The ltration algorithm has recently been introduced as a way of increasing the speed of ab initio modelling calculations using Cartesian Gaussian basis functions. It works by developing a novel set of basis functions which are constructed specifically for the system being modelled. It has been implemented in the ab initio density functional theory based modelling package AIMPRO. The standard ltration process is found to be accurate when the ltration radius is increased to at least 10 Bohr radii in silicon. The standard ltration process uses all the basis functions centred on points inside a sphere centred on each atom in turn. By rejecting some of these functions (a trimming process), the ltration process can be speeded up, however there will be a resulting loss of accuracy. Three approaches to developing a ltered basis for an atom are considered, and compared. The most successful criterion for function trimming is found to be where functions are kept which exceed a threshold value on the surface of a sphere. Structural optimisation using ltration produce accurate nal structures, even when using parameters that give rise to poorly converged absolute energies. For the most time consuming elements of a calculation, a rapid ltration process is possible. However, very poor ltration thresholds introduce small inconsistencies between energies and forces, which can make optimisation difficult if algorithms are chosen that use both the energy and force. Algorithms that only use forces are implemented, and shown to be stable and produce accurate structures. This is further demonstrated using a new implementation of the Lanczos method for determining transition states. This is compared against the current AIMPRO method, the nudged elastic band. The new method is far superior in terms of speed, and offers greater stability towards the end of calculations.

Surface waves are electromagnetic waves that are bound to the interface between to media. Zenneck surface waves, the subject of this thesis, have been known about for more than a century. Most recent research has been either very academic in nature or has focused on how to attenuate or stop them propagating with surface waves in general being considered a nuisance and an inefficiency. However, it is the opinion of the author that the Zenneck surface wave has several properties that could provide significant advantages over traditional three-dimensional (3D) wireless communications techniques and one-dimensional (1D) wires in some applications. Yet, to date, no one has utilised its unique and potentially highly useful properties. This research has extended the many existing studies to much higher frequencies, for the first time practically demonstrating Zenneck surface wave propagation above 20 GHz. It has also produced pioneering proof of principle demonstrations at 24 GHz and 60 GHz to prove the assertion that Zenneck surface waves are a viable alternative to existing wired and wireless solutions. To the author’s knowledge, this is the first piece of work to quantitatively assess the loss associated with corners through either simulations or measurements. It is this author’s assertion that this research has reinvigorated Zenneck surface waves as an area of research with Newcastle University recently employing a PhD student to study the utility of Zenneck surface waves for on-chip and off-chip interconnects.

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Application of wide-area monitoring and control for future smart grids with substantial wind penetration and advanced network control options through FACTS and HVDC (both point-to-point and multi-terminal) is the subject matter of this thesis. For wide-area monitoring, a novel technique is proposed to characterize the system dynamic response in near real-time in terms of not only damping and frequency but also mode-shape, the latter being critical for corrective control action. Real-time simulation in Opal-RT is carried out to illustrate the effectiveness and practical feasibility of the proposed approach. Potential problem with wide-area closed-loop continuous control using FACTS devices due to continuously time-varying latency is addressed through the proposed modification of the traditional phasor POD concept introduced by ABB. Adverse impact of limited bandwidth availability due to networked communication is established and a solution using an observer at the PMU location has been demonstrated. Impact of wind penetration on the system dynamic performance has been analyzed along with effectiveness of damping control through proper coordination of wind farms and HVDC links. For multi-terminal HVDC (MTDC) grids the critical issue of autonomous power sharing among the converter stations following a contingency (e.g. converter outage) is addressed. Use of a power-voltage droop in the DC link voltage control loops using remote voltage feedback is shown to yield proper distribution of power mismatch according to the converter ratings while use of local voltages turns out to be unsatisfactory. A novel scheme for adapting the droop coefficients to share the burden according to the available headroom of each converter station is also studied. The effectiveness of the proposed approaches is illustrated through detailed frequency domain analysis and extensive time-domain simulation results on different test systems.

