Boron nitride sealants in transformers and their components

Abstract

A transformer arrangement is disclosed. The transformer arrangement comprises a transformer tank, electrical power transformer components arranged inside the transformer tank, and at least one sealing element arranged to prevent leakage of a liquid into or out of a component (5) provided inside the transformer tank (2), or to prevent leakage of the liquid out of the transformer tank. The sealing element (3, 4) arranged to prevent leakage comprises Boron Nitride.

Description

[0001] BORON NITRIDE SEALANTS IN TRANSFORMERS AND THEIR COMPONENTS

[0002] TECHNICAL FIELD

[0003] The present disclosure generally relates to construction of a transformer. More particularly, it relates to a sealing element used in a transformer.

[0004] BACKGROUND

[0005] In order to ensure that there is no oil leakage from a transformer, sealing elements are used to safely contain oil within housing of the transformer. The sealing elements in transformers are also used to prevent entry of moisture into the transformer housing. The transformers heavily rely on different dielectric liquids to successfully dissipate heat and enhance electrical insulation. For short or long duration overloading, the sealing elements must consist of nonflammable materials that can withstand high temperatures.

[0006] SUMMARY

[0007] Sealing elements for transformers are required to possess exceptional compatibility with different dielectric insulating liquid in a transformer tank. Examples of Dielectric insulating liquids include mineral oil, natural esters, and synthetic esters. The sealing elements are further required to have an ability to withstand a transformer environment. Transformers rely heavily on the different dielectric insulating liquids to successfully dissipate heat and enhance electrical insulation. Therefore, sealing elements are required to have exceptional chemical and thermal resistance in the transformer sector in order to allow continued stability of the transformer against degradation and swelling upon exposure to the high temperature transformer environment. This is critical in areas of short or long duration overloading where the sealing elements must consist of non-flammable materials that can withstand temperatures as high as up to 200 degree Celsius.

[0008] It is important to consider that locations of low voltage connections are extremely critical locations as they must tolerate very high temperatures and operate with the oil expansion conservative system strictly adhering to international code ISO 3320-1. It is therefore an object of the present disclosure to provide a sealing element used in a transformer, to achieve all or at least some of the above-discussed requirements thereby providing an environmentally friendly and efficient solution.

[0009] This and other objects are achieved by means of an improved sealing element as defined in the appended claims. The term exemplary is in the present context to be understood as serving as an instance, example or illustration.

[0010] According to an aspect of the present disclosure, a transformer arrangement is provided. The transformer arrangement comprises a transformer tank and an electrical insulating liquid housed inside the transformer tank, electrical power transformer components arranged inside the transformer tank, and at least one sealing element arranged to prevent leakage of a liquid into or out of a component provided inside the transformer tank, or to prevent leakage of the liquid out of the transformer tank, characterized in that the sealing element comprises Boron Nitride (BN), wherein at least a part of the sealing element is exposed to contact with said electric insulating liquid, and that said part of the sealing element comprises the BN and wherein said part of the sealing element comprises a coating of the BN.

[0011] Advantageously, the usage of boron nitride as a sealing element has high potential in transformer applications due to its ability to withstand extreme temperatures and pressures as well as being chemically inert and possess corrosion protection capabilities.

[0012] In some embodiments, the electrical insulating liquid comprises one of mineral oil, a natural ester, or a synthetic ester.

[0013] In some embodiments, the sealing element comprises a gasket.

[0014] According to some embodiments, the gasket is positioned between a first component and a second component of the transformer arrangement, wherein the first component is clamped to the second component such that the gasket is subjected to a clamping force.

[0015] According to some embodiments, the second component is a wall of the transformer tank, the wall has a through hole, and the first component is inserted into the through hole and clamped to the wall, wherein the gasket is ring-shaped and extends around the through hole. According to some embodiments, the first component is only clamped to, but not inserted into the through hole, wherein the sealing element is clamped between the first component and the wall.

[0016] According to some embodiments, the first component comprises an electric bushing.

[0017] In some embodiments, the sealing element comprises a lubricating mass provided in an interface between two components that form part of the transformer arrangement and that are movable in relation to each other.

[0018] In some embodiments, the lubricating mass comprises a grease filled with particles of the BN.

[0019] In some embodiments, the transformer arrangement comprises a tap changer comprising a gasket which has a coating of the BN.

[0020] In some embodiments, said part of the sealing element comprises impregnated BN into a base material. Advantageously, the proposed coating of the BN will have the potential to minimize the risk of abrasion-related failures and extends the lifespan of the transformers and their components. Other advantages may be readily apparent to one having skill in the art. Certain embodiments may have some, or all the recited advantages.

