Browsing by Author "Prasad, WD"

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item: Conference-Full-text
1st International Conference on Electrical Engineering 2016 (Pre Text)
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Rajapakse, A; Prasad, WD
item: Conference-Full-text
An adaptive protection scheme for small scale microgrids based on fault current level
(Institute of Electrical and Electronics Engineers, Inc., 2018-09) Peiris, WLT; Eranga, WH; Hemapala, KTMU; Prasad, WD; Samarasinghe, R; Abeygunawardana, S
With the growing of the “Microgrid” concept in the modern world, new protection systems are required. This protection system should be handled the all configurations and all conditions of the microgrids and suitable for small scale less expensive microgrids. This paper proposed a reliable, online, adaptive and accurate method for microgrid protection by using fault current level of the system considering the modes of operation, dynamic nature of the Distributed Generators (DGs) and different types of the loads. This is an adaptive protection scheme for a microgrid; where a Microgrid Central Protection Unit (CPU) monitors the microgrid continuously using a communication medium, whenever fault is detected in the network, the relay settings of the microgrid are altered adaptively based on instructions issued by CPU. This method can be operated accurately by estimation fault current level of the Microgrid at the instant and using that relay tripping current at any disturbance and can be calculated at any condition. By using this protection strategy, can create self-operated microgrid and can avoid human interference to the microgrid operation, design and calculation.
item: Conference-Abstract
Applicability of enterprise resource planning in human resource management in high-rise building construction
(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 2019-07) Bosco, AJ; Wickramasinghe, BMSM; Disaratna, V; Prasad, WD; Abeysooriya, R
Human Resource (HR) Management is of great significance in construction industry as it has a direct impact on the performance of construction projects. Mostly construction of high-rise buildings faces the challenge of managing its HR with the rapid design and development of them. Thus, the industry has come out with some strategies to overcome them. However, these strategies did not provide a complete solution. Therefore, construction industry needs an appropriate way to manage its HR and thus calling for an Information Technology (IT) solution which in turn is Enterprise Resource Planning (ERP) system. Consequently, the aim of investigating the applicability of ERP in managing HR in high-rise building construction became a paramount concern in this research. Accordingly, this research was adopted a qualitative approach with a set of semi-structured interviews focusing industrial professionals and ERP experts to accomplish the aforementioned aim. Subsequently, the collected data were analyzed rigorously through content analysis. The relationship between information from the literature sources and from the industry professionals with respect to main advantages of ERP system and key features of ERP system, it is recommendable to be used in managing HR through overcoming HR challenges completely in high-rise building construction.
item: Thesis-Abstract
Clean energy & regulatory interventions for greenhouse gas emmission mitigation in the Sri Lanka power sector
Prasad, WD; Wijayatunga, P
Renewable Portfolio Standard (RPS) is rapidly emerging as a popular mechanism among policy makers to increase the penetration of renewable in the electricity markets, requiring the electricity supply industry to include a minimum level of electricity generation from renewable energy sources. Sri Lankan energy policy has set a target of 10% of grid electricity by 2015 to come from non-conventional energy sources (NCRE). Mini-hydro, biomass including dendro power and wind energy, which have been identified as the three leading, sustainable, non-conventional forms of renewable energy promoted in Sri Lanka for electricity generation to feed into the national grid. The present installed capacity of grid-connected non-conventional renewable energy based electricity generation in Sri Lanka is around 100 MW and these plants are mainly connected to the primary distribution system. All these plants contribute to the nation's energy requirement generating only a small fraction of total generation amounting to approximately 2.5%. The longterm least-cost power generation expansion plan has given rise to the installation of oil-fired and coal-fired thermal plants to meet the increasing demand. This process does not give adequate consideration to the alternate supply-side options such as those based on NCRE. The study presented in this thesis first investigates the impact of alternate generation options like NCRE based technologies, clean fuel options and reciprocating diesel engines with small capacities in the Sri Lankan power system considering Traditional Resource Planning based on minimizing total economic cost. . The mam intention of this study IS to investigate technological and regulatory interventions especially the impact of the RPS of 10% on the least-cost power generation expansion plan of Sri Lanka considering available renewable technologies as supply-side options together with their technical potential and economic feasibility. The study also examines the impact of these interventions on overall power sector emissions and. the greenhouse gas emissions- (GHG) in particular. The sensitivity of the outcomes of the 10%-.!3-PSto different supply side interventions are also presented in the thesis. It has been found that the 10% RPS target by 2015 can be achieved with an additional cost burden of US$ 57.25 million on the government. The results also show that mini hydropower is the best NCRE based technology which needs minimum financial incentives when achieving the target. Wind power and dendro power require substantial government incentives if they are to playa role in RPS.
