A study of insulation failure in a high voltage current transformer
- Authors: Jimoh, A. A. , Mahlasela, V. S. , Nicolae, Dan-Valentin
- Date: 2005
- Subjects: Electric power transmission
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22348 , uj:16190 , ISBN: 9075815085 , Citation: Jimoh, A.A., Mahlasela, V.S. & Nicolae, D.V. 2005. A study of insulation failure in a high voltage current transformer. EPE 2005 Conference, Dresden, Germany, 11-14 September 2005. DOI:10.1109/EPE.2005.219752
- Description: Abstract: The ageing and deterioration of insulation in high voltage (HV) plants have been a source of concerns to utilities. Breakdown of insulation leads to failures of HV equipment. The ageing and eventual failure of insulation in a high voltage curTent transformer (JHVCT) is the subject of investigation in this paper. A lumiiped parameter model ofHVCT is developed. This model is used to study the influlence of deteriorating and failed iinsulation on the state variables of the HVCT. Somie possible scenarios that could lead to a CT failure are investigated in this paper. For all the scelarios considered, steady alid transient equations relating the state variables of the mlodel have been developed and analyzed. The objectives of these analyses are to establish the behavioural claracteristics of the state variables, establish the interactions between these variables, and investigate the possible generations of harmonics under the various scenarios of deteriorating and outright failure of insulation in the CT. The paper concludes with a discussion of the results obtained
- Full Text:
Overview of tapping methods from high voltage transmission lines
- Authors: Nicolae, Dan-Valentin , Jimoh, A. A. , Van Rensburg, J. F. J. , Case, M. J.
- Date: 2005
- Subjects: Tapping tools , High-voltage accelerators
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22415 , uj:16200 , ISBN:9536037432 , Citation: Nicolae, D.V., Siti, M.W. & Jimoh, A.A. 2005. Overview of tapping methods from high voltage transmission lines. EDPE 2005 Conference, Dubrovnik, Croatia 26-29 September 2005.
- Description: Abstract: This paper takes an overview of various electric energy tapping methods from high voltage transmission lines.Some of these have been studied and implemented previously, some of them are in advance stage of implementation and other new methods have just been started and they are at the initial stage of modeling and simulation. this paper briefly covers the tapping methods for ac transmission lines including two new methods that are at the final stage of research. Dc transmission presents a more challenging situation, but this paper manages to present a few new methods for energy tapping.
- Full Text:
The use of multi agent system for monitoring and control of the smelting process in the mining metallurgical sector
- Authors: Siti, M. , Jordaan, J. , Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2005
- Subjects: Metallurgy , Power energy , Voltage detectors
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22052 , uj:16160 , ISBN: 0780393279 , Citation: Siti, M. et al. 2005. The use of multi agent system for monitoring and control of the smelting process in the mining metallurgical sector. IEEE PES 2005 Inaugural Conference and Exposition in Africa, South Africa, 11-15 July, 2005:326-331.
- Description: Abstract: This paper is focusing on the development of intelligent agent technology and application of that technology to the mining and metallurgical sector.We have shown how networks of communicating and cooperating intelligent software agents can be used to implement complex distributed systems. in the mining and metallurgical industries there are processes which cannot tolerate interruption, such as some sequential line chemical processes.
- Full Text:
A study of the impact of broken neutral in a distribution system
- Authors: Xivambu, M. , Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2006
- Subjects: Electric wiring , Neutral density filters
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22058 , uj:16153 , Citation: Xivambu, M., Jimoh, A.A. & Nicolae, D.V. 2006. A study of the impact of broken neutral in a distribution system. IASTED, September, 2006, Gaborone, Botswana.
- Description: Abstract: In this paper a study of the impact of the neutral conductor in a distribution system is presented. The causes which determine faults of the neutral conductor together with its effects are presented. The paper proposes a solution which will minimize the impact of the neutral failure.
