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The research on the nanofluid as an alternative transformer oil has been widely attracted the concern of many researchers as the effectiveness as insulation and cooling agent of the existing transformer oil is not achieved satisfactory to accommodate the rising demand of high voltage rate. In this study, nanofluid with a nanomaterial, Carbon Nanotube (CNT), with and without Polyvinylpyrrolidone (PVP) has been formulated, and their AC breakdown voltage of the mineral oil (MO) according to IEC 60156 standard has been characterized. The concentration of CNT study is 0.005, 0.01, 0.015 and 0.02 g/L. It is found that the optimum concentration in nanofluids without PVP is 0.005g/L of nanofluids concentration with the highest breakdown voltage 53.52. In comparison, the highest breakdown voltage for nanofluids with PVP is 33.4kV at 0.01g/L. The existence of PVP in the nanofluids seems not significantly affect the dielectric performance of the degradation of the nanofluid from 5% to 43%. Hence, nanofluids with CNT addition are proofed as a good additive in insulation oil for future transformer applications.

This paper studies the electrical efficiency of carbon nanotubes (CNT) with nanosized diameter inserted into palm-based oil at various concentrations (0, 0.0125, 0.025, 0.0375, 0.05, 0.125, 0.25 and 0.5 g/L). Dispersion methods, including sonication and drying process were systematically applied for producing stable CNT nanofluids. Several parameters such as electrical properties (AC breakdown voltage) and dielectric properties (dissipation factor, relative permittivity and resistivity) were measured accordingly based on IEC 60156 and IEC 60247 international standards. The test results reveal that the higher concentration of CNTs dispersed in palm oil, the lower AC breakdown voltages produced. At 0.5 g/L concentration, the average of 50 breakdown was 22.30 kV, which is 72.33% decrement compared to palm oil without any nanofiller. Besides, the permittivity and resistivity of CNT nanofluids decrease as concentrations increased, while dissipation factor increases along with CNT concentrations. In order to further support this indication, Raman analysis is measured to relate the behavior of AC breakdown voltages and chemical structure of CNT nanofluids. Based on the Raman spectra at 2800-3200 cm-1 region, it is shown that the value of total unsaturated fatty acid and total fatty acid decreased as concentrations of CNT increased. This occurrence directly influences the degradation performance of AC breakdown voltages.

The performance of liquid insulation in power transformer is vulnerable to particles, especially the metallic particles. This paper presents the experimental study on the effect of metallic particles on the palm oil (PO) as dielectric insulating fluid under lightning impulse breakdown voltage. The type of PO used in this study is refined, bleached and deodorized Palm Oil (RBDPO) Olein. Two different types of metallic particles (copper and iron) with different concentrations (clean, low, medium, and high) were studied. The lightning impulse test has been carried out according to IEC 60897 standard and under the influence of a uniform electric field. For the comparative purpose, similar test has been carried out with mineral oil (MO). The presence of metallic particles reduces the average lightning impulse breakdown voltage of MO and PO but shows less significant effect to MO. This is because the streamers in the PO propagate faster and further than in the MO at the same voltage level. Hence, causing the breakdown voltage of PO lower than MO. Under negative lightning impulse, the breakdown voltage of MO is slightly higher than RBDPO. From the study, the increment of the number of particle level contamination will reduce the lightning impulse breakdown voltages of the PO.

This paper presents a sealed ageing study of palm oil, corn oil, and rice bran oil with and without the presence of insulation paper. The oils were aged at four different durations which are at 2 days, 30 days, 90 days, and 180 days at a constant temperature of 90°C. The properties of vegetable oils as well as insulation paper under ageing were then analysed through AC breakdown voltage, dielectric losses, relative permittivity, resistivity, moisture, and acidity of the oils. It is found that the AC breakdown voltage of oils with the presence of insulation paper is lower than the oils without the insulation paper. The AC breakdown of oils with and without insulation paper increase with the ageing time which reflect the amount of moisture in oil. For dielectric loss, the value is increased with time and dielectric loss with paper shows lower value than without paper. RBO shows higher dielectric losses for both conditions. In term relative permittivity, it can be concluded that the relative permittivity increases when the time ageing increase. It is seen that relative permittivity of palm oil is the highest change in duration of time ageing from 1.8 to 2.0 for both conditions. Throughout the ageing time, the acidities of all the oil samples remain at low level for ageing without paper. However, with the presence of paper, the number of acidities for all oil samples increased with the time. With the presence of Kraft paper, the viscosity will decrease over time duration. But, without the presence of Kraft paper, the viscosities were almost stable for all samples.

