A Theory of Non-Steany State Moisture Absorption by Annular Polymeric Dielectrics

Equations are derived describing the isothermal, non-steady state diffusion of moisture into an annular dielectric enclosing a cylindrical, impermeable conductor. The correct solution of the diffusion equation is compared with approximations based on the plane sheet or the solid cylinder. It is shown that these approximations can lead to considerable error when estimating diffusion coefficients from cable water absorption data, or when calculating water contents using known diffusion coefficients.