SE451650B - Three=phase earth connector for gas-insulated switchgear - Google Patents

Abstract

The earth connector incorporates three movable contact plugs (1), which work in conjunction with corresp. fixed counter contacts (2) formed as casings with spring-loaded contact fingers. The fixed contacts are fastened to the respective phase conductors (3) supported by insulators (4) at the two flanged ends of e.g. an aluminium cast capsule (5). The movable contact plugs are each joined to a contact bar (6) extending outwards through the metal capsule, an insulating tube (7), a metal casing (8), and a glass tube (9). The copper yoke (10) joining the contact plugs mechanically inside the capsule incorporates electrically insulating intermediary pieces (11) so that the plugs are insulated from each other. When the earth connector is in its 'off' position, the plugs and yoke are enclosed by a fixed field control screen (12) of conductive plastic. This screen is slotted downwards so that the contact plugs can be moved freely towards the fixed contacts. A manoeuvring control used comprises a manually turnable screw (13) aligned with the one movable contact. The positions of the movable contacts can be checked visually through a viewing glass connected to at least two of them.

Description

25 30 451 650 Quick earths must also be able to switch on at full voltage. This requirement does not apply to working earths, which is why these can be performed with relatively slow contact movement.

In addition to its above-mentioned primary task - to provide safe grounding - <a grounding switch for gas-insulated switchgear can also be used to advantage as an input for measurements on the high-voltage system. For example, during control and audit work, it may be of interest to measure the resistance of the main circuit, including contact transition resistances in switches and disconnectors. Furthermore, in connection with this, it may be desirable to measure the opening and closing times of the devices, etc., in order to be able to form an opinion of the condition of the respective device.

It is known to arrange for the said measuring purposes an insulation between the switchgear housing and the earthen mechanism housing, which is connected to the housing by means of a rail. When a measurement is to be performed, the rail is disconnected and measuring voltage is transmitted to the main current path via the earth's movable contact from a voltage source connected to the mechanism housing. In the case of three-phase encapsulated switchgear, three-phase earths with individually 6 movable contacts have been used, which entails a complication.

DISCLOSURE OF THE INVENTION The object of the present invention is to further develop a multiphase earthing coupler of the type stated in the preamble of claim 1, so that a simpler connection to the phase conductors in the encapsulated rail system is obtained, when it is desired to make measurements on this. This is achieved according to the invention in that the earthing coupler is designed as stated in the characterizing part of claim 1.

By mechanically connecting the movable contacts via insulating intermediate parts, it is achieved that measurements can easily be performed externally on the respective phase after only one maneuvering movement.

The movable contact system is suitably embodied with the pin-shaped movable contacts arranged next to each other in the same plane and interconnected inside the housing by an insulating yoke common to all phases. 10 15 20 25 451 ssn The operation can suitably be carried out by means of an elongate screw which is arranged in line with the contact bar of the middle phase (in the case of three-phase earthing) and which cooperates with a nut fixed to the bar. The screw is operated by hand with an insulated hex key.

Visual indication of the contact position is provided by glass tubes surrounding the contact rods outside the metal housing.

DESCRIPTION OF THE FIGURES The invention will be described in more detail in connection with an exemplary embodiment shown in the accompanying drawing, in which Fig. 1 shows a cross section through a hand-operated three-phase earth according to the invention, and Fig. 2 shows the same earth in top view.

DESCRIPTION OF EMBODIMENTS ä The three-phase earthing shown in the drawing contains three movable contact plugs 1, each of which cooperates with a fixed counter-contact 2, which is designed as a sleeve with spring-loaded contact fingers. The fixed contacts 2 are attached to the respective phase conductor 3, which is supported by insulators Å at the two flanged ends of an enclosure 5 cast, for example, of aluminum.

The movable contact plugs 1 are connected to their respective contact rod 6 which extends through the metal housing 5 through an insulating tube 7, a metal sleeve 8 and a glass tube 9.

The contact plugs 1 are mechanically connected inside the housing by a yoke 10 of, for example, copper, which includes electrically insulating spacers 11, whereby the contact plugs are insulated from each other.

Fig. 1 shows the earth in its off position, the contact plugs 1 and the yoke 10 being enclosed by a field-guiding field 12 of conductive plastic attached to the housing 5. The screen is slotted at the bottom, so that the contact plugs can be moved freely against the fixed contacts 2.

J! 10 __; k !! 451 650 The actuation and position fixing takes place by means of a screw 13 axially pushing in the upper part of the contact bar contact bar, which cooperates with a nut fixed to the contact bar. The screw is turned by hand with an isolated hex key. The control phase of the middle phase is covered by a lock 16 which can be locked by means of a padlock 15, which also prevents involuntary maneuvering and forms a final seal against the gas enclosed in the housing, which is usually SF6 gas of a certain overpressure. 91 The contact position is indicated by electrical limit position switches 21 and 22 arranged at the upper end of the contact rods in the outer phases. One limit position switch 21, which indicates the off position, is actuated directly by the upper end of the associated contact rod. The second limit switch 22, which indicates the position, is fixedly connected to a drawbar pushing into the associated contact rod, which is arranged to be coupled to the contact rod and is axially displaced a certain operating distance when the earth reaches the position. The limit switches are equipped with line connectors 23.

H The contact position can also be checked visually through the glass tubes 9 surrounding the contact rods. By arranging such glass tubes in all phases, a safe position indication is achieved even if, for example due to material defects or other unforeseeable reasons, a break would occur on the yoke 10.

The movable contacts 1 communicate with the metal sleeves 8 via sliding contacts 17 with multi-contact type contact elements. The metal sleeves 8 are in turn connected to the earthed metal housing 5 via connection plates 18. When using the earth as a connecting means to the ordinary conductor system for measurements on this, the connection plates 18 are removed, whereby measurements can be performed separately on each phase.

Claims (3)

5,451,650 PATENT REQUIREMENTS Ground coupler comprising a gas-enclosing metallic housing (5) containing a number of pin-shaped movable contacts (1) supported by a yoke (10) which are normally in electrical connection with the housing (5), a corresponding number of counter-contacts (2) connected to each other phase conductor (3) in a gas-insulated, metal-encapsulated high-voltage switchgear, and an actuator (13) for displacing the movable contacts between an off position and an additional position (earthing position), in which the movable contacts (1) provide contact with the counter-contacts (2) , characterized in that the movable contacts (1) are mechanically connected via electrically insulating spacers (11), and that the electrical connection of the contacts to the housing (5) is made by means of separable connection conductors (18) arranged outside the housing. Ground coupler according to Claim 1, characterized in that the actuator consists essentially of a manually rotatable actuating screw (13) arranged in a line with one movable contact. Ground coupler according to Claim 1 or 2, characterized in that the position of the movable contacts (1) is visually controllable by sight glass (9) or the like arranged in connection with at least two of the contacts.