 12 of the device 10 and a secondary point 14 of the device 10, which may each be a connection terminal of the device 10. The cut-off device 10 therefore divides the conductor 11 into two segments: a first segment 11.1 connected to the primary point 12 and a second segment 11.2 connected to the secondary point 14. Thus, the cutoff device 10 includes a main circuit 16 between the primary point 12 of the device 10 and the secondary point 14 of the device 10, through which, in the conducting configuration of the cutoff device 10, an operating current flows under the high DC nominal operating voltage of the cutoff device 10 (the high nominal operating voltage of the network). This operating current flows in the conductor 11, the intensity of which is equal to or less than the nominal strength of the device. In practice, depending on the instantaneous needs of the network, the operating strength flowing through the conductor 11 at a given moment can vary by being equal to or less than the nominal strength. On the other hand, in the event of an electrical fault, the strength of the current flowing through the cutoff device may exceed this nominal strength for a short period of time. The cutoff device 10 is configured to fulfill the role of a circuit breaker, i.e., it has the ability to interrupt currents of greater than the nominal strength, resulting either during charging at the nominal strength or in the presence of a fault current of greater than the nominal strength. However, this same cutoff device remains capable of interrupting currents of less than the nominal strength.

[0053] Cutoff device 10 includes at least one cutoff module 18 interposed in main circuit 16 between a first point 20 and a second point 22 in main circuit 16 for cutoff module 18. In the example of FIG. 1 , which includes only one cutoff module 18, first point 20 and second point 22 in main circuit 16 are points in main circuit 16 that are at the same potential as primary point 12 and secondary point 14, respectively, of cutoff device 10 that bound main circuit 16 of cutoff device 10.

[0054] Referring below to FIG. 7, it will be seen that the cutoff device may include several cutoff modules 18a, 18b, 18c, ..., which may be placed electrically in series in the main circuit 16 between the primary point 12 and the secondary point 14 of the cutoff device 10.

[0055] The cutoff module 18 comprises at least three branches electrically parallel to one another between a first point 20 and a second point 22 .

[0056] The cut-off module 18 comprises a main branch 24 between a first point 20 and a second point 22, and at least one main cut-off device 26 of the mechanical type interposed in the main branch 24 between the first point 20 and the second point 22, ensuring electrical cut-off in the main branch 24. The main cut-off device 26 is switchable between a closed state, allowing current to flow through the main branch 24, and an open state, ensuring electrical cut-off in the main branch 24 by interrupting the current flow at the moment of zero intensity crossing in the main branch 24. The main branch 24 of the module 18 is one through which an operating current flows in normal operation of the network when the cut-off device 10 is in its conducting configuration. In normal operation of the network, therefore, when the cut-off device 10 is in its conducting configuration, the operating current flowing in the conductor 11 is passed through the main cut-off device 26 according to a steady or quasi-steady state.

[0057] In a mechanical-type main cutoff device 26, electrical cutoff is achieved by the displacement, particularly separation, of one or more pairs of electrical contacts. The displacement of the electrical contacts is typically performed by an operating member or a mechanical, pneumatic, hydraulic, or electric actuator, possibly through kinematic transmission mechanics. This displacement can be monitored electronically, for example, by the electronic control device 100. As mentioned above, in the presence of current and / or high voltage, the mechanical separation of the electrical contacts can cause an electrical arc to be established between the device's two electrical contacts due to high energy storage in the network the device protects. As long as the electrical arc remains established by the mechanical separation, the main cutoff device 26 does not perform an electrical cutoff, because the presence of the arc allows current to continue flowing through the switch. As will be seen below, the present invention provides a means to ensure electrical cutoff, in the sense of effectively interrupting the flow of current. The main cutoff device 26 may consist of a single main cutoff device or several main electrical cutoff devices arranged electrically in series and / or parallel. The main cut-off device 26 can be a so-called "metal-enclosed" device in which the electrical contacts are enclosed in a sealed container filled with an insulating fluid, or even more preferably a "vacuum" device (sometimes called a "vacuum bulb") in which the electrical contacts are enclosed in a sealed container at a pressure below atmospheric pressure, particularly below 100 mbar, especially below 10 microbar. The main cut-off device 26 is advantageously capable of interrupting electric arcs of currents having a high rate of change of intensity at the instant of zero crossing (di / dt), typically a rate of change of intensity of 100 A per microsecond or more.

[0058] The cutoff module 18 also includes an absorption branch 28 arranged electrically in parallel with the main branch 24 between a first point 20 and a second point 22 of the considered cutoff module 18, and at least one general-purpose surge protection device 30 is interposed in the absorption branch 28 between the first point 20 and the second point 22 of the considered module.

[0059] Such a general-purpose surge protector 30 allows for limiting the amplitude of the potential difference at the terminals of any component or set of components with which it is placed in parallel. A surge protector, or "voltage surge arrester," is therefore a device that limits voltage peaks at its terminals. Surge protectors generally comprise electrical components with variable resistance depending on the electrical voltage at their terminals. The change in resistance is generally not linear with respect to the electrical voltage at the terminals of the surge protector. Generally, below the transition voltage at the terminals of the surge protector, the resistance of the surge protector is high, with no or relatively small decrease in resistance with increasing voltage, and the surge protector preferably passes a leakage current of less than 1 ampere (A), or even less than 100 milliamperes (mA). In contrast, above the transition voltage at the terminals of the surge protector, the resistance of the surge protector decreases rapidly with increasing voltage, reaching a clipping voltage value, or a protection voltage at which the resistance of the surge protector becomes low or even very low. In other words, a surge protector acts as a voltage limiter at its terminals over a selected current interval, and when the surge protector passes the maximum scaled current, it opposes the protection voltage. Below the transition voltage, it tends to prevent current from passing. Above the transition voltage, it allows current to pass through the surge protector, slightly increasing the voltage at its terminals. As is known, the transition voltage is generally not a precise value, but rather corresponds to a transition voltage range. However, in this specification, the transition voltage of a surge protector is defined as the voltage at which the surge protector passes one ampere (A). The protection voltage is the voltage across the terminals of the surge protector when the maximum scaled current is passed through it. Among surge protectors, surge arresters are particularly known, which may include varistors and TVS (Transient Voltage Suppressor) diodes, such as "Transil™" diodes. Notably, within the scope of the present invention, surge protectors, particularly the general-purpose surge protector 30, may include metal oxide varistors (or MOVs). The universal surge protector 30 may be designed as a set of several separate components arranged electrically in series and / or parallel.Each separate component may be, for example, a surge arrester, particularly a varistor such as a metal oxide varistor, or a "TVS" diode. Preferably, a set of several separate components arranged electrically in series and / or parallel behaves from the perspective of the rest of the device as a single surge protector with equivalent transition voltages and protection voltages for the set.

[0060] As can be seen, the absorption branch does not include a switch. Therefore, the general-purpose surge protector 30 must be selected so that its transition voltage is greater than the voltage likely to appear at the terminals of the cutoff module 18 when the cutoff device 10 is operating in an electrically open configuration under the network's nominal operating voltage. For example, the general-purpose surge protector 30 may be selected so that its protection voltage is 1.2 to 2 times, e.g., 1.6 times, the nominal operating voltage of the module 18, which is the voltage at which the cutoff module 18 operates when the cutoff device 10 is operating under the network's nominal operating voltage. As shown in Figures 1, 3, and 6, when the cutoff device 10 includes only a single cutoff module 18, the nominal operating voltage of the module 18 is equal to the nominal operating voltage of the cutoff device 10 and also equal to the nominal operating voltage of the network. As shown in FIG. 7, when the cutoff device 10 includes several cutoff modules 18a, 18b, 18c, the nominal voltage of each module 18a, 18b, 18c, which is the voltage likely to appear at the terminals of each cutoff module 18a, 18b, 18c when the cutoff device 10 is operated and in an electrically open configuration under the nominal operating voltage of the network, is only a fraction of the nominal operating voltage of the cutoff device 10 and therefore only a fraction of the nominal operating voltage of the network, since this voltage is then distributed among the various cutoff modules 18a, 18b, 18c.

[0061] Due to the presence of the universal surge protection device 30 interposed in the absorbing branch 28 and the selection of its transition voltage value, it can be assumed that in normal operation of the network when the cut-off device 10 is in its conducting configuration, no current flows in the absorbing branch.

[0062] The cut-off module 18 according to the present invention further comprises at least one switching branch 32 arranged electrically in parallel with the main branch 24 and the absorbing branch 28 between the first point 20 and the second point 22 of the cut-off module 18 under consideration.

[0063] Interposed electrically in series in the switching branch 32 between the first point 20 and the second point 22 are a first switching capacitor C1 and a switching switch designated as at least a first plasma tube switch 34.

[0064] Plasma tube switches are described in documents US 5,828,176 A (plane cross-field plasma switch) or US 10,256,067 and US 2019 / 0295801 (gas switch), which may be referenced. Generally, the plasma tube switch, and thus the first plasma tube switch 34.1, includes an anode 36.1, a cathode 38.1, and a control grid 40.1 within a sealed vessel 42.1 containing a fluid, such as helium, nitrogen, or the like, that can be ionized to generate a plasma. The control grid 40.1 is typically positioned between the anode 36.1 and the cathode 38.1, such that a plasma path conducting a large current between the anode 36.1 and the cathode 38.1 is initiated when a control voltage is momentarily applied to the control grid 40.1. By inducing a reverse polarization of control grid 40.1, and thus applying a reverse control voltage, the current flowing from anode 36.1 to cathode 38.1 is temporarily trapped by control grid 40.1, thereby interrupting the plasma path and making the already ionized fluid between control grid 40.1 and anode 36.1 insulating again. Thus, plasma tube switch 34.1 can be controlled toward an open state, blocking any current passing between its anode 36.1 and its cathode 38.1, or toward a closed state, allowing current to pass between its anode 36.1 and its cathode 38.1, by the value and polarity of the voltage applied to control grid 40.1. For example, plasma tube switch 34.1 can be of the "cross-field switch" type, in which a magnet is positioned to generate a magnetic field parallel to the conductive surface of one electrode of the plasma tube switch, and thus perpendicular to the electric field generated by the voltage between the two electrodes 36.1, 38.1. In some cases, the plasma tube switch 34.1 also includes an active electrode 44.1 within the enclosure 42.1, whose role is to maintain a weak plasma between the active electrode 44.1 and the cathode 38.1. The current strength of this plasma may be on the order of a few milliamps to a few amps, depending on the type and pressure of gas within the enclosure 42.1.In all cases, the principle of operation of the plasma tube switch is based on the possibility of creating a plasma that begins conducting current between anode 36.1 and cathode 38.1 by applying a closing potential to control grid 40.1, which creates a positive voltage relative to the cathode. In contrast, applying an opening potential to control grid 40.1, which creates a negative voltage relative to the cathode, causes this plasma to be interrupted, thereby restoring electrical isolation between anode 36.1 and cathode 38.1 and thus interrupting any current passing between anode 36.1 and cathode 38.1 of plasma tube switch 34.1. Thus, when a voltage supply is applied to a potential activation electrode 44.1, only a potential plasma current remains between activation electrode 44.1 and cathode 38.1.

[0065] The plasma tube switch 34.1 has the great advantage that it can be designed using currently known structures to reliably interrupt high currents, e.g., greater than 500 A, e.g., as much as 1,000 A, at DC voltages of 50,000 volts (50 kV) or more, in very short time intervals. Larger scaling is undoubtedly possible, but currently economic conditions are less favorable. Thus, if the cutoff device must be scaled to interrupt larger currents, a cutoff module 18 can be implemented that includes several parallel switching branches, each equipped with at least a plasma tube switch, thereby distributing the power among several parallel-operating switching branches and, therefore, several parallel plasma tube switches. Additionally, once opened, the plasma tube switch can be designed using currently available technology to withstand voltages at its terminals of greater than 50 kV, or even greater than 100 kV. If the cutoff device must be scaled to withstand higher voltages, it is possible to implement cutoff device 10 including several cutoff modules 18a, 18b, 18c, ... arranged electrically in series in the main circuit 16 of the cutoff device 16 to distribute the voltage among several plasma tube switches in series, as shown in Figure 7, with each cutoff module comprising at least a plasma tube switch.

