AU2020307052A1

AU2020307052A1 - Circuit breaker for direct currents

Info

Publication number: AU2020307052A1
Application number: AU2020307052A
Authority: AU
Inventors: Sohel AHMAD; Ulrich Kahnt
Original assignee: Elpro GmbH
Current assignee: Elpro GmbH
Priority date: 2019-06-28
Filing date: 2020-06-26
Publication date: 2022-01-27
Also published as: DE102020116974A1; CN114303215A; EP3991195A1; WO2020260673A1

Abstract

The invention relates to a direct-current high-speed circuit breaker (SSM) which is suitable for and is provided for switching off high direct currents in the event of loading or a short circuit, comprising an isolating switch (VS), a turn-off circuit (LK), and a return conductor (RL), wherein the turn-off circuit (LK) is provided for and is suitable for generating a current in the opposite direction of the direct current to be interrupted, and the return conductor (RL) is provided for and is suitable for discharging direct currents out of the direct-current high-speed circuit breaker (SSM). A first free-wheeling circuit (iFK) is provided in the direct-current high-speed circuit breaker (SSM), said free-wheeling circuit being provided for and being suitable for reducing overvoltages and/or current peaks occurring during the switching process. The invention also relates to a corresponding method for separating a DC circuit in an arc-free manner.

Description

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CIRCUIT BREAKER FOR DIRECT CURRENTS

The invention relates to a high-speed DC circuit breaker apparatus (SSM) that is suitable and intended for switching off high direct currents in the event of load and short circuit, comprising a disconnector (VS), a quenching circuit (LK), and a return conductor (RL), wherein the quenching circuit (LK) is intended and suitable for generating a current in the opposite direction to the direct current to be interrupted, and wherein the return conductor (RL) is intended and suitable for conducting direct currents away from the high-speed DC circuit breaker apparatus (SSM), and to a corresponding method for arc-free disconnection of a DC circuit.

Prior art

In order to ensure trouble-free and safe operation of vehicles operated with direct currents, e.g. electric trains, it is necessary for safety reasons to disconnect the power supply to the disrupted outgoing line quickly and reliably from the DC network in the event of undesired operating states or damage. Since a direct current cannot be switched off sufficiently quickly by means of conventional switching devices having metal switching contacts so slowly as to subject the system to significant loading, hybrid switches, among other things, are used which comprise a combination of a metal switching path and a semiconductor switching path. On account of the high current strengths, these hybrid switches require high-quality semiconductor components that are expensive to buy. Switching apparatuses that switch off the direct current of the power supply by means of an opposing direct current are simpler in design.

DE 102 18 806 B4 presents a high-speed circuit breaker module of this kind. The module comprises a switching device between the line and busbar of the rectifier substation. A quenching circuit is arranged in parallel to this switching device, which quenching circuit consists of a quenching capacitor, which is connected in series to a switching unit consisting

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of two quenching thyristors arranged antiparallel. A test branch is also arranged in parallel to the switching device. The test branch consists of a series circuit consisting of a test thyristor, a current-measuring element, and a test resistor. The high-speed DC circuit breaker apparatus also comprises a free-wheeling circuit, which comprises one branch for each current direction, from the busbar to the return conductor and from the line to the return conductor, in each of which branches two free-wheeling diodes connected in series are arranged. A fuse with a reporting system is assigned in parallel to one free-wheeling diode in each branch of the free-wheeling circuit. The dimensioning of the free-wheeling diode and of the fuse is selected such that only a small amount of the free-wheeling current flows via the relevant fuse in each case, while the majority of the free-wheeling current flows via the free-wheeling diode arranged in parallel to the fuse.

This high-speed circuit breaker module is designed for switching off systems having a grid voltage of up to 750 V and a nominal current strength of up to 4000 A with overloads that are usual for railroad currents. However, this module cannot be used for systems available in the future that are operated at up to 1500 V and 4000 A on account of the doubling of the power.

An object of the present invention is therefore to provide a high-speed DC circuit breaker module that is improved with respect to the prior art such that systems operated with direct current and with a higher power than before can be switched off quickly and reliably. Another object of the present invention is to provide a method for operating a high-speed DC circuit breaker module by means of which systems operated with direct current and with a higher power than before can be switched off quickly and reliably.

The above-mentioned object is achieved by means of the high-speed DC circuit breaker apparatus according to claim 1.

