A novel approach for the identification of critical nodes and transmission lines for mitigating voltage instability in power networks
- Alayande, Akintunde Samson, Nwulu, Nnamdi
- Authors: Alayande, Akintunde Samson , Nwulu, Nnamdi
- Date: 2019
- Subjects: Voltage instability , Reliability , Security
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/406829 , uj:34220 , Citation: Alayande, A.S. & Nwulu, N. 2019. A novel approach for the identification of critical nodes and transmission lines for mitigating voltage instability in power networks.
- Description: Abstract: Voltage collapse is a major issue combating the effectiveness and optimal operation of modern power systems in recent times. This has been a great threat to the security and the reliability of a modern power system and has been a growing concern to power system engineers, researchers and the utilities recently. A prompt identification of the sets of transmission lines whose outage could lead to a cascading failure and the sets of nodes where voltage collapse could erupt is therefore a vital issue for a reliable and secure power system operation. An alternative approach to solving these problems is therefore presented in this paper. The problem is viewed from the graph-theoretical perspective, considering the topological properties of the networks. Application of the fundamental circuit theory is employed and the Bus-to-Line matrix (BLM) is formulated. This matrix provides insights about the interconnections of the components within the network. This valuable information is captured and used for identifying the critical elements where a suitable location for reactive power support could be placed to avoid voltage collapse of the network. The effectiveness of the proposed approach is tested using a simple 10-bus power network. The results obtained are compared with that obtained from the existing approaches. The results obtained show a strong correlation and agreement and proved the efficiency of the proposed approach.
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- Authors: Alayande, Akintunde Samson , Nwulu, Nnamdi
- Date: 2019
- Subjects: Voltage instability , Reliability , Security
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/406829 , uj:34220 , Citation: Alayande, A.S. & Nwulu, N. 2019. A novel approach for the identification of critical nodes and transmission lines for mitigating voltage instability in power networks.
- Description: Abstract: Voltage collapse is a major issue combating the effectiveness and optimal operation of modern power systems in recent times. This has been a great threat to the security and the reliability of a modern power system and has been a growing concern to power system engineers, researchers and the utilities recently. A prompt identification of the sets of transmission lines whose outage could lead to a cascading failure and the sets of nodes where voltage collapse could erupt is therefore a vital issue for a reliable and secure power system operation. An alternative approach to solving these problems is therefore presented in this paper. The problem is viewed from the graph-theoretical perspective, considering the topological properties of the networks. Application of the fundamental circuit theory is employed and the Bus-to-Line matrix (BLM) is formulated. This matrix provides insights about the interconnections of the components within the network. This valuable information is captured and used for identifying the critical elements where a suitable location for reactive power support could be placed to avoid voltage collapse of the network. The effectiveness of the proposed approach is tested using a simple 10-bus power network. The results obtained are compared with that obtained from the existing approaches. The results obtained show a strong correlation and agreement and proved the efficiency of the proposed approach.
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Exploring the driving factor on prepaid electricity meter rejecting the largest township of South Africa
- Kambule, Njabulo, Yessoufou, Kowiyou, Nwulu, Nnamdi, Mbohwa, Charles
- Authors: Kambule, Njabulo , Yessoufou, Kowiyou , Nwulu, Nnamdi , Mbohwa, Charles
- Date: 2019
- Subjects: Electricity consumption , Education , Prepaid electricity meter
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/406836 , uj:34221 , Citation: Kambule, N. et al. 2019. Exploring the driving factor on prepaid electricity meter rejecting the largest township of South Africa.
- Description: Abstract: Technology rejection phenomenon manifests itself differently across different societies. Over the past two decades, low income households in Soweto have persistently rejected prepaid electricity meters. Until now, the basis of the rejection in the region remains scientifically underexplored. We therefore conduct an exploratory study of pertaining prepaid meter rejection in Soweto. Through triangulation research and survey approach, 88 households based in Orlando East and Diepkloof were interviewed by means of a questionnaire. Our findings show that three aspects contributing to this phenomenon, namely: lack of quality consultation and education, the high levels of electricity consumption, and unattainable politically motivated promises are the main reasons that currently fuel prepaid meter rejection. We emphasise that the current state of the Free Basic Electricity (FBE) (2003) policy also fuels rejection, as it remains socio-economically inadequate and irrelevant for indigent households. We therefore note the need for an FBE policy review and update as well as the establishment of a policy monitoring committee to ensure implementation and enforcement.
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- Authors: Kambule, Njabulo , Yessoufou, Kowiyou , Nwulu, Nnamdi , Mbohwa, Charles
- Date: 2019
- Subjects: Electricity consumption , Education , Prepaid electricity meter
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/406836 , uj:34221 , Citation: Kambule, N. et al. 2019. Exploring the driving factor on prepaid electricity meter rejecting the largest township of South Africa.
- Description: Abstract: Technology rejection phenomenon manifests itself differently across different societies. Over the past two decades, low income households in Soweto have persistently rejected prepaid electricity meters. Until now, the basis of the rejection in the region remains scientifically underexplored. We therefore conduct an exploratory study of pertaining prepaid meter rejection in Soweto. Through triangulation research and survey approach, 88 households based in Orlando East and Diepkloof were interviewed by means of a questionnaire. Our findings show that three aspects contributing to this phenomenon, namely: lack of quality consultation and education, the high levels of electricity consumption, and unattainable politically motivated promises are the main reasons that currently fuel prepaid meter rejection. We emphasise that the current state of the Free Basic Electricity (FBE) (2003) policy also fuels rejection, as it remains socio-economically inadequate and irrelevant for indigent households. We therefore note the need for an FBE policy review and update as well as the establishment of a policy monitoring committee to ensure implementation and enforcement.
