Diagnosing Axial Movements in Transformer Windings by Leakage Flux Monitoring

Abstract

Monitoring transformers is essential to ensure reliable operation of a power system as they are possibly the most critical equipment present in all generation, transmission, and distribution network. Having such monitoring amenable for online implementation is even more desirable. Mechanical deformations are difficult to detect with existing online condition monitoring tools as they hardly lead to any perceivable change in quantities that can be measured from terminals. Leakage flux, amongst all the power frequency parameters, is the most sensitive to changes in winding geometry. Understanding how the spatial distribution of leakage flux is altered by winding deformation would help in diagnosing such damages, preferably at their infancy, by means of flux sensors mounted along the axial height of a winding. As a preliminary study, only axial movements in the winding are considered in this paper. A Finite Element model was developed in Ansys Maxwell to emulate various degrees of axial movement at different places in the winding. The aspects of leakage flux based online winding damage diagnosis at their incipient stage, are investigated in detail with the computed leakage flux distribution and their results presented.