Current interruption device and current interruption method

Abstract

According to the present invention, a main circuit breaker (110) is disposed in the path of a main current (Icb). A commutation circuit (150) is connected in parallel to the main circuit breaker (110), and is configured to superimpose an oscillating current (Ios), the amplitude of which periodically increases after the main circuit breaker (110) is opened, on the main current. The commutation circuit (150) includes an AC power source that operates after the main circuit breaker (110) is opened, and generates the oscillating current (Ios) such that, after activation of the AC power source, the rate of increase in amplitude having the same polarity as the main current (Icb) is smaller than the rate of increase in amplitude having a polarity opposite to that of the main current (Icb).

Description

Current interruption device and current interruption method

[0001] The present disclosure relates to a current interruption device and a current interruption method.

[0002] In DC systems such as DC power transmission, current interruption devices are used to interrupt DC current in the event of a fault. Because zero-crossing points of the current do not occur in DC systems, current interruption devices are known that are configured to generate zero-crossing points by superimposing AC current on the current to be interrupted.

[0003] For example, Japanese Patent No. 7017510 (Patent Document 1) describes a control method in which, when a main circuit breaker is controlled to open in order to interrupt the main current, energy is injected into a loop through which an AC current flows that is superimposed on the main current in order to realize a zero crossing, thereby rapidly increasing the amplitude of the AC current.

[0004] Furthermore, the patent also describes limiting the rate of rise and peak of the current flowing through the loop by arranging an energy absorbing element to limit the voltage across the inductive element in the loop.

[0005] Patent No. 7017510

[0006] In the circuit breaking device of Patent Document 1, the amplitude of the AC current exceeds the main current to be cut off, causing a zero crossing point of the main current. Therefore, by injecting energy, the amplitude of the AC current is suddenly increased, and it is expected that a large main current can be quickly cut off.

[0007] On the other hand, in Patent Document 1, the amplitude of the AC current superimposed on the main current is increased, thereby increasing the maximum value of the main current in the period until the zero-crossing point occurs. As a result, there is a concern that as the energy injected into the arc discharge generated in the opened main circuit breaker increases, the electrical conductivity of the arc discharge increases and the current interruption performance deteriorates. There is also a concern that an increase in the maximum value of the main current will lead to an increase in the size of the current interruption device including the main circuit breaker.

[0008] The present disclosure has been made to solve such problems, and an object of the present disclosure is to improve the current interruption performance in interrupting direct current and to reduce the size of the device.

[0009] According to one aspect of the present disclosure, there is provided a current interruption device. The current interruption device includes a main circuit breaker arranged in a path of a main current and a commutation circuit. The commutation circuit is connected in parallel to the main circuit breaker and configured to superimpose an oscillating current, the amplitude of which periodically increases, on the main current after the main circuit breaker opens. The commutation circuit includes an AC power supply that operates after the main circuit breaker opens, and generates the oscillating current such that, after startup of the AC power supply, the rate of increase in amplitude of a current with the same polarity as the main current is smaller than the rate of increase in amplitude of a current with an opposite polarity to the main current.

[0010] According to another aspect of the present disclosure, there is provided a current interruption method, comprising the steps of: opening a main circuit breaker disposed in a path of a main current in response to detection of an abnormality in the main current; starting an AC power supply in a commutation circuit connected in parallel to the main circuit breaker in response to the opening of the main circuit breaker; and using a current whose amplitude periodically increases when the AC power supply is activated, superimposing an oscillating current generated by the commutation circuit on the main current such that the rate of increase in amplitude of a current with the same polarity as that of the main current is smaller than the rate of increase in amplitude of a current with an opposite polarity to that of the main current.

[0011] According to the present disclosure, the amplitude of the oscillating current of the same polarity as the main current that is superimposed on the main current after the main circuit breaker is opened is suppressed, and therefore the maximum value (absolute value) until the zero-cross point of the main current is reduced, thereby suppressing the energy injected into the arc discharge that occurs after the main circuit breaker is opened, thereby improving the current interruption performance and making the device more compact.

[0012] 1 is a block diagram illustrating the configuration of a current interruption device according to a first embodiment. FIG. 1 is a conceptual waveform diagram illustrating the interruption operation of a fault current by a current interruption device according to a comparative example. FIG. 2 is a conceptual waveform diagram for illustrating the basic concept of the operation of the current interruption device according to the first embodiment. FIG. 3 is a conceptual waveform diagram illustrating a first operation example of the commutation circuit shown in FIG. 1. FIG. 4 is a conceptual waveform diagram illustrating a second operation example of the commutation circuit shown in FIG. 1. FIG. 5 is a conceptual waveform diagram illustrating a third operation example of the commutation circuit shown in FIG. 1. FIG. 6 is a conceptual waveform diagram illustrating a fourth operation example of the commutation circuit shown in FIG. 1. FIG. 7 is a circuit diagram illustrating the configuration and operation of a current interruption device according to a second embodiment. FIG. 8 is a circuit diagram further illustrating the operation of the current interruption device shown in FIG. 8. FIG. 9 is a circuit diagram illustrating the configuration of a current interruption device according to a modification of the second embodiment. FIG. 10 is a circuit diagram further illustrating the configuration and operation of a current interruption device according to a third embodiment. FIG. 11 is a circuit diagram further illustrating the operation of the current interruption device shown in FIG. 12. FIG. 12 is a timing chart illustrating a first operation of the current interruption device shown in FIG. 12. FIG. 13 is a timing chart illustrating a second operation of the current interruption device shown in FIG. 12. FIG. 14 is a circuit diagram illustrating the configuration and operation of a current interruption device according to a fourth embodiment. FIG. 17 is a conceptual waveform diagram illustrating the operation of the current interruption device shown in FIG. 16. FIG. 18 is a circuit diagram illustrating the configuration and operation of a current interruption device according to a fifth embodiment. FIG. 19 is a circuit diagram further illustrating the operation of the current interruption device shown in FIG. 18. FIG. 19 is a circuit diagram illustrating the configuration and operation of a current interruption device according to a modified example of the fifth embodiment. FIG. 20 is a first flowchart illustrating the control process of a current interruption method according to the present disclosure. FIG. 21 is a second flowchart illustrating the control process of a current interruption method according to the present disclosure. FIG. 22 is a first circuit diagram illustrating a modified example of a current interruption device according to the present disclosure. FIG. 23 is a second circuit diagram illustrating a modified example of a current interruption device according to the present disclosure.

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings will be denoted by the same reference numerals, and their description will not be repeated in principle.

[0014] First Embodiment In a first embodiment, the concept of a current interruption device according to the present disclosure will be described.

[0015] Fig. 1 is a block diagram illustrating the configuration of a current interruption device 100 according to embodiment 1. As shown in Fig. 1 , the current interruption device 100 includes a main circuit breaker 110, a control circuit 120, and a commutation circuit 150.

[0016] The main circuit breaker 110 is disposed on a path of a main current Icb generated between the power source 10 and the load 20. The main circuit breaker 110 is configured to be able to open and close contacts using a mechanical switch, a semiconductor relay, or the like. The main circuit breaker 110 is normally closed, and is configured to open in response to an open command Sop from the control circuit 120.

[0017] The control circuit 120 can generate an opening command for the main circuit breaker 110 when an overcurrent is detected, based on the current detected by the current sensor 101 arranged in the path of the main current Icb.

[0018] The commutation circuit 150 is connected in parallel to the main circuit breaker 110, and generates an oscillating current Ios that is superimposed on the main current Icb after the main circuit breaker 110 opens. In response to the issuance of an opening command Sop to the main circuit breaker 110, the control circuit 120 provides the commutation circuit 150 with a control signal instructing it to start generating the oscillating current Ios.

[0019] 1, the control circuit 120 is an element of the current interruption device 100, but the control circuit 120 may also be an external element of the current interruption device 100. In other words, the opening command Sop of the main circuit breaker 110 and the control signal of the commutation circuit 150 may be input from outside the current interruption device 100.

[0020] 2 is a conceptual waveform diagram illustrating the fault current interruption operation of a current interruption device according to a comparative example, which shows an interruption operation similar to that of Patent Document 1.

