Quantifying the Level of Exposure of Uganda's 132kV Transmission Network to Transient Faults

Abstract

Uganda’s power system has grown over the years with an increase in the transmission line network and generation capacity. Conversely, over time, the transmission grid has experienced several transient faults with some resulting in cascading failures and total system collapse, thus the need to quantify the level of exposure of the transmission network to transient faults. This dissertation report describes the study done to quantify the level of exposure of Uganda’s 132 kV transmission network to transient faults. The quantification process relied on well-established resilience metrics with a high maturity index. Key metrics considered in the study included the lost generation capacity, its associated value, the quantity of lost load, and its respective value. The study also proposed strategies to reduce the level of exposure and the quantification of the new exposure level of the transmission network was undertaken. Findings from the study revealed that the 132 kV transmission lines that are most exposed to transient faults include: Masaka West-Tanzania, Lugogo-Clock tower, Masaka West-Mbarara North, Nkenda Fortportal 2 and Isimba Bujagali 1. The current exposure of the 132 kV network, expressed in terms of the value of lost generation and load, amounts to 3,577,966,151 UGX. Based on the aspects of criticality and cost, the study proposed strategies to reduce this exposure level that include: the inclusion of a 13 MVAR series capacitor on Masaka West – Tanzania line to increase the transient stability of the grid, review of the distance protection relays for Bujagali Iganga 1 to eliminate the aspect of transient over reach that increases the exposure level, installation of bird guards on transmission lines that are prone to birds and the enhancement of vegetation management on transmission lines that pass through corridors with a lot of vegetation. Further analysis involved sizing the series capacitor for the Masaka West-Tanzania feeder at various degrees of compensation and the results demonstrated that a 13 MVAR series capacitor with a degree compensation of 70 percent yielded the lowest exposure level amounting to 686,108,682.00 UGX. This solution yields a 35.7% reduction in exposure and presents a viable investment with a cost-to-benefit ratio of 1.67. The results obtained from this study will aid in the planning, operation, control, and optimization of Uganda’s 132 kV transmission network to reduce the level of exposure of the network to transient faults and prevent their negative cascading impacts.