DESCRIPTION
Power Transformers are one of the major assets of power utilities and they are also critical elements in the power system, since their outage may result in costly and time consuming repair and replacement Hence managing these assets is an important task of the utilities. As moisture, oxygen, temperature and contaminants are the key factors which affect the life span of the Transformers, the important challenge before utilities is to reduce these deteriorating agents so that the life of the Transformers can be enhanced.
The life of a Transformer is often regarded as the life of its insulation. This is so because other parts Or components can either be repaired or replaced when they become defective, but the aging and deterioration of the solid insulation is difficult to be reversed or repaired.
Moisture is one of the most important degrading agent and the conventional and existing procedures employed to reduce moisture and to improve the insulation properties are either inadequate or costly and complex.
The invention submitted for patent "Flexible external bellow for Transformer insulation preservation and drying" is cost effective, simple, involves no complex procedures, is easily retrofittable in existing Transformers.
In this system, a sealed expandable bellow made of Polyether Thermoplastic Polyurethane is connected after the silica gel breather in the pipe line from the conservator of the Transformer. The conservator

air space is filled with dry Nitrogen and the bellow is at the ground level. When Transformer oil expands due to loading, oil level in the conservator rises pushing the Nitrogen gas present over the oil space in the conservator, into the expandable bellow.
The reverse happens at low loads and low ambient temperatures. The Nitrogen gas in the bellow is drawn back into the conservator air space due to drop in pressure created in the conservator air space. The material of the bellow found most suitable for this application is Polyether Thermoplastic Polyurethane (Polyether TPU) which has adequate strength, elasticity, inert nature, UV withstanding capability, abrasive resistance etc.
The system would make a Transformer a sealed type, providing complete immunity from external moisture and oxygen. It reduces Transformer ageing, reduces maintenance cost & time and reduces failures. When retrofitted in an old in-service Transformer, it prevents further moisture and oxygen entry from the atmosphere from the day of fitting, and would gradually remove already present moisture from the solid and liquid insulations as silica gel would now act as an adsorbent for the internal moisture. As the Nitrogen in the conservator air space moves between the bellow and conservator, it gets dried by the silica gel and moisture migration from Paper to oil, oil to Nitrogen and from Nitrogen to silica gel would be a continuous process. Silica gel can be periodically dried and the natural drying process of the Transformer can be ensured.
Further, if an annual degassing for dissolved oxygen in oil is carried out and the air space in the conservator is refilled with fresh dry Nitrogen, the bellow, the pipelines etc are tested for leaks if any, and

replaced if found leaky or damaged, the Transformer would in all probability require no other maintenance in respect of its insulation.
Advantages of the "Flexible external bellow for Transformer insulation preservation and drying" for a Transformer are
a) It can be fitted to both new and old Transformers without any modification to the conservator or Transformer.
b) It does not hinder expansion or contraction of oil or breathing action of the Transformer.
c) It prevents the two deteriorating agents namely moisture and oxygen entry in to the Transformer during its normal functioning.
d) In older Transformers where moisture percentage is normally high, it offers natural drying mechanism and gradually improves the overall insulation dryness of the Transformer.
e) It also acts as a leak detector in the air space of the Transformer.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig (1) is a complete and general arrangement of invention in a Power Transformer and parts identification list.
Fig (2) illustrates the bellow and its connected parts.
Fig (3) shows the pipe line which is connected between the conservator and breather of the Transformer, the nozzle which is connected in the conservator.
Fig (4) shows the adapter which is connected between the Breather and bellow