[0021] 2 , when the main current Icb becomes excessive in response to the occurrence of a fault, the main circuit breaker 110 is opened at time t0. After time t0, the oscillating current Ios generated by the commutation circuit 150 is superimposed on the main current Icb. As a result, the main current Icb is represented by the sum of the DC current (corresponding to the fault current) before the main circuit breaker 110 is opened and the oscillating current Ios.

[0022] 2, the commutation circuit 150 generates an AC current (resonant current) using a resonant circuit as an oscillating current Ios whose amplitude increases periodically, similar to Patent Document 1. In the comparative example, it can be seen from the waveform of the main current Icb that the rate of increase in the amplitude of the oscillating current Ios is the same for both current directions (polarities).

[0023] At time t0, when the main circuit breaker 110 is opened, an arc discharge occurs between the open contacts. After time t0, the main current Icb shown in Fig. 2 passes through the location where the arc discharge occurred. The oscillating current Ios, whose amplitude increases, is superimposed on the main current Icb, quickly generating a zero-crossing point where Icb = 0 (time t1 in Fig. 2). Under normal conditions, the interruption of the main current Icb is completed at the timing when this zero-crossing point occurs, and Icb = 0 is maintained even after time t1.

[0024] However, if a large amount of energy is injected into the arc before the zero-cross point occurs, the arc temperature rises, increasing the electrical conductivity. If the electrical conductivity increases, the current cannot attenuate at the zero-cross point, and the current continues to flow thereafter, which may result in an interruption error.

[0025] Since the energy injected into the arc depends on the magnitude of the main current Icb after the main circuit breaker 110 is opened, there is a concern that the maximum value I1 of the main current Icb after time t0, which is caused by the oscillating current Ios being amplified to generate the zero-crossing point, may become excessive, causing the above-mentioned interruption abnormality.

[0026] Therefore, in the current interruption device according to the present disclosure, the oscillating current Ios superimposed by the commutation circuit 150 is controlled to suppress the main current Icb.

[0027] FIG. 3 is a conceptual waveform diagram for explaining the basic concept of the operation of the current interruption device according to the first embodiment.

[0028] As shown in FIG. 3, the commutation circuit 150 shown in FIG. 1 generates an oscillating current Ios whose amplitude periodically increases to generate a zero-crossing point and is superimposed on a main current Icb including a DC current (fault current) Io to be interrupted, such that the rate of increase in the amplitude of the current with the same polarity as the main current Icb is smaller than the rate of increase in the amplitude of the current with the opposite polarity to the main current Icb.

[0029] In the example of Figure 3, the fault current I0, i.e., the main current Icb when the main circuit breaker 110 is open, is positive, so the amplitude of the oscillating current Ios increases in the negative direction every cycle, while the rate of increase in the positive amplitude is more suppressed than the rate of increase in the negative amplitude.

[0030] As a result, the maximum value I1 of the main current Icb after the main circuit breaker 110 is opened (after time t0) is significantly reduced compared to Fig. 2. As a result, by reducing the energy injected into the arc after the main circuit breaker 110 is opened and reducing the temperature and electrical conductivity of the arc, the reliability of current interruption at the zero-crossing point can be increased, thereby improving interruption performance. Furthermore, reducing the maximum value (absolute value) of the main current Icb until current interruption can particularly contribute to the miniaturization of the main circuit breaker 110 in design.

[0031] As will be explained in the following embodiments, various circuit configurations can be applied to the commutation circuit 150 for realizing the concept shown in FIG. 3, as can be understood from the operational examples of FIGS. 4 to 7.

[0032] 4 to 7 show conceptual waveform diagrams of the main current Icb superimposed with the oscillating current Ios by the commutation circuit 150 in the first to fourth operation examples of the commutation circuit 150, respectively.

[0033] As an example, as shown in the first operation example of FIG. 4, the commutation circuit 150 can suppress the maximum value I1 of the main current Icb between times t0 and t1 by superimposing an oscillating current Ios, which is obtained by half-wave rectifying a sinusoidal current with a constant period whose amplitude increases periodically, on the main current Icb.

[0034] Alternatively, as shown in the second operation example of FIG. 5, the commutation circuit 150 can suppress the maximum value I1 of the main current Icb between times t0 and t1 by superimposing the oscillating current Ios, which is obtained by full-wave rectifying a sinusoidal current with a constant period whose amplitude increases periodically, on the main current Icb.

[0035] 6, the period Tc of the oscillating current Ios superimposed on the main current Icb by the commutation circuit 150 does not necessarily have to be constant. Similarly, as shown in the third operation example in Fig. 7, the oscillating current Ios superimposed on the main current Icb by the commutation circuit 150 is not limited to a sinusoidal current and may be, for example, a square wave current.

[0036] However, in general, as disclosed in Patent Document 1, the commutation circuit 150 can be efficiently configured by generating an oscillating current Ios to be superimposed on the main current Icb based on a sinusoidal current with a constant period corresponding to a resonant frequency generated using a resonant circuit. In the second and subsequent embodiments, configuration examples of the commutation circuit 150 for realizing the current interruption device according to the first embodiment will be sequentially described.

[0037] Second Embodiment Fig. 8 is a circuit diagram illustrating the configuration and operation of a current interruption device 100A according to a second embodiment.

[0038] 8, a current interruption device 100A is configured to include a commutation circuit 150A instead of the commutation circuit 150 in the current interruption device 100 of Fig. 1. That is, the main circuit breaker 110 is arranged in the same manner as in Fig. 1, and is connected between a node N1 connected to the power supply 10 and a node N2 connected to the load 20.

[0039] In the following description, the direction in which the main current Icb flows from the power supply 10 to the load 20 (from left to right in the figure) is defined as the "positive direction" of the current, and the opposite direction (from right to left in the figure) is defined as the "negative direction."

[0040] The commutation circuit 150A includes a resonant circuit 151 including an AC power supply 160, a capacitor C1, and a rectifying element 170. The AC power supply 160 is activated or stopped in response to a control command PACon from the control circuit 120 ( FIG. 1 ). When activated (for example, while the control command PACon is at H level), the AC power supply 160 outputs an AC voltage of a predetermined frequency.

[0041] The resonant circuit 151 includes an inductor L1 and a capacitor C2 in addition to the AC power supply 160. The inductor L1 is connected in series with the AC power supply 160 between nodes N3 and N4. The capacitor C2 is connected between nodes N3 and N4. As a result, when the AC power supply 160 is operating, a resonant current whose amplitude increases with each cycle is generated as a loop current Irp due to a resonance phenomenon caused by the inductor L1 and the capacitor C2. At this time, the main circuit breaker 110 has already opened, but is in the state between times t0 and t1 in FIGS. 2 to 7, and the main current Icb continues to flow with arc discharge until a zero-crossing point occurs and breaking is completed.

[0042] The AC power supply 160 can be configured as desired using a power converter such as an inverter configured with a semiconductor switching element (not shown), or a transformer or variac including an output on / off switch, as long as its operation and stop can be controlled. The frequency of the AC voltage generated by the AC power supply 160 is set corresponding to a resonance frequency determined as a circuit constant by the inductor L1 and the capacitor C.

[0043] The resonant circuit 151 is connected to the main circuit breaker 110 via a capacitor C1 and a rectifying element 170. The capacitor C1 is connected between the nodes N1 and N3. The rectifying element 170 is configured by a rectifying element (diode) without a control terminal, and is connected between the nodes N2 and N4, with the direction from the node N4 to the node N2 as the forward direction.

[0044] 8 and 9 further show the current paths when the current interruption device 100A operates to interrupt the positive main current Icb. Hereinafter, with respect to the loop current Irp generated by the resonant circuit 151, the direction in which the loop current Irp flows from the node N4 to the node N3 within the resonant circuit 151 is defined as the "positive direction," and the direction in which the loop current Irp flows from the node N3 to the node N4 is defined as the "negative direction."

[0045] 8 shows a current path during a period in which the loop current Irp is negative (Irp<0) during a period in which the AC power supply 160 operates in response to the opening of the main circuit breaker 110. During this period, the rectifying element (diode) 170 is turned on, causing the loop current Irp to flow from node N4 toward node N2, pass through the main circuit breaker 110 and node N1, and return to node N4, following the loop path shown by the dotted line in FIG. 8. As a result, an oscillating current Ios, which is opposite in direction to the main current Icb, is superimposed on the main current Icb.

