Browsing by Author "Perera, HYR"

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item: Conference-Abstract
Acoustic profiling and non linear acoustics finite element modeling of Sugathadasa Indoor Stadium
(2019) Wijesiriwardana, R; Perera, HYR
Acoustic performance of an arena is measured and classified by it’s acoustic parameters. The acoustic parameters are used for the designing of the sound systems and improving the arena’s acoustic performance by proper sound proofing. According to international standards DIN EN 18041, sports arena comes under type A5 and can be changed into type A4/A3/A2 education and communication/presentation halls or type A1 musical halls. During our profiling work some of critical acoustic parameters of Sugathadasa indoor stadium were measured and estimated according to the ISO EN 3382 standard. The primary measurement parameters, reverberation time (RT60dB), center time (TS), early energy fraction (D50) and objective clarity (C80) were measured and then are used for identifying and classifying the arena. The arenas also need to satisfy the noise criteria (NC) standards depending on the event that the arenas are used for and also considering the surrounding environment. Generally, the arenas are changed temporarily depending on an event by increasing the acoustic absorption area and various other sound proofing methods. This paper contains acoustic profile, reverberation time, center time, early energy fraction, noise criteria, the sound clarity index measurements of the Sugathadasa indoor arena. Moreover, the acoustic space of the arena was modelled with nonlinear FEA methods taking the Khokhlov-Zabolotskaya-Kuznetsov (KZK) nonlinear wave equation and Timothy Walsh (TW) numerical formulation of the KZK model. Nonlinear acoustic wave equation was used considering the lager acoustic space of the arena and complex structural, geometrical and surface elements of the arena such as steel trusses, columns, beams, diffusers, absorbers, resonators and reflectors. Moreover, to find the best locations for the speaker arrays the acoustic parameters were estimated by exciting the acoustic space with sound sources at selected locations. The locations were selected by using the simulated result of acoustic ray tracing based FE modelling. By using these results best locations for the arena speaker system was determined. In addition to find out the acoustic frequency response of the current sound system, the arena was excited with white noise, pink noise and brown noise audio signals and then the responses were measured by using microphones placed at selected locations
item: Thesis-Abstract
Alternative power supply options for safe shutdown of Lakvijaya power plant in a total blackout
(2015-02-08) Priyantha, GWV; Perera, HYR
Lakvijaya Power station with a capacity of 300MW is designed to deliver generated power to national grid initially over Veyangoda transmission lines. But there is no other auxiliary power supply from the grid. In addition to above lines, there is no other auxiliary power supply from the grid. Since commissioning of the plant, two incidents have taken place showing the inadequacy of the existing arrangement. At 12.15 hours on 7th June 2011, the Plant had been in operation at 260MW & 181MVar and Veyangoda line 1 and 2 tripped from Veyangoda end which resulted in an Island wide blackout. Lakvijaya machine tripped without stabilizing at the house load. Consequently the plant was without an electricity supply. At the same time Standby diesel generator of 800 kVA failed to start. Further, Plant DC supply failed causing an unsafe shutdown resulting damages and lifetime reductions to the plant and its subsystems such as rupturing of the diaphragm in LP turbine, drop in drum water level below tripping limit, rising condenser hot well level closer to the tripping limit, rising condenser vacuum pressure up to tripping limit, rising condenser steam temperature to a level which effect to condenser tubes and damaging of bearing due to pressure dropped in jacking oil pressure etc. A similar failure took place on 08th August 2012. This study is carried out to investigate the different options available to improve power supply situation eliminating such incidents in future. Initially all subsystems of the plant had been thoroughly analyzed and identified all possible bad consequences on the subsystems due to improper shutdown. A time analysis was done to find out the time taken by each subsystem to reach its tripping limits or withstanding time of subsystem before component failure during such an improper shutdown process. After collecting data from the site, detailed power system analysis including load flow studies were conducted using the ‘Power World Simulator’ software package considering possible unit auxiliary standby power supply options available during blackout condition. In that analysis below mentioned seven possible options were identified and studied. i) from Kothmale power plant, ii) from Kelanitissa Fiat gas turbine power plant, iii) from Kelanitissa combine cycle power plant, iv) from Kerawalapitiya combine cycle power plant, v) from Heladanavi diesel plant at Puttalam through 220kV line , vi) from Heladanavi diesel plant at Puttalam through 33kV line, vii) from 6×2.5MW diesel plants at Lakvijaya power station . Finally it was identified and concluded that 6 of 2.5MW standby synchronized diesel generators with 15sec restoration time should be installed.
