Browsing by Author "Lucas, JR"

Now showing 1 - 20 of 74

item: Thesis-Abstract
Analysis of bulk consumer demand for tariff design
(2014-08-12) Gunaratne, DH; Lucas, JR; Siyambalapitiya, T
Bulk consumers are the main revenue generating category of the electricity consumer mix in Sri Lanka. Their contribution has a large impact on demand in the power distribution network. The tariff applied, the metering system and the analysis of their consumption is very important to the utility and to the consumer. Optimizing the resources in the power distribution network is very important to the utility. The utility has to encourage the consumer to manage the load scientifically. The energy consumed should be charged in a fair manner. Paying a reasonable bill is appreciated by any consumer. In this context, application of a 'cost reflective' tariff is fair by the consumer and the utility. As a country on the whole, it is an important attempt to utilize the energy in the most cost effective manner. This would help the country facing the energy crisis, sustain the industries and employment, and enhance the power quality and reliability. The objective of this research is to investigate individual and collective demand profiles of bulk consumers, and to encourage them to implement demand management measures. This is done by introducing a better cost reflective tariff. Thereby, both the consumer and the utility would be benefited. Electronic digital meters, with remote meter reading facility, were introduced very recently. These meters provide detailed information about the consumer's demand profile and give an in-depth view of their electricity consumption. Studying these demand profiles show that there are many consumers with a poor power factor, consuming a large amount of reactive power from the system, transmitted all the way from the point of generation. This causes excessive burdens on the network for handling extra current and causing excessive power and energy losses. In this research, an effective sample of bulk consumers who consume a large amount of reactive power is considered. In order to encourage them to improve their power factor, it is suggested to introduce a charge for reactive power consumption (in Rs/kvarh). Considering a sample, the price of a unit of reactive energy is calculated based on, if the utility does the power factor correction and if the consumer does the correction. It will be shown that, it is more appropriate for the consumer to do the power factor correction on their own. This suggested charge is much reasonable to both the utility and the consumer. A charge for the consumption of reactive power would be cost reflective and would reward high power factor consumers by giving a lower maximum demand charge. Thereby, the consumers with a poor power factor are encouraged to improve their power factor. With this enhancement to the tariff, both the utility and the consumer will be benefited. The maximum demand charge is imposed to reduce the demand of system in general. However, it does not deal the issues of low power factor, in a cost reflective manner. It is also imposed, to compel the consumer to manage his demand-peaks as much as possible. Both these components contribute to the maximum demand charge. By removing the power factor contribution from the presently applied 'Maximum Demand' charge, the demand-peak component can be isolated. Thus, the new maximum demand charge would inevitably become a lesser charge. The demand-peak component is a burden to the utility during the system peak period. During the off peak period, these individual demand-peaks will not cause much difficulty to the utility to cope up with. Therefore, it should be applied on a time of day basis. It is reasonable to apply a lesser charge (as an incentive) during off-peak, and a higher charge during peak load time period. Thereby, the bulk consumers are encouraged to shift on to off peak time. This enhanced tariff structure would benefit both the consumer and the utility. The study concludes by suggesting a charge for the monthly reactive energy consumption, while recommending a reduction in the present maximum demand charge. Further, the bulk consumers are categorized into five types, based on their demand profile. These may be used in extending the study to design a maximum demand charge base on time of day.
