EP2417613B1 - Tap change device with solid state switching - Google Patents

Description

The invention relates to a tap changer with semiconductor switching elements for uninterrupted switching between winding taps of a tapped transformer. The invention is based on a tap changer according to the principle of a load selector.

Tap changers are known in various embodiments; they are basically differentiated in load selectors and devices with separate selector for powerless selection of the new winding tap to be switched to and separate diverter switch for subsequent actual switching. A good overview of the different types of construction is provided by the publication " Axel Krämer: On-Load Tap Changers for Power Transformers ", MR Publication 2000 , On the local side 7f the special features are explained.

Regardless of the design, all tap changers have a common load dissipation, which, regardless of the current position of the tap changer, establishes a connection to the transformer, usually the main winding.

For example, is from the WO 99/60588 a tap-changer, which, as is common practice in the prior art, contains such a single load dissipation. In the known solution, this load dissipation is designed as an electrically conductive diverter ring, which comprises a switching column concentric. On the Ableitring grinds a part of a contact bridge, the other part of the respective fixed step contact electrically contacted.

A very similar arrangement of a tap changer is already out of the DE 38 33 126 A1 known. Especially the local figure 4 shows a continuous derivative, here in a schematic linear representation.

For tap changers with mechanical contacts or with vacuum switching cells as switching means these continuous Ableitringe or, in linear operation of the tap changer, and discharge rails are unproblematic; They allow a structurally simple structure.

For tap changers with semiconductor switching elements, however, there are several disadvantages. Due to the permanent concern of the operating voltage and the stress of the power electronics by lightning impulse voltage high isolation distances are required, which is undesirable. Furthermore, complex high-voltage bushings through the transformer wall are necessary. Overall, the known load leads to a permanent load on the power electronic components.

EP 0 124 904 discloses a tap changer having the features of the preamble of the first claim.

The object of the invention is to eliminate these disadvantages and to provide a tap changer with semiconductor switching elements, which avoids the high load of these switching elements and ensures a galvanic separation of the tap changer of the transformer winding in steady state operation.

This object is achieved by a generic tap changer having the features of the first claim.

The subclaims relate to advantageous developments of the invention.

The particular advantage of the solution according to the invention is that in stationary operation, all connection lines of the power electronic components are galvanically isolated from the transformer winding. The power electronic components are thus reliably separated from the lightning impulse voltage as well as the permanent load with the operating voltage. Only during the switching phase, ie the actual load switching, is there a galvanic connection with the transformer winding.

Figur 1

einen erfindungsgemäßen Stufenschalter in schematischer Darstellung

Figur 2

eine weitere Ausführungsform eines erfindungsgemäßen Stufenschatters

Figur 3

einen erfindungsgemäßen Stufenschalter in abweichender Beschaltung am Transformator

The invention will be explained in more detail below with reference to exemplary embodiments. Show it:

FIG. 1

a step switch according to the invention in a schematic representation

FIG. 2

a further embodiment of a Stufenschatters invention

FIG. 3

a tap changer according to the invention in different wiring on the transformer

In FIG. 1 a tap changer is shown having a power electronic diverter switch 1. In this case, two semiconductor switches 2 and 3 are provided, each having an electrical input 4 and 5 and a common electrical output 6. The diverter switch 1 thus consists of two paths: one for the disconnecting side, one for the acquiring side, realized in each case by a semiconductor switch 2 or 3. The electrical inputs 4, 5 and the electrical output 6 are by means of feedthroughs 7 in a mechanical Contact system 8 led.

The mechanical contact system 8 has a contact carriage 9, which is indicated in the figure only by a dashed line. The contact carriage 9 has contact bridges 10, 11, 12, 13 which are fixedly arranged on it. The contact bridges 10 ... 13 are electrically conductive, but isolated from each other; they have at their ends in the figure only indicated, known per se contact rollers, grinding arrangements or similar means. On the contact bridges 10 to 13 and an additional hinged further contact roller 14 will be discussed later in detail. Everyone in the FIG. 1 Step contacts 15 shown corresponds to a winding tap n, n + 1, ... the control winding of the tapped transformer.

Furthermore, three contact rails 16, 17, 18 are provided in the mechanical contact system, which are each electrically conductive and of which in each case one is electrically connected to the electrical input 4 or the electrical input 5 or the electrical output 6 of the semiconductor switches 2, 3 ,

According to the invention, the load dissipation is divided, d. H. there is no known from the prior art continuous discharge or the like provided. Instead, here individual Ableitkontakte 19.1, 19.2, 19.3, 19.4, 19.5 are arranged, which, seen in the direction of movement of the contact carriage 9, in their extension correspond to the fixed stage contacts 15. In other words, location and dimensioning of the Ableitkontakte 19.1 to 19.5 corresponds - in another horizontal plane - location and dimensioning of the fixed tap changer contacts 15th

In the embodiment shown here, the contact rails 16 to 18 and the individual Ableitkontakte 19.1 to 19.5 are guided parallel to each other; the contact carriage 9 in this case performs a linear, translational movement for contacting. The individual Ableitkontakte 19.1 to 19.5 are connected to each other via an electrical connection, a derivative 20 and guided to the main winding 21. The Ableitverbindung 20 can be made both inside and outside the tap changer.

