JP3754424B2 - Permissible current detector for superconducting equipment and power system using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a permissible current detector for superconducting equipment and a power system using the same.
[0002]
[Prior art]
In recent years, high-temperature superconductor materials have been actively developed by many research institutions and companies, and research toward the practical application of power superconducting equipment such as power cables, transformers, and current limiters using high-temperature superconductors has been carried out. Development is underway. For example, the superconducting fault current limiter stops the current supply by using a resistance generated when the superconductor transitions from the superconducting state to the normal conducting state. Although the current superconducting current limiter has a small capacity and is insufficient to be applied to a power system, improvement of the element structure and increase in capacity by series paralleling of current limiting elements have been proposed (for example, Patent Document 1). reference).
[0003]
If such a superconducting device for electric power is connected to the power system and a malfunction occurs in the superconducting device, high-quality power cannot be stably supplied. High reliability is required. One of the problems of superconducting equipment is that the critical current of the superconductor deteriorates and the allowable current value decreases. For this reason, it is necessary to detect the allowable energization current value at the time of installing the superconducting device and at the regular inspection, and to perform maintenance and replacement promptly when it is deteriorated.
[0004]
In general, the allowable conducting current of a superconductor is evaluated by measuring a minute voltage generated when a current close to an assumed critical current is passed. However, during normal energization in the power system, the current capacity of the superconducting device is set to about 50 to 90% of the critical current of the superconductor. For this reason, it is normal that a voltage is not generated in a state where normal energization is performed, and a voltage is generated only at the time of abnormality such as when the critical current of the superconducting device is greatly deteriorated. Even if the voltage can be detected at the time of such an abnormality, there is a problem that the device is damaged. On the other hand, when the superconducting device is disconnected from the power system and an allowable energization current is to be evaluated, complicated operations such as installation and switching of alternative devices occur.
[0005]
From the background as described above, it is desired that an abnormality can be detected by measuring an allowable energization current of a superconducting device in a normal use state, that is, in a state of being normally energized by being connected to a power system.
[0006]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 11-204845
[Problems to be solved by the invention]
An object of the present invention is to provide a device capable of detecting an allowable energization current in a state where a superconducting device for electric power is connected to an electric power system, and an electric power system using the device.
[0008]
[Means for Solving the Problems]
An allowable energization current detection device for a superconducting device according to an aspect of the present invention is an apparatus for detecting an allowable energization current of a superconducting device including a superconductor connected to a power system from a power supply source to a load, A current source that supplies a superimposed current for a time shorter than the cycle of the energization current while energizing the superconducting device while maintaining a superconducting state, means for measuring a voltage signal generated in the superconducting device, and the voltage signal And a means for detecting an allowable energization current of the superconducting device based on the above.
[0009]
In the apparatus according to the present invention, it is preferable that the current source is a pulse current source, and a pulse current synchronized with a peak of an energized current is supplied as the superimposed current.
[0010]
The apparatus according to the present invention preferably further includes a controller for controlling the current source so as to increase the superimposed current until the voltage generated in the superconducting device becomes 1 μV / cm or more per length of the superconductor.
[0011]
In the apparatus according to the present invention, the means for detecting an allowable energization current of the superconducting device is based on a voltage obtained by removing an inductance of the superconducting device and a voltage due to a connection resistance from a voltage generated in the superconducting device. It is preferable to determine the allowable energization current of the device.
[0012]
The device according to the present invention preferably has a switch for disconnecting the current source and the voltage measuring means from the power system when the voltage generated in the superconducting device reaches a predetermined value.
[0013]
A power system according to another aspect of the present invention includes a power system including a power supply source, a load, and a superconducting device including a superconductor connected therebetween, and energizes the superconducting device while maintaining a superconducting state. A current source that supplies a superimposed current for a time shorter than the cycle of the energized current, a means for measuring a voltage signal generated in the superconducting device, and an allowable energizing current of the superconducting device based on the voltage signal. It has a means for detecting and a bypass current path for bypassing the superconducting device.
[0014]
The power system according to the present invention preferably includes a filter circuit that removes an electrical signal other than the frequency of the energized current between the superconducting device and the load.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a schematic configuration of a power system according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a power system including a power system in which a superconducting fault current limiter is connected as a superconducting device between a power supply source (substation) and various power consumption systems as loads. Although not shown in FIG. 1, a plurality of power plants are connected to lend and borrow power between power plants, and power is sent from one power plant to a plurality of substations.
