Pub Date : 1999-09-28DOI: 10.1109/AFRCON.1999.821867
S. Els, A. Els, J. Jordaan, R. Zivanovic
This paper presents the use of projection statistics method to detect and downweight leverage points that appear in power system state estimation. A 14-bus system is used to compare the difference between a state estimator using projection statistics and one not using projection statistics.
{"title":"Projection statistics for power system state estimation","authors":"S. Els, A. Els, J. Jordaan, R. Zivanovic","doi":"10.1109/AFRCON.1999.821867","DOIUrl":"https://doi.org/10.1109/AFRCON.1999.821867","url":null,"abstract":"This paper presents the use of projection statistics method to detect and downweight leverage points that appear in power system state estimation. A 14-bus system is used to compare the difference between a state estimator using projection statistics and one not using projection statistics.","PeriodicalId":103036,"journal":{"name":"1999 IEEE Africon. 5th Africon Conference in Africa (Cat. No.99CH36342)","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126102931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1999-09-28DOI: 10.1109/AFRCON.1999.821907
B. Cannas, G. Celli, F. Pilo
MV distribution networks constitute the backbone of power distribution systems and for this reason utilities justifiably strive to improve their performance. In the paper heuristic algorithms and methodologies for the optimal planning of MV networks are proposed and implemented in an efficient software package. By using the above mentioned methodology it is possible to solve the problem of the optimal MV distribution network planning by realising "open loop network" structures which permit improving service quality.
{"title":"Optimal MV distribution networks planning with heuristic techniques","authors":"B. Cannas, G. Celli, F. Pilo","doi":"10.1109/AFRCON.1999.821907","DOIUrl":"https://doi.org/10.1109/AFRCON.1999.821907","url":null,"abstract":"MV distribution networks constitute the backbone of power distribution systems and for this reason utilities justifiably strive to improve their performance. In the paper heuristic algorithms and methodologies for the optimal planning of MV networks are proposed and implemented in an efficient software package. By using the above mentioned methodology it is possible to solve the problem of the optimal MV distribution network planning by realising \"open loop network\" structures which permit improving service quality.","PeriodicalId":103036,"journal":{"name":"1999 IEEE Africon. 5th Africon Conference in Africa (Cat. No.99CH36342)","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122451395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1999-09-28DOI: 10.1109/AFRCON.1999.821871
F. Okafor, T.O. Akinbulire
Component failures have been found to constitute a major source of disturbance inputs into the Nigerian power system. Consequently, conventional power system stabilizers may prove inadequate. This paper describes the design of a power system stabilizer where the reliability of critical components is made part of the design criteria. Simulation studies show improved robustness and speed of response.
{"title":"Power system stabilizer for the Nigerian power system-design and simulation","authors":"F. Okafor, T.O. Akinbulire","doi":"10.1109/AFRCON.1999.821871","DOIUrl":"https://doi.org/10.1109/AFRCON.1999.821871","url":null,"abstract":"Component failures have been found to constitute a major source of disturbance inputs into the Nigerian power system. Consequently, conventional power system stabilizers may prove inadequate. This paper describes the design of a power system stabilizer where the reliability of critical components is made part of the design criteria. Simulation studies show improved robustness and speed of response.","PeriodicalId":103036,"journal":{"name":"1999 IEEE Africon. 5th Africon Conference in Africa (Cat. No.99CH36342)","volume":"146 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128432830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1999-09-28DOI: 10.1109/AFRCON.1999.821911
K. D. Palmer, J. Cloete
Most planar spiral antennas are made as complementary structures, i.e. with equal slot and arm widths. This paper is a study of the properties of the thin-slot and thin-arm spiral where the slot is respectively narrower or greater than the spiral arm, and includes results for free space and in the presence of a ground plane. A numerical study is conducted for a range of arm-to-slot ratios, from 5% to 95% where 50% is the complementary case. The results show that changing the arm-to-slot ratio can be used to vary the input impedance, but that the thin-arm case is of limited practical value. Results are compared to theoretical expectations and independent numerical results. As an introduction, a discussion on the band theory and a physical insight into the power flow near the antenna is presented.
