On-load tap changer and its operating method

Abstract

Selected winding tap N J A selector 5 for pre-selecting in a no-current state, and the current winding tap N J-1 Pre-selected winding tap N J Winding taps N1...N of the control winding 4 of the tap transformer 2, which includes a changeover switch 6 for actually switching the load. J ,...,N N An on-load tap changer 1 for switching between them without interruption. In this case, a protective device 7 is connected in series between the selector 5 and the changeover switch 6, and the protective device 7 is configured to limit the short-circuit current that occurs during a fault in the on-load tap changer 1 and / or the control winding 4.

Description

[Technical Field]

[0001] The present invention relates to an on-load tap changer for switching between winding taps of a control winding of a tap transformer without interruption, and to a method for operating an on-load tap changer. [Background technology]

[0002] As is well known, on-load tap changers are used to switch between multiple different winding taps of the control windings of a tap transformer without interruption, and thus to control the voltage. Generally, these winding taps consist of a selector for pre-selecting the winding taps of the tap transformer that need to be switched in a current-free state, and a changeover switch for actually switching from the previously connected winding taps to the newly selected winding taps without interruption. To pre-select these winding taps in a current-free state, the selector generally has two movable selector contacts connected to these winding taps. To actually switch the load, the changeover switch generally has multiple changeover contacts and multiple resistors. These changeover contacts are located in the main load branch of the on-load tap changer and are used to directly connect the winding taps connected by each selector contact to the load derivation via the main load branch. These resistors are used to briefly limit the ring current that energizes the changeover switch during the switching process and are also called transition resistors.

[0003] If the on-load tap changer does not operate correctly, it can cause a failure. The possible failure is a short circuit in the on-load tap changer, or more precisely, a short circuit in the changeover switch, caused by a flashover between the two main load branches. Since the two main load branches are each electrically connected to one winding tap of the control winding via one selector contact, this can cause a short circuit between taps. More precisely, this means that a short-circuit current flows through the main load branches, the selector contacts, and the control tap of the control winding of the tap transformer.

[0004] To protect transformers from greater damage or even destruction during short circuits, circuit breakers capable of reliably interrupting high currents in abnormal situations are installed in the power grid. However, interruption requires a relatively long time, for example, 50 ms, for the circuit breaker to operate. During this period, the short-circuit current flows unrestricted through the on-load tap changers and the conductive components of the transformer. This short-circuit current can cause serious damage to the on-load tap changers and transformers. Such damage must be avoided.

[0005] A device for limiting short-circuit current during such a fault is known from German Patent No. 102020110935. This device includes a current sensor and a tripping element located on the first power line of an on-load tap changer. The current limiting element is located in parallel with the tripping element. The current sensor is configured to transmit a first measurement signal indicating the measured current in the first power line of the on-load tap changer to the control device of the device. The tripping element is operable by the control device to interrupt the energization in the first power line of the on-load tap changer. As a result, the energized current is commutated to the current limiting element. A drawback of this known solution is that additional monitoring means, particularly a sensor system, are required on the power line to recognize the short-circuit current and, based on this, to actively activate the protective device, i.e., the tripping element, by the control device. Another drawback arises from the requirements of the tripping element itself. In the event of a fault, it must respond in an extremely short time, within 0.1 to 1.0 milliseconds, to prevent greater damage to the transformer, so semiconductor switching elements are particularly suitable as tripping elements. These elements are extremely sensitive and therefore prone to frequent failure. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] German Patent No. 102020110935 [Overview of the project] [Problems that the invention aims to solve]

[0007] Against this background, the present invention proposes the subject matter of the independent claim. Preferred embodiments of the present invention are described in the dependent claims. [Means for solving the problem]

[0008] According to the first feature, the present invention proposes an on-load tap changer for switching between winding taps of a control winding of a tap transformer without interruption, comprising a selector for pre-selecting a selected winding tap of the control winding in a current-free state, and a changeover switch for actually switching the load from the current winding tap to the winding tap pre-selected by the selector. A protective device is connected in series between the selector and the changeover switch, and the protective device is configured to limit the short-circuit current that occurs in the on-load tap changer, more specifically the selector and / or changeover switch and / or protective device and / or control winding during a fault. Thus, damage to the on-load tap changer and transformer can be avoided until the circuit breaker activates and reliably interrupts the fault current.

