On-load tap changer and method for operating the on-load tap changer

Abstract

A plurality of winding taps N1,...,N of the tap transformer 20, having a changeover switch 40 for switching from a first fixed contact 11 to a second fixed contact 12 of the tap transformer 20, a selector 30 for preselecting the fixed contacts 11, 12 in a currentless state, and a first control device 14. J ...,N N an on-load tap changer (10) for uninterruptedly changing between a power supply and a load, the diverter switch (40) comprising a plurality of semiconductor switch elements (47, 48) and a plurality of mechanical switch elements (43, 44) for the changeover; a selector (30) comprising a first selector arm (31) and a second selector arm (32) operable independently of one another and contacting respective fixed contacts of said fixed contacts; a first control device (14) configured to issue changeover commands and to operate the first selector arm (31), the second selector arm (32) and the plurality of mechanical switch elements (43, 44) by means of a motor drive (13); the on-load tap changer (10) comprising a second control device (15) configured to operate the plurality of semiconductor switch elements (47, 48), the first control device (14) operating the motor drive (13) during the changeover depending on the second control device (15).

Description

[Technical Field]

[0001] The present invention relates to an under-load tap changer for switching between multiple winding taps of a tap transformer while a load is applied and no current is being generated. [Background technology]

[0002] An on-load tap changer consists of a mechanical tap selector for pre-selecting each winding tap that needs to be switched in a current-free state, and a switching switch having a semiconductor switching element as a switching means for actually switching the current winding tap to the newly selected winding tap without interruption while a load is still applied.

[0003] This type of on-load tap changer has mechanical contacts in addition to power electronics-based switching mechanisms, and is therefore generally also called a hybrid on-load tap changer.

[0004] Such hybrid on-load tap changers are known from European Patent No. 2319058. This hybrid on-load tap changer has two load branches. Each of these load branches connects one winding tap to a common load short-circuit connection via a series circuit consisting of one mechanical switch and two IGBTs connected in opposite directions and arranged in parallel with the mechanical switch. One diode is provided in parallel with each IGBT. Similarly, one varistor is provided in parallel with each individual IGBT. In steady-state operation, each of these load branches is bypassed by one mechanical steady-state main contact. These IGBTs on both sides are controlled by a common IGBT driver. A drawback of this solution is that the on-load tap changer does not have a monitoring function such as operating the mechanical switching contact only when the availability of the semiconductor switching element is confirmed. If one IGBT fails unnoticed and the switching process continues, it can cause a short circuit between taps, leading to serious and destructive consequences for the under-load tap changer and tap transformer. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] European Patent No. 2319058 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Therefore, the object of the present invention is to provide an improved concept for a hybrid load tap changer that enables failure-free and more reliable operation of the hybrid load tap changer. [Means for solving the problem]

[0007] This problem is solved by the subject matter of each independent claim. Another embodiment is the subject matter of an independent claim.

[0008] The improved concept stems from the idea that multiple mechanical switching contacts are operated depending on the availability of multiple semiconductor switching elements, and that these semiconductor switching elements have one individual control unit that works in cooperation with another control unit that operates these mechanical switching contacts by one motor drive unit.

[0009] According to a first aspect of the improved concept, an on-load tap changer is provided for switching between multiple winding taps of a tap transformer without interruption. The on-load tap changer comprises a changeover switch for switching from a first fixed contact to a second fixed contact of the on-load tap changer, a selector for pre-selecting these fixed contacts in a current-free state before actually switching under load, a first control unit, and a second control unit. The changeover switch comprises a plurality of semiconductor switching elements and a plurality of mechanical switching elements for the switching. The selector comprises a first selector arm and a second selector arm. These selector arms are operable independently of each other and can contact each of their respective fixed contacts. Each fixed contact is electrically connected to one winding tap of the tap transformer. The total number of these fixed contacts depends on the number of winding taps.

[0010] The first control device is configured to issue a switching command and, depending on this switching command, operate the first selector arm, the second selector arm, and the plurality of mechanical switch elements using a motor drive unit. The second control device is configured to operate the plurality of semiconductor switch elements. During the switching of the on-load tap changer, the first control device operates the motor drive unit depending on the second control device.

[0011] This ensures that the switching process in the on-load tap changer and the operation of the multiple mechanical switch elements continue or are performed only when the multiple semiconductor switch elements are properly operated and therefore there is no risk of short circuits between taps.

[0012] The motor drive unit can be configured as a DC motor, a brushless motor, a servo motor, or especially a torque motor. Preferably, the motor drive unit is configured as a stepper motor.

[0013] According to at least one embodiment, the on-load tap changer includes a first sensor for measuring a first measurement value indicating a voltage drop at a first semiconductor switch element, and a second sensor for measuring a second measurement value indicating a voltage drop at a second semiconductor switch element.

[0014] The first sensor is configured to transmit the first measurement value to the second control unit. The second sensor is configured to transmit the second measurement value M2 to the second control unit. Similarly, the second control unit is configured to transmit a status message S to the first control unit depending on the first measurement value and / or the second measurement value M2.

[0015] According to at least one embodiment, the second control device is configured to send a status message "Error" or a status message "OK". For example, if a semiconductor switch element has failed, the status message "Error" indicates that the ON or OFF process of the semiconductor switch element was unsuccessful. The status message "OK" indicates that the ON or OFF process of the semiconductor switch element was executed without error. Ta This indicates that.

[0016] The second control device is -When the first sensor transmits a measurement value that exceeds a preset first limit value within a preset period, - when the first sensor transmits a measurement value that does not exceed a preset second limit value within a preset period, and - when the second sensor transmits a measurement value that does not exceed a preset third limit value within a preset period, and - when the first sensor and / or the second sensor do not transmit a measurement value within a preset period, it is configured to transmit a status message "Error" to the first control device.

