Reliability evaluation of an electric power distribution system : a case study in Gauteng Metropolitan Municipality
- Authors: Choma, August M.
- Date: 2018
- Subjects: Engineering - Management , Electric power distribution , Electric power systems
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/293822 , uj:31957
- Description: M.Ing. (Engineering Management) , Abstract: The electrical power is a basic public service. The electrical power reliability is very essential since most of the infrastructures are dependent on it. Unplanned power outages may compromise the services such as transport, communications systems and emergency and the security services. Unplanned power outages are also inconvenient and very costly to both commercial and residential customers. As a result, the research study identify the factors that contribute to poor reliability of distribution networks and from the findings the alternative strategies are proposed and discussed. The study is intended to help electrical utilities such as municipalities to efficiently investigate the distribution network that is affected and apply the scheduled reliability development tactics to achieve the best performance. The literature review was carry out to review the existing body of the knowledge in relation to the root causes of unplanned power outages, overview of distribution reliability performance indices and the solutions that can be used to improve the performance of distribution system. A case study strategy was presented within one of the Gauteng Metropolitan Municipality with three year (2015-2017) historical power outage data of medium voltage feeders. It was found that most of these failures of medium voltage feeders under the case study take place due to equipment failures contributing high (total of 37 fault incidents in three years). Equipment failures presented a high risk, in particular the LV (Low voltage) transformer fault. Overhead line faults contributed to total of 29 fault incidents, 25 faults incidents for underground cable faults, 14 fault incidents for copper/cable theft, 12 fault incidents for electricity theft, 9 fault incidents for vandalism and 7 faults incident for extreme weather events. New factors such as motor vehicle accident, Feld fire and found no fault (unknowns) were discovered from the case study and not covered from the literature review. Metropolitan Municipality currently uses only expected reliability indices of each year to assess the distribution network performance. The research study presented the predictive reliability assessment strategy that can be used by managers and engineers of the municipality for predicting the distribution network problems of medium voltage feeders, which is by using the probability distribution of both SAIFI and SAIDI of each year.
- Full Text:
- Authors: Choma, August M.
- Date: 2018
- Subjects: Engineering - Management , Electric power distribution , Electric power systems
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/293822 , uj:31957
- Description: M.Ing. (Engineering Management) , Abstract: The electrical power is a basic public service. The electrical power reliability is very essential since most of the infrastructures are dependent on it. Unplanned power outages may compromise the services such as transport, communications systems and emergency and the security services. Unplanned power outages are also inconvenient and very costly to both commercial and residential customers. As a result, the research study identify the factors that contribute to poor reliability of distribution networks and from the findings the alternative strategies are proposed and discussed. The study is intended to help electrical utilities such as municipalities to efficiently investigate the distribution network that is affected and apply the scheduled reliability development tactics to achieve the best performance. The literature review was carry out to review the existing body of the knowledge in relation to the root causes of unplanned power outages, overview of distribution reliability performance indices and the solutions that can be used to improve the performance of distribution system. A case study strategy was presented within one of the Gauteng Metropolitan Municipality with three year (2015-2017) historical power outage data of medium voltage feeders. It was found that most of these failures of medium voltage feeders under the case study take place due to equipment failures contributing high (total of 37 fault incidents in three years). Equipment failures presented a high risk, in particular the LV (Low voltage) transformer fault. Overhead line faults contributed to total of 29 fault incidents, 25 faults incidents for underground cable faults, 14 fault incidents for copper/cable theft, 12 fault incidents for electricity theft, 9 fault incidents for vandalism and 7 faults incident for extreme weather events. New factors such as motor vehicle accident, Feld fire and found no fault (unknowns) were discovered from the case study and not covered from the literature review. Metropolitan Municipality currently uses only expected reliability indices of each year to assess the distribution network performance. The research study presented the predictive reliability assessment strategy that can be used by managers and engineers of the municipality for predicting the distribution network problems of medium voltage feeders, which is by using the probability distribution of both SAIFI and SAIDI of each year.
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Modelling of different long-term electrical forecasts and its practical applications for transmission network flow studies
- Authors: Payne, Daniel Frederik
- Date: 2009-02-26T12:22:02Z
- Subjects: Electric power-plants , Load forecasting , Electric power systems , Electric power distribution , Load dispatching
- Type: Thesis
- Identifier: uj:8174 , http://hdl.handle.net/10210/2179
- Description: D.Phil , The prediction of the expected transmission network loads as required for transmission network power flow studies, has become very important and much more complex than ten to twenty years ago. Therefore a single forecast is no longer the answer to the problem. The modelling of different long-term electrical forecasts makes it possible to compare a number of different forecasts. The modelling provides the further option that each expected load can be entered as a range and then the developed balancing algorithm checks for consensus (feasibility). If feasibility exists, then the different forecasts are reconciled (a feasible solution is determined). Factors such as international and national market trends, economical cycles, different weather patterns, climate cycles and demographic changes are studied. The factors that have significant impact on the transmission electrical loads are integrated in ten different forecasts. It thus gives more insight into the electrical industry and makes the forecast results more informative and therefore reduces the uncertainty in the future expected loads.
- Full Text:
- Authors: Payne, Daniel Frederik
- Date: 2009-02-26T12:22:02Z
- Subjects: Electric power-plants , Load forecasting , Electric power systems , Electric power distribution , Load dispatching
- Type: Thesis
- Identifier: uj:8174 , http://hdl.handle.net/10210/2179
- Description: D.Phil , The prediction of the expected transmission network loads as required for transmission network power flow studies, has become very important and much more complex than ten to twenty years ago. Therefore a single forecast is no longer the answer to the problem. The modelling of different long-term electrical forecasts makes it possible to compare a number of different forecasts. The modelling provides the further option that each expected load can be entered as a range and then the developed balancing algorithm checks for consensus (feasibility). If feasibility exists, then the different forecasts are reconciled (a feasible solution is determined). Factors such as international and national market trends, economical cycles, different weather patterns, climate cycles and demographic changes are studied. The factors that have significant impact on the transmission electrical loads are integrated in ten different forecasts. It thus gives more insight into the electrical industry and makes the forecast results more informative and therefore reduces the uncertainty in the future expected loads.
