CS259083B1 - Electric earthing switch with short-circuit - Google Patents

Abstract

Electrical earthing switch and short-circuiting switch, designed for encapsulated, gas-insulated busbar. The contact system of the short-circuiting switch has a movable contact formed as a tube of electrically conductive material, coaxially placed in insulation in the hollow cavity of the movable contact of the earthing switch. The terminal of the movable contact of the short-circuiting switch is conductively connected to a flexible insulated conductor, the other end of which is connected to the terminal of the electrical bushing. Inside the lower rose-shaped contact of the earthing switch, a fixed lamellar contact of the short-circuiting switch is coaxially placed, conductively connected to the 8 lower rose-shaped contact.

Description

The invention relates to an electrical earthing switch with a short circuit for high voltage distribution.

In grounded busbar distribution systems, electrical earthing switches are used in order to prevent life-threatening voltages from being used on electrical equipment on temporary work. In encapsulated busbars connecting the generator to the transformer (in power plants), additional grounding requirements are placed on the earthing switches, such as the possibility of passing the rated current for a specified time needed to set the differential protections of the generator, generator) and the possibility of switching currents induced by the remanent magnetism of the generator during its idling. In particular, this last requirement takes on; importance in the context of increasing the power of generators.

Here, the earthing switch is required to be able to conduct the rated currents in the on state and to switch on and off the short-circuit currents when the generator is idling, ie the retentive generator currents. It must be ensured that, when closing, the short-circuit contacts are closed earlier than the earthing contacts and, on the other hand, the earthing contacts first open before the short-circuit contacts are opened.

The prior art earthing switch with a shorting device uses for this purpose a special movable contact connected via an interrupter mechanism to an autopneumatic or vacuum arc quenching system, the arc quenching system being a structural part of the earthing switch.

However, this arrangement does not allow precise setting of the switching point of the arc extinguishing system contacts depending on the movement of the earthing contact and moreover contains a large number of components, which reduces the reliability of the system. A solution in which the movable contact of the earthing switch is supplemented by short-circuit contacts designed for separate switching of retentive currents seems to be more suitable. This contact system is isolated from the earthing switch contact and is designed to close before the earthing switch is closed. The earthing switch comprises only this short-circuit contact with the respective terminals and the actual switching of the remanent currents is effected by a switch located outside the earthing switch. This short-circuit grounding switch structure is arranged such that the short-circuit contact is rigidly connected to the earthing switch contact through the insulating member, the short-circuit contact terminal being located asymmetrically within the earthing contact. This outlet is made up of several parts which slide into each other when the contacts move. The design consists of a large number of precisely machined parts, which can cause malfunctions during operation.

The aforesaid drawbacks are eliminated by the short-circuiting earthing switch according to the invention, characterized in that the movable short-circuit contact is formed as a tube of electrically conductive material coaxially housed in the insulation in the cylindrical cavity of the movable earthing contact. a conductor, the other end of which is connected to the outlet of the electrical bushing and furthermore that within the lower ground contact of the earthing switch there is coaxially located a fixed lamella contact of the shorting conductively connected to the lower rose contact.

The advantages of the earthing switch with the short-circuit device according to the invention lie above all in the exact function of the short-circuit device with respect to the movement of the earth contact of the earthing switch. By suitable selection of the shape and length of the movable and fixed contact of the shorting device, it is possible to achieve that the needle contacts are connected, respectively. disconnects at a predetermined time with respect to the position of the movable earthing contact.

This ensures that the external remanent current switch, such as a contactor or vacuum switch, can switch these currents at the most appropriate moment. By using a flexible connection conductor for connecting the movable contact of the short-circuit to the outlet of the electrical bushing, a simple and reliable connection is achieved without the use of other mechanical parts. Another advantage is the simplicity of construction and the relatively small dimensions compared to previous designs.

An example of an embodiment of the invention in which a short-circuit grounding switch is shown in longitudinal section is shown in the accompanying drawing.

