Insulation condition evaluation of 750 kV power transformers based on frequency domain spectroscopy

The reliability of oil-immersed power transformers depends on the insulation system to a large extent, and the lifetime decrease with the deterioration of the insulation system. Therefore, insulation diagnosis and lifetime evaluation for oil-immersed transformers are necessary. In this paper, diagnostics of transform insulation are analyzed, and a new diagnostic technique based on frequency domain spectroscopy (FDS) is presented. The 750 kV transform operated in Lanzhou East Substation is measured on-site with the FDS method. The experimental results show that the moisture content in transformer pressboard is eligible, and its insulation condition is well. And the experimental results are consistent with those of the conventional preventive test. The validity of FDS method is proved, and it is promising as a novel preventive test method.