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The level of competitiveness of the South African electricity industry
- Authors: Goldstuck, Alison
- Date: 2012-01-24
- Subjects: Eskom (Firm) , Competition , Electric power distribution
- Type: Thesis
- Identifier: uj:1945 , http://hdl.handle.net/10210/4304
- Description: M.Comm. , South Africa's demand for electricity is expected to outstrip the industry's generation capacity by 2010. If the government wants to avoid this situation, the construction of new plants must commence. At the moment this task has been delayed because the Government is at loggerheads with COSAU and Eskom about restructuring the electricity supply industry. This debate will remain unsolved unless the government can substantiate why exposing the industry to competition will improve its performance. Unfortunately this task is not as simple as it seems. Even though competition is one of the most widely used terms in economics, it still remains an elusive concept. The ambiguity regarding tl1e meaning of competition arises from the failure to divorce the concept of competition from a market structure; as a consequence an operational meaning of what it means to compete \n terms of contemporary business behaviour does not exist. As a result activities associated with industrialisation, such as a changing production function, the development of new products and t~chniqu'::s and business structures are not related to the concept of competition. In order to develop n clear understanding of "what it means to compete", this dissertadon uses a behavioural definition of competition to determine why exposing firms to. competitive pressure improves their performance, reflected in superior static and dynamic efficiency levels. Based on this conceptual framework, Schumpeter' s approach to competition, which emphasises innovation, profits and the entrepreneur as the agent of improvement combined with the idea that it is the uneven development of knowledge that matters in the process of creative destruction", is accepted (Metcalfe & Ramlogan &Uyarra: 2001). Based on the above notion of competition, competitive pressure positively influences firms' performance, improving their static and dynamic efficiency levels. A micro-economic analysis of a C!)IDp.etitive electricity industry is conducted in order to test the abov~ assumption. This case study demonstrates that the competitive process ultimately improves thr: integration of knowledge throughout the supply chain, which is used an input to stimulate innovation within firms and exploit new technologies (Murphy, 2002:21). As a result, firms facing competition will try to retaii1 their market position 2 by exploiting all knowledge and exploring all avenues of technological invention, before selecting the best method (Khan: 1998). In addition, this case study illustrates that stimulating dynamic efficiency goes beyond developing and implementing "hardware" (computers, CCGT plants, fuel cells etc). Although technology plays an important role in shaping industrial organisation, it is not the catalyst that drives innovation and change. Rather organisational innovation changes market participants' schemas, breeding new ideas that become the input to create technology. Therefore organisational innovation has profound efficiency consequences (Williamson, 1994: 183). If technological and organisational inncvation is intertwined, then innovation is a complex evolutionary process, which occurs over time. Furthermore innovation cannot occur in a vacuum, but is interconnected, interwoven and interdependent with an industry's physical and institutional context (Perez, 2000). Based on the stylised facts a competitive market provides the institutional context that stimulates innovation, and therefore it might be worth incurring the transactions costs and short-term losses in order to create these opportunities.
- Full Text:
- Authors: Goldstuck, Alison
- Date: 2012-01-24
- Subjects: Eskom (Firm) , Competition , Electric power distribution
- Type: Thesis
- Identifier: uj:1945 , http://hdl.handle.net/10210/4304
- Description: M.Comm. , South Africa's demand for electricity is expected to outstrip the industry's generation capacity by 2010. If the government wants to avoid this situation, the construction of new plants must commence. At the moment this task has been delayed because the Government is at loggerheads with COSAU and Eskom about restructuring the electricity supply industry. This debate will remain unsolved unless the government can substantiate why exposing the industry to competition will improve its performance. Unfortunately this task is not as simple as it seems. Even though competition is one of the most widely used terms in economics, it still remains an elusive concept. The ambiguity regarding tl1e meaning of competition arises from the failure to divorce the concept of competition from a market structure; as a consequence an operational meaning of what it means to compete \n terms of contemporary business behaviour does not exist. As a result activities associated with industrialisation, such as a changing production function, the development of new products and t~chniqu'::s and business structures are not related to the concept of competition. In order to develop n clear understanding of "what it means to compete", this dissertadon uses a behavioural definition of competition to determine why exposing firms to. competitive pressure improves their performance, reflected in superior static and dynamic efficiency levels. Based on this conceptual framework, Schumpeter' s approach to competition, which emphasises innovation, profits and the entrepreneur as the agent of improvement combined with the idea that it is the uneven development of knowledge that matters in the process of creative destruction", is accepted (Metcalfe & Ramlogan &Uyarra: 2001). Based on the above notion of competition, competitive pressure positively influences firms' performance, improving their static and dynamic efficiency levels. A micro-economic analysis of a C!)IDp.etitive electricity industry is conducted in order to test the abov~ assumption. This case study demonstrates that the competitive process ultimately improves thr: integration of knowledge throughout the supply chain, which is used an input to stimulate innovation within firms and exploit new technologies (Murphy, 2002:21). As a result, firms facing competition will try to retaii1 their market position 2 by exploiting all knowledge and exploring all avenues of technological invention, before selecting the best method (Khan: 1998). In addition, this case study illustrates that stimulating dynamic efficiency goes beyond developing and implementing "hardware" (computers, CCGT plants, fuel cells etc). Although technology plays an important role in shaping industrial organisation, it is not the catalyst that drives innovation and change. Rather organisational innovation changes market participants' schemas, breeding new ideas that become the input to create technology. Therefore organisational innovation has profound efficiency consequences (Williamson, 1994: 183). If technological and organisational inncvation is intertwined, then innovation is a complex evolutionary process, which occurs over time. Furthermore innovation cannot occur in a vacuum, but is interconnected, interwoven and interdependent with an industry's physical and institutional context (Perez, 2000). Based on the stylised facts a competitive market provides the institutional context that stimulates innovation, and therefore it might be worth incurring the transactions costs and short-term losses in order to create these opportunities.
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Demand management strategies for efficient electricity demand management strategies for efficient electricity
- Authors: Ebrahim, Yumna
- Date: 2012-07-19
- Subjects: Electric power distribution , Demand side management (Electric utilities)
- Type: Mini-Dissertation
- Identifier: uj:8832 , http://hdl.handle.net/10210/5245
- Description: M.Comm. , The aim of this dissertation was to determine the potential of Demand Side Management (DSM) and its merits as a short to medium term response in wake of the current electricity supply crisis in South Africa. The research focussed on the different types of DSM alternatives used locally and internationally. Electricity is of great importance to any economy, and is the key input to industrial processes and hence economic growth. Since 2008, South Africa is facing a shortage of generation capacity. The study focussed on demand for electricity by sector and discussed the different types of DSM measures which have been used successfully in countries such as Brazil and Mexico. The results of the study indicate that the residential sector has the most potential for DSM savings. These are savings which can be made without any implementation costs, and merely by changing behaviour and attitudes toward energy efficiency. The target for the residential sector savings is 10%. Results show that this 10% saving in the residential sector is a target which can be easily attained. In addition, the residential sector has a poor load shape, with high demand during morning and evening peak, placing a burden on the national grid and resulting in the use of expensive peak generation capacity. Reducing residential sector demand for electricity will result in the added benefit of improving load shape. The study concludes with recommendations to overcome barriers faced by DSM, and also discusses benefits of rolling out RTP pricing to the residential sector.
