HK1189707B - Tap changer and vacuum interrupter for such a tap changer - Google Patents

Description

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

The present invention also relates to a novel vacuum switch tube particularly suitable for such a step switch.

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.

In the case of insufficient shock resistance of the stepper switch, a short-term stepper short circuit may occur if the vacuum switch tube is blown in the load branch not conducting the load current.

This leads in many cases to oversizing of the circuits and, in particular, of the vacuum switches 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The unpublished DE 10 2010 024 255 therefore proposes a step switch in which a first winding connection of a first main current branch via a serial circuit consisting of a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 mechanical switch and the second electrical switch is made via a mechanical switch with a two-wire circuit with a mechanical resistor, which is a device capable of providing a mechanical connection between the first and the second main current converter.

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 switches 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 for uninterrupted switching between winding contacts of a step transformer, which allows a reduction in complexity and the required individual components, in particular making mechanical switching devices disposable and also having a high shock resistance.

These tasks are solved by a step switch with the characteristics of the first claim and by a vacuum switch tube particularly suitable for such a step switch with the characteristics of the sixth claim, the respective subclaims being particularly favourable to further training of the invention.

The step switch according to the invention is based on the general idea of combining a main contact and a mechanical switch of a first load branch and an additional resistance contact of a second load branch in a single vacuum switch tube with a common housing. The vacuum switch tube according to the invention is also based on the general inventive idea of replacing the functionalities of the two vacuum switches and an additional mechanical switch, required by the state of the art, by a single vacuum switch tube according to the invention by combining the design of a vacuum switch tube with several movable contact systems arranged in separate and mutually sealed vacuum switching chambers, in other words: the vacuum switch tube according to the invention is designed to incorporate the switches previously required separately, namely the two vacuum switches which switch the load and the additional mechanical switch, which no longer function, and to convert the switch, which is now operated as a single switch in a vacuum switching stage, into a vacuum switching device, which is now arranged in a separate vacuum switching chamber, but also into a mechanical switch.

The dielectric strength of the novel vacuum tube is increased by arranging the individual vacuum switch paths of the several contact systems in separate, i.e. mutually sealed, vacuum switch chambers but in a common housing. In other words, the danger of potential differences between the different contact systems which could lead to an overlapping arc is eliminated by providing several separate vacuum switch chambers in which the contact systems are electrically coupled to each other.

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 1 a step switch according to the state of the art Figure 2 a vacuum switch tube according to the invention for a step switch in a schematic representation.

The second load branch has an analogue tube V4 and a mechanical switch U2 connected in series to it, and a further load branch R2 and a load switch V3 connected in parallel to it. The step switch, known as the resistance contact vacuum switch, therefore has two vacuum tubes per four branches, representing the vacuum tubes. The vacuum phase of the load is n per phase, which corresponds to the individual vacuum switching elements in the following position: Vacuum switch tube V1Vacuum switch tube V3 closesVacuum switch tube V2 opensVacuum switch tube V4 closes; the switch is complete.

Figure 2 shows a vacuum switch tube 1 according to the invention with a first contact system I, a second contact system II and a third contact system III, all of which are formed as vacuum switch lines. In addition, the contact systems I, II and III are each separated in space in a separate vacuum switch chamber 2, 3 and 4, but arranged in a common housing 5 enclosing all contact systems I, II and III. In the lateral transformation area of the individual vacuum chambers 2, 3 and 4, several insulating ceramics 6 are provided.The contact 9 can be connected separately and independently by operation of the movable contact 8 to a fixed contact 11 electrically. The fixed contact 11 is located on a fixed electrically conductive contact 12 provided inside the housing 5 which penetrates the separation between the vacuum chamber 3 and 4 along the longitudinal axis s1 and has another fixed contact 13 at its end opposite the fixed contact 11. The tight separation between the axis chambers 2 and 3 is ensured by a sliding electrically conductive plate 14 designed along the axis s1 on which a fixed contact 15 and 16 are fixed to each side of the long axis via a conductive electrical bar 17 and 18.This allows the fixed contacts 16 to be connected to the fixed contact 10 or the fixed contact 15 to the fixed contact 13 by moving the plate 14 vertically. In the area of the wall of the housing 5 there are known folding beams 19 which allow the plate 14 to move vertically.

