Development of corona-based power supplies for remote repeater stations for overhead HVDC power transmission systems
- Authors: Kaseke, R
- Date: 2012
- Language: English
- Type: Thesis , Doctoral , PhD (Physics)
- Identifier: vital:11595 , http://hdl.handle.net/10353/d1006787
- Description: More and more people worldwide are becoming “carbon conscious”. This means they are becoming increasingly aware of the imminent adverse effects of global warming. Of late there has been an urgent drive for governments to be on the forefront of all carbon mitigation initiatives. One such drive involves the United Nations Framework Convention on Climate Change whose parties have been meeting regularly under the banner of Conference of Parties (COP) since 1995. At this conference, parties to the convention review progress made in dealing with climate change. Also key to the deliberations in such meetings are better ways of developing cleaner “carbon free” energy sources. Energy sources of this nature are commonly known as renewable energy sources. In essence global energy trends are constantly moving towards development of more renewable energy sources. It is an undeniable fact that some of viable renewable energy sources especially those with bulk capacity are usually located remotely from load centers. This inevitable reality necessitates the construction of long distance bulk power transmission corridors to link generation sites with load centers. Due to its many inherent advantages over High Voltage Alternate Current (HVAC) for long distance power transmission, High Voltage Direct Current (HVDC) is gradually winning the favor of many utilities. In fact, recent advances in HVDC technology have encouraged many utilities to explore the possibility of harnessing remotely located renewable energy sources which would have otherwise not been viable with HVAC transmission. Through the unfortunate and inevitable phenomenon known as corona effect, overhead HVDC conductors suffer real power losses to the air dielectric surrounding them. Through corona, part of the energy carried on the transmission line is expended through ionization and movement of charges in the air dielectric. This study combined physics, mathematical as well engineering concepts to review corona phenomenon around HVDC lines with specific emphasis on space charge generation and motion within ionized DC fields as well as the influence of temperature on corona discharge or power loss. Also, unlike HVAC, performance of an HVDC system relies heavily on the availability of a reliable and robust telecommunication system. One of the key ways of ensuring reliability of a telecommunication system is by making sure that reliable power supplies are in place to power remote repeater stations. A novel concept of quasi-autonomous corona-based power supply (or QC power supply in short) that works on the principle of magnetohydrodymic (MHD) power generation was developed. A small scale experiment was then designed to assess the feasibility of such power supplies. The experiment was conducted with DC supply of a maximum rated voltage of 30 kVDC and generated up to 6 VDC at an optimum ambient temperature of 23°C. These results have confirmed that with further development QC power supplies have the potential of proving reliable power to remotely located repeaters or any other small critical loads along the stretch of the HVDC transmission line. Practical HVDC transmission systems operate voltages in the excess of 500 kV. By linear extrapolation of the above mentioned results; one would expect to yield up to 100-, 120- and 160-VDC from a 500-, 600- and 800- kV HVDC system, respectively. Although the study succeeded in conceptualizing a CMHD idea upon which the novel QC power supply was developed, quite extensive and rigorous design, modeling, prototyping and experimentation processes are still required before the first QC power supply can be commissioned on a practical HVDC line
- Full Text:
- Date Issued: 2012
- Authors: Kaseke, R
- Date: 2012
- Language: English
- Type: Thesis , Doctoral , PhD (Physics)
- Identifier: vital:11595 , http://hdl.handle.net/10353/d1006787
- Description: More and more people worldwide are becoming “carbon conscious”. This means they are becoming increasingly aware of the imminent adverse effects of global warming. Of late there has been an urgent drive for governments to be on the forefront of all carbon mitigation initiatives. One such drive involves the United Nations Framework Convention on Climate Change whose parties have been meeting regularly under the banner of Conference of Parties (COP) since 1995. At this conference, parties to the convention review progress made in dealing with climate change. Also key to the deliberations in such meetings are better ways of developing cleaner “carbon free” energy sources. Energy sources of this nature are commonly