Extending the power transmission capability to 765 kV through emerging EHV/UHV transformers

Abstract

Bulk transfer of power requires EHV (Extra High voltage) and UHV (Ultra High voltage) Transmission lines. After thorough study of characteristics and specifications implemented in other parts of the world and related equipment based on insulation coordination studies, CEA working group decided next AC Transmission voltage in the country as 765 kV (Nominal Voltage), with 800 kV as system highest voltage. EHV transmission is going to become backbone supported by UHV AC and HVDC transmission which are essentially required by the country's geographical needs. EHV transformers because of their massive sizes and complicated designs require specific considerations to address reliability issues. Reliability is the sum total of reliable specification, reliable design, reliable material, reliable manufacturing and off-course reliable O&M at site. Therefore, different aspects related to design issues and their possible solutions have been discussed in the paper. EHV class transformer during manufacturing requires special process to follow which are also discussed here. Here also, material quality aspects, transportations constraints and commissioning & installation, in process checks, have been covered. Other than manufacturing and installation, normal operating condition and their performance also needs constant attention on site and that also discussed here.