[0021] According to some embodiments, the transformer arrangement comprises any of:

[0022] - at least two interconnected transformer tank walls,

[0023] - a bushing,

[0024] - a tank for housing the electrically insulating fluid, connected to the transformer tank through first piping,

[0025] -a cooling tank for cooling of the electrically insulating fluid, connected to the transformer tank through second piping,

[0026] - a pipe connection between pipes of the first piping or between pipes of the second piping, -a manhole in a wall of the transformer tank and a manhole cover,

[0027] - a drain valve, for draining of the electrically insulating fluid from the transformer tank,

[0028] - at least one of a temperature sensor a pressure sensor or a flowmeter extending through a wall of the transformer tank or through a wall of the first piping or second piping, wherein the sealing element is any of

[0029] - a sealing element between said interconnected tank walls of the transformer tank, - a sealing element between said bushing and wall of the transformer tank,

[0030] - a sealing element between said first piping and a wall of the transformer tank,

[0031] - a sealing element between said second piping and a wall of the transformer tank,

[0032] - a sealing element of said pipe connection,

[0033] - a sealing element between said manhole cover and a wall of the transformer tank,

[0034] - a drain valve sealing element, and

[0035] - a sealing element between any of a temperature sensor, a pressure sensor or a flow meter and a wall of the transformer tank or a wall of the first or second piping.

[0036] According to some embodiments, the transformer arrangement comprises

[0037] - at least two interconnected transformer tank walls and wherein the sealing element is a sealing element between said interconnected tank walls of the transformer tank.

[0038] According to some embodiments, the transformer arrangement comprises an active transformer part inside the transformer tank and a medium or high voltage bushing extending through a wall of the transformer tank and configured for the connection of an electric conductor with the active transformer part, wherein the sealing element is a sealing element between the bushing and said wall of the transformer tank.

[0039] According to some embodiments, the transformer arrangement comprises

[0040] - a tank for housing the electrically insulating fluid, connected to the transformer tank through first piping and the sealing element is a sealing element between said first piping and a wall of the transformer tank.

[0041] According to some embodiments, the transformer arrangement comprises

[0042] - a cooling tank for cooling of the electrically insulating fluid, the cooling tank being connected to the transformer tank through second piping, and wherein the sealing element is a sealing element between said second piping and a wall of the transformer tank.

[0043] According to some embodiments, the transformer arrangement comprises - a tank for housing the electrically insulating fluid, connected to the transformer tank through first piping and the first piping comprises pipes connected by a pipe connection, and wherein the sealing element is a sealing element of the pipe connection.

[0044] According to some embodiments, the transformer arrangement comprises

[0045] - a cooling tank for cooling of the electrically insulating fluid, connected to the transformer tank through second piping, and the second piping comprises pipes connected by a pipe connection and wherein the sealing element is a sealing element of the pipe connection.

[0046] According to some embodiments, the transformer arrangement comprises

[0047] - a manhole in a wall of the transformer tank and a manhole cover and wherein the sealing element is a sealing element between said manhole cover and a wall of the transformer tank.

[0048] According to some embodiments, the transformer arrangement comprises

[0049] - a drain valve, for draining of the electrically insulating fluid from the transformer tank, and wherein the sealing element is a drain valve sealing element.

[0050] According to some embodiments, the transformer arrangement comprises

[0051] - at least one of a temperature sensor a pressure sensor or a flowmeter extending through a wall of the transformer tank, and wherein the sealing element is a sealing element between any of a temperature sensor, a pressure sensor or a flow meter and a wall of the transformer tank.

[0052] According to some embodiments, the transformer arrangement comprises

[0053] - a tank for housing the electrically insulating fluid, and piping extending from the tank for housing the electrically insulating fluid to the transformer tank, and a valve for controlling a flow of said fluid in said piping, wherein the sealing element is a sealing element of said valve.

[0054] BRIEF DESCRIPTION OF THE DRAWING

[0055] The foregoing will be apparent from the following more particular description of the example embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the example embodiments.

