RU2405225C2 - Dielectric insulating gasket for vacuum tube - Google Patents

Abstract

FIELD: electrical engineering. ^ SUBSTANCE: proposed gasket allows easy and simple assembly-disassembly of vacuum tube. Inner and outer contact surfaces of said gasket are smooth, each consisting of two cylindrical parts of different taper (31A, 31B and 32A, 32B). At least one of lateral surfaces comprises annular recess (35). Each gasket has inner and outer contact surfaces. Invention allows ruling out partial electric discharge, on the one side, between the case inner contact surface and gasket outer contact surface, and, on the other side, between vacuum tube outer surface and gasket inner surface. Inner and outer contact surfaces are cylindrical or tapered with respect to gasket axis. Each lateral surface consists of convex and concave parts. Lateral surfaces consists of two different-inclination parts. Gasket cross section features square shape. ^ EFFECT: easy and simple assembly-disassembly of vacuum tube. ^ 19 cl, 22 dwg

Description

FIELD OF THE INVENTION

The present invention relates to the field of electrical equipment and electrical systems and, in particular, to switches and switching devices using vacuum tubes operating on medium and high voltage.

A particular application of the invention is the transfer of electricity through an air line network.

State of the art

In electrical systems and devices for circuit breakers, vacuum tubes are used that must withstand voltages, including dielectric voltages between the contacts inside the tube in vacuum, and also between the outer ends of the tube in ambient air. In order to ensure the necessary compactness, to homogenize the dielectric resistance between the energized contacts and the outer ends of the vacuum circuit breakers, it is required to use insulating elements other than air, even outside the vacuum tubes.

In particular, these are solid or fluid dielectric insulators, such as SF6 greenhouse gas. Indeed, the insulation of vacuum tubes in air does not make it possible to obtain satisfactory dielectric characteristics at small sizes.

However, insulation of vacuum tubes in a dielectric gaseous medium such as SF6 is expensive. Indeed, it is necessary to use a sealed container equipped with current inputs, and such devices are very harmful to the environment, in particular in terms of pollution, disposal and the greenhouse effect.

The solid insulation systems of vacuum tubes are very temperature sensitive and do not allow dismantling and disassembling at the end of the service life after fastening and gluing. This has negative environmental effects.

To reduce this environmental impact, it has been proposed to use a mixed insulating material that combines both a solid insulator and a gaseous insulator, such as atmospheric pressure air, or other gases, such as nitrogen. In this case, the solid insulator occupies a small volume, since it is performed in the form of a gasket, which performs the sealing function with respect to gas and the dielectric function. However, in known technical solutions, this type of insulation does not provide high dielectric characteristics for vacuum tubes.

The vacuum tube 101 shown in FIG. 1 is surrounded by two gaskets 102A and 102B at two ends of its outer surface. The upper gasket 102A is installed near the stationary contact of the vacuum tube 101, while the lower gasket 102B is installed near the movable contact. The entire device is housed in a rigid housing 103 made of insulating material. However, the gaskets 102A and 102B are designed in such a way that air remains at the level of their surfaces 104 in contact with the inner wall of the rigid housing 103.

On figa in partial section shows a detail of the surface 104 shown in figure 1. This surface comprises several sharpened edges 105, separated from each other by an intermediate space 106.

On figv also in partial section shows the same location of the gasket from the prior art. This gasket is inserted into the rigid body 103, and its edges are flattened or, rather, bent in one direction under the pressure of the internal wall of the housing 103 acting on the side of each edge 105. Consequently, air remains between each edge 105 along the line B-B '. Similarly, air may remain along line A-A 'on another surface. This air, having a low dielectric strength, significantly limits the dielectric characteristics of the system. The ignition arc can easily move radially inside each intermediate space 106, trying to reach the weakest point on the circumference of the next edge 105, and thus spread in the next intermediate space 106. The dielectric strength of the device is a function of the sum of the weakest points on each circumference of the gasket 102. In addition , the thickness of the insulator in some places of this gasket 102 is too small to provide good dielectric characteristics. It should be noted that the shape of the gasket 102 from the prior art does not allow disassembly and disassembly at the end of the service life due to the irreversible effect of the edges 105.

The present invention is to obtain high dielectric characteristics with small sizes of vacuum tubes by improving their insulation, in particular, preventing the passage of electrical discharges or sparks along the contact surfaces of the gasket during operation. In addition, the aim is to comply with environmental protection requirements. In this regard, the goal is to ensure complete and easy disassembly of the insulation system at the end of the life of the vacuum tube. In addition, the objective is to reduce the used solid insulating material. Due to this, it is proposed to reduce the cost in comparison with a system using fully solid insulation.

