CH713237A2 - Switch for DC. - Google Patents

Abstract

The invention relates to a DC switch, comprising: a first lead terminal (A) and a second lead terminal (B), a mechanical switching element (100) having first and second terminals (101, 102) for switching one between the first Lead terminal (A) and the second lead terminal (B) by a first current path between the first terminal (101) of the mechanical switch and the second lead terminal (B) and by a second current path between the second terminal (102) of the mechanical switch and the first A line (A) flowing current, an injection circuit (200, 206, 207, 300, 303) having a first and a second terminal (201, 301), comprising a series circuit of at least one capacitance (200), optionally at least one inductor (206 ), optionally at least one resistor (207), and one or more electronic switching elements (300). The injection circuit (200, 206, 207, 300, 303) and the mechanical switching element (100) form a circuit, and a varistor (303) is connected in parallel with each of the one or more electronic switching elements (300) of the injection circuit. Furthermore, the invention relates to a method for opening a switch.

Description

Description: The invention relates to the field of switches for electrical systems, and in particular to switches for direct current according to the preamble of claim 1.

PRIOR ART In energy transmission, for example, errors or lightning strikes lead to short circuits between the transmission lines or between the transmission line and earth, which can result in high short-circuit currents. The adjacent network areas can be destabilized by these currents and components can be damaged. Circuit breakers are used in power transmission to switch off these short-circuit currents. Since in AC networks the short-circuit current rises only slowly due to the relatively high system inductances and a current zero crossing occurs regularly, purely mechanical switches can be used. In DC voltage networks, on the other hand, the networks only have a relatively lower inductance, which means that short-circuit currents rise more quickly. The components are also more susceptible to high fault currents, in particular this applies to semiconductors in converters. Furthermore, there is no natural zero current, which means that the arc does not go out automatically in a mechanical switch.

[0003] There are currently three options for switching off these short-circuit currents. The first possibility is rapid mechanical switches with a resonance circuit in order to generate a current zero crossing (EP 0 758 137 A1). The second solution is a circuit breaker based only on semiconductors (WO 2016 007 489 A1). Since the first option is generally relatively slow and the second option generates high conduction losses during normal operation, a third option is currently being investigated, which combines the mechanical switch for normal operation and the semiconductor for switching off the short-circuit currents. These hybrid DC voltage switches for switching off short-circuit currents are currently mainly based on one of two options. The first possibility is the introduction of an element, often a semiconductor element that can be switched off, which enables the current to be commutated from a mechanical switch into parallel power semiconductors, but instead generates additional losses in normal operation. The mechanical switch is then opened without current and the semiconductors connected in parallel are switched off (WO 2011 057 657 A1). A second possibility is to inject a current into the mechanical switch in the opposite direction to the flow of the short-circuit current with the same or higher amplitude, so that the arc in the mechanical switch that is opened goes out and the mechanical switch blocks. In both cases, varistors are then used to discharge the line inductances.

A hybrid DC switch with current injection can be implemented in different ways. The basic function can be implemented with a few elements using the topology from WO 2012 100 831 A1 in Fig. 1. A hybrid DC switch with current injection has a mechanical switch 100 as a current-carrying element. A connection 101 of the mechanical switch 100 is connected to a line connection B and a second connection 102 of the mechanical switch 100 is connected to a line connection A. A circuit 2 for generating a current pulse is in parallel. It consists of a capacitance 201, a thyristor 202 and an inductor 206. The capacitance 200 is charged with positive polarity at a connection 201 which is connected to the connection 101 of the mechanical switch 100. An anode 203 of the thyristor 202 is connected to the terminal 102 of the mechanical switch 100. A cathode 204 of the thyristor 202 is connected to a terminal 205 of the capacitor 200 via the inductance 206. There is a varistor 500 in parallel with the mechanical switch 100 and in parallel with the capacitor 200 there is a charging circuit 600 which is used to charge the capacitor 200.

In order to interrupt a current from the line connection A to the line connection B, the topology from WO 2012 100 831 A1 is used as follows. The mechanical switch 100 is opened. An arc arises from the current. In order to let the arc extinguish after the mechanical switch 100 has been completely opened, the thyristor 202 is switched on, as a result of which a current pulse is generated by the mechanical switch 100. If the current pulse is the same size as the current from line connection A to line connection B, that is to say the current in mechanical switch 100 is zero, the arc extinguishes and mechanical switch 100 blocks. The current from the line connection A to the line connection B then first commutates into the circuit 2 until the capacitance 200 is charged to such an extent that the varistor 500 begins to conduct. This is designed so that the current from line connection A to line connection B drops.

