At present, work on the 1200 kV transmission system is in progress in India. Research work is going on at National Test Station, Bina, where 1200 kV setup with single-circuit and double-circuit line is installed. In order to investigate the performance of ultra-high voltage (UHV) system, the design modifications and other technical studies related to the transmission system, its simulation study is required. A UHV autotransformer is the main part of any UHV transmission system. Early research suggested the use of single-phase three-winding transformer model of PSCAD software (4.2 version) to model an ultra-high voltage autotransformer. The novel method uses a bank of three ‘single-phase three-winding autotransformers’ and a three-phase star-star autotransformer with tertiary (with provision of a Star or delta connection of tertiary winding and choice of delta lag or lead) model of PSCAD 4.6 version. This paper presents the modeling and simulation and validation of 1200 kV UHV autotransformer using these models. The simulation results are validated and verified through the actual field test results, and it is found that the autotransformer module of PSCAD 4.6 software is suitable for simulation study of the UHV installation.