[0046] 9 shows the current path during the period when the loop current Irp is in the positive direction (Irp>0). During this period, the rectifying element (diode) 170 is turned off, causing the loop current Irp to flow from node N3 via capacitor C2 back to node N4, along the loop path shown by the dotted line in FIG. 9. It can be seen that, as the loop current Irp flows through the resonant circuit 151 in this manner, the oscillating current Ios, which flows in the same direction as the main current Icb, is not superimposed on the main current Icb.

[0047] FIG. 10 is a timing chart illustrating the operation of the current interruption device 100A shown in FIG.

[0048] 10 , when an occurrence of an accident is detected at time ts, the main circuit breaker 110 is opened at time t0. As an example, the control circuit 120 shown in FIG. 1 can issue an open command Sop for the main circuit breaker 110 in response to the detection value of the main current Icb by the current sensor 101 exceeding a predetermined judgment value, but the detection of the accident and the issue of the open command Sop for the main circuit breaker 110 may be performed outside the current interruption device 100A (100).

[0049] Furthermore, at time tb after the main circuit breaker 110 is opened, a control command PACon is generated to operate the AC power supply 160. Note that if the main circuit breaker 110 is configured with mechanical contacts and therefore requires several ms to completely open, the operation of the AC power supply 160 may be started without waiting for the main circuit breaker 110 to completely open.

[0050] When the AC power supply 160 is activated (turned on), a resonant current (loop current in FIGS. 8 and 9 ) whose amplitude increases with each cycle is generated in the resonant circuit 151. When the loop current Irp is generated, the rectifying element (diode) 170 is automatically turned on or off depending on the polarity (direction) of the loop current Irp, as shown in FIGS.

[0051] As a result, after the main circuit breaker 110 is opened, the main current Icb on which the oscillating current Ios is superimposed via the rectifying element (diode) 170 can be made to have a waveform in which a half-wave rectified AC current (resonant current) is superimposed as the oscillating current Ios, as shown in Fig. 4. That is, in the second embodiment, the rectifying element 170 can configure one example of a "current path control circuit." Furthermore, the path of the loop current Irp including the main circuit breaker 110 shown in Fig. 8 corresponds to one example of a "first loop path," and the path of the loop current Irp bypassing the main circuit breaker 110 shown in Fig. 9 corresponds to one example of a "second loop path."

[0052] As a result, according to the current interruption device 100A, after the main circuit breaker 110 opens in response to an accident, a zero-crossing point of the main current Icb can be generated by superimposing an AC current (resonant current) of opposite polarity (negative direction) to the main current, and the main current Icb can be controlled so as not to be superimposed with an AC current (resonant current) of the same polarity (positive direction) as the main current.

[0053] As a result, the commutation circuit 150A can generate the oscillating current Ios superimposed on the main current Icb so that the rate of increase (0) of the amplitude of the current with the same polarity as the main current is smaller than the rate of increase of the amplitude of the current with the opposite polarity to the main current. This suppresses the maximum value I1 of the main current Icb after the main circuit breaker 110 opens, thereby improving the current interruption performance and reducing the size of the device.

[0054] 8, as described above, it is possible to suppress the maximum value I1 when the positive main current Icb is interrupted. On the other hand, if the connection direction of the rectifying element (diode) 170 is reversed, it is possible to achieve a configuration in which the maximum value I1 (absolute value) is suppressed when the negative main current Icb is interrupted.

[0055] Specifically, in Figures 8 and 9, the rectifying element 170 can be connected between nodes N2 and N4, with the direction from node N2 to node N4 being the forward direction. In this way, depending on whether the rectifying element (diode) 170 is turned on or off, a positive AC current (resonant current) having the opposite polarity to the main current Icb is superimposed on the negative main current Icb, while a negative AC current (resonant current) having the same polarity as the main current Icb is not superimposed. Therefore, similar to Figures 8 and 9, the commutation circuit 150A can generate the oscillating current Ios superimposed on the main current Icb such that the rate of increase (0) of the amplitude of the current with the same polarity as the main current is smaller than the rate of increase of the amplitude of the current with the opposite polarity to the main current. This similarly suppresses the maximum value I1 of the main current Icb after the main circuit breaker 110 opens.

[0056] Modification of Second Embodiment In a modification of the second embodiment, a configuration example that can suppress the maximum value I1 (absolute value) regardless of the direction of the main current Icb will be described.

[0057] FIG. 11 is a circuit diagram illustrating the configuration of a current interruption device 100B according to a modification of the second embodiment.

[0058] 11 , current interruption device 100B differs from current interruption device 100A according to the second embodiment in that it includes commutation circuit 150B instead of commutation circuit 150A. Commutation circuit 150B differs from commutation circuit 150A ( FIG. 8 ) in that it includes rectifier circuit 171, the polarity of which can be controlled, connected between nodes N2 and N4 instead of rectifier element 170, the polarity of which is fixed, and in that it includes polarity determination unit 121. The configuration of other parts of current interruption device 100B is similar to that of current interruption device 100A ( FIGS. 8 and 9 ), and therefore detailed description thereof will not be repeated.

[0059] The rectifier circuit 171 includes rectifier elements (for example, thyristors) 170a and 170b, each having a control terminal, connected in anti-parallel between nodes N2 and N4.

[0060] The rectifying element 170a has the same polarity as the rectifying element 170 in FIG. 8 and is connected between the nodes N2 and N4, with the direction from node N4 to N2 being the forward direction. The rectifying element 170a operates or stops in response to a control signal RCa. For example, when the control signal RCa is at an H level, the rectifying element 170a performs a rectifying operation of being conductive (ON) or non-conductive (OFF) depending on the current direction, similar to the rectifying element 170 ( FIG. 8 ). On the other hand, when the control signal RCa is at an L level, the rectifying element 170a stops and is maintained non-conductive (OFF).

[0061] In contrast, rectifying element 170b is connected in anti-parallel to rectifying element 170a between nodes N2 and N4, with the direction from node N2 to N4 being the forward direction. Rectifying element 170b operates or stops in response to control signal RCb. For example, when control signal RCb is at H level, rectifying element 170b performs a rectifying operation, while when control signal RCb is at L level, rectifying element 170b stops and is maintained non-conductive (off).

[0062] The polarity determination unit 121 generates control signals RCa and RCb to selectively operate one of the rectifying elements 170a and 170b depending on the polarity of the main current Icb (fault current) to be interrupted when the control circuit 120 opens the main circuit breaker 110. The polarity of the main current Icb can be determined based on the detection value of the current sensor 101.

[0063] When the polarity of the main current Icb to be interrupted is positive (Icb>0), the polarity determination unit 121 operates the rectifying element 170a while setting the control signal RCa to an H level and the control signal RCb to an L level in order to stop the rectifying element 170b. This allows the current interruption device 100B to operate in the same manner as the current interruption device 100A described in Figures 8 and 9 in order to interrupt the positive main current Icb.

[0064] In contrast, when the main current Icb to be interrupted is negative (Icb<0), the polarity determination unit 121 operates the rectifying element 170b while setting the control signal RCb to an H level and the control signal RCa to an L level in order to stop the rectifying element 170a. This allows the current interruption device 100B to operate in the same manner as the current interruption device 100A when the connection direction of the rectifying element 170 is reversed in Figures 8 and 9.

[0065] As described above, the current interruption device 100B according to the second embodiment can selectively operate the rectifying elements 170a and 170b depending on the polarity of the main current Icb (fault current) to be interrupted by the bipolar rectifier circuit 171. As a result, regardless of the direction of the main current Icb, an AC current (resonant current) that has been half-wave rectified so that the amplitude increase rate (0) of the current with the same polarity as the main current is smaller than the amplitude increase rate of the current with the opposite polarity to the main current can be superimposed on the main current Icb as the oscillating current Ios. This allows the same effect as the current interruption device 100A according to the second embodiment to be achieved for both positive and negative fault currents (main current Icb).

[0066] In the modification of the second embodiment, an example of a "current path control circuit" can be configured by rectifying elements 170a and 170b and polarity determination unit 121. Furthermore, rectifying element 170a corresponds to an example of a "first rectifying element," and rectifying element 170b corresponds to an example of a "second rectifying element."