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The high-speed DC circuit breaker apparatus comprises a disconnector and a quenching circuit. The quenching circuit is intended and suitable for generating a direct current in the opposite direction to the direct current to be interrupted. The high-speed DC circuit breaker apparatus according to the invention is arranged between the line to be supplied with current and the current busbar. The disconnector is usually a vacuum disconnector by means of which a supply current can be interrupted quickly and reliably. Furthermore, the high-speed DC circuit breaker apparatus comprises a return conductor, which is intended and suitable for conducting direct currents away from the high-speed DC circuit breaker apparatus. According to the invention, the high-speed DC circuit breaker apparatus also comprises a first free-wheeling circuit, which is intended and suitable for eliminating overvoltages and/or current peaks that occur during the switching process. The first free wheeling circuit is connected to the return conductor and prevents damage to the components arranged in the high-speed DC circuit breaker apparatus in the event of voltage peaks of more than 1500 V in the apparatus. The high-speed DC circuit breaker apparatus according to the invention can therefore be used for DC networks in the range of typically 220 V to 1000 V and with a current strength of as much as 8 kA.

In a development of the invention, a second free-wheeling circuit is provided. The second free-wheeling circuit comprises a connection for a return conductor. The second free wheeling circuit ensures that the energy present in the inductors of the line is dissipated quickly by means of free-wheeling currents after rapid disconnection by the disconnector. Any voltage peaks are eliminated by means of the first free-wheeling circuit.

In another aspect of the invention, the first and second free-wheeling circuit extend partially in parallel and are only partially guided through the high-speed DC circuit breaker apparatus. This ensures that current only flows through the first free-wheeling circuit in the event of voltage peaks. The second free-wheeling circuit dissipates electrical energy that regularly arises during disconnection. Both free-wheeling circuits are also separated from one another by means of a rectifier diode. In particular, the second free-wheeling circuit is

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arranged partially outside the high-speed DC circuit breaker apparatus. The high-speed DC circuit breaker apparatus can therefore be arranged in confined spaces, in particular.

In another design of the invention, the first free-wheeling circuit comprises a current-limiting device. The current-limiting device is usually an electrical resistor that advantageously has a high thermal conductivity. The current-limiting device in the first free-wheeling circuit therefore converts the conducted electrical energy into heat very efficiently and quickly.

In another embodiment of the invention, the current-limiting device of the first free-wheeling circuit is arranged in the high-speed DC circuit breaker apparatus. The current-limiting device is therefore protected from weather influences by the housing of the high-speed DC circuit breaker apparatus and can additionally be provided with a cooling system in order to efficiently dissipate the heat generated in the current-limiting device.

In another embodiment of the invention, the current-limiting device of the first free-wheeling circuit of the high-speed DC circuit breaker apparatus is a chopper circuit and/or positive temperature coefficient (PTC) resistor. The electrical resistance of the current-limiting device thus increases with the temperature, which increases on account of the current flow in the current-limiting device, and thus limits the electrical current flowing through the first free-wheeling circuit.

In another embodiment of the invention, the quenching circuit comprises a quenching capacitor. The current-limiting device of the first free-wheeling circuit is connected in parallel to the quenching capacitor. The quenching capacitor is constantly charged between discharge procedures in order to ensure the operational readiness of the high-speed DC circuit breaker apparatus.

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The above-mentioned object is also achieved by means of the method for switching direct currents according to claim 8. Developments of the method are described in claims 9 to 14.

The method according to the invention for switching direct current comprises four method steps: In a first method step, the electrical voltage of a conductor connected to a high-speed DC circuit breaker apparatus is tested. For this purpose, a control device is connected to a current-detection element, by means of which the electrical conductor can be tested for undesired operating states, damage, and a faulty power supply. In the second method step, a disconnector in the high-speed DC circuit breaker apparatus is activated. The disconnector disconnects the busbar, which supplies the DC-conducting conductor with electrical energy, from the energy supply. In the third method step, the electrical circuit is disconnected by opening two switching contacts for interrupting a continuous current. By opening the switching contacts, an arc is produced between the switching contacts. In the fourth method step, the arc that is formed between the switching contacts after the disconnector is activated is quenched. For this purpose, an electrical current that is directed counter to the current flowing in the disconnector is conducted into the disconnector. Both electrical currents are superimposed on one another and cancel each other out such that the resulting current strength is 0 A.

According to the invention, the high-speed DC circuit breaker apparatus is discharged in the event of high voltages and/or currents. As a result, in the event of voltage peaks of more than 1500 V in the high-speed DC circuit breaker apparatus, damage to the components arranged therein is prevented.

