FIELD OF INVENTION
This invention relates to a Sealed Breathing system for Oil / liquid filled eJeetrical equipment like transformers/ Reactors/ Stabilizers ete. to avoid harm to dry insulation of transformer, thereby inereasing the life of transformer to a great extent as Di-electric liquids are hygroscopic in nature and prone to absorb moisture from surroundings, if not isolated adequately.
BACKGROUND OF INVENTION
At present, the oil/ liquid filled equipment e.g. transformer are provided with a conservator at top end to allow space for expansion/ contraction (Breathing) of oil/ liquid due to change in temperature caused by loading of device or due to change in ambient temperature.
There are two type of breathing systems available at present:
a. Free-breathing system:
The oil conservator is a single mild sheet steel tank connected with main transformer tank through a pipe.
Another pipe provided at top end of conservator allows ingress/ exit of air through a device called Silica-gel breather. The breather is filled with a desiccant called Silica-gel. The silica-gel is provided to absorb a part of moisture present in the incoming air.
The moisture absorbing capacity/ability of silica-gel breather decreases with time/ usage. Frequent replacements of Silica-gel
material arc required as the efficiency is very low. II not replaced timely, it loses its function in totality.
Due to its failure/in- effectiveness, moist air from open atmosphere enters the conservator, which further leads to deterioration of properties of liquid/ oil-filled in the conservator.
The desired prime properties of oil/ liquid are low water content (measured in PPM) and high break-down voltage ( measured in KV), apart from various other properties like Di-electric dissipation factor and specific resistivity, which also get adversely affected due to moisture entry.
The entry of moist air to conservator causes oxidation of oil/ liquid and deteriorates such properties mentioned above.
Even a new/ fresh Silica-gel breather is not capable of absorbing full moisture present in the air in transit/ flow, there:by causing deterioration of oil/ liquid in conservator.
b. Sealed breathing system:
There are two type of "Sealed breathing systems" at present.
i. Balloon / Air-cell:
A balloon is provided inside the conservator to keep outside air isolated from transformer oil / liquid. The conservator is completely filled with oil / liquid. The balloon remains in inflated position when the transformer is at ambient temperature. The single outlet of balloon is connected with a
Silica gel breather. Willi the increase in heat / temperature, (he oil / liquid expand and pressurizes balloon to get deflated to some extent. Some air inside the balloon exits through Silica-gel breather. As the temperature falls down, some outside air enters balloon through the Silica-gel breather and again inflates the balloon. The moist air remains inside the balloon. The oil / liquid remains in touch with outside surface of balloon, thereby isolating the air from oil / liquid.
There are many disadvantages of balloon system which are detailed below:
a. A special type of construction in conservators is required with
many joints/ gaskets and probable leaking points.
b. In case puncture of balloon takes place, it does not come to
notice immediately. This failure can convert the sealed
breathing system to frcc-breathing system, thereby causing
hidden and serious secret harm to the transformer.
c. Replacement is expensive and calls for outage of transformer
nearly for one day thus affecting service and equipment
availability.
d. The system cannot be installed with thousands of
transformers operating in the field with free-breathing
system; so, retro-fitting is not possible.
e. It can be used in large transformers only. It is not economical
to use them in medium and small size distribution
transformers due to cost factor.
f. Magnetic oil gauge floating arm generally gets stuck with the balloon layers causing error in reading, and calling for maintenance.
ii. Diaphragm system:
The conservator is made in 2 pieces and a flexible diaphragm is provided. Oil / liquid remains present at the half bottom end of conservator, and air remains present in the upper half of conservator, both isolated by a thin flexible diaphragm made of silicon fabric generally, which bulges when the temperature rises and vice-versa.
The disadvantages of diaphragm are many as enumerated below:
a. A special type of construction in conservators is required with
many joints/ gaskets and probable leaking points.
b. In case puncture of diaphragm takes place, it does not come
to notice immediately. This failure can convert the sealed
breathing system to free-breathing system, thereby causing
hidden and serious secret harm to the transformer.
c. Replacement is expensive and calls for outage of transformer
nearly for one day thus affecting service and equipment
availability.
d. The system cannot be installed with thousands of
transformers operating in the field with free-breathing
system. So, retro-fitting is not possible.
c. It can be used in large transformers only. It is not feasible / economical to use them in medium and small size distribution transformers due to cost factor.
