Circuit breaker

Abstract

The circuit breaker according to the present invention comprises: a power supply terminal (A); a load terminal (B); a main current interruption mechanical switch (MS) connected between the power supply terminal (A) and the load terminal (B); and commutation paths (S1, C, L, S2, D1, L, S1, C2, S2, D1, S1, C2, L2, S2). The commutation path is connected in parallel to the main current interruption mechanical switch (MS) and comprises, in series, a capacitor (C, C2), an inductor (L, L2), a first auxiliary current interruption mechanical switch (S1) and a second auxiliary current interruption mechanical switch (S2). The first auxiliary current interruption mechanical switch (S1) and the second auxiliary current interruption mechanical switch (S2) are connected to each other in the commutation path by means of at least a capacitor (C; C2) and are actuated simultaneously.

Description

Technical Field

[0001] This invention relates to a circuit breaker, and more specifically, to a DC circuit breaker for low, medium or high voltage applications. Background Technology

[0002] International patent application WO2015 / 062644 discloses a circuit breaker comprising: a current-interrupting switch connected in a transmission line; a commutation path connected in parallel with the current-interrupting switch, including a capacitor, an inductor, and an auxiliary current-interrupting switch connected in series, the commutation path and the current-interrupting switch forming a resonant circuit; a nonlinear resistor connected in parallel with the current-interrupting switch and the commutation path; and a disconnecting switch connected in series with the current-interrupting switch, the commutation path, and the nonlinear resistor connected in parallel in the transmission line.

[0003] Using disconnecting switches to electrically isolate the load in such circuit breakers has several disadvantages. The first disadvantage is that the disconnecting switch must withstand the load current of the transmission line and short-time short-circuit current, thus requiring it to meet numerous requirements. Another disadvantage is that it cannot be immediately actuated to electrically isolate the load after the main switch current is interrupted. Summary of the Invention

[0004] The present invention aims to at least partially overcome these shortcomings.

[0005] Therefore, a circuit breaker is provided, comprising: - Power terminals, - Load terminals, - Main current interruption switch, connected between the power supply terminal and the load terminal. - The commutation path, connected in parallel to the main current interruption switch, includes a capacitor, an inductor, and a first auxiliary current interruption switch connected in series. The feature is that the commutation path further includes a second auxiliary current interruption switch, which is separated from the first auxiliary current interruption switch by at least the capacitor, and is synchronously controlled with the first auxiliary current interruption switch.

[0006] More specifically, the main current interruption switch, the first auxiliary current interruption switch, and the second auxiliary current interruption switch are all mechanical switches and are actuated simultaneously. This provides inherent electrical isolation for the load.

[0007] The capacitors, inductors, and first auxiliary switches in the commutation path can be arranged in any order. Generally, when referring to series connections of components in this document, the order in which these components are connected does not necessarily correspond to the order in which they are cited. Inductors can be the inherent inductance of the cables in the commutation path and may or may not have additional windings. Capacitors can consist of multiple capacitors connected in series and / or in parallel.

[0008] The second auxiliary switch can replace the disconnecting switch of the circuit breaker disclosed in WO2015 / 062644 and ensure electrical isolation between the load and the main current interrupting switch. Since the second auxiliary switch only intervenes during the main switch de-energization and is not located in the transmission line (like the first auxiliary switch), it does not need to meet the requirements of a disconnecting switch. Furthermore, unlike a disconnecting switch, the second auxiliary switch participates in the de-energization process, thus providing electrical isolation to the load immediately after the main switch is de-energized.

[0009] Another advantage of these two auxiliary switches is that they allow the capacitors to be pre-charged using the power supply voltage before the main switch is turned on, without the need for an expensive, insulated external power source.

