D.Ing. / Transmission networks change continuously when new supply requests are made, network reinforcements are installed and equipment configuration changes. Therefore, network design, operation and control requirements change. To manage this, controllers are being developed to assist human network controllers who might not always be specialists in equipment operation and characteristics. A transmission network comprises multiple variables, some dependent on others. The resistive portion of a load (PLoad) and the total reactive power (Q) installed close to the load can be set in relation to each other. This relationship forms the basic concept of the QP ratio for a transmission network. This ratio is not standardly used as a variable in network operation or control. This thesis explores this new QP ratio in more depth for application in different networks. This concept is developed and investigated in detail and equations are derived from first principles. The usability of the QP ratio is described and calculations are done for existing networks. It is shown that each network has its own unique QP ratio that can be used as information for human operators or as part of a controller device. This information can assist in determining actions required to be taken by controllers and operators. This thesis investigates aspects related to the use of a QP ratio in transmission networks as far as system operation and network control is concerned. The information provided in this thesis could be developed further to assist in implementing of the QP ratio in transmission network control rooms or systems. This will contribute to the provision of more reliable, robust and controlled electrical networks.

M.Ing. (Electrical And Electronic Engineering) / In this dissertation, an investigation into reducing Electromagnetic Interference (EMI) through design is presented. Root generation mechanisms of Electromagnetic Interference are often neglected during the design process and later treated symptomatically. Mitigation of Electromagnetic Interference at source often reduces cost and physical size of electronics. This dissertation demonstrates the process and results by which schematic balance mitigates EMI. In addition, the introduction of Geometric Balance and physically designing circuits to be Geometrically Symmetrical are presented and tested to determine whether the design produces mitigating EMI results. Multiple Printed Circuit Boards (PCB’s) were developed and tested against each other to demonstrate schematic balance and other EMI generation mechanisms. The final PCB was designed to be Geometrically Symmetrical and the test results compared. The results illustrate the varying performance of each PCB due to their differing design. The Geometrically Symmetrical PCB presented the best results due to various improvements which include physical layout size and semiconductor placement. An additional important phenomenon discovered was the amount of EMI generated during MOSFET Driver operation. This contributed to a significant amount of EMI during the no-load phase of testing.

M.Ing. (Electrical Engineering) / Induction heating has been used in practice for many years. The main goal of this study is to investigate the use of a single-turn coil in a typical induction heater. The work starts off with a background study of elecrroheat and specifically high-frequency induction heating. Finite element simulations were conducted on different coil shapes and compared with each other. The converter. with control and driver circuits. used in the, experimental setup, as well as the experimental construction and results are described. The work is concluded with an evaluation of the project.

