EP2530693A1 - Tap changer - Google Patents
Tap changer Download PDFInfo
- Publication number
- EP2530693A1 EP2530693A1 EP11168222A EP11168222A EP2530693A1 EP 2530693 A1 EP2530693 A1 EP 2530693A1 EP 11168222 A EP11168222 A EP 11168222A EP 11168222 A EP11168222 A EP 11168222A EP 2530693 A1 EP2530693 A1 EP 2530693A1
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- EP
- European Patent Office
- Prior art keywords
- positioning
- contact
- tap changer
- positioning loop
- loop
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H9/00—Details of switching devices, not covered by groups H01H1/00 - H01H7/00
- H01H9/0005—Tap change devices
- H01H9/0027—Operating mechanisms
Definitions
- the present invention relates the field of power transmission, and in particular to tap changers for controlling the output voltage of a transformer.
- Tap changers are used for controlling the output voltage of a transformer by providing the possibility of switching in, or switching out, additional turns in a transformer winding.
- a tap changer comprises a set of fixed contacts, each of which is connectable to a different tap of a regulating winding of a transformer, where the taps are located at different positions in the regulating winding.
- a tap changer further comprises a moveable contact which is connected to a current collector at one end, and connectable to one of the fixed contacts at the other end. By switching in or out the different taps, the effective number of turns of the transformer can be increased or decreased, thus regulating the output voltage of the transformer.
- a tap changer thus includes various parts at different electrical potentials.
- the distance between such two such parts should exceed a distance over which the insulation medium, in which the tap changer is immersed, can withstand the maximum expected potential difference between the two parts.
- the insulation distances vary between different insulation media. In dry tap changers, which are insulated by means of air, the insulation distances are approximately one order of magnitude larger than in conventional oil insulated tap changers. Thus, air insulated tap changers for use in high voltage applications tend to be very large, and therefore space-consuming and unwieldy to handle.
- a problem to which the present invention relates is how to obtain a compact design of a tap changer.
- the tap changer for connection to a regulating winding of a transformer.
- the tap changer comprises a tap selector including: a set of fixed contacts comprising at least two fixed contacts, each arranged to be connected to a tap of the regulating winding; at least one current collector located at a distance from the set of fixed contacts so that a contact gap space is formed therebetween; and at least one contact carrier including at least one moveable contact arranged to electrically bridge a contact gap between a current collector and a fixed contact.
- the tap changer further comprises a drive system for moving the at least one contact carrier from one fixed contact position to another, where the drive system comprising at least one electrically insulating, mechanically flexible positioning loop provided with a plurality of evenly distributed positioning items. The positioning loop is attached to the contact carrier in order to allow for transmission of a driving force thereto.
- an electrically insulating and mechanically flexible positioning loop By use of an electrically insulating and mechanically flexible positioning loop, a compact design of the tap changer can be achieved.
- Such positioning loop allows for a design where the contact gap is determined by the insulation distance required between the fixed contacts and the current collector, thus allowing for a compact design in the contact gap direction.
- a compact design in the extension direction is also facilitated, since the drive system is confined to the same space regardless of at which fixed contact position the moveable contact is currently located.
- the positioning loop can advantageously be at least partly located in the contact gap space.
- a mechanically advantageous design of the drive mechanism can hereby be achieved, and since the positioning loop is electrically insulating, the minimum requirements on the contact gap will not be effected.
- a point of mechanical connection of the positioning loop to the contact carrier is located within a distance of [0.2d gap ; 0.8d gap ] from the current collector in the contact gap direction.
- the point of mechanical connection is located within a distance of [0.45d gap ; 0.55d gap ], in order to improve the mechanical advantage in relation to forces acting on the ends of the moveable contact.
- the positioning loop could be implemented as a timing belt, having evenly distributed positioning items formed as integral teeth, holes or protrusions.
- the positioning loop could alternatively be implemented as a chain.
- the drive system advantageously further comprises at least one drive wheel the periphery of which is provided with evenly distributed positioning items arranged to interact with the positioning items of the positioning loop, so that upon rotation of the drive wheel, the contact carrier will perform a linear movement.
- the positioning loop can advantageously be formed from an electrically insulating material which is expected to experience, during its lifetime, a mechanical crimpage/elongation in the range of ⁇ 1% due to temperature changes, moisture changes and mechanical creep.
- the electrically insulating material could for example be a polymer-composite comprising a liquid crystal polymer or a para-aramid synthetic material.
- the positioning loop can pre-stressed so that the initial pre-stressed elongation of the positioning loop is larger than the largest expected sum of the mechanical creep elongation, the change in the length of the positioning loop due to thermal expansion and the change in the positioning loop due to moisture elongation, in order to ensure a tension in the positioning loop throughout its lifetime.
- the drive system comprises a wheel the centre of which may be adjusted in order to adjust the length of the positioning loop.
- a suitable pre-stress can be applied to the positioning loop, ensuring that there will be a tension in the positioning loop throughout its lifetime, allowing for example for flow of time, for temperature changes, and for changes in moisture content.
- the spacing of the positioning items of driving wheel exceeds the spacing of the corresponding positioning items of the positioning loop.
- the ratio of the spacing of the positioning items of the driving wheel to those of the positioning loop falls within the range of [1.0005; 1.006].
- the drive system can further comprise an electrically insulating linear guide located in the contact gap space for mechanically guiding the movement of the contact carrier.
- the contact carrier could for example have a guiding part arranged to follow the linear guide.
- the tap changer could comprise a clamp for mechanically connecting the positioning loop to the contact carrier, wherein the clamp and/or the contact carrier is provided with at least one positioning item to mesh with at least one corresponding positioning item of the positioning loop.
- Fig. 1a schematically illustrates a tap changer 100 which is connected to a regulating winding 105 having a set of different taps 110.
- the tap changer of Fig. 1a is of diverter switch type, and comprises a diverter switch 115 and a tap selector 120.
- the tap selector 120 of Fig. 1a comprises two current collectors 125, two moveable contacts 130 and a set of fixed contacts 135, where each fixed contact 135 is arranged to be connected to one of the taps 110 of the regulating winding.
- a moveable contact 130 is arranged to electrically bridge a contact gap between a current collector 125 and a fixed contact 135.
- the linear tap changer should be construed as a mechanically linear tap changer, unless stated otherwise.
- the two current collectors 125 together form a current collector part.
- the current collector part is formed by the single current collector 125, etc.
- the following description will, for illustrative purposes only, be made in terms of a tap changer having two current collectors 125 and two moveable contacts 130. The invention is however equally applicable to a tap changer having a different number of current collectors 125 and/or moveable contacts 130, such as a single current collector 125, three current collectors 125, etc.
- the diverter switch 115 of Fig. 1a comprises two series connections of a main contact 140 and a transition contact 145, with a transition resistor 150 connected in parallel with the transition contact 145.
- Each of the series connections are, at one end, connected to a respective one of the two current collectors 125, and, at the other end, connected to an external contact 155 of the tap changer 100.
- the two moveable contacts 130 are, at one end, in electrical contact with a respective one of the current collectors 125.
- a moveable contact 130 can move along the current collector 125 to which it is connected, in order to reach different positions at which the other end of the moveable contact 130 is in electrical contact with one of the fixed contacts 135.
- the moveable contacts 130 could for example be sliding contacts arranged to slide along the current collectors 125, to allow for electrical connection between the current collectors 125 and the different fixed contacts 135.
- 1a is arranged so that if one of the moveable contacts 130 is in contact with a fixed contact 135, connected to a first tap, the other moveable contact 130 is in contact with a second fixed contact 135, adjacent to the first tap and connected to a second tap 110.
- the electrical path through the tap changer 100 ends at the external contact 155 at one end, and at the other end at the fixed contact 135 which is currently connected to the regulating winding 105. At the other end of the regulating winding 105 is provided a further contact 175, so that a path is provided through the tap changer 100 and the regulating winding 105 between contacts 155 and 175.
- An example of a diverter switch 115 is described in EP0116748 .
- the diverter switch 115 of Fig. 1a is an example only, and any suitable type of diverter switch 115 can be used.
- the different fixed contacts 135 When the tap changer 100 is in use, the different fixed contacts 135 will be at different potential levels, corresponding to the different potential levels of the different taps 110 of the regulating winding 105. Thus, the potential difference between the current collectors 125 will correspond to the potential difference between two adjacent taps 110, U adj . U adj is typically constant throughout the regulating winding 105. Only one fixed contact 135 at a time will be connected, via the moveable contact 130, to the current collector 125 which is currently connected to the external connection 155 of the tap changer, this fixed contact 135 being referred to as the connected fixed contact 135.
- the potential difference between a current collector 125 and a particular fixed contact 135 varies depending on at which position the moveable contact 130 is connected, and could be considerably larger than the potential difference between two adjacent fixed contacts 135.
- the maximum potential difference between a current collector 125 and a fixed contact 135 occurs when one of the end fixed contacts 135, denoted 135e in Fig. 1a , are connected and forms part of the current path through the tap changer 100.
- the potential difference between the current collector 125 that is connected, and the end fixed contact 135e which is not connected corresponds to the entire voltage across the regulating winding 100, U reg .
- U reg also referred to as the regulation voltage, is illustrated in Fig. 1 a by arrow 170.
- the distances between two parts at different potential should reach or exceed the minimum distance over which the medium, in which the tap changer 100 is immersed, can withstand the voltage obtained between the two parts.
- Such insulation distances depend on the medium surrounding the tap selector 120, and increase with increasing rated regulation voltage (which typically depends on the rated voltage of the transformer as well as on the desired number of taps 110).
- the particular regulation voltage used for defining the insulation distances is often a test voltage and are one of the parameters for which the tap changer 100 is rated.
- the direction y as indicated by the coordinate system in Fig. 1a , in which direction the current collectors 125 extend, will in the following be referred to as the extension direction of the linear tap changer 100.
- the actual distance between two adjacent fixed contacts 135 will hereinafter be referred to as the adjacent contact distance, d adj
- the actual distance between a current collector 125 and the fixed contacts 135 will be referred to as the contact gap, d gap .
- d adj should reach or exceed
- d gap should reach or exceed .
