TRANSFORMER ARRANGEMENT

Description

1 / 13 “TRANSFORMER ARRANGEMENT” TECHNICAL FIELD

[0001] The present invention relates to a transformer arrangement with an auxiliary winding. In particular, the invention relates to limiting short-circuit currents in such auxiliary windings. BACKGROUND

[0002] In conventional transformers, when auxiliary power is needed, an auxiliary winding, such as a tertiary winding, can be arranged coaxially with the main windings, i.e., with the primary and secondary windings. See Figure 1. The auxiliary winding can, for example, be used to supply power to devices in a transformer substation, such as lighting, heating, and cooling in the transformer substation. Auxiliary windings are particularly useful in remote locations that do not have access to the regular power grid. Tertiary winding arrangements increase the radial size of the transformer windings and the transformer as a whole. This also increases the cost of the transformer. Another type of auxiliary winding is the yoke winding, i.e., an auxiliary winding arranged around a transformer yoke.As an auxiliary winding, this winding around the breech is smaller, lighter, and cheaper when compared to a coaxial tertiary winding.

[0003] The windings on the yoke traditionally have a voltage level below 1 kV, which can be considered a low-voltage application. Lately, windings on the yoke have been used around 7 kV, which can be considered a medium-voltage application. In medium-voltage applications, an external enclosure is required. The enclosure comprises a fuse that protects the auxiliary winding against high currents. Petition 870260055217, dated 08 / 06 / 2026, page 11 / 54 2 / 13 short-circuit, since the auxiliary winding is not inherently short-circuit proof. However, external enclosures require additional on-site work and maintenance. SUMMARY

[0004] Therefore, one of the objectives of the invention is to provide an improved transformer arrangement with an auxiliary winding protected against harmful short-circuit currents. In particular, the auxiliary winding is a winding around the yoke and the transformer arrangement does not require an enclosure.

[0005] According to a first aspect of the present invention, the objective is achieved, at least in part, by a transformer arrangement according to claim 1.

[0006] Thus, a transformer arrangement is provided with at least one transformer comprising a transformer core, which comprises a lower yoke and an upper yoke, both interconnected by at least one element extending along a first axis. The transformer arrangement further comprises at least one first winding and a second winding arranged coaxially around at least one element. In addition, an auxiliary winding is arranged around at least one element and is positioned axially between the first and second windings and the lower yoke or the upper yoke. The auxiliary winding is magnetically coupled to at least the first winding and / or the second winding.The transformer arrangement further comprises a series reactor connected to the auxiliary winding and at least one support element positioned between an axial end of the first and second windings and the lower and / or upper yoke. The auxiliary winding may be supported by the support element and at least partially incorporated into the support element. Petition 870260055217, dated 08 / 06 / 2026, page 12 / 54 3 / 13

[0007] The first axis may be substantially vertically aligned. The auxiliary winding is positioned around the element between an axial end of the first and second windings and the upper or lower yoke, i.e., axially between the first and second windings and the upper or lower yoke. The auxiliary winding is positioned so as to be magnetically coupled to the first and second windings and configured to supply a portion of the power from the main windings to at least one auxiliary device.

[0008] When the transformer is a multiphase transformer, such as a three-phase transformer, the transformer comprises multiple elements, for example, one element per phase. Each element can be equipped with an auxiliary winding, resulting in a three-phase power supply for auxiliary equipment and devices. Obviously, each auxiliary winding can be connected to a respective reactor in series.

[0009] The series reactor comprises at least one impedance element connected in series with the auxiliary winding. The reactor is passive during normal operation of the auxiliary winding. When a short circuit occurs in the auxiliary winding, a sudden increase in the current flowing through the reactor generates a magnetic field that induces an opposing current in the reactor, which in turn reduces and limits the short-circuit current.

[0010] The support element is an element configured to mechanically support the windings. The support element may be made of an electrically insulating material and may be in physical contact with the windings. The support element may be, for example, a common spacer ring.

[0011] If the auxiliary winding is positioned below a lower axial end of the first and second windings, the Petition 870260055217, dated 08 / 06 / 2026, page 13 / 54 The 4 / 13 support element can be supported on the lower breech, and the auxiliary winding can be supported by the support element on an upper side of the support element.