On the other hand, in European application EP 1017142 A1, a circuit breaker comprising a mixed insulation system is described.

Disclosure of invention

In this regard, the main object of the present invention is a dielectric insulating gasket for a vacuum tube, designed to isolate a vacuum tube by using at least one gasket installed around the vacuum tube inside the housing, with each gasket containing an inner contact surface and an outer contact surface, wherein the inner and outer contact surfaces are connected by two side surfaces.

According to the invention, since the inner contact surface of the housing and the outer surface of the vacuum tube are smooth, both the inner and outer contact surfaces of the gasket are smooth, do not contain any cavity and are part of the group formed by surface shapes containing convex surfaces with respect to the longitudinal axis of the gasket and surfaces having an inclination that does not change direction with respect to the longitudinal axis of the gasket. Thus, during installation of the gasket there is no gas pocket in the boundary zones, on the one hand, between the inner contact surface of the housing and the outer contact surface of the gasket and, on the other hand, between the outer surface of the vacuum tube and the inner contact surface of the gasket, thereby eliminating any the possibility of a partial electric discharge, on the one hand, between the inner contact surface of the housing and the outer contact surface of the gasket and, on the other hand between the outer surface of the vacuum tube and the inner contact surface of the gasket.

This elimination of the possibility of passage of the discharge is determined by the ability of the gasket to perfectly adhere to the outer surface of the vacuum tube or to the inner surface of the casing, preventing the formation of electric sparks, which can lead to carbonization of the gasket and / or outer surface of the vacuum tube or the inner side of the casing and thus , paths for current.

The main embodiment provides that these inner and outer contact surfaces of the gasket are cylindrical.

According to a second embodiment, these inner and outer contact surfaces of the gasket are tapered.

According to the third embodiment of the inner and outer contact surfaces of the gasket, each of them is made of two conical parts having different taper and connected by a certain radius of mating, forming an expanding V.

In these last two embodiments, it should be noted that in their general direction, these inner and outer surfaces are preferably conical and have opposite taper with respect to each other.

With regard to the overall implementation of the gasket, the width of the inner and outer contact surfaces is preferably equal to or greater than 5 mm in order to limit the possibility of the appearance and passage of a discharge at the level of these boundary zones.

It is also preferred that the minimum thickness of the gasket along its longitudinal axis is at least 4 mm. These two sizes can significantly increase the dielectric strength of the gasket.

In various provided embodiments, the gasket comprises a recess in cross section to limit forces within the gasket.

As for the side surfaces, to control thermal expansions, these side surfaces can be made of two parts with different slopes.

Preferably, at least one of said side surfaces is rounded and the other straight.

It is also preferred that these side surfaces are partially rounded, with one part concave and the other convex.

The gasket may have a trapezoidal section, that is, both contact surfaces, internal and external, are parallel to the axis of rotation of the gasket, and the side surfaces have an inclination of the opposite direction.

The cross section of the gasket may be H-shaped.

The cross section of the gasket may be N-shaped.

The cross section of the gasket may be M-shaped.

It may also be square or rectangular.

In the case where the cross section of the gasket contains a recess, it may have a W-shaped or U-shaped.

Brief Description of the Drawings

The present invention and its various technical features will be more apparent from the following description with reference to the accompanying drawings, in which:

figure 1 is a view illustrating the use of two gaskets, according to the prior art;

figa and 2B is a partial section of the active part of the strip according to the prior art;

figa is a longitudinal section of a gasket according to the present invention;

figv is a longitudinal section of two gaskets according to the present invention;

figa-4D is a detailed view of four options for performing gaskets in accordance with the present invention;

figa-5M is a view of sections of various gaskets in accordance with the present invention.

The implementation of the invention

As shown in figa and 3B, the vacuum tube 1 is installed in the housing 10, forming the pole of the electric device medium or high voltage. In this example, the housing 10 forms the hard pole of the device used, such as a chopper. When this breaker is in the open position, the movable contact 5A of the vacuum tube 1 and the fixed contact 5B, each of which is made at the end of the vacuum tube 1, have different electrical potentials. Therefore, it is necessary to ensure the dielectric insulation of the vacuum tube 1 by installing between these two movable 5A and fixed 5V contacts, forming two electrodes with different potentials, a gasket 20, which is a dielectric insulating gasket. After installation, the gasket 20 prevents the passage of sparks or discharges along the dotted lines A-A 'and B-B'. In this regard, it should be recalled that the dielectric strength of the vacuum inside the vacuum tube 1 is much higher than the dielectric strength of the air outside the vacuum tube 1.

