On-load tap changer

Abstract

The invention relates to a load tap changer (1) for performing an uninterrupted switching between winding taps (N1,... N J ,... N N ) of a step-up transformer (2). The load tap changer (1) comprises a selector (3) and a load transfer switch (4). The load transfer switch (4) has a first load branch (5.1) and a second load branch (5.2), each load branch (5.1, 5.2) having at least one vacuum interrupter (6.1, 6.2, 7.1, 7.2). Each vacuum interrupter (6.1, 6.2, 7.1, 7.2) is switchable between an open state (31), in which a movable contact (11) and a fixed contact (12) are not in contact, and a closed state (32), in which the movable contact (11) and the fixed contact (12) are in contact in at least one contact point (13). Each vacuum interrupter (6.1, 6.2, 7.1, 7.2) has a defined spherical area (14) outside the contact point (13), respectively. The load transfer switch (4) is designed in such a way that the vacuum interrupters (6.1, 6.2, 7.1, 7.2) are arranged in a housing (29) in such a way that components of the load transfer switch (4) through which a current flows are arranged outside the defined area (14).

Description

TECHNICAL FIELD

[0001] The invention relates to a load tap changer for switching between winding taps of a stepped transformer without interruption. BACKGROUND

[0002] Known load tap changers are usually composed of a selector for selecting the respective winding tap of the transformer to which the switching is to take place without power and a load transfer switch for transferring the actual load from the present winding tap to the selected new winding tap. The switching takes place by mechanically operating different switches. The requirements for the operating mechanics increase when the load increases, i.e. when the current and voltage are high. SUMMARY

[0003] It is therefore the object of the invention to provide an improved load tap changer which withstands increased mechanical and electrical loads when the current and voltage are high.

[0004] According to the improvement, a load tap changer for switching between winding taps of a stepped transformer without interruption is proposed, the load tap changer having a selector for preselecting the selected winding tap to which the switching is to take place without power and a load transfer switch for transferring the actual load from the present winding tap to the preselected winding tap. The load transfer switch comprises a first load branch and a second load branch and at least one vacuum interrupter in at least one of the first load branch and the second load branch. Each vacuum interrupter has a movable contact and a fixed contact and can assume an open state in which the movable contact and the fixed contact are not in contact and a closed state in which the movable contact and the fixed contact are in contact in at least one contact point. From the contact point, each vacuum interrupter has a defined spherical area. The vacuum interrupters of the load transfer switch are arranged in a housing in such a way that components of the load transfer switch through which a current flows are outside the defined area. According to at least one preferred embodiment, the load transfer switch is designed in such a way that components of the load transfer switch through which a current flows at the moment when a vacuum interrupter is operated from the closed state to the open state are arranged outside the defined area.

[0005] This arrangement allows a compact design of the load tap changer in a safe mode of operation despite increasing current and voltage.

[0006] According to at least one embodiment, the spherical area has a radius of at least 80 mm and at most 200 mm around the contact point.

[0007] According to at least one embodiment, the components of the load change-over switch, through which the current flows, are the first electrical line of the first load branch and / or the second electrical line of the second load branch and / or the third electrical line of the first load branch and / or the fourth electrical line of the second load branch and / or the electrically conductive connection element and / or the first mechanical switch contact and / or the second mechanical switch contact and / or the transfer resistor and / or the vacuum interrupter in the closed state, which are arranged outside the defined region of the vacuum interrupter.

[0008] According to at least one embodiment, the first load branch of the load change-over switch comprises a first vacuum interrupter and a second vacuum interrupter.

[0009] According to at least one embodiment, at least the first electrical line, the second electrical line, the second vacuum interrupter of the first load branch, the third electrical line and the first mechanical switch contact are arranged outside the defined region of the first vacuum interrupter of the first load branch.

[0010] According to at least one embodiment, the second load branch of the load change-over switch comprises a first vacuum interrupter and a second vacuum interrupter.

