Project Report

PROJECT REPORT ON “TRANSFORMER OIL”

SUBMITTED TO:-Dr. Pamita Avasthi.Lect. Applied Sciences And Humanities Dept..N.I.T. Hamirpur.

ACKNOWLEDGEMENT

Here by we say thanks to our highly respected and knowledgeable teacher Dr.Pamita Awasthi(lecturer,NITH) for giving us opportunity to work upon this topic and for her kind support and guidance throughout the course of this project. It was a precious opportunity for us to explore the wide field of transformer oil. Since this topic relates highly with our branch (electrical and electronics engg.), so the knowledge achieved while working on this topic would be highly beneficial for us in upcoming years.

Thanks a lot!!! SUBMITTED BY:-

NITESH KUMAR (group co-ordinater)

ANKIT KARIRYAA

APURAV GUPTA

ARPIT CHUGH

BHIMESH SHARMA

DEEPAK BANSAL

GAURAV ADHIR

GAURAV GARG

KANISHAK CHAUHAN

NAVEEN K. YADAV

PRASHANT KUMAR.

CONTENTS:-

1. Transformer-an introduction.

2. Role of transformer oil.

3. Terminologies and properties related with a transformer oil.

4. Types of transformer oil.

5. Mineral oil as transformer oil.

6. Re-refining of mineral oil.

7. Silicone as transformer oil solution.

8. Vegetable oil as transformer oil.

9. References.

TRANSFORMER- An Introduction

A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductorsTransformers come in a range of sizes from a thumbnail-sized coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons used to interconnect portions of national power grids. All operate with the same basic principles, although the range of designs is wide.(1.1)CONSTUCTION:- The construction of a transformer may vary depending upon the requirement, but the basic outline of each is same, The transformer consists of two coils (usually copper) called WINDINGS which are wrapped around a core. The winding that is connected to the source is called the PRIMARY WINDING. The winding that is connected to the load is called the SECONDARY WINDING.  Latest transformers use the cores made by stacking of different layers of thin steel laminations to minimize energy losses. Each lamination is

insulated from its neighbors by a thin non-conducting layer of insulation.

(1.2)BASIC PRINCIPLE:-The transformer is based on two principles: firstly, that an electric current can produce a magnetic field (electromagnetism) and secondly (FARADAYS LAW) that a changing magnetic field within a coil of wire induces a voltage across the ends of the coil (electromagnetic induction). Changing the current in the primary coil changes the magnitude of the applied magnetic field. The changing magnetic flux extends to the secondary coil where a voltage is induced across its ends.

(1.3)TYPES OF TRANSFORMERS:-

Autotransformer Polyphase transformers Leakage transformers Resonant transformers Audio transformers Instrument transformers

(1.4)APPLICATIONS OF TRANSFORMERS:-

A major application of transformers is to increase voltage before transmitting electrical energy over long distances through wires. Wires have resistance and so dissipate electrical energy at a rate proportional to the square of the current through the wire. By transforming electrical power to a high-voltage (and therefore low-current) form for transmission and back again afterwards, transformers enable economic transmission of power over long distances. Consequently, transformers have shaped the electricity supply industry, permitting generation to be located remotely from points of demand. Transformers are also used extensively in electronic products to step down the supply voltage to a level suitable for the low voltage circuits they contain.

Signal and audio transformers are used to couple stages of amplifiers and to match devices such as microphones and record player s to the input of amplifiers. Audio transformers allowed telephone circuits to carry on a two-way conversation over a single pair of wires.

ROLE OF TRANSFORMER OIL

A transformer may be oil cooled or air cooled. Small transformers do not generate significant heat and are cooled by air circulation and radiation of heat. Power transformers rated up to several hundred kVA can be adequately cooled by natural convective air-cooling, sometimes assisted by fans.