[0067] Third Embodiment In a third embodiment, another example of the configuration of a commutation circuit that can accommodate a bidirectional main current Icb and generates a half-wave rectified oscillating current Ios will be described.

[0068] FIG. 12 is a circuit diagram illustrating the configuration and operation of a current interruption device 100C according to the third embodiment.

[0069] 12 , current interruption device 100C differs from current interruption device 100A in that it includes a commutation circuit 150C instead of commutation circuit 150A. Commutation circuit 150C differs from commutation circuit 150A in that it includes a resonant circuit 152 including an AC power supply 160, a full-bridge circuit 180, and a polarity determination unit 122. The configuration of other parts of current interruption device 100C is the same as that of current interruption device 100A ( FIGS. 8 and 9 ), and therefore detailed description will not be repeated. That is, main circuit breaker 110 is disposed in the same manner as in FIG. 1 and is connected between node N1 connected to power supply 10 and node N2 connected to load 20.

[0070] The resonant circuit 152 includes an inductor L1 and a capacitor C2 in addition to the AC power supply 160. The inductor L1 and the capacitor C2 are connected in series with the AC power supply 160 between nodes N3 and N4. This allows the resonant circuit 152 to generate a loop current Irp (resonant current) whose amplitude periodically increases when the AC power supply 160 is in operation. Regarding the loop current Irp output from the series resonant resonant circuit 152, the direction in which it flows from node N4 to node N3 within the resonant circuit 152 is defined as the "positive direction," and the direction in which it flows from node N3 to node N4 is defined as the "negative direction."

[0071] The full-bridge circuit 180 has a plurality of switching elements S1 to S4 and anti-parallel diodes Dr1 to Dr4 of the plurality of switching elements S1 to S4, which are connected between nodes N3 and N4 (both ends of the resonant circuit 152) and nodes N1 and N2 (both ends of the main circuit breaker 110). That is, the nodes N1 to N4 correspond to the "first node" to the "fourth node," respectively.

[0072] The switching elements S1 to S4 are controlled to be turned on and off by control signals Sc1 to Sc4 from the polarity determination unit 122. For example, the switching elements S1 to S4 can be configured with transistors such as insulated gate bipolar transistors (IBGTs). The full bridge circuit 180 operates to switch the path of the loop current Irp generated by the resonant circuit 152 through the on / off control of the switching elements S1 to S4.

[0073] 12 , switching element S1 is connected between nodes N3 and N1, and allows current to flow from node N3 to N1 when it is on. When switching element S1 is off, anti-parallel diode Dr1 allows current to flow from node N1 to N3. Similarly, switching element S2 is connected between nodes N3 and N2, and allows current to flow from node N3 to N2 when it is on. When switching element S2 is off, anti-parallel diode Dr2 allows current to flow from node N2 to N3.

[0074] Furthermore, switching element S3 is connected between nodes N2 and N4, and allows current to flow from node N2 to N4 when it is on. When switching element S3 is off, anti-parallel diode Dr3 allows current to flow from node N4 to N2. Similarly, switching element S4 is connected between nodes N1 and N4, and allows current to flow from node N1 to N4 when it is on. When switching element S4 is off, anti-parallel diode Dr4 allows current to flow from node N4 to N1.

[0075] The polarity determination unit 122 generates control signals Sc1 to Sc4 for multiple switching elements S1 to S4 depending on the direction (polarity) of the main current Icb (fault current) detected by the current sensor 101 and the direction (polarity) of the loop current Irp (resonance current) detected by the current sensor 102.

[0076] 12 and 13 further show the current path when the current interruption device 100C operates to interrupt the positive main current Icb.

[0077] When the positive main current Icb is interrupted, the polarity determination unit 122 turns on the switching elements S2 and S4 while the loop current Irp is positive (FIG. 12) and turns off the switching elements S1 and S3. On the other hand, the polarity determination unit 122 turns off the switching elements S1 to S4 while the loop current Irp is negative (FIG. 13).

[0078] As a result, during the period when the loop current Irp is in the positive direction ( FIG. 12 ), the loop current Irp from the resonant circuit 152 passes from node N3 through switching element S2 (on) and node N2, is superimposed with reverse polarity on the main current Icb, and passes through the main circuit breaker 110. Furthermore, the loop current Irp returns to the resonant circuit 152 through node N1, switching element S4 (on), and node N4.

[0079] On the other hand, during the period when the loop current Irp is in the negative direction ( FIG. 13 ), the loop current Irp from the resonant circuit 152 flows from node N4 through the anti-parallel diodes Dr3 and Dr4 of switching elements S3 (off) and S4 (off), the anti-parallel diodes Dr1 and Dr2 of switching elements S1 (off) and S2 (off), and node N3, and then returns to the resonant circuit 152 without passing through the main circuit breaker 110.

[0080] As a result, it can be seen that an AC current (loop current Irp) of the opposite polarity is superimposed on the main current Icb, while an AC current (loop current Irp) of the same polarity is not superimposed on the main current Icb.

[0081] FIG. 14 is a first timing chart illustrating a first operation of the current interruption device 100C to interrupt the forward main current Icb.

[0082] 10, when a fault is detected at time ts, the main circuit breaker 110 is opened at time t0. Furthermore, depending on whether the main current Icb is positive at time t0, it is possible to select a switching element that is turned on during a period in which the loop current Irp has a polarity opposite to that of the main current Icb.

[0083] Furthermore, at time tb after the main circuit breaker 110 is opened, a control command PACon is generated to operate the AC power supply 160. As a result, the resonant circuit 152 generates a loop current Irp (resonant current) whose amplitude increases every cycle.

[0084] After the loop current Irp is generated, the polarity determination unit 122 controls the on / off of the switching elements S1 to S4 depending on the polarity (direction) of the loop current Irp. As described in FIG. 12, during the period when the loop current Irp is positive, the control signals Sc1 to Sc4 are generated to turn on the switching elements S2 and S4 and turn off the switching elements S1 and S3. As a result, it can be understood that the negative AC current (resonant current) passes through the main circuit breaker 110 and is superimposed on the positive main current Icb (Icb>0).

[0085] On the other hand, during the period when the loop current Irp is negative, as described in FIG. 13, control signals Sc1 to Sc4 are generated to turn off the switching elements S1 to S4, thereby forming a return path for the loop current Irp through the anti-parallel diodes Dr1 to Dr4.

[0086] As a result, after the main circuit breaker 110 is opened, the main current Icb on which the oscillating current Ios is superimposed via the full bridge circuit 180 can be made to have a waveform in which a half-wave rectified AC current (resonant current) is superimposed as the oscillating current Ios, as shown in Figure 4.

[0087] FIG. 15 shows a timing chart illustrating a second operation of the current interruption device 100C to interrupt the negative main current Icb.

[0088] Comparing FIG. 15 with FIG. 14, when the negative main current Icb is cut off, the on / off states of the switching elements S1 to S4 during the period when the loop current Irp is positive are switched from those in FIG. 14 (when the positive main current Icb is cut off).

[0089] Specifically, similar to FIG. 14 , after the occurrence of an accident is detected at time ts, the main circuit breaker 110 is opened at time t0, and the AC power supply 160 is activated at time tb, the switching elements S1 and S3 are selected as the switching elements to be turned on during the period when the loop current Irp is in the positive direction, in accordance with the main current Icb being in the negative direction at time t0.

[0090] As a result, it can be seen that in FIG. 12, when switching elements S1 and S3 are turned on (switching elements S2 and S4 are turned off) instead of switching elements S2 and S4, a positive AC current (resonant current) passes through the main circuit breaker 110 and is superimposed on the negative main current Icb (Icb<0).

[0091] On the other hand, during the period when the loop current Irp is in the negative direction, control signals Sc1 to Sc4 are generated to turn off the switching elements S1 to S4, and as in Figure 13, a return path for the loop current Irp is formed by the anti-parallel diodes Dr1 to Dr4, which does not pass through the main circuit breaker 110.

[0092] As a result, after the main circuit breaker 110 is opened, the half-wave rectified AC current (resonant current) can be superimposed as the oscillating current Ios on the negative main current Icb.