item: Thesis-Full-text
Assesment of rooftop solar netmetering concept : consumer and utilty point of view
Nalani, JGS; Perera, HYR; Rodrigo, A
Global energy needs continue to grow, whilst fossil fuels still outstrip renewable energy in terms of supportive policies and subsidies. With growing concern towards climate change, many countries across the world are rethinking their energy strategy and incorporation alternative methods of energy generation. Of all the different modes of renewable energy technologies, Solar PV technology has caught the most attention. With environmental concerns and energy needs increasing, the world is promoting renewable energy technologies. Today, the PV systems price is decreasing, which gives it a competitive edge. The aim of this study is to research the viability of rooftop solar PV systems under certain circumstances. The study performs a cost beneficial analysis for the lifetime of the solar PV system making use of economic analysis on residential consumer perspectives and avoided cost analysis on utility point of view. The research concluded with several findings. Basically it concluded that the investment on Roof Top Solar is worthwhile when monthly consumption exceed 200 kWhs. Therefore, according to the present tariff structure and cost of solar PV Systems, Net Metering is not economical for monthly average consumption below 150 units. In utility point of view, it has been found that the reduction of avoided cost is rapidly increasing. But the rate at which the reduction of avoid cost increasing is decreasing and it becomes constant after 20 years. rooftop solar electricity generation cannot replace any marginal plant during the period of study concerned. There is no detailed study has been conducted in Sri Lanka in this particular area of study. The outcome of the research provides important and useful information for consumers, electricity utilities as well as the policy makers in energy sector.
item: Conference-Full-text
Assessment of cost of unserved energy for Sri Lankan commercial sector
(IEEE, 2018-05) Colambage, DP; Perera, HYR; Chathuranga, D
The investments for the improvements of power system to fulfill the energy requirements of electricity customers need to meet the reliability improvement targets. Thus, it is essential to obtain a clear and accurate assessment of Cost of Unserved Energy as an input to the power system planning process. Sri Lanka is currently using an approximated value of Cost of Unserved Energy calculated in 2002 considering only the Industrial Sector. It is important to update this value. This research was conducted to assess the Cost of Unserved Energy based on consumer survey method. The survey and analysis parts are conducted in three separate categories as Industrial, Commercial and Residential. This paper presents the results for Commercial sector, separately for momentary, planned and unplanned non-momentary interruptions. It is expected that the results of this study helps the power sector to provide a better service, taking the views of the customers and the national importance of electricity as an esential input for economic growth.
item: SRC-Report
Assessment of cost of unserved energy for Sri Lankan commercial sector
(2018) Perera, HYR; Colambage, D. Punsara
The investments for the improvements of power system to fulfill the energy requirements of electricity customers need to meet the reliability improvement targets. Thus, it is essential to obtain a clear and accurate assessment of Cost of Unserved Energy as an input to the power system planning process. Sri Lanka is currently using an approximated value of Cost of Unservcd Energy calculated in 2002 considering only the Industrial Sector. It is important to update this value. This research was conducted to assess the Cost of Unservcd Energy based on consumer survey method. The survey and analysis parts arc conducted in three separate categories as Industrial, Commercial and Residential. This paper presents the results for Commercial sector, separately for momentary, planned and unplanned non-momentary interruptions. It is expected that the results of this study helps the power sector to provide a better service, taking the views of the customers and the national importance of electricity as an esential input for economic growth.
