Key Technology and Engineering Application of the On-site Assembly UHV AC Transformer

In the construction of Ultra High Voltage (UHV) AC project in china, the UHV AC transformer is very difficult to transport. Disintegrating transportation and on-Site assembly is an effective way to reduce transportation weight, solve transportation problems and reduce transportation costs. In China's Yuheng-Weifang UHV transmission project, the UHV auto-transformer with disintegrating transportation and on-site assembly is used in Jinzhong substation by Sate Grid Corp. of China for the first time. It is also the first engineering application of 1000kV class on-site assembly transformer at home and abroad. Compared with the conventional UHV Transformer, the design and manufacture of the On-site Assembly UHV Transformer is more difficult. The requirements of site assembly workshop and drying method and process were also studied emphatically. Through the research, it is concluded that the 1000MVA/1000kV main transformer has a better economic performance with the dual core limbs structure and the whole disassembly scheme, and the spare room as an assembling workshop is an economical design scheme. In engineering practice, the on-site assembled UHV Transformer adopts a movable gas phase drying device, which effectively improves the drying quality. In the acceptance test, no-load loss and no-load current measurement, load loss and short-circuit impedance measurement tests are added to test the influence of field assembly on the circuit and magnetic circuit. No-load loss measurement at 100% rated voltage and load loss at 50% rated current are achieved on site. At present, 4 on-Site assembly UHV transformers have been applied and work well in Jinzhong substation. The application of 1000kV on-site assembly transformers is helpful to enlarge the geographical range of UHV and EHV large transformer applications and reduce investment in equipment. The key technologies and successful application experience are introduced in this paper.