HK1187734B - Tap changer having vacuum interrupters - Google Patents

Description

The invention relates to a step switch with vacuum switch tubes for uninterrupted switching between winding contacts of a step transformer.

DE 20 21 575 is a step switch with a total of four vacuum switches per phase, each of which has one vacuum switch tube as the main contact and another vacuum switch tube in series with a switch resistor as the resistor contact.

In the case of a continuous load change from the previous winding connection n to a new, preselected winding connection n+1, the main contact of the disconnecting side is first opened, followed by the resistance contact of the receiving side, so that a compensating current limited by the overclocking resistors flows between the two stages n and n+1.

After the previously closed resistance contact has opened the switch side, the main contact of the receiving side then closes so that the entire load current from the new winding socket n+1 leads to the load line; the switch is completed.

However, in various applications of such known phase switches with vacuum switching tubes for controlling power transformers, a high shock resistance of up to 100 kV and well above is required. Such undesirable shock voltages, the magnitude of which is largely due to the construction of the phase transformer and the winding parts between the individual taps, are, on the one hand, lightning shock voltages resulting from the impact of lightning on the mains; on the other hand, switch shock voltages may also occur caused by unpredictable switching shocks in the control network.

If the phase switch is not sufficiently resistant to the shock, a short-term phase short circuit or an undesirable break in the ceramic or steam screen of vacuum tubes in the load branch not conducting the load current may occur, which may not only cause their long-term damage but is generally undesirable.

This often leads to oversizing of the circuit boards and, in particular, of the vacuum tubes in order to ensure that they can withstand the voltage requirements described.

The unpublished DE 10 2010 024 255 therefore proposes a step switch in which a first winding connection of a first main current branch via a serial circuit consisting of a first mechanical switch and a first switch, i.e. a vacuum switch tube or alternatively a semiconductor component, is connected to a load line. In an analogous symmetrical design, a second winding connection of a second main current branch via a serial circuit consisting of a second mechanical switch and a second switch, i.e. a second vacuum tube or an alternative second semiconductor component, is also connected to the load line. Furthermore, a mechanical connection between the first main current switch and the second main current converter can be made by means of an electrical switch between the first and second main current switch, with a mechanical resistor, and a second electrical connection between the first and second main current converter is made by means of an electrical switch.

In other words, the known step switch has a mechanical switch in each main and auxiliary current branch connected in series with the respective vacuum switch tube, which ensures a completely galvanic separation of the respective uncoupled winding socket and thus a high shock resistance.

All step switches known from the state of the art require several vacuum switches and additional mechanical switching devices per phase, which is unfavourable and especially expensive due to the high space requirements of the individual switches and the associated construction and mechanical effort.

The present invention is therefore intended to specify a step switch with vacuum switch tubes for uninterrupted switching between winding contacts of a step transformer, which allows a reduction in complexity and the required individual components, in particular by making mechanical switching devices disposable and, in addition, has a high shock resistance.

This task is solved by a step switch with vacuum switching tubes with the characteristics of the first claim, the subclaims being particularly favourable to further training of the invention.

The step-switch according to the invention with vacuum switch tubes is based on the general idea of combining in a single vacuum switch tube with two separate movable contact systems the functionalities of at least one conventional vacuum switch tube, which switches under load, and another, according to the state of the art mechanical switches. In other words, the step-switch according to the invention will combine the two switches required so far, namely at least one vacuum switch tube and one other mechanical switch tube, no longer as in the state of the art, as individual components, and installed separately in the step-switch, but only in a single vacuum switch tube with two vacuum switches.

In a preferred embodiment of the invention, the switch chambers of the vacuum switch tube for the vacuum switch contact for the load switch and the further vacuum switch contact for the unload switch, which functionally replaces the previously used mechanical switch, are arranged in a separate and mutually tightly closed vacuum chamber, thus ensuring the permanent dielectric strength of the vacuum chamber for the vacuum switch contact for the mechanical switch, since no vapor can be isolated in the follicular sections of this vacuum chamber from the surroundings of a load switch.

Vacuum tubes with two contact points are already known in themselves.