{"title":"The thin-slot and thin-arm planar spiral antenna operated with and without a ground-plane","authors":"K. D. Palmer, J. Cloete","doi":"10.1109/AFRCON.1999.821911","DOIUrl":"https://doi.org/10.1109/AFRCON.1999.821911","url":null,"abstract":"Most planar spiral antennas are made as complementary structures, i.e. with equal slot and arm widths. This paper is a study of the properties of the thin-slot and thin-arm spiral where the slot is respectively narrower or greater than the spiral arm, and includes results for free space and in the presence of a ground plane. A numerical study is conducted for a range of arm-to-slot ratios, from 5% to 95% where 50% is the complementary case. The results show that changing the arm-to-slot ratio can be used to vary the input impedance, but that the thin-arm case is of limited practical value. Results are compared to theoretical expectations and independent numerical results. As an introduction, a discussion on the band theory and a physical insight into the power flow near the antenna is presented.","PeriodicalId":103036,"journal":{"name":"1999 IEEE Africon. 5th Africon Conference in Africa (Cat. No.99CH36342)","volume":"101 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128677912","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1999-09-28DOI: 10.1109/AFRCON.1999.821924
J. Matlacz, K. D. Palmer
This paper reports on two reflector antenna options investigated to improve the bandwidth of a free space material measurement system. An offset ellipsoidal reflector and a pair of offset parabolic dishes are considered as the options to generate the required focused beam. Both are shown to be viable, but the parabolic dishes are preferred due to suitable low cost ones being available for the domestic satellite TV market. Measured and computed results show that the operating frequency band of the original system may be doubled.
{"title":"Modelling and measurement of focused ellipsoidal and parabolic reflector antennas for free space material measurements","authors":"J. Matlacz, K. D. Palmer","doi":"10.1109/AFRCON.1999.821924","DOIUrl":"https://doi.org/10.1109/AFRCON.1999.821924","url":null,"abstract":"This paper reports on two reflector antenna options investigated to improve the bandwidth of a free space material measurement system. An offset ellipsoidal reflector and a pair of offset parabolic dishes are considered as the options to generate the required focused beam. Both are shown to be viable, but the parabolic dishes are preferred due to suitable low cost ones being available for the domestic satellite TV market. Measured and computed results show that the operating frequency band of the original system may be doubled.","PeriodicalId":103036,"journal":{"name":"1999 IEEE Africon. 5th Africon Conference in Africa (Cat. No.99CH36342)","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121714430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1999-09-28DOI: 10.1109/AFRCON.1999.821957
A. Schoonwinkel, R.P. Gerber, J. Cloete
A post graduate programme in satellite communications engineering that will provide human resources for the South African telecommunications industry is described. Houwteq, a former satellite development facility, is revitalised as a campus, while the academic education is supplied by Stellenbosch University. The experience from a successful microsatellite development programme is applied to provide hands-on applied research at masters degree and PhD level.
{"title":"Houwteq facilities revived for engineering human resource development","authors":"A. Schoonwinkel, R.P. Gerber, J. Cloete","doi":"10.1109/AFRCON.1999.821957","DOIUrl":"https://doi.org/10.1109/AFRCON.1999.821957","url":null,"abstract":"A post graduate programme in satellite communications engineering that will provide human resources for the South African telecommunications industry is described. Houwteq, a former satellite development facility, is revitalised as a campus, while the academic education is supplied by Stellenbosch University. The experience from a successful microsatellite development programme is applied to provide hands-on applied research at masters degree and PhD level.","PeriodicalId":103036,"journal":{"name":"1999 IEEE Africon. 5th Africon Conference in Africa (Cat. No.99CH36342)","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114806430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1999-09-28DOI: 10.1109/AFRCON.1999.821917
V. Roje, D. Poljak
A simplified model of the human body immersed in an electromagnetic field is considered. The body is represented by a cylindrical scatterer placed vertically on a perfect ground, according to the wire antenna theory. The Pocklington type integral equation with exact kernel is solved by the boundary element method. Modifying the Green's function the influence of the body loss is discussed.