To overcome these problems, an effort has been undertaken to devise a simple, cost-effective, sensitive and sealed breathing system titled as "Flexi-Conservator Breathing System" in which liquid has been used to create an isolation in a new manner rather than using rubber / silicon fabric.
OBJECTS OF THE INVENTION
The main objective of the present invention is to develop a sealed breathing system for Oil / liquid filled electrical equipment like transformers/ Reactors/ Stabilizers etc.
Another objective of the present invention to provide such a sealed breathing system in which liquid has been used to create an isolation in a new manner rather than using rubber / silicon fabric.
Yet another objective of the present invention is to devise a conservator with simple construction having minimum joints/ gaskets so that there should not be any leaking points.
Still another objective of the present invention to have such an isolation, created in the developed system by using liquid / oil, which should not get punctured making it totally safe and leak-proof.
Yet another objective of the present invention is to retro-fit the system with transformers operating in the field with free-breathing system without
altering the existing design of transformer and without outage: of service for a long time.
A further objection of the present invention is to develop the system compatible and economical to use on various size of transformers, be it small or medium or large.
An additional object of the present invention is that such a system should take few minutes to connect and in which no replacement or maintenance is needed on account of prevention of pre-mature failure of transformer caused by moisture entry in transformer oil.
Yet another additional object of the invention is that system should extend the life of transformer and reduce maintenance by preventing ageing process caused by moisture ingress in oil of transformer.
The foregoing has outlined some of the pertinent objectives of the invention. These objectives should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention within the scope of disclosure. Accordingly, other objectives and a full understanding of the invention and the detailed description of the preferred embodiment in addition to the scope of invention are to be defined by the claims.
STATEMENT OF INVENTION
Accordingly, the present invention provides a A flexi conservator breathing system comprising of conservator, having plurality of interconnected chambers each provided with liquid level gauge to observe
liquid level, installed on a new or any operating eleetrieal device like transformer, filled with dielectric liquid at ambient temperature and connected on one end to main lank (5) through a pipeline optionally having gas operated relay (4) and a silica-gel breather (3) on the other end, placed either at higher level or on ground level depending upon any operating electrical device like transformer, new or already installed.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objectives and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings wherein:
Figure 1: Flexi-Conservator Breathing System Model I Figure 2: Flexi-Conservator Breathing System Model II
While the invention is described in conjunction with the illustrated embodiment, it is not intended to limit the invention to such embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the inventions disclosure as defined by the claims.
DETAILED DESCRIPTION OF THE INVENTION
For the purpose of promoting an understanding of the principles of the invention, reference is now to be made tp the embodiment illustrated in the drawings and specific language is used to describe the same. It is nevertheless to be understood that no limitations of the scope of invention is hereby intended, such alterations and further modifications in the illustrated bag and such further applications of the principals of the invention as
illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
It is a known fact that transformers operating with moisture content below 1% (measured by dry weight of insulation) can operate safely for 35-40 years in comparison to the transformers having moisture content 3-3.5% which have life span of less than 10 years.
Main reason for early aging and failure of transformer is moisture ingress in oil.
Moisture is the main enemy and killer of transformers. It is extremely desirable to keep oil / liquid dry and free from moisture. Moisture, if present in oil above permissible limits, travels to solid insulation of transformer and causes ageing which is an irreparable loss. It is a fact that ageing of liquid insulation can somehow be reversed but ageing of solid insulation cannot be reversed.
In the current invention, an attempt has been made to prevent moisture present in air, from coming in contact with oil/liquid thereby spoiling the properties of oil/liquid which further causes harm to insulation of transformer and reduces its life to a great extend.
