Abstract: This paper introduces the rapid fault locating process of a 220 kV main transformer when a tripping accident occurred, which utilized the oil chromatographic analysis, electrical test and winding deformation diagnosis. Besides, the processing procedure in the factory is also included. Through the in-depth accident analysis, it is found that the ability of the transformer winding to resist the impact of short-circuit current is not only related to the design, manufacturing technique and material selection of the transformer, but also depends on the operation and management. Therefore, it is necessary to optimize the design and type-slection of transformer and improve the operating conditions. Particularly, the necessity of a power outage for winding deformation diagnosis should be determined according to the impact of cumulative frequency and the level of the short-circuit current of the large transformer, which has suffered the impact of short circuit current several times, but has no abnormal operations. The expert argumentation should be carried out when necessary. The necessity of repairing or replacement should be determined according to the degree of winding deformation to prevent the large transformer to operate with trouble.

Key words: transformer, fault diagnosis, processing procedure, suggestions and measures