In WO 2014 117 807 A1, shown in Fig. 2, three possible extensions of the basic structure from the mechanical switch 100, the circuit 2 and the varistor 500 are presented. A first extension is a resistor 503. It is connected to the cathode 204 of the thyristor 202 and a return conductor C, the return conductor of the current from line connection A to line connection B, which has a lower potential than line connection B. A second extension is a thyristor 601. A cathode 602 of the thyristor 601 is connected to the connection 201 of the capacitance 200 and an anode 603 of the thyristor 601 is connected to the cathode 204 of the thyristor 202. A third extension is a diode 400. An anode 401 of diode 400 is connected to connection 101 of mechanical switch 100 and a cathode 402 of diode 400 is connected to connection 102 of mechanical switch 100.

[0007] The benefits and the mode of operation of the three extensions of WO 2014 117 807 A1 are explained below. The first extension with the resistor 503 allows the capacitance 200, the inductance 206 and the resistor

CH 713 237 A2

503 a current flow from the line connection B to the return conductor C, which thus charges the capacitance 200. Since the resistor 503 is relatively large, it has no influence on the switching behavior of the hybrid DC voltage switch. A charging circuit as in WO 2012 100 831 A1 is therefore not necessary. The second extension with the thyristor 601 allows the polarity of the capacitance 200 to be reversed. For this, the thyristor 601 is switched on. A current through inductor 206 and capacitance 200 reverses polarity. The third extension with the diode 400 makes it possible to use a current pulse which can also be significantly higher than the current from the line connection A to the line connection B. The current pulse then commutates on the diode 400 after the arc has been extinguished. Only after the current pulse is smaller than the current from line connection A to line connection B, both mechanical switch 100 and diode 400 block. The advantage of the extension is that the current pulse does not have to be adapted to the current from line connection A to line connection B. , It is sufficient if the current pulse is large enough to switch off the maximum possible current from line connection A to line connection B. Furthermore, after the arc has been extinguished, there is no voltage across the mechanical switch 100 for a short time, making the arc less likely to re-ignite.

US 2014 376 140 A1, shown in Fig. 3 also uses the mechanical switch 100 and the varistor 500. However, as a circuit to generate the current pulse, a series circuit 7 is made of a thyristor 700, a capacitance 703, an inductor 706 and a thyristor 707 used. An anode 701 of the thyristor is connected to the connection 102 of the mechanical switch and a cathode 702 of the thyristor 700 is connected to the connection 704 of the capacitance 703. A cathode 709 of the thyristor 707 is connected to the connection 101 of the mechanical switch 100 and an anode 708 of the Thyristor 707 via inductance 706 with a connection 705 of the capacitance 703. The capacitance 703 is charged with positive polarity at the connection 705. Furthermore, a cathode 801 of a thyristor 800 is connected to the connection 705 of the capacitance 703 and an anode 802 of the thyristor 800 via an inductor 803 to the connection 102 of the mechanical switch 100. An anode 902 of a fourth thyristor 900 is connected to the cathode

702 of thyristor 700 and a cathode 901 of thyristor 900 is connected to terminal 101 of mechanical switch 100.

In order to interrupt a current from the line connection A to the line connection B, the thyristor 700 and the thyristor 707 are switched on. A current pulse is generated by series connection 7 and the mechanical switch 100, as a result of which the arc in the mechanical switch 100 is extinguished. After the polarity of the capacitance

703 reversed, the thyristor 800 is turned on, whereby the current in the thyristor 700 decreases and the thyristor 700 blocks. The thyristor 900 is then switched on, as a result of which the current in the thyristor 707 drops and the thyristor 707 blocks. The current from the line connection A to the line connection B then recharges the capacitance 703 with the original polarity before the varistor 500 begins to conduct and the current drops.

A first problem with the topologies is that the voltage across the mechanical switch 100 cannot be controlled after the mechanical switch 100 locks. With the diode 400 from WO 2014 117 807 A1, or the current through the inductor 803, the thyristor 800, the inductor 706 and the thyristor 707, there is only a certain period of time in which there is no great voltage across the mechanical switch 100. However, the voltage rise is then determined, as in WO 2012 100 831 A1, by the capacities of the topologies. However, the use of the maximum possible voltage via the mechanical switch 100 at any time during the switching process is decisive for the performance of the DC voltage switch.