[0056] Fig. 1 discloses a schematic perspective view of an example of a part of a transformer arrangement according to the invention, seen from a first direction;

[0057] Fig. 2 shows the part of the transformer arrangement of Fig. 1 seen from a second direction;

[0058] Fig. 3 shows the part of the transformer arrangement of Figs. 1 and 2 seen from a third direction;

[0059] Fig. 4 shows a wall element to be attached on top of the part of the transformer arrangement shown in figs. 1-3;

[0060] Fig. 5 shows further parts of a transformer arrangement according to the present disclosure;

[0061] Fig. 6 shows a transformer tank with high and medium voltage bushings mounted thereon;

[0062] Fig. 7 is a cross-sectional view showing structural details of the bushing assembly; and

[0063] Fig. 8 shows parts of a transformer arrangement according to the present disclosure.

[0064] DETAILED DESCRIPTION

[0065] Aspects of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings. The transformer arrangement disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to like elements throughout.

[0066] The terminology used herein is for the purpose of describing particular aspects of the disclosure only and is not intended to limit the invention. It should be emphasized that the term "comprises / comprising" when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Figs. 1-3 disclose different views of parts an example transformer arrangement 1 for an electrical system. The transformer arrangement 1 includes a transformer tank 2, electrical power transformer components arranged inside the transformer tank 2, and at least one sealing element (not shown in figs. 1-3 but exemplified with reference numbers 3 and 4 in fig. 7). The at least one sealing element is arranged to prevent leakage of a fluid into or out of a component provided inside the transformer tank 2, or to prevent leakage of the fluid out of the transformer tank 2. The sealing elements disclosed herein preferably comprise Boron Nitride (BN), preferably a coating of Boron Nitride on a core of other material than BN, for example a polymer core.

[0067] Figs. 4-5 disclose various positions where the sealing elements can be used in order to prevent leakage of the transformer dielectric insulating liquid. Certain applications of the BN- comprised sealing elements include positing a layer of the sealing element in between two or more joints or components. Further, the sealing elements comprising the BN is used at positions like between two components that form part of the transformer arrangement 1 and that may be movable in relation to each other.

[0068] The usage of BN as a sealing element material in transformer arrangements has high potential in transformer applications due to the ability of the BN to withstand extreme temperatures and pressures as well as being chemically inert and possess corrosion protection capabilities. The availability of different boron nitride polytypes will allow selection of the most appropriate polytype as it pertains to the coefficient of friction and wear resistance material specification requirements for different application scenarios of the transformers and electrical power transformer components. Property of the BN has a potential to minimize the risk of abrasion-related failures and extends the lifespan of the transformers and the transformer components. Furthermore, BN is a non-toxic material and therefore does not exhibit chemical activity in biological systems. Due to its excellent safety profile and lubricious properties, BN finds widespread use in various applications, including cosmetics and food processing equipment.

[0069] According to the disclosed exemplifying embodiment of the present disclosure, the transformer arrangement 1 comprises an electrical insulation liquid housed inside the transformer tank 2. A type of transformer is an oil-immersed transformer. The transformers operate in high-energy and high-heat situations. The oil-filled transformer suspends the transformer tank that is filled with the electrical insulation liquid. The electrical insulation liquid cools as well as insulates the transformer. In order to avoid liquid deterioration, the transformer liquid is kept at an approximate operating temperature of less than 85°C. Further, for the transformer to run efficiently and for preventing excessive liquid deterioration, daily average operating temperature should be approximately 30°C. Transformer windings and transformer core are submerged in the transformer liquid. The transformer liquid acts as a cooling agent and an insulator. The transformer insulation liquid moves through the transformer windings, transformer coils, and the transformer core through convection, thereby preventing the transformer from overheating.

[0070] According to an embodiment of the present disclosure, the transformer arrangement 1 comprises the electrical insulation liquid comprising of one of mineral oil, a natural ester fluid (FR3), Silicone, or a synthetic ester. The transformer insulating liquid can be Paraffin-based transformer insulating liquid or naphthenic-based transformer insulating liquid. The mineral oil is a hydrocarbon-based insulating liquid that is distilled from naphthenic-based oils. It is most widely used insulating liquid for the transformers. The mineral oils have a low viscosity which makes them an effective liquid for cooling by natural convection. FR3 has been developed to provide a more environmentally friendly version for higher flashpoint liquids, ranging for applications requiring a less flammable liquid-filled transformer. The FR3 liquids are typically seed oil based rather than hydrocarbon-based. Further, Silicone is a synthetic liquid. It is less widely used in the transformers. High fire point of the silicone makes it suitable for applications that requires a less flammable liquid. The synthetic esters are manufactured from carboxylic acids and alcohols. Compared to the mineral oils, synthetic esters offer an advantage of higher viscosity indexes, low pour points, high flash points, low temperature fluidity, low volatility, high thermal stability, and oxidation resistance. Further, the synthetic esters possess excellent lubricity characteristics.

