Effects of nanosecond impulse and step excitation in pulsed electro acoustic measurements on signals for space charge determination in high-voltage electrical insulation

•Presence of space charges in HV insulation can influence the operational stresses.•Effects of nanosecond impulse and step excitation in PEA are shown.•Experimental results showed the main PEA effect during the transition phase of the excitation voltage.•Correspondence between pulse and step excitation was presented.•Presented results extend the insight into PEA – especially with a focus on diagnostic applications.