CN114303215A

CN114303215A - Direct current breaker

Info

Publication number: CN114303215A
Application number: CN202080047033.5A
Authority: CN
Inventors: 乌利齐·坎特; 萨赫勒·阿哈穆德
Original assignee: Ebolo Co ltd
Current assignee: Ebolo Co ltd
Priority date: 2019-06-28
Filing date: 2020-06-26
Publication date: 2022-04-08
Also published as: WO2020260673A1; EP3991195A1; AU2020307052A1; DE102020116974A1

Abstract

The present invention relates to a high-speed direct current breaker device (SSM) suitable and intended for cutting off high direct currents in the event of loads and short circuits, said high-speed direct current breaker device comprising a disconnector (VS), a quenching circuit (LK) and a return conductor (RL), wherein the quenching circuit (LK) is intended and adapted for generating a current in a direction opposite to the direct current to be interrupted, and wherein the return conductor (RL) is intended for and adapted to conduct a direct current away from the high-speed direct current breaker apparatus (SSM), and wherein a first freewheel circuit (iFK) is provided in the high speed direct current breaker device (SSM), the first freewheel circuit is intended and suitable for eliminating overvoltage and/or current peaks occurring during the switching process, and the invention relates to a corresponding method for arc-free disconnection of a direct-current circuit.

Description

Direct current breaker

The invention relates to a high-speed direct current breaker device (SSM) suitable and intended for breaking high direct current in the event of loads and short circuits, 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 the direct current away from the high-speed direct current breaker device (SSM), and to a corresponding method for arc-free breaking of the direct current circuit.

Prior Art

In order to ensure fault-free and safe operation of vehicles operated with direct current, such as power trains, the supply of power to the interrupted outgoing line must be disconnected from the direct current network quickly and reliably in the event of an undesired operating state or damage for safety reasons. Since the direct current cannot be switched off fast enough by means of conventional switching devices with metallic switching contacts to subject the system to considerable loads, hybrid switches comprising a combination of metallic and semiconductor switching paths are used in particular. Due to the high current strength, these hybrid switches require high quality semiconductor components, which are expensive to purchase. The switching device for cutting off the direct current of the power supply by means of the reverse direct current is simpler in design.

DE 10218806B 4 shows such a high-speed circuit breaker module. The module includes a switchgear between the lines of the rectifying substation and the bus bars. A quenching circuit is arranged in parallel with this switching device, which quenching circuit consists of a quenching capacitor connected in series with a switching cell consisting of two quenching thyristors arranged anti-parallel. The test branch is also arranged in parallel with the switching device. The test branch comprises a series circuit of a test thyristor, a current measuring element and a test resistor. The high-speed direct current breaker device further comprises a freewheel circuit comprising one branch for each current direction from the bus bar to the return conductor and from the line to the return conductor, in each of which branches two freewheel diodes connected in series are arranged. A fuse with a reporting system is assigned in parallel to one freewheeling diode in each branch of the freewheeling circuit. The dimensions of the freewheel diode and the fuse are chosen such that in each case only a small amount of freewheel current flows via the associated fuse, while the majority of the freewheel current flows via the freewheel diode arranged in parallel with the fuse.

This high speed circuit breaker module is designed for breaking systems with grid voltages up to 750V and nominal amperages up to 4000A, overload of which is a common case of railway currents. However, due to the power doubling, this module cannot be used for future emerging systems operating at up to 1500V and 4000A.

It is therefore an object of the present invention to provide a high-speed direct current breaker module which is improved with respect to the prior art, so that systems which operate with direct current and at higher power than before can be switched off quickly and reliably. Another object of the invention is to provide a method for operating a high-speed dc breaker module, by means of which systems running at dc and at higher power than before can be switched off quickly and reliably.

The above object is achieved by means of a high speed direct current breaker apparatus according to claim 1.

The high speed direct current breaker device comprises a disconnector and a quenching circuit. The quenching circuit is intended and adapted for generating a direct current in a direction opposite to the direct current to be interrupted. The high-speed direct current breaker device according to the invention is arranged between a line to be supplied with power and a current bus. The disconnector is usually a vacuum disconnector, by means of which the supply current can be interrupted quickly and reliably. Furthermore, the high speed direct current breaker device comprises a return conductor intended and adapted for conducting direct current away from the high speed direct current breaker device. According to the invention, the high-speed direct current circuit breaker device also comprises a first free-wheeling circuit intended and adapted for eliminating overvoltage and/or current peaks occurring during the switching process. The first freewheel circuit is connected to the return conductor and prevents damage to components arranged in the high-speed direct current breaker apparatus in case the voltage peak in the arrangement exceeds 1500V. Therefore, the high-speed dc breaker device according to the invention can be used in dc networks typically in the range of 220V to 1000V and with a current strength of up to 8 kA.