[0071] The transformer arrangement 1 comprises sealing elements that are arranged to prevent leakage of the electric insulating liquid into or out of components provided inside the transformer tank 2, or to prevent leakage of the insulating liquid out of the transformer tank 2 and to prevent air ingress in order to limit moisture intake and degradation of the dielectric insulating liquids. The sealing elements are arranged such that at least a part of each sealing element is exposed to contact with said electric insulating liquid, wherein said part of the sealing element comprises a coating of Boron Nitride, BN.

[0072] At least some of the sealing element comprises a gasket. Boron Nitride coatings are applied to the surface of these gaskets to provide and enhance lubricant properties of the gaskets and to offer an excellent electrical insulation. The BN may be present in the sealing element in form of impregnated BN into a base material.

[0073] In general, each sealing element, preferably formed as a gasket, of the present disclosure is positioned between a first component and a second component of the transformer arrangement, wherein the first component is clamped to the second component such that the gasket is subjected to a clamping force. Examples of such first and second components will be given hereinbelow with reference to the drawing, in particular with reference to figs. 5, 7 and 8. It should be mentioned that fig. 8 is a schematic view, and that it only discloses principles, and that, therefore, there are differences regarding positions and design of different components with regard to what is shown in the other figures. However, the same main principles are shown as in the other figures.

[0074] With reference to figs. 6-8, the transformer arrangement 1 comprises an active transformer part inside the transformer tank 2 and a plurality of medium or high voltage bushings 5 extending through a first wall 7 and a second wall 11 of the transformer tank 2. Each bushing 5 extends through a through hole 8 in one of the transformer tank walls 7, H and is configured for the connection of an electric conductor with the active transformer part. The at least one sealing element comprises a first sealing element 3 between the bushing 5 and said wall 7, 11 of the transformer tank 2 and a second sealing element 4 between an upper shield 30 of the bushing 5 and an upper conductor assembly 31 of the bushing 5. As can be seen in fig. 6, so called turrets 10, are also arranged around the bushing 5 on the outside of the transformer tank 2, for further electrical insulation of the bushing 5. The turrets 10 may comprise an oil- filled casing and be provided with sealing elements according to the present invention, i.e. sealing elements with a BN coating for preventing leakage of oil from the turret 10.

[0075] The transformer arrangement 1 comprises at least two interconnected transformer tank walls

[0076] 7, 11. A sealing element (not shown) having a BN coating is preferably arranged between said interconnected tank walls 7, 11 of the transformer tank 2. With reference to figs. 1 and 4, the sealing element may comprise a gasket extending on and around the periphery of the first wall 7 such that it is clamped between the first wall 7 and the second wall 11 when the second wall 11 is mounted on top of the first wall 7. Other wall configurations, and thus corresponding sealing configurations, than one disclosed are, of course, also within the claimed scope of the invention. For example, the first wall 7 may comprise a plurality of side walls connected to each other, wherein sealing element according to the invention is provided between each pair of interconnected side walls.

[0077] The transformer arrangement also comprises a tank 12 for housing the electrically insulating fluid, connected to the transformertank 2 through first piping 13. A sealing element according to the invention (not visible on the drawing) is provided between said first piping 13 and a wall 11 of the transformer tank 2. The tank 12 for housing the electrically insulating fluid may be used for regulation of the pressure and regulation of the amount of electrically insulating fluid inside the transformer tank 2.

[0078] The tank 12 for housing the electrically insulating fluid also comprises pipes 18, 19 connected by a pipe connection 16, wherein a sealing element according to the invention (not visible on the drawing) is a sealing element of the pipe connection 16.

[0079] A cooling tank 14 for cooling of the electrically insulating fluid is connected to the transformer tank 2 through second piping 15, and a sealing element according to the invention (not visible on the drawing) is positioned between said second piping 15 and a wall 11 of the transformer tank 2.

[0080] The cooling tank 14 for cooling of the electrically insulating fluid also comprises pipes 20, 21 connected by a pipe connection 17 (reference is made to fig. 5 which is a more detailed view than the very schematic one in fig. 8), wherein a sealing element according to the invention (not visible on the drawing) is a sealing element of the pipe connection 17. The pipe connection 17, or the second piping 15, preferably also includes a pump and a valve for controlling the flow of liquid to and from the cooling tank 14. Sealings according to the invention, with BN coating, may also be provided in such a pump or valve. A plurality of manholes (not visible on the drawing) are provided in a wall 11 of the transformer tank 2, and each manhole is covered by a manhole cover 23, wherein a sealing element according to the invention (but not visible on the drawing) is arranged between said manhole cover 23 and a wall 11 of the transformer tank 2 in which the manhole is provided. The manhole 23 enables entrance into and inspection / reparation works inside the transformer tank 2. The manhole cover 23 is removably clamped to the wall surrounding the manhole, and the sealing element is thereby clamped between the wall and the manhole cover 23.

