Traction transformers serve as the core power supply equipment for the 25kV/50Hz Thailand railway electrification project, directly determining the operational safety and stability of the rail line. Subject to Thailand’s distinctive operating conditions including high temperature and high humidity, coastal salt spray corrosion, drastic load fluctuations caused by frequent train acceleration and braking, and intense vibration, such transformers require customised design balancing environmental adaptability and operational reliability. Reliability testing acts as a critical guarantee for long-term stable service of the equipment.

Tailored for local operating conditions in Thailand, the traction transformers predominantly adopt three-phase to single-phase transformers with Vv connection, compatible with the bilateral power supply scheme for the 25kV overhead contact line system. The windings utilise low-loss conductors and transposition technology together with high-grade silicon steel sheet cores to effectively suppress harmonic losses and vibration noise. Meanwhile, enhanced protection configurations are deployed: Class H heat-resistant insulation and anti-salt-spray coatings are adopted, matched with a forced air cooling system to accommodate tropical high-temperature conditions. A fully sealed oil tank and seismic reinforcement structure are implemented to withstand strong vibration and salt spray erosion. Sufficient overload margin is reserved to cope with load shocks arising from frequent train starts and stops.

All reliability tests comply with standards specified for Thailand railway projects. Factory acceptance tests cover electrical characteristics, insulation performance, sealing performance, vibration tests and other items, with particular emphasis on temperature rise tests, short-circuit withstand capability tests and environmental simulation tests. These replicate operating conditions such as high temperature, salt spray and vibration to verify equipment adaptability. During on-site grid connection, further commissioning including load switching tests, harmonic measurement and a 72-hour continuous full-load endurance test shall be completed. This ensures the transformers meet operational requirements of Thailand’s electrified railway network and establishes a solid foundation for secure and stable power supply along the line.