As shown in FIG. 3B, in the case of using two gaskets, they isolate the annular space 24 bounded by the side surface of each of the gaskets 20, the outer surface 6 of the vacuum tube 1 and the inner surface 16 of the housing 10. The space 24 thus insulated contains a gaseous fluid such like air or other fluid of the same type. Thus, the two gaskets 20 and the space 24 limited by them form a dielectric barrier between two movable 5A and fixed 5B contacts with different potentials. This configuration avoids any dielectric ignition or bypass of one of the gaseous elements limited by the gaskets 20, either due to passage or due to breakdown. In particular, dielectric tightness or dielectric strength is ensured, inter alia, by the following three aspects:

- close contact between the gaskets 20 and the vacuum tube 1, in particular along its outer surface 6 along the line A-A ', and the contact between the gaskets 20 and the housing 10, in particular along its inner surface 16 along the line B-B';

- radial compression of the gaskets 20, which are made of elastomeric material, and

- the thickness of the insulating elastomeric material of each strip 20 with correctly defined dimensions.

In this regard, it is noted that in the embodiment described with reference to FIG. 3B, each gasket 20 has a cross section consisting of two conical parts 20A and 20B of opposite inclination. In other words, the cross section of this gasket is approximately U-shaped. Here is an example of a relatively simple gasket shape, and more complex shapes will be described below.

A very important technical feature of the gasket in accordance with the present invention is that the peripheral outer surface as well as the peripheral inner surface of each gasket 20 is smooth. Indeed, a housing 10 is used, the inner surface 16 of which is smooth, and likewise, the vacuum tube 1 has a smooth outer surface 6. Thus, the presence of residual air between these surfaces at the time of installation is avoided. The overall shape of the gasket is optimized to obtain a heterogeneous but sufficient contact pressure in the boundary zone of the gasket / housing and gasket / vacuum tube. The stresses of pressing the gasket around the vacuum tube 1 exceed the stresses at the level of pressing the gasket to the housing 10. This allows the gasket to remain in place on the vacuum tube 1 during installation, dismantling and disassembly.

As can be seen from this figv, the position of the gaskets 20 on the vacuum tube 1 is optimized and they are positioned on the vacuum tube in areas where dielectric fields contribute to an increase in dielectric strength. In particular, these spacers 20 are not in contact with the electrodes formed by the movable 5A and the fixed 5B contacts. Otherwise, there is a danger of breakdown of the gaskets when a very strong local electric field appears. Indeed, the presence of a protrusion on one of these electrodes can lead to an electric field concentration. If the dielectric gasket is in contact with one of these electrodes, the latter is affected by an excessively strong electric field, and it can be damaged as a result of breakdown.

On figa shows in detail the first embodiment of the gasket.

The outer contact surface, which is made smooth, essentially consists of two surfaces 31A and 31B, both of which are conical with respect to the axis 30 of the gasket and have a different inclination, forming a U-shaped shape that is very open to the outside. Their pairing is formed by the outer radius RE of the pairing. Similarly, the inner contact surface consists of two parts 32A and 32B with a different inclination relative to the axis 30, while one of them, in this case, the surface 32A, may be cylindrical. These two inner contact surfaces are also connected by an inner mating radius RI. These RE and RI mating radii avoid residual air during installation of the gasket. Gaskets 20 are shown mounted around the vacuum tube 1 and inside the housing 10 with smooth contact surfaces, however, it must be emphasized that these external and internal contact surfaces are smooth until the gaskets are installed.

In this embodiment, both side surfaces also consist of several parts. One of them comprises a recess 35 formed by two truncated conical surfaces 35A connected by a radial surface 35B. This recess allows you to limit the forces inside the gasket when it is compressed during the installation phase of the vacuum tube in the housing.

Similarly, the other side surface consists of two surfaces 33A and 33B, which are made in the form of a truncated cone and have a different slope, forming an open U-shape. The rest of the side surfaces are formed by radial parts 34C, on the one hand, and 34A and 34B, connecting the recess 35 with the inner contact surface, on the other hand.

This embodiment has the appearance of U, one of the vertical parts of which is slightly extended downward. Other possible gasket cross sections will be indicated below.

Regardless of the intended shape, the thickness in the direction parallel to the direction of the axis 30 of the gasket must be equal to or greater than 4 (four) millimeters. Due to this, of course, the mechanical strength is increased, but above all, the dielectric strength of the gasket is increased, which, in particular, significantly limits the possibility of a discharge due to breakdown of the gasket.

