Physical Quantities Measurable by the Current Integration Method - Conductivity, Space Charge, and Permittivity

The current integration method revitalized by Prof. Takada is an innovative and useful tool for evaluating the dielectric properties and insulation integrity of polymer insulating materials and devices using them. Despite its simple and classic principle, as it is relatively new, its theoretical basis is not necessarily well understood. In this presentation, we first describe the theoretical basis of the current integration method and discuss the possibility of estimating various physical properties of insulating materials. It appears self-evident that the method can measure the leakage current passing through materials. This method is not suitable as a space charge measurement tool because it cannot, for instance, quantify stationary space charges that do not induce an electric current. It is also uncertain whether this method can estimate the accumulation and decay of the space charge formed in insulating materials if we analyze the integrated charge when the voltage applied to the sample is cut off and the circuit is short-circuited after completing normal measurements. When only a sample's dielectric constant or volume resistivity is known, this method allows us to determine the other property without knowing the specific shape and dimensions of the sample.