A second problem is the existence of an inductive voltage divider after the mechanical switch 100 has been switched off. As long as the mechanical switch 100 remains switched on, the entire mains voltage is due to the line inductances. When the mechanical switch 100 blocks, the current steepness of the current from the line connection A to the line connection B is additionally determined by the inductor 206, or by the inductors 706 and 803. This inductive voltage divider generates a voltage jump at the mechanical switch 100.

A third problem with topologies is loading capacities. The charging circuit 600 from WO 2012 100831 A1 means an additional effort, in particular since it is at the potential of the line at the line connection B. WO 2014 117 807 A1 uses resistor 503 to charge the capacitor. However, this is only possible if the mechanical switch 100 is switched on. It is therefore not possible to switch the DC voltage switch off immediately after switching on. US 2014 376 140 A1 loads the capacity during the switch-off process for the next switch-off process. A problem remains here that the capacitance 703 is not recharged, that is to say the parasitic losses are not compensated for. In addition, for the latter two topologies, it is difficult or impossible to reload the capacitance 200 or the capacitance 703 after an unsuccessful arc extinguishing process, depending on the point in time at which it is re-ignited. WO 2012 100 831 A1 needed a fast and complex charging circuit 600 for this.

It is therefore an object of the invention to provide a switch for direct current of the type mentioned, which eliminates the disadvantages mentioned above.

This object is achieved by a switch for direct current with the features of claim 1.

This switch for direct current therefore has:

CH 713 237 A2 a first line connection and a second line connection, a mechanical switch with a first and a second connection, for switching a between the first line connection and the second line connection through a first current path between the first connection of the mechanical switch and the second line connection and by a second current path between the second connection of the mechanical switch and the first line connection current flowing, an injection circuit with a first and a second connection, comprising a series connection of at least one capacitance, optionally at least one inductor, optionally at least one resistor, and one or a plurality of switches, the injection circuit and the mechanical switch forming a circuit, a varistor being connected in parallel with each of the one or more switches of the injection circuit.

Through the circuit from the injection circuit and the mechanical switch, a current can flow when the mechanical switch is closed or has been opened and has not yet reached full blocking capacity.

The method for opening a switch, starting from a closed state of the mechanical switch, has the following steps:

- opening the mechanical switch;

- Turning on one or more of the switches, whereby a current flows through the mechanical switch, the at least one capacitance, the one or more switches, the at least one inductance and the at least one resistor.

In other words: this current flows through the circuit which is formed by the injection circuit and the mechanical switch.

In the following, the subject matter of the invention is explained in more detail with the aid of preferred exemplary embodiments which are illustrated in the accompanying drawings. Each shows schematically:

Fig. 1-3

Fig. 4

Fig. 5

Fig. 6

Fig. 7

Fig. 8

Fig. 9-11

Fig. 12-13

Fig. 14-18

Fig. 19

Fig. 20

Switch for direct current according to the prior art;

the arrangement of a generalized switch between two lines; a switch with current injection with partially controllable voltage; time profiles of voltages and currents in the circuit according to Fig. 5; a variant of the circuit according to Fig. 5;

time profiles of voltages and currents in the circuit according to Fig. 7; further variants of the circuit according to Fig. 5;

Variants of the circuit with a demagnetization circuit;

Variants of the circuit for precharging an injection capacity;

time profiles of voltages and currents in the circuit according to Fig. 18;

an exemplary combination of different variants.

Ways of Carrying Out the Invention

Switchable switches The invention relates to a switch for direct current. As shown in Fig. 4, the switch is used between two lines at a line connection A and a line connection B. The switch can also include a connection to a return conductor C, on which the return current of a current flows from the line connection A to the line connection B. The task of the switch is to draw a current from the line connection A.

CH 713 237 A2

Interrupt line connection B and demagnetize the lead inductances, marked in Fig. 4 with L1, L2 L3 and L4. This includes in particular switching off short-circuit currents.

