Impacts of distributed generation on transmission and distribution losses in Sri Lankan power system

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