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
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TLE OF THE INVENTION
Apparatus and Method for impregnation of a Condenser Bushing
PLICANTS
mpton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 , Maharashtra, India, an Indian Company
MENTOR
kkeveetil Sethumadhavan of Crompton Greaves Ltd, CG Global R&D, Product hnology Centre, Kanjur Marg (east), Mumbai - 400042, Maharashtra, India, an ian National.
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
The invention relates to an apparatus and method for impregnation of a wound structure of a condenser bushing. BACKGROUND OF THE INVENTION
Bushings are devices that can carry current at high potential through a grounded barrier, for example, a transformer tank. In order to decrease and control the electric field near the bushing, condenser bushings are provided. The heart of the condenser bushing is the condenser core which provides insulation between a central conductor, which is at line potential, and the grounded mounting flange. The core of the condenser bushing is formed by winding electrical quality crepe paper or Kraft paper on a conductor rod such as an aluminum mandrel. Sheets of aluminum foil are inserted, at regular intervals, between the conducting rod and the crepe paper. The condenser bushings are then impregnated with either oil (OIP, oil impregnated paper) or with resin (RIP, resin impregnated paper). RIP bushings have the advantage that they are dry (oil free bushings). Methods by which the condenser bushings are resin impregnated includes pouring the resin mixture from top of the mould containing the condenser bushing or immersing the condenser bushing into a tank flooded with resin. The condenser bushing is then heated and vacuumized to impregnate it. Impregnation of the condenser bushing by employing such techniques does not ensure a void free impregnation of the resin along the wound structure of the condenser bushing thereby resulting in a weak insulation. Essentially, a lot of resin is also wasted while pouring the resin onto the mould containing the condenser bushing or immersing the condenser bushing into the tank filled with resin.

OBJECTS OF THE INVENTION
An object of the invention is to provide an apparatus and method for void free
impregnation of the wound structure of a condenser bushing thereby providing a better
insulation of the condenser bushing.
Another object of the invention is to minimize the wastage of the resin during the
impregnation of the condenser bushing with resin.
DETAILED DESCRIPTION OF THE INVENTION
In order to achieve the aforesaid and other objectives, according to the invention, an apparatus and method is provided for impregnating the wound structure of a condenser bushing. The apparatus comprises of a temperature and vacuum controlled casting chamber for housing a mould for the wound structure of the condenser bushing to be impregnated with the resin and a temperature and vacuum controlled resin chamber for heating and storing the resin. The resin chamber is mounted at an elevation for maintaining a pressure head difference with the mould and connected to the mould at the bottom thereof through a degassing chamber to allow degassed resin to impregnate the wound structure from the bottom thereof. A method for impregnating the wound structure of a condenser bushing comprises the steps of disposing a mould enclosing the wound structure of the condenser bushing to be impregnated within a temperature and vacuum controlled casting chamber and effecting a flow of resin from bottom to top of the casting chamber by capillary action of the resin for impregnating the wound structure of the condenser bushing from bottom to top thereof.

These and other aspects, features and advantages of the invention will be better understood with reference to the following detailed description, accompanying drawings and appended claims, in which,
Fig 1 illustrates a schematic view of an apparatus for impregnating a wound structure of a condenser bushing with resin according to one embodiment of the invention. The apparatus comprises of a casting chamber 1, a mould 2 for the wound structure 3 of the condenser bushing to be impregnated with resin, a resin chamber 4, a degassing chamber 5 and a dispensing tube 6. The casting chamber I, resin chamber 4, degassing chamber 5 and the dispensing tube 6 are adapted to be vacuumized and temperature controlled. Vacuum is controlled and monitored within the casting 1, resin 4 and degassing chambers 5 by means of a vacuum pump 7 and a vacuum gauge 8 respectively connected thereto. An electrical heating element 9 controlled by a control panel 10 is embedded within the walls of the casting chamber 1 for maintaining a high temperature therein whereas an outer jacket 11 circulating hot oil or water and being controlled by a control panel is provided on the walls of the resin 4 and degassing chambers 5 for maintaining a high temperature therein. The resin chamber 4 is also provided with a stirrer 12 for stirring the resin at a high temperature and vacuum. The filling of resin in the mould 2 is monitored by means of a window 13 provided on a top portion of the casting chamber 1. The mould 2 containing the condenser bushing whose wound structure 3 is to be impregnated with the resin is placed within the casting chamber 1. The resin chamber 4 is mounted at an elevation with respect to the mould 2 so as to maintain a pressure head difference with it. Such an Arrangement allows the resin to