DE 3344367 concerns a vacuum tube with two pairs of contacts electrically connected in series in a single vacuum chamber, which can be operated simultaneously.

DE 197 56 308 C1 concerns a similar vacuum tube with two switching lines on a common axis and internal contact pressure springs.

EP 0 258 614 B1 describes the combination of a vacuum switch tube and a specific circuit on a step switch, where several switching lines are arranged in a vacuum space, which requires a complicated arrangement of the vacuum switch tube with ring-shaped fixed contacts.

DE 10 2006 033 422 B3 finally describes another vacuum switch tube with multiple functionalities, whereby ring-shaped fixed contacts and internal contact pressure springs are also required.

The invention is further illustrated by illustrations.

It shows: Figure 1a step-change according to the state of the artFigure 2a vacuum switch tube according to the invention for a step-change in a schematic representationFigure 3an embodiment of a vacuum switch tube according to the invention for a step-change in a schematic embodimentFigure 4another step-change known from the state of the artFigure 5another embodiment of a vacuum switch tube according to the invention for a step-change.

The switch is not shown, but the switch selector, which before the actual load switching, makes the powerless selection of the new winding connection, here n+1, to which it is to be switched, is not shown. The load switch has two load branches A and B, each electrically connected to a winding connection n or n+1. The switch has a main current branch and an auxiliary current branch in each load branch.

The first main current branch makes an electrical connection from the winding socket n via a mechanical switch U1 and a vacuum tube V1 connected in series to it to the load compartment LA. In an analogous symmetrical design, the second main current branch makes an electrical connection from the winding socket n via a mechanical switch U2 connected in series and a vacuum tube V2 also connected to the load compartment LA.

Between the winding connection n and the mechanical switch U1 of the first main current branch, a first auxiliary current branch with an inserted resistor R1 is branched, by means of which an electrical connection can be made with the mechanical switch U2 of the second main current branch. In an analogous way, between the winding connection n+1 and the mechanical switch U2 of the second main current branch, a second auxiliary current branch with an inserted resistor R2 is branched, by means of which an electrical connection can be made with the mechanical switch U1 of the first main current branch. Depending on the position of the respective switches, the first auxiliary current branch can thus make an electrical connection by means of the electrical switch n1 through the vacuum switch R1+2 and the second auxiliary current branch by means of the mechanical switch R1+1 through the vacuum switch R1 and the second auxiliary current branch, namely, the electrical connection L1 through the vacuum switch R1+2 and the electrical connection L1 through the vacuum switch R2 through the vacuum switch R1.

Figure 1 shows the stationary operation of the switched winding socket n, where the load current flows from the winding socket n via the mechanical switch U1 and the closed vacuum tube V1 directly to the load line LA.

Figure 2 shows a vacuum switch tube according to the invention. It has two separate contact systems I and II, arranged in separate vacuum chambers 10 and 20, whereby the contact system I is a mechanical switch, designated U1 or U2 in Figure 1 and the contact system II is a vacuum switch tube, designated V1 or V2 in Figure 1.Both contacts 4 and 5 can be electrically connected separately and independently by means of the respective socket 2 or 3 and a corresponding fixed contact 6 or 7 respectively. On the side opposite the fixed contact 6 only the movable contact 4 can be electrically connected to another contact 11. In addition, the upper fixed contact 6 is electrically connected to a first upper plate 12 and the lower fixed contact 7 to a second lower plate 13. The two plates 12 and 13 protrude over the side wall of the housing 1 in such a way that electrical connections can be made to them.The known contact springs which interact with the two and three bolts are not shown here for the sake of clarity, but an upper 7 and a lower 8 are shown, which may be of equal or different formation.

Thus, with the vacuum switch tube in the contact system I according to the invention, a mechanical switch is functionally replaced by a vacuum switch contact that switches without load. If the described vacuum switch tube is mirrored on a step switch in Figure 1, then according to the invention the two previously separate switching elements V1 and U1 or V2 and U2 are now combined in a single vacuum switch tube with the separately controllable contact circuits I and II. If the contact 11 of the vacuum switch tube according to the invention is connected via a resistor R2 with the switching switch n + 1, the upper electrically conductive plate 12 with the switching switch n, the un-conductive electrical plate 13 with the switching switch LA 13 with the switching switch LA 13 below the switch plate 1 and the switch switch switch switch n + 1 are connected in a mechanical connection, which is particularly easy to create and thus easy to operate.