[0016]
As shown in FIG. 1, 66 kV power transmitted from a power station (not shown) is stepped down to 6.6 kV at a substation 100 and transmitted to a plurality of loads (power consumption systems). In FIG. 1, a general household (A system), a factory (B system), and a hospital (C system) are shown as examples of loads.
[0017]
In such a power system, for example, when a short-circuit accident occurs at point X of the B system in the figure, the impedance is suddenly reduced, so that the current concentrates on the B system. As a result, the power transmission capacity to the C system is reduced, causing problems such as a voltage drop. As a countermeasure, a breaker 101 is provided in each power system, and when a short-circuit accident occurs, the power system is immediately cut off and separated from other power systems. However, since it takes a time on the order of milliseconds until the circuit breaker 101 operates, it is currently impossible to connect power systems that do not allow an instantaneous power failure or voltage drop. In order to solve this problem, a superconducting fault current limiter 102 is connected to each power system. Superconducting fault current limiter 102 instantaneously transitions to normal conduction when a current exceeding an allowable amount flows, generates resistance, and prevents a large current from flowing. However, conventionally, an abnormality of the superconducting fault current limiter 102 or the like cannot be detected easily.
[0018]
In the power system according to the embodiment of the present invention, the allowable conducting current detection device 103 is provided for the superconducting current limiter 102. As will be described in detail later, the allowable conducting current detector 103 is connected to the superconducting fault current limiter 102 in the power system, and allows detection of the allowable conducting current of the superconducting fault limiter 102 while the normal conducting current is flowing. Therefore, it is possible to quickly determine the deterioration of the superconducting fault current limiter 102 and perform maintenance or replacement, thereby improving the stability of the power system.
[0019]
In the power system according to the embodiment of the present invention, a bypass current path 106 that bypasses the superconducting current limiter 102 may be provided via the changeover switch 105. In this configuration, the allowable energizing current detector 103 always monitors whether the allowable energizing current of the superconducting fault current limiter 102 has decreased, and if a decrease is observed, an alarm is sent to the centralized control center 107, from which The changeover switch 105 is operated by a control signal, and maintenance can be performed by switching to the bypass current path 106 or a spare superconducting fault current limiter (not shown).
[0020]
With reference to FIG. 2 and FIG. 3, a description will be given of an allowable conduction current detection device for a superconducting fault current limiter according to an embodiment of the present invention. FIG. 2 is a block diagram showing the connection status of the superconducting fault current limiter during normal energization. FIG. 3 is a configuration diagram showing a connection state between the allowable energization current detection device and the superconducting fault current limiter.
[0021]
As shown in FIGS. 2 and 3, the superconducting fault current limiter 1 is installed in a cooling vessel 2 and cooled to 77K or less by liquid nitrogen or a refrigerator. The superconducting fault current limiter 1 is connected in series between a power supply source 3 (such as a power plant or a substation) and a power consumption system as a load 4. The superconducting fault current limiter 1 has a function of generating resistance and stopping current when a short circuit accident occurs in the power system and a large current flows.
[0022]
As shown in FIG. 2, a current measuring device 5 is connected in series with the superconducting current limiter 1, and a voltage measuring device 8 is connected in parallel with the superconducting current limiter 1 via a high voltage probe 6 and an optical isolation 7. Yes. Thus, during normal energization, the current flowing through the superconducting fault current limiter 1 is constantly observed by the current measuring device 5 and the voltage generated in the superconducting current limiter 1 is constantly observed by the voltage measuring device 8. The high voltage probe 6 and the optical isolation 7 are provided to step down to 1/1000 because a high voltage of 6.6 kV or 66 kV is applied to the superconducting current limiter 1 during current limiting operation. For this reason, it is difficult to measure a minute voltage of about several mV to several tens of mV corresponding to the critical current criterion during normal energization.
[0023]
FIG. 3 is a configuration diagram showing a connection state between the allowable conducting current detection device and the superconducting fault current limiter according to the embodiment of the present invention at the time of periodic inspection. As illustrated in FIG. 3, the allowable energization current detection device 9 surrounded by a broken line includes devices such as a pulse current source 10, a voltage measurement device 11, a current measurement device 12, and a data processing device 13. The pulse current source 10 is connected to the current introduction terminals 31 and 32 of the superconducting fault current limiter 1 and supplies the superconducting device 1 with a superimposed current for a shorter period of time than the period of the energizing current in a state of normal energization while maintaining the superconducting state. To do. The voltage measuring device 11 is connected to the voltage measuring terminals 33 and 34 of the superconducting fault current limiter 1 and measures a voltage signal generated by the superconducting device. The current measuring device 12 observes the current flowing through the superconducting fault current limiter 1. The data processing device 13 detects the allowable energization current of the superconducting device 1 based on the voltage signal measured by the voltage measuring device 11.