[0009] According to a preferred embodiment of an on-load tap changer, the selector has a first selector arm and a second selector arm, and the changeover switch has a first changing side electrically connected to the first selector arm via a first current path and a second changing side electrically connected to the second selector arm via a second current path. Furthermore, the protective device has a first resistor which can be connected to and disconnected from the first current path by a first changing element arranged in parallel with the first resistor, and a second resistor which can be connected to and disconnected from the second current path by a second changing element arranged in parallel with the second resistor. In other words, the resistors can be connected or disconnected via the changing elements.

[0010] In other words, according to the present invention, the resistor in the protective device is used to limit the short-circuit current that occurs during a fault.

[0011] According to a preferred embodiment, the resistor in the protective device is formed as an ohmic resistor.

[0012] Preferably, the first switching element and the second switching element are formed as mechanical switching contacts.

[0013] Preferably, the first switching element and the second switching element are formed as vacuum switching tubes.

[0014] According to another embodiment, the first switching element and the second switching element are formed as semiconductor switching semi-elements.

[0015] According to one embodiment, during the switching process of the on-load tap changer, the first resistor is connected to the first current path or the second resistor is connected to the second current path. In other words, during all switching processes, one of the two resistors of the protective device is always connected to the electrical circuit, so that indirect or passive protection against short-circuit current is ensured. Therefore, active activation of the protective device is unnecessary. Consequently, additional monitoring means for recognizing fault conditions, such as a current sensor in the current path, can be omitted.

[0016] In another embodiment, the first and / or second resistors are temporarily energized during the switching process. That is, at least one resistor in the protective device is not merely connected during the switching process, but is actively incorporated during the switching process. This has the advantage that the resistors can be designed to be smaller because the current load is distributed between the resistors in the changeover switch and the resistors in the protective device. This can reduce costs.

[0017] In another embodiment, when the first selector arm is not energized, the first resistor is connected to the first current path, and when the second selector arm is not energized, the second resistor is connected to the second current path.

[0018] According to a preferred embodiment, when the on-load tap changer is in a first steady state in which the on-load tap changer is connected to the current winding tap, the second resistor is or is connected to the second current path, and when the on-load tap changer is in a second steady state in which the on-load tap changer is connected to a new winding tap, the first resistor is or is connected to the first current path. That is, in other words, when the on-load tap changer is in a steady state, one of the two resistors of the protection device is always connected to the electrical circuit, so that indirect or passive protection against short-circuit current is ensured. Therefore, active activation of the protection device is not required. Therefore, additional monitoring means for recognizing a fault situation, such as a current sensor in the current path, can be omitted.

[0019] According to another embodiment, the protection device has a first steady main contact arranged in parallel with the first resistor and the first switching element and configured to conduct a steady current during the steady state of the on-load tap changer, and a second steady main contact arranged in parallel with the second resistor and the second switching element and configured to conduct a steady current during the steady state of the on-load tap changer.

[0020] According to another embodiment, the switching disconnector has a third steady main contact attached to the first switching side of the switching disconnector and configured to conduct a steady current during the steady state of the on-load tap changer, and a fourth steady main contact attached to the second switching side of the switching disconnector and configured to conduct a steady current during the steady state of the on-load tap changer.

[0021] According to a preferred embodiment, in the first steady state, the first steady main contact and the third steady main contact are energized, and in the second steady state, the second steady main contact and the fourth steady main contact are energized.

[0022] According to another embodiment, the protective device, the changeover switch and / or selector are mechanically connected via a common drive mechanism such that the changing elements of the protective device and the changing elements and / or selector arms of the changeover switch are operated in a dependent manner.

[0023] According to a preferred embodiment, the common drive unit includes a first gear mechanism attached to a protective device, a second gear mechanism attached to a changeover switch and / or selector, a connecting shaft mechanically connecting the first gear mechanism and the second gear mechanism, a drive shaft, and a common motor drive unit. The motor drive unit is operated by a control device. The control device can be configured as any configuration. For example, the control device may be configured as a voltage regulator or a control room. Depending on the configuration, communication connection with the drive unit may be implemented as a wired or wireless connection.

[0024] According to another embodiment, the protective device and the changeover switch and / or selector are electronically connected via a common control device such that the changing elements are operated in a dependent manner. The common control device can be configured as any; for example, the control device may be configured as a voltage controller or as a control room.

