Studies on resonance phenomena caused by energization of transformer

This paper presents an analysis of high frequency resonance caused by switching on the unload transformers, including its equivalent circuit, basic equations, resonance conditions, origin of harmonic energy and its analytical methods. Two typical resonance phenomena from HVDC and HVAC transmission systems are studied by means of EMTP, and the simulation results provided a good agreement with the field measurement. The potential problems caused by energization of transformer and its countermeasures for different system conditions are discussed.