CN114072891B - Tap changer barrier in a power transformer - Google Patents

Abstract

The present disclosure relates to an on-load tap changer (OLTC) (1) for a fluid filled power transformer. The OLTC comprises a barrier (2) sealingly arranged to separate an electrically insulating tap changer fluid (3) of the OLTC from an electrically insulating transformer fluid (13) in a transformer tank of the power transformer. The OLTC further comprises a diverter switch unit (4) arranged in the tap-changer fluid and fixed to an inner side surface (9 a) of a back plate (16) of the barrier. The OLTC further comprises a tap selector unit (5) arranged in the transformer fluid and fixed to an outer side surface (9 b) of the back plate. The shunt switch unit and the tap selector unit are electrically connected to each other via a phase hole in the back plate, and the back plate is arched such that the back plate is shaped like a longitudinal envelope section of a circular, elliptical or parabolic cylinder, preferably a circular cylinder.

Description

Tap changer barriers in power transformers

Technical field

The present disclosure relates to an On-LoadTap Changer (OLTC) for a fluid-filled power transformer.

Background technique

The tap changer barrier system is used to separate the tap changer insulating fluid, which is susceptible to contamination by particles formed by the diverter switch, from the insulating fluid of the transformer. Typically, the backing plate of the barrier system is flat and relatively thick to be able to withstand pressure differences and structural deformations in the interface between the transformer fluid and the OLTC. Problems with these thick barriers include that they take up a lot of space, they are difficult to stress-relieve from strong electric fields, and they are difficult to fabricate from homogeneous materials and prone to shrinkage cracks and internal bubbles. Therefore, a thicker barrier also reduces the number of manufacturing methods that may be used (especially if a good structural material is used (such as an epoxy glass system)), which may be preferable if the material should be put through a transformer drying process.

JP discloses a gas OLTC having an insulating isolation barrier for separating gas with higher pressure in the transformer from gas with lower pressure in the OLTC.

Contents of the invention

It is an object of the invention to provide an improved barrier for separating the insulating fluid of a tap changer from the insulating fluid of a transformer to avoid contamination of the transformer fluid, and for protecting the tap changer from contamination of the transformer fluid during operation of the power transformer. Effect of pressure changes in transformer fluid. The tap changer is usually an OLTC, as exemplified in this article.

According to an aspect of the invention, an on-load tap changer (OLTC) for a fluid-filled power transformer is provided. The OLTC includes a barrier sealingly arranged to separate the electrically insulating tap changer fluid of the OLTC from the electrically insulating transformer fluid in the transformer tank of the power transformer. The OLTC also includes a diverter switching unit arranged in the tap changer fluid and fixed to the inside surface of the backing plate of the barrier. The OLTC also includes a tap selector unit arranged in the transformer fluid and fixed to the outside surface of the back plate. The shunt switch unit and the tap selector unit are electrically connected to each other via phase holes in the back plate, and the back plate is arched so that the back plate is shaped like a circular cylinder, an elliptical cylinder or a parabolic cylinder Longitudinal envelope section of a body (preferably a circular cylinder).

According to another aspect of the present invention, there is provided an arcuate back plate of a barrier, or a barrier including said back plate, for connecting the electrically insulating tap changer fluid of an OLTC to the electrical current in a transformer tank of a power transformer. Isolation transformer fluid separation. The back plate includes a phase aperture for permitting a diverter switching unit disposed in the tap changer fluid and secured to an inboard surface of the back plate and a tap selector disposed in the transformer fluid and secured to an outboard surface of the back plate. The units are connected (eg electrically (eg galvanically) and/or mechanically). The backing plate also includes keyways in the inner or outer surface (preferably in the outer surface) along the longitudinal end surface of the backing plate for allowing the barrier to be sealingly disposed in the OLTC. The back plate is arched such that the back plate is shaped like a longitudinal envelope section of a circular cylinder, an elliptical cylinder or a parabolic cylinder, preferably a circular cylinder.

According to another aspect of the invention, a fluid filled power transformer is provided including an embodiment of an OLTC of the present disclosure.

By designing the barrier, or more specifically its backing, in an arched shape, the barrier can better withstand pressure changes without deforming (e.g. flexing inward or outward like a flat barrier is prone to), and can therefore Made thinner. Thinner barriers have advantages including taking up less space, using less material, and reducing electric field problems. The arched form also allows the backplate to be integrated into the tap changer in a more space-saving manner, making the tap changer more compact and less bulky.