[0081] A drain valve 24, for draining of the electrically insulating fluid from the transformer tank 2 is provided, and a sealing element according to the invention (not visible on the drawing) is a drain valve sealing element for preventing leakage via the drain valve.

[0082] The transformer arrangement 1 further comprises at least one of a temperature sensor, a pressure sensor, or a flowmeter, indicated with 25, extending through a wall 11 of the transformer tank or any of said first or second piping 13, 15, wherein a sealing element according to the invention is arranged between any of said temperature sensor, pressure sensor or flow meter 25 and a wall 11 of the transformer tank 2 or a wall of said piping 13, 15.

[0083] In the piping 13 extending from the tank 12 for housing the electrically insulating fluid to the transformer tank 12 there is a valve 9 for controlling a flow of said fluid in said piping 13. A sealing element according to the invention forms a sealing element of said valve 9.

[0084] In cases in which the components between which there is provided a sealing according to the invention, where the components are moveable in relation to each other, the sealing element may comprise a lubricating mass provided in an interface between the two components. The lubricating mass comprises a grease filled with particles of the BN. Such a grease is a mixture of the Boron Nitride (BN) and a non-petroleum-derived wax. The BN helps to reduce the friction in conjunction with the wax matrix. The grease is suitable to be applied at a room temperature or even to hot surfaces ranging from 100-200 degree Celsius without skittering.

Claims

WE CLAIM:

1. A transformer arrangement (1), comprising: a transformer tank (2); electrical power transformer components arranged inside the transformer tank, wherein the transformer arrangement comprises an electrical insulation liquid housed inside the transformer tank (2); and at least one sealing element (3, 4) arranged to prevent leakage of a liquid into or out of a component (5, ) provided inside the transformer tank, or to prevent leakage of the liquid out of the transformer tank, characterized in that the sealing element (3, 4) comprises Boron Nitride, BN, wherein at least a part of the sealing element (3, 4) is exposed to contact with said electric insulating liquid, and that said part of the sealing element (3, 4) comprises the BN, and wherein said part of the sealing element (3, 4) comprises a coating of the BN.

2. The transformer arrangement (1) according to claim 1, wherein the electrical insulating liquid comprises one of mineral oil, a natural ester, or a synthetic ester.

3. The transformer arrangement (1) according to any preceding claim, wherein the sealing (3, 4) element comprises a gasket.

4. The transformer arrangement according to claim 3, wherein the gasket (3) is positioned between a first component (5) and a second component (7) of the transformer arrangement, wherein the first component (5) is clamped to the second component (6) such that the gasket (3) is subjected to a clamping force.

5. The transformer tank according to claim 4, wherein the second component is a wall (7, 11) of the transformer tank (2), the wall (7, 11) has a through hole (8), and the first component (5) is inserted into the through hole (8) and clamped to the wall (7, 11), wherein the gasket (3) is ring-shaped and extends around the through hole (8).

6. The transformer tank according to claim 5, wherein the first component (5) comprises an electric bushing.

7. The transformer arrangement (1) according to any preceding claim, wherein the sealing element comprises a lubricating mass provided in an interface between two components that form part of the transformer arrangement (1) and that are movable in relation to each other.

8. The transformer arrangement (1) according to claim 7, wherein the lubricating mass comprises a grease filled with particles of the BN.

9. The transformer arrangement (1) according claim 1, wherein said part of the sealing element (3, 4) comprises impregnated BN into a base material.