[0012] If the auxiliary winding is positioned above an upper axial end of the first and second windings, the auxiliary winding may be supported by the support element on an upper side of the support element.

[0013] Optionally, the auxiliary winding is configured to supply auxiliary power from the transformer through the reactor in series to at least one auxiliary device.

[0014] The auxiliary winding is magnetically coupled to the first and second windings of the transformer. Energy can thus be generated in the auxiliary winding and supplied to auxiliary devices and equipment. These devices and equipment may be energy consumers used locally at a transformer substation, for example, devices for lighting, heating and / or cooling, such as when the transformer substation is located in a remote location and is not connected to a grid that could supply power to the devices. The auxiliary winding is sized and configured to supply power at a voltage level suitable for the auxiliary devices.

[0015] Optionally, the support element is a ring comprising a ring-shaped groove or cavity that encircles the element. The auxiliary winding may be disposed in the ring-shaped groove or cavity.

[0016] Thus, the auxiliary winding is mounted with the transformer without increasing its size, since the auxiliary winding is housed in an existing component, i.e., in the slot or cavity of the support element. In the case of a slot, the auxiliary winding is arranged in the slot, partially embedded in the element. Petition 870260055217, dated 08 / 06 / 2026, page 14 / 54 5 / 13 support element. In the case of a cavity, the auxiliary winding can be completely embedded and encapsulated within the support element.

[0017] Optionally, the rated power of at least the first winding or the second winding is greater than 100 MVA and the rated voltage of at least the first winding or the second winding is greater than 66 kV.

[0018] Optionally, the auxiliary winding has a rated voltage above 1 kV.

[0019] Optionally, a series reactor impedance is configured to limit short-circuit currents in the auxiliary winding below 30 kA rms.

[0020] Optionally, at least one transformer is a three-phase transformer or three single-phase transformers and in which three auxiliary windings, each connected to a respective reactor in series, are connected in a star configuration or in a delta configuration.

[0021] The star connection is also known as a Y connection or a Y-connection.

[0022] Optionally, the transformer arrangement further comprises a transformer tank, in which the transformer is encapsulated in the transformer tank and immersed in oil in the transformer tank.

[0023] Optionally, the series reactor is located inside the transformer tank. Thus, the series reactor does not increase the size of the transformer, unlike a conventional medium-voltage enclosure for short-circuit current protection, as discussed in the background section above. The terminals of any auxiliary windings can be routed to the outside of the transformer tank. A star or delta configuration of the auxiliary windings can be connected inside the tank. Petition 870260055217, dated 08 / 06 / 2026, page 15 / 54 6 / 13 transformer which involves a three-phase transformer. In the case of three single-phase transformers, each transformer is encapsulated in its respective transformer tank, and the star or delta configuration of the auxiliary windings is connected outside the transformer tanks.

[0024] The above aspects, appended claims and / or examples described above and further on may be suitably combined, as would be evident to anyone skilled in the art.

[0025] Additional features and advantages are described in the following description, claims, and drawings, and, in part, will be readily apparent to those skilled in the art or recognized by practice of the invention as described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other objects, advantages and features of the invention will be evident from the following description of one or more embodiments, with reference to the accompanying drawings, where:

[0027] Figure 1 shows a cross-sectional view of a prior art transformer arrangement comprising a tertiary winding as an auxiliary winding.

[0028] Figure 2 shows a cross-sectional view of a transformer arrangement, according to a first aspect of the present invention.

[0029] Figure 3 shows a cross-sectional view of a transformer arrangement, according to an embodiment of the present invention.

[0030] Figure 4 conceptually shows an example three-phase transformer, according to an embodiment of the present invention.

[0031] Figure 5 shows an example of a realization of Petition 870260055217, dated 08 / 06 / 2026, page 16 / 54 7 / 13 present invention for a transformer connected in a delta configuration.

[0032] Figure 6 shows an example of an embodiment of the present invention for a transformer connected in a star configuration. DETAILED DESCRIPTION OF EXAMPLES OF EMBODIMENTS OF THE INVENTION

[0033] The present invention is developed in more detail below, with reference to the accompanying drawings which show examples of embodiments. The invention should not be seen as limited to the described examples of embodiments. Similar numbers refer to similar elements throughout the description.