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- Authors: Ebrahim, Yumna
- Date: 2012-07-19
- Subjects: Electric power distribution , Demand side management (Electric utilities)
- Type: Mini-Dissertation
- Identifier: uj:8832 , http://hdl.handle.net/10210/5245
- Description: M.Comm. , The aim of this dissertation was to determine the potential of Demand Side Management (DSM) and its merits as a short to medium term response in wake of the current electricity supply crisis in South Africa. The research focussed on the different types of DSM alternatives used locally and internationally. Electricity is of great importance to any economy, and is the key input to industrial processes and hence economic growth. Since 2008, South Africa is facing a shortage of generation capacity. The study focussed on demand for electricity by sector and discussed the different types of DSM measures which have been used successfully in countries such as Brazil and Mexico. The results of the study indicate that the residential sector has the most potential for DSM savings. These are savings which can be made without any implementation costs, and merely by changing behaviour and attitudes toward energy efficiency. The target for the residential sector savings is 10%. Results show that this 10% saving in the residential sector is a target which can be easily attained. In addition, the residential sector has a poor load shape, with high demand during morning and evening peak, placing a burden on the national grid and resulting in the use of expensive peak generation capacity. Reducing residential sector demand for electricity will result in the added benefit of improving load shape. The study concludes with recommendations to overcome barriers faced by DSM, and also discusses benefits of rolling out RTP pricing to the residential sector.
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The evaluation of project success and failure in an electricity distribution environment
- Shongwe, Chantyle Madidimalo
- Authors: Shongwe, Chantyle Madidimalo
- Date: 2017
- Subjects: Eskom (Firm) , Electric power-plants - South Africa - Management , Distributed resources (Electric utilities) , Electric power distribution
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/242328 , uj:24991
- Description: M.Ing. (Engineering Management) , Abstract: South Africa’s power utility distribution division executes numerous projects every financial year.The utility utilises project-management processes to execute these projects. Numerous projects in the organisation are found to have succeeded; while various other projects appear to have barriers. Projects are also delayed at the execution of the project life-cycle stage. As a result of delayed projects, reviews of the Capital expenditure (Capex) show inconsistency, as from the years 2012 to 2015. Delayed projects have caused an under expenditure of the approved budget. There are numerous times when the capital expenditure was overspent due to pressure by management for completion of the backlog of projects and critical projects within the year. This leads to a requirement for critical analysis of the utility’s distribution-project successes and failures. The objective of the research is to critically review and understand what leads to the utility distribution projects’ successes and failures. The literature was gathered to build up information on the topic. The literature from published articles, books and organisation reports is reviewed. The research makes use of both qualitative and quantitative methods. A comprehensive questionnaire is selected as the instrument for the data collection. The questions are guided by the literature review’s findings on the topic. Based on the clear correlation found between the literature’s findings and questionnaire’s results, the following summarised project success factors at distribution division were found: Management support Proper planning Scope management Competency of the project manager Effective communication Competent contractor The respondents also revealed budget and material issues, as contributing to project failure. Furthermore, organisation-specific, results analysis and recommendations are detailed in the dissertation.
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- Authors: Shongwe, Chantyle Madidimalo
- Date: 2017
- Subjects: Eskom (Firm) , Electric power-plants - South Africa - Management , Distributed resources (Electric utilities) , Electric power distribution
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/242328 , uj:24991
- Description: M.Ing. (Engineering Management) , Abstract: South Africa’s power utility distribution division executes numerous projects every financial year.The utility utilises project-management processes to execute these projects. Numerous projects in the organisation are found to have succeeded; while various other projects appear to have barriers. Projects are also delayed at the execution of the project life-cycle stage. As a result of delayed projects, reviews of the Capital expenditure (Capex) show inconsistency, as from the years 2012 to 2015. Delayed projects have caused an under expenditure of the approved budget. There are numerous times when the capital expenditure was overspent due to pressure by management for completion of the backlog of projects and critical projects within the year. This leads to a requirement for critical analysis of the utility’s distribution-project successes and failures. The objective of the research is to critically review and understand what leads to the utility distribution projects’ successes and failures. The literature was gathered to build up information on the topic. The literature from published articles, books and organisation reports is reviewed. The research makes use of both qualitative and quantitative methods. A comprehensive questionnaire is selected as the instrument for the data collection. The questions are guided by the literature review’s findings on the topic. Based on the clear correlation found between the literature’s findings and questionnaire’s results, the following summarised project success factors at distribution division were found: Management support Proper planning Scope management Competency of the project manager Effective communication Competent contractor The respondents also revealed budget and material issues, as contributing to project failure. Furthermore, organisation-specific, results analysis and recommendations are detailed in the dissertation.
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The voltage dip risk factor for distribution networks
- Authors: Park, Jeanne
- Date: 2009-02-26T12:21:50Z
- Subjects: Electric power distribution , Quality control
- Type: Thesis
- Identifier: uj:8173 , http://hdl.handle.net/10210/2178
- Description: M.Ing. , Electrical quality of supply affects every consumer, from the homeowner to large industry and mining. Customer awareness of poor power quality is increasing due to the more sensitive nature of modern equipment. The positioning of a new plant is therefore very important and cannot only be determined by the availability of resources in the area. To determine the quality of the electricity in a certain network, years of historical data is required. To get enough information regarding a distributions network performance would require voltage dip measurements at a few places in the network for at least three years. For this reason a new method are used in this study. By using the existing information in a network, like: • The amount of lightning strikes per year • The amount of electrocuted birds • The type of protection used • The amount of vandalism incidents on a line per year • The tower footing resistance • The fault level in the network The fuzzy logic principle can be used to determine how susceptible a network is to voltage dips, by determining the favourable and unfavourable conditions for a number of membership functions. Conventional set theory (Boolean) states that an element is either a member of a set or not. Fuzzy logic is an extension of conventional set theory enabling an element to belong to a set degree. This study will look at all the important factors influencing voltage dips, and to use these factors in a fuzzy logic program to determine the voltage dip risk factor for new customers setting up plant in a specific network. The voltage dip risk factor will then determine if it is cost effective for a customer to take on the additional cost in dip proofing his plant.