DESCRIPTION OF THE PREFERRED EMBODIMENT
Polyurethane (sheeting) - This specialized sheeting displays good resilience, good low temperature flexibility, excellent hydrolytic stability and resistance to attack by micro organisms. It is inherently protected from the adverse effects of ultra violet rays and thus prolonged exposure to direct sunlight does not degrade the material. Hence, long-life is ensured for the invention.
DETAILS OF THE INVENTION
The invention comprises of a pillow-type bag fitted on the external surface with an adapter. The said pillow type bag is made out of the said materials described in the preceding paragraphs. The said materials are marked and cut to the desired shapes (in this embodiment it is a rectangle) comprising a top and a bottom panel of the said material. The top panel is fitted to an adapter with an internal diameter ranging from 1/10* of an inch to one inch. The said adapter is made up of a suitable rigid material, in this embodiment it is Aluminium. But is also capable of being made out of other metals such as GI, Brass etc or out of Engineering Plastics such as Nylon®, Hypalon®, Teflon®, ABS, Polystyrene etc and serve the purpose of forming a rigid adapter which acts as a spout. The said adapter is attached to the said bellows (in this embodiment from the inner side of the top panel and is securely fastened from the inner end by using suitable washers / "0" rings etc to attain absolute air-tightness)
The said adapter is fitted as per detailed description above, projects out of the linear surface of the top panel of the said bellows. The top end of the adapter is.suitably threaded with gas-tight threads ranging from 15mm to 20 mm. The outwardly projecting portion of the said

adapter of the said bellows is capable of being attached to the conservator outlet pipe and/or to the silica gel container which may be placed between the conservator pipe and the bellows.
The said bellows may be placed at various levels, externally, in each embodiment the lowest level being the ground level of the Transformer and the highest being adjacent to the conservator tank of the Transformer.

air space is filled with dry Nitrogen and the bellow is at the ground level. When Transformer oil expands due to loading, oil level in the conservator rises pushing the Nitrogen gas present over the oil space in the conservator, into the expandable bellow.
The reverse happens at low loads and low ambient temperatures. The Nitrogen gas in the bellow is drawn back into the conservator air space due to drop in pressure created in the conservator air space. The material of the bellow found most suitable for this application is Polyether Thermoplastic Polyurethane (Polyether TPU) which has adequate strength, elasticity, inert nature, UV withstanding capability, abrasive resistance etc.
The system would make a Transformer a sealed type, providing complete immunity from external moisture and oxygen. It reduces Transformer ageing, reduces maintenance cost & time and reduces failures. When retrofitted in an old in-service Transformer, it prevents further moisture and oxygen entry from the atmosphere from the day of fitting, and would gradually remove already present moisture from the solid and liquid insulations as silica gel would now act as an adsorbent for the internal moisture. As the Nitrogen in the conservator air space moves between the bellow and conservator, it gets dried by the silica gel and moisture migration from Paper to oil, oil to Nitrogen and from Nitrogen to silica gel would be a continuous process. Silica gel can be periodically dried and the natural drying process of the Transformer can be ensured.
Further, if an annual degassing for dissolved oxygen in oil is carried out and the air space in the conservator is refilled with fresh dry Nitrogen, the bellow, the pipelines etc are tested for leaks if any, and

replaced if found leaky or damaged, the Transformer would in all probability require no other maintenance in respect of its insulation.
Advantages of the "Flexible external bellow for Transformer insulation preservation and drying" for a Transformer are
a) It can be fitted to both new and old Transformers without any modification to the conservator or Transformer.
b) It does not hinder expansion or contraction of oil or breathing action of the Transformer.
c) It prevents the two deteriorating agents namely moisture and oxygen entry in to the Transformer during its normal functioning.
d) In older Transformers where moisture percentage is normally high, it offers natural drying mechanism and gradually improves the overall insulation dryness of the Transformer.
e) It also acts as a leak detector in the air space of the Transformer.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig (1) is a complete and general arrangement of invention in a Power Transformer and parts identification list.
Fig (2) illustrates the bellow and its connected parts.
Fig (3) shows the pipe line which is connected between the conservator and breather of the Transformer, the nozzle which is connected in the conservator.
Fig (4) shows the adapter which is connected between the Breather and bellow