The first contact bridge 10 can connect at its one free end the tap changer contacts 15, at its other free end it runs on the contact rail 16, which is electrically connected to the input 4 of the first semiconductor switch 2. The second contact bridge 11 can also connect the solid tap changer contacts 15 at its one free end, at its other free end it runs on the further contact rail 17, which is electrically connected to the input 5 of the second semiconductor switch. The third contact bridge 12 runs with its one free end on the contact rail 18, which is electrically connected to the common electrical output 6 of the power electronic circuit breaker. Its other free end corresponds to the Ableitkontakten 19.1 to 19.5. Spatially between the two illustrated contact bridges 10 and 11, the further contact bridge 13 is provided, the Ableitkontaktbrücke, which can be contacted at a free end with the fixed tap changer contacts 15 and can be contacted at its other end to the Ableitkontakten 19.1 to 19.5. Symmetrical to the described contact bridge 12 is still the contact bridge 14 is arranged, which is electrically connected to the contact bridge 12 and also the Ableitkontakte 19.1 to 19.5 can connect.

It can be seen that both the contact bridge 12 and thus the common output 6 of the power electronic diverter switch and the contact bridge 13 with one of the Ableitkontakte 19.1 to 19.5 depending on the position of the switching carriage 9 can be electrically connected. In steady state operation, the contact bridge 13 takes over the direct electrical connection between the respectively connected tap changer contact 15 and the respective discharge contact; depending on the switching position of this one of the Ableitkontakte 19.1 to 19.5. The contact bridges 10 and 11, which lead to the inputs of the power electronic diverter switch 1, however, are not connected; the semiconductor switches 2 and 3 are enabled.

In a load switching of the contact carriage 9 is moved to the left or right - depending on whether in the direction of "higher" or "lower" to be switched. As a result, one of the two contact bridges 10 or 11 runs on the newly connected tap changer contact 15 and thus establishes an electrical connection to the corresponding input 4 or 5 of the respective semiconductor switch 2 or 3 ago. At the same time the contact bridge 13 gets out of contact with one of the fixed tap changer contacts 15th

The switching is completed when the contact carriage 9 has been moved so far that the contact bridges 10 and 11 both again disengaged and the contact bridge 13 has taken over the continuous current flow again.

FIG. 2 shows a further embodiment of the invention with a circular arrangement. Here, too, semiconductor switches 2 and 3 are provided which each have a separate electrical input 4 or 5 and a common electrical output 6. In this case, contact rollers 22, 23, 24 are provided which each run on a contact ring 25, 26, 27. These contact rings 25 to 27 correspond in function to the contact rails 16 to 18 FIG. 1 , On a concentric circle here the solid tap changer contacts 15 are provided. Shown is the central switching shaft 28. Furthermore, here Ableitkontakte 19.1 to 19.3 are shown. These Ableitkontakte 19.1 to 19.3 are arranged in a different horizontal plane than the fixed tap changer contacts 14. However, they have the same contact geometry as well as vertical arrangement as the solid tap changer contacts 15th

Furthermore, an indicated only by a dashed line switching segment 29 is provided of insulating material which is rotatable for load switching by the switching shaft 28 by an angle corresponding to the distance between two fixed tap changer contacts 14 and two Ableitkontakten 19.1 ... 19.3. On the switching segment 29 contact rollers 30, 31, 32 are provided in a first horizontal plane, which can be contacted with the fixed tap changer contacts 15. Furthermore, further contact rollers 33, 34, 35 are provided in a second horizontal plane, which can be contacted depending on the position of the switching segment with one of the Ableitkontakte 19.1 to 19.3. The contact roller 30 is electrically connected via the contact ring 25 to the input 4 of the first semiconductor switch 2. The contact roller 32 is electrically connected via the contact ring 26 to the input 5 of the second semiconductor switch 3. The lower contact rollers 33 and 35 are both on the contact ring 27 with the common output 6 of the two semiconductor switches 2 and 3 in combination. Upper contact roller 31 and lower contact roller 34 finally have an electrically conductive connection 36, such that the contact roller 31, which is arranged spatially between the contact rollers 30 and 32, directly via the lower contact roller 34 - position-dependent - connected to one of the Ableitkontakte 19.1 to 19.3 can be.

As explained, performs in this embodiment of the invention, the switching segment 29 and with him the contact rollers 30 to 35 at each load switching a rotational movement.

