DE3427873A1 - Electrical vacuum switch - Google Patents

Abstract

Conventional vacuum switches, especially for large continuous and short-circuit currents, can be confronted with the following problems: Contact problems: a) severe heating of the switching contacts in the vacuum and difficulty of heat dissipation b) electrodynamic repulsion of the switching contacts c) high contact pressure - contact welding - particle formation during separation - reduced dielectric strength d) high contact pressure - increased drive energy. Drive problems in the case of multiple interruption: a) high design cost in the case of a direct drive of each individual movable switching contact b) even when outer continuous current and inner arc switching contacts should have already been used, large switching contact masses which have to be accelerated still remain. The following design measures provide a solution to these problems: Switching contacts are also arranged externally in parallel with the switching contacts in the vacuum switching housing. In the case of more than one internal pair of switching contacts (8, 12) and (9, 13), the number of outer switching contacts is relatively reduced by at least one pair. In the case of two inner movable switching contacts, both are mechanically coupled, and the switch drive acts on only one of the two switching contacts. <IMAGE>

Description

Electric vacuum switch

The invention relates to electrical vacuum switches according to the preamble of claim 1.

Area of application The vacuum switches are used to switch electrical circuits to close and keep closed in medium and high voltage networks as well as to open and to keep open.

State of the art and criticism Proposals for the implementation of vacuum switches According to the preamble of claim 1, the documents contain: DE-OS 21 25 295; Patent Specification 12 27 833, P.O. London; US Patent Office 3,405,245.

The disadvantages that can potentially arise from the conventional contact arrangement are summarized in key words below in groups: High contact lifting forces increasing with the square of the current; for compensation: higher mechanical contact pressure; accordingly increased drive expenditure.

Hot and cold welding of the contacts; Particle formation when breaking up the welding; dielectric problems.

Additional structural reinforcement of the switch housing and / or Additional components for absorbing the contact force; High contact heating at high nominal currents; costly measures to dissipate the heat loss; particular timeliness of the problem Contact heating and heat dissipation from the switch housing with more than one Contact pair, which in turn is favorable for the control of high nominal voltages; Lack of a satisfactory solution to the drive problem for vacuum switches with two fixed and two movable contact pieces in the switch housing.

A proposed solution to this drive problem as described in the publication DE-OS 31 48 142 appears: "... and that the switching paths (37 to 40) of a common pressure space (42) are surrounded, which contains a controllable pressure medium (Fig. 2). ", Should have a rather theoretical character, it would be much too time-consuming to the compressed gas in the entire installation space of the vacuum switch with the one for switching on and off to control the required speed, i.e. its pressure within milliseconds to change; Quite apart from that, the required high contact pressure could be achieved in the Hardly realize switched-on state.

Task The invention is essentially based on the task of the disadvantages set out above in conventional vacuum switches with only Avoid vacuum contacts.

In particular, these disadvantages should be avoided in the case of vacuum switches with two scarf dreams in their scarf housings This 245 kV Switch pole only assigns three series-connected and simple from the main drive actuating permanent current contacts on.

The drives for the pairs of arcing contacts in the three switch housings are reduced to three simple self-contained assemblies.

This results in very little effort to drive the 245 kV switch poles: both in terms of construction and energy requirements.

The possibly reinforced spring-loaded actuator of a 36 kV vacuum switch should be enough.

The considerable reduction in the Development costs; in particular, the effort for the high-performance test circuit is reduced relative to the high-performance test circuits required for switches with low pressure gas and low oil by more than an order of magnitude: Because short-circuit generators with high performance - in Very expensive to purchase and operate - they are no longer needed.

Exemplary embodiments FIG. 1: assembly drawing of the switch housing; Longitudinal section through the permanent current contact pieces.

Fig. 2: Longitudinal section through the switch housing rotated by 90 degrees View of the arc contact drive.

Inside a pressure vessel (not shown) filled with insulating gas at least one switch housing A is arranged. Located in this switch housing the movable contact pieces are to the left of the center line in the switched-off state and to the right of it in the switched on.

The switch housing is formed by the metal cylinder (1) and the bushing insulators (2, 3) attached to its end walls with the end disks (4.5). Bearing bodies (6, 7) are inserted into the central openings of the cover disks for guiding the movable conductor bolts (8,9). Both bearing bodies have gaps on for communication of the surrounding insulating gas with the space between the movable Power supply bolt, bellows indicated by dashed lines (10,11) and the back the movable contact discs (12, 13).

