Switch

Abstract

To suppress surge current generated by charges stored in a capacitor in a circuit breaker in which a mechanical switch and the capacitor are connected in parallel.SOLUTION: This circuit breaker comprises: a mechanical switch 1 for switching between power supplying and cutting-off; a capacitor 21 which is provided in parallel to the mechanical switch 1 and in which current flows when the mechanical switch 1 is opened; and a damping circuit 3 that suppresses surge current generated by charges stored in the capacitor 21 when the mechanical switch 1 is turned on again.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a switch.

Background Art

[0002] As a switch that opens and closes the load current during the normal operation of a power circuit or power equipment and protects the equipment on the load side by interrupting accident currents (especially short-circuit accident currents) in cooperation with a protective relay to prevent the spread of accidents to the upstream side, a conventional one using a semiconductor switch is known. For example, in Patent Document 1, when an accident is detected by either a voltage or current detection circuit, the accident current is diverted and interrupted from a high-speed switch to a semiconductor element (gate turn-off thyristor) within 1 / 8 cycle, and it is described that the accident current can be limited.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above Patent Document 1, interruption and diversion to a semiconductor element are performed using a semiconductor switch, but it is considered that a configuration using a switch in which a mechanical switch and a capacitor are connected in parallel can be inexpensive and obtain the same effect.

[0005] However, if the mechanical switch is re-closed after the mechanical switch is opened and the diversion to the capacitor is completed, the charge accumulated in the capacitor may circulate through the mechanical switch, possibly generating a surge current.

[0006] Therefore, the present invention has been made to solve the above problems, and in a switch in which a mechanical switch and a capacitor are connected in parallel, the main problem is to suppress the surge current generated by the charge accumulated in the capacitor.

Means for Solving the Problems

[0007] That is, the switch according to the present invention includes a mechanical switch that switches the supply and cutoff of power, a capacitor provided in parallel with the mechanical switch, and a current that flows when the mechanical switch is opened. And a damping circuit that suppresses the surge current generated by the charge accumulated in the capacitor when the mechanical switch is re-energized.

[0008] In the switch configured as described above, the impedance of the closed circuit including the capacitor and the damping circuit increases when the mechanical switch is re-energized. Therefore, when the charge accumulated in the capacitor circulates through the closed circuit, the circulating current becomes small, and the generation of the surge current can be suppressed. Specifically, the surge current can be prevented from immediately before the mechanical switch is re-energized to several cycles after re-energization.

[0009] As a mode in which the above-described effects are significantly exhibited, as a specific embodiment for suppressing the surge current, it is preferable that the damping circuit is composed of a resistance element, a reactor element, or a combination of the resistance element and the reactor element.

[0010] When the damping circuit is constantly turned on in the switch, it may interfere with the normal operation of the switch. Therefore, it is preferable that the damping circuit further includes a changeover switch that switches between a turned-on state and a turned-off state.

[0011] In order to control the timing of switching the switching switch, the switch of the present invention further includes a control unit for controlling the switching switch. The control unit preferably controls the switching switch to put the damping circuit into an on state between after the mechanical switch is opened and before it is re-closed. With this configuration, the surge current can be suppressed immediately after the mechanical switch is re-closed.

[0012] There may be a case where the accident current cannot be efficiently limited due to the frequency characteristics of the capacitor. In order to solve this problem, it is preferable to further provide a current-limiting adjustment circuit provided in parallel with the capacitor to supplement the current-limiting by the capacitor.

[0013] When the mechanical switch is opened, in order to prevent arc discharge, the capacitor has a capacitance C of the capacitor, a rated voltage V of the circuit in which the switch is provided, a transient time T which is the time from the start of opening of the mechanical switch until the change amount of the voltage across the mechanical switch stabilizes, and a breaking current i flowing through the mechanical switch when the mechanical switch is opened SW as it is preferably one that satisfies the following formula (1). C×(V / T)>i SW (1)

Advantages of the Invention

[0014] According to the present invention configured as described above, in a switch in which a mechanical switch and a capacitor are connected in parallel, the surge current generated by the charge accumulated in the capacitor can be suppressed.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0016] Hereinafter, an embodiment of a switch 100 according to the present invention will be described with reference to the drawings.

