EP4661042A1

EP4661042A1 - On-load tap changer, transformer and operating method

Info

Publication number: EP4661042A1
Application number: EP24180210.7A
Authority: EP
Inventors: Todor Panteleev Kokev; Veselin NIKOLOV; Petar Hranov
Original assignee: Hitachi Energy Ltd
Current assignee: Hitachi Energy Ltd
Priority date: 2024-06-05
Filing date: 2024-06-05
Publication date: 2025-12-10
Also published as: WO2025252369A1

Abstract

In one embodiment, the on-load tap changer (1) is for a distribution transformer (10) and comprises:
- a driving system (2) including a force store unit (31),
- a slow-moving selector contact package (4), and
- a fast-moving selector contact package (5),
wherein
- the driving system (2) is to move the slow-moving selector contact package (4) with a first speed and the fast-moving selector contact package (5) with a second, higher speed from a first selector contact (11) to a second selector contact (12) of the transformer (10),
- the driving system (2) is to begin movement of the fast-moving selector contact package (5) later than movement of the slow-moving selector contact package (4), and
- the force store unit (31) is loaded during movement of the slow-moving selector contact package (4) and is unloaded to drive movement of the fast-moving selector contact package (5) .

Description

An on-load tap changer and a transformer comprising such an on-load tap changer are provided. An operating method for such a transformer is also provided.
Documents US 2023/0230786 A1 , US 2023/0230781 A1 , WO 2023/001962 A1 and WO 2018/148812 A1 refer to components for on-load tap changers.
A problem to be solved is to provide a compact on-load tap changer.
This object is achieved, inter alia, by an on-load tap changer, a transformer and an operating method as defined in the independent claims. Exemplary further developments constitute the subject-matter of the dependent claims.
For example, the on-load tap changer, OLTC for short, is for a transformer, like a distribution transformer, and has a slow-moving selector contact package and a fast-moving selector contact package configured to be moved with a higher speed than the slow-moving selector contact package. The fast-moving selector contact package is configured to start moving after the slow-moving selector contact package. When the OLTC performs switching, both the slow-moving and the fast-moving selector contact package move from a first selector contact to a second selector contact of the transformer.
Thus, a design of an on-load tap changer for uninterrupted switching between different winding taps of a transformer can be provided. With its reduced dimensions it can be implemented in small distribution transformers. For example, the OLTC uses a linear movement design for uninterrupted switching between the different winding taps.
For example, two pairs of moving selector contacts' packages are present for each electric phase which, when in a switching cycle, execute linear motion and connect to the next pair of the fixed selector contacts. Moving contacts packages can thus be supported with linear guidance. Moving selector contacts' packages are electrically connected through sliding via linear conductors to switching means which are, for example, vacuum interrupters. For each on-load tap changer phase, input motion from a motor drive is separated to a slow-motion driving transmission and to a fast-motion driving transmission. Slow motion driving transmission is charging a force store unit in a driving mechanism and, for example, a screw threaded spindle drives linearly a slow-motion movable contacts' package to the adjacent fixed selector contact. When driving the slow-moving contacts' package, another force store unit, for example, between the slow-motion contacts' package and the fast-motion contacts' package, start its charging.
When the force store unit in the driving mechanism is unlocked, it actuates the fast-motion transmission for driving the switching means and driving unlocking arms for the force-store unit between slow-motion contacts' package and the fast-motion contacts' package, for example. When the fast-motion contacts' package is unlocked, it is driven to the adjacent fixed selector contact, thus aligning with the previously switched slow-motion contacts' package.
In at least one embodiment, the on-load tap changer, OLTC, is configured for a transformer, like a distribution transformer, and comprises:

a driving system including a first force store unit,
a slow-moving selector contact package, and
a fast-moving selector contact package,
wherein
the driving system is configured to move the slow-moving selector contact package with a first speed and the fast-moving selector contact package with a second speed from a first selector contact of the transformer to a second selector contact of the transformer, the second speed is higher than the first speed,
the driving system is further configured to begin movement of the fast-moving selector contact package later than movement of the slow-moving selector contact package, and
the first force store unit is loaded during movement of the slow-moving selector contact package and is unloaded to drive movement of the fast-moving selector contact package.