In a development of the invention, a second freewheel circuit is provided. The second freewheel circuit includes a connection for the return conductor. The second freewheeling circuit ensures that the energy present in the inductor of the line after a fast switch-off by the disconnector is dissipated quickly by means of the freewheeling current. Any voltage peaks are eliminated by means of the first freewheel circuit.

In another aspect of the invention, the first and second freewheel circuits extend partly in parallel and are only partly guided through the high-speed direct current breaker device. This ensures that current flows through the first freewheel circuit only in the event of a voltage peak. The second freewheel circuit dissipates electrical energy that is often generated during turn-off. The two freewheel circuits are also separated from each other by means of a rectifier diode. In particular, the second freewheel circuit is partly arranged outside the high-speed direct current breaker device. Thus, in particular, a high-speed direct current breaker apparatus can be arranged in a limited space.

In a further embodiment of the invention, the first freewheel circuit comprises a current limiting device. The current limiting means are typically resistors which advantageously have a high thermal conductivity. Thus, the current limiting device in the first freewheel circuit converts the conducted electrical energy into heat very efficiently and quickly.

In another embodiment of the invention, the current limiting device of the first freewheel circuit is arranged in a high-speed direct current breaker apparatus. The current limiting device is thus protected from the weather by the housing of the high-speed direct current circuit breaker apparatus and may additionally be equipped with a cooling system in order to effectively dissipate the heat generated in the current limiting device.

In another embodiment of the invention, the current limiting means of the first freewheel circuit of the high-speed direct current circuit breaker device is a chopper circuit and/or a Positive Temperature Coefficient (PTC) resistor. The resistance of the current limiting device thus increases with temperature (which increases due to the current flow in the current limiting device) and thus limits the current flowing through the first freewheel circuit.

In another embodiment of the invention the quenching circuit comprises a quenching capacitor. The current limiting means of the first freewheel circuit are connected in parallel with the quenching capacitor. In order to ensure the operational readiness of the high-speed direct current circuit breaker device, the quenching capacitor is continuously charged between the discharging processes.

The above object is also achieved by means of a method for switching direct current according to claim 8. The development of the method is described in claims 9 to 14.

The method according to the invention for switching a direct current comprises the following four method steps: in a first method step, the voltage of a conductor connected to a high-speed direct current circuit breaker device is tested. For this purpose, the 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 faulty supply. In a second method step, a disconnector in the high-speed direct current circuit breaker device is activated. The disconnector disconnects the bus bar supplying the dc conductor with electrical energy from the energy source. In a third method step, the circuit is opened by opening the two switching contacts to interrupt the continuous current flow. By opening the switch contacts, an arc is generated between the switch contacts. In a fourth method step, the arc formed between the switching contacts after the activation of the disconnector is quenched. To this end, a current in the opposite direction to the current flowing in the disconnector is conducted to the disconnector. The two currents are superimposed on each other and cancel each other out so that the resulting amperage is 0A.

According to the invention, the high-speed direct current breaker device discharges in the event of high voltage and/or high current. As a result, in the case where the voltage peak value exceeds 1500V in the high-speed direct current breaker apparatus, damage to the components arranged therein is prevented.

In another embodiment of the invention, the arc is quenched by discharging a pre-charged quenching capacitor. The quenching capacitor is charged between the discharging processes to ensure operational readiness of the high speed direct current circuit breaker device such that a current is generated which is opposite to the current of the arc when the capacitor is discharged.

In another embodiment of the invention, the quenching capacitor of the high speed direct current breaker device is discharged in case of a high voltage. The quenching capacitor is charged between the discharging processes to ensure operational readiness of the high speed direct current circuit breaker device such that a current is generated which is opposite to the current of the arc when the capacitor is discharged.

In a development of the invention, the quenching capacitor of the high-speed direct current circuit breaker device is discharged by means of a chopper and/or a PTC resistor connected in parallel. The chopper and/or PTC resistor typically have a high thermal conductivity. Thus, the discharge of the electrical energy stored in the capacitor is converted very efficiently and quickly into heat.

