Transmission line redundancy for grid resilience enhancement: The concept of Transmission Lines contributing to Energy Not Supplied (TLENS) on Malawi’s transmission grid

Enhancing power grid resilience, such as redundancy, is crucial for ensuring a reliable energy supply amid increasing environmental challenges. Transmission line redundancy involves identifying lines to be prioritised for improvement and how to improve the identified lines. The challenge remains to identify critical lines using specified transmission level indicators that quantify how the failure of lines affects electricity delivery and factors to consider when planning for redundancy. This paper introduces a novel resilience indicator called Transmission Lines’ Contribution to Energy Not Supplied (TLENS), which measures how specific transmission line failures impact overall energy not supplied (ENS). Using TLENS, critical lines were identified, and redundancy effectiveness was evaluated. Further, TLENS was integrated with network topology, disaster exposure maps and stakeholder consultations to formulate and prioritise redundancy choices. Using DIgSILENT PowerFactory, a case study was conducted to observe grid behaviour through its reliability analysis toolbox. The study identified Nanjoka – Nkhotakota, Nkhotakota-Dwangwa, Dwangwa-Chintheche and Kapichila – Mlambe as substantial ENS contributors, posing significant resilience risks. Combining multiple redundancy scenarios achieved the lowest TLENS. However, regions prone to disasters might benefit more from either loop connections (alternative supply routes) than parallel line redundancy and distributed generation or making the lines more robust. This research offers a comprehensive framework for future grid resilience efforts and recommends exploring the comprehensive cost-benefit analysis of viable redundancies.