[0025] According to a preferred embodiment, the protective device is operated by a first drive unit, a first drive shaft, and a first gear mechanism, and the changeover switch and / or selector is operated by a second drive unit, a second drive shaft, and a second gear mechanism. The first drive unit and the second drive unit are operated dependently by a common electronic control unit. Depending on the configuration, the communication connection between the first drive unit and the second drive unit can be implemented as a wired or wireless connection.

[0026] In a particularly preferred embodiment, the mechanical and / or electronic connection between the protective device and the changeover switch is configured such that the first steady-state main contact and the third steady-state main contact open simultaneously, and the second steady-state main contact and the fourth steady-state main contact open simultaneously.

[0027] According to another embodiment, the protective device is housed in a first case filled with an insulating medium, and the changeover switch is housed in a second case filled with an insulating medium, the first case being housed inside and / or outside the transformer case, and the second case being housed inside and / or outside the transformer case.

[0028] According to a preferred embodiment, the first case and the second case are arranged in parallel within the transformer case.

[0029] According to a second feature, the present invention proposes a method for operating an on-load tap changer for switching between winding taps of a control winding of a tap transformer without interruption. The on-load tap changer comprises a selector for pre-selecting a selected winding tap in a current-free state, a changeover switch for actually switching the load from the current winding tap to the pre-selected winding tap, and a protective device connected in series between the selector and the changeover switch. In this case, according to the present invention, the on-load tap changer switches from a first steady state in which it is in contact with the current winding tap to a second steady state in which it is in contact with a new winding tap. The protective device is configured to limit the short-circuit current that occurs during a fault in the on-load tap changer and / or the control winding.

[0030] According to one embodiment, the protective device is configured to limit the short-circuit current that occurs in the on-load tap changer and / or control winding and / or transformer in the event of a failure under steady conditions.

[0031] According to another embodiment, the protective device is configured to limit the short-circuit current that occurs in the on-load tap changer and / or control winding and / or transformer in the event of a fault during switching.

[0032] According to another embodiment, the selector has a first selector arm and a second selector arm, the changeover switch has a first changing side electrically connected to the first selector arm via a first current path and a second changing side electrically connected to the second selector arm via a second current path, and the protection device has a first resistor which can be connected to the first current path by a first changing element arranged in parallel with the first resistor and can be disconnected from the first current path, and a second resistor which can be connected to the second current path by a second changing element arranged in parallel with the second resistor and can be disconnected from the second current path. In this case, when switching from a first steady state to a second steady state, the second resistor is connected to or connected to the second current path, the load current in the on-load tap changer is switched from the first changing side to the second changing side of the changeover switch, and the first resistor is connected to the first current path.

[0033] According to another embodiment, when switching in the reverse direction from the second steady state to the first steady state, the first resistor is connected to or is connected to the first current path, the load current in the changeover switch is switched from the second switching side of the changeover switch to the first switching side, and the second resistor is connected to the second current path.

[0034] According to another embodiment, the protective device has a first steady-state main contact arranged in parallel with the first resistor and the first switching element, and a second steady-state main contact arranged in parallel with the second resistor and the second switching element, and the changeover switch has a third steady-state main contact attached to the first switching side of the changeover switch and a fourth steady-state main contact attached to the second switching side of the changeover switch. In this case, when switching from the first steady state to the second steady state, the first steady-state main contact and the third steady-state main contact are opened simultaneously when the second resistor is connected to the second current path or after the second resistor has been connected to the second current path.

[0035] According to another embodiment, when switching from the second steady state to the first steady state in the reverse direction, the second steady main contact and the fourth steady main contact are opened simultaneously when the first resistor is connected to the first current path or after the second resistor is connected to the second current path.

[0036] Further embodiments and configurations of this method can be directly derived from various embodiments of on-load tap changers. In particular, individual or multiple components and arrangements described with respect to on-load tap changers can be appropriately configured to carry out this method.

