Circuit Models of Q(t) Data and Analyses of Saturation Time Dependency on Delay Parameters

In recent years, there has been a considerable increase in the use of DC power equipment in the industry, making it crucial for insulation materials to withstand high DC electric fields. The current integration method (Q(t) measurement) is one of the most useful and effective methods to measure the time dependency of charges. However, the mathematical/physical model of Q(t) measurement is not advanced because obtained data are not completely analyzed, particularly the methods in which delay parameters affect the charge saturation time of insulators. In this study, we analyze the delay property of Q(t) data by solving differential equations with some approximations. In addition, sample sheets of polyimide and polyethylene terephthalate are tested for experimental purposes. The results indicate that circuit properties can be estimated from the analysis of experimental Q(t) data based on the assumption of a circuit model. The proposed analysis method can be used for further discussions regarding the analytical estimation of timing of charge saturation, and the relationship between circuit models and the space charges phenomenon.