[0010] The circuit breaker of the present invention may include one or more of the following additional features: - Both the main current interruption switch and the auxiliary current interruption switch are vacuum interrupters; - The first auxiliary current interruption switch and the second auxiliary current interruption switch are mechanically driven by the same actuator; - The first auxiliary current interruption switch, the second auxiliary current interruption switch, and the main current interruption switch are mechanically driven by the same actuator; - The energy absorber is connected in parallel to a portion of the converter path, including a capacitor; - At least one of the first auxiliary current interruption switch and the second auxiliary current interruption switch is connected between the energy absorber and the main current interruption switch. This connection method for the energy absorber avoids the use of a series isolating switch; - In the commutation path, capacitors and inductors are connected between the first auxiliary current interruption switch and the second auxiliary current interruption switch, and energy absorbers are connected between the first auxiliary current interruption switch and the second auxiliary current interruption switch.

[0011] In the commutation path, a capacitor and an inductor are connected between a first auxiliary current interruption switch and a second auxiliary current interruption switch. An energy absorber is connected between the power supply terminal and the second auxiliary current interruption switch, and is connected in parallel with the series connection of the first auxiliary current interruption switch, the capacitor, and the inductor. Due to these characteristics, the energy absorber is only energized during current interruption. - The energy absorber is a non-linear resistor; - The capacitor is pre-charged; - The first and second resistors are connected to the commutation path so that the capacitor can be pre-charged by the current from the power supply terminal. - The first resistor is part of a first path from the power supply terminal to the first terminal of the capacitor, and the second resistor is part of a second path from the second terminal of the capacitor to the second power supply terminal. No switch is provided in either the first or second path. These features facilitate pre-charging of the capacitor without the need for an actuating switch. - A diode (which can be a group of diodes) is connected in parallel to the main current interruption switch when the second auxiliary current interruption mechanical switch is closed; - Set up a diode (which can be a group of diodes) that is connected in parallel to a portion of the commutation path, including a capacitor; - At least one of the first auxiliary current interruption switch and the second auxiliary current interruption switch is connected between the diode and the main current interruption mechanical switch. This diode connection method avoids the use of a series isolating switch; The diode is connected in parallel with the first auxiliary current interruption switch, the capacitor, and the inductor, and is connected between the power supply terminal and the second auxiliary current interruption switch. With this diode connection method, the diode is only energized during current interruption. - A second commutation path is provided, which is connected in parallel to the main current interruption switch and includes a first auxiliary current interruption switch and a second auxiliary current interruption switch, an inductor or a second inductor, and a second capacitor connected in series. Such an additional commutation path is provided, which shares at least the auxiliary switch with the first commutation path, but has its own capacitor, and is capable of optimizing current interruption according to the current direction in the main current interruption switch; - The (first) commutation path further includes a first diode, and the second commutation path further includes a second diode; - The second auxiliary current interruption switch is connected between the energy absorber and the load terminal, and the energy absorber is directly connected to the power supply terminal. - The second resistor can precharge the second capacitor with current from the power supply terminal. Attached Figure Description

[0012] Other features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: - Figure 1 This is a circuit diagram showing a circuit breaker according to a first embodiment of the present invention; - Figure 2 This is a diagram illustrating the mechanical operation sequence of the three vacuum interrupters of a circuit breaker according to a first embodiment of the present invention; - Figure 3 This is a diagram illustrating another mechanical operation sequence of the three vacuum interrupters of a circuit breaker according to a first embodiment of the present invention; - Figure 4 This is a circuit diagram showing a variation of a circuit breaker according to a first embodiment of the present invention; - Figure 5 This is a circuit diagram showing a circuit breaker according to a first embodiment of the present invention, the circuit breaker being provided with a resistor for charging the capacitor of the circuit breaker; - Figure 6 This is a circuit diagram illustrating a circuit breaker according to a second embodiment of the present invention; - Figure 7 This is a circuit diagram showing a circuit breaker according to a third embodiment of the present invention; - Figure 8 This is a circuit diagram illustrating a variation of a circuit breaker according to a third embodiment of the present invention; - Figure 9 This is a circuit diagram showing a circuit breaker according to a third embodiment of the present invention, the circuit breaker being provided with a resistor for charging the capacitor of the circuit breaker. Detailed Implementation

[0013] according to Figure 1 A schematic diagram illustrates an electrical device capable of making or breaking the current between power terminal A and load terminal B, comprising the following components: - MS: A vacuum interrupter connected in a power transmission line and operated as the main switch of a device.

