CZ303970B6 - Three-pole grounding switch for high and very high voltages - Google Patents

Abstract

In the present invention, there is disclosed a three-pole grounding switch for high and very high voltages provided with grounding rods (4), being at their ands at the point of their contact heads (7) interconnected by an electrically conducting partition (5) provided with contacts (8), wherein preferably the central grounding rod (4) is coupled with a frame (1) by means of an elastic conductive jumper (6).

Description

A three-pole high and very high voltage earthing switch provided with earthing rods (4) which are interconnected at the ends of the contact heads (7) by a conductive bar (5) provided with contacts (8), most preferably the middle earthing rod (4) by means of a flexible conductive coupling (6).

^{1 3} 4 ₆

Three-pole earthing switch for high and very high voltage

Technical field

The invention relates to the construction of a three-pole earthing switch for three-phase high and very high voltage networks.

BACKGROUND OF THE INVENTION

Until now, three-pole earthing switches for high and very high voltage networks have been designed to contain a frame located at ground potential. Three insulators were placed on the frame with contact heads at their ends. Three separate bearings with shafts mechanically connected to the drive were also mounted on the frame. Grounding rods with contacts were mounted on the shafts in place of the insulators. Each of the three earthing rods was separately conductively connected to the frame by a flexible conductive connector. Thereby, each earthing rod and the flexible conductive coupling formed a separate branch circuit from the network potential up to the frame, each branch being loaded with a full short-circuit current passing into the ground frame at the short circuit. Therefore, a full short-circuit current passed through each branch of the circuit, which loaded the current-carrying parts with Joule losses and the electrodynamic effects of the short-circuit current. This means that each grounding rod and each flexible conductive coupling had to be rated for the full short-time short-circuit current and the heat generated by the Joule losses. The short-circuit current, especially its dynamic component, generated high electrodynamic forces in the long conducting loops of the individual phases from the contact head to the frame, which placed great demands on the design of the earthing rods and the drive of the earthing and drive. In this arrangement, the circuit components had to be constructed more robustly with a much higher consumption of both conductive and structural material. Overall, the cost of production and the weight of the earthing switch were higher, increasing the cost of the earthing switch.

SUMMARY OF THE INVENTION

These drawbacks are largely overcome by the three-pole high and very high voltage earthing switch of the invention, consisting of a frame placed at ground potential and a drive coupled to the drive shaft to which the earthing rods are fastened. Three insulators with contact heads at the ends of the frame are located on the frame at a phase spacing. SUMMARY OF THE INVENTION The ground rods are interconnected at the ends of the contact heads by a conductive bar provided with contacts, one of the ground rods (most preferably middle) being connected to the frame by means of a flexible conductive connector.

The contacts can be fixed at the ends of the earthing rods.

Overview of the figure in the drawing

The three-pole earthing switch for high and very high voltages according to the invention can be seen from the enclosed figure, which is a simplified axonometric view of the three-pole earthing switch in the on position for the 110 kV network.

DETAILED DESCRIPTION OF THE INVENTION

A practical embodiment of a three-pole earthing switch according to the invention is shown in the attached Figure 1.

It is a three-pole earthing switch for the 110 kV network. The device is shown in the switched-on state. On the frame 1, located at the ground potential, three insulators 2 are fixed in one plane at the phase spacing, at the ends of which there are contact heads 7. On the frame 1 there are also three bearings 3 with a drive shaft 9 connected at one end to the drive 10. On the drive shaft 9 there are fixed three earthing rods 4 connected to each other by a conductive bar 5, where the contacts 8 are firmly connected in the place of the insulators 2. Contacts 8 are inserted into contact heads 7. At ground potential the middle earthing rod 4 is connected The connection of the device to the mains is ensured by the busbars 11 located in the upper part of the insulators 2.

The conductive partition 5 with the contacts 8 is located as close as possible to the contact heads 7 on the insulators 2. This creates a favorable short circuit for conducting the short-circuit current. In the case of a three-phase short-circuit, the short-circuit currents are added (subtracted) so that only a small differential current is led from the conductive partition 5 to the earthing rods 4 and the flexible conductive coupling 6. In the case of a symmetrical short-circuit current, the resulting current is almost zero. If a single-phase short-circuit occurs, the current passes through only one phase and the current is 60% of the full short-circuit current at the three-phase short-circuit. The total short-circuit current is therefore considerably smaller. These facts affect the electrodynamic forces and mechanical stress of the whole circuit. The strain on the earthing switch drive itself is reduced.

This results in previous savings, which are both material on earthing rods and savings of flexible couplings, and also in reducing the number and sizing of mechanical parts. Equally important is the possibility of using a more convenient grounding drive and increasing its reliability.

Industrial applicability

The three-pole high and very high voltage earthing switch according to the invention can be advantageously used in all substations of high and very high voltage networks of 16 to 245 kV.

PATENT CLAIMS

Claims (2)

1. A three-pole high and very high voltage earthing switch, consisting of a frame located at ground potential, on which three insulators are placed in a plane at the phase spacing, with contact heads at their ends and a drive connected to the drive shaft to which the earthing rods, characterized in that the earthing rods (4) are interconnected at the ends of the contact heads (7) with a conductive bar (5) provided with contacts (8), wherein one of the earthing rods (4), preferably medium, is connected by a gash (1) by means of a flexible conductive coupling (6). The three-pole high and very high voltage earthing switch according to claim 1, characterized in that the contacts (8) are fastened at the ends of the earthing rods (4). 1 drawing