- any further electrically conducting parts are present in the space formed between the current collector 125 and the arrangement of fixed contacts 135, the contact gap d gap will often have to be increased. This is for example the case when the moveable contact 130 is connected to a metallic drive mechanism for providing a force required to move the moveable contact 130 between different fixed contact positions. In this case, the distance between the fixed contacts 135 and such drive mechanism, as well as the distance between the current collector(s) and such drive mechanism, should both reach or exceed .
- the actual distances d adj and d gap of the tap changer of Fig. 1a have been indicated in the drawing.
- the contact cap d gap in Fig. 1a is shown to be independent on position y along the extension direction.
- the contact gap d gap should, when d gap is independent on position, reach or exceed the maximum required insulation distance i.e. the insulation distance at the end fixed contacts 135e.
- the term insulation distance will be used to refer to the maximum required insulation distance.
- a space referred to as the contact gap space is defined by the current collectors 125 and the set of fixed contacts 135, in which space the electric field is to a large extent determined by the potential difference between the current collectors 125 and the fixed contacts 135.
- the contact gap space 165 is here defined as the space confined by i) an (imaginary) plane through the centers of the current collectors 125, if more than one; ii) an (imaginary) plane through the rows of fixed contacts 135, if more than one row; iii) a set of (imaginary) semi-cylinders parallel to the extension direction, each semi-circle having a radius corresponding to the contact gap space, where the center of a corresponding (full) cylinder coincides with the location of row of fixed contacts 135 or a current collector 125; iv) the "top" and “bottom” (imaginary) spherical surfaces having their centers at the end of the current collectors 125 and adjacent end fixed contacts 135e.
- FIG. 1 b A sectional view of the contact gap space 165 as seen from along the extension direction of the tap changer 100 is shown in Fig. 1 b.
- FIG. 1c A more compact version of the contact gap space, referred to as the compact contact gap space 175, is shown in Fig. 1c .
- the compact contact gap space 175 is a sub-space of the contact gap space 165.
- the compact contact gap space 175 is defined for a tap changer 100 having two current collectors 125 or less as the space confined by the surfaces as defined in i), ii) and iv) above, as well as by v) (imaginary) semi-cylinders having a diameter corresponding to the contact gap, and the centers of which are located at the centre of the line interconnecting a current collector 125 with the corresponding fixed contact 135.
- the contact gap space 165 (and the compact contact gap space 175) will be smaller than if two or more current collectors 125 are provided. Unless the contact gap space 165 is shielded from external electric fields, the potential difference between the current collectors 125 and the fixed contacts 135 will typically further be influenced by the surrounding electrical fields, thus requiring a larger contact gap d gap , and thereby a larger contact gap space, than if no external fields were present in the contact gap space 165.
- an air insulated tap changer 100 In a tap changer 100 which is air insulated, the insulation distances need to be considerably larger than in an oil insulated tap changer 100. For example, in an air insulated tap changer 100 wherein an insulation distance is 30 cm, the corresponding insulation distance could typically be around 3 cm in an oil insulated tap changer. Thus, an air insulated tap changer 100 typically needs to be physically larger than if the tap changer 100 were insulated by means of 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 a skyscraper); or in environmentally sensitive areas, where the risk of contamination should be minimized.
- air insulated tap changer 100 should here be construed to include tap changers 100 which are insulated by air, or by air-like gases in a controlled space, such as tap changers 100 insulated by nitrogen gas (N 2 ), tap changers 100 insulated by air at a controlled pressure, etc.
- tap changers 100 which are insulated by air, or by air-like gases in a controlled space, such as tap changers 100 insulated by nitrogen gas (N 2 ), tap changers 100 insulated by air at a controlled pressure, etc.
- the insulation distances of a tap changer depend on the voltage rating of the tap changer and the insulation medium.
- a conventional design of the tap changer may be impractical due to the size required in order to fulfill the insulation requirements.
- a more compact design of a tap changer is desired.
- a tap changer having a drive system for moving the moveable contact(s) from one fixed contact position to another, where the drive system comprises an electrically insulating, mechanically flexible, positioning loop.
- the positioning loop is mechanically connected to the moveable contact for transmission of a driving force thereto.
- Alternative designs of a drive system for providing the force for moving a moveable contact 130 include a metallic ball screw as described in CN2879373 or a Geneva rod as described in US4,562,316 .
- a metallic ball screw as described in CN2879373 or a Geneva rod as described in US4,562,316 .
- the inventive drive system facilitates for a considerably more compact design in the direction of the contact gap, since no flashover will occur to the insulating positioning loop.
- the contact gap can be set at approximately the contact gap insulation distance , even if the positioning loop is located in the contact gap space 165 (it may still be desirable to use a contact gap which exceeds , for example in order to ensure adequate insulation even when the electric field within the contact gap space 165 is influenced by external electric fields).
- the inventive drive mechanism facilitates for a considerably more compact design in the extension direction of the tap selector 120 since the positioning loop, as opposed to the Geneva rod, will be confined to the same space, regardless of at which fixed contact position the moveable contact 130 is currently located.
- FIG. 2a An example of a drive system 200 comprising an electrically insulating and mechanically flexible positioning loop 205 is shown in Fig. 2a .
- the drive system 200 of Fig. 2a further comprises a driving wheel 210 arranged to mesh with the positioning loop 205 for driving thereof.
- the driving wheel 210 thus includes, on its periphery, a set of evenly distributed positioning items 213, to engage with corresponding positioning items 300 of the positioning loop (cf. Figs. 3a-3d ).
- the driving wheel 210 is arranged to be driven by a shaft 214 which is connected to an electric motor via a gear box (not shown).
- the drive system 200 of Fig. 2a further comprises three pulleys 215.
- the pulleys 215, together with the driving wheel 210, define a path for the positioning loop 205.
- the positioning loop 205 of Fig. 2a is mechanically connected to a contact carrier 220 via a clamp 225 for clamping the positioning loop 205 to the contact carrier 220.
- the contact carrier 220 of Fig. 2a is arranged to carry the moveable contact 130 and includes a flange 230 providing a counterpart to the clamp 225, facilitating for the clamping of the positioning loop 205 to the contact carrier 220.
- the positioning loop 205 of Fig. 2a when brought to move by the driving wheel 210, thus transfers a force to the contact carrier 220 along the extension direction of the tap selector 120.
- the contact carrier 220 of Fig. 2a further includes a guiding part 235 in the form of a circular tube which is open along its axial direction, the guiding part 235 being arranged to run along a guiding rod of the tap changer 100 for appropriate guiding of the contact carrier 220 in the extension direction of the tap changer 100.
- a guiding part 235 of a contact carrier 220 could alternatively be of another shape, such as a closed tube, a hollow parallelepiped, etc.
- a guiding rod (not shown) of the tap changer 100 could advantageously be of a cross section which corresponds to the cross section of the guiding part 235.
- the guiding part 235 and the flange 230 are integral parts of the contact carrier 220
- a separate guide 235 and/or a separate flange 230 attached to the contact carrier 220 could be provided; the flange 230 could be replaced by different means of attaching the positioning loop 205; etc.
- the positioning loop 205 could, in a simple embodiment, be directly attached to the moveable contact.
- the contact carrier 220 could simply consist of one or more moveable contacts 130.
- a guide 235 would generally be advantageous.
- the four wheels/pulleys of Fig. 2a together define a path for the positioning loop such that the path can provide a linear motion of the moveable contact 130 in the extension direction of the tap changer 100 in the region between the current collectors 125 and the set of fixed contacts 135.
- Such a path can be defined in many different ways by use of a different number of wheels 210/215, or by simply arranging the wheels 210/215 in a different manner.
- a suitable wheel configuration should comprise at least one driving wheel 210 and at least one pulley 215, where the distance between at least two of the wheels 210/215 define at least one linear path part of along the extension direction of the tap changer 100.
- FIG. 2b-2d Further examples of drive systems 200 of alternative wheel configurations defining a path having such linear part are schematically shown in Figs. 2b-2d .
- the drive system 200 of Fig . 2b comprises one driving wheel 210 and one pulley 215;
- the drive system 200 of Fig . 2c comprises one driving wheel 210 and two pulleys 215; while the drive system 200 of Fig . 2d comprises one driving wheel 210 and four pulleys 215.
- a different wheel configuration may be advantageous.
- the diverter switch 115 is located behind the current collectors 125 as seen from the fixed contacts 135, the configuration shown in Fig. 2a would be beneficial.
- the driving wheel 210 will not be part of forming the linear path part in the extension direction of the tap changer, but will be located in line with the diverter switch 115 in the y-direction.
- the same driving shaft 214 could be used for controlling the movement of the moveable contact 130 and for controlling the diverter switch 115, while the point of attachment between the positioning loop 205 and the contact carrier 220 can be provided in the contact gap space 165.
- a wheel configuration wherein a return path of the positioning loop 205 runs parallel to the part of the path which provides a linear movement of the moveable contact 130 is beneficial in order to save space (cf. Figs. 2a , 2b, 2d ).
- Which wheel 210/215 is the driving wheel 210 could e.g. be selected in accordance with the most favourable location of the driving shaft 214.
- the configurations shown in Figs. 2a-2d include a single driving wheel 210. In an alternative implementation, two or more driving wheels 210 could be employed.
- FIGs. 3a-3d different embodiments of a positioning loop 205 are shown (only part of a positioning loop 205 has been shown for illustration purposes).
- Each embodiment of the positioning loop 205 is provided with a plurality of evenly distributed positioning items 300, which positioning items are designed to mesh with corresponding positioning items 213 of a driving wheel 210 of the drive mechanism (cf. Fig. 2a ) and thereby mechanically convey rotary movement of the wheel into linear movement of the moveable contact 130.
- the positioning loop 205 of Fig . 3a is a timing belt provided with evenly distributed integral teeth on the inside of the timing belt, so that the positioning loop can run along the circumference of a positioning wheel.
- the positioning loop 205 of Fig . 3b is also a timing belt which is provided with evenly distributed positioning items 300 in the form of integral teeth, designed to mesh with a sprocket, where the teeth are provided at the inside, as well as outside, of the timing belt.
- the positioning loop 205 of Fig . 3c is a timing belt which is provided with evenly distributed positioning items 300 in the form of circular holes, which are designed to mesh with a driving wheel 210 having evenly distributed cylindrical or part-spherical protrusions along its circumference.
- the holes could be of a different shape, such as elliptic, rectangular or triangular, designed to mesh with wheel protrusions of a corresponding shape.