- Full Text:
Controlled power flow capacitive divider for electric power tapping
- Authors: Jimoh, A. A. , Munda, J. , Britten, A. C. , Nicolae, Dan-Valentin
- Date: 2006
- Subjects: Electric power systems , Capacitance meters
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/15982 , uj:15724 , ISBN: 1-4244-0121-6 , Citation: Jimoh, A.A. et al. 2006. Controlled power flow capacitive divider for eletric power tapping. In: Proceedings of the 12th International Power Electronics and Motion Control Conference, 30 August-1st September, 2006, Portoroz. DOI: 10.1109/EPEPEMC.2006.4778611-1477
- Description: Abstract: Capacitive divider systems for tapping electric power from high voltage transmission lines are known to exhibit certain detrimental problems of stability, sub-resonance harmonic oscillations, and ferroresonance when coupled with non-linear loads. On the other hand, they can improve reactive power flow, power factor and contribute to improved harmonic filtration of the larger power system. This paper, therefore, proposes a controlled power flow conditioner as an essential integral component of a capacitive divider system to control power transfer between the high voltage transmission line, capacitive divider system, and the load. The ultimate objective of this conditioner is to mitigate or minimize the attendant problems associated with coupling the system to the load, and optimize the derivable benefits to the larger network.
- Full Text:
Performance analysis of a three-phase induction motor with capacitance injection
- Authors: Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2006
- Subjects: Three-phase machines , Induction motors , Reactive compensation , Power factor correction
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22554 , uj:16209 , Citation: Jimoh, A.A. & Nicolae, D.V. 2006. Performance analysis of a three-phase induction motor with capacitance injection. OPTIM, 10th International Conference on Optimization of Electrical and Electronic Equipments, 17-20 May, 2006, Brasov, Romania.
- Description: Abstract: In this paper a static switched capacitor with an auxiliary three-phase stator winding, which is only magnetically coupled to the stator main winding, is explored for improving the starting and operating power factor of a three-phase induction motor. The scheme improves the power factor of the motor without compromising significantly on other performances. Important advantages of the scheme include preventing harmonics in the line current, and eliminating regeneration possibility as well as preventing high inrush currents at starting.
- Full Text:
Controlled capacitance injection into a three-phase induction motor through a single-phase auxiliary stator winding
- Authors: Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2007
- Subjects: Fusion power plants , Electromagnetic induction , Reactor fuel reprocessing
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/18755 , uj:16039 , Citation: Jimoh, A.A. & Nicolae, D.V. 2007. Controlled capacitance injection into a three-phase induction motor through a single-phase auxiliary stator winding.IEEE International Electric Machines and Drives Conference, Antalya, Turkey, May 03-05, 2007:1183-1188. DOI:10.1109/IEMDC.2007.383598
- Description: Abstact: In this paper a controlled static switched capacitor three-phase auxiliary winding fed by a three-phase PWM with single-phase auxiliary winding, which is only magnetically inverter is proposed with some positive results. This solution coupled to the stator main winding, is explored for improving the is, however, complex and there are some doubts about the starting and operating power factor of a three-phase induction controller presented. Other solution presented in [7, 8] is motor. The scheme improves the power factor of the motor applicable only to a wound rotor machine, as the rotor is without compromising significantly on other performances. Important advantages of the scheme include preventing required to be connected to an external circuit. harmonics in the line current, and eliminating regeneration In this paper a single-phase stator auxiliary winding that is possibility as well as preventing high inrush currents at starting
- Full Text:
DC current source to voltage source CT-based converter
- Authors: Nicolae, Dan-Valentin , Jimoh, A. A. , Van Rensburg, J. F. J.
- Date: 2007
- Subjects: Energy storage , Transformer substations
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/20504 , uj:16106 , Citation: Nicolae, D.V., Jimoh, A.A. & Van Rensburg, J.F.J. 2007. DC current source to voltage source CT-Based converter,International Aegean Conference on Electric Machines and Power Electronics & Electromotion Joint Conferences, Bodrum, Turkey, September 10-12, 2007:665-670. DOI10.1109/ACEMP.2007.4510587
- Description: Abstract: As generally known there is no energy transfer between a dc current and a current transformer. After a brief overview of other methods for tapping energy from the high voltage direct current transmission line, this paper presents the concept of a new dc to ac current source converter utilizing a current transformer. The advantage of this converter is that it is connected in series to the dc line and that at any moment in time the current flow is kept continuous. This paper presents the concept of the converter and simulation results.