The barrier backsheet may be made of a suitable material for allowing the barrier to pass through the drying process of the transformer, for example made of an epoxy glass material (e.g. wound wire),

This may also be adapted to withstand pressure differences between the tap changer and the transformer fluid (eg transformer oil, ester fluid or other electrically insulating fluid) and any structural deformations associated therewith.

It should be noted that any features of any one of the aspects may be applied to any other aspect where appropriate. Likewise, any advantages of any one of these aspects may be applied to any of the other aspects. Other objects, features and advantages of the appended embodiments will become apparent from the following detailed disclosure, from the appended dependent claims and from the accompanying drawings.

Generally speaking, all terms used in the claims should be interpreted according to their ordinary meaning in the technical field, unless expressly defined herein. All references to "an element, device, component, means, step, etc." shall be construed publicly to refer to at least one instance of that element, device, component, means, step, etc., unless expressly stated otherwise. Unless expressly stated, the steps of any method disclosed herein need not be performed in the exact order disclosed. The use of "first," "second," etc. with respect to different features/components of the present disclosure is intended only to distinguish the features/components from other similar features/components and is not intended to confer any order or hierarchy to the features/components.

Description of drawings

Embodiments will be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a schematic cross-sectional side view of a liquid-filled power transformer including an OLTC according to an embodiment of the invention.

Figure 2 is a schematic cross-sectional side view of an OLTC according to an embodiment of the present invention.

Figure 3 is a schematic perspective view of an embodiment of an arched back panel of an OLTC according to an embodiment of the present invention.

Detailed ways

Embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments are shown.

However, other embodiments in many different forms are possible within the scope of this disclosure. Rather, the following embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Throughout the description, like numbers refer to like elements. Figure 1 shows a power transformer 10 comprising a tap changer 1 (typically an OLTC), here a fluid-fill filled with an electrically insulating fluid 13, such as a gas or a liquid, typically a liquid such as an oil or an ester liquid. The electrically insulating fluid is arranged for insulating the transformer winding 14 of the transformer 10 .

The transformer 10 includes a transformer box 11 which encloses the transformer windings 14 and contains an insulating fluid 13, with walls 12 (typically side walls, eg vertical side walls 12) in which the tap changer can be arranged.

The tap changer 1 is arranged to connect different alternating current (AC) phases to different taps along corresponding phase windings of the transformer winding 14 to control the power output of the transformer 10 .

FIG. 2 shows a tap changer 1 arranged in a wall 12 of a power transformer 10 , for example as in FIG. 1 . The tap changer 1 may comprise a tap changer tank 15 which together with the barrier 2 forms a housing containing an electrically insulating tap changer fluid 3 such as a gas or a liquid, typically a liquid such as an oil or ester liquid. The barrier 2 is sealingly fixed to the tap changer box 15 , for example by a metal (such as aluminum) profile 8 of the barrier, so that the tap changer fluid 3 remains separated from the transformer fluid 13 on the other side of the barrier 2 . The barrier is therefore impermeable to the tap changer fluid as well as the transformer fluid.

In some embodiments, the barrier 2 may be fixed directly to the transformer tank 11, for example to its sides 12, whereby a tap changer tank 15 for separating the tap changer fluid from the transformer fluid may not be required.

