JP2011010483A - Current separator and current-breaking device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current separator that attains a high surge current withstand amount, while maintaining a low minimum fusing current and executes operational cooperation with another current breaker.SOLUTION: A power-distribution board 150 includes a ground leakage breaker 160 and a lightning protection device 180. The lightning protection device 180 has a separator 100. The separator 100 includes a first fuse and a fuse parallel circuit connected in parallel to the first fuse; the fuse parallel circuit has a second fuse having the same fusing time-current characteristics as those of the first fuse, and a voltage switch connected in series to the second fuse and composed by connecting two diode groups in inverse parallel, wherein a plurality of diodes are connected in series in each group; and the threshold voltage of the voltage switch is set so as to allow execution of operation cooperation, in such a manner that the separator 100 operates, earlier to the operation of the ground leakage breaker 160, when an abnormal current is detected.

Description

  The present invention relates to a current separator and a current interrupting device, and more particularly, to a current separator included in one current interrupting unit in a current interrupting device having a plurality of current interrupting units, and the current interrupting device.

  An example of a device that interrupts current when an abnormal current is detected is a separator for a lightning protection device. There are lightning protection devices for direct lightning and induction lightning. For example, for general housing, it is recommended to install a lightning protection device on the distribution board for the purpose of countermeasures against induced lightning according to the extension regulations of the Japan Electric Association. Yes. A configuration example of a distribution board of a general house shown in the extension regulations is as shown in FIG. 9, and a lightning protection device 980 includes a lightning surge protection element 981 that is turned on when a lightning surge enters the distribution board 950, and a lightning surge protection element. 981 is composed of a separator 900 that cuts off a fault current that continues to flow when a fault occurs in the short-circuit mode. For this reason, the separator 900 does not perform a blocking operation for a lightning surge of a short time (several hundreds μs or less) in which the lightning surge protection element 981 operates normally and has a peak of several kA to several tens of kA. On the other hand, it is required that the continuous fault current that flows when the lightning surge protection element 981 fails in the short-circuit mode be reliably cut off. The current value of the fault current is in a wide range from several tens of amperes to a maximum of 5 kA, and the separator is required to operate even at a relatively low fault current of about several tens of amperes flowing continuously.

  In Patent Document 1, as a separator, a thermal fuse that interrupts a fault current and a disconnected conductor that interrupts a surge current exceeding the withstand capability of a lightning surge protection element are used in series. In this configuration, the minimum operating current is determined by the characteristics of the thermal fuse, and the surge resistance is determined by the characteristics of the disconnected conductor. Therefore, the minimum operating current can be lowered and the surge resistance can be increased.

  A fuse generally used as a separator has a fusing time-current characteristic as shown in the graph of FIG. As shown in the area A in this figure, the fuse blows in a short time when a large current flows, and the fusing time becomes longer as the current decreases. Further, in the region B, fusing is performed at a current value Imin called a minimum fusing current, but fusing does not occur at a current lower than that. This is because the heat from the fuse element, which has no effect because the time is short in the region A, will have an effect in the region B, so the heat generated by the current flowing through the fuse and the heat dissipation are balanced, and below the minimum fusing current. This is because the energy required for fusing is not stored in the fuse element.

  When a fuse with such characteristics is applied to a separator, it is necessary to raise the fusing time-current characteristic upward in order to prevent it from being blown by a lightning surge. When the fault current is low, it becomes difficult to blow. As an example, a fuse with a minimum fusing current of 50 A can withstand an induced lightning surge with a peak current of about 10 kA but cannot withstand an induced lightning surge with a peak current of about 20 kA. It must be higher than 50A.

  As a method for improving the surge withstand capability while keeping the minimum fusing current low, in Patent Document 2 and Patent Document 3, there is a circuit configuration in which a second fuse and a diode connected in series to the first fuse are connected in parallel. It is disclosed.