[0037] The present invention will be described in detail below with reference to the drawings, based on representative practical embodiments. Components that are identical, functionally identical, or have the same effect may be indicated by the same reference numerals. Components that are identical or have the same function are described only in the first drawing they appear in. Such descriptions are not necessarily repeated in subsequent drawings. [Brief explanation of the drawing]

[0038] [Figure 1] A schematic example of a known on-load tap changer is provided. [Figure 2] A first embodiment of the on-load tap changer of the present invention is schematically illustrated. [Figure 3a] Figure 2 illustrates the switching sequence of the on-load tap changer of the present invention. [Figure 3b] Figure 2 illustrates the switching sequence of the on-load tap changer of the present invention. [Figure 3c] Figure 2 illustrates the switching sequence of the on-load tap changer of the present invention. [Figure 3d] Figure 2 illustrates the switching sequence of the on-load tap changer of the present invention. [Figure 3e] Figure 2 illustrates the switching sequence of the on-load tap changer of the present invention. [Figure 3f] Figure 2 illustrates the switching sequence of the on-load tap changer of the present invention. [Figure 3g] Figure 2 illustrates the switching sequence of the on-load tap changer of the present invention. [Figure 3h] Figure 2 illustrates the switching sequence of the on-load tap changer of the present invention. [Figure 4]Schematically illustrate the arrangement of a representative embodiment of the on-load tap changer of the present invention within a tap transformer. [Figure 5] Schematically illustrate the arrangement of another representative embodiment of the on-load tap changer of the present invention within a tap transformer. **Embodiments for Carrying Out the Invention**

[0039] The drawings merely show embodiments of the present invention and do not limit the present invention to the illustrated embodiments.

[0040] In FIG. 1, an embodiment of a known on-load tap changer 1 from the prior art for a tap transformer 2 is schematically illustrated. The tap transformer 2 includes a main winding 3 and a control winding 4 having different winding taps N1,..., N J ,..., N N which are connected or disconnected by the on-load tap changer 1. For this reason, the on-load tap changer 1 includes a selector 5 that can contact different winding taps N1,..., N J ,..., N N of the control winding 4 by two movable selector contacts, and a switching switch 6 that switches from the actually connected winding tap to a newly selected winding tap. At the position of the switching switch 6 shown in FIG. 1, the load current is energized from the actually connected winding tap N J+1 to the load lead-out section 33 through the respective selector contacts and the switching switch 6.

[0041] In FIG. 2, a first embodiment of the on-load tap changer of the present invention is schematically illustrated. The on-load tap changer 1 is used to switch between winding taps N J , N J+1 of the control winding 4 of the tap transformer 2 without interruption.

[0042] The on-load tap changer 1 includes a winding tap N J of the control winding 4 that contacts the winding tap N J+1The on-load tap changer 1 includes a selector 5 having a first selector arm 8 and a second selector arm 9 that make contact with the tap. Furthermore, the on-load tap changer 1 includes a changeover switch 6 having a first changing side 10 and a second changing side 11. The first changing side 10 is electrically connected to the first selector arm 8 via a first current path 12, and the second changing side 11 is electrically connected to the second selector arm 9 via a second current path 13.

[0043] A protective device 7 is connected in series between the selector 5 and the changeover switch 6. The protective device 7 is configured to limit the short-circuit current that occurs in the on-load tap changer 1 and / or tap transformer 2, more precisely in the control winding 4, in the event of a fault. The protective device 7 consists of two parts. The protective device 7 includes a first ohmic resistor 14. The first ohmic resistor 14 can be connected to and disconnected from the first current path 12 by a first switching element 16 arranged in parallel with the first ohmic resistor 14. A first steady-state main contact 18 is arranged in parallel with the first ohmic resistor 14 and the first switching element 16 and is configured to conduct a steady-state current during the steady state of the on-load tap changer 1. Depending on which steady state or switching step the on-load tap changer 1 is currently in during switching, an electrical connection formed across the first current path 12 and the first switching side 10 of the changeover switch 6 via the first ohmic resistor 14 and / or the first switching element 16 and / or the first steady main contact 18 can be selectively established between the first selector arm 8 and the load lead section 33. Furthermore, the protective device 7 includes a second ohmic resistor 15. The second ohmic resistor 15 can be connected to and disconnected from the second current path 13 by a second switching element 17 arranged in parallel with the ohmic resistor 15. A second steady main contact 19 is arranged in parallel with the second ohmic resistor 15 and the second switching element 17 and is configured to conduct steady current during the steady state of the on-load tap changer 1. Depending on which steady state or switching step the on-load tap changer 1 is currently in during switching, an electrical connection formed across the second current path 13 and the second switching side 11 of the changeover switch 6 via the second ohmic resistor 15 and / or the second switching element 17 and / or the second steady main contact 19 can be selectively established between the second selector arm 9 and the load lead section 33.