In another embodiment of the invention, the continuous current is conducted via a metal contact having a vacuum chamber. The vacuum chamber comprises a disconnector by means of which the supply current can be interrupted in a fast and reliable manner. Furthermore, no plasma is formed in the vacuum chamber which dirties the contacts and requires laborious cleaning at regular intervals. In addition, the vacuum chamber has good insulation against current and high safety level for people, especially maintenance personnel.

In a further embodiment of the invention, the current and/or the voltage flowing through the high-speed direct current circuit breaker device is dissipated by means of a second freewheeling circuit. The second freewheeling circuit ensures that the energy present in the inductor of the line after a fast switch-off by the disconnector is dissipated quickly by means of the freewheeling current. Any voltage peaks are eliminated by means of the first freewheel circuit.

In another embodiment of the invention, the second freewheel circuit conducts current via the connection for the return conductor. The return conductor conducts the dc current away from the high speed dc breaker apparatus.

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

The figures show:

FIG. 1: circuit diagram of an exemplary embodiment of a high-speed direct current breaker device according to the present invention

FIG. 2 a: when the time t of the switching process is 0ms, the current flow for disconnecting the switching device and triggering the quenching thyristor for high currents

FIG. 2 b: when the time t of the switching process is 0ms, the current flow for disconnecting the switching device and triggering the quenching thyristor for high currents

FIG. 3 a: when the time t of the switching process is 0.25ms, the current flow for disconnecting the switching device and triggering the quenching thyristor for high currents

FIG. 3 b: when the time t of the switching process is 0.25ms, the current flow for disconnecting the switching device and triggering the quenching thyristor for high currents

FIG. 4 a: current flow for disconnecting the switching device and triggering the quenching thyristor for high currents when the time t of the switching process is >1.2ms

FIG. 4 b: current flow for disconnecting the switching device and triggering the quenching thyristor for high currents when the time t of the switching process is >1.2ms

FIG. 5 a: when the time t > of the switching process is 2ms, the current flow for disconnecting the switching device for high currents and triggering the quenching thyristor is initiated

FIG. 5 b: current flow for disconnecting the switching device and triggering the quenching thyristor for high currents when the time t of the switching process is >2ms

FIG. 6 a: when switching the internal freewheel circuit, the current flow for disconnecting the switching device and triggering the quenching thyristor for large currents is set to 2ms at the time t > of the switching process

FIG. 6 b: when switching the internal freewheel circuit, the current flow for disconnecting the switching device and triggering the quenching thyristor for large currents is set to 2ms at the time t > of the switching process

Fig. 1 shows a schematic arrangement of the circuitry of a device SSM according to the present invention. In this and the following exemplary embodiments, the high speed circuit breaker device SSM is arranged on a direct current traction power supply. The high-speed circuit breaker device SSM is connected on one side to the bus SS of the traction power supply and on the other side to the line ST by means of a double-pole disconnector DT. In the disconnected state, the line is electrically isolated from the bus by means of a double-pole disconnector DT.

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

An internal freewheeling circuit iFK is also arranged in parallel with the vacuum switch VS and is connected between the quenching capacitor K and the quenching thyristors LT1, LT 2. The internal freewheel circuit iFK includes a thyristor CT, an anti-parallel freewheel diode D connected in series, and a resistor (chopper and/or PTC resistor) between them.

A test circuit PK, which checks the current state of the line before it is turned back on, is also arranged in parallel with the vacuum switch VS. The test circuit PK comprises a series circuit of a switch VP, a current measuring element Tp and a test resistor PW. The test thyristor VP is triggered to test 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 device comprises a second free-wheeling circuit eFK comprising two branches, one of which is arranged between the connections of the vacuum switch VS and the other of which is arranged between the line ST and the return conductor RL. The second freewheel circuit eFK includes a freewheel diode D. The second freewheeling circuit eFK ensures that after the galvanic isolation path is established in the vacuum switch VS, the energy present in the inductor of the line is quickly dissipated by means of the freewheeling current. When the operating current reaches a predetermined limit value, the switching-off process is automatically triggered by means of the control device EBG.

The control device EBG processes the recorded measurements and outputs corresponding control commands to the vacuum switch VS and the quenching thyristors LT1, LT 2. After evaluation of the current signal from the current detection element T and the rate of current increase, the opening process of the vacuum switch VS is automatically initiated in accordance with the set limit value. The quenching thyristors LT1, LT2 are actuated in a time-optimized manner depending on the operating current to be switched and the size of the quenching circuit, in particular the capacitance of the quenching capacitor K. Line tests are also carried out with the aid of the control device EBG, in which the line resistance is calculated taking into account the current output voltage. In addition, the control device EBG regulates the actuation of the thyristor CT and thus the activation of the internal freewheel circuit iFK in case of high power.

