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HARVEST

University of Saskatchewan's Repository for Research, Scholarship, and Artistic Work

Welcome to HARVEST, the repository for research, scholarship, and artistic work created by the University of Saskatchewan community. Browse our collections below or find out more and submit your work.

 

Recent Submissions

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A PROBABILISTIC ASSESSMENT OF TRANSIENT STABILITY
(1979-08) Kuruganty, Pratapa Rudra Sastry; Billington, R.
The application of probabilistic techniques in the quantitative evaluation of power system reliability is gaining in popularity as utilities and regulators are recognizing the inadequacy of qualitative methods when uncertainties associated with generation, transmission and distribution of electrical energy are to be considered in the assessment procedure. Probability methods are being used extensively in the area of static adequacy assessment, however, their application to transient stability evaluation has not been widely accepted. This thesis illustrates a procedure to include the probabilistic aspects associated with the type, location and clearance of faults in the transient stability evaluation procedure. A new transient stability index, which considers the probabilistic phenomena is developed. The procedure for obtaining this index and its response to the system parameters affecting stability are demonstrated for a single machine-infinite bus system. The protection system plays an important role in maintaining system stability. The probability distributions of fault clearing time used in calculating the stability indices must be obtained by reliability modelling of the protection system. This modelling procedure is illustrated for a simple distance impedance scheme. Extension of the basic technique to multimachine systems is illustrated for a hypothetical system. Two types of indices namely the line and system indices are developed. The response of the stability index to system parameters is investigated for the multimachine system. Two methods of system simplification, to obtain approximate stability indices useful in initial system planning studies are investigated for this system. The techniques proposed are applied to two practical models based on the Saskatchewan Power Corporation (SPC) system using actual system outage statistics. These data were then used to create an additional index, "Expected Frequency of Transient Instability" for the 33 bus model of the Saskatchewan Power Corporation system.
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Adequacy Equivalents in Composite Power Systems
(1987-09) Kumar, Sudhir; Billington, Roy; Allan, R. N.; Grassman, W.; Cotcher, David
In a modern society, load shedding and poor quality of power supply have severe economic and social consequences. There is little disagreement among the suppliers, the users, and the regulatory agencies that providing an adequate supply of electric power is of prime importance. Adequacy evaluation of a composite power network relates to the examination of both generation and transmission facilities required to satisfy the demand at the bulk customer load points. Most power utilities use deterministic methods to conduct adequacy studies on their systems. The drawback of these methods is that they are not responsive to many of the parameters which actually influence system adequacy. There is, however, a growing interest in the power industry in using probabilistic methods as they provide more realistic results with regard to the identification of system weaknesses, comparison of alternative system designs, and the justification of new facilities. This thesis is concerned with the adequacy evaluation of composite power networks using probabilistic methods. It extends the state of the art and provides insight into adequacy evaluation of both moderate sized and large power systems by evaluation, analysis and solution of some specific problem areas. The pertinent factors such as the consideration of high level independent outages, station originated and common cause outages, and corrective actions taken under an outage event, affect the calculation of adequacy indices for a power system. These factors are identified and their effects are illustrated using three test systems. The adequacy indices calculated for a network do not provide absolute measures regarding the performance of the network and these indices should be interpreted in conjunction with the factors involved in arriving at their values. The adequacy indices reported in this thesis are obtained by solving a network using the network flow method and the A.C. load flow method. The differences in the indices for the standard IEEE Reliability Test System (RTS) resulting from using these solution techniques at various load levels are discussed. The computation time required to calculate adequacy indices considering all credible outages in a large power network can be very large. In this thesis, two new approaches that can be used to conduct a number of adequacy studies in a small area of interest (AI) of a large power system are described. The first approach considers outages only in a part of a network that affect to a great extent the adequacy performance of the AI. The second approach determines the adequacy of the AI after developing an adequacy equivalent for the remaining part of the network. This approach can also be used to consider further higher level outages in a network. The application of each method under various situations is illustrated for the three test systems and their interconnected networks. The weaknesses and the strengths of each technique are also discussed. It is expected that the proposed methods will provide a good framework for power utilities when studying the adequacy of their systems.
