Contribution for the Study of Inductive Fault Current Limiters in Electrical Distribution Grids

Inductive type fault current limiters with superconducting tapes are emerging devices that provide technology for the advent of modern electrical grids, helping to mitigate operational problems that such grids can experience as well as preventing the often-costly upgrade of power equipment, namely protections. The development of such limiters leads to several design challenges regarding the constitutive parts of those devices, namely the magnetic core, primary winding and superconducting secondary. Fault current limiters are required to operate at overcurrents during a certain amount of time. The operation at such currents can lead to harmful effects due to mechanical, electromagnetic and thermal stresses, especially in the superconducting tape. Since the operation principle of fault current limiters envisaged in this thesis is based on the superconducting-normal transition of superconducting materials, the study of its transient behaviour is an important research subject. In this work, an electromagnetic methodology based on the characteristics of the constitutive parts of the limiters, previously developed and compared to finite element modelling simulations with very similar results, is simulated and validated with experimental results. Furthermore, the current in the superconducting tape is modelled from experimental results with the purpose of predicting the temperature of the material during normal and fault operation conditions, by employing a thermal-electrical analogy. These results are also compared to experimental measurements. A fast simulation tool, with computation times in the order of minutes, is also developed in Simulink, from Matlab environment. With the developed simulation tool, it is possible to quickly predict the transient electromagnetic-thermal behaviour of an inductive type fault current limiter operating in electrical grids, namely the line current and primary linked flux, as well as current and temperature in the superconducting tape

Design and development of auxiliary components for a new two-stroke, stratified-charge, lean-burn gasoline engine

A unique stepped-piston engine was developed by a group of research engineers at Universiti Teknologi Malaysia (UTM), from 2003 to 2005. The development work undertaken by them engulfs design, prototyping and evaluation over a predetermined period of time which was iterative and challenging in nature. The main objective of the program is to demonstrate local R&D capabilities on small engine work that is able to produce mobile powerhouse of comparable output, having low-fuel consumption and acceptable emission than its crankcase counterpart of similar displacement. A two-stroke engine work was selected as it posses a number of technological challenges, increase in its thermal efficiency, which upon successful undertakings will be useful in assisting the group in future powertrain undertakings in UTM. In its carbureted version, the single-cylinder aircooled engine incorporates a three-port transfer system and a dedicated crankcase breather. These features will enable the prototype to have high induction efficiency and to behave very much a two-stroke engine but equipped with a four-stroke crankcase lubrication system. After a series of analytical work the engine was subjected to a series of laboratory trials. It was also tested on a small watercraft platform with promising indication of its flexibility of use as a prime mover in mobile platform. In an effort to further enhance its technology features, the researchers have also embarked on the development of an add-on auxiliary system. The system comprises of an engine control unit (ECU), a directinjector unit, a dedicated lubricant dispenser unit and an embedded common rail fuel unit. This support system was incorporated onto the engine to demonstrate the finer points of environmental-friendly and fuel economy features. The outcome of this complete package is described in the report, covering the methodology and the final characteristics of the mobile power plant