The tap changer 1 includes a shunt switching unit 4 arranged in a tap changer box 15 and at the inside of the barrier 2 , and a selector switching unit 5 arranged in the transformer box 11 at the outside of the barrier 2 . The shunt switches of the shunt switch unit 4 are in electrical communication with the tap selector(s) (typically one per phase) of the tap selector unit 5 via the phase holes 33 (see FIG. 3 ) in the back plate 16 of the barrier 2 . In order to separate the transformer fluid 13 from the tap changer fluid 3 and thereby, for example, avoid contamination of the transformer fluid 13 with contaminants formed by the diverter switching unit 4 , the diverter switching and/or tap selector units 4 and 5 are hermetically arranged at the back. around the phase holes 33 on the corresponding side 9 of the plate 16 . Thus, the shunt switch unit 4 is fixed to the inner surface 9a of the back plate 16, and the tap selector unit 5 is fixed to the outer surface 9b of the back plate, for example via some sealing means at the phase holes. The tap changer 1 may conventionally also comprise a motor 6 and a drive shaft 7 for driving the diverter switches of the diverter switching unit 4 . In accordance with embodiments of the present invention, the backplate 16 is typically arcuate outwardly in the direction of the interior of the transformer 10 and the windings 14 , but may instead be arcuate inwardly in some embodiments. Thus, the inner or outer surface 9a or 9b (preferably the outer surface 9b) has a convex shape, and the other surface 9b or 9a (preferably the inner surface 9a) has a concave shape. The arching may be in two dimensions, but is typically in only one dimension (perpendicular to the plane of the back panel 16 and along the longitudinal axis 36 of the barrier 2 (see Figure 3)), such that the back panel is shaped like The longitudinal envelope section of a cylinder, such as a circular, elliptical or parabolic cylinder, preferably a circular cylinder.

By designing the barrier 2 in an arched shape, the barrier can better withstand pressure changes without deforming, and can therefore be made thinner. If instead a flat barrier is used as according to the prior art, pressure applied to either side of the barrier will cause the barrier to deflect inwards or outwards respectively, which will also increase the resistance of the barrier to, for example, a tap changer box or a transformer box. Risk of leakage of insulating fluid at the interface unless a thicker and therefore less flexible backing sheet is used. The thinner barrier of the present invention has advantages including taking up less space, using less material, and reducing electric field problems (stress relief of the insulating material and the insulating material surface of the backsheet 16). The arched form may also allow the backplate to be integrated into the tap changer 1 in a more space-saving manner, making the tap changer more compact and less bulky.

Traditionally, with a flat barrier, the thickness of the backing is approximately 5% of the width of the backing. However, according to some embodiments of the invention, less than 5% (eg, 1 to 4%, such as about 2%) of the backplane width may be sufficient when comparing equal loads. This is mainly due to the arch shape, but also due to the improved materials that may be used when using the arch shape. As an example, the backing plate 16 may be made by a well-controlled process, such as filament winding using an epoxy glass material 39 . By using this material, the backsheet can also be included in the drying process of the transformer 10 without being damaged.

FIG. 3 shows an embodiment of an arched back panel 16, such as described with respect to FIG. 2 . The backing plate may have a longitudinal axis 36, which in some embodiments may also be the axis of symmetry of the backing plate. The backplate includes phase holes 33, here three phase holes 33a, 33b and 33c, one for each phase of the three-phase AC system.

Because the backing plate is arcuate along the longitudinal axis 36, it may include two substantially straight and generally parallel longitudinal side surfaces 34a and 34b, and two curved and generally parallel lateral side surfaces 35a and 35b. The arched form of the back plate means that the pressure exerted on the outside surface 9b of the barrier is typically borne by the longitudinal side surfaces 34 at their interface/fixation with the tap changer box 15 . Respective longitudinal keyways 38a and 38b may be arranged along respective longitudinal side surfaces 34a and 34b in the outer side surface 9b, these longitudinal keyways being arranged to cooperate with (or engage with) corresponding keys of, for example, a fastening system comprising the profile 8, For example to sealingly fasten the barrier 2 to the tap changer box 15 or the transformer box 11 . Therefore, pressure applied to the inner surface 9a of the backing plate can be borne by the keyways 38 at their interface with the securing system. If the back plate 16 is instead arcuate inwardly, the keyway 38 may instead be arranged in the inside surface 9a.

The backing plate 16 may be made of a suitable material 39 that is impermeable to the tap changer and transformer fluids 3 and 13 and is suitable to withstand any pressure differences between the tap changer and transformer fluids during operation of the transformer. and any structural deformations associated with it. The material 39 may also be adapted to allow the backing plate 16 to pass through the drying process of the transformer 10 . The material 39 may, for example, comprise or consist of an epoxy glass material (eg a wound wire).

To help prevent the barrier 2 from slipping in the longitudinal direction, and to minimize thermal and structural movement of the barrier, the longitudinal side surfaces 34 of the backing plate 16 may be provided with protrusions 37 extending outwardly therefrom. The protrusions 37 may, for example, engage corresponding recesses or holes in a fastening system such as the profile 8 and thus secure the barrier in the longitudinal direction with or without cooperation with keys and keyways (if present). In the example of Figure 3, a respective protrusion 37a or 37b is provided in each of the longitudinal side surfaces 34a and 34b (eg, in the middle thereof).