JP 2007-288114 A Japanese Utility Model Publication No. 55-136149 Japanese Utility Model Publication No. 58-83746

  For example, as shown in FIG. 9, the distribution board used when drawing into the house from the commercial power source is another type of leakage breaker (ELCB) 960 with an overcurrent protection function as a circuit breaker. Protection components are also used, and it is necessary to coordinate the operation of the protection components to be cut off correctly in response to various failures in the power supply system and the electrical and electronic equipment that is the load. For example, if all three of the lightning surge protection elements 981 installed in the single-phase three-wire L1, L2 and the neutral wire N fail in the short-circuit mode, the fault current is supplied from the commercial power supply to the leakage breaker 960 with an overcurrent protection function. After passing through the L1 and L2 separator 900 and the failed lightning surge protection element 981, the L1 to the L2, N, and the centralized grounding terminal 990, and the L2 to the L1, N, and the centralized grounding terminal 990, respectively. It flows depending on the impedance of the path. At this time, the correct protection operation is that the separator 900 operates and cuts off the fault current. However, depending on the relationship between the operating characteristics of the separator 900 and the leakage breaker 960 with the overcurrent protection function, the overcurrent protection function is provided. The earth leakage breaker 960 may operate first, and in this case, not only the fault current but also the power supply to the house through the breaker 970 is stopped.

  That is, when the lightning surge protection element 981 fails in the short-circuit mode, the correct operation coordination is that the separator 900 always operates before the leakage breaker 960 with an overcurrent protection function. For this reason, if the rated current of the leakage breaker 960 with an overcurrent protection function is 50 A, the rated current of the separator 900 needs to be at least less than 50 A, and further, the range up to a maximum value of 5 kA of fault current Is required to operate before the leakage breaker 960 with an overcurrent protection function. An earth leakage breaker with an overcurrent protection function as a circuit breaker generally operates only when overcurrent or earth leakage continues longer than about several ms, and it is several hundred μs such as a lightning surge. It doesn't work in the phenomenon below.

  The lightning protection device separator used in such a distribution board must not operate with lightning surges and must operate reliably with low current and continuous failure current. In order to coordinate the operation with such other protective components, it is desired to be able to change to a desired fusing time-current characteristic.

  The present invention has been made in view of the above circumstances, and in a current breaker including a plurality of current breakers, a current separator included in one current breaker has a high surge while keeping the minimum fusing current low. It is an object of the present invention to provide a current separator that can obtain a withstand capability and can coordinate operation with other current interrupting devices.

  The current separator of the present invention is a current separator included in the first current interrupting unit in a current interrupting device having a first current interrupting unit and a second current interrupting unit, the first fuse, A first fuse parallel circuit connected in parallel with one fuse, wherein the first fuse parallel circuit is connected in series to the second fuse and the second fuse, and a voltage exceeding a threshold voltage is applied. And a bidirectional switch means through which current flows when the current is interrupted by the first fuse and the second fuse being blown together, The threshold voltage is equal to an operating time of the first current cutoff unit at a current value exceeding a minimum cutoff current value of each of the first current cutoff unit and the second current cutoff unit. Operation time Ri is set to be short, current separator.

  In the current separator of the present invention, the bidirectional switch means may be formed by connecting a plurality of diodes in parallel in opposite directions.

  In the current separator of the present invention, the bidirectional switch means may be formed of a bidirectional thyristor.

  The current separator according to the present invention further includes a second fuse parallel circuit connected in parallel to the first fuse parallel circuit, and the second fuse parallel circuit includes a third fuse and a third fuse. The switch means is connected in series and has bidirectional switch means having a threshold voltage different from the threshold voltage.

  The current separator of the present invention further includes a cascade parallel circuit connected in parallel to the second fuse, the cascade parallel circuit including a cascade fuse and cascade voltage switch means connected in series to the cascade fuse. It is possible to have.

  A current interrupt device of the present invention is a current interrupt device that interrupts current when an abnormal current is detected, and includes a first fuse and a first fuse parallel circuit connected in parallel with the first fuse. The first fuse parallel circuit includes a second fuse and a voltage exceeding a threshold voltage connected in series to the second fuse. And a bidirectional switch means through which current flows, and the current interruption in the first current interruption part is performed by blowing both the first fuse and the second fuse, and The threshold voltage exceeds the minimum cutoff current of the first current cutoff unit and the operating time of the first current cutoff unit at a current value exceeding the minimum cutoff current of the second current cutoff unit is at the arbitrary current value. Second current interruption Is set to be shorter than the operating time of, it is a current interrupting device according to claim.