Some power transformers are immersed in transformer oil that both cools and insulates the windings. Transformer oil, or insulating oil, is usually a highly-refined mineral oil that is stable at high temperatures and has excellent electrical insulating properties. It is used in oil-filled transformers, some types of high voltage capacitors and high voltage switches and circuit breakers, fluorescent lamp, ballasts. Its functions are to insulate, to suppress corona and arcing, and to serve as a coolant.

C ut away view of three-phase oil-cooled transformer. The oil reservoir is visible at the top. Radiative fins aid the dissipation of heat.

Transformer oil is considered as the blood of the transformer. Oil is used as a coolant and dielectric in the transformer and helps keeping it in a good condition and assists in preventing deterioration of insulation which is immersed in oil. Oil in transformer construction serves the double purpose of cooling and insulating. It also provides part of the electrical insulation between internal live parts.

TERMINOLOGIES AND PROPERTIES RELATED WITH A TRANSFORMER OIL

(3.1).Dissolved Gas Analysis

Dissolved Gas Analysis is widely accepted as the most reliable tool for the earliest detection of incipient faults in transformers and tap selector units. Hydrocarbon (mineral-based) oils and silicones are used as insulation fluids in transformers because of their high dielectric strength, heat transfer properties and chemical stability. Under normal operating conditions very little decomposition of the dielectric fluid occurs. However, when a thermal or electrical fault develops, dielectric fluid and solid insulation will partially decompose. The low molecular weight decomposition gases include hydrogen, methane, ethane, ethane, ecetylene, carbon monoxide and carbon dioxide. These fault gases are soluble in the dielectric fluid. Analysis of the quantity of each of the fault gases present in the fluid allows identification of fault processes such as corona, sparking, overheating and arcing.

(3.2).Acidity

High acidities accelerate the degradation of the paper insulation and causes corrosion of the steel tanks. Oil Analysis Services normally suggests changing the oil

when the acidity approaches 0.3mgKOH/g, but expresses concern when it reaches 0.1mgKOH/g. It is believed that acidity increases exponentially with time.

(3.3).Electric Strength

A measure of the ability of an insulating fluid to withstand electric stress (voltage) without failure. Fluids with high dielectric strength (usually expressed in volts or kilovolts), are good electrical insulators.

(3.4).Colour

In the past, there used to be a British Standard which gave a range of colours from 1-10; 1 being white/yellow and 10 being dark brown/black heavily oxidised oil. We use a similar colour range to gauge if there is any sudden deterioration in the oil during the time it is being analysed for different species.

Colour has also been useful in the past as a cross check of the sample identity. For example, a sudden change from dark to light colour can indicate an oil change or incorrect sample designation.

(3.5).Polychlorinated Biphenyl Analysis

In the past, PCB’s were insulating liquids used for their non-flammable properties, mainly in transformers where a fire would be unacceptable, and as the dielectric fluid

in capacitors. Unfortunately, the mineral oil used in transformers, switchgear etc. has become cross-contaminated over the years bys PCB fluid being placed in dirty mineral oil tanks, by using oil conditioning equipment for both mineral and PCB liquids and by capacitors leaking into mineral oil systems.

PCB’s are fairly non-biodegradable and do tend to collect in food chains and as a result, legislation has been brought in to prevent widespread contamination. Liquids containing over 50mg/kg(or 50 ppm by weight) must be classed as injurious substances and disposal must be by high temperature incineration, which is expensive. In fact oil suppliers have agreed not to supply oil containing more than 10mg/kg and by the same token, any oil taken away over 10mg/kg is expensive to dispose of even though it may not be as high as 50/mg/kg.

(3.6).Water Content

The water content of an oil sample is measured using an automatic Mitsubishi moisture meter, which is based on the Karl Fischer titration and coulometric end-point. All laboratories use these instruments now to measure dissolved water and probably over 90% use the Mitsubishi model. The instrument is calibrated electronically but is checked with the aid of standard water in methanol solutions. The water content is given in mg/kg(ppm).