In some embodiments of the invention, the back panel is arched such that the outer side surface has a concave shape and the inner side surface has a concave shape. However, in other embodiments, the inner surface has a convex shape and the outer surface has a concave shape. As discussed above, the backboard can be arched in one or two dimensions, but is usually arched in only one dimension.

In some embodiments of the invention, the barrier 2 is sealingly arranged by being sealingly fixed to the tap changer box 15 of the OLTC 1 .

However, in other embodiments, the barrier 2 may additionally or alternatively be sealingly fixed directly to the transformer box 11 , possibly drained to the tap changer box 15 .

In some embodiments of the invention, the barrier 2 is sealingly disposed by a keyway 38 along the longitudinal end surface 34 of the backing plate 16 in the inner side surface 9a or the outer side surface 9b of the backing plate 16, preferably in the outer side surface 9b middle. In some embodiments, the barrier 2 is sealingly disposed by a metal profile 8 of the barrier disposed along the longitudinal end surface 34 of the backing plate 16 and typically engages a keyway 38 by protruding keys in the profile 8 that are configured to fit into the recess of the keyway(s) 38 .

In some embodiments of the invention, the OLTC is hermetically arranged in the opening of the side wall 12 of the transformer box 11 . This may facilitate easy installation and access to the OLTC 1 from outside the transformer box 11 .

In some embodiments of the invention, backing plate 16 is made of epoxy glass material 39 . In some embodiments, backing plate 16 is made from wire wrapping of epoxy glass material 39 . The resulting material 39 can therefore be electrically insulating and strong, and able to withstand the drying process of the transformer, whereby the backing plate can be installed in the transformer 10 before drying.

The present disclosure has been described above mainly with reference to several embodiments. However, as one skilled in the art will readily appreciate, other embodiments than those disclosed above are equally possible within the scope of the present disclosure as defined by the appended claims.

Claims (9)

1. An on-load tap changer (1) for a fluid-filled power transformer (10), said on-load tap changer comprising: A barrier (2) sealingly arranged to separate the electrically insulating tap changer fluid (3) of the on-load tap changer from the electrically insulating transformer fluid (13) in the transformer tank (11) of the power transformer separation; A diverter switching unit (4) arranged in the tap changer fluid (3) and fixed to the inner surface (9a) of the backing plate (16) of the barrier; and a tap selector unit (5) arranged in the transformer fluid (13) and fixed to the outer surface (9b) of the backing plate; wherein the shunt switch unit and the tap selector unit are electrically connected to each other via a phase hole (33) in the back plate; It is characterized in that the back plate (16) is arched so that it is shaped like a longitudinal envelope section of a circular cylinder, an elliptical cylinder or a parabolic cylinder. 2. On-load tap changer according to claim 1, wherein the back plate (16) is arched such that the outer surface (9b) has a convex shape and the inner surface (9a) has a convex shape. Concave shape. 3. On-load tap changer according to claim 1, wherein the barrier (2) is sealingly arranged by a tap changer box (15) sealingly fixed to the on-load tap changer (1) . 4. On-load tap changer according to any one of claims 1-3, wherein the barrier (2) is sealingly arranged by means of a keyway (38) along the longitudinal end surface (34) of the back plate , the keyway (38) is in the inner surface or outer surface (9a; 9b) of the back plate (16). 5. On-load tap changer according to claim 4, wherein the barrier (2) is formed by a metal profile (34) arranged along the longitudinal end surface (34) of the back plate and engaging the keyway (38) 8) Arrange in a sealed manner. 6. The on-load tap changer according to any one of claims 1-3, wherein the on-load tap changer (1) is hermetically arranged on the side wall (12) of the transformer box (11). in the mouth. 7. On-load tap changer according to any one of claims 1-3, wherein the back plate (16) is made of epoxy glass material (39). 8. On-load tap changer according to claim 7, wherein the backing plate (16) is made of wire winding of the epoxy glass material (39). 9. A fluid-filled power transformer (10) comprising an on-load tap changer (1) according to any one of claims 1 to 8.