In another embodiment of the invention, the arc is quenched by discharging a previously charged quenching capacitor. The quenching capacitor is charged between the discharge procedures to ensure the operational readiness of the high-speed DC circuit breaker apparatus such that an electrical current that is directed counter to the electrical current of the arc is generated when the capacitor is discharged.

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In another embodiment of the invention, the quenching capacitor of the high-speed DC circuit breaker apparatus is discharged in the event of high voltages. The quenching capacitor is charged between the discharge procedures to ensure the operational readiness of the high-speed DC circuit breaker apparatus such that an electrical current that is directed counter to the electrical current of the arc is generated when the capacitor is discharged.

In a development of the invention, the quenching capacitor of the high-speed DC circuit breaker apparatus is discharged by means of a chopper and/or PTC resistor connected in parallel. Choppers and/or PTC resistors usually have a high thermal conductivity. The discharge of the electrical energy stored in the capacitor is therefore converted into heat very efficiently and quickly.

In another embodiment of the invention, the continuous current is guided via a metal contact having a vacuum chamber. The vacuum chamber comprises the disconnector by means of which a supply current can be interrupted in a quick and reliable manner. In addition, no plasma that soils the contacts and that would periodically necessitate laborious cleaning is formed in the vacuum chamber. Moreover, the vacuum chamber is so well insulated against electrical currents that the level of safety for people, in particular maintenance personnel, is high.

In another design of the invention, the currents and/or voltages flowing through the high speed DC circuit breaker apparatus are dissipated by means of a second free-wheeling circuit. The second free-wheeling circuit ensures that the energy present in the inductors of the line is dissipated quickly by means of free-wheeling currents after rapid disconnection by the disconnector. Any voltage peaks are eliminated by means of the first free-wheeling circuit.

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In another embodiment of the invention, the second free-wheeling circuit guides the current via a connection for a return conductor. The return conductor conducts direct currents away from the high-speed DC circuit breaker apparatus.

Exemplary embodiments of the device according to the invention and of the method according to the invention are shown in the drawings in a schematically simplified manner and are explained in more detail in the following description.

The figures show:

Fig. 1: A circuit diagram of an exemplary embodiment of the high-speed DC circuit breaker apparatus according to the invention

Fig. 2 a: Current flows for opening the switching device and triggering the quenching thyristor for large currents at the time t=0 ms of the switching procedure

Fig. 2 b: Current flows for opening the switching device and triggering the quenching thyristor for large currents at the time t=0 ms of the switching procedure

Fig. 3 a: Current flows for opening the switching device and triggering the quenching thyristor for large currents at the time t=0.25 ms of the switching procedure

Fig. 3 b: Current flows for opening the switching device and triggering the quenching thyristor for large currents at the time t=0.25 ms of the switching procedure

Fig. 4 a: Current flows for opening the switching device and triggering the quenching thyristor for large currents at the time t>1.2 ms of the switching procedure

Fig. 4 b: Current flows for opening the switching device and triggering the quenching thyristor for large currents at the time t>1.2 ms of the switching procedure

Fig. 5 a: Current flows for opening the switching device and triggering the quenching thyristor for large currents at the time t>=2 ms of the switching procedure

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Fig. 5 b: Current flows for opening the switching device and triggering the quenching thyristor for large currents at the time t>2 ms of the switching procedure

Fig. 6 a: Current flows for opening the switching device and triggering the quenching thyristor for large currents at the time t>=2 ms of the switching procedure, when internal free-wheeling circuit switched

Fig. 6 b: Current flows for opening the switching device and triggering the quenching thyristor for large currents at the time t>=2 ms of the switching procedure, when internal free-wheeling circuit switched

Fig. 1 shows the schematic setup of the circuit of the device SSM according to the invention. In this and the following exemplary embodiments, the high-speed circuit breaker apparatus SSM is arranged on a DC traction power supply. The high-speed circuit breaker apparatus SSM is connected to the busbar SS of the traction power supply on one side and to the line ST on the other side by means of a two-pole disconnector DT. In the switched-off state, the line is galvanically isolated from the busbar by means of the two-pole disconnector DT.

