Tap changer and transformer device

Abstract

The present disclosure relates to a tap changer (300) arranged to be connected to a regulating winding (105) of a rated regulating voltage. The tap changer (300) comprises a converter switch (315), a tap selector (320) and a set of tap changer contacts (385). The tap selector (320) and the converter switch (385) are encapsulated in a shielding structure (390), the shielding structure being arranged to shield the tap selector (320) and the converter switch (315) from external electric fields, the shielding structure (390) being arranged to be electrically connected to a connected tap of the regulating winding (105). The present disclosure also relates to a transformer device (400) comprising at least one such tap changer (300).

Description

Technical Field

[0001] The present disclosure relates to a tap changer, and more particularly, to an on-load tap changer having a shielding structure. The present disclosure also relates to a transformer device including such a tap changer. Background Art

[0002] Tap changers are used to control the output voltage of a transformer by providing the possibility of connecting or disconnecting additional turns in the transformer winding. The tap changer comprises a set of fixed contacts that can be connected to a plurality of taps of a regulating winding of the transformer, wherein the taps are located at different positions in the regulating winding. The tap changer also comprises a movable contact that is connected to a current collector at one end and is connectable to one of the fixed contacts, the so-called connected tap, at the other end. By connecting or disconnecting different taps, the effective number of turns of the transformer can be increased or decreased, thus regulating the output voltage of the transformer. Tap changers are usually customized for specific applications, in particular when the tap changer is intended for higher transformer voltage ratings.

[0003] An important design factor of tap changer and transformer device is insulation distance. Insulation distance generally refers to the distance between components that should be kept electrically insulated from each other. Insulation distance depends on multiple factors, such as field strength, insulating material, position of components and geometry of components. Tap changer is exposed to external and internal potential / field. External field can be the potential between phases, such as the phase of a multiphase transformer device, or the potential between phase and ground. Internal field refers to the potential between components in tap changer. Since external field and internal field are usually superimposed in conventional tap changer in transformer device, it is difficult and time-consuming to calculate and predict the field strength in different positions and design, customize and adapt tap changer for specific transformer device. Mainly due to the superimposed external field and internal field, and due to the complex task of predicting the field, the distance between components must be designed to be relatively large as a safety measure.

[0004] EP2509089B1 discloses a tap changer having a shielding structure, the shielding structure comprising two parts, one of which is at least partially formed by fixed contacts, and the other part is arranged at the potential of the connected tap. The shielding structure insulates the tap selector so that only the internal potential needs to be considered when designing the tap selector, such as for determining insulating materials, insulation distances between components and / or for positioning components relative to each other. However, the unconnected taps are exposed to external potentials between phases. Therefore, the unconnected taps have high insulation requirements to consider the potential between phases and the potential towards the ground. Summary of the invention

[0005] It is therefore an object of the present disclosure to provide a tap changer with improved performance and simpler customer interface. A transformer arrangement comprising the disclosed tap changer is also provided, the transformer arrangement being more compact and having a smaller footprint and increased effect per square meter.

[0006] According to a first aspect of the present disclosure, this object is achieved by a tap changer, which is arranged to be connected to a regulating winding of a rated regulating voltage, and the tap changer includes a diverter switch, a tap selector and a set of tap changer contacts, wherein the tap selector and the diverter switch are encapsulated in a shielding structure, the shielding structure is arranged to shield the tap selector and the diverter switch from an external electric field, and the shielding structure is arranged to be electrically connected to a connected tap of the regulating winding.

[0007] By encapsulating the converter switch and the tap selector in the shielded structure connected to the potential of the connected taps, the internal parts, such as the converter switch and the tap selector, are almost completely protected from external electric fields. The design of the tap changer is thereby simplified, since only the internal fields need to be considered when determining the insulation properties such as materials and distances, which means that the tap changer can be used in a wider range of applications without extensive customization and adaptation. Furthermore, the insulation distances can be reduced, since the external fields are not superimposed on the internal potential in any significant way, which results in a more compact design.

[0008] The potential of the shielding structure is made to provide a smaller and more predictable potential difference at the potential of the connected tap than in the unshielded case, i.e. the internal potential difference between the components surrounded by the shielding structure, which are exposed to external fields and potentials, such as between the tap and an adjacent phase of the regulating winding or between a tap and ground. This will be explained in more detail below.

[0009] The tap changer contacts of the tap changer include selectable contacts connectable to taps of the regulating winding, and external contacts connectable to adjacent windings / phases, to shield structures, to selectable taps, etc. The tap changer contacts are sometimes referred to herein as customer interfaces.

[0010] According to one aspect of the present disclosure, the tap selector is electrically connected to the group of tap changer contacts comprising at least two tap changer contacts, at least a portion of the tap changer contacts being arranged to be connected to a corresponding tap of the regulating winding, wherein the group of tap changer contacts are arranged at an opening of the shielding structure, and wherein the tap changer contacts are arranged on one side of the tap changer.

