Five Initial Facts: Sumatra Blackout Not Caused by Sabotage

Bareskrim and PLN have conducted a thorough investigation into the widespread blackout in Sumatra several days ago. One finding shows no evidence of sabotage causing the power outage. The interim investigation results were presented directly by Deputy Chief of the Criminal Investigation Agency (Bareskrim), Inspector General Nunung Syaifuddin, who detailed findings from his team and PLN’s investigation into the Sumatra blackout. As reported, a widespread power outage occurred across multiple regions of Sumatra on Friday, May 22. Power was completely cut off in central Medan, with major roads plunged into darkness as street lights and traffic signals went out, including Balai Kota, Guru Patimpus, Gatot Subroto, Gajah Mada, and S. Parman roads. Key findings include: No Sabotage Inspector General Nunung Syaifuddin confirmed no sabotage was involved in the blackout incident, suspecting technical issues and extreme weather as the causes. ‘We can confirm there is no indication of sabotage or intentional acts in this incident,’ Nunung said at a press conference at Bareskrim in Jakarta on Monday, May 25. ‘The preliminary suspicion points to technical issues and extreme weather causing disruptions to the power system,’ he added. Damaged Cables Not Neatly Cut Inspector General Nunung Syaifuddin then explained why they concluded there was no sabotage, stating the broken cables showed uneven cuts. ‘We can confirm this is not sabotage because the damage or broken cables and networks are not neatly cut. They appear frayed,’ he stressed. ‘If it were sabotage, the cuts would be neater, as from tool use,’ Nunung added. Bareskrim has interviewed several witnesses regarding the incident, ensuring the investigation follows procedures and is accountable. ‘All investigative processes are conducted professionally, transparently, and comprehensively to scientifically and accountably determine the root cause,’ he explained. Three Possible Causes Inspector General Nunung Syaifudin further stated that a joint team had conducted a crime scene investigation at Transmission Tower 175 and 176 in Tempino Village, Mestong District, Muaro Jambi Regency, where a 275 kV extra-high voltage overhead transmission line cable on the Muara Bungo-Sungai Rumpeh route was found broken. ‘We can confirm there is no indication of sabotage or intentional acts in the blackout incident. The preliminary suspicion points to technical issues and extreme weather causing disruptions to the power transmission system,’ Nunung said. Nunung outlined three potential technical causes being investigated by the Forensic Laboratory (Puslabfor) regarding the cable break: mechanical factors causing cable friction, and tension on cables due to extreme weather. ‘The preliminary causes of the transmission cable break are still under investigation, including mechanical friction and wind effects, heat from loose connections creating gaps, or tension and swaying due to extreme weather,’ he explained. The cable fragments have been secured by the Police Forensic Laboratory (Puslabfor) for further analysis. Nunung stated that Sumatra’s power system has been fully restored. ‘The power system in Sumatra has been fully restored. According to official statements from PT PLN, electricity supply across Sumatra has returned to 100% normal and is operating safely and stably,’ Nunung added. Power Swing Phenomenon Meanwhile, PLN Transmission Director Edwin Nugraha Putra detailed the sequence of events leading to the Sumatra blackout, stating that a power swing or high-voltage oscillation was the primary cause of the interconnected system collapse. Edwin initially apologised to affected communities in Jambi, Riau, West Sumatra, North Sumatra, and Aceh. ‘PT PLN sincerely apologises, especially to communities in Riau, Jambi, West Sumatra, North Sumatra, and Aceh, for last Friday’s power outage,’ Edwin said. Edwin then explained that Sumatra’s power system relies on two main lines: the East Line (500 kV) and West Line (275 kV). The disruption began when extreme weather hit Jambi. ‘A 275 kV transmission fault occurred from New Aur Duri towards Sumsel 5, which feeds into the eastern 500 kV line. Heavy rain and strong winds caused both circuits to trip, taking the 500 kV line offline,’ Edwin explained. The eastern line failure caused electricity flow from the south (Palembang-Lampung) to abruptly switch to the western 275 kV line. This massive current shift triggered a technical power swing phenomenon,’ Edwin added. ‘This current shift caused a power swing, or high oscillation in voltage and frequency, due to the shift to the 275 kV line,’ Edwin said. ‘When the oscillation reached a certain technical threshold, the western 275 kV line had to isolate itself to prevent wider disruptions. At that point, the Muara Bungo to Sungai Rumbai section…’