[0017] In other cases, the second control device transmits a status message "OK".

[0018] The first limit value is preferably 2 to 10 volts, and particularly preferably, the first limit value is 5 volts.

[0019] The second limit value is preferably 40 to 80 volts, and particularly preferably, the second limit value is 50 volts.

[0020] The third limit value is preferably 40 to 80 volts, and particularly preferably, the third limit value is 50 volts.

[0021] Preferably, the second control device is configured as a microcontroller, and is configured to receive, evaluate the measurement value via an analog input unit and / or by a comparator, and output the status message depending on the evaluation.

[0022] Preferably, the first control device is similarly configured as a microcontroller.

[0023] Preferably, the first sensor and the second sensor are configured as a voltage divider having two ohmic resistors.

[0024] According to at least one embodiment, the first control unit is configured to receive a status message from the second control unit and, depending on the status message and the time in which the status message arrives during the switching process, return the motor drive unit to its initial position or continue the switching. Continuing the switching specifically means that, during further progress of the switching, the multiple mechanical switching elements and the first and / or second selector contacts of the changeover switch are operated by the motor drive unit, for example, via a common drive shaft.

[0025] Preferably, the first control device is -When the first sensor transmits a measurement value to the second control device that exceeds the first limit value within a predetermined period, -When the first sensor transmits a measurement value to the second control device that does not exceed the second limit value within a predetermined period, - The motor drive unit is configured to return to its initial position if the first sensor does not transmit a measurement value to the second control device within a preset period.

[0026] Preferably, the second control device is -When the second sensor transmits a measurement value that exceeds the third limit value within a predetermined period to the second control unit, -The motor drive unit is further configured to operate and continue switching if the second sensor does not transmit a measurement value to the second control unit within a preset period.

[0027] According to at least one embodiment, a status message is transmitted from a second control device to a first control device by optical fiber or wirelessly, for example, via Bluetooth or wireless communication. The optical fiber may be embedded in a synthetic resin, for example, a drive shaft, or it may be configured independently without a coating.

[0028] According to at least one embodiment, the on-load tap changer has a third sensor for measuring a third measurement indicating the time progression of current in a plurality of semiconductor switch elements. The third sensor is configured as a current sensor, and in particular as an AC current sensor.

[0029] The third sensor is configured to transmit the third measurement to the second measuring device. Similarly, the second control device is further configured to turn off a plurality of semiconductor switch elements depending on the third measurement. Here, "depending on the third measurement" specifically means "depending on the time progression of the current supplied to the plurality of semiconductor switch elements." Preferably, the off-step is performed during the zero crossing of the current.

[0030] According to at least one embodiment, the changeover switch comprises a first main branch section that connects the first selector arm to a load-ground connection section via a first mechanical switch element, a second main branch section that connects the second selector arm to the load-ground connection section via a second mechanical switch element, a first auxiliary branch section having a first semiconductor switch element and configured in parallel with the first main branch section, and a second auxiliary branch section having a second semiconductor switch element and configured in parallel with the second main branch section.

[0031] Preferably, the mechanical switch element is configured as a steady-state main contact.

[0032] According to at least one embodiment, a voltage-dependent resistor is arranged in parallel with the first auxiliary branch and / or the second auxiliary branch, or in parallel with the first semiconductor switch element and / or the second semiconductor switch element. The voltage-dependent resistor is configured as a varistor.

[0033] According to at least one embodiment, the on-load tap changer is configured such that neither semiconductor switching element is activated when switching is performed during the operation of the first selector arm and / or the second selector arm.

[0034] According to at least one embodiment, the on-load tap changer is configured such that when switching is performed during the operation of the plurality of semiconductor switch elements, the first selector arm and the second selector arm are in contact with different fixed contacts.

[0035] According to at least one embodiment, the second control unit has a power storage unit that is charged when the first selector arm and the second selector arm are in contact with adjacent, different fixed contacts. This charging is performed by a tap voltage generated at a described position between the first and second selector arms. The power storage unit supplies the power necessary to operate the plurality of semiconductor switch elements and transmits status messages from the second control unit to the first control unit. Thus, the second control unit and the plurality of semiconductor switch elements are operated independently by the generated tap voltage. Therefore, no additional power supply from an external source, such as the first control unit, is required.

[0036] The energy storage unit is preferably composed of a ceramic capacitor and therefore has high heat resistance. Since the energy storage unit is continuously recharged while the second control device and the plurality of semiconductor switching elements are in operation, the energy storage unit only needs to be protected from the maximum load that occurs. To charge the energy storage unit, a switching power supply having an extremely wide input voltage range that functions even at low tap voltages is preferably used for charging.

[0037] Preferably, the second control device is configured to monitor the charging of the energy storage unit by measuring the voltage at the analog input unit and to send a status message "OK" to the first control device when the energy storage unit is fully charged. Preferably, the first control device is configured to return the motor drive unit to its initial position if the status message does not arrive within a preset period.

[0038] According to at least one embodiment, the plurality of semiconductor switching elements are configured as IGBT switching elements and / or thyristors and / or MOSFET switching elements and / or integrated gate commutation thyristors (IGCTs). Preferably, each of the plurality of semiconductor switching elements is configured as an IGBT having a diode in a bridge circuit, and particularly preferably as an IGBT having a diode in a full-wave bridge circuit.

[0039] According to at least one embodiment, the first control device is positioned above the motor drive unit with respect to the longitudinal axis L of the on-load tap changer, and the second control device is positioned below the changeover switch with respect to the longitudinal axis L of the on-load tap changer.