[0014] - ACTMS: Actuator used to drive the main switch MS.

[0015] - S1, S2: Two vacuum interrupters that act as auxiliary switches. Their operation is completely synchronized and preferably operated by a common actuator ACT.

[0016] - ACT: Actuator used to drive both auxiliary switches S1 and S2 simultaneously.

[0017] - EA: A device used to absorb line energy and reduce line current. This function can be achieved using a nonlinear resistor, such as a metal oxide varistor (MOV), like a zinc oxide varistor, which also has voltage limiting functionality. EA elements can be other types of varistors, or other nonlinear resistors such as PTC resistors, or semiconductor types such as transient absorbers (transorbers), or liquid metal arc energy absorption elements.

[0018] - C: Capacitor, which is precharged at a specified voltage in the parallel path to discharge during switching operation.

[0019] - L: The series inductor of the discharge circuit can be the cable inductor of circuits MS, S1, C, and S2.

[0020] The loop or circuit MS, S1, C, L, S2 is a resonant circuit. The path or branch S1, C, L, S2 is a commutation path; when auxiliary switches S1 and S2 are closed, this path diverts current from the transmission line. The second auxiliary switch S2 is preferably directly connected to the load terminal B.

[0021] For DC current interruption using a vacuum interrupter as the main switch, an additional parallel path needs to be connected to the two poles of the main switch MS. This path includes at least a capacitor C and an inductor L for transient current commutation, and preferably includes an energy absorption path containing an energy absorber EA connected across both auxiliary switches S1 and S2.

[0022] Figure 2 The mechanical operation sequence and three mechanical positions are shown. In the stationary state, the three vacuum interrupters MS, S1, and S2 are open. With S1 and S2 remaining open, when vacuum interrupter MS closes, the actuator current is switched on to supply power to load B. The current switching sequence is as follows: first, the main switch MS is opened, and then immediately the two auxiliary switches S1 and S2 are closed simultaneously. The simultaneous closing of S1 and S2 causes the capacitor C across the main switch MS to discharge, generating a reverse current and forcing the current flowing through the main switch MS to cross zero. When i C equals i L At this time, the current in the main switch MS path is interrupted. Once the current flowing through the main switch MS is interrupted, all current will flow through auxiliary switches S1 and S2, and capacitor C will be recharged, but in the opposite voltage direction. Due to the presence of the parallel energy absorber EA, the voltage rise across capacitor C will be limited. At this time, auxiliary switches S1 and S2 will open, and current will still flow through the vacuum arc in auxiliary switches S1 and S2. The voltage rise across the energy absorber EA will reduce the line current flowing through auxiliary switches S1 and S2 to a sufficiently low level, and then drop below the critical value corresponding to the cutoff current, which is an inherent characteristic of vacuum interrupters S1 and S2. At this time, the current flowing through the device is cleared, and the electrical isolation between the load and the power supply is also fully restored.

[0023] Figure 4 for Figure 1 A variation of the embodiment is provided, in which one pole of the energy absorber EA is directly connected to the power supply terminal A. In this case, at the moment when current commutates from capacitor C to energy absorber EA, the current flowing through the first auxiliary switch S1 is interrupted earlier than the current flowing through the second auxiliary switch S2.

[0024] Once the isolation between the two ends of the circuit breaker is restored, the capacitor C can be recharged with the required voltage and polarity. Preferably, it is recharged through a resistor R. high and R low Charged by the power supply voltage, where the resistance R high Connect to power terminal A, resistor R low Connect to ground G, such as Figure 5 As shown, assume G is the ground terminal of the power supply.

[0025] Figure 1 , Figure 4 and Figure 5 Key features of the device: • Due to the vacuum gap between the main switch MS and the second auxiliary switch S2, electrical isolation between the load side and the power supply side can be achieved immediately after the current is interrupted, without the need for an additional series isolator.

