BUSHING COMPRISING A CONDENSER BODY AND ELECTRICAL FACILITY WITH BUSHING

Abstract

A bushing comprises an electrical conductor and a condenser body through which the electrical conductor extends, wherein the condenser body comprises electrically insulating layers and electrically conducting layers, wherein the electrically insulating layers comprise an oil-impregnated paper comprising at least one of a thermally upgraded paper and a paper comprising synthetic fibers.

Claims

1. A bushing comprising: an electrical conductor and a condenser body through which the electrical conductor extends, wherein the condenser body comprises electrically insulating layers and electrically conducting layers, wherein the electrically insulating layers comprise an oil-impregnated paper, wherein the paper comprises at least one of a thermally upgraded paper and a paper comprising synthetic fibers, and wherein the paper is impregnated by ester oil.

2. The bushing of claim 1, wherein the paper is based on cellulose.

3. The bushing of claim 1, wherein the paper is a thermally upgraded paper with a nitrogen level in a range of 1% to 4%.

4. The bushing of claim 1, wherein the paper comprises heat-resistant synthetic fibers in a form of an aramid polymer.

5. The bushing of claim 1, wherein the paper has a thermal class rating of at least 120? C.

6. An electrical facility comprising: a bushing that includes an electrical conductor and a condenser body through which the electrical conductor extends, wherein the condenser body comprises electrically insulating layers and electrically conducting layers, wherein the electrically insulating layers comprise an oil-impregnated paper, wherein the paper comprises at least one of a thermally upgraded paper and a paper comprising synthetic fibers, and a wall in which the bushing is installed.

7. The electrical facility of claim 6, comprising a tank filled by ester oil.

8. The electrical facility of claim 7, wherein the paper of the bushing is impregnated by the ester oil.

9. The electrical facility of claim 6, being a transformer facility comprising one or more transformer windings, wherein the transformer windings comprise a further paper in a form of at least one of a thermally upgraded paper and a paper comprising heat-resistant synthetic fibers.

10. The electrical facility of claim 9, wherein the paper of the bushing and the paper of the transformer winding have at least one of the same thermal upgrade and the same synthetic fibers.

11. The electrical facility of claim 6, wherein the paper is based on cellulose.

12. The electrical facility of claim 6, wherein the paper is a thermally upgraded paper with a nitrogen level in a range of 1% to 4%.

13. The electrical facility of claim 6, wherein the paper comprises heat-resistant synthetic fibers in a form of an aramid polymer.

14. The electrical facility of claim 6, wherein the paper has a thermal class rating of at least 120? C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Further features, refinements and expediencies become apparent from the following description of the exemplary embodiments in connection with the figures. In the figures, elements of the same structure and/or functionality may be referenced by the same reference signs. It is to be understood that the embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale.

[0021] FIG. 1 is a schematic sectional view of a bushing according to an embodiment, and

[0022] FIG. 2 is a schematic view of a transformer according to an embodiment.

DETAILED DESCRIPTION

[0023] FIG. 1 shows a bushing 1 comprising a conductor 2. The bushing 1 and conductor 2 may be suitable for high voltage. The bushing 1 may be used in an electrical facility such as a switching or transformer facility. The facility may be a high-voltage facility.

[0024] The bushing 1 may provide an electrical connection of the facility through a wall 3 from the outside 5 to the inside 6. The wall 3 may be on earth potential or at least on an electric potential substantially different from the potential of the conductor 2. The bushing 1 provides the insulation between the wall 3 and the conductor 2. The wall 3 may be an outer wall of a transformer or switching facility, for example.

[0025] The insulation comprises a condenser body 4 comprising insulating layers 7 of an insulating material. Electrically conducting layers 8 are located at specific positions between the insulating layers 7. The condenser body 4 can be formed by winding a foil of insulating material on which electrically conductive material is applied at specific positions.

[0026] The bushing 1 further comprises an insulating material 10 enclosing the conductor 2. The bushing 1 further comprises insulating shreds 9 for enlarging a creeping distance at an outer surface of the bushing 1. Porcelain may be used as a material providing the insulation.

[0027] The bushing 1 may be an oil-to-air type insulation, for example. In other embodiments, the bushing 1 may be an oil-to-SF6 gas type or an oil-to-oil bushing, for example.

[0028] The insulating material of the insulating layers 7 can be in the form of a paper 16, such as kraft paper, for example. The paper 16 may be plain or in the form of crepe paper. The paper 16 may be cellulose-based.

[0029] The paper 16 can be thermally upgraded. A thermally upgraded paper 16 has been chemically modified to reduce the decomposition rate of the paper. Exemplarily, the modification serves to neutralize acids and reduce oxidation which may be caused by thermal degradation of the cellulose over the lifetime. Ageing effects may be reduced either by partial elimination of water forming agents (as in cyanoethylation) or by inhibiting the formation of water through the use of stabilizing agents (as in amine addition, dicyandiamide). The thermally upgraded paper may be in accordance with the standards IEC 554-3-1 and IEC 554-3-5 (DIN VDE).