Demand of softwood fiber has rapidly increased as a result from the variety of new softwood products. Therefore, nonwood fibers have been introduced as alternatives in pulp for presspaper making to supplement the limited wood fiber resources. Malaysia is the second largest producer of oil palm where the empty fruit bunch (EFB) has a potential to be developed as an insulating paper. This paper aims to determine the performance of EFB as non-wood fiber to evaluate its use as potential presspaper insulation in power transformer. The sample of EFB paper was produced through kraft pulping and laboratory handsheet process. The performance of EFB and kraft paper was evaluated by impulse breakdown test. The study is focused on the performance of insulating paper that were aged with the transformer oil at 90 °C for 30 days. In order to investigate the impulse breakdown voltage of the insulating paper, multistage impulse generator was used. As the aging temperature increases,the breakdown voltage will decrease.The thickness of insulating paper also has an effect to the breakdown strength as the thicker the insulating paper, the higher the breakdown voltage will be. For no aging sample, kraft fibres dominate the breakdown strength at 28.11 kV/mm, while for sample aged at 90 °C, EFB fibres dominate the breakdown strength at 3.62 kV/mm higher than the average of kraft fibres due to an effect of fibres arrangement between fibre-to-fibre bonding after the aging.

This work aimed to study the influence of contamination profiles and humidity on flashover electrical characteristics of polluted insulators. Firstly, the flashover tests on cap and pin glass insulators under four pollution levels represented by salinity were conducted. Eight artificial contamination profiles based on the solid layer method have been modeled for the selected insulators. The numerical analysis has been used to determine the insulator electrical characteristics such as potential, electric field, and power dissipation under proposed contamination profiles using finite element methods (FEM). Next, the power dissipation has been simulated with consideration of thermal stress propagation in locations with high power. Finally, flashover voltage gradient tests have been conducted under various humidity and contamination profiles. The values of the flashover voltage gradient due to pollution were determined as the percentage of the value of the flashover voltage gradient in the clean condition which was identified as the reference point. The numerical model indicated that the initiation of arc generally occurs at area in which the electric field and power dissipation is maximum. It was also observed from experimental results that the flashover voltage gradient under different contamination profiles has different values depends on the location and dimension of the pollution region.

Due to the increasing demand on developing good insulation, several researchers have performed experimental studies to prove the effectiveness and capabilities of transformer oil. This is done by suspending nanosized solid particles in the oil (nanofluid) for transformer applications. In brief, this paper presents a compilation of research studies which is divided into three parts. Part I discuss the preparation of the nanofluid which involves different types of nanomaterials, the optimal amount of concentrations, and applicable synthesisation methods for producing stably suspended nanofluids. In Part II, the nanofluid’s performances including the electrical breakdown voltages, impulse tests, and thermal and dielectric behaviour are reviewed in depth and compared. Part III emphasizes the limitation of nanofluids. Most researchers have agreed that appropriate concentrations of nanomaterials and the preparation method for nanofluids mainly affect the performance of nanofluids especially in terms of electrical properties. Meanwhile, types of nanomaterials and base oil also play a vital role in producing nanofluids as a better alternative transformer oil. However, among a few researchers, there are concerns regarding the issue of agglomeration and inconsistencies of findings that need to be resolved. Therefore, a few aspects must be taken into consideration to produce the next generation of high heat dissipation insulation.

Transformer oil does not only serve as an insulating liquid, but also in removing heat from the windings and cores. Mineral oil (MO) has been widely used in transformers for more than 150 years. Recently, researchers have attempted to search for alternative insulating oils due to the possibility that MO will run out in the future together with the concern on fire safety and environmental pollution. Among the potential oils is rice bran oil (RBO). This work presents the studies of the lightning impulse (LI) of RBO behavior under various electric fields, gap distances and testing methods. The electrical performances of LI tests show that RBO and Palm Oil (PO) have lower LI breakdown voltage than MO under both uniform and non-uniform electric fields. However, the difference in LI breakdown voltages between RBO, PO and MO are slightly small which is less than 20%. In addition, there is no significant effect in the various testing methods under both uniform field and non-uniform field where the percentages of difference are less than 12% and 8% respectively. The data of LI breakdown voltage were statistically analysed to predict the withstand voltage and 50% breakdown voltage of oil samples by using Weibull distribution. The Weibull distribution of MO, PO and RBO has well fit with the fitting line. Finally, the relationship between LI voltages under a non-uniform field with various parameters of PO and RBO was obtained and proposed. From this work, it can be concluded that RBO shows promising results to be considered as an alternative to MO in transformer applications.