[0011] The opening of the shielding structure is arranged to allow access to the tap changer contacts, such as for attaching a connecting cable to the tap changer contacts. The opening of the shielding structure is adapted to be restricted to the area required by the tap changer contacts to allow access to the tap changer contacts.

[0012] "One side of the tap changer" in this context means that the tap changer contacts are arranged on a side of the tap changer facing in a general direction, such as a side facing a regulating winding of a transformer. In other words, the tap changer contacts are arranged in a defined area of ​​the tap changer and do not spread out around the tap changer. The tap changer contacts are also arranged in an area defined by the opening of the shielding structure, such as inside the opening of the shielding structure. Thus, the connecting cables from the regulating winding can approach the tap changer contacts in parallel from a general direction.

[0013] According to an aspect of the present disclosure, the shield structure at least partially covers the set of tap changer contacts at the opening of the shield structure.

[0014] Thus, a portion of the set of tap changer contacts is considered to be covered by the shielding structure if the edge of the opening extends beyond the surface occupied by the tap changer contacts so that a normal drawn from the surface occupied by the tap changer contacts and from the center point of at least one tap changer contact intersects the inner surface of the shielding structure.

[0015] The tap changer contacts at the openings of the shielding structure constitute irregularly shaped objects, which may cause increased / concentrated field strengths, such as at pointed ends or sharp corners, which in turn may lead to destructive flashovers. Thus, the shielding structure may cover and shield a portion of the tap changer contacts from external electric fields. By arranging the contacts in a limited area and facing a single direction, the uncovered contacts may be dielectrically shielded by a connecting cable, as described below.

[0016] According to an aspect of the present disclosure, the shielding structure comprises a first compartment and a second compartment separated by an electrical insulation barrier, and wherein the first compartment comprises a first insulating medium and the converter switch, and wherein the second compartment comprises a second insulating medium and the tap selector.

[0017] The first and second insulating media can be fluids, such as oils, for example mineral oils, such as silicone oil, hydrocarbon oils or ester-based liquids / oils. The second insulating medium can be the same as the insulating medium contained in the transformer box. In this way, when the tap changer is assembled with the transformer box, the second compartment can share the insulating medium with the transformer inside the transformer box. The first compartment can be fluid-tight with the second compartment so that the first and second insulating media do not mix. In this way, contaminants, such as residues generated by the operation of the converter switch, do not contaminate the second compartment and the second insulating medium of the transformer box.

[0018] According to an aspect of the present disclosure, the tap changer further includes a change-over selector arranged in the first compartment, and wherein the change-over selector is a positive / negative switching type or a coarse / fine switching type.

[0019] Since the change-over selector may also contaminate the insulating medium, it is preferably arranged in the first compartment together with the diverter switch.

[0020] According to an aspect of the present disclosure, the second compartment of the shielding structure includes the opening, and wherein the set of tap changer contacts are arranged at the opening.

[0021] In this way, the opening of the shielding structure can be arranged inside the transformer box. Therefore, when the tap changer is assembled with the transformer box, the tap changer contacts can be arranged inside the transformer box. Therefore, a connecting cable can be conveniently connected between the tap of the regulating winding and the tap changer contacts.

[0022] According to an aspect of the present disclosure, the shielding structure is made of a conductive material.

[0023] The shielding structure thus forms an efficient shield, protecting the inner part of the tap changer from external electric fields.

[0024] According to another aspect of the present disclosure, a transformer device includes a transformer having at least one regulating winding with a rated regulating voltage, the at least one regulating winding having a tap. The transformer device also includes at least one tap changer as described above, the at least one tap changer having a shielding structure. Each of the at least one tap changer is electrically connected to a corresponding regulating winding so that its shielding structure is electrically connected to a connected tap of the corresponding regulating winding.

[0025] According to an aspect of the present disclosure, at least a portion of the tap changer contacts of the tap changer are electrically connected to a corresponding tap of the regulating winding via an electrically insulated connecting cable.

[0026] According to an aspect of the present disclosure, the connecting cables are arranged in parallel at least adjacent to the tap changer contacts.

[0027] Arranging the connecting cables in parallel is a convenient way to wire the transformer arrangement. Furthermore, it allows dielectric shielding of the tap changer contacts. Arranging the connecting cables in parallel at least in the vicinity of the tap changer contacts means that the connecting cables are arranged in parallel at least in the delimited area of ​​the opening of the shielding structure at which the tap changer contacts are arranged.

[0028] According to an aspect of the present disclosure, at least one of the connection cables is arranged to dielectrically shield at least one other of the tap changer contacts before being connected to one tap changer contact.

[0029] The connecting cable is arranged to provide dielectric shielding of at least a portion of the tap changer contacts. Dielectric shielding is provided by arranging the connecting cable adjacent to at least one tap changer contact and connecting the connecting cable to another tap changer contact. Tap changer contacts that cannot be provided with dielectric shielding in this way are arranged to be covered by the shielding structure, as described above. By arranging the tap changer contacts in a defined area, such as at the opening of the shielding structure, the connecting cable can be arranged adjacent to at least a portion of the tap changer contacts before connecting to other tap changer contacts.