If the vacuum switch tube 1 described in Figure 2 is mirrored on a step switch in Figure 1, the two previously separate switch elements V1, V3 and U1 or V2, V4 and U2 are now combined in a single vacuum switch tube 1 with the separately controllable contact systems I, II and III according to the invention.

Claims (10)

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, wherein each load branch comprises a vacuum switching tube (V1 V4) acting as a main contact and mechanical switching means (U1, U2) connectible in series therewith, wherein an auxiliary current branch connectible in parallel with the corresponding load branch is provided for each phase to be switched, wherein each auxiliary current branch comprises at least one switchover resistance (R1, R2) and in series a further vacuum switching contact (V2, V3) acting as an auxiliary contact and wherein not only the load branches, but also the auxiliary current branches of the two load branches are connected with a common load diverter, characterised in that the vacuum switching contact (V1), which acts as main contact, of the first load branch, and the mechanical switching means (U1) arranged in series therewith of the first load branch and the vacuum switching contact (V3), which acts as auxiliary contact, of the second load branch are constructionally combined in a single vacuum switching tube (1) with a common housing (5), the vacuum switching contact (V4), which acts as main contact, of the second load branch, and the mechanical switching means (U2) arranged in series therewith of the second load branch and the vacuum switching contact (V2), which acts as auxiliary contact, of the first load branch are combined in a further single vacuum switching tube (1) with a common housing (5) and a respective separate hermetically sealed vacuum switching chamber (2, 3 and 4) is provided for each vacuum switching contact (V1, V3; V2, V4) and for each mechanical switching means (U1; U2) within the common housing (5) of each of the first-mentioned vacuum switching tube and the further vacuum switching tube..
2. Tap changer according to claim 1, characterised in that the vacuum switching contacts (V1 ... V4) and the further mechanical switching means (U1, U2), which are provided in the separate vacuum switching chambers (2, 3 and 4), each form a respective separate contact system (I, II and III).
3. Tap changer according to claim 1 or 2, characterised in that the first contact system (I) forms the mechanical switching means (U1 or U2).
4. Tap changer according to any one of claims 1 to 3, characterised in that the second contact system (II) forms the vacuum switching contact (V1 or V4).
5. Tap changer according to any one of claims 1 to 4, characterised in that the third contact system (III) forms the vacuum switching contact (V2 or V3).
6. Vacuum switching tube for a tap changer according to claims 1 to 5, characterised in that a common housing (5) enclosing the entire vacuum switching tube (1) is provided and that provided within the housing (5) is a plurality of contact systems (I, II and III), which are arranged along a common longitudinal axis (S1) and which are arranged in each instance to be separated physically and hermetically in a separate vacuum switching chamber (2, 3 and 4).
7. Vacuum switching tube according to claims 6, characterised in that the first contact system (I) comprises a lower plunger (8), which is movable along the longitudinal axis (S1) and to which is fastened a contact member (9) contactable by a contact member (12) fastened to a fixed plunger (12).
8. Vacuum switching tube according to one of claims 6 and 7, characterised in that the second contact system (II) has at the opposite end to the contact member (12) a contact (13) which is similarly fastened to the plunger (12) and which is contactable with a contact member (15) fastened by way of a web (17) to an electrically conductive plate (14) displaceable along the longitudinal axis (S1).
9. Vacuum switching tube according to any one of claims 6 to 8, characterised in that the third contact system (III) comprises a contact member (10), which is fastened to an upper fixed plunger (7) and which is contactable with a contact member (16) fastened by way of a web (18) to the electrically conductive plate (14) displaceable along the longitudinal axis (S1).
10. Vacuum switching tube according to any one of claims 7 to 9, characterised in that several insulating ceramic members (6) are provided in each vacuum switching chamber (2, 3 and 4) in the region of the lateral wall of the housing (5).