Extra/Ultra High Voltage Transformers: Recent Practices in India

EHVAC & HVDC transmission has been growing to cater demographic power needs of India. Minimizing transmission loss in bulk transfer of power over long distances requires upgradation of transmission voltage level from existing 400kV to 765kV EHVAC (Extra High voltage AC) and 800 kV HVDC (High Voltage DC) Transmission lines in India. Thus, Extra High Voltage/Ultra High Voltage (EHV/UHV) transformer requires specific considerations because of its massive size and complicated design for enhanced reliability. The considerations include choice of appropriate material, manufacturing process, Erection & Commissioning (E&C) and on-site Operation & Maintenance (O&M). The paper presents a comprehensive assessment of various design and manufacturing constraints of EHV/UHV class transformer in Indian perspective and some aspects are compared with already established 400kv Class transformers technology. The assessment is presented on material quality, transport constraints, installation, commissioning and other design parameters.