Moisture, in combination with the fibre in main tanks and selectors and carbon in diverters, dramatically

reduces the electric strength of the oil to very unsafe levels which can result in plant failure.

(3.7).Resistivity

The resistivity of a liquid is a measure of its electrical insulating properties under conditions comparable to those of the test.

High resistivity reflects low content of free ions and ion-forming particles and normally indicates a low concentration of conductive contaminants.

These characteristics are very sensitive to the presence in the oil of soluble contaminants and ageing products.

TYPES OF TRANSFORMER OIL

1.PREVIOUSLY USED TRANSFORMER OILS:-Prior to about 1970, Polychlorinated biphenyl (PCB) was often used as a dielectric fluid since it was not flammable. However, they are toxic, and, under incomplete combustion, PCBs can form highly toxic products such as Furan etc.

DRAWBACKS OF USING PCB:-

1. Bio-accumulative, persistent and potentially toxic.

2. Very resistant to chemical and biochemical degradation, and therefore also persists in the environment.

3. Soluble in fats and oils, and therefore also tends to accumulate in the fatty tissues of living organisms.

Due to the stability of PCB and its environmental accumulation, it has not been permitted in new equipments since late 1960's.

MINERAL OIL AS TRANSFORMER OIL

For over one-hundred years, petroleum-based mineral oils purified to “transformer oil grade” have been used in liquid filled transformers. Synthetic hydrocarbon fluids, silicone, and ester fluids were introduced in the latter half of the twentieth century, but their use is limited to distribution transformers. Several billion litres of transformer oil are used in transformers worldwide. The popularity of mineral transformer oil is due to availability and low cost, as well as being an excellent dielectric and cooling medium.

(5.1)METHODS TO DETERMINE THE PROPERTIES OF MINERAL TRANSFORMER OIL:-

Standard Test Method for Oxidation StabilityThis test method determines the resistance of mineral transformer oils to oxidation under prescribed accelerated aging conditions. Oxidation stability is measured by the propensity of oils to form sludge and acid products during oxidation. This test method is applicable to new oils, both uninhibited and inhibited, but is not well defined for used or reclaimed oils.

TEST METHOD:A test specimen of mineral transformer oil is oxidized at a bath temperature of 110°C, in the presence of a copper catalyst coil, by bubbling oxygen through duplicate test specimens for 72 and 164 h, respectively. The oil is evaluated at the end of each aging period by measuring the amount of sludge and acid formed. The test specimen is diluted with n-heptane and the solution filtered to remove the sludge. The sludge is dried and weighed. The sludge-

free solution is titrated at room temperature with standard alcoholic base to the end point indicated by the color change (green-brown) of the added p-naphthol-benzein solutionSignificance and UseThe oxidation stability test of mineral transformer oils is a method for assessing the amount of sludge and acid products formed in transformer oil when the oil is tested under prescribed conditions. Good oxidation stability is necessary in order to maximize the service life of the oil by minimizing the formation of sludge and acid. Oils that meet the requirements specified for this test tend to minimize electrical conduction, ensure acceptable heat transfer, and preserve system life. There is no proven correlation between performance in this test and performance in service, since the test does not model the whole insulation system (oil, paper, enamel, wire). However, the test can be used as a control test for evaluating oxidation inhibitors and to check the consistency of oxidation stability of production oils.

Standard Test Method for Analysis of Gases Dissolved in Electrical Insulating Oil by Gas ChromatographyThis test method covers three procedures for extraction and measurement of gases dissolved in electrical insulating oil having a viscosity of 20 cSt (100 SUS) or less at 40°C (104°F), and the identification and determination of the individual component gases extracted. Other methods have been used to perform this analysis.The individual component gases that may be identified and determined include:Hydrogen—H2Oxygen—O2Nitrogen—N2Carbon monoxide—COCarbon dioxide—CO2Methane—CH4Ethane—C2H6Ethylene—C2H4Acetylene—C2H2Propane—C3H8Propylene—C3H6Gas content of oil by volume—in Method A, the total volume of gases, corrected to 760 torr (101.325 kPa) and 0°C, contained in a given volume of oil, expressed as a percentage. In Methods B and C, the sum of the individual gas concentrations corrected to 760 torr (101.325 kPa) and 0°C, expressed in percent or parts per million.Headspace— a volume of gas phase in contact with a volume of oil in a closed vessel. The vessel is a headspace vial of 20-mL nominal capacity.

