Monomers, polymers, charge-transfer complexes of 2-benzylidene-1,3-dithioles (Dithiafulvenes), and 1,3-dithiolium (Dithiafulvenium) salts of dithioesters and poly(dithioesters) were synthesized. The infrared, nuclear magnetic resonance (NMR) and ultra violet spectra of these materials were also reported. Condensation polymerization of piperidinium tetrathio terephthalate with α-halocarbonyl compounds using phase-transfer techniques yielded poly(dithioesters) that upon dehydrative cyclization with sulfuric acid gave poly(1,3-dithiafulvenium) salts. Polymerization of substituted dithiafulvenes with diacid chlorides, p-phenylene diisocyanate or terephthalaldehyde yielded polymers with inherent viscosities of 0.10 dL/g to 0.21 dL/g. The electric resistivity of the charge-transfer complexes of several dithiafulvenes and the electron donors TCNQ and TNF measured by the two-probe method was found to be >10⁶ Ω.cm at room temperature, hence behaving like insulators. Polyesters and polyesterimides of 4,4'-sulfonyl diphenol were synthesized. The low molecular weight polymers had viscosities of 0.12 to 0.20 dL/g. The polymers formed brittle films and their IR and NMR spectra were reported.

No description available.

A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering Degree awarded with distinction on 8 December I998 Johannesburg, 1998 / This report discusses high phase order (HPO) technology, i.e. the use of more than the conventional 3 phases for transmission of electric power, its use in the compaction of lines, and power density maximization over existing servitudes. It is structured in four parts. The first part introduces the concepts, establishes the need, and lists the advantages ofHPO. The second part deals with the technology itself and shows that it is possible to analyze HPO systems using symmetrical component analysis, lists common transformer configurations, covers protection, and so on. The third part analyses 5 case studies, the first 3 being analytical, and the last 2 being the first experimental test line, and the world's :first utility application ofHPO lines. The fmal section is a South African case study and compares an HPO line to an existing 400 kV 3-phase line and shows that the former is 87.5% more expensive to implement than the latter. Comparing the 3-phase and 6-phase lines on a more even basis, yielded a breakeven distance of225.86 km, above which the 6-phase option becomes more economical. These results are then explained and discussed in the conclusions section.

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in ful lment of the requirements for the degree of Master of Science in Engineering. June 2016 / It has been reported in literature that newly installed cable accessories can pass typical commissioning tests and yet show signi cant PD activity leading to premature failure in the long term. This research report details the partial discharge (PD) characterisation of three arti cial defects in MV cable terminations, at both power and very low frequency (VLF). The defects included a semi-conductor feather, a tram line in the cross-linked polyethylene (XLPE) insulation and an XLPE ring cut. The experimental methodology involved subjecting the terminations to a standard overvoltage withstand test, after which the PD activity was monitored, at 0.1 Hz and at 50 Hz excitation frequencies. All the defects passed the overvoltage test, despite some showing signi cant discharges. The defects gave distinct phase-resolved PD patterns that are e ectively invariant of excitation frequency. The PD magnitudes at power frequency were typically bigger than at VLF, while the PD inception voltages tended to be lower at VLF. The PD magnitudes of the semi-conductor feather defect surface discharges were found to increase with increasing applied voltage, while no increase was observed for the tram line and ring cut void discharges. The results show that common installation defects in MV cable terminations can be suitably characterised using VLF PD measurements / MT2016

With the increased attention on high efficiency and energy savings, power electronic energy conversion equipment is increasingly incorporated in all levels of the power system. The drawback of such equipment is the generation of nonsinusoidal currents in the power distribution network due to the nonlinear operation. Harmonic currents may distort the line voltages and lead to several unwanted effects including equipment overheating, system failure, interference with communication systems, etc. In response to these concerns, this research presents an active filter for the cancellation of harmonic line current distortion. The active filter used in this research is connected in parallel with the nonlinear load and is designed for a three-phase three-wire industrial power system. The filter consists of a voltage source inverter connected through a coupling inductor to the terminals of the ac-source. The inverter is controlled via a space vector-pulse width modulation (SVPWM) algorithm that is generated using a digital signal processor (DSP). In order to reduce the distortion resulting from the switching nature of the active filter inverter, a switching ripple filter is connected in parallel. The control algorithm of the active filter is based on the rotating reference frame theory. For each harmonic which is to be cancelled, a corresponding synchronous reference frame is generated to extract the harmonic phase and magnitude. With this information, each harmonic current component can be separately controlled and the proposed algorithm can therefore compensate for hardware effects such as measuring delays and component transfer functions. For the extraction of the harmonic components, a finite impulse response filter is used in order to quickly react to changing load currents. An adapting algorithm is implemented to compensate for slowly varying system parameters. Simulations under varying load and transient conditions are performed. The results show nearly perfect cancellation performance for the proposed active filter control algorithm. / Graduation date: 2001

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 178-186).

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references (leaves 33-35). Also available in electronic version. Access restricted to campus users.

Thesis (M. Sc.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 74-78).

Thesis--M. Phil., University of Hong Kong, 1981.

Thesis (M. Phil.)--University of Hong Kong, 1988.