This study aims to evaluate the ageing performance of Kraft and Kenaf insulation press-paper in Natural Ester (NE), which could be applied in a power transformer. Kenaf fiber was produced by Kraft pulping process is considered as potential insulation press-paper due to higher cellulose. Due to environmental concerns, NE uses have been considered an alternative to mineral oil. In this experiment, an accelerated ageing test was carried out with transformer insulation press-paper. Kraft and Kenaf press-paper were impregnated in NE with a copper strip of 90°C and 140°C for 10,20 30 days. Fourier transform infrared spectroscopy (FTIR) result showed that O-H's absorption intensity decreased, while C-H, C=O, and C-O bond increased with the ageing time. The viscosity measurements have been used to compare the stability of aged NE with Kraft and Kenaf press-paper at different ageing time. It is found that the viscosity results showed aged NE with Kraft press-paper is higher than Kenaf presspaper as the duration of ageing increase.

The transformer is used as a device to step-up or step-down electrical power and operate continuously for a long period. Mineral oil is the medium most used as a transformer insulation since it has been functioned as cooling agent for its properties but has been substituted over a period of time. In this research, some properties of wasted mineral oil recycled under different process and doping with various concentration of Carbon Nanotube (CNT); 0.001g/L, 0.005g/L, 0.01g/L, 0.015g/L, 0.02g/L, 0.025g/L, 0.03g/L and 0.035g/L) are studied accordingly. It is observed that, there is 96.90% enhancement in case of AC breakdown voltage at 0.005 g/L concentrations compared to wasted mineral oil without any addition of nanoparticles. Tan delta value, permittivity and resistivity of oil samples also reflect the value of breakdown voltage obtained in this study. It is figure out that, CNT nanofluid can reach the greatest breakdown efficiency as good insulating oil at 0.005g/L CNT concentration which promising advantage for future transformer applications.

In this paper, the electrical, dielectric, Raman and small angle X-ray scattering (SAXS) structure behavior of disposed transformer oil in the presence of multi-walled carbon nanotube (MWCNT) were systematically tested to verify their versatility for preparing better alternative transformer oil in future. MWCNT nanofluids are prepared using a two-step method with concentrations ranging from 0.00 to 0.02 g/L. The test results reveal that 0.005 g/L concentration possesses the most optimum performance based on the electrical (AC breakdown and lightning impulse) and dielectric (permittivity, dissipation factor and resistivity) behavior. According to the trend of AC breakdown strength and lightning impulse pattern, there were 212.58% and 40.01% enhancement indicated for 0.005 g/L concentration compared to the disposed transformer oil. The presence of MWCNT also yielding to the decrement of dissipation factor, increased on permittivity and resistivity behavior of disposed transformer oil which reflected to the performance of electrical properties. Furthermore, it is found that these features correlated to the structural properties as systematically verify by Raman and SAXS analysis study.

This paper presents an alternative approach for predicting critical voltage of pollution flashover by using Artificial Intelligence (AI) technique. Data from experimental works combined with the theoretical results from well-known theoretical modelling are used to derive algorithm for Artificial Neural Network (ANN) and Adaptive Neuro-fuzzy Inference System (ANFIS) for determining critical voltage of flashover. Series of laboratory testing and measurement are carried for 1:1, 1:5 and 1:10 ratios of top to bottom surface salt deposit density on cup and pin insulators. Insulators variables such as height H, diameter D, form factor F, creepage distance L, equivalent salt deposit density (ESDD) and flashover voltage correction are identified and used to train the AI network. Comparative studies have evidently shown that the proposed (AI) technique gives the satisfactory results compared to the analytical model and test data with the Coefficient of determination R-Square value of more than 97%.

Natural ester oil is one of the alternative materials that can be used to increase the supply of transformer oil. This research discloses the investigation of breakdown voltage of mixed oil virgin coconut oil (VCO) with refined, bleached and deodorized palm kernel oil (RBDPKO) under the effect of different temperature and different gap distance. The test was organized based on the guideline in IEC 60156 standard for AC supply under uniform field (sphere-sphere). The ratio of mixed oils in this experiment are 0% VCO, 20% VCO, 40% VCO, 60% VCO, 80% VCO and 100% VCO. The result indicates that, the ratio of 20% VCO was the highest breakdown voltage for mixed oil at different temperature which was 48.7 kV (40°C) and 57.9 kV (80°C). The increasing of the temperature and the distance gap gave impact on the breakdown strength.