item: Thesis-Abstract
Assessment of efficiency and condition based optimum loading of transmission lines
Chandrakumara, WDAJ; Perera, HYR; Fernando, LAS
Transmission lines in any transmission network is the critical part or the one of the major limiting factors for power transfer capability of the transmission network. The thermal power transfer capability of Overhead Transmission lines is primarily a function of the height of the conductor above the ground. This height affects the safety of the public and is therefore clearly specified in legislation. Different methods for determination of Power Transfer capability of transmission lines are available. These include deterministic and various probabilistic approaches. The latter include a model simulating condition that affect the safety of the transmission line relating specially to the conductor position from which a measure of safety is developed. This measure can be used by designers to optimally design the transmission line from current loading point of view. The deterministic approach has been used by most utilities around the world, as it is quick and simple. That method assumes bad cooling conditions that will result in the line design temperature being achieved. Probabilistic methods use actual weather data and conditions prevailing on the line to determine the likelihood or probability of a certain condition. In this project, condition was taken as the conductor temperature rising up to the design temperature, which is 75 degree Celsius. Designing of transmission lines in Sri Lanka has been done considering average weather conditions through out the year. Whereas in the real situation, weather conditions are seasonally varying. Therefore, based on the seasonal variation of weather condition in Sri Lanka, existing transmission network can be optimally loaded delaying future construction of transmission lines
item: Thesis-Abstract
Benchmark the Sri Lankan power system by Power quality monitoring and Analysis
Shanthi, KPK; Perera, HYR
The increased requirements on supervision, control, and performance in modern power systems make power quality monitoring a common practise for utilities. To get the present status of the power quality in the network is so vital as these data are necessary to benchmark the system. Though utilities around the world have done this type of surveys for their system, the similar monitoring project has not been done for the CEB network. Aim of the work presented in this thesis is the benchmark the Sri Lankan Power system by selecting most suitable sites distributed in all over the island. This part would be much important as the selection should be made represent the entire network. This thesis report firstly introduces the reader to the available standards of power quality, comparisons and how they are applied to monitor the Sri Lankan power network. The objectives of the analysis include the identification of the event origin, the accurate description of the power quality indices in a compact way and the interpretation of all phenomena related to the event However, the actual power quality database must be maintained with data in standard formats for comparisons, analysis, and reports. As standards bodies define performance indices for power quality, utilities may want to benchmark system performance using these indices so that they can offer differentiated services for customers that have special requirements. After careful analysis of the results obtained from each site it was found that the quality of the power at each location was quite satisfactory, with the exception of flicker and voltage dips which addressed the cases separately. The application of the standard, EN 50160, to our system is widely discussed as it is the first "electricity as a product" standard in the world. Voltage dips are common events on the electric power network. They can affect a wide range of electrical equipment and are of particular concern to industrial applications. The survey duration must be sufficient to include the full range of all the factors that affect sag incidence and it is therefore accepted that a minimum period for acceptable results is one year [3]. Though one year monitoring for a site is not practically possible with this project, the short term results were also produced and discussed for future projects about exercising suitable dip reporting methods. As the background activities certain cases related to the network reactive power switching are also discussed and remedial actions are also proposed.
item: Thesis-Abstract
Centralized high frequency supply system for lighting systems
Ranjith, HDA; Perera, HYR
The cost of power generation is continuously increasing everywhere in the world. In Sri Lankan context this has an added effect as the low cost hydropower resources have been exhausted while the demand is continuously increasing at a rate of around 8%. however this effect can be diluted to some extent if proper Demand Side Management options arc utilized. One such option commonly and effectively used is the replacement of incandescent lamps through fluorescent lamps. For industrial and commercial lighting. the standard linear fluorescent tubes give the best efficacy at low cost. However for domestic applications and also for some commercial applications linear fluorescent tubes arc not aesthetically pleasing and thus compact fluorescent lamps arc widely used for such applications.
item: Thesis-Abstract
Development of a software package for calculating current rating of medium voltage power cables
Wijeratna, DGAK; Perera, HYR; Lucas, JR; Peiris, JHC
CableAmp, a Windows based software has been developed to calculate the cable ampacity of medium voltage power cables laid in free air or directly buried in the ground. The highly graphical user interface allows easy usage. The user inputs the required data of the cable design as well as the cable installation method. CableAmp then calculates the continuous current rating (at 100% load factor) of the power cables laid in free air or directly buried in the ground. It is applicable to extruded solid insulation, rated from 6 kV to 33 kV. An increased peak current rating, called the cyclic current rating, can also be obtained from the software package for a specified load profile. The calculation procedure is in accordance with International Standard IliC 287. The report presents the theory for the software, and also validates the results obtained b> the software by comparison with manufacturers current ratings for standard cables.ystem
item: Thesis-Full-text
Economics of reaching year 2015 non-conventional renewable electricity generation target
Indatissa, AS; Perera, HYR
As per 2008 National Energy Policy, it is envisaged to reach I 0% of electricity energ) generation by end of year 2015 from Non-Conventional Renevvable Electricity (NCRE) generation sources. As per generation data, NCRE projects have generated around 525 GWh of electric energy during 2009. To reach this envisaged amount by end of year 2015, total annual NCRE contribution has to be increased to 1700 GWh as per year 2005 and 2008 Long-Term Generation Expansion Plan (L TGEP) demand predictionsTo encourage more private investments on NCRE resources for grid connected power generation, Sustainable Energy Authority (SEA) has introduced cost based and source specific tariff system. However. \\hen implementing this new tarifT structure. SEA has to subsidize this ne\\ tariff system since its tariff is higher than present CEB avoided cost tariff especially during initial years of operation. In this study. present CEB avoided cost calculation methodology has been reviewed to reflect more realistic avoided cost as per Small Power Purchase Agreement (SPPA) guidelines. With proposed modifications to the present methodology of avoided cost calculation, avoided cost of CEB has been forecasted for until year 2020 based on data available in L TGEPs. Also based on the identified potential NCRE sources. tariJT commitments of SEA has been calculated under constant terms for each year when reaching year 2015 NCRE generation endeavor. Here. analysis has been done under differentscenarios to analyze the return on overall investment with varying fossil fuel prices. Net rc\enue of SF/\ \\ill largely depend on fuel prices. plants implementation and retiring schedules as well as combination of NCRE power plants in operation. As per the considered scenarios, to breakcven the NCRE tariff investment. average crude oil pricesshould at least reach I 00- 120 US $ per barrel.