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

Fig. 3 shows the current flow for switching off the switching device SSM for high currents and triggering the quenching thyristors LT1, LT2 at time t of 0.25 ms. Fig. 3a) shows the circuits of the high-speed direct current circuit breaker device according to fig. 1, which are active at this time. When a settable operating current of, for example, 4kA is reached, the control unit EBG issues a switch-off command to the vacuum switch VS and the drive starts to separate the contacts of the vacuum switch VS (fig. 3 a). An arc is generated 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 a maximum distance between the contacts of 2 mm. The short-circuit current IL continues to flow during the contact lifting via a switching arc formed inside the vacuum chamber (fig. 3 b).

Fig. 4 shows the current flow for opening the switching device SSM and triggering the quenching thyristors LT1, LT2 for large currents at times t >1.2 ms. Fig. 4a) shows the circuits of the high-speed direct current circuit breaker device according to fig. 1, which 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 a value of 0A, since the vacuum switch VS itself cannot cut off the flowing short-circuit current IL. For this purpose, the control unit EBG actuates the quenching thyristor LT1, which activates the quenching circuit LK. By precharging the quenching capacitor K a current ISU (fig. 4b) is generated in the quenching circuit LK, which current is opposite to the current IL (fig. 4a) flowing in the vacuum switch VS. The two currents flowing in the vacuum switch VS, i.e. the short-circuit current IL and the quenching current ISU, are superimposed on each other. The two currents, i.e. the short-circuit current IL and the quenching current, each have a current in opposite directions with such a magnitude that the resulting switching current reaches a value of 0A. 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 on 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 no longer ignited and the short-circuit current IL is cut off.

In particular, current rail vehicles, also including non-rail motor vehicles (e.g. electric cars or electric buses), are able to feed back energy generated during negative acceleration into the overhead line or into the integrated battery (recuperation). Therefore, it should also be assumed for the switching device SSM according to the invention that the current direction is opposite to the above-described current direction (fig. 2 to 4). In this case, the current ISU in the vacuum switch VS and in the quenching circuit LK also flows in the opposite direction to the above-mentioned one. As a result, the quenching capacitor K in the quenching circuit LK is also charged and polarized in the opposite 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 traction currents of different polarities, without additional components.

Fig. 5 shows the current flow for switching off the switching device SSM for high currents and triggering the quenching thyristors LT1, LT2 at time t > -2 ms. Fig. 5a) shows the circuits of the high-speed direct current circuit breaker device according to fig. 1, which are active at this time. At this time, since the arc in the vacuum switch VS has been extinguished, the current IeFK flows through a second freewheeling circuit eFK arranged partly outside the high-speed circuit breaker device SSM and through a quenching circuit LK (fig. 5a), wherein the quenching capacitor K serves as an intermediate storage. The quenching capacitor K is also recharged (pre-charged) in the process. The external freewheel circuit eFK ensures that the energy present in the line ST is dissipated due to the flowing freewheel current IeFK after the galvanic isolation path has been established (fig. 5 b). In order to safely and reliably interrupt the flowing direct current IL even in an abnormal situation, it may be provided to trigger the quenching thyristors LT1, LT2 repeatedly. Thus, the method according to the invention shown in fig. 2 to 5 can be repeated, if desired.

Fig. 6 shows the current flow for switching off the switching device SSM for high currents and triggering the quenching thyristors LT1, LT2 at time t >2 ms. To absorb any overload voltage spikes UKC that may occur, the internal freewheel circuit iFK is switched in this exemplary embodiment. Fig. 6a) shows the circuits of the high-speed direct current circuit breaker device according to fig. 1, which are active at this time. The energy stored in the high-speed circuit breaker device SSM at this time charges the quenching capacitor K after the arc in the vacuum switch VS is quenched (see fig. 5). In this process, a charging voltage UKC may be reached that exceeds the safety limits of the high speed circuit breaker device SSM and any other components connected thereto, so that damage may occur. If the charging voltage exceeds 1500V, the internal freewheel circuit iFK is activated (FIG. 6 a). For this reason, the control device EBG triggers the thyristor CT (fig. 6b) when the resistance in the quenching circuit LK exceeds 300m Ω. If the charging voltage UKC of capacitor K drops below the value of 1100V, the thyristor is disabled again. The triggering and disabling of the thyristor CT is repeated until the charging voltage UKC of the capacitor K is always below 1500V. As a result, the resulting overvoltage UKC remains below the arc voltage that is often present in conventional high speed circuit breakers.

