WO1998009310A1

WO1998009310A1 - Load interrupter switch

Info

Publication number: WO1998009310A1
Application number: PCT/EP1997/004617
Authority: WO
Inventors: Vitus Högl
Original assignee: Elektrotechnische Werke Fritz Driescher & Söhne Gmbh
Priority date: 1996-08-26
Filing date: 1997-08-25
Publication date: 1998-03-05
Also published as: AU4618397A; EP0920705B1; ES2144880T5; DK0920705T3; CA2263881A1; DE59701481D1; SK282723B6; HU222705B1; CZ58599A3; ES2144880T3; SK23899A3; HUP9903117A2; PT920705E; RS49698B; HUP9903117A3; EP0920705B2; EP0920705A1; DK0920705T4; PL187251B1; YU10299A

Abstract

The invention concerns a load interrupter switch (1) for voltages in the kV range, with a vacuum interrupter chamber (2) which is surrounded in a gap-free manner by a sleeve (4) formed from elastomer material having high dielectric strength. The sleeve (4) is in turn clamped by the two halves (11 and 12) of the housing of the load interrupter switch (1). In this way, external flashover of the high voltage between the end plates (24 and 25) of the vacuum interrupter chamber (2) is effectively prevented during switching operations without the need for liquid or gaseous media. In this way, in contrast to conventional load interrupter switches, complicated monitoring is unnecessary and the load interrupter switch is not harmful to the environment.

Description

description

Load switch

The invention relates to a load switch for voltages above 1 kV with a vacuum interrupter, the contacts of which are closed or opened by means of a switching mechanism, the vacuum interrupter enclosing the switching contacts lying in vacuum with metallic end plates and a cylindrical housing middle part made of electrical Insulating material which is surrounded by a dielectric medium.

Such load switches are e.g. Known as switch disconnectors in railway operations. In this case, the vacuum interrupter in the switch-on position with the switching mechanism housed in an insulating material housing is electrically shunted with the main current path designed for the full nominal current of the device. When switching off, the main contacts first open without current and commutate the current to the series connection of vacuum switching chamber and auxiliary switching point, which has an actuating fork. As soon as the main contacts have moved far enough away from each other, the vacuum interrupter is quickly actuated using a tilting mechanism and the switch-off arc occurring inside the interrupter chamber is safely extinguished in the first zero current passage without any external appearance.

It has been shown in practice, however, that the vacuum interrupters or -ka mern used relatively have large dimensions and are associated with high manufacturing costs. For this reason, vacuum interrupters of a lower voltage range than that for which the switch is designed have been used for some time. As a result, both the dimensions and the manufacturing costs can be reduced, the active part in the vacuum interrupter generally permitting such use.

With the reduction in size, the distance between the metal end plates of the housing of the vacuum interrupter also decreases. Therefore, the external insulation, which is used during and after the shutdown, is not sufficient with free air in the area.

To solve this problem, the vacuum interrupters are placed in a medium with higher dielectric strength. Insulating oil such as mineral or silicone oil, various esters or an insulating gas such as sulfur hexafluoride (SF ₆ ) are used. These media displace the air in the vicinity of the vacuum interrupters and because they have a high dielectric strength, an external flashover is prevented.

However, these media have the disadvantage that they are not harmless with regard to their environmental compatibility. Since such load switches have been in use for many years, leaks due to aging of components and due to external influences cannot be completely ruled out. The medium may therefore escape into the environment. Another disadvantage of such media is that they require ongoing control. When using insulating oil, for example, the oil level must be checked and since such load switches are installed on tall masts in most applications, a corresponding effort is necessary here. The same applies in the case of insulating gas, in which the pressure must be checked.

Furthermore, it is also known to externally isolate the vacuum interrupters by encapsulating them with e.g. Improve epoxy resin. However, aging processes can result in an air gap and thus an external rollover of the vacuum interrupter in the area between the epoxy resin shell and the outer housing. Such aging processes cause z. B. Stress cracks due to the shrinkage of the cast resin jacket, embrittlement due to ineffective flexibilizers that were used during casting or gap formation due to detachment of the resin jacket from the outer casing of the vacuum interrupter chamber due to different material expansion with frequent hot-cold alternating stress. This danger cannot therefore be completely eliminated. Another disadvantage is that a vacuum interrupter cast in such a manner is only accessible when the casing is disassembled when it is disassembled.