- the positioning loop 205 of Fig . 3d is a string provided with evenly distributed positioning items 300 in the form of spherical beads, where a bead is designed to mesh with a corresponding positioning item in the form of a recess in the circumference of a driving wheel 210. Further embodiment of the positioning loop 205 may be contemplated.
- the positioning loop 205 could be implemented as an insulating chain - for instance in the shape of a bicycle chain or similar, manufactured from an insulating material.
- the circumference of a driving wheel 210 comprises a plurality of evenly distributed positioning items 213 for engaging with corresponding positioning items 300 of the positioning loop 205, such positioning items for example being teeth (the driving wheel 210 thus being a sprocket), protrusions or recesses.
- the circumference of the pulleys 215 could be smooth, or, if desired, the circumference of one or more of the pulleys 215 could comprise a plurality of evenly distributed positioning items 213.
- FIG. 4a An example of an embodiment a contact carrier 220 and a clamp 225 for attaching the positioning loop 205 to the moveable contact 130 is schematically shown in Fig . 4a , where the contact carrier 220 includes a guiding part 235 for interacting with a guiding rod, as well as a flange 230 for interacting with the clamp 225. Either the clamp 225 and/or the flange 230 could furthermore advantageously be provided with positioning items 213 arranged to engage with the positioning items 300 of the positioning loop 205.
- Either the clamp 225 and/or the flange 230 could moreover be provided with a track 410 for receiving the positioning loop 205, in order to mechanically stabilize the positioning loop 205 in the direction perpendicular to the linear movement of the moveable contact 130 (i.e. perpendicular to the extension direction).
- the clamp 225 could for example be attached to the flange 230 by means knurling and a suitable screw arrangement.
- the holes, through which the attachment screws 415 are to be inserted may be of an elongated shape in one of the contact carrier 220 and the clamp 225, while the corresponding holes in the other of the contact carrier 220 and the clamp 405 are circular.
- the elongated shape could advantageously provide a play of half the distance between the positioning items 213 of the driving wheel 210, or more.
- a clamp 225 In Fig. 4b , an example of a clamp 225 is shown, where the clamp 225 is provided with positioning items 213 as well as a track 410 for receiving the positioning loop 205, the positioning items 213 being located in the track 410.
- all or part of the surfaces 420, and/or all or part of the corresponding surfaces of the contact carrier 220 (flange 230), could be knurled.
- An alternative implementation of a clamp 225 is shown in Fig . 4c , where the clamp 225 comprises a surface provided with positioning items 213, which surface is provided with holes for receiving attachment screws 215.
- the clamp design shown in Fig. 4b is desirable, since holes through the positioning loop 205 may reduce the mechanical strength of the material.
- the positioning loop 205 could be a closed loop which is attached to the contact carrier 220, or could be an open piece of belt/band/string/etc., which is formed into a loop and attached to the contact carrier 220.
- the correspondence between the rotation of the driving wheel 210 and the transportation of the moveable contact 130 along the extension direction of the tap changer will be well defined.
- the moveable contact 130 By rotating the driving wheel 210 through a certain angle, determined by the relationship between the radius of the driving wheel and the distance between two adjacent fixed contacts 135, the moveable contact 130 will move from one fixed contact position to an adjacent fixed contact position.
- a positioning loop 205 for the transfer of a force from a rotating shaft 214 to the moveable contact 130 provides a flexible solution as to the angle of rotation required for obtaining a movement of the moveable contact 130 between two adjacent fixed contact positions-the certain angle for obtaining this movement will be determined by the ratio between the radius of the driving wheel 210, R, and the distance between adjacent fixed contacts 135, d adj .
- a certain angle of rotation for obtaining movement between two adjacent fixed contacts 135 can thus be obtained by a design having the required ratio between R and d adj .
- the wheel configuration comprising at least one driving wheel 210 and at least one pulley 215 operates to keep the positioning loop 205 in the desired position.
- the predetermined relationship between rotary movement of the driving wheel and the linear movement of the moveable contact 130 applies at all times.
- any slipping between the driving wheel 210 and the positioning loop 205 should be avoided. Such slipping can be avoided by keeping the positioning loop 205 stretched.
- the length of the positioning loop 205 will typically depend on time (through mechanical creep), on temperature and on the moisture content of the positioning loop 205.
- the length of the positioning loop 205 will typically depend on the temperature expansion of a structure which keeps the wheels 210/215 in position, as well as on the temperature expansion of the positioning loop itself.
- the positioning loop 205 could advantageously be pre-stressed before the tap changer 100 is used for the first time.
- the positioning loop 205 could advantageously be pre-stressed so that the initial pre-stressed elongation of the loop is larger than the largest expected sum of the mechanical creep elongation, the change in the length of the positioning loop due to thermal expansion and the change in the positioning loop due to moisture elongation.
- the positioning loop 205 can be expected to stay stretched at all times, thus avoiding a slacking positioning loop 205 (the stress in the loop may on the other hand vary over time).
- a well-defined relationship between the angle of rotation of the driving wheel 210 and the obtained movement of the moveable contact 130 can thus be obtained.
- the spacing d 300 of the positioning items 300 of the positioning loop 205 could advantageously be slightly smaller than the spacing d 213 of the corresponding positioning items 213 of the driving wheel 210 and the clamp 225 (and of the pulleys 215, when applicable), so that by initially stretching of the positioning loop 210, the spacing d 300 of the position loop positioning items 300 can be made to coincide with the spacing d 213 of the corresponding positioning items 213.
- An optimal ratio of d 213 to d 300 will typically depend on the creep properties of the material from which the positioning loop 205 is formed.
- At least one of the wheels 210/215 is arranged so that the position of the centre of the wheel 210/215 can be adjusted, thereby allowing for the adjustment of the length of the positioning loop 205.
- the position of the centre of the other wheels will typically be fixed.
- a wheel 210/215, the centre of which can be adjusted, will in the following be referred to as an adjustable wheel.
- a length adjustment mechanism could be implemented either at a drive wheel 210 or at a pulley 215, although it is often best implemented in relation to a pulley 215 rather than a driving wheel 210, since the location of the centre of the driving wheel 210 should correspond to the location of the transmission shaft 214.
- Adjustability of a wheel 210/215 could be implemented by use of suitable assembly tools upon installation of the tap changer 100, or by means of an integrated length adjustment mechanism, examples of which are shown below in Figs. 5a and 5b .
- the position of the wheel can thus be adjusted to achieve a desired length of the positioning loop 205.
- a length adjustment mechanism operates to obtain a desired elongation rather than a desired force on the positioning loop 205.
- Adjustment of the length of the positioning loop 205 can for example be performed in an iterative manner upon installation of the tap changer 100, until a desired spacing of the positioning items 300 of the positioning loop 205 has been obtained.
- a material with a low creep coefficient would be desired, so that the part of the elongation due to creep will occur during installation of the tap changer, rather than when the tap changer 100 is in use.
- the initial pre-stressed elongation of the positioning loop 205 could for example be in the order of 0.05-0.5 %, although depending on the circumstances, a different elongation may be used.
- a length adjustment mechanism could for example operate to provide a circular or a linear displacement of an adjustable wheel.
- An example of a circular length adjustment mechanism 500 is shown in Fig. 5a
- a linear length adjustment mechanism 500 is shown in Fig. 5b .
- the circular adjustment mechanism 500 of Fig . 5a is an eccentric, which comprises a cylindrical plug 505 having a shaft 510 arranged to accept the wheel 210/215 at a location which is offset from the center of the plug 505, so that by rotating the plug 505, the location of the wheel (and hence the elongation of the positioning loop 215) may be adjusted.
- the eccentric 500 further includes screws (not shown), by means of which the plug 505 can be fixed in place when the location of the wheel 210/215 has been adjusted. Ball bearings
- the linear adjustment mechanism 500 of Fig . 5b comprises a shaft 510 arranged to accept the wheel 210/215, where the shaft 510 is arranged on a guide 515 which is linearly movable within a guide holder 520.
- the linear adjustment mechanism 500 further includes screws (not shown), by means of which the plate 515 can be fixed in place when the location of the wheel has been adjusted.
- part or whole of the positioning loop 205 can be located in the contact gap space 165 as defined in relation to Fig. 1b , without influencing the electric field distribution in the contact gap space 165.
- a part of the positioning loop path which defines a straight path, for the contact carrier 220 to move along could be located in the contact gap space 165.
- the point of the attachment between the drive system 200 and the contact carrier 220 can be located in the contact gap space 165 without having to extend the contact gap d gap beyond the contact gap insulation distance, .
- a moveable contact 130 experiences a risk of being exposed to mechanical and electrical forces, e.g. due to friction between the moveable contact 130 and the fixed contacts 135 and/or the current collector 125; or due to electrical short-circuit forces in case of short circuit currents in a nearby conductor, etc. Such undesired forces act to move the moveable contact 130 from its correct position, thus giving rise to a risk for electrical arcing.
- positioning loop 205 need not be directly mechanically connected to the contact carrier 220 but could be mechanically connected to the moveable contact 130 via an intermediary part, such as an electrical insulating or non-insulating part (e.g. a bar).
- An electrically insulating positioning loop 205 could advantageously be made from an insulating material which exhibits low mechanical creep, for example a polymer of good creep resistance. Since accurate correspondence between the spacing of the positioning items 300 of the positioning loop 205 and the spacing of the corresponding positioning items 213 of a driving wheel 210 will ensure accurate positioning of the moveable contact 130 at the different fixed contact positions, a material which exhibits very low long term creep would be advantageous. For example, a material having creep properties in the range of 0-0.3 % during lifetime would be suitable. Low moisture absorption is also desirable since moisture can influence the mechanical strength properties, such as elongation and/or strength, as well as the electrical conductivity, of the material.
- An example of mechanically flexible and electrically insulating materials which can be designed to have the desired creep properties is polymer-cord composite materials, where a polymer, such as polyurethane, polyester, or rubber, is reinforced with cords of an electrically insulating and mechanically creep resistant material, so that the cords are embedded in a polymer matrix.
- the cords could for example be made from a liquid crystal polymer, which can for example be melt spun into a high performance material.
- Vectran® is an example of a liquid crystal polymer. Vectran® is a wholly aromatic polyester made by the acetylation polymerisation ofp-hydroxybenzoic acid and 6-hydroxy-2-naphthoic. The molecular structure of Vectran® is shown in Fig . 6 .