Discussion—other vessel volumes may also be used, but the analytical performance may be somewhat different than that specified in Method C.parts per million (ppm) by volume of (specific gas) in oil—the volume of that gas corrected to 760 torr (101.325 kPa) and 0°C, contained in 10 6 volume of oil.Sparging —agitating the liquid sample using a gas to strip other gases free.Volume concentration of (specific gas) in the gasSample—the volume of the specific gas contained in a given volume of the gas sample at the same temperature and pressure (as the measured total volume), expressed either as a percentage or in parts per million.

TEST METHOD: Method A—Dissolved gases are extracted from a sample of oil by introduction of the oil sample into a pre-evacuated known volume. The evolved gases are compressed to atmospheric pressure and the total volume measured. Method B—Dissolved gases are extracted from a sample of oil by sparging the oil with the carrier gas on a stripper column containing a high surface area bead.Method C—Method C consists of bringing an oil sample in contact with a gas phase (headspace) in a closed vessel purged with argon. The dissolved gases contained in the oil are equilibrated in the two phases in contact under controlled conditions (in accordance with Henry’s law). At equilibrium, the headspace is over pressurized with argon and then the content of a loop is filled by the depressurization of the headspace against the ambient atmospheric pressure. The gases contained in the loop are then introduced into a gas chromatograph. There may be some differences in the limits of detection and precision and bias between Methods A, B, and C for various gases. A portion of the extracted gases (Method A) or all of the extracted gases (Method B) or a portion of the headspace gases (Method C) is introduced into a gas chromatograph.

Calibration curves are used in Method C to establish the concentration of each species. The composition of the sample is calculated from its chromatogram by comparing the area of the peak of each component with the area of the peak of the same component on a reference chromatogram made on a standard mixture of known composition. Significance and UseOil and oil-immersed electrical insulation materials may decompose under the influence of thermal and electrical stresses, and in doing so, generate gaseous decomposition products of varying composition which dissolve in the oil. The nature and amount of the individual component gases that may be recovered and analyzed may be indicative of the type and degree of the abnormality responsible for the gas generation.

(5.2)DRAWBACKS OF USE OF MINERAL OIL AS TRANSFORMER OIL:-

Though mineral oil is really very efficient to be used as transformer oil, still there are certain reasons which create a concern in minds of environmentalists to think upon its usage:-

1. Petroleum products are eventually going to run out, and there could be serious shortages even by the mid-twenty-first century. Conserving the petroleum reserves and recycling are vital for petroleum- based products,—plastics, pharmaceuticals, organic chemicals, and so on. Until we develop economically viable alternate energy sources, there is no easy replacement for gasoline, jet fuel, and heating oil.

So there should be some replacement of mineral oil(as transformer oil) with a more eco-friendly option and something that could be easily available to us. With the recent advancements of science and technology, it has been seen that vegetable oil has emerged as a strong contender to replace mineral oil as the transformer oil.