The previously known forms of execution are therefore complex, for universal use, e.g. on overhead line masts, only of limited use or are often rejected because of a possible danger to the environment.

The German utility model G 93 14 754 Ul discloses a vacuum interrupter with an encapsulation resistant to internal pressure. Encapsulating this vacuum switching tube consists of an inner layer made of hard plastic foam and an outer burst-proof jacket. The inner layer, which is preferably made of a polyurethane foam, is uniformly porous in order to enable the best possible thermal insulation according to the teaching of this document, so that in the event of a fault no temperature sufficient to ignite the surrounding gas can be reached. The burst-proof jacket is designed as a winding body and consists of threads or tapes that are impregnated with a hardened plastic. It is formed close to the foam layer and dimensioned so that it can absorb the bursting force that occurs in the event of a fault within the vacuum interrupter.

In this prior art, the casing of the tube also contains a firmly foamed plastic material, the properties of which can be impaired by aging. In particular, embrittlement or detachment of the foam layer from the outer casing of the tube can occur. In addition, disassembly of this encapsulated vacuum interrupter is only possible if the casing is destroyed.

The invention is therefore based on the object of providing a load switch which can be safely used over a long period of time without control and can also be dismantled.

This object is achieved in that the housing is surrounded by a prefabricated sleeve which engages behind the edges of the two end plates and consists of an elastomer material with high dielectric strength, which is pressed onto the housing without gaps. It is of great advantage here that, due to the elastic properties of the sleeve, no gap remains on the periphery of the housing. An external rollover on the vacuum interrupter via such an air gap is therefore not possible.

It is also advantageous that the edges of the two

Front plates of the vacuum interrupter can be gripped behind by the cuff and the path for a possible rollover can be significantly lengthened. This prevents this case even more reliably.

Since the use of the sleeve eliminates the use of liquid or gaseous media, the load switch according to the invention has numerous other advantages.

This eliminates the complex control activities for checking the fluid levels and the pressure status. The load switch can therefore be used in continuous operation for many years without having to check the sleeve acting as a dielectric medium.

Furthermore, this prevents the environment from being adversely affected by escaping media, so that the load switch according to the invention e.g. can also be used without hesitation in water protection areas. This provides a permanent load switch that can be used universally.

Another advantage is that the assembly of the circuit breaker according to the invention is considerably simplified. So training with a prefabricated cuff a pre-assembly of the arrangement, which is why no effort for a final assembly or a filling is necessary, for example, high up on the mast. Since no liquid or gaseous medium is handled, the effort for the transport and installation of the circuit breaker according to the invention is considerably simplified.

The circuit breaker according to the invention is easy to manufacture and allows disassembly if necessary. In addition könττe ^~ n interrupter vacuum can be kept low, the space required and the cost.

Advantageous developments of the invention result from the features of the subclaims.

The fact that the dimensions of the sleeve are selected such that the sleeve applies a preload to the vacuum interrupter chamber reliably prevents an air gap between the sleeve and the housing of the vacuum interrupter chamber. The relatively large dimensional tolerances of the vacuum interrupter can thus also be compensated for. This further increases the reliability of the circuit breaker.

It is also advantageous if a complementary pressure housing made of insulating material is provided on the outside of the sleeve, which prestresses the outer circumference of the sleeve in the elastic region. This ensures, on the one hand, that the sleeve presses firmly against the vacuum interrupter and, furthermore, that there is no air gap on the outer circumference of the sleeve, which could allow an external rollover. The possible distance for an external rollover is thereby increased to a level at which this is practically no longer possible. This further increases the operational safety and reliability of the circuit breaker. Furthermore, the vacuum interrupter is centered and fixed in the pressure housing.

If the sleeve has at least one sealing bead running in the axial direction of the pressure housing, which comes to rest in the assembly joint of the pressure housing, a sealing of the pressure housing against external influences is also achieved. This reliably prevents e.g. Dirt and especially water can penetrate the pressure housing. Failure of the load switch can thus be effectively avoided. Furthermore, the one-piece design of the sleeve with the sealing bead facilitates the assembly of the arrangement.