- Full Text:
- Authors: Park, Jeanne
- Date: 2009-02-26T12:21:50Z
- Subjects: Electric power distribution , Quality control
- Type: Thesis
- Identifier: uj:8173 , http://hdl.handle.net/10210/2178
- Description: M.Ing. , Electrical quality of supply affects every consumer, from the homeowner to large industry and mining. Customer awareness of poor power quality is increasing due to the more sensitive nature of modern equipment. The positioning of a new plant is therefore very important and cannot only be determined by the availability of resources in the area. To determine the quality of the electricity in a certain network, years of historical data is required. To get enough information regarding a distributions network performance would require voltage dip measurements at a few places in the network for at least three years. For this reason a new method are used in this study. By using the existing information in a network, like: • The amount of lightning strikes per year • The amount of electrocuted birds • The type of protection used • The amount of vandalism incidents on a line per year • The tower footing resistance • The fault level in the network The fuzzy logic principle can be used to determine how susceptible a network is to voltage dips, by determining the favourable and unfavourable conditions for a number of membership functions. Conventional set theory (Boolean) states that an element is either a member of a set or not. Fuzzy logic is an extension of conventional set theory enabling an element to belong to a set degree. This study will look at all the important factors influencing voltage dips, and to use these factors in a fuzzy logic program to determine the voltage dip risk factor for new customers setting up plant in a specific network. The voltage dip risk factor will then determine if it is cost effective for a customer to take on the additional cost in dip proofing his plant.
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Small power tapping limit on dc-link of VSC HVDC transmission system
- Nnachi, Agha F., Munda, Josiah L., Nicolae, Dan-Valentin, Mpanda, Augustin Mabwe
- Authors: Nnachi, Agha F. , Munda, Josiah L. , Nicolae, Dan-Valentin , Mpanda, Augustin Mabwe
- Date: 2013
- Subjects: Elecric power systems , Electric power distribution
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/18266 , uj:15977 , ISBN: 978-1-4799-0224-8 , Citation: Nnachi, A.F., Munda, D.V. & Mpanda, A.M. 2013. Stability improvement of a HVDC transmission stability improvement of a HVDC transmission link between weak AC systems by multi-terminal scheme, IEEE Africon, 9-11 September, 2013. DOI: 10.1109/AFRCON.2013.675810
- Description: Abstract Power tapping from HVDC transmission corridor to serve rural areas has been the focus of many researchers and network planners. The tapping stations are to be of small power ratings so that it will not interfere with the main control and stability of the HVDC network. Several research works have assumed tap-off of different percentages of the main HVDC terminal rating without justification. This paper therefore proposes a simple analytical technique used to determine power tapping limit on DC-link of a VSC HVDC network. Effect of power tapping below and above the analytical tap limit is illustrated by results from simulation carried out in Matlab/Simulink, hence validating the proposed technique.
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- Authors: Nnachi, Agha F. , Munda, Josiah L. , Nicolae, Dan-Valentin , Mpanda, Augustin Mabwe
- Date: 2013
- Subjects: Elecric power systems , Electric power distribution
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/18266 , uj:15977 , ISBN: 978-1-4799-0224-8 , Citation: Nnachi, A.F., Munda, D.V. & Mpanda, A.M. 2013. Stability improvement of a HVDC transmission stability improvement of a HVDC transmission link between weak AC systems by multi-terminal scheme, IEEE Africon, 9-11 September, 2013. DOI: 10.1109/AFRCON.2013.675810
- Description: Abstract Power tapping from HVDC transmission corridor to serve rural areas has been the focus of many researchers and network planners. The tapping stations are to be of small power ratings so that it will not interfere with the main control and stability of the HVDC network. Several research works have assumed tap-off of different percentages of the main HVDC terminal rating without justification. This paper therefore proposes a simple analytical technique used to determine power tapping limit on DC-link of a VSC HVDC network. Effect of power tapping below and above the analytical tap limit is illustrated by results from simulation carried out in Matlab/Simulink, hence validating the proposed technique.
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Power transformer failure management on the Eskom distribution network in Limpopo
- Authors: Sako, Maite Martha
- Date: 2016
- Subjects: Eskom (Firm( , Electronic transformers , Electric power distribution , Electric power systems
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/242337 , uj:24992
- Description: M.Ing. (Engineering Management) , Abstract: Electricity is a crucial key component in the everyday life influencing the economy, safety, health, productivity and comfort of the people. Power utilities continue to make the continuity of electricity supply to the consumers their first priority. Power transformers are the crucial part of the power system network because they regulate the voltage either up or down on the electrical network for safe use by the consumers. Their reliable operation on the network is very critical because it directly impacts the reliability and stability of the entire electrical network connected to it. One of the major challenges power utilities face is the failure of substation power transformers on the distribution network. Sudden failures of these transformers cause the interruption of supply to the customers. For the utility, it causes high transformer repair costs and revenue loss. The power utility is also forced to replace the failed power transformers in order to reduce the outage time for the affected customers. Although power transformers have become the heart of the distribution network, the success rate for these transformers to complete their full life cycle is not a guarantee. The performance of the power transformers on the Limpopo distribution network has not reached the projected target set by the plant performance department in the past four years and this is cause for great concern. There was a number of power transformer failures recorded in the substations. After investigations were conducted, it was found that the major causes for these failures were aging, overloading, improper maintenance schedule, internal faults and insufficient security measures in substations in remote areas. This dissertation looks at the methodologies that are currently being implemented to ensure that the installed substation power transformers approach or complete their full life cycle. It further proposes the improvement of the methodologies currently being implemented. The conclusion reached in this study is that in order for the substation power transformer failures on the Eskom distribution network in Limpopo to decrease, the methods that can alleviate the problem include: installation of an online monitoring system on the power transformers; improvement of the maintenance schedule; installation of a backup transformers in single transformer substations; improvement of the security measures in substations that are located in remote areas; putting asset replacement plans in place for transformers that are approaching their...
- Full Text:
- Authors: Sako, Maite Martha
- Date: 2016
- Subjects: Eskom (Firm( , Electronic transformers , Electric power distribution , Electric power systems
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/242337 , uj:24992
- Description: M.Ing. (Engineering Management) , Abstract: Electricity is a crucial key component in the everyday life influencing the economy, safety, health, productivity and comfort of the people. Power utilities continue to make the continuity of electricity supply to the consumers their first priority. Power transformers are the crucial part of the power system network because they regulate the voltage either up or down on the electrical network for safe use by the consumers. Their reliable operation on the network is very critical because it directly impacts the reliability and stability of the entire electrical network connected to it. One of the major challenges power utilities face is the failure of substation power transformers on the distribution network. Sudden failures of these transformers cause the interruption of supply to the customers. For the utility, it causes high transformer repair costs and revenue loss. The power utility is also forced to replace the failed power transformers in order to reduce the outage time for the affected customers. Although power transformers have become the heart of the distribution network, the success rate for these transformers to complete their full life cycle is not a guarantee. The performance of the power transformers on the Limpopo distribution network has not reached the projected target set by the plant performance department in the past four years and this is cause for great concern. There was a number of power transformer failures recorded in the substations. After investigations were conducted, it was found that the major causes for these failures were aging, overloading, improper maintenance schedule, internal faults and insufficient security measures in substations in remote areas. This dissertation looks at the methodologies that are currently being implemented to ensure that the installed substation power transformers approach or complete their full life cycle. It further proposes the improvement of the methodologies currently being implemented. The conclusion reached in this study is that in order for the substation power transformer failures on the Eskom distribution network in Limpopo to decrease, the methods that can alleviate the problem include: installation of an online monitoring system on the power transformers; improvement of the maintenance schedule; installation of a backup transformers in single transformer substations; improvement of the security measures in substations that are located in remote areas; putting asset replacement plans in place for transformers that are approaching their...