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A COMPACT DIRECT PSK MODULATOR FOR VERY SMALL APERTURE TERMINALS
(1989-11) Krishnamurthi, Kathiravan; Kumar, S.
Very Small Aperture Terminals(VSATs) find wide ranging application in private data networks. Transmitters in these networks use PSK modulation at low data rates (<1Mb/s) with a power output of 1-2 W. It is attractive to realize the modulation function using a high power direct modulator at the transmit frequency. At the data rates encountered, premodulation low pass filtering is the alternative to postmodulation bandpass filtering. In these circumstances, the modulation should preserve the filtered baseband spectrum. This thesis is devoted to the design of a direct microwave modulator for the VSATs. The thesis also provides solution for spectrum spreading problem caused by the modulator non-linearities. Predistortion is applied to the filtered baseband data to counteract the modulator non-linearities. A versatile digital approach for combining the predistortion and prefiltering function is proposed. This concept of realizing modulators in a compact fashion paves the way for combining baseband and microwave signal processing in a single MMIC chip.
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SECURITY EVALUATION OF POWER SYSTEMS
(1988-02) Komolafe, Olusola Aderibigbe; Fleming, R. J.; Sachdev, M. S.
This thesis deals with security analysis of power systems. The thesis proposes procedures for the simulation of equipment outages, for the evaluation of the relative severity of various system contingencies, and for the determination of appropriate means of alleviating the serious effects of these outages. In the outage simulation technique, a subsystem comprising a specified tier of buses in the neighborhood of the outage is used to simulate an outage. The sensitivity matrix obtained from the base case load flow is used to calculate the post outage state of the subsystem. The line on outage is then replaced by its equivalent real and reactive power injections to calculate the post outage state of the equipment elements outside the subsystem. A comparison of the sensitivity and refactorization techniques is also performed. A voltage performance index capable of detecting voltage violations 'and large voltage deviations is proposed. These techniques are adapted for contingency selection. These techniques are compared with others using the proposed performance index. Two techniques of alleviating voltage and reactive power injection violations are developed. The first technique adjusts the voltage magnitudes of generator buses in the system, while in the second, the voltage magnitudes of generator buses, autotransformer tap settings and reactive compensators in a specified subsystem, in the neighborhood of the violation, are adjusted. The sensitivity technique, and the power injection along with the economic dispatch techniques are used for line overload alleviations. These techniques are applied to the 14-bus and 118-bus IEEE test systems, the 26-bus model of the Saskatchewan Power Corporation transmission network, and the 231-bus model of the Saskatchewan-Manitoba interconnected networks.
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APPLICATION OF MODAL TRANSFORMATION FOR FAULT ANALYSIS AND DIGITAL DISTANCE RELAYING
(1985-08) Kolla, Sri Rsmsnjaneyulu; Sachdev, M. S.
Transmission lines are usually protected by distance relays that measure the apparent distances of faults and compare them with the relay settings to determine if the fault is inside the protected zone. The information required for setting relays is generally obtained from fault analysis studies. Presently, electromechanical and solid state components are used for implementing distance relay schemes. During the past 15 years, the development of digital processor based relays has received considerable attention. The symmetrical and Clarke components are generally used for the analysis of faulted power systems. Fault conditions derived from these transformations have been used in digital distance relays. The symmetrical components transformation includes phase shifting operators and can only be used in conjunction with steady state phasors. The Clarke components transformation is composed of real elements and can be applied to instantaneous voltages and currents. However, this transformation includes irrational numbers and its use in on-line application requires multiplications that are time consuming This thesis describes the application of a real transformation, called the Modal Transformation, for the analysis of faulted power systems and application in digital distance relays. Conditions describing shunt faults and open circuits on transmission lines are derived. Modal networks and their inter-connections representing faults are described. A fault analysis program that uses the modal transformation is described. A distance relaying criterion for shunt faults is derived and a relay scheme based on this criterion is developed. The design and software simulation of the relay scheme is described. The performance of the relay was tested using fault data obtained from the EMTP program for shunt faults on a six bus model of the SPC system. Test results are also included in the thesis.
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Desktop Interface to Asynchronous Transfer Mode Networks
(1996) Khanzode, Sameer; Dodds, David E.
Asynchronous Transfer Mode (ATM) is a new communication technology proposed for the implementation of Broadband ISDN, a network which integrates various services such as voice, video and data. To access an ATM network, the voice, video and data signals must be converted to ATM cells. These cells are then multiplexed and transmitted over the transmission facility. This thesis presents the design of an ATM network access system which supports one telephone voice service and one PC data service Three designs are described in the thesis: the first is an ATM adapter, the second is -a cell multiplexer circuit and the third is for serial transmission of ATM cells at a rate of 1.544 Mb/s over twisted pair cable. These three designs have been implemented and tested in the laboratory using the DS1 port of a Northern Telecom ATM switch.