If the sealing bead also has a thickening that can be squeezed in the assembly joint of the pressure housing, the reliability of this seal on the pressure housing is further increased.

The fact that protruding and circumferential screens are arranged on the outer circumference of the sleeve essentially parallel to the end plates, the risk of an external rollover is further reduced.

It is a further advantage if the cuff has at least one recess for receiving material of the cuff displaced under the pressure load. It is thereby achieved that the cuff fits cleanly on the peripheral surface of the vacuum interrupter chamber without the cuff being damaged by the applied compressive forces. This further increases the reliability of the circuit breaker. The at least one recess is advantageously designed as a circumferential annular groove in the inner periphery of the sleeve. This results in an even pressure distribution over the entire circumference of the vacuum interrupter.

If the cuff is provided with at least one pocket on at least one end face in the area of at least one end plate, the length of the vacuum interrupter chamber can be adjusted in the assembled state without the material of the cuff being damaged, since it can escape into the at least one pocket can. The reliability of the sleeve and thus the operational safety of the load switch is increased.

If the at least one pocket is also ring-shaped, a uniform distribution of the pressure load on the end face of the cuff is achieved.

The cuff according to the invention is preferably made of EPDM (ethylene-propylene terpolymer) or silicone rubber, which have good elastic properties and are not compressible. Such materials allow a secure sealing of the interface between the vacuum interrupter and the sleeve or between the sleeve and the pressure housing of the load switch. A rollover can thus be safely avoided.

Because the load switch is designed as a load break switch, in which a visible isolating path is arranged in series with the vacuum interrupter, a visual check can also be carried out from a greater distance in order to determine whether the load switch is closed. If a circuit is connected in parallel to the vacuum interrupter or parallel to the vacuum interrupter / visible isolating section when the load switch is switched on, the vacuum tube is relieved when the load switch (switch disconnector) is in the closed state. This has the advantage that the vacuum interrupter is only acted upon by the high voltages present during the switching operations. A continuous current can be conducted which is higher than the nominal current of the switching chamber or the series connection of vacuum switching chamber and visible isolating section. This significantly increases the lifespan of the circuit breaker.

The invention is explained in more detail below in an exemplary embodiment with reference to the figures of the drawing. It shows:

Figure 1 is a sectional view of a circuit breaker according to the invention, with a section in the parting plane of the pressure housing on the left side of the main axis and a section in another plane through a housing half of the pressure housing to the right of the main axis; and

FIG. 2 shows a simplified sectional illustration along the line A-A in FIG. 1.

As shown in the figures, a load switch 1 has a pressure housing with two housing halves 11 and 12, which are made of insulating material and are essentially mirror images. In the housing halves 11 and 12 there are, inter alia, a vacuum interrupter 2 and a switching mechanism 3 arranged. The arrangement and function of the vacuum interrupter 2 and the switching mechanism 3 correspond to the known designs, which is why a detailed explanation is given here. It is essential that the vacuum interrupter 2 has switching contacts inside, which are closed or opened by the switching mechanism 3. For this purpose, the switching mechanism 3 is formed with an eccentric actuating element 31, which acts on a movable contact 21 of the vacuum switching chamber 2.

In addition to the movable contact 21, the vacuum interrupter chamber 2 has a fixed contact 22 which is arranged opposite the movable contact 21. The vacuum interrupter 2 also has a housing 23 which is provided with metallic end plates 24 and 25 which close off a cylindrical housing middle part 26. The middle housing part 26 is made of electrically insulating material. A high vacuum prevails within the vacuum interrupter chamber 2, which ensures a safe arc interruption when switched off and a safe voltage hold when switched off.

In order to ensure that there is no external flashover of the voltage between the end plates 24 and 25 of the vacuum interrupter 2, a sleeve 4 made of EPDM (ethylene-propylene terpolymer) is arranged around the vacuum interrupter 2. The sleeve 4 is designed such that it encompasses the edges of the two end plates 24 and 25 of the vacuum interrupter 2. Furthermore, the dimensions of the sleeve 4 are selected so that tolerance deviations of the vacuum interrupter chamber 2 can be compensated for and the sleeve 4 is nevertheless pretensioned on the circumferential surface of the vacuum um-Sehaltkämmer 2 is present. As a result, there is no continuous air gap between the end plates 24 and 25.