  In the current interrupting device of the present invention, the first current interrupting unit may be a lightning protection device further including a lightning surge protection element, and the second current interrupting unit may be a leakage breaker. .

It is the schematic of the distribution board containing the separator for lightning protection apparatuses which concerns on 1st Embodiment of this invention. 1B shows a circuit of the separator of FIG. 1A. FIG. It is a graph which shows the fusing time-current characteristic of a separator and a fuse. It is a graph which shows the operation time-current characteristic of a separator and an earth-leakage circuit breaker. It is a block diagram of the separator which concerns on 2nd Embodiment of this invention. It is a graph which shows the current-voltage characteristic of the bidirectional thyristor of FIG. It is a block diagram of the separator which concerns on 3rd Embodiment of this invention. It is a graph which shows the characteristic of the separator of FIG. It is a block diagram of the separator which concerns on 4th Embodiment of this invention. It is a figure which shows the distribution board structure of a general house. It is a graph which shows the fusing time-current characteristic of a general fuse.

  Hereinafter, first to fourth embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS. 1A, 1B, 2 and 3. FIG. FIG. 1A shows a configuration example of a distribution board 150 including a lightning protection circuit separator 100 according to the first embodiment of the present invention. The distribution board 150 includes a leakage breaker 160 with an overcurrent protection function that cuts off the supply of electricity when leakage and overcurrent are detected, a breaker 170 that cuts off the supply of electricity when an overcurrent is detected, A lightning protection device 180 that has a low impedance when a lightning surge enters the distribution board and avoids a surge current, and a centralized grounding terminal 190 to which a ground wire of each electric / electronic device is connected are provided. When a lightning surge enters the distribution board 150 through a commercial power source, the lightning protection device 180 connects the power lines L1 and L2 and the neutral line N from the leakage breaker 160 with an overcurrent protection function via the concentrated ground terminal 190, respectively. The lightning surge protection element 181 and the separator 100 are connected to each other.

  FIG. 1B specifically shows the circuit of the separator 100. The separator 100 includes a fuse 110 and a fuse parallel circuit 120 connected in parallel to the fuse 110, and the fuse parallel circuit 120 is connected to the fuse 130 having the same fusing time-current characteristics as the fuse 110 and the fuse 130. And a voltage switch unit 140 formed by connecting two diode groups connected in series in parallel in opposite directions.

  The voltage switch unit 140 has a threshold voltage that can be changed depending on the number of diodes in series. When a voltage equal to or higher than the threshold voltage is applied, a current flows. When the applied voltage is lower than the threshold voltage, no current flows. . For example, when the forward voltage per diode constituting the voltage switch unit 140 and the series number are 0.7V and 2 series, respectively, the threshold voltage of the voltage switch unit 140 is 0.7V × 2 = 1.4V. Become. Furthermore, when the resistance of the fuse 110 and the fuse 130 is 3 mΩ, the voltage across the fuse 110 becomes 1.4 V when the total current entering the separator 100 is 467 A (= 1.4 V ÷ 3 mΩ). When the current exceeds 467A, the current starts to flow through the fuse parallel circuit 120. When the same calculation is performed for the case where four diodes are connected in series, the threshold voltage of the voltage switch unit 140 is 0.7 V × 4 = 2.8 V, and the current starts to flow through the fuse parallel circuit 120. The total current entering is from 933A (= 2.8V ÷ 3mΩ).

  Consider a case where the threshold voltage of the voltage switch unit 140 is 1.4 V and a fault current of 100 A (> Imin) flows through the separator 100. Even if it is assumed that the current of 100A flows through the fuse 110, the voltage drop is 0.3V (= 100A × 3mΩ), which is less than the threshold voltage of 1.4V of the voltage switch unit 140. Almost no current flows through 120. For this reason, almost all of the fault current 100 </ b> A flows through the fuse 110, and the fuse 110 is blown out with a unique fusing time of the fuse 110. Subsequently, when the fuse 110 is blown, the current of 100A flows through the fuse parallel circuit 120, and the fuse 130 of the fuse parallel circuit 120 has the same fusing time-current characteristics as the fuse 110, and thus the same as the fuse 110. Fusing in time. Therefore, the separator 100 has the property that the minimum fusing current Imin is the same as that of the fuse 110 alone, but the total fusing time is doubled.