- thermotropic liquid crystal polymers could also be contemplated.
- suitable flexible and insulating materials is the para-aramid synthetic fibres, such as Kevlar or Twaron. Both the liquid crystal polymers and the para-aramid synthetic fibres show a high creep resistance, a low coefficient of thermal expansion and low moisture absorption.
- a suitable ratio of d 213 to d 300 could for example lie within the range of [1.0005; 1.004] when the positioning loop 205 comprises liquid crystal polymers and within the range of [1.0005; 1.006] when the positioning loop 205 comprises para-aramid synthetic materials. Under some circumstances, an even larger value of this ratio may be beneficial, such as e.g. if the expected temperature contraction (negative elongation) of the structure in which the drive system 200 is suspended is large. In many implementations, however, a ratio within the range of [1.001; 1.003] for liquid crystal polymers and within the range of [1.003; 1.004] for para-aramid synthetic materials will be sufficient.
- Suitable materials which could be used for the cord of a polymer-cord composite in a positioning loop 205 include glass fibre.
- the positioning loop 205 is implemented in the form of a chain or similar, the material itself does not have to be flexible, since the flexibility is provided in the mechanical design of the loop.
- suitable rigid materials which could be used for the positioning loop when implemented as a chain include composites of polyester/glass; epoxy/glass; polyphthalamide/glass.
- FIG. 7 An example of a tap selector 120 wherein the moveable contact 130 is moved from one fixed contact position to another by means of a driving system 200 having an electrically insulating, mechanically flexible positioning loop 205 is shown in Fig . 7 .
- the moveable contact 130, the fixed contacts 135 with cables 160, and the current collector 125 with a cable 700 for connecting to a diverter switch 115 are shown, as is the driving system 200 comprising the positioning loop 205, a drive wheel 210, pulleys 215, and guiding rod 705.
- the guiding rod 705, as well as the positioning loop 205 is made from an electrically insulating material such as a polymer or a ceramic material.
- a guiding part 235 of the contact carrier 220 could contain a low friction part or coating, made of a suitable low friction material (e.g. polytetrafluoreten (PTFE)). Low friction between the guiding part 235 and the contact carrier 220 could alternatively be achieved by providing the guiding rod 705 with a coating of low friction material.
- a suitable low friction material e.g. polytetrafluoreten (PTFE)
- the tap changer 100 of which the tap selector 120 is shown in Fig. 7 has one moveable contact 130.
- a tap changer 100 having more than one independently moveable contacts 130 can advantageously be provided with one positioning loop 205 for each independently moveable contact 130.
- a single positioning loop 205 would be sufficient for the jointly moveable contacts 130.
- the invention could advantageously be used in an on-load tap changer 100, where the regulation of the transformer output voltage takes place while the transformer is in operation, as well as in a non-excited, off-load tap changer.
- the insulation distances are so much larger in air than in oil or for example SF6, the benefits of a compact design are more pronounced in an air insulated tap changer.
- the invention can advantageously be applied also in oil or SF6 insulated designs, which can then be very compactly designed.
Abstract
Description
- The present invention relates the field of power transmission, and in particular to tap changers for controlling the output voltage of a transformer.
- Tap changers are used for controlling the output voltage of a transformer by providing the possibility of switching in, or switching out, additional turns in a transformer winding. A tap changer comprises a set of fixed contacts, each of which is connectable to a different tap of a regulating winding of a transformer, where the taps are located at different positions in the regulating winding. A tap changer further comprises a moveable contact which is connected to a current collector at one end, and connectable to one of the fixed contacts at the other end. By switching in or out the different taps, the effective number of turns of the transformer can be increased or decreased, thus regulating the output voltage of the transformer. A tap changer thus includes various parts at different electrical potentials. In order to satisfy insulation requirements, the distance between such two such parts should exceed a distance over which the insulation medium, in which the tap changer is immersed, can withstand the maximum expected potential difference between the two parts. The higher the voltage rating of the tap changer, the larger will the insulation distances be for the same insulation medium. Furthermore, the insulation distances vary between different insulation media. In dry tap changers, which are insulated by means of air, the insulation distances are approximately one order of magnitude larger than in conventional oil insulated tap changers. Thus, air insulated tap changers for use in high voltage applications tend to be very large, and therefore space-consuming and unwieldy to handle.
- A problem to which the present invention relates is how to obtain a compact design of a tap changer.
- One embodiment provides a tap changer for connection to a regulating winding of a transformer. The tap changer comprises a tap selector including: a set of fixed contacts comprising at least two fixed contacts, each arranged to be connected to a tap of the regulating winding; at least one current collector located at a distance from the set of fixed contacts so that a contact gap space is formed therebetween; and at least one contact carrier including at least one moveable contact arranged to electrically bridge a contact gap between a current collector and a fixed contact. The tap changer further comprises a drive system for moving the at least one contact carrier from one fixed contact position to another, where the drive system comprising at least one electrically insulating, mechanically flexible positioning loop provided with a plurality of evenly distributed positioning items. The positioning loop is attached to the contact carrier in order to allow for transmission of a driving force thereto.
- By use of an electrically insulating and mechanically flexible positioning loop, a compact design of the tap changer can be achieved. Such positioning loop allows for a design where the contact gap is determined by the insulation distance required between the fixed contacts and the current collector, thus allowing for a compact design in the contact gap direction. Furthermore, a compact design in the extension direction is also facilitated, since the drive system is confined to the same space regardless of at which fixed contact position the moveable contact is currently located.
- The positioning loop can advantageously be at least partly located in the contact gap space. A mechanically advantageous design of the drive mechanism can hereby be achieved, and since the positioning loop is electrically insulating, the minimum requirements on the contact gap will not be effected. In one embodiment, a point of mechanical connection of the positioning loop to the contact carrier is located within a distance of [0.2dgap; 0.8dgap] from the current collector in the contact gap direction. Hereby is achieved that the influence on forces acting on the moveable contact will be small. In one implementation, the point of mechanical connection is located within a distance of [0.45dgap ; 0.55dgap], in order to improve the mechanical advantage in relation to forces acting on the ends of the moveable contact.
- The positioning loop could be implemented as a timing belt, having evenly distributed positioning items formed as integral teeth, holes or protrusions. The positioning loop could alternatively be implemented as a chain.
- The drive system advantageously further comprises at least one drive wheel the periphery of which is provided with evenly distributed positioning items arranged to interact with the positioning items of the positioning loop, so that upon rotation of the drive wheel, the contact carrier will perform a linear movement.
- In order to obtain a time-independent relation between the rotation of a drive wheel and the linear movement of the moveable contact, the positioning loop can advantageously be formed from an electrically insulating material which is expected to experience, during its lifetime, a mechanical crimpage/elongation in the range of ± 1% due to temperature changes, moisture changes and mechanical creep. The electrically insulating material could for example be a polymer-composite comprising a liquid crystal polymer or a para-aramid synthetic material.
- In order to ensure a pre-defined relation between the rotation of a drive wheel and the linear movement of the moveable contact, the positioning loop can pre-stressed so that the initial pre-stressed elongation of the positioning loop is larger than the largest expected sum of the mechanical creep elongation, the change in the length of the positioning loop due to thermal expansion and the change in the positioning loop due to moisture elongation, in order to ensure a tension in the positioning loop throughout its lifetime.
- In one embodiment, the drive system comprises a wheel the centre of which may be adjusted in order to adjust the length of the positioning loop. Hereby is achieved that a suitable pre-stress can be applied to the positioning loop, ensuring that there will be a tension in the positioning loop throughout its lifetime, allowing for example for flow of time, for temperature changes, and for changes in moisture content.
- In order to facilitate for the application of a pre-stress to a positioning loop made from an elastic material, the spacing of the positioning items of driving wheel exceeds the spacing of the corresponding positioning items of the positioning loop. In one implementation, the ratio of the spacing of the positioning items of the driving wheel to those of the positioning loop falls within the range of [1.0005; 1.006].
- The drive system can further comprise an electrically insulating linear guide located in the contact gap space for mechanically guiding the movement of the contact carrier. The contact carrier could for example have a guiding part arranged to follow the linear guide.
- The tap changer could comprise a clamp for mechanically connecting the positioning loop to the contact carrier, wherein the clamp and/or the contact carrier is provided with at least one positioning item to mesh with at least one corresponding positioning item of the positioning loop.
- Further aspects of the invention are set out in the following detailed description and in the accompanying claims.
-
- Fig. 1a
- is a schematic illustration of a tap changer.
- Fig. 1b is
- a sectional view of a contact gap space of a tap selector as seen from along the extension direction of the tap changer.
- Fig. 1 c
- is a sectional view of a compact contact gap space of a tap selector as seen from along the extension direction of the tap changer.
- Fig. 2a
- is an illustration of an example of a drive system for providing movement to a moveable contact, where the drive system comprises a mechanically flexible positioning loop.
- Figs. 2b-d
- schematically illustrate different drive system configurations, each providing an alternative path for the positioning loop.
- Figs. 3a-3d
- illustrate different embodiments of a positioning loop.
- Fig. 4a
- shows attachment means for connecting a positioning loop to a moveable contact.
- Fig. 4b
- shows an example of a clamp for attaching a positioning loop to a contact carrier.
- Fig. 4c
- shows another example of a clamp for attaching a positioning loop to a contact carrier.
- Fig. 5a
- shows circular length adjustment mechanism for adjusting the length of the positioning loop.
- Fig. 5b
- shows linear length adjustment mechanism for adjusting the length of the positioning loop.
- Fig. 6
- shows the molecule structure of Vectran®, a material which could be used for cords in a polymer-cord composite from which a positioning loop may be formed.
- Fig. 7
- shows an example of a tap selector wherein the drive system for moving the moveable contact comprises an insulating positioning loop.
