Browsing by Author "Lucas, R"

Now showing 1 - 7 of 7

item: Conference-Abstract
Effect of the shape of the solid insulators on creeping discharge propagation under AC voltages
Ediriweera, S; Jayarathna, P; Samarasinghe, R; Lucas, R
This paper studies the use of circular and square shaped solid insulators on creeping discharge propagation over solid/liquid dielectric interfaces under AC voltages. A point-plane electrode arrangement based test apparatus is used to initiate creeping discharges over solid/liquid interfaces and the discharge propagation is captured using a camera. Two shapes of solid material samples are used to analyze the effect of using different shaped dielectric samples for the creeping propagation under AC voltages. Two types of solid materials, glass and acrylic, immersed in copra coconut oil are tested. Discharge length of the discharge patterns and the fractal dimension calculated by box counting method are used to explain the effect of square shaped and circular shaped dielectric samples for the morphology of creeping discharges. Results show that the shape of the solid dielectric material does not have a significant effect on the discharge length, fractal dimension and the shape of the discharge pattern.
item: Thesis-Full-text
Fractal analysis of creeping discharges propagating over solid insulators immersed in insulating oil
(2018) Ediriweera, WEPS; Samarasignhe, R; Lucas, R
A solid/liquid insulation interface is considered to be one of the weakest points in a composite insulation system as it facilitates creeping discharges on the interface when the electric field strength exceeds a threshold value. This thesis presents an original study on the use of alternative liquid and solid insulation materials to minimize the effect of damages which occur due to creeping discharge activity. A point-plane electrode arrangement based test apparatus energized by a high voltage supply is used for analysing propagation of creeping discharges over solid/liquid interfaces using visual observation. Firstly, an algorithm is developed to determine the fractal dimension of creeping discharges propagating over various solid/liquid insulating interfaces. In particular, it focuses on the variation in creeping discharge patterns with the use of pure epoxy and Nano-composite epoxy samples. The results show that the pattern propagation depends on the surface profile and the dielectric constant of the solid material. Next, the effect of the thickness of solid materials on the propagation characteristics of creeping discharges is studied and the results show that capacitive mechanism plays a major role on pattern propagation irrespective of the kind of solid material. Next, the effect of oil level on creeping discharge propagation over solid/liquid interfaces is studied and the results show that when the oil level increase, amount of ramification and propagation of streamers decreases. Finally, this thesis studies the effect of using alternative oils such as copra type coconut oil, virgin type coconut oil, soya bean oil and sunflower oil on creeping discharge propagation. The results show that there is an inverse relationship between the amount of tree formation and the dielectric constant of the liquid. The investigations show that use of nano-composite materials and alternative oils have a significant effect on creeping discharge propagation over solid/liquid insulating interfaces.
item: Article-Abstract
Macro scale modelling of wind plants in long term planning studies : a Sri Lankan case study
(2015-08-20) Mudannayake, A; Lucas, R; Siyambalapitiya, T
Harnessing Non Conventional Renewable Energy (NCRE) sources as small-scale embedded generation is rapidly increasing around the world. Modelling most NCRE based generation becomes an arduous task owing to their extremely volatile nature of resource availability along with present day economic, technical, social and environmental constraints. In this context, Sri Lanka is no exception. According to the energy policy-2006, energy share from NCRE is targeted to reach 10% of total electricity generation by 2015. According to National Renewable Energy Laboratory (NREL) report [1],wind energy potential in Sri Lanka is high compared with other technologies; mini hydro and biomass. Recent commissioning of about 30 MW of wind plants in Kalpitiya peninsula is an indication of investor interest in wind energy development for power generation. Therefore, modelling of wind power plants in long term planning can no longer be simple, such as representation as a lumped equivalent thermal plant with high Forced Outage Rate (FOR).Preparation of a macro scale wind plant model for Sri Lanka has not been undertaken before using the economic optimisation tool Wien Automatic System Planning (WASP)package. This gap is addressed in this paper. Two models ' were initially prepared to be compatible with WASP. An in-depth study using (i) Modified Load Duration Curve method and (ii)Run of River (ROR)type hydro equivalent wind model based on five state probabilistic distributions, were investigated. Compatibility of new models was tested with WASPfor dispatching as embedded generators. Considering the model simplicity, requirement of time & effort for sensitivity analyses and modifications, the later approach was concluded as the most appropriate for long term planning studies.