[0066] The voltage drop across the terminals between the anode 36.1 and cathode 38.1 of the plasma tube switch 34.1 is significant when current is applied, and can range from 50 to 1,000 volts. This voltage drop depends on the specific characteristics of the plasma tube switch, particularly the pressure and type of gas in the sealed vessel and the material of the cathode 38.1. This voltage drop can cause significant energy dissipation during the conduction time of the plasma tube switch 34.1, and if the conduction time is long, it can damage the electrodes in the plasma tube. Thus, it is conceivable that the conduction time of the plasma switch should be as short as possible, given the need to minimize its volume and cost.

[0067] Furthermore, the current strength that needs to be provided to the plasma tube control grid 40.1 is high, requiring strengths of tens of amperes to control closing in order to enable current to be conducted between its anode and its cathode, and a strength comparable to the anode current and therefore of the same order of magnitude as the fault current to be cut, to control the opening of this plasma tube switch, i.e., to enable current to be interrupted between its anode and its cathode.

[0068] Note that, as mentioned above, a plasma tube switch allows current to pass in only one direction between its anode and its cathode, allowing flowing current to pass from its anode (where electrons exit the plasma tube switch) to its cathode (where electrons enter the plasma tube switch).

[0069] Therefore, the first embodiment of the present invention shown in Figure 1 will only allow the fault current to be interrupted if the fault is located in the first segment 11.1 of conductor 11, if conductor 11.1 is at the positive conductor potential in the transmission line. If conductor 11.1 is at the negative conductor potential in the transmission line, the first embodiment of the present invention shown in Figure 1 will allow the fault current to be interrupted if the fault is located in the second segment 11.2 of conductor 11. In fact, the first embodiment of the present invention shown in Figure 1 will allow the fault current to be interrupted only if it flows in a direction going from second point 22 to first point 20.

[0070] First plasma switch 34.1 is positioned in switching branch 32 to separate switching branch 32 into a first section 32.1 coupled to cathode 38.1 of first plasma tube switch 34.1 and a second section 32.2 coupled to anode 36 of first plasma tube switch 34.1. Thus, in the illustrated example, first section 32.1 of switching branch 32 couples cathode 38.1 of first plasma tube switch 34.1 to first point 20 of cutoff module 18, and second section 32.2 of switching branch 32 couples anode 36.1 of first plasma tube switch 34.1 to second point 22 of cutoff module 18.

[0071] To control the first plasma switch 34.1, the cut-off module 18 of the cut-off device 10 includes a control system 46.1 for the first plasma tube switch 34.1, which functions, inter alia, to monitor the potential applied to the control grid 40.1 of the first plasma tube switch 34.1 in order to control the plasma switch in either its open or closed state.

[0072] As will be understood below, first plasma tube switch 34.1 is intended to be controlled towards its closed state and allow current to flow only during switching phases of main cut-off device 26, in particular during phases of switching main cut-off device 26 from its closed state to its open state. Apart from these switching phases, first plasma tube switch 34.1 is intended to be maintained in its open state so that no current flows in switching branch 32, in particular during nominal conduction phases in which main cut-off device 26 is maintained in its closed state and allows operating current to flow through conductor 11, or during isolation phases in which main cut-off device 26 is maintained in its open state and interrupts the current flow in conductor 11.

[0073] Thus, the control system 46.1 must include at least one potential source and at least one pilotable switch to be able to control the potential applied to the control grid 40.1 of the first plasma tube switch 34.1.

[0074] The control system 46.1 of the first plasma tube switch 34.1 is powered by a first switched capacitor C1 located in the first section 32.1 of the switched branch 32, which is coupled to the cathode 38.1 of the first plasma tube switch 34.1. Conventionally, the first switched capacitor C1 includes two conductive armatures C1p and C1d positioned opposite each other and separated by an electrical insulator, with the proximal armature C1 coupled to the cathode 38.1 of the plasma tube switch 34.1 and the distal armature C1d on the opposite side of the cathode 38.1 of the plasma tube switch from the proximal armature C1p. The distal armature C1d of the first switched capacitor C1 is therefore coupled to a first point 20 of the cutoff module 18, and in the illustrated embodiment, is interposed with an optional coil 82, described below. Of course, first switched capacitor C1 can be designed as a set of several separate capacitors arranged electrically in series and / or parallel with one another, in which case first switched capacitor C1 is an electrically equivalent capacitor of this set, as will be explained below. Thus, first switched capacitor C1 serves, among other things, as a source of potential intended to be applied to control grid 40.1 of plasma tube switch 34.1. In addition to its first function of providing a voltage source for control system 46.1 of first plasma tube switch 34.1, it also performs a second function, which involves generating an oscillating current in switching branch 32 and injecting a reverse current into main branch 24 in order to facilitate the extinguishing of an electric arc likely to appear between the electrodes of main cutoff device 26 at the moment of its opening.

[0075] As will be seen below, control system 46.1 includes a pre-charge circuit 48.1 for first switched capacitor C1. This pre-charge circuit 48.1 allows for the introduction of a predetermined electrical voltage across the two armatures C1p, C1d of switched capacitor C1, sufficient to provide the potential necessary to control plasma tube switch 34.1, particularly to control plasma tube switch 34.1 to transition to its closed state, prior to any switching of main cutoff device 26. In this example, pre-charge circuit 48.1 includes DC voltage source 50.1, which includes a positive terminal 52.1, in this embodiment, coupled to distal armature C1d of switched capacitor C1 through resistor 53.1, and a negative terminal 54.1, in this embodiment, coupled to proximal armature C1p of switched capacitor C1, also through another resistor 55.1. Resistors 53.1, 55.1 of pre-charge circuit 48.1 may have the same resistance value or may have different values. In practice, only one of the two resistors may be sufficient. Resistors 53.1, 55.1 serve to limit the charge / discharge current provided by DC voltage source 50.1. Thus, in this embodiment, designed to allow fault current to be interrupted only if it flows in the direction from second point 22 towards first point 20, pre-charge circuit 48.1 ensures pre-charging of switched capacitor C1 such that its distal armature C1d is positively charged with respect to its proximal armature C1p.

[0076] The control system 46.1 of the first plasma tube switch 34.1 includes at least a first pilotable switch 58.1 which, in a closed state, supplies a voltage derived from the electrical voltage across the armature of the first switched capacitor C1 to the control grid 40.1 of the first plasma tube 34.1.

[0077] Generally, the first pilotable switch 58.1 is piloted according to a first closing pulse to control the closing of the first plasma tube switch 34.1, and is piloted according to a second closing pulse to control the opening of the first plasma tube switch 34.1 after the charge polarity of the first switched capacitor C1 is reversed.

[0078] In general, control system 46.1 can take a variety of forms. Of these various possible forms, two families of embodiments can be identified specifically for control system 46.1: a first family of embodiments that ensure a direct connection between the distal armature C1d of switched capacitor C1 and control grid 40 via a pilotable switch 58.1; and a second family of embodiments that ensure an indirect connection between the switched capacitor and control grid 40.1 of plasma tube switch 34.1 via a power converter and a pilotable switch. These two families have in common the interposition of a pilot 56.1 between switched capacitor C1 and plasma tube switch 34, this pilot 56.1 comprising a first pilotable switch 58.1.

[0079] The first pilot family 56.1 may take, for example, any of the forms shown in Figures 2A, 2B, 2C, 2D, and 2E, respectively (including possible variations thereof).

[0080] 2A shows one embodiment in which pilot 56.1 can take the form of a simple pilot-enabled switch 58.1 interposed on conductor 60 connecting distal armature C1d of switched capacitor C1 to control grid 40.1 of plasma tube switch 34.1. Preferably, first pilot-enabled switch 58.1 is a two-way switch capable of conducting and blocking current in both directions between control grid 40.1 of first plasma tube switch 34.1 and distal armature C1d of first switched capacitor C1. Momentary closure of first pilot-enabled switch 58.1 allows monitoring of the closure and opening of first plasma tube switch 34.1. Initially, the distal armature C1d is considered to be in positive polarity relative to the cathode 38.1 of the first plasma tube switch 34.1, so that momentary closure of the pilotable switch 58.1 can generate a positive pulse voltage in the control grid 40.1 to control the closure of the first plasma tube switch 34.1, making it conductive to any current passing from its anode 36.1 to its cathode 38.1. Such current would therefore likely pass through the plasma tube switch 34.1 and would likely reverse the voltage across the armatures C1d, C1p of the first switched capacitor C1, causing the distal armature C1d to be in negative polarity relative to the cathode 38.1. Thus, starting from this state, by temporarily closing the first pilotable switch 58.1, it becomes possible to apply a negative voltage to the control grid 40.1 to control the opening of the plasma tube switch 34.1, thereby interrupting the passage of any current.

[0081] 2A illustrates a variation that can be implemented when the first plasma tube switch 34.1 further includes an activation electrode 44.1. In this case, the pilot 56.1 can advantageously include a supply branch 62 that supplies the activation electrode 44.1 of the first plasma tube switch 34.1. In the illustrated example, the supply branch 62 includes a resistor 64 interposed in a conductor connecting the distal armature C1d of the switched capacitor C1 to the control grid 40.1 of the first plasma tube switch 34.1. Typically, the resistor 64 is scaled so that the supply current to the activation electrode 44.1 has a magnitude comprised between 1 milliamp and 1 amp.

[0082] 2B shows a variant of pilot 56.1 in which first pilotable switch 58.1 is designed as two unidirectional electronic switches 58a, 58b, e.g., IGBTs (insulated gate bipolar transistors), electrically interleaved in series and opposite directions between control grid 40.1 of first plasma tube switch 34.1 and distal armature C1d of first switched capacitor C1, with each IGBT 58a, 58b comprising a freewheeling diode disposed antiparallel to the IGBT. During operation, the two IGBTs 58a, 58b are normally open. One of the two IGBTs 58a, 58b is controlled toward its closed state to control the closing of first plasma tube switch 34.1, and the other of the two IGBTs 58a, 58b is controlled toward its closed state to control the opening of first plasma tube switch 34.1. The design of the first pilotable switch 58.1 in the form of two one-way electronic switches makes it possible to permit precise piloting of the switching instant of the first plasma tube switch 34.1 in a simple and economical way.

[0083] 2B, independently of the particular embodiment of pilotable switch 58.1 shown in this figure, it is of course shown that, in the case where plasma tube switch 34.1 includes an activation electrode 44.1, a possible supply branch 62 supplying activation electrode 44.1 may include a diode 66 that passes current in branch 62 only from the distal armature C1d of switched capacitor C1 to activation electrode 44.1. The presence of this diode 66 makes it possible to maintain the plasma inside plasma tube switch 34.1, even if the voltage at the terminals of first switched capacitor C1 is reversed, thereby ensuring that first plasma tube switch 34.1 remains in its closed configuration, thereby allowing current to flow.

[0084] 2C shows a variant of the pilot 56.1 in which the supply branch 62 supplying the potential active electrode 44.1 includes a supply switch 68 that controls whether the active electrode 44.1 is powered. In this example, the supply switch 68 is associated in series with a diode 66 in the supply branch 62, which allows current to flow in the branch 62 only from the distal armature C1d of the switched capacitor C1 toward the active electrode 44.1. Furthermore, the supply switch 68 that controls whether the active electrode 44.1 is powered can be designed as an electronic switch, such as in the form of an IGBT, with a freewheeling diode placed anti-parallel to the IGBT and opposite the diode 66. In its closed state, the supply IGBT 68 short-circuits the freewheeling diode, allowing current to flow in the branch 62 from the distal armature C1d of the switched capacitor C1 to the active electrode 44.1. Therefore, supply switch 68, which controls whether or not power is supplied to activation electrode 44.1, can be closed to supply power to activation electrode 44.1 just prior to the command to close plasma tube switch 34.1. For example, supply switch 68 can be closed 100 microseconds (μs) to 10 milliseconds (ms) before the command to close plasma tube switch 34.1. This ensures good control of the instant at which plasma tube switch 34.1 switches to its closed state.

