EP2586049B1 - Tap changer - Google Patents

Description

The present invention relates to a tap changer for uninterrupted switching between at least two winding taps of a tapped transformer with the features of the independent claim.

From the DE 10 2007 004 530 A1 a connection switch is known, which consists of a connection selector and a switch with vacuum breakers. The changeover switch has three phases which serve to guide the load. Two of the phases each consist of a vacuum interrupter and a resistor connected in series. The third phase has an auxiliary switch and a vacuum interrupter connected in series. When switching from one connection winding to the next, a targeted actuation of the vacuum interrupter and the auxiliary switch attempts to limit the load on the vacuum interrupters.

From the WO 2006/004527 A1 is a Lastumschalter an on-load tap changer known, the two load branches, namely main branch and resistance indicator has. The main branch consists of a vacuum interrupter and a main switching contact, with both parts connected in series. The resistance branch consists of a vacuum interrupter, a resistance contact and a resistor, whereby all parts are connected in series. The changeover in the diverter switch always takes place after the selector has selected the winding to be switched over to. Both the main switching contact and the resistance contact are designed such that the switching takes place by a rotational movement in the always same direction. Each time you switch over, the main switch contact is always pressed in front of the resistor switch contact. The diverter switch is thus more compact and less maintenance intensive.

From the DE 20 21 575 is known a tap changer, which has a total of four vacuum interrupters per phase. In each of the two existing load branches each have a vacuum interrupter as the main contact and a further vacuum interrupter, in series with a cross-over resistance, provided as a resistor contact.

In an uninterrupted load changeover from the previous winding tap n to a new, preselected winding tap n + 1, the main contact of the turn-off side is first opened, after which the resistance contact of the receiving side is closed, so that between the two stages n and n + 1 through the Overload resistors limited compensating current flows. After the previously closed resistive contact of the disconnecting side has opened, the main contact of the receiving side closes, so that the entire load current from the new winding tap n + 1 leads to the load discharge, whereby the switching is completed.

The vacuum interrupters used in this known tap-changer and numerous similar known embodiments, which are used instead of conventional mechanical contacts for load switching, have a number of advantages. Since the contacts themselves are encapsulated in a vacuum, high switching capacities can be achieved. The encapsulated, hermetically sealed contacts also can not lead to the fouling and contamination of the surrounding insulating oil in the tap-changer by contact erosion or arcing. Furthermore, vacuum interrupters are now available as very compact components; they have a small footprint and require only relatively low actuation forces.

In various applications of such known tap changer with vacuum interrupters for controlling power transformers, however, is a high Surge withstand voltage of preferably up to voltages of 100 kV and more clearly required beyond. Such unwanted surge voltages, the amount of which is largely due to the structure of the tapped transformer and the winding parts between the tapping stages are, on the one hand, lightning impulse voltages that result from the impact of lightning in the network. On the other hand, switching impulse voltages can occur, which are caused by unpredictable switching shocks in the network to be controlled. If the impulse withstand voltage of the on-load tap-changer is insufficient, short-term step short circuit or undesirable breakdown of the ceramic or vapor shield of affected vacuum interrupters may occur in the load branch not leading to the load current, which may not only cause their long-term damage, but is generally undesirable.

From the DE 23 57 209 A and the DE 26 04 344 A It is already known to provide protective spark gaps or voltage-dependent resistors or both to combat high surge voltages between the load branches; However, these agents are inadequate in various cases and can not or completely exclude harmful impulse stresses in their effect.

An object of the present invention is to propose a tap changer of the type mentioned above with high surge voltage resistance, also referred to as a0-strength.

This object of the invention is achieved with the subject matter of the independent patent claim. Features of advantageous developments of the invention will become apparent from the dependent claims. To achieve the object of the invention, a tap changer for uninterrupted switching between at least two winding taps of a tapped transformer with the features of independent claim 1 is proposed. In this tap changer, a load branch is provided with a path comprising a series arrangement of at least one vacuum interrupter and at least one mechanical switching element, which in the present context can also be referred to as a variably adjustable or switchable switching contact. Furthermore, the tap changer has two resistance branches, each having a series arrangement of at least one vacuum interrupter, at least one mechanical switching element and have a resistance. In this way, the at least two winding taps can be variably coupled together and / or acted upon with a load dissipation. According to the present invention, the total of at least three vacuum interrupters and at least three mechanical switching elements with a defined time offset to each other in each case different switching directions can be switched together. In addition, the mechanical switching element in the load branch on a switching time between the two winding taps of the tapped transformer, in which the contact of the switched with the mechanical switching element in series vacuum interrupter is open. The circuit arrangement according to the invention forms a so-called. Three-cell circuit, in which a soft switching on and off is made possible. This circuit is particularly suitable for a combination with a rotational energy storage.

