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FuGM type bushing for electric field relaxing

IP.com Disclosure Number: IPCOM000199881D
Publication Date: 2010-Sep-20
Document File: 3 page(s) / 389K

Publishing Venue

The IP.com Prior Art Database

Abstract

It is a kind of capacity bushing (condenser bushing) composed of a center conductor and a condenser core wound around the center conductor. The condenser core that wound around the center conductor is formed by alternatively binding conductive foil layers with insulating layers. The conductive foil is a kind of metal foil or an electrically conductive layer coated with conductive or semi-conductive paint. In this case, the metal foils are used to form the electrically conductive layer, which are inserted between the insulating layers and spaced apart from each other by a given distance corresponding to insulating layers with the thickness of 1 mm to 2 mm. The insulating layers are made of functionally graded material (FuGM) with various relative permittivity. The relative permittivity of each insulating layers between two metal foils is different, which help to control the electric field and stress concentration. Advantages of the Invention A new concept of FuGM structure which effectively improve electric field distribution inside bushing, and relax the stress concentration. Benefit for compact design of bushing and optimized insulation structure

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FuGM type bushing for electric field relaxing

Viki-Chun Li, Huigang Sun, Wei Deng

Principal Applications/Uses of the Invention

Functionally graded material insulation bushing

Problem Overcome by the Invention

Electric field stress concentration

Detailed Description of the Invention

It is a kind of capacity bushing (condenser bushing) composed of a center conductor and a condenser core wound around the center conductor. The condenser core that wound around the center conductor is formed by alternatively binding conductive foil layers with insulating layers. The conductive foil is a kind of metal foil or an electrically conductive layer coated with conductive or semi-conductive paint. In this case, the metal foils are used to form the electrically conductive layer, which are inserted between the insulating layers and spaced apart from each other by a given distance corresponding to insulating layers with the thickness of 1 mm to 2 mm. The insulating layers are made of functionally graded material (FuGM) with various relative permittivity. The relative permittivity of each insulating layers between two metal foils is different, which help
to control the electric field and stress concentration.

FIG.1 shows one embodiment of a FuGM bushing according to the invention. In this embodiment, around a center conductor are wound by FuGM insulating layers, the circle 1~7 represent changed material permittivity at different location (layer), and the permittivity is increased from minimum to maximum value from circle 1 to circle 7.

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Fig.1 Configuration of FuGM bushing

Increasing the number of the metal foils can help to improve the distribution of electric field and to decrease the stress concentration.Of course, this effect is only applicable in certain extent. In the other hand, since the insertion of metal foil between the insulating layers makes the processing complex, the increased number of metal foils will make the production of the condenser core more complex. Furthermore, the higher voltage of the condenser bushing will result in longer condenser core and larger thickness thereof.

Many attempts have been made to decrease the number of the metal foils which are inserted between the insulating layers to improve the productivity of the condenser core, but up to now there have not fully satisfactory results. That is, if the number of the metal foils is reduced, the

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space between the metal foils becomes large, which makes the electric field to be concentrated...