[0044] In a typical embodiment, the first switching element 16 and the second switching element 17 are formed as vacuum switching tubes 16 and 17. However, in this case, other mechanical switching elements and / or semiconductor switching elements can also be used.

[0045] The changeover switch 6 has a plurality of changing contacts and a plurality of resistors to perform the switching. However, since the specific circuit configuration of the changeover switch is not an essential element in the implementation of the present invention, the configuration of the changeover switch 6 described below should be interpreted as merely an example, and basically, other suitable and known configurations of changeover switches may be used for the configuration of the present invention. According to a typical embodiment of the present invention, a third steady-state main contact 20 is attached to the first switching side 10 of the changeover switch 6, and a fourth steady-state main contact 21 is attached to the second switching side 11 of the changeover switch 6. The steady-state main contacts 20 and 21 are configured to carry out the steady-state current of the on-load tap changer 1 in a known manner. Furthermore, the first switching side 10 includes a first vacuum switch 34, and a first transition resistor 36 having a second vacuum switch 35 connected in series with the first vacuum switch 34. Similarly, the second switching side 11 includes a second vacuum switch 37, and a second transition resistor 39 having a fourth vacuum switch 38 connected in series with the second vacuum switch 37. Furthermore, a first mechanical switch 40 is provided between the electrical connection portion of both vacuum switch tubes 34 and 35 of the first switching side 10 and the load outlet portion 33, and similarly, a second mechanical switch 41 is provided between the electrical connection portion of both vacuum switch tubes 37 and 38 of the second switching side 11 and the load outlet portion 33.

[0046] In Figure 2, the load-operated tap changer 1 controls the winding tap N. J It is in a steady state where it is connected. Accordingly, the load current is from control winding 4 to winding tap N JThe protective device 7 is energized via the first selector arm 8. In the protective device 7, the load current is further energized via the steady main contact 18 and the first vacuum switch 16, and from there energized via the first current path 12 to the first switching side 10 of the changeover switch 6. There, the load current energizes the load output section 33 via the third steady main contact 20, the vacuum switch 34 and the first mechanical switch 40. If a fault occurs during the steady state of the on-load tap changer 1, the second ohmic resistor 15 is connected, and the short-circuit current generated by the fault can be limited. Therefore, this protection is always passively present during the steady state of the on-load tap changer and does not need to be actively activated in particular by the starting mechanism. Similarly, in the second steady state, i.e., the winding tap N J+1 When the first selector arm 8 is not energized, the first ohmic resistor 14 of the protective device 7 is passively connected.