2.DISPOSAL OF MINERAL OIL:- Mismanagement of waste lube oil is a serious environmental problem. Industries do not take care of environmental hazards associated with these oils. Some is emptied in to sewers for going directly into water waste, adversely affecting water treatment plants. Some is dumped directly on to the ground to kill weeds or is poured on

to dirty roads or is dumped in deserts, where it can contaminate surface and ground water. These oils are also soluble in fats and therefore also tend to accumulate in the fatty tissues of living organisms. Therefore it gets assimilated into the food chain and significant levels of toxic oils appear in the body fats of predatory birds, and of sea mammals such as seals, otters and dolphins. Effects of these oils on these organisms include inability to reproduce successfully, with birth defects in young, and with their deaths through immune deficiency. And studies have shown that there is a huge decline in the population of seals and other fishes in Baltic and Wadden sea which are used as place to dump these oils. These oils are also responsible for the contamination of rice and other important crops in Japan and China. A major accident involving spilling of transformer oil in water bodies resulted in death of 400 people and diseases in another 1600 in Taiwan. Worldwide PCB poisoning has resulted in more than 2000 causalities.

(5.3)LEGISLATIVE REFORMS FOR PROPER DISPOSAL OF MINERAL OIL BASED TRANSFORMER OIL:- Although India is the first country that has made constitutional provisions for protection and improvement of the environment and the Directive Principles of State Policy of the Constitution, Article 48-A of Chapter IV enjoins the state to make endeavor for protection and improvement of the environment and for safeguarding the forest and wild life of the Country. But still much is needed

to be done so that proper disposal and re-refining of the transformer oil is made mandatory in the country.

Hence, The Government of India established a Department of Environment (DoEn), in November 1980, to oversee the planning, promoting, and coordinating of environmental programs at the national or central government level.Subsequently, a full-fledged Ministry of Environment and Forests (MoE&F) was constituted in 1985 to oversee these functions and for policy formulation at the national or central government level. The MoE&F also issues new acts and rules in addition to amending existing acts and rules.The Central Pollution Control Board (Central Board), a statutory body attached to the MoE&F, administers the executive responsibilities for the enforcement of several major Acts. Directly and indirectly, through twenty-eight State Pollution Control Boards (State Boards), the Central Board oversees the implementation of various laws enacted for the protection of the environment by these boards. The disposal and management of the transformer oil comes under the Hazardous Waste (Management & Handling) Rules Act, 1989. The Central Board has established Minimal National Standards (MINAS) for discharge of the oil from the various agencies including the state electricity boards and other related industries. MINAS then are implemented through the State Boards. The State Boards have the authority to set standards (within the state) to more stringent levels than required by MINAS; however, they cannot relax these standards. In addition, the State Boards oversee the management and discharge of the oil, and issue

consent letters to industries for discharge and authorizations for the management and handling of the same. (5.4)BASEL CONVENTION:- India is also a party to the Basel Convention on transboundary movement of hazardous wastes which was signed in Basel in Switzerland. The basic objectives of the Basel Convention are control and reduction of transboundary movements of hazardous and other wastes subject to the Basel Convention, prevention and minimization of their generation, environmentally sound management of such wastes and active promotion of the transfer and use of cleaner technologies.As a Party to the Convention, India is obliged to regulate and minimise the import of Hazardous Waste or other wastes for disposal or sham re-cycling and also to prohibit export of waste to Parties, which have prohibited the import of such wastes. Further, hazardous waste generated in the country is also required to be managed in an environmentally sound manner.

BUT, as we know there is a gap between lip and the sip.The management of waste oil in India is mainly done by unauthorized persons which leads to pollution of environment mainly the water bodies which on turn leads to availability of water that is unfit for drinking purpose and also the loss of aquatic life.

RE-REFINING OF OIL CAN SERVE THE PURPOSE

(6.1)Economic reasons:

The most important advantage of Re-Refining is economic. Industries are using more and more lubricants and this means more and more expenditure on lubricants. If the option of Re-Refining is adopted by these industries a lot of expenditure on lubricants can be saved the saving can be as high as up to 50%.

(6.2)Conservation of precious petroleum product:

In India all lube oil is imported. If Used Oils generated in the country is processed and lube base oil is recovered the import bill can be reduced. Therefore Re-Refining is an import substitute.If the demand of imports of Lube Oil is reduced because of Re-Refining the advantage of Re-Refining is saving of foreign exchange for the Country. Like other advanced Countries in India Re-Refining of Used Oil should be made mandatory.

