DE3416050A1 - LOAD SELECTOR FOR STAGE TRANSFORMERS - Google Patents

Abstract

1. Load selector for step transformers with main (16) and step windings (18) for switching over from one tap to the next with fixed step contacts (1 to 14), which are arranged in a circle in an insulating cylinder (17) and are connected with the taps, and with switching contacts (20, 21, 22) of three current branches, which can be rotated simultaneously in the circle and are constituted by rollers, on a common contact carrier (15), - in which all three switching contacts (20, 21, 22), in each case, in their rest position conduct the potential of the same step contact (1 to 14) and lie in the direction of the switching movement in a series one after the other and - in which radial movements of the switching contacts (20, 21, 22) in respect of the contact carrier (15) are controlled by the fixed step contacts (1 to 14) which simultaneously constitute cams, characterised - in that the centre distance and accordingly for the contact carrier (15) the angle of rotation between a fixed step contact (1) connected to the main winding (16) and the two fixed step contacts (2 or 14) adjacent to said contact (1) is 20% to 60% greater than the centre distance or the angle of rotation between the other fixed step contacts (2 to 14) and - in that the sides of the step contact (1) connected to the main winding (16) and the sides facing said contact (1) of the two adjacent step contacts (2 to 14) bear extensions which are similar to a horn in cross section and are held at a distance from the surface of the insulating cylinder (17), the distances of which extensions from each other are approximately equal to the distances of the other step contacts (2 to 14) in the direction of the switching movement.

Description

Load selector for step transformers

The invention relates to load selectors for step transformers with master and step windings for switching from one tap to the next with the taps arranged on a circle in an insulating cylinder connected fixed step contacts and with swiveling on the circle at the same time, represented by roles Switching contacts of three branches on a common contact carrier. All three switching contacts lead in their rest position the potential of the same step contact and lie in the direction of the switching movement in a row one behind the other. Radial movements of these switching contacts in relation to the contact carrier are controlled by the fixed step contacts that also act as cams. Switching contact arrangements for Such load selectors are known for example from DE-OS 33 26 549 and DE-OS 34 01 297.

DE-OS 29 14 928 and DE-OS 31 23 894 show the usual arrangement of the step contacts of load selectors equal distances between each other on a circle in an insulating cylinder. They are each the same Phase associated step contacts combined on a single circle. However, this arrangement leads to increasing nominal voltages and the usual number of stages of 11 and 13 stages even with transformer nominal voltages over 60 kV too often uneconomically large diameters for the insulating cylinder and the associated Structure of the load selector. In particular, the requirement to have a withstand impulse voltage between neighboring To ensure contacts of approx. 300 kV, to increase the required distances.

Krt 2 Sir / 04/27/1984

The invention is therefore based on the object of providing load selectors with switching contact arrangements of the type described at the outset Kind to design so that their manufacture and use in transformers with rated voltages of more than 60 kV is possible with full guarantee of operational safety and the expected service life.

According to the invention this is achieved in that the center-to-center distance between a fixed step contact lying on the main winding and the two fixed step contacts adjacent to it is 20 % to 60 % greater than the center-to-center distance between the remaining fixed step contacts and that the sides of the step contact and lying on the main winding the sides of the two adjacent step contacts facing this have horn-like projections in cross-section, the distances from one another approximately equal to the distances between the other step contacts in the direction of the switching movement of the switching contacts.

According to an advantageous further development of the invention, the fastening means are located outside the insulating cylinder the electrodes covering the step contacts have a smaller distance from one another than the associated electrodes Step contacts within the insulating cylinder.

According to expedient embodiments of the invention, it is provided that the leakage current paths emanating from the step contact located in the main winding are at least 20% greater than the electrically parallel distances between the step contacts and that the sides of the step contacts flanking the smaller center distances have bulges directed towards one another, through the the associated leakage current paths are less than 20 % larger than the electrically parallel distances.

According to a further development of the invention, the step contacts are only in their edge zones in the run-up area of the switching contacts convex, but in their central area according to the radius of the pivoting path the switch contacts are concave.

The construction of a load selector according to the invention has the advantage that using essentially already Components used for lower nominal voltages also in load selectors intended for higher nominal voltages remain usable, the most important advantage of which is a relatively small diameter for the step contacts load-bearing insulating cylinder is accessible. These advantages result from the implementation of a load selector with different center distances of the step contacts, because the switching contacts represented by roles in the positions on step contacts with normal width on the left and right of the step contact and in contrast to this, in the positions on widened step contacts, the contact roles of the switching contacts not on the side of the step contacts, but on their inner surface.

An embodiment of the invention is described in more detail with reference to a drawing. It shows:

Fig. 1 shows the circuit for a transformer with trunk and step winding and

2 shows the arrangement of the step and switching contacts provided for a phase in an insulating cylinder.