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Zero-Sequence current-based detection of electricity theft in informal settlements
- Authors: Louw, Quentin Elliott
- Date: 2017
- Subjects: Electric power - Control , Electric power distribution
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280387 , uj:30128
- Description: M.Tech. , Abstract: Losses in a power system are defined by technical and non-technical losses. Technical losses are attributed to the dissipation of power, while non-technical losses are associated with factors contributed to by external conditions such as poor administration, revenue collection and electricity theft by illegal connections or tampering. Although a pervasive worldwide phenomenon, South Africa is not immune to this situation, and is even placed in a weakened condition due to the country’s high unemployment rate, socio-economic pressures and the fact that the constitutional bill of rights affords all South African the right to electricity. The problem is specific to areas where economic activity is perceived to be more attractive, and in such case, the Gauteng province, the smallest province out of the nine South African provinces, contributes the highest portion of the country’s economic gross domestic product. This perceived economic haven creates migration of the population to areas such as Gauteng, conceiving large population densities that require the right to basic infrastructure, but failing to become economically active. These large population desities create unexpected challenges for the local supply authorities due to the formation of the informal settlements on un-proclaimed lands where legal infrastrurure services cannot be provided resulting in the population takeing matters into their own hands and connecting illegally to nearby legal power infrastructure. Supply authorities are confronted with a dilemma: 1. They have to protect the network from unintended contact incidents by humans or animals 2. Are faced with no revenue collection, and 3. Deal with poor quality of supply to the paying customer. Mitigating techniques have been suggested in literature into the management of the engineering challenges associated with this problem, but none have formulated a resolve that would address a one stop solution. Theft of electricity in worldwide utilities do not involved one specific modus operandi, and in the South African case, one such a modus operandi in informal settlements, occurs by connecting directly to the source distribution transformer with any means of cable. This results in cables laying bare on the ground or alternatively connecting the dwelling load between phase and earth, disregarding the neutral. This research focuses on these cables laying on the ground or hazard connections (phase to earth), and presents an hypothesis in the use of zero-sequence current based (ZSC) detection as a means of detection and possibly isolation of the supply of the particular network. The largest limitation variable in the calculation of these zero-sequence currents is attributed to the soil resistivity of the ground where the conductors are placed, or connected to as a return path for the load. Field tests were conducted as part of the methodology to establish various soil resistivities across the Gauteng province close to these informal settlements. These results based on the atmospheric, moisture and temperature conditions were used to calculate perspective ZSC. Further analysis was conducted using DIgSILENT Powerfactory analysis software simulation,..
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- Authors: Louw, Quentin Elliott
- Date: 2017
- Subjects: Electric power - Control , Electric power distribution
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280387 , uj:30128
- Description: M.Tech. , Abstract: Losses in a power system are defined by technical and non-technical losses. Technical losses are attributed to the dissipation of power, while non-technical losses are associated with factors contributed to by external conditions such as poor administration, revenue collection and electricity theft by illegal connections or tampering. Although a pervasive worldwide phenomenon, South Africa is not immune to this situation, and is even placed in a weakened condition due to the country’s high unemployment rate, socio-economic pressures and the fact that the constitutional bill of rights affords all South African the right to electricity. The problem is specific to areas where economic activity is perceived to be more attractive, and in such case, the Gauteng province, the smallest province out of the nine South African provinces, contributes the highest portion of the country’s economic gross domestic product. This perceived economic haven creates migration of the population to areas such as Gauteng, conceiving large population densities that require the right to basic infrastructure, but failing to become economically active. These large population desities create unexpected challenges for the local supply authorities due to the formation of the informal settlements on un-proclaimed lands where legal infrastrurure services cannot be provided resulting in the population takeing matters into their own hands and connecting illegally to nearby legal power infrastructure. Supply authorities are confronted with a dilemma: 1. They have to protect the network from unintended contact incidents by humans or animals 2. Are faced with no revenue collection, and 3. Deal with poor quality of supply to the paying customer. Mitigating techniques have been suggested in literature into the management of the engineering challenges associated with this problem, but none have formulated a resolve that would address a one stop solution. Theft of electricity in worldwide utilities do not involved one specific modus operandi, and in the South African case, one such a modus operandi in informal settlements, occurs by connecting directly to the source distribution transformer with any means of cable. This results in cables laying bare on the ground or alternatively connecting the dwelling load between phase and earth, disregarding the neutral. This research focuses on these cables laying on the ground or hazard connections (phase to earth), and presents an hypothesis in the use of zero-sequence current based (ZSC) detection as a means of detection and possibly isolation of the supply of the particular network. The largest limitation variable in the calculation of these zero-sequence currents is attributed to the soil resistivity of the ground where the conductors are placed, or connected to as a return path for the load. Field tests were conducted as part of the methodology to establish various soil resistivities across the Gauteng province close to these informal settlements. These results based on the atmospheric, moisture and temperature conditions were used to calculate perspective ZSC. Further analysis was conducted using DIgSILENT Powerfactory analysis software simulation,..