[0030] According to an aspect of the present disclosure, the transformer having the at least one regulating winding is accommodated in a transformer tank containing an electrical insulating medium, and wherein a shielding structure encapsulating the at least one tap changer is arranged on a wall of the transformer tank.

[0031] The tap changer may be arranged on the wall of the transformer tank so that a portion of the tap changer, ie a portion of the shielding structure, is located inside the transformer tank. Thus, the tap changer may be conveniently interconnected with the transformer inside the tank.

[0032] According to one aspect of the present disclosure, the transformer arrangement comprises a Y-coupled transformer having three regulating windings and three tap changers, and wherein the three tap changers are encapsulated in a shielding structure electrically connected to a commonly connected tap of the three regulating windings.

[0033] Thus, only one shielding structure is required for three tap changers, since the phases of the Y-coupled transformer share the potential of the selected tap. Therefore, adjacent phases do not produce superimposed potentials. Therefore, the shielding structure is mainly used to protect the internal components from the influence of external potentials between the components and the ground. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Other objects, advantages and features of the present disclosure will become apparent from the following description of one or more embodiments with reference to the accompanying drawings, in which:

[0035] FIG. 1 is a schematic illustration of a prior art tap changer

[0036] FIG. 2 shows a transformer device of the prior art.

[0037] Figure 3 is a schematic illustration of a prior art tap changer according to the present disclosure

[0038] Figure 4 A transformer device according to the prior art of the present disclosure is shown.

[0039] Figure 5 is a schematic illustration of an optional change-over selector of the positive / negative switching type

[0040] Figure 6 is a schematic illustration of an optional change-over selector of the coarse / fine switching type

[0041] Figure 7 is a side view of the tap changer of the present disclosure

[0042] Figure 8 yes Figure 7 Top view of the tap changer

[0043] Fig. 9 is a side view of a transformer device according to the present disclosure

[0044] Fig.10 Shown for Figure 8 Connection arrangement of tap changer

[0045] Fig.11 shows simulated electric field lines in a transformer arrangement according to the present disclosure DETAILED DESCRIPTION

[0046] The present disclosure is described in more detail below with reference to the attached drawings showing examples of embodiments. The present disclosure should not be considered limited to the examples of the described embodiments; on the contrary, it is defined by the attached patent claims. Throughout the description, the same numbers refer to the same elements.

[0047] FIG. 1 schematically illustrates a tap changer 100 connected to a regulating winding 105 having a set of different taps 110. The tap changer of FIG. 1 is of the converter switch type and comprises a converter switch 115 and a tap selector 120. The tap selector 120 of FIG. 1 comprises two collectors 125, two movable contacts 130 and a set of fixed contacts 135, wherein each fixed contact 135 is arranged to be connected to one of the taps 110 of the regulating winding. The tap changer 100 of FIG. 1 has fifteen different fixed contacts 135, and the regulating winding 105 has fifteen taps 110. The tap changer 100 of FIG. 1 is mechanically linear in the sense that the collector 125 is implemented as a linear rod and the fixed contacts 135 are arranged in a linear manner. In the following, unless otherwise specified, the term linear tap changer should be interpreted as a mechanical linear tap changer. The two collectors 125 together form a collector part. In a tap changer 100 having a single current collector 125, the current collector portion is formed by the single current collector 125 or the like.

[0048] The exemplary diverter switch 115 comprises two series connections of main contacts 140 and transition contacts 145, wherein a transition resistor 150 is connected in parallel with the transition contacts 145. Each of the series connections is connected at one end to a respective one of the two current collectors 125 and at the other end to an external contact 155 of the tap changer 100. Other configurations of the diverter switch are possible.

[0049] The two movable contacts 130 are in electrical contact with a corresponding one of the current collectors 125 at one end. The movable contact 130 can be moved along the current collector 125 connected thereto to reach different positions at which the other end of the movable contact 130 is in electrical contact with one of the fixed contacts 135. The movable contact 130 can be, for example, a sliding contact arranged to slide along the current collector 125 to allow electrical connection between the current collector 125 and different fixed contacts 135. The driving of the movable contacts 130 of FIG. 1 is arranged so that if one of the movable contacts 130 is in contact with the fixed contact 135 connected to the first tap, the other movable contact 130 is in contact with the fixed contact 135 connected to the tap 110 adjacent to the first tap 110.

[0050] By switching the main contacts 140 and the transition contacts 145 in a conventional manner, one or the other of the movable contacts 130 will make electrical contact with the external contact 155 and thus provide an electrical path through the tap changer 100. Similarly, the two current collectors 125 will take turns to be part of the electrical path of the tap changer 100. The electrical path through the tap changer 100 terminates at one end at the external contact 155 and at the other end at the now connected fixed contact 135. An embodiment of a diverter switch 115 is described in EP0116748. As previously mentioned, the diverter switch 115 of FIG. 1 is only one embodiment and any suitable type of diverter switch 115 may be used.