[0040] Preferably, the first control device is located outside the housing of the tap transformer. The motor drive unit and / or semiconductor switch element and / or second control device can be located outside or inside the housing of the transformer.

[0041] According to at least one other embodiment, the on-load tap changer further comprises second and third changeover switches, second and third selectors, and second and third control devices for the second and third phases to be adjusted of the tap transformer. A plurality of semiconductor switch elements of each changeover switch are each attached to a second control device. The first control device is configured to issue a switching command and to operate the first selector arm and the second selector arm of each selector, and the plurality of mechanical switch elements of each changeover switch, by a single motor drive unit. Each second control device is configured to operate a plurality of semiconductor switch elements assigned to it. In this case, during the switching, the first control device operates the motor drive unit depending on the respective second control device.

[0042] According to at least one other embodiment, the on-load tap changer further comprises second and third motor drive units, second and third changeover switches, second and third selectors, and second and third second control devices for the second and third phases of the tap transformer to be adjusted. Each selector, i.e., a first selector arm and a second selector arm, and each of the mechanical switch elements of the changeover switch, are attached to the respective motor drive unit for operation. This attachment is performed mechanically, for example, by a drive shaft and a gear mechanism. Each of the semiconductor switch elements of the changeover switch is assigned to a second control device. The first control device is configured to issue switching commands and operate the respective motor drive units, the attached first selector arm and second selector arm, and the attached mechanical switch elements. Each second control device is configured to operate the semiconductor switch elements assigned to it. In this case, the first control device operates each motor drive unit during the switching process, depending on the respective second control device.

[0043] According to a second aspect of the improved concept, a method is provided for operating an on-load tap changer configured according to a first aspect of the improved concept.

[0044] As has already been described with respect to the first aspect of the improved concept or one embodiment of one of several associated preferred embodiments, the above description, preferred features and / or advantages also apply to the method.

[0045] This method is - The first control device generates a switching command to switch from the first fixed contact to the second fixed contact of the on-load tap changer, - A step of operating one or more mechanical switch elements, one first selector arm, and one second selector arm by a motor drive unit and dependent on the first control device, - The step of operating one or more semiconductor switch elements with a second control device.

[0046] In this case, the motor drive unit is operated by the first control device in reliance on the second control device during switching.

[0047] According to at least one embodiment, during operation of the first selector arm and / or the second selector arm, none of the semiconductor switch elements of the plurality of semiconductor switch elements are activated.

[0048] According to at least one embodiment, the method is - Another step of measuring at least one first measurement indicating the voltage drop at the first semiconductor switch element and transmitting the first measurement to the second control device by the first sensor, -Another step of measuring at least one second measurement indicating the voltage drop at the second semiconductor switch element and transmitting the second measurement to the second control device by the second sensor, -Another step of transmitting a status message to the first control unit by the second control unit, depending on the first measurement and / or the second measurement; -The motor drive unit is operated by the first control device in accordance with the status message.

[0049] According to at least one embodiment, the operation of the mechanical switch element, the selector arm, and the semiconductor switch element after the generation of the switching command is as follows: -The motor drive unit opens the second mechanical switch element and switches the second selector arm to the second fixed contact, - A step of charging the energy storage unit of the second control device, - The step of turning on the first semiconductor switch element with the second control device, - The step of opening the first mechanical switch element with the motor drive unit, - The step of turning off the first semiconductor switch element with the second control device, - The step of turning on the second semiconductor switch element with the second control device, - The step of closing the second mechanical switch element with the motor drive unit, - The step of turning off the second semiconductor switch element with the second control device, - A step of switching the first selector arm from the first fixed contact to the second fixed contact, -The step of closing the first mechanical switch element.

[0050] According to at least one other embodiment, the first semiconductor switching element is turned off in a time-dependent manner to the current. Preferably, the off-step is performed during the zero crossing of the current.

[0051] According to at least one other embodiment, after the second semiconductor switch element is turned on, the switching continues in any case, independent of the status message of the second control device.

[0052] Other embodiments and implementations of the method can be directly derived from various embodiments of on-load tap changers. In particular, the individual and / or multiple components and / or apparatus for carrying out the method described in relation to on-load tap changers may be configured according to the method.

[0053] The present invention will be described in detail below with reference to the drawings, based on representative embodiments. Components that are equivalent, functionally equivalent, or have equivalent effects may be denoted by the same reference numerals. Equivalent components or components with equivalent functions are described only in the first drawing where they appear, as necessary. Consequently, such descriptions are not repeated in subsequent drawings. [Brief explanation of the drawing]

[0054] [Figure 1]A typical embodiment of an on-load tap changer is schematically shown. [Figure 2] A typical configuration of a representative embodiment of an on-load tap changer based on an improved design within a tap transformer is schematically shown. [Figure 3] A typical embodiment of an on-load tap changer based on an improved design is schematically shown. [Figure 4a] Figure 3 shows a typical switching sequence for an on-load tap changer. [Figure 4b] Figure 3 shows a typical switching sequence for an on-load tap changer. [Figure 4c] Figure 3 shows a typical switching sequence for an on-load tap changer. [Figure 4d] Figure 3 shows a typical switching sequence for an on-load tap changer. [Figure 4e] Figure 3 shows a typical switching sequence for an on-load tap changer. [Figure 4f] Figure 3 shows a typical switching sequence for an on-load tap changer. [Figure 4g] Figure 3 shows a typical switching sequence for an on-load tap changer. [Figure 4h] Figure 3 shows a typical switching sequence for an on-load tap changer. [Figure 4i] Figure 3 shows a typical switching sequence for an on-load tap changer. [Figure 4j] Figure 3 shows a typical switching sequence for an on-load tap changer. [Figure 4k] Figure 3 shows a typical switching sequence for an on-load tap changer. [Figure 4l] Figure 3 shows a typical switching sequence for an on-load tap changer. [Figure 4m] Figure 3 shows a typical switching sequence for an on-load tap changer. [Figure 5]A schematic diagram shows a typical configuration of another representative embodiment of an on-load tap changer based on an improved design concept within a tap transformer. [Modes for carrying out the invention]

[0055] The drawings merely illustrate embodiments of the present invention, and are not limited to the illustrated embodiments.