[0026] • Neither the first auxiliary switch S1 nor the second auxiliary switch S2 needs to withstand the continuous thermal current flowing through the circuit breaker. Furthermore, auxiliary switches S1 and S2 do not need to withstand short-time short-circuit currents; only the main switch MS must withstand this current. If a series isolator is used, then the isolator must withstand these currents.

[0027] • Due to the presence of auxiliary switches S1 and S2, the capacitor can be as follows: Figure 5 As shown, it is charged by the power supply voltage, requiring no additional high-cost, insulated, high-voltage external DC power supply, and can even be used before the main switch MS is turned on.

[0028] • Figure 4 The embodiments described have several other interesting features. In most cases, the energy absorber EA is not biased, thus eliminating the common overheating risk associated with energy absorbers EA. This is because when an energy absorber, such as EA, is continuously biased close to its rated voltage, leakage current flows through it, causing it to heat up even in idle conditions. This excessively high temperature significantly reduces the line energy it can absorb. To address this, a larger energy absorber would have to be selected. Furthermore, continuous leakage current exacerbates aging effects and drastically shortens the energy absorber's lifespan. The solution shown in this embodiment allows for the selection of a smaller energy absorber EA with a less demanding voltage limit.

[0029] • For applications requiring rapid switching, it is well known that a Thomson coil can be used as the actuator for the main switch MS. Similarly, a Thomson coil can also be used as the actuator for auxiliary switches S1 and S2 to achieve rapid switching operation.

[0030] • The common actuator ACT of auxiliary switches S1 and S2 ensures that the two components are synchronously and briefly closed and immediately opened.

[0031] • In similar Figure 3 In another embodiment, the actuator ACT can also simultaneously cause the main switch MS to operate in the opposite direction to the auxiliary switches S1 and S2. In this case, three different positions are also required: the intermediate position (rest position), in which all switches MS, S1, and S2 are open; the on position, in which the main switch MS is closed to supply power to the load B, and the auxiliary switches S1 and S2 are further open; and the off position, in which the auxiliary switches S1 and S2 are closed, and the main switch MS is significantly open. The last position is a brief operation during the switching process, which is always immediately followed by the opening of the auxiliary switches S1 and S2, returning all switches to the intermediate position (rest position).

[0032] As mentioned above, the current flowing through the main switch MS will be cleared at the zero-crossing point, i.e., i C =i L More precisely, when the current flowing through the main switch MS is lower than the characteristic cutoff current level i of the vacuum interrupter. chop At that time, i.e., ||i L -i C ||≤i chop As experts in vacuum interrupters know, for various reasons, the plasma (arc) within the interrupter may fail to extinguish, causing a reverse increase in the current within the vacuum interrupter's MS (magnetic interrupter). This situation can easily lead to an interruption failure. This fault can be readily observed by increasing the di / dt at the zero-crossing point of the MS current.

[0033] Based on the explanation of this phenomenon, at the current zero-crossing point, the density and temperature of the plasma inside the arc-extinguishing chamber need a certain amount of time to decay in order to meet the current interruption condition and restore electrical isolation. If this condition is not met, plasma re-ignition may occur after the current zero-crossing point.

[0034] The classic way to prevent this adverse situation is to reduce the di / dt characteristic of the capacitor discharge circuit by lowering the resonant frequency of the LC circuit, but this must be done at the cost of using a higher energy capacitor C.

[0035] The present invention also provides an implementation method, namely, as follows: Figure 6 As shown, diode D is inserted into the discharge circuit so that when the capacitor current is greater than the line current, i.e., when i C ≥i LWhen the diode is turned on, it limits the voltage across the arc-extinguishing chamber. The diode D can consist of multiple diodes connected in series and / or parallel. Clearly, when diode D is on, it prevents its voltage from increasing beyond its forward voltage drop. Since the diode is directly connected in parallel with the main switch MS when the second auxiliary switch S2 is closed, it limits the rise in plasma voltage to a very low value. The forward voltage of the diode (a few volts) is much smaller than the arc voltage of the arc-extinguishing chamber (approximately 20 volts), which forces the plasma to cool and collapse within the arc-extinguishing chamber.