[0011] According to at least one embodiment, at least the first electrical line, the second electrical line, the second vacuum interrupter of the second load branch, the fourth electrical line and the second mechanical switch element are arranged outside the defined region of the first vacuum interrupter of the second load branch.

[0012] According to at least one embodiment, at least the second vacuum interrupter of the second load branch, the third electrical line, the fourth electrical line and the mechanical switch element are arranged outside the defined region of the second vacuum interrupter of the first load branch.

[0013] According to at least one embodiment, at least the second vacuum interrupter of the first load branch, the third electrical line, the fourth electrical line and the mechanical switch element are arranged outside the defined region of the second vacuum interrupter of the second load branch.

[0014] According to at least one embodiment, the first winding tap is electrically connected to the load lead via the first load branch via a series circuit comprising the first vacuum interrupter and the second vacuum interrupter, and the second winding tap is electrically connected to the load lead via the second load branch via a series circuit comprising the first vacuum interrupter and the second vacuum interrupter.

[0015] According to at least one embodiment, a transfer resistor is arranged in parallel to the vacuum interrupters of the first load branch and of the second load branch, respectively.

[0016] According to at least one embodiment, the transfer resistor is arranged outside the defined region of the second vacuum interrupter of the first load branch and outside the defined region of the second vacuum interrupter of the second load branch.

[0017] According to at least one embodiment, a first mechanical switch contact is provided between the second vacuum switch tube and the load lead of the first load branch, and a second mechanical switch contact is provided between the second vacuum switch tube and the load lead of the second load branch.

[0018] According to at least one embodiment, the mechanical switch contacts are arranged outside the defined area of the vacuum switch tubes.

[0019] According to at least one embodiment, the mechanical switch contacts are configured as circuit breakers.

[0020] According to at least one embodiment, in the first load branch, the first vacuum switch tube and the second vacuum switch tube are electrically connected to each other via a first electrical lead, and the second vacuum switch tube and the first mechanical switch element are electrically connected to each other via a third electrical lead, and in the second load branch, the first vacuum switch tube and the second vacuum switch tube are electrically connected to each other via a second electrical lead, and the second vacuum switch tube and the second mechanical switch element are electrically connected to each other via a fourth electrical lead.

[0021] According to at least one embodiment, the electrical leads are respectively electrically connected to the vacuum switch tubes via connection elements.

[0022] According to at least one embodiment, the leads respectively have a first end and a second end, the first end being electrically connected to the movable contact of the vacuum switch tube via a connection element, and the second end being electrically connected to the fixed contact of the vacuum switch tube via a connection element.

[0023] According to at least one embodiment, a persistent main contact is additionally provided in parallel to each load branch, which assumes at least a portion of the continuous electrical conduction in steady-state operation and is electrically connected to the load lead.

[0024] According to at least one embodiment, the vacuum switch tubes are arranged circularly around a switching axis.

[0025] According to at least one embodiment, the first mechanical switch contact and the second mechanical switch contact are arranged symmetrically about an axis lying on the switching axis.

[0026] According to at least one embodiment, the two vacuum switch tubes are arranged symmetrically about the axis. BRIEF DESCRIPTION OF DRAWINGS

[0027] The application is explained in detail below with the aid of exemplary embodiments with reference to the accompanying drawings. Components which have the same function or the same effect can be provided with the same reference signs. Identical components or components having the same function can only be explained with reference to the first occurrence of the figure. Said explanation need not necessarily be repeated in subsequent figures.

[0028] In the drawings:

[0029] Figure 1 a schematic diagram of a step-up transformer with an on-load tap changer according to the improvement is shown;

[0030] Figure 2 a schematic diagram of winding taps of a step-up transformer is shown;

[0031] Figure 3 a schematic diagram of an exemplary embodiment of an on-load tap changer according to the improvement is shown;

[0032] Figures 4a to 4f an exemplary switching process of an on-load tap changer in Figure 3 is shown;

[0033] Figure 5 an exemplary embodiment of a load transfer switch according to the improvement is shown;

[0034] Figure 6 another view of the exemplary embodiment in Figure 5 is shown;

[0035] Figure 7 another view of the exemplary embodiment in Figure 5 is shown;

[0036] Figure 8 another view of the exemplary embodiment in Figure 5 is shown. DETAILED DESCRIPTION

[0037] The drawings show only embodiments of the application, however, without limiting the application to the embodiments shown.