5 shows an embodiment of the topology of the hybrid DC voltage switch with current injection with partially controllable voltage. The DC voltage switch is used between line connection A and line connection B of two lines. The topology has a mechanical switch 100 between the line connection A and the line connection B. A first connection 101 of the mechanical switch 100 is connected to the line connection B and a second connection 102 of the mechanical switch 100 is connected to the line connection A. A first connector 201 of a capacitor 200, also called an injection capacitor, charged with positive polarity at this first connector 201 is connected to the first connector 101 of the mechanical switch 100. One or more switchable switches 300 connected in series, e.g. IGBTs are connected to the second connection 102 of the mechanical switch 100. A collector or first connection 301 of the switch 300 is connected to the second connection 102 of the mechanical switch 100. A series circuit comprising an inductor 206 and a resistor 207 is located between a second terminal 302 of the switch 300 on the emitter side and a second terminal 205 of the capacitance 200 (with negative polarity). A varistor 303 is connected in parallel with each or more switches 300. Furthermore, a varistor 600 is connected between the first connection 201 of the capacitance 200 and the second connection 302 of the switches 300. The positioning of the inductor 206 and the resistor 207 can be changed as desired in the series circuit comprising the capacitor 200, the inductor 206 and the resistor 207 from FIG. 5. One or more current measurements 106 can be added if necessary. Thus, there can be a current measurement between line connection A and the second connection 102 of the mechanical switch 100 or between the first connection 301 of the switch 300 and the second connection 102 of the mechanical switch 100.

The mechanical switch 100 is used to keep the losses low in normal operation. The capacity 200 is pre-charged. A schematic representation of the switch-off process and the occurring voltages and currents can be seen in Fig. 6. In order to switch off a current from line connection A to line connection B, the mechanical switch 100 is first opened (t1).

As soon as the mechanical switch 100 is open (t2), all or part of the switches 300 are switched on, so that a pulse current through the mechanical switch 100, the capacitance 200, the switches 300, the inductor 206 and the resistor 207 is generated becomes. As soon as the pulse current is equal to the short-circuit current, the arc in the mechanical switch 100 extinguishes and the mechanical switch 100 blocks (t3). Inductor 206 and resistor 207 are used to define the shape of the current pulse. They can also be omitted or implemented by the parasitic inductance or the parasitic resistance of the pulse circuit. If only some of the switches 300 are turned on, a current flow through the varistors 303 is possible, which can also influence the shape of the pulse current.

As soon as the mechanical switch 100 no longer conducts, the short-circuit current commutates into the path through the capacitor 200, the switch 300, the inductor 206 and the resistor 207. The capacitor 200 is charged with the reverse polarity by the short-circuit current. The voltage between the connections 101 and 102 of the mechanical switch 100 is determined by the voltage across the capacitance 200, the switches 300, the inductance 206 and the resistor 207. By deliberately switching off one or more switches 300, the short-circuit current commutates to the parallel ones Varistors 303. This makes it possible to control the voltage between the connections 301 and 302 of the switches 300 and thus to partially control the voltage via the mechanical switch 100, which is a first problem with the topologies with current injection used hitherto, since these temporarily the voltage across the mechanical switch 100 is only dependent on passive components. The maximum reverse voltage of the mechanical switch 100 can thus be used and a faster drop in the short-circuit current is achieved. FIG. 6 shows a switch on and then a switch off of some of the switches 300. As soon as the capacitance 200 is fully charged, the current commutates to the varistor 600. After reaching the maximum voltage across the mechanical switch 100 (t4), only the energy in the line inductances in the varistors 303 and 600 is reduced until the short-circuit current is zero will (t5). The varistors 303 and 600 are also used to limit the maximum voltage across the individual switches 300 and the capacitance 200 and thus to avoid their destruction by overvoltage.

Complete voltage control An advantageous extension of the invention from FIG. 5 is to replace the varistor 600 with a diode 601, also called a commutation diode. An anode 603 of diode 601 is connected to connection 302 of switches 300 and a cathode 602 of diode 601 is connected to connection 201 of capacitance 200. The extension is shown in Fig. 7. A schematic representation of the switch-off process and the occurring voltages and currents can be seen in Fig. 8.

