EP1938350B1 - Dielectric insulation seal for a vacuum tube - Google Patents

Abstract

The gasket makes it possible for the apparatus, in particular the vacuum bottle, to be assembled and disassembled relatively easily and conveniently. It imparts high dielectric performance to the apparatus. The inside and the outside contact surfaces of the gasket are smooth, and, for example, each of them can be made up of two cylindrical portions (31A & 31B; 32A & 32B) of different concinnities. At least one of the side surfaces has an annular recess (35). Application to switchgear using vacuum bottles for operating at high and medium voltages.

Description

Field of the invention

The invention relates to the field of electrical equipment and installations, and in particular switches and switching devices using vacuum bulbs operating at medium and high voltages.

A particular application is that for the air transport of electricity.

Prior art and problem

In switchgear and switchgear, switches use vacuum interrupters that must withstand dielectric stresses, inter alia, between the contacts inside the bulb, in the vacuum, but also between the outer ends of the bulb. bulb placed in the ambient air. In order to homogenize the dielectric strength between the live contacts and the external ends of the vacuum interrupters, the compactness required requires the use of insulating elements other than the air outside the vacuum ampoules.

Solid insulators or dielectric fluids, such as the SF6 greenhouse gas, are particularly thought of. Indeed, the isolations of vacuum bulbs in the air do not make it possible to obtain suitable dielectric performance with reduced dimensions.

However, isolations of vacuum bulbs in a dielectric gaseous fluid, such as SF6, are expensive. Indeed, it is necessary to use a sealed tank equipped with current feedthroughs and these provisions are very unfavorable to the environment, especially with respect to pollution, recycling and the greenhouse effect.

The solid insulation systems of vacuum bulbs are very sensitive in temperature and do not allow disassembly or dismantling at the end of life, during adhesion or bonding. This has very harmful consequences for the environment.

In order to reduce this impact on the environment, it has been proposed to use a mixed insulator using both a solid insulator and a gaseous fluid insulator, such as air at atmospheric pressure or other gases such as nitrogen. In this case, the solid insulation is of a reduced volume, because it is made in the form of a seal having a gas-tight function and a dielectric function. However, according to the known embodiments of the prior art, this type of insulation does not allow to obtain high dielectric performance for vacuum bulbs.

With reference to the figure 1 , a vacuum bottle 101 is surrounded, at both ends of its outer surface, two seals 102A and 102B. The top seal 102A is placed on the fixed contact contact side of the vacuum bottle 101, while the bottom seal 102B is placed on the side of the moving contact. The assembly is placed in a rigid shell 103 made of insulating material. However, the structure of the seals 102A and 102B is such that air is trapped at their contact surfaces 104 with the inner wall of the rigid shell 103.

Indeed, the Figure 2A represents, in partial section, a detail of the surface marked 104 on the figure 1 . This consists of several lips 105 of pointed section, separated from each other by a gap space 106.

The Figure 2B represents, still in partial section, the same location of the joint according to the prior art. The latter has been introduced into the rigid shell 103 and its lips are crushed, or rather slightly folded each in the same direction, by the pressure of the inner wall of the shell 103 on one side of each lip 105. Air is thus trapped between each lip 105 along a line B-B '. Similarly, air may be trapped along the line A-A 'on the other surface. This air of low dielectric strength, considerably limits the dielectric performance of the system. Indeed, a priming arc can easily move radially within each interface space 106, in order to fetch the weakest point on the circumference of the next lip 105 and thus propagate to the next gap space 106 . The dielectric strength of the assembly is a function of the sum of the weakest points on each circumference of the seal 102. In addition, the thickness of insulation in certain parts of this seal 102 is too weak to obtain significant dielectric performance. Finally, the shape of this seal 102 according to the prior art is not very favorable to disassembly or dismantling at the end of life because of the anti-return effect of the lips 105.