The earthing switch with shorting consists of the upper flange 11, fixedly connected by the insulating tube 2 to the lower flange 2. The upper flange 2 has the upper rosette contact 6, the lower flange 2 has the lower rosette contact 6. The upper flange 2 3® is rigidly connected to a housing not shown in the drawing and the lower flange 2 to the busbar outlet 3. Between the upper rosette contact 2 and the lower rosette contact 2 there is a linearly displaceable earthing contact 2 of the earthing switch. A tubular extension 18 is further attached to the upper flange 23 in which the guide ring 22 is movably mounted, fixedly connected by means of a nut 2 to the movable contact 2 of the earthing switch. The movable contact 12 of the shorting device is formed as a tube of electrically conductive material, which is coaxially embedded in an epoxy resin insulation 11 in the cylindrical cavity 21 of the earth contact 2, which serves also as a space for the drive screw 8. The insulated terminal 14 of the movable contact 12 of the shorting device is connected by a screw connection 15 connected by a flexible insulated conductor 16 and a nut 19 to the outlet of the electrical bushing 22 mounted in the cover 17. A short-circuit contact 21 that is conductively connected to the lower rosette contact 2 ® three at the same time as the busbar terminal J. The movable contact 12 of the shorting device exceeds the movable contact 2 of the earthing switch by one fifth of its diameter. The fixed short-circuit contact 21 exceeds the lower rosette contact by one fifth of the lightness of the movable short-circuit contact 12.

- 4 The function of the earthing switch with the short circuit is as follows:

After starting the motor drive (not shown) in detail, the drive screw 8 begins to rotate, the rotational movement of which is transmitted to the nut 2, which turns the rotary movement of the drive screw 8 into a linear one. As a result, the movable earthing contact 2 connected to the nut 2 by the guide ring 10 begins to move from the basic off position to the second, on position. Before reaching the earthed end of the earthing switch, the fixed short-circuit contact 21 of the short-circuit is connected to the movable short-circuit contact 12, thereby connecting the electrical circuit between the lower flange 2 via the fixed short-circuit contact 21 of the short-circuit. The remanent current switch, which may be, for example, a contactor by which the remanent currents of the generator in which the earthing switch is connected, is connected to this outlet. These currents are closed before the earthing switch 2 is plugged into the lower rosette contact. After the retentive currents have been closed by the short circuit contact system, the next earthing switch 2 moves this contact to the lower rosette contact so that the earthing switch can transfer _{to its} full rated current system dimensioned. When switching off, the function is reversed. First, the earthing switch contact system, i.e. the earthing contact 2 of the earthing switch, opens, leaving the lower rosette contact 2, whereby the fixed short-circuit contact 21 of the shorting device and the shorting moving contact 12 remain connected for some time. After disconnecting the earth contact 2 of the earthing switch and the lower rosette contact 2 ®, the closed contact 12 of the shorting device with the fixed flap contact 21 of the shorting device switches off the external remanent current switch, i.e. the contactor. As the movable short-circuit contact 12 moves further, the short-circuit contact system and the earthing switch move as far as the basic off position.

The earthing switch with a short-circuit device according to the invention can be used for encapsulated busbars for high rated currents, in particular connection.

nothing to connect the generator to the transformer in power plants.

Claims (3)

SUBJECT OF THE INVENTION A short-circuiting electric earthing switch for an encapsulated, gas-insulated busbar comprising an upper rosette contact, a movable contact, a lower rosette contact, and a short-circuit contact system, characterized in that the short-circuit movable contact (12) is formed as an electrically conductive tube. material, coaxially housed in the insulation (11) in the cylindrical cavity (13) of the earthing contact (7), wherein the short circuit movable contact (12) is conductively connected to a flexible insulated conductor (16), the other end of which is connected to an electrical lead-through (20) outlet and furthermore that within the lower earthing switch (5) a fixed short-circuit contact (21) of the shorting conductor is connected coaxially to the lower rosette contact (5). 2. An electric earthing switch with a shorting device according to claim 1, characterized in that the moving contact (12) of the shorting device exceeds the moving contact (7) of the earthing switch by at least one tenth of its groundness. 3. An electric earthing switch with a short-circuiting device according to claim 1, characterized in that the fixed short-circuit contact (21) of the short-circuiting device exceeds the lower rosette contact (5) by at least one tenth of the lightness of the movable contact (12).