(6.3)Protection of Environment:Re-Refining of Used Oil is advantageous for saving the Environment from pollution. Reckless dumping of Used Oil can cause damage to land and Water and burning of Used Oil as fuel can pollute air. Re-refining of used oil while saving the environment from pollution generates prosperity to the generator of used oil.

(6.4)Utilization of hazardous waste :

Used oil is termed as hazardous. Lube oil does not wear out with use it only gets contaminated with water, carbon and fuel etc. that means used oil when it is ready for rejection can be re-used. Re-refining of used oil is the best mode of disposal of used oil. Re-refining of the used oil is the most

rational and lucrative solution for the problem of disposal of hazardous waste.

(6.5)RE-REFINING TECHNIQUES:

1. Acid clay process.

2. Vacuum distillation with clay treatment.

3. Thin Film evaporation process.

4. Vacuum distillation with hydro treating.

SILICONE AS TRANSFORMORMER OIL SOLUTION

The safety and dependability of a transformer oil can be increased by replacing the mineral oil with silicone transformer liquid.(7.1)DEFINITION: Silicone Transformer Liquid is a di-methyl silicone insulating material for power transformers provides a unique combination of dependable safety features and high-performance characteristics.

(7.2)Features and advantages:

1. Increase security. 2. Reduce power outages. 3. Increase safety 4. Dependability in transformers 5. Increase security, reduce fire and explosion risk -- Extremely stable, "less flammable" 6. Improve fire safety -- Lower heat release rate, lower smoke generation 7. lower toxicity of combustion byproducts than other transformer oils 8. Reduce power outages -- Thermal stability and oxidation resistance 9. provide long life and low maintenance 10. Meet electrical codes -- Meets US electrical code requirements, indoors and out, as well as various IEC requirements

(7.3)Further importance : Silicone Transformer Liquid allows use of proven, reliable liquid transformer designs indoors or outdoors close to buildings where hydrocarbon fluids may present a fire hazard.Specifically engineered and thoroughly tested for use in electrical power systems, Silicone Transformer Liquid is among the least hazardous of all known engineering materials, making it an excellent alternative to organic transformer oil.

Other alternatives:

Besides, the nontoxic, stable silicone-based or fluorinated hydrocarbons, where the added expense of a fire-resistant liquid offsets additional building cost for a transformer vault. Natural or synthetic esters are becoming increasingly common as alternative, to naphthenic mineral oil too. Esters are non toxic, readily biodegradable, and have higher flash points than mineral oil.But besides having several advantages, there is still a need to find a more eco-friendly option…

BUT HERE WE HAVE A SOLUTION:- VEGETABLE OIL AS

THE TRANSFORMER OILWith the recent advancements of science and technology, it has been seen that vegetable oil has emerged as a strong contender to replace mineral oil as the transformer oil. Investigations on food quality vegetal oils have shown favourable dielectric characteristics as insulating material for electrical devices. In order to comply with possible applications, characterizations of different seed oils and chemical derivatives have been carried out. Results are compared to unused mineral oils and synthetic organic esters specified values : the electrical properties of

vegetable products are close to those of conventional insulating fluids. Investigations on food quality vegetal oils have shown favourable dielectric characteristics as insulating material for electrical devices. In order to comply with possible applications, characterizations of different seed oils and chemical derivatives have been carried out. Results are compared to unused mineral oils and synthetic organic esters specified values : the electrical properties of vegetable products are close to those of conventional insulating fluids.

(8.1)PRIOR USE OF VEGETABLE OILS IN TRANSFORMERS In the past, capacitors were the only kind of electrical equipment considered for the use of vegetable oil. Castor and cotton seed oils were considered for use in capacitors (with cellulose insulation) as early as 1962.The higher dielectric constants of these fluids provide a better match with cellulose than mineral oil.