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Fault clearance and transmission system stability enhancement using unified power flow controller
- Ewaoche, Okampo John, Nwulu, Nnamdi
- Authors: Ewaoche, Okampo John , Nwulu, Nnamdi
- Date: 2018
- Subjects: MATLAB , Simulink , FACTS
- Language: English
- Type: Conference proceeding
- Identifier: http://hdl.handle.net/10210/290614 , uj:31552 , Citation: Ewaoche, O.J. & Nwulu, N. 2018. Fault clearance and transmission system stability enhancement using unified power flow controller.
- Description: Abstract: Fault current introduces voltage and reactive power imbalances which are major problems in power systems. This study shows the ability of Unified Power Flow Controller (UPFC) to clear a single line to ground fault and improves transmission system stability. The device under review is one of the most advanced classes of Flexible Alternating Current Transmission System (FACTS) devices. A 30-bus transmission line system is modelled with MATLAB/Simulink software. Two cases were simulated to evaluate the performance of UPFC. In Case 1, the 30-bus network system is modelled and simulated without a compensating device whilst Case 2, the system is modelled with UPFC. The system models are designed to have a single line to ground fault with resistance 0.010Ω and ground resistance of 0.001Ω occurring at bus 1. The fault is expected to cause instability in the system and be cleared after 0.04s in both cases. The simulated results of the two cases were compared to determine the performance of UPFC in improving the voltage stability and power profile of the system. The results show that UPFC has the ability of stabilizing voltage and power profile of transmission system. The study has thus, increased insight on the use of the device in transmission system stability and control.
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- Authors: Ewaoche, Okampo John , Nwulu, Nnamdi
- Date: 2018
- Subjects: MATLAB , Simulink , FACTS
- Language: English
- Type: Conference proceeding
- Identifier: http://hdl.handle.net/10210/290614 , uj:31552 , Citation: Ewaoche, O.J. & Nwulu, N. 2018. Fault clearance and transmission system stability enhancement using unified power flow controller.
- Description: Abstract: Fault current introduces voltage and reactive power imbalances which are major problems in power systems. This study shows the ability of Unified Power Flow Controller (UPFC) to clear a single line to ground fault and improves transmission system stability. The device under review is one of the most advanced classes of Flexible Alternating Current Transmission System (FACTS) devices. A 30-bus transmission line system is modelled with MATLAB/Simulink software. Two cases were simulated to evaluate the performance of UPFC. In Case 1, the 30-bus network system is modelled and simulated without a compensating device whilst Case 2, the system is modelled with UPFC. The system models are designed to have a single line to ground fault with resistance 0.010Ω and ground resistance of 0.001Ω occurring at bus 1. The fault is expected to cause instability in the system and be cleared after 0.04s in both cases. The simulated results of the two cases were compared to determine the performance of UPFC in improving the voltage stability and power profile of the system. The results show that UPFC has the ability of stabilizing voltage and power profile of transmission system. The study has thus, increased insight on the use of the device in transmission system stability and control.
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Temporal analysis of electricity consumption for prepaid metered low and high income households in Soweto, South Africa
- Kambule, Njabulo, Yessoufou, Kowiyou, Nwulu, Nnamdi, Mbohwa, Charles
- Authors: Kambule, Njabulo , Yessoufou, Kowiyou , Nwulu, Nnamdi , Mbohwa, Charles
- Date: 2019
- Subjects: Electricity consumption , High income household , Low income household
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/404639 , uj:33942 , Citation : Kambule, N. et al. 2019: Temporal analysis of electricity consumption for prepaid metered low and high income households in Soweto, South Africa. , https://doi.org/10.1080/20421338.2018.1527983
- Description: Abstract : This study explores the temporal trend in electricity consumption since the introduction of prepaid meters in low income households of Soweto, and compares the findings with high income households. Monthly electricity consumption data (over 96 months: 2007-2014) on 4427 households in Soweto, for both low and high income households, was collected from Eskom. Using a simple linear model to analyse consumption trends in low income households, we ascertain that electricity consumption has decreased by 48% since the inception of prepaid meters. Nonetheless, it is noted that 60% of household incomes are spent on electricity bills, which is way above the threshold set for energy poverty. Comparatively, high income households consume lower electricity than low income households do. Overall, the prepaid meter programme is producing expected results for Eskom but remains a challenge for low income households, which are still entrenched in energy poverty. We call for an energy policy that is tailored for each income groups and the formulation of laws and policies to protect the energy vulnerable households.
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- Authors: Kambule, Njabulo , Yessoufou, Kowiyou , Nwulu, Nnamdi , Mbohwa, Charles
- Date: 2019
- Subjects: Electricity consumption , High income household , Low income household
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/404639 , uj:33942 , Citation : Kambule, N. et al. 2019: Temporal analysis of electricity consumption for prepaid metered low and high income households in Soweto, South Africa. , https://doi.org/10.1080/20421338.2018.1527983
- Description: Abstract : This study explores the temporal trend in electricity consumption since the introduction of prepaid meters in low income households of Soweto, and compares the findings with high income households. Monthly electricity consumption data (over 96 months: 2007-2014) on 4427 households in Soweto, for both low and high income households, was collected from Eskom. Using a simple linear model to analyse consumption trends in low income households, we ascertain that electricity consumption has decreased by 48% since the inception of prepaid meters. Nonetheless, it is noted that 60% of household incomes are spent on electricity bills, which is way above the threshold set for energy poverty. Comparatively, high income households consume lower electricity than low income households do. Overall, the prepaid meter programme is producing expected results for Eskom but remains a challenge for low income households, which are still entrenched in energy poverty. We call for an energy policy that is tailored for each income groups and the formulation of laws and policies to protect the energy vulnerable households.
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