item: Conference-Full-text
Comparison of techniques based on current signature analysis to fault detection and diagnosis in induction electrical motors
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Fontes, AS; Cardoso, CAV; Oliveira, LPB; Rajapakse, A; Prasad, WD
The wide use of electrical induction motors in industries throughout the world requires, increasingly, more precision in fault diagnosis. Techniques of predictive maintenance such as Motor Current Signature Analysis (MCSA) and Motor Current Square Signature Analysis (MSCSA) are used to detect and diagnose faults patterns, characterized by the stator current spectrum, in induction motors. In this article, these techniques are applied and compared for different faults in real motors, such as inter-turn short circuit in the stator winding and eccentricity in the air gap. To assist in the comparison of these patterns of the stator current spectrum with and without faults, a theoretical model of a healthy electrical induction motor was used, with the same values of the real supply voltages, which generated the frequency spectrum patterns. The results presented in this article, which should be emphasized, demonstrated that the techniques mentioned above were suitable for the cited faults, whose comparison between the techniques showed the suitability of each one.
item: Conference-Abstract
Cost effective battery storage for intermittency of solar
(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 2019-07) Nayanathara, PMD; Perera, HS; Abeyrathne, RAHMPNN; Lucas, JR; Prasad, WD; Abeysooriya, R
Renewable energy, especially Solar Energy, has become a popularly sought solution for the current energy situation in Sri Lanka. It is included in the ‘Long Term Generation Expansion Plan of the Ceylon Electricity Board (CEB)” as well [1]. However, the unpredictable, varying and intermittent nature of the solar hinder all these plans. Wide varying nature of solar power is such that the daily infeed may vary within 20% to 90% of the installed during the same week. Said constant power fluctuations and the inability to control the infeed utilizing system inertia lowers the quality of service provided to the CEB by the power producers. This impacts adversely on the interest towards solar from both the sides; CEB and the power producer. To overcome this problem, the CEB recommends solar producers to install a battery storage to store the energy produced during daylight hours enabling that energy to be utilized later. This recommendation has not been welcomed by the producers due to cost related issues. Hence, this research proposes a more economically feasible solution for the discussed matter. It consists of a forecasting system to predict the solar power output sufficiently in advance to the CEB System Control Center and a relatively smaller battery storage equipped with an automatic switching mechanism to maintain the predicted output. This value-added solar output should be rewarded under an updated tariff scheme.
item: Conference-Full-text
DC microgrid as a solution for utilisation of solar photovoltaic sources
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Bandara, AIMH; Binduhewa, P; Ekanayake, J; Rajapakse, A; Prasad, WD
MicroGrid (MG) is a convenient solution to integrate renewable energy sources to the existing power network. Though ac MicroGrids are widely studied, researches are focused towards the implementation of dc MicroGrids in order to improve the utilization of renewable sources with dc power output. In this study a MicroGrid architecture for commercial buildings and domestic houses with solar photovoltaic (PV) as the renewable energy source is proposed. The dc MicroGrid was implemented in PSCAD/EMTDC software package and simulations studies were conducted to validate the operation.
item: Conference-Abstract
Develop a series arc fault detector to minimize the risk of domestic electrical fires
(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 2019-07) Somathilaka, SP; Sumathipala, WMKS; Senarathna, NT; Hewapathirana, HE; Hemapala, KTMU; Lucas, JR; de Silva, PSN; Prasad, WD; Abeysooriya, R
This study is about the development of a series arc fault detector, which can be used to minimize the risk of domestic electrical fires. Electricity is a common cause of fire in residential buildings. If a parallel electrical arc fault is developed it can be detected from the residual current circuit breaker. If the arc current is higher than the rated current of the circuit, it can be detected from the miniature circuit breaker. But, if a series arc fault is developed which is lower than the rated current of the circuit, it cannot be detected by those conventional devices. In this study, an arc generator which could be connected to any electrical equipment was developed for generating a series arc fault. A set of different methods such as Fast Fourier Transform, Derivative Analysis, Discrete Wavelet Transform and Continuous Wavelet Transform were used to analyze the current and voltage waveforms in the presence and absence of series arc fault. However, only some of those methods yielded promising results. Moreover, an analysis about the parameters which will affect the risk of fire was conducted. Further research regarding the development of the series arc fault detector is in progress.
