Sumatra blackout likely caused by SUTET cable failure due to metal fatigue, wind: expert

A total electricity blackout that affected large parts of Sumatra last week was likely caused by the snapping of an Extra High Voltage Overhead Line (SUTET) cable in the Jambi region, according to Syarif Hidayat, a lecturer from the electrical engineering department at the Bandung Institute of Technology (ITB). The widespread outage occurred on Friday afternoon, May 22, 2026, impacting communities across Aceh, North Sumatra, West Sumatra, Riau, and Jambi. As of Monday, PT PLN (Persero) was still working to restore power to all customers.

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The most likely cause of the wire snapping is metal fatigue, then being blown by strong winds.

Based on media reports and circulating photographs, Syarif identified the broken component as a transmission wire. "The most likely cause of the wire snapping is metal fatigue, then being blown by strong winds," he told Tempo on Monday, May 25, 2026. He explained that metal wires are prone to prolonged vibration when exposed to wind, increasing the risk of breakage, particularly near connection points. While the SUTET system also has a ground wire designed to protect against lightning, Syarif noted that transmission wires, being larger (300 sq mm compared to the ground wire's approx. 70 sq mm), should theoretically be more resilient. He stressed that the exact cause of the incident in Jambi requires further investigation through forensic testing.

Syarif pointed out that this is not an isolated incident, recalling a similar ground wire failure in Jakarta in November 2025 that led to a major fire. In that case, the fallen ground wire contacted a transmission wire, causing a short circuit and subsequent explosions. "As soon as a fault occurs, the electricity flow is automatically cut off by the protection system at the substation to localize the disturbance," Syarif explained. The power outages extended to power generation sites, and restarting thermal power plants (PLTU) can take two to three days.

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As soon as a fault occurs, the electricity flow is automatically cut off by the protection system at the substation to localize the disturbance.

Furthermore, Syarif highlighted systemic issues within Sumatra's electricity infrastructure. He described the transmission network as weak and more limited compared to Java's system. "So when a disturbance occurs, there are no alternative lines. As a result, everything collapses," he stated. The lack of alternative connections means that when a line fails, there is no other way to link power plants to demand, leading to a surplus of power at generation sites and a deficit for consumers.

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So when a disturbance occurs, there are no alternative lines. As a result, everything collapses.