flow into the mould 2 from bottom to top from the resin chamber 4 through the degassing chamber 5 and the dispensing tube 6 without applying any momentum thereto. Resin reaches the mould 2 without any application of external momentum by the gravitational force and the pressure head difference between the resin chamber 4 and the mould 2. Resin rises in the mould 2 from its bottom to top by capillary action. The degassing chamber 5 is mounted just below the resin chamber 4 for allowing the resin to drop therein by gravitational force. The degassing chamber 5 degasses the resin by sprinkling it over a stack of glass cones 14 provided therein at a high temperature and vacuum. The dispensing tube 6 is affixed to the mould at a portion just above its base portion for a void free impregnation of the wound structure 3 therein. The dispensing tube 6 is adapted to transport the resin at a controlled vacuum and temperature. The dispensing tube is also equipped with a valve 15 for controlling the amount of resin being allowed to flow into the mould. Resin being flown into the mould 2 rises from bottom to top by capillary action of the resin thereby impregnating the wound structure enclosed within the mould 2.
The method for impregnating the wound structure of a condenser bushing comprises the steps of disposing a mould enclosing the wound structure of the condenser bushing to be impregnated within a temperature and vacuum controlled casting chamber and effecting a flow of resin from bottom to top of the casting chamber by capillary action of the resin for impregnating the wound structure of the condenser bushing from bottom to top thereof. The resin with which the wound structure of the condenser bushing is impregnated is stored in a resin chamber located at an elevation with respect to the casting chamber so as to maintain a pressure head difference with it. The resin chamber is

connected to the bottom portion of the casting chamber through a degassing chamber so as to allow degassed resin to flow into the mould of the casting chamber without applying any external momentum to it. The resin rises from bottom to top of the casting chamber thereby impregnating the wound structure of the condenser bushing from bottom to top.
According to the invention, an apparatus and method for impregnating the condenser bushing enables a thorough and void free impregnation of the wound structure of the condenser bushing and renders a substantial savings of the resin. The apparatus is simple, inexpensive and easy to construct.
The components of the apparatus may vary. There can be different ways and means for maintaining and controlling the temperature and vacuum within the casting, resin and degassing chambers as well as the dispensing tube instead of the electrical heating apparatus and the hot oil/water jacket.
Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiment, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the invention as defined.

We claim:
1. An apparatus for impregnating the wound structure of a condenser bushing with
resin, said apparatus comprising of
• a temperature and vacuum controlled casting chamber for housing a mould for the wound structure of the condenser bushing to be impregnated with the resin;
• a temperature and vacuum controlled resin chamber for heating and storing the resin, the resin chamber being mounted at an elevation for maintaining a pressure head difference with the mould and connected to the mould at the bottom thereof through a degassing chamber to allow degassed resin to impregnate the wound structure from the bottom thereof.

2. The apparatus as claimed in claim 1, wherein the resin flows into the mould without imparting any momentum to the resin directly up through the wound structure from the bottom thereof by capillary action.
3. The apparatus as claimed in claim 1, wherein said resin chamber and the degassing chamber is temperature controlled by providing an outer jacket for circulating hot water therein.
4. The apparatus as claimed in claim 1, wherein said resin chamber is provided with a stirrer for stirring the resin.
5. The apparatus as claimed in claim 1, wherein the degassing chamber is mounted below the resin chamber for allowing the resin to drop therein by gravitational force.

6. The apparatus as claimed in claim 1, wherein said degassing chamber comprises of at least one conical structure for fine dispersion of the resin received from the resin chamber
7. The apparatus as claimed in claim 1, wherein a dispensing tube is provided for allowing the resin to flow from the degassing chamber into the mould from its bottom thereof.
8. The apparatus as claimed in claim 1, wherein said dispensing tube is provided with a valve at the mould end for controlling the flow of resin into the mould.
9. The apparatus as claimed in claim 1, wherein said casting chamber is provided with a window at a top portion thereof for monitoring the amount of resin flowing therein.
10. A method for impregnating the wound structure of a condenser bushing with resin, said method comprising the steps of:

• disposing a mould enclosing the wound structure of the condenser bushing to be impregnated within a temperature and vacuum controlled casting chamber and
• effecting a flow of resin from bottom to top of said casting chamber by capillary action of the resin for impregnating the wound structure of the condenser bushing from bottom to top thereof.
11. The method as claimed in claim 10, wherein said resin is stored in a temperature
and vacuum controlled resin chamber being placed at an elevation for maintaining
a pressure head difference with the mould and connected to the mould at the
bottom thereof to impregnate the wound structure from the bottom thereof.

12. The method as claimed in claim 11, wherein said resin chamber is connected to the mould through a degassing chamber for degassing the resin.
13. The method as claimed in claim 10, wherein said degassed resin is allowed to rise over the condenser bushing and stored in a reservoir mounted at a top portion of the mould so as to utilize said stored resin to compensate shrinkage of the resin within the mould during gelling / curing.
Dated this 2nd day of December 2008