[0024]
4A to 4D show waveforms of the normal energization current It, the pulse current Ip supplied from the pulse current source 10, the current If flowing in the superconducting current limiter 1, and the voltage Vf generated in the superconducting current limiter 1. Indicates. As shown in this figure, the pulse current Ip is supplied in a superimposed manner in synchronization with the peak of the normal energization current It having a frequency of 50 Hz. At that time, the voltage Vf generated by the superconducting fault current limiter 1 is input to the data processing device 13, and a voltage corresponding to the allowable current-criteria criterion (generated voltage of 1 μV / cm per length of the superconductor) is generated. Control is performed by sending a control signal from the data processing device 13 to the pulse current source 10 so as to increase the magnitude of the pulse current until reaching the criterion. In such a procedure, the allowable conduction current of the superconducting fault current limiter 1 is determined, and the deterioration of the superconducting fault current limiter 1 is determined by comparing with the critical current at the time of installation recorded in advance.
[0025]
As shown in FIG. 4, it is preferable that the current If, which is applied to the superconducting fault current limiter 1 during the periodic inspection, in which the energization current It and the pulse current Ip are superimposed, has a periodic waveform. This is because a periodic waveform can be easily averaged, and the accuracy of detecting the allowable energization current is improved. In order to make the current If flowing in the superconducting fault current limiter 1 into a periodic waveform, the frequency of the pulse current Ip is set to be an integral multiple of the frequency of the current flowing It, and the current flowing It and the pulse current Ip are synchronized. Is preferred.
[0026]
If a current exceeding the critical current flows through the superconductor, Joule heat is generated. If the amount of generated heat is large, the temperature rises and the superconducting fault current limiter 1 may be quenched. In that case, a large amount of liquid nitrogen evaporates, and in the worst case, the damage to the equipment is reached. Therefore, in order to prevent the superconducting fault current limiter 1 from reaching quenching, the peak value of the superimposed pulse current is preferably not more than 3 times, more preferably not more than 1.5 times the critical current at the time of installation. The pulse width is preferably ½ or less, more preferably 1/10 or less of the period of the energization current.
[0027]
On the other hand, if the frequency of the pulse current is too high, the superconducting fault current limiter has an inductance with respect to alternating current, so that a voltage is generated and it is difficult to determine the allowable energizing current. For this reason, the frequency of the pulse current is preferably 100 kHz or less. In addition to the inductance of the superconducting fault current limiter during normal energization, the voltage generated by the connection resistance is very small. Therefore, in order to further improve the accuracy of the allowable energization current, the voltage generated during normal energization is monitored, and the voltage due to the inductance and connection resistance is removed from the voltage generated when the pulse current is applied. It is preferable to determine the allowable energization current based on the extracted voltage. It is preferable that the data processor 13 removes the voltage due to the inductance and the connection resistance.
[0028]
In the power system according to the embodiment of the present invention, another power system may be connected to the power supply source. When a short circuit accident occurs in the power system, a high voltage is generated in the superconducting fault current limiter 1 used in the present invention, so that the allowable energizing current detector 9 may be destroyed. For this problem, it is effective to employ the configuration shown in FIGS. FIG. 5 shows a pulse current source 10 in which a switch 15 and a high frequency transformer 16 are provided at the output of the pulse current generator 14. FIG. 6 shows a voltage measuring device 11 in which a switch 18 is provided at the input of the voltage measuring device 17. The pulse current source 10 and the voltage measuring device 11 shown in these drawings can be disconnected from the power system by turning off the switches 15 and 18 when the voltage generated in the superconducting current limiter 1 reaches a predetermined value. is there.
[0029]
When the pulse current is supplied, the voltage generated in the superconducting fault current limiter 1 is from several tens mV to 1 V at most, which is very small compared to the voltage 6.6 kV or 66 kV of the power system, and the influence on the load 4 is Very small. However, depending on the load 4, it may be desired to remove noise having a large frequency. To solve this problem, as shown in FIG. 7, a filter circuit 19 is installed between the superconducting current limiting device 1 and the load 4 to remove an electric signal having a large frequency that is generated when a pulse current is applied. It is preferable that the power system is configured.
