Thesis (Ph. D.)--Victoria University (Melbourne, Vic.), 2006. / Includes bibliographical references.

Thesis (Professional Degree)--University of Missouri, School of Mines and Metallurgy, 1924. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed March 3, 2010) Includes bibliographical references (p. 187-194) and index (p. 195-199).

D. Ing. / This dissertation deals with the important issue of reliability management for 3kV DC Traction Substations used by the national railway company in South Africa. Maintenance is one of the critical and most costly phases in the lifecycle of any plant. It looks at the total life cycle of the equipment in a typical substation, but the focus in the latter chapters is on the maintenance. Through improved maintenance management, the reliability of the system can be improved. The approach to maintenance is addressed as a predictive strategy, avoiding even more costly nonproductive time due to downtime caused by failure or induced by maintenance. Condition monitoring and assessment is described as one of the effective tools in the maintenance engineer’s armoury to apply a predictive approach. A direct link between predictable maintenance and reliability is explored. In the definition of reliability, concepts such as time and expected performance can be linked to a predictable delivery of the designed function. In other words, if down time is expected and can be prepared for, it is more acceptable than the unexpected. In essence, the system is still reliable as it performs according to expectation. The concept of predictable maintenance can be applied wider than just the 3kV traction substation. The process of identifying critical equipment, to measure the condition and to take decisions based on the rate of change in the condition can be used in any maintenance environment, even outside electrical. The crucial ingredient to this is to understand that condition monitoring is not based on fixed values, but the rate at which these values change. This is called Fuzzy logic. Can we predict the future? If yes, how accurate will the predictions be?

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1923. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed June 1, 2010) Includes bibliographical references (p. 22) and index (p. 37-38).

M.Ing. / The importance of maintenance in industry and specifically in the electrical distribution industry has never really been challenged. Maintenance has none of the glamour of other functions such as Marketing or Research, nor has it enjoyed close attention received by other aspects of business such as production and sales. Yet management remains painfully aware of the consequences and cost to the business when the maintenance job is not properly executed. What has, in recent years, exacerbated matters somewhat (in the electrical distribution business) is the reluctance of utility undertakings to invest heavily in a business that is to undergo a vast transformation arising from the creation of the National Electricity Regulator (NER). This will entail the amalgamation of some 400 plus different electricity distributors, by far the most in the guise of municipal undertakings, into a few Regional Distributors and Metro's. During this phase of uncertainty, the electricity departments of many municipalities have been allowed to deteriorate as maintenance and refurbishment funds were moved into other areas that would remain within the control of the municipalities. Eskom also has allowed, to a certain extent, its own distribution infrastructure to deteriorate over the last decade or so due to a focus being placed on the distribution and delivery of electric power to remote and informal settlement areas. Now on the eve of the re-organisation of the electricity supply industry into Regional Distributors and Metro's, the existing network infrastructures are far from being in an ideal situation to cope with the added business constraints to be placed on the supply industry under the scope of Regulation. This dissertation looks at an integrated maintenance strategy for one component of the electricity infrastructure namely, the distribution substation. The Electricity Supply Industry (ESI) is on the brink of vast changes that will reform the industry. Already there are cracks developing in the existing supply infrastructure resulting in power blackouts in several major centres. With the coming of the Regional Electricity Distributors, additional constraints will be placed on the supply industry. It is vital that maintenance management in the ESI start to work proactively in optimising maintenance to achieve a best return on hard gained funding in the coming years.