item: Thesis-Abstract
Effect of humidity on partial discharges of generator stator
(2015-02-22) Tirimanna, TDAS; Perera, HYR
It was observed that the insulation condition of some generators is not up to the standard level when analyze the results of condition monitoring tests done on hydro generators of CEB. This situation prompted generator insulation level to be monitored closely. Hence, the Asset Management Hydro Electrical Branch of CEB recently initiated online monitoring of partial discharge (PD) activity in hydro machines. Partial discharge can cause progressive deterioration of insulation and end result of which may be eventual breakdown of the insulation. If partial discharges can be controlled to a certain level, possibility of unexpected winding failures can be reduced and loss of outages and repair cost can be avoided and the reliability level of the generators can be increased. Majority of main hydro power generators of Sri Lanka have been constructed in wet zone with water present lower close below the generator. Therefore these factors can give rise to higher humidity levels around such generators. The purpose of this research was to investigate the effect of humidity on partial discharge in hydro generators. For this study New Laxapana Unit 2 generator was selected and a partial discharge monitoring system was installed for online monitoring facilities. Using the data extracted from this system, behavior of PD variations against relative humidity was analyzed. In addition to that using an experimental setup PD activity was measured under controlled humidity conditions. Both these analyses confirmed that there is an effect of humidity on PD activity. Keywords: partial discharge, epoxy, mica
item: Thesis-Full-text
Effective fault isolation methods to improve 33kV network reliability
Weeratunga, SMMS; Perera, HYR
Improving reliability in power system is very important to the utilities as well as to the country as it is an important attribute of the supply quality and increases the end user satisfaction. The aim of this study is to investigate the fault identification and isolation techniques to improve reliability. This study focuses on the following; 1. Reliability status of 33kV network of C.E.B. 2. Type of faults in 33kV network and outage reduction methods. 3. Develop a mathematical model for reliability evaluation. 4. Analyze protection scheme of C.E.B 33kV network. 5. Design new protection scheme to reduce outages. The analyzed reliability indices of C.E.B are far below compared to internationally Accepted levels. In this study reliability status of 33kV network is analyzed using event log data of reclosers and breakdown reports of Consumer Service Centers. The author is working atRegion-04, C.E.B and two switching gantries of Region-04 are selected to analyze events one in wet zone and other in coastal zone. It can be seen that outage time and fault frequency are high during both monsoon periods,86% of faults are tine to earth, 67% of faults are of transient nature and the repair time in case of overcurrent fault is high due to poor workmanship in line connections. With this study predominant causes of faults in the network can be identified by using event log of recloser. The several methods for outage reduction are identified, installation of fault indicators for remote indication and remote operation of reclosers, using line sectionalize devices. The protection scheme of 33kV network is analyzed to find techniques to reduce outages. The downstream protective devices (fuse on Spurs) beyond the recloser do not distinguish permanent and transient faults. It can be seen nuisance fuse blowing in spurs as well as nuisance recloser lockout affecting all customers in feeder. A new protection scheme is designed to overcome the above problems. The developed method isolates unhealthy spurs from healthy sections, improves reliability and reduces maintenance cost and extent of unserved energy.
