HARVEST
University of Saskatchewan's Repository for Research, Scholarship, and Artistic Work
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A STUDY OF DISCONTINUOUS THIN GOLD FILMS AND GOLD-SILICON MONOXIDE CERMETS
(1971-04) Morris, James Eliot; Booth, A. D.
This thesis considers the mechanisms of conduction and nucleation in discontinuous thin metal films for application to thin film cermet resistors.
A review of previously suggested theories shows that only two are viable, the first based on a thermionic emission model, the second on an electrostatically charge activated tunneling one. It is shown that the accepted thermionic theory is in error and this is
corrected. The charge activated theory is extended to include the case of the oblate spheroidal shape of the metallic particles in a
discontinuous metal film and also the non-uniform distribution of field in the film.
Both theories are then evaluated in the light of appropriate experiments and both are shown to be capable of explaining qualitatively the phenomena of non-ohmic field effect and the possession of an activation energy. The variations in film conductivity under stress and upon exposure to air lead to the rejection of the thermionic model. Although full quantitative agreement of theory and experiment has not been reached, due to extreme difficulty in accurately determining film structures, most of the experimental results described are adequately accounted for by the charge activation model.
The origins of surface charge on the substrate, which is a cause of the oblate spheroid shape of the islands in discontinuous films, are determined, its effects are examined, and the necessary procedures to reduce it are discussed. A detailed discussion of several of the experimental techniques employed in the study is included.
An extension of the conduction theory to gold-silicon monoxide cermets is developed and the results are shown to be in qualitative agreement with the charge activated model. This comparison of theory and experiment serves to emphasize the existence of electron traps in the insulating phase and the radiation heating effects of the silicon monoxide deposition source and suggests directions in which this study could be usefully continued.
A FEASIBILITY STUDY FOR PROTECTING TRANSMISSION LINES USING TRAVELING WAVES
(2003) Munian, Tamije Selvy
Faults occur in power systems because of the failure of insulation and structures. The faults almost always result in the flow of large quantities of currents. Protective relays are used, therefore, for detecting the faults and isolating the faulted section of the system before the damage spreads. Traditionally, electromechanical and static technologies have been used for designing and manufacturing relays. More recently, advancements in the VLSI technology have resulted in the development of microprocessor-based numerical relays. Several algorithms have been proposed in the past, which are suitable for using in numerical relays for detecting the occurrence of faults. These algorithms convert the samples taken from the waveforms to phasors of the fundamental and harmonic frequencies. The conversion techniques usually take time that is at least one-cycle of the fundamental frequency. This time is 16 ms for a 60 Hz system and 20 ms for a 50 Hz system.
This thesis describes two techniques for designing high-speed numerical relays. The first technique uses sampled voltages and currents from the local terminal of the line. The second technique uses samples of voltages and currents from the local terminal and processed information from the remote terminal of the line. Both techniques are based on the arrival of traveling waves starting by the onset of faults. The first differences are used to detect the instants of the arrival of the voltage and current traveling waves.
The performance of the proposed techniques was investigated by computer-based simulations. Different types of faults on different locations in a sample power system were simulated using the electromagnetic transient program, EMTDC. The impacts of
hardware constraints were also evaluated. Some of the cases investigated during this project are reported. The results indicate that the proposed techniques are suitable for protecting a transmission line. Their operating times are less than 4 ms compared to 10 ms or more for the presently available relays.
MEASUREMENT OF POLARIZATION MODE DISPERSION IN OPTICAL WAVEGUIDES
(1996-04) Morrison, Shawn Joseph Dylan; Daku, B. L.; Wood, H. C.
This thesis is based on the measurement of polarization mode dispersion (PMD) in optical waveguides. The study takes as its starting point a recently reported measurement methodology known as the fixed polarizer wavelength scan technique. A new method of determining the level of PMD from a fixed polarizer wavelength scan is developed. The new method involves the use of Fourier transformation techniques to allow viewing of the PMD as an RMS spread in the time domain. Finally, waveguides from four different
processes, modified chemical vapor deposition (MCVD), over-jacketed MCVD, outside vapor deposition (OVD), and dispersion shifted OVD, all cabled in an industry standard loose tube type cable, are characterized for PMD performance. It is believed that this measurement technique will result in a low cost method for fiber and cable process optimization for this important form of dispersion.
A CONTROL STRATEGY FOR PWM INVERTER-INDUCTION MOTOR DRIVE
(1985-07) Mohapatra, Dipti Ranjan; Fleming, R. J.