[0047] Figures 3a to 3h illustrate the switching sequence of the on-load tap changer of the present invention according to Figure 2. Starting from the steady position in Figure 2, in the first switching step shown in Figure 3a, the first steady main contact 18 in the protective device 7 and the third steady main contact 20 in the changeover switch 6 are opened simultaneously, and the second mechanical switch 41 of the changeover switch 6 is closed at the same time. Preferably, the steady main contacts 18 and 20 are operated via mechanical coupling by a common drive unit and / or electronic coupling by a common control unit. In this case, the load current is energized in the protective device 7 only through the first vacuum switch 16 and in the changeover switch 6 only through the first vacuum switch 34. In the next step (see Figure 3b), the first vacuum switch 34 is also opened. As a result, the load current is commutated in the changeover switch 6 to the first transition resistor 36 and the second vacuum switch 35. Subsequently, in the next step, the fourth vacuum switch 38 of the changeover switch 6 is closed (see Figure 3c), and the circulating current is turned to winding tap N JThe first selector arm 8, the first vacuum switch 16 of the protective device 7, the first current path 12, the first transition resistor 36, the second vacuum switch 35 and the first mechanical switch 40 of the switching switch 6 are energized, the second mechanical switch 41, the fourth vacuum switch 38, the second transition resistor 39 and the second current path 13 are energized, and finally the ohmic resistor 15 and the second selector arm 9 of the protective device 7 are energized, and the new winding tap N must be switched. J+1 Returning to the previous step, in this switching step, the second ohmic resistor 15 is used to limit the current. In the next step (see Figure 3d), the second vacuum switch 35 of the switching switch 6 is opened. After that, the load current is exclusively supplied to the new winding tap N J+1 The current then energizes the second selector arm 9 and the second ohmic resistor 15 of the protective device 7, and from there energizes the second switching side 11 of the changeover switch 6 via the second current path 13. There, the current is supplied to the load outlet 33 via the second transition resistor 39, the fourth vacuum switch 38, and the second mechanical switch 41. In the next step shown in Figure 3e, the third vacuum switch 37 of the changeover switch 6 is closed. At this time, the current in the changeover switch 6 is supplied to the load outlet 33 via the third vacuum switch 37 and the second mechanical switch 41. In the next step (see Figure 3f), the fourth steady-state main contact 21 of the changeover switch 6 is closed and the first mechanical switch 40 is opened. Therefore, the load current in the changeover switch is then supplied to the load outlet 33 via the third vacuum switch 37, the fourth steady-state main contact 21, and the second mechanical switch 41. Subsequently, the first vacuum switch 16 of the protective device 7 is opened, and at the same time, the second vacuum switch 17 of the protective device 7 is closed (Figure 3g). At this time, in the protective device 7, the load current is energized through the second vacuum switch 17 without passing through the second ohmic resistor 15. In the final step shown in Figure 3h, the second steady-state main contact 19 of the protective device 7 is closed. Thus, the new steady-state position of the on-load tap changer 1 is achieved, and the switching process is completed. At this time, the load current is directed to the winding tap N J+1Current is supplied from the second selector arm 9, the second vacuum switch 17, and the second steady-state main contact 19 of the protection device 7, and then supplied to the second switching side 11 of the changeover switch 6 via the second current path 13, where it is supplied to the output section 33 via the third vacuum switch 37, the fourth steady-state main contact 21, and the second mechanical switch 41. If a fault occurs during the steady state of the load tap changer 1, the first ohmic resistor 14 is connected, which can limit the short-circuit current generated by the fault.

[0048] As is evident from the described switching sequence, the second ohmic resistor 15 of the protective device 7 is incorporated into the normal switching process of the on-load tap changer 1 (see Figures 3c, 3d, 3e, and 3f). Similarly, the first ohmic resistor 14 of the protective device 7 is incorporated into the reverse switching process, i.e., for example, the winding tap N J+1 From winding tap N J It is incorporated when switching. Incorporating the ohmic resistors 14 and 15 of the protective device 7 into the normal switching process of the on-load tap changer 1 has the advantage that the transition resistors 36 and 39 of the changeover switch 6 can be designed to be small, thereby reducing costs.

[0049] Basically, according to this embodiment, either the first ohmic resistor 14 or the second ohmic resistor 15 of the protection device 7 is connected both during the steady state and during the switching process of the on-load tap changer 1. As a result, passive protection of the on-load tap changer 1 and the transformer 2 is ensured. According to the switching sequence in the switching direction shown in Figures 2 and 3a to 3f, the second ohmic resistor 15 is connected at the positions or switching steps shown in Figures 2 and 3a to 3f, and the first ohmic resistor 14 is connected at the positions or switching steps shown in Figures 3g and 3h. In the reverse switching direction, the ohmic resistors 14 and 15 are connected in the opposite direction.

[0050] Figure 4 schematically illustrates the arrangement of a typical embodiment of the on-load tap changer 1 of the present invention within a tap transformer 2. The protective device 7 is located in a first case 30 filled with an insulating medium (not shown), and the changeover switch 6 is located in a second case 31 filled with an insulating medium (not shown). The selector 6 is located directly below the changeover switch 6. The first case 30 and the second case 31 are located in parallel in a transformer case 32, which is similarly filled with an insulating medium (not shown), and are each located in the transformer case 32 via a single fixing flange 42. The protective device 7, the changeover switch 6, and the selector 5 are mechanically connected via a common drive mechanism. This drive mechanism includes a first gear mechanism 26 attached to the protective device 7, a second gear mechanism 27 attached to the changeover switch 6 and the selector 5, a connecting shaft 28 that mechanically links the first gear mechanism 26 and the second gear mechanism 27, and a drive shaft 29 that mechanically connects the drive unit 22 to the second gear mechanism 27. Accordingly, a common drive unit 22 is provided. This drive unit 22 operates either the protective device 7 or the changeover switch 6 or the selector 5 via the drive shaft 29, the connecting shaft 28, and both gear mechanisms 26 and 27.