Components that correspond to one another are provided with the same reference symbols in both figures. 35

A main winding 16 of any phase of a transformer lies between a high-voltage terminal 23 and a step contact 1. A step winding 18 is electrically connected to the main winding 16 via a turner 19 Connected in series, the voltage tapped from the step winding 18 being added depending on the position of the reverser that of the main winding 16 is added to or subtracted from this.

Connected to the low-voltage end of the main winding or to the taps of the step winding 18 Step contacts 1 to 14 are arranged and lie in a plane on the inside of an insulating cylinder 17 consequently on a circle. On this circle, switching contacts 20, guided by a contact carrier 15, 21 and 22 moves, in a known manner, a load current line 24 without interruption from step contact switch to step contact.

Due to the constant connection of the step contacts 2 to with the associated taps of the step winding 18 lies between each of these step contacts 2 to 14 which are adjacent to one another, only the one of each Step tapped, relatively small step voltage even when impulse withstand voltages occurs. For the distances and the length of the leakage current paths between adjacent tap contacts 2 to 14 The sizes achieved in the usual load selectors are therefore sufficient. This also applies to an increase in the nominal and the operating voltage of the transformer to values above 60 kV.

Between the step contact 1 and, depending on the position of the reverser 19, the step contact 14 or the step contact 2, however, the much greater voltage lies

of the entire step winding 18. If now the nominal and If the operating voltage of the transformer increases, the voltage on the step winding 18 and thus also increases also the electrical load on the space between the step contact 1 and the step contact 14 or the step contact 2.

Deviating from the center spacings provided so far with regard to the switching contact arrangement, the center spacings between the step contacts 1 and the step contact 14 or the step contact 2 are 50 % larger than the other center distances according to the invention in the exemplary embodiment shown.

In order to still use one and the same switch contact arrangement To be able to select all step contacts 1 to 14, step contacts 1, 2 and 14 are wider than the step contacts 3 to 13 carried out by their facing sides with horn-like projections in cross-section are provided. This is an approximate for the lateral distance for all step contacts 1 to 14 reached the same level. Surprisingly, it is sufficient that only the leakage current path between the step contact 1 and the adjacent step contacts 2 and 14 remain enlarged if an increase in the nominal and the operating voltage of the transformer is set to values above 60 kV.

The illustrated embodiment shows an arrangement with thirteen stages. Corresponding is an enlargement the center-to-center distance of a tap contact connected to the end of the main winding from the neighboring one Step contacts are also possible with other step numbers, for example eleven or fifteen.

2 figures

5 claims

List of reference symbols

1-14 step contacts

15 contact carriers of 20, 21,

16 trunk winding

17 insulating cylinders

18 step winding

19 turner

20,21,22 switching contacts, which in a known manner without interruption from step contact to step contact switch

23 high voltage clamp from

24 load power line

Claims (5)

Claims lJ load selector for step transformers with main (16) and step windings (18) for switching from one tap to the next with fixed step contacts (1 to 14) arranged on a circle in an insulating cylinder (17) and connected to the taps and with on the circle simultaneously pivotable switching contacts (20, 21, 22) represented by rollers of three current branches on a common contact carrier (15) - With all three switching contacts (20, 21, 22) in their rest position each having the potential of the same step contact (1 to 14) and lie in a row in the direction of the switching movement and - With radial movements of the switching contacts (20, 21, 22) relative to the contact carrier (15) of the simultaneously Fixed step contacts (1 to 14) representing cams are controlled, characterized, - That the center-to-center distance and correspondingly for the contact carrier (15) the pivot angle between a fixed step contact (1) lying on the main winding (16) and the two fixed step contacts (2 or 14) adjacent to it is 20 % to 60 % greater than that Center-to-center distance or the pivot angle between the other fixed step contacts (2 to 14) and - That the sides of the step contact (1) lying on the main winding (16) and the sides facing it of the two adjacent step contacts (2 to 14) horn-like in cross-section and spaced from the surface of the insulating cylinder (17) held extensions, the distances from each other approximately equal to the The distances between the remaining step contacts (2 to 14) are in the direction of the switching movement. 2. Load selector according to claim 1, characterized in that outside the insulating cylinder (17) lying electrodes covering the fastening means of the step contacts (1 to 14) have a smaller distance from one another than the associated step contacts (1 to IA). 3. Load selector according to claim 1 and 2, characterized in that the leakage current paths originating from the step contact (1) lying on the main winding (16) are at least 20 % greater than the electrically parallel distances between the step contacts (1, 2 or 14 ). 4. Load selector according to claim 1 to 3, characterized in that the smaller Center-to-center distances flanking sides of the step contacts (2 to 14) bulges directed towards one another through which the associated leakage current paths are less than 20% greater than the electrically parallel ones lying distances. 5. Load selector according to claim 1 to 4, characterized in that the step contacts (1 to 14) are convex bulging only in their edge zones in the contact area of the switching contacts (20, 21, 22), in their central area, however, according to the radius of the pivoting path of the switching contacts (20, 21, 22) are concave.