This paper presents a study of the lightning breakdown voltages of Palm Oil (PO) and Coconut Oil (CO) under a non-uniform field with consideration on the polarity effect at various gap distances. All tests were carried based on a needle-sphere electrode configuration and various gap distances ranging from 2 to 25 mm under positive and negative voltage polarities. Three different testing techniques were used in this study including rising-voltage, up-and-down and multiple-voltage methods. The PO used in this study was Refined, Bleached and Deodorised Palm Oil (RBDPO) Olein. Three different samples of RBDPO and one sample of CO were tested. The Weibull distribution was used as a statistical approach to determine the withstand voltages of all samples at 1% and 50% probabilities for each type of oil. Under positive voltage polarity, it was found that the 50% breakdown voltages of RBDPO and CO were comparable with Mineral Oil (MO) whereby the highest percentage of difference among all gap distances was less than 15%. RBDPO and CO have lower 50% breakdown voltages than MO under a negative lightning impulse for which the highest percentage of difference can be up to 40%.

The performance of liquid insulation in power transformers is susceptible to conductive particles. This paper presents the experimental study of the influence of copper particles of on the AC breakdown voltage and dielectric properties of palm insulating oil (PO). The PO used in this study is the Refined Bleached and Deodorized Olein type (RPDPO). The PO was contaminated with copper particles of various concentrations (0.1g, 0.5g and 1g). The AC breakdown voltage and dielectric properties such as dielectric dissipation factor, relative permittivity, and resistivity were measured in this experiment. Similar experiments were conducted for mineral oil (MO) for comparison purpose. From this study, the AC breakdown voltage of PO and MO reduces with the increase of copper particle concentration. The copper particles having less effect on the AC breakdown voltage of the PO than on MO. This is due to it has a higher viscosity. The relative permittivity and dissipation factor of PO and MO increase with increasing of copper particle concentration while the resistivity shows opposite relationship. The influence of copper particles on PO and MO is significant at higher temperatures than low temperatures. Similar results were observed for MO.

Investigating of insulator performance is a continuing concern within the power system, so the study of the insulator parameters is required. The present paper aims to use new criteria and approach to predict the occurrence of flashover of (100 * 60 mm) plates of silicon rubber insulator using harmonics component of leakage current. the signal of leakage current of insulator with different pollution levels was measured under different weather conditions. Furthermore, to evaluate the effect of weather variables, various values of water conductivity were used for the experiments. The new criteria (Ki) is ratio of sum of leakage current harmonics value at frequencies 0-100 Hz to sum of leakage current harmonics value at frequencies150-500 Hz have determined. The proposed criteria can be used as wireless diagnostic tools for contamination levels flashover can occurred. Test was conducted by two wetting methods of sample SIR insulator is spray and dipping, different voltages 7kV and 14 kV have been applied. Test results shown high performance of this method.

Nanofluids can be regarded as next-generation heat transfer fluid that has enormous potential to enhance the performance of insulating oil in the transformer. In this study, the breakdown voltage of new colloidal mineral insulation oil and natural ester oil (palm oil) was systematically investigated and compared. Carbon nanotubes (CNT) nanofluid is formulated by dispersing CNTs in mineral and palm oil. The AC breakdown voltage test is performed accordingly to the methods and precautionary steps based on IEC 60156. For a successful forecast, instead of referring to the average and lowest possible breakdown failure data, there are few types of distributions (Weibull, normal, Gumbel and generalized extreme value (GEV)) that were used in order to represent a better probability of breakdown failure. In most cases, the experimental results followed Weibull and GEV distributions than other distributions. Thus, Weibull and GEV distributions were used to indicate the probability of breakdown failure of CNT nanofluids. The results indicated that CNT is considered as a potential material that would be possible to enhance the performance of mineral oil but with appropriate concentrations of CNTs. However, contradictory results occurred for CNT based palm oil, where the trend of breakdown voltage is lower than mineral oil value.

Transformer is an important component in power system. Lightning impulse will cause an overvoltage that will damage the transformer. Hence, transformer need an insulation that can protect it and withstand lightning impulse. Mineral oil (MO) was the most commonly used oil as liquid insulation. Although MO provide an excellent performance in transformer, it still gives bad impact due to it low flash point, fire point and not biodegradable. Virgin coconut oil (VCO) offer a great potential for replacing MO as an insulating in transformer due to it high flash point, high fire point and biodegradable. This project presents the examination of breakdown voltage of both oil at both polarity, with and without copper particle, and at thermal aging and before thermal aging. Test conducted under uniform field sphere-sphere with lightning impulse voltage. Breakdown test were conducted according to ASTM 3300 standard for lightning impulse by using rising method. For thermal aging process, oil sample being heated at 100 °C for 100 hours. BDV for negative polarity was higher compared with positive polarity. Influence of thermal aging and void contamination shows that there was reduction in BDV of oil sample. Result shows that, although BDV for VCO under all condition is lower compared with MO, but it is still comparable and acceptable.