According to at least one embodiment, the OLTC is a one-phase OLTC. Otherwise, the OLTC can be a multi-phase OLTC, like a three-phase OLTC. For simplicity, in the following reference is made to a one-phase OLTC unless indicated otherwise, but the statements below apply analogously for a multi-phase OLTC.
According to at least one embodiment, the second speed is at least twice or at least five times the first speed. Alternatively or additionally, the second speed is at most hundred times or at most twenty times the first speed. The first and second speed may refer to an average speed of the respective package from the first selector contact to the second selector contact, that is, to a distance between the respective positions of the packages divided by the time required for the overall movement.
According to at least one embodiment, the driving system further comprises a first shaft coupled to the slow-moving selector contact package. For example, the first shaft is a screw-threaded spindle. By means of the first shaft, especially by rotating the first shaft, the slow-moving selector contact package is driven, that is, moved between the selector contacts.
According to at least one embodiment, the driving system further comprises a second shaft. For example, the second shaft is also coupled to the slow-moving selector contact package. This means, for example, that the second shaft is led through the slow-moving selector contact package. However, the second shaft may not need to exert driving force on the slow-moving selector contact package to move the latter.
According to at least one embodiment, the second shaft includes one or a plurality of cam profiles. The at least one cam profile, or at least one of the cam profiles, is configured to trigger a movement of the fast-moving selector contact package. For example, upon rotation of the second shaft, a tongue of the cam profile interacts with part of the driving system at the fast-moving selector contact package. For example, by means of the cam profile the first force store unit can be released.
According to at least one embodiment, the slow-moving selector contact package comprises one or a plurality of unlocking arms. For example, the at least one unlocking arm is coupled to the second shaft. This means, for example, that the at least one unlocking arm is either directly acted by the second shaft or that a movement of the at least one unlocking arm is triggered by the second shaft. It is possible that the at least one unlocking arm is not coupled to the first shaft.
According to at least one embodiment, the unlocking arm is configured to unlock the first force store unit after being charged by the movement of the slow-moving selector contact package, the charging is done by rotation of the first shaft. For example, the first force store unit is charged by moving the slow-moving selector contact package by means of the first shaft, and then discharging of the first force store unit is triggered via the unlocking arm by means of the second shaft.
According to at least one embodiment, the driving system further comprises one or a plurality of motors. By means of the at least one motor, the first shaft may be driven. It is possible that the first shaft is the only component of the driving system to be directly driven by the motor. For example, the second shaft is coupled to the first shaft by a driving mechanism so that movement of the second shaft is determined by the first shaft.
According to at least one embodiment, the driving system further comprises a second force store unit. For example, the second force store unit is located at or next to an end of the first shaft and is charged via the driving mechanism by rotation of the first shaft. Thus, the motor can be configured to directly drive the first shaft and to load the second force store unit during movement of the slow-moving selector contact package.
According to at least one embodiment, the second force store unit is unloaded upon arrival of the slow-moving selector contact package at the second selector contact to drive the second shaft. For example, the second force store unit is coupled to a Geneva drive that acts on the second shaft. That is, by means of the second force store unit the Geneva drive can rapidly be acted when the slow-moving selector contact package is at the right position. Thus, by means of the second force store unit the second shaft can be moved and consequently the discharging the first force store unit can be triggered.
According to at least one embodiment, the rotation of the second shaft releases the unlocking arm. Hence, the second force store unit may drive the Geneva drive or a similar means, then rotates the second shaft, releases the unlocking arm and triggers unloading the first force store unit so that the fast-moving selector contact package starts moving.
According to at least one embodiment, the OLTC further comprises a collector rail as power output line. For example, the collector rail is split into a first electric collector rail and a second electric collector rail. The electric collector rails may briefly be referred to as collectors. For example, the collectors lead to a neutral terminal of the transformer. Correspondingly, the selector contact may lead to a line terminal.
According to at least one embodiment, the slow-moving selector contact package is guided along the first electric collector rail and the fast-moving selector contact package is guided along the second electric collector rail. For example, the electric collector rails run in parallel with each other. It is possible that there are further rails for guidance of the slow-moving and/or fast-moving selector contact packages. Possibly, the second electric collector rail may be split into two sub-rails.
According to at least one embodiment, the first force store unit is mechanically coupled to the fast-moving selector contact package. For example, the first force store unit comprises to end plates between which a spring is mounted as the first force store unit. The fast-moving selector contact package may be placed between the end plates and the first force store unit may run through the fast-moving selector contact package.
According to at least one embodiment, trajectories of the slow-moving selector contact package and of the fast-moving selector contact package run collinearly. Especially, the trajectories run along parallel straight lines. However, other trajectories are possible as well.
According to at least one embodiment, the driving system is configured to start the movement of the fast-moving selector contact package upon arrival of the slow-moving selector contact package at the second selector contact. Thus, it is possible that firstly only the slow-moving selector contact package moves and that then only the fast-moving selector contact package moves. In other words, the slow-moving and the fast-moving selector contact packages may move sequentially but not simultaneously.
According to at least one embodiment, the driving system further comprises one or a plurality of auxiliary rails. For example, the at least one auxiliary rail is assigned to the fast-moving selector contact package only and not to the slow-moving selector contact package.