[0038] Figure 1 a schematic diagram of a step-up transformer 2 with an on-load tap changer 1 having a selector 3 and a load transfer switch 4 is shown. The on-load tap changer 1 is driven by a motor 22.

[0039] Figure 2 a regulating winding 25 (see Figure 1 ) of the step-up transformer 2 is shown, which has different winding taps N1,... N J ,... N N . The winding taps N1,... N J ,... N N are switched on or off by the on-load tap changer 1. The switching on or off can be effected by any means, for example by the selector 3, the load transfer switch 4, etc. The manipulation of the on-load tap changer 1 is effected via the motor 22.

[0040] Figure 3A schematic diagram of an exemplary embodiment of an on-load tap changer 1 is shown. According to the improvement, the on-load tap changer 1 comprises a selector 3 having at least one first fixed contact 23.1 and at least one second fixed contact 23.2, which can be connected with winding taps N1,... N J ,... N N of a step transformer 2, respectively. The total number of fixed contacts is related to the number of winding taps N1,... N J ,... N N . Furthermore, the on-load tap changer 1 has a first movable selector contact 24.1 and a second movable selector contact 24.2, which can be contacted with the respective fixed contacts 23.1, 23.2 of a regulating winding 25, respectively. The on-load tap changer 1 further comprises a load transfer switch 4 having a first load branch 5.1 and a second load branch 5.2. According to this exemplary embodiment, the first load branch 5.1 connects the first fixed contact 23.1 with a load lead 8 via a series circuit comprising a first vacuum switch tube 6.1 and a second vacuum switch tube 6.2, and the second load branch 5.2 connects the second fixed contact 23.2 with the load lead 8 via a series circuit comprising a first vacuum switch tube 7.1 and a second vacuum switch tube 7.2. A shunt resistor 9.1 or 9.2 is connected in parallel to the first vacuum switch tube 6.1 or 7.1, respectively. A first mechanical switching element 18.1 is provided between the second vacuum switch tube 6.2 and the load lead 8, and a second mechanical switching element 18.2 is provided between the second vacuum switch tube 7.2 and the load lead 8. A first conductor 10.1 electrically connects the first vacuum switch tube 6.1 and the second vacuum switch tube 6.2 with each other, and a second conductor 10.2 electrically connects the first vacuum switch tube 7.1 and the second vacuum switch tube 7.2 with each other. Furthermore, a third conductor 10.3 connects the second vacuum switch tube 6.2 with the first mechanical switching element 18.1, and a fourth conductor 10.4 connects the second vacuum switch tube 7.2 with the second mechanical switching element 18.2. Furthermore, an additional permanent main contact 19.1, 19.2 is provided in parallel to each load branch 5.1, 5.2. Figure 2 The on-load tap changer 1 is shown in a steady state, in which at least a part, in particular a larger part than via the load branch 5.1, of the load current flows from the winding taps via the first fixed contact 23.1 to the load lead 8 via the permanent main contact 19.1, 19.2.

[0041] Figures 4a to 4e An exemplary switching process of the on-load tap changer 1 according to the improvement is described, in which the second fixed contact 23.2 is switched to the first fixed contact 23.1 or to the respective winding tap N1,... NJ ,... N N above.

[0042] In step a (see Figure 4a ), the permanent main contact 19.2 is closed or remains closed. The on-load tap changer 1 is in a steady state in which at least a part of the load current, in particular a larger part than via the load branch 5.2, is drawn from the respective winding tap N J+1 via the second fixed contact 23.2 to the load lead 8.