-
Fig. 1a schematically illustrates atap changer 100 which is connected to a regulating winding 105 having a set of different taps 110. The tap changer ofFig. 1a is of diverter switch type, and comprises a diverter switch 115 and atap selector 120. Thetap selector 120 ofFig. 1a comprises twocurrent collectors 125, twomoveable contacts 130 and a set of fixedcontacts 135, where eachfixed contact 135 is arranged to be connected to one of thetaps 110 of the regulating winding. Amoveable contact 130 is arranged to electrically bridge a contact gap between acurrent collector 125 and afixed contact 135. Thetap changer 100 ofFig. 1a is mechanically linear in the sense that thecurrent collectors 125 are implemented as linear rods, and the fixedcontacts 135 are arranged in a linear fashion. In the following, the term linear tap changer should be construed as a mechanically linear tap changer, unless stated otherwise. The twocurrent collectors 125 together form a current collector part. In atap changer 100 having a singlecurrent collector 125, the current collector part is formed by the singlecurrent collector 125, etc. The following description will, for illustrative purposes only, be made in terms of a tap changer having twocurrent collectors 125 and twomoveable contacts 130. The invention is however equally applicable to a tap changer having a different number ofcurrent collectors 125 and/ormoveable contacts 130, such as a singlecurrent collector 125, threecurrent collectors 125, etc. - The diverter switch 115 of
Fig. 1a comprises two series connections of amain contact 140 and atransition contact 145, with a transition resistor 150 connected in parallel with thetransition contact 145. Each of the series connections are, at one end, connected to a respective one of the twocurrent collectors 125, and, at the other end, connected to anexternal contact 155 of thetap changer 100. - The two
moveable contacts 130 are, at one end, in electrical contact with a respective one of thecurrent collectors 125. Amoveable contact 130 can move along thecurrent collector 125 to which it is connected, in order to reach different positions at which the other end of themoveable contact 130 is in electrical contact with one of the fixedcontacts 135. Themoveable contacts 130 could for example be sliding contacts arranged to slide along thecurrent collectors 125, to allow for electrical connection between thecurrent collectors 125 and the different fixedcontacts 135. The driving of themoveable contacts 130 ofFig. 1a is arranged so that if one of themoveable contacts 130 is in contact with afixed contact 135, connected to a first tap, the othermoveable contact 130 is in contact with a secondfixed contact 135, adjacent to the first tap and connected to asecond tap 110. - By switching of the
main contacts 140 andtransition contacts 145 in a conventional manner, one or the other of themoveable contacts 130 will be in electrical contact with theexternal contact 155, and thus provide an electrical path through thetap changer 100. Hence, the twocurrent collectors 125 will take turns at being part of the electrical path through thetap changer 100. The electrical path through thetap changer 100 ends at theexternal contact 155 at one end, and at the other end at the fixedcontact 135 which is currently connected to the regulating winding 105. At the other end of the regulating winding 105 is provided afurther contact 175, so that a path is provided through thetap changer 100 and the regulating winding 105 betweencontacts EP0116748 . The diverter switch 115 ofFig. 1a is an example only, and any suitable type of diverter switch 115 can be used. - When the
tap changer 100 is in use, the different fixedcontacts 135 will be at different potential levels, corresponding to the different potential levels of thedifferent taps 110 of the regulating winding 105. Thus, the potential difference between thecurrent collectors 125 will correspond to the potential difference between twoadjacent taps 110, Uadj. Uadj is typically constant throughout the regulating winding 105. Only one fixedcontact 135 at a time will be connected, via themoveable contact 130, to thecurrent collector 125 which is currently connected to theexternal connection 155 of the tap changer, this fixedcontact 135 being referred to as the connected fixedcontact 135. - The potential difference between a
current collector 125 and a particular fixedcontact 135 varies depending on at which position themoveable contact 130 is connected, and could be considerably larger than the potential difference between two adjacent fixedcontacts 135. In alinear tap changer 100, the maximum potential difference between acurrent collector 125 and afixed contact 135 occurs when one of the end fixedcontacts 135, denoted 135e inFig. 1a , are connected and forms part of the current path through thetap changer 100. In this case, the potential difference between thecurrent collector 125 that is connected, and the end fixedcontact 135e which is not connected, corresponds to the entire voltage across the regulating winding 100, Ureg. Ureg, also referred to as the regulation voltage, is illustrated inFig. 1 a byarrow 170. - In order to prevent flashover within the
tap changer 100 when in use, the distances between two parts at different potential should reach or exceed the minimum distance over which the medium, in which thetap changer 100 is immersed, can withstand the voltage obtained between the two parts. Such insulation distances depend on the medium surrounding thetap selector 120, and increase with increasing rated regulation voltage (which typically depends on the rated voltage of the transformer as well as on the desired number of taps 110). The particular regulation voltage used for defining the insulation distances is often a test voltage and are one of the parameters for which thetap changer 100 is rated. - Two insulation distances which are often of particular interest are the required insulation distance between adjacent
fixed contacts 135, this distance referred to as the adjacent contact insulation distance, as well as the distance between acurrent collector 125 and the fixedcontacts 135, this distance referred to as the contact gap insulation distance, . The contact gap insulation distance typically varies along the length of thetap changer 100, so thatcurrent collectors 125 and the fixedcontacts 135 can occur at the end fixedcontacts 135e - the nearer the centre of the arrangement of fixed contact(s) 135, the smaller the maximum potential difference between thecurrent collector 125 and the fixedcontacts 135. The direction y as indicated by the coordinate system inFig. 1a , in which direction thecurrent collectors 125 extend, will in the following be referred to as the extension direction of thelinear tap changer 100. - The actual distance between two adjacent fixed
contacts 135 will hereinafter be referred to as the adjacent contact distance, dadj, while the actual distance between acurrent collector 125 and the fixedcontacts 135 will be referred to as the contact gap, dgap. In order to prevent flashover in the tap changer, dadj should reach or exceed , while dgap should reach or exceed . If any further electrically conducting parts are present in the space formed between thecurrent collector 125 and the arrangement of fixedcontacts 135, the contact gap dgap will often have to be increased. This is for example the case when themoveable contact 130 is connected to a metallic drive mechanism for providing a force required to move themoveable contact 130 between different fixed contact positions. In this case, the distance between the fixedcontacts 135 and such drive mechanism, as well as the distance between the current collector(s) and such drive mechanism, should both reach or exceed . - The actual distances dadj and dgap of the tap changer of
Fig. 1a have been indicated in the drawing. The contact cap dgap inFig. 1a is shown to be independent on position y along the extension direction. The contact gap dgap should, when dgap is independent on position, reach or exceed the maximum required insulation distance i.e. the insulation distance at the end fixedcontacts 135e. In the following, the term insulation distance will be used to refer to the maximum required insulation distance. - A space referred to as the contact gap space is defined by the
current collectors 125 and the set of fixedcontacts 135, in which space the electric field is to a large extent determined by the potential difference between thecurrent collectors 125 and the fixedcontacts 135. Thecontact gap space 165 is here defined as the space confined by i) an (imaginary) plane through the centers of thecurrent collectors 125, if more than one; ii) an (imaginary) plane through the rows of fixedcontacts 135, if more than one row; iii) a set of (imaginary) semi-cylinders parallel to the extension direction, each semi-circle having a radius corresponding to the contact gap space, where the center of a corresponding (full) cylinder coincides with the location of row of fixedcontacts 135 or acurrent collector 125; iv) the "top" and "bottom" (imaginary) spherical surfaces having their centers at the end of thecurrent collectors 125 and adjacent end fixedcontacts 135e. A sectional view of thecontact gap space 165 as seen from along the extension direction of thetap changer 100 is shown inFig. 1 b. A more compact version of the contact gap space, referred to as the compactcontact gap space 175, is shown inFig. 1c . The compactcontact gap space 175 is a sub-space of thecontact gap space 165. The compactcontact gap space 175 is defined for atap changer 100 having twocurrent collectors 125 or less as the space confined by the surfaces as defined in i), ii) and iv) above, as well as by v) (imaginary) semi-cylinders having a diameter corresponding to the contact gap, and the centers of which are located at the centre of the line interconnecting acurrent collector 125 with the corresponding fixedcontact 135. - When only one
current collector 125 is provided, the contact gap space 165 (and the compact contact gap space 175) will be smaller than if two or morecurrent collectors 125 are provided. Unless thecontact gap space 165 is shielded from external electric fields, the potential difference between thecurrent collectors 125 and the fixedcontacts 135 will typically further be influenced by the surrounding electrical fields, thus requiring a larger contact gap dgap, and thereby a larger contact gap space, than if no external fields were present in thecontact gap space 165. - In a
tap changer 100 which is air insulated, the insulation distances need to be considerably larger than in an oil insulatedtap changer 100. For example, in an air insulatedtap changer 100 wherein an insulation distance is 30 cm, the corresponding insulation distance could typically be around 3 cm in an oil insulated tap changer. Thus, an air insulatedtap changer 100 typically needs to be physically larger than if thetap changer 100 were insulated by means of 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 a skyscraper); or in environmentally sensitive areas, where the risk of contamination should be minimized. The term air insulatedtap changer 100 should here be construed to includetap changers 100 which are insulated by air, or by air-like gases in a controlled space, such astap changers 100 insulated by nitrogen gas (N2),tap changers 100 insulated by air at a controlled pressure, etc. - As mentioned above, the insulation distances of a tap changer depend on the voltage rating of the tap changer and the insulation medium. For higher voltage ratings, and in particular in high voltage dry tap changers being insulated by means of a gas, a conventional design of the tap changer may be impractical due to the size required in order to fulfill the insulation requirements. Hence, a more compact design of a tap changer is desired.
- According to the invention, a tap changer is provided having a drive system for moving the moveable contact(s) from one fixed contact position to another, where the drive system comprises an electrically insulating, mechanically flexible, positioning loop. The positioning loop is mechanically connected to the moveable contact for transmission of a driving force thereto.