[0085] 2D shows a variation of pilot 56.1 in which a current limiter 70 is inserted in series with first pilot-enabled switch 58.1 in conductor 60 connecting distal armature C1d of switched capacitor C1 to control grid 40.1 of the plasma tube switch. Current limiter 70 prevents capacitor C1 from discharging too quickly and also limits the strength through pilot-enabled switch 58.1. In this example, the current limiter is an asymmetric limiter that limits current only in the direction from distal armature C1d of switched capacitor C1 to control grid 40.1 of first plasma tube switch 34.1, and therefore only during a command to close first plasma tube switch 34.1. This is advantageous because the current required to command a plasma tube switch to close is generally much smaller than the current required to command it to open. To this end, current limiter 70 includes a resistor 72 and a diode 74 in parallel with each other, with diode 74 shorting out resistor 72 when current flows from monitoring grid 40.1 to the distal armature C1d of first switched capacitor C1. In this FIG. 2D, current limiter 70 provides no resistance while first plasma tube switch 34.1 is open. In the variation shown in FIG. 2E, current limiter 70 remains asymmetric, with a second resistor 76 placed in current limiter 70 in series with diode 74, and second resistor 76 and diode 74 in parallel with first resistor 72. Thus, first resistor 72 and second resistor 76 independently define current limits in both directions between first switched capacitor C1 and control grid 40.1 of first plasma tube switch 34.1, allowing the current provided to control grid 40.1 to be adjusted as closely as possible to the current required for the close and open commands, respectively, while protecting pilotable switch 58.1. In practice, second resistor 76 is typically scaled to have a lower resistance than first resistor 72.

[0086] The second family of pilots 56.1 may take, for example, any of the forms shown in Figures 2F, 2G, and 2H, respectively (including possible variations thereof).

[0087] In these embodiments, the control system 46.1 of the first plasma tube switch 44.1 includes a DC-DC power converter 78 having a source side electrically coupled to the distal armature C1d of the first switched capacitor C1 and having a control side that supplies the control grid 40.1 of the first plasma tube switch 34.1 via the first pilotable switch 58.1.

[0088] The presence of this electrical converter makes it possible to decouple the scaling issues of the capacitor (especially with regard to voltage resistance and capacitance) so that, on the one hand, it can fulfill its role in generating an oscillating current that allows the arc of the main switching device to be extinguished, and, on the other hand, it can fulfill its role in supplying power to the control grid 40.1 of the first plasma tube switch 34.1.

[0089] As can be seen in the figure, the distal armature C1d of the first switched capacitor C1 is coupled to the input terminal 78.1 of the DC-DC power converter 78, and the proximal armature C1p is coupled to the electrical neutral point 78.2 of the DC-DC power converter 78.

[0090] The control side of power converter 78 includes a positive terminal 78.3 and a negative terminal 78.4. In the example shown in Figures 2F, 2G, and 2H, first pilot-enabled switch 58.1 includes a first pilot-enabled start switch 58a interposed between the positive terminal 78.3 of power converter 78 and the control grid 40.1 of first plasma tube switch 34.1, and a second pilot-enabled stop switch 58b interposed between the negative terminal 78.4 of power converter 78 and the control grid 40.1 of first plasma tube switch 34.1. First pilot-enabled start switch 58a and second pilot-enabled stop switch 58b are normally open switches, and control system 46.1 is configured so that only one of the two pilot-enabled switches 58a, 58b is controlled toward its closed state at a time. When first pilot-enabled start switch 58a is controlled toward its closed state, it allows control current to flow toward control grid 40.1, thereby closing first plasma tube switch 34.1. When second pilot-enabled stop switch 58b is controlled toward its closed state, it allows control current to flow away from control grid 40.1, thereby opening first plasma tube switch 34.1. As shown in the embodiment of FIG. 2G, it is also possible to provide a resistor 72 in electrical series with first pilot-enabled start switch 58a interposed between positive terminal 78.3 of power converter 78 and control grid 40.1, and / or a resistor 76 in electrical series with second pilot-enabled stop switch 58b interposed between negative terminal 78.4 of power converter 78 and control grid 40.1 of first plasma tube switch 34.1, to limit current during the closing and / or opening of first plasma tube switch 34.1, respectively.

[0091] In this second family of pilots 56.1, if the first plasma tube switch 34.1 includes the activation electrode 44.1, the pilot 56.1 may include a supply branch 62 that couples the activation electrode 44.1 of the first plasma tube switch 34 to a positive terminal 78.3 on the control side of the DC-DC power converter 78. Preferably, a resistor 64 is inserted in the branch 62 to limit the current in this supply branch 62. As shown in Figures 2G and 2H, a supply switch 68 may be inserted in the supply branch 62, with the supply switch 68 having the same role and operation as described with reference to the embodiment of Figure 2C.

[0092] In both cases, the device according to the present invention allows these functions to be performed using a first switched capacitor C1 with a voltage resistance that can be much lower than the nominal operating voltage of the cut-off module 18 and, therefore, significantly lower than the nominal operating voltage of the network into which the conductor 11 is inserted. In practice, the present invention takes advantage of the high voltage resistance of plasma tube switches, which is generally about ten times higher than that of electronic switches, and their powerful current cut-off capabilities. Therefore, the cut-off module 18 includes a first switched surge protection device 80.1 electrically connected in parallel with the first switched capacitor C1. This first switched surge protection device 80.1 is therefore connected by its two terminals to two points on either side of the first switched capacitor C1, respectively, in the first section of the switched branch.

[0093] The first switching surge protector 80.1 limits the voltage at the terminals of the first switching capacitor C1. Therefore, in general, in a cut-off device 10 intended for an extra-high voltage network, i.e., where the DC nominal operating voltage in the network is greater than 75 kV, the first switching surge protector 80.1 can limit the voltage at the terminals of the first switching capacitor C1 to a voltage of 10 kV or less. Generally, the first switching surge protector 80.1 can have a protection voltage of less than 10% of the nominal operating voltage of the cut-off module. However, it should be noted that the first switching surge protector 80.1 necessarily limits the pre-charge voltage that can be applied to the first switching capacitor C1. Alternatively, this pre-charge voltage can be used to control the plasma tube switch 34.1. In addition to providing a voltage boosting device in the control system 46.1 of the first plasma tube switch 34.1, it is ensured that the protection voltage of the first switching surge protector 80.1 is higher than the voltage required to control the plasma tube switch 34.1, which is generally greater than 1 kV, for example, 1 kV to 5 kV. For example, the switching surge protector 80.1 can be selected so that its protection voltage is 1.5 to 2.5 times, for example, 2 times, the pre-charge voltage of the switching capacitor C1 that it must protect.

[0094] Thanks to this, the present invention makes it possible to use a switched capacitor C1 that does not have to withstand voltages higher than those defined by the protection voltage of the switched surge protector 80.1, thus reducing the cost and space requirements of the first switched capacitor C1.

[0095] As will be seen below, the occurrence of switched current oscillations in the switching branch 32 is caused by a modulation of the current in the loop formed by the main branch 24 of the cut-off module 18 and the switching branch 32 when the first plasma tube switch 34.1 is in its closed state. This loop, which in particular includes the first switching capacitor C1, necessarily has a certain inductance such that it forms an LC circuit which generates a current ripple during transient phases, which in a manner that will be explained below will be used to interrupt an electric arc that is likely to form in the main cut-off device 26 in its open state.

[0096] The switching inductance can be provided by the self-inductance of the components making up the loop, particularly 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 insufficient, the loop formed by the main branch 24 and the switching branch 32 can include a coil 82. This coil is preferably located in the switching branch 32. In such a case, the coil 82 could be located in the second section 32.2 of the switching branch 32. In the example of FIG. 1, the coil 82 is located in the first section 32.1 of the switching branch, but not between the first switching capacitor C1 and the first plasma tube switch 34.1, but rather between the first switching capacitor C1 and the first point 20 of the main circuit 16. The switching inductance is scaled to limit the rate of change of the current through the main cutoff device 26 when the switching branch 32 becomes conductive to the current due to the closure of the plasma tube switch 34.1. The rate of change of current in the switching branch 32 must be limited by the components of this branch to a value corresponding to the ability of the main cutoff device 26 to interrupt an electric arc. Therefore, the device is scaled to ensure interruption of the arc in the main electrical cutoff device 26 when the current through this device passes through zero, even when the magnitude of the current flowing through the main circuit 16 is low or very low compared to the nominal operating intensity to which the main circuit is scaled. For example, if the main cutoff device 26 is capable of interrupting an electric arc with a high rate of change of intensity (di / dt) and a current with an intensity gradient of typically 100 A / microsecond or more, the precharge voltage of the switching capacitors and the switching inductance of the cutoff module are scaled to limit the rate of change of current through the main cutoff device 26 to a value less than 100 A / microsecond when the switching branch 32 becomes conductive to the current by closing the plasma tube switch 34.1.

[0097] It should be noted that it is preferable to use switched capacitors at the relatively low voltages made possible by the present invention for implementing a plasma tube switch. In practice, switched capacitors with relatively high capacitance values ​​are used at relatively low voltages. Therefore, the natural frequency of discharge of the switched capacitors in the switching loop (therefore the loop is essentially of an LC type) is relatively low. For example, the cutoff module 18 could be scaled so that the natural frequency of discharge of the switched capacitors in the switching loop is less than 3 kHz, preferably less than 1 kHz, and more preferably less than 300 Hz.

[0098] For this reason, it is ensured that for the loop formed by the main branch and the switching branch, the cut-off device includes a switching inductance whose value is greater than or equal to the ratio between, on the one hand, the difference between the pre-charge voltage of the switching capacitor C1 and the voltage drop at the terminals of the plasma tube switch, and, on the other hand, the maximum value of the rate of change of intensity (di / dt_max) at which the main cut-off device 26 can interrupt an electric arc generated by a low-intensity current.

[0099] The general principle of operation of cutoff module 18 as shown in Figure 1 will be understood from the principle of operation described in connection with cutoff module 18 as shown in Figure 3. As mentioned above, cutoff module 18 as shown in Figure 1 enables current interruption in conductor 11 when a fault current flows through cutoff module 18 from second point 22 to first point 20, for example, in the event of a ground fault in first segment 11.1 of conductor 11. More specifically, in this configuration, the cutoff assistance system formed by switching branch 32 and energy absorbing branch 28 becomes available to help extinguish an electric arc that is likely to appear in main cutoff device 26 during its opening. Thus, cutoff module as shown in Figure 1 is a unidirectional cutoff module with respect to the direction of fault current flow and thus, for example, with respect to the location of the fault.

[0100] For this reason, the present invention also proposes a cut-off device comprising at least one bidirectional cut-off module 18 as shown in FIG. 3, configured to ensure current interruption in the conductor 11 regardless of the direction of flow of the fault current through the cut-off module 18, and therefore both when, for example, the ground fault is located in the first segment 11.1 of the conductor 11 and when the ground fault is located in the second segment 11.2 of the conductor 11.

[0101] Thus, the bidirectional cutoff module 18 of Figure 3 includes all of the elements described above in relation to Figure 1 in the same arrangement and with the same possibilities for variation. In addition to these elements, the cutoff module 18 includes a second plasma tube switch 34.2 in its switching branch 32 interposed between the first point 20 and the second point 22 of the main circuit of the cutoff module 18, the second plasma tube switch 34.2 being electrically parallel to the first plasma tube switch 34.1 but in the opposite direction in the switching branch 32 as the first plasma tube switch 34.1.

[0102] The second plasma tube switch 34.2 also includes an anode 36.2, a cathode 38.2, and a control grid 40.2. The first plasma tube switch is oriented in the opposite direction, such that the cathode 38.2 of the second plasma tube switch 34.2 is coupled to the second section 32.2 of the switching branch 32, and the anode 36.2 of the second plasma tube switch 34.2 is coupled to the first section 32.1 of the switching branch 32.

[0103] Note that the second plasma tube switch 34.2 is positioned in the switching branch 32 so as to be interposed between the first switched capacitor C1 and the second point 22 of the cutoff module 18. Thus, the proximal armature C1p of the first switched capacitor C1 is coupled to the anode 36.2 of the second plasma tube switch 34.2.