item: Article-Abstract
Modelling of mini hydro plants in long term planning studies : a Sri Lankan case study
(2015-08-20) Mudannayake, A; Lucas, R; Siyambalapitiya, T
The development of green energy and cutting down fossil fuel fired brown energy is now matured from the voluntary commitment stage up to a level of fixing national policy targets even in developing countries [1], [2] including Sri Lanka [3]. Thus, the share of Non Conventional Renewable Energy (NCRE)in electricity generation is becoming crucial in modern generation planning studies. As a result, many advanced research studies have been conducted around the world [8]-[13].In particular, no national level detailed study has yet been conducted to model the macro impacts of large numbers. of distributed mini hydro plants, in long term planning studies. Owing to the increasing share of contribution from mini hydro power plants, especially as embedded, non-dispatchable generation, simplified models such as the thermal equivalent model with high Forced Outage Rate (FOR)which is the current practise will no longer be justifiable. A suitable model should accommodate the seasonal variation of energy availability as well as the operational aspects specific to embedded generation. This study proposes a.probabilistic model to meet this vital requirement of the entire group of mini hydro plants. The operational aspects of the model have been verified by using the optimisation tool Wien Automatic System Planning (WASP), the same planning tool used by the Ceylon Electricity Board (CEB)and many other utilities worldwide for generation planning. Special attention has been paid to ensure that the model will be suitable for conducting sensitivity studies. The predictability of the model has been checked with past data. Although a Sri Lankan case study was applied to validate the model, the technique is more general and can be adapted for any other case studies as well.
item: Article-Abstract
Profile of the Sri Lankan eEectrical engineering industry
(2015-08-24) Jayasekara, B; Lucas, R; Namasivayam, S; Udawatta, L; The electrical and electronic industry in Sri Lanka, although relatively small in itself, is a key service industry to other industrial sectors as well. In the study presented, a sample of around 300 companies/industries has been the surveyed from around 500 identified companies to obtain the profile of the electrical engineering industry. From the surveyed companies, more than 76.8%are in the electrical industry and these companies account for over 81.1% of the total employment provided. The energy supply sub sector provided 36.7% of the total employment, and is influenced heavily by the large workforce of the CEB.The electrical services industry, which is mostly dominated by the small enterprises, contributes to 20.9%, while electrical products sector accounts for 23.5% of the employment. The majority of the industry's employment is concentrated in the operational grades (75.8%)where the technical skills requirements are quite specific for a particular role and quite diverse for different roles. The skills requirement becomes more generalized, with more emphasis for managerial qualifications, as one goes higher up in the occupational structure. At the operational levels, the vast majority of the workers are with either GCE OIL or A/L qualifications (65.2%). On the other hand, higher education qualifications are much more sought after at the managerial level and decision making level with 72.2% of the managers and 88.8% of the decision makers possessing a degree or above qualifications. The growth potential of the electrical and electronic industry has been estimated, based on census and statistics of GDP growth rates of similar industries, by categorising the industry into five sub-sectors, namely energy supply, electrical products, electrical services, export oriented electronics, and local consumer electronics and services. The forecasted annual growth of employment for the industry is 14.4%(Electricalindustry 13.7%and electronics industry 16.8%).
The electrical and electronic industry in Sri Lanka, although relatively small in itself, is a key service industry to other industrial sectors as well. In the study presented, a sample of around 300 companies/industries has been the surveyed from around 500 identified companies to obtain the profile of the electrical engineering industry. From the surveyed companies, more than 76.8%are in the electrical industry and these companies account for over 81.1% of the total employment provided. The energy supply sub sector provided 36.7% of the total employment, and is influenced heavily by the large workforce of the CEB.The electrical services industry, which is mostly dominated by the small enterprises, contributes to 20.9%, while electrical products sector accounts for 23.5% of the employment. The majority of the industry's employment is concentrated in the operational grades (75.8%)where the technical skills requirements are quite specific for a particular role and quite diverse for different roles. The skills requirement becomes more generalized, with more emphasis for managerial qualifications, as one goes higher up in the occupational structure. At the operational levels, the vast majority of the workers are with either GCE OIL or A/L qualifications (65.2%). On the other hand, higher education qualifications are much more sought after at the managerial level and decision making level with 72.2% of the managers and 88.8% of the decision makers possessing a degree or above qualifications. The growth potential of the electrical and electronic industry has been estimated, based on census and statistics of GDP growth rates of similar industries, by categorising the industry into five sub-sectors, namely energy supply, electrical products, electrical services, export oriented electronics, and local consumer electronics and services. The forecasted annual growth of employment for the industry is 14.4%(Electricalindustry 13.7%and electronics industry 16.8%).