- Full Text:
Improving synchronous reluctance machine performance by direct capacitance injection through an auxiliary winding
- Authors: Ogunjuyigbe, A. S. O. , Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2007
- Subjects: Synchronous generators , Capacitors , Power-factor meters
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/20415 , uj:16094 , Citation: Ogunjuyigbe, A.S.O., Jimoh, A.A. & Nicolae, D.V. 2007. Improving synchronous reluctance machine performance by direct capacitance injection through an auxiliary winding. ICEMS’07 International Conference on Electrical Machines and Systems 2007, October 8-11, Seoul Olympic Parktel, Seoul, Korea:1055-1060
- Description: Abstract: Synchronous reluctance machine with a conventional rotor structure and a 3-phase auxiliary winding attached to a balanced capacitance for power factor improvement will find application in high speed , high power drives. This paper presents an understanding of its operation using the electromagnetic as well as the electric circuit concepts. Analytical and simulation results of this machine configuration show that the torque as well as the power factor performance is better compared to conventional reluctance machine.
- Full Text:
Multilevel high power converters for reversible power flow between utilities and power pool transmission corridor
- Authors: Nnachi, A. F. , Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2007
- Subjects: Circuit breakers , Wind-powered generation , Power transmission
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/20003 , uj:16066 , ISBN 078038606x , Citation: Nnachi, A.F., Jimoh,A.A. & Nicolae, D.V. 2007. Multilevel high power converters for reversible power flow between utilities and power pool transmission corridor. IEEE AFRICON'07, Windhoek, Namibia, 26-28 September 2007:1-8. DOI:10.1109/AFRCON.2007.4401473
- Description: Abstract: Multilevel converters have emerged as the state of the art high power conversion for applications in reversible power flow. Electric power could be tapped from or injected to the grid regardless of the discrepancies in voltage levels, frequency, phase number and different modes of operation of the grid and the system. This paper presents an overview of different topologies of multilevel converters and modulation strategies with a verification of back-to-back neutral point converter for bidirectional power flow application
- Full Text:
On-line remote and automatic switching of consumers' connection for optimal performance of a distribution feeder
- Authors: Popoola, O. , Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2007
- Subjects: Phase transformations , Voltage-frequency converters
- Language: English
- Identifier: http://hdl.handle.net/10210/20144 , uj:16073 , ISBN:078038606x , Citation: Popoola, O., Jimoh, A.A. & Nicolae, D. 2007. On-line remote and automatic switching of consumers' connection for optimal performance of a distribution feeder, IEEE AFRICON’07, Windhoek, Namibia, 26-28 September, 2007:1-6. DOI:10.1109/AFRCON.2007.4401536
- Description: Abstract: Load balancing on phases is performed using a conventional trial and error approach. With this approach, service interruption is unavoidable; hence rearrangement of consumers load distribution points on phases cannot be performed frequently. Also phase voltage and current imbalances might improve using this approach but the change does last for too long. To get the secondary distribution to operate at its optimal performance, a technique in the form of remote and automated technology is needed. This paper contributes such a technology at the low voltage side of the distribution network. The proposed static transfer switching technology is based on the open-transition switch that enables transfer or arrangement of consumer loads in a three-phase system within milliseconds and supervisory control system for effective co-ordination, computational and control of other intelligent units
- Full Text:
Phase load balancing in the secondary distribution network using fuzzy logic
- Authors: Siti, M. W. , Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2007
- Subjects: Circuit breakers , Transmission
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/20257 , uj:16084 , ISBN:078038606x , Citation: Siti, M.W., Jimoh, A.A. & Nicolae, D.-V. 2007. Phase load balancing in the secondary distribution network using fuzzy logic. IEEE AFRICON’07, Windhoek, Namibia, 26-28 September, 2007:1-7. DOI:10.1109/AFRCON.2007.4401569