[0051] As mentioned above, the regulating winding 105 has a set of taps 110, which are shown as being connected to the fixed contacts 135 of the tap changer 100 via a connecting cable 160. The connecting cable 160 itself does not form part of the tap changer 100, but is provided as part of the transformer device, as an electrical connection between the tap changer and the transformer. The other end of the regulating winding 105 is provided with an external contact 165. Depending on which tap 110 is currently connected to the fixed contact 135, the electrical path between the external contact 155 and the external contact 165 will include a different number of regulating winding turns. The regulating winding 105 is not usually considered as part of the tap changer 100, and is therefore surrounded by a solid line in FIG. 1 .

[0052] When the tap changer 100 is in use, different fixed contacts 135 will be at different potential levels, corresponding to the different potential levels of different taps 110 of the regulating winding 105. The collector 125 that is currently connected will be at the potential of the connected tap 110, while the other collector 125 that is currently disconnected will be at the potential of the tap 110 adjacent to the connected tap 110. Therefore, the potential difference between the collectors 125 will correspond to the potential difference U between two adjacent taps 110. adj .Uadj , which is generally constant throughout the regulating winding 105. Only one tap 110 at a time will be connected to the movable contact 130 currently connected to the external connection 155 of the tap changer, and this tap 110 is referred to as the connected tap 110.

[0053] On the other hand, the potential difference between the current collector 125 and a particular fixed contact 135 varies depending on at which position the movable contact 130 is connected, and this potential difference can be quite large. In the linear tap changer 100, the maximum potential difference between the current collector 125 and the fixed contact 135 occurs when one of the end fixed contacts 135 (indicated as 135e in FIG. 1 ) is connected and forms part of the current path through the tap changer 100. In this case, the potential difference between the connected current collector 125 and the unconnected end fixed contact 135e corresponds to the entire voltage U across the regulating winding 100. reg .U reg , also called the regulating voltage, is illustrated in FIG1 by arrow 170. In order to prevent flashover between the current collector 125 and the fixed contact 135, the distance between the current collector 125 and the fixed contact 135 should reach or exceed a minimum distance at which the medium in which the tap changer 100 is immersed can withstand a certain regulating voltage U reg , the voltage obtained between the current collector and the fixed contact 135 at the position of the movable contact 130 that produces the highest voltage between the current collector 125 and the fixed contact (this position of the movable contact 130 that produces the highest voltage varies between different fixed contacts). This distance is denoted as d insul The insulation distance d , hereinafter referred to as the rated regulation voltage insulation distance of the tap changer, or simply the insulation distance, depends on the medium surrounding the tap selector 120 and increases with increasing rated regulation voltage (which generally depends on the rated voltage of the transformer and the desired number of taps 110). In addition, the insulation distance d of the tap changer is insul Typically, the tap changer 100 varies along its length such that d insul =d insul (y), where y represents the position along the extension direction of the linear tap changer. The maximum possible potential difference between the current collector 125 and the fixed contact 135 can occur at the end fixed contact 135e, and the closer to the center of the arrangement of the fixed contact 135, the smaller the maximum potential difference between the current collector 125 and the fixed contact 135. The insulation distance at the end fixed contact 135e is represented as d endrinsul The regulated voltage used to define the insulation distance is typically a test voltage and is one of the parameters for which the tap changer 100 is rated.

[0054] The actual distance between the current collector 125 and the fixed contact 135 is referred to herein as the contact gap d gap , and is indicated by arrow 175 in FIG1 . The contact cap in FIG1 is shown independent of the position y along the extension direction. This represents a typical design in which the contact gap d gap is constant and corresponds approximately to d endrinsul However, it varies with the position along the extension direction, such that d gap (y) The smaller contact gap d towards the center of the tap changer 130 gap =d gap (y) may be beneficial in some circumstances.

[0055] Contact gap d gap Depends on the insulating medium. In the air-insulated tap changer 100, the contact gap d gap It needs to be much larger than in an oil-insulated tap changer 100. For example, in an air-insulated tap changer 100 in which the insulation distance is 30 cm, the corresponding insulation distance in an oil-insulated tap changer can typically be about 3 cm. Therefore, an air-insulated tap changer 100 typically needs to be physically larger than the case where the tap changer 100 is insulated by oil. However, in many applications, air insulation is preferred over oil insulation, such as inside buildings where the risk of fire should be minimized (e.g., in skyscrapers), or in environmentally sensitive areas where the risk of contamination should be minimized. The term air-insulated tap changer 100 should be interpreted herein to include a tap changer 100 insulated by air or by an air-like gas in a controlled space, such as a tap changer 100 insulated by nitrogen (N2), a tap changer 100 insulated by air under controlled pressure, a tap changer 100 insulated by SF6, and the like.