item: Thesis-Abstract
Feasibility study on cogeneration from diesel engine power plants in Sri Lanka
(2015-06-26) Jayawardana, MP; Perera, HYR
Sri Lankan power system heavily depends on thermal oil plants and 58% of the annual energy demand is generated by such power plants as at year 2012. The installed capacity of diesel plants in Sri Lanaka is 540 MW. By 2012, all of them operated in open cycle. Exhaust gas temperatures ranging from 300-400 °C emit to the environment without contributing to much of useful work. With the increase of fossil fuel prices, generation costs have increased significantly. Government is subsidizing the electricity to make electricity affordable to the general public. This results in substantial financial losses to Ceylon Electricity Board. Exhaust gas can be directed through a heat recovery steam generator, which is able to produce super-heated steam. This superheated steam can be utilized to run a steam turbine in accordance as an application of Rankine Cycle. In this study, cogeneration potential of 100 MW “Heladhanavi” diesel engine power plant is considered. Furthermore, technical, environmental and economic feasibility is evaluated. There is a potential of 4MW power generation through cogeneration. The heat recovery reduces exhaust gas temperature to 230 °C. Dispersion of flue gas is analyzed with the aid of USEPA Dispersion model and Pasquily Stability Criteria. The existing stack height is sufficient according to dispersion model results. The power generated from recovered heat is able to save six million fuel liters per year and reduce CO2 emission amounting to 21,000 metric tons per year. Extending the same methodology for all remaining diesel engine power plants operating in the country, it has been estimated that an overall capacity addition of around 19MW can be achieved through cogeneration. Project Internal Rate of return has estimated and to be 21.6% at current tariff published by PUCSL, but there are several risks associated with the investment. Main issues to the investors are, remaining periods of power purchase agreements, which are not long enough and the reducing plant factors due to coal plant additions. Therefore, regulatory bodies should identify the potential cogeneration and they should encourage investments.
item: Thesis-Abstract
Impact of embedded genaration on 33 KV distribution system voltage
Chandraratne, PSS; Perera, HYR
Recently introduced schemes of Embedded Generation on the radial distribution lines have several remarkable advantages though· they produce some of the technical problems on the network. One of the major problems encountered is the variation of steady state voltage during the switching on/off operation of the Embedded Generators. The consumers connected on the line are subjected to larger variations during such operations. This research focuses on the study of the steady state voltage variation patterns and proposes solutions to mitigate the problem. The utilities impose several standards and require meeting specifications in connecting generators on the distribution network. Focusing on the effects on the locally connected COnStHl1erSto the network, both domestic and industrial, they are subjected to most of the prevailing technical problems arisen out of connecting Generators on the lines. Mainly, the problem of steady state voltage variations experienced by the consumer and finding ways of mitigating the same is discussed in this research paper. Data collection, application of load flow theories, modelling in SynerGEE software, analysis, application of mitigate measures on the model and the conclusion of the outcome of the research work are presented. A statistical way of approach is used to obtain the percentage of consumers affected in the case studies undertaken during the study. Recommendations are made that lead to mitigation of the problem concerned.
item: Thesis-Full-text
Impact of new generation conductors on techno economics of 132Kv transmission lines
Rajapaksha, RCP; Perera, HYR; Wijayapala, WDAS
Demand for the electric power has been increasing rapidly due to human activities all over the world. It is essential to generate, transmit and distribute the power requirement to load centers as they demand. Therefore, Capacity of transmission network needs to be increased frequently either by uprating, upgrading of existing transmission lines or/and adding of transmission lines to the transmission network. It is getting harder and harder to find routes for transmission lines due to increased social objection cause due to their uncountable social impact and environmental damage during the construction which cannot be totally compensated. Therefore, requirement of delivering more power to the load centers through overhead conductors has come to a discussion and large variety of new generation conductors (HTLS - High Temperature Low Sag Conductors and LL-Low Loss conductors) are introduced with the intention of mitigating some of the disadvantages shown by the conventional conductors and to uprate and upgrade the existing transmission lines. Among them, enhanced power capacity, low loss performance, improved conductor sag behavior and anti-cohesiveness behaviors can be considered vital. However, it can be observed that, conventional conductors are still used more frequently for new transmission lines by power utilities around the world due to lack of service experience in use of new generation conductors over conventional conductors that have been given a greater service in power transmission. Therefore, impact of new generation conductors for on techno economics of 132kV double circuit transmission lines is studied by designing and modelling of transmission lines for different ground terrains with different types of new generation conductors over conventional conductor. Accordingly, new generation conductors show promising results in overall techno economic viability of transmission line over conventional conductors, and among them low loss conductors show superior performance.
