Browsing by Author "Banda, HMW"

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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: Conference-Full-text
The impact of distributed generation on transmission and distribution losses in Sri Lankan power system
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Priyangika, AAC; Wijayapala, WDAS; Banda, HMW; Rajapakse, A; Prasad, WD
Share of Non-Conventional Renewable Energy (NCRE), small hydro, wind, solar, bio-mass etc based electricity generation in Sri Lanka at present is 10% of the total annual generation. The Government of Sri Lanka has declared a national target of 20% from NCRE by 2020[1]. Most of NCRE power plants have been connected to the distribution network and are termed as Distributed Generators (DGs). With the increase of share of DGs, it affects system reliability, power quality and economic operation of the distribution network. This paper focuses on the impact of economic operation of transmission and distribution network due to distributed generation in Sri Lankan power system. Network simulation studies have been carried out for transmission network and for four grid substations to which many DGs have been connected. The analysis revealed that transmission network losses have reduced with increase penetration of DGs to the system while distribution network losses are dependent on the amount of DG capacities connected to the distribution network. However, there is a reduction of network losses when overall network is considered thereby giving financial benefit from DGs added to the system.
item: Thesis-Full-text
Impacts of distributed generation on transmission and distribution losses in Sri Lankan power system
(2016-09-06) Priyangika, AAC; Wijayapala, WDAS; Banda, HMW
According to the National Energy Policy and Strategies of Sri Lanka [1], the Government will endeavour to reach a minimum level of 10% of electrical energy supplied to the grid to be from Non- Conventional Renewable Energy sources by year 2015. Further, Government of Sri Lanka has revised the target to reach 20% of electricity supply is expected to be generated by renewable energy by year 2020. Main Non Conventional Renewable Energy Sources available in Sri Lanka are Wind, Small hydro, Solar and Biomass. They are also called as Distributed Generation (DG) units which are located especially close to load centers of the distribution network. When driven for such a national target as a utility, impacts of these technologies should be evaluated to maintain power quality and the stability of the power system. There are considerable impacts of DG units to utility as well as to consumers. While improving power quality and stability, DG is a financial benefit to the utility and to the country. One of the main impacts of the DG for the utility is reduction of losses. The objective of this study is to estimate the impact of distributed generation on transmission and distribution losses in Sri Lanka power system. Transmission network and the part of the distribution network were separately studied and used to calculate the losses by using PSSE software and SynerGEE software. Badulla, Kiribathkumbura, Rathnapura and Ukuwela, grid substations with the feeders which are connected to considerable amount of DGs are selected for analysis. According to the results, transmission network always gives a loss reduction by introducing DGs. But in distribution network, only some feeders give a positive value for the loss reduction when DGs are present. The study shows that, when total network is considered, always there is a loss reduction and a financial benefit from DGs added to the system.
item: Thesis-Full-text
Load harmonic mitigation: a case study at Uva provincial council building
Ratnayake, RMSK; Perera, R; Banda, HMW
This thesis presents the application of active filters to mitigate the harmonic problems in an office building. Harmonics in electrical system induce additional heating. This causes premature aging, reduction of efficiency and life of the electrical equipments and components in the system. Harmonic problems can be caused by disturbances originating in the supply system, from customer's premises and from the nearby installations. The problem is due to the non-linear loads showing different current waveforms when supplied by a distorted or perfect sinusoidal voltage. Growing use of non-linear load equipment and technologies in commercial buildings has increased the severity of the problem. This is common to Uva Provincial Council (UPC) building, as well, where a large number of connected computers, UPS and other peripherals are major sources of harmonics. The site measurements revealed that the non-linear loads generate TDD up to 15 % and the individual harmonic distortion up to 38 % of the fundamental. These values exceed the maximum limits prescribed by the power quality standards, lEE 519-1992. To mitigate the harmonic effects, various available techniques are reviewed. The active power filter (APF) is selected as a solution, as it has become the popular and advantageous options among the many practices available today. The operation of common APF topologies, namely the shunt, series and hybrid APF s are discussed in detail, and shunt APF is identified as the most simple and advantageous choice for this purpose. This is followed by a review of various strategies of harmonic detection and APF controlling. After comparing the performances of these strategies with the real life applications, suitable techniques for harmonic detection and APF controlling are formulated. Finally, a computer model of thus developed shunt active filter is simulated using MATLAB / Simulink environment. Based on the case study, the thesis discusses alternatives and provides some practical solutions to the problem of harmonics in office buildings.
item: Conference-Full-text
Techno-economic feasibility of using 400 kV for the 2032 transmission system of Sri Lanka
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Alahendra, GB; Banda, HMW; Lidula, NWA; Rajapakse, A; Prasad, WD
Congestion occurs on the nation’s electric transmission grids with the addition of new generation to meet the increasing electricity demand. Therefore, reliable, efficient and better quality of supply urge introduction of new higher voltage levels for power transmission. However, it has to be technically feasible and economically justifiable for the country. Technical feasibility and economic justification of introducing a higher voltage than that of existing voltage to transmit bulk power to load centers from bulk power generating stations in Sri Lanka is discussed in detail in this research.