Fault Diagnosis and Analysis of a High Overload Vegetable Oil Distribution Transformer

In response to an insulation fault in a high overload vegetable oil distribution transformer, the transformer fault was analyzed and located through chromatography in the transformer oil, combined with various experimental methods. The internal discharge fault was determined to be located at the upper end of the C-phase winding through disassembly. Based on the relationship between the temperature of bubble formation and the moisture content of solid insulation, combined with the actual operating conditions of high overload operation, it is confirmed that poor sealing causing moisture on the insulating cardboard is the fundamental cause of the malfunction.