Economic selection of distribution transformers for rural electrification projects in North Central Province

Abstract

The total cost of a transformer includes the initial purchase costs, maintenance cost and the cost due to losses of the transformer throughout the lifetime. Cost of losses depends on tariff, load curve and load growth over the life of the transformer. The cost due to losses will be a cost for the country as a whole since this will affect to the total generation capacity to meet the country’s demand. Therefore the proper selection of transformers is vital for any electrical installation. The Ceylon Electricity Board gives special concessions to electrify rural areas to uplift the living standard of the people in rural areas by providing the electricity, which is a basic need. The rural electrification project 4-extension is proposed to conduct in North Central Province targeting an electrification level towards 100% in North Central Province. With this project 550 new distribution transformers will add to the electricity distribution system in North Central Province. In this study, an economic analysis is done for proper selecting of distribution transformers for this rural electrification project. The load factor of the rural areas of the Province is calculated by collecting the load curves of the selected transformers already installed in rural areas. According to the findings the load factor of the rural areas of North Central Province is 0.4. The load growth rate of the rural areas was analyzed by collecting the historical data of 367 Nos. identified transformers which are installed in rural areas. Exported energy from each transformer since year 2002 was collected in order to determine the load growth rate. This research project concludes that the average load growth rate of the rural areas of the North Central Province is 5% per annum with a standard deviation of 2%. If the initial peak load of the transformer is less than 30 kVA, the most economical transformer is 63 kVA. Similarly for the initial peak load of 30-40 kVA, 40-100 kVA and 100-160 kVA the most economical transformer installations are 100kVA, 160kVA and 250kVA respectively.