  Here, the resistance of the fuse 110 is assumed to be 3 mΩ constant, but in reality, the fuse resistance increases as the fuse element temperature rises due to heat generated by the current, and is about 5 times the resistance at room temperature immediately before melting. For this reason, the voltage across the fuse 110 becomes higher than the above-mentioned calculation result as the current continues to flow. Therefore, in reality, the current starts to be shunted to the fuse parallel circuit 120 at all currents lower than the above calculation result.

On the other hand, assuming that a high peak surge current of 20 kA, for example, enters the separator 100, assuming that the total current is almost evenly divided between the fuse 110 and the fuse parallel circuit 120, the voltage across the fuse 110 is 30 V (= 20 kA / 2 × 3 mΩ), which greatly exceeds the threshold voltage of 1.4 V of the voltage switch unit 140. Therefore, the voltage switch unit 140 is turned on as assumed, and the surge current is divided into the fuse 110 and the fuse parallel circuit 120. Will be. Assuming that the current flowing through the fuse 110 is I ₁₁₀ , the voltages applied to both ends of the fuse 110 and the fuse parallel circuit 120 are equal. Therefore, I ₁₁₀ × 3 mΩ = (20 kA−I ₁₁₀ ) × 3 mΩ + 1.4 V. Are 10.2 kA and 9.8 kA, respectively. Similarly, when the diodes of the voltage switch unit 140 are four series, I ₁₁₀ × 3 mΩ = (20 kA−I ₁₁₀ ) × 3 mΩ + 2.8 V, and the currents flowing through the fuse 110 and the fuse 130 are 10.5 kA and 9 respectively. .5 kA. Due to the threshold voltage of the voltage switch unit 140, the shunt currents to the fuse 110 and the fuse 130 are not completely uniform, and the difference increases as the threshold voltage increases. 110 and the fuse 130 are almost equally divided, and the separator 100 can conduct a surge current about twice as much as that of a single fuse. However, since the forward voltage of the diode increases as the current increases, the current shunted to the fuse parallel circuit 120 becomes even smaller than the above calculation.

  FIG. 2 shows the fusing time-current characteristic L100 (solid line) obtained by the separator 100 in comparison with the characteristic L110 (dotted line) of one fuse 110. In the separator 100, the minimum fusing current is the same as that of the single fuse 110, and the surge withstand is approximately doubled. In addition, there is a transition region having a steep slope between the region where the surge withstand is approximately twice and the minimum fusing current. This is because the current starts to flow in the fuse parallel circuit 120 when the current determined by the threshold voltage of the voltage switch unit 140 is exceeded, and the proportion of the total current increases as the current increases from there, and eventually reaches about 20 kA. Then, the transition is made to be almost equal to the fuse 110, and the portion where the ratio of the current flowing through the fuse parallel circuit 120 increases becomes the transition region.

  FIG. 3 shows two types of characteristics L101 (solid line) and L102 (one-dot chain line) for the separator 100 and a characteristic L160 (dotted line) of the leakage breaker 160 with an overcurrent protection function. The characteristics L101 and L102 of the separator 100 are due to the difference in threshold voltage of the voltage switch unit 140, and are shifted to the left by increasing the number of diodes in series to increase the threshold voltage. That is, in this case, L101 has a larger number of diodes in series than L102 and has a higher threshold voltage. This is because if the threshold voltage is increased, the voltage switch unit 140 is not turned on unless the current is larger, and the current is not divided into the fuse parallel circuit 120.

