Mechanical strength of power transformers in service

Eigenvalue Analysis for Investigation of Tilting of Transformer Winding Conductors Under Axial Short-Circuit Forces

“…The cumulative effect of short-circuit forces [3] and the manufacturing variations [8] may lead to an initial tilt angle in winding conductors. This section describes a formulation for determining the initial critical tilt angle for disk windings by using the state-space approach.…”

“…The tilting failure may result in a damaged insulation on conductors, force amplification due to conductor displacements, and interturn short circuits [6]. In service conditions, the short-circuit forces are cumulative in effect [3]. Thus, final failures may not necessarily be due to a severe fault but they may occur because of the cumulative effect of successive short circuits, which may progressively increase the tilting.…”

Cumulative Deformation Analysis for Transformer Winding Under Short-Circuit Fault Using Magnetic–Structural Coupling Model

“…Besides, there are so many transformers whose service life have exceeded more than twenty years that the mechanical strength of the windings material decrease rapidly with the increasing of the aging problem, and the ability to withstand the SC current impact also decreases. Manuscript Under the short-circuit fault, the magnetic leakage field inside the transformer and the electromagnetic force applied in windings may be affected by winding deformations [3]. Especially for the superconducting transformer, the spaces between the winding discs usually allow for the flow of liquid nitrogen and can be adjusted to minimize any circulating currents that flow in the parallel circuits [4].…”

Analysis of electromagnetic forces in high voltage superconducting fault current limiters with saturated core

“…These electromagnetic forces present as radial and axial forces [9][10][11]. Analysis of electromagnetic forces within a power-transformer is well established [9][10][11][12][13][14][15][16][17][18][19]. It was shown that such forces are potential sources for damage.…”

“…The problem faced when applying the models used in the analysis of power transformer on FCL design is that transformer models are generally based on round core-coil arrangement [9][10][11][12][13][14][15][16][17][18][19], whereas FCL cores and coils often have different geometries. Since fault current limiting for high voltage applications is a relatively new technology, the effects of electromagnetic forces in HTS FCL coils have never been reported.…”