[0034] The terminology used in this document is intended to describe only particular aspects of the invention and is not intended to limit the invention. As used in this document, the singular forms a, an and the are intended to include the plural forms as well, unless the context clearly indicates otherwise. Unless defined otherwise, all terms (including technical and scientific terms) used in this document have the same meaning as commonly understood by one skilled in the art to which this invention pertains.

[0035] Figure 1 illustrates a cross-sectional view of a prior art transformer 10', comprising a transformer core 12 with a lower yoke 14 and an upper yoke 16 interconnected by an element 18 extending along a first axis a. A first inner winding 20 and a second outer winding 22 are arranged coaxially around the element 18. An auxiliary winding 23 in the form of a tertiary winding is arranged coaxially with the first and second windings 20, 22, around the element 18. The auxiliary / tertiary winding 23 is Petition 870260055217, dated 08 / 06 / 2026, page 17 / 54 8 / 13 magnetically coupled to at least the first winding 20 and / or the second winding 22. A tertiary winding 23, as shown in Figure 1, may be designed to withstand short-circuit currents.

[0036] According to one aspect of the present invention, the tertiary winding 23 as an auxiliary winding can be replaced by a breech winding 28, as shown in Figure 2. The breech winding is attractive because it is smaller, lighter, and cheaper than a tertiary winding 23, which is conventionally arranged coaxially with the first and second windings 20, 22. The breech winding 28 previously required an enclosure (not shown) containing fuses to protect the breech winding 28 against damaging short-circuit currents. Adding an enclosure to the transformer consumes space in the transformer substation, where space is generally limited. Furthermore, the cost of enclosures has increased significantly, making the breech winding an unattractive solution as an auxiliary winding.

[0037] The present invention makes the enclosure unnecessary and results in a transformer arrangement 1 comprising a transformer 10 with an auxiliary winding 28, wherein the transformer arrangement 1 is smaller or similar in size to a conventional transformer 10' with a tertiary winding.

[0038] Figure 2 shows the transformer arrangement 1 with at least one transformer 10. The transformer arrangement comprises a transformer core 12 which includes a lower yoke and an upper yoke 16 interconnected by at least one element (18) extending along a first axis a. At least one first winding 20 and a second winding 22 are arranged coaxially around the at least one element 18. An auxiliary winding 28 is arranged around the at least one element 18, po Petition 870260055217, dated 08 / 06 / 2026, page 18 / 54 9 / 13 axially coupled between the first and second windings 20, 22 and the lower yoke 14 or the upper yoke 16. The auxiliary winding is magnetically coupled to at least the first winding 20 and / or the second winding 22. Transformer arrangement 1 further comprises a series reactor 30 connected to the auxiliary winding 28.

[0039] The first axis a may be substantially vertically aligned. The auxiliary winding 28 is positioned around element 18 between an axial end of the first and second windings 20, 22 and the upper yoke 16 or the lower yoke 14, i.e., axially between the first and second windings 20, 22 and the upper yoke 16 or the lower yoke 14. The auxiliary winding 18 is positioned so as to be magnetically coupled to the first and second windings 20, 22 and configured to supply a portion of the power from the main windings (the first and second windings 20, 22) to at least one auxiliary device (not shown).

[0040] When the transformer 10 is a multiphase transformer 10, like a three-phase transformer 10, the transformer 10 comprises multiple elements 18, for example, one element per phase 18. Each element 18 can be equipped with an auxiliary winding 28, resulting in a three-phase power supply for auxiliary equipment and devices. Each auxiliary winding 28 can be connected to a respective series reactor 30.

[0041] The series reactor 30 comprises at least one impedance element connected in series with the auxiliary winding. The series reactor is passive during normal operation of the auxiliary winding 28. When a short circuit occurs in the auxiliary winding 28, a sudden increase in current through the series reactor 30 generates a magnetic field that induces an opposing current in the series reactor 30, which, in turn, reduces and limits the short-circuit current. Petition 870260055217, dated 08 / 06 / 2026, page 19 / 54 10 / 13 circuit both in the series reactor and, more importantly, in the auxiliary winding 28.