known as renewable energy sources. In essence global energy trends are constantly moving towards development of more renewable energy sources. It is an undeniable fact that some of viable renewable energy sources especially those with bulk capacity are usually located remotely from load centers. This inevitable reality necessitates the construction of long distance bulk power transmission corridors to link generation sites with load centers. Due to its many inherent advantages over High Voltage Alternate Current (HVAC) for long distance power transmission, High Voltage Direct Current (HVDC) is gradually winning the favor of many utilities. In fact, recent advances in HVDC technology have encouraged many utilities to explore the possibility of harnessing remotely located renewable energy sources which would have otherwise not been viable with HVAC transmission. Through the unfortunate and inevitable phenomenon known as corona effect, overhead HVDC conductors suffer real power losses to the air dielectric surrounding them. Through corona, part of the energy carried on the transmission line is expended through ionization and movement of charges in the air dielectric. This study combined physics, mathematical as well engineering concepts to review corona phenomenon around HVDC lines with specific emphasis on space charge generation and motion within ionized DC fields as well as the influence of temperature on corona discharge or power loss. Also, unlike HVAC, performance of an HVDC system relies heavily on the availability of a reliable and robust telecommunication system. One of the key ways of ensuring reliability of a telecommunication system is by making sure that reliable power supplies are in place to power remote repeater stations. A novel concept of quasi-autonomous corona-based power supply (or QC power supply in short) that works on the principle of magnetohydrodymic (MHD) power generation was developed. A small scale experiment was then designed to assess the feasibility of such power supplies. The experiment was conducted with DC supply of a maximum rated voltage of 30 kVDC and generated up to 6 VDC at an optimum ambient temperature of 23°C. These results have confirmed that with further development QC power supplies have the potential of proving reliable power to remotely located repeaters or any other small critical loads along the stretch of the HVDC transmission line. Practical HVDC transmission systems operate voltages in the excess of 500 kV. By linear extrapolation of the above mentioned results; one would expect to yield up to 100-, 120- and 160-VDC from a 500-, 600- and 800- kV HVDC system, respectively. Although the study succeeded in conceptualizing a CMHD idea upon which the novel QC power supply was developed, quite extensive and rigorous design, modeling, prototyping and experimentation processes are still required before the first QC power supply can be commissioned on a practical HVDC line
- Full Text:
- Date Issued: 2012
Microfinance Institutions (MFIs) and rural poverty reduction in the Eastern Cape Province South Africa: a case of Amathole Rural District
- Authors: Mamutse, Zivai Tapfumanei
- Date: 2012
- Subjects: Entrepreneurship -- South Africa -- Eastern Cape , Eastern Cape -- South Africa -- Economic policy , Eastern Cape -- South Africa -- Social conditions , Eastern Cape -- South Africa -- Economic conditions
- Language: English
- Type: Thesis , Masters , M Soc Sc (Dev)
- Identifier: vital:11440 , http://hdl.handle.net/10353/d1007231 , Entrepreneurship -- South Africa -- Eastern Cape , Eastern Cape -- South Africa -- Economic policy , Eastern Cape -- South Africa -- Social conditions , Eastern Cape -- South Africa -- Economic conditions
- Description: The government of South Africa has seen many financial reforms in the finance industry since the attainment of freedom in 1994. Many microfinance institutions (MFIs) have emerged in the name of poverty reduction, however the impact of MFIs on poverty reduction in rural areas has not been significantly high. Poverty has been reduced but still the inequality gap has even widened (HSRC, 2004). The study is concerned with analysing the impact of MFIs in poverty reduction among the rural poor. Empirical evidence from many developing nations around the world has shown that microfinance is a tool that is relevant in reducing poverty within rural areas. This study investigates the impact of microfinance institutions on household income levels, education and business skills. The study followed a qualitative approach in terms of the research methodology and a survey research design. Data was collected using questionnaires, scheduled interviews, focus group discussions and key informants. Two sample techniques were used for the selection of the MFIs and the household respondents, that is purposive sampling and cluster sampling. In total, 150 households, 