[0056] The potential difference between the collector 125 and the fixed contact 135 of the tap changer 100 of FIG. 1 will be further affected by the surrounding electric field. In a three-phase power system, the tap changer 100 is typically part of a three-phase tap changer system that includes three different tap changers 100 connected to three phases of a three-phase transformer. Therefore, the electric field at the tap changer 100 will be affected by the other two phases of the tap changer system 100 and the electric field around the transformer to which the tap changer 100 is connected, as well as other electric fields. For example, the potential difference between the collector 125 and the fixed contact 135 will be affected by the ground potential. Therefore, the contact gap d gap should be large enough to allow the regulated voltage U regAnd the potential difference caused by the internal electric field superimposed on the external electric field. Since the external electric field will vary from application to application depending on the insulation requirements to ground and between phases, the size of the contact gap and other parts of the tap changer 100 must usually be customized according to the requirements of each application. This makes the tap changer 100 expensive to manufacture.

[0057] FIG. 2 illustrates a three-phase transformer 200 with three transformer phases 205. The illustrated transformer is a transformer of a delta configuration, but in the following, without reference to its configuration, the transformer will generally be denoted by the reference numeral 200. Each transformer phase 205 has one regulating winding 105. In the configuration shown in FIG. 2 , the regulating winding 105 is located at the end of one (inner or outer) transformer winding - this is given only as an illustrative embodiment, and the regulating winding 105 may have alternative locations, such as in the center of the transformer winding. In FIG. 2 , various potential differences occurring in the three-phase transformer 200 are indicated. U reg , as presented above, represents the voltage across the entire regulating winding 105. transf is the voltage between the two phases of the transformer. phase is the voltage between two regulating windings serving two different transformer phases 205; and U earth is the (highest) potential of the regulating winding 105. The tap changer 100 is not shown in FIG. 2. Typically, one tap changer 100 will be connected to each regulating winding 105 of a transformer 200, although there are also configurations in which a single tap changer 100 can be used to regulate three transformer phases 205. The potential of the tap selector 120 of the tap changer 100 lies within the potential range of the regulating winding 105 to which it is connected, i.e. within the range [U earth , U earth -U reg ]Inside.

[0058] Insulation distances in high voltage AC equipment are usually dimensioned according to the rated lightning impulse level. The rated lightning impulse voltage level U is for a specific value of the highest voltage of the equipment. mIt can be found in standards such as IEC 60214-1. The rated lightning impulse voltage found in the standard is valid for the insulation to earth and for the insulation between phases. The rated impulse voltage level on the regulating winding 105 will depend to some extent on the rating of the transformer 200, but also on the placement and size of the regulating winding 105. During the impulse voltage, the capacitance from the regulating winding 105 to the surroundings (especially from the free end created when the movable contact 130 approaches the external contact 165) and the capacitance within the regulating winding 135 itself will play a more important role than the transformer magnetic circuit. Therefore, it is usually necessary to specify a specific impulse voltage level on the regulating winding 135 - referred to herein as the rated regulating voltage - and for a specific U related to the distance to earth. m The tap changer 100 is rated.

[0059] According to the present disclosure, a tap changer 300, such as an on-load tap changer (OLTC), is enclosed in a shielding structure 390 arranged to shield the tap changer 300 from external electric fields. Figure 3 Such a tap changer 300 connected to a regulating winding 105 of a rated regulating voltage is schematically shown. The tap changer 300 comprises a converter switch 315, a tap selector 320 and a set of tap changer contacts 385. The term "tap changer contacts" includes all connectable contacts of the tap changer 300, which, depending on the application, may include fixed contacts 335, connections for external contacts 155 and external contacts 165, shielding contacts 382 ( Figure 8 )wait. Figure 3 The exemplary tap changer 300 shown in is shown as a linear tap changer, such as the tap changer 100 of the prior art, but the present disclosure is not limited to linear tap changers. The tap selector 320 and the converter switch 315 are encapsulated in a shielding structure 390, which is arranged to shield the tap selector 320 and the converter switch 315 from external electric fields. The shielding structure 390 is arranged to be electrically connected to a connected tap of the regulating winding 105. The shielding structure 390 can be electrically connected to the connected tap via a shielding connection 380, such as between the shielding structure 390 and the external contact 155 or between the shielding structure 390 and the tap changer contact 385 (e.g., shielding contact 382 ( Figure 8 In the latter embodiment, the shield contact 382 will in turn be electrically connected to the connected tap.

[0060] As stated above, external electric fields are effectively shielded by the shielding structure 390 . Figure 4 A comparison is shown with the prior art three-phase transformer 200 of FIG2 . The shield structure 390 removes (or significantly reduces) the external potential between the phases and the potential between the fixed contact 335 and ground.reg - It represents the voltage across the entire regulating winding 105, i.e. the maximum internal potential difference - basically determines the contact gap d gap 375( Figure 3 ) is the only potential that needs to be considered. Since the superimposed external field is not a significant factor for the presently disclosed tap changer 300, the contact gap d can be reduced compared to the prior art tap changer 100. gap , thereby producing a more compact tap changer 300. The tap changer 300 with the disclosed shielding structure 390 can also be used in a wider range of applications, i.e., in a wider range of electric field environments, which means that less customization and adaptation is required when manufacturing the tap changer 300.