Similarly, if the inner and outer contact surfaces 32A and 32B have a sufficiently large axial height, forming extensive, rather than point, support surfaces, they primarily contribute to increasing the dielectric strength of the gasket. The axial height must therefore be at least 5 (five) millimeters. In addition, it should be noted that the electric fields at the interface formed by the inner contact surfaces 32A and 32B and the outer surface of the vacuum tube are larger than the fields at the interface formed by the outer contact surfaces 31A and 31B and the inner surface of the housing. Thus, the width of the inner contact surfaces 32A and 32B is greater than the width of the outer contact surfaces 31A and 31B. With the same pressure value, this allows the gasket to remain in place on the vacuum tube during installation, dismantling and disassembly.

The gasket is made of elastomeric material. During installation, its deformation allows sufficient contact pressure to be obtained at the level of its internal contact surfaces 32A and 32B and at the level of its external contact surfaces 31A and 31B. The system is slightly temperature sensitive. Indeed, due to the shape of its side surfaces, the gasket can expand freely during temperature increases and contract during temperature drops.

Indeed, the ratio of the pressurized surfaces, i.e., the inner 32A and 32B and the outer contact surfaces 31A and 31B, to the free surfaces, i.e. to the side surfaces 33A, 33B, 34A, 34B, 35A and 35B, is sufficiently limited so that the elastomeric material gaskets could expand and contract freely under the influence of temperature. This allows you to significantly limit the thermomechanical stresses inside the gasket. Depending on the ratio of loaded surfaces to free surfaces, these thermomechanical stresses can lead to damage to the systems.

Such a gasket is qualitatively rated for a rated voltage of 38 kV. It can withstand voltages of CEI and ANSI standards: continuous voltage with a frequency of 50 Hz / 60 s / 95 kV, impact voltage of 200 kV with partial discharges less than or equal to 5 pC. It withstands temperatures from -40 ° C to + 115 ° C in continuous operation.

Other embodiments are shown in detail in FIGS. 4B, 4C and 4D.

FIG. 4B shows an embodiment of a gasket generally having a shape similar to that of the gasket shown in FIG. 4A, except that the outer 41 and inner 42 contact surfaces are cylindrical and parallel to the axis 40 of the gasket. The gasket also includes a recess 45 extending to the side surface, complemented by two parts 44A and 44B of the side surface. The other side surface includes a portion 44C mating perpendicular to the inner contact surface 42.

On figs shows an embodiment of the gasket with a tapered outer 51 and inner 52 contact surfaces having an inclination in opposite directions. The rest of the side surfaces has a view similar to the previous embodiment, that is, it contains a recess 55, supplemented by two side parts 54A and 54B, while the other side surface is supplemented by the side part 54C.

Finally, FIG. 4D shows a fourth embodiment in which the outer 61 and inner 62 contact surfaces are curved with a relatively large radius of curvature. It should be noted that the general direction of these two surfaces is slightly inclined relative to the axis 60 of the gasket, that is, the general direction has the appearance of a truncated cone and is opposite from one surface to another. This type of gasket also includes a side recess 65, complemented by two side parts 64A and 64B, with the other side surface complemented by a side part 64C.

On figa-5M illustrated the ability to perform gaskets with a cross section different from the gasket shown in figure 4. Indeed, the cross section shown in FIG. 5A is a rectangle. Thus, the side surfaces are perpendicular to the axis 50, while the inner contact surface and the outer contact surface are parallel to this axis.

Similarly, FIG. 5B shows a square section.

The cross section shown in figs is trapezoidal, while the inner contact surface and the outer contact surface remain concentric with the axis 50, however, the side surfaces respectively have an opposite inclination.

The cross section shown in FIG. 5D contains lateral surfaces formed by two parts with an opposite inclination relative to the perpendicular to the lateral axis 50, that is, forming slightly convex surfaces.

The cross section shown in FIG. 5E contains a lateral surface perpendicular to the axis 50 and a rounding is convex.

The cross section shown in FIG. 5F contains two side surfaces of two parts of different and opposite inclination, forming one side surface convex in the form of V, and the other side surface concave in the form of V.

Fig. 5G shows a gasket, one of whose side surfaces is formed by two surfaces of opposite inclination, forming a convex side surface, and the other is formed by a slightly rounded surface.

On fign shows a gasket, each of the side surfaces of which consists of two parts and, in particular, contains a concave part and a convex part, and these side surfaces are S-shaped.

The cross section shown in FIG. 5I has a cross section in the form of H, with a four-sided recess in each side surface.

Fig. 5J shows a cross section of a U-shape.

Figure 5K shows a section of a W-shaped gasket.

Fig. 5L shows a cross section of an M-shape.

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

The dielectric characteristics of a device equipped with such gaskets are relatively high with fairly compact dimensions of the device.