15 MFIs and five key informants were interviewed. Descriptive analysis methods were employed and the study showed that only 10 percent of the total households have been able to access microfinance. The number of people who gained business skills was also low (10 percent). The MFIs who provide financial services excluding the other services like business training programmes were 80 percent of the total number of MFIs interviewed. This data showed that only a few (20 percent) MFIs are willing to go an extra mile rendering business skills to their clients. Overally the major finding of the study was that although, MFIs are reaching out to the rural communities, their levels of outreach is still very low within the rural areas. However this does not mean that the impact of MFIs funding is not felt among the rural poor. The levels of income and educational benefits have been increased and felt by the 10 percent of the rural poor clients. This study advocates for an entrepreneurship development pathway to poverty reduction. Microfinance should be used as a source of finance to initiate entrepreneurial activities among the poor in order to generate income. In this study, the use of microfinance finance for consumption by the poor is discouraged because it depletes the funds that can be channeled for selfhelp projects within the rural communities. The study findings motivated the recommendations that encourage an inclusive financial system that is capable of reaching out to the rural poor.
- Full Text:
- Date Issued: 2012
- Authors: Mamutse, Zivai Tapfumanei
- Date: 2012
- Subjects: Entrepreneurship -- South Africa -- Eastern Cape , Eastern Cape -- South Africa -- Economic policy , Eastern Cape -- South Africa -- Social conditions , Eastern Cape -- South Africa -- Economic conditions
- Language: English
- Type: Thesis , Masters , M Soc Sc (Dev)
- Identifier: vital:11440 , http://hdl.handle.net/10353/d1007231 , Entrepreneurship -- South Africa -- Eastern Cape , Eastern Cape -- South Africa -- Economic policy , Eastern Cape -- South Africa -- Social conditions , Eastern Cape -- South Africa -- Economic conditions
- Description: The government of South Africa has seen many financial reforms in the finance industry since the attainment of freedom in 1994. Many microfinance institutions (MFIs) have emerged in the name of poverty reduction, however the impact of MFIs on poverty reduction in rural areas has not been significantly high. Poverty has been reduced but still the inequality gap has even widened (HSRC, 2004). The study is concerned with analysing the impact of MFIs in poverty reduction among the rural poor. Empirical evidence from many developing nations around the world has shown that microfinance is a tool that is relevant in reducing poverty within rural areas. This study investigates the impact of microfinance institutions on household income levels, education and business skills. The study followed a qualitative approach in terms of the research methodology and a survey research design. Data was collected using questionnaires, scheduled interviews, focus group discussions and key informants. Two sample techniques were used for the selection of the MFIs and the household respondents, that is purposive sampling and cluster sampling. In total, 150 households, 15 MFIs and five key informants were interviewed. Descriptive analysis methods were employed and the study showed that only 10 percent of the total households have been able to access microfinance. The number of people who gained business skills was also low (10 percent). The MFIs who provide financial services excluding the other services like business training programmes were 80 percent of the total number of MFIs interviewed. This data showed that only a few (20 percent) MFIs are willing to go an extra mile rendering business skills to their clients. Overally the major finding of the study was that although, MFIs are reaching out to the rural communities, their levels of outreach is still very low within the rural areas. However this does not mean that the impact of MFIs funding is not felt among the rural poor. The levels of income and educational benefits have been increased and felt by the 10 percent of the rural poor clients. This study advocates for an entrepreneurship development pathway to poverty reduction. Microfinance should be used as a source of finance to initiate entrepreneurial activities among the poor in order to generate income. In this study, the use of microfinance finance for consumption by the poor is discouraged because it depletes the funds that can be channeled for selfhelp projects within the rural communities. The study findings motivated the recommendations that encourage an inclusive financial system that is capable of reaching out to the rural poor.
- Full Text:
- Date Issued: 2012
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