[0056] Figure 1 schematically shows a typical embodiment of an on-load tap changer 10 for a tap transformer 20. The tap transformer 20 consists of a main winding 21 and several different winding taps N1,...,N that are connected or disconnected by the on-load tap changer 10. J ...,N N The load tap changer 10 is equipped with an adjustable winding 22 having the following characteristics. Therefore, the load tap changer 10 controls the different winding taps N1,...,N of the winding 22 by two movable selector contacts. J ...,N N It has a selector 30 that can be contacted and a changeover switch 40 that actually switches the load from the currently connected winding tap to a new winding tap that has been pre-selected. The load current is connected to the currently connected winding tap N J or N J+1 Current is supplied from each of the selector contacts and the changeover switch 40 toward the load grounding connection part 17.

[0057] Figure 2 schematically shows a typical configuration of a typical embodiment of an on-load tap changer based on an improved design concept within a tap transformer.

[0058] The on-load tap changer 10 includes a selector 30 (not shown) for pre-selecting fixed contacts in a current-free state, a changeover switch 40 (not shown) for actually switching the load using a plurality of mechanical switch elements and a plurality of semiconductor switch elements, a motor drive unit 13, a first control device 14, and a second control device 15. Furthermore, the on-load tap changer 10 has three sensors located within the changeover switch 40. Two sensors 51 and 52 are voltage sensors and are configured to transmit measured values ​​M1 and M2, which indicate the voltage drop at the semiconductor switch elements, to the second control device 15. A third sensor 53 is a current sensor and is configured to transmit a third measured value M3, which indicates the time progression of the current at the semiconductor switch element, to the second control device 15. Furthermore, the second control device 15 has a power storage unit 18 located directly within the second control device 15. In this example, the first control device 14 is positioned above the motor drive unit 13 and outside the tap transformer 20 with respect to the longitudinal axis L of the on-load tap changer 10. In this case, the second control device 15 and the energy storage unit 18 are positioned below the changeover switch 40 with respect to the longitudinal axis L.

[0059] Figure 3 schematically shows a typical embodiment of an on-load tap changer based on the improved design.

[0060] According to the improved design, the on-load tap changer 10 has at least one fixed contact 11 and one second fixed contact 12, which can be connected to the winding taps of the regulating winding 22 of the tap transformer 20, respectively. The total number of these fixed contacts depends on the number of winding taps. Each fixed contact 11, 12 has a first contact surface and a second contact surface. Furthermore, the on-load tap changer 10 includes selectors having a first selector arm 31 and a second selector arm 32 that are independently operable and can contact each of these fixed contacts. In this case, the first movable contact 31 can contact the first contact surface of these fixed contacts 11, 12, but not the second contact surface. Accordingly, the second contact 32 can contact the second contact surface of these fixed contacts 11, 12, but not the first contact surface. Figure 3 shows an overview of a typical embodiment of an on-load tap changer, and it is important to note that the arrangement of these opposing contact surfaces is not necessarily required.

[0061] The load tap changer 10 further includes a changeover switch 40 that actually switches the load between pre-selected fixed contacts 11 and 12. The changeover switch 40 has a total of four current branching sections. The first main branching section 41 connects the first selector arm 31 to the load ground connection section 17 via the first mechanical switch element 43. The second main branching section 42 connects the second selector arm to the load ground connection section 17 via the second mechanical switch element 44. The first auxiliary branching section 45, which has a first semiconductor switch element 47, is arranged in parallel with the first main branching section 41, and the second auxiliary branching section 46, which has a second semiconductor switch element 48, is arranged in parallel with the second main branching section 42. Furthermore, one varistor 49 is provided in parallel with the first auxiliary branching section 45 and the second auxiliary branching section 46, respectively.

[0062] A first sensor 51, configured as a voltage sensor, is arranged in parallel with the first mechanical switch element 43. Correspondingly, a second sensor 52, similarly configured as a voltage sensor, is arranged in parallel with the second mechanical switch element 44. A third sensor 53, configured as a current sensor, is arranged at the common load grounding connection point.

[0063] Two control devices are provided to operate the on-load tap changer 10. The first control device 14 is configured to issue switching commands and operate the first selector arm 31 and the second selector arm 32, as well as the first mechanical switch element 43 and the second mechanical switch element 44, by a motor drive unit (not shown). Switching commands are issued to maintain the primary or secondary voltage of the tap transformer 20 within a predetermined voltage band. For this purpose, a voltage regulator 50 is provided to monitor the maintenance of the predetermined voltage band. Furthermore, the second control device 15 of the on-load tap changer 10 is configured to operate the first semiconductor switch element 47 and the second semiconductor switch element 48. For this purpose, the second control device 15 has a power storage unit (not shown). When the first selector arm 31 and the second selector arm 32 contact adjacent different fixed contacts 11 and 12, the power storage unit is charged by the voltage difference generated between the first selector arm 31 and the second selector arm 32. The first control device 14 receives a status message S from the second control device 15. The first control device 14 operates a motor drive unit (not shown) depending on the status message.