item: Thesis-Abstract
Implementation of fiber optic communication in CEB transmission network
Fernando, WMKDS; Perera, HYR
used in Ceylon Electricity Board (CEB) to optical fiber communication to serve the increasing communication requirements (voice & data) with power system expansion in progress.// As a first step, CEB has added one Optical Fiber Ground Wire (OPGW) with twenty four optical fibers to all new lines constructed after year 2000. It was identified that the incorporation of optical fibers to selected lines linking generation stations and grid substations to System Control Centre (SCC) can make the backbone optical fiber communication network.// Thirty numbers of transmission lines of total length 562.1 km can link all important generation stations and grid substations to SCC of CEB and those lines were selected to incorporate optical fibers for stage I communication network of this study.// Optical fibers manufactured to different standards are available in the market. It was found that the optical fibers manufactured to the standard ITU-T-G.652 is the best for the stage I communication network.// The replacement of one shielding wire by OPGW is the best method to incorporate optical fibers to CEB transmission lines, out of the different methods used in the world to incorporate optical fibers to overhead lines. It is beneficial for CEB to select a single OPGW type to replace all types of ground shielding wires in transmission lines selected for stage I communication network. OPGW types available in the market with overall diameter 11.80 mm, ultimate tensile strength 68.0 KN and tube (to enclose the fibers) made of stainless steel with aluminum clad was selected as the best suited OPGW for this purpose.// Practical problems and cost associated with power outages proved that the live-line stringing is more economical for the lines selected for stagel. Supply and live-line installation cost of OPGW for stage I is 7,796 USD/km (805,716 LKR km, as per the present exchange rate) and it is 15.6 % higher than the supply and dead-line installation cost of the same. Further, it was found that the addition of one OPGW mentioned above to new 132 kV double circuit Zebra lines is only 3.2 % of the total construction cost of the line. Therefore, adding one OPGW to all new transmission lines to be constructed in CEB is justifiable.// There is a good opportunity for CEB to enter into a communication business using the extra fibers available with its transmission network which covers all populated areas of the inland. However, it is to be studied in detail before entering to this challenging business.
item: Thesis-Abstract
Improvement of CEB distribution protection to enhance system reliability
(2014-08-01) Wijeweera, CD; Perera, HYR; Wijekoon, HM
Distribution protection and system reliability have become equally important concepts since the inception of power systems. With more and more sensitive equipment coming in to industries, the requirement of protection and higher reliability of power system is been highlighted. Problems with system reliability result in costly loss of production to critical processes create a dilemma for both the serving utility & the consumer. The protective devices and switches play an important role in the reliability of electrical distribution systems by minimizing the impact of interruption. In this project, a method for identifying the type and location for protection devices and switches on the distribution system using cost-based optimization is proposed. Data has been obtained from the data loggers in the re-closers, DDLO fusers and transformers which are connected to the Labugama feeder of the Ranala gantry energized by the Kosgama grid substation. The proposed method is based on the existing reliability analysis and reliability analysis, after introducing various components, e.g., Sectionalizes, Auto-recloses and switching gantry. The detailed design of the protection devices and the switches are determined by minimizing the total cost of reliability that comprises apparatus investment, maintenance, and interruption cost. Chapters 03 to 05 concentrate mainly on the selection of technologies and sample feeder which represents the total system. Chapters 06 will discuss the way of data collection and analysis. Suggestions on possible improvements to reduce number of customer interruptions and customer interruptions duration while maintaining same degree of protection will discuss under the chapter 07.
