Reliability of UHV Transformers On behalf of CIGRE SC A2 - AG A2.5 (UHV AC & DC Transformers)

In the UHV transmission systems, the reliability of the UHV transformer is most important, because their are connecting and transforming the large electric power in the electric power networks between UHV transmission systems and other voltage levels of the transmission systems. Then every country, every utility is carrying out the on-site tests to verify the reliability and/or life time of the UHV transformers. This paper introduce these tests results based on the recent UHV projects in the world.

It is necessary to verify the UHV transformers insulation after long way transportation and field installation. Among the insulation tests on site, the long-duration induced AC voltage test (ACLD) with partial discharge measurement may be the most difficult one, which requires the test equipments with high performance, such as high voltage, huge power and lower PD level of the main body. Furthermore, the field has a complex environment that would impact the test. This paper also introduced the experience of UHV transformers ACLD test on site in China, and the ‘Mobile On-site Partial Discharge Detection Testing System for UHV transformers(MPDS-1000)’ developed by China Electric Power Research Institute. India is starting the UHV project with the highest system voltage of U_m 1200 kV. Then, this paper indicates the checking flow of the 1200 kV project whole of the design to the on-site acceptance test and the initial energizing tests.

Japan is highlighted the long-term field test more than ten years. And it was verified the life time of the UHV transformers more than 142 years based on the over level of the energizing long term field tests at the field test station.