- Description: Abstract: The electrical network system is to ensure that an adequate supply is available to meet the estimated load of the consumers in both the near and more distant future. This must of course, be done for minimum possible cost consistent with satisfactory reliability and quality of the supply. In order to avoid excessive voltage drop and minimize loss, it may be economical to install apparatus to balance or partially balance the loads. It is believed that the technology to achieve an automatic load balancing lends itself readily for the implementation of different types of algorithms for automatically rearranging the connection of consumers on the low voltage and of a feeder for optimal performance. In this paper the fuzzy logic is been implemented to balance the load in the secondary part of the transformer
- Full Text:
The use of support vector machine for phase balancing in the distribution feeder
- Authors: Siti, M. W. , Jimoh, A. A. , Jordaan, J. A. , Nicolae, Dan-Valentin
- Date: 2007
- Subjects: Electric power transmission , Distribution channels
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/21374 , uj:16146 , ISSN: 0302-9743 , Citation: Siti, M.W. et al. 2007. The use of support vector machine for phase balancing in the distribution feeder. ICONIP 2007, Neural Information Processing Lecture Notes in Computer Science, 4985:721-729 , DOI:10.1007/978354069162475
- Description: Abstract: Phase voltage and current unbalances in power system distribution networks are major factors leading to extra losses, communication interference, equipment overloading, and malfunctioning of the protective relay, which consequently results in service quality and operation efficiency being reduced. As a better alternative to the traditional practices of manual trial and error, and the contemporary solution technique of network reconfiguration or load rearrangement, this paper investigates and proposes a novel method that is based on the use of the historical data and artificial intelligence for eliminating or minimizing phase unbalance problems. The proposed method is based on support vector machine
- Full Text:
Comparative analysis of third harmonic injection PWM and SPWM control techniques for UPS inverter
- Authors: Wanjekeche, T. , Nicolae, Dan-Valentin , Jimoh, A. A.
- Date: 2008
- Subjects: Uninterruptible power supply , Pulse width modulation
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/20338 , uj:16086 , Citation: Wanjekeche, T., Nicolae, D. V. & Jimoh, A. A. 2008. Comparative analysis of third harmonic injection PWM and SPWM control techniques for UPS inverter. Proceedings of The IASTED International Conference on Power and Energy Systems, 8-10 September 2008, Gaborone, Botswana.
- Description: Abstract Pulse Width Modulation (PWM) techniques has been researched for three decades but there are no explicit guidelines on how one can choose the desired technique for particular application especially in power processing devices. Thus choosing a particular PWM technique for UPS application remains a challenging task since UPS operate under varying load conditions. All the techniques appear to give superior performance as well as short-comings when it comes to control of UPS inverter. This paper presents analytical and simulated results that demonstrate the equivalence between the two types of PWM control techniques and the superior performance when considering high conversion factor (C.F.) and Total Harmonic Distortion (THD) for UPS application.
- Full Text:
Dynamic model and control of power converters for grid connected renewable energy systems
- Authors: Nnachi, A. F. , Nicolae, Dan-Valentin , Jimoh, A. A.
- Date: 2008
- Subjects: Electric current converters , Renewable energy sources
- Language: English
- Type: Conference procedings
- Identifier: http://hdl.handle.net/10210/20449 , uj:16099 , Citation: Nnachi, A.F., Nicolae, D.V. & Jimoh, A.A. 2008. Dynamic model and control of power converters for grid connected renewable energy systems. Proceedings of the Second IASTED Africa Conference Power and Energy Sysyems (Africa PES 2008), 8-10 September, 2008, Gaborone, Botswana.
- Description: Abstract: In order to investigate certain dynamic events of a grid connected renewable energy system (RES), a systematic model and control is developed. The RES with its converter is taken as a controlled dc current source and the grid side converter model is based on approximate power balance of the dc-link and the ac-side. Here an AC-side decoupled current controller in dq reference frame and simplified net dc-bus voltage controllers are implied. Among different dynamic events that is studied, the response of the system during three-phase to ground fault, step change in reference DC voltage, active and reactive power change are studied and presented.
