The transport ministry said MAHB’s technical probe into the incident identified the cause as a circulating current in the wires between the 33kV substation supplying power to Terminal 2 and the terminal’s 11kV substations.

“This caused localised heating at the cable terminations, leading to a flashover (short circuit).

“The high soil resistivity also indirectly contributed (to the incident) by impeding the effective discharge of the current to earth, increasing thermal stress on the sheath wires,” the ministry said in a statement today.

It said MAHB had also repaired the cable terminations, installed sheath voltage limiters to reduce the effects of circulating currents and improved the maintenance regime with partial discharge tests and thermographic inspections.

It said MAHB’s long-term measures included studying the viability of an automatic transfer switch system for secondary power supplies, optimising generator use, tightening the timetable for planned preventive maintenance from three months to two, and implementing a thorough study of soil resistivity throughout the wires.

“MAHB has confirmed that no critical airport operations were affected by the incident.

“The ministry will continue to monitor the implementation of MAHB’s follow-up measures to ensure that the safety, efficiency and reliability of KLIA’s systems remain at the highest level,” it said.

KLIA Terminal 2 experienced a temporary power disruption late last month due to an issue involving one of its cables.

While the blackout did not affect airport operations, transport minister Loke Siew Fook said then that the 28 minutes it took to restore electricity was “very long and difficult to accept”.

On Sept 17, he ordered MAHB to redesign the electrical infrastructure at KLIA Terminal 2 to remove the risk of further power outages.