[0104] Symmetrically to the first plasma tube switch 34.1, the cutoff module 18 includes a control system 46.2 for the second plasma tube switch 34.2, which includes a second switched capacitor C2 disposed in series with the second plasma tube switch 34.2 in the switching branch 32 between the first point 20 and the second point 22 in the second section 32.2 of the switching branch 32, and thus coupled to the cathode 38.2 of the second plasma tube switch 34.2. The second switched capacitor C2 also includes a proximal armature C2p coupled to the cathode 34.2 of the second plasma tube switch 34.2 and a distal armature C2d on the opposite side of the proximal armature C2p from the cathode 38.2 of the second plasma tube switch 34.2. Thus, the distal armature C2d of the second switched capacitor C2 is coupled to the second point 22 of the cutoff module 18.

[0105] Note that the second switched capacitor C2 is positioned in the switched branch 32 so as to be interposed between the first plasma tube switch 34.1 and the second point 22 of the cutoff module 18. Thus, the proximal armature C2p of the second switched capacitor C2 is coupled to the anode 36.1 of the first plasma tube switch 34.1.

[0106] In this example, cutoff module 18 is a bidirectional module in which the two plasma tube switches are identical in terms of electrical characteristics, except that they are installed in opposite directions. Similarly, in this example, second switched capacitor C2 has the same electrical characteristics (voltage resistance, capacitance, etc.) as first switched capacitor C1. This identical scaling allows fault currents of the same amplitude and dynamics to be managed, regardless of the direction of flow through cutoff device 10. However, in some cases where it is possible to anticipate risks of electrical faults of different nature on one side and the other side of cutoff device 10, different scaling could be envisioned for the two plasma tube switches and / or the second switched capacitor C2 relative to the first switched capacitor C1.

[0107] The cutoff device 10 includes a pre-charge circuit 48.2 for the second switched capacitor C2. The pre-charge circuit 48.2 for the second switched capacitor C2 can be separate and independent from the pre-charge circuit 48.1 for the first switched capacitor C1, as shown in Figure 3. The pre-charge circuit 48.2 for the second switched capacitor C2 can be an identical copy of the pre-charge circuit 48.1 for the second switched capacitor C1.

[0108] In contrast to that described above with respect to first plasma tube switch 34.1, control system 46.2 for second plasma tube switch 34.2 includes at least a second pilotable switch which, in a closed state, supplies control grid 40.2 of second plasma tube switch 34.2 with a voltage derived from the electrical voltage across armature C2p, C2f of second switched capacitor C2. Control system 46.2 for second plasma tube switch 34.2 may take the same form as that described above with respect to control system 46.1 for first plasma tube switch 34.1.

[0109] Therefore, control system 46.2 for second plasma tube switch 34.2 can be designed in a manner similar to that described above with reference to Figures 2A-2E so that, when the second pilotable switch is in its closed state, control grid 40.2 for second plasma tube switch 34.2 is coupled to distal armature C2d of second switched capacitor C2. Similarly, control system 46.2 for second plasma tube switch 34.2 may also include a supply branch that supplies activation electrode 44.2, if the second plasma tube switch 34.2 includes such an electrode. Alternatively, control system 46.2 for second plasma tube switch 34.2 may include a DC-DC power converter having a source side coupled to distal armature C2d of second switched capacitor C2 and a control side that supplies control grid 40.2 for second plasma tube switch 34.2 through the second pilotable switch, similar to that described with reference to Figures 2F, 2G, and 2H. In this case, if the second plasma tube switch 34.2 includes the activation electrode 44.2, the control system 46.2 may include a supply branch connecting the activation electrode 44.2 of the second plasma tube switch to the positive terminal of the control side of the second DC-DC power converter.

[0110] In addition to the first switched capacitor C1, the cut-off device 10 is designed to allow the use of a second switched capacitor C2, which can withstand voltages that can be much lower than the nominal operating voltage of the network in which the conductor 11 is inserted. The cut-off module 18 therefore includes a second switched surge protection device 80.2 electrically parallel to the second switched capacitor C2. This second switched surge protection device 80.2 is therefore connected by its two terminals to two points on the second section 32.2 of the switched branch 32, respectively, on either side of the second switched capacitor C2. The second cut-off surge protection device 80.2 makes it possible to limit the voltage at the terminals of the second switched capacitor C2 while a fault current is flowing through the switched branch. Typically, in a cut-off device 10 intended for extra-high voltage networks, i.e., where the DC nominal operating voltage in the network is greater than 75 kV, the voltage at the terminals of the second switched capacitor C2 can therefore be limited by the second switched surge protector 80.2 to a voltage of 10 kV or less. Typically, the second switched surge protector 80.2 could be scaled for a protection voltage such that the sum of the protection voltages of the first switched surge protector 80.1 and the second switched surge protector 80.2 is lower than the nominal operating voltage of the cut-off module 18.

[0111] 3 makes it possible to permit current to pass according to two flow directions in switching branch 32. First plasma tube switch 34.1 can be controlled in its closed state to permit current to pass according to one flow direction in switching branch 32, i.e., from second point 22 to first point 20. Second plasma tube switch 34.2 can be controlled in its closed state to permit current to pass according to the other flow direction in switching branch 32, i.e., from first point 20 to second point 22.

[0112] Two current cutoff scenarios likely to be implemented by the cutoff device 10 of FIG. 3 are now described.

[0113] A first current cutoff scenario will be described in relation to Figures 4A-4H, which represent timing diagrams of the changes in various electrical quantities in the cutoff device 10 of Figure 3. A second current cutoff scenario will be described in relation to the timing diagrams of Figures 5A-5H. To establish these timing diagrams, we have arbitrarily taken into account the convention that the current flowing through the cutoff device 10 from a first point 20 to a second point 22 (and thus from left to right in Figure 3) is a positive current.

[0114] In the two scenarios described, the convention used is to consider the case of an initial current (called the operating current) flowing in the negative direction, i.e., going from the second point 22 to the first point 20. However, the direction of the initial current, i.e., the operating current, is not important and could therefore be in the opposite direction in both scenarios.

[0115] In both scenarios, up until the instant t1, the cutoff device 10 is in its conducting configuration, corresponding to the normal operation of the network, and therefore an operating current flows through the conductor 11. In this example, the absolute value of the operating current is on the order of 1,500 A (here, negative, according to the chosen convention). In this conducting configuration, the main cutoff device 26 is in its closed state, so the entire operating current flows through the main branch 24 of the cutoff device 10 (FIG. 4A), and the voltage V26 at the terminals of the main cutoff device 26 can be considered to be zero (FIG. 4F). In this conducting configuration, the two plasma tube switches 34.1 and 34.2 are in their open states, so the currents I34.1 and I34.2 through them, respectively, are zero (FIGS. 4B and 4C), and therefore the current in the switching branch 32 is zero. It should be noted that the control voltage V40.1 (FIG. 4G) applied to the control grid 40.1 of the first plasma tube switch 34.1 and the control voltage V40.2 (FIG. 4H) applied to the control grid 40.2 of the second plasma tube switch 34.2 are both equal to the fault voltage, which in this example is zero voltage. However, it will be noted that some plasma tube switches operate by default by applying a fault voltage to the control grid that is negative with respect to the cathode. Such plasma tube switches that operate with a negative fault voltage on the control grid would advantageously be implemented using a pilot 56.1 that includes a DC-DC power converter, as in the example of FIGS. 2F-2H.

[0116] For both scenarios, we describe the case where the first switched capacitor C1 is precharged with a voltage V C1 ( FIG. 4E ) at its terminals, which is a positive voltage in the sense that the distal armature C1d is positively charged with respect to the proximal armature C1p. In other words, the voltage V C1 = V C1d - V C1p is positive, with V C1d being the potential of the distal armature C1d and V C1p being the potential of the proximal armature C1p. The absolute value of the precharge voltage V C1i at the terminals of the first switched capacitor C1 can advantageously be less than 10 kV, here equal to 2 kV, for example. However, it will be understood that it is also possible to precharge the first switched capacitor C1 with the opposite polarity, i.e., by charging the distal armature C1d negatively with respect to the proximal armature C1p.

[0117] 3, the second switched capacitor C2 will always be precharged with the same voltage polarity as the first switched capacitor C1. This means that if, for the first switched capacitor C1, the distal armature C1d is positively charged with respect to the proximal armature C1p, then for the second switched capacitor C2, the distal armature C2d is negatively charged with respect to the proximal armature C2p, so that the voltage Vc2 at the terminals of the second switched capacitor C2, defined by Vc2 = Vc2p - Vc2d (Vc2d is the potential of the distal armature C2d and Vc2p is the potential of the proximal armature C2p), will be positive.

[0118] It is assumed that at the moment t1, an electrical fault, for example a fault of the "ground fault" type, occurs in the first segment 11.1 of the electrical conductor 11. In this first scenario described herein, the location and type of the electrical fault generates a fault current flowing through the cut-off device 10 in the negative direction, i.e., from the second point 22 to the first point 20. It is immediately observed that the absolute value of the intensity through the device increases with the appearance of this electrical fault, and therefore the absolute value of the intensity I24 of the current in the main branch 24 (FIG. 4A) increases, and that this absolute value follows an increasing curve that depends on the electrical characteristics of the network, the electrical characteristics of the electrical conductor 11, and the characteristics of the electrical fault itself, in particular its location and fault tolerance in the first segment 11.1 of the electrical conductor 11.

[0119] At instant t2, a command to open the main cutoff device 26 is sent. This instant t2 is separated from the instant t1 of the fault occurrence by a fault detection delay, preferably comprised between 100 μs and 5 ms, e.g., approximately 1 ms. Preferably, if the first plasma tube switch 34.1 also includes the activation electrode 44.1, this instant t2 is selected to supply the activation electrode. This allows a plasma to be established between the activation electrode 44.1 and the cathode 34.1, thereby enabling the first plasma tube switch 34.1 to conduct current, even before receiving a command to electrically close the first plasma tube switch 34.1. Following receipt of the opening command, the main opening device begins its opening movement. In a known manner, this opening is achieved by separating the two electrodes of the main cutoff device 26. This opening is achieved gradually, with the electrodes gradually separating from each other. The instant at which the electrodes are first separated from the main cutoff device 26 is designated t2'. Typically, this moment t2' is separated from the moment t2 of sending the opening command by a time of approximately 0.3 to 30 ms. In terms of voltage and intensity at the terminals of the main cutoff device 26, an electric arc forms between the electrodes of the main cutoff device 26 at the moment of their separation t2'. This electric arc generates a large amount of energy, rapidly increases the temperature, and causes ionization of the dielectric medium formed between the two electrodes of the main cutoff device chamber 26. Therefore, electrical cutoff is not performed, regardless of the mechanical separation of the electrodes. As a result, the voltage V26 at the terminals of the main cutoff device 26 remains zero (ignoring the arc voltage), and the intensity I24 of the current in the main branch continues to increase in absolute value according to the same characteristic curve (see Figures 4A and 4F).

[0120] At moment t3, a procedure for assisting in the current cutoff begins with the main cutoff device 26, which is at least partially open at that time. Preferably, moment t3 corresponds to the partially open state of the main cutoff device 26 and thus to the minimum separation distance between the electrodes of the main cutoff device 26, which is predetermined to allow the main cutoff device 26 to withstand the protective voltage generated by the switching surge protective devices 80.1, 80.2 present in the switching branch 32 if the electric arc is extinguished between the electrodes. The time interval between moment t2' and moment t3 can therefore be referred to as the partial mechanical opening time interval, and depends, inter alia, on the separation ratio of the electrodes of the main cutoff device 26 and the level of the protective voltage of the switching surge protective devices 80.1, 80.2. During the partial mechanical opening time interval, no electrical cutoff is performed. Therefore, the partial mechanical opening time interval depends on the protection voltage of the switching surge protectors 80.1, 80.2. However, it has been found that the present invention makes it possible to implement switching surge protectors 80.1, 80.2 with protection voltages that are very low compared to the nominal operating voltage of the cutoff modules. Thus, for protection voltages of the switching surge protectors 80.1, 80.2 that are less than 10 kV, it is possible to reach a duration of the partial mechanical opening time interval that may be less than 50 microseconds, or even less than 20 microseconds. This is highly advantageous, since it reduces the total time that an arc is likely to remain in the main cutoff device 26. In fact, the sooner procedures can be initiated to assist in cutting off the current in the main cutoff device 26, the sooner the moment "tc" of extinction of the electric arc between the electrodes of the main cutoff device 26, as described below, can be reached. Therefore, with each opening, little electric arc energy is generated between the electrodes of the main cutoff device 26, and therefore little electrode erosion occurs.