The object of the invention is therefore to obtain significant dielectric performance with reduced dimensions for vacuum interrupters, by acting on their isolation, in particular by preventing the path of electric discharges or sparks along the contact surfaces of the gasket. service. It is furthermore desired to remain in conformity with the environment. Complete and easy dismantling of the insulation system at the end of life of the vacuum bulb is therefore desired. In addition, it is proposed to use less insulating solid material. This is in line with a cost reduction, compared to a system with fully solid insulation.

On the other hand, the European patent application EP 1 017 142 A1 discloses a circuit breaker switch having a mixed insulation system

The document DE 8403264 U describes a device according to the preamble of claim 1.

Summary of the invention

For this purpose, the main object of the invention is a dielectric insulation seal for vacuum interrupter for isolating a vacuum interrupter by using at least one seal placed around the vacuum interrupter inside the vacuum interrupter. a housing, each joint having an internal contact surface and a surface of external contact, two lateral surfaces connecting the internal and external contact surfaces.

According to the invention, the internal and external contact surfaces of the joint are smooth, have no cavities and are part of the group consisting of surface forms comprising the convex surfaces with respect to the longitudinal axis of the joint and the surfaces having a slope. which does not reverse, with respect to the longitudinal axis of the joint. Thus, no gas pocket is imprisoned during the assembly of the gasket, in the interfaces, on the one hand between the internal contact surface of the housing and the surface of the external contact of the gasket and, on the other hand, between the external surface. of the vacuum interrupter and the internal contact surface of the seal, in order to eliminate any risk of occurrence of partial electrical discharge between, on the one hand the internal contact surface of the housing and the outer contact surface of the seal and on the other hand between the external surface of the vacuum bottle and the internal contact surface of the seal.

This resistance to tracking is characterized by the ability of the seal to perfectly match the outer surface of the vacuum bottle or the inner face of the envelope to oppose the formation of electric sparks that would carbonize the surface of the jont and or the outer surface of the vacuum bulb or the inner face of the envelope, and thus provide a path to the current.

A main embodiment provides that these inner and outer surfaces of the seal contact are cylindrical.

A second main embodiment provides that these inner and outer surfaces of the seal contact are tapered.

A third main embodiment of the inner and outer surfaces of the seal contact is that they are each constituted by two conical parts of different conicity and connected by a determined connection radius and forming a flared V.

In these last two embodiments, it is noted that it is preferable for the general orientation of these inner and outer surfaces to be conical and of inverted conicity with respect to each other.

As regards the general construction of the joint, it is also preferable for the width of the internal and external contact surfaces to be equal to or greater than 5 mm in order to limit the risks of starting or routing at these interfaces.

It is also very interesting that the minimum thickness of the joint along the longitudinal axis of the joint is at least 4 mm. These two measurements make it possible to considerably increase the dielectric strength of the seal.

In various embodiments provided, the seal has a recess in its cross section, to limit the forces in the joint.

With regard to the lateral surfaces, in order to control the thermal expansions, it is also provided that these side surfaces can be in two parts having different inclinations.

It is also expected that at least one of these lateral surfaces is rounded, the other being straight.

It is also expected that the side surfaces are rounded in part, a portion being concave, a portion being convex.

It is also expected that the seal may have a trapezoidal section, that is to say two external and internal contact surfaces parallel to the axis of revolution of the seal, the side surfaces being inclined in an inverted manner.

The cross section of the joint can be H-shaped.

The cross section of the seal may also be N-shaped.

She can also be in the shape of M.

It can also square or rectangular shape.

In the case where the cross section of the seal has a recess, it may be W-shaped or U-shaped.

List of Figures

• figure 1, déjà décrite, une vue montrant l'utilisation de deux joints selon l'art antérieur ;
• figures 2A et 2B, en coupe partielle, la partie active d'un joint selon l'art antérieure ;
• figure 3A, en coupe l'utilisation d'un joint selon l'invention ;
• figure 3B, en coupe, l'utilisation de deux joints selon l'invention ;
• figures 4A à 4D, quatre réalisations détaillées de joints selon l'invention ; et
• figures 5A à 5M des sections de joints différents selon l'invention.

