JPH0810937Y2 - Insulation support structure for current leads for cryogenic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a low temperature gas-cooled power supply lead in which electric power from an external power supply is passed through a superconducting coil housed in a cryogenic container. The present invention relates to a structure of an insulating flange for insulating and supporting a container, and particularly to an insulating structure for preventing a decrease in withstand voltage due to water droplets.

[Conventional technology]

FIG. 4 is a schematic sectional view showing a general structure of a superconducting electromagnet device as a cryogenic device. In the figure, a superconducting coil 3 is housed in a low-temperature container (also called an adiabatic vacuum container) 2 including a vacuum chamber 2A and a helium container 2B while being immersed in liquid helium 9 as a cryogenic refrigerant to maintain a superconducting state. . The current lead 1 is inserted into the cryocontainer 2 through an insertion port 6 having a flange 6A projecting from the top of the cryocontainer 2, the low temperature terminal 4B at the lower end thereof is connected to the superconducting coil 3, and the normal temperature terminal at the upper end thereof. An exciting current is passed through the superconducting coil 3 by connecting the 4A to an external power source (not shown).

The current lead 1 has a structure in which a bundle of lead conductors is inserted into an outer cylinder 5 having an intermediate flange 5A, and the gap is used as a passage for low-temperature helium gas 9G to perform heat exchange,
Intrusion heat that enters from the side of the room temperature terminal 4A due to conduction of the lead conductor and Joule heat generated in the lead conductor causes low temperature terminals.
It is configured to prevent entry into the 4B side and reduce vaporization loss of liquid helium 9.

Further, the current lead 1 includes the intermediate flange 5A and the cryogenic container 2
Is connected to and electrically insulated from each other by an insulating flange 11 made of glass fiber reinforced plastic (abbreviated as GFRP) material or the like, which is interposed between the flange 6A on the side and the outer cylinder 5
Are covered by an insulating layer 8.

[Problems to be solved by the device]

The withstand voltage between the grounded cryocontainer 2 and the current lead 1 is determined by the helium gas gap between the outer tube 5 and the insertion port 6 of the current lead, as shown in the cross-sectional view of the main part in FIG. Long G
And the helium gas side creepage distance a of the insulating flange 11 and the atmosphere side creepage distance b. These insulation distances are
When the superconducting coil 3 locally changes to normal conduction (called quench) or protects it, the insulation distance of each part is determined to withstand the high voltage caused by the sudden change in current. Since the insulation strength is only about one tenth that of atmospheric pressure air, the insulation dimension is usually determined by the gap length G on the helium gas side and the creepage distance a. Among these, the gap length G can be shortened by covering the outer periphery of the current lead with the insulating layer 8 to reduce the gap length by utilizing the reinforcing effect thereof. This is a major issue in downsizing the support structure.

However, in the gas-cooled current lead, the low-temperature helium gas 9G passes through the lead and is discharged from the upper part to the outside, so that the room temperature terminal 4A side is also cooled, and the moisture in the atmosphere is frosted on the surface. And become attached. The frost melts due to the heat generated when a large current is passed, forming water droplets
It drops on the upper surface of 5A. Since the dropped water drops travel down the outer peripheral surface of the insulating flange, the outer peripheral surface of the insulating flange becomes wet even though it is used indoors, and its withstand voltage performance deteriorates. For this reason, there occurs a situation in which the portion of the creepage insulation distance b flashes over due to the high voltage generated with the quench. As a result, the thickness of the insulating flange 11 which should originally be determined by the creepage distance a on the helium gas side is determined by the distance b on the atmosphere side, and the thickness of the insulating flange is increased in order to increase this, and the length of the current lead is correspondingly increased. Inconvenience that this also increases.

In order to avoid such a situation, it is known that the insulating flange 11 has a U-shaped cross section and the atmosphere-side creepage distance c is extended, as shown in the cross-sectional view of the main part in FIG. . However, even when the insulating flange is formed in this manner, the water droplets travel down the surface of the insulating flange along the creepage distance c, and therefore the withstand voltage performance is not improved.
Since the depth of the internal thread 12 required for flange connection is required,
In many cases, the thickness or diameter of the insulating flange becomes large, and there is a demand for improvement in the insulating structure of the insulating flange that can prevent deterioration of withstand voltage performance due to wetting.