DESCRIPTION OF THE PREFERRED EMBODIMENT
Polyurethane (sheeting) - This specialized sheeting displays good resilience, good low temperature flexibility, excellent hydrolytic stability and resistance to attack by micro organisms. It is inherently protected from the adverse effects of ultra violet rays and thus prolonged exposure to direct sunlight does not degrade the material. Hence, long-life is ensured for the invention.
DETAILS OF THE INVENTION
The invention comprises of a pillow-type bag fitted on the external surface with an adapter. The said pillow type bag is made out of the said materials described in the preceding paragraphs. The said materials are marked and cut to the desired shapes (in this embodiment it is a rectangle) comprising a top and a bottom panel of the said material. The top panel is fitted to an adapter with an internal diameter ranging from 1/10* of an inch to one inch. The said adapter is made up of a suitable rigid material, in this embodiment it is Aluminium. But is also capable of being made out of other metals such as GI, Brass etc or out of Engineering Plastics such as Nylon®, Hypalon®, Teflon®, ABS, Polystyrene etc and serve the purpose of forming a rigid adapter which acts as a spout. The said adapter is attached to the said bellows (in this embodiment from the inner side of the top panel and is securely fastened from the inner end by using suitable washers / "0" rings etc to attain absolute air-tightness)
The said adapter is fitted as per detailed description above, projects out of the linear surface of the top panel of the said bellows. The top end of the adapter is.suitably threaded with gas-tight threads ranging from 15mm to 20 mm. The outwardly projecting portion of the said

adapter of the said bellows is capable of being attached to the conservator outlet pipe and/or to the silica gel container which may be placed between the conservator pipe and the bellows.
The said bellows may be placed at various levels, externally, in each embodiment the lowest level being the ground level of the Transformer and the highest being adjacent to the conservator tank of the Transformer.

CLAIMS
1. We claim A "FLEXIBLE EXTERNAL BELLOW FOR TRANSFORMER INSULATION PRESERVATION AND DRYING" manufactured out of Industrial Polymer Sheeting and such manufacturing being made with the aid of High Frequency Welding and in another embodiment by Ultrasonic Welding for the purpose of receiving/storing and recycling the air and gases contained in electrical transformers;
2. We claim the bellows as claimed in claim (1) fitted with a suitable nozzle/valve at its top surface and such nozzle/valve being made out of light-weight metal/alloy and/or light-weight engineering plastic purpose of such nozzle/valve being the main opening to receive and return air and gases contained in electrical transformers;
3. We claim the bellows as claimed in claim (1) being attached to the transformer's air & gas breather pipe line for the purpose of receiving, storing and returning the transformer's air/gases with or without drying;
4. We claim such bellows as claimed in claim (1) being made of flexible, U.V. protected sheets made of Polyether/Polyester Thermo Plastic Polyurethane and top and bottom of said bellows being attached to each other by the process of High Frequency Welding and in another embodiment by Ultrasonic Welding and joining of material by supplying HF energy in the form of an electromagnetic field (27.12 MHz) and pressure to the material surfaces to be joined;
5. We claim the bellows as claimed in claim (1) manufactured in different sizes in various embodiments ranging from length of 400
. mm to 1200 mm with widths in different . sizes in various

embodiments ranging from 300 mm to 1200 mm and with such thickness (height) ranging from 10 mm to 1000 mm in various embodiments;
6. We claim the bellows as claimed in claim (1) manufactured by the process of obtaining said Industrial Polymer Sheeting as claimed in claim (1), marked to pre-determined shapes, cut accordingly and said bellows having a top and a bottom panel cut from said materials (Polymer Sheetings) and said cut panels being suitably pre-treated to enable high frequency/ultrasonic Welding and said cut and pretreated panels being affixed with said nozzle as claimed in claim (1) to the top panel and top and bottom panels being joined to each other by the said process of high frequency welding/ ultrasonic welding;
7. We claim the bellows as claimed in claim (1) wherein in another embodiment the basic sheetings used in another embodiment are made out of textile fabric impregnated/laminated/coated with Polymer materials such as Poly Vinyl Chloride, Ethyl Vinyl acetate, Polyurethane and other substrates which are weldable by using the process of High Frequency welding/Ultrasonic welding;