[0042] The auxiliary winding 28 can be configured to supply auxiliary power from transformer 10 through the series reactor 30 to at least one auxiliary device through terminals 34. The auxiliary winding 28 is magnetically coupled to the first and second windings 20, 22 of transformer 10. Power can thus be generated in the auxiliary winding 28 and supplied to auxiliary devices and equipment. These devices and equipment may be energy consumers used locally in a transformer station, for example, devices for lighting, heating and / or cooling, such as when the transformer station is located in a remote location and is not connected to a grid that could supply power to the devices. The auxiliary winding 28 is sized and configured to supply power at a voltage level suitable for such auxiliary devices.

[0043] Figure 3 illustrates that the transformer arrangement 1 may further comprise at least one support element 24 positioned between an axial end of the first and second windings 20, 22 and the lower yoke 14 and / or the upper yoke 16. The auxiliary winding 28 may be supported by the support element 24.

[0044] The support element 24 is an element configured to mechanically support the first and second windings 20, 22. The support element 24 may be formed from an electrically insulating material and may be in physical contact with the first and second windings 20, 22. The support element 24 may be, for example, a common spacer ring 24.

[0045] If the auxiliary winding 28 is positioned below a lower axial end of the first and second windings 20, 22, the support element 24 can be supported on the lower yoke. Petition 870260055217, dated 08 / 06 / 2026, page 20 / 54 11 / 13 and the auxiliary winding 28 can be supported by the support element 24 on an upper side of the support element 24.

[0046] If the auxiliary winding 28 is positioned above an upper axial end of the first and second windings 20, 22, the auxiliary winding 28 can be supported by the support element 24 on an upper side of the support element 24.

[0047] The support element may be a ring 24 comprising a ring-shaped slot or cavity 25, which circumscribes the element 18. The auxiliary winding 28 may be disposed in the ring-shaped slot or cavity 25. The auxiliary winding 28 may thus be mounted with the transformer 10 without increasing the size of the transformer 10, since the auxiliary winding 28 is housed in an existing component, i.e., in the slot or cavity 25 of the support element 24. In the case of a slot, the auxiliary winding 28 is disposed, in the slot, partially embedded in the support element 24. In the case of a cavity, the auxiliary winding 28 may be completely incorporated and encapsulated in the support element 24.

[0048] When at least one auxiliary winding 28 is used for medium voltage applications, the rated power of at least the first winding 20 or the second winding 22 is greater than 100 MVA and the rated voltage of at least the first winding 20 or the second winding 22 is greater than 66 kV. The auxiliary winding has a rated voltage above 1 kV. In order to protect the auxiliary winding 28 against damage caused by short-circuit currents, it is preferable that the impedance of the series reactor 30 be configured to limit the short-circuit currents in the auxiliary winding 28 below 30 kA rms.

[0049] Figure 4 conceptually shows the transformer arrangement 1, which comprises a three-phase transformer 10. As Petition 870260055217, dated 08 / 06 / 2026, page 21 / 54 As shown in Figure 12 / 13, a multiphase transformer 10 may have an auxiliary winding 28 arranged around each element 18. The elements 18 are not shown in Figure 4, but it should be understood that a first and a second winding 20, 22 are arranged in a respective element 18 for each phase of the transformer 10.

[0050] Furthermore, and according to the present invention, each auxiliary winding 28 has a series reactor 30 connected in series.

[0051] The transformer arrangement 1 may further comprise a transformer tank 32, and the transformer 10 may be encapsulated in the transformer tank 32 and immersed in insulating oil in the transformer tank 32. The series reactor 30 may be located inside the transformer tank 32. Thus, the series reactor 30 does not increase the size of the transformer 10, unlike a conventional medium-voltage cabinet for short-circuit current protection, as discussed in the background section above. The terminals 34 of any auxiliary windings 28 may be led to the outside of the transformer tank 32.

[0052] As is known in the art, three-phase transformers can be connected in a star configuration or a delta configuration. The auxiliary windings 28, each connected to a respective series reactor 30, of these three-phase configurations can be connected correspondingly in a star configuration or a delta configuration.

[0053] Figure 5 shows three auxiliary windings 28 of a three-phase transformer arrangement 1, which are connected in a delta configuration. Terminals 34', 34”, 34”' indicate terminals for the three phases that can be connected to supply power to auxiliary systems.

