To meet long term Power transfer requirement by 2025 and beyond as well as for optional utilization of right of way, large capacity transmission corridors at next higher voltage level at 1200 kV (UHV) are being planned interconnecting the generating resources/pooling stations with the load centers.
To develop 1200 kV technology indigenously, POWERGRID is developing 1200 kV testing substation at BINA, MP with 1200 kV experimental line where several Indian manufacturers are contributing their 1200 kV equipments for long term testing for validation and optimization of 1200 kV technology.
With present limitations of transport as well as manufacturing infrastructure, it is decided to produce 333 MVA, 1150/”3/400/”3/33 kV single phase Auto Transformers framing a bank of 1000 MVA, 3 phase which is expected to be one third of the futuristic commercial transformer. VEL is contributing one such Transformer which is now in advanced stage of manufacture.
UHV transformers because of their size and construction have to be most reliable. Hence, design of such large rating transformers both in terms of voltage and current pose several challenges to designers.
Transport limitations enroute is the biggest challenge since two halves of 1200 kV coils are to be accommodated (with mid-entry of 1200 kV lead) in the available window height. Then, there are problems related to 1200 kV lead exit, large electromagnetic fields, hotspots etc.
This paper mainly focuses on design experience gained in the design of 333 MVA transformer at VIJAI, addressing design challenges in the following major areas: Electrostatic Design (Dielectric Design) Electrodynamic Design (Short Circuit withstand Capability) Electromagnetic Design (Eddy & Stray Loss Control) Thermal Design (Hotspot Control) Structural Design (Vacuum, Pressure, and Transportation withstand Capability)