[0121] In this first scenario, the cutoff assistance procedure is triggered by electrically closing the first plasma tube switch 34.1. In practice, the principle is to control the closure of the plasma tube switch, which allows the fault current to flow through the switching branch 32. In FIG. 4G, it can be seen that the control system 46.1 sends an electrical closing pulse in the form of a voltage pulse on the monitoring grid 40.1 of the first plasma tube switch 34.1 at the instant t3. It will be recalled that in this scenario, the first switching capacitor C1 is precharged so that its distal armature C1d is positively charged relative to its proximal armature C1p, and thus positively charged relative to the cathode 38.1 of the first plasma tube switch 34.1. Thus, the electrical closing pulse can be established by direct conduction between the distal armature C1d and the monitoring grid 40.1 of the first plasma tube switch 34.1 (as in the pilots of FIGS. 2A-2E) or by closing the switch 58a connecting it to the positive terminal of the DC-DC power converter (as in the pilots of FIGS. 2F-2G). By reading the following description of the second scenario, it will be understood what to do if the switched capacitor desired to be activated was polarized in the opposite direction at the precharge moment. It should be noted that application of the electrical closing pulse then cancels the current I24 in the main branch (FIG. 4A) and switches it completely through the first plasma tube switch 34.1 (FIG. 4B), which is now conductive to the current, to the switching branch 32. It can be seen that the switching time of the current from the main branch to the switching branch 32 is at most equal to one-fourth of the period of oscillation of the current in the loop formed by the main branch 24 and the switching branch 32, and that this oscillation can be assimilated to the discharge of a capacitor in an LC or RLC circuit.

[0122] In fact, the closure of the first plasma tube switch 34.1 allows the electrical closure of the loop formed by the main branch 24 and the switched branch 32, forming an oscillating LC circuit. It is recalled that at the moment of closure, two switched capacitors C1 and C2 are precharged. They are arranged in series in the switched branch and have the following equivalent capacitance Ceq:

[0123]

number

[0124] In this first scenario, the direction of the fault current in the main circuit and the directions of polarization of the two switched capacitors are such that the current oscillations generated in the LC loop formed by the main branch 24 and the switched branch 32 cause a zero crossing of the current in the main branch 24 during the first quarter of the period of the oscillations generated by the LC loop. Thus, in the illustrated example, from the moment "tc" of the first zero crossing of the current in the main branch 24, it is considered that the electric arc between the electrodes of the main cut-off device 26 is extinguished. Thus, at the moment "tc", the main cut-off device 26 reaches its electrically open state.

[0125] The duration of the time interval between the instants "t3" and "tc" is typically on the order of tens to hundreds of microseconds, for example 50-500 microseconds.

[0126] The duration of the electric arc through the electrical cut-off device 26, which lasts from the moment t2' when the electrodes first separate from the main cut-off device 26 to a maximum value at the moment "tc", is therefore particularly short. This makes it possible to reduce the erosion of the electrodes of the main electrical cut-off device 26. It also makes it possible to reduce the heat generated by the arc. This is therefore favorable for the reliability of the main electrical cut-off device 26 and makes it possible to reduce its cost.

[0127] The rate of change of intensity (di / dt) during the zero crossing of the current in the main branch 24 made possible by the switching branch with the plasma tube switch 34.1 will be best utilized by a main cutoff device 26 capable of interrupting electric arcs with high rates of change of intensity (di / dt), typically with intensity gradients of 100 A / microsecond or more. Therefore, a "vacuum switch" type main cutoff device 26 is particularly suitable.

[0128] It is noted that in this cutoff scenario, it is the first plasma tube switch 34.1 that is controlled towards the closed state, as this is the switch of the two plasma tube switches that allows current flow along a direction corresponding to the direction of the fault current that would occur through the cutoff device 10 due to an electrical fault.

[0129] In a known manner, it is observed that the first plasma switch 34.1 remains in its closed state allowing the passage of current (FIG. 4B), even after the electrical closing pulse (FIG. 4G) in its control grid 40.1 has disappeared.

[0130] The sum of the voltages appearing at the terminals of the first switched capacitor C1 and the second switched capacitor C2 is applied to the terminals of the main cutoff device 26 after the moment "tc" of the electric arc cutoff. From this point on, the rate of change (dv / dt) of the voltage V26 at the terminals of the main cutoff device 26 is limited by the ratio of the current intensity in the main circuit 16 to the total capacity of the switched branch, which can be expressed as Ceq = C1 × C2 / (C1 + C2). Furthermore, the voltage peak is limited by the sum of the protective voltages of the two switched surge protection devices 80.1, 80.2. These two electrical limits, related respectively to the rate of change and the voltage peak of the voltage V26, define the scaling of the components so that the cutoff device 26 maintains the absence of current and prevents the re-ignition of the electric arc between the electrodes of the main cutoff device 26, thereby allowing deionization of the medium between the electrodes of the main cutoff device 26 and thus the continuation of the relative remote movement between the two electrodes.

[0131] 4E, it can be seen that the voltage V C1 at the terminals of the first switched capacitor C1 passes from an initial positive value to a very rapidly reached negative value at instant t4, thereby causing current to flow through the switching branch 32, reversing the polarization of the first switched capacitor C1. Instant t4 corresponds to the terminals of the first switched capacitor C1 reaching a voltage equal to a protection voltage determined by the first switched surge protector 80.1, which is connected by two terminals on either side of the first switched capacitor C1. By becoming conductive, the first switched surge protector 80.1 limits the voltage at the terminals of the first switched capacitor C1 to a predetermined value equal to the protection voltage Vp80.1 of the first switched surge protector 80.1. The protection voltage Vp80.1 preferably has an absolute value of less than 10 kV, in this example approximately 3 kV, in order to limit the cost and volume of the first switched capacitor C1. The same switching voltage and the introduction of the same protection voltage can be observed at the terminals of the second switched capacitor.

[0132] At the next moment t5, the main electrical cutoff device 26 is deemed to be able to withstand the protective voltage established by the general-purpose surge protector 30. This suggests, for example, that the electrodes of the main electrical cutoff device 26 have reached a sufficient distance and that the dielectric medium between the electrodes of the main electrical cutoff device 26 has been deionized. The latter has therefore regained its electrical insulating power in its open state. Thus, it is possible to interrupt the flow of current in the switching branch 32 by electrically opening the first plasma tube switch 34.1. This is achieved by the control system 46.1 sending an electrical opening pulse to the control grid 40.1 of the first plasma tube switch 34.1 at moment t5 (FIG. 4G). Note that at this moment t5, when the electrical opening of the first plasma tube switch 34.1 is controlled, the polarity of the first switched capacitor C1 is such that the distal armature C1d is at a negative potential relative to the proximal armature C1p, and therefore also relative to the cathode 38.1 (FIG. 4E). Therefore, the electrical opening pulse applied to the control grid 40.1 can be obtained simply by bringing the distal armature C1d of the first switched capacitor C1 into electrical communication with the control grid 40.1 of the first plasma tube switch 40.1 (in the pilot case of FIGS. 2A-2E) or by closing the stop switch 58b, which connects it to the negative terminal of the DC-DC power converter (in the pilot case of FIGS. 2F-2G). In this example, the electrical opening pulse is applied for an electrical opening pulse time until moment t6 to ensure electrical cutoff in the first plasma tube switch 34.1. This electrical opening pulse time is, for example, equal to at least 1 microsecond. It should be noted that the electrical opening pulse can be maintained until an electrical closing pulse is required. Note that the duration that current actually flows through control grid 40.1 after such an electrical opening pulse will generally be comprised between 1 microsecond and 100 microseconds, and that the intensity of this current actually flowing through control grid 40.1 is of the same order of magnitude as the current that is cut off between anode 36.1 and cathode 38.1 through first plasma tube switch 34.1.

[0133] The time required for electrically opening the plasma tube switch is typically on the order of hundreds of nanoseconds to tens of microseconds. Note that interrupting the current in the plasma tube switch does not cause re-arcing in the main cutoff device 26 because the main cutoff device 26 has already been electrically opened and the dielectric medium between the contacts is deionized. In addition, the current flowing through the plasma tube switch is switched to the absorbing branch 28, which is scaled to withstand a recovery voltage higher than the protection voltage of the general-purpose surge protector 30 inserted in the absorbing branch 28, and therefore absorbs all of the dielectric energy in the power line without creating an arc ignition in the plasma tube switch.

[0134] When the plasma tube switch is controlled in an electrically closed state to allow current flow between its anode and its cathode, it operates in a mode in which the ratio of current density to cathode electrode area is much smaller than in the arcing mode. For example, this ratio is 100 A / cm. 2 In a "perpendicular magnetic field" type plasma tube switch, in which the magnetic field is applied parallel to the conductive surface of one cathode electrode of the plasma tube switch, the magnetic field prevents this arcing as long as it is within its nominal operating range.

[0135] In particular, it should be remembered that plasma tube switches have current interrupting capabilities that not all electrical switches have.

[0136] From the moment the first plasma tube switch 34.1 reaches its open state, no more current flows in the switching branch 32 (FIG. 4B). As a result, a high voltage appears at the terminals of the universal surge protector 30, which are electrically parallel to the switching branch 32 and the main branch 24, through which no more current can flow. This voltage is imposed by the fault current. However, the universal surge protector 30 begins to operate by limiting the voltage at the terminals of the cut-off module 18 to the value of its protection voltage Vp30 (FIG. 4F). From this, a drop in the absolute value of the current intensity is observed in the conductor 11, corresponding to the dissipation of the inductive and capacitive energy stored in the conductor, which is the energy dissipated in the universal surge protector 30. It can be seen that no current flows in either the main branch 24 or the switching branch 32 or the absorbing branch 28, thus isolating the first segment 11.1 and the second segment 11.2 of the conductor 11 between them (by ignoring possible leakage currents (typically less than 1 A) through the general-purpose surge protection device 30), and the open configuration of the cut-off device 10 is then quickly reached. The voltage of the network, which in this example is of the order of 80 kV, is then established on both sides of the cut-off device.

[0137] Note that in this first cutoff scenario, second plasma tube switch 34.2 is not involved and remains in its open configuration throughout the entire scenario. Naturally, control system 46.2 for second plasma tube switch 34.2 remains inactive, except for second switched capacitor C2 inserted in second section 32.2 of the switched branch, whose capacitance intervenes in the law of current evolution in switched branch 32. This is due to the fact that a fault hypothesis was assumed that would cause a fault current to flow in the opposite direction to that which second plasma tube switch 34.2 would flow in the closed state.

[0138] It is noted that the second plasma tube switch 34.2 of Figure 3 does not intervene in this first scenario, so it will be appreciated that the first embodiment of the invention shown in Figure 1, with a single plasma tube switch 34.1 that can only conduct current in a negative direction (according to any convention chosen above), would operate exactly as described above. However, in this case, it is important to ensure that the first switched capacitor C1 is fully precharged with the polarity described above, i.e., with the distal armature C1d positively charged relative to the proximal armature C1p.

[0139] In the second current cut-off scenario shown in Figures 5A to 5F, it is assumed that the cut-off module 18 has symmetric scaling with respect to the scaling of the two plasma tube switches 34.1, 34.2 on the one hand and the first switched capacitor C1 and the second switched capacitor C2 on the other hand.

[0140] In this second scenario, we describe the case where both the first switched capacitor C1 and the second switched capacitor C2 are pre-charged with voltages CV1i, VC2i, which are positive voltages in the following sense: For the first switched capacitor C1, the distal armature C1d is positively charged with respect to the proximal armature C1p. For the second switched capacitor C2, the distal armature C2d is negatively charged with respect to the proximal armature C2p.

[0141] As will be appreciated, it could equally well be provided that both the first switched capacitor C1 and the second switched capacitor C2 are precharged with voltages VC1i, VC2i which are negative voltages in the following sense. For the first switched capacitor C1, the distal armature C1d is negatively charged with respect to the proximal armature C1p. For the second switched capacitor C2, the distal armature C2d is positively charged with respect to the proximal armature C2p.

