Papers by Keyword: Transformer

Abstract: 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.

Abstract: In city, identification for 3 phase-4 wires power distribution lines is difficult due to compound installation of overhead and underground lines, transposition, bad view caused by trees or big buildings. It is necessary that the correct and fast identification method is required for load balancing among distribution lines. Tracing off-line method with high power impulse signal injection has been used recently. Our proposed method uses to identify live lines with very small power high frequency signal injection based on data communication technology. Two end communication terminals are required to be synchronized between them for determination on electrically same phases. Challenging issue is to achieve synchronization without GPS providing synchronizing time. A novel power transformer and phase identification system is designed and implemented. The system consists of a transmitter and a receiver with power-line communication module. Some experiments are conducted to verify the theoretical concepts in a big commercial building.

Abstract: This paper describes multi-band low noise amplifiers (LNAs) utilizing input matching transformers. We investigate a conventional dual-band LNA circuit utilizing a transformer, and show our analysis and simulation results for its circuit. Based on this, we propose a triple band LNA with transformers. We have calculated characteristics of the dual-band and triple-band LNAs. As the results, the LNAs show gain of 20dB while maintaining good input matching, in the frequencies at 2.59GHz, 3.50GHz and 5.41 GHz. Then we discuss configuration and design of coupling coefficients of the transformers.

Abstract: The electromagnetic field of the active part of oil-immersed transformers 160kVA and 630kVA has been modelled in the present paper. Finite element method and ANSYS program have been employed for the field modelling. Based on the created model, the field distribution with values of the magnetic flux density has been obtained, as well as the Joule losses have been calculated. Two variants of the model - with and without tank are studied and compared.

Abstract: The world’s energy requirement has been dominated by petroleum oil resources for years in many applications, especially in the area of electricity generation and utilization. Mineral oil application in power system equipment can be potentially hazardous to the environment, especially when there are incidents of transformer explosion, which caused spillages of oil to the soils or water streams and thereby pollute the surrounding environments. This paper is aimed at finding a substitute for the use of mineral oil as transformer oil. Experiments on breakdown voltages, flash points, pour points, viscosities, densities and insulation resistances on conventional mineral oil and some selected vegetable oils were conducted, analyzed and compared to the internationally accepted standards, ASTM (America Standard Test of Material). Rubber seed oil, Palm oil, Mellon oil, Ground oil and Palm kernel oil were found to have good electrical, chemical and thermal properties which the transformer oil has.

Abstract: The combination of solid insulation (usually cellulose paper) and liquid insulation (usually mineral oil) yield good dielectric properties at fair cost. However, arising concerns on environmental effect of mineral oil when leakage and its risk of fire has force researches for alternative fluids. One of the suitable options for replacement of mineral oil is biodegradable oil that is plant-based, high biodegradability, non-toxicity and high fire point. Some refining and modification to crude vegetable oils resulting to suitable transformer dielectric fluid such as BIOTEMP®, ENVIROTEMP® FR3 and PFAE (palm fatty acid ester). Application of these oils in small scale distribution transformers give positive feedback so far, hence, led to development of biodegradable oil-based large power transformer. Monitoring of the oil for power transformer is important to ensure its reliability and avoid unnecessary cost of failure. Dissolved Gas Analysis (DGA) is one of the methods for oil monitoring of transformer. This method analyzes oil condition to detect incipient faults so that relevant actions can be made before actual failures occur. This paper will review the hydrocarbon gases or known as faults gases for monitoring and faults diagnosis for mineral and biodegradable oil-filled transformer. Past works about DGA on biodegradable oil such as sunflower, soybean, and corn oil are analyzed. Any different on gases production of oil through different tests will be discuss further in this paper.

Abstract: Distribution transformer in Malaysian electricity network is categorized as major element on delivering electricity throughout the nation. Advanced diagnostic tools are used to monitor any technical problem of transformer to sustain its capability in the long run. One type of it which is currently being used in worldwide is Frequency Response Analysis (FRA). The reliability from this method is proven worldwide in diagnosing transformer condition especially a mechanical movement. FRA technique is done by comparing the response result in transformer initial condition to its current condition. The interpretation of transformer condition from the response is based on frequency sub-bands. Each frequency sub-bands are indicating any movement parts of transformer and electrical faults. Currently, there are three worldwide standards established for interpreting the FRA results but both of them are different in frequency sub-bands range. Up to now, there are no research papers comparing the fault detection capabilities from frequency sub-bands range for both standards. In this paper, comparative study is done to visualize and interpret the capabilities from three standards (IEEE Std C57.149 2012, DL/T911-2004 and Cigre WG A2/26); by focus on the frequency sub-bands range.

Abstract: The article examines the methods of calculating capacitive currents in a measuring transformer based on a resistive voltage divider. The developed methods may be used to optimize the design of resistive dividers.

Abstract: Insulation is one of the most important parts in the power transformer. Palm oil impregnated paper is investigated to replace the mineral oil impregnated paper due to the high viscosity of palm oil compared to the viscosity of the mineral oil. This paper discussed on ultrasonic radiation technique that was used to reduce the viscosity of the vegetable oil (palm oil) for transformer insulation application. The ultrasonic equipment produces 500W heating power, 240W ultrasonic power at a fixed frequency of 40 kHz. Ultrasonic radiation was applied on oil samples at 30 °C, 50 °C and 75 °C by using the sonicator water bath for several periods of time. The results show up to 42.6 % reduction from the original viscosity of palm oil and proved to have a long term effect on the viscosity of palm oil. The cavitation bubbles that occur in the sample during radiation is one of the mechanism in viscosity reduction.

Abstract: The interests in multiphase (more than three) system are escalating recently especially in the motor drive applications. Thus, this paper introduces the graphical phasor diagram method in designing the multiphase transformer connection. The proposed method eases the design process of the static multiphase transformer that produces multiphase output from the standard three phase input. The transformer connection was simulated in ANSYS Maxwell and the multiphase waveform with appropriate phase angle was obtained. The design of five-phase transformer using graphical phasor and simulation results from the finite elements software are presented in this paper.