- By providing a drive system which comprises an electrically insulating and mechanically flexible positioning loop, a compact design of the
tap changer 100 is achieved. - Alternative designs of a drive system for providing the force for moving a
moveable contact 130 include a metallic ball screw as described inCN2879373 or a Geneva rod as described inUS4,562,316 . Compared to a metallic ball screw which, if located in the contact gap space would drastically increase the required contact gap, the inventive drive system facilitates for a considerably more compact design in the direction of the contact gap, since no flashover will occur to the insulating positioning loop. Thus, by use of an electrically insulating and mechanically flexible positioning loop, the contact gap can be set at approximately the contact gap insulation distance , even if the positioning loop is located in the contact gap space 165 (it may still be desirable to use a contact gap which exceeds , for example in order to ensure adequate insulation even when the electric field within thecontact gap space 165 is influenced by external electric fields). Furthermore, compared to a Geneva rod, the inventive drive mechanism facilitates for a considerably more compact design in the extension direction of thetap selector 120 since the positioning loop, as opposed to the Geneva rod, will be confined to the same space, regardless of at which fixed contact position themoveable contact 130 is currently located. - An example of a
drive system 200 comprising an electrically insulating and mechanicallyflexible positioning loop 205 is shown inFig. 2a . Thedrive system 200 ofFig. 2a further comprises adriving wheel 210 arranged to mesh with thepositioning loop 205 for driving thereof. Thedriving wheel 210 thus includes, on its periphery, a set of evenly distributedpositioning items 213, to engage withcorresponding positioning items 300 of the positioning loop (cf.Figs. 3a-3d ). Thedriving wheel 210 is arranged to be driven by ashaft 214 which is connected to an electric motor via a gear box (not shown). Thedrive system 200 ofFig. 2a further comprises threepulleys 215. Thepulleys 215, together with thedriving wheel 210, define a path for thepositioning loop 205. - The
positioning loop 205 ofFig. 2a is mechanically connected to acontact carrier 220 via aclamp 225 for clamping thepositioning loop 205 to thecontact carrier 220. Thecontact carrier 220 ofFig. 2a is arranged to carry themoveable contact 130 and includes aflange 230 providing a counterpart to theclamp 225, facilitating for the clamping of thepositioning loop 205 to thecontact carrier 220. Thepositioning loop 205 ofFig. 2a , when brought to move by thedriving wheel 210, thus transfers a force to thecontact carrier 220 along the extension direction of thetap selector 120. - The
contact carrier 220 ofFig. 2a further includes a guidingpart 235 in the form of a circular tube which is open along its axial direction, the guidingpart 235 being arranged to run along a guiding rod of thetap changer 100 for appropriate guiding of thecontact carrier 220 in the extension direction of thetap changer 100. A guidingpart 235 of acontact carrier 220 could alternatively be of another shape, such as a closed tube, a hollow parallelepiped, etc. A guiding rod (not shown) of thetap changer 100 could advantageously be of a cross section which corresponds to the cross section of the guidingpart 235. The design illustrated inFig. 2a where the guidingpart 235 and theflange 230 are integral parts of thecontact carrier 220 is an example only, and alternative designs may be contemplated. For example, aseparate guide 235 and/or aseparate flange 230 attached to thecontact carrier 220 could be provided; theflange 230 could be replaced by different means of attaching thepositioning loop 205; etc. Thepositioning loop 205 could, in a simple embodiment, be directly attached to the moveable contact. In its simplest implementation, thecontact carrier 220 could simply consist of one or moremoveable contacts 130. However, fortap changers 100 having a larger number of fixed contact positions and larger isolation distances, aguide 235 would generally be advantageous. - The four wheels/pulleys of
Fig. 2a , jointly referred to aswheels 210/215, together define a path for the positioning loop such that the path can provide a linear motion of themoveable contact 130 in the extension direction of thetap changer 100 in the region between thecurrent collectors 125 and the set of fixedcontacts 135. Such a path can be defined in many different ways by use of a different number ofwheels 210/215, or by simply arranging thewheels 210/215 in a different manner. A suitable wheel configuration should comprise at least onedriving wheel 210 and at least onepulley 215, where the distance between at least two of thewheels 210/215 define at least one linear path part of along the extension direction of thetap changer 100. Further examples ofdrive systems 200 of alternative wheel configurations defining a path having such linear part are schematically shown inFigs. 2b-2d . Thedrive system 200 ofFig. 2b comprises onedriving wheel 210 and onepulley 215; thedrive system 200 ofFig. 2c comprises onedriving wheel 210 and twopulleys 215; while thedrive system 200 ofFig. 2d comprises onedriving wheel 210 and fourpulleys 215. Depending on the design of thetap changer 100, a different wheel configuration may be advantageous. For example, in a design wherein the diverter switch 115 is located behind thecurrent collectors 125 as seen from the fixedcontacts 135, the configuration shown inFig. 2a would be beneficial. In this configuration, thedriving wheel 210 will not be part of forming the linear path part in the extension direction of the tap changer, but will be located in line with the diverter switch 115 in the y-direction. Thus, thesame driving shaft 214 could be used for controlling the movement of themoveable contact 130 and for controlling the diverter switch 115, while the point of attachment between thepositioning loop 205 and thecontact carrier 220 can be provided in thecontact gap space 165. Furthermore, in many tap changer designs, a wheel configuration wherein a return path of thepositioning loop 205 runs parallel to the part of the path which provides a linear movement of themoveable contact 130 is beneficial in order to save space (cf.Figs. 2a ,2b, 2d ). - Which
wheel 210/215 is thedriving wheel 210 could e.g. be selected in accordance with the most favourable location of the drivingshaft 214. The configurations shown inFigs. 2a-2d include asingle driving wheel 210. In an alternative implementation, two ormore driving wheels 210 could be employed. - In
Figs. 3a-3d , different embodiments of apositioning loop 205 are shown (only part of apositioning loop 205 has been shown for illustration purposes). Each embodiment of thepositioning loop 205 is provided with a plurality of evenly distributedpositioning items 300, which positioning items are designed to mesh withcorresponding positioning items 213 of adriving wheel 210 of the drive mechanism (cf.Fig. 2a ) and thereby mechanically convey rotary movement of the wheel into linear movement of themoveable contact 130. Thepositioning loop 205 ofFig. 3a is a timing belt provided with evenly distributed integral teeth on the inside of the timing belt, so that the positioning loop can run along the circumference of a positioning wheel. These integral teeth are designed to mesh with adriving wheel 210 in the form of a sprocket having a corresponding toothing. Thepositioning loop 205 ofFig. 3b is also a timing belt which is provided with evenly distributedpositioning items 300 in the form of integral teeth, designed to mesh with a sprocket, where the teeth are provided at the inside, as well as outside, of the timing belt. Thepositioning loop 205 ofFig. 3c is a timing belt which is provided with evenly distributedpositioning items 300 in the form of circular holes, which are designed to mesh with adriving wheel 210 having evenly distributed cylindrical or part-spherical protrusions along its circumference. If desired, the holes could be of a different shape, such as elliptic, rectangular or triangular, designed to mesh with wheel protrusions of a corresponding shape. Thepositioning loop 205 ofFig. 3d is a string provided with evenly distributedpositioning items 300 in the form of spherical beads, where a bead is designed to mesh with a corresponding positioning item in the form of a recess in the circumference of adriving wheel 210. Further embodiment of thepositioning loop 205 may be contemplated. For example, thepositioning loop 205 could be implemented as an insulating chain - for instance in the shape of a bicycle chain or similar, manufactured from an insulating material. - The circumference of a
driving wheel 210 comprises a plurality of evenly distributedpositioning items 213 for engaging withcorresponding positioning items 300 of thepositioning loop 205, such positioning items for example being teeth (thedriving wheel 210 thus being a sprocket), protrusions or recesses. The circumference of thepulleys 215 could be smooth, or, if desired, the circumference of one or more of thepulleys 215 could comprise a plurality of evenly distributedpositioning items 213. - An example of an embodiment a
contact carrier 220 and aclamp 225 for attaching thepositioning loop 205 to themoveable contact 130 is schematically shown inFig. 4a , where thecontact carrier 220 includes a guidingpart 235 for interacting with a guiding rod, as well as aflange 230 for interacting with theclamp 225. Either theclamp 225 and/or theflange 230 could furthermore advantageously be provided withpositioning items 213 arranged to engage with thepositioning items 300 of thepositioning loop 205. Either theclamp 225 and/or theflange 230 could moreover be provided with atrack 410 for receiving thepositioning loop 205, in order to mechanically stabilize thepositioning loop 205 in the direction perpendicular to the linear movement of the moveable contact 130 (i.e. perpendicular to the extension direction). Theclamp 225 could for example be attached to theflange 230 by means knurling and a suitable screw arrangement. In order to facilitate for achieving an adjustment possibility of the location of themoveable contact 130 in relation to the fixedcontact 135, the holes, through which the attachment screws 415 are to be inserted, may be of an elongated shape in one of thecontact carrier 220 and theclamp 225, while the corresponding holes in the other of thecontact carrier 220 and the clamp 405 are circular. The elongated shape could advantageously provide a play of half the distance between thepositioning items 213 of thedriving wheel 210, or more. - In
Fig. 4b , an example of aclamp 225 is shown, where theclamp 225 is provided withpositioning items 213 as well as atrack 410 for receiving thepositioning loop 205, thepositioning items 213 being located in thetrack 410. In order to improve the attachment between theclamp 225 and thecontact carrier 220, all or part of thesurfaces 420, and/or all or part of the corresponding surfaces of the contact carrier 220 (flange 230), could be knurled. An alternative implementation of aclamp 225 is shown inFig. 4c , where theclamp 225 comprises a surface provided withpositioning items 213, which surface is provided with holes for receiving attachment screws 215. Thus, by this design, which is simpler than the design of theclamp 225 ofFig. 4c , holes will be required in thepositioning loop 205 for the attachment screws. Typically, the clamp design shown inFig. 4b is desirable, since holes through thepositioning loop 205 may reduce the mechanical strength of the material. - In yet another implementation of the attachment of the
positioning loop 205 to thecontact carrier 220, no clamp is provided, but thepositioning loop 205 is screwed directly onto thecontact carrier 220. - The
positioning loop 205 could be a closed loop which is attached to thecontact carrier 220, or could be an open piece of belt/band/string/etc., which is formed into a loop and attached to thecontact carrier 220. - By use of the positioning loop, the correspondence between the rotation of the
driving wheel 210 and the transportation of themoveable contact 130 along the extension direction of the tap changer will be well defined. By rotating thedriving wheel 210 through a certain angle, determined by the relationship between the radius of the driving wheel and the distance between two adjacent fixedcontacts 135, themoveable contact 130 will move from one fixed contact position to an adjacent fixed contact position. The use of apositioning loop 205 for the transfer of a force from arotating shaft 214 to themoveable contact 130 provides a flexible solution as to the angle of rotation required for obtaining a movement of themoveable contact 130 between two adjacent fixed contact positions-the certain angle for obtaining this movement will be determined by the ratio between the radius of thedriving wheel 210, R, and the distance between adjacentfixed contacts 135, dadj. A certain angle of rotation for obtaining movement between two adjacent fixedcontacts 135 can thus be obtained by a design having the required ratio between R and dadj. - In addition to participating in the transmission of a movement from the
shaft 214 to thepositioning loop 205 and thereby to themoveable contact 130, the wheel configuration comprising at least onedriving wheel 210 and at least onepulley 215 operates to keep thepositioning loop 205 in the desired position. In order to ensure correct operation of thetap changer 100, it is important that the predetermined relationship between rotary movement of the driving wheel and the linear movement of themoveable contact 130 applies at all times. Hence, any slipping between thedriving wheel 210 and thepositioning loop 205 should be avoided. Such slipping can be avoided by keeping thepositioning loop 205 stretched. - The length of the
