2007 IEEE Power Engineering Society Conference and Exposition in Africa - PowerAfrica, 2007
The effect of space charge was investigated through corona current measurements. The tests were c... more The effect of space charge was investigated through corona current measurements. The tests were carried out in an indoor corona cage with and without aluminium foil cover, and on a monopolar test line with a high speed fan to simulate and assess the effect of wind on the space charge. The results obtained demonstrated that the corona current in the cage and the test line is more dependent on conductor voltage and resistance of the air gap. It has also been shown that the blowing of the wind on a test line conductor and the assisted draining away of charge carriers from the corona cage gap had the effect of reducing corona current.
2014 International Conference on the Eleventh industrial and Commercial Use of Energy, 2014
This paper presents a quantitative, multi-method approach to tackle power system reliability prob... more This paper presents a quantitative, multi-method approach to tackle power system reliability problems affecting sustainable energy supply. Through case studies and analysis, it underscores the urgency for a shift in asset management paradigms in the developing world where cost of un-served energy may account for up to 27.7% of energy sales. It applies systems thinking philosophy to analyse root causes of problems, then uses statistical and probabilistic inferences to solve them. Failure statistics for transmission and distribution transformers are processed using least squares method, maximum likelihood estimation and method of moments in order to determine Weibull life modelling parameters. Modelling of reliability functions and costs associated with planned and run-to-failure strategies were implemented using MATLAB algorithms based on the parameter estimates. Results show that the run-to-failure strategy achieves short term cost savings, but it eventually leads to unsustainable energy supply. They further show how problems cascade down from the generation to the distribution business units. The study advances use of Loss of Energy Expectation and Loss of Load Expected as metrics to augment traditional use of availability in order to measure the loss margin. The model developed can be used in risk management, in power asset management planning and in developing strategies on industrial and commercial use of energy in power utilities.
Proceedings of the Inaugural IEEE PES 2005 Conference and Exposition in Africa
Cost effective higher current rated power electronic technology makes possible the conversion of ... more Cost effective higher current rated power electronic technology makes possible the conversion of high voltage alternating current circuits for high voltage direct current employment. This strategy is promoted so as to yield greater power transfers by using the same physical power line and installed conductor cross sectional area. This idea was shared and discussed by study committee B4 at the 2004 proceedings of Cigre in Paris, France. Here study committee working group members reported on the tri-pole proposal of using one phase of the conventional AC line as the positive pole, another phase as the negative pole and the remaining third phase to be periodically swapped between positive and negative poles; yielding almost 2,5 times the power transfer capability of the HVAC line. Along a similar path, the paper reports on Eskom's initial investigation into recycling two of the existing 400 kV lines emanating from Matimba power station. Additional 1800 MW thermal generation is planned alongside the existing 3600 MW power station. A known constraint is the acquisition of additional power line servitudes to evacuate the increased power generation. The real estate area surrounding Matimba power station is emerging as prime investment for environmentally sensitive international investors
1999 IEEE Africon. 5th Africon Conference in Africa (Cat. No.99CH36342)
This paper presents results of an artificial neural network model used to predict hourly peak dem... more This paper presents results of an artificial neural network model used to predict hourly peak demands of loads in a newly electrified area. Average forecast errors of less than 10% were achieved, using only limited historical data of the area's load patterns.
[1991] Proceedings of the 3rd International Conference on Properties and Applications of Dielectric Materials
The effect of Freon 113 additives (1%-10%) on DC corona current in SF/sub 6/ is investigated in a... more The effect of Freon 113 additives (1%-10%) on DC corona current in SF/sub 6/ is investigated in a 20 mm point-plane gap, in the pressure range 0.1-0.2 MPa. Freon 113 is found to reduce corona current, the effect increasing with Freon content. The observed effect is attributed to increased electron attachment and reduction in ion mobility in the mixtures. The results obtained are discussed in terms of known streamer corona models in SF/sub 6/, and chemical and physical properties of Freon 113. It is suggested that the observed effect might be related to the high attachment cross-section of Freon 113, and its ability to form stabler and heavier negative ions.<<ETX>>
2004 International Conference on Power System Technology, 2004. PowerCon 2004.
... D. Naidoo is with Eskom Distribution, Kwazulu Natal, South AGica (e mail: naidocdr@eskom. co.... more ... D. Naidoo is with Eskom Distribution, Kwazulu Natal, South AGica (e mail: naidocdr@eskom. co.za). ... The sign of W& is used to indicate whether the fault is located on the line ... regarding line currents needs to be transmitted to the various converter stations, the signal propa-gation ...