[0017] <Configuration of Switch 100> As shown in FIG. 1, the switch 100 is provided in a main circuit C that connects, for example, a commercial power system and a load, and switches the supply and interruption of power.

[0018] Specifically, this switch 100 includes a mechanical switch 1 that switches the supply and interruption of power, a commutation circuit 2 provided in parallel with the mechanical switch 1, a damping circuit 3 provided in series with the commutation circuit 2, and a changeover switch 5.

[0019] The mechanical switch 1 is configured to be opened and closed driven at a predetermined opening time in response to a signal transmitted from the control device 4.

[0020] The commutation circuit 2 is configured such that current flows (commutates) when the mechanical switch 1 is opened, and it limits the current. Specifically, this commutation circuit 2 is connected in parallel to the mechanical switch 1 and includes a capacitor 21 and a resistance element 22 that are connected in series with each other. The capacitor 21 is specifically, for example, a film capacitor or the like.

[0021] The damping circuit 3 is configured such that when the mechanical switch 1 is reopened after being opened, a surge current generated by the charge accumulated in the capacitor 21 flows through it. Specifically, this damping circuit 3 is connected in parallel to the commutation circuit 2 and includes a resistance element 31 and a reactor element 32.

[0022] The switching switch 5 is connected in parallel to the damping circuit 3 and is configured to switch between a state in which the damping circuit 3 is turned on and a state in which it is not turned on according to a signal transmitted from the control device 4.

[0023] <Operation of the switch 100> The operation of the switch 100 will be described. During normal operation of this switch 100, the mechanical switch 1 is closed, and most of the current flows through the mechanical switch 1. Also, the switching switch 5 is closed, and no current flows through the damping circuit 3.

[0024] When the control device 4 detects an abnormality in the voltage or current of the main circuit C, the control device 4 outputs an open signal to the mechanical switch 1. When the mechanical switch 1 is opened, the impedance of the commutation circuit 2 composed of the series circuit of the capacitor 21 and the resistance element 22 becomes smaller than the arc resistance of the mechanical switch 1, so the current commutates to the commutation circuit 2 and the current is limited. Note that even in this state, the switching switch 5 remains closed.

[0025] After commutation and current limiting are performed, the control device 4 outputs an open signal to the switching switch 5 to open the switching switch 5. When the switching switch 5 is opened and the damping circuit 3 is turned on, next, the control device 4 outputs a close signal to the mechanical switch 1 to turn on the mechanical switch 1. Then, as shown in FIG. 2, a closed circuit D composed of the mechanical switch 1, the commutation circuit 2, and the damping circuit 3 is formed.

[0026] Since the capacitor 21 has accumulated the charges stored when the current is commuted in the commutation circuit 2, when the closed circuit D is formed, a re-commutation of the charges to the mechanical switch 1 occurs, and a current flows so as to circulate through the closed circuit D. In this way, the charges remaining in the capacitor 21 can be discharged.

[0027] Here, since the damping circuit 3 is included in the closed circuit D, the impedance of the entire circuit is sufficiently large, and the generation of surge current in the closed circuit D is suppressed during several cycles from before to after the re-activation of the mechanical switch 1.

[0028] After several cycles have elapsed since the mechanical switch 1 is re-activated and most of the current returns to the steady operation state where the current flows through the mechanical switch 1, the control device 4 outputs a close signal to the switching switch 5 to close the switching switch 5.

[0029] <Selection of Capacitor 21> Note that in the switch 100 of the present embodiment, the capacitor 21 is selected so that when the mechanical switch 1 is opened, the current flowing through the mechanical switch 1 is instantaneously commuted to the commutation circuit 2 without generating an arc.

[0030] FIG. 3 shows an example of the operation waveform when an arc is generated during current interruption in the case where the switch 100 does not include the commutation circuit 2 (that is, includes only the mechanical switch 1). In the switch 100 of the present embodiment, in order to commutate the current to the commutation circuit 2 without generating an arc during current interruption, the resistance of the commutation circuit 2 is the arc resistance R shown in FIG. 3 arkThe minimum value (interrupt current i sw It is necessary to select the resistor 22 so that it is smaller than (when sw is maximum).