  Looking at the relationship between the characteristics of the separator 100 and the leakage breaker 160 with an overcurrent protection function, when the characteristic of the separator 100 is L101, it does not intersect with L160, and when it is L102, it intersects with L160. When L101 is always positioned below, such as L101 and L160, the separator 100 operates before the leakage breaker 160 with the overcurrent protection function regardless of the magnitude of the fault current of the lightning surge protection element 181. The earth leakage breaker 160 with the overcurrent protection function does not operate due to the fault current of the lightning surge protection element 181. On the other hand, in the case of L102 where the characteristics intersect, there is a region where the curve of L160 is lower than L102, and when the fault current of the lightning surge protection element 181 falls within that range, an overcurrent protection function is provided rather than the separator 100. The earth leakage circuit breaker 160 will operate first. When the earth leakage breaker 160 with the overcurrent protection function is operated, the power supply to the load side through the breaker 170 is also stopped, so that the separator 100 always has the earth leakage interruption with the overcurrent protection function at the failure current of the lightning surge protection element 181. It is correct operation coordination to operate before the device 160. That is, the threshold voltage of the separator 100 is set to have the characteristic of L101. In setting the threshold voltage, it is necessary to allow for an increase in the resistance of the fuse 110 as the fuse element temperature rises.

  Therefore, in the separator 100, a high surge current withstand capability can be obtained while keeping the minimum fusing current low, and the operation time of the separator 100 is set to be shorter than the operation time of the leakage breaker 160. Therefore, it is possible to reliably cut off a low and continuous failure current without unnecessarily fusing with a lightning surge and to realize operation coordination with the earth leakage breaker 160.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIGS.

  FIG. 4 shows a separator 200 for a lightning protection device according to the second embodiment of the present invention. The separator 200 is installed in the same device as the lightning protection device 180 of the distribution board 150 shown in the first embodiment, and the description of these devices is the same as that of the first embodiment. Since it is the same, it abbreviate | omits. The separator 200 includes a fuse 110 and a fuse parallel circuit 220 connected in parallel to the fuse 110, and the fuse parallel circuit 220 is connected to the fuse 230 having the same fusing time-current characteristics as the fuse 110 and the fuse 230. And a voltage switch unit 240 using a bidirectional thyristor. The current-voltage characteristic of the voltage switch unit 240 is as shown in FIG. 5 and is a high resistance characteristic that does not allow a current to flow until the switching voltage (± Vbr), and switches to a low resistance characteristic when the switching voltage is reached. Therefore, the voltage switch unit 240 can be used as a device having the same function as that in which the threshold voltage in the voltage switch unit 140 of the first embodiment is a switching voltage. Further, since the voltage switch unit 240 is close to 0 V when conducting, the fuse 110 and the fuse parallel circuit 220 are used in comparison with the voltage switch unit 140 using the series connection of the diodes of the first embodiment. Can be made more evenly close to each other.

  Therefore, in the separator 200, a high surge current withstand capability can be obtained while keeping the minimum fusing current low, and the operation time of the separator 200 can be set to be shorter than the operation time of the earth leakage breaker. Without unnecessarily fusing with a lightning surge, it is possible to reliably cut off low and continuous fault currents and realize operation coordination with the earth leakage breaker.

[Third Embodiment]
A third embodiment of the present invention will be described with reference to FIGS.

  FIG. 6 shows a lightning protection device separator 300 according to a third embodiment of the present invention. The separator 300 is installed in a device similar to the lightning protection device 180 of the distribution board 150 shown in the first embodiment described above, and the description of these devices is the same as in the first embodiment. Since it is the same, it abbreviate | omits. Like the separator 100 according to the first embodiment, the separator 300 includes a fuse 110 and a fuse parallel circuit 120 connected in parallel to the fuse 110, and further includes a fuse parallel circuit 320 connected in parallel to the fuse 110. I have. The fuse parallel circuit 320 includes a fuse 330 having the same fusing time-current characteristics as the fuse 110 and the fuse 130 and a voltage switch unit 340. The voltage switch unit 340 has the same basic configuration as the voltage switch unit 140 of the fuse parallel circuit 120, but has a different threshold voltage by changing the number of diodes in series.

