Investigation Of Alternatives From Local Raw Materials For Power Transformer Liquid Dielectrics

CHAPTER ONE

INTRODUCTION

 

• Background To The Research

Various equipment engaged in electric power system’s operations have, for decades, made use of hydrocarbon mineral oil products  for their lubrication, cooling and insulation, thus constituting over dependence on petroleum crude oil by-products. About 34.3% of the world’s energy is said to come from petroleum oil, while 25.1, 20.9, 13.3, and 6.5 percents are from coal & peat, natural gas, renewables (hydro, traditional, tide, solar, geothermal) and nuclear respectively [1].

Gas flaring and exhausts of gases by diverse combustion engines, with their consequent environmental pollutions, hazards and discomforts like global warming are rapidly placing crude oil with its by-products a global threat, that if researches for alternatives (especially in bio-diesel, lubricants, coolants and insulating oil), are not vigorously carried out by developing countries, industrial activities and productions that mostly depend on bulk electricity might be ‘grounded’, thereby stalling industrialisation and other socio-economic developments.

 

Numerous consumer nations depend on foreign suppliers. These foreign nations have not only succeeded in enslaving these consumer nations, economically and technologically, but have also made them hostages for eventual international social and political aggressions such as wars, coup d’états, terrorisms, assassinations, cannibalism, to mention but a few. Consequently desires for technological diversification with dispatch, is causing drifts from dependency on fossil fuels to searches for alternatives, as reliance on imported petroleum and its by-products like transformer mineral oils, coupled with its terrifying fluctuating prices is creating immeasurable apprehension among users.

 

Furthermore, anyone who has been involved in a transformer oil spill or leak management knows the headache, as well as the expense of clean-ups and remediation, as most transformers today mainly use insulating and cooling fluids derived from the non-environmentally friendly petroleum crude oil. Utilities, at such emergencies, have no little choice but to develop extensive contingency plans and detailed procedures at these clean-ups which require training of personnel and purchase of special equipment to handle such challenges, moreso, when the spilleage involves oils contaminated by the toxic polychlorinated biphenyl (PCB) in transformers and transmission lines.

 

My job schedule for more than two decades as the Head of Electrical Laboratory Tests and Power Equipment Maintenance at the Ajaokuta Steel Company Limited, further ignited my curiosity toward finding alternatives to transformer mineral oil due to the persistent health risks and hazards arising from uncontrolled and unprevented body contacts of transformer’s operating and maintenance personnel with these toxic oils at plants. The destruction of surrounding vegetations, flower yards, fields and landscapes by the used toxic oil-discards at such maintenance periods was usually consequent to the poor biodegradability of petroleum-based transformer oil. Certainly, such was working against the ethics and pupose of the engineer who is primarily trained to better the living condition of man and his environment, rather than aiding and witnessing their gradual expiration. Also the economic and technological disadvantages to our country, Nigeria, from the protracted dependence on imported mineral oil for our transformers, were not outside the vision that spured this research work.

Environmentally friendly fluids could be substituted in transformers and transmission lines, thereby reducing or eliminating these elaborate procedures and implications with their attendant consequences.

Due to the need to achieve these substitutes, crops or other similar agricultural sources are already successfully considered as potential sources of biodiesel and today are being surveyed for extention to power industries for use in transformer operations.

 

In Nigeria, some native oil seed plants which grow well in fallow lands could be investigated as potential sources of alternative to fossil fuel as cooling and insulating oils for power transformers. Consequently the seven vegetable oils selected for study in this research are derived from Palm Fruit Mesocarp, Palmkernel Nut, Coconut, Soya bean Seed, Beniseed (sesame), Groundnut and Melon Seed.

 

An additional demerit on the mineral oil is the discovery of the presence of polychlorinated biphenyls (PCBs) in some of the exports by manufacturers. These are highly toxic and poisonous to human health and environment. Though PCB offered good cooling quality in mineral oils, its production for domestic use was primarily banned in many developed countries as far back as 1977 and finally banned from usage in 1979 in the US, due to its high toxicity and persistence chemical stability (poor degradation) in environments, except in closed application, like already operating transformers prior to enforcement of the ban. Additionally any industrial use, for example in improvement of cooling properties of mineral oil  must not exceed the global legal percentage doping, which according to the law of Environmental Protection Agency (EPA), must be clearly embossed on the body of the content. [2][3]. Unfortunately many developing countries ignorantly welcome this hazardous ‘dump’ as great blessings.

Prior the discovery of crude oil in Nigeria, the country was known for its great agricultural and human resources, as well as crop farming. Her vision for emancipating that endowment rapidly fissiled out and abandoned, for decades, by the discovery of crude oil. Subsequent teeming youths and graduates saw careers in oil exploration and petroleum more prospective and less hectic than the traditional non mechanised system of farming, within the contemporary time. Undoubtedly the nation has been reasonably robbed of the immense traditional contribution of Gross Domestic Product (GDP) in agriculture, which stood at about 70%, prior the oil era to the present 30% in crop farming and export as food, for human consumptions. [4][5]

Poor biodegradation of mineral oil wastes and discards has been disadvantageous to vegetation and human environment, thus making mineral oil unfriendly to human, agriculture and crop farming.

 

It is in view of these that this research on investigation of alternatives for power transformer liquid dielectrics from local raw materials, with major focus on the vegetable oils suitable for the cooling and insulation of power transformers, is presently embarked upon.

