PLN Reveals Cause of Mass Power Outage in Sumatra
PT PLN (Persero) has disclosed the cause of the widespread blackout that affected several areas of Sumatra on Friday night (22 May 2026). Weather disturbances are suspected to have been the initial trigger, cascading to disrupt the electricity system in multiple regions.
PLN’s Chief Executive Darmawan Prasodjo said the initial indications show the disturbance occurred on the 275 kilovolt (kV) transmission corridor between Muara Bungo and Sungai Rumbai, Jambi. The fault on this transmission line caused the system to disconnect from the Sumatra electricity network. As a result, supply and demand imbalances occurred in several areas.
PLN explained that some power stations experienced an oversupply of electricity because the power flow was interrupted. This condition triggered a rise in frequency and voltage, causing the protection system to operate automatically. ‘The generators automatically exit the system, or in layman’s terms, the plants automatically tripped,’ Darmawan said.
On the other hand, the areas that lost generation supply faced shortages. Frequency and voltage fell until other plants also tripped out of the system. PLN stated this condition created a domino effect spreading to various regions.
‘The disturbance on the transmission corridor affected part of Sumatra’s transmission system, causing a drop in frequency due to the heavy load on the generators and triggering a domino effect of disturbances in several areas,’ Darmawan said.
The outage affected the electricity system from Jambi, Riau, North Sumatra and Aceh. Other areas such as South Sumatra were also affected.
PLN emphasised that this outage is different from previous outages caused by flash floods and landslides in Aceh, North Sumatra and West Sumatra. According to Darmawan, in the earlier incident damage was triggered by the breakage of transmission and the collapse of power pylons due to the disaster. ‘This is a very different situation compared with the disasters in North Sumatra, West Sumatra, and Aceh at that time,’ Darmawan added.