- Full Text:
A comprehensive study of power system harmonics
- Kasemuana Matototo, Seraphin
- Authors: Kasemuana Matototo, Seraphin
- Date: 2014-04-16
- Subjects: Electric power systems , Harmonics (Electric waves) , Electric power distribution , Electric networks
- Type: Thesis
- Identifier: uj:10802 , http://hdl.handle.net/10210/10309
- Description: M.Tech. (Electrical and Electronic Engineering) , With the increasing use of nonlinear loads in power systems, harmonic pollution becomes more frequent with disastrous consequences on the electrical network and other loads. Harmonic currents cause problems such as system resonance, protective relays and switchgear malfunction, communication interference, incorrect meter, equipment and process failure, over heating of transmission and distribution systems, insulation degradation and power transformer failure. It appears therefore absolutely essential to determine the current profile of the loads connected to the same Point of Common Coupling (PCC). This study aims to assess a distorted power system in order to determine the characteristics components of distorted waveforms (DC components, fundamental and harmonics components), and to quantify the respective distortion contributions in the power network. The numerical method is applied to analyse the current waveforms captured with the aid of the digital scope meter (DSO) 1200 series at different sections of the network. The power network under study is designed, constructed and analysed with the MatLab/Simulink 7.0 package. In both methods, the Individual Harmonic Distortion (IHD) and the current total harmonic distortion (ITHD) for the line, the non-linear and linear loads are computed for the harmonic components 5th, 7th, 11th and 13th. The results showed that for the analysis of the power system, numerical analysis based on the resultant harmonic curve method and the MatLab/Simulink as applied to the network all converged to highlight that harmonic components appear both on the line, the PCC and the linear load. This is due to the fact that the converter characteristic harmonics (5th, 7th, 11th, 13th…) are found in the network components (line, PCC, linear load…). The resultant harmonic curve method indicated a randomly distributed percentage IHD in different sections of the network for harmonic orders higher than 7th, whereas the Matlab/Simulink results normally show a non-uniform decay pattern of the IHD as the harmonic order increases within the respective section of the network.
- Full Text:
- Authors: Kasemuana Matototo, Seraphin
- Date: 2014-04-16
- Subjects: Electric power systems , Harmonics (Electric waves) , Electric power distribution , Electric networks
- Type: Thesis
- Identifier: uj:10802 , http://hdl.handle.net/10210/10309
- Description: M.Tech. (Electrical and Electronic Engineering) , With the increasing use of nonlinear loads in power systems, harmonic pollution becomes more frequent with disastrous consequences on the electrical network and other loads. Harmonic currents cause problems such as system resonance, protective relays and switchgear malfunction, communication interference, incorrect meter, equipment and process failure, over heating of transmission and distribution systems, insulation degradation and power transformer failure. It appears therefore absolutely essential to determine the current profile of the loads connected to the same Point of Common Coupling (PCC). This study aims to assess a distorted power system in order to determine the characteristics components of distorted waveforms (DC components, fundamental and harmonics components), and to quantify the respective distortion contributions in the power network. The numerical method is applied to analyse the current waveforms captured with the aid of the digital scope meter (DSO) 1200 series at different sections of the network. The power network under study is designed, constructed and analysed with the MatLab/Simulink 7.0 package. In both methods, the Individual Harmonic Distortion (IHD) and the current total harmonic distortion (ITHD) for the line, the non-linear and linear loads are computed for the harmonic components 5th, 7th, 11th and 13th. The results showed that for the analysis of the power system, numerical analysis based on the resultant harmonic curve method and the MatLab/Simulink as applied to the network all converged to highlight that harmonic components appear both on the line, the PCC and the linear load. This is due to the fact that the converter characteristic harmonics (5th, 7th, 11th, 13th…) are found in the network components (line, PCC, linear load…). The resultant harmonic curve method indicated a randomly distributed percentage IHD in different sections of the network for harmonic orders higher than 7th, whereas the Matlab/Simulink results normally show a non-uniform decay pattern of the IHD as the harmonic order increases within the respective section of the network.
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Evaluating an empirical relationship between recloser placement and reliability improvement in distribution networks
- Authors: Thomas, Ponny
- Date: 2016
- Subjects: Electric networks , Electric power distribution , Electric power transmission , Eskom (Firm)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/213003 , uj:21065
- Description: Abstract: The National Energy Regulator of South Africa (NERSA) has implemented an Incentive- Based Regulation (IBR) scheme that either rewards or penalizes distributors on the System- Average Interruption-Duration Index (SAIDI) and other network performance indices [1]. The optimal placement of automatic reclosers (auto-reclosers) is seen as a cost-effective measure to reduce the system-average interruption-duration index (SAIDI) impact along a medium voltage (MV) feeder. An auto-recloser is seen as a function of distribution automation (DA), thus reducing customer impact. A great advantage of a correctly implemented and operated DA system can improve network reliability significantly. This dissertation evaluates the empirical relationship between recloser placement and reliability from the perspective of control and instrumentation within ESKOM. It also puts forward an additional performance-improvement framework that can be implemented to achieve RAM (Reliability, Availability and Maintainability) management. Loop automation functionality is also under discussion; this is a Distribution-System Automation-scheme that restores the supply to the fault-free sections of a network, if they have been disconnected, because of a fault in another section of the network. Loop automation can also restore the normal network configuration automatically, when the faulty section is repaired. The process of isolating the faulty section and re-configuring the network to restore supply back to the fault-free sections is the first capability of Loop Automation. This research investigation assesses two different scenarios, namely: A conventional implementation of auto-reclosers on MV networks using Eskom reliability standard; and (ii.) the findings of a case-study using this recloser implementation (loop automation) to improve the reliability and the system’s performance. Results obtained are presented and discussed. , M.Phil. (Engineering Management)
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- Authors: Thomas, Ponny
- Date: 2016
- Subjects: Electric networks , Electric power distribution , Electric power transmission , Eskom (Firm)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/213003 , uj:21065
- Description: Abstract: The National Energy Regulator of South Africa (NERSA) has implemented an Incentive- Based Regulation (IBR) scheme that either rewards or penalizes distributors on the System- Average Interruption-Duration Index (SAIDI) and other network performance indices [1]. The optimal placement of automatic reclosers (auto-reclosers) is seen as a cost-effective measure to reduce the system-average interruption-duration index (SAIDI) impact along a medium voltage (MV) feeder. An auto-recloser is seen as a function of distribution automation (DA), thus reducing customer impact. A great advantage of a correctly implemented and operated DA system can improve network reliability significantly. This dissertation evaluates the empirical relationship between recloser placement and reliability from the perspective of control and instrumentation within ESKOM. It also puts forward an additional performance-improvement framework that can be implemented to achieve RAM (Reliability, Availability and Maintainability) management. Loop automation functionality is also under discussion; this is a Distribution-System Automation-scheme that restores the supply to the fault-free sections of a network, if they have been disconnected, because of a fault in another section of the network. Loop automation can also restore the normal network configuration automatically, when the faulty section is repaired. The process of isolating the faulty section and re-configuring the network to restore supply back to the fault-free sections is the first capability of Loop Automation. This research investigation assesses two different scenarios, namely: A conventional implementation of auto-reclosers on MV networks using Eskom reliability standard; and (ii.) the findings of a case-study using this recloser implementation (loop automation) to improve the reliability and the system’s performance. Results obtained are presented and discussed. , M.Phil. (Engineering Management)
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Critical success factors for instrumentation and control projects within the power industry in South Africa
- Authors: Mathew, Sheeba
- Date: 2016
- Subjects: Eskom (Firm) , Electric utilities - South Africa - Equipment and supplies , Electric utilities - Management , Demand-side management (Electric utilities) , Electric power distribution
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/242274 , uj:24984
- Description: M.Ing. (Engineering Management) , Abstract: The energy sector in South Africa has experienced major shortfalls in meeting the country’s energy demands. This lack of generating capacity is attributed to delays in the approval of new infrastructure and the increase in the country’s economic growth between the years 1994 and 2007 [1]. The electricity producer Eskom Holdings SOC (State Owned Company) Limited, has since implemented initiatives that are aimed to address the energy supply shortfalls. One such initiative is the refurbishment of the existing operational fleet of coal fired power stations. The overall intention of this initiative being to extend plant operating life, improve reliability and availability as well as to align these assets to current safety standards. The operating life of power stations often resides between forty to fifty years. Within this lifecycle instrumentation & control (I&C) upgrades are planned and executed to secure the continued reliable operation of the generating assets. These projects often entail the full upgrade or refurbishment of the power station’s process control system [2]. The research identifies the critical success factors to be considered for I&C projects rolled out within the energy generating sector in South Africa. The study is established on a comprehensive literature review that provides insight into the South African energy industry, I&C environment and business architectural framework processes. The review covers the spectrum of people, plant and processes and sheds light onto the critical success factors (CSFs) to be considered during the different project phases. The identified CSFs are used to formulate the framework of a survey distributed amongst key stakeholders from the operating, engineering, maintenance and project management fraternity. The results of the survey is analysed to identify the relevant CSFs across the different project phases. An insight into the organisation’s change management maturity is provided by evaluating the identified CSFs with those established through the literature review. The research work concludes with the proposal of CSFs for I&C projects within the power generation industry and provides recommendations for future studies.