2006 International Conference on Power System Technology, 2006
Corona audible noise measurements were carried out in a small indoor corona cage under DC fields ... more Corona audible noise measurements were carried out in a small indoor corona cage under DC fields and dry conditions. The aim of the experiments was to determine possible audible noise levels under local climatic conditions. The variation between the corona audible noise and the static conductor surface gradient was investigated for stranded aluminium conductors. The results obtained were compared with the EPRI, CRIEPI and BPA predictions generated from the EPRI ACDC line software. The results demonstrated good agreement with the predictions in terms of trends.
Electricity demand in the informal settlements is increasing rapidly, as more and more people are... more Electricity demand in the informal settlements is increasing rapidly, as more and more people are getting connected and appreciating the advantages of electrical energy. Most of the consumers are low income earners, and their load profile is characterised by predominant morning and evening peaks, resulting in poor load factors. With over a million such customers expected to be connected to the system, their demand pattern is bound to impact on the overall system load profile. Therefore, an understanding of their demand characteristics is going to be essential, in order to develop appropriate measures for improving energy utilisation patterns of such customers, as well as bise design parameters for their reticulation systems.
This paper develops a new PLC model and investigates the impact of the load, line length, and dia... more This paper develops a new PLC model and investigates the impact of the load, line length, and diameter of the transmission line on the channel transfer function over the frequency range of 1-20 M Hz. The results show that with 42 degrees of freedom, the proposed model leads to an average RM SE value of approximately 5.2 dB. With the same conditions, the Phillips model leads to an average RM SE value of approximately 1.62 dB.
1999 IEEE Africon. 5th Africon Conference in Africa (Cat. No.99CH36342)
The 19th National Congress of the Communist Party of China solemnly announced that China has ente... more The 19th National Congress of the Communist Party of China solemnly announced that China has entered a new era, and all walks of life in our country have made great and excellent progress compared with the past. Since the founding of the People's Republic of China, under the impetus of the continuous and consistently development of economic, technological, and science strength and growth, China has continuously strengthened and promoted the reform of the distribution network and made important progress. Based on this, this paper now expounds the form of power electronics in the distribution network, mainly from the equipment level and system and two aspects of analysis; secondly, this paper analyses the current situation of power electronic equipment in distribution network from the theoretical point of view. Finally, the influence of power electronic transformer on distribution network is studied.
The multipath propagation models in power-line communication channel (PLC) are some of the most s... more The multipath propagation models in power-line communication channel (PLC) are some of the most successful models which are based mainly on scattering points located where the impedance mismatch occurs. In such models, not only the desired signal, but also one or more delayed and attenuated versions of it get to the receiver. The attenuation is basically due to difierent routes that the signal will take before getting to the receiver hence at the end there are many signals that reach the load at difierent times. In this submission, we investigate the number of branches and the numbers of re∞ections that occur at each node; the Mie scattering theory is applied to nodes in the network in order to determine the resulting speciflc signal attenuation in the network. The proposed model is compared to the theoretical model and the estimated error determined by root mean square and chi-square tests. Finally, a power law model is proposed where only the frequency range is needed to estimate ...
The multipath propagation of the power-line communication channel (PLC) arises from the presence ... more The multipath propagation of the power-line communication channel (PLC) arises from the presence of several branches and impedance mismatches that cause multiple reflections. Each path comprises of scattering points that are reflected at specific number of times at specific points of discontinuity along its routes. Scattering points located where impedance mismatch occurs and can be seen as spherical point with an approximation diameter size as for the branch. In such models, not only the desired signal, but also one or more delayed and attenuated versions of it get to the receiver. In [1], scattering points' spatial allocation, by which path amplitude distributions and path arriving time distributions are proposed to follow the lognormal distri-bution for different number of branches. Based on those findings in [1], in this submission, we investigate the number of branches and the numbers of reflections that occur at each node; the scattering point diameter density is derived i...