[0064] In the embodiment shown in Figure 3, the load tap changer 10 is in a steady position. The first selector arm 31 and the second selector arm 32 are both on the fixed contact 11. As a result, the second control device 15 is in a no-current state, and therefore the semiconductor switch elements 45 and 46 are in a stopped state. The load current IL flows in the same proportion from the contacted fixed contact 11 to the load ground connection 17 through both selector arms 31, 32, the first main branch section 41 and the second main branch section 42, and the closed mechanical switch elements 43 and 44.

[0065] Figures 4a to 4m show typical switching sequences for an under-load tap changer according to Figure 3.

[0066] After the first control device 14 generates a switching command, the motor drive unit is operated, which causes the second mechanical switch element 44 to open first (Figure 4a).

[0067] Next, the second selector arm 32 is moved from the first fixed contact 11 to the second fixed contact 12 (Figure 4b).

[0068] In Figure 4c, both selector arms 31 and 32 are on different fixed contacts 11 and 12 at this point, and the motor drive unit 13 stops. The (not shown) energy storage unit has a tap voltage U at this point. SP The battery is charged by the battery, and therefore power is supplied to the second control unit 15 to operate the semiconductor switch elements 45 and 46. After the battery is charged, the second control unit 15 sends a status message S "OK" to the first control unit 14. If this signal does not arrive within a preset time, for example 50 ms, the first control unit 14 instructs the motor drive unit 13 to return to its initial position.

[0069] If the switching process proceeds normally, in the next step, the first semiconductor switch element 47 is turned on by the second control device 15, as shown in Figure 4d. At this point, the resistance of the first semiconductor switch element 47 is much greater than that of the first mechanical switch element 43, so no large current flows through the first semiconductor switch element 47.

[0070] Simultaneously, the first control device 14 operates the motor drive unit 13 again, after which the first mechanical switch element 43 opens (Figures 4e and 4f). After that, the motor drive unit 13 is stopped again.

[0071] The steps shown in Figures 4d to 4f are monitored by the second control device 15 using the first voltage sensor 51. The first voltage sensor 51 measures the voltage drop across the first semiconductor switch element 47 and transmits this first measured value M1 to the second control device 15. When the load current is applied to the first semiconductor switch element 47, the voltage becomes several volts, for example, 5 volts. In this case, the second control device 15 transmits a status message S "OK" to the first control device 14, and the switching process continues normally. However, if the first semiconductor switch element 47 is faulty, an arc occurs when the first mechanical switch element 43 is opened. In this case, the voltage becomes several times larger, for example, 20 volts. In this case, the second control device 15 transmits a status message S "Error" to the first control device 14. The first control device 14 then instructs the motor drive unit 13 to return to its initial position.

[0072] If the switching process proceeds normally, in the next step (4g), the time progression of the current in the first semiconductor switch element 47 is monitored by the second control device 15 using the current sensor 53. The first semiconductor switch element 47 is turned off during the zero crossing of the current (Figure 4g).

[0073] The disconnection process of the first semiconductor switch element 47 is monitored by the second control device 15 using the first voltage sensor 51. When the first semiconductor switch element 47 is successfully turned off, the load current further energizes the varistors 49, which are arranged in parallel with the semiconductor switch elements 47 and 48, as shown in Figure 4h. This increases the voltage drop across the first semiconductor switch element 47, i.e., increases the forward voltage of the varistor to several hundred volts. The second control device 15 monitors whether the voltage exceeds a predetermined threshold, for example, 50V, within a predetermined period. If the voltage exceeds a predetermined threshold, for example, 50V, within a predetermined period, the second control device 15 sends a status message S "OK" to the first control device 14, and the switching process continues normally. If, however, the voltage remains below a predetermined limit, this is a sign of an abnormality in the disconnection function of the first semiconductor switch element 47, and the second control device 15 sends a status message S "Error" to the first control device 14. The first control device 14 then instructs the motor drive unit 13 to return to its initial position.

[0074] If the disconnection process for the first semiconductor switch element 47 is successful, the second semiconductor switch element 48 is immediately connected by the second control device 15.

[0075] The voltage drop across the second semiconductor switch element 48 is monitored using the second voltage sensor 52, and this step is also monitored again by the second control device 15. When the voltage drops to the forward voltage of the second semiconductor switch element 48, the connection is successful, and the load current flows to the second auxiliary branch 46, as shown in Figure 4i. The second control device 15 monitors whether the voltage dropping across the second semiconductor switch element 48 falls below a predetermined threshold, for example, 50V, within a predetermined period. If the voltage falls below the predetermined threshold, for example, 50V, within a predetermined period, the second control device 15 sends a status message S "OK" to the first control device 14, and the switching process continues normally. If the voltage does not fall below the predetermined threshold, for example, 50V, within a predetermined period, the second control device 15 recognizes an abnormality and sends a status message "Error" to the first control device 14. However, the switching process is no longer interrupted from this point onward. This is because the load switching process is already halfway complete, and returning to the initial position requires greater control effort.

[0076] Therefore, the first control device 14 instructs the motor drive unit 13 to continue. In this case, the second mechanical switch element 44 is closed first (Figure 4j).

[0077] Next, the second control device 15 de-conducts the second semiconductor switch element 48 (Figure 4k). The second semiconductor switch element 48 is de-conducted based on the detection of a decrease in the voltage drop across the second semiconductor switch element 48 as a result of the second mechanical switch element 44 closing. However, the timing of this de-conductivity is not important. This is because voltage is no longer supplied to the second control device 15 and the voltage in the energy storage unit decreases, so this de-conductivity is performed last.

[0078] In the next step, as a result of further operation of the motor drive unit 13, the first selector arm 31 is moved from the first fixed contact 11 to the second fixed contact 12 (Figure 4l).