[0031] To explain the method of selecting the capacitor 21 of this embodiment more specifically, let the capacitance of the capacitor 21 be C, the rated voltage of the main circuit C where the mechanical switch 1 is provided be V, and the time from the start of the opening (or opening pole) of the mechanical switch 1 until the change amount of the voltage across the mechanical switch 1 stabilizes (also referred to as the transient time) be T, and the interrupt current (maximum) flowing through the mechanical switch 1 when the mechanical switch 1 is opened be i SW As such, the capacitor 21 is selected so as to satisfy the following formula (1). Also, considering the error of each parameter, it is more preferable to select the capacitor 21 so as to satisfy the formula (1)' with a margin. C×(V / T)>i SW (1) C×(V / T)>1.3×i SW (1)'

[0032] The derivation method of the above formula (1) will be explained. In FIG. 1, let the current flowing through the capacitor 21 during commutation be i c、 Assuming that the potential difference applied to the capacitor 21 is dv / dt, the current i c can be expressed by the following formula (2). i c =C×(dv / dt) (2) When the mechanical switch 1 is closed, most of the current flows through the switch with low impedance, so i c ≒0, that is, the potential difference dv / dt applied to the capacitor 21≒0. At the moment when the mechanical switch 1 is opened, due to the voltage change between the terminals of the mechanical switch 1, the current i c flowing through the capacitor 21 increases. At this time, assuming that commutation to the commutation circuit 2 can be completed without generating an arc, it can be said that the voltage between the terminals of the switch rises to the rated voltage of the circuit at the moment when the mechanical switch 1 is opened. Therefore, in this case, dv / dt in the formula (2) is "rated voltage V / switch transient time T", and the current i flowing through the capacitor 21c becomes Equation (3). i c = C × (V / T) (3)

[0033] From Equation (3), it can be seen that in order to maintain the current i flowing through the capacitor 21 even when the transient time T is longer, a larger C (proportional to the length of the transient time T) is required. In Equation (3), this is described in terms of the relationship between "the current i flowing through the capacitor 21 on the left side calculated by calculating without changing the value of the transient time T on the right side" c and the breaking current i of the mechanical switch 1, as follows. In order to divert the breaking current to the commutation circuit 2 without generating an arc when the mechanical switch 1 is opened, the current i c flowing through the capacitor 21 and the breaking current i SW of the mechanical switch 1 need to satisfy the following Equation (4). c The current i SW flowing through the capacitor 21 and the breaking current i i c > i SW (4) By applying the above Equation (2) to the said Equation (4), the above Equation (1) is derived.

[0034] <Advantages of this Embodiment> According to the switch 100 of this embodiment configured as described above, when the mechanical switch 1 is re-closed, the impedance of the closed circuit D including the capacitor 21 and the damping circuit 3 increases. Therefore, when the charge accumulated in the capacitor 21 circulates through the closed circuit D, the circulating current becomes small, and the generation of surge current can be suppressed. Specifically, surge current can be prevented from immediately before the mechanical switch 1 is re-closed to several cycles after re-closure.

[0035] Further, according to the switch 100 of this embodiment, due to the transient phenomenon immediately after the mechanical switch 1 is opened, the impedance of the capacitor 21 can be made smaller than the arc resistance of the mechanical switch 1. Therefore, when the mechanical switch 1 is opened, it is possible to instantaneously divert and limit the current to the commutation circuit 2 without generating an arc.

[0036] <Alternative Embodiment> Note that the present invention is not limited to the above-described embodiment.

[0037] For example, in the switch 100 of the above embodiment, the commutation circuit 2 includes the resistance element 22, but it may not include this.

[0038] Also, in the switch 100, the damping circuit 3 includes the resistance element 31 and the reactor element 32, but it may be a single resistance element, a single reactor element, or a combination of a resistance element and a reactor element, etc.

[0039] As another embodiment, as shown in FIG. 4, in the switch 100, the damping circuit 3 may be connected in series to the mechanical switch 1. In this case, the switching switch 5 needs to be connected in parallel to the damping circuit 3.

[0040] The operation of the switch 100 in the present embodiment will be briefly described below.

[0041] First, in accordance with the open signal from the control device 4, by opening the mechanical switch 1, the current is commutated and limited in the commutation circuit 2. Note that in this state, the switching switch 5 is closed and no current flows through the damping circuit 3.

[0042] After the commutation and current limiting are performed, in accordance with the open signal from the control device 4, the switching switch 5 opens and the damping circuit 3 is turned on. When the damping circuit 3 is turned on, next, in accordance with the close signal from the control device 4, the mechanical switch 1 is turned on again.