[0043] In step b (see Figure 4b ), the permanent main contact 19.2 is opened and the first mechanical switch contact 18.1 is closed. The current now flows via the first vacuum switch tube 7.1 of the second load branch 5.2, the second conductor 10.2, the second vacuum switch tube 7.2 of the second load branch 5.2, the fourth conductor 10.4 and the second mechanical switch contact 18.2 to the load lead 8.

[0044] In step c (see Figure 4c ), the first vacuum switch tube 7.1 of the second load branch 5.2 is opened. During the opening process, the second vacuum switch tube 7.2, the fourth conductor 10.4 and the second mechanical switch contact 18.2 are flowed through by the current and are spatially arranged outside the defined area 14 (see, for example Figures 6 to 8 ) of the vacuum switch tube 7.1. The current then flows from the fixed contact 23.2 via the relay resistor 9.2, the second vacuum switch tube 7.2, the fourth conductor 10.4 and the second mechanical switch contact 18.2 to the load lead 8.

[0045] In step d (see Figure 4d ), the second vacuum switch tube 6.2 of the first load branch 5.1 is closed. The load current is now distributed onto the first load branch 5.1 and the second load branch 5.2. In addition, a ring current is superimposed.

[0046] In step e (see Figure 4e ), the second vacuum switch tube 7.2 of the second load branch 5.2 is opened. During the opening process, the second vacuum switch tube 6.2 of the first load branch 5.1, the first mechanical switch element 18.1 of the first load branch 5.1, the second mechanical switch element 18.2 of the second load branch 5.2 and the connection conductor 27 to the relay resistor 9.1 or 9.2 of the first load branch 5.1 or of the second load branch 5.2 are flowed through by the current and are spatially arranged outside the defined area 14 (see, for example Figures 6 to 8the load lead 8 via the first load branch 5.1, the second vacuum interrupter 6.2, the third conductor 10.3 and the first mechanical switch contact 18.1.

[0047] In step f (see 4f), the first vacuum interrupter 6.1 of the first load branch 5.1 is closed. The current now flows via the first vacuum interrupter 6.1, the first conductor 10.1, the second vacuum interrupter 6.2, the third conductor 10.3 and the first mechanical switch contact 18.1 to the load lead 8.

[0048] In step g (see Figure 3 ), the persistent main contact 19.1 in the first load branch 5.1 is closed and the second mechanical switch contact 18.2 in the second load branch 5.2 is opened. The on-load tap changer 1 is again in a steady state as shown and explained in Figure 3

[0049] Figure 5 and Figure 6 show an exemplary embodiment of a load transfer switch 4 according to the described improvement, which is shown from two different side perspective views for the sake of clarity. Four vacuum interrupters 6.1, 6.2, 7.1, 7.2 are arranged circularly around a switching axis 20 and have a movable contact 11 and a fixed contact 12, respectively. The vacuum interrupters 6.1 and 6.2 are conductively connected to each other via a first electrical conductor 10.1 and the vacuum interrupters 7.1 and 7.2 are conductively connected to each other via a second electrical conductor 10.2. The conductive connections are realized via connection elements 17, which are configured as screws and / or laces, for example. Here, a first end of the first electrical conductor 10.1 is electrically connected via a connection element 17 with the movable contact 11 of the vacuum interrupter 6.1 and a second end is electrically connected via a connection element 17 with the fixed contact 12 of the vacuum interrupter 6.2. A first end of the second conductor 10.2 is electrically connected via a connection element 17 with the movable contact 11 of the vacuum interrupter 7.1 and a second end is electrically connected via a connection element 17 with the fixed contact 12 of the vacuum interrupter 7.2. The movable contact 11 and the fixed contact 12 of each vacuum interrupter 6.1, 6.2, 7.1, 7.2 are in contact in at least one point 13 in the closed state of the vacuum interrupter. From the respective contact point 13, each vacuum interrupter 6.1, 6.2, 7.1, 7.2 defines a spherical area 14, respectively. For the sake of clarity, the contacts 11 and 12, their contact points 13 are drawn in only a few vacuum interrupters and provided with one reference numeral in Figures 4 and Figure 5