[0061] The tap changer 300 of the present disclosure may further include a changeover selector 350 . Figure 5 and Figure 6 Two types of change-over selectors are shown schematically. Figure 5 , a changeover selector 350a for positive / negative switching is shown. The changeover selector 350a extends the regulation range to twice the voltage of the tapped winding by connecting the main winding to different ends of the regulation winding 105 and thereby reversing the magnetic flux generated by the regulation winding 105. Figure 6 A changeover selector 350b for coarse / fine switching is shown, which extends the regulation range to twice the voltage of the tapped winding by connecting or disconnecting the coarse regulation winding 106. The changeover selector 350 may be connected to the tap changer 300 in a conventional manner and may optionally be included by the tap changer 300, encapsulated in a shielding structure 390.

[0062] Figure 7 A side view of an exemplary conceptual design of a tap changer 300 is illustrated. As shown, a shield structure 390 encapsulates a diverter switch 315, a tap selector 320, and a tap changer contact 385. As stated above, the tap changer 300 may also optionally include a change-over selector 350. The shield structure is preferably made of a conductive material such as aluminum. The shape of the illustrated shield structure 390 is exemplary only and is primarily intended to illustrate the scope of the package.

[0063] The tap changer contacts 385 may be disposed on the dielectric surface 302 and may be electrically connected to the diverter switch 315 , the tap selector 320 , and / or the optional change-over selector 350 via lead-throughs (not shown) in the dielectric surface 302 , as desired.

[0064] The number of tap changer contacts 385 can vary depending on the application. Therefore, the tap selector 320 is electrically connected to a set of tap changer contacts 385 including at least two tap changer contacts 385. At least a portion of the tap changer contacts 385 is arranged to be connected to a corresponding tap of the regulating winding. The portion of the tap changer contacts 385 connected to a corresponding tap 110 of the regulating winding 105 is a set of fixed contacts 335 selectable by the tap selector 320.

[0065] The set of tap changer contacts 385 are disposed at the opening 392 of the shield structure 390, such as within the opening 392 of the shield structure 390. Figure 7 , the opening 392 is shown as a dashed portion of the shielding structure 390. The tap changer contacts 385 are arranged on one side of the tap changer 300, i.e., such that they are arranged on a side of the tap changer 300 facing in one general direction, such as the side facing the regulating winding 105 of the transformer 200.

[0066] The openings 392 of the shielding structure 390 are arranged to allow access to the tap changer contacts, such as for attaching a connecting cable to the tap changer contacts 385. The openings 392 of the shielding structure 390 are also adapted to be limited in size to the area required for the tap changer contacts 385, which allows convenient access to the tap changer contacts 385 while providing optimal shielding from external electric fields.

[0067] The tap changer contacts 385 at the openings 392 of the shielding structure 390 (the tap changer contacts are exposed to the external electric field) constitute irregularly shaped objects, which can cause increased / concentrated field strengths, such as at pointed ends or sharp corners of the contacts, which in turn can lead to destructive flashovers. The shielding structure 390 at least partially covers a set of tap changer contacts 385 located at the openings 392 of the shielding structure 390. If a line 303 drawn from the center point of the tap changer contact 385 and normal to the surface 302 intersects the inner surface of the shielding structure 390, the tap changer contact 385 can be defined as being covered by the shielding structure 390. For purposes of explanation, in Figure 7 Such a line 303 is drawn in FIG. 3 to show how the rightmost contact in the figure is covered by the shielding structure 390. Figure 8 is further illustrated in Figure 8 yes Figure 7 The edge 392' of the opening 390 is at the top of the tap changer 300. Figure 8 The edge 392 ′ extends beyond the rightmost line 385 ′ of the tap changer contacts 385 so that they are covered by the shielding structure 390 .

[0068] Figure 8It is further shown how the shield structure 390 can be electrically connected to the connected taps via the shield connection 380. Figure 8 In the exemplary embodiment of , shield connection 380 connects shield structure 390 to tap changer contact 385, which in the illustrated case is a dedicated shield contact 382. Shield contact 382 is in turn electrically connected to the connected taps. Figure 8 The shield connection 380 is illustrated as a cable connection, but it can be any kind of galvanic connection.

[0069] Also like Figure 7 , the shielding structure 390 includes a first compartment 394 and a second compartment 396 separated by an electrical insulation barrier 398. The first compartment 394 includes a first insulating medium and a converter switch 315. If a conversion selector 350 is included in the tap changer 300, the conversion selector 350 is arranged in the first compartment. The second compartment 396 includes a second insulating medium and a tap selector 320. The first insulating medium and / or the second insulating medium can be a fluid, such as an oil, for example a mineral oil, such as a silicone oil, a hydrocarbon oil or an ester-based liquid / oil.

[0070] The second compartment 396 of the shielding structure 390 further comprises an opening 392. Thus, the set of tap changer contacts 385 are also arranged in the open second compartment 396 at the opening 392.