Opposite the movable contacts are the fixed ones Contacts, advantageously carried out according to the teaching of the document DE-OS 34 22 958 contains.

The permanent- and short-time current contacts surround it symmetrically with fixed and movable ones Hollow cylinder sectors.

The fixed continuous current switch (16) is horizontal with its Connection plate (17) on the cover plate (4) of the bushing insulator (2) attached. From this plate, the profiles (18) protrude for the connection of the Ends of the power ribbon (19); it electrically connects the stationary contact piece with the movable conductor bolt (8). The conductor bolt carries on its front side with corresponding fixed and movable contact pieces are arranged.

For the drive of the two movable contact pieces should be a A closed drive system that can be used as an independent assembly can be found.

Solution The solution of the set tasks is achieved by the following measures Achieved: parallel to two fixed and two movable contact pieces within an evacuated switch housing will only be a stationary one outside of it and arranged a movable contact piece.

The drive of the switch acts directly on the outer movable contact piece one that delays an inner movable contact piece when it is switched off carries.

The inner contact, moved by the outer contact, is actuated synchronously the other inner contact piece by means of a drive device that is electrically isolated from it.

When switching on, the movable inner and outer contact pieces operated independently of each other: the outer movable contact piece from the switch mechanism; the inner movable contact pieces from the gas pressure acting on them.

During the switch-off, the outer movable contact opens in front of the inner movable contact pieces.

The inner movable contact pieces close during switch-on in front of the outer movable switch piece.

These and other features of the switch according to the invention are shown in first as well as in the following claims.

Achievable advantages From the multi-purpose contact pieces more conventional Vacuum switches are arcuate switch pieces by the invention, and they leave optimize themselves technologically for their solo function.

The contact pieces outside of the vacuum are used specifically for permanent and short-term current conduction and can also be optimized for this function.

Outside the vacuum switch housing stands for the continuous current contact pieces sufficient construction space available; therefore there is no problem to dimension their cross-sections sufficiently. Excessive electricity heat losses arise Not a priori and expensive heat dissipation bodies are unnecessary.

The external contact system can easily be designed so that the Contact pressure is increased electrodynamically; to an expensive compensation of the electrodynamic contact lifting forces can be dispensed with.

The installation of vacuum switches is made possible by the above measures also allows for large continuous currents in ceramic and metallic encapsulation.

Double switching room vacuum switching units with implemented according to the invention Permanent and arc current contacts as well as with axial magnetic field action on the Switching arcs, in particular according to the publication DE-OS 34 22 958, are reliable and economical building blocks for multiple interrupting switch poles high rated voltages; E.g. for one of only three double shell dream housings 245 kV switch pole with a nominal short-circuit breaking current built up for each around 90 kV nominal voltage of at least 40 kA.

a fork-shaped structure (20) for the movable mounting of one each Lever end of two equal-armed force reversing levers (21). Above the fork structure if necessary, the bracket (22) also limits the switching stroke in a damping manner.

It should be added that on both sides of the connecting plate (17) the hollow cylinder sectors (29) are located as stationary contact bodies.

The cylinder sectors (23) of the movable continuous current contact (24) slide on the bearing bodies (25) which are attached to the ends of the connecting body (26) are arranged.

The cylinder sectors (23) of the movable contact piece connects the Flat body (27); at the same time it serves as a driver for the lower movable contact piece (9,13) during switch-off. In the front zone of the movable hollow cylinder sectors contact fingers (28) are attached. When switched on - to the right of the The center line can be seen - these fingers on the fixed contact sectors (29) Contact.

The electrical commutation connection from the lower movable one Conductor bolt (9) to which the movable permanent current contact parts connect Plate (27) makes the electrical tape (30); it is for this purpose on the profile pieces (31) on the connecting plate and on the traverse (32) on the conductor bolt attached. This traverse already forms an element of the drive system for the upper movable contact piece (8,12).

The profile body (31) also carry the web (33), which extends downwards expands into a tab. What is not shown engages in the eyelet of this tab Connecting element to the switch drive, also not shown.

From the profile bodies (31) to the outside support rails (34) for the drive rod (35) to two or three in the case of a multiple interruption, here to be able to drive vacuum switching devices, which are no longer shown.