(8.2)PROBLEMS ASSOCIATED WITH THE USE OF VEGETABLE OIL AS TRANSFORMER OILMost obviously, edible seed oils and food grade products cannot be as stable as petroleum-based oils and other non-biodegradable dielectric fluids. Oxidation and hydrolysis are the main ageing mechanisms which degrade the vegetable oil for further use. Oxidation rate is lowest for

mono unsaturated oils and highest for tri unsaturated oils (e.g. linseed oil with high tri unsaturated content, a typical drying oil).

(8.3)MODIFICATIONSTo make vegetal formulated oil more stable, oxidation inhibitors and metal passivators (presence of copper and iron are known to enhance the degradation process) probably will need to be added to the basic fluid. Such additives will have to be selected exclusively among food grade materials. To reduce the ageing process, some synthetic inhibitors like DBPC (2,6-di-tert-butyl-pcresol) can be added. Some sulphur compounds are also present in mineral oils and act as natural inhibitors. As esters oils are more biodegradable than mineral oil, they tend to havea lower oxidation stability. This lower oxidation stability can enforce transformer manufacturers to use a sealed design (not free breathing), although vegetable oil suppliers could also add an inhibitor which should be as "green" as possible.

TYPICAL OIL SEEDS FROM WHICH OIL IS EXTRACTED FOR TRANSFORMER USE

Vegetable oil is a natural resource available in plenty; it is a fairly good insulator, and is fully biodegradable. The first commercial product was BIOTEMP®, patented in the U.S. in September 1999 by ABB and developed at its Raleigh, NC-based transformer lab. The base fluid was high oleic oil with over 80 percent oleic content. These oils are produced mostly from seeds that have been developed by selective breeding; more recently, gene manipulation techniques have been used.

COMPARISON BETWEEN THE PROPERTIES OF MINERAL OIL, VEGETABLE OIL AND SILICONE FLUID

(8.4)BIODERADABILITYThe most remarkable feature of vegetable oils that gives it an edge over mineral oil is its biodegradability, which is as high as 97-99%. The most accepted test is the CEC-L-33 test developed to test biodegradability of lubricating oils in an aquatic environment.

(8.5)ABILITY TO MEET SPECIAL CHALLENGES

COLD WEATHERThe use of vegetable oils in transformers that are exposed to cold weather has been an issue. The pour point of vegetable oils does not go below –30 oC, even after adding pour point depressants. Without additives, the fluid could freeze at subzero temperatures. To address this issue, vegetable oil-filled transformers were frozen to –50 oC or below in lab cooling chambers and then energized. There

have been no failures. Since vegetable oil is a mixture of esters that freeze at different temperatures, there is no sudden freezing or thawing.

(8.6)CONCLUSION So it can be said that after considering the harmful effects of mineral oil as the transformer oil, it is really necessary to find a more eco-friendly option and vegetable oil can really serve this purpose very well. Today with the advancement of science and technology, standard of life has gone up. But as we know, to gain something, we are asked to sacrifice something as well and what we are sacrificing is our environment. So it is the high time that we wake up and take up the responsibility to save the environment. It is up to us, whether we want to make it easy for the upcoming generations or to push them in the chamber of darkness and poison.

REFERENCES

1.”Vegetable oils for liquid filled transformer” by T.V. Oommen(IEEE WEBSITE).2.”A new vegetable oil based transformer fluid: development and verification” by T.V. Oommen, E.J. Walsh, C.C. Claiborne and J.P. Baker(IEEE WEBSITE).3.”Vegetable oil as substitute for mineral oil” by Y. Bertrand and L.C. Hoang(IEEE WEBSITE).4.Wikipedia files on internet.5.Mineral oil analysis techniques available on internet.6. Journal of Research of the National Institute of Standards and Technology by Wise, Stephen A.