High voltage transmission system availability and system security are key performance criteria for electricity utilities worldwide. System disturbances need to be cleared quickly and accurately in order to minimise the impact of faults and to facilitate speedy system restoration. In this context, the South African utility, Eskom has maintained a process of refreshing protective relaying technology as older equipment becomes obsolete and is no longer capable of meeting the utility’s requirements. The difficulties which a process of equipment renewal presents the organisation with include the risk of incorrectly applying the newer technologies within the complex electrical network. The application of new technology is affected by the complexities of the newer technology with respect to the older, more familiar technologies. Some of the difficulties can be addressed with revised commissioning procedures or the use of modern test equipment. Enhanced relay algorithms and settings calculation methodologies can however not be simplified. Protective relay maloperations cannot always be completely avoided and when they do occur, these must be investigated and addressed to prevent future recurrences. The research covered by this dissertation focuses on a number of protective relay maloperations on transmission lines using impedance protection algorithms. The research undertaken identifies the previously unidentified causes of the maloperations and describes a relay settings solution for improving the accuracy of the protective relays. The methodology that was followed in the research covers the following aspects: • Identification and highlighting of some of the protection relay maloperations that occurred during system faults, • Review of the fundamental principles involved in system fault analysis, • Comprehensive study of the theory involved in the calculation of an overhead line conductor self and mutual-inductance, as well as the calculation of the positive, negative and zero sequence impedances of an overhead line, • Brief evaluation of the effect of load impedance on relay measurements and the impact on fault clearing operation, • Analysis of the theoretical operation of various numerical relays during singlephase- to-earth faults in radial and meshed (complex) network conditions, • Mathematical calculations using typical Newton-Raphson methods to study the impact of resistive single-phase-to-earth faults on the voltage and current measurements at the relaying position with the exclusion of the capacitive components between conductors and conductors and earth, • Comparison and evaluation of mathematical calculations and system studies using network simulation software which included all steady state network parameters, • Review and analysis of actual system faults that had been previously analysed without definitive conclusion. The faults were re-analysed in an attempt to correlate findings with the hypothesis of the research, • Comparison of the performance of protective relay impedance charactersitics using positive sequence domain versus loop domain analysis techniques. This study concluded that significant benefits can be achieved by analysing system faults and relay operation using loop quantities in primary impedance values as opposed to positive sequence or apparent impedance quantities in secondary values. The inherent differences between the positive or apparent impedance characteristics of the relays are nullified when considered in the loop impedance domain, provided that the relays reach settings were calculated correctly. The study also showed that load current cannot be ignored when calculating settings as it has significant impact on the actual impedance measured during fault conditions. It is therefore crucial that when relays from different manufacturers are being used to protect the same circuit that the differences between the relays and the subsequent measurements are clearly understood and compensated for. Finally relay setting changes have been proposed for implementation based on the findings of this research. The combination of the theory, network simulations and secondary injections performed on the relays all correlate and therefore validate the research. It is left for the utility and or users of these relays to evaluate the results of this research and implement the necessary changes as applicable. / Thesis (MSc (Electrical Engineering))--North-West University, Potchefstroom Campus, 2012

Resource management in wireless networks is one of the key factors in maximizing the overall throughput. Contrary to popular belief, dividing the resources in a dense network does not yield the best results. A method that has been developed recently shares the spectrum amongst all the users in such a way that each node can potentially utilize about half of all the available resources. This new technique is often referred to as Interference Alignment and excels based on the fact that the amount of the network resources assigned to a user does not go to zero as the number of users in the network increases. Unfortunately it is still very difficult to implement the interference alignment concepts in practice. This thesis investigates some of the low-complexity solutions to integrate interference alignment ideas into the existing wireless networks. In the third and fourth chapters of this thesis, it is shown that introducing relays to a quasi-static wireless network can be very beneficial in terms of achieving higher degrees of freedom. The relays store the signals being communicated in the network and then send a linear combination of those signals. Using the proposed scheme, it is shown that although the relays cannot decode the original information, they can transform the equivalent channel in such a way that performing interference alignment becomes much easier. Investigating the required output power of the relays shows that it can scale either slower or faster than the output power of the main transmitters. This opens new doors for the applications that have constraints on the accessible output powers in the network nodes. The results are valid for both $X$ Channel and Interference Channel network topologies. In Chapter Five, the similarities between full-duplex transmitters and relays are examined. The results suggest that the transmitters can play the relay roles for offering easier interference alignment. Similar to the relay-based alignment, in the presented scheme full-duplex transmitters listen to the signals from other transmitters and use this information during the subsequent transmission periods. Studying the functionality of the full-duplex transmitters from the receivers' side shows the benefits of having a minimal cooperation between transmitters without even being able to decode the signals. It is also proved that the degrees of freedom for the $N$-user Interference Channel with full-duplex transmitters can be $\sqrt{\frac{N}{2}}$. The results offer an easy way to recover a portion of degrees of freedom with manageable complexity suited for practical systems.

