Polarization & depolarization current (PDC) measurement in cellulose insulating materials

The study of electrical insulating materials can never be overemphasized. When these materials are subjected to either electrical or thermal stresses each one respond in a uniquely different way from one another. The response of insulating materials to its stressors is a stochastic process with varying dependent variables. The discovery of newer or composite insulating materials, having better electrical properties, have further deepened this lack of understanding. Researchers and engineers have utilized the dielectric relaxation in the materials as an assessment tool. Polarization and Depolarization Current (PDC) is one of such assessment tools to measure the relaxation current when a sudden stress is applied or removed. This paper presents study of the relaxation current in Kraft paper and how moisture diffusion in it affects the conductivity of the Kraft paper. This assessment technique was done using a multi physics software; COMSOL Multiphysics. COMSOL Multiphysics has been chosen because dielectric relaxation has a multidisciplinary science of physic, chemistry and electrical engineering involved in the process. 100V dc was applied across cellulose molecule and the resulting conductivity, σ and moisture diffusion was measured and presented. The result shows the interesting relationship between conductivity & changes in moisture in the solid insulation.