According to at least one embodiment, the fast-moving selector contact package and the auxiliary rail are provided with a mutual mechanical interlock. For example, at the auxiliary rail there are distinct interlock positions associated in a one-to-one manner with positions of the first selector contact and the second selector contact, seen along the auxiliary rail. Thus, by means of the interlocks the fast-moving selector contact package may snap onto the interlock positions and consequently at the selector contact positions. For example, the auxiliary rail comprises a grid or pattern corresponding to the selector contact positions.
According to at least one embodiment, the fast-moving selector contact package and the slow-moving selector contact package each comprise one or a plurality of contact clamps. The at least one contact clamp per package is configured to electrically contact the first selector contact and the second selector contact at respective static positions of the fast-moving selector contact package and the slow-moving selector contact package. That is, at the selector contact positions the packages may clamp onto the selector contacts. Between the selector contact, there may not be any clamping to a line terminal of the transformer. A length of the clamps along a direction of movement of the packages during switching is, for example, at most 30% or at most 20% or at most 100 of a distance between adjacent ones of the selector contacts.
A transformer additionally provided. The transformer comprises one or a plurality of the OLTCs as indicated in connection with at least one of the above-stated embodiments. Features of the transformer are therefore also disclosed for the OLTC and vice versa.
In at least one embodiment, the transformer comprises an OLTC and a first selector contact and a second selector contact being electrically connected with a winding of the transformer, for example, via switching means like vacuum interrupters. During changing the selector contact by means of the OLTC, the first and/or the selector contact may be disconnected from the winding using the switching means. The first selector contact and a second selector contact are assigned in a one-to-one manner to different winding taps of the winding.
For example, the first and second selector contacts are arbitrary adjacent selector contacts chosen from a plurality of the transformer's selector contacts. By way of example, overall the transformer comprises at least two or at least five and/or at most 30 or at most twelve of the selector contacts. Each one of the selector contacts is assigned to exactly one of the winding taps. It is possible that all the selector contacts are of a same design.
According to at least one embodiment, the transformer is a distribution transformer. For example, the transformer is configured for a maximum electric load of at most 5 MVA or at most 1 MVA or at most 0.2 MVA. Alternatively or additionally, the transformer is configured for a maximum electric load of at least 10 kVA or at least 100 kVA.
According to at least one embodiment, the first selector contact and the second selector contact each comprise a first terminal and a second terminal. For example, the first and second terminals of a specific one of the selector contacts are at a same electric potential. For example, the first and second terminals are different ends of a metal bar comprised by the respective one of the selector contacts.
According to at least one embodiment, the first terminals are electrically contacted by means of the slow-moving selector contact package. Alternatively or additionally, the second terminals are electrically contacted by means of the fast-moving selector contact package. Thus, also in case that only one of the packages is contacted with the first or second terminals, respectively, the associated winding tap is electrically connected by the OLTC. Except for a short period of time during movement of the slow-moving and/or fast-moving selector contact package, for example, only one of the selector contacts is electrically connected by the OLTC.
According to at least one embodiment, the transformer further comprises a first electric switch element and/or a second electric switch element. The switch elements are, for example, vacuum interrupters. It is possible that the first and/or second switch elements are part of the OLTC; however, the first and/or second switch elements may also be components not exclusively used by the OLTC so that these components may not be regarded as part of the OLTC.
According to at least one embodiment, the transformer further comprises a resistor package and/or a preventive autotransformer. By means of the resistor package and/or a preventive autotransformer, current limitation and/or voltage limitation can be achieved during tap change.
According to at least one embodiment, the resistor package and the preventive autotransformer are assigned to the second electric switch element only and not to the first electric switch element. Thus, only when the second electric switch element is in an electrically conductive state, that is, is closed, the resistor package and/or a preventive autotransformer are used.
According to at least one embodiment, the first electric switch element is directly assigned to the winding. For example, it is possible that the first electric switch element is the only active electric component between the winding and the selector contacts.
According to at least one embodiment, the second electric switch element is configured to be closed upon movement of the fast-moving selector contact package. That is, current flows through the resistor package and/or the preventive autotransformer only upon movement of the fast-moving selector contact package is triggered and as long as the fast-moving selector contact package is in movement.
In other words, with beginning the movement of the fast-moving selector contact package the second electric switch element is closed and with ending said movement the second electric switch element is opened. For example, only directly at the beginning of said movement and directly at the ending of said movement the first and the second electric switch element are closed, that is, are in a conductive state.
According to at least one embodiment, the first electric switch element is configured to be opened only when the second electric switch element is closed. That is, the first electric switch element only opens during movement of the fast-moving selector contact package.
An operating method for the transformer is additionally provided. By means of the method, a transformer as indicated in connection with at least one of the above-stated embodiments is operated. Features of the transformer are therefore also disclosed for the method and vice versa.
In at least one embodiment, the operating method is for operating a transformer, like a distribution transformer, and comprises the following steps, for example, in the stated order:

