Experience in determining technical condition and evaluating the lifetime of transformers based on the results of a comprehensive diagnostic examination

Abstract

The article considers a comprehensive approach to assessing the residual lifetime for transformers with a significant service of more than 30 years. Using the example of a comprehensive diagnostic examination of two transformers, it is demonstrated that transformers have different options for aging the active part and the approach to resource assessment should be different. The first option is a uniform general «aging» of the active part, the fact of aging affects reliability after 50–60 years. The second option is the occurrence of a local defective node with vibration (VIBRO) and electric discharge phenomena (ERA), the defect appears spontaneously after 15–25 years. The appearance of critical defects can be recorded on-line using innovative techniques. The processes that determine the aging of the nodes of the active part are the phenomena of «VIBRO»–«ERA»–«THERMO»–«HARG». By analyzing the parameters and dynamics of phenomena, it is possible to assess the technical condition and resource. This approach is confirmed by the analysis of the technical condition of typical variants of defects in transformers.