Restoration Outlook for Nanao Ota Thermal Power Station Unit 2

Overview of the Incident

On 2025-12-30, an abnormality was detected in the main transformer of Nanao Ota Thermal Power Station Unit 2 (rated output 700,000 kW), resulting in automatic shutdown. Internal inspection confirmed significant damage, including melting of part of the copper conductors, necessitating extensive repairs including replacement of internal transformer components. The cause is estimated to be insulation breakdown due to a lightning strike. Measures such as reinforcing lightning arresters will be implemented going forward.

Outlook and Performance Impact

Restoration is expected around spring 2027. During the outage, supply capacity will be secured through operation of other thermal and hydroelectric power plants and market procurement. An impact of approximately 20 billion yen on fiscal 2026 performance is anticipated due to increased costs for substitute power procurement; however, this may fluctuate based on future information.