optionally, receiving an instruction to switch between the different winding taps,
upon receiving the optional instruction, disconnecting the slow-moving selector contact package from the first selector contact and moving the slow-moving selector contact package to the second selector contact, and charging the first force store unit,
upon arrival of the slow-moving selector contact package at the second selector contact, contacting the slow-moving selector contact package with the second selector contact and unloading the first force store unit so that the fast-moving selector contact package is disconnected from the first selector contact and so that movement of the fast-moving selector contact package is initiated, and
upon arrival of the fast-moving selector contact package at the second selector contact, contacting the fast-moving selector contact package with the second selector contact.

An on-load tap changer, OLTC, a transformer and an operating method described herein are explained in greater detail below by way of exemplary embodiments with reference to the drawings. Elements which are the same in the individual figures are indicated with the same reference numerals. The relationships between the elements are not shown to scale, however, but rather individual elements may be shown exaggeratedly large to assist in understanding.
In the figures:

Figure 1: is a schematic top view of an exemplary embodiment of an OLTC described herein,
Figure 2: is a schematic top view of an exemplary embodiment of a transformer comprising an OLTC described herein,
Figures 3: to 5 are schematic perspective views of an exemplary embodiment of an OLTC described herein with the slow-moving and the fast-moving selector contact package being both at the first selector contact,
Figures 6: to 9 are schematic perspective views of the OLTC of Figures 3 to 5 with the fast-moving selector contact package still being at the first selector contact while the slow-moving selector contact package being at the second selector contact,
Figure 10: is a schematic representation of a circuit diagram of an exemplary embodiment of an OLTC described herein,
Figure 11: is a schematic block diagram of an exemplary embodiment of an operating method for OLTCs described herein, and
Figure 12: is a schematic view of an exemplary embodiment of a transformer comprising a plurality of OLTCs described herein.