[0079] This eliminates the need to supply voltage to the second control device 15. Finally, during the further movement of the motor drive unit 13, the first mechanical switch element 43 is also closed again (Figure 4m). Thus, the switching process is completed. The under-load tap changer 10 is once again in the steady position. In this steady position, both selector arms 31 and 32 are on the fixed contact 12.

[0080] The switching process is performed similarly in the opposite direction.

[0081] Figure 5 schematically shows a typical arrangement of another representative embodiment of an on-load tap changer based on an improved design concept within a tap transformer.

[0082] In this embodiment, the on-load tap changer 10 further includes second and third motor drive units 13, second and third changeover switches 40, second and third selectors 30, and second and third control devices 15 each having one energy storage unit 18 for the second and third phases to be adjusted (not shown) of the tap transformer 20. Each selector 30, i.e., a first selector arm and a second selector arm (not shown), and each of the (not shown) mechanical switch elements of the changeover switch 40 are attached to the respective motor drive unit 13 for operation. Each of the (not shown) semiconductor switch elements of the changeover switch 40 is attached to one second control device 15. One first central control device 14 is provided for all three phases. This first central control device 14 is configured to issue switching commands and operate each motor drive unit 13 depending on the respective second control device 15 attached to the corresponding phase.

[0083] The disclosure herein and the advantages accompanying such disclosure should be noted as being understood by the description herein. Further, it is clear that various changes can be made to the form, construction, and arrangement of the components without departing from the disclosed subject matter or omitting the advantages of all materials. The described embodiments are merely illustrative, and such changes are included within the scope of the appended claims. Further, it can be seen that the present invention is defined by the appended claims. Although this application relates to the invention described in the claims, it may also encompass the following configurations as other embodiments. 1. A changeover switch (40) for switching from the first fixed contact (11) to the second fixed contact (12) of the tap transformer (20), A selector (30) for pre-selecting the fixed contacts (11, 12) in a current-free state, and a first control device (14), comprising a tap transformer (20) with multiple winding taps (N 1 ,...,N J ...,N N The on-load tap changer (10) for switching between ) without interruption, The aforementioned changeover switch (40) has a plurality of semiconductor switch elements (47, 48) and a plurality of mechanical switch elements (43, 44) for the purpose of switching, The selector (30) has a first selector arm (31) and a second selector arm (32) that can be operated independently of each other and can contact each of the fixed contacts of these fixed contacts. The first control device (14) is configured to issue a switching command and operate the first selector arm (31), the second selector arm (32), and the plurality of mechanical switch elements (43, 44) by the motor drive unit (13), The on-load tap changer (10) has a second control device (15) configured to operate the plurality of semiconductor switch elements (47, 48), During the switching, the first control device (14) operates the motor drive unit (13) of the load tap changer (10) in accordance with the second control device (15). 2. A first sensor (51) for measuring a first measurement value M1 indicating the voltage drop at the first semiconductor switch element (47), The on-load tap changer (10) according to claim 1, further comprising a second sensor (52) for measuring a second measured value M2 indicating a voltage drop at a second semiconductor switch element (48), The first sensor (51) is configured to transmit the first measurement value M1 to the second control device (15), and the second sensor (52) is configured to transmit the second measurement value M2 to the second control device (15). The second control device (15) is configured to send a status message S to the first control device (14) on load tap changer (10) depending on the first measurement value M1 and / or the second measurement value M2. 3. The first control device (14) is configured to receive the status message S from the second control device (15) and, depending on the status message S, return the motor drive unit (13) to its initial position or continue switching, as described in paragraph 2 above. 4. The status message S is transmitted by optical fiber or wirelessly to the on-load tap changer (10) described in 3 above. 5. A load tap changer (10) according to any one of 1 to 4, further comprising a third sensor (53) for measuring a third measured value M3 indicating the time progression of current in the plurality of semiconductor switch elements (47, 48), The third sensor (53) is configured to transmit the third measurement value M3 to the second control device (15), The second control device (15) is further configured to disconnect the semiconductor switch elements (47, 48) depending on the second measured value M2, as described in any one of the above 1 to 4, for the on-load tap changer (10). 6. The aforementioned changeover switch (40) is The first selector arm (31) is connected to the load ground connection part (17) via the first mechanical switch element (43) in the first main branch section (41), The second selector arm (32) is connected to the load grounding connection part (17) via the second mechanical switch element (44) in the second main branch section (42), A first auxiliary branch section (45) having a first semiconductor switch element (47) is configured in parallel with the first main branch section (41), The on-load tap changer (10) according to claim 1, further comprising a second auxiliary branch section (46) having a second semiconductor switch element (48) configured in parallel with the second main branch section (42). 7. The load tap changer (10) according to 6 above, wherein a voltage-dependent resistor (49) is arranged in parallel with the first auxiliary branch section (45) and / or the second auxiliary branch section (46). 8. The second control device (15) is an on-load tap changer (10) according to any one of 1 to 7 above, having a power storage unit (18) that is charged when the first selector arm (31) and the second selector arm (32) are in contact with different fixed contacts. 9. The semiconductor switch elements (47, 48) are configured as IGBT switch elements and / or thyristors in the on-load tap changer (10) according to any one of 1 to 8 above. 10. The first control device (14) is positioned above the motor drive unit (13) with respect to the longitudinal axis L of the load tap changer (10), The on-load tap changer (10) according to any one of claims 1 to 9 above, characterized in that the second control device (15) is positioned below the changeover switch (40) with respect to the longitudinal axis L of the on-load tap changer (10). 11. With respect to the second and third phases to be adjusted of the tap transformer (20), The second and third changeover switches (40), The second and third selectors (30), A load tap changer (10) according to any one of 1 to 10 above, having a second and a third control device (15), Each of the multiple semiconductor switch elements (47, 48) of each changeover switch (40) is attached to a second control device (15), The first control device (14) is configured to issue a switching command and operate the first selector arm (31) and the second selector arm (32) of each selector (30) and the plurality of mechanical switch elements (43, 44) of each changeover switch (40) with at least one motor drive unit (13). Each second control device (15) is configured to operate a plurality of semiconductor switch elements (47, 48) assigned to the second control device (15), During the switching, the first control device (14) operates the load tap changer (10) which relies on each of the second control devices (15) to operate the at least one motor drive unit (13). 12. The steps include: generating a switching command by the first control device (14) for switching the first fixed contact (11) to the second fixed contact (12) of the load tap changer (10); and operating one or more mechanical switch elements (43, 44), one first selector arm (31), and one second selector arm (32) by one motor drive unit (13) and dependent on the first control device (14); A method for operating an on-load tap changer (10) configured in particular according to any one of the above 1 to 11, comprising the step of operating one or more semiconductor switch elements (47, 48) with a second control device (15), The motor drive unit (13) is operated by the first control device (14) in reliance on the second control device (15) during switching. 13. The method according to 12, wherein none of the semiconductor switch elements of the plurality of semiconductor switch elements are operating while the first selector arm (31) and / or the second selector arm (32) are being operated. 14. Another step is to measure at least one first measurement value M1 indicating the voltage drop at the first semiconductor switch element (47) (see reference 1 above) using the first sensor (51), and to transmit the first measurement value M1 to the second control device (15), Another step is to measure at least one second measurement value M2 indicating the voltage drop at the second semiconductor switch element (48) using the second sensor (52), and to transmit the second measurement value M2 to the second control device (15), Another step is to transmit a status message S to the first control device (14) by the second control device (15) depending on the first measurement value M1 and / or the second measurement value M2, The method according to 12, further comprising the step of operating the motor drive unit (13) by the first control device (14) in accordance with the status message S. 15. The operation of the mechanical switch elements (43, 44), the selector arms (31, 32), and the semiconductor switch elements (47, 48) after the generation of the switching command is as follows: The motor drive unit (13) opens the second mechanical switch element (44) and switches the second selector arm (32) to the second fixed contact (12), The steps include charging the energy storage unit (18) of the second control device (15), The steps include turning on the first semiconductor switch element (47) with the second control device (15), The first mechanical switch element (43) is opened by the motor drive unit (13), The first semiconductor switch element (47) is turned off by the second control device (15), The steps include turning on the second semiconductor switch element (48) with the second control device (15), The steps include closing the second mechanical switch element (44) with the motor drive unit (13), The steps include turning off the second semiconductor switch element (48) with the second control device (15), The steps include switching the first selector arm (31) from the first fixed contact (11) to the second fixed contact (12), The method according to 12, further comprising the step of closing the first mechanical switch element (43). 16. The method described in 15, wherein the first semiconductor switch element (47) is turned off depending on the time progression of the current. 17. The method according to 15, wherein, after the second semiconductor switch element (48) is turned on, the switching is continued in all cases without depending on the status message S of the second control device (15). [Explanation of symbols]