The invention and its various technical features will be better understood on reading the following description, illustrated with several figures respectively representing:

• figure 1 , already described, a view showing the use of two joints according to the prior art;
• Figures 2A and 2B , in partial section, the active part of a seal according to the prior art;
• figure 3A in section the use of a seal according to the invention;
• figure 3B in section, the use of two seals according to the invention;
• Figures 4A to 4D four detailed embodiments of joints according to the invention; and
• Figures 5A to 5M different seal sections according to the invention.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS OF THE INVENTION

With reference to Figures 3A and 3B , a vacuum bulb 1 is placed in a housing 10 constituting the pole of a medium or high voltage electrical equipment. In this example, the housing 10 is therefore the rigid pole of an equipment used such as a circuit breaker. When the latter is in the open position, a movable contact 5A of the vacuum bulb 1 and a fixed contact 5B, each placed at one end of a vacuum bulb 1, are at different electrical potentials. It is therefore necessary to ensure the dielectric isolation of the vacuum bulb 1 by placing between these two movable contacts 5A and 5B constituting two electrodes of different potentials, a seal 20 constituting a dielectric insulation seal. Once in place, the seal 20 prevents the flow of sparks or discharges along the dashed lines AA 'and BB'. For the record, it is noted that the dielectric strength of the vacuum inside the vacuum bulb 1 is much higher than the dielectric strength of the air outside the vacuum bulb 1.

• le contact intime entre les joints 20 et l'ampoule à vide 1, notamment par sa surface externe 6, le long de la ligne A-A' et au contact entre les joints 20 et le boîtier 10, notamment par sa surface interne 16, le long de la ligne B-B' ;
• la compression radiale des joints 20 qui sont en matériau élastomère ; et
• l'épaisseur de la matière élastomère isolante de chaque joint 20 correctement dimensionné.

With reference to the figure 3B , in the case of the use of two joints, these isolate an annular space 24 delimited by a lateral surface of each of the seals 20, an outer surface 6 of the vacuum bottle 1 and an inner surface 16 of the housing 10. The space 24 thus contained contains a gaseous fluid, such as air or another fluid of the same type. In other words, these two seals 20 and the space 24 they delimit form a dielectric barrier between the two movable contacts 5A and fixed 5B of different potentials. This configuration makes it possible to avoid any dielectric initiation or bypassing of one of the gaseous elements delimited by the joints 20, either by routing or by perforation. More precisely, the dielectric seal or dielectric strength is ensured inter alia by three elements which are:

• the intimate contact between the seals 20 and the vacuum bottle 1, in particular by its external surface 6, along the line AA 'and in contact between the seals 20 and the housing 10, in particular by its internal surface 16, along line BB ';
• the radial compression of the seals 20 which are elastomeric material; and
• the thickness of the insulative elastomeric material of each correctly sized gasket.

For this purpose, it can be seen that in the embodiment described on the figure 3B , each joint 20 has a section consisting of two tapered portions 20A and 20B inverted inclination. In other words, the section of this joint is coarse U-shape. This is only an example of a relatively simple form of the joint, other more elaborate forms are described in the following paragraphs.

A very important technical feature of the seal according to the invention is that the outer peripheral surface and the inner peripheral surface of each seal 20 are smooth. Indeed, using a housing 10 whose inner surface 16 is smooth, likewise, the vacuum bottle 1 has a smooth outer surface 6. In correspondence, the inner and outer surfaces of each seal 20 are smooth. This avoids trapping air between these surfaces at the time of assembly. The general shape of the joint is optimized, in order to obtain contact pressures at the joint interfaces / housing and joint / vacuum bulb that are not homogeneous, but sufficient. The clamping constraints of the seal around the vacuum bottle 1 are greater than those at the clamping of the seal against the housing 10. This allows the seal to remain in place on the vacuum bulb during assembly, disassembly and dismantling.