[0093] 14 and 15 in accordance with the polarity (positive direction / negative direction) of the main current Icb when the main circuit breaker 110 is open, and generates control signals Sc1 to Sc4 in accordance with the polarity of the loop current Irp in accordance with the selected switching pattern. As a result, as can be seen from a comparison between FIGS. 14 and 15, the switching elements (S1, S3 / S2, S4) that are turned on during the period when the loop current Irp has an opposite polarity to that of the main current Icb (Irp>0) are changed in accordance with the polarity (positive direction / negative direction) of the main current Icb.

[0094] As described above, according to the current interruption device of the third embodiment, by controlling the on / off of the switching elements S1 to S4 constituting the full bridge circuit 180, the oscillating current Ios superimposed on the main current Icb can be generated so that the rate of increase (0) of the amplitude of the same polarity as the main current Icb is smaller than the rate of increase of the amplitude of the opposite polarity to the main current Icb, regardless of the direction of the main current Icb to be interrupted. As a result, for both positive and negative fault currents (main current Icb), the maximum value I1 (absolute value) of the main current Icb after the main circuit breaker 110 is opened can be suppressed, thereby improving the current interruption performance and reducing the size of the device.

[0095] In the third embodiment, a full-bridge circuit 180 including a plurality of switching elements S1 to S4 and anti-parallel diodes Dr1 to Dr4, and a polarity determination unit 122 that generates control signals Sc1 to Sc4, can constitute one example of a "current path control circuit." The current path shown in Fig. 12 corresponds to one example of a "first loop path," and the current path shown in Fig. 13 corresponds to one example of a "second loop path."

[0096] Fourth Embodiment In a fourth embodiment, a further example of the configuration of the commutation circuit that can accommodate the main current Icb in both directions will be described.

[0097] FIG. 16 is a circuit diagram illustrating the configuration and operation of a current interruption device 100D according to the fourth embodiment.

[0098] 16, current interruption device 100D differs from current interruption device 100 in that it includes a commutation circuit 150D instead of commutation circuit 150 in current interruption device 100 of FIG. Commutation circuit 150C includes a resonant circuit 152 including an AC power supply 160, a current limiting circuit 190 connected in parallel with resonant circuit 152, and a polarity determination unit 122. The configuration of other parts of current interruption device 100D is the same as that of current interruption device 100, and therefore detailed description thereof will not be repeated. That is, main circuit breaker 110 is disposed in the same manner as in FIG. 1 and is connected between node N1 connected to power supply 10 and node N2 connected to load 20.

[0099] 12 (Embodiment 3), the resonant circuit 152 has an AC power supply 160, an inductor L1, and a capacitor C2 connected in series between nodes N3 and N4. As with FIG. 12, the direction in which the loop current Irp (resonant current) generated by the resonant circuit 152 flows from node N3 to node N4 within the resonant circuit 152 is defined as the "positive direction," and the direction in which the current flows from node N4 to node N3 is defined as the "negative direction."

[0100] Current limiting circuit 190 has a resistor element 191 as a current limiting element, and a switch element 192, which are connected in series between nodes N3 and N4. Switch element 192 is configured by a transistor switch or the like, and is on / off controlled by a control signal Ssw from polarity determination unit 122.

[0101] The polarity determination unit 122 generates a control signal Ssw for the switch element 192 depending on the direction (polarity) of the main current Icb (fault current) detected by the current sensor 101 and the direction (polarity) of the loop current Irp (resonance current) detected by the current sensor 102.

[0102] FIG. 16 further illustrates the current path when the current interruption device 100D operates to interrupt the forward main current Icb.

[0103] When the positive main current Icb is cut off, the polarity determination unit 122 generates a control signal Ssw so as to turn on the switch element 192 during the period when the loop current Irp is positive, and to turn off the switch element 192 during the period when the loop current Irp is negative.

[0104] As a result, during the period when the loop current Irp flows in the negative direction, i.e., from left to right in the drawing within the resonant circuit 152, the loop current Irp flows only through the path PT1 that passes through the main circuit breaker 110, without flowing through the path PT2 that passes through the current limiting circuit 190. As a result, an AC current of opposite polarity to the main current Icb (Icb>0) is superimposed on the main current Icb.

[0105] In contrast, during the period when the loop current Irp flows in the positive direction, i.e., from right to left in the figure within the resonant circuit 152, the loop current Irp is divided into a path PT1 that passes through the main circuit breaker 110 and a path PT2 that passes through the current limiting circuit 190 when the switch element 192 is turned on, and only the current on the path PT1 is superimposed on the main current Icb as the oscillating current Ios.

[0106] FIG. 17 shows a conceptual waveform diagram illustrating the operation of current interruption device 100D interrupting the forward main current Icb.

[0107] As shown in FIG. 17 , after the main circuit breaker 110 is opened to interrupt the positive main current Icb (Icb>0) as a fault current, the AC power supply 160 is operated, generating a loop current Irp (resonant current) whose amplitude increases with each cycle.

[0108] While the loop current Irp is in the positive direction (Irp>0), the switch element 192 is turned on, and while the loop current Irp is in the negative direction (Irp<0), the switch element 192 is turned off. As a result, an AC current of the opposite polarity to the main current Icb is superimposed on the main current Icb without being diverted, while the remaining current diverted to the current limiting circuit 190 is superimposed on an AC current of the same polarity as the main current Icb.

[0109] 16, the oscillating current Ios is superimposed on the main current Icb, and the rate of increase in the amplitude of the oscillating current Ios with the same polarity as the main current Icb is controlled to be smaller than the rate of increase in the amplitude of the oscillating current Ios with the opposite polarity to the main current Icb. This makes it possible to suppress the maximum value of the main current Icb after the main circuit breaker 110 opens.

[0110] Referring again to FIG. 16, when blocking the negative main current Icb (Icb<0), the polarity determination unit 122 can generate a control signal Ssw so as to turn off the switch element 192 during the period in which the loop current Irp is positive, and turn on the switch element 192 during the period in which the loop current Irp is negative.

[0111] In this way, by reversing the on / off of the switch element 192 relative to the polarity of the loop current Irp, during the period when the loop current Irp flows in the positive direction, that is, from right to left in the drawing within the resonant circuit 152, the loop current Irp flows only through the path PT1 that passes through the main circuit breaker 110, without flowing through the path PT2 that passes through the current limiting circuit 190. This makes it possible to superimpose an AC current of opposite polarity to the main current Icb (Icb<0) on the main current Icb.

[0112] On the other hand, during the period when the loop current Irp flows in the negative direction, that is, from left to right in the drawing within the resonant circuit 152, the loop current Irp is diverted into a path PT1 that passes through the main circuit breaker 110 and a path PT2 that passes through the current limiting circuit 190, by turning on the switch element 192. As a result, even with respect to the negative main current Icb, an AC current of the opposite polarity to the main current Icb is not diverted but is superimposed as the oscillating current Ios, while with respect to the AC current of the same polarity as the main current Icb, the remaining current diverted to the current limiting circuit 190 is superimposed as the oscillating current Ios.

[0113] Therefore, according to the current interruption device of embodiment 4, by adjusting the on / off control of the switch element 192 according to the direction of the main current Icb to be interrupted, it is possible to suppress the maximum value (absolute value) of the main current Icb after the main circuit breaker 110 is opened, for both positive and negative fault currents (main current Icb).

[0114] In the fourth embodiment, the current limiting circuit 190 including the switch element 192 and the polarity determination unit 122 that generates the control signal Ssw can constitute one example of a "current path control circuit." Also, the path PT1 (when the switch element 192 is off) shown in Fig. 16 corresponds to one example of a "first loop path," and the path PT2 (when the switch element 192 is on) corresponds to one example of a "second loop path."

[0115] Fifth Embodiment In a fifth embodiment, a configuration example of a commutation circuit that generates a full-wave rectified oscillating current Ios will be described.

[0116] FIG. 18 is a circuit diagram illustrating the configuration and operation of a current interruption device 100E according to the fifth embodiment.

[0117] 18, current interruption device 100E differs from current interruption device 100 in Fig. 1 in that it includes a commutation circuit 150E instead of commutation circuit 150. The configuration of other parts of current interruption device 100E is the same as that of current interruption device 100, and therefore detailed description will not be repeated. That is, main circuit breaker 110 is arranged in the same manner as in Fig. 1, and is connected between node N1 connected to power source 10 and node N2 connected to load 20.