[0142] In all cases, the absolute values ​​of the pre-charge voltage VC1i at the terminals of the first switched capacitor C1 and the pre-charge voltage VC2i at the terminals of the first switched capacitor C2 can advantageously be less than 10 kV, here for example equal to 2 kV.

[0143] At the moment t1, an electrical fault is assumed to occur. In this second scenario, unlike the first scenario, this electrical fault occurs in the second segment 11.2 of the conductor 11, but remains, for example, of the "ground fault" type. In this second scenario described here, the location and type of the electrical fault generates a fault current flowing through the cut-off device 10 in the forward direction, i.e., from the first point 20 to the second point 22. As already observed in the first scenario, the absolute value of the intensity through the device increases with the appearance of this electrical fault, so that the absolute value of the intensity I24 of the current in the main branch 24 (FIG. 5A) increases, this absolute value following an increasing curve that depends on the electrical characteristics of the network, the electrical characteristics of the conductor 11, and the characteristics of the electrical fault itself, in particular its location and fault tolerance in the second segment 11.2 of the conductor 11.

[0144] For the first scenario, a command to open the main cutoff device 26 is sent at instant t2 according to the same procedure as described above for the first scenario. Following receipt of the opening command, the main opening device begins its opening movement. The moment of initial separation of the electrodes of the main cutoff device 26 is designated t2'. Again, the gradual separation of the two electrodes of the main cutoff device 26 allows an electric arc to occur, so that electrical cutoff is not achieved despite the mechanical separation of the electrodes. As a result, the voltage V26 at the terminals of the main cutoff device 26 remains zero (by ignoring the arc voltage (see FIG. 5F)), and the intensity I24 of the current in the main branch continues to increase in absolute value (and, in any convention described above, in algebraic value (FIG. 5A)).

[0145] Regarding the first scenario, the procedure for assisting the cut-off of the current in the main cut-off device 26 is triggered at the moment t3 when the main cut-off device 26 is in an at least partially open state corresponding to a separation of its electrodes, for which it is predetermined that, if the electric arc is extinguished between the electrodes, the main cut-off device 26 is able to withstand the protective voltage generated by the switching surge protection devices 80.1, 80.2 present in the switching branch 32. During the partial mechanical opening time interval, no electrical cut-off is performed (FIG. 5A).

[0146] It has already been shown that in this second scenario, the cutoff assistance procedure implements the electrical closure of second plasma tube switch 34.2, which is the only one that can allow the fault current to flow through switching branch 32. For this reason, it is therefore necessary for control system 46.2 to send an electrical closure pulse to monitoring grid 40.2 of second plasma tube switch 34.2 at instant t3, corresponding to a positive potential with respect to cathode 38.2 of second plasma tube switch 34.2. In addition, to enable switching of the fault current from the main branch to the switching branch, and thus the flow of the fault current in the positive direction here, the voltage at the terminals of first switching capacitor C1 and second switching capacitor C2, respectively, is negative.

[0147] However, this second scenario is defined in the context of the first switched capacitor C1 already being charged, thereby causing its distal armature C1d to be positively charged relative to its proximal armature C1p and therefore positively charged relative to the cathode 38.1 of the first plasma tube switch 34.1, and the second switched capacitor C2 already being charged, thereby causing its distal armature C2d to be negatively charged relative to its proximal armature C2p and therefore negatively charged relative to the cathode 38.2 of the second plasma tube switch 34.2. In practice, this choice is quite reasonable, since it is assumed that the cutoff device 10 of FIG. 3 is intended to interrupt current regardless of the direction of the fault current through the cutoff device 10. However, the selection of the pre-charge polarity of the first switched capacitor C1 and the second switched capacitor C2 is made before the likely direction of the fault current is known.

[0148] This configuration therefore means that the fault current flow direction would not be able to switch into the switching branch with this polarization direction of the switching capacitors C1 and C2. Additionally, with respect to the embodiment of the control system shown in FIGS. 2A-2F, an electrical closing pulse cannot be established by placing the distal armature C2d in direct electrical communication with the monitoring grid 40.2 of the second plasma tube switch 34.2. This second scenario also provides an intermediate step of reversing the polarity of the first and second switching capacitors C1 and C2 at the instant "tinv" after the instant t2 of sending the command to open the electrical cutoff device 26, but before the instant t3 at which an electrical closing pulse must be sent to the control grid 40.2 of the second plasma tube switch 34.2. This intermediate step of reversing the polarity of the switching capacitors is implemented in a particularly simple manner by triggering the closing of the first plasma tube switch 34.1 at the instant "tinv." As can be seen in Figures 5A and 5B, this closure of the first plasma tube switch 34.1 causes an overcurrent in the main branch 24 by creating a negative discharge current in the switching branch 32 (this negative current is imposed by the polarity of the charges on the two switching capacitors C1 and C2) that is added in the positive direction in the main branch 24 above the fault current. As long as the two switching capacitors C1 and C2 discharge, however, this discharge current is very short. In fact, this discharge occurs in the loop formed by the switching branch 32 and the main branch 24 in series with each other, an LC-type loop in which the discharge current is scaled to be oscillatory. Because only the first plasma tube switch 34.1 is conductive at this stage, allowing current to flow through the switching branch only in one direction, the discharge of the switching capacitors C1 and C2 in the switching branch 32 can only occur for half an oscillation period, not a full oscillation period. Therefore, after half an oscillation period, it can be seen that the voltages at the terminals of the two switching capacitors C1 and C2 are reversed.As a result, the situation then arises where, with respect to the second switched capacitor C2, the distal armature C2d is positively charged relative to the proximal armature C2p, and thus relative to the cathode 38.2 of the second plasma tube switch 34.2. This configuration, brought about by the polarity reversal of the two switched capacitors C1 and C2, makes it possible, on the one hand, to create an electrical closing pulse of the second plasma tube switch 34.2 in the form of a voltage pulse at the instant t3 by placing the distal armature C2d in direct electrical communication with the monitoring grid 40.2 of the second plasma tube switch 34.2 (which includes the embodiment of control system 46.2 shown in Figures 2A-2E). But on the other hand, another function of this reversal of the polarity of the two switching capacitors C1 and C2 is to allow a switching current to flow in the switching branch 32 in the positive direction through the second plasma tube switch 34.2, which at the same time leads to cancelling the current I24 in the main branch 24 from the moment "tc" corresponding to the cut-off of the electric arc through the main electric cut-off device 26, at the moment when the intensity of the current passing through crosses zero (see Figure 5A).

[0149] 5E, it can be seen that the voltage V C1 at the terminals of the first switched capacitor C1 and the voltage V C2 at the terminals of the second switched capacitor C2 move from the negative value obtained by the first reversal to a positive value, thereby causing a new reversal of the polarization of the first switched capacitor C1 and the second switched capacitor C2 due to the current flowing through the switching branch 32. The instant t4 corresponds to the achievement at the terminals of the first switched capacitor C1 of a voltage equal to the protection voltage Vp80.1 determined by the first switched surge protector 80.1 connected by two terminals on each side of the first switched capacitor C1, and to the achievement at the terminals of the second switched capacitor C2 of a voltage Vp80.2 equal to the protection voltage determined by the second switched surge protector 80.2 connected by two terminals on each side of the second switched capacitor C2. By becoming conductive, the first switched surge protector 80.1 limits the voltage at the terminals of the first switched capacitor C1 to a predetermined value equal to its protection voltage Vp80.1. Similarly, by becoming conductive, the second switched surge protector 80.2 limits the voltage at the terminals of the second switched capacitor C2 to a predetermined value equal to its protection voltage Vp80.2 (see FIG. 5E). Like the protection voltage Vp80.1, the protection voltage Vp80.2 is preferably less than 10 kV in absolute value, in this example approximately 3 kV, to limit the cost and volume of the second switched capacitor C2. The sum of the protection voltages Vp80.1, Vp80.2 of the first switched capacitor C1 and the second switched capacitor C2, respectively, is preferably less than 20 kV in absolute value, in this example approximately 6 kV.

[0150] At the next instant t5, the dielectric medium contained between the electrodes of the main cut-off device 26 is deemed to be deionized, the gap between the electrodes is wide enough to maintain the protective voltage established by the universal surge protector 30 in the absorbing branch, and it is possible to interrupt the flow of current in the switching branch 32 by electrically opening the second plasma tube switch 34.2 (the first plasma tube switch 34.1 has already been opened again after the step of reversing the polarity of the switched capacitor). This is effected by the control system 46.2 sending an electrical opening pulse to the control grid 40.2 of the second plasma tube switch 34.2 at the instant t5. It should be noted that at this moment t5 when the electrical opening of the second plasma tube switch 34.2 is controlled, the polarity of the second switched capacitor C2 is such that the distal armature C2d is at a negative potential relative to the proximal armature C2p and therefore also relative to the cathode 38.2, so that the electrical opening pulse applied to the control grid 40.2 can be obtained simply by bringing the distal armature C2d of the second switched capacitor C2 into electrical conductivity with the control grid 40.2 of the second plasma tube switch 40.2 (in the case of the pilots in Figures 2A-2E) or by closing the stop switch 58b which connects it to the negative terminal of the DC-DC power converter (in the case of the pilots in Figures 2F-2G).

[0151] From the moment t5 when the second plasma tube switch 34.2 reaches its open state, no more current flows through the switching branch 32 (FIGS. 5B, 5C). As a result, as in the first scenario, a high voltage appears at the terminals of the universal surge protector 30, which are electrically parallel to the switching branch 32 and the main branch 24, through which no more current can flow (FIG. 5F). This voltage is imposed by the network voltage and the dielectric energy stored in the network. However, the universal surge protector 30 begins to operate by limiting the voltage at the terminals of the cutoff module 18 to the value of its protection voltage Vp30. From there, a drop in the absolute value of the current intensity is observed in the conductor 11, corresponding to the dissipation of the dielectric and capacitive energy stored in the device 10 and the energy dissipated in the universal surge protector 30 (FIG. 5D). It can be seen that no current flows in either the main branch 24 or the switching branch 32 or the absorbing branch 28, thus isolating the first segment 11.1 and the second segment 11.2 of the conductor 11 between them (by ignoring the leakage current of the general-purpose surge protection device 30, which is generally less than 1 A), and the open configuration of the cut-off device 10 is then quickly reached. The voltage of the network, which in this example is of the order of 80 kV, is then established on both sides of the cut-off device.

[0152] In the two scenarios detailed above, the assumption was made that the first switched capacitor C1 had the distal armature C1d positively charged relative to the proximal armature C1p, and the second switched capacitor C2 had the distal armature C2d symmetrically charged negatively relative to the proximal armature C2p. We also referred to the reverse assumption that the first switched capacitor C1 had the distal armature C1d negatively charged relative to the proximal armature C1p, and the second switched capacitor C2 had the distal armature C2d symmetrically charged positively relative to the proximal armature C2p. In this reverse assumption, the appearance of a positive fault current, as per the above convention, would involve the implementation of a method similar to that described for the first scenario, but implementing only a single plasma tube switch, but in this case the second plasma tube switch 34.2, without polarity reversal of the switched capacitors C1 and C2. In this reverse hypothesis, the appearance of a negative-going fault current in the above practice would involve implementing a method similar to that described for the second scenario by first implementing the second plasma tube switch 34.2 to create a polarity reversal in the switched capacitors C1 and C2, and then implementing the first plasma tube switch 34.1 to allow the switched current to flow in the negative direction in the switched branch, thereby assisting in the electrical cutoff in the main cutoff device 26.