As can be seen from this figure 3B , the position of the seals 20 on the vacuum bottle 1 is optimized in that the latter are positioned on the latter in areas where the dielectric fields are favorable to large dielectric strengths. In particular, these seals 20 are not in contact with the electrodes formed by 5A and fixed 5B mobile contacts. In the opposite case, a significant risk of perforation of the joints exists in the case where a too intense local electric field would appear. Indeed, a strike on one of the electrodes would lead to a concentration of electric fields. In the case where a dielectric seal would be in contact with one of these electrodes, it would suffer too much electric field and could be degraded by perforation.

The Figure 4A shows a first detailed realization of the joint.

The outer surface of contact which is therefore smooth consists in fact of two surfaces 31A and 31B, both conical with respect to the axis 30 of the joint, their inclination being different, so as to form a very open U outwards . Their junction consists of an external connection radius RE. Similarly, the internal contact surface consists of two parts 32A and 32B, both of different inclination, with respect to the axis 30, one of them, in this case the surface 32A can be cylindrical. These two internal contact surfaces are also connected by an internal connection radius RI. These connecting radii RE and RI help to avoid trapping air during assembly of the joint. If the seals 20 have been shown mounted around the vacuum bottle 1 and in the box 10 with smooth contact surfaces, it should be emphasized that these external and internal contact surfaces are smooth, when the seals are not mounted.

In this embodiment, the two lateral surfaces also consist of several parts. One of them comprises a recess 35 constituted by two frustoconical surfaces 35A joined by a radial surface 35B. This recess 35 limits the forces within the seal, when it is compressed, during the assembly phase of the vacuum bulb in the housing.

Similarly, the other side surface consists of two surfaces 33A and 33B, themselves frustoconical, of different inclination so as to form a very open U. The remainder of the side surfaces consists of radial portions 34C, on the one hand, and 34A and 34B, which join the recess 35 to the internal contact surfaces, on the other hand.

This embodiment is similar to a U of which one of the vertical parts extends slightly downwards. Other possible sections of the seal, particularly in the form of a letter, are set out below.

Whatever the form envisaged, the thickness in the direction parallel to that of the axis 30 of the joint must be equal to or greater than 4 (four) millimeters. The mechanical strength is obviously enhanced, but it is especially the dielectric strength of the seal which is increased, including greatly reducing the risk of priming perforation of the seal.

Similarly, if the internal contact surfaces 32A and 32B and external have a sufficiently large axial height, constituting important bearing surfaces and not punctual, they contribute especially to increase the dielectric strength of the joint. An axial height of at least 5 (five) millimeters is required. It should be noted that the electric fields at the interface formed by the internal contact surfaces 32A and 32B and the external surface of the vacuum bottle are greater than those at the interface formed by the surfaces. external contacts 31A and 31B and the inner surface of the housing. The width of the internal contact surfaces 31A and 31B is therefore greater than that of the external contact surfaces 32A and 32B. An equal value of clamping pressure, during assembly, disassembly and dismantling, this allows the seal to remain in place on the vacuum bulb.

The seal is an elastomeric material. During its assembly, its deformation makes it possible to obtain sufficient contact pressures at its internal contact surfaces 32A and 32B and at its outer contact surfaces 31A and 31B. The system is insensitive to temperature. Indeed, due to the shape of its side surfaces, the seal is free to expand during temperature increases and to contract during temperature decreases.

Indeed, the ratio of the pressure surfaces, that is to say the internal contact surfaces 32A and 32B and external 31A and 31B, on the free surfaces, that is to say the lateral surfaces 33A, 33B, 34A, 34B, 35A and 35B is sufficiently restricted, so that the elastomeric material constituting the joints can expand and contract freely in temperature. This considerably limits the constraints thermomechanical within the joint. These thermomechanical stresses can, depending on the ratio of the surfaces loaded on the free surfaces, damage the systems.

