Mechanical oscillations on overhead transmission lines
- Authors: Du Plessis, Pieter
- Date: 2014-05-08
- Subjects: Overhead electric lines , Telecommunication lines
- Type: Thesis
- Identifier: uj:10966 , http://hdl.handle.net/10210/10539
- Description: D.Ing. (Mechanical Engineering) , This research proposed to develop a mathematical model for the prediction of aeolian vibration levels on overhead transmission lines in order to be able to ensure that damping systems are designed optimally in future. In order to enhance the understanding of aeolian and wake-induced vibration further, it also proposed to implement and apply the fluid flow simulation technique of Computational Fluid Dynamics (CFD) to both single conductors and conductor bundles. The Introduction of the CFD tool to the field of transmission line vibration, will ensure that bundles could be optimally designed for future applications. Wind-induced vibrations are known to cause expensive damage to the conductors and related hardware through fatigue or clashing of the bundled conductors. The primary cause of conductor aeolian vibration is the alternate shedding of wind-induced eddies from the top and bottom sides of the conductor, whereas wake-induced oscillations is peculiar to bundled conductors and arises from effects of the shielding of leeward conductors in bundles by windward ones. In order to study the phenomenon of aeolian vibration, research was undertaken utilising a full scale transmission line test station close to Kroonstad in the Orange Free State. Commercially available computer based packages were used for the development and simulation of both the mathematical model and fluid flow. During the flow simulations, an actual Zebra conductor and Zebra bundle configuration were utilised. For the development of the mathematical model, the pratical results, as measured at the Kroonstad transmission line test station during Phase I, were utilised. From the tests performed during Phase I, it was concluded that the damping solutions, currently used by Eskom as tested during Phase I, are all effective in controlling the aeolian vibration. The Stockbridge damper proved to be avery effective damper. Two models for the prediction of aeolian vibration levels were derived. Results showed that the vibration levels could be estimated to the correct order of magnitude and in many cases the precise values. The accuracy of the model was further improved by the inclusion of the Strouhal number as a function of windspeed. It has been decided by the author 10 develop and design a low cost vibration activity indicator for aeolian vibration measurements. The T-R-I-V-A-I has shown that it is a repeatable, reliable device, Ideally suited for line vibration detection. A new device, the W-I-V-I, has also been designed and implemented by the author for the detection and quantification of wake-induced vibration. During the simulation of the flows around a conductor in the steady state, it was established that the flow around as smooth cylinder and a Zebra conductor, is very similar, however, it was established that the rough outer surface of the Zebra conductor acts as a vortex generator. It has been found that a stability relationship exists between the degree of symmetry of the pressure cell, directly in front of the leeward conductor and the wake-induced vibration. Results for the unsteady flow situation showed the initiation and dispersion of the vortices as they are generated alongside the conductor. It is recommended that the developed model's accuracy be further enhanced. It should be established if .there are families of curves and data that belong together and that contribute to the amount of scatter in the parameters measured such as vibration amplitude, Strouhal number, etc. The applicability of CFD to the transmission line field should be enhanced, with the view of increasing bundle performance, both from an electrical and mechanical point of view.
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The management of a research and development organisation with a view to corporatisation
- Authors: Du Plessis, Pieter
- Date: 2012-08-20
- Subjects: Engineering - Management , Organizational change , Privatization
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/10210/382187 , uj:2748 , http://hdl.handle.net/10210/6188
- Description: M.Phil. , Within the South African context a government of national unity has been elected. Before and after the election, mention was made of the corporatisation and/or the privatisation of state owned assets and parastatals such as Eskom, Telkom and Spoomet. The corporatisation and/or privatisation of these state assets would result in an increase in funds for the government to spend on the Reconstruction and Development Programme, as well as lead to the increase in efficiency of some of these state owned assets. Every day more comment is being made on the possibility of Eskom corporatising. This research proposed to study certain current management philosophies and methodologies being used within Eskom's Technology, Research and Investigations (T-R-I) with a view to corporatisation. This was done by comparing current management practices found in T-R-I, to both literature and prominent engineering companies in South Africa. Topics included the concept of engineering management, marketing, organisational structures, project management and change management. A literature review on strategic planning was also performed and this lay the foundation for personalised interviews with managers in prominent South African engineering companies. The interviews were conducted by means of a structured questionnaire and a statistical analysis, and comparisons of the various methodologies in terms of strategic planning within these engineering companies, were subsequently performed. A visit was also undertaken to Australian utilities which have already been through the corporatisation process. Here, first hand knowledge of the various experiences of corporatisation was obtained. T-R-I is a multi-disciplinary engineering consulting organisation which undertakes investigations, studies, applied research and testing for Eskom and other companies. It employs 308 technical people in modem laboratories. T-R-I operates in an engineering environment and following from the literature search, it is believed that T-R-I should apply the principles of engineering management. A comprehensive overview of marketing and all the aspects associated therewith was performed. It is recommended that T-R-I develop a marketing intelligence system and one comprehensive marketing plan. T-R-I also needs to develop a decision support system that will assist in making better analyses and decisions as far as product development and entry into the market is concerned. Competitors also need to be studied in more detail. Three organisational designs were investigated, i.e. the functional organisation, the product organisation and the matrix organisation. Since all of T-R-I's work is based on projects, it is recommended that T-R-I follow a matrix type structure for the effective execution of its projects. Six key activities for successful change implementation were highlighted in this study. Strategic planning was analysed by means of what literature promotes as an effective business plan. The purpose of the vision, mission, philosophy, environmental analysis and goals was discussed and comparisons were made between the literature studies and T-R-I's business plan. A structured questionnaire was developed in order to facilitate interviews with managers of five prominent South African engineering companies. A detailed statistical analysis of the resultant discussions is presented in the thesis. The questionnaire extracted information on organisational nature, organisational principles of operation, people development, management aspects and strategic planning. By comparing T-R-I's current methodology and detailed contents of the business plan to these five engineering companies, it was found that T-R-I acknowledged and responded to all of the main issues and methodologies. The Australian electricity industry has already been corporatised. A visit to five utilities in Australia was undertaken to discuss how corporatisation has affected them. What was very clear in the discussions, was that T-R-I will not survive as an "Eskom only" service provider but that it needs to expand its market. T-R-I cannot take it for granted that it has a captive market in Eskom. All of the Australian utilities visited, however, indicated that they believed that corporatisation was well worth it. It is, however, recommended that comparative studies be performed in order to evaluate what companies did to transform from parastatals or military supporting companies to successful companies in the private sector (eg. Denel, Sentech and the Atomic Energy Corporation). In-depth studies focusing on these organisations will add to the identification of those inefficiencies within T-R-I that would enhance its capabilities, should they be positively addressed, in order to sustain itself in the future and be a successfully corporatised entity.
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