[0051] Figure 5 schematically illustrates the arrangement of another typical embodiment of the on-load tap changer 1 of the present invention within the tap transformer 2. The above description of the embodiment shown in Figure 4 applies mutatis mutandis to the embodiment shown in Figure 5, and only the differences will be described below. According to the typical embodiment shown in Figure 5, the protective device 7, the changeover switch 6, and the selector 5 are electronically coupled via a control device 23. The control device 23 operates the first drive unit 24 and the second drive unit 25 in coordination with each other. The first drive unit 24 is mechanically functionally linked with the first gear mechanism 26 attached to the protective device 7 via a first drive shaft 43, and the second drive unit 25 is mechanically functionally linked with the second gear mechanism 27 attached to the changeover switch 6 and the selector 5 via a second drive shaft 44.

[0052] The present disclosure and its many advantages are intended to be understood from the above description. Furthermore, it is clear that the shape, structure, and arrangement of the components can be modified in various ways without departing from the disclosed subject matter or without impairing any substantial advantages. The embodiments described are for illustrative purposes only, and such modifications are covered by the appended claims. Furthermore, it is clear that the invention is defined by the appended claims. [Explanation of symbols]

[0053] 1. On-load tap changer 2-tap transformer 3. Main winding 4 2 control windings 5 Selector 6 Switch switch 7 Protective devices 8. First selector arm 9. Second selector arm 10 6 First switching side 11 6's second switching side 12. First current path 13. Second current path 14 7 First ohmic resistor 15 7 second ohmic resistor 16 7 First switching element 17 7 Second switching element 18 7 First steady-state main contactor 19 7's second steady-state main contactor 20 6 third steady-state main contactor 21 6's fourth steady-state main contactor 22 Drive unit 23 Control device 24 7 drive unit 25 Drive units 5 and 6 26. First gear mechanism 27. Second gear mechanism 28 Connecting shaft 29 22 drive shafts 30 Case 1 31 Case 2 32 Transformer Cases 33 Load derivation section 34 6 No. 1 vacuum switch 35 6 No. 2 vacuum switch 36 6 first transition resistor 37 6 Third vacuum switch tube 38 6 No. 4 vacuum switch 39 6 second transition resistor 40 6 First mechanical switch 41 6 Second mechanical switch 42 Fixing flanges for 30 and 31 43 First drive shaft 44. Second drive shaft

Claims

1. - Selected winding tap (N Ｊ A selector (5) for pre-selecting in a no-current state, - Current winding tap (N Ｊ－１ ) A pre-selected winding tap (N Ｊ ) a changeover switch (6) for actually switching the load, The winding tap (N) of the control winding (4) of the tap transformer (2) １ ... N Ｊ , . . , N Ｎ A load-operated tap changer (1) for switching between ) without interruption, - The protective device (7) is connected in series between the selector (5) and the changeover switch (6), and the protective device (7) is configured to limit the short-circuit current that occurs during a fault in the on-load tap changer (1) and / or the control winding (4).

2. - The selector (5) has a first selector arm (8) and a second selector arm (9), - The changeover switch (6) has a first changing side (10) which is electrically connected to the first selector arm (8) via a first current path (12), and a second changing side (11) which is electrically connected to the second selector arm (9) via a second current path (13). - The protective device (7) is, ○A first resistor (14) that can be connected to the first current path (12) by a first switching element (16) arranged in parallel with the first resistor (14), and can be disconnected from the first current path (12), ○A second resistor (15) that can be connected to the second current path (13) by a second switching element (17) arranged in parallel with the second resistor (15), and can be disconnected from the second current path (13), A load-on tap changer (1) according to claim 1, having the following features.

3. - The on-load tap changer (1) according to claim 2, wherein during the switching process of the on-load tap changer (1), the first resistor (14) is connected to the first current path (12) or the second resistor (15) is connected to the second current path (13).

4. - The on-load tap changer (1) according to claim 2 or 3, wherein the first resistor (14) and / or the second resistor (15) are temporarily energized during the switching process.