[0036] Figure 7 The upgrade scheme uses two diodes D1 and D2 and two capacitors C1 and C2, so that when the line current i L Less than the corresponding capacitor current i in the opposite direction C1 or i C2 When the second auxiliary switch S2 is closed, the voltage can be forcibly reduced to zero. In this configuration, we not only limit the voltage across the main switch MS as previously described, but also force the voltage across the main switch MS to zero because the sum of the opposite forward voltage drops of the two diodes D1 and D2 directly applied to the main switch MS is zero when the second auxiliary switch S2 is closed. Furthermore, during the disconnection operation, regardless of the line current i... L Regardless of the direction, this scheme remains the same. In this embodiment, if the current i in the transmission line... L Flow from power source to load (e.g.) Figure 7 If the current in the transmission line flows from the load to the power source, then the switching path consists of D1, L, S1, C2 and S2.

[0037] Figures 6 to 9 Key features of the device: • Improvements brought about by one or two diodes allow the LC resonant frequency to be increased by reducing the inductance L, thereby enabling the interruption of higher currents than without using diodes, without increasing the capacitor size.

[0038] • Due to the function of switches MS and S2, electrical isolation between the load side and the power supply side can be achieved immediately after the current is interrupted without the need for an additional isolator.

[0039] • In these setups, thermal current and short-time short-circuit current are still borne solely by the main switch MS.

[0040] • Another embodiment of the dual-diode configuration is based on positive i L and negative i L Different breaking requirements necessitate the use of different groups C1-L1 and C2-L2, such as... Figure 8 As shown. For example, if the negative i L The breaking requirement is less than positive i LIf the interruption requirement is met, a smaller and cheaper capacitor can be installed on the C1 side than on the C2 side, and vice versa.

[0041] • Due to the presence of auxiliary switches S1 and S2, such as Figure 9 As shown, capacitors C1 and C2 can be charged by the power supply voltage without the need for an expensive, insulated, high-voltage external power supply.

[0042] This invention is not limited to the embodiments disclosed in the above specification. In particular, Figures 1 to 9 Any combination of the various embodiments constitutes a part of this disclosure.

Claims

1. A circuit breaker, comprising: - Power terminal (A) - Load terminal (B) - A main current interruption mechanical switch (MS) is connected between the power supply terminal (A) and the load terminal (B), and - A commutation path (S1, C, L, S2; D1, L, S1, C2, S2; D1, S1, C2, L2, S2) is connected in parallel to the main current interruption mechanical switch (MS) and includes a capacitor (C; C2), an inductor (L; L2), a first auxiliary current interruption mechanical switch (S1), and a second auxiliary current interruption mechanical switch (S2) connected in series, wherein the first auxiliary current interruption mechanical switch (S1) and the second auxiliary current interruption mechanical switch (S2) are connected to each other in the commutation path through at least the capacitor (C; C2) and are simultaneously actuated.

2. The circuit breaker according to claim 1, wherein, The main current interruption mechanical switch (MS), the first auxiliary current interruption mechanical switch (S1), and the second auxiliary current interruption mechanical switch (S2) are vacuum interrupters.

3. The circuit breaker according to claim 1 or 2, wherein, The first auxiliary current interruption mechanical switch (S1) and the second auxiliary current interruption mechanical switch (S2) are mechanically actuated by the same actuator (ACT).

4. The circuit breaker according to claim 1 or 2, wherein, The first auxiliary current interruption mechanical switch (S1), the second auxiliary current interruption mechanical switch (S2), and the main current interruption mechanical switch (MS) are mechanically actuated by the same actuator (ACT).

5. The circuit breaker according to any one of claims 1 to 4, further comprising an energy absorber (EA) connected in parallel to a portion of the commutation path including the capacitor (C; C2).