The relay channel plays an integral role in network communication systems. An intermediate node acts as a relay to facilitate the communication between the source and the destination. If the rate of codewords is less than the capacity of the source-relay link, the relay can decode the source's messages and forward them to the destination. On the contrary, if the rate of codewords is greater than the capacity of the source-relay link, the relay cannot decode the messages. Nevertheless, the relay can still compress its observations and then send them to the destination. Obviously, if the relay-destination link is of a capacity high enough such that the relay's observations can be losslessly sent to the destination, then the maximum message rate can be achieved as if the relay and the destination can jointly decode. However, when the relay-destination link is of a limited capacity such that the relay's observation cannot be losslessly forwarded to the destination, then what is the maximum achievable rate from the source to the destination? This problem was formulated by Cover in another perspective [7], i.e., what is the minimum rate of the relay-destination link such that the maximum message rate can be achieved? We try to answer this Cover's problem in this thesis. First, a sufficient rate to achieve the maximum message rate can be obtained by Slepian-Wolf coding, which gives us an upper bound on the optimal relay-destination link rate. In this thesis, we show that under some channel conditions, this sufficient condition is also necessary, which implies that Slepian-Wolf coding is already optimal. Hence, the upper bound meets exactly the minimum value of the required rate. In our approach, we start with the standard converse proof. First, we present a necessary condition for achieving the maximum message rate in the single-letter form. Following the condition, we derive a theorem, which is named as "single-letter criterion". The "single-letter criterion" can be easily utilized to verify different channels. Then we show that for two special cases: when the source-relay link and the source-destination link of the relay channel are both binary symmetric channels (BSCs), and when they are both binary erasure channels (BECs), Slepian-Wolf coding is optimal in achieving the maximum message rate. Moreover, the maximum message rates of these two special channels are also calculated in this thesis.

In this thesis, I conduct the hardware prototyping of a two-way relay system using the National Instruments FlexRIO hardware platform. First of all, I develop several practical mechanisms to solve the critical synchronization issues of the systems, including Orthogonal Frequency-Division Multiplexing (OFDM) frame synchronization at the receiver, source to source node synchronization, and handshaking between the sources and relay nodes. Those synchronization methods control the behavior of the two source nodes and the relay node, which play critical roles in the two-way relay systems. Secondly, I develop a pilot-based channel estimation scheme and validate it by showing the successful self-interference cancellation for the two-way relay systems. In particular, I experiment the self-interference cancellation technique by using several channel estimation schemes to estimate both source to relay channels and relay to source channels. Moreover, I implement the physical layer of a 5 MHz OFDM scheme for the two-way relay system. Both the transmitter and receiver are designed to mimic the Long Term Evolution (LTE) downlink scenario. The physical layer of the transmitter has been implemented in Field-Programmable Gate Arrays (FPGAs) and executed on the hardware board, which provides high throughput and fundamental building blocks for the two-way relay system. The physical layer of receiver is implemented in the real-time controller, which provides the ?exibility to rapidly recon?gure the system. Finally, I demonstrate that the 5MHz OFDM based two-way relay system can achieve reliable communications, when the channel estimation and system synchronization can be correctly executed.

Thesis (M.A.)--Memorial University of Newfoundland, 2001. / Bibliography: leaves 124-135.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1971. / Typescript. Vita. Description based on print version record. Includes bibliographical references (leaves 788-824).

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains vii, 49 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 47-49).

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains v, 61 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 45-46).

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references and index.

Background and Literature: Technology is slowly but surely finding its way into the therapy room. As such, it is moving from the position of being used to aid therapy, such keeping notes on a computer, to being used to facilitate therapy such as online counselling. The sub-type of online counselling known as internet relay chat is a form of counselling that relies solely upon text alone; having no visual or audial cues to aid the therapy and is what this study focuses on. The therapeutic use of self is a difficult concept to define even 55 years after being first introduced. It is a concept that pervades all therapeutic approaches in some way and can be referred to as the planned use of personality, insights, perceptions, and judgments as part of the therapeutic process. It is therefore an important part of therapeutic work with five types of use of self being identified in the literature: use of personality, use of belief system, use of relational dynamics, use of anxiety and use of self-disclosure. However, prior to completing this study it was unknown as to how this core skill could be translated to internet relay chat. Methodology: Eight participants provided transcripts from 20-minute long internet relay simulated counselling sessions. These sessions were part of a training exercise with participants being students from the University of Manchester who were practising online counselling with each other. This study was a mixed-methods study following an explanatory sequential design. The first quantitative stage was a directed content analysis that coded the transcripts for therapeutic uses of self. The second stage was a qualitative grounded theory analysis that analysed semi-structured interviews that looked at the reasons behind why the uses of self from the first stage were used and their perceived impact. Findings: The directed content analysis found that therapeutic uses of self could indeed be translated within this medium with 53 occurrences of self-disclosure, 45 uses of relational dynamics and 15 uses of personality. There were no examples of use of belief system or use of anxiety within this study. The grounded theory analysis resulted in 463 open codes, which were organised under the core category of therapeutic use of self online. This was succeeded by 7 axial codes which were, Conducting Research, Context of Internet Relay chat, Impact of Using Uses of Self, Patterns of Behaviour, Reasons for Using Uses of Self or Not, Therapeutic Use of Self and Impact of Training Exercise. Discussion and Conclusions: The use of self differed from the way it is reported to be used in the participant's face-to-face work and the compensatory techniques used proved similar to those found in the existing literature. It is recommended that that this is a useful exercise for trainee counselling psychologists to undertake as part of their training. This holds value as not all participants knew what a therapeutic use of self was, despite their importance within therapy. It is also beneficial due to the shift in communication we as a society are experiencing.