The requirement for new and existing outdoor air insulated substations to support larger blocks of power in restricted spaces requires an investigation into new bus conductor systems. This study has considered the use of supported, as opposed to suspended, round tubular conductors that have high current capacity necessary for this purpose. The advantages are associated with the fact that smaller clearances are attainable as a result of the restriction of horizontal deflection under fault conditions, and vertical deflection under own weight (sag) due to the rigidity of the tubular conductors as long as the bus tube is correctly sized for the application. Since the tubes are sized for mechanical strength, they are generally oversized electrically, allowing greater flexibility in busbar configuration. Forces due to gravity, wind vibration, fault current and tubular conductor thermal expansion, as well as the restrictions on electromagnetic fields have been considered. The design criteria for conductor and insulator strength calculations also formed part of the study. The study was carried out in a step-by-step analysis of the above considerations. An Excel based programme was developed to analyse the sensitivity of conductor and insulator strength calculations, due to errors in the estimation of various parameters that are required for these calculations. The tolerances in manufacturing and deviations in experimental data were determined and used to evaluate the results obtained and provide a level of confidence that any errors that may arise could be mitigated against by choosing the correct components. The result of the study is a design guide that allows substation designers to develop tubular busbar systems that will operate successfully in the conditions they were designed for. The guide provides an integrated design approach with methods for calculating the forces to which rigid bus structures are subjected. / Thesis (M.Sc.)-University of KwaZulu-Natal, 2008.

Thesis submitted in fulfillment of the requirements for the degree Master of Technology: Electrical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology / The electric power distribution network, an essential section of the electric power system, supplies electrical power to the customer. Automating the distribution network allows for better efficiency, reliability, and level of work through the installation of distribution control systems. Presently, research and development efforts are focused in the area of communication technologies and application of the IEC 61850 protocol to make distribution automation more comprehensive, efficient and affordable. The aim of the thesis is to evaluate the relevance of the IEC61850 standard-based technology in the development and investigation of the distribution automation for a typical underground distribution network through the development of a distribution automation algorithm for fault detection, location, isolation and service restoration and the building of a lab scale test bench Distribution Automation (DA) has been around for many decades and each utility applies its developments for different reasons. Nowadays, due to the advancement in the communication technology, authentic and automatic reconfigurable power system that replies swiftly to instantaneous events is possible. Distribution automation functions do not only supersede legacy devices, but it allows the distribution network to function on another lever. The primary function of a DA system is to enable the devices on the distribution network to be operated and controlled remotely to automatically locate, isolate and reconnect supply during fault conditions. Utilities have become increasingly interested in DA due to the numerous benefits it offers. Operations, maintenance and efficiencies within substations and out on the feeders can be improved by the development of new additional capabilities of DA. Furthermore, the new standard-based technology has advanced further than a traditional Distribution Supervisory and Control Data Acquisition (DSCADA) system. These days the most important components of a DA system include Intelligent Electronic Devices (IEDs). IEDs have evolved through the years and execute various protection related actions, monitoring and control functions and are very promising for improving the operation of the DA systems. The thesis has developed an algorithm for automatic fault detection, location, isolation and system supply restoration using the functions of the IEC61850 standard-based technology. A lab scale system that would meet existing and future requirements for the control and automation of a typical underground distribution system is designed and constructed. The requirement for the lab scale distribution system is to have the ability to clear faults through reliable and fast protection operation, isolate faulted section/s, on the network and restore power to the unaffected parts of the network through automation control operation functions of the IEC61850 standard. Various tests and simulations have been done on the lab scale test bench to prove that the objective of the thesis is achieved. Keywords: IEC61850 Standard, Distribution automation, Distribution automation system, IEDs, Lab scale test bench, Protection, Algorithm for automatic control