Figure 1 illustrates an exemplary embodiment of an on-load tap changer 1, OLTC for short, for a transformer 10. The OLTC 1 comprises a driving system 2 that includes a first force store unit 31. For example, the first force store unit 31 includes a spring for storing a mechanical energy and for exerting mechanical force upon being released.
Moreover, the OLTC 1 includes a slow-moving selector contact package 4 and a fast-moving selector contact package 5. The driving system 2 is configured to move the fast-moving selector contact package 5 with a higher speed than the slow-moving selector contact package 4 from a first selector contact 11 of a transformer 10 to a second selector contact 12 of the transformer 10. For example, the fast-moving selector contact package 5 needs as most half the time or at most a fifth of the time from the first 11 to the second selector contact 12 as required by the slow-moving selector contact package 4. The first and second selector contacts 11, 12 are assigned to different winding taps of the transformer 10.
The driving system 2 is further configured to begin a movement of the fast-moving selector contact package 5 to the second selector contact 12 later than a movement of the slow-moving selector contact package 4 to the second selector contact 12. The first force store unit 31 is loaded during the movement of the slow-moving selector contact package 4 to the second selector contact 12. The first force store unit 31 is unloaded to drive the movement of the fast-moving selector contact package 5 when the slow-moving selector contact package 4 reaches the second selector contact 12.
For example, the slow-moving selector contact package 4 is guided along a first shaft 21. Optionally, the fast-moving selector contact package 5 may be guided along an auxiliary rail 23.
In Figure 2, the transformer 10 comprising the OLTC 1 is illustrated. The transformer 10 further comprises the first selector contact 11 and the second selector contact 12. These selector contacts 11, 12 are two adjacent ones of a plurality of selector contacts 19 of the transformer 10. Each one of the selector contacts 19 is assigned to one winding tap of a winding 17 of the transformer 10. With the OLTC 1, switching between the selector contacts 19 and, thus, between the winding taps is enabled. The selector contacts 19 could be distributed along the first shaft 21 in an equidistant manner.
Optionally, the transformer 1 includes a first 151 and a second electric switch element152, like vacuum interrupters. The electric switch elements 151, 152 may be part of the OLTC 1. The transformer 1 may have a source line 18 supplying the winding 17 with electric power and an electric collector 6 outputting the electric power at a different voltage.
Otherwise, the same as to Figure 1 may also apply to Figure 2, and vice versa.
In Figures 3 to 9, an exemplary embodiment of the OLTC 1 is shown in more detail. In this regard, Figures 3 to 5 refer to the OLTC 1 with both the slow-moving 4 and the fast-moving selector contact package 5 being at the first selector contact 11, while Figures 6 to 9 show the situation with the fast-moving selector contact package 5 still being at the first selector contact 11 and the slow-moving selector contact package 4 already having moved the second selector contact 12.
In this embodiment of Figures 3 to 9, the packages 4, 5 each comprise contact clamps 41, 51 which clamp onto the selector contacts 11, 12, 19. It is possible that the contact clamps 41, 51 are always in a closed state so that the contact clamps 41, 51 slide off and onto the selector contacts 11, 12, 19 when the packages 4, 5 move.
The driving system 2 comprises the first shaft 21 and a motor 27. For example, the slow-moving selector contact package 4 is driven by the first shaft 21 which comprises, for example, a screw threaded spindle. That is, when the first shaft 21 rotates, the package 4 moves forward or backward, depending on a direction of rotation of the first shaft 21. The first shaft 21 is driven by the motor 27. It is possible that the first shaft 21 is the only component of the OLTC 1 which is directly driven by the motor 27.
Further, there is a second shaft 22. The second shaft 22 comprises one or a plurality of cam profiles 29. Optionally, the second shaft 22 runs through the package 4, however, the second shaft 22 does not provide forward or backward movement of the package 4 but may serve as guidance of the package 4. Moreover, the package 4 slides along a first electric collector rail 61 to output the electric power from the transformer 10.
The fast-moving selector contact package 5 slides along a second electric collector rail 62 which may be configured as a double rail for improved guidance of the package 5. Also, the second electric collector rail 62 is configured for power output. It is possible that both collector rails 61, 62 are neutral lines. The driving system 2 may optionally include an auxiliary rail 23 to also guide the package 5. For reliable positioning of the package 5 along the auxiliary rail 23, there can be an interlock 28 that fixes the package 5 at distinct interlock positions 25 assigned to positions of the selector contacts 11, 12, 19. The interlock 28 may comprise a lever interacting with protrusions or holes arranged at the auxiliary rail 23.
In addition, the driving system 2 includes a driving mechanism 26, a first force store unit 31 and a second force store unit 32. The first force store unit 31 is located at the fast-moving selector contact package 5, for example. The second force store unit 32 is located at an end of the second shaft 22 next to the driving mechanism 26, for example.
The first force store unit 31 may be or may include a spring attached to a first end plate 71 and a second end plate 72 between which the fast-moving selector contact package 5 is located. The spring may run through the package 5, for example. When the slow-moving selector contact package 4 moves from the first selector contact 11 to the second selector contact 12, the first end plate 71 moves together with eh slow-moving selector contact package 4 so that the first force store unit 31, that is, by way of example a spring, is loaded, see Figures 6 to 9. When the first force store unit 31 is released, then the second end plate 72 is pulled by the first force store unit 31 to the first end plate 71 so that the fast-moving selector contact package 5 moves towards the first end plate 71.
The first force store unit 31 is released, for example, by means of an unlocking arm 24 of the driving system 2. For example, the unlocking arm 24 interacts with the interlock 28. In other words, the unlocking arm may release the interlock 28 from the respective interlock position 25 so that the fast-moving selector contact package 5 can move freely. Consequently, the fast-moving selector contact package 5 is pushed by the second end plate 72 to the position of the second selector contact 12. The unlocking arm 24 is triggered by the cam profile 29 of the second shaft 22 next to the slow-moving selector contact package 4.
As the arrangement of the plates 71, 72 and the first force store unit 31 is essentially symmetrical along the second electric collector rail 62, movement in the opposite direction happens analogously.
The driving mechanism 26 of the driving system 2 is configured to also load the second force store unit 32 when the first shaft 21 is rotated by the motor 27. Hence, with rotation of the first shaft 21, both force store units 31, 32 are charged, the second force store unit 32 by means of the driving mechanism 26 and the first force store unit 31 by means of the movement of the slow-moving selector contact package 4.
The second force store unit 32 is released, for example, when the slow-moving selector contact package 4 has arrived at the desired position, that is, at the adjacent selector contact 12. This means, for example, that the first shaft 21 has made a specific number of turns. When the specific number of turns is reached, the second force store unit 32 is released. Upon being released, the second shaft 22 starts to rotate so that the unlocking arm 24 can be triggered. Moreover, the driving mechanism 26 may comprise a further drive, like a Geneva drive 261. By means of the Geneva drive 261, rotation of the second shaft 22 and/or driving of the electric switch elements 151, 152 can be controlled. For example, there are switch arms 262, 263 from the driving mechanism 26 to each one of the switch elements 151, 152 to individually mechanically address the switch elements 151, 152, see, for example, Figure 9. The switch elements 151, 152 may only be addressed between starting and ending the movement of the fast-moving selector contact package 5 and may otherwise be kept in their positions.
Otherwise, the same as to Figures 1 and 2 may also apply to Figures 3 to 9, and vice versa.
In Figure 10, the electric wiring of the OLTC 1 is schematically illustrated in a simplified manner. That is, the OLTC 1 may provide a first electric path and a second electric path between the electric collector 6 and the winding 17 to which the selector contacts 11, 12 are assigned. In the first electric path, there is the first electric switch element 151. If the first electric switch element 151 is closed, that is, in a conductive state, then the respective selector contact 11, 12 is directly connected with the electric collector 6. The second electric path comprises the second electric switch element 152 as well as the resistor package 16 and/or the preventive autotransformer 13.
Otherwise, the same as to Figures 1 to 9 may also apply to Figure 10, and vice versa.
In Figure 11, an operating method for the OLTC 1 in the transformer 10 is explained in more detail.
In optional method step S1, the OLTC receives an instruction to switch between two adjacent ones of the different winding taps, that is, between two adjacent ones of the selector contacts 19, for example, from the first selector contact 11 to the second selector contact 12.
In method step S2, upon receiving the instruction, the motor 27 starts to rotate the first shaft 21. Thus, the slow-moving selector contact package 4 starts moving from the first selector contact 11 to the second selector contact 12. Due to this movement,