The transformer oil and impregnated paper are widely used as electrical insulation design of power transformers. The dielectric strength of the oil paper insulation in transformers may reduce with the high contamination level of cellulose particle in the transformer oil. Furthermore, it may generate partial discharge or even breakdown with particle accruement. This paper presents experimental studies on the effect of cellulose particles on AC breakdown voltages and Partial Discharge (PD) characteristic of palm oil (PO). A mineral oil (MO) was also tested and used as comparison. In total, liquids with three cellulose particle contamination levels, i.e. low, medium, and high were investigated. Results show that the AC breakdown strength of PO is comparable to that of MO at clean condition. Meanwhile, the presence of cellulose particles reduce the AC breakdown strength of both PO and MO. It is summarized that the particle effect on liquid breakdown is associated with increase of cellulose particle concentration and the viscosity of the liquid itself. Due to higher viscosity of PO, AC breakdown voltage of PO is less significant than that of MO. The analysis of PD data was conducted by utilizing Partial Discharge Inception Voltage (PDIV) and Phase resolved partial discharge (PRPD) patterns. The influence of cellulose particles on PD activity does not show much change, but there is slight increase the PDIV value. When subjected to particle, results from PD test show that the PD activity is mainly due to void discharge.

In this paper, a study is carried out to investigate the dielectric, physical and chemical properties of Palm Oil (PO) and Coconut Oil (CO) under open thermal ageing condition. The type of PO used in this study is Refined Bleached and Deodorized Palm Oil (RBDPO) Olein. The ageing experiment was carried out at 85 °C and 115 °C for 1, 3, 5, 7 and 14 days. Several parameters were measured such as AC breakdown voltage, dielectric dissipation factor, relative permittivity, resistivity, viscosity, moisture and acidity throughout the ageing duration. Based on the study, it is found that there are no significant changes on the AC breakdown voltages and relative permittivities for both RBDPO and CO. At ageing temperature of 115°C, there are clear reduction trends of dielectric dissipation factor for CO and resistivities for most of RBDPO. On the other hand, no clear trends are observed for viscosities, moisture and acidities of RBDPO and CO throughout the ageing duration.

In recent years, there are a number of studies that have been carried out to explore the alternative for Mineral Oil (MO) as dielectric insulating fluid in transformers due to the increasing tight regulation on safety and environment. Vegetable oils have been identified as suitable candidate since it is biodegradable, non-toxic and high flash/fire points which ensure more in-service safety. Among the types of vegetable oils considered for transformers application are Palm Oil (PO) and Coconut Oil (CO). This paper presents an experimental study on the lightning breakdown voltages of PO and CO under non-uniform electric field based on needle-sphere electrodes configuration at 3 small gap distances. The type of PO used in this study is Refined Bleached and Deodorized Palm Oil (RBDPO) Olein. The main focus of this study is to examine the lightning breakdown performance of RBDPO and CO under different test conditions and assess its suitability as dielectric insulating fluid in transformers. The effect of voltage polarities (positive and negative) and testing methods (risingvoltage, up-and-down and multiple-voltage) were investigated. The data obtained from all tests were analysed by Weibull distribution in order to determine the withstand voltages for each type of oils. It was found that the breakdown voltages of RBDPO and CO are comparable with MO under positive lightning impulse. Under negative lightning impulse, the breakdown voltage of MO is slightly higher than RBDPO and CO. There is no significant effect of testing methods and voltage polarities on lightning breakdown voltages of RBDPO and CO. Based on the statistical analysis, it is found that the breakdown voltages of RBDPO and CO at 1% probability are slightly lower than MO.

In recent years, there have been a number of interests on the Palm Oil (PO) and Coconut Oil (CO) as a potential alternative dielectric insulating fluid in transformers which stimulate different types of studies on these oils properties. Among the important studies is the lightning impulse properties. This paper presents the investigation on the lightning impulse breakdown voltage of PO and CO under non-uniform electric field. The PO used in this study is Refined, Bleached and Deodorized Palm Oil (RBDPO) Olein type. The influence of the testing methods, rising-voltage and up-and-down are investigated at 2 gap distances for both oils. It was found that the lightning breakdown voltage performance for some of the RBDPO and CO are comparable to MO.

