Net polarization in cable dielectrics Q/P comes from manufacturing processes such as extrusion and especially the e-beam cross-linking Radiation-Induced charge storage and polarization effect (Schematic graph taken from p.254 in Electret by B. Gross)

Pyroelectric response for XLPE/PEEK cable with different temperature change

Mathematical model Thermal Solving the heat diffusion by direct implicit difference (with non-linear thermal diffusivities for polymers and varying radial intervals). Mechanical Non-linear thermal expansion of polymer. Electrical The electric field within polymer is determined by iterating the discretized Poisson's equation to give zero potential difference between the shorted electrodes. The charge density on electrodes can be calculated by using Gauss's law. The derivative of the charge gives the current in external circuit.

Modeling: thermal part Time-backward difference method with varying D and intervals in cylindrical coordinates: Rearrangement: at boundary. Transfer matrix:

Modeling: electric Part Poisson’s equation in cylindrical coordinates: where Discretize: Short-circuit --> conductor and shield are in equal potential Assume a surface field at the conductor E 0 Iterate E 0 to the value which gives zero potential difference Calculate the surface charge on the conductor by using Gauss’s law Calculate the TIC response

The detailed electronic circuits

High field conduction in polymeric dielectrics Objective to understand the fundamentals of high electric field phenomena in polymeric dielectrics as related to the induction of failure therein.

Summary of the experimental results

EL and SCLF V max -2V c > 0

Diffusion across the interface Top : Diffusion profile close to semicon/insulation interface. (the absorbance peak at 1735 wavenumber for ester groups) Bottom : Variation of dc breakdown strength with distance from semicon/insulation interface Data taken from J. Bezille, CEIDP 92, p567.

Summary Summary The guarded needle method and electro-luminescent measurement are insightful tools for the study of the induction of failure under high electrical field. The above two measurement methods are complementary the guarded needle measurement provides a level of quantitative detail the electro-luminescent test is helpful for the study of the semicon- dielectric interface properties