High-Frequency Transformer And Reactor Models For Network Studies

Transformers are critical components in any power system. The reliable and safe operation of a transformer requires that the stresses imposed by the environment are kept within acceptable limits. Prediction of dielectric stresses from transient overvoltages requires the ability to simulate the overvoltages in the system, e.g. due to lightning strokes, normal switching operations, fault initiation and clearing, and repetitive voltage flanks from power electronic converters. The stresses involve phase-ground voltages at terminals and inside the transformer, longitudinal stresses at the winding end caused by non-linear voltage distribution along the winding, and resonant voltage buildup inside the winding and between external terminals. Adequate models are also needed in general transient studies, where the transformer is just one of many components. The transformer model should preferably be compatible with Electromagnetic Transient (EMT) programs for its use in general studies, in addition to more specialized in-house simulation programs.