item: Article-Abstract
Profile of the Sri Lankan electrical engineering industry
Jayasekara, B; Lucas, R; Namasivayam, S; Udawatta, L
The electrical and electronic industry in Sri Lanka, although relatively small in itself, is a key service industry to other industrial sectors as well. In the study presented, a sample of around 300 companies/industries has been the surveyed from around 500 identified companies to obtain the profile of the electrical engineering industry. From the surveyed companies, more than 76.8% are in the electrical industry and these companies account for over 81.1% of the total employment provided. The energy supply sub sector provided 36.7% of the total employment, and is influenced heavily by the large workforce of the CEB. The electrical services industry, which is mostly dominated by the small enterprises, contributes to 20.9%, while electrical products sector accounts for 23.5% of the employment. The majority of the industry’s employment is concentrated in the operational grades (75.8%) where the technical skills requirements are quite specific for a particular role and quite diverse for different roles. The skills requirement becomes more generalized, with more emphasis for managerial qualifications, as one goes higher up in the occupational structure. At the operational levels, the vast majority of the workers are with either GCE O/L or A/L qualifications (65.2%). On the other hand, higher education qualifications are much more sought after at the managerial level and decision making level with 72.2% of the managers and 88.8% of the decision makers possessing a degree or above qualifications. .The growth potential of the electrical and electronic industry has been estimated, based on census and statistics of GDP growth rates of similar industries, by categorising the industry into five sub-sectors, namely energy supply, electrical products, electrical services, export oriented electronics, and local consumer electronics and services. The forecasted annual growth of employment for the industry is 14.4% (Electrical industry 13.7% and electronics industry 16.8%).
item: SRC-Report
A Tool for estimating remaining life of power transformers
(2017) Samarasinghe, R; Lucas, R; Ediriweera, S; Jayarathna, P
Part 1- Modelling the Lumped Parameter Network of a Power Transformer using Sweep Frequency Response Analysis Accurate modeling of power transformers is beneficial for fault diagnosis and the health condition assessment of the power transformers. This project proposed a novel approach of synthesizing the lumped parameter equivalent circuit of a power transformer using its frequency response by utilizing artificial neural networks and the genetic algorithms. A physically realizable transfer function derived using the sweep frequency response data of a power transformer is used to construct its lumped parameter equivalent circuit model. Then, the parameters of the model are estimated using an artificial neural network and the genetic algorithm. All parameters, objectives and constraints of the genetic algorithm and the artificial neural network are set appropriately to ensure accurate results within the shortest time span. The entire approach is validated by means of an error analysis. The proposed method is easy to implement and can be used effectively to improve the reliability of power system though accurate fault identification and health assessment of power transformers. In addition, by replacing general equivalent circuit with the proposed model, the accuracy of transient analysis results can be significantly enhanced as the high frequency behavior is simulated using lumped parameter network. Part 2 - Fractal Characteristics of Creeping Discharges Propagating on Solid/Liquid Dielectric Interfaces A solid/liquid dielectric interface is considered a weak point in a composite insulation system, as it facilitates creeping discharges on the interface. This project proposes the use of nano-dielectrics to minimize the effect of damages which occur due to creeping discharge activity on such interfaces. A point-plane electrode arrangement-based test apparatus, energized by a high voltage supply, is used for analyzing the propagation of creeping discharges over solid/liquid interfaces using visual observation. An algorithm is used to determine the fractal dimension of creeping discharges propagating over various solid/liquid insulating interfaces. The results show that the use of nanofillers can increase the dielectric breakdown strength of epoxy by 7%.