[0054] Figure 6 shows three auxiliary windings 28 of a three-phase transformer arrangement 1, which are connected in Petition 870260055217, dated 08 / 06 / 2026, page 22 / 54 13 / 13 star configuration. Terminals 34', 34”, 34'” indicate terminals for the three phases that can be connected to supply power to auxiliary systems. Terminal 34”” illustrates the neutral point of the star configuration. As mentioned above, the star configuration is also known as the Y configuration or Y-configuration. Petition 870260055217, dated 08 / 06 / 2026, page 23 / 54

Claims

1 / 3 CLAIMS 1. Transformer arrangement (1) comprising at least one transformer (10) which includes: - a transformer core (12) comprising a lower yoke (14) and an upper yoke (16) interconnected by an element (18) extending along a first axis (a); - a first winding (20) and a second winding (22) arranged coaxially around the element (18), characterized in that it comprises: - an auxiliary winding (28) arranged around the element (18), and positioned axially between an axial end of the first and second windings (20, 22) and the lower yoke (14) or the upper yoke (16), the auxiliary winding (28) being magnetically coupled, at least, to the first winding (20) and / or to the second winding (22), and a series reactor (30) connected to the auxiliary winding (28) and configured to limit short-circuit currents in the auxiliary winding (28);a support element (24) positioned between the axial end of the first and second windings (20, 22) and the lower yoke (14) and / or the upper yoke (16), wherein the support element (24) is formed of electrically insulating material and configured to mechanically support the auxiliary winding (28), and wherein the auxiliary winding (28) is at least partially incorporated into the support element (24).

2. Transformer arrangement, according to claim 1, characterized in that the support element (24) comprises an annular slot or cavity (25) that circumscribes the element (18), the auxiliary winding (28) being disposed in the annular slot or cavity (25) and at least partially incorporated in the support element (24).

3. Transformer arrangement according to claim 1, characterized in that the support element (24) is formed of electrically insulating material and is disposed between the auxiliary winding (28) and at least one of the windings (20, 22).

4. Transformer arrangement (1), according to claim 1, characterized in that the auxiliary winding (28) is configured to supply auxiliary power from the transformer (10) through the reactor in series (30) to at least one auxiliary device.

5. Transformer arrangement (1), according to claim 1, characterized in that the support element is a ring (24) comprising a ring-shaped slot or cavity (25), wherein the ring-shaped slot or cavity (25) circumscribes the element (18), and wherein the auxiliary winding (28) is received within the ring-shaped slot or cavity (25).

6. Transformer arrangement, according to any of the preceding claims, characterized in that the auxiliary winding (28) is encapsulated by the support element (24).

7. Transformer arrangement (1), according to any of the preceding claims, characterized in that a rated power of at least the first winding (20) or the second winding (22) is greater than 100 MVA and the rated voltage of the first winding (20) or the second winding (22) is greater than 66 kV.

8. Transformer arrangement (1), according to any of the preceding claims, characterized in that the auxiliary winding (28) has a rated voltage above 1 kV.

9. Transformer arrangement (1), according to any of the preceding claims, characterized in that a series reactor impedance (30) is configured to limit the short-circuit currents in the auxiliary winding below 30 kA rms (28).

10. Transformer arrangement (1), according to any of the preceding claims, characterized in that at least one transformer (10) is a three-phase transformer (10) or three single-phase transformers (10) and in which three auxiliary windings (28), each connected to a respective reactor in series (30), are connected in a star configuration or in a delta configuration.

11. Transformer arrangement (1), according to any of the preceding claims, characterized in that it further comprises a transformer tank (32), wherein the transformer (10) is encapsulated in the transformer tank (32) and is immersed in oil in the transformer tank (32).

12. Transformer arrangement (1), according to claim 11, characterized in that the series reactor (30) is located inside the transformer tank (32).

13. Transformer arrangement (1), according to any of the preceding claims, characterized in that the auxiliary winding (28) is configured to operate without an external short-circuit protection enclosure.

14. Transformer arrangement (1), according to any of the preceding claims, characterized in that the series reactor (30) is disposed within a transformer tank (32) filled with insulating fluid. Petition 870260055217, dated 08 / 06 / 2026, page 26 / 54

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