the contact clamps 41 are released from a first terminal 114 of the first selector contact,
the second force store unit 32 is loaded by means of the driving mechanism 26, and
the first force store unit 31 is loaded by means of movement of the slow-moving selector contact package 4.

Method step S2 lasts until the contact clamps 41 make contact with a first terminal 124 of the second selector contact 12. Up to this point, the fast-moving selector contact package 5 remains unaffected and the contact clamp 51 still clamps on a second terminal 115 of the first selector contact 11. During method step S2, the first electric switch element 151 is closed and the second electric switch element 152 is opened, and current flows from the first selector contact 11 via the fast-moving selector contact package 5 to the second electric collector rail 62.
In method step S3, the slow-moving selector contact package 4 gets into contact with the first terminal 124 of the second selector contact 12. That is, the slow-moving selector contact package 4 reaches it end position or gets close to its end position. 'Close' means, for example, that a distance between the final end position at the second selector contact 12 and an actual position of the slow-moving selector contact package 4 along the first shaft 21 is at most 90% or at most 50% or at most 30% of a length of the contact clamps 41 along the first shaft 21.
Arrival of the slow-moving selector contact package 4 at the first terminal 124 triggers the following actions:

the second force store unit 32 is released, and
the second shaft 22 starts to rotate.

In method step S4, the effects of method step S3 emerge:

the second electric switch element 152 is closed by means of the Geneva drive 261 and the second switch arm 263,
afterwards, the first electric switch element 151 is opened by means of the first switch arm 262, and
the unlocking arm 24 is triggered by the second shaft 22 so that the first force store unit 31 is released and the fast-moving selector contact package 5 starts to move after the first electric switch element 151 has been opened.

Thus, for a short period of time both electric switch elements 151, 152 are in a closed state, for example, for at most 0.1 s or for at most 0.01 s. Subsequently, the first electric switch element 151 is opened so that then the contact clamps 51 of the fast-moving selector contact package 5 can leave the second terminal 115 of the first selector contact 11.
In method step S6, the contact clamps 51 of the fast-moving selector contact package 5 arrive at the second terminal 125 of the second selector contact 12. Thus, the fast-moving selector contact package 5 reaches its end position or gets close to its end position. Upon making contact between the contact clamps 51 and the second terminal 125,

the first electric switch element 151 is closed by means of the driving mechanism 26,
subsequently the second electric switch element 152 is opened, and
optionally the fast-moving selector contact package 5 interlocks with the auxiliary rail 23.