item: Thesis-Full-text
Development of a generalized methodology for blackout restoration : a case study of Sri Lankan power system
Sirisena, KLU; Prasad, WD; Fernando, R
Blackouts are been reported throughout the history worldwide and nowadays, a moment without electricity causes a greater loss of lives and economy. On the other hand, restoration of a blacked-out power system requires expertise of experienced engineers which is not completely reliable under certain system complexities. Generally, it turns out to be a trial and error approach under the guidance of experts. This paper proposes a generalized aiding methodology for solving the restoration problem by assessing the next system state for a given decisions of the system operator. With adequate system information (pre-outage data, equipment availability etc.), this proposed decision support methodology could mitigate unexpected cascaded tripping events which occur owing to lack of confidence in next state during restoration. The case study considers restoring of a crucial subsystem of Sri Lankan power system, Colombo – Kelanitissa system along with Laxapana System. Successful attempts shall fulfil load flow while maintaining system parameters and stability during switching operations. The results compare and depict the success in solving the restoration problem with proposed real-time, offline methodology against trial and error approach. Further it suggests the requirement of parallel computer based simulations on restoration of other sub systems and synchronizing events during actual implementation.
item: Conference-Full-text
Development of a test platform for synchrophasor applications with real-time digital simulator
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Gurusinghe, DR; Rajapakse, AD; Rajapakse, A; Prasad, WD
The rapid advance of synchrophasor technology and the growth of phasor measurement unit (PMU) installations in the recent years have substantially increased the feasibility of deploying practical synchrophasor applications. These novel applications need to be thoroughly evaluated before their actual implementations on real power systems. The most feasible solution is to use real-time power system simulators. Therefore, this paper presents a real-time digital simulator (RTDS) based test platform to implement and to validate various synchrophasor applications range from simple monitoring algorithms to advanced response based wide area monitoring, protection and control systems. The proposed test platform can also be used to validate PMU performances as well as to assess cyber-security issues of synchrophasor networks. The effectiveness of the test platform is demonstrated with a real-time monitoring application.
item: Conference-Full-text
Development of an automated microscopic imaging system for TB screening
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Samarasinghe, HDTG; Sampath, LLR; Thilakarathna, HRMMVB; Gopura, RARC; Lalitharatne, TD; Amarasinghe, YWR; Rajapakse, A; Prasad, WD
This paper proposes an automated microscopic imaging system (MIS) for TB screening. Mainly, the system consists of integrated hardware and software components for sputum smear slides feeding, controlling and carrying out microscopic and image processing functions of the system. The MIS is used to distinguish TB positive and negative cases. The hardware system and controlling mechanism of MIS are discussed. Algorithms for focusing of the microscope and image processing are presented. Experiments are carried out to evaluate the proposed automated microscopic imaging system
item: Conference-Full-text
Evaluation of the impact of integrating pumped-storage systems in a small power system with high wind penetration
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Peiris, KRD; Kalpage, KMT; Perera, KAIRP; Wickramarathna, MTAP; Siriwardana, MGCI; Lidula, NWA; Rajapakse, A; Prasad, WD
High wind penetration in a small power system can create overwhelming stability issues at contingencies. Hybrid wind and pumped-storage systems are widely adopted to harness the maximum wind energy potential locally. Similarly, integration of pumped-storage power plants can be considered for islands or small power systems to integrate more wind farms while improving stability of the system. A small power system was derived based on the IEEE-12 bus system to evaluate the system behavior with increased wind penetration and pumped-storage integration. The integrated system was simulated in PSCAD/EMTDC to analyze the system transient stability under different scenarios. The studies revealed that the integration of pumped-storage systems into small power systems with high wind penetration not only supports more wind penetration into the system but also improves the transient stability.