item: Thesis-Full-text
Analysis of surface flash over of 33 kV insulator due to saline pollution
Janaka, NHC; Lucas, JR; Fernando, R
Ceylon Electricity Board (CEB) has the responsibility of Transmission, most of the Generation and Distribution of electric power in Sri Lanka. Contamination-driven insulator failure is a problem that incessantly plagues distribution systems. It erodes power quality and diminishes system reliability. Contamination levels can continue to grow unless abated by natural cleaning or if not taken measures to wash insulators at the distribution level in a preventative maintenance mode. When contamination is combined with moisture, a pollution layer forms and provides a path for leakage current to flow. Increases in contamination severity result in heightened levels of leakage current activity. As a result of rapid development and growth of populated areas, several high voltage power transmission systems operating at various voltages up to 132 kV have been put into service and flashover difficulties with insulators of these systems caused by pollution of different types have been experienced. Not only the transmission network but also the distribution network of 33kV, running in coastal belt, has experienced frequent insulator flashover making a burden to the maintenance Engineers. In order to assess the pollution behavior of insulators in the distribution network, 33kV pin type insulator was selected as a sample insulator and been subjected to natural pollution at three selected localities for considerable period. The naturally polluted , insulators have been subjected for conductivity test and by which the equivalent salt deposit density (ESDD) which points out the pollution severity is calculated. Subsequently, artificially contaminated insulators of different pollution severities were tested for power frequency and impulse test in the High Voltage Laboratory of University of Moratuwa. To better understand the progression of insulators from a healthy state to failure, the flashover voltage (FOV) of insulator must be studied. This study was focused on the following key areas.  Experiment of 33kV Pin Insulator contamination severity based on Zone categorization (Zone-I, 2 and 3) • Prediction of surface flashover voltage of Insulators over ESDD and tabulate the figures for reasonable ESDD values. • Streamline the process of Insulators treatment under preventive maintenance. • Review the levels of insulator's specific creepage distances placed at different pollution severity in Sri Lanka co-relating with IEC regulation. Experimented results state that insulator contamination level improves over the duration in ad hoc basis and could be utilized to build up a trend curve to predict a relationship against the insulator exposure duration. It is recommended that insulators in Zone 1 have to be treated after 8 months from the date of last treatment and those in Zone 2 & 3 to be treated after 18 months under preventive maintenance to get away from flashover. It is also recommended to review the required specific creepage distance of insulator installed in non-polluted areas due to the fact that the current practice of insulators placement in all over is with specific creepage distance of 25mm/kV which is recommended for high polluted zones as per IEC regulation
item: Thesis-Full-text
Analysis of transient overvoltage in medium voltage distribution network of Ceylon Electricity Board
Weerawardena, WAV; Lucas, JR; Banda, HMW
This thesis presents the analysis of transient overvoltages in medium voltage (33kV) network and the research is based on feeder lines in the Uva province. Parameters which influence lightning performance of overhead distribution lines such as line height, line length, type of structure, availability of shield wire and flash density in the area are discussed in details. More over, failures due to transient overvoltages and its impact on the reliability of the network are analyzed in this study. Lightning may cause flashovers from direct strokes or induced voltage from nearby strokes. Direct lightning to power distribution lines causes insulation flashovers in great majority of the cases. Therefore the goal of this research is to estimate the lightning performance level of feeder lines and investigate improvements. Shielding effect from nearby trees, critical flashover voltages for different flashover paths and deterioration of insulation with aging are also discussed. Thus the analysis of lightning related incidents such as transformer failures, arrester failures and nuisance fuse blows are presented. The study of transformer installation reveals that arrester lead length becomes critical during a lightning discharge since it generates high voltage stress in the winding which may fail the distribution transformer. Earth rod impulse resistance is also an important parameter which increases the voltage stress. It is necessary to develop models, using, electrical parameters for simulation of transient overvoltages. The PSCAD software is especially developed to study transient simulations of power systems. Variation of transient overvoltages due to strikes to phase wires, strikes to earth wire, and variation due to striking distance are discussed in this study. Further, simulation of surge arrester performance and nuisance fuse blows are also presented. Finally, the study presents applications to achieve zero lead length in substation, introduction of surge durable fuses and procedures which can be implemented to improve lightning performance in the MV network.
item: Thesis-Abstract
Analyzing economic benefit and performance of step - lap cores over conventional cores in distribution transformers
(2014-07-31) Gunawardhana, TCDA; Lucas, JR
The step-lap core manufacturing technique for distribution transformers can be considered as an emerging technology in the transformer industry in the Asian region, but a well practiced design in the European and other developed countries where transformer industry is updated with modern facilities with high tech machinery in their production lines. The LTL Transformers (Pvt.) Ltd., the sole manufacturer of distribution transformers in Sri Lanka has taken the initiative to purchase a modern core cutting line with the step-lap technology. This project focuses on studying the behavior of core joint and does a comparative evaluation of the performance and economics of conventional cores and step-lap cores in distribution transformers. In particular, the effects of core joints on core performance were studied. A Feasibility study was done on the LTL design cores. The Step-lap cores were manufactured using the available core cutting line and the performance data were compared with diet of conventional type cores. The study shows that the core loss in distribution transformers can be reduced by about 8% with the introduction of the step-lap core. The study concludes by showing that replacing the conventional core cutting line with modern high-tech machine for producing step-lap cores is viable with a payback period of 7 to 8 years.