A number of studies have been carried out previously to investigate the suitability of palm oil as dielectric insulation fluid in transformers. Among the important studies is the ageing performance of palm oil. In this paper, a study was carried out to investigate the dielectric properties of Refined Bleached and Deodorized (RBDPO) Olein after subjected to thermal ageing. A low temperature ageing was carried out at 85°C for 5 days. The AC breakdown voltage, dielectric dissipation factor, relative permittivity and resistivity of RBDPO were examined throughout the ageing duration. It was found that the RBDPO performs reasonably well under low temperature ageing.

The properties of Palm Oil (PO) and Coconut Oil (CO) offer the potential for transformers with non-toxicity, high fire and flash points and better environmental compatibility while compared with those filled with Mineral Oil (MO). This potential has led to intensive studies of electrical performance of biodegradable oil especially in evaluating the electrical performance under lightning impulse voltage in recent years. This paper presents the investigation on the impulse breakdown voltage of PO and CO in such a uniform field. The PO used in this study is Refined, Bleached and Deodorized Palm Oil (RBDPO) Olein type. Two testing methods, rising-voltage and up-and-down are considered for both oils with different gap distances (2.0 mm and 3.8 mm). Testing methods including rising-voltage method and up-and-down method have no notable influence on the breakdown voltages of RBDPOs and CO compared to MO.

Glass insulators, due to its diverse characteristics, were used widely around the world for high voltage transmission lines. Surfaces of the insulators are exposed to high electrical, mechanical, and thermal stresses over the period of service. Accumulation of contamination distort stresses distribution along the insulators that may lead to flashover under severe condition. In this paper, Obenaus pollution model has been adopted to propose a dynamic mathematical modelling to determine flashover critical voltage with regard to parameters such as pollution conductivity, arc length, and width of layer of contamination on the surface of glass insulator. In addition, laboratory experimental works have been carried out according to IEC60305 to validate the results from numerical approach, which indicate a good agreement.

The detection of heart abnormality activity of a patient is important when an abnormal symptom occurred. This project is aimed to detect the disease by using hybrid multilayer perceptron (HMLP) network. Several data from the electrocardiogram (ECG) signal is extracted to be set as input parameters. In order to get the best result, several activation function are used such as logistic, hyperbolic, exponential, step and square root. The result obtained is then compared among the activation function and other detection techniques.

Vegetable oils such as Palm Oil (PO) and Coconut oil (CO) are being considered as substitutions to mineral oil in power transformers. Lightning impulse strength is important for insulation design of power transformer and routine test for high voltage power transformer in industries. This paper covers the testing of the lightning impulse breakdown voltages of Coconut Oil (CO) and Palm Oil (PO) relative to Mineral Oil (MO) under quasi-uniform field. Furthermore, understanding the performance of breakdown voltages and electric field distribution in the insulating oil of a transformer during transient is important. Therefore, in this paper, electric field analysis was performed to evaluate the effect of the input voltage condition on electric field distribution. ANSYS software was used for perform electric field calculations based on the finite element methods.

Sustainable development is growing importance issues nowadays and requires the consideration of environmental criteria to develop of all new materials and equipment. A better balance must be found in properties of oils so that the impact on the environment can be minimized. In transformers, a stable liquid, inert, with good electrical and thermal properties is necessary and the liquid must be non-toxic to environment and readily biodegradable. The objective of this research is to make a comparative study of different vegetable oils: palm oil, corn oil, rice bran oil and analyze the dielectric properties such as relative permittivity, dielectric constant and resistivity with variation temperature 30°C-90°C and breakdown voltage with different ageing time 30 days, 90 days and 180 days. The dielectric properties data of the vegetable oils are compared with the transformer oil (mineral oil) and appropriate causes for similarities and different have been discussed.Sustainable development is growing importance issues nowadays and requires the consideration of environmental criteria to develop of all new materials and equipment. A better balance must be found in properties of oils so that the impact on the environment can be minimized. In transformers, a stable liquid, inert, with good electrical and thermal properties is necessary and the liquid must be non-toxic to environment and readily biodegradable. The objective of this research is to make a comparative study of different vegetable oils: palm oil, corn oil, rice bran oil and analyze the dielectric properties such as relative permittivity, dielectric constant and resistivity with variation temperature 30°C-90°C and breakdown voltage with different ageing time 30 days, 90 days and 180 days. The dielectric properties data of the vegetable oils are compared with the transformer oil (mineral oil) and appropriate causes for similarities and different have been discussed.

Ultra-high frequency (UHF) partial discharge sensors are widely used for conditioning monitoring and defect location in insulation system of high voltage equipment. Designing sensors for specific applications often requires an iterative process of manufacturing, testing and mechanical modifications. This paper demonstrates the use of finite-difference time-domain (FDTD) technique as a tool to predict the frequency response of UHF PD sensors. Using this approach, the design process can be simplified and parametric studies can be conducted in order to assess the influence of component dimensions and material properties on the sensor response. The modelling approach is validated using gigahertz transverse electromagnetic (GTEM) calibration system. The use of a transient excitation source is particularly suitable for modeling using FDTD, which is able to simulate the step response output voltage of the sensor from which the frequency response is obtained using the same post-processing applied to the physical measurement.