  The threshold voltages of the voltage switch unit 140 and the voltage switch unit 340 are 1.4 V and 2.8 V, respectively, the resistances of the fuse 110, the fuse 130, and the fuse 330 are all 3 mΩ, and the separator 300 has a failure of 100 A (> Imin). Consider the case where current flows. Even if it is assumed that the current of 100A flows through the fuse 110, the voltage drop is 0.3V (= 100A × 3mΩ), and the threshold voltages of the voltage switch unit 140 and the voltage switch unit 340 are 1.4V and 2. Since it is less than 8V, almost no current flows through the fuse parallel circuit 120 and the fuse parallel circuit 320. For this reason, almost all of the fault current 100 </ b> A flows through the fuse 110, and the fuse 110 is blown out with a unique fusing time of the fuse 110. Subsequently, even if it is assumed that the current of 100 A flows through the fuse parallel circuit 120 after the fuse 110 is blown, the voltage drop is 1.7 V (= 100 A × 3 mΩ + 1.4 V), and the voltage switch unit 340 Therefore, almost no current flows in the fuse parallel circuit 320. For this reason, almost all of the fault current 100 </ b> A flows through the fuse 130, and the fuse 130 has the same fusing time-current characteristics as the fuse 110, so that it is blown in the same time as the fuse 110. Subsequently, when the fuse 130 is blown, the current of 100A flows through the fuse parallel circuit 320, and the fuse 330 of the fuse parallel circuit 320 has the same fusing time-current characteristics as the fuse 110 and the fuse 130. 110 and the fuse 130 are blown in the same time. Therefore, in the separator 300, the minimum fusing current Imin is the same as that of the fuse 110 alone, but the total fusing time is tripled.

  On the other hand, assuming that a high peak surge current of 20 kA, for example, enters the separator 300, assuming that the total current is almost evenly shunted to the fuse 110, the fuse parallel circuit 120, and the fuse parallel circuit 320, the voltage across the fuse 110 is 20 V (= 20 kA / 3 × 3 mΩ), which greatly exceeds the threshold voltages 1.4 V and 2.8 V of the voltage switch unit 140 and the voltage switch unit 340, respectively. Both voltage switch units 340 are turned on, and the surge current is shunted to the fuse 110, the fuse parallel circuit 120, and the fuse parallel circuit 320. Assuming that the surge current is I, the currents flowing in the fuse 110, the fuse parallel circuit 120, and the fuse parallel circuit 320 are calculated as (I / 3 + 467) A, (I / 3) A, and (I / 3-467) A, respectively. If the surge current is 20 kA, they are 7.13 kA, 6.67 kA, and 6.20 kA, respectively. Due to the threshold voltages of the voltage switch unit 140 and the voltage switch unit 340, the shunt current to the fuse 110, the fuse 130, and the fuse 330 is not completely uniform, but the surge current having a large peak value is the fuse 110, the fuse 130, As a result, the separator 300 can conduct a surge current approximately three times as large as that of a single fuse. However, since the forward voltage of the diode increases as the current increases, the current shunted to the fuse parallel circuit 120 and the fuse parallel circuit 320 becomes even smaller than the above calculation.

  FIG. 7 shows a fusing time-current characteristic L300 (solid line) obtained by the separator 300. For comparison, L101 (dotted line) obtained in the first embodiment and characteristic L110-3 (one-dot chain line) when three fuses 110 are arranged in parallel are also shown. When L300 is compared with L101, the surge resistance on the short time side is further increased and the minimum fusing current is the same due to the increase in the number of fuse parallel circuits. However, in L300, the region related to the operation coordination with the circuit breaker has a curve higher than that of L101, and L101 is more preferable for the operation coordination. However, as compared with L110-3, which has the same surge withstand capability with a normal fuse, the minimum fusing current is low and the operation coordination is easy to realize.

  Therefore, also in the separator 300, a high surge current withstand capability can be obtained while keeping the minimum fusing current low, and the operation time of the separator 300 can be set to be shorter than the operation time of the earth leakage breaker, Without unnecessarily fusing with a lightning surge, it is possible to reliably cut off low and continuous fault currents and realize operation coordination with the earth leakage breaker.

[Fourth Embodiment]
A fourth embodiment of the present invention will be described with reference to FIG.