The description of the invention is detailed under the following two sub-models viz:
a) Model I : For new transformers
(3 Chamber flexi-conservator breathing system)
b) Model II : For old transformers
(operating in the field with free-breathing systems)
a) Model I: for new transformers
(Three-Chamber flexi-conservator breathing system)
The conservator is a single piece of MS Sheet steel tank provided with two partitions inside made of sheet steel, creating three chambers inside the conservator, the first being connected to transformer tank through a pipe.
The first sheet steel partition is open at the top. The first chamber is filled with oil connected to main tank of transformer through a pipe.
The second partition is open at the bottom and sealed at the top. Hence oil filled in second chamber freely flows to third chamber and their levels are same at ambient temperature. The third chamber outlet is connected to a Silica-gel breather through a pipe as done conventionally. This is not required but provided as a back-up protection/ additional safety measure.
Optionally, dry nitrogen gas can be filled in first and second chamber. Dry nitrogen gas is better due to its inert nature.
As the temperature rises, the level of oil in first chamber also rises, creating some pressure on oil in second chamber. As the pressure increases due to further rise in temperature, the oil level in second chamber comes down due to pressure at its top, forcing the oil level in third chamber to rise, making them functioning like two liquid pistons. The air present above third chamber exists to open atmosphere due to rise in level of oil / liquid in third chamber.
As the temperature falls down, the level of liquid in the third chamber reduces permitting outside air inlet through Silica-gel breather. The oil level in second chamber rises and in first chamber falls down.
So, the oil present in second and third chamber act like a barrier / isolation working as liquid pistons and keep the main transformer oil present in the first chamber totally isolated from atmospheric air. The air only comes in contact with oil liquid surface present in third chamber and can deteriorate oil in second and third chamber which has no physical contact with main oil present in the first chamber.
Thus the purpose of keeping the main transformer oil isolated from external air is achieved.
Working:
The conservator tank has three chambers, shown in figure as (13), (14) and (15), partitioned by a MS sheet wall.
Sheet wall (1) isolates first chamber (13) from second chamber (14).
The sheet wall (1) is open at the top end.
Sheet wall (2) is open at the bottom end, making second chamber (14) and third chamber(15) common, allowing oil filled in second chamber (14) to freely flow to third chamber (15) and vice versa.
All the three chambers are filled with a common type of oil/ di-electric liquid. Dry air or dry nitrogen can be filled in empty space in first chamber (13) which can freely travel to second chamber (14), as sheet wall (1) is open at the top end.
All three chambers are provided with flanged openings at top (9), (10) and (11).
Third chamber (15) is provided with a pipe connection (6) at top which further connects it to Silica-gel breather or such kind of equivalent breathing device (3).
First chamber (13) is connected with main transformer tank (5) through a pipe optionally provided with protective device called Buchholz Relay (4).
The level in first chamber (13) varies up and down with the change in temperature of main tank oil (5).
The system is initially filled with a di-electric liquid / oil at ambient temperature, say at a level (7) shown in the figure.
As the oil temperature in main transformer tank rises due to loading or rise in ambient temperature, the oil expands and level (7) rises further towards top. The volume of first chamber (13) is so selected that oil level rises up-to 75mm-100mm (depending on design volume of conservator) below top end at maximum permissible operating temperature conditions.
With the rise of level in first chamber (13), a positive pressure is created above oil level in first chamber (13) and second chamber(14), which pushes down the oil present in second chamber (14) and rise of liquid level in third chamber (15), making the oil / liquid present in second chamber (14) and third chamber (15) act like a piston and a liquid flexi-barrier.
As the liquid level (8) in second chamber (14) falls down, the liquid level in third chamber (15) rises, (hereby pushing out (he air available above liquid level through a connected breather.
As the temperature falls down, the reverse process happens i.e. fall of liquid level (7), rise of liquid level (8a) and fall of liquid level (8b), thereby permitting outside atmospheric air to flow inside the third chamber (15) through a breathing device.
So, this system uses liquid as a flexible barrier/ isolation between oil in first chamber (13) and atmospheric air. The liquid / oil in first chamber (13) never comes in direct contact with atmospheric air, which may contain high moisture level.
