The effectiveness of single-pole autoreclosure in maintaining power system stability is largely determined by the speed with which secondary arc extinction and hence autoreclosure can be achieved. Realistic simulation techniques are of obvious importance in relation to the design of systems employing single pole autoreclosure and, in this thesis, digital methods are developed to enable the faulted response of e.h.v. feeders subjected to secondary arcing phenomena to be more realistically simulated than hitherto had been possible. The new techniques are also of importance in relation to programmable based protection test equipment. The realistic simulation of the secondary arcing phenomena is of obvious importance in relation to pre-determining the shunt reactor compensation necessary to achieve acceptable autoreclosure dead-times in long line applications. Based upon experimental data, methods of modelling the non-linear behaviour of the earth fault arc path in both conducting and extinction states are described, together with the techniques developed for incorporating such models into practical e.h.v. system interconnections. The thesis concludes by illustrating and discussing the results of computational studies relating to typical 500 kV feeders employing single-pole autoreclosure.

The main aim of this work is to demonstrate that communication-type equipment systems can effectively be simulated on a digital computer. A time domain digital simulator ICOSS is first developed. ICOSS provides a facility for interactive simulation of most receiver/transmitter types of communication structure, by specifying individual signal processing modules, each of which can be described mathematically. Simulation using ICOSS operates interactively where the user can construct, edit, change some of the parameters, run the program and look at the result in one simulation session. ICOSS, being a time domain digital simulator is capable of handling feedback operation and stochastic processes. The examples of simulation in this thesis are more inclined towards solving some of the practical problems encountered in developing certain communication equipment systems. The work also includes the investigation by computer simulation of some practical problems which are difficult or impossible to measure effectively in practice, but which can be investigated by means of computer simulation. The simulation results clearly show that system studies by simulation provide a simple and effective approach to system design before the final system is actually built in the laboratory. In the simulation process, the analytic signal lowpass equivalent is used because it is a powerful and cost effective modelling technique for communication system. The thesis begins in chapter one with the introduction of the modelling concept and various areas of simulation that can be applied in communication. Chapter two describes briefly the theory and operation of the phase locked loop and its fast acquisition technique, which are used in the simulation work of later chapters. Analytic signal and lowpass equivalent modeling techniques used throughout the simulation work are demonstrated at the beginning of chapter three. Chapter three also introduces ICOSS - the time domain interactive Communication System Simulator, developed at the School of Electrical Engineering, University of Bath. Its structure, implementation and operation are described. The development of ICOSS is tested by simulating practical systems, that is, a phase locked loop and its fast acquisition technique, and comparing the simulation and practical results as implemented in chapter four. The significance of the sampling frequency in computer simulation, and subsequently its effect on computer processing time and cost is also demonstrate in chapter four by carrying out various simulation tests. One of the main aims of modelling is to model a system with the minimum number of sample points, in order to reduce the amount of computation and hence valuable computing time. Chapter five investigates by simulation the effect of noise, a typical example of a stochastic process, on the performance of the phase locked loop and its fast acquisition loop. The results are compared with practical measurements. In a practical case, it is difficult to monitor and measure the loop performance at low signal to noise ratios, but it can be performed easily by using computer simulation. Chapter six simulates the effect of time delay on the acquisition performance of the phase locked loop and its fast acquisition technique. The effect of delay in the loop is particularly important because it is difficult and almost impossible to investigate effectively in a practical system. Chapter seven concludes by summarising the work and results of simulation of the preceding chapters, including future development of ICOSS. Appendix A provides a brief instruction guide to the use of ICOSS for future users.

The advantages of series capacitor compensated lines in long distance transmission are well known. There are, however, problems encountered in the protection of such lines and these basically arise because, under faulted conditions, the primary system parameters are often subjected to rapid changes due largely to capacitor protective gap operation. The successful longer term development of new transmission line protection techniques is heavily dependent upon a detailed knowledge of the behaviour of practical compensated e.h.v. feeder configurations. In this thesis methods have been developed for accurately simulating the responses of series compensated system using digital simulation techniques based on frequency domain methods. The digital simulation of practical series compensated systems with shunt reactors has hitherto presented a particularly difficult problem. This thesis highlights these problems and outlines the basis of the techniques which have been developed to overcome them. In particular, the basis of some of the novel techniques developed for simulating the essentially random nature of series capacitor spark gap operation together with the non-linearities associated with single pole autoreclosure techniques has been explained. Interesting results relating to the responses of a practical 500 kV long distance transmission interconnection and its effect on the performance of modern distance protection has been presented. By examining the performance of the present day distance protection as applied to series compensated lines with spark gap operations, this work has contributed to the solution of a major problem associated with such lines.