[0153] In the examples shown in FIGS. 1 and 3, cutoff module 18 includes a single switching branch 32 interposed with a single plasma tube switch 34.1 for the embodiment of FIG. 1, and two plasma tube switches 34.1, 34.2 installed in parallel and opposite directions for the embodiment of FIG. 3. It was found that in both cases, one of the plasma tube switches is made conductive in the cutoff-assist configuration of main cutoff device 26, allowing fault current to flow through switching branch 32 and then returned to an open state. Thus, in both cases, the plasma tube switch must carry a high current and then interrupt the remaining fault current, which may also be high. However, it should be noted that the minimum time for which the plasma tube switch must be made conductive, which may also be referred to as the minimum conduction time of the plasma tube switch, must cover the time for switching the fault current from main branch 26, including main cutoff device 26, to switching branch 32, and also the deionization time of the dielectric medium contained between the electrodes of main cutoff device 26. However, it has been found that the time for switching the fault current is less than one-fourth the period of the oscillating current generated by the switching branch 32. This fault current switching time is therefore less than the value given by the following equation:

[0154]

number

[0155] If a single plasma tube switch cannot withstand the maximum fault current strength to which it is desired to scale cutoff device 10, it is straightforward to modify cutoff module 18 by adding at least one auxiliary switching branch 32' including at least one plasma tube switch in parallel with switching branch 32, and thus in parallel with main branch 24 and absorption branch 28, with auxiliary switching branch 32' preferably having the same configuration as switching branch 32 described with reference to Figures 1 and / or 3, respectively.

[0156] 6 also illustrates a cutoff device 10 having a cutoff module 18 that includes all the same elements as those described in connection with the cutoff module 18 of FIG. 3, but additionally includes a main branch 24, an absorption branch 28, and an auxiliary switching branch 32' electrically parallel to the switching branch 32 between the first point 20 and the second point 22. At least a first auxiliary plasma tube switch 34.1' is interposed in the auxiliary switching branch 32' and includes an anode 36.1', a cathode 38.1', and a control grid 40.1'. The first auxiliary plasma tube switch 34.1' is interposed in the auxiliary switching branch 32.1' to separate the auxiliary switching branch 32' into a first section 32.1' connected to the cathode 38.1' of the first auxiliary plasma tube switch 34.1' and a second section 32.2' connected to the anode 36.1' of the first auxiliary plasma tube switch 34.1'.

[0157] First auxiliary plasma tube switch 34.1' is installed in auxiliary switching branch 32' in the same direction as first plasma tube switch 34.1 in switching branch 32. This results, for example, in the fact that anode 36.1' of first auxiliary plasma tube switch 34.1' is coupled to the same one of first point 20 and second point 22 as anode 36.1 of first plasma tube switch 34.1 (here indirectly, each via a respective capacitor C1; C1').

[0158] Generally, this first auxiliary plasma tube switch 34.1' can be controlled in the same and synchronous manner as the first plasma tube switch 34.1, so that in the cutoff assistance configuration, the current through device 10 is distributed between two plasma tube switches at the level of the considered module 18, and each plasma tube switch must therefore carry or block a current that is less than the total current through cutoff device 10. If auxiliary switching branch 32' has the same electrical characteristics as switching branch 32, the current in each switching branch 32, 32' will be divided by two relative to the current that would flow in the switching branch if there was only one switching branch.

[0159] Of course, it will be advantageous to provide that cutoff module 18 includes a control system 46.1' for first auxiliary plasma tube switch 34.1' similar to that described for first plasma tube switch 34.1. This control system 46.1' will therefore advantageously include a first auxiliary switched capacitor C1' in series with first auxiliary plasma tube switch 34.1', located in auxiliary switching branch 32' between first point 20 and second point 22, in first section 32.1' of auxiliary switching branch 32', i.e., in the section coupled to cathode 38.1' of first auxiliary plasma tube switch 34.1'. The first auxiliary switched capacitor C1' includes a proximal armature C1p' coupled to the cathode 38.1' of the first auxiliary plasma tube switch 34.1' and a distal armature C1d' on the opposite side of the cathode 38.1' of the first auxiliary plasma tube switch 34.1' from the proximal armature C1p'.

[0160] Similarly, the cutoff device 10 includes a pre-charge circuit 48.1' for the first auxiliary switched capacitor C1'. This pre-charge circuit may be a separate pre-charge circuit from that of the first switched capacitor C1 and may therefore take a similar form to that described above. However, in the example of Figure 6, the first switched capacitor pre-charge circuit and the first auxiliary switched capacitor pre-charge circuit include a common voltage source 50.1 that supplies the first switched capacitor C1 and the first auxiliary switched capacitor C1' in parallel. Thus, the common DC voltage source 50.1 includes: On the other hand, in this embodiment, Here, through resistor 53.1, the distal armature C1d of the first switched capacitor C1 is connected to ●Here, through resistor 53.1', the distal armature C1d' of the first auxiliary switched capacitor C1' Connected positive terminal 52.1. On the other hand, in this embodiment, ●Here again through resistor 55.1, the proximal armature C1p of the first switched capacitor C1 is connected to ●Here again through resistor 55.1', ​​the first auxiliary switched capacitor C1' is connected to the proximal armature C1p' Connected negative terminal 54.1.

[0161] It has been found that in bidirectional devices, it is possible to have opposite polarity for DC voltage source 50.1, since it is known to reverse the precharge polarity of the switched capacitors. Preferably, resistors 53.1, 55.1, 53.1', 55.1' of precharge circuit 48.1 have the same resistance. These resistors make it possible to limit the current in the precharge circuit and balance the current in the various parallel branches of the precharge circuit.

[0162] Of course, insofar as the cutoff module 18 shown in Figure 6 includes a switching branch 32 having two plasma tube switches electrically parallel and opposite in direction, it is preferably provided that this cutoff module 18 also includes, in an auxiliary switching branch 32', two auxiliary plasma tube switches 34.1', 34.2' interleaved in parallel and opposite in direction in the auxiliary switching branch 32'. In other words, as shown in Figure 6, the auxiliary switching branch 32' preferably has all the same elements as the switching branch 32.

[0163] 6 includes a single auxiliary switching branch 32'. However, to further increase the ability of cutoff module 18 to support higher intensity currents, it will be understood that the cutoff module may be provided with one or more other auxiliary switching branches of the same type as auxiliary switching branch 32' just described, but that the other auxiliary switching branches are disposed electrically in parallel with main branch 24, absorbing branch 28, switching branch 32, and auxiliary switching branch 32', respectively, between first point 20 and second point 22.

[0164] In the example illustrated and described above, the cut-off device 10 includes a single cut-off module 18. It is therefore understood that the cut-off module 18, if single, must be designed to withstand the nominal operating voltage of the network. This implies, in particular, constraints on the voltage resistance of the plasma tube switches 34.1, 34.2. Furthermore, it should be noted that the voltage resistance of the plasma tube switches 34.1, 34.2 can easily be as large as the main cut-off device 26 of the module 18. This is all the more true if the main cut-off device 26 is of the "vacuum bulb" type, since in this case the plasma tube switch and the "vacuum bulb" are based on the same vacuum tube technology.

[0165] However, to obtain a cutoff device 10 with even higher opening and withstand voltage capabilities, or to use components (particularly plasma tube switches) with reasonable cost and space requirements, one may choose to fabricate the cutoff device 10 (such as that shown in FIG. 7 ) with several cutoff modules 18 a, 18 b, 18 c, ... interposed electrically in series in the main circuit 16 of the cutoff device 10 between the primary point 12 and the secondary point 14 of the cutoff device 10. Thus, each cutoff module 18 a, 18 b, 18 c, ... extends between its own first point 20 a, 20 b, 20 c, ... and its own second point 22 a, 22 b, 22 c, ... in the main circuit 16. Each cutoff module 18 a, 18 b, 18 c, etc. can have any of the configurations described above, including the configuration envisioned above including at least one auxiliary switching branch 32′ in parallel with the switching branch 32. The cut-off modules 18a, 18b, 18c, etc. can be identical to one another.

[0166] It has been noted that in all the above-mentioned examples, the supply and control of the plasma tube switches located in the switching branches 32, 32' are carried out using control systems 46.1, 46.1', 46.2, 46.2' that do not impose any electrical or electronic components on the main branch 24 of the cut-off module 18. Therefore, in the conductive configuration in which the current through the cut-off device 10 passes in this main branch 24, there are no components belonging to the control systems of the plasma tube switches that risk permanently dissipating electrical energy during normal operation of the network. Therefore, no cooling system is required to cool such components.

[0167] In all of the above examples, only the main cutoff device 26, the plasma tube switch, and the general-purpose surge protector 30 must be scaled to withstand the high DC nominal operating voltage of the module 18 under consideration, which may typically be greater than 75,000 V. In contrast, the first and second switched capacitors C1 and C2, and the first and second switched surge protectors 80.1 and 80.2, can be scaled for cutoff modules of cutoff device 10, including cutoff device 10 with a single cutoff module 18, having a nominal operating voltage greater than 75,000 V and scaled for such networks with withstand voltages that may be less than 10,000 V. Thus, these components scaled for voltages that may be as much as 10 times lower than the nominal operating voltage of the network can have reduced space requirements and costs.

[0168] For the cutoff module 18, the scaling of the minimum capacitance of the switched capacitors can be determined as a first approximation by the following equation:

[0169]

number

[0170] It has further been found that each cutoff module 18 is scaled so that the equivalent inductance value L_equ of the loop formed by the main branch 24 and the switching branch 32 of the cutoff module 18 is greater than a minimum value L_min that allows the electric arc to be extinguished in the main cutoff device 26 while switching the current to the switching branch 32. Therefore, this equivalent inductance value L_equ must be greater than a minimum value given by the following equation:

[0171]

number

[0172] The above formula therefore makes it possible to determine the minimum equivalent capacitance C_equ that can be obtained, from which the individual capacitance of each of the switched capacitors can be determined.

[0173] In general, for a two-way device 10 as shown in FIG. 3 (and thus with a single cut-off module 18 in this example), it would be possible to have, for example, the following values: I_to=10kA VC1=VC2=2kV(V_c_equ=4kV) L_equ=20 microhenries V_on_34=500V (di / dt)max=200A / μs The equivalent capacitance of all of the switched capacitors in device 10 is greater than 100 microfarads (so, for example, C1=C2=400 microfarads (C_equ=200 μF)).

[0174] Furthermore, it was noted above that the time during which the plasma tube switches 34.1,... are made conductive is very short, being less than 1 ms. However, this time is also approximately the time during which current is likely to pass through the switching surge protectors 80.1,..., which must then dissipate the corresponding electrical energy. Because the time is short, there is no need to overscale the volume and cost of such switching surge protectors.

[0175] 3 and 6, where the switching branches include two plasma tube switches arranged electrically in parallel and opposite directions, the two plasma tube switches can be designed as separate unidirectional plasma tube switch components. However, it is possible to envision designing these two unidirectional plasma tube switches in a paired configuration.

[0176] As mentioned above, it should be noted that pilots 56.1,... of control systems 46.1,... of plasma tube switches in the switching branches do not require any autonomous power supply, since their supply is ensured through the associated switching capacitors. It should also be noted that, whatever the embodiment of pilots 56.1,... as shown in Figures 2A-2H, the control system 46.1 of the plasma tube switches can be designed with a single pilotable switch that needs to be piloted to control the associated plasma tube switch, resulting in low complexity.

[0177] The device 10 according to the present invention may include or be associated with one or more electronic control units 100, which in particular control / pilot the control systems 46.1, ..., of the plasma tube switches in the switching branches, the pilots 56.1, ..., and the main electrical cut-off device 26. The electronic control unit generally comprises at least one processor and at least one electronic memory, and may comprise or be coupled to one or more electronic communication circuits for communicating with one or more computer networks or the like, and / or one or more interface electronic circuits, and / or one or more input / output electronic circuits. The electronic control unit may comprise or be associated with one or more displays. The electronic control unit may comprise or be associated with one or more sensors, for example, one or more intensity sensors and / or one or more voltage sensors, configured to measure values ​​of physical parameters in the cut-off device 10 or in the electrical installation in which the device 10 is intended to be integrated. The electronic control unit is programmed to implement all or part of the method for opening the device as described above. Advantageously, it is possible for the electronic control device 100 to provide for the communication of its control / pilot commands, in particular to the pilots 56.1, ... of the control systems 46.1, ..., by means of signals galvanically isolated against high voltage. These signals may be optical signals carried by optical fibers. They may also be electrical signals isolated by transformers. They may also be electromagnetic signals carried by wireless communication links.

[0178] The electrical cutoff device 10 as described above therefore forms a current circuit breaker particularly suitable for currents under high DC voltages, particularly those above 75 kV, which reduces overall space requirements and costs and allows for sufficient cutoff performance to be obtained using components that have minimal energy losses in normal operation.