Dielectric strength is high at the interface between the gasket and the housing and between the gasket and the vacuum tube.

Inside the gasket, dielectric strength is also high.

The ability to prevent the passage of discharges is determined by the ability of the gasket to perfectly adhere to the outer surface of the vacuum tube or to the inner side of the casing to withstand the appearance of electric sparks that can carbonize the gasket surface and / or the outer surface of the vacuum tube between A and A ', and / or the inner side of the casing between B and B '(figa and 3B) and thus create a passage for the current either between A and A', or between B and B '.

Dismantling the device at the end of its service life is quite easy, and the amount of insulating material used is reduced, which complies with environmental standards.

This solution has a relatively low cost, can be easily implemented in the industry, thanks to high-speed technology of molding and assembly without the use of glue.

The system is not very sensitive to temperature fluctuations, since the gaskets can expand or contract freely.

Reinstallation is easy, given that the gasket is easily deformed.

The mentioned system is made collapsible.

Claims (19)

1. A dielectric insulating gasket for a vacuum tube, designed to insulate the vacuum tube (1) by at least one gasket (20) mounted around the vacuum tube (1) inside the housing (10), each gasket containing an inner contact surface (32A, 32B, 42, 52 and 62) and the outer contact surface (31A, 31B, 41, 51 and 61), while the inner and outer contact surfaces are connected by two side surfaces, characterized in that the inner contact surface (16) of the housing (10) and the outer surface part (6) of the vacuum tube (1) is made smooth, while the inner (32A, 32B, 42, 52 and 62) and outer (31A, 31B, 41, 51 and 61) contact surfaces of the gasket are smooth and do not contain any cavity and are part of a group formed by surface shapes containing convex surfaces with respect to the longitudinal axis (30, 40, 50 and 60) of the gasket and surfaces having a slope that does not change direction with respect to the longitudinal axis (30, 40, 50 and 60 ) gaskets, and during installation of the gasket there is no gas pocket in the border areas, on one side they are between the inner contact surface (16) of the housing (10) and the outer contact surface (31A, 31B, 41, 51 and 61) of the gasket and, on the other hand, between the outer surface (6) of the vacuum tube (1) and the inner contact surface (32A, 32B, 42, 52, and 62) of the gasket, thereby eliminating the possibility of a partial electric discharge on one side between the inner contact surface (16) of the housing (10) and the outer contact surface (31A, 31B, 41, 51 and 61) of the gasket and the other side between the outer surface (6) of the vacuum tube (1) and the inner the contact surface (32A, 32B, 42, 52, and 62) of the gasket. 2. The gasket according to claim 1, characterized in that the axial height of the inner contact surface (32A and 32B) and the outer contact surface (31A and 31B) is equal to or greater than 5 mm. 3. The gasket according to claim 1, characterized in that the minimum thickness of the gasket along its longitudinal axis is 4 mm. 4. The gasket according to claim 1, characterized in that the inner (32A and 32B) and outer (31A and 31B) contact surfaces are cylindrical about the axis of the gasket. 5. The gasket according to claim 1, characterized in that the inner (51) and outer (52) contact surfaces of the gasket are conical. 6. The gasket according to claim 1, characterized in that the inner and outer contact surfaces consist of two parts (51A, 51B) and (52A, 52B) having different inclination and connected by a certain radius of coupling (RE, RI), forming V- figurative extension. 7. Gasket according to claim 5 or 6, characterized in that the inner (32A, 32B) and outer (31A, 31B) contact surfaces have a common oblique direction relative to the axis (30) of the gasket, namely the conical direction. 8. The gasket according to claim 1, characterized in that its cross section contains a recess (35). 9. The gasket according to claim 1, characterized in that each of the side surfaces consists of a convex part and a concave part. 10. The gasket according to claim 1, characterized in that the cross section of the gasket is H-shaped. 11. The gasket according to claim 1, characterized in that the side surfaces consist of two parts with different slopes. 12. The gasket according to claim 1, characterized in that at least one side surface is rounded. 13. The gasket according to claim 1, characterized in that the cross-section of the gasket is square. 14. The gasket according to claim 2, characterized in that the cross-section of the gasket is rectangular. 15. The gasket according to claim 1, characterized in that the cross-section of the gasket is trapezoidal in shape. 16. The gasket according to claim 1, characterized in that the cross section is N-shaped. 17. The gasket according to claim 1, characterized in that the cross section is M-shaped. 18. The gasket according to claim 1, characterized in that the cross section is made in a U-shape. 19. The gasket according to claim 1, characterized in that the cross section is made W-shaped.

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