The sleeve 4 is in turn encompassed and biased by the housing halves 11 and 12 of the load switch 1. Because of the bias voltage is between the sleeve 4 and the mounted half housings 11 and 12 before, no air gap which would be a external flashover of the voltage between the end plates 24 and 25 of the vacuum Schaltkammer- -erlauben ^{^?.}

According to the illustration in FIG. 1, the sleeve 4 has ring-shaped shields 41 which are received in corresponding cutouts in the housing halves 11 and 12. The flap 41 is used in a known manner to extend the path (creepage distance) along the surface.

The sleeve 4 also has four recesses 42 which are arranged on the inner circumferential surface and have an annular shape. When the housing halves 11 and 12 are closed, pressure is exerted on the cuff 4 and since this is made of an elastomer material which is elastic but essentially not compressible, the cutouts 42 allow the material of the cuff 4 to escape into the spaces formed thereby . In this way, damage to the sleeve 4 is prevented and a good seal of the interface between the sleeve 4 and the vacuum interrupter 2 is achieved.

At the end of the sleeve 4, which overlaps the end plate 25 in the area of the fixed contact 22, an annular pocket 43 is also formed. Since vacuum interrupters 2 have relatively large length tolerances, length adjustment or positioning of the vacuum interrupter 2 in the load switch 1 may be necessary. In order to allow the necessary deformation of the sleeve 4 in this end region, the annular pocket 43 serves as a chamber for a volume compensation of the displaced material.

According to the illustration in FIG. 2, the sleeve 4 also has a sealing bead 44 with a thickening 45. These are each arranged on the two assembly joints of the housing halves 11 and 12 of the circuit breaker 1 for sealing against external influences. The thickening 45 is received in appropriately designed recesses or grooves on the joint surfaces of the housing halves 11 and 12 and squeezed when the housing halves 11 and 12 are closed. The sealing bead 44 with the thickening 45 has a length which essentially corresponds to the total length of the sleeve 4. However, it can also be formed in one piece with the sleeve 4 as a round cord for sealing the pressure housing in the entire assembly joint area of the housing halves 11 and 12.

When the load switch 1 is opened during operation, the contacts 21 and 22, which are pretensioned by springs, are released by the switching mechanism 3, so that these open the switching contacts in the vacuum switching chamber 2. Due to the high voltage present, which can be 45 kV, for example, depending on the application, the arrangement tends to search for a way for a possible voltage discharge by an arc. Because of the vacuum, this is not possible within the vacuum interrupter chamber 3. Since the cuff 4 bears against the housing 23 of the vacuum interrupter chamber 2 and is likewise connected to the pressure housing of the load switch 1 under preload, there is no air gap which would allow a voltage flashover. A rollover through the material of the sleeve 4 is also not possible due to the high dielectric strength of the material used for the sleeve 4. Such an external rollover is therefore prevented.

In one application example, the load switch is used as a switch disconnector and arranged in series with a visible isolating path. Here, a main current path designed for the continuous operating current is connected in parallel to the vacuum interrupter and an auxiliary switching point in series therewith, as a result of which the vacuum tube is relieved when the load-break switch is switched on. To switch off the load-break switch, the main contact is first opened in a known manner, as a result of which the voltage is passed completely via the vacuum interrupter 2. Then the contacts 21 and 22 of the vacuum interrupter 2 are disconnected and the connection is completely interrupted without arcing in the load switch 1.

In addition to the exemplary embodiment shown here, the invention permits further design approaches.

The dimensions and shape of the sleeve 4 can vary depending on the construction and type of the vacuum interrupter 2. In any case, it is essential that the sleeve 4 rests against the vacuum interrupter 2 in such a way that no air gap between them is possible. The cuff 4 does not have to be formed with shields 41, but can also have a differently designed or smooth outer circumferential surface if the safety of the load switch 1 permits it, for example due to low voltages present.