- Full Text:
- Authors: Mathew, Sheeba
- Date: 2016
- Subjects: Eskom (Firm) , Electric utilities - South Africa - Equipment and supplies , Electric utilities - Management , Demand-side management (Electric utilities) , Electric power distribution
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/242274 , uj:24984
- Description: M.Ing. (Engineering Management) , Abstract: The energy sector in South Africa has experienced major shortfalls in meeting the country’s energy demands. This lack of generating capacity is attributed to delays in the approval of new infrastructure and the increase in the country’s economic growth between the years 1994 and 2007 [1]. The electricity producer Eskom Holdings SOC (State Owned Company) Limited, has since implemented initiatives that are aimed to address the energy supply shortfalls. One such initiative is the refurbishment of the existing operational fleet of coal fired power stations. The overall intention of this initiative being to extend plant operating life, improve reliability and availability as well as to align these assets to current safety standards. The operating life of power stations often resides between forty to fifty years. Within this lifecycle instrumentation & control (I&C) upgrades are planned and executed to secure the continued reliable operation of the generating assets. These projects often entail the full upgrade or refurbishment of the power station’s process control system [2]. The research identifies the critical success factors to be considered for I&C projects rolled out within the energy generating sector in South Africa. The study is established on a comprehensive literature review that provides insight into the South African energy industry, I&C environment and business architectural framework processes. The review covers the spectrum of people, plant and processes and sheds light onto the critical success factors (CSFs) to be considered during the different project phases. The identified CSFs are used to formulate the framework of a survey distributed amongst key stakeholders from the operating, engineering, maintenance and project management fraternity. The results of the survey is analysed to identify the relevant CSFs across the different project phases. An insight into the organisation’s change management maturity is provided by evaluating the identified CSFs with those established through the literature review. The research work concludes with the proposal of CSFs for I&C projects within the power generation industry and provides recommendations for future studies.
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Reliability assessment of medium voltage underground cable network using failure prediction methods
- Authors: Mehlo, Nqaba A.
- Date: 2018
- Subjects: Electric power distribution , Electric power transmission , Underground electric lines , Electric cables
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/293865 , uj:31962
- Description: M.Phil. (Engineering Management) , Abstract: In recent years, electricity supply has become the driving force behind economic growth in many cities, urban areas and businesses around the world. As a result, utilities are under pressure to supply reliable electricity to their customers at all times. Most power outages take place in the distribution network, and the most used distribution network in the city and urban areas is Medium Voltage (MV) underground cable distribution network is due to space constraint. The power disruption statistics in Europe and South Africa indicates that the rate of power outages is high in the MV network adding up to 80% of the entire electrical distribution network. However, the national regulator expects the City of Tshwane to manage these interruptions effectively and to improve network reliability. This dissertation will begin by giving a detailed description of the City of Tshwane MV underground cable network. Thereafter, the research will identify, quantify and characterize factors that cause cable failures and poor reliability of this network. It is very important for the municipality to understand these causes before making any asset management decisions in the network since condition assessment or replacement of underground cables is very difficult and restoration times are long due to the complexity of cable access. The research also looked at the available solutions in various literatures that can benefit the municipality in terms of knowledge. Some of the solutions include different network configurations. The research methodology used in this paper is a quantitative approach, which applies statistical analysis methods for failure prediction, and a qualitative method is also applied for in-depth explanation of the data. The focus of this research is a case study about the City of Tshwane municipality, using secondary data. MV underground cable failure data evaluation was divided into four stages so that important network behaviour characteristics could be analysed. The first stage was MV network data and information acquisition. The second stage consisted of cable failure analysis, where equipment failure was the highest. The main cause of equipment failure is insulation failure. In the third stage, Pearson’s linear correlation method is used to evaluate the relationship between cable failure behaviour and various climatic seasons (temperature and rainfall). The findings were not...
- Full Text:
- Authors: Mehlo, Nqaba A.
- Date: 2018
- Subjects: Electric power distribution , Electric power transmission , Underground electric lines , Electric cables
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/293865 , uj:31962
- Description: M.Phil. (Engineering Management) , Abstract: In recent years, electricity supply has become the driving force behind economic growth in many cities, urban areas and businesses around the world. As a result, utilities are under pressure to supply reliable electricity to their customers at all times. Most power outages take place in the distribution network, and the most used distribution network in the city and urban areas is Medium Voltage (MV) underground cable distribution network is due to space constraint. The power disruption statistics in Europe and South Africa indicates that the rate of power outages is high in the MV network adding up to 80% of the entire electrical distribution network. However, the national regulator expects the City of Tshwane to manage these interruptions effectively and to improve network reliability. This dissertation will begin by giving a detailed description of the City of Tshwane MV underground cable network. Thereafter, the research will identify, quantify and characterize factors that cause cable failures and poor reliability of this network. It is very important for the municipality to understand these causes before making any asset management decisions in the network since condition assessment or replacement of underground cables is very difficult and restoration times are long due to the complexity of cable access. The research also looked at the available solutions in various literatures that can benefit the municipality in terms of knowledge. Some of the solutions include different network configurations. The research methodology used in this paper is a quantitative approach, which applies statistical analysis methods for failure prediction, and a qualitative method is also applied for in-depth explanation of the data. The focus of this research is a case study about the City of Tshwane municipality, using secondary data. MV underground cable failure data evaluation was divided into four stages so that important network behaviour characteristics could be analysed. The first stage was MV network data and information acquisition. The second stage consisted of cable failure analysis, where equipment failure was the highest. The main cause of equipment failure is insulation failure. In the third stage, Pearson’s linear correlation method is used to evaluate the relationship between cable failure behaviour and various climatic seasons (temperature and rainfall). The findings were not...
