JPH07170652A - Grounding protection device for superconducting coil - Google Patents

Abstract

PURPOSE:To protect a superconducting coil from a damage due to quenching by positively detecting grounding in superconducting state to prevent quenching when the superconducting coil generates a grounding accident. CONSTITUTION:In the grounding protection device of superconducting coils 5a and 5b in a configuration for housing a plurality of superconducting conductors covered with an insulator in a coil case by winding them and then supporting them in a heat-insulation vacuum container via a heat-insulator while insulating them against grounding, a DC power supply 8 for detecting grounding for applying a voltage between the superconductors 5a and 5b and a coil support 6 and a voltage detector 8 for monitoring whether the voltage between a superconductor where a voltage is applied by the DC power supply 7 for detecting grounding and a coil case are provided. Further, a protection operator 9 for releasing a DC circuit breaker 3 provided at a power supply circuit to the superconducting coils when a voltage is detected by the voltage detector 8 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground fault protection device for a superconducting coil for plasma confinement in a nuclear fusion device, for example.

[0002]

2. Description of the Related Art In recent large-scale fusion devices, the size of the device has been increasing, and at the same time, it is necessary to increase the coil current in order to strengthen the plasma confining magnetic field. Then, it is necessary to apply the superconducting coil so as to realize the distribution of the coil current required for plasma confinement and prevent the power supply capacity from becoming too large.

By the way, several cooling methods have been devised and studied for the superconducting coil. Among them, the conductors of the forced cooling system have been attracting attention because they have mechanical strength and superconducting stability suitable for large coils.

The forced cooling conductor is a coil conductor of a system in which liquid helium or supercritical helium is made to flow as a refrigerant in a metal conduit containing a superconducting element wire to cool it. Here, the configuration of the forced cooling type superconducting coil will be described with reference to FIG. As shown in FIG. 5, the strands of wire 21 are stored in a rectangular tube-shaped conduit 22, and the outside thereof is covered with an insulator 23 to form a forced cooling conductor so that the refrigerant flows in the conduit 22. ing. A plurality of rows of such forced cooling conductors are vertically and horizontally arranged and wound to form a superconducting coil 24. An insulator 25 is provided on the outer periphery of the superconducting coil 24 to insulate it from the ground. The structure is such that the vacuum container 27 is supported by the support 28.

A conventional superconducting coil protection device using such a forced cooling conductor has a structure as shown in FIG. In FIG. 6, 31 is a transformer whose primary side is connected to an AC power source, 32 is a rectifier that converts AC power input from the secondary side of this transformer 31 into DC power,
Superconducting coils 35a and 35b are connected in series to the output terminal of the rectifier 32 via a DC breaker 33, and a protective resistor 34 is connected in parallel to the series circuit. Also,
A voltage detector 36 is provided in parallel with the superconducting coils 35a and 35b.
a and 36b are respectively provided, one end of the current detector 37 is connected between the connection points of the superconducting coils 35a and 35b, and the other end is connected to the ground point 39 via the ground resistance 38.

On the other hand, 40 is a balance detector to which the voltage detection signals detected by the voltage detectors 36a and 36b are input. This balance detector 40 is composed of superconducting coils 35a and 35a.
The change in voltage due to the occurrence of a ground fault at 35b is detected. Reference numeral 41 denotes a protective operation device that operates to interrupt the DC breaker 33 when a ground fault current detection signal is input from the current detector 37 and a voltage change detection signal is input from the balance detector 40.

In the superconducting coil protection device having such a structure, the AC power input from the AC power source through the transformer 31 is converted into DC power by the rectifier 32, and this is converted through the DC breaker 33 into the superconducting coil. 35a, 35b
Is being supplied to. Now, if a ground fault occurs while the superconducting coils 35a and 35b are in the normal conducting state, a ground fault current flows from these superconducting coils 35a and 35b to the ground point 39 through the ground resistor 38, and this ground fault is generated. The current is detected by the current detector 37. Further, at this time, the balance detector 40 detects a voltage change due to a ground fault current flowing from the superconducting coil based on the voltage detection signals of the superconducting coils 35a and 35b input from the voltage detectors 36a and 36b, respectively.

Therefore, the protection operation device 31 is the current detector 37.
When the ground fault current detection signal is input and the voltage change signal is input from the balance detector 40, the DC breaker 33 is opened and the superconducting coils 35a and 35b can be protected.

However, when the superconducting coils 35a and 35b are in the superconducting state, even if a ground fault occurs, the resistance value of the superconducting coil itself is smaller than the circuit resistance value of the ground fault route, so that the ground fault current is superconducting. The coil tends to flow easily, and the voltage change appearing in the main circuit becomes very small, making detection difficult.