  FIG. 8 illustrates a lightning protection device separator 400 according to a fourth embodiment of the present invention. The separator 400 is installed in the same device as the lightning protection device 180 of the distribution board 150 shown in the first embodiment, and the description of these devices is the same as that of the first embodiment. Since it is the same, it abbreviate | omits. Like the separator 100 according to the first embodiment, the separator 400 includes a fuse 110 and a fuse parallel circuit 120 connected in parallel to the fuse 110, and further includes a cascade parallel circuit 420 connected in parallel to the fuse 130. I have. The cascade parallel circuit 420 includes a fuse 430 and a voltage switch unit 440 having the same fusing time-current characteristics as the fuse 110 and the fuse 130. The voltage switch unit 440 has the same basic configuration as the voltage switch unit 140 of the fuse parallel circuit 120, but the voltage switch unit 140 has a higher current capacity than the voltage switch unit 440.

  The threshold voltages of the voltage switch unit 140 and the voltage switch unit 440 are both 1.4 V, the resistances of the fuse 110, the fuse 130, and the fuse 430 are all 3 mΩ, and a fault current of 100 A (> Imin) flows through the separator 400. Think about the case. Even if it is assumed that the current of 100A flows through the fuse 110, the voltage drop is 0.3V (= 100A × 3mΩ), which is less than the threshold voltage of 1.4V of the voltage switch unit 140. Almost no current flows through 120. Further, since almost no current flows through the fuse 130, the voltage drop of the fuse 130 is almost 0 V and is less than the threshold value 1.4 V of the voltage switch unit 440, so that almost no current flows through the cascade parallel circuit 420. For this reason, almost all of the fault current 100 </ b> A flows through the fuse 110, and the fuse 110 is blown out with a unique fusing time of the fuse 110. Subsequently, even if it is assumed that the current of 100 A flows through the fuse parallel circuit 120 after the fuse 110 is blown, the voltage drop of the fuse 130 is 0.3 V (= 100 A × 3 mΩ). Since the threshold voltage is less than 1.4V, almost no current flows in the cascade parallel circuit 420. For this reason, almost all of the fault current 100 </ b> A flows through the fuse 130, and the fuse 130 has the same fusing time-current characteristics as the fuse 110, so that it is blown in the same time as the fuse 110. Subsequently, when the fuse 130 is blown, the current of 100A flows through the cascade parallel circuit 420, and the fuse 430 of the cascade parallel circuit 420 has the same blowing time-current characteristics as the fuse 110 and the fuse 130. 110 and the fuse 130 are blown in the same time. Accordingly, the separator 400 has the property that the minimum fusing current Imin is the same as that of the fuse 110 alone, but the total fusing time is tripled.

  On the other hand, assuming that a high peak surge current of 20 kA, for example, enters the separator 400, assuming that the total current is almost evenly shunted to the fuse 110, the fuse parallel circuit 120 and the cascade parallel circuit 420, the voltage across the fuse 110 is 20 V (= 20 kA / 3 × 3 mΩ), which is much higher than the threshold voltage of 1.4 V of the voltage switch unit 140, and the voltage across the fuse 130 is 18.6 V (= 20 kA / 3 × 3 mΩ−1. 4V), which greatly exceeds the threshold voltage of 1.4 V of the voltage switch unit 440, so that both the voltage switch unit 140 and the voltage switch unit 440 are turned on as assumed, and the surge current is in parallel with the fuse 110. The current is shunted to the circuit 120 and the cascade parallel circuit 420. Assuming that the surge current is I, the currents flowing through the fuse 110, the fuse parallel circuit 120, and the cascade parallel circuit 420 are calculated as (I / 3 + 467) A, (I / 3) A, and (I / 3-467) A, respectively. If the surge current is 20 kA, they are 7.13 kA, 6.67 kA, and 6.20 kA, respectively. Due to the threshold voltages of the voltage switch unit 140 and the voltage switch unit 440, the shunt currents to the fuse 110, the fuse 130, and the fuse 430 are not completely equal, but the surge current having a large peak value is the fuse 110, the fuse 130, As a result, the separator 400 can conduct a surge current about three times as large as that of a single fuse. However, since the forward voltage of the diode increases as the current increases, the current shunted to the fuse parallel circuit 120 and the cascade parallel circuit 420 becomes even smaller than the above calculation. The characteristics obtained by the fourth embodiment are the same as the characteristics obtained by the third embodiment shown in FIG.