positioning loop 205 will typically depend on time (through mechanical creep), on temperature and on the moisture content of thepositioning loop 205. When arranged in the path defined by thewheels 210/215, the length of thepositioning loop 205 will typically depend on the temperature expansion of a structure which keeps thewheels 210/215 in position, as well as on the temperature expansion of the positioning loop itself. - In order to be in control of the length of the
positioning loop 205, so that the predetermined relationship between rotary movement of the driving wheel and the linear movement of themoveable contact 130 does not vary when the temperature and/or the moisture content changes, thepositioning loop 205 could advantageously be pre-stressed before thetap changer 100 is used for the first time. Thepositioning loop 205 could advantageously be pre-stressed so that the initial pre-stressed elongation of the loop is larger than the largest expected sum of the mechanical creep elongation, the change in the length of the positioning loop due to thermal expansion and the change in the positioning loop due to moisture elongation. In this way, thepositioning loop 205 can be expected to stay stretched at all times, thus avoiding a slacking positioning loop 205 (the stress in the loop may on the other hand vary over time). A well-defined relationship between the angle of rotation of thedriving wheel 210 and the obtained movement of themoveable contact 130 can thus be obtained. - In order to achieve such well-defined relationship, the spacing d300 of the
positioning items 300 of thepositioning loop 205 could advantageously be slightly smaller than the spacing d213 of thecorresponding positioning items 213 of thedriving wheel 210 and the clamp 225 (and of thepulleys 215, when applicable), so that by initially stretching of thepositioning loop 210, the spacing d300 of the positionloop positioning items 300 can be made to coincide with the spacing d213 of thecorresponding positioning items 213. An optimal ratio of d213 to d300, , will typically depend on the creep properties of the material from which thepositioning loop 205 is formed. - In one embodiment of the wheel configuration, at least one of the
wheels 210/215 is arranged so that the position of the centre of thewheel 210/215 can be adjusted, thereby allowing for the adjustment of the length of thepositioning loop 205. The position of the centre of the other wheels will typically be fixed. Awheel 210/215, the centre of which can be adjusted, will in the following be referred to as an adjustable wheel. In principle, a length adjustment mechanism could be implemented either at adrive wheel 210 or at apulley 215, although it is often best implemented in relation to apulley 215 rather than adriving wheel 210, since the location of the centre of thedriving wheel 210 should correspond to the location of thetransmission shaft 214. - Adjustability of a
wheel 210/215 could be implemented by use of suitable assembly tools upon installation of thetap changer 100, or by means of an integrated length adjustment mechanism, examples of which are shown below inFigs. 5a and 5b . The position of the wheel can thus be adjusted to achieve a desired length of thepositioning loop 205. In other words, a length adjustment mechanism operates to obtain a desired elongation rather than a desired force on thepositioning loop 205. - The combination of a length adjustment mechanism and a smaller spacing of the
positioning items 300 than the spacing of thecorresponding positioning items 213 facilitates for simple installation of thedrive system 200. Adjustment of the length of thepositioning loop 205 can for example be performed in an iterative manner upon installation of thetap changer 100, until a desired spacing of thepositioning items 300 of thepositioning loop 205 has been obtained. Ideally, a material with a low creep coefficient would be desired, so that the part of the elongation due to creep will occur during installation of the tap changer, rather than when thetap changer 100 is in use. The initial pre-stressed elongation of thepositioning loop 205 could for example be in the order of 0.05-0.5 %, although depending on the circumstances, a different elongation may be used. - A length adjustment mechanism could for example operate to provide a circular or a linear displacement of an adjustable wheel. An example of a circular
length adjustment mechanism 500 is shown inFig. 5a , while a linearlength adjustment mechanism 500 is shown inFig. 5b . Thecircular adjustment mechanism 500 ofFig. 5a is an eccentric, which comprises acylindrical plug 505 having ashaft 510 arranged to accept thewheel 210/215 at a location which is offset from the center of theplug 505, so that by rotating theplug 505, the location of the wheel (and hence the elongation of the positioning loop 215) may be adjusted. The eccentric 500 further includes screws (not shown), by means of which theplug 505 can be fixed in place when the location of thewheel 210/215 has been adjusted. Ball bearings - The
linear adjustment mechanism 500 ofFig. 5b comprises ashaft 510 arranged to accept thewheel 210/215, where theshaft 510 is arranged on aguide 515 which is linearly movable within aguide holder 520. Thelinear adjustment mechanism 500 further includes screws (not shown), by means of which theplate 515 can be fixed in place when the location of the wheel has been adjusted. - By use of a
driving system 200 which comprises an electrically insulating and mechanicallyflexible positioning loop 205, part or whole of thepositioning loop 205 can be located in thecontact gap space 165 as defined in relation toFig. 1b , without influencing the electric field distribution in thecontact gap space 165. For example, a part of the positioning loop path which defines a straight path, for thecontact carrier 220 to move along, could be located in thecontact gap space 165. Thus, the point of the attachment between thedrive system 200 and thecontact carrier 220 can be located in thecontact gap space 165 without having to extend the contact gap dgap beyond the contact gap insulation distance, . By placing the point of attachment between thedrive system 200 and thecontact carrier 220 in thecontact gap space 165, a direct transfer of the force from thedriving wheel 210 to thecontact carrier 220 along the extension direction of thetap changer 100 can be achieved. An example of such adrive system 200 is shown below inFig. 7 . For mechanical purposes, it will often be advantageous to place at least part of thepositioning loop 205 in thecompact contact space 175 as defined in relation toFig. 1c . - Placing the point of attachment in the
contact gap space 165, and advantageously in the range of 0.3dgap or less from the centre of the contact gap in the contact gap direction, gives an advantageous mechanical stability to thetap selector 120, by means of which the positioning may be improved. Amoveable contact 130 experiences a risk of being exposed to mechanical and electrical forces, e.g. due to friction between themoveable contact 130 and the fixedcontacts 135 and/or thecurrent collector 125; or due to electrical short-circuit forces in case of short circuit currents in a nearby conductor, etc. Such undesired forces act to move themoveable contact 130 from its correct position, thus giving rise to a risk for electrical arcing. Such forces will act on themoveable contact 130, and by placing the point of attachment of themoveable contact 130 to thepositioning loop 205 in the middle region of the contact gap, the mechanical advantage will typically be optimal. Oftentimes, the optimal location of the point of attachment will be in at the centre of the contact gap, although other considerations may be in favour of an alternative location. Please note thatpositioning loop 205 need not be directly mechanically connected to thecontact carrier 220 but could be mechanically connected to themoveable contact 130 via an intermediary part, such as an electrical insulating or non-insulating part (e.g. a bar). - An electrically insulating
positioning loop 205 could advantageously be made from an insulating material which exhibits low mechanical creep, for example a polymer of good creep resistance. Since accurate correspondence between the spacing of thepositioning items 300 of thepositioning loop 205 and the spacing of thecorresponding positioning items 213 of adriving wheel 210 will ensure accurate positioning of themoveable contact 130 at the different fixed contact positions, a material which exhibits very low long term creep would be advantageous. For example, a material having creep properties in the range of 0-0.3 % during lifetime would be suitable. Low moisture absorption is also desirable since moisture can influence the mechanical strength properties, such as elongation and/or strength, as well as the electrical conductivity, of the material. - An example of mechanically flexible and electrically insulating materials which can be designed to have the desired creep properties is polymer-cord composite materials, where a polymer, such as polyurethane, polyester, or rubber, is reinforced with cords of an electrically insulating and mechanically creep resistant material, so that the cords are embedded in a polymer matrix. The cords could for example be made from a liquid crystal polymer, which can for example be melt spun into a high performance material. Vectran® is an example of a liquid crystal polymer. Vectran® is a wholly aromatic polyester made by the acetylation polymerisation ofp-hydroxybenzoic acid and 6-hydroxy-2-naphthoic. The molecular structure of Vectran® is shown in
Fig. 6 . Other naphthalene-based thermotropic liquid crystal polymers could also be contemplated. Another example of suitable flexible and insulating materials is the para-aramid synthetic fibres, such as Kevlar or Twaron. Both the liquid crystal polymers and the para-aramid synthetic fibres show a high creep resistance, a low coefficient of thermal expansion and low moisture absorption. - In an embodiment wherein the spacing d300 of the
positioning items 300 of thepositioning loop 205 is smaller than the spacing d213 of thecorresponding positioning items 213 as discussed above, a suitable ratio of d213 to d300, , could for example lie within the range of [1.0005; 1.004] when thepositioning loop 205 comprises liquid crystal polymers and within the range of [1.0005; 1.006] when thepositioning loop 205 comprises para-aramid synthetic materials. Under some circumstances, an even larger value of this ratio may be beneficial, such as e.g. if the expected temperature contraction (negative elongation) of the structure in which thedrive system 200 is suspended is large. In many implementations, however, a ratio within the range of [1.001; 1.003] for liquid crystal polymers and within the range of [1.003; 1.004] for para-aramid synthetic materials will be sufficient. - Other materials which could be used for the cord of a polymer-cord composite in a
positioning loop 205 include glass fibre. When thepositioning loop 205 is implemented in the form of a chain or similar, the material itself does not have to be flexible, since the flexibility is provided in the mechanical design of the loop. Examples of suitable rigid materials which could be used for the positioning loop when implemented as a chain include composites of polyester/glass; epoxy/glass; polyphthalamide/glass. - An example of a
tap selector 120 wherein themoveable contact 130 is moved from one fixed contact position to another by means of adriving system 200 having an electrically insulating, mechanicallyflexible positioning loop 205 is shown inFig. 7 . Themoveable contact 130, the fixedcontacts 135 withcables 160, and thecurrent collector 125 with acable 700 for connecting to a diverter switch 115 are shown, as is thedriving system 200 comprising thepositioning loop 205, adrive wheel 210,pulleys 215, and guidingrod 705. The guidingrod 705, as well as thepositioning loop 205, is made from an electrically insulating material such as a polymer or a ceramic material. A guidingpart 235 of thecontact carrier 220 could contain a low friction part or coating, made of a suitable low friction material (e.g. polytetrafluoreten (PTFE)). Low friction between the guidingpart 235 and thecontact carrier 220 could alternatively be achieved by providing the guidingrod 705 with a coating of low friction material. - The
tap changer 100 of which thetap selector 120 is shown inFig. 7 has onemoveable contact 130. Atap changer 100 having more than one independentlymoveable contacts 130 can advantageously be provided with onepositioning loop 205 for each independentlymoveable contact 130. In atap changer 100 having two or moremoveable contacts 130, which can only be moved in a joint movement, asingle positioning loop 205 would be sufficient for the jointlymoveable contacts 130. - The invention could advantageously be used in an on-
load tap changer 100, where the regulation of the transformer output voltage takes place while the transformer is in operation, as well as in a non-excited, off-load tap changer. - Since the insulation distances are so much larger in air than in oil or for example SF6, the benefits of a compact design are more pronounced in an air insulated tap changer. However, the invention can advantageously be applied also in oil or SF6 insulated designs, which can then be very compactly designed.
