Analysis of Factors Influencing the Intensity of Transformer Oil Ageing in Long-Term Operation (original) (raw)
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Several efforts have been made over the past years to study the electrical, physical and chemicals properties of insulating oils. Among those efforts there is a property of natural aged oils (real oil samples corresponding to the scale of industrial transformers). This is investigated in this paper to determine the lifetime of naturally aged oil with different applied electric field and different shapes. This paper presents an experimental work to study the lifetime of transformer oil as a function of conduction current. In this paper, the electrification current in the tested oil is measured for different temperatures. Finally, tests have been carried out on oil samples under testing with different services period to determine the relation between breakdown voltage and the oil lifetime under uniform and nonuniform fields.
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The consumption of electric power is constantly increasing due to industrialization and population growth. This results in much more severe operating conditions of transformers, the most important electrical devices that make integral parts of power transmission and distribution systems. The designed operating life of the majority of worldwide transformers has already expired, which puts the increase of transformer reliability and operating life extension in the spotlight. Transformer oil plays a very important role in transformer operation, since it provides insulation and cooling, helps extinguishing sparks and dissolves gases formed during oil degradation. In addition to this, it also dissolves moisture and gases from cellulose insulation and atmosphere it is exposed to. Further and by no means less important functions of transformer are of diagnostic purpose. It has been determined that examination and inspection of insulation oil provide 70% of information on transformer condit...
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In order to maintain continuous power supply in the electrical system, condition monitoring of the sensitivity equipments in power system is very essential. Among those equipment in which more concentration required is Power transformer. To determine the performance of transformer, it is necessary to have investigations on ageing of transformer oil due to thermal degradation. In this work an effort has been made to analyze various critical parameters like acidity, Breakdown Voltage (BDV), viscosity, volume resistivity, loss tangent, dielectric constant and spectral response for different range of thermal degradation of transformer oil with various compositions of materials like pressboard and Kraft paper. As initiative an exclusive Thermal-UltraViolet (UV) analysis has been carried out to investigate the spectral response of transformer oil. By estimating the condition of oil, the unexpected failure of transformer and power outages can be prevented.
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Corresponding Author: Aging Study and Lifetime Estimation of Transformer Mineral Oil
Problem statement: Power transformer is the most expensive equipment in electrical network; and the mineral oil has the main roles of insulating and cooling in it. Oil is subjected to the degradation because of the ageing, high temperature and chemical reactions such as the oxidation. Then the oil condition has to be checked regularly and reclaimed or replaced when necessary, to avoid the sudden failure of the transformer. It will be very desirable also if we can predict the transformer oil remaining lifetime, from time to time. Approach: An experimental study was accomplished on the used oil specimens coming from several power transformers of various ages, working in Iranian power network, to recognize the correlation between the real age of the oil and the rate of its different characteristics and to know the most appropriate property which can represent its ageing. Accelerated aging experiments were accomplished on oil specimens at different temperatures. Furthermore a method for estimation of the remaining lifetime of the oil, using Arrhenius law, was employed. Results: According to our experiments, it was verified that, by using Celsius degrees and natural logarithm, the Arrhenius law can be applied properly to the thermal degradation phenomena of the oil. Conclusion: It was shown that the presented method can be used to study the degradation of transformer mineral oil and to estimate its remaining lifetime.
Power transformer undergo aging overtime that degrades its insulation system. Oil-immersed paper insulation degradation in transformer can be assessed through the change in oil characteristics and the dissolved gases. Data related to these parameters are abundant, but study on correlation among these parameters and the operating time of power transformer is still limited. This paper presents statistical insights into aging of transformer insulation system through oil characteristics, dissolved gases and the operating time of transformer. As much as 219 in service 150 kV transformers population testing data were included in this study. The data was analyzed using linear regression correlation analysis to Figureure out the dependency of each parameters. Statistical correlation between each properties of oil insulation, dissolved gases and operating time were carried out. There are some oil properties that have correlation with operating time, which are color scale, IFT and acidity. Moreover, color scale, IFT and acidity shows dependency among them. IFT tends to gradually decrease while acidity increases as operating time trend rises. On the other hand, operating time are also highly correlated with CO and CO2, which are commonly known as the main product of paper insulation degradation in transformers. Correlation among prior correlated parameters found that CO is strongly correlated with color and IFT. Subsequently, a high correlation coefficient of parameter to operating time could be interpreted that the ageing process happens during the life of a transformer changes certain parameters which these changes should be noticed for better decision making whether the transformer still feasible to be used in the system with certain maintenance or should be replaced.
Parameters affecting the static electrification of aged transformer oils
2011 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, 2011
In this contribution, experimental investigations onto the factors affecting the static electrification of aged transformer oils are undertaken. The effect of aging byproducts (as assessed by Dissolved Decay products, Turbidity, Interfacial Tension and Acid number) of the oil on the streaming current is reported. The results indicate that the electrification currents generally increase with aging by-products of oil. The sign, the amplitude and the time constant of the electrification currents are also affected. The influence of each "impurity" is emphasized and discussed.
Thermal lifetime of transformer electroinsulating oils
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The paper deals with the evaluating the thermal lifetime of the electro insulating transformer oil as part of the prognosis of the remaining lifetime of the transformer as a whole. The thermal-oxidative ageing accelerated tests have been carried out for the oil samples TR 25A at the temperatures of 100 - 130°C, with the control of the oxygen content, the temperature and the catalysts. The measured parameters have been the dielectric losses factor, the index of neutralization at the temperature of 20°C, and the interfacial tension against the water at the temperature of 20°C. The data proceeding allow the obtaining the model of thermal-oxidative degradation process, described by a combined function in dependence on temperature and time. The proposed combined function expression was experimental validated. Based on this relation, a procedure for prognosis the lifetime of the oil was established.