Neglected frequencies analysis on switching operations in extra-high voltage electrical power substations

•Classification of circuit breakers (CB) and disconnect switches (DS) in an air insulated substation using machine learning algorithms using real data waveforms.•Data augmentation technique applied to High-frequency transient overvoltage waveforms to expand and balance database.•Definition of the most relevant frequencies in the classification of switches and circuit breakers using Feature Selection.•Critical analysis of the definition of oscillatory transients in the IEEE Standard Practice for Monitoring Electric Power Quality.