EP4625451A1

EP4625451A1 - Boron nitride sealants in transformers and their components

Info

Publication number: EP4625451A1
Application number: EP24166941.5A
Authority: EP
Inventors: Shelly Anne ARREGUIN
Original assignee: Hitachi Energy Ltd
Current assignee: Hitachi Energy Ltd
Priority date: 2024-03-27
Filing date: 2024-03-27
Publication date: 2025-10-01
Also published as: WO2025202420A1

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 provided inside the transformer tank, or to prevent leakage of the liquid out of the transformer tank. The sealing element arranged to prevent leakage comprises Boron Nitride.

Description

TECHNICAL FIELD

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

BACKGROUND

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 non-flammable materials that can withstand high temperatures.

SUMMARY

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.
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.
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.
According to an aspect of the present disclosure, a transformer arrangement is provided. The transformer arrangement comprises a transformer tank, an 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).
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.
In some embodiments, the transformer arrangement comprises an electrical insulating liquid housed inside the transformer tank.
In some embodiments, the electrical insulating liquid comprises one of mineral oil, a natural ester, or a synthetic ester.
In some embodiments, the sealing element is arranged to prevent leakage of the electric insulating liquid into or out of the component provided inside the transformer tank, or to prevent leakage of the insulating liquid out of the transformer tank.
In some embodiments, 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.
In some embodiments, said part of the sealing element comprises a coating of the BN.
In some embodiments, the sealing element comprises a gasket.
In some embodiments, the transformer arrangement comprises an electric cable bushing and a tape forming a part of the electric cable bushing, wherein the BN accommodates curing epoxy in the electric cable bushing.
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.
In some embodiments, the lubricating mass comprises a grease filled with particles of the BN.
In some embodiments, the transformer arrangement comprises a tap changer comprising a gasket which has a coating of the BN.
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 of the recited advantages.

BRIEF DESCRIPTION OF THE DRAWING

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.

Fig. 1: discloses a schematic diagram of an example transformer arrangement with sealing elements;

DETAILED DESCRIPTION

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.
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.
Fig. 1 discloses a schematic diagram of an example transformer arrangement 100 for an electrical system. The transformer arrangement 100 includes a transformer tank 20, electrical power transformer components 30 arranged inside the transformer tank, and at least one sealing element (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11). 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 20, or to prevent leakage of the fluid out of the transformer tank 20. The sealing element comprises Boron Nitride (BN). Fig. 1 discloses various positions where the sealing elements can be used in order to prevent leakage of the transformer dielectric insulating liquid. For example, the sealing elements 1 and 9 is used at inlet/outlet hole where the BN in the sealing element is effective to provide sealing as well as insulation. Similarly, the sealing element 2 is used to seal holes as well as to provide insulation with the transformer liquid. Certain applications of the BN-comprised sealing elements include positing a layer of the sealing element in between two or more joints, as shown in Fig. 1, element 8. Further, the sealing element comprising the BN is used at positions like between two components that form part of the transformer arrangement 100 and that are movable in relation to each other, element 6 in the Fig. 1.
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.
According to an embodiment of the present disclosure, the transformer arrangement 100 comprises an electrical insulation liquid housed inside the transformer tank 20. 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.
According to an embodiment of the present disclosure, the transformer arrangement 100 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.
According to an embodiment of the present disclosure, the transformer arrangement 100 comprises the sealing element that is arranged to prevent leakage of the electric insulating liquid into or out of the component provided inside the transformer tank 20, or to prevent leakage of the insulating liquid out of the transformer tank and to prevent air ingress in order to limit moisture intake and degradation of the dielectric insulating liquids. The sealing element is arranged such that 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.
According to an embodiment, the BN is present in the sealing element in form of a coating. The part of the sealing element that is exposed to contact with said electric insulating liquid comprises a coating of the BN. According to an example, the sealing element comprises a gasket. Boron Nitride coatings applied on the surface of these gaskets to provide and enhance lubricant properties of the gaskets and to offer an excellent electrical insulation. Further, according to an embodiment, the BN is present in the sealing element in form of impregnated BN into a base material.
According to a further embodiment, the transformer arrangement 100 comprises an electric cable bushing and a tape forming a part of the electric cable bushing. The BN accommodates curing epoxy in the electric cable bushing.
According to an embodiment, 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. 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

A transformer arrangement, comprising:
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 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.
The transformer arrangement according to claim 1, wherein the transformer arrangement comprises an electrical insulation liquid housed inside the transformer tank.
The transformer arrangement according to claim 2, wherein the electrical insulating liquid comprises one of mineral oil, a natural ester, or a synthetic ester.
The transformer arrangement according to claim 2 or 3, wherein the sealing element is arranged to prevent leakage of the electric insulating liquid into or out of the component provided inside the transformer tank, or to prevent leakage of the insulating liquid out of the transformer tank.
The transformer arrangement according to any one of claims 2-4, 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.
The transformer arrangement according claim 5, wherein said part of the sealing element comprises a coating of the BN.
The transformer arrangement according to any preceding claim, wherein the sealing element comprises a gasket.
The transformer arrangement according to any preceding claim, wherein the transformer arrangement comprises an electric cable bushing and a tape forming a part of the electric cable bushing, wherein the BN accommodates curing epoxy in the electric cable bushing.
The transformer arrangement 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 and that are movable in relation to each other.
The transformer arrangement according to claim 9, wherein the lubricating mass comprises a grease filled with particles of the BN.
The transformer arrangement according claim 5, wherein said part of the sealing element comprises impregnated BN into a base material.