5. - When the first selector arm (8) is not energized, the first resistor (14) is connected to or connected to the first current path (12). - An on-load tap changer (1) according to any one of claims 2 to 4, wherein the second resistor (15) is connected to or connected to the second current path (13) when the second selector arm (9) is not energized.

6. The protective device (7) is - A first steady-state main contact (18) is arranged in parallel with the first resistor (14) and the first switching element (16), and is configured to supply a steady-state current during the steady state of the load tap changer (1), - A second steady-state main contact (19) is arranged in parallel with the second resistor (15) and the second switching element (17), and is configured to supply a steady-state current during the steady state of the load tap changer (1), A load tap changer (1) according to any one of claims 2 to 5.

7. The changeover switch (6) is - A third steady-state main contact (20) is attached to the first switching side (10) of the changeover switch (6) and is configured to supply a steady-state current during the steady state of the on-load tap changer (1), - A fourth steady-state main contact (21) is attached to the second switching side (11) of the changeover switch (6) and is configured to supply a steady-state current during the steady state of the on-load tap changer (1), A load-operated tap changer (1) according to any one of claims 2 to 6.

8. - The on-load tap changer (1) according to any one of claims 2 to 7, wherein the protective device (7) and the changeover switch (6) are mechanically connected via a common drive device (22) such that the changing elements (16, 17, 18, 19, 20, 21, 34, 35, 37, 38) are operated in a dependent manner.

9. - The on-load tap changer (1) according to any one of claims 2 to 7, wherein the protective device (7) and the changeover switch (6) are electronically connected via a common control device (23) such that the changing elements (16, 17, 18, 19, 20, 21, 34, 35, 37, 38) are operated in a dependent manner.

10. - The protective device (7) is located in the first case (30), - The changeover switch (6) is located in the second case (31), - The first case (30) is located inside and / or outside the transformer case (32), - The second case (31) is an on-load tap changer (1) according to any one of claims 1 to 9, which is located inside and / or outside the transformer case (32).

11. The winding tap (N) of the control winding (4) of the tap transformer (2) １ ... N Ｊ ,..., N Ｎ A method for operating a load tap changer (1) for switching between them without interruption, The under load tap changer (1) selects the winding tap (N Ｊ A selector (5) for pre-selecting the current winding tap (N Ｊ－１ ) A pre-selected winding tap (N Ｊ The system includes a changeover switch (6) for actually switching the load, and a protective device (7) connected in series between the selector (5) and the changeover switch (6). - Load tap changer (1) is set to the current winding tap (N Ｊ－１ From the first steady state in which it contacts the ), the load-on tap changer (1) changes to a new winding tap (N Ｊ Switched to a second steady state in contact with ), - The protective device (7) is configured to limit the short-circuit current that occurs during a fault in the on-load tap changer (1) and / or control winding (4).

12. - The selector (5) has a first selector arm (8) and a second selector arm (9), - The changeover switch (6) has a first changing side (10) which is electrically connected to the first selector arm (8) via a first current path (12), and a second changing side (11) which is electrically connected to the second selector arm (9) via a second current path (13). - The protective device (7) includes a first resistor (14) which can be connected to and disconnected from the first current path (12) by a first switching element (16) arranged in parallel with the first resistor (14), and a second resistor (15) which can be connected to and disconnected from the second current path (13) by a second switching element (17) arranged in parallel with the second resistor (15), When switching from the first steady state to the second steady state, - The second resistor (15) is connected to or is connected to the second current path (13), - The load current in the load tap changer (1) is switched from the first switching side (10) to the second switching side (11) of the changeover switch (6), - The method according to claim 11, wherein the first resistor (14) is connected to the first current path (12).

13. - The protective device (7) includes a first steady-state main contact (18) arranged in parallel with the first resistor (14) and the first switching element (16), and a second steady-state main contact (19) arranged in parallel with the second resistor (15) and the second switching element (17). - The changeover switch (6) has a third steady-state main contact (20) attached to the first switching side (10) of the changeover switch (6) and a fourth steady-state main contact (21) attached to the second switching side (11) of the changeover switch (6). - When the second resistor (15) is connected to the second current path (13), or after the second resistor (15) is connected to the second current path (13), - The method according to claim 11, wherein the first steady-state main contactor (18) and the third steady-state main contactor (20) are opened simultaneously.

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