Power loss assessment and reduction in transmission line: case study of Rulindo-Gabiro

Abstract

This research focuses on analyzing and minimizing power loss in high-voltage transmission networks, specifically on the 64 km, 110 kV Rulindo-Gabiro line from the Rwanda Energy Group (REG). A comprehensive literature review examines the methods for assessing bulk transmission capacity and quantifying energy losses. Key issues include calculating the energy lost during electrical transmission across the grid and identifying technological measures to reduce these losses. The study analyse the energy losses in the transmission line based on actual data collected from the site. Using ETAP-PowerStation for system modeling, a single-line diagram of the existing network was developed, followed by load flow analysis, incorporating peak loads from REG. This analysis calculates total peak capacity loss across various voltage levels and identifies loss contributions from line and transformer components. The impact of load and line length variations on transmission losses is also examined. The "Loss Factor " is used to estimate annual average power loss, translating peak loss values from load flow analysis into annual energy loss figures. This approach is detailed in the literature section, with analyses by employing this methodology. Efficiency improvements for REG's grid are explored, applying industry-standard loss-reduction methods, including line double circuiting, nominal voltage uprating, and reactive power compensation. Lines identified for potential upgrades were evaluated based on power dissipation. For double circuiting, high-loss lines at 110 kV were prioritized, while voltage uprating targets included select levels. Reactive power compensation was applied selectively to enhance voltage profiles across the grid. The study quantifies the annual energy savings from each loss-reduction approach, presenting these in terms of financial gains. Conclusions and recommendations for optimizing the Rulindo-Gabiro line are provided. The study found initial power losses of 195.8 kW (1.23%). The introduction of a double-circuit transmission line significantly reduced active power losses from 195.8 kW to 129 kW, representing an improvement of 34.11%. Similarly, reconductoring the transmission line using twin conductors decreased losses to 137.8 kW, marking a 29.62% Page v of 68 enhancement in efficiency from actuary values. Additionally, reactive power compensation through the installation of capacitor banks improved the power factor from 0.78 to 0.92 and reduced active power losses from 186.22 kW to 139.78 kW, marking a 24.93%, which subsequently reduced reactive power losses and improved overall power quality. These upgrades also improved voltage stability, reducing the voltage drop from 1.63% to 1.27%.