Heart abnormality often occurs regardless of gender, age and races. This problem sometimes does not show any symptoms and it can cause a sudden death to the patient. In general, heart abnormality is the irregular electrical activity of the heart. This paper attempts to develop a program that can detect heart abnormality activity through implementation of Multilayer Perceptron (MLP) network. A certain amount of data of the heartbeat signals from the electrocardiogram (ECG) will be used in this project to train the MLP network by using several training algorithms with Tansig activation function.

Insulation oils are a vital part in power transformers. Insulation oil is not only work as electrical insulation but also as a coolant inside the transformer. Due to the increasing tight regulations on the environment and safety in recent years, vegetable oils are being considered for insulation oils in power transformer. This paper presents two conditions of Rapeseed Oil (RO), which are as received (new) and dried (dry) under difference uniform field electrodes configuration (mushroom-to-mushroom and sphere-to-sphere) with gap distance at 2.5 mm as recommended by the international standards. A comparative study of AC breakdown voltage, dissipation factor (tan δ), and resistivity under variation of temperature were investigated. The experimental works were done according to the IEC 60156 and IEC 60247 standards. The results indicated that the breakdown voltages of both condition are comparable to mineral oil. The dielectric constant and resistivity of two conditions are decreased along with the increasing temperature. However, the dissipation factor properties rose up along with the temperature. The Weibull distribution was used to determine the withstand voltages at 1% and 50% for RO in two probabilities conditions.Insulation oils are a vital part in power transformers. Insulation oil is not only work as electrical insulation but also as a coolant inside the transformer. Due to the increasing tight regulations on the environment and safety in recent years, vegetable oils are being considered for insulation oils in power transformer. This paper presents two conditions of Rapeseed Oil (RO), which are as received (new) and dried (dry) under difference uniform field electrodes configuration (mushroom-to-mushroom and sphere-to-sphere) with gap distance at 2.5 mm as recommended by the international standards. A comparative study of AC breakdown voltage, dissipation factor (tan δ), and resistivity under variation of temperature were investigated. The experimental works were done according to the IEC 60156 and IEC 60247 standards. The results indicated that the breakdown voltages of both condition are comparable to mineral oil. The dielectric constant and resistivity of two conditions are decreased along with the increasing...

This project will explain and develop an understanding about magnetic refrigeration which uses solid materials as the refrigerant. These solid materials demonstrated the end product known as magneto caloric effect, which resulted in the increasing and decreasing of temperature when magnetized or demagnetized of the magnetic field. Inside these materials, a major change occurred at the entropy which can be manipulated by the application or removal of the magnetic field. Thus, magnetic refrigeration is based on a fundamental thermodynamic property of the magnetic materials. Additionally, to study the effectiveness of La0.7Pr0.3Fe11.6Si1.4 by comparing to commercial Gadolinium have been implemented. The study finds that the high temperature annealing is more beneficial compared to the low temperature annealing in terms to produce high quality of structure in order to improve magnetic refrigerator performance.

Most of power transformer design today is still using oil filled type which laminated iron core with paper insulated copper conductors. Oil is an important part in power transformers as electrical insulation, information carrier and cooling medium. Besides oil, paper insulation also plays important role as dielectric material of transformer. The influence of oil especially vegetable-based oil and paper insulation on the dielectric strength of transformer oil has attracted many researchers to do investigation. This paper presents a study of the quasi-uniform field AC breakdown voltages under bare electrodes, paper insulation for barrier and covered electrodes (to replicate the transformer windings) of Palm Oil (PO), Coconut Oil (CO) and Mineral Oil (MO). The data obtained from all tests were analyzed using Gaussian and Weibull distribution to determine the withstand voltages for each type of oils. The experiments were using test cell as specified by IEC 156 with 2.5 mm gap distance under uniform field.

Vegetable oils are being considered as potential alternatives to mineral oil, due to their better environmental performance and for their high fire point. Although these liquids have been used in distribution transformer, it is still a significant step to adopt vegetable oils in power transformer due to high cost and high level of safety and reliability required in service for these units. Vegetable oils such as Palm oil (PO), Corn oil (CO), and Rice Bran oils (RBO) offer suitable alternative for mineral oil. It is anticipated that most of the un-aged oil could satisfy the minimum requirement for dielectric insulation liquids in transformer. However, since transformers in service could be subjected to heat and multiple environmental parameters, the oil could be subjected to ageing. The chemical properties of the oil may change and its performance could be affected by the presence of ageing-by-products such as moisture and acids. Therefore, considering the application of new dielectric insulation liquids such as PO, CO and RBO in transformer, it is crucial to first examine its ageing performances at laboratory level. This paper focused on the effect of ageing on the electrical and physicochemical properties of PO, CO, and RBO. Sealed ageing experiments were set at 90°C for 30 days, 90 days and 180 days. Before the ageing process, the samples were dried in a vacuum oven at pressure less than 0.8kP at 85°C for 48 hours in order to remove the moisture content in the oils. Then the oils were impregnated with the Kraft paper and continue to age for selected duration time. The electrical properties (relative permittivity, dielectric losses, resistivity and breakdown strength), mechanical properties (viscosity and tensile strength) and chemical properties (moisture and acidity) of the oils were measured throughout the ageing periods. It can be concluded that the laboratory accelerated thermal ageing experiment reveals that all vegetable oils in this study are resistant toward oxidation based on the stable viscosity and low acidity measurements of vegetable oils throughout the ageing duration even with the presence of oxygen. The AC breakdown voltages of vegetable oils can still comply with the recommended limit of new vegetable oil set by ASTM 6781 even after subjected to ageing. In general most of properties of vegetable oils are comparable with mineral oil.

Dissolved gas analysis (DGA) is often use by theutility companies to monitor the health and to detect any faults of their transformers. The concentration and proportion of various gases dissolved in the oil are used to indicate whether there is an electrical or thermal fault within the transformer. A lot of data have been published in the literature on DGA levels for a mineral oil. However, the data for vegetable oils are relatively sparse even though the vegetables oils have been used for more than 10 years in distribution transformers. In this paper, the concentration of dissolved gasses under electrical performance in rice bran oil (RBO) and palm oil(PO) were investigated. These two oils were selected since they show promising potential as alternative insulating dielectric liquid for transformer and easily obtained in Malaysia. Three different gaps (2.5mm, 5mm and 10mm) with sphere to sphere configuration were used in this study. The samples were filtered for three times and dried at 85°C for 48 hours before testing. The AC breakdown experiments were performed in the high voltage laboratory for 100 times. The dissolved gasses from the electrical breakdown voltages were obtained in 2 liter sealed test cell. The gasses concentrations were measured using Gas Chromatography equipment. There were six concentrations of gases contained in the samples which are Hydrogen (H2), Methane (CH4), Ethane (C2H6), Ethylene (C2H4), Acetylene (C2H2) and Carbon monoxide (CO). These gasses were interpreted using IEC ratio, Roger ratio, Dornenburg ratio method and Duval Triangle method in order to investigate whether the existing techniques are suitable for RBO and PO. From the experiments, C2H2 and H2 were the highest amount of gases detected for all samples. The Duval triangle method is the best method in detecting the fault for these oils under electrical breakdown. However, the ratio methods have some limitation in predicting the faults.

In recent years, silicone rubber (SIR) insulators are use widely on high voltage transmission lines, particularly in heavy polluted environment. The performance of SIR in highly dependent on electric field profile that may lead to other serious problem such as ageing and flashover phenomenon. In this paper, electric field and potential distribution around insulator profile were computed using finite element method approach. Insulator geometrical profile i.e. shed radius, inclination angle, width and length has been varied and analyzed. Simulation results reveal that electric field is greatest at area near to the ground and high voltage terminal. Several recommendations have been proposed on insulator profile in achieving optimized electrical performance of the insulator.

Interests on nanomaterials for enhancing the insulation properties of dielectric liquid are growing in recent years. This paper presents experimental studies dealing with the influence of carbon nanotube (CNT) nanomaterials in AC breakdown voltages. The observations of AC electrical breakdown voltages of CNT disperse in mineral oil at 2.5mm gap distance were recorded. Five different amounts of concentrations of CNT in mineral oil are within the range from 0.01 to 0.20g/L. By analyzing the AC breakdown voltage using normal distribution, the probability of breakdown failure can be estimated for designing insulation in transformer. In order to test the validity of normal distribution, Shapiro-Wilk technique was used in this experiment. Based on the investigations, it is shown that 0.01g/L and 0.05g/L CNT nanofluids were possible to enhance dielectric strength of mineral oil. These three concentrations are considered to have a greater potential to be as alternative transformer oil. However, as for 0.10g/L and 0.20g/L CNT nanofluids, AC breakdown voltages show the opposite outcome.