[0050] Figure 7 and Figure 8 ​​An exemplary embodiment of a load transfer switch is shown in a plan view. The load transfer switch 4 has a housing 29 in which the vacuum switch tubes 6.1, 6.2, 7.1 and 7.2 are arranged. The housing 29 is essentially cylindrical and consists of GFK (glass fiber reinforced) plastic. The vacuum switch tubes 6.1, 6.2 are arranged symmetrically to the vacuum switch tubes 7.1, 7.2 in the housing 29. For example, the vacuum switch tube 7.2 is arranged opposite the vacuum switch tube 6.1 and the vacuum switch tube 7.1 is arranged opposite the vacuum switch tube 6.2. Thereby, the largest possible spacing is generated between the vacuum switch tubes 7.1 and 6.1 and between the vacuum switch tubes 6.2 and 7.2. A first mechanical switch contact 18.1 or a second mechanical switch contact 18.2 is arranged symmetrically to each other between the vacuum switch tubes 6.1 and 6.2 of the first load branch 5.1, and also between the vacuum switch tubes 7.1 and 7.2 of the second load branch 5.2. In Figure 7 It is shown in that the second conductor 10.2 and the second vacuum switch tube 7.2 of the second load branch 5.2 are arranged outside the defined area 14 of the first vacuum switch tube 7.1 of the second load branch 5.2. In Figure 8 It is also shown in that the second vacuum switch tube 6.2 of the first load branch 5.1 is arranged outside the defined area 14 of the second vacuum switch tube 7.2 of the second load branch 5.2.

[0051] List of reference signs

[0052] 1 on-load tap changer

[0053] 2 step-up transformer

[0054] 3 selector

[0055] 4 load transfer switch

[0056] 5.1 first load branch

[0057] 5.2 second load branch

[0058] 6.1 first vacuum switch tube of the first load branch

[0059] 6.2 second vacuum switch tube of the first load branch

[0060] 7.1 first vacuum switch tube of the second load branch

[0061] 7.2 second vacuum switch tube of the second load branch

[0062] 8 load lead

[0063] 9.1, 9.2 transfer resistor

[0064] 10.1 first conductor

[0065] 10.2 second conductor

[0066] 11 movable contact

[0067] 12 fixed contact

[0068] 13 center point / contact point

[0069] 14 defined area

[0070] 15.1, 15.2 first end

[0071] 16.1, 16.2 second end

[0072] 17 connecting element

[0073] 18.1 first mechanical switch contact

[0074] 18.2 second mechanical switch contact

[0075] 19.1, 19.2 permanent main contact

[0076] 20 switching shaft

[0077] 21 axis

[0078] 22 motor

[0079] 23.1, 23.2 fixed contact of the selector

[0080] 24.1, 24.2 movable selector contact

[0081] 25 regulating winding

[0082] 27 connecting conductor

[0083] 29 housing

[0084] (N1,... NJ,... NN) winding taps

Claims

1. Used for winding taps (N1, ... N) in a graded transformer (2) J ...N N An on-load tap changer (1) that allows for uninterrupted switching between ) and ), the on-load tap changer comprising: Used for power-free pre-selection to the selected winding tap (N J Selector (3) on ) Used to tap from the current winding (N) J-1 Actual load is switched to the pre-selected winding tap (N). J The load transfer switch (4) on the load transfer switch (4) has a first load branch (5.1) and a second load branch (5.2). The first load branch (5.1) of the load transfer switch (4) includes a first vacuum switch tube (6.1) and a second vacuum switch tube (6.2). The second load branch (5.2) of the load transfer switch (4) includes a first vacuum switch tube (7.1) and a second vacuum switch tube (7.2). Each vacuum switch tube has a movable contact (11) and a fixed contact (12), and Each vacuum switch tube can occupy an open state (31) and a closed state. In the open state, the movable contact (11) and the fixed contact (12) are not in contact, and in the closed state, the movable contact (11) and the fixed contact (12) are in contact at at least one contact point (13). A spherical region (14) is defined by the contact point (13) of the fixed contact (12) and the movable contact (11) of each vacuum switch tube; and The vacuum switch tube of the load transfer switch (4) is configured such that the current-carrying component of the load transfer switch (4) is located outside the defined spherical region (14). Its features are, The first load branch (5.1) taps one winding tap (N) respectively. J The load is electrically connected to the load lead (8) via a series circuit consisting of a first vacuum switch (6.1) and a second vacuum switch (6.2) including the first load branch (5.1). The second load branch (5.2) taps one winding tap (N) respectively. J+1 The load lead (8) is electrically connected to the load lead via a series circuit consisting of a first vacuum switch (7.1) and a second vacuum switch (7.2) including the second load branch (5.2). A first mechanical switch contact (18.1) is provided between the second vacuum switch tube (6.2) of the first load branch (5.1) and the load lead (8); and a second mechanical switch contact (18.2) is provided between the second vacuum switch tube (7.2) of the second load branch (5.2) and the load lead (8).