- Full Text:
On-line automatic switching of consumers' connections for improved performance os a distribution feeder
- Popoola, O., Jimoh, A. A., Nicolae, Dan-Valentin
- Authors: Popoola, O. , Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2009
- Subjects: Electric power distribution , Electric networks
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/21132 , uj:16116 , ISBN: 978-1-4244-3811-2 , Citation: Popoola, O., Jimoh, A.A. & Nicolae, D.V. 2009. On-line automatic switching of consumers' connections for improved performance os a distribution feeder. Proceedings of the IEEE Power Systems Conference & Exposition, 15-18 March, 2009, Seattle, USA. DOI: 10.1109/PSCE.2009.4840160
- Description: Abstract: Resolving imbalances on phases is performed using conventional trial and error approach which involves service interruption. Phase current and voltage may improve however the resultant effect does not last for too long. To improve the performance of the secondary distribution system there is a need for an on-line and automating technology. The aim of this paper is to pioneer a method and technology for resolving imbalances in a secondary distribution system as a result of the uneven distribution of single phase load across a three phase power system. The technology developed involves monitoring, acquisition/display of collected data and self changing switching actions electronically for rearrangement or transfer of consumer loads. The proposed switching technology is based on opentransition switch that enables transfer or rearrangement of consumer loads in a three-phase system within milliseconds with supervisory control system. Validation of the proposed technology was carried out using these methodologies: Matlab (Simulink), Virtual Instrumentation-Lab VIEW and Hardware implementation.
- Full Text:
- Authors: Popoola, O. , Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2009
- Subjects: Electric power distribution , Electric networks
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/21132 , uj:16116 , ISBN: 978-1-4244-3811-2 , Citation: Popoola, O., Jimoh, A.A. & Nicolae, D.V. 2009. On-line automatic switching of consumers' connections for improved performance os a distribution feeder. Proceedings of the IEEE Power Systems Conference & Exposition, 15-18 March, 2009, Seattle, USA. DOI: 10.1109/PSCE.2009.4840160
- Description: Abstract: Resolving imbalances on phases is performed using conventional trial and error approach which involves service interruption. Phase current and voltage may improve however the resultant effect does not last for too long. To improve the performance of the secondary distribution system there is a need for an on-line and automating technology. The aim of this paper is to pioneer a method and technology for resolving imbalances in a secondary distribution system as a result of the uneven distribution of single phase load across a three phase power system. The technology developed involves monitoring, acquisition/display of collected data and self changing switching actions electronically for rearrangement or transfer of consumer loads. The proposed switching technology is based on opentransition switch that enables transfer or rearrangement of consumer loads in a three-phase system within milliseconds with supervisory control system. Validation of the proposed technology was carried out using these methodologies: Matlab (Simulink), Virtual Instrumentation-Lab VIEW and Hardware implementation.
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The impact of inverter side PV plant on HVDC commutation failures
- Simelane, Nondumiso Patricia
- Authors: Simelane, Nondumiso Patricia
- Date: 2020
- Subjects: Photovoltaic power systems , Electric power distribution , Electric current converters , Building-integrated photovoltaic systems
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/413211 , uj:34803
- Description: M.Phil. (Electrical Engineering in Power and Energy Systems) , Abstract: The high-voltage direct current (HVDC) system is a crucial technology in transmission; however, this system suffers from commutation failure. Commutation failure is defined as an adverse dynamic event that occurs when a converter valve that is supposed to turn off continues to conduct without transferring its current to the next valve in the firing sequence. Commutation failure disturbs the power transfer, yields a large overcurrent in the converter, and causes a voltage drop in an alternating current (AC) network. Although commutation failure in HVDC systems has been studied using many other compensating devices, academic researchers have not given enough attention to evaluating the impact of distributed generation (DG) on the power system. Within this gap and based on the publications researched, no published material could be found regarding the impact of a photovoltaic (PV) plant on HVDC commutation failures. This research project seeks to focus on the impact of an inverter side PV plant on HVDC commutation failures. In this dissertation, the objective is to evaluate the impact of the inverter side PV plant on HVDC commutation failures. The case studies are done by considering the commutation failure severity, the magnitudes of the remaining voltages after different types of faults occurring, and the recovery time required to clear a fault. Case studies are performed in a network with a PV plant and also without a PV plant. The network was set up in Power System Computer-Aided Design (PSCAD) software to find the critical voltages. Further simulations were done in this study using Power System Simulator for Engineering (PSS/E) software. A network by Conférence Internationale des grandes réseaux...
- Full Text:
- Authors: Simelane, Nondumiso Patricia
- Date: 2020
- Subjects: Photovoltaic power systems , Electric power distribution , Electric current converters , Building-integrated photovoltaic systems
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/413211 , uj:34803
- Description: M.Phil. (Electrical Engineering in Power and Energy Systems) , Abstract: The high-voltage direct current (HVDC) system is a crucial technology in transmission; however, this system suffers from commutation failure. Commutation failure is defined as an adverse dynamic event that occurs when a converter valve that is supposed to turn off continues to conduct without transferring its current to the next valve in the firing sequence. Commutation failure disturbs the power transfer, yields a large overcurrent in the converter, and causes a voltage drop in an alternating current (AC) network. Although commutation failure in HVDC systems has been studied using many other compensating devices, academic researchers have not given enough attention to evaluating the impact of distributed generation (DG) on the power system. Within this gap and based on the publications researched, no published material could be found regarding the impact of a photovoltaic (PV) plant on HVDC commutation failures. This research project seeks to focus on the impact of an inverter side PV plant on HVDC commutation failures. In this dissertation, the objective is to evaluate the impact of the inverter side PV plant on HVDC commutation failures. The case studies are done by considering the commutation failure severity, the magnitudes of the remaining voltages after different types of faults occurring, and the recovery time required to clear a fault. Case studies are performed in a network with a PV plant and also without a PV plant. The network was set up in Power System Computer-Aided Design (PSCAD) software to find the critical voltages. Further simulations were done in this study using Power System Simulator for Engineering (PSS/E) software. A network by Conférence Internationale des grandes réseaux...
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