Dynamic Polarization Depolarization Losses under Non Equilibrium Radial Heat Diffusion Conditions
Dynamic radial thermal gradients shift peak electric field stress outward and double dielectric depolarization losses compared to isothermal estimates.
Radial Heat Diffusion
Meaning
Outward movement of thermal energy from the central conductor of a cable through the insulation layer to the surrounding environment. The rate of radial heat diffusion determines the temperature distribution across the insulating sheath during continuous power transmission. This heat flow is governed by the thermal conductivity of the polymer and the external boundary conditions.
Thermal Control
Heat must be dissipated efficiently to prevent the conductor temperature from exceeding the degradation threshold of the cross-linked polyethylene. A high rate of radial heat diffusion keeps the internal temperature low, allowing the cable to carry higher current loads. Specialized additives are sometimes incorporated into the polymer matrix during the compounding stage to enhance this thermal pathway.
Assessment Method
Prototyping and testing are used to verify the actual heat transfer rates of different insulation formulations. Steady-state heat run tests measure the temperature difference between the conductor and the outer jacket under controlled electrical load. These evaluations are completed before selecting the final insulation compound for full-scale extruder trials.
Operational Consequence
Inadequate thermal dissipation leads to a rapid build-up of heat, which accelerates the degradation of the polymer and can cause premature electrical breakdown. If the actual production yield exhibits lower thermal diffusion than predicted by the supplier’s model, the cable rating must be downgraded. A verified heat dissipation profile ensures that the transmission system can operate at its maximum capability without risking thermal run-away, and it guarantees that the insulated conductors can withstand prolonged operation at maximum rated current levels without structural deterioration.