[0030]
Although the case where the superconducting device is a superconducting fault current limiter has been described above, the superconducting device includes a superconducting cable, a superconducting transformer, and the like. In addition, although the case where the allowable energization current detection device is incorporated as a part of the power system together with the superconducting device connected between the power supply source and the load (power consuming device) has been described, the allowable energization current detection device can be moved It can also be used for periodic inspection by being housed in a simple rack and properly connected to superconducting equipment. Therefore, it is possible to periodically check the allowable energization currents of a plurality of superconducting devices having different installation locations. Needless to say, the allowable current can be detected by the device according to the present invention even when the superconducting device is not connected to the power system.
[0031]
【Example】
Next, specific examples will be described with reference to the drawings.
[0032]
[Example 1]
FIG. 8 shows a configuration diagram of a power system using the superconducting fault current limiter and the allowable energizing current detector in the present embodiment. The superconducting fault current limiter 1 is installed in the cooling vessel 2 and is connected in series between the power supply source 3 and the load 4 while being cooled to 77K with liquid nitrogen. The superconducting current limiter 1 has a capacity of 6.6 kV (peak voltage 9.3 kV) / 1 kA (peak current 1.4 kA), and is a module in which a plurality of current limiting elements using a Y-based high-temperature superconducting thin film are connected in series and parallel. It consists of The length of the Y-based high temperature superconducting thin film was 4 m.
[0033]
The allowable energization current detector 9 in the present embodiment is indicated by a broken line. The current introduction terminals 31 and 32 of the superconducting fault current limiter 1 have a pulse current source (described in detail later) formed of an LC resonance circuit. The voltage measuring devices 17 are connected to each other. The current measuring device 12 observes the current flowing through the superconducting fault current limiter 1. The data processing device 13 detects the allowable energization current of the superconducting device 1 based on the voltage signal measured by the voltage measuring device 17.
[0034]
The pulse current source includes a high-frequency transformer 16 (winding ratio 1: 100, response frequency 50 to 5 kHz), a switch 15 that cuts off an LC resonance circuit, a thyristor switch 22, a capacitor 21, an inductance 20, and a charger 23 that charges the capacitor. Has been. The capacitor 21 is composed of a plurality of capacitors, and the capacitance can be varied by switching the number of connections. Similarly, the inductance 20 is provided with a plurality of terminals capable of selecting the line length, and the inductance can be varied by switching the line length. In this embodiment, the capacitance of the capacitor and the inductance was set to 25 μF and 1 mH, respectively. Therefore, when the thyristor switch 22 and the switch 15 are turned on, a current having a frequency of 1 kHz can flow. In addition, the charging voltage of the capacitor can be varied in the charger. For example, when charged at 100 V, the peak current of the pulse current Ip was 1.6 kA. The magnitude of the pulse current was adjusted by the charging voltage of the capacitor.
[0035]
9A and 9B show the waveforms of the normal conduction current It of 500 A (peak current 700 A) and the voltage Vf generated in the superconducting current limiter 1. During normal energization, a voltage due to inductance and connection resistance was observed in the superconducting fault current limiter 1, and the peak voltage was about 1.4 mV. From this result, it was found that the connection resistance was about 2 μΩ. The inductance of the superconducting current limiting device 1 was as small as about 50 nH, and most of the generated voltage was due to connection resistance.
[0036]
10A to 10D, the current If flowing in the superconducting fault current limiter 1 when the pulse current of 1 kA (peak current 1.4 kA) is superimposed on the normal energizing current, and generated in the superconducting current limiter 1 The waveform of the voltage Vf to perform is shown. As shown in (a), the pulse current was supplied in synchronization with the peak of the energized current by operating the thyristor switch 22. (B) is an actually measured voltage waveform, and (c) is a waveform obtained by averaging the waveforms of 1000 cycles by the data processor 13. (D) is the voltage waveform which removed the voltage by the connection resistance and inductance of the superconducting fault current limiter 1 from the averaged voltage of (c).
