Investigation of supraharmonics' influence on partial discharge activity using an internal cavity sample

•Supraharmonic oscillations are emitted by power electronic converters.•They can magnify partial discharge activity in afflicted insulation systems.•Oscillations placed in the fundamental waveform’s peak have the strongest effect.•Lower oscillation’s natural frequencies seem to intensify the activity more.•The increased discharge activity is expected to degrade insulation systems quicker.