Sumatra Blackout Reveals Vulnerable Points in Power Grid

JAKARTA, KOMPAS.com – The recent widespread power outage in Sumatra has exposed vulnerabilities in a critical part of the electricity transmission system: mid-span joints.

The disruption causing blackouts across several provinces is likely triggered by mechanical stress from strong winds on transmission lines, particularly at cable joint points.

“Given the pattern of the disturbance and the location of the damage at cable joints, weather factors are very likely to have contributed to this incident,” stated Djoko Darwanto, an Electricity System Analyst at Bandung Institute of Technology (ITB), in a written statement on Friday, 29 May 2026.

Preliminary joint investigations by Bareskrim, Puslabfor, and PLN identified three possible causes for the transmission cable failure: thermal stress due to weather, issues at the joint areas, and mechanical stress from load and wind effects.

“Conditions below may seem mild, but at conductor level, winds can be strong enough to cause cables to move and pull against each other,” he explained.

“This creates repeated stress on the cables,” Djoko added.

He noted that repeated movement from wind can increase pressure on cable joints, especially when the system is under high load.

According to him, joint areas are among the most critical in transmission systems as they experience combined effects of vibration, temperature changes, and pressure distribution when cables move due to wind.

“The pressure distribution at joints differs from that of intact cable sections,” he said.

“This is why these areas are closely monitored in transmission systems,” Djoko continued.

He also mentioned that disturbances caused by weather, vibration, and mechanical stress do not always produce easily detectable early indicators, even through routine thermal drone inspections.

“If thermal drone results previously showed normal conditions, such incidents could still occur,” Djoko said.

“Certain conditions only emerge when the system is under operational stress,” he added.

During the investigation press conference, authorities displayed cable sections as evidence for laboratory testing. These samples were taken from the damaged cable sections for further analysis.