Core saturation effects of geomagnetic induced currents in power transformers

Abstract

Saturation of the magnetic core of transformers in a power system is an important effect that can be attributed to solar Geomagnetic InducedCurrents (GICs). This saturation can conduce to voltage-control problems, generating harmonic currents, and heating of the transformer internalcomponents, leading to gas relay alarm/operation and possible damage. This paper presents an analog physical reduced scale model of GICs inpower transformers. The instrumentation employed to carry out this study consists of a single-phase reduced scale transformer, a controllablecurrent source, a resistive load and a data acquisition system. The work establishes not only that it is possible to model the behavior of magneticvariables and to extrapolate the results to large full size power transformers, but also provides insight into GICs generation and their effects onpower transformers. Obtained results are related to the non-linear behavior of GICs due to asymmetric saturation of the magnetic core in the powertransformer, where computational model simulation is not able to give acceptable outcomes. Results are discussed for several GICs magnitudes,which include voltage, current, harmonics waveforms, magnetic core point of operation, the behavior of the stray flow, instantaneous power andcore temperature.