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MODAL CONTROL OF MACHINE INTERACTIONS
(1978-05) Kalamadi, Gurunath Bhaskarrao; Fleming, R. J.
The interactions among the individual machines in a power plant can pose problems in maintaining the quality of power generated at the plant. The individual controllers on each machine are not designed to handle these interactions. Using modal control theory, one method of minimising the machine interactions has been arrived at. First, a detailed model for the plant is constructed and from this, a reduced-order model describing the rotor dynamics of the machines in the plant is formulated. Using the reduced-order model, modal control theory is applied to minimise the machine interactions. Network reduction techniques necessary for the simulation of multi-machine plants are also given.
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Power System Adequacy Assessment
(1993-03) Jonnavithula, Satish; Billington, R.
T1 le basic objective of the research was to examine the possibility of predicting reliability indices at customer load points considering, outages in the three major zones of a power system, i.e, generation, transmission and distribution.) These indices provide a quantitative assessment of the contribution made by the various segments at the system to customer reliability. The impacts on the overall customer load point adequacies of the pertinent factors associated with generation, transmission and distribution systems are examined in this thesis by application to two test systems. Reliability parameters known as performance indices can also be obtained from past experience of the system. Assessment of past system performance is important because in addition to providing a quantitative record, these indices provide a datum against which to measure future predictive performance. This thesis illustrates how future performance indices can be estimated using existing predictive assessment techniques. Load interruption and poor quality of electric supply have severe economic and social consequences in a modern society and therefore power utilities try to provide an adequate supply of electrical energy to all their customers. In the event of electrical energy deficiencies resulting from composite generation and transmission component outages, a decision must be taken regarding which load points and customers will suffer the loss. There is an increasing interest in economic load curtailment strategies in the event of energy deficiencies resulting from composite generation and transmission component outages. As a result of adopting such cost effective curtailment strategies, the reliability may be improved at some load points and adversely affected at others. It is therefore important to determine how these load curtailment strategies can influence the customer load point reliability indices. This thesis presents some cost effective load curtailment strategies and their impacts on overall customer load point reliability indices.
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APPLICATION OF KALMAN FILTERS IN DIGITAL RELAYS
(1985-08) Johnson, Neil Garnis; Sachdev, M. S.; Wood, H. C.
The function of a protective relay is to detect a fault in a power system, determine whether the fault is in the relay's zone of protection, and, if necessary, to output a signal to trip one or more circuit breakers. Interest in implementing the relaying function digitally has increased during the last fifteen years. A major part of a digital relay is the digital filter that is used to estimate voltage and current phasors. The capabilities of microprocessors being marketed have been increasing steadily. This has prompted the use of considerably more complex algorithms in digital relays. One such algorithm is the Kalman filter. This project investigates the use of the Kalman filtering technique to estimate voltage and current phasors from sampled data. A major consideration in designing the filters is the reduction of the effects of harmonics and decaying de components which are often present in voltages and currents during faults. Several filters have been developed in this thesis. The importance of modeling all components expected in the inputs has been demonstrated.
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Design and Implementation of an ATM Cell Router
(1995) Jain, Kavita; McCrosky, Carl; Williamson, C.; Kusalik, T.; Bolton, R.
The standard for emerging high speed digital telecommunication networks is Broadband Integrated Digital Networks (B-ISDN). Recent standards decisions have determined that B-ISDN will consist( of Asynchronous Transfer Mode (ATM) cell formats and switching coupled with Synchronous Optical Network (SONET) transfer on fibre. One of the key requirements for B-ISDN is the development of affordable and reliable ATM switches. This thesis proposes, models, designs, and implements a novel ATM switch design for use in B-ISDN. A direct binary hypercube network is selected as the switching fabric of the switch. The proposed switch uses a fault-tolerant, self-routing, distributed routing algorithm, known as the Saturated Constant Shuffle (SCS) routing algorithm. The basic SCS routing algorithm is 'loss-free'. The switch design is optimized by simulation-based performance evaluation of the SCS routing algorithm and several variants. A logic equation specification of the switch architecture is given in Verilog. Several possible floorplans for a VLSI implementation are considered. Finally, as part of a larger team project, a complete VLSI implementation of the switch is produced.