The vacuum switch VS is arranged between the busbar SS of the traction power supply and the line ST and serves, on the one hand, to guide operating currents, load or short-circuit currents in both current directions and, on the other hand, to quickly establish a galvanic isolation path. The vacuum switch VS is driven by means of an electromagnetic drive. A current-detection element T that detects the operating and fault currents is arranged in the current path of the vacuum switch. A quenching circuit LK is arranged parallel to the vacuum switch VS between the busbar SS of the traction power supply and the line ST. This quenching circuit LK consists of a quenching capacitor K and two antiparallel quenching thyristors LT1, LT2 in series with said quenching capacitor.

The internal free-wheeling circuit iFK is also arranged in parallel to the vacuum switch VS, and the connection is between the quenching capacitor K and the quenching thyristors LT1,

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LT2. The internal free-wheeling circuit iFK comprises a thyristor CT, an antiparallel free wheeling diode D connected in series, and a resistor (chopper and/or PTC resistor) therebetween.

A test circuit PK that checks the present state of the line before same is switched back on is also arranged in parallel to the vacuum switch VS. The test circuit PK consists of a series circuit consisting of a switch VP, a current-measuring element Tp, and a test resistor PW. The test thyristor VP is triggered for testing the line and the current flowing through the test resistor PW is detected by means of the current-measuring element Tp.

Furthermore, the high-speed circuit breaker apparatus comprises a second free-wheeling circuit eFK, which comprises two branches, one of which is arranged between the connection of the vacuum switch VS and the other of which is arranged between the line ST and the return conductor RL. The second free-wheeling circuit eFK comprises the free wheeling diode D. The second free-wheeling circuit eFK ensures that the energy present in the inductors of the line is dissipated quickly by means of free-wheeling currents after the galvanic isolation path has been established in the vacuum switch VS. The switch-off procedure is automatically triggered by means of the control device EBG when the operating current reaches a set limit value.

The control device EBG processes the recorded measurement values and outputs the corresponding control commands to the vacuum switch VS and to the quenching thyristors LT1, LT2. The opening procedure for the vacuum switch VS is automatically initiated in accordance with the set limit values upon evaluation of the current signal from the current detection element T and the rate of current increase. The quenching thyristors LT1, LT2 are actuated in a time-optimized manner depending on the operating current to be switched and the dimensioning of the quenching circuit, in particular the capacity of the quenching capacitor K. The line test is also carried out by means of the control device EBG in that the line resistance is calculated taking into account the present output voltage. Moreover, the

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control device EBG regulates actuation of the thyristor CT and thus the activation of the internal free-wheeling circuit iFK in the event of high power.

Fig. 2 shows the current flows for opening the switching device SSM and triggering the quenching thyristor LT1, LT2 for large currents at the time t=0 ms. Fig. 2 a) shows the circuit according to Fig. 1 in operation. In this and the following representations, the switching command is given at the time 0.101 s (Fig. 2 b). In other words, the vacuum switch VS is closed at this time. At the time t=0 ms, a short-circuit current IL to beswitched off occurs, i.e. a short circuit on the line ST is fed by the traction power supply via the busbar SS (Fig. 2 a). The increasing short-circuit current IL (Fig. 2 b) is detected by means of the current detection element T in the current path of the vacuum switch VS.

Fig. 3 shows the current flows for opening the switching device SSM and triggering the quenching thyristor LT1, LT2 for large currents at the time t=0.25 ms. Fig. 3 a) shows the circuits of the high-speed DC circuit breaker apparatus according to Fig. 1 that are active at this time. When a settable operating current of e.g. 4 kA is reached, the control unit EBG issues the switch-off command to the vacuum switch VS, and the drive starts separating the contacts of the vacuum switch VS (Fig. 3 a). An arc is produced between the contacts of the vacuum switch VS. The contacts open in a uniform manner along the contact path of the vacuum switch VS, with the maximum distance between the contacts being 2 mm. The short-circuit current IL continues to flow via the switching arc forming inside the vacuum chamber during lifting of the contact (Fig. 3 b).

