Viability of Capacitor-Coupled substations on Uganda's Electricity Transmission Network

Abstract

Uganda with a current generation capacity of 1346.6 MW identifies electricity through its Vision 2040 as a primary input to foster socio-economic transformation of its citizens to middle income status. Consequently, the National grid is under radical expansion with increase in the number of transmission lines to evacuate the generated power to load centres and with 794 MW average peak demand against the total generation installed capacity represents an excess in generation of 41%. Within 5 years from 2020-2025, Uganda expects to increase electricity consumption per capita from 100 kwh to 578 kwh and foster a reduction in the cost of electricity to USD 5 cents for all processing and manufacturing enterprises: Increased households with access to electricity from 21 percent to 60 percent. Electricity is transmitted from Generation power plants that are located at remote centres to load centres that have electricity demands where the electricity is stepped down to lower usable voltage by industries and homesteads. The stepped down electricity is then distributed to remote often scattered load centres many kilometers from the load centres using long radial distribution lines even in areas where the transmission lines traverse. Since line losses are a function of distance, the long lines come with increased line losses and higher capital investments, something which highly impacts the end user electricity tariff. Therefore, there is need to for a solution that can provide power to remote areas where the High Voltage Transmission Lines Traverse. This solution shall not only help in increasing electricity access but as well as reduce on high capital investments and power losses involved in wheeling power to these remote areas. An Unconventional Rural Electrification Solution that uses capacitor voltage divider technology was formulated and assessed. The Capacitor-Coupled Substation will tap off power from the High Voltage Transmission Lines and step it down to Medium Voltages that can further stepped down by an Auxiliary Service Transformer at the dispersed remote centres to electrify homes and small factories. Application of the Capacitor-Coupled Substation to a case study of Uganda’s 132 kV network, revealed network stability within specified loading limits of 50% and 100% of the designed 28.37 MVA while keeping the 132 kV Network Voltage drop within acceptable voltage limits of ±5%.