In contrast to the embodiment shown in Figure 2, the enclosing housing 1 is divided into two parts, so that the contact system I is enclosed by a first housing part 1.1 and the contact system II by a second housing part 2.2. The upper socket 2 is firmly connected to the first housing part 1.1 so that a movement of the socket 2 along the symmetry axis s1 can be transmitted to the first housing part 1.1 and, when switched accordingly, the upper contact 6 is either in fixed contact with the upper housing part 11 or in movable contact 4 charged.

In this embodiment, too, a mechanical switch is replaced functionally by a vacuum switch switch in the contact system I with the vacuum switch tube according to the invention. If contact 11 of the vacuum switch tube according to the invention is connected to the winding socket n, the upper socket 2 to the winding socket n+1 via a resistor R2 and the lower socket 3 to the load line LA, the step switch described in Figure 1 can be mechanically realized with particular ease.

Figure 4 shows another step-change, which is a state-of-the-art step-change, with a first load branch containing a main contact vacuum switch tube V3 and a mechanical switch U3 connected in series, and a parallel switch resistor R3 and a vacuum switch tube V4 connected in parallel.

Figure 5 shows another embodiment of a vacuum switch tube in which the contact system I replaces the two vacuum switches V3 and V5 and V6 and V4 of the step switch in Figure 4 and the contact system II forms the respective switch U3 and U4 respectively. This embodiment also has two spacially separate vacuum chambers 10 and 20 which take up the respective contact tube I and II. It provides for a common housing 1 enclosing the entire vacuum switch tube.Both contacts 4 and 5 can be electrically connected separately and independently by means of the respective socket 2 and 3 respectively to a corresponding fixed contact 6 and 7 respectively. On the side opposite the fixed contact 6 the movable contact 4 can be connected to another contact 11 so that the movable contact 4 can interact electrically with either the fixed contact 6 or the further contact 11. In addition, the upper fixed contact 6 and the lower fixed contact 7 are electrically connected.The known contact springs which interact with the two and three sockets are not shown here for the sake of clarity, but an upper 7 and a lower 8 are shown, which may be of equal or different formation.

If the vacuum switch tube described in Figure 5 is mirrored on a step switch in Figure 4, the two previously separate switch elements V3, V5 and U3 or V6, V4 and U4 are now combined in a single vacuum switch tube with the separately controllable contact systems I and II according to the invention.

Claims (3)

1. Tap changer with vacuum switching tubes for uninterrupted changeover between winding taps of a tapped transformer, wherein two load branches are provided for each phase to be switched, characterised in that each load branch comprises in a main current branch a vacuum switching contact, which acts as a main contact, and a mechanical switching means connectible therewith in series, for each phase to be switched an auxiliary current branch connectible in parallel with the corresponding load branch is provided, each auxiliary current branch in the current-conducting state comprises at least one switch-over resistance and a vacuum switching contact acting as an auxiliary contact, not only the main current branch, but also the auxiliary current branch of each load current branch is connectible with a common load diverter, in each load branch at least one vacuum switching contact (V₁; V₂; V₃ and V₅; V₄ and V₆) of a main or auxiliary current branch and a further mechanical switching means (U_1; U₂; U₃; U₄) correspondingly connectible in series therewith are arranged, constructionally combined into a single vacuum switching tube with two separately movable contact systems (I and II), in a common housing (1) enclosing the entire vacuum switching tube and the separate contact systems (I and II) are arranged in separate vacuum chambers (10; 20).
2. Tap changer according to claim 1, characterised in that the first contact system (I) forms the mechanical switching means (U₁ or U₂) and the second contact system (II) forms the vacuum switching contact (V₁ or V₂).
3. Tap changer according to claim 1, characterised in that the first contact system (I) comprises the two vacuum switching contacts (V₃ and V₅ or V₄ and V₆) and the second contact system (II) respectively forms a mechanical switching means (U₃ or U₄).