[0118] The commutation circuit 150E includes a resonant circuit 152 including an AC power supply 160, and a diode bridge circuit 185 for full-wave rectification. Similar to FIG. 12 (Embodiment 3) and FIG. 16 (Embodiment 4), the resonant circuit 152 has an AC power supply 160, an inductor L1, and a capacitor C2 connected in series between nodes N3 and N4. As with FIGS. 12 and 16, the direction of the loop current Irp (resonant current) generated by the resonant circuit 152 when the AC power supply 160 is operating is defined as the "positive direction" in the resonant circuit 152, and the direction of the loop current Irp from node N3 to node N4 is defined as the "negative direction" in the resonant circuit 152, and the direction of the loop current Irp from node N4 to node N3 is defined as the "negative direction."

[0119] The diode bridge circuit 185 has diodes D1 to D4, which are an example of a "rectifying element" that does not have a control terminal. The diode D1 is connected between the nodes N1 and N3, with the forward direction being from the node N1 to the node N3. The diode D2 is connected between the nodes N2 and N3, with the forward direction being from the node N3 to the node N2.

[0120] Furthermore, diode D3 is connected between nodes N2 and N4 with its forward direction being from node N4 to node N2, and diode D4 is connected between nodes N1 and N4 with its forward direction being from node N1 to node N4.

[0121] 18, the positive loop current Irp flows from node N3 through diode D2 (conducting), node N2, main circuit breaker 110, node N1, and diode D4 (conducting) to node N4, accompanied by conduction of diodes D2 and D4 in the diode bridge circuit 185. As a result, by guiding the negative loop current Irp (Irp<0) to the main circuit breaker 110, it is possible to superimpose an AC current of the opposite polarity on the positive main current Icb.

[0122] 19 , the negative loop current Irp flows from node N4 to node N3 via diode D3 (conducting), node N2, main circuit breaker 110, node N1, and diode D1 (conducting), accompanied by conduction of diodes D1 and D3 in the diode bridge circuit 185. As a result, by reversing the polarity of the positive loop current Irp (Irp>0) and directing it to the main circuit breaker 110, it is possible to superimpose an AC current of the opposite polarity on the positive main current Icb.

[0123] As a result, with the current interruption device 100E according to the fifth embodiment, by arranging the full-wave rectifying diode bridge circuit 185, it is possible to superimpose, as the oscillating current Ios, an AC current that has been full-wave rectified so that the rate of increase (0) of the amplitude of the same polarity as the forward main current Icb (fault current) is smaller than the rate of increase of the amplitude of the opposite polarity to the main current Icb, with respect to the forward main current Icb (fault current). This similarly makes it possible to suppress the maximum value (absolute value) of the main current Icb after the main circuit breaker 110 opens.

[0124] In the configuration example of FIG. 18, as described above, it is possible to suppress the maximum value when the positive main current Icb is interrupted. However, if the connection direction (polarity) of the diodes D1 to D4 that constitute the diode bridge circuit 185 is reversed, it is possible to suppress the maximum value (absolute value) when the negative main current Icb is interrupted.

[0125] Specifically, in the diode bridge circuit 185, the diode D1 can be connected with its forward direction being from the node N3 to the node N1, and the diode D2 can be connected with its forward direction being from the node N2 to the node N3. Furthermore, the diode D3 can be connected with its forward direction being from the node N2 to the node N4, and the diode D4 can be connected with its forward direction being from the node N4 to the node N1.

[0126] As a result, a full-wave rectified positive AC current (resonant current) having the opposite polarity to the negative main current Icb is superimposed on the negative main current Icb, while a negative AC current (resonant current) having the same polarity as the main current Icb is not superimposed on the negative main current Icb. This makes it possible to suppress the maximum value (absolute value) of the main current Icb after the main circuit breaker 110 opens when the negative main current Icb is interrupted.

[0127] In the fifth embodiment, a full-wave rectifying diode bridge circuit 185 formed of diodes D1 to D4 can constitute one example of a "current path control circuit." The current path when Irp<0 shown in Fig. 18 corresponds to one example of a "first loop path," and the current path when Irp>0 shown in Fig. 19 corresponds to one example of a "second loop path."

[0128] Modification of Embodiment 5 In a modification of embodiment 5, another example of the configuration of the commutation circuit that can accommodate the main current Icb in both directions and generates a full-wave rectified oscillating current Ios will be described.

[0129] FIG. 20 is a circuit diagram illustrating the configuration of a current interruption device 100F according to a modification of the fifth embodiment.

[0130] 20 , current interruption device 100F differs from current interruption device 100E according to embodiment 5 in that it includes commutation circuit 150F instead of commutation circuit 150E. The configuration of other parts of current interruption device 100F is similar to that of current interruption device 100E ( FIGS. 18 and 19 ), and therefore detailed description thereof will not be repeated.

[0131] The commutation circuit 150F differs from the commutation circuit 150E in that it has a diode bridge circuit 187 instead of the diode bridge circuit 185, and in that it further has a polarity determination unit 121 similar to that in FIG.

[0132] The diode bridge circuit 187 has rectifier elements (e.g., thyristors) D1a to D4a and D1b to D4b each having a control terminal. The rectifier elements (thyristors) D1a to D4a are connected between the node N1 or N2 and the node N3 or N4, respectively, with the same polarity (connection direction) as the diodes D1 to D4 that make up the diode bridge circuit 185 (FIG. 18).

[0133] Each of the rectifying elements (thyristors) D1a to D4a operates or stops in response to a control signal RCa from the polarity determination unit 121. For example, when the control signal RCa is at H level, each of the rectifying elements D1a to D4a performs a rectifying operation by becoming conductive (ON) or non-conductive (OFF) depending on the current direction, similar to the diodes D1 to D4 (FIG. 18). On the other hand, when the control signal RCa is at L level, each of the rectifying elements (thyristors) D1a to D4a stops operating and remains non-conductive (OFF).

[0134] The rectifying elements (thyristors) D1b to D4b are connected in anti-parallel to the rectifying elements (thyristors) D1a to D4a, respectively. Each of the rectifying elements (thyristors) D1b to D4b operates or stops in response to a control signal RCb from the polarity determination unit 121. For example, when the control signal RCb is at H level, each of the rectifying elements D1b to D4b performs a rectifying operation in accordance with the current direction, while when the control signal RCb is at L level, each of the rectifying elements (thyristors) D1b to D4b stops and is maintained non-conductive (off).

[0135] As in Figure 11 (variant of embodiment 2), the polarity determination unit 121 generates control signals RCa and RCb to selectively operate one of the rectifier elements (thyristors) D1a to D4a and the rectifier elements (thyristors) D1b to D4b depending on the polarity of the main current Icb (fault current) to be interrupted when the control circuit 120 opens the main circuit breaker 110.

[0136] When the polarity of the fault current to be interrupted is positive (Icb>0), the polarity determination unit 121 operates the rectifier elements (thyristors) D1a to D4a, while setting the control signal RCa to an H level and the control signal RCb to an L level in order to stop the rectifier elements (thyristors) D1b to D4b. This allows the current interruption device 100F to operate in the same manner as the current interruption device 100E described in Figures 18 and 19 when interrupting the positive main current Icb.

[0137] In contrast, when the polarity of the fault current to be interrupted is negative (Icb<0), the polarity determination unit 121 operates the rectifier elements (thyristors) D1b to D4b, while setting the control signal RCb to an H level and the control signal RCa to an L level in order to stop the rectifier elements (thyristors) D1a to D4a. This allows the current interruption device 100F to operate in the same manner as the current interruption device 100E when the connection direction (polarity) of the diodes D1 to D4 is reversed in Figures 18 and 19.

[0138] As a result, according to the current interruption device 100F of the modified embodiment of the fifth embodiment, by arranging the bipolar diode bridge circuit 187, it is possible to superimpose, on the main current Icb as the oscillating current Ios, an AC current that has been full-wave rectified so that the rate of increase (0) of the amplitude of the same polarity as the main current (fault current) to be interrupted is smaller than the rate of increase of the amplitude of the polarity opposite to that of the main current, depending on the polarity of the main current Icb to be interrupted. As a result, it is possible to obtain the same effect as the current interruption device 100E of the fifth embodiment for both positive and negative fault currents (main current Icb).

