Feature extraction of mechanical faults from phase variation in transformer vibration

In this paper, the relationship between the phase variation in transformer vibration and the mechanical stability of the transformer is presented for the first time. First, the systems of winding vibration and core vibration are both described by Hammerstein-type models consisting of linear and nonlinear parts. Then the links between the phase angle of the fundamental winding/core vibration and system properties are established based on those Hammerstein-type models. They indicate that the phase variation can be used as an effective indicator of deterioration in transformer stability due to mechanical defects in the winding and core. To validate this claim, laboratory experiments and field tests are conducted. In the laboratory experiment, two mechanical faults-looseness of the winding clamping structure and winding deformation-are introduced to a 110 kV power transformer. The results show that both winding clamping looseness and winding deformation will cause larger phase variation in the winding-induced vibration and core-induced vibration. In the field tests, this relationship is also observed on an abnormal 220 kV power transformer. All the findings show that the proposed indicators can provide efficient fault-related information for evaluation of a winding's mechanical health condition. (C) 2021 Elsevier Ltd. All rights reserved.