According to a preferred embodiment of the tap changer according to the invention, the switching point of the mechanical switching element in the load branch is independent of the switching direction in each case within a phase in which the vacuum interrupter is open. In addition, the vacuum interrupters of the two resistance branches turn each other with a time delay so that they are not opened simultaneously at any one time.

Furthermore, a preferred embodiment variant permanent main contacts provide that produce a direct line connection between the respective winding tap of the tapped transformer and the load dissipation in the closed position switch. The contact of such a permanent main contact switch preferably opens on the disconnecting side before all other switching elements (MSV, TTV, MTF, TTF), while the contact closes on the aufschaltenden page to all other switching elements.

A preferred embodiment of the tap changer according to the invention provides a rotatable switching shaft, the actuators are assigned for each actuation phase for the mechanical switching elements or vacuum interrupters, wherein the actuators are each associated with the control shaft rotatable, concentric cams with frontal or peripheral contours. These end or circumferential contours can be formed in particular by projections, cams o. The like., Which are used to actuate the switching elements and / or vacuum interrupters are suitable. In addition, the switching times triggered by the cams are independent of their direction of rotation or of the direction of rotation of the switching shaft.

• Fig. 1 zeigt ein Ablaufdiagramm zur Verdeutlichung der Schaltabläufe eines Ausführungsbeispiels eines erfindungsgemäßen Stufenschalters während eines Schaltzyklus in jeweils unterschiedliche Schaltrichtungen.
• Fig. 2 zeigt ein Schaltbild zur Verdeutlichung der Verschaltung der Widerstands- und Lastzweige des erfindungsgemäßen Stufenschalters.
• Fig. 3 zeigt ein weiteres Ablaufdiagramm zur Verdeutlichung der Schaltabläufe eines alternativen Ausführungsbeispiels des erfindungsgemäßen Stufenschalters während eines Schaltzyklus in jeweils unterschiedliche Schaltrichtungen.
• Fig. 4 zeigt anhand eines weiteren Schaltbildes eine vereinfachte Variante eines Stufenschalters ohne die in Fig. 2 gezeigten Dauerhauptkontakte.

The invention will be explained in more detail with reference to embodiments using the drawings described below.

• Fig. 1 shows a flowchart for illustrating the switching sequences of an embodiment of a tap changer according to the invention during a switching cycle in each case different switching directions.
• Fig. 2 shows a circuit diagram to illustrate the interconnection of the resistance and load branches of the tap changer according to the invention.
• Fig. 3 shows a further flow diagram to illustrate the switching sequences of an alternative embodiment of the tap changer according to the invention during a switching cycle in each case different switching directions.
• Fig. 4 shows on the basis of another circuit diagram a simplified variant of a tap changer without the in Fig. 2 shown permanent main contacts.

The embodiments of the circuits described below and the coordinated switching operations and sequences of the mechanical switching elements and vacuum interrupters are not intended to be limiting, but serve to explain the functions and the switching capabilities of a tap changer according to the invention. The presentation of the Fig. 1 to a flowchart of the switching sequences of a first embodiment of a tap changer 10 of the invention (see. Fig. 2 ) during a switching cycle in each different switching directions clarify. The upper diagram illustrates the switching sequence of a total of six individual switching units existing tap changer 10 in a first switching direction, characterized by a drive direction in the diagram from left to right, while the lower diagram shows the switching sequence in the opposite direction, characterized by a drive direction in the diagram of right to left.

The schematic representation of Fig. 2 shows a circuit diagram with the various components of the tap changer 10, which can be rotated and switched in both switching directions, which in Fig. 2 is characterized by the optional switching directions n → n + 1 and n ← n + 1. The in Fig. 2 The tap changer 10 forms a load branch or load path 18, which runs in the middle of the circuit diagram between two resistance branches 20 and 22 on the circuit diagram. The load path 18 comprises a series arrangement of a vacuum interrupter MSV and a mechanical switching element MTF, which in the present context can also be referred to as a variably adjustable or switchable switching contact. The mechanical switching element MTF acts as a changeover switch, which connects the vacuum interrupter MSV either electrically conductively to the first 12 or the second winding tap 14.

