Sumatra Power Outage Highlights Indonesia’s Grid Resilience Gaps

Widespread rolling blackouts struck Sumatra in June as severe weather caused trips on two 500 kV transmission circuits, forcing power transfers to a weaker 275 kV corridor. The resulting voltage and frequency oscillations compelled operators to split the island’s grid into northern and southern zones to contain the disturbance. The north suffered supply shortages and forced generator trips, while the south maintained protection without major outages. The Institute for Essential Services Reform (IESR) warned the event underscores the need to assess not only reliability but also resilience of Indonesia’s electricity system against increasingly frequent extreme weather linked to climate change.

The incident involved damage to 12 PT PLN transmission towers on the Galang–Simangkuk 275 kV and Tebing Tinggi–Sei Rotan 150 kV lines, attributed to heavy rain and strong winds. IESR director Deon Arinaldo called for comprehensive evaluation of the grid’s capacity to withstand such climate‑driven shocks.