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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.

In compliance with the green energy policy, mitigation from high fossil fuel dependency is becoming a new objective for most countries, including Malaysia. Wave energy is among extensively explored renewable energy relatively clean, sustainable, and inexhaustible resources. To this day, neither definite wave energy technology nor widely available commercial wave farm supplying the grid has existed. Therefore, wave energy harvesting is the most compelling solution, especially in regions where the possibility of grid connection is low in the nearest future. Like other renewable energy, the voltage amplitude and frequency generated from waves are unstable and may vary continuously. This uncertainty has created energy transfer challenges since the grid requires a stable and uninterrupted energy supply. Therefore, power electronics devices are employed to modulate the controller circuits' pulse width. Further understanding of the relationship between wave energy conversion technology and its power conversion, particularly for nearshore applications, is summarized. This work also discussed selected wave energy conversion research and power conversion system implemented and studied in Malaysia. Finally, this review can provide extensive overview and broad understanding into power conversion system for Wave Energy Conversion, especially for nearshore applications.

Ultra high frequency (UHF) partial discharge sensors are widely used for condition monitoring and defect location in the insulation systems of high voltage equipment. Designing sensors for specific applications often requires an iterative process of manufacture, test, and mechanical modifications. This paper demonstrates the use of finite-difference time-domain (FDTD) simulation as a tool to predict the frequency response of a UHF sensor design. 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 modeling approach is validated using a broadband UHF sensor calibration system, which uses the step response of the sensor to determine its frequency-domain transfer function. 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. Comparisons between simulation and measurement are made for three different sensors, demonstrating sensitivity agreement to within about 10%. Some examples of simple parametric studies carried out using the FDTD model are also presented.