10. The transformer arrangement (1) according to any preceding claim, wherein the transformer arrangement (1) comprises any of:- at least two interconnected transformer tank walls (7, 11),- an electric cable bushing (5),- a tank (12) for housing the electrically insulating fluid, connected to the transformer tank (2) through first piping (13),-a cooling tank (14) for cooling of the electrically insulating fluid, connected to the transformer tank (2) through second piping (15),- a pipe connection (16, 17) between pipes (18, 19) of the first piping (13) or between pipes (20, 21) of the second piping (15),-a manhole in a wall (11) of the transformer tank (2) and a manhole cover (23),- a drain valve (24), for draining of the electrically insulating fluid from the transformer tank (2),- at least one of a temperature sensor, a pressure sensor, or a flowmeter (25) extending through a wall (11) of the transformer tank (2) or through a wall of the first piping (13) or second piping (15), and- a tank (12) for housing the electrically insulating fluid, with piping (13) extending from the tank (12) for housing the electrically insulating fluid to the transformer tank (2), and a valve (28) for controlling a flow of said fluid in said piping (13),wherein the sealing element (1-11) is any of- a sealing element between said interconnected tank walls (7, 11)) of the transformer tank (2),- a sealing element (3) between said electric cable bushing (5) and wall (7) of the transformer tank (2),- a sealing element between said first piping (13) and a wall (11)) of the transformer tank (2),- a sealing element between said second piping (15) and a wall (11) of the transformer tank (2),- a sealing element of said pipe connection (16, 17),- a sealing element between said manhole cover (23) and a wall (11) of the transformer tank (2),- a drain valve sealing element,- a sealing element between any of a temperature sensor, a pressure sensor or a flow meter (25) and a wall (11) of the transformer tank (2) or a wall of the first or second piping (13, 15) and- a sealing element of said valve (28) in said piping (13).

11. The transformer arrangement (1) according to any preceding claim, wherein the transformer arrangement (1) comprises- at least two interconnected transformer tank walls (7, 11) and wherein the sealing element is a sealing element between said interconnected tank walls (7, 11) of the transformer tank (2).

12. The transformer arrangement (1) according to any preceding claim, wherein the transformer arrangement (1) comprises an active transformer part inside the transformer tank (2) and a medium or high voltage bushing (5) extending through a wall (7) of the transformer tank and configured for the connection of an electric conductor (29) with the active transformer part, wherein the sealing element (3) is a sealing element between the bushing (5) and said wall (7) of the transformer tank (2).

13. The transformer arrangement (1) according to any preceding claim, wherein the transformer arrangement comprises- a tank (12) for housing the electrically insulating fluid, connected to the transformer tank (2) through first piping (13) and the sealing element is a sealing element between said first piping (13) and a wall (11) of the transformer tank (2).

14. The transformer arrangement (1) according to any preceding claim, wherein the transformer arrangement comprises- a cooling tank (14) for cooling of the electrically insulating fluid, the cooling tank (14) being connected to the transformer tank (2) through second piping (15), and wherein the sealing element is a sealing element between said second piping (15) and a wall (11) of the transformer tank (2).

15. The transformer arrangement (1) according to any preceding claim, wherein the transformer arrangement comprises- a tank (12) for housing the electrically insulating fluid, connected to the transformer tank (2) through first piping (13) and the first piping (13) comprises pipes (18, 19) connected by a pipe connection (16), and wherein the sealing element is a sealing element of the pipe connection (16).

16. The transformer arrangement (1) according to any preceding claim, wherein the transformer arrangement (1) comprises- a cooling tank (14) for cooling of the electrically insulating fluid, connected to the transformer tank (2) through second piping (15), and the second piping (15) comprises pipes (20, 21) connected by a pipe connection (17) and wherein the sealing element is a sealing element of the pipe connection (17).

17. The transformer arrangement (1) according to any preceding claim, wherein the transformer arrangement (1) comprises- a manhole in a wall (11) of the transformer tank (2) and a manhole cover (23) and wherein the sealing element is a sealing element between said manhole cover (23) and a wall (11) of the transformer tank (2).

18. The transformer arrangement (1) according to any preceding claim, wherein the transformer arrangement comprises- a drain valve (24), for draining of the electrically insulating fluid from the transformer tank (2), and wherein the sealing element is a drain valve sealing element.

19. The transformer arrangement (1) according to any preceding claim, wherein the transformer arrangement (1) comprises- at least one of a temperature sensor, a pressure sensor, or a flowmeter (25) extending through a wall (11) of the transformer tank, and wherein the sealing element is a sealing element between any of a temperature sensor, a pressure sensor or a flow meter (25) and a wall (11) of the transformer tank (2).

20. The transformer arrangement (1) according to any preceding claim, wherein the transformer arrangement (1) comprises- a tank (12) for housing the electrically insulating fluid, and piping (13) extending from the tank (12) for housing the electrically insulating fluid to the transformer tank (12), and a valve (9) for controlling a flow of said fluid in said piping (13), wherein the sealing element is a sealing element of said valve (9).

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