Early Retirement of Coal-Fired Power Plants Impact on the Java Madura Bali System

The accelerated retirement of coal-fired power plants (CFPPs) has become a key component in Indonesia's energy transition policy, especially within the Java Madura Bali power system. This study evaluates the technical impacts of early CFPPs retirement on frequency stability and transmission losses during the transition period from 2025 to 2030. Sequential scenario-based simulations were conducted using DIgSILENT PowerFactory, the study models projected retirements and large-scale integration of renewable energy sources across the regional grid. The results show that the immediate loss of synchronous inertia after CFPPs retirement leads to lower frequency nadir and higher risk of under-frequency events. Transmission loss analysis further reveals that the impact of early retirement is strongly influenced by the spatial distribution of both retired units and replacement generation. Specifically, retiring coal plants located far from major load centers can reduce overall losses when the replacement power plant is located closer to demand areas.