item: Thesis-Abstract
Application of sensor network in locating moving trains for rail gate security system
(2016-05-20) Perera, WDSP; Lucas, JR; Femando, DGR
This research project is designed for rail gate security system for vehicles and pedestrian. Currently, the railway system of Sri Lanka does not have a correct system to monitor and indicate correct positions of trains. Therefore vehicle drivers and pedestrians imagine the location of trains and try to cross level crossings. Hence accidents happen at rail gates. A suitable security system should be arranged at rail gates. Hence this project is done to find the correct position of the train. The outcome of the research would provide a time indicator and a distance indicator are fixed at level crossings. The time indicator indicates time duration of trains approaching the level crossings and the distance indicator indicates the distance in between the train and the level crossing. This timely information to the people who try to cross level crossings on foot or by vehicles will be very useful to protect their lives. Also this will be a good source for Sri Lanka railway system to track trains and protect human beings. This project consists of three main subsystems such as 1. When a train passes a specified detection point, the time indicator counts down and the distance indicator indicates the distance in between the train and the level crossing. 2. When the train passes other specified detection points the time indicator and the distance indicator indicates time as zero. 3. When the train passes the level crossing rest the computer program.
item: Conference-Full-text
Automatic Governor for Tie-line Control : A Teaching Tool
(2015-08-03) de Silva, LUN; Deegala, DDMI; Karunathilake, IMM; Kumari, PHSSDI; Lucas, JR; de Silva, PSN
Power transmission between interconnected systems is a major concern in the present electrical engineering context and is of utmost importance to Electrical Engineering undergraduates. A voltage scaled power system simulator with two interconnected areas has been designed, for educational purposes, using vacuum circuit breakers, a diesel generator, a motor-generator set, transmission lines, bus bars, loads etc. Synchronization of two areas and a power controller of the tie line between the two areas have been implemented. In addition, students can learn about different interactions, such as synchronous and isochronous operation of generators with large systems. This paper finally discusses the possible experiences of interconnected power systems that undergraduate students could be exposed to.
item: Conference-Abstract
Automatic governor for Tie-line control : a teaching tool
De Silva, LUN; Deegala, DDMI; Karunathilake, IMM; kUMARI, PHSSDI; Lucas, JR
Power transmission between interconnected systems is a major concern in the present electrical engineering context and is of utmost importance to Electrical Engineering undergraduates. A voltage scaled power system simulator with two interconnected areas has been designed, for educational purposes, using vacuum circuit breakers, a diesel generator, a motor-generator set, transmission lines, bus bars, loads etc. Synchronization of two areas and a power controller of the tie line between the two areas have been implemented. In addition, students can learn about different interactions, such as synchronous and isochronous operation of generators with large systems. This paper finally discusses the possible experiences of interconnected power systems that undergraduate students could be exposed to.
item: Conference-Full-text
Capacitance and tan δ measuring equipment for high voltage insulation modelling and simulation modelling and simulation
(IEEE, 2016-05) Gamage, CM; Nupehewa, JM; Kodikara, KKCS; Chathuranga, SAD; Samarasinghe, R; Lucas, JR; Jayasekara, AGBP; Bandara, HMND; Amarasinghe, YWR
Capacitance and tan δ measurements are usually carried out to check the healthiness of an insulation. Measuring equipment based on different methodologies to test insulation in cables, transformer bushings etc. are available. This paper presents the development of such a measuring equipment for a high voltage (HV) laboratory of a University. The design is divided into three parts as filter unit, test unit, and the measuring unit. These units are separately modeled and simulated using software (MATLAB and PSpice). Filter unit and the test unit are combined to analyze the results through simulation. Simulation results are used to improve the design.
item: Thesis-Abstract
Clearance to buildings from overhead transmission lines
Kodithuwakku, KS; Lucas, JR; Wijayapala, WDAS
Withthe increasing demand for electricity supply and the country development, Searching of Transmission Line corridor across populated areas is a major difficulty faced by the utility company. Further, most of the funding agents are very much concerned bout the environmental impacts due to the constructions. The width of Transmission Line corridor is proposed for two different Transmission Voltagesand the sharing of single corridor for more lines and the required widths are proposed. Possibility of building construction and planting of trees within the Transmission Line corridor is decided and the maximum heights for constructions are also proposed.
item: Conference-Full-text
Coconut oil as an alternative to transformer oil
(2001) Abeysundara, DC; Weerakoon, C; Lucas, JR; Gunatunga, KAI; Obadage, KC
The paper presents a study which has been carried out to use coconut oil as insulation in transformers. Among the important properties considered are the dielectric strength of coconut oil which corresponds to less than 20 kV for a 2.5 mm sphere gap and the pour point which is approximately 23°C. To retain the oil in liquid form at low temperatures, several pour point depressants were tried. Some of them depressed the pour point, but also lowered the dielectric strength and proved unsatisfactory. In order to have improved properties, a purified form of coconut oil was used in the investigation. In this, the free fatty acids have been neutralized (reduced to 0.02%). Deodorization by steam distillation at 200°C has removed odorizing and tasting compounds of lower boiling points. The moisture has been reduced by heating to over 100°C. The demoisturized coconut oil sample showed promising results. The dielectric strength improved to 60kV or even higher dependant on the moisture reduction of the sample. Since the distribution transformer tank (manufactured by Lanka Transformers Ltd) is a sealed container and oil is filled inside a vacuum chamber, moisture inclusion after manufacture is prevented. As an alternative to reducing the pour point, repeated experiments on the dielectric strength of solidified and partially solidified coconut oil samples were carried out, and it was found that solidification does not appear to have any adverse effect on the dielectric strength. Coconut oil solidifies without creating voids, keeping its dielectric strength unreduced. When exposed to heavy magnetic fields, oil with a higher unsaturated degree of fats may break but coconut oil having a very low degree of unsaturated fats, ensures consistent properties at heavy magnetic fields essential for insulating oils.
item: Thesis-Full-text
Condition monitoring and assessment of power transformers using sweep frequency response analysis and dissolve gas analysis.
Fernando, MPM; Lucas, JR; Rodrigo, WDAS
Power transformer can be considered as the key element in an electricity power system. Cost and the time of installation of a power transformer are significantly higher than the installation of other equipment. Applied electrical and thermal stresses due to various factors always deteriorate the condition of transformers. In this sense, it is important to monitor and assess the condition of Power Transformers to ensure longer operation as well as to maintain a reliable operation of a power system. Sweep Frequency Response Analysis (SFRA) can be used to assess the mechanical integrity of transformers. The test measures the transfer function response of the active part of the transformer. The three frequency responses of three phases should be identical except to inherited variations, and therefore, it can be considered as a fingerprint for a transformer. If any physical changes occur within and between the elements of the transformer, it will affect the frequency response, which can be used to detect any abnormality. However, correct interpretation of the measured response in determining the transformer condition is a critical challenge, as interpretation of frequency response is still not fully established. On the other hand, Dissolve Gas Analysis (DGA) can be used to assess the possible stresses that could have been applied on the oil immersed transformers based on the concentration of specific gases dissolved in oil. Several diagnosis tools recommended by international standards are available and they have been using by utilities over a period of time with reasonable reliability. In this study, SFRA and DGA measurement data were collected from set of power transformers in operation, and analyzed those approaching to develop a methodology to assess the condition of power transformers, correlating outcomes from SFRA and DGA. For this, transformers taken for the study were categorized based on their SFRA data by analyzing behavior of the response of the three phases and their Page | iv similarity. Several indices were introduced to quantify the similarity. In the other hand, the selected transformers were categorized based on their DGA data considering the recommendations provided by available standards and diagnosis tools. Further, a Computing Tool was developed using MATLAB, for the easy evaluation of the SFRA and DGA measurements. Finally, several case studies were carried out justifying the proposed methodology verifying the benchmarking of the introduced indices against several faulty and good transformers.
item: Thesis-Abstract
Condition monitoring of power transformers using frequency response analysis
Tilakeratne, RP; Lucas, JR; Perera, KBMI
Power transformers are the most expensive and important equipment of a high voltage power system. Therefore it is essential to have a suitable and effective condition monitoring system to assess the conditions of power transformers well in advance to maintain the reliability of the power system by averting unexpected expensive failures. Conventional condition .monitoring techniques do not conclusively indicate mechanical conditions of the transformer such as winding movement, loss ·of clamping pressure, disc movements etc. which can take place during handling and transport, short circuit forces, faults in the power system network near the transformer or a high voltage stress which affects inductance or capacitance. This project thesis deals with Frequency Response' Analysis technique for condition monitoring of power transformers, which is suitable for detecting the deformation of transformer windings. A mathematical model for obtaining frequency response characteristics has been developed for 'a typical transformer, and the effect of variation of parameters on frequency response has been examined. Case studies based on frequency response tests on typical 31.5 MVA, 132/33 kV grid transformers have been presented. Case studies reveal that any mechanical deformation in the transformer winding is clearly reflected in the frequency response characteristics. The frequency response characteristics obtained in the field for different aged power transformers are found to be somewhat similar in nature to those obtained analytically using ladder network equivalent circuit.
item: Conference-Abstract
Condition monitoring system for outdoor insulators
(2018-05) Karunarathna, IMAM; Karunathilaka, KTL; Wanasinghe, WMHM; Sampath, GKL; Lucas, JR; Samarasinghe, R; Narayana, M; Chathuranga, D
High Voltage insulators are vital components in transmission and distribution systems in a power network. Most of the insulators are used in open air applications where they are subjected to different environment conditions. Exposure to these different weather conditions and contaminations determine their performance as insulators. Condition monitoring ot power line insulators is an important requirement for asset management engineers in a power network in order to maintain a healthy power system. There are several techniques that have been introduced to fulfil this requirement. One ot the techniques ot measuring surface leakage current is introduced here. This paper highlights the concepts of measuring surface leakage current for insulators under contaminated conditions. Results show that the surface leakage current is closely related to the insulator condition.
item: Conference-Full-text
Condition monitoring system for outdoor insulators
(Institute of Electrical and Electronics Engineers, Inc., 2018-09) Karunarathna, IMAM; Karunathilaka, KLT; Wanasinghe, WMHM; Sampath, GKL; Lucas, JR; Samarasinghe, R; Samarasinghe, R; Abeygunawardana, R
High Voltage insulators are vital components in transmission and distribution systems in a power network. Most of the insulators are used in open air applications where they are subjected to different environmental conditions. Exposure to these different weather conditions and contaminations determine their performance as insulators. Condition monitoring of power line insulators is an important requirement for asset management and engineers in a power network in order to maintain a healthy power system. There are several techniques that have been introduced to fulfill this requirement. One of the techniques of measuring surface leakage current is introduced here. In this paper, rainy weather conditions are simulated in an artificial rain making chamber and the performance of insulators are examined at different contamination levels. This paper highlights the concepts of measuring surface leakage current for insulators under contaminated conditions. Results show that the surface leakage current is closely related to the insulator condition.
item: Thesis-Full-text
Coordination and Selection of MV and LV Fuses for Distribution Transfprmer Protection
(2015-02-22) Sandasiri, DDKG; Lucas, JR
The Ceylon Electricity Board (CEB) has the responsibility of distributing electricity to the consumers in Sri Lanka except few areas which belong to the Lanka Electric Company (LECO). When considering about the distribution network, distribution transformers play the major role. Protection of transformers is therefore very much important. Transformer failure rate and the distribution network reliability are major concerns of the CEB. Distribution transformer failure rate is high in theCEB network and also the fuse usage is unacceptably high. Present CEB fuse selection practice and practical situation at the field have been analyzed to find out better solution for above problems. Theory behind distribution transformer fuse selection has been discussed in detail. K type expulsion fuses are the recommended primary side fuses by the CEB. The study has proposed several changes to the existing fuse selection practice recommended by the CEB. The present distribution transformer protection scheme do not provide over load protection. It has been identified that nearly 13% transformers had failed annually due to over load within the Southern Province. The study revealed that lower capacity of transformers such as 100kVA and 160kVA have the higher probability of getting overloaded. Furthermore, 15% of distribution transformers installed in the Southern Province have at least one phase overloaded. A Primary side K type fuse does not provide overload protection to the distribution transformer. Hence, secondary side fuse should provide the over load protection but above findings tell that the expected task cannot be achieved by the present system. The study has proposed three options to solve this problem. Introduction of a primary fuse which is having special Time Current Characteristic (TCC) curve is the first option. The fuse type is called “SloFast” and it has a duel TCC curve.The SloFast fuse TCC curve behaves very much parallel to the transformer damage curve at some low level of current unlike K type fuse TCC curve, which intersects transformer damage curve at some low level of current. The second option is adding a main secondary fuse in between the transformer secondary terminal and the feeder fusses. So that the feeder fuse does the overload protection of the feeder conductor and the main secondary fuse does the overload protection of distribution transformer. The third option is limitation of the number of outgoing feeders from a transformer. This is very important for the distribution transformers having low capacities such as 100kVA and 160kVA, because the probability of getting overloaded is high with the present feeder arrangement. It is recommended the maximum number of feeders for each distribution transformer capacity