[0030] The thermally upgraded paper may be treated with nitrogen. As an example, a nitrogen level in the thermally upgraded paper may be within a range of 0.5% to 5%, for example. More specifically, the nitrogen level may be in a range of 1% to 4%, for example.

[0031] Additionally or alternatively, the insulating layers 7 may comprise a paper 16 comprising synthetic fibers. As an example, the fibers may be aramid fibers. The fibers may be highly heat-resistant. Also in this case, the thermal class rating can be increased and the lifetime prolonged.

[0032] Exemplarily, the paper 16 may comprise cellulose and an aramid polymer. The aramid fibers may serve as a binder for the base material of the paper 16 such as cellulose, for example. As an example, a paper of the trademark Nomex? can be used.

[0033] The insulating layers 7 are oil-impregnated. According to specific embodiments, the insulating layers 7 are impregnated by ester oil. The ester oil may be synthetic or natural ester oil.

[0034] Ester oil has the advantage of biodegradability in contrast to mineral oil, for example. Accordingly, the bushing is ecofriendly. The costs for safety installations and equipment can be lowered. In this case, the bushing is also suitable for indoor applications.

[0035] In addition to that, ester oil has a high moisture saturation point and, thus, removes moisture from the paper 16. This increases the lifetime of the paper 16 and prevents generation of free water. In addition to that, ester oil has a low pour point of ?56? C., such that the bushing is suitable for very low temperature areas. Furthermore, ester oil has a high fire point, above 200? C., which makes the bushing safer.

[0036] Exemplarily, the bushing may comprise thermally upgraded papers impregnated by ester oil. Such a paper may have a thermal class rating of 140? C. In comparison, a thermally upgraded paper impregnated by mineral oil may have a thermal class rating of 130? C. In a further comparison, a paper which is not thermally upgraded and is impregnated by mineral oil may have a temperature limit of 105? C.

[0037] In a fault or overload condition during transformer operation, the bushing 1 can be subjected to high currents and high temperature, which may boost aging of the paper. Aging may lead to a substantive loss of insulating properties. Due to the higher thermal class for the thermally upgraded paper, aging of the paper is reduced. Thus, the bushing 1 has a high overload capability, providing safer operation with a high life expectancy. Accordingly, fire hazard during manufacturing, testing and operation is reduced. In addition to that, the risk of breakage of an insulation such as a porcelain insulation is reduced. In addition to that the bushing can have a smaller diameter d without increasing the rate of aging.

[0038] FIG. 2 shows an electrical facility 15, which may be a high voltage facility. The electrical facility 15 may be a transformer facility or a switchgear facility, for example.

[0039] The electrical facility 15 comprises a bushing 1 leading through a wall 3. The bushing 1 can be the bushing 1 of FIG. 1.

[0040] In the shown embodiment, the wall 3 is the wall 3 of a tank 17 in which a functional element of the electrical facility is located. The electrical facility 15 may be a transformer and the functional element may be at least one transformer winding 11. An electrical connection 12 leads from the conductor 2 to the transformer winding 11.

[0041] The tank 17 may be filled with an insulating liquid 13. The insulating liquid 13 may be ester oil. Exemplarily, also the paper 16 of the bushing 1 may be impregnated with ester oil.

[0042] In this case, both for the bushing 1 and the tank 17 a biodegradable liquid is used such that the transformer arrangement 15 is environment-friendly. In addition to that, the bushing 15 is adapted to the high overload capability of the ester-filled tank 17 such that the overload capability for the entire electrical facility 15 is increased.

[0043] The transformer winding 11 may comprise a further paper 18. The further paper 18 may provide insulating layers in the transformer winding 11. The further paper 18 may be at least one of a thermally upgraded paper or a paper comprising synthetic fibers. As an example, the further paper 18 and the paper 16 of the bushing 1 may have the same temperature class. Both the further paper 18 of the transformer winding 11 and the paper 16 of the bushing 1 may have the same thermal upgrade or may comprise the same synthetic fibers.

REFERENCE SIGNS

[0044] 1 bushing

[0045] 2 electrical conductor

[0046] 3 wall

[0047] 4 condenser body

[0048] 5 outside

[0049] 6 inside

[0050] 7 electrically insulating layer

[0051] 8 electrically conducting layer

[0052] 9 shred

[0053] 10 insulating material

[0054] 11 transformer winding

[0055] 12 electrical connection

[0056] 13 insulating liquid

[0057] 14 transformer insulation

[0058] 15 electrical facility

[0059] 16 paper of bushing

[0060] 17 tank

[0061] 18 paper of transformer winding

[0062] d diameter