Transformer Tertiary Stabilizing Windings. Part II: Overheating Hazard on Tank Walls

In this paper the evaluation of the overheating hazard due to zero sequence flux on tank walls of power transformers is presented, taking into account the influence of the Tertiary Stabilizing Winding (TSW). Three-phase three-limb core form transformers are considered in this work, where the component of the zero sequence flux closes its path over the tank wall and cover. This paper complements a previous companion paper where cases of full single-phase load and single phase-to-ground faults are studied with and without delta-connected TSW. Those previously calculated zero sequence currents are here the input sources for computing the zero sequence flux. For that, two methodologies are used. One is based on the Reluctance Network Method (RNM) applying the RNM2D_0 software. The second one is based on the Finite Element Method (FEM). A practical application is presented and both computational methods are compared in order to validate the results.