Intrabuilding power distribution circuits offer a number of unique advantages for local area networking. To enable the selection of proper error-control codes and protocols for reliable data communication services, error pattern statistics of intrabuilding power line channels are obtained. Also, error-causing disturbances are identified and their relationships to specific types of error patterns are determined. It is found that error occurrence is highly periodic, with periodicity being a function of the power line frequency which is nominally 60Hz in North America. Furthermore, results indicate that error pattern behaviour is relatively insensitive to communication carrier frequency and modulation schemes. Based on the measurement results, hybrid ARQ with bit-interleaving is suggested for reliable data transmission at high data rate (19,200bps). Burst error correcting codes can be used to reduce decoder cost and complexity with some sacrifices in performance. At lower data rates (1,200bps or below), effective error control can be accomplished more easily. Finally, the attenuation characteristics of a number of typical power line channels are presented. It is found that high frequency bypass can be used to improve signal transmission between different phases of the distribution transformer. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The propagation characteristics of lightning surges in compressed SF₆ gas insulated power substation was studied using an electromagnetic transients program. Numerical models were developed to represent the behaviour of different system components especially under lightning over-voltage conditions. The characteristics of lightning surge propagation in overhead multi-phase untransposed transmission lines was analysed first. Modal analysis, together with special rotation techniques to fit time domain solutions were then used to simulate the wave propagation in multi-phase untransposed line in an electromagnetic transients program. Non-linear voltage-dependent corona attenuation and distortion phenomena were also investigated. Available field test results could be duplicated to within 5%. The characteristics of lightning surge propagation in multi-phase single-core SF₆ cables was studied next. A program was developed to obtain the cable parameters for typical cable configurations. The amount of core current returning through its own sheath and through the earth were computed to illustrate the single phase cable representation for wave propagation in single core SF₆ cables. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 29, 2007) Includes bibliographical references.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2017. / Transmission lines are a vital part of the electrical distribution system, as they provide the path to transfer power between generation and load. Factors like de-regulated market environment, economics, etc. have pushed utilities to operate transmission lines close to their operating limits. Any fault, if not detected and isolated quickly will cascade into a system wide disturbance causing widespread outages for a tightly interconnected system operating close to its limits. Current differential criterion is used with success to protect various elements in power systems, i.e. transmission lines, power transformers, generators and busbars. The alpha plane differential relaying system provides sensitive protection for transmission lines, security and dependability for external faults. This thesis focuses on three terminal alpha plane differential protection with the aim to develop a complete test method using OMICRON test universe software essentially defining security, dependability and sensitivity of the alpha plane characteristic. The research analyses the three terminal alpha plane characteristic and existing primitive test methods and develops an improved test method using IEC 61850 standard. The primitive methods are time consuming and result in unnecessary prolonged outages. These methods have been discussed and improved in the thesis by implementing IEC 61850 standard. First the standard IED Capability Description (ICD) file is modified by developing new logical nodes using AcSELerator Architect and XML Maker software. Then the developed logical nodes, three terminal differential protection alpha plane characteristic with its additional infeed/outfeed check logic, and the developed test method are tested simultaneously using Test Universe software. A laboratory test bench is built using three SEL311L relays, two CMC 356 Omicron injection devices, PC, MOXA switch, CMIRIG-B time synchronising unit, SEL 2407 satellite synchronised clock, and a DC power supplier. The test method developed in this research vindicates benefits of IEC 61850 standard over hard wired systems. Prolonged outage times due to test set preparation using hard wires are drastically reduced. The thesis findings and deliverables will be used as a solution to industrial problems, postgraduate studies of other students and research project.

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering in the High Voltage Research Group School of Electrical and Information Engineering Johannesburg, June 2017 South Africa / Servitude availability in space-constrained built-up areas within the Johannesburg or Central Load Network (CLN) poses every-day challenges for power system engineers. Strengthening the backbone 88/275 kV transmission system within the CLN becomes even more difficult when multi-circuit transmission lines are required for increased power transfer capabilities. When uprating is considered to increase the power transfer capability, the withstand levels of existing external insulation demands an optimisation to find a new stress versus strength balance that allows reliable operation of substations at higher voltages. The research includes primarily an investigative simulation study to evaluate the current Eskom available design clearances in terms of their withstand capability when subjected to over-voltage transients. Two voltage range classes were evaluated and the results are discussed. For voltage range 1, it was found that the over-voltage stress was low enough to allow for a higher nominal operating voltage while maintaining the existing clearances. For voltage range 2, existing clearances are also found to be conservative and smaller safety margins will most likely be acceptable. From a transient analysis evaluation, voltage uprating is considered as a very attractive option to increase the power transfer capability of existing substations. Current Eskom clearances for 88 kV and 275 kV are expected to perform well during transients generated in uprated systems. Electrode grading to improve the field gradients in the substation will require attention to increase gap factors. Additional surge arresters are considered to be a cost effective solution to control over-voltages throughout the whole uprated substation. The physical modification of substations to replace strung conductors with tubular conductors, ensuring sufficient outage time to refurbish and rebuild with new equipment will be the most challenging part of uprating existing substations. / MT 2017