item: Conference-Abstract
Cost effective battery storage for intermittency of solar
Nayanathara, PMD; Perera, HS; Abeyrathne, RAHMPNN; Lucas, JR
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-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
A dc link for the power system simulator
(Electrical Engineering Society (EESoc) of Department of Electrical Engineering, University of Moratuwa, 2015-12) Abeyrathne, PM; Abeysinghe, AMGT; Karunanayake, IM; Ranasinghe, PMH; Dias, MP; Lucas, JR; Jayasekara, AGBP
High Voltage Direct Current (HVDC) links are used for bulk power transmission due to its advantages over the alternating current (ac) transmission. A HVDC link between India and Sri Lanka has also being proposed. Hence it is a timely needfor the students in local universitiesto be able to study the behaviour of HVDC transmission. This paper presents the design of a DC link for a locally assembled Power System Simulator as a teaching tool.The objective is to use this design as a learning tool to study the behaviour of HVDC transmission under normal and abnormal operation. It is expected to be used for laboratory experiments related to HVDC transmission and Power Electronics, hence providing the opportunity for visualization of the behaviour of performance parameters at the significant points of the model.
item: Thesis-Full-text
Design of the power feeding system for electrified railways case study: Panadura -Veyangoda railway sector
Thotagamuwage, S; Widanagama Arachchige, LN; Siyambalapitiya, T; Lucas, JR
In railway systems, electrical traction is more efficient, comfortable and more economical than diesel traction. Since the railway transportation is a major public transportation means in Sri Lanka, having an efficient and reliable electrified railway transportation system will increase the capacity of railway transportation and attract more passengers daily receiving the service. This research is based on the proposed Panadura – Veyangoda railway electrification project. It is of vital importance to identify the required maximum power of the predicted system at the peak hours prior to designing the traction system. MATLAB Simulink software has been applied for the modelling the speed, power and distance of the train movement between stations with respect to time. Using the simulation results obtained from MATLAB Simulink model, a load flow study for the total train movements between Panadura station to Veyangoda station at peak hour is carried out in DIgSILENT Power Factory software to obtain the maximum power required for each traction substation. Finally, the traction substation components are sized and layout of the system and earth grid arrangement is presented for Ratmalana traction substation as a case in point. This software models can be applied for any other railway electrification systems to be predicted by modifying and changing their parameters accordingly.
item: Thesis-Full-text
Determination of earth resistivity profile in mul ti layer soil
Dhrmadasa, IT; Lucas, JR
Soil structure investigation is very important in many Engineering applications. The Electrical Engineers extensively use the soil structure information when designing grounding systems. The sub soil structure with its resistivity distribution has a direct impact on the performance of the grounding system, that is, the electrode resistance and the surface voltage distribution. In Applied Geophysics a variety of soil structure investigation methods are used. Among these, the Electrical Resistivity Method has become very popular due to its simplicity. The resistivity method measures apparent resistivity of the ground to a direct current flow. The field data contain apparent resistivity values and geometry information. When the field data is interpreted, it detects the discontinuity of resistivity distribution in a location of interest. This interpretation can be done One dimensionally( lD), Two-dimensionally (2D) or Three-dimensionally (3D) depending on the application's necessity. The interpretation of resistivity field data using inversion techniques may be ambiguous. Conventional ID DC resistivity inversion techniques include graphical methods requiring interpolation and judgment and computer based iterative calculation methods. The work presented in this thesis, investigates a new resistivity data inversion tool, Neural networks(NNs). Neural Networks are capable of solving several types of problems, including parameter estimation, parameter prediction, pattern recognition, classification and optimization. Also recently the use of Neural Networks in the Geophysics parameter estimation problems has Shown strong results. With this recent trend in the applicability of the NN's for the non linear geophysical inversion problems NN's is proposed as the inversion tool for parameter estimation or Sub surface interpretation. The main intention of this study is to investigate the applicability of NNs as a fast and accurate inversion tool for field resistivity data. The study considers the approach and capabilities of the NNs in inversion of field resistivity data to interpret ID, 2D or 3D sub soil Structure with resistivity discontinuities.