- Although various aspects of the invention are set out in the accompanying independent claims, other aspects of the invention include the combination of any features presented in the above description and/or in the accompanying claims, and not solely the combinations explicitly set out in the accompanying claims.
- One skilled in the art will appreciate that the technology presented herein is not limited to the embodiments disclosed in the accompanying drawings and the foregoing detailed description, which are presented for purposes of illustration only, but it can be implemented in a number of different ways, and it is defined by the following claims.
Claims (15)
- A tap changer (100) for connection to a regulating winding (105) of a transformer, the tap changer comprising:a tap selector (120) including:a set of fixed contacts comprising at least two fixed contacts (135), each arranged to be connected to a tap (110) of the regulating winding;at least one current collector (125) located at a distance from the set of fixed contacts so that a contact gap space (165) is formed therebetween; andat least one contact carrier (220) including at least one moveable contact (130) arranged to electrically bridge a contact gap between a current collector and a fixed contact; the tap changer further comprising:a drive system (200) for moving the at least one contact carrier from one fixed contact position to another, the drive system comprising at least one electrically insulating, mechanically flexible positioning loop (205) provided with a plurality of evenly distributed positioning items (300), the positioning loop being attached to the contact carrier in order to allow for transmission of a driving force thereto.
- The tap changer of claim 1, wherein the positioning loop is at least partly located in the contact gap space (165).
- The tap changer of claim 1 or 2, wherein
the positioning loop is a timing belt. - The tap changer of claim 3, wherein
the positioning items are evenly distributed integral teeth. - The tap changer of claim 3, wherein
the positioning items are evenly distributed holes. - The tap changer of claim 1 or 2, wherein
the positioning loop is a chain. - The tap changer of any one of the above claims, wherein
the positioning loop is formed from an electrically insulating material which is expected to experience, during its lifetime, a mechanical crimpage/elongation in the range of ± 1% due to temperature changes, moisture changes and mechanical creep. - The tap changer of any one of the above claims, wherein
the electrically insulating material is a polymer-composite comprising a liquid crystal polymer or a para-aramid synthetic material. - The tap changer of any one of the above claims, wherein
wherein the drive system comprises a wheel (210; 215) the centre of which may be adjusted in order to adjust the length of the positioning loop. - The tap changer of any one of the above claims, wherein
the drive system further comprises at least one drive wheel (210) the periphery of which is provided with evenly distributed positioning items (213) arranged to interact with the positioning items of the positioning loop, so that upon rotation of the drive wheel, the contact carrier will perform a linear movement. - The tap changer of claim 10, wherein
the spacing of the positioning items (213) of driving wheel exceeds the spacing of the corresponding positioning items (300) of the positioning loop. - The tap changer of any one of the above claims, further comprising
a clamp (225) for mechanically connecting the positioning loop to the contact carrier, wherein the clamp and/or the contact carrier is provided with at least one positioning item (213) to mesh with at least one corresponding positioning item of the positioning loop. - The tap changer of any one of the above claims, wherein
the drive system further comprises an electrically insulating linear guide (705) located in the contact gap space for mechanically guiding the movement of the contact carrier. - The tap changer of any one of the above claims, wherein
a point of mechanical connection of the positioning loop to the contact carrier is located within a distance of [0.2dgap; 0.8dgap] from the current collector in the contact gap direction. - The tap changer of any one of the above claims, wherein
the positioning loop is pre-stressed so that the initial pre-stressed elongation of the positioning loop is larger than the largest expected sum of the mechanical creep elongation, the change in the length of the positioning loop due to thermal expansion and the change in the positioning loop due to moisture elongation, in order to ensure a tension in the positioning loop throughout its lifetime.
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP11168222.5A EP2530693B1 (en) | 2011-05-31 | 2011-05-31 | Tap changer |
PCT/EP2012/060024 WO2012163907A1 (en) | 2011-05-31 | 2012-05-29 | Tap changer |
CN201280025605.5A CN103563031B (en) | 2011-05-31 | 2012-05-29 | Tap change over switch |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP11168222.5A EP2530693B1 (en) | 2011-05-31 | 2011-05-31 | Tap changer |
Publications (2)
Publication Number | Publication Date |
---|---|
EP2530693A1 true EP2530693A1 (en) | 2012-12-05 |
EP2530693B1 EP2530693B1 (en) | 2017-05-03 |
Family
ID=44851927
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP11168222.5A Not-in-force EP2530693B1 (en) | 2011-05-31 | 2011-05-31 | Tap changer |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP2530693B1 (en) |
CN (1) | CN103563031B (en) |
WO (1) | WO2012163907A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2985773A1 (en) * | 2014-08-13 | 2016-02-17 | ABB Technology AG | On-load tap-changer for dry transformers and dry transformer |
CN114132785A (en) * | 2021-12-06 | 2022-03-04 | 盐城市智成机械制造有限公司 | Compression roller tightness adjusting system |
Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CH247544A (en) * | 1943-02-23 | 1947-03-15 | Hermes Patentverwertungs Gmbh | Voter arrangement with selectors driven by a pulling element, especially for regulating transformers. |
EP0116748A1 (en) | 1983-01-07 | 1984-08-29 | Mitsubishi Denki Kabushiki Kaisha | On-load tap changer |
US4514602A (en) * | 1982-12-27 | 1985-04-30 | Owen D W | Switching apparatus |
US4562316A (en) | 1984-06-07 | 1985-12-31 | Asea Electric, Inc. | High voltage linear tap changer |
DE8812280U1 (en) * | 1988-09-28 | 1988-11-17 | Siemens Ag, 1000 Berlin Und 8000 Muenchen, De | |
DE29723441U1 (en) * | 1997-07-23 | 1998-10-01 | Reinhausen Maschf Scheubeck | Load gear for motor drives on tap changers or the like. |
CN2879373Y (en) | 2006-06-15 | 2007-03-14 | 刘歆 | No-excitation double-row contact strip-type tapped switch |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1134634A (en) * | 1965-02-25 | 1968-11-27 | Ferguson Res Ltd Harry | Belt tensioner |
JP2640826B2 (en) * | 1988-04-30 | 1997-08-13 | 三ツ星ベルト株式会社 | V belt drive |
JPH06109087A (en) * | 1993-05-27 | 1994-04-19 | Sony Corp | Belt transmission mechanism |
CN201213092Y (en) * | 2008-04-16 | 2009-03-25 | 辽宁金立电力电器有限公司 | Combined bar shaped non-exciting shunting switch |
-
2011
- 2011-05-31 EP EP11168222.5A patent/EP2530693B1/en not_active Not-in-force
-
2012
- 2012-05-29 WO PCT/EP2012/060024 patent/WO2012163907A1/en active Application Filing
- 2012-05-29 CN CN201280025605.5A patent/CN103563031B/en not_active Expired - Fee Related
Patent Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CH247544A (en) * | 1943-02-23 | 1947-03-15 | Hermes Patentverwertungs Gmbh | Voter arrangement with selectors driven by a pulling element, especially for regulating transformers. |
US4514602A (en) * | 1982-12-27 | 1985-04-30 | Owen D W | Switching apparatus |
EP0116748A1 (en) | 1983-01-07 | 1984-08-29 | Mitsubishi Denki Kabushiki Kaisha | On-load tap changer |
US4562316A (en) | 1984-06-07 | 1985-12-31 | Asea Electric, Inc. | High voltage linear tap changer |
DE8812280U1 (en) * | 1988-09-28 | 1988-11-17 | Siemens Ag, 1000 Berlin Und 8000 Muenchen, De | |
DE29723441U1 (en) * | 1997-07-23 | 1998-10-01 | Reinhausen Maschf Scheubeck | Load gear for motor drives on tap changers or the like. |
CN2879373Y (en) | 2006-06-15 | 2007-03-14 | 刘歆 | No-excitation double-row contact strip-type tapped switch |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2985773A1 (en) * | 2014-08-13 | 2016-02-17 | ABB Technology AG | On-load tap-changer for dry transformers and dry transformer |
WO2016023660A1 (en) * | 2014-08-13 | 2016-02-18 | Abb Technology Ag | On-load tap-changer for dry transformers and dry transformer |
CN114132785A (en) * | 2021-12-06 | 2022-03-04 | 盐城市智成机械制造有限公司 | Compression roller tightness adjusting system |
CN114132785B (en) * | 2021-12-06 | 2023-07-25 | 盐城市智成机械制造有限公司 | Compression roller tightness adjusting system |
Also Published As
Publication number | Publication date |
---|---|
CN103563031A (en) | 2014-02-05 |
WO2012163907A1 (en) | 2012-12-06 |
CN103563031B (en) | 2016-03-23 |
EP2530693B1 (en) | 2017-05-03 |
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