[0010]

As described above, in the conventional ground fault protection device for a superconducting coil, it is difficult to detect the ground fault unless the superconducting coil shifts from the superconducting state to the normal electric state to generate an abnormal voltage. Therefore, when the ground fault is detected, the superconducting coil has already been quenched.

Therefore, when quenching occurs, helium as a refrigerant is gasified, and due to the rapid increase in pressure, the conductor,
Damages the insulation and various instruments. In addition, once quenching occurs, it takes a huge amount of time and a large amount of refrigerant to cool again and energize. Therefore, it is necessary to prevent quenching as much as possible.

The present invention is a superconducting coil capable of reliably detecting a ground fault in a superconducting state so as not to cause a quench when the superconducting coil causes a ground fault and protecting the superconducting coil from damage caused by the quench. An object of the present invention is to provide a ground fault protection device.

[0013]

The present invention takes the following means in order to achieve the above object. (1) A structure in which a plurality of superconducting conductors covered with an insulating material are wound and housed in a coil case, which are supported in a heat insulating vacuum container via a heat insulating support, and which is energized by a power supply. In the ground fault protection device, a ground fault detection power supply for applying a voltage between the superconducting conductor and the coil case, and a change between the superconducting conductor and the coil case voltage applied by the ground fault detecting power supply. And a protection operation means for controlling the power supply to the superconducting coil when a voltage change is detected by the voltage detection means. (2) In the configuration of (1) above, the protection resistor and the backflow prevention diode are connected to the energization circuit of the ground fault detection power supply that applies a voltage between the superconducting conductor and the coil case. (3) A plurality of superconducting conductors covered with an insulator are wound and housed in a coil case, which is supported in a heat-insulating vacuum container through a plurality of heat-insulating supports, and which is energized by a power supply. In a coil ground fault protection device, a ground fault detection power source for applying a voltage between the superconducting conductor and the coil case, a plurality of current detection means respectively provided between the heat insulating support and the ground, When a current is detected by some of the current detecting means, a protection operating means for controlling the power supply to the superconducting coil is provided.

[0014]

In the ground fault protection device for a superconducting coil having the above-mentioned configuration (1), the superconducting conductor and the coil case are insulated from each other, but a ground fault occurs between the superconducting conductor and the coil case due to some cause. Then, the current from the power supply for ground fault detection flows into the coil case through the superconducting conductor, and the voltage of the power supply for ground fault detection drops, so this voltage change is detected by the voltage detection means and the power supply to the superconducting coil is detected. It becomes possible to protect the superconducting coil by controlling.

Further, in the ground fault protection device for a superconducting coil having the above-mentioned constitution (1), in addition to the above-mentioned action, even in the case of a ground fault in a normal conducting state, a diode causes a reverse current from the side of the superconducting coil. It is possible to prevent the current from flowing in and reduce the current flowing from the ground fault detection power supply by the protection resistor.

Further, in the ground fault protection device for a superconducting coil having the above-mentioned constitution (3), in addition to the function of the above-mentioned constitution (1), the ground fault current is detected by the current detector of any deviation. Depending on the height, the ground-faulted portion can be reliably detected.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit configuration of a first embodiment of a ground fault protection device for a superconducting coil according to the present invention. In FIG. 1, 1 is a transformer whose primary side is connected to an AC power source, and 2 is a rectifier that converts the alternating current input from the secondary side of this transformer 1 into direct current. The superconducting coils 5a and 5b are connected in series via the device 3, and the protective resistor 4 is connected in parallel to the series circuit.

On the other hand, 6 is a coil supporting member for supporting the superconducting coils 5a and 5b, and a ground fault detecting DC power source 7 for applying a DC voltage is connected between the coil supporting member 6 and one of the superconducting coils 5b. . Further, a voltage detector 8 is connected in parallel with the ground fault detection DC power supply 7, and the voltage detection signal detected by the voltage detector 8 is input to a protection operation device 9 for opening and closing the DC circuit breaker 3. In this case, the voltage detector 8 detects the voltage between the superconducting conductor and the coil case.

Further, the series connection point of the superconducting coils 5a and 5b is connected to the ground point 11 via the ground resistance 10 and the coil support 6. In the ground fault protection device for a superconducting coil having such a structure, a ground fault occurs between the superconducting coils 5a, 5b and the coil support 6 for some reason when the superconducting coils 5a, 5b are energized in a superconducting state. Then, almost no change appears in the voltage and current of the superconducting coil itself. However, at this time, the current from the ground fault detection DC power supply 7 flows from the superconducting coils 5a and 5b into the coil case, and the voltage of the ground fault detection DC power supply 7 decreases.

Therefore, by detecting this voltage change by the voltage detector 8 and inputting the detection signal to the protection operator 9, the DC breaker 3 is opened, so that the superconducting coils 5a, 5b are protected. You can As a result, the ground fault of the superconducting coil can be detected even in the superconducting state, so that damage to the superconducting coil due to quenching can be reduced.