2. The on-load tap changer according to claim 1, wherein, The spherical region (14) has a radius of 80 mm and 200 mm around the contact point (13).

3. The on-load tap changer according to claim 1, wherein, The components of the load transfer switch (4) through which current flows are the first conductor (10.1) of the first load branch (5.1) or the second conductor (10.2) of the second load branch (5.2) or the conductive connecting element (17) or the first mechanical switch contact (18.1) or the second mechanical switch contact (18.2), which are disposed outside the spherical region (14) of each vacuum switch tube.

4. The on-load tap changer according to claim 3, wherein, At least the second electrical conductor (10.2), the second vacuum switch tube (7.2) of the second load branch (5.2) and the fourth electrical conductor (10.4) are disposed outside the spherical region (14) defined by the first vacuum switch tube (7.1) of the second load branch (5.2).

5. The on-load tap changer according to claim 4, wherein, At least the second vacuum switch tube (6.2), the third electrical wire (10.3) and the fourth electrical wire (10.4) of the first load branch (5.1) are disposed outside the spherical region (14) defined by the second vacuum switch tube (7.2) of the second load branch (5.2).

6. The on-load tap changer according to any one of claims 1 to 3, wherein, The first mechanical switch contact (18.1) and the second mechanical switch contact (18.2) are configured as circuit breakers.

7. The on-load tap changer according to claim 5, wherein, In the first load branch (5.1), the first vacuum switch tube (6.1) and the second vacuum switch tube (6.2) are electrically connected to each other via the first electrical wire (10.1), and the second vacuum switch tube (6.2) is electrically connected to the first mechanical switch contact (18.1) via the third electrical wire (10.3). In the second load branch (5.2), the first vacuum switch tube (7.1) and the second vacuum switch tube (7.2) are electrically connected to each other via the second electrical wire (10.2), and the second vacuum switch tube (7.2) and the second mechanical switch contact (18.2) are electrically connected to each other via the fourth electrical wire (10.4).

8. The on-load tap changer according to claim 7, wherein, The electrical conductors (10.1, 10.2, 10.3, 10.4) are electrically connected to the vacuum switch tubes (6.1, 6.2, 7.1, 7.2) via connecting elements (17).

9. The on-load tap changer according to any one of claims 1 to 3, wherein, A continuous main contact (19.1, 19.2) is provided in parallel with the first load branch (5.1) and the second load branch (5.2), respectively. The continuous main contact undertakes at least a portion of continuous conduction during steady-state operation and is directly conductively connected to the load lead (8).

10. The on-load tap changer according to any one of claims 1 to 3, wherein, The first vacuum switch tube (6.1) and the second vacuum switch tube (6.2) of the first load branch (5.1) and the first vacuum switch tube (7.1) and the second vacuum switch tube (7.2) of the second load branch (5.2) are arranged in a circular manner around the switching axis (20).

11. The on-load tap changer according to claim 10, wherein, The first mechanical switch contact (18.1) and the second mechanical switch contact (18.2) are symmetrically arranged about the axis (21) of the switching shaft (20).

Images