Such a seal has been qualified on a nominal voltage application of 38kV. It has the capacity to hold IEC and ANSI standard voltages: 50Hz / 60s / 95kVeff withstand voltage, 200kVc lightning shock voltage with partial discharges less than or equal to 5pC. It withstands temperatures from -40 ° C to + 115 ° C continuously.

Other detailed achievements are described on the Figures 4B, 4C and 4D .

The Figure 4B shows an embodiment of the joint having a general shape similar to that shown in FIG. Figure 4A , except that the contact surfaces, external 41 and internal 42 are cylindrical and parallel to the axis 40 of the seal. The latter always has a recess 45 opening onto a lateral surface completed by two lateral surface portions 44A and 44B. The other lateral surface consists of a portion 44C perpendicularly joining the internal contact surface 42.

The figure 4C represents an embodiment of the seal with outer conical surfaces 51 and 52, with opposite inclinations. The remainder of the side surfaces and design similar to the previous ones, namely that it has a recess 55 completed the two side portions 54A and 54B, the other side surface being completed, a side portion 54C.

Finally, a fourth achievement is described by the Figure 4B , on which the outer and outer contact surfaces 61 and 61 are curved by a relatively large radius of curvature. Note that the general orientation of these two surfaces and slightly inclined relative to the axis 60 of the seal, that is to say, a frustoconical general orientation and opposite from one surface to another. This type of seal also has a lateral recess 65, completed with two lateral portions 64A and 64B, the other lateral surface being completed with a lateral portion 64C.

The Figures 5A to 5M show that it is possible to give the joint a section different from that described in figure 4 . Indeed, the section represented by Figure 5A is a rectangle with. In other words, the lateral surfaces are perpendicular to the axis 50, while the internal contact and external contact surfaces are parallel thereto.

Similarly, the Figure 5B shows a section of the seal in the shape of a square.

The section represented by the Figure 5C is trapezoidal, the internal contact surfaces and external contact being always concentric with the axis 50, but the side surfaces having respectively opposite inclination.

The section represented by the figure 5D comprises lateral surfaces consisting of two inclination portions opposite to the perpendicular to the lateral axis 50, that is to say forming slightly convex surfaces. The section represented by the figure 5E has a lateral surface perpendicular to the axis 50, and a rounded convex shape.

The section represented by the surface 5F has side surfaces in two parts, of different and opposite inclinations, forming a V-shaped convex lateral surface and a concave V-shaped lateral surface.

The figure 5G shows a seal whose side surfaces are formed for one by two opposite inclination surfaces forming a convex lateral surface and a slightly rounded lateral surface.

The figure 5H shows a seal whose lateral surfaces are in two parts each, and more precisely comprises a concave portion and a convex portion, these lateral surfaces being S-shaped.

The section represented by the figure 5I is an H-shaped section, a quadrilateral shaped recess being formed in each lateral surface.

The figure 5J shows a U-shaped section.

The figure 5K shows a section of the W-shaped joint.

The figure 5L shows a section in the shape of M.

Finally, figure 5M shows an N-shaped section.

Advantages of the invention

The dielectric performances of an apparatus equipped with such seals are relatively important for a rather compact character of the apparatus.

The dielectric strength is important at the contact interfaces between the seal and the housing and the seal and the vacuum bulb.

Similarly, inside the seal, the dielectric strength is important.

This tracking resistance is characterized by the ability of the seal to perfectly match the outer surface of the vacuum bottle or the inner face of the envelope to oppose the formation of electric sparks that would carbonize the surface of the seal and / or the outer surface of the vacuum bulb between A and A 'and / or the inner face of the envelope between B and B' ( Figures 3A and 3B ) and thus provide a current path between either A and A 'or between B and B'.

The dismantling of the equipment at the end of its life is quite easy and the quantities of insulating materials are reduced, which is in accordance with the standards of the environment.