IEEE Power and Energy Society Conference and Exposition in Africa: Intelligent Grid Integration of Renewable Energy Resources (PowerAfrica), 2012
The multipath model of powerline communication is limited because measurements are initially requ... more The multipath model of powerline communication is limited because measurements are initially required for some attenuation parameters. In this paper, new analytical approach of specific attenuation is suggested for higher frequencies for N = 4 paths at 10 MHz to 100 MHz. Based on this finding, the multipath model is suggested for higher frequencies. The results show that with the new model the attenuation span between 68.5 to 71.5 dB.
Abstract The purpose of this study is to make a preliminary assessment of the wind resource in So... more Abstract The purpose of this study is to make a preliminary assessment of the wind resource in South Sudan. This is mainly to get data on the quality of the wind resource at different locations in the country and investigate its suitability for the development of wind power generation projects of all sizes. Wind data for 33 locations, covering the period from 1981 to 2019, were requested from Modern-Era Retrospective analysis for Research and Applications version 2 or MERRA-2. The data were then analysed to produce a variety of statistics that describe the quality of the wind resource in each location. Long-term monthly and annual averages together with wind direction were computed for each location at a height of 10 m above ground level. Wind speeds were extrapolated to hub heights of 30 and 50 m above ground level and fitted to five different distribution functions to get the parameters for estimating wind power density. Results show that at 10 m above ground level, the long-term annual average wind speeds range between 5.08 m/s and 2.36 m/s while wind power density range between 128.36 W/m2and 14.39 W/m2. Development of utility-scale wind power plants is marginal in two locations while small-wind turbines development may be possible in the north-north eastern locations. Further research is proposed to explore the possibility of deployment of large-scale wind turbines at locations north-north east. Investigating the wind resource in other locations using alternative methods as well as possibility of development of small wind turbines is suggested.
2007 IEEE Power Engineering Society Conference and Exposition in Africa - PowerAfrica, 2007
The effect of space charge was investigated through corona current measurements. The tests were c... more The effect of space charge was investigated through corona current measurements. The tests were carried out in an indoor corona cage with and without aluminium foil cover, and on a monopolar test line with a high speed fan to simulate and assess the effect of wind on the space charge. The results obtained demonstrated that the corona current in the cage and the test line is more dependent on conductor voltage and resistance of the air gap. It has also been shown that the blowing of the wind on a test line conductor and the assisted draining away of charge carriers from the corona cage gap had the effect of reducing corona current.
2014 International Conference on the Eleventh industrial and Commercial Use of Energy, 2014
This paper presents a quantitative, multi-method approach to tackle power system reliability prob... more This paper presents a quantitative, multi-method approach to tackle power system reliability problems affecting sustainable energy supply. Through case studies and analysis, it underscores the urgency for a shift in asset management paradigms in the developing world where cost of un-served energy may account for up to 27.7% of energy sales. It applies systems thinking philosophy to analyse root causes of problems, then uses statistical and probabilistic inferences to solve them. Failure statistics for transmission and distribution transformers are processed using least squares method, maximum likelihood estimation and method of moments in order to determine Weibull life modelling parameters. Modelling of reliability functions and costs associated with planned and run-to-failure strategies were implemented using MATLAB algorithms based on the parameter estimates. Results show that the run-to-failure strategy achieves short term cost savings, but it eventually leads to unsustainable energy supply. They further show how problems cascade down from the generation to the distribution business units. The study advances use of Loss of Energy Expectation and Loss of Load Expected as metrics to augment traditional use of availability in order to measure the loss margin. The model developed can be used in risk management, in power asset management planning and in developing strategies on industrial and commercial use of energy in power utilities.