Since it is neither hot nor cold in the arrangement according to the invention If there are switching gases, these drive rods need heat-resistant insulating material not to pass.

In Fig. 2 is rotated by 90 degrees compared to Fig. 1 by the Switch housing A guided a longitudinal section; so the drive system becomes the movable one Arc contact pieces (8,12) and (9,13) are visible. Located to the left of the center line it is switched off, to the right of it when it is switched on.

The disconnection drive force begins to act as soon as the driver engages (27) on the movable continuous current switch piece on the cross member (32) on the lower one movable arc switch (9,13) strikes. Through the insulation rods (36) it is fed to the outer arms of the reversing lever (21) with equal arms. These levers are pivotably mounted in the attachment (37). Your inner arms transmit the driving force symmetrical and therefore without transverse forces on the upper movable conductor bolt (8th). A stop bracket (22) is provided to limit and dampen the switch-off stroke; it also serves as a base for the connector (38).

It should also be pointed out that in the drive according to the invention of the two movable arcing contact pieces advantageously the external driving force only need to attack one of them: the main switch drive turns on the switch housing looks as if only one movable contact element is to be actuated were.

From Figs. 1 and 2 it is clear that during a switch-off the movable permanent current switching contact (28) opens in front of the arcing contacts (12, 13).

Only after rushing through a somewhat longer switching path than the switching path between a pair of arcing pieces is the lower movable arcing piece taken along by the continuous current switch.

When switched on, the pressure of the outer Iso-1 gas actuates the movable arc-shaped contact pieces as soon as they have been removed from the continuous current scarf piece to be released. The pressure application area is around 30 cm2 Chooses an absolute pressure of 2.5 bar for the insulating gas SF6 is liquefied If this insulating gas only works at around minus 50 degrees Celsius - this results in a Engagement force of 750 N Notwithstanding this example, the present arrangement has about enough degrees of freedom to determine the switch-on force only during to be able to adapt the design decisions resulting from the development.

After closing the arc switch, the movable one reaches Continuous current contact after a path that is slightly longer than a switching distance in a vacuum, the switch-on position. This also means that it is practically arc-free Switching on the permanent current contacts guaranteed.

Such a simple and reliable coordination of the switching paths of Continuous and arc current contacts eliminate electrical problems on the continuous current contacts a priori.

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Claims (7)

Claims 1. Vacuum switch: with a switch housing made of electrical insulating or electrically conductive material; with two or more coaxially arranged Dream scarf; with electrical feedthroughs and power supply lines to be movable Contact pieces; with electrical shields; with devices for gas-tight Supply of driving force; characterized in that within a switch housing A is at least two fixed (14) and (15) and two movable (8, 12) and (9,13) Contact pieces are located that outside of a switch housing A are stationary (16) and movable (24) contact pieces are arranged with one opposite the electrical inner contact pieces connected in parallel by at least one reduced number each, that when switching on inner contact pieces (8,12) and (9,13) close first and electrically bridged in the closed state by outer contact pieces (16) and (24) be, and that when switching off outer contact pieces open first and between they have at least the same dielectric strength as between inner opening ones Contact pieces. 2. Vacuum switch according to claim 1, characterized in that a switch drive acts on an outer movable contact piece (24) that a outer movable contact piece on a first inner movable contact piece (8,12) acts, and that a first inner movable contact piece on a second inner one movable contact piece (9,13) acts. 3. Vacuum switch according to claim 1, characterized in that the actuation of the first inner movable contact piece by the outer movable one Contact with a time delay takes place compared to the actuation of the outer one movable contact piece through the switch drive 4. Vacuum switch according to claim 1, characterized in that the actuation of the second inner movable contact piece by the first inner movable contact piece simultaneously or almost simultaneously takes place when the first inner movable contact is actuated by the outer movable contact piece. 5. Vacuum switch according to claim 1, characterized in that a pneumatic pressure is exerted on inner movable contact pieces (8,12) and (9,13) is, and that the pneumatic force is released to close the contact pieces is controlled by a movable outer contact piece (24). 6. Vacuum switch according to the preamble of claim 1, thereby characterized in that between the first and second movable contact pieces a mechanical Coupling is established, and that a switch drive is only on one of the two contact pieces acts. 7. Vacuum switch according to claim 6, characterized in that the mechanical coupling between the first and second movable contact pieces in the is formed substantially symmetrically.