This thesis is concerned with the properties of a particular discrete transform, and its applications to the classification of multi-valued ("m-ary" ) logic functions and m-ary combinatorial logic analysis and synthesis. The transform used is composed of a complete set of orthogonal functions, namely Chrestenson Functions, and the methods developed are applicable for all m, m = 2, 3, ... . The definition of multi-valued systems and some examples of multivalued circuits are given in chapter 1. The necessity of a generalised design method which is not based on a particular algebra is considered and the scope of the thesis is stated. Chapter 2 introduces the algebraic notation, and continues to show the expansions of fully specified m-ary functions in (i) Lagrange form, (ii) generalised Reed-Muller form, and (iii) as polynomials' over the field of real numbers. Chapter 3 is an application of the mathematical developments covered in the previous chapter. Based on generalised Reed-Muller coefficients a realisation of m-ary functions using Universal-Logic-Modules is described. The realisation in this case is restricted to m being a power of a prime. The complex polynomial expansion of m-ary functions is considered in chapter 4. The coefficient set obtained is termed the "spectrum" of the given function. The effects of various operations in the function domain on the spectral values are investigated, and a classification of m-ary functions is described. Applications of spectral properties developed for m-ary combinatorial logic design are shown in examples. The implementation of any m-ary function involves some form of decomposition using physically available logic functions. The spectral properties developed in chapter 4 are further pursued in chapter 5 with an investigation into the relationships between the spectra of the logic functions involved in such a decomposition, and the spectrum of the overall function being realised. With the development of these spectral decomposition relationships, the range of tools for the spectral analysis of m-ary combinatorial logic is completed. Throughout this thesis emphasis is placed on the generality of techniques developed, such that these techniques may be applicable to whatever higher-valued logic microelectronic circuit realisations may evolve in the future.

Time encoded speech (TES) proposes the transmission of speech by segmenting the waveform between real-zero crossings. Speech comprises two types of sound - voiced and unvoiced. The segment rate is low for voiced sounds and high for unvoiced sounds. Matching of the variable segment generation rate to the constant transmission rate is achieved by inserting storage buffers. Since the variation in generation rate can be large for a particularly fricative utterance, the storage buffer has to be large, and consequently, the delay in transmission is large. This thesis presents a technique which reduces the buffer size requirements and hence the delay in transmission. The technique, hybrid-TES, achieves these reductions by identifying the high segment generation regions of the speech waveform; and by storing and transmitting special symbols to indicate the reconstruction of these regions by spectrally shaped random noise.

The basic requirements for insulation for overhead transmission lines also the problems of 'ageing' by 'weathering' and the effects of surface contamination are briefly surveyed. Correlation between the basic properties of polymeric insulating materials and their structure is considered. The causes of progressive degradation are discussed in some detail, with particular consideration of degradation by 'tracking' and 'erosion' and failure by flashover, in the presence of surface contamination. Test procedures which are used to assess the relative tracking resistance of insulating materials are C:escribed, with particular emphasis on the tests recommended by the International electrotechnical commission, which have been used by the candidate to assess a variety of resin bonded and elastomeric materials. The equipment used for these tests is described and the results of investigations to determine factors which affect the reproducibility of results are presented. Factors which should be specified in the test recommendations are summarized in Section 9.1. The current v voltage characteristics of short, current limited discharges in air have been investigated and used to estimate the rete of power dissipation by single discharge across dry bands. If the rate of heat dissipation were uniform along the length of the discharges, the temperature rise at the surface of the insulation would be insufficient to cause thermal degradation, unless discharges recur at the sane site for several seconds. However, the temperature rise would beg greater, if heating were concentrated at the 'roots of the discharge. This is indicated by a marked polarity effect found when inclined plane tests were made with half wave rectified voltage. A limited number of tests on polyester matt glass mouldings showed that doubling the electrode spacing increased the voltage to cause track initiation and failure by 1.55 times. This is consistent with failure by thermal degradation when account is taken of the greater flow of contaminant at the higher test voltage.

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Note: / The diffraction of an acoustic wave by an aperture in an infinite plane screen is investigated experimentally and theoretically. Measurements are restricted to circular and square apertures illuminated by an acoustic wave of wavelength of about 3 cm. The diffracted field is examined over a considerable range of distances relative to the plane of the aperture.

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