Transient electric field of the combined insulation structure under positive periodic square waveform voltage:Analytical analysis and application

The working voltage of the high-voltage high-power electronic devices is the positive periodic square waveform(PPSW)voltage,which is much different from the conventional AC or DC voltage.For the composite insulation structure of devices,it is important to analyse the transient electric field under the PPSW voltage.However,the existing investigations are often conducted under the electrostatic field due to the high frequency of the PPSW voltage.Thus,the transient characteristics of the electric field are missed.To obtain some qualitative conclusions,this paper focusses on the theoretical analysis of the transient characteristics of electric field for the composite insulation structure under the PPSW voltage.First,the formula of the electric field intensity and the interfacial charge density are derived analytically.Second,the influence of the cycle and the duty cycle on the transient characteristics are investigated.Third,the maximum of the electric field intensity and the interfacial charge density in the positive square waveform steady-state are discussed in detail.Besides,the engineering calculation methods for obtaining these maximum values are also suggested.Lastly,an actual model is employed to testify the validity of the analytical analysis.This work is significant for the numerical calculation of the transient electric field of composite insulation structure under the PPSW voltage in engineering.