Transformer Saturation Methods and Transformer Response to Low Frequency Currents

This paper investigates transformer saturation effects and laboratory setups to cause transformer saturation. Low frequency currents (LFC), such as geomagnetically induced currents (GIC), in the high-voltage transmission grid can cause transformer saturation. As a consequence, the current gets distorted and the power demand increases. Special test setups are analyzed in laboratory measurements with small-scale transformers, two 50 kVA power transformers and simulations. Advantages and limitations of the different setups are highlighted, with respect to their feasibility in the field and laboratory. The power demand and current distortion during transformer saturation are correlated with the superimposed LFC. An increased non-active power demand was measured for an increase in asymmetrical current distribution between the phases. Furthermore, symmetrical and asymmetrical LFC distributions between the phases are investigated. Recommendations for future work regarding laboratory measurements and transformer setup is given.