 

• Statement of the Problem

This research is to investigate dielectric alternatives, from natural ester-based oils (triglycerides), for use in power transformer cooling and insulation, consequent to:

• Poor biodegradeablility of mineral oil discards resulting in rapid global loss of vegetations and habitat environments.
• Higher levels of toxicity posing hazards to humans and operators of transformers.
• Enslavement of developing countries by the developed task masters through unaffordable high costs of transformer oils, thus redering countries poorly and hopelessly industrialised for decades, with eventual high rate of unemployment, poverty and social crimes. Oil alternatives through agricultural products could easily revamp this threat, accomplishing a safe-landing for the developing countries.
• Relatively lower flash points of 135^oC for mineral oils (as against 250^oC and above for vegetable oils), thus posing dangers to operators of transformers and environment in the course of accidental explosions due to high oil temperatures at sparkings during on-load tap changing or excess overloadings and transient faults etc.

These constitute statements of problem that gave birth to this research.

1.3       Purpose of the Study

The purpose of this research is

1. To subject samples of local vegetable oils to Electric, Chemical, Thermal and Physical tests for the purpose of identifying their characteristics and use as dielectrics and coolants in that application for transformers..
2. To establish further the usefulness and suitability of various natural vegetable oil as advantages to power transformers’ operation and power industries in general, by investigating their food technology and dietary properties.

• To evaluate the technical advantages (vis-à-vis the performance characteristics) of the envisaged new products over conventional ones, in terms of efficiency, durability and safety.

1. To further enhance technological and economic development of the country through the discovery and diversification of the use and importance of natural vegetable oil for power transformer operations.

1.4       Significance of the Study

This research will have a multiplier effect.

The significance of the study is in the fact that the success of this research will place Nigeria and most vegetable oil producing countries on more socio-techno-economic advantages for the following reasons:

1. The discovery will become an exciting new technological innovation as well as challenging exposures and experience toward human capacity building for the electric power manufacturing industries.
2. More job opportunities will be created for young graduates, which in turn will have positive social influence on them and for the country

• Level of environmental hazards and damages to vegetation and living things, including man, due to global warming and low biodegradability of crude oil prodects will hopefully be reduced if vegetable oil should replace, to a great percentage, the roles played by the toxic mineral oil and its by-products in power industries.

1. Many relevant government agencies, eg NERC, Energy Commission of Nigeria, etc will find the reseach helpful in formulation of policies.

1.5       Scope of the Study

The dielectric alternatives will be limited to some locally available vegetable oils. The selected samples for the research are Soya bean, Groundnut, Beniseed, Palm Mesocarp,

Coconut, Palm Kernel and Melon oils.

1.6       Limitations of the Study

• Limitation of testing devices for some sophisticated tests

Though reasonable tests were carried out on the specimens, some of the tests could not be done due to lack of sophisticated testing devices required for such tests in the country. Such tests which include Interfacial Tension Test (IFT), Oxidation Stability Test (OST), Dissolved Gas Analysis (DGA) Test, could not be carried out at Ajaokuta Steel Company laboratory due to lack of the required testing devices and facilities. Discussions on such tests will be based on results obtained by other researchers in the literature review

1.6.2        ENVIRONMENTAL FACTORS

Temperature, humidity, irrigation etc, play tremendous role in the cultivation and production of the oil seeds and grains which are the sources for the production of these fatty acid oils. Unpredictable weather conditions have always caused unpredictable outputs and quality of crop products.

Humidity and moisture have always been unfriendly to liquid dielectrics for its high hygroscopic characteristics. Oil sampling for tests require expertise and utmost care against prolonged exposure to atmosphere in order to reduce level of absorbed moistures from free air, which could affect test results.

To limit these negative effects on the samples, to the barest minimum, the following were ensured:

• Sampling of the oil was done with speed and accuracy.

Sampling from parent container into the sampling bottle must be as brisk as possible, not exceed 30 seconds so as to reduce percentage dissolution of air and moisture to a negligible value.

Accuracy requirement includes

• Dry cleaning through warming of sampling container and corking-up till sampling moment.
• Rinsing every item to be used in sampling (e. g. funnel) with oil from the parent container, before use.
• Getting the mouth of parent container rid of any particles, pollutants, etc by rinsing with the content oil.
• Rinsing twice the sampling container with oil sample from parent container, before final sampling and corking for the laboratory.
• Sample container should be immediately cleaned with clean cotton material respectively dedicated for the various sample containers.
• Container is to be immediately named for avoidance of mistaken identification.
• During sampling process, efforts were made to avoid contact of fingers with the sampled oil or internals of the containers, as such could introduce contamination
• Heating of the sampling and testing laboratory environment to a temperature of at least 33^oC to ensure humidity level of about 96% (maximum) of the Saturation Value, at the particular heated temperature value.

Transformer surroundings are heated for 24hrs, prior to sampling time by means of several 1000Watt incandescent lamps, positioned around vicinity of the oil for test abd the testing laboratory so as to establish an environment of moisture content (absolute value) at least 4 to 10% lesser than the Saturation value at the heated environmental temperature of say, 33^oC to 35^oC. This will gurantee a Relative Humidity value acceptable for oil sampling. (See Appendix 12).

 

 

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