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Most of the high voltage cables installed in the United Kingdom for power transmission and distribution are approaching the end of their designed life. This is likely to lead to an increased prevalence of circuit faults resulting directly from insulation degradation and breakdown due to ageing. This will lead to customer interruption and regulatory penalties. A program for the wholesale replacement of vast cable networks is impracticable, not economically viable and most likely unnecessary. A more pragmatic and affordable approach to extending the life time of these ageing assets, incorporating targeted cable replacement, may be achieved through the use ofcondition based maintenance strategies utilizing online partial discharge monitoring technologies. Partial discharges (PD) are the early symptoms of insulation degradation that can ultimately lead to complete breakdown of the insulation system. Presented in this thesis are novel contributions to the area of online PD diagnostics for underground medium voltage cables. The work encompasses various issues with installation of PD sensors in cable networks, data acquisition procedures and signal processing techniques for post processing of PD data. A novel approach of using power frequency current transformer for detecting PD is proposed. This approach is validated using laboratory tests and on-site trials using the PD monitoring hardware developed. PD source location using double ended method is widely accepted due to theaccuracy in discharge site location compare to single ended approach. However, this method is not widely used due to its complex system design, time synchronization and communication requirement between measurement units at both ends of the cable network. In this thesis, double ended PD source location system using a novel time based triggering logic is implemented in field programmable gate arrays with GPS. System design, laboratory results and on-site trials are presented. Denoising of PD signals using second generation wavelet transform are comparatively faster than classical wavelet based techniques. This second generation wavelet transform using kurtosis based thresholding is developed and tested using synthetic and on-site data. A PD signal interpretation algorithm is applied to analyse the data acquired from the 11kV PILC cable network from 33/11kV substation using the system developed.

This thesis is concerned with the use of Artificial Intelligence techniques to support human designers. The thesis argues that support for human designers can be improved by adopting an AI-based rather than a geometry-based approach to engineering design. Design Support Systems (DSSs) are proposed as an effective means of delivering this improved support. Representing and reasoning about tolerance statements in design is introduced as a valid area to test these claims. Tolerance statements describe the allowable variations in the geometry of a designed artefact. Two distinct, but related problems involving the use of tolerance statements in design are tackled, namely: tolerance combination (including the way tolerance distributions combine), and tolerance allocation. The problem of tolerance combination (and distribution) involves determining the necessary consequences of the application of known tolerance statements to one or more designed artefact features. Tolerance allocation concerns the assignment of tolerance statements during the design process. Solutions to this second problem are essential before manufactured instances of designed artefacts can be tested for compliance with design descriptions. The use of an experimental DSS, the Edinburgh Designer System (EDS), to solve design problems is illustrated. The implementation of techniques to improve the support of tolerance combination and tolerance allocation is described and where possible has been tested using EDS. The way that design is situated within the product creation process is investigated and the derivation of parts list information from an EDS design description is demonstrated. The thesis concludes that the AI-based approach can improve support for human designers, but that further research will be required to demonstrate the effective delivery of this support through DSSs.

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This thesis is concerned with the use of Software Engineering abstraction constructs to help in the process of understanding computer programs that are built as part of experiments in the Symbolic Paradigm. It is also concerned with developing and testing a method to analyse these programs in an organised and structured way. In a series of three experiments, the use of abstraction constructs to help the process of transforming a program to a more abstract form, and how to do this in a structured way, was incrementally investigated. This involved first exploring the use of abstraction constructs to achieve higher degrees of abstraction in a small example; the next step was to use the understanding of their use and of how to transform a program in a bigger exanple, from which a more clearly defined role of the abstraction constructs, and an initial scheme for transforming a program, was achieved; the last step involved investigating a complete form of an analysis procedure to analyse experimental programs built by incremental prototying, and that is supported by the use of abstraction constructs. The result is the Prototype Analysis Method (PAM): a static analysis method to help in the understanding of incrementally built experimental computer programs in AI. An essential part of this method is a transformation process that is supported by the use of Software Engineering abstraction constructs, and of test sets from dynamic analysis for validation. This research clearly demonstrates the successful application of Software Engineering abstraction constructs is an important aspect of AI research. Results from this research also point to further interesting issues such as the relation between Knowledge Level descriptions and abstract Symbol Level descriptions.