The extension has no effect on the generation of the pulse current until the mechanical switch 100 blocks (t3). Then the diode 601 becomes conductive and the voltage across the mechanical switch 100 is only determined by the number of switches 300 that are switched off, or their parallel varistors 303. The short-circuit current commutates from the capacitor 200 to the diode 601 during the further switch-off process tension

CH 713 237 A2 completely controllable without the influence of the capacitance 200, the inductance 206 or the resistor 207. This firstly solves the first problem of previous topologies. The voltage across the mechanical switch 100 can thus be adjusted at any time. The extension also solves a second problem of previous topologies with inductance in pulse generation. Since the inductor 206 is completely bridged as soon as the mechanical switch 100 blocks, a voltage jump at the mechanical switch 100 is no longer possible due to the formation of an inductive voltage divider by the inductor 206 with the line inductances. Furthermore, the capacitance 200 can be designed for smaller voltages, or can also be realized with a smaller capacitance.

Another advantage of the extension is the possibility to already charge the line with the switches 300 and the diode 601 without having to switch on the mechanical switch 100. One advantage is that in the event of a short circuit after the switches 300 are switched on, this enables the line connection A and the line connection B to be disconnected quickly. A second advantage is that the mechanical switch 100 can thereby be switched on without voltage.

Extension for Limiting the Current Rise with an Inductor A possible extension of the topology of FIG. 5 is an inductor 105, also called current rise limiting inductance, between the connection 201 of the capacitance 200 and the line connection B, as shown in FIG. 9. Alternatively, it would also be possible to have an inductance between the line connection A and the connection 102 of the mechanical switch 100, or both an inductance, also called a partial current limit inductance, between the line connection A and the connection 102 of the mechanical switch 100 and also between the line connection B and the connection 201 of the capacitance 200. The inductance 105 limits the maximum current rise of the short-circuit current. The extension can also be applied to the topology from Fig. 7 and all subsequent extensions.

Extension with saturating inductance In the various embodiments of the invention it is possible to add a saturating inductor 103, as shown in Fig. 10. The saturating inductance 103, which saturates even at low currents, is connected between the first connection 101 of the mechanical switch 100 and the first connection 201 of the capacitance 200. The saturating inductance 103 has no influence on the principle of operation of the hybrid DC voltage switch with current injection. At low currents, however, the saturating inductor 103 is not saturated and thus limits the current steepness during the zero crossing in the mechanical switch 100, which makes the arc re-igniting less likely. The extension can also be applied to the topology from Fig. 7 and all subsequent extensions.

Extension with parallel diode to the mechanical switch 100 In the various embodiments of the invention, it is possible to use a diode 400, also called a parallel diode, in parallel with the mechanical switch 100. The extension of the topology of Fig. 5 is shown in Fig. 11. An anode 401 of the diode 400 is connected to the first connection 101 of the mechanical switch 100 and a cathode 402 of the diode 400 is connected to the second connection 102 of the mechanical switch 100. By using the diode 400, higher pulse currents than the short-circuit current can also be used. The pulse current then commutates from the mechanical switch 100 into the diode 400 at the zero crossing until the pulse current is again less than the short-circuit current. As soon as neither the mechanical switch 100 nor the diode 400 conduct, the switch-off process of the hybrid DC voltage switch with current injection continues as previously described. The extension can also be applied to the topology from Fig. 7 and all subsequent extensions.

Extensions for demagnetizing the line inductances After the current in the mechanical switch 100 has been interrupted, the stored energy in the line inductances must be reduced. This is done with the varistors 303 and, if present, with the varistor 600. Since there is no alternative path for the current from the line connection A to the line connection B, the line inductances from line connection A are discharged as quickly as the line inductances from line connection B and the voltage of the mechanical switch 100 is divided accordingly.

Extension to demagnetize the line inductances with a diode and a resistor. A possible extension of the circuit is a first demagnetization circuit with a diode 900, also called a demagnetization diode, and a resistor 903, also called a demagnetization resistor, shown in Fig. 12. A cathode 901 from the diode 900 is connected via the resistor 903 to the connection 201 of the capacitance 200 and an anode 902 of the diode 900 is connected to the return conductor C.

The following applies here and in general: the return conductor C is provided to conduct a return current of a current flowing between the first line connection A and the second line connection B.

The extension has the consequence that after blocking the mechanical switch 100 and, if present, the diode 400, the current from line connection A to line connection B does not have to remain the same. The current in Lei6

CH 713 237 A2 line connection B can also sink more slowly than the current in line connection A, since the current in line connection B can also flow via diode 900 and resistor 903. The voltage for discharging the inductances from line connection B is defined by the resistor 903 and the voltage for discharging the inductances from line connection A is defined by the voltage across the mechanical switch 100. The current in line connection A can thus be reduced more quickly by appropriately designing the resistor 903 and thus the energy, which is obtained via line connection A, is reduced. The extension can also be applied to the topology from Fig. 7 and all subsequent extensions.