An object of the present invention is to prevent deterioration of withstand voltage performance due to wetting without increasing the size of the insulating flange.

[Means for solving the problem]

In order to solve the above problems, according to the present invention, a flanged insertion port protruding from the upper portion of a cryogenic container accommodating a superconducting coil, and the normal temperature part to be inserted into the cryogenic container from this insertion port A gas-cooled current lead for supplying electric power to a superconducting coil is insulated and supported via an insulating flange interposed between the intermediate flange of the current lead and the flange on the insertion port side, It is assumed that the flange is provided with a draining collar portion projecting in a ring shape along the outer circumference thereof.

Also, the main portion of the insulating flange has a rectangular cross section,
The lower edge portion on the outer peripheral side is composed of a draining collar portion extending downward by a predetermined length.

Further, it is assumed that the insulating flange is composed of a main body portion having a rectangular cross section, and a draining collar portion projecting laterally from the upper edge portion on the outer peripheral side thereof in an inverted L-shape in cross section.

[Action]

In the configuration of the present invention, since the drain flange is provided along the outer circumference of the insulating flange made of GFRP material or ceramic material, the water droplets flowing down the outer peripheral surface of the insulating flange are Since the water cut collar part functions as an umbrella when it falls into the atmosphere and a dry zone that does not get wet with water droplets can be secured inside the water cut collar part, the flashover accident due to the high voltage that accompanies the quench is caused by this dry zone. It is prevented by the withstand voltage performance of the
Can be determined by

In addition, the creepage distance of the dry zone can be extended without increasing the size of the insulating flange depending on the position of the root of the draining collar and the shape of the draining collar. It can be extended downward to form a drainage collar. Further, by providing the inverted L-shaped drainage collar portion, a drainage collar portion having a large creepage distance can be obtained.

[Embodiment] Hereinafter, the present invention will be described based on an embodiment.

FIG. 1 is a sectional view of an essential part showing an insulating support structure of a current lead for a cryogenic device according to an embodiment of the present invention.
The same parts as those of the conventional technique are denoted by the same reference numerals, and detailed description thereof will be omitted. In the figure, an insulating flange 21 is made of glass fiber reinforced plastic (GFRP) material, and is provided with a ring-shaped draining collar portion 22 extending downward with a uniform thickness on the outer peripheral side of a main body having a rectangular cross section. The current lead 1 is airtightly connected to the cryogenic container 2 and insulated and supported by being interposed between 5A and 6A and being connected at a plurality of points with bolts 7.

In the insulating support structure of the current lead configured as described above, the water droplets dropped on the upper surface of the intermediate flange 5A are transmitted along the outer peripheral surface having the creepage distance B of the insulating flange 21 and are drained at the lower edge thereof to be the upper surface of the cryogenic container 2. As a result, the creepage distance B forms a wet surface and the inner wall surface on the ring forms a dry zone having a creepage distance D. Assuming that the superconducting coil is quenched in this state, most of the high voltage will be borne by the dry zone. Therefore, the drainage collar
If the protrusion length of 21 (dimension close to the creepage distance D) is set to withstand a high voltage, a flashover accident can be prevented in advance. At this time, since the thickness of the insulating flange 21 is determined by the creepage distance a on the helium gas side, it is not necessary to increase the thickness of the insulating flange or the length of the current lead.
The protruding length of the drainage collar may be set to a dimension that is one tenth of the creepage distance a plus the thickness of the flange 6A in consideration of the difference in insulating strength between helium gas and air. It is possible to obtain an insulating support structure having wettability without hindering the tightening work and without increasing the size of the device.

FIG. 2 is a cross-sectional view showing a different embodiment of the present invention, in which the main portion having a rectangular cross section of the insulating flange 31 made of GFRP has an inverted L-shaped cross section on the side of the outer peripheral side upper edge portion. The point different from the above-mentioned embodiment is that the water drop collar portion 32 is provided, and since the water droplets propagate along the creepage distance E and drop at the lower edge thereof, the creepage distance F portion becomes a dry zone and the insulating flange It is possible to obtain an insulating support structure that maintains a sufficiently long dry creepage distance without extending the thickness or the current lead. In the case of this embodiment, the withstand voltage on the atmosphere side when wet with water drops is determined by the spark voltage of the air gap Ga, which is shorter than the dry creepage distance F, so that it is possible to withstand the high voltage generated with the occurrence of quench. By determining the gap length Ga, an insulating support structure having excellent wettability can be obtained.

