A Study on the Non-linearity of Dielectric Response in Time Domain of Oil-paper Insulation

Up to date, an increasing interest arises on the dielectric response measurement in time and frequency domain to assess the condition of the oil and paper insulations of electrical equipment. The polarization and depolarization current (PDC) is widely accepted as a simple but effective technique dielectric response in time domain, which is based on the linear dielectric system. In the presented paper, the PDC technique is applied to study the non-linearity of dielectric response in time domain of oil-paper insulations. Two sample configurations, i.e., a layer of oil immersed paper sample and two layers of an oil gap and oil immersed paper layer, are used to study the effect of structure on the non-linearity. The nonlinearity of dielectric response is evaluated under various voltages and various sample configurations. It is found that a non-linearity of dielectric response in time domain of multilayer of oil and paper occurs in extremely low field region, much lower than that of a single layer of oil immersed paper. Charge carrier's motions in the oil gap and interface polarization shall play a critical in the non-linearity.