item: Thesis-Full-text
Improvement of reliability & lifetime of oil immersed power transformers through condition monitoring
(2015-09-16) Samarasinghe, SAKP; Perera, HYR
Power Transformers are very critical in any power system and they are very expensive. Maintaining the Reliability and Well-being of Power Transformers shall be the fundamental responsibility of Electrical Engineers. Proper periodical maintenance of Power Transformers, Carrying necessary tests including Condition Monitoring Tests and attending to foreseen faults will enhance the reliability and life time of them. Fault diagnosis using the condition monitoring test results by skilled engineers and Keeping technical staff and required spare parts readily available will make the power system more reliable by avoiding unexpected and expensive outages. Therefore it is important to have an Index for a transformer that can imply the present condition. Selected condition monitoring tests for the Winding and Insulation oil are used to determine the Transformer Fitness Index (FI) which will indicate the well-being of the transformer. Depending upon the Fitness Index, recommendations are made how to increase the lifetime (If Possible) and the reliability. This thesis describes the insulation paper, Insulation Oil, faults and testing methods for winding and oil. In the literature survey, detailed study about the selected tests and analyzed available test results of various power transformers of Ceylon Electricity Board (CEB) by referring to IEEE, ICE standards and relevant books. Two prequalification tests were selected to detect the moisture content in the insulation. If both prequalification tests are passed Fitness tests were done and FI values were calculated. Depending on the FI values, recommendations and statements on the transformer condition is described. Those statements will be very helpful for the improvement of reliability and life time of existing transformers and to take the decision which transformers are to be replaced and when to be replaced.
item: Thesis-Full-text
Influence of different parameters on the cost function of lakvijaya power station
Harshana, IGC; Perera, HYR
Every power plant has its own cost function that describes how its cost varies with the power output. This data is used to find the incremental cost of each unit generated – hence the order in which the plant is dispatched in the merit list prepared by System Control Centre (SCC) of Ceylon Electricity Board (CEB). Lakvijaya Power Station (LVPS) is in operation for more than six years now, but its cost function has not been defined yet. Main target of this research is to define the cost function of LVPS and to determine the independent parameters affecting the function. There are many parameters that affect the efficiency of the power plant. One is the temperature of inlet air which is used to convey pulverized coal to the furnace and to supply air required for combustion. Another key parameter is the cooling water temperature which is used as the coolant of the condenser. Next one is excess oxygen content in flue gas. Furthermore, mill temperature, power output, main steam pressure and main steam temperature were considered. By using load levels, cost data and quadratic regression, the cost function was derived. Then the most influencing factors were identified using Pearson correlation analysis. As the second step, it was studied how the selected parameters affect the cost function. Multiple regression was used for those calculations. SPSS package was the selected tool for this analysis. Validation for the final output was done for many cases and that proved realistic behavior of the derived function. This relationship can be used to identify the parameters affecting the efficiency and to which extent it influences the cost function. This function is recommended to be used for decision making and for the efficiency calculation of Lakvijaya Power Station
item: Thesis-Abstract
INTELLIGENT LOAD SHEDDING MECHANISM FOR CEB NETWORK
(2015-10-29) Rajapaksha, RVDHN; Perera, HYR
Load Shedding plays a major role as the guard which protects the power system from a disturbance-induced collapse. In Sri Lanka, Ceylon Electricity Board being the major power network authorizer practice „under-frequency load shedding‟ with the support of under-frequency load shedding relays. There are some drawbacks of this under frequency load shedding scheme which promotes power system authorizers to shift into a computerized power management system to form an „automated load shedding scheme‟. An intelligent load shedding system can provide faster and optimal load relief by utilizing actual operating conditions and knowledge of past system disturbances [1] As the first step in this study, a research survey was done about present load shedding system practiced in Ceylon Electricity Board. Past failure analysis was done to identify major drawbacks of the system. During literature survey characteristics of an intelligent load shedding system were observed and the way of forming an intelligent load shedding system in a power network was studied. Through selection of southern part of CEB network including seven grid substations, two major hydro power plants, two thermal power plants and three mini hydro power plants, model was designed using MATLAB software. Initially a data bank was formed including load data, generation data for the selected network. Load data at each grid substation for a week day, Saturday and for Sunday were formed based on the load equations derived depending on the time of the day (off-peak, day-peak, night-peak). Generation data was adjusted according to the total load requirement. Feeders that can be shed were selected considering the category of load connected at each feeder and categorization by System Control center as high priority feeders and low priority feeders. Coding was built up in MATLAB software after importing excel sheets consisting all the data collected and modeled to create a „Graphical User Interface‟(GUI). Further code was extended for the load shedding process which activates once a power imbalance occurs between generation and demand. Simulation was done for tripping of major hydro power plants which contribute to load shedding process. Further comparisons were done between existing load shedding mechanism which is under frequency load shedding(UFLS)and Intelligent Load Shedding (ILS) mechanism in Power System Simulator for Engineering(PSS/E) software which is the software used by System Control Center branch in transmission division for analyzing and simulating power system performance. It is concluded that reasonable improvements can be achieved through application of intelligent load shedding mechanism to CEB network which contributes to quality of uninterrupted supply to consumers.