However, the operating principle is the same: In steady state operation, the respective switched solid tap changer contact 15 is electrically connected directly to one of the Ableitkontakte 19.1 to 19.3 via the contact roller 34, while the semiconductor switches 2 and 3 not only enabled, but also galvanically separated from the transformer winding are. Only when switching is, depending on the direction of rotation, in each case one of the two inputs 4 or 5 of the power electronic diverter switch by means of the associated contact roller 30 and 32 briefly with the respective fixed tap changer contact 15, to be switched to. At the same time, then, d. H. only during the switching, depending on the direction of rotation of the contact rollers 33 or 35, the electrical connection to one of the Ableitkontakte 19.1 to 19.3.

FIG. 3 shows an altered wiring of the tap changer according to the invention to the transformer. Here, a per se known power switching switch 37 is still provided in the transformer. By means of this Umstellers 37 winding parts 38 and 39 of the transformer can be switched to increase the total available number of voltage levels differently.

In all embodiments, the described tap changer according to the invention has the great advantage over the prior art that all connection lines to and from the power electronic diverter switch are galvanically isolated from the transformer winding. The oil paths between the individual contact bridges and the individual contact pieces take over the insulation between these components. The power electronic diverter switch is thus separated in the invention both the lightning impulse voltage and the permanent load with the operating voltage. Only during the actual load switching, a switching phase in the time range of about 100 ms, there is a galvanic connection to the transformer winding and thus is the operating voltage. The insulation of the bushings 7 and the insulation distances in air can be performed correspondingly lower compared to the prior art.

Claims (9)

1. Tap changer with semiconductor switching elements for uninterrupted changeover between fixed tap changer contacts (15) electrically connected with winding taps of a tapped transformer,
   wherein the fixed tap changer contacts (15) are arranged along a path, and
   wherein a contact carriage (9, 29) is movable along the path,
   characterised in that arranged on the contact carriage (9, 29) are electrically conductive, mutually insulated contact bridges (10, 11, 13; 30, 32, 36) and two further contact bridges (12, 14; 33, 35) in turn electrically insulated relative thereto, but electrically connected together, by which in stationary operation selectably one of the fixed tap changer contacts (15) is directly connectible with a load diverter (20) and during the changeover a respective one of the fixed tap changer contacts (15) is temporarily connectible with an input (4, 5) of one of the semiconductor switches (2, 3) and in addition the output (6) of the respective semiconductor switch (2, 3) with the load diverter (20) and that the load diverter (20) comprises fixed, divided diverter contact members (19.1 ... 19.5) such that the semiconductor switching elements (2, 3) in stationary operation are electrically separated from the load diverter (20) and thus the transformer winding.
2. Tap changer according to claim 1, characterised in that the fixed, divided diverter contact members (19.1 ... 19.5) are arranged in a further path parallel to the path of the fixed tap changer contacts (15) and in the same three-dimensional and geometric pattern as these.
3. Tap changer according to claim 1 or 2, characterised in that the fixed tap changer contacts (15) and the fixed diverter contact members (19.1 ... 19.5) are respectively arranged along a planar path and the contact carriage (9) is linearly movable.
4. Tap changer according to claim 1 or 2, characterised in that the fixed tap changer contacts (15) and the fixed diverter contact members (19.1 ... 19.5) are respectively arranged on a circular path concentrically around a fulcrum of the rotatable contact carriage (9).
5. Tap changer according to any one of claims 1 to 4, characterised in that the semiconductor switching elements (2, 3) are IGBTs.
6. Tap changer according to any one of claims 1 to 5, characterised in that the two semiconductor switching elements (2, 3) each have a separate electrical input (4, 5) and a common electrical output (6).
7. Tap changer according to any one of claims 1 to 6, characterised in that provided parallel to the path of the tap changer contacts (15) are electrically conductive, but mutually insulated contact rails (16, 17, 18; 25, 26, 27), each of which is electrically connected with one of the electrical inputs (4, 5) or with the electrical output (6).
8. Tap changer according to claim 7, characterised in that the path of the diverter contact members (19.1 ... 19.5), which in turn are electrically connected with the load diverter (20), is provided parallel to the contact rails (16, 17, 18; 25, 26, 27), and electrically insulated relative thereto.
9. Tap changer according to any one of claims 1 to 8, characterised in that the contact bridges (10, 11, 12, 13, 14; 30, 32, 33, 35, 36) are so dimensioned and three-dimensionally arranged on the contact carriage (9, 29) that they co-operate with the contact rails (16, 17, 18; 25, 26, 27) or one of the diverter contact members (19.1 ... 19.5) and an electrical connection is producible by them, in dependence on switching, selectably between one of the fixed tap contacts (15) directly with one of the diverter contact members (19.1 ... 19.5) or an electrical connection is producible between one of the fixed tap contacts (15) with one of the electrical inputs (4, 5) as well as additionally a further electrical connection between the electrical output (6) and one of the diverter contact members (19.1 ... 19.5).

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