  Therefore, in the separator 400, a high surge current withstand capability can be obtained while keeping the minimum fusing current low, and the operation time of the separator 400 can be set to be shorter than the operation time of the earth leakage breaker. Without unnecessarily fusing with a lightning surge, it is possible to reliably cut off low and continuous fault currents and realize operation coordination with the earth leakage breaker.

  In each of the above-described embodiments, the characteristics of the fuses are the same. However, if the minimum fusing current is the same, even if a fuse having a different fusing time, such as a different fusing time, is used, It does not change the technical idea of the invention.

  Further, in each of the embodiments described above, a diode or a bidirectional thyristor is used as an element used in the voltage switch unit, but other elements such as a varistor through which a current flows when a voltage exceeding a threshold voltage is applied. It may be used. Further, elements having different characteristics may be used in combination.

  Further, in each of the above-described embodiments, the separator is included in the lightning protection device in the distribution board. However, in the current interrupting device having a plurality of current interrupting units, the current separation included in any of the current interrupting units. If it is a vessel.

  100, 200, 300, 400 Separator, 110, 130, 230, 330, 430 fuse, 120, 220, 320 fuse parallel circuit, 140, 240, 340, 440 Voltage switch unit, 150 distribution board, 160 Overcurrent protection Earth leakage breaker with function, 170 breaker, 180 lightning protection device, 181 lightning surge protection element, 190 central ground terminal, 420 cascade parallel circuit.

Claims (7)

In a current interrupting device having a first current interrupting unit and a second current interrupting unit, a current separator included in the first current interrupting unit,
A first fuse;
A first fuse parallel circuit connected in parallel with the first fuse,
The first fuse parallel circuit includes:
A second fuse;
Bi-directional switch means connected in series to the second fuse and through which a current flows when a voltage exceeding a threshold voltage is applied;
The interruption of the current in the first current interruption part is performed by melting both the first fuse and the second fuse,
The threshold voltage is equal to an operating time of the first current cutoff unit at a current value exceeding a minimum cutoff current value of each of the first current cutoff unit and the second current cutoff unit. Current separator set to be shorter than the operating time of the unit.   2. The current separator according to claim 1, wherein the bidirectional switch means is formed by connecting a plurality of diodes in parallel in opposite directions.   2. A current separator according to claim 1, wherein said bidirectional switch means is formed by a bidirectional thyristor. A second fuse parallel circuit further connected in parallel to the first fuse parallel circuit;
The second fuse parallel circuit includes a third fuse and a switch unit that is connected in series to the third fuse and has bidirectional voltage threshold voltage different from the threshold voltage. Item 4. The current separator according to any one of Items 1 to 3. A cascade parallel circuit connected in parallel to the second fuse;
The current separator according to claim 1, wherein the cascade parallel circuit includes a cascade fuse and cascade voltage switch means connected in series to the cascade fuse. A current interrupting device that interrupts current when an abnormal current is detected,
A first current interrupting unit having a first fuse and a first fuse parallel circuit connected in parallel with the first fuse;
A second current interrupting unit,
The first fuse parallel circuit includes a second fuse and bidirectional switch means through which a current flows when a voltage exceeding a threshold voltage connected in series to the second fuse is applied,
The interruption of the current in the first current interruption part is performed by melting both the first fuse and the second fuse,
The threshold voltage exceeds the minimum cutoff current of the first current cutoff unit and the operating time of the first current cutoff unit at a current value exceeding the minimum cutoff current of the second current cutoff unit is the arbitrary current. The current interrupting device is set to be shorter than the operation time of the second current interrupting unit in terms of value. The first current interrupter is a lightning protection device further comprising a lightning surge protection element,
The current interrupting device according to claim 6, wherein the second current interrupting unit is an earth leakage circuit breaker.

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