In optional method step S7, finishing the tap changing is confirmed.
Hence, uninterrupted switching between taps can be achieved.
Otherwise, the same as to Figures 1 to 10 may also apply to Figure 11, and vice versa.
In Figure 12, a more detailed representation of an example of a transformer 10 is shown. In this example, the transformer 10 is for three electric phases and, thus, comprises three of the OLTCs 1 which are assigned in a one-to-one manner to the phases. The OLTCs 1 are each located at a high-voltage side of the corresponding selector contacts 11, 12, 19 of the winding 17 and connected to the respective collector. As an alternative to three one-phase OLTCs 1, there can be one three-phase OLTC, not shown. The same applies to all other examples of the transformer 10 and the OLTC 1.
For example, the winding 17 comprises three units each having a regulation winding 171 connected with the selector contacts 11, 12, 19 and a high-voltage winding 172 connected with the source by means of transformer bushings 173. All three units of the winding 17 are applied on a same soft iron structure 174.
Further, for example, the OLTCs 1 can be arranged in a linear, straight manner. An overall length of the three OLTCs 1 along the winding 17 is, for example, the length of the winding 17 along the same direction of extend, for example, with a tolerance of at most 40% or at most 15% of said length of the winding 17. Especially, the overall length of the three OLTCs 1 can be smaller than said length of the winding 17 so that a compact, space-saving arrangement is possible. All three OLTCs 1 may be of the same design.
Otherwise, the same as to Figures 1 to 11 may also apply to Figure 12, and vice versa.
The components shown in the figures follow, unless indicated otherwise, exemplarily in the specified sequence directly one on top of the other. Components which are not in contact in the figures are exemplarily spaced apart from one another. If lines are drawn parallel to one another, the corresponding surfaces may be oriented in parallel with one another. Likewise, unless indicated otherwise, the positions of the drawn components relative to one another are correctly reproduced in the figures.
The invention described here is not restricted by the description on the basis of the exemplary embodiments. Rather, the invention encompasses any new feature and also any combination of features, which includes in particular any combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.

List of Reference Signs

1: on-load tap changer, OLTC
2: driving system
21: first shaft
22: second shaft
23: auxiliary rail
24: unlocking arm
25: interlock position
26: driving mechanism
261: Geneva drive
262: first switch arm to the first electric switch element
263: second switch arm to the second electric switch element
27: motor
28: interlock
29: cam profile
31: first force store unit
32: second force store unit
4: slow-moving selector contact package
41: contact clamp
5: fast-moving selector contact package
51: contact clamp
6: electric collector
61: first electric collector rail
62: second electric collector rail
71: first end plate
72: second end plate
10: transformer, e. g. distribution transformer
11: first selector contact
114: first terminal
115: second terminal
12: second selector contact
124: first terminal
125: second terminal
13: preventive autotransformer
14: insulation body
151: first electric switch element
152: second electric switch element
16: resistor package
17: winding
171: regulation winding
172: high-voltage winding
173: transformer bushing
174: soft iron structure
18: source
19: further selector contact
S: method step

Claims

An on-load tap changer (1), OLTC, for a transformer (10) comprising:
- a driving system (2) including a first force store unit (31),

- a slow-moving selector contact package (4), and

- a fast-moving selector contact package (5),
wherein

- the driving system (2) is configured to move the slow-moving selector contact package (4) with a first speed and the fast-moving selector contact package (5) with a second speed from a first selector contact (11) of the transformer (10) to a second selector contact (12) of the transformer (10), the second speed is at least twice the first speed,

- the driving system (2) is further configured to begin a movement of the fast-moving selector contact package (5) to the second selector contact (12) later than a corresponding movement of the slow-moving selector contact package (4), and