- Full Text:
Synchronous reluctance machine with controlled capacitance injection
- Authors: Ogunjuyigbe, A. S. O. , Jimoh, A. A. , Nicolae, Dan-Valentin , Agee, J. T.
- Date: 2008
- Subjects: Capacitators , Switched capacitator circuits
- Language: English
- Type: Conference procedings
- Identifier: http://ujcontent.uj.ac.za8080/10210/382760 , http://hdl.handle.net/10210/18737 , uj:16038 , Citation: Ogunjuyigbe, A.S.O. et al. 2008. Synchronous reluctance machine with controlled capacitance injection. OPTIM'08, 22-24 May, Brasov, Romania. DOI: 10.1109/OPTIM.2008.4602384
- Description: Abstract This paper describes a detailed analysis, verified by practical experimental results, of a synchronous reluctance machine with two similar stator windings and capacitance injection using a static switch. The steady state equivalent circuit is developed and used to investigate leading capacitance injection into the machine via a balanced three phase auxiliary winding that is only magnetically coupled to the main winding. The scheme was found to improve the torque and power factor performance of the machine as well as reduce harmonics in the line current. Two switching topologies were utilized for the static control in this arrangement, and both were found to present good and comparable results. Experimental results corroborate the simulations.
- Full Text:
Test results on synchronous reluctance machine with auxilliary winding for leading reactive power injection
- Authors: Ogunjuyigbe, A. S. O. , Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2008
- Subjects: Synchronous machinery , Performance standards , Capacitance injection
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/16468 , uj:15776 , Citation: Ogunjuyigbe, A.S.O., Jimoh, A.A. & Nicolae, D.V. 2008. Test results on synchronous reluctance machine with auxilliary winding for leading reactive power injection. Proceedings of the second IASTED Africa Conference Power and Energy Systems (AfricaPES 2008)September 8-10, 2008, Gaborone, Botswana
- Full Text:
A cascaded NPC/H-bridge inverter with simplifiied control strategy and minimum component count
- Authors: Wanjekeche, T. , Nicolae, Dan-Valentin , Jimoh, A. A.
- Date: 2009
- Subjects: Electric inverters , Harmonics (Electric waves) , Power electronics
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/22319 , uj:16188 , ISBN: 978-1-4244-3919-5 , Citation: Wanjekeche, T., Nicolae, D.V. & Jimoh, A.A. 2009. A cascaded NPC/H-bridge inverter with simplifiied control strategy and minimum component count. Proceedings of IEEE-Africon, 23-25 September, 2009, Kenya. DOI: 10.1109/AFRCON.2009.5308551
- Description: Abstract: Please refer to full text to view abstract Please refer to full text to view abstract
- Full Text:
A novel 9-level multilevel inverter based on 3-level NPC/H-bridge topology for photovoltaic applications
- Authors: Wanjekeche, T. , Jimoh, A. A. , Nicolae, Dan-Valentin
- Date: 2009
- Subjects: Harmonics , Photovoltaic power generation , Electric power generation
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/10210/21278 , uj:16136 , Citation: Wanjekeche, T, Jimoh, A.A. & Nicolae, D.V. 2009. A novel 9-level multilevel inverter based on 3-level NPC/H-bridge topology for photovoltaic applications. International Review of Electrical Engineering, 4(5):769-777. , ISSN: 1827-6660
- Description: Abstract: Please refer to full text to view abstract Please refer to full text to view abstract
- Full Text:
LV self balancing distribution network configuration for minimum losses
- Authors: Nicolae, Dan-Valentin , Siti, M. W. , Jimoh, A. A.
- Date: 2009
- Subjects: Distribution systems , Electric networks , Low voltage systems
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/21377 , uj:16144 , ISBN: 978-1-4244-2235-7 , Citation: Nicolae, D.V., Siti, M.W. & Jimoh, A.A. 2009. LV self balancing distribution network configuration for minimum losses. Proceedings of the IEEE PowerTech Conference, 26-02 July, 2009, Bucharest, Romania. DOI: 10.1109/PTC.2009.5282233
- Description: Abstract: please refe to full text to view abstract Please refer to full text to view abstract
- Full Text: