Eskom is experiencing problems in the field of protection maintenance and in-service breakdowns which negatively influence the quality of electrical supply to the consumer, an integral component of the utility business. These facts initiated the research into the further development of a generic relay to be implemented as a strategic spare for the replacement of several schemes operating within Eskom’s southern region. These include the electromechanical, solid state and numerical distance protection relay and scheme failures on the 132 / 66 kV feeder network. Hence, the primary objective of the research is to develop, test and configure the strategic spare in terms of software and peripheral hardware for the input and output terminal connections, generic equations and settings for the purpose of the scheme replacements. The various schemes are assessed for stepped distance and permissive intertripping for three or single pole operation. This is done in conjunction with the internal and external circuit diagrams in order to understand the detailed operation of the scheme and to ensure the effective implementation of the strategic spare. The generic relay is configured for the emergency replacement of the various schemes during in-service breakdowns. This constitutes a temporary installation and therefore the downtime in essence, of all the distance protection schemes that require replacement, is limited to a minimum. This dissertation therefore explores the implementation of the strategic spare.

Generation loss contingencies in electric power systems result in a deviation of system frequency from nominal, a condition which must be corrected promptly in order to prevent further degradation of the power system. Automatic load-shedding using underfrequency relays is one of the techniques used to correct abnormal frequency deviations and prevent the risk of uncontrolled outages. If sufficient load is shed following a contingency to preserve interconnections and keep generators on-line, the system can be restored with relative speed and ease. On the other hand, if a declining frequency condition is not dealt with adequately, a cascading disconnection of generating units may develop, leading to a possible total system blackout. / This thesis develops and tests a new systematic method for setting underfrequency relays offering a number of advantages over conventional methods. A discretized swing equation model is used to evaluate the system frequency following a contingency, and the operational logic of an underfrequency relay is modeled using mixed integer linear programming (MILP) techniques. The proposed approach computes relay settings with respect to a subset of all plausible contingencies for a given system. A method for selecting the subset of contingencies for inclusion in the MILP is presented. The goal of this thesis is to demonstrate that given certain types of degrees of freedom in the relay setting problem, it is possible to obtain a set of relay settings that limits damage or disconnection of generating units for each and every possible generation loss outage in a given system, while attempting to shed the least amount of load for each contingency.

Series compensating capacitors were initially introduced in transmission networks mainly to increase the / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2009.

performance of high voltage outdoor insulators can be greatly affected by weather conditions. The weather conditions under investigation are cold temperatures coupled with high humidity levels. Weather data from a number of coastal stations around South Africa was analyzed to determine whether surface condensation was likely on outdoor insulators under these weather conditions. A heat transfer equation was used to determine the response of the insulator surface temperature to the environmental temperature. It was found that surface condensation would occur on the insulator surfaces which would lead to sudden, heavy wetting of the surface. Outdoor insulators in coastal environments are often heavily polluted, due to salt spray, and when wet, a conductive layer can form on the insulator surface. This conductive layer can result in appreciable leakage currents flowing on the insulator surface, often leading to premature failure. The finite element method program, Maxwcll, was used to simulate the outdoor insulators both under these polluted, wet conditions and under unpolluted conditions. Both cases were simulated for a silicone rubber, glass cap-and-pin and two EPDM outdoor insulators. The polluted insulators were simulated with varying pollution severities. The results of the simulations are analyzed and the surface resistances of the wet polluted insulators were calculated. An experiment was' set up to mask the environmental weather conditions found which would lead to surface condensation. The insulators under test were placed in a chilled weather chamber which introduced a steam fog to simulate the humidity. The leakage current was measured and recorded for comparison with the simulation results. The results of the weather chamber test showed that surface condensation resulted in more severe wetting than manual wetting. The weather chamber surface resistances calculated were much lower than those calculated by the Maxwcll simulations. This was due to the difference it humid particle temperature in the condensation rate equations used for the Maxwell simulations, and the humid particle temperature of the steam fog used in the weather chamber. Polluted coastal outdoor insulators exposed to the above weather conditions will experience larger than normal leakage currents which will lead to premature failure of the units. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2008.