A second path 20, which corresponds to the first resistance branch, is formed by a series connection of a further vacuum interrupter TTV ₁ and a mechanical switching element TTF ₁ and a resistor R ₁ . A third path 22, which corresponds to the second resistance branch, is formed by a series connection of a further vacuum interrupter TTV ₂ and a mechanical switching element TTF ₂ and a resistor R ₂ . By switching the two mechanical switching elements TTF ₁ and TTF ₂ and by opening and closing the two vacuum interrupters TTV ₁ and TTV ₂ and by switching the mechanical switching element MTF in the load branch and by opening and closing the corresponding vacuum interrupter MSV, the two winding taps 12 and 14 of Stepped transformer 16 are variably coupled to each other and / or acted upon with a load dissipation LA.

The presentation of the Fig. 2 further shows two additional switch or permanent main contacts MC (MC ₁ and MC ₂ ), which are additionally provided on the off and aufschaltenden side. These so-called permanent main contacts MC or additional switches each carry a continuous current. In addition, they are preferably connected so that the contact MC ₁ on the disconnecting side before all other switching elements (MSV, TTV, MTF, TTF) opens and the contact MC ₂ closes on the aufschaltenden page after all other switching elements. As based on the Fig. 2 ₁ , the first contact MC _{1 is} disposed between the first winding tap 12 and the load dissipation, while the second contact MC _{2 is} disposed between the second winding tap 14 and the load dissipation.

The three vacuum interrupters MSV, TTV ₁ and TTV ₂ and the three mechanical switching elements MSV, TTF ₁ and TTF ₂ are according to Fig. 1 with a defined time offset to each other in each case different switching directions (n → n + 1 or n + 1 → n) jointly switchable. As based on the Fig. 1 (top, n → n + 1) can be seen, first opens the arranged in the third path 22 and the second resistance branch vacuum interrupter TTV ₂ , before with a short time offset the associated mechanical switching element TTF ₂ in the same path 22 of the first winding tapping 12th to the second winding tapping 14 of the tapped transformer 16 switches. Subsequently, the vacuum interrupter MSV located in the load branch 18 opens before the switch MTF located in the same path 18 switches over from one to the other winding tapping 12 or 14 during the opening phase of the tube MSV. Subsequently, the vacuum interrupter TTV ₁ located in the second path 20 or in the first resistance branch opens before the vacuum interrupter MSV in the load branch 18 closes. During the open phase of the tube TTV ₁ , the corresponding switching element TTF ₁ switches over in this branch 20. After completion of the switching operation of the mechanical switching element TTF ₁ in the second path 20, the corresponding vacuum interrupter TTV ₁ closes again, bringing the switching cycle accordingly Fig. 1 is completed.

Since the in Fig. 1 Above or below illustrated cycles in both switching directions not or only marginally different, can be dispensed with a detailed description of the switching operation in the other switching direction (n ← n + 1) at this point. Due to the in-stage switch 10 located mechanically rigid coupling of the three switching elements and vacuum interrupters in the three branches of the switching operation in the reverse direction in the reverse order as previously with reference to the upper illustration of Fig. 1 described.

The presentation of the Fig. 3 is in another flowchart, the switching sequences of an alternative embodiment of a tap changer 10 of the invention (see. Fig. 2 ) during a switching cycle in each different switching directions clarify. The upper diagram in turn illustrates the switching sequence of the existing of a total of six individual switching units tap changer 10 in a first switching direction, characterized by a drive direction in the diagram from left to right, while the lower diagram shows the switching sequence in the opposite direction of switching, characterized by a drive direction in the diagram from right to left.