Once the current is 0A and all voltages UKC, UiFK have dissipated, the double disconnector DT (fig. 7a) and fig. 7b) is opened). This reactivates the switching means SSM.

Description of the reference numerals

SSM high-speed direct current breaker device

LK quenching circuit

iFK internal freewheel circuit

eFK external free-wheeling circuit

PK test circuit

LT1, LT1 quenching thyristor

K quenching capacitor

Resistor of CW internal freewheel circuit

SS bus

VS vacuum switch

DT isolating switch

EBG control device

Thyristor of CT internal follow current circuit

RL return conductor

D freewheeling diode

Current measuring element of Tp test circuit

T current detection element

Resistor of PW test circuit

UKC quenching the voltage of the capacitor

Voltage of UiFK internal freewheeling circuit

IL load current/short circuit current

ISU high speed breaker current

ILK quench circuit current

Iefk external freewheel circuit current

Claims

1. A high-speed direct current breaker device (SSM) suitable and intended for switching off high direct current in case of loads and short circuits, comprising:

an isolating switch (VS),

a quenching circuit (LK),

wherein the quenching circuit (LK) is intended and adapted for generating a current (ILK) in a direction opposite to the direct current (IL) to be interrupted, and

a return conductor (RL),

wherein the return conductor (RL) is intended and adapted for conducting a direct current away from the high-speed direct current breaker apparatus (SSM),

it is characterized in that

A first free-wheeling circuit (iFK) is provided in the high-speed direct current breaker device (SSM), said first free-wheeling circuit being intended and adapted for eliminating overvoltage (UiFK) and/or current peaks occurring during a switching process.

2. High speed direct current breaker device (SSM) according to claim 1,

it is 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. High speed direct current breaker device (SSM) according to claim 1 or 2,

it is characterized in that

The first and second freewheel circuits (CH, eFK) extend partly in parallel and are only partly guided through the high-speed direct current breaker device (SSM).

4. High-speed direct current breaker apparatus (SSM) according to one or more of the preceding claims,

it is characterized in that

The first free-wheeling circuit (iFK) includes a current limiting device (CW).

5. High speed direct current breaker device (SSM) according to claim 4,

it is characterized in that

The current limiting arrangement (CW) of the first freewheel circuit (iFK) is arranged in the high-speed direct current breaker device (SSM).

6. High speed direct current breaker device (SSM) according to claim 4 or 5,

it is characterized in that

The current limiting means (CW) of the first freewheel circuit (iFK) of the high-speed direct current breaker device (SSM) is a chopper circuit and/or a PTC resistor.

7. High-speed direct current breaker apparatus (SSM) according to one or more of claims 4 to 6,

it is characterized in that

Said quenching circuit (LK) comprising a quenching capacitor (K),

wherein the current limiting means (CW) of the first freewheel circuit (iFK) is connected in parallel with the quenching capacitor (K).

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

testing electrical characteristic variables of conductors connected to a high speed direct current breaker device (SSM),

-activating a disconnector (VS) in the high-speed direct current breaker device (SSM),

-breaking the circuit by opening the two switching contacts (DT) to interrupt the continuous current (IL),

quenching the arc formed between the switch contacts after activation of the disconnector (VS),

it is characterized in that

The high-speed direct current circuit breaker device (SSM) discharges at a high voltage (UiFK) and/or a high current.

9. Method for switching a direct current according to claim 8,

it is characterized in that

Quenching the arc by discharging a pre-charged quenching capacitor (K).

10. Method for switching a direct current according to claim 8 or 9,

it is characterized in that

The quenching capacitor (K) of the high-speed direct current breaker device (SSM) is discharged at a high voltage (UiFK).

11. Method for switching a direct current according to claim 10,

it is characterized in that

The quenching capacitor (K) of the high-speed direct current breaker device (SSM) is discharged by means of a chopper and/or PTC resistor (CW) connected in parallel.

12. Method for switching a direct current according to one or more of claims 8 to 11,

it is characterized in that

The continuous current (IL) is conducted via a metal contact with a vacuum chamber.

13. Method for switching a direct current according to one or more of claims 8 to 12,

it is characterized in that

The current (ISU) and/or the voltage (UKC) flowing through the high speed direct current breaker device (SSM) is dissipated by means of a second freewheeling circuit (eFK).

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

it is characterized in that

The second free-wheeling circuit (eFK) conducts a current (IeFK) via a connection for a return conductor (RL).