Proceedings of the Inaugural IEEE PES 2005 Conference and Exposition in Africa
Cost effective higher current rated power electronic technology makes possible the conversion of ... more Cost effective higher current rated power electronic technology makes possible the conversion of high voltage alternating current circuits for high voltage direct current employment. This strategy is promoted so as to yield greater power transfers by using the same physical power line and installed conductor cross sectional area. This idea was shared and discussed by study committee B4 at the 2004 proceedings of Cigre in Paris, France. Here study committee working group members reported on the tri-pole proposal of using one phase of the conventional AC line as the positive pole, another phase as the negative pole and the remaining third phase to be periodically swapped between positive and negative poles; yielding almost 2,5 times the power transfer capability of the HVAC line. Along a similar path, the paper reports on Eskom's initial investigation into recycling two of the existing 400 kV lines emanating from Matimba power station. Additional 1800 MW thermal generation is planned alongside the existing 3600 MW power station. A known constraint is the acquisition of additional power line servitudes to evacuate the increased power generation. The real estate area surrounding Matimba power station is emerging as prime investment for environmentally sensitive international investors
1999 IEEE Africon. 5th Africon Conference in Africa (Cat. No.99CH36342)
This paper presents results of an artificial neural network model used to predict hourly peak dem... more This paper presents results of an artificial neural network model used to predict hourly peak demands of loads in a newly electrified area. Average forecast errors of less than 10% were achieved, using only limited historical data of the area's load patterns.
[1991] Proceedings of the 3rd International Conference on Properties and Applications of Dielectric Materials
The effect of Freon 113 additives (1%-10%) on DC corona current in SF/sub 6/ is investigated in a... more The effect of Freon 113 additives (1%-10%) on DC corona current in SF/sub 6/ is investigated in a 20 mm point-plane gap, in the pressure range 0.1-0.2 MPa. Freon 113 is found to reduce corona current, the effect increasing with Freon content. The observed effect is attributed to increased electron attachment and reduction in ion mobility in the mixtures. The results obtained are discussed in terms of known streamer corona models in SF/sub 6/, and chemical and physical properties of Freon 113. It is suggested that the observed effect might be related to the high attachment cross-section of Freon 113, and its ability to form stabler and heavier negative ions.<<ETX>>
2004 International Conference on Power System Technology, 2004. PowerCon 2004.
... D. Naidoo is with Eskom Distribution, Kwazulu Natal, South AGica (e mail: naidocdr@eskom. co.... more ... D. Naidoo is with Eskom Distribution, Kwazulu Natal, South AGica (e mail: naidocdr@eskom. co.za). ... The sign of W& is used to indicate whether the fault is located on the line ... regarding line currents needs to be transmitted to the various converter stations, the signal propa-gation ...
2006 International Conference on Power System Technology, 2006
Corona audible noise measurements were carried out in a small indoor corona cage under DC fields ... more Corona audible noise measurements were carried out in a small indoor corona cage under DC fields and dry conditions. The aim of the experiments was to determine possible audible noise levels under local climatic conditions. The variation between the corona audible noise and the static conductor surface gradient was investigated for stranded aluminium conductors. The results obtained were compared with the EPRI, CRIEPI and BPA predictions generated from the EPRI ACDC line software. The results demonstrated good agreement with the predictions in terms of trends.
Electricity demand in the informal settlements is increasing rapidly, as more and more people are... more Electricity demand in the informal settlements is increasing rapidly, as more and more people are getting connected and appreciating the advantages of electrical energy. Most of the consumers are low income earners, and their load profile is characterised by predominant morning and evening peaks, resulting in poor load factors. With over a million such customers expected to be connected to the system, their demand pattern is bound to impact on the overall system load profile. Therefore, an understanding of their demand characteristics is going to be essential, in order to develop appropriate measures for improving energy utilisation patterns of such customers, as well as bise design parameters for their reticulation systems.
This paper develops a new PLC model and investigates the impact of the load, line length, and dia... more This paper develops a new PLC model and investigates the impact of the load, line length, and diameter of the transmission line on the channel transfer function over the frequency range of 1-20 M Hz. The results show that with 42 degrees of freedom, the proposed model leads to an average RM SE value of approximately 5.2 dB. With the same conditions, the Phillips model leads to an average RM SE value of approximately 1.62 dB.
