How a Single Transmission Failure Left 13 Million Without Power in Sumatra

JAKARTA, Investortrust.id — Indonesia’s state-owned electricity monopoly PT PLN (Persero) is racing to stabilize the power grid on Sumatra island after a massive blackout cut electricity to 13.1 million customers. By Saturday morning, technicians successfully restored power to more than 8.3 million subscribers following a night of widespread darkness across multiple provinces.

The crisis began Friday at 6:44 PM local time when severe weather triggered a failure on the 275-kilovolt (kV) Muara Bungo–Sungai Rumbai Extra-High Voltage Air Line (SUTET) transmission network in Jambi province. The localized failure rapidly cascaded into a "separated system" event, fracturing the grid and plunging major economic hubs from West Sumatra to Aceh into a total blackout.

The grid collapse exposes the fragile infrastructure balancing act in Sumatra, an island pivotal to Indonesia’s mining, palm oil, and manufacturing output. For global investors tracking Southeast Asian supply chains, unexpected industrial blackouts represent a major operational risk. While PLN’s rapid response mitigated prolonged industrial paralysis, the dependency on slow-starting coal assets highlights vulnerabilities in the region's energy resilience.

Grid Fracture and the Domino Effect

The transmission failure created an immediate power deficit, overloading the rest of the network and triggering a regional grid collapse. PLN Chief Executive Officer Darmawan Prasodjo explained during a press conference on Saturday that the high-voltage line failure initiated a dangerous chain reaction.

"The disruption on the transmission segment had a widespread impact on parts of the Sumatra transmission system, causing a drop in frequency due to heavy generator loads and triggering a domino effect of disruptions across several regions," Darmawan stated.

PLN managed to repair and re-stabilize the core transmission line within two hours of the initial fault. However, reviving the power plants that tripped during the surge has proven to be a much steeper technical challenge for the state utility.

The 20-Hour Coal Bottle-Neck

To accelerate the recovery, PLN prioritized fast-starting energy assets like hydroelectric and gas turbines to inject immediate power back into the grid. These quick-response facilities allowed engineers to begin restoring sub-stations and critical municipal infrastructure overnight.

In contrast, the island’s heavy-duty baseload infrastructure faces a much slower path back to full capacity. Darmawan noted that the utility's massive coal-fired thermal power plants (PLTU) cannot simply be switched back on overnight.

"Thermal power plants like PLTU require more time, between 15 to 20 hours starting from start-up, synchronization, and full operation," Darmawan added during the Saturday briefing.

Massive Mobilization on the Ground

As of Saturday at 10:00 AM local time, PLN reported that 3,192 megawatts (MW) of electricity supply had been restored out of the 5,334 MW knocked offline. Additionally, 157 out of 176 affected substations are now fully operational, bringing millions of households and commercial businesses back online.

The recovery has advanced rapidly in West Sumatra, where PLN Unit Induk Distribusi Sumatera Barat (the company's regional distribution division) confirmed that 100% of its primary substations were energized by 5:00 AM on Saturday. Local residents in Bukittinggi reported that home electricity began sputtering back to life between 1:00 AM and 3:00 AM on Saturday.

PLN has deployed hundreds of specialized personnel working continuous 24-hour shifts across Jambi, West Sumatra, Riau, North Sumatra, and Aceh to finalize grid synchronization. The company issued an official apology for the widespread economic disruption and urged customers to track live restoration updates via its digital application, PLN Mobile.