[0139] In a modified example of the fifth embodiment, one example of a "current path control circuit" can be configured by a "first rectification element group" composed of rectification elements (thyristors) D1a to D4a, a "second rectification element group" composed of rectification elements (thyristors) D1b to D4b, and a polarity determination unit 121 that generates control signals RCa and RCb.

[0140] Next, the control process of the current interruption method by the current interruption device according to the present disclosure will be described. Figure 21 is a first flowchart illustrating the control process of the current interruption method according to the present disclosure. Each step of the flowchart shown in Figure 21 can be executed by a control circuit 120 and polarity determination units 121 and 122 arranged inside or outside the current interruption device 100 (100A to 100F).

[0141] 21 , the control circuit 120 determines in step (hereinafter simply referred to as “S”) 110 whether or not a trip command has been issued in response to the occurrence of an accident in a state in which the main current Icb is generated by the closed circuit of the main circuit breaker 110. The trip command can be generated by the control circuit 120 based on the value of the main current Icb detected by the current sensor 101, but may also be given from outside the control circuit 120.

[0142] When a disconnection command is generated (YES in S110), the control circuit 120 starts a control process to open the main circuit breaker 110 and interrupt the main current Icb in S120. On the other hand, during a period when a disconnection command is not generated (NO in S110), the process from S120 onwards is not started, and the main circuit breaker 110 is maintained in a closed state.

[0143] In step S130, the control circuit 120 activates the AC power supply 160 to start generating a loop current using the resonant circuits 151 and 152. Furthermore, in step S140, the path of the loop current is switched depending on the polarity of the loop current, thereby controlling the oscillating current Ios superimposed on the main current Icb. More specifically, the oscillating current Ios superimposed on the main current Icb (fault current) is controlled so that the rate of increase in the amplitude of the current with the same polarity as the main current is smaller than the rate of increase in the amplitude of the current with the opposite polarity to the main current.

[0144] In S140, as described above, in current interruption devices 100C (FIG. 12) and 100D (FIG. 16), the polarity determination unit 122 switches the control signals Sc1 to Sc4 and Ssw for controlling the on / off of switching elements S1 to S4 or switch element 192 depending on the polarity of the loop current Irp. On the other hand, in current interruption devices 100A (FIG. 8), 100B (FIG. 11), 100E (FIG. 18), and 100F (FIG. 20), which use rectifying elements, the path of loop current Irp is controlled without switching the control signal in S140.

[0145] After the main circuit breaker 110 is opened and the AC power supply 160 is activated, when a zero-crossing point occurs in the main current Icb on which the oscillating current Ios is superimposed, the main current Icb is normally interrupted unless the electrical conductivity of the arc discharge at that time is excessively high. Therefore, in S150, the control circuit 120 determines whether the interruption of the main current is complete based on the value of the main current Icb detected by the current sensor 101. Until the interruption of the main current is complete (NO in S150), the processes of S130 and S140 are repeated to continue generating the loop current Irp for superimposing the oscillating current Ios on the main current Icb.

[0146] When the control circuit 120 detects that the main current has been interrupted (YES in S150), it stops the AC power supply 160 and stops the generation of the loop current Irp in S160. This allows the current interruption process by the current interruption device 100 to be completed normally. Note that if the NO determination in S150 continues for more than a predetermined time after the start of the current interruption process, it is possible to notify the occurrence of an abnormality.

[0147] In addition, in current interruption devices 100B (FIG. 11), 100C (FIG. 12), 100D (FIG. 16), and 100F (FIG. 20) that can interrupt the main current Icb in both directions, step S140a shown in FIG. 22 is additionally executed.

[0148] Referring to FIG. 22, step S140a includes steps S141 to S144 which are executed the first time the process of S140 is performed.

[0149] In S141, the polarity determination unit 121 or 122 determines the polarity of the main current Icb when the main circuit breaker 110 is opened, i.e., whether the main current Icb to be interrupted is positive or negative. Then, in S142, the control circuit 120 branches the process according to the determination result in S141. As a result, when the main current Icb to be interrupted is positive (YES in S141), the control circuit 120 selects pattern A in S143 and generates a control signal for the commutation circuit 150. On the other hand, when the main current Icb to be interrupted is negative-positive (NO in S141), the control circuit 120 selects pattern B in S144 and generates a control signal for the commutation circuit 150.

[0150] As an example, in current interruption devices 100B (FIG. 11) and 100F (FIG. 20), pattern A (S143) selects the patterns of control signals RCa and RCb so that rectifying element 170a or D1a to D4a is activated while rectifying element 170b or D1b to D4b is fixedly deactivated (RCa=H level, RCb=L level).On the other hand, pattern B (S144) selects the patterns of control signals RCa and RCb so that rectifying element 170b or D1b to D4b is activated while rectifying element 170a or D1a to D4a is fixedly deactivated (RCb=H level, RCa=L level).

[0151] Similarly, in the current interruption device 100C (FIG. 12), pattern A (S143) selects the patterns of the control signals Sc1 to Sc4 so that the switching elements S2 and S4 are turned on and off according to the polarity of the loop current Irp while the switching elements S1 and S3 are fixed to the off state. On the other hand, pattern B (S144) selects the patterns of the control signals Sc1 to Sc4 so that the switching elements S1 and S3 are turned on and off according to the polarity of the loop current Irp while the switching elements S2 and S4 are fixed to the off state.

[0152] In the current interruption device 100D ( FIG. 16 ), pattern A (S143) selects a pattern of the control signal Ssw such that the switch element 192 is turned off during the positive period of the loop current Irp and turned on during the negative period. On the other hand, pattern B (S144) selects a pattern of the control signal Ssw such that the switch element 192 is turned on during the positive period of the loop current Irp and turned off during the negative period.

[0153] In this embodiment, the control circuit 120 and the polarity determination units 121 and 122 can be configured by a microcomputer that realizes the above-mentioned control signal generation function by software processing through the execution of a predetermined program, etc., using A / D converted values ​​of the detection values ​​of the current sensors 101 and 102 as inputs. Alternatively, at least a part of the control circuit 120 and the polarity determination units 121 and 122 may be configured to realize at least a part of the above-mentioned control signal generation function by hardware processing using a dedicated electronic circuit, a logical operation circuit, etc.

[0154] Furthermore, in the second to fifth embodiments and their modifications, configuration examples have been described in which the oscillating current Ios is generated to be superimposed on the main current Icb using a resonant current, in accordance with the operational examples shown in FIGS. 4 and 5 , and in particular, configuration examples of the commutation circuit 150 that generates the oscillating current Ios by half-wave rectifying or full-wave rectifying the resonant current, but the configuration of the commutation circuit 150 is not limited to these configuration examples.

[0155] 6 and 7 , any circuit configuration can be applied to the commutation circuit 150 as long as it is possible to generate an AC current to be superimposed on the main current Icb such that the rate of increase in amplitude of a current with the same polarity as the main current Icb is smaller than the rate of increase in amplitude of a current with an opposite polarity to the main current Icb after the AC power supply is started in response to the opening of the main circuit breaker 110. For example, by configuring the AC power supply 160 to generate a square wave current, it is possible to realize a waveform of the main current Icb after the oscillating current Ios is superimposed, as shown in FIG.

[0156] In addition, in each of the above-described embodiments and their modifications, the commutation circuits 150A to 150F can be configured to further include an energy absorption element.

[0157] As an example, Fig. 23 shows a configuration example in which the commutation circuit 150A of the current interruption device 100A according to the second embodiment further includes an energy absorption element 195. Similarly, Fig. 24 shows a configuration example in which the commutation circuit 150 of the current interruption device 100C according to the third embodiment further includes an energy absorption element 195.

[0158] 23 and 24, each of the commutation circuits 150A and 150C further includes an energy absorption element 195 connected between nodes N1 and N2 in addition to the configurations in FIGS. 8 and 13. That is, in the commutation circuits 150A and 150C, the energy absorption element 195 is connected in parallel with the main circuit breaker 110.

[0159] The energy absorption element 195 is a type of nonlinear resistor that is normally high resistance but has the characteristic of becoming low resistance when a certain voltage (clamp voltage) is applied. For example, the energy absorption element 195 may be a lightning arrester, an arrester, a varistor, or a zinc oxide (ZnO) element.