1999 IEEE Africon. 5th Africon Conference in Africa (Cat. No.99CH36342)
The 19th National Congress of the Communist Party of China solemnly announced that China has ente... more The 19th National Congress of the Communist Party of China solemnly announced that China has entered a new era, and all walks of life in our country have made great and excellent progress compared with the past. Since the founding of the People's Republic of China, under the impetus of the continuous and consistently development of economic, technological, and science strength and growth, China has continuously strengthened and promoted the reform of the distribution network and made important progress. Based on this, this paper now expounds the form of power electronics in the distribution network, mainly from the equipment level and system and two aspects of analysis; secondly, this paper analyses the current situation of power electronic equipment in distribution network from the theoretical point of view. Finally, the influence of power electronic transformer on distribution network is studied.
The multipath propagation models in power-line communication channel (PLC) are some of the most s... more The multipath propagation models in power-line communication channel (PLC) are some of the most successful models which are based mainly on scattering points located where the impedance mismatch occurs. In such models, not only the desired signal, but also one or more delayed and attenuated versions of it get to the receiver. The attenuation is basically due to difierent routes that the signal will take before getting to the receiver hence at the end there are many signals that reach the load at difierent times. In this submission, we investigate the number of branches and the numbers of re∞ections that occur at each node; the Mie scattering theory is applied to nodes in the network in order to determine the resulting speciflc signal attenuation in the network. The proposed model is compared to the theoretical model and the estimated error determined by root mean square and chi-square tests. Finally, a power law model is proposed where only the frequency range is needed to estimate ...
The multipath propagation of the power-line communication channel (PLC) arises from the presence ... more The multipath propagation of the power-line communication channel (PLC) arises from the presence of several branches and impedance mismatches that cause multiple reflections. Each path comprises of scattering points that are reflected at specific number of times at specific points of discontinuity along its routes. Scattering points located where impedance mismatch occurs and can be seen as spherical point with an approximation diameter size as for the branch. In such models, not only the desired signal, but also one or more delayed and attenuated versions of it get to the receiver. In [1], scattering points' spatial allocation, by which path amplitude distributions and path arriving time distributions are proposed to follow the lognormal distri-bution for different number of branches. Based on those findings in [1], in this submission, we investigate the number of branches and the numbers of reflections that occur at each node; the scattering point diameter density is derived i...
IEEE Power and Energy Society Conference and Exposition in Africa: Intelligent Grid Integration of Renewable Energy Resources (PowerAfrica), 2012
The multipath model of powerline communication is limited because measurements are initially requ... more The multipath model of powerline communication is limited because measurements are initially required for some attenuation parameters. In this paper, new analytical approach of specific attenuation is suggested for higher frequencies for N = 4 paths at 10 MHz to 100 MHz. Based on this finding, the multipath model is suggested for higher frequencies. The results show that with the new model the attenuation span between 68.5 to 71.5 dB.
Abstract The purpose of this study is to make a preliminary assessment of the wind resource in So... more Abstract The purpose of this study is to make a preliminary assessment of the wind resource in South Sudan. This is mainly to get data on the quality of the wind resource at different locations in the country and investigate its suitability for the development of wind power generation projects of all sizes. Wind data for 33 locations, covering the period from 1981 to 2019, were requested from Modern-Era Retrospective analysis for Research and Applications version 2 or MERRA-2. The data were then analysed to produce a variety of statistics that describe the quality of the wind resource in each location. Long-term monthly and annual averages together with wind direction were computed for each location at a height of 10 m above ground level. Wind speeds were extrapolated to hub heights of 30 and 50 m above ground level and fitted to five different distribution functions to get the parameters for estimating wind power density. Results show that at 10 m above ground level, the long-term annual average wind speeds range between 5.08 m/s and 2.36 m/s while wind power density range between 128.36 W/m2and 14.39 W/m2. Development of utility-scale wind power plants is marginal in two locations while small-wind turbines development may be possible in the north-north eastern locations. Further research is proposed to explore the possibility of deployment of large-scale wind turbines at locations north-north east. Investigating the wind resource in other locations using alternative methods as well as possibility of development of small wind turbines is suggested.
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