[0084] 10. On-load tap changer 11 1st fixed contact 12 2nd fixed contact 13 Motor drive unit 14. First Control Device 15. Second control device 16 1st fixed contact 17. Load grounding connection 18. Energy Storage Unit 20-tap transformer 21 Main winding 22 Adjustment winding 30 Selectors 31 First selector arm 32. Second selector arm 40 Switch switch 41. First Main Branch 42 Second Main Branch 43. First mechanical switching element 44. Second mechanical switching element 45. First Auxiliary Branch 46 Second Auxiliary Branch 47. First Semiconductor Switching Element 48. Second Semiconductor Switching Element 49 Voltage-dependent resistors 50 Voltage Regulator 51 First Sensor 52 Second Sensor 53 Third Sensor (N1,...,N J ...,N N ) Wire-wound tap S Status message M1 First measurement value M2 Second measurement value M3 3rd measurement value L Long axis

Claims

1. A tap transformer (20) has a changeover switch (40) for switching from a first fixed contact (11) to a second fixed contact (12), a selector (30) for pre-selecting the fixed contacts (11, 12) in a no-current state, and a first control device (14), and multiple winding taps (N １ , . . , N Ｊ ..., N Ｎ A load tap changer (10) for switching between ) without interruption, The aforementioned changeover switch (40) has a plurality of semiconductor switch elements (47, 48) and a plurality of mechanical switch elements (43, 44) for switching, The selector (30) has a first selector arm (31) and a second selector arm (32), and the first selector arm (31) and the second selector arm (32) are operable independently of each other and can contact each of the fixed contacts of the fixed contacts. The first control device (14) is configured to issue a switching command and operate the first selector arm (31), the second selector arm (32), and the plurality of mechanical switch elements (43, 44) by the motor drive unit (13), The on-load tap changer (10) includes a second control device (15) configured to operate the plurality of semiconductor switch elements (47, 48), The system includes a first sensor (51) for measuring a first measurement value M1 indicating the voltage drop at a first semiconductor switch element (47), and a second sensor (52) for measuring a second measurement value M2 indicating the voltage drop at a second semiconductor switch element (48). The second control device (15) is configured to transmit a status message S to the first control device (14) depending on the first measurement value M1 and / or the second measurement value M2. The first control device (14) is configured to return the motor drive unit (13) to its initial position or continue switching during the switching of the on-load tap changer (10), depending on a status message S from the second control device (15).