The rapid development of the microprocessor and the software associated with it has contributed significantly towards the modernisation of control systems. The developments in solid state technology have already made it possible for ac induction machines to be considered as alternatives to de machines in adjustable speed applications. Considering the present trend in microprocessor technology, the replacement of solid state controllers by software based controllers is inevitable.
The work reported in this thesis involved the development of a microprocessor based control strategy for a pulse width modulated inverter induction motor drive. The switching sequence for the SCRs of an auxiliary impulse commutated McMurray inverter are described. The development of the control strategy is the highlight of the thesis.
The basic concepts of the control strategy are explained. The - harmonics analysis of the simulated output voltage waveform and the advantages of the' new control strategy over the existing methods are given.
A TECHNIQUE FOR ANALYSIS OF ANN BASED FAULT DIRECTION DISCRIMINATOR
(2003) Mital, Lagan; Sachdev, M. S.; Sidhu, T. S.
Artificial Neural Networks (ANNs) have demonstrated their potential in modeling nonlinear processes and complex processes that consist of interactions of time varying voltages and currents experienced during power system faults. Generalization and prediction capabilities give them the ability to correctly process the data that broadly resemble the data they were trained on. ANNs trained to recognize non-noisy patterns are able to correctly identify patterns with either some segments missing or with some segments added to the input data. This property gives them a fault tolerant characteristic.
In spite of the numerous advantages of ANNs, there are some acceptability issues. One of the issues is that most training data are obtained from simulations. It is necessary that the data should correctly represent all the conditions the network is likely to encounter. Another issue is that the performance of an ANN can not be explained in the manner in which the performance of most electromechanical and electronic devices can be. The acceptability for their use in critical applications, such as power system
protection, would increase if a technique for analyzing their performance could be developed and demonstrated. This would allow the users to validate the performance of an ANN when it becomes necessary to investigate the correctness of its performance.
Analytical methods for explaining the weights and biases of a trained network are not readily available. The only means of verifying the performance of a trained network is to perform extensive testing. It is hard to verify that the neural network has properly trained for all possible scenarios of actual operating conditions.
Because the output of a neuron can be quantized to specified logic levels, the output was treated as a multi-valued logic in this project. At this time, no technique is available for minimizing multi-valued logic that could handle a large number of inputs when there are several neurons in the input, hidden and output layers.
This thesis presents a new technique for the multi-valued logic minimization for large number of inputs. The possibility of making the `explanation' capability an integral part of a trained ANN and the verification of the quality of the training it received is also
examined. The technique predicts the behavior of ANNs for the training data as well as for all possible inputs. The technique also makes it possible to implement ANNs on Programmable Logic Arrays. The proposed technique was applied to the ANN based fault directional discriminator. Some results are presented as well in this thesis.
Investigation of a 900 MHz CMOS Fractional-N Phase- Locked Loop Based Frequency Synthesizer
(1999) Mujiono, Totok; Bolton, R. J.; Burton, R. T.; Gander, R. E.; Klymyshyn, D. M.; Sidhu, T. S.
The rising demand for radio frequency (RF) communication system products and the improvement of many aspects of CMOS technology have been the main drivers for the desire to implement the RF transmitter/receiver circuit with a higher level of integration. One of the important blocks in the RF transmitter/receiver is the frequency synthesizer, which is responsible for generating a local oscillator signal for the modulation/demodulation process. The circuit topology most suitable for its implementation is the fractional-N phase-locked loop (PLL).
This thesis discusses the principles of the fractional-N PLL-based frequency synthesizer (fractional-N PLL synthesizer), the procedure of designing the fractional-N PLL synthesizer, and the possibility of implementation at 900 MHz using the CMOSIS5 0.5 micron technology. The design chosen for investigation has a frequency step of 0.2 MHz and frequency range of 880 MHz to 920 MHz.
The fractional-N PLL used for the frequency synthesizer is a third-order PLL; however, for design purpose a second-order PLL was used to simplify the calculations, which are done in the frequency domain. The design was then transferred to the time domain where the system level design of the fractional-N PLL synthesizer (time domain, third-order) was done using the Simulink tool in MATLAB. The simulation was run for both small values of N and large values of N. The simulation results show that there are minor differences compare to the calculation (in the s-domain, second order). It is also shown that the fractional-N design affects the output signal generated due to introduction of spurious noise into the voltage controlled oscillator.
The design of the 900 MHz fractional-N PLL synthesizer blocks was performed at the schematic level. Each circuit block has been verified using Spectre, a circuit simulator available in the Cadence design system. The simulation for the entire circuit was not performed due to constraints on available system resources. The fractional-N PLL synthesizer circuit employs 643 active and passive devices and dissipates 17 mW of power, excluding the loop filter. Based upon the results of the investigation, the CMOSIS5 technology appears appropriate to implement the fractional-N PLL synthesizer.