[0037]
The length of the Y-based high-temperature superconducting thin film used for the superconducting fault current limiter 1 is 4 m, and the voltage corresponding to the critical current criterion (1 μV / cm) is 0.4 mV. Using the results of (a) and (d), the current value reaching 0.4 mV was estimated to be about 1.7 kA. When this power system was used for a long period of time, the allowable energization current decreased. A setting was made to issue an alarm when the allowable energization current dropped to 80% of the critical current at the time of installation, and the superconducting current limiter was replaced.
[0038]
[Example 2]
In the same power system as in Example 1, a short-circuit accident occurred in another power system connected to the same power supply source when the allowable energization current was periodically detected. FIG. 11 shows waveforms of the current If flowing in the superconducting fault current limiter 1 and the voltage Vf generated in the superconducting current limiter 1 at that time. Since the voltage generated in the superconducting current limiting device 1 has reached 5 V, which is the criterion for quenching, a signal is sent from the data processing device 13 to the switches 15 and 18, and the pulse current source and the voltage measuring device are disconnected from the power system. As a result, it was possible to avoid damage by avoiding the application of a high voltage to the allowable energizing current detector 9 with the operation of the superconducting fault current limiter 1.
[0039]
[Example 3]
As shown in FIG. 7, a power system was configured in which a filter circuit 19 that removes an electrical signal other than the frequency of the energized current was connected between the superconducting current limiter 1 and the load 4. 12A and 12B show waveforms of voltages applied to the load when the filter circuit 19 is not provided and when the filter circuit 19 is provided. By providing the filter circuit 19, it is possible to prevent a voltage drop of the load 4 that occurs when a pulse current is supplied to the superconducting fault current limiter 1, and a more stable power supply is possible.
[0040]
[Example 4]
FIG. 13 shows a power system in the present embodiment. In this power system, the power generation equipment 51 and the power consuming device 52 are connected by a superconducting cable 54 cooled to 77 K or less by the liquid nitrogen circulation device 53, and allowable energization is performed via switches 57, 57 at both ends of the superconducting cable 54. A current detection device 55 is connected. Further, an alarm device 56 is connected to the allowable energization current detection device 55.
[0041]
In a state where the normal conducting current is supplied to the superconducting cable 54, a pulse current having a pulse width of 1 msec is superimposed in synchronization with the current peak of the normal conducting current, and the peak value of the pulse current is increased at a constant rate to 1 μV / cm. By supplying the voltage until the voltage is generated, the allowable energization current of the superconducting cable 54 can be detected.
[0042]
When the normal energizing current exceeds 80% of the critical current at the time of installation, the alarm device 6 is operated to issue a pass alarm. On the other hand, even when the allowable energization current becomes 80% or less of the critical current at the time of installation, the alarm device 6 is operated to issue an alarm for replacement, and the superconducting cable 54 is replaced based on the alarm. Moreover, in the electric power system having the allowable energization current detection device 55 according to the present embodiment, it is possible to issue a warning by detecting a decrease in the allowable energization current due to the temperature rise of liquid nitrogen.
[0043]
Although only one superconducting cable is shown in FIG. 13, when the distance is long, a plurality of superconducting cables are relayed, and a liquid nitrogen circulation device is provided corresponding to each superconducting cable. In such a case, it is desirable to connect the allowable energization current detection device 55 according to the present invention to all the superconducting cables. However, the allowable energization current detection device 55 can be disconnected by the connection switch 57. It is not necessary to prepare the allowable energization current detection device 55 corresponding to all superconducting cables.
[0044]
The allowable energizing current detection device according to the present invention can be applied to devices using superconducting wires such as SMES and superconducting transformers, and power systems including these devices.
[0045]
Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.
[0046]
【The invention's effect】
As described above, according to the present invention, it is possible to detect an allowable energization current of a superconducting device in a state where the superconducting device for power is connected to the power system. As a result, it is possible to promptly determine the deterioration of the superconducting device, perform maintenance and replacement, and construct a power system with excellent stability.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a power system according to an embodiment of the present invention.
FIG. 2 is a configuration diagram showing a connection state of the superconducting fault current limiter during normal energization.
FIG. 3 is a configuration diagram showing a connection state between an allowable energization current detection device and a superconducting fault current limiter according to an embodiment of the present invention.
FIG. 4 is a current waveform diagram when the allowable energization current detector according to the embodiment of the present invention is applied to a superconducting fault current limiter.
FIG. 5 is a configuration diagram of a pulse current source of the allowable energization current detection device according to the embodiment of the present invention.