2. The load tap changer (10) according to claim 1, wherein the first sensor (51) is configured to transmit the first measurement value M1 to the second control device (15), and the second sensor (52) is configured to transmit the second measurement value M2 to the second control device (15).

3. The status message S is transmitted by optical fiber or wirelessly to the on-load tap changer (10) according to claim 1 or 2.

4. A load tap changer (10) further having a third sensor (53) for measuring a third measured value M3 that shows the time change of current in the plurality of semiconductor switch elements (47, 48), The third sensor (53) is configured to transmit the third measurement value M3 to the second control device (15), The on-load tap changer (10) according to any one of claims 1 to 3, wherein the second control device (15) is further configured to disconnect the semiconductor switch elements (47, 48) depending on a second measured value M2 indicating a voltage drop at the second semiconductor switch element (48).

5. The aforementioned changeover switch (40) is The first selector arm (31) is connected to the load ground connection part (17) via the first mechanical switch element (43) in the first main branch section (41), The second selector arm (32) is connected to the load grounding connection part (17) via the second mechanical switch element (44) in the second main branch section (42), A first auxiliary branch section (45) having a first semiconductor switch element (47) is configured in parallel with the first main branch section (41), The on-load tap changer (10) according to claim 1, further comprising a second auxiliary branch section (46) having a second semiconductor switch element (48) configured in parallel with the second main branch section (42).

6. The on-load tap changer (10) according to claim 5, wherein a voltage-dependent resistor (49) is arranged in parallel with the first auxiliary branch section (45) and / or the second auxiliary branch section (46).

7. The on-load tap changer (10) according to any one of claims 1 to 6, wherein the second control device (15) has a power storage unit (18) that is charged when the first selector arm (31) and the second selector arm (32) are in contact with different fixed contacts.

8. The on-load tap changer (10) according to any one of claims 1 to 7, wherein the semiconductor switch elements (47, 48) are configured as IGBT switch elements and / or thyristors.

9. The first control device (14) is positioned above the motor drive unit (13) with respect to the longitudinal axis L of the load tap changer (10), The on-load tap changer (10) according to any one of claims 1 to 8, characterized in that the second control device (15) is positioned below the changeover switch (40) with respect to the longitudinal axis L of the on-load tap changer (10).

10. With respect to the second and third phases to be adjusted in the tap transformer (20), The second and third changeover switches (40), The second and third selectors (30), A load tap changer (10) according to any one of claims 1 to 9, comprising a second and a third control device (15), Each of the multiple semiconductor switch elements (47, 48) of each changeover switch (40) is attached to a second control device (15), The first control device (14) is configured to issue a switching command and operate the first selector arm (31) and the second selector arm (32) of each selector (30) and the plurality of mechanical switch elements (43, 44) of each changeover switch (40) with at least one motor drive unit (13), Each second control device (15) is configured to operate a plurality of semiconductor switch elements (47, 48) assigned to the second control device (15), During the switching, the first control device (14) operates the load-on tap changer (10) depending on the second control device (15) for at least one motor drive unit (13).

11. A method for operating an on-load tap changer (10) configured according to any one of claims 1 to 10, comprising the steps of: generating a switching command by a first control device (14) for switching the on-load tap changer (10) from a first fixed contact (11) to a second fixed contact (12); operating one or more mechanical switch elements (43, 44), one first selector arm (31), and one second selector arm (32) by one motor drive unit (13) and dependent on the first control device (14); and operating one or more semiconductor switch elements (47, 48) by one second control device (15), wherein The motor drive unit (13) is operated by the first control device (14) in reliance on the second control device (15) during switching.

12. The method according to claim 11, wherein none of the semiconductor switch elements of the plurality of semiconductor switch elements are operating while the first selector arm (31) and / or the second selector arm (32) are being operated.

13. Another step is to measure at least one first measurement value M1 indicating the voltage drop at the first semiconductor switch element (47) using the first sensor (51), and to transmit the first measurement value M1 to the second control device (15), Another step is to measure at least one second measurement value M2 indicating the voltage drop at the second semiconductor switch element (48) using the second sensor (52), and to transmit the second measurement value M2 to the second control device (15), Another step is to transmit a status message S to the first control device (14) by the second control device (15) depending on the first measurement value M1 and / or the second measurement value M2, The method according to claim 11, further comprising the step of operating the motor drive unit (13) by the first control device (14) in accordance with the status message S.

14. The operation of the mechanical switch elements (43, 44), the selector arms (31, 32), and the semiconductor switch elements (47, 48) after the generation of the switching command is as follows: The first control device (14) opens the second mechanical switch element (44) and switches the second selector arm (32) to the second fixed contact (12), The steps include charging the energy storage unit (18) of the second control device (15), The steps include turning on the first semiconductor switch element (47) with the second control device (15), The first mechanical switch element (43) is opened by the first control device (14), The first semiconductor switch element (47) is turned off by the second control device (15), The steps include turning on the second semiconductor switch element (48) using the second control device (15), The steps include closing the second mechanical switch element (44) with the first control device (14), The steps include turning off the second semiconductor switch element (48) with the second control device (15), The first selector arm (31) is switched from the first fixed contact (11) to the second fixed contact (12), The method according to claim 11, further comprising the step of closing the first mechanical switch element (43).

15. The method according to claim 14, wherein the first semiconductor switch element (47) is turned off depending on the time progression of the current in the plurality of semiconductor switch elements (47, 48).

16. The method according to claim 14, wherein, after the second semiconductor switch element (48) is turned on, the switching of the second mechanical switch element (44), the second semiconductor switch element (48), the first selector arm (31), and the first mechanical switch element (43) is continued in all cases without depending on the status message S of the second control device (15).

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