PT PLN (Persero) said more than 8.3 million customers across Sumatra had their electricity restored by Saturday morning following a widespread blackout that disrupted power supply in several provinces after a transmission failure in Jambi.
The state-owned electricity company confirmed that around 4.8 million customers were still without power as restoration work continued across the island.
PLN President Director Darmawan Prasodjo said the utility was continuing efforts to normalize the Sumatra electricity system after disruptions occurred on the 275-kilovolt Muara Bungo–Sungai Rumbai extra-high-voltage transmission line in Jambi.
According to PLN, the initial disturbance took place at around 6:44 p.m. local time on Friday and quickly affected multiple interconnected power systems across Sumatra.
Darmawan explained that severe weather was suspected to be the main trigger behind the transmission disruption, which later spread into broader instability across the island’s power grid.
“The disruption in the transmission section affected part of the Sumatra transmission system, causing a frequency drop due to heavy generator loads and triggering a domino effect of disturbances in several regions,” Darmawan said.
The outage affected electricity distribution in multiple provinces including Jambi, West Sumatra, Riau, North Sumatra and Aceh.
PLN stated that repair work on the damaged transmission line was completed within approximately two hours after the initial disruption occurred.
Following the transmission repair, the company shifted its focus toward restarting power plants that had automatically shut down during the grid disturbance and synchronizing them back into the transmission network.
Darmawan said hydroelectric and gas-fired power plants were prioritized during the early stages of recovery because they could return to operation more quickly than thermal facilities.
Meanwhile, coal-fired power plants required significantly more time to resume full operations.
“Thermal power plants such as coal-fired plants require between 15 and 20 hours from start-up to synchronization and full operation,” he explained.
PLN said the recovery process was being conducted simultaneously across transmission networks, substations and generation facilities throughout the affected regions.
As of 10:00 a.m. local time on Saturday, PLN had successfully restored more than 3,192 megawatts of electricity supply out of the 5,334 megawatts previously disrupted by the outage.
The company also reported that 157 substations out of the 176 affected substations had resumed operations.
With those improvements, electricity service had been restored to approximately 8,351,670 customers across Sumatra.
Darmawan said thousands of PLN personnel and technical teams had been deployed across the field to accelerate restoration efforts.
“At present, all PLN officers and technical teams are working around the clock in the field. The recovery process is continuing and we are fully committed to restoring electricity supply to the public gradually and safely,” he said.
PLN also confirmed that it was coordinating closely with Indonesia’s Ministry of Energy and Mineral Resources, local governments, security agencies and other stakeholders to ensure recovery operations proceeded smoothly.
The utility apologized to customers affected by the blackout and pledged to continue restoration efforts until the entire system returned to normal conditions.
“We sincerely apologize for the inconvenience caused. We remain on full alert so the electricity system can recover quickly and the public can once again enjoy reliable electricity service as soon as possible,” Darmawan added.
The widespread blackout drew public attention because of its scale and because Sumatra is one of Indonesia’s largest interconnected electricity systems outside Java.
Millions of households, businesses and industrial facilities reportedly experienced service interruptions after the transmission disturbance spread across the regional grid.
Electricity disruptions were also reported to have affected transportation systems, telecommunications infrastructure and commercial activities in several provinces during Friday evening.
PLN has not yet released detailed estimates regarding the total economic impact of the blackout.
Earlier, PLN Executive Vice President for Corporate Communications and Social Responsibility Gregorius Adi Trianto confirmed that the outage originated from disturbances along the Muara Bungo–Sungai Rumbai transmission corridor in Bungo Regency, Jambi.
Gregorius, commonly known as Greg, said severe weather conditions were responsible for the transmission disruption.
“Based on the investigation results, there was a disturbance on the 275 kV Muara Bungo–Sungai Rumbai transmission line in Bungo Regency, Jambi Province caused by severe weather,” he said.
The transmission line involved in the disruption carries electricity at 275 kilovolts, making it one of the critical components connecting electricity systems across Sumatra.
Large-scale transmission failures in interconnected grids can rapidly spread instability because generation units and substations depend on balanced frequencies and synchronized operations.
When a major transmission line fails unexpectedly, power plants may automatically disconnect from the system to protect equipment from overloads or abnormal operating conditions.
Such cascading failures can result in widespread blackouts if the grid is unable to stabilize quickly enough.
Indonesia’s power infrastructure has faced increasing pressure in recent years due to rising electricity demand, expanding industrial activity and increasingly unpredictable weather patterns linked to climate variability.
Extreme weather events, including heavy rainfall, strong winds and lightning strikes, have increasingly been identified as risks to transmission infrastructure in several regions.
PLN has invested heavily in transmission expansion and grid modernization projects in recent years as part of efforts to improve reliability and support Indonesia’s broader economic development agenda.
The Sumatra electricity system plays a crucial role in supporting industrial zones, mining operations, palm oil processing facilities and urban population centers throughout the island.
Any prolonged disruption to the system can therefore have significant economic and logistical consequences.
The incident also highlighted the complexity of restoring interconnected power grids after major disturbances.
Unlike smaller local outages, island-wide transmission failures require careful synchronization between multiple generation facilities and substations to prevent additional instability during the recovery process.
PLN officials stressed that restoration must be conducted gradually to avoid overloading the system while bringing generation capacity back online.
Industry observers noted that hydroelectric and gas-fired plants are often used in emergency restoration because of their faster ramp-up capabilities compared with coal-fired facilities.
Coal-fired plants typically require extensive start-up procedures involving boiler heating, turbine preparation and synchronization processes before electricity can be safely delivered to the grid.
Despite the progress reported Saturday morning, PLN still faces the challenge of restoring service to nearly five million remaining customers spread across multiple provinces.
The company has not yet announced a precise timeline for complete normalization of the Sumatra electricity network.
However, officials insist recovery efforts are progressing steadily and that the majority of affected substations and generation units have already resumed operation.
The blackout also renewed discussion about Indonesia’s broader energy resilience and grid reliability strategy as electricity demand continues to grow nationwide.
Analysts say improving transmission redundancy, expanding smart grid technology and strengthening weather resilience infrastructure could become increasingly important priorities for PLN in the years ahead.
For now, the utility remains focused on completing restoration efforts while monitoring the stability of the Sumatra transmission network to prevent additional disruptions during the recovery phase.
