Master of Philosophy (M.Phil.)

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Browsing Master of Philosophy (M.Phil.) by Subject "ELECTRICAL ENGINEERING"

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    item: Thesis-Abstract
    Remote meter reading over power distribution lines
    Gamage, K; Karunadasa, JP; Dias, D; Ranaweera, A
    The thesis presents the development of a simple technique for remote reading of utility meters using the low voltage power distribution network. Remotely reading electricity, gas and water meters have distinct advantages over traditional metering methods. Several communication technologies have been designed and implemented for this purpose using wireless techniques, telephone lines, power transmission and distribution lines. In this study, the last one has been selected as the basis for the development of a remote meter reading system applicable to Sri Lanka. Power line communication over low voltage distribution lines is a cost effective method for data transmission. But it is complex due to large number of branches, tapings, transformers, different line configurations etc., that are present in the distribution network. The main task of this research is to develop suitable techniques for transfer of data over this network. The basic concept of data transmission in this application is the change of voltage and current wave at the supply end and the load end respectively of the power system. A series of current pulses are generated representing the data to be transmitted from the consumer end. Similarly, a series of voltage pulses are generated at the supply end to represent the commands to be sent to the consumer. These current and voltage pulses are superimposed with the line current and the line voltage at the load end and the supply end respectively on the power line signal. The prototype system presented in this thesis shows simulation as well as experimental results relating to the data transmitter, and the software design for the communication subsystem interfacing the meter to the distribution lines. A series of measurements are also carried out to find a suitable time of the day tor the data transmission. Associated problems such as harmonics generated due to the insertion of data and the effects of load changes in the distribution network are also discussed.
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    item: Thesis-Full-text
    Stability and security analysis of India-Sri Lanka HVDC interconnection
    Perera, AGCU; Rodrigo, WDAS; Wijayapala, WDAS
    This thesis concentrates on the stability performance of HVDC-HVAC interaction of the transnational HVDC interconnection between Sri Lanka and India. This transmission line under consideration since mid-1970 and the prefeasibility study was done by India in cooperated with Sri Lanka together. In this study it was focused on modeling the HVDC link between Indian and Sri Lankan power grids with the basic control system and studying the transient stability performance of the HVDC interconnection under the Sri Lankan transmission network perturbed conditions. The complete system was modeled on PSCAD/EMTDC software. The complete system was divided into five subsystems while modeling as, rectifier side AC source, converter transformers and converters, DC transmission line, HVDC control system and inverter side detailed Sri Lankan network. The simulations were done for steady state conditions, for system accuracy verification and for different system perturbed conditions. The analysis was done based upon the maximum power curve, Short circuit ratio (SCR) and time domain analysis. It was found that; modeled Sri Lankan network is a strong network for the proposed HVDC interconnection in steady state condition. However, there is a considerable impact on the stability of HVDC-HVAC interaction under different perturbed scenarios of Sri Lankan AC network. This study discusses the results obtained from the qualitative and quantitative analysis. was The results obtained from this study can be taken as guidance during the planning and designing stage of the proposed DC interconnection to have an idea on stability of the AC-DC interaction. The DC power operating curve, maximum DC power infeed to inverter side Sri Lankan network, AC system strength behavior during different disturbances, time domain faults behavior, impact ofAC system impedance on the stability are the facts which are discussing in this thesis. Therefore, this thesis can be consider as guidance for the planning stage ofthe proposed interconnection
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    item: Thesis-Full-text
    Under frequency load shedding for power systems with high variability and uncertainty
    Bambaravanage, DYT; Kumarawadu, S; Rodrigo, A
    Emergency load shedding for preventing frequency degradation is an established practice all over the world. The objective of load shedding is to balance load and generation of a particular Power System. In addition to the hydro and thermal generators each with less than 100 MW, today, the Power System of Sri Lanka is comprised of three coal Power Plants: each has a generation capacity of 300 MW, Yugadanavi combined cycle Power Plant (300 MW generation capacity) and a considerably extended transmission network. To cater consumers with high quality electricity, a reliable Power System is a must. Therefore, it has become timely necessity to review the performance of the present CEB Load Shedding Scheme and suggest amendments where necessary. The objective of this research is to explore a better Under Frequency Load Shedding Scheme (UFLSS) which can face probable contingencies and maintain stability of the system while catering more consumers. The suggested UFLSSs can address the recent changes taken place in the Sri Lanka Power System too. A simulation of the Power system of Sri Lanka was designed with software PSCAD. Its validity was checked through implementing actual scenarios which took place in the power system under approximately-equal loaded condition and by comparing the simulated results and actual results. Then a performance analysis was done for the Ceylon Electricity Board (CEB) Under Frequency Load Shedding Scheme which is being implemented in Sri Lanka. Having identified the drawbacks of the CEB Under Frequency Load Shedding Scheme, the new UFLSSs (LSS-I and LSS-II) were suggested. The Load Shedding Scheme – I (LSS-I) is designed based on power system frequency and its derivative under abnormal conditions. Without doing much modification to the prevailing UFLSS, and utilizing the available resources, the suggested LSS-I can be implemented. The LSS-II gives priority for 40% of the system load for continuous power supply, and it is comprised of two stages. During the stage-I, approximately 30% of the load is involved with the Load Shedding action. During the stage-II, the disintegration of the power system is done. This involves the balance 30% of the load. At 48.6 Hz the disintegration of the power system takes place. By disintegrating the power system at the above mentioned frequency, all islands as well as the national grid can be brought to steady state condition without violating the stability constraints of the Sri Lanka power system. During disintegration of the Power System, special attention must be paid for: • Generation & load balance in each island and in the national grid. • Reactive power compensation in islands and in the national grid. • Tripping off of all isolated transmission lines (which are not connected to effective loads). Through simulations the effectiveness of the UFLSSs were evaluated. They demonstrate better performance compared to that of the currently implementing CEB scheme. Results highlight that the UFLSS should exclusively be specific for a particular Power System. It depends on factorssuch as power system practice, power system regulations, largest generator capacity, electricity consumption pattern etc.