FIG. 3 is a sectional view showing another embodiment of the present invention,
The insulating flange 41 is made of a ceramic material, and the upper edge portion is provided with a draining collar portion 42 extending outward in an inverted L shape, which is different from the above-described embodiments, and the draining collar portion 42 functions as an umbrella. Insulation flange 41
Is determined by the creepage distance a on the helium gas side, and an insulating support structure for the current lead in which the withstand voltage does not drop due to water droplets can be obtained without increasing the length of the insulating flange and the current lead. At both ends of the insulating flange 41, a metal fitting 43 is directly coupled to the intermediate flange 5A, and the other metal fitting 44 is at the cryogenic container 2
It is connected to the side flange 6A.

[Effect of device]

As described above, this invention is configured such that the drain flange is provided on the insulating flange for insulating and supporting the gas cooling type current lead in the cryogenic container. As a result, the drainage collar functions as a drainage umbrella, and a dry zone that does not get wet with water droplets is formed on the shaded part to prevent deterioration of withstand voltage performance. It is possible to avoid both the decrease in withstand voltage performance caused by frost melting and dripping and wetting the surface of the insulating flange, and the increase in the insulating dimension of the insulating flange required to avoid this, and therefore the large size of the device. It is possible to provide an insulating support structure for a current lead for a cryogenic device, which has excellent wettability without increasing the size and length of the current lead and can withstand a high voltage stably.

Also, if the lower edge of the insulating flange is extended downward in a skirt shape to form a drainage collar, the idle space for flange connection can be used for the drainage collar, and the insulation flange can be extended laterally in an inverted L shape. If the drainage collar is formed by using it, a considerable part of the outer peripheral surface of the insulating flange can be utilized for the dry zone, and the withstand voltage can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an insulating support structure of a current lead for a cryogenic device according to an embodiment of the present invention, FIG. 2 is a sectional view showing a different embodiment of the present invention, and FIG. 4 is a cross-sectional view showing another embodiment of the present invention, FIG. 4 is a schematic cross-sectional view showing a general structure of a cryogenic device, FIG. 5 is a cross-sectional view of a main part showing a conventional insulating support structure, and FIG. It is sectional drawing of the principal part which shows a different insulating support structure. 1 ... current lead, 2 ... low temperature container, 3 ... superconducting coil, 4A room temperature terminal, 4B ... low temperature terminal, 5 ... outer cylinder, 6 ...
Insertion port, 6A …… Flange, 5A …… Intermediate flange, 8 ……
Insulating layer, 9 ... Liquid helium, 9G ... Helium gas, 1
1,21,31,41 …… Insulation flange, 22,32,42 …… Drainage collar, a …… Creation distance on helium gas side, B, b, E …… Wetted creepage distance on atmosphere side, D, F: Dry creepage distance (dry zone), G: Helium gas cap length, Ga: Air gap length.

Claims (3)

[Scope of utility model registration request] 1. A flanged insertion opening projecting from an upper portion of a cryogenic container accommodating a superconducting coil, and gas cooling which is inserted into the cryogenic container through the insertion port and supplies electric power from a room temperature portion to the superconducting coil. The current lead of the formula is insulated and supported via an insulating flange interposed between the intermediate flange of the current lead and the flange on the insertion port side, and the insulating flange has a ring shape along the outer periphery thereof. An insulating and supporting structure for a current lead for a cryogenic device, characterized in that it comprises a draining collar portion projecting from the. 2. The cryogenic apparatus according to claim 1, wherein the insulating flange is composed of a main body portion having a rectangular cross section and a draining collar portion having a lower edge portion on the outer peripheral side thereof extended downward by a predetermined length. Insulation support structure for current leads. 3. The insulating flange comprises a main body portion having a rectangular cross section, and a draining collar portion projecting laterally from an upper edge portion on the outer peripheral side of the main body portion in an inverted L shape. An insulating support structure for a current lead for a cryogenic device according to claim 1.