FIG. 2 shows a circuit configuration of a second embodiment of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. Only different points will be described here. Second
In the embodiment, as shown in FIG. 2, a ground fault detection DC power supply 7 for applying a DC voltage between the coil support 6 and one of the superconducting coils 5b is provided on the plus side thereof with a diode 12 of the illustrated polarity and on the minus side. The protective resistors 13 are connected to each other. In this case, the diode 12 is for preventing a reverse current from flowing from the superconducting coil side, and the protection resistor 13 is for protecting the ground fault detection DC power supply 7 from overcurrent.

According to this structure, the same effect as that of the first embodiment can be obtained, and the current flowing through the detection circuit is reduced even in the case of a ground fault in the normal conduction state, so that the DC power supply for ground fault detection can be obtained. Can be protected.

FIG. 3 shows an example of the configuration of the third embodiment of the present invention. The same parts as those in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted. Only different points will be described here. In the third embodiment, as shown in FIG. 3, a thyristor converter 14 is provided instead of a rectifier as a converter for converting AC power input via the transformer 1 into DC power.

With this structure, the same effect as the second embodiment can be obtained, and the output current of the thyristor converter 14 is controlled without shutting off the DC / DC breaker 3. It is possible to control the speed of the coil current decrease and protect the coil while suppressing the plasma voltage.

FIG. 4 is a block diagram showing a forced cooling type superconducting coil and a protection circuit therefor according to a fourth embodiment of the present invention. In the fourth embodiment, as shown in FIG. 4, in the superconducting coil 5b supported by a plurality of coil supports 6, the output conductor 15 is connected to the positive side of the ground fault detecting DC power supply 7, and the negative side is connected. Is connected to each coil support 6 through a plurality of independent current detectors 16, and other than that is the same as the circuit configuration of FIG.

With such a structure, not only the same effect as the first embodiment can be obtained, but also the ground-faulted portion can be surely known. Needless to say, the same effect can be obtained by using the AC power supply or the high frequency power supply as the ground fault detection DC power supply described in each of the above-described embodiments. Further, in each of the above-described embodiments, the forced cooling type superconducting conductor has been described, but it goes without saying that other superconducting conductor systems can be similarly applied and implemented.

[0027]

As described above, according to the present invention, when the superconducting coil has a ground fault, the ground fault is surely detected in the superconducting state so that the quench does not occur, and the superconducting coil is accompanied by the quench. A ground fault protection device for a superconducting coil that can protect from damage can be provided.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing a first embodiment of a ground fault protection device for a superconducting coil according to the present invention.

FIG. 2 is a circuit configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a circuit configuration diagram showing a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a forced cooling type superconducting coil and a protection circuit therefor according to a fourth embodiment of the present invention.

FIG. 5 is a perspective view for explaining the configuration of a forced cooling type superconducting coil.

FIG. 6 is a circuit configuration diagram showing a conventional protection device for a superconducting coil.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transformer, 2 ... Rectifier, 3 ... DC breaker, 4 ... Protective resistor, 5a, 5b ... Superconducting coil, 6 ... Coil support, 7 ... Ground fault detection DC power supply, 8 ... Voltage detector, 9 ... Protective operation device, 10 ... Ground resistance, 11 ... Grounding point, 12 ... Diode, 13 ... Protective resistor, 14 ... Thyristor converter, 15 ... Lead conductor, 16 ... Current detector.

Claims (3)

[Claims] 1. A superconducting device in which a plurality of superconducting conductors covered with an insulating material are wound and housed in a coil case, which are supported in a heat insulating vacuum container through a heat insulating support, and which is energized by a power supply. In a coil ground fault protection device, a ground fault detection power source for applying a voltage between the superconducting conductor and the coil case, and a voltage applied between the superconducting conductor and the coil case by the ground fault detecting power source. The superconducting coil is provided with a voltage detecting means for monitoring whether or not there is a change, and a protection operating means for controlling the power supply to the superconducting coil when a voltage change is detected by the voltage detecting means. Ground fault protection device. 2. The superconducting device according to claim 1, wherein a protective resistor and a backflow prevention diode are connected to an energizing circuit of a ground fault detecting power source for applying a voltage between the superconducting conductor and the coil case. Coil ground fault protector. 3. A structure in which a plurality of superconducting conductors covered with an insulator are wound and housed in a coil case, which is supported in a heat insulating vacuum container via a plurality of heat insulating supports, and is energized by a power supply. In a ground fault protection device for a superconducting coil, a ground fault detecting power source for applying a voltage between the superconducting conductor and the coil case, and a plurality of current detecting means respectively provided between the heat insulating support and the ground. And a protection operation means for controlling a power supply to the superconducting coil when a current is detected by any one of the current detecting means.