item: Conference-Full-text
Factor analysis, hessian local linear embedding and isomap for epilepsy classification from EEG
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Prabhakar, SK; Rajaguru, H; Rajapakse, A; Prasad, WD
In this present generation, more than 1% of the whole world’s population is affected by this seizure disorder. Due to genetic predispositions like tumours, strokes and drug misuse, epilepsy is caused. Epilepsy is a common brain disorder in which cluster of neuronal signals function abnormally. For preventing seizures, medications are available but only some patients can respond well to the medication. Other remedial measures such as neurostimulation, surgery, maintaining a healthy diet are not always successful in treating the patient. Because of epilepsy, the patients have to live with persistent anxiety throughout their lives and also leading a normal life and performing day to day and social tasks becomes more difficult for them. For the analysis and diagnosis of epilepsy, the detection and classification of seizures forms the most important step. The vital information regarding the dynamics of the brain can be easily measured by Electroencephalogram (EEG). Since the recordings of the EEG data are pretty long, the obtained data is too huge to process and so, in this study, the dimension of the EEG data is reduced by Dimensionality Reduction (DR) techniques such as Factor Analysis (FA), Hessian Local Linear Embedding (HLLE) and Isomap (IM). The dimensionally reduced values are then classified with the help of Genetic Algorithm (GA) and Generalized Regression Neural Network (GRNN). The performance metrics are analyzed with parameters such as performance index, sensitivity, specificity, time delay, quality value and accuracy. The results show that when FA, HLLE and Isomap are classified with GRNN, then a perfect classification of 100% and an accuracy of 100% are obtained. If the dimensionality reduction techniques classified with GA are compared, then a high accuracy of 95.24% is obtained when it is classified with HLLE-GA combination.
item: Conference-Extended-Abstract
Impact of alternative generation planning options on electri city tariffs
(2007) Prasad, WD; Wijayatunga, PDC
Sri Lanka is predominantly a fossil fuel importing country with relatively high rainfall mainly in the central hilly region. This factor has led to the heavy dependence on hydropower to satisfy its power generation needs during the past century. Presently this hydropower dominated Sri Lankan power system is moving towards thermal system domination. This is due to the limitation of economic hydro-power resources and the fact that a major component of these economic resources has already been exploited. Further Ceylon Electricity Board (CEB), institution responsible for generation planning, considers only candidate thermal options together with four candidate hydropower options when preparing the base case expansion plan. Long-term least-cost power generation expansion plan has therefore given rise to the installation of oil-fired and coal-fired thermal plants to meet the increasing demand of the country [1].
item: Conference-Full-text
The impact of distributed generation on transmission and distribution losses in Sri Lankan power system
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Priyangika, AAC; Wijayapala, WDAS; Banda, HMW; Rajapakse, A; Prasad, WD
Share of Non-Conventional Renewable Energy (NCRE), small hydro, wind, solar, bio-mass etc based electricity generation in Sri Lanka at present is 10% of the total annual generation. The Government of Sri Lanka has declared a national target of 20% from NCRE by 2020[1]. Most of NCRE power plants have been connected to the distribution network and are termed as Distributed Generators (DGs). With the increase of share of DGs, it affects system reliability, power quality and economic operation of the distribution network. This paper focuses on the impact of economic operation of transmission and distribution network due to distributed generation in Sri Lankan power system. Network simulation studies have been carried out for transmission network and for four grid substations to which many DGs have been connected. The analysis revealed that transmission network losses have reduced with increase penetration of DGs to the system while distribution network losses are dependent on the amount of DG capacities connected to the distribution network. However, there is a reduction of network losses when overall network is considered thereby giving financial benefit from DGs added to the system.
item: Conference-Abstract
Improved maximum power point tracking of solar pv systems for faster and accurate convergence
(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 2019-07) Wanigasekara, DC; Hettiarachchi, UM; Weerasinghe, WPTS; Ranasinghe, ERIACC; Prasad, WD; Abeysooriya, R
The maximum power of a PV module represents variations due to temperature, irradiation and load. In the conventional mode maximum power point tracking algorithms are applied to maximize efficiency, reliability by constantly extracting maximum power. The conventional methods that mentioned in literature have several disadvantages in terms of efficiency, accuracy and flexibility specifically under varying weather conditions. It is mainly because of non-linearity in PV module current-voltage characteristics as well as DC-DC converters. Under this project new intelligent control methods for maximum power point tracking will be tested. Basically, fuzzy logic-based hill climbing method will be proposed and tested to obtain faster and accurate converging to the maximum power point during steady state and varying weather conditions. This artificial intelligence approach would simplify exiting methods and provide with proper modeling of nonlinear systems. In achieving this goal, maximum power point system consisting PV module, buck, boost, buck-boost converter, fuzzy logic controller is designed and simulated using Mat lab Simulink and experimentation studies would be carried out. In the latter stage, it is proposed to extend this project by combining fuzzy logics and neural networks so that the system can identify its maximum power point by itself through self-learning rather implementing only an algorithm as in conventional methods.