FIG. 6 is a configuration diagram of a voltage measurement device of the allowable energization current detection device according to the embodiment of the present invention.
FIG. 7 is a configuration diagram of a power system in which a filter circuit is installed between a superconducting fault current limiter and a load according to an embodiment of the present invention.
FIG. 8 is a configuration diagram of a power system using a superconducting fault current limiter and an allowable energizing current detection device according to Embodiment 1 of the present invention.
FIG. 9 is a waveform diagram of a normal energizing current flowing in the superconducting fault current limiter and a voltage generated in the superconducting fault current limiter in Embodiment 1 of the present invention.
FIG. 10 is a waveform diagram of a current flowing in a superconducting current limiter and a voltage generated in the superconducting current limiter when a pulse current is superimposed on a normal energizing current in Example 1 of the present invention.
FIG. 11 is a waveform diagram of a current flowing in a superconducting fault current limiter and a voltage generated in the superconducting fault current limiter when a short circuit accident occurs in another power system in Example 2 of the present invention.
FIG. 12 is a waveform diagram of a voltage applied to a load in a power system without a filter circuit and a power system without a filter circuit in Example 3 of the present invention.
FIG. 13 is a configuration diagram of a power system in Embodiment 4 of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Superconducting current limiting device, 2 ... Cooling container, 3 ... Power supply, 4 ... Load, 5 ... Current measuring device, 6 ... High voltage probe, 7 ... Optical isolator, 8 ... Voltage measuring device, 9 ... Allowable energizing current detection device, DESCRIPTION OF SYMBOLS 10 ... Pulse current source, 11 ... Voltage measuring device, 12 ... Current measuring device, 13 ... Data processing device, 14 ... Pulse current generator, 15 ... Switch, 16 ... High frequency transformer, 17 ... Voltage measuring device, 18 ... Switch, DESCRIPTION OF SYMBOLS 19 ... Filter circuit, 20 ... Inductance, 21 ... Capacitor, 22 ... Thyristor switch, 23 ... Charger, 31, 32 ... Current introduction terminal, 33, 34 ... Voltage measurement terminal, 51 ... Power generation equipment, 52 ... Power consumption apparatus, 53 ... Liquid nitrogen circulation device, 54 ... Superconducting cable, 55 ... Allowable energization current detection device, 56 ... Alarm device, 57 ... Switch, 100 ... Substation, 101 ... Circuit breaker, 102 ... Superconductivity FCL, 103 ... allowable energization current sensing device, 105 ... changeover switch, 106 ... bypass current path, 107 ... centralized control center.

Claims (7)

A device for detecting an allowable energization current of a superconducting device including a superconductor connected to an electric power system from a power supply source to a load,
In a state where the superconducting device is energized while maintaining a superconducting state, a current source that supplies a superimposed current for a time shorter than the cycle of the energized current;
Means for measuring a voltage signal generated in the superconducting device;
And an apparatus for detecting an allowable energization current of the superconducting device based on the voltage signal. 2. The apparatus according to claim 1, wherein the current source is a pulse current source, and a pulse current synchronized with a peak of the energization current is supplied as the superimposed current. 3. The controller according to claim 1, further comprising a controller for controlling a current source so as to increase a superimposed current until a voltage generated in the superconducting device is 1 μV / cm or more per length of the superconductor. An allowable energizing current detector for the superconducting equipment described. The means for detecting an allowable energization current of the superconducting device determines an allowable energization current of the superconducting device based on a voltage obtained by removing an inductance of the superconducting device and a voltage due to a connection resistance from a voltage generated in the superconducting device. The allowable conducting current detection device for a superconducting device according to any one of claims 1 to 3, wherein 5. The switch according to claim 1, further comprising a switch that disconnects the current source and the voltage measuring unit from the power system when a voltage generated in the superconducting device reaches a predetermined value. 6. An allowable energizing current detector for the superconducting equipment described. A power system having a power supply source, a load, and a superconducting device including a superconductor connected therebetween;
In a state where the superconducting device is energized while maintaining a superconducting state, a current source that supplies a superimposed current for a time shorter than the cycle of the energized current;
Means for measuring a voltage signal generated in the superconducting device;
Means for detecting an allowable energization current of the superconducting device based on the voltage signal;
A power system comprising: a bypass current path that bypasses the superconducting device. The power system according to claim 6, further comprising a filter circuit that removes an electrical signal other than a frequency of an energized current between the superconducting device and the load.

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