Extension to demagnetize the line inductances with a diode and switches with parallel varistors. A possible extension of the circuit is a second demagnetization circuit with a diode 900, also called a demagnetization diode, and one or more switches 904, each with a parallel varistor 907, also demagnetization switches, respectively - Called varistors. The extended topology is shown in Fig. 13. A cathode 901 of the diode 900 is connected via the series connection switch 904, for example IGBT, to the connection 201 of the capacitance 200 and an anode 902 of the diode 900 is connected to the return conductor C. An emitter 905 of the switch 904 is connected to the connection 201 of the capacitance 200 and a collector 906 of the switch 904 is connected to the cathode 901 of the diode 900. A varistor 907 is parallel to all or each individual switch 904.

The extension has the result that after blocking the mechanical switch 100 and, if present, the diode 400, the current from line connection A to line connection B does not have to remain the same. The current in line connection B can also decrease more slowly than the current in line connection A, since the current in line connection B can also flow via diode 900 and the IGBT 904 or the varistors 907. After blocking the mechanical switch 100 and, if present, the diode 400, the IGBT 904 must be switched on. As in the extension of Fig. 12, the current in line connection A thus drops faster than in line connection B. Due to the IGBT 904, almost the entire voltage across the mechanical switch 100 is used to lower the current in line connection A. After the current in line connection A has dropped to zero, the IGBT 904 is switched off and the varistor 907 is used to lower the current in line connection B. The extension allows the current through line connection A to be reduced more quickly, as a result of which the energy drawn via line connection A is reduced. The extension can also be applied to the topology from Fig. 7 and all subsequent extensions.

Capacity loading extensions 200

Expansion to Charge the Capacitance with a Diode and a Resistor The charging of the capacitance 200 can be carried out in different ways. In the case of an expansion, this is possible by connecting the connection 302 of the switches 300 to the return conductor C, which has a lower potential than the line connection B. The connection consists of a diode 500, also called a charging diode, and a resistor 503, also called a charging resistor. An anode 501 of diode 500 is connected to connection 302 of switches 300 and a cathode 502 of diode 500 is connected to return conductor C via resistor 503. Through this charging circuit, a current flows from line terminal B to the return conductor C, which charges the capacitance 200. Resistor 503 is used to limit the maximum charging current. The extended topology is shown in Fig. 14. If the recharging is to be carried out in a controlled manner, a thyristor or another switch, generally also called a charging switch 500 ', can be used instead of a diode, as shown in FIG. 15. If the capacitance 200 is to be charged to a voltage lower than the voltage between the conductor connection B and the return conductor C, switches which can switch off a current, for example IGBTs, can be used as the charging switch, as shown in FIG. 16. In this case, a varistor 504, also called a charging varistor, can also be used in parallel with each charging switch 500 'or IGBT. The extension can also be applied to the topology from Fig. 7 and all subsequent extensions.

Extension with diode and current increase-limiting inductance An extension for charging the capacitance 200 is represented by a diode 700, also called a further charging diode, in FIG. 17. For the extension, the inductance 105 or current increase-limit inductance is in a first current path between the first connection 201 the capacitance and the conductor connection B are necessary. An anode 702 of the diode 700 is connected to the second connection 205 of the capacitance 200 and a cathode 701 of the diode 700 is connected to the line connection B.

The extension has the consequence during the switch-off process that the capacitance 200 does not have to be permanently precharged, but is charged by the increase in a short-circuit current. The rise in the short-circuit current in the inductor 105 requires a voltage across the inductor 105. This voltage makes the diode 700 conductive and the capacitor 200 is charged. Only the voltage from the capacitor 200 allows a current rise in the inductor 105. As soon as the current in the inductor 105 is so high that the inductor 105 carries the full short-circuit current, the diode 700 blocks. Capacitor 200 is thus charged by the current rise. If the capacitance 200 and the inductance 105 are correctly designed, the charging process is shorter than the time required to detect the short circuit and

CH 713 237 A2

Take countermeasures. The generation of the current pulse with the switches 300, the switching off of the mechanical switch 100 and the voltage control via the mechanical switch 100 with the switches 300 remain unchanged.