- the first force store unit (31) is loaded during the movement of the slow-moving selector contact package (4) and is subsequently unloaded to drive the movement of the fast-moving selector contact package (5).
The OLTC (1) according to the preceding claim,
wherein the driving system (2) further comprises a first shaft (21) coupled to and driving the slow-moving selector contact package (4), and a second shaft (22) also coupled to the slow-moving selector contact package (4),

wherein the second shaft (22) includes a cam profile (29) triggering movement of the fast-moving selector contact package (5).
The OLTC (1) according to the preceding claim,
wherein the slow-moving selector contact package (4) comprises an unlocking arm (24) coupled to the second shaft (22),

wherein the unlocking arm (24) is configured to unlock the first force store unit (31) after being charged by the movement of the slow-moving selector contact package (4) due to rotation of the first shaft (21).
The OLTC (1) according to any one of the two preceding claims,
wherein the driving system (2) further comprises a motor (27) and a second force store unit (32),

wherein the motor (27) is configured to directly drive the first shaft (21) and to load the second force store unit (32) during movement of the slow-moving selector contact package (4),

wherein the second force store unit (32) is unloaded upon arrival of the slow-moving selector contact package (4) at the second selector contact (12) to drive the second shaft (22) .
The OLTC (1) according to the two preceding claims, wherein rotation of the second shaft (22) releases the unlocking arm (24).
The OLTC (1) according to any one of the preceding claims, further comprising a first electric collector rail (61) and a second electric collector rail (62),
wherein the slow-moving selector contact package (4) is guided along the first electric collector rail (61) and the fast-moving selector contact package (5) is guided along the second electric collector rail (62),

wherein the first force store unit (31) is mechanically coupled to the fast-moving selector contact package (5).
The OLTC (1) according to any one of the preceding claims, wherein trajectories of the slow-moving selector contact package (4) and of the fast-moving selector contact package (5) run collinearly.
The OLTC (1) according to any one of the preceding claims, wherein the driving system (2) is configured to start the movement of the fast-moving selector contact package (5) upon arrival of the slow-moving selector contact package (4) at the second selector contact (12).
The OLTC (1) according to any one of the preceding claims, wherein the driving system (2) further comprises an auxiliary rail (23),
wherein the fast-moving selector contact package (5) and the auxiliary rail (23) are provided with a mutual mechanical interlock (28),

wherein at the auxiliary rail (23) there are distinct interlock positions (25) associated in a one-to-one manner with positions of the first selector contact (11) and the second selector contact (12), along the auxiliary rail (23).
The OLTC (1) according to any one of the preceding claims,
wherein the fast-moving selector contact package (5) and the slow-moving selector contact package (4) each comprise a contact clamp (41, 51) configured to electrically contact the first selector contact (11) and the second selector contact (12) at respective static positions of the fast-moving selector contact package (5) and the slow-moving selector contact package (4).
A transformer (10) comprising:
- an OLTC (1) according to any one of the preceding claims, and

- a first selector contact (11) and a second selector contact (12) being electrically connected with a winding (17) of the transformer (10),
wherein the first selector contact (11) and a second selector contact (12) are assigned in a one-to-one manner to different winding taps of the winding (17).
The transformer (10) according to the preceding claim, wherein the first selector contact (11) and the second selector contact (12) each comprise a first terminal (114, 124) and a second terminal (115, 125) at a same electric potential,
wherein the first terminals (114, 124) are electrically contacted by means of the slow-moving selector contact package (4) and the second terminals (115, 125) are electrically contacted by means of the fast-moving selector contact package (5).
The transformer (10) according to any one of the two preceding claims,
further comprising a first electric switch element (151) and a second electric switch element (152),

further comprising a resistor package (16) and a preventive autotransformer (13),

wherein the resistor package (16) and the preventive autotransformer (13) are assigned to the second electric switch element (152),

wherein the first electric switch element (151) is directly assigned to the winding (17), and

wherein the second electric switch element (152) is configured to be closed during movement of the fast-moving selector contact package (5).
The transformer (10) according to the preceding claim, wherein the first electric switch element (151) is configured to be opened only when the second electric switch element (152) is closed.
An operating method for a transformer (10) according to any one of claims 11 to 14, comprising the following steps:
- receiving an instruction to switch between the different winding taps,

- upon receiving the instruction, disconnecting the slow-moving selector contact package (4) from the first selector contact (11) and moving the slow-moving selector contact package (4) to the second selector contact (12), and charging the first force store unit (31),

- upon arrival of the slow-moving selector contact package (4) at the second selector contact (12), contacting the slow-moving selector contact package (4) with the second selector contact (12) and unloading the first force store unit (31) so that the fast-moving selector contact package (5) is disconnected from the first selector contact (11) and so that movement of the fast-moving selector contact package (5) is initiated, and

- upon arrival of the fast-moving selector contact package (5) at the second selector contact (12), contacting the fast-moving selector contact package (5) with the second selector contact (12).