[0071] In another embodiment of the present disclosure, Fig. 9 As shown in , the transformer device 400 includes a transformer 420 having at least one regulating winding 105 of a rated regulating voltage. Each of the at least one regulating winding 105 is included in a phase winding 405 of the transformer 420. At least one regulating winding 105 has a tap 110. The transformer device 400 also includes at least one tap changer 300 having a shielding structure 390 as described above. Each of the at least one tap changer 300 is electrically connected to a corresponding regulating winding 105, so that its shielding structure 390 is electrically connected to a connected tap of the corresponding regulating winding 105.

[0072] A transformer 420 having at least one regulating winding 105 is housed in a transformer tank 430 containing an electrical insulating medium. Fig. 9 In the exemplary embodiment of , three tap changers 300 are shown, but only two phase windings 405 / regulating windings 105 are shown. The third phase winding 405 / regulating winding 105 can be imagined to be located outside the figure on the right.

[0073] The shielding structure 390 encapsulating at least one tap changer 300 may be disposed on the wall 440 of the transformer tank 430. By arranging the tap changer 300 on the wall 440 of the transformer tank 430, a portion of the tap changer 300, i.e., a portion of the shielding structure 390, may be disposed inside the transformer tank 430. Therefore, the tap changer 300 may be conveniently interconnected with the transformer inside the tank via the tap changer contacts 385.

[0074] The portion of the shielding structure 390 disposed inside the transformer box 430 is preferably a second compartment 396, which includes the tap selector 320 and the tap changer contact 385. The second insulating medium of the second compartment 396 may be the same insulating medium as the insulating medium contained in the transformer box 430. In this way, when the tap changer 300 is assembled with the transformer box 430, the second compartment may share the insulating medium with the transformer 400 inside the transformer box 430. The first compartment 394 may be fluid-tight with the second compartment 396 so that the first insulating medium and the second insulating medium do not mix. In this way, contaminants, such as residues generated by the operation (switching) of the diverter switch 315, do not contaminate the second insulating medium of the second compartment 396 or the insulating medium of the transformer box 430. Since the change-over selector 350 may also contaminate the insulating medium, it is preferably disposed in the first compartment 394 together with the diverter switch 315.

[0075] A noteworthy special case of a transformer arrangement 400 (not shown in the drawings) includes a Y-coupled transformer 420 having three regulating windings 105 and three tap changers 300. The three tap changers 300 can be encapsulated in a single shielding structure 390 electrically connected to a common connected tap of the three regulating windings 105, because the phases of the Y-coupled transformer share the potential of the selected tap. Therefore, adjacent phases do not produce a superimposed potential. Therefore, the shielding structure is primarily used to protect the internal components from the influence of the external potential between the components and the ground.

[0076] for Fig. 9 For the sake of clarity of the illustration, the wiring between the tap changer 300 of the transformer 420 and the regulating winding 105 is shown in FIG. Fig. 9 However, at least a portion of the tap changer contacts 385 of the tap changer 300 is electrically connected to a corresponding tap 110 of the regulating winding 105 via the electrically insulated connecting cable 160. In particular, each of the fixed contacts 335 of the tap changer contacts 385 is connected to a corresponding tap 110 of the regulating winding 105. Fig.10 Shows Figure 8300, wherein a plurality of connecting cables 160 are added for illustrative purposes. The connecting cables 160 are arranged in parallel at least in the vicinity of the tap changer contacts 385, i.e. at least in the bounded area of ​​the opening 392 of the shielding structure 390, at which the tap changer contacts 385 are arranged. The parallel arrangement of the connecting cables is a convenient way to wire the transformer device 400. At least one of the connecting cables 160 is arranged to dielectrically shield at least one other of the tap changer contacts 385 before being connected to one of the tap changer contacts 385.

[0077] Since the tap changer contacts 385 are arranged in a limited area of ​​the opening 392, the connecting cables 160 can approach the tap changer contacts 385 in parallel from one general direction. This can be advantageously used to provide dielectric shielding for the tap changer contacts 385 that are not covered by the shielding structure 392. Dielectric shielding is provided by arranging the electrically insulated connecting cable 160 adjacent to at least one tap changer contact 385 and connecting the connecting cable 160 to another tap changer contact 385. Because the inserted dielectric material of the insulated connecting cable 160 acts as a shield for the contact, the electric field is reduced at the bypassed tap changer contact 385. The tap changer contacts 385 that cannot be provided with dielectric shielding in this way are arranged to be covered by the shielding structure 390, as described above. By arranging the tap changer contacts 385 in a defined area, such as at the opening 392 of the shielding structure 390, the connecting cable 160 can be arranged adjacent to at least a portion of the tap changer contacts 385 before connecting to other tap changer contacts 385. Thus, all uncovered tap changer contacts 385 can be provided with a dielectric shield.

[0078] exist Fig.10 In the embodiment shown in , connecting cable 160a dielectrically shields tap changer contact 385a before connecting to tap changer contact 385b. Connecting cable 160b dielectrically shields tap changer contact 385c before connecting to tap changer contact 385d. Connecting cable 160c dielectrically shields tap changer contact 385e and tap changer contact 385f before connecting to tap changer contact 385g covered by shielding structure 390. For clarity, Fig.10 Not shown are all connecting cables 160 to be connected to the tap changer contacts 385 .

