FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
PROVISIONAL SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
Novel method of electrical connection to condenser element
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Mandlik Manoj Kisan, Sethumadhavan Thekkeveetil and Lobo Anthony Marcel of Crompton Greaves Ltd , Product technology group, CG Global R&D Centre, Kanjur (East), Mumbai 400042, Maharashtra, India and John Yesuraj Devaraj of Crompton Greaves Limited, Design department, Switch Gear (SI) Division, A-3.M.I.D.C, Ambad, Nasik - 422010, Maharashtra, India, all Indian Nationals
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention:

FIELD OF THE INVENTION
This invention relates to novel method for electrical connections to the condenser element of electrical bushing for measurement, protection and operation purpose.
BACKGROUND OF THE INVENTION
Resin impregnated bushings consists of insulation like cellulose or polymer and electrodes arrangement made of thin copper or aluminum sheets radially spaced for voltage grading which is subsequently impregnated with impregnating compound like polymeric resins to form a solid mass after curing. Resin impregnated paper bushings of condenser type are wound loose to facilitate the impregnation. The looseness of the winding makes it difficult to provide the electrical connection to the last condenser electrode due inadequate clamping pressure. During impregnation, resin also forms a thin insulating layer over the condenser electrodes making it more difficult to have an electrical connection. The condenser electrodes having very less thickness also makes it extremely difficult to have soldering or brazing like connections.
Prior art literatures are related to the Oil impregnated paper (OIP) bushings. OIP bushings are tightly wound which allows proper claming pressure between condenser elements and flexible conductors / strips also forming a grove during winding process by means slitting paper is easy and allows access to the last condenser element. As there is no need of solidification of the impregnated mass accessing condenser electrode is easy.
Prior art patent of US 3647938 claims about attachment of flexible conductor to the condenser element by means of soldering, proper clamping or the like and playing flexible electrical conductor along between adjacent layers of additional electrical insulation material and bringing it out beyond the outer most layer of electrical insulation material for attaching to proper terminal. This does not specify the method of clamping of flexible conductor to the condenser element and also demands for playing the conductor with additional insulating layers. Its difficulty to have this type of arrangement in Resin impregnated bushings, as the insulation and electrodes


arrangement is completely sealed in a container for impregnation and subsequent curing which denies access to the flexible conductor brought out beyond the outer most layer of electrical insulation.
Prior art US 3875327 claims ground layer is interleaved with the tap layer and is also wound around the insulation system. This arrangement will work for OIP busing as they are very tightly wound and the adequate pressure is obtained between ground layer and tap layer. However, this arrangement will not work for Resin impregnated bushings as they are loosely wound and just interleaving (the ground layer with tap layer) without pressure or clamping and resin will penetrate to form an insulating layer in between ground layer and tap layer
OBJECTS OF INVENTION
An object of this invention is to provide easy and proper electrical connection to electrode of condenser bushing of Resin impregnated type for measurement, protection and operation purpose.
Another object of this invention is to provide an effective electrical connection between condenser element to the flexible conductors / strips.
Another objective of this invention is to allow loose bushing winding for thorough impregnation.
Another objective of this invention is to provide easy access to the last condenser electrode and increased reliability and higher productivity.
DETAILED DESCRIPTION OF THE INVENTION
Resin impregnated bushing consists of insulation like cellulose or polymer and


electrodes arrangement made of thin copper or aluminum sheets for voltage grading which is subsequently impregnated with impregnating compound like polymeric resins to form a solid mass after curing. Resin impregnated bushings of condenser type are wound loose to facilitate the impregnation. The looseness of the winding makes it difficult to provide the electrical connection to the condenser electrodes due to inadequate clamping pressure. During impregnation resin also forms a thin insulating layer over the condenser electrodes making it more difficult to have an electrical connection. The electrodes having very less thickness also makes it extremely difficult to have soldering or brazing like connections.
According to one of the embodiments of the invention, a solder joint is prepared between a relatively thicker and flexible conductor or strip made of material such as tinned copper or any other conducting material and piece of flexible mesh of conducting material such as tinned copper or any other conducting material of any shape. The other end of the flexible conductor or strip kept over the condenser electrode at a pre-decided location. The tape preferably high temperature adhesive tape is applied covering some portion of the flexible conductor or strip and condenser electrode and hence mechanically locking flexible conductor or strip and condenser electrode. The process of adhesion by locking also results into electrical connection between flexible conductor or strip and condenser electrode. The entire arrangement explained forms a part of the winding and impregnated subsequently to form a solid mass. An opening by drilling is created in the solid mass exposing the flexible mesh of conducting material whose location was recorded during the procedure of winding. The exposed and accessible flexible mesh of conducting material is then soldered with flexible copper conductor. The flexible cooper conductor can be used as tap for


electrically connecting the condenser element for measurement, protection and operation purpose.
According to another embodiment of the invention, electrically conductive adhesive based on multi component epoxy resin and metallic filler preferably of silver composition in its uncured form is applied between the condenser element and piece flexible mesh of conducting material of any shape. Genuine pressure is applied over the contact area and allow adhesive to cure at room temperature or at an elevated temperature. After curing, this gives good electrical and mechanical contact condenser element and piece flexible mesh of conducting material. The entire arrangement explained forms a part of the winding and impregnated subsequently to from a solid mass. An opening by drilling is created in the solid mass exposing the flexible mesh of conducting material whose location was recorded during the procedure of winding. The exposed and accessible flexible mesh of conducting material is then soldered with flexible copper conductor. The flexible cooper conductor can be used as tap for electrically connecting the electrically connecting the condenser element for measurement, protection and operation purpose.
According to the present invention, is to provide an easy and proper electrical connection to electrode of condenser bushing of Resin impregnated type for measurement, protection and operation purpose using use of high temperature adhesive tape for adhesion of flexible conductor or strip and condenser electrodes, soldering the flexible tinned copper strip to copper mesh, creating an opening in solid mass and soldering flexible copper conductor to copper mesh


According to the present invention, a method of tapping consists of flexible conductor or strip is connected with desired condenser electrode using high temperature adhesive tape to provide proper clamping pressure and result in electrical connection, soldering the other end of above flexible conductor or strip to flexible mesh of conducting material; and all the above is cast together with remaining insulation and electrodes assembly wound together.
According to another embodiment of the present invention, a conductive adhesive is used between desired condenser element and flexible mesh of conducting material, which allowed curing to form an electrical connectivity between the above; and now all the above is cast together with remaining insulation and electrodes assembly wound together.
In accordance to the present invention, the resultant products out of either of the above said processes are further cast together with remaining insulation and electrodes assembly wound together.
In accordance to the present invention, further an opening is created in the casting by drilling in the solid mass exposing the flexible mesh of conducting material whose location was recorded during the procedure of winding and soldering flexible conductor to exposed flexible mesh of conducting material to get electrical connectivity to the condenser electrode.


In accordance to the present invention, is to allow loose bushing winding for thorough impregnation.
Dated this 28th day of March 2008

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