This solution is relatively low cost, easily industrialized, thanks to the high speed series molding and assembly without bonding.

The assembly is not very sensitive to temperature variations, the joints being free to expand or contract.

The setting up is easy, considering that the seal is easily deformable.

Finally, the system is removable.

Claims (19)

1. A dielectric insulation gasket for a vacuum bottle, said gasket being designed to insulate a vacuum bottle (1) by using at least one gasket (20) aground the vacuum bottle (1) inside a casing (10), the gasket having an inside contact surface (32A, 32B, 42, 52, and 62) and an outside contact surface (31A, 31B, 41, 51, and 61), two side surfaces interconnecting the inside and the outside contact surfaces;
   said gasket being characterized in that the inside contact surfaces (32A, 3213, 42, 52, and 62) and outside contact surfaces (31A, 31B, 41, 51, and 61) of the gasket are smooth, presenting no cavity and forming part of a group constituted by surface shapes comprising surfaces that are convex relative to the longitudinal axis (30, 40, 50, and 60) of the gasket and the surfaces presenting a gradient that does not reverse relative to the longitudinal axis (30, 40, 50, and 60) of the gasket,
   in such a manner, that when assembling the gasket, no gas pockets are trapped in the interfaces, neither between the inside contact surface (16) of the casing (10) and the outside contact surface (31A, 31B, 41, 51, and 61) of the gasket nor between the outside surface (6) of the vacuum bottle (1) and the inside surface (32A, 32B, 42, 52, and 62) of the gasket, thereby removing any risk of partial electrical discharges appearing between, firstly the inside contact surface (16) of the casing (10) and the outside contact surface (31A, 31B, 41, 51, and 61) of the gasket and secondly between the outside contact surface (6) of the vacuum bottle (1) and the inside contact surface (32A, 32B, 42, 52, and 62) of the gasket.
2. A gasket according to claim 1, characterized in that the axial height of the inside contact surface (32A and 32B) and of the outside contact surface (31A and 31B) is equal to or greater than 5 mm.
3. A gasket according to claim 1, characterized in that the minimum thickness of the gasket along the longitudinal axis of the gasket is 4 mm.
4. A gasket according to claim 1, characterized in that the inside contact surface (32A and 32B) and the outside contact surface (31A and 31B) are cylindrical relative to the gasket axis.
5. A gasket according to claim 1, characterized in that the outside contact surface (51) and the inside contact surface (52) are conical.
6. A gasket according to claim 1, characterized in that the inside contact surface and the outside contact surface are each made up of two conical portions (51A & 51B and 52A & 52B) having different inclinations and interconnected via a determined interconnection curve (RE, RI) forming a flared V-shape.
7. A gasket according to claim 5 or claim 6, characterized in that the inside contact surface (32A, 32B) and the outside contact surface (31A and 31B) are of general direction inclined relative to the axis (30) of the gasket, i.e. of conical general direction.
8. A gasket according to claim 1, characterized in that its cross-section is provided with a recess (35).
9. A gasket according to claim 1, characterized in that each of the side surfaces is made up of a convex portion and of a concave portion.
10. A gasket according to claim 1, characterized in that the cross-section of the gasket is H-shaped.
11. A gasket according to claim 1, characterized in that the side surfaces are made up of two portion of different inclinations.
12. A gasket according to claim 1, characterized in that at least one side surface is rounded.
13. A gasket according to claim 1, characterized in that the cross-section of the gasket is square in shape.
14. A gasket according to claim 2, characterized in that the cross-section of the gasket is rectangular in shape.
15. A gasket according to claim 1, characterized in the cross-section of the gasket is trapezium-shaped.
16. A gasket according to claim 1, characterized in that its cross-section is N-shaped.
17. A gasket according to claim 1, characterized in that its cross-section is M-shaped.
18. A gasket according to claim 1, characterized in that its cross-section is U-shaped.
19. A gasket according to claim 1, characterized in that its cross-section is W-shaped.

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