The three vacuum interrupters MSV, TTV ₁ and TTV ₂ and the three mechanical switching elements MSV, TTF ₁ and TTF ₂ are according to Fig. 3 with a defined time offset to each other in each case different switching directions (n → n + 1 or n + 1 → n) jointly switchable. As based on the Fig. 3 (top, n → n + 1) can be seen, first opens the arranged in the third path 22 and the second resistance branch vacuum interrupter TTV ₂ , before with a short time offset the associated mechanical switching element TTF ₂ in the same path 22 of the first winding tapping 12th to the second winding tapping 14 of the tapped transformer 16 switches. Subsequently, the vacuum interrupter MSV located in the load branch 18 opens before first the vacuum interrupter TTV ₂ closes and then the changeover switch MTF located in the load path 18 switches over from one to the other winding tapping 12 or 14 during the opening phase of the tube MSV. Subsequently, the vacuum interrupter TTV ₁ located in the second path 20 or in the first resistance branch opens, so that the corresponding switching element TTF ₁ switches over in this branch 20 during the open phase of this tube TTV ₁ . After opening the tube TTV ₁ closes the tube located in the load path 18 MSV. After completion of the switching operation of the mechanical switching element TTF ₁ in the second path 20, the corresponding vacuum interrupter TTV ₁ closes again, bringing the switching cycle accordingly Fig. 3 (above, n → n + 1) is completed.

Since the in Fig. 3 Distinguish both above and below illustrated cycles in both switching directions only at one point, can be dispensed with a detailed description of the switching operation in the other switching direction (n ← n + 1) at this point. Only the switching time of located in the load path 18 mechanical switching element MTF differs in both switching directions. Thus, the switching element MTF opens in the switching direction shown above (n → n + 1) immediately after closing the vacuum interrupter TTV ₂ in the third path 22 and stops the switching only after the vacuum interrupter TTV ₁ in the second path 20 has been opened. When switching back (n + 1 → n), however, the actuation of the switching element MTF begins when the tube TTV _{2 is} still closed and ends at a time at which the vacuum interrupter TTV _{2 is} open. This switching delay in the switching-back direction for the switching element MTF can, for example, by a suitable freewheeling element o. The like. Are triggered, which can provide the desired hysteresis in the switching operations in different switching directions. Due to the in-stage switch 10 located mechanically rigid coupling of the other two switching elements and the total of three vacuum interrupters in the three branches of the switching operation in the reverse direction in reverse order, moreover, as previously with reference to the upper illustration of Fig. 3 described.

The presentation of the Fig. 4 shows a simplified circuit of the tap changer 10, in which the permanent main contacts or mechanical contacts MC (see FIG. Fig. 2 ) absence. In this alternative or optionally to be understood variant of the tap changer 10 are only the already Fig. 2 described three branches 18, 20 and 22 present.

Claims (5)

1. Tap changer (10) for uninterrupted switching over between at least two winding taps (12, 14) of a tapped transformer (16), wherein a load branch with a path (18), comprising a series arrangement of at least one vacuum switching tube (MSV) and at least one mechanical switching element (MTF), is provided, and wherein two resistance branches (20, 22), each comprising a series arrangement of at least one vacuum switching tube (TTV₁; TTV₂), at least one mechanical switching element (TTF₁; TTF₂) and a resistance (R₁; R₂), are provided, wherein the at least two winding taps (12, 14) can be variably coupled together and/or acted on by a load shunt (LA), wherein the, in total, at least three vacuum switching tubes (TTV₁; TTV₂; MSV) and at least three mechanical switching elements (TTF₁; TTF₂; MTF) are switchable in common with defined offset in time with respect to one another in respectively different switching directions, and wherein the mechanical switching element (MTF) in the load branch has a switch-over instant between the two winding taps (12, 14) of the tapped transformer (16) at which the contact of the vacuum switching tube (MSV) connected in series with the mechanical switching element (MTF) is open.
2. Tap changer according to claim 1, in which the switch-over instant of the mechanical switching element (MTF) in the load branch is independent of the switching direction of the respective vacuum switching tube (MSV) open within a phase.
3. Tap changer according to claim 1 or 2, in which the two vacuum switching tubes (TTV₁; TTV₂) of the parallel resistance branches (20, 22) switch offset in time relative to one another and are not open simultaneously at any point in time.
4. Tap changer according to any one of claims 1 to 4, which additionally has two mechanical permanent main contacts (MC), which in closed switch setting produce a direct conductive connection between the respective winding tap (12; 14) of the tapped transformer (16) and the load shunt (LA).
5. Tap changer according to any one of claims 1 to 5, which comprises a rotatable switching shaft, with which actuating elements for each actuating phase for the mechanical switching elements (TTF₁; TTF₂; MTF) or vacuum switching tubes (TTV₁; TTV₂; MSV) are associated, wherein the actuating elements are respectively associated with concentric cam discs, which are rotatable by the switching shaft, with end-face or circumferential profiles, projections, dogs or the like.

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