[0079] Thus, the tap changer 300 is effectively protected from external fields by the shielding structure 390 electrically connected to one connected tap of the regulating winding 105 and by the connecting cable 160 providing a dielectric shield for the tap changer contacts 385. Fig.11 The external electric field is shown in Fig.11 is a simulation of a tap changer 300 according to the invention arranged in a transformer environment. Fig. 9 The shielding structure 390 is simplified and has the same Figure 7-Figure 10 300 and the opening 392 of the shield structure 390 is larger than required. In addition, the tap changer contacts 385 are not included. To further simplify the simulation, the phase winding 405 to which the tap changer 300 on the right is connected is grounded.

[0080] The image shows how shield structure 390 effectively shields the volume enclosed by shield structure 390, but the electric field penetrates the volume through opening 392. In fact, through smaller openings 392 and through the dielectric shielding provided by connecting cable 160, the penetrating electric field can be significantly / completely reduced.

[0081] Modifications and other embodiments of the disclosed embodiments will occur to those skilled in the art who have benefited from the teachings presented in the foregoing description and the associated drawings. Therefore, it should be understood that the embodiments are not limited to the specific embodiments disclosed, and modifications and other embodiments are intended to be included within the scope of the present disclosure. Although specific terms may be employed herein, they are used only in a general and descriptive sense, and not for the purpose of limitation.

Claims

1. A tap changer (300) arranged to be connected to a regulating winding (105) of a rated regulating voltage, the tap changer (300) comprising a converter switch (315), a tap selector (320) and a set of tap changer contacts (385); It is characterized in that The tap selector (320) and the converter switch (315) are encapsulated in a shielding structure (390), the shielding structure (390) being arranged to shield the tap selector (320) and the converter switch (315) from external electric fields, the shielding structure (390) being made of a conductive material and being arranged to be electrically connected to a connected tap of the regulating winding (105), wherein the tap selector (320) is electrically connected to the set of tap changer contacts (385) comprising at least two tap changer contacts (385), at least a portion of the tap changer contacts (385) being arranged to be connected to the regulating winding (105) and a corresponding tap (110), wherein the set of tap changer contacts (385) are arranged at an opening (392) of the shielding structure (390), and wherein the tap changer contacts (385) are arranged on one side of the tap changer (300), and wherein the shielding structure (390) includes a first compartment (394) and a second compartment (396) separated by an electrical insulation barrier (398), and wherein the first compartment (394) includes a first insulating medium and the converter switch (315), and wherein the second compartment (396) includes a second insulating medium and the tap selector (320).

2. The tap changer (300) of claim 1, wherein the shielding structure (390) at least partially covers the set of tap changer contacts (385) at the opening (392) of the shielding structure (390).

3. The tap changer (300) according to claim 2, wherein at least one of the at least two tap changer contacts (385) is covered by the shielding structure (390).

4. The tap changer (300) according to claim 1, wherein the tap changer (300) further includes a change-over selector (350) arranged in the first compartment (394), and wherein the change-over selector (350) is a positive / negative switching type or a coarse / fine switching type.

5. The tap changer (300) of claim 1, wherein the second compartment (396) of the shielding structure (390) includes the opening (392), and wherein the set of tap changer contacts (385) are arranged at the opening (392).

6. A transformer device (400), comprising: - a transformer (420) having at least one regulating winding (105) with a rated regulating voltage, the at least one regulating winding (105) having a tap (110); - at least one tap changer (300) according to any one of claims 1 to 5, the tap transformer (300) having a shielding structure (390); and It is characterized in that each of the at least one tap changer (300) is electrically connected to a corresponding regulating winding (105), so that the shielding structure (390) of the tap transformer (300) is electrically connected to a connected tap of the corresponding regulating winding (105).

7. The transformer device (400) according to claim 6, wherein at least a portion of the tap changer contacts (385) of the tap changer (300) is electrically connected to a corresponding tap of the regulating winding (105) via an electrically insulating connecting cable (160).

8. The transformer device (400) according to claim 7, wherein the connecting cable (160) is arranged in parallel at least adjacent to the tap changer contact (385).

9. The transformer device (400) according to claim 7, wherein at least one of the connecting cables (160) is arranged to dielectrically shield at least one other of the tap changer contacts (385) before connection with one tap changer contact (385).

10. The transformer device (400) according to claim 6, wherein the at least one regulating winding (105) is accommodated in a transformer box (430) containing an electrically insulating medium, and wherein the shielding structure (390) encapsulating the at least one tap changer (300) is arranged on a wall (440) of the transformer box (430).

11. The transformer device (400) according to claim 6 comprises a Y-coupled transformer (420) having three regulating windings (105) and three tap changers (300), and wherein the three tap changers (300) are encapsulated in a shielding structure (390) electrically connected to a commonly connected tap of the three regulating windings (105).

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