Claims

1. A current cutoff device under high DC voltage, comprising: a main circuit (16) through which current flows under the high DC nominal operating voltage of the cut-off device (10) in a conducting configuration of the device; and at least one cutoff module (18, 18a, 18b, 18c) interposed in the main circuit (16) between a first point (20, 20a, 20b, 20c) and a second point (22, 22a, 22b, 22c) of the main circuit (16) relative to the cutoff module, the cutoff module comprising: a main branch (24) between the first point and the second point of the cutoff module, the main branch (24) having at least one main electrical cutoff device (26) of a mechanical type interposed therein between the first point (20) and the second point (22); an absorption branch (28) electrically in parallel with the main branch (24) between the first point and the second point of the cutoff module, with at least one universal surge protector (30) interposed in the absorption branch (28) between the first point (20) and the second point (22); a switching branch (32) electrically parallel to the main branch (24) and the absorption branch (28) between the first point and the second point of the cut-off module, wherein at least a first switching capacitor (C1) is disposed in the switching branch (32) between the first point and the second point of the cut-off module, and a switching switch (34.1) is capable of allowing current flow in the switching branch (32); a loop formed by the main branch (24) and the switching branch (32) of the cutoff module, the loop of the cutoff module having a switching inductance; The changeover switch includes at least a first plasma tube switch (34.1) including an anode (36.1), a cathode (38.1), and a control grid (40.1), the first plasma tube switch (34.1) being interposed in the changeover branch (32) between the first point and the second point of the cutoff module, thereby separating the changeover branch into a first section (32.1) coupled to the cathode (38.1) of the first plasma tube switch (34.1) and a second section (32.2) coupled to the anode (36.1) of the first plasma tube switch, and the first changeover capacitor (C1) being disposed in the first section (32.1) of the changeover branch coupled to the cathode (38.1) of the first plasma tube switch (34.1); the control system (46.1) of the first plasma tube switch is powered by the first switched capacitor (C1); the first switched capacitor includes a proximal armature (C1p) coupled to the cathode of the first plasma tube switch and a distal armature (C1d) on the opposite side of the cathode of the first plasma tube switch from the proximal armature (C1p); the device includes a circuit (48.1) for precharging the first switched capacitor (C1); the cut-off module (18, 18a, 18b, 18c) includes a first switched surge protector (80.1), the first switched surge protector having a protection voltage lower than the nominal operating voltage of the cut-off module, and electrically connected in parallel with the first switched capacitor (C1); the control system (46.1) of the first plasma tube switch (34.1) includes at least a first pilotable switch (58.1, 58a, 58b), which, in a closed state, supplies a voltage derived from an electrical voltage across the armature (C1p, C1d) of the first switched capacitor (C1) to the control grid (40.1) of the first plasma tube switch (34.1); Current cut-off device under high DC voltage.

2. 2. The device of claim 1, wherein during the opening of the cut-off device (10), the first pilotable switch (58.1, 58a, 58b) is piloted according to a first closing pulse to control the closing of the first plasma tube switch (34.1) after the main electrical cut-off device (26) has partially mechanically opened, and according to a second closing pulse to control the opening of the first plasma tube switch (34.1) after reversing the charge polarity of the first switched capacitor (C1), thereby defining the conduction time of the first plasma tube switch between its closing and opening.

3. 3. The device of claim 1, wherein the first pilotable switch (58.1), in a closed state, electrically couples the control grid (48.1) of the first plasma tube switch (34.1) to the distal armature (C1d) of the first switched capacitor.

4. 4. The device of claim 3, wherein the first pilotable switch (58.1, 58a, 58b) is a two-way switch capable of conducting and blocking current in both directions between the control grid (40.1) of the first plasma tube switch (34.1) and the distal armature (C1d) of the first switched capacitor (C1).

5. 5. The device according to claim 4, characterized in that the first pilotable switch is designed as two one-way electronic switches (58a, 58b) interposed in series and opposite directions between the control grid (40.1) of the first plasma tube switch (34) and the distal armature (C1d) of the first switched capacitor (C1), each one-way electronic switch (58a, 58b) comprising a freewheeling diode installed anti-parallel to the one-way electronic switch.

6. 6. The device according to claim 1, wherein the control system (46.1) of the first plasma tube switch (34.1) includes a supply branch (62) supplying the activation electrode (44.1) of the first plasma tube switch (34.1), the supply branch (62) connecting the activation electrode (44.1) of the first plasma tube switch to the distal armature (C1d) of the first switched capacitor (C1).

7. 7. The device of claim 6, wherein the supply branch (62) includes a supply switch (68) capable of conducting and blocking current in the supply branch (62) and a resistor (64) interposed in the supply branch.

8. 8. The device according to claim 7, characterized in that the supply switch (68) is piloted to close after receiving a command to interrupt the current by the cut-off device.

9. 3. The device of claim 1, wherein the control system (46.1) of the first plasma tube switch (34.1) includes a DC-DC power converter (78) having a source side coupled to the distal armature (C1d) of the first switched capacitor (C1) and a control side feeding the control grid (40.1) of the first plasma tube switch (34.1) via the first pilotable switch (58.1).

10. 10. The device of claim 9, wherein the control side of the power converter includes a positive terminal (78.3) and a negative terminal (78.4), and the first pilotable switch (58.1) includes a first pilotable start switch (58a) interposed between the positive terminal (78.3) and the control grid (40.1) of the first plasma tube switch (34.1), and a second pilotable stop switch (58b) interposed between the negative terminal (78.4) and the control grid (40.1) of the first plasma tube switch (34.1).

11. 11. The device of claim 10, wherein the control system (46.1) of the first plasma tube switch (34.1) includes a supply branch (62) supplying the activation electrode (44.1) of the first plasma tube switch (34.1), the supply branch connecting the activation electrode (44.1) of the first plasma tube switch to the positive terminal (78.3) of the control side of the DC-DC power converter (78).

12. 12. The device according to claim 1, wherein the voltage at the terminals of the first switched capacitor (C1) is limited by the first switched surge protection device (80.1) to a protection voltage of less than 10% of the nominal operating voltage of the cut-off module.

13. A device according to any one of the preceding claims, characterized in that the first switched capacitor (C1) has a capacitance greater than 100 microfarads.

14. 14. The device according to claim 1, wherein the pre-charge voltage of the first switched capacitor and the switched inductance of the cut-off module are scaled to limit the rate of change of the current through the main cut-off device (26) when the switching branch (32) becomes conductive to current by closing the plasma tube switch (34.1) to a value corresponding to the rate at which the main cut-off device (26) can interrupt the electric arc.

15. 15. The device according to any one of claims 2 to 14, characterized in that the conduction time of the first plasma tube switch during opening of the cut-off device (10) is less than 1 millisecond, preferably less than 300 microseconds, more preferably less than 100 microseconds.

16. the changeover switch includes a second plasma tube switch (34.2) including an anode (36.2), a cathode (38.2), and a control grid (40.2), the second plasma tube switch (34.2) being interposed in the changeover branch (32) between the first point and the second point of the cutoff module (18) in electrical parallel with and in the opposite direction to the first plasma tube switch (34.1), whereby the cathode (38.2) of the second plasma tube switch is coupled to the second section (32.2) of the changeover branch (32) and the anode (36.2) of the second plasma tube switch is coupled to the first section (32.1) of the changeover branch; a second switched capacitor (C2) disposed in the second section (32.2) of the switched branch (32) connected to the cathode (38.2) of the second plasma tube switch (34.2); the control system (46.2) of the second plasma tube switch (34.2) is powered by the second switched capacitor (C2); the second switched capacitor (C2) includes a proximal armature (C2p) coupled to the cathode (38.2) of the second plasma tube switch (34.2) and a distal armature (C2p) on the opposite side of the cathode of the second plasma tube switch from the proximal armature (C2p); the device (10) includes a pre-charging circuit (48.2) for the second switched capacitor; the cut-off module (18, 18a, 18b, 18c) includes a second switching surge protector (80.2), the second switching surge protector having a protection voltage such that the sum of the protection voltages of the first switching surge protector (80.1) and the second switching surge protector (80.2) is lower than the nominal operating voltage of the cut-off module, and the second switching surge protector is electrically connected in parallel with the second switching capacitor (C2); 16. The device according to claim 1, wherein the control system (46.2) of the second plasma tube switch (34.2) includes at least a second pilotable switch which, in a closed state, supplies the control grid (40.2) of the second plasma tube switch (34.2) with a voltage derived from the electrical voltage across the armature (C2p, C2d) of the second switched capacitor (C2).

17. 17. The device of claim 16, wherein the second pilotable switch, in a closed state, electrically couples the control grid of the second plasma tube switch to the distal armature of the second switched capacitor.

18. 17. The device of claim 16, wherein the control system (46.2) of the second plasma tube switch (34.2) includes a second DC-DC power converter having a source side coupled to the distal armature (C2d) of the second switched capacitor (C2) and a control side feeding the control grid (40.2) of the second plasma tube switch (34.2) via the second pilotable switch.

19. 19. The device according to any one of claims 16 to 18, characterized in that the control system of the second plasma tube switch includes a supply branch supplying the activation electrode of the second plasma tube switch.

20. 20. The device of claim 19 in combination with claim 18, wherein the supply branch connects the active electrode of the second plasma tube switch to the positive terminal of the control side of the second DC-DC power converter.

21. The at least one cutoff module (18, 18a, 18b, 18c) includes at least one auxiliary switching branch (32') electrically parallel to the switching branch (32), the absorption branch (28), and the main branch (24) between the first point and the second point of the cutoff module, together with at least a first auxiliary plasma tube switch (34.1') including an anode (36.1'), a cathode (38.1'), and a control grid (40.1'), and the first auxiliary plasma tube switch (34.1') controls the auxiliary switching branch (32') between the first point and the second point of the cutoff module.

21. The device according to claim 1, wherein the auxiliary switching branch (32') is interleaved with a first section (32.1') ​​connected to the cathode (38.1') of the first auxiliary plasma tube switch (34.1') and a second section (32.2') connected to the anode (36.1') of the first auxiliary plasma tube switch (34.1'), and wherein at least a first auxiliary switched capacitor (C1') is arranged in the first section (32.1') ​​of the auxiliary switching branch (32') connected to the cathode (38.1') of the first plasma tube switch (34.1').

22. the anode (36.1') of the first auxiliary plasma tube switch (34.1') is connected to the same point among the first point and the second point of the cutoff module as the anode (36.1) of the first plasma tube switch (34.1) of the at least one cutoff module; the at least one cut-off module includes a control system (46.1') for the first auxiliary plasma tube switch supplied by the first auxiliary switched capacitor (C1'); the first auxiliary switched capacitor (C1') includes a proximal armature (C1p') coupled to the cathode (38.1') of the first auxiliary plasma tube switch (34.1') and a distal armature (C1d') on the opposite side of the proximal armature (C1p') from the cathode (38.1') of the first auxiliary plasma tube switch (34.1'); the device includes a pre-charging circuit (48.1') for the first auxiliary switched capacitor (C1'); the device includes a first auxiliary switching surge protector (80.1'), the first auxiliary switching surge protector having a protection voltage lower than the nominal operating voltage of the cut-off module, electrically connected in parallel with the first auxiliary switching capacitor (C1'); 22. The device according to claim 21, characterized in that the pre-charging circuit (48.1) of the first switched capacitor (C1) and the pre-charging circuit (48.1′) of the first auxiliary switched capacitor (C1′) comprise a common voltage source (50.1) supplying the first switched capacitor (C1) and the first auxiliary switched capacitor (C1′) in parallel.

23. 23. The device according to claim 21 or 22, characterized in that the at least one cut-off module is interposed in parallel and opposite directions in the auxiliary switching branch (32') and includes two auxiliary plasma tube switches (34.1', 34.2').

24. A device according to any one of claims 1 to 23, characterized in that the device comprises several cut-off modules (18a, 18b, 18c) interposed in series in the main circuit (16), each between a first point (22a, 22b, 22c) and a second point (22a, 22b, 22c) of the main circuit (16) for the cut-off module under consideration.

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