SYNCHRONIZATION PERFORMANCE OF MULTI-USER DIRECT-SEQUENCE SPREAD-SPECTRUM INDOOR RADIO
(1994-07) Mekkoth, Ajith Sankar; Kumar, Surinder
The performance of a sliding window code acquisition circuit in a direct-sequence spread-spectrum indoor mobile radio system is analysed. The performance measure used is the variance of error in the acquired code-phase position. The channel is assumed to have multipath nature and a five correlator RAKE receiver is considered in the analysis. The results presented can be used to make the necessary system tradeoffs so that the system objectives can be realized. The effect of integration time, spreading gain and spectral shape of the signal on the acquired code phase error is brought out. A relationship between the signal to noise ratio degradation and code phase jitter is also presented.
RELIABILITY EVALUATION OF COMPOSITE GENERATION AND TRANSMISSION SYSTEMS
(1978-12) Medicherla, Thandava Krishna Prasad; Billington, R.; Sachdev, M. S.
The problem of composite generation and transmission system reliability evaluation is now receiving considerable attention as utilities are finding it necessary to quantitatively evaluate individual load point and overall system reliability indices. This thesis extends the available techniques for composite generation and transmission system reliability evaluation to calculate bus and system indices by including line overload alleviation and common mode outages in the analysis. A new set of indices in addition to those presently available are defined and evaluated for an adequate assessment of a composite system. Computationally fast digital computer programs which examine all first and second order simultaneous independent outage combinations of generating units and transmission lines have been developed. Effects of various factors on calculated reliability indices are illustrated using various test systems.
Overload of transmission lines is one of the problems encountered in network reliability evaluation. Two computationally efficient line overload alleviation techniques suitable for composite system reliability evaluation and for use in conjunction with the Newton-Raphson and decoupled load flow techniques are described. Additional sets of bus and system indices based upon load curtailment necessary for alleviating line overloads are also defined. The effectiveness of line overload alleviation techniques for evaluating more accurate bus and system reliability indices is demonstrated.
A common mode or common-cause outage is an event having a single external cause with multiple failure effects where the effects are not consequences of each other. Several possible common-cause outage models are analyzed in. this thesis. The effect of common-cause outages on reliability indices is also discussed using three test system studies. The impact of system peak load variation and system modifications on bus and system indices are also examined with reference to a 30-bus model of the Saskatchewan Power Corporation System.
SECOND ORDER LOAD FLOW TECHNIQUES
(1975-12) Medicherla, Thandava Krishna Prasad; Sachdev, M. S.
Real and reactive power injections into a bus, which are functions of magnitudes and phase angles of bus voltages, can be expressed as Taylor's series in the neighborhood of estimated values. Using the first three terms of this series, a second order load flow model has been developed in this thesis. An algorithm has also been devised to solve this model. In this algorithm, the state vector is first calculated by a conventional Newton-Raphson load flow iteration. Using the calculated values of the state vector and the elements of the Jacobian matrix, second order terms are estimated and subtracted from the residual vector. The modified residual vector obtained in this manner is then used to compute the new state vector. This procedure is repeated until the elements of the latest state vector are within permissible tolerance. The magnitudes and phase angles of the bus voltages are then updated. The total procedure is then repeated until a converged solution is obtained. Six simplified versions of the second order algorithm have also been investigated.
In addition to the Second Order Load Flow technique, a decoupled second order load flow model has been derived. An algorithm based on this approach has also been suggested. Two modified versions of the decoupled second order load flow algorithm have also been investigated.
The proposed second order and decoupled second order load flow algorithms have been used for computing load flows of nine test systems. The results of these studies are presented in this thesis and are compared with those of the Newton-Raphson and the decoupled load flow techniques.
ANALOG SIMULATION OF A SYNCHRONOUS GENERATOR
(1966-02) McDonald, James R.; Fleming, R. J.
This thesis describes parallel sets of tests which were carried out on a synchronous generator and on an analog computer simulation of it. The purpose of these tests was to establish the validity of the "Xad Base" per unit system for use in extensive machine studies. The "Xad Base" per unit system is a logical extension of the well known two-axis "Park" representation for a synchronous generator. It makes use of machine parameters which are readily available either from manufacture's design data or from measurements which can be easily made at the terminals of the machine.
The pertinent synchronous machine theory, the procedure followed for measuring the machine parameters required in the analog simulation, and the tests conducted on the analog computer as ,well as the actual generator are detailed in this thesis.
In general the results were found to be satisfactory.