This research is aimed at analyzing the performance of the restricted earth fault relay used on a 400kV capacitor bank scheme used on the Eskom Transmission network. After the commissioning of two Capacitor Banks using the above mentioned scheme design the plant was energized. As a result of the energization the Shunt Capacitor Bank (SCB) then experienced spurious trips. The cause of the trips was found to be the operation of the restricted earth fault relay. In this research project, restricted earth fault protection on SCBs in the Eskom Transmission environment will be the area of interest. The proposed research will analyze the current SCB protection scheme in service specifically looking at the restricted earth fault circuit design and relay performance. An equivalent model of the SCB from primary plant perspective based on theory will be derived. Recording and analyzing of Comtrade transient waveforms respectively, when the bank is nergized, will be done in order to provide a reference base to work from. Manual alculations of various parameters from the derived model including transient inrush currents and fault currents will be performed to access applicable scheme parameters. Further calculations will include the voltage setting for the restricted earth fault relay. As a result of the analysis a recommendation will be made on a viable solution or a revised design will be put forward, based on the results, to improve the scheme’s performance. The protection scheme is used on the two 400kV 100MVAR capacitor banks 11 and 12 at Hydra Substation.

This work demonstrates the use of digital simulation for analyzing protection system performance. For studies of complex, multi-relay protection systems, digital simulation provides utility engineers with an attractive alternative to relay testing techniques. The cost of digital simulation facilities can be lower than the cost of comparable testing facilities; relay hardware does not have to be made available for the test laboratory. Digital simulation would ordinarily be impractical for security and dependability studies, due to the thousands of individual simulations involved. The number of simulations needed can be greatly reduced by using a technique called "numerical logic replacement" for implementing the protection scheme logic. This unconventional technique makes near-misoperation visible from individual simulations. The likelihood of overlooking potential misoperation is thus much lower than with the usual direct (Boolean) implementations. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

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Orientador: Rubén Augusto Romero Lázaro / Banca: José Roberto Sanches Mantovani / Banca: Sergio Azevedo de Oliveira / Banca: Luis Gustavo Wesz da Silva / Banca: João Bosco Augusto London Junior / Resumo: Este trabalho aborda o problema de planejamento da expansão da rede de transmissão (PERT) e utiliza o modelo CC no horizonte de planejamento estático, em duas variações: com restrições de segurança N-1 (PERTES) e a formulação usual, sem restrições de segurança (PERTE). As meta-heurísticas busca tabu, GRASP e busca local iterada foram implementadas utilizando o framework ParadisEO e os parâmetros foram ajustados com auxílio do software paramILS. Os algoritmos foram testados em 42 sistemas teste divididos em 6 grupos de sistemas: Garver 6 barras (4 sistemas teste), IEEE 24 barras (10 sistemas teste), Sul Brasileiro 46 barras (4 sistemas teste), Sudeste Brasileiro 79 barras (4 sistemas teste), Nordeste Brasileiro 87 barras (8 sistemas teste) e Colombiano 93 barras (12 sistemas teste). Os testes verificaram a viabilidade de utilizar o framework ParadisEO para implementação de meta-heurísticas para o PERT. Além disso, foi criado um conjunto de informações de referência para utilização em trabalhos futuros com os problemas PERTE e PERTES / Abstract: This work deals with the energy network transmission expansion planning problem (TEP) and uses two variations of the CC model on the static planning horizon: with N-1 security constraints (STEPS) and the usual formulation, without security constraints (STEP). The meta-heuristics tabu search (TS), GRASP and iterated local search (ILS) were implemented using the framework ParadisEO and the parameters tunning were made with the aid of paramILS. The algorithms were tested in 42 test systems divided into 6 groups: Garver 6 bars (4 test systems), IEEE 24 bars (10 test systems), 46 South Brazilian bars (4 test systems), Brazilian Southeast 79 bars (4 test systems), Brazilian Northeast 87 bars (8 test systems) and Colombian 93 bars (12 test systems). The tests showed the viability of ParadisEO framework to implement meta-heuristics for the TEP problem. In addition, a large benchmark for use in future STEP and SSTEP works was created. / Doutor

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