Enhancing transmission line resilience through n-k contingency analysis and mitigation on the transmission network of Uganda

Abstract

This project addresses the critical need to enhance the resilience of power transmission networks by use of N-k contingency analysis and mitigation strategies. The resilience,reliability and stability of electrical grids are paramount for ensuring continuous and secure energy supply to consumers. The operational status of transmission lines significantly influences the electric power system, with line outages posing economic and safety risks.Recently the transmission lines of the Ugandan transmission network have been affected by these contingencies and this shows that there are still resilience shortages on the grid. Therefore the main aim of the project was to analyze the impact of line outages on the whole transmission network and propose mitigation strategies which can be adopted to enhance transmission line resilience. The case study was the present transmission network of Uganda and the network data was collected from the National Control Centre under Uganda Electricity Transmission Company Limited (UETCL). The network was modeled in DigSILENT Power Factory software 15.1, load flow and N-1, N-2 contingency analysis were carried out and the ranking of the contingencies was performed to assess the vulnerability of these lines using resilience performance indices. From the analysis of the results, the vulnerable lines on the network were 33 kV Ishasha - Runkungiri, 33 kV Ishaka-Runkungiri, 33 kV Mbarara-Ishaka, 132 kV Owenfalls-Lugogo, 132 kV Kampala North- Namanve, 220 kV Bujagali-Kawanda, 132 kV Bujagali-Isimba, 66 kV Owen falls-Lugazi, 33 kV Mpanga-Kahungye, 220 kV Kenya-Tororo are greatly affected by line outages on the network. Using the voltage performance index, it is identified that transmission lines 66 kV Owen falls-Lugazi, 33kV Mpanga-Kahungye, 220 kV Kenya-Tororo experience great voltage violations whereas lines 132 kV Lugogo-Owen falls, 220 kV Kawanda-Bujagali, 132 kV Kampala North-Namanve, 132 kV Bujagali-Isimba experience extreme loading violations basing on active power performance indices due to single line outage on the network. Under two line outage scenarios, transmission lines of 132 kV Lugogo-Owenfalls, 220kv Kawanda-Bujagali, 132kv Bujagali-Isimba, 132 kV Kampala North-Namanve, 132 kV Namanve-Namanve South, 220 kV Kenya-Tororo, 132 kV Owen falls-T-off Mukono, Muvumbe-T-off Muvumbe, 33 kV Kabale- T-off Muvumbe, 132 kV T off Mukono –Namanve, 132 kV Bugoye-Nkenda are greatly affected. In order to enhance the transmission resilience, we recommended the installation of the phase measurement units and increased cases of redundancy on the existing network by the system operators. With these mitigation strategies proposed put into play, the transmission line resilience of the Ugandan transmission network can be enhanced and cases of blackouts due to line outages on the network be reduced.