Abstract
The short circuit withstand capability of power transformers describes the ability of the windings to withstand electromagnetic forces resulting from current density in the conductors and magnetic stray fields. Especially operationally aged transformers often have a reduced short circuit strength what can lead to irreversible deformation of windings if high fault currents occur. Short circuit strength is to some degree dependent on the mechanical strength of the conductors. Mainly the cellulosic insulation materials experience degradation during operation time due to high temperatures and moisture. Hence a reduction in short circuit strength can be correlated to some degree with the aging of the cellulose. In this paper the influence of paper insulation around Continuously Transposed Conductors (CTC) on their mechanical strength will be analyzed by a simplified analytical model as well as by a FEA based mechanical simulation model.
Highlights
Continuously Transposed Conductors (CTC) deliver an important contribution for the increase of power transformersefficiency compared to the conventional paper-insulated solid conductors
In this paper only radial force components are considered as the rigidity of CTC especially in radial direction is much lower compared to a solid conductor with identical outer dimensions
The reason here for is that in axial direction the cross-section of CTC compared to a solid conductor is only divided into two stacks, while radial direction is divided into usually 10 to 40 single strands
Summary
CTC deliver an important contribution for the increase of power transformersefficiency compared to the conventional paper-insulated solid conductors. The reason here for is that in axial direction the cross-section of CTC compared to a solid conductor is only divided into two stacks, while radial direction is divided into usually 10 to 40 single strands. Radial forces acting on the inner winding are directed inwards resulting in a bending stress.
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