Denna rapport behandlar behovet av lokalkraft i Vattenfalls transformatorstationer. Tre vanligt förekommande transformatorstationer - stamstation, regionstation och fördelningsstation - har studerats. Alla transformatorstationer behöver lokalkraft för att fungera. Begreppet lokalkraft syftar till den matning som förser en transformatorstations utrustning med el. Apparater som försörjs av lokalkraften är bland annat motorer för brytare, transformatorkylning, kontrollutrustning, värme och belysning. Ok-lindning är ett exempel på en lokalkraftslösning, vilket är det alternativ som Vattenfall vanligtvis använder. Denna lindning är placerad i huvudtransformatorn och består av ett fåtal varv runt järnkärnan. Spänningen från ok-lindningen är aldrig exakt 400 V och därför krävs en matchningstransformator. Rapporten beskriver även kort några andra lokalkraftslösningar samt några tillfälliga effektuttag. Studien undersöker hur stort det teoretiska lokalkraftsbehovet är och vad det är för utrustning som har störst effektförbrukning i de tre stationstyperna. Effekterna delas upp i tre kategorier: ställverk, kontrollanläggning och lokal. Det beräknade lokalkraftsbehovet är i stamstationen 140 kVA, i regionstationen 54 kVA och i fördelningsstationen 25 kVA. Resultaten visar att det teoretiska lokalkraftsbehovet i samtliga studerade stationer är lägre än de standardstorlekar Vattenfall tillämpar som är på 400 kVA, 250 kVA och 100 kVA. / This thesis studies the auxiliary power requirement in Vattenfall's substations. Three common substations - national grid substation, regional grid substation and distribution grid substation - have been studied. All substations need auxiliary power to function properly. Auxiliary power is what powers the substation equipment, for example motor drives, transformer cooling, control equipment, heating and lighting. Auxiliary winding is one solution to supply auxiliary power, which is the option that Vattenfall commonly uses. The winding is placed in the main transformer and consists of a few turns around the iron core. The voltage from an auxiliary winding is never exactly 400 V and a matching transformer is therefore required. The report also briefly describes a few other auxiliary power solutions and a few temporary power consumptions. The study examines the theoretical auxiliary power requirements and what kind of equipment that has the highest power consumption in each of the three types of substations. The power consumption is divided into three categories, switchgear, control equipment and premises. The calculated auxiliary power requirement is 140 kVA for the national substation, 54 kVA for the region substation and 25 kVA for the distribution substation. The results show that the theoretical auxiliary power requirement in all of the studied substations is lower than the standard auxiliary winding sizes used by Vattenfall, which is 400 kVA, 250 kVA and 100 kVA.

This dissertation deals with the important issue of reliability management for 3kV DC Traction Substations. A general introduction explaining the changes that took place in the railway environment is followed by a description of the system. Understanding the components of the system is important but care must be taken not to go into too much detail. The level at which the system is broken down will be sufficient for this study. Some relevant reliability theory is discussed and applied to the 3kV DC system. An analysis of the failure modes and criticality helps to identify the components that need special focus during the inspections. With a good understanding of the above aspects a process for the inspection of substations is formulated. To design a process that can be used throughout an organisation, certain test must be done. The tests include determining the influence of expertise and experience of the person carrying out the inspections. The result of this study is an inspection process for 3kV DC traction substations that can be used to obtain a good idea of the condition of the system in order to make maintenance decisions that will improve the reliability of the system. / Prof. J.H.C. Pretorius Prof. W.A. Cronje

As the IEC 61850 digital substation standard becomes progressively adopted by utilities throughout the world, entirely computerized methods will completely replace traditional strategies for monitoring the power system. Although newer techniques offer enhanced efficiency and controllability, their reliability is not as established as that of conventional practices. Modern approaches require extensive validation and analysis before they can be implemented on a widespread basis. One specific area of interest is the performance of protection systems that utilize voltage and current samples digitized directly at their source. This research presents a complete test bench for evaluating sampled values-based protection schemes and measures their efficacy under several different operating conditions. It is shown that the novel system operates correctly for the situations it is expected to, with minimal latency compared to traditional practices. / Master of Science / Power system infrastrcutures are changing rapidly from analog arrangements to entirely digital methods. This offers numeous benefits such as increased efficiency, lower cost, higher accuracy, and even improved safety. However, digital implementations do not have an as proven track record as compared to conventional practices, leading to concerns about their reliaiblity. This research tests the performance an en entirely digital protection scheme by using various hardware components. The results are analyzed and show that the novel scheme operates correctly, albeit with a slight delay as compared to traditional methods.