This kind of isolation keeps the oil in first chamber (13) safe and its oxidation/ deterioration due to moist air is totally prevented. In fact, the moist air can only contaminate liquid / oil present in third chamber (15), which has no physical connection with liquid / oil of first chamber (13).
b) Model II : For old transformers operating in the field with free-breathing system
The principal is same as mentioned above with a slight modification in construction.
The free-breathing transformers (i.e prior art) are provided with a single chamber conservator and a breather.
In the present invention, a separate tank with two chambers, partitioned by a sheet steel wall and open at the bottom end is placed at ground level and connected to conservator pipe after removal of breather.
The functioning of system takes place in the identical manner as explained for model I, with a difference that first chamber is in the main conservator and second and third chamber, acting as liquid piston, at the ground level.
With this arrangement, any existing transformer with free-breathing system can be converted to sealed breathing system transformer with-in few minutes, without altering the design of transformer.
Working:
This system is designed to fit on the transformers and similar devices, which are in operation in the field with free breathing system.
The system can be fitted to any transformer operating in the field with¬in few minutes without altering the basic design of transformer, but converting the free-breathing system to Sealed breathing system.
A two chamber conservator C2 is placed on the ground and connected with existing single chamber conservator C1 of free-breathing transformer through a pipe (11).
The conservator C1 acts like first chamber (13) in the previous system; and two chambers in Conservator C2 act like second chamber (14) and third chamber(15).
The function is totally similar to model I, except that second chamber (14) and third chamber(15) are placed at ground level.
In a nutshell, the invention is simple in nature and performs the funetion of keeping moist air isolated from oil / liquid of transformers in an efficient manner. The system is not prone to failure as the liquid piston principal is used, puncture of which can-not take place. The system keeps the transformer dry, which is a prime requirement for safe and long operation of transformers.
The system has been developed, standardized, established and evaluated at internal and external laboratory settings for determination of sensitivity and specificity with several hundreds of various types of transformers. The stability of system at different operating conditions has also been done for establishment of transformers' extended life.
The present invention is not intended to be limited in scope by the specific embodiments and examples which are intended as illustration of a number of aspects of the scope of this invention. Those skilled in art will know or to be able to ascertain using no more than routine experimentations many equivalents to the specific embodiments of the invention described herein.
It is to be further noted that present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention which is further set forth under the following claims:

I Claim
1. A flexi-conservator breathing system eomprising of conservator, having plurality of interconnected chambers each provided with liquid level gauge to observe liquid level, installed on a new or any operating electrical device like transformer, filled with dielectric liquid at ambient temperature and connected on one end to main tank (5) through a pipeline optionally having gas operated relay (4) and a silica-gel breather (3) on the other end, placed either at higher level or on ground level depending upon any operating electrical device like transformer, new or already installed.
2. A breathing system as claimed in claim 1, wherein operating electrical device like transformer could be either new transformer or already installed transformer in the field.
3. A breathing system as claimed in claim 1, wherein said conservator comprises of at least either three chambers with gas-escape valve in case of a new transformer or two chambers in case of a transformer already installed in the field.
4. A breathing system as claimed in claim 1 and claim 3, wherein said conservator in particular three chamber conservator comprises of first chamber separation wall (1), open from the top, is connected to second chamber (14) and second chamber (14) is connected to third chamber (15) through isolation wall having opening at the bottom allowing oil filled in second chamber (14) to third chamber (15) and vice versa.
5. A breathing system as claimed in proceeding claims, wherein second
Chamber (14) and third chamber (15) of said three chamber conservator
are interconnected and tilled with dielectric liquid similar to liquid in the first chamber.
6. A breathing system as claimed in claim 1, wherein said conservator comprises of at least two chambers, in case of a transformer already installed in the field, which are interconnected through an opening at the bottom end of partition wall (2).
7. A breathing system as claimed in claim 1 and claim 6, wherein one chamber of said two chamber conservator, placed at ground level and filled with liquid, is connected to silica-gel breather (3) and the second chamber of which is connected to overhead isolated chamber inlet through a pipe.
8. A breathing system as claimed in proceeding claims, as substantially described herein with reference to the accompanying drawings for the use on any size of liquid filled electrical device like transformer from 6 KVA to any higher rating.