An advantage of the circuit is the passive charging of the capacitance 200 during the increase in the short-circuit current, as a result of which the capacitance 200 is charged only in the event of a fault and not during the entire operation. Since this happens automatically during the current rise, the switch-off process with current injection is not delayed. This is also part of the solution to a third problem, that after the arc is re-ignited, the capacity must be recharged to repeat the turn-off process. In this case, since the short-circuit current continues to increase, it is possible to charge the capacitance 200 again when the switches 300 are switched off.

A pulse current can then be generated again in order to generate a current zero crossing in the mechanical switch 100. The extension can also be applied to the topology from Fig. 7 and all subsequent extensions.

Extension for precharging capacitance 200 before switching on the mechanical switch 100 via return conductor C. A disadvantage of the circuit in FIGS. 15 and 17 is that the capacitance 200 can only be charged by means of the diode 500 and the resistor 503 if the mechanical switch 100 is turned on.

An extension for charging circumvents this problem by replacing the diode 500 and the resistor 503 with a thyristor 800, a resistor 803, an inductor 804 and a diode 805. The extension is shown in Fig. 18. An anode-side connection 801 of the thyristor 800 is connected to connection 205 of the capacitance 200. The resistor 803 and the inductor 804 are in series between a cathode-side connection 802 of the thyristor 800 and the return conductor C. A cathode-side connection 806 of the diode 805 is connected to the connection 201 of the capacitance and an anode-side connection 807 of the diode 805 is connected to the return conductor C. A resistor 808 can be used as a further element between the connection 801 of the thyristor 800 and the return conductor C.

The charging process before switching on the mechanical switch 100 is shown in Fig. 19. The expansion for charging begins the charging process after the line has been charged and before the mechanical switch 100 is closed. The switch 300 is switched on. As soon as thyristor 800 is switched on (tO), a voltage is present across resistor 803 and inductor 804 and the current in inductor 804 increases. The maximum current is limited by resistor 803. As soon as the current in the inductor 804 has reached a certain value, the switches 300 are switched off (t1) and the current commutates to the capacitance 200 and the diode 805 and charges the capacitance 200. The thyristor 800 and the diode 805 (t2) then block. This process can be repeated several times in order to charge the capacitance 200 to an arbitrary voltage. The extension allows the capacitance 200 to be charged without turning on the mechanical switch 100, whereby the hybrid DC voltage switch can be turned off again immediately after the mechanical switch 100 is closed, which is part of the third problem of many topologies with current injection at present. When the DC voltage switch is switched on, capacitance 200 is charged via resistor 808, so that parasitic losses do not discharge the capacitance 200 over time. The extension is also applicable to the topology from Fig. 7 and all subsequent extensions, except the extension for loading the capacitance with the diode 500 and the resistor 503, whereby the circuit does not require a diode 805 when using the extensions with diode 900.

Combination of Variants As already mentioned for the individual variants, the extensions can all be combined with one another. The topology from FIG. 7 with the inductance 105, the saturating inductance 103, the diode 400, the diode 700, the charging circuit consisting of thyristor 800, resistor 803, inductor 804 and resistor 808, and the extension for demagnetizing from diode 900, is exemplary. Switch 904 and varistor 907 shown in Fig. 20.

Claims (10)