Fig. 4 shows the current flows for opening the switching device SSM and triggering the quenching thyristor LT1, LT2 for large currents at the time t>1.2 ms. Fig. 4 a) shows the circuits of the high-speed DC circuit breaker apparatus according to Fig. 1 that are active at this time. In order to quench the arc between the contacts of the vacuum switch VS, the current Isu flowing therein must assume the value of 0 A, because the vacuum switch VS itself is not able to switch off a flowing short-circuit current IL. For this purpose, the control

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unit EBG actuates the quenching thyristor LT1, which activates the quenching circuit LK. By precharging the quenching capacitor K, a current Isu is generated in the quenching circuit LK (Fig. 4 b) that is directed counter to the current IL flowing in the vacuum switch VS (Fig. 4a). The two currents flowing in the vacuum switch VS, i.e. the short-circuit current IL and the quenching current Isu, are superimposed on one another. The two currents, i.e. the short-circuit current IL and the quenching current, each have a current in opposite directions of such a strength that the resulting switching current attains a value of 0 A. As a result, the arc in the vacuum switch VS is extinguished. When the arc is extinguished, the instantaneous voltage UKC of the quenching capacitor K increases across the switching path. If this voltage UKc does not exceed the instantaneous dielectric strength of the switching path in the vacuum switch VS, the arc is not reignited and the short-circuit current

IL is switched off.

Current rail-bound vehicles, but also non-rail-bound motor vehicles (e.g. electric cars or buses) in particular, are able to feed the energy generated during negative acceleration back into the overhead line or into the integrated battery (recuperation). As such, for the switching device SSM according to the invention as well, this should be assumed to be a current direction that is counter to that presented above (Fig. 2 to 4). In such a case, a current Isu in the vacuum switch VS and in the quenching circuit LK also flows in the opposite direction to that presented above. As a result, the quenching capacitor K in the quenching circuit LK is also charged and polarized in the reverse direction. The subsequent procedure for quenching the arc in the vacuum switch VS is the same. The switching device SSM according to the invention is therefore also suitable for different polarities of the traction current without the need for additional components.

Fig. 5 shows the current flows for opening the switching device SSM and triggering the quenching thyristor LT1, LT2 for large currents at the time t>=2 ms. Fig. 5 a) shows the circuits of the high-speed DC circuit breaker apparatus according to Fig. 1 that are active at this time. At this time, due to the arc in the vacuum switch VS having been extinguished, a current leFK flowsthrough the second free-wheeling circuit eFK, which is arranged in part

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outside the high-speed circuit breaker apparatus SSM, and through the quenching circuit LK (Fig. 5 a), wherein the quenching capacitor K functions as an intermediate store. The quenching capacitor K is also recharged (precharged) in the process. The external free wheeling circuit eFK ensures that the energy present in the line ST is dissipated on account of the flowing free-wheeling currents leFK after the galvanic isolation path has been established (Fig. 5 b). In order for a flowing direct current IL to besafely and reliably switched off in exceptional situations as well, it can be provided for the quenching thyristors LT1, LT2 to be triggered repeatedly. As such, the method according to the invention as represented in Fig. 2 to 5 can be repeated if necessary.

Fig. 6 shows the current flows for opening the switching device SSM and triggering the quenching thyristor LT1, LT2 for large currents at the time t>= 2 ms. In order to absorb any overload voltage peaks UKC that may occur, the internal free-wheeling circuit iFK is switched in this exemplary embodiment. Fig. 6a) shows the circuits of the high-speed DC circuit breaker apparatus according to Fig. 1 that are active at this time. The energy stored in the high-speed circuit breaker apparatus SSM at this time charges the quenching capacitor K after the arc in the vacuum switch VS has been quenched (cf. Fig. 5). In the process, charging voltages UKCcan be reached which exceed a safety limit for the high-speed circuit breaker apparatus SSM and any other components connected thereto such that damage can occur. If the charging voltage exceeds 1500 V, the internal free-wheeling circuit iFK is activated (Fig. 6 a). For this purpose, the control device EBG triggers the thyristor CT when the resistance in the quenching circuit LK exceeds 300 mQ (Fig. 6 b). If the charging voltage UKC of the capacitor K falls below a value of 1100 V, the thyristor is disabled again. The triggering and disabling of the thyristor CT are repeated until the charging voltage UKC of the capacitor K is constantly under 1500 V. The arising overvoltage UKC therefore remains below the arc voltages that often occur in conventional high-speed circuit breakers.

As soon as the current is 0 A and all voltages UKC, UiFK have dissipated, the double disconnector DT is opened (Fig. 7 a) and b)). This reactivates the switching device SSM.