[0160] In the main circuit breaker 110, a high voltage (recovery voltage) is generally generated between the poles of the mechanical circuit breaker after current is interrupted. Therefore, by arranging the energy absorption element 195, the energy of this high voltage can be absorbed, thereby preventing the application of high voltage to other parts of each commutation circuit and each current interruption device.

[0161] In addition to the examples shown in Figures 23 and 24, it is also noted that in the modified example of embodiment 2, embodiment 4, and embodiment 5 and its modified examples, it is possible to further arrange an energy absorption element 195 connected in parallel with the main circuit breaker 110 in each of the commutation circuits 150B, 150D to 150F.

[0162] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0163] 10 power supply, 20 load, 100, 100A to 100F current interruption device, 101, 102 current sensor, 110 main circuit breaker, 120 control circuit, 121, 122 polarity determination unit, 150, 150A to 150F commutation circuit, 151, 152 resonance circuit, 160 AC power supply, 170 rectifier element (diode), 170a, 170b, D1a to D4a, D1b to D4b rectifier element (with control terminal), 171 rectifier circuit, 180 full bridge circuit, 185, 187 diode bridge circuit, 190 current limiting circuit, 191 resistor element, 192 switch element, 195 energy absorption element, C, C1, C2 capacitor, D1 to D4 diode, Dr1 to Dr4 anti-parallel diode, I0 fault current, I1 Maximum value (main current), Icb main current, Ios oscillating current, Irp loop current (resonant current), L1 inductor, N1 to N4 nodes, PACon control command (AC power supply), PT1, PT2 path, RCa, RCb, Sc1 to Sc4, Ssw control signal, S1 to S4 switching elements, Sop open command (main circuit breaker).

Claims

1. A main circuit breaker is placed in the path of the main current, The system includes a commutator connected in parallel to the main circuit breaker, configured to superimpose an oscillating current with periodically increasing amplitude onto the main current after the main circuit breaker opens, The commutation circuit includes an AC power supply that operates after the main circuit breaker is opened, and the current interruption device generates the oscillating current such that, after the AC power supply is started, the rate of increase in the amplitude of the same polarity as the main current is smaller than the rate of increase in the amplitude of the opposite polarity to the main current.

2. The commutation circuit is, A resonant circuit having the aforementioned AC power supply, an inductor, and a capacitor, which generates a resonant current when the AC power supply is operating, The current interruption device according to claim 1, comprising a current path control circuit that generates the oscillating current such that the rate of increase of the amplitude of the same polarity as the main current is smaller than the rate of increase of the amplitude of the opposite polarity to the main current by switching the path of the resonant current.

3. The current interruption device according to claim 2, wherein the current path control circuit is configured to allow the resonant current to flow through a first loop path including the main circuit breaker during periods when the resonant current is of opposite polarity to the main current, and to allow the resonant current to flow through a second loop path that bypasses the main circuit breaker during periods when the resonant current is of the same polarity as the main current.

4. The current path control circuit has a rectifier element connected between the resonant circuit and the main current path, The current interruption device according to claim 3, wherein the first loop path is formed when the rectifier element is conducting, and the second loop path is formed when the rectifier element is not conducting.

5. The current path control circuit is, A first rectifier element having a control terminal is connected between the resonant circuit and the path of the main current, A second rectifier element having a control terminal is connected in antiparallel to the first rectifier element, between the resonant circuit and the path of the main current, The system includes a polarity determination unit that provides control signals to the control terminals of the first and second rectifier elements in such a way that, depending on the polarity of the main current when the main circuit breaker is open, one of the first and second rectifier elements is activated while the other rectifier element remains non-conductive, The current interruption device according to claim 3, wherein the first loop path is formed when the one rectifier element is conducting, and the second loop path is formed when the one rectifier element is not conducting.

6. The current path control circuit is, A current-limiting circuit having a current-limiting element and a switching element connected in parallel with the resonant circuit and connected in series, The system includes a polarity determination unit that controls the on / off state of the switch element according to the polarity of the main current and the polarity of the resonant current when the main circuit breaker is open, The current interruption device according to claim 3, wherein the switching element is controlled to turn on to form the second loop path during periods when the resonant current is of the same polarity as the main current, and to turn off to form the first loop path during periods when the resonant current is of opposite polarity to the main current.

7. The current path control circuit is, A full-bridge circuit having a plurality of switching elements and antiparallel diodes for each of the plurality of switching elements is connected between the first and second nodes connected to both ends of the main circuit breaker and the third and fourth nodes connected to both ends of the resonant circuit. The system includes a polarity determination unit that controls the on / off state of the plurality of switching elements according to the polarity of the main current and the polarity of the resonant current when the main circuit breaker is open, The current interruption device according to claim 3, wherein the polarity determination unit controls the on / off status of the plurality of switching elements such that a first loop path is formed when some of the plurality of switching elements are turned on during the period when the resonant current is of opposite polarity to the main current, while each of the plurality of switching elements is turned off during the period when the resonant current is of the same polarity as the main current, thereby forming a second loop path by the antiparallel diode.

8. The current interruption device according to claim 7, wherein the polarity determination unit controls the on / off status of the plurality of switching elements so as to change some of the switching elements that are turned on during the period when the resonant current is of opposite polarity to the main current, according to the polarity of the main current when the main circuit breaker is open.

9. The current path control circuit is configured to allow the resonant current to flow through a first loop path including the main circuit breaker during periods when the resonant current is of opposite polarity to the main current, while allowing the resonant current with reversed polarity to flow through a second loop path including the main circuit breaker during periods when the resonant current is of the same polarity as the main current, as described in claim 2.

10. The current path control circuit is, The current interruption device according to claim 9, comprising a diode bridge circuit for full-wave rectification connected between first and second nodes connected to both ends of the main circuit breaker and third and fourth nodes connected to both ends of the resonant circuit.

11. The current path control circuit is, A first group of rectifier elements, consisting of a plurality of rectifier elements having control terminals, is connected between the first and second nodes connected to both ends of the main circuit breaker and the third and fourth nodes connected to both ends of the resonant circuit, so as to form a diode bridge circuit for full-wave rectification. A second group of rectifier elements, each of which is connected in antiparallel to the first group of rectifier elements, and which is composed of rectifier elements having control terminals, The current interruption device according to claim 9, further comprising: a polarity determination unit that provides control signals to the control terminals of the first rectifier element group and the second rectifier element group in such a way that, depending on the polarity of the main current when the main circuit breaker is open, one of the first rectifier element group and the other rectifier element group is activated while the other rectifier element group remains non-conductive.

12. The current interruption device according to any one of claims 1 to 5 and 7 to 11, wherein the commutation circuit generates the oscillating current by half-wave rectifying or full-wave rectifying an alternating current whose amplitude increases periodically.

13. The current interruption device according to claim 1, wherein the commutation circuit generates the oscillating current based on a rectangular wave current whose amplitude increases periodically, generated by the AC power supply.

14. The current interruption device according to any one of claims 1 to 11 and 13, wherein the commutation circuit further includes an energy absorption element connected in parallel to the main circuit breaker.

15. In response to the detection of an abnormality in the main current, the main circuit breaker located in the path of the main current is opened. The steps include: activating the AC power supply in the commutation circuit connected in parallel to the main circuit breaker in response to the opening of the main circuit breaker; A current interruption method comprising the steps of superimposing an oscillating current generated by the commutation circuit onto the main current using a current whose amplitude increases periodically when the AC power supply is in operation, such that the rate of increase in amplitude of the same polarity as the main current is smaller than the rate of increase in amplitude of the opposite polarity to the main current.

16. The step of superimposing the oscillating current onto the main current is: The current interruption method according to claim 15, comprising the step of generating the oscillating current by switching the path of the resonant current generated by the resonant circuit having the AC power supply, an inductor, and a capacitor.

17. The steps include determining the polarity of the main current when the main circuit breaker is open, The current interruption method according to claim 16, further comprising the step of selecting a control pattern for a circuit element that is on / off controlled to switch the path of the resonant current, according to the polarity of the main current that has been determined.

18. The current interruption method according to claim 15, wherein the oscillating current is generated by half-wave rectification or full-wave rectification of an alternating current whose amplitude increases periodically.

19. The current interruption method according to any one of claims 15 to 18, further comprising the step of stopping the AC power supply in response to the disappearance of the main current after the opening of the main circuit breaker.