claims 1. Switch for direct current, comprising a first line connection (A) and a second line connection (B), a mechanical switch (100) with a first and a second connection (101, 102), for switching one between the first line connection (A) and the second line connection (B) through a first current path between the first connection (101) of the mechanical switch and the second line connection (B) and through a second current path between the second connection (102) of the mechanical switch and the first line connection (A) CH 713 237 A2 flowing current, an injection circuit (200, 206, 207, 300, 303) with a first and a second connection (201, 301), comprising a series connection of at least one capacitance (200), optionally at least one inductance (206 ), optionally at least one resistor (207), and one or more switches (300), the injection circuit (200, 206, 207, 300, 303) and the mechanical switch (100) forming a circuit, parallel to each of the one or more switches (300) of the injection circuit each have a varistor (303) connected. 2. Switch according to claim 1, wherein the injection circuit has a commutation element which is connected in parallel to a series circuit comprising the at least one capacitance (200), the optional at least one inductor (206) and the optional at least one resistor (207), the Commutation element is a further varistor (600) or a commutation diode (61). 3. Switch according to one of the preceding claims, comprising a current rise limitation inductor (105) which is connected in the first or in the second current path, or two partial current rise limitation inductors, one of which is switched in the first and one in the second current path. 4. Switch according to one of the preceding claims, comprising a saturating inductor (103), which between the first connection (101) of the mechanical switch (100) and the first connection (201) of the injection circuit (200, 206, 207, 300, 303 ) is switched. 5. Switch according to one of the preceding claims, comprising a diode (400) which is connected in parallel to the mechanical switch (100), an anode (401) of the diode (400) with the first connection (101) of the mechanical switch (100 ) and a cathode (402) of the diode (400) is connected to the second connection (102) of the mechanical switch (100). 6. Switch according to one of the preceding claims, comprising - a first demagnetization circuit (900, 903) comprising a series connection of a demagnetization diode (900) and a demagnetization resistor (903), which is connected between the first line connection (A) and a return conductor (C); or - A second demagnetization circuit (900, 903) comprising a series connection of a demagnetization diode (900) and one and one or more demagnetization switches (904), each with a parallel demagnetization varistor (907), which is connected between the first line connection (A) and a return conductor (C) is. 7. Switch according to one of the preceding claims, comprising a charging circuit for charging the capacitance (200) of the injection circuit, the charging circuit and the capacitance (200) in a current path between the first connection (101) of the mechanical switch (100) and a return conductor (C), and the charging circuit is one of the following circuits: - A series connection of a charging resistor (503) and a charging diode (500); or - A series connection of a charging resistor (503) and a charging switch (500 '); or - A series connection of a charging resistor (503) and a charging switch (500 ') with a charging transistor (504) connected in parallel to the charging switch (500'); wherein, if the present claim depends on a claim in which the return conductor (C) is already mentioned, the return conductor (C) mentioned in the present claim is equal to the return conductor (C) already mentioned. 8. Switch according to one of the preceding claims, depending on claim 3, wherein a current increase limiting inductance (105) is connected in the first current path between the second line connection (B) and a first connection (201) of the capacitance (200) and a further charging diode ( 700) is connected to the second line connection (B) with a cathode (701) and is connected to a second connection of the capacitance (200) with an anode (702). 9. Switch according to one of claims 1 to 7, comprising a further charging circuit for charging the capacitance (200) of the injection circuit, the capacitance (200) having a first connection (201) to the first connection (101) of the mechanical switch (100 ) is connected and the further charging circuit has a first branch (800, 803, 804) and a second branch (805), and wherein - The first branch (800, 803, 804) has a series connection of a further charging switch (800), a further charging resistor (803) and a charging inductor (804), and this series connection between a second connection (205) of the capacitance (200) and a return conductor (C) is connected, - The second branch (805) has a further charging diode (805) which is connected with an anode (807) to the return conductor (C) and with a cathode (806) to the first connection (101) of the mechanical switch, and - wherein, if the present claim depends on a claim in which the return conductor (C) is already mentioned, the return conductor (C) mentioned in the present claim is equal to the return conductor (C) already mentioned. 10. A method for opening a switch according to one of the preceding claims, comprising the steps, starting from a closed state of the mechanical switch (100): CH 713 237 A2 -Open the mechanical switch (100); - Turning on one or more of the switches (300), whereby a current through the mechanical switch (100), the at least one capacitance (200), the one or more switches (300), the optional at least one inductor (206) and the optional at least one resistor (207) flows. CH 713 237 A2 illustration 1 CH 713 237 A2 Figure 2 CH 713 237 A2 Figure 3 902 900 901 CH 713 237 A2 Figure 4 CH 713 237 A2 LO CD C Zi p Zi jQ < CH 713 237 A2 Figure 6 CH 713 237 A2 Figure 7 CH 713 237 A2 Figure 8 CH 713 237 A2 Figure 9 CH 713 237 A2 Ο CD £ = = 3 _Ω JD < CH 713 237 A2 Figure 11 CH 713 237 A2 Figure 12 900 902 CH 713 237 A2 Figure 13 902 CH 713 237 A2 Figure 14 marg CH 713 237 A2 Figure 15 m m CH 713 237 A2 Figure 16 o o m cn CH 713 237 A2 Figure 17 CH 713 237 A2 Figure 18 cn cn -805 CH 713 237 A2 Figure 19 CH 713 237 A2 Figure 20 en m 906