6. The circuit breaker according to claim 5, wherein, At least one of the first auxiliary current interruption mechanical switch (S1) and the second auxiliary current interruption mechanical switch (S2) is connected between the energy absorber (EA) and the main current interruption mechanical switch (MS).

7. The circuit breaker according to claim 5 or 6, wherein, In the commutation path, the capacitor (C) and the inductor (L) are connected between the first auxiliary current interruption mechanical switch (S1) and the second auxiliary current interruption mechanical switch (S2), and the energy absorber (EA) is connected between the first auxiliary current interruption mechanical switch (S1) and the second auxiliary current interruption mechanical switch (S2).

8. The circuit breaker according to claim 5 or 6, wherein, In the commutation path, the capacitor (C) and the inductor (L) are connected between the first auxiliary current interruption mechanical switch (S1) and the second auxiliary current interruption mechanical switch (S2), and the energy absorber (EA) is connected between the power supply terminal (A) and the second auxiliary current interruption mechanical switch (S2). The energy absorber (EA) is connected in parallel with the series connection of the first auxiliary current interruption mechanical switch (S1), the capacitor (C), and the inductor (L).

9. The circuit breaker according to any one of claims 5 to 8, wherein, The energy absorber (EA) is a nonlinear resistor.

10. The circuit breaker according to any one of claims 1 to 9, wherein, The capacitors (C; C2) are pre-charged.

11. The circuit breaker according to any one of claims 1 to 10, further comprising a first resistor (R high ) and the second resistor (R) low ), the first resistor (R) high ) and the second resistor (R) low The capacitor (C; C2) is connected to the commutation path so that the capacitor (C; C2) can be precharged using the current from the power supply terminal (A).

12. The circuit breaker according to claim 11, wherein, The first resistor (R) high ) is part of the first path from the power supply terminal (A) to the first terminal of the capacitor (C; C2), and the second resistor (R) low () is a part of a second path from the second terminal of the capacitor (C; C2) to the second power supply terminal (G), in which no switch is provided in the first path and no switch is provided in the second path.

13. The circuit breaker according to any one of claims 1 to 12, further comprising a diode (D; D2) connected in parallel to a portion of the commutation path including the capacitor (C; C2).

14. The circuit breaker according to claim 13, wherein, At least one of the first auxiliary current interruption mechanical switch (S1) and the second auxiliary current interruption mechanical switch (S2) is connected between the diode (D; D2) and the main current interruption mechanical switch (MS).

15. The circuit breaker according to claim 7, further comprising a diode (D), the diode (D) being connected in parallel with the first auxiliary current interruption mechanical switch (S1), the capacitor (C) and the inductor (L) in series connection, and connected between the power supply terminal (A) and the second auxiliary current interruption mechanical switch (S2).

16. The circuit breaker according to any one of claims 1 to 12, further comprising a second commutation path (S2, D2, L, S1, C1; S2, D2, S1, C1, L1), the second commutation path (S2, D2, L, S1, C1; S2, D2, S1, C1, L1) being connected in parallel to the main current interruption mechanical switch (MS) and comprising the first auxiliary current interruption mechanical switch (S1) and the second auxiliary current interruption mechanical switch (S2) connected in series, the inductor (L) or the second inductor (L1) and the second capacitor (C1).

17. The circuit breaker according to claim 16, wherein, The commutation path (D1, L, S1, C2, S2; D1, S1, C2, L2, S2) further includes a first diode (D1), and the second commutation path (S2, D2, L, S1, C1; S2, D2, S1, C1, L1) further includes a second diode (D2).

18. According to the circuit breaker of claim 16 or 17, which is dependent on claim 5, the second auxiliary current interruption mechanical switch (S2) is connected between the energy absorber (EA) and the load terminal (B), and the energy absorber (EA) is directly connected to the power supply terminal (A).

19. The circuit breaker according to any one of claims 16 to 18, which are dependent on claim 11 or 12, wherein the second resistor (R) low This allows the second capacitor (C1) to be precharged using the current from the power supply terminal (A).

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