JP4619975B2 - Superconducting current limiter, superconducting current limiting system, and superconducting current limiting control method - Google Patents

Description

  The present invention relates to a superconducting current limiting device having a superconducting current limiting coil, a superconducting current limiting system including the superconducting current limiting device, and a superconducting current limiting control method using the superconducting current limiter.

  The current limiter is a device that is installed at a connection point that connects between power systems, and suppresses excessive current that passes through the connection point in the event of a system failure or voltage drop in a healthy system caused by excessive current. . Recently, development of a superconducting fault current limiter including a superconducting current limiting coil formed of a superconducting element has been actively promoted.

  For superconducting fault current limiters, various operation methods have been proposed and prototypes and tests have been carried out, and are classified into “resistance type” methods and “inductance” methods according to the type of impedance generated. The “resistance type” method utilizes a resistance increasing phenomenon based on the transition of the superconducting current-limiting coil from the superconducting state to the normal conducting state (see, for example, Patent Document 1). The present invention is directed to this resistance type superconducting fault current limiter.

  By the way, at customer sites where received power has been liberalized, there are increasing cases of introducing regular private generators (hereinafter abbreviated as “in-house”) for reasons such as reducing electricity charges. It is coming. When a customer introduces a self-developed service, the customer does not separate the site from the power company and operate it as an independent system, but continues to receive power from the power company. In many cases, it is expected that power can be supplied stably and continuously.

  In this case, if an accident such as a short circuit or a ground fault occurs in the grid on the power company side, an excessive short circuit current may flow from the private generator installed on the consumer side toward the accident point. A superconducting fault current limiter is a stationary device that can instantaneously limit such an excessive fault current during a short-circuit fault. In other words, in normal times, by supplying grid current to a superconducting wire that has no resistance, electricity can be passed through with almost no loss, but once a grid fault occurs, the superconducting wire is quenched by an excessive short-circuit current at the time of the accident ( And has a function of instantaneously suppressing the short-circuit current to a predetermined value or less with the generated resistance.

  Since the superconducting current limiter utilizes the quenching of the superconducting wire (normal conduction) in this way, it can in principle enter the protective operation without malfunction or malfunction. When an accident occurs, the current is suppressed from the first wave of the rising of the accident current, and depending on the design, it can be suppressed to about several times less than the normal operating current.

  FIG. 4 is a block diagram showing a conventional superconducting current limiting system configured using the resistance type superconducting current limiter as described above. In this figure, a first power system 1 is connected to a system bus 3 via a system circuit breaker 2. In this conventional example and an embodiment of the present invention to be described later, as the first power system 1, for example, a self-generated system such as a self-generator facility owned by various companies or autonomous organizations (hospitals, universities, etc.) is used. Assumed.

  A superconducting current limiter 4 having a disconnector 5 and a superconducting current limiting coil 6 is connected to the system bus 3. Although not shown in FIG. 4, the superconducting current-limiting coil 6 is housed in a container called a cryostat, and is kept in a superconducting state by cooling the liquid refrigerant sealed inside the cryostat.

  A load 8 is connected to a point P1 of the system bus 3 via a load circuit breaker 7, and a load 10 is connected to the point P2 via a load circuit breaker 9. Therefore, power is supplied from the first power system 1 to the load 8 via the system circuit breaker 2 and the load circuit breaker 7, and from the first power system 1 to the load 10, the system power is supplied. Electric power is supplied through the circuit breaker 2, the superconducting fault current limiter 4, and the load circuit breaker 9.

As described above, power is basically supplied from the first power system 1 to the loads 8 and 10 , but also from the second power system 11, the system circuit breaker 12 and the step-down voltage transformer. Electric power is supplied through the device 13. In this conventional example and an embodiment of the present invention described later, a commercial power system of an electric power company is assumed as the second power system 11. In addition, in FIG. 4, as shown with the broken line, the 2nd electric power grid | system 11 and the circuit breaker 12 are electric power company side facilities, Therefore, other elements are facilities on a company or autonomous organization side. is there.

  Next, the operation of FIG. 4 will be described. Now, the power from the first power system 1 is supplied to the load 8 via the system circuit breaker 2 and the load circuit breaker 7, and the system circuit breaker 2, the superconducting fault current limiter 4, and the load circuit It is assumed that the load 10 is being supplied via the circuit breaker 9. In this state, the superconducting current limiting coil 6 is maintained in the superconducting state by cooling the refrigerant in the cryostat.

  In this state, if a short circuit accident occurs in the load 10 or the second power system 11, for example, the current level flowing through the superconducting current limiting coil 6 rises, and the temperature of the superconducting current limiting coil 6 becomes Joule. It rises with heat. When the temperature of the superconducting current-limiting coil 6 reaches a certain level or higher, the superconducting current-limiting coil 6 that has been in the superconducting state until then transitions to the normal conducting state (quenching). Due to this transition, the resistance of the superconducting current-limiting coil 6 is greatly increased, so that an increase in the accident current is suppressed to a certain level or less.

Thereafter, the load circuit breaker 9 or the system circuit breaker 12 is opened, and the load 10 or the second power system 11 is disconnected from the first power system 1. Then, after the cause of the accident is removed, the load circuit breaker 9 or the system circuit breaker 12 is turned on again. At this time, the superconducting current limiting coil 6 that has been transferred to the normal conducting state is restored to the superconducting state again by a freezing operation of a cryogenic refrigeration apparatus (not shown) that cools the inside of the cryostat.
JP 2001-298858 A

  In the resistance type superconducting fault current limiter 4 shown in FIG. 4 described above, it is possible to quickly generate resistance in the event of a system fault and to suppress the fault current from the first wave. The resistance at the time of current limiting is determined by the magnitude of current allowed on the circuit side at the time of an accident, and is about 5Ω to 10Ω. Since the resistance generation of the superconducting current-limiting coil 6 due to quenching is utilized, it is possible to protect instantaneously and reliably, but during current-limiting operation, a voltage is applied to the resistance of the superconducting current-limiting coil 6 having this finite value. In order to continue, it is necessary to consider that the superconducting wire forming the superconducting current-limiting coil 6 does not cause deterioration of characteristics, burnout, or burning due to Joule heat generation.