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LIST OF REFERENCE SIGNS

SSM high-speed DC circuit breaker apparatus

LK Quenching circuit

iFK Internal free-wheeling circuit

eFK External free-wheeling circuit

PK Test circuit

LT1, LT1 Quenching thyristors

K Quenching capacitor

CW Resistor of internal free-wheeling circuit

SS Busbar

VS Vacuum switch

DT Disconnector

EBG Control device

CT Thyristor of internal free-wheeling circuit

RL Return conductor

D Free-wheeling diode

Tp Current-measuring element of test circuit

T Current-detection element

PW Resistor of test circuit

UKC Voltage of quenching capacitor

UiFK Voltage of internal free-wheeling circuit

IL Current of load/short-circuit current

Isu Current of high-speed circuit breaker

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ILK Current of quenching circuit

leFK Current of external free-wheeling circuit

Claims

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1. A high-speed DC circuit breaker apparatus (SSM) that is suitable and intended for

switching off high direct currents in the event of load and short circuit, comprising:

• a disconnector (VS), • a quenching circuit (LK), wherein the quenching circuit (LK) is intended and suitable for generating a

current (ILK) in the opposition direction to the direct current (IL) to be interrupted, and

0 a return conductor (RL),

wherein the return conductor (RL) is intended and suitable for conducting direct currents away from the high-speed DC circuit breaker apparatus

(SSM),

characterized in that

a first free-wheeling circuit (iFK) is provided in the high-speed DC circuit breaker apparatus (SSM) that is intended and suitable for eliminating overvoltages (UiFK)

and/or current peaks that occur during the switching process.

2. The high-speed DC circuit breaker apparatus (SSM) according to claim 1,

characterized in that

a second free-wheeling circuit (eFK) is provided, wherein the second free-wheeling circuit (eFK) comprises a connection for a return

conductor (RL).

3. The high-speed DC circuit breaker apparatus (SSM) according to claim 1 or 2,

characterized in that

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the first (CH) and the second (eFK) free-wheeling circuit extend partially in parallel

and are only partially guided through the high-speed DC circuit breaker apparatus (SSM).

4. The high-speed DC circuit breaker apparatus (SSM) according to one or more of the

preceding claims, characterized in that

the first free-wheeling circuit (iFK) comprises a current-limiting device (CW).

5. The high-speed DC circuit breaker apparatus (SSM) according to claim 4,

characterized in that

the current-limiting device (CW) of the first free-wheeling circuit (iFK) is arranged in

the high-speed DC circuit breaker apparatus (SSM).

6. The high-speed DC circuit breaker apparatus (SSM) according to claim 4 or 5,

characterized in that

the current-limiting device (CW) of the first free-wheeling circuit (iFK) of the high

speed DC circuit breaker apparatus (SSM) is a chopper circuit and/or PTC resistor.

7. The high-speed DC circuit breaker apparatus (SSM) according to one or more of

claims 4 to 6, characterized in that

the quenching circuit (LK) comprises a quenching capacitor (K),

wherein the current-limiting device (CW) of the first free-wheeling circuit (iFK) is connected in parallel to the quenching capacitor (K).

8. A method for switching direct currents, comprising the method steps of:

* testing an electrical characteristic variable of a conductor connected to a high-speed DC circuit breaker apparatus (SSM),

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• activating a disconnector (VS) in the high-speed DC circuit breaker

apparatus (SSM), * disconnecting the electrical circuit by opening two switching contacts (DT) for

interrupting a continuous current (IL),

• quenching the arc that is formed between the switching contacts after the disconnector (VS) is activated,

characterized in that

the high-speed DC circuit breaker apparatus (SSM) is discharged in the event of high voltages (UiFK) and/or currents.

9. The method for switching direct currents according to claim 8,

characterized in that the arc is quenched by discharging a previously charged quenching capacitor (K).

10. The method for switching direct currents according to claim 8 or 9,

characterized in that

the quenching capacitor (K) of the high-speed DC circuit breaker apparatus (SSM) is discharged in the event of high voltages (UiFK).

11. The method for switching direct currents according to claim 10,

characterized in that

the quenching capacitor (K) of the high-speed DC circuit breaker apparatus (SSM) is

discharged by means of a chopper and/or PTC resistor (CW) connected in parallel.

12. The method for switching direct currents according to one or more of claims 8 to 11,

characterized in that

the continuous current (IL) is guided via a metal contact having a vacuum chamber.

13. The method for switching direct currents according to one or more of claims 8 to 12,

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characterized in that

the currents (su) and/or voltages (UKc) flowing through the high-speed DC circuit breaker apparatus (SSM) are dissipated by means of a second free-wheeling circuit

(eFK).

14. The method for switching direct currents according to claim 13,

characterized in that the second free-wheeling circuit (eFK) guides the current (leFK) via a connection for a

return conductor (RL).