<![CDATA[Ensuring a stable and sustainable electricity supply requires effective planning that balances cost efficiency and system reliability. This study explores the optimization of Basic Generation Cost (BPP) in PT PLN (Persero)'s Electricity Supply Business Plan (RUPTL) 2025-2034 while considering the reliability of the Sumatra power system. Using Digsilent PowerFactory, simulations incorporating Unit Commitment and Economic Dispatch methodologies were conducted to achieve cost reductions without compromising system stability. The significant result of this theses is optimization with economic dispatch reduces BPP up to 41,4% compared to conventional methods, enhancing power system cost efficiency. Increasing voltage reliability from 0.99 p.u. in 2025 to 1.01 p.u. in 2034. Higher renewable energy integration in 2034 reduces fuel costs but increases challenges in maintaining frequency and voltage stability. Strategic recommendations include increasing transmission capacity, implementing energy storage systems, and optimizing unit commitment to balance cost and reliability. This research offers valuable insights for power system planning, addressing energy transition challenges and facilitating the integration of renewable energy sources in Sumatra. Keywords: Basic Generation Cost, System Reliability, Economic Dispatch, Digsilent PowerFactory]]>