  Therefore, when designing the superconducting fault current limiter 4, it is necessary to consider the duration of current flow of the limited current flowing through the quenched superconducting wire at the time of a system fault. The current-carrying duration of the current limiting current is determined by detecting the relay or the like when the normal circuit breakers 2, 7, 9, and 12 connected to the system or load circuit are removed from the short circuit due to an accident such as lightning. This is the shorter time between the accident section being identified and shut off. Even if a short circuit accident due to an accident such as lightning is eliminated, the temperature of the superconducting wire that has been limited and is in a normal conducting state has risen due to heat generated by energization, and does not return to the superconducting state instantaneously. For this reason, the current limiter is designed so that the time until the fault current that has been limited is interrupted by the circuit breakers 2, 7, 9, 12, etc. installed in the system or the load is continued. It will be necessary.

  The system or load protection circuit breakers 2, 7, 9, 12 and the like connected to the power system block a section based on detection means such as a protection relay so as to disconnect the fault point from the system or the load. Usually, the detection time of the protection relay is about several hundred ms (milliseconds) from the occurrence of the accident. Therefore, the superconducting wire is required to withstand overvoltage application for a period of several hundred ms after the occurrence of the accident.

The amount (volume) of the superconducting wire used for forming the superconducting current limiting coil 6 is defined by the system conditions. When the normal conducting resistance of the superconducting wire is 5Ω and this is connected to the 6.6 kV system, assuming a two-phase short circuit, a voltage of 6.6 kV is applied to both ends of the superconducting wire, so If the time until 9, 12, etc. work is 200 ms, the energy input to the superconducting wire of the current limiter at that time is
6600V × (6600V / 5Ω) × 300ms = 2.58 MJ
Therefore, it is necessary to prevent the superconducting wire from deteriorating or burning at least with this energy. For that purpose, it can be said that it is not always sufficient in terms of heat capacity to set the resistance value simply by ensuring both the cross-sectional area and the required length of the superconducting wire to obtain a normal current carrying capacity. Therefore, deterioration and burnout cannot be prevented. Therefore, in order to prevent such deterioration and burning, conventionally, a large amount of superconducting wire has to be used.

  In addition, with the use of such a large amount of superconducting wire, the cryogenic refrigeration device for removing heat generated by AC loss that normally occurs from a large amount of superconducting wire also becomes large, and heat conduction from the refrigeration device In some cases, the heat input due to can be added and the system including the refrigeration system cannot be constructed.

  A large amount of energy input to the superconducting wire forming the superconducting current-limiting coil 6 means that a large amount of refrigerant evaporates when the current is limited. If the refrigerant is liquid nitrogen, about 20 liters of liquid nitrogen will evaporate due to the above heat generation. From the viewpoint of increasing the pressure, it is necessary to open it to the atmosphere and evaporate it. As a result, it was necessary to replenish liquid nitrogen, and a system with extremely poor maintainability had to be constructed.

  Further, when a high-temperature superconducting wire such as Y (yttrium) is used as the superconducting wire forming the superconducting current-limiting coil 6, liquid nitrogen is a promising candidate refrigerant for cooling the superconducting current-limiting coil 6. In this case, the amount of refrigerant such as liquid nitrogen that evaporates during the current limiting operation of the superconducting current limiting coil 6 is determined by the resistance value of the superconducting wire, but in designing the superconducting current limiting device 4, a certain amount of liquid nitrogen evaporates. It is assumed that

  Here, once the current limiting operation is started due to a system fault, the evaporated liquid nitrogen is evaporated outside the cryostat, or the evaporated gas confined inside the cryostat is liquefied and recondensed by a cryogenic refrigeration unit. It will be. If the evaporation is performed outside the cryostat, there is a problem that the number of times that the current can be limited is not ensured during the maintenance of the system.On the other hand, if the liquid is confined and liquefied and recondensed inside the cryostat, the current limiting is performed again. The problem arises as to whether the system side can tolerate the time until it becomes possible.

  Furthermore, when a system fault occurs at a point far from the location where the superconducting current limiting device 4 is installed, the fault current is limited by the function of the superconducting current limiting coil 6, but the temporary power supply voltage Therefore, the circuit breakers 2, 7, 9, 12 and the like may not operate to interrupt the accident section. For this reason, even after the accident is removed, the superconducting wire of the superconducting current-limiting coil 6 that has been normally conducted continues to receive a system voltage so that a normal tidal current flows, and sometimes the wire can be returned to the superconducting state. There are cases where this is not possible. In such a case, since energy is continuously input to the superconducting wire for a long time, the superconducting wire is burned out.

  Therefore, in order to avoid such burning, a configuration in which a rectifier circuit or a switching circuit composed of a power semiconductor element such as a thyristor or a diode is used as a part of the superconducting current limiter 4 to shut off the system circuit at high speed. Is also conceivable. According to such a configuration, it is also possible to cut off the system current with a 3/4 wave by a method such as rectifying the current at the zero cross point.

  However, when a power semiconductor element is connected to the system circuit, the loss in the semiconductor element increases as the normal system current exceeds about 400 A. For this reason, in the case of a configuration in which, for example, a superconducting current limiting coil and a diode bridge are combined, there is a problem of constant energization loss. That is, the larger the energizing current, the more serious the device loss and size increase, and the more difficult it becomes to put it to practical use. In addition, assuming a configuration using a normal conducting reactor without using a superconducting current-limiting coil, the loss due to the constant current flowing through the reactor and the problem of equipment enlargement become more serious, making it more difficult to put into practical use. Become.

  As described above, the conventional superconducting fault current limiter 4 increases the amount of superconducting wire used, and concomitantly increases the capacity of the refrigeration apparatus, thereby increasing the size of the entire device. When the circuit breaker for use or load is not opened, there is a high possibility that the superconducting wire itself forming the superconducting current limiting coil 6 will be deteriorated and damaged by the temperature rise, and the liquid nitrogen evaporating gas is used during the current limiting operation. It had various problems such as poor maintainability due to transpiration.

  That is, the conventional superconducting fault current limiter 4 has the reliability of the equipment, the maintainability, and the large size due to the fact that resistance heating of the superconducting wire of the superconducting current limiting coil 6 continues for a certain time or more during the current limiting operation. There was still room for improvement in terms of control.

  The present invention has been made in view of the above circumstances, and it is possible to improve the reliability and maintainability of the device, and to reduce the size of the device, a superconducting current limiter, a superconducting current limiting system, and a superconducting current limiting control. It aims to provide a method.