[0043] By turning on the mechanical switch 1 and the damping circuit 3, a closed circuit D' composed of the mechanical switch 1, the commutation circuit 2, and the damping circuit 3 is formed as shown in FIG. 5. Then, the charge remaining in the capacitor 21 is discharged by the closed circuit D', so that the generation of surge current in the closed circuit D' is suppressed during several cycles from before to after the mechanical switch 1 is turned on.

[0044] After the mechanical switch 1 is re-energized and several cycles have elapsed, when returning to the steady operation state where most of the current flows through the mechanical switch 1, the control device 4 outputs a closing signal to the switching switch 5 to close the switching switch 5.

[0045] As yet another embodiment, as shown in FIG. 6, in the switch 100, the damping circuit 3 may be connected in parallel to the mechanical switch 1 and the commutation circuit 2. In this case, the switching switch 5 needs to be connected in series to the damping circuit 3.

[0046] The operation of the switch 100 in this embodiment will be briefly described below.

[0047] First, in accordance with the opening signal from the control device 4, by opening the mechanical switch 1, the current is commuted and limited in the commutation circuit 2. Note that in this state, the switching switch 5 is open and no current flows through the damping circuit 3.

[0048] After commutation and current limiting are performed, in accordance with the closing signal from the control device 4, the switching switch 5 closes and the damping circuit 3 is energized. Also, in this state, the mechanical switch 1 remains open.

[0049] By energizing the damping circuit 3, a closed circuit D″ composed of the commutation circuit 2 and the damping circuit 3 is formed as shown in FIG. 7. Then, the charge remaining in the capacitor 21 is discharged by the closed circuit D″, thereby suppressing the generation of surge current in the closed circuit D″ during several cycles before and after the switching switch 5 is energized.

[0050] After the switching switch 5 is energized and several cycles have elapsed, when the control device 4 outputs a closing signal to the mechanical switch 1 and the mechanical switch 1 is re-energized and returns to the steady operation state where most of the current flows through the mechanical switch 1, the control device 4 outputs an opening signal to the switching switch 5 to open the switching switch 5.

[0051] Also, as shown in FIG. 8, the switch 100 may include a current limiting adjustment circuit 6. In this way, for example, when the FRT requirement is demanded, such as when a renewable energy power source is connected to the load side, it is possible to cope with it. As a specific embodiment of the current limiting adjustment circuit 6, a resistance element that is hardly affected by the resonance frequency is preferable.

[0052] In addition, it goes without saying that the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit thereof.

Explanation of reference numerals

[0053] 100 ··· Switch 1 ··· Mechanical switch 2 ··· Commutating circuit 21 ··· Capacitor 22 ··· Resistance element 3 ··· Damping circuit 31 ··· Resistance element 32 ··· Reactor element 4 ··· Control device 5 ··· Changeover switch 6 ··· Current limiting adjustment circuit

Claims

1. A mechanical switch for switching the supply and interruption of power, A capacitor provided in parallel with the mechanical switch and for which current is diverted when the mechanical switch is open, A damping circuit for suppressing the surge current generated by the charge accumulated in the capacitor when the mechanical switch is re-closed, A changeover switch provided in parallel with the damping circuit and for switching between a state in which the damping circuit is on and a state in which it is off, A control unit for controlling the changeover switch, The control unit controls the changeover switch to turn on the damping circuit between when the mechanical switch is opened and when it is re-closed; a switchgear.

2. The switchgear according to claim 1, wherein the damping circuit is composed of a resistive element, a reactive element, or a combination of the resistive element and the reactive element.

3. The switchgear according to claim 1 or 2, further comprising a current-limiting adjustment circuit provided in parallel with the capacitor and for supplementing the current-limiting effect of the capacitor.

4. The capacitor is such that the capacitance of the capacitor is C, the rated voltage of the circuit in which the switchgear is provided is V, the transient time T is the time from the start of opening of the mechanical switch until the change amount of the voltage across the mechanical switch stabilizes, and the interruption current flowing through the mechanical switch when the mechanical switch is opened is i ＳＷ and, the switchgear according to any one of claims 1 to 3 satisfies the following formula (1). C × (V / T) > i ＳＷ (1)

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