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Inadequacies of analysis of pre-construction activities on cost overruns in construction projects
(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 2019-07) Shehara, PLAL; Ranasinghe, M; Prasad, WD; Abeysooriya, R
Cost overrun is considered as one of the critical issues in the construction sector projects in many of the developing countries. It has been identified that pre-construction factors affect mainly on time and cost overruns in construction projects. The focus here is on mainly four pre-construction factors which are selected from review of literature. They are conducting geotechnical site investigations, identification of availability of sufficient knowledge to do the project, identification of availability of skilled labour, identification of required material, machinery and equipment. This research study attempts on identifying the severity of the adequacy of these four pre-construction factors on cost overruns and to develop a relationship between cost overrun variation with the adequacy level of analysis of those pre-construction factors. A thorough review of literature was done to identify the four pre-construction factors and then a questionnaire survey was conducted to obtain the responses from industry experts regarding construction cost overruns related with the adequacy levels of analysis of four factors for a selected project. The survey data obtained were analysed by determining Relative Importance Index, Regression Analysis and Sensitivity Analysis techniques. The results obtained from the analysis techniques are interpreted under this research study based on the limitations.
item: Conference-Full-text
Integrated control strategy for grid connected photovoltaic array, battery storage and supercapacitors
(Institute of Electrical and Electronics Engineers, Inc., 2018-09) Silva, CMMRS; Premadasa, PND; Dassanayake, DMCT; Pradeep, RAH; Sirithunge, C; Chandima, DP; Prasad, WD; Samarasinghe, R; Abeygunawardana, S
Upon various renewable based power generation, Solar Photovoltaic (PV) technology is continually developing nowadays. However, the major drawback of this technology is the intermittent issue due to the rapid fluctuations in solar insolation level. Energy storage systems such as batteries and super capacitor banks are used to reduce the above problem. There is a requirement of an integrated controller strategy in order to achieve a power generation unit which includes power share among those energy storage units in between with solar PV array. Using a hybrid system of a battery bank and a super-capacitor bank over using a battery bank alone, helps to increase the lifetime of the batteries. Integrated control strategy is the common method used to control the solar PV array with energy storage units in order to supply the required islanded demand and supply excess energy to the grid while maintaining the DC-link stability through the synchronized control of DC-DC power electronic converters. This paper presents an integrated control strategy for grid connected PV array together with a battery bank and a super-capacitor bank. This further state mathematical proof for the sizing of storage devices. Performance of the integrated control strategy was evaluated using a practical experiment by developing customized DC-DC power electronic converters.
item: Conference-Full-text
Local detection of distribution level faults in a distributed sensor monitoring network using HMM
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Balachandran, T; Aravinthan, V; Thiruvaran, T; Rajapakse, A; Prasad, WD
The Smart distribution system initiative requires an increased usage of the distribution feeder-level communication infrastructure to improve automation. Using a distributed sensor network for monitoring the distribution system is proposed by various researchers. Such distributed sensor communication architecture requires information to be received within an allowable delay and a minimum processing time at the control center. Increasing the number of sensors in the network also increases the data flow in the communication medium. Therefore, to reduce the burden in the communication medium, an event driven communication protocol could be utilized. This communication architecture assumed that the sensors used a local fault detection system to detect the abnormal event before communicating with the control center. This work focusses on local detection of faults in a distributed sensor network using a Hidden Markov Model considering a minimum processing time.
item: Conference-Full-text
Mainstreaming renewable energy developments into traditional planning: a Sri Lanka case study
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Chathuranga, JHKK; Wijayapala, WDAS; Wijayatunga, PDC; Rajapakse, A; Prasad, WD
This study examines the Sri Lankan generation planning practices and recommends several methodological changes and models to successfully integrate and evaluate Non-Conventional Renewable Energy (NCRE) resources in the present planning approaches. The paper proposes the peak period capacity factor method to calculate the capacity credit of NCRE generation. A methodology is presented to model a wind power plant in Wien Automatic System Planning Package IV (WASP IV) and also to evaluate the benefits of modeled NCRE plants. The Mean Variance Portfolio Theory (MVPT) is proposed as a complementary planning tool to assess the risks of generation portfolios and finally, these concepts are applied on the Sri Lankan system to demonstrate the applicability.