As means for solving the above problems, the superconducting fault current limiter according to the present invention is normally maintained in a superconducting state, and allows current to pass between a plurality of power systems or between at least one power system and a load. It is a mechanical circuit breaker with a superconducting current-limiting coil that allows a low resistance state and suppresses an increase in accident current by increasing resistance based on a transition from the superconducting state to the normal conducting state when an accident occurs, and a movable contact mechanism. Based on the detection of a predetermined event indicating that an accident has occurred in at least one of the power system and the load, the circuit breaker for the current limiting coil connected in series to the superconducting current limiting coil. open, opening of the connected power system breaker to the electric power system, or by comprising a circuit breaker control means for at a timing earlier than the opening of the connected load breaker to the load And butterflies.

Further, the superconducting current limiting system according to the present invention connects a superconducting current limiting device between a plurality of power systems or between at least one power system and a load, and an accident occurs in at least one of the power system and the load. In the superconducting current limiting system that suppresses an increase in the accident current by the current limiting operation of the superconducting current limiter when it occurs, the superconducting current limiter is normally maintained in a superconducting state, and the plurality of electric powers Allow current to pass between systems, or between at least one power system and the load in a low resistance state, and in the event of an accident, increase the accident current by increasing resistance based on the transition from the superconducting state to the normal conducting state. and suppressing superconducting current limiting coil, a mechanical circuit breaker having a movable contact mechanism, the circuit breaker for the series connected current limiting coil in the superconducting current limiting coil, the electric power system and the load Based on the detection of a predetermined event that indicates that an accident has occurred in at least one, the opening of the circuit breaker for the current limiting coil, opening of the connected power system breaker to the power system, or connected to the Load Load Circuit breaker control means that is performed at a timing earlier than the opening of the circuit breaker.

Further, the superconducting current limiting control method according to the present invention is normally maintained in a superconducting state, and allows a current to pass between a plurality of power systems or between at least one power system and a load in a low resistance state. In the event of an accident , a circuit breaker for a current-limiting coil , which is a mechanical circuit breaker with a movable contact mechanism, against a superconducting current-limiting coil that suppresses an increase in the accident current by increasing resistance based on the transition from the superconducting state to the normal conducting state Are connected in series, and when a predetermined event indicating that an accident has occurred in at least one of the power system and the load is detected, the circuit breaker for the current limiting coil is connected to the power system. It is characterized in that it is performed at a timing earlier than the opening of the system circuit breaker or the opening of the load circuit breaker connected to the load .

  According to the present invention, the circuit breaker for the current limiting coil is connected in series to the superconducting current limiting coil, and the circuit breaker control means is configured to be opened based on detection of a predetermined event. It is possible to reduce the size of the device as well as improving reliability and maintainability.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3. In these figures, components other than the superconducting fault current limiter are given the same reference numerals as in FIG.

FIG. 1 is a configuration diagram of a superconducting fault current limiter according to a first embodiment of the present invention and a superconducting current limiting system using the same. A consumer who intends to introduce a self-powered system as the first power system 1 reduces the amount of power received from the power company to his loads 8 and 10 while continuing to receive power from the second power system 11. On the other hand, it is normal to employ a system that supplies power to a part of the power supply to the load in the office from the self-generated system installed by itself. And by such a system, while aiming at the reduction of the energy cost for the electric power supply of a private generator with a cheap unit price, even if an accident occurs in the 2nd electric power system 11, the 1st electric power which is an in-house power system The energy supply can be stably continued from the system 1.

  If an accident such as a three-phase ground fault occurs due to a lightning strike or the like on the second power system 11 side, a large accident current flows from the first power system 1 side toward the accident point. The accident current flowing from the first power system 1 may cause a situation in which the short-circuit capacity rating of the circuit breaker 9 connected to the point P2 that is the customer side position near the power receiving point is exceeded. Therefore, when the first power system 1 is installed, it is assumed that a load circuit breaker 9 having a sufficiently large short-circuit capacity is used, which entails a great investment in equipment.

  Further, as another influence caused by the accident current flowing from the first power system 1, an excessive voltage flows from the first power system 1 toward the accident point, so that an instantaneous voltage drop (instantaneous drop) occurs on the load 8 side. There is a problem that occurs. If this load 8 is an important load in a semiconductor production line, for example, depending on the magnitude and time of the voltage drop at the time of occurrence of a sag, the entire product of single crystal wafers to be produced over a period of half to several days is affected. In addition, there is a possibility that the product cannot be shipped as a defective product and suffers a great deal of damage. In the superconducting current limiting system according to the present embodiment, such a situation can be avoided by the function of the superconducting current limiting device 14.

  The superconducting current limiting device 14 shown in FIG. 1 includes a disconnector 15, a superconducting current limiting coil 16 connected in series to the disconnecting device 15, and a current limiting coil circuit breaker connected in series to the superconducting current limiting coil 16. 17, circuit breaker control means 18 for controlling the opening and closing operations of the current limiting coil circuit breaker 17, and information for controlling the current limiting coil circuit breaker 17 for the circuit breaker control means 18. And predetermined event detection means 19 for giving.

  The predetermined event detection means 19 is a predetermined event indicating that an accident has occurred in at least one of the first power system 1, the second power system 11, and the loads 8, 10, that is, a current-limiting coil breaker. Information about whether 17 should be released is given.

  In the present embodiment, it is assumed that any one of the following three events or a combination of these events is used as the predetermined event.

  (I) Between the first power system 1 and the second power system 11, or between the first power system 1 and the loads 8 and 10, and between the second power system 11 and the loads 8 and 10. The voltage at has dropped below a predetermined level (this voltage drop is detected by a voltage sensor).

  (Ii) Between the first power system 1 and the second power system 11, or between the first power system 1 and the loads 8, 10, and between the second power system 11 and the loads 8, 10. The current flowing through the current has risen above a predetermined level (this current rise is detected by a current sensor).

  (Iii) Superconducting current limiting coil 16 has transitioned from the superconducting state to the normal conducting state (this transition is detected by an increase in the voltage across the coil).

  By combining the above events (i) to (iii), or by adding other events as appropriate, if necessary, malfunction of the current limiting coil circuit breaker 17 caused by noise or the like mixed into the sensor or It is also possible to prevent the occurrence of malfunction, or to reduce or minimize the frequency of occurrence.

  In the present embodiment, it is assumed that the current limiting coil circuit breaker 17 is not a circuit breaker using a power semiconductor element such as a thyristor or a diode, but a mechanical circuit breaker having a movable contact mechanism.

  Next, the operation of FIG. 1 will be described. If the above-described three-phase ground fault occurs on the second power system 11 side, the first power system 1 goes to the fault point of the second power system 11 via the superconducting current limiter 14. A large accident current is about to flow. Due to the increase in the accident current, the superconducting current limiting coil 16 in the superconducting state is quickly quenched (normalized).

  In addition, due to the increase in the accident current, the predetermined event detecting means 19 detects, for example, that the voltage between the points P1 and P2 has dropped below a predetermined level as an event corresponding to the above (i), and interrupts the detection signal. To the controller control means 18. The circuit breaker control means 18 opens the current limiting coil circuit breaker 17 based on the input of this detection signal.

At this time, the opening operation of the current limiting coil breaker 17 is performed at a timing earlier than that of the system circuit breaker 12 or the load circuit breaker 9, for example, in a short time within 60 ms after the quenching of the superconducting current limiting coil 16. . Therefore, since it is avoided that an excessive current flows through the superconducting current limiting coil 16 for a long time as long as several hundred ms as in the prior art, the superconducting current limiting coil 16 does not deteriorate or burn out.

  Here, the current-limiting coil circuit breaker 17 is a mechanical circuit breaker having a movable contact mechanism as described above, and can break the circuit in all three phases within about 60 ms after detecting an accident such as a quench. Is. In this way, by using a mechanical circuit breaker as the current limiting coil circuit breaker 17, the loss during normal energization can be reduced to a level that can be almost neglected. The size can be accommodated as a component device in a normal panel.

  Then, in about 60 ms after the start of the current limiting operation of the superconducting current limiting coil 16, voltage application to the superconducting current limiting coil 16 is stopped by opening the current limiting coil breaker 17, and the coil current becomes zero. No resistance heat is generated in the normal conducting superconducting current limiting coil 16.

  Therefore, the superconducting wire forming the superconducting current-limiting coil 16 is designed with a conductor volume that can tolerate a temperature rise due to heat generation for 60 ms, so that the amount of expensive superconducting conductor used is small. Equipment can be configured.

  Note that the current limiting coil circuit breaker 17 in this embodiment is assumed to perform an opening operation within 60 ms after quenching, but the time from when a general circuit breaker obtains an opening command until it is actually opened. Is normally about 60 ms to 300 ms. Although the price tends to increase as the time to open becomes shorter, there is usually no significant difference in equipment price from about 60 ms to 300 ms. When selecting a circuit breaker within this range, reliability, equipment size, The circuit breaker that meets the application will be selected depending on the repeated resistance characteristics.

  In terms of only the breaking speed of the current limiting coil breaker 17, it is possible to develop a high-speed breaker with a breaking time shorter than 60 ms. However, the high-speed circuit breaker currently under development has a configuration in which a power semiconductor element such as a thyristor or a diode is used in the energization circuit before the price increases. A circuit breaker configured using such a power semiconductor element has a greater loss as the voltage and current increase. Therefore, the circuit breaker can be used only in limited places where the voltage and current of the installation system are below a certain level. However, it should be considered that it cannot be practically used in a place where a large current of several hundreds to 1000 A or more always flows like the superconducting current limiting device targeted in the present invention. Therefore, in this embodiment, a mechanical circuit breaker is used as the current limiting coil circuit breaker 17.

  Furthermore, in this embodiment, the circuit breaker control means 18 opens the current limiting coil circuit breaker 17 earlier than the system circuit breaker 12 or the load circuit breaker 9 operates. Regarding the circuit breaker 9, it is possible to adopt a configuration in which the circuit breaker control means 18 performs the control. That is, the circuit breaker control means 18 opens the current limiting coil circuit breaker 17 based on the signal from the predetermined event detection means 19 and simultaneously opens the load circuit breaker 9. Therefore, the opening timing of the load circuit breaker 9 can be made earlier than before, and the load 10 can be protected more quickly and reliably.

  By the way, during the current limiting operation of the superconducting current limiting coil 16, the evaporation amount of the refrigerant such as liquid nitrogen in which the superconducting current limiting coil 16 is immersed and the pressure increase in the cryostat due to the evaporated gas cause the superconducting current limiting coil 16 to form. It is determined by the resistance value of the wire and the current limiting operation duration. In this embodiment, since the current limiting operation time of the superconducting current limiting coil 16 can be reduced to a short time, the amount of refrigerant evaporated compared to the conventional case where the current limiting operation continues until the accident recovery. And the pressure rise can be greatly reduced.

For example, assuming that the current limiting operation time is about 60 ms, in the case of a superconducting fault current limiter design with a rating of 6.6 kV / 600 A and a resistance of 4Ω, the amount of heat generated when the refrigerant is liquid nitrogen is Since it can be obtained by multiplying the square of the current by the resistance and the current limiting operation time,
[Current limiting current] ² x [Resistance] x [Current limiting operating time]
= 2000 ² × 4Ω × 60ms
= 9.6 × 10 ⁵ [J]
It becomes. Therefore, the amount of evaporated nitrogen is
[Amount of evaporated nitrogen] = 9.6 × 10 ⁵ [J] / 160 [J / cc]
= 6000 [cc] = 6 [liters]
Will be enough. If the diameter of the liquid nitrogen container of the cryostat is about 1 m, the evaporation of 6 liters of liquid nitrogen causes only a drop in liquid level of less than 0.8 cm. Therefore, in the case of a design in which the pressure rise during evaporation is released to the atmosphere, even if the current limiting operation is continuously performed about 10 times, the liquid level of liquid nitrogen is about 10 cm from the uppermost surface of the superconducting coil and the liquid volume is 80 liters. If an extra amount is injected, the current limiting operation can be continued without any problem.

  In this embodiment, the system can be configured so that the evaporated nitrogen gas is sealed so as not to evaporate out of the cryostat, and the pressure does not increase to a problem even after several continuous current limiting operations. Is possible. The liquid nitrogen gas that has evaporated and stayed in the cryostat can be liquefied and recondensed over several tens of hours after the current limit by attaching a cryogenic refrigerator such as a GM refrigerator to the cryostat. Maintenance-free operation is possible even after current limiting.

  Here, as in the conventional example shown in FIG. 4, it is assumed that there is no current limiting coil breaker 17 and the superconducting current limiting coil 16 continues the current limiting operation until the accident is removed. For example, if the system breaker 12 is interrupted 300 ms after the start of the current limiting operation by the protective relay, in this case, five times as much energy is put into the normally conducted superconducting current limiting coil 16, so that it is about 30 liters or more. Of liquid nitrogen evaporates. Therefore, after several current-limiting operations, operation cannot be performed without re-injection, resulting in a large amount of labor for maintenance. Therefore, it is clear that the present embodiment has a great merit.

  The above comparison with the conventional example is a comparison when the circuit breaker operates, but when a system fault occurs in a place far away from the installation location of the superconducting fault current limiter (for example, about several hundred km) A more noticeable difference appears. That is, in general, the system circuit breaker or the load circuit breaker is intended to isolate the accident section, and therefore, many circuit breakers are often protected in cooperation with a protection relay or the like. And when the system fault is close to the installation position of the superconducting fault current limiter, the system circuit breaker or the load circuit breaker can also be reliably opened and shut off, but in the case of a system fault at a distant place, In the vicinity of the installation position of the superconducting fault current limiter, the accident current only rises to about 1.5 to 2 times the normal current.

  Therefore, although the superconducting current-limiting coil performs the current-limiting operation by quenching, a state appears in which the voltage is only slightly lowered over a time of about several hundred ms. In such a state, since the accident section is far, it is not determined that the accident is caused by the detection setting, and the system circuit breaker or the load circuit breaker often does not perform the breaking operation. In some cases, the blocking operation may not be performed in most cases. For this reason, the system voltage continues to be applied to the normal conducting superconducting current-limiting coil even after the accident is removed, and the superconducting current-limiting coil is surely burned out due to continuous voltage application for a long time. However, in the configuration of FIG. 1, the current flowing in the superconducting current limiting coil 16 is reliably interrupted in about 60 ms after quenching by opening the current limiting coil circuit breaker 17, and thus the superconducting current limiting device 14. It is possible to stably perform the protection function without falling into such a dangerous situation.

  As described above, in the configuration of FIG. 1, the evaporation of liquid nitrogen during the current limiting operation can be suppressed to a minimum. Therefore, even after the superconducting current limiting coil 16 is quenched and the current limiting coil breaker 17 is opened. If the superconducting current limiting coil 16 returns to the superconducting state, it is possible to turn on the current limiting coil breaker 17 and immediately return the superconducting current limiting device 14 to the energized state.

  Therefore, a circuit breaker of a type that can be turned on again by a turn-on command is adopted as the current-limiting coil circuit breaker 17, and after the current-limiting coil circuit breaker 17 is opened by the current-limiting operation of the superconducting current-limiting coil 16, predetermined conditions are met. It is possible to set a sequence so that the circuit breaker control means 18 re-inserts the current limiting coil circuit breaker 17 and the superconducting current limiting device 14 can be set to the initial state when the above is established.

  As the predetermined condition, for example, an accident on the second power system 11 side is removed (that is, an event indicating the occurrence of an accident is detected on either the second power system 11 side or the load 10 side). It is considered that the superconducting current limiting coil 16 has returned to the superconducting state, a sufficient time has passed for the superconducting current limiting coil 16 to return to the superconducting state, or a combination of these conditions. It is done.

  Of the above re-input conditions, “a sufficient time for the superconducting current-limiting coil 16 to return to the superconducting state” may be, for example, about 30 seconds to several minutes. It may not have been removed. In such a case, since the accident current increases again at the moment of re-input, quenching of the superconducting current limiting coil 16 and opening of the current limiting coil breaker 17 are performed again. Therefore, after that, it is set to prohibit re-introduction, and after the investigation of the accident situation and safety confirmation by the human system are performed, re-introduction of the current-limiting coil circuit breaker 17 is permitted only manually. be able to.

  When the circuit breaker 17 for current limiting coil is turned on again, the AC phase on the first power system 1 side must match the AC phase on the second power system 11 side. The control means 18 is sequenced so that the current limiting coil breaker 17 is re-introduced in cooperation with the system device that matches the AC phase. Therefore, after an accident occurs, the time from re-input that normally takes 1 hour to half a day is automatically re-input within 30 seconds to several minutes or less according to the configuration of FIG. Is possible. Therefore, it is possible to realize the omission of manpower while greatly improving the function.

  As described above, the circuit breaker 17 for the current limiting coil can be reintroduced in principle when a predetermined reintroduction condition is satisfied, but there are certain exceptions. This exception is, for example, a reference value in which a detection value related to a pressure or a pressure increase in a cryostat housing the superconducting current-limiting coil 16 after the superconducting current-limiting coil 16 transitions from the superconducting state to the normal conducting state is set in advance. Or the temperature in the cryostat or the detection value related to the temperature rise exceeds a preset reference value. The circuit breaker control means 18 receives these detection signals. In such a case, the circuit breaker control unit 18 stops recharging the current limiting coil circuit breaker 17 regardless of whether or not a predetermined recharging condition is satisfied. It has become.

  Next, in the present embodiment, since the evaporative gas from the liquid refrigerant can be recondensed by adopting a configuration equipped with a cryogenic refrigeration apparatus, this will be described in detail.

  The superconducting current limiting coil 16 is housed in a cryostat in which a refrigerant such as liquid nitrogen is sealed. For example, when the rating of the superconducting current limiter 14 is 6.6 kV / 600 A, the amount of evaporated nitrogen during current limiting operation is about 6 As already mentioned, it becomes liters. The liquid nitrogen of about 6 liters that evaporates can be made to evaporate out of the cryostat. Thereby, for example, it is possible to operate so as to compensate for the decreased liquid nitrogen during the maintenance of the cryogenic refrigeration apparatus performed once a year. The decrease in liquid nitrogen due to the generation of evaporating gas is caused by the heat generation of the current lead during normal energization, the AC loss of the superconducting current limiting coil 16, the heat intrusion into the cryostat, etc. It is possible to liquefy and recondense the gas.

  A cryostat equipped with a cryogenic refrigeration apparatus can be configured to contain the refrigerant gas generated during the current-limiting operation in the cryostat without evaporating to the outside. If evaporative gas remains in the gas state at the top of the cryostat, the pressure in the cryostat will be about 1000 hPa, depending on the design, so the pressure resistance of the cryostat can be set to accommodate the pressure increase during current limiting. By doing so, it is possible to prevent evaporation gas from evaporating to the outside.

  However, even if a cryogenic refrigeration system is equipped, the evaporated gas generated during the current limiting operation cannot be recondensed and liquefied within a short time. However, the number of times the superconducting fault current limiter 14 actually operates is about 10 times a year at most. Therefore, if the evaporated gas generated in a certain current limiting operation is liquefied and recondensed for several days to 10 days before the next current limiting operation, it is not necessary to supply liquid nitrogen. A system can be configured.

  In addition, system faults such as instantaneous voltage drop may occur several times or more in a short time during the day. The current at the time of instantaneous voltage drop is usually considerably smaller than the accident current due to a short-circuit accident or the like in the close range. Therefore, even if the current-limiting operation is performed several times in a short time, the amount of the evaporated gas at this time is small, and in most cases, it is not necessary to evaporate the gas to the outside. As described above, in the superconducting current limiter 14 in which the sequence is set so that the interruption is performed in about 60 ms after the start of the current limiting operation and the reintroduction is performed after about 30 seconds to several minutes have elapsed, a plurality of instantaneous voltage drop occurring in a distant place is performed. On the other hand, it is possible to realize a system that can automatically cope with a plurality of repetitions of the current limiting operation on the premise that the current limiting → interrupt → accident removal → re-introduction programming is possible.

  In addition, as described above, if the cryogenic refrigeration apparatus is equipped, the cryogenic refrigeration apparatus at the liquid nitrogen temperature is more heated than the current lead or the current limiting device superconducting coil in the normal energization state. By setting the refrigerating capacity to exceed, liquid nitrogen can be prevented from gradually evaporating, and maintenance-free operation becomes possible.

  In this case, since the heat generation and the refrigeration capacity are balanced at a temperature lower than the boiling point temperature of liquid nitrogen and the operation temperature is in an equilibrium state, the superconducting fault current limiter 14 can be stably operated. By using sensible heat from the temperature of this stable equilibrium operation state to the boiling point temperature of liquid nitrogen, the evaporated gas generated as bubbles from the surface of the superconducting wire normally conducted during current limiting operation is converted into liquid nitrogen. In the process of rising to the liquid level, a part or majority of the bubbles are designed to be recondensed to liquid nitrogen by heat exchange with supercooled nitrogen, and it is possible to suppress an increase in the internal pressure of the cryostat due to evaporating gas is there.

  The inventors of the present invention have actually confirmed how bubbles of evaporated nitrogen gas generated from the surface of the superconducting wire disappear in supercooled nitrogen. That is, the generation of bubbles in boiling liquid nitrogen is visually recognized and recorded by a high-speed video camera. In the current limiting operation, the internal pressure of the cryostat is hardly increased, and only a slight temperature increase of about 1K is allowed for the supercooled nitrogen so that the next current limiting operation can be performed within about 1 minute. Confirmed that design is possible.

  By the way, in general, most of the accidents in the system experienced at a certain point are accidents relatively far from the superconducting fault current limiter 14. This is a natural consequence of the possibility of lightning strikes in the immediate range of the superconducting fault current limiter 14 being lower than the possibility of lightning strikes in a wide range including far away. In the case of a remote accident, the accident current is about several kA, which is considerably smaller than several kA to several tens kA in the case of an accident in the close range. Therefore, normally, the energy generated during the current limiting operation of the superconducting current limiting coil 16 is much smaller than in the case of an accident in the closest range, and the amount of evaporation of refrigerant such as liquid nitrogen and the pressure rise in the cryostat are significantly small. It will be a thing. For this reason, the time during which re-injection can be performed is shortened, and the number of times that the current can be continuously limited without dissipating the evaporated gas increases. In other words, the general characteristics of current limiters that the majority of accident locations are far away are particularly fortunate for superconducting current limiters, so they are expected to be applied as highly compatible protective devices. it can.

  Furthermore, in a remote accident that accounts for the majority of accident phenomena, the thermal history of the superconducting current-limiting coil 16, that is, a rapid temperature rise due to energy input after normalization and a thermal stress due to rapid re-cooling after current limiting. This is much smaller than in the case of an accident in the immediate range. Therefore, it is not necessary to assume the occurrence of a situation in which the characteristics of the superconducting wire deteriorate semipermanently even in many current-limiting operations. In this respect, it can be expected that the device is extremely reliable in principle.

  Next, a superconducting current limiting device according to a second embodiment of the present invention and a superconducting current limiting system using the same will be described with reference to FIG. The superconducting current limiter 14A shown in FIG. 2 is different from the superconducting current limiter 14 shown in FIG. 1 in that the current to be passed through the superconducting current limiting coil 16 and the current limiting circuit breaker 17 connected in series to the superconducting current limiting coil 14 is bypassed. A bypass path 20 is formed, and a bypass switch 21 that is normally open is provided in the bypass path 20. The bypass switch 21 may be a bypass disconnector, or may be a bypass breaker that can control the current limiting coil breaker 17.

  The effect by having comprised the bypass path 20 which has the switch 21 for bypasses as mentioned above is demonstrated below. When the first power system 1 is stopped for inspection, or when the power reception from the second power system 11 to the loads 8 and 10 is temporarily stopped, the superconducting current limiter 14A depends on the situation on the load side. The magnitude and direction of the current passing through may change temporarily.

  For example, the load 8 often has a relatively important load because the superconducting fault current limiter 14A can protect the influence of an accident from the second power system 11 that is the power company side equipment. The proportion of such an important load tends to increase more and more as the number of computer-controlled devices increases, depending on the type of business.

  And the power reception from the 2nd electric power grid | system 11 is stopped temporarily, the electric power is supplied to the load 8 and 10 from the 1st electric power grid | system 1 side which is a self-development side, and about the equipment by the side of a customer in this state Maintenance or maintenance of the cryogenic refrigeration unit equipped in the cryostat of the superconducting fault current limiter 14A (maintenance of the cryogenic refrigeration unit is required at least once a year). is there. In this case, the current passing through the superconducting fault current limiter 14A from right to left is larger than before the power reception from the second power system 11 is stopped because the supply to the load 10 is increased. Yes.

  The cryogenic refrigeration unit equipped in the cryostat is of course insulated from the superconducting current limiting coil 16 to which a system voltage of at least 6.6 kV or more is applied and its current lead member, but the superconducting current limiting coil 16 is energized. Maintenance in the state where the operation is performed, that is, in a live line state is not preferable in terms of safety management. Therefore, when carrying out maintenance of the cryogenic refrigeration apparatus, the superconducting current-limiting coil 16 must be in a state of being electrically cut off so that a live line state does not occur. According to the present embodiment, by using the bypass 20, maintenance of various facilities on the customer side and the cryogenic refrigeration apparatus can be safely performed while allowing the system current to pass through the superconducting current limiter 14 </ b> A. Can be implemented.

  Further, according to the configuration of the present embodiment in which the bypass path 20 is formed, it is possible to obtain an effect that it is not necessary to unnecessarily increase the refrigeration capacity of the cryogenic refrigeration apparatus.

That is, the value of the critical current of the superconducting current-limiting coil 16 is set to about twice or less of the operating current. This is a balance between reducing the sensitivity and reducing the number of current limiting operations as much as possible when the magnitude of the fault current to be detected by the superconducting current limiting coil 16 is made extremely large compared to the normal current. This is a result of consideration. This also leads to an energy-saving design of the equipment by reducing the amount of superconducting wire used, reducing AC loss in the superconducting wire, reducing the load on the cryogenic refrigeration system, and the like.

  On the other hand, the capacity of the cryogenic refrigeration apparatus is usually designed in accordance with the normal operating current. For example, when the normal operation current is 400 A, the temporary allowable energization current value of the superconducting wire is designed so that 600 A, which is higher than the normal operation current, can be applied due to the inspection work on the customer side. However, the refrigeration capacity of the cryogenic refrigeration apparatus is always set to 400 A, which is the energization current.

  Therefore, when energization at 600 A continues for a certain time or more, the thermal load exceeds the freezing force, the liquid nitrogen temperature gradually starts to rise from the equilibrium temperature, reaches the boiling temperature, and the liquid nitrogen begins to evaporate. If the bypass path 20 is not formed, the maintenance must be performed while the superconducting current-limiting coil 16 is energized with 600 A. In this case, the above-described situation occurs. Is inevitable. In this case, it is possible to design the capacity of the cryogenic refrigeration apparatus so that the time to the liquid nitrogen boiling temperature (77 K) is about several hours to half a day even if 600 A energization continues for a certain time or more. Then, it becomes over-spec in comparison with the refrigeration capacity of a normal refrigeration apparatus, which is not appropriate.

  However, according to the present embodiment, when carrying out maintenance, the current that has been flowing through the superconducting current limiting coil 16 can be commutated to the bypass 20, so that the length of 600 A of the superconducting current limiting coil 16 can be increased. There is no need to increase the refrigeration capacity of the cryogenic refrigeration system in response to the time energization.

  The operation of switching the energization path to the bypass path 20 is performed by the following procedure, for example. First, the power supply amount from the first power system 1 is switched so that the passing current of the superconducting current limiting device 14A is changed from 400A to 600A. Following this, power supply from the second power system 11 to the loads 8 and 10 is stopped, the bypass switch 21 is immediately turned on, and the current-limiting coil circuit breaker 17 is opened. Thereafter, the disconnector 15 is opened by manual operation or the like.

  Thereafter, maintenance is performed on the customer side equipment, or maintenance is performed on the cryogenic refrigeration apparatus provided in the cryostat of the superconducting fault current limiter 14A. However, it usually takes about a half day to a day until the maintenance is completed, and the superconducting fault current limiter 14A has lost its current limiting function during that time. It is preferable to select a season and date and time when there is a low possibility that an accident such as a momentary voltage drop will occur in the power system.

  In the maintenance of the cryostat or the cryogenic refrigeration apparatus, liquid nitrogen in the cryostat can be prevented from evaporating at all to the outside, so that it is not necessary to supply liquid nitrogen in principle. However, if the current limiting operation continues during the operation period, or if some of the liquid nitrogen has evaporated to the outside for some other reason, it is possible to replenish the liquid nitrogen after the maintenance is completed. is there.

  In addition, maintenance of the cryogenic refrigeration system can be performed with the cryostat cooled and without opening it to atmospheric pressure. However, depending on the surrounding conditions, the cryostat may be heated to room temperature, It is also possible to carry out in an open state.

  Next, a superconducting fault current limiter according to a third embodiment of the present invention and a superconducting current limiting system using the same will be described with reference to FIG. In the configuration of FIG. 3, the first power system 1 and the system circuit breaker 2 illustrated in FIGS. 1 and 2 are omitted. This is because, in the present embodiment, the customer-side equipment is at a close distance from the power company-side equipment, and the loads 8 and 10 are premised on receiving power from the second power system 11. However, as in FIGS. 1 and 2, it can be described as a configuration including the first power system 1 and the system circuit breaker 2, but in this case, the first power system 1 is suspended. It will be described as being in a state.

  The superconducting current limiter 14B of FIG. 3 differs from the superconducting current limiter 14A of FIG. 2 in that a bypass circuit breaker 22 and an impedance member 23 (for example, a reactor coil) connected in series to the bypass path 20 are provided. This is the point. The bypass circuit breaker 22 can be controlled by the circuit breaker control means 18, and the impedance member 23 is sufficient to suppress the inrush current to the load 8 when the bypass circuit breaker 22 is turned on. It has impedance.

  In addition, the load 8 in the present embodiment is an important load that must be continuously supplied without interruption of power from the second power system 11.

  Next, the operation of FIG. 3 will be described. Various devices other than the load 8 are connected to the downstream side of the superconducting current limiting device 14B (that is, the right side in FIG. 3). If a short circuit accident occurs in these devices, a large accident current from the second power system 11 tends to flow toward this accident point. Due to this increase in the accident current, the superconducting current limiting coil 16 in the superconducting state is quickly quenched, and the circuit breaker control means 18 opens the current limiting coil circuit breaker 17 within 60 ms after quenching, as in the case of FIG. To do.

  However, the circuit breaker control means 18 of this embodiment inputs the bypass circuit breaker 22 prior to opening the current limiting coil circuit breaker 17 at this time. Therefore, according to the present embodiment, the power from the second power system 11 can be continuously supplied to the load 8 without causing a cut-off state. At this time, the impedance member 23 can prevent the inrush current from flowing into the load 8 side.

  After the above accident is removed, the circuit breaker control means 18 reopens the current limiting coil circuit breaker 17 and then opens the bypass circuit breaker 22. The conditions for reintroducing the current limiting coil circuit breaker 17 may be the same as those already described in the first embodiment.

  That is, the condition that the accident has been removed, the superconducting current limiting coil 16 has returned to the superconducting state, the time sufficient for the superconducting current limiting coil 16 to return to the superconducting state has passed, or these conditions It is a combination. Also, the conditions for prohibiting re-insertion may be the same as in the first embodiment.

1 is a configuration diagram of a superconducting current limiter according to a first embodiment of the present invention and a superconducting current limiting system using the same. The block diagram of the superconducting current limiting device which concerns on the 2nd Embodiment of this invention, and a superconducting current limiting system using the same. The block diagram of the superconducting current limiting device which concerns on the 3rd Embodiment of this invention, and a superconducting current limiting system using the same. The block diagram of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 1st electric power system, 2 ... System breaker, 3 ... System bus, 4 ... Superconducting current limiting device, 5 ... Disconnector, 6 ... Superconducting current limiting coil, 7 ... Load circuit breaker, 8 ... Load, DESCRIPTION OF SYMBOLS 9 ... Load circuit breaker, 10 ... Load 1, 11 ... 2nd electric power system, 12 ... System circuit breaker, 13 ... Transformer, 14, 14A, 14B ... Superconducting current limiter, 15 ... Disconnector, 16 ... Superconducting current limiting coil, 17 ... Circuit breaker for current limiting coil, 18 ... Circuit breaker control means, 19 ... Predetermined event detecting means, 20 ... Bypass path, 21 ... Bypass switch, 22 ... Bypass circuit breaker, 23 ... Impedance Element.

Claims (14)

It is always kept in a superconducting state, allowing current to pass between multiple power systems or at least one power system and a load in a low resistance state, and transitioning from a superconducting state to a normal conducting state when an accident occurs A superconducting current-limiting coil that suppresses an increase in accident current by increasing resistance based on
A mechanical circuit breaker having a movable contact mechanism, and a circuit breaker for a current limiting coil connected in series to the superconducting current limiting coil;
Based on the detection of a predetermined event indicating that an accident has occurred in at least one of the power system and the load, the circuit breaker for the system connected to the power system is opened, Circuit breaker control means for performing the timing earlier than the opening of the load circuit breaker connected to the load ;
A superconducting current limiting device characterized by comprising: When a superconducting fault current limiter is connected between multiple power systems or between at least one power system and a load, and a fault occurs in at least one of the power system and the load, In the superconducting current limiting system that suppresses the increase of the accident current by the flow operation,
The superconducting fault current limiter is
It is always kept in a superconducting state, and allows a current to pass between the plurality of power systems or between at least one power system and the load in a low resistance state. When an accident occurs, the superconducting state is changed to the normal conducting state. A superconducting current-limiting coil that suppresses an increase in accident current by increasing resistance based on the transition of
A mechanical circuit breaker having a movable contact mechanism, and a circuit breaker for a current limiting coil connected in series to the superconducting current limiting coil;
Based on the detection of a predetermined event indicating that an accident has occurred in at least one of the power system and the load, the circuit breaker for the system connected to the power system is opened, Circuit breaker control means for performing the timing earlier than the opening of the load circuit breaker connected to the load ;
A superconducting current limiting system characterized by comprising: The predetermined event is:
The voltage between the plurality of power systems or between at least one power system and the load has dropped below a predetermined level;
The current flowing between the plurality of power systems or between at least one power system and the load has increased to a predetermined level or more;
The superconducting current-limiting coil has transitioned from a superconducting state to a normal conducting state;
The superconducting current limiting system according to claim 2, comprising at least one of the following. The circuit breaker control means is capable of controlling not only the current limiting coil circuit breaker but also the load circuit breaker, and opening the current limiting coil circuit breaker and connecting to the load. The opened circuit breaker is opened at the same time,
The superconducting current limiting system according to claim 2 or 3, wherein The circuit breaker control means reopens the current limiting coil circuit breaker when a predetermined condition is satisfied after opening the current limiting coil circuit breaker.
The superconducting current limiting system according to any one of claims 2 to 4 . The predetermined condition is:
An event indicating that an accident has occurred for either the power system or the load is no longer detected,
The return to the superconducting state of the superconducting current-limiting coil has been detected,
A sufficient set time has elapsed for the superconducting current-limiting coil to return to the superconducting state,
The superconducting current limiting system according to claim 5 , comprising at least one of the following. The circuit breaker control means is configured to detect a detection signal related to a pressure or a pressure increase in a cryostat housing the superconducting current limiting coil, or a detection related to a temperature or temperature increase after the superconducting current limiting coil is changed from a superconducting state to a normal conducting state. When a signal is input and the value of these detection signals exceeds a preset reference value, it is set so as to stop the reclosing of the current limiting coil breaker regardless of whether or not the predetermined condition is satisfied. The
The superconducting current limiting system according to claim 5 or 6 . A liquid refrigerant is sealed inside the cryostat that houses the superconducting current-limiting coil, and the gas refrigerant that is vaporized from the liquid surface of the liquid refrigerant is discharged to the outside during the current-limiting operation of the superconducting current limiter. It has a sealed structure that can prevent
The refrigeration operation is normally performed so that the liquid refrigerant sealed inside the cryostat reaches thermal equilibrium at a temperature lower than the refrigerant boiling temperature, and the gaseous refrigerant generated by vaporization from the liquid surface is recondensed and liquefied. Equipped with possible cryogenic refrigeration equipment,
A superconducting current limiting system according to any one of claims 2 to 7 . In the superconducting current limiting device, a bypass path is formed for bypassing the current to flow through the superconducting current limiting coil and the circuit breaker for the current limiting coil connected in series to the superconducting current limiting coil. There is a bypass switch that is always open on the road,
The superconducting current limiting system according to any one of claims 2 to 8 . The bypass switch is a bypass circuit breaker controllable by the circuit breaker control means.
The superconducting current limiting system according to claim 9 . When there is a load that should continuously supply power from either power grid without interruption
When the circuit breaker control means opens the current limiting coil circuit breaker, the circuit breaker control means keeps the bypass circuit breaker in the input state prior to the opening.
The superconducting current limiting system according to claim 10 . An impedance member having sufficient impedance to suppress inrush current to the load is connected in series to the bypass circuit breaker.
The superconducting current limiting system according to claim 11 . The circuit breaker control means, after turning on the bypass circuit breaker, and further opening the current limiting coil circuit breaker,
A predetermined event indicating that an accident has occurred for either the power system or the load is no longer detected;
The return to the superconducting state of the superconducting current-limiting coil has been detected,
A sufficient set time has elapsed for the superconducting current-limiting coil to return to the superconducting state,
Re-opening the circuit breaker for current limiting coil when at least one of the conditions is satisfied, and then reopening the circuit breaker for bypass.
13. The superconducting current limiting system according to claim 11 or 12, It is always kept in a superconducting state, allowing current to pass between multiple power systems or at least one power system and a load in a low resistance state, and transitioning from a superconducting state to a normal conducting state when an accident occurs A current-limiting coil circuit breaker, which is a mechanical circuit breaker having a movable contact mechanism, is connected in series to a superconducting current-limiting coil that suppresses an increase in accident current by increasing resistance based on
When a predetermined event indicating that an accident has occurred in at least one of the power system and the load is detected, the circuit breaker for the system connected to the power system is opened, Or at a timing earlier than the opening of the load circuit breaker connected to the load,
Superconducting current limiting control method characterized by the above.

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