{"title":"Wire antenna model of the human body exposed to the low frequency electromagnetic field","authors":"V. Roje, D. Poljak","doi":"10.1109/AFRCON.1999.821917","DOIUrl":"https://doi.org/10.1109/AFRCON.1999.821917","url":null,"abstract":"A simplified model of the human body immersed in an electromagnetic field is considered. The body is represented by a cylindrical scatterer placed vertically on a perfect ground, according to the wire antenna theory. The Pocklington type integral equation with exact kernel is solved by the boundary element method. Modifying the Green's function the influence of the body loss is discussed.","PeriodicalId":103036,"journal":{"name":"1999 IEEE Africon. 5th Africon Conference in Africa (Cat. No.99CH36342)","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114841612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1999-09-28DOI: 10.1109/AFRCON.1999.821860
W. Vosloo, J.P. Holzhausen
Three 22 kV insulators with similar creepage lengths (glass, silicone rubber and EPDM rubber, the last two having identical profiles) were energised at Koeberg Insulator Pollution Test Station. Data are presented for a humid four day period, including leakage current and weather data. The interaction of the environment and the insulators is discussed.
{"title":"A comparison of glass cap and pin, silicone rubber and EPDM rubber insulators over a four day period at Koeberg Insulator Pollution Test Station","authors":"W. Vosloo, J.P. Holzhausen","doi":"10.1109/AFRCON.1999.821860","DOIUrl":"https://doi.org/10.1109/AFRCON.1999.821860","url":null,"abstract":"Three 22 kV insulators with similar creepage lengths (glass, silicone rubber and EPDM rubber, the last two having identical profiles) were energised at Koeberg Insulator Pollution Test Station. Data are presented for a humid four day period, including leakage current and weather data. The interaction of the environment and the insulators is discussed.","PeriodicalId":103036,"journal":{"name":"1999 IEEE Africon. 5th Africon Conference in Africa (Cat. No.99CH36342)","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122259226","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1999-09-28DOI: 10.1109/AFRCON.1999.821832
H. du T. Mouton, F. Combrink, J. Enslin
This paper introduces a new active resonant snubber topology suited to high power converters. The main feature of this snubber is that the peak current rating of the auxiliary switches is small compared to that of the main switches. The basic operation of the snubber is analyzed. This is followed by an experimental evaluation of the basic operating principles.
{"title":"An active resonant snubber for high power IGBT converters","authors":"H. du T. Mouton, F. Combrink, J. Enslin","doi":"10.1109/AFRCON.1999.821832","DOIUrl":"https://doi.org/10.1109/AFRCON.1999.821832","url":null,"abstract":"This paper introduces a new active resonant snubber topology suited to high power converters. The main feature of this snubber is that the peak current rating of the auxiliary switches is small compared to that of the main switches. The basic operation of the snubber is analyzed. This is followed by an experimental evaluation of the basic operating principles.","PeriodicalId":103036,"journal":{"name":"1999 IEEE Africon. 5th Africon Conference in Africa (Cat. No.99CH36342)","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121742453","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1999-09-28DOI: 10.1109/AFRCON.1999.821852
R. Chibani, E. Berkouk, G. Manesse
The aim of this paper is to present the working principle of the PM synchronous machine fed by a five level NPC voltage inverter. This inverter has a PWM current rectifier as DC source. Firstly, the authors present a model of the inverter by elaborating its knowledge model. Then, they present a control strategy of this inverter based on pulse width modulation. To prove the efficiency of this inverter, the authors use it in the speed control of a PM synchronous machine (suppose that the DC source of the inverter is ideal in the first time). After that, they present the PWM current rectifier and use it as a DC source of the inverter and give the results of the cascade which have the five level inverter as the output bridge.
{"title":"PWM current rectifier-five NPC level inverter cascade. Application to the PM synchronous machine","authors":"R. Chibani, E. Berkouk, G. Manesse","doi":"10.1109/AFRCON.1999.821852","DOIUrl":"https://doi.org/10.1109/AFRCON.1999.821852","url":null,"abstract":"The aim of this paper is to present the working principle of the PM synchronous machine fed by a five level NPC voltage inverter. This inverter has a PWM current rectifier as DC source. Firstly, the authors present a model of the inverter by elaborating its knowledge model. Then, they present a control strategy of this inverter based on pulse width modulation. To prove the efficiency of this inverter, the authors use it in the speed control of a PM synchronous machine (suppose that the DC source of the inverter is ideal in the first time). After that, they present the PWM current rectifier and use it as a DC source of the inverter and give the results of the cascade which have the five level inverter as the output bridge.","PeriodicalId":103036,"journal":{"name":"1999 IEEE Africon. 5th Africon Conference in Africa (Cat. No.99CH36342)","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1999-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115895298","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：