In the example shown, the cutouts 42 in the sleeve 4 have semicircular cross sections and are formed at four locations around the vacuum interrupter 2. Both the shape and the number of annular recesses 42 can differ from this. Furthermore, it is also possible, instead of the embodiment shown, to provide the cutouts 42 with an annular shape at certain points on the inner circumferential surface of the sleeve 4.

The pocket 43 in the cuff 4 can also be provided on both end faces. In addition, the shape and number of the pocket 43 can also vary in a manner similar to the recesses 42.

The sleeve 4 can be used in any way in connection with vacuum interrupters 2, which also includes other switching elements as switch disconnectors. Use in circuit breakers and the like is also conceivable.

The pressure housing can also consist of more than two housing parts, the number of sealing beads 44 being adapted to the number of assembly joints.

Furthermore, parallel to the vacuum interrupter 2, a continuous current or main current contact system can also be provided, which allows the load switch 1 to be to design a specific vacuum interrupter 2 for different nominal or continuous currents.

The invention thus creates a load switch 1 for voltages in the kV range with a vacuum interrupter 2, which is encompassed without a gap by a sleeve 4 made of elastomer material with high dielectric strength. The cuff 4 is in turn clamped by the housing halves 11 and 12 of the load switch 1. In this way, an external flashover of the high voltage between the end plates 24 and 25 of the vacuum interrupter 2 is effectively prevented during the switching process, without the need for liquid or gaseous media. In contrast to conventional load switches, this does not require a lot of control and the load switch is harmless to the environment.

Claims

claims

1. Load switch (1) for voltages above 1 kV, with a vacuum interrupter (2), the contacts (21,

22) can be closed or opened by means of a switching mechanism (3), the vacuum switching chamber (2) comprising a housing (23) with metallic end plates (24, 25) surrounding the switching contacts lying in the vacuum and a cylindrical housing middle part (26) has electrically insulating material which is surrounded by a dielectric medium,

characterized,

that the housing (23) is surrounded by a prefabricated sleeve (4) which engages behind the edges of the two end plates (24, 25) and consists of an elastomer material with high dielectric strength, which is pressed onto the housing (23) without gaps .

2. Load switch according to claim 1, characterized in that the dimensions of the sleeve (4) are selected such that the sleeve (4) rests with a bias against the circumference of the vacuum interrupter (2).

3. Load switch according to claim 1 or 2, characterized in that on the outside of the sleeve

(4) a complementary pressure housing (11, 12) made of insulating material is provided, which pressurizes the outer circumference of the sleeve (4).

4. Load switch according to claim 3, characterized in that the sleeve (4) has at least one in the axial direction of the pressure housing (11, 12) sealing bead (44) which comes to rest in the assembly joint of the pressure housing (11, 12) .

5. Load switch according to claim 4, characterized in that the sealing bead (44) has a thickening (45) which can be squeezed in the assembly joint of the pressure housing (11, 12).

6. Load switch according to one of claims 1 to 5, characterized in that on the outer circumference of the sleeve (4) substantially parallel to the end plates (24, 25) of the vacuum interrupter (2) projecting and rotating screens (41) are arranged are.

7. Load switch according to one of claims 1 to 6, characterized in that the sleeve (4) has at least one recess (42) for receiving material displaced during the pressure load by the pressure housing (11, 12).

8. Load switch according to claim 7, characterized in that the at least one recess (42) are designed as a circumferential annular groove.

9. Load switch according to one of claims 1 to 8, characterized in that at least one pocket (43) is formed on the sleeve (4) in the region of the end plate (25) and / or the end plate (24).

10. Load switch according to claim 9, characterized in that the at least one pocket (43) is designed as an annular groove.

11. Switch according to one of claims 1 to 10, characterized in that the sleeve (4) is made of silicone rubber or EPDM (ethylene-propylene terpolymer).

12. Switch according to one of claims 1 to 11, characterized in that it is designed as a switch disconnector, in which a visible isolating path is arranged in series with the vacuum interrupter.

13. Load switch